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NEP 7 IO Gy = Z “iy E \ ZN = Z = z Ly ARTES SMITHSONIAN INSTITUTION NOILNLILSNI_NVINOSHLINS Saluvugia_ LIBRARIES SMITHSONIAN _ INSTITU ae 2 @ 2 Seo hat Zz Ww 2 z "S e 2 GN = “ = S <3, a < =i, \ ee c Se c ae = 2 5 Y ce = fs za = Z; re) a rs) Saco fe) = S) 4 z 5 z eee) z a 2 MLIASNI_NVINOSHLINS SAlYvagiT LIBRARI ES_ SMITHSONIAN INSTITUTION | NOILNLILSNI/_NVINOSHLINS pSaluve = 08 fe) — ey, Zi = fe) ee fe) = \ 5 0 = x = = 5 > ASQ ‘ = > = i: > = > be 14) Sx WS = So] Le “og = wD = NN Bes E. Bs = 2 = mo NW 2 Or m 2 m = en as Zz a z O z= 7) & ARIES SMITHSONIAN INSTITUTION NOILMLILSNI_NVINOSHLINS SaluWvu al) os - = Zee g | < = py, = = < 2 \w i 8,5 2 Yy,* : 2 3 2 WIN 8 YG 2 3 Yt; 2 : > CAA oO YY G&G = SOT GH. t= z2 Ss Ceo mie \ Y y 1 ee Sg Ny ekg: ait ; Oa ie ' ] . MW vi { why - b i) i - af i ¥ ; j ; P ik ‘ t = i | ww \ ) ¢ ¥ ¢ jl : i s ; i : i i me ; { i ale VELIGER A Quarterly published by CALIFORNIA MALACOZOOLOGICAL SOCIETY, INC. Berkeley, California Volume 23 July 1, 1980 to April 1, 1981 4 eT , ; : : 2 namin ane 1 mehr Ahonen a lin a Lae ae: by ergot Vol. 23; No. 4 THE VELIGER Page iii RE SS SSS SSS SSNS TABLE or CONTENTS A cephalic dimple in the terrestrial snail Achatina acha- tina. RONALD CHASE & MICHELE PIOTTE on. 241 A comparison of Fijian forms of Conus coronatus and Conus aristophanes. (CAPBIBE WAS YR eee See eet Fmt te ea Sec eta ert ts 363 A comparison of two Florida populations of the Coquina Clam, Donax variabilis Say, 1822 (Bivalvia : Dona- cidae). I. Intertidal density, distribution, and migra- tion. PAW LP STEPHEN IMIIKKELSEN | fee tcccecsn-narcmtaee 230 A new species of Favartia (Caribiella) from the Galapagos Islands. Emity H. Vokes & ANTHONY D’ATTILIO .......... 15 A new species of Lepidopleurus Risso, 1826 (Mollusca : Polyplacophora) in the deep waters of the eastern Pacific. PNINHONITON | PERRET RIA eure neater wench ern ae 55 A new species of muricacean gastropod. 1B INL, OOETRBI YN Necro te elena eet neers ee en 19 A new species of Stenosemus Middendorff, 1847 (Mol- lusca : Polyplacophora) in the abyssal northeastern Pacific. ZANITONTOD oy BE RRET RA ee ney oe sr tna ee eae eas 325 A niche analysis of coexisting Thais lapillus and Urosal- pinx cinerea populations. DAW ID Ey NSM RETES ONT gree ree Seren crm neen een eect, 277 A note on the diet of Beringius kennicottiw (Dall, 1871). TO NAMED [eee SELUE) Keg tes eee se ett center cs 153 A possible relationship between size and reproductive be- havior in a population of Aplysia punctata Cuvier, 1803. Cary Otsuka, Yves Roucer & ETHEL ToBACH 159 A survey of the softbottom molluscs of Cockburn Sound, Western Australia. Frep E. WeLis & Timotuy J. THRELFALL ........... 131 Behavior of the gastropod Amphissa columbiana (Proso- branchia : Columbellidae). | BYRUBU GIST NAGI SI SINE cette tet aes a ee ye nee 275 Biting as a defense in gastropods of the genus Busycon (Prosobranchia : Melongenidae). PAT Dea) ea VN; BUD ONG cnet tact cc erotica a ten erent Mace acer 357 Casmaria atlantica Clench (Mollusca : Gastropoda) : Thoughts on its evolution. J. GiBSON-SMITH & W. GIBSON-SMITH ocessseesnee 352 Chaetogaster limnaei (Oligochaeta : Naididae) inhabit- ing the mantle cavity of the Asiatic clam Corbicula fluminea in Barkley Lake, Kentucky. James B. SickeEL & MARK B, LYLES nceccecsssesnonn 361 Collections of gastropods from the Cascade Mountains of Washington. BRANLEY ALLAN BRANSON ooo cescecsssonnnrnrnsnee 171 Comments on two misunderstood Fusinids (Gastropoda : Fasciolariidae) from the tropical Eastern Pacific. EERO SEE OO RANG 7 semen na ear eet en eG 4, Comparative shell ultrastructure of lyonsiid bivalves. ROBERTS SPREZAN TY oy en ern o sn Rte 289 Correction. LLWISESSCHMEKEL Gs ey Pee nee LOD Crude oil effects on mortality, growth and feeding of young oyster drills, Urosalpinx cinerea (Say). Distribution, activity, and food habits of juvenile Tegula funebralis and Littorina scutulata (Gastropoda : Pro- sobranchia) as they relate to resource partitioning. EREREN DOP ENSENG | Ou cau Els tae) lee ol 239 Effects of temperature and salinity on the embryological development of Murex pomum Gmelin, 1791. EuNA A. Moore & FINN SANDER recssecssenensnnin 309 Evolution and function of asymmetry in the archaeo- gastropod radula. GAR ORE OS ELICKMAN | putea yee eae ee ee ca 189 Food sources and feeding behavior of Nautilus macrom- phalus. PETER WARD & MARY K. WICKSTEN uses 119 Four previously undescribed Indo-Pacific terebrids (Mol- lusca : Gastropoda). PRWiITGAWIBRATGHER! se Sie canton Retin ne hee PMN 329 Growth and mortality in the ribbed mussel Geukensia demissa (Bivalvia : Mytilidae). NEARKGD) SS DERTNESS artes ea er ear dna 62 Growth and production in exploited and unexploited pop- ulations of a rocky shore gastropod, Turbo sarmaticus. A. McLAcHLAN & H. W. LOMBARD .....ccsssnnennenn 221 Growth, mortality, and longevity of Certthidea decollata (Linnaeus) (Gastropoda : Prosobranchia) from Bay- head Mangroves, Durban Bay, South Africa. Victor G. Cockcrort & A. T. FORBES uc 300 Habitat notes on Gastrocopta riograndensis Sterki. 1 SUNG SORT) WAPI FDC Ob << ery ee tee Rr Uo EP 180 Heat tolerance in the black abalone, Haliotis cracherodii Leach, 1814: Effects of temperature fluctuations and acclimation Anson Hines, SUSAN ANDERSON & IMMGETAE TL BRISBING octet cscs serena cemiectua is 113 Identification of some planktonic prosobranch larvae off Beaufort, North Carolina. CATHERINE THIRIOT-QUIEVREUX eccsscsncsstcessnememene I Page iv THE VELIGER Vol. 23; No. 4 Larval and post-larval development of the window-pane shell, Placuna placenta Linnaeus (Bivalvia : Placuni- dae) with a discussion on its natural settlement. JeNTDY ANE | Uy CODING) cre ctrceet cree nee rere emberramncrenren 141 Late quaternary Bankia (Bivalvia : Teredinidae) from Humboldt County, California. Grorce L. KENNEDY, ANTHONY D’ArtTILIo, SAMUEL D. Morrison & KENNETH R. LAJOIE ........00- 75 Life history studies of the estuarine nudibranch Tenellia fuscata (Gould, 1870). Larry G. Harris, Mark Powers & JULIA RYAN 70 Magnetic radular teeth and geomagnetic responses in chitons. Jack Tomutnson, Desra REILLY & ROBERT IBALTERING ceca cutee taa detente cates meme atte: 167 Male characteristics in female Nassarius obsoletus: Vari- ations related to locality, season and year. BUAKE MAN: O: SMITH oon ey ete ren ee menea meneame 212 Movement, reproduction, defense and nutrition as func- tions of the caudal mucus in Ariolimax columbianus. ISVAUS* ON RICHTER AN nlet siete nism tant ei taeh 43 Neustonic feeding in early larvae of Octopus dofleini (Wilker). NEFERE Ys Bi yMARLIAVE ccecccciaunte meen ie ae ee 350 New distributional records for two California nudi- branchs. WiInciAMiB. JAECKIE Moe oe ee Se ae 240 New records from the tropical Eastern Pacific for Re- cluzia palment (Dall, 1871). MeEROYIH:, POOR MAN, ii dcsssce teenies Seren ca ae 183 New species of Fusinus (Gastropoda : Fasciolariidae) from the tropical Eastern Pacific. IEEROY/ EL. POORMAN (cect cies cemceceue atcha te eee 339 Note on the status and distribution of Littorina flava King & Broderip, 1832. IDANTER SPRINGZ.. fcceteiti it See ua vee eee 373 Notes on Recent and fossil Neritidae. 9. On the alleged occurrence of Neritina cf. N. donovani Récluz in the Vigo Formation, Luzon, Philippines. ETN aksee Kec VATE NTS) cere at eer ene a eee ee ea meek Observations on feeding in Maxwellia santarosana (Dall) (Gastropoda : Muricidae). INUAR Va SWVIGK STEN an rane cree nae meiner 96 Physiological effects of desiccation and hypoxia on the intertidal limpets Collisella digitalis and Collisella pelta. Bruce Leon BoesE & AusTIN W. PRITCHARD ........... 265 Preliminary studies on the association between Pleono- Sporium squarrosum (Rhodophyta) and Cryptochi- ton stelleri (Polyplacophora). KARcAyMGDeRnap UM ns hee) i Uae 317 Pulsellum salishorum spec. nov., a new scaphopod from the Pacific Northwest. ESLS1®), MARS ETAL ot pectissstsficaisesescnnes cate onse enema 149 Range extension for Pterotyphis fimbriatus (A. Adams, 1854). Jens HEMMEN & CHRISTA HEMMEN unseen 96 Range extension of three species of Teredinidae (Mollus- ca : Bivalvia) along the Pacific coast of America. MicHer E... HENDRICK Xs) 93 Recent changes in the Department of Invertebrate Zoolo- gy, California Academy of Sciences. DAPHNE PAUTIN: DUNN jenn ee 373 Rectification of the generic placement of Sclerodoris tanya (Marcus, 1971), comb. nov., a nudibranch from southern California, with a range extension to the Gulf of California, Mexico. HANS BERTSCE (.2.caacchlane ean 217 Redescription of a rare North Atlantic doridacean nudi- branch, Aegires sublaevis Odhner. T.. Ev THOMPSON ® ci cde nen 315 Reproductive biology of Asstminea californica (Tryon, 1865) (Mesogastropoda : Rissoacea). BRUCE Hi FOWLER ieicscccsstenoneactste one er eee 163 Reproductive biology of three species of abalones (Hali- otis) in southern California. THEODORE TUTSCHULTE & JOSEPH H. CONNELL 195 Review of the muricid genus Acanthotrophon (Mollusca : Gastropoda). EMiLyHVORES oo eect cance ae ene 10 Siphonal eyes of the giant clams (Bivalvia : Tridacnidae) and their relationship to adjacent Zooxanthellae. Peter. V, FANKBONER cintgecscc cree tae cna eee 245 Size gradients and shell polymorphism in limpets with consideration of the role of predation. B. HEART WIGK ao eran ance reece ae ee 254 Spawning in a British Columbia population of northern abalone, Haliotis kamtschatkana. PAuL ALLAN BREEN & BRUCE EDWARD ADKINS ...... 177 Studies on the formation of the crossed lamellar structure in the shell of Strombus gigas. Hrrosui Naxauara, Mitsuo KakeE! & GERRIT BEVELANDER veers eaten arene ante ae aee 207 Sublittoral observations of behaviour in the Chilean “loco” Concholepas concholepas (Mollusca : Gast- ropoda : Muricidae). Ranpvom DuBors, Juan C. CastILia & ROBERTO CACCIOUATTO: | cciintatesnisialattieancmt eine peat 83 Synopsis of the genus Piseinotecus with description of Piseinotecus evelinae spec. nov. (Gastropoda : Nudi- branchia ). ' WOISE) SCHIMEIED Wer us ckornat cence centage amare ai Vol. 23; No. 4 Temperature and growth of maturing Haliotis kamt- schatkana Jonas. TiN MWe LE NSAL, C3, Ufc, IN MG VED OI Oy ecert re eee ter rere 321 Terrestrial pulmonate reproduction: seasonal and annual variation and environmental factors in Helmintho- glypta arrosa (Binney) (Pulmonata : Helicidae). KENNETH LL. VAN DER LAAN cccsccsceeesscssessensnsennsneneee 48 The digestive system of the moon snail Polinices lewisu (Gould, 1847 with emphasis on the role of the oeso- phageal gland. Rosert G. B. Rem & JOAN A. FRIESEN Weenie 25, The effect of Pinnotheres hickmani on the meat yield (condition) of Mytilus edulis measured several ways. OM sr PREGENIZER Otc ere tee nec tasstaetisertntiotnpensatennne 250 The effect of salinity on crystalline style occurrence in the estuarine snail, I/yanassa obsoleta (Say) (Mol- lusca : Neogastropoda), and its potential signifi- cance with respect to local distribution. LawreENce™ L. Curtis & L. E. HURD Qs 155 ‘The littoral Polyplacophora of Shell Beach, San Luis Obispo County, California. BARRY, FOLSOM PUTMAN ‘iiscsccsncsccceccrcistrsssrtscneanstenerte 348 .The organisation and chemistry of the byssus of some bi- valves of the Waltair Coast, India. Anisa BANu, K. SHyMASUNDaRI & K. HANUMANTHA 1 RYN) rents tere res te th eter ae ee ee ee ee 77 The sexual cycle and reproductive modality in Littorina saxatilis Olivi (Mollusca : Gastropoda). DomIniQguE CAUGANT & JOSEPH BERGERARD .......... 107 The status of Pholadomya candida G. B. Sowerby, I, 1823. J. Grpson-SMitH & W. GIBSON-SMITH once 35 The ultrastructure and mineralogy of the dart from Philo- mycus carolinianus (Pulmonata : Gastropoda) with a brief survey of the occurrence of darts in land snails. PSTSTSRSS sev OME DAG ree ate cacre nh ein ea cate ceteanecahctcseai os 35 Two disjunct populations of Euglandina singleyana (W. G. Binney) (Spiraxidae) in central Texas. IRAVIMOND ® WYNNE GIRS oo esastiee nen ccatccnesatoenseineatatinn 112 AUTHOR INDEX AvkINS, Bruce Epwarpb see BREEN, PauL ALLAN & — ANDERSON, SuSAN see HinEs, ANSON et al. BALLERING, RoBERT see TOMLINSON, Jack T. et al. Banu, Anisa, K. SoayMasunpari & K. HANUMANTHA 1S UNO) te ree ree at eh ce eee ee et 77 BERGERARD, JOSEPH see CauGANT, DomINIQUE & — IBERTNESS,) MUARKIGD . ccckareneie est ugtta ie seme tu ad 62 TREN EIGER Page v IBERTS CH EUAN Siete rere iieisen nA aie Ne - 217 BEVELANDER, Gerrit see NAKAHARA, Hrrosui e¢ al. BorsE, Bruce Leon & AUSTIN W. PRITCHARD oeunn 265, BRANSON, BRANLEY ALLAN ooesssseststatususissssssnssiesienes 171 IBRATCHIER Ma WALAN eect tte tnamianastlcnaak a aateans 329 BREEN, Paut ALLAN & Bruce Epwarp ADKINS ..... 177 BrisBin, MicHAEL see Hinges, ANSON et al. CaccioLaTTo, Roserto see DuBois, RANDOM ef al. CastTILLa, JUAN C. see DuBots, Ranpoo eé al. CaucanT, DoMINIQUE & JOSEPH BERGERARD ..ereein 107 CHASE, RONALD & MICHELE PIOTTE wesc 241 CPARKAVIKSERRY” Bi trate eee Giza, Menace ne ae 8 (382) COANE UGENE Viger ane eden cee cae (188), (381) CockcroFT, VICTOR G. & A. T: FORBES usecase 300 CoNnNELL, JoSEPH H. see TUTSCHULTE, THEODORE & — Curtis, LAWRENCE A. & L. E. HURD wessessssssisicessuns 155 D’Attitio, ANTHONY see VoKEs, Emity H. & — see also: KENNEDY, GEorcE L. et al. DuBois, Ranpom, Juan C. Castitto & Roserto CACCIOUATITO Fert eee EN aD tetoonea 83 DUNN: DAPEINE PAUSTIN) Cecrcctnc cece creatorcencertorenctocrettete 373 EDWARDS, STEVEN EF, wasscsssessssnsssssnssne 125 DANIKBONERS ETER)) Vi teats Secs see titentocntace tne ccees 245 BERREIRASPANTONION Ji ccnscsccsencncser er sniccncetioses 55, 325 Forses, A. T: see CockcroFt, Victor G. & — ROWPER BRU GE SL are ee tata are rete 163 FRIESEN, JoaN A. see Rem, Rozzrt G. B. & — (GIBSON-SMITH, J. & W. GIBSON-SMITH ooesssssnsen 352, 355 Gisson-SmirTuH, W. see Grsson-SmitH, J. & — Harris, Larry G., Mark Powers & JULIAN RYAN 70 ULAR WAC HB sh i can acto a 254 HEMMEN, JENS & KRISTINA HEMMEN oosssmssnsnsnenen 96 HemMMeEN, Kristina see HEMMEN, JENS & — ETENDRICK XA MICHAEL (Ess ate nnccacct castro cniucaesnsesoncen 93 HickMAN, Caroie S. (105), (106), 189, (380), (381) Hines, ANson, SuSAN ANDERSON & MICHAEL ESRI BUEN oss tssnsccratecssinict nt tcebacet oc oeos 113 Hupp, L. E. see Curtis, LAwRENcE A. & — IPA. CIEE, BWV TELTA MB ieee caterer tate asc nosenaticowisacs 240 JENSEN, JEFFREY T. ......... 333 AJ TEATES O NVA VID) SANS re scetesee ce etree ace om seirecanee ns arta Be 277 Kakel, Mitsuo see NAKanarA, Hirosui et al. IGEEN GAG MYRA 2. eassccccaraialannie (107), (287), (381) KENNEDY, GeorcE L., ANTHONY D’AttTILI0, SAMUEL D. Morrison & KENNETH R. LA JOEE oesnsininsoe 75 IKENIT IBRE TIONG ete cae teria aint ananteasioanhece 275 Lajorz, KENNETH R. see KENNEDY, Georce L. et al. IE ESWV/TS soni Cape se tate ee arcsec tae 363 Lomsarp, H. W. see McLacutan, A. & — Lyes, Marx B. see SickEL, JAMES B. & — IMARETAVE; JJEPRREY( Bao ctan-dnccitnnatcacieni alata guns 350 Page vi WVU NTGHSUN Oi, LDRUGHD, remem menor eres encore eer IMCDERMID ys KARA scence renee eae ernnmoracere McLacutan, A. & H. W. LoMBARD ..........0 INETE NIG PELE NRG ING trae ones et orise as MIKKELSEN, PAUL STEPHEN oeescsesscssessse Moore, EUNA A. & FINN SANDER oessessnssnsntsnnssnsenenes . 309 Morrison, SAMUEL D. see KENNEDY, GEorGE L. e¢ al. NaxanHara, Hirosui1, Mrrsuo Kaxer & GERRIT IBEVERANDER iia cise Sect aurectesnian coset eouttteomrttestetecies 207 NECK RAYMOND WiG ieee ceancennanenseen nes 112, 180 GP TVER AS Bog MU cee raed sae ae notanareeieemamanncrcrreeaes 19 Otsuka, Cary, Yves Roucer & ETHEL ToBACH..... 159 AUP Acy is Co. Jie WE. AUB rrnctesastecscrtiongnserire tees easton 321 PauL, J. M. see A. J. PAUL & — ProtTr, MicHELE see CHASE, RONALD & — IROORMAN;, IGEROY. Pi ptscticnitee steatencanscrsnine 183, 339, 345 Powers, Marx see Harris, Larry G. e¢¢ al. PREGENZER, |G Wooo. sash,..gaect see ceretaanrssientntinsncsuathecsantenencres 250 PREZANT; ROBERT), Seyi ote gti ccataettherusier senna een wera 289 IBRIN GZ, / DANIEL: cc cccccnescsce aes eee eet ieee ee ee 373 PrircHarD, AuSTIN W. see BoEsE, BRucE LEon & — RU TMAN, /DARRY) FOLSOM g.oicc-.cn canter cu eatencbenetearrne 348 Rao, K. HANUMANTHA see BANu, ANISA é¢ al. Rew, RoBert G. B. & JOAN A. FRIESEN wens ~ 25 REILLY, DeBra see TOMLINSON, JAcK T. ef al. IRIGH TER, UAUS) Qe aurea utare: in eae eee oe 43 Roucer, Yves see Otsuka, Cary et al. THE VELIGER_ Vol. 23; No. 4 RYAN, JULIAN see Harris, Larry G. e¢ al. SANDER, Finn see Moore, Euna A. & — SCHMEKEL,, LUISE ssis:sssuscstcuciascateencan nate cect 21, 282 SUIMEK,, RONALD: De. ojitecihcnudsncihnieationmeceseenen eee - 153 SHYMASUNDARI, K. see BaNu, ANISA et al. SICKEL, JAMES B, & MARK B, LYLES oesescsssesnnssnsstais 361 SMITH, BLAKEMAN) 9. ssscscasiustincssiacinsenssen cession ee ORE 212 SOLEM, ALAN) cesdsiscccticacktyaindtiinnatesleostee ea (101) STOHLER, RUDOLF ........... (107), (188), (287), (288), Bet rina ee eerieerereanient stealer (382), (383): THIRIOT-QUIEVREUX, CATHERINE oocessessssesisnsenemenesene I THOMPSON, Te Eee. scssscassarctssnasunintetstenecinsticee seco 315 THRELFALL, TrMoTHy J. see WELLS, Frep E. & — ToxsacH, ETHEL see OtsuKA, Cary é¢ al. ToMLINSON, Jack T., DEBRA REmty & ROBERT BBALLEERING & o-ecnccrsescastecesecocccosesttteoer entrees eet 167 TTOMPA, ALEX. So) ci. ceisncesssscnenestinciccncsirmertenionctnaneeeaeaaees 35 TUTSCHULTE, THEODORE & JosEPH H. CONNELL... 195 VAN DER LAAN, KENNETH L, ...esesssssnscnenemnnenintumenenes 48 Voxes, Eminy H.o0e aioe ees VoKEs, Emity H. & ANTHoNy D’ATTIL10 ...... Ward, PETER & MARY K. WICKSTEN oes WELDON, PAU: [J sssistisssutictecssecssonscnrcos neuncanees cent aeons WELLS, Frep E. & Timotuy J. THRELFALL ......cec WICKSTEN, | Mary K.. .i.ci..c.s nana see also: WARD, PETER & — Youn, ADAM: Yoo. o.ccscci.ccninctiecncunncname eee 14! ef WLUAM HL D YE M H. DALE Vol t. * SECTIONAL LIBRARY DIVISION OF MOLLUSKS Welle VELIGER A Quarterly published by CALIFORNIA MALACOZOOLOGICAL SOCIETY, INC. Berkeley, California ISSN 0042-3412 VOLUME 23 JuLy 1, 1980 NuMBER I CONTENTS Identification of some Planktonic Prosobranch Larvae Present off Beaufort, North Carolina. (4 Plates) CATHERINE MWHIRIOT-OUIEVREUXK Gul. 5g sis he) ek ee ees I Review of the Muricid Genus Acanthotrophon (Mollusca : Gastropoda). (2 Plates) ANETTA EAR, © KCE'S Wren geste i afliteay pias, vs Sane eatnle yee! le) dur ities;blee: ete. 6) LO A New Species of Favartia (Caribiella) from the Galapagos Islands. (3 Text figures ) EMirievg le VOKE SHR AN DHONY DYATTILION ell os 2) hel «es Seseucie soso ce EH A New Species of Muricacean Gastropod. (2 Plates) DB} BACs (ORINDA 8 Mek FIVE TE ERE By TE Tor CS UNAS ge ate a ee nicer a (0) Synopsis of the Genus Piseinotecus with description of Piseinotecus evelinae spec. nov. (Gastropoda : Nudibranchia) . (5 Text figures) WEWISEPSCHIME KE oe anemey cc inlee Suwanee Obani te: ay ual oi Scan a 2 The Digestive System of the Moon Snail Polinices lewisii (Gould, 1847) with Emphasis on the Role of the Oesophageal Gland. (1 Plate; 7 Text figures) ROBERTA GAD a REIDEE | OANP AW ERIESEN | oa ses oe es he el 25 The Ultrastructure and Mineralogy of the Dart from Philomycus carolinianus (Pul- monata : Gastropoda) with a Brief Survey of the Occurrence of Darts in Land Snails. (1 Plate; 2 Text figures) PATER Sa ae MiP Agen matt a eat ie gs aera ga Be IIS. Nisei griies al verze ce ce) 3 [Continued on Inside Front Cover] Distributed free to Members of the California Malacozoological Society, Inc. Subscriptions (by Volume only) payable in advance to Calif. Malacozool. Soc., Inc. Volume 23: $37.50 plus $1.50 for postage (U.S.A. only) For ALL foreign countries: Swiss Francs 60.- plus SF 7.- for postage Single copies this issue $22.00. Postage additional. Send subscription orders to California Malacozoological Society, Inc. 1584 Milvia Street, Berkeley, CA 94709, U.S.A. Address all other correspondence to Dr. R. StoHLER, Editor, Department of Zoology University of California, Berkeley, CA 94720 Second Class Postage Paid at Berkeley, California ConTENTs — Continued Movement, Reproduction, Defense, and Nutrition as Functions of the Caudal Mucus in Ariolimax columbianus. (1 Plate) Kraus, O. RICHTER: (2:5 35 Wein a. Meg semen ee cee iien eu tance aa em Terrestrial Pulmonate Reproduction: Seasonal and A::nual Variation and Environ- mental Factors in Helminthoglypta arrosa (Binney) (Pulmonata : Heli- cidae) . (1 Text figure) KENNETH, L. VAN; DER(LAAN | 20 37s: (G.) Gjk oo oe ee ee A A New Species of Lepidopleurus Risso, 1826 (Mollusca : Polyplacophora) in the Deep Waters of the Eastern Pacific. (1 Plate; 5 Text figures). ANTONIO J. FERREIRA Bune : eet: hoa nies Ane Growth and Mortality in the Ribbed Mussel Geukensia demissa (Bivalvia -Dheis senacea ). (5 Text figures) Mark D. BERTNESS ..... . : Stee cries o's ee OZ Life History Studies of the Estuarine Nudibranch Tenellia fuscata eaulkh 1870). Larry G. Harris, Mark Powers & JuLIA RYAN... . : BF) Late Quaternary Bankia (Bivalvia : Teredinidae) from Humboldt Guee Cali- fornia. (1 Text figure) Gerorcr L. Kennepy, ANTHONY D’Arritio, SamuzL D. Morrison & KENNETH 1 Oe 07 9 (0)! OE een Se Gl oa Heatar oo. og? o | FS The Organisation and Chemistry of the Byssus of some Bivalves of the Waltair Coast, India. (3 Text figures) ANISA Banu, K. SHyMASUNDARI & K. HANUMANTHA Rao... .... =. «77 Sublittoral Observations of Behaviour in the Chilean “Loco” Concholepas concho- lepas (Mollusca : Gastropoda : Muricidae). (2 Text figures) Ranpom DuBors, Juan C. CasTILta & RoBERTO CaccIOLATTO.. . . ... . 83 Range Extensions of Three Species of Teredinidae (Mollusca : Bivalvia) Along the Pacific Coast of America. WY Aore Cee) OAV obey More Ge G iG “og Gd) G80 0.0 6 06:0 0 0.00 0 SF Notes on Recent and Fossil Neritidae. 9. On the Alleged Occurrence of Neritina cf. N. donovana Récluz in the Vigo Formation, Luzon, Philippines. HENK)K: MITENTSH 5 30) 5 oe eo Seoiittn ter ures ke eet cin CeCe ne NODES & NEWS us bol.) ves nek ae em 96 Observations on Feeding in Maxwellia santarosana - (Dall) “(Cannan Muricidae). Mary K. WicksTEN Range Extension for Pterotyphis fimbriatus (A. Adams, 1854). JENS HEMMEN & Curista HEMMEN BOOKS, PERIODICAUST& PAMPHIC BIS 021s) clei Nn its cnonat- weer EEO Note: The various taxa above species are indicated by the use of different type styles as shown by the following examples, and by increasing indentation. ORDER, Suborder, DIVISION, Subdivision, SECTION, SUPERFAMILY, Famizy, Subfamily, Genus, (Subgenus) New Taxa Vol. 23; No. 1 THE VELIGER Page 1 Identification of Some Planktonic Prosobranch Larvae Present off Beaufort, North Carolina CATHERINE THIRIOT-QUIEVREUX Station Zoologique, Villefranche-sur-Mer, France? and Duke University Marine Laboratory, Beaufort 2 iy North Carolina 28516, U.S. A. (4 Plates) INTRODUCTION THE PELAGIC GASTROPOD LARVAE of the northeast Atlantic coast of America have seldom been studied and only a few species have been identified from the plankton (Le- BOUR, 1945; ROBERTSON, 1971; SCHELTEMA, 19714, b, 1972; THIRIOT-QuIEVREUX & SCHELTEMA, 1979). Descrip- tions of the larvae come mostly from studies on breeding and development of benthic species (D’AsarRo, 1965, 1970; A. SCHELTEMA, 1969; R. SCHELTEMA, 1962; SCHELTEMA & SCHELTEMA, 1963, 1965; see ROBERTSON, 1971 for an exhaustive account of the literature). PorTER (1974) recorded more than 500 species of Mol- lusca from the estuarine and oceanic waters of North Car- olina. In contrast, there have been no descriptions of the prosobranch larvae from this area which is at the inter- section of the Virginian, Carolinian and Caribbean mol- Juscan provinces. Thus, the aim of the present work has been to make a qualitative study of the planktonic larvae, so that they may be identified. To this end, several meth- ods have been used, namely: Comparison with earlier studies on the larval develop- ment of species from the northeast Atlantic. Because the shape of the shell is usually characteristic of the family and of the genus, comparisons have been made with descriptions of larvae from other regions (e. g., Lezour, 1937 — Plymouth, England; THorson, 1946 — western Baltic; THmRIOT-QuIévREUX, 1969, 1976 — Med- iterranean; FRETTER & PILKINGTON, 1970 — North Sea; TayYLor, 1975 — Hawaii; PILKINGTON, 1974, 1976 — O- tago, New Zealand). ' Present address Comparisons of larval shells with well preserved proto- conchs of juvenile gastropods, the latter either collected at low tide or observed in museum specimens. Rearing of larvae through metamorphosis up to and including the development of juvenile whorls. METHODS During the summer of 1977 and 1979, surface plankton tows were taken regularly in neritic waters off Beaufort, North Carolina, at different locations inside and outside of Beaufort Inlet to a distance of 32km (20 miles) off shore but within the margin of the continental shelf. The tows were taken with a 35cm diameter net with mesh of approximately 240 ym. The samples were diluted in a large finger-bowl and gastropod larvae were removed with a pipette and placed in small petri dishes for further observation. Because they are species specific characters, the shape and colour of the shell, velum, foot and body were noted for each species. Then, the larvae were either fixed in neutral 95% alcohol or kept for a few days to study their metamorphosis. Benthic juvenile shells were collected at low tide at Shackleford Jetty, Cape Lookout Bight and Middle Marsh. One dredge haul was taken off Morehead City. ‘Thanks to the help of divers under the direction of Dr. Searles, I had the opportunity to have samples collected from a sand bottom at a depth of 20m. These collections provided many juveniles in which the protoconchs were well preserved. The shells were fixed in neutral 95% al- cohol. Page 2 THE VELIGER Vol. 23; No. 1 For scanning electron microscope observations, the shells were rinsed in distilled water, cleaned ultrasonically for 5 - 10 seconds, air dried, then put on a stub and coated with gold. Micrographs were taken with a Cambridge SEM (Sq Scientific Instrument) at the Centre Océano- logique de Bretagne, France. OBSERVATIONS In the following account, all larvae are described at a stage close to metamorphosis. All veligers have 2 eyes, 2 tentacles and an operculum. LrTToRINIDAE Littorina irrorata (Say, 1820) (Figure 1) Shell, 14 whorls, globose, transparent, light chestnut col- or, length 450 um. Embryonic whorl smooth, larval whorls with small pa- pillae which are arranged in spiral ridges, a prominent round beak extends anteriorly at the aperture. Velum, 2 rounded lobes, colorless. Foot, triangular, colorless; digestive gland green. This veliger is similar to those of Littorina neritoides (FRETTER & PILKINGTON, 1970; THIRIOT-QUIEVREUX & Basio, 1975) and L. pincta (STRUHSAKER & CosTLow, 1968). The different types of larval development in the Littorinidae were reviewed by Muteikovsky (1975). Litiorina irrorata produces pelagic egg capsules (Brnc- HAM, 1972) and according to GALLAGHER & Rem (1974), a free swimming veliger is hatched after 4 days of develop- ment within the capsule. Littorina irrorata is a common species in the marshes of the Beaufort area. A juvenile specimen from the mu- seum collections of the Duke Marine Laboratory showed a protoconch similar to this larval shell. RIssOINIDAE Rissoina, species 1 (Figures 2, 3) Shell, 3 whorls, smooth, transparent, colorless, except at the sutures and columella which are brown; length 450 pm, aperture with a rectangular beak or sinugerous outer lip. Velum, bilobed, colorless. Foot with a slight dark pigmentation; dark pigment between the eyes. Rissoina, species 2 (Figures 4, 5) Shell, 34 whorls, length 500 jzm, shape same as species 1, but the embryonic whorl is more prominent; smooth ex- cept for a fine transverse line at the lower part of the last whorl. Velum, bilobed, colorless. Foot, colorless; dark pigment on the stomach and in- testine and between the eyes; digestive gland yellow-green. Rissoina, species 3 (Figures 6, 7) Shell, 34 whorls, length 550 um, diameter of last whorl 390 um; same shape as species 1 and 2. Embryonic whorl smooth, larval whorls with small papillae, particularly numerous near the sutures, one transverse cord on the lower part of the last whorl. Velum, bilobed, colorless. Foot, colorless; dark pigment on stomach, intestine and mantle edge. These three veligers have the characteristic shape of the larvae of Rissoina bruguiert described by RICHTER & THORSON (1975). Explanation of Figures 1 to 13 Figure 1: Littorina irrorata, larva X< 200 Figures 2 and 3: Rissoina sp. 1, (=R. catesbyana), larva X200 Figures 4g and 5: Rissoina sp. 2, larva X 200 Figures 6 and 7: Rissoina sp. 3, (=R. decussata), 6: 100; 7: X200 Figures 8 and 9: Caecum pulchellum; 8: juvenile with proto- conch 200; g: adult X100 Figures 10 to 13: Bitttum varium - 10 and 71: larva Xa00 12: juvenile 200; 1g: juvenile 100 THE VELIGER, Vol. 23, No. 1 [TuirioT-Quiévreux] Figures 7 to 73 Vol. 23; No. 1 DEsJARDIN (1948), OLSSON & HarBISON (1953) and Coan (1964) studied the systematics of the Rissoinidae and, together, produced several synonymies. PorTER (1974) recorded 4 species in North Carolina, namely, Rissoina catesbyana Orbigny (= R. chesnelt Michaud, — R. scalarella C. B. Adams), R. decussata Montagu, R. flor- idana Olsson & Harbison, and Zebina browniana (Orbig- ny) (= Rissoina browniana). Moore (1969) raised R. catesbyana from the egg to the pelagic larval stage. Several specimens of Rissoina catesbyana were collec- ted from sand in 20m. The protoconch measured 340 um in length, but the first juvenile whorl covers the proto- conch to a slight extent. In a transparent specimen in which the whole of the last whorl can be seen, the proto- conch measured 440 xm. The size and shape of the proto- conch of R. catesbyana correspond to the larval shell of Rissoina species1. Specimens of R. decussata at the Acad- emy of Natural Sciences of Philadelphia have a well preserved protoconch which measures 500 um in length. This corresponds to the size of the larval shell of Rzssoina species 3. Rissoina species 2 is still unidentified. CAECIDAE Caecum pulchellum Stimpson, 1851 (Figures 8, 9) Shell, planorbiform, 1 whorl, smooth, colorless. Velum, 2 rounded lobes, bordered with dark pigment. Foot, colorless; digestive gland green, dark pigment on oesophagus and intestine. Marcus & Marcus (1963) observed the pelagic de- velopment of Caecum pulchellum and measured the larva on hatching (60 um). Caecum antillarum also has a pelagic development (BANDEL, 1975) and, from European waters, the plank- tonic larva of Caecum glabrum is well known (FRETTER & PILKINGTON, 1970). Juvenile specimens of Caecum pulchellum collected at Shackleford and Cape Lookout with the protoconchs still attached, confirmed the identification. The protoconch disappears in adult specimens (Figure 9). CERITHIDAE Bittium varium Pfeiffer, 1840 (Figures 10 to 73) Shell, 24 whorls, transparent but slightly horn-colored, especially at the outer lip, smooth except for 1 transverse spiral line on the lower part of the body whorl. THE VELIGER Page 3 Velum, bilobed, colorless. Foot, triangular with 2 longitudinal bands of dark pig- ment; digestive gland, green or yellow. Marcus & Marcus (1963) described a pelagic develop- ment for Bittiwm varium collected in Si0 Paulo, while Hovusrick (1977) noted a smooth larval shell except for a median spiral ridge on the second whorl in his new de- scription of Bittium. Bitttum varium is a common species and was collected at Shackleford, Cape Lookout and Middle Marsh. Scan- ning electron microscope views of the apex of juvenile specimens show a protoconch which exactly corresponds to the size and apical view of the larval shell (Figures 11, oO) This veliger differs from that of Bittium alternatum (Tumriot-Qutévreux & ScHELTEMA, 1979). In B. alter- natum, the embryonic whorl is more convex and the oma- mentation of the body whorl consists of 3 spiral ridges rather than one as in B. varium. Cerithium atratum (Born, 1778) (Figures 14 to 17) Shell, 24 whorls, horn-colored. Embryonic whorl, smooth; larval whorls with short axial ribs on the upper part and spiral cords which are crossed by fine opisthocline axials on the lower part; aperture with a sinugerous outer lip. Velum, 2 lobes of unequal size, colorless. Foot and body, colorless. Cerithium atratum has a pelagic development. Hous- RICK (1974) and BaNDEL (1975) observed the larvae immediately after hatching. JuNc (1975) found this lar- va in the sediments of Leg 15, site 147, Deep Sea Drilling Project and identified it as Bitttwm sp. A. This veliger looks similar to that of Cerithium vulgatum from the Mediterranean (RicHTER & THORSON, 1975). A juvenile of Cerithium atratum, collected at Shackle- ford, had a well preserved protoconch that showed this characteristic ornamentation. Cerithium sp. (Figures 78, 19) Shell, 24 whorls, same shape as that of Cerithium atratum, horn-colored. Velum, bilobed, colorless. Embryonic whorl, smooth; larval whorls with small papillae on the upper third of the whorl and several spiral cords covering the rest of the whorl. Page 4 THE VELIGER Vol. 23; No. 1 Velum and body, as Cerithium atratum. This veliger was collected frequently in plankton tows outside of Beaufort Inlet. June (1975) described this larval shell as Bittium sp. B. Hovuprick (1974) described the genus Cerithium in the western Atlantic and 3 of the species described showed a pelagic development (C. atratum, C. literatum and C. guinaicum). Cerithium literatum is recorded in North Carolina (PorTER, 1974), but no juveniles with well preserved protoconchs were found in the field or in the collections of the Smithsonian Institution. CERITHIOPSIDAE Seila adamsi (H. C. Lea, 1845) (Figures 20 to 29) Shell, 5 whorls, spire elongate, transparent, but sutures, columella and lower part of the last whorl brown-chest- nut in color; aperture with a prominent sinugerous outer lip; lower part of last whorl flat. Embryonic whorl with small papillae, parallel and close to the sutures of the larval whorls there is a single trans- verse line with minute axial riblets. Velum, 2 oval lobes of unequal size (right is larger), colorless. Foot, pointed, colorless, except for a slight amount of dark pigmentation in the mid-region of the mesopodium ; a small red-brown spot near the mantle edge. One larva reached metamorphosis and developed one juvenile whorl which showed the characteristic orna- mentation of Sela (keeled spiral cords). Several specimens of Seila adamsi with very well pre- served protoconchs were collected at Cape Lookout, in a dredge haul taken in the port of Morehead City and from sand in 20m, specimens of an undescribed variety of S. adamsi were found. The shells of S$. adams: and of the undescribed variety were found to co-occur in the same localities. The name of Seila adams var. beauforti is pro- pesed for this new variety. Not only does the size of the protoconch differ, but the width between transverse cords of the teleoconch whorls also differs. The protoconch of the variety has 3 smooth, globose whorls, which are more con- vex than in Seila adamsi. Except for size, the ornamenta- tion of the postlarval whorls is the same as in Seila adam- st. The color is the same in both. Width of Width between Length of last whorl of 2 cords of protoconch protoconch the first postlarval whorl Seila adamsi 400pm 250 um 70 pm. var. beauforti 700 ym 470 um. 100 ym Seila adamsi (Lea, 1845) was first described as Cerithi- um terebrale Adams, 1840. This description was revised by CLENcH & TURNER (1950), who did not specify the number of larval whorls. OLsson & HARBISON (1953), in their monograph on the Pliocene Mollusca of southern Florida noticed that Recent specimens of Seila adamst have a protoconch with 2 smooth globose whorls, whereas the fossils have a “slender protoconch of about 3 whorls.” Dati (1927) describes a species Seila subalbida from off Fernandina, Florida, but noted that the nuclear whorls were always lost. Among holotype specimens of Seé/a in the collections of the Smithsonian Institution, I find that the holotype of S. alfredensis Bartsch, 1915 (no. 186802, Port Alfred, South Africa) looks very similar to Seila adamsi var. beauforti. BARTSCH (1915) noted in his de- scription: “nuclear whorls smooth, well rounded, forming a bulbous apex.” The width between adjacent spiral cords of S. alfredensis is identical to the variety. This discussion of the systematics of Seila, while di- gressive, shows the need for a revision of the genus. Cerithiopsis greeni C. B. Adams, 1839 (Figures 30 to 33) Shell, 5 whorls, light horn-colored, but darker at the sutures and columella, rectangular outer lip. Explanation of Figures 14 to 29 Figures 14 to 17: Cerithtum atratum-14 and 55: larva 200 16: juvenile X 200 17: juvenile X50 Figures 18 and 19: Cerithium sp., larva X200 Figures 20 to 25: Seila adamsi-20: larva X100: a1: detail Figures 26 to 29: Seila adams var. beauforti 26: juvenile of the larva 200; 22: juvenile X 100; 23: 50; 27: adult, upper part of the shell X50 adult X50; 24: detail of the protoconch X200 28: lower part of the shell X 50; 2g: detail of 25: detail of juvenile whorls X 200 juvenile whorl X200 THE VELIcER, Vol. 23, No. 1 [TuHiri0oT-QulévrEux] Figures 14 to 29 Vol. 23; No. 1 Embryonic whorl, obtuse, smooth; all but the last lar- val whorl with a transverse cord immediately above the sutures and which is crossed by minute axial riblets; last larval whorl with 2 transverse cords. Velum, 2 colorless lobes of unequal size. Foot, colorless; dark pigment on digestive tube and mantle. Cerithiopsis greent was collected at Shackleford and Cape Lookout. The protoconch (Figure 33) shows the characteristic transverse line parallel to the suture, but the minute axial riblets on the sutures are usually eroded. June (1975) identified this larva as Cerithiopsis sp. C. Cerithiopsis hero Bartsch, 1911 ? (Figures 34 to 37) Shell, 5-6 whorls, elongate, transparent, but chestnut col- ored at the sutures and columella, lower part of the last whorl flat. Embryonic whorl pointed and ornamented with cone- shaped tubercles which become less numerous and smaller at the distal end of the whorl; larval whorls smooth, sutures marked by short orthocline axials. Velum, 2 colorless lobes, oval in shape, the right one much larger than the left one. Dark pigmentation between the eyes, on the intestine and on the base of the foot; sometimes there are yellow spots at the edge of the foot. This veliger was described by LEBour (1945) from the plankton of Bermuda as Cerithiopsis sp. C. June (1975: 123; figs. 95-99) recorded this larva as “unidentified spe- cies A.” Ann Sears of McGill University has also found it in the plankton off Barbados (personal communication). ‘This veliger was collected several times in the plankton off Beaufort in July and August 1977 and in July 1979. One veliger successfully metamorphosed and the orna- mentation of the beginning of the first juvenile whorl could be seen before the animal died (Figure 36). In the 20m sand sample I found 2 juveniles with well pre- served protoconchs (Figure 37). Unfortunately, the iden- tification of these juveniles is difficult. PorTER (1974) recorded 9 different species of Cerithi- opsis from North Carolina. These include C. greeni and C. emersont (= C. subulata) which have a larva with characteristic axial ribs on the larval shell (Tuuuot- QuifvrEux & SCHELTEMA, 1979). Having examined all these species in the collections of the Academy of Natural Sciences of Philadelphia and in the collections of the Smithsonian Institution, I find that no shell showed either the pointed protoconch or the ornamentation of the Beau- fort juveniles. A further search through the holotypes of THE VELIGER Page 5 the Cerithiopsidae in the Smithsonian Institution and through the descriptions of species recorded on the east coast by Appotr (1974), (WaTSon, 1881; DaLL «& STIMPSON, 1901 ; DALL, 1889, 1927; BARTSCH, 1911, 1912; Dat & BartscH, 1911; CLENCH & TURNER, 1950; and Oxsson & HarBIson, 1953) shows nothing that resembles this kind of protoconch, not even in some former genus, such as Stilus or Laskeya. Some of these species do have a protoconch with axial ribs (e. g., C. abrupta Watson, C. sigsbeana Dall, C. rugulosum C. B. Adams), while others have a protoconch with smooth cylindrical whorls (e. g., C. crystallinum Dall, C. georgina Dall, C. aconti- um Dall). Finally, I have found the protoconch on shells which were wrongly placed with other species such as Cerithi- opsis emersoni, and I tentatively identify the juveniles which I have collected as C. hero Bartsch, 1911. The apex of the holotype is broken, but some shells of C. hero in the Henderson collection of the Smithsonian Institu- tion, have an elongate protoconch as in the Beaufort juveniles and with identical ornamentation on the post- larval whorls. In his description, BAkTScH (1911) noted “the nuclear whorls are at least three, smooth, scarcely increasing in size and forming a cylindrical apex; post- nuclear whorls ornamented with three strong spiral cords and quite regular somewhat retractive axial ribs.” In fact, the pointed embryonic whorl is often broken, and must be particularly weak, but the shape of the broken apex can be seen as cylindrical. Nevertheless, the identi- fication of this larva as Cerithiopsis hero is proposed. Cerithiopsis sp. (Figures 38 to 41) Shell, 44 whorls, transparent, light horn colored, sutures and columella darker; same shape as Certthiopsis greeni. Embryonic and larval whorls with minute papillae, more numerous near the sutures, one transverse line on the lower part of the last whorl. Velum, bilobed, colorless. Foot, slightly pigmented; scattered dark pigmentation on the body, more intense on the intestine. Juveniles with protoconchs of this type were collected at Shackleford and Cape Lookout, but the shape of this smooth protoconch with its sub-cylindrical whorls and the ornamentation of the juvenile are common within the Cerithiopsidae and could correspond to several species (e. g. Cerithiopsis pulchella Jeffreys, C. georgina Dall, C. cynthia Bartsch, C. bicolor C. B. Adams and C. pupa Dall & Stimpson). Page 6 APORRHAIDAE Aporrhais occidentalis Beck, 1836 (Figures 42, 43) Shell, 24 whorls, globose, colorless, smooth, diameter 700 um at a stage close to metamorphosis. Embryonic whorl, coiled, almost planorbiform, deep umbilicus, extended columella and prominent beak at the aperture. Velum 4-lobed, with large spot of brown pigment at the extremity of each lobe and bordered with a fine line of brown pigment. The lobes are curved when the larva is swimming. Foot, colorless, asymmetric with a spur on the right side; digestive gland yellow, dark pigment on the stom- ach, intestine and mantle edge. This larva was identified as Aporrhais occidentalis. Comparison with the larval shell of A. serresiana (Tuirt- oT-QuifvREUX, 1976) shows that both larval shells have the same shape with an extended columella, a prominent beak, a deep umbilicus and a similar spur on the foot. They differ in the number of their velar lobes. Aporrhais occidentalis is the only species of Aporrhais recorded in the Beaufort area. These larvae were common in July 1977 and 1979. On a specimen in the collection of the Smithsonian Institution, one could still see the obtuse embryonic whorl. The planktonic veligers of several species of the Apor- rhaidae have been described (Aporrhais pespelicant — Lr- BOUR, 1937; THORSON, 1946 — A. serresiana — THIRIOT- QutifvrEevux, 1976; — Pterocera bryonia — Gouar & EIs- AWAY, 1967; — Strombus tricornis — EISAway & SORIAL, 1968; — Strombus gigas — D’Asaro, 1965; and — Strom- bus maculatus — TayLor, 1975). Among the characters in common, the asymmetry of the foot is described for all veligers and seems to be a THE VELIGER Vol. 23; No. 1 peculiarity of the Aporrhaidae family. The number of velar lobes is usually 6, but Strombus tricornis, like Apor- rhais occidentalis, has only 4 lobes. HIPPONICIDAE Cheilea equestris (Linnaeus, 1758) (Figures 44, 45) Shell, 24 whorls, transparent, colorless, body whorl about 2 of total length. Embryonic whorl with irregular crests; larval whorls with zigzag spirals. Velum, 4-lobed, broad, lobes colorless. Foot, with thick operculum and slender metapodium, brown pigment on the front and on the base of the foot; digestive gland brownish. ‘The ornamentation of the embryonic whorl is charac- teristic of this species. BANDEL (1975) described the larva of Cheilea equest- ris just after hatching and it is very similar to the veliger of Cheilea dillwyni (Taytor, 1975). Cheilea equestris is the only species of Cheilea recorded in North Carolina. A specimen in the shell collection of the Institution of Marine Science of the University of North Carolina showed a well preserved protoconch with the characteristic ornamentation of this species. NASSARIDAE Nassarius albus (Say, 1826) (Figures 46 to 48) Shell, 3 whorls, globose, pale yellow, broad siphonal canal, conspicuous beak at aperture. Explanation of Figures 30 to 45 Figures 30 to 33: Cerithiopsis greeni go: larva X 200 31: juvenile X 100; 32: adult X50; 33: de- tail of the protoconch of the adult specimen 500 Figures 38 to 41: Cerithiopsis sp. Figures 34 to 37: Cerithiopsis hero 34: larva X 100 35: detail of the embryonic part of the larva X500; 36: detail of juvenile stage close to the metamorphosis Xa200 37: juvenile X 100 38: larva X100 3=—_ 399: detail of the larva 500; go: adult X50; 4: detail of the protoconch of the adult specimen X 200 Figures 42 and 43: Aporrhais occidentalis, larva X200 Figures g4 and 45: Cheilea equestris, larva %200 Tue VELIGER, Vol. 23, No. 1 [TurioT-QuiEvREUx] Figures yo to 45 Vol. 23; No. 1 Velum, 4 elongate lobes bordered by a line of pale brown pigment, very broad spots of pale brown pigment at the extremity of each lobe. Foot, with 2 metapodial tentacles, dark pigmentation in the propodial region; digestive gland, yellow, dark pig- mentation on the ctenidium and between the eyes. This veliger shows all the characters of the Nassariidae as described by LEeBour (1937), THORSON (1946), CHRISTIANSEN (1964), SCHELTEMA (1962) and ScHEL- TEMA & SCHELTEMA (1963). It differs from Nassarius wibex and N. trivittatus in having broad brown spots on the extremity of the velar lobes. BANDEL (1975) described the larvae of Nassarius albus just after they hatched. Juveniles of Nassarius albus, with a well preserved pro- toconch (Figures 47, 48) were collected at Shackleford. CoLUMBELLIDAE Mitrella lunata (Say, 1826) (Figures 49 to 52) Shell, 34 whorls, globose, light yellow but the columella is slightly horn-colored. Embryonic whorl, smooth, 150 wm in diameter; larval whorls with minute papillae, last larval whorl with 1 spiral on the lower part; columella twisted and decorated with short striations. Velum, broad lobes of unequal size, becomes slightly 4-lobed when the larva is swimming, conspicuous line of dark pigment along the border of the velum. Foot, triangular, with dark pigmentation on the middle part of the mesopodium; digestive gland yellowish. Several specimens of Mitrella lunata were collected at__. Shackleford and Cape Lookout. The protoconchs could still be observed in very young specimens. The diameter of the embryonic whorls (150 um), the shape of the pro- toconch and the number of larval whorls are character- istic of this species. The length of the protoconch is 700m and the length of the larval shell is 780 um. The difference is due to the fact that the first juvenile whorl slightly covers part of the larval shell. Larvae of Anachis translirata and A. avara (SCHELTE- MA & SCHELTEMA, 1963; A. SCHELTEMA, 1969) were also found in the plankton. The larvae of Mitrella lunata differ from the larvae of Anachis in having a twisted columella. THE VELIGER Page 7 TURRIDAE Nannodiella oxia (Busch, 1885 ) (Figures 53, 54) Shell, 34 whorls, translucent, pale brown, but brown at the sutures and columella; siphonal canal long, prominent beak at the aperture. Embryonic whorl with small star-shaped tubercles; lar- val whorls with minute pustules, first part of third whorl with opisthocline ribs; body whorl with 3 strong spiral costae, the middle costa being the widest. Velum, 4-lobed, bordered by a line of dark pigment along both preoral and postoral ciliary bands, with yellow chromatophores forming a continuous band in region of food groove, and scattered elsewhere. Foot, elongate, with some dark pigmentation on the middle of the mesopodium, lateral yellow spots. With the help of Dr. V. O. Maes of the Philadelphia Academy of Sciences, this larva was identified as that of Nannodiella oxia, following a comparison with a speci- men having a well preserved protoconch and showing the characteristic spiral costae. This species is recorded in North Carolina (Porter, 1974). Kurtziella limonitella (Dall, 1884) (Figures 55 to 57) Shell, 3 whorls, globose, colorless, transparent, broad siphonal canal. Embryonic whorl, smooth; body whorl with 3 spiral rows of tubercles crossed by thin axial ribs on the upper part and with 4 spiral costae on the lower part. Velum, 4-lobed, very broad, covering the shell as the animal swims, a line of dark red pigment along both pre- oral and postoral ciliary bands, yellow chromatophores at the edge and at the extremities of the lobes. Foot, long, narrow, dark pigmentation in center of sole and scattered yellow spots on the mesopodium. This veliger looks similar to the veliger of Mangelia nebula (LEBOUR, 1934; FRETTER & PILKINGTON, 1970), The velum is identical. A juvenile with a well preserved protoconch (Figures 56, 57) was found in the 20m sand sample and, with the help of Dr. V. O. Maes, identified as Kurtziella limonitella. Page 8 THE VELIGER Vol. 23; No. 1 CONCLUSION The plankton of the Beaufort area is rich in prosobranch veligers. I was able to distinguish about 50 species in col- lections taken in July and August. Some are already de- scribed: Crepidula fornicata (WERNER, 1955) ; Alaba incerta, Janthina sp. (ROBERTSON, 1071) ; Anachis trans- lirata and A. avara (SCHELTEMA, 1969): Cerithiopsis subulata, Triphora nigrocincta and Crepidula plana (Tu1- RIOT-QUIEVREUX & SCHELTEMA, 1979). Several other lar- vae were identified to genus (Epitonium spp., Natica spp., Modulus sp., Simnia sp. and Cypraea sp.) or to family (Turridae). The species collected during the summers of 1977 and 1979 were mostly the same. Holoplanktonic larvae were seldom found, but in 2 plankton tows made 30km (20 miles) off Beaufort, I found a few larvae of Firoloida des- maresti, Atlanta lesueurt and A. helicinoides. This em- phasizes the neritic character of the plankton of the Beaufort region. ACKNOWLEDGMENTS This work was supported in part by an exchange program of the National Science Foundation and the Centre Natio- nal de la Recherche Scientifique and by a grant from Duke University. Much help has been received from Dr. R. Robertson of the Academy of Natural Sciences, Philadelphia, who pro- vided information on the literature and kindly allowed me free use of the collections in his care. Thanks are also due to Dr. V. O. Maes, Academy of Natural Sciences, Phila- delphia, for help in the identification of Turridae veligers, and to Dr. J. Rosewater (Smithsonian Institution) and Dr. H. Porter (Institute of Marine Sciences, Morehead City) for the opportunity to look at shell collections. All the collecting was done at the Duke University Marine Laboratory and I wish to thank all who helped me with the shipboard work. I have to thank also Dr. J. Allen for revising the manu- script and Gene Rosenberg for helping with the English. Literature Cited Aszotr, Rosgrr Tvoxse 1974. American seashells. 22d ed.; 66 : + ; t- (fa color). Van Nostrasd Reahold Gites Seat, oa ae Banve1, Kraus 1975. _ Embryonalgehause karibischer Meso- und Neogastropoden (Mollusca). Abh. math, naturwiss. KL Akad. Wissensch. u. Lit. Mainz, Jahrg. 1975, 1: 1- 133 BartscH, Paut 1gt1. | New marine mollusks from Bermuda. Proc. U. S. Nat. Mus. 41 (1861): 303-306; pit. 28 (12 October 1911) 1915. Report on the Turton collection of South African marine mol- lusks, with additional notes on other South African shells contained in the United States National Museum. U. S. Nat. Mus. Bull. gz: $05 Pp.; 54 pits. (28 July 1915) BinoHam, Frasier O. 1972. Several aspects of the reproductive biology of Littorina irrorata (Gastropoda). The Nautilus 86 (1): 8-10 CarisTIANSEN, Marit ELLEN 1964. Some observations on the larval stages of the gastropod Nassart- us pygmaeus (Lamarck). Publ. Staz. Zool. Napoli 34: 1-8 Crenox, Wititam James & Rute Dimon Turner 1950. The Western Atlantic marine mollusks described by C. B. Adams. Harvard Univ. Mus. Comp. Zool. Occ. Papers on Mol- lusks 1 (15): 233-404 Coan, Eucene Victor 1964. A proposed revision of the rissoacean families Rissoidae, Risso- inidae, and Cingulopsidae (Mollusca: Gastropoda). The Veliger 6 (3): 164-171; 1 text fig. (1 January 1964) Darr, Wirttam Hearey 1889. Reports on the results of dredging, under the supervision of Alexander Agassiz, in the Gulf of Mexico (1877-78) and in the Car- ibbean sea (1879-80), by the U.S.Coast Survey Steamer “Blake,” ... XXDX Report on the Mollusca.—Part II. Gastropoda and Scaph- opoda. Bull. Mus. Comp. Zool. Harvard 18: 1 - 492; plts. 10-40 (January - June 1889) 1927. Small shells from dredgings off the southeast coast of the United States by the United States Fisheries steamer “Albatross” in 1885 and 1886. Proc. U.S. Nat. Mus. 70 (2667): 1-194 (20 April 1997) Proc. U.S. Nat. Mus. (8 May 1911) Dart, Wirttiam Hearey « Paut BartscH igi11. New species of shells from Bermuda. 40 (1820): 277 - 288 Dart, Witttam Hearzy « CHarres Torrey Simpson 1901. The Mollusca of Porto Rico. Bull. U. S. Fish. Comm, go (1): 951-524; plts. 53 - 58 (November 1901) D’Asaro, CHarves N. 1965. Organogenesis, development and metamorphosis in the queen conch, Strombus gigas, with notes on breeding habits. Bull. Mar. Sci. 15 (2): 359-416; 17 text figs. (2g July 1965) 1970. Egg capsules of prosobranch mollusks from South Florida and the Bahamas and notes on spawning in the laboratory. Bull. Ma- rine Sci. 20: 129 - 132 DesJARDIN, Max 1948-1949. Les Rissoina de I’lle de Cuba. Paris 88-89: 193 - 208 Eisaway, A. M. « A. E. Sortat 1968. The egg masses, development and metamorphosis of Strombus (Monodactylus) tricornus Lamarck. Proc. Malacol. Soc. London 38 (1): 13-27 Fretter, Vera & Marcaret C. PILKINGTON 1970. Prosobranchia, veliger larvae of Taenioglossa and Stenoglossa. Conseil Intern. Explor. Mer; Zooplankton sheets 129 - 199: 1-26 Journ. de Conchyl. Explanation of Figures 46 to 57 Figures 46 to 48: Nassarius albus 46: larva X100; 47: juvenile X50; 48: juvenile X 100 Figures 49 to 52: Mitrella lunata 49 and 50: larva 100; 51 and 52: juvenile X100 Figures 53 and 54: Nannodiella oxia 53: larva X100 54: detail of the apex of the larva X5§00 Figures 55 to 57: Kurtziella limonitella 55: larva; X100 56: juvenile X 100; 57: juvenile X50 + 7 oe ' nee Nm is eo) ~ © NE mn o tl 3} 3a) jem =) a = m4 - ‘= =) Q & S} = q ca SS Tue VELIGER, Vol. 23, No. 1 Vol. 23; No. 1 GaLLaoHer, SusAN B. « Georce K. Rem 1974. Reproductive behavior and early development in Littorina seab- ra angulifera and Littorina irrorata (Gastropoda, Prosobranchia) in the Tampa Bay region of Florida. Malacol. Rev. 7 (2): 105-125; 9 text figs. (30 September 1974) Gomag, H. A. F a A. M. Ersawy 1967. The egg-masses and development of five rachiglossan proso- branchs (from the Red Sea). Publ. Mar. Biol. Stn. Al-Ghardaga 14: 215 - 268 Houvsrick, Ricwarp S. 1974. The genus Cerithium in the Western Atlantic. 5 (50): 33-84 1977. Reevaluation and new description of the genus Bittium (Ceri- thiidae). The Veliger 20 (2): 101-106; 1 plt. (1 October 1977) Juno, PETER 1975. Quaternary larval gastropods from Leg 15, Site 147, Deep Sea Drilling Project. Preliminary report. The Veliger 18 (2): 109 - 126; 20 pits. (1 October 1975) Lepour, Mary V. 1934. The eggs and larvae of some British Turridae. Biol. Assoc. U. K. 19: 541 - 554 1937. The eggs and larvae of the British prosobranchs with special reference to those living in the plankton. Journ. Mar. Biol. Assoc. U. K. 22: 105 - 166 1945. The eggs and larvae of some prosobranchs from Bermuda. Proc. Zool. Soc. London 114: 462 - 489 Marcus, E. «& E. Marcus 1963. Mesogastropoden von der Kiiste Sao Paulos. Abh. Math. Naturwissensch. Kl. J. Nr. 1. Akad. Wiss. u. Lit.: 1 - 104 MILeixovsky, Simon A. 1975. Types of larval development in Littorinidae (Gastropoda: Pro- sobranchia) of the world Ocean, and ecological patterns of their distribution. Mar. Biol. g0 (2): 129-135 Moorg, D. R. 1969. Systematics, distribution and abundance of the West Indian micro-mollusks, Rissoina catesbyana d’Orbigny. Trans. Gulf Coast Assoc. Geol. Soc. 19: 425 - 426 Oxsson, Axe, ADOLPH & ANNE HarBISON 1953. Pliocene Mollusca of southern Florida, with special reference to those from St. Petersburg. Monogr. Acad. Nat. Sci. Phila. 8: 457 pp. PILKINGTON, Marcaret C. 1974. \ The eggs and hatching stages of some New Zealand prosobranch mollusks. Journ. Roy. Soc. New Zealand 4 (4): 411-431 1976. Description of veliger larvae of monotocardian gastropods oc- curring in Otago plankton hauls. Journ. moll. Stud. 42: 337 - 360 Porter, H. G. 1974. The North Carolina marine and estuarine Mollusca. An atlas of occurrence. The Univ. North Carol. Inst. Mar. Sci. Morehead City: 351 Pp. Rowe, GotTHARD « GUNNAR THORSON 1975- Pelagische prosobranchier-larven des Golfes von Neapal. Ophelia 13: 109 - 185 RopertTson, Rosert 1971. Scanning electron microscopy of planktonic larval marine gastro- pod shells. The Veliger 14 (1): 1-12; 9 pits. (1 July 1971) Johnsonia Journ. Mar. THE VELIGER Page g Ropgatson, Roagar 1974- | Marine prosobranch gastropods: larval studies and systematics. Thalassia Jugosl. 10 (1/2): 213-298 ScueiTema, Ametiz H. 1969. Pelagic larvae of New England gastropods. IV. Anachis trans- lirata and Anachis avara (Columbellidae, Prosobranchia). Vie Milieu 20 (1A): 94-104 Scue tema, Ruporr S. 1962. Pelagic larvae of New England intertidal gastropods. I.Nassa- rius obsoletus (Say) and Nassarius vibex (Say). Trans. Amer. microsc. Soc. 81: 1-11; 4 plts.; 2 tables 1971a. The dispersal of the larvae of shoal water benthic invertebrate species over long distances by ocean currents. In D. J. Crisp, ed., Fourth Mar. Biol. Symp. Cambridge, Cambr. Univ. Press: 7-28; 7 text figs. 1971b. Larval dispersal as a means of genetic exchange between geo- graphically separated populations of shallow water benthic marine gast- ropods. Biol. Bull. 140: 284-322 Scue.ttema, Rupoxr S. a Ameviz H. ScHELTEMA 1965. Pelagic larvae of New England intertidal gastropods. III. Nas- Sarius trivittatus. Hydrobiol. 25: 321 - 329; 2 text figs.; 2 pits. STRUHSAKER, JEANNETTE WuiPPLe & JoHN D. CostLow 1968. Larval development of Littorina picta (Prosobranchia, Meso- Gastropoda) reared in the laboratory. Proc. Malacol. Soc. London 38: 153-160 Taytor, J. B. 1975. Planktonic prosobranch veligers of Kaneohe Bay, Hawaiian Is- lands. Ph. D. dissertation, Univ. Hawaii (in prep. £ publ.) Turiot-Qurévreux, CATHERINE 1969. Caractéristiques morphologiques des véligéres planctoniques de Gastéropodes de la région de Banyuls-sur-Mer. Vie Milieu 20 (2B): 333 - 366 1976. Description de la larve d’Aporrhats serresiana (Michaud) (Mol- lusca Prosobranchia) dans le plancton méditerranéen. Vie Milieu 26 (2A): 299 - 304 TuirioT-Quiévreux, CATHERINE & Cetso Ropriaugz Basio 1975. Etude des protoconques de quelques prosobranches de la région de Roscoff. Cah. Biol. Mar. 16: 135 - 148 Turriot-Quifvreux, CATHERINE & Rupotr S. ScHELTEMA 1979. Pelagic larvae of New England gastropods. V. Bittium alter- natum, Triphora nigrocincta, Cerithtopsis emersont, Lunatia heros and Crepidula plana. Malacologia, in press THorson, GUNNAR 1946. Reproduction and larval development of Danish marine bottom invertebrates with special reference to the planktonic larvae in the sound (@resund). Medd. Komm. Danm. Fish, Havund (Plankton) 4 (1): 1-523; 199 text figs. Watson, Roszert Booo 1881. Mollusca of the Challenger Expedition. London 15: 119 WERNER, B. 1955. Uber die Anatomie, die Entwicklung und Biologie des Veligers und die Veliconcha von Crepidula fornicata L. Helgoland wissen. Meeresunters. 5: 169-217 Journ. Linn. Soc., Page 10 THE VELIGER Vol. 23; No. 1 Review of the Muricid Genus Acanthotrophon (Mollusca : Gastropoda ) BY EMILY H. VOKES Department of Geology, Tulane University, New Orleans, Louisiana 70118 (2 Plates) SINCE MY sTUDY of the muricid genus Aftiliosa in the western Atlantic (VoKEs, 1976) new information has caused a major shift in the position of certain of the forms originally assigned to that genus. Prior to the Attiliosa paper there were two superficially similar species in the Florida area that were confused under the name “Coralliophila’ philippiana Dall, 1889. In that paper it was shown that the two were not the same and they were separated as Attiliosa phillipiana (Dall) and Attiliosa striata (Gabb). The latter takes its name from a species described as “Muricidea” striata by Gaps (1873) from beds of unknown age in the Dominican Republic. Subsequent collecting in the Dominican area has pro- vided numerous examples of “Muricidea” striata and it can be seen that this name was incorrectly applied to the second species. The type of “M.” striata is now known to come from the early Pliocene Gurabo Formation. All speci- mens are small, the largest seen measuring but 13.4 mm in height. It is less elongate than the “philippiana’ form, which occurs in beds of Pliocene and Pleistocene age as well as in the Recent fauna of the Florida area. Most im- portantly, the protoconchs of the two are different. The illustrations of the various examples referred to Attiliosa striata by Vokes prompted a paper by RADWIN & D’ATTILIOo (1978) in which they not only agreed that the two supposed forms of “philippiana” were distinct species, but suggested that they represent two different genera— philippiana being referred to Attiliosa, and striata to Acanthotrophon—and moreover, the two genera should be referred to two different subfamilies—Attiltosa to Muri- cinae and Acanthotrophon to Muricopsinae. The basis for this change of subfamily was the nature of the radula. At first consideration, I was reluctant to accept such a change on a radular basis alone. However, upon reflection, I real- ized that one of the major attributes of the subfamily Muricopsinae is the extreme variability of shel! form, in contrast to the conservative nature of the Muricinae. This was further demonstrated by the timely discovery of sev- Explanation of Figures 7 to 9 Acanthotrophon striatus (Gabb) Figure 1: Holotype; ANSP 3249; height 12.3mm; diameter 7.0 mm. Gurabo Formation, Dominican Republic X4 Figure 2: USNM 298655; height 4.1mm; diameter 2.7mm. Lo- cality: TU 1227A. Gurabo Formation, Dominican Republic X10 Acanthotrophon striatoides Vokes, spec. nov. Figure 3: Holotype, USNM 298656; height 21.3mm; diameter 14.0mm. Locality: TU 1240. Moin Formation, Costa Rica Figure 4: Paratype A, USNM 240682; height 26.4mm; diameter 15-7mm. Locality: TU 726. Caloosahatchee Formation, Flor- ida X2 Figure 5: Paratype B, USNM 240685; height 30.7mm; diameter 17.3mm. Locality: TU 759. Bermont Formation, Florida X2 Figure 6: Paratype C, AMNH 1827009; height 23.6mm; diameter 12.5 mm. Locality: Off Sanibel Island, Florida; 55m. X2 Figure 7: Paratype D, AMNH 183199; height 24.8 mm; diameter 13.2mm. Locality: Off Briar Reef, Florida X2 Figure 8: Paratype E, USNM 298657; height 20.0mm; diameter 12.8mm. Locality: TU 1240. Moin Formation, Costa Rica X10 Figure 9: Paratype F, USNM 298658; height 19.0mm; diameter 12.9mm. Locality: TU 1240. Moin Formation, Costa Rica X%3 Tue VELIGcER, Vol. 23, No. 1 [Voxes] Figures za to gb Figure 3a Figure 8 Figure ga Vol. 23; No. 1 eral well-preserved specimens of the now nameless species in the Pleistocene of Costa Rica, all of which show a marked scabrousness suggesting kinship with the Muri- copsinae. One of these specimens was figured by RADWIN & D’Arriuio (1978: text fig. 2) as Acanthotrophon striatus. This specimen was included because it resembled so nearly the extremely scabrous A. carduus (Broderip), which can be accepted as muricopsine with no difficulty. Thus we see that the genus Attiliosa in the western Atlantic is now confined to two species: A. philippiana and A. aldridgei (Nowell-Usticke, 1969). The type of the genus is A. nodulosa (Adams, 1855) from the eastern Pacific. So far as known, these are the only members of the group and, as Radwin and D’Attilio indicate, should be allocated to the subfamily Muricinae. The genus Acanthotrophon in the western Atlantic now includes two species: Acanthotrophon striatus (Gabb) (Figures 1, 2) and a second species named below as A. striatoides (Figures 3-9). In the eastern Pacific there is a species-complex also referred to Acanthotrophon, includ- ing A. sorenseni (Hertlein and Strong, 1951), type of the genus, A. carduus (Broderip, 1833), and A. sentus Berry, 1969. In the Radwin and D’Attilio paper, in the guise of Editor, I commented (VoKEs in RaDwin & D’AtTILI0, 1978: 134) upon the similarities of the Pacific and the At- lantic members of this complex and added: “They probably all should be referred to the same species for which Acanthotrophon carduus (Broderip) would be the oldest name.” This statement brought forth a number of Pacific specimens from Carol Skoglund and from Leroy Poorman, which were augmented by a loan of even more specimens from James McLean, at the Los Angeles County Museum. With this wealth of material available it is now possible to make the following observations upon the species in question. The first named of the group is Acanthotrophon carduus (Broderip, 1833). It is also the most widely distributed. The type came from Peru (Figure 1o—a specimen essen- tially identical to the type) and the species ranges as far north as Mazatlan, Mexico. Specimens from the southern Mexican Coast (Figure 11) are very like the typical form, but in the Gulf of California, where the range of A. carduus overlaps that of A. sorensent, we see a peculiar variant (Figure 17). The shell is more elongate, especially the siphonal canal, and the spines are reduced. The elongate canal, in particular, gives it a resemblance to A. sorenseni and some specimens (Figure 18) begin to look not unlike A. sentus. But the inflated body whorl, the anal notch, the large umbilicus, the strong apertural lirations, and the color are all closer to A. carduus. Are these specimens yet another species? Or are they just extreme variants of A. THE VELIGER Page 11 carduus? More material may give a better indication as to the correct placement of these odd specimens but for now they will be considered as “sp. nov.” Acanthotrophon carduus is the member of the species- complex that demonstrates the same sort of variability seen in the Atlantic cognate. It is the most elaborately ornamented of all (Figure 12) and may be distinguished by the presence of strong lirations on the inner side of the outer lip and by a marked umbilicus. There is a pro- nounced anal notch that is indicated on each whorl as a series of strong loops on the subsutural ramp, a feature lacking in all other members of the genus. The proto- conch is essentially the same as that of A. sorensent (Figure 15) but not quite as attenuated. Both species have three conical whorls, approximately 0.6mm in diameter. The color of A. carduus tends to be white to light brown, with the spines somewhat darker; the aperture is always white. Acanthotrophon sorenseni (Hertlein and Strong, 1951) type of the genus, is confined to the Gulf of California, north of Mazatlan. It has a more slender, less ornamented shell; only the shoulder spines are well-developed, but these are frequently long and up-turned (Figures 73, 14). The lirations inside the outer lip are only weakly devel- oped. The siphonal canal is almost straight and, as a result, the shell is non-umbilicate. The color of the shell is a medium brown and the aperture is a conspicuous lavender color. The operculum is darker brown than that of A. carduus. Acanthotrophon sentus Berry, 1969, is ornamented by fewer spiral ribs, but the individual spines are longer. There are only the faintest of lirations within the aperture, if any at all. In the collections of the Los Angeles County Museum there are 5 specimens, all showing this same morphotype (Figure 16). Most are from the Galapagos Islands but the form is not confined to this area, one un- questionable A. sentus was taken on Isla Clarion, in the Revillagigedo Islands, some 1000 km off the coast of Co- lima, Mexico, and a second was from Isla del Coco, about 500km off Costa Rica. Acanthotrophon sentus is appar- ently the offshore form of the complex. The specimen figured by Rapwin & D’Atrtitio (1978: figs. 3, 3a) as Acanthotrophus sentus, from Sonora, Mex- ico, is actually A. sorenseni, my error in identification (again acting as Editor). The worn holotype of A. sorensent does not indicate the true strength of the spiral ornamen- tation. For this reason, the holotype (CAS 9611) is here refigured (Figure 14) for comparison with an unworn ex- ample (Figure 13). With this sort of intergrading of ornamentation one might easily conclude that the 3 Pacific species are syn- onymous. However, there does seem to be a good geo- Page 12 graphic basis for the separation of A. sorenseni as a valid northern species and A. sentus as an offshore form. (See Appendix I for distribution data.) Here is a situation of speciation in action, identical to that demonstrated by the Hexaplex (Muricanthus) radix-ambiguus-nigritus com- plex, which also occurs along the eastern Pacific coast from Peru to the Gulf of California. The member of the group that is found in the western Atlantic from the middle Pliocene to the Recent, which I originally referred to Acanthotrophon striatus, is not that form and is here named as a new species. Although re- sembling the Pacific cognate, it may be distinguished by the protoconch, which is almost twice the diameter of that in the Pacific species. The shell differs from true A. striatus in being larger, more elongate, more elaborately ornamented and, in particular, in the nature of the proto- conch. The Dominican species has a protoconch of only one and one-half bulbous whorls, approximately 0.7mm in diameter (see Figure 2), which is large relative to the overall size of the shell. The younger species has a proto- conch (Figure 8) of two and-one-half whorls, in which the middle whorl is larger than the terminal one. It is approx- imately 1mm in diameter, larger than any of the other species in the group, although the overall size of the shell is comparable—some Florida Plio-Pleistocene specimens are as large as 30mm, most others average about 25mm. Four of the species may have small denticles at the anterior end of the columellar lip but the development of these varies. In Acanthotrophon carduus all of the larger shells have them, as do the larger specimens of A. striatoides. Likewise, in A. striatus the larger examples THE VELIGER Vol. 23; No. 1 have them. But in A. sorenseni, of over 30 examples stud- ied only 2 very large shells had extremely tiny denticles at the fold of the columellar wall into the canal. None of the examples of A. sentus available show any trace of these denticles. The line of true Attiliosa almost certainly came from the early Miocene Poirieria (Panamurex) mauryae Vokes, 1970, as originally suggested (VoKEs, 1976: 103). How- ever, rather than A. striatus being the first known form, it is Attzliosa aldridgez. In the early Pliocene Gurabo For- mation we have several specimens of the latter, so that my statement (1976: 102) that Aftiliosa first occurs in the lower Pliocene Gurabo Formation is still correct, only the name of the species has changed. But the origin of the muricopsine genus Acanthotrophon is a total mystery. The shell form is most like that of the genus Murexsul, which is world-wide since the Eocene. But the exact stages of development from Murexsul to Acanthotrophon are un- known. One would assume that Acanthotrophon striatus is the ancestor to the Recent species and that probably the line of descent goes through A. striatoides also, before the Pacific line branched off in the (?) lower Pliocene. This would explain the extreme similarity between the eastern Pacific and western Atlantic species. There is only one flaw in this reasoning. The development of protoconchs usually seen in the muricids is a move from the multi- whorled form to a lesser number. In this instance A. striatus has the one and one-half whorl protoconch and the younger species have more. So it may prove in time that A. striatus is an offshoot of a different lineage. Explanation of Figures zo to 18 Acanthotrophon carduus (Broderip) Figure 10: AHF 210-34; height 22.9mm; diameter 15.0mm. Lo- cality: Bahia de Santa Elena, Ecuador, 9-12 m x14 Figure 11: Poorman Collection; height 22.9mm; diameter 16.3 mm. Locality: off Punta Jualapan, Colima, Mexico; 30m X 14 Figure 12: LACM 38-8; height 30.1 mm; diameter 20.9mm. Lo- cality: off Zihuatanejo, Guerrero, Mexico, 36 - 73 x14 Acanthotrophon sorenseni (Hertlein « Strong) Figure 13: Poorman Collection; height 27.9mm; diameter 18.0 mm. Locality: Bahia de San Carlos, Guaymas, Sonora, Mexi- co; 100m X2 Figure 14: Holotype, CAS 9611; height 32.2mm; diameter 20.0 mm. Locality: Gorda Banks, off Cabo San Lucas, Baja Cali- fornia Sur, Mexico; 109m xX 14 Figure 15: Poorman Collection; height 16.0mm; diameter 13.4 mm. Locality: Bahia de San Carlos, Guaymas, Sonora, Mexi- co; 100m X10 Acanthotrophon sentus Berry Figure 16: AHF 155-34; height 23.2mm; diameter 16.0mm., Lo- cality: Tagus Cove, Albemarle Island, Galapagos Islands, go to 110m Xe Acanthotrophon ? spec. nov. Figure 17: Skoglund Collection; height 35.8mm; diameter 19.5 mm. Locality: Danzante Channel, Puerto Escondido, Baja Cal- ifornia Sur, Mexico; 45 -60m X14 Figure 18: Skoglund Collection; height 38.0omm; diameter 24.5 mm. Locality: off Guaymas, Sonora, Mexico; 45 m Xi1¢ Tue VELIcER, Vol. 23, No. 1 [Vokes] Figures roa to 18b Figure 15 Figure 78b Vol. 23; No. 1 THE VELIGER Page 13 ACKNOWLEDGMENTS The writer is deeply indebted to Carol Skoglund, Phoenix, Arizona; Leroy Poorman, Winchester, California; James H. McLean, Los Angeles County Museum; and Barry Roth, California Academy of Sciences, for the loan of the majority of the specimens utilized in this study. Without them it would have never happened. Acanthotrophon striatoides E. H. Vokes, spec. nov. (Figures 3-9) Muricidea philippiana DA.L, 1889, Harvard Mus. Comp. Zool. Bull. 18: 213 (in part, Key West specimen only) ; 1889, U. S. Natl. Mus., Bull. 37: 120 (Key West specimen only cited). Coralliophila philippiana (Dall). M. SmitTH, 1953, Illus. Cat. Recent Species Rock Shells, p. 33; plt. 20, fig. 20 (Dall’s Key West specimen). Attiliosa philippiana (Dall). S. E. Hogrue, 1970, Tulane Stud. Geol. Paleont. 8 (2): 63 (not of Dall). Attiliosa philippiana (Dall). Rapwin & D’ATTILIO, 1976, Murex Shells of the World: 26; plt. 3, fig. 10 (not of Dall). Attiliosa striata (Gabb). VoKEs, 1976, Tulane Stud. Geol. Paleont. 12 (3): 111 (in part, not of Gabb) ; plt. 7, figs. 2-9; pit. 8, figs. 1-8. Acanthotrophon striatus (Gabb). RapwIN & D’ATTILIO, 1978, Tulane Stud. Geol. Paleont. 14 (3): 131; text figs. 1, 1a, 2 (not of Gabb) . Diagnosis: Seven post-nuclear whorls in adult, plus a protoconch of 24 bulbous turns. Spiral ornamentation beginning abruptly with 2 small sharp cords, most pro- nounced on first 2 whorls, gradually fading to become a single faint ridge connecting shoulder spines. On body whorl from 3 to 7 cords, with usually 3 of these stronger, separated by a space from another cord at base of body- whorl, usually very strong (but not always); an additional I or 2 smaller cords on the extended siphonal canal. Axial ornamentation beginning with 7 to 9 small nodes, grad- ually becoming spinose varices with sharp spines where spiral cords cross these varices, their strength relative to that of the cord, shoulder spine always the longest. Sur- face scabrous; in some, where the axial growth lines cross the spiral cords, smaller spinelets. Suture undulating, sub- sutural ramp unornamented except for faint recurved growth lines reflecting the anal notch. Aperture oval, outer lip flaring at posterior end and bearing within about 8 lirations. Inner lip appressed at posterior end, standing free at anterior end; smooth except for a series of small denticles of variable number, strength, and shape, at ex- treme anterior end. Siphonal canal moderately long, slightly recurved at distal end; moderate to large umbilical opening formed by series of previous terminations of the canal. Dimensions of holotype: 14.0. height 21.3mm, diameter Holotype: USNM 298656. Type locality: “TU 1240, Barrio Los Corales, hill top at end of road that passes Standard Fruit Company’s box factory, 1.8km north of main highway at Pueblo Nuevo, which is 2km west of Puerto Limén, Costa Rica. Occurrence: Agueguexquite Formation, middle Plio- cene; Veracruz, Mexico. Pinecrest Beds, middle Pliocene; Caloosahatchee Formation, late Pliocene; Bermont For- mation, early Pleistocene; southern Florida. Moin Forma- tion, lower and middle Pleistocene; Costa Rica. Recent, southern Florida. Figured specimens: Figure 3, USNM 298656 (holo- type). Figure 4, USNM 240682 (paratype A); height 26.4 mm, diameter 15.7mm; locality TU 726. Figure 5, USNM 240685 (paratype B); height 30.7 mm, diameter 17.3mm; locality TU 759. Figure 6, AMNH 182709 (paratype C); height 23.6mm, diameter 12.5 mm, locality, southwest of Sanibel, Florida, 55m. Figure 7, AMNH 183199 (para- type D); height 24.8mm, diameter 13.2 mm; locality, off Briar Reef, Florida. Figure 8, USNM 298657 (paratype E); height 20.0mm, diameter 12.8mm; locality TU 1240. Figure 9, USNM 298658 (paratype F); height 19.0mm, diameter 12.9mm; locality TU 1240. Other occurrences: TU locality numbers 201, 638, 727, 933, 991, 954, 1177, 1307. APPENDIX I The following are locality records for the Pacific species (* marks figured specimens). Acanthotrophon carduus LACM 36564—Mazatlan, Sinaloa, Mexico. LACM 65-16—18-27 m, Banderas Bay, Pta. Mita, Jalisco, Mexico. *Poorman Collection—go m, off Pta. Juluapan, Colima, Mexico. *LACM 38-8—36-73 m, off Zihuatanejo, Guerrero, Mexico. LACM 72-57—21 m, off Pta. Quepos, Prov. of Puntarenas, Costa Rica. AHF 251-34—27 m, Secas Isls., Golfo de Chiriqui, Panama. LACM 7o-15—Intertidal, Venado Island, Canal Zone, Panama. AHF 423-35—36 m, off Port Utria, Dept. of Choco, Colombia. AHF 831-38—18-36 m, Isla de Gorgona, off Guapi, Dept. of Cauca, Colombia. Page 14 THE VELIGER Vol. 23; No. 1 LACM 66-114—9 m, Bahia de Sta. Elena, Ecuador. AHF 209-34—18 m, Bahia de Sta. Elena, Ecuador. AHF 210-34—9-12 m, Bahia de Sta. Elena, Ecuador. Acanthotrophon sentus AHF 141-34—Beach, Sulphur Bay, Isla Clarion, Revillagigedo Islands, Mexico (ca. 1000 km west of Colima). AHF 779-38—n55-91 m, Isla Nuez, Isla del Coco, Costa Rica (ca. 500 km southwest of Puntarenas). LACM 66-210—34 m, James Bay, Isla San Salvador (James Isl.) , Galdpagos Islands, Ecuador. AHF 197-34—64-73 m, Post Office Bay, Isla Santa Maria (Charles Isl.), Galapagos Islands, Ecuador. *AHF 155-34—90-110m, Tagus Cove, Isla Isabella (Albemarle Isl.), Galapagos Islands, Ecuador. Acanthotrophon sorensent AHF 566-36—36m, Isla Tiburén, Sonora, Mexico Poorman Collection—100 m, Bahia de San Carlos, Guaymas, Sonora, Mexico. *CAS 9611 (holotype)—109 m, Gorda Banks, off Cabo San Lucas, Baja California Sur, Mexico. Acanthotrophon ? spec. nov. ®Skoglund Collection—45-60 m, Danzante Channel, Puerto Escon- dido, Baja California Sur, Mexico. AHF 580-36—36 m, southeast of Isla San Marcos, off Santa Rosalia, Baja California Sur, Mexico. AHF 1087-40—27-33m, Ensenada de San Francisco, Guaymas, Sonora, Mexico. LACM 11253—155 m, off Sonora, Mexico. Poorman Collection—6o m, Bahia San Carlos, Guaymas, Sonora, Mexico. *Skoglund Collection—45 m, off Guaymas, Sonora, Mexico. APPENDIX II LOCALITY DATA The following are Tulane University fossil locality num- bers: 201. Bermont Fm., spoil banks at pit just south of Belle Glade (at Belle Glade Camp), Palm Beach Co., Florida. 638. Agueguexquite Fm., roadcut and quarry on Mexico High- way 180, 14 miles east of junction with side road into Coatzacoalcos, Veracruz, Mexico. 726. Caloosahatchee Fm., Hendry County rock pit, % mile north of Florida Highway 80, three miles west of La Belle (SE % Sec. 14, 1438, Re8E), Hendry Co., Florida. 727. Bermont Fm., borrow pits 2.2 miles east of U.S. Highway 27, 15 miles south of South Bay, Palm Beach Co., Florida. 759. Bermont Fm., spoil banks north side of Caloosahatchee River, two miles west of Ortona Lock (NE ¥ Sec. 29, T428, RoE), Glades Co., Florida. 933. Pinecrest Beds, material exposed during construction of “Alligator Alley,” 21.5 miles-east of Florida Highway go, Collier Co., Florida. 954. Moin Fm., hill cut immediately behind Standard Fruit Co. box factory, just west of cemetery at Pueblo Nuevo, about 2 km west of Puerto Limén, Costa Rica. 991. Caloosahatchee Fm., Cochran rock pit, 2% miles west of La Belle, on north side of Florida Highway 80, Hendry Co., Florida. 1177. Caloosahatchee Fm. and Pinecrest Beds mixed, Mule Pen Quarry, north side Florida Highway 846, 9.1 miles east of U.S. Highway 41 at Naples Park (SE ¥ Sec. 24, T48S, R26E), Collier Co., Florida. 1227A. Gurabo Fm., Arroyo Zalaya, which crosses the road to Janico from Santiago de los Caballeros, 11 km south of the bridge over Rio Yaque del Norte, at Santiago, Dominican Republic. 1227A is a thin lens, resulting from a turbidity flow, which is located on the north side of the arroyo between the old bridge (washed out) and the new bridge. 1240. Moin Fm., Barrio Los Corales, hilltop at end of road that passes Standard Fruit Company's box factory, 1.8km north of main highway at Pueblo Nuevo, which is 2km west of Puerto Limén, Costa Rica. 1307. Moin Fm., hill top approximately halfway between Puerto Limon and Barrio Los Corales and about o., km north of highway at Pueblo Nuevo, Costa Rica. Literature Cited Apams, ARTHUR 1855. Descriptions of twenty-seven new species of shells from the col- lection of Hugh Cuming, Esq. Proc. Zool. Soc. London for 1854: 311-317 (8 May 1855) Berry, SAMUEL STILLMAN 1969. Notices of new eastern Pacific Mollusca VIII. Leafl. in Malac. 1 (26): 159-166 BRopERiP, WILLIAM JOHN 1833. Characters of new species of Mollusca and Conchifera collect- ed by Mr. Cuming. Proc. Zool. Soc. London, Part II (for 18§2): 173-179 (14 January 1833) Dati, Wim Hearey 1889. Reports on the results of dredging under the supervision of Alexander Agassiz, in the Gulf of Mexico (1877-78) and in the Carib- bean Sea (1879-80), by the U.S. Coast Survey steamer “Blake”, etc. XXIV. Report on the Mollusca.—Part II. Gastropoda and Scapho- poda. Bull. Mus. Comp. Zool. 18: 1 - 492; pits. 1-40 (January to June 1889) (17 December 1969) Gass, Witt1amM More 1873. On the topography and geology of Santo Domingo. Trans. Amer. Phil. Soc. (N. S.) 15 (1): 49-259; 1 map Hert.ein, Leo GeorcEe & ARCHIBALD McC.ure STRONG 1951. Eastern Pacific expeditions of the New York Zoological Society. XLIII. Mollusks from the west coast of Mexico and Central America. Part X. Zoologica 36 (5): 67-100; 11 plts. (20 August 1951) Nowe u-Usticke, Gorpon W. 1969. A supplementary list of new shells of St. Croix. Publ. Co., Wynnwood, Pa. 32 pp.; 6 plts. Rapwin, Gzorce Epwarp & ANTHONY D’ATTILIO 1976. Murex shells of the world. An illustrated guide to the Muricidae. Stanford Univ. Press, Stanford, Calif. x+284 pp.; 192 numbered figs. +6 unnumbered figs. in text; 32 col. plts. 1978. | Comments on subfamilial relationships in two amphi-American muricid genera — Acanthotrophon and Attiliosa. Tulane Stud. Geol. Paleont. 14 (3): 131-134; 7 text figs. (28 December 1978) Voxeg, Emity Hoskins 1970. Cenozoic Muricidae of the Western Atlantic region. Part 5, Ptery- notus and Poirieria. Tulane Stud. Geol. Paleont. 8 (1): 1-50; plts. 1-7 (17 June 1970) 1976. Cenozoic Muricidae of the Western Atlantic region. Part 7, Calo- trophon and Attiliosa. Tulane Stud. Geol. Paleont. 12 (g): 10% to 192; pits. 1-7 (15 September 1976) Livingston Vol. 23; No. 1 THE VELIGER Page 15 A New Species of Favartia (Carthiella) from the Galapagos Islands EMILY H. VOKES Department of Geology, Tulane University, New Orleans, Louisiana 70118 ANTHONY D’ATTILIO Natural History Museum, San Diego, California 92112 (3 Text figures) Tue GatApacos IsLanps have been recognized as a “‘lab- oratory of evolution” since the time of Charles Darwin. As we become better acquainted with the molluscan fauna we see there are many endemic species that have near relatives on the mainland of the Tropical East Pacific. Among the muricids, for example, there are Maxwellia angermeyerae (Emerson and D’Attilio, 1965), Pteropur- pura deroyana Berry, 1968, Murexsul jacquelinae Emer- son and D’Attilio, 1969, Murexiella radwini Emerson and D’Attilio, 1970, and Paziella galapagana (Emerson and D’Attilio, 1970). This paper is the report of yet another form, heretofore misidentified as Favartia erosa (Broderip), which is its “next of kin” living on the Pacific mainland from Mexico to Panama (KEEN, 1971: 532). The species “Murex” erosus Broderip, 1833, has been placed in a variety of genera since its description, including “Ocinebra,” “Muricidea,” and “Aspella.” The rationale for the latter assignment lay in the peculiar habit of the species to abort some of the later varices and to develop a dorso-ventrally flattened shell, reminiscent of Aspella. Other than this the two, as we know now only distantly related forms, have little in common. In the first edition of Sea Shells of Tropical West America KEEN cited erosa as Aspella (Dermomurex) (1958: 365). By the second Edition (1972: 532) she and other muricid workers had realized that the species was better referred to the genus Favartia. But there was still a feeling that the shell was not quite properly placed in that taxon. The problem was resolved in 1972 by PErRIL- LIAT, who proposed a new subgenus (still in the mistaken idea that the nearest relationship was with Aspella) as Aspella (Caribiella), with the type the Caribbean species “Murex” intermedius C. B. Adams, 1850. Unfortunately, that name is preoccupied by Murex intermedius Brocchi, 1814, a fossil C'ymatium from Italy. However, it had been suggested as far back as Tryon (1880, p. 239) that the Caribbean species was the same as that described by KIENER, without locality’, as Murex alveatus (1842: 94; pit. 46, fig. 2). But because the species had been confused with “M.” erosus [for example, REEvE (1845: plt. 32) states: “Hab. Panama (found under stones at low water); Cuming”] the identity has tended to be overlooked. When one compares mature specimens of Murex intermedius (the lectotype figured by CLENcH & TURNER, 1950: plt. 39, fig. 15 is immature) with Kiener’s illustration, the iden- tity seems incontestable. ™ In 1869 TroscHEL figured the radula of a species he cited as “Ocinebra alveata” from St. Thomas (Das GebiB der Schnek- ken, 2 (3): 119; plt. 11, fig. 10). It is an excellent rendering of the peculiar “three-dimensional” muricopsine rachidian tooth but we were all too blind to see it until Radwin & D’Attilio began their work on the muricid radula. Compare Troschel’s figure with the lower drawing in our Figure 3. Page 16 At the time of Perrilliat’s work, she and the senior author were in correspondence over the matter and orig- inally she intended to propose a new name for the pre- occupied M. intermedius. In a letter she advised that she would call it Aspella (Caribiella) elegans, n.n. pro Murex intermedius Adams non Brocchi. With this knowledge the Catalogue of the genus Murex Linné (VoKEs, 1971) went to press with the name Aspella elegans Perrilliat Montoya, “1971,” (n.n. pro intermedius Adams), type of the sub- genus Caribiella. Due to problems in publication, with which we can all sympathize, Perrilliat’s paper did not appear until 1972, and when it did the name elegans was not to be seen! Presumably, she had taken Vokes’ suggestion on the prob- ability of Murex alveatus being the same and deleted the new name at the last minute. As a result, Murex inter- medius is cited as the type species of her new subgenus Aspella (Caribiella). Fortunately, the International Code of Zoological Nomenclature (Art. 13) states that names published after 1930 must be accompanied by some sort of description or we would be cursed with having to cite the taxon as “Caribiella Perrilliat in Vokes, 1971.” To further complicate the matter, the Mexican fossil that is figured as “Murex intermedius” (PERRILLIAT, 1972: 83; plt. 39, figs. 14, 15; plt. 4o, figs. 1, 2) is not the same as the Recent Caribbean shell but is a new species much closer to Favartia erosa. Also, the age of the Santa Rosa | beds is now known to be uppermost Miocene (N 17, ac- cording to Dr. W. H. Akers, personal communication), not to be correlated with the mid-Pliocene Agueguexquite Formation. Nevertheless, the Santa Rosa species is important, as it is certainly the ancestor of both the Atlantic Favartia alveata and the Pacific F. erosa as well as the new species here described. More than any of the Recent species, it shows the dorso-ventral flattening, the resemblance to As- pella being even stronger than in the younger forms. The spiral ornamentation is very close to that of F erosa. It seems most unlikely that this highly ornamented shell is closely related to the smooth, almost polished shell of As- pella. Furthermore, radular differencesshow that themem- bers of the genus Aspella have a typical muricine radula, but E erosa aud its kin have the three-dimensional radula of the Muricopsinae (see Figure 3). Because of the 1971 cut-off date, in Murex Shells of the World, Rapwin & D’Artitio (1976) did not include Caribiella, placing the species in the genus Favartia s.s. However, the peculiar Aspella-like habitat of the flattened shell, plus the greatly elongated spire, seems worthy of a subgeneric distinction. THE VELIGER Vol. 23; No. 1 MuricwaE Rafinesque, 1815 Muricopsinae Radwin « D’Attilio, 1971 Favartia Jousseaume, 1880 Favartia JoUSSEAUME, 1880, Le Naturaliste, Année 2, no. 42, P. 335. Type species: Murex breviculus Sowerby, by OD. Subgenus Caribiella PERRILLIAT, 1972 Caribiella PERRILLIAT, 1972, Paleontologia Mexicana, no. 22)782) Type species: Murex intermedius C. B. Adams [= Murex alveatus Kiener], by OD. Favartia (Caribiella) purdyae Vokes & D’Attilio, spec. nov. (Figure 1) Description: Shell of moderate size, with protoconch of two smooth, bulbous whorls, exact termination indistinct; six post-nuclear whorls. Early axial ornamentation of about nine small varices lapping onto the protoconch. Cer- tain varices strengthened, relative to others by fourth tele- oconch whorl; with, by 6th whorl, only 2 strong varices, at the aperture and the opposite side, remaining; interme- diate varices reduced to simple buttress-like structures visible primarily at the suture. Spiral ornamentation at first of 2 rounded cords, be- coming increasingly flattened on the outer side, by 4th whorl appearing almost fused together with only a narrow groove dividing them. On the body whorl, 5 such flattened cords. On top of each cord 4 or 5 thin, incised spiral lines, together with the axial growth lines giving a striking “woven” texture to the surface. On the siphonal canal another strong spiral cord, separated from those on the body whorl by a wide interspace; the varices crossing this space giving rise to a series of deep pits circling the base of the body whorl. Spire elevated, height approximately twice width; suture impressed but obscured by the varical buttresses. Aperture circular, surrounded by a raised peri- stome; outer lip slightly crenulated by the terminal varix. Siphonal canal short, broad, almost sealed but open by a very narrow slit; distal end strongly recurved; with a small fasciole formed by the termination of the previous canals. Color of shell varying from almost all white to purple- Vol. 23; No. 1 Figure 1 Favartia (Caribiella) purdyae Vokes & D’Attilio, spec. nov. brown with a white band circling the base of the body whorl ; larger varices and aperture white. In well-preserved specimens a thin white intritacalx frosting the entire shell, but normally worn off except in the deeper pits along the suture and the base of the body whorl. Dimensions of holotype: Height 15.0mm, diameter 8.0 mm. Holotype: San Diego Natural History Museum TS¥776. Type locality: Isla Plasa, Galapagos Islands (leg. J. DeRoy, 1969), from the collection of Ruth Purdy. Discussion: Some time back Ruth Purdy (Mrs. Ben Purdy) of San Diego, California, sent the senior author a strange specimen from the Galapagos Islands, which she had obtained under the name “Aspella indentata,” inquir- ing as to what it might actually be. The shell was imme- diately recognized as a new species, the Galapagos endemic form of Favartia erosa. This report is the final result of the THE VELIGER Page 17 question and it gives the authors great pleasure to honor Mrs. Purdy, who has so generously shared her western American muricid material over the years. Although closely related to the mainland Favartia erosa, this new species differs in the nature of the surface orna- mentation. The spiral cords have the appearance of hav- ing been pressed down with a flat-iron, so that they are completely flat, with faintly incised spiral and axial lines superimposed upon them (see Figure 1). The entire surface has a smooth aspect in contrast to the elaborately sculp- tured effect of the ornamentation of F. erosa (see Figure 2). Figure 2 Favartia (Caribiella) erosa (Broderip) The elongation of the fully adult shell appears greater in F. erosa than in F. purdyae, because the angle of the spire is less acute in EF purdyae. Other specimens in the type lot are more elongate than is the holotype, but never is the extreme long, narrow shell shape of F. erosa achieved, Page 18 THE VELIGER Vol. 23; No. 1 although the shells attain comparable sizes (the largest paratype of F. purdyae is 16.5 mm in height). Figure 3 Favartia (Caribiella) purdyae Vokes & D’Attilio, spec. nov. Academy Bay, Isla Santa Cruz, Galapagos Islands. All teeth are from the same ribbon but resting differently on the slide, showing varying aspects of the structure Paratypes: In addition to the holotype the following material was examined: AMNH 117941, 2 specimens from Academy Bay, Isla Santa Cruz (Carmen Anger- meyer, 1964); AMNH 139469, 1 specimen from Puerto Nujiez, Isla Santa Cruz (Carmen Angermeyer, 1965); 2 specimens from Academy Bay, Isla Santa Cruz, inter- tidally under rocks (J. deRoy, 1965—Shasky Collection); 3 specimens from north Isla Santa Cruz, intertidally (J. deRoy, 1968—Shasky Collection. The writers would like to acknowledge their gratitude to Donald Shasky, MD, for the loan of these specimens. Literature Cited Apams, Cuaries BAKER 1850. Description of supposed ‘hew species of marine shells which in- habit Jamaica. Contrib. to Conch. (4): 56-68 (January 1850) Berry, SAMUEL STILLMAN 1968. Notices of new eastern Pacific Mollusca VII. Leafi. Malac. 1 (25): 155-158 (September 1968) Broccut, GiovANNI BatTIsTA 1814. | Conchologia fossile subapennina ... Silvestro Broperip, WILLIAM JoHN 1833. Characters of new species of Mollusca and Conchifera collected by Mr. Cuming. Proc. Zool. Soc. London for 1832: 173-179 (14 January 1833) vol. 2, 556 pp., Milan, CiencH, WituiaM James & RutH Drxon TurRNER 1950. The western Atlantic marine mollusks described by C. B. Adams. Mus. Comp. Zool. Harvard Univ., Occ. Pap. 1 (15): 233-403; plts. 29 - 49 (26 June 1950) Emerson, WitiiaM KeitH # ANTHONY D’ATTILIO 1965. Aspella (Favartia) angermeyerae, n. sp. The Nautilus 79 (1): 1-4; plt. 1 (July 1965) 1969. A new species of Murexsul (Gastropoda : Muricidae) from the Gal&pagos Islands. The Veliger 11 (4): 324-325; plt. 50; 1 text fig. (1 April 1969) 1970. ‘Three new species of muricacean gastropods from the Eastern Pacific. The Veliger 12 (3): 270-274; plts. 39, 40; 4 text figs. (1 January 1970) Keen, A. Myra 1958. Sea shells of tropical west America; marine mollusks from Lower California to Colombia. Stanford Univ. Press, Stanford, Calif: i-xi + 624 pp.; 1700 text figs.; 10 colored plts. (5 Dec. 1958) Kagn, A. Myra, with the assistance of Jauzs Hammton McLean 1971. Sea Shells of Tropical West America; marine mollusks from Baja California to Peru. aed ed. Stanford Univ. Press, Stanford, Calif i-xiv + 1064 pp.; ca. 4000 figs.; a2 color plts. (1 September 1972) Krener, Louis Cmar.gs 1842-1843. Spécies général et iconographie des coquilles vivantes; genre Rocher. 9: 1-130; pits. 1-47 (plates: 1842; text: 1843] PERRILLIAT, MARIA DEL CARMEN 1972. | Monograffa de los moluscos del Mioceno medio de Santa Rosa, Veracruz, Mexico. Pt. 1 (Gasterépodes: Fissurellidae a Olividae). Paleontologia Mexicana (32): 1-119; pits. 1-51; 1 table; 1 map Regvz, Lover. Auoustus 1845-46. Conchologia Iconica: or illustrations of the shells of mollus- cous animals. Monograph of the genus Murex. London, pits. 1-36 (April 1845 to April 1846) Tryon, Gzorocz WASHINGTON, Jr. 1880. Muricinae, Purpurinae. In: G. W. Tryon, Jr. & H. A. Pilsbry, Manual of Conch. (1) 2: 1 - 289; plts. 1-70 Voxes, Emity Hoskins 1971. Catalogue of the genus Murex Linné (Mollusca: Gastropoda) : Muricinae, Ocenebrinae. Bull. Amer. Paleont. Ithaca, N. Y. 61 (268): 1-141 (26 August 1971) Vol. 23; No. 1 THE VELIGER Page 19 A New Species of Muricacean Gastropod B. M. OLIVERA Department of Biology, University of Utah, Salt Lake City, Utah 84112 (2 Plates) THE DIVERSITY AND ABUNDANCE of marine mollusks is probably greatest in the central and southern Philippines. The use of gill or tangle nets in these areas has resulted in the collection of many well known rare species such as Conus gloriamaris and C'ypraea valentia, as well as a remarkable array of new muricacean forms. One of the smallest and most distinctive of these new forms is an undescribed species of the genus Murexiella. Considering the relatively deep water habitat of this spe- cies, and its small size, it is not surprising that it has not previously been collected. The new taxon is quite variable in color and pattern. Twelve specimens from the Cebu- Bohol area of the central Philippines have been exam- ined, MUuRICIDAE Muricopsinae Murexiella Clench and Pérez Farfante, 1945. Type species: Murex hidalgo: Crosse, 1869 (by OD). Murexiella peregrina Olivera, spec. nov. Description: The holotype is 10mm in length, and spec- imens examined vary from 9.5 to 15mm. The shell is fusi- form with an elevated spire and 6 postnuclear whorls. The protoconch is translucent, brown or cream colored, and consists of 24 whorls. The shell is variable in sculpture and color. A constant feature is the presence of 4 varices on the adult body whorl. The siphonal canal is open, moderately long and strongly recurved. The fasciole is formed by the termination of the 3 previous canals. The varical margin is thick, and both the varical margin and the leading edge of the varix are decorated with scaly lamellae. Generally, there are 5 spines on the varices of the body whorl, connected by a scabrous web; in addition, the varix extends to the siphonal canal where there are usually 3 additional spines, 2 rather short and a central long spine. In one of the paratypes, there are 6 spines on a varix. In another paratype, only 2 siphonal spines are present, one of which has become bifurcate. There are deep grooves between the spines, on the abapertural side of each varix. A number of fine shallow grooves is present on the spines; the length of the spines is somewhat variable, the shoulder spine tends to be somewhat broader and longer than the others, and weakly frondose. The aperture is ovate, and no anal notch is visible. The peristome is strongly elevated. The aperture is shiny white except for brown spots at the outer lip. The outer lip has lobe-like crenulations reflecting the dorsal spiral structure. The shell color is variable. In general, there are dark brown markings at the suture, especially close to the aba- pertural side of a varix. There is usually another dark marking, of variable size, at the anterior portion of the body whorl. In all specimens examined, there is a dark brown marking at the base of the siphonal canal where it starts to recurve. In most specimens, there is also a dark brown marking towards the very tip of the siphonal canal. One group of specimens (holotype; paratypes 1-6) has a marked change in color towards the anterior of the body whorl. The posterior body whorl (nearest the suture) and the earlier whorls can be colored deep red, pinkish or brown; and the anterior body whorl (nearest the siphonal canal) can be creamy white, or light brown. In a second Page 20 THE VELIGER Vol. 23; No. 1 group of specimens, however, there is a uniform light brown color throughout the body whorl except for the dark brown markings noted above (paratypes 7-11). In all specimens, the siphonal canal is translucent, and notice- ably lighter in color than the remainder of the shell. There is also considerable variation in the sculpture of the species examined. The early whorls show 3 cords, the shoulder cord being the broadest; the cords are generally decorated with scales. In most specimens, these cords be- come very weak or obsolete. The body whorl only shows weak shallow cording, and is almost smooth. Two of the paratypes, however, exhibit strong cords up to the body whorl. The operculum was not examined; however, the oper- culum of the holotype is lodged deep in the aperture. Material examined: Holotype is deposited at the Na- tional Museum of Natural History, Smithsonian Institu- tion, USNM 783326. Paratypes 1-3 (Olivera collection); Paratype 4, University of Utah Museum of Natural His- tory, Molluscan collection No. 2000. Paratypes 5-11, all Olivera collection. Type locality: Panglao, Bohol Island, Philippines, taken by use of gill or tangle nets in approximately 80m of water. All specimens examined come from this locality, except paratype 11, which is from Punta Engafio, Mactan Island, Philippines. Remarks: The present species is highly distinctive in several ways. The relatively small size, the 4 varices per whorl, and the long, strongly recurved siphonal canal dis- tinguish it from other species. Probably the closest relative is the recently described Murexiella martini Shikama, 1977, but that shell attains a much larger size (28mm), and has 3 varices on the body whorl (see also EMERSON & D’AtTILIo, 1979). The only other species at all similar is the new world Murexiella levicula Dall, 1889 (also see VoKEs, 1968; Farr, 1976; Rapwin & D’Arriio, 1976). Explanation of Figures z and 2 (on the Plate) The strongly recurved siphonal canal of M. peregrina im- mediately distinguishes it from this species. The great variation seen in different specimens of the species, from within a relatively narrow area in the central Philippines suggests that when collecting is done in other localities, even more variation might be expected. This taxon is named in honor of two sisters, Mercedes Peregrino and Gloria Peregrino Guerrero whose gracious- ness and hospitality have made shell collecting in the Philippines such a pleasure in the last 25 years. ACKNOWLEDGMENTS I am grateful to Dr. W. K. Emerson, A. D’Attilio, V. Dan and M. Beals for supplying literature or specimens. With- out the generous advice of Dr E. H. Vokes, this manu- script would not have been written. Literature Cited Ciznco, Wiriuam James « I. Pérez FARFANTE 1945. The genus Murex in the western Atlantic. 1-56; plts. 1-28 Crossz, JosepH CHartes HippoLyTe 1869. Diagnosis molluscorum novorum. 408 - 410 Dari, Witttam HEALEY 1889. Reports on the results of dredging, under the supervision of Alexander Agassiz, in the Gulf of Mexico (1877-78) and in the Carib- bean Sea (1879-80) by the U. S. Coast Survey steamer “Blake” . XXIV. Report on the Mollusca.—Part II. Gastropoda and Scaphopoda. Bull. Mus. Comp. Zool. 18: 1 - 492; plts. 1 - 40 (January-June 1889) Emerson, Wittiam KeitH « ANTHONY D’ATTILIO 1979. Six new living species of muricacean gastropods. The Nau- tilus 9g (1): 1-10 Fair, RuTH 1976. The Murex book: an illustrated catalogue of recent Muricidae. Sturgis Printing Co., 138 pp.; 23 plts.; 67 text figs. Rapwin, Gzorcz Epwarp « ANTHONY D’ATTILIO 1976. Murex shells of the world. An illustrated guide to the Muricidae. Stanford Univ. Press, Stanford, Calif x+284 pp.; 192 numbered figs. +6 unnumbered figs. in text; 32 col. plts. SHIkaMA, TOKIO 1977. Descriptions of new and noteworthy Gastropoda from western Pacific and Indian Oceans. Sci. Reprt. Yokohama Natl. Univ., Sect. 2, Biol. & Geol. Sci. 24: 9-23 1968. Cenozoic Muricidae of the western Atlantic region. Part 4, Hexaplex and Murexiella. Tulane Stud. Geol. Paleont. 6: 85 - 126 Johnsonia 1 (17): Journ. de Conchyl. 17: Explanation of Figure 3 Murexiella peregrina Olivera, spec. nov. Left, top to bottom, paratypes 1, 2, 5, 7. Right, top to bottom, paratypes 3, 8, 9, 6 (Collection Olivera). Paratype 9, 15mm. Posterior half of the body whorl of paratypes 1, 2, 3 is pinkish to yellowish brown; paratypes 5, 6, bright red; 7, 8, 9, brown. All Panglao, Bohol, Philippines THE VELIGER, Vol, 23, No. 1 [OxiverA] Figures 1 and 2 Figure 2 Murexiella peregrina Olivera, spec. nov. Figure 1: Holotype, dorsal aspect. U.S. N. M. No. 783326; 10mm Panglao, Bohol, Philippines Figure 2: Holotype, ventral aspect [OxtverA] Figure 3 Lael fe) Z 3 a ie) > = a te) _ = i] > i} q oa Vol. 23; No. 1 THE VELIGER Synopsis of the Genus Piseinotecus with Description of Piseinotecus evelinae spec. nov. LUISE SCHMEKEL Zoologisches Institut der Universitat, HiifferstraBe 1 D-4400 Minster, Bundesrepublik Deutschland (5 Text figures) Stupymnc THE AEOLDACEA of the Mediterranean I found in 1965 and 1966 two specimens of an unknown small Aeolid resembling externally a Flabellina with cerata on stalks and with annulated rhinophores, but with a uni- seriate radula, thus belonging to the genus Piseinotecus. I agree with EpMuNps (1970: 39) and pu Bots-Rey- MOND Marcus (1977: 15) that the acleioproct genus Piseinotecus Marcus, 1955, does not belong to the Cuthon- idae where Marcus (1955: 176) placed it first because of the unusual shape of the radula plates, the proximal position of the receptaculum (Diaulie II, ScHMEKEL, 1970) and the absence of a penial gland. Epmunps (loc. cit.) put Piseinotecus into a new family, Piseinotecidae (compare also pu Bors-REYMonD Marcus, loc. cit.), a family which “connects” the pleuroproct with the Acleio- procta. The mediterranean Calmella Eliot, 1906 (type- species Eolidia di cavolinii Vérany, 1846: 26) is very similar to Pzseinotecus. Calmella cavolinii has the recep- taculum in the same position (SCHMEKEL, 1970: 143£; figs. 6a, 7), no penial gland, a simple penis, the anus in the same position and the same modus of branching of the digestive gland. Only the radula is different; it is uniseri- ate in young and triseriate in old specimens of Calmella cavolini (I have to correct what I reported in 1965: 458f. I examined more and larger animals from different localities) and triseriate in Calmella bandeli du Bois-Rey- mond Marcus, 1976, while Piseinotecus always has a uni- seriate radula. PISEINOTECIDAE Edmunds, 1970 239 Aeolidacea acleioprocta with a uniseriate radula. Rhino- phores often smooth. Cerata raised on stalks in tufts or in tows. Only one row or tuft arising from the anterior di- gestive gland. Page 21 Figure 1 Pisetnotecus evelinae Schmekel, spec. nov. Holotype after fixation (alive 6 mm) A = anus Page 22 THE VELIGER Vol. 23; No. 1 Piseinotecus Marcus, 1955 Acleioproct Eolidacea with uniseriate radula. Rhinophores smooth or finely annularily wrinkled, often a little longer than the oral tentacles. Cerata raised in tufts on stalks or in rows; only one row or tuft arising from the anterior digestive gland. Foot with short angled corners. Mastica- tory border of jaw with one row of denticles. Tooth horseshoe-shaped with a prominent median cusp and denticles on each side. Receptaculum proximal to the cap- sule and mucous gland, penis unarmed, without penial gland. Type-species: Pzsernotecus divae Marcus, 1955. [Marcus, 1955: 176-178; figs. 244 - 248] Piseitnotecus evelinae Schmekel, spec. nov. Material: Naples: 2 specimens; the first, when alive 6mm in length, Capo Miseno, 15m, 17 XII 1964; the second, 3.5mm when alive, Punto Pizzago, om, 3 III 1966. Holotype: Alive 6mm, 17 XII 1964, 15m, Capo Figure 2 Piseinotecus evelinae Schmekel, spec. nov. Dorsal and ventral aspects Miseno (Naples, Italy), deposited in the Naturhistori- sche Museum, Basel, Switzerland. Description: Alive, the slender body of the larger speci- men is 6mm long; after fixation it is 4mm with a maxi- mum height of 0.8mm in the pericardial region. The maximum width of 0.5mm is at the head and in the region of the first group of cerata. The foot is rounded anteriorly, with short but distinct projections on the corners, and a very short, pointed tail. In the living animal, the rhinophores are up to 1.8mm long, the oral tentacles 1.5mm. After fixation both are 1mm in length and have a basal diameter of 0.14mm. The pointed, cylindrical rhinophores have fine annular wrinkles which are discernible even when they are fully extended. Figure 3 Piseinotecus evelinae Schmekel, spec. nov. Arrangement of the Cerata A — anus G — gonopore N — nephroproct (?) On either side of the body there are 7 groups of cerata opposite each other. The 3 anterior groups have a com- mon stalk up to 0.2 mm in length, which branches once in the first and second groups. On the stalk, or on its branches, the cerata are situated in bundles at the same level. ‘The branches of the first group have 3 and 5 cera- ta, the second 3 and 2 cerata. The next 2 groups bear 3 cerata, the fifth group 2, groups 6 and 7 only one ceras each. At the end there is an unpaired, medianly situated ceras. All cerata are narrow, spindle-shaped and terminal- ly pointed, with a maximum length of 1mm and a width of 0.14mm after fixation. The anus is situated immediately in front of the stalk of the second group of cerata; the nephroproct [not seen with certainty] in front of the anus, and the gonopore below the first group of cerata. The jaw is oval and 0.3mm long. Its cutting edge is denticulated with pointed denticles of up to 0.01 mm. Vol. 23; No. 1 Figure 4 Piseinotecus evelinae Schmekel, spec. nov. jaw In the posterior region of the masticatory border there are 2 rows of short denticles. The radula formula of a specimen of 3.5mm length is 22 X0-1-0. The horseshoe-shaped tooth, with a maxi- mum length and breadth of 0.03mm has a prominent cusp, only slightly stronger than the 6-8 denticles on each side; the denticles are of nearly equal size. Only the marginal denticles are shorter. Piseinotecus evelinae is covered all over with opaque white, only the midgut gland in the cerata is deep brown, lying below a transparent epithelium. DISCUSSION The following species of Piseinotecus have been described: Synopsis: Piseinotecus divae Marcus, 1955: 177-178; figs. 244-248; Sao Sebastiao (Brasil). Smooth rhino- phores, longer than the oral tentacles. Cerata united in bundles on very short common stalks. Radula 12 X0-1°0; cusp large and prominent with 12 small denticles on either side. Jaws with one series of denticles. Body whitish with a greenish-grey digestive gland. Piseinotecus sphaeriferus (Schmekel, 1965) SCHMEKEL, 1965: 452 - 461; figs. 1-5; Naples (Italy). Ref.; EDMUNDS, 1970: 39. THE VELIGER Page 23 Figure 5 Piseinotecus evelinae Schmekel, spec. nov. radula Smooth rhinophores, as long as the oral tentacles. Cera- ta united in bundles on very short common stalks. Radula 14 X0-1°0, cusp very large and prominent with up to 14 fine denticles on either side. Jaws with one series of denticles. Body transparent with distinct opaque white spots; digestive gland brownish. A green “ball” which perhaps is a glandular region of the digestive gland is situated at the base of each ceras. Piseinotecus gonga EDMUNDS, 1970: 35-36; figs. 15, 16A; Dar es Salaam (Tanzania). Page 24 THE VELIGER Vol. 23; No. 1 Smooth rhinophores, larger than the oral tentacles. The cerata are arranged vertically in rows, but do not arise from common stalks. Radula 17 X0'1:0. Each tooth has long basal processes, a prominent cusp and 6-9 small denticles on each side. Body suffused with pale brown, the dorsal surface covered with evenly spaced purple- brown and half as many cream spots. Rhinophores and oral tentacles with bands of dark green about % of their length. Piseinotecus kima EDMUNDS, 1970: 36-39; figs. 16, B, 17; Dar es Salaam (Tanzania). Smooth rhinophores, longer than the oral tentacles. Cerata arranged in vertical rows without stalks. Radula 16 Xo0-1:0. The teeth have huge basal processes, a prom- inent cusp and 7-9 small denticles on each side. Body transparent with scattered orange-yellow and smaller white spots. Rhinophores and oral tentacles with pale green bands. The annulated rhinophores, the shape of the radula tooth -— with small median cusp and nearly equally strong denticles on the sides -— and the masticatory border of the jaw with 2 rows of denticles separate Pisei- notecus evelinae from all the species of Pzsetnotecus listed above. The species is dedicated to Dr. Eveline du Bois-Rey- mond Marcus with greatest respect and profound thanks for her patient help and wise encouragement during many years. ACKNOWLEDGMENTS The research upon which this paper is based was sup- ported by the Deutsche Forschungsgemeinschaft. I am grateful for the use of the facilities of the Stazione zoolegi- ca di Napoli. I would like to thank Dr. Eveline du Bois- Reymond Marcus, who kindly reviewed the manuscript. The drawings were done by Klaus Moths. Literature Cited EpmuNDs, MALcoLm 1970. Opisthobranchiate Mollusca from Tanzania. II. Eolidaces (Cuthonidae, Piseinotecidae and Facelinidae). Proc. Malac. Soc. London 39 (1): 15-57; figs. 1-24 (April 1970) Eurot, Cartes Norton EpcEcoMBE 1906. Notes on some British nudibranchs. 7 (3): 333 - 382 cus, ERNST 1955. | Opisthobranchia from Brazil. Bol. Fac. Fil. Gi. Letr. Univ. Sao Paulo Zool. 20 (2): 89 - 261; plts. 1-30 Marcus, Eve.ine pu Bois-REYMoND 1976. Opisthobranchia von Santa Marta, Colombia. trop. Fauna Environm. 11: 119 - 150 1977. An annotated checklist of the Western Atlantic warm water opisthobranchs. Journ. Mollusc. Stud. 4: 1-22 (Nov. 1977) ScHMEKEL, LUISE 1965. Calmella sphaertfera n. sp., ein neuer Aeolidier aus dem Mittel- meer (Gastr., Opisthobranchia). Pubbl. Staz. Zool. Napoli $4: 452-461 1968. Ascoglossa, Notaspidea und Nudibranchia im Litoral des Golfes von Neapel. Rev. Suisse Zool. 75 (6): 103-155; 21 text figs. (March 1968) 19702. Anatomie der Genitalorgane von Nudibranchiern (Gastropoda, Euthyneuren). Pubbl. Staz. Zool. Napoli 38 (1): 120-217; 67 figs. Journ. Mar. Biol. Assoc. Studies Neo- 1970b. Filabellina babai n. sp., ein neuer Aeolidier (Gastr. Nudibran- chia) aus dem Mittelmeer. Vérany, GIovANNI BATTISTA 1846. Catologo degli animali invertebrati marini del Golfo di Genova e Niza Pubbl. Staz. Zool. Napoli 38: 316 - $27 Mus. Storia Nat. Genova 1 - 30 Vol. 23; No. 1 THE VELIGER Page 25 The Digestive System of the Moon Snail Polinices lewista (Gould, 1847) with Emphasis on the Role of the Oesophageal Gland ROBERT G. B. REID anp JOAN A. FRIESEN Department of Biology, University of Victoria, Victoria, British Columbia, Canada V8W 2Y2 (1 Plate; 7 Text figures) INTRODUCTION Polinices lewisti (Gould, 1847), the moon snail, is a large naticid mesogastropod which preys upon bivalves. It feeds either by drilling a hole in the shell of its prey or by attack- ing exposed soft parts. Although this is a conspicuous an- imal, and common intertidally on sandy shores along the North Eastern Pacific, there are aspects of its biology which are unknown. Since the moon snail is large it is a particularly suitable organism for studies on digestive physiology and functional morphology. Of particular interest is the prominent oesophageal gland, whose relatively large size suggests an important digestive role. In some prosobranchs the oesophagus bears a glandular region which varies in complexity within the subclass. FRETTER & GRAHAM (1962) have provided a survey of the prosobranch oesophagus and its associated glands. The simplest condition consists of lateral out- pouchings of the oesophagus, the epithelium of which is glandular and secretes mucus and some digestive en- zymes. In some neogastropods the mid-oesophageal re- gion forms a discrete glandular structure known as the gland of Leiblein which opens into the oesophagus via a single anterior duct. This gland is reported to secrete sev- eral proteolytic enzymes but no amylolytic nor lipolytic enzymes (OweEN, 1966). The mesogastropods present an intermediate condition, where the oesophageal gland connects with the oesophagus throughout the length of the gland. HirscH (1915) found that the oesophageal gland in Natica secreted proteolytic enzymes, and that the digestive gland contained proteolytic, amylolytic and lipo- lytic enzymes, and the gastric juice was also proteolytic. There have, however, been no recent studies of the naticid oesophageal gland in particular nor of the naticid diges- tive system in general. Of related interest, however, is the study by BERNARD & BacsHAw (1969) on the histology of the accessory boring organ of Polinices lewisit. Preliminary observations on the oesophageal gland in Polinices revealed that it has two distinct regions, the largest portion being composed of a brown reticulate tis- sue and the small anterior portion being white. No men- tion of such a differentiation appears in the literature and in the present study an effort is made to determine how the structural differences of the two tissues relate to their particular roles in digestion. MATERIALS anp METHODS Specimens of Polinices lewists were collected in the low intertidal area at Cherry Point and Rathtrevor Beach on the east coast of Vancouver Island, and by diving off Diana Island, Dixon Island and Flemming Island in Bark- ley Sound on Vancouver Island. Collections were made from June to October 1978. Field observations on feeding were made at the time of collection. Dissection and tissue extraction were carried out shortly after collection. Small pieces of the oesophageal gland and digestive diverticula were fixed in Bouin’s fluid with mercuric chlo- ride for histological studies. These were subsequently em- Page 26 bedded in paraffin, sectioned at 6-8 um and stained with iron haematoxylin, eosin and alcian blue. Gastric juice was extracted with a fine pipet inserted through the dorsal wall of the stomach and centrifuged at 4°C and 15000 rpm to remove particulate matter. Gastric juice pH was found to be pH 6.0. Tissue extracts of the oesophageal gland and digestive diverticula were prepared by homogenizing with cold distilled water and centrifuging at 4°C and 15000 rpm for 3 hours. Sub- samples of the homogenates were taken to determine fat- free dry weight. The supernatants were stored in 0.2mL (portions) at —20° C for later use in enzyme studies. The two tissue types of the oesophageal gland were treated separately for histological and histochemical work. However, the small amounts of white tissue present re- stricted the range of tests which could be made on it alone and for most quantitative enzyme assays the entire oeso- phageal gland was used. A number of animals were kept alive in the aquarium for histochemical tests and gross gut morphology. Ciliary currents were traced with the use of fine, carborundum and “‘Aquadag” carbon particle suspensions. Histochemical Survey Three different histochemical techniques were used to test for the presence of digestive enzymes in Polinices. All tech- niques are based on the coupling of hydrolysis products with a diazonium dye. The substrates, dyes and methods used are all as outlined in Pearse (1961) and as used by Rem (1966). Esterase activity was detected at pH 6.5 using a-naphthy! acetate as a substrate and stained with fast blue B salt. Sodium a-naphthyl phosphate provided a substrate for phosphatases. Acid phosphatase was detected with fast garnet GBC salt at pH 10 and alkaline phos- phatase with fast violet B salt at pH 5. Tris-maleate buffer was used in all cases. L-leucyl-4-methoxy-B-naphthylamide was used as a substrate for leucine aminopeptidase (LAP). Fast blue B salt was used in staining and incubation carried out with an acetate buffer at pH 6.5. The starch-gel electrophoresis technique was used for the separation of esterases, phosphatases and proteases as described by Rem (1966). For esterases and phosphatases this involved incubating the horizontally sliced gels in the media referred to above. Incubation was carried out at, 22°C for 30 minutes for esterases and up to 2 hours for phosphatases. Proteolytic activity was demonstrated electrophoretically using a gel- THE VELIGER Vol. 23; No. 1 atin overlay as a substrate. Incubation was at 37°C for 12 hours. Tissue from freshly killed specimens was frozen to a mounting block with dry ice and quenched with liquid nitrogen. Sections were made at 16um at —20°C and post-fixed in 10% formalin. The sections were incubated in the same staining mixtures as used for electrophoresis. Fresh tissue was also sectioned on the cryostat after being fixed in cold 10% formalin for 2 hours and em- bedded in gelatin. The presence of digestive enzymes was then stained for in the same manner. Quantitative Assays In all enzyme assays the gastric juice was used undiluted and results are expressed per mL per unit time. Results for the oesophageal gland and digestive diverticula are expressed as per gram dry weight per unit time. However, it should be noted that the digestive capacity of these tis- sues must also be considered in terms of their relative size. The average ratio of fat-free dry weight in grams of the oesophageal gland and digestive diverticula to the stom- ach volume in mL for an individual animal is: 0.75 : I : 9.8 oesophageal gland : stomach : digestive diverticula A quantitative determination of amylase activity was made by a modification of BERNFELD’s (1955) method. Using starch as a substrate the reaction mixture was meas- ured spectrophotometrically initially and after 60 minutes incubation at 37° C to determine the amount of reducing sugars released during digestion. Digestion over 60 min- utes by a standard containing 0.2 mL of a 50% solution of hog pancreatic amylase (Sigma Co. Ltd.) represented 100% hydrolysis. a-glucosidase activity was estimated using the glucose- oxidase test with maltose as a substrate (Glucostat Re- agent, Worthington Diagnostics, New Jersey). Lipase activity was estimated by calculating the percent hydrolysis of the synthetic triglyceride, tributyrin. Using phenolphthalein as an indicator the reaction mixture was titrated back to neutrality with 0.o2 N KOH after incu- bation. Proteolytic activity was measured over a pH range of 2.0-9.5 using a phosphate-citrate “Universal” buffer (NorTHRUP, 1923). A modification of the method of Kunirz (1947) as described by Rem & RAUCHERT (1972) using a 1% solution of bovine serum albumin was em- ployed. The products of hydrolysis were measured spectro- photometrically after incubation at 280nm and activity calculated per equivalent weights or volumes. One activ- Woll235 Now1 ity unit caused an increase in absorbence of 0.001 per minute. It was postulated that the white tissue of the oesopha- geal gland might contain enzyme precursors which would be activated in the presence of food. This tissue was tested for the presence of protease precursors by allowing the tissue extract to autolyse at room temperature for 6 hours before proceeding with the albumin digestion technique. White tissue extract was also activated with a 1% solu- tion of hog pancreatic trypsin (Sigma Co. Ltd.). The re- action mixture was buffered to pH 6.5 with Tris-maleate buffer. RESULTS Functional Morphology of the Alimentary Tract General Description The alimentary tract (Figure 1) consists of the buccal ap- paratus, which houses the radula, a long oesophagus, from which the oesophageal gland arises, a capacious stomach, a short mid-gut, and a hind-gut which can be differentiated morphologically into a short hind-gut region and a longer rectal region. The posterior part of the oesophagus, the stomach, and the mid-gut are embedded in the large di- gestive diverticula. The ducts of the digestive diverticula empty into the stomach at two openings, one at the oeso- phageal (posterior) end of the stomach and the other at the intestinal (anterior) end. In describing the generalized prosobranch gut FRETTER & GRAHAM (1962) distinguish between the topographical and morphological position of organs. This deals with the changes of position brought about by torsion. Throughout this paper we mean the topographical position when we describe any organ as anterior, posterior, dorsal or ventral. Oesophagus Except in the region of the oesophageal gland the interior surface of the oesophagus is elaborated into ciliated longi- tudinal folds, whose cilia bear food particles posteriorly toward the stomach. Oesophageal Gland In the region of the oesophageal gland the ventral surface of the oesophagus loses the longitudinal ridging found in the rest of the oesophagus and forms instead much smaller, diagonally-arranged ridges. The ventral surface of the oesophagus, called here the oesophageal groove, is THE VELIGER Page 27 Figure 1 Diagram of the alimentary tract of Polinices leunsit. The stomach lies at the dorsal surface of the mass of the diverticula. The portion of the oesophagus which is surrounded by the digestive diverticula is located ventrally. A — anus AV - anterior duct vestibule B — buccal mass C — cut end of digestive diverticula D - digestive diverticula HG -— hind-gut M - Mouth MG -— mid-gut O — oesophagus OG - oesophageal gland (brown tissue) PV — posterior duct vestibule R —- rectum S -— stomach W - white tissue of oesophageal gland bounded on the right by a ventral typhlosole. Overhang- ing the oesophageal groove there is a large dorsal typhlo- sole which functionally divides the lumen of the oeso- phagus into two regions: the oesophageal groove and the Page 28 THE VELIGER Vol. 23; No. 1 lumen of the oesophageal gland (Figure 2a). The oeso- phageal gland is a complex elaboration of the dorsal wall of the oesophagus. It is enclosed in a muscular capsule. Its O Diagram of the posterior half of the oesophageal gland of Polinices lewisii posteriorly. The small arrows indicate the direction of cili- ary currents on the surfaces of the organ. The large arrows indicate the general flow of fluid in the two lumina. C — cut surface of the gland F — transverse dorsal fold of the gland G - oesophageal groove M — mucus-secreting por- tion of dorsal typhlosole O - oesophagus T —- dorsal typhlosole V - ventral typhlosole interior surface is thrown into thick transverse folds which are lined with ciliated, glandular epithelia, referred to here as the brown tissue (Figure 3). A small anterior por- tion of the oesophageal gland is differentiated into a his- tologically and histochemically distinct white tissue. The interior folding also occurs in the region of the white tissue. The folding gives the lumen of the oesophageal gland a large surface area. There are three distinct ciliary tracts in the oesophageal gland. The cilia on the adoral and abo- ral faces of the dorsal folds beat downwards towards the oesophageal groove. Along the postero-ventral edges of the dorsal folds there are small ciliated grooves whose cilia beat from left to right. Along the right side of the oeso- phageal gland, where it joins the right side of the oeso- phageal groove there is a small ridge whose cilia beat transversely, across the ridge, into the oesophageal groove. On the dorsal typhlosole which arises from the left side of the oesophagus the cilia beat transversely into the oeso- phageal groove. Along the edge of the dorsal typhlosole which is closest to the oesophageal groove there are mucus cells which produce copious amounts of mucus. Partic- ulate material in the oesophageal groove is carried diag- onally and posteriorly to come into contact with the mucus secretion of the dorsal typhlosole. The mucus-bound par- ticles are rapidly formed into a twisted, continuous string. The ciliation of the oesophageal gland ensures that all par- ticulate material coming into contact with the interior surface is removed to the oesophageal groove. We can only speculate as to the circulation of fluid between the oeso- phagus proper and the oesophageal gland. In a partially closed system such as the oesophageal gland all ciliary cur- rents must be responded to with counter currents. Some oesophageal fluid probably flows anteriorly in the oeso- phageal gland lumen in response to the posterior flow in the oesophageal groove (Figure 3). Within the oesophageal gland lumen there must be some turbulent mixing of the fluids. Thus, while the larger particulate material is cleared rapidly from the oesophageal gland it is possible Explanation of Figure 2 a & b) Cross-section of the oesophagus and oesophageal gland through its widest point. Stained with iron haematoxylin, eosin and alcian blue. dt — dorsal typhlosole cytes lu - lumen of oesophagus ms — muscular sheath vt — ventral typhlosole m — muco- re — radiating canals c & d) Cross-section through anterior portion of oesophageal gland showing junction of white and brown tissue. Stained with iron haematoxylin and eosin. w — white tissue b — brown tissue e) Section through gastric epithelium and digestive diverticula stained with iron haematoxylin and eosin. . £) White and brown tissue of oesophageal gland stained for leucine aminopeptidase. w — white tissue b — brown tissue g) Gastric epithelium stained for alkaline phosphatase. 2o / 2a to 2¢ Figures SEN] [Rew « FRE No. 1 Vol. 23, ELIGER, Tue V SCAM Mlk ALON 990 alt} Vol. 23; No. 1 that fine suspended particles and dissolved nutrients come into contact with the epithelia of the gland. The contrac- tion and relaxation of the muscular capsule of the oeso- phageal gland also causes an exchange of fluid. Stomach The stomach is an elongated sac which lies under the dor- sal surface of the visceral mass (Figure 1). The oesophagus Figure 4 Diagram of the stomach of Polinices lewisi. The stomach has been opened by a cut along the mid-dorsal line, with a smaller cut near the oesophageal opening permitting the reflection of the left wall of the stomach. The ciliated ridges and grooves of the lateral ciliated tract have been exaggerated; these are not obvious at low magnification. Arrows indicate the direction of ciliary currents on the surface of the stomach. AV - anterior duct vestibule I — intestinal groove L — lateral ciliated tract M - mid-gut O — oesophagus PV - posterior duct vestibule R — rejectory groove T - major typhlosole THE VELIGER Page 29 empties into the stomach at its posterior end, and the mid- gut opens at the anterior end. There are two gastric vesti- bules into which ducts of the digestive diverticula open. The first is situated at the entrance of the stomach, a short distance from the oesophageal opening. The other lies near the end of the stomach. There are two ciliated longitudinal grooves which run the length of the stomach. The right rejectory groove arises as a. confluence of the ciliated grooves which leave the openings of the oesophagus and duct vestibule (Figure 4). It carries dense particulate ma- terial towards the mid-gut, ventrally along the right side of the stomach. The left rejectory groove arises from a confluence of very small ciliated striations at the oesophag- eal end of a wide, dorsally situated, ciliated tract which extends the length of the stomach on the left side. Near the opening of the mid-gut the left rejectory groove tra- verses the stomach towards the right and joins the right rejectory groove to become the intestinal groove. The dor- sal ciliated tract, within which the left rejectory groove lies, has very fine transverse striations whose cilia beat across the tract towards the left rejectory groove. The right, ventral edge of the dorsal tract is bounded by a flat ridge, an extension of the oesophageal typhlosole whose cilia beat transversely towards the right rejectory groove. The whole interior surface of the stomach on the right side forms a ciliated tract whose cilia beat transversely towards the right rejectory groove (Figure 5). The general ciliation of the stomach walls creates a transverse, clock- wise circulation of gastric juice, as viewed from the pos- terior (Figure 5). Food strings which enter the stomach are too large to fit the right and left rejectory grooves and are Figure 5 Diagram of a solid section of the stomach of Polinices lewisit. Small arrows indicate ciliary currents on the surfaces of the stomach. The large arrow indicates the general circulation of gastric juices. I — intestinal groove L — lateral ciliated tract R — rejectory groove Page 30 subjected to the general gastric circulation. In the stomach food particles are released from the food strings and sub- jected to further digestion by the gastric enzymes. Small, dense particles are removed in the rejectory grooves to the intestine. Large particles which may resist digestion are gradually moved forward towards the mid-gut opening. Sometimes twisted strings of portions of tough muscle tis- sue are found in the stomach and these will eventually be rejected via the mid-gut. The ciliation around the duct vestibules directs currents away from the duct openings. There is a swirling counter- current set up in the vestibule. There is a confluence of 5 or 7 ducts in the posterior vestibule. A similar number enter the elongated anterior vestibule. The stomach narrows anteriorly, and at the point where the left rejectory groove joins the right rejectory groove the major typhlosole arises (Figure 5). The major typhlo- sole enters the mid-gut and within a short space is reduced in size to a small ridge which is only slightly larger than the other longitudinal ridges which line the mid-gut. There is no vestige of a style sac region. The relatively fea- tureless stomach is consistent with Fretter and Graham’s descriptions of the gastric morphology of carnivorous mesogastropods (FRETTER & GRAHAM, 1962). At the point where the mid-gut reaches the anterior edge of the digestive diverticula it takes a right angle turn to the right (Figure 1) and the internal morphology changes. The longitudinal ridges break up into irregular rectangular protrusions. This hind-gut region bends ante- riorly to enter the mantle region, and expands to form a large rectum. The anus opens at the right side of the mantle cavity. HISTOLOGY Oesophageal Gland: Figure 2a shows a cross-section of the oesophageal region of the gland at its widest point (cf. Figure 3). The lumen of the oesophageal groove can be seen to be continuous with the lumen of the gland itself. Two large diagonally ridged typhlosoles with ciliated epi- thelia project into the oesophageal groove from the dorsal and ventral surfaces. These are homologous to the dorsal folds described by FRETTER & GRAHAM (1962) for meso- gastropods. Laterally the epithelium is also ciliated although more finely ridged. Interspersed through the epi- thelia are cells which stain positively with alcian blue indi- cating that they are mucus-secreting cells. The distal sur- face of the dorsal typhlosole is composed entirely of large mucocytes which bear no cilia (Figure 2a). THE VELIGER Vol. 23; No. 1 The transverse folds of the gland itself (Figure 2b) are made up of a fine network of cells and are cut by canals radiating from the oesophageal region. The network is composed of a thin mesh of connective tissue supporting a single layer of epithelial cells. These cells contain large nuclei. Mucocytes and ciliated cells are interspersed throughout the gland but are most abundant lining the mouths of the large canals as they empty into the oeso- phageal groove. Anterior to the entrance of the oesophagus the ventrally placed white tissue anastomoses with the brown tissue (Figures 2c & d). White tissue cells differ markedly from brown tissue cells in having a diffusely granulated appear- ance. Small granules can be seen breaking off the tips of the white tissue cells into the lumen of the gland. The digestive diverticula (Figure 2c) are composed of many small digestive tubes leading into larger more densely staining tubules. The inner epithelia of these ducts are folded and bear cilia. The stomach epithelium is thrown into large folds. The cells are large, columnar cells fringed with cilia. Histochemical Survey Esterase, acid and alkaline phosphatases and leucine aminopeptidases (LAP) are found in stomach epithelium, digestive diverticula and the brown tissue of the oesophag- eal gland. The white tissue of the oesophageal gland showed only weak LAP activity. Figure 2f shows a cross-section of fresh-frozen oeso- phageal tissue stained for LAP. The enzyme present in the brown tissue cells is concentrated around the distal edges of the cells. Phosphatases are present in the same location. Positive staining for esterase in both the oesophageal gland and the digestive diverticula occurs throughout the cells and tissues. In the digestive diverticula positive staining for LAP and phosphatases is seen in the epithelium of both the large and small tubules. Enzymes in the stomach epithe- lium are concentrated along the distal edges of the cells. Figure 2g shows stomach epithelium stained for alkaline phosphatase. Electrophoretic Survey Figure 6 shows the results of the electrophoretic survey. The relative clarity and strength of the enzyme bands or zymograms is indicated by stippling. Vol. 23; No. 1 B a B b ZZZZZa ZZZZZA ZzZZ (ZZZ7Z7Z (27777) 0g 8) dd og g] dd B c B d (ZZZZ2Z\ (ZZZZZ) (ZZZZZ) aaere (ZZZZZ) (ZZ7ZZ) WZZZZ) WZZZ7Za ZZZZZD UZZZZ2. CLZZZD ZZZZZI WZZZZA YZZZZD LZZZZA WZZZZZa ~CZZZ7Z7D 77777 (ZZZZZA I W777 wy7 i! mates og gj dd og 8) dd Figure 6 Zymograms showing distribution of digestive enzymes of Polinices lewisii as separated by electrophoresis. og — oesophageal gland gj — gastric juice diverticula I — point of insertion of extracts of moving boundary at termination of run (a) — acid phosphatase (b) — alkaline phosphatase (c) — esterase (d) — proteinase dd — digestive B — position Phosphatase: In the oesophageal gland there are 4 phos- phatases operating at an acid pH. In the alkaline range these same 4 bands are present as well as one more, faster running band. The gastric juice has 2 bands corresponding to the slowest two of the oesophageal gland in both the acid and alkaline range. The slowest moving band is also present in the digestive diverticula. Esterase: There are 5, esterases in the oesophageal gland. The prominent fast-moving band is seen in the digestive diverticula but not the gastric juice. The next four bands correspond to similar bands in the gastric juice and diges- THE VELIGER Page 31 tive diverticula. There is one slow-moving band found in the gastric juice and digestive diverticula which does not occur in the oesophageal gland. Protease: There are 4 strong proteases found in the gastric juice. Two faint, fast-moving bands which are seen in the oesophageal gland do not appear to correspond to any of the gastric juice zymograms. No enzyme bands are produced by the digestive diverticula. Quantitative Assays Carbohydrases a—Amylase activity: over a 60 minute incubation pe- riod amylases in the gastric juice showed a 16% substrate hydrolysis compared to 21% in the oesophageal gland and 79% hydrolysis in the digestive diverticula. Maltase (a—glucosidase) activity: The oesophageal gland extract has the greatest maltase activity, liberating 135.8 mg/mL glucose per minute. The digestive diver- ticula showed substantially less activity with 48.3 mg/mL glucose released per minute. The gastric juice showed low- est activity, releasing 28.3 mg/mL glucose per minute. Lipases The oesophageal gland showed no evidence of lipase ac- tivity. The gastric juice showed 0.8% hydrolysis of the substrate after 30 minutes. There was no further change after 60 minutes. The digestive diverticula exhibited sim- ilarly weak lipolytic activity with 1.1% hydrolysis after 60 minutes of incubation. Proteinases The pH profiles for albumin digestion by the three ex- tracts are seen in Figure 7. Both the oesophageal gland and digestive diverticula extracts show high activity peaks at about pH 2.3. The digestive diverticula extract has another major peak at pH 6.0 then tapers off in the alkaline range. The oesophageal gland extract shows lesser peaks occur- ring at pH 3.8, 4.6, and 6.6 with activity plateauing in the pH 7.8-9.2 range. In the gastric juice the bulk of proteo- lytic activity occurs in the alkaline range with major peaks at pH 7.6 and 8.4. Smaller peaks occur at pH 3.2 and 4.4. If these results are adjusted according to the weight to volume ratios of the oesophageal gland, stomach and digestive diverticula, as noted above in “Materials and Page 32 @ gastric juice A digestive diverticula 20 Bl cesophageal gland ee units/ml or g dry wt/min Activity Figure 7 The effect of pH on the digestion of albumin by digestive tract extracts at 37°C Methods,” the overall proteolytic activity of the digestive diverticula would appear to be seven times that of the oesophageal gland. This does not, however, take into ac- count the fact that the apparently inert white tissue of the oesophageal gland can be experimentally activated to pro- duce high levels of proteolysis. The results of protease activation in the oesophageal white tissue are shown in the histogram in Figure 8. Un- activated white tissue exhibited no proteolytic activity whatsoever. Self-activated extract showed slight activity; 4.2 units/g dry weight/minute. Extract activated with trypsin showed relatively high activity at 48.3 units/g dry weight/minute. ; THE VELIGER Vol. 23; No. 1 50 n (st) > fo} (oe) (o} Activity units g dry wt/min ° ua sa t ta Figure 8 Digestion of albumin by oesophageal gland white tissue extract at pH 6.5 and 37°C. ua — unactivated sa — self-activated ta — trypsin activated t — digestion of albumin by 1% trypsin NOTE on FEEDING One of the prey types most frequently seen under attack by Polinices were small specimens of Tresus nuttalli (Conrad, 1853). These were not bored but were being eaten at the siphon base or at the ventral mantle edge. The gape in this species is such that preparatory boring of the prey is not necessary. The region of the prey which was being eaten had a soft “pre-digested’” appearance. In one specimen of Polinices which had an unusually full stomach the proportion of white tissue in the oeso- phageal gland was noted to be much reduced. DISCUSSION Polinices lewisit has the ability to digest a variety of sub- strates. Although enzyme production occurs to some extent in all 3 sites examined, the digestive diverticula, due to their large size constitute the most significant digestive organ. This study has shown, however, that the oesophag- eal gland and to a lesser extent the gastric epithelium also make important contributions to digestion in Polinices. Vol. 23; No. 1 Of the enzymes assayed for, lipase activity alone appears to be so low as to be insignificant in a digestive role. This is not surprising since bivalves, the main food source of Polinices, store food reserved mainly in the form of glyco- gen. This was noted by Bernarp as early as 1850 and more recently by LANE et al. (1952) who reported 50% of the dry weight of Teredo pedicillata to be stored glycogen. Polinices has a correspondingly high carbohydrase activ- ity. The major site of amylase production is the digestive diverticula. This has also been noted by KrisTENSEN (1972) for the neogastropod Nassarius reticulatus. Per unit weight, the oesophageal gland secretes the greatest amount of a-glucosidases. Although maltase se- cretion in the foregut would seem inappropriately placed in terms of overall carbohydrate digestion, the occurrence of such glands in this region is not unusual in Mollusca. In Cryptochiton stellert the posterior salivary glands or “sugar glands” secrete large volumes of maltase (MEEUSE & FLEUGEL, 1958). As might be expected in a carnivorous animal, proteo- lytic enzymes are found throughout the digestive tract. The capacity for protein digestion in the digestive diver- ticula is amply illustrated. The activity in the acid pH range suggests that cathepsins are responsible for most of the proteolytic activity of the digestive diverticula. Peaks at around pH 2 and pH 6 probably represent the action of cathepsins D and B respectively. Rem & RAUCHERT (1976) concluded that cathepsin D found intracellularly in the digestive diverticula of Tresus has a non-digestive role. This is probably also true for gastropods. Alkaline proteases in the gastric juice are probably of the tryptic type. These enzymes conceivably originate from both the oesophageal gland and the digestive diverticula. Histochemical evidence of membrane associate LAP indi- cates that some protein digestion in the stomach is from enzymes derived from or attached to the gastric epi- thelium. Unactivated extracts of whole oesophageal gland show cathepsin and alkaline protease activity. However, it is the enzymological role of the white tissue which is of greatest interest. The occurrence of inactive enzyme precursors as in the white tissue of the oesophageal gland is a phenom- enon which is virtually unknown in invertebrate digestion although Gisson « Drxon (1969) recorded the presence of a chymotrypsin-like zymogen activation mechanism in Metridium senile. The activity levels obtained experimen- tally by us for trypsin-activated white tissue are probably THE VELIGER Page 33 much lower than those produced naturally. This is be- cause of the loss of much zymogen granular material in our preparations. The ability to produce enzymes in an inactive form is useful if digestion is to occur at a distance from the site of enzyme production and secretions must pass through tis- sues unprotected from enzymatic action. This situation could occur if Polinices were secreting digestive enzymes or their precursors externally into the prey animal. The oesophageal gland is capable of a muscular contraction which would provide a means for moving secretions through the oesophagus against ciliary currents. Partial digestion would soften food material for ingestion. The softened condition of some prey gives some confirmation of this hypothesis. The ciliary mixing of food particles and enzyme secre- tions within the lumen of the oesophageal gland itself would facilitate further digestion. The large size of the gland and the large amount of surface area available pre- sent the possibility that a major function of the oesopha- geal gland is absorption. As mentioned earlier, the oesophageal gland of the mesogastropods is of an intermediate complexity. How- ever, nowhere in the literature is there mention of a proso- branch oesophageal gland which is composed of two such distinct tissue types as is the case in Polinices. The cyto- plasm of the white tissue cells has a granular appearance, probably due to the presence of zymogen granules. These cells bear a close resemblance to cells of the gland of Leib- lein found in neogastropods (FRETTER & GRAHAM, 1962) while the brown tissue resembles typical cells seen in the more “primitive” prosobranchs. It is possible that the oesophageal gland of Polinices represents a transitional stage between the alternating ciliated and secretory cells of the “lateral pouch” of lower prosobranchs and the ex- clusively secretory tissue of the neogastropod’s gland of Leiblein. In conclusion, the oesophageal gland of the moon snail Polinices has a major role in the digestive physiology of the species. It may have a supplementary role in absorp- tion and intracellular digestion. It is differentiated ante- riorly into a tissue which specializes in the secretion of a masked proteinase precursor. A number of circumstantial points of evidence permit the inference that the role of the oesophageal gland proteinases is extra-organismic pre- digestion of food to facilitate its ingestion. These enzymes would also contribute to the gastric digestive process. Page 34 THE VELIGER Vol. 23; No. 1 3 - KrisTENnsEN, J. HyLLEBERG Literature Cited 1972. | Carbohydrases of some marine invertebrates with notes on their food and on the natural occurrence of the carbohydrates studied. Mar. Biol. 14 (2): 130-142 (May 1972) Brrwaap, C. Kunitz, M. 1850. Sur une nouvelle fonction du foie chez homme et les animaux. Compt. rend. Acad. Sci. $1: 571-574 Bernarp, Frank R. « J. W. BacsHaw 1969. Histology and fine structure of the accessory boring organ of Polintces lewisit (Gastropoda, Prosobranchiata). Journ. Fish. Res. Brd. Canada 26: 1451 - 1457 BgRNFELD, PETER 3955. Amylases, @ and f. In: Methods in Enzymology; S. P Colowick & N. O. Kaplan, eds., vol. 1; 149-154. Acad. Press New York Pautrer, Vera & ALastam GRAHAM 1962. British prosobranch molluscs, their functional anatomy and eco- logy. London, Ray Soc. xvi+755 pp.; 316 figs. Grsson, D. « G. H. Drxon 1969. | Chymotrypsin-like proteases from the sea anemone Metridium senile. Nature 222 (5195): 753-756 (24 May 1969) Himscn, Gotrwart Cur. 1915. Die Ernahrungsbiologie fleischfressender Gastropoden. Zool. Jahrb. Abt. allgem. Zool. Physiol. 35: 291 - 310 Rep, Roszrt G. B. 1947. Crystalline soybean trypsin inhibitor - II. General properties. Journ. Gener. Physiol. 5: 263 - 274 Lang, C. E., G. S. Posner & L. J. GREENFIELD 1952. The distribution of glycogen in the shipworm, Teredo (Lyrodus) pedicellata Quatrefages. Bull. Mar. Sci. Gulf and Caribb. 2: 385 - 392 Mzeusgz, J. D. & W. FLEuGEL 1958. Carbohydrate-digesting enzymes in the sugar gland juice of Cryptochiton stelleri Middendorff (Polyplacophora, Mollusca). Arch. Neerl. Zool. 13: 301 - 313 Norturup, Joun H. 1923. The mechanism of the influence of acids and alkalies of the digestion of proteins by pepsin or trypsin. Journ. Gen. Physiol. 5: 263 - 274 (21 September 1922) Owen, GarETH 1966. Digestion. In: Physiology of Mollusca. Karl M. Wilbur & C. M. Yonge, eds. Acad. Press, New York & London: 53-96; 8 figs. Pzarsz, ANTHONY Guy EVERSON 1968. Histochemistry, Theoretical and Applied. vol. 1, 3™ ed.; Chur- chill, London, 759 pp. 1966. Digestive tract enzymes in the bivalves Lima hians Gmelin and Myz arenaria L. Journ. Comp. Biochem. Physiol. 17: 417 - 438 (5 July 1966) Rem, Rosert G. B. « KatHy RaucHERT 1972. Protein digestion in members of the genus Macoma (Mollusca: Bivalvia). Comp. Biochem. Physiol. 41A: 887 - 895 1976. | Catheptic endopeptidases and protein digestion in the horse clam Tresus capax (Gould). Comp. Biochem. Physiol. 54B: 467 - 472 Vol. 23; No. 1 THE VELIGER Page 35 The Ultrastructure and Mineralogy of the Dart from Philomycus carolinianus (Pulmonata : Gastropoda ) with a Brief Survey of the Occurrence of Darts in Land Snails ALEX S. TOMPA Division of Molluscs, University of Michigan, Ann Arbor, Michigan 48109 (1 Plate; 2 Text figures) INTRODUCTION IT Is FAIRLY COMMON knowledge to students of inverte- brates that during dissection of the surprisingly complex reproductive system of the land snail Helix, one even- tually uncovers a pouch called the dart sac which almost invariably contains a fairly long calcified spear about 1 cm long. It is hard, brittle, white, and appears to be made of some form of calcium. It can be characterized as a long, hollow cone with a very sharp point. It sports 4 equally sharp-looking blades along the length of the shaft. While it is generally acknowledged to be a reproductive struc- ture, its function and method of use are shrouded in mys- tery (i.¢., ignorance). For example, many general texts dealing with Helix mating refer to dart “shooting” behav- ior and the issue of whether this sharp dart was ever forcefully catapulted through the air to pierce the partner was not clear to many early malacologists. Although the term dart “shooting” is still regularly used, we now know that the dart is not propelled but is pushed and thrust against the body of a mating partner and eventually winds up (usually) penetrating the body wall, especially on the right side of the recipient’s foot. Since Helix is a simul- taneous hermaphrodite, both members of the mating cou- ple stab each other with the dart at approximately the same time. What is totally enigmatic is the purpose of this struc- ture during the lengthy (almost a day long) mating ritual of the snails. Current theories either lack critical support- ing facts or suggest a lack of any function for the dart. This is discussed in the last sections of this paper. The existence of darts in certain snails of the family Helicidae has been known and documented since more than one hundred years ago, especially for the snails found in England and Germany (AsHrorp, 1883, etc.). The dart goes by several synonyms in the literature, including gyp- sobelum, hasta amatoria, dard, Liebespfeil, spiculum amoris, telum veneris, or most commonly, the love dart. Most people who assign some functional significance to this structure deal with the general realm of an “excitatory structure.” For land pulmonate snails, there are two basic types of excitatory structures (TayLor, 1894-1914), 1) the sarcobelum, defined as a fleshy and (often) erectile appendage arising from the area of the penis, capped with a hard, sharp tip in only a few cases, and 9) the gyp- sobelum or dart, which is a sharp, hard, usually calcified structure, often arising from the female side of the repro- ductive system, usually piercing the mating partner’s body during some stage of the courtship. Taytor (op. cit.) fur- ther subdivides the class gypsobelum into 4 types on the basis of the presence or absence of blades on the shaft, or on the number of blades possessed if present (see Discus- sion, and inset of Figure 5). Surprisingly, we still do not even know which families of land snails possess darts; no extensive list has been at- tempted. Major works on darts, such as those by ASHFORD (1883) or HunT (1979) mention only the families Helici- dae, Ariophantidae and Zonitidae as possessing them. For Page 36 this reason, I have searched the literature and compiled a much more comprehensive list (Table 1). If we are to have Table 1 Families of Land Pulmonates in which Darts occur 1. Helicidae 6. Helicellidae 2. Zonitidae 7. Helminthoglyptidae 3. Philomycidae 8. Bradybaenidae 4. Ariophantidae g. Parmarionidae 5. Urocyclidae 10. Vitrinidae ¥1. Valloniidae? ' any idea of the function of the dart, we must first know which snails possess them and then see what is different about reproduction and courtship in these snails possess- ing darts. We hardly even know how the dart is formed, of what types of chemicals and minerals it is composed, etc. (but see HuNT, 1979; PRENANT, 1930, for the latest infor- mation). And of course, almost all of the known work is based on the common European garden snails, Helix (H. aspersa, H. pomatia). For this paper, it was decided to examine the structure, composition and biology of the dart of an entirely different snail, the North American slug Philomycus carolinianus. This is one of the very few North American snails to possess a dart, and its biology appears substan- tially different from that of Helix. Therefore, from its study we may get a better idea of what a dart is or is not, and how an animal can evolve different ways of using darts. The most striking difference between Philomycus and Helix is that the former does not lose or detach the dart during mating, but retracts it after the appropriate use and presumably uses the same dart in all subsequent matings. Helix, of course, generally loses its dart during mating and takes about one week (at room temperature) to regenerate it, during which time it is recalcitrant to mating. Another interesting point about Philomycus is that it elaborates a rather massive dart, using a lot of cal- cium, yet it is a slug lacking any external shell (7.¢.,it is less dependent on calcium in the environment), though it may ' Watson (1920) states that Astrorn’s (1883) record of darts in Vallonia is taken from very old literature. Neither Watson nor STEENBERG (1917) could confirm the existence of darts in Vallonia pulchella and several species of Acanthinula. Asu- ForD himself (1883) specifically stated that this record was sub- ject to confirmation or correction. THE VELIGER Vol. 23; No. 1 or may not have a very thin, vestigial internal shell (see Pirssry, 1948 and Crapp, 1919 for the controversy about presence of an internal shell). The family Philomycidae is a group of slugs of North America, China, Japan and Java; they are aulacopod. The mantle covers the entire back of the animal. This family may have been an early branching from endodontid stock, which also gave rise to the large arionid group of slugs (Pirspry, 1948). The American genera include Philomycus and Pallifera. Philomycus differs not only from Pallifera, but from all other philomycids in possessing the aforementioned calcified dart. It is contained in a dart sac, a diverticulum of the vagina. This dart and its sac were first described by Lemy (1842) when this genus was still known as Tebennophorus. Pitspry (1948) states that this dart is not homologous with that of the Helicidae. MATERIAL ann METHODS Animals for this work were obtained over several years from near Ann Arbor, Michigan. The snails were kept in plastic containers with wet bark and fed mushrooms; their general good health in captivity is suggested by the fact that several snails laid eggs. For the isolation of darts, the reproductive system was dissected from freshly drowned specimens, then placed into a solution of Clorox (5.25% sodium hypochlorite), which. dissolves all organic matter but leaves calcified structures intact. Darts isolated by this method, from slugs both small and large, were then removed from the Clorox, rinsed quickly in distilled water and air-dried. Specimens for electron microscopy were mounted with silver paint on aluminum stubs, then coated with a thin layer of gold metal, and examined at 15kV ina JEOL JSM U-3 scan- ning electron microscope. In order to determine the min- eral composition of the darts, specimens were ground gently into a fine powder and examined with CuK: radia- tion with a Ni filter, at 35 kV, 15 mA, for 3-6 hours with an 11.5cm diameter Debye-Scherrer camera loaded with Kodak Medical X-ray Film in the Straumanis way. Line positions were measured and the material was identified by the Hanawalt method, using ASTM cards and spe- cially prepared calcium carbonate standards of calcite and aragonite (see Tompa, 1976a for details). For an examination of the presence of an organic matrix within the dart, individual, unfixed darts were placed into a solution of 1% Alcian Blue 8 GX in 3% acetic acid; a blue-green coloration detects general acid mucopolysac- charides (PEARSE, 1968) at the same time decalcifying the entire dart. Vol. 23; No. 1 RESULTS In Philomycus, there was no significant variation in intra- species dart morphology except those differences which can be explained by dart growth. From a large series of slugs whose darts were examined, a plate was constructed to suggest the probable changes during dart growth and maturation (Figures 1-4). These results indicate that be- sides size changes, the major differentiation of a fully grown dart occurs in its increased area of attachment to the dart sac base. Thus, the least mature dart (Figure 1) has a basically unmodified posterior section while the old- est and most complex gypsobelum has a large, wide area like the head of a thumbtack at the site of tissue insertion and anchorage (Figure 4). What are presumed to be inter- mediate stages are illustrated by Figures 2, 3 (see also Figure 6). From these micrographs, it is immediately apparent that the Philomycus dart is really sharp only at the most anterior part, at the very tip. This suggests that during mating the slugs use darts to affect only minimal tissue penetration, probably to the level of the arrow in Figure 2; then the dart is presumably withdrawn to be used again on another occasion. From the mineralogical examination by x-ray diffrac- tion studies, it was found that the dart is made of calcium carbonate, exclusively in the form of aragonite (better than a 5% detection level). This result is consistent with the finding that Helix darts are also aragonitic (PRENANT, 1930; Hunt, 1979; Tompa, unpublished). The body shell of those land snails is also made of aragonite but the egg shells of land snails are made of the calcite polymorph (Tompa, 1976a). While direct access to darts of other snails, in good con- dition, was not possible, the literature was surveyed to find 1) which families of land snails possess darts, and 2) what is the general range of shapes and forms en- countered. The short table presented (Table 1) indicates what is probably a reasonably complete account of the families of snails bearing darts. The reason for this pres- entation is the fact that there is no single source where such an extensive compilation can be found. Most workers, e.g. ASHForD (1883) or Hunt (1979) cite only the Helici- dae, Zonitidae and Ariophantidae; other pertinent ex- amples are clearly not evident to general readers of mol- luscan literature. There occur cases where calcified structures are indeed found in the terminal genital regions, but they are penial spines rather than darts. The former would function in holding fast (the mating couple) whereas the latter is for THE VELIGER Page 37 piercing and penetrating the partner’s body. As there are more than 60 families of land pulmonate snails according to classifications such as TAYLOR & SOHL (1962), it can be seen that most families of snails lack this calcified acces- sory reproductive organ. An examination of the literature on the reproductive anatomy of snails reveals that darts come in a fairly wide variety of shape, form and size and that the number of darts contained in an animal also varies. Figure 5 presents a sample of the variety of darts encountered in land snails, showing either a lateral view, a cross-section, or both. The drawings are not arranged in any specific order, taxo- nomic or otherwise. For a comparison of how much detail is missing in such line drawings, compare the scanning electron micrographs of Figures 1-4 with the equivalent drawing, Figure 5: 3e, for Philomycus carolinianus. What all of these darts have in common is that they are all hard structures, in the shape of an elongated, hollow cone, with a sharp anterior tip suitable for penetrating soft tissues. The inset on the right side of Figure 5 shows cross- sections of the four major forms on which darts are built. From top to bottom, using TayLor’s (1894-1914) termi- nology, they are: haplostyla, which is a rod with no blades; dispathostyla, which has 2 blades; tetraspathostyla, with 4 blades; and heterospathostyla, which has 8 lateral blades. All the darts shown in the rest of Figure 5 can be derived from these 4 basic types. Because Philomycus slugs apparently do not shed their darts, it was thought worthwhile to see if larger slugs have larger darts, or instead, if all slugs have the same sized darts. From one collection locality, 7 Philomycus slugs of different sizes were taken (they are rarely found in larger aggregations). They were all found near each other, and were then uniformly drowned in Nembutal-containing water overnight, and fixed in 70% ethanol with 2% propylene phenoxytol and 5% glycerol. By this means, variables such as most recent access to food, degree of hydration, effects of relaxation and fixation (on size) were kept as constant as possible. The slugs were measured in terms of maximum body length and weight, then the darts were dissected out and their lengths were measured. In this series of animals, the body sizes range from 2.2cm long (1.0 gm wet fixed weight) to 5.3 cm long (6.2 gm wet fixed weight). The relationship of dart length as a function of total body length is demonstrated in Figure 6. Although the sample size is not large, the immediately apparent increase of dart length with increasing body size is significant (r=0.89; p 15g) slugs, which showed no significant differ- ence within size classes with respect to the presence of a caudal mucus plug: X* = 0.301, p > 0.05, df = 2. Animal size, however, is highly correlated with plug size, larger individuals being consistently characterized by larger plugs: X* = 20.01, p< 0.001, df = 4. Overall wetness was unrelated to plug presence or size, as demonstrated by X? comparisons on rainy and dry days: X* = 1.37, p > 0.05, df = 2. However, more fir needles, leaf tissue, dirt, and other detritus were attached to the mucus plug on cool dry days, suggesting that the plug is stickier under these conditions. These field observations and comparisons establish the fact that the caudal mucus is a common appendage of Ariolimax. A review of the literature and additional field and laboratory observations indicate that this mucus may play a role in movement, reproduction, defense against predators, and nutrition. MoveEMENT My field observations appear to be the first documen- tation of arionid use of caudal mucus for descent from vegetation (Figure 2). Ariolimax columbianus lowers itself from trees and shrubs by using its weight to stretch the elastic caudal mucus plug into a long thin strand until the footsole is attached to an accessible substrate. Once estab- lished, the slug crawls away and the strand breaks. Strands up to 1.75m have been measured in slugs weighing over 208. Mature slugs frequently bend Pteridium aquilinum (Linnaeus; Kuhn, 1879) and other succulent herbs towards the ground by their weight; the stretched mucus strand ensures that the stressed plant is not released before the slug is totally free and repositioned. Less often, the plug functions as a sticky anchoring point for the tail while the head is searching for a suitable substrate. REPRODUCTION Precopulatory behavior was observed in at least 5 pairs of slugs and revealed that the behavioral sequence in- cluded the mutual examination of caudal mucus and the aggressive slug partially or totally ingesting the caudal plug of the less aggressive mate. An unusually long pre- occupation with the caudal mucus during the exploratory slime-licking stage of several precopulatory pairs led to " mucus ingestion by one member of the pair. From my field observations, there is no doubt that pre- copulatory examination of the caudal and skin mucus plays an important role in premating courtship behavior of Ariolimax columbianus. Feeding on the skin mucus was always observed, whereas feeding on the caudal mucus was only occasionally observed in mating slugs. DEFENSE AGAINST PREDATORS The body slime of Limax maximus has been noted to repel predaceous beetles by fouling their mouth parts (RoLLo, 1978). Body slime of Ariolimax columbianus is also distasteful to predators, but it is apparent from ex- periments that the fouling function of the caudal plug is of greater significance. Feeding experiments demonstrate that caudal plug mucus deters shrews. In 10 feeding trials, Sorex obscurus and S. vagrans discontinued attacks on 8 and S. trowbridgii on 7 slugs. All shrews spent at least 5 to Tue VELIcER, Vol. 23, No. 1 [RicHTER] Figures 7 and 2 Figure 1 Location and characteristics of the caudal mucus plug of Ariolimax columbianus Figure 2 Caudal mucus function in descent from vegetation (notice the elastic nature of the mucus) Vol. 23; No. 1 60 minutes attempting to dislodge stuck portions of plug (often mixed with litter and dirt) from mouth, face, and feet, thus permitting the attacked slug to escape. Attacks on control slugs without plugs were successful in all cases, with the exception of two trials using S. obscurus and S. vagrans. Large size (> 14.5 g) may have protected the slugs from attack in these cases. From these and other observations using larger slugs, it appears that Arzolimax may achieve a size above which it is no longer vulnerable to shrew attack. Neurotrichus gibbsi, the shrew-mole, was unsuccessful only once in attacks on slugs with plugs, suggesting that the caudal mucus does not play a significant role in defense against N. gibbsi. This relatively large animal readily at- tacked slugs, and it is apparent that slugs of all sizes are easy prey. I have observed several predaceous ground beetles (Carabus sp.) and slugs (e. g., Limax maximus) attack Artolimax columbianus at the tail. The sticky caudal mucus is a highly effective defense against beetle attacks, fouling the mouth, mandibles, and tarsi. Antagonistic slugs such as L. maximus frequently bite off and eat the caudal mucus plug, thus allowing Ariolimax to escape. NuTRITION Although no attempt was made to specifically quantify the potential food value of the caudal mucus, my observa- tions indicate that a small but significant percentage of a- riolimacids feed on the plug. It remains uncertain whether the plug was eaten to remove adhering detritus or whether it was consumed to supplement the diet. My documenta- tion of instances in which the total plug was eaten indicate that 5% of all feeding observations involved slugs that had totally ingested their own caudal mucus. Because most plugs in these cases lacked detritus and since no subse- quent mating attempts were observed, feeding on these plugs suggests a nutritional function. DISCUSSION Selection for caudal mucus production in Ariolimax columbianus may occur for multifarious reasons, most im- portant of which may be movement, reproduction, defense against predators, and nutrition. While descent and repro- ductive functions are similar to those postulated for the pedal mucus (Barr, 1926; Pitssry, 1948; Quick, 1960), the conspicuous plug formed by the caudal gland is unique in location and texture and exhibits additional uses not observed for the pedal mucus. THE VELIGER Page 45 The elastic properties of caudal mucus aid arboreal Ariolimax columbianus to descend from vegetation and maneuver among plants. Although Kew (1902) regarded thread spinning as an accidental circumstance arising from locomotor needs and the result of a continuous supply of pedal mucus, my observations show the thread derived from caudal mucus of Ariolimax to be highly functional. Clearly, it is an asset to an arboreal existence because it enables slugs to lower themselves from great heights. Con- trary to Kew (op. cit.), who had often seen A. columbianus drop from trees and noted that injury as a result of drop- ping was infrequent, I have seen few slugs drop, and in fact have observed that slugs are reluctant to “let go,” even after considerable harassment, suggesting that drop- ping injuries for this arboreal species may be significant. Both Richter (unpublished observations) and Rollo (per- sonal communication) have noted that injury from pred- ators and other slugs can be a major contributor to death. Because of their soft moist skin and high water content, injured slugs quickly succumb to infection and disease. In Ariolimax columbianus, a reproductive function of the caudal mucus appears to exist, although the method by which it operates is undetermined. The fact that ario- limacids intensively investigate and sometimes eat the caudal mucus of prospective mates during courtship strongly suggests that plug chemistry may be a valuable indicator of reproductive condition and responsiveness. NEWELL (1966) postulated that a pheromone is secreted into the pedal mucus when a slug becomes responsive to mating, and Roto (1978) suggests that pheromones may be localized within feces and are associated with slug hom- ing behavior. Pheromone secretion and storage may also be a function of the caudal gland and mucus. The tenacious characteristics of the caudal mucus and its dorsal-distal location appear to have evolved in re- sponse to predators which capture slugs by scenting along the mucus trail and attacking the tail. This hunting strat- egy was observed by TERRY (1974) and Richter (see above) in shrews (Sorex sp.); by HAND & INGRAM (1950) in snakes (Thamnophis ordinoides, Baird and Girard, 1852); by Richter (unpublished observations) in salamanders (Dicamptodon ensatus Eschscholtz, 1833); by Richter (unpublished observations), Russell (personal communica- tion), RoLLo (1978), GREENE (1975), and Hanp & INGRAM (op. cit.) in insects (¢.g., Scaphinotus sp. and Carabus sp.); and by Hanp & INcRam (op. cit.) in the mollusk Haplo- trema minimum (Ancey, 1888). However, the caudal mucus of Ariolimax, in conjunction with the rapid and large secretion of body mucus, is only sometimes effective against these predators. Page 46 Hanp & INGRAM (1950) observed that garter snakes, predatory snails, and beetles attack and eat Prophysaon slugs from the posterior and hypothesized that this species self-amputates the tail to temporarily feed the predator while the slug escapes. Ariolimax columbianus, although also an arionid, does not exhibit a self-amputating tail, but rather has the ability to repel attacks by using its caudal mucus to foul the mouth parts, temporarily feed, or otherwise occupy the predator. GREENE (1975), for ex- ample, has observed larva of Scaphinotus regularis (Le Conte, 1868) attacking and masticating the defensive plug of snails, thus allowing snails to escape. Presumably, in Artolimax the plug is an adaptation in response to similar predator pressure. Considering that slugs and snails are, percentagewise, the most important food item of the com- mon western shrew (Sorex pacificus Coues, 1877), and the second most important item in the diets of four others (S. trowbrid git; S. vagrans; Sorex yaquinae Jackson, 1918; and Sorex bendirii Merriam, 1884) according to Wuit- AKER & MASER (1976), a sticky caudal plug could signif- icantly increase slug survival from these predators. In fact, this has been observed in laboratory experiments with 2 of the above species (see text). Of the slug-eating insects, the predaceous ground beetles (Carabidae) and the glow-worms/fireflies (Lampyridae) are the most voracious. INGRAM (1946) observed that Scaphinotus interruptus (Ménétriés, 1844) typically attack Deroceras agreste L. (reticulatum Miller, 1774) and Milax gagetes (Draparnaud ; Lovett and Black, 1920) along the head and mantle, whereas Russell (unpublished paper) observed that Scaphinotus marginatus (Fischer, 1822) attacks Prophysaon sp. at both the anterior and posterior ends, depending on whether or not the prey was approached by tracking its slime trail. Against anterior attacks by beetles and glow-worms (small and uncommon lampyrids of the Pacific Northwest), the caudal mucus would be ineffective. Lampyrid larvae, for example, attack and inject a deadly toxin into the anterior nerve center, immobilizing and capturing slugs (ScHWALB, 1961) regard- less of slime and caudal plug defense. Little published information is available regarding the nutritional aspects of the caudal mucus. For Ariolimax columbianus, M. Denny (in RoL1o, 1978) found that the pedal mucus contained from 30% to 35% dry weight of protein concomitant with a 90% to 98% water content. Barr (1928) observed that lime granules were an impor- tant component of the plug of Avion ater and concentra- tions of granules in the caudal mucus of Ariolimax may exist. WILson (1968) determined that the mucus of the snail Lymnaea trunculata (Miiller, 1774) contained in- organic sodium and potassium ions, free glucose, 16 amino acids, and free lipids. THE VELIGER Vol. 23; No. 1 To what extent these compounds may occur in the caudal mucus of Ariolimax is unknown; nevertheless, if present, they may be of nutritional significance to slugs. Stresses for calcium do occur in molluscs (WILson & SALEUDDIN, 1974), especially when environmental sources are inadequate or at periods of high demand (e.g., during egg production). Feeding on the caudal plug immediately prior to copulation may thus have a joint nutritional and reproductive function, and the frequent observations of this occurrence in the literature (ADAMS, 1910; Barr, 1928; LaNctois, 1965; TayLor in STEPHENSON, 1968; Roo, 1978) suggest that this may be the case. The most intriguing aspect of this study has been the variety of actual and potential uses of caudal mucus ex- hibited by Artolimax columbianus. The present study has shown the importance of the caudal mucus in defense against predators and in descent from vegetation. Its role in nutrition and reproduction remains undetermined. Bio- chemical studies on plug nutritional composition (in rela- tion to available diet and physiological needs) and caudal plug gland characteristics (with respect to pheromones) in context of sexual development are necessary to elucidate the last two postulated roles. SUMMARY 1. The caudal mucus plug of Arolimax columbianus was characterized and investigated to determine its func- tion by field observations and laboratory experiments. 2. A conspicuous caudal mucus plug covers the caudal pit, regardless of slug size and environmental wetness. Plug size is also highly correlated with slug size. 3. Observations indicated that the caudal mucus plays an important role in defense against predators and in the slug’s arboreal existence. 4. The caudal mucus may provide nutrients and play a role in precopulatory behavior; however, no suppor- tive evidence presently exists. ACKNOWLEDGMENTS The author gratefully acknowledges Carol Terry for pro- viding shrews and shrew-moles and helping in early pre- dation experiments, and Dr. David Rollo for discussions regarding many aspects of slug behavior described in the text. Additionally, this paper has benefited from sugges- tions by John Dragavon, Dr. Richard Taber, and an anon- ymous reviewer. Mary Lou McDonald edited and pre- pared the manuscript. The work reported in this paper Vol. 23; No. 1 THE VELIGER Page 47 was supported in part by NSF Grant Number DEB 74-20744 AOA to the Coniferous Forest Biome Ecosystem Analysis Study. This is Contribution Number 353 from the Coniferous Forest Biome. Literature Cited ApaMs, LIoneEL E. 1910. Observations on the pairing of Arion ater L. 13 (4): 116-119: 6 figs. Barr. R, AILEEN Journ. Conch. (October 1910) 1926. Some observations on the pedal gland of Milax. Quart. Journ. microsc. Sci. 70: 647-667: 2 plts.: 11 figs. 1928. Some notes on the mucus and skin glands of Arion ater. Quart. Journ. microsc. Sci. 71: 503-525: 2 plts.: 5 text figs. Conover, W. J. 1971. Practical nonparametric statistics. New York; 462 pp.: 24 tables GREENE, ALBERT 1975. Biology of five species of Cychrini (Coleoptera: Carabidae) in the steppe region of southeastern Washington. Melanderia 19: 1 - 43; 3 figs.; 9 tables Hanp, Cavet H. & Wirtiam Marcus INGRAM 1950. Natural history observations on Prophysaon andersoni (J. G. Cooper), with special reference to amputation. Bull. Calif. Acad. Sci. 49: 15-28; 7 figs. (January-April 1950) INGRAM, Wittiam Marcus 1946. Mollusk food of the beetle Scaphinotus interruptus (Mén.) Bull. So. Calif: Acad. Sci. 45 (1): 34-36; 1 table Kew, H. Wat tis 1902. On the mucus-threads of land-slugs, Part II. 10: (5): 153-165; 7 figs. LANGLo!s, THomas H. 1965. The conjugal behavior of the introduced European giant gar- den slug, Limax maximus L., as observed on South Bass Island, Lake Erie. The Ohio Journ. Sci. 65: 298-304; 17 figs. (September 1965) NEWELL, P FE 1966. The nocturnal behavior of slugs. 146-159; 14 figs. John Wiley & Sons. Inc., Journ. Conch. Med. Biol. Illust. 16: Pirssry, Henry Auocustus 1948. Land Mollusca of North America (north of Mexico). Phila- delphia Acad. Sci. Monogr. 3, 2 (2): 521-1113; figs. 282 - 585 (19 March 1948) Quick, H. E, 1960. British slugs (Pulmonata: Testacellidae, Arionidae, Limacidae). Bull. Brit. Mus. (Nat. Hist.) (Zool) 6: 105-226; 2 plts. 19 figs.; 23 maps RicHTerR, Kraus O. 1976. The foraging ecology of the banana slug Ariolimax columbianus Gould, Arionidae. plts.; 32 figs.: 23 tables Roto, C. Davip 1978. The behavioral ecology of terrestrial slugs. Univ. British Columbia; 442 pp.; 65 figs.; 73 tables RunuHamM, Norman W. «& P J. Hunter 1970. Terrestrial slugs. Hutchinson Publ. London; 184 pp.; 57 figs.; 15 tables ScuHwats, Hans Hetmut 1961. Beitrage zur Biologie der einheimischen Lampyriden Lampyris noctiluca Geoffr. Analyse ihres Beutefang- und Sexualverhaltens. Zool. Jahrb. 88 (4): 399-550; 100 figs. STEPHENSON, J. W. 1968. A review of the biology and ecology of slugs of agricultural Ph. D. dissert. Univ. Washington; 228 pp.; 12 (December 1976) Ph. D. thesis, importance. Proc. Malacol. Soc. London 38: 169 - 178 Terry, Carou JAMES 1974. Ecological differentiation of three species of Sorex and Neuro- trichus gibbsi in western Washington. ton: 101 pp.; 7 figs.; 32 tables WHITAKER Jr., JOHN O. & Curis Maser 1976. Food habits of five western Oregon shrews. 50 (2): 102-107 WHITAKER Jr., JoHN O. & R. E. MumForp 1972. Food and ectoparasites of Indian shrews. 53 (2): 329-335 Witson, Cuan «A. S. M. SALEUDDIN 1974. Evidence that Otala lactea (Miiller) utilizes calcium from the Master’s thes., Univ. Washing- Northwest Sci. (May 1976) Journ. Mammal. shell. Proc. Malacol. Soc. London 41 (3): 195 - 200 Witson, R. A. 1968. An investigation into the mucus produced by Lymnaea trunca- tula, the snail host of Fasciola hepatica. Comp. Biochem. Physi- ol. 24: 629 - 633; 1 table Page 48 THE VELIGER Vol: 23S Nom Terrestrial Pulmonate Reproduction: Seasonal and Annual Variation and Environmental Factors in Helminthoglypta arrosa (Binney) (Pulmonata : Helicidae) KENNETH L. van ver LAAN Marine Science Institute, University of California, Santa Barbara, California 93106 and Bodega Marine Laboratory, University of California, Bodega Bay, California 94923 (1 Text figure) INTRODUCTION I REPORT HERE ON SEASONALITY in breeding, length of time between copulation and oviposition, length of time between oviposition and egg hatching, egg viability, and variation in reproductive rates in a population of the terrestrial pulmonate Helminthoglypta arrosa (Binney, 1855). I also consider the effects of water availability, food availability, and temperature on these aspects of repro- duction. The snail population inhabited a lupine scrub stand (Lupinus arboreus Sims) on Mussel Point, Bodega Head, Sonoma County, California (38°’20’ N, 123°04' W), about 104km north of San Francisco. Helminthoglypta arrosa (1) occurs along the north- central California coast (PirsBRY, 1939), (2) aestivates during annual dry periods from mid-spring to early autumn (VAN DER Laan, 1975b), and (3) terminates shell growth prior to reproductive maturity. The presence of a reflected shell lip indicates termination of growth: the adult phase. In four and one quarter years of field and laboratory observations (detailed below), snails with re- flected shell lips were the only individuals that copulated and oviposited. The sequence of breeding events in Helminthoglypta starts with copulation in the autumn at the end of long- term aestivation. Oviposition follows in the winter 40 to go days after copulation, and hatching occurs in early spring approximately 60 days after oviposition. I made no histo- logical examinations but presume that in Helmintho- glypta, as in other pulmonates (cf., DUNCAN, 1975), egg development precedes and embryogenesis follows ovipo- sition. Duration of embryogenesis for H. arrosa thus was assumed to be the time between oviposition and hatching. On the other hand, in the absence of histological examina- tions, I made no assumption about the duration of ovarian development. This is because fertilization can occur be- fore, or sometime after, copulation due to the fact that some pulmonates self-inseminate while others store sperm from another animal up to a year’s duration (DUNCAN, 1975): METHODS Field study of copulation. I estimated seasonality and frequency of copulation in 1968 and 1969 for Helmin- thoglypta by walking through the lupine scrub stand (hereafter: “study area”) and counting the number of adult snails and the number of snails copulating. I started each walk in late September prior to the time that copu- lation was first noted in 1966 and 1967. I continued the walks at least three weeks later than the last copulating snails were noted. Walks were conducted when snails were active: at night or during the day under conditions of overcast, fog, drizzle, or rain. Laboratory study on temperature effects. I examined the relationships between temperature and duration of em- bryogenesis and between temperature and the probability Vol. 23; No. 1 of hatching in laboratory experiments. Three egg masses of 63, 54, and 45 eggs were collected between 15 January and 4 March, 1969. I kept each third of each egg mass in the laboratory under constant temperatures of 4.4, 10.0, or 15.6° C. Periodically, hatched and unhatched eggs were counted. Hatchlings were removed upon discovery. Regular field collections and observations. Variations in the densities of snails and snail eggs were used to estimate variations in reproductive output, in seasonality of ovi- position and of egg hatching, and in duration of embryo- genesis. I estimated egg and snail densities every 6 weeks or less between March, 1966, and December, 1969. These densities were determined by hand sorting through the vegetation and the upper 8cm of soil at randomly selected quadrats. Neither snails nor eggs were found lower than 4cm below the leaf litter during the study. Quadrats were usually 40 in number and 642cm’ (see VAN DER Laan, 1971, for details). I gained additional information on reproduction in Helminthoglypta from regular field observations which I made at least weekly and usually semiweekly from March, 1966, to June, 1970. Environmental factors. ture, and food supply in the field were monitored. Pref- erences for particular plants as food were established in laboratory experiments and field observations (vAN DER LAAN, 1975a). The abundance of the preferred plants was estimated by recording the total length each plant inter- cepted along 1m at each quadrat in regular collections taken November, 1967, to December, 1969. Rainfall was collected in a standard rain gauge on Mussel Point and the amount recorded daily except for weekends. Ambient maximum and minimum tempera- tures 5cm above the soil surface were recorded at least four times per week from November, 1967, to January, 1970. Remarks on statistical treatment. rection was used for small sample sizes in the analyses of frequencies. Throughout I consider p < 0.05 to be signif- icant. More exact probabilities, where calculated, are reported. Variations in rainfall, tempera- Yates continuity cor- RESULTS Season and Duration of the Mating Season I observed Helminthoglypta copulating only in October and November and never at other times of the year in the THE VELIGER Page 49 field (Table 1). In contrast, in the four and one quarter years of my study, one pair of laboratory-maintained snails copulated in March, 1966. Table 1 Field observations of copulation: total number of adult snails observed and in copulo and percentage in copulo dur- ing the 1968 and 1969 mating seasons. For each year, no animals copulated prior to or after the dates shown below. Number of Number of snails adult snails Percentage Date in copulo observed in copulo 1968 October 11 2 134 1.4 October 12 0 191 0.0 October 22 0 195 0.0 November 1 0 222 0.0 November 2 0 246 0.0 November 5 2 199 1.0 x 4 1187 1969 October 8 14 217 6.4 October 10 0 190 0.0 October 14 2 232 0.9 November 2 5 201 P38) November 3 4 210 19 November 7 0 140 0.0 November 15 2 214 0.9 November 26 2 164 1.2 2} 29 1568 For the two years of my study I first noted copulating pairs on 11 October, 1968, and on 8 October in 1969. Onset of breeding was coincident with reactivation from long-term aestivation and occurred within 24 hours of the first October rainfall that thoroughly wetted the vege- tation and leaf litter. In contrast to this circumstance is that, after heavy rains in August and September of 1968, snails emerging from aestivation did not copulate but re- entered aestivation. I observed the last snails copulating on 5 November for 1968 and 26 November for 1969. I saw no snail in copulo in subsequent semi-weekly field obser- vations, which I continued into spring, nor in more intense 15 min. searches, which I continued until mid-January and which totaled 1272 snails and six and three-quarters Page 50 hrs. in 1968 and go snails and one and three-quarters hrs. in 1969. Frequency of Copulation In every instance, except one, I observed mutual copu- lation in Helminthoglypta. The mean percentage of adults in copulo was greater in 1969 compared to 1968 (Table 1). In both years the highest proportion of snails in copulo was observed within the first 24 hrs. following onset of the mating seasons (11 October, 1968; 8 October, 1969 (Table 1). The highest percentage of snails copulating 8 October, 1969, was significantly greater than for 11 October, 1968 (X? = 5.02, d.f.=1, p<0.05, n for 1968=140 snails, n for 1969 = 217). The density of food at the onset of the breeding season in 1969, which was the year of higher copulation fre- quencies, was greater than in 1968; however, this differ- ence was not significant (1.6% cover of food plants on 10 October, 1968 and 6.5% on 8 October, 1969, X* = 1.96, Chi == fin /)) 5 Os). Cumulative monthly rainfall in September and Octo- ber, 1969 (38.1 and 105.6mm), was also greater than in 1968 (5.1 and 53.3mm) and higher, although not signif- icantly so, than mean monthly rainfall for 1967 to 1977 (14.3 and 49.0mm). Rainfall for November, the end of the mating season, on the other hand, was lower in 1969 (48.3 mm) than in 1968 (203.0mm). Helminthoglypta was active at field temperatures above 4° C and in copulo only at ambient temperatures of 10 to 15°C at night or during the days when it was overcast, foggy, drizzling, or raining. When snails were active, they were just as likely to copulate during the day as dur- ing the night. Copulation rates during the night were not significantly different from rates during the day (Table 2). I also noted no significant correlations (Pearsons prod- uct-moment coefficient) of copulation frequencies with maximum or minimum temperature in the 24 hrs. pre- vious to the observation walks I took during the breeding seasons. Variations in Reproductive Output During my regular field collections I found 37 egg masses. Oviposition sites and sizes of eggs were in exact agreement with previously reported observations (INGRAM, 1947) for Helminthoglypta arrosa occurring on Point Reyes, approximately 22 km southeast of Mussel Point. In my study all egg masses were in shallow holes in the soil THE VELIGER Vol. 23; No. 1 Table 2 Percentage of adult snails in copulo during daylight and nighttime (n = total number of adult snails observed during the breeding season). Daylight Nighttime 1968 — x? = 0.01, d.f. = 1, p > 0.90 Percent 0.35 0.32 n 571 616 1969 — x? = 2.43, d.f. =1, p > 0.90 Percent 2.50 1.40 n 639 929 1968 and 1969. Combined — x? = 1.50, d.f. = 1, p > 0.10 Percent 1.48 0.97 n 1218 1545 below the leaf litter. The mean diameter of eggs was 2.2 mm (n = 104, standard deviation = 0.2mm). As in Hel- minthoglypta tudiculata (INGRAM & ADOLPH, 1942), eggs at oviposition had an elastic translucent outer membrane. Later the membrane became opaque, white and slightly stiffer. The mean number of eggs per egg mass was 75.6 (range 45-171, standard deviation = 30.0). The number of eggs per egg mass did not vary significantly (Model I ANOVA, F = 0.24, d.f. = 2, 31) among the 1967, 1968, and 1969 egg laying seasons. However the density of eggs/ m? and hence the number of eggs was significantly greater (X? = 52.1, d.f. = 2, p<0-001) in 1969 than in 1967 and 1968; hence, fecundity was highest in 1969. Variation in egg densities between years was likely a result of greater egg production per adult snail since densities of adults were not significantly different among years for the months (November to March) when presumably eggs were ovi- posited (X* = 2.84, d.f. = 2, n.s.). There was, moreover, a negative nonsignificant correlation (r = —o.590, n = 14) between egg and adult densities. Variation in rainfall, however, appears to be important in egg production. Egg density was positively correlated (r = 0.977, n = 3, p<(0.05) with total rainfall between December and March, the peak season of egg appearance (see below and Figure 1). Seasonality of Egg Appearance and Egg Hatching High densities of eggs occurred in my regular field col- lections starting in late November and ending in early Vol. 23; No. 1 400 360 Number/m? CT I NO re) SQ 2) ° ) e) les) oO a fo) Figure 1 Density (number/m?) of eggs (-—--) and hatchlings ( ) on Mussel Point from March, 1966, to December, 1969. Inflexion points represent actual collection dates April. Viable eggs were found in the field as late as June. Peak numbers of eggs were evident between late Decem- ber and early March (Figure 1). I collected newly hatched snails (recognized by their small size, their lack of shell growth, and the hirsute con- dition of their shells) in peak numbers in March and April and as early as February and as late as August (Figure 1). I also found young-of-year in late summer that were small, had no shell growth, and were hirsute. These snails prob- THE VELIGER Page 51 ably hatched in late spring rather than in summer since they were all in aestivation when collected. Aestivation for the whole population, moreover, starts in mid- to late spring (VAN DER LAAN, 1975b). Length of Time between Copulation and Ovipo- sition, Duration of Embryogenesis, and Probability of Hatching Results from the laboratory study indicated that Hel- minthoglypta eggs are likely to be fertile if oviposited: 94% of all eggs held at the highest temperature hatched. I also found that with higher temperatures, eggs hatched sooner and more successfully (Table 3). In the field the modal length of time between copula- tion and egg hatching for Helminthoglypta was 6 months: between early October, when copulation frequencies were high, and March and April, when peak hatching occurred. The maximum possible development time was 8 months: the time between the first copulation and the latest hatch- ings (early June) and the minimum possible time was 23 months: the time between the end of the copulation sea- son (late November) and the first hatchings (mid-Feb- ruary). Recall that I was not able to estimate the duration of ovarian development. Since snails could have stored sperm or self-inseminated, fertilization could have occurred prior to or sometime after copulation. I note, however, that the time between copulation and oviposition can be as short as 42 days; in 1968 copulation was first observed on 11 Octo- ber and eggs were first collected on 22 November. Based on the difference in time between the start of the peaks in numbers of eggs and of hatchlings (Figure 1) and assuming that embryogenesis starts with oviposition, I Table 3 Cumulative percentage of eggs hatching kept in the laboratory at three temperatures for three egg masses, collected in the field winter 1969. N = number of eggs in each egg mass. Days = days held at each tempetature. Temperature Collected 15 January Collected 11 February Collected 4 March (°C) N = 45 N = 63 N = 54 Days 1] 16 19 74 5 1] 19 27 74 5 ll 19 27 74 4.4 0 0 0 0 0 0 0 0 0 0 5 83 83 83 10.0 53 73 73 73 0 0 0 0 0 78 100 = = = 15.5 67 93 93 93 0 0 71 90 90 100 - — — = Page 52 THE VELIGER Vol. 23; No. 1 estimated the modal duration of embryogenesis for Hel- minthoglypta to be 2 months. DISCUSSION Most reproductive events in Helminthoglypta arrosa occur during the annual wet season. The exceptions are: sperm development, which must take place prior to copulation, and ovarian development, which may also occur earlier than mating. Copulation is coincident with the start of the wet season, and hatching is completed by the start of the dry season. Food availability, water availability, and tem- perature have direct and indirect and proximate and ulti- mate effects on reproduction. These external factors also interact with each other. Food availability depends on water availability. Higher primary productivity occurs in the wetter years, and, as in other Mediterranean climates, plant phenological events depend on rainfall patterns. In addition, times of lower temperatures are coincident with times of higher rainfall (vAN DER LAAN, 1971). For Helminthoglypta arrosa rainfall appeared to be the only variable that explained differences in copulation rates between years of my study. Neither food availability nor temperature was significantly different between years. For some snails and slugs temperature plays a role in determining the seasonality of mating (DUNCAN, 1975). In many other terrestrial pulmonates rainfall and water availability are the principal correlates of seasonality (DuNcAN, op. cit.; HEATWOLE & HEATWOLE, 1978). Tim- ing of the onset of the breeding season for Helminthoglypta arrosa may depend on both food and water availability, but probably is not dependent on temperature variations. Relatively low autumn temperatures slow soil desiccation, and temperatures below 4° C, which occurred only twice during the two breeding seasons, resulted in snail inactiv- ity. Otherwise snails were active under the full range of temperatures that occurred during the breeding seasons. Food may be an ultimate factor in initiation of the mating season. The abundance of food plants rapidly increased from early to late autumn (a two- to ten-fold increase in abundance during my study). Water availability is both a proximate and ultimate factor in initiating the mating seasons. Rainfall in early October results in annual reac- tivation from long-term aestivation (vAN DER LAAN, 1975b) by thoroughly wetting the leaf litter and soil. Thus, rainfall probably is the signal for the onset of copulation. High water availability is absolutely necessary for snail activity and facilitates snail feeding, acting thereby as an ultimate factor. The mating season could have ended simply because every potentially reproductive animal was inseminated or every animal used up an annual sperm supply, or both. By assuming that Helminthoglypta remained in copulo 6.5 hrs., as did Helix aspersa (Miller) (HeRzBerc & HERZBERG, 1962) and by assuming that snails were active at night and during days that had fog, overcast, rain, or drizzle, I found that a projection of copulation frequen- cies indicated that 100% of the Helminthoglypta arrosa population would have copulated by mid-November in 1969; my observation was that copulation ceased at the end of November, 1969. In 1968, a year of low copulation frequencies, only 50% of the population would have cop- ulated by late November. Copulation, however, ended at the start of November. Furthermore, copulation ended by late November in 1966, 1967, and 1970. Thus, variation in environmental factors rather than sperm supply is strongly implicated in terminating the mating season. Late autumn variation in rainfall, food availability, and temperature did not appear to be proximate factors in the cessation of the breeding season, but springtime patterns in water availability and in food availability were ultimate factors in terminating the mating season. Copulation later than the end of November could result in very high mortal- ity for eggs and newly hatched snails on Mussel Point. Given a development period of 6 months, copulation that oc- curred later than November would result in unhatched eggs or newly hatched snails in mid-spring or later. Such eggs and hatchlings would probably die at very high rates. Helminthoglypta eggs, like slug eggs (RUNHAM & HUNTER, 1970), have no known specializations to prevent water loss. In fact, most eggs I collected in late spring were quite brittle or even cracked open. Newly hatched snails in late spring face a declining food supply (I recorded a drop in food plant abundance from 50% to 12% cover in March to May, 1969) and a substantial reduction in water avail- ability occurs each spring (mean monthly rainfall for 1967 to 1979 was 45-7mm for April, 8.5mm for May, and 3.7 mm for June). This cohort also experiences very high mortality during the annual dry periods (vAN DER Laan, 1975b). I note that late autumn cessation of copulation as an adaptation to springtime patterns in water and food may be peculiar to the Mussel Point population. Helmin- thoglypta arrosa was observed in copulo in February on Pt. Reyes, 22km southeast of my study area (INGRAM, — 1947). I postulate that egg size and moisture availability affect the duration of embryogenesis in terrestrial gastropods. Furthermore, even though I could not determine the age of eggs when they were collected, it appears that there is Vol. 23; No. 1 THE VELIGER Page 53 an inverse relationship between duration of embryogenesis and temperature (Table 3). This is consistent with the results obtained by Carrick (1942) for Agriolimax agrestis Linnaeus. Given this inverse relationship, duration of embryo- genesis for Helminthoglypta arrosa in the field (mode = 2 months) is probably lengthened by the cool temperatures on Mussel Point (minimum temperatures ranged between 2.5 and 7.5°C for December to April in the two years of my study, while maximum temperatures were 15.8 to 17.4° C). I note that embryogenesis in the field took one and one-half months in Puerto Rican tree snails (HEat- WOLE & HEATWOLE, 1978) and 30 to 45 days in the African giant snail (Ajayi et al., 1978). Egg size (suggested here as a correlated variable) was not reported for the African snail. Puerto Rican snails, however, had eggs about 4 times larger than Helminthoglypta eggs. I compared three other aspects of reproduction in Helminthoglypta arrosa to other pulmonates. First, mean clutch size (75.6 eggs/mass) was higher than that for most similarly sized helicids (11-96 eggs/clutch) and approxi- mated the median clutch size for terrestrial pulmonates in general (Hyman, 1967). Secondly, the hatching rate that I recorded for H. arrosa (94%) is close to the 91.3% rate for Achatina fulica Bowdich from Hawaiian popula- tions held at room temperature (KEKAUOHA, 1966). Agriolimax agrestis, however, had no egg mortality at 5° C and 37% mortality at 20° C (Carrick, 1942). Finally, the total presence of mutual copulation observed for Helmin- thoglypta arrosa is in contrast to INGRAM & ADOLPH’S (1942) observations of frequent one-way copulations in laboratory-maintained Helminthoglypta tudiculata, but is in keeping with Hyman’s (1967) conclusion that pul- monates generally practice reciprocal insemination. Mu- tual mating may, in fact, always occur in H. arrosa, since mutual copulation could have occurred just after or just before my single brief observation of one-way copulation. SUMMARY 1. Seasonality in mating, length of time between copula- tion and oviposition, duration of embryogenesis, egg viability, and variation in egg production were stud- ied in a northcentral California coastal population of the land snail Helminthoglypta arrosa (Binney, 1855). The effects of water availability, food availability, and temperature on these aspects of reproduction are discussed. 2. Copulation was reciprocal in every instance except one observation of short duration. 3. Copulation only occurred in October and November, began after reactivation from long-term aestivation, was coincident with heavy and frequent rainfall that thoroughly wetted the leaf litter and soil, and was coincident with a rapid increase in abundance of food plants. 4. It is argued that the timing of the cessation of the mating season is adapted to the spring decline in water and food availability that hatchlings experi- ence. 5. Copulation rates were higher in 1969 than in 1968 when rainfall was significantly higher and food abun- dance was higher, although not significantly so. 6. Variation in copulation rates during the mating sea- son was not significantly different between daytime and nighttime and was not significantly correlated with variation in either maximum or minimum tem- peratures. 7. Eggs averaged 2.2mm in diameter (n = 105, s.d. = 0.2mm). The mean numbers of eggs/egg mass (75.6) were not significantly different among three years; however, the density of eggs (number/m’) was sig- nificantly higher for one year. Variation in egg den- sity was positively correlated with rainfall. Further- more, changes in population egg production depended on changes in reproductive output/adult since adult densities did not vary among years. 8. In laboratory experiments eggs held at 15.6, 10.0, and 4.4°C hatched sooner and more successfully the higher the temperature. g. In the field the modal length of time between copu- lation and hatching was 6 months (range 2% to 8 months) with a model duration of 2 months for embryogenesis. Duration of embryogenesis was prob- ably lengthened by low field temperatures. ACKNOWLEDGMENTS I wish to thank Alice Kingsbury, Armand Kuris, José Javier Alid, Eric Hochberg and an anonymous reviewer for helpful suggestions on the manuscript. Data were col- lected at the Bodega Marine Laboratory (B.M.L.), Uni- Page 54 THE VELIGER Vol. 23; No. 1 versity of California (U.C.), Bodega Bay, while holding a pre-doctoral fellowship No. 5 For GM3643-03 from the National Institute of Health at the Department of Zoology, U.C., Berkeley. Data were analyzed while sponsored by NSF Grant No. OCE 78-08489 at the Marine Sciences Institute, U.C., Santa Barbara. The Director, Cadet Hand, and the staff at B.M.L. provided important logistic sup- port. Literature Cited Ajayi, S. S., O. O. Tewe, C. Moriarty « M. O. Awesu 1978. Observations on the biology and nutritive value of the African giant snail, Archachatina marginata. E. Afr. Wildl. Journ. 16 (2): 85-95; 2 text figs. (June 1978) Carrick, RoBERT 1942. The grey field slug, Agriolimax agrestis L. and its environment. Ann. Appl. Biol. 29: 43 - 55; 4 text figs. Duncan, CHRISTOPHER J. 1975- Reproduction. In: Vera Fretter & J. Peake, eds., Pulmonates. Acad. Press, London, New York, xxix+417 pp.; illust. VAN DER Laan, KENNETH LERoy HEATWoOLE, Harotp & Aupry HEATWOLE 1978. Ecology of Puerto Rican camaenid tree-snails. Malacologia 17 (2): 241-315; 40 text figs. HERZBERG, FRED & ANNE HERZBERG 1962. Observations on reproduction in Helix aspersa. Amer. Midl. Nat. 68 (2): 297-306; 5 text figs. (October 1962) Hyman, Lipsiz HenrieTTa 1967. The Invertebrates. 6, Mollusca 1: viit+792 pp.; illust. McGraw- Hill Book Co., N. Y, St. Louis, London IncRAM, WILLIAM Marcus 1947. A contribution to the natural history of Helminthoglypta arrosa (‘Gld’ Binney) and Helminthoglypta nickliniana awania Bartsch. Bull. So. Calif. Acad. Sci. 46 (2): 81-83 (May-August 1947) INGRAM, WILLIAM Marcus & HELEN M. ADoLPH 1942. Life history data on Helminthoglypta tudiculata. Bull. So. Calif; Acad. Sci. 41 (2): 97-101 (May-August 1942) KEKAvuOoHA, WILLARD 1966. Life history and population studies of Achatina fulica. The Nautilus 80(1): 3-10 (July 1966) and 80(2): 39-46 (October 1966) ; 2 text figs. Pitssry, Henry AucustTus 1939. Land Mollusca of North America (north of Mexico). Acad. Nat. Sci. Philadelphia Monogr. 3; 1 (1): i-xvii, 1-573, i-ix; text figs. 1-377 (6 December 1939) RunuaM, N. W. « P J. Hunter 1970. Terrestrial slugs. 8 plts.; 5 text figs. Hutchinson Univ. Libr. London 1 - 184; 1971. The population ecology of the terrestrial snail, Helminthoglypta arrosa (Pulmonata: Helicidae). vii+235 pp.; illust. Ph. D. thesis, Univ. Calif. Berkeley, California 1975a. Feeding preferences in a population of the land snail Helmintho- glypta arrosa (Binney) (Pulmonata: Helicidae). (4): 354-359 The Veliger 17 (1 April 1975) 1975b. Aestivation in the land snail Helminthoglypta arrosa (Binney) (Pulmonata: Helicidae). The Veliger 17 (4): 360-368; 1 text fig. (1 April 1975) Vol. 23; No. 1 THE VELIGER Page 55 A New Species of Lepidopleurus Risso, 1826 (Mollusca : Polyplacophora ) in the Deep Waters of the Eastern Pacific ANTONIO J. FERREIRA! Research Associate, California Academy of Sciences, Golden Gate Park, San Francisco, California 94118 (1 Plate; 5 Text figures) UPoN COMPLETION OF A REVIEW of the chiton family Lepidopleuridae Pilsbry, 1892, in the eastern Pacific (FERREIRA, 1979), a few lots of lepidopleurids which had been left unexamined were brought to my attention. As fortune would have it, one of these lots proved to be of great scientific interest. The material, generously loaned by Dr. William A. Newman, Scripps Institution of Oceanography, La Jolla, California, consists of 5 specimens preserved in alcohol, bearing the label: “MV 65-I-57/off Baja California Sur, SW of Cabo San Lucas/beam trawl, 1580-1370 fathoms [2891-2507 m]/22°30.8N, 110°03.8’W tr. 22°37.2’N, 110°15.5 W/Carl L. Hubbs & party on Horizon, VII, 29-30, 1965.” One of these specimens, about 3cm in length, is clearly identifiable as Leptochiton alveolus (Lovén, 1846); the other 4 specimens are of a hitherto undescribed species of the genus Lepidopleurus Risso, 1826 (not Dall, 1879). POLY PLACOPHORA de Blainville, 1816 Neoloricata Bergenhayn, 1955 LEPMOPLEURDAE Pilsbry, 1892 Lepidopleurus Risso, 1826 Lepidopleurus scrippsianus Ferreira, spec. nov. (Figures 1 to 6 and 7 to 11) ' Mailing address for reprints: California 95128, U.S.A. 2060 Clarmar Way, San Jose, Diagnosis: Chitons of moderate size, white color. Valves rugose, strongly beaked. End valves and lateral areas of intermediate valves thick and prominent, smooth surface, with coarse concentric growth rugae. Central areas with irregularly distributed microgranules. Articulamentum white, with no slits. Sutural laminae small, triangular; sinus wide. Mucro posterior. Gills posterior. Girdle upper surface covered with large, juxtaposed spiculoid processes; under surface reduced to fine cuticle without scales. Rad- ula with tricuspid major lateral teeth. Description: Holotype - The specimen, rugose in ap- pearance, subcarinate, preserved in alcohol, measures 12.1 mm in length, 8.2mm in width. Tegmentum (Figure 5) uniformly white. Anterior valve with smooth surface ex- cept for coarse, concentric growth rugae. Intermediate valves strongly beaked. Lateral areas elevated and prom- inent; tegmental surface smooth except for coarse, irreg- ular, concentric growth rugae. Central areas minutely granular, the granules irregularly placed and variably spaced. Posterior valve moderately inflated; mucro at the posterior 1/3 of the valve; postmucro with concentric growth lines, strongly convex, sloping sharply. Articula- mentum (Figure 6) chalky white, without insertion teeth or slits; in the intermediate valves, posterior 1/3 of artic- ulamental surface covered by the broadly reflected teg- mentum. Sutural laminae small, triangular; sinus very wide. On valve viii: width of sinus/width of sutural lam- inae = 2.48mm/1.68 mm = 1.48. Width of valve i/width of valve viii = 5.77mm/5.67mm = 1.02. Gills adanal, posterior, about 20 plumes per side, extending 40% of length of foot. Girdle creamy white, velvety in appear- ance, relatively thick and wide; maximum width (at level of valve iv), 2.2mm. Girdle upper surface uniformly cov- ered with juxtaposed spiculoid processes, 100 um long, Page 56 THE VELIGER Vol. 23; No. 1 20 um wide, with pointed tips, often broken and jagged (Figure 7); undersurface completely devoid of any scale- like formations, reduced to a thin cuticle. Radula, 5.8mm long (48% of the specimen’s length), comprises about 60 100 pm Figure 7 Lepidopleurus scrippsianus Ferreira, spec. nov. Holotype (CASIZ Type Collection no. 00716) ; spiculoid processes of the girdle’s upper surface. Camera lucida drawing by Barbara Weitbrecht measured bar=100um rows of mature teeth. Median tooth about 70 um long and 30 zm wide in the front where it bears a small blade, enlarges posteriorly to a width of 48 um; first lateral tooth, about 65 wm long, 45 um wide, bears large tuberosity at the inner anterior corner bordering a socket-like forma- tion (Figure 8). Major lateral tooth with a tricuspid head, about 80 um wide and 100mm long at the longest cusp (Figure 9). Spatulate tooth (“Seitenplatte”) with strongly ie 100 zm Figure 8 Lepidopleurus scrippsianus Ferreira, spec. nov. Holotype (CASIZ Type Collection no. 00716); median and first lateral teeth of radula. Camera lucida drawing by Barbara Weit- brecht measured bar=100nm fasciculated texture and a rake-like appearance (Figure 10). Outer marginal teeth about 80 um long, 105 wm wide (Figure 11). The specimen, disarticulated, with girdle and radula mounted on separate slides, is in the repository of the Cali- fornia Academy of Sciences, Department of Invertebrate Zoology, CASIZ Type Series No. 00716, CASIZ Type Slides Nos. 533, 534, and 535. Paratypes: Ihree specimens from the same lot, slightly curled, preserved in alcohol, with the same color and gen- eral characteristics of the holotype; lengths and widths (including girdle), 20x 10mm, 15x8mm, and13 x 7mm. Paratypes deposited, respectively, at the Scripps Institu- tion of Oceanography, California Academy of Sciences (CASIZ Type Series 00717), and Natural History Mu- Explanation of Figures 1 to 6 Lepidopleurus scrippsianus Ferreira, spec. nov. Figure 1: Paratype, 15mm long (CASIZ Type Collection no. 00717); dorsal view Figure 2: Same as in Figure 1; side view Figure 3: Same as in Figure 1; close-up of left side slope Figure 4: Same as in Figure 1; close-up of central and lateral areas Figure 5: Holotype (CASIZ Type Collection no. 00716) ; close-up of dorsal surface of anterior, intermediate, and posterior valves Figure 6: Same as in Figure 5; close-up of articulamental surface : of anterior, intermediate, and posterior valves Tue VE ticER, Vol. 23, No. 1 [FERREIRA] Figures 1 to 6 Figure 6 Vol. 23; No. 1 THE VELIGER Page 57 seum of Los Angeles County (LACM 1700). Color slides of the 2 largest paratypes, CASIZ Color Slides Series Nos. 1493, 1494, and 1495 (Allyn G. Smith’s photographs). 100 pm Figure 9 Lepidopleurus scrippsianus Ferreira, spec. nov. Holotype (CASIZ Type Collection no. 00716); head of major lateral tooth of radula. Camera lucida drawing by Barbara Weit- brecht. measured bar=1o0oynm hoS5000g, 100 pm Figure 10 Lepidopleurus scrippsianus Ferreira, spec. nov. Holotype (CASIZ Type Collection no. 00716); spatulate tooth (“Seitenplatte”) of radula. Camera lucida drawing by Barbara Weitbrecht measured bar = 100m ee 100 pm Figure 11 Lepidopleurus scrippsianus Ferreira, spec. nov. Holotype (CASIZ Type collection no. 00716) ; outer marginal teeth of radula. Camera lucida drawing by Barbara Weitbrecht measured bar=1o0oum Type Locality: - Off Baja California Sur, southwest of Cabo San Lucas, Mexico (22°30.8’N, 110°03.8’W through 22°37.2’N, 110°15.5'W), at a depth of 2891- 2507m. Distribution: — Lepidopleurus scrippsianus is known only from the type lot. Remarks: The genus Lepidopleurus Risso, 1826 (not Dall, 1879) is based upon Chiton cajetanus Poli, 1791, its type species by subsequent designation (HERRMANNSEN, 1847: 582). Although many lepidopleurids have been orig- inally assigned to Lepidopleurus, L. cajetanus, with its rugose, thick, heavily sculptured shell is “strikingly differ- ent” (PitsBry, 1892: 16) from other species of “Lepido- pleurus” which, being “relatively delicate and smooth- shelled (BERRY, 1917: 233), are now allocated for the most part to Leptochiton Gray, 1847 (type species: Chiton cinereus Montagu, 1803 [= C. asellus Gmelin, 1791] (not C. cinereus Linnaeus, 1767) by subsequent designation, Gray, 1847). The recognition of fundamental differences between Lepidopleurus and Leptochiton has been var- iously handled by chiton workers (Dat, 1879; Pirssry, 1892; IREDALE, 1914a; Berry, 1917 ; A. G. SmitH, 1960a; Van BELLE, 1975); the systematic arrangement adopted here and elsewhere (FERREIRA, 1979b), recognizes both, Lepidopleurus and Leptochiton, as distinct genera. Lepidopleurus (sensu stricto] has been known only from its type species, L. cajetanus, a common European species distributed throughout the Mediterranean Sea, Canary Page 58 THE VELIGER Vol. 23; No. 1 Islands, and the coast of Portugal and Spain, in the sub- littoral zone to a depth of 40m (VAN BELLE, 1978). The finding of L. scrippsianus in the eastern Pacific at a depth of over 2500m adds appreciably to the understanding of the genus. Lepidopleurus scrippsianus resembles L. cajetanus in several important respects, such as the 1) general shape, 2) rugose and thick shell, 3) beaked valves, 4) prominent lateral areas, 5) posterior mucro, 6) strongly convex post- mucro, 7) posterior gills, 8) unslit articulamentum, 9) small, triangular sutural laminae, 10) very wide sinus, and 11) tricuspid major lateral teeth of radula. The 2 species differ sharply in the 1) end valves and lateral areas (with regular, concentric folds in L. cajetanus; with irregularly spaced, ill-formed growth rugae on an otherwise smooth surface in L. scrippsianus), 2) central areas (with longi- tudinal riblets in L. cajetanus; with no riblets but a micro- granular surface in L. scrippsianus), 3) upper surface of girdle (with striated scales in L. cajetanus; with juxtaposed spicules in L. scrippsianus), 4) undersurface of girdle (with imbricating, flat scales in L. cajetanus; scaleless in L. scrippsianus), ») radula’s 6th tooth [Seitenplatte, or major uncinus] (fasciculated texture of the spatulate cusp in L. scrippsianus; no fasciculated texture observable in L. cajetanus), and 6) habitat (sublittoral in L. cajetanus; near abyssal in L. scrippsianus). Lepidopleurus scrippsianus exhibits 2 anatomical fea- tures which, for their uniqueness and possible implications, deserve further comment: The fasciculated texture of the spatulate tooth of the radula, and the absence of scales on the undersurface of the girdle. The fasciculations or striae of the spatulate tooth are close together, neatly drawn in their course parallel to the long axis of the tooth; they continue to the curved outer edge of the tooth which as- sumes a comb-like appearance. In this manner, the spat- ulate tooth of L. scrippsianus is reminiscent of the mono- placophoran neopilinid’s first marginal tooth (McLean, 1979), and the marginal teeth of some docoglossan limpets in the family Lepetidae. This observation seems to support McLean’s (op. cit.) hypothesis of a close affinity among the Polyplacophora, Monoplacophora, and Docoglossa. In the case of L. scrippsianus, the radular similarities with neopilinids and certain limpets are reinforced by the rela- tively small size of the median (rachidian) tooth. The absence of scales or any scale-like processes on the undersurface of the girdle of Lepidopleurus scrippsianus is also quite intriguing. All other Recent species of chitons known to me have scales on the underside of the girdle; probably such scales have a protective function, with adaptative value to these hard substrate dwellers. Thus, a scaleless undersurface such as found in L. scrippsianus sug- gests a soft substrate habitat that would pose no threat of imminent trauma to the moving girdle. Until now, a soft bottom habitat has not been known in chitons [although a few species are facultative dwellers on kelp stipes]; fur- ther investigation of deep water chiton species, still very poorly known, may well reveal other species, with a scale- less undersurface, associated with the soft bottoms of ooze of the abyssal sea floors. In this respect, it seems significant to note that fossil chiton species are known to have lived on mud bottoms. Pterochiton concinnus (Richardson, 1965) described from the Mazon Creek area, Middle Pennsylvanian of Illinois, was quite clearly a soft bottom dweller (YocHELSON «& RIGHARDSON, 1979). Specimens of P. concinnus were found, as Dr. Eugene Richardson, Field Museum of Nat- ural History, Chicago, graciously explains, enclosed in rock derived from a “silty mud. There are no rocks such as chitons might be expected to clamp onto. They had no choice but to wander on a mud surface which is what we mean by ‘soft bottom.’ Naturally . . . firm enough to sup- port a vagrant chiton... The Francis Creek Shale [of the Mazon Creek area] . . . was deposited in small increments that immediately consolidated to a sufficiently firm state to support the vagrant benthos. We have one instance of a curled chiton lying 3 centimeters below a straight one. As I interpret it, the lower one was killed (perhaps by fresh water preceding the mud) and then buried by 3 cm of mud, and then the other fellow wandered along and was buried alive.” (Dr. E. Richardson, in litt., 28 August 1979). But the argument for soft bottom living in the case of Lepido- pleurus scrippsianus is not totally unequivocal, for there were some hard surfaces available in the collecting area. Field notes for the station MV 65-1-57 (kindly supplied by Spencer R. Luke, Scripps Institution of Oceanography), where L. scrippsianus was found indicate a soft, muddy bottom; but it also shows that there were some rocky, “asphaltic” pieces in the area, and that the chitons (1 specimen of Leptochiton alveolus, and the 4 specimens of Lepidopleurus scrippsianus) together with limpets and several specimens of a Neopilina sp., were picked off a “very hard and heavy” piece of wood. Still, taking into account two relevant anatomical features of L. scrippst- anus, the unusually wide girdle (providing for a broader contact surface and better distribution of weight) and the scaleless undersurface (inadequately prepared to meet the harshness of hard substrata), it seems that the bulk of the evidence speaks for an association between this nearly abyssal species and a soft bottom. Lepidopleurus scrippsianus inhabits exceptionally deep water as may be appreciated from a compilation of deep- water chiton species and their respective bathymetric Vol. 23; No. 1 THE VELIGER Page 59 Table 1 Compilation of deep-water chiton species with respective bathymetric ranges. Depth (m) ; : Species se ts Citedian Lepidopleurus vitjazi Sirenko, 1977 7657 - 6920 SIRENKO, 1977 Leptochiton alveolus (Lovén, 1846) 164 4825 FERREIRA, 1979b; Kaas, 1979 Leptochiton incongruus (Dall, 1908) 589 3612 - 3541 DALL, 1908; FERREIRA, 1979b Lepidopleurus scrippsianus Ferreira, n. sp. 2891 - 2507 FERREIRA, herein 1980 Leptochiton pergranatus (Dall, 1889) 208 2161 Kaas, 1972 Lepidopleurus planus Nierstrass, 1905 2053 Nierstrass, 1905 Lepidopleurus rissoi Nierstrass, 1905 216 2053 Nierstrass, 1905 Ischnochiton abyssicola A. G. Smith & Cowan, 1966 216 2000 A. G. SmitH & Cowan, 1966 Leptochiton assimilis Thiele, 1909 [? = L. rugatus] 8 2000 JAKOvLEVA, 1952 Placiphorella atlantica (Verrill & E. A. Smith, 1882) 640 1470 - 1420 THIELE, 1909; Kaas, 1979 Lepidozona retiporosa (Carpenter, 1864) 0) 1463 - 1262 FERREIRA, 1978 Lepidozona scabricostata (Carpenter, 1864) 0 1460 - 1260 FERREIRA, 1978 Lepidopleurus lineatus Nierstrass, 1905 450 1301 Nrerstrass, 1905 Lepidopleurus setiger Nierstrass, 1905 289 1301 Nrerstrass, 1905 Lepidopleurus similis E. A. Smith, 1894 1235 E. A. Smitu, 1894 Leptochiton leloupi Kaas, 1979 800 1085 Kaas, 1979 Leptochiton tenuis Kaas, 1979 800 1080 Kaas, 1979 Connexochiton platynomenus Kaas, 1979 800 1050 Kaas, 1979 Ischnochiton exaratus (Sars, 1878) 100 1000 - 880 LeELoup, 1956; Kaas, 1979 Ischnochiton dorsuosus (Haddon, 1886) [? = I. exaratus] 199 1000 DELL, 1964; Ricui, 1971 Leptochiton cancellatus (Sowerby, 1839) 0 920 Kaas, 1979 Leptochiton binghami (Boone, 1928) 659 885 FERREIRA, in ms.; BOONE, 1928 Ischnochiton albus (Linnaeus, 1767) 0 815 JAKOvLEvA, 1952; Kaas, 1979 Ischnochiton dallii (Haddon, 1886) 732 Happon, 1886 Oldroydia percrassa (Dall, 1894) 0 731 - 640 FERREIRA, 1979b Callochiton gaussi Thiele, 1908 5-0 730 DELL, 1964; HEDLEY, 1916 Ischnochiton stearnsi Dall, 1902 412 715 A. G. SMITH & Cowan, 1966 Nuttalochiton mirandus (Thiele, 1906) 126 640 ARNAUD, 1974 Cryptochiton stelleri (Middendorff, 1847) 0 600. JAKOvLEVA, 1952 Hanleya hanleyi (Bean 1844) 1G 555 JAKovieva, 1952 Placiphorella borealis Pilsbry, 1892 0 500 JAKOvLEva, 1952 Placiphorella uschakovi Jakovleva, 1952 0 500 JAKovLEva, 1952 Leptochiton diomedeae Berry, 1917 463 - 446 Berry, 1917 Leptochiton rugatus (Pilsbry, 1892) 0 458 FERREIRA, 1979b Hanleyella oldroydi (Dall, 1919) 18 455 - 420 FERREIRA, 1979b Ischnochiton nipponicus Berry, 1918 357 Is. Taki, 1962 Leptochiton kerguelensis Haddon, 1886 0 342 ARNAUD, 1974 Callistochiton colimensis (A. G. Smith, 1961) 0 340 - 330 FERREIRA, 1979a Leptochiton asellus (Gmelin, 1791) 40 300 JAKovLEva, 1952 Tonicella rubra (Linnaeus, 1767) 0 300 JAKovieva, 1952 Lepidozona willetti (Berry, 1917) 40-13 274 FERREIRA, 1978 Guryanovillia kobjakovae Jakovleva, 1952 50 270 JAKOvLEVA, 1952 Hanleya tropicalis Dall, 1881 234 DaALL, 1881 Tonicella marmorea (Fabricius, 1780) 0 230 SIRENKO, 1974 Lepidozona sinudentata (Carpenter in Pilsbry, 1892) 0 200 FERREIRA, 1978 Page 62 THE VELIGER Vol. 23; No. 1 Growth and Mortality in the Ribbed Mussel Geukensza demissa m otil \ dat (Bivalvia : Dreissenaeea ) BY MARK D. BERTNESS Department of Zoology, University of Maryland, College Park, Maryland 20742 (5 Text figures) INTRODUCTION On THE EAST coast of North America Geukensia (for- merly Modiolus and Arcuatula) demissa (Dillwyn, 1817), is a major component of salt marsh communities. This mud-dwelling mussel is generally found in close associa- tion with the salt-tolerant angiosperm S'partina alterniflora and occurs from the Gulf of St. Lawrence, to northeast Florida (AssotT, 1974). Geukensia demissa is highly eury- topic, being able to tolerate temperatures of —22°C to 40°C (KANWISHER, 1955; LENT, 1969) and salinities of 5%o to 75% (WELLS, 1961; LENT, 1969). This tolerance for environmental extremes allows G. demissa to inhabit an extremely high intertidal habitat, where it is exposed to terrestrial conditions for up to 83% of the time (KUENZ- ler, 1961). The present study was stimulated by the observation that mussels found on the outer coast of Maryland were noticeably larger than conspecifics which pene- trate a considerable distance into the Chesapeake Bay estuary. It was hypothesized that this situation could arise from three documented patterns: 1) ‘The growth rates and maximum attainable sizes of the mussels could vary between habitats due to differences in the physical envi- ronment as found in other marine organisms (SEED, 1969; Lewis « BowMAN, 1975; PAINE, 1976). Environmental variation could cause this pattern either by direct physio- logical limitations on growth rates in a particular physical regime or by causing parallel variation in critical resource levels. 2) Predation pressure could be less severe in the outer coast environment so that the larger outer coast mussels could be attaining a size refuge from predation (as in CONNELL, 1972). 3) Growth rates and survival could be density dependent, enabling sparse mussels to reach larger sizes (as in SUTHERLAND, 1970). This paper presents data on the population structure, growth rates, predation intensity, and mortality of mussels from three locations along the Chesapeake Bay to eluci- date the cause of this size pattern. Since intraspecific vari- ation in the size attained by bivalves in different habitats can be accompanied by divergence in shell shape (SEED, 1968), consideration is also given to the allometric rela- tionships of the mussels at the three study sites. METHODS Study Sites Three study areas were selected to represent differences in salinity and temperature fluctuation on a gradient from the open coast to well within Chesapeake Bay (Figure 1). The most conspicuous biotic component of all three study sites was the grass Spartina alterniflora, on whose roots Geukensia demissa is predominantly found. The Tom’s Cove study site on Chincoteague Island (37°52’N, 75°25 W) is an extensive lagoonal salt marsh. The fauna and flora of this area are similar to those described by TEAL (1962). The second study area, Cape Charles (37°10’ N, 76°00’ W), is located on the inside mouth of Chesa- peake Bay. The third sampling location, Crisfield (37°25/ N, 76°00’ W), is located well into Chesapeake Bay. The areas sampled at the last two sites, within Chesapeake Bay proper, were the small fringe marshes characteristic of these areas. Annual temperature and salinity fluctuations in the Chesapeake Bay area are extremely great. At Crisfield, for example, water temperatures range from 0° C to 32° C, while salinities range from 13.7% to 20.4% annually (1959-1961). From Chesapeake Bay to the outer coast Wolo Now THE VELIGER Page 61 Hepiey, CHARLES 1916. Mollusca. In: Australasian Antarctic Expedition 1911-1914. Scient. Reprts., Series C (Zoology & Botany) 4 (1): 80 pp.; 9g plts.; 3 text figs. (6 November 1916) HERRMANNSEN, AucusT NIcoLAus 1846. Indicis generum malacozoorum primordia. vol. 1: 637 pp. (p. 582: 25 May 1847) IrREDALE, Tom 1914. Some more notes on Polyplacophora. Part I. 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I. ‘ 1974. Taxonomy of the genus Tonicella (Ischnochitonidae) . Zool. Journ. Moscow, USSR 53 (7): 988-997 {in Russian] 1977. Vertical distribution of chitons of the genus Lepidopleurus (Le- pidopleuridae) and its new ultra-abyssal species. Zool. Journ. Mos- cow, USSR 56(7): 1107-1110 {in Russian] SmitH, ALLYN GooDWIN 1960. The type species of Lepidopleurus Leach in Risso, 1826. The Veliger 2 (4): 75-77; plt. 17 (1 April 1960) SmitH, ALLYN Goopwin & Ian McTaccart Cowan 1966. A new deep water chiton from the Northeastern Pacific. Occ. Pap. Calif. Acad. Sci. 56: 1-15; 21 figs. (30 June 1966) SmitH, EpcAar ALBERT 1894. Natural history notes from H. M. Indian marine survey steamer “Investigator,” Commander C. F Oldham, R. N. — Series II, No. 10. Report upon some Mollusca dredged in the Bay of Bengal and the Arabian Sea. Ann. Mag. Nat. Hist. (6) 14: 157-164; plts. 3-5 Sowersy, GzorcEe BrRETTINGHAM 2nd 1841. The Conchological Illustrations. A catalogue of the Recent spe- cies of Chitones, pp. 1-8 [1840]. Corrected list of figures, pp. 9, 10 [? June 1840]. Descriptive catalogue of British chitons, pp. 1-7 [? 1839] TAKI, Isao 1962. A list of the Polyplacophora from Japanese Islands and vicinity. Venus 22 (1): 29-53 (August 1962) THIELE, JOHANNES 1906. Uber die Chitonen der deutschen Tiefsee-Expedition. In: Carl Chun (ed.), Wissenschaftliche Ergebnisse der deutschen Tiefsee-Expedi- tion auf dem Dampfer “Valdivia” 1898-1899. Jena, 9: 325 - 336; pit. 29 (31 May 1906) 1908. Die Antarktischen und Subantarktischen Chitonen. Deutsche Siidpolar-Expedition 1901-1903, 10 (Zool. )2: 9-23; 1plt. 1909-1910. Revision des Systems der Chitonen. Stuttgart. 132 pp.; 10 plts. Van Bere, RicHarp A. 1975- Sur la classification des Polyplacophora: IJ. Classification systématique des Lepidopleurina (Neoloricata), avec la description de Helminthochitoninae, nov. subfam. (Lepidopleuridae) et de Mesochiton nov. gen. (Helminthochitoninae). Inform. Soc. Belge Malacol. 4 (6): 135-145; 3 plts. (15 December 1975) 1978. De Europese Polyplacophora. Lepidopleurus cajetanus. Gloria Maris 17 (9): 33-36; pit. 6 (October 1978) VeERRILL, ADDISON EMERY & Epcar A. SMITH 1882. In: A E. Verrill, Notice of the remarkable marine fauna occu- pying the outer banks of the southern coast of New England, No. 7, and of some additions to the fauna of Vineyard Sound. Amer. Journ. Sci. (3) 24 (139-144): 360-371 [footnote to p. 365] (July-Dec. 1882) Yocuetson, Eris L. & Evcenz S. RicHARDSON 1979. Polyplacophoran molluscs of the Essex fauna (Middle Pennsyl- vanian, Illinois) . PP. 321 - 332 in: Matthew H. Nitecki (ed.), Ma- zon Creek fossils. Acad. Press, London, New York, 565 pp. Page 62 THE VELIGER Vol; 23: Nowa Growth and Mortality in the Ribbed Mussel Geukensia demissa (Bivalvia : Mytilidae) BY MARK D. BERTNESS Department of Zoology, University of Maryland, College Park, Maryland 20742 (5 Text figures) INTRODUCTION ON THE EAST coast of North America Geukensia (for- merly Modiolus and Arcuatula) demissa (Dillwyn, 1817), is a major component of salt marsh communities. This mud-dwelling mussel is generally found in close associa- tion with the salt-tolerant angiosperm Spartina alterniflora and occurs from the Gulf of St. Lawrence, to northeast Florida (AsBotT, 1974). Geukensia demissa is highly eury- topic, being able to tolerate temperatures of —22°C to 40° C (KANWISHER, 1955; LENT, 1969) and salinities of 5%o to 75% (WELLS, 1961; LENT, 1969). This tolerance for environmental extremes allows G. demissa to inhabit an extremely high intertidal habitat, where it is exposed to terrestrial conditions for up to 83% of the time (KUENz- ler, 1961). The present study was stimulated by the observation that mussels found on the outer coast of Maryland were noticeably larger than conspecifics which pene- trate a considerable distance into the Chesapeake Bay estuary. It was hypothesized that this situation could arise from three documented patterns: 1) The growth rates and maximum attainable sizes of the mussels could vary between habitats due to differences in the physical envi- ronment as found in other marine organisms (SEED, 1969; Lewis « BowMAN, 1975; PAINE, 1976). Environmental variation could cause this pattern either by direct physio- logical limitations on growth rates in a particular physical regime or by causing parallel variation in critical resource levels. 2) Predation pressure could be less severe in the outer coast environment so that the larger outer coast mussels could be attaining a size refuge from predation (as in CONNELL, 1972). 3) Growth rates and survival could be density dependent, enabling sparse mussels to reach larger sizes (as in SUTHERLAND, 1970). This paper presents data on the population structure, growth rates, predation intensity, and mortality of mussels from three locations along the Chesapeake Bay to eluci- date the cause of this size pattern. Since intraspecific vari- ation in the size attained by bivalves in different habitats can be accompanied by divergence in shell shape (SEEp, 1968), consideration is also given to the allometric rela- tionships of the mussels at the three study sites. METHODS Study Sites Three study areas were selected to represent differences in salinity and temperature fluctuation on a gradient from the open coast to well within Chesapeake Bay (Figure 1). The most conspicuous biotic component of all three study sites was the grass Spartina alterniflora, on whose roots Geukensia demissa is predominantly found. The Tom’s Cove study site on Chincoteague Island (37°52’N, 75°25 W) is an extensive lagoonal salt marsh. The fauna and flora of this area are similar to those described by TEAL (1962). The second study area, Cape Charles (37°10° N, 76°00’ W), is located on the inside mouth of Chesa- peake Bay. The third sampling location, Crisfield (37°25’ N, 76°00’ W), is located well into Chesapeake Bay. The areas sampled at the last two sites, within Chesapeake Bay proper, were the small fringe marshes characteristic of these areas. Annual temperature and salinity fluctuations in the Chesapeake Bay area are extremely great. At Crisfield, for example, water temperatures range from 0° C to 32° C, while salinities range from 13.7%> to 20.4% annually (1959-1961). From Chesapeake Bay to the outer coast On page 62 of our July 1980 issue there appcars a very serious error. We are totally mystified as to how it did occur since the wrong line was neither in the manuscript nor in the galley proofs submitted to and returned by the author. Unfortunately, the same error was also introduced on the index page. We present herewith a corrected sub- stitute page with the request that it be inserted in place of the offending page and that the word Dreissenacea be stricken out on the index page. We assume full responsi- bility and offer our apologies to our readers, but especially to the author. R. Stohler, Editor Vol. 23; No. 1 if (he Cape Charles Chesapeake Bay an 7 4 o Atlantic Ocean Figure 1 Map of the Chesapeake Bay Area showing the Study Sites these extremes are considerably reduced due to the buffer- ing effect of the Atlantic Ocean. Annual monthly mean temperatures and salinities for the three study areas re- flect this trend, even though the extremes are masked. At Crisfield mean monthly conditions have a range of 2.6° C to 28.1° C and 15.3%. to 17.8%. At Cape Charles, which is located at the mouth of Chesapeake Bay, mean monthly conditions range from 4.6°C to 26.3°C and 20.1%, to 24.3% . Outside of Chesapeake Bay at Wachapreague, Virginia mean monthly water conditions range from 4.6°C to 26.2°C and 27.5%. to 32.8%. These data are from government records (U.S.D.C., 1973), except for the open coast site (Wachapreague, Virginia) which were provided by the Virginia Marine Institute. The Wacha- preague data are for a location similar to the Tom’s Cove study site and are thought to accurately represent the physical environment at Tom’s Cove. These data illustrate the differing environmental conditions at which organ- THE VELIGER Page 63 isms at the study sites are exposed while submerged, and indicate a gradient of increasing physical stress from the open coast into Chesapeake Bay. Terrestrial environmen- tal conditions would also be expected to exhibit this pat- tern due to the buffering effect of the open ocean on local climate. Sampling Methods and Measurements At each site at +0.5m above mean tidal height a 4m? quadrat was tossed randomly into thick Spartina alterni- flora cover harboring Geukensia demissa. This was re- peated 5 times at each study site. To supplement this sampling, at each site 5 additional quadrats were hap- hazardly tossed into areas of identical tidal height, but without dense S. alterniflora cover. Each study site was also intensively searched for empty shells and the shells were examined for signs of predation. All sampling was done in November 1976. In the laboratory the collected mussel clumps were sep- arated and sieved to retain all mussels larger than 2mm, a process that should assure detection of most newly settled mussels (LooSANOFF & Davis, 1953). Mussels were then cleaned of epiphytes and byssal threads, aged, and meas- ured. Mussels were aged by counting external growth rings (annuli) on the shells. Growth rings are caused by retrac- tion of the shell-secreting mantle edge into the shell dur- ing harsh environmental conditions. The degree of devel- opment of these rings, therefore, will be proportional to the stress that caused them (SEED, 1969). In the Chesa- peake Bay area both temperature and salinity are highly variable seasonally resulting in the formation of strong annual rings. Disturbance rings caused by other than sea- sonal events are relatively minor and easily distinguished from major seasonal interruptions. Lent (personal com- munication) has verified that the disturbance lines in Del- aware Bay Geukensia demissa represent annual lines. The method used to count the growth lines was identical to that described by SEED (of. cit.). First year growth was considered to be the first annual growth ring found after the spat settled. After aging, each mussel was measured to 0.01 mm with vernier calipers for length (maximum anterior-posterior dimension), height (maximum dorso-ventral dimension), and width (maximum lateral axis dimension). Then each mussel was opened and its tissue removed. Both the shell and tissue were dried at 75°C to a constant dry weight and weighed to 1 milligram on an analytical balance. Page 64 RESULTS Population Structure Quadrat sampling indicated that mussel densities were considerably higher at Tom’s Cove than at the other two more estuarine study areas. A total of 528 Geukensia demissa were collected at Tom’s Cove (140, 70, 108, 115, and 95 mussels found in individual quadrats, X G. demissa per 4m’ = 105.6). At Cape Charles 5 quadrat samples yielded a total of 111 mussels (33, 39, 18, 12, and g; X Tom’s Cove Cape Charles Number of Mussels Crisfield 10 20 30 40 50 60 70 80 go I00 I10 Length in millimeters Figure 2 Shell lengths histograms of the Geukensia demissa individuals sampled at the three study sites (Tom’s Cove, n=210; Cape Charles, n=111; Crisfield, n=133) THE VELIGER Vol. 23; No. 1 G. demissa per 4+m*= 22.2). At Crisfield 5 quadrats yielded 65, 45, 22, 40, and 61 mussels (X G. demissa per }m’ = 46.6) for a total of 233. Quadrat sampling on sub- strate lacking Spartina alterniflora at Tom’s Cove revealed densities of 12, 8, 0, 4, and 18 G. demissa, while at the other 2 locations mussels were only found closely asso- ciated with S. alterniflora. These two patterns where (1) G. demissa densities decrease from the open coast to more estuarine environments, and (2) high G. demissa den- sities are found associated with the marsh grass S. alter- niflora agree with all my observations in the Chesapeake Bay Area. Figure 2 illustrates the size (length) distribution of mus- sels found at each study site. There is a progressive increase in both the average and maximum size of the mussels from Crisfield to Cape Charles to Tom’s Cove. This is corre- lated with their position along the temperature/salinity gradient. Both the Tom’s Cove and Crisfield populations approximate a normal distribution of body sizes; how- ever, the Cape Charles population is distinctly bimodal. The age distributions of the 3 mussel populations are illustrated in Figure 3. In the Tom’s Cove population Number of Mussels oo aN [e) [o) ix) fe) _ ° Ae Oo Ge Bog 7 Os Age in Years 3.) 5) cane Figure 3 Age histograms of the Geukensia demissa individuals sampled at the three study areas (Tom’s Cove, n=210; Cape Charles, n=1115 Crisfield, n= 133) there is a constant attenuation of the number of individ- uals with increasing age, implying predictable recruitment and constant mortality. In the Cape Charles and Cris- field populations age class representation is erratic, indi- cating unpredictable settlement or survival of juveniles. The bimodal nature of the Cape Charles size class distri- bution is also evident in the age class structure (Figure 3). Vol. 23; No. 1 The break in the age class distributions corresponds to a lack of four-year-old mussels. Four years before the sam- ples were taken a severe tropical storm hit the Chesapeake area (Tropical Storm Agnes, July 1972). The storm was followed by lowered salinity in much of the bay, which was known to have had a detrimental effect on the marine epifauna (ANDREWS, 1973). Data from the present study indicate that G. demissa population recruitment was ham- pered by the storm, either by reduced fecundity of adults or high mortality of mussel larvae and recently settled juveniles. The age distribution of the 3 populations shows a pro- gressive increase in the longevity of Geukensta demissa from the outer coast study site to the estuarine Crisfield location. This increase is contrasted by the decrease in mussel size observed along the same gradient. Growth Rates Cumulative growth curves for the mussels sampled at each study site, constructed by averaging the sizes of individ- uals found in each age class, are presented in Figure 4. At each location the mussels have an attenuating growth rate with age. The growth rates differ significantly be- tween sites (p < 0.05, ANOVA). Growth rates are highest on the outer coast (Tom’s Cove) and decrease as one moves into Chesapeake Bay (Cape Charles and Crisfield). Tom’s Cove A oat A Cape Jes Get 7 , Crisfield 100 80 60 40 Mean Length in Millimeters 20 I 2 3 4 5 6 i 8 9 10 Age in Years Figure 4 Cumulative growth curves for the Geukensia demissa found at the three study sites. Vertical bars indicate one standard deviation and accurately reflect statistical differences ( < 0.05, ANOVA) THE VELIGER Page 65 The differing maximum and average size of mussels from the 3 study sites (Figure 2), then, appear to be attributed to growth rate differences. The four-year-old Cape Charles mussels show a reduced growth rate which is anomalous relative to the other age classes (Figure 4). This again points to the effect of the tropical storm that year. Mortality As has been noted by previous researchers (LENT, 1969; KUENZLER, 1961) predation on Geukensia demissa does not appear to be common. This probably results from the higher intertidal position of G. demissa, which is physio- logically too stressful for most potential marine predators. ConneELL (1970) has suggested that in physically stressful environments predation is rarely sufficiently potent to alleviate competition among prey species. However, in the extremely high intertidal salt marsh environment, G. demissa has no apparent interspecific competitors. At each study site thorough searches were made for loose, empty Geukensia demissa shells to assess the cause of their death. Approximately equal areas were searched at each location. A total of 92 empty whole shells were found (55 Tom’s Cove, 21 Cape Charles, and 16 Crisfield) and carefully examined for evidence of predation. Shells varied greatly in condition, indicating that they remained in the vicinity of their death for considerable periods of time. None of the mussels, however, gave any evidence of mortality due to predation. Potential predators of Geukensia demissa at the study sites included gastropods, birds, crustaceans, a ray, and terrestrial mammals. Most of these predators damage the shells of bivalve prey and their presence would be detected by examining dead shells. None of the gastropod predators observed at the study sites (Busycon canaliculatum, Uro- salpinx cinereus, Eupleura caudata, and Polinices dupli- cata) were observed as high as the Spartina alterniflora/ Geukensia demissa association on the beach. The latter 3 gastropod species are drills and would leave distinctive drill holes (CaRRIKER, 1955). Bird predation would also leave damaged shells as evidence of their activity (NorTON- GRIFFITHS, 1967). The blue crab Callinectes sapidus was found at all 3 study areas high enough on the beach to prey upon G. demissa. However, the crab’s access to the mussels could be severely hampered by S. alterniflora, and its feeding method would involve shell damage which could be detected in the field. The cow-nosed ray, Rhino- ptera bonasus, is an important local molluscivore, but con- fines its activities to deeper waters than those inhabited by G. demissa (R. Orth, personal communication). KUENZLER Page 66 THE VELIGER Vol. 23; No. 1 (1961) suggests that the raccoon, Procyon lotor, is an im- portant predator on ribbed mussels. Emerged G. demissa respond quickly to shadows or disturbance by closing their valves, a response which is conveyed to other mussels within a clump (LENT, 1969) and strongly suggests adap- tation to resist terrestrial predators. The strong byssal thread attachment of G. demissa would also deter pre- dation by mammals. At some locations, predation by P. lotor is evident by animal tracks and broken shells (S. K. Pierce, personal communication). However, predation by P. lotor appears to be localized and was not observed at any of the study sites. Predation, however, could limit the lower vertical dis- tribution of the mussels, since the majority of their pred- ators are found in the lower intertidal zone. S. K. Pierce (personal communication) found that in situ Geukensia demissa experienced little or no predation at his study area (Alligator Point, Florida), but mussels transferred to the adjacent subtidal zone experienced severe predation within a week by a gastropod drill. Since predation does not appear to be an important fac- tor in mussel mortality, the cause of Geukensia demissa death is of interest. Most empty shells were found still attached by their byssal threads within thriving clumps of mussels, and not collected on the searches for loose mus- sels. Dead in situ mussels were observed at Tom’s Cove and Crisfield, but none could be found at Cape Charles. The quadrat sampling confirmed this observation. At Tom’s Cove 35 dead in sztu mussels were collected repre- senting 16.6% of the quadrat mussels (X density = 105 per 4m’). Thirteen dead in situ G. demissa were found (12% of total) at Crisfield (X density = 46.0 per 4m’). At Cape Charles mussel density was low (X = 22.2 per +m’) and no dead in situ mussels were found. These results sug- gest that the occurrence of dead in situ mussels is density dependent. Density dependent mortality implies that intra- specific competition may be a significant mortality factor in G. demissa populations. Figure 5 shows size and age histograms for the in situ dead mussels from Tom’s Cove. In contrast to comparable histograms for the live populations (Figures 2, 3), these distributions from Tom’s Cove reveal that the dead mus- sels were significantly older (p < 0.05, ANOVA) but were not larger (p >0.05, ANOVA) than the living mussels. This is probably due to the fact that small mussels are capable of considerable movement, while large mussels are incapable of mobility due to their bulk. The length at which mussels become virtually sessile has been shown to be approximately 45mm (LENT, 1969). This corresponds with the increased incidence of dead in situ mussels found Number of Mussels 20 40 60 80 100 Length in millimeters 123 456 7 Age in Years Figure 5 Size and age histograms of the dead in situ Geukensia demissa found in the Tom’s Cove quadrats in the mussel clumps (Figure 5). Small mussels apparently are able to avoid density-dependent mortality by their mobility, but as they become immobile with increased size they become vulnerable to density-dependent mortality. Similarly, Harcer (1968, 1972) showed that the small mussel, Mytilus edulis, by virtue of its mobility, competi- tively excludes the large M. californianus in protected waters. This is accomplished by moving to the outside of mussel clumps and avoiding competition for space result- ing in the death of the large M. californianus. The mechanism whereby immobile Geukensia demissa suffer density-dependent mortality, however, is not clear. (1) Disease and parasites are potentially density-depend- ent mortality factors, but no data are available to clarify this possibility. (2) The larger mussels could be crushed in the growing clump. However, the fact that larger heavier shells of the mussels were found dead in sztu, and the fact that none had damaged shells argue against this possibility. (3) A large immobile mussel could be trapped in a position where it encounters siltation that could impede both feeding and respiration. Reduced growth rates and size of dead mussels support this con- clusion. Comparison of the shell size parameters of the twvo most common age classes of dead zm situ mussels with the comparable age classes of live mussels from Tom’s Cove (Table 1) reveals that dead mussels in these age classes were significantly smaller than living mussels (p = 0.05, ANOVA). Vol. 23; No. 1 THE VELIGER Page 67 Table 1 Mean Sizes (millimeters + standard deviation) of 3- and 4- year old Geukensia demissa found either dead or alive in Tom’s Cove mussel clumps. 3 years old 4 years old = ] = = = N xX X X N x X X Length Width Height Length Width Height Dead Mussels 10 64.6 + 8.0 Zi elin=ty 249 20.0 + 2.2 10 74.8 + 7.5 31.5 + 3.7 23.3 + 2.9 Alive Mussels 32 78.7 + 7.8 32.8 + 2.6 24.0 + 2.1 18 88.1 + 7.1 34.4 + 2.0 Page ae Mets) All size differences between dead and alive mussels are significant at the p < 0.05 level (ANOVA). Shell Shape and Size Since shell allometry can be modified in mussels by growth rate and density (SEED, 1968), shell growth was investigat- ed in the populations studied. Regressions of shell height and width upon shell length (Table 2) were highly signif- icant at each study area. However, these relationships did not differ significantly between study areas (p> 0.05, ANOVA). In Mytilus edulis both high density and in- creased growth rates caused mussels to grow more rapidly in length than in the other dimensions (SEED, 1968). If this were the case in the present study, mussels from Tom’s Cove with higher population densities and growth rates would have indicated this trend. In addition, SEED (op. cit.) found that as M. edulis grows in length, the height to width ratio decreases significantly. This was found. to be the case with the Geukensia demissa in this study (Table 2). However, the relationship was not altered significantly by differences in growth rate between study areas (p> 0.05, ANOVA) as found by SEED (of. cit.). Significant differences were found in the shell weight to tissue weight ratios between the study sites (Table 2). Cris- field mussels have proportionately more shell weight than those of either of the other sites (p < 0.05, ANOVA), and Cape Charles mussels have more shell weight than Tom’s Cove Geukensia demissa (p< 0.05, ANOVA). Since cal- cium availability may be low in low salinity waters, the opposite relationship might have been expected between the study areas (LOWENSTAM, 1954; GraAus, 1974). The results on growth rates (Figure 4) shed light on this appar- ent contradiction. The slow-growing mussels from Cris- field have the heaviest shells while the rapidly growing Table 2 Shell shape and body size relationships of Geukensia demissa found at the study sites (Tom’s Cove = 210, Cape Charles N = 111, Crisfield N = 130). Significance was determined by ANOVA. Parameters Study site Regression equation Significance Length vs Height Tom’s Cove Y = 2.75 + 0.38X p < 0.001 (X) (Y) Cape Charles Y = 2.37 + 0.38X% p < 0.001 Crisfield Y = 1.25 + 0.40X p <0.001 Length vs Width Tom’s Cove Y = —0.77 + 0.32K p <0.001 Cape Charles Yi == 0152) O32 p < 0.001 Crisfield SOS S00 a OseP.< p < 0.001 Length vs Height/Width Tom’s Cove Y = 1.6-0.003X p < 0.05 Cape Charles Y = 1.6-0.003X p <0.05 Crisfield Y = 1.6-0.004X p > 0.05 Shell vs Tissue Tom’s Cove Y = 0.01 + 0.08X p < 0.001 Weight Weight Cape Charles Y = 0.09 + 0.06% p < 0.001 Crisfield Y = 0.06 + 0.04X p < 0.001 Page 68 THE VELIGER Vol. 23; No. 1 Tom’s Cove mussels have the thinnest shells of the popu- lations sampled. When mussels cease growing in external dimensions due to inclement environmental conditions, they continue to secrete material on the interior of the shell. Therefore, if harsh environmental conditions ac- count for the slower growth of estuarine mussels, an in- crease in shell weight would be expected. DISCUSSION Populations of Geukensia demissa from the 3 study areas revealed an interesting pattern. The Tom’s Cove mussels had a higher growth rate, attained a larger maximum size, but were not as long-lived as the mussels in either of the 2 other populations studied. From the open coast to the more severe estuarine environment the mussels showed progressively decreasing growth rates and maximum size, but increasing longevity. This pattern has also been noted in locally varying populations of Mytilus edulis (SEEp, 1969; SAvILoy, 1953) and Patella vulgata (Lewis & Bow- MAN, 1975). FRANK (1975) found an inverse relationship between growth rate and longevity between latitudinally separated populations of Tegula funebralis. He noted that the pattern where high latitude mollusks grow slowly, but live longer than lower latitude conspecifics, is common, and proposed 3 mechanisms predicated on genetic isola- tion. However, results reported in this paper as well as other work on more local patterns, in what appear to be genetically continuous populations (SEED, of. cit.; SAVILov, op. cit-; Lewis & BowMAN, op. cit.; PAINE, 1976) suggest a more general hypothesis. The explanations for the pattern noted by FRANK (1975) are based on latitudinal variations in predation, erratic larval recruitment, and temperature. Predation pressure would not appear to be a causal factor in the similar growth rate/longevity relationship found in Geukensia demissa due to the dearth of predation on this species. The larval recruitment argument (MurpHy, 1968) sug- gests that in areas of erratic recruitment, selection for lon- gevity will be strong. The third explanation, based on the principle of allocation (Levins, 1968), proposes that in- creases in one life history parameter caused by environ- mental factors must be compensated by adjustments in other life history features. In each of these cases a genet- ically mediated trade-off between increased growth rate leading to large size (= increased fecundity) and longevity is proposed. Local patterns in organism size and longevity have been documented for numerous marine invertebrates (Seep, 1969; SaviLov, 1953; Lewis & BowMAN, 1975; PAINE, 1976) in addition to the results of the present study. Habi- tat limitation on the maximum size attainable for a species at a specific location has been demonstrated by transplant- ing animals beween areas where differing sizes were found (SEED, op. cit.; PAINE, op. cit.). These results suggest that variations in size and longevity are habitat-induced effects and not genetically based. The results of the present paper suggest the conclusion that growth and size parameters of Geukensia demissa are determined by differences in the physical regime in each habitat, and are probably con- trolled by the length of the growing season and the occur- rence of physical stress. Differences in the quantity and quality of food between habitats may be an important factor, but ultimately would also be governed by physical conditions. The inverse relationship between size and lon- gevity between G. demissa populations that are most likely genetically continuous suggests that the principle of allo- cation (Levins, 1968) is operating on the phenotypic level. Mussels which are able to achieve fast growth rates by virtue of their habitat may channel more of their re- sources into reproduction at the expense of maintenance, while mussels in habitats that do not allow high growth rates may invest more into general maintenance to assure reproductive success over a longer life span. This sort of phenotypic plasticity in life history characteristics would be a successful strategy in dealing with temporally and spatially unpredictable habitats. Results suggesting the existence of intraspecific compe- tition leading to density-dependent mortality in Geukensia demissa are not entirely unexpected. The ability of this mussel to withstand wide environmental variability (WELLS, 1961; LENT, 1969) and evolve specific adapta- tions for an extremely harsh high intertidal life (Lent. cp. cit.; PrERcE, 1970) allows escape from predators and from interspecific competitors and allows the attainment cf high population densities in a physically stressful envi- ronment. However, having mastered life in the high inter- tidal zone to the point of attaining high population den- sities, populations are located too high in the intertidal region for predators, competitors, or both to alleviate the effect of intraspecific competition. ACKNOWLEDGMENTS I am grateful to Leo Buss, Mark Hay, David Inouye, Mar- gie L. Reaka, and Gary Vermeij for critically reading earlier drafts of this manuscript. Vol. 23; No. 1 THE VELIGER Page 69 Literature Cited AspotTT, Ropert TUCKER 1974. American seashells. Nostrand Reinhold, New York AnprEws, J. D. 1973. Effects of tropical storm Agnes on epifaunal invertebrates in Virginia estuaries. Chesap. Sci. 14 (4): 223 - 234 CarRIKER, MELBOURNE ROMAINE 1955. Critical review of biology and control of oyster drills Urosalpinx and Eupleura. U.S. D. 1. Special Sci. Reprt., Fish. No. 148: 1 - 150 ConnzELL, Joseru H. 1970. On the role of natural enemies in preventing competitive ex- clusion in some marine animals and rainforest trees. In: Dynamics of numbers in populations. Adv. Study Inst. Symp., Oosterbeck, Nether- lands 1972. Community interactions on marine rocky intertidal shores. Ann. Rev. Ecol. Syst. 3: 169 - 192 Frank, PETER WOLFGANG 1975. 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Ecology 57 (5): 858- 873 Pierce, S. K. 1970. Water balance in the genus Modiolus (Mollusca: Bivalvia: My- tilidae) : osmotic concentrations in changing salinities. Comp. Bio- chem. Physiol. 36: 535 - 545 Savitov, A. I. 1953. | The growth and variation in growth of the White Sea inverte- brates Mytilus edulis, Mya arenaria, and Balanus balanoides. Trudy Inst. Onkol. 7: 198 SEED, RAYMOND 1968. Factors influencing shell shape in the mussel Mytilus edulis. Journ. Mar. Biol. Assoc. U. K. 48: 561 - 584 1969. The ecology of Mytilus edulis L. (Lamellibranchiata) on ex- posed rocky shores. II. Growth and mortality. Oecologia (Berlin) 3: 317-350 SUTHERLAND, JOHN PATRICK 1970. Dynamics of high and low populations of the limpet Acmaea scabra (Gould). Ecol. Monogr. 40 (2): 169-188; 19 text figs. TeaL, Joun M. 1962. Energy flow in the salt marsh ecosystem of Georgia. Ecol. 43: 614 - 624 Unitep States DEPARTMENT OF COMMERCE 1976. Surface water temperature and density of the Atlantic coast. NOS publ. 31-1, Washington, D. C. Page 70 THE VELIGER Vol. 23; No. 1 Life History Studies of the Estuarine Nudibranch Tenellia fuscata (Gould, 1870) LARRY G. HARRIS', MARK POWERS’, anp JULIA RYAN ®* INTRODUCTION THE SMALL AEOLID nudibranch Tenellia fuscata (Gould, 1870) can occur in large numbers on concentrations of hydroids in New England estuarine environments (CHAM- BERS, 1934; CLARK, 1975). CLARK (op. cit.) reported that T. fuscata had THompson’s (1967) type 2 or lecitho- trophic development and that veligers settled and under- went metamorphosis shortly after hatching. Rasmussen (1944), working with the closely related Embletonia pallida Alder and Hancock, 1854 (= Tenellia adspersa Nordmann, 1845) reported two developmental patterns at two sites in a Danish estuary; the differences were related to salinity and temperature: At 12%, and 17.5° C many veligers metamorphosed within the egg cap- sule and crawled out of the egg mass as vermiform larvae or they hatched as veligers and metamorphosed shortly thereafter. At 20%, and an average temperature of 22.5° C many veligers swam around for 30 to 120 hours before settling. RocinsKaya (1970) reviewed the ecology of T. adspersa and stated that populations in the Asov Sea at 12%. salinity have contained development. The purpose of this study was to determine the effects of salinity and temperature on the developmental pattern in Tenellia fuscata. Cultivation of this euryhaline, eury- thermal species was attempted at 4 salinities (5, 10, 20, and 30%.) and 3 temperatures (4°, 13°, and 20°C). Data were collected on the development times and types, growth and fecundity rates and life spans. MATERIAL anp METHODS The experimental animals were the F:1 progeny of individ- uals collected from the Great Bay Estuary (New Hamp- " Zoology Department, University of New Hampshire, Durham, New Hampshire 03824 * 8 Concord Way, Portsmouth, New Hampshire 03801 3 15 Pickering Street, Portsmouth, New Hampshire 03801 shire) and a marina in Beverly, Massachusetts. They were maintained in 10cm diameter stacking dishes and fed the euryhaline hydroid Cordylophora lacustris (Allman, 1844), collected at the base of the Oyster River Dam in Durham, New Hampshire. The hydroids were cultured on glass slides held in plastic trays in aquaria at a salinity of 16%; they were fed nauplii of Artemia salina (Linnaeus, 1755). Replicate experiments were performed at 4 salinities, 5, Io, 20, and 30%, in three temperature regimes 4° C, 13°C and at room temperature (about 20°C). Pairs of individuals were isolated in 5cm diameter finger bowls throughout their life cycle. Water was changed daily; in order to reduce thermal shock at lower temperatures, stock solutions were maintained at the desired temperatures. Daily observations were made with a binocular dissect- ing microscope equipped with an ocular micrometer. The measurements made included body length, egg mass num- ber, egg number, and developmental stage. To obtain in- formation on rates of development and larval type, indi- vidual egg masses were isolated and observed daily. RESULTS anp OBSERVATIONS The results of the life cycle studies are summarized in Table 1. The complete life cycle from egg to reproducing adults was observed at all 4 salinities at 20° C. The nudi- branchs did best at 20° C and at 30%, salinity. The second best results were obtained at 20%, salinity at 20° C. The results at 13 and 4°C were poor, though this may have been due to laboratory conditions rather than Tenellia fuscata’s inability to survive under these physical condi- tions. The results of studies at 20° C and 30%, salinity will be described and then compared to those at other salinities and temperatures. At 20°C and 30%, salinity the life cycle of Tenellia from egg laying to death averaged 30 days. It was slightly less at 10%, salinity (27 days) and at 5%. salinity (28 days) at 20°C. Animals did not survive well at the other tem- peratures, particularly at 4°C. The generation time for Vol. 23; No. 1 THE VELIGER Page 71 Table 1 Summary of life history data and fecundity information for Tenellia fuscata grown at several temperatures and salinities. Temperature 20°C 13°C Salinity 30 ppt | 20 ppt | 10 ppt 5 ppt 30 ppt 20 ppt 10 ppt PO Oren Pehle) rehire ze vrs |i Time (days) to: hatching 5 = 5 6 8-9 12 13 11 metamorphosis 5-6 = 5-6 6-7 9 13 14 12 Ist egg mass 20 21 18 16-17 18 death 31 33 31 27 28 Length (mm) at: veliger 0.125 0.125 0.125 0.125 0.125 vermiform stage 0.345 — 0.275 0.25 0.31 Ist egg mass 4.35 4.47 4.04 3.85 3.92 25th day 4.90 4.90 5.17 5.04 4.14 death 4.40 4.69 4.67 4.75 3.97 Largest size 7.35 mm 5.59 mm 5.61mm | 4.37 mm % Increase in length/day from: metamorphosis to Ist egg mass 6.14 — 10.35 9.35 10.23 Ist egg mass to 25th day 2.24 2.19 3.64 2.62 759 25th day to death 1.89 —0.56 aele8 —3.05 —1.43 Average fecundity per individual 2686.51 681.5 2073 1246 1014.5 79 374 417 289 Average # of eggs per egg mass 38.11 34.08 47.65 23.07 29.92 9.88 51 40 53 Number of egg masses per individual 70.5 20 43.50 54 35 8 7.3 10.4 5.5 Average # of egg masses per day 5.22 4 6.2 6.75 5.95 3.2 358) 3.67 3 Egg Size (mm) 0.125 0.125 0.125 0.125 1 = Number of individuals observed, Tenellia was 20 days from egg to egg at 30%, salinity and it was slightly faster at the lower salinities. Growth rates from metamorphosis to death in Tenellia showed three phases (Table 1). The animals grew very fast, increasing their length by 6-10% per day from the time of metamorphosis to the time the first egg mass was produced. At that point the growth rate decreased to approximately 2% per day until day 25, a time in which animals were at or near the greatest length they would achieve. From day 25 to the time of death, approximately day 31, the growth rate was negative with the animal de- creasing in overall length by a few tenths of a millimeter. This trend was consistent at all four salinities at 20C. No growth rate information was obtained for the other two temperature regimes. The fecundity of Tenellza fuscata is quite high consider- ing the size of the animal and the size of the eggs (Table 1). In the F: generation at 20 ° and 30%, salinity animals pro- duced almost 2 700 eggs per individual. This was reduced in the F2 generation to approximately 680 eggs per indi- vidual. The number of egg masses per individual per day was slightly over 5 in the F: generation and 4 in the F2 generation. The average number of eggs per spawn was 38 and 34 respectively in the two generations. The largest variable between these two generations at 30%, salinity was in the total number of egg masses produced per indi- vidual, 70 in the F: and 20 in the Fe. The fecundity in the Fi and Fe generations at 20%, salinity and 20°C were somewhat similar, though the Fi had a lower fecundity than at 30%, and the F2 a higher fecundity than the Fe at Page 72 30% . The number of egg masses per day was higher in both the F: and F2 generations at 20%, salinity though the total number of egg masses was lower than that for the F1 generation at 30%. At 10%, salinity the fecundity was within the range of variation found at the 2 higher salin- ities. The fecundity at 5%. salinity was much lower than at the higher salinities; also, none of the eggs developed at this salinity. There was a slowdown in development time from ap- proximately 5-6 days from egg-laying to metamorphosis at 30 and 20%, to 8-9 days at 5%. salinity. At 13°C the development time was approximately 12-14 days at 30, 20 and 10%,. At 4° C no animals were observed to complete development; one egg mass was placed at 4° at the two- cell stage; it took two months for the embryos to reach the 12 cell stage. Shortly thereafter the embryos died. Also, adult Tenellia fuscata maintained at 4° C did very poorly, seldom fed and showed little or no growth. One of the initial areas of interest was developmental type. At all salinities and temperatures where development did occur it was Type 2 development of THompson (1967) or lecithotrophic. The sequence through to pedi-veliger stage and metamorphosis to the vermiform stage took place whether the animals were within the egg capsule or out swimming and crawling. There was no indication of a factor required to induce metamorphosis. If the stroma of the egg mass was broken down early, then the veligers hatched before the propodium had developed and actively swam. The veligers were rather inactive, spending much of their time on the bottom. After the propodium had formed on day five or later, depending on the salinity and temperature, the animals were then observed to swim and crawl intermittently. By day six at 20° C and 30%, salinity, the animals had completed metamorphosis and were found only on the stems of the Cordylophora provided as food. Therefore, the determining factor in whether the veligers were pelagic for any period of time appeared to be the time taken for the stroma of the egg mass to break down, which released the egg capsules and initiated hatching behavior in the veligers. The stock culture of Tenellia fuscata was initially main- tained at 13°C and 30%, salinity but with the success of cultivation at 20°C and 30%. most animals used for the later experiments were derived from animals maintained at the latter temperature and salinity. Egg masses contain- ing uncleaved zygotes or embryos in the early cleavage stages were incapable of surviving transfer to lower salin- ities whether it be from 30%, to 20%, or 20%, to 10%. or 10%, to 5%. Embryos were able to survive salinity changes THE VELIGER Vol. 23; No. 1 only after they had begun rotating within the egg cap- sules. In all cases, metamorphosed nudibranchs were bet- ter able to survive changes in salinity than were develop- ing veligers. At the lowest salinities, 10%. and 5%o, survival was poor both among larvae and adults transferred from higher salinities. Embryos transferred to these salinities showed high mortality and those that did continue to develop tended to have abnormal appearing shells. However, ab- normal shells did not inhibit survival and metamorphosis was completed in these individuals. At 10%, salinity eggs laid by the individuals in that culture developed, but did not survive to metamorphosis. At 5%. none of the eggs produced by the one pair raised at this salinity began to cleave. DISCUSSION The results of this study suggest that Tenellia fuscata does best at higher salinities and temperatures. Field collec- tions from the Great Bay Estuary indicated that the appearance of this nudibranch at sites within the estuary corresponded with the appearance of certain hydroid spe- cies and the nudibranchs were observed farther up the estuary as salinities and temperatures increased. The Great Bay Estuarine System has a wide range in salinity and temperature. Salinities in the upper bay fluc- tuate from about 5%, during the spring thaw to 32%, in late summer. Temperatures range from —1.5° C in late winter to about 27° C in August. Hydroid species found in the estuary tend to show a sequential appearance keyed to temperature and salinity conditions (NoRMANDEAU, 1976). The short life cycle and high fecundity in Tenellia fuscata are obvious adaptations for exploiting a transient food source (MILLER, 1961, 1962; THOMPSON, 1964). Tenellia fuscata has an ecology similar to that described for T. adspersa (RASMUSSEN, 1944; ROGINSKAYA, 1970), though it does not seem to have a high tolerance for low salinities. The lowest salinity recorded by CLarK (1975) was 16%, while 20%, was the minimum salinity recorded at collection sites during this study. RASMUSSEN (1944) found T. adspersa at 12%. and it is reported in salinities down to 5%. (RocINSKAyYA, 1970). At 20°C adult nudi- branchs did survive and reproduce at salinities of 10%. and 5%, but the development of embryos was incomplete (10%) or no development occurred (5%o). Before the experiments began, Tenellia were maintained at 13°C and 30%, salinity. Under these conditions sur- Vol. 23; No. 1 THE VELIGER Page 73 vival, growth and reproduction were excellent, so the poor results at this temperature during the experiments was surprising. Most of the experiments at the lower tempera- tures were attempted during the time when there was trouble with toxic substances diffusing from plastic culture trays and the Cordylophora was doing poorly. The un- healthy hydroid food may have affected the well-being of the nudibranchs. One of the primary goals of this study was to see if changing temperatures or salinities or both would affect development type as suggested by RasMusSEN (1944). Rasmussen found that Tenellia adspersa at 22.5%. salinity and 20-25 C hatched in 4 days and swam about for 30 to 120 hours before undergoing metamorphosis while at 12%, salinity and 17° C the veligers metamorphosed before leav- ing the egg mass at 9 days. In both cases metamorphosis was complete by 9 days and hatching time was the primary difference. The 5 to 9 days development to metamorphosis at the higher temperature and salinity is comparable to the results at 20° C and 20%, and 30%, in this study, while the g days to metamorphosis at hatching at the lower salinity and temperature is faster than that observed at 13° C and 20%. (14 days). Therefore, while development time and pattern did not vary in T. adspersa, temperature and salinity do appear to influence the rate of development in T. fuscata. The influence of temperature and salinity on the physiology of animals is well documented (NEWELL, 1970). In this study, the development times at 20°C and 30%, 20%, 10%, and 5%. were 6, 6, 7 and g days respectively, suggesting that salinity, independent of temperature, can influence the developmental rate,at least in T. fuscata. The second factor that appears to be important. here is the rate of breakdown of the stroma of the egg mass. Veligers will not attempt to hatch from their capsules until the gelatinous matrix of the egg mass has broken down sufficiently to release the capsules (Harris, 1973). If the stroma does not break down, the veligers continue development through metamorphosis and hatch in the vermiform stage. Evidence from this study and previous experience by the senior author (HarRIS, 1973, 1975) in- dicate that external factors such as bacterial action, bur- rowing by micrometazoa and water motion are primarily responsible for the breakdown of the stroma of nudibranch egg masses. It seems likely that the differences in hatching time for Tenellia adspersa observed by RASMUSSEN (1944) were influenced by the rates at which the egg masses broke down at the two salinity and temperature regimes. One of the more interesting findings of this study was the inability of zygotes and early embryos to tolerate salin- ity changes. Only after embryos had begun to rotate within the capsules were they able to survive a drop in salinity. An organism living within a fouling community at a fixed point in an estuary does not experience a single tempera- ture or salinity on a tidal cycle,but rather a range of salin- ities and temperatures. An animal may not be able to sur- vive permanently at one of the extremes of this range, but it may be able to endure short exposures as long as the remainder of the time the environmental conditions are well within its range of tolerance. It was found that Tenellia grown at one salinity produced eggs that were not able to adjust to a drop in salinity though early veligers were capable of osmoregulating. It would be interesting to see if adult Tenellia exposed to a cyclical range of salinities produced eggs with a greater tolerance to salinity fluctu- ation. If one is to understand the ecology and physiological adaptiveness of estuarine organisms, these must be tested under conditions similar to the actual fluctuating environ- ment in which they typically occur. SUMMARY 1. The estuarine aeolid nudibranch Tenellia fuscata was raised under laboratory conditions to compare several as- pects of its life cycle when grown at various temperature (20, 13, and 4°C) and salinity (30, 20, 10, and 5%.) regimes. The parameters compared included growth rate, generation time, fecundity and development type. 2. Growth and survival were best at 30 and 20%, salin- ities at 20° C. Development time from egg laying to meta- morphosis increased at 10 and 5%, at 20°C and also at the lower temperatures. 3. There was no difference in the development type; variation in the stage at which the young nudibranchs hatched was dependent on the rate at which the stroma of the egg mass deteriorated. 4. Eggs and embryos were not able to tolerate decreases in salinity until they were rotating in the egg capsule. It was suggested that, since estuarine forms experience a con- stantly fluctuating environment, tolerance levels might be best understood if they were studied using a system that mimicked the natural fluctuating environment. Page 74 THE VELIGER Vol. 235\Newa Literature Cited CHAMBERS, LESLIE A. 1934. Studies on the organs of reproduction in the nudibranchiate mol- lusks, with special reference to Embletonia fuscata Gould. Bull. Amer. Mus. Nat. Hist. 66: 599 - 641 Crarx, Kerry Bruce 1975. Nudibranch life cycles in the Northern Atlantic and their rela- tionship to the ecology of fouling communities. Helgol. wiss. Mee- resunters. 27 (1): 28-69; 14 text figs. Harris, LARRY GARLAND 1973. Nudibranch associations. in: Current topics in comparative pathobiology. T. C. Cheng, ed. Acad. Press, Inc. New York II: 213-315 1975- Studies on the life history of two coral-eating nudibranchs of the genus Phestilla. Biol. Bull. 149: 539 - 550 Miiier, MicHaEL CHARLES 1961. Distribution of food of the nudibranchiate Mollusca of the south of the Isle of Man. Journ. Anim. Ecol. 30 (1): 95-116 (May 1961) 1962. Annual cycles of some Manx nudibranchs, with a discussion of the problem of migration. Journ. Anim. Ecol. g1: 545 - 569 NEWELL, RicHARD CHARLES 1970. Biology of Intertidal Animals. Inc., New York. 555 pp. NoRMANDEAU ASSOCIATES 1976. Piscataqua River ecological studies, 1975 monitoring studies. Report No. 6 for Public Service Company of New Hampshire RASMUSSEN, ERIK 1944. Faunistic and biological notes on marine invertebrates. I. The eggs and larvae of Brachystomta rissoides (Hanl.), Eulimella nitidtssima (Mont.), Retusa trunculata (Brog.) and Embletonia pallida (Alder and Hancock) (Gastropoda marina). Vidensk. Medd. Dansk Na- turhist. Foren. 102: 207 - 233 Rocinsxkaya, I. S. 1970. Tenellia adspersa, a nudibranch new to the Asov Sea, with notes on its taxonomy and ecology. Malacol. Rev. 3 (2): 167-174 (13 March 1971) Amer. Elsevier Publ. Co., THompPpson, THOMAS EVERETT 1964. Grazing and the life-cycles of British nudibranchs. Pp. 275 to 297 in D. J. Crisp (ed.), Grazing in Terrestrial and marine En- vironments. Blackwell, Oxford 1967. Direct development in a nudibranch, Cadlina laevis, with a dis- cussion of developmental processes in Opisthobranchia. Journ. Mar. Biol. Assoc. U. K. 47 (1): 1-22; 8 text figs. Vol. 23; No. 1 THE VELIGER Page 75 Late Quaternary Bankia (Bivalvia : Teredinidae) from Humboldt County, California GEORGE L. KENNEDY ', ANTHONY D’ATTILIO’, SAMUEL D. MORRISON ;, AND KENNETH R. LAJOIE’ (1 Text figure) Fossil teredinids (Mollusca: Bivalvia) occur only spo- radically in Tertiary and Quaternary marine deposits along the Pacific margin of the western United States. Most occurrences are of the typical (but generically un- identifiable) calcareous tubes and associated sediment- filled burrows most often found in fossilized wood. Shells and pallets, however, are extremely rare and have been reported previously only by DuRHAM & ZULLO (1961: 1; figs. 1-3), from the Oligocene [= upper Eocene, Refugian Stage] Lincoln Formation of western Washington (Bankia lincolnensis), and by Kern (1973: 82), from the lower Pliocene Towsley Formation of southern California (Bankia sp. cf. B. setacea) We report here a third occur- rence, of Bankia sp. cf. B. setacea (Tryon), from a Holo- cene marine terrace south of Cape Mendocino, southern Humboldt County, California (LACMIP loc. 5814 and USGS Cenozoic loc. M7208). Species of Bankia can be separated from all other tere- dinids by their cone-in-cone pallets. However, identifica- tion of fossil teredinids is tenuous because the periostracal ornamentation on the calcareous part of the pallets is not preserved in fossils, although it is the periostracal part that is largely used in distinguishing living teredinid species, particularly in the genus Bankia (TurNER, 1966: 14). As an example, pallets of Bankia lincolnensis Durham and Zullo, from the late Eocene, do not exceed the limits of variation seen in dried pallets of modern B. setacea (Tur- NER, 1966: 16). Although these taxa undoubtedly do not * U.S. Geological Survey, Menlo Park, California 94025 2 San Diego Natural History Museum, San Diego, California 92112 3 Department of Geology, Humboldt State University, Arcata, California 95521 represent the same biologic species, it is not possible to separate them on the basis of their pallet morphology alone. The Humboldt County specimen is also indistin- guishable from specimens of B. setacea. Because of the sim- ilarity of pallets and because the only Bankia found living along the northeast Pacific margin is B. setacea (Tryon, 1863), we tentatively assign our specimen (Figure 1) to that species. The specimen of Bankia was discovered in a well- rounded piece of driftwood within a sparsely fossiliferous basal conglomerate lying directly on a terrace abrasion platform about 4m above sea level. The specimen was associated with an invertebrate fauna of approximately 25 to 30 species, mainly mollusks, all of which are found today along the Humboldt County coast. Only Cryptomya californica (Conrad, 1837), Macoma inquinata (Deshayes, 1855), and Tresus capax (Gould, 1850) were found in situ and several paired valves of each species were found. Periostracum was still present on all three species, as were ligaments on the Macoma. The piece of unidentified driftwood containing the Bankia was approximately 7-8 cm long and contained only one burrow, extending from one end to the other and doubling back on itself at least once. The average burrow diameter was 5-7mm. The short calcareous part of the tube was plugged by carbonate-cemented debris. One pal- let was partly cemented into the debris plug, and individ- ual cones from the pallets were loose in the burrow, prob- ably dislodged by disturbance after collection. A piece of one pallet is illustrated in Figure 1. Both valves of the Bankia were found nestled together in perfect condition at the opposite end from the calcar- eous tube, but were both damaged during their excavation. Page 76 THE VELIGER Vol. 23; No. 1 Figure 1 LACMIP hypotype 4943, segments of cone-in-cone pallet of Bankia sp. cf. B. setacea (Tryon), from south of Cape Mendocino, Hum- boldt County, California (LACMIP loc. 5814). Height of incom- plete specimen ~4 mm, oriented with posterior (apertural) end up. Illustration by A. D?Aitilio The valves, and a small piece of the wood showing part of the burrow, have been retained with the pallets. The re- mainder of the wood was used for radiocarbon dating to establish the Holocene age of the marine terrace (3130 100 years BP; University of Miami radiocarbon labora- tory, UM-1587). ACKNOWLEDGMENTS We are grateful to Warren O. Addicott, John M. Armentrout, Ellen J. Moore, Ruth D. Turner, and an anonymous reviewer for commenting on the manuscript. LOCALITY LACMIP loc. 5814 and USGS Cenozoic loc. M7298. Holocene emergent marine terrace. Sparsely fossiliferous basal conglomerate lying on abrasion platform and exposed in low sea cliff on west side of Mattole Road ~ 2.93kmS 17.25° E of Cape Mendocino lighthouse and ~1.0kmN 28° W of Devils Gate, Humboldt County, California (USGS Cape Mendocino, Calif. quad., 1969 ed., 7.5’ ser., scale 1:24,000). Elevation ~ 4m (13.35 feet) above sea level (MHWL) and ~ 1.5 m above back edge of beach. Lati- tude 40°24'53.7” N , longitude 124°23’44.1” W. Collected by G. L. Kennedy, S. D. Morrison, and K. R. Lajoie, 15 February 1979. Literature Cited DuruHaM, JoHN Wyatr & Victor Aucust ZULLO 1961. The genus Bankia Gray (Pelecypoda) in the Oligocene of Wash- ington. The Veliger 4 (1): 1-4; 3 text figs. (1 July 1961) Kern, JOHN PHILIP 1973. Early Pliocene marine climate and environment of the eastern Univ. Calif. Publ. Geol. Sci. (30 March 1973) Ventura basin, southern California. 96: i- viii + 117 pp.; 27 figs. Turner, Ruta Dron 1966. A survey and illustrated catalogue of the Teredinidae (Mollusca: Bivalvia). i-x+1-265 pp.; plts. 1-64; text figs. 1-25; 1 table Mus. Comp. Zool., Harvard Univ., Cambridge, Mass. (4 March 1966) Vol. 23; No. 1 THE VELIGER Page 77 The Organisation and Chemistry of the Byssus of some Bivalves of the Waltair Coast, India ANISA BANU, K. SHYMASUNDARI ano K. HANUMANTHA RAO Zoology Department, Andhra University, Waltair-530 003, India (3 Text figures) INTRODUCTION “ADULT BIVALVES and related mussels secrete a complex extra-organismal structure, the ‘Byssus’ which serves as a mechanism by which these sessile molluscs attach to littoral substrata” (YONGE, 1962). The study on byssus dates back to the late 17" century when Heme (1684) made a study of the byssus with its roots in the foot of the animal but he considered it to be a plant. In the early 18° century, REAUMUR (1711) gave the first accurate description of the byssus of Mytilus. Coupin (1892) and BouTANn (1895) investigated the byssus in a wide range of lamellibranchs. X-ray diffraction photographs of the byssus threads of Mytilus and Pinna were furnished by FAURE-FREMIET & Boupony (1938), and they reported them to be of collagen type. Brown (1952) claimed that the fibres were colla- gen hardened and were comparable to those of the insect cuticle. MELNIcK (1958) reported the presence of colla- gen in the phylum Mollusca. PIkKKARAINEN et al. (1968) reported on the occurrence of collagens in Mytilus edulis and Pinna nobilis. This was followed by some important contributions on the presence of collagen in the byssus of M. edulis (Pujot et al., 1970), on the analysis of secre- tions of the byssus (MaHE£o, 1970), on the biophysical characteristics of the byssus threads (BAIRATI & VITELLARO, 1970) and on tanning in byssus threads (RAVINDRANATH & RAMALINGAM, 1972). Description of byssus in Arca zebra was furnished by PETER et al. (1973), while ENGEL et al. (1971), ScHWaRTz et al. (1972) and BoweEN et al. (1974) made further studies on the attachment discs of the byssus threads. TaMaRIN et al. (1976) are of the opin- ion that the formation of a colloidal dispersion in water is necessary for the attachment of active sites. Extensive morphological and histochemical studies on byssus in Lithodomus lithophaga were made by BoLocnoni et al. (1975). Recently, ALLEN et al. (1976) made observa- tions on the formation and mechanical properties of the byssus threads in Mytilus edulis. MATERIALS anp METHODS The present work deals with the physical properties as well as the solubility of the byssus threads in 11 species of bivalves, which have been collected in and around Visa- khapatnam. They are Perna viridis, Perna indica, Septi- fer bilocularis, Modiolus metcalfei, Arca symmetrica, Bar- batia obliquata, Isognomon nucleus, Pinctada margariti- fera, Pinna vexillum, Beguina variegata and Mytilopsis sallet. The byssus threads of these bivalves were carefully separated from their foot along with the root region. They were then washed thoroughly with water to remove the adhering sand and other particles. A single, whole byssus thread was separated from the bundle and examined under the microscope. For the solubility tests, the byssus threads were tested in both cold and boiling water, ammonia, alcohol, con- centrated hydrochloric acid, concentrated hot HCl, con- centrated sulphuric acid, concentrated nitric acid, hot concentrated acetic acid, cold concentrated acetic acid, aqueous alkaline sodium sulphide, hot concentrated pot- ash, aqueous sodium hypochlorite, aqueous lithium iodide and lead acetate tests. A dilute solution of ferric chloride is used to find the reaction of orthodiphenols. OBSERVATIONS In Arca symmetrica (Figure 1A) and Barbatia obliquata (Figure 1B) the byssus threads are yellowish brown in colour and translucent. They are strip-like without a distinct division being made of a root, stem and the threads. The proximal part of the byssus is embedded in the posterior groove of the foot. At the distal part are the attachment discs by which the byssus threads get at- tached to the substratum. In the case of Modiolus met- calfei (Figures 1C & c), Septifer bilocularis (Figures 1D THE VELIGER Vol. 23; No. 1 Figure 1 A: Byssus thread of Arca symmetrica B: Byssus thread of Barbatia obliquata C: Corrugations seen on one side of the thread of Modiolus met- calfei c: Attachment disc of Modiolus metcalfei D: Soft flattened part of the thread in Septifer bilocularis d: Attachment disc of Septifer bilocularis & d), Perna viridis (Figures 2B « b), Perna indica (Fig- ures 2C &c) and Pinna vexillum (Figures 3C « c), the byssus threads when just formed are yellowish brown, translucent and soft in appearance. But in all these forms the mature byssus threads are tough and dark brown in colour. In all these cases the threads are divisible into a root region which is embedded in the byssus gland at the region of the posterior groove of the foot, and a stem region that is continuous with the root region and is hard to the touch. To this stem are attached thousands of byssus threads. Each byssus thread again shows a posterior region Figure 2 > : Branched proximal part of the byssus thread of Isognomon nucleus : Attachment disc of Isognomon nucleus : Soft, flat part of the byssus thread of Perna viridis : Attachment disc of Perna viridis : Proximal part of the byssus thread of Perna indica : Attachment disc of Perna indica : Branched proximal part of the byssus thread of Pinctada mar- garitifera : Attachment disc of Pinctada margaritifera pearwe [ov which is flat and soft and which occupies about } of the length of the byssus thread. These threads are attached to the stem by a ring of material at the proximal region. The surface of this proximal part is corrugated completely in Perna viridis, Perna indica and Septifer bilocularis. In S. bilocularis the corrugations are more numerous com- pared to those of the former 2 species. Peweo--; wut Szo'o a Figure 3 : Proximal region of the byssus thread of Beguina variegata : Rounded tip of Beguina variegata : Flattened part of the byssus thread of Mytilopsis sallei Attachment disc of Mytilopsis sallei : Proximal part of the byssus thread of Pinna vexillum : Attachment disc of Pinna vexillum 8S ATwWER pS In Modiolus metcalfei these corrugations are seen only on one side, and the other side is a straight line. In Mytil- opsis sallei (Figures 3B «& b) the posterior region of the byssus thread is flat without any corrugations of any sort. It is quite hard when compared to the byssus of Per- na viridis and Perna indica. But the ring part by which this is attached to the stem region of the byssus thread is quite conspicuous. In Beguina variegata (Figures 3A «& a) there is no distinct division into a posterior soft and a distal hard cylindrical portion. There is also no distinct, THE VELIGER Page 79 separate attachment disc by which these threads get at- tached to the substratum. The entire thread is cylindrical and hard, with a distal rounded tip. It is attached to the substratum with this rounded tip. Continuous with this proximal, soft, flat portion is a rounded cylindrical hard portion of the byssus thread which occupies the remaining + of the length of the byssus thread. This situation is ob- served in Perna viridis, Perna indica, Modiolus metcalfei, Mytilopsis salle: and Septifer bilocularis. In Pinna vexillum the byssus thread is remarkable in that the stem region is bifurcated in the proximal portion, each branch having a separate root region by which it is embedded in the byssus gland. To the stem part are at- tached the byssus threads. In this species there is no soft, flat, corrugated proximal region, the entire thread being straight, cylindrical and hard. In Isognomon nucleus (Figure 2A & a) and Pinctada margaritifera (Figure 2D « d) the proximal region of the thread is soft, flat, yellowish green in colour and not cor- rugated, but is branched. This forms 4 of the length of the thread. The remaining 2 of the thread is hard, flat, and green in colour. At the distal end of the byssus thread is the attachment disc which is flower-like except in Pinctada margaritifera, Isognomon nucleus, Barbatia obliquata and Arca symmet- rica. The attachment proper is soft and translucent in ap- pearance and light yellowish in colour. Byssus threads in Barbatia obliquata and Arca symmet- rica appear to occupy the entire length of the groove. They are soft in both forms. In Pinna vexillum they are hard and cylindrical. In Beguina variegata each byssus thread is smooth and all the threads joined together give a very soft, smooth and bushy appearance. In Pinctada margari- tiferaand Isognomon nucleus the threadsare dark greenin colour except for the root part which is of a lighter shade and transparent. Unlike the byssus root of other species, the root in these 2 species is branched. In order to determine the nature of the byssus threads, the following solubility tests were conducted. In all the species no part of the byssus is soluble in cold water. Even in boiling water they are not soluble except that they un- dergo writhing contractions. Maximum shortening is ob- served in the byssus root region, but the contractions in the thread region are not much pronounced. None of them are soluble either in ammonia or in alcohol. In concentrated HCl the byssus threads dissolved slowly, the byssus itself turning to a wine-red colour. In concentrated hot HC] the reaction is hastened. However, in Pinna vexil- lum, the stem region of the byssus thread dissolves at a moderate rate. Swelling or dissolution in dilute acids or alkalis is stated to indicate the presence of electrovalent Page 80 THE VELIGER Vol. 23; No. 1 linkages. The dissolution of byssus threads in concen- trated sulfuric acid is quite rapid except in Mytilopsis sallet, Isognomon nucleus and Pinctada margaritifera, where it is slow. In Arca symmetrica and Barbatia ob- liquata rapid dissolution is observed. In nitric acid all the threads dissolve slowly, yielding a yellow solution, but in Arca symmetrica and Barbatia obliquata the process is very slow. They do not dissolve in aqueous alkaline sodium sulfide, which generally is supposed to dissolve all types of keratin material. Hot concentrated potash dissolves the byssus material except in Mytilopsis sallec and Barbatia obliquata. All the byssus threads are slightly soluble in hot concentrated acetic acid, but complete dissolution does not occur. In cold concentrated acetic acid they dissolve very slowly. Aqueous sodium hypochlorite, which dissolves quinone tanned proteins (BROWN, 1952), has been found to dissolve all parts of the byssus threads of all the species examined. This suggests the presence of aromatic tanning. The dissolution process progressively increases on applica- tion of heat. The lead acetate test for sulphur has little effect on the byssus threads, indicating that sulphur con- tent is low. Agents, such as aqueous lithium iodide, cause swelling of the root region of the byssus threads. The fact that mature threads dissolve at a slower rate than the younger threads indicates that they are older and harder and hence slow to dissolve. Orthodiphenols react with even a dilute solution of fer- ric chloride to produce a green colour turning to red on addition of sodium bicarbonate. A dilute solution of ferric chloride was used for soaking the byssus threads. The change of colour to green in the stem and the threads in the case of Perna viridis, Perna indica, Modiolus metcal- fei, Isognomon nucleus, Pinna vexillum and Pinctada margaritifera is very pronounced. In Mytilopsis sallet no change could be observed in mature byssus threads, but the younger threads turned green. This may be due to the fact that in the mature threads, being dark brown in col- our, the change in colour was masked. The change of colour in the byssus threads of Septifer bilocularis and Beguina variegata is faint. In Barbatia obliquata and Arca symmetrica the root part turns green. On soaking them in sodium carbonate, the whole part turns red in all the species. From these solubility tests it could be inferred that the byssus threads are not keratin, because none of them is soluble in aqueous alkaline sodium sulfide, which specifi- cally dissolves keratin by breaking the electrovalent and disulfide bonds. But they dissolved completely in aqueous sodium hypochlorite, which dissolves quinone-tanned proteins. Hence it could be concluded that the byssus thread is a quinone-tanned protein. The quinone-tanning of the byssus thread occurs during its formation. The sul- phur content of the byssus thread is found to be low, as the results obtained with the lead acetate test were negligible. In addition to this, the non-solubility of these threads in aqueous alkaline sodium sulfide indicates that the disulfide bonds are minimal in number. Though the byssus threads of these 11 species have morphological differences, their reactions in differing solvents are the same, hence their chemical nature appears to be similar. When the threads were soaked in a dilute solution of ferric chloride, they turned green. When they were sub- sequently treated with sodium carbonate, they turned red. This change of colour is typical of orthodiphenols which act as precursors in quinone-tanning. DISCUSSION The observations made on the byssus threads of all the species examined are in agreement with those given by BRowN (1952). All the byssus threads have been found to end in a root region and the roots are attached to the stem part. The threads are attached to the substratum by means of the attachment disc. TAMARIN et al. (1976) re- ported that the attachment disc is the only adhesive inter- face between the byssus and the external environment. The thread when first formed is white, then slowly turns yellow and then becomes brown. This is due to the phe- nomenon of tanning. Pinna vexillum has a stem which is bifurcated. Puyot (1967) stated that the byssus of Pinna nobilis corresponds only to the stem of Mytilus edulis. In the present study it has been revealed that the poste- rior corrugated root region is the extensible part in a byssus thread. MERcER (1952) has also shown that the byssus threads are extensible. However, the degree of ex- tensibility varies from fibre to fibre. BRown (1952) stated that the proximal region of the byssus thread is the most extensible but ALLEN e¢ al. (1976) are not in agreement with this statement. According to TAMARIN (1975), the byssus stem is formed by the secretions of the cells of the musculo-glan- dular region at the base of the stem generator and that secretion pressure in the gland forces it out. BRowN (1952) is of the opinion that the formation of the thread is asso- ciated with periodic secretory activity at the mouth of the byssus gland and the newly secreted material does not fuse with that previously secreted. From our observations it has been revealed that as the material is being added from the glands, the stem increases in length. The threads are formed in the groove and the attachment disc is Vol. 23; No. 1 formed by the depression of the groove. As the stem increases in length, the threads attached to it are carried far away from the groove region. SCHLOSSBERGER (1856) and KRUKENBERG (1881 & 1882) analysed the byssus threads of Mytilus and con- cluded them to be conchiolin. Based on the sulphur con- tent of the material, FauRE-FrEmiIET « Boupony (1938) stated it to be keratin. On boiling the byssus threads in water, they exhibited contractions. Brown (1952) has shown that either alteration in shape or dissolution in boiling water indicates the presence of weak linkages easi- ly broken by thermal agitation. In the present study it has been shown that the byssus threads are not keratin because they are insoluble in aque- ous alkaline sodium sulfide (BRowNn, 1952). It could be quinone-tanned protein because they dissolved in aqueous sodium hypochlorite. Brown (op. cit.) pointed out that quinone-tanning of the byssus threads may be occurring during their formation. The change of colour of the byssus threads to green in dilute ferric chloride solution and the subsequent change to reddish mauve in a solution of so- dium carbonate is characteristic of orthodiphenols. This observation is in accordance with BRown (op. cit.), who stated that orthodiphenols act as precursors in quinone- tanning. Quinone-tanning has been reported in the byssus and periostracum of Mytilus edulis and byssus of Dreis- sena (Brown, 1950). The presence of quinone-tanning in these byssus threads is further confirmed by the histochemical reactions of the white, phenol and enzyme glands whose secretions lead to the formation of the byssus threads. The white gland and the phenol gland supply phenolic proteins which are acted upon by the polyphenol oxidase from the enzyme gland leading to the formation of the byssus thread. The tanning of the byssus thread takes place by an ‘auto-quinone’ mechanism (AnisA BaNu, 1977). This is in direct sup- port of SMyTH’s (1954) findings that the byssus thread is a phenolic protein, which under enzyme action becomes tanned by the combination of the amino portion and the quinone nucleus of adjacent molecules. He termed this process auto-quinone tanning. The function of the byssus is to secure the post-larva to a substratum when it is undergoing metamorphosis. In younger forms it fixes them for shorter or longer periods. The strength and extensibility of the byssus threads and their distribution allows the bivalves to withstand both the pounding of the waves and the drag of the advancing and receding tides. The byssus threads are generally present in a circle around the base of the foot and help the animal to withstand wave action from any direction. The animal may remain fixed in one place for many months and the THE VELIGER Page 81 high chemical resistance of the byssus keeps it from de- caying. When the mussel moves it either breaks the byssus threads or pulls them off entirely by strong contractions of the byssus muscles. Literature Cited ALLEN, J. A., M. Coox, D. J. Jackson, S. Preston « E. M. WortH 1976. Observations on the rate of production and mechanical proper- ties of the byssus threads of Mytilus edulis. Journ. Moll. Stud. 42: 279 - 289 Banu, ANISA 1977. Studies on the histology and histochemistry of foot and shell in some byssus bearing pelecypods. Ph. D. Thesis, pp. 1 - 270 Barratt, Jr., A. & L. Z. ViTELLARO 1970. Biophysical characteristics of Mytilus byssus. Congr. Leningrad: 192 Borocnant, F, A. Marta & V. G. Maria 1975. Histochemical and histomorphological study of the byssal ap- paratus of Lithodomus lithophaga. Arch, Zool exp. gen. 116: 229 to 244 Boutan, L. 1895. Recherches sur le byssus des lamellibranches. exp. gen. 3: 297 - 338 Bowen, H. J., PR W. D. Mitcuett « T. D. OHANNESSIAN 1974. Dental cement from marine sources. Tech. Reprt. Franklin Inst. Res. Lab., Philadelphia. No. C2871-FR Brown, C. H. 1950. A review of the methods available for the determination of the types of forces stabilizing structural proteins in animals. Quart. Journ. Microsc. Sci. g1: 331 - 339 F952. Some structural proteins of Mytilus edulis. Microsc. Sci. 93: 487 - 502 Courin, H. 1892. Les mollusques. Paris, Carré Encet, R. H., R. E. Hiriman, M. J. Near « H. L. QuINBY 1971. A study of adhesive mechanisms of various species of the sea mussel, Reprt. No. NIH-NIDR 70: 2237 Fauré-Fremiet, E. « C. T. Boupony 1938. Etude roentgenographique des kératines sécrétées. Chim. Biol. 20: 24 Heme, A. V. 1684. Anatomie Mytuli, belgice mossel. KRuKENBERG, C. F W. 1881. Vergleichend physiologische Studien. 1. Reihe, 5. Abtheil. 56. Heidelberg 1882. Vergleichend physiologische Studien. 2. Reihe, 1. Abtheil 59. Heidelberg Mauéo, R. 5 1970. Study on the settling process and secretion of the byssus of Mytilus edulis. Cahiers de Biol. Mar. 11: 475 - 483 MELNIK, S. C. 1958. Occurrence of collagen in the phylum Mollusca. Nature (London) 181: 1483 Mercer, E. H. 1952. Observations on the molecular structure of byssus fibres. Austral. Journ. Mar. Freshwater Res. §: 199 - 205 Peter, A. S., A. Potin & E. Conway 1973. Histological analysis of the mechanism of the byssus of Arca zebra. 68th Annual. Meet. Amer. Soc. Zool. PIKKARAINEN, J., J. RANTANEN, M. VasTAMAK!, K. Lampiano, A. Kari & E. KuLonen 1968. On collagens of invertebrates with special reference to Mytilus edulis. Europ. Journ. Biochem. 4: 555 - 560 Pujou, J. P 1967. Le complex byssogéne des mollusques bivalves. Histochimie com- parée des sécrétions chez Mytilus edulis L. et Pinna nobilis L. Bull. Soc. Linn. Normandie 8: 308 - 332 Pujot, J. P, J. Bocquet, Y. TirFon & M. RoLtanp 1970. Analysis of the calcified byssus of Anomia ephippium (bivalve mollusk). Calcif. Tiss. Res. 5: 317-326 IX Int. Anat. Arch. Zool. Quart. Journ. Bull. Soc. Amstelodami Page 82 THE VELIGER Vol. 23; No. 1 RAVINDRANATH, M. H. & K. RAMALINGAM 1972. Histochemical identification of Dopa, Dopamine and Catechol in phenol gland and mode of tanning of byssus threads in Mytilus edulis. Acta Histochem. 42: 87 - 94 Reaumur, R. A. E de 1711. Histoire de l’Académie Royale des sciences. Paris, 114 SCHLOSSBERGER, J. 1856. Zur naheren Kenntniss der Muschelschalen, des Byssus und der Chitinfrage. Ann. d. Chem. & Pharm. 98: 99 - 120 ScHwartz, W. E., G. W. Kinzer, M. J. Neat & R. E. Hitman 1972. A study of the adhesive mechanisms of various species of the sea mussel. Reprt. No. NIH-NIDR 70: 2237 SmytTa, J. D. 1954. A technique for the histochemical demonstration of polyphenol oxidase and its application to egg-shell formation in helminths and byssus formation in Mytilus. Quart. Journ. Microsc. Soc. 95: 139 to 152 Tamarin, A. 1975. An ultrastructural study of byssus stem formation in Mytilus californianus. Journ. Morph. 145: 151-177 Tamarin, A., P Lewis & J. ASKEY 1976. The structure and formation of the byssus attachment plaque in Mytilus. Journ. Morph. 149: 199 - 222 Yoncz, CHARLES MAuRICE 1962. On the primitive significance of the byssus in the Bivalvia and its effects in evolution. Journ. Mar. Biol. Assoc. U. K. 42: 113-125 Vol. 23; No. 1 THE VELIGER Page 83 Sublittoral Observations of Behaviour in the Chilean “Loco” Concholepas concholepas (Mollusca : Gastropoda : Muricidae) RANDOM DvBOIS', JUAN C. CASTILLA?, ann ROBERTO CACCIOLATTO:3 (2 Text figures) INTRODUCTION THe Muricw, Concholepas concholepas (Bruguiére, 1789) or “loco” as it is commonly known, currently is Chile’s most valuable mollusc. According to Servicio Agricola y Ganadero (personal communication Mr. Juan Lopehan- dia) a record of more than 14000 metric tons were fished in 1977. This figure can be compared with the previous maximum of 6 700 tons fished in 1972 approximately val- ued at US $3 500000 (CasTILLA & BECERRA, 1975). New external markets opening principally in Japan guarantee both a continuing demand and a threat to this resource’s existence. Though the bathymetric range of Concholepas extends from the intertidal zone to depths of 30- 40m, it has be- come increasingly difficult to find areas inhabited by this species, notably in the littoral zone. That a critical point is fast approaching in this species’ survival appears to be substantiated in the ever increasing fishing effort required to equal old levels of extraction. At present, results from several laboratory studies exist in the literature. These include, egg development (GALLARDO, 1973); oxygen consumption (CaRrMoNa, 1970); mating behaviour (CasTILLa, 1974) and spawning behaviour (CasTILLA & CancrNo, 1976). Field studies however are few and confined primarily to short term growth studies (ToBELLA, 1975); or preliminary popula- tion dynamic analysis (Lozapa et al., 1976). ' Peace Corps Volunteer (University del Norte, Coquimbo, Chile), now: Island Resources Foundation, Red Hook Center, P O. Box 33, St. Thomas, U.S. Virgin Islands oo801 2 Laboratorio de Zoologia, Departamento de Biologia Ambiental y de Poblaciones, Instituto de Ciencias Biolégicos, Universidad Catolica de Chile, Casilla 114-D, Santiago, Chile 3 Centro de Investigaciones Submarinas, Universidad del Norte, Coquimbo, Chile That these studies are needed is obvious from the gaps in the knowledge of this species’ growth rates, migratory patterns and general behaviour. For shallow subtidal work there exist few sampling techniques that can prove equal to SCUBA. Since its in- troduction SCUBA has rapidly gained acceptance as a valuable scientific tool (KizR & GraNT, 1965; Larsson, 1968; PAINE, 1976). As part of an in situ growth study of Concholepas, this methodology was employed to study several facets of the species’ behaviour with the end to complement results reported from previous laboratory studies. DESCRIPTION or tHe STUDY SITES The Bahia La Herradura is a small horseshoe-shaped bay (Figure 1A) located at 29°58’ S, 71°23’ W. The quartz feldspar dominated sand composing most of the bottom (BUTENKO, 1974) is broken up sporadically by granitic in- trusions. One such intrusion is a series of small subtidal rocks surrounded by a coarse sand bottom called Knowsley Rocks. Of the six rocks making up these series the largest was chosen as the principal study rock (Figure 1A-R1) in meeting the following criteria: accessibility; sufficiency in appropriate food and habitat to support a large intro- duced study population; and presence of and existing Concholepas population prior to the study. Situated in 10-12m of water, the principal rock measured approx- imately 15m in length and 7m in height, with an esti- mated overall exposed surface area of 239m’. Five transects to estimate total cover of dominant species were made using a 0.5 m* quadrant. Areas were sampled every 2 meters from base to top. Dominant sessile organisms were the barnacle Balanus psittacus (Molina, 1782), B. laevis Bruguiére, 1789, calcareous tube worms, bryozoans, THE VELIGER Vol. 23; No. 1 A We ¥ AS CIS Pier Knowsley ‘ “p> Nosks ——ee R2 *- 160 Ry cniey 30°,(Horno) scale 1 : 320 , YY : Coquimbo scale 1 : 24 000 ( Herradura ) BAY LA HERRADURA 36 KNOWSLEY ROCKS x Hornos Rocks Pacific Ocean |G scale 1 : 160 scale 1 : 3200 1B CALETA DE HORNOS S& HORNOS ROCKS Figure 1 Figure 1A shows Bay La Herradura; topographic outline of Knows- their profile (topographic underwater work carried out by Mr. ley Rocks and profile of R, and R, Manuel Berrios and Mr. Alvaro Pacheco from the Centro Investi- gaciones Submarinas, Universidad del Norte, Coquimbo) Figure 1B shows Caleta de Hornos (Fishermen’s Cove about 50 km N of Bay La Herradura) ; topographic outline of Hornos Rocks and Vol. 23; No. 1 and algae. Predominant motile organisms were the mol- lusc Priene rude (Broderip, 1833), Tegula (Chlorostoma) tridentata (Potiez & Michaud, 1838), Nassarius gayi (Kiener, 1835), Calyptraea (Trochita) trochiformis (Born, 1778), Concholepas concholepas and the echinoderms Tetrapygus niger (Molina, 1782) and Meyenaster gelatinosus (Meyen, 1834). Caleta Hornos (Figure 1B) is a small fishing village situated some 50km to the north of Bahia de La Herra- dura. The study rock (Figure 1B) composed of three smaller sections (R 1, R2, R3) separated by fissures, is located in 7-8m of water some 100m from the coast, sur- rounded by a coarse sand bottom. The rock as a whole measured 8m in length with a height of 4-5m with an estimated 103 m’ of exposed surface area. Though about one-half the size of the location described above, its iso- lated position and rich biotic community suited the study’s purposes. Seven transects as described above were sam- pled. The principal difference in community composition was the dominance of the tunicate Pyura chilensis Molina, 1782 and the small numbers of the mollusc Calyptraea (Trochita) trochiformis observed. Otherwise, the macro- fauna community members appeared similar in the two study areas. MATERIALS ann METHODS The study which began in August 1976 was completed September 1977. As many “locos” as possible were col- lected from the study areas for tagging, though occasion- ally “locos” from adjacent rocks or other areas were used. Size range varied between 5- 10cm maximum shell diam- eter. Tagging consisted of boring two 1 mm diameter holes at the shell base using a rotary electric high speed drill. Small plastic tags numbered with a press punch were then attached with nylon fish filament. A total of 173 and 348 individuals were marked and released during the study at Knowsley Rock (Figure 1A-R1) and Hornos Rock (Figure 1B-R1, R3) respectively. All observations were made by divers utilizing SCUBA, at least 60 days after tagging. A total of 36 hours under- water diving time (day and night) was compiled among the 3 principal investigators and an occasional 4th. Stand- ardization in observations was attempted within the limi- tations of the methodology through reviews prior to each dive. Reviews consisted of outlining objectives of the dives, specific criteria to be used in making observations and defining of each diver’s observation zone. Each diver THE VELIGER Page 85 retained a specific zone through the study, thus obtaining a familiarity with it. Five aspects of behaviour were designated both as of interest and feasible for underwater observation. They were a) Short term movement rates. Velocity rates were calculated from measurements taken with ruler and diving watch over 5-15 minute observation periods. b) Long term movement rates. Observations of movement activity and points of dispersal over 16-23 hour period were also noted in tagged animals. c) Diurnal-noc- turnal activity. Dives were made separated by 8 hour intervals beginning approximately at 16:00 hrs. Observa- tions for activity were subdivided into: feeding; move- ment; sexual; and egg laying. Diving lanterns were used during night dives; no obvious alterations of activity pat- terns were observed by the use of lanterns. d) Food preference. A compilation of prey organisms recorded when observing feeding behaviour has been included in the results. e) Microhabitat and substrate selectivity. Descriptions of place of attachment and substrate were noted with all observations. f) Escape behaviour. Ap- parent escape behaviours observed in “locos” from the predatory sea star Meyenaster gelatinosus are described. RESULTS 1. Short Term Movements Observations were made over short periods of time (5 - 15 minutes) of both “locos” actually found in the proc- ess of movement and animals displaced to a second location (relocated) to discern the effect of substrate on movement velocity. Table 1 shows the results. A total of 22 velocity measurements were recorded, including repetitions of the same animal. Substrate varied, consisting of: a) loose sediments (sand; broken shells); b) soft substrate (algal mat);c) hard substrate (exposed rock; barnacles; litho- thamnioid algae). Maximum velocity was observed, in one case, on the algal mat, 13cm/min, during the day. Velocities of 10 cm/min were observed at several occasions, surprisingly on loose substrate as well as the species’ more natural sur- face preferences, hard substrate. Means of hard substra- tum velocities compared between undisturbed and relo- cated animals were similar (6.50 and 5.97cm/min respectively). Due to the paucity in data no statistical comparisons could be made, though these means are felt to be more reflective of the “locos” movement rates than the above maxima. Page 86 THE VELIGER Vol. 23; No. 1 Table 1 Concholepas concholepas Day and night displacement velocities with varying substrate. Subtidal observations, 2 to 10m. (*)indicates repetitive measurements in same animal. L = loose substrate H = hard substrate S = soft substrate Undisturbed Relocated : : substrate substrate observation| period of | velocity |observation|period of velocity number | the day kind type the day kind (cm/min) 1(*) sand-broken shells L 1 algal mat S 1] 2(*) sand-broken shells L 10 2 algal mat S 2 3 algal mat S 2 3 algal mat S 1 4 sand L 6 4(*) exposed rock H 10 5 exposed rock H 4.7 5(*) exposed rock H 5 6 exposed rock H 5.5 6(*) exposed rock H 4 7 Lithothamnioid algae H 10 7(*) exposed rock H 10 8 Lithothamnioid algae H 7.5 8 algal mat S 13 9 Lithothamnioid algae H 6.3 9 barnacle H 1.5 10 Lithothamnioid algae H 5.0 10 broken shells L 2.5 11(*) Lithothamnioid algae H 3.8 12(*) Lithothamnioid algae H 7.5 00:00-03:30 Hrs 11:00-16:30 Hrs These movements occurred for short periods of time (5-15 minutes), usually terminating when a possible food source was encountered or the animal was blocked by surface irregularities. 2. Long Term Movements and Dispersal In order to determine behavioural tendencies in the “locos” movements over longer periods of time, 2 kinds of experiments were designed. A. Three sets of dives were programed for recording number and position of tagged “locos” previously located on both experimental rocks. Each set consisted of 3 dives over a 16 hour period recording location and change in the position of the animals where 2 or more successive observations were made. Distances were determined where movement occurred based on careful “mapping” of the “locos” and assuming straightline movement. It can be seen (Table 2) that of the 70 separate move- ment observations made over the 16 hour period, only in 8 cases did the “locos” remain stationary. The number of “locos” observed to move between T:i1-T2, 00:00- 08:ooh, was significantly greater than To-T:i, 16:00- 00:00h (P< 0.5,x” test, using Yates’ correction for con- tinuity). Average distances traveled were significantly greater during the night than day (P< 0.001, Wilcoxon 2 sample non-parametric test). Maximum distance trav- eled in an 8 hour period for a “loco” was 8m at night. B. The second experiment was outlined to discern any tendencies in dispersal patterns from “locos” artificially grouped. A second series of dives was completed over a 25 hour period at Caleta de Hornos. Three sets of 10 tagged “locos” were placed in 3 distinct areas on the rock. Two of the areas were small hollow depressions near the top of the rock. The 3rd area consisted of a slightly sloping plain located at mid depth. Five repetitive dives were made, 1, 3, 6, 13 and 25 hours after the initial placement of “locos” (To). Principal observations were emigrations from original areas, direction traveled and substrate pref- erence. As can be observed in Figure 2, highest levels of Vol. 23; No. 1 THE VELIGER Page 87 Table 2 Concholepas concholepas Displacement and average distances travelled at different times. T, = 16:00 hrs; T, = 00:00 hrs; T, = 08:00 hrs Total number of “locos” used in experiment, 39. X? between “locos” showing displacement and stationary behaviour at T,-T, and T,-T, = 5247 (using Yates’ correction for continuity, with one degree of freedom, P < 0.5) ] | Displacement “locos” T-T Displacement “locos” T;-T2 | Site and date |N. observed, N. observed |N. “locos” remaining at To | N. Average displ. (m) ateli || N. Average displ. (m) | stationary T9-T»2 Hornos’ rock, 14/12/76 | 8 | 2 1.2 6 5.5 3 Knowsley’s rock, 28/1/77 9 2 115) 10 37 3 Knowsley’s rock, 5/6/77 8 2 1.5 5 4.0 3 "= as = = + TOTALS | 25 6 X=1.4 21 X = 4.4 9 emigration occurred between 17:00-00:00 hours. At 00:00 hours 29 out of the 30 original “locos” had left (emigrated) the original areas. During this dive 21 “locos” out of the original 30 were sighted (observed by divers); 12 out of those 21 had sought out fissures or crevices. A tendency for the animals to seek out the fissures, possibly for purposes of protection, is observed. Finally, the num- ber of observations (“locos” observed by divers) fell off after Ts due to problems in observation at Ts (night dive) and the increasing grouping of the animals in inaccessible fissures. 3. Diurnal - Nocturnal Activity Observations were made during 4 sets of dives, 2 at each study location. Each set of dives consisted of 3 dives separated by 8 - 10 hour intervals beginning approximately at 14:30-16:30h. Observations for activity were; move- ment; feeding; sexual and egg laying. Feeding activity criteria consisted of any abnormally large extension of the foot of the animal over a possible food source or “bulldozing” movement on barnacles, a typical feeding mechanism of the animal when eating its prey (CASTILLA et al., in preparation). Sexual activity criteria were obser- vations of the 2 “locos” in the adjacent or mounted posi- tions as described by CasTILLa (1974). Finally, egg laying was easy to discern by the presence of eggs and method of attachment as described by CasTILLA & CANCINO (1976). Table 3 shows the results. It can be observed that dur- ing the night dives about 50% of the observed “locos” were active, while during the daylight hours (morning or Table 3 Concholepas concholepas Percentage active and inactive animals during 4 sets of dives at Caleta de Hornos and Knowsley Rocks (15/12/1976 — 25/07/1977) Times between which Number of Number of dives were performed observations active “locos” 14:30 - 16:30 288 32 00:00 - 03:00 223 102 10:30 - 11:30 233 27 % active 95% confidence % inactive “locos” binomial limits “locos” 11.11 (7.58 - 15.80) 88.89 45.74 (41.7 - 54.4) 54.26 11.59 (7.03 - 16.2) 88.41 Page 88 THE VELIGER Vol. 23; No. 1 Table 4. Concholepas concholepas Substrate and microhabitat selection observed in “locos” studied at Caleta de Hornos and Knowsley rocks (day and night observations) Areas and Open areas Protected areas habitat —_———s Rock in| Rock Rock Observations Sand Rock/Sand (exposed) (crevices) (large fissures) Number 2 83 199 301 726 So 0.15 6.33 15.98 22.96 55.38 noon) over 88% of the animals observed were inactive. Major activity was dominated by feeding and movement or displacement. 4. Microhabitat and Substrate Selectivity Possible areas of “locos” attachment were: sand; rock- sand interphase (at base of study rocks); exposed rocks and crevices, depressions or fissures. Under the category of “rock” were included both bare and biotically en- crusted rocks (i.e., encrusting calcareous algae). Table 4 shows the results. Out of 1311 observations made during this study only 2 animals were observed on sand. A rather large percentage, 6.337%, was observed at the rock-sand interphase of the studied rocks, attached to the rock sub- stratum, with at least 50% of the shell covered by sand. Table 5 Estimated cover of Hornos and Knowsley Rocks, September — November, 1976). Percentage of observed “locos” preying on spe- cific prey (58 nocturnal, 38 diurnal observations) % estimated cover % preyed by locos Organisms Hornos’ rock Prey Balanus psittacus Balanus laevis Verruca sp. Pyura chilensis 25 Reon Encrusting Lithothamnioid algae Serpullidae Bugula neritina 51 Bugula flabellata “algal mat” Motile Tegula tridentata Nassarius gayi Prione rude Calyptraea trochiformis ; 5 Crepipatella dilatata Concholepas concholepas Tetrapigus niger Bare rock 6 Knowsley’s rock Hornos’ rock Knowsley’s rock 30 22 34 5 39 66 2s 5 pa 1 34 #4 50 9 5 Vol. 23; No. 1 THE VELIGER Page 89 Excluding sand and sand-rock interphase, nearly 95% of the animals were found on hard rocky substratum, showing a clear preference for those protected rocky areas which provided both a secure place of attachment and possible protection. 5. Food Preference Table 5 shows the results of transects made on the 2 rocks studied and percentage of “locos” preying on spe- cific prey items. The main difference in prey availability between the 2 rocks was the dominance of the barnacle Balanus psittacus at Knowsley’s rock while the tunicate Pyura chilensis dominated at Hornos. Availability of Balanus laevis was the same on both rocks. In spite of low percentage cover of this species (5%), it was preferred on both rocks by Concholepas. Pyura chilensis, the most abundant prey organism at Hornos, had second ranking choice as prey; the same can be said for B. psittacus at Knowsley. Here, where the “locos” had only two choices (B. psittacus and B. laevis) the percentage of “locos” con- suming B. /aevis was nearly twice as much as in Hornos, where 4 prey choices were possible. 6. Escape Behaviour During the study 2 types of escape behaviour were ob- served. First, the starfish Meyenaster gelatinosus (a “loco” predator) was observed to mount a “loco” specimen with its stomach in contact with the apex of the shell. No activity was observed in the mollusc during the mounting process. After the sea star had attached itself the mollusc shell elevated 2-3cm above its normal position. Shortly thereafter, a rapid series of 180° clockwise-counter clock- wise “spins” took place. This appeared to deter the pred- ator as it quickly departed, the whole process taking some 3-5 minutes. These same steps were observed 3 times in succession with the same starfish but separate prey speci- mens, all with the same result. No other movement was observed in Conchole pas other than those described above. A second case of escape behaviour was observed as a “falling reflex.” This behaviour was recorded in 3 individ- uals of Concholepas at 3 distinct times. In all cases, the attachment substratum was rock, inclined at approxi- mately a 30° slope. No movement was observed in the individuals and no stimulus provided by the observer other than a possible obstruction of the local currents or air bubbling. In all cases disattachment from the substratum occurred and the specimens “tumbled” downslope to the crevice below. The same “reflex” was observed during one night-dive while illuminating a “loco” with a diving torch. Castilla and Cancino (in litteris) observed the same “fall- ing reflex” while introducing the hand into glass aquaria where “locos” were kept in laboratory conditions. They associated the reflex to rheotactic or chemotactic causes, or both. Locos fishermen have reported the reflex as occur- ring massively during dislodging of “locos” on vertical or semi-vertical rocky-walls, vibrations transmitted through the rocks have been argued as the cause of the phenom- enon. DISCUSSION Prosobranchs as a general rule are slow movers and tend to be somewhat inactive (HyMAN, 1967). This generaliza- tion appears also to apply to Concholepas concholepas. Though maximum velocity rates of 10-13cm/min were measured in short term movements, rates of about 6cm/ min are considered more representative of an average velocity for this species. Maximum displacement observed for a “loco” over an 8 hour period was 8m. Assuming straight line movement this would represent 1.66 cm/min. Nevertheless, a more plausible assumption, based on iso- lated observations, would be a displacement behaviour based on short, rapid “spurts” probably with some devia- tions from a straight line path. If this is valid, the calcu- lated average speed is within the expected range. Though several assumptions have been made, these rate values in Concholepas fall within the common range described pre- viously for other prosobranchs (Hyman, 1967). Neverthe- less, some faster rates for marine gastropod molluscs have been reported: 13cm/min for Cypraea exanthema (OtmstTEaD, 1917); 36cm/min for Polinices duplicata (CoPELAND, 1922). Little is known about long term migratory patterns in this species. Though capture-recapture data from the sites is available from this work, it is unclear for the popula- tions studied what importance emigration has compared to mortality. Searches by the authors of tagged “locos” in areas adjacent to the study rocks extending to the coast line were made with little success. Nevertheless, the knowledge that this species is capable of traveling on unconsolidated surfaces at a moderate speed (at least for short periods of time) increases the possibilities of long distance migration. Actually, 3 recoveries at Caleta de Hornos of tagged “locos” (reported by local fishermen) — 2 inshore from the experimental rock and one offshore — demonstrated the ability of Concholepas to travel 200 - 400 m over a period of about 6-8 months. Although casual, this information agrees with unpublished observations of Castilla and Cancino (in prep.) for a different locality Page go THE VELIGER Vol. 23; No. 1 30r- O——O—— 0 i Y cumulative number of wv. locos emigrating from 3 original 26 ___ grouping sites 22 rs g 18 a eee, locos observed during dives & O ae (2 Soe e a ee © jocos observed in fissures o o Q € = Zz Th OE ai Tr 2 11:00 12:00 14:00 17:00 00:00 Figure 2 Concholepas concholepas. Artificial grouping of 30 “locos” at 3 sites on Hornos Rocks and observations at different times. Experi- ment carried out 25 July 1977 about 300km south of Caleta de Hornos (rocky shore of Los Molles). If these data are correct, it should be possible to postulate rate of movements of Concholepas of the range shown by Newman (1966) for Haliotis midae (229- 2433 yards per annum). Distances over which Concho- lepas can travel within a one year period are of extreme interest from the locos’ fisheries management point of view. Activity levels were low in this species with numerous records of animals remaining stationary over 8 hour pe- riods and some over longer periods (15 hours or more). CasTILLa (1974; 1976) and CasTILLa & CaNcINo (1976) have noted increase in all activities in the laboratory at night, including food intake, locomotion, sexual activity and egg laying. These were confirmed in the field with greater activity towards midnight and the following hours. SpicHT et al. (1974) listed barnacle and bivalve preda- tion as a characteristic typical of muricids. Laboratory experiments by CasTILLA & CaNncino (1976) confirmed this in Concholepas but also noted that the ascidian Pyura chilensts, limpets and even other Concholepas may be part of the animal’s diet. Though no bivalves were observed in the study, 3 species of barnacle and one tunicate were present and preyed on. The study shows that one of the species of barnacles, Balanus laevis, was the loco’s pre- ferred prey. Observations throughout the study confirmed a gre- gariousness and thigmotactic behaviour in Concholepas. Large congregations of “locos” were repeatedly observed in fissures and large crevices, although they did not neces- sarily maintain the same position. Activities such as sexual and laying of egg capsules were also observed in these “fissure” areas. This also appears to substantiate labora- tory findings, as the animals always seek the corners of the aquaria to lay their egg capsules. Escape behaviour in molluscs from predatory sea stars has been abundantly described in the literature. Almost the identical behaviour as described above, has been ob- served in the abalone Haliotis sp. to sea star predation (FEDER, 1963). Feder suggested that it is rare to find evidence of sea star predation on the Californian species of Haliotis, possibly a result of the effectiveness of this escape behaviour. Recently, Dayton et al. (1977) studied the feeding biology of the Chilean sea star Meyenaster gelatinosus, a predator of “loco.” They stated that Concholepas did not exhibit a running response in front of this sea star but rather tended to clamp down on the substratum in an apparent “toughing it out” tactic. This paper describes 2 new escape tactics, namely shell raising Vol. 23; No. 1 THE VELIGER Page 91 and spinning movements and a “falling reflex.” Our ob- servations indicate that Concholepas has no protection by its size from attacking M. gelatinosus or the intertidal sun- star Heliaster helianthus (Lamarck, 1816). If this is so, escape behaviour tactics, as the ones described in this paper or by Dayton et al. (1977) should prove to be im- portant biological components in Concholepas concho- lepas. As for the “falling reflex” phenomenon it is known that Chilean “loco” divers have often described it as a dis- attachment of the animals from the substrate with no apparent external stimulation. This has been advantageous in removal of a mollusc that commonly requires direct application of force with flat iron bars. Often removal of one “loco” with force precipitates this “falling” behaviour in the other animals, thus saving time in their removal. Though this behaviour could possibly be advantageous as an escape mechanism under the correct conditions, such as currents or sloping substrate, it remains to be fully ex- plained how the mollusc is capable of detecting a diver or another organism’s presence, or which is the trigger stim- ulus. SUMMARY Sublittoral observations (36 hours underwater diving time) have confirmed that the “loco” Concholepas concholepas (Bruguiére, 1789) travels at velocity rates typical of proso- branchs. Maximum velocity rates of 10-13 cm/min were measured; rates of about 6 cm/min are considered average velocities for short term movements. It was found that Concholepas is capable of locomotor activity on uncon- solidated substrate, although it shows clear preference for solid rock substrate. Moreover, among these there is a clear preference for small or large crevices, showing thig- motactic behaviour. Nocturnal behaviour patterns of Concholepas are clearly demonstrated (locomotion, feed- ing, sexual activity). Main prey organisms consumed by the “loco” are barnacles (Balanus laevis, Balanis psittacus, Verruca sp.) and the ascidian Pyura chilensis; B. laevis is clearly preferred by the subtidal group of “locos” studied. Two new types of escape behaviour of Concholepas from predators are described, namely “shell raising and spinning movements” and a “falling reflex.” It is argued that these escape tactics from predators must be of crucial importance to Concholepas. ACKNOWLEDGMENTS We thank “Fundacion Chile” for financial support of this work. This work is part of a study on growth and behav- iour of the species (U. del Norte—Fundacién Chile, Case 402-C). We sincerely thank Dorothy Hogg, Peace Corps Volunteer, who helped us with dives. We thank the work of Mr. M. Berrios and Mr. A. Pacheco, topographer of CIS, Coquimbo. Juan Cancino and Chita Guisado helped us with field work and made useful suggestions to the manuscript. Daniel Moraga and Hernan Castillo, techni- cians of the Laboratorio de Zoologia, Universidad Catdlica de Chile contributed field assistance. Carlos Flores, arti- sanal fisherman in Caleta de Hornos, was important to the success of this study. One of us, R. DuBois, worked in the research project while being a Peace Corps Volunteer in Chile. Literature Cited BuTeENko, S. J. 1974. Estudio geolégico en la Bahia de la Herradura. Informe de Avance. Cent. Investig. Submar. Univ. del Norte, Coquimbo, Chile (unpubl. reprt.) Carmona, M T. 1970. Consumo de oxigeno en relacién al peso en ejemplares jévenes de Concholepas concholepas (Bruguiére) (Mollusca, Muricidae). Revist. Biol. Mar. Univ. Chile 14: 51-54 CasTILLa, Juan C. 1974. Notes on mating behaviour of Concholepas concholepas (Mol- lusca, Gastropoda, Muricidae) from Chile. The Veliger 16 (3): 291 - 292 (1 January 1974) 1976. A unique mollusc. Sea Frontiers 22 (5): 302-304 Casta, Juan C. & R. Becerra 1975. | The shellfisheries of Chile: an analysis of the statistics 1960- 1973. Proc. Internat. Symp. Coast. Upwelling. Coquimbo, Chile, Nov. 1975: 61-90; J. C. Valle, ed. CasTitta, Juan C. & J. Cancino 1976. Spawning behaviour and egg capsules of Concholepas concho- lepas (Mollusca: Gastropoda). Mar. Biol. 37: 255 - 263 CopeLanp, M. 1922. Ciliary and muscular locomotion in the gastropod genus Poly- nices. Biol. Bull. 42: 132-142 Dayton, P K., R. J. Rosentuar, L. C. MaHEen & T. ANTEZANA 1977. Population structure and foraging biology of the predaceous Chilean asteroid Meyenaster gelatinosus and the escape biology of its prey. Mar. Biol. 39: 361 - 370 Fever, Howarp MizcHELL 1963. Gastropod defensive responses and their effectiveness in reducing predation by starfishes. Ga.uarbo, C. 1973. Desarrollo intracapsular de Concholepas concholepas (Bruguiére) (Gastropoda, Muricidae). Publ. occ. Mus. nac. Hist. nat. Santia- go de Chile 16: 3 - 16 Hyman, Lissiz HENRIETTA 1967. The Invertebrates 6, Mollusca 1: viit+792 pp.; 249 text figs. McGraw-Hill Book Company, San Francisco Kier, P M. « R. E. Grant 1965. Echinoid distribution and habitats, Key Largo Coral Reef Pre- serve, Florida. Smith. Misc. Coll. 149 (b): 1-61 Ecology 44 (3): 505-512 Page 92 THE VELIGER Larsson, B. A. S. 1968. | SCUBA studies on vertical distribution of Swedish rocky bot- tom echinoderms. A methodological study. Ophelia 5: 137-156 Lozapa, E., M. T. Lopez & R. DEsQquEYRoux 1976. Aspectos ecolégicos de poblaciones chilenas de loco Concholepas concholepas (Bruguiére, 1789) (Mollusca, Gasteropoda, Muricidae). Biol. Pesq. Chile (8): 5-29 Newman, G. G. 1966. | Movements of the South African abalone, Haliotis midae. Invest. Reprt. Div. Sea Fish. S. Africa 56: 1 - 20 O.msteD, J. 1917. Locomotion of certain Bermudian molluscs. Journ. Exp. Zool. 24: 223 - 236 Painz, Rosert TREAT 1976. Biological observations on a subtidal Mytilus californianus bed. The Veliger 19 (2): 125-130; 1 text fig. (1 October 1976) Spicut, Tom M., C. BrmxeLanp « A. Lyons 1974. Life histories of large and small murexes (Prosobranchia: Mu- ricidae). Mar. Biol. 24: 229-242 Toserra, G. M. 1975. | Crecimiento de Concholepas concholepas (Bruguiére, 1789) (Moll. Gast. Muricidae). Bol. Soc. Biol. de Concepcion 44: 185 - 189 Vol. 23; No. 1 Vol. 23; No. 1 THE VELIGER Page 93 Range Extensions of Three Species of Teredinidae (Mollusca : Bivalvia ) Along the Pacific Coast of America BY MICHEL E. HENDRICKX Estacién Mazatlan UNAM, P.O. Box 811 Mazatlan, Mexico ONLY A FEW SPECIES of Teredinidae have been reported on the Pacific Coast of Mexico. According to what has been clearly stated by TuRNER (1966) this might reflect the poorness of the local fauna or be an indication of the lack of work on this group of animals in the area. The coast of Sinaloa, Mexico, mainly consists of sandy beaches, occasionally interrupted by river mouths, lagoon inlets or esteros. Areas of rocky shore are scattered and of little extent. During the rainy season, from July to October, river discharge into the ocean is considerable and large amounts of dead wood, ranging from small twigs to entire trunks, are eventually deposited in the coastal zonc, some of them being trapped at the edge of the esteros and lagoons and on the banks of rivers. Rotted wood is frequently dredged up in the subtidal zone along the coastline and is also occasionally washed up on the beaches. In the course of 1978 and 1979, pieces of rotting wood of various sizes were found in the area of Mazatlan, Sina- loa, Mexico, and examined for shipworms. The present paper deals with the results obtained from those obser- vations and reports range extensions for 3 species of Tere- dinidae. Teredo (Teredo) bartschi Clapp, 1923 Previous Distribution: Although it used to be a species restricted to the Caribbean, it has recently been reported by R. Turner (KEEN, 1971) at La Paz, Baja California Sur, Mexico. New Record: El Tanque Canal, Caimanero Lagoon, Sinaloa, Mexico. Two specimens were collected in a partly submerged dead trunk on the edge of an artificial canal connecting the Caimanero Lagoon to the open sea through an estero (Estero Agua Dulce). Salinity at the time of sampling was 33%. Previous studies (MENz, 1976; PAUL, 1977) have shown variations in salinity in this area to be quite large (11 to 48%). The total lengths of the animals col- lected were 12.5 and 17.6mm, respectively, and mature larvae were found in the brood pouch of the larger speci- men, which demonstrates that the organisms were in fa- vourable reproductive condition. Teredo (Teredo) bartschi might thus be able successfully to colonize this area if environmental conditions for spawning, survival and settlement of the larvae were advantageous. The present note extends the distributional range of this species to continental Mexico and confirms the pene- tration of this teredinid into Pacific tropical waters. Several young and partly damaged specimens, probably of the same species, were collected 3 months later, after a storm, in a piece of dead wood washed ashore 30km north of Mazatlan. The same piece of wood was also heavily infested by Martesia fragilis Verrill « Bush, 1808. Bankia (Neobankia) zeteki Bartsch, 1921 Previous Distribution: Canal Locks, Balboa and Canal Zone, Panama (TurNER, 1966). Also reported at Puerto Armuelles, on the Pacific Coast of Panama (CLENCH & TURNER, 1946; KEEN, 1971). New Record: Off Teacapan, Sinaloa, Mexico. The present record extends the distribution of this spe- cies northward to the area off Teacapan, representing a considerable extension of its previously known range (about 3500km) along the Pacific Coast of America. Three large specimens (46.6 to 54.2 mm total length) were found in a piece of rotten wood dredged up by a shrimp boat Page 94 trawling a few kilometers off the coast. The trawling depth has been estimated as at least 12m. Bankia (Neobankia) destructa Clench & Turner, 1946 Previous Distribution: La Cieba, Honduras (TuRNER, 1966) and Eastern Panama (KEEN, 1971). Caribbean species. New Record: El Tanque Canal, Caimanero Lagoon, Sinaloa, Mexico. The present record is the first of this species on the Pacific side of America. This fully confirms the prediction of R. Turner (KEEN, 1971) who considered this species as a possible candidate to pass through the Panama Canal. Environmental conditions were similar as for Teredo bartschi as the only specimen of Bankia destructa (20.5 mm total length) was found in the same trunk. TurRNER (1966) discussed the problems of deciding whether new records represent established fauna or chance occurring individuals from other areas. The latter case applies in the present study only to the damaged juvenile specimens of probably being Teredo bartschi col- lected north of Mazatlan. Indeed, observation of the log dredged off Teacapan and of the dead trunk found in El Tanque Canal showed that they had obviously been there for a long time. Moreover, the presence of mature larvae of T: barischi could signify an important step towards colonization of the area by the species. The presence of Bankia destructa and B. zeteki along the coast of Sinaloa clearly demonstrates the dispersal potential of shipworms from the Caribbean through the Panama Canal and along the Pacific Coast of America. This was discussed by KEEN THE VELIGER Vol. 23; No. 1 (1971) who listed 10 species of Teredinidae previously reported in the Caribbean that could possibly (according to Turner) be dispersed in the Panamic province. Banka destructa, included in that list, as well as B. zeteki, have been shown in this study to possess the capability to occu- py more northern latitudes than previously thought pos- sible, as does Bankia (Neobankia) orcutti Bartsch, 1923 reported from Bahia Bacochibampo in the Gulf of Cali- fornia. Including this last species and Bankia (Bankiella) gouldi (Bartsch, 1908), there are now 4 members of the genus Bankia reported from the Pacific waters of Mexico. ACKNOWLEDGMENTS The author wishes to express his gratitude to Dr. Ruth Turner for confirmation of identifications of specimens of Teredinidae. Literature Cited CrencH, Witiiam James & RutH Dixon Turner 1946. The genus Bankia in the Western Atlantic. 1-28 Keen, A. Myra 1971. Sea shells of tropical West America: marine mollusks from Baja California to Peru, 24 ed. Stanford Univ. Press, Stanford, Calif i-xiv+ 1064 pp.; ca. 4000 text figs.; 22 col. plts. (21 September 1971) Menz, ANDREW 1976. Bionomics of penaeid shrimps in a lagoon complex on the Mexi- can Pacific coast. Ph. D. Thesis, Univ. Liverpool, 145 pp. Pau, RICHARD 1977. Bionomics of crabs of the genus Callinectes (Portunidae) in a lagoon complex on the Mexican Pacific coast. Ph. D. Thesis, Univ. Liverpool, 136 pp. Turner, RutH Drxon 1966. A survey and illustrated catalogue of the Teredinidae. Mus. Comp. Zool. Harvard, 265 pp.; 64 plts. Johnsonia 2 (19): Vol. 23; No. 1 THE VELIGER Page 95 Notes on Recent and Fossil Neritidae. g. On the Alleged Occurrence of Neritina cf. N. donovana Récluz in the Vigo Formation, Luzon, Philippines HENK K. MIENIS Zoological Museum, Mollusc Collection, Hebrew University of Jerusalem, Israel RecentLy PopeNoE & KLEINPELL (1978) mentioned Neritina cf. Neritina donovana Récluz, 1843, as com- monly occurring in the blue-gray marls cropping out on the right bank of the Bahay River, 1219m (4000 ft) S 25°E of the mouth of Apad Creek, and about 366m (1200 ft) upstream from the abandoned oil well on the left bank of the river, Bondoc Peninsula, Tayabas Prov- ince, Philippines. These marls belong to the so-called Vigo formation and are placed in the Late Pliocene or Early Pleistocene. The supposed occurrence of Neritina cf. N. donovana in the Vigo formation requires two remarks. 1.) The specimen figured by PopENoE & KLEINPELL (1978: plt. 1, figs. 4 and 6) does not belong to that taxon but to Clithon (Clithon) rugata (Récluz, 1842), of which very fine figures have been published by SoweRBy (1849: plt. 100, figs. 3-4) and REEvE (1855: plt. 15, figs. 69a-69b). Clithon rugata is well characterized by its rugose sculp- ture and it seems to be restricted in its distribution to freshwater streams in the Philippines. It has been found on the islands: Negros (RécLuUz, 1842: 75), Guimaris (USNM 419513, according to PopENOE & KLEINPELL, 1978: text fig. 3, sheet 1) and Luzon (ZMA, ex Wallacea Expedition) . The shells of Neritina donovana Récluz, 1843, on the other hand, are smooth except for fine regular growth lines. The colour pattern of N. donovana (vide REEVE, 1855: plt. 6, figs. 25a-25c) resembles, however, very much the sculptural pattern of Clithon rugata and has most probably caused the erroneous identification. I agree with von Martens (1879: 154) and consider Neritina donovana as belonging to the polymorphic spe- cies group of Clithon (Clithon) diadema (Récluz, 1841). 2.) PopENOE & KLEINPELL (1978: text fig. 3, sheets 1-3) mentioned 51 species from the marls in which Clithon rugata was commonly encountered. A critical study of these 51 taxa revealed that all, except C. rugata, are strictly marine in their way of life. More strikingly, C. rugata is the only fluviatile element among the 141 mollusc species mentioned by Popenoe and Kleinpell from the Vigo formation. In my opinion it is, therefore, rather doubtful that Clithon rugata belongs really to the fauna of the Vigo formation. I wonder whether it is not possible that C. rugata is actually living in the Bahay River and that some specimens have been washed into the marls cropping out of the banks. Literature Cited Martens, Epuarp CarL von 1879. Die Gattung Neritina. Neues Syst. Conch. Cab. 2 (10): 1 - 303; pits. A, 1-23 Niirnberg Popenog, WILuts P & RoBert M. KLEINPELL 1978. Age and stratigraphic significance for lyellian correlation of the fauna of the Vigo Formation, Luzon, Philippines. Occ. Pap. Calif. Acad. Sci. No. 129: 1 - 73; 4 text figs.; 18 plts. (22 June 1978) Récxuz, C. A. 1842. Description de neuf espéces de Nérites nouvelles, suivie d’obser- vations sur les Nerita cornea et dubia. Rev. Zool. (Soc. Cuv.) 5: 73-79 Reeve, Lovett Aucustus 1855-1856. Monograph of the genus Neritina. pits. London SowerBy, Gzorce BRETTINGHAM 20d 1849. Monograph of the genus Neritina. 507 - 546; plts. 109-116 London Conch. Icon. 9: 37 Thes. Conch. 2 (10): Page 96 NOTES & NEWS Observations on Feeding in Maxwellia santarosana (Dall) (Gastropoda : Muricidae) BY MARY K. WICKSTEN Allan Hancock Foundation, University of Southern California, University Park Los Angeles, California 90007 THE CARNIVOROUS SNAIL Maxwellia santarosana (Dall, 1905) ranges from Point Estero, California to San Bar- tolomé Bay, central Baja California, Mexico. It occurs on sublittoral rocky bottoms (McLean, 1978). On 14 April 1978 I collected one of these snails while SCUBA diving at a depth of 12m off Blue Cavern Point, Santa Catalina Island, California. The snail was on a rocky reef covered with sessile invertebrates including the pelecypod Chama arcana Bernard, 1976. When placed into an aquarium containing C’. arcana, the snail drilled holes into the shells of three of the pelecypods and consumed them. Two more Maxwellia santarosana were collected at 10-12m on rocky reefs off Abalone Cove, Palos Verdes Peninsula, Los Angeles County, California during April and June, 1979. These snails ignored live blue mussels (Mytilus edulis Linnaeus, 1758) in the aquarium in which they were kept. One of the snails, however, attacked a Chama arcana. The snail moved toward the pelecypod two days after the prey was placed in the tank. On the following day, the snail began drilling the lower valve, about 3mm from the hinge. The snail continued to drill and feed for 9 additional days. On the oth day, the shell opened, revealing an intact hinge but no tissue except for an adductor muscle and a strip of mantle. The remaining tissue was consumed by a scavenging sea urchin (Lyte- chinus anamesus Clark). The drill hole tapered from the outside inward, the outer diameter being 1.5mm and the inner diameter less than 1 mm. The feeding habits of Maxwellia santarosana have not been reported previously. However, Maxwellia gemma (Sowerby, 1879) can drill holes and consume clams. Like M. santarosana, this species does not break the hinge, but THE VELIGER Vol. 23; No. 1 eats the tissue through the hole. Maxwellia gemma takes only 4 days to eat a clam. Its drill hole is straight-sided, not tapered (WILLIAMS, 1976). The species of prey was not recorded. However, photographs accompanying the article show the prey to be a venerid clam, probably Protothaca staminea (Conrad, 1837). I conclude that both species of Maxwellia are predators on the pelecypods of rocky sub- tidal to low intertidal zones. Literature Cited McLgzan, James HAMILTON 1978. Marine shells of southern California. Nat. Hist. Mus. Los Angeles County, Sci. Ser. 24 (Rev. Edit.): 1-104; 54 plts. (20 March 1978) WiiuiaMs, LoRALYNN 1976. Drilling and feeding habits of some California carnivorous gast- ropods. Of Sea and Shore 7 (3): 141-147; 27 text figs. Range Extension for Pterotyphis fimbriatus (A. Adams, 1854) BY JENS HEMMEN ann CHRISTA HEMMEN 22 GrillparzerstraBe, D-6200 Wiesbaden, W. Germany DuRING A COLLECTING TRIP to Costa Rica in July and August 1979 we found a fine but crabbed specimen of Pterotyphis fimbriatus (A. Adams, 1854) at Playa Jaco, Puntarenas Province, Costa Rica, intertidally among rocks. KEEN (1971) as well as Rapwin & D’AttTILIo (1976) report this apparently rare species from the Central Mex- ican coast only: Barra de Navidad and Bahia Cuasteco- mate (Jalisco) and Sayulita (Nayarit). The record of our specimen thus extends the known range approximately 10 degrees south. ACKNOWLEDGMENT We wish to thank Mr. H. Mihlhausser, Freiburg, Western Germany, for examining the specimen. Literature Cited Keen, A. Myra 1971. Sea shells of tropical West America: marine mollusks from Baja California to Peru, 27d ed. Stanford Univ. Press, Stanford, Calif. i-xiv+ 1064 pp.; ca. 4000 text figs.; 22 col. plts. (21 September 1971) Rapwin, Georce Epwarp & ANTHONY D’ATTILIO 1976. Murex shells of the world. An illustrated guide to the Muricidae. Stanford Univ. Press, Stanford, Calif. x+284 pp.; 192 numbered figs. +6 unnumbered figs. in text; 32 col. plts. Vol. 23; No. 1 THE VELIGER Page 97 Generous Donation by the San Diego Shell Club Shortly after our April issue had gone to press, there arrived another generous donation to our Endowment Fund from our friends in the San Diego Shell Club. We are very grateful for this continued evidence of their sup- port and implied encouragement in our efforts. ee oe 1980 SEATTLE MEETING OF THE AMERICAN SOCIETY OF ZOOLOGISTS, AMERICAN MicroscopicaL Society, AMERI- CAN SocleTy oF LIMNOLOGY & OCEANOGRAPHY, ANIMAL BEHAvior Society, CANADIAN SoclETY oF ZooLocy, Eco- LOGICAL SoclETY oF AMERICA, SOCIETY OF SYSTEMATIC ZooLocy AND WESTERN SociETy oF NATURALISTS. The University of Washington is hosting this meeting at the Seattle Center, December 27 to 30, 1980. A call for papers will be issued in April 1980 and all abstracts will be due in August. Advance registration is $25.00 regular and $12.50 for students. Symposia are being arranged at present on the following topics: (1) Insect systems: milestones and new horizons in endocrinology; (2) Fish reproduction and develop- ment; (3) Evolutionary morphology and interrelation- ships of the actinopterygian fishes; (4) Evolution of immune regulation; (5) Visual cells in evolution; (6) Locomotion and exercise in arthropods; (7) Pattern for- mation; (8) Role of uptake of organic solutes in nutrition of marine organisms; (g) Bioluminescence in marine or- ganisms; (10) Benthic marine algae, how and why they got where they are; (11) Use of artificial substrates in aquatic community, structural and functional analysis; (12) Organism and flow: the influence of small-scale geophysical processes on biological activities; (13) Geo- chemical/biochemical processes at the sediment-water interface of the deep sea; (14) Studies of light and life in natural waters; marine shallow water crustaceans; (16) Ecological ap- proaches to pest outbreak problems; (17) Theoretical ecology: To what extent has it added to our understand- ing of the natural world? (18) Lizard ecology fifteen years later; (19) From individual to species recogni- tion: Theories and mechanisms; (20) Testing new meth- (15) The biology and ecology of ods of shape analysis; and in biogeography. For more information and abstract forms contact: Mary Witey, Business Manager American Society of Zoologists Box 2739 California Lutheran College Thousand Oaks, CA 91360 (21) Alternative hypotheses Jake Nils 1 Symposia on the feeding mechanisms of predatory mol- lusks and the functional morphology (form and structure) of cephalopods (squid, octopus and cuttlefish) will high- light the annual meeting of the American Malacological Union July 19 to 25 at Louisville, Kentucky. The group, composed of scientists and hobbyists, will undertake field trips in search of fossil shells and freshwa- ter and land mollusks. Workshops are planned to identify these mollusks, as well as to consider collections of marine shells, organization of collections, underwater photo- graphy and marine aquaria. Headquarters for the meetings will be the Executive Inn in Louisville. Host will be the Louisville Concho- logical Society which is arranging such fun activites as a moonlight cruise aboard the Belle of Louisville, Shell Club Night, the President’s Reception, and the annual banquet. Those attending need not be members of the A. M. U. Papers will be presented during the scientific sessions of the meeting and a cash prize will be offered for the best student paper. Also scheduled is an auction of books, papers and prints on molluscan and natural history sub- jects. Additional information may be obtained from Dr. C.F E. Roper, President, AMU, Division of Mollusks, National Museum of Natural History, Smithsonian Institution, Washington, D. C. 20560. OPEN POSITION ror MALACOLOGIST Frecp Museum or Naturat History announces a search for an Assistant Curator of Invertebrates in the Depart- ment of Zoology. Appointment of the successful candi- date, who must have a Ph. D. or substantially completed all degree requirements, will take place about January 1, 1981, for a three year term. Preference will be given to workers on the systematics of freshwater or marine mol- Page 98 lusks. Research will be of the candidate’s choice, with 50% time available. Further information can be obtained from: Dr. Robert K. Johnson, Chairman, Invertebrates Search Committee, Divison of Fishes, Field Museum of Natural History, Roosevelt Road at Lakeshoe Drive, Chicago, Illinois 60605, U.S. A. The search will close in September 1980. Field Museum of Natural History is an Equal Opportu- nity Employer. Publication Date of THE VELIGER THE PUBLICATION DATE of The Veliger is the date printed on the index page; this applies even if the date falls on a legal holiday or on a Saturday or Sunday, days when the U. S. Postal Service does not expedite second class mail matter. That the printed date is the actual date of pub- lication under the rules of the International Commission on Zoological Nomenclature is based on the following facts: 1) The journal is delivered to the Post Office on the first day of each quarter, ready for dispatch; 2) at least three copies are mailed either as first class items or by air mail; 3) about 20 copies are delivered in person to the mail boxes or to the offices of members in the Berkeley area; 4) two copies are delivered to the re- ceiving department of the General Library of the Univer- sity of California in Berkeley. Thus our publication is available in the meaning of the Code of the ICZN. 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We have, however, not been able to get any confirmation from the postal authorities in this area. If it turns out later to be true, we may be forced THE VELIGER Vol. 23; No. 1 to ask our members and subscribers in foreign countries for a supplemental payment to cover the increase. This will be especially true in the cases where the journal is being sent by Air Mail. Regarding UNESCO Coupons We are unable to accept UNESCO coupons in payment, except at a charge of $4.25 (to reimburse us for the ex- penses involved in redeeming them) and at $0.95 per $1.- face value of the coupons (the amount that we will receive in exchange for the coupons). We regret that these char- ges must be passed on to our correspondents; however, our subscription rates and other charges are so low that we are absolutely unable to absorb additional expenses. Moving? 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Publications: Effective January 1, 1978, all back volumes still in print, both paper covered and cloth bound, will be available only from Mr. Arthur C. West, P. O. Box 730, Oakhurst, CA(alifornia) 93644. The same applies to the supple- ments still in print with certain exceptions (see below). Prices of available items may be obtained by applying to Mr. West at the address given above. Volumes 1 through 8 and 10 through 12 are out of print. Supplements not available from Mr. West are as fol- lows: Supplements to vol. 7 (Glossary) and 15 (Ovulidae) are sold by “The Shell Cabinet, P O. Box 29, Falls Church, VI(rginia) 22046; supplement to vol. 18 (Chitons) is available from “The Secretary,’ Hopkins Marine Station, Pacific Grove, CA(lifornia) 93950. Supplements Supplement to Volume 3: [Part 1: Opisthobranch Mollusks of California by Prof. Ernst Marcus; Part 2: The Anaspidea of California by Prof. R. Beeman, and The Thecosomata and Gymnosomata of the Cali- fornia Current by Prof. John A. McGowan] Supplement to Volume 6: out of print. Supplement to Volume 7: available again; see announce- ment elsewhere in this issue. Supplement to Volume 11: [The Biology of Acmaea by Prof. D. P. Assorr et al., ed.} Supplement to Volume 14: [The Northwest American Tellinidae by Dr. E. V. Coan] Supplement to Volume 16: [The Panamic-Galapagan Epitoniidae by Mrs. Helen DuShane] [Growth Rates, Depth Preference and Ecological Succes- sion of Some Sessile Marine Invertebrates in Monterey Harbor by Dr. E. C. Haderlie] Supplement to Volume 17: Our stock of this supplement is exhausted. Copies may be obtained by applying to Dr. E. C. Haderlie, U. S. Naval Post-Graduate School, Mon- terey, CA (lifornia) 93940. WE ARE PLEASED to announce that an agreement has been entered into by the California Malacozoological Society, Inc. with Mr. Steven J. Long for the production and sale of microfiche reproductions of all out-of-print editions of the publications of the Society. 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Endowment Fund In the face of continuous rises in the costs of printing and labor, the income from the Endowment Fund would materially aid in avoiding the need for repeated upward adjustments of the membership dues of the Society. It is the stated aim of the Society to disseminate new infor- mation in the field of malacology and conchology as widely as possible at the lowest cost possible. To Prospective Authors Postal Service seems to have deteriorated in many other countries as well as in the United States of America. Since we will absolutely not publish a paper unless the galley proofs have been corrected and retummed by the authors, the slow surface mail service (a minimum of 6 weeks from European countries, 8 to 12 weeks from India and Africa) may make a delay in publication inevitable. 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If correspondence is needed pertaining to a manu- script, we must expect prompt replies. If a manuscript is withdrawn by the author, sufficient postage for return by certified mail within the U.S.A. and by registered mail to other countries must be provided. We regret that we must insist on these conditions; however, the exorbitant in- creases in postal charges leave us no other choice. Some recent experiences induce us to emphasize that manuscripts must be in final form when they are sub- mitted to us. Corrections in galley proofs, other than errors of editor or typographer, must and will be charged to the author. Such changes may be apparently very simple, yet may require extensive resetting of many lines or even entire paragraphs. Also we wish to stress that the require- ment that all matter be double spaced, in easily legible form (not using exhausted typewriter ribbons!) applies to all portions of the manuscript — including figure explana- tions and the “Literature Cited” section. It may seem inappropriate to mention here, but again recent experience indicates the advisability of doing so: when writing to us, make absolutely certain that the cor- rect amount of postage is affixed and that a correct return address is given. The postal service will not forward mail pieces with insufficient postage and, if no return address is given, the piece will go to the “dead letter’’ office, in other words, it is destroyed. Vol. 23; No. 1 BOOKS, PERIODICALS, PAMPHLETS Faunistics 1979: A Comparative Review New Zealand Mollusca, Marine, Land and Freshwater Shells by A. W. B. Powe tt. William Collins Publishers Ltd., Box 1, Auckland, New Zealand. xiv + 500 pp.; 82 plts.; many text figures. $60.00 (New Zealand). 1979 Hawaiian Marine Shells E. Atison Kay. Reef and Shore Fauna of Hawaii, Sec- tion 4: Mollusca. Bernice P. Bishop Museum Special Pub- lications 64 (4). xviii + 653 pp.; 195 text figs. Bernice P. Bishop Museum Press, Honolulu, Hawaii. $30.00 (U. S. A.). 1979 The near simultaneous appearance of these two long awaited regional surveys marks a fitting malacological close to the 1970’s. Both volumes were many years in preparation, significantly delayed in production, and have been eagerly awaited by biologists, professional malaco- logists and amateur shell collectors. The books are alike in attempting to cover the fauna of an important geo- graphic area, but do so in quite different ways that reflect both the state of the art in regard to knowledge of their respective faunas, and the backgrounds of the authors. Both books are milestones of which their authors can be proud. Both will stimulate much additional work, which in time will lead to revisions and expansions of these volumes. Both authors are to be congratulated on the skill and dedication with which they have brought together scattered information in a coherent and usable fashion. ‘These volumes belong in every museum library and are a “must” for persons interested in almost any aspect of molluscan life in the respective areas covered. E. Alison Kay’s Marine Shells of Hawati is the first attempt to monograph all the marine mollusks of Hawaii. Major emphasis is on species found in less than 50m, but some new deep water taxa are named. There is only casu- al mention of pelagic taxa. Hawaii lies far from the main Indo-Pacific marine fauna, of which few molluscan fam- THE VELIGER Page 1o1 ilies have been monographed in this century. The major effort of Dr. Kay had to be aimed at establishing if a name previously proposed could be correctly applied to Hawaiian specimens. For nearly 20 years, museum collec- tions throughout the Western World benefited from her repeated visits to compare specimens with types or au- thentically determined material. As a result of her long hunt, 976 species of Hawaiian marine mollusks are re- ferred to by name. Descriptions are given of 49 new species, and in several groups, such as the Aplacophora and certain nudibranchs, reference is made to unstudied and undescribed new taxa. Recordsof single collections are duly listed. Often reference is made to taxa described from deep waters, but the primary emphasis is on supply- ing a scientific name for almost every shallow water ma- rine shell known to occur in Hawaii. For many species, the statement “This species was described from the Ha- waiian Islands” is all that is said about distribution and affinities. It is, given our state of knowledge for many marine families, ALL that can be said at this time. Re- lating them to extralimital taxa is yet to be accomplished. Dr. Kay has performed a monumentally useful task in providing usable names for the Hawaiian marine mollus- can fauna. Specialists on other areas of the world and on particular groups will propose synonymies and borrow material from Hawaii to revise taxa which in time will substantially change the names listed. Marine Shells of Hawau successfully organizes knowledge of a little known fauna and provides a framework of names from which both systematic and faunistic work within Hawaii can proceed. It will be of great use to the malacologists of the 1980’s and beyond. It also attempts to be a biological compendium by including illustrationsof larvae, egg cases, radular teeth, a few habitat shots, occasional line draw- ings of animals, and some life history data. Very few data are presented on local distribution and variation. A tremendous amount of literature had to be combed, and the bibliography lists 1 025 titles. Only 196 of these are pre-1860. An impressive 226 papers were issued in the 1960’s, 130 are cited from 1970-1974, 37 of 1975- 1978 vintage were added during production, and even 3 in press or 1979 titles were written in at the last minute. Much of the surge in 1960-1978 literature resulted from efforts encouraged by the Hawaiian Malacological Soci- ety and by students of Dr. Kay. An excellent introductory review of the major ecological zones and history of col- lecting and study reflect the special interests of Dr. Kay. As a specialist on non-marine mollusks, and hence a casual user of this volume for curatorial or general pur- poses, I will not try to comment on systematic details. Classification of the mollusks is in a state of flux and no two specialists will agree on an overall classification. Dr. Page 102 THE VELIGER Vol. 23; No. 1 Kay has made a valiant and successful attempt to seek aid in reaching taxonomic decisions and gives a quite good synthesis of current knowledge. Certain features of the presentation are annoying and both format and pro- duction could have been improved. Fair to quite good black and white photographs are shown on a black back- ground, but rather poorly printed. Frequently dark sec- tions of an image merge into the background, effectively obscuring shape. The scanning electron microscope photo- graphs are good and well reproduced. The decision to print in quite large size poor to indifferent drawings such as figures 23, 30, 33, 37, 66, 91 and 93 was most un- fortunate. Their contrast with figure 9 is considerable. Equally unfortunate was devoting an entire page to fig- ure 58. The use of a single “format description” for each spe- cies assures uniformity, but substitution of simple compar- ative notes to aid identification of that particular species might have been of greater value to the user. The descrip- tions are not detailed, and in the general absence of keys, this lack of comparative information becomes more seri- ous. Particularly in the many descriptions of new species, comparisons with previously named taxa are so brief as to be nearly useless. For example, distinguished by “small size and depressed outline” (p. 39), “lack of beaded ca- rina” (p. 55), “smaller size and fewer whorls” (p. 77), are definitely not up to modern taxonomic standards. I doubt that this book should have been used to present descriptions of new taxa in view of the restrictive format for each species. Another very important problem is that only a single size is given for each species. This is highly misleading and confusing. At least giving a size range to indicate adult variation would have been far preferable and of great value to the user. Citation of only a single size for a new species is not defensible today. Family and generic discussions include general data on anatomical structure and biology, a highly useful feature that hopefully will stimulate much interest in the animal. Sometimes keys are provided to genera within a family, but rarely are there any aids to species identifications other than matching specimen to picture. To include such comparisons in addition to the descriptions would have greatly enlarged the size of the book. My own preference would have been to use comparative remarks to facilitate identifications, but Dr. Kay’s format may be preferred by others. Finally, the absence of a list of new taxa makes locating these somewhat difficult. [Editor’s note: Dr. Solem care- fully prepared a list of all new taxa described and gave the page numbers where to find them. However, we do not consider a review the proper place for supplying such extensive remedial information; it is rather hoped that a list for inclusion in all copies of the book would be prepared by either the author or the publisher. ] The price is a modern miracle, making this one of the true bargains in current shell literature. The Bishop Museum Press is to be commended on its making this volume more widely available by holding down the price. A. W. B. Powell’s New Zealand Mollusca is a worthy descendant from more than a century of investigations on the systematics and biogeography of New Zealand mol- lusks. The early monographic compilations of E W. Hutton in 1873 and 1880 laid a firm basis for the awe- some Manual of the New Zealand Mollusca issued by Henry Suter in 1913-1915. This last fully illustrated work stimulated a tremendous amount of work on New Zea- land mollusks, of which the multitude of studies by A. W. B. Powell stand preeminent. Few malacologists anywhere have published as widely on so many groups, and fewer have had the ability to influence others to become inter- ested scientists and professional scholars. The many sys- tematic papers and monographs, published by Dr. Powell between 1921 and 1974, plus the highly successful multi- edition checklist and introduction, whose first edition appeared 1937 and the 5" edition in 1977, fully prepared Dr. Powell for this attempt to replace Suter’s Manual with a modern version. A more than 50-year period of personal exposure to New Zealand mollusks and study, plus the benefit of major early works, gave him a magnificent basis for preparing this volume. Full use has been made of this base. Utilizing the best of a half century of illustrations and photographs from his previous publications, exten- sive use of figures from the works of Winston E Ponder and R. K. Dell, and many new illustrations for this volume give a highly polished appearance to the book, reflecting his notable artistic skills. Rather than adopting a uniform illustration pattern, darker shells are shown on white backgrounds, and lighter shells on black. Line cuts are reproduced at appropriate size. The color work is extensive and excellent, while the habitat and collecting photographs are both interesting and historically im- portant records. Use of bold face type in the text for species headings provides easy visual separation and is a great aid to the reader. Visually this book is a delight. The text has been “... not designed to cater for the specialist alone, but is, rather, a book that has something for everyone, and the mere beginner will find the work not only a starting point, but also a reference work that should sustain interest as his or her knowledge of the subject increases with experience gained over the years” (p. xiii). Time and finances forced hard choices, and “some of the less important species have abridged descrip- Vol. 23; No. 1 THE VELIGER Page 103 tions, and many of the little known minutae are un- figured. In all cases, however, references are given, so that a specialist in any group will have no difficulty in tracing the relevant literature”’ (p. xiil). The species accounts thus are basically comparative re- marks, focusing on “key characters” and obvious differ- ences. They are thus quite easy to use, and, for the most part, very effective in facilitating identifications. While one could have wished for a neat progression of figures in systematic order, practicalities of using figures from previous publications have resulted in numerous depar- tures from sequence. Identifying an unknown shell be- comes more of a browse at random, then reference to index (for page number), then to perhaps scattered illus- trations for similar species to compare with the unknown. Not totally convenient, but a practical compromise. Introductory and general material is at a bare mini- mum. New Zealand is fortunate in having a number of good ecologically oriented books on the sea shore, and Dr. Powell wisely chose to refer the reader to other works for basic data. The text is rife with collecting notes, indica- tions of local variations, suggestions about remaining problem taxa, notes about introductions or rare tropical waifs, and a wealth of anecdotes that only the spiritual guide to the very successful ““Conchology Section of the Auckland Institute and Museum” and meeter of public inquiries for a half century could have accumulated. The basic references stop in 1974. While Dr. Kay chose to rewrite in the text, Dr. Powell opted for a brief anal- ytic addendum (pp. 497-500) to review subsequent lit- erature, mainly published in New Zealand through 1978. Many overseas references from this period are not in- cluded, and thus the work is less “up to the minute” than Hawaiian Marine Shells. Since Powell’s book had been in proof for almost 4 years, this lack of last minute revision is understandable. New Zealand Mollusca also differs in that it covers land and freshwater species in addition to the marine taxa. Recognizing the disinterest of most collectors in these groups, the turmoil that exists in generic and species limits of New Zealand land snails at present, few illustra- tions are given of the charopid and punctid groups. Classi- fication follows the preliminary revisions of Climo. For the larger Paryphantidae and endemic Placostylus, more detailed treatment is presented. The slug family Athoraco- phoridae is briefly listed with a sample of taxa figured in outline. Given the current state of knowledge, these were very wise decisions. One can only say that New Zealand Mollusca is a fitting work to result from a half century of study. It is highly usable, will fully meet its objective of stimulating further work, and is very well produced. Only its contemporary price of NZ$6o0.00 will discourage purchase of what should be viewed as a model product. Comparing the two volumes is really impossible. Dr. Powell could start where Dr. Kay finished. He had a solid monographic review produced by Henry Suter. He then had 50 years of accumulating additional data, or- ganizing and synthesizing. The amount of work required was equal for both writers, but the tasks were very differ- ent. Production of the Powell volume is far superior, and the format chosen is one that I find much easier to use, but this is a personal point of view. We have what are un- questionably two of the most important faunal volumes on mollusks produced in the last few decades. Both are excellent, and both are filled with charming flashes of personality and wit, whether it is Powell referring to conchologist, malacologist and paleontologist as ‘Fine words to confuse a statistician when filling out one’s census paper” or Kay’s statement that “The oysters are perhaps the most famous of all bivalves, beloved by gourmets, lyricized by poets, and cursed by systematists.” Comparing the classifications used is a good introduc- tion to the flux and flow of contemporary malacology. Every systematist will find fault with both presentations, depending upon his own current bias, which will be sub- ject to change next year. Both in their placement of fam- ilies, and in the family limits used many differences be- tween Powell and Kay could be chronicled. This would serve little purpose other than to expose my own preju- dices or current lapses of ignorance of what marine malacologists are thinking. In faunal works such differ- ences are unimportant. It is possible, and useful, to compare the patterns of diversity revealed in these volumes. Both can serve as an index of what is known today — that is, an approximation of actual diversity levels. Summarizing the class level and total marine diversity (Table 1), New Zealand has a much larger fauna with a higher proportion of bivalves and polyplacophorans. The cephalopod figures are not comparable as Powell included and Kay excluded pelagic taxa. Given that New Zealand is a continental fragment with considerable antiquity that extends from sub-Antarc- tic to sub-tropical climate regimes, while Hawaii is much younger and situated firmly within the tropics, such a difference could be expected. Another way is to record diversity within families, and to see which families are diverse in which area. Kay listed an additional 6 families as being present in Hawaii, but did not give species names or numbers. These are omitted from the analysis. No attempt has been made to iron out differences in family limits, so the data base is less than perfect. Nevertheless, the trends shown on ‘Tables 2 and 3 are worth noting. Although New Zealand has nearly twice Page 104 Table 1 Comparative Faunal Composition Hawaii New Zealand Gastropoda 826 (84.6%) 1369 (74.8%) Bivalvia 140 (14.47 ) 353 (19.37 ) Polyplacophora 4 (0.4%) 59 «((3.2%) Scaphopoda N.C. 10 (0.5%) Cephalopoda 6 (0.6%) 40 (2.2%) Aplacophora N.C. I Total 976 1832 N.C. = Not Covered as many species, the number of families is only 17.7% (26) greater. Table 2 compares the number of species found in families in each area. There are clear differences. Families with only 1-3 species each comprise 55.1% (81) of the Ha- THE VELIGER Vol. 23; No. 1 waiian and 38.2% (66) of the New Zealand families. The New Zealand figure probably is inflated by the more finely subdivided nudibranchs, with the real difference being even more dramatic. Considerably higher levels of infamily diversity are reached in New Zealand, and the differences of which families are diverse are dramatic. Table 3 lists families with notable regional differences in diversity. Only those with a significant change in numbers are included. Many of these differences would be expec- ted on the basis of climate, but the extent of certain dif ferences in non-climate limited taxa is intriguing. As a corollary to these differences, very few families have an approximately equal level of moderate diversity in both regions. These 8 are listed in Table 4. There are very few areas in the world for which equi- valent modern volumes exist. In their absence, detailed faunistic comparisons are not possible. In the absence of adequate monographic treatments of most families, prep- arations of such faunistic reviews are discouragingly diffi- cult. To invest years of research time and effort, to endure the agonizing editorial process and production delays, to Table 2 Family Level Diversity sss SSS NAR Gastropoda Bivalvia Others Totals Demarest ua email New Zealand linenean aia New Zealand Hawaii New Zealand Hawaii New Zealand 1 22 20 12 9 4 2 38 31 2-3 26 25 14 8 3 2 43 35 4-6 20 28 8 4 2 28 44 7-9 13 10 2 4 3 15 17 10 - 15 6 10 3 9 3 9 21 16 - 20 2 5 3 2 8 2] = 25 31 36 215 3 5 26 - 30 12 17 116 1 2 31 - 40 43 18 4 1 41 - 50 34 19 3 1 51 - 60 210 2 61 - 70 15 yi 1 1 71 - 80 112 1 81 - 90 213 2, 101 - 125 15 1 151 - 175 14 il Grand Totals 147 173 1Rissoidae, Cymatiidae, Pyramidellidae 9Eatoniellidae 2Thaididae 10Muricidae, Columbellidae 3Cypraeidae, Conidae, Dorididae, Terebridae 1 Buccinidae 4Costellariidae, Triphoridae, Mitridae 2Cyclostrematidae 5Turridae 15Trochidae, Pyramidellidae 6Fissurellidae, Eulimidae, Naticidae 14Rissoidae 7Cerithiopsidae 15Cyamiidae, Veneridae ®’Marginellidae 16Philobryidae Vol. 23; No. 1 THE VELIGER Page 105 Table 3 Divergent Diversity Levels Family Unit Number of Species in: Hawaii New Zealand Scissurellidae 3 17 Fissurellidae 6 21 Patellidae 4 14 Acmaeidae - 18 Trochidae 8 86 Turbinidae 4 13 Cyclostrematidae 4 74 (= Skeneidae) Neritidae 9 I Rissoidae 24 170 Eatonielleidae 2 44 Caecidae 8 I Cerithiopsidac 6 29 Triphoridae 46 6 Cypraeidae 34 2 Columbellidae 9 51 Buccinidae II 67 Volutidae - 18 Marginellidae 5 31 Cancellariidae - 13 Turridae 62 101 Conidae 34 I Terebridae 39 4 Pyramidellidae 24 88 Actaeonidae 2 10 Nuculidae I 16 Nuculanidae - 12 Philobryidae - 26 Erycinidae - 19 Cyamiidae - 22 Veneridae 5 22 Cuspidariidae 3 12 Chitonidae I 15 Acanthochitonidae 2 12 find a source for publishing such large tomes becomes in- creasingly difficult. To find an intellectual security and ego large enough to contemplate such a project requires a unique person. To have that individual in a position where such long term endeavors are not destructive of career potentials also is required. Table 4 Similar Diversity Levels Family Number of Species in: Hawaii New Zealand Vermetidae a) 8 Epitoniidae 13 14 Eulimidae 20 21 Cymatiidae 21 19 Fasciolariidae 10 12 Aplysiidae 9 7 Mytilidae II 12 Tellinidae 9 8 Malacology is very lucky that E. Alison Kay and A. W. B. Powell made their decisions many years ago, per- severed to completion, and brought forth for use such important aids to the next generations. May their ex- amples inspire other scientists to attempt, and, more important perhaps, administrators to encourage and sup- port equivalent efforts. Alan Solem Department of Zoology Field Museum of Natural History Chicago, Illinois 60605, U.S.A. Sensibility in the Publication of Names of New Taxa E. Alison Kay’s inclusion of descriptions of 49 new species of mollusks in Marine Shells of Hawaii has elicited some lively discussion. The polarization of positive and negative reactions prompts me to comment briefly on the matter. Faunal manuals traditionally serve primarily as aids in identification and are not expected sources of new taxo- nomic descriptions. Furthermore, the regional faunal manual does not achieve so broad or automatic a distri- bution as journals that standardly publish descriptive taxonomy. Prompt dissemination of information via Bio- logical Abstracts and the Zoological Record is also guaranteed by the more standard publication route. More importantly, journals that publish descriptive taxonomy generally (but not always) have rigorous requirements Page 106 that conform to the spirit as well as the letter of the Code and modern standards with respect to designation of types, repositories, description of type localities, discussion of variation in populations, adequacy of illustration, meas- urements of specimens, etc. Publishers of books generally lack this concern. The faunal manual thus is not the ideal place to introduce new names. On the other hand, there are precedents. A. Myra Keen introduced 13 new names in the second edition of Sea Shells of Tropical West America. We might well ask ourselves how much longer we would have waited for both these volumes had we expected their authors first to publish their new names elsewhere. E. Alison Kay could have added 49 titles to her bibliography, but, fortunately for us, she had better things to do with her time. The times force us to think increasingly hard about economy in publication and reduction in redundancy of treatment. Unfortunately neither volume includes complete infor- mation, but then descriptions of new taxa in Science fall far short of reflecting the “state of the art.” Two simple suggestions emerge from this: First, authors who publish new names in faunal manuals should be en- couraged to alter their format to include additional de- tailed information and more extensive illustration of new taxa. Secondly, a list of new taxa should appear promi- nently in the table of contents or as a special index. Carole S. Hickman Department of Paleontology University of California, Berkeley Pathways in Malacology Edited by S. vAN DER SpoEL, A. C. VAN BruccEN, and J. Lever. Bohn, Scheltema & Holkema, Utrecht, The Netherlands. 295 pp.; illust. US$ 72.00. 1979. Eleven invited papers presented at the Sixth Interna- tional Congress of Unitas Malacologica Europaea provide reviews, all in English, of an extraordinary range of topics in molluscan biology and paleobiology. Several of the re- views are written expressly for the malacologist who is not well versed in physiology, biochemistry, and development and who does not routinely read the non-molluscan and non-organismally oriented journals in which the majority of papers using mollusks as subjects in fact appear. J. Joosse provides a richly documented review of recent advances in molluscan endocrinology and A. de Zwaan THE VELIGER Vol. 23; No. 1 provides a concise, simplified (but not so extensively docu- mented — the reader is referred to other review papers) discussion of the control and pathways of energy meta- bolism in mollusks. Likewise, a review of the chemical, environmental engineering, and biological control of the freshwater snail hosts of schistosomiasis by E. A. Malek, serves to remind us that mollusks are a source of suffer- ing to 200 million of the world’s inhabitants and a right- fully major focus of research. Two papers in the volume indicate a revival of interest in the long-debated, but unresolved, question of the ori- gin and adaptive significance of torsion in gastropods. Neither paper resolves the controversy, but J. Lever pro- vides a concise review of torsion theories and an inter- esting attempt to relate torsion to an inferred raising of the grazing zone at the beginning of the Cambrian Period as oxygen levels rose and phytoplankton appeared. A more complete review of current ideas regarding the physical, chemical, and biological events in the Late Pre- cambrian and Cambrian that may have affected early mollusk evolution has been published by La Barbera (1978, Nature 201: 1147-1149). In a less speculative vein, N. H. Verdonk presents developmental evidence for the appearance of pronounced asymmetry in the gastro- pod embryo long before the onset of torsion. This work is particularly interesting in its experimental approach to isolating morphogenetic controls and inspires confidence that ongoing research may provide us with some resolu- tion of this problem in the near future. The little-explored subject of molluscan perception and behavior is treated by M. J. Wells, who offers fascinating experimental data on visual and tactile discrimination by Octopus vulgaris. Two authors deal with aspects of the molluscan shell. A. S. M. Saleuddin discusses the process and control of shell formation, including the organic matrix, crystal de- position, formation and tanning of the periostracum, and shell regeneration. C. M. Yonge describes the process of cementation in bivalves, with an excellent summary of the multiple evolutionary pathways leading to the adap- tation. Comprehensive treatments of two less familiar groups of mollusks are a welcome addition to the collection. J. Knudsen reviews literature on the deep-sea bivalves that has appeared since 1970, emphasizing its bearing on untested theory and controversial generalizations about the nature of the deep-sea fauna. M.-L. Furnestin pro- vides an extensively documented account of the use and prospects for refined use of planktonic mollusks as indica- Vol. 23; No. 1 THE VELIGER Page 107 tors of hydrological and ecological conditions, including applications to problems in the fossil record. The fossil record of the Mollusca also figures promi- nently in A. Solem’s consideration of the historical bio- geography of land snails, which emphasizes the Paleo- zoic origins and stable distributions for many groups over long periods of geologic time. Because of its price, this book will not achieve wide distribution and readership. It will, nonetheless, be of interest to molluscan specialists and lay-readership inter- ested in keeping abreast of some fast-moving areas of research and areas that have not been treated synthetical- ly for many years. It is hoped that the book will be ordered by all major libraries. Carole S. Hickman, Dept. of Paleontology University of California, Berkeley Die heteromorphen Ammoniten des Dogger by GerHarp Dietv. Stuttgarter Beitrage zur Naturkun- de, Ser. B, No. 33: 1-973 11 plts.; 20 text figs. 1978 Stuttgart, Western Germany (1 April) On the basis of over 2500 specimens of Ammonoidea from Middle, West and South Europe, SW-Asia and South America, the author comes to the conclusion that of 38 previously described species only 12 are valid and 3 species must be considered of uncertain systematic value. The paper is well documented and well illustrated. About 120 works are cited in the bibliography. In coming to his conclusions, the author considered stratigraphy, taxon- omy, phylogeny and ecology of the various taxa involved. R. Stohler FAO Species Identification Sheets for Fishery Purposes, Western Central Atlantic Ocean, Fishing Area 31 by R. Tucker Apzott. Rome, Italy. 29 looseleaf sheets, portions on bivalves, gastropods and chitons. Reprints available by sending gummed addressed label and $1.- (stamps or currency) to American Malacologists, Inc., P.O. Box 2255, Melbourne, Florida 32901, U.S. A. (December 1978) The first few sheets of each portion are devoted to “Technical and General Remarks” (on light blue paper), which are followed by a “Picture Guide to edible Bivalves (Gastropods) occurring in the Area”. On the white sheets following the blue ones are found excellent drawings of the commoner species of the particular group of mollusks, with a pictorial comparison with similar species occurring in the same area. In addition to the scientific name there are given one “common name” each in English, French and Spanish; this might be interpreted as a continuing effort on the part of Dr. Abbott to “standardize” the so- called common names in at least 3 languages. These FAO sheets should prove helpful to tourists visiting markets where mollusks are offered for food and to commercial fishermen. R. Stohler Shells on Stamps of the World by Kouman Y. ARAKAWA. 234 pp.; 16 plt., of which 12 in color. Publ. by The Biological Society of Nagasaki Pre- fecture. Available in U.S.A. only from American Mala- cologists, Inc., PR O. Box 2255, Melbourne, Florida 32901, U. S. A. for $14.50; postage extra. (1979) This book will be welcomed by the stamp collector who specializes in stamps with shell motifs. In addition to postage stamps, Dr. Arakawa has also included 2 plates of Japanese postal cancellations showing shells. The end decorations of the various sections are reproductions of symbols adopted by various societies and clubs. The names of shells illustrated are given in Japanese and in Latin. The major part of the book is a list ar- ranged alphabetically by country of issuance with the stamps in chronological order. Although much of the text is in Japanese, there are sufficient English comments to make the material accessible to the non-Japanese collec- tor. R. Stohler The Bulletin of the Institute of Malacology, Tokyo is a new malacological publication in Japan. Volume 1, number 1, was issued May 30, 1979, by the Institute of Malacology, 6-36, Midoricho 3 Chome, Tanashi City, Tokyo 188, Japan. The subscription price is not cited on the cover. The editor is Dr. Sadao Kosuge, director of the Coral Museum. The Institution is also sponsored by Page 108 THE VELIGER Yamae Funds and the N. T: Foundation, as well as by the Coral Museum. The first issue of the bulletin has four articles: a description of two new species of Muricidae; descriptions of two new subgenera and seven new species of Latiaxis; a report on mollusks dredged in Ishikaro Bay; and a report on mollusks collected in 1970 by an expedi- tion to the East China Sea. The first three are by Dr. Kosuge alone, the last with K. Inoué as junior author. The first two of these papers are illustrated by three halftone plates of excellent quality. Volume 1, number 2 of this new Bulletin was published in November, 1979. It has five papers by Dr. Sadao Ko- suge, all describing new species. The first four are on the genera Calliostoma, Guildfordia, Conus, and Penicillus. The fifth is a list of species taken in the Central Pacific from the tops of sea-mounts, with descriptions of 12 new species in the genera Brttiwm, Polinices, Bursa, Fusin- us, Pseudolatirus, Mitra, Terebra, Architectonica, Solari- axis, Bullina, and Euciroa. All descriptions are in English. Also issued by the Institute is the first of a projected new series: North Pacific Shells (1). Genus Volutopsius Morch. The paper, which is in both Japanese and Eng- lish, is by Ranji Tiba and Sadao Kosuge. It is Occasional Paper of the Institute of Malacology, Tokyo, no. 1, pp. 1 - 26, with 11 halftone plates as text figures, Nov., 1979. The figures are reproductions of original illustrations or photographs of type specimens, and brief synonymies are given for all the North Pacific species of this genus. A. Myra Keen Vol. 23: Nowa THE VELIGER is open to original papers pertaining to any problem concerned with mollusks. This is meant to make facilities available for publication of original articles from a wide field of endeavor. Papers dealing with anatomical, cytological, distributional, ecological, histological, morphological, phys- iological, taxonomic, etc., aspects of marine, freshwater or terrestrial mollusks from any region, will be considered. Even topics only indi- rectly concerned with mollusks may be acceptable. In the unlikely event that space considerations make limitations necessary, papers dealing with mollusks from the Pacific region will be given priority. However, in this case the term “Pacific region” is to be most liberally interpreted. It is the editorial policy to preserve the individualistic writing style of the author; therefore any editorial changes in a manuscript will be sub- mitted to the author for his approval, before going to press. Short articles containing descriptions of new species or lesser taxa will be given preferential treatment in the speed of publication provided that arrangements have been made by the author for depositing the holotype with a recognized public Museum. Museum numbers of the type specimens must be included in the manuscript. Type localities must be defined as accurately as possible, with geographical longitudes and latitudes added. Short original papers, not exceeding 500 words, will be published in the column “NOTES & NEWS”; in this column will also appear notices of meetings of the American Malacological Union, as well as news items which are deemed of interest to our subscribers in general. Articles on “METHODS & TECHNIQUES” will be considered for publication in another column, provided that the information is complete and tech- niques and methods are capable of duplication by anyone carefully fol- lowing the description given. Such articles should be mainly original and deal with collecting, preparing, maintaining, studying, photo- graphing, etc., of mollusks or other invertebrates. A third column, en- titled “INFORMATION DESK,” will contain articles dealing with any problem pertaining to collecting, identifying, etc., in short, problems encountered by our readers. In contrast to other contributions, articles in this column do not necessarily contain new and original materials. Questions to the editor, which can be answered in this column, are in- vited. The column “BOOKS, PERIODICALS, PAMPHLETS” will attempt to bring reviews of new publications to the attention of our readers. Also, new timely articles may be listed by title only, if this is deemed expedient. Manuscripts should be typed in final form on a high grade white paper, 812” by 11”, double spaced and accompanied by a carbon copy. A pamphlet with detailed suggestions for preparing manuscripts intended for publication in THE VELIGER is available to authors upon request. A self-addressed envelope, sufficiently large to accom- modate the pamphlet (which measures 5/2” by 81/2’), with double first class postage, should be sent with the request to the Editor. EDITORIAL BOARD Dr. Donatp P. Azsorrt, Professor of Biology Hopkins Marine Station of Stanford University Dr. WarrEN O. AppicotTT, Research Geologist, U. S. Geological Survey, Menlo Park, California, and Consulting Professor of Paleontology, Stanford University Dr. Hans Bertscu, Curator of Marine Invertebrates San Diego Museum of Natural History Dr. Jerry DonouueE, Professor of Chemistry University of Pennsylvania, Philadelphia, and Research Associate in the Allan Hancock Foundation University of Southern California, Los Angeles Dr. J. Wyatr Duruam, Professor of Paleontology Emeritus University of California, Berkeley, California Dr. Cavet Hann, Professor of Zoology and Director, Bodega Marine Laboratory University of California, Berkeley, California Dr. Caroie S. HicKMAN, Assistant Professor of Paleontology University of California, Berkeley, California Dr. A. Myra KEEN, Professor of Paleontology and Curator of Malacology, Emeritus Stanford University, Stanford, California Dr. Victor LoosanorF, Senior Biologist, Emeritus U.S. National Marine Fisheries Service EDITOR-IN-CHIEF Dr. Rupoitr STOHLER, Research Zoologist, Emeritus University of California, Berkeley, California Dr. Joun McGowan, Professor of Oceanography Scripps Institution of Oceanography, La Jolla University of California at San Diego Dr. Franx A. Pitre.xa, Professor of Zoology University of California, Berkeley, California Dr. Robert RoBertson, Pilsbry Chair of Malacology Department of Malacology Academy of Natural Sciences of Philadelphia Dr. PeTEeR U. Roppa, Chairman and Curator, Department of Geology California Academy of Sciences, San Francisco Dr. Ciype FE. E. Roper, Curator Department of Invertebrate Zoology (Mollusca) National Museum of Natural History Washington, D. C. Dr. JupirH Terry SmirH, Visiting Scholar Department of Geology, Stanford University Stanford, California Dr. Ratpu I. Smiru, Professor of Zoology University of California, Berkeley, California Dr. Cuares R. STASEK, Bodega Bay Institute Bodega Bay, California Dr. T. E. THompson, Reader in Zoology University of Bristol, England ASSOCIATE EDITOR Mrs. Jean M. Cate Rancho Santa Fe, California ty ae | “ot iF s TU Gkeket i MEVE 2 So SF Mek . © SECTIONAL LIBRARY * ¥43 DIVISION OF MOLLUSKS ISSN 0042-9913 ~~ Ww \ = MUTT = THE A PELIGER A Quarterly published by CALIFORNIA MALACOZOOLOGICAL SOCIETY, INC, Berkeley, California VoLUME 23 OcToBER 1, 1980 CONTENTS The Sexual Cycle and Reproduitive Modality in Littorina saxatilis Olivi (Mol- lusca : Gastropoda). (4 Text lgures) DomMiniQuE CAUGANT «& JOsEpH BEeRGERARD 5 . . . . . ie eco TOr Two Disjunct Populations of Euglandina singleyana (W.G. Binney) ( Spiraxidae) in Central Texas. INSTRRORTD TRL INSGRS gg he oe ro sediment VMN alas: a mn Semen Heat Tolerance in the Black Abalone, Haliotis cracherodii Leach, 1814: Effects of Temperature Fluctuation and Acclimation. (3 Text figures) Anson Hines, Susan ANDERSON & MICHAEL VBRISBINN) 42 Guo. si so Sean 113 Food Sources and Feeding Behavior of Nautilus macromphalus. (1 Plate; 2 Text figures) PETER Warp & Mary K. WIcKSTEN . ci EOLA CUPS SORA (Oona AL Ae SPE NEN Me ho Crude Oil Effects on Mortality, Growth and Feeding of Young Oyster Drills, Urosalpinx cinerea (Say). (3 Text figures ) STEVEN FE Epwarps . . ame: : F Bi co ol Satan OG) A Survey of the Softbottom Molluscs of Cockburn Sound, Western Australia. (7 Text figures) Frep E. WELLs « Timorny J. RHRED RADI Meats iia y ee ete se 131 Larval and Postlarval Development of the Window-Pane Shell, Placuna placenta Linnaeus (Bivalvia : Placunidae) with a Discussion on its Natural Settlement. (3 Plates; 1 Text figure) Apam L. Younc ee te Tee Wm an onl eee oy eNeMa oyu ere fz Vis) 1S) tS aves AT [Continued on Inside Front Cover] re ie Line as Ye Distributed free to Members of the California Malacozoological Society, Inc. Subscriptions, by Volume only, payable in advance to Calif. Malacozool. Soc., Inc. Volume 23: $37.50 plus $1.50 for mailing charges (U.S.A. only) For ALL foreign countries: Swiss Francs 60.- plus SF 7.- for postage Single copy this issue $14.00; postage extra Send subscription orders to California Malacozoological Society, Inc. 1584 Milvia Street, Berkeley, CA 94709, U.S.A Address all other correspondence to Dr. R. Stouter, Editor, Depatment of Zoology University of California, Berkeley, California 94720, U.S.A. Second Class Postage Paid at Berkeley, California CoNTENTS — Continued Pulsellum salishorum spec. nov., a New Scaphopod from the Pacific Northwest. (1 Plate; 5 Text figures) Este MARSHALL) 200.0) ):3) cee 0 Saag) es ene) oe) OR ee ee TG A Note on the Diet of Beringius kennicottii (Dall, 1871). (1 Plate) Ronatp Lb. ‘SHIMEeK (2! 05 ls Sh non een ot me ULE oe Canepa er TS The Effect of Salinity on Crystalline Style Occurrence in the Estuarine Snail, Ilya- nassa obsoleta (Say) (Mollusca : Neogastropoda), and its Potential Signifi- cance with Respect to Local Distribution. (1 Text figure) LAWRENGE/A. Curtis «1. EEluRp) 7.) 20 see eo ee ere eT A Possible Relationship Between Size and Reproductive Behavior in a Population of Aplysia punctata Cuvier, 1803. Cary Otsuka, Yves Roucer « ETHEL TopacH. . . ..... =. =. « « I59 Reproductive Biology of Assiminea californica (Tryon, 1865) (Mesogastropoda : Rissoacea) . (3 Text figures) BrRucE | H. FOWLER) (esr IE es ce Sct cet oy enn cre eT Magnetic Radular Teeth and Geomagnetic Responses in Chitons. (1 Text figure) Jack TomMuInson, Desra REILLY & ROBERT BALLERING . ...... . . 167 Collections of Gastropods from the Cascade Mountains of Washington. BRANLEY ALLAN BRANSON) |. 60) 070550 Gy) SU ho comm Pel a ce ke ram aT Spawning in a British Columbia Population of Northern Abalone, Haliotis kamt- schatkana. PAuL ALLAN BREEN & BRUCE EDWARD) ADKINS) = 20-0. = 2) = eg Habitat Notes on Gastrocopta riograndensis Sterki. RAYMOND W. NECK). ° 00) 05.6) LR Dae ae eine nn er OO NOTES: & NEWS * i (2) 550 et Pian Et one cnete e r e TOS New Records from the Tropical Eastern Pacific for Recluzta palmen (Dall, 1871). Leroy H. PoorMAN BOOKS, PERIODICALS Sa RAMP EME E Sie ier ntel etre pier itera nan mane mEETIOG: Note: The various taxa above species are indicated by the use of different type styles as shown by the following examples, and by increasing indentation. ORDER, Suborder, DIVISION, Subdivision, SECTION, SUPERFAMILY, Famity, Subfamily, Genus, (Subgenus) New Taxa Vol. 23; No. 2 THE VELIGER Page 107 The Sexual Cycle and Reproductive Modality in Littorina saxatilis Olivi (Mollusca : Gastropoda’ DOMINIQUE CAUGANT ann JOSEPH BERGERARD Station Biologique — F 29211 — Roscoff - France (4 Text figures) INTRODUCTION Littorina saxatilis Olivi, 1792 is a highly polymorphic species within which many subspecies and varieties have been described (DAUTZENBERG & FISCHER, 1912; JAMES, 1968). One subspecies, Littorina nigrolineata, has such well defined ecological, morphological, and physiological characteristics that it has been held to be a distinct species (Saccut, 1975; HELLER, 1975). The chief diagnostic char- acteristics for species distinction have been within the reproductive modality, as demonstrated by DrycLuNn (1955): L. nigrolineata is oviparous, while L. saxatilis is generally considered to be ovoviviparous. The most defin- itive confirmation of specific status has been electropho- retic analysis of the leucine aminopeptidase (CAUGANT & BERGERARD, 1979). The sexual cycle of Littorinidae has been especially well investigated in Littorina littorea. LINKE (1933) described a sexual rest-phase in males, with an absence of the penis. Unlike other species of marine gastropods, in L. littorea the penis is not resorbed but is shed at the end of the breed- ing season (GRAHAME, 1969). STREIFF & LE BRETON (1970) have demonstrated an endocrinological control of both penis regression and penis morphogenesis. (Total number of males) —(Number of immature males) While Berry (1961) has described an analogous cycle in Littorina saxatilis, with regression of the genital organs of male and female in the summer, BERGERARD (1971) has shown that the cycle varies in different populations. Study of a population in Brittany (north of the “ile de Batz’’) showed that regression occurs only in old animals ( BERGE- RARD, 1975). Concomitant with an electrophoretic analysis of iso- zymes, the sexual state of several populations of Littorina saxatilis on the north coast of Brittany has been deter- mined at different times of the year; samples of 100 indi- viduals from each locality were examined. The popula- tions included those of the variety rudis from rocky shores with various degrees of exposure to wave action and a population from a sandy shore habitat, where only the “typical” form, identical to those of the lagoon of Venice, was found. SEXUAL CYCLE tn MALES Three sexual stages were defined in the males, on the basis of degree of development of the penis, testicle, and seminal vesicle: immaturity, maturity, and regression. The per cent of maturity in a population (the proportion of repro- ductively capable males) was computed as follows: (Number of mature males) xX 100 Page 108 THE VELIGER Vol. 23; No. 2 The variations of per cent maturity throughout the year for 3 populations on rocky shores (Bloscon, Brignogan, and Pors-Hir) and for the population on a movable substrate (Bight of Kernic) are shown in Figure 1. % mature males May 1978 August 1978 November 1978 February Dates of Samplings 1979 Figure 1 Variations in the per cent of maturity in males throughout the year Stations: Bight of Kernic A Brignogan @ Pors-hir A Bloscon O For the rudis variety, the sexual cycle is similar at the 3 stations, with a maximum maturity (close to 100%) in November, and a maximum regression in May. The pop- ulation at Bloscon, which was followed for 2 years, showed a similar cycle each year. On the other hand, the popula- tion of typical Littorina saxatilis at the Bight of Kernic locality displayed a maximum maturity in summer (May and August), then regressed from November onward, reaching a minimum of mature males in February. Thus, the cycle in this population appears to be the reverse of that in L. saxatilis rudis. SEXUAL CYCLE tin FEMALES Four sexual stages were defined in the females, on the basis of ovary, annex gland, and brood pouch development: im- maturity, gestation (i.e., incubation), maturity without ges- tation, and regression. The per cent of maturity in a pop- ulation was determined as follows: (Number of incubating females) + (Number of mature but non-incubating females) Figures 2 and 3 show variation in these parameters dur- ing the year. The cycle of females (Figure 2) appears to be more complex than that of males: two populations show fairly similar cycles (Bloscon and Brignogan), with a minimum of maturity in August and 100% maturity in February, coinciding with the cycle of the males in the same population. However, the other population of the rudis variety, from Pors-Hir, reached maximum maturity in August, while the values for the 3 other samples are rel- atively the same as those for the previously mentioned sta- tions. There is also a similarity in the per cent of gestation in the Bloscon and Brignogan populations (Figure 3): they were low during the whole year (always below 50%) and showed no cyclic variation. This may have led to the belief that the females, in some populations, do not have a sexual cycle (PELSENEER, 1934). At Pors-Hir, the August sample showed an increased per cent of incubating females (nearly 90%); this would explain the peak of female matu- rity at this period. As was noted for the per cent of matu- rity, the 3 other samples were similar to those at Bloscon and Brignogan. The three populations of Littorina saxatilis rudis showed a minimum of mature but not incubating females in August. % mature females May 1978 August 1978 November 1978 February Dates of Samplings ieee Figure 2 Variations in the per cent of maturity in females throughout the year Stations: Bight of Kernic A Pors-hir A Brignogan @ Bloscon O x 100 (Total number of females) —(Number of immature females) The per cent of gestation was computed by: (Number of incubating females) (Total number of females) —(Number of immature females) eats (oye) Vol. 23; No. 2 % incubating females August 1978 November 1978 February May 1978 Dates of Samplings 1979 Figure 3 Variations in the per cent of gestation throughout the year Stations: Bight of Kernic A Brignogan 9 Pors-hir A Bloscon O The female population at the Bight of Kernic also be- haved very differently from the other populations. All indi- viduals were mature in May, August, and November, and the population exhibited a great regression in February. It is important to note here that when females show regres- sion of the ovary and annex glands, the majority is still in gestation; the brood pouch often contaiis some well devel- oped embryos. In this case, the regression mechanism appears to be somewhat different, as it begins even before the brood pouch is completely empty. The proportion of incubating females to mature females ranged from 40% to 50% for the rudis variety and was more than 80% for typical Littorina saxatilis. (adjacent column —>) Figure 4 Breakdown of the population of Pors-Hir by shell height for the various sexual states in August and November, 1978 Sexual states: immature female (4 mature female without embryos, SS similar to oviparous female regressed female incubating female THE VELIGER Page 109 Figure 4 shows a breakdown of the female population at Pors-Hir by size for the various sexual states during Aug- ust and November, 1978. While in August most of the Number of individuals Number of individuals 50 100 150 Shell height in 1/10 mm Page 110 THE VELIGER Vol. 23; No. 2 females with shell height greater than 9mm were incu- bating, in November those greater than 10mm were ma- ture, but non-incubating. While the young females are still incubating, most have reached a state of maturity quite analogous to females of the oviparous species Littorina nigrolineata. Animals derived from various Breton populations of Littorina saxatilis (ile Grande, Bloscon, fle Callot) were raised individually so that the spawning process could be observed in each. In these populations, animals which had shells similar to those of the ovoviviparous L. saxatilis pro- duced spawns like L. nigrolineata and with a high fre- quency. As in L. nigrolineata, young animals emerge directly from spawns without passing through a pelagic stage. The time required for embryonic development also seems similar (about one month). DISCUSSION Oviparity in Littorina saxatilis was first observed by SESHAPPA (1947) in the form rudissima. In 1948, he con- cluded that, “‘here is a case of the same species exhibiting both the oviparous and the viviparous modes of reproduc- tion even in the same locality,” a phenomenon previously observed in several species of Gastropoda: Helix carthus- ana, Achatina panthera, Balea perversa (PELSENEER, 1935, cited by SesHaPpPA, 1948). This conciusion subse- quently was contested on the grounds of mistaken identity, i.e., confusion with L. nigrolineata. In 1978, HANNAFoRD-ELLIS described a new species, Littorina arcana, morphologically identical to L. saxatilis and sympatric with it, but differing in mode of reproduc- tion. She noted a ciliated field which differs in extent in the viviparous and oviparous females (1979). Since this “field” is situated close to the jelly-gland, which changes into the brood pouch in ovoviviparous females, its value as a specific character seems contestable, especially since in males it is involved with prostate development. Two modes of reproduction in the same species seem much more likely: indeed, electrophoretic analysis of the incubating and mature but non-incubating females reveals no significant difference for 3 enzymatic systems: esterases, leucine aminopeptidase, and glucose-6-phosphate dehy- drogenase; these are the enzymatic systems which allowed differentiation of Littorina nigrolineata (CAUGANT, 1979). In addition, as shown by the changes in the sexual stages of females in Pors-Hir between August and November, 1978 (cf. Figure 4), it must be admitted that some animals do indeed pass from viviparity to oviparity since most of the females passed from one stage of maturity to the other. This does not require significant modification of the female genital system, since only the jelly gland is modified in the Ovoviviparous form (GAILLARD, 1977; WEBBER, 1977). The capacity to adopt other reproductive patterns dur- ing certain periods of the year has selective advantage for the species. Indeed, if oviparity increases the reproductive capacity of the individual (HuGHEs, 1978), ovoviviparity during the summer would provide the best protection against desiccation. The reproductive modality of Littorina saxatilis, there- fore, appears not to be as fixed as has been believed. Ovi- parity exists in most of the populations. Nevertheless, an exception has to be made for the population of the Bight of Kernic, in which the per cent of gestation is very high throughout the year. This population is also exceptional with regard to the rudis variety, because there is an aver- age 6-month delay in the sexual cycle for males as well as for females; the regression of the genital system occurs in winter. In the 3 populations of rudis, the male sexual cycle does not vary: exposure of the stations to wave action does not influence the cycle. On the other hand, the female cycle shows much greater variations among stations. This con- firms BERGERARD’s observations (1971). This variation could result from higher mortality in exposed localities, so that the cycle is frequently incomplete. If the mean sizes of the incubating females and the ma- ture but non-incubating females in Pors-Hir are compared, there is a significant difference (P = 0.01), since incubating females are on the average smaller than non-incubating females (10.6 against 11.4mm). This difference is equiv- alent to the increase in mean size of the animals in a few months (Dacuzan, 1975; MorETEAU, 1976). So it is diffi- cult to decide whether the passage from one mode of reproduction to another is reversible. This conversion ap- pears to be influenced both by the age of the animal and by the ecological conditions at the stations. ACKNOWLEDGMENT We wish to thank Ms. A. Cueff for technical assistance. Literature Cited BERGERARD, JOSEPH 1971. Facteurs écologiques et cycle sexuel de Littorina saxatilis (Olivi) (Mollusques, Gastéropodes). Cah. Biol. Mar. 12: 187 - 193 1975: Cycle sexuel saisonnier dans une population naturelle de Lit- torina saxatilis (Olivi) (Gastéropode, Prosobranche). Zool. France 100 (2): 193-145 Bull. Soc. Vol. 23; No. 2 THE VELIGER Page 111 Berry, A. J. 1961. Some factors affecting the distribution of Littorina saxatilts (Olivi) . Journ. Anim. Ecol. 30: 27-45 Caucant, Dominique 1979. Variabilité enzymatique chez quelques espéces du genre Littorina. 3rd Cycle Thesis, Univ. Paris, Orsay, 94 pp. Caucant, DomINIQUE & JosEPH BERGERARD 1979. Variabilité de la leucine aminopeptidase chez Littorina saxa- tilis (Olivi) et Littortna nigrolineata (Gray) (Gastéropodes, Proso- branches). Arch. Zool. Expérim. Gén, 120 (2): 247 - 262 Dacuzan, J. 1975. Recherches sur les Littorinidae; recherches écophysiologiques chez quatre espéces: L. neritoides (L.), L. saxatilis (Olivi), L. littorea (L.) et L. littoralis (L.). Thesis, Univ. Rennes, 400 pp. DavuTZENBERG, PHILIPPE & HENRI FISCHER 1912. Mollusques provenant des campagnes de |’ “‘Hirondelle” et de la “Princesse Alice’ dans les mers du Nord. Rés. Camp. Sci. Prince Monaco 37: 187 - 202 Deryciun, CLAUDE 1955- Biologie comparée de deux sous-espéces de Littorina saxatilis (Olivi) (Gastéropode, Prosobranche) . D. E. S., Univ. Paris, 36 pp. Gaitarp, J. M. 1977. Le polymorphisme de Littorina saxatilis (Olivi) (Gastropoda, Prosobranchia) . Malacologia 16 (1): 11-14 (12 August 1977) GraHAME, J. 1969. Shedding of the penis in Littorina littorea. Hannarorp-Euis, Ceuia J. 1978. _Littorina arcana sp. nov.: a new species of winkle (Gastropoda Prosobranchia: Littorinidae). Journ. Conchol. 29: 301 Nature 221: 976 1979. Morphology of the oviparous rough winkle, Littorina arcana Hannaford-Ellis, 1978, with notes on the taxonomy of the L. saxatilis Journ. Conchol. species-complex (Prosobranchia: Littorinidae). $0: 43 - 56 Heuer, J. 1975. The taxonomy of some Bnitish Littorina species with notes on their reproduction (Mollusca: Prosobranchia). Zool. Journ. Linn. Soc. 56: 131-151 Hucues, Rocer N. 1978. Demography and reproductive mode in Littorina neritoides and the Littorina saxatilis species-complex. Haliotis 9 (2): 91-98 James, B. L. 1968. The characters and distribution of the sub-species and varieties of Littorina saxatilis (Olivi) in Britain. Cah. Biol. Mar. 9: 143 - 165 Linke, OrTo 1933- Morphologie und Physiologie des Genital Apparates der Nord- see Littorinen. Wissenschaft]. Meeresunters. Abt. Helgoland 19 (5): 3-52 MoreTEAvu, JEAN-CLAUDE 1976. Etude sur la croissance le Littorina saxatilis (Olivi) rudis (Maton). Cah. Biol. Mar. 17: 463 - 484 PELSENEER, PAUL 1934. La durée de la vie et Age de maturité sexuelle chez certains mol- lusques. Ann. Soc. R. Zool. Belg. 64: 93-104; 1 fig. Saccut, C. FE 1975. Littorina nigrolineata (Gray), Gastropoda, Prosobranchia. Cah. Biol. Mar. 16: 111 - 120 SesHappa, G. 1947. Oviparity in Littorina saxatilis (Olivi). Nature 160: 335 - 336 1948. Nomenclature of the British Littorinidae. Nature 162: 702 - 703 StreirF, W. & J. Le BrETON 1970. Etude endocrinologique des facteurs régissant la morphogénése et la regression du pénis chez un mollusque prosobranche gonochorique L. littorea. Compt. Rend. Acad. Sci. Paris 270: 547 - 549 Wesper, H. H. 1977- Reproduction of marine invertebrates. IV. Molluscs: Gastro- pods and Cephalopods. A. C. Giese & J. S. Pearse, (eds.). Acad. Press, New York, pp. 1-114 Page 112 THE VELIGER Vol. 23; No. 2 Two Disjunct Populations of Euglandina singleyana (W. G. Binney) RAYMOND W. NECK Pesquezo Museum of Natural History, 6803 Esther Street, Austin, Texas 78752 Euglandina singleyana (W. G. Binney, 1892) is a moderate- to-large-sized predatory land snail with a distribution centered in the Hill Country of central Texas and extend- ing westward to the Stockton Plateau just west of the Pecos River (FULLINGTON & PRATT, 1974). Narrow range tongues occur along the Guadalupe/San Antonio River systems down onto the Coastal Plain. Recently two new disjunct populations have been located outside of the pub- lished range of this species. Discovery of these populations of E. singleyana have resulted from a larger study on the ecology, biogeography and evolution of Texas Euglandina. The river system north of the Guadalupe/San Antonio is the Colorado River. Euglandina singleyana occurs in the upper part of this drainage system. No records have been known downstream from central Travis County where it occurs in woodlands on scarps of the Austin Chalk. A thriving population has been located on dissected slopes of the La Grange Bluff in Fayette County. This bluff of the Oakville Escarpment rises more than 70m above the level of the Colorado River. The Oakville Formation consists of alternating layers of massive calcareous sand- stone and clay/shale. Dissection of this massif by an inter- mittent drainage has produced an area which is physio- graphically (and biotically) similar to that of the Texas Hill Country. Specimens of Euglandina singleyana have been found at several locations on these slopes as well as at the top of the massif. Exceptionally dense populations have been located at the base of the sandstone ledges where sufficient soil has developed on the underlying clay/shale layer. Accumulations of 25 dead shells in a linear area of about 4 m’ have been found in particularly favorable areas. Origin of this outlier population is assumed to involve downstream rafting (for a distance of 100km) from the Hill Country, similar to the probable origin of a disjunct population of the Texas alligator lizard (Gerrhonotus lio- cephalis infernalis), which is also present at this site (NECK et al., 1979). Time of colonization is purely conjectural. Although no living snails were found during a survey of this site during late summer 1978, a number of fresh shells were found with full periostracum. Human impact may have been a recent detrimental factor acting upon this population. No confirmed records of Euglandina singleyana have been reported north of the Colorado River. CHEATUM & Burt (1934) reported a single dead shell in drift along White Rock Creek in Datlas; this specimen is apparently lost, and personal investigations at this site revealed no Euglandina. A series reportedly collected from Lake Dallas, Denton County, has not been verified by contem- porary field investigators (FULLINGTON & PraTT, 1974). Recently, a small relict population has been located in a side canyon of Bear Creek within Fort Hood, Bell County. A viable egg was discovered on 6 June 1976 and a living adult was located on 30 April 1978. Both individuals were in a deep soil/leaf litter accumulation behind a boulder forming a particularly mesic microhabitat. Upper canyons of this creek are refugia for a number of organisms which require more mesic microhabitats than are generally avail- able in central Texas. Such organisms include bigtooth maple (Acer grandidentatum), small-mouthed salamander (Ambystoma texanum), and several terrestrial gastropods (unpublished records). The origin of the Owl Creek population differs substan- tially from the La Grange Bluff population. Ancestral Euglandina singleyana must have migrated overland to this area. Even if snails arrived by riparian corridors, there would have been some overland travel between river basins. Bear Creek is part of the Brazos River drainage; no previous records are known for the Brazos River drain- age. Time of this northward movement by E. singleyana was during an unknown period of the Pleistocene that was more mesic and possibly, though not necessarily, warmer than the present. At some subsequent time the northern part of the range of E. singleyana became unsatisfactory for survival; at least one relict population has survived in a localized favorable area, however. Literature Cited CuHeatum, E. P « C. E. Burt 1933. An annotated list of the snails of Dallas County, Texas. Field & Lab. 2: 1-8 Fu.uineton, R. W. & W. L. Pratt, Jr. 1974. The aquatic and land Mollusca of Texas. Part 3: The Helicini- dae, Carychiidae, Achatinidae, Bradybaenidae, Bulimulidae, Cionel- lidae, Haplotrematidae, Helicidae, Oreohelicidae, Spiraxidae, Strept- axidae, Strobilopsidae, Thysanophoridae, Valloniidae (Gastropoda) in Texas. Dallas Mus. Nat. Hist. Bull. 1 (3): 48 pp.; illust. Neck, Raymonp W, D. H. Risxinp « K. PETERSON 1979. Geographical distribution. Gerrhonotus liocephalus infernalis. Herp. Rev. 10: 118 Wolks23' No: 2 THE VELIGER Page 113 Heat Tolerance in the Black Abalone, Haliotis cracherodii Leach, 1814: Effects of Temperature Fluctuation and Acclimation ANSON HINES "?, SUSAN ANDERSON? anp MICHAEL BRISBIN 3 (3 Text figures) INTRODUCTION THE CORRELATION of higher thermal tolerance with higher vertical distribution of intertidal mollusks is well known (e. g.. Davies, 1970; FRAENKEL, 1968; SANDISON, 1968; Wotcort, 1973; and many others). However, examinations of temperature as a limiting environmental factor should consider the effects of the acclimation temperature and of temperature fluctuations during the tidal cycle on the ther- mal tolerance of an intertidal organism. The black abalone, Haliotis cracherodii Leach, 1814, is common in the inter- tidal zone of California at levels of 0.3 to 1.0 meters above mean lower low water, but its thermal tolerance has not been reported previously. Although the effects of tempera- ture on the larval development rate of several other species of abalone from California have been studied (LeicHTon, 1972; 1974), the thermal tolerance of adults of only red abalone, Haliotis rufescens Swainson, 1822, has been inves- tigated (EBERT, 1974). The present study provides com- parative information on the heat tolerance of adult black abalone, which were tested for 96 hours to determine the temperature at which 50 percent of the sample survived, 1. e., the median effective temperature (ETs0). The ability of the abalone to hold onto a substrate was used as the criterion for irreversible thermal damage in these experiments, because it is difficult to assess physio- logical death in this animal. Animals acclimated to both 11°C and 16°C were tested to provide information on ' TERA Corporation, 2150 Shattuck Avenue, Berkeley, Califor- nia 94704 2 Corresponding address: Chesapeake Bay Center for Environ- mental Studies, Smithsonian Institution, PR O. Box 28, Edge- water, Maryland 21037 3 Lockheed Center for Marine Research, 6350 Yarrow Drive, Suite A, Carlsbad, California 92008 seasonal changes in thermal tolerance of Haliotis crache- rodiu. Abalone in the experiments were either continuously submerged in heated water or periodically exposed to cooler air. Measurements of mortality rates at constant test temperatures provided standardized comparisons of ther- mal tolerance of the abalone, but this provided rather un- realistic experimental conditions. In the field, the tidal cycle would impose fluctuating temperatures, with stressful periods lasting about 6-12 hours. Therefore, the response of abalone exposed to repeated, short intervals of thermal stress was compared to their response to long, constant stress. Although intertidal organisms in central California are usually exposed to fluctuations of warm air and cool seawater, the experimental design of using heated test water and cooler air helped eliminate the variable of desic- cation during heat stress. Because the fluctuating thermal regimes produced much lower “heat doses” than the con- stant conditions, and because black abalone were not ex- pected to have evolved physiological mechanisms for tol- erating continuous stress for as long as 96 hours, we pre- dicted that abalone in fluctuating regimes would have bet- ter survivorship than those in constant conditions. Al- though the present report confirms this prediction, we found that the response to heat stress in black abalone was extremely abrupt once lethal temperatures were reached, and that exposure to a fluctuating regime produced only a small increase in the ET» value. MATERIALS anp METHODS This study was conducted at the Pacific Gas and Electric Company Thermal Effects Laboratory at the Diablo Can- yon Nuclear Power Plant on the central California coast of San Luis Obispo County. Large (10-15 cm shell length) Page 114 THE VELIGER black abalone collected in the Diablo Canyon area were acclimated to either 11.5 or 16° C in the laboratory for at least one week prior to the start of the experiment. During the experiment, abalone from each of the two acclimation regimes were maintained either continuously submerged or held in a cycle of six hours submergence alternating with six hours exposure to air in laboratory tanks, which were equipped with a machine that automatically raised and lowered their water level. Thus, there were 4 experi- mental groups: 11° C acclimated tidal and non-tidal aba- lone, and 16° C acclimated tidal and non-tidal abalone. There were 2 phases to the experiment. The first phase during June, 1978, measured the thermal tolerance of 16° C acclimated non-tidal abalone moving freely on the bottom of the tanks. The second phase during August, 1978, measured the thermal tolerance of 16°C tidal, 11°C tidal, and 11°C non-tidal abalone held in trays, which positioned the animals at a constant level in the simulated tidal cycle. A supplemental experiment was run to determine the core body temperature of 13-14cm long abalone during exposure to air following heat stress. Following immersion in seawater at 25° C for 2 hours, the seawater was drained and the abalone were exposed to air at 19-20°C for 6 hours. At successive intervals during this period, the core body temperatures of two abalone were measured by re- moving them from the substrate and quickly inserting a thermistor probe through the foot into the center of a body mass. The temperature of each abalone was meas- ured only once, and the animals were discarded. During exposure to air, the abalone cooled rapidly, and within 2 hours their core body temperatures equaled the air tem- perature + 0.2°C. Core body temperatures remained within + 0.3° C of the air temperature for the rest of the 6-hour period. In the main experiments, non-tidal test abalone were held for 96 hours at test seawater temperatures ranging from 24.7 to 29.4° C. Seawater temperatures were raised from the acclimation temperatures to the test tempera- tures within one hour. Control groups of animals were observed at 11.5 and 16° C, respectively. Air temperatures encountered by abalone during tidal exposure to air aver- aged 14.8°C over 11.5°C water, 17.5°C over 16°C water, and 21.2 to 21.9°C over the test water of 26.5 to 28.5° C. Within any one test group, the air temperature varied up to + 1.2° C, but water temperatures varied only =O" 2 Throughout the 96 hour tests, each abalone was ob- served and gently prodded at 6-hour intervals to determine its ability to hold to a surface. Following the methods of EBeErtT (1974), loss of the ability of an abalone to hold to Vol. 23; No. 2 a surface constituted “ecological death” during the exper- iment. Abalone which lost the ability to hold in tests dur- ing the second phase of the experiment were returned to 16° C to check for recovery. At each observation period, systematic notes were made of the abalone’s behavior, checking for such things as shell orientation, tentacular response, spawning, body turgor, and unusual behavior. Usually 10, and in a few cases 20, abalone were tested in each group. A total of 418 abalone, including control groups, were used in this experiment. Probit analysis of the mortality data was used in accordance with Standard Methods (1976). Other statistical treatments are ex- plained in the Results. RESULTS The time courses of mortality for all the test temperatures during the second phase and for some of the test tempera- tures during the first phase of the experiment are shown in Figure 1. The response to elevated temperatures is ex- 10 8 6 28.4°C : Sg 2 Ta.) ,\ i ae 27.6 27-4 Cumulative mortality (number of abalone) ¢ 24 Ade AS eal 72 96 - Time of test conditions (hours) Vol. 23; No. 2 THE VELIGER mortality Percent Page! 115 26.0 27.0 28.0 Temperature (°C) Figure 2 Representative probability plots of the mortality of black abalone from the four experimental groups at 24 and 66 hours into the 96 hour test period. Note that mortality is plotted on a probability scale. Test conditions which resulted in either no or 100% mortality are in- dicated by arrows. Probit regression lines were fitted by eye and tremely abrupt in that, when lethal temperatures are reached, the temperature range from no mortality to 100% mortality is only about 1.0°C for any one experi- (< on facing page) Figure 1 The time course of mortality of Haliotis cracherodi from the four experimental groups at five test temperatures. Only some of the data for the 16° C acclimated, non-tidal group, which was run as a separate experiment, are included for the most comparable temper- atures. CQ) = 11° C acclimated non-tidal group; @ = 11°C ac- climated tidal group; A = 16°C acclimated non-tidal group; A = 16°C acclimated tidal group ignore the spurious result from the 16°C acclimated tidal group tested at 27.0°C (circled). © = 11°C acclimated non-tidal group; @ = 11° C acclimated tidal group; A. = 16° C acclimated non-tidal group; A = 16° C acclimated tidal group mental group. As might be expected, the precise tempera- ture at which a given response occurred depended upon the experimental group, but based on the results of this experiment, it is predicted that no mortality would occur at or below 25°C and 100% mortality would occur at or above 28.0° C for all experimental groups. The mortality data for each six hour observation period were plotted on a probability scale versus temperature (see Figure 2 for examples from the 24 and 66 hour observations). These plots show good co-linearity of points necessary for probit analysis. The only exception to co- linearity occurred in the 16° C acclimated tidal group at 27° C, which experienced high mortality relative to ani- mals of the same group at other temperatures. Careful observation of the animals at 27°C did not reveal any Page 116 abnormalities. All of the animals at 27° C were males (by chance), however, the mortality rates of males was not significantly different from that of females (y2= 1.1493 for the first phase, and x2 = 0.4736 for the second phase, 1 d.f., p>o.10). Thus, the anomalous response of the 27° C animals remains unexplained, and these data were omitted from the probit analysis below. Probit regression lines were fitted by eye to determine the temperature which would result in 50% mortality for each of the 4 experimental conditions at each 6-hour period. For ex- ample, at 24 hours the non-tidal group acclimated to 11°C had a 50% mortality rate at 27° C (see Figure 2). The temperatures at 50% mortality derived from the probability plots were used to generate the curves of time to 50% mortality versus temperature shown in Figure 3. As determined by the temperature producing an effect in Time to 50% mortality (hours) 26.0 27.0 28.0 29.0 30.0 31.0 Temperature (°C) Figure 3 Temperature tolerance of Haliotis cracherodit from the four experi- mental groups. The ET,, temperatures at each 6 hour observation were determined from the probability plots, as shown in Figure 2. The 16° C acclimated non-tidal group was tested first and the other 3, groups were tested together at a later date. Note that time to 50% mortality is plotted on a log scale. Q = 11°C acclimated non- tidal group; @ = 11°C acclimated tidal group; A = 16°C acclimated non-tidal group; A = 16° C acclimated tidal group THE VELIGER Vol. 23; No. 2 50% of the sample (ETs0), the 11° C acclimated non-tidal group had the lowest thermal tolerance (96 hour ETs0= 26.1° C), followed by the 11° C tidal group (96 hour ETso = 26.6° C), and by the 16° C tidal group (96 hour ETs0 = 27.2° C). The 16° C acclimated non-tidal group was tested in a separate experiment under slightly different conditions earlier in the summer. This group had the highest 96 hour ETso (27.4° C); however, it had a thermal tolerance inter- mediate between the 11° C acclimated tidal and the 16° C acclimated tidal groups for the test period from 6 to 65 hours. Mortality between the 11° C acclimated tidal, the 11°C acclimated non-tidal, and the 16°C acclimated tidal groups was significantly different (x2 = 7.789, 2 d.f.; p0 point has high adaptive value. SUMMARY 1. The thermal tolerance of adult Haliotis cracherodu acclimated to 11.5°C and 16°C was determined for animals exposed to constant temperatures during con- Page 118 THE VELIGER Vol. 23; No. 2 tinuous submergence and to fluctuating temperatures during a simulated tidal cycle. Loss of the ability of an abalone to hold a surface constituted “ecological death.” 2. The response to elevated temperature was extremely abrupt in that, when lethal temperatures are reached, the temperature range from no mortality to 100% mor- tality was only about 1.0° C for any one experimental group. 3. As determined by probit analysis, the 96 hour ETso value of the 11°C acclimated/non-tidal group was 26.1° C, that of the 11° C acclimated/tidal group was 26.6° C, and that of the 16° C acclimated/tidal group was 27.2° C. The 16° C acclimated/non tidal group in separate tests had a 96 hour ET,, value of 27.4° C, but it had a thermal tolerance intermediate between the 11° C/tidal and the 16° C/tidal groups for the test period from 9 to 65 hours. 4. The revival of abalone returned to 16° C after failing to hold during part of the experiment was only 15.8%. 5. Sperm spawned during the tests were motile below 27° C, but non-motile above 27° C. 6. The behavioral response of Haliotis cracherodi to heat stress was described. ACKNOWLEDGMENTS This work was supported by the Pacific Gas and Electric Company, and we thank the Department of Engineering Research for help. Karl F. Ehrlich and David L. Mayer gave technical advice during the study, and Phillip A. Lebednik provided critical comments on the manuscript. Kristi Elliott, Vicki Frey, Larry Gomes, Gary McComber, Jerry Muszynski, Roger Phillips, Tony Rincon, and Fred Steinert assisted in the experiments. Literature Cited Davies, PETER SPENCER 1970. Physiological ecology of Patella. IV. Environmental and limpet body temperatures. Journ. Mar. Biol. Assoc. U. K. 50: 1069 - 1077 EsertT, Earv E. 1974. Red abalone temperature tolerance study. In: Calif. Dept. Fish Game, Diablo Canyon Power Plant Site Ecological Study Annual Re- port, July 1973-June, 1974. Mar. Resources Administr. Rprt. No. 74-10: 75 - 87 FRAENKEEL, G. 1968. The heat resistance of intertidal snails at Bimini, Bahamas, Ocean Springs, Miss., and Woods Hole, Mass. Physiol. Zool. 41: 1-13 LzicHTon, Davp L. 1972. Laboratory observations on the early growth of the abalone, Haliotts sorenseni, and the effect of temperature on development and settling success. Fish. Bull. 70: 373 - 381 1974. The influences of temperature on larval and juvenile growth in three species of Southern California abalones. Fish. Bull. 72: 1137 - 1145 Sanpison, Eyvor E. 1968. Respiratory response to temperature and temperature tolerance of some intertidal gastropods. Journ. Exp. Mar. Biol. Ecol. 1: 271-281 STANDARD METHODS FOR THE EXAMINATION OF WATER AND WASTEWATER 1976. Analyzing results of quantal bioassays. In: Fourteenth Edi- tion, Amer. Health Assoc., Washington, D. C., pp. 733 - 743 Wotcott, THomas G. 1973- Physiological ecology and intertidal zonation in limpets (Ac- maea): a critical look at “limiting factors.” Biol. Bull. 145: 389 - 422 Vol. 23; No. 2 THE VELIGER Page 119 Food Sources and Feeding Behavior of Nautilus macromphalus BY PETER WARD Department of Geology, University of California, Davis, California 95616 AND MARY K. WICKSTEN Allan Hancock Foundation, University of Southern California, Los Angeles, California 90007 (1 Plate; 2 Text figures) INTRODUCTION LITTLE IS KNOWN about food sources of Nautilus, the last externally-shelled chambered cephalopod. Crustacean carapace material has been reported from dissected Nautilus from a variety of locales (OweEN, 1832; WILLEY, 1902; HAVEN, 1972), but no specific identifications have been made, nor have any observations been made which could confirm or deny reports that Nautilus are largely scavengers (STENZEL, 1964). An understanding of food and feeding habits in Nautilus is important for two rea- sons. First, beaks of recent Nautilus show similar mor- phology to those of many fossil cephalopods and have been used to analogize feeding modes and food sources in both nautilids and ammonoids (LEHMAN, 1971; SaunpbeErS et al., 1978). Secondly, there is indirect evi- dence that Nautilus are extremely numerous on fore reef slopes at a variety of Western Pacific locales and hence may be important constituents of the benthic communi- ties. The Philippine Islands alone export over twenty thousand shells to the United States each year, which are mostly live-caught (D. Dugdale, pers. com.) while studies in New Caledonia (Warp & MartIN, 1978), Fiji (WARD et al., 1977) and Palau (SAUNDERS & SPINOSA, 1978) suggest that populations are large in 100-600 m depths. The restriction of Nautilus to deep water habitats over most of its range requires the use of baited traps to acquire specimens for study. This methodology virtually eliminates reliable sampling of prey sources based on dissection of the alimentary canal and identification of the contents, since a variety of small fish and crustaceans are almost invari- ably present within the trap containing the Nautilus. It thus becomes impossible to know whether food material dissected from the gut represents natural prey captured before the Nautilus entered the trap, or was captured opportunistically by the Nautilus while within the restric- tive confines of the trap. During the last several years one of us (Ward) has had the opportunity to study one species of Nautilus which can be found in water shallow enough to permit hand-capture at night through the use of SCUBA equipment. Specimens of Nautilus macromphalus Sowerby, 1849 have long been known to migrate into relatively shallow waters at night on the seaward sides of barrier or fringing reefs sur- rounding New Caledonia and the Loyalty Islands (Wit- LEY, 1902), thus representing one of the few locales within the geographic range of Nautilus where animals can be captured without the necessity of deep trapping (Warp, 1979). Nine N. macromphalus have been captured over three years time from both New Caledonia and Lifou (one of the Loyalty Islands), thereby providing an opportunity for the study of gut contents of naturally captured animals, rather than those from traps. The purpose of this paper is to report these findings, along with observations on feeding behavior, and alimentary canal acidities. MATERIALS anp METHODS The habitat of N. macromphalus in New Caledonia has been discussed by Warp & Martin (1978), Warp (1979) and Warp & MartTIN (1979). All Nautilus were captured by SCUBA divers in depths varying between 10 and 30 m. Alimentary canal contents were dissected from crop, Page 120 THE VELIGER Vol. 23; No. 2 — buccal capsule intestine —— pH 5.5 -6.8 crop pH 5.8-6.0 Ce at ——-—. stomach pH 4.8-5,.5 7 PH 4.7-5.4 Figure 1 Digestive tract of Nautilus macromphalus removed from body. Digestive gland (mid-gut gland) has been removed for clarity. Average pH of each organ listed below organ stomach, and intestine (Figure 1) of the Nautilus after capture, dried, and weighed with a balance. The dried material was sent to the Allan Hancock Foundation, Uni- versity of Southern California for identification. Acidities within the alimentary canal were made on freshly cap- tured Nautilus with a pH meter. Observations on feeding behavior were made in the natural environment and in the Aquarium of Noumea, Noumea, New Caledonia. RESULTS ALIMENTARY CANAL CoNTENTS The weight, identification, and number of individual prey from the nine captured Nautilus macromphalus are listed in Table 1. Twenty-three separate prey identifica- tions have been made from the nine Nautilus. Of these, 15 are hermit crabs. These hermit crabs may have been of substantial size (about 10cm). The second most important ~ prey source is brachyuran crabs, all of small size. Fresh crustacean exuviae may also be a food source for Nautilus macromphalus. On 3 separate occasions Nautilus have been observed in the natural habitat ingesting por- tions of newly molted lobster exuviae. One of these was swimming several meters above a 10m deep bottom, carry- Food material identification Aniculus aniculus sp. (1 specimen) unidentifiable Diogenidae fragment Diogenidae (1 specimen), Aniculus aniculus (3 specimens total) bony fish fragments, lobster fragments (Palinuridae, Panulirus?) lobster fragments (Palinuridae) (same specimen as above) Aniculus aniculus (1 specimen), Majidae (1 specimen) Diogenidae (1 specimen) Diogenidae (same specimen as above) Aniculus aniculus (1 specimen) brachyuran, unident. (1 specimen) brachyuran, unident. (same specimen as crop) Aniculus aniculus (2 specimens) Diogenidae (1 specimen) Aniculus aniculus (2 specimens) Aniculus aniculus (1 specimen), Brachyuran, unident. (1 specimen) Ranindae, Aniculus aniculus (one specimen each) Diogenidae: Aniculus aniculus Diogenidae: Aniculus aniculus (same specimen as above) Galatheidae (one specimen) (same specimen as above) Table 1 Specimen Organ Dry Wt. (grams) 4(1) crop 2.5114 stomach 0.1187 unidentifiable intestine 2.829 unidentifiable 2. crop 0.005 stomach 0.852 intestine 1.171 Aniculus aniculus 3. crop 1.149 stomach 0.694 intestine 2.565 4, crop 2.254 stomach 0.764 intestine 1.4792 By, crop 0.345 stomach 1.783 intestine 2.840 6. crop 0.3345 stomach 1.248 intestine : 3.260 We crop 0.009 unidentifiable stomach 0.263 intestine no measurement 8. crop 0 stomach 0.075 intestine 1.047 9. crop 0.2074 stomach 0.1241 intestine 0.352 unidentifiable Mean Weight Crop 0.757 Stamach (1) 658 Vol. 23; No. 2 THE VELIGER Page 121 ing the molt of a large spiny lobster (Panulirus longipes Milne-Edwards) (Warp & Martin, 1978). Two others have been observed on the bottom eating molts (MaGnieR & LapouTeE, 1978). The Nautilus actually ingest portions of these molts since one specimen was dissected (Number 3, Table 1), and had fragments of the molt in the crop and stomach. Additionally, molts of various crustaceans were placed in aquaria with freshly captured Nautilus. In every case the carapace was seized, and the legs and tail portions eaten. In one case (Figures 2 to 7) a large molt of Panulirus longipes was offered in the aquarium to a N. macrom- phalus. Over a two-hour period the telson, uropods, abdo- men, several of the walking legs, and all of the swimmerets were consumed. In most of the dissected Nautilus larger volumes of crustacean material were present in the intestine than in the crop and stomach, indicating that feeding may have commenced only soon before capture. It seems possible that the large volume of intestinal material represents the previous night’s feeding. Carapace material is size-sorted within the intestine, but even the largest intestinal frag- ments are smaller than those from within the crop, suggest- ing that significant amounts of hard-part fragmentation occurs after ingestion, probably in the cuticle-lined stomach. ALIMENTARY CANAL ACIDITIES The anatomy of the Nautilus alimentary canal has been described in detail by GrirFIn (1900), and will be only summarized here. The main organs are the buccal capsule, composed of the jaws, radula, and salivary glands; the highly distensible esophagus or crop; the muscular stom- ach; the caecum; the five-lobed hepatopancreas (now mid- gut gland [BrppER, 1976]); and the intestine. The anus empties into the mantle cavity. The presence of jaws with heavily calcified cutting-edges (recently discussed in detail by SAUNDERS et al., 1977) is a unique feature among the living cephalopoda. The acidities of the alimentary canal of Nautilus mac- romphalus and N. pompilius are listed and compared with values of several other cephalopods (Table 2). Acidity ap- pears to increase slightly from crop to stomach, decrease slightly in the caecum, and drop markedly from proximal to distal (anus) ends of the intestine. All measurements were made on Nautilus which had eaten within 24 hours of the time of measurement. BippErR (1966) has postulated that the crop in Nautilus is for storage only, and plays no part in active digestion. The observations here of acidic fluids within crop contents may indicate that the initial breakdown of food occurs within the crop. In several specimens of both Nautilus macromphalus from New Caledonia and N. pompilius LINNAEUS, 1758 from the Fiji Islands dissection of the caecum has revealed the presence of crustacean carapace particles within the folds of the caecum wall. These particles are always worn and etched compared to other material passing through the alimentary canal, suggesting that they may have been trapped within the caecum for extended periods and thus allowing acid dissolution. The presence of this material is in contrast to other cephalopods, which allow no large hard part or large particulate material to enter the caecum (Brpper, 1976). Table 2 pH Values of Nautilus Intestine Specimen Crop Stomach Caecum Proximal M dial Distal Nautilus macromphalus NC75-21 6.0 eo) 5.4 5.5 — — NC75-22 5.8 4.7 4.8 — — 6.8 Nautilus pompilius F76-19 5.9 5.4 5.5 — 5.8 — F76-21 9 5.1 5.3 — 6.0 — Octopus vulgaris 9.3) = as} — — — — = Loligo forbesi 5.6 - 5.8 6.2 — — — = Sepia officinalis — 5,2 - 5.8 — — = Page 122 FEEDING BEHAVIOR Nautilus appear to locate food through a combination of smell and touch (WELLS, 1966b). After moving to the general location of food, presumably moving toward in- creasing concentrations of attractant in the water, the Nautilus must search the bottom until contact with the food is made by the tentacles. This searching behavior, with tentacles in a “‘cone of search” orientation, was first described by Bipper (1961). In New Caledonia, we maintained Nautilus macrom- phalus in aquaria and fed them nightly as described by Martin et al., 1978. Fresh fish and crustacean meat would be taken immediately; rancid meat, however, and meat which had been left uneaten in the aquarium for more than 12 hours was not accepted as food. Meat which was unfamiliar to the Nautilus, such as chicken or red meat, would cause a hesitation of several seconds between first contact with the tentacles and acceptance. Perhaps the most striking aspect of feeding behavior was the rapid flight which would ensue immediately after ac- ceptance or capture of food. While grasping and moving newly acquired food toward the buccal capsule, the Nautilus would begin swimming rapidly above the tank bottom. This behavior would occur whether other Nautilus were present in the aquarium or not. Such behavior may be an escape response, for in crowded tanks fighting by two animals for a single piece of food was common. WILLEY (1902) postulated that in nature the Nautilus are gregar- ious, travelling in schools above the bottom in search of food. This interesting hypothesis may be supported by our observations, for one might expect some behavioral mech- anism to reduce intra-group competition or robbery be- tween large and small Nautilus were they to normally travel in groups. THE VELIGER Vol. 23; No. 2 DISCUSSION Our observations on alimentary canal contents from NautNus macromphalus suggest that hermit crabs, partic- ularly Aniculus aniculus, are favored prey. It is not known if these crabs are actively sought out, or simply represent the most common species encountered by opportunistically foraging Nautilus. Also, it is not known if live hermit crabs were killed, or if the hermit crab exoskeletons in the Nautilus alimentary canal represented molts found and in- gested by the Nautilus. In habit and food sources Nautilus is similar to the octo- pus, for both are nocturnal feeders, preying on bottom dwelling crustaceans of considerable size. The octopus, however, has evolved a number of specializations for this diet which are absent in Nautilus. Octopus kills its prey with a toxin and the prey is dismembered and partially digested while still in the arms of the predator. A protease separates the crustacean meat from the carapace, and the hard parts are discarded. The result is that few hard parts enter the octopus digestive system. Nautilus, on the other hand, must kill its struggling prey with the beak, and in- gests hard parts as well as flesh. The ingestion of crusta- cean molts by N. macromphalus in New Caledonia, pre- sumably for the nutritional value of the internal, non- cutaneous lining of the molt, furtier underscores the fact that the Nautilus digestive system seems to be adapted to passing large volumes of crustacean carapace through the system without ill effect. A by-product of this type of diet in Nautilus may be the production of renal uroliths, recently shown to be com- posed of phosphatic hydrogel (McCoNnNELL & WaRD, 1978). Calcium phosphate uroliths are not uncommon among invertebrates, but have only been reported from Nautilus Explanation of Figures 2 to 7 Figures 2, 3: Photographs of Nautilus macromphalus observed in 10m of depth off the barrier reef of New Caledonia, October 20, 1979, approximately 8:00 PM. Nautilus was carrying freshly molted exoskeleton of lobster Panulirus longipes Milne-Edwards first observed. Similar natural observations of N. macromphalus with lobster molts were made in 1977 and 1978 Figures 4 to 7: Freshly captured Nautilus macromphalus offered molt of Panulirus sp. in aquarium, 1977. Telson, swimmerets, several legs and most of abdomen were consumed over a 2-hour period in daylight THE VELIGER, Vol. 23, No. 2 [Warp « WIcKSTEN] Figures 2 to 7 Vol. 23; No. 2 THE VELIGER Page 123 and Sepia among the cephalopods. Martin (1975) has proposed that these concrements are not an excretory product, but rather represent a storage product for cal- cium. Nautilus sequentially secretes calcareous partitions during chamber formation, and it is probable that these partitions are calcified quite quickly, for only after calci- fication has occurred can removal of the cameral liquid filling the chamber be accomplished. Martin suggested that the concrements serve as a calcium storage that is mobilized to the secretory mantle when chamber formation occurs. To test this idea we dissected a number of Nautilus and removed the concrements. The weight of concrements for specimens of N. pompilius from the Fiji Islands and N. macromphalus from New Caledonia were then ascer- tained by drying and weighing. If concrements were being used as a storage product for calcium, and then mobilized for septal secretion, there should be some relationship be- tween cameral liquid volume in the most recently formed chamber (which has its highest value immediately after secretion of the new chamber, and then diminishes as the © Nautilus macromphalus © Nautilus pompilius chamber volume (mL ) Co) 0.5 1.0 1.5 2.0 concrement weight (grams) Figure 8 Concrement (renal urolith) weight as a function of cameral liquid volume in two species of Nautilus, Nautilus macromphalus and Nautilus pompilius from the Fiji Islands. The plot suggests that little or no relationship exists. An alternate hypothesis is that the concrements represent a waste product of the crustacean exoskeleton intake of the diet, rather than a storage source of calcium as pro- posed by Martin (1975). chamber is emptied through the siphuncle), and the weight or mass of concrements. Presumably, Nautilus with newly formed chambers (high cameral liquid volumes) should show low, or non-existent concrement masses. The observed relationship (Figure 8) shows no observable pat- tern for specimens of either N. macromphalus or N. pom- pilius. The alternate hypothesis is that the concrements represent an excretory product which may be related to the very high intake of calcium and phosphorus of the crustacean diet. Table 3 Summary of Prey No. of Individuals Brachyuran Crabs 4 a. Majidae (1) b. Family unidentified (3) Hermit crabs (Diogenidae) 15 Sand crabs (Raninidae) 1 Galatheids (Galatheidae) 1 Lobsters (Palinuridae) 1 Fish remains 1 Total identified prey 23 Literature Cited Brwper, ANNE M. 1962. Use of the tentacles, swimming and buoyancy control in the pearly Nautilus. Nature 196: 451 - 454 1966. Feeding and digestion in cephalopods. Jn: K. Wilbur & C. M. Yonge (eds.), Physiology of the Mollusca 2: 97 - 124 1976. New names for old: the cephalopod “‘mid-gut gland.” Zool. 180: 441 - 443 GRIFFIN, L. E. 1900. The anatomy of Nautilius pompiltus. Mem. 8: 103 - 197 Haven, Norinez 1972. The ecology and behavior of Nautilus pompilius in the Philip- Journ. Nat. Acad. Sci. Biog. pines. The Veliger 15 (2): 75-80; 2 plts.; 2 text figs. (1 Oct. ’72) LEHMANN, ULRICH 1971. New aspects of ammonite biology. Proc. Natl. Amer. Pale- ontol. Convent: 1251 - 1269 Maonier,Y. & P Lasoute 1978. Guides sous-marin de Nouvelle Calédonie. Pacif.:: 160 pp. Martin, ARTHUR WESLEY 1975. Physiology of the excretory organs of cephalopods. Fort- schritte der Zoologie 23: 112-123 Martin, ARTHUR Wes ey, I. Catara-Stucki & Peter D. Warp 1978. The growth rate and reproductive behavior of Nautilus macrom- phalus. Neues Jahrb. Geol. Palaont. Abh. 156 (2): 207-225 McConne tt, D. & Peter D. Warp 1978. Nautiloid uroliths composed of phosphatic hydrogel. Science 199: 208 - 209 OweEN, RICHARD 1832. Memoir on the pearly Nautilus with illustrations of its external form and internal structure. 68 pp.; 8 plts. (London) Les édit. du Page 124 THE VELIGER Vol. 23; No. 2 SaunbeErRsS, W. B. & CLaupDE SPINOSA 1978. Sexual dimorphism in Nautilus from Palau. Paleobiol. 4 (3): 349-358 Saunpers, W. B., CLaupe Spinosa, C. TricHert & R. C. Banks 1978. The jaw apparatus of Recent Nautilus and its paleontologic implications. Palaeontol. 21: 99-111 Warp, PETER D. 1979. Cameral liquid in Nautilus and ammonites. Paleobiol. 5 (1): 40-49 Warp, Peter D. & ARTHUR WESLEY MARTIN 1978. On the buoyancy of the pearly Nautilus. Journ. Exper. Zool. 205: (1): 5-12 1980. Depth distribution of Nautilus pomptlius in Fiji and Nauttlus macromphalus in New Caledonia. The Veliger 22 (3): 259 - 264; 1 plt.; 6 text figs. (1 January 1980) Warp, P, R. Stone, G. WESTERMANN & A. MARTIN 1077. Notes on animal weight, cameral fluids, swimming speed, and color polymorphism of the cephalopod Nautilus pompilius in the Fiji Islands. Paleobiol. 3: 377 - 388 We ts, Mary JANE 1966. Cephalopod sense organs. In: K. M. Wilbur & C. M. Yonge (eds.) Physiology of the Mollusca 2: 523 - 545 WILLeY, ARTHUR 1902. Contribution to the natural history of the pearly Nautilus. Zoo- logical results based on material from New Britain, New Guinea, Loyal- ty Islands. Part VI: 691 - 830; plts. 75-83; 15 text figs. Cambridge Univ. Press, London Vol. 23; No. 2 THE VELIGER Page 125 Crude Oil Effects on Mortality, Growth and Feeding of Young Oyster Drills, Urosalpinx cinerea (Say) STEVEN EF EDWARDS Cook College, Rutgers University, New Brunswick, New Jersey 08401 (address for reprints: Department of Resource Economics, University of Rhode Island, Kingston, RI 02881) (3 Text figures) INTRODUCTION RECENTLY, PRESSURES FOR OIL pollution research have come from continued accidents, growth of tanker traffic, increased off-shore drilling, and plans for special terminal facilities in estuaries. Additionally, sewage, storm sewer and industrial effluents, tanker-shoreline storage, and small craft operations constitute chronic sources of oil pollution to coastal estuarine regions (FARRINGTON & QUINN, 1973) which are particularly rich in marine life. The ability of sediments to store and slowly release petroleum hydro- carbons for several years (BLUMER & SASS, 1972; VANDER- MEULEN, 1977) plus the ability of filter feeding bivalves to concentrate hydrocarbons (BLUMER et al., 1970; Fon, 1976; STEGEMAN, 1977) pose special problems for benthic, carnivorous gastropods. This paper is concerned with the effects of Nigerian crude oil on the survival and on the growth and predation rates of the common oyster drill Urosalpinx cinerea (Say, 1822) under laboratory conditions. MATERIALS anp METHODS In all experiments Nigerian crude oil was absorbed onto kaolin clay particles at the ratio of 1 part oil to 9 parts clay by weight (10% oil-clay). The absorption technique is described by Noyes (1978) and proceeded by first dis- solving the crude oil in pentane followed by adding the appropriate amount of kaolin clay (90% of oil plus clay), shaking the mixture thoroughly, and evaporating the pen- tane at 45° C under a vacuum until the mixture was dry. The resultant oil-clay was mixed thoroughly, covered and refrigerated at 5° C. From this a stock solution of 100mg L* oil was prepared daily and diluted to provide the con- centration of oil desired. During the summer of 1975, egg cases of Urosalpinx cinerea were collected from the Delaware Bay tidal flats at the New Jersey Oyster Research Laboratory in Cape May and kept in the laboratory in running bay water until hatching. Groups of 10 snails were placed in 800mL beakers at selected treatment oil levels (0 to 1omg L” oil) in duplicates following procedures required for random- ization. In a preliminary study it was found that kaolin clay alone at 100mg L” (equal to the clay concentration in the highest concentration of oil-clay used in any experi- ment) did not inhibit growth of hatchling snails. There- fore, no clay-only controls were employed in the experi- ments presented here. Heights of hatchlings were meas- ured to the nearest 0.01 mm (tip of siphonal canal to the apex of the spire) with a calibrated stereomicroscope at the beginning of the experiment and then on days 4, 8, 12 and 15. Mortalities were recorded on these days also. The bay water and oil-clay treatments were replaced daily with minimal disturbance to the snails’ activity. Labora- tory cultured oyster spat (1-7 days old) were supplied (in excess) as food. In the fall of 1975 a similar experiment was conducted for 7 weeks with larger, juvenile snails dredged from the Delaware Bay. These were measured to the nearest 0.1 mm with a vernier caliper. In this experiment, the same pro- cedures were followed as with the hatchlings except that there were 11 drills per tooomL beaker, the oyster spat were older (about 3 months), and each beaker was gently aerated. Water and cotton traps were used to remove any volatilized oil in the air source. Treatments consisted of bay-water and clay-only controls and oil concentrations between 0.5 and 3mg L”. Oyster spat were supplied in excess at 7 day intervals. Heights were measured until week six. In order to gain insight as to why oil reduced the growth of hatchlings, the number of spat drilled and eaten was also counted for 7 weeks. Page 126 Analysis of variance (ANOVA), Student-Newman- Keuls (SNK), and simple linear regression (SLR) statis- tical procedures (Zar, 1974) along with procedures for combining probabilities (Soka & RoHLF, 1969) were used to analyze the data. RESULTS Growth of Hatchlings In calculating the mean heights of hatchlings at the end of the 3 growth experiments, duplicate data were com- bined due to the lack of significant differences between duplicates (Table 1). Mean initial heights ranged between 1.40mm at 1omg L” to 1.55mm at 0.5 and 2mg L’ oil. After 15 day chronic exposures the mean heights of hatch- lings were significantly less at 1mg L”™ oil and greater in experiments one and two and at 2mg L” oil and greater in experiment three. Two-way ANOVA (experiment x concentration) fol- lowed by SNK testing of duplicate data revealed that in- creases in mean heights were not significantly different among experiments at similar oil concentrations. These data were thus combined in Figure 1 to give the time series of mean heights. Growth rates diverged after 4 days of oil exposure with growth of snails at 0.5 mg L” oil and in the THE VELIGER Vol. 23; No. 2 3.00 () 0.5 2.50 F I z dap a A) 3 g 2.00 [jE ™ 5 a fo 5 r 10 mA 1.215 Co) 4 8 12 15 Time, days Figure 1 Urosalpinx cinerea Mean height of hatchlings at different oil concentrations after 15 days. Data were averaged between duplicates and among experi- ments (Table 1) for each concentration. The 95% CI are illus- trated for the control and for 1 mgL™ oil (the lowest concentra- tion of significant difference) on days 8 and 15. Concentration curves are indicated by numerical values in mg L“ Table 1 Urosalpinx cinerea. Heights of Delaware Bay hatchlings (x + SE; duplicate data combined) in 3 experiments after 15 day exposures to different oil concentrations. n: number of hatchlings; F: F-value from one-way ANOVA; P,: probability that the null hypothesis (Ho: all means are equal) for the F-test is true; P; : probability that the treatment means do not differ from the control mean according to SNK testing; ns: not significant (P > 0.20). Mean heights (mm) Oil level Experiment 1 Experiment 2 Experiment 3 (mg 1—!) n x SE Pi n x SE Py n x SE Py 0 20 2.93 £0.18 — 20 3.17 £0.14 - 20 2.78 £0.18 — 0.5 — — — - — — 20 2.76 £0.15 ns 1 20 2.90 + 0.13 <0.01 20 2.20 = 0.04 <0.01 20 2.61 £0.18 ns 2 — - - — — — 20 2.04 £ 0.09 <0.03 3 - - - 20 1.95 = 0.05 0.01 20 2.08 + 0.08 <0.03 5 20 1.71 £0.03 <0.01 20 2.02 = 0.06 <0.01 = = = 10 20 1.75 = 0.03 <0.01 — — — — _ — F 24.70 23.61 6.60 P2 <0.01 <0.01 <0.01 Vol. 23; No. 2 THE VELIGER Page 127 control proceeding at a near constant rate while the growth of snails at 1, 2 and 3mg L” oil declined. Growth of snails exposed to 5 and romg L” oil was negligible after 4 days. Mean growth of hatchlings in the control (0.1 mm day“) was significantly greater than hatchling growth at 1 mg L” (0.06 mm day”, P < 0.01) and greater (0.03 and 0.02mm day” at 2 and 1omgL”, respectively, P < 0.01), when height increases were averaged over the 15 day experimental period. Mortality of Hatchlings Mortalities increased as oil concentration increased in each experiment, being significant (P < 0.044) in exper- iment two(Table 2). After the probabilities from each experiment’s simple linear regression ANOVA were com- bined (SokaL & RouHLF, 1969), an overall significant (P < 0.05) effect between oil concentration and mortality was evident. Mean percent mortalities (X -+_ SE) among experiments increased from 38.3 = 6.0% in the control to 61.7 + 9.1%, 67.5 + 7.5% and 75 + 5% at 1, 3 and 1omg L” oil, respectively. Growth of Juveniles As for hatchlings, mean height data between dupli- cates were combined due to lack of significant differences. Initial mean heights ranged from 10.4mm at 2mg L” to 10.6mm in the bay-water control (Figure 2). Growth of juvenile snails in the bay-water control, the clay-only con- trol, and at 0.5mg L” oil proceeded at nearly constant and equal rates (0.5mm month”) during the 6 week expo- Table 2 Urosalpinx cinerea. Mortality figures of Delaware Bay hatchlings after 15 day exposures to different oil concentrations. Means between duplicates with the range in parenthesis are given. n: number of hatchlings; F: F-value from the simple linear regression ANOVA; P;: probability that the null hypothesis (Ho: slope = 0) for the SLR F-test is true; P,: combined probability (Sokal and Rohlf, 1969) that the null hypothesis is true. Number of deaths Oil level Experiment 1 Experiment 2 Experiment 3 (mg 1—!) n x x n x (range) (range) (range) 0 10 4 10 3 10 4.5 (3 - 5) (2 - 4) (3 - 6) 0.5 — =— - = 10 4.5 (3 - 6) 1 10 7 10 6 10 5.5 (6 - 8) (4-8) (3 - 8) 2 — — — — 10 6 (4- 8) 3 - — 10 6.5 10 7 (5 - 8) (6 - 8) 5 10 6.5 10 8 =r = (6 - 7) (8 , 8) 10 10 7.5 - - — - (7 - 8) F 3.21 6.73 2.07 P; <0.14 <0.04 <0.22 P, <0.042 Page 128 11.50 O without clay O with clay 5 O without cla’ «p> 11.00 Y\ eo} 59 C3) a r=] a o = 10.50 10.25 io) I 2 3 4 5 6 Time, weeks Figure 2 Urosalpinx cinerea Mean height of juvenile snails for combined duplicates at different oil concentrations after 6 weeks. The significant differences between the two controls and 2 and 3 mg L" oil after 6 weeks is indicated by 95% CI at the former (bay-water and clay-only controls’ mean heights were both equal to 11.3 mm) and at 3 mg L" oil. Concen- tration curves are indicated by numerical values. w/ = with w/o = without sure period. Growth of snails at 1 mg L” oil was also fairly constant (except week two) but averaged less (0.36mm month”). Mean growth of snails at 2 and 3mg L” oil was minimal (0.03 and 0.07mm month’, respectively) and significantly less (P < 0.01) than growth of snails in the controls. Feeding of Juveniles The cumulative number of oyster spat eaten per snail per week (mean values) at various oil concentrations are given in Figure 3. Mean spat consumption by snails in the bay-water control, the clay-only control and at 0.5 mg L” oil diverged from those of snails exposed to 1 mg L” oil and greater during the first week. The divergence continued at a slower rate during the following 3 to 4 weeks. After 4 weeks mean cumulative spat consumption at 1mg L” oil and greater was significantly (P < 0.01) less than the control values. After week 5 the snails exposed to the higher oil concentrations fed at the same rate as the control snails; however, the significant differences were maintained. THE VELIGER Vol. 23; No. 2 150 100 Mean cumulative number spat eaten on re) Time, weeks Figure 3 Urosalpinx cinerea Mean cumulative oyster spat consumption between duplicates. The significant differences between the bay-water control and 1mg L™ oil and greater are indicated by 95% CIs at the former and at 2mg L~ oil on weeks 4 and 7. Concentration curves are indicated by numerical values. w/ = with w/o = without Mortality of Juveniles There were no oil related mortalities during the 7 week exposure period. One snail died in the clay-only control and two snails died in each of the other treatments. DISCUSSION Moore & Dwyer (1974) reported in a literature review that soluble aromatic derivative levels between 1 to 100 mg L” are lethal to marine gastropods, and that chronic sublethal dosages up to 1 mg L” disrupt the physiological and behavioral activities of marine organisms including gastropods. In this study, chronic exposure of Urosalpinx cinerea hatchlings to 1mg L™ dosages of Nigerian crude oil and greater caused a significant reduction in the growth rates after 8 days (P < 0.05) when compared to control snails. Growth of the older juvenile snails was reduced sig- nificantly at 2mg L”™ oil and greater after 6 weeks (P < 0.05) and there were no oil related deaths. However, there were significant (P < 0.05) oil related mortalities for hatchlings. BYRNE & CALDER (1977) also report growth reduction and mortality for Mercenaria sp. larvae after 6 Vol. 23; No. 2 THE VELIGER Page 129 and 10 day exposures to various crude and refined oils. My results also corroborate other recent reports of oil-induced growth reduction and mortality (KREBS & BURNS, 1977; Noyes, 1978; VANDERMEULEN, 1977). Unfortunately, no feeding data were collected during the hatchling experiments; however, the feeding data from the juvenile snail growth experiment are of consid- erable interest. Reductions in feeding of marine organisms exposed to similar oil concentrations, as occurred during the first 5 weeks of my experiment, are commonly re- ported (ATEMA, 1977; EISLER, 1975; GILFILLAN, 1975; WELLS & SPRAGUE, 1976). Although the oyster spat were pumping (evident from pseudofeces), oil can interfere with chemotaxis (ATEMA, 1977; BoyLAN & TRIPP, 1971; Jacopson & BoyLan, 1972). However, snails at 1mg L” oil and greater fed at about the same rate as did snails in the controls after 5 weeks, although they did not grow nearly as much. This may be due to increased respiratory demands resulting from exposure to oil. GILFILLAN (1975) found that carbon assimilation into tissue decreased while respiration increased when the bivalves Mytilus edulis and Modiolus demissus were exposed to crude oil extracts and VANDERMEULEN (1977) reported similar results for indi- viduals of the bivalve Mya arenaria inhabiting the location of an oil spill. Exposure of the gastropod Littorina littorea to Bunker C crude oil increased its respiration rate (Har- GRAVE & NEWCOMBE, 1973). H. Haskin and G. Noyes (Noyes, 1978) prepared the 10% oil-clay (which was made available to me) for their extensive work on the effects of various petroleums on the survival, growth and behavior of the oyster Crassostrea virginica. They reasoned that organisms inhabiting turbid estuaries (which includes Urosalpinx cinerea) such as the Delaware would be exposed to oils absorbed onto fine par- ticles. Their belief has been supported by reports that oil will absorb onto clay and other suspended particles (e.g., detritus and plankton) in saline water (BassIN & IcHtvE, 1977; Lee et al., 1978; MEYERS & QUIAN, 1973) and by a report that most of the hydrocarbons found in the water column of the Delaware Bay are associated with particles (WHIPPLE & PaTTRIcK, 1977; cited by Noyes, 1978). Noyes (1978) reported that 10% oil-clay (Nigerian crude) caused significant increases in mortality and a reduction in feeding by adult oysters (C. virginica) after 5 to 10 week chronic exposures to 0.3 mg L” oil and greater. I know of only one other study using oil absorbed onto clay; Fossato & CONZONIER (1976) reported significantly increased mor- talities (15 to 70%) of the bivalve Mytilus edulis when exposed to 0.2 to 0.4mg L”™ diesel fuel absorbed onto kaolin clay particles. I did not analyze for actual aqueous concentrations of hydrocarbons or the chemical composition of the Nigerian crude oil. Noyes (1978) reported an approximate 60% recovery (range: 20 to 100%) of the adsorbed Nigerian crude after it was added to sea water. He suggested that the difference could be due to loss of volatile components as well as possible incomplete removal of hydrocarbons from kaolin using GRUENFELD’s (1973) analysis. An ex- trapolation of ANDERSON et al.’s (1974) data on the per- cent dissolution of 2 other crude oils (Kuwait and Louisi- ana crudes) suggest that if they were added to saline water at 1omg L” and less, nearly 100% would dissolve. Their data also show that the most toxic components of crude oils (the aromatics) would be enriched in solution relative to n-paraffins of similar molecular weight when compared to the parent crude. The above discussion lends insights into the probable behavior of the oil-clay in hatchling experiments which were not aerated. Concerning the experiment with juve- nile snails which included gentle aeration the oil concen- tration probably decreased over time. ANDERSON et al. (1974) reported 88% and 89% reductions in total hydro- carbons for oil-in-water dispersions of Kuwait and Louisi- ana crudes, respectively, after 24 hours aeration. Reduc- tions in total n-paraffins (95% and 97%) exceeded reduc- tions in total aromatics (52% and 69%) during this time. Bicrorp (1977) reported a 50% reduction in dissolved hydrocarbons after 24 hours with aeration. Although one must be cautious in translating the results of a laboratory study such as this to the estuary, it does indicate that behavioral and physiological mechanisms of the oyster drill may be significantly altered by chronic ex- posures to a crude oil adsorbed on clay. The chronic oil concentrations used in these experiments are realistic espe- cially when one considers spills and port areas and the tendency of sediments to store and release petroleum hy- drocarbons for several years (BLUMER & SASS, 1972; FAR- RINGTON, 1977; Kress & BuRNS, 1977; SANDERS, 1977; VANDERMEULEN, 1977). ACKNOWLEDGMENT I wish to thank Dr. H. H. Haskin and Dr. G. N. Noyes for the use of their facilities and for their guidance. Page 130 THE VELIGER Vol. 23; No. 2 Literature Cited ANDERSON, J. W,, J. M. Nerr, B. A. Cox, H. E. Tatem « G. M. Hichtower 1974. Characteristics of dispersions and water-soluble extracts of crude and refined oils and their toxicity to estuarine crustaceans and fish. Mar. Biol. 27: 75 - 88 ATEMA, JELLE 1977. The effects of oil on lobsters. Bassin, N. J. & T. Icutve 1977. Flocculation behavior of suspended sediments and oil emulsions. Journ. Sediment. Petrology 47 (2): 671-677 Bicrorp, T. E. Oceanus 20: 67-73 1977. Effects of oil on behavioral responses to light, pressure and gravity in larvae of the rock crab, Cancer irroratus. Mar. Biol. 43: 137-148 Biumer, Max & JEREMY Sass 1972. Oil pollution: persistence and degradation of spilled oil. Science 176: 1120-1122 Biumer, Max, M. G. Sousa & JeREMy Sass 1970. Hydrocarbon pollution of edible shellfish by an oil spill. Mar. Biol. 5: 195 - 202 Boytan, D. B. « B. W. Tripp 1971. Determinations of hydrocarbons in seawater extracts of crude oil and crude oil fractions. Nature 230: 44 - 47 Byrne, C. J. & J. A. CALDER 1977. Effects of the water-soluble fraction of crude, refined and waste oils on the embryonic and larval stages of the quahog clam, Mercenaria sp. Mar. Biol. 40: 225 - 231 EIsLeR, RONALD 1973. Latent effects of Iranian crude oil and a chemical oil dis- persant on Red Sea mollusks. Israel. Journ. Zool. 22: 97 - 105 FARRINGTON, JOHN 1977- The biogeochemistry of oil in the sea. FARRINGTON, JOHN & E G. Quinn 1973- Petroleum hydrocarbons in Narragansett Bay I. Survey of hydro- Oceanus 20: 5-14 carbons in sediments and clams (Mercenaria mercenaria). Estuar. estl. mar. Sci. 1: 71-79 Fona, W. C. 1976. Uptake and retention of Kuwait crude oil and its effects on oxygen uptake by the soft shell clam, Mya arenaria. Journ. Fish. Res. Brd., Canada 33: 2774 - 2780 Fossato, V. U. « W. J. CANzoNIER 1976. Hydrocarbon uptake and loss by the mussel Mytilus edulis. Mar. Biol. 36: 243 - 250 GitrFitian, E. S. 1975- Decrease of net carbon flux in two species of mussels caused by extracts of crude oil. Mar. Biol. 29: 53 - 57 GRUENFIELD, MICHAEL 1973. Extraction of spilled oils from water for quantitative analysis by infrared spectroscopy. Environ. Sci. Technol. 7: 636-639 Harcrave, Barry & C. P NewcomBez 1973. Crawling and respiration as indices of sublethal effects of oil dispersant on an intertidal snail, Littorina littorea. Journ. Fish. Res. Brd. Canada go: 1789 - 1792 Jacosson, S. M. « D. B. BoyLan 1972. Effect of seawater soluble fraction of kerosene on chemotaxis in a marine snail, Nassartus obsoletus. Nature 241: 213-215 Kress, Cuarves T. e KatHryn A. Burns 1977. Long term effects of an oil spill on populations of the salt marsh crab Uca pugnax. Science 197: 484 - 486 Lez, RicHarp F, Wayne S. Garpner, J. W. ANDerRson, J. W. BLayLock & J. Barweti-CLarKE 1978. Fate of polycyclic aromatic hydrocarbons in controlled ecosystem enclosures. Environ. Sci. Technol. 12 (7): 832 - 837 Meyers, Puitup A. & JamMES G. QuINN 1973. Association of hydrocarbons and mineral particles in saline solu- tion. Nature 244: 23-24 Moorg, S. FE « R. L. Dwyer 1974. Effects of oil on marine organisms: a critical assessment of published data. Noyes, Georce N. 1978. Effects of petroleum on adults and larvae of the American oyster, Crassostrea virginica Gmelin. Ph. D. Thesis, Rutgers Univ., New Brunswick, N. J.; 177 pp. SanDEeRS, Howarp L. 1977. The West Falmouth spill — Florida 1969. 15-2 Soka, Rosert R. & F James RoHLF 1969. Biometry. 776 pp.; W. H. Freeman & Co., San Francisco California STEGEMAN, JOHN J. 1977- Fate and effects of oil in marine animals. 59 - 66 VANDERMEULEN, JOHN H. 1977- The Chedabucta Bay spill — Arrow 1970. WELLS, PG. « J. B. Spracue 1976. Effects of crude oil on the American lobster (Homarus ameri- canus) larvae in the laboratory. Journ. Fish. Res. Brd. Canada 33: 1604 - 1614 Wuipp te, W. & R. PatTTRIcK 1977- Petroleum in the Delaware estuary. A report to the National Science Foundation RANN program under grant No. ENV 74-14810- AO3, Rutgers Univeristy and Philadelphia Academy of Natural Sci- ences. 440 pp. [cited by Noyzs, 1978] Zar, JERROLD H. 1974. Biostatistical analysis. wood Cliffs, N. J. Water Res. 8: 819 - 827 Oceanus 20: Oceanus 20: Oceanus 20: 31 - 39 620 pp.; Prentiss Hall, Inc. Engle- Vol. 23; No. 2 THE VELIGER Page 131 A Survey of the Softbottom Molluscs of Cockburn Sound, Western Australia BY FRED E. WELLS ann TIMOTHY J. THRELFALL Western Australian Museum, Perth, Western Australia (7 Text figures) INTRODUCTION EARLY IN THIS CENTURY Petersen in a series of papers began quantitative investigations of marine level bottom communities. Following Petersen’s work a number of stud- ies were undertaken of the marine level bottom communi- ties in various parts of the world. These are reviewed by THorSON (1957). Most of the early work was done in the North Atlantic, often in open sea areas. More recently studies have been initiated in restricted coastal marine em- bayments (SANDERS, 1960; RHoaps & YOUNG, 1970; Pop- HAM & ELLIS, 1971; DRISCOLL & BRANDON, 1973). Several studies have been done in the last several years in the Aus- tralian state of Victoria (PoorE & RAINER, 1974; CoLE- MAN, 1976; Curr & CoLEMAN, 1979). The molluscan fauna of Cockburn Sound, Western Australia, is a classic example of a mollusc community of a marine soft bot- tom in a restricted embayment. This paper presents the results of a survey of the softbottom areas of Cockburn Sound. PHYSIOGRAPHY Cockburn Sound is the only large marine embayment ” along the 1300km of the Western Australian coastline between Shark Bay on the west coast and King George Sound on the south coast. The Sound has an area of ap- proximately 130km’ and is located at 32°12’S and 115° 43 E. The Sound is bordered on the east by the Australian mainland. Pt. Peron forms the southern boundary, Garden Island and Carnac Island the western border, and Par- melia Bank the northern extent (Figure 1). The margins of Cockburn Sound are primarily sandy beaches with a few rocky outcrops of aeolianite limestone. CARNAC : Isl. f: e WOODMAN’S SECS) PARMELIA BANK % mele ty DEEP BASIN ‘ ‘ ' ‘ i) cn 74 > 4 1 ‘ \ \ ‘ i ! ! ry ® 4 ‘ , COCKBURN ‘ : | cr {) A . ‘ Ours © SOUND e : Physical features of Cockburn Sound, Western Australia Page 132 THE VELIGER Vol. 23; No. 2 The Sound has a diverse marine flora and fauna and a high level of productivity (CHITTLEBOROUGH, 1970). It is located in a faunal overlap zone and has a mixture of tropical and warm temperate species (WELLS, 1980). The rich marine biota has prompted a number of studies, most of which are unpublished theses done at the University of Western Australia. Published accounts of the biology of marine animals in Cockburn Sound include Witson «& Hopckin (1967), LENANTON (1974) and PENN (1975). Several benthic habitats are found in Cockburn Sound: open sand, beds of the seagrass Posidonia, rocky intertidal shores, isolated reefs of living and dead coral heads of Turbinaria, and softbottom areas. The latter are areas of muddy sand or mud bottoms which cover most of the area of the Sound. The main feature of Cockburn Sound is the central basin, which has a uniform depth of 18 to 21m. The cen- tral basin constitutes 60% of the bottom of the Sound, and has a layer of fine-grained sediments with a calcium car- bonate content of 65 to 83% (Davies, 1963). The 5m of sediment on the bottom has accumulated over the 5000 years since Cockburn Sound was flooded by rising sea levels. NUNN (1966) commented on the high organic con- tent of the sediments: 50% of the bottom material was fecal pellets, 40% sediment and 10% was a combination of living and dead foraminiferan tests, the exoskeletons of molluscs and echinoderms, and plant detritus. The deep basin slopes rapidly upwards on its western border with Garden Island and on its southern end to the Southern Flats. A shallow shelf of 10m depth lies to the east of the central basin. The eastern shelf slopes gradually to the shoreline to the east. It comprises 26% of the Sound area. The bottom on the eastern shelf is primarily sand, though there are a few coral outcrops (CHITTLEBOROUGH, 1970)- MATERIALS anp METHODS A taxonomic survey of the molluscs of Cockburn Sound divided the Sound into a grid of 178 squares 0.9km on a side (WiLson, KENpRicK & BREARLEY, in prep.). In the present study a table of random numbers was used to select 30 of the stations for sampling. The stations selected are shown on Figure 2. Curr & CoLEMAN (1979) have shown that this technique of random sampling yields the same results as would be obtained from a stratified random sampling method. Each of the selected stations was sam- pled at the center of the square with a 0.1m* Van Veen grab during the period of 27 February to 1 March 1978. The grab was operated from a 1om motor launch, the M.V. Henrietta. Stations were located by triangulation from prominent features on the shoreline. Four replicate samples were made at the initial stations (16, 17, and 21) but the number of samples was reduced to 3 for later sta- tions because of the quantity of material being collected. The bottom at stations 16, 17, 85 and 157 was covered with beds of seagrass Posidonia australis. The Van Veen grab did not function well in the seagrass beds, and data from these stations are only approximate. The bottom at the remaining stations was either sand or mud and the grab functioned with a high degree of effectiveness. The sam- pler was completely filled with 20L of sediment on the majority of the hauls made in sand or mud bottoms. A sediment sample of about 300 mL was removed from the first sample collected at each station prior to sieving. The sediment samples were frozen at the end of each day and remained frozen until they were analyzed. After the samples were thawed organic material was removed by Figure 2 Stations sampled with a Van Veen grab in Cockburn Sound, Western Australia, during February and March 1978 Vol. 23; No. 2 THE VELIGER Page 133 heating the sediment to 50° C and adding hydrogen per- oxide. The samples were stored at 50° C overnight. Addi- tion of hydrogen peroxide the following morning produced no further reaction. The samples were wet sieved through a series of graded screens with mesh apertures of 1 000, 500, 250, 125 and 63 wm. Excess water was decanted from the finest fraction (after the sediment had settled) and all fractions were stored from 3 to 4 days at 80° C until they were completely dried. Each fraction was weighed sep- arately and the weights for each station were converted to g values (a geological measure of sediment grain size) on the Udder-Wentworth scale (BLatr et al., 1972). The highest value of 5 is assigned to the fraction less than 63 wm and the lowest value of 1 is assigned to the fraction which passes through the 1000 wm sieve but is retained on the 500 wm sieve. Sediment characteristics were determined using methods described in SverpRUP, JOHNSON & FLEM- ING (1942) and BucHANAN (1971). The sediment charac- teristics of each station are shown on Table r. After the 300 mL sediment sample was removed through the top of the Van Veen grab the remainder of the sample was sieved through a 1.7mm mesh. Samples were sieved on board the M.V. Henrietta as they were collected. All material retained on the sieve was preserved in 10% for- Table 1 Numerical characteristics of the sediments of the 30 stations investigated in Cockburn Sound, Western Australia. Sediment characteristics Biological indices Station Percentage Median Sorting silts and 0) coefficient | Skewness clays 16 2.1 0.48 +0.08 10.1 17 1.4 0.30 +0.05 0.0 21 1.4 0.50 +0.10 0.4 27 2.6 0.35 kao 30.0 32 3.2 1.22 ei) 02 37.6 38 3.6 1.40 —0.45 48.0 44 4.0 0.58 —0.08 52.0 59 1.1 1.08 +0).28 6.9 60 3.5 1.20 —0.30 47.7 64 1.4 0.88 +0.18 6.5 70 4.5 0.58 mg O22 71.6 72 2.9 1.42 +0.18 40.9 85 4.2 0.60 —0.20 61.2 87 4.2 0.70 —0.20 57.4 92 3.8 0.88 more 45.3 93 3.8 0.68 —0.12 39.5 101 4.6 0.58 O32 71.5 103 4.0 0.75 —0.20 51.0 113 4.3 0.65 —0.25 61.2 117 4.7 0.35 —0.15 80.2 119 4.6 0.30 —0.10 82.8 122 4.8 0.19 —0.04 87.7 126 4.7 0.22 —0.08 89.5 129 4.6 0.32 —0.08 81.8 130 4.7 0.30 —0.10 83.1 132 4.6 0.30 i Orl2 80.8 149 4.7 0.25 —0.07 89.7 157 1.1 0.38 +0.10 3.9 164 4.8 0.22 —0.08 87.3 167 3.8 1.02 mi 32 46.2 Shannon- Evenness Depth Number of Wiener H’/H (m) species Simpson H' max 9.3 7 0.86 0.73 0.87 11.4 6 0.79 0.69 0.89 19.8 5 0.79 0.68 0.97 19.8 6 0.65 0.64 0.82 10.8 4 0.74 0.53 0.88 9.9 5 0.82 0.62 0.89 19.8 3 0.52 0.36 0.76 8.4 5 0.84 0.66 0.93 9.3 6 0.95 0.76 0.97 8.4 10 0.94 0.96 0.96 19.8 3 0.54 0.36 0.76 12.6 1 = = — 9.0 5 0.61 0.56 0.80 3.6 2 0.02 0.02 0.08 17.1 9 0.54 0.49 0.51 18.0 6 0.48 0.41 0.52 19.5 7 0.74 0.67 0.79 19.8 5 0.58 0.47 0.68 15.9 7 0.75 0.65 0.77 19.8 8 0.85 0.79 0.88 6.0 3 0.90 0.46 0.95 19.2 4 0.86 0.55 0.92 15.0 8 0.70 0.58 0.90 15.6 6 0.64 0.49 0.64 16.5 6 0.45 0.37 0.48 19.2 4 0.67 0.49 0.82 19.2 6 0.42 0.30 0.39 2.0 8 0.86 0.84 0.93 19.0 9 0..87 0.65 0.68 6.9 3 0.83 0.46 0.96 Page 134 malin buffered with borax. The samples were transferred to freshwater in the laboratory and sorted. All individuals that had been collected live were retained and stored in 70% alcohol. Individuals were sorted to species as com- pletely as possible and counted. Specimens were blotted dry with paper towels and weighed to the nearest 0.1 g. Bivalve mollusc shells were broken open, the animal was blotted dry, and both animal and shell fragments were weighed together. A Simpson and a Shannon-Wiener index were calcu- lated for each station using the formulae presented by Kress (1972) (Table 1). Overlaps between stations were determined by Jaccard’s coefficient as described by Pop- HAM & ELLs (1971). These data were used to construct a dendrogram using the techniques for the weighted pair group method using average linkage (Soka & SNEATH, 1963). The primary species of the community which oc- curs below the 10 m line were determined with the ranking method outlined by SANDERS (1960). One of the key features in the structure of benthic com- munities is the channelling of energy resources between the constituent organisms of the community. To obtain a preliminary indication of the sources of energy utilized by the molluscs of Cockburn Sound the 34 species collected were assigned to the six feeding categories established by PoorE & Ratner (1974). Little direct information is avail- able on the feeding mechanisms and food preferences of Western Australian molluscs. While the details of feeding vary between species in a genus or family, the basic feeding mechanisms and types of food consumed are usually con- sistent. The assignments used here were based on the feed- ing mechanisms employed by taxonomically closely related species as reported by Morton (1958), PoorE & RAINER (1974) and THompson (1976). RESULTS Distribution of molluscs: A total of 138 species belonging to eight phyla were col- lected. Molluscs dominated the study. They constituted 72-19% of all individuals collected and 89.56% of the biomass. The dominance of molluscs can be attributed to bivalves, which alone comprised 71.30% of the total num- bers and 85.18% of the total biomass collected. Amphi- neurans and gastropods were minor elements of the mol- luscan fauna; no cephalopods or scaphopods were col- lected. Coelenterates and echinoderms were the second and third most important groups in terms of numbers, but crustaceans and polychaetes were second and third in bio- THE VELIGER Vol. 23; No. 2 ke Gees EEEE > ro00 Figure 3 Density of molluscs (no./m?) collected in Van Veen grab samples made in Cockburn Sound, Western Australia, in February and March 1978 mass. Thus, there was no group which was clearly second in importance. Because of the predominance of molluscs the discussion which follows will deal only with that group. A summary of the data on the molluscs collected is given in Table 2. Figures 3 and 4 show the mean density and biomass of all molluscs collected at each of the 30 sampling sites. Low densities of animals were found in most stations in the Vol. 23; No. 2 THE VELIGER Page 135 Table 2 Species of molluscs collected in Cockburn Sound, Western Australia. Number Number Density | Weight Species of of (no/m?) (g/m?) individuals stations Mean Maximum Mean Maximum | Class Amphineura Ischnochiton contractus (Reeve, 1847) 1 1 0.1 1.4 0.00 0.02 Ischnochiton sp. 2 2 0.2 383} 0.04 0.69 Class Bivalvia Anomua cf. A. trigonopsis Hutton, 1877 254 10 28.1 473.3 21.37 317.97 Arcopagia (Pinguitellina) sp. 7 6 0.7 6.7 0.02 0.43 Chama ruderalis Lamarck, 1819 3 3 0.3 33 0.76 14.45 Circe sulcata Gray, 1838 149 18 16.2 141.1 16.82 163.87 Dosinia incisa (Reeve, 1850) 646 18 71.4 1551.2 222.26 1551.24 Epicodakia sp. 8 8) 0.6 SY, 0.24 6.88 Fulvia aperta Bruguiere, 1789 1 1 0.1 3.3 0.08 2.47 Hitatella australis (Lamarck, 1818) 10 6 Ill 13.3 0.07 1.05 Laternula creccina (Reeve, 1860) 2 1 0.2 3.3 0.11 3:23 Lithophaga sp. 1 1 0.1 Ze) 0.01 0.18 Mactra ovalina Lamarck, 1818 1 1 0.1 3.3 0.04 1.26 Malleus meridionalis Cotton, 1930 1 it 0.1 3.3 3.85 115.43 Megacardita incrassata (Sowerby, 1825) 5 4 val 16.7 12.38 187.47 Musculsta glaberrima Lamarck, 1819 874 23 96.2 640.0 48.4] 507.82 Mytilus edulis planulatus Lamarck, 1819 3 1 0.3 10.0 6.61 198.37 Paphia crassisulca (Lamarck, 1818) 29 15 Be) 10.0 35.74 233.33 Phaxas cultellus Linnaeus, 1758 47 19 bal 16.7 5.88 43.80 Solemya cf. S. velesiana Iredale, 1931 2 2 0.2 3.3 0.00 0.06 Tawera lagopus (Lamarck, 1818) 1 1 0.1 1.4 0.37 11.03 Tellina (Tellinangulus) sp. i 1 0.1 33 0.02 0.51 Tellina (Tellinides) sp. 121 14 13.5 15333 3.55 33.70 Theora lubrica (Gould, 1861) 1 1 0.1 3.3 0.00 0.05 Timoclea cardiocles (Lamarck, 1818) 3 1 0.3 383 0.03 0.88 Class Gastropoda Astralium tentorium (Thiele, 1930) 1 1 0.1 3.3 TM} 213.83 Bedeva paivae Crosse, 1864 2 2 0.2 2.5 0.25 0.40 Bulla botanica (Hedley, 1918) 4 1 0.4 13.3 0.15 4.43 Nassarius pauperus (Gould, 1850) 1 1 0.1 725) 0.00 0.09 Pervicacia sp. 2 2 0.2 3.3 0.04 0.52 Polinices conicus (Lamarck, 1822) 1 1 0.1 313) 0.50 14.96 Pyrene scripta (Lamarck, 1822) 1 1 0.1 1.4 0.02 0.57 Trigonostoma scalarina (Lamarck, 1822) 1 1 0.1 3.3 0.09 2.57 Vermetid sp. 3 1 0.2 Ue 0.12 3.55 northern area of Cockburn Sound (Figure 3), along the western side, and in the southern end of the Sound. Den- sities in these areas ranged from a minimum of 3/m? at Station 72 to a maximum of 330/m? at Station 87; most of the stations had densities less than 100/m?. Only sta- tions 44, 60, 87 and 164 were above that level. An area of high density was found in the mideastern portion of Cock- burn Sound. This area encompasses Stations 92, 93, 103, 113, 126, 129, 130 and 149. Animal densities in this region ranged from a minimum of 160/m’ at Station 103 to a maximum of 1367/m’ at Station 129. The map of biomass for all molluscs collected (Figure 4) shows a similar high biomass for the mideastern sector of Cockburn Sound. Biomass figures at stations outside the mideastern region ranged from o g/m’ at Station 72 to 330 g/m’ at Station 60. The area of high biomass extends further west than the Page 136 Figure 4 Biomass of molluscs (g/m?) collected in Van Veen grab samples made in Cockburn Sound, Western Australia, in February and March 1978 area of high density, and includes Stations 103, 117, 122, 132. Wet weights in the mideastern region ranged from 336 g/m’ at Station 132 to 2027 g/m* at Station 126. Two bivalves dominated the molluscan fauna of Cock- burn Sound in terms of both density and biomass. Muscu- lista glaberrima contributed 43.5% of the total number of molluscs but was only 12.5% of the biomass. Dosinia incisa constituted 32.3% of the numbers and 57.4% of the total THE VELIGER Vol. 23; No. 2 biomass. The next most important species numerically were Anomia cf. A. trigonopsis and Circe sulcata. The density of Musculista glaberrima follows the same pattern shown for all species collected and that for all molluscs. Densities of the species (Figure 5) were low over most of the Sound. The species was entirely absent at 7 of the 22 stations outside the mideastern region. The maxi- mum density in the remaining 14 stations was 83/m’. Within the mideastern region area of Stations 87, 92, 93, 113, 126, 129, 130 and 149 densities varied from 93/m” at Station 113 to 640/m’ at Station 129. Densities at stations Density of Musculista glaberrima (no./m?) collected in Van Veen grab samples made in Cockburn Sound, Western Australia, in February and March 1978 Vol? 23; No: 2 THE VELIGER Page 137 within the mideastern region averaged 252/m’; outside that area densities averaged only 40/m’. The biomass of M. glaberrima in the mideastern zone ranged from 2 g/m? at Station 87 to 508 g/m’ at Station 129. In general, the stations with the highest densities also had the highest bio- mass. Station 87 was an exception. Although the popula- tion density of M. glaberrima at this station was high (327/m?), the individuals were juveniles and the biomass of the species at this station was only 2 g/m’. The pattern of high densities and biomasses in the mid- eastern region of Cockburn Sound is best shown by the distributional maps of Dosinia incisa (Figure 6). The spe- cies is absent or rare at stations outside the mideastern region, with an average density of only 10/m’. For this species Station 87 and 149 are outside the region of high abundance. The stations inside the mideastern region had a mean density of 315/m’. Maximum densities were en- countered at Station 92 (650/m’) and Station 93 (667/m’). These stations and Station 129 also had the highesi bio- mass figures. High biomass figures were also obtained at Stations 101, 103, 117 and 122, which are outside the region of maximal density. This is caused by the presence of a few large individuals of D. incisa in the samples. The two most abundant molluscs, Musculista glaber- rima and Dosinia incisa, were centered in the mideastern region of Cockburn Sound. The two species were not evenly distributed within this area. Musculista glaberrima was most dense at the stations adjacent to the eastern shore of Cockburn Sound. These stations were 87, 126,.130 and 146. The biomass of MM. glaberrima was concentrated at Stations 126, 129 and 130, all of which were adjacent to one another. Somewhat lower biomass was recorded at Station 146 to the south. In contrast to M. glaberrima, the highest densities for D. incisa were at Stations 92 and 93 to the northwest. Densities for D. incisa at Stations 126 and 129 were only one-third of those recorded at Stations g2 and 93. However, the individuals at Stations 126 and 129 were large and the highest biomasses were recorded at these stations. The third most abundant mollusc, Anomia cf. A. trigo- nopsis, had a distributional pattern similar to that exhib- ited by M. glaberrima. The maps of Circe sulcata are sim- ilar to those of Dosinia incisa. Thus, all of the distributional patterns examined—den- sity and biomass distributions of all molluscs collected, and the four most abundant molluscs examined individually— are all similar. Density and biomass figures are low in the northern sector of Cockburn Sound, along the western side of the Sound and in the southern end. Maximum densities and biomasses were recorded in the mideastern region of Oo 4 Ol B-~ > 1000 Figure 6 Density of Dosinia incisa (no./m?) collected in Van Veen grab samples made in Cockburn Sound, Western Australia, in February and March 1978 the Sound at Stations 92, 93, 113, 126, 129, 130 and 146. In some species high densities and biomasses were also encountered at Stations 103, 117, 122 and 132 to the west of the main area of high density and biomass readings. There was some variation between species within the mid- eastern region but this was not significant. Level of Association Page 138 Community structure of molluscs: The left side of the dendrogram (Figure 7) has a cluster of stations with an affinity level of 0.42. This cluster in- cludes all of the stations with depths of 10m or more ex- cept for station 149, which has an association level of 0.30 with the cluster. Station 85, from a depth of 9.0m is the only station in the cluster from a depth of less than 10m. The shallow stations, which were collected around the cen- tral basin, do not fall into a single aggregation. This is to be expected, as stations 38, 59, 60, 64 and 87 are to the east of the central basin; 119 is to the west; 16, 17 and 21 are to the north; and 157 and 167 are to the south. All of these stations have species in common with the stations of the central basin. The values of Sanders’ (1960) ranking tech- nique are: Musculista glaberrima 224; Dosiniaincisa 166; Circe sulcata 114; Anomia cf. A. trigonopsis 108; Paphia crassisulca 88; Megacardita incrassata 86; and Phaxas cul- tellus 86. The community of the central basin can thus be labelled the Musculista glaberrima-Dosinia incisa com- munity. THE VELIGER Vol. 23; No. 2 Feeding types: The feeding types for each species are shown on Table 2. Seventeen of the 34 species were infaunal suspension feed- ers. Sixteen of the remaining species were divided among four feeding categories; predators (5 species), epifaunal suspension feeders (4), grazers (4), and surface deposit feeders (3). Only one species of scavenger was collected in the Van Veen grab samples. Infaunal suspension feeders, all of which are bivalves, dominated the samples, constituting 82.2% of all individ- uals collected and 89.5% of the molluscan biomass. The four species of epifaunal suspension feeders, three of which were bivalves, contributed an additional 11.6% of all indi- viduals collected and 7.5% of the biomass (Table 3). Thus 93.8% of all molluscs collected in tne study were suspen- sion feeders, dependent on the overlying waters for their food resources. These animals were 97.0% of the total molluscan biomass. In comparison with the suspension feeders the remain- ing four feeding categories were minor elements of the Station Number Gy Seely Ep =~ © f=?) o oa a ~ 3 ~ [oz] Gy a vs) = ee) ~ a fo») 2 Ss - S fo} g 2 2 = a ~ SH oO 38 3 Ss a — [->) _ 1.0 1.0 0.9 0.9 0.8 0.8 0.7 0.7 0.6 i 0.6 0.5 0.5 0.4 0.4 0.3 0.2 0.2 Ou 0.1 0.0 a6 Figure 7 Dendrogram of the go stations sampled in Cockburn Sound, Western Australia, in February and March 1978 with a Van Veen grab Vol. 23; No. 2 THE VELIGER Page 139 Table 3 Characteristics of the feeding types of molluscs collected in Cockburn Sound, Western Australia. Number of Percentage of Percentage of Feeding type species individuals biomass Suspension feeders 4 11.6 7.5 (epifaunal) Suspension feeders 17 82.2 89.5 (infaunal) Surface deposit 3 5.8 0.9 feeders Grazers 4 0.3 1.8 Predators 5 0.2 0.2 Scavengers 1 0.0 0.0 TOTALS 34 100.1 99.9 fauna. Surface deposit feeders were the most numerous of the minor feeding categories with 5.8% of all individuals (Table 3) and grazers were the largest biomass component, with only 1.8%. Together the four feeding categories of surface deposit feeders, grazers, predators and scavengers accounted for only 6.3% of the individuals collected and 2.97% of the biomass. DISCUSSION Molluscs dominated the study, comprising 72.19% of all individuals collected and 89.56% of the biomass. Among the molluscs the four most common species (Musculista glaberrima, Dosinia incisa, Anomia cf. A. trigonopsis, and Circe sulcata) constituted 95.8% of the molluscan biomass. The dominance of a few species in an ecosystem is a com- mon feature and is not limited to Cockburn Sound. Work- ing in Buzzards Bay, Massachusetts, on the American northeast coast, SANDERS (1960) found that 2 species, the mollusc Nucula proxima and the polychaete Nephthys incisa, were 76.1% of all individuals collected. DriscoLi & Branpon (1973) later looked at the molluscs of the northwestern area of Buzzards Bay. Four facies were inves- tigated, three of which were characterized by fine sedi- ments with g values of 2.5 or greater. In each of the fine sediments the three most common molluscs were 85.0 to 94.2% of all individuals collected. Working in Western Port, Victoria, CoLEMAN (1976) recorded the top 12 of 121 species as 66% of all individuals. The dominance of one or a small group of species in a community has led to their use as indicator species to char- acterize the community. A review of the early work in marine softbottom communities was published by THor- SON (1957). The molluscs of the central basin of Cockburn Sound fit into the classical scheme for delineating marine softbottom communities. In the case of Cockburn Sound the community is designated the Musculista glaberrima - Dosinia incisa community. Ruoaps & Younc (1970) proposed a trophic amensal- ism hypothesis in which deposit feeders on a mud bottom inhibit populations of suspension feeding species by clog- ging filtering mechanisms, burying newly settled larvae or preventing their attachment, or by preventing sessile epi- fauna from attaching. Three distributions of trophic groups were found in the areas of Buzzard’s Bay, Massa- chusetts, studied by Rhoads and Young: (1) areas of homogeneous suspension feeding groups; (2) those of homogeneous deposit feeding groups; and (3) mixed groups. The molluscan fauna of the central basin of Cock- burn Sound is composed of 95.7% suspension feeders, 4.1% deposit feeders and 0.2% of other feeding types. Thus, the central basin fits into the first category of Rhoads and Young, that of homogeneous suspension feeders. How- ever, this category is characterized by an inadequate food supply for deposit feeding species. NuNN (1966) reported that 50% of the bottom material of the central basin is composed of fecal pellets which should supply a rich food source for deposit feeding species. The factors excluding deposit feeders from the central basin of the Sound are as yet unclear. The molluscan fauna of the deep basin is not uniform. Total densities varied from 20 to 1367/m* and total bio- mass ranged from 2 to 2027 g/m*. The number of species recorded at each station varied from 1 to g and the indices were also markedly different. The changes in animal num- bers are matched by differences in the physical parameters of the environment. Depths of the stations varied from about 9 to 20m. Sediment characteristics were also vari- able; the g values ranged from 2.6 to 4.8 and the percent- age of silts and clays from 30.0 to 87.8. There was no clear correlation between animal densities and any of the phys- ical parameters measured. We believe this is due to the small numbers of stations sampled in the deep basin. A more intensive investigation of the deep basin should dis- close the factors causing variations in animal densities. In an unpublished taxonomic survey of Cockburn Sound based on samples made from 1956 to 1960, WILson, KEN- DRICK & BREARLEY (in prep.) list 13 species of molluscs as being characteristic of the central basin. All except two, Nuculana verconts and Pecten modestus, were collected in the present study, but freshly dead shells of both were found. There is some evidence that the population density Page 140 THE VELIGER Vol. 23; No. 2 of N. verconis is erratic. The species may alternate be- tween increasing its density markedly during favourable periods and suffering decreases during unfavourable times. Fluctuations such as this have been recorded in bivalve molluscs by Cor (1957). The population of P. modestus was reduced by commercial fishing conducted circa 1970, but the fresh shells collected in 1978 indicate the presence of a viable population of this species in the central basin of Cockburn Sound. Thus, the absence of 2 of the species that Wilson, Kendrick and Brearley considered to be char- acteristic of the central basin can be easily explained, and there is no evidence of substantial changes in the molluscan fauna of the central basin in the last 20 years. Witson, Kenprick & BREARLEy (in prep.) considered 12 gastropods to be characteristic of the Posidonia beds on the eastern shelf. Only one of these species was collected in this study. Posidonia has largely disappeared from the eastern shelf, probably as a result of industrial develop- ment (Scott, 1976). With the disappearance of the sea- grass the characteristic molluscs have disappeared also. The species have not been lost to Cockburn Sound as they still occur on the seagrass beds of Parmelia. Bank, the southern flats and the fringes of Garden Island. Witson, Kenprick & BrEaRLEY (in prep.) recorded the species characteristic of the central basin in isolated sand patches on the eastern shelf. These species have become more com- mon on the shelf as the amount of sand bottem increased. ACKNOWLEDGMENTS A study of this nature cannot be undertaken without a tre- mendous amount of assistance from a number of people. We would like to thank all who have assisted the project in so many different ways. The use of the M.V. Henrietta was arranged by G. Henderson of the Department of Mar- itime Archaeology of the Western Australian Museum. The assistance of C. Bryce, C. Powell and R. Richards in operating the Henrietta and the Van Veen grab was in- valuable. Dr. B. R. Wilson and Dr. R. G. Chittleborough read and criticized early versions of the manuscript. The report was typed by M. Wallis. L. Baxter was helpful in a number of ways throughout the study. The investigation was funded by the W.A. Department of Conservation and Environment. Literature Cited Bratt, H., G. MrppLeTon « R. Murray 1972. Origin of sedimentary rocks. Prentiss-Hall. BucuHanan, Joun B. 1971. Measurement of the physical and chemical environment of sediments. in N. A. Horme « A. N. McIntyre (Eds.) Methods for the study of marine benthos. Blackwell, Oxford, pp. 30 - 51 Englewood cliffs, New Jersey. CuirTLesoroucH, R. GRAHAM 1970. Conservation of Cockburn Sound (Western Australia). A case study. Australian Conservation Found. Spec. Publ. 5: 27 pp. Cor, WesLey RosweELui 1957. Fluctuations in littoral populations. pp. 935-939 in J. W. Hedgpeth (ed.). 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The influence of deposit-feeding organisms on sediment stability and community trophic structure. Journ. Mar. Res. 28: 150-178 SANDERS, Howarp L. 1960. Benthic studies in Buzzards Bay. III. The structure of the soft- bottom community. Limnol. Oceanogr. 5: 138 - 153 Scott, W. D. and Co. in conjunction with MEAGHER & LEPREVOST 1976. A review of the environmental consequences of industrial de- velopment in Cockburn Sound. Report for the Environmental Pro- tection Authority of Western Australia SoxaL, Ropert R. & Peter H. A. SNEATH 1963. Principles of numerical taxonomy. Co., San Francisco SverpruP, HaraLtp ULrRik, Martin Wicco JoHNsON & RicHARD HoweELi FLEMING 1942. The Oceans, their physics, chemistry, and general biology. Prentice-Hall, New York: 1087 pp.; 265 text figs. Tuompson, THOMAS EvERETT 1976. Biology of opisthobranch molluscs. Ray Soc. London. vol. 1: 207 pp.; plts. 1-8, 10-21; 106 text figs. TuHorSON, GUNNAR 1957- Bottom communities (sublittoral or shallow shelf). In: J. W. HepcretH (ed.): Treatise on Marine Ecology and Paleoecology 1, Geol. Soc. Amer. Mem. 67: 461 - 534 WELLs, Frep ETHAN 1980. The distribution of shallow-water marine prosobranch gastropod molluscs along the coastline of Western Australia. The Veliger 22 (3): 232-247; 5 text figs. (1 January 1980) Witson, Barry R. & Ernest P Hopkin 1967. A comparative account of the reproductive cycles of five species of marine mussels (Bivalvia: Mytilidae) in the vicinity of Fremantle, Western Australia. Austral. Journ. Mar. Freshwater Res. 18: 175 - 203 Witson, Barry R., Gzorce W. Kenprick & ANNE BREARLEY In prep. The benthic fauna of Cockburn Sound, Western Australia. Part 1. Prosobranch gastropods and bivalve molluscs. xvi+359 pp.; Freeman Vol. 23; No. 2 THE VELIGER Page 141 Larval and Postlarval Development of the Window-Pane Shell, Placuna placenta Linnaeus, (Bivalvia : Placunidae) with a Discussion on its Natural Settlement ADAM L. YOUNG Aquaculture Department, Southeast Asian Fisheries Development Center, Philippines (3 Plates; 1 Text figure) INTRODUCTION Placuna placenta Linnaeus, 1758 (Figure 1) isa member of the superfamily Anomiacea, a familiar group of “saddle oysters” composed of 2 families (Anomiidae and Placuni- dae), 7 genera and at least 20 known species. The com- monest species of its genus, and one of the best known of bivalve species, P. placenta occurs from the Gulf of Aden and around India and the Malay Peninsula to the southern coast of China and along the north coast of Borneo to the Philippines (YONGE, 1977), living unattached on the sur- face of mud flats and sandy mud beaches. In the Philippines, it is often fished up in large numbers (millions) and used for glazing windows and veranda roofs and for the manufacture of lamp-shades, trays, etc. In spite of its abundance and economic importance, almost nothing is known about the biology of this species. Horney (1909) studied the anatomy, distribution and economic uses. BLaNco (1956) studied the infestation of this species with the pea crab Pinnotheres and later (BLANco, 1958) tried to farm it. More recently Yonge (1977) made a comprehensive review of the form and evolution in the Anomiacea and proposed a new family Placunidae for the two genera Placuna and Placunanomia. There is no knowledge about the life history of any species of Placuna, nor have the larvae been described from plankton samples. This paper describes the larval and postlarval develop- ment of Placuna placenta from the straight hinge stage to the adult (60 mm) and presents micro-photographs of each ' Contribution No. 73, Aquaculture Department, Southeast Asi- an Fisheries Development Center, Philippines Figure 1 Adult Placuna placenta, 90mm long. Internal view of opened valves. Left valve at top. Page 142 stage. Such information will serve as the basis for sound management practices and aid future mariculture efforts with this valuable shellfish. MATERIALS anp METHODS Adult Placuna placenta (60-100mm) were obtained from commercial skin divers along Iloilo Strait, the Philippines. These were kept in the laboratory in running seawater at 28-30° C at a salinity of 27-29%. Mature window-pane shells that have been kept in running water for 3-5 days were easily induced to spawn by halting the flow of water for 3-5 hours and then changing the water completely. Earlier attempts to induce spawning by rapidly fluctuating water temperatures, adding stripped gametes to the water or pricking the adductor muscle were unsuccessful. Like- wise, although gametes could be stripped from apparently mature individuals and further treatment with ammonium hydroxide is not necessary, only a relatively small number of eggs can be obtained and only a low percentage of these develop normally. Subsequent treatment of fertilized eggs approximated those of LoosanorFF & Davis (1963) and CHANLEy (1975). Fertilized eggs were first sieved (mesh size 25 sm) to dis- card excess sperms and then cultured at concentrations of approximately 30/mL in 100-L cylindrical fiberglass tanks containing freshly sand-filtered seawater. Every third day water was changed by siphoning it through a piece of plankton netting of appropriate mesh size to collect the larvae. Larvae were fed after each change of water with Isochrysis galbana at the rate of 30-50 cells/uL of larval culture. Spat and juveniles were fed daily with a mixture of Isochrysis galbana Parke (1949), Phaeodactylum tricor- nutum Bohlin, 1897 and Nitzschia closterium (Ehrenberg) W. Sm. (1853) to make a total concentration of 100 cells/ pL of larval culture. Larvae were maintained at about 27° Cin water of 28-29%, salinity. Periodically larvae were examined microscopically and preserved in 10% buffered formalin. Preserved larvae were measured to the nearest 5mm with a calibrated ocular micrometer. Descriptive THE VELIGER Vol. 23; No. 2 terminology conforms to that defined and illustrated in CHANLEY & ANDREWS (1971). Dimensions of larvae are given in micrometers (um). Length is the maximum antero-posterior dimension; height, the maximum dorso- ventral dimension; and depth, the maximum left-right dimension. RESULTS Spawning and Gametes Female window-pane shells released unfertilized eggs with a sudden contraction of the adductor muscle which forcefully expels the eggs through the postero-ventral mar- gin. Strong jets of water produced by spawning females are easily observed in shallow spawning trays. Males re- leased spermatozoa in steady streams. Eggs were released singly or, rarely, in short strings. They were golden yellow and about 45 wm in diameter. Larval Development The main features of development are presented in Table 1 and Figure 2. Fertilized eggs developed into straight-hinge veligers in less than 24 hours. The smallest straight-hinge veliger observed was 50 um long x 43 wm high although most were above 80m in length. The hinge line ranges from from 40-55 4m, more commonly 50-55 wm, and does not increase in length with larval growth. During early development, the length is about 10 jum greater than the height. Later, when length reaches 150 um, height starts to increase more rapidly so that at lengths from 180-220 pm, height is either equal to or greater than the length, at times by as much as 20pm. After metamorphosis, length is again greater than the height and remains so in adults. Larvae are noticeably inequivalve at all stages of - development, although there is no overlap of the ventral margins. The left valve is well rounded and bears a prom- inent umbo (Figures 4A-C). The umbo (of the left valve) Explanation of Figure 2 Composite photomicrographs of larval Placuna placenta Individual larvae arranged with anterior end at right, their length > height dimensions given in pm under each. Ranges of length measurements of grouped larvae at right are in um. Note meta- morphosed larvae showing distinct dissoconch in bottom photograph Tue VE IcER, Vol. 23, No. 2 ; [Youna] Figure 2 225 X 223 215-240 Figure 2 Vol. 23; No. 2 THE VELIGER Page 143 Table 1 Summary of major features of larval development in Placuna placenta cultured at 27°C and 28-29%c salinity. Stage Age Siete Shape/distinguishing features Fertilized egg 0 Dia. 45 um Golden yellow, spherical. Straight-hinge 20-30 h L: 50-105 Smallest veliger 50 X 43 um; hinge line commonly 50-55 ym, H: 43-98 slightly curved, not increasing in length with growth. Ends of nearly D: 25-52 equal length. Shells inequivalve. HL: 40-55 Umbo veliger 2-8 days L: 100-200 Shells inequivalve. Right valve flat with undeveloped umbo. Left H: 80-200 valve rounded. At lengths beyond 150 um umbo of left valve projects D: 50-75 well above the shoulders as a prominent knob. Shells nearly transparent; digestive organs situated almost beneath umbo. No byssus notch. Anterior end longer, more pointed. Ventral margin bluntly pointed. Pediveliger 8-10 days L: 180-220 Foot functional at L = 170 um. Eyespots at L = 150, commonly obscured H: 180-220 by opaque mass of digestive gland. Metamorphosis at L: 220-230. D: 65-80 Spat 10-11 days Typically Foot long, well developed. Velum absent. Dissoconch delineated by L: 230 narrow dark band. Shells nearly transparent. E3220 ene D: 80 began to form in larvae over 100 pm, rounded at first but projecting well above the shoulders as a prominent knob in larvae over 150 um long. The fully developed umbo is the knobby type of CHANLEY & ANDREWS (1971) and is the most pronounced character of Placuna placenta larvae. The anterior end is longer and more pointed than the posterior, although this difference is slight until larvae exceed 130 um long. The ventral margin is bluntly pointed in larvae over 140 pm (Figure 2). Eyespots were first noticed in week-old larvae larger than 150 ym, but these were often obscured by the opaque mass of the digestive gland which is located almost beneath the umbo. These eyespots were retained past metamor- phosis and could be observed even in juveniles 1-2mm long. A developing foot could be observed in larvae over 130 yum but this did not become fully developed and func- tional until after larval lengths exceeded 170 um. The foot is initially blunt but soon becomes grooved, flattened and pointed distally. It is conspicuously long, usually measuring as long as the shell, ciliated along its entire length, but lacks a “heel” or byssal spur. Pediveligers crawled readily, at times traversing con- siderable distances on the glass bottoms of the containers (2-L beakers) in which they were placed for observation. Average measurements of pediveliger larvae were 190 x 190 pm with a depth of 75 um. Settlement and Metamorphosis By the eighth day after spawning, when larval lengths exceeded 200 um, most of the larvae had settled to the bottom of the culture tanks (fiberglass) and crawled ex- clusively. Larvae metamorphosed at lengths ranging from 220-230 um. At these lengths, the velum had disintegrated and the larvae possessed a few gill loops. Metamorphosed larvae showed a well developed, grooved foot and ex- tremely thin and transparent dissoconch growth clearly delineated from the prodissoconch by a narrow, dark band. This distinct demarcation line between larval and post- larval shell averaged 230 wm long (Figures 2, 3B, C, D). Metamorphosed larvae crawled vigorously and exten- sively, especially when they were disturbed. Byssal attach- ment was not observed, although a few metamorphosed larvae (230 um) bore algal debris on the anterior end of their shells. Postlarval Development Post-larvae grew rapidly in the laboratory and were mostly 1mm long after 10 days, becoming 3-3.5mm after another 10 days (approximately 1 month from fertiliza- tion). At the end of the second month, they were mostly 6-8mm, some as much as 14mm long. After the fifth Page 144 THE VELIGER Vol. 23; No. 2 month, they were mostly 45-50mm, a few as much as 60 mm long. Growth of the shell after metamorphosis was asymmet- rical; shell growth posteriorly exceeded growth in the ante- rior direction. In effect, the umbo was shifted anteriorly from its original central position to almost the very ante- rior tip of the long hinge line in juveniles over 3mm (Figures 3E-H). Length of the shell was greater than the height at all stages after metamorphosis. The laterally flattened valves of the post-larva and juvenile are thin and delicate, and are still transparent and colorless at a length of 2mm. The inequivalve larval form is less pronounced in juveniles; the right valve is generally flat to slightly con- cave, the other valve marginally convex. In juveniles over 5mm the left valve is slightly reddish on the exterior. A very prominent feature of the shells of juveniles over 600 pm in length is a short gape on the antero-dorsal mar- gin formed by a slight arching of the valves at the anterior tip of the dorsal margin. The 2 lips of this gape are much thickened and clearly contrasted against the transparent and colorless valves as a white “sleeve” (Figures 3E-H, 4D). Observations of post-larvae and juveniles ranging from 1-12mm revealed that the foot is protruded usually through this “sleeve,” and that the gape is sealed by a coming together of the mantle edges in this region. This gape is usually grown over by shell growth in individuais 40-50 mm long. Juveniles slightly over 1.0mm in length possessed 15-18 pairs of gill filaments and this number increased to about 50 in 3mm juveniles (Figure 3G). Tentacles began to form at the mantle margins in juveniles approximately 2.7mm long. All other internal organs, excepting the gonad, were well developed in post-larvae over 500 um. The long and active foot of the pediveliger is retained past metamor- phosis and becomes a highly contractile and protractile organ. In juveniles over 3mm, the foot is much flattened and heavily pigmented at the margins of its bluntly pointed tip, with a conspicuous central groove (Figure 3H). Obser- vation of juveniles (over 1mm) placed on a cavity slide filled with muddy water revealed that the foot served to keep both the mantle cavity and the shell margin clean. Juveniles 1-8mm placed in glass beakers (water un- aerated) for study were observed to crawl about actively especially when disturbed, and they often crawled up the sides of the beakers and attached themselves near the water surface by a single byssal thread. The juveniles also secreted byssus while crawling up, for if the water were agitated or if they were mechanically dislodged, they swung about wildly but did not drop. Microscopic exam- ination of these spats revealed the presence of an extremely thin and transparent byssal thread which was difficult to photograph. However, juveniles over 5mm _ produced strong and thick (also single) threads which were plainly visible. On 5 separate occasions, juveniles ranging from 1 to 4 mm were observed to float either horizontally or vertically, but these readily sank when pushed below the water sur- face. Juveniles ranging from 2-10mm placed in shallow Pyrex baking dishes (water unaerated) provided with either fine sand or loose mud survived well but were unable to move about with their foot. These commonly “plunge head-on” into the substrate by repeated (every 4-8 sec- onds) sharp contractions of the adductor muscle. With the animal flat on the surface of the mud/sand, the sequence of movements is as follows: 1. The valves separate widely. 2. The foot is protruded and probes the substrate, at times penetrating it vertically. 3. Simultaneous with the withdrawal of the foot, the adductor muscle contracts sharply, causing water in the mantle cavity to be forced out ventrally as Explanation of Figure 3 Composite photomicrographs of postlarval Placuna placenta. Anterior end is left A. Pediveliger 188 um X 190m B. Newly metamorphosed larva 230 um X219 pm C. 330 wm X 270 wm E. 1.0mm Xo0.8 mm D. 360 pm X 300 pm F. 1.9mmX1.6mm G. 3.0mm X 2.6mm ’ H. Young adult 4.8mmX4.7mm. Grooved foot apparent. Note “sleeve” on antero-dorsal margin of shell THE VELIGER, Vol. 23, No. 2 Figure 3 [Youno] Figure 3 Vol. 23; No. 2 THE VELIGER Page 145 a powerful jet as in pectinid escape movements. This effectively thrusts the shell forward (with hinge foremost) and into the substrate. This sequence of movements is repeated until the animal is completely under the substrate. Such burrowing efforts were exhibited both on sand and on mud, although it was apparent that the animals had great difficulty with sand, as very few could penetrate the sandy substrate, and those that did seldom went in more than half way. On one occa- sion a 7.3mm long juvenile taken out of the sand into which it had burrowed showed a strong byssal thread to which grains of sand had adhered. Once the animal is under the substrate, the foot starts clearing away the mud around its shell edges (except at the hinge) until a semicircular depression is formed in the mud at the very margin of the shell and normal respira- tory, feeding and cleansing currents can be resumed. In effect, the animal bears a layer of mud on its shell which serves to camouflage it. Hinge Structure The larval hinge of Placuna placenta is not taxodont. In straight-hinge veligers the hinge is composed of a single provincular tooth at either end of the hinge line on both valves. In slightly separated valves, the hinge shows a single tooth and a groove (for the tooth of the other valve) at each end of the hinge line (Figure 4A), but in whole larvae there appear to be two provincular teeth at either end. In umbo veligers over 150 zm dentition is not similar on both valves. In the left valve, there are 2-3 large projecting provincular teeth on either end of an intermediate tooth- less area, for which there are corresponding cavities or “sockets” on the right valve (Figures 4B, C). The large oval ligament is internal and central. In spats 280 um long, the ligament is enlarged and occupies almost the entire intermediate toothless area of the provinculum (Figure 4C). This presumably involves the appearance of the sec- ondary periostracal ligament responsible for union of the valves dorsally. Juveniles over 4mm clearly show the di- verging arms of the primary ligament responsible for the opening thrust. The evolution of these separate ligamental structures has been fully explained and illustrated by YoncE (1977). DISCUSSION Larval development has not been described for any species of Placuna. However, larval development of one species of the related genus Placunanomia (Family Placunidae) and of several species in the related family Anomiidae has been described. From the description of Placunanomia patelliformis (BERNARD, 1896), Anomia lischkei (Mrya- ZAKI, 1935), Anomia squamula and Anomia patelliformis (JORGENSEN, 1946), Anomia simplex (REEs, 1950; Loosa- NOFF & Davis, 1963; LoosanorF, et al., 1966; CHANLEY & ANDREWS, 1971), Anomia sp. (Mrvazakl, 1962) and Monia squama (REEs, 1950), the following common char- acteristics are notable: inequivalve form; poorly devel- oped umbo on the right valve; nearly colorless larval shells, with the digestive organs situated almost beneath the umbo; larvae nearing metamorphosis bear an inden- tation on the anterior shell margin known as the byssus notch, the appearance of this feature inconsistent. Larvae of Placuna placenta have many characteristics common to larval Anomiidae. The larval shell is inequi- valve, the umbo of the left valve knobby and cap-like. Larvae are pale in color, with the digestive organs situ- ated almost right beneath the umbo. However, the byssus notch which, when present, is a diagnostic feature of Anomia larvae, was not observed in Placuna. YONGE (1977) reports that in very young specimens (post-larvae) “a minute circular foramen with a short, completely fused connection with the dorsal margin is present on the under- side of the right valve” and clearly shows the entrance to this byssal notch in his fig. 46. In view of these findings, it is possible that in P. placenta larvae the byssal notch is reduced to a vestigial structure. The shell of Placuna placenta larvae is inequivalve at all stages of development (Figure 4) and this condition is observed even in postlarvae, but there is no overlapping of the shell margins as reported for Anomia lischkei by Mrva- ZAKI (1935). Compared with the micro-photographs of the larvae of Anomia simplex by Loosanorr et al. (1966, fig. 13), the larvae of P placenta (Figure 2) have a more pro- nounced knobby umbo. Further, in Placuna the anterior end is longer and more pointed, and the ventral margin is shorter and more bluntly pointed. Shell dimensions of Placuna and Anomia larvae are approximate to each other and can not be used for distinguishing one from the other. Hinge structure in the superfamily Anomiacea has been described only in Placunanomia (BERNARD, 1896) and Anomia squamula (JORGENSEN, 1946) and in general by Rees (1950). These authors reported a taxodont hinge consisting of 3-5 well developed teeth on either side of an intermediate area which is so thin that teeth are absent or extremely minute. This is not the case in Placuna placenta; the hinge is not taxodont and dentition is not similar on both valves. The left valve bears 2-3 large projecting pro- vincular teeth on either end of an intermediate toothless Page 146 THE VELIGER Vol. 23; No. 2 area, for which there are corresponding cavities on the right valve (Figure 4B, C). Metamorphosis in Placuna placenta larvae commonly occurs at 220-230 um, slightly later than Anomia which metamorphoses at 180-215 Wm (CHANLEY & ANDREWS, 1971). Metamorphosis in P. placenta is characterized by the disappearance of the velum and appearance of an active foot. Moreover, metamorphosed larvae displayed extremely thin and transparent dissoconch growth clearly delineated from the prodissoconch by a narrow dark band. LoosanoFF (1961) observed this phenomenon in Anomia simplex and termed it “partial” or interrupted metamor- phosis. Although direct observations were not made on settling larvae, it is very likely that Placuna placenta larvae attach byssally at metamorphosis, although the byssally attached stage may be very brief (C. M. Yonge, personal communi- cation). This view accords with evidence from observa- tions of algal debris accumulated on the shells of larvae 230 um long (size at metamorphosis) and of strings of algal debris in the cultures at about the time of metamorphosis, and with Yonce’s (1977) report and figures of a byssal notch on the underside of the right valve of very young specimens (retained even in large specimens). The appear- ance of strings of algal debris (not pseudofeces) in the cul- tures and on the larval shells at about the time of meta- morphosis could very well be caused by extremely thin and “invisible” byssal threads secreted by pediveligers and metamorphosing larvae and suggests that P. placenta lar- vae attach byssally at metamorphosis. GRUFFYDD & BEAu- MONT (1972) observed the phenomenon with Pecten max- imus larvae and reported that “two or three days before metamorphosis, the shells of the larvae seem to become very sticky, since debris and algae stick to the surface.” Byssal attachment at metamorphosis could be to the sur- face film, to any floating object, or to a seaweed or other objects on the sea bottom. Considering the number of metamorphosing larvae, the chances of these encountering an object either at the water surface or on the sea bottom would not be great, and thus the most likely site of meta- morphosis would be the surface film. NELSON (1928) has shown Mytilus edulis dissoconchs up to 4 mm to be capable of hanging from the surface film with their foot, by means of a byssal thread, or with the aid of the tentacles of the incurrent siphon, maintaining their position solely through surface tension. Considering the size and shape of meta- morphosing Placuna placenta larvae, there is little doubt that they are capable of attaching to the surface film, especially as juveniles (1-4 mm) have, in fact, been observed to float in laboratory cultures. If the site of metamorphosis is the surface film, it fol- lows that the byssally-attached stage must be very brief and that the larvae metamorphose very rapidly, as wind and wave will soon dislodge them. Rapid growth after meta- morphosis has indeed been observed in the laboratory, where metamorphosed larvae grew from an initial length of 330 um to 360 um in 12 hours, becoming 550 um long after another 24 hours. After being dislodged from their initial attachments to the surface film the newly meta- morphosed larvae may either sink to the bottom or re- main in the plankton. Indeed, the larvae of many clams, e.g., Saxidomus giganteus, Protothaca staminea, Venerupis japonica (QUAYLE & BouRNE, 1972) and Chama congre- gata (LA BarBERA & CHANLEY, 1971) settle to the bottom at metamorphosis and undergo an extensive free-crawling stage (‘‘byssal plantigrade” stage, CARRIKER, 1961), grow- ing considerably before finally burrowing (at about 5mm long) or cementing themselves permanently (at about 350 pam, in Chama) by one or other valve. This “‘byssal planti- grade’ stage has also been observed in laboratory cultures of Anomia simplex by LoosanorF (1961) and LoosaANoFF & Davis (1963). However, as Placuna differs from these clams and from Anomia in that the adult lives completely unattached on the surface of mud flats, and as mud is not the most suitable of substrates for surface movement, it is more reasonable to believe that the metamorphosed larvae Explanation of Fighre 4 Larval and postlarval hinge structure of Placuna placenta Except in A, anterior end is right. Left valve uppermost A. Internal view of valves 90 pm long B. Dorsal view of slightly separated valves 210m long. Internal ligament visible at center of hinge line. Note lack of umbo in right (lower) valve C. Dorsal view of valves 280 pm long. Note enlarged ligament D. Dorsal view of shell 4.8mm long. Note the two arms of the primary ligament, anterior the shorter THE VELIGER, Vol. 23, No. 2 [Younc] Figure 4 D Figure 4 Vol. 23; No. 2 remain planktonic—with the aid of byssal threads. The threads would increase the viscous drag exerted on the shells of the larvae and enable them to be carried along on relatively weak currents (1 cm/sec). Such a mechanism of transport in young postlarval bivalves has been reported by Sicurpsson e¢ al., who observed the phenomenon in 21 species (of which the anomiid Heteranomia squamula is one) of lamellibranch larvae representing eleven super- families, and who termed it “byssus drifting.”’ Circumstan- tial evidence for such a mechanism occurring in P. placenta larvae comes from observations (cited earlier) of juveniles byssally attached to the sides of the beakers and of the thin and transparent thread secreted by these while crawling. Upon encountering an object the “byssus drifting” post- larvae may attach themselves byssally, finally dropping to the bottom at a later stage, or, they may stay adrift (if no object is encountered) for prolonged periods before settling to the bottom. This final settlement must be in response to a stimulus received from the desirable type of bottom through its overlying water. NELSon (1928), CoLMaNn (1933), WILSON (1952), BAYNE (1965), and Crisp (1965, 1967) have established that marine invertebrate larvae metamorphose only in response to a specific stimulus and are capable of delaying metamorphosis and entering an extended searching phase until such a stimulus is received. Moreover, SCHELTEMA (1961) has shown that metamor- phosis-inducing factors (“biologically-active substances”) are probably water-soluble and may be transferred from the substratum to the adjacent water, so that metamor- phosing larvae can recognize a favourable site without actual contact with the substrate itself. Scheltema’s findings shed light on the seemingly “spon- taneous” metamorphosis and settling of the Placuna placenta larvae in the present study. As water (sand-fil- tered) used in the larval cultures was taken from an area where Placuna naturally occurs in abundance (therefore a favourable site), it does seem probable that the labora- tory-reared larvae were stimulated by metamorphosis- inducing factors already present in the water. The final sedentary phase of the life history of Placuna probably occurs at a size of 600 um, coincident with the appearance of the “sleeve” on the antero-dorsal margin of the shell. Unattached and unable to move, the juveniles and adults are entirely at the mercy of water movements, and are commonly congregated into shallow waters where they pile up in vast numbers and are fished up by divers. This has been confirmed by personal observations using SCUBA diving equipment; after a storm adult Placuna placenta (60-100 mm) were found piled up in great num- bers in 3-5 m of water. Specimens used in the present study were collected from such a pile. Also, personal observations THE VELIGER Page 147 of P. placenta in their natural habitat have revealed that this animal (although truly unattached and immobile) lives not on the surface of the mud, as is generally described, but under a mud-camouflage, commonly bearing a layer (15-20mm) thick) of mud or silt on its shell, the presence of the organism detectable only by the shallow semicircular depression in the mud representing the area cleared by the foot in keeping the shell edges clean. The burrowing move- ments (cited earlier) of juveniles observed in the laboratory suggest that this camouflage is effected not so much by silt settling on the shells as by a deliberate effort of the animal to be inconspicuous to predators. SUMMARY Stages of development of the window-pane shell, Placuna placenta, from the straight-hinge veliger to the adult are described. Mature larvae metamorphose at lengths from 220-230 wm. Larvae probably attach byssally to the water surface at metamorphosis and remain in the plankton for some time before finally settling on the mud bottom. ACKNOWLEDGMENTS I wish to thank Sir Maurice Yonge, F.R.S., University of Edinburgh, Paul Chanley and Wilfredo G. Yap for their interest and valuable guidance, and for reading and com- menting on the original version of the manuscript. Thanks are also extended to the staff of the Phycology Laboratory, Aquaculture Department, Southeast Asian Fisheries De- velopment Center for providing the necessary algal food and to Ma. Teresa de Castro for helping culture and meas- ure the larvae. Literature Cited Bayne, B. L. 1965. Growth and the delay of metamorphosis of the larvae of Mytilus edulis (L.). Ophelia 2 (1): 1-47 BERNARD, FE 1896. Troisiéme note sur le developpement et la morphologie de la coquille chez les lamellibranches (Anisomyaires). Bull. Soc. geol. Frang. 24 (3): 412-449 Bianco, G. 1965. Notes on the infestation of Kapis (Placuna placenta L.) with the pea crab Pinnotheres. Philipp. Journ. Fish. 4: 141 - 144 1958. Kapis farming at tidal flats of Bacoor Bay, Luzon. Philipp. Journ. Fish. 6: 9- 15; 2 plts. CarrikeR, MELBOURNE ROMAINE 1961. Interrelation of functional morphology, behavior and autoecolo- gy in early stages of the bivalve Mercenaria mercenaria. Journ. Elisha Mitch. Sci. Soc. 77 (2): 168-241; 39 text figs. (Nov. 1961) Cuan_ey, Paut E. 1975. Laboratory cultivation of assorted bivalve molluscs. In: W. L. Smith & M. H. Chanley (eds.): Culture of marine invertebrate animals. pp. 297-318; Plenum Press, New York Page 148 THE VELIGER Vol. 23; No. 2 GHantey, Paut « Jay D. ANDREWS 1971. Aids for identification of bivalve larvae of Virginia. logia 11 (1): 45-119; 51 text figs. Cotman, J. 1933- The nature of the intertidal zonation of plants and animals. Journ. Mar. Biol. Assoc. U. K. 18: 435 - 476 Crisp, Dennis J. 1965. Surface chemistry, a factor in the settlement of marine inverte- brate larvae. Bot. Gothoburg. III. Proc. 5th Mar. Biol. Symp., Goteborg, 1965: 51 - 65 1967. Chemical factors inducing settlement in Crassostrea virginica (Gmelin). Journ. Anim. Ecol. 36 (2): 329 - 335 GruFFyp, Li. D. & A. K. BEAUMONT 1972. A method for rearing Pecten maximus in the laboratory. Mar. Biol. 15: 350 - 355 Hornet, J. Malaco- (8 October 1971) 1909. Report upon the anatomy of Placuna placenta, with notes upon its distribution and economic uses. Rprt. mar. Zool. Okhamandal 1: 43-97 Jorcensen, C. B. 1946. Lamellibranchia. In: Reproduction and larval develop- ment of Danish marine bottom invertebrates, with special reference to the planktonic larvae in the Sound (@resund), by G. Thorson. Medd. Komm. Danm. Fisk. Havundersgg., Copenhagen, Ser. Plankton 4 (1): 277-311; 28 text figs. LaBarspera, M. & Pau, CHANLEY 1971. Larval and postlarval development of the corrugated jewel box clam Chama congregata Conrad (Bivalvia: Chamidae). Bull. Mar. Sci. 21 (3): 733-744 LoosANoFF, VicTorR LYon 1961. Partial metamorphosis in Anomta simplex. 2070 - 2071 LoosanorFr, Victor Lyon & Harry Cart Davis 1963. Rearing of bivalve mollusks. In: F S. Russell (ed.), Ad- vances in marine biology 1: 1-136; 49 text figs. Acad. Press, Inc., London & New York Science 193: Loosanorr, Victor Lyon, Harry Cart Davis & Paut E. CHANLEY 1966. Dimensions and shapes of larvae of some marine bivalve mol- lusks. Malacologia 4 (2): 351-435; 61 text figs. (31 Aug. 1966) Mryazakl, I. 1935- On the development of some marine bivalves, with special reference to the shelled larvae. Journ. Imp. Fish. Inst. gr (1): I-10 1962. On the identification of lamellibranch larvae. Bull. Japan. Soc. Sci. Fish 28 (10): 955 - 966 Netson, THuRLow CHRISTIAN 1928. Pelagic dissoconchs of the common mussel, Mytilus edulis, with observations on the behaviour of the larvae of allied species. Biol. Bull. Woods Hole 55: 180 - 192 Quayiz, Daniet B. & New Bourne 1972. The clam fisheries of British Columbia. Fish. Res. Brd. Canada, Nanaimo Biol. Sta. Bull. 179: 73 - 104 Rezs, C. B. 1950. The identification and classification of Jamellibranch larvae. Hull. Bull. Mar. Ecology 3 (19): 73-104 ScHELTEMA, RupotrF S. 1961. Metamorphosis of the veliger larvae of Nassarius obsoletus (Gastropoda) in response to bottom sediment. Biol. Bull. 120 (1): 92-109 Sicurpsson, J. B., C. W. Titman « PA. Davis 1976. The dispersal of young postlarval bivalve molluscs by byssus threads. Nature 262: 386 - 387 Witson, Douctas P. 1952. The influence of the nature of the substratum on the meta- morphosis of the larvae of marine animals, especially the larvae of Ophelia bicornis Savigny. Ann. Inst. Oceanogr. (Monaco) 27: 40-156 Yonce, CHARLES MAURICE 1977. Form and evolution in the Anomiacea (Mollusca: Bivalvia). — Pododesmus, Anomia, Patro, Enigmonia (Anomiidae) ; Placunanomia, Placuna (Placunidae, Fam. Nov.). Phil. Trans. Roy. Soc. London, B. 276 (950): 453-527 Vol. 23; No. 2 THE VELIGER Page 149 Pulsellum salishorum spec. nov., A New Scaphopod from the Pacific Northwest BY ELSIE MARSHALL Washington State Museum, University of Washington, Seattle, Washington 98195 (1 Plate; 5 Text figures) ONLY TWO GENERA OF SCAPHOPODA, Dentalium and Cadulus, have been reported from Puget Sound, the Strait of Juan de Fuca and British Columbia (BERNARD, 1970; Koz.orr, 1974). In this paper, a new species, belonging to the genus Pulsellum, is described from this region. This is the first record of the genus from the United States West Coast. GADILIDA Starobogatov, 1974 SIPHONODENTALDDAE Simroth, 1894 Pulsellum Stoliczka, 1868 Type species: Pulsellum lofotense M. Sars, 1865, Pulsellum salishorum Marshall, spec. nov. Description: The white shell is moderately curved and attains a size of 10mm, with an average of 8.5mm (74 specimens measured). The apical aperture is circular with the diameter 0.5mm. The oral aperture is also circular, with a diameter of 1.3mm. The surface of adult shells is dull with a great deal of erosion. Juvenile shells are glossy. Growth rings are faintly visible under magnification. The widest point is at the oral aperture. The living animal has a translucent tubular foot with a crenulated disk. When contracted, the disk, which has a short central projection, is invaginated (Figure 1). During extension of the foot, the disk evaginates (Figure 2). In the radula the lateral tooth is hood-shaped and has three moderately sharp cusps. The central tooth is tra- pezoidal, with a concave lower edge. The marginal tooth is in the form of a parallelogram, with an anterior projec- tion and a corresponding posterior socket (Figures 3, 4). Etymology: Pulsellum salishorum is named for the Coast Salish Indians from the area in which it was found. pedal disc central projection _{. foot . proboscis “ mantle i § a captacula | “mantle wy . \ cavity mantle edge Figure 1 Pulsellum salishorum Sagittal section of the front part of the body of Pulsellum salish- orum. The central projection of the disk is evident in the invagi- nated part of the retracted foot Page 150 THE VELIGER Vol. 23; No. 2 Figure 2 Pulsellum salishorum The live animal with the foot extended central Figure 3 Pulsellum salishorum A half row of radular teeth showing 3 of the 5 teeth disarticulated Figure 4 Pulsellum salishorum Three rows of radular teeth showing the overlapping laterals Holotype: The holotype (Figure 6, top row, left), is de- posited in the United States National Museum, Washing- ton, D.C. (USNM 782263). The shell measures 9.5 mm in length. The oral aperture is 1.37 mm, and the apical aper- ture is 0.5 mm in diameter. Paratypes: 6 specimens in the United States National Museum, Washington, D.C. (USNM 782264). 6 specimens in the American Museum of Natural His- tory, New York City, N.Y. (AMNH 198610). -6 specimens in the Los Angeles County Museum, Los Angeles, California (#1929 in type collection). 4 specimens in the National Museum of Canada, Ottawa, Ontario (#86068). 4 specimens in the Academy of Natural Sciences, Phila- delphia (ANSP 352474). 4 specimens in the Washington State Museum, Univer- sity of Washington, Seattle, Washington (#35663). Type Locality: East Sound, Orcas Island, San Juan Islands, Washington (48°36’ N, 122°51’ W); 18-22 meters. Distribution: South Lopez Island, San Juan Islands, Washington, to Bowen Island, British Columbia: 3-91 meters. Localities Collected: 1. Sucia Island, San Juan Islands, Washington; entrance to Echo Bay; dredged in 15-18 meters, broken shell and sandy mud bottom; August, 1973; I specimen; Coll. Elsie Marshall. 2. Tunstal Bay, Bowen Island, British Columbia; dredged in 36 meters; August 9, 1971; 8 specimens; Coll. George Holm and Terry Smith. 3. Friday Harbor, San Juan Island, San Juan Islands, Washington; sandy mud; dredged in 36-27 meters; May 7, 1974; Coll. R. L. Shimek. . McKay Harbor, S. Lopez Island, San Juan Islands, Washington; dredged, 12-6 meters; sandy mud; May 14, 1974; 3 specimens; Coll. Elsie Marshall. . East Sound, Orcas Island, San Juan Islands, Washing- ton; dredged in 27 meters; gelatinous mud; July 8, 1976; 7 specimens; Col]. Elsie Marshall. . Between Jones and Yellow Island, San Juan Islands, Washington; dredged in 54-91 meters; November 21, 1976; Coll. Friday Harbor Laboratories. . same as #5; April 3, 1977; 30 specimens; Coll. Elsie Marshall. . Cowlitz Bay, Waldron Island, San Juan Islands, Washington; in 22 meters; sandy mud; April 4, 1977; 4 specimens; Coll. Elsie Marshall. g. same as #5; August 16, 1977; 39 specimens; Coll. Elsie Marshall. wu or srenba aul aedg ‘epeueD jo umMasny [euOneN] Egzzgl WNSN ‘edAjojoy ey st usurroods do} ‘suaumoads addjered € [Leg ‘saavayyAA SuDssagv snjnpoy Wysry ayy {susumtoads € f-aou ‘dads ‘Jeysueyy tumsoysyvs uingjasing yay 9 amnsry [TIvHsuvpy] & ON ‘&% ‘JOA ‘AXOIIAA FH], . Vol. 23; No. 2 THE VELIGER Page 151 10. same as #5; April 13, 1979; 12 specimens; Coll. Elsie Marshall. Collecting Data: Generally found in sandy mud or gelatinous mud. It is found with Oenopota fidicula, Cyclichna alba, Polinices pallida, Turbonilla macount, Turbonilla aurantia, Bittium challisae, Odostomia sp., and Dentalium rectius. Discussion: The genus Pulselluwm is distinguished from the other genera in Siphonodentaliidae by having the shell “moderately to strongly curved, slightly tapering, largest diameter at the oral aperture, typically circular in section, rarely compressed dorso-ventrally; surface smooth, with- out sculpture other than growth lines; apex simple, with- out lobes or slits; foot of animal with a pedal disk as in Siphonodentalium, but pedal disk convex, not concave, and provided with a central filament” (EMERSON, 1962). Because there are no other Pacific Coast species of Pulsellum, I compare P. salishorum with the 2 species of the genus from the U.S. East Coast. Pulsellum occidentale Henderson, 1920 and P. bushi Henderson, 1920, are found below 157 m from Georges Bank to Cape Hatteras on the Atlantic Coast. The shells of these 2 species are smaller than P. salishorum, averaging 3.5mm and 5 mm respec- tively, in length. The angle of the oral aperture of P. salishorum is straight, whereas that of P. occidentale is oblique. The shell of P. bushi is almost straight, with P. salishorum having a moderate curve. Other Scaphopoda of small size and similar to Pulsellum salishorum are found on the West Coast, and it was nec- essary to compare them. Siphonodentalium quadrifissatum (Pilsbry and Sharp, 1898), is found in California, and the shell is similar to Pulsellum salishorum. However, the apex of the shell of the former is cut into lobes, while the latter has a simple apical aperture. In P. salishorum, the disk of the foot has a central process, while in Siphonodentalium the disk is without a central process. Although the genus Entalina is not found on the U.S. West Coast, it was necessary to study the description of this genus, as it is included in S:phonodentaliidae. The shell of Pulsellum salishorum is without sculpture and, aside from barely visible growth lines and erosion, is smooth. In the genus Entalina, the shell has many longi- tudinal riblets. The shell of Pulsellum salishorum has the greatest diameter at the oral aperture, and the pedal disk of the foot has a central process. Cadulus has the ‘greatest diam- eter near the middle or between the median portion and the oral aperture; . . . lacking a central filament or prec- ess” (EMERSON, 1962). Pulsellum salishorum is similar to Cadulus aberrans Whiteaves, 1887, collected at Quatsino Sound, northwest Vancouver Island, B.C., in 1885. The average size of C. aberrans is larger (13.5mm). Three paratype speci- mens of C. aberrans from the National Museum of Canada, Ottawa, are shown with three specimens of salishorum collected at Orcas Island, Washington (Fig- 1.4 diameter (mm) — _ — a is) a) = fe) 2 © 0.8 0.7 0.6 0.5 0.4. BO 7 & @ © Bh 1-1 length (mm) ONS Ih m2 3) a4 Figure 5 Comparison of diameters of Cadulus aberrans Whiteaves, 1887, and Pulsellum salishorum Marshall, spec. nov. at different positions (indicated by dots) along the length of the shell. Solid lines re- present P. salishorum, dashed lines, C. aberrans. Means and 95% confidence limits are shown. Note that the diameter of P salish- orum is greater apically than that of C. aberrans, although the shell of the latter is longer. For most of the shell lengths, the diameters of the two species do not differ significantly. o length indicates the position of the apical aperture. Sixteen specimens of each species were examined. Page 152 THE VELIGER Vol. 23; No. 2 ure 6). A photograph of 16 of the 25 paratype specimens of C. aberrans was also examined. In order to compare the shell shapes of Cadulus aber- rans and Pulsellum salishorum, widths at regular inter- vals were measured from photographs (Figure 5). In 13 of the 16 specimens of Cadulus aberrans there was a constriction immediately behind the oral aperture. There is no such constriction in the specimens of Pulsellum salishorum. The apical aperture is larger in all 3 speci- mens of P. salishorum, although all 3 are shorter than the 3 C. aberrans (Figure 5). In Cadulus stearnsi Pilsbry and Sharp, 1897 (syn. Dentalium simplex Pilsbry and Sharp, 1897), taken off Tillamook, Oregon, in 1437m, the shell is thicker, glossier, and the expansion rate is greater than Pulsellum salishorum. ACKNOWLEDGMENTS To Dr. Alan Kohn for his patience in reading this paper, for giving of his advice, taking photographs, and examining specimens at the United Staies National Museum. Dr. Ronald Shimek originally urged me to work on this project. Alan Riggs measured the shells and constructed Figure 5. Dr. William K. Emerson loaned me the large photograph of the paratype speci- mens of Cadulus aberrans. Muriel F I. Smith of the National Museum of Canada loaned the three paratype specimens of C. aberrans. William Siem developed film and printed pictures, and Laura Lewis made all the draw- ings of the Pulsellum salishorum, except the shell with the live animal. Many people encouraged me, but the most encouragement came from my patient husband, Tom. He and our younger son, Peter, dredged many times, sometimes in very adverse conditions, to be sure that I had all the specimens that I needed. Literature Cited BERNARD, FRANK R. 1970. A distributional checklist of the marine molluscs of British Columbia: based on faunistic surveys since 1950. Syesis 3 (1-2): 75 - 94 Emerson, WILuiAM KeiTH 1962. A classification of the scaphopod mollusks. Journ. Paleo. 30 (3): 461-482; plts. 76-80; 2 text figs. (May 1962) HeENpDeERSON, JoHN B. 1920. A monograph of the East American scaphopod mollusks. Smithson. Inst., USNM Bull. 111: vit+177 pp.; plts. 1-20 Koz.orr, EUGENE 1974. Keys to the intertidal invertebrates of Puget Sound, the San Juan Archipelago, and adjacent regions. Univ. Wash. Press, Seattle, Wash. x+226 pp.; illust. Pitssry, Henry Aucustus & B. SHARP 1897-1898. Scaphopoda. In: G. W. Tryon, Jr.: Manual of Concho- logy 17 (65): 1-80; plts. 1-9 [11 May, 1897]; 17 (66): 81 - 144; plts. 10-26 [15 October 1897]; 17 (67): 145-224; pits. 27-37 [3 May 1898] Starozsocatoy, YA. I. y 1974. Ksenokowkhii i ikh znacheniye dlya filogenii i sistemy nekoto- rykh klass mollyuskov. Paleo. Zhur. 1: 3-18; 6 figs. [English: Xenoconchias and their bearing on the phylogeny of systematics of some molluscan classes. in Paleo. Journ. Amer. Geol. Inst. 1974, 8 (1): 1-13; 6 figs.] Vol. 23; No. 2 THE VELIGER Page 153 A Note on the Diet of Beringius kennicotti (Dall, 1871) RONALD L. SHIMEK Department of Biological Sciences, University of Alaska, Anchorage, Alaska 99504 Mailing address: Friday Harbor Laboratories, Friday Harbor, Washington 98250 (1 Plate) THE GENUS Beringius is characteristically found in the Northeastern Pacific and Arctic Oceans (ABBOTT, 1974). Beringius beringit (Middendorff, 1849) and B. kennicottu (Dall, 1871) are probably the most common representa- tives of this genus from southcentral Alaskan waters westward into the Bering Sea (MacInTosH, 1976, 1978; P. A. Raymore, personal communication). In some areas of the Bering Sea, B. kennicotti is relatively abundant, apparently forming a major component of the large (shell length > 70mm) gastropod fauna. The depth of these regions often exceeds 100m; however, rendering the ani- mals unobservable. In southcentral Alaskan waters B. kennicottii is present in shallower waters, although it is not abundant. During an investigation of the diets of intertidal Nep- tunea pribiloffensis (Dall, 1919) and N. lyrata (Gmelin, 1791), 23 Beringius kennicottii (mean length = 93.8 + 10.6mm; mean width= 45.5-+ 6.8mm) were observed and collected from Bluff Point Beach, about 2km W of the city of Homer, Alaska (59°38’N; 151°27’W). They were collected in the lowest exposed intertidal areas, 1.0 to 1.5m below mean lower low water, on a silt-covered sandstone bench. The animals were frozen in a refrig- erator-freezer, returned to the laboratory, and their gut contents examined. Relatively undigested small polychaete annelids were found in two Beringius kennicottii collected in June and July, 1979. The polychaetes were identified by reference to Bansz & Hosson (1974) as Phyllodoce maculata (Lin- naeus, 1767). Phyllodoce maculata density (quantitatively determined by infaunal analysis) ranged from 100 to 300m. No other recognizable gut contents were observed, only mucus being found in the remainder of the examined animals. Two of the animals were observed feeding on Tealia crassicornis (Figure 1) a relatively large (oral disk > 8 cm) anthozoan. Beringius kennicottu feeds on Tealia by insert- ing its proboscis into the column of the actinarian, rasping off and ingesting the septa and gastrodermis. One feeding animal was marked zn situ with a rubber band on 6-IX-79, observed still feeding on 7-IX-79, and collected for gut analysis on 8-IX-79 when it had moved a short distance from the Tealia. The Tealia was examined and most of the septa and large areas of the gastrodermis had been eaten. When first observed the Tealia had detached from the substratum, but was still responsive to touch. When aban- doned by the snail, the Teaiia was flaccid and appeared dead. The gut of this B. kennicotti contained only copious amounts of mucus. Tealia crassicornis distribution in the area was patchy; however, it commonly exceeded 2m”. While prosobranch predation on polychaetes is com- mon, predation on actinarians is relatively rare, being best documented in the Epitoniidae (PERRON, 1978). The actin- arian fauna of the southcentral Alaskan region is diverse and abundant and epitoniids are rare, perhaps allowing the exploitation of this potential food resource by Beringius. If all species of Beringius have the capability to consume actinarians, the common occurrence of these gas- tropods in some boreal seas might be indicative of distri- butional patterns of anthozoans. ACKNOWLEDGMENTS This study was partially supported by a summer research grant from the University of Alaska, Anchorage. The field assistance of Mary Beattie is also gratefully acknowledged. The author thanks an anonymous reviewer for several helpful suggestions. Page 154 THE VELIGER Vol. 23; No. 2 Literature Cited AspotTT, Ropert TUCKER 1974. American seashells. qed ed. 663 pp.; 24 ool. pits. Ven Nostrand Reinhold, New York Bansg, K. « K. D. Hopson 1974. Benthic errantiate polychaetes from British Columbia and Wash- ington. Fish. Res. Brd. Canada Bull. 185: 1 - 111 MacIntosH, RicHarD A. 1976. A guide to the identification of some common Eastern Bering Sea snails. Proc. Rprt. U. S. Dept. Comm. NOAA, NMFS, Seattle, Washington, 23 pp. 1978. Egg capsule and young of the gastropod Beringtus beringt (Middendorff) (Neptuneidae). The Veliger 21 (4): 439-441; 1 plt. (1 April 1979) PERRON, F. 1978. The habitat and feeding behavior of the wentletrap Epitontum greenlandicum. Malacologia 17 (1): 63-71; 1 text fig. (17 Feb.) Washington, 27 pp. THE VELIGER, Vol. 23, No. 2 [SHIMEK] Figure 1 Figure 7 Beringius kennicottu (Dall, 1871) feeding on Tealia crassicornis (Muller, 1776) The sea anemone has detached from the sub- stratum and is lying upon another (nonfeeding) Beringius kenni- cottu. ‘The arrow indicates the proboscis of the feeding snail. Scale bar = 5cm Vol. 23; No. 2 THE VELIGER Page 155 The Effect of Salinity on Crystalline Style Occurrence in the Estuarine Snail, I/yanassa obsoleta (Say), (Mollusca : Neogastropoda) and its Possible Significance with Respect to Local Distribution LAWRENCE A. CURTIS anv L. E. HURD Program in Ecology, School of Life and Health Sciences, and College of Marine Studies, University of Delaware Newark, Delaware 19711 (1 Text figure) INTRODUCTION THE PROSOBRANCH NEOGASTROPOD, Ilyanassa obsoleta (Say, 1822), is an abundant organism in many coastal habitats along the eastern seaboard of North America. It also occurs on the Pacific coast, but is not native there. Fluctuating salinity is a major environmental factor in many of these habitats. I/yanassa obsoleta has been shown to be affected in various ways by lowered salinity: for example, Dimon (1905) noted that snails were restricted to the higher salinity regions of estuaries. She also showed that snails are rendered inactive by freshwater, but can survive many hours of exposure to it. NAGABHUSHANAM (1968) and BERGMANN & GRAHAM (1975) showed that long-term exposure to a salinity of approximately 6%, is lethal. Crisp (1969) pointed out that lowered salinity af fects behavioral responses. A crystalline style occurs in this species (NoGucHI, 1921; JENNER, 1956), and has been recognized as an important adaptation for digestion (JENNER, 1956; SCcHELTEMA, 1964; Brown, 1969; Curtis « Hurp, 1979). Brown (1969) noted that the style is temporally inconstant and suggested that presence or absence is related to type of food ingested. RoBertTson (1979), working in Georgia, within a 24-hour period, collected data and correlated style absence with low tide. Since all of Robertson’s snails that lacked a style also lacked food in the gut, he inferred a tidally regulated feeding rhythm. Work done in Dela- ware during the summers of 1978 (Curtis, in press) and 1979 suggests a different pattern to style occurrence. Extensive, continuous day and night sampling showed that styles tended to be absent from snails in the hours after dawn (0800-1000h), regardless of tidal stage. Moreover, other data resulting from this work suggest that style oc- currence is not consistently related to presence or type of food in the gut (Curtis & Hurd, in prep.). During these studies styles were occasionally low in occurrence or absent in snails collected out of association with the post-dawn period. On several occasions this was associated with low salinity in the water overlying the snails collected. Since lowered salinity is known to affect J. obsoleta we ran the following experiments to test whether lowered salinity could bring about a loss of crystalline style. MATERIALS anp METHODS All specimens of Ilyanassa obsoleta used in this work were collected from the Cape Henlopen sandflat in Delaware, located just inside the mouth of Delaware Bay (75°6’ W, 38°47’N). Snails ranged in shell height from 17mm to 26mm. Salinity of the water over the sandflat can vary between about 10%, (low tide; heavy rain) and 31%, an- nually. The normal range of salinity is between 25%, and 30% o- All control and treatment groups employed consisted of 1o snails each. The efficacy of this sample size was deter- mined from the results of other work carried out at the same location on this sandflat during the summers of 1978 and 1979, in which the temporal occurrence of the crystal- Page 156 line style was examined. In these studies, 10 snails were collected each hour, over periods of time ranging from 18-28 consecutive hours. A total of 1650 snails was thus examined. We found that the overall probability of finding a snail with a style (chosen at random) was 62 - 4%, indi- cating a reliable consistency in this population. The rela- tive probabilities of collecting 10 snails from this popula- tion with 10/10, 9/10 ... 0/10 having styles was calcu- lated through expansion of the binomial expression: (p+q)*, where p = probability of possessing a style (= 0.62), q= probability of not having a style (= 0.38), and k= number of snails in the sample (= 10). This pro- cedure revealed that 10 snails is an adequate sample size for this population, since the probability of 10/10 snails having a style by chance alone is < 1%. The criterion for style loss in the population is < 3/10 snails, since random collections of 10 snails with 3 or fewer having styles would occur by chance alone with a probability of <1% At 1400h on 19 July 1979, 40 snails were collected ran- domly from the sandflat population and taken immediately to the nearby laboratory for treatment, where they were randomly separated into four groups of 10 snails each. These four groups were placed in separate finger bowls containing different dilutions of baywater: 28%, (full strength baywater at the time of collection), 20%, 15%o, and 10%,. Dilutions were made by the addition of distilled water to baywater, and all salinities were measured with a refractometer. The time of immersion was 1410h, and all snails in this experiment were forced to remain sub- merged for a period of 60 minutes, during which time their behavior was observed. At the end of this time, snails were removed (all at once) from the finger bowls and ex- amined by dissection under a dissecting microscope as rapidly as practicable, for condition of the crystalline style (fully formed, partially formed, or absent). All dissections and observations were completed within 50 minutes fol- lowing removal from the finger bowls (i.e., by 1600h). Previous experience has shown us that removal of the snails from water for this length of time will not by itself cause style loss (CurtTIS, in press). In addition to the four treatment groups described above, three field control groups of 10 snails each were also collected and examined by dissection during the course of the experiment. The first of these groups (collection con- trol) was collected at the same time as the 40 laboratory treatment animals (1400h), and dissected immediately to determine style occurrence in the field at the beginning of the experiment. A second group (collection +50 min. con- trol) was collected and dissected just prior to the removal of snails from the finger bowls in the laboratory (1450h). THE VELIGER Vol. 23; No. 2 The third control group (collection+135 min. control) was collected after all observations had been made on the laboratory snails (1615h). This third group served as an overall measure of changes in style occurrence in the field population while the experiment was in progress. The direct effect of different concentrations of bay- water on style dissolution time was also tested. Fully formed styles were removed from sandflat snails collected separately from those above. Upon removal, styles were immediately transferred to separate vials containing either 28%. (full strength baywater), 20%. or 10%) baywater. As before, dilutions were made by the addition of distilled water to baywater. Dissolution time for each style was determined by observing its gradual disappearance with the aid of a dissecting microscope. Ten styles were tested at each concentration. All tests were performed at room temperatures. RESULTS During the 60 minute immersion in experimental bay- water dilutions, there were obvious differences in behavior among the four groups of living snails. Snails in the 28%, group actively crawled about the finger bowls, but did not attempt to escape. The groups immersed in 20%, and 15% attempted to crawl up and out of the water, and had to be pushed back repeatedly. Snails in the 10%, dilution simply pulled into their shells and lay quiet throughout the period of immersion. Figure 1 shows the number of snails having either a fully formed or partially formed crystalline style in each of the four experimental (A) and three control (B) groups. All snails from the three control groups (collection control, collection +50 min. control, and collection + 135 min. con- trol) had styles present. Therefore, style occurrence in the field population did not change over the course of the experiment. Since all control snails collected from the field had styles (Figure 1B), the expected probability of style occurrence in the treatment groups during the course of the study is 1.0 (10/10 snails). We compared this expected value with observed value frequencies in our laboratory treatment groups (Figure 1A) in a chi-square, and found that snails immersed in 15%, and 10%, dilutions were significantly affected by treatment (xy?=11.3, df=1, Po.10). Further, where styles were present at 10%, or 15% , they were always of a flimsy con- sistency (partially formed). Vol. 23; No. 2 THE VELIGER Page 157 2) ue (A) 10 (B) 2 ks} o oO 6 e cS 8 . eS b 7 = 3 n = I = 5 Ss 5 S | & a z . & °o be ® 3 i: Z a /, by 10 15 20 28 ° 50 110 135 Salinity (¥,) Time (min.) relative to immersion of laboratory experimental snails Figure 1 The number of individuals of Ilyanassa obsoleta with crystalline styles for each group of 10 snails examined: (A) snails collected at same time and immersed in different salinities for one hour; (B) snails collected from field at various times relative to immer- sion of laboratory snails, as controls. Shaded areas of bars represent the number of snails with fully formed styles, and unshaded areas represent those with partially formed styles. For (B), salinity at time 0 was 28%), and was 30%, thereafter. * indicates time of com- pletion of dissection for all laboratory snails. The results of this experiment led us to ask whether the effect of diluted baywater on crystalline style occurrence shown by the snails exposed to 10%, and 15%. was direct, or actively mediated in some way by the snails. To answer this question, fully formed styles were extracted from re- cently collected snails and placed in three of the same dilutions used in the snail immersion experiment (see Materials and Methods). Mean dissolution times for styles removed from snails and immersed in various dilutions were: 16 minutes (10%), 13 minutes (20%,) and 12 minutes (28%,). One- way ANOVA indicates no significant difference among these groups (F227 = 2.21, P > 0.10). Therefore, baywater salinities between 10%, and 28%, do not directly affect the rate of dissolution for styles removed from the snails. Indeed, the trend (though nonsignificant) for in vitro styles is the opposite of that exhibited by styles in vivo for these same salinities. DISCUSSION Our results indicate that crystalline style occurrence in Ilyanassa obsoleta is affected by ambient salinities of 10%. and 15%, but relatively unaffected by salinities of 20%, and 28%. Further, this effect is not due to the direct action of saline water on the style at these salinities, but is medi- ated in some manner by the living snails. The dilutions used in this experiment represent the range of naturally occurring environmental salinities in the sandflat habitat, as well as in other nearby habitats such as salt marshes. Although 28%, to 30%, is more common, salinity drops to 15%. and 10%, upon the occasion of heavy rainwater input at low tide. That snails in the field are actually affected in this way by salinity of overlying water is supported by additional observations made during the 1978-1979 studies (Curtis, in prep.). There were five occasions when salinity dropped well below 20%, (range 16% -10%0). On four of Page 158 THE VELIGER Vol. 23; No. 2 these, three or fewer out of ten collected snails possessed styles, which meets our statistical criterion for significant style loss in the population. The single nonsignificant result was when only four out of ten snails possessed styles. There- fore, the results of this experiment have implications for the role of salinity in determining the niche of this species in nature. SHuMway (1979) showed that oxygen consumption in several species of snails, including a close relative of Ilyanassa obsoleta (Nassarius reticulatus), dropped to zero as seawater was gradually diluted to 30% (approximately 10.5%). This corroborates our result suggesting that style maintenance is dependent upon the physiological condi- tion of the snail, rather than upon salinity of the water per se. Indeed, low salinity likely brings on general phys- iological stress, with style loss being only one manifestation. For example, Crisp (1969) showed that reduced salinity (15%0) reduced the positive rheotactic response of I. obsoleta. It has long been known that I/yanassa obsoleta is ad- versely affected by low salinity waters (Dimon, 1905; NAGABHUSHANAM, 1968; Crisp, 1969; KASSCHAU, 1972; BERGMANN & GRAHAM, 1975), and the inference has been that lethal salinities in large measure determine local spa- tial distribution in estuaries. This seems a reasonable infer- ence, since gastropod mollusks apparently do not osmo- regulate (AVENS & SLEIGH, 1965; PRossER, 1973). Lethal salinity for I. obsoleta seems to be around 6%, (NAGABHU- SHANAM, 1968; BERGMANN & GRAHAM, 1975). Our results suggest that snails are severely affected at a salinity level considerably above 6%, somewhere between 15%, and and 20% . Since the style is an important aspect of I. obso- leta’s digestive apparatus (JENNER, 1956; SCHELTEMA, 1964; Brown, 1969; Curtis & Hurp, 1979), its loss likely will curtail nutrient procurement activities. Thus, local distribution in estuarine habitats will not be set by the perimeter of lethal salinities for J. obsoleta. Dimon (1905) showed that these snails can survive exposure even to fresh water for a limited time (18h). The important factor in setting a perimeter for distribution, with regard to salinity, may be the amount of time potential habitat areas are sub- jected to salinities below the critical level for style main- tenance, relative to the total amount of time required for adequate nutrient procurement. As a matter of general observation, I/yanassa obsoleta does seem to be restricted to higher salinity regions of estuaries (Dimon, 1905). It would be interesting to exam- ine the correlation between distributions of salinity and of I. obsoleta in the field. This seems not to have been done, and it would reveal information about the relative impor- tance of salinity as a niche factor for this important and abundant species. ACKNOWLEDGMENTS We are grateful for the continuing high quality assistance of L. Collins and K. Corbett in collecting and processing of specimens. Support for this study was provided by a Sea Grant from NOAA. Literature Cited Avens, A. C. « M. A. SLEIGH 1965. Osmotic balance in gastropod molluscs - I. Some marine and littoral gastropods. Comp. Biochem. Physiol. 16A: 121-141 BERGMANN, J. R. & M. G. GRAHAM 1975. Salinity as a factor defining the habitat of the mud snail, Nassarius obsoletus. Proc. Malacol. Soc. London 41: 521 - 525 Brown, STEPHEN CLAWSON 1969. The structure and function of the digestive system of the mud snail Nassavius obsoletus (Say). Malacologia 9 (2): 447-500 (20 July 1970) Crisp, Mary 1969. Studies on the behavior of Nassarius obsoletus (Say). (Mollusca: Gastropoda). Biol. Bull. 196: 355 - 373 Curtis, LAWRENCE A. in press. Daily cycling of the crystalline style in the omnivorous, deposit- feeding estuarine snail, Ilyanassa obsoleta (Say): Mar. Biol. Curtis, Lawrence A. & L. E. Hurp 1979. On the broad nutritional requirements of the mud snail, Ilya- nassa (Nassarius) obsoleta (Say), and its polytrophic role in the food web. Journ. exp. mar. Biol. Ecol. 41: 289 - 297 Dimon, A. 1905. Nassa obsoleta. Cold Spring Harbor Monogr. 5: 1 - 48 JENNER, CHARLES EDWIN 1956. | Occurrence of a crystalline style in Nassarius. Biol. Bull. III: 304 Kasscnau, M. R. 1972. Temperature-salinity interactions on Nassarius obsoletus. Bull. So. Carol. Acad. Sci. 34: 104 NaGABUSHANAM, R. 1968. Effect of low salinity on the mud snail, Nassarius obsoletus (Say) (Mollusca: Gastropoda). Sci. & Cult., India 34: 132 - 133 Nocucui, H. 1921. Cristispira in North American shellfish. A note on a spirillum found in oysters. Journ. exp. Medic. 34: 295 - 315 Prosser, CLirrorp Lapp 1973- Comparative animal physiology. 3t4 ed.; 966 pp. W. B. Saunders Co., Philadelphia, Penna. Rosertson, J. R. 1979. Evidence for tidally correlated feeding rhythms in the eastern mud snail, Ilyanassa obsoleta. The Nautilus 93: 38 - 40 ScHELTEMA, Rupotr S. 1964. Feeding and growth in the mud-snail Nassarius obsoletus. Chesapeake Sci. 5: 161 - 166 Suumway, S. E. ree 1979. The effects of fluctuating salinity on respiration in gastropod molluscs. Comp. Biochem. Physiol. 63A: 279 - 284 Vol. 23; No. 2 THE VELIGER Page 159 A Possible Relationship between Size and Reproductive Behavior in a Population of Aplysia punctata Cuvier, 1803 BY CARY OTSUKA"3, YVES ROUGER? anp ETHEL TOBACH'! INTRODUCTION AS PART OF A COMPARATIVE STUDY of the behavioral adap- tations of Aplysia (Tosacu, et al., 1965; LEDERHENDLER, et al., 1975; LEDERHENDLER, et al., 1977; LEDERHENDLER & ToBACH, 1978; ToBacH, 1978), a study of Aplysia punc- tata was carried out in the intertidal waters of Concar- neau, France (47°53'22” N, 3°54’10” W). From June 21, 1979, through July 28, 1979, observations were conducted approximately 800m W of the Laboratoire de Biologie Marine, Collége de France. The field site measured ap proximately 240m? and was enclosed by large rocks cov- ered primarily by Fucus serratus. The basin consisted of coarse sand, scattered rocks of different sizcs covered with several species of algae. These were, in addition to the E serratus, Palmaria marina, Enteromorpha spp., Lomen- taria articulata, Laminaria digitata, Ulva spp., and Chondrus spp. The rocks were usually covered by more than one algal species; the most abundant were Fucus, Enteromorpha and Ulva. The maximum tidal range was approximately 4.3m and during periods of extreme low tides, the entire area became exposed. Surface water tem- perature ranged from 15° to 20° C with a fairly constant salinity of 34%p. * Department of Animal Behavior, American Museum of Natural History, New York; and the Biology Department, City College, The City University of New York; for reprints write to E. Tobach ? Institut National pour Recherche Agronomique, Laboratoire de Biologie Marine, Collége de F rance, Concarneau, Bretagne, France 3 Research supported by grants from the Arts Foundation and the Lerner Fund for Marine Research of the American Museum of Natural History. We wish to thank Director Yves Legal, Collége de France, for his support and cooperation PROCEDURES Vegetation, substrate and rocks were systematically searched by sight and touch for animals, for one half hour before and after the lowest point of the Table 1 Field observations of Aplysia punctata. Median Number of K Range Date animals | Weight (1979) found! | (g) “| From To 6/21(AM) 18 48 30 75 6/21(PM) 15 35 15 55 6/22 18 38 10 53 6/23 18 42 30 70 6/24 24 40 25 65 6/25 20 45 25 65 6/26 4 45 30 <50 6/27 21 40 <30 65 6/28 14 38 <30 50 6/29 14 48 25 70 6/30 1 55 — = 7/1 10 45 >25 75 7/4 1 50 ~ ~ 7/7 15 45 35 75 7/8 14 40 >20 70 7/9 10 40 25 75 7/10 12 40 30 65 7/12 23 40 25 50 7/13 30 40 20 65 7/15 10 40 30 65 7/16 3 45 25 45 7/22 5 35 25 50 7/24 12 40 25 65 7/25 4 30 20 40 7/27 1 40 _ — ‘Only animals found for the first time are listed. Page 160 THE VELIGER Vol. 23; No. 2 tide. Once animals were located, records were made of type of contact and weights by volumetric measurements in graduated cylinders to the nearest 5mL. A Hartner Balance, model LP105, was used to determine the net weights of animals which were also measured volumetri- cally. The difference in measurements by the two methods was not noteworthy (=: 0.5g) and it was assumed that mL=g. Animals were tagged according to methods de- veloped by Tobach (LEDERHENDLER et al., 1975). Given the restrictions of time and tidal conditions, the data obtained can only be understood within this context. As Table 1 shows, there was a considerable variation in the number of animals found on any day. RESULTS anp DISCUSSION Table 1 lists the days on which observations were made, the number of animals tagged and their weights. It should be noted that during the month of August, on 15 days of searching, 2-6 animals were found on only 4 days. Between the 11th and 26th of August (last observation date), no animals were found. Table 2 shows the number of times animals were found in contact or copulating. In addition, 194 sea hares were found not engaged in either activity. Table 2 Aplysia punctata copulating or in contact: Number of times seen. Number of animals A. Copulating 2 3 4 89 7 SP B. Contact 2 3 4 7 22 9 5 2 “Weights of one chain of 4 not obtained. Table 3 shows that a significant number of copulating pairs found during the observation period were composed of sperm donors which were smaller than sperm recipients (one-sample Chi-squared test (SIEGEL, 1956), p< 0.001). Given the results of this statistical analysis, pairs in which donors were smaller than recipients were classed as “typical,” and others as “‘atypical.” Table 4 shows that the donor in the most frequently found relationship, 7.e., “typical” donor (D‘), is, indeed, smaller than the recipient in the “typical” relationship (R‘). R‘ is smaller than either of the other animals in the “atypical” pairing, that is, R*; where “t” stands for “typical” and “a” stands for “atypical.” The recipient in the typical pairing (R‘) is also larger than the recipient in the atypical pairing (R°). The lack of a significant difference in weight between R‘ and D* would seem to indicate that at a certain weight, these sea hares are as likely to be found acting as sperm donors as sperm recipients. In the laboratory, 2 sea hares (Aplysia punctata Cuvier, 1803), weighing 3g and 8.7g were seen copulating, the smaller being the sperm donor. The smaller sea hare was seen acting as sperm donor until it weighed 7.1g two weeks later. Subsequently both animals assumed both roles and laid eggs. The sea hare that acted as recipient in the early copulations first laid eggs when it weighed 11.6g. LEDERHENDLER (1978) reported that a pair of A. dactylo- mela first copulated when weighing 58 g and 53 g, the for- mer being the sperm donor. However, subsequent to this first copulation, the smaller of the 2 was the sperm donor on the 3 occasions when copulation took place. The size relationship seems to be similar in the A. dactylomela, which appear to attain greater size than A. punctata (see CarEFOOT, 1967 for A. punctata and Tobach, unpubl. data for Bimini; and LEDERHENDLER et al., 1977, for Puerto Rico for A. dactylomela). The weights of the laboratory Aplysia punctata are in a very different range from those observed in the field. However, in the pair described above which was followed daily in the laboratory, the size relationship was consistent with the field data. These data are preliminary in that the sampling tech- nique was restricted to a particular field population at only one point in their daily activity under one tidal con- Vol. 23; No. 2 THE VELIGER. Page 161 Eee ere eee ———————————eeeeeEeEeEeE=—EeEeeeeeeee Table 3 Patterns of copulation and individual weights of Aplysia punctata. A. Paired Animals Donor smaller Donor larger Donor equal than recipient than recipient to recipient Number of pairs? 564 252 8 Weights (g) Donor: Median 30 50 43 Range from 20 25 30 to 70 75 60 Recipient: Median 50 35 See above Range from 30 25 to 75 65 B. Chains of 3 and 4 Animals Copulatory relationships® Donor Donor and recipient Recipient Typical Chain of 3 20 30 40 of 3 25 30 40 of 4 30 35 60 40 Atypical Chain of 3 45 40 35 of 3 60 40 30 Mixed Chain of 3 40 30 40 of 3 25 40 35 of 3 35 35 65 of 4 30 30 70 44 3X? = 37.8; p < 0.001. 4This relationship, i.e., donor (D) < recipient (R) in weight, is classed as “typical” (“t”), because of the significant X2. >This relationship, i.e., donor > recipient is classed as “atypical” (“a”), for the same reason. ®Categories “typical,” and “atypical” based on statistical analysis of data for paired animals in “A” above. “Mixed” indicates that donor/ recipient was “typical” for one part of the chain and “atypical” in another part. dition. These findings suggest, however, that the commonly Literature Cited held belief that Aplysia assume both roles soon after meta- hosis needs to be re-examined, and that further stud Carzroor, T. H. ee ‘ y 1967. Studies on a sublittoral population of Aplysia punctata. is warranted. Journ. Mar. Biol. Assoc. U. K. 47: 335-350 Vol. 23; No. 2 Page 162 THE VELIGER Table 4 Analysis’ of weights of copulating pairs of Aplysia punctata. Distribution according to median weight (40g) for combined groups iu Da > R@ pt“p” > 0.05 D2 < R42; “p” < 0.02 D2 and R@; do not differ: “p” > 0.10 Rt > R4; “p” < 0.001 Siece., S. 1956. Nonparametric statistics for the behavioral sciences. Mc- Graw-Hill Book Co., New York LEDERHENDLER, Izya, Larry BeLt & ETHEL ToBACH 1975. Preliminary observations on the behavior of Aplysia dactylomela (Rang, 1828) in Bimini waters. The Veliger 17 (4): 347-3533 1 text fig. (1 April 1975) LEDERHENDLER, Izya, K. Herrices & ETHEL ToBACH 1977. Taxis in Aplysia dactylomela (Rang, 1828) to water-borne stimuli from conspecifics. Anim. Learn. Behav. 5: 355 - 358 LEDERHENDLER, Izja & ETHEL ToBACH 1977- Reproductive roles in the simultaneous hermaphrodite Aplysia dactylomela. Nature 270: 238 - 239 ToxsacH, ETHEL 1978. Further field notes on the behavior of Aplysia dactylomela. The Veliger 20 (4): 359-360 (1 April 1978) Tosacu, ETHEL, PETER GoLp & Amy ZIEGLER 1965. Preliminary observations of the inking behavior of Aplysia (Varria). The Veliger 8 (1): 16-18 (1 July 1965) Vol. 23; No. 2 THE VELIGER Page 163 Reproductive Biology of Assiminea californica (Tryon, 1865) (Mesogastropoda : Rissoacea ) BRUCE H. FOWLER Department of Biological Sciences, San Jose State University, San Jose, California 95192 (3 Text figures) INTRODUCTION Assiminea californica (Tryon, 1865) is A SMALL mud snail inhabiting coastal saltmarshes from Vancouver Island, Canada to Cabo de San Lucas, Baja California, Mexico (KEEN, 1971). Although this snail occurs com- monly in California saltmarshes, there is little information in the literature except for occasional appearances in spe- cies lists. The reproductive biology of the genus Assiminea is known for only a few species. The anatomy of the repro- ductive systems of Assiminea grayana Fleming, 1828 is de- scribed and illustrated by Krux (1935: 431, 449; figs. 15, 21). Portions of the reproductive anatomy of several Phil- ippine Assiminea are described and diagramed by ABgotr (1958: plts. 16, 19, 20, 21, 23, 24). The larval morphology, oviposition, and seasonality of A. grayana are discussed by SANDER (1950 and 1952), and SANDER & SIEBRECHT (1967). Some ecological aspects of hatching are discussed by SEELEMAN (1968). The genus Assiminea is dioecious. ACKNOWLEDGMENTS This account is based on a portion of a thesis submitted in partial fulfillment of the requirements for the degree Master of Arts to San Jose State University, San Jose, California (FowLER, 1977). Although several people were helpful in the research and writing, two were instrumental to its conception and completion. Dr. Vida C. Kenk of San Jose State Univer- sity served as a supervisor, mentor, and friend throughout the research and writing. James T. Carlton of The Uni- versity of California, Davis provided the initial idea and early information of this subject. I would also like to thank the City of Palo Alto for permission to work in their saltmarshes. MATERIALS anp METHODS All snails used for this study were collected in the salt- marshes of San Francisco Bay at Palo Alto, California. Collections were carried out at least once each month to monitor possible seasonal changes in reproductive anat- omy. Snails from Elkhorn Slough, Bodega Harbor and Humboldt Bay, California, were used for anatomical com- parison. Reproductive anatomy was determined by dissection of living animals in an isotonic sea-water solution. Snail innervation was determined by dissection and by obser- vation through the integument of animals cleared in dis- tilled water for a few hours. Testis epithelium was examined histologically by stain- ing the whole testis with aceto-orcein (1%) for 1 hour after a 45-60 minute soak in distilled water. The testis was then ruptured, spread on a slide, and allowed to dry. The prep- aration was covered with mounting medium and coverslip. Young snails were reared on a thin layer of mud in cov- ered petri dishes that were moistened periodically with distilled water. Adults were placed in the dishes for a few days until they had laid several eggs, then removed. REPRODUCTIVE ANATOMY The reproductive systems of snails from all localities are identical to the systems of snails from San Francisco Bay. Male System: The testis lies in the third whorl of the shell (Figure 1); the mantle between the shell and testis is heavily pig- mented. The exterior epithelium of the testis is covered with small yellow granules which become more dense toward the ends of the lobes. The interior consists of a clear colorless fluid that usually does not contain sperm. pn sd Figure 1 Male genital system of Assiminea californica i — intestine il - intestinal loop Pp — penis pn — penial nerve pst — prostate sd - spermduct portion of vas deferens sv — seminal vesicle portion of vas deferens t — testis vd — vas deferens Sperm are produced in localized areas within the epi- thelium; cells in certain areas undergo meiosis forming spermatids in large numbers, while elsewhere little meiotic activity takes place. Periodically, the cells that hold the fully developed sperm cells rupture; the sperm aggregate in parallel, forming bundles of several cells attached at their heads. At these times the sperm bundles fill the tes- ticular lobes and lumen while traveling to the vas deferens. The vas deferens consists of several distinct sections. The long folded section near the testis acts as a seminal vesicle; the sperm within cause it to be a characteristic iridescent orange in life. A thin empty tube connects this folded sec- tion to the prostate. Emerging from the prostate it becomes a highly ciliated and rigid sperm duct. The duct parallels the intestine for a short distance before entering the head of the animal. At the base of the penis it makes a double loop before continuing to the penis tip. The prostate, variable in size and shape, lies next to the intestine in the region of the intestinal loop. This organ is THE VELIGER Vol. 23; No. 2 innervated by two small nerves from the right visceral ganglion. The large flat penis originates at the center of the an- imal’s back within the mantle cavity. The epidermis around the tip is thickened, and the sperm duct protrudes through this thickening as an annulated projection (Figure 2a). The penis is innervated by a single large nerve from the right pedal ganglion. tep a pa 20 pm oe Figure 2 Assiminea californica a — penis tip b — sperm pa — annulated tip of penis tep — thickened epidermis The sperm dissociates from the bundles within the vas deferens, but remains more or less parallel to the other sperm. The sperm possesses an extremely long tail which undulates in corkscrew-shaped waves. The sperm head is small and vermiform (Figure 2b). Female System: The ovary extends from the third whorl to the apex of the shell, intermingled with the digestive gland (Figure 3). Unlike the testis, the mantle is not heavily pigmented be- tween the ovary and shell. Contents of the ovary are of a grainy white nature with several eggs in various stages of maturation. ae Vol. 23; No. 2 THE VELIGER Page 165 The oviduct follows the columella down to the seminal receptacle. Just before connection to the seminal recep- table the oviduct becomes a thick rigid loop. The contents of this loop, usually including sperm, are churned about rapidly by ciliary action. Shortly after the connection to the receptacle the oviduct enlarges into a chamber within the albumen gland. The bursa connects to the oviduct at this chamber. The oviduct continues through the capsule gland to the genital pore. The pore and the anus are in close proximity to the right ciliary trough which leads to the anterior foot. The albumen and capsule glands join together into one continuous glandular mass. These glands are innervated by two small nerves from the right visceral ganglion, which arise from the same region of the ganglion as the prostate nerves in the male. The seminal receptacle contains sperm throughout the year. The sperm tails are in constant motion within the bulb but the heads are attached to or are in close proximity Nee fp Figure 3 Female genital system of Assiminea californica b — bursa cg — capsule gland fp — female pore i — intestine il — intestinal loop © — ovary od — oviduct odc - oviduct chamber po — pallial oviduct sr — seminal receptacle ag — albumen gland cl — ciliated loop of oviduct to the bulb wall. The sperm within give the receptacle its characteristic iridescent orange appearance. MORPHOLOGY or EGG CAPSULES AND YOUNG In habitat containers, egg capsules are found to be pushed into the mud and deposited singly. The capsules are nearly spherical, about 0.5mm in diameter. A thin sticky mucus coating causes mud and detritus particles to adhere to the egg, rendering it almost undetectable visually in the substrate mud. The young snail emerges by splitting the wall, but there does not appear to be any pre-deter- mined line of weakening on the egg capsule. The thin transparent capsule wall allows observation of the devel- oping embryo during all stages of development. The veliger stage passes completely within the capsule and the young at hatching crawls away from the empty case. The animal is not pigmented at hatching, appearing translucent blue-white in color; the protoconch is calcified and consists of 1.5 whorls. The animal becomes noticeably pigmented after several weeks within the habitat con- tainer. SEASONALITY The reproductive anatomy of these snails shows no sign of atrophy during any part of the year. Snails, however, are more active during the wetter portions of the tidal cycle (during the spring tides), and during rainy weather. Cop- ulating pairs are only found during these times of high humidity, but are never found submerged in water. DISCUSSION The male reproductive systems of the species in the genus Assiminea are very similar in structure consisting of the multi-lobed yellow testis, a long and usually folded vas deferens (ABBOTT, 1958: 223, 224). The prostate gland is large in Assiminea grayana (FRETTER & GRAHAM, 1962: 583) as is the prostate in Asstminea californica. The penis (or verge) of Assiminea varies in form from a long thin appendage that may have a swollen tip, to a shorter thicker form (ABBOTT, of. cit: 224). Other features of the penis are a fleshy flap on one side of the penis in Assizminea habei habei Abbott, 1958 (ABsort, of. cit.: 253, plt. 16, figs. 7, 11) and swellings or bumps in Asstminea grayana (KRULL, 1935: 433, fig. 15). Page 166 THE VELIGER Vol. 23; No. 2 The female system is known only from Assiminea gray- ana and consists of an ovary, short oviduct, which makes a loop similar to that in A. californica just before connec- tion to the bursa, a seminal receptacle, and glandular mass. Unlike A. californica, the oviduct in A. grayana spirals slightly through the glandular mass before reaching the female pore. (KRULL, 1935: fig. 21) Egg deposition and larval development are known only from Assiminea grayana which, while ovipositing eggs singly, deposits them in a mass of several small capsules (SANDER, 1952: 133-134; fig. 1). These masses are over- laid by a covering of fecal pellets (SANDER & SIEBRECHT, 1967: 142). The eggs hatch as free-swimming veligers (SANDER, 1950: 148; fig. 2), but the hatching of the veli- gers may be delayed; the eggs may sit ready to hatch for several days to months (SEELEMAN, 1968: table pp. 364- 365; SANDER & SIEBRECHT, 1962: 144-145; table 1). The reasons for such different reproductive strategies in Assiminea grayana and A. californica are unknown at this time. A consequence of the lecithotelic (large, yolky egg) and crawl-away young of A. californica is that the pockets of the populations of this snail, while geographically close, are somewhat isolated. Genetic mixing would only occur by the chance transport of individuals or eggs. More study is needed to determine the extent of popu- lation differences (if any) from throughout the range of Assiminea californica. Literature Cited Assott, RoBertT TUCKER 1958. The gastropod genus Assiminea in the Philippines. Proc. Acad. Nat. Sci. Phila. 110: 213-278; plts. 15-25 Fow er, Bruce HANSEN 1977. Biology and life history of the saltmarsh snail Asstminea cali- fornica (Tryon, 1865). M. A. thesis, Dept. Biol. Sci. San Jose State Univ. 165 pages; 28 plts. Fretrer, Vera & ALASTAIR GRAHAM 1962. British prosobranch molluscs, their functional anatomy and eco- logy. London, Ray Soc. xvi+755 pp.; 316 figs. Keen, A. Myra 1971. _ Sea shells of tropical West America: marine mollusks from Baja California to Peru, 224 ed. Stanford Univ. Press, Stanford, Calif. i-xiv+ 1064 pp.; ca. 4000 text figs.; 22 col. plts. (21 September 1971) Kru, HERBERT 1935. | Anatomische Untersuchungen an einheimischen Prosobranchiern und Beitrage zur Phylogenie der Gastropoden. Zool. Jahrb., Anat. Ont. 60: 399 - 464; 21 figs. SANDER, KLAus von 1950. Beobachtungen zur Fortpflanzung von Assiminea grayana Leach. Arch. Molluskenk. 79: 147-149; 3 figs. 1952. Beobachtungen zur Fortpflanzung von Assiminea grayana Leach (2). Arch. Molluskenk. 81: 133-134; 2 figs. SANDER, KiAus von # LiutTa SIEBRECHT 1967. Das Schliipfen der Veligerlarve von Assiminea grayana Leach (Gastropoda, Prosobranchia). Zeitschr. Morph. Okol. Tiere 60: 141-152; 5 figs. SEELEMAN, URSULA 1968. Zur Uberwindung der biologischen Grenze Meer-Land durch Mollusken II. Untersuchungen an Limapontia capitata, Limapontia depressa und Assiminea grayana. Oecologia 1: 356-368; 8 figs. Vol. 23; No. 2 THE VELIGER Page 167 Magnetic Radular Teeth and Geomagnetic Responses in Chitons JACK TOMLINSON’, DEBRA REILLY? anp ROBERT BALLERING 3 (1 Text figure) SPENCER THorRPE discovered that chiton radulae have ferromagnetic teeth (reported by ToMLINSON, 1959). An- alysis by LowENSTAM (1962, 1967; Towr & LowENSTAM, 1967) revealed that the material on the teeth contains magnetite, lepidocrocite and iron-bearing apatite. Al- though CarEroor (1965) suggests that this material is pri- marily an adaptation to feeding, LowENsTAM (1962) spec- ulated that this magnetite material might enable homing orientation in chitons, but ErsscHuTz et al. (1967) dispute this. Frank A. Brown, Jr., and his colleagues have done much work with magnetic compass reactions, primarily with the snail Nassarius (Illyanassa) obsoletus (Say, 1822) and with planarians (1965). Work prior to 1964 is re- viewed by MapELEINE BarNnoTHy (1964). More recent work on magnetic field orientation includes bacteria (BLAKEMORE, 1975; FRANKEL et al., 1979), bees (GouLD et al., 1978), flies (BECKER, 1965; BECKER & SPECK, 1964; Picton, 1966; WEHNER & LABHART, 1970), elasmobranchs (H. R. Brown et al., 1979) and birds (BooKMAN, 1977; KEETON, 1971; KREITHEN & KEETON, 1974; SOUTHERN, 1975; WatcotrT et al., 1979, W. & R. WitTscHKo, 1972). KirscHvinkK & LOwENSTAM (1979) studied chiton mag- netite with implications for marine sediment natural mag- netizations. RATNER & JENNINGS (1968) tested chitons in magnetic fields ranging from normal to 8000 gauss. The chitons showed reduced movement in above-normal magnetic fields. They reported that the chiton seemed equally likely to orient in any compass direction. The reduction of chiton movement by stationary mag- nets may be due to the pull on the ferromagnetic radula. If this is so, then a moving magnetic field might be very ' Present address and address correspondence to: Department of Biological Sciences, San Francisco State University, 1600 Hollo- way Avenue, San Francisco, CA(lifornia) 94132 2 Present address: Biology Department, University of California, Berkeley, CA 94720 3 Present address: Weed Junior High School, Weed, CA 96094 stimulating indeed. The handiest moving magnetic field readily available in most laboratories is a standard lab- oratory magnetic stirrer. One of us (J.T.) put a Lepidozona sp. on a Corning HCT Plate Stirrer, of approximately 700 gauss, and in 10 minutes the chiton had made a backing turn of almost 360°. Several species of chitons have clearly indicated detection of the field. Species include Katharina tunicata (Wood, 1815), Lepidozona cooperi (Carpenter in Pilsbry, 1892), L. mertensii (Middendorff, 1846), Mopalia lignosa (Gould, 1846) and Nuttallina californica (Reeve, 1847). In order to determine that it was the rotating magnetic field and not vibration or other extraneous stimulation, we placed a sheet of steel (16 gauge) between various brands of stirrer and the chiton. The response was greatly re- duced, to the extent that movements could not be distin- guished from non-rotating (power-off) conditions. If the chiton moved with its anterior end off the sheet of steel, or if the chiton were placed on a thin sheet of plastic over the steel and the steel pulled out gradually, a very strong response was shown immediately after the radular area was exposed to the rotating magnet. Since it can be demonstrated that chitons can detect this magnetic field, it would not be surprising if they can detect the earth’s magnetic field. Field measurements were made by all three authors independently, and by several other students as well, although the initial observation was Ballering’s. A compass was placed directly above each chiton seen, the bezel was turned until the needle indicated north, and the headings were recorded and plotted on polar coordinates (Figure 1: A-C, I-K). It can be seen from inspection that the predominant orientation is north- erly. Chi-square tests of chitons observed oriented 271-89° (northerly) versus 91-269° (southerly), with equal numbers expected, yielded probabilities of less than 1 in 10000 (P ) Figure 1 Polar coordinate plots of the compass headings (anterior ends) of chitons at various intertidal areas of central California. Length of line is proportional to number of individuals: Circle is 5, broken circle 10 individuals. A dot above each array indicates true north, a line indicates magnetic north. All are Mopalia muscosa, except B and C. A-C. Data by El-Ahmadiyyah: A. Pebble Beach State Park. 37°14’N2 B. Katharina tunicata. Fort Ross. 38°31’ N? C. Katharina tunicata. Bodega Bay. 38°18’ N' D -F Data by Vital, all from Pillar Point, 37°30’ N D. On 1 mm plate aluminum? E. On 6mm plate steel F Surrounded by steel pipe 4 - 6 mm thick G -H. Data by Klise, all from Mussel Rock. About 37°40’N G. In aluminum roaster pan with lid * H. In steel roaster pan with lid I-K. Data by Ballering I. RCA Reef. 37°56’N'™ (see text) J. Duxbury Reef. 37°54’ N? K. Pebble Beach State Park. 37°14’ N? L-M. Data from Reilly, all from Duxbury Reef. 37°54’ N L. In aluminum pans with lids* M. In iron and steel pans with lids ' Significant at the 0.01 level Significant at the 0.001 level nificant. Stephen Vital placed over a hundred chitons (Mopalia muscosa) on identically-painted sheets of alumi- num or steel plate. The chitons initially deposited facing east or west on the aluminum plates for 30 minutes ori- ented northerly very significantly (P | © 4.80 10.4 22.5 5.5 5.0 9:5 22.0 5:5 4-75 10.2 21.0 5.0 4.50 PoLYGYRDDAE The basic taxonomy in this family follows that of Pixs- BRY (1940). Triodopsis germana (Gould, 1851) Although widely distributed throughout the western slopes of the Cascades, T. germana does not appear to be abundant inland from the coastal lowlands. The following specimens were secured: 4 (8), 5 (6), 26(2), 67 (2), 78 (2). Triodopsis devia (Gould, 1846) There are few records for this species from Washington, most of them coming from the lowlands around Puget Sound (Pitspry, 1940). The five specimens reported here were secured from Station 20. Allogona townsendiana (Lea, 1838) As indicated elsewhere (BRANSON, 1977), A. townsend- zana is more or less restricted to the moist western portions of Washington, hence it was surprising to find the 8 living specimens at Station 5. At the time, this park was newly opened and disturbance had been held to a minimum. Vespericola columbiana (Lea, 1838) This is the most widespread and abundant polygyrid snail in the state of Washington, particularly in lowland situations. The following specimens are reported: 4 (8), 5 (6), 6 (4), 8 (2), 23 (2), 25 (4), 27 (2), 33 (2), 34 (6), 35 (4), 37 (2), 49 (2), 56 (2), 59 (4), 6 (2), 62 (4), 65 (10), 67 (4), 68 (6), 74 (8), 75 (2), 84 (6). HAPLOTREMATIDAE Haplotrema vancouverensis (Lea, 1839) Widely distributed from northern California to Alaska, this species penetrates farther inland and to higher eleva- tions than I previously believed, although it is most abun- dant in the lowlands and coastal areas west of the moun- tains. At Mount Baker, the species is not uncommon near timberline (1 372m) and at Mount Rainier living speci- mens were collected at 1 525m elevation. Specimens taken from the higher elevations tend to be more olive-green and lighter behind the aperture than ones living in lowland situations. The following specimens are reported: 4 (14), 6 (10), 9 (4), 26 (8), 30 (2), 33 (6), 34 (14), 35 (4), 37 (6), 43 (2), 51 (2), 58 (6), 59 (2), 67 (4), 68 (4), 72 (6), 74 (2), 81 (2). Haplotrema sportella (Gould, 1846) This species, coarse-sculptured and variable, also has a relatively wide distribution in the Cascades and adjacent areas. Our collections include the following data: 5 (18), THE VELIGER Page 175 Vol. 23; No. 2 8 (2), 9 (12), 10 (8), 63 (2), 65 (10), 66 (8), 67 (4), 37 (2), 40 (4), 59(2), 24 (4), 26 (14), 27 (4), 33 (6), 68 (6), 72 (2), 74 (16), 76 (2), 78 (2), 80 (4), 84 (4). ZONITIDAE Euconulus fulvus (Miiller, 1774) Distributional records for this species are rather scanty in Washington, doubtless because of inadequate collect- ing. The following specimens were collected: 9 (2), 12 (2), 13 (2), 14 (2), 18 (2), 19 (6), 27 (2), 31 (2), 59 (2), 60 (2), 80 (2). Retinella electrina (Gould, 1841) Apparently quite uncommon in the Pacific Northwest. A total of three specimens, one each from stations 8, 45, and 75, were collected, all from beneath large rocks. Retinella binneyana occidentalis H. B. Baker, 1930 Likewise, not an exceptionally common species. All specimens reported here exhibit a fine spiral sculpturing under magnification: 18 (4), 33 (2), 56 (2), 76 (2). Pristiloma stearnsi (Bland, 1875) A single specimen was secured at Station 9 from leaf litter. The species was also rarely encountered on the Olympic Peninsula (BRANSON, 1977). Pristiloma arcticum (Lehnert, 1884) Although I previously reported this species from the Olympic Peninsula (BRANSON, 1977) and mounts Baker and Adams, near timberline, during this investigation specimens were collected at Mount Rainier National Park: 60 (2), 62 (4), 68 (6). Pristiloma lansingi (Bland, 1875) Probably the most abundant Pristiloma on the Olympic Peninsula (BRANSON, 1977), P. lansingi shares its abun- dance with the next species in the Cascades. Specimens were collected from the following localities: 67 (2), 68 (2), 74 (2), 76 (2), all from leaf litter. Pristiloma johnsoni (Dall, 1895) This species ranges farther downslope towards the low- lands than most other Pristiloma. For example, the speci- mens from station 33 were found near sea level. Collec- tions: 26 (4), 27 (6), 31 (2), 33 (2), 65 (4). Pristiloma wascoense (Hemphill, 1911) This transparent species was previously known in Wash- ington only from a site 1 540m high on the Olympic Penin- sula (BRANSON, 1977). The collections reported here are all from Mount Rainier: 54 (2), 58 (6). Both sites are above 1500 m in elevation. Zonitoides arboreus (Say, 1816) Although occurring on both the dry and wet sides of the mountains, as documented by our collections, Z. arboreus is much more common in the dry zones of eastern Wash- ington than in the west. Collections: 9 (2), 12 (10), 15 (10), 17 (4), 19 (2), 20 (5), 22 (2), 50 (5). Striatura pugetensis (Dall, 1895) Typical specimens were collected from the following sites: 26 (2), 27 (4), 31 (4), 33 (2), 45 (2), 56 (2), 62 (2), 65 (4), 66 (8), 74 (2), 75 (2), 76 (2), 80 (4). Vitrina alaskana Dall, 1905 Found both at high elevations, as at stations 54 and 57, this fragile species was also found at lower elevations on the eastern slopes of the mountains. The habitat condi- tions at Station 19, from which the largest collection was taken, are extremely arid. Collections: 12 (6), 14 (4), 15 (8), 18 (6), 19 (20), 20 (2), 54 (2), 57 (10). ENDODONTIDAE Discus cronkhitei (Newcomb, 1865) There are few records for this species in Washington (Pitspry, 1946; BRANSON, 1977), and the single specimen from Station does not increase the knowledge much. Punctum randolphi (Dall, 1895) Ranging from near sea level to nearly timberline, P. randolphi is widespread on the western slopes of the Cascades, where it is nearly as common as the next spe- cies. Collections: 33 (2), 66 (8), 67 (2), 68 (2), 75 (2), 76 (12). Punctum conspectum (Bland, 1865) Collections: 15 (2), 27 (2), 31 (2), 56 (2), 57 (2), 58 (18). PUPILLIDAE Pupilla hebes (Ancey, 1881) This is the only common pupillid at and above timber- line in the Cascades, although our collections only include four specimens from Station 68, all living. Vertigo columbiana Sterki, 1892 Collections: 68 (3). Vertigo modesta (Say, 1824) Collections: 60 (2). VALLONDDAE Planogyra clappi (Pilsbry, 1898) Collections: 33 (4), 76 (2). Page 176 THE SLUGS The state of Washington truly has a mammoth slug problem, principally because of Arion ater (BRANSON, 1977; Hanna, 1966). The moist, heavily vegetated coastal areas are perfect habitats for slugs, some areas producing as many as 50 individuals per square meter, particularly in the coastal strawberry fields. In these situations, exotic species far outnumber the native ones. LIMACIDAE Deroceras reticulatum (Miller, 1774) Commonly found around human habitations in Wash- ington (BRANSON, 1977) Collections: 5 (2). Deroceras laeve (Miller, 1774) Collections: 7 (2), 33 (4). Limax maximus Linnaeus, 1758 This large exotic slug has a spotty distribution in Wash- ington, mostly around human habitations and disturbed areas. Collections: 8 (2), 26 (2), 33 (3), 47 (2). ARIONIDAE Some of the more important references to the destruc- tive members of this family are Pirsspry (1948), Quick (1949), BurcH (1960), HANNA (1966), CHICHESTER & Getz (1969), RoLLo & WELLINGTON (1975). Arion ater (Linnaeus, 1758) In coastal humid Washington, A. ater is the most com- mon slug encountered, far outnumbering native slugs, and at some sites in Mount Baker National Forest (Station 28, for example) the species is approximately twice as abun- dant as the native banana slug, the black variety being three times as common as the orange or red. The follow- ing specimens were retained for the records but do not indicate relative abundance: 5 (6), 8 (1), 26 (4), 28 (4), 30 (1), 32 (2), 33 (6), 39 (1), 40 (1), 47 (1)—a huge population in this park, over 200 specimens being counted at one garbage can—70 (1 )—50 per square meter counted at the margin of this strawberry field. Prophysaon andersoni (J. G. Cooper, 1872) Collections: 20 (2). Prophysaon foliolatum (Gould, 1851) Although quite common along the periphery of the Olympic Peninsula, only one specimen was taken from the THE VELIGER Vol. 23; No. 2 mainland (Station 72). The type locality for the species lies near Fort Townsend on the Peninsula (Pitspry, 1948). Prophysaon vanattae Pilsbry, 1948 The most widespread and abundant Prophysaon in mainland Washington and adjacent Canada. Collec- tions: 2 (2), 9 (6), 19 (8), 26 (2), 37 (2), 47 (4), 50 (4), 59 (2), 60 (2), 69 (2), 71 (2), 79 (4). Ariolimax columbianus (Gould, 1851) Collections: 5 (6), 9 (4), 23 (2), 26 (2), 28 (4), 30 (4), 33 (2), 45 (2), 47 (4), 59 (4), 62 (1), 72 (2), 74 (2). Hemphillia dromedarius Branson, 1972 Collections: 6 (1), 37 (1), 48 (1), 49 (1), 59 (2). Literature Cited Branson, BRANLEY ALLAN 1969. Distribution notes on western and southern snails. Sterki- ana 36: 21 1972. Hemphillia dromedarius, a new arionid slug from Washington. The Nautilus 85: 100- 106 1975a. Radtodiscus hubrichti (Pulmonata: Endodontidae), a new spe- cies from the Olympic peninsula, Washington. The Nautilus 89: 47-48 1975b. Hemphillia pantherina, a new arionid slug from Washington. The Veliger 18 (1): 93-94; 1 text fig. (1 July 1975) 1977. Freshwater and terrestrial Mollusca of the Olympic Peninsula, Washington. The Veliger 19 (3): 319-330; 1 plt.; 1 text fig. (1 January 1977) Branson, BranLEyY ALLAN, Morcan Emory Sisk e« C. J. McCoy, Jr. 1966. Observations on and distribution of some western and south- western mollusks. The Veliger 9 (2): 145-151 (1 October 1966) Burcu, JoHN BayarD 1960. Some snails and slugs of quarantine significance to the United States. Sterkiana 2: 13-53 CuicHester, L. F « L L. Getz 1969. | The zoogeography and ecology of arionid and limacid slugs intro- duced into northeastern North America. Malacologia 7(2-3): 313 - 346 (13 October 1969) Hanna, G Da.ias 1966. Introduced mollusks of western North America. Occas. Pap. Calif. Acad. Sci. 48: 1 - 108; plts.1 - 4; 85 text figs. (16 February 1966) HENDERSON, JUNIUS 1929. The non-marine Mollusca of Oregon and Washington. Univ. Color. Stud. 17: 47 - 190 1936. The non-marine Mollusca of Oregon and Washington—supple- ment. Univ. Color. Stud. 23: 251 - 280 Pirssry, Henry AuGustTus 1903. Shells of Douglas County, central Washington. The Nauti- lus 17 (7): 84 (6 November 1903) 1939. Land Mollusca of North America (north of Mexico). Acad. Nat. Sci. Phila. Monogr. (3) 1 (1): i-xviiit1-573+1- ix; figs. A, B, 1 - 377 (6 December 1939) 1940. Land Mollusca of North America (north of Mexico). Acad. Nat. Sci. Phila. Monogr. (3) 1 (2): i-vilit575 - 994+i- ix; figs. 378 - 580 (1 August 1940) 1946. Land Mollusca of North America (north of Mexico). Acad. Nat. Sci. Phila. Monogr. (3) 2 (1): i-voii +1-520; figs. 1-281 (6 December 1946) 1948. Land Mollusca of North America (north of Mexico). Acad. Nat. Sci. Phila. Monogr. (3) 2 (1): i- viiit1 - 520; figs. 1-281 282 - 585 (19 March 1948) Quick, H. E. 1949. Synopsis of the British fauna. No. 8. Slugs (Mollusca). Testa- cellidae, Arionidae, Limacidae. Linn. Soc. London 8: 1 - 29 Roxio, C. Davw & W. G WELLINGTON 1975. ‘Terrestrial slugs in the vicinity of Vancouver, British Columbia. The Nautilus 89: 107-115 Vol. 23; No. 2 THE VELIGER Page 177 Spawning in a British Columbia Population of Northern Abalone, Haliotis kamtschatkana BY PAUL ALLAN BREEN anp BRUCE EDWARD ADKINS Department of Fisheries and Oceans, Fisheries and Marine Service, Resource Services Branch Pacific Biological Station, Nanaimo, British Columbia, Canada VoR 5K6 INTRODUCTION THE NORTHERN ABALONE (Haliotis kamtschatkana Jonas, 1845) has supported a commercial fishery of 500000- 1 000 000 pounds (225-450 t) annually in British Columbia since 1976. Because of interest in both management prob- lems and artificial culture, the reproductive biology of abalones worldwide has been well studied (see Mottet, 1978 for review). However, the spawning behaviour and season of H. kamtschatkana are not well described either in British Columbia or elsewhere. The season of spawning is of direct interest in regulating the fishery, especially if abalone are less valuable as a product or are more vul- nerable to damage near spawning. Spawning behaviour also has some implications for management, which will be discussed below. QuayLE (1971) studied reproduction in this species by examining gonad sections from at least 25 individuals per month, taken from several British Columbia locations. Although his study lasted several years, he could find no demonstrable cycle, and he found ripe abalone through- out the year. Some recovering gonads were observed from April through June, and a spontaneous spawning was observed in May among individuals held in the laboratory; both suggesting natural spawning in that part of the year. Hahn (unpub. MS) studied seasonal changes in gonad index and spawning phase in this species at a California site, and found that spawning occurred in March or April of three consecutive years. As Quayle had observed, there was considerable variation around the seasonal pattern, and partially spawned individuals were found throughout the year. OBSERVATIONS These observations were made on 16 July 1979, on the east coast of Lyell Island (52°38.4’N; 131°27.3’ W), one of the Queen Charlotte Islands. This area has been closed to commercial fishing since 1975, and has a dense popu- lation of abalone in a wide range of sizes (BREEN & ADKINS, 1979). The substrate is solid smooth bedrock, undulating over a shallow slope and broken by wide shallow crevices and patches of boulders. Before the time that we observed spawning, we col- lected, tagged and replaced approximately 500 abalone by 1500hrs. Plastic spaghetti tags (Floy Tag Company, Seattle) were threaded through two respiratory pores and tied. This operation was carried out on board a nearby boat concurrently with collecting. Tagged abalone were replaced as new collections were made, so that abalone were returned and replaced within a couple of hours from the time they were removed. During our collecting, we noticed that the abalone ap- peared to be unusually weakly attached to the substrate. Ordinarily we remove abalone by inserting a dull-edged diving knife under the lateral edge of the foot and twisting it, which dislodges the animal from its substrate quickly and without injury if done carefully. Normally it is possible to ‘surprise’ only a small proportion of abalone and remove them with a simple lateral push before they clamp more firmly to the rock. On this day, however, almost all abalone were very loosely attached, and we collected them by sim- ply picking them off the rock with our hands. The gonads of most individuals collected were large and turgid. Whereas handling usually causes abalone to retract Page 178 the foot tightly into the shell, these individuals remained relaxed but active, allowing easy marking and examina- tion. Many of the males exuded sperm during the tagging process. In the early afternoon, we observed a general spawning in progress at the collection site. More than half the aba- lone were involved. Many had formed close aggregations in which only one was attached to the rock, the rest being attached to that one or to others in turn attached to the bottom one. The largest group observed contained six indi- viduals. The uppermost abalone were sometimes 20-25 cm above the substrate to which the lowermost was attached. All individuals seemed only loosely attached to the rock or each other, and nearly all in such groups were spawning. Individual spawners of both sexes were also observed. Some of these were near non-spawners, but others were alone. Tagged as well as untagged individuals were spawn- ing; tagged individuals comprised no more than about 20% of the whole population within the area we exam- ined. Females spawned at intervals of 15-120 sec. by releas- ing sharp puffs of eggs, clearly visible. Male spawning was slower, more continuous and less active, punctuated by irregular strong pulses of sperm. Most of the spawning groups, and also many single spawners, had reached the highest point available in their immediate area: usually this was a ridge of bedrock or a boulder top. We found a pair of individuals approximately 1m from the bottom on a stipe of bull kelp (Nereocystis luetkeana). In addition, many had raised their bodies as far from their substrate as possible. Spawning was first observed at 1500 h and was still in progress at 1830 h when our last dive was made. The weather at the time was sunny, calm, and hot. The previous day had been the same; several days before that had been overcast but calm. Water temperature could un- fortunately not be measured, but we estimated surface temperature to be greater than 15° C. There was no sharp thermocline within the depths we observed, but the sur- face was noticeably warmer. The collecting site was lo- cated 2-5 m below chart datum, and in 3-9 m actual depth. LLW occurred at noon. The moon was in last quarter, and so LLW was between its minimum and maximum for this cycle. Visibility was at least 12 m in the early morning, but in the afternoon had decreased to 2-3m. This may have been partly as a result of the spawning, but we had ob- served decreasing visibility with rising tides on previous dives nearby. A small percentage of male red sea urchins [Strongylo- centrotus franciscanus (A. Agassiz, 1863)], limpets [Colli- sella ochracea (Dall, 1871)], and serpulid worms (Serpula vermicularis Linnaeus, 1767) were also observed spawning, THE VELIGER Vol. 23; No. 2 but no spawning females of these species could be found. Evening plankton tows were made at this location two and three days after spawning was observed, but no veli- gers were found. On 18 July at a nearby site, both males and females exuded gametes during tagging, and 8-cell larvae were obtained several hours after these were mixed in dishes. DISCUSSION Our activities may have triggered this spawning. The aba- lone we collected and replaced were all disturbed by handling and being exposed to the warm air for varying periods up to 30 min. MotTet (1978) reported handling and exposure as natural spawning stimuli. Liberation of sperm is a common occurrence when abalone are dis- turbed, and many of the males we handled exuded sperm during marking. If they continued to do so when replaced, then a considerable quantity of sperm must have been lib- erated. The presence of sex products in the water is also reported as a natural trigger for spawning (CaRLISLE, 1945), and thus marked animals may have stimulated the rest of the population to spawn. In any case, externally the abalone appeared ripe, and their uncharacteristic behav- iour may have been preliminary to a completely natural spawning. The temperature experienced by an abalone at this place would have been lowest in the morning, rising as the tide fell, with a maximum near noon; then falling again as the tide changed. If tidal temperature rhythms are a common trigger for spawning in this species, then the sea- son of spawning might vary greatly, depending on local weather conditions. Oysters in Pendrell Sound, British Columbia, whose spawning is triggered by surface tem- perature, have spawned from early June to late August in different years (QUAYLE, 1974). Whatever the reason, wide variability in reported spawning season appears to be the rule in most abalone species world-wide (MorttTeET, 1978). ; The small but unusual aggregations we observed, in which abalone were climbing on top of one another, have not been reported before. Aggregation might easily func- tion as a mechanism for ensuring maximum contact be- tween eggs and sperm, and hence a high fertilization rate. Kixucui et al. (1974) report that optimum fertilization is obtained at sperm densities of 100000- 1 900000/mL. Di- lution of sperm below this concentration would take place at a relatively small distance from spawning males. The size and number of spawning groups indicate that they have a strong adaptive role, as suggested above. If so, then severe decreases in local density might have a strong Vol. 23; No. 2 THE VELIGER Page 179 effect in reducing recruitment rate, beyond that expected from the simple reduction in the number of spawning adults. We estimate that the British Columbia abalone fishing has reduced the mean density of Queen Charlotte Islands abalone above 102mm length by 75% since 1975 (BREEN, 1980). At many sites, more drastic decreases have occurred. Recruitment failures as a result of intense harvesting are thus not surprising. The tendency for abalone to be as high up as possible during spawning was also reported by QuayLeE (1971), and Ino (1966) reported upward vertical migration be- fore spawning in Haliotis discus hannat. He observed that abalone spawning in laboratory tanks were all near the top of the water, and that some even crawled out of the tanks and fell onto the floor. This behaviour may be an indirect mechanism for aggregation, as adult density is greatest in shallow water in this part of British Columbia (BREEN & ADKINS, 1979). Alternatively, it could act as a mechanism for releasing the eggs in the warmest water available; or, finally, it could act as another mechanism for ensuring high fertilization rate. Egys released from a high place, where they fall through a water column before coming to rest on the bottom, might be exposed to more sperm than eggs which fall to the bottom immediately after being spawned. These observations extend the known spawning season of Haliotis kamtschatkana in British Columbia into mid- summer. ACKNOWLEDGMENTS We gratefully thank D. B. Quayle for helpful discussion and criticism, and Anne Parkinson, June Steube, Roy Hin- der, and Steve Head for their assistance in the field. Literature Cited BREEN, PAuL ALLAN 1980. Measuring fishing intensity and annual production in the aba- lone fishery of British Columbia. Canad. Tech. Reprt. Fish. Aquat. Sci. (in press) Breen, Paut ALLAN & Bruce EDWARD ADKINS 1979. A survey of abalone populations on the east coast of the Queen Charlotte Islands, August 1978. Fish. Mar. Serv. MS Reprt. 1490: 125 pp. Car.isLz, JouN G., Jr. 1945. The technique of inducing spawning in Haliotis rufescens Swain- son. Science 102 (2657): 566-567 Ino, TAKASHI 1966. Awabi to sono zoyoshoku. (The abalone science and its propa- gation in Japan.) Nippon Suisan Shiggen Hogo Kykai, booklet 11 (Fish. Res. Brd. Canada, Trans. Ser. 1078, 1968) Kixucui, SHoco & NaGAHISHA UKI 1974. Technical study on artificial spawning of abalone, genus Haliotis, III. Reasonable sperm density for fertilization. Bull. Tohoku Reg. Fish. Res. Lab. 34: 67-72 (Engl. abstr.) Mortret, MaDELon GREEN 1978. A review of the fishery biology of abalones. Fish. Tech. Reprt. 37: 81 pp. Quay ez, Daniet BRANCH 1971. Growth, morphometry and breeding in the British Columbia abalone (Haliotis kamtschatkana Jonas). Fish. Res. Brd. Canada Tech. Reprt. 279: 84 pp. 1974. Data report. Pendrell Sound oyster breeding 1950-1970. Fish. Res. Brd. Canada MS Reprt. 1291: 389 pp. Wash. Dept. Page 180 THE VELIGER Vol. 23; No. 2 Habitat Notes on Gastrocopta riograndensis Sterki BY RAYMOND W. NECK Pesquezo Museum of Natural History, 6803 Esther Street, Austin, Texas 78752 Reports oF Gastrocopta riograndensis Sterki, 1892 have been spotty with respect to collection and to geographic locality. The original specimens (STERKI 1891, 1892) came from Hidalgo, Hidalgo County, Texas. The first compila- tion of Texas records (SINGLEY, 1893) merely repeated this record. Singley apparently made the initial collection and sent these snails to Sterki who “semi-described” the new species. Prtspry (1917) considered the Hidalgo specimens to be river drift and added Brownsville (Cameron County) to the locality listing, but these were also river drift spec- imens; he also listed two localities from the Mexican states of Tamaulipas and San Luis Potosi. Later CHEATUM (1935) reported G. riograndensis from Limpia Canyon, Jeff Davis County, Texas, from a bed of humus below Quercus gravesu, but he also reported that “Pilsbry is not certain of the identification since the shell is possibly that of a juvenile specimen.” (This specimen, DMNH 346, is in poor shape.) The second summary of Texas snail records (STRECKER, 1935) still listed only the Sterki and Cheatum records. Husricut (1960) recovered 100 spec- imens in beach drift samples taken from sand dunes 1.6 km S of the now closed Boca Chica Pass in Cameron County approximately 4.8km north of the mouth of the Rio Grande. Of course, original provenance of these specimens is unknown. CHEATUM & FULLINGTON (1973) included Starr County from the Cheatum Collection, but added that the habitat of this species was unknown (“Our spec- imens were recovered from stream drift’). A number of these specimens (DMNH 1547) are very fresh in appear- ance, however. The Dallas Museum of Natural History has specimens of G. riograndensis collected by R. W. Fulling- ton from drift in McKittrick Canyon, Guadalupe Moun- tains National Park, Culberson County, Texas (DMNH 3273). PRATT (1976) did report G. riograndensts from rem- nant brush tracts in Hidalgo County. Pratt ( in litt.) has found G. riograndensis at a number of sites in Cameron and Hidalgo Counties in tracts of native brush. It seems to be rare except for a tract found within Bentsen-Rio Grande Valley State Park. The restricted contemporary distribution of Gastrocopta rlograndensis is apparently a long-standing character of this species. Pliocene and Pleistocene distribution of this species may also have been limited. This species apparently did not have an extended distribution into the high eleva- tions of the southeastern Rockies in extreme west Texas or southern New Mexico, because it has not been found in Pleistocene sediments (METCALF, 1967; METCALF & JOHN- SON, 1971; METCALF & SMARTT, 1974; METCALF, 1977). Extension of G. rograndensis into the Great Plains was not reported by TayLor (1960, 1966). However, presence of this species is reported from Quaternary deposits of Oklahoma (LEonarRD & FRANZEN, 1944) and northeastern New Mexico (FRYE, et al., 1978). This latter study reported no contemporary specimens in modern drift samples. Frye & LEONARD (1957) reported it questionably from Kansan deposits of Garza County and from deposits ten- tatively dated as IIlinoian of Briscoe County. Both of these counties are located along the eastern margin of the Great Plains in north Texas. Husricut (1962) reported G. rio- grandensis from an undated Pleistocene terrace in Brooks County in the South Texas Plains. Significance of this locality cannot be determined at this time. I collected Gastrocopta riograndensis approximately 42.3km S of Alpine, Brewster County, Texas, on State Highway 118 at approximate elevation of 1325m. The Crossen Mesa consists of a ridge of Tertiary (probably Eocene) calcareous tuff (volcanic ash, igneous in origin but deposited in an aqueous sedimentary environment) known as the Pruett Formation (see GotpicH & Ets, 1949). Dominant vegetation of the talus slope and out- wash consists of creosotebush, Larrea tridentata (DC.) and tarbush, Flourensia cernua DC. Also present were mesquite, Prosopis glandulosa var. glandulosa Torr.; tasa- jillo, Opuntia leptocaulis DC.; white-thorn acacia, Acacia neovernicosa Isely; and Warnock grama, Bouteloua war- nocku Gould and Kapadia. Mature and immature indi- viduals were found under rocks (tuff) and old juniper fence posts along the roadside at the foot of a gentle talus slope. Vol. 23; No. 2 THE VELIGER Page 181 Heavy rains had soaked this area during the month before this collection was made, but little moisture was evident at time of collection. Specimens have been deposited with the Dallas Museum of Natural History (DMNH 5360). Many areas in West Texas now covered by a creosote- tarbush community were originally desert grassland (Ha- VARD, 1885; HuMPHREY, 1958). Creosote invasion areas of West Texas have previously been found to be devoid of snails (METCALF, 1967: “a habitat seemingly inimical to terrestrial gastropods”). The area of collection is within an area delimited by MirstEap (1960) as one of 5 (3 in Texas, 2 in Mexico) areas of Chihuahuan Desert where relict populations of vertebrates exist at present. Fossil land snails have been recovered from undated Quaternary terrace deposits associated with Calamity Creek probably within 2km of the collection site of Gastrocopta riograndensis (ALBRITTON & BRYAN, 1939). No specimens of G. riograndensis were found although both G. contracta (Say, 1822) and G. procera duplicata (Sterki, 1912) were reported (identifications were provided by E. P. Cheatum). Time of deposition is unknown but later ter- race deposits yielded no Gastrocopta (CHEATUM in AL- BRITTON & BRYAN, 1939). Given the previous collections of Gastrocopta nogrand- ensis in wooded environments, I believe that the occur- rence in a creosote bush area was a short-term phenomenon following heavy rains. The collection site was favorable to survival of this snail because inter-rock crevices in the talus slope provide ample protected spaces in which the snails could survive for a probably short period of time. These animals probably originated from a wooded canyon habi- tat somewhere above the site of collection. FRANZEN & Lronarp (1947) concluded that G. riograndensis was a “woodland snail” based on paleobotanical work on the source formation of the Oklahoma record (CHANEY & Euias, 1936). Records of CHEATUM (1935), PRaTT (1976) and my collection verify this interpretation even though the snails I found had temporarily expanded beyond their presumed woodland habitat. Lest the occurrence of fence posts as a key part of the microhabitat of Gastrocopta riograndensis in the Chihua- huan Desert indicate a human-related origin of this pop- ulation, I have 2 observations to refute this possibility. A nearby roadside park revealed no land snails when exam- ined. Two localities in Alpine were located which con- tained land snails; neither contained G. riograndensis but both yielded G. procera (Gould) (see Neck, 1976, for dis- cussion of one of these sites). The currently-known geographic distribution of Gastro- copta riograndensts is very scattered. The known popula- tions appear to represent survival in locally favorable micro-habitats; undoubtedly additional populations will be found in the future. ACKNOWLEDGMENTS I thank W. Fullington for review of an earlier draft of this paper and identification of Gastrocopta riograndensis and D. H. Riskind for identification of Bouteloua and Acacia. W. L. Pratt provided unpublished details of his collections which were invaluable in producing this work. Literature Cited ALBRITTON, CLAupDE Carro_t, Jr. e Kirk Bryan 1939. Quaternary stratigraphy in the Davis Mountains, Trans-Pecos, Texas. Bull. Geol. Soc. Amer. 50: 1423-1474; 11 plts. Craney, R. W.« M. K. Exias 1936. Late Tertiary floras from the High Plains; with a chapter by Curtis J. Hesse on the Lower Pliocene vertebrate fossils from the Ogal- lala Formation (Laverne Zone) of Beaver County, Oklahoma. Carnegie Inst. Wash. Publ. 476: 72 pp. Cueatum, E_mer Puiip 1935- Gastropods of the Davis Mountains vicinity in West Texas. The Nautilus 48 (3): 112-116; plt. 5 (19 January 1935) Cueatum, Evmer Puiip & R. W. FuLLINGTON 1973. The aquatic and land Mollusca of Texas. Part 2: The Recent and Pleistocene members of the Pupillidae and Urocoptidae (Gastro- poda in Texas. Dallas Mus. Nat. Hist. Bull. 1 (2): i-iiit1-67; 7 pits.; 14 text figs. Denyes, H. A. 1956. Natural terrestrial communities of Brewster County, Texas, with special reference to the distribution of the mammals. Amer. Midld. Natur. 55: 289 - 320 FRANZEN, DoroTHEA SUSANNA & ARTHUR Byron LEONARD 1947. Fossil and living Pupillidae (Gastropoda: Pulmonata) in Kansas. Univ. Kans. Sci. Bull. 31: 311-411 Frye, J. C. « ARTHUR Byron LEONARD 1957- Studies of Cenozoic geology along the eastern margin of Texas High Plains, Armstrong to Howard Counties. Univ. Texas Bur. Econ. Geol. Rept. Investig. 32: 62 pp. Fryz, J. C., ARTHUR Byron Lzeonarp & H. D. Grass 1978. Late Cenozoic sediments, molluscan faunas and clay minerals in northeastern New Mexico. New Mex. Bur. Mines & Min. Res. Circ. 160: 32 pp. GotpicH, S. S. &« M. A. ELms 1949. Stratigraphy and petrology of the Buck Hill Quadrangle, Texas. Bull. Geol. Soc. Amer. 60: 1133 - 1182 Havarp, V. 1885. Report on the flora of western and southern Texas. Proc. U. S. Nat. Mus. 8: 449 - 533 HusricuT, Lesiiz 1960. Beach drift land snails from southern Texas (exclusive of Poly- gyridae). The Nautilus 74 (2): 82-83 1962. Land snails from the Pleistocene of southern Texas. Sterki- ana 7: 1-4 Humpurey, R. R. 1958. A history of vegetational change and an analysis of causes. Bot. Rev. 24: 198 - 217 LEONARD, ARTHUR Byron & DoroTHEA SUSANNA FRANZEN 1944. Mollusca of the Laverne Formation (Lower Pliocene) of Beaver County, Oklahoma. Univ. Kans. Sci. Bull. go (P&1, no. 2): 15-39 Page 182 THE VELIGER Vol. 23; No. 2 Mercatr, ArTiz Lou 1967. Late Quaternary mollusks of the Rio Grande Valley — Caballo Dam, New Mexico to El Paso, Texas. Univ. Tex. El Paso Sci. Ser. 1: 62 pp. 1977. Some Quaternary molluscan faunas from the northern Chihu- ahuan Desert and their paleoecological implications. In: Trans. Symp. Biol. Res. Chihuah. Desert Region, U. S. & Mexico (eds. R. H. Wauer & D. H. Riskind: 53-66 (Alpine, Texas, 1974). U. S. D. I. Nat. Park Serv. Trans. & Proc. Ser. 3: 658 pp. Mertcatr, Artiz Lou « W. E. JoHNSON 1971. Gastropods of the Franklin Mountains, El] Paso County, Texas. Southw. Natur. 16: 85 - 109 Mercatr, ArtTiE Lou & R. A. SMARTT 1974. Gastropods of Howell’s Ridge, Grant County, New Mexico: a fauna in the process of extinction? Southw. Natur. 19: 57 - 64 Mivsteap, WILLIAM W. 1960. Relict species of the Chihuahuan Desert. 5: 75 - 88 Neck, Raymonp W. 1976. Micro-distribution of land snails in an artificial talus slope. Sterkiana 62: 19 Prussry, Henry AucustTus 1917. Gastrocopta. pits. 1-13; figs. 1- 18 [Gastrocoptinae] Southw. Natur. p. 69 in: Man. Conch. (2) 24 (93): 1-112; (4 December 1916) Pratt, Witt1am Lioyp 1972. Land snails of the Chisos Mountains, Big Bend National Park, Texas. Bull. Amer. Malacol. Union 1972: 8-9 1976. Land snail distribution in remnant natural areas in the lower Rio Grande Valley, Texas. Bull. Amer. Malacol. Union 1976: 50 SINGLEY, J. A. 1893. A preliminary list of the land, fresh-water, and marine Mollusca of Texas. Geol. Surv. Texas, 4th Ann. Reprt. 1892: 299 - 343 STERKI, VICTOR 1891. On Pupa rupicola Say, and related forms. The Nautilus 4 (12): 139 - 143 (5 April 1891) 1892. Preliminary list of North American Pupillidae (north of Mexi- co). The Nautilus 6 (1): 2-8 (15 May 1892) Strecker, J. K., Jr. 1935. Land and fresh-water snails of Texas. Trans. Tex. Acad. Sci. 17: 4-44 Taytor, DwicHTt WILLARD 1960. Late Cenozoic molluscan faunas from the High Plains. U.S. Geol. Surv. Prof. Paper 337: 94 pp. 1966. Summary of North American Blancan non-marine mollusks. Malacologia 4 (1): 1-172 (18 August 1966) Tyer, R. C. 1975. The Big Bend. A history of the last Texas frontier. Nat. Park Serv., U. S. D. I., Washington, D. C., 288 pp. Vol. 23; No. 2 NOTES & NEWS New Records from the Tropical Eastern Pacific for Recluzia palmert (Dall, 1871) BY LEROY H. POORMAN 15300 Magnolia Street, Space 55, Westminster, CA 92683 Lymnaea palmeri Dall, 1871, was described with a bleached white beach specimen as the holotype. The loca- tion given was “near the mouth of the Taqui River, near Guaymas, Mexico.” This is presumed to be the Yaqui River which crosses Mexican Highway 15 at Bacum, about 15 kmN of Ciudad Obregon, Sonora. Ciudad Obregon is a modern city which did not exist in 1871. The mouth of the river is about 120 km SE of Guaymas. More recently, authors have recognized the marine ori- gin of the species and have assigned it to the genus Recluzia Petit, 1853. The last several years have brought to our attention 3 reports of this seemingly rare pelagic species. The first of these was made by Edith Abbott, San Dimas, California. She collected a beach specimen and a very small specimen with float which was washing in on the tide near Puerte- citos, Baja California Norte, Mexico. In June, 1978, Jewel Covey, San Carlos, Sonora, Mex- ico, found a fresh specimen without float on Cochori Beach near Guaymas. In June, 1979, Phil and Jewel Covey were walking the beach 12km south of Matanchen, Nayarit, Mexico. In a small sandy area surrounded by rocks, they collected 23 specimens. These had been deposited by the receding tide and were not yet dry. An extensive search along the beach did not yield other specimens. There had been no on-shore wind nor heavy surf for the preceding few days. Most of these specimens still had floats attached and represented all stages of growth. The largest specimen is 34.5mm in height and 22.3 mm in diameter. The smallest is approximately 4mm in height. The longest float is 95 mm in length. The floats are made up of irregular clear THE VELIGER Page 183 bubbles of mucus which has been “set” by sea water. They retain much flexibility, even after 6 months in 60% alco- hol. The outer half of each mature float is worn and de- composing, showing some fine olive-green algae and stumps of old egg capsules. The inner half is tightly packed with clusters of sausage-shaped egg capsules, each of which is about 3mm in length and 1mm in diameter and is attached to the float by a stalk about 4mm in length. One capsule when opened contained many hundreds of embry- onic shells. The largest float supported several hundreds of capsules. A fresh animal has a shell with a velvety olive-tan perio- stracum. One specimen was cleaned, revealing a light chestnut-brown shell that compared well with the descrip- tion and figure of Recluzia rollandiana Petit, 1853. The same specimen from Nayarit was also compared with a specimen of R. rollandiana collected from the south Texas beach by Wayne and Audrey Holiman, Edinburgh, Texas. No significant differences were noted. Due to the generosity of Phil and Jewel Covey, I was able to examine and photograph the Nayarit material. Also, we now have in our collection 2 specimens and can discontinue a search with lasted for 25 years. Literature Cited Assort, Ropert Tucker 1974. American Seashells. acd ed., Van Nostrand Reinhold Qo., New York; 663 pp., 4000+ text figs.; 24 plts. (in color) Dai, Witutiam HEatey 1871. Descriptions of sixty new forms of mollusks from the west coast of North America and the North Pacific Ocean, with notes on others already described. Amer. Journ. Conch. 7 (2): 93-160; plts. 13-16 (2 November 1871) Keen, A. Myra 1971. Sea shells of tropical West America: marine mollusks from Baja California to Peru, 274 ed. Stanford Univ. Press, Stanford, Calif. i-xiv+1064 pp.; ca. 4000 text figs.; 22 col. plts. (21 September 1971) PETIT DE LA SAUSSAYE, S. 1853. Description de coquilles nouvelles. 116-120; plt. 5 Journ. de Conchyl. 4: (February 1853) W. 5. M. The 14 Annual Meeting of the Western Society of Mala- cologists will be held at San Diego State University, San Diego, California between June 23 and 26, 1981. The meeting will feature symposia and contributed papers on molluscan topics, exhibits, shell and book auc- Page 184 THE VELIGER Vol. 23; No. 2 tion, and field trips. All interested persons are invited to attend. For more information contact Bruce Fowler, 5512 Blossom Terrace Court, San Jose, CA(lifornia) 95124. The Western Society of Malacologists Annual Report, which includes abstracts of presented papers, contributed papers, and membership list, is distributed to Regular and Student Members. Applications for membership should be sent to Mrs. Kay Webb, Treasurer, 501 Anita Street, #186, Chula Vista, California 92011. Dues are: Regular Members, $7.50 (with additional Family Members $1.00 each), and Student Members $3.00. Newly elected officers for the fiscal year 1980-1981 are: President Carol Skoglund First Vice-President Donald R. Shasky Second Vice-President David R. Lindberg Secretary Bruce H. Fowler Treasurer Kay Webb Members-at-Large Carole S. Hickman Ernest C. Haight CALIFORNIA MALACOZOOLOGICAL SociETY, Inc. is a non-profit educational corporation (Articles of In- corporation No. 463389 were filed January 6, 1964 in the office of the Secretary of State). The Society publishes a scientific quarterly, the VELIGER. 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The postal service will not forward mail pieces with insufficient postage and, if no return address is given, the piece will go to the “dead letter” office, in other words, it is destroyed. Page 188 THE VELIGER Vol. 23; No. 2 BOOKS, PERIODICALS, PAMPHLETS A Review of the Triviidae (Mollusca: Gastropoda). by Crawrorp N. Carte. San Diego Society of Natural History, Memoir 10: 126 pp.; 177 figs. $15.- (plus tax in California). Library, San Diego Museum of Natural His- tory, P. O. Box 1390, San Diego, CA ga2112 (20 June 1979) A concerned reader has called to our attention that Craw- ford Cate’s latest paper on the Cypraeacea has not yet been noted in this journal and may thus escape the atten- tion of workers who may want to refer to it. Each of the groups reviewed in his trilogy — the Ovu- lidae, the Eratoidae and now the Triviidae — is a prime candidate for modern treatment by a student well versed in taxonomic and nomenclatural procedure, knowledge- able about ecological and biogeographic theory, and cog- nizant of biological variation. In the case of each group, Cate has provided some material useful for such an in- depth study, including a list of taxonomic units, good illustrations of type material, and reproductions of origi- nal descriptions. Moreover, in providing world-wide groupings of the species of this family, some important hypotheses are set forth that merit close attention by subsequent workers. There are certain aspects of Cate’s treatment that may cause future confusion, particularly the convoluted no- menclatural interpretations. For example, Cate has con- fused the misuse of earlier names with homonymy. The generic units are rather finely split for the admittedly limited present state of knowledge, and there are only limited comparative statements. Eugene Coan Department of Geology California Academy of Sciences Alphabetical revision of the (sub)species in recent Conidae 1. abbas to adansonii 2. adansoni to albuquerquei by H. E. Coomans, R. G. MooLeNnBEEK & E. WILS Basteria 43: 9- 26 and 43: 81 - 105, respectively; 1979. This projected total revision of the Conidae on the species and subspecies level promises to be a very important un- dertaking. A careful study of large (or, at least, as large as is possible to assemble) numbers of shells of each taxon, including type specimens where available, forms the basis for each decision the authors make when deciding the validity of a given taxon. Considering the caliber of the workers involved in this revision, nothing less than such great care and utmost reliability can be expected. Taxa considered valid are illustrated with photographs from primary types, where available, and from lectotypes or neotypes. A valuable adjunct is formed by the distribu- tional maps on which localities of studied specimens and reliable localities reported in the literature are indicated. A systematic revision is planned by the authors to be presented at the completion of the work. Although there seems to be no indication at this time that a compilation of the various installments is planned, it may be hoped that such a gathering together under one cover of the valuable information will, eventually, be made available, one way or another. Until the completion of the undertaking, however, in order to remain abreast of the findings, it will be necessary to keep the journal Basteria close at hand. R. Stohler 1,000 World Sea Shells, rare to common, with values by A. Gorpon MELvIN & Lorna Stronc MELVIN, 170 pp. of which 16arecolor platesand 36 black-and-white plates. Charles E. Tuttle Company, Rutland, Vermont 05701. $18.50. 30 July 1980 This is a second volume by the same authors and with al- most the same title; however, no duplication of material in the earlier volume is to be found in this one. Collectors should not expect this — nor any other simi- lar — book to give accurate monetary values of the shells listed; the prices should be considered (like the E.PA. mileage estimates for new cars) of value only for com- parison. The book, undoubtedly, will be used by some shell collectors to identify their treasures. The hardcover book, attractively bound in blue linen, measures 23.0 by 15.2cm and is 17 mm thick; it thus can, if desired, be carried in a good-sized coat pocket to ac- company the collector in the field or to a shell shop. R. Stohler THE VELIGER is open to original papers pertaining to any problem concerned with mollusks. This is meant to make facilities available for publication of original articles from a wide field of endeavor. Papers dealing with anatomical, cytological, distributiox. al, ecological, histological, morphological, phys- iological, taxonomic, etc., aspects of marine, freshwater or terrestrial mollusks from any region, will be considered. Even topics only indi- rectly concerned with mollusks may be acceptable. In the unlikely event that space considerations make limitations necessary, papers dealing with mollusks from the Pacific region will be given priority. However, in this case the term “Pacific region” is to be most liberally interpreted. It is the editorial policy to preserve the individualistic writing style of the author; therefore any editorial changes in a manuscript will be sub- mitted to the author for his approval, before going to press. 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Such articles should be mainly original and deal with collecting, preparing, maintaining, studying, photo- graphing, etc., of mollusks or other invertebrates. A third column, en- titled “INFORMATION DESK,” will contain articles dealing with any problem pertaining to collecting, identifying, etc., in short, problems encountered by our readers. In contrast to other contributions, articles in this column do not necessarily contain new and original materials. Questions to the editor, which can be answered in this column, are in- vited. The column “BOOKS, PERIODICALS, PAMPHLETS” will attempt to bring reviews of new publications to the attention of our readers. Also, new timely articles may be listed by title only, if this is deemed expedient. Manuscripts should be typed in final form on a high grade white paper, 812” by 11”, double spaced and accompanied by a carbon copy. A pamphlet with detailed suggestions for preparing manuscripts intended for publication in 'THE VELIGER is available to authors upon request. A self-addressed envelope, sufficiently large to accom- modate the pamphlet (which measures 51/2” by 82”), with double first class postage, should be sent with the request to the Editor. EDITORIAL BOARD Dr. Donatp P. Azzott, Professor of Biology Hopkins Marine Station of Stanford University Dr. Warren O. Appicott, Research Geologist, U. S. Geological Survey, Menlo Park, California, and Consulting Professor of Paleontology, Stanford University Dr. Hans Bertscu, Curator of Marine Invertebrates San Diego Museum of Natural History Dr. Jerry DonouueE, Professor of Chemistry University of Pennsylvania, Philadelphia, and Research Associate in the Allan Hancock Foundation University of Southern California, Los Angeles Dr. J. Wyatt Duruam, Professor of Paleontology Emeritus University of California, Berkeley, California Dr. Capet Hanp, Professor of Zoology and Director, Bodega Marine Laboratory University of California, Berkeley, California Dr. Carote S. HickMAN, Assistant Professor of Paleontology University of California, Berkeley, California Dr. A. Myra KEEN, Professor of Paleontology and Curator of Malacology, Emeritus Stanford University, Stanford, California Dr. Victor LoosanorF, Senior Biologist, Emeritus U.S. National Marine Fisheries Service EDITOR-IN-CHIEF Dr. Rupotr STOHLER, Research Zoologist, Emeritus University of California, Berkeley, California Dr. Joun McGowan, Professor of Oceanography Scripps Institution of Oceanography, La Jolla University of California at San Diego Dr. Frank A. Pite.xa, Professor of Zoology University of California, Berkeley, California Dr. Ropert Rosertson, Pilsbry Chair of Malacology Department of Malacology Academy of Natural Sciences of Philadelphia Dr. Peter U. Roppa, Chairman and Curator, Department of Geology California Academy of Sciences, San Francisco Dr. CiypeE F. E. Roper, Curator Department of Invertebrate Zoology (Mollusca) National Museum of Natural History Washington, D. C. Dr. JupirH Terry Smiru, Visiting Scholar Department of Geology, Stanford University Stanford, California Dr. Ratpu I. Srru, Professor of Zoology University of California, Berkeley, California Dr. Cuares R. STASEK, Bodega Bay Institute Bodega Bay, California Dr. T. E. THompson, Reader in Zoology University of Bristol, England ASSOCIATE EDITOR Mrs. Jean M. Cate Rancho Santa Fe, California me f- JO V4 No|\I. ISSN 0042-99113 S Ni AT H S @) N lA NV Vighe VELI A Quarterly published by CALIFORNIA MALACOZOOLOGICAL SOCIETY, INC. Berkeley, California JAN 7 6 1981 VOLUME 23 JANUARY 1, 1981 NuMBER 3 CONTENTS Evolution and Function of Asymmetry in the Archaeogastropod Radula. (2 Plates) CAROLERO WICK MANGE Tenn nee PANE anche ie sh Jot > ees es ie ve -@. TBO Reproductive Biology of Three Species of Abalones (Haliotis) in Southern California. (3 Plates; 7 Text figures) THeroporeE TuTSCHULTE & JoseEpH H. CONNELL . . . - «© © «© © © « «© 195 Studies on the Formation of the Crossed Lamellar Structure in the Shell of Strombus gigas. (2 Plates) Hrrosu1 Naxauwara, Mitsuo KaKkel « GerRIT BEVELANDER . « +» «© « « « «+ 207 Male Characteristics in Female Nassarius obsoletus: Variations Related to Locality, Season and Year. (2 Text figures) IG PAK MANES 1S MOLE INE teeters mercer neon ear ee nee ceva met 5 de 5 5 Pie Rectification of the Generic Placement of Sclerodoris tanya (Marcus, 1971), comb. nov., A Nudibranch from Southern California, with a Range Extension to the Gulf of California, Mexico. (1 Plate; 1 Text figure) ELAN SHDERTS CHimmrier mp Me wns fet: cme Se ten Re i ng Ue Me ie els TY Growth and Production in Exploited and Unexploited Populations of a Rocky Shore Gastropod, Turbo sarmaticus. (10 Text figures) LMRNVICICACTIBANES OLIV MICOMBARD) 4) i bs se ee ew se ORT A Comparison of Two Florida Populations of the Coquina Clam, Donax variabilis Say, 1822 (Bivalvia : Donacidae). I. Intertidal Density, Distribution, and Migration. (8 Text figures) PAU OTLERHENGVMIKKEDSEN( 6. © 1.Wcin) sic) ies ie ea eas cw) ss 230 [Continued on Inside Front Cover] Distributed free to Members of the California Malacozoological Society, Inc. Subscriptions, by Volume only, payable in advance to Calif. Malacozool. Soc., Inc. Volume 24: $37.50 plus mailing charges $1.50 U.S.A; $5.- for all foreign addresses Single copies this issue $16.-. Postage extra. Send subscription orders to California Malacozoological Society, Inc. 1584 Milvia Street, Berkeley, CA 94709, U.S.A Address all other correspondence to Dr. R. STOHLER, Editor, Depatment of Zoology University of California, Berkeley, California 94720, U.S.A. Second Class Postage Paid at Berkeley, California ConTENTsS — Continued New Distributional Records for Two California Nudibranchs. ATG UINNC I PNR 5 5 bo 6 8 OO A Cephalic Dimple in the Terrestrial Snail Achatina achatina. (2 Plates) RonaLp CuHaAseE & MICHELE PIOTTE Siphonal Eyes of Giant Clams (Bivalvia : Tridacnidae) and their Relationship to Adjacent Zooxanthellae. (2 Plates; 1 Text figure) PETER V. FANKBONER at Sees atin) cart Acavabsrey eau Ranch ePeaey rea The Effect of Pinnotheres hickmani on the Meat Yield (Condition) of Mytilus edulis Measured Several Ways. (2 Text figures) C. L. PREGENZER . Size Gradients and Shell Polymorphism in Limpets with Consideration of the Role of Predation. (9 Text figures) B. Hartwick er es Mey MoE. ov 5 eG ot! GoGo Physiological Effects of Desiccation and Hypoxia on the Intertidal Limpets Colli- sella digitalis and Collisella pelta. (7 Text figures) Bruce Leon BogsE & Austin W. PriTcHARD ob tet n SALTO ESOP a sre hier emer Behavior of the Gastropod Amphissa columbiana (Prosobranchia : Columbellidae). BreTTON W. KENT A Niche Analysis of Coexisting Thais lapillus and Urosalpinx cinerea Populations. Davw A. JILLSOoN NOTES & NEWS BOOKS, PERIODICALS & PAMPHLETS ..... - 240 . 241 - 245 - 250 - 254 . 265 - 275 6 aT - 282 - 287 Note: The various taxa above species are indicated by the use of different type styles as shown by the following examples, and by increasing indentation. ORDER, Suborder, DIVISION, Subdivision, SECTION, SUPERFAMILY, Fairy, Subfamily, Genus, (Subgenus) New Taxa Vol. 23; No. 3 THE VELIGER Page 189 Evolution and Function of Asymmetry in the Archaeogastropod Radula CAROLE S. HICKMAN Department of Paleontology, University of California, Berkeley, California 94720 (2 Plates) INTRODUCTION THE MOLLUSCAN RADULA is a complex morphological apparatus of extraordinary beauty in its bilateral symmet- ry and orderly repetition of identical units. Abnormali- ties or malformations that disrupt complex orderly pat- terns of radular morphology consequently have attracted attention as curiosities. A few have been figured by ob- servant students of molluscan natural history (PEILE, 1922; 1932). Asymmetry is not always an abnormal condition, how- ever. It is a fundamental feature of the rhipidoglossate radula of primitive marine archaeogastropods. It is curious that various forms of asymmetry have been re- corded meticulously in drawings for more than a century without accompanying descriptive recognition of their form or possible adaptive significance. It is even more curious that many an observant malacologist has exam- ined an asymmetric radula, subconsciously corrected it, and rendered it perfectly symmetrical in a drawing that otherwise faithfully records morphological detail. In this paper I provide evidence that several different types of asymmetry have evolved independently in the radulae of marine archaeogastropods and propose that there is an underlying asymmetry that is a primitive and important functional feature of the molluscan radula. Radular asymmetry functions primarily to facilitate effi- cient folding of the radula during the final part of the feeding stroke and to permit efficient storage when the radula is not in use. It is most pronounced in radulae in which there is accompanying development of large, strongly-cusped outer lateral or inner marginal pairs of major food-preparing teeth. Asymmetry is more complex, however, and may be subtle. Ability of the animal to mani- pulate the two horns of the odontophore separately can result in an asymmetry of use, as evidenced by asymmetri- cal feeding tracks. Asynchronous rapid alternate collaps- ing of marginal tooth rows on either side of the radula also represents an asymmetry of use that may occur in radulae that are not physically asymmetrical. Physical asymmetry varies from simple skewing of rows to pro- nounced asymmetry of the rachidian tooth and develop- ment of lateral tooth pairs that are not reflective (2. é., not mirror images of one another). Within a family or genus the degree of asymmetry may vary considerably, and features of asymmetry can be use- ful as taxonomic characters. Multiple origins and losses of certain features of physical asymmetry suggest a rela- tively simple genetic control, although the generative mechanism is sufficiently poorly understood that it is not possible to speculate at this time as to the nature of the changes involved. PHYSICAL ASYMMETRY Physical (conformational) asymmetry occurs in radulae of all 5 marine archaeogastropod superfamilies with living rhipidoglossate representatives. In its simplest form it involves a skewing of the row so that teeth on one side of the radula are higher or more anterior in placement than their counterparts on the opposite side. In extreme cases the rachidian is strongly asymmetrical and lateral tooth pairs are not mirror images. Physical asymmetry is most pronounced in the Pleurotomariacea, Fissurellacea, and Cocculinacea. It is secondarily absent or only faintly developed in the Trochacea and Neritacea. Page 190 THE VELIGER Vol. 23; No. 3 PLEUROTOMARIACEA Radular form is highly variable within the 3 families of pleurotomariacians with living representatives. When a- symmetry occurs it is usually the right side of each row that is higher or skewed anteriorly. Note in the radula of Pleurotomaria (Perotrochus) quoyana Fischer « Bernardi, 1856, that the right inner lateral tooth is situated above or more anterior than the left inner lateral (Figure 1). This same conformational asymmetry appears in 2 illustrations by Bouvier & FISCHER (1902: figs. H, L), who provide the most detailed drawings of the radula; but it is illus- trated as bilaterally symmetrical by other authors (e. g., Dati, 1889; WoopwarbD, 1901; BARNARD, 1962; AzUMA, 1964). Asymmetry in Pleurotomaria extends beyond sim- ple skewing to pronounced asymmetry of the rachidian tooth itself (Figure 2). Although the radula of Pleuroto- maria (Perotrochus) midas Bayer, 1965, is very similar in most morphological details to that of P quoyana, the asymmetry is reversed. In the former it is the left side of each row that is skewed anteriorly and the left side of the base of the rachidian that marks the farthest anterior point of attachment of any tooth to the radular mem- brane (Figure 3). Conformational asymmetry is also well developed in the Haliotidae. Although there is no distinct asymmetry of the rachidian tooth itself, as in Pleurotomaria, it is clearly attached asymmetrically to the radular membrane. In Figure 4 note that the long axis of the radula of Haliotts rufescens Swainson, 1822, does not bisect the rachidian and that the right lateral teeth are situated more anteri- orly than the left laterals. The heavy major food-preparing teeth (Figure 13) are thereby folded alternately into the tooth row from either side of the radula in the fashion of teeth on a zipper. Physical asymmetry cannot be documented in the deli- cate radula of the Scissurellidae and is interpreted as secondarily lost or greatly reduced. In the illustration of the radula of Scissurella crispata (Fleming, 1828) (Fig- ure 5) note that the rachidian tooth is bilaterally sym- metrical both in form and placement. There is a slight indication that the right lateral teeth are farther anterior than the left, but this relationship is not consistent along the length of the radula. FISSURELLACEA Physical radular asymmetry is more pronounced in fissur- ellacean limpets than in any other group of gastropods and extends beyond skewing of rows and asymmetrical attachment of teeth to the radular ribbon to unmistake- able and pronounced asymmetry of isolated rachidian teeth and development of lateral tooth pairs that are not mirror images. Unlike most pleurotomariacians, fissurell- aceans develop row skewing that is reversed, with the teeth on the left side of the radula higher or more anteri- orly placed than those on the right (Figures 6, 7, 8). Asym- metry is poorly developed in primitive fissurellacean rad- Explanation of Figures 7 to 12 Figure 1: Pleurotomaria (Perotrochus) quoyana Fischer & Bernar- di, 1856. Asymmetric rachidian and lateral teeth. Rosenstiel School of Marine and Atmospheric Sciences, University of Miami, Gerda Sta. G-897 Bar = 100pm Figure 2: Pleurotomaria (Perotrochus) quoyana. Detail of rachidi- an tooth from same specimen, showing asymmetric attachment to radular membrane. Bar = 100ynm Figure 3: Pleurotomaria (Perotrochus) midas Bayer, 1965. Detail of rachidian tooth showing reverse asymmetry (the left side of the base is higher or farther anterior) from that of P (P) quoyana. Gerda Sta. G-10-16. Bar = 200 pm Figure 4: Haliotis rufescens Swainson, 1822. Asymmetric rachidian and lateral teeth. University of California, Museum of Paleonto- logy Loc. UCMP R-3200. Bar = 200 pm Figure 5: Scissurella crispata (Fleming, 1828). Rachidian and lat- erals with no discernable asymmetry. R/V Oregon Sta. BMT-9. Bar = 40 pm Figure 6: Fissurella nimbosa (Linnaeus, 1758). Strongly asym- metric fissurelline radula with left side of row skewed anterior. Los Angeles County Natural History Museum Loc. LACM 76-30. Bar = 400pm Figure 7: Hemitoma octoradiata (Gmelin, 1791). Strongly asym- metric hemitomine radula with left side of row skewed anterior. LACM A.8983.68. Bar = 200 pm Figure 8: Montfortula rugosa (Quoy « Gaimard, 1834). Slightly asymmetric emarginuline radula. LACM 68-81. Bar = 400 pm Figure g: Fissurella nimbosa. Detail of strongly asymmetric fissurel- line rachidian tooth. LACM 76-30. Bar = 50um Figure 10: Megatebennus bimaculatus (Dall, 1871). Strongly a- symmetric diodorine rachidian tooth. UCMP E-3789. Bar = 200 pm Figure 11: Montfortula rugosa. Slightly asymmetric emarginuline rachidian. UCMP R-3201. Bar = 20pm Figure 12: Afontfortula rugosa. Rachidian from individual from a different population, for comparison with Figure 11. LACM 68- 81 Bar = 504m THE VELIGER, Vol. 23, No. 3 [HickMaAN] Figures 1 to 12 = Vol. 23; No. 3 ulae and is inferred to have developed independently within the superfamily. This pattern is consistent through- out the group and is so pronounced that it could not be ignored in illustrating radulae in the same way that it has been ignored in the Pleurotomariacea (see, for ex- ample, the illustrations by THIELE, 1891: plts. 26, 27). Recognition of asymmetry in the fissurellid radula is not wholly restricted to drawings. Discussing the genus Fissurella, THIELE (1891: 290) remarks “Die Asymmetrie der Radula ist stark ausgepragt,” but he failed to wonder about its significance. Likewise, MARKEL (1966: 1132) clearly recognized the condition, although he attributed it to the position of the odontophoral cartilages rather than to anything physically inherent in the radula itself: “Die Radula der Fissurellidae unterscheidet sich sehr wesentlich von derjenigen der tibrigen Rhipido- glossa. Sie hat namlich gewaltig grosse aussere Later- alzahne. Eingeklappt tberragen die Spitzen dieser Zahne die Mittellinie der Radula. Sie konnen nur deshalb in der Radulatasche untergebracht werden, weil sie gegeneinander verschoben sind, d. h. die Glieder der Radula stehen schrag zur Langsachse der Radula.” Pronounced radular asymmetry is always associated with the development of large outer lateral or inner mar- ginal, major, food-preparing teeth. A consistent feature of the fissurellid radula is the pairing of heavy, multi- cusped outer lateral teeth (Figures 6, 7, 8). As in the Haliotidae, asymmetry permits these teeth to fold to- gether alternately in compact, zipper-like fashion during retraction at the close of the feeding stroke. The radula is stored with the outer laterals folded alternately in the radula sac. Teeth in the process of being secreted show the same offset configuration. The amount of deviation from bilateral symmetry in the rachidian tooth is variable in fissurellids. In the sub- families Fissurellinae (Figure g) and Diodorinae (Fig- ure 10) there is strong asymmetry, while in the primitive Emarginulinae (Figures 17, 12) the rachidian may be nearly bilateral. In the deep-water, emarginate-shelled Zeidora A. Ad- ams, 1860, which has been considered the most primitive genus in the Fissurellidae (FARFANTE, 1947) the radula is unique in having the more anteriorly situated lateral teeth on the right side of the radula as in the Pleuroto- mariacea (Figure 15). It is possible that Zeidora repre- sents an independent evolutionary step to limpet form from the remainder of the Fissurellidae. THE VELIGER Page 191 COCCULINACEA Asymmetry is also inherent in the groundplan of the radulae of cocculinacean gastropods, a group of predom- inantly bathyal, abyssal, and hadal small-shelled limpets that feed on unconventional food sources such as wood and plant material of terrestrial origin (WoLFF, 1979). Radular form is superficially similar to that of fissurella- cean limpets in the reduced development of the rachidian and inner lateral teeth and corresponding development of large, heavy, multicusped, outer-lateral, major food- preparing teeth (Figures 76, 17). The asymmetry differs from that of the fissurellaceans in that the rows slope obliquely in the opposite direction, with laterals on the right side situated higher or more anteriorly. In the folded or collapsed position the main cusps of the large outer lateral teeth fit alternately and compactly together, which could not happen without the asymmetric offset. I]lustrations of the cocculinacean radula generally ig- nore the asymmetry (e. g., THIELE, 1891: plt. 25). Mos- KALEV (1976) has represented it correctly in 3 drawings that accompany descriptions of new cocculinacean gen- era, although there is no mention of asymmetry in the text. There are many other unique features of the cocculina- cean radula, such as the unusual form of the marginal teeth, that suggest that these limpets have a long history of radular evolution distinct from other extant rhipido- glossate archaeogastropods (Hickman, in MS). The rachidian tooth fails to develop in many cocculina- ceans, and it is not clear whether it has been through a non-bilateral phase in its evolution. In the genus Pseudococculina Schepman, 1908, the outer lateral teeth are less well formed, heavy, uncusped plates, and the asymmetry of the radula is correspondingly reduced. TROCHACEA The Trochacea comprises gastropods of a great diversity of substrate and feeding preferences. There is a corres- pondingly broad range of radular morphology within the superfamily (HicKMAN, 1979). In most trochaceans, how- ever, the central and lateral teeth are well developed, prominently cusped, and arranged in a strict bilaterally symmetrical configuration. Asymmetry is uncommon. When it does develop, it is associated with reduction of Page 192 THE VELIGER Vol. 23; No. 3 eee een the rachidian and lateral teeth and development of heavi- ly cusped, inner-marginal food-preparing teeth. In the family Turbinidae there is a range of asym- metries in radulae of similar basic groundplan. The radu- la of Astraea undosa (Wood, 1828) (Figure 18) shows a slight skewing of rows that might be overlooked. How- ever, the development of unmistakable skewing and pro- nounced asymmetry of the rachidian tooth is apparent in the similar radula of Turbo (Callopoma) fluctuosus Wood, 1828 (Figure zg), and the rachidian and laterals are reduced in size. This asymmetry allows efficient folding and interleaving of predominating inner marginal teeth. In spite of the apparent lack of physical asymmetry in the radulae of the majority of trochaceans, there is new evidence of behavioral and operational asymmetry (Mor- RIS, 1980). This evidence will be discussed below. NERITACEA As in the Trochacea, physical asymmetry is not a promi- nent feature of the neritacean radula. There is a striking uniformity in expression of the basic radular plan in living representatives of this ancient (of Paleozoic origin) superfamily. Neritaceans, like fissurellaceans and coccu- linaceans, have reduced rachidian and lateral teeth and developed elaborate, large, major food-preparing teeth with spoon-shaped cusps. Although one might expect asymmetry to develop to accommodate these cusps, nerita- ceans appear to have compensated for the size of these teeth in another way. By broadening the area occupied by the rachidian and inner lateral teeth, it is possible to roll the radula into a tube without overlapping of these large paired teeth. There is no distinct hinge between the large outer lateral teeth and the central part of the radu- lar ribbon. The teeth are not collapsed over the rachidian and inner laterals. It is possible, however, that there is some asymmetry or asynchrony of use of the major food-preparing teeth. This is suggested in the simulated functional configura- tion of the radula of Nerita undata Linnaeus, 1758 (Fig- ure 14). Teeth in any given pair may not strike the sub- strate simultaneously. This cannot, of course, be estab- lished from a crude simulation and depends upon the muscular and behavioral responses of the animal. OPERATIONAL AND BEHAVIORAL ASYMMETRY Physical asymmetry of radulae suggests that mechanical action of offset, major food-preparing tooth pairs on either side of a tooth row may not be synchronous. The feeding stroke is so rapid and individual teeth so minute that direct observational testing of this hypothesis is not possible. Morris (1980) has observed radular action of Tegula funebralis (A. Adams, 1855) by means of slow motion cinematography. When a single feeding stroke is analyzed one frame at a time, it becomes clear that the row ends of marginal teeth sweep inward, collapse, and disappear into the mouth alternately rather than syn- chronously as the radula is withdrawn. This unsuspected asynchrony may be a universal feature of rhipidoglossate radular function that requires physical alternation or interleaving of the outer marginal row halves during retraction. Behavioral asymmetry of radular use arises from abili- ty of the animal to manipulate the 2 horns of the odonto- phore independently and is not necessarily coupled with Explanation of Figures 13 to 22 Figure 13: Haliotis rufescens Swainson, 1822. Strongly asymmetric radula with offset inner marginal teeth. UCMP R-3200. Bar = 200 um Figure 14: Nerita undata Linnaeus, 1758. Radula in simulated operational configuration suggesting possibilities for asymmetric or asynchronous use of major food preparing teeth. UCMP R-3202. Bar = 200m Figure 15: Zeidora sp. Asymmetric radula with reverse skewing from other fissurellacean taxa. United States National Museum (USNM) 761482. Figure 16: Cocculina sp. Strongly asymmetric cocculinacean radu- la with right side skewed anterior. 1253 m, off British Columbia. Bar = 100 pm Bar = 40pm Figure 17: Cocculina sp. Detail of left outer lateral major food preparing teeth from specimen in Figure 16. Bar = 20pm Figure 18: Astraea undosa (Wood, 1828). Moderately asymmetric trochacean radula. UCMP E-2330. Bar = 200 ym Figure 19: Turbo fluctuosus Wood, 1828. Strongly asymmetric trochacean radula. UCMP E-2336. Bar = 100pnm Figure 20: Solariella obscura (Couthouy, 1838). Abnormal asym- metry resulting from fusion of rachidian and left inner lateral tooth. USNM 226790. Bar = 50ym Figure 21: Lirularia lirulata (Carpenter, 1864). Note unequal numbers of lateral teeth on either side of rachidian. LACM 63- 30 Bar = 100um Figure 22: Margarites costalis (Gould, 1841). Note unequal num- bers of lateral teeth on either side of rachidian. USNM 34336. : Bar = 100pm THE VELIGER, Vol. 23, No. 3 [Hickman] Figures 19 to 22 i ee L / i { i: = =) j : 4 , : ' Vol. 23; No. 3 physical asymmetry of the radula. Behavioral modifica- tion of symmetry is confirmed by asymmetrical feeding tracks. Morris (1980) has documented asymmetrical feeding tracks of Tegula funebralis, and pronounced asym- metry is evident in MARKEL’s (1966) illustrations of feeding tracks of Haliotis and fissurellid limpets. EVOLUTIONARY ORIGINS In view of the multiple advantages of asymmetry in the action and compaction of the rhipidoglossate radula, it should not be surprising that it has evolved numerous times. It is similar to a number of other mechanically important, adaptive convergences that have been super- imposed on basic radular groundplans across the order Archaeogastropoda (HickMAN, 1976; 1977; 1979). It is closely related to the independent trends in many groups to develop heavy outer-lateral or inner-marginal, food- preparing teeth and to reduce the amount of material invested in producing rachidian and inner lateral teeth. Likewise, loss of asymmetry seems to accompany second- ary reduction in the prominence of heavy outer laterals or inner marginals, as in the genus Pseudococculina. Although asymmetry may affect a large number of radular characters simultaneously, it is most likely under relatively simple genetic control. The secretion of the radula is not well understood, but there must be an underlying asymmetric deformation in the arrangement of the odontoblast cells that secrete individual radular teeth. The existence of both right- and left-skewed asym- metry within a single genus (e. g., Pleurotomaria) suggests that a single or a very small number of factors controls this aspect of physical asymmetry. OTHER KINDS or ASYMMETRY There are 2 other sources of asymmetry in radulae that are not to be confused with the functionally important types described above as integral parts of the basic groundplans of rhipidoglossate radulae. These other kinds of asymmetry are restricted to individuals within populations. The first is the radular abnormality referred to in the opening paragraph of the paper. Abnormalities that disrupt symmetry are doubtless of somatic origin (HickMAN, 1980): they can be induced experimentally under laboratory conditions (IsaRANKURA & RUNHAM, 1969). An example of abnormal asymmetry is illustrated by a specimen of Solariella obscura (Couthouy, 1838) in which the rachidian and left inner lateral teeth have re- peatedly fused along the length of the radula (Figure 79). THE VELIGER Page 193 A second form of asymmetry is development of an un- equal number of lateral teeth on either side of the rachidi- an. This situation has been observed in individuals of several trochid species in the subfamily Margaritinae. In Lirularia lirulata (Carpenter, 1864) (Figure 20), a spe- cies in which the rachidian and laterals are reduced to thin basal plates, a specimen from an otherwise normal population has 6 lateral plates to the left of the rachidi- an and 5 to the right. Likewise, a specimen of Margarites costalis (Gould, 1841) (Figure 27) has 4 laterals to the left of the rachidian and 5 to the right. The number of laterals is variable in the Margaritinae, both among and within genera, and it is possible that evolutionary changes in the base number for a species may involve only one side of the radula at a time. SUMMARY anp CONCLUSIONS Asymmetry is a fundamental feature of the rhipidogloss- ate archaeogastropod radula, having evolved in different forms in each of the 5 extant marine archaeogastropod superfamilies. The most simple physical asymmetry is a skewing of rows. More complicated forms involve asym- metrical placement of teeth on the radular membrane, and, in extreme cases, asymmetry of the rachidian and production of lateral tooth “pairs” that are not mirror images. Asymmetry functions to effect efficient collapse of tooth rows as the radula is withdrawn and to permit compact alternate storage of large, major food-preparing teeth when the radula is not in use. Even in the absence of physical asymmetry, there may be an underlying asyn- chrony of operation. Behavioral asymmetry of odonto- phore use is confirmed by asymmetrical feeding tracks produced by conformationally symmetrical radulae. Recognition of radular asymmetry in the literature is restricted to illustrations and a few explicit references to its formal appearance. Most authors have unconsciously corrected it in illustrations, and the question of its func- tional significance has not been explored heretofore. The genetic control of the phenomenon must be rela- tively simple, but it cannot be understood without further detailed studies of the generative mechanism. ACKNOWLEDGMENTS This paper documents one of a number of patterns of adaptive convergence in archaeogastropod radulae. Many individuals and institutions have contributed material to the larger project. I must single out J. H. McLean, Los Angeles County Natural History Museum to thank Page 194 THE VELIGER Vol. 23; No. 3 for his special efforts in providing specimens of poorly known taxa. Scanning electron micrographs have been taken with a Cambridge 150 Stereoscan in the Depart- ment of Anatomy, University of California, San Fran- cisco. The advice and assistance of J. A. Long and J. R. Morgan are gratefully acknowledged. Discussions with T. E. Morris have expanded my appreciation and under- standing of the phenomena discussed above. This work was suported in part by National Science Foundation Grant DEB 77-145109. Literature Cited Azuma, Masao 1964. Notes on the radula of Perotrochus africanus (Tomlin, 1948). The Venus 22 (4): 350-355 (15 March 1964) BARNARD, KepPpEL HaRcourT 1962. Notes on the animals of Gyrina gigantea (Lam.) and Pleuro- tomaria africana Tomlin. Proc. Malacol. Soc. London g5: 155 - 158 Bouvier, Euczne-Louis « H. FiscHER 1902. L’organisation et les affinités des gastéropodes primitifs d’aprés Pétude anatomique du Pleurotomarta beyrichi. Journ. Conchyliol. 47: 77-151; plts. 4-7 Dati, WILLIAM HEALEY 1889. Reports on the results of dredging, under the supervision of Alexander Agassiz, in the Gulf of Mexico (1877-78) and in the Car- ibbean sea (1879-80), by the U.S.Coast Survey Steamer “Blake,” --- XXIII Report on the Mollusca.—Part II. Gastropoda and Scaph- opoda. Bull. Mus. Comp. Zool. Harvard 18: 1 - 492; plts. 10-40 (January - June 1889) FARFANTE, ISABEL PEREZ 1947. The genera Zeidora, Nesta, Emarginula, Rimula and Puncturel- la in the Western Atlantic. Johnsonia 2 (24): 93-148; plts. 41 to 64 (7 July 1947) HickMaAN, Caro.e STENTZ 1976. Form, function, and evolution in the archaeogastropod radula. Geol. Soc. America Abstr. with Programs 8 (6): 917-918 (abstr.) (September 1976) 1977. Integration of electron scan and light imagery in study of mol- luscan radulae. The Veliger 20 (1): 1-8; 1 plt.; 4 text figs. (1 July 1977) 1979. Adaptive morphology of the trochid gastropod radula. Geol. Soc. America Abstr. with Programs 11 (3): 84 (abstr.) (Febr. 1979) 1980. Gastropod radulae and the assessment of form in evolutionary paleontology. Paleobiology 6 (in press) IsARANKURA, K. & NormMAN W. RuNHAM 1969. Studies on the replacement of the gastropod radula. Malaco- logia 7 (1): 71-91; figs. 1-13 (31 March 1969) MARKEL, KonrapD 1966. Uber funktionelle Radulatypen bei Gastropoden unter besonderer Beriicksichtigung der Rhipidoglossa. Vie et Milieu (A) 17: 1121 to 1138; 11 text figs. Morris, Tom EL.iotr 1980. Morphological and functional dynamics of the rhipidoglossan radula of Tegula funebralis (Mollusca : Gastropoda). M. A. Thesis, Dept. Paleont. Univ. Calif. Berkeley (March 1980) Moska ey, Lev I. 1976. Concerning the generic diagnostics of the Cocculinidae (Gastro- poda, Prosobranchia). pp. 59-70 in Z. A. Filatova (ed.): Deep water bottom fauna of the Pacific Ocean. Works P P Shirshov Inst. Oceanol., Acad. Nauk, USSR 99 (in Russian) Peire, ALFRED JAMES 1922. Some notes on radulae. Proc. Malacol. Soc. London 15 (1): 13-18; 5 figs. (April 1922) 1932. Radular malformations and abnormalities. Proc. Malacol. Soc. London 20 (2): 103-104 THIELE, JOHANNES 1891. Part 7, pp. 249 - 334 tn Franz Hermann Troschel, Das Gebiss der Schnecken. WotrF, ToRBEN 1979. Macrofaunal utilization of plant remains in the deep sea. Sarsia 64: 117-136 Woopwarp, MartTIN FOUNTAIN 1901. The anatomy of Pleurotomaria beyrichit Hilg. Microscop. Sci. 44: 215 - 268 (July 1932) Quar. Journ. Vol. 23; No. 3 THE VELIGER. Page 195 Reproductive Biology of Three Species of Abalones (Haliotis) in Southern California THEODORE TUTSCHULTE anp JOSEPH H. CONNELL Department of Biological Sciences, University of California at Santa Barbara, Santa Barbara, California 93106 (3 Plates; 7 Text figures) INTRODUCTION THIS STUDY WAS UNDERTAKEN as part of a broader inves- tigation of the factors determining the local distributions and abundances of 3 co-existing populations of California abalones, Haliotis fulgens Philippi, 1845, H. corrugata Wood, 1828, and H. sorenseni Bartsch, 1940, commonly known as green, pink and white abalones, respectively. The life history features of primary importance in this regard are age at first reproduction, the number of off- spring produced in each age interval, and the length of the reproductive span. We feel that by comparing the differences between various features of the reproductive life of very similar species in the same place, we may gain some understanding of the relative importance of the various environmental forces that have shaped these strategies. AREAS anp METHODS All collections, except for a few of the white abalones examined for age at maturity, were made between April, 1969 and April, 1973 in the Isthmus region of Santa Cata- lina Island within an 800m radius of the coordinates 33°27'N, 118°29'W. The depths and frequency of collec- tions are described in more detail below. This area faces the mainland across the 32km wide San Pedro Channel and thus is protected from westerly and southwesterly oceanic swells and the occasional south- easterly storms occurring in this region, but is exposed to wind and waves from the northwest, north and northeast. Except for periods of northwest storms, there is very little wave action, but the area is regularly swept by strong tidal currents that sometimes reach a speed of 3 knots. There are dense beds of giant kelp (Macrocystis pyrifera (Lin- naeus) C. A. Agardh, 1820) along the shore and on off- shore reefs. These beds extend from approximately 2m to 20m below MLLW. A dense understory beneath the Macrocystis canopy is comprised of a variety of red and brown algae. Between the 20 and 4om depth levels, the large leaf kelps Laminaria farlowiw Setchell, 1893 and Agarum fimbriatum Harvey, 1862 are the dominant algal forms. The seasonal variation in ocean temperatures at 2 depths in this area is shown in Figure 1. The difference between the depths illustrates the development of the summer thermocline. The simple reproductive system of Haliotis has been well described (CRoFTs, 1929, 1937; NEWMAN, 1967; Younc & DEManrtTINI, 1970). The single gonad of these dioecious prosobranchs opens into the right nephridium from which the gametes are discharged directly into the sea via the right nephridiopore. The gonad forms a sheath of tissue surrounding the liver and these two glands com- prise a “conical appendage.” The surface areas of the germinal epithelia that line the lumina of the ovary and the testis are greatly increased by tubes and sheets of con- nective tissue extending between the inner and outer gonad walls. This germinal epithelium is the site of gameto- genesis. In general, the reproductive cycle of an organism is characterized by six distinct phases: activation (incitement of gametogenesis), gametogenesis, enlargement of the gonad as the result of increase in the number or size of gametes, spawning of the gametes, resorption of unshed gametes, and a resting period (GIESE, 1959; BooLooTIAN, 1966). The pattern of events may vary from the above gen- eralized description, depending upon the reproductive physiology of the organism. For instance, HoLLAND & Giese (1965) found that in the purple sea urchin, the gonad increases in size before gametogenesis due to nutri- ent storage in addition to the gamete accumulation follow- ing gametogenesis. Both NEwMaAn (1967) and WEBBER & Giese (1969), who worked on black abalones, report ex- tensive gametogenesis immediately following spawning Page 196 THE VELIGER Vol. 23; No. 3 with no evidence of resorption of gametes, suggesting the absence of the resorption and resting stages. Figures 2 and 3 show the structures of the ovary and testis of Haliotis sorenseni (white abalone) before and after spawning. The 22 20 18 16 Temperature (°C) 14 12 fo) features illustrated are quite similar in the two other spe- cies studied. A variety of gonad bulk indices have been used in the past to indicate the reproductive state of abalones (INo & 1972 1973 1974 Figure 1 Seasonal variation of ocean temperatures off Bird Rock in the isth- mus area of Santa Catalina Island. Monthly averages of daily sur- face (C)) and 20m depths (@) thermometer readings are shown with two standard deviations (vertical bars). The asterisks mark two values obtained by estimating by eye the average values of continuous 30 day recordings from a Ryan model D-go thermo- graph. Raw data courtesy of the Santa Catalina Marine Biological Laboratory. Explanation of Figure 2 Photomicrographs of vertical sections of the ovaries of mature white abalones (int — integument; trab — trabecula; lu - lumen; d.gl. — digestive gland; ooc — oocyte). a. Ovary just before spawning phase. — b. Ovary after spawning. X 34 THE VELIGER, Vol. 23, No. 3 [TuTscHULTE « CONNELL] Figure 2 A eee ee Wc @: pn eS, ' AV “> vt ~ A sf eg } — aN . * : a . aly : Covlay: outer ey. 4 a ie Se ees ce \ g mh. th C x N as Ws. 3 te: ie ws Petat ee , : oe} Siete ee es S853 a = he ae ote “S Xs , oe bs : , . pis oe Hn s+ - ; B E f * *, ie Oe ee a + S85- d AL aS Pe a ry. = Gad s a -e * oe igang Sew be 3 Soe ZS ph S Oo, x} eke Zed deep ~ ia . e a * e? |. @ "eS". °@- 340,98: ~@ & ' ey noe oe 3 ao: SS cy 4 ‘@ Oe Nee, -59 2 Mey © jem 4 1 x wt tun 2 aay e° 9@ 5 27.2 5 Fe as a ee a # ~ — © e ate ve ce be eo @,5 Pe ee > 72 ~ . 5 i > % s é a er 2 e ne ¢ eg ¢ Caen 4 4 = hee ogu 2 23 < = > ® oe me) 2 t] ss . * ; . ; < So 4 nm "> (1% 44 O55 4 seg = 2 “Oa oo eee Pa 57 Pi wy "a | > a Seep 989, . 19 ve t , * 499. wee eat haa te Opie Veg ia, Vol. 23; No. 3 Harapa, 1961; Boo.ooTian, et al., 1962; NEWMAN, 1967; WEBBER & GIESE, 1969). All except Webber & Giese’s are derived from measurements of thickness or cross-sectional area of gonadal tissue relative to body size as indicated by liver diameter, shell length or cross-sectional area of the base of the conical appendage. Webber & Giese used the weight of the gonad relative to body weight. For this study, we calculated a gonad bulk index in a slightly different way. Samples of 12 to 20 sexually mature animals of each species were collected at intervals from April, 1969 to April, 1973. During the first year the col- lections were made at approximately five-week intervals with samples of pinks taken from the 3, 19, and 30m depths, whites from the 19 and 30m depths, and greens from the 3 m depth only. After the first year, samples were usually collected bi-monthly; pinks were taken from the 3 and 30m depths, whites from the 30m depth only and greens from 3m as in the first year. The pattern of sam- pling reflects the differing depth distributions of the three species in this area: pinks occur from the intertidal zone to below 50m depth, greens are found only in waters shal- lower than about 8m and whites occur mainly between 16m and 50m depths. Within a few hours of collection, each abalone was re- moved from its shell and weighed (after excess water was blotted off), its shell length was measured, a sample of its gonadal tissue was fixed in Bouin’s fluid, and its viscera were frozen. It was deemed impractical to routinely deter- mine gonad volume by dissecting the gonad from the di- gestive tissue of each animal in this study, as WEBBER & Giese (1969) did with black abalones. Since most of the gonadal tissue is contained in the conical appendage, the linear dimensions of the gonadal and hepatic tissue within this appendage were taken from the frozen structure and used to calculate a lower estimate of gonad volume, de- noted EGV. The equation used in this calculation was obtained by treating the conical appendage and the por- tion of the liver within it as concentric cones with parallel sides (see Figure 4). The validity of this procedure was tested by comparing the result of the above described calculation to the result of a procedure in which successive one-centimeter cross- sections of the conical appendage were measured and the gonad volume in each section estimated as a hollow frus- tum. The two estimates were applied to a series of 40 animals and the agreement was found to be very close, based upon a t test, p > 0.999. For a gonad bulk index we divided EGV by body weight. The means and ranges of index values from pop- ulation samples taken at intervals through the year indi- THE VELIGER Page 197 cate the degree of reproductive synchrony within a popu- lation. A high rate of change of the index shows that the reproductive cycles of the individuals are synchronous. If the cycles of the individuals in the population are syn- chronized, at least to a moderate degree, then mean index values show the period of the cycle and the times of year of gonad growth and spawning. To prepare the gonads for a study of histological changes, the gonadal tissue samples fixed in Bouin’s fluid were dehydrated in a tertiary butyl alcohol series, em- bedded in Paraplast, serially sectioned at 10 um, stained in Harris’ hematoxylin, counterstained with eosin and mounted in Preservaslide. Size frequency distributions of oocytes were obtained by using a planimeter to measure areas of all oocytes sectioned through the nucleolus in a large series of photomicrographs of ovarian tissue from each reproductive collection. The absolute abundances of oocytes were calculated from counts in measured areas of the prepared slides, and are expressed in relation to the body weight of the animal (Figure 9). RESULTS Reproductive Cycles The gonad indices in the periodic samples from the 3 populations are shown in Figures 5, 6, and 7. Figure 5 shows that, following gonad enlargement beginning in August-September, the white abalones spawned between February and April in all 4 years, the males being slightly earlier in 1973 than in the other years at 30m depth. In addition to the high degree of synchrony and regularity of the annual cycle exhibited by this population at 30m depth, they were also moderately well synchronized with those at the shallow margin of the population’s distribu- tion (1969-70), showing only a short lag at the beginning of the growth and spawning phases. The shallow popula- tion in 18m spawned in February and March when the temperature at that depth was not changing much, having decreased rapidly 4 to 6 months before (Figure 8). In con- trast, the deeper population at 30m spawned in March and April during a time of rapid temperature fall (Figure 8). This high degree of reproductive synchronization de- spite the markedly different temperature regimes at the two depths raises a question concerning the relevance of temperature levels and fluctuations which are usually re- garded as key exogenous factors affecting the various phases of the reproductive cycles of invertebrates (GrEsE, 1959). Page 198 THE VELIGER Figure 4 Method for estimating volume of gonadal tissue in conical append- age. The measurements are: arc length (AS) and a, b, x, y from cut at AS/2. To calculate the estimated gonad volume (EGV), the appendage and liver were treated as concentric cones with Vol. 23; No. 3 parallel sides. The equation for EGV is as follows: EGV = a AS 96 [8 (Gisja Mesa areal )9 x+y Vol. 23; No. 3 180 150 oo agence tenn neeneneeey rod Gonadal Bulk Index THE VELIGER Page 199 18m depth Figure 5 Reproductive cycle of white abalones as indicated by the mean gonad bulk indices, usually 9 females and 9 males per sample. Vertical bars represent the 95% confidence limits of the mean. As seen in Figure 6, gonad growth of the greens takes place in the spring followed by a spawning that extends from early summer to early fall in contrast to the abrupt spawning of the whites. Thus, the spawning season of greens is more prolonged and less synchronous than in whites. This observation is in general agreement with the reported breeding season for this species near Ensenada, Mexico (Cota, 1970) and at Cedros Island, Mexico (SEVILLA, et al., 1965). Figure 7 suggests that the reproductive cycle of the pink population is the least synchronized of the 3 species. At all 3 depths, the male and female gonad bulk indices some- times indicate a spawning followed by a rapid increase (e. g., April, 1970). This, plus the lower amplitude of change in pinks as compared to the others, suggests either that each individual spawns more than once in a year, or that they are not well synchronized in their annual spawn- ings. Alternative explanations that they ripen or release Page 200 a fe) m no (2) oO {e) D o) Gonadal Bulk Index 30 THE VELIGER Vol. 23; No. 3 6m depth Figure 6 Reproductive cycle of green abalones using samples from 6m depth. Symbols as in Figure 5. only a small fraction of their gametes at one time are un- likely, as will be discussed below (Figures 9 and 10). Size frequency analyses of year classes suggest that there are several settlements from the plankton per year (TUTSCHULTE, 1976). Figure 7 indicates that spawning occurred sometime between late winter and early summer of each year over the entire depth range of pinks. The question of the period of oogenesis relative to the spawning cycle of abalones is unsettled. NEwMaAn (1967) showed that in the South African abalone there are two populations of oocytes in the ripe ovary: mature oocytes (200 to 300 wm diam.) ready to be spawned in the current season and immature oocytes (40 to 90 um diam.). On the basis of his observation that the ovaries of recently spawned females contained a large population of the smaller-sized oocytes, he concluded that these oocytes in a ripe ovary would be “released at the next but one spawn- ing.” Such a pattern is known for vertebrates. The frog Rana temporaria, for example, has been shown (Grant, 1953) to have three populations of oocytes in the ovary at first maturity (age 3 yr.), spawning in the fourth year only those ova that differentiated into primary oocytes in the first year. The next population of gametes is spawned the following year, and so on, with a new population beginning oogenesis each year and requiring 3 years to mature. On the other hand, oocyte growth in some organisms is very rapid; mouse eggs increase from 20 to 70 pum (2. €., reach maturity) in 16 days (BaLINSKy, 1960). We have found that pink, green, and white abalones also have two different sized groups of oocytes before spawning and often only small ones after spawning (Figures 2 and 10). How- ever, size frequency distributions of oocytes coupled with ovary bulk measurements of females taken from the white population at intervals during the reproductive cycle (Figure 9) do not support the hypothesis that the smaller sized oocytes are retained during one spawning season for later maturation and release in the following cycle. The Explanation of Figure 3 Photomicrographs of vertical sections of the testes of mature white abalones (int — integument; sp — sperm; spc — spermato- a. Testis just before spawning phase X 134 cytes; tub — tubule) b. Testis after spawning phase THE VELIGER, Vol. 23, No. 3 [TurscHULTE & CoNNELL] Figure 3 > = Fi f Fie) Ss Be SAG Fight mq go Gonadal Bulk Index THE VELIGER Page 201 6m depth 18m depth Figure 7 Reproductive cycle of pink abalone. Symbols as in Figure 5. total number of growing oocytes in the spent ovary is much smaller than in the preceding spawning period and is far too small to account for the quantity of mature “eggs” present later in the same cycle. Note in Figure 8 the great increase in numbers of small oocytes less than 6000 (jum)? in area (< gom diam.) from May through February as the relative ovary volume increased ten-fold. In other words, these data show that the maturation of many new oocytes must take place within the current spawning cycle. Indeed, these data suggest that newly differentiated primary oocytes mature in a few months or less and that oogenesis may take place within one year, rather than extend over two or more annual cycles. Fecundity Gonad volume measurements provide estimates of fecundity, the potential capacity of a female to produce eggs. Since we have found that the white and green pop- ulations at Santa Catalina Island are well synchronized and the pink populations are moderately so, we have esti- mated population fecundities from changes in values of average ovary volumes of samples taken at intervals dur- ing the annual cycles. We calculated the volume spawned per unit body weight for each population by taking the differences between the highest and lowest mean values for the year of estimated ovary volume per unit body weight. Because. the pinks had not finished spawning at the end of the fourth season (March, 1973), the average of the lowest mean values for the preceding 3 years was used to calculate the change in ovary volume in this pop- ulation for the 1972-73 season. The volume spawned per unit body weight multiplied by the average body weight of sexually mature females times the estimated average number of mature oocytes per unit volume of ovary yields an estimate of the average number of oocytes produced per female per year. There is probably some breakdown and resorption of mature oocytes, especially among pinks, so that not all reduction of ovary volume represents shed oocytes. Even Page 202 THE VELIGER Vol. 23; No. 3 so, we believe that these are reasonable estimates of fecundities. Since pinks seem not to be well synchronized, their calculated values may be underestimates. In any one collection, some individuals may have been spawned out while others may have had partially filled or full gonads, so the averages over the year tend not to reach the great amplitudes shown by whites and greens (compare Figures 5, 6 and 7). The calculations (Table 1) indicate that on the basis of eggs per gram of body weight, greens expend nearly twice and whites about three times the reproductive effort that pinks do, and that pinks at shallow depths ex- pend more reproductive effort than those at greater depths. Table 1 shows that for all 3 populations 1970-71 was a year of maximum fecundity. The years of least fe- cundity varied between species and for the pinks between depths. Sex Ratios Approximately 1100 pink, 500 green, and 600 white abalones were collected between April, 1969 and Decem- ber, 1972. These samples showed no significant variation for a 1:1 ratio (for all sizes pooled) for the 3 species at this location (Table 2). Younc & DeMartini (1970) also Table 1 Estimated fecundities (eggs released/year) of pink, green, and white abalones at Catalina Island in the interval April 1969 to March 1973. Average Number Average Number Average Number Average Number Ave of Eggs of Eggs Ave of Eggs of Eggs BW Spawned per Spawned per BW Spawned per Spawned per Depth |Season| N; (gm) N/N3; gm $ per Yr per Yr Ni} (gm) N.2/N3! gm % per Yr per Yr Pinks Greens 3-9m | 69-70 | 79 423 5/8 2610 1.10 X 106 74 580 6/7 4420 2.56 X 106 70-71 | 44 402 7/8 5770 2.32 X 106 43 520 6/11 6630 3.45 X 106 71-72 | 70 376 10/53 3320 1.25 X 108 69 452 7/11 5740 2.59 X 106 72-73 | 74 301 10/2 3690 1.12 X 106 47 415 6/2 4950 2.05 X 106 x 376 3848 1.45 X 106 491 5.435 2.67 X 10° T Pinks Whites 27-33 m| 69-70 | 48 524 6/43 2030 1.06 X< 10° 50 624 4/8 8300 5.18 X 10° 70-71 | 28 562 9/8 3810 2.14 X 106 53 615 10/10 10620 6.53 X 106 71-72 | 75 491 13/12 1610 0.79 X 106 52 514 7/7 7170 3.69 X 10° 72-73 | 34 508 12/2 860 0.44 X 106 42 416 12/2 10120 4.21 X 106 x 521 2078 1.11 x 106 542 9052 4.90 x 106 1N, = all females collected in reproductive samples during the season. Nz = sample size of female collection with highest average gonad bulk index value for the season. N; = sample size of female collection with lowest average gonad bulk index value for the season. BW = body wet weight without shell. 2See text for explanation. 3Overlap in confidence limits of highest and lowest values (see Fig. 6). Explanation of Figure ro Photomicrograpth of a transverse section of the conical appendage of a 67mm shell length (4 year old) female pink abalone. The ovary surrounds the digestive gland (int — integument; lu - m. ooc. — apparently ma- d. gl. — digestive gland) X 196 lumen; g. 00c. — growing oocyte; ture oocyte; THE VELIGER, Vol. 23, No. 3 [TurscHuLTE & CONNELL] Figure 10 Vol. 23; No. 3 THE VELIGER Page 203 Table 2 Sex ratios of mature abalones collected from the Isthmus region of Santa Catalina Island. April, 1969 to April, 1973. Wet Weight of body Percent Less Shell (g) Total Females p Pinks <600 779 53.4 0.031 >600 324 41.0 <0.001 Total 1103 49.8 n.s. Greens <600 312 55.1 0.040 >600 189 46.0 ns. Total 501 51.7 n.s. Whites <650 404 56.9 0.003 >650 234 38.5 <0.001 Total 638 50.2 n.s. found the sex ratio to be 1:1 in a population of H. rufescens Swainson, 1822 (red abalone). However, our data do show significantly more females than males in the smaller size group of all 3 populations and significantly more males in the larger size groups of pinks and whites (the proportion of large males in the green sample is greater than 0.5, but not significantly so). These results suggest the possibility that sexually mature males (at least of pinks and whites) have higher survival or growth rates, or both, than females do. Equal sex ratios are reported for the British abalone, H. tuberculata Linnaeus, 1758 (CroFTs, 1937) and for the South African abalone, H. midae Linnaeus, 1758 (NEWMAN, 1967). The sex ratios reported here for pink, green, and white abalones differ from the general rule stated by FRETTER & GRAHAM (1964) that females of most dioecious mollus- can species tend to be more numerous than males and that this tendency increases with the age of the individuals, 2. é.,that males have a higher death rate. Age at Maturity Since spent ovaries of mature female white abalones contained only growing oocytes and no relict “eggs,” we have assumed that young females with ovaries containing growing oocytes will reach maturity within the year and that the absence of mature eggs in older females is not evidence that the individual has yet to reach sexual ma- 17 16 15 Was Temperature (°C) II 10 we i I AS © Wy ID) wos yp AS 1969 1970 Figure 8 Average ocean temperatures at 20m (ff) and 30m ([)) depths in the study area between 2 July 1969 and 21 July 1970. The points represent estimates by eye of the average values of 15-30 day thermograph recordings. turity. We have made a similar assumption for males: the presence of spermatocytes in the testis indicates that the individual will reach maturity within the year. Examina- ion of histological sections of the gonads of pink and green abalones supports the view that the reproductive events discussed above are similar for these two species also. The data on gonad bulk and histological changes pre- sented above indicate that the members of the pink aba- lone population in shallow water at the Isthmus of Cata- lina Island were spawning in May, 1971. In that month, Oocyte Area (1037) al 3- 204 Page 204 4 April 1972 28 July 1972 10 March 1972 +— THE VELIGER 20 Sept. 1972 Vol. 23; No. 3 25 Jan. 1973 400 200 00 10 00 200 100 100 100 100 200 2 Relative Oocyte Frequency per Gram Body Weight 400 Figure 9 Size frequency distributions of oocytes and mean ovary volumes (connected points) of females from white population samples taken at intervals from 10 March 1972 to 30 April 1973. The height of the axis opposite each date indicates the largest oocyte measured from that collection. we collected a series of 50 animals ranging from 39 to 119mm shell length (4.6 to 147g body weight) from this population and examined histological sections of their gonads. Three of the 5 males in the 39 to 48mm (5 to gg) size group had apparently mature spermatozoa and all males in the series had differentiated spermatocytes. All females of over 44mm (6g) had growing oocytes, 3 of the 11 females between 59 and 74mm length had apparently mature oocytes, yet only one of the 8 females between 78 and 119mm had mature oocytes. Figure 9 shows many growing oocytes and a few apparently mature oocytes in the ovary of a 67mm female pink. Therefore, since all the abalones in the pink collection, including 11 between 39 and 49mm, had spermatocytes or growing oocytes, and since growth rate data (Tut- SCHULTE, 1976) show that pinks reach this size at about three years of age, we conclude that these animals would have reached sexual maturity between the ages of 3 and 4 years. Actually, 3 of the 5 males in this size group had apparently mature spermatozoa. Moreover, we observed a female pink of 52mm shell length and two male pinks of 44 and 54mm length spawning in the laboratory. The female had been 32 mm long (about two years old) when collected from the wild 7 months before spawning and the Vol. 23; No. 3 smaller male had been 25mm long (about 14 years old) when collected 20 months before spawning. Several thou- sand larvae resulting from this spawning developed nor- mally for the 15 days they were maintained in the lab- oratory. This observation substantiates the view that some members of the pink population mature at age 3 years. Others may not mature until age 5 or older, but the aver- age age at maturity is probably about 4 years. We collected a series of 28 greens ranging from 34 to 128mm shell length in late June 1971, at the beginning of the spawning season of this species (Figure 6). Histological sections of this series showed 13 females ranging from 61 to 128mm shell length with growing oocytes, 9 males ranging from 89 to 128mm with spermatocytes, and 6 individuals between 34 and 90mm showing no differen- tiated gametocytes. The same assumptions made in the analysis of the pinks led to the conclusion that most greens reach maturity between 5 and 7 years, since they have sim- ilar growth rates. The white population in the Isthmus area of Santa Catalina Island was very deep and had an uneven age structure (TUTSCHULTE, 1976). This made it difficult to collect animals in the size range needed to determine age at maturity. To supplement these samples we have in- cluded data from white populations at Coal Oil Point and Gull Island in Santa Barbara County. Studies at these locations (Tutschulte, in prep.) indicate that the relation- ship of size to age in these populations is about the same as for whites at Catalina. Thirteen females in this pooled series ranging from 88 mm shell length (46 g soft body weight) to 134 mm (181g) had ovaries containing growing oocytes. Eight males in the same size range had testes containing spermatocytes. Most of these individuals had mature gametes as well. Only one individual contained no gametocytes. These data taken together with growth rate information (Tur- SCHULTE, 1976) suggest that whites mature at ages 4 to 6 years. DISCUSSION Although the overall sex ratio is 1:1, it changes with age. This is interesting for the questions it raises concerning sex specific growth and survival rates. It implies that, follow- ing sexual maturity, females have either lower growth rates or higher mortality rates or both as compared to males. If the growth rates were lower, it implies that the fraction of total energy that is devoted to reproduction may be greater for females than for males. THE VELIGER Page 205 On the other hand, the fact that males produce about the same volume of gametes per unit body weight as females do implies that males actually make an equal or even greater reproductive effort. This is because a given volume of sperm probably requires as much or more energy to produce than an equal volume of “eggs”; most of the cytoplasm of a spermatocyte is discarded during the mat- uration of a sperm (E. Triplett, pers. comm.). If this is so, it suggests that growth rates will not be any slower in females, and that the change in sex ratio is caused by a higher rate of mortality in females. Females could be less resistant to adverse physical conditions or more vulnerable to predators or disease. The population of white abalones is characterized by a high degree of reproductive synchrony, a single short spawning period, intermediate age at maturity, and the highest fecundity of the 3 species. The greens have an intermediate degree of synchronization, with usually a single but longer spawning period, the latest age at matu- rity, and an intermediate fecundity. The pinks have the lowest degree of synchrony (considering the population as a whole over its depth range, there are probably several spawnings over the year), the earliest age at maturity, but seem to have the lowest fecundity of the 3 species. How- ever, this low fecundity may be only apparent; as discussed above, it may have been underestimated by our methods. Also, if individual pinks spawn more than once per year, this would increase their fecundity. As a result, their repro- ductive effort might even equal that of the whites. So per- haps the really important difference between pinks on the one hand and greens and whites on the other with respect to reproductive effort is not the amount of energy ex- pended but rather the timing of its expenditure. The white and green populations are specialized in their reproductive cycles and in their depth distributions. Greens spawn in summer and are restricted to the shallow sublittoral zone. Whites spawn in winter and are found only in relatively deep water. Pinks are more generalized in both their repro- ductive cycle and their depth distribution, spawning dur- ing most of the year and completely overlapping the distributions of the two more specialized species. SUMMARY 1. White abalones are highly synchronized in their an- nual reproductive cycles; the entire population spawns within a few weeks in winter. Greens are less synchro- nized, with a spawning period that extends through the summer and early fall. Pinks are the least synchro- Page 206 THE VELIGER Vol. 23; No. 3 nized in their reproductive cycles, with several spawn- ings over the year. Thus the whites and greens may be said to be specialized while the pinks are generalized in their reproductive cycles. 2. Pinks mature as early as age 3, whites at 4 and greens at age 5 years. 3. Among these 3 populations, whites show the highest apparent fecundity, the average female shedding about 5 million mature oocytes per year. Greens pro- duce about half and pinks possibly only one-fourth as many eggs as the whites do. 4. For all ages combined, there is an even sex ratio in all 3 species. However, females predominate at earlier ages and males at older ages. This implies that, after maturity is reached, females have lower survival or lower growth rates, or both. 5. During each annual cycle whites produce a new batch of oocytes that matures and is shed within the year. This is also probably true for other species both here and in other places. This finding is at variance with earlier conclusions of other workers. ACKNOWLEDGMENTS We wish to thank the many people who helped with the diving involved in the field work for this study. We are also indebted to the staff of the University of Southern Cali- fornia Santa Catalina Marine Biology Laboratory for their hospitality in providing laboratory space and equipment. We thank Ms. Ielene Morrow for preparing the histo- logical sections and Mr. John Eppinger for making the photomicrographs. Literature Cited Bauinsky, B. I. 1960. An introduction to embryology. W. B. Saunders, Philadelphia Boo.oomTian, R. A. 1966. Reproductive physiology. In Physiology of Echinodermata (R. A. Boolootian, ed.) ; Interscience, New York, pp. 561 - 613 Bootootian, R. A., A. FARMANFARMAIAN & ARTHUR C. GiEsE 1962. On the reproductive cycle and breeding habits of two western species of Haliotis. Biol. Bull. 122: 183-193 Cora, I. F 1970. Fecundacion artificial y dessarrollo embrionario de Haliotts ful- gens Philippi, 1845 y Haliotis rufescens Swainson, 1822 en condiciones aquario. Univ. Auton. Baja Calif, Ocean. Thesis Crorts, D. R. 1929. Haliotis. Liverpool Mar. Biol. Comm. Mem. No. 29 1937. The development of Haliotis tuberculata, with special refer- ence to organogenesis during torsion. Phil. Trans. (B) 228: 219 - 268 FretTTER, VERA & ALASTAIR GRAHAM 1964. Reproduction. In Physiology of the Mollusca (K. M. Wil- bur & C. M. Yonge, eds.). Acad. Press, New York, pp. 127 - 156 Gigse, A. C. 1959. Comparative physiology: annual reproductive cycles of marine invertebrates. Ann. Rev. Physiol. 21: 547-576 Grant, P 1953. Phosphate metabolism during oogenesis in Rana temporaria. Journ. Exp. Zool. 124: 513 - 543 Ho.ianp, N. D. « A. C. Giese 1965. An autoradiographic investigation of the gonads of the purple sea urchin (Strongylocentrotus purpuratus). Biol. Bull. 128: 241-258 Ino, TAKASHI & K. HARADA 1961. On the spawning of abalone in the vicinity of Ibaragi Prefec- ture. Tokai Regional Fish. Res. Lab. Bull. 31: 275 - 281 Newman, G. G. 1967. Reproduction of the South African abalone, Haliotis midae. Div. Sea Fish. S. Afr. Investig. Reprt. No. 64 Sevitta, Maria Luisa, H. HERNANDEZ, Eva Monpracon, O. N. FaRFAN A. GIovaNINI & A. HERNANDEZ 1965. Estudio histologico comparativo de algunos moluscos de import- ancia economica en México. Inst. Nac. Invest. Biol. Pesqs,, Dir. Gener. Pesca. S. I. C. Serv. Trav. D. v III 22: 1-19 TuTscHULTE, THEODORE C. 1976. The comparative ecology of three sympatric abalones. Ph. D. dissert., Univ. Calif. San Diego WesBeER, HERBERT H. & ARTHUR C, GIESE 1969. Reproductive cycle and gametogenesis in the black abalone, Haliotis cracherodii (Gastropoda : Prosobranchiata). Mar. Biol. 4: 152-159 Youn, James S. & Joun D. DeMartTini 1970. The reproductive cycle, gonadal histology, and gametogenesis of the red abalone, Haliotis rufescens (Swainson). Calif Fish & Game 56: 298 - 309 Vol. 23; No. 3 THE VELIGER Page 207 Studies on the Formation of the Crossed Lamellar Structure in the Shell of Strombus gigas HIROSHI NAKAHARA, MITSUO KAKEI anp GERRIT BEVELANDER Department of Oral Anatomy, I. Josai Dental College, Sakado, Saitama-ken, Japan and The Bermuda Biological Station for Research, St. Georges W. Bermuda (2 Plates) INTRODUCTION THE CROSSED LAMELLAR arrangement common to most molluscan shells has been described by many investigators (such as BacciLp, 1930; Taytor et al., 1969; KoBAYASHI, 1971; Wise, 1971; Uozumi et al., 1972; Omori et al., 1976). Previous studies indicate that this layer is made up of slender rod-shaped aragonite crystals called third order lamellae. These unit crystals are assembled parallel to each other to form thick sheets (second order lamellae). The several sheets are then arranged alternately to form the largest unit (first order lamellae). Although the fine structure of the crossed lamellar layer has been described, the formation and growth is poorly understood. In the nacreous and prismatic layers of some bivalve molluscs, it has been shown that some of the or- ganic substance forms envelopes or compartments prior to mineral crystal formation (BEVELANDER & NAKAHARA, 1969a; NAKAHARA & BEVELANDER, 1971). A study of the crossed lamellar structure similar to those referred to above would considerably enhance our understanding of mineralization in the molluscan shell (TayLor, 1973). The present study was undertaken to show the fine structural features of the organic and mineral phase of the developing and mature shell of a gastropod, Strombus gigas Linnaeus, 1758. In addition, the amino acid compo- sition of the calcified crossed lamellar layer was ascer- tained in order to further elucidate the mechanism of mineralization in this shell structure. MATERIAL anp METHODS Young specimens of Strombus gigas (queen conch, order Mesogastropoda) were collected in Bermuda waters dur- ing the month of July. The specimens measured about 13.cm in height (25 cm in the adult). The young Strombus shells do not have a thickened outer lip. In place of the outer lip, they have a sharp growing shell edge outside the aperture. The growing shell edges were fixed immediately after collecting. Only materials trom the margin of the shell were used in this study. Pieces of thin shell edges were removed and immersed in 5% glutaraldehyde solu- tion in cacodylate buffer adjusted to pH 7.4 for 30 min- utes at 5° C. The pieces were then washed briefly 3 times in buffer, followed by exposure to 1% osmium tetroxide buffered in cacodylate at pH 7.4 for 30 minutes. To avoid dissolution of crystals, fixation periods were of relatively short duration. Fixed materials were routinely dehydrated and embedded in Araldite 502. Mature shell specimens were cracked into small pieces and partially demineralized in 9% EDTA2Na (pH = 7.5) for one hour, then fixed and embedded as described above. Ultrathin sections were cut with a diamond knife, stained with saturated uranyl ace- tate and lead citrate (2% in o.1N NaOH) double stain. Unstained sections were also used for observation of Ca- carbonate crystals. Thick sections of 1 to 2pm stained with toluidine blue were used for light microscopy. For scanning electron microscopy, fractured shell specimens were coated with gold in ion spattering equipment. For amino acid analysis, samples of shell were decalcified in 5.7N HCl. During the decalcification, shell organic com- Page 208 THE VELIGER Vol. 23; No. 3 ponents were broken up into minute fragments. The or- ganic fragments were then collected by centrifugation in a glass tube for 20 minutes at 3.000 rev/min. Amino acid analysis was then performed according to the method pre- viously described (BEVELANDER & NAKAHARA, 1975). OBSERVATIONS anp RESULTS Scanning electron micrographs indicate that the entire calcified layer of the Strombus gigas shell including the area adjacent to the periostracum consists of a crossed lamellar structure (Figures 1, 2). The formation of the shell proper is preceded by the elaboration of the periostracum which is composed of sev- eral different layers in Strombus (Figure 3) similar to those of other gastropod species such as Littorina littorea (BEVE- LANDER & NAKAHARA, 1970) and Lymnaea stagnalis (KNIPRATH, 1970, 1972). The periostracum in mature Strombus is relatively thick (550-600 xm), while that of Littorina is several microns and Lymnaea only 2.5 um. Initiation of calcium carbonate deposition occurs at the site where the periostracum reaches its greatest thickness (Figure 3). In the first instance, a very thin organic incre- ment is deposited on the inner surface of the periostracum, which exhibits very low electron density except for a thin surface zone and the area close to the periostracum. This initial layer contains thread-like or fine granular particles which apparently become globular or tubular envelopes. Subsequently, crystals appear within these envelopes (Fig- ure 4). In the space outside the envelope, no significant structural components were observed with the exception of a very small amount of scattered, weakly stained amor- phous material. The zone of mineralization increases in thickness and during this time obliquely arranged organic envelopes and rod-shaped Ca-carbonate crystals within envelopes con- tinue to be elaborated. Envelopes containing crystals hav- ing a similar orientation form groups giving rise to second order lamellae. The adjacent groups of obliquely directed envelopes containing crystals are oriented in an alternate arrangement. These growth processes result in an arrange- ment that is characteristic of the typical crossed lamellar structure (Figures 5-7). Envelopes consisting of a thin single layered electron- dense membranous structure, 3 to 104m in thickness, which intimately surround the growing crystals, often ap- pear granular (Figure 8). As the thickness of the early shell layer increases, each crystal becomes thicker, and as a re- sult of this process, adjacent envelopes come into contact with each other. Approximately 100 um or more from the area where the crystals are initiated, the thickening of the crystals appears to take place more rapidly than at the site where the crystals are first laid down. Furthermore, the growing crystals in this region are intimately covered with enve- lopes as they were in regions where mineralization was first initiated (Figures g, 10). It was pointed out above that the only discernible or- ganic substance in the matrix of the developing shell was the envelopes enclosing the crystals (Figures 6, 8). Exam- ination of several growing stages of more mature regions that are located some distance from the initial calcification areas (Figures 10, 11) illustrate a similar situation in this regard, viz: virtually complete lack of particulate material in the matrix other than the envelopes surrounding the crystals. The amino acid analysis of the Strombus shell (Table 1) indicates that aspartic acid is present in the highest con- centration. Glutamic acid also shows a relatively high con- tent. Other components which are present in considerable amounts are: serine, leucine, proline, cysteine (cystine) Explanation of Figures 1 to 5 Figure 1: Scanning electron micrograph of fracture surface of young Strombus shell. Whole calcified shell shows crossed lamellar structure (CL). In — inner surface of shell X 170 Figure 2: Scanning electron micrograph of fracture surface. Show- ing alternate arrangement of obliquely oriented slender crystals (CL). P — periostracum X10 000 Figure 3: Photomicrograph of section of growing shell margin. P — periostracum; arrow — margin of the calcified part of shell X 160 Figure 4: Electron micrograph of early stage of mineral crystal formation. Light spaces surrounded by envelopes (En) were for- merly occupied by crystals. Some envelopes are devoid of crystals (arrow). P — Periostracum. Section stained in uranyl acetate and lead citrate X 57000 Figure 5: Unstained section, later stage than that of Figure 4. Showing alternately arranged envelopes (En) and crystals (arrow). P — periostracum X 13000 THE VELIGER, Vol. 23, No. 3 [NAKAHARA, KAKEI & BEVELANDER] Figures 7 to 5 WO, QBE ING, THE VELIGER Page 209 Table 1 Amino acid composition Crossed lamellar structure Nacre Strombus gigas Pinctada radiata} amino acid residues per mM | residues pL 1000 total moles per per moles per residues g | 1000 g Aspartic acid 183 1.07 120 18.1 Threonine 4] OM |) = 10 1.7 Serine 54 0.40 60 11.5 Glutamic acid 92 0.48 38 Bed Proline 59 0.40 16 2.8 Glycine 54 0.56 233 62.1 Alanine 43 0.37 j 212 47.5 Cysteine 93 0.30 \ 13 li Valine 8 0.05 | 22 3.8 Methionine 16 0.08 17 283 Isoleucine 37 0.22 15 2.3 Leucine 76 0.45 } 77 11.8 Tyrosine 52 0.22 32 3.6 Phenylalanine 43 0.20 30 3.7 NH3 4 0.19 | 9 10.3 Lysine 62 0.33 8 1.1 Histidine 6 0.03 18 2.3 Arginine 76 0.34 | GS 7.5 IBEVELANDER & NAKAHARA 1975 and arginine. Glycine and alanine, which are the major components of the nacreous layer in many mollusc groups, are present in relatively low amounts. The content of protein in the crossed lamellar structure of Strombus shell measured 0.07% by weight. DISCUSSION The present study reveals that the formation and growth of the crystals in the crossed lamellar structure of Strombus occurs within single-layered organic envelopes. It is also obvious that these envelopes are the only prominent or- ganic structure in either the developing or mature shell. Uozumi e¢ al. (1972) reported that the organic substance of the crossed lamellar structure is composed of one mem- brane (equivalent to “envelope”) that exhibits a homo- geneous and uniform structure. Our results confirm this observation, and in addition, indicate that the organic structures in the mature crossed lamellar shell are rem- nants of the envelopes which intimately cover each grow- ing aragonite crystal in the developing shell Previous studies indicate that similar envelopes are pres- ent in several kinds of other calcified tissues; growing pris- matic layer of the pearl oyster Pinctada radiata (NAKA- HARA & BEVELANDER, 1971), nacreous layer of several bivalves species (ERBEN & WATABE, 1974), aragonite crys- tals in the inner ligament of bivalves (BEVELANDER & NAKAHARA, 1969b; Marsu e¢ al., 1978), aragonite crys- tals in a green alga, Halimeda incrassata (NAKAHARA & BEVELANDER, 1978b). Mineral crystals grow within enve- lopes in all these organisms. Shell structures of frequent occurrence other than the crossed lamellar variety are the nacre and the prismatic layer. These varieties contain conspicuous organic struc- tures other than the envelope; the interprismatic wall in the prismatic layer (NAKAHARA & BEVELANDER, 1971) and the “sheet” in the nacre (BEVELANDER & NAKAHARA, 1969a, 1979). These “sheets” and interprismatic walls are the structures that form the compartments in which crys- tals grow in an orderly manner (BEVELANDER & NAKAHARA, 1978). Unlike the examples cited above, the crossed lamel- lar structure in Strombus contains neither “sheet’’-like component to form the compartment observed during shell development, nor other adhering substance between the adjacent envelopes in the decalcified mature shell. The only identifiable organic structure is the envelope. The low-protein content of the crossed lamellar structure (0.07% in Strombus) in comparison with that of the nacre and prismatic layer of some snails and bivalves (1 to 5%, Hare & ABERSON, 1965) may be indicative of the relative simplicity of the organic matrix and the envelope in the crossed lamellar structure. The result of amino acid analysis indicates a marked difference between the composition of Strombus crossed lamellar structure and nacre (Table 1). Several reports (Grécorre et al., 1955; Hare & ABERSON, 1965; BrEvE- Page 210 THE VELIGER Vol. 23; No. 3 LANDER & NAKAHARA, 1975; WADA, 1976) report that glycine and alanine are the dominant amino acids in nacre. In the prismatic layer, glycine is present in the highest concentration. The acidic amino acids (aspartic and glutamic) in some bivalves, however, are relatively sparse in nacre and the prismatic layer. Recent studies (unpublished) show that the aspartic acid residues of the envelopes of the prismatic layer of some other bivalves is relatively high. The present analysis shows that the acidic amino acids (aspartic and glutamic) are the most prevalent residues in the organic substance of the Strombus crossed lamellar structure. Since the envelope is the dominant structure in it, it would appear that the amino acid com- position of the Strombus shell represents a fairly close approximation of the envelope substance. The possibility that some amino acid residues may be due to material other than the envelope cannot be ruled out. We maintain, however, that any contribution to the total amino acid content of the organic material being considered would, according to our observations, be relatively small or negli- gible. Recently Marsu et al., 1978 reported that the organic sheaths (envelope) of the aragonite crystals in the ligament of bivalves contain a high content of acidic amino acids. Several investigators have pointed out that the acidic amino acids play an important role in the initiation and growth of calcium carbonate minerals (HaRE, 1963; WEINER & Hoop, 1975; DEGENS, 1976). The structural and behavioral similarity of the envelopes of Strombus de- scribed in this report, as well as those of the bivalve liga- ment (BEVELANDER & NAKAHARA, 1969b; Marsu et al., 1978) and the prismatic layer (NAKAHARA & BEVELANDER, 1972), lead us to consider that the aspartic acid of the envelopes in these and several other calcified structures is analagous and suggests that the “envelope” material may be essential for and contribute to the mechanism of min- eral nucleation and growth. SUMMARY The first step in the formation of the crossed lamellar structure in young specimens of Strombus gigas is the deposition of shell organic substance on the inner surface of the periostracum, and subsequent nucleation of aragon- ite crystals in it. The crystals initially develop within tube- like envelopes formed in the organic matrix. The envelopes and crystals increase in length and are oriented alternately, which is typical of the mature crossed lamellar structure. The crystals also grow laterally, and finally come in con- tact with each other. In the more mature stages of shell formation envelopes also enclose the growing crystals. There are no prominent organic structures other than the envelopes in developing and mature shell. Amino acid analysis shows a significantly high acidic amino acid con- tent, and relatively low concentration of glycine and ala- nine in shell organic substance. Since the presence of acidic amino acids has been implicated in the initiation of Explanation of Figures 6 to 71 Figure 6: Uranyl acetate, lead citrate double stained section of early calcified shell similar to stage shown in Figure 5. Note the tubelike envelopes devoid of crystals (En), and envelopes contain- ing crystals (arrow) X 38000 Figure 7: Later stage than Figures 5 and 6, about 70m from area of crystal initiation. Thickness of calcified shell increases and more crystals appear, all the crystals are enclosed within envelopes. Note the alternate orientation of crystals. CL - crossed lamellar structure; P — periostracum. Section stained with uranyl acetate and lead citrate X 10000 Figure 8: Higher magnification of crossed lamellar structure, similar to stage in Figure 7, showing electron dense envelopes (En) enclosing all of the growing crystals. Some envelopes are only partly occupied by crystals (arrow). The space outside the envelopes ap- pears devoid of any particulate organic structures. Uranyl acetate and lead citrate stain i X 10000 Figure g: Unstained section of growing shell surface area, more advanced stage than represented in the preceding figures. Thick, rod-shaped crystals are arranged in alternate directions. >< 37000 Figure ro: Stained section of growing shell surface. Growing crys- tals are covered with single layered envelopes (En). Some envel- opes devoid of crystals are shown (arrow) stained with uranyl X 100000 Figure rr: Illustrates an incomplete demineralized portion of mature Strombus shell (demineralized before embedding) showing acetate and lead citrate intact envelopes surrounding the remaining crystals. The rest of the envelopes (where all crystals were completely dissolved) were dissociated and lost. The only discernible organic material in this incompletely demineralized material is the envelope. This indicates there is no adhering substance such as the sheets between envelopes in the mature shell ——— ee [NAKAHARA, KaAkeEI & BEVELANDER] Figures 6 to 11 gf RB ge Q —_e Figure z7 ia ae” Vol. 23; No. 3 THE VELIGER Page 211 . F ; 9 9 6 ° KNIPRATH, ERNST mineralization in other molluscan species, 1t may be im- 1970. Die Feinstruktur der Periostrakumgrube von Lymnaea stag- plied that a similar situation holds for the crossed lamellar nalis. Biomineraliz. 3: 1 - 11 ; 1972. Formation and structure of the periostracum in Lymnaea stag- structures in Strombus. nalis. Calc. Tiss. Res. 9: 260-271 KoBayYASHI, Iwao 1971. Internal shell microstructure of Recent bivalvian molluscs. Literature Cited BEVELANDER, GeRRIT & HirosH1 NAKAHARA 1969a. An electron microscope study of the formation of the nacreous layer in the shell of certain bivalve molluscs. Calc. Tiss. Res. 3: 84 - 92 1969b. An electron microscope study of the formation of the ligament of Mytilus edulis and Pinctada radiata. Calc. Tiss, Res. 4: 101 - 112 1970. An electron microscope study of the formation and structure of the periostracum of a gastropod, Littorina littorea. Calc. Tiss. Res. 5: 1-12 1975. Structure and amino acid composition of pearls exposed to sea water for four hundred years. Earth Sci. 29: 87-91 1980. Compartment and envelope formation in the process of biologi- cal mineralization. Proc. 34 internat. Biomineral. Symp., Tokai Univ. Press, Tokyo (in press) Bgcsixp, O. B. 1930. The shell structure of the mollusks. Selsk., Skr. 2: 232 - 235 DeoEns, Econ T. 1976. Molecular mechanisms on carbonate, phosphate, and silica de- position in the living cell. Topics curr. chemist. 64: 1 - 112 ErBEN, Henrico K. # Norimitsu WATABE K. dansk. Vidensk. 1974. Crystal formation and growth in bivalve nacre. Nature 248: 128 - 130 Grécorre, Cuartes, GH. DucHATEAU & MARCEL FLORKIN 1965. La trame protidique des nacres et des perles. Ann. Inst. Océanogr. 31: 1 - 36 Hare, Epoar 1963. Amino acids in the proteins from aragonite and calcite in the shells of Mytilus californianus. Science 199: 216 - 217 Harz, Epoar « P H. ABERSON 1965. Amino acid composition of some calcified proteins. Car- negie Inst. Wash. Yearb. 64: 223 - 231 Sci. Reprt. Niigata Univ. (E) Geol. Mineral. 2: 27-50 Marsu, Mary, Gary HAMILTON & RoNALD Sass 1978. The crystal sheaths from bivalve hinge ligaments. Res. 24: 45-51 NaKanwarA, HrrosHi & Gerrit BEVELANDER 1971. The formation and growth of the prismatic layer of Pinctada radiata. Calc. Tiss. Res. 7: 31-45 1978. The formation of calcium carbonate crystals in Halimeda incras- sata with special reference to the role of the organic matrix. Japan. Journ. Phycol. 26: 9-12 1979. An electron microscope study of crystal calcium carbonate for- mation in the mouse otolith. Anat. Rec. 193: 233-242 Omort, Masaz, Iwao Kosayasui, MatsutTaro SxHipata, KatsuTomo Mano #& Hmetosui Kamrya 1976. On some problems concerning calcification and fossilization of taxodontid bivalves. In: The mechanisms of mineralization in the invertebrates and plants. pp. 403 - 426; Univ. So. Carol. Press, Columbia, N. CG. Taytor, Joun D., Wittiam J. KENNEDY & ANTHONY HALL 1969. The shell structure and mineralogy of the bivalvia. Tucroaneeion Calc. Tiss. Nuculacea-Trigonacea. Bull. Brit. Mus. [Nat. Hist.] Zool Suppl. 3: 1-125 1973. The structural evolution of the bivalve shell. Paleont. 16: 519 - 534 Uozuml1, Satoru, Keiji Iwata & YosHIHIRO Toco 1972. The ultrastructure of the mineral in and the construction of the crossed-lamellar layer in molluscan shell. kaido Univ. (4) 15: 447-478 Wana, Kojr 1976. Amino acid composition of organic matrices in various pearls cultured by Pinctada fucata. Bull. Natl. Pearl Res. Lab. 20: 2209- 2213 WEINER, STEPHEN & Leroy Hoop 1975. Soluble protein of organic matrix of mollusk shells: A potential template for shell formation. Science 190: 987 - 989 Wisz, SHERWOOD W. 1971. Shell ultrastructure of the taxodont pelecypod Anadara notabilis (Roding). Eclogae geol. Helv. 64: 1-12 Journ. Fac. Sci. Hok- Page 212 THE VELIGER Vol. 23; No. 3 Male Characteristics in Female Nassarius obsoletus: Variations Related to Locality, Season and Year BY BLAKEMAN S. SMITH! Department of Biophysics and Environmental Biology University of Rochester School of Medicine and Dentistry, Rochester, New York 14642 (2 Text figures) INTRODUCTION THE DIOECIOUS PROSOBRANCH mollusk Nassarius obsole- tus (Say, 1822) [==Ilyanassa obsoleta] is the most abun- dant stenoglossan in the intertidal zone along much of the east coast and along limited parts of the west coast of North America. Within the subclass Prosobranchiata virtually all mem- bers of the Diotocardia and the Stenoglossa are dioecious along with most members of the Taenioglossa (FRETTER & GRAHAM, 1962.). However, SmiTrH (1971) reported that some female Nassarius obsoletus had one or more male characteristics, namely: 1) a penis with a duct leading to 2) a vas deferens which passed back to the ventral channel of the capsule gland and 3) convolution of the normally straight gonadial oviduct. Since this phe- nomenon did not resemble any known form of intersexu- ality, SmirH (op. cit.) called it imposex. He also reported that imposex varied greatly among nearby localities sampled on one occasion. A similar pattern has been briefly mentioned by JENNER (1979). A further study (SmirH, 1980) provided a detailed examination of the reproductive anatomy of normal snails and those with imposex. Neither gross anatomy nor light microscopy re- vealed any evidence of hermaphroditism. A graded sys- tem for the evaluation of the frequency of occurrence of imposex and its intensity of expression was proposed. This method was used to show that imposex was not related to any known pseudohermaphroditism associated with age of animals or parasitism by trematodes. The presence of a penis in females has been reported for at least 37 species of snails (JENNER, 1979; SMITH, 1980), but locational variations and variability in expres- ' Present address: Health Effects Program, Electric Power Re- search Institute, P O. Box 10412, Palo Alto, CA 94303 sion over one or more years have been poorly investigated. The current study examines the variation in the frequen- cy of imposex and its intensity of expression among 4 localities. It also examines its seasonal and yearly varia- tions. It is, consequently, the first exhaustive field study of imposex male characteristics in snail populations. METHODS Adult snails were collected either at random or by strip- ping of a standard quadrat. They were collected at inter- vals from 1972 through 1976 from 4 localities bordering on Long Island Sound in Westport and Fairfield, Connect- icut. These stations were: HB (41°07'44” N; 73°17/13” W), adjacent to Ye Yacht Yard in Southport Harbor; S (41°07'35”N; 73°17'23”’ W), amongst rock outcroppings at the mouth of Southport Harbor; OMB (41°06’49”N; 73°20'42” W), about 5 km west of S and in a part of Old Mill Beach used for swimming and moorage of a few pleasure boats; BH (41°07’01”N; 73°19/08” W), land- ward to Burial Hill Beach in a salt marsh protected from human impact. BH was approximately halfway between OMB and S and was connected to OMB through marsh channels and tidal ponds. A final sample was collected from 37°34’30”N; 122°15'30” W, near the western ter- minus of the San Mateo-Hayward Bridge in San Fran- cisco Bay, California. For dissections, the shell was cracked in a vise and re- moved; the soft parts were examined with a stereomicro- scope. Most reproductive features were visible from the surface, but a single sagittal cut through the mantle made pallial details easier to see. Identification of repro- ductive structures was based on FRETTER (1941), FRETTER & GRAHAM (1962) and MaGNER (1950). Imposex was quantified according to the regimen set forth in Smrru, Vol. 23; No. 3 THE VELIGER Page 213 (1980; Table 1). It is based on 1) the percentage of the snails in a sample with imposex (R) and 2) the average intensity of imposex in bearer snails (J). For example, if 4 snails in a sample of 40 had imposex, and all 4 were at maximal expression, for each of 3 characteristics, then R= 10% and I = 9.0 The greatest amount of imposex theoretically possible in this scheme of evaluation was R= 100% and I = 9.0. The difference in imposex between samples was evalu- ated using the test of significance between 2 proportions (BrunING & KinTz, 1977) and the Kolmogorov-Smir- nov test (SOKAL & RoHLF, 1969). RESULTS When examined during the same monthly periods in 1972-1973, snails from locality HB always had significant- ly more imposex (p < 0.05) than those from OMB, either in terms of R, I, or both (Figure 1). Taken together with 80 aD ° aS fo) Intensity of imposex. R Intensity of imposex, J Figure 1 Variation in ymposex over a period of 18 months at localities HB and OMB (1972 - 1973) more limited sampling of populations at S and BH during this period (Table 1), it is apparent that all 4 localities varied significantly from one another (p< 0.05) in terms of R, I, or both. Similarly, when sampled on comparable Table 1 Variation in imposex over a period of 2-5 years. Samples were grouped according to origin of snail and within each group samples were categorized according to the time of year when collected. Statistical comparisons were made among samples collected on similar dates for each of the localities. Date Sample Locality Sampled Size R(%) I HB 6 May 72 27 100 3.7 15 May 73 77 97 3.82 27 May 75 49 98 4.72 24 May 76 40 98 4.3 24 July 72 19 100 5.4 25 July 73 61 98 5.8 19 July 75 55 98 6.0 31 July 76 52 98 5.2 28 Oct 73 24 96 5.1 20 Oct 75 57 100 5.1 5 Dec 72 45 100 4.0 20 Nov 75 54 96 5.0 S 2 Aug 73 68 97 2.62 20 Aug 75 46 91 3.62 2 Aug 76 40 95 3.3 OMB 26 July 72 38 58! ed, 25 July 73 78 321 1.5 BH 19 May 75 72 0 0 17 May 76 60 0 0 22 Oct 73 20 0) 0 1 Nov 75 75 0 0 1Comparison significant by the test of significance between two proportions, p < .05. 2Comparison significant by the Kolmogorov-Smirnoy test, p < .05. dates during 1975 and 1976, populations from localities HB, S, and BH were all distinct from one another _(p 2 a> fe) Intensity of imposex. ~ fo) Figure 2 Variation in imposex over a period of months at localities HB, S and BH (1975 - 1976) score of zero indicated a sample which did not draw even one snail with imposex. Annual samples (Table 1) showed no clear trend to- _ wards a change in imposex over the span of 5 years. Of the 20 comparisons, only 3 yielded a significant differ- ence in R or I (p < 0.05). Based on the data in Table 1 and Figures 1, 2, it is clear that throughout the year and over a period of years the 4 localities may be ranked according to decreasing imposex in the order HB, S, OMB, BH. Of the 40 female Nassarius obsoletus collected from San Francisco Bay, 6 had imposex (R 15%) with J = 2.0. All 6 had a penis limited to a small protrusion on the head mass and all had a duct passing from the protrusion towards the edge of the mantle skirt. DISCUSSION The most prominent features of the current data on Nassarius obsoletus are the differences among localities. Along the 5km of the Connecticut shoreline containing localities HB, S, OMB and BH the incidence of imposex varies from almost 0% at BH to almost 100% at HB. A similar pattern can be derived from the data of JENNER (1979). She sampled N. obsoletus from Radio Island, THE VELIGER Vol. 23; No. 3 Beaufort, North Carolina (34°43’N; 76°41’W), Bogue Sound, Morehead City, North Carolina (36°43’N; 76° 40’W), School Marsh, Wrightsville Beach, North Caro- lina (34°11'-15’N; 77°46’-49’W) and Banks Channel, Wrightsville Beach, North Carolina (34°12'N; 77°48’ W). Her data show that at Radio Island, R =o%, while in nearby Bogue Sound R = 96%. Snails from School Marsh had no imposex, while a population from nearby Banks channel had R = 97%. Great differences between adjacent localities were also apparent in Nucella lapillus (BLABER, 1970). He measured the occurrence of a penis in females and found an average incidence of 85% below the Marine Laboratory in Plymouth, England (50°22’00” N; 4°08’00” W), but only 29% at Rum Bay in Plymouth (50°22’05” N; 4°08’38” W), 1 km distant from the Labo- ratory. : Such a pattern of expression could be attributed either to a genetic cline (METTLER & GREGG, 1969) or to a mo- saic of environmental influences. Sufficient isolation to establish a cline in Nassarius obsoletus is unlikely. At one stage of the life cycle, egg capsules may be attached to loose pieces of seaweed. These may be flushed from the intertidal zone by the ebb tides which drain much of the habitat of N. obsoletus. Laboratory studies indicate that about 8 to 16 days after deposition of the egg cap- sules, free swimming veliger larvae escape from them and remain in the plankton for about 11 to 23 days (SCHELTE- MA, 1967). During this period tidal currents of more than 1 km/hr (U.S. Dept. Commerce, NOAA, 1973) have the potential of exchanging enough veligers among the locali- ties studied to prevent significant genetic drift. This is supported by Goocu, SmirH « Knupp (1972) who, using polyacrylamide gel electrophoresis, found no sig- nificant difference in gene frequencies of a polymorphic locus for lactic dehydrogenase (LDH) in N. obsoletus taken from OMB and a site near locality S. Indeed, along a transect extending from Woods Hole, Massachusetts (41°31’N; 76°40’ W) to Beaufort, North Carolina (34° 43N; 76°40’ W), a distance of more than 700km, they found no significant gene frequency differences at either the LDH locus or at a general protein locus. The presence of imposex in Connecticut and California illustrates that it exists in widely separated populations between which the exchange of genes is probably ex- tremely limited. Nassarius obsoletus was introduced to the west coast coincidental to the transfer of adult and seed oysters from the east coast. The oysters were introduced during the period 1860-1910, and those shipments bring- ing the mud snail to San Francisco Bay probably occurred in the period 1904-1907 (CARLTON, 1975, 1979). The shipment of some adult and seed oysters to the west coast Vol. 23; No. 3 THE VELIGER Page 215 still persists and, although under tight controls (CARLTON, 1975), some N. obsoletus juveniles or egg cases may be transported along with these oysters. BLABER (1970) col- lected data on the presence of a penis in female Nucella lapillus from Millport, Scotland (55°45’N; 4°54’W), Black Rock, Sussex, England (50°50’N; 0°09’ W) and Plymouth, England (50°22’N; 4°08’W), all sampled in December and January. Despite the great distances be- tween localities, he found the abnormality in all instances (Millport, R==5%; Black Rock, R= 30%; Plymouth, R=77%). For the presence of a penis in female Nucella lapillus and the expression of imposex in Nassarius obsoletus to be explained by a genetic cline, the difference between popu- jations would have to be ordered along the distance of separation. This was not found in either Nassarius obso- letus or Nucella lapillus. Instead, the differences between nearby populations were often greater than for widely separated populations. Such a pattern is suggestive of Jocal environmental influences on the phenotype. The amount of imposex is relatively constant over a period of years. The current data, collected during 1972- 1976, show no trend towards a change in imposex in samples collected from any of the 4 localities. This is sup- ported by an earlier study on Nassarius obsoletus (SMITH, 1971), which reported in September 1970 R = 98% at HB and 23% at OMB. These values are well within the range of observations for the period 1972-1976. Stability over the years was also mentioned by JENNER (1979). In studies of Ocenebra erinacea FERAL (1976) reported that the percentage of females with a penis in the Basin of Arcachon, France in February 1973 and January 1974 was also relatively constant (95% and 90%, respectively). There are variations in the intensity of imposex within a year, the most marked being a sharp decline near the start of the breeding season in April and May, followed by a gradual return to previous levels over the span of the summer. Such variations never overshadowed the differ- ences among localities HB, S, OMB and BH. Monthly variations in penis expression have also been studied in female Ocenebra erinacea from the Basin of Arcachon (FERAL, 1976). She reported that the most marked de- pression in penis expression was in April, just before egg capsules were deposited. In March 1973 the frequency of penis expression in females was 95%, in April 56% and in May 95%. FERAL (1975) reported that affected female Ocenebra erinacea have a morphogenetic hormone causing the growth and differentiation of a penis. Such a hormone normally occurs in the male. Similar hormones controlling the growth, differentiation and resorption of secondary sexual characteristics have been found in both gonochor- istic and ambisexual marine gastropods, often having activity across species lines (STREIFF, 1966, 1977; STREIFF & Le BRETON, 1970a, 1970b). The results of this study open the possibility that a chemical factor, occurring locally in marine environments stimulates the release or mimics the action of such a hormonal substance in fe- males of Nassarius obsoletus. SUMMARY 1) The superimposition of male characteristics on fe- males of the dioecious species, Nassarius obsoletus, was Called imposex. It was graded according to the frequency of affected individuals in the populations and the intensity of expression in the subpopulation of affected individuals. 2) The expression of imposex varied greatly among localities along a 5km segment of Connecticut shoreline. A marsh population had a frequency close to 0%; a yacht basin population had a frequency close to 100%, with intensity averaging about 5 points out of a theoretical maximum of 9. 3) At any given locality the expression of imposex remained nearly constant at the same season over a period of years. 4) Significant variations occurred within a year, usu- ally in the spring, but did not overshadow the differ- ence among localities. 5) The pattern of expression was suggestive of an en- vironmentally induced anatomical abnormality rather than a genetic cline. 6) Reinterpretation of data published for 2 other spe- cies of snails yields a similar pattern of expression. ACKNOWLEDGMENT I thank David R. Lindberg of the California Academy of Sciences and the Oceanic Society (San Francisco) for collecting and shipping snails from San Francisco Bay. Literature Cited BiaBer, STEPHEN J. M. 1970. The occurrence of a penis-like outgrowth behind the right ten- tacle in spent females of Nucella lapillus (L.). Proc. Malacol. Soc. London 39: 23: - 233 Page 216 THE VELIGER Vol. 23; No. 3 Brunine, James L. « B. L. Kintz 1977- Computational Handbook of Statistics. 2nd ed.; 308 pp.; illust. Scott, Foresman, Glenview, Illinois Carton, JAMES THEODORE 1975- Introduced intertidal invertebrates. in James T. Carlton « Ralph I. Smith, eds. “Light’s Manual: Intertidal invertebrates of the Central California coast.” 3d ed. i-xvii+716 pp.; illus. Berkeley, Calif. (Univ. Calif. Press) 1979. Introduced invertebrates of San Francisco Bay. in T. John Conomos, ed. San Francisco Bay: the urbanized estuary. 435 pp.; illust. San Francisco, Calif. (Pacif: Divis., AAAS) Ferra, CoLetre 1975- Mise en évidence des facteurs déterminant l’apparition et le cycle d’un tractus génital male externe chez les femelles d’Ocenebra erinacea (L.) du bassin d’Arcachon. Bull. Soc. Zool. Frang, 100 (2): 251 (abstract) 1976. Etude statistique de la présence d’un tractus génital male ex- terne chez les femelles d’un mollusque gastéropode gonochorique: Oce- nebra erinacea (L.). Cah. Biol. Mar. 17: 61 - 76 FRETTER, VERA 1941. The genital ducts of some British stenoglossan prosobranchs. Journ. Mar. Biol. Assoc. U. K. 25: 173 - 211 FRETTER, VERA & ALASTAIR GRAHAM 1962. British Prosobranch Mollusks. i- xvi+755 pp., illust. Ray Soc., London Goocn, James L., BLAKEMAN S. SmiTtH & Donna Knupp 1972. Regional survey of gene frequencies in the mud snail Nassartus obsoletus. Biol. Bull. 142 (1): 36-48 JENNER, MaxTHA GARRETT 1979. Pseudohermaphroditism in Ilyanassa obsoleta (Mollusca : Neo- gastropoda). Science 205: 1407 - 1409 Macner, A. 1950. ‘The histology of the reproductive system of Nassartus obsoletus (Say). M. S. thesis, Duke University Metter, LAWRENCE E. & THomas G. Greco 1969. Population genetics and evolution. Cliffs, N. J. (Prentice-Hall) xiit+212 pp., Englewood ScHELTEMA, RupotF S. 1967. The relationship of temperature to the larval development of Nassarius obsoletus (Gastropoda). Biol. Bull. 132: 253 - 265 SmitH, BLAKEMAN S. 1971. Sexuality in the American mud snail, Nassarius obsoletus (Say). Proc. Malacol. Soc. London 39: 377 - 378 1980. The estuarine mud snail, Nassarius obsoletus: Abnormalities in the reproductive system. Journ. Moll. Stud. (in press) SoxaL, Ronert R. & FE James RoHLF 1969. Biometry: The principles and practice of statistics in bio- logical research. xxi+776 pp.; illus. Freeman Co., San Francisco, Calif. STREIFF, WILFRIED 1966. Etude endocrinologique du déterminisme du cycle sexuel chez un mollusque hermaphrodite protandre Calyptraea sinensis (L.). I. Mise en évidence par culture in vitro des facteurs hormonaux conditionnant Pévolution du tractus génital male. Ann. Endocr. 27 (3 suppl.): 385 - 400 1967. Etude endocrinologique du déterminisme du cycle sexuel chez un mollusque hermaphrodite protandre Calyptraea sinensis (L.). II. Mise en évidence par culture in vitro de facteurs hormonaux condition- nant l’évolution du tractus femelle. Ann. Endocr. 28: 461 - 472 StreirF, WILFRIED & Jacques Lz BRETON 1970a. Etude endocrinologique des facteurs régissant la morphogenése ct la régression du pénis chez un mollusque prosobranche gonochorique, Littorina littorea. Compt. Rend. hebdom. Séances Acad. Sci. Paris 270: 547-549 1970b. Etude comparée en culture in vitro des facteurs résponsables de la morphogenése et de la régression du tractus génital male externe chez deux mollusques gastropodes prosobranches Crepidula fornicata (espéce protandre) et Littorina littorea (espéce gonochorique). Compt. Rend. hebdom. Séances Acad. Sci. Paris 270: 632 - 634 U. S. DEPARTMENT OF CommeErcE, NOAA 1973. National Oceanic Survey. Tidal current charts, Long Island Sound and Block Island Sound. 5th ed. Vol. 23; No. 3 THE VELIGER Page 217 Rectification of the Generic Placement of Sclerodoris tanya (Marcus, 1971), comb. nov., A Nudibranch from Southern California, with a Range Extension to the Gulf of California, Mexico HANS BERTSCH Waikiki Aquarium, 2777 Kalakaua Avenue, Honolulu, Hawaii 96815 (1 Plate; 1 Text figure) In 1971 EveLInE Marcus NAMED a new species of nudi- branch Doris tanya, based on one specimen collected at Newport Bay, California. Since then, this species has been found commonly in several intertidal and subtidal arcas of San Diego and from Gulf of California, Mexico, locali- ties. Examination of several of these animals has revealed that the original taxonomic placement is erroneous and needs rectification. SYNONYMY anp REFERENCES Doris tanya MARCUS, 1971: 357-362; figs. 4-8. SPHON, 1972: 63. SPHON, 1973: 5. MARCUS, 1973: 5. Halgerda sp. HERTZ, 1978: 99; fig. 1. MATERIAL EXAMINED AND DISTRIBUTION Southern California 1) 2 specimens, Flood Control Channel, Mission Bay, San Diego; leg. Ed Brothers, 14 July 1973, snorkeling. 2) 4 specimens, Flood Control Channel; leg. James R. Lance, 16 July 1973, snorkeling. 3) 1 specimen, Flood Control Channel; leg. Don Cadien, 10 November 1973. 4) 1 specimen, Flood Control Channel, Mission Bay, San Diego; leg. Jake Patton, May 1974, 6 feet deep (LACM A.9075). 5) 1 specimen, Sunset Cliffs (foot of Hill St.), Pt. Loma, San Diego; leg. J. Lance, 22 June 1974, intertidal. 6) 2 specimens, South Casa, La Jolla; leg. Antonio J. Fer- reira and J. Lance, 20 July 1974, intertidal. 7) 2 specimens, S. Casa; leg. J. Lance, 30 July 1977, inter- tidal (length and width of living animals: 64mm x 28 mm and 51 mm x 24 mm). 8) 1 specimen, S. Casa; leg. J. Lance, 27 August 1977, inter- tidal (49 mm x 23 mm living). 9) 4 specimens, S. Casa; leg. J. Lance, 4 July 1978; inter- tidal. 10) 2 specimens, S. Casa; leg. J. Lance, 21 July 1978, inter- tidal. 11) 1 specimen, Shell Beach, La Jolla; leg. Jules Hertz, 27 July 1978, intertidal (HB 674) . 12) 2 specimens, San Diego area; leg. James R. Lance, Aug- ust 1978, intertidal (HB 675). 13) 1 specimen, Flood Control Channel, Mission Bay, San Diego, leg. H. Bertsch and David Myers, 26 August 1978, 6 feet deep (HB 676). 14) 8 specimens, S. Casa; leg. J. Lance, 15 Sept. 1978, inter- tidal. 15) 3 specimens, La Jolla; leg. J. Lance, early October 1978, intertidal (HB 746). 16) 1 specimen, S. Casa, leg. D. Cadien and J. Lance, 11 June 1979, intertidal (13 mm long). 17) 1 specimen, Scripps Canyon, La Jolla; leg. John Meuse, g October 1979, 60 feet depth (76 mm x 34 mm living). Gulf of California, Mexico 18) 1 specimen, Cholla Bay, Sonora; leg. Constance Boone, 10 June 1975, under rock, intertidal. 19) 1 specimen, Puerto Penasco, Sonora; leg. H. Bertsch, 1 August 1975, 10-15 feet deep, below extreme low tide (HB 291). 20) 1 specimen, N. end of San Felipe, Baja California; leg. David K. Mulliner, 1 June 1973, intertidal (—5 foot low tide) . 21) 1 specimen, Isla San José, Baja California Sur; leg. Heidi Hahn, 12 April 1975, 50 feet deep. Page 218 THE VELIGER Vol. 23; No. 3 The last 4 entries extend the range of Sclerodoris tanya from the Californian faunal province (open Pacific coast of southern California) to the subtropical Gulf of Cali- fornia (Panamic faunal province). The sudden recent appearance of Sclerodoris tanya in southern California is intriguing and invites speculation. James Lance (personal communication) has been collect- ing nudibranchs in the San Diego area and keeping com- plete field notes of species found since 1951. In over 350 field trips prior to 1973, he had not seen S. tanya. The species was not missed nor overlooked—it was not present. The species has since appeared regularly for 7 years during the summer and autumn months (Figure 1). 15 I0o- Number of Specimens JFMAMJJASOND Figure 1 Monthly frequency of collecting Sclerodoris tanya in the San Diego area, 1973 - 1979 Sclerodoris tanya was probably not introduced from Japan, as were Okenia plana Baba, 1960a (STEINBERG, 1963) and Eubranchus misakiensis Baba, 1960b (BEHRENS, 1971). It does not appear to be an Indo-Pacific species nor Atlantic species. Sclerodoris tanya probably did not orig- inate in subtidal waters and move to the intertidal area; if so the extensive scuba diving activity in the San Diego region should have resulted in the collection of this species. I suggest that Sclerodoris tanya was originally endemic to the Gulf of California (where the opisthobranch fauna is more poorly known) and has extended its range northward to the warm temperate waters of southern California. Nu- merous species of opisthobranchs have such an amphi- provincial distribution, occurring both in the Californian marine faunal province and the tropical west American province (BERTSCH, 1973). ANATOMY Representative lengths of 9 living animals measured: 76, 64, 51, 49, 38, 30, 25, 25 and 13mm. Cross-section outline of animal’s body an isosceles trapezoid because of a prom- inent flattened ridge lengthwise down the dorsum between the rhinophores and gills. The top of the ridge and the lateral slopes each are textured with a row of depressions (Figure 2). These pits are encircled by minor ridges that often give rise to prominent round tubercles. The pine- cone appearance mentioned by Marcus (1971: 358, “the notal warts are wide cones beset with lesser ones, like pine- cones’) is an artifact of preservation. When an animal was placed directly into 70% ethanol, it contracted so that the cratered depressions were no longer obvious, and the tubercles bunched up and crowded together. The differ- ences in notal texture and sculpture illustrated by Marcus (1971: figs. 4 and 5) are simply the differences between the living animal and a preserved specimen. The highly rugose notum is similar to that seen in other members of the genus Sclerodoms. Living S. tanya resemble a rough, jagged rock or a sponge, and are cryptic within their natural surroundings. Body color appears a gray-brown, because the whitish background is almost completely occluded by numerous minute, close, chocolate-brown dots. Irregular darker black-brown coloration appears in the depressions. The tips of the papillae are often covered with splashes of chocolate-brown, and very small white dots. Explanation of Figures 2 to 7 Figure 2: Living Sclerodoris tanya (collected by Jules Hertz, 27 July 1978) and its egg mass. Photograph by David Mulliner Figures 3 to 7: Scanning electron micrographs of the radula of Sclerodoris tanya (specimen 746-a); microscopy by H. Bertsch and Robert Pettyjohn Figure 3: Entire radula X 32.4 Figure 4: Main functional teeth in middle of halfrow xX 162 Figure 5: Innermost teeth of half-row X 378 Figure 6: Outermost lateral teeth xX 756 Figure 7: Newest developing rows of teeth (posteriormost part of radula) X 95-2 Tue VeuicErR, Vol. 23, No. 3 [BertTscH] Figures 2 to 7 Vol. 23; No. 3 THE VELIGER Page 219 Portions of the internal anatomy need commentary. The radular sac protrudes past the buccal bulb; there are very long, thin salivary glands (cf. Marcus, 1971: fig. 4). Table 1 Radular formulae of Sclerodoris tanya. Maximum number Specimen Number of rows of teeth per half-row HB291 21-22 29-33 HB 674 23-24 27-31 HB 675-A Damaged 25-26 HB 675-B 23-24 27-29 HB 676 26 31-36 HB 746-A 25-26 27-30 HB 746-B 22-24 28-30 HB 752 25 42-43 Marcus, 1971 23 33 The combined radular formula from 9 specimens is 21- 26 rows, with 25-43 teeth per half-row (Table 1 lists the individual formulae). There is no rachidian tooth. Sclero- doris tanya has simple, smooth, hamate teeth (Figures 3 and 4); degree of curvature of the erect shaft (sensu Boom, 1976) and size of teeth vary within the half-row; compare the shapes of the innermost (Figure 5), central (Figure 4) and outermost (Figure 6) lateral teeth. The base of all teeth (Figures 5 and 6) has a lateral flange on the inner surface, which partially underlies the adjacent tooth, possibly giving within-row tooth support for the rasping teeth. Such support has been documented previously for other nudibranchs (cf. FERREIRA & BERTSCH, 1975: 327). Newly developing teeth (Figure 7) form the free erect shaft first as very thin needles. Thickening and basal devel- opment subsequently follow. DISCUSSION Marcus (1971) placed this species within the catch-all genus Doris primarily because of the anatomy of portions of the reproductive system. However, familiarity with numerous living specimens indicates generic placement within that group of dorids that exhibit a reticulate pattern of ridges and depressions on the dorsum. Moreover, the reproductive system of Doris tanya does not differ from that of known species of Sclerodoris (cf. EomMuUNDs, 1971; and RupMan, 1978). Following RupMAN ( of. cit.), Table 2 lists 8 differentiating structural traits of Halgerda Bergh, 1880, and Sclerodoris Eliot, 1904, and the features that characterize the Marcus species as Sclerodoris. Based on the present comparative analysis of the species, it should be classified as Sclerodoris tanya. Accordingly, this is the first species of S'clerodoris known from the eastern Pacific. Table 2 Differentiating morphological traits of Halgerda and Sclerodoris, compared with Sclerodoris tanya. After Rupman, 1978; Marcus, 1971; and personal observation. The Marcus (1971) terms spermatheca and spermatocyst are equivalent to RupMan’s (1978) gametolytic sac and exogenous sperm sac respectively. Halgerda Sclerodoris Sclerodoris tanya Smooth, jelly-like firm feel of mantle Large gill axes, scanty pinnules Openings to rhinophore and gill pockets smooth Integument enclosing viscera usually very dark brown or black viscera Radular sac is long and curved buccal sac Gametolytic sac enclosed in gland of the prostate Short salivary glands Hard, rough mantle; spiculate Gills tripinnate and bushy Large rhinophore clubs on long narrow stalks Rhinophore club not on long stalk Opening of rhinophore and gill pockets slightly raised and crenulate Light colored integument surrounding Radular sac projects a little way out of Gametolytic sac separate from prostate Rough surface spiculate Multipinnate gills Rhinophore club not on long stalk Branchial pouch of 6-lobed margin Light colored integument surrounding viscera Radular sac projects out of buccal sac Spermatheca (gametolytic sac) separate from prostate Salivary glands long and narrow, extending Long, narrow salivary glands back under digestive gland Page 220 THE VELIGER Vol. 23; No. 3 Other known species of Sclerodoris are Indo-Pacific (from Africa to Hawaii and Japan). ACKNOWLEDGMENTS I am grateful to Gale Sphon (Los Angeles County Natural History Museum) for giving me specimens; David Myers (San Diego) for collecting assistance; David K. Mulliner (San Diego) for giving me specimen information and the photograph; Dr. Donald A. Thomson and Sr. Xicotencatl Saldivar, for allowing me to use the facilities of the Uni- versity of Arizona-Universidad de Sonora Cooperative Marine Station at Puerto Penasco, Sonora, Mexico; Rob- ert Pettyjohn for help with the scanning electron micros- copy; Anthony D’Attilio for the graph; Deanne Deméré for typing; Judith Dyer (Librarian, SDNHM) for obtain- ing needed references; and Judith Bertsch for comments on the manuscript. I especially thank James R. Lance (La Jolla) who generously let me use his collecting records of Sclerodoris tanya, and gave me critical advice for the preparation of this article. Partial funding for this re- search was supplied by the San Diego Natural History Museum. Literature Cited Basa, KixuTARO 1960a. The genera Okenia, Goniodoridella and Goniodoris from Japan (Nudibranchia-Goniodorididae) . Publ. Seto Mar. Biol. Lab. 8 (1): 79-83; plts. 7-8 (May 1960) 1960b. Two new species of the genus Eubranchus from Japan (Nudi- branchia-Eolidacea). pit. 34 Publ. Seto Mar. Biol. Lab. 8 (2): 299 - 302; (December 1960) BEHRENS, Davip W. 1971. Eubranchus misakiensis Baba, 1960 (Nudibranchia : Eolidacea) in San Francisco Bay. The Veliger 14 (2): 214-215 (1 October) Berou, Lupwic SopHus RupoLr 1880. Beitrage zur Kenntniss der japanischen Nudibranchien. I. Verhandl. K. K. Zool.-Bot. Gesellsch. Wien (Abhandl.) 30: 155 - 200; 5 pits. 4 (April 1880) BertscH, Hans 1973- Zoogeography of opisthobranchs from tropical west America. The Echo, West. Soc. Malac. Ann. Reprt. 5: 47-54 (5 March 1973) Bioom, STEPHEN A. 1976. Morphological correlations between dorid nudibranch predators and sponge prey. The Veliger 18 (3): 289-301; 1 text fig. (1 January 1976) EpmMunps, Matcotm 1971. Opisthobranchiate Mollusca from Tanzania (Suborder: Dorida- cea). Zool. Journ. Linn. Soc. London 50 (4): 339-396; 1 plt.; 23 text figs. (November 1971) Eviot, CHartes Norton EpcEcoMBE 1904. On some nudibranchs from East Africa and Zanzibar. Part 3. Proc. Zool. Soc. London 1904 - 2: 354-385; plts. 22 - 24 (18 April 1905) FERREIRA, ANTONIO J. & Hans BertscH 1975- Anatomical and distributional observations of some opistho- branchs from the Panamic faunal province. The Veliger 17 (4): 323 - 3303; 3 pits.; 1_text fig. (1 April 1975) Hertz, JuLEs 1978. Unusual find. The Festivus 10 (11): 99; 1 text fig. (November 1978) Marcus, EveLINnE bu Bors-REYMOND 1971. On some euthyneuran gastropods from the Indian and Pacific Oceans. Proc. Malac. Soc. London 39 (5): 355-369; 20 text figs. (August 1971) 1973- On the scientific names of new species. The Tabulata 6 (1): 5 (1 January 1973) Rupman, WILLIAM B. 1978. The dorid opisthobranch genera Halgerda Bergh and Sclero- doris Eliot from the Indo-West Pacific. Zool. Journ. Linn. Soc. 62 (1): 59-88; 1 plt.; 15 text figs. (24 January 1978) Spon, Gare G. 1972. An annotated checklist of the nudibranchs and their allies from the west coast of North America. Opisthobranch Newsletter 4 (10-11): 53-79 (October-November 1972) 1973- Siamese tails # 2. The Tabulata 6(1): 5 (1 January) STEINBERG, JoAN EMILY 1963. Notes on the opisthobranchs of the west coast of North America — III. Further nomenclatorial changes in the order Nudibranchia. The Veliger 6 (2): 63 - 67 (1 October 1963) Vol. 23; No. 3 THE VELIGER Page 221 Growth and Production in Exploited and Unexploited Populations of a Rocky Shore Gastropod, Turbo sarmaticus A. McLACHLAN anp H. W. LOMBARD Zoology Department, University of Port Elizabeth, Republic of South Africa (10 Text figures) INTRODUCTION THE “ALIKREUKEL,” Turbo sarmaticus Linnaeus, 1758 is a large edible gastropod, common on rocky shores along the south coast of South Africa where it is collected pri- vately for eating and for use as bait. Unlike the “perlemo- en,” Haliotis midae, it is not exploited commercially de- spite the large populations that may develop in the lower intertidal and subtidal zones. The only completed work on this species is a paper on biochemical composition (Mc- LacHLANn & LomsarD, 1979) and an unpublished M. Sc. thesis by Lombard in 1977. Growth has been studied in some other intertidal gastropods from rocky shores in this region (NEWMAN, 1968; BraNcH, 1974), but no produc- tion estimates have been published. The aims of this study were to obtain information on growth and production in Turbo sarmaticus near the centre of its range. The close proximity of both an ex- ploited population and a population subject only to natu- ral mortality allowed further investigation of the effects of removal of adults on population structure and produc- tion in a large edible gastropod. MATERIALS anp METHODS Two study areas were chosen on opposite sides of the headland at Cape Receife near Port Elizabeth, 34° 00'S, 25°30’ E. Flat Rocks faces north eastwards and is partly protected from the swell (which approaches mainly from the south-west) by the headland. The second area, Skoen- makerskop, faces southwards and is exposed to fairly heavy wave action. Flat Rocks is a boulder strewn shore of gentle slope while Skoenmakerskop is steeper with deep pools and gullies. Temperatures in the shallows at Port Elizabeth have an annual range of 10-25°C with monthly means of about 21°C in January and 15°C in July and August. Temperatures at Skoenmakerskop can occasion- ally be several degrees lower than at Flat Rocks due to brief local upwelling in summer. The Turbo sarmaticus population is heavily exploited at Flat Rocks but virtually untouched at Skoenmakerskop because of its limited ac- cessibility. Morphometric Characteristics To obtain the relationship between shell breadth, shell “length” and operculum diameter 70 animals collected from both localities and covering a full size range were measured to 0.1 mm with vernier calipers. These measur- ments are illustrated in Figure 1. Shell breadth/dry body mass relationships were determined for 61 animals from Skoenmakerskop and 88 from Flat Rocks. Shell breadth was measured to 0.1 mm and dry mass obtained at 100°C after removal of shell and operculum. Sampling Because of a vertical zonation of size classes, sampling covered the whole zone occupied by Turbo sarmaticus down to about 1 m below the spring low tide level (LWS). The intertidal area over which animals were collected totalled 460m? at Skoenmakerskop and 600m* at Flat Rocks. Sampling was done every second month from Feb- ruary 1975 to July 1976. All animals were measured to Page 222 THE VELIGER Vol. 23; No. 3 — — — — Breadth —--— --— Length Figure 1 View of Turbo sarmaticus from above the spire showing length and breadth measurements and position of plastic tag 1mm shell breadth and immediately returned to the col- lection area. Growth Estimate From the sampling results length/frequency histograms with 4mm class intervals were constructed and year clas- ses separated using probability paper (CassIE, 1954). Tagging wasalsoused to estimate growth rates. At Skoen- makerskop 187 animals larger than 20mm shell breadth were tagged in May 1975. This was done by taking them back to the laboratory, drilling 2 small holes above the aperture (Figure 1) and attaching a small plastic tag with nylon line. All animals were measured to 0.1 mm shell breadth and returned to the collection area within 24 hours after being kept overnight in an aquarium. This was not done at Flat Rocks because of human interference. From both the mean values from the size/frequency his- tograms and the tagging results Ford-Walford plots were constructed to estimate the constants L~ and K in the von Bertalanffy growth equation (Crisp, 1971) which is: L, —. ( I —.e K(tto) ) where L is shell breadth at age t, L is the average maxi- mum shell breadth to which animals in the sampled population grow, K is a constant (4 of the rate of kata- bolism) and t, is the hypothetical age when Turbo sar- maticus would have had a shell breadth of omm if it had grown according to the equation. Growth rings could not be identified in the opercula. Production Production was estimated for each age class as both growth and mortality at both study areas as outlined by Crisp (1971): Lae Pp =ZAW, Ni where P, is production by growth, AW, is the increase in mean individual mass over time interval t and N, is the mean number of individuals in the year class over time interval t. nee PNG where Px is production by mortality, AN, is the decrease in numbers over time interval t and W, is the mean individual mass over time interval t. RESULTS Morphometric Characteristics The relationships determined were as follows: Operculum diameter (mm) = 0.504 shell breadth (mm) + 1.791 (r = 0.997, p < 0.001) Shell length (mm) = 1.232 shell breadth (mm) + 2.751 (r = 0.999, p < 0.001) For Flat Rocks: Log dry mass (mg) ~2.36log,, shell breadth (mm) — 0.207 (r=0.993, Pp <0.001) For Skoenmakerskop: Log dry mass (mg) —2.89 log, shell breadth (mm) — 0.173 (r==0.989, p< 0.001) Skoenmakerskop animals are initially heavier but by a shell breadth of about 70mm have become lighter than animals of the same shell breadth at Flat Rocks. The latter 2 regressions did, however, not differ significantly (analysis of covariance) and are illustrated in Figure 2. Population Sampling On both shores the populations exhibited vertical size class zonation with small individuals in rock pools on the mid shore and large animals at and below LWS (Figure 3), this trend being significant (linear regression, p<(0.05) on both shores. The size/frequency histograms for Skoenmakerskop and Flat Rocks are given in Figures 4 and 5 with 4mm shell breadth intervals. The mean Vol. 23; No. 3 THE VELIGER Page 223 20 o+ + e 6 e@ =e Skoenmakerskop A + + * +4 Flat Rocks fi + 16 e @ @ e tHe 6 e + ene a = > 3 aQ fey A 8 4 ) fo) 20 40 60 80 Shell Breadth (mm) Figure 2 The relationship between dry body mass and shell breadth for Turbo sarmaticus from Skoenmakerskop and Flat Rocks. See text for equations Page 224 THE VELIGER Vol. 23; No. 3 Flat Rocks 80 20 Shell breadth (mm) 20 Ez “Se oO at g oe 20 S © 40 80 120 160 200 Horizontal Distance (m) 5 Skoenmakerskop ° 80 = 2 20 ex gs : : ~ 60 Z s 3 40 o 5 2 20 nN 40 30 20 a 40 & Sp Bs 20 cp) vo EO) 2% re —2 Horizontal Distance (m) 40 : 20 Figure 3 Profiles of the intertidal zones and intertidal size distributions of 6 Turbo sarmaticus at Flat Rocks (above) and Skoenmakerskop BS 2B 2) Bf 45 GB OL SD (below). Vertical heights are from mean low water of springs. Class Intervals (mm) Means + one standard deviation and ranges of size of Turbo sar- maticus are indicated Figure 4 Vol. 23; No. 3 THE VELIGER Page 225 Figure 5 Size frequency histograms for Turbo sarmaticus from Flat Rocks. Dates of sampling and total number of animals collected are indi- cated. Arrows indicate cohort means (adjacent column —>) values for shell breadth for year classes separable with probability paper are indicated with arrows. Three classes were separable at Skoenmakerskop and 4 at Flat Rocks. The smallest class was first collected in September with mean shell breadth around 5 mm at both areas. Spawn- ing occurs during November-March (Lomparb, 1977) and settlement was therefore probably mainly in July. Tagging Forty-eight tagged animals were recovered of which 8 were recovered twice and one 3 times. Figure 6 illus- trates growth rates of animals in the size classes 21-40 mm, 41-60 mm and > 61mm shell breadth based on growth increments between tagging and recovery. Faster growth rates for the smaller classes and increased growth in sum- mer are clearly evident. In Figure 7 this is converted to depict growth increments as a function of initial shell breadth, and mean values from the size/frequency histo- grams are included. Numbers 600 m=? Growth The Ford-Walford plot with the histogram and tagging data is given in Figure 8. The 3 lines shown do not differ significantly (analysis of covariance). As the tagging data cover mainly the larger sizes and mean values from the histograms cover the smaller sizes, the two were pooled for Skoenmakerskop to obtain a combined equation: L,.1 = 0.6441, + 28.505 (r—0.989, p< 0.01) From these data Lx and K in the von Bertalanffy growth equation are 80.070 and 0.440 for Skoenmakers- kop and 86.857 and 0.271 for Flat Rocks. The following (< on facing page) Figure 4 Size frequency histograms for Turbo sarmaticus from Skoenmakers- kop. Dates of sampling and total number of animals collected are indicated. Arrows indicate cohort means 5 13 20 29 37 45 53 61 69) 77 Class Intervals (mm) Page 226 Growth Rate (mm month") Months 1975 | 1976 Figure 6 Growth rate of three size classes (given in mm shell breadth) of Turbo sarmaticus at Skoenmakerskop based on tagging results ++ + Tagging 28 e°% e Histograms Y=— 0.356 X+28.505 (r=— 0.966) 24, 1 [e} Increase in Shell Breadth (mm y-') fo) 20 40 60 80 Initial Shell Breadth (mm) THE VELIGER Shell Breadth (mm) Vol. 23; No. 3 von Bertalanffy growth equations are then derived for these 2 populations (Figure 9): Skoenmakerskop: L, = 80.07 (1 —e°44(**°°27) ) Flat Rocks: Ly == 86:85 7(0— en aes) This suggests that growth is initially faster at Skoen- makerskop but levels off sooner at Flat Rocks (Figure g). 100 80 60 AG par rer Skoenmakerskop ee Flat Rocks 20 fo) I .2 3 4 5 6 7 Age (years) Figure 8 Ford-Walford plots for Turbo sarmaticus based on (1) tagging re- sults from Skoenmakerskop ; (2) population sampling results (histograms) from Skoenmakerskop; and (3) population samp- ling results from Flat Rocks Production Production estimates based on the population samples are given in Tables 1 and 2. Older year classes that could not be accurately separated were pooled. At Skoenmakers- kop Py exceeded P,, indicating a drop in biomass over the study period. Steady state production (P) was great- est for the older classes due to their large standing crops, but steady state production/biomass ratios (P/B) were maximum for the o + class. The low P/B for the 1 + class is probably due to inaccurate separation of classes. (< adjacent column) Figure 7 Relationship between shell breadth and annual growth rate in Turbo sarmaticus based on tagging data and from size frequency histograms for Skoenmakerskop Wall, gis INO). @ THE VELIGER Page 227 L,,.= 0.642 L,+28.496 (r=o.997) L,,,=0-687 L,+27.693 (r=o.g18) (3)--—-- L,,, =9.757 L,+20.993 (r=o.982) fe) 20 40 60 80 L, (mm) Figure 9 von Bertalanffy growth curves for Turbo sarmaticus from Skoen- makerskop and Flat Rocks The overall mean biomass was 8.40g.m7? and the overall mean annual P/B 0.48y". At Flat Rocks the general pattern was similar but younger age classes made a greater contribution to total production. P/B ratios decreased from younger to older age classes. The overall mean biomass and P/B ratios were 1.71g.m * and o0.69y '. This area thus supports a smaller standing crop composed mainly of younger individuals. As a result of the higher P/B ratios of younger classes, Flat Rocks thus has a higher overall P/B. Reproductive output (P,) for these 2 populations has been estimated (LomparD, 1977) on the basis of changes in gonad mass in adults. This was found to give annual P,/B ratios of 0.08y ' and 0.07y" for Skoenmakerskop and Flat Rocks, making the Prora,/B ratios 0.56y' and o.76y', respec- tively. The unexploited population at Skoenmakerskop thus exhibits higher biomass, greater contribution by adults, lower P,/B but slightly higher contribution to reproductive output than the exploited population at Flat Rocks. The mean energy values of dry tissue of Turbo sarmati- cus were 19.55kJ.g' and 19.51kJ.g" at Skoenmakerskop and Flat Rocks, respectively (McLAcHLAN & LomBarD, 1979) and do not differ significantly (t-test). Production in energy terms thus amounted to 91.96kJ.m?.' and 25.36kJ.m™*.y' at these 2 localities, respectively. Because of widely differing numbers in different year classes no reliable estimate of mortality could be ob- tained for Skoenmakerskop. The rapid drop-off in num- ‘Table 1 Results of analysis of Turbo sarmaticus population at Schoenmakerskop over 460 days during 1975/6. N = mean numbers, W = mean mass, B = mean biomass, Pm = production by mortality, Pg = production by growth, P = steady state production. Year Class o+ 1+ Q+ 3+> Total N 460m—2 13.86 116.43 197.29 153.00 480.58 Wg-1 0.33 2.57 8.17 12.74 23.81 B g. 460m—2 4.58 299.51 1611.86 1949.22 3865.17 Pyy g- 460m—2460d—1 4.32 —313.14 750.80 2058.78 2500.76 Pc g. 460m—2460d—! 13.42 424.67 1359.76 425.08 9999.93 P g. 460m—2460d—1 8.87 55.77 1055.28 1241.93 2361.85 P/B 460d—! 1.94 0.19 0.65 0.64 0.61 P/By-! 1.54 0.15 0.52 0.51 0.48 THE VELIGER Vol. 23; No. 3 Table 2 Results of analysis of Turbo sarmaticus population at Flat Rocks over 507 days during 1975/6. Symbols as in Table 1. Page 228 o+ 1+ N 600m—2 322.29 116.71 We-! 0.22 1.30 B g. 600m—2 70.90 151.72 Pyy - 600m—2507d—1 251.54 285.40 Pog. 600m—2 . 507d—! 199.45 —43.11 P g. 600m—2 . 507d—! 225.50 121.15 P/B 507d—1 3.18 0.80 P/B y—} 2.29 0.58 Year Class Bar 3+ 4+> Total 105.57 38.43 17.14 600.14 3.04 7.43 11.58 23.57 320.93 285.53 198.48 1027.56 403.04 316.95 54.65 1311.58 259.57 262.71 —11.60 667.02 331.31 289.83 21.53 989.32 1.03 1.02 0.11 0.96 0.74 0.73 0.08 0.69 bers with age yielded a significant (p< 0.05) regression for Flat Rocks (Figure 10). From this the age specific mortality rate (Z) was calculated. Z—o0.81"', which gives an annual mortality rate (1-e”) of 0.56. 1000 e In(numbers) =6.15-0.81 Age (years) r=- 0.85 600 m=? 9. 1 2 3 4 Age (years) Figure 10 Survivorship/mortality of Turbo sarmaticus at Flat Rocks DISCUSSION Figure 2 indicates greater initial dry body mass per shell breadth at Skoenmakerskop than at Flat Rocks, but ani- mals at the latter locality become heavier above a shell breadth of about 65 mm, although this difference is not statistically significant. The apparently greater dry mass of large (adult) individuals at Flat Rocks is probably due to greater gonad mass because animals for the breadth/ mass regressions were collected in February which is the end of the ripe period at Flat Rocks, but 2 months after the ripe period at Skoenmakerskop (LoMBARD, 1977). Seasonal growth was evident with maxima in summer for all size groups. NEWMAN (1968) found the reverse in Haliotis midae where the reproductive cycle influenced growth rates. BRancH (1974) found slowest growth in winter when gonads develop in Patella longicosta. He also suggested that food value was an important determinant of growth in South African Patellidae. Seasonal changes in growth have also been ascribed to temperature (Ur- SIN, 1965), food supply (Cox, 1962) and reproductive cycle (Sakai, 1962; BLackMorE, 1969). As all 3 size classes of Turbo sarmaticus exhibited the same seasonal growth pattern, reproductive effects must be excluded and temperature or food, or both, are probably the major factors. The 0+ class grew 23 mm at Flat Rocks and 29mm at Skoenmakerskop in their first year. However, this differ- ence is not significant (t-test). These values are based on the assumption that settlement occurred in July at both localities. It has already been stated that the ripe period at Flat Rocks is slightly later than at Skoenmakerskop and thus settlement may occur as much as one or two months later. Further, exploitation could be expected to cause a shift to the left of year class modes at Flat Rocks by re- moval of larger individuals. On the other hand, the slight- ly higher summer temperatures at Flat Rocks may accel- erate growth there. Food is unlikely to be responsible for these differences as energy values of Turbo sarmaticus flesh from the 2 shores do not differ significantly. The Flat Rocks population consisted mainly of 0-50 mm individuals and the removal of especially the larger animals is reflected in elimination (P,) being nearly double production (P,). The population was thus not in Vol. 23; No. 3 THE VELIGER Page 229 a steady state during the study period. Settlement was ex- tremely high, 1064 0+ animals being collected in the study area in February 1976. Numbers dropped rapidly, however, and there were less than 50 individuals older than 3 years. This is in marked contrast to Skoenmakers- kop, where elimination and production nearly balanced and the population, dominated by adults, was in steady state. The maximum number of 0+ individuals collected at Skoenmakerskop was 44 (September, 1975), while more than 150 animals older than 3 years were present. There is thus a very stable adult population at Skoen- makerskop with low recruitment each year and the major mortality probably occurring before settlement. The low numbers of 0+ individuals during the study period (1+ animals were 4 times as abundant) may also be the re- sult of a poor year and suggests fluctuations in recruit- ment. Despite a much higher apparent settlement and a higher P/B ratio, the exploited population at Flat Rocks had a biomass only 20% and mean annual production only 27% that at Skoenmakerskop. Converting produc- tion estimates over 1.5 years to annual values may involve some error as growth is seasonal and all seasons were not equally represented. However, the additional half year covered an equal proportion of warm and cold months so that seasonal growth differences should cancel out. The steady state P/B ratios obtained are approximately as would be expected for a species with a maximum life span over 10 years and populations with the majority of individuals older than 1 year (WATERS, 1969; ZAIKA, 1972), but are low compared to values for some boreal molluscs (BURKE & MANN, 1974). Differences between these 2 populations may not only be due to exploitation as the effects of temperature and wave action have not been evaluated. However, the similarity of the growth and length/mass curves of the 2 populations suggests that these effects are small. Gotikov & MENSHUTKIN (1973) state that quantita- tive relationships between supporting production, biomass and growth production may serve as a measure for asses- sing the degree of exploitation of a population. Supporting production (Ps) they define as the total biomass of in- dividuals less than 1 year old plus the mass increase of older animals retained in the population. These values are as follows (P = steady state production) : P Ps B Ps/B Skoenmakerskop 4.03g.m™.y? 3.75g.m-2.y"! Flat Rocks 1.17g.m™.y* 0.98g.m-2.y! 8.40g.m? 0.45 I.71g.m? 0.57 The ratios P,/B roughly fit the predictions of GoLtkov & MENSHUTKIN (1973) on the basis of population age structure. P/P, ratios are 1.07 for Skoenmakerskop and 1.19 for Flat Rocks. The population structure at Flat Rocks suggests that ex- ploitation starts well below the size of sexual maturity (about 60mm shell breadth). Small animals are mostly collected for bait by anglers while the larger ones are eaten. The average meat (foot only) yield of a large specimen is about 8g dry mass. Bearing in mind the low biomass, relatively slow growth rate and this small yield, commer- cial exploitation of Turbo sarmaticus does not appear feasible unless very high prices could be obtained. Literature Cited Biackmorg, D. T. 1969. Studies of Patella vulgata L. I. Growth, reproduction and zonal distribution. Journ. Exp. Mar. Biol. Ecol. 3: 200 - 213 Brancu, G. M. 1974. The ecology of Patella from the Cape Peninsula, South Africa. 3. Growth rates. Trans. roy. Soc. Afr. 41: 161 - 193 Burkg, M. V. « K. H. Mann 1974. Productivity and production: biomass ratios of bivalve and gast- ropod populations in an eastern Canadian estuary. Journ. Fish. Res. Brd. Canada 31: 167-177 Cassiz, R. M. 1954. Some uses of probability paper in the analysis of size fre- quency ditributions. Austral. Journ. Mar. Freshwater Res. 5: 513 to 522 Cox, KeirH W. 1962. California abalones, family Hialiotidae. Fish Bull. 118, Calif. Dept. Fish & Game, Sacramento; 142 pp.; illust. Crisp, D. J. 1971. Energy flow measurements. In: Methods for the study of marine benthos; N. A. Holme & A.D. McIntyre, eds.: 197-279. IBP Handbook no. 16; Oxford & Edinburgh, Blackwell Scient. Publ. Gouixoy, A. N. & V. V. MENSHUTKIN 1973. Estimation of production properties of mollusc populations. Mar. Biol. 20: 6- 13 LompBarp, H. W. 1977. The population dynamics of an energy flow through Turbo sar- maticus on two rocky shores in the East Cape. M. Sc. Thesis, Univ. Port Elizabeth, So. Africa (in Afrikaans) McLacuuan, A. & H. W. LomBarp 1980. Seasonal variations in energy and biochemical components of an edible gastropod (Mollusca). Aquaculture 19: 117 - 125 Newman, G. G. 1968. Growth of the South African abalone, Haliotis midae. Investl. Reprt. Div. Sea Fish. So. Africa 67: 1 - 24 Sakal, SEICHI 1962. Ecological studies on abalone, Haliotis discus hannai Ino. 4. Studies on growth. Bull. Japan. Soc. Fish. 28: 899 - 904 Ursin, E. 1965. On the seasonal variation of growth rate and growth para- meters in Norway Pout (Gadus esmarkt) in the Skagerrak. Medd. Danm. Fish. og Havunders 4: 17 - 29 Waters, T. FE 1969. The turnover ratio in production ecology. Amer. Natur. 103: 173-185 ZaiKA, V. EB. 1972. Specific production of aquatic invertebrates. Kiev, Nan- kova Dumka (im Russian) Page 230 THE VELIGER Vol. 23; No. 3 A Comparison of Two Florida Populations of the Coquina Clam, Donax vartabilis Say, 1822 (Bivalvia : Donacidae) I. Intertidal Density, Distribution and Migration ' BY PAUL STEPHEN MIKKELSEN Harbor Branch Foundation, Inc.; RR 1, Box 196; Fort Pierce, Florida 33450 (8 Text figures) INTRODUCTION Donax variabilis Say, THE COQUINA CLAM, lives in the surf zone on sandy exposed beaches of the eastern United States and the northern Gulf of Mexico. The nomenclature of this species was, until recently, in a state of confusion. Morrison (1970, 1971) pointed out that the correct name for the species is Donax protracta Conrad, 1849. However, the name Donax variabilts Say, 1822 was proposed for con- servation (Boss, 1970) and subsequently accepted by the 1.C.Z.N. (MELVILLE, 1976). Donax variabilis occupies the intertidal zone from the high (EDGREN, 1959) to low tide mark (Pearse, ef al., 1942). Densities are variable, to a maximum of about 15 600/m” (EpGREN, of. cit.). Many authors (ALpRICH, 1959; LoEscH, 1957; PEaRSE, et al., 1942; TIFFANY, 1971; TURNER & BELDING, 1957) have noted intertidal migrations of D. variabilis. TiFFANY (op. cit.) and TURNER & BeLpING (op. cit.) have stated that this migratory behav- ior is stimulated by the acoustic shock of breaking waves. Contrarily, only once (Epcren, op. cit.) has D. variabilis been reported as nonmigratory. I report here a second case of a nonmigratory population, even greater densities, and possible explanations for the intertidal distribution of two populations of D. variabilis. MATERIALS anp METHODS Coquinas were collected once each month, from April through September, 1976, from the intertidal zone of ex- ™ Contribution number 187 of the Harbor Branch Foundation, Inc. posed sandy beaches on the central eastern (Indialantic Beach; 28°5.7’N Lat., 80°33.4’W Long.) and southwest- ern (Sanibel Island; 26°25.3’N Lat., 82°4.8’W Long.) coasts of Florida (Figure 1). The transect method of sam- pling was used (Figure 2.) An initial sample was collected at the point of maximum wave recession at the time of sampling. Additional samples were taken at 1 m intervals along transect A, normal to the beach face, to the point of maximum wave advancement at the time of sampling. The latter point was nearest the backshore and became saturated only temporarily by the swash of the waves. Transects B, C, and D were at 25m intervals. Transects E, F, G, and H were 5 m apart. The closer-spaced transects were selected to eliminate the possibility of missing local- ized aggregations by using too large a sampling interval. The number of cores taken per monthly sample varied due to changing width of the swash zone, with a monthly aver- age of 40 cores at Sanibel Island and 49 at Indialantic Beach. At Indialantic Beach, collections were taken about 3 hours after low tide, on the rising lowest tide of the month, and precisely at low tide on the lowest ebb tide of the pre- ceding weekend at Sanibel Island, except the first collec- tion (April, 1976) which was made midway between a low and a high tide. This change in timing at Sanibel Island was made after having observed the nonmigratory behav- ior of the Donax on that beach. Specimen samples were collected,using a 15.0cm diam- eter (0.018 m’) polyvinyl chloride (PVC) corer, to a depth of 10cm. Because the clams are restricted to the upper- most 4cm of sand (EDGREN, 1959), the core contained all living specimens. Samples were sieved, using a 1.2mm Vol. 23; No. 3 THE VELIGER Page 231 mesh. Sand samples were taken in an identical fashion, immediately adjacent to the specimen cores, but with a 5.ocm diameter corer and to a depth of 4cm. Standard granulometric sieve analyses (INMAN, 1952) were con- ducted on each sample. Surf zone water temperature was measured to + 0.5° C, North Latitude kilometers oe 82° 81° 80° kilometers North Latitude 26°26’ Location of sample sites (* and salinity was taken by refractometer to the nearest 0.5% . Beach profiles were measured by triangulation (KiNG, 1972) at 1m intervals from the seaward limit of dune vegetation to the base of the surf zone at the time of sampling. Wave height of 10 consecutive waves at their breaking point was measured using a graduated staff. kilometers North Latitude 4 ll AN 80°36’ 80°34" West Longitude 82°04’ 82°02’ West Longitude Figure 1 ): (A) General location; (B) India- lantic Beach and (C) Sanibel Island Page 232 THE VELIGER Vol. 23; No. 3 Transect: A B Cc DEF GH fo) ; <—@ Line of Maximum Wave Recession 3) I a im ot a 2 oO a o 2 S eS 3 8 e 6 — sj a é g Q 5 oO 3 1S) 6 © Line of Maximum Meters: 0 25 50 75 85 95 Wave Advancement Se EXPOSED BEACH =— > 1 Figure 2 Diagrammatic representation of the sampling grid RESULTS Beach slope exhibited a mean drop of about 5.2cm/m (a slope of 3.0°) at Sanibel Island and 12.0cm/m (a slope of 6.9°) at Indialantic Beach. The beach at Sanibel ap- peared to be slightly more stable than Indialantic Beach, based on comparison of slope variation (Figure 3). Mean wave height was 23 cm at Sanibel and 91 cm (4 x greater) at Indialantic. Irregular semidiurnal tides at Sanibel ranged about 0.8m, while at Indialantic Beach the tides were regular semidiurnal and averaged 1.2 m (Doty, 1957; U.S. Coast and Geodetic Survey, 1975), or 1.5 x greater than the range for Sanibel Island. Surf zone temperature and salinity ranges were 21.0-27.5°C and 30.0-35.0%, at Sanibel Island, while at Indialantic Beach the ranges were 23.0-27.5 C and 30.0-36.0%>. The mean particle size (Dso) of the sand was 0.58mm (coarse sand; WENTWORTH, 1922) on Indialantic Beach and 0.26 mm (medium sand) on Sanibel Island. Mean par- ticle size at Indialantic generally decreased progressing up the beach face, while at Sanibel the mean particle size re- mained relatively constant (Figure 4a). Both beaches had a uniform sand (uniformity coefficient =D,./Dyw< 5) with Sanibel Island being comparatively less uniform than Indialantic Beach (Deo/Di0 = 3.14 and 2.61, respectively). The less uniform sand at Sanibel Island was due to the presence of an abundance of variably-sized large shell frag- ments. Mean particle size and uniformity coefficients were nearly constant between transects, although some varia- tion in the uniformity coefficient was evident at Sanibel (Figures 4b, 5b). This slight variation was probably due to the sorting and subsequent deposition of large shell frag- ments by waves, and beach scalloping. THE VELIGER Page 233 INDIALANTIC BEACH Beach Depth (m) So ooo July eeeeee August September SANIBEL ISLAND Beach Width (m) Figure 3 Beach profiles A total of 28 832 specimens of Donax variabilis were collected from Sanibel Island, and 477 from Indialantic Beach. The ratio of Sanibel to Indialantic Donax per linear meter of beach was 60:1 (Table 1). At either loca- tion, there was little difference in numbers collected per transect between those at 25m intervals and those 5m apart. However, because the Sanibel Island clams were concentrated in the lower intertidal levels and the India- lantic Beach Donax were more dispersed in the wider surf zone, the ratio of the density per square meter of Sanibel to Indialantic Donax was, on the average, 80:1 (Table 1). These ratios are based on a monthly average of 33 372 individuals at Sanibel and 552 at Indialantic per linear meter of beach, and mean densities of 7 141/m” at Sanibel and 88/m’ at Indialantic (Table 1). However, common densities at Sanibel frequently reached 20000/m* and Page 234 THE VELIGER Vol. 23; No. 3 Table 1 Density and numbers. Sanibel Island Indialantic Beach N/m? of area sampled| N/linear m of beach Transects Transects Sanibel Indialantic [Sanibel Indialantic | A-D E-H Total # cores Total # cores April 72 39 342 200 42 7 49 38 12 17 29 4] May 10395 96 36383 672 3561 1678 5239 28 43 54 97 56 June 2654 166 16919 1058 1220 1216 2436 51 4] 111 152 51 July 13114 124 62292 714 4179 4791 8970 38 37 66 103 46 August 5424 49 32544 343 1738 2948 4686 48 20 29 49 56 Sept. 11189 54 51749 324 4081 3371 7452 37 31 16 47 48 a Total — — — —_ 14821 14011 28832 240 184 293 477 298 Mean 7141 88 33372 552 2470 2335 4805 40.0 31 49 80 49.7 Std. Dev. 5210 50 22563 321 1715 1708 3249 8.3 12 36 46 5.9 Coeff. of 73% 57% 68% 58% 69% 73% 68% 20.8% 39% 73% 58% 11.8% variation once reached 60000/m’ in a small localized area during September. At Indialantic in June and July, densities were commonly 1500/m’, with a maximum of 2500/m? for a localized area during July. Intertidal distribution and den- sity was patchy at both beaches, but Donax seemed to “prefer” the shallower beach slope, finer sand, and lower wave energy of Sanibel Island. The Indialantic population was always near the center of the swash zone (Figure 6). The clams were active, and made frequent migrations up and down the beach face, assisted by the wash of the surf. Although at each low tide the Indialantic Donax were washed into the subtidal re- gion (personal observation), they regained their intertidal position with the subsequent incoming tide. At Sanibel, the Donax were nonmigratory and existed in high concentra- tions in the lower fifth of the intertidal zone, in a band about 4-5m in width (Figure 6a) and could be found at this position at any stage of the tide. There was little varia- tion in the distribution of Donax down the length of the beaches (Figure 6b). DISCUSSION Population Density Because no difference was noted in the abundance of predators or in environmental parameters between sample sites (Mikkelsen, unpublished data), the large difference in the population of Donax variabilis may be attributed to the physical differences in the habitats, e.g., the beach pro- files, wave energy, and sand grain size. The clams’ “pref- erence” for a shallower sloped beach can be supported in part by EpcrEN’s (1959) observations on Clearwater Beach, Florida “. . . . that conditions near the pier, which resulted from or were reflected in the shallower slope of the beach, were somewhat more favorable for Donax than they were further north,” where the beach “became pro- gressively steeper.” It was presumably the wave moderat- ing action of a nearby pier which decreased the wave height on this section of beach, producing a shallow beach Explanation of Figures 4 and 5 on the following page Figure 4 Variation of mean sand particle size with (A) core level and (B) transect ( Sanibel; - — — Indialantic) Figure 5 core level and — — — Indialantic) Variation of uniformity coefficient with (A) (B) transect ( Sanibel; THE VELIGER Vol. 23; No. 3 EO) Gap os ey tgs ey Ugh O- © ° ° (urut) azig aprieg uray x 0 ° =i: =: (2) (um) ozIg gpnivg Uva ) o -Q & oO wt jar o wn no = 9 0 9 19 O ° Mean -_=— ean fee =--—-—= @“-<-=—> | eo -_=— Sd - ° 4 Core Level (m) up the Beach Face Figure 4 \ \ ' ! 4 t ' ! ' ! t ! t ! ! --— t ] 1 V I I | i] I I ! | | i | U ! ! I \ \ -- =- Ooo +a Oo AN O CHO MCI O Sn mnCT EO) Juoroyyoory AyuOsIUA, September BS a ° A St) (3) CS) we) Si! CI an Oo Gis (ey) OI Gy Siti Si © quaroyyjeory AyrurrojuQ E Transect: D 4 Core Level (m) up the Beach Face Figure 5 Page 236 THE VELIGER Vol. 23; No. 3 A z - 80 a as 40/7 Oo 20174 of a ee 20 | E ce): ae a B (boo ae co OF 3 =: ean ro) oO ae 5: a 5 5 = August AY A 207 ene eto |_| oF ; H °H 20/4 0 u Meneses | Se Se Ee ES a Ed) fo) I 2 3 4 5 6 7 Core Level (m) up the Beach Face A B C D E F G H Transect Figure 6 Location of the population of Donax variabilis as it varied with (A) core level and (B) transect ( Sanibel; — — — Indialantic) slope which Edgren described as “somewhat more favor- able for Donax.” The lower intertidal levels at Sanibel were often very crowded with individuals. These extremely high densities may be the result of the nonmigratory be- havior in the presence of wave action, resulting in the subsequent deposition and accumulation of animals at the lower intertidal level. The size of the Donax populations also appeared to fluctuate with the change in beach profile. For example, the decrease in the intertidal population at Sanibel in June (Table 1) may have been caused by the same conditions which removed a large amount of sand from the beach (Figure 7). As a consequence, a portion of the population may have been washed into the subtidal region, thus be- coming unable to readily regain its intertidal position by the time of sampling. Similarly, at Sanibel in July, an in- crease in both population size and area under the beach profile occurred, indicating the deposition of both sand and Donax into the intertidal region, probably from subtidal areas. The small yield of specimens from the first collection in April at Sanibel was not because the speci- mens were washed offshore, but rather because the collec- tion was taken midway between a low and high tide. Because of this sampling strategy, it appears that the pop- ulation which had remained in the lower intertidal region and did not migrate up the beach face with the incoming tide was almost completely missed. Salinity changes (Fig- ure 8) during the sampling months did not appear to have influenced fluctuations in the size of the populations. The dense, larger population of Donax variabilis at Sanibel Island may be considered resurgent, that is, peri- odically but irregularly experiencing nearly complete ex- terminations, especially during warm months, followed by re-establishment of the population in subsequent years Square Meters (@) Vol. 23; No. 3 THE VELIGER Page 237 August September Number of Donax variabilis collected per month, and area under the beach profiles ( Sanibel; - - - Indialantic) (communication with Sanibel residents and personal ob- servation). However, massive exterminations do not seem to occur at Indialantic Beach in populations of either Donax variabilis or the sympatric D. parvula Philippi, 1849. The cause of the Sanibel Island Donax population exterminations remains unknown. A possible explanation was provided by GuNTER (1947) who attributed massive oyster catastrophes in the Gulf of Mexico to high tempera- tures combined with excessive salinity. However, it is pos- sible that he found only the indirect cause for such deple- tions. These temperature and salinity conditions could have facilitated an infestation of the clams by the parasite Dermocystidium marinum Mackin, Owen, and Collier, 1950, which is known to severely deplete populations of the oyster, Crassostrea virginica (Gmelin, 1791), in the Gulf of Mexico (Mackin, 1951) and the Chesapeake Bay (see Joyce, 1972). Although this aspect was not investi- gated, Dermocystidium marinum or other parasites may infest Donax and affect the population size. Coe (1957) stated that resurgent populations of Donax have been noticed on both coasts of the United States, but did not mention the species involved. Such resurgences have been noticed for Donax gouldii Dall, 1921 (Coe, 1953, 1955, 1956; JOHNSON, 1966b, 1968), Donax vittaius DaCosta, 1778 (PELSENEER, 1928), and Donax “tumida” Philippi, 1849 (= Donax texasiana Philippi, 1847) (LoEscH, 1957). Extensive, rapid depletions in the size of D. gouldi populations have been attributed to such causes as exposure to freshwater emanating from a hot spring area and high temperatures (JOHNSON, 1966b), Log,, of Number of Donax Collected (A) Salinity (%)) iS) 32 31 30 April May June July August Figure 8 Monthly variation in surf zone salinity ( Sanibel; - - - Indialantic) infestation by parasites (PELSENEER, 1928; Cor, 1956), and various environmental and biological factors (JoHN- SON, 1968). Thus, both biological and environmental fac- tors may contribute to rapid population declines in the genus Denax and probably for D. variabilis. Migratory Behavior and Intertidal Distribution Many authors (ALDRICH, 1959; ANSELL & TREVALLION, 1969; EDGREN, 1959; JACOBSON, 1955; JOHNSON, 1966a, 1966b; Mort, 1938, 1950; PoHLo, 1967; STOLL, 1937, 1938; TIFFANY, 1971; TRUEMAN, 1971; TURNER & BELD- ING, 1957; WADE, 1964, 1965, 1967a, 1967b; Irwin, 1973) have reported on the intertidal migrations of Donax spp. and speculated on or tested the stimulus for migra- tion. In addition to D. variabilis, other species of Donax noted to be nonmigratory are D. gouldii (see HepcrETu, 1957; PoHLo, op. cit.), D. faba Gmelin, 1791, and D. vittatus DaCosta, 1778 (see ANSELL & TREVALLION, of. cit.). In considering the many reports involving intertidal migrations, it is unfortunate that only a few (EDGREN, of. cit.; JOHNSON, 1966a; TURNER & BELDING, of. cit.; WADE, 1967a) have noted such parameters as beach slope, wave impact, and sand particle size in an attempt to correlate these factors with migrations. TIFFANY (op. cit.) and Tur- NER & BELDING (op. cit.) experimentally determined that the migratory behavior of D. variabilis was controlled by the acoustic shock/stimulation of the breaking waves on the beach. September Page 238 EpcrEn’s (1959) observations on Clearwater Beach and my own on Sanibel Island (both on the west coast of Florida) showed Donax variabilis to be nonmigratory. However, Edgren observed that the Donax maintained a position near the high tide mark while my observations showed the species to maintain a very low intertidal posi- tion. Although the wave size at Sanibel (a low energy beach) may be small, the population surely experienced some degree of acoustic wave shock, and yet the clams were not stimulated to migrate. Nonmigratory behavior of both the Clearwater Beach and Sanibel Island Donax populations may also be influenced by beach slope. How- ever, it is difficult to compare Sanibel’s slope of 3.0° with Edgren’s non-quantitative “quite gentle slope.” On Tur- ner Beach, Captiva Island, about 15 km northwest of the Sanibel sample site, where the beach slope, wave impact, and sand grain size are greater, Donax variabilis is migra- tory. The nonmigratory behavior of the Sanibel Island Donax could thus be a result of, or the lack of one or a combination of these factors. The combination of small waves and low beach slope causes large areas of the beach to be exposed with a small drop in the tide, thereby inhib- iting the ability of Donax to follow the tide. If regular migrations did occur at Sanibel, the individuals could easily become stranded above the swash zone for long periods of time due to the irregular semidiurnal tide. By maintaining a low intertidal position, the Sanibel Donax avoided this. In addition to beach profiles, tidal regime, and wave energy, sand particle size and permeability may affect Donax intertidal migrations and distribution. At India- lantic, Donax had no apparent difficulty in burying in the coarse sand. At Sanibel, many clams did not, or probably could not bury themselves completely, and once dislodged were washed about on the surface of the sands throughout several consecutive wave periods before partially resecur- ing themselves in the sand. The Sanibel sand is of medium grain size and is firm when wet. This sand has a perme- ability (see KRUMBEIN & Monk, 1942) an order of mag- nitude lower than Indialantic Beach sand, and is not appreciably loosened by wave wash. The movement of the clams by waves had a tendency to concentrate and deposit the individuals in the lower intertidal zone (Figure 6a). This concentration and deposition was similar to that of the larger sand and shell fragments (Figures 4a, 5a). SUMMARY Donax variabilis Say, 1822 was collected monthly from late spring to early fall of 1976 from two locations on the THE VELIGER Vol. 23; No. 3 central eastern (Indialantic) and southwestern (Sanibel Island) coasts of peninsular Florida. Sanibel Island sup- ported a population of D. variabilis 60 times greater in size and 80 times as dense as that of Indialantic Beach, probably due to lower beach slope and wave energy at Sanibel. Intertidal migrations occurred constantly at Indialantic Beach, with the Donax maintaining a position about the center of the swash zone. Sanibel Island Donax were nonmigratory and lived predominantly at low inter- tidal levels. This unusual nonmigratory behavior is thought to be a local adaptation to cope with the combination of low beach slope and wave energy in conjunction with irregular semidiurnal tides and low sand permeability. Therefore, the magnitude and degree of beach slope, tidal regime, wave energy, and sand particle size and perme- ability necessary for intertidal migrations of D. variabilts remain uncertain. ACKNOWLEDGMENTS I am particularly indebted to Drs. Robert H. Gore and Robert W. Virnstein, whose help was a major asset in the preparation of this paper. My gratitude is also due to Drs. Kerry B. Clark and James A. Lasater for their con- tributions. I also thank Sally Hatton, Debbie’ Wells, Ed- ward Kobovitz, and Alan Siegel for their enthusiastic assistance with the sampling, and especially Paula Mikkel- sen for her help with the collecting and sorting of the specimens and preparation of the original thesis manu- script. This work comprises a portion of a master’s thesis at Florida Institute of Technology, Melbourne, Florida. Literature Cited AvpricH, J. W. 1959. Activities of coquina clams. Atlant. Nat. 4 (1): 41-43 ANSELL, ALAN Davip & ANN TREVALLION 1969. Behavioral adaptations of intertidal mollusks from a tropical sandy beach. Boss, KENNETH J. 1970. Donax variabilis Say, 1822 (Mollusca: Bivalvia): proposed vali- dation under the plenary powers. Z. N. (S.) 1923. Bull. Zool. Nom. 27: 205 - 206 Coz, WESLEY ROSWELL 1953. Resurgent populations of littoral marine invertebrates and their dependance on ocean currents and tidal currents. Ecology 34 (1): 225-229; 1 text fig. 1955. Ecology of the bean clam, Donax gouldi [sic], on the coast of southern California. Ecology 36 (3): 512-514; 2 text figs. 1956. Fluctuations in populations of littoral marine invertebrates. Journ. Mar. Res. 15 (3): 212 - 2323 9 text figs. 1957. Fluctuations in littoral populations. In: Joel W. Hedg- peth (ed.), Treatise on marine ecology and paleoecology. vol. 1. Eco- logy. Mem. 67, Geol. Soc. Amer.: 935 - 939; 2 text figs. Conrap, TimotHy ABBOTT 1849. Descriptions of new fossil and Recent shells of the United States. Journ. Acad. Nat. Sci. Phila. (2) 1: 207-209 Journ. Exp. Mar. Biol. Ecol. 4 (1): 9-35; 14 text figss. Vol. 23; No. 3 THE VELIGER Page 239 a DaCosta, EMANUEL MENDES 1778. Historia naturalis testaceorum Brittaniae, or the British concho- logy. London, 254 pp.; 17 pits. Dax, WituiAM HEALEY 1921. Summary of the marine shellbearing mollusks of the northwest coast of America, from San Diego, California, to the Polar Sea, mostly contained in the collection of the United States National Museum, with illustrations of hitherto unfigured species. U.S. Nat. Mus. Bull. 112: 1 - 217; 22 pits. (24 February 1921) Doty, Maxwe.t STANFORD 1957- Rocky intertidal surfaces. In: Joel W. Hedgpeth (ed.), Treatise on marine ecology and paleoecology. vol. 1. Ecology. Mem. 67, Geol. Soc. Amer.: 535-585; 18 text figs. Epcren, Ricuarp A. 1959. Coquinas (Donax variabilis) on a Florida beach. 40 (3): 498-502; 3 text figs. GMELIN, JOHANN FRIEDRICH 1791. Caroli a Linne systema naturae per regna tria naturae. Editio decima tertia. Lipsiae (Leipzig), Germany, 1 (6): cl. 6 GunTER, GorDON 1947. Catastrophism in the sea and its paleontological significance, with special reference to the Gulf of Mexico. Amer. Journ. Sci. 245: 669 - 676 HeEpcGPETH, Jo—EL WALKER 1957: Sandy beaches. In: Joel W. Hedgpeth (ed.), Treatise on marine ecology and paleoecology. vol. 1. Ecology. Mem. 67, Geol. Soc. Amer.: 587-608; 11 text figs. INnMAN, D. L. 1952. Measures for describing the size distribution of sediments. Journ. Sed. Petrol. 22 (3): 125-145 Irwin, THomas H. 1973- The intertidal behavior of the bean clam, Donax gouldii Dall, 1921. The Veliger 15 (3): 206-212; 2 plts.; 3 text figs. (1 Jan. ’73) Jacopson, Morris KarRLMANN 1955- Observations on Donax fossor at Rockaway Beach, New York. The Nautilus 68 (3): 73-77 (11 February 1955) Jounson, Puy tuts T. 1966a. On Donax and other sandy beach inhabitants. 9 (1): 29-30 1966b. Mass mortality in a bivalve mollusk. (3): 429-431; 1 text fig. 1968. Population crashes in the bean clam, Donax gouldi [sic], and their significance to the study of mass mortality in other marine in- Ecology The Veliger (1 July 1966) Limnol. Oceanogr. 11 vertebrates. Journ. Invert. Pathol. 12: 349 - 358; 1 text fig. Joyce, Epwin A. 1972. A partial bibliography of oysters, with annotations. Florida Dept. Nat. Res. spec. publ. no. 34, 846 pp. Kine, C. A. M. 1972. Beaches and coasts. and ed., New York, St. Martin’s Press 570 pp. Krumesein, W. C. « G. D. Monx 1942. Permeability as a function of the size parameters of unconsoli- dated sand. Amer. Inst. Mining Metallurg. Engrs. Tech. Publ. No. 1492, Petrol. Tech., pp. 1-11 Lozscu, Haroitp Cari 1957- Studies on the ecology of two species of Donax on Mustang Island, Texas. Publ. Inst. Mar. Sci., Univ. Texas 4: 201 - 227; 19 text figs. Mackin, J. G. 1951. Histopathology of infection of Crassostrea virginica (Gmelin) by Dermocystidium marinum Mackin, Owen, and Collier. Bull. Mar. Sci. Gulf. Carib. 1 (1): 72-87 Mack, J. G., H. M. Owen «& A. Coiiizr 1950. Preliminary note on the occurrence of a new protistan parasite, Dermocystidium marinum n. sp. in Crassostrea virginica (Gmelin). Science 111 (2883): 328-329 MELvILtE, R. V. 1976. Opinion 1057. Donax variabilis Schumacher, 1817 (Mollusca: Bivalvia) suppressed under the plenary powers; type species designated for Latona Schumacher, 1817. Bull. Zool. Nom. 33(1): 19-21 Mor1, Syuit1 1938. Donax semigranosus Dunker and the experimental analysis of its behavior at flood tide. Zool. Mag. Tokyo (= Dobutsugoku Zasski) 50 (1): 1-12 1950. Characteristic tidal rhythmic migration of a mussel, Donax semigranosus Dunker, and the experimental analysis of its behavior. Zool. Mag. Tokyo (= Dobutsugoku Zasski) 59 (4): 87-89 Morrison, JosepH Paut ELDRED 1970. East Florida Donax. 1971. Western Atlantic Donax. 545 - 568; 2 pits. Pearse, A. S., Harotp J. Hum « G. W. WHarTon 1942. Ecology of sand beaches at Beaufort, North Carolina. Ecol. Monogr. 12 (2): 136-190 PELSENEER, R. 1928. Les parasites des mollusques et les mollusques parasites. Bull. Soc. Zool. France 53: 158 - 189 PuitipP!, RuDoLPH AMANDUS Seafari 12 (7): 1-2; 3 text figs. Proc. Biol. Soc. Wash. 83 (48): 1847. | Testaceorum novorum centuria. Zeitschr. f. Malakozool. 4: 71-77 1849. Centuria altera testaceorum novorum (contin.). Zeitschr. f. Malakozool. 5 (10): 145-150 Pou to, Ross H. 1967. _ Aspects of the biology of Donax gouldi [sic] and a note on evolution in Tellinacea (Bivalvia). The Veliger 9 (3): 330-337; 5 text figs. (1 January 1967) Say, THOMAS 1822. An account of some of the marine shells of the United States. Journ. Acad. Nat. Sci. Phila. 2: 302 - 325 SToti, Eva 1937. Beobachtungen iiber die Fortbewegung bei einigen grabenden Muscheln. Rev. Suisse Zool. 44: 383 1938. Sur la mode de locomotion de quelques mollusques marins. Trav. Stat. Biol. Roscoff 16: 3 - 33 Tirrany, WituiAM J., III 1971. The tidal migration of Donax variabilis Say (Mollusca: Bival- via). The Veliger 14 (1): 82-85; 2 text figs. (1 July 1971) TRuEMAN, E. R. 1971. The control of burrowing and the migratory behavior of Donax denticulatus (Bivalvia: Tellinacea). Journ. Zool. 165 (4): 453 - 469; 9 text figs. Turner, Harry Jackson, Jr. « Daviw L. BeLDING 1957- The tidal migrations of Donax variabilis Say. Oceanogr. 2 (2): 120-124 Unitep States Coast anp GEopetic SURVEY 1975- High and low water predictions; East coast of North and South Limnol. America. Washington, U. S. Govt. Print. Off.; 290 pp. Wape, Barry A. 1964. Notes on the ecology of Donax denticulatus (Linné). Proc. Gulf Carib. Fish. Inst. (17th Ann. Sess.): 36-41 1965. Studies on the biology of the beach clam, Donax (Bivalvia: Donacidae) in the West Indies. Ph. D. thesis, Univ. West Indies, Jamaica; 271 pp.; 55 figs. 1967a. Studies on the biology of the West Indian beach clam Donax denticulatus Linné. I. Ecology. Bull. Mar. Sci. 17 (1): 149-174; 7 text figs. 1967b. On the taxonomy, morphology, and ecology of the beach clam, Donax striatus Linné. Bull. Mar. Sci. 17 (3): 723-740; 5 text figs. WENTWORTH, C. K. 1922. A scale of grade and class terms for clastic sediments. Journ. Geol. 30 (5): 377-392 Page 240 THE VELIGER Vol. 23; No. 3 New Distributional Records for Two California Nudibranchs WILLIAM B. JAECKLE 207 Beryl Avenue, Mill Valley, California DuRING SURVEYS OF INTERTIDAL opisthobranch mollusk communities in northern and central California, two nudi- branchs were collected which represent a geographical range extension for each species. Both specimens were sighted in zone 3 rocky intertidal habitats (RICKETTS & CaLvin, 1968). Ancula lentiginosa Farmer, in Farmer and Sloan, 1964 Relatively few sightings of the goniodorid Ancula lenti- ginosa have been reported since the original description. LaNcE (1966) reported observing a specimen in a rocky intertidal region at Bahia de los Angeles, Baja California, establishing the southern extent of the geographical dis- tribution. Along the California coast A. lentiginosa has been reported from La Jolla (FARMER & SLOAN, 1964), from Santa Barbara County (SpHoN & Lance, 1968), in San Luis Obispo County (RoLLER & Lona, 1969) and from Asilomar Beach, Monterey County (NyBakKEN, 1978). One specimen of Ancula lentiginosa was collected at the Frontier Arts Nature Reserve, Marin County (Lat. 37° 52/22” N; Long. 122°36'56” W) on August 9, 1979. This specimen exhibited the solid freckled coloration pattern as described by FARMER & SLOAN (1964). Previous to this sighting, the northern limit of the geographical range was considered to be Elkhorn Slough, Monterey County (Gary McDonald, personal communication 5-XI-1979). The specimen collected in Marin County extends the northern limit of the geographical range 117.3km. This specimen has been deposited in the invertebrate collection at the California Academy of Sciences, San Francisco, as a voucher specimen #1102. Hallaxa chant Gosliner and Williams, 1975 Reported sightings of Hallaxa chan: are limited primarily to the original description (GosLINER & WILLIAMS, 1975). NyBAKKEN (1978) sighted a specimen at Asilomar Beach, Monterey County. McDonaLp & NyBAKKEN (1978) re- ported 3 specimens from Morro Bay, San Luis Obispo County, feeding upon the encrusting ascidian Didemnum carnulentum Ritter and Forsyth, 1917. A single specimen of Hallaxa chani was collected at Abalone Beach, Humboldt County (Lat. 41°07’20”N; 94941 Long. 124°09’32” W) on April 28, 1979. The specimen was observed on the angiosperm Phyllospadix scouleri Hoof, 1839; GosLinER & WILLIAMS (1975) cite Phyllo- spadix as an algal substrate particularly associated with H. chant. The external coloration and morphology of the collected specimen is consistent with the original descrip- tion. The preserved specimen was sent to Dr. Terrence M. Gosliner who confirmed its identity. The previous northernmost occurrence for this species is Bird Rock, Tomales Point, Marin County (Lat. 38°14’ N; Long. 123°00’ W); the southern extent of the geo- graphical distribution is Shell Beach, San Luis Obispo County (Lat. 35°12’N; Long. 120°43’W) (GosLINER & WILLIAMS, 1975). The collected specimen from Humboldt County represents a northern geographical range exten- sion of 320km. ACKNOWLEDGMENTS I would like to thank Dr. Gosliner for his support and en- couragement and Mr. Gary McDonald for his assistance. Literature Cited Farmer, WESLEY MERRILL & ALLAN J. SLOAN 1964. A new opisthobranch mollusk from La Jolla, California. The Veliger 6 (3): 148-150; plt. 18; 2 text figs. (1 January 1964) Gos.LinER, TERRENCE M. & Gary C. WILLIAMS 1975. A genus of dorid nudibranch previously unrecorded from the Pacific coast of the Americas, with the description of a new species. The Veliger 17 (4): 396-405; 11 text figs. (1 April 1975) Lanog, James RoBEert 1966. New distributional records of some northeastern Pacific Opistho- branchiata (Mollusca: Gastropoda) with descriptions of two new species. The Veliger 9 (1): 69-81; 12 text figs. (1 July 1966) McDonatp, Gary R. « Jamzs WiLLaRD NYBAKKEN 1978. Additional notes on the food of some California nudibranchs with a summary of known food habits of California species. The Veliger a1 (1): 110-119 (1 July 1978) NYBAKKEN, JAMES WILLARD 1978. Abundance, diversity and temporal variability in a California intertidal nudibranch assemblage. Mar. Biol. 45 (2): 129-146; 15 text figs. (1 July 1977) Ricketts, Epwarp FE « Jack Catvin 1952. Between Pacific tides. Stanford Univ. Press, Stanford, Calif. v-xilit 3-502; 46 plts.; 134 text figs. Rouuzer, Ricwarp A. & STEVEN J. Lone 1969. An annotated list of opisthobranchs from San Luis Obispo County, California. The Veliger 11 (4): 424-430 (1 April 1969) SpHon, Gare G. & James Ropert LANcE 1968. An annotated list of nudibranchs and their allies from Santa Barbara County, California. Proc. Calif. Acad. Sci. 36 (3): 73-84; 1 fig. (25 September 1968) Vol. 23; No. 3 THE VELIGER Page 241 A Cephalic Dimple in the Terrestrial Snail Achatina achatina BY RONALD CHASE anp MICHELE PIOTTE Biology Department, McGill University, 1205 Avenue Docteur Penfield Montreal, Quebec, Canada H3A 1Br (2 Plates) INTRODUCTION SEVERAL TYPES OF specialized dermal structures have been reported in pulmonate molluscs. These include the “fossette triangulaire caudale” (Anpré, 1898) or “caudal gland” (Barr, 1928) of the slug Arion, the “frontal or- gan” of African snails in the order Gymnarion (BrNbER, 1965), and the “head-wart” found in the snail Euhadra peliomphala (Taxi, 1935; TAKEDA & TSURUOKA, 1979). Each of these structures has a different morphology, but they all occur along the dorsal mid-line and each is thought to serve a function in courtship behavior. We have observed a dermal alteration in Achatina a- chatina which is distinguishable from each of the struc- tures noted above, but which nonetheless appears to be analogous in some respects. While our observations are preliminary, we feel that it may be productive to bring our findings to the attention of other workers who have greater access to specimens of A. achatina for laboratory and field studies. METHODS The present study is based on specimens of Achatina acha- tina that were raised in the laboratory from several clut- ches of eggs. The breeding population was obtained through the courtesy of Dr. J. M. K. Hodasi, University of Ghana, who has recently published a life history of the species (Hopasi, 1979). Our principal use of the snails was for neurobiological studies. The snails were main- tained on a sandy substrate in plastic enclosures that measured 50cm X 40cm X 4ocm. They were fed fresh vegetables and ground rat chow moistened with water and fortified with vitamins (Vionate, Squibb) and cal- cium carbonate. Lighting was provided by overhead flu- orescent lamps in an LD 12:12 regime. Ten animals were selected for repeated examinations of the skin of the head. The examinations were made under a dissecting microscope. Following each examina- tion, detailed notes and drawings were made to record the appearance of the skin. The observations were con- ducted over a period of 3 months at intervals that aver- aged about 2 weeks. Histological observations were carried out on pieces of skin that were cut away following a 0.5 mL injection of 1% succinylcholine to relax the animal. The tissues were fixed in Bouin’s solution, dehydrated and embedded in paraffin wax. Sections were cut to a thickness of 5 um and stained using Masson’s Trichrome method. RESULTS Gross Morphology The cephalic dimple is illustrated by the 2 examples shown in Figures 7 and 2. The location of the dimple was invariably at the vertex, just posterior to the anterior tentacles. The triangular shape shown in Figure 1 was more common than the square shape in Figure 2. In contrast to adjacent skin regions, the dimple is character- ized by an absence of tubercles and a paler coloration. The size of the dimple ranged from approximately 1 mm? to approximately 4 mm’. Page 242 THE VELIGER Vol. 23; No. 3 We first noted the appearance of dimples in animals that were approximately 9 months of age. Within 1 month thereafter, a majority of the animals in our population of over 150 specimens manifested a dimple. Two months later, no dimples could be found. The population suffered total mortality during a one month period that com- menced 3 months after the dimples had disappeared. The repeated close examination of selected animals revealed that alterations of skin color also occur on the vertex in the region between the anterior tentacles. Small patches or spots approximately 0.5 mm? were observed to be either yellow, white, grey or dark in comparison to adjacent skin. Such alterations were not seen elsewhere on the head. Individual snails commonly displayed a suc- cession of color changes in the same area over a period of several weeks, but the particular sequence of color changes varied from animal to animal. Also, while the colored spots were frequently seen both before and after the appearance of a dimple, there was no reliable correla- tion between any sequence of color changes and either the appearance or disappearance of the dimple. In contrast to our observations of dimples in Achatina achatina, we have never observed the same structure in hundreds of specimens of A. fulica maintained in the laboratory over a continuous 6 year period. Histology When viewed at low magnification under a light micro- scope, the surface of normal skin at the vertex is marked by a continuous array of tubercles (Figure 3). By con- trast, in dimpled snails the corresponding region of skin is remarkably flat, and completely devoid of tubercles (Figure 4). The tubercles in regions adjacent to the dimple have a normal appearance. On either side of the dimple, a muscle attaches to the underlying connective tissue (Figure 4). The epithelium of normal skin consists of columnar cells, with a striated border (Figure 5). In the region of the dimple, the epithelium is cuboidal or squamous (Fig- ure 6); the striated border is still present but it 1is very thin. Pigment cells are common beneath the epi- thelium of normal skin, but absent in the corresponding area of the dimple. The transition between normal skin and dimpled skin is characterized by a progressive change in the shape of the epithelial cells, from columnar to cuboidal (Figure 7). At the center of the dimple there is a local aggregation of cells that extends beneath the epithelial monolayer (Fig- ures 4 and 8). The nature of these cells is unknown. They have an ovoid shape and multiple nuclei. DISCUSSION The head dimple of Achatina achatina is similar to, and yet different from, each of several other dermal peculi- arities already reported in the literature. It resembles the “fossette triangulaire caudale” (ANDRE, 1898) or “cau- dal gland” (Barr, 1928) of the slug Arion in that it occurs on the mid-line, it is a depression of the skin sur- face, pigment cells are absent, and it frequently takes the form of a triangle (Figure 1). The major differences are that in Achatina the dimple is found on the head rather than on the tail, and there is no concentration of secretory cells, at least in our material. The location of the Achatina dimple corresponds close- ly to the location of the “frontal organ” described by BINDER (1965) and the “head-wart’’ first described by Explanation of Figures 7 to 4 Figure 1: Photograph of the head of a living snail, Achatina acha- tina. The dimple is located on the vertex, just posterior to the anterior tentacles Bar length equals 5.0mm Figure 2: The dimple on a second specimen, photographed at a higher magnification than in Figure z Bar length equals 3.0mm Figure 3: Histological section of normal skin taken from the ver- tex region between the anterior tentacles Bar length = 2.0mm Figure 4: Histological section through the dimple. Asterisks indi- cate the location of muscle attachments Bar length = 2.0mm Pb ainsig P oy r sainsty [ILLOIg ¥ ASVHD] & ‘ON ‘SS "JOA “AXOITAA TH], ‘ ) i 2 me j An fi ¢ ( os r 1 é } i y ; { 5 f f ry =i ) Cy r : Fi oo i un : ia uy f : no 1 a f Ye 1 ? a i ; at Vol. 23; No. 3 Taki (1935) and subsequently by TAKEDA «& TSURUOKA (1979). All of these structures are found on the vertex in the region between the 2 pairs of tentacles. However, the latter 2 structures are protuberant, whereas the dimple is recessed from the normal dermal surface. Fur- thermore, the head-wart is characterized by elongated epi- thelial cells (TakepA & TsuRuUoKA, 1979), whereas the dimple is characterized by cuboidal epithelial cells. The dimple in Achatina achatina also resembles the leucodermic lesions found in A. fulica and described by Meap (1979), but a number of distinctions lead us to doubt a common etiology. One, the lesions consist of dermal rather than epidermal alterations; the converse is true of the dimple. Two, while the lesions are common in the intertentacular area, they also occur on the tentacles themselves and on other exposed parts of the body; the dimple appears only at the single discrete location be- tween the anterior tentacles. Three, in A. fulica, the symp- tomatology associated with the lesions involves a progres- sion of incidence and severity ultimately leading to death; in our population of A. achatina, the dimples had entirely disappeared 3 months prior to the onset of mortality. Four, while we have maintained a large laboratory colony of A. fulica for many years, no leucodermic lesions have been observed on specimens of A. fulica either during the occurrence of the dimple in A. achatina, or during the preceding 3 years, or during the subsequent year. Al- though the foregoing considerations suggest that the leuco- dermic lesions of A. fulica and the dimple of A. achatina are fundamentally different, we recognize that a variety of lesion-like markings have been reported in terrestrial gastropods (see Mean, 1979), and it is possible that the dimple is, in fact, pathogenic. Alternatively, the dimple may play a functional role in sexual reproduction. This possibility is suggested by re- ports that the head-warts of other snails, located in the same region as the dimple, secrete a substance that either attracts or arouses sexual partners (YAMADA, 1962; BINDER, 1977; TAKEDA & TsuRUOKA, 1979). The se- cretions which collect in the caudal organ of Arion are also thought to serve a sexual function (Barr, 1928). Circumstantial evidence in support of a reproductive role for the dimple is the fact that it made its appearance in our population during the summer months, which is most THE VELIGER Page 243 frequently the season for egg-laying in our laboratory col- ony. At that time, the reproductive organs of dimpled specimens were well developed, as indicated by the size of the ovotestis, the albumen gland and the penis. Of possible significance in the light of these findings is the common observation that the approach to courtship in snails is from the front, whereas it is from the rear in slugs (DuNcAN, 1975). This behavioral distinction might account for the different placements of the head dimple and the caudal organ, which are otherwise morphological- ly similar. Furthermore, although our histological mate- rial did not reveal an abundance of secretory cells in the dimple, as has been described for the caudal organ, we did observe a dense aggregation of unidentified sub-epithelial cells (Figures 4 and 8). If we had examined the histology of the dimple at a later time during the season, or in more mature specimens, we might have observed that these cells subsequently developed a secretory appearance. Our preliminary findings emphasize the need for more extensive observations of cephalic dermatology in Acha- tina achatina. Especially useful would be information re- lating the incidence of dimples to the ecology and life history of this species in natural populations. Since the enormous size of A. achatina makes it a highly favorable experimental subject, especially for neurobiological stu- dies, it is important to establish what functional role, if any, is served by the head dimple. ACKNOWLEDGMENTS We are grateful to Dr. J. M. K. Hodasi for supplying specimens. Mr. Robert Lamarche contributed expert photographic assistance. This study was funded by a grant from the Natural Science and Engineering Research Council of Canada. Literature Cited AnpbRE, EmILe 1808. La fossette triangulaire caudale des Arions. Zool. 5: 179 - 182 Barr, AILEEN R. 1928. Some notes on the mucous and skin glands of Arion ater. Quart. Journ. microsc. Sci. 71: 503-525; 2 plts.; 5 text figs. Rev. Suisse Page 244 THE VELIGER Vol. 23; No. 3 Binper, EuGENE 1965. Structure de lorgane sexuel frontal des Gymnarion des Monts Nimba. Rev. Suisse Zool. 72: 584 - 593 1977. La pariade chez le genre Gymnarton Pilsbry, 1919. Rdle de Yorgane frontal. Arch. Molluskenk. 107: 249 - 255 Duncan, CHRISTOPHER J. 1975- Reproduction. In: Vera Fretter & J. Peake, eds., Pulmonates. Acad. Press, London, New York, xxix+417 pp.; illust. Hopasi, J. M. K. 1979. Life history studies of Achatina achattna. Journ. Moll. Stud. 45: 328 - 339 Meap, ALBERT RAYMOND 1979. Economic malacology, with particular reference to Achatina fultca. Acad. Press London; 150 pp. Taxepa, Naokuni & Hitomr TsuRUOKA 1979. A sex pheromone secreting gland in the terrestrial snail, Euhad- ta peliomphala. Journ. Exp. Zool. 207: 17 - 26 Yax1, Iwao 1935- Notes on a warty growth on the head of some land snails. Journ. Sci. Hiroshima Univ. Ser. B, Div. 1, 3: 159- 183 Yamapa, JUMPEI 1962. On the rearing of land snails, mainly of Euhadra: Their copu- lation, spawning, and the relation between the head-wart and repro- duction. Venus (Japan. Journ. Malacol.) 22: 180-199 Explanation of Figures 5 to 8 Figure 5: Epithelial layer of normal skin Bar length = 25um Figure 6: Epithelial layer of dimpled skin Bar length = 254m Figure 7: Transition between normal skin (left) and dimpled skin (right) Bar length equals 150um Figure 8: Sub-epithelial aggregation of unidentified cells at the center of the dimple. The same cellular density is visible at lower Magnification in Figure 4 Bar length equals 200m [CHASE & PioTTE] Figures 5 to 8 Tue VE icER, Vol. 23, No. 3 Vol. 23; No. 3 THE VELIGER Page 245 Siphonal Eyes of Giant Clams (Bivalvia : Tridacnidae) and their Relationship to Adjacent Zooxanthellae PETER V. FANKBONER Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, Canada V5A 186 (2 Plates; 1 Text figure) INTRODUCTION THE SYMBIONTIC RELATIONSHIP between giant clams and zooxanthellae has intrigued tropical marine biologists for nearly a century. Beginning with the meticulous work by Brock (1888), this interest has led to studies which have established a clear relationship between zooxanthellae and the extraordinary morphology, behaviour and nutrition of giant clams (YONGE, 1936 & 1975; MuscaTINE, 1967; FANKBONER 1971a & 1971b; GoREAU, GOREAU & YONGE, 1973). Yet, some aspects of the nature of giant clam- zooxanthellae symbiosis have not been satisfactorily re- solved. For instance, in YoNGE’s (1936) seminal paper on the biology of giant clams, he noted particularly dense masses of zooxanthellae enclosing the numerous subepi- thelial hyaline bodies of the clams’ hypertrophied siphons. From their histology, it appeared to Yonge that the hya- line bodies were lens-like in their construction, but lacked the optic nerve and retina normally associated with a func- tional photoreceptor. Thus, on this evidence, he concluded that tridacnid hyaline bodies functioned as light collecting lenses for internal illumination of zooxanthellae. Thirty years later, Stasek modified Yonge’s earlier inter- pretations of structure and function of the hyaline organs. In his studies on Tridacna maxima, SrasEK (1966) ob- served an optic nerve, retinal cells with neurites and a multicellular lens in these organs; from these data and supporting behavioural observations (STASEK, 1965), he contended that the hyaline body was a true eye. Electron microscope studies on the eyes of T7ridacna crocea and T. maxima by KawacuTi & Masucui (1969) substantiated many of STASEK’s (1966) interpretations. Unfortunately, the conclusions of KawacuT! & Masucui (1969) were lim- ited by photoreceptor preparations which they candidly confess received “unsuccessful fixation.” This latter con- dition is most apparent in preparations of the so-called multicellular lens of Tridacna and leaves much doubt as to whether this structure is a lens. It seems crucial to YONGE’s (1936) very interesting idea on internal solar enhancement of zooxanthellae that the question of the presence or absence of a “lens” in the tri- dacnid siphonal photoreceptor be resolved. Thus, in the following account I have examined the ultrastructure of the tridacnid eye in the context of its purported relation- ship to the masses of zooxanthellae surrounding it. MATERIALS anp METHODS Collection of Giant Clams Size ranges of Tridacna gigas Linnaeus, T. maxima Réding, 1798 and T. squamosa Lamarck, were collected by free-diving in shallow coral reef waters adjacent to the islets Mijikadrek, Jinimi and Bokandretok at Enewetak Atoll, Marshall Islands. Within 1-3 hours of collection, the giant clams were submerged in several meters of water on the windward reef flat facing the Mid-Pacific Marine Laboratory, Enewetak Island, or within laboratory out- door aquaria. Photic and Tactile Responses of Giant Clams Daylight reactions of tridacnid eyes to touch, shadowing and near distance images were observed in situ at Ene- wetak Island. For elimination of possible artifactual re- sponses by clams to underwater pressure or sound waves Page 246 THE VELIGER Vol. 23; No. 3 produced by the observer’s swimming, duplicates of the above experiments were run on clams in outdoor labora- tory aquaria as controls. Finally, to ascertain the influence of darkness upon giant clams’ behaviour, tridacnids were also observed nocturnally for response to artificial light and touch. Light and Electron Microscopy Tridacnid eyes were dissected from the siphons within rectangular blocks of tissue measuring about 3mm x 3mm x 7mm. Tissue blocks were submerged for 1 hour at 0° C in 2% osmium tetroxide buffered in Dorey’s solution B (1965). To facilitate better fixative compatibility with the tissue, 3.5% potassium chloride was substituted for the sucrose originally prescribed in the Dorey formula. Fixed tissues were dehydrated (Dorey, 1965) and embedded with Epon 812. For light microscopy, one micrometer thick serial sections were cut and stained with Richardson’s stain (RICHARDSON, JARETT & FINKE, 1960). Ultrathin sections were cut at a thickness of 70 to 85 nm and stained with lead and uranium prior to viewing with a Phillips EM 300 electron microscope. RESULTS In their natural posture, the umbos of giant clam valves are lowermost, a position that allows zooxanthellae con- tained in fleshy hypertrophied siphonal tissucs to be ex- posed to the sun (Figure 1). Tridacnid cyes are situated adjacent to the margins of the siphons and often appear as a wavy line of dark-centred papillae against a dappled, multi-hued background of siphonal pigmentation. In specimens of Tridacna gigas exceeding 60cm in length, however, the eyes are additionally dispersed over non- marginal portions of the exposed siphons and especially the edges of the siphonal apertures. The number of eyes per individual clam can be extraordinarily large and re- flects, no doubt, the vast siphonal surface area exposed to reef predators when Tridacna is actively filter feeding and sunning. During a recent trip to Enewetak Atoll, I at- tempted to count the total number of siphonal eyes from a freshly captured gocm long T. gigas weighing about 250 kg. However, after having hopelessly lost count several times, I made a rough estimate of over 3 000 eyes for this particular clam! Whereas this is an outstanding number of eyes for a single organism (the maximum for the Animal Kingdom), it is by no means the upper limit for this spe- cies; IT. gigas may grow to a length of nearly 140cm (RoSEWATER, 1965). In the daytime, Tridacna reacts quickly to shadows passing over its siphonal eyes by rapid closure of its shell valves. Attempts to touch the siphonal surface without eliciting a valve closure reaction were generally unsuccess- ful unless care was taken to approach the clam very slowly and/or from a direction subtending the surface curvature of the siphonal mass. Tridacna maxima and T. squamosa were notably more sensitive and faster to react to shadow- ing, moving objects and touch than was T. gigas. Reactions of clams in outdoor aquaria were similar to those observed in the field. There were, however, striking differences in the behav- iour of clams observed nocturnally versus those studied in daylight hours. For instance, by midnight, the valves of tridacnid clams were almost completely closed, and there was little evidence of respiratory exchange. Several min- utes exposure of siphonal tissues to artificial light produced no observable reaction, and the siphonal tissue itself ap- peared insensible to touch. Owing, in great part, to the presence of symbiontic zooxanthellae, the organization of the giant clam eye and its associated components is comparatively atypical of molluscan eyes and, indeed, of invertebrate eyes in gen- eral. For instance, each eye (ph) is encircled by several to many dense layers of olive-green zooxanthellae which, in conjunction with some epithelial pigmentation, act as a pigment cup to improve visual acuity by providing direc- tional sensitivity (Figures 2 & 3). As noted by YoncE (1936), the concentrations of these algal cells surrounding the siphonal eyes are conspicuously greater than concen- trations seen in other subepithelial haemal spaces. Inter- Explanation of Figures 1 to 3 Figure 1: Tridacna maxima photographed in situ at Enewetak Atoll, Marshall Islands. Exposed fleshy folds of the hypertrophied siphons contain symbiotic zooxanthellae.. Pigmented spots distribu- ted along the margins of the siphonal folds are eyes. Figure 2: Higher magnified view of the syphonal eyes of Tidacna maxima. ph — eye; z — zooxanthellae Figure 3: One ym thick section through a siphonal eye of Tridacna squamosa. ep — epidermis; n — nerve; ph — eye z — zooxanthellae [FANKBONER] Figures 7 to 3 Tue VELIGER, Vol. 23, No. 3 my Vol. 23; No. 3 THE VELIGER Page 247 mixed with the zooxanthellae of the siphonal eyes are con- nective tissues, nerves, muscle strands, plus scattered phagocytes and peculiar light reflecting amoeboid cells called iridocytes (KAwAGUTI, 1966; FANKBONER, 1971a). The eye (ph) is ovoid or spindle-shaped, with the long axis perpendicular to the siphonal surface, and is com- posed of approximately 280 to 350 polygonal retinal cells (15-20 um in diameter) contained by a thin envelope of connective tissue (Figure 3). An optic nerve (n) arises from the side or basal corner of each eye as described by STASEK (1966); I did not, however, find synapses within the eye capsule. The eye’s retinal cells are characterized by a tangled 0.5-4.0 um thick mass of microvilla (mv) that completely surrounds the cell soma (Figures 4 & 5). These microvilli do not arise from the cell’s plasma membrane; rather, they originate from the membranes of ciliary blebs (cb), several of which project from each retinal cell (Figure 5). Owing to their peculiar convoluted and entangled condition in ultrastructural preparations, it was often not possible to determine the cell of origin in these ciliary microvilla (Fig- ures 4 & 5). Although they differ markedly in the gross anatomy of their eyes, the ciliary blebs of Tridacna are ultrastruc- turally identical, in nearly all respects, to siphonal eye photoreceptive sites established in the closely related genus Cardium (BarBER & LAND, 1967; BARBER & WRIGHT, 1969). In Tridacna, the axoneme of the ciliary bleb in- cludes only an outer sheath consisting of a circlet of micro- tubule doublets of complete A and B microtubules (a 9 x 2+ configuration). Typically, the outer sheath main- tains its integrity at the cilium’s basal plate, but from the plate distally, the microtubule doublets splay outwards (Figures 5 and 6) within the ciliary bleb and are seen within some of the microvilli. The kinetosome has a simple type II organization (PirELKa, 1974) and its sheath con- sists of a proximal circlet of offset triplet microtubules continuing into doublet microtubules distally. The micro- tubule doublets lack arms in the axoneme, but both the axoneme and kinetosome possess thin linkages between the innermost portions of A and B microtubules of adjacent doublets. Unlike Cardium (BarBER & LaNnp, 1967), the photoreceptor kinetosome in Tridacna lacks both a basal foot and striated rootlets. The nucleus (nu) of each retinal cell is central and con- tains a single nucleolus. Surrounding the nucleus and ex- tending toward the cell borders in a more or less stellate configuration are strands of microfilaments (Figures 3 & 4). Interestingly, this characteristic feature of tridacnid retinal cells was noted and figured by Brock in 1888, but Figure 6 Reconstructed ciliary receptor of tridacnid retinal cell ax — axoneme microtubules cv — ciliary microvilli cb — ciliary bleb cp — basal plate k — kinetosome sr — soma of retinal cell has been apparently overlooked by nearly all workers who have followed. The microfilament strands are most exten- sively developed in the eye’s centermost retinal cells and are likely cytoskeletal in function. Other cytoplasmic organelles include mitochondria (m), vesicles, Golgi ap- paratus, rough and smooth endoplasmic reticulum and glycogen grains (gly). The latter are of particular note because their density and distribution are quite variable in tridacnid retinal cells, and they may be found both in the free state and contained within vacuoles (Figures 4 & 5). From preparations I have examined, it is clearly the vari- able distribution of glycogen in tridacnid retinal cells which is responsible for rendering the appearance of pro- nounced basiphilia seen in peripheral retinal cells; the comparative absence of glycogen in the centremost retinal cells accounts for the latter’s relative transparency (Figure 3). This concentration differential in glycogen distribution likely influenced the thinking of earlier authors who mis- takenly reported two or three different cell types in the tridacnid eye, whereas my observations show only one. DISCUSSION Earlier reports that the siphonal eyes of Tridacna contain a lens (StasEK, 1966; KAwacuTi & MasBucHt, 1969) ap- pear to be mistaken. All preparations of siphonal eye Page 248 material which I have examined clearly showed a solid mass of retinal cells devoid of a lens. However, this is not to say that Yoncr’s (1936) hypothesis that the tridacnid eye (hyaline organ) enhances photosynthesis in adjacent siphonal zooxanthellae via collection and redirection of sunlight is not viable. Indeed, the retinal cells of Tridacna are optically transparent, and the eye’s shape is dimen- sionally similar to a biconvex lens. Thus, it would be extra- ordinary if light intensity were not appreciably greater adjacent to the eye’s capsule than in other siphonal tis- sues. Whether this apparent association of algal cells and the eye’s capsule has arisen directly as a consequence of enhanced illumination for the zooxanthellae and/or im- proved visual acuity for the photoreceptor is open to ques- tion. For instance, most reports on eyes in soft-bodied marine invertebrates figure the eye as being more or less enclosed by a haemal space; yet, these organisms do not host symbiontic plant cells. It would seem more likely that zooxanthellae are situated adjacent to tridacnid siphonal eyes because space is available to them there and, owing to the proximity of this space to the siphonal surface, con- ditions there are optimal for their growth. The absence of a lens structure in the siphonal eye has not limited visual sensitivity in Tridacna to simple shadow perception. Behavioural field notes by McMicHaex (1974) and Srasek (1965 & 1966) agree with mine in that we have all observed visual detection of nearby movements by giant clams. Presumably, this ability to “‘see” helps reduce the feeding success rate of animals that are believed to prey on Tridacna such as sea turtles (BusTARD, 1972), grazing fishes (STASEK, 1965) and sea birds (McMicwact, 1974). It is interesting to note that, at Enewetak Atoll, periods of darkness are coincidental with cessation of feed- ing activities by most coral reef predators and especially fishes (SMITH & PAULSON, 1974); this condition has ob- vious advantages for Tridacna because, during the night time, siphonal eyes would not be effective for predator detection. Precisely how the tridacnid eye, which is little more than a ball of retinal cells enclosed by a pigment cup, is able to perceive nearby moving objects is unclear. The algal THE VELIGER Vol. 23; No. 3 pigment cup must allow the eye directional sensitivity, but, lacking a focusing lens organ, that a single eye can resolve even a crude image seems doubtful. However, the presence of up to several thousand eyes on the siphonal surface of Tridacna would indicate that visual detection of motion must involve several to many eyes at one time. Should this be the case, it is possible that the clam’s sensitivity to mov- ing objects is facilitated by a small number of siphonal eyes functioning in a co-operative fashion—much like a very primitive compound eye in which the photoreceptor elements are morphologically separated. SUMMARY Giant clams of the genus Tridacna possess up to several thousand eyes upon the surface of their exposed hyper- trophied siphons; this extraordinary number of eyes is unique in the Animal Kingdom. The siphonal eyes of Tridacna are simple photoreceptors that lack a lens, but possess a pigment cup made of several to many layers of olive-green zooxanthellae. Each eye contains 280 to 350 polygonal retinal cells (15-20 zm in diameter) which bear numerous ciliary blebs. Retinal cell blebs possess a ciliary axoneme composed of 9 x 2 +0 microtubule doublets which splay outwards from the cilium’s basal plate. The ciliary blebs gave rise to many microvilli that are believed to be the photoreceptive portion of the retinal cell. Whereas tridacnid eyes possess directional sensitivity, be- cause they lack-a lens, they are individually incapable of image discrimination. However, both the ability of giant clams to detect nearby movements and the high density of eyes on the siphonal surface indicate that tridacnid eyes may function co-operatively in small numbers much like the elements of a primitive compound eye. Owing to the transparency of the retinal cells and the biconvex shape of the siphonal eye, it is apparent that Yonge’s hypothesis that zooxanthellae surrounding the eye’s capsule may de- rive more sunlight than other similar siphonal tissues is reasonable. Explanation of Figures 4 and 5 Figure 4: Electron photomicrograph of retinal cells in the eye of Tridacna gigas. cv — ciliary microvilli; gly — glycogen; mf — microfilaments; nu — nucleus; arrows - ciliary receptor of retinal cell Figure 5: Fine structure of retinal cell border showing ciliary re- ceptors. cb — ciliary bleb; cp — basal plate; cv — ciliary microvilli; gly — glycogen; k — kinetosome microtubules; m — mitochondrion THE VELIGER, Vol. 23, No. 3 [FANKBONER] Figures 4 and 5 —~ Vol. 23; No. 3 THE VELIGER Page 249 ACKNOWLEDGMENTS I wish to acknowledge the assistance and cooperation of Dr. Ernst S. Reese, Director of the Mid-Pacific Marine Laboratory, Enewetak Atoll, Marshall Islands. This re- search was funded by a grant to the Hawaiian Institute of Marine Biology from the U.S. Department of Energy and grant A6966 from the National Research Council of Canada. Literature Cited Barber, V. C. & M. F Lanp 1967. Eye of the cockle, Cardium edule: Anatomical and physiological investigations. Experientia 23: 677 - 678 Barber, V. C. « D. E. Wricht 1969. ‘The fine structure of the eye and optic tentacle of the mollusc Cardium edule. Journ. Ultrastruct. Res. 26: 515 - 528 Brock, J. 1888. | Uber die sogenannten Augen von Tridacna und das Vorkommen von Pseudochlorophyllkérpern im Gefasssystem der Muscheln. Zeit- schr. wiss. Zool. 46: 270 - 288 Bustarp, H. R. 1972. Sea turtles. Collins, London, 120 pp. Dorey, A. E. 1965. The organization and replacement of the epidermis in acoelous turbellarians. Quart. Journ. Microsc. Sci. 106: 147-172 FANKBONER, PETER VAUGHN 1971a. Intracellular digestion of symbiontic zooxanthellae by host amoebocytes in giant clams (Bivalvia: Tridacnidae), with a note on the nutritional role of the hypertrophied siphonal epidermis. Biol. Bull. 141: 222 - 234 1971b. Self righting by tridacnid clams. Nature 280: 579 - 580 Goreau, R. F, N. I. Gorzau & CHartes Maurice YONGE 1973. On the utilization of photosynthetic products from zooxanthellae and of dissolved amino acid in Tridacna maxima f. elongata (Mollusca: Bivalvia) . Journ. Zool., London 169: 417 - 454 Kawacutl, S. 1966. Electron microscopy on the mantle of the giant clam with special references to zooxanthellae and iridophores. Biol. Journ. Okayama Univ. 12: 81 - 92 Kawacutl, S. # K. MasucnHi 1969. Electron microscopy on the eyes of the giant clam. Biol. Journ. Okayama Univ. 15: 87 - 100 McMicuHae., Donatp FE 1974. Growth rate, population size and mantle coloration in the small giant clam Tridacna maxima (Réding), at One Tree Island, Capricorn Group, Queensland. Proc. Sec. Intl. Coral Reef Sympos. 1: 241 - 254 MuscatTINE, LEONARD 1967. | Glycerol excretion by symbiontic algae from corals and Tridacna, and its control by the host. Science 156: 516-519 PirELKA, DorotHy Riccs 1974. Basal bodies and root structures. In: Cilia and flagella, M. A. Sleigh (ed.). Acad. Press London, 500 pp. RicnHarpson, K. C., L. Jaretr & E. H. FINKE 1960. Embedding in epoxy resins for ultra-thin sectioning in electron microscopy. Stain Technol. 35: 313 - 323 RosEWwatTER, JOSEPH 1965. The family Tridacnidae in the Indo-Pacific. Moll. 1: 347 - 396 SitH, R. L. & A. C. PAULSON 1974. Food transit times and gut pH in two Pacific parrotfishes. Copeia No. 3: 796 - 799 StaseK, CHARLES ROBERT 1965. Behavioral adaptation of the giant clam Tridacna maxima to the presence of grazing fishes. The Veliger 8 (1): 29-35a; 2 plts. 3 text figs. (1 July 1965) 1966. The eye of the giant clam (Tridacna maxima). Calif. Acad. Sci. Occ. Pap. no. 58: 9 pp. Yoncz, Cuartes Maurice 1936. Mode of life feeding, digestion and symbiosis with zooxanthellae in the Tridacnidae. Sci. Reprt. Great Barrier Reef Exped. 1: 283 - 321 1975. Giant clams. Indo-Pacif. Sci. Amer. 2392: 96 - 105 Page 250 THE VELIGER Vol. 23; No. 3 The Effect of Pinnotheres hickman: on the Meat Yield (Condition) of Mytilus edulis Measured Several Ways C. L. PREGENZER School of Zoology, University of New South Wales, P.O. Box 1, Kensington, New South Wales, Australia, 2033 (2 Text figures) INTRODUCTION LOWERED MEAT CONTENT of bivalves caused by pinno- therid crabs has been reported by several authors, e.g., Haven (1958) for Crassostrea virginica by Pinnotheres ostreum, KruczyNnski (1972) for Argopecten irradians concentricus by Pinnotheres maculatus, and ANDERSON (1975) for Mytilus californianus by Fabia subquadrata. There are two possible causes of lowered meat yields. Damage to the gills, the mere presence of the crab on gills, or both. Or, the crab may be eating the potential food of the host. Observation of the feeding behaviour of Pinno- theres pisum (ORTON, 1920) and P. ostreum (STAUBER, 1945) showed that both obtain food by scraping the chelae over the host’s gills and transferring the food-laden mucous strands to their mouths. The crabs did not eat pseudo- faeces. CAINE (1975) observed that P. maculatus scrapes the food from the gill with its fourth walking leg which is then wiped clean by the chela and the food is transferred to the mouth. It would appear that crabs do eat their hosts’ food, although the food of mussels has not been pre- cisely defined. KruczyNnsx1 (1975) showed that crabs consume the same food as the host by feeding radio- actively labelled phytoplankton to bay scallops infested with P. maculatus. Gut analysis of the crabs revealed the tagged phytoplankton, which indicated that the crabs ate the scallops’ food. In an attempt to determine what effect Pinnotheres hickmani had on Mytilus edulis the condition indices of wild and cultured mussels were determined from several locations in Australia. The condition indices of those found to have crabs were compared to those without crabs. Only the data from Port Phillip Bay were useful. Subsequently an experiment was undertaken comparing the condition indices of non-infected mussels with those of mussels man- ually infected with P. hickmani. Condition index is a term used to refer to the amount of soft tissue present in a bivalve. To be useful in comparing meat content of ‘bivalves of different size, the amount of meat present is compared to the space bounded by the valves when fully closed, i.e.,the internal volume. Condi- tion index, expressed as a percentage, can be measured by comparing the weight of soft tissue to the internal volume of the bivalve. meat weight internal volume Traditionally, condition index has been measured using oven dried meats (MEpcoF & NEEDLER, 1941). Barb (1958) showed that use of meat volume, rather than weight was also valid. Condition Index = xX 100 METHODS The condition index of 600 wild mussels from various localities throughout their distribution in Australia was determined using oven dried meats, meat volumes and meats dried with absorbent paper (henceforth referred to as wet meat to distinguish from oven dried meat). The internal volume was determined using the method of ANDREWS (1963). The various methods of determining condition were compared to determine the validity of using meat weights dried with absorbent paper since this was more expedient than using oven dried meats or meat volumes. For the experiment 37 female and 23 male crabs were introduced into juvenile mussels from a culture raft in an area where mussels were known to have insignificant infes- tations of crabs and other harmful symbionts (PREGENZER, 1978). A blunt scalpel was used to force open the valves of the mussel just far enough to insert the crab without caus- ing damage to either the crab or the mussel. It had pre- Vol. 23; No. 3 THE VELIGER Page 251 viously been determined that neither the crab nor the mussel would be harmed by this procedure. Sixty mussels of approximately the same size were selected as a control. Both control and experimental mussels were numbered and placed in cubic cages 0.3m on an edge and enclosed with 1.5cm mesh wire. The cages were suspended 0.6m apart under the raft from which the mussels were taken. The cages were cleaned of epiphytic organisms once a month so that water flow to the mussels inside would not be hindered. The experiment was terminated after a period of infes- tation of 44 months, and just before the mussels were ex- pected to reach peak condition. Condition indices were determined for each mussel following the procedures mod- ified from Mepcor & NEEDLER (1941), Bairp (1958) and ANDREWS (1963). RESULTS The correlation between condition indices measured by wet meat weights and meat volumes was highly significant (r=0.99, Figure 1). The correlation coefficient between 60 50 30 20 20 go 40 50 60 %o Figure 1 A linear regression of condition indices measured by meat volume (Y axis) and by wet meat weight (X axis) Figure 2 A linear regression of condition indices measured by meat volume (Y axis) and by dry meat weight (X axis) wet and dry meat weights was not as high (r = 0.76) but it was acceptable at the 99.9% level (Figure 2). Every tenth value is plotted in Figures 1 and 2. On only two occasions were the condition indices of uninfested wild mussels greater than those housing crabs, i.e.,7 XI 1974 and 12 XII 1974 (Table 1). At the termination of the experiment no male crabs and only 20 female crabs were recovered from the experimen- tal mussels. One female was recovered from the control group. Five of the experimental mussels and 16 control mussels were lost due to natural mortality, the cleaning procedure and unknown causes (perhaps storms or curious people). There was no significant difference in growth (length increase) or shell weight between the control and exper- imental groups. There was a significant difference between the condition indices of the experimental and control groups, when calculated with either wet or dry meat weights (Table 1). Experimental mussels which lost their crabs during the experiment showed a significant differ- ence, when compared to control, and to experimental mus- sels which retained their crabs, in both wet and dry weight condition indices. The condition of these mussels was greater than those which retained their crabs and less than the control mussels (Table 2). Page 252 THE VELIGER Vol. 23; No. 3 Table 1 A comparison of condition indices and meat weights of mussels experimentally infected with crabs, those mussels whose crabs left and control groups. Wet meat determinations Dried meat determinations With crabs Control Crabs left host With crabs Control Crabs left host Condition index g/cc X 100 x 28.9 2Y/all 33.2 41 6.4 bull S 6.2 8.5 5.8 1.6 2.6 1.4 N 19 43 36 19 41 36 t = 3.72 t = 3.20 t = 3.50 t = 2.66 Rej. Ho, P > 0.001 Rej. Ho, P > 0.05 Rej. Ho, P > 0.01 Rej. Ho, P = 0.01 Meat weights ¢ 4 3.78 5.11 4.14 0.55 0.90 0.64 S 0.94 1.30 1.10 0.26 0.43 0.22 N 19 43 36 19 43 36 t = 3.96 t = 3.44 t = 3.26 t = 3.29 Rej. Ho, P > 0.001 Rej. Ho, P > 0.002 Rej. Ho, P = 0.002 | X designates mean, S the standard deviation, and N the number of values. Table 2 Mean condition indices for mussels with (w) and without (w/o) crabs from Port Phillip Bay, Australia. X indicates the mean C.I., S the standard deviation, and N the number of mussels. w/o Ww w/o w 24-4-74 26-6-74 ».4 32.75 31.69 36.42 34.05 S 5.68 6.81 6.88 8.94 N 18 27 18 22 t = 0.53 t = 0.95 11-7-74 29-8-74 Xx 36.70 31.25 22.47 20.36 S 7.14 6.30 8.21 5.01 N 10 39 32 16 t = 2.32 t = 0.92 Reject Ho at P = 0.05 12-12-74 x 51.13 44.31 S 3.28 6.00 N 12 13 t = 3.29 Reject Ho at P = 0.01 Wet meat weights of mussels which retained the crabs were 26% lower and dried meat weights 39% lower than the wet and dry meat weights of control mussels, respec- tively. DISCUSSION Techniques The high correlation between condition measured by wet meat weights and condition measured by meat vol- umes is not surprising. Since the density of mussel meat and water are so similar, the meats weigh very little in water. ANDREWS (1963) noted that the specific gravity of oyster meats was similar to that of salt water. The lower correlation coefficient between wet and dry meat is probably due to variable amounts of water con- tained in the mussel meats. However, the high level of probability( 99.9%) of the correlation between the 2 meth- ods suggests that the variability of water content is not a sufficiently strong argument to prevent the valid use of wet meat weights to determine condition. Wet meat weights and dry meat weights were used by DETHLEFSEN (1974) to determine condition indices but he did not comment on the comparison of the two techniques. Vol. 23; No. 3 Effect on Condition The information from Port Phillip Bay mussels gives a more reliable indication of the effect of the crab than does other field work. Both the crabs and the mussels were all first-year class, since they were taken from a raft which was in the water less than one year, and the number of infested and non-infested mussels was approximately equal. During most of the year the mussels were infested with small and immature crabs. The highly significant difference in condition and meat weights between infested and non-infested mussels in December (Table 2) suggests two things: (i) the effect of the crab is only noticeable when condition is high; (ii) condition is reduced only by larger crabs. The condition index of the control mussels from the experiment was less than the condition index of the mus- sels sampled from Port Phillip Bay in December, 1974, but was still very significantly different from that of the experimental group. This indicates that although the mus- sels were not up to full condition, the adult crabs signif- icantly lowered condition. The presence of larger crabs for only a short period of time also lower condition (Table 1). The greater reduction of dry meat weights compared to the reduction of wet meat weights suggests that the crabs’ presence produces a lower quality of meat since a higher water content is indicated in infested mussels. ANDERSON (1975) reported a lower glycogen level in Mytilus cali- fornianus infested with Fabia subquadrata. Perhaps the higher water content of infected mussels reflects a lower glycogen content. The significance of finding a female crab in a control mussel is not certain. It is unlikely that the mussel was invaded from wild crab stocks due to the extremely low abundance of Pinnotheres hickmani in that area. It is also unlikely the crab could have invaded a control mussel after leaving an experimental mussel since large female crabs are virtually non-swimmers. THE VELIGER Page 253 CONCLUSION It is equally valid to measure condition using dried meat weights, wet meat weights or meat volumes. Mature female Pinnotheres hickmani can significantly reduce condition and meat yields of mussels by as much as 26%, possibly because of consumption of a significant quantity of food which the mussel has filtered. Both male and female crabs decrease the pumping rates of Mytilus edulis (PREGENZER, 1979) and this must contribute to the lowered meat yields. Which of these two factors plays the greater role in reduced condition is not important. Re- duced condition caused by crabs is a possible cause of lost revenue to the mussel farmer. Literature Cited ANDERSON, Grecory L. 1975- The effects of intertidal height and the parasitic crustacean Fa- bia subquadrata Dana on the nutrition and reproductive capacity of the California sea mussel Mytilus californianus Conrad. The Veliger 17 (3): 299-306; 2 text figs. (1 January 1975) AnprREws, J. D 1963. Measurement of shell growth in oysters by weighing in water. Nat. Shellfish. Assoc. Proc. 52: 1-11 Bairp, R. H. 1958. Measurement of condition in mussels and oysters. Journ. Cons. perm. int. Explor. Mer. 23: 249 - 257 Caring, E. A. 1975: Feeding of Pinnotheres maculatus Say (Brachyura: Pinnother- idae). Forma et Functio 8: 395 - 404 DETHLEFSEN, V. 1975- The influence of Mytilicola intestinalis Steuer on the meat content of the mussel Mytilus edulis. L. Aquacult. 6: 83-97 Haven, D. 1958. Effects of pea crabs on oysters. 49: 77-86 Kruczynskx, W. L. 1972. ‘The effect of the pea crab Pinnotheres maculatus Say on the growth of the bay scallop Argopecten irradians concentricus Say. Chesapeake Sci. 13: 218-220 Mepcor, J. C. « A. W. H. NEEDLer 1941. The influence of temperature and salinity on the condition of oysters (Ostrea virginica). Journ. Fish. Res. Brd. Canada 5: 253 - 257 Orton, J. H. 1920. Mode of feeding and sex phenomena in the pea crab Pinno- theres pisum. Nature 106: 533 - 534 PREGENZER, C. 1978. Parasites and commensals associated with Mytilus edulis in Australia. Ph. D. thesis, Univ. New So. Wales, Kensington, N.S. W. 1979. The effect of Pinnotheres hickmani on pumping rates in Mytilus edulis. Austral. Journ. Mar. Freshwater Res. g0 (4): 547-550 Proc. Nat. Shellfish. Assoc. Page 254 THE VELIGER Vol. 23; No. 3 Size Gradients and Shell Polymorphism in Limpets with Consideration of the Role of Predation B. HARTWICK Department of Biological Sciences, Simon Fraser University Burnaby, British Columbia, Canada V5A 186 (9 Text figures) INTRODUCTION Rocky sHorEs are generally inhabited by a number of different limpet species which have overlapping vertical distributions and which show considerable variation in size and colour or shell pattern. This variation is, however, of an ordered nature. Definite shore-level size gradients have been detected in limpets (VERMEIJ, 1972; 1973; BREEN, 1972). Size gradients have also been found in a variety of other intertidal organisms including other gas- tropods (Epwarps, 1969; BERTNESS, 1977; Loupa, 1979) and bivalves (READING, 1979). Explanations for these size gradients have included vertical migration (FRANK, 1965; BREEN, 1972), differential growth (Loupa, 1979), physiological stress (WoLcoTT, 1973) and differ- ential mortality (VERMEIJ, 1972). The explanation by Ver- meij is based on the idea that gradients in mortality occur and that postlarval prereproductives will generally be found in a zone of minimum mortality. BERTNEss (1977) has questioned this interpretation in his study of carniv- orous snails (Thaididae). Size gradients in these snails are regulated by behavioural responses to light and gravity and the selective advantage in the size gradient pattern appears to be related to a similar pattern in their prey, the barnacle. The snails are placed in close proximity to the size classes and species of barnacles which are preferred and most efficiently utilized. The size gradient in the bal- anoids is presumably developed by a tidally induced gra- dient of available feeding times. In the case of limpets, it seems probable that both mi- gration and predation mortality are involved. That migra- tion is an important factor is well brought out by Frank’s paper (FRANK, 1965) in which it was shown that fingered limpets, Collisella digitalis (RATHKE, 1833) ascended in the fall and winter and descended to a lesser extent in the spring. Such net upward movements (also detected by BREEN, 1972) result in older and larger individuals occur- ring at higher levels. Both Frank and Breen suggest that such movements are adaptive and very possibly related to predation pressure. The action of predators has been considered by PALMER (1977) as the probable force behind shell form and sculp- ture in Ceratostoma foliatum (GMELIN, 1791) and other gastropods (VERMEIJ, 1976; PALMER, 1979) and behind the existence of shell polymorphisms in limpets (GIESEL, 1970). As early as 1945, Test noted the absence of conspic- uous forms of limpets on the intertidal and suggested that their resemblance to the substrate was the result of con- tinual selective predation by visual predators like shore- birds. Giesel accepted predation by shorebirds as an ex- planation for the presence of 2 morphs of Collisella digi- talis, one form tending to inhabit rock surfaces and the other being associated with the gooseneck barnacle Pollicipes polymerus (SowERBy, 1833). According to Giesel, disruptive selection was the force behind the estab- lishment and maintenance of the polymorphism. Visual predators were also thought to be an important factor in the colour polymorphism detected in Crepidula convexa Say, 1822 (HoaGLUND, 1977). Although predation has been cited as an important proc- ess affecting both size and shell pattern of limpets and other forms on the intertidal, evidence for such a role is sadly lacking. This is especially true for avian predators which in a number of studies have been singled out as important. HoacLunp (1977) made one observation of a gull attacking a snail, Littorina littorea (Linnaeus, 1758), with 2 Crepidula convexa attached and on this basis sug- gested that visual predators which detect pigment differ- Nol. 23; No. 3 ences were important to the colour polymorphism in Crepidula. BREEN (1972) did not observe any predation by shorebirds. GrrsEL (1970) based his premise partly on the coincidence of the timing of greatest disruption of pattern frequencies in limpets with the seasonal occur- rence of high densities of oystercatchers and other shore- birds but had no supporting data on foraging by the birds. The present study was initiated in order to confirm the existence of reported patterns of size and shell colour in Collisella digitalis, to extend the study to other limpet spe- cies and to examine the influence of Black Oystercatchers Haematopus bachmani Audubon on the observed patterns. Previous studies had indicated that these birds utilized many limpets, including C. digitalis, in their diet (Hart- WICK, 1976). MATERIALS ann METHODS The study took place on Cleland Island on the west coast of Vancouver Island, Canada. This is a small island with exposed rocky shores and a considerable population of Black Oystercatchers which utilize these shores for feeding (Hartwick, 1974). Much of the study took place in 2 shore areas with relatively uniform topography and expo- sure and well developed zonation. Quadrats (0.093 m’) were randomly placed along transects and all limpets within the quadrats were removed. Previous observations (Hartwick, 1976) had indicated that oystercatchers might hunt differently in the different zones occurring on exposed rocky shores. Since these zones were arranged vertically, they were used to stratify sampling. The zones considered were a high intertidal rockweed zone (largely Fucus and Endocladia), the mussel bed (Mytilus califor- nianus Conrad, 1837), groves of sea palms (Postelsia) and finally, the lower intertidal, which can be designated as the Laminaria zone. Sampling then was carried out within these 4 zones. All limpets were identified to species, meas- ured by vernier calipers (length) and given a colour code. Shell scoring was a modified version of that described by GiEsEL (1970). The rim and apex were scored o for white, 1 for grey, 2 for brown and 3 for black, while the striping on the general shell surface was scored as 0 for plain white, 1 for light with a single stripe, 2 for mostly light with more than a single dark band, 3 for when dark shades predom- inate, and striping is heavy, 4 for almost all brown with very little white, 5 for mottled brown-black and 6 for black or dark grey-black. Final score was obtained by adding the 3 scores together for each limpet so that a maximum score of 12 represented a uniformly dark limpet while the lowest THE VELIGER Page 255 score of o represented a light limpet. This scoring scheme worked well and was consistent when different people used it. Black Oystercatchers feeding in the area were observed and limpets attacked by the birds on the intertidal were carefully collected after observation. Preyed upon limpets were identified, measured and scored for shell patterns. Limpets of similar size were collected and scored for shell pattern. Light and dark ones were separated and then placed in arrays of 20 in rockweed and open rock areas where Oystercatchers were known to forage. The sequence in which the birds attacked light and dark lim- pets within these alternating arrays was noted (see Hart- Wick, 1978a, for details on the method). Counts of limpets within the quadrats provided esti- mates of density. Sampling for limpets was carried out monthly from July 1976 to July 1977, although several winter collections were missed entirely or partly because of heavy sea conditions. Foraging time spent in each of the zones was recorded for 5 different pairs of birds at various times in their breeding cycle. Observations were made by telescope or binoculars from blinds or from vantage points some dis- tance away. RESULTS Trends in Shell Length Limpet species examined included Collisella digitalis (RATHKE, 1833), C. pelta (RATHKE, 1833), Notoacmea persona (RATHKE, 1833), and N. scutum (RATHKE, 1833). The mean lengths for all limpet species combined were significantly different in each of the 4 designated zones (p < 0.05). Limpets showed an increasing size gradient from the high intertidal (mean length = 8.63 + 2.80mm) down to the Postelsia beds (mean length = 11.30 + 3.44 mm) with a slight drop in mean size in the lower intertidal or Laminaria zone (Table 1). The trend in shell length for Collisella digitalis was sim- ilar to that described for all species combined. Mean shell length peaked in the Postelsia bed (Table 1). The species was scarce in the lower intertidal. Seasonal changes in mean length of all limpets combined were observed in all 4 zones. The data in Table 1 indicate that a pattern of increasing length occurs in the rockweed and mussel bed zones from October to April and then there is an abrupt decrease in April and May. In the Postelsia bed mean shell length increases from May to reach a high Page 256 THE VELIGER Table 1 Time of Sampling July/76 June July Mean Shell Length + SD (n) Vol. 23; No. 3 Shore-level trends in shell length for all limpet species combined and for Collisella digitalis alone at various times in the year. Data on Collisella digitalis alone are given in brackets. Sample size is also indicated in brackets. A dash indicates data not available. Rockweed zone 8.14 + 1.63 (161) (8.37 + 1.54, 135) 9.49 + 1.98 (166) (9.53 + 1.66, 131) 8.89 + 1.69 (102) (8.89 + 1.69, 102) 8.94 + 1.82 (68) (8.94 + 1.82, 68) 10.28 + 1.67 (12) (10.28 + 1.67, 12) 8.12 + 1.61 (139) (8.16 + 1.61, 134) 7.93 + 1.70 (162) (8.19 + 0.79, 130) 8.98 + 5.67 (161) (9.17 + 6.03, 139) Mussel bed Postelsia grove 7.69+ 2.69 (351) (8.57 + 2.86, 195) 9.47 + 2.07 (236) (9.68 + 1.82, 204) 8.77 + 1.99 (160) (8.79 + 3.29, 133) 10.05 + 1.48 (29) (10.05 + 1.48, 29) 10.44 + 1.72 (19) (10.44 + 1.72, 19) 9.34 + 2.29 (189) (9.36 + 1.87, 148) 8.89 + 1.80 (286) (9.42 + 1.69, 200) 9.38 + 1.42 (230) (9.66 + 1.31, 189) 11.54 + 1.51 (110) (10.16 + 2.38, 33) 11.71 + 4.17 (151) (9.63 + 2.40, 87) 12.35 + 3.71 (71) (10.22 + 2.43, 34) 8.05 + 3.60 (30) (7.86 + 3.13, 11) 9.86 + 3.20 (62) (9.54 + 1.96, 12) 11.48 + 3.59 (145) (10.78 + 1.64, 23) overall means 8.63 + 2.80 (971) (8.75 + 2.81, 851) 8.86 + 2.11 (1500) (9.31 + 2.17, 1117) 11.30 + 3.44 (564) (9.85 + 2.35, 200) 100 Percent Frequency 50 Length (mm) Figure 1 Frequency histograms for shell length of all limpets in each of the designated zones: (a) rockweed; bed; (d) Laminaria zone (b) mussel bed; (c) Postelsia Laminaria zone 12.34 + 5.14 (7) 8.83 + 3.67 (3) 9.65 + 5.4 (39) (5.00 + 0.0, 1) 9.19 + 3.21 (65) (8.37 + 0.90, 3) 12.28 + 3.40 (33) 10.15 + 4.04 (147) (c) n=569 Percent Frequency THE VELIGER Page 257 10 15 20 Length (mm) Figure 2 Frequency histograms for shell length of Collisella digitalis in each of the designated zones: (a) rockweed; (b) mussel bed; (d) Pos- telsia bed in October and then drops during the winter. In the Laminaria zone limpet length increases over summer from May to July and then decreases abruptly in August at a time when mean length in Postelsia is rapidly increasing. Seasonal fluctuations occurred in mean length of Colli- sella digitalis but trends were difficult to identify. The shore level size gradients are further illustrated by Figure 1. Proceeding in a down-shore direction there is an increase in the frequency of limpets over 10mm in length and a decrease in the proportion of limpets under 10mm. More than 80% of the limpets in the rockweed and mussel bed zones were less than 10mm in length. The Postelsia bed had the highest percentage (59.9%) of limpets over 10mm in length. Limpets greater than 15 mm were found most frequently in Postelsia beds and Laminaria zone. Based on the total sample of 3187 limpets, those with shell lengths greater than 15mm comprised only 6.9%. When Collisella digitalis is considered by itself, a some- what similar pattern is detected (Figure 2). A greater per- centage of limpets less than 10mm in length are found in the rockweed area than below it. Fingered limpets in the mussel bed tended to be less than 15 mm in length. Small numbers of large fingered limpets are found in both the rockweed zone or upper intertidal and the Postelsia beds. Attempts to relate fingered limpet size to substrate type provide some significant patterns (Figure 3). The fre- quency of fingered limpets over 10mm in length was gen- erally higher on Pollicipes and bare rock than on mussel bed or balanoid barnacles. Almost all of the limpets over 15mm in length occurred on bare rock. Limpets on bar- nacles had the highest frequency (91.97%) of limpets with shell length less than 10mm. Mean shell lengths of Collisella digitalis were not statistically different on the 4 substrate types with the exception of those on barnacles which were on average smaller (p < 0.01). There are, however, significant differences in mean lengths on par- ticular substrates in the lower part of the mussel bed com- pared with the upper part. The mean shell length of C. digitalis on Pollicipes, or Mytilus or Balanus is greater when these occur in the upper mussel bed than when the same substrates are examined lower down (p < 0.01). For example, the mean length of limpets on mussels in the lower mussel bed is 8.48 =-- 1.82mm while those in the upper mussel bed have a mean length of 9.62 + 1.48. There was also a significant increase in mean length of fingered limpets on bare rock surface in the upper mussel bed (8.22 + 1.20mm) as compared with those on the same substrate above the mussel bed (10.6 + 1.95mm). Thus, shore level size gradients with increasing size in an up-shore direction are detectable when similar substrates are compared. If fingered limpets on the different surfaces are compared within the mussel bed zone only, those on Pollicipes tend to be larger than those on the other 3 substrates in the same zone. Similarly, when fingered lim- Page 258 THE VELIGER Vol. 23; No. 3 100 on goosenecks n=609 Percent Frequency on mussels n=429 on barnacles n=37 on bare rocks n=4 34 Length (mm) Figure 3 Frequency histograms of shell length of Collisella digitalis on various substrates pets using mussels as a substrate are compared in quadrats containing mussels only and in quadrats containing both mussels and gooseneck barnacles limpet shell length tends to be greater when goosenecks are present than when absent (p < 0.01). Shell Length of Predated Limpets In an earlier study (Hartwick, 1976), shell lengths of limpets taken by Black Oystercatchers were shown to be relatively large. In the present study, limpets taken by these birds were again relatively large. In fact, pooling all species, 79% of 222 predated limpets were over 15mm in length. Many of these were taken in the Postelsia beds and Laminaria zones. Similarly, Collisella digitalis attacked by the birds tended to be large, with 95% over 1omm and 31% over 15mm. The tendency for oystercatchers to select larger limpets was also shown in another study involving arrays of limpets placed on the intertidal (Hartwick, 1978a). Trends in Shell Patterns Considering Collisella digitalis by itself first, a unimodal distribution of pattern scores is exhibited in each zone (Figure 4). Fingered limpets inhabiting the rockweed zone had a higher pattern score than those in the mussel and Postelsia beds. Thus, 62% of C. digitalis in rockweed had pattern scores greater than 4 compared with only 39% and 38% in mussel and Postelsia beds, respectively. Com- parison of mean pattern scores in the various zones based on collections over the full year indicates that the rockweed zone is inhabited by limpets with higher pattern scores than those on either the mussel or Postelsia (p < 0.01). Interestingly, the range in pattern scores decreases in a down-shore direction from the upper intertidal down to Postelsia (Figure 4). If only fingered limpets greater than 10mm in length are considered for the summer months when predation by oystercatchers is heavy, the shell pattern distribution is unimodal at a score of 4 (Figure 5). A similar pattern dis- Vol. 23; No. 3 THE VELIGER Page 259 40 63 ° Percent Frequency to 3 10 Oo I 2 3 a & O 7 8 Pattern Score Figure 4 Distribution of shell pattern scores for Collisella digitalis in each of the designated zones: telsia bed tribution arises when all sizes of Collisella digitalis are con- sidered in the rockweed and mussel bed combined. When pattern scores of Collisella digitalis are compared on each of the different substrates, again interesting differ- ences arise. Dark limpets with pattern scores greater than g have the highest frequency on bare rock (Figure 6). Very 30 Percent Frequency nd S) ra fe} ON AIG Qe S Ae a Aes he OMT Bh NG Pattern Score Figure 5 Distribution of shell pattern scores for Collisella digitalis over 10 mm in length for all zones combined over the summer months (a) rock weed; (b) mussel bed; (c) Pos- few of these occur on gooseneck barnacles, mussels or other barnacles. Mean scores for limpets on the different sub- strates are significantly different. Thus, the mean score on rock was 7.99 + 2.88 (n = 434) which was significantly (p = o.o1) higher than that on gooseneck barnacles (4.62 = 2.24, n = 609). The pattern score of limpets on barnacles other than Pollicipes was lowest of all (3.57 = 1.80, n = 37). Pattern scores of limpets on Mytilus were similar to those on Pollicipes. If Collisella digitalis limpets on the same substrate are compared at different shore levels a significant increase in shell pattern score is detectable in an up-shore direction. Thus, limpets on gooseneck barnacles in the lower mussel bed had mean pattern scores (3.78 + 1.55, n = 209) less than those in the upper mussel bed in the same area (4.22 = 1.77, n = 70) which in turn were lighter than those above (5.53 =+ 2.09, n = 298). However, the darkest lim- pets occurred on bare rock above the mussel bed. Shell patterns were also determined for all limpet spe- cies combined for all sizes and for limpets with shell lengths over 10mm (Figure 7). Most limpets fell in intermediate categories with pattern scores between 3 and 6. There may be a bimodality detectable with modes at 4 and 11. Com- parisons of mean pattern scores for all species combined in each of the zones indicates a trend toward higher pat- tern scores in a down-shore direction at least in mid sum- mer but the pattern is not clear at other times. However, Page 260 THE VELIGER Vol. 23; No. 3 20 on goosenecks n=609 20 on mussels n=429 10 a (S) S| uo 3 foal o ~ ey a | 5 20 = on barnacles Ay n=37 10 30 on bare rocks 20 n= 434 10 BRO 7 8 2 iO) ni 12 1g Pattern Score BPigA Figure 6 Distribution of shell pattern scores of Collisella digitalis on various substrates limpets inhabiting Postelsia and Laminaria zones were definitely darker than those at higher levels. Thus, the mean pattern score for all limpets combined in the Postelsia bed varied over the year from 6.12 to 7.62 and those in the Laminaria zone varied from 5.67 to 9.83. Mean scores in the upper 2 zones tended to be in the range 4.24 to 6.88 with most approximately 5.00. Pattern Scores of Predated Limpets When limpets attacked by oystercatchers are scored for shell patterns, the distribution obtained is shifted toward Percent Frequency i} ° 10 OB By a BIO SG) iG) ul LR Aw Pattern Score Figure 7 Distribution of shell pattern scores of all limpet species combined for the summer months (June, July, August): (a) all limpets; (b) limpets over 10mm in length 20 ° Percent Frequency oO {e) 20 Or 23 AR O72) B © vO wi 1B 1g} Pattern Score Figure 8 Distribution of shell pattern scores of limpets preyed upon by Black Oystercatchers: (a) all limpets; (b) Collisella digitalis only Vol. 23; No. 3 the darker end of the scale compared with that of limpets in the habitat (Figure 8). Very few (22.64%) light shaded limpets with scores less than 6 were preyed upon. Only 3 limpets out of 256 had a score of o and these were en- crusted in a faded coralline red algae common to the Laminaria zone. Collisella digitalis accounts for most of the lighter coloured limpets which were attacked with 49% of this species having pattern scores less than 6 (Figure 8). When oystercatchers began feeding on limpets arranged in arrays of alternating dark and light forms, the attacks were randomly distributed in terms of shading. Two sample sequences are as follows (LDDLLDLDLD) and (LDLDLDDLLDLDDDLLLDLDL). Based on one sam- ple runs tests, these and other sequences recorded are not different from random (p < 0.05). Other similar experi- ments have suggested that size is more important (Hart- WICK, 1979). Variation in Density of Limpets The abundance of limpets, based on counts within the quadrats (0.093 m’), varied over the year. In the rock- weed and mussel bed zones the mean number of limpets per quadrat was generally high in the summer months, decreasing to low values over fall and winter (Figure 9). Density of limpets was generally highest in the mussel bed. Trends in the lower zones were difficult to detect but there appears to be a drop in numbers in the Postelsia bed in the early fall and a possible increase in numbers in both Postelsia beds and Laminaria zone in the spring. The in- crease in abundance in the upper intertidal and mussel bed in early summer was accompanied by a drop in mean size. Decreases in numbers in the Postelsia zone in the fall were accompanied by increases in mean length. Foraging of Black Oystercatchers In a separate study (Hartwick, 1976), the foraging behaviour of these birds was described and different modes of hunting in various parts of the intertidal were noted. Limpets were utilized to a large extent by adults them- selves and by both adults and chicks once the chicks are moved to the feeding area. The birds tend to select large limpets especially when feeding the young. Observations during this early study indicated that the birds may walk directly and rapidly to an area with large limpets on, for example, an accessible rockface. They may remove one or more of these and carry them to the young. At times, how- THE VELIGER Page 261 80 @ rockweed A mussel bed © Postelsia bed ( Laminaria zone 790 60 rr ™ Hs \ yl ! iy iy I t 1 iy ! i ! i 1 @ aN, Density (mean number of individuals per quadrat 0.093 m?) Ry Sol AB RS BE eR AV TG RN PEF SIS LOLS LE S Time (months) Figure 9 Variation in the density of limpets over time in each of the desig- nated zones ever, limpets are ignored and mussels or other prey are utilized. In the present study, records of the foraging time spent by 5 pairs in each of the zones (except for Postelsia) indi- cated that most of the time (57%) was spent in the mussel bed while a lesser and equal time was spent in the rock- weed zone and Laminaria zone (22% and 21%, respec- tively). Earlier records (HarTWick, 1973) suggest that most foraging time is spent in the low to mid mussel bed but that the particular pattern for any pair is affected greatly by the stage in the reproductive cycle. A pair of adults that is involved in mating or has just lost a clutch will often spend almost all of their time feeding on limpets and other small items on the mussel bed. The higher and lower areas may be utilized more and more as the season progresses. Page 262 THE VELIGER Vol. 23; No. 3 DISCUSSION If all limpet species are considered as one on the rocky shores of Cleland I., then there is a definite shore-level size gradient fromsmall to large ina down-shore direction, at least beyond the dense beds of Postelsia. Similarly, Loupa (1979) noted a trend of increasing size with de- creasing shore level of various gastropods. This pattern was also observed for 4 species of snails in the Puget Sound region (BERTNESS, 1977) and is said to be characteristic of middle and lower intertidal gastropods throughout the world (VERMEIJ, 1972). On Cleland Island then, limpets inhabiting the middle and upper intertidal areas are on the average smaller than those found associated with Postelsia or farther down the shore. If Vermeij’s hypothesis is correct, we would expect the intensity of predation to be minimal at the middle and higher levels of the inter- tidal. Black Oystercatchers are visual predators with a diet consisting of approximately 40% limpets (Hartwick, 1976). The birds feed on all 4 species of limpets considered in the present study. Adult birds feed readily on limpets less than 1.5 cms in length while they tend to offer larger sized limpets to their young especially when the young are near the nest. Much of their foraging occurs within the mussel bed; and where Postelsia occurs, they are apt to forage at times within the Postelsia for limpets and other prey items. There are a number of reasons why oystercatchers may not have a great effect on limpets before or during the early stages of their breeding season (i.e.,in the period prior to June). In winter and early spring the birds are often found foraging in protected mudflats rather than at their summer breeding site (HARTWICK & BLAyLock, 1979). On arriving at the breeding site the birds spend a considerable time defending their territories and engaging in mating activities. They also make foraging trips away from their territories (HARTWICK, 1978b), so that their impact within the territory may be minimal at this time. As the breeding season progresses chicks make an appearance and the adults search more for larger limpets to carry to the young at the nest. The adults themselves continue to feed on smaller limpets. In late summer and fall, observations on foraging (HaRTWIcK, 1976) indicate heavy use of small and medium sized limpets by both adults and young in the upper mussel bed and rockweed areas. Usually the young birds are with the adults in the feeding territory at that time. However, the sudden appearance of large limpets brings a rapid response by foraging adults. The large lim- pets are quickly taken and usually offered to the chicks. The rapidity of the response suggests that the birds would effectively remove many of the larger limpets in the middle and high intertidal except in places of inaccessibility. The effect would be greatest in territories in which the birds successfully reared a brood. Predation on the large limpets would occur mainly in late summer and early fall. In the lower intertidal limpets occurring below the mussel bed are often covered by Laminaria and other plants. The birds must probe underneath to find the prey. Observations suggest that low, low tides are times of low food availability within some territories (HARTWICcK, 1978b). The algal cover and the short exposure time may make the lower zone a suitable refuge from extensive pre- dation by these birds. In the case of Collisella digitalis, there exists consider- able evidence for a trend of increasing size with increasing shore-level (FRANK, 1965; BREEN, 1972; VERMEIJ, 1972). This trend was also detected for C. digitalis in the present study when similar substrates were compared. Moreover, the largest sizes of this limpet species were found on steep rockfaces often in mid to high intertidal and in places relatively inaccessible to oystercatchers. When all samples of C’. digitalis are combined though, the gradient in size is similar to that of the other species, increasing in a down- shore direction. It should be noted that when the mussel bed was thick, only limpets within bill depth of Black Oystercatchers were examined (see Hartwick, 1973 for method ). Thus, deep within the mussel bed matrix consid- erable numbers of very small individuals would shift the size gradient to that postulated (VERMEIJ, 1972) for high intertidal forms. Small fingered limpets were also com- mon on balanoid barnacles in areas which GIESEL (1970) referred to as having background heterogeneity. In the middle intertidal C. digitalis on Pollicipes tended to be larger in size than those on other substrates in the same zone. According to GiESEL (1970), many C. digitalis migrate to Pollicipes after initial settlement and these Pollicipes-type limpets survive better in late spring and in summer when the risk of desiccation is high and algal productivity is low. However, food intake of these limpets will depend on the amount of time available for foraging on rock surfaces nearby. In early spring and in fall the advantages are shifted toward limpets inhabiting rock surfaces where algal productivity is high at a time when desiccation is less of a risk (GIESEL, 1970). Bird pre- dation is thought to overlie and interact with these two Vol. 23; No. 3 opposing tendencies. Giesel suggested that bird predation would be greatest in high intertidal areas with long expo- sure times and low background heterogeneity. Giesel’s work dealt mainly with shell polymorphism in C’. digitalis. In high intertidal areas selection against light coloured conspicuous limpets would be intense and Giesel reported that large light coloured limpets did disappear from rock surfaces. Similarly, large dark coloured limpets disap- peared from Pollicipes beds. In the present study, the re- sponses of adult birds to arrays of limpets suggest that size of limpet is important but colour pattern is not. The birds may be restricting the larger limpets in the middle and high intertidal to steep rockfaces inaccessible to predation. Their influence on colour pattern frequency is not so clear. GiEsEL (1970) found that limpets on Pollicipes became lighter as their size increased. That is, average pattern score was a decreasing function of limpet size. Presumably dark animals were being selected against. According to Giesel, the polymorphism in C. digitalis first appears in very small sizes. By the time the limpets reach 4-8 mm in June, there is a well established bimodality. Giesel links this with an apparent heavy selection against limpets with intermediate pattern scores in the period February to May. However, this effect may not be attributable to predation by oystercatchers. As noted earlier, the impact of the birds on limpets may be less in that period of time than later on. Moreover, collections of predated shells in this and pre- vious studies on Cleland Island indicate that the birds feed on limpets ranging in size from 5 mm to over 30mm. The small amount of predation by oystercatchers on limpets near the bottom end of the size range would probably not have the disruptive effect postulated by Giesel. On the other hand, Black Oystercatchers did feed most heavily on C. digitalis with pattern scores intermediate between those on bare rock and those on Pollicipes. Thus, 82% of pre- dated C. digitalis were scored from 4 to 7 while those in- habiting Pollicipes and rock surfaces had pattern modes near 4 and 10, respectively. If other shorebirds migrating through the area in early spring take small limpets, then the combined effect of their predation with that of oyster- catchers may be significant. GiEsEL (1970) refers to high densities of oystercatchers in the period of February to May but similar observations were not made on Cleland Island. Giesel also suggests that high Pollicipes densities may be a strong feeding stimulus with areas of low Pollicipes density being less attractive to the avian predators. Foraging studies on Black Oyster- THE VELIGER Page 263 catchers suggest that at times their foraging is closely tied to the availability of relatively large mussels (HarTWick, 1976) rather than Pollicipes. However, whether this is true when the birds are in flocks is not known. The data on shell patterns for all limpet species com- bined is interesting. It appears that the birds are feeding most on limpets with pattern scores intermediate between modes occurring at 4 and 11. When only limpets over 10mm are considered, the birds are taking relatively dark forms. Since there was no evidence of selection of one colour pattern over another in the experiments the greater frequency of darker limpets taken by the birds must reflect their tendencies to forage in areas where those are most prevalent. It is not possible at this time to explain general patterns of shell colour on the basis of predation by oyster- catchers. Evidence that vertical migrations occur in limpets (FRANK, 1965; BREEN, 1972) must also be considered. Such migrations may occur in all 4 limpet species and will contribute to changes in abundance and mean size over time. The observed increases in mean size of limpets in the mussel bed and rockweed zones during the late fall and winter may reflect net upward movements similar to the migrations described for Collisella digitalis by Frank. The increase in the number of small individuals in early sum- mer observed in the present study was consistent with the pattern noted by BREEN in 1972. Differential growth, migration and other processes will clearly play a role in determining the final patterns on the intertidal. Both VERMEIJ (1972) and BERTNESS (1977) point out that it may well be naive to look for a universal explanation for intraspecific shore-level size gradients. Considering the sizes of limpets taken by oystercatchers the size gradients observed are such that large limpets end up in the lower intertidal where a partial refuge from oyster- catcher predation exists. Higher intertidal forms are often restricted to near vertical rock surfaces inaccessible to oystercatchers. The middle intertidal is a zone of intense predation by oystercatchers but the predation is not di- rected at the very small sizes which occur in such abun- dance within the mussel bed. ACKNOWLEDGMENTS Special thanks to both William Blaylock and Les Tulloch for their help in the study. Funding was provided by the National Research Council, Canada. Page 264 THE VELIGER Vol. 23; No. 3 Literature Cited Bertness, Marx D. 1977- Behavioral and ecological aspects of shore-level size gradients in Thats lamellosa and Thats emarginata. Ecology 58: 86-97 Breen, Paut ALLAN 1972. Seasonal migration and population regulation in the limpet Acmaea (Collisella) digitalis. The Veliger 15 (2): 133-141; 7 text figs. (1 October 1972) Epwarps, DaLias Craic 1969. Zonation by size as an adaptation for intertidal life in Olivella biplicata. Amer. Zool. 9: 399 - 417 FRANK, PETER WOLFGANG 1965. | The biodemography of an intertidal snail population. Eco- logy 46 (6): 831-844; 8 text figs. GreseL, James T. 1970. On the maintenance of a shell pattern and behavior polymorph- ism in Acmaea digitalis, a limpet. Evolution 24 (1): 98-119 Hartwick, E. B. 1973. Foraging strategy of the Black Oystercatcher Haematopus bach- mani. Ph. D. thesis, Univ. British Columb. 1974. Breeding ecology of the Black Oystercatcher (Haematopus bachmant Audubon). Syesis 7: 83 - 92 1976. Foraging strategy of the Black Oystercatcher (Haematopus bachmani Audubon). Canad. Journ. Zool. 54 (2): 142-155 1978a. Some observations of foraging by Black Oystercatchers (Haema- topus bachmant Audubon). Syesis 11: 55-60 1978b. The use of feeding areas outside of the territory of breeding Black Oystercatcher. Wilson Bull. 90 (4): 650-652 Hartwick, E. B. & W. Braytock 1979. Winter ecology of a Black Oystercatcher population. Stud. Avian Biol. 2: 207-215 Hoacianp, K. ELaine 1977. A gastropod color polymorphism: one adaptive strategy of phenotypic variation. Biol. Bull. 152: 360-372 Loupa, S. M. 1979. Distribution, movement and diet of the snail Searlesta dira in the intertidal community of San Juan Island, Puget Sound, Washing- ton. Mar. Biol. 51: 119 - 131 PALMER, ALLISON RICHARD 1977. Function of shell sculpture in marine gastropods: hydrodynamic destabilization in Ceratostoma foliatum. Science 197: 1293 - 1295 1979. Fish predation and the evolution of gastropod shell sculpture: experimental and geographical evidence. Evolution 32 (2): 697 - 713 ReEapinG, C. J. 1979. Changes in the downshore distribution of Macoma balthica (L.) in relation to shell length. Estuar. Coast. Mar. Sci. 8: 1-13 Tzst, Avery RANsoME GRANT 1945. Ecology of California Acmaea. Ecology 26 (4): 395-405 (1 October 1945) VERMEIJ, GEERAT J. 1972. Intraspecific shore-level size gradients in intertidal molluscs. Ecology 53 (4): 693 - 700 1973- | Morphological patterns in high intertidal gastropods: adaptive strategies and their limitations. Mar. Biol. 20 (4): 319-346 1976. Interoceanic differences in vulnerability of shelled prey to crab predation. Nature 260: 135 - 136 Wotcott, THomas G. 1973. Physiology, ecology and intertidal zonation in limpets (Acmaea): a critical look at “limiting factors.” Biol. Bull. 145: 389-422 Vol. 23; No. 3 THE VELIGER Page 265 Physiological Effects of Desiccation and Hypoxia on the Intertidal Limpets Collisella digitalis and Collisella pelta BY BRUCE LEON BOESE' ano AUSTIN W. PRITCHARD Department of Zoology, Oregon State University, Corvallis, Oregon 97331 and Oregon State University Marine Science Center, Newport, Oregon 97365 (7 Text figures) INTRODUCTION Collisella digitalis (Rathke, 1833) is an upper intertidal limpet found from California to Alaska (GrirFITH, 1967). This limpet is often exposed to aerial conditions for more than one tidal cycle and has been observed as much as gm above MLLW in areas of optimal spray conditions (WotcotT, 1973). Collisella pelta (Rathke, 1833) is dis- tributed from Mexico to Alaska (GRIFFITH, op. cit.) and the animals are submerged and exposed on every tidal cycle. On the central Oregon coast the lower distribution limit of C. digitalis overlaps the upper limits of C. pelta. Numerous attempts have been made to relate the tidal zonation of marine gastropods to differences in tempera- ture tolerance, osmotic tolerance, and desiccation resist- ance (SouTHWARD, 1958; Harbin, 1968; SANDISON, 1968; WotcotT, 1973). Enhanced tolerances in upper inter- tidal limpets of the family Acmaeidae have been attrib- uted to the increased water-holding capacity, lower de- siccation rates, and cellular adaptations to tolerate high electrolyte concentrations (SHOTWELL, 1950; SEGAL, 1956a; SEGAL & DEHNEL, 1962; WoLcoTT, 1973). Differences in aerial oxygen consumption and heart rate have been reported in several marine gastropods from different intertidal zones (SEGAL, 1956b; SANDISON, 1966; MicauLer, 1967; RUSSELL-HUNTER & McManon, 1974; McManon & RusseLit-Hunter, 1977). The effect of prolonged desiccation on these parameters has not, to our knowledge, been examined. It has been suggested that anaerobic energy pathways may be used by some marine intertidal gastropods under conditions of prolonged desic- ' Present address: Northrop Services Inc., O. S. U. Marine Sci- ences Center, Newport, OR 97365 cation (EMERSON & DUuERR, 1967; NEWELL, 1973; Mc- Manus & JAMES, 1975). However, with the exception of McManus & James, most of the studies on anaerobic metabolism in gastropods have been carried out on fresh- water or terrestrial forms (Von Branp et al., 1950; Ou- DEJANS & VAN Der Horst, 1974; STOREY, 1977). Wo tcotTT (1973) observed that Collisella digitalis of- ten secreted mucus under conditions of desiccation, which dried around the shell margin and retarded water loss. Extensive loss of moisture or “sealing off” of the respira- tory surfaces during desiccation may result in some degree of reliance on anaerobic metabolism in upper level limpets. It is also possible that upper intertidal gastropods may be able to regulate aerobic metabolic processes during aerial desiccation to a greater extent than species in the lower intertidal zones. Either of the above strategies may allow upper intertidal species more time during tidal exposure to exploit resources. In this study heart rate, survivorship and accumulation of lactate, succinate and alanine were compared to zonally separate upper intertidal limpets during desiccation and hypoxia. Oxygen consumption during prolonged desicca- tion was also examined. MATERIALS anp METHODS Collection and Maintenance of Animals Collisella digitalis (15-25 mm in length) and C. pelta (25-40mm in length) were collected at low tides from Yaquina Head and Boiler Bay, Oregon. Collisella pelta were collected from 0.4m to 1.5m above MLLW while C. digitalis were collected from 1.0m to 2.5m above ML Page 266 THE VELIGER Vol. 23; No. 3 LW. Before experimentation, the limpets were kept in a circulating sea water system (30%,) at 12-15°C under constant light, for 3-5 days. Two experimental tempera- tures (15°C and 30°C) were used in this study. Fifteen degrees Celsius is near the maximum sea surface tempera- ture recorded on the Oregon Coast (Gonor, 1970), while internal temperatures of 30°C have been observed in C. digitalis (WotcotT, 1973). Desiccation Experiments 1. HEART RATE DETERMINATION Aerial heart rate at 15°C and 30°C was determined by impedance recording. Two leads from a length of ba- thythermograph wire were inserted under theshell through a small hole drilled to expose the mantle tissue over the heart. The leads were sealed in place with beeswax and cyanoacrylate glue, and attached to an impedance pneu- mograph and chart recorder. The limpet was allowed to attach to a platform disk which was placed within a nylon screen cage. This assembly was put in a 1 L capacity plexiglass aquarium and submerged in 15°C sea water. After 3 hours of submergence the sea water was drained and silica gel desiccant was poured slowly to a depth of about 6cm around the outside of the cage that contained the attached limpet. The aquarium was then placed in a constant temperature room maintained at one of the experimental temperatures, and aerial heart rate record- ed. The experiment was terminated when there was no discernible heart beat. Data were reduced to number of beats per minute by counting and averaging 3 I-minute intervals every 30 minutes. For heart beats of less than 15 beats per minute a 10-minute sample was taken. For extremely slow and irregular records, the entire 30-minute interval was count- ed and averaged. 2. SURVIVORSHIP ann WATER LOSS The following procedure was used to determine sur- vivorship and total water loss with desiccation. Limpets were weighed after blotting with Kimwipes to remove excess water, placed ventral side down in individual plas- tic disposable beakers (100 mL) and sealed in a desicca- tor containing silica gel. The desiccator was kept in a constant temperature room. No more than 3 limpet test groups (20 limpets per group) were kept in the desiccator during any experimental run. Desiccation times in each experimental run were staggered so that at least 5 hours elapsed between the removal of one experimental group and the next. This was done to insure that exposure to moist constant temperature room air was kept at a prac- tical minimum, and that sufficient time was allowed be- tween desiccator openings to allow maximum moisture ex- traction by the desiccant. The above experimental pro- cedure was repeated several times in order to obtain data values separated by 2 to 5 hours for use in plotting a sur- vivorship curve. After removal from the desiccator, the limpets were reweighed and submerged ventral side down on a plastic tray in running sea water. The criterion for mortality was failure to reattach to the substrate and the absence of discernible foot movement after 24 hours. All limpets were then dried to a constant weight at 70°C and the weight of the shell and body determined. 3. LACTATE DETERMINATIONS For experiments where lactate determinations were made, animals were weighed and desiccated as above. A rough estimate of percent water loss was determined, based on the amount of weight loss during desiccation. If this estimate exceeded the maximum percent water loss tolerated in the survivorship experiment, or if the limpet displayed obvious signs of mortality (blackened, dry, head and foot), lactate values were not determined for that individual. Control limpets were treated as in the survivor- ship experiment except that moist paper toweling was substituted for desiccant. In order to obtain enough tissue for extraction of lactate it was necessary to pool limpets (3 to 5 for Collisella digitalis, 1 to 3 for C. pelta). Eight to 10 pooled samples for each desiccation or control ex- posure time were extracted separately. After removal from the desiccator, the limpets were weighed, the viscera separated from the shell and quickly frozen and powdered in a mortar and pestle filled with liquid nitrogen. The frozen powder for each separate extraction was weighed and homogenized with 3.5 vol of perchloric acid (6%) in a chilled tissue homogenizer (Potter, Elvehjem, 15 mL). After centrifuging (25 000g, 10 min at 4°C), the pellet was reextracted with 2.5 vol of perchloric acid (6%), re- centrifuged, and the supernatants combined. Supernatants were filtered (0.45 4m Millipore), and lactate values de- termined on 0.1 mL of the extract by spectrophotometric measurement of NAD/NADH conversion, using kits pro- vided by Sigma Chemical Company, with internal stand- ards. Final concentrations were corrected to a fresh, un- desiccated shell-less weight value, and reported as umole: g wet wt’. 4. OXYGEN CONSUMPTION Aerial oxygen consumption (uL:g dry wt'-h™) was determined at 15°C and 30°C in a Gilson differential Vol. 23; No. 3 THE VELIGER Page 267 CE respirometer. Twenty to 40 limpets were handled and desiccated as above at either 15°C or 30°C. After a pre- determined desiccation time, all the limpets were removed from the desiccator and weighed. Maximum desiccation time was based upon survivorship data for each species at the given desiccation temperature. If estimates of percent water loss exceeded the maximum tolerance observed in the survivorship experiments, or limpets showed obvious signs of mortality (see above), the limpet was discarded. Control limpets (15°C) were removed from the flowing sea water system, blotted dry, and weighed. Three to 6 desiccated animals were placed in a dry 100 mL respiro- meter chamber (Collisella pelta), or 15 mL respirometer chamber (C. digitalis) and allowed to equilibrate for 2 hours at their exposure temperature. Control limpets were handled as above except that a minimal volume of sea water was added to moisten the floor of the chamber. For desiccated limpets, half hour readings were taken for 3 hours and averaged. For control limpets, half hour oxy- gen consumption measurements were taken for a 3 hour period. After oxygen uptake determinations, all the lim- pets were removed from the respiration chambers, re- weighed, and dried to constant weight. If the weight had changed by more than 5 mg (approximately 0.5%) during the course of the experiment, the data were discarded. Anoxic Stress Experiments For the experiments involving exposure to anoxia, lim- pets were first weighed and placed in an 8L capacity “Tupperware” plastic container, the lid of which had been fitted with 2 plastic hose connectors which served as in- take and exhaust ports. This lid was sealed to the con- tainer and the contents equilibrated for 3 hours in moist aerial conditions. After this period, intake and exhaust hoses were attached and the chamber rapidly gassed with moist nitrogen for 10 min, after which a slight positive pressure was maintained to insure against leakage. This pressure was monitored by placing the exhaust hose under water in an Erlenmeyer flask with the flow rate regulated at 5 to 10 bubbles per minute. Heart rate was determined by impedance recording prior to, during, and after anoxic exposure. Survivorship was determined using the same criteria as in the desicca- tion experiments. For determination of anaerobic end products limpets were pooled and homogenized as in the desiccation ex- periments. L-alanine was determined by the method of WILLIAMSON (1974). Succinate was determined by a fluorometric method (WILLIAMSON & CorKEy, 1969). L-lactate was determined as in the desiccation experi- ments. RESULTS Figure 1 depicts the percent of water lost during desicca- tion of Collisella digitalis and C. pelta at 15°C. Each 60 50 40 30 % Water Loss 20 10 fo) 10 20 go 40 50 60 70 Time (hours) % Water Loss (a) 10 20 go 40 50 60 70 Time (hours) Figure 1 a) Percent of water loss in Collisella pelta exposed to dry air at 15°C. Values are means of 10 to 20 individuals + 2 standard errors b) Percent of water loss in Collisella digitalis. Symbols as in a Page 268 THE VELIGER Vol. 23; No. 3 value is the mean water loss of all surviving organisms at that particular exposure time. The figure shows that there is a more rapid initial water loss with exposure in C. digit- alis than in C. pelta. Both species show a rapid water loss for the first 10 hours of exposure with a more gradual rate of loss after this time. Figure 2 compares survivorship of Collisella digitalis and C. pelta during aerial desiccation at 15°C and 30°C, and when exposed to moist nitrogen at 15°C. Although C. digitalis loses water at a greater initial rate, Figure 2a shows that C. digitalis is more tolerant of desiccation eS LON 207) 1300401 50), Col 70m (GONE OC mm comme than C. pelta at both 15°C and 30°C and survives a Time (hours) longer exposure. Table 1 summarizes these data and shows that mean survival time and mean water loss tolerated (LD,.) was considerably greater for C. digitalis than for C. pelta at both experimental temperatures. Figure 2b depicts the survivorship of C. digitalis and C. pelta when exposed to moist nitrogen at 15°C. Collisella digitalis survives anoxia considerably longer (LD,,.—=33 hours) an than C. pelta (LDs.= 19 hours). 100 _, 60 5 IE (adjacent column —>) cA et Figure 2 a) Survival of Collisella pelta and Collisella digitalis in dry air at 20 15°C and 30°C. Each value represents the percentage of individu- als that survived exposure from an initial sample size of 20 @ Collisella pelta, 15°C ©. Collisella digitalis, 15°C A Collisella pelta, 30°C A Collisella digitalis, 30°C rc) b) Survival of Collisella pelta and Collisella digitalis during expo- Time (hours) sure to moist nitrogen at 15°C. Symbols as in a Table 1 Mean survival time and water loss tolerated by Collisella pelta and Collisella digitalis when desiccated at two temperatures. Mean Survival Time Mean Water Loss Tolerated (%)! hours (LD5o estimate) 15°C 30°C 15°C 30°C Collisella pelta 50 8 31.8+7.1 31.5 + 6.6 Collisella digitalis 62 13 61.1 + 7.1 59.4 + 8.5 1Percent water loss + 2 standard errors. Vol. 23; No. 3 Figure 3a represents the averaged aerial heart rate data from individual Collisella digitalis during the period of exposure to dry air (15°C and 30°C) and moist air (15°C). The maximum aerial heart rate at both 15°C and 30°C occurred approximately 90 min after the sea water was drained from the chamber and the animals exposed to aerial conditions. The maximum heart rate recorded at 30°C was approximately 14 times higher than the maximal rates (moist and desiccated) at 15°C. The moist aerial control rate at 15°C was nearly constant for 30 hours, but exhibited a gradual decline to one half the maximal rate from 60 to 80 hours after the start of desiccation (not shown). No control rates were measured beyond 80 hours of exposure. At 15°C heart rate remained oO 4 38 12 16 20 24 28 Time (hours) fo) 4 8 12 16 20 24 28 Time (hours) Figure 3 a) Aerial heart rate of Collisella digitalis when exposed to moist air (controls) at 15°C (©), dry air at 15°C (@), and dry air at 30°C (A). Each point is the mean of 4 to 7 individuals. Method of estimating average heart rate is described in text b) Aerial heart rate of Collisella pelta. Symbols as in a THE VELIGER Page 269 constant and near the maximum aerial rate for 6 to 10 hours after the start of desiccation. After that period the rates dropped rapidly with loss of a recordable heart rate beyond 17 hours of exposure. At 30°C heart rates dropped rapidly after 2 to 3 hours of exposure, with loss of a recordable heart rate 5 to 7 hours after the onset of exposure (Figure 3). The heart rate responses of Collisella pelta to aerial conditions are shown in Figure 3b. In contrast to C. digit- alis, maximum aerial heart rate occurred immediately after exposure to aerial conditions. Moist aerial control rates were nearly constant for 30 hours with a gradual decline in heart rates to approximately one half of the aerial maximum occurring from 40 to 60 hours after ex- posure to aerial conditions (not shown). Maximum aerial rates at 30°C were approximately 14 times those at 15°C. Collisella pelta, in contrast to C. digitalis, exhibited a progressive reduction in heart rate at 15°C, with loss of a recordable trace occurring between 33 and 27 hours after the start of desiccation. At 30°C the reduction of heart rate was more rapid, with loss of a recordable heart rate occurring 12 to 18 hours after the start of desiccation (Figure 3b). Upon exposure to moist nitrogen, both species (Figures 4a and 4b) show an immediate bradycardia with com- plete bradycardia evident in Collisella digitalis (Figure 4b). After return to normoxic conditions heart rate re- covers rapidly in both species with an initial overshoot of the preexposure rate, followed by a gradual return to a “typical” aerial heart rate. Figure 5 depicts the results of desiccation on the oxy- gen consumption of Collisella digitalis and C. pelta at 15°C and 30°C in comparison to moist aerial controls. (15°C). At 30°C, oxygen consumption of C. digitalis (Figure 5a) decreased throughout the length of exposure. At 15°C, the rate of oxygen consumption is nearly con- stant with only a gradual decline to about 60% of the un- desiccated aerial control rate (15°) after 46 hours of desiccation. In contrast, the oxygen consumption for C. pelta (Figure 5b) declined with increasing length of desiccation at both experimental temperatures. After about 16 hours of exposure to 15°C desiccating conditions the oxygen consumption rate remained constant at ap- proximately half of the undesiccated control rate. A more pronounced reduction in oxygen consumption occurred at 30°C. Moist aerial control rates for both species remained constant throughout the exposure time. Oxygen consump- tion experiments were terminated at both temperatures when excessive mortalities occurred after prolonged de- siccation. Page 270 Time (hours) Ol 23 456012 34 56012 34 56 78 giolli2 Time (hours) Figure 4 a) Aerial heart rates of four individual Collisella pelta before, during and after exposure to moist nitrogen at 15°C b) Aerial heart rates of three individual Collisella digitalis before during and after exposure to moist nitrogen at 15°C 2 Figure 6 summarizes the accumulation of whole-body lactate in both species during desiccation (15°C and 30° C) in comparison to moist aerial controls (15°C). For _THE VELIGER pL O, dry weight .h+ pL O, dry weight? . h* Vol. 23; No. 3 oo [o) fo} 12 16 20 24 28 32 40 Time (hours) 36 500 100 60 28 16 20 Time (hours) 12 24 32 Vol. 23; No. 3 THE VELIGER Page 271 (< on facing page) Figure 5 a) Aerial oxygen consumption of Collisella digitalis when exposed to moist air (controls) at 15°C (©), dry air at 15°C (@), and dry air at 30°C (A). Values are means of 6 to 10 determinations + 2 standard errors. b) Aerial oxygen consumption of Collisella pelta. Symbols as in a Collisella digitalis (Figure 6a) at both desiccating tem- peratures, lactate accumulates gradually over moist aeri- al control amounts. For C. pelta (Figure 6b) during desic- cation at 15°C, lactate accumulation began after about 15 hours of desiccation. At 30°C, lactate accumulation began at 4 to 7 hours of desiccation. Total amount of lactate accumulated in C. pelta is similar to that of C. digitalis. Control lactate values in both species did not change significantly during exposure to moist air at 15°C. No data were taken beyond 12 hours of desiccation at 30°C due to excessive mortalities. Figure 7 isacomparisonof the accumulation of I-lactate in Collisella digitalis and C. pelta when exposed to moist nitrogen. Both species accumulate |-lactate during anoxia, with C. digitalis accumulating a larger amount than C. pelta. The increase in lactate with time of anoxia is nearly linear for C. digitalis for the entire period of exposure, while C. pelta reaches a peak level of lactate within 4 hours. Table 2 is a comparison of control levels of 3 end pro- ducts (alanine, succinate, and lactate) in Collisella pelta and C. digitalis with the amounts present after 12 hours of exposure to moist nitrogen at 15°C. Significant in- creases in lactate and succinate occurred in C. pelta while no increase in alanine was noted. In C. digitalis, only lactate increased significantly over controls after 12 hours of exposure to anoxia. ie) aS nh (e} pmol Lactate -g fresh weight* S OB 4 © B Wo WH ws GG Gs —o op Time (hours) to to ° Co rary [op & © 6 8 10 12 14 16 18 20 22 24 26 28 Time (hours) mol Lactate: g fresh weight" iS Figure 6 a) Lactate accumulations in Collisella digitalis when exposed to moist air (controls) at 15°C (@), dry air at 15°C (C), and dry air at 30°C (A). Values are means of 8 to 10 pooled samples + 2 standard errors b) Lactate accumulations in Collisella pelta. Symbols as in a DISCUSSION The observation that Collisella digitalis tolerates a greater total water loss than C’. pelta is not surprising. Upper in- tertidal gastropods are considered by several authors to Table 2 Mean values of three anaerobic end products present in Collisella pelta and Collisella digitalis after 12 hours exposure to moist nitrogen at 15°C. Control animals taken directly from holding tanks. Numbers in parentheses represent number of samples. Lactate Succinate Alanine Collisella pelta Controls 1.5 + 0.5 (9) 0.05 + 0.02 (13) 3.1 + 0.8 (8) 12 Hours 8.0 + 2.1 (7)? 0.20 + 0.03 (12)2 3.3 + 0.8 (8) Collisella digitalis Controls 5.2 + 1.3 (9) 0.09 + 0.03 (6) 2.5 + 0.8 (8) 12 Hours 15.1 + 2.6 (9)2 0.12 + 0.02 (7) 3.8 + 1.7 (6) Values are pmole - g wet wt—! + 2 standard errors. *Significantly different at p < 0.01 (t-test). Page 272 mol Lactate: g fresh weight"! fo) 2 4 6 8 10 12 14 Time (hours) Figure 7 Lactate accumulation in Collisella digitalis and Collisella pelta during exposure to moist nitrogen at 15°C. Each value is the mean of 8 to 10 determinations have relatively larger amounts of extra-visceral water than lower intertidal forms (SHOTWELL, 1950; SEGAL, 1956a; SeEcAL & DEHNEL, 1962). The usefulness of this water in delaying appreciable loss of tissue water has been questioned seriously by Wotcott (1973), who suggests that the greater tolerance of desiccation in upper inter- tidal Acmaeidae is due to a greater tolerance of internal osmotic concentration. Although mean survival times at 30°C were consider- ably shorter than at 15°C in both species, similarities in LD,, values for water loss at both temperatures (Table 1) indicate that mortality is caused by water loss rather than by exceeding thermal tolerances. Thermal tolerances were not included in this study. Harpin (1968), how- ever, noted that 80% of Collisella digitalis survived 15 hours at 29°C and 70% survived 10 hours at 31.5°C; C. pelta have been shown to withstand 15 min immersions in 34°C water (Wotcortrt, 1973). The percent of water loss tolerated in this study by both species is considerably less than reported by WoLcotT (1973) and Rotanp & Rinc (1977). Although zoogeo- graphic differences cannot be discounted, variation in technique may account for much of this difference, espe- cially the manner in which the limpets were allowed to attach to the substrate. WoLcott (1973) allowed limpets to attach when submerged, while in this study, limpets were first blotted dry and placed on a dry substrate. This would tend to reduce the initial weight of the limpets and therefore the percent of water loss during desiccation. THE VELIGER Vol. 23; No. 3 The nearly constant heart rate and oxygen consumption of Collisella digitalis during the first few hours of desic- cation at 15°C is in contrast to C. pelta which showed a marked reduction in both parameters (Figures 3 and 5). Craic (1968) noted that C. pelta remains stationary while emerged, rarely moving while awash. In contrast, C. digitalis commonly move while awash (MILLER, 1968; Mittarp, 1968), and have been observed as much as gm above MLLW in areas where optimal spray conditions occur (WotcoTT, 1973). The regulation of heart rate and oxygen consumption during desiccation may allow C. digitalis to maintain an active feeding stature not possible in C. pelta under similar conditions. The relatively larger amounts of extra-visceral water in Collisella digitalis (SEGAL & DEHNEL, 1962) may at least partly account for the initial regulation of heart rate and oxygen consumption during desiccation at 15°C by keeping respiratory tissues hydrated longer. WoLcotr (1973) described two phases of water loss in limpets; an initial rapid evaporative phase where free water being lost from exterior surfaces is the rate-limiting factor, and a much slower diffusion phase where rates of water loss are determined by the rate at which water is being supplied from the underlying tissues. The evaporative phase of water loss in C. digitalis is more extensive than that of C. pelta (Figures 1a and tb), possibly due to a larger relative amount of “stored water.” Whatever ad- vantage this water gives C. digitalis at 15°C may be lost at 30°C, as no regulation can be inferred from either the heart rate or oxygen consumption data, which decline during initial exposure (Figures 3a and 5a). The initial regulation of heart rate and oxygen consumption observed in C. digitalis (Figures 3a and 5a) is probably not re- lated to mucous barrier formation. Although formation of mucous barriers was observed in C. digitalis, this oc- curred only during the later stages of desiccation, and they were not as extensive as those described by WoLcotr (1973). Surprisingly, C. digitalis shows a more rapid water loss than C. pelta, a species which does not pro- duce a mucous barrier (Figure 1). Both species survived prolonged exposure to a moist nitrogen environment (Figure 2b). The bradycardia that occurred in both Collisella digitalis and C. pelta upon ex- posure to hypoxic conditions (Figures 4a and 4b) has been reported in bivalves and overshoots in heart rate sim- ilar to those observed in both limpet species after termina- tion of exposure to moist nitrogen have been observed following prolonged aerial exposure and hypoxia (Trur- MAN, 1967; HELM & TRUEMAN, 1967; TAyLorR, 1976; BAYNE, 1971; BayNeE et al., 1976). Post-exposure over- shoots in heart rate may be indicative of the repayment of an oxygen debt (TRUEMAN, 1967; HELM & TRUEMAN, Vol. 23; No. 3 THE VELIGER Page 273 1967) due in part to the accumulation of the products of anaerobic metabolism. Recent research on anaerobiosis in invertebrates has established that lactate, which is formed in vertebrate tissues during hypoxia, is often only an initial end product in many bivalve molluscs, with alanine and succinate playing a more significant role (DEZwANN, KLUYTMANS & ZANDEE, 1976). Neither species in this study accumu- lated statistically significant amounts of alanine in their tissues after 12 hours of anoxia. Although succinate in- creased significantly in Collisella pelta during anoxia, the maximum amount accumulated would contribute less than 4% of the ATP yield that is accounted for by lactate accumulation. In C. digitalis succinate did not accumulate significantly over control values. In contrast, both species accumulate lactate in statistically significant amounts in a moist nitrogen atmosphere. Collisella pelta reaches a maximum accumulation after approximately 4 hours of anoxia, while C. digitalis continues to produce lactate over a longer period. This, coupled with the enhanced survivorship of C. digitalis and the larger total amount of lactate accumulated by C. digitalis compared to C. pelta, is consistent with the hypothesis that upper inter- tidal Acmaeidae are capable of more extensive anaerobic respiration than lower intertidal representatives. Under desiccation stress an increase in lactate was noted in both species, although lactate accumulation in Collisella pelta at 15°C did not begin until 15 hours of desiccation, well beyond the limit for tidal exposure in that species. The amount of lactate present in C. pelta after 12 hours of exposure to dry air at 15°C is consider- ably less than the amount produced after 12 hours of exposure to moist nitrogen (Table 2). Greater amounts are accumulated at 30°C, but C. pelta is probably ex- posed to such a high temperature only rarely. Laboratory desiccation can only roughly estimate the time course of desiccation in the environment, but the results do sug- gest that anaerobic metabolism is not used routinely by C. pelta during periodic tidal exposures. In contrast, C’. dig- italis appears to accumulate lactate throughout the period of desiccation at 15°C (Figure 6). The amount of lactate present in C. digitalis after 12 hours of exposure to dry air at 15°C and 30°C, compares favorably to the amount present after 12 hours of exposure to anoxia (Table 2). This similarity in the amount of lactate accumulated sug- gests that anaerobic metabolism may be of importance during short-term exposures to dry air that might occur in the zonational range of C. digitalis. The literature contains relatively little information con- cerning metabolic end product accumulation during desic- cation in intertidal animals. BARNES, FINLAYSON & P1aTI- GoRSKY (1963) observed lactate accumulations in the barnacle, Balanus balanoides, during prolonged desicca- tion (up to 16 hours). Although mean rates of accumu- lation in B. balanoides are roughly comparable to rates of accumulation in Collisella digitalis and C. pelta, B. balan- otdes survives desiccation for a much longer time and eventually accumulates up to 10 times the maximal amount of lactate observed in either limpet species in this study. WiESER (1980) studied the accumulation of lac- tate, alanine, and succinate in the marine gastropods, Littorina littorea, Monodonta lineata, and Nassarius reti- culatus, exposed to dry air and nitrogen environments. He found that alanine accumulated in similar amounts under desiccation and nitrogen induced anaerobiosis, while succinate accumulated only during nitrogen expo- sure. In contrast to the results observed in C. pelta and C. digitalis, lactate did not accumulate in any of the gastro- pods Wieser studied. Wieser speculated that alanine ac- cumulates during desiccation indicated a shift to anaero- biosis with alanine also serving to stabilize potential osmotic differences between water in the mantle cavi- ty and cellular fluids. In a study reported by McManus & JAMES (1975), the marine gastropod, Littorina saxatilts rudis, survived up to 3 weeks of desiccation and produced significant amounts of alanine, succinate, and lactate as anaerobic end products in a 2:1:1 ratio. In contrast to both of these studies, the ability of C. digitalis and C. pelta to respire aerobically when severely desiccated (Figure 5) may reduce the necessity of relying on anaerobic meta- bolism under desiccation conditions. Both species main- tained a high rate of oxygen consumption at 15°C when severely dried, even after heart stoppage. This indicates that cutaneous respiration is important to both species but especially to C. digitalis. Control moist aerial oxygen con- sumption rates of C. digitalis are about half the rates measured by Doran & McKenzie (1972). In their study the respiratory chambers were agitated, which may ac- count for this difference. In this study, no change in oxygen consumption was noted in either limpet species during the period of exposure to moist air at 15°C (Fig- ure 5). In conclusion, Collisella digitalis, when compared to C. pelta, has several physiological characteristics which may enhance its ability to use the upper intertidal zone during desiccating conditions. During the first few hours of desic- cation at 15°C, C. digitalis is able to maintain a rela- tively constant heart and oxygen consumption rate, while C. pelta, exposed to identical conditions, exhibits rapidly declining rates. After severe desiccation at 15°C, the oxy- gen consumption of C. digitalis is greater and has declined less from control values compared to C. pelta. Collisella digitalis survives desiccation at both 15°C and 30°C for a longer period and can tolerate more water loss than C. pelta; C. digitalis shows greater capacity for anaerobic metabolism than C. pelta. Comparisons of the time course Page 274 THE VELIGER Vol. 23; No. 3 of lactate accumulations in both species during desicca- tion (15°C) and while in a moist nitrogen atmosphere suggest that anaerobic pathways may be useful during tidal exposure to desiccating conditions in C’. digitalis but probably not in C. pelta. While |-lactic acid accumulated in both species during prolonged desiccation, oxygen con- sumption rates were maintained at a relatively high rate. This suggests that extensive anaerobic metabolism is un- likely in either limpet species during normal tidal ex- posures. ACKNOWLEDGMENTS This work was partially supported by a Sigma Xi Grant- in-Aid of Research. We would like to thank Dr. William A. Bridger of the University of Alberta at Edmonton for supplying succinate thiokinase. This work was carried out in partial fulfillment of the requirements for the degree of Doctor of Philosophy, Department of Zoology, Oregon State University. Literature Cited Barnes, Haroxp, D. M. Finrayson & J. PraticorsKy 1963. The effect of desiccation and anaerobic conditions on the behav- ior, survival and general metabolism of three common cirripedes. Journ. Anim. Ecol. 32: 233 - 252 Bayne, BRIAN LEICESTER 1971. Ventilation, the heart beat and oxygen uptake by Mytilus edulis L. in declining oxygen tension. Comp. Physiol. Biochem. 49 (4A): 1065 - 1085 Bayne, Brian Leicester, CuristopHer J. Bayne, T. C. CarerooTt « R. J. THompson 1976. The physiological ecology of Mytilus californianus Conrad. 2. Adaptation to low oxygen tension and air exposure. Oecologia (Berlin) 22 (3): 229-250 Craic, Peter C 1968. The activity pattern and food habits of the limpet Acmaea pelta. The Veliger 11 (Supplement): 13-19; plt. 1; 5 text figs.; 1 table (15 July 1968) DeZwaan, A., J. H. E M. Kruytmans « D. I. ZanpeEE 1976. Facultative anaerobiosis in molluscs. Biochem. Soc. (Lon- don), Symposia 41: 133 - 168 Doran, SHARON Rose & Donatp S. McKENzIE 1972. Aerial and aquatic respiratory responses to temperature varia- tions in Acmaea digitalis and Acmaea fenestrata. The Veliger 15 (1): 38-42; 2 text figs. (1 July 1972) Emerson, Davp N. « Freperick G. Duerr 1967. Some physiological effects of starvation in the intertidal proso- branch Littorina planaxis (Philippi, 1847). Comp. Biochem. Phys- iol. 20 (1): 45-62 Gonor, JEFFERSON JoHN 1970. Oregon coastal marine animals, their environmental tempera- tures and man’s impact. Ore. State Univ. School Oceanogr. Tech. Reprt. No. 199 GrirritH, L. M. 1967. The intertidal univalves of British Columbia. Province. Mus. Dept. Recr. Conserv. Handbook No. 26 Haropin, Dane D. P 1968. A comparative study of lethal temperatures in the limpets Acmaea scabra and Acmaea digitalis. The Veliger 11 (Supple- ment): 83 - 87; 4 text figs. (15 July 1968) Hem, M. M. « E. R. TRUEMAN 1967. ‘The effect of exposure on the heart rate of the mussel, Mytilus edulis (L). Journ. Comp. Biochem. Physiol. 21 (1): 171-177 Brit. Columb. McMahon, Rosert FE « W. D. Russe_t-HuNTER 1977. Temperature relations of aerial and aquatic respiration in six littoral snails in relation to their vertical zonation. Biol. Bull. 152 (1): 182 - 198 McManus, D. P « B. L. James 1975. Anaerobic glucose metabolism in the digestive gland of Lit- torina saxatilis rudis (Maton) and in the daughter sporocysts of Microphallus similis (Jag.) (Digenea: Microphallidae). Journ. Comp. Biochem. Physiol. 5 (3B): 293 - 297 Micater, H. 1967. Aerial and aquatic respiration of certain trochids. Experi- entia 23 (1): 52 MILiarp, CAROL SPENCER 1968. The clustering behavior of Acmaea digitalis. The Veliger 11 (Supplement): 45-51; 4 text figs. (15 July 1968) Miter, ALAN C. 1968. Orientation and movement of the limpet Acmaea digitalis on The Veliger 11 (Supplement): 30-44; 18 (15 July 1968) Amer. Elsevier Publ. Co., vertical rock surfaces. text figs. NEWELL, RicHARD CHARLES 1970. Biology of intertidal animals. Inc., New York Oupgjyans, R. C. H. M. «& D. J. van ver Horst 1974. Aerobic-anaerobic biosynthesis of fatty acids and other lipids from glycolytic intermediates in the pulmonate land snail Cepaea nemoralis (L.). Journ. Comp. Biochem. Physiol. 47 (1B): 139 - 147 Rowanp, W. & RicHarp A. RING 1977. Cold, freezing, and desiccation tolerances of the limpet Acmaea digitalis (Eschscholtz). Cryobiology 14 (2): 228-235 Russe.i-Hunter, W. D. « Ropert F McMaHon 1974. Patterns of aerial and aquatic respiration in relation to vertical zonation in four littoral snails (abstract). Biol. Bull. 147 (2): 496 - 497 SANDISON, Eyvor E. 1968. Respiratory responses to temperature and temperature toler- ance of some intertidal gastropods. Journ. Exp. Mar. Biol. Ecol. 1 (2): 271-281 SEGAL, EARL 1956a. Adaptive differences in water holding capacity in an inter- tidal gastropod. Ecology 37 (1): 174-178 1956b. Microgeographic variation as thermal acclimation in an inter- tidal mollusc. Biol. Bull. 111 (1): 129-152 Seca, Eart & Paut Augustus DEHNEL 1962. Osmotic behavior in an intertidal mollusc: Acmaea limatula. Biol. Bull. 122 (3): 417-430 SHOTWELL, JESSE ARNOLD 1950. Distribution of volume and relative linear measurement in Acmaea, the limpet. Ecology 31 (1): 51-61 SoutHwaprp, A. J. 1958. | Note on the temperature tolerances of some intertidal animals in relation to environmental temperature and geographical distribution. Journ. Mar. Biol. Assoc. U. K. 37 (1): 49 - 66 Storey, KENNETH B. 1977. Lactate dehydrogenase in tissue extracts of the land snail, Helix aspersa: unique adaptation of LDH subunits in a facultative anaerobe. Journ. Comp. Biochem. Physiol. 56 (2B): 181 - 187 Tay or, A. C. 1976. Burrowing behavior and anaerobiosis in the bivalve Arctica tslandica (L.). Trueman, E. R. 1967. The activity and heart rate of bivalve molluscs in their natural habitat. Nature (London) 214 (5090): 832 - 833 Von Branp, THeopor, Harry D. BAERNSTINE & BENJAMIN MEHLMAN 1950. Studies on anaerobic carbohydrate consumption of some fresh water snails. Biol. Bull. 98 (3): 266-276 Wieser, W. 1980. Metabolic end products in three species of marine gastropods. Journ. Mar. Biol. Assoc. U. K. 60: 175 - 180 WILuiAMson, Dermont H. 1974. L-alanine determination with alanine dehydrogenase. pp. 1679 to 1682 in Hans Ulrich Bergmeyer (ed.): Methods of enzymatic analysis, vol. 4. Acad. Press New, York Wi.uiaMson, J. R. & B. E. Corxey 1969. Assays of intermediates of the citric acid and related com- pounds by fluorometric enzyme methods. PP. 434-513 in John M. Lowenstein (ed.), Methods in enzymology, vol. 13. Acad. Press, New York Wo tcott, THomas G. 1973. Physiological ecology and intertidal zonation in limpets (Ac- maea): a critical look at “limiting factors.” Biol. Bull. 145 (2): 389 - 422 Journ. Mar. Biol. Assoc. U. K. 56 (1): 95-109 Vol. 23; No. 3 THE VELIGER Page 275 Behavior of the Gastropod Amphissa columbiana (Prosobranchia : Columbellidae) BY BRETTON W. KENT" GASTROPODS HAVE EVOLVED a diverse array of behavioral mechanisms for escaping from predators. Leaping, flip- ping, accelerated locomotion and interposition of soft body parts are all important components of gastropod escape responses (BULLOCK, 1953; FEDER,1963; MarcoLin,1964a and b; Gonor, 1965, 1966; KoHN & WATERS, 1966; and ANSELL, 1969). Here I report on an unusual escape re- sponse by the snail Amphissa columbiana Dall, a common rocky intertidal species from the Pacific coast of North America. I have observed the escape responses of Amphissa columbiana at infrequent intervals between April 1974 and June 1976. Individuals were collected at Boiler Bay, Oregon and maintained in the laboratory in a recirculat- ing seawater system for periods of up to 5 weeks. Obser- vations were made both in the water tables of the seawater system and in large enameled trays. Two predatory sea stars, Pisaster ochraceus (Brandt) and Leptasterias hexac- tis (Stimpson) were used to elicit escape responses. I exam- ined 2 different situations. First, an actively crawling snail was confronted with a sea star. Second, a snail was held in place with forceps until a sea star attached several tube feet to the shell. Actively crawling snails exhibit a stereotyped response to contact with a sea star. The tentacles and siphon are immediately withdrawn, the snail turns and rapidly crawls away. Frequently the shell swings through an arc of about 120° during retreat. The mean crawling rate increases significantly (Mann-Whitney U test, p= 0.01) after con- tact from 2.8 to 5.8 mm/sec. In the second situation, where the sea star was allowed to attach to the snail, Amphissa columbiana exhibits a 1 Present address: Department of Zoology, University of Mary- land, College Park, MD 20742 more diverse repertoire. The basic response consists of two phases. Initially the shell is violently twisted and crawling rate increases rapidly. Usually these actions are sufficient to detach the tube feet and allow the snail to retreat rapidly. The second phase differs markedly from the first. The rapid body movements of the first phase become less vio- lent but do not cease completely. The most obvious feature of this phase is the use of the snail’s proboscis to detach the tube feet adhering to the shell. As each tube foot is touched by the proboscis tip it releases its hold on the shell and is withdrawn. When only a few tube feet remain at- tached the snail escapes by twisting the shell free and rap- idly retreating. Whether the radula rasps the tube feet during proboscis eversion is unclear. Rasping is not neces- sary to cause tube foot withdrawal, because this can occur when the tube feet are gently prodded (Marcotin,1964a). FIsHLYN & Puituips (1980) report a similar use of the everted proboscis by another columbellid, Alia carinata (Hinds), but it is unclear whether radular rasping was actually observed. However, elsewhere I have shown that the melongenids Busycon contrarium (Conrad) and B. spiratum (Lamarck) do use radular rasping in conspecific encounters and to deter predatory snails (Kent, in prep.). Amphissa columbiana has 4 possible escape responses; I) use twisting and running only, 2) use proboscis eversion only, 3) use twisting and running followed by proboscis eversion, and 4) use proboscis eversion fol- lowed by twisting and running. The first 3 responses are commonly observed, with individual A. columbiana rather stereotyped in which response they used. The fourth pos- sible response was never observed. The reasons why this response is not used are unclear, but it may be related to the heightened aggressiveness needed to attack a predator with the proboscis. Page 276 THE VELIGER Vol. 23; No. 3 Literature Cited ANsELL, ALAN Davip 1969. Defensive adaptations to predation in the Mollusca. Mar. Biol. Assoc. India, Proc. Symp. Mollusca 2: 487 - 512 Buttock, THEoporE Homes 1953. Predator recognition and escape responses of some intertidal gastropods in the presence of starfish. Behaviour 5: 130-140 Feper, Howarp M. 1963. | Gastropod defensive responses and their effectiveness in reducing predation by starfishes. Ecology 44: 505-512 FisHityNn, Desay A. & Davin W. Puitiips 1980. | Chemical camouflaging and behavioral defenses against a preda- tory seastar by three species of gastropods from the surfgrass Phyllo- spadix community. Biol. Bull. 158: 34 - 48 Gonor, JEFFERSON JOHN 1965. Predator-prey reactions between two marine prosobranch gastro- pods. The Veliger 7 (4): 228-232 (1 April 1965) 1966. Escape responses of North Borneo strombid gastropods elicited by the predatory prosobranchs Aulica vespertilio and Conus marmoreus. The Veliger 8 (4): 226-230 (1 April 1966) Koun, ALAN JAcoss & VIRGINIA WATERS 1966. Escape responses of three herbivorous gastropods to the predato- ry gastropod Conus textile. Anim. Behav. 14: 340 - 345 Marco.in, ABE S. 1964a. The mantle response of Diodora aspera. Anim. Behav. 12: 187 - 194 1964b. A running response of Acmaea to seastars. Ecology 45: 191 - 193 Vol. 23; No. 3 THE VELIGER Page 277 A Niche Analysis of Coexisting Thavs lapillus and Urosalpinx cinereus Populations BY DAVID A. JILLSON Department of Zoology, University of Vermont, Burlington, VT 05405 INTRODUCTION THE MuRIcD GAsTRoPops Thais lapillus (Linnaeus, 1758) and Urosalpinx cinerea (Say, 1822) inhabit rocky inter- tidal shores of the northeastern United States. An exten- sive literature on the food habits of these species docu- ments their principal prey as oysters, clams, mussels and barnacles (e. g., CARRIKER, 1955; CONNELL, 1961a,1961b; Woop, 1968; MENGE, 1978a, 1978b). Although these snails feed upon similar prey in rocky intertidal habitats, there are no reports of competitive interactions between 'Thais and Urosalpinx populations. This is at least partly because their geographical distributions do not overlap widely. Urosalpinx is a native of North America and ranges from Nova Scotia to northeast Florida (AxBsBoTrT, 1974), although populations have been introduced to the British Isles and to the west coast of the United States (Woop, 1968). Thais (Nucella) lapillus is found on west- em and eastern shores of the North Atlantic Ocean, where it is reported from southern Labrador to New York in North America and from Norway to Portugal in Europe (AszorT, op. cit.). In North America, their local habitat requirements differ. In the northern extent of its range, Urosalpinx is found in isolated populations in sheltered waters (CARRIKER, 1955). North of Cape Cod, Massa- chusetts, ‘Thais is reported from rocky habitats varying in wave exposure from wave swept headlands to sheltered coves (MENGE, 1978a). The present study provides information on the distribu- tion, abundance and food habits of coexisting Thais and Urosalpinx populations. Aspects of the feeding niche of these animals are contrasted to gain insight into patterns of resource utilization by both species. These patterns indicate that Thazs and Urosalpinx may compete for prey in certain habitats. MATERIAL anp METHODS The study area was located in the town of Narragansett, on the western shore of Rhode Island Sound, approxi- mately 5km N of Point Judith, Rhode Island (41°25’N; 71°27’W). Three distinct rocky intertidal habitats were present: rock ledge directly exposed to wave action, semi- protected boulders sheltered from direct wave action by offshore rocks and shoals, and a large enclosed tide pool, completely sheltered from wave exposure. The area in- habited by ‘Thais and Urosalpinx in the tidal pool con- sisted of an intertidal band extending around the 50m circumference of the pool. Equal area sampling in the more exposed habitats allowed direct comparison of snail density among habitats. All specimens of Urosalpinx and Thais inhabiting each of the 3 habitats were counted by sequentially visiting the study area during day time low tide periods from June to August 1975. Snails located on barnacles or mussels were examined for the presence of the proboscis inserted between barnacle opercula, or pres- ence of a drill hole on barnacles or mussels. Snail shell length, mussel shell length and diameter of the basal portion of barnacle tests were measured. Quadrat sampling was conducted in each habitat to estimate the distribution and abundance of prey species. A 0.25 m7? quadrat was located along the intertidal zone of each area by placing the corner of the quadrat on co- ordinates selected from a random number table. Fifty quadrats were censused in the protected tide pool, 30 quadrats in the semiprotected habitat and 20 quadrats in the exposed habitat. Due to increased prey abundances at the more exposed habitat, fewer quadrats were sampled there. Page 278 THE VELIGER Vol. 23; No. 3 RESULTS Abundance and Distribution of Predators and Prey A total of 534 specimens of Thais and 339 specimens of Urosalpinx was censused over the 8 week period. Both snail species were in similar abundance in protected and semiprotected habitats, but no Urosalpinx were found in the exposed habitat, although Thais were very abun- dant there (Table 1). Urosalpinx specimens were com- Table 1 Mean size + std error (cm) and density for Thais lapillus and Urosalpinx cinerea in three habitats. the absence of these snails from wave swept locations. Thais shell length was significantly smaller (p< 0.05) in the exposed area than in the tide pool or semiprotected habitats. Urosalpinx shells were significantly larger (p< 0.05) than Thazs shells in protected and semiprotected habitats. Except for one Urosalpinx specimen feeding on the snail Littorina littorea, both gastropod predators con- sumed only mussels, Mytzlus edulis and acorn barnacles, Balanus balanoides. Both prey species increased in popu- lation density dramatically with increasing wave exposure (Table 2). Using the the variance-to-mean ratio of indi- viduals per quadrat as a measure of spatial dispersion (PreLou, 1969; ELtioTT, 1971), barnacles and mussels had strongly clumped distributions (Table 2), with prey Species Habitat Shell Length Number per m? Table 2 Thais protected 1.93 + .03 29) semiprotected 1.94 + .02 3.4 SHVOIEL LOY) 25 Oe ae Distribution and abundance of Balanus balanoides and Urosalpinx protected 2.17 + .02 3.1 Mytilus edulis in three habitats. semiprotected 2.25 + .03 3.6 exposed _ 0.0 Index of Number Species Habitat Dispersion! per 0.25 m2 Balanus protected 23.1 20.4 + 3.1 semiprotected 24.7 40.5 = 5.8 Pode sak: exposed 71.0 60.1 =E 14.6 monly found individually on open rock faces, whereas B ia Thai : d f : tj Mytilus protected 15.2 2.1 = 0:9 ais specimens occurred more often in aggregations pemiprotcced 151 149+97 numbering 10 - 30 individuals in crevices and other shel- exposed 102.2 75.2 + 19.6 tered locations. The tendency for Urosalpinx to occupy relatively unprotected microhabitats may partly explain \(variance/mean)(N—1) Table 3 Mean prey size + std error (cm) available and eaten. Prey Size Eaten Species Habitat Prey Size Available Thais N Urosalpinx N Balanus balanoides protected 45+ .01 0.46 + .04 29 0.44 + .04 17 semiprotected 57+ O01 0.33 + .032 14 0.45 + .042 23 exposed 60 + .02 0.29 + .022 26 = 0 Mytilus edulis protected 2.07 + .09 2.28 + .32 9 2.05 = .17 32 semiprotected 2.28 + .09 1.84 + .23 11 2.66 + .15 42 exposed | 0.87 + .03 1.36 + .112 47 = 0 2H: x drilled = x available rejected at p< 0.05. Vol. 23; No. 3 THE VELIGER Page 279 in the exposed habitat showing the greatest degree of aggregation. Chi-square contingency tests for association between mussels and barnacles (PiELou, op. cit.) indi- cated that the 2 prey species were distributed independ- ently of one another in each habitat. Specimens of Balanus increased in size with increasing wave exposure, whereas mussels were moderately large in the protected and semi- protected habitats, and were significantly smaller (p< 0.001) in the exposed environment (Table 3). Prey Sizes Eaten A total of 250 snails were observed feeding, 114 Uro- salpinx and 136 Thais. The mean size of prey specimens eaten by each snail species in each habitat was contrasted with the mean size of prey available in the same habitat. Single classification analysis of variance showed that bar- nacles and mussels consumed by either predator in the tide pool were not significantly different from the mean sizes available (Table 3). In the semiprotected habitat, Thats and Urosalpinx took smaller barnacles than the mean size available, but both predators preyed upon av- erage-sized mussels there. In the exposed habitat, Thais ate smaller than average barnacles, and larger than aver- age mussels. YOSHIYAMA & ROUGHGARDEN (1977) derived a com- petition function, a, which measures the amount of over- lap between 2 species having bivariate gaussian resource utilization functions. a(D,, D,) = exp (-4 fe 1 DE 20, In the present case, D, is the difference between the mean size of mussels eaten and available, o,” is the variance in size of mussels, and D, and o,” are the differences between the size of barnacles eaten and available, and variance in size of barnacles, respectively. Urosalpinx exploited the bivariate resource quite fully in protected and semipro- tected habitats (Table 4). 'Thazs had a declining overlap with available food sizes as the habitat became progres- sively more exposed, indicating more pronounced prey size selection in exposed habitats. YOSHIYAMA & ROUGHGARDEN’s (1977) measure was also used to calculate the niche overlap for prey size between Thais and Urosalpinx. D, was the difference between mean size of mussels eaten by Thais and Urosal- pinx, D, was the difference in barnacle size eaten by the 2 predators, and o,’ and a,” were as above. The niche over- lap was highest (0.98) in the tide pool, but dropped to 0.76 in the semiprotected habitat. The overlap between predatory snails was zero in the exposed habitat because of the absence of Urosalpinx there. Table 4 Thais lapillus and Urosalpinx cinerea niche breadth values. Niche Breadth Bivariate Species Habitat Prey Size? _— Prey Species‘ Thais protected 99 91 semiprotected 31 87 exposed .08 1.00 Urosalpinx protected 1.00 .92 semiprotected .89 1.00 exposed = — 3Overlap between prey size eaten and available. 4Overlap between prey species eaten and available. Prey Species Eaten The degree of preference for each type of prey was in- vestigated by calculating Perraitis’ (1979) measure of niche breadth: B= (q:/p:)”" © (1-q:/1-p.)"™" where p, is the frequency of barnacles in a predator’s diet and q, is the frequency of barnacles available in the habitat. The value of B may range from o to 1, with small- er values representing ecological specialists using resour- ces in proportions dissimilar to their availability, and larger B values representing ecological generalists using resources in the same proportion they occur in the envi- ronment. Prey availability was estimated by assuming that the frequency of encounter of a prey species was proportional to the relative cover of that prey in the habitat. The relative cover of a species was estimated by multiplying the area occupied by an average-sized indi- vidual in a given habitat by the density of that species. The niche breadth values showed Thais and Urosalpinx to be generalist feeders in all habitats, achieving values between 0.87 and 1.0 (Table 4). The amount of niche overlap between 2 species com- peting for the same species of prey was measured as the probability that a particular species’ utilization curve could have been drawn from that of another species (PET- RAITIS, 1979). The specific overlap between Thais and Urosalpinx is: Page 280 THE VELIGER Vol. 23; No. 3 O12 = (P2/Pr)”' © (1—p2)/(1-ps)™™" where p, and p, are the utilization frequencies of barna- cles by ‘Thais and by Urosalpinx, respectively. The mean overlap (0,. + 0.,/2) in the protected, semiprotected and exposed habitats was 0.70, 0.91 and 0.0, respectively. The comparatively low overlap between predators in the tide pool was caused by Thazs eating somewhat more bar- nacles and Urosalpinx eating fewer barnacles than expec- ted on the basis of prey availability. DISCUSSION Species which utilize common resources in the same community are thought to ameliorate the effects of compe- tition via resource partitioning; that is, they subdivide resources on the basis of consumer morphology or behavior (SCHOENER, 1974). In many communities, similarity of species along one dimension implies dis- similarity along another (e.g., MacArTHurR, 1958; SCHOENER, 1970; Copy, 1974). Clearly, Urosalpinx and Thais eat similar types and sizes of prey, and may show evidence of competition for prey. Several individuals of each species were maintained on a diet of mussels in a 36 L capacity aquarium for several months. Neither species gave any indication of aggressive interactions, leading one to expect that interference com- petition (GILL, 1974; RoTHSTEIN, 1978) is not impor- tant. During periods of low food availability, these snails may compete by a differential ability to locate or con- sume prey. Competition was most likely in the protected tide pool where the abundance of mussels and barnacles was the lowest. Thais and Urosalpinx were not selective about which prey size was eaten in that habitat, as de- monstrated by the nearly complete overlap between prey size eaten and available. Similarity along the prey size dimension was complemented by dissimilarity along the prey species dimension. Urosalpinx’s diet consisted of 35% barnacles and 65% mussels, whereas Thais ate 76% barnacles in a habitat where the relative availability of barnacles was 55%. The substantially greater prey population densities in the semiprotected habitat reduced the likelihood of com- petition by providing the predators with a large spectrum from which to select. Thais and Urosalpinx ate small- er barnacles than average, failing to take advantage of the substantially larger barnacles there. Woop (1968) reported that Urosalpinx could penetrate the opercular plates of a barnacle and ingest.the contents in 20 minutes, whereas if the snail were to drill the barnacle test, several hours would be required. In the present study, Thais and Urosalpinx fed upon barnacles by drilling and by piercing the operculum, but data on the relative frequency of each method were not recorded. If drilling were a com- mon mode of feeding upon barnacles, drilling smaller barnacles may require less time and shorter periods of exposure to dislodging wave action, favoring predation on smaller than average barnacles in wave swept habitats. Interspecific competition was zero in the exposed habi- tat because of the lack of Urosalpinx there. Where free of its competitor, ‘Thais demonstrated strong prey size selection, but no prey species preference. These data im- plicate prey size as the more important niche dimension for Thais. Experimental studies involving manipulation of Thais and Urosalpinx densities in various habitats are needed to document the relative importance of compe- tition on prey choice by these predators. ~ CONCLUSION I conclude that competition between Thais and Uro- salpinx is most likely along sheltered rocky shores where these predators may reduce the intensity of competition for prey of a given size by feeding preferentially on differ- ent prey species. The intensity of competition may be transitory on a seasonal and yearly basis in response to fluctuations in the abundance of predators and prey caused by physical or biological disturbances. ACKNOWLEDGMENTS I thank E. H. Jillson for assistance in the field; R. E Costantino, J. M. Herbers, R. B. Whitlatch and an anon- ymous referee for comments on the manuscript. Literature Cited AxsBotT, ROBERT TUCKER 1974. American seashells. and ed.; 663 pp.; 4000+ figs.; plts. 1 - 24 (in color). Van Nostrand Reinhold Co., New York CarrikeER, MELBOURNE ROMAINE 1955- Critical review of biology and control of oyster drills, Urosal- pinx and Eupleura. U. S. Fish Wildl. Serv. Spec. Sci. Reprt. 148: 1-151 Copy, Martin L. 1974. Competition and the structure of bird communities. ton Univ. Press, Princeton, N. J.; 318 pp. ConngELL, Josern H. 1961a. Effects of competition, predation by Thais lapillus and other factors on natural populations of the barnacle Balanus balanoides. Ecol. Monogr. 31: 61 - 104 1961b. The influence of interspecific competition and other factors on the distribution of the barnacle Chthamalus stellatus. Ecology 42: 710 - 723 Prince- Vol. 23; No. 3 THE VELIGER Page 281 ExuiotT, J. M. 1971. Some methods for the statistical analysis of samples of benthic invertebrates. Scientif. Publ. 25. Freshwater Biol. Assoc. Westmor- land, Britain. 148 pp. Gitt, Douctas E. 1974. Intrinsic rate of increase, saturation density, and competitive ability. II. The evolution of competitive ability. Amer. Natur. 108: 103-116 MacArtHuur, Rosert H. 1958. Population ecology of some warblers of northeastern coniferous forests. Ecology 39: 599- 619 Mencgz, Bruce A. 1978a. Predation intensity in a rocky intertidal community. Relation between predator foraging activity and environmental harshness. Oecologia 34: 1-16 1978b. Predation intensity in a rocky intertidal community. Effect of an algal canopy, wave action and desiccation on predator feeding rates. Oecologia 34: 17-35 PETRAITIS, PETER S. 1979. Likelihood measures of niche breadth and overlap. Ecology 60: 703-710 PreLou, Evetyn C. 1969. An introduction to mathematical ecology. Wiley, New York, 286 pp. RoTHSTEIN, STEPHEN I. 1979- Gene frequencies and selection for inhibitory traits, with special emphasis on the adaptiveness of territoriality. Amer. Natur. 113: 317 - 331 ScHOENER, THomaAsS W. 1970. Nonsynchronous spatial overlap of lizards in patchy habitats. Ecology 51: 408 - 418 1974. Resource partitioning in ecological communities. Science 185: 27 -39 Woop, LANGLEY 1968. Physiological and ecological aspects of prey selection by the marine gastropod Urosalpinx cinerea (Prosobranchia : Muricidae). Malacologia 6 (3): 267 - 320 (30 June 1968) YosuHrtvAMA, RONALD M. & JONATHAN ROUGHGARDEN 1977- Species packing in two dimensions. Amer. Natur. 111: 107-121 Page 282 THE VELIGER Vol. 23; No. 3 NOTES & NEWS CORRECTION At the Malacological Congress in Perpignan in Septem- ber 1980, Dr. Ph. Bouchet kindly called my attention to the fact that Piseinotecus evelinae (see The Veliger, vol. 23, Pp. 21 to 24) was most probably synonymous with Flabellina gabinierei Vicente, 1975 [Trav. scient. du Parc National de Port-Cros, vol. 1, pp. 67 to 74]. This is indeed the case. Unfortunately, my material does not include any specimens with an adult anterior genital complex. If, based on the genital apparatus, no changes become ap- parent, the species must, on the basis of a radula with a single row and on the acleioproct anus, indeed be called Piseinotecus gabinierei (Vicente, 1975). Luise Schmekel Subscription Rates and Membership Dues We are pleased to announce that at its annual business meeting the Executive Board of our Society has decided to maintain the subscription rate for volume 24 of The Veliger at US$ 37.50 plus $1.50 for mailing charges to domestic addresses; however, it is necessary to increase the charge for mailing to all foreign addresses to US$5.- because the postage rates are scheduled to be doubled in 1981. Also, because many of our subscribers have en- countered difficulties in transmitting the necessary funds in Swiss Francs, we have closed our Swiss Postcheck (Gi- ro) account, effective December 31, 1980. Thus, all payments henceforth must be in U. S. funds. At the same meeting it was also decided to keep the membership dues at the same level as for volume 23, with the mailing charges for domestic addresses at $1.50 and those for ALL foreign addresses increased to US$5.-. Because of some irregularities that have occurred in the recent past, we must stress that membership renewals with the correct amount must reach us on or before April 15 each year; if payment is received after that date, a re-instatement fee of $1.- is required. From the foregoing it should be evident that we make a strong effort to combat inflation. But we must ask for cooperation by all our members and subscribers. POSITION tn MALACOLOGY NaTIoNAL Museum or NaturAL History SMITHSONIAN INSTITUTION The Department of Invertebrate Zoology anticipates a tenure-track opening on the scientific staff for a fresh- water or terrestrial malacologist to function as an associ- ate curator-researcher at the GS 11 level ($20611) beginning February 1, 1981. We are particularly inter- ested in all candidates with a Ph. D. and strong back- grounds in current biology, molluscan anatomy and evo- lutionary biology. Send curriculum vitae, copies of pub- lications, and statement of longterm research goals to Dr. Richard S. Houbrick, Search Committee, Depart- ment of Invertebrate Zoology, National Museum of Natu- ral History, Smithsonian Institutntion, Washington, D. C. 20560. The Smithsonian Institution is an equal opportunity employer. CALIFORNIA MALACOZOOLOGICAL Society, Inc. is a non-profit educational corporation (Articles of In- corporation No. 463389 were filed January 6, 1964 in the office of the Secretary of State). The Society publishes a scientific quarterly, the VELIGER. Donations to the Society are used to pay a part of the production costs and thus to keep the subscription rate at a minimum. 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Vol. 23; No. 3 Publication Date of THE VELIGER THE PUBLICATION DATE of The Veliger is the date printed on the index page; this applies even if the date falls on a legal holiday or on a Saturday or Sunday, days when the U.S. Postal Service does not expedite second class mail matter. That the printed date is the actual date of pub- lication under the rules of the International Commission on Zoological Nomenclature is based on the following facts: 1) The journal is delivered to the Post Office on the first day of each quarter, ready for dispatch; 2) at least three copies are mailed either as first class items or by air mail; 3) about 20 copies are delivered in person to the mail boxes or to the offices of members in the Berkeley area; 4) two copies are delivered to the re- ceiving department of the General Library of the Univer- sity of California in Berkeley. Thus our publication is available in the meaning of the Code of the ICZN. 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Box 730, Oakhurst, CA(alifornia) 93644. The same applies to the supple- ments still in print with certain exceptions (see below). Prices of available items may be obtained by applying to Mr. West at the address given above. Volumes 1 through 8 and 10 through 12 are out of print. Supplements not available from Mr. West are as fol- lows: Supplements to vol. 7 (Glossary) and 15 (Ovulidae) are sold by “The Shell Cabinet, PO. Box 29, Falls Church, VI(rginia) 22046; supplement to vol. 18 (Chitons) is available from “The Secretary,’ Hopkins Marine Station, Pacific Grove, CA(lifornia) 93950. Supplements Supplement to Volume 3: [Part 1: Opisthobranch Mollusks of California by Prof. Ernst Marcus; Part 2: The Anaspidea of California by Prof. R. Beeman, and The Thecosomata and Gymnosomata of the Cali- fornia Current by Prof. John A. McGowan] Supplement to Volume 6: out of print. Supplement to Volume 7: available again; see announce- ment elsewhere in this issue. Supplement to Volume 11: [The Biology of Acmaea by Prof. D. P. Aszorr et al., ed.} Supplement to Volume 14: [The Northwest American Tellinidae by Dr. E. V. Coan] Supplement to Volume 16: [The Panamic-Galapagan Epitoniidae by Mrs. Helen DuShane] [Growth Rates, Depth Preference and Ecological Succes- sion of Some Sessile Marine Invertebrates in Monterey Harbor by Dr. E. C. Haderlie] Supplement to Volume 17: Our stock of this supplement is exhausted. Copies may be obtained by applying to Dr. E. C. Haderlie, U. S. Naval Post-Graduate School, Mon- terey, CA (lifornia) 93940. WE ARE PLEASED to announce that an agreement has been entered into by the California Malacozoological Society, Inc. with Mr. Steven J. Long for the production and sale of microfiche reproductions of all out-of-print editions of the publications of the Society. The microfiches are available as negative films (printed matter ap- pearing white on black background), 105mm X 148mm and can be supplied immediately. 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Some issues are present in only one or two copies, while others may be present in 10 or more copies. As we are anxious to make room, we will offer these numbers at an exceptionally low price. This list may be obtained by sending a self-addressed, stamped envelope to the Veliger, 1584 Milvia Street, Berkeley, CA(lifornia) 94709. Foreign correspondents should en- close one international postal reply coupon. Requests for the list, for which return postage is not provided, will be ignored. Membership open to individuals only - no institutional or society memberships. Please send for membership ap- plication forms to the Manager or the Editor. Membership renewals are due on or before April 15 each year. If renewal payments are made after April 15 but before March 15 of the following year, there will be a re-instatement fee of $1.-. Members whose dues pay- ments (including the re-instatement fee) have not been received by the latter date, will be dropped from the rolls of the Society. They may rejoin by paying a new initiation fee. The volume(s) published during the time a member was in arrears may be purchased, if still available, at the regular full volume price plus applicable handling charges. Backnumbers of the current volume will be mailed to new subscribers, as well as to those who renew late, on the first postal working day of the month following receipt of the remittance. The same policy applies to new members. Tue VELIGER is not available on exchange from the Cali- fornia Malacozoological Society, Inc. Requests for re- prints should be addressed directly to the authors con- cerned. We do not maintain stocks of reprints and also Vol. 23; No. 3 THE VELIGER Page 285 cannot undertake to forward requests for reprints to the author(s) concerned. 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It is the stated aim of the Society to disseminate new infor- mation in the field of malacology and conchology as widely as possible at the lowest cost possible. To Prospective Authors Postal Service seems to have deteriorated in many other countries as well as in the United States of America. Since we will absolutely not publish a paper unless the galley proofs have been corrected and returned by the authors, the slow surface mail service (a minimum of 6 weeks from European countries, 8 to 12 weeks from India and Africa) may make a delay in publication inevitable. We strongly urge that authors who have submitted papers to the Veli- ger make all necessary arrangements for expeditious read- ing of the proofs when received (we mail all proofs by air mail) and their prompt return by air mail also. 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We regret that we must insist on these conditions; however, the exorbitant in- creases in postal charges leave us no other choice. Some recent experiences induce us to emphasize that manuscripts must be in final form when they are sub- mitted to us. Corrections in galley proofs, other than errors of editor or typographer, must and will be charged to the author. Such changes may be apparently very simple, yet may require extensive resetting of many lines or even entire paragraphs. Also we wish to stress that the require- ment that all matter be double spaced, in easily legible form (not using exhausted typewriter ribbons!) applies to all portions of the manuscript — including figure explana- tions and the “Literature Cited” section. It may seem inappropriate to mention here, but again recent experience indicates the advisability of doing so: when writing to us, make absolutely certain that the cor- rect amount of postage is affixed and that a correct return address is given. The postal service will not forward mail pieces with insufficient postage and, if no return address is given, the piece will go to the “dead letter’ office, in other words, it is destroyed. Page 286 THE VELIGER Vol. 23; No. 3 General Notice Because of an increasing number of strange occurrences your editor deems it important to clarify our policy with respect to correspondence. 1. We never reply to letters that do not reach us. Since the U. S. postal service no longer forwards mail pieces that are not franked properly, correspondents waiting for our reply might consider the possibility that their letter falls into this category. 2. We do not acknowledge the receipt of a manuscript unless a self-addressed, stamped envelope is enclosed. 3. We do not reply to complaints regarding the non-ar- rival of our journal, if these complaints are made at a time when the claimed issue could not possibly have reached its destination. In view of the poor postal ser- vice throughout the world, it is unrealistic to expect, for example, the July issue in a shorter period than from 2 to 3 weeks in the United States, in less than 4 to 6 weeks in Europe, and in less than 2 to 4 months in other areas of the world; South American countries, in par- ticular, have to expect maximum delays. It should be obvious that we are not responsible for the postal ser- vice. 4. We particularly object to complaints about non-receipt of issues which are scheduled to be published as much as 6 months after the complaint was sent! A little con- sideration of what is possible and what is absurd should help to obviate such untimely complaints. 5. We are receiving an increasing number of requests for our list of individual back numbers that are still avail- able, as well as for our suggestions to prospective au- thors. These requests state that a self-addressed stamped envelope is enclosed — but somehow the writer must have forgotten to do so. These requests also are not answered by us. We consider that our policy is justified for several reasons: the requirement for self-addressed, stamped en- velopes has been stated in every issue of the Veliger for the past several years. Since we are a non-profit organiza- tion, we prefer to reserve our energy and our resources for productive purposes. However, we do conscientiously, and usually exhaustively, reply to all correspondence that we consider legitimate. Moreover, such correspondence is usually answered the same day as received, with the reply posted the next morning at the main post office in Berke- ley. What happens afterwards is beyond our control. Policy Regarding Reprints It seems necessary to bring the following points to the notice of prospective authors: All manuscripts submitted for inclusion in The Veliger are subject to review by at least two scientists; acceptance is entirely on the basis of merit of the manuscript. Al- though many scientific journals assess page charges, the Executive Board of our Society, for the time being at least, wishes to avoid this possible financial handicap to the younger contributors. However, because of the high cost of halftone plates, a suitable contribution to reimburse the Society must be sought. Similarly, while it was hoped at the “birth” of The Veliger that a modest number of reprints could be sup- plied to authors free of charge, this has not as yet become possible. We supply reprints at cost. Unfortunately, in recent years it has become “‘fashionable” for some authors and some institutions to ignore paying for reprints ordered and supplied in good faith or to delay payment for a year or more. This causes financial losses to the Society since our debts are paid promptly. Since the Society is in fact not making any profit, it is necessary to introduce a policy which, it is hoped, will protect us against negli- gence or possible dishonesty. In the case of manuscripts from sources outside of the United States, if a manuscript is accepted, we will inform the author of the estimated cost of reprints and require a deposit in U.S. funds to cover these costs. If such a deposit is not made, we will not supply any reprints. In the case of non-payment by domes- tic authors or institutions, we will pursue legal recourses. Vol. 23; No. 3 BOOKS, PERIODICALS, PAMPHLETS — Pacific Coast Nudibranchs A Guide to the Opisthobranchs of the Northeastern Pacific by Davi W. Beurens. Sea Challengers, 1851 Don Ave., Los Osos, CA (lifornia) 93402. 112 pp.; 162 color plates; $14.95 (soft cover; ISBN 0-930118-05-7) ; $24.95 (hard cover; ISBN 0-930118-04-9) ; November 1980. The main title of this handsome book is somewhat mis- leading, since, as indicated by the subtitle, other opistho- branchs are included. The book is well organized. The introduction has a general account of the subclass, fol- lowed by a sub-chapter on anatomy; the radula is dis- cussed briefly and 4 good scanning electron micrographs illustrate some of the points; next are discussed the rhino- phores, the cerata and opisthobranch reproduction. A glossary is provided and 6 pages of line drawings help in understanding the special terminology. A key to the orders of the opisthobranchs precedes the description of the orders and suborders. The main body of the book is de- voted to a discussion of species described mainly from California with color photographic illustrations of all species. For each species are given: a “common” name [most of these newly invented]; the currently as valid accepted scientific name with an etymological interpretation of that name; synonyms are listed where appropriate; this is followed by “Identification,” a description of the spe- cies; under “Natural History” are given some ecological notes and, when known, food habits; size ranges and geo- graphical ranges conclude the entries. The superb figures are labelled with the “common” name and photocredit is given to the various nudibranch enthusiasts, most of whom would put professional photo- graphers to shame. Where photocredits are not indicated, the author is responsible for the original photograph. One feature is most unusual: about 25 undescribed spe- cies are illustrated with some data on size and occurrence. What makes this part unusual is the fact that various individuals are actively engaged in studying these newly discovered forms with a view of describing them. The hope is, of course, that other nudibranch enthusiasts will communicate their observations if and when they encounter specimens of these forms. Our personal objection to the manufacturing of so- called “common” names has been expressed in these pages THE VELIGER Page 287 before. It seems to us that a real student of these admitted- ly highly attractive life forms could as easily remember the scientific name (for example,Onchidoris muricata) as its constructed “common” name (in the example “muricate dorid”). However, this does not actually de- tract from the overall value of this very valuable aid to the present as well as the numerous future students of a somewhat difficult group of organisms. In other words, we warmly recommend this book. R. Stohler Catalogo dei molluschi conchiferi viventi nel Mediterraneo. by Piero Piant. Boll. Malocologico, Unione Malacologica Italiana, Milan, vol. 16, no. 5/6, pp. 113 - 224; May-June, 1980. An up-to-date list of the Mediterranean molluscan fauna has long been needed, and one is now supplied by a councillor of the Italian Malacological Union. It leans heavily on the work of recent European authors such as Nordsieck, Van der Spoel, Golikov & Starobogatov, and Thompson. A page of explanation of format is in English. Synonymy for some of the species is given in footnotes, and species of doubtful status are indicated, as are type species of the generic and subgeneric units. It is indexed by genera. Collectors should find it a useful addition to their library. A. Myra Keen An outline of classification of living shelled marine mollusks. by Kay CunNINGHAM VAUGHT. Privately printed (mul- tilithed ) ; 93 pp.; 1980. This is a well-indexed synoptic list of generic and sub- generic names, principally of gastropods and bivalves, though scaphopods and chitons are also mentioned. It is arranged systematically and is offered as a tool — es- pecially for collectors who have limited library facili- ties — for use in arranging material. The compiler has sifted through some 34 major publications; her biblio- graphy lists 19 titles published since 1970. To reconcile the classifications of the various authors is a major under- taking, which she has on the whole done well. The work is admittedly incomplete, and users may detect misspel- Page 288 THE VELIGER Vol. 23; No. 3 lings and other errors. However, these can be weeded out in subsequent editions if there is cooperation from users who discover the utility of the work and encourage the compiler by supplying new data. Her address is: Mrs. Kay C. Vaught, Apdo. 1351, Cuernavaca, Morelos, Mexico. Even while writing this review, I found in the list the answer to a question that was beyond the scope of the books I had at hand. A. Myra Keen Uber die Pectiniden-Gattung Parvamussium im Jura by Hetmut Ho.per. Stuttgarter Beitrage zur Natur- kunde, Ser. B, Nr. 38: 37 pp.; 6 plts.; 12 text figs. 15 December 1978 Uber zwei alpine Ammoniten __ aus dem Oberen Muschelkalk SW-Deutschlands by Max Utricus. Stuttgarter Beitrage zur Naturkunde, Ser. B, Nr. 39; 13 pp.; 1 plt.; 2 text figs. 1 December 1978 Zur Stratigraphie des Ober-Bajocium (Braunjura 6/e-Grenzschichten) am Plettenberg bei Balingen, Wiirttemberg by Gerp Dret1, Rosert Fiaic & Eucen GLick. Stutt- garter Beitrage zur Naturkunde, Ser. B, Nr. 40: 16 pp.; 5 text figs. 1 November 1978 Zur Stratigraphie des Ober-Bajocium (Braunjura 6/e-Grenzschichten) der Zollernalb (Schwabische Alb, Baden-Wiurttemberg ) by Gerp Diet & Rotr Huccer. Stuttgarter Beitrage zur Naturkunde, Ser. B, Nr. 43: 14 pp.; 4 text figs. 15 March 1979 Uber den Jura am Grossen Hassberg (Unterfranken, N-Bayern) mit Bemerkungen zum Rat by Gert Bioos. Stuttgarter Beitrage zur Naturkunde, Ser. B, Nr. 44: 53 pp.; 3 plts.; 8 text figs. 1 May 1979 These five papers are concerned with ammonites. R. Stohler THE VELIGER is open to original papers pertaining to any problem concerned with mollusks. This is meant to make facilities available for publication of original articles from a wide field of endeavor. Papers dealing with anatomical, cytological, distributional, ecological, histological, morphological, phys- iological, taxonomic, etc., aspects of marine, freshwater or terrestrial mollusks from any region, will be considered. Even topics only indi- rectly concerned with mollusks may be acceptable. In the unlikely event that space considerations make limitations necessary, papers dealing with mollusks from the Pacific region will be given priority. However, in this case the term “Pacific region” is to be most liberally interpreted. It is the editorial policy to preserve the individualistic writing style of the author; therefore any editorial changes in a manuscript will be sub- mitted to the author for his approval, before going to press. Short articles containing descriptions of new species or lesser taxa will be given preferential treatment in the speed of publication provided that arrangements have been made by the author for depositing the holotype with a recognized public Museum. Museum numbers of the type specimens must be included in the manuscript. Type localities must be defined as accurately as possible, with geographical longitudes and latitudes added. Short original papers, not exceeding 500 words, will be published in the column “NOTES & NEWS”; in this column will also appear notices of meetings of the American Malacological Union, as well as news items which are deemed of interest to our subscribers in general. 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Manuscripts should be typed in final form on a high grade white paper, 812” by 11”, double spaced and accompanied by a carbon copy. A pamphlet with detailed suggestions for preparing manuscripts intended for publication in THE VELIGER is available to authors upon request. A self-addressed envelope, sufficiently large to accom- modate the pamphlet (which measures 51/2” by 81/2’’), with double first class postage, should be sent with the request to the Editor. EDITORIAL BOARD Dr. Donatp P. Assortt, Professor of Biology Hopkins Marine Station of Stanford University Dr. Warren O. Appicott, Research Geologist, U. S. Geological Survey, Menlo Park, California, and Consulting Associate Professor of Paleontology, Stan- ford University Dr. Jerry Dononue, Professor of Chemistry University of Pennsylvania, Philadelphia, and Research Associate in the Allan Hancock Foundation University of Southern California, Los Angeles Dr. J. Wyatr Duruam, Professor of Paleontology University of California, Berkeley, California Dr. Caper Hanp, Professor of Zoology and Director, Bodega Marine Laboratory University of California, Berkeley, California Dr. Jorn W. Hepcretu, Adjunct Professor Pacific Marine Station, University of the Pacific Dillon Beach, Marin County, California Dr. A. Myra KEEN, Professor of Paleontology and Curator of Malacology, Emeritus Stanford University, Stanford, California Dr. Vicror Loosanorr, Professor of Marine Biology Pacific Marine Station of the University of the Pacific EDITOR-IN-CHIEF Dr. Rupoir STOHLER, Research Zoologist, Emeritus University of California, Berkeley, California Dr. Joun McGowan, Associate Professor of Oceanography Scripps Institution of Oceanography, La Jolla University of California at San Diego Dr. Franx A. Prre.xa, Professor of Zoology University of California, Berkeley, California Dr. Rosert Rosertson, Pilsbry Chair of Malacology Department of Malacology Academy of Natural Sciences of Philadelphia Dr. Peter U. Roppa, Chairman and Curator, Department of Geology California Academy of Sciences, San Francisco Dr. JupirH Terry SmitH, Visiting Scholar Department of Geology, Stanford University Stanford, California Dr. Ratpu I. Smiru, Professor of Zoology University of California, Berkeley, California Dr. Cares R. STASEK, Bodega Bay Institute Bodega Bay, California Dr. T. E. THompson, Reader in Zoology University of Bristol, England ASSOCIATE EDITOR Mrs. JEAN M. Cate Rancho Santa Fe, California ISSN 0042-9988 THE ELIGER A Quarterly published by CALIFORNIA MALACOZOOLOGICAL SOCIETY, INC. Berkeley, California ~\ VOLUME 23 APRIL I, 1981 NUMBER 4 CoNTENTS Comparative Shell Ultrastructure of Lyonsiid Bivalves. (12 Plates) INOBER TAO BEREZANT gee) ap ede fey 80 era ua aah ide ree ei Saree We ve BO Growth, Mortality and Longevity of Cerithidea decollata Linnaeus (Gastropoda : Prosobranchia) from Bayhead Mangroves,‘Durban Bay, South Africa. (6 Text figures) WICTORNGCOCKCROFT, & AL HORBES ©. 44/2600 6 sie ee es BOO Effects of Temperature and Salinity on the Embryological Development of Murex pomum Gmelin, 1791. (2 Plates) BUNA AH VIO ORETEPMINNISANDERG) pion vel Wel cial le spines Ne viet) es 6) he, 1309 Redescription of a Rare North Atlantic Doridacean Nudibranch, Aegires sublaevis Odhner. (2 Text figures) Ub Big: TETECOING ISKONNE Ge ae 0 ce Shichi Ui ec Bats na NP ety PR RO Re een ee 4 Preliminary Studies on the Association Between Pleonosporium, squarrosum (Rho- dophyta) and Cryptochiton stelleri (Polyplacophora) . (1 Plate; 2 Text figures) KARVAUM CIDER MID mera wee wN ie Ntccsire Weak cu Nea MME i Te Temperature and Growth of Maturing Haliotis kamtschatkana Jonas. (4 Text figures ) Ace) RAUL es). Mi PAUI 20 8 e) = eee ebatirs) ec Mieiies ah ee’, ae SSE A New Species of Stenosemus Middendorff, 1847 (Mollusca : Polyplacophora) in the Abyssal Northeastern Pacific. (1 Plate; 5 Text figures) IAN TONION| pERREIRAG 2 ie ier fice ie. eh so iue ieee ln vet oe) ey MWe) ae) ee, ei en 325 [Continued on Inside Front Cover] EE Distributed free to Members of the California Malacozoological Society, Inc. Subscriptions, by Volume only, payable in advance to Calif. Malacozocl. Soc., Inc. Volume 24: $37.50 plus mailing charges $1.50 U.S. A; $5.- for all foreign addresses Single copies this issue $16.-. Postage extra. Send subscription orders to California Malacozoological Society, Inc. 1584 Milvia Street, Berkeley, CA 94709, U.S.A Address all other correspondence to Dr. R. Stouuer, Editor, Department of Zoology University of California, Berkeley, California 94720, U.S.A. Second Class Postage Paid at Berkeley, California Contents — Continued Four Previously Undescribed Indo-Pacific Terebrids (Mollusca : Gastropoda). (1 Plate) Twita BRATCHER . Distribution, Activity, and Food Habits of Juvenile Tegula funebralis and Littorina scutulata (Gastropoda : Prosobranchia) as they Relate to Resource Parti- tioning. (4 Text figures) JEFFREY T. JENSEN New Species of Fusinus (Gastropoda : Fasciolariidae) from the Tropical Eastern Pacific. (1 Plate; 8 Text figures) LEROY POORMAN (o's 2006 Wd el Ss ee oer Comments on Two Misunderstood Fusinids (Gastropoda : Fasciolariidae) from the Tropical Eastern Pacific. (1 Plate) LEROY POORMAN (6/56 bs) 2 ater 2 ei hate ey rent She oes oe The Littoral Polyplacophora of Shell Beach, San Luis Obispo County, California. Barry Forsom PutMAn (20d, 2/15 circa ok eee ered renee tar umes Neustonic Feeding in Early Larvae of Octopus dofleini (WULKER). (1 Plate) Jerrrey B: MARUIAVE %s050 a Gen) of), 2d 6) oe Re eee One eae Casmaria atlantica Clench (Mollusca : Gastropoda) : Thoughts on its Evolution. (2 Text figures) J. Gmpson-SmitH & W. GIBSON-SMITH . . « « « «© © « © © © 0 «© «@ The Status of Pholadomya candida G. B. Sowerby, I, 1823. (1 Text figure) J. Grsson-SmirH & W.Gipson-SMITH, . . . . + «© - « © © «© © o «@ Biting as a Defense in Gastropods of the Genus Busycon (Prosobranchia : Melon- genidae). (1 Plate) Paut J. WELDON , Chaetogaster limnaei (olvoaaee: Naididae) Tahabienen the Mantle “Gaui of the Asiatic Clam, Corbicula fluminea, in Barkley Lake, Kentucky. James B. Sicket «& Marx B. LyLes A Comparison of Fijian Forms of Conus coronatus and Conus aristophanes. (4 Text figures) C. P Lewis NOTES & NEWS Note on the Status and Distribation of Littorina aie thee & Brees. ieee DANIEL PRINCz Recent Changes in the Department of Invertebrate Zoology, California Acad- emy of Sciences. DaPune Fautin DuNN BOOKS, PERIODICAES & PAMPEIE ES) ) =) cuicalicmm- intimin naits in Tont= + 329 - 333 - 339 - 345 - 348 » 350 » 352 - 355 - 357 . 361 - 363 - 373 Note: The various taxa above species are indicated by the use of different type styles as shown by the following examples, and by increasing indentation. ORDER, Suborder, DIVISION, Subdivision, SECTION, SUPERFAMILY, Famity, Subfamily, Genus, (Subgenus) New Taxa Vol. 23; No. 4 THE VELIGER Page 289 Comparative Shell Ultrastructure of Lyonsiid Bivalves ' ROBERT S. PREZANT College of Marine Studies, University of Delaware, Lewes, Delaware 19958 (12 Plates) INTRODUCTION DISTINCT GENERIC CHARACTERISTICS and a small number of marine genera make the bivalve family Lyonsiidae an excellent group for the examination of ecological and evo- lutionary implications of functional morphology. The Lyonsiidae is composed of only three marine genera, each possessing a series of readily distinguishable characteristics (PREZANT, 1980a) related to three divergent habitats. Lyonsia, perhaps the most primitive genus of the family, are thin shelled, weakly endobyssate and live partially buried in fine sands or muds usually in intertidal or rela- tively shallow waters. Entodesma, the thickest shelled genus of the group, occurs nestled in intertidal or subtidal crevices (rocky shorelines, algal holdfasts, sponge or ascid- ian mats), secured by numerous, strong byssal threads. The third genus Mytilimeria, which is monotypic, has assumed a sessile life-style living embedded within compound tuni- cates. Mytilimeria, like Lyonsia, are very thin shelled and may also produce a few, weak byssi when removed from their hosts. YoncE (1952) envisaged a direct lineage of evolutionary descent for the Lyonsiidae which was based, to a large extent, upon trends in lyonsiid habits. This lineage entailed a direct progression from free-living Lyonsia to sedentary Entodesma to sessile Mytilimeria. Based upon much of the data gathered by YoNGE (1952), as well as by several other authors (MorcaAN & ALLEN, 1976; Narcui, 1968; PREZANT, 1979a,b, 1980a), PREZANT (1980b) has hypoth- esized a divergent lineage for this group; one branch lead- ing from an ancestral lyonsiid to Lyonsia and a separate branch leading to Entodesma and Mytilimeria. Supportive evidence for one of the proposed phylogenies may be * University of Delaware, College of Marine Studies Contribution No. 152 found in the ultrastructure of lyonsiid shells and perios- tracum. STANLEY (1970) and ANSELL (1967) related shell form of Lyonsia to burrowing habits, but no efforts have been made to relate various shell ultrastructures to the range of habits found within the family. In fact, the only examina- tions of pandoracean shell ultrastructure have been the short analyses by Boccitp (1930), OBERLING (1964) and TAyYLor et al. (1973) in their comprehensive works on bi- valve shell structure and mineralogy. OBERLING (op. cit.) listed the shell structure of the Lyonsiidae as being com- posed of an inner nacreous layer and an external grained structure. The “grained structure” was defined by Oberling as a “structure composed of irregular gran- ules.” Tay or et al. (1969) examined 16 species of Pan- doracea including species of Pandora, Periploma, La- ternula and Thracia, but did not examine any mem- bers of the Lyonsiidae. The shells of all pandoraceans that were examined by Taytor et al. (op. cit.) were aragonitic and, with the exception of Thracia, had a sim- ple outer prismatic layer and two distinct nacreous layers (lenticular and sheet) usually separated by a narrow band of myostracum. Shells of Thracia were two layered, both layers being homogeneous. Many species of Thracia are nestlers similar to several species of Entodesma. Similari- ties in shell ultrastructure may occur. Various shell structures possess specific mechanical char- acteristics that may protect or otherwise “serve” the mol- lusc and are adapted to particular life styles (TAYLOR & LayMAN, 1972). Many bivalves located in physically de- manding environments (high energy beaches, rocky inter- tidal) have developed shells with a large proportion of nacre (e.g., Pholadomyidae, Pteriacea) (Taytor et al., 1969; TayLor « LayMAN, 1972), nacre being a very strong shell component. High proportions of nacre may also be found within the shells of many thin shelled bivalves (Pin- nacea, Pandoracea) (TayLor & LayMAN, 1972). Page 290 The present work was undertaken to answer two pri- mary questions. One, are there any modifications of shell or periostracum ultrastructure among the various genera of Lyonsiidae which reflect environmental adaptations, and two, are there any phylogenetic clues that may be obtained by an examination of these structural differences? METHODS ann MATERIALS Shells were obtained from both live and museum collec- tions. Specimens collected live included: Lyonsta floridana Conrad, 1849 from Blind Pass, Sanibel Island, Florida; L. hyalina Conrad, 1831 from Nahant Bay, Massachusetts; Entodesma saxicola Baird, 1863 from Shaw Island, Friday Harbor, Washington; and L. californica Conrad, 1837 and Mytilimeria nuttalli Conrad, 1837 from along the coast of Santa Monica, California. Museum specimens (usually dried valves) included: L. gouldii Dall, 1915 (Museum of Comparative Zoology, Harvard University, Cambridge, Massachusetts), L. californica (Los Angeles County Mu- seum of Natural History, Los Angeles, California), L. pugetensis Dall, 1913, E. beana (Orbigny, 1842), E. fretalis (Dall, 1915), and E. patagonica (Orbigny, 1846) (United States National Museum, Washington, D.C.), E. cuneata (Gray, 1828), E. truncatissima Pilsbry, 1865 and E. pata- gonica (Academy of Natural Sciences of Philadelphia, Philadelphia, Pennsylvania) and L. californica and E. saxi- cola (California Academy of Sciences, San Francisco, Cali- fornia). Specimens of E. saxicola were also obtained from the preserved collection of the Pacific Biological Station, Nanaimo, British Columbia, and specimens of E. fretalis and E. chilensis (Philippi, 1845) were obtained from speci- mens collected in Corral Bay, Chile, for the Universidad de Austral de Chile. All specimens were dehydrated in a series of increasing concentrations of ethanol through absolute, gently frac- tured within a lintless cloth and either dried in a 60°C oven for 5-10 days or, in specimens with thick perio- stracum, critical point dried in a Denton DCP-1 critical point drier using liquid carbon dioxide as a transfer agent. When only calcareous shell ultrastructure was to be exam- ined, some specimens were treated in a 5% solution of sodium hypochlorite for 2-90 minutes (depending upon species and thickness of periostracum) prior to dehydra- tion. Selected specimens of the fractured valves were mounted on aluminum SEM stubs using silver paint. The paint was carefully allowed to flow along the base of the specimen to help decrease charging under the electron beam. Specimens were coated with a thin film of carbon and gold in a Denton Vacuum 515 Evaporator and exam- THE VELIGER Vol. 23; No. 4 ined in a Philips PSEM 501 scanning electron microscope at accelerating voltages of 15-30kV. The periostracum of Mytilimeria nuttalli usually peeled away when the clam was removed from its tunicate host. In order to study this thin, outer organic layer, the edge of living bivalves was exposed by trimming away the por- tion of the surrounding tunicate covering the siphonal edge of the bivalve while the bulk of the valves still remained within the ascidian test. The clam was then allowed to grow for several weeks in the laboratory on a diet of Thalassiosira pseudonana and Isochrysis galbana, after which time the newly grown periostracum was sampled and treated for scanning electron microscopy as previously described. Confirmatory observations of periostracal struc- tures were made in the rare cases when the periostracum remained intact after the bivalve was excised from its host. RESULTS The general morphology of the shells of the three marine genera of lyonsiid bivalves reflects well the diverse envi- ronments in which they are found. Lyonsia are free-living bivalves that produce weak byssal attachments for stabili- zation within fine sand sediments. These thin shelled lyonsiids are elongate, anteriorly rounded and posteriorly truncated, and can be found partially buried in the sub- stratum with only a small posterior portion of the shell exposed. For added stability, strength and camouflage, the exterior of the shell is covered with tightly adhering sand or other sediment. Entodesma produce several thick, strong byssi that help secure these thicker shelled bivalves in their typical habi- tats of rocky intertidal crevices, algal holdfasts, or nestled among tunicates or sponges. This genus also has a fairly elongated shell that typically is drawn out posteriorly. Shells of Entodesma are often distorted as a result of con- forming to tight external quarters. In an apparent trend towards increasing sedentarianism, the third genus, Mytilimeria, has assumed a totally sessile life-style and is found embedded within compound tuni- cates. Within the confines of the ascidian, this endosym- biont has evolved a thin, rounded shell. Juveniles (YoncE, 1952), and adults when removed from their host, can pro- duce a few, weak byssal threads. The roles of the thick shell and strong byssus, as found in Entodesma, have been incidentally assumed by the surrounding ascidian mass in Myytilimeria and the extraneous sand cover in Lyonsia. All three genera of Lyonsiidae have periostracum that overlaps the edge of their valves. This, at least in the free- living members, helps protect the mantle cavity by folding Vol. 23; No. 4 THE VELIGER Page 291 Table 1 A brief survey of comparative differences in thickness of various shell layers and periostracum of several species of marine Lyonsiidae (— = absent, + = thin layer, ++ = thick layer, +++ = very thick layer). Number in parenthesis following species name is maximum length (in mm) of species examined. Granular Species Periostracum homogeneous Lyonsia floridana (12) + = Lyonsia californica (25) ar = Lyonsia pugetensis (29) a = Lyonsia hyalina (22) ar a Lyonsia gouldti (18) al a Entodesma beana (15) aF ar = (juvenile) Entodesma beana (28) atoate = (adult) Entodesma fretalis (30) Far a Entodesma chilensis (29) shale = Entodesma patagonica (16) oF = Entodesma saxicola (96) AP APSar IE SF Entodesma truncatissima (67) APSR ar ++ Entodesma cuneata (34) AP ar ar Par Mytilimeria nuttalli (38) aF + Lenticular Sheet Ring Prismatic nacre nacre nacre + + ++ — + ++ + + + + ++ - + + ++ — + + ++ — + - ++ — + ++ + — + ++ ++ - ++ ++ 4 - 4 ++ + — 4 ++ ++ — + ++ + — a+ ++ + — +++ + ++ + inward and forming a protective cover for openings into this chamber (such as siphonal or pedal gapes). The shell and periostracal ultrastructures for each genus are discussed separately below, and outlined in Table 1. All figures are scanning electron micrographs. Lyonsta While there are some minor ultrastructural variations in the shell and periostracum of species within this genus, the overall structure is quite similar. The valves are usually covered by a thin spinulose periostracum which ranges in color from greenish brown (Lyonsia arenosa, L. flabellata, L. ventricosa) to tannish white (L. hyalina, L. californica, L. floridana). There are fine radial striations of the perio- stracum which run from the umbones to the ventral edge of the shell (Figures 1-3). These average 0.5mm apart along the ventral edge of a specimen of L. floridana 6.0mm long. At intervals these radial striae fan out in web-like patterns (Figure 3). This is sometimes caused by a corresponding pattern in the underlying prismatic layer but more often is a superficial mucoid web produced by arenophilic mantle glands (PREZANT, 1980b). The mucoid products, produced by this series of small, multicellular glands lining the mantle edge (PREZANT, 1979a, 1980b), are secreted over portions of the shell and help hold sand grains in place over the perio- stracum. Several concentric ridges, which may conform to growth lines, are usually present on the shell (Figure 2). In L. floridana these concentric ridges are separated by about 0.18-0.25 mm at the shell’s periphery. The concen- tric ridges appear as suspended wave crests over which the radial ornamentation and mucoid strands run. Numerous shell spinules (Figure 4), which are elaborations of the underlying prismatic layer and the periostracum proper (PREZANT, 1979b), also ornament the shell radially. The periostracum of Lyonsia is typically very thin, usually less than 1.0um in thickness. The thickness of the entire shell varies from 20 to 550m, depending upon species and stage of growth. Dissolution of the periostracum in L. hyalina reveals shallow pits covering the surface of the prismatic layer (PREZANT, 1979b). The prismatic layer is usually very thin in Lyonsia (Fig- ures 4-6). This layer is typically less than 1.0m thick beneath a concentric ridge in L. floridana. In L. californica the concavity beneath a concentric ridge is filled with a granular type of shell (Figures 7-9) that appears spherulitic in nature. The spherules, about 5 »m in diameter, are often composed of small laths arranged normal to the shell sur- face (Figure 9). These laths are usually less than 1 zm in cross diameter. The lath-like structure of these spherulites is not always distinct and the spherules may appear, in some cases, to be composed of small, irregular, polygonal Page 292 THE VELIGER Vol. 23; No. 4 grains. There is little indication of this type of shell struc- ture in other species of Lyonsia. The region beneath a con- centric ridge in L. floridana is filled with a dense, amor- phous extension of the prismatic layer (Figures 10-12). Most species of Lyonsia possess a biphasic nacre (outer lenticular and inner sheet nacre) (Figure 13). Usually the lenticular nacre is thinner in overall breadth than the sheet nacre. The lenticular nacreous layer in L. hyalina com- poses only 1/6 of the entire shell nacre (about 50m of lenticular nacre and 250m of sheet nacre) in a 14mm long specimen. The lenticular nacre, which is laid down by the mantle edge, is usually arranged in deep stacks, sev- eral layers thick. In L. hyalina the individual layers of lenticular nacre vary from 0.3 to 0.5 wm thick. In L. gouldit the lenticular tablets may reach 0.9m in thickness but gradually thin nearer the prismatic layer so that just beneath the latter the tablets are only 0.4 um thick. Near the shell edge only lenticular nacre is found and when viewed in this region the stacks are evident and may be piled deeper than seven layers thick in L. californica before total intralamellar fusion is obtained (Figures 14-15). The transition from lenticular to sheet nacre often occurs at the level of the pallial myostracum. The sheet nacre of Lyonsia is consistently composed of thinner indi- vidual lamellae than the lenticular nacre. This type of nacre is deposited as small nuclei which grow into poly- gonal tablets (usually hexagons or pentagons) prior to fusion into a single sheet (Figures 16-19). Sheet nacre is often deposited in a stepwise fashion producing a ter- race effect as one layer grows above and in front of an- other (Figure 17). Sheet nacre often composes the bulk of the shell in Lyonsia. The mature crystals, prior to fusion, in L. floridana reach a maximum diameter of 5 wm (Fig- ures 18-19) while in L. californica they obtain a maximum diameter of only 3 um. Sheet nacre in L. hyalina averages less than 0.25 wm in tablet thickness while it may reach 0.8 um in L. floridana. Small circular impressions situated centrally within mature, hexagonal crystals indicate the initial site of nucleation (Figure 18). Numerous species of Lyonsia possess many narrow tubules which penetrate the shell and are especially evident in the nacre (Figure 20). These tubules usually run normal to the shell surface. The boundaries of these tubules (Figure 20) are sharp. It is not known if extensions of the mantle penetrate these canals. Lyonsia californica has two modifications of the typical nacre development for this genus. In this species, the layer of lenticular nacre is thicker than the sheet nacre, and sec- ondly, there is a modified type of nacre formation found predominantly along the internal border of the shell but not along the outermost, lenticular regions. A short dis- tance from the shell edge is a band of nacre that appears to be formed by circumferential nucleation along the periphery of mature, hexagonal crystals of sheet nacre (Figures 21-25). These nuclei are deposited along the edge of the oor face of tablets composing the underlying nacre- ous layer. The nuclei enlarge and merge and produce a layer that, in fracture section, appears similar to sheet nacre. Intermediate stages of this fusion leave hollow rings of nacre along the internal shell surface (Figure 24). Ring nacre is usually low-lying; 7. e., the nuclei grow in a hori- zontal plane relative to the shell surface and produce flat, low relief profiles. In some cases, however, the circum- ferential ring nacre nuclei form tall spires prior to fusion (Figures 26-27). This tall form of ring nacre appears rarely and randomly. The merger zone from ring nacre to typical sheet nacre is a gradual transition zone where incomplete rings dominate until only typical sheet nacre development is present (Figures 21-22). This is the only species of Lyonsia in which ring nacre formation was found. The myostracum of Lyonsia forms a narrow prismatic band of crystals underlying the pallial, retractor, and ad- ductor muscles (Figures 28-32). In small specimens of these thin shelled bivalves, myostracum can compose up to half the shell thickness along the pallial attachment (L. hya- lina) (Figure 4). The transition from nacre to myostracum is distinct. In L. floridana the myostracum averages 24 ym thick in a fairly large (14mm long) specimen (Figure 30). The myostracal surface is smooth (Figure 32). The grow- ing nacre front gradually deposits nuclei over the trailing muscle scar edges until the myostracum is submerged by the nacre (Figures 28-29). Dense bundles of aragonitic fibers (Figure 33) are incor- porated into the ligamental resilium and extend towards the central lithodesma. These needles run perpendicular to the shell surface. In Lyonsia floridana the needles aver- age 39 um in length and measure less than 0.5 wm in diam- eter. Entodesma The ultrastructural difference between shells of Lyonsta and large, thicker shelled species of Entodesma is obvious. Smaller, thinner shelled species of Entodesma are, how- ever, quite similar in shell ultrastructure to Lyonsia. The periostracum of Entodesma is thick (Figures 34-95) and usually ornamented with several radial striations. The radial striae of Entodesma are also often splayed out in web-like patterns as a result of mucoid secretions or actual periostracal structure (Figure 36). The periostracum ranges in color from golden-brown in E. saxicola to green- brown in E. chilensis. A specimen of E. saxicola 60mm long has a 0.11mm thick periostracum. A specimen of THE VELIGER, Vol. 23, No. 4 [PREZANT] Figures 1 to oN ‘ i i Teg r ' anh c : = ta x (i 4 } 3 Ne i ree et \ Tue VELIGER, Vol. 23, No. 4 [PrEzANT] Figures 7 to 12 Tue VELIGER, Vol. 23, No. 4 [PrezAntT] Figures 13 to 20 Tue VELIGER, Vol. 23, No. 4 [PREZANT] Figures 21 to 27 Vol. 23; No. 4 E. beana with a shell 0.65mm thick may have a perio- stracum as thick as 754m. This outer organic layer is homogeneous in texture (Figures 34-35) and readily frac- tures in dry specimens. There are usually several concentric folds of the periostracum as well as wrinkling, especially near the posterior region of the shell. The extensive perio- stracum typically overlaps the shell edges. The periostracal surface may be partially covered with a sparse coat of extraneous articles picked up from the environment. These particles adhere to the periostracum through the adhesive properties lent to this organic layer by secretions of the arenophilic radial mantle glands especially found in juve- nile specimens (PREZANT, 1980b). Shell spinules were not observed in any species of Entodesma examined in this study; however, BartscH & REHDER (1939) found the surface of young shells of Entodesma lucasanum to be cov- ered with small, radially aligned, white pustules. Specimens of Entodesma saxicola, truncatissima and cuneata, all thick shelled species typically found nestled within rocky intertidal crevices, possess a thick, well- defined, granular homogeneous shell layer (the “grained structure” of OBERLING, 1964) beneath the periostracum (Figures 37-39). The merger of periostracum with this homogeneous layer appears as an amorphous confluence of the organic periostracum filling in sinuses created by the gaps between the superstructures of the homogeneous layer (Figure 39). This homogeneous layer is composed of large polygonal blocks of spherules (Figures 40-44) varying from 12-35 um in maximum diameter in E. truncatissima and E. saxicola (Figures 40, 43-44). The spherules located closer to the umbo in E. saxicola are smaller, averaging 7-14pm in diameter (Figure 42). The spherules, which form discrete structures set in a thick conchiolin, are superstructures which are composed of densely packed granules that closely approximate a true homogeneous layer. These granules (Figure 44) are less than 1.0m in diameter. Smaller, thinner shelled species of Entodesma, which are more often found subtidally and nestled among tunicates or sponges or algal holdfasts, lack a homogeneous shell layer. Thus, this layer was absent in E. beana, patagonica, chilensis and fretalis. At the base of the homogeneous layer in forms with thicker shells and beneath the periostracum in the thinner shelled species, is a thin, usually poorly defined prismatic layer (Figures 45-53). In the thinner shelled species the prismatic layer forms a narrow band just below the perio- stracum that measures about 11 wm in height in a speci- men of Entodesma beana 13mm long. Prisms in a slightly larger (16mm long) specimen of E. chilensis average 22 #m in height and 0.8-1.24m in diameter (Figure 69). THE VELIGER Page 203 With the periostracum removed, by dissolution in a weak solution of sodium hypochlorite, the surface of the pris- matic layer in the thinner shelled species is rugose with the surface of each individual prism projecting outward as a small knob (Figures 47-48). In thicker shelled species the prismatic layer is very thin, being 6-8 wm tall in E. saxicola (Figures 49-52). The granular nature of the homogeneous layer in these species often appears to be an extension of the thin prismatic layer (Figure 49). The prismatic layer in some species (E. cuneata, E. truncatissima) is irregular and merges indiscriminately with the homogeneous layer (Figures 50-52). Sometimes the grainy textured prisms are elongate and extend well into the homogeneous layer (Figure 57). The granular homogeneous layer, while present through- out most of the shell of Entodesma saxicola, is noticeably absent from some regions near the umbo. In a single spec- hmen 24mm long, approximately 3mm to the posterior side of the umbo, there was a very thick dorsal homo- geneous layer (Figures 53, 58), which, moving ventrad, is lost and the bulk of the shell thickness is replaced by a wedge of tall prisms (Figures 54-58). This wedge initiates suddenly as tall, thin prisms about 275 um in height and about 0.7mm ventrad from the dorsum of the shell in this region. The wedge gradually tapers for about 300 ym before vanishing. The junction between the dorsal homo- geneous layer and the wedge is sharp. The prismatic wedge is bounded internally by a thin nacreous layer and exter- nally by a thin prismatic layer with which it merges dor- sally. The external prismatic layer and wedge separate as the wedge tapers ventrally and the wedge is then bounded on either side by nacre (Figure 56). There isno comparable prismatic wedge on the anterior side of the umbo in this specimen. The thin, outer prismatic layer in the posterio- dorsal region is composed of small, granular prisms (Figure 54) and the shell exterior, with periostracum removed, is reminiscent of thinner shelled species of Entodesma that lack a homogeneous layer. The thin prismatic layer of E, saxicola in the umbonal region eventually redevelops an association with an outer, granular homogeneous structure. In all members of the genus the outer prismatic layer merges with a lenticular nacre (Figure 59). This merger appears as a gradual fusion of the basal portions of the prisms and the nacreous tablets. In all mature individuals, the nacre is biphasic (Figures 60-61) composed of a thick lenticular and usually a thinner sheet nacre (Figures 62- 65). In Entodesma fretalis and E. chilensis the lenticular nacreous tablets average 1.0 um in thickness and are tightly packed together. Small specimens (11mm length) of E. patagonica have lenticular tablets averaging less than 0.5 pm in thickness. Explanation of Figures 7 to 6 Figure 7: Lyonsia floridana. Periostracal surface with radial stria- tions and attached sand grains. Horizontal field width = 960 ym Figure 2: Lyonsia floridana. Concentric growth ridges intersect radial striations on periostracal surface. Horizontal field width = 906 pm Figure 3: Lyonsia californica. Web-like radial ridge of outer cal- careous shell surface. In 5% sodium hypochlorite for 3 minutes. Horizontal field width = 125 pm Figure 4: Lyonsia hyalina. Longitudinal shell fracture revealing outer truncated shell spinules, thin prismatic layer, thick nacre, and well developed myostracum Horizontal field width = 100pm Figure 5: Lyonsia hyalina. Blocky prismatic above well developed nacre, radial fracture. Horizontal field width = 25 um Figure 6: Lyonsta gouldii. Blocky prismatic above thick nacre, radial fracture. Honzontal field width = 30pm Explanation of Figures 7 to 12 Figure 7: Lyonsia californica. Outer concentric ridge fracture with thin prismatic cover. Horizontal field width = 60pm Figure 8: Lyonsta californica. Concentric ridge fracture illustrating irregular, grainy spherules composing bulk of ridge substance. Horizontal field width = 30m Figure 9: Lyonsia californica. Concentric ridge fracture showing small, regular laths oriented normal to shell surface. Horizontal field width = 15 ym Figure 10: Lyonsia floridana. Concentric ridge fracture with thin outer prismatic cover, underlying nacre, and thick myostracum. Horizontal field width = 60 pm Figure 11: Lyonsia floridana. Concentric ridge fracture showing irregular extensions of prisms composing mndge. Horizontal field width = 30 pm Figure 12: Lyonsia floridana. Concentric ridge fracture showing grainy structure underlying prismatic layer; extensions of prisms composing ridge are evident. Horizontal field width = 15 um Explanation of Figures 13 to 20 Figure 13: Lyonsia pugetensts. Biphasic nacre, radial fracture through mid-portion of valve. Lenticular nacre is present at top of micrograph. Horizontal field width = 20pm Figure 14: Lyonsia californica. Lenticular nacre, internal surface. Horizontal field width = 35 pm Figure 15: Lyonsia californica. Lenticular nacre, internal surface. Horizontal field width = 18 pm Figure 16: Lyonsia hyalina. Sheet nacre, internal surface near growing edge. Horizontal field width = 30pm Figure 17: Lyonsia hyalina. Sheet nacre, terraced appearance of growing edge. Horizontal field width = 75 »m Figure 18: Lyonsia floridana. Sheet nacre, internal surface near growing edge. Horizontal field width = 35 pm Figure 19: Lyonsia floridana. Sheet nacre, internal surface. Rem- nants of thin intercrystalline organic layer stretch between crystal tablets. Horizontal field width = gym Figure 20: Lyonsia hyalina. Nacre, fracture section. Two tubules pierce nacre; a single dislodged portion of lamella reveals the nar- row circular lumen of a single tubule. Horizontal field width =20 ym Explanation of Figures 21 to 27 Figure 21: Lyonsia californica. Ring nacre, surface view. Numer- ous stages of ring nacre development are evident above typical sheet nacre. Horizontal field width = 120m Figure 22: Lyonsia californica. Ring nacre, surface view. Several stages of ring nacre formation, from incomplete, newly forming rings, to well developed tablets are apparent. Horizontal field width = 60 ym Figure 23: Lyonsia californica. Initial stages of ring nacre show small nuclei deposited along oor face of mature tablets. Horizontal field width = 20pm Figure 24: Lyonsia californica. Later stage of ring nacre forma- tion shows thickened circumferential walls. Horizontal field width = 404m Figure 25: Lyonsia californica. Differential growth of circumscrib- ing nuclei of a single ring may produce variable sizes of crystals composing a ring. Horizontal field width = 204m Figure 26: Lyonsia californica. Tall ring nacre, surface view, show- ing rambling walls above sheet nacre. Horizontal field width = 204m Figure 27: Lyonsia californica. Superficial fracture through a dense aggregate of tall ring nacre. Typical sheet nacre is evident at lower left of micrograph. Horizontal field width = 80pm Page 294 Sheet nacre composes less of the shell thickness in most species of Entodesma although in large specimens of E. saxicola it accounts for half the nacre. Tablets of sheet nacre are almost always thinner than those of lenticular nacre (Figure 66). Sheet nacre tablets of E. chilensis vary from 0.5 to 0.8 um while they average 0.5 um in E. fretalts. The sheet nacre tablets of E. beana range from 0.3 to 0.4 pm in thickness. Under close examination the sheet nacre of E. beana appears to have a grainy texture (Figure 66). Sheet nacre is, as usual, laid down in thin layers deposited in a terrace-like fashion (Figures 67-68). No ring nacre has been found in any species of Ento- desma. In a single species, Entodesma beana, small specimens 15mm long have been found to lack lenticular nacre. In juveniles of this species the shell is composed of a fairly tall (14.5 wm) prismatic layer while the bulk of the shell is sheet nacre (Figure 67) with tablets ranging in thickness from 0.2 to 0.4m. The shell of larger E. beana (28mm long), like most lyonsiids, does possess a biphasic nacre with the major portion being lenticular. OBERLING (1964) first found tubules within the nacre of Entodesma saxicola. All species of Entodesma examined have narrow tubules randomly penetrating the shell nacre as well. E. beana, in particular, possesses numerous tubules which run normal to the shell surface (Figure 69). The tubules average 0.5 wm in diameter. There is no histolog- ical or ultrastructural indication of mantle tissue pene- trating the tubules. Entodesma, like Lyonsia, possess a well-defined myo- stracum located beneath the adductor, retractor and pal- lial muscles (Figures 70-73). The myostracum underlying the adductors of E. beana is composed of simple prisms which may exceed 30 ym in height (Figure 77). The pallial myostracum of E. saxicola may measure as little as 4.4 ~m in thickness (Figure 70) in a valve that is 60mm long and over 1.0mm thick. The juncture between myostracum and nacre is very sharply demarcated. Mytilimeria The periostracum of this endosymbiont is modified to allow a close adhesion between the bivalve and its ascidian host. This outer, brown organic layer is very thin and usually peels away and remains attached to the tunicate when the clam is removed. There is no regular surface ornamentation of the periostracum but it is covered with numerous, randomly situated, small crater-like pits (Figure 74). These pores have raised external rims circumscribing them which are about 4.5 um in height. The pores them- THE VELIGER Vol. 23; No. 4 selves vary from 4.5m to 25.0um in diameter. These periostracal modifications may play a role in the adhesion of the bivalve to the tunicate by providing an increased surface area. It is possible that extensions from the ascidian penetrate the pores but this has not been verified. Just beneath the periostracum is a thin (35-40 um thick in a 22mm long specimen) granular homogeneous layer (Figures 75-77) similar to that found in some Entodesma species. The layer is composed of large irregular polygons, 6-25 pm in greatest diameter, composed of tightly bound granules 0.1-0.5 wm in diameter. The spherules in M. nut- tall: are usually compressed in the plane of the shell width. Mytilimeria have a well developed prismatic layer com- posed of blocky prisms (Figures 75, 78-80). The shell of M. nuttalli, upon drying, will often split into two portions; the level of disjunction is usually just above the prismatic layer. A fracture along this plane reveals the surface of the prisms with a thin remnant of a granular homogeneous structure (Figures 76-77). The prisms are very broad and range in height from 20 to 50um. There is a high degree of geometric selection (TayLor ef al., 1969) within the prismatic layer usually leaving many small, isolated, trian- gular prisms intermixed with the taller, column-like prisms (Figure 79). Biphasic nacre constitutes the major component of the shell of Mytilimeria and may compose more than 95% of the entire shell thickness. The zone of merger between the prismatic layer and the lenticular nacre is distinct (Figure 80). The shell may separate along a plane within the nacre upon drying,revealing a smooth nacreous surface (Figures 81-82) with shallow depressions indicative of initial crystal growths. Tablets of lenticular nacre average 0.5-0.9 um in thickness (Figures 83-84) and show grainy texture similar to that noted in Entodesma beana (Figure 66). Lenticular nacre nuclei of M. nuttalli are usually deposited as small polygons. Nuclei of the sheet nacre are circular (Figure 85) prior to growth and fusion. Sheet nacre lamellae average 0.2-0.3 wm in thickness. In some specimens, there were in- dications of ring nacre formation, located near the inner umbonal region of the shell (Figure 86) similar to that in Lyonsia californica. The close proximity to the umbo, and thus the ligament, of ring nacre in M. nuttalli is evidenced by the array of dislodged aragonitic fibers loosened from the resilium (Figure 86). Nuclei surrounding the oor face of underlying ring nacre crystals appear to be of the tall, prism-like type. M ytilimeria, as with the other lyonsiids, has a well devel- oped myostracum that ranges from 4 to 6um in thickness (Figures 80, 87). Tue VELIGER, Vol. 23, No. 4 [PREZzANT] Figures 28 to 33 THE VELIGER, Vol. 23, No. 4 [PREZANT] Figures 34 to 44 casey een et a en ee et AG 0 | eee ee wi : 2 ae a ' oe) " 1 nar ‘ dt Sa 3 4 7 M F 4 i i ve ion Tue VELIGER, Vol. 23, No. 4 [PREZANT] Figures 45 to 52 Tue Ve icER, Vol. 23, No. 4 [PrREZANT] Figures 53 to 58 Vol. 23; No. 4 DISCUSSION CARPENTER (1847) considered the shell of Lyonsia to con- sist of nacre and an outer prismatic layer. This has more or less been the stock interpretation since the mid-1800’s, tentatively confirmed by Taytor et al. (1973) for most Pandoracea (although they did not examine any lyonsiid bivalves per se). All Lyonsiidae can be recorded as charac- terized by the presence of a thin prismatic layer, well developed myostracum, and, in mature specimens, a pre- dominance of biphasic nacre. The dominance of nacre and modifications of the shell ultrastructure are evidently an evolutionary response to environment and habitat. The preponderance of nacre, typically as an external lenticular and an internal sheet nacre, is evident in Lyonsia, Mytilimeria, and thin shelled species of Ento- desma. This type of shell is of obvious benefit to free-living bivalves exposed to the rigors of burrowing or an intertidal existence. If we assume a free-living ancestor (YONGE, 1952; RUNNEGAR, 1974) for the lyonsiids, then it is clear why nacre, always aragonitic (TayLor et al., 1969; Car- TER, 1980), and the strongest, most fracture resistant shell structure found in bivalves (TayLor & LayMAN, 1972), has assumed so large a role in the make-up of these exo- skeletons. Modern species of Lyonsia, in their partially buried position, are often found in shallow, sometimes intertidal, marine habitats where they are exposed to shifting tides and sediments and numerous predators. Many species of Entodesma (saxicola, truncatissima, cune- ata) are exposed to the even more “hostile” environment of a rocky intertidal zone. These latter species, with thick shells and periostracum, have developed an outer granular homogeneous layer. The smaller, often thinner shelled, species of Entodesma (fretalis, chilensis, beana) are typi- cally found nestled among, and buffered by, colonies of tunicates or sponges. They lack a thick homogeneous layer. Mytilimeria, embedded within compound ascidians, has a thin shell consisting primarily of nacre but has remnants of a granular homogeneous layer which may be indicative of its relationship to Entodesma. Shell structure in each genus is adapted to a particular biotype. The principally nacreous, thin shells of Lyonsia have been secondarily strengthened by the addition of an extraneous sand coat which adheres to a mucoid layer secreted over the thin periostracum (PREZANT, 19792, 1980b). This extra coat serves the mollusc in protecting the shell, stabilizing the bivalve in shifting sediments by in- creasing external surface area and adding weight to the shell, and acting as camouflage (PREZANT, 1979a). Shell spinules, radially ornamenting the shells of Lyonsia, aid in THE VELIGER Page 295 adhesion of foreign particles to the valves and in stabiliza- tion within the substratum (PREZANT, 1979b). Radially arranged calcareous strings composed of mi- nute rods on the shell of Lyonsia norvegica were reported by ALLER (1974) but did not occur in any of the species in the present study. These calcified ornamentations occurred principally in the posterior, free region of the periostra- cum, and were seen to break free from the periostracum in this area as well (Aller, pers. comm.). The string- like structures found in the periostracum of species of Lyonsia examined here were “polymerized” secretory products of the multicellular arenophilic mantle glands (PREZANT, 1979a, 1980b) and are primarily non-calcareous glycoproteins. The periostracum of most species of Entodesma is thick and pliable. Usually externally frayed, it serves to protect the bivalve from minor movements within its crevice home. The periostracum of rocky intertidal species of this genus characteristically is thicker than that of those species which nestle among ascidians or sponges. In juveniles of this genus, the periostracum is also made partially adhesive by mantle secretions, and the small clams, and adults where arenophilic mantle glands are retained, cement foreign particles to their shells. The functions of this some- what sparse extraneous cover may be similar to those of Lyonsia. Glands producing the adhesive material are grad- ually lost in some species of Entodesma as they grow in overall size and shell thickness. Large specimens of Ento- desma are tightly fitted and well secured within their often crowded quarters and can produce numerous thick and strong byssi for added stability. These two factors, in con- junction with the thickened shell, likely obviate the “need” for an extraneous sediment coat over the shell of large adults. In Mytilimeria many of the functions of the shell and periostracum have been assumed by their host tunicate colony. There is no obvious modification of the shell or mantle edge to allow adhesion of foreign particles (these are not readily available anyway). The thick ascidian test provides the bivalve with structural support, camouflage, and protection. These factors in conjunction with the firm attachment of the tunicate to the substratum have allowed regression of the mollusc’s byssal system and arenophilic mantle glands system. The bivalve does maintain a tight connection within the tunicate by a physically adherent periostracum. Possibly thin extensions from the ascidian colony extend into the numerous pores which cover the bivalve’s periostracum. Shell tubules are well known features of bivalve mol- luscs, especially among the Sphaeriidae (ScurROpER, 1907) and Arcoida (WALLER, 1979). Tubules are formed, Explanation of Figures 28 to 33 Figure 28: Lyonsia californica. Region of juncture between sheet nacre (left of micrograph) and myostracum (right of micrograph) , surface view. Honzontal field width = 3o um Figure 29: Lyonsia californica. Sheet nacre growing edge, radial fracture. Nacre (left of micrograph) gradually accrues over my- ostracum of the anterior adductor scar (right of micrograph) . Horizontal field width = 60pm Figure 30: Lyonsia floridana. Posterior adductor myostracum, frac- ture. Sheet nacre is at top of micrograph. Horizontal field width = 60pm Figure 31: Lyansia floridana. Pallial line myostracum, fracture. Horizontal field width = 16ym Figure 32: Lyonsta californica. Anterior adductor scar, surface view and radial fracture. Horizontal field width = 30pm Figure 33: Lyonsia floridana. Aragonitic fibers of resilium. Horizontal field width = 604m Explanation of Figures 34 to 44 Figure 34: Entodesma saxicola. Thick periostracum (top of micro- graph) overlies granular homogeneous shell layer, radial fracture. Horizontal field width = 180 um Figure 35: Entodesma beana. Shell, radial fracture. P, periostra- cum; n, nacre. Horizontal field width = 475 pm Figure 36: Entodesma chilensis. Webbed radial striation on shell surface. Horizontal field width = 450 um Figure 37: Entodesma truncatissima. Shell, longitudinal fracture. P, periostracum; H, hamogeneous layer; p, prismatic; n, nacre. Horizontal field width = 520ynm Figure 38: Entodesma truncatissima. Outer shell region, longitudi- nal fracture. P, periostracum; H, granular homogeneous; p, pris- - matic; n, nacre. Horizontal field width = 180m Figure 39: Entodesma saxicola. Merger of periostracum and gran- ular homogeneous layer, longitudinal fracture. Organic remnants are evident among the homogeneous structures. P, periostracum; H, granular homogeneous. Horizontal field width = 45 pm Figure go: Entodesma truncatissima. Merger of prismatic (bottom of micrograph) and outer homogeneous layer, longitudinal fracture. Horizontal field width = 45 pm Figure 41: Entodesma cuneata. Granular homogeneous layer, ra- dial fracture. Horizontal field width = 40pm Vigure 42: Entodesma saxicola. Granular homogeneous structure near umbo, radial fracture. Horizontal field width = 1:20pm Figure 43: Entodesma saxicola. Granular homogeneous structure near shell edge, radial fracture. Horizontal field width = 120yum Figure 44: Entodesma saxicola. Granular homogeneous structure showing grainy substructure, radial fracture. Horizontal field width = 30pm Explanation of Figures 45 to 52 Figure 45: Entodesma beana. Outer shell, radial fracture showing merger of periostracum and thin prismatic above thick lenticular nacre; P, periostracum; p, prismatic; n, nacre. Horizontal field width = 120pm Figure 46: Entodesma beana. Outer shell, radial fracture. Merger of periostracum with prismatic layer, and prismatic layer with lenticular nacre. Horizontal field width = 60pm Figure 47: Entodesma chilensis. Outer shell, radial fracture and surface view. In 5% sodium hypochlorite, 90 min. Removal of periostracum reveals roughened surface of underlying shell. Horizontal field width = 60pm Figure 48: Entodesma chilensis. Calcified shell surface. In 5% sodium hypochlorite, 90 min. Horizontal field width = goym Figure 49: Entodesma saxicola. Merger of granular homogeneous and prismatic layers, and prismatic and nacreous layers, longitudinal fracture. H, granular homogeneous; p, prismatic; n, nacre. Horizontal field width = 180m Figure 50: Entodesma cuneata. Prismatic layer, radial fracture. In 5% sodium hypochlorite, 90 min. Horizontal field width = 55 pm Figure 51: Entodesma truncatissima. Merger of granular homo- geneous and prismatic layers, and prismatic and nacreous layers. Variety in prism sizes is evident. Horizontal field width = 60pm Figure 52: Entodesma cuneata. Outer calcareous shell, longitudi- nal fracture. Variety of prism size and elongation of homogeneous superstructures are evident. Horizontal field width = 1t1ropm Explanation of Figures 53 to 58 Figure 53: Entodesma saxicola. Prismatic wedge near umbo, ra- dial fracture. Thin, outer prismatic is at right of micrograph. In 5% sodium hypochlorite, go min. Horizontal field width = 960m Figure 54: Entodesma saxicola. Prismatic layer near shell umbo, radial fracture. In 5% sodium hypochlorite, go min. Horizontal field width = 504m Figure 55: Entodesma saxicola. Prismatic wedge near umbo, ra- dial fracture. In 5% sodium hypochlorite, 90 min. Horizontal field width = 280 pm Figure 56: Entodesma saxicola. Prismatic wedge near umbo tapers ventrally, radial fracture. In 5% sodium hypochlorite, 90 min. Horizontal field width = 240m Figure 57: Entodesma saxicola. Prismatic wedge near umbo, radial fracture. In 5% sodium hypochlorite, 90 min. Horizontal field width = 100pm Figure 58: Entodesma saxicola. Granular homogeneous along dor- salmost border of shell, radial fracture. In 5% sodium hypochlorite, go min. Horizontal field width = 280 pm " it Bios PN cad Page 206 THE VELIGER Vol. 23; No. 4 in the Arcoida by shell-dissolving extensions of the mantle epithelium. WALLER (1979) suggests that internal chemical repellents, within the tubules, may function as inhibitors to predatory borers. In the Arcoida the tubules penetrate the entire shell and the inner surface of the periostracum (WALLER, 1979), but in Lyonsia and Entodesma shell tubules only penetrate calcareous, subperiostracal layers. There is no evidence that epithelial extensions invade the tubules in any lyonsiid, but a careful analysis of this asso- ciation is still necessary. The presence of a sand cover over the periostracum of species of Lyonsia would seem to obviate the anti-boring mechanism as a primary function of shell tubules, how- ever, not all specimens retain a total sand cover. The par- tial penetration of the shell by tubules also argues against a principally defensive role. Shell tubules may, however, act as a secondary defense system for the bivalves. This is a possibility in epifaunal Entodesma species where extra- neous sediment coatings are usually sparse and often are totally absent. No shell tubules have thus far been located in Mytilimeria nuttalh. The evolutionary implications of this are evident if the tubules do indeed serve a protective function. Ring nacre formation described here has not been re- ported before,although molluscan nacre development and structure have been studied in detail (Wapa, 1961, 1972; MutveEl, 1970; ERBEN, 1972). Wana (1960, fig. 3; 1961, fig. 104) found nacreous crystal formation resembling ring nacre in Pinctada martensiz,but it is not as clearly orga- nized or distinctly circumferential, and was mentioned only in passing. MutTveEI (1970) found a type of partial ring nacre in Pinna in which there was a marginal nucleation ridge along the 110 faces of the inner crystal. This ridge was absent from the o1o faces and was absent in mature crystals. The wide variation in nacre types may be ac- counted for by alterations of mantle activity that reflect different physiological conditions of the mollusc (Wapa, 1960), such as differences in growth conditions, variations in extrapallial fluid (especially pH, viscosity and impuri- ties), and changes in environment (Wapa, 1972). The functions, or stimuli for production of ring nacre in Lyonsia californica and Mytilimeria nuttalli are un- known. Ring nacre in L. californica occurs primarily along the line of pallial attachment but it is doubtful that this shell microstructure plays any role in the connection of the mantle to the shell. Instead it seems likely that we are seeing the genesis of newly deposited, modified nacre that has not yet been submerged by sheet nacre or myostracum. It has not yet been possible to distinguish submerged ring nacre from sheet nacre in fracture sections, so it is impos- sible to say when deposition of ring nacre begins. Neither have submerged taller, spire-like ring nacre crystals been recognized in fractures. The majority of shells of Lyonsia californica and Mytt- limeria nuttalli examined were all from a single location along the California coast. Information concerning grow- ing conditions and environment was not available. Since changes in shell mineralogy (LowENSTAM, 1954; CARTER & EICHENBERGER, 1977) and shell structure (PALMER, 1980) may reflect local changes in habitat or environment, it is possible that ring nacre is deposited as a result of some environmental factors. It would seem that ring nacre would, if nuclei grow at similar rates, develop faster than sheet nacre. The fusion of multiple nucleation sites which circumscribe a single mature crystal would produce a com- pleted lamella faster than typical sheet nacre development which incorporates the growth or maturation of single nuclei situated upon underlying tablets. Thus,under good growing conditions ring nacre development would accrue mature tablets and lamellae at a faster rate. Ring nacre in Mytilimeria nuttalli is more variable in position than in Lyonsia californica, but is usually located close to the umbos. Ring nacre was not found in every specimen of M. nuttalli examined. This may indicate variability based upon environmental or developmental factors. The latter is unlikely as similar specimens varied in possession of ring nacre. Since many individuals from the same environment also varied in the possession of ring nacre, this would also seem to argue against environmental control. These bivalves, however, were not processed im- mediately for scanning electron microscopy, and transfer and holding conditions varied. Thus, environment cannot be ruled out as a possible contributing factor. The ultrastructure of the shell of Entodesma varies within the genus. Small, thinner shelled species possess a shell similar to that of Lyonsia. These shells have a high proportion of nacre which likely serves to strengthen the shell. Species of Entodesma found in rocky intertidal zones do not possess thin shells. They have developed a thick shell by the addition of a thick homogeneous layer. This some- what less organized shell layer may be energetically cheaper to produce. Thus the mollusc can develop a thick shell for less expenditure of energy than if the shell was mostly elaborated as nacre. The value of the homogeneous shell layer extends beyond this. Structurally the homoge- neous layer is excellent at dissipating fractures (TAYLOR & LayMAN, 1972). In the case of a granular homogeneous layer, fractures which permeate the shell would travel only as far as the first organic barrier and would be dissipated from there among the smaller granules or larger spherules. [PREZANT] Figures 59 to 67 Tue VELIGER, Vol. 23, No. 4 THE VELIGER, Vol. 23, No. 4 [PrezAnt] Figures 68 to 73 THE VELIGER, Vol. 23, No. 4 [PREZANT] Figures 74 to 79 THE VELIGER, Vol. 23, No. 4 [PREZANT] Figures 80 to 87 | : | EA CTE SET PERS EO eed Vol. 23; No. 4 THE VELIGER Page 297 Small calcareous spherules or laths located beneath the concentric striae in Lyonsia may serve a similar anti-frac- ture purpose, as well as allowing increased shell surface area with structural support at potentially inexpensive energy costs. The homogeneous layer in some species of Entodesma reflects the environmental conditions of their habitats, while the presence of a thin homogeneous layer in Mytili- meria may indicate a common lineage between this genus and Entodesma. The granular homogeneous layer in the thin shelled Mytilimeria may also serve to dissipate frac- tures among the many heterogeneous calcareous units sep- arated by thin, winding organic sheets. Long, regular organic boundaries,on the other hand, between prismatic or crossed lamellar units, for example, would tend to pre- cipitate fracture lines (TayLor & LAYMAN, 19724). A gran- ular homogeneous layer is, however, most likely phylo- genetically derivable from a decrease in individual shell unit size through a physical partitioning of any calcareous shell microstructure (TAYLoR, 1973; TAyYLor et al., 1973). Fhe homogeneous layer in lyonsiids probably is derived from a degradation of the prismatic layer. The presence of well defined prismatic layers in Lyonsia and the gradual merger of a less distinct prismatic layer with the homo- geneous layer in some species of Entodesma supports this view. The presence of a well developed prismatic layer in Entodesma species lacking a homogeneous layer also lends support to this possibility. Ultrastructural shell changes may evolve in three ways according to TayLor (1973): through 1) the loss of a shell layer, 2) a change in orientation or 3) a complete structural change. The first type is the most common (TayLor, 1973). In the lyonsiids we are seeing a structural change in the development of the homogeneous layer. TayLor (1973) notes that the homogeneous structure may have eyolved as a means of producing a rapidly crystallized shell layer. Thus,the homogeneous structure may develop faster than other shell structures of comparable physical support and resistance. The homogeneous shell structure is rare in molluscs and occurs only sporadically within the group (CarTER, 1979b). The lyonsiids are the only group among the Pandoracea, other than some thraciids, which possess, at least in some members, any type of homogeneous shell layer. Among the subclass Anomalodesmata, outside the Pandoracea, it also occurs in some species of Poromyacea. The large spherules in Entodesma, which compose the superstructure of the granular homogeneous layer, are similar to spherulitic structures found by Taytor et al. (1973) in Thracia. In the latter, toward the outside of the shell, the homogeneous crystallites are arranged in “columnar growths” which intermingle with the periostracum. These crystallites, which are 3 um in diameter,merge together as growth pro- ceeds and develop into larger spherulites of a typical homo- geneous structure. In section the homogeneous granules of Thracia are also slightly flattened as they are in Mytili- mena. The exact origin or function of the prismatic wedge found near the umbo of Entodesma saxicola is unknown. CarTER & EICHENBERGER (1977) found calcitic “insets” forming tapering wedges in the shell of several species of Veneracean bivalves. These wedges represent an ontoge- netic change in mineralogy of the outer aragonitic pris- matic layer. Among Veneracea with a biphasic mineralogy, data thus far indicate environmental control over the rela- tive proportions of calcium carbonate allomorphs (CARTER & EICHENBERGER, 1977). The shell of lyonsiid bivalves is typically all aragonitic. The mineralogy and frequency of occurrence of the prismatic wedge in E. saxicola is yet to be determined, but the presence of this shell modification does indicate variability in deposition and formation. While broad generalizations concerning specific shell types within a given taxon can be made, care must be taken not to disallow plasticity in the molluscan exoskeleton. The recurrent patterns of shell microstructures, never- theless, are well known among shelled invertebrates; hence the common nacreous theme (GrécorrE, 1967; WISE, 1969; MuTVEI, 1970, 1972a,b; ERBEN, 1974). At the ultra- structural level, however, variations exist in development, substructure, and texture (Popov & Barskov, 1978). Popov & Barskov (1978) suggest that fine “textural patterns” are useful tools even “When the microstructure of different genera is similar .. .”. The rarity of a granular homo- geneous structure in molluscan shells and the similarity in fine structure of this layer in Entodesma and Mytilimeria point to a common lineage and further separate these gen- era from Lyonsia. Lyonsiid evolution, as outlined by PRrEzANT (1980b), originates from a free-living ancestor from which two sep- arate lineages diverged. The ancestral shell was composed of a thin prismatic layer, an inner nacre, and pallial and adductor myostracum. This is similar to the basic primitive molluscan shell type, predicted by TayLor (1973), based upon the shell ultrastructure of monoplacophorans. The primitive lyonsiid probably possessed a thin periostracum as well and gradually developed accessory arenophilic mantle glands resulting in an adherent extraneous coat. The divergent evolutionary branches entailed a lineage leading to modern Lyonsia and an “Entodesma’” branch from which Mytilimeria originated. The Lyonsia branch maintained the life-style and shell structure of the ances- tral lyonsiid, but the Entodesma species moved into diverse Explanation of Figures 59 to 67 Figure 59: Entodesma saxicola. Merger of prismatic and lenticular nacre layers, radial fracture. Horizontal field width = 8pm Figure 60: Entodesma chilensts. Biphasic nacre, longitudinal frac- ture. 1, lenticular nacre; s, sheet nacre. Horizontal field width = 60m Figure 61: Entodesma fretalis. Biphasic nacre, radial fracture. 1, lenticular nacre; s, sheet nacre. Horizontal field width = 904m Figure 62: Entodesma fretalis. Merger of prismatic and lenticular nacre layers, radial fracture. In 5% sodium hypochlorite, 90 min. Horizontal field width = 30pm Figure 63: Entodesma chilensis. Merger of prismatic and lenticu- lar nacre layers, longitudinal fracture. Horizontal field width = 60pm Figure 64: Entodesma chilensis. Lenticular nacre, longitudinal frac- ture. Horizontal field width = 16pm Figure 65: Entodesma saxicola. Calcareous shell, radial fracture. Pallial myostracum separates lenticular and sheet nacre. m, myos- tracum; ], lenticular nacre; s, sheet nacre. Horizontal field width = 95 pm Figure 66: Entodesma beana. Sheet nacre, longitudinal fracture. Horizontal field width = 7 »m Figure 67: Entodesma beana. Prismatic layer overlies sheet nacre in juvenile specimen. Horizontal field width = 15 um Explanation of Figures 68 to 73 Figure 68: Entodesma saxicola. Sheet nacre, superficial fracture. Horizontal field width = 60pm Figure 69: Entodesma beana. Tubules penetrating nacre, longitu- dinal fracture. Horizontal field width = 60pm Figure 70: Entodesma saxicola. Pallial myostracum, radial fracture. Horizontal field width = 15 pm Figure 71: Entodesma beana. Posterior adductor myostracum, lon- gitudinal fracture. Horizontal field width = 60pm Figure 72: Entodesma chilensis. Radial shell fracture revealing sub- merged trails of myostracum penetrating thick nacre. Horizontal field width = 480 um Figure 73: Entodesma chilensis. Pallial myostracum, radial fracture. Horizontal field width = 60m Explanation of Figures 74 to 79 Figure 74: Mytilimeria nuttalli. Periostracal surface. Horizontal field width = 160pm Figure 75: Mytilimeria nuttalli. Outer calcareous shell (outer shell split from inner at level just below prismatic) , longitudinal fracture. Outer homogeneous layer is at top of micrograph above a well de- veloped prismatic layer. In 5% sodium hypochlorite, 2 min. Horizontal field width = g90ym Figure 76: Mytilimeria nuttalli. Inner surface view of prismatic layer showing grainy remnants of granular homogeneous structure. Horizontal field width = 60pm Figure 77: Mytilimeria nuttalli. Inner surface of prismatic layer following split from granular homogeneous layer. Horizontal field width = 15 um Figure 78: Mytilimeria nuttalli. Calcareous shell, radial fracture beneath outer homogeneous layer. p, prismatic; n, nacre; m, myos- tracum. Horizontal field width = 170 pm Figure 79: Mytilimeria nuttalli. Prismatic layer, longitudinal frac- ture. Geometric selection is evident. Horizontal field width = 160m Explanation of Figures 80 to 87 Figure 80: Mytilimeria nuttalli. Medial shell, radial fracture. Outer homogeneous layer split off. In 5% sodium hypochlorite, 10 min. Pp, prismatic; m, myostracum; n, nacre. Horizontal field width = 55 ym Figure 81: Mytilimeria nuttalli. Sheet nacre, internal surface view. Surface exposed by splitting off of prismatic layer. In 5% sodium hypochlorite, 10 min. Horizontal field width = 3opm Figure 82: Mytilimeria nuttalli. Sheet nacre, inner surface view as in Figure 81. Horizontal field width = topm Figure 83: Mytilimeria nuttall:. Lenticular nacre, radial fracture. Horizontal field width = 19pm Figure 84: Mytilimeria nuttalli. Lenticular nacre, radial fracture. Horizontal field width = 1oym Figure 85: Mytilimeria nuttalli. Sheet nacre, surface view, showing newly deposited nuclei. Horizontal field width = 15 pm Figure 86: Mytilimeria nuttalli. Ring nacre, surface view near um- bo. Aragonite fibers from resilium are dispersed over this region. Horizontal field width = 604m Figure 87: Mytilimeria nuttall:. Myostracal band above sheet nacre. Horizontal field width = 15 ym ; if Page 208 THE VELIGER Vol. 23; No. 4 habitats, and the thick shelled species of rocky intertidal zones developed a thick periostracum and homogeneous layer. Mytilimeria, splitting from these forms, retained a thin homogeneous layer. Supporting evidence for this line- age based on soft part morphology is offered elsewhere (PREZANT, 1980a,b). Examination of the comparative shell ultrastructure of bivalves of the family Lyonsiidae has uncovered several questions in need of further study. Environmental influ- ence over shell structure during speciation has been well studied (TAyLor & LayMAN, 1972; TAYLOR, 1973). Less well known is the intraspecific influence of environ- ment. The ring nacre and prismatic wedge may both be examples, within the lyonsiids, which can be used to examine this question. The energetics of shell pro- duction remains a virtually untouched field. Variations in energy expended to produce various shell components could answer some questions concerning the ecology of many species. There may be limitations, based upon nutri- tion and energy expenditure, reflected in shell production that limit the distribution or growth of certain bivalves. Within the lyonsiids, for example, habitation of rocky intertidal zones may correlate with the evolutionary devel- opment of a thickened shell, which in turn may energet- ically necessitate the formation of a granular homogeneous layer. The ability to deposit this shell constituent in this type of stressful environment would call for a rapid crystal- lization (which Taytor (1973) hypothesized for the homo- geneous layer) at a low energy cost. The shell ultrastructure of molluscs may then be more than a tool for interpreta- tions of functional morphology. Close analysis of shell ultrastructure may also yield valuable clues to molluscan physiology, ecology and evolution. ACKNOWLEDGMENT I am most grateful for the loan or donation of the many specimens used in this study obtained from: Dr. J. A. Allen, University Marine Biological Station, Millport, Scotland; Dr. F. Bernard, Pacific Biological Station, Nanaimo, B.C.; Dr. K. Boss, Museum of Comparative Zoology, Harvard University, Boston, MA; Drs. D. D. Chivers and W. Lee, California Academy of Sciences, San Francisco, CA; Dr. G. Davis, Academy of Natural Sciences of Philadelphia, Philadelphia, PA; R. Dillon, University of Pennsylvania, Philadelphia, PA; R. Fay, Pacific Bio- Marine Labs, Venice, CA; Dr. R. Fernald, Friday Harbor Laboratories, University of Washington, Friday Harbor, WA; C. Gallardo, Instituto de Zoologie, Universidad Aus- tral de Chile, Valdivia, Chile; Dr. J. H. McLean, Los Angeles County Museum of Natural History, Los Angeles, CA; Dr. J. Rosewater, National Museum of Natural His- tory, Smithsonian Institution, Washington, D.C.; and Dr. R. Virnstein, Harbor Branch Foundation, Inc., Fort Pierce, FL. My sincere thanks are also extended to Drs. R. T. Abbott, M. R. Carriker, F. C. Daiber, R. E. Hillman, and N. W. Riser for critical reviews of the manuscript. Collection of many live specimens and the writing of this manuscript was greatly aided by the help and encourage- ment of F. Prezant. Thanks also to A. Ammon and P. Sav- age for typing the manuscript. Literature Cited Auber, Ropert R. 1974. Prefabrication of shell ornamentation in the bivalve Laternula. Lethaia 7: 43 - 56 ANSELL, ALAN Davip 1967. Burrowing in Lyonsia norvegica (Gmelin) (Bivalvia: Lyonsii- dae). Proc. malacol. Soc. London 37: 387 - 393 BartscH, PauL & HARALD ALFRED REHDER 1939. Mollusks collected on the presidential cruise of 1938. son. Misc. Coll. 98 (10): 1-18; plts. 1-5 Bosaitp, O. B. 1930. ‘The shell structure of the mollusks. Skr. kgl. Danske Viden- sk. Selsk., nat.-mat. Afd. 9 Rk. 112: 231 - 326; 15 plts.; 10 figs. CarRPENTER, WILLIAM 1847. Report on the microscopic structure of shells. Part II. Rep. Brit. Assoc. Adv. Sci., 17th meeting: 93 - 134 CarTER, JoszEPH GayLorD 1980. Environmental and biological controls on bivalve shell mineral- ogy and microstructure + Appendix IIB. Bivalve shell mineralogy and microstructure. In: D. C. Rhoads & R. A. Lutz (eds.), Skeletal growth of aquatic organisms: biological records of environmental change, vol. 1, Geobiology Series. Plenum Publ. Co., N. Y.: pp. 69-114, 627-874 Carter, JosepH Gaytorp & Nancy L. EICHENBERGER 1977- Ontogenetic calcite in the Veneracea (Mollusca: Bivalvia). Geol. Soc. Amer. Abstr., Ann. Meetg. Seattle, WA: 922 Ersen, Heinricu K. 1972. Uber die Bildung und das Wachstum von Perlmutter (On the formation and growth of nacre). Biomineralization 4: 16-46 Grécorre, CHARLES 1967, Sur la structure submicroscopique de la conchioline des mol- Smith- lusques. Biol. Rev. 42: 653 - 688 LowEnsTAmM, HEINz A. 1954. Factors affecting the aragonite:calcite ratios in carbonate-se- creting marine organisms. Journ. Geol. 62 (3): 284-322 Morcan, Ruona E. « JoHN A. ALLEN 1976. On the functional morphology and adaptations of Entodesma saxicola (Bivalvia: Anomalodesmacea). Malacologia 15 (2): 233 - 240 (15 July 1976) Mutve1, Harry 1970. Ultrastructure of the mineral and organic components of mol- luscan nacreous layers. Biomineralization 2: 49-72 1972a. Formation of nacreous and prismatic layers in Mytilus edulis L. (Lamellibranchiata). Biomineralization 6: 96 - 100 1972b. Ultrastructural relationships between the prismatic and nacreous layers in Nautilus (Cephalopoda). Biomineralization 4: 81 - 86 NarcHi, WALTER 1968. The functional morphology of Lyonsta californica Conrad, 1857 (Bivalvia). The Veliger 10 (4): 305-313; 7 text figs. (1 April ’68) Oszer ino, J. J. 1964. Observations on some structural features of the pelecypod shell. Mitt. naturf. Gesellsch. Bern 20: 1 - 63 Vol. 23; No. 4 THE VELIGER Page 299 Parmer, Rosert E. 1980. Observations on shell deformities, ultrastructure, and increment formation in the bay scallop Argopecten irradtans. Mar. Biol. 58: 15 - 23 Porov, S. V. a I. S. Barskow 1978. Shell structure of mollusks and its value in phylogeny and classi- fication. Malacol. Rev. 11: 152-153 (abstr.) PrezaANT, Robert STEVEN 19792. The structure and function of the radial mantle glands of Lyon- sia hyalina (Bivalvia: Anomalodesmata). Journ. Zool. London 187: 505-516 1979b. Shell spinules of the bivalve Lyonsia hyalina. 93: 93 - 95 1980a. Taxonomic re-evaluation of the bivalve family Lyonsiidae. The Nautilus: in press 1980b. The arenophilic radial mantle glands of the Lyonsiidae (Bival- via: Anomalodesmata) with notes on lyonsiid evolution. Malaco- logia 20 (2): 267 - 289 RuNNEGAR, BRUCE 1974. Evolutionary history of the bivalve subclass Anomalodesmata. Journ. Paleontol. 48 (5): 904 - 939 Scuroper, O. 1907. Beitrige zur Histologie des Mantels von Calyculina (Cyclas) lacustris Miller. Zool. Anz. 31 (15/16): 506-510 STANLEY, STEVEN M. 1970. Relation of shell form to life habits of the Bivalvia (Mollusca). Geol. Soc. Amer. Mem. 125: i-xiiit+296; plts. 1-40; figs. 1-48 7 (December 1970) The Nautilus Tay or, JoHN Davin 1973. | The structural evolution of the bivalve shell. 519 - 534 Paleontol 16: Taytor, Joun Davin, Wittiam James KeNnNepy # ANTHONY HALL 1969. The shell structure and mineralogy of the bivalvia. Introduction. Nuculacea-Trigonacea. Bull. Brit. Mus. Nat. Hist. Zool. Suppl g: 1-125; 29 plts.; 77 figs. 1973. The shell structure and mineralogy of the bivalvia. II. Lucina- cea-Clavagellacea. Conclusions. Bull. Brit. Mus. Nat. Hist, 22: 255 to 294; 33 text figs.; 15 plts. TayLor, JonN Davip & Martin LayMaNn 1972. The mechanical properties of bivalve (Mollusca) shell struc- tures. Paleontol. 15: 73 - 87 Wana, Koj1 1960. Crystal growth on the inner shell surface of Pinctada martensii (Dunker) I. Journ. Electronmicros, 9: 21 - 23 1961. Crystal growth of molluscan shells. Bull. Natl. Pearl Res. Lab. 7: 703 - 828 1972. Nucleation and growth of aragonite crystals in the nacre of some bivalve molluscs. Biomineralization 6: 141 - 159 Wa ter, Tuomas RicHARD 1980. Scanning electron microscopy of shell and mantle in the order Arcoida (Mollusca: Bivalvia). Smithson. Contr. Zool. No. 319: 1-55; 46 figs.; 1 table (16 June 1980) Wi.pur, Kart M. 1972. Shell formation in mollusks, pp. 103 - 145 In: M. Florkin & B. T. Sheer (eds.), Chemical Zoology, vol. VII: Mollusca. 567 pp.; Acad. Press, New York Wisz, SHERWOOD W,, Jr. 1969. Study of molluscan shell ultrastructures. Proc. 2nd Ann. Symp.: 207 - 216 Yonoe, CHARLES Maurice 1952. Structure and adaptation in Entodesma saxicola (Baird) and Mytilimerta nuttalli Conrad. Univ. Calif Publ. Zool 55 (10): Scan. Elect. Microsc. 499 - 45° Page 300 THE VELIGER Vol. 23; No. 4 Growth, Mortality, and Longevity of Certthidea decollata (Linnaeus) ( Gastropoda : Prosobranchia ) from Bayhead Mangroves, Durban Bay, South Africa VICTOR G. COCKCROFT' ann A. T. FORBES Department of Biological Sciences, University of Natal, Durban, Republic of South Africa (6 Text figures) INTRODUCTION Cerithidea decollata (Linnaeus, 1758) occurs extensively on South African and Mogambican shores between 34°S and 23°S (Day et al., 1952; Day, 1974). Like southeast Asian species of the genus (BERRY, 1972; SASEKUMAR, 1974), C. decollata alternately ascend and descend man- grove trees in rhythm with the tides (CAwSTON, 1922; MacnaE, 1963; Brown, 1971; Day, 1974). There is, however, little agreement on the exact periodicity of these movements in C’.. decollata and no information on any of the population parameters. These inadequacies prompted an in-depth study of C. decollata. In general, a workable index of an organism’s well- being may be found in its growth rate, survival rate and rate of reproduction. In gastropods the determination of size involves the estimation of shell size and its relation to the equivalent body mass. The estimation of growth and mortality are essential in understanding the dynamics of a species. In this context, the growth of cohorts of differ- ent sized Cerithidea decollata were monitored for one year. The losses of individuals from each cohort were used in estimating mortality. This study was conducted in Bayhead mangroves, Dur- ban Bay (29°51’S; 31°o1’E), South Africa. Durban Bay is an almost completely enclosed body of water extending inland for 5.6km. The mangrove lies on the southeast shore of the bay and increasing harbour development has reduced this once extensive stand to little more than a remnant of 0.5 km’. + Present address: Port Elizabeth Museum, P O. Box 13147, Hume- wood 6013, Republic of South Africa MATERIAL ann METHODS Aljl measurements of Cerithidea decollata were of maxi- mum width as decollation of the shell apex made length measurements unreliable. Growth was investigated in the g size classes between 4mm and 12mm in width. In smaller (< 10mm) snails, growth involves a rotation about the shell axis such that the dorsal surface becomes the ventral surface over time. Thus, any marking method, other than ringing the shell, would have made recapture difficult, resulting in large losses. As the shell surface available for marking was lim- ited and the number of colours needed for individual marking prohibitive, a cohort system of marking was used. At a spring high tide, 10 snails of each size class (co- hort) were collected and the snails of each cohort marked with a different colour acrylic paint. The maximum width of each snail within a cohort was measured, enabling later calculation of cohort mean size. Snails were subse- quently released at the base of a previously marked Avi- cennia marina tree. At 15 high spring tides over the next 370 days, all marked snails within a 35m radius of the “home” tree were collected, measured and subsequently released at the base of the “home” tree. When losses in a cohort approximated 30%, new indi- viduals were marked and added to give a new cohort. The new cohort mean size was always within 0.2mm of the mean of the previous cohort. The growth of this new cohort was then monitored. The number of new snails marked and the number re- covered at each measurement were recorded to allow an estimate of losses over the entire period. X Cohort Width (mm) — Vol. 23; No. 4 In addition to the field study, two laboratory studies were undertaken. The first monitored the growth of 4mm and 5mm width cohorts which after some time were no longer represented in the field study. In the second study the growth of 29 snails between 1.8mm and 4mm in width was investigated. Snails this small were only found in the mangroves 48 days before completion of the work reported here. THE VELIGER Page 301 RESULTS Growth The growth of the 9 cohorts of Cerithidea decollata monitored is shown in Figures 1, 2, and 3. The growth of 4mm, 7mm, 1omm, and 12mm width cohorts is plotted consecutively (Figure 1), as is that for cohorts 5mm, 8 Age (days) el 1500 Figure 1 The growth of 4mm (O——CO), 7mm (@ @), 1omm ((+—1)) and 12mm ({—§+-§) width cohorts of Cerithidea decollata plotted consecutively. s.e€. — mean vertical line; —~—I consecutive plot of old and newly constituted cohorts; -— ---- the theoretical von Bertalanffy growth curve for these data; - @----- theoretical width at day o Page 302 THE VELIGER Vol. 23; No. 4 mm, 11mm, and 12mm (Figure 2) and snails of 6mm, gmm, and 12mm maximum width (Figure 3). (Differ- ent cohorts of the same size class are also plotted consec- utively. ) Growth was seasonal, showing an acceleration during the summer months and a depression during the winter X Cohort Width (mm) months. This trend is especially obvious in the smaller size classes. Proportional summer growth decreases as size in- creases, while winter growth is relatively constant through- out the sizes (Figure 4). Derived von Bertalanffy growth equations (von BERTA- LANFFY, 1964) were used to fit curves to the growth data; o 500 Ie (Cese) 1000 1500 Figure 2 The growth of 5mm (Q——O), 8mm (@ @), 11mm consecutive plot of old and newly constituted cohorts; -— ---- the (OG (1) and 12mm (§§+—) width cohorts of Cerithidea decollata plotted consecutively. s.e€. mean vertical line — —t_ theoretical von Bertalanffy growth curve for these data; — @----- theoretical width at day o Vol. 23; No. 4 the equation for growth in width having the form: Wi, = Wi[1-e*"*?] where Wi, = width at time t Wi = asymptotic or maximum width k = coefficient of catabolism, a constant re- presenting the catabolism of body mate- rials per unit mass and time X Cohort Width (mm) THE VELIGER Page 303 t, == theoretical age at which the snail would have zero width with the same growth pat- tern as that observed in later life t = age of the snail Asymptotic width (Wi) can be estimated from a Ford-Wal- ford plot where the cube root of width at time t (Wi,4) is plotted against the cube root of maximum width at Age (days) LOO? 1500 Figure 3 The growth of 6mm (O——(), 9mm (@ @) and 12mm old and newly constituted cohorts; — ---- the theoretical von Ber- ((J——L)) width cohorts of Cerithidea decollata plotted consecu- tively. s.e. mean vertical line; — consecutive plot of talanffy growth curve for these data; -— @----- theoretical width at day o Page 304 75 50 Growth (Width) Increment % 4 5 6 7 THE VELIGER Vol. 23; No. 4 Figure 4 The % growth of nine width cohorts (4.0- 4.9mm to 12.0- 12.9 mm) of Cerithidea decollata in summer (@----- @) September to March inclusive; and in winter (@——@) April to August in- clusive 8 9 10 II 12 13 Snail Width (mm) time t-++ 1 year (Wi, + 1%) (Hanks, 1972). This yield- ed an asymptotic width of 16.45mm, using Bartlett’s method to fit the ‘best fit’ straight line (Sumpson et al., 1960). Size at day O was taken as 1.8mm, the size of the smallest snail found. The von Bertalanffy functions and estimates of Wi and size at day O were fitted to the raw data by computer. This yielded data that were an empirically ‘good fit’ to the raw data but gave a biologically unrealistic estimate of Wi (45.5mm). Subsequently, the Wi were recalculated for each set of data — those presented in Figures 1, 2, and 3 — as before but taking the time t tot +1 asa much shorter interval; z.e., not one year, but from each measurement to the next. This yielded Ford-Walford plots that showed summer and winter growth patterns; 7. é., sig- moidal type growth patterns. “Best fit’ straight lines to each of these plots, using Bartlett’s method, gave Wi estimates of 13.078mm for the data in Figures 1 and 2, and a Wi estimate of 14.6mm for the data in Figure 3. For each set of data log e (Wi— Wi.) was then plotted against t. As the age at any size class was not known, ages for the smallest size snails in each set of data had to be assumed. It was assumed that 4.7mm width snails were approxi- mately 150 days old, 5.4mm snails were approximately 200 days old, and 6.5mm snails were approximately 280 days old. These assumptions were based on a logarithmic curve (Y =0.1128-+ 4.5047 Ln X) fitted to a consecu- tive plot of the mean annual growth rate of each cohort. The logarithmic curve is significantly (p < 0.01; r=0.97) correlated to these data. The slope of the line fitted to these data by the least squares regression method gave estimates of k for each set of data. The value of t where it has an ordinate of 500 Survivors Fa (o} {eo} S 200 400 600 800 Time (days) log e Wi gave an estimate of t, in each case. The 3 von Bertalanffy growth equations obtained were as follows: 1. For growth of 4mm, 7mm, tomm, and 12mm width snails plotted consecutively (Figure 1): Wi, = 13.078 [1 — e087 “"74)] mm 2. For growth of 5mm, 8mm, 11mm, and 12mm width snails plotted consecutively (Figure 2) : Wit — 13078) [x—e @) S"25)[imm 3. For growth of 6mm, gmm, and 12mm width snails plotted consecutively (Figure 3) : Wi, = 14.6 [1-e° 7 “)] mm Values of t, are in years. The von Bertalanffy curves ob- tained from the 3 functions are plotted against their respective raw data in Figures 1, 2, and 3. _THE VELIGER Page 305 Figure 5 Survivorship curve for the nine width cohorts of Cerithidea decol- lata shown. For each cohort, the number of snails lost during the period it took that cohort to reach the next cohort -— at the mean annual growth rate - was calculated 1000 1200 1400 1600 Interpolation from the von Bertalanffy curves gave an estimated age of modal size Cerithidea decollata (12.0 to 12.9mm) of approximately 3 years (in all 3 equations). The predicted age at asymptotic width in all 3 cases was in excess of g years. No growth was observed in snails kept in the laboratory. Mortality Of the 125 Cerithidea decollata marked during the field study, 78 were recovered at the end of the period — 37.6% of those marked were lost. These losses can be attributed to 3 factors: movement of snails beyond the search area; loss of the marking paint; mortality. Page 306 As the maximum time between any 2 successive meas- urements was 43 days, it is unlikely from determined rates of dispersal (CockcroFT, 1978) that many snails moved further than 35m from the ‘home’ tree. The paint on all snails recovered was still clearly visible even after many months. Thus, if possible losses due to paint loss and move- ment are ignored, maximum losses due to mortality would approximate 38% /year. Examination of the survivorship curve (Figure 5) indicates constant age/size specific sur- vival between 4 mm and 12 mm size cohorts. ‘This, in turn, suggests that a mean annual mortality of approximately 38% can be applied to all sizes between 4mm and 12mm, inclusive. DISCUSSION No distinction between types of mortality was investigated in this study. Several broken marked shells were found in the vicinity of the experimental sites and the mangroves are littered with broken Cerithidea decollata shells, indi- cating considerable predation on this species. A 38% mortality for 4mm to 12mm width Centhidea decollata is low when compared with estimates in the liter- ature. Mortality in various species of Littorina has been estimated at between 70% and 90% (BorKowSKI, 1974), juvenile mortality often exceeding that of the adults (OpuM & SMALLEY, 1959; BorKowSKI, op. cit.). Com- FORT (1957) observed that high juvenile mortality and lower adult mortality is common in a number of mollusc species. Calculated production data for C. decollata sug- gest that the annual mortality of snails > 13mm is less than 38% and approximates 25% (CockcroFt, in prep.). This, and an increased mortality for snails 4mm and less in width would result in a ‘concave type’ of survivorship curve in contrast to Figure 5 and would correlate well with the longevity estimated from the growth data. Similar sized gastropods of the same species often show variable growth rates (WRIGHT, 1976; BRETOS, 1978) and this is often attributed to sex differences (BoRKow- SKI, op. cit.). A criticism of cohort growth measurement, as used in this study, is that new individuals marked and added to a cohort may be at different growth stages to the original marked individuals because of sex differences or other factors. However, by accepting the original and subsequent cohorts as separate and treating them as such, the possible resultant variation can be minimised. In a number of marine gastropods from temperate latitudes, growth decreases or ceases during the colder months of the year (VoHRA, 1970; PoorE, 1972; Bor- THE VELIGER Vol. 23; No. 4 KOWSKI, 1974; BRETOS, 1978). An increased growth in summer is usually associated with increased temperatures, consequently the marked growth of Cerithidea decollata in summer and its depression in winter was probably due to the 9°C difference in mean temperatures recorded in the mangroves between seasons (CocKcroFT, in prep.) Although all monitored sizes of Cerithidea decollata showed seasonally variable growth, there were clear dif- ferences between the annual growth rates of snails less than 10mm in width and those greater than 1omm in width. This is obvious when considering Figures 1 through 4, but particularly so if one considers the annual growth increment as a proportion of original ash-free dry mass (Figure 6). Proportional ash-free dry mass gain falls dramatically as size increases, only falling below 100% in sizes above 10.0mm in width. The growth of snails larger than 10mm consists of expanding and consolidating the shell lip, rather than adding whorls and increasing body size. Several authors have recorded differences between juvenile and adult gastropod growth rates (Comrort, 1957; OpUM & SMALLEY, 1959; VoHRA, 1970; PoorE, 1972; BoRKOWSKI, 1974), the difference usually being attributed to adult summer spawning (VoHRA, op. cit.; BorkKowskI, op. cit.). However, adult Haliotis iris show the same growth pattern as juveniles, suggesting that gonad production in this species is not the sole cause of the summer adult growth depression (Poore, op. cit.). The different growth accent or site of larger C. decollata, the concurrent decreased annual proportional growth and de- pression of the growth rate would appear to be directly associated with the approach to asymptotic size, suggest- ing that gonad production is not the only factor contribut- ing to depression of growth in adults. The processed growth data yielded Wi estimates of 13.078mm and 14.6mm. A Wi estimate of 13.078mm would seem too low but less than 5% of 6500 snails meas- ured were larger than 13.9mm. The greater Wi estimate (14.6mm) obtained for the 6mm, gmm, and 12mm snail growth plot (Figure 3) may result because juveniles originating late in a season and only attaining 6mm at the culmination of the growing season are thus a growth stage ahead of similar sized individuals originating early the following season. These former individuals would then grow to a larger size before expansion and consolidation of the shell lip commences. If this is accepted, it would suggest that a population may have several asymptotic widths, depending on the stage of a growing season at which a juvenile is recruited. Assumptions had to be made as to the age of 4mm, 5 mm, and 6mm size classes and consequently the fit of the /year (X 10) X %a-f d. w. gain Vol. 23; No. 4 THE VELIGER 4 5 6 7 8 9 10 II Maximum Width (mm) Figure 6 Annual proportional (%) growth rate of nine width cohorts (4.0 - 4.9mm to 12.0-12.9mm) of Cerithidea decollata calculated curves and any interpolations from these must be viewed with caution. Any change in the assumed age of the smaller snails would cause a displacement of the rele- vant calculated curve. Fortunately, the similarity of the 3 calculated functions and interpolations made from them suggest that the basic age assumptions were not grossly in error. All 3 curves predict a similar size at day O (1.77mm, Figure 1; 1.72mm, Figure 2; 1.2mm, Figure 3) and all Page 307 correspond fairly well to the size of the smallest snail found (1.8mm). The 3 curves predict a size of 4mm will be attained at 96, 117, and 118 days (Figures 1, 2, and 3, respectively) after appearance at day O. Similarly, the predicted time to reach a size of 6mm ranges between 194 and 224 days. These results suggest a good correlation between the curves. Interpolation from the von Bertalanffy curves gave an estimated age of modal size Cerithidea decollata (12.0 to 12.9mm) of approximately 3 years (for all 3 functions). The predicted age at asymptotic width in all 3 cases was in excess of g years. This is close to the 12 year longevity of certain wild populations of prosobranchs (Rao, 1937). The whelk Dicathais orbita has a mean longevity of 5 years and an estimated maximum age of 19 years (PHIL- LIPS & CAMPBELL, 1974). FRANK (1965) has estimated the maximum age of Tegula funebralis to be between 24 and 30 years. PoorE (1972) estimated the longevity of Haliotis tris as more than 10 years. Comrort (1957) has estimated the longevity of a number of natural gastropod populations to range between 1 and 13 years. It is obvious that longevity varies markedly between species, the esti- mated longevity of C. decollata falling well within the range. Apparent copulatory behaviour was observed between individuals in September and October in 2 successive years (personal observation). Despite intensive investigation, however, no egg masses were found and no juvenile snails were found in dissected adults. Consequently, an absolute growth curve for Cerithidea decollata cannot be at- tempted as yet,since no absolute width/age relationship is known. Literature Cited Berry, A. J. 1972. The natural history of West Malaysian mangrove faunas. Malay. Nat. Journ. 25 (2): 135-152 BEerTALANFFY, LupwiG VON 1964. Basic concepts in quantitative biology of metabolism. Helgo- lander Wiss. Meeresunters. 9: 5 - 37 BorKowskI, THomas V. 1974. Growth, mortality, and productivity of south Floridian Littor- inidae (Gastropoda: Prosobranchia). Bull. Mar. Sci. 24: 409 - 438 Bretos, MARTA 1978. Growth in the keyhole limpet Fissurella crassa Lamarck (Mol- lusca : Archaeogastropoda) in northern Chile. The Veliger 21 (2): 268 - 273; 5 text figs. (1 October 1978) Brown, D. S. 1971. Ecology of Gastropoda in a South African mangrove swamp. Proc. malacol. Soc. London 3g: 263 - 279 CawstTon, F. G. 1922. Some molluscan inhabitants of the Natal lagoons. So. Aff. Journ. Sci. V. XIX: 277-279 Page 308 THE VELIGER Vol. 23; No. 4 CocxcrortT, Victor G. 1978. Ecology of Cerithidea decollata Linn. (Gastropoda: Prosobran- chia) in Bayhead mangroves, Durban Bay, South Africa. M. Sc. thesis, Univ. Natal, Durban, So. Africa Comrort, ALEXANDER 1957. The duration of life in molluscs. Proc. malacol. Soc. Lon- don g2 (6): 219-241; 2 figs. Day, Joon HemswortH 1974. | The ecology of Morrumbene estuary, Mogambique. Trans. roy. Soc. So. Afr. 41: 43 - 97 Day, Joun Hemsworth, N. A. H. Mivrarp « A. D. Harrison 1952. The ecology of South African estuaries. Part 3. Knysna, a clear open estuary. Trans. roy. Soc. So. Afr. 33 (3): 367-413 Hangs, J. 1972. Growth of the African elephant (Loxodonta africana). E. Afr. Wildl. Journ. 10: 251 - 272 Macnag, WILLIAM 1963. | Mangrove swamps in South Africa. Journ. Ecol. 51: 1-25 Ovum, Eucene Pueasants & A. E. SMALLEY 1959. Comparison of population energy flow of a herbivorous and a deposit feeding invertebrate in a salt marsh ecosystem. Proc. Natn. Acad. Sci. U. S. A. 45: 617 - 622 Poorg, G. C. B. : 1972. Ecology of New Zealand abalones, Haliotis species (Mollusca: Gastropoda). g. Growth. New Zeal. Journ. mar. freshwat. Res. 6 (4): 534-559 SasEKumMaR, A. 1974. Distribution of macrofauna on a Malayan mangrove shore. Journ. Anim. Ecol. 45 (1): 51-69 Snapson, Gzorcz GayLorp, ANNE Rog & RicHarp C. LEwonTIN 1960. Quantitative zoology. rev. ed., viiit44o pp.; illust. Har- court, Brace & Co., New York Vonra, E C. 1970. Some studies on Cerithidea cingulata (Gmelin, 1790) on a Singapore sandy shore. Proc. malacol. Soc. London gg: 187-201 Wricut, Mary BercENn 1976. Growth in the black abalone, Haliotis cracherodii. The Veliger 18 (2): 194-199; 4 text figs. (1 October 1976) Vol. 23; No. 4 THE VELIGER Page 309 Effects of Temperature and Salinity on the Embryological Development of Murex pomum Gmelin, 1791 EUNA A. MOORE Department of Biology, University of the West Indies, Barbados AND FINN SANDER Bellairs Research Institute, St. James, Barbados (2 Plates) INTRODUCTION THIS Is THE FOURTH in a series of papers (SANDER & Moore, 1978; Moore & SANDER, 1978; SANDER & Moorz, 1979) that seeks to clarify the physiological ecology of Murex pomum Gmelin, 1791. In the earlier papers the developmental and respiratory norms were established and the effects on respiration of adults caused by varia- tions in temperature and salinity were investigated, as well as their tolerance limits to these single factors. In most animal organisms, however, especially those that develop without post-natal care, the larval stage is the most critical for species survival. Murex pomum pro- vides some larval protection in the encapsulation of the eggs and retention of the larvae until late pediveliger or early protoconch stage, but despite this protection mortal- ity of larval and immediate post larval stages is of the order of 98-99% under normal conditions (SpicHT, 1975; Moore & SANDER, 1978). Although organisms are usually evolutionarily adapted to their environment, many can exist in the fiducial limits outside their optimal range. In our earlier studies it was postulated that developmental and hatching times of Murex pomum might be functions of temperature, and by extrapolation, of latitude. McLaren (1965) advanced the case that at times many poikilotherms “found food equal to, or in excess of their needs; at these times developmen- tal rate may be strictly related to temperature.” Though this postulate ignores the effect of other stress factors the tenet is applicable to present experiments. Some theoret- ical considerations of these effects of temperature are also given in a review by MarcaLfF (1955). This is an era when there is a great surge in develop- ment of coastal areas for recreational, industrial or aqua- cultural purposes. According to KinNneE (1971), major changes in temperature and salinity conditions of large areas due to changes in geomorphy, man-made construc- tions or effluents, may lead to death at the species or eco- system level (important studies on the effects of progres- sive reductions in the salinities of bays regained from the sea are being conducted by Dutch scientists). In this exercise eggs of Murex pomum deposited at ambient conditions were subjected to different conditions of temperature and salinity in order to test the vulner- ability of the species to changes in these two environmental parameters. ACKNOWLEDGMENTS Messrs. Peter Farnum and Irwin Skeete provided tech- nical assistance in this investigation. The work was sup- ported jointly by a grant from the Research and Publica- tions Committee of the University of the West Indies to the first author and a grant in aid of research from the National Research Council of Canada to the second author. Page 310 THE VELIGER Vol. 23; No. 4 MATERIALS anp METHODS Two different sets of specimens of Murex pomum collected from St. Vincent in June, 1978, and February, 1980, were transferred to Barbados and, as in the previous studies, maintained in as near normal conditions as possible. Mem- bers of the first set laid several batches of eggs between July and September and those of the second lot deposited large masses of oothecae between March and April. From these depositions selected oothecal masses were treated as follows: (1) Each egg mass was blotted and weighed. (2) Subsamples of the mass were weighed and the egg cases in each sample counted. The average number of egg cases in these subsamples gave an estimate of the number in the total mass. This also gave the average weight per egg case. (3) Similarly, numbers of eggs in subsamples of egg cases were counted and the total egg number esti- mated from these. (4) One portion of the oothecal mass was suspended in a mesh basket in the water table so that eggs could develop normally. (5) Other sample portions were put in experimental chambers in sea water at temperatures 16, 19, 22, 25, 28, 31, 34, 37° C and salinities of 22, 25, 28, 31, 37, 40, 43 and 46% . The water in these containers was changed regularly. (6) The course of pre-hatching, hatching and post- hatching events under each condition was followed. The developmental pattern of the species under ambient conditions had previously been determined (Moore & SANDER, 1978) but repeat experiments were conducted for the purposes of confirmation and as a more immediate standard against which to measure the extent of departure consequent on the introduced physiochemical variations. Based on the established norm, the following schedule of easily visually determined events was set up and used as references: A. Egg deposition. Timing here is important for char- acterisation of the time/developmental sequence. B. Darkening of egg mass. This takes place by the 18™-23"" day by which time the shell has 2} whorls, most of the organs have developed, a foot has been formed, the four-lobed velum is formed and the larvae are quite active. Darkening results from development of orange and brown pigmen- tation in the shell and other structures. C. First sign of veligers in water. These appear on the 23"°-24™ day and swim very actively with the velum. D. Emergence of pediveligers and commencement of successful hatching, approximately the 26™ day. The foot is then the more active organ for mobility. E. Hatching peak 32*%”-33" day. F. End of hatching—39™-40™ day. RESULTS The results of experiments 1-6 as set out in Materials and Methods are given in Tables 1, 2, 3, 4 and 5 and Figures I, 2,3 and 4. Spawning times: Recorded spawning times of March 1976 and 1980, April 1976, 1980, June 1976, July, August and September 1978 and October 1977 strongly suggest year-round reproductive activity in Murex pomum and would agree with the observations of BANDEL (1976) off Santa Marta, Columbia. Egg numbers: It is to be noticed from Table 1 that the range of egg numbers and average number of eggs per capsule differ significantly from that reported by Moore & SANDER (1978). This would mean that the ratio of nurse eggs per developing embryo would also be significantly different. But all the other statistics show that the adult specimens of the experimental lot are of larger size (includ- ing a record size of 13.2 x 7.6cm), that they deposited larger size capsules and that the average capsule weight was greater. The significant point is that the average num- ber of hatchlings is of the same order as in the earlier report. It is therefore only the food supply in the capsule that is increased. Normal developmental pattern: The sequence and time of developmental events at ambient conditions (28° C and 34%o) described earlier were confirmed in detail in these two latter runs, further underscoring the norm for the spe- cies. (Tables 2 and 3). Temperature effects: ‘Table 2 shows most dramatically that the embryological process is sharply de-limited within a span of 10°C, well inside the tolerance limits of the Explanation of Figures 1 to 3 Figure 1: Condition of eggs of 24 days at 19°C temperature Figure 2: Larva at normal 24-day stage Figure 3: State of deterioration of eggs after 40 days exposure at 19°C temperature Tue VE.icER, Vol. 23, No. 4 [Moore « SANDER] Figures 7 to 3 Figure 1 Figure 2 Figure 3 Vol. 23; No. 4 THE VELIGER Page 311 Table 1 Summary of data on the test animals and spawn. H, L, T and W denote height, length, thickness and width respectively. Collection Average Average Average Average Average Average site size of adults size of capsules weight of Number of eggs Number of hatchlings © Number of of in mm (N = 60) in mm (N = 20) capsules per capsule per capsule nurse eggs samples L W H W At in g (N = 182) (N = 100) (N = 100) per embryo St. Vincent 11.0 6.5 8.7 9.2 2.3 0.0751 512 15 34.5 Range (9.9-13.2) (5.9-7.6) (28-1092) (6-28) Table 2 Temperature Effects Day of occurrence of events under experimental conditions Major Developmental Events 16° 19° 220 252 28° 312 34° 372 A. Egg deposition 1 1 1 1 1 1 1 1 B. Darkening of capsules — — 26 21 18 14 — - C. Emergence of veligers with velum — — 29 26 23 20 _ - D. Pediveligers = = 32 30 26 23 -- _ E. Hatching peak - — 40-45 38-43 32-33 28 — — FE. End of hatching — - 50 45 38-39 35 — — Table 3 Salinity Effects ’ Day of occurrence of events under experimental conditions Major Developmental Events 22% 25% 28% 31% 34% 37% 40% 43% 46% A. Egg deposition i 1 1 1 1 1 1 1 1 B. Darkening of capsules — 24 18 18 18 19 23 — _ C. Emergence of veligers with velum — 26 25 23 23 24 28 = — D. Pediveligers — 29 28 26 26 28 32 = = E. Hatching peak - 36-42 33-35 32-34 32-33 32-39 33-42 = = F. End of hatching — 45 44 44 38-39 46 46 _ = adults of 10-37° C. Further, within this span a 3° C change exposed to 19° C for 25 days and then returned to ambient in temperature produces quite noticeable differences in the conditions failed to develop. timing of the events. Eggs exposed to temperatures of 19° C and 16°C showed only first and second cleavage; pre- Salinity effects: Although the chosen intervals of vari- sumably these events took place between deposition time tions in salinity are the same as those for temperature, and the time of transfer to experimental conditions. Fig- there is no quantitative conversion scale between the two ures 1 and 2 compare the eggs at 19° C after 24 days expo- physical factors so that the tabular appearance of a greater sure and a larva developed at ambient conditions of the tolerance to salinity could be superficial; however, it does 24th day stage; while Figure 3 shows eggs at 19° C after appear though that the eggs are less sensitive to salinity 40 days exposure where deterioration is obvious. Eggs differences than to temperature changes. Page 312 THE VELIGER Vol. 23; No. 4 Eggs exposed to salinities outside the effective range showed disruption. The more important effects of salinity seemed to have been exerted at stage C which corresponds to the time when the escape windows are opened and there would be influx of the external fluid. The salinity differ- ence would then be directly contingent on the larvae. It was particularly noticeable that at the extremes of the scale the larvae, having reached the normal pediveliger stages, tended to remain inside the capsule rather than make the mass exodus as is characteristic of the normal. Survival rate over the next two days of hatchlings at 25%. and 40%. was extremely low. DISCUSSION Egg numbers: It was pointed out in an earlier study (Moore & SANDER, 1978) that the obtained ratio of nurse eggs per hatchling (3:3: 1) was low in comparison to other studies—those ranging from 5 for Murex torrefactus (CERNOHORSKY, 1955) to 91.4 for M. quadrifons (KNupb- SEN, 1950). The present ratio falls near to the median of these quotations. The point of importance in this set of statistics is that despite the larger number of nurse eggs the number of hatchlings remains roughly the same. One interpretation of this observation is that the nurse eggs are unfertilised eggs destined as food supply or eggs with some genetic aberrations which frustrate normal develop- ment. In several of the capsules opened immediately after the pediveligers had emerged, from 20 to 77 nurse eggs were found remaining in the capsules, suggesting that the larvae had had more than enough food. It is also signif- icant that these showed first, second or no cleavage at all. McLarEN (1965) has pointed out that in some marine organisms that show indeterminate growth, their growth rates and final sizes are functions of food supply while their development rates may be relatively unaffected. The work of SpicHT (1976), where his hatchlings survived for more than a month without food, points to one of two inter- pretations: either that the species has a high resistance to starvation or that the young have ingested enough nourish- ment from the supply provided in the capsules to last for a long period and yet show growth. If spawning time or season is a genetically predicated event, then number of eggs and supportive material will be a function of food availability in the period immediately prior to the spawn- ing session. However, from previous and present data it can reason- ably be concluded that larger animals deposit more eggs, the greater number of eggs constituting an increased food supply for the larvae - not increased fecundity as such, where fecundity is interpreted to mean number of viable offspring — but is rather an investment in the survivability of the offspring. If the SpicHT (1975) hypothesis (that sur- vivability in prosobranch snails is a function of size, hence of growth rate, and describes a curvilinear relationship) holds, then hatchlings of a larger initial size and much faster growth rate as depicted in Tables 4 and 5 and Fig- ures 4 and 5 should have distinctly enhanced chances of survival. Temperature/salinity effects: As is usual for marine invertebrates, the rate of embryonic development of Murex pomum appears to be both salinity and temperature de- pendent. Our data show a direct relationship between temperature and developmental rate (Table 2). The latter was roughly a linear function of this factor so that the Table 4 Size measurements (in mm) of 10 hatchlings from present study and average measurements compared with those of earlier study. L = length; W = width. Hatchlings L WwW 1 2.30 1.92 2 2.30 1.92 3 2.69 2.30 4 2.69 2.30 5 2.69 2.30 6 2.69 2.30 7 2.84 2.30 8 2.88 2.32 9 2.92 2.35 10 2.96 2.35 Present avg. 2.69 2.23 Previous avg. 1.59 1.22 Explanation of Figures 4 and 5 Figure 4: Variation in size and shell development of 5 representa- tive 4-month old juveniles ; Figure 5: Largest of the 4-month old juveniles showing finely fluted borders delineating varices THE VELIGER, Vol. 23, No. 4 [Moore « SANDER] Figures 4 and 5 Figure 5 Vol. 23; No. 4 Table 5 Size measurements (in mm) of 10 juveniles of 4 months compared with one of same age from earlier study. L = length; W = width. Number of L WwW corrugated whorls 9.0 3) 3.5 8.0 4.6 3.0 7.8 4.6 Ina) 7.1 4.0 2.0 6.5 3.9 2.0 6.0 3.5 2.0 6.0 3.3 1.8 approx. 6.0 3.4 1.8 approx. 5.9 3.5 2.0 5.9 3.2 1.7 approx. Previous sample 3.3 1.9 <1 approximate time of first hatching can be predicted from the prevailing temperature during early development. The apparent lesser sensitivity of the zygotes and em- bryos to salinity might be explained by the low perme- ability nature of the material of the oothecae which makes it a fairly effective osmotic barrier. Furthermore, if the material of the egg and the surrounding albumin is largely of hydrophobic proteins, then no appreciable osmotic movement will be set up except at the extremes of the experimental range. If this is the case,then temperature, being more pervasive, will show more definitive effects. There are numerous examples of temperature and/or salinity dependence of mollusc developmental times (e.g., FEDERIGHI, 1931; HASKIN, 1935; COLE, 1942; McGowan, 1954 (cited in McMaHon & SUMMERS, 1971); CARRIKER, 1955; GANAROS, 1958; HAMaBE, 1960; FiELDs, 1965 (cited in McMaHon & SUMMERS, 1971); CHOE, 1966; CaLa- BRESE, 1969; HAGERMAN, 1970; McMaHoNn & SUMMERS, 1971; Hrs-BrENKo, CLAUS & Busic, 1977) and embryo lethal limits have been determined for a number of species. It is not particularly remarkable that the effective range of temperature and salinity for viability of embryos and young is well within that of the described tolerance limits of the adults. In the first instance, exposure of adults to these extremes did not exceed 48 hours while developing larvae were exposed for upwards of 60 days and reference to the survival tables (SANDER & Moore, 1979) will show that ranges incurring no fatalities for the adults were 15° THE VELIGER Page 313 to 32° C temperature and 19 to 46%, salinity, respectively. CALABRESE & Davis (1970) and others have demon- strated a greater sensitivity to environmental conditions in early embryonic stages of molluscs than in adults, proving the larval stage to be the critical link in the life cycle. The proximate and ultimate effects of temperature and salinity on the respiratory physiology of Murex and other organisms have been discussed at some length (SANDER & Moore, 1977 & 1979), but of all the systems likely to be affected the enzymic one is possibly the most critical in embryological development. RNA synthesis, protein syn- thesis, and cell division are the prime activities during early embryogenesis and morphogenesis. These involve nuclear transcription, and translation at sites of synthesis in the cell. The control of cellular activities at the levels of tran- scription and translation are considered fundamental. Both the synthetic and control activities are multi-step proc- esses mediated by enzymes whose effectivity are tempera- ture-linked, not only for the energy of activation but for optimal operative range. It has been shown, for example, in sea urchin eggs that ‘maternal’ mRNA - that made during o6genesis — is stored in an active form. After fertilisation, and before new transcription begins, the ‘maternal’ mRNA is translated at a high rate (EBERT & SuSSEX, 1970). This rate could be temperature sensitive. Osmotic imbalances could conceivably also affect the mo- bility of activating ions required for the initiation of amino acids polymerisation. The McLaren postulate, mentioned earlier, goes on to propose that final adult size, and more particularly fecun- dity, is a function of temperature during development. McLaren formulated the equation (V or S=a(T-a)”) incorporating the B&LEHRADEK’s (1935) temperature function in which S=size, V =the rate of metabolic function and a, b, and c are constants. By this token, if food supply is sufficient, the average individual size and size of a population of Murex should be characteristic for the temperature operative at spawning time. In other words, mean size and population size should show a normal distribution curve over the latitudinal temperature range of 22° to 31° C. This possibility could bear investigation as at present there are not enough data to support or disprove this hypothesis. The tolerances established in the present study for Murex pomum development may, of course, be further modified in the natural marine environment, where other factors may also affect the salinity and temperature toler- ances of these snails. Generally, though, the area of distri- bution of Murex pomum is one in which both salinity and temperature allow the successful spawning, subsequent gamete development and growth, and survival of the lar- Page 314 THE VELIGER _ Vol. 23; No. 4 vae. The measured tolerance limits (Tables 2 and 3) should, therefore, reflect the broad area of distribution of this species in nature, and, indeed, the known range from South Carolina in the south-eastern United States to Trin- idad in the West Indies (ABzort, 1958; HUMPHREY, 1975) confirms this. Temperatures and salinities in open coastal areas in this extended region are within the tolerance lim- its determined here. The normal hazards to planktonic larvae, which may be retained in estuaries or carried into areas of stagnation, where they are subjected to extremely varying conditions of temperature or salinity, or both, is not expected to pose a serious problem for Murex pomum, which undergoes direct development to the crawling stage (Moore & SANDER, 1978). Literature Cited ApsotTt, Ropert TucKER 1958. The marine mollusks of Grand Cayman Island, British West In- dies. Monogr. Acad. Nat. Sci. Philadelphia 11: i-viit1-138; 11 maps; 5 plts.; 7 text figs. (31 December 1958) Banpex, Kraus 1976. Morphologie der Gelege und Gkologische Beobachtungen an Muriciden (Gastropuda) aus der siidlichen Karibischen See. Verh. Naturf. Ges. Basel 85 (1/2): 1-92; 20 text figs. (31 March 1976) BELEHRADEK, J. 1935. | Temperature and living matter. Borntrager, Berlin; 277 pp. Carasrese, ANTHONY 1969. Individual and combined effects of salinity and temperature on embryos and larvae of the coot clam, Mulinia lateralis (Say). Biol. Bull. 197 (3): 417-428; 2 figs. CaraBrese, ANTHONY & Harry Caru Davis 1970. Tolerances and requirements of embryos and larvae of bivalve mollusks, Helgolander wissensch. Meeresunters. 20: 553 - 564 Carrixer, MELBOURNE ROMAINE 1955- Critical review of biology and control of oyster drills Urosalpinx and Eupleura. U.S. D. I. Special Sci. Reprt., Fish. No. 148: 1 - 150 CzrnoHorsky, WALTER OLIVER 1966. The radula, egg capsules and young of Murex (Chicoreus) torre- factus Sowerby (Mollusca : Gastropoda). The Veliger 8 (4): 231 to 2393; 6 text figs. (1 April 1966) Cuoer, SANG 1966. On the eggs, rearing, habits of the fry, and growth of some Cephalopoda. Bull. mar. Sci. 16: 390 - 348 Coz, Hersert AuBREY 1942. The American whelk tingle, Urosalpinx cinerea (Say), on British oyster beds. Journ. mar. biol. Assoc. U. K. 25: 477-508 Exsert, James D. a Ian M. Sussex 197¢. Interacting systems in development. Holt, Rinehart & Wins- ton, Inc., New York; 136 figs.; 121 photographs; 338 pp. Protoplasma Monogr. No. 8. FEDERIGHI, HENRY 1931. Studies on the oyster drill (Urosalpinx cinerea Say). Bull. U. S. Bur. Fish. 47 (4): 85-115 (January 1931) FizLps, W. Gorpon 1965. The structure, development, food relations, reproduction and life history of the squid Loligo opalescens Berry. Calif Dept. Fish Game. Fish Bull. 131: 108 pp.; 59 text figs. Ganaros, ANTHONY FE 1958. On the development of early stages of Urosalpinx cinerea (Say) at constant temperatures and their tolerance to low temperatures. Biol. Bull. 114 (2): 188-195; 4 photogr. Hacerman, Lars 1970. The influence of low salinity on survival and spawning of Elysia viridis (Montagu) (Opisthobranchia, Sacoglossa). Sarsia 42: 1-6; 1 fig.; 3 photogr. Hamase, Mototsusu 1960. Observations of early development of a squid, Loligo bleekeri Keferstein. Ann. Reprt. Japan. Sea Reg. Fish Res. Lab. 6: 149 - 155 Haskin, Haro.tp H. 1935- Investigations on the boring and reproduction activities of oys- ter drills, Urosalpinx cinerea and Eupleura sp. Unpubl. Reprt. U. S. Bur. Fish. Hrs-Brenxo, M., C. Craus « S. Busic 1977. Synergistic effects of lead, salinity and temperature on embry- onic development of the mussel Mytilus galloprovincialis. Mar. Biol. 44: 109-115; 6 figs.; 2 photogr. Humpgrey, M. 1975- Seashells of the West Indies. Glasgow; 351 pp.; 32 plts.; 20 figs. Kinng, OTTo 1971. Marine ecology. Vol. 1, prt. 1. Wiley - Interscience, New York. KNUDSEN, JorGEN 1950. Egg capsules and development of some marine prosobranchs from tropical West Africa. Atlantide Reprt. 1: 85-130; 31 figs.; 7 photogr. Marcaer, RaMoNn 1935. Temperature, dimensions y evolucion. Barcelona 19: 13 - 94 McGowan, JoHN ARTHUR 1954. Observations on the sexual behavior and spawning of the squid Loligo opalescens at La Jolla, California. Calif. Fish & Game 4o: 47-54 McLaren, Ian A. 1965. Some relationships between temperature and egg size, body size, development rate, and fecundity of the copepod Pseudocalanus. Limnol. Oceanogr. 10 (4): 528-538; 3 figs.; 1 photogr. McManovn, J. J. « W. C. Summers 1971. | Temperature effects on the developmental rate of squid (Loligo pealet) embryos. Biol. Bull. 141: 561 - 567; 2 figs. Moore, Euna A. & Finn SANDER 1978. Spawning and early life history of Murex pomum Gmelin, 1791. The Veliger 20 (3): 251-259; 2 plts.; 2 text figs. (1 January 1978) SANDER, Finn & Euna A. Moore 1978. | Comparative respiration in the gastropods Murex pomum and Strombus pugilis at different temperatures and salinities. Comp. Biochem. Physiol. 60A: 99-105; 4 figs. 1979. | Temperature and salinity tolerance limits of the marine gastro- pod Murex pomum. Comp. Biochem. Physiol. 64A: 285 - 289; 2 figs. SricHT, Tom M. 1975. Ona snail’s chance of becoming a year old. Oikos 26: 9-14 1976. Hatching size and the distribution of nurse eggs among proso- branch embryos. Biol. Bull. 150: 491 - 499; 3 figs. William Collins & Sons Ltd., Proc. Inst. Biol. Apl. Vol. 23; No. 4 THE VELIGER Page 315 Redescription of a Rare North Atlantic Doridacean Nudibranch, Aegires sublaevis Odhner ' T. E. THOMPSON Zoology Department, University of Bristol, England (2 Text figures) INTRODUCTION In June 1979, Dr. W. Sterrer gave me for study a living nudibranch, 9mm in length, which was part of a collec- tion of 5 individuals with spawn found in 2m depth at North Rock, one of the furthest offshore localities in Ber- muda. These nudibranchs had been found on a yellow sponge (Clathrina sp.), the coloration of which they closely matched. Three more specimens of this unusual nudi- branch, previously unrecorded from Bermuda, were later given to me by Dr. K. B. Clark; they had been preserved in Bermuda in July 1979. These formed the basis for a histological study carried out on my return to Bristol. This material proved to match fairly closely the type description given by ODHNER (1932) of a species from Tenerif in the Canary Islands, Aegires sublaevis, based upon a single 11 mm individual. Ros (1976) confirmed the presence of this species in the Canary Islands and later (Ros, 1977) published a colour photograph showing it living on the sponge Clathrina coriacea on Fuerteventura. Meanwhile, Norpsieck (1972) had introduced a new generic name for Odhner’s species, Serigea (type A. sub- laevis Odhner), but without a proper diagnosis and with- out explaining why a new genus should be needed. Aegires sublaevis is an unusually interesting doridacean, with an amphiatlantic distribution and, moreover, it dis- plays links between the typically Atlantic genus Aegires Lovén, 1844 (type Polycera punctilucens Orbigny, 1837) and the equivalent Indo-Pacific genus Notodoris Bergh, 1875 (type N. citrina Bergh, 1875). The present redescrip- tion may facilitate discovery in other parts of its range. DESCRIPTION External Features (Figure 1). The body of the gmm specimen was tough and hard in life, belying its frail ap- ’ Contribution 857 from the Bermuda Biological Station rhinophore branchial lobe Figure 1 Diagnostic features of Aegires sublaevis, gmm long, North Rock, Bermuda, June 1979. (a) from the dorsal aspect; (b) ventral view of the head; (c) side view of the rhinophore; (d) camera lucida drawing of a representative radular tooth (row 2 from the growing end, tooth 12 from the mid-line) Page 316 pearance. The colour was pale lemon yellow, with a pat- tern of dark brown spots as shown in Figure 1 (a). The slender body bore scattered low mamillae. A low ridge was evident mid-dorsally, bifurcating anteriorly and part- ing again at its rear, some little way behind the rhino- phores. The posterior ridges led to the gills, 3 in number. Each gill was protected by a tough branchial lobe, and con- sisted of simple lamellae. The smooth rhinophoral ten- tacles (Figure 1 (c)) each issued from a pit located in the centre of a prominent antero-lateral pallial flap. The metapodium was long and slender, occupying about one half of the total body-length. Ventrally, the propodium was undivided (not bilami- nate); the rounded head lacked oral tentacles. The spawn, like the parent, was lemon yellow in colour. Anatomy and Histology. The ovotestis and the anterior genital mass were well developed. Serial sections showed median dorsal jaw I a a 3 ne io buccal mass musculature Figure 2 Transveree section through the buccal mass of Aegires sublaevis THE VELIGER Vol. 23; No. 4 that the terminal part of the vas deferens was lined by numerous chitinous hooks, probably becoming external on eversion of the intromittent organ. The anus and the adjacent nephroproct were behind the crescent of gills. Two features of importance were observed in the buccal mass. First, there were large numbers of complex glands opening into the oral canal; second, there was a substantial median dorsal thickening of the chitinous lining of the buccal canal. This median structure may be presumed to act in concert with the radula during feeding and warrants the appellation of a jaw (Figure 2). The radular formula was 16 x 13.0.13 (Odhner’s 11mm specimen had the formula 17 x 17.0.17). All the teeth were blunt hooks, 105 wm in the longest dimension (Figure 1 (d)). DISCUSSION Knowledge of this species extends considerably our understanding of the genus Aegires, which typically ex- hibits numerous soft pallial papillae and a pliable body. Aegires sublaevis shows interesting annectent features by which the genus may be compared with the equivalent Indo-Pacific Notodoris. It resembles Notodoris (e.g., N. gardineri Eliot, 1906, recently redescribed by THomMPson (1975)) in its inflexible body, but differs in its possession of a median jaw and of simple radular teeth (bifid in the Indo-Pacific genus). Both genera possess spines on the vas deferens. In conclusion, it may be noted that the genus Sertgea Nordsieck, 1972 is neither properly constituted (lacking a diagnosis) nor necessary. Literature Cited Norpsizck, Fritz 1972. Die europdischen Meeresschnecken (Opisthobranchia mit Pyrar midellidae; Rissoacea). Stuttgart, Gustav Fischer Verlag; xiii+397 pp.; 4 color plts.; 37 b&w. plts. Opune_r, Nits HJALMAR 1932. Beitrage zur Malakozoologie der Kanarischen Inseln. Lamelli+ branchien, Cephalopoden, Gastropoden. Ark. f. Zool. 2gA (14): 1-116; plts. 1, 2 Ros, JoANDOMENEG 1976. Sistemas de defensa en los Opistobranquios. tica 2: 41-77 1977. La defensa en los opistobranquios. tember issue: 48 - 57 THompson, THOMAS EvERETT 1975. Dorid nudibranchs from eastern Australia (Gastropoda, Opistho- branchia). Journ. Zool. 176: 477-517 Oecologia Aqua- Investig. y Cienc., Sep- Vol. 23; No. 4 RE WERCER Page 317 Preliminary Studies on the Association Between Pleonosporium squarrosum (Rhodophyta ) and Cryptochiton stelleri (Polyplacophora ) KARLA McDERMID Hopkins Marine Station of Stanford University, Pacific Grove, California 93950 (1 Plate; 2 Text figures) INTRODUCTION THE GIANT CHITON, Cryptochiton stellert (Middendorff, 1846) is known from northern Japan to southern Cali- fornia for its thick brick-red girdle covered by tufts of crimson calcareous bristles (SmiTH, 1975). Close examina- tion of this mollusk reveals that the dorsal surface often supports a miniature forest of algae. Pleonosporium squar- rosum Kylin (Ceramiaceae), the 2-3 cm tall red alga, is a leading member of the epizoic community. Pleonosporium Squarrosum appears very selective in its habitats which are limited to pilings of docks at Friday Harbor, Washington (KyLin, 1925), and on the backs of a few subtidal inverte- brates in Monterey, California (ApBott « HoLLENBERG, 1976). The small and inconspicuous nature of these plants has perhaps caused them to be overlooked in other areas. A report by MacGinirie & MacGinit1e (1968) indicated that there is no distinctive flora or fauna on the backs of Cryptochiton, but my own study shows abundant and fre- quent growth of algae on their backs. The purpose of this study was to investigate the incidence, distribution, cau- sality, and natural history of the association between the chiton and one of its most common colonizers, Pleono- sporium squarrosum. MATERIALS ann METHODS Work on this interrelationship was done from April to June, 1980. The Cryptochiton stellert populations at sev- eral locations on the central California coast were sam- pled: in the kelp bed off Mussel Point in Monterey Bay (36°37'08” N; 121°54'27” W) at a depth of 7.5-9 m; in the Point Alones kelp bed east of Mussel Point at a 7.5m depth; from the tidepools at Pescadero Point at a -0o.27m tide level; and from the intertidal zone on a -0.42m tide at Stillwater Cove in Carmel Bay (Figure 1). These sites were chosen because they represent differences in wave ex- posure and tidal level. Cryptochiton stellert population density was estimated by swimming or walking through quadrats of 5m?, and the number of Cryptochiton with and without Pleonospo- 122° W Mussel Pt. \Pt. Alones, Monterey Sullwater Pescadero Pt. 36°N Paciric OcEAN Figure 1 Monterey Peninsula area of Central California showing the four study locations Page 318 rium squarrosum was noted. Random specimens were col- lected, tagged, weighed, and measured. Percent cover by P. squarrosum was analyzed by generating 50 random polar coordinate points marked on a transparent sheet of plastic that was pinned to the center of the back of each chiton. The presence or absence of P. squarrosum was re- corded under these 50 points; other epizoic life was noted. A search was also conducted for P. squarrosum growing on substrates other than Cryptochiton. In the laboratory, samples of Pleonosportum squarrosum were picked off the backs of Cryptochiton. Counts were made of female, male, polysporangia-bearing, and sterile plants. Some vegetative axes were cut for culture and experimentation. Polysporangial plants were chosen for spore germination tests. All the cultures were grown in disposable plastic petri dishes with filtered (0.22 ym) sea water, a nutrient sea water mixture, and germanium diox- ide to retard diatom growth. Substrate, temperature, light, and air exposure were variables during the experiments. RESULTS A. WEIGHT, SIZE, AND DisTRIBUTION The 39 chitons collected ranged in length from 15-28 cm with wet weights between 260 g and 1330g. The speci- mens were similar in size and age to those previously studied by MacGinirim: « MacGinirie (1968). Of the Cryptochiton samples, the dorsal surfaces were algae- covered or were bare-backed (Table 1). Pleonosporium Squarrosum was absent on the backs of the Cryptochiton at Pescadero Point and at Stillwater Cove, both intertidal collections; P. sguarrosum was found on the Cryptochiton from Mussel Point and Point Alones kelp beds, both sub- tidal collections. These data would indicate that Pleono- Sporium squarrosum is a subtidal species. B. Densrry AND PoPULATION STRUCTURE OF Pleonospo- rium squarrosum The two populations from Mussel Point and Point Alones kelp beds showed, not only a difference in percent THE VELIGER Vol. 23; No. 4 Table 1 Distribution data on Cryptochiton stelleri at different locations and percentage of Cryptochiton stelleri with Pleonosporium squarrosum growth Percentage Location Mean density of chitons with (chitons/m?) P. squarrosum Mussel Point Kelp Bed 3 m deep 0.10 0 7.5-9m deep 0.40 54.4 Point Alones Kelp Bed 7.5 m deep 0.06 92 Pescadero Point 0.29 0 Stillwater Cove 0.24 0 of Pleonosporium-covered Cryptochiton, but also a differ- ence, statistically discernible at the 5% level, in the den- sity of P. squarrosum on the individual chitons (Figure 2). The sampled Mussel Point Cryptochiton had sparse growth with a mean of 6.7% cover; whereas, the Point Alones chitons had dense Pleonosporitum growth with a mean of 37.2%. Of the chitons that did show Pleonosporium squarrosum cover, the presence of the alga seemed most common within a radius of 6.5cm from the center point of the chiton’s back or on the dorsal humps made by the under- lying plates. Sixteen of the 18 Cryptochiton with P. squar- rosum demonstrated this centralized concentration of algae. To estimate population structure of Pleonosporium squarrosum, a random sample of 167 plants was picked. Counts indicated 68% sterile plants, 14% polysporangia- bearing plants (Figure 3), 11% male plants with sperma- tangia (Figure 4), and 8% female plants with procarps (Figure 5). C. Host Sprciriciry or Pleonosporium squarrosum Specificity of Pleonosporium squarrosum for Crypto- chiton stelleri was investigated. Possible substrates for P. Explanation of Figures 3 to 5 Figure 3: Pleonosportum squarrosum with polysporangia ; scale 50 um Figure 4: Male Pleonosporium squarrosum with spermatangia scale 50 um Figure 5: Female Pleonosporium squarrosum with procarp struct- ure scale 30 pm Tue VELIGER, Vol. 23, No. 4 [McDeErmip] Figures 3 to 5 Figure 5 Hi a mean X, = 37.2 median = 29.5 Percent cover by Pleonosporium squarrosum Individual Chitons Individual Chitons from from Mussel Point Point Alones Figure 2 Density of Pleonosporium squarrosum on individual Cryptochiton stelleri from two populations Squarrosum were carefully scrutinized: wharf pilings at Monterey Harbor and Stillwater Cove, carapaces of the decorator crab Loxorhynchus crispatus (StIMPsoN, 1857), colonies of hydroids, tubes of the worm Diopatra ornata (Moore, 1911) found in the subtidal Cryptochiton habitat, clam and abalone shells, subtidal rock faces, subtidal algae, and even the sandy sea bottom on which Cryptochiton crawl. Although Assotr & HoLLENBERG (1976) report P. squarrosum on decorator crabs and hydroids, no such spec- imens were observed on these substrates or on any other non-chiton substance. D. Oruer Epizoic Lirt Forms In addition to Pleonosponum squarrosum, many other epizoic algae were discovered on the backs of Cryptochiton stellert. The various algae included: colonial diatoms; blue-green Lyngbya sp.; green Bryopsis sp., Cladophora sp., Enteromorpha linza (Linnaeus) J. Agardh, and Ulo- thrix sp.; brown Giffordia sandriana (Zanardini) Hamel, and Sphacelaria sp.; and red Goniotrichum sp., Hetero- siphonia japonica Yendo, Platythamnion sp., Polyneura latissima (Harvey) Kylin, Polysiphonia pacifica Hollen- berg, Pterosiphonia dendroidea (Montagne) Falkenberg, THE VELIGER Page 319 and Rhodoptilum plumosum (Harvey and Bailey) Kylin. However, none of these algae occurred with the consistent abundance of P. squarrosum. Epizoic organisms also inhabited Cryptochiton stellert backs: gastropods—Tegula brunnea (Philippi, 1848) and Ocenebra spp. crawled on the dorsal surfaces; nematodes entwined themselves among the chiton bristles; tiny hermit crabs clung tightly to epizoic algae; and amphipods or copepods occasionally nestled in the chiton wrinkles. DISCUSSION This study documents the presence of Pleonosportum squarrosum on the backs of Cryptochiton stelleri in the Monterey Peninsula area. There are now many questions to be answered, not only because the reasons for the chiton- alga association remain an enigma, but also because earlier studies (MacGinitie & MacGinirTiE, 1968) seemed to indi- cate that nothing grew or could grow on the backs of Cryptochiton. Future investigations should include a care- ful search for a northern Cryptochiton-Pleonosporium relationship because P. squarrosum does make an inter- tidal appearance in Washington; and Cryptochiton are plentiful intertidally along the Oregon coast (PALMER & FRANK, 1974), at Friday Harbor and northward. My study found differences in prevalence and density of Pleonosporium squarrosum on Cryptochiton in two ad- jacent kelp beds. More research would explore these dif- ferences which occur in areas separated by only a sand channel, yet distinguished by dissimilar swell exposure, water depth, salinity and chiton density. Preliminary experimentation conducted as part of this study showed that Pleonosporium squarrosum successfully germinated on non-chiton substrates; died at elevated tem- peratures of 24°C and above; displayed greatest vegeta- tive axis growth at subtidal light levels; and lacked toler- ance for exposure to the drying effects of air. Additional testing involving these environmental variables would help explain the habitat selectivity of the alga. Another investi- gation focused on Tegula brunnea which are commonly found crawling on the backs of intertidal and shallow sub- tidal Cryptochiton. These herbivorous snails ate P. squar- rosum in the laboratory and may be a limiting factor in the alga’s distribution. In a field study, chitons which were tagged and released did move enough in 2 days to suggest that Cryptochiton is a probable dispersal agent for P. squarrosum. These preliminary experiments, as well as the initial observations of distribution and density, give evidence of the association between Cryptochiton stelleri and Pleono- Page 320 THE VELIGER Vol. 23; No. 4 sporium squarrosum: P. squarrosum clearly prefers C. stellert as a source of space and refuge. ACKNOWLEDGMENTS Many thanks to all those who helped, especially to Dr. Isabella Abbott and to my chiton friends. Literature Cited AspotT, IsaBeLia A. & GzorcEe J. HoLLENBERG 1976. Marine algae of California. xii+827 pp.; illus. Stanford, Calif.; Stanford Univ. Press Kyun, Haratp 1925. The marine red algae in the vicinity of the Biological Station at Friday Harbor, Washington. Lunds Univ. Arsskr., N. FE, Avd. 2, 21: 1-87; pit. 37 MacGiniT1z, Georce Esper & NetTiz MacGIniTIz 1968. Notes on Cryptochiton stellert (Middendorff, 1846). The Veliger 11 (1): 59-61; pit. 6 (1 July 1968) PaLMER, JOHN BeacH & PETER WOLFGANG FRANK 1974. Estimates of growth of Cryptochiton stellert (Middendorff, 1846) in Oregon. The Veliger 16 (3): 301-304 (1 Jan. 1974) SmitH, ALLYN GoopwiINn 1975- Smaller molluscan groups. In: R. I. Smith « J. T. Carl son (eds.), Light’s Manual: Intertidal invertebrates of the central California coast. xvii+716 pp.; 156 plts. Berkeley, Califi; Univ. of Calif. Press Vol. 23; No. 4 THE VELIGER Page 321 Temperature and Growth of Maturing Haliotis kamtschatkana Jonas A. J. PAUL anv J. M. PAUL University of Alaska, Institute of Marine Science, Seward Marine Station, Seward, Alaska 99664 (4 Text figures) INTRODUCTION THE PINTO ABALONE, Haliotis kamtschatkana Jonas, 1845, supports a small commercial fishery along the outer coast of southeast Alaska, but its restricted distribution and low population densities preclude large-scale expansion of the fishery. On a world wide basis the demand for abalone meats, which generally exceeds supply, has generated in- terest in expanding the harvest of these gastropods. In areas of Japan and the state of California (U.S.A.) where Haliotis spp. have been overharvested, small hatchery- reared abalone are used to supplement natural reproduc- tion. Similar techniques could be used along the inner coast of southeastern Alaska to expand natural or domesti- cated populations of abalone. To be economically success- ful, the culture of domesticated abalone must rely on selec- tion of habitats suitable for rapid growth. Currently, little information is available on the relation- ship of temperature and the various biological functions of pinto abalone. This species spawns in the spring when the water temperature reaches approximately 9° C (QuayLe, 1971; Paut et al., 1977) and thermal death occurs if indi- viduals are kept at 16° C to 17° C (unpublished data). The objective of this study was to observe shell growth of ma- turing pinto abalone at different temperatures. Maturing individuals were selected because they grow rapidly and individual differences in growth are pronounced. The tem- peratures examined are typical of southeastern Alaska dur- ing the spring and summer growth period. METHODS Mean sea water temperatures of 5.5 ° C (standard devia- tion 0.8), 8.5° C (standard deviation 0.6), 11.5° C (stand- ard deviation 0.8) and 13.5°C (standard deviation 0.5) were maintained in 4 tanks by adjusting the flow rates of the incoming water. Sea water salinity was naturally be- tween 32%. and 33%. Two size groups of Haliotis kamt- schatkana with shell lengths of 48.0mm to 50.4mm, and 50.5 mm to 52.5 mm were introduced into each tank. Indi- vidual tanks contained 6 abalone from each size class. The abalone in each tank were provided with the fol- lowing species of algae as food: Enteromorpha linza (Lin- naeus) J. Agardh, Ulva lactuca Linnaeus, Laminaria groenlandica Rosenvinge, Nereocystis luetkeana (Mertens) Postels & Ruprecht, Alaria marginata Postels & Ruprecht, and Rhodymenia palmata (Linnaeus) Greville. These spe- cies of algae were selected because they produced good growth rates when fed to pinto abalone in an earlier study (Paut et al., 1977). The amount of algae in each tank was far in excess of daily consumption rates. At the end of 60 days of growth, shell length and shell width were remeas- ured and compared with the initial measurements. Indi- viduals held at 11.5° C and 13.5° C were measured again on the ro5th day of growth. A linear regression was used to find the mathematical relationships between tempera- ture and growth. The validity of the correlation coefficient (r) was measured using the formula t = Vvr /(I-r); where v=n-2. The 95% confidence was used in determining significance. RESULTS At 5.5°C the abalone in both size groups exhibited very little growth (Table 1, Figure 1) with changes in average length of less than 1%. At 8.5°C there was a 1.5mm or 3.0% and 0.6mm or 1.2% increase in shell length and width for the 48.5 to 50.4mm pinto abalone held for 60 days (Table 1, Figures 1 and 2). This size abalone kept at 13.5°C exhibited 4.6mm or 9.4% and 3.7mm or 7.5% Page 322 Water temperature Xe 5.5 8.5 11.5 13.5 5.5 8.5 11.5 13.5 Average increase in shell length and width in mm of Haliotis kamtschatkana THE VELIGER Table 1 kept at 5.5, 8.5, 11.5 and 13.5 degrees centigrade. (x = mean, SD = standard deviation, R = range) Initial length (mm) x/SD/R 49.8 0.6 48.2 - 50.0 49.5 0.4 48.8 - 50.0 49.2 1.0 48.5 - 50.4 48.9 0.7 48.5 - 50.0 51.2 0.5 50.6 - 52.0 51.0 0.6 50.6 - 51.8 51.2 17 50.6 - 51.9 51.3 0.5 51.0 - 52.3 %Increase in Length Vol. 23; No. 4 Added length Initial Added width Added length Added width (mm) at day 60 width (mm) (mm) at day 60 (mm) at day 105 (mm) at day 105 x/SD/R x/SD/R x/SD/R x/SD/R x/SD/R 0.4 35.4 0.3 = = 0.2 1.0 0.2 = Es 0-1.0 34.0 - 37.6 0- 0.6 — = 15 35.9 0.6 is = 0.7 1a 0.6 Sa ue 0.5 - 2.4 35.2 - 36.6 0-1.4 = _ 1.9 35.2 2.0 3.7 3.1 0.4 1.0 1.4 0.4 2.1 1.5-2.4 34.5 - 36.2 0-3.3 3.3 - 4.1 0.5 - 5.5 4.6 35.0 3.7 5.0 4.5 1.2 0.8 1.0 17 1.5 3.3 - 6.1 34.4 - 35.6 3.1 - 5.3 2.5 - 6.6 3.2 - 6.6 0.5 36.5 0.2 S = 0.2 1.3 0.2 w ms 0.3 - 0.7 34.0 - 37.0 0-0.4 at ik 1.1 36.4 1.5 — — 0.7 1.1 1.0 _ - 0-1.6 35.9 - 38.2 0-2.4 — — 3.8 36.2 2.1 6.2 3.8 1.2 1.3 0.8 1.9 1.6 3.0 - 4.7 34.4 - 37.2 1.4- 3.3 4.5-8.5 1.8 - 5.3 3.8 36.5 2.6 6.0 3.9 1.7 0.9 1.6 1.6 1.5 2.8 - 6.7 35.2 - 37.5 1.3 -5.1 2.9 -7.8 2.3 - 6.1 48.0 - 50.4.mm 50.5 - 52.5mm 5:5 8.5 11.5 = 13.5 5-5 8.5 iid eee Temperature (°C) Figure 1 -The percent increases in shell length of two groups of Haliotis kamtschatkana, initial shell lengths 48.0mm to 50.4mm, and 50.5 mm to 52.5mm, held at 5.5°C, 8.5°C, 11.5°C and 13.5°C for 60 days. Vol. 23; No. 4 % Increase in Width weap 5:5 8.5 11.5 13.5 THE VELIGER 48.0 - 50.4 mm 50-5 - 52-5 mm Page 323 Temperature (°C) Figure 2 Concurrent percent increases in shell width of the two size groups of Haliotis kamtschatkana in Figure 1 after being reared at 5.5°C, 8.5°C, 11.5°C and 13.5°C for 60 days. change in these same dimensions. At 11.5° C growth rates of abalone in this size group were intermediate between those held at 8.5°C and 13.5° C (Table 1, Figures 1 and 2). The regression analysis for the relationship between temperature and increase in shell length of 48.0mm to 50.4mm pinto abalone resulted in a positive correlation coefficient (9.7) and the t-distribution was significant. At 8.5° C the mean increase in shell length in 50.5 mm to 52.5mm pinto abalone was only 1.1mm or 2.1% as compared to 3.8mm or 7.4% for abalone maintained at 13.5° C (Table 1, Figure 1). Similar changes in shell width were observed (Table 1, Figure 2). The 3.8mm and 2.1 mm increase in shell length and width for this size abalone held for 60 days at 11.5° C were almost identical to the change in size of their cohorts kept at 13.5°C (Table 1, Figures 1 and 2). The t-distribution determined by regres- sion analysis of change in length after 60 days for 50.5 mm to 52.5 mm specimens kept at all 3 water temperatures was not significant. Similar calculations with 60 day growth data from just the 8.5° C and 13.5° C group, and then only the 11.5°C and 13.5°C group resulted in t-distributions that were significant and not significant, respectively. After 105 days the 48.5 to 50.4mm pinto abalone held at 11.5°C increased an average of 3.7mm or 7.5% in length and 3.1mm or 6.3% in width while their cohorts held at 13.5° C increased 5.0mm or 10.2% and 4.5mm or 9.2% in length and width respectively (Table 1, Figures 3 and 4). The 50.5mm to 52.5mm abalone kept at 11.5°C and 13.5°C for 105 days exhibited average increases in 18 48.0 - 50.4 mm %lIncrease in Length nN 11.5 13.5 11.5 13.5 Temperature (°C) Figure 3 The percent increases in shell length of two groups of Haliotis kamtschatkana, initial shell lengths 48.0mm to 50.4mm and 50.5 mm to 52.5 mm, held at 11.5°C and 13.5°C for 105 days. Page 324 THE VELIGER Vol. 23; No. 4 eee area accel 48.0 - 50.4 mm 50-5 - 52-5 mm % Increase in Width YY Yy YY yy 11.5 13.5 11.5 13.5 Temperature (°C) Figure 4 Concurrent percent increases in shell width of the two size groups of Haliotis kamtschatkana in Figure 3 after being reared at 11.5°C and 13.5°C for 105 days. length of 6.2mm and 6.0mm, and width of 3.8mm and 3.9mm respectively (Table 1). The correlation coefficients for both size groups of abalone comparing temperature and growth in 105 days were not significant. DISCUSSION Pinto abalone begin to mature at about 50mm shell length. The results of this study suggest that little shell growth of pinto abalone of this size occurs when water temperatures are below 8.5° C. Maximum average increase in shell size of pinto abalone occurred at 13.5°C in the 48.5mm to 50.4mm group. However, in the presence of excess food the 50.5mm to 52.5mm size abalone exhibited similar growth rates at 11.5° C and 13.5° C. In the larger group it is possible that gonad maturation inhibited shell growth (PauL, et al., 1977). Throughout southeastern Alaska mean monthly surface sea water temperatures of 13° C to 14°C are restricted to the months of July and August while June and September temperatures are on the order of 11° C to 12° C. The surface water temperatures the re- mainder of the year are below 11° C and thus too low for extensive growth of pinto abalone. The effects of tempera- ture on growth of pinto abalone at other stages of maturity remain to be described. SUMMARY 1. Two groups of maturing Haliotts kamtschatkana, 48.0 mm to 50.4mm, and 50.5 mm to 52.5mm shell length were held at 5.5°, 8.5°, 11.5° and 13.5° C and fed to excess on a variety of algae. 2. Shell growth of pinto abalone was inhibited at 5.5° C and little growth occurred at 8.5° C. 3. Sea temperatures of 11.5°C were necessary before notable shell growth was observed in pinto abalone and maximum growth rates required 13° to 14°C. ACKNOWLEDGMENTS This work is the result of research sponsored in part by the Alaska Sea Grant Program, sponsored by NOAA office of Sea Grant, Department of Commerce, under Grant 04-6-158-44039 and by the University of Alaska with funds appropriated by the State of Alaska. Facilities were provided by the Institute of Marine Science, Seward Marine Station. The abalone were collected by A. Schmidt, Alaska Department of Fish and Game, Sitka. This paper is contribution number 410 from the Institute of Marine Science, University of Alaska. Dr. H. Feder from the University of Alaska kindly agreed to review the manuscript. Literature Cited Paut, Aucustus Joun, Jupy McDonatp Pauzr, Donatp W. Hoop é Ricwarp ANTHONY Nevk 1977. | Observations on food preferences, daily ration requirements and growth of Haliotis kamtschatkana Jonas in captivity. The V 19 (3): 303-909; 4 text figs. (1 January 1977) Quayzez, Danie, BrancH 1961. | Growth, morphometry and breeding in the British Columbia abalone (Haliotts kamtschatkana Jonas). Fish. Res. Brd. Canada, Tech. Rprt. No. 279: 84 pp. Vol. 23; No. 4 THE VELIGER Page 325 A New Species of Stenosemus Middendorff, 1847 (Mollusca : Polyplacophora ) in the Abyssal Northeastern Pacific BY ANTONIO J. FERREIRA ' Research Associate, California Academy of Sciences, Golden Gate Park, San Francisco, California 94118 (1 Plate; 5 Text figures) THE EXAMINATION OF 20 lots of eastern Pacific chitons in the Benthic Invertebrate Collection of the Scripps Institu- tion of Oceanography, La Jolla, California (SIO), made available through the generosity of Dr. William A. New- man and Spencer R. Luke brought to light 3 specimens of a new species of abyssal chiton which further study re- vealed to belong to Stenosemus Middendorff, 1847, here elevated to generic rank. POLYPLACOPHORA de Blainville, 1816 Neoloricata Bergenhayn, 1955 IscHNOCHITONDAE Dall, 1889 Stenosemus Middendorff, 1847 Stenosemus chiversi Ferreira, spec. nov. (Figures 1 to 4 and 5 to9) Diagnosis: Small, elongated chitons, strongly carinate. Tegmentum white, irregularly rugose to coarsely granu- lose. Valves with well defined, laterally pinched beaks. Mucro anterior. Girdle with imbricated cylindrical scales. Slit formula (holotype), 28/3-4/25. Sutural laminae con- tinuous across shallow sinus. Gills posterior, abanal. Rad- ula with unicuspid major lateral teeth. Description: Holotype — The specimen, preserved in ethyl alcohol, 1 Mailing address for reprints: 2060 Clarmar Way, San Jose, California 95128, U.S.A. measures, including the girdle, 18.3 mm in length, 9.3 mm in width (at the level of valve iv), and 4.3mm in height. Strongly carinate jugal angle about 90°. Tegmentum uni- formly white, except for some black, fuliginous material adhering to the shell and girdle. Lateral areas of inter- mediate valves well defined but only slightly raised. The whole tegmentum sculptured with irregular rugosities (Figures 1 to 4), weaker at the jugum, bolder at the periphery; in the end valves and lateral areas these rugosi- ties acquire a vaguely concentrical, zig-zag disposition; towards the jugum, the rugosities break up into coarse granules increasingly less defined. Valves slightly beaked, particularly in the posterior valves, iv to vii, where the beaks have a quite unique laterally pinched appearance (Figure 3). Mucro anterior, well defined, almost pointed, with the same pinched look; postmucro area straight, at a 45° slope. Articulamentum chalky white. Insertion plates short; teeth small, irregularly shaped; slit formula 28/3-4/25. Eaves moderately spongy. Sutural laminae del- icate, relatively short, continuous along a very shallow, almost obsolete sinus through a pectinated sinusal plate. Girdle about 1.0mm wide, covered with white cylindrical scales (Figure 5) strongly imbricated in a manner that only their blunt round tips show; the scales, about 300 wm in height, 70 zm in width, have a dull surface without orna- mentation. Undersurface of girdle covered with rectan- gular, translucent scales, about 100 zm long, 16 wm wide (Figure 6). Gills abanal, in the posterior half of the foot, about 15 plumes per side. Radula 4.5mm long (25% of the length of the specimen) comprises about 90 rows of mature teeth. Median tooth (Figure 7), oval shaped, about 35 zm wide, 80 pum long; first lateral teeth elongated; sec- ond (major) lateral teeth with slender, unicuspid head (Figure 8), about 904m long, 25mm wide at the base; 400 wm Figure 5 Stenosemus chiversi Ferreira, spec. nov. Holotype (CASIZ No. 017683) ; cylindroid scales of girdle’s upper surface. Camera lucida drawing by Barbara Weitbrecht 100mm Figure 6 Stenosemus chiversi Ferreira, spec. nov. Holotype (CASIZ No. 017683) ; scales of the girdle’s undersurface. Camera lucida drawing by Barbara Weitbrecht. Seitenplatte simple in shape but very long, 250-280 um at the main shaft (Figure 9); outer marginal teeth 55m long, 60 um wide. THE VELIGER Vol. 23; No. 4 5Oum Figure 7 Stenosemus chiverst Ferreira, spec. nov. Holotype (CASIZ No. 017683); median and first lateral teeth of radula. Camera lucida drawing by Barbara Weitbrecht. Type Locality: North eastern Pacific, 14°52’N, 125° 26’ W, 4390m, as collected by R. Dick, R/V Prospector, with a benthos free fall grab, 13 September 1975. Type Material: Holotype, disarticulated, with girdle and radula mounted in slides, deposited at the California Academy of Sciences, Department of Invertebrate Zoology (CASIZ, Cat. # 017683). A paratype, with the same dimensions of the holotype, part of the same lot (SIO M1188) deposited at the Benthic Invertebrate Collection of the Scripps Insti- tution of Oceanography. Another paratype (SIO M 1419), collected “N of Equator & E of Hawaii, at Explanation of Figures 7 to 4 Figure 1: Stenosemus chiversi Ferreira, spec. nov. Paratype, ca. 18mm long (SIO 1188) ; side view Figure 2: Same as in Figure 1; close-up of central and lateral areas ‘Figure 3: Same as in Figure 1; close-up of seventh valve to show beak (arrow) Figure 4: Stenosemus chiverst Ferreira, spec. nov. Holotype (CA SIZ No. 017683) ; dorsal view of the posterior valve [Ferrera] Figures 7 to 4 Tue VELIcER, Vol. 23, No. 4 r ‘ Fy San if Vol. 23; No. 4 50m Figure 8 Stenosemus chiversi Ferreira, spec. nov. Holotype (CASIZ No. 017683) ; head of major lateral tooth of rad- ula. Camera lucida drawing by Barbara Weitbrecht. THE VELIGER Page 327 (?) 4572m, August 1977” in the course of a dredge for manganese nodules by Kennicot Corporation, measures about 12mm in length, deposited at CASIZ (Cat. #017684). Remarks: Stenosemus Middendorff, 1847 (Type Spe- cies, Chiton albus Linnaeus, 1767, by SD, WincKworTH, 1926; synonyms — Lophyrus Sars, 1878 [not Poli, 1791, nomen nullum], Chondropleura Thiele, 1906, Lepido- pleuroides Thiele, 1928, Lophyrochiton Jakovleva, 1952) has long been accepted as a subgenus of Ischnochiton Gray, 1847 (WiNcKworTH, 1926, 1934; A. G. Smrru, 1960; Van BELLE, 1977; Kaas & VAN BELLE, 1980). Van BELLE (1977) defined Stenosemus by its small poste- rior valve, weak tegmental sculpture, and the insertion plates of the intermediate valves which possess a variable number (1 or 2) of slits. The recognition that a number of species other than C. albus are part of the same taxon re- quires a broader definition of Stenosemus and indicates its elevation to generic rank. By their overall similarities, the following species are here considered to be members of Stenosemus: S. albus (Linnaeus, 1767), its type species; S. exaratus (Sars, 1878); S. acelidotus (Dall, 1919); S. stearnsti (Dall, 1902); S. abyssicola (Smith & Cowan, 1966); and S. chiversi Fer- reira, spec. nov. Taken globally, these species lay a foun- dation for an understanding and definition of Stenosemus: 1) lepidopleurid-like [already noted by Winckwortn, 1926, and THIELE, 1928, for S. albus] its elongated shape, whitish color, simple sculpture, and posterior gills, 2) long, cylindrical, strongly imbricated girdle scales, 3) variability in the number of slits in the intermediate valves, and very numerous slits in the end valves, 4) a very shallow to obsolete sinus with almost continuous sutural laminae, and 5) a deep-water habitat. The pres- ence of a large number (25+) of slits in the end valves, and the almost continuous sutural laminae with shallow to absent sinus in Stenosemus are features reminiscent of Callochiton Gray, 1847. The fact that the girdle scales of Callochiton—strongly imbricated, needle-like—bear some (< adjacent column) Figure 9 Stenosemus chiversi Ferreira, spec. nov. Holotype (CASIZ No. 017683) spatulate teeth (“Seitenplatte”) of radula. Camera lucida drawing by Barbara Weitbrecht. Page 328 similarity in their shape and disposition to those of Stenosemus suggests a phylogenetic link between the two genera. The species here considered under Stenosemus appear to represent two distinct groups: 1) the group of Steno- semus albus, S. exaratus and S. chiversi characterized by an elongated body, posterior gills, and unicuspid major teeth in the radula, and 2) the group of S. stearnsi, S. acelidotus, and S. abyssicola with a less elongated body, gills that extend to the anterior end of the foot, and (in S. abyssicola) bicuspid radula [the radula is not known in S. acelidotus and S. stearnsii]. Like other Stenosemus, S. chiverst appears to favor a very deep-water habitat. Its presence in depths of 4390- 4572m places it near the top of the list of deep-water chitons (see FERREIRA, 1980, Table 1), surpassed only by Lepidopleurus vitjaz Sirenko, 1977, and Leptochiton alveolus (Lovén, 1846). The species is here named chiversi after Dustin Chivers, Department of Invertebrate Zoology, California Academy of Sciences, who was instrumental in bringing these speci- mens to my attention, and who, in the course of many years, has generously given me much of his time, knowl- edge, and friendship. ACKNOWLEDGMENTS For their assistance in several phases of this work, appre- ciation is here expressed to Dustin Chivers, Dalene Drake, and Barbara Weitbrecht of the California Academy of Sciences, San Francisco, and Dr. William A. Newman and Spencer R. Luke of the Scripps Institution of Ocean- ography, La Jolla, California. THE VELIGER. Vol. 23; No. 4 Literature Cited Dau, WitiiamM HEALEY 1902. Illustrations and descriptions of new, or imperfectly known shells, chiefly American, in the U. S. National Museum. Proc. U. S. Natl. Mus. 24 (1264): 499 - 566; plts. 27-40 pet ; (gi March 1902) 1919. Descriptions of new species of chitons from the Pacific coast of America. Proc. U.S, Natl. Mus. 55 (2283): 499 - 516 (7 June 19) Ferrera, ANTONIO J. 1980. A new species of Lepidopleurus Risso, 1826 (Mollusca : Poly- placophora) in the deep waters of the eastern Pacific. The Veliger ag (1): 55-61; 1 plt.; 5 text figs. (1 July 1980), Gray, Joun Epwarp 1847. Additional observations on Chitones. Proc. Zool. Soc. Lon- (post 10 November 1847) don 15 (178): 126-127 Jaxovieva, A. M. 1952. Shell bearing mollusks (Loricata) of the seas of USSR. Acad. Nauk U. S. S. R. no. 45: Keys to the fauna of USSR, 127 pp. (English translation, Jerusalem, 1965) Kaas, Pret & Ricuarp A. VAN BELLE 1980. Catalogue of living chitons, Dr. W. Backhuys publ, Rotter- dam, 144 pp. (May 1980) LinNAEUs, CaRoLus 1767. Systema naturae, Editio duodecima reformata. “Vermes Testa- cea” 1 (2): 533-1327 MpEnDorFF, ALEXANDER THEODOR VON 1847. Beitrage zu einer Malacozoologia Rossica. I. Chitonen. Acad. Imper. Sci. St. Petersburg., Mém. Sci. Nat. 4: 9-151; 14 plts. ( August 1 Pout, IoszepHO XAvERIO Lt a 1791. ‘Testacea utriusque Siciliae eorumque historia et anatome tabu- lis aeneis illustrata. Parma, 1: 1-11; pits. 3, 4 Sars, Gzorce Ossian 1878. Bee til Kundskaben om Norges Arktiske fauna. I. Mollusca regionis ticae Norvegiae. Christiania. 466 pp.; its.5 3 SsarH, AttyN GoopwiIn bible itht gi *) 1960. Amphineura, pp. I41 - 176 ian: Raymond CG. Moore, ed., ‘Treatise on invertebrate paleontology, Part I, Mollusca 1, Geol. Soc. Amer. and Univ. Kansas Press, xxilit+I1 - 1951 SmirH, AtLyN Goopwin # Ian McTaccart Cowan 1966. A new deep water chiton from the Northeastern Pacific. Occ. Pap. Calif. Acad. Sci. 56: 1-15; a1 figs. (g0 June 1966) THizLe, JOHANNES 1906. Uber die Chitonen der deutschen Tiefsee-Expedition. In: Wissenschaftliche Ergebnisse der deutschen Tiefsee-Expedition auf dem Dampfer “Valdivia”, 1898-1899 (C. Chun, ed.), 9: 325-936; pit. 29. Jena, Gustav Fischer (31 May 1906) 1928. _Loricaten, Gastropoden, Scaphopoden und Bivalven der “Hel- goland” und “Poseidon” Expeditionen. Fauna Arctica 5: 564 Van Berg, RicHarp A. 1977. Sur la classification des Polyplacophora: III. Classification sys- tématique des Subterenochitonidae et des Ischnochitonidae (Neolori- cata: Chitonina). Inform. Soc. Belg. Malacol. 5 (2): 15-40; pita 45 (December, 1977) WINcKWorTH, RONALD 1926. Notes on British Mollusca - I. Journ. Conchol. 28 (1); 19-15 (March 1926) 1934. Notes on nomenclature. Middendorff’s classification of chitons. Proc. Malacol. Soc. London a1 (1): 9 (March 1994) Vol. 23; No. 4 THE VELIGER Page 329 Four Previously Undescribed Indo-Pacific Terebrids (Mollusca : Gastropoda ) TWILA BRATCHER (1 Plate) IN FOURTEEN YEARS of examining and identifying tere- brids from various institutions and private collectors, I have come across a number of undescribed species. Several specimens of one of these have been in my own collection for many years, unidentified. I needed to wait for addi- tional material before describing some of these species. For others, I needed to do additional research. Four of these are now being described in this paper. TEREBRDAE Morch, 1852 Terebra Bruguiére, 1789 Terebra boucheti Bratcher, spec. nov. (Figures 1 and 2) Diagnosis: A shiny medium-large terebrid shell, white or white with reddish-brown blotches and omamented with round bead-like nodes. Description: Shell size moderately large; color shiny white; outline of whorls concave with convex double sub- sutural band and projecting rows of nodes; protoconch of 34 extremely long whorls, the last whorl being twice the length of the preceding one; first 2 whorls of teleoconch extremely angulate because of sharp nodes projecting from center of whorl, a row of smaller, less conspicuous nodes both anterior and posterior to projecting row; 2 rows of nodes becoming equal in size after 47" whorl and forming subsutural band; sculpture posterior to band con- sisting of 2 rows of smaller nodes; subsutural band on later whorls consisting of a row of shiny elongate nodes with obsolete spiral cords in interspaces, followed by a row of slightly smaller nodes, a broad channel between; re- mainder of whorl sculptured by 4 rows of small nodes aligned vertically and connected both spirally and axially by shiny cords; body whorl with double subsutural band followed by 3 rows of smaller nodes, the one at the periph- ery being slightly more pronounced; sculpture anterior to periphery of heavy spiral cords; aperture quadrate; colu- mella recurved; siphonal fasciole almost smooth, with microscopic striations, and a sharp keel. Dimensions: Holotype 47.5 x 7.7mm. Paratypes from 41.4 X 7.3 to61.8x 12.3mm. Type Locality: Philippine Islands. 14°16’N; 120°31’ E; Musorstrom Expedition, Station 10, 70 to 67 meters. Type Material: Holotype MNHN. Paratypes MNHN (1); BM(NH) no. 198019 (1); LACM no. 1364 (1); USNM no. 782260 (1); Bratcher coll. (2); Parkinson coll. (1). Distribution: Philippines to Solomon Islands. Discussion: The most outstanding feature of this species is the long whorled protoconch followed by extremely angulate early whorls caused by a keel of small nodes in the center of the first whorls of the teleoconch. This is one of the shiniest of the terebrids. There is almost no varia- tion in the sculpture of the early whorls of the specimens examined. In the later whorls some specimens show more pronounced axial and spiral cords with smaller nodes at the intersections. Of the paratypes, 3 are white, the re- mainder blotched with orange brown. Specimens with orange brown blotching have been in some collections labeled as Terebra adamsi E. A. Smith, 1878, though there is little resemblance to that species; T. adams: has small orange-brown dots, is turreted in outline, and the only nodes are those on the subsutural band. Terebra boucheti should be compared with several other Indo-Pacific species: T. torquata Adams & Reeve, 1850 is similar in size and somewhat similar in sculpture though it lacks the nodes anterior to the subsutural band, Page 330 THE VELIGER Vol. 23; No. 4 has a mamillate protoconch of 14 whorls, and lacks the high gloss; T. elliscrosst Bratcher, 1979 has a white shell with small paired dots rather than wide blotches. It lacks the keeled angulate early whorls of the teleoconch and the beaded nodes anterior to the subsutural band; T. insalli Bratcher « Burch, 1967 has a more slender shell and also lacks the angulate early whorls and the beading. This species is named in honor of Dr. Philippe Bouchet, curator at the Muséum National D’Histoire Naturelle, Paris, France. Terebra troendlei Bratcher, spec. nov. (Figures 3 and 4) Diagnosis: A medium sized white shell with orange spots on a flat subsutural band and with axial ribs on the early whorls, the later whorls being smooth. Description: Shell size medium; color, white with low gloss, ornamented with orange blotches on subsutural band; outline of whorls weakly convex; protoconch of 3 conical whorls; sculpture of earliest whorls of teleoconch of indistinct axial ribs; ribs becoming strong at 4™ whorl, fading again at 10" whorl; no spiral sculpture except for a microscopically punctate groove marking the flat sub- sutural band; orange blotches on band beginning at 8™ whorl; body whorl smooth except for subsutural groove and microscopic axial striae; aperture quadrate; columella curved, with one weak plication at anterior end; siphonal fasciole with fine striae and a sharp keel. Dimensions: Holotype 27.6 x 7.9mm. Paratypes from 11.9 xX 2.9mm to 33.5 x 8.3mm. Type Locality: Entrance to Hana Hevane Bay, Tahu- ata Island, Marquesas, depth 10 meters, sand bottom. Type Material: Holotype, MNHN. Paratypes AM no. C122397 (1); AMNH no. 181848(1); BM(NH) no. 198023 (1); CAS no. 60676 (1); MNHN (4); MORG no. 21.175 (1); USNM no. 773511 (1); Bratcher coll. (4); Cernohorsky coll. (1); Mabry coll. (1); Tréndle coll. (4) . Distribution: Marquesas Islands. Discussion: In shape this species resembles both Terebra chlorata Lamarck, 1822 and T. felina Dillwyn, 1817, though the whorls are shorter than those of either species. The color pattern differs from both. Terebra chlorata has orange blotches, stripes, and markings throughout the shell in addition to those on the band; T. felina has orange dots posterior to the suture rather than on the band. The protoconch of T. chlorata differs from that of T. troendlei,though that of T. felina is similar. The holo- type of this species was illustrated by Salvat & Rives as Terebra sp. “A” in Coquillages de Polynésie. Of the 21 specimens examined, 18 had cracks in the shell, many of them large. All had been mended. This species is named for Jean Troéndle of Tahiti, who first brought it to my attention. Terebra swobodai Bratcher, spec. nov. (Figures 5 and 6) Diagnosis: A slender beige colored shell with angulate outline of whorls and with small nodes where spiral cords cross axial cords, forming square pits between inter- sections. Description: Shell size medium; color, beige, the area anterior to suture being faintly lighter; outline of whorls angulate; protoconch missing in type material; early whorls of teleoconch flat-sided and weakly turreted; sculp- ture of early whorls of a noded subsutural band, narrow axial ribs, and weak spiral cords; subsutural band on later whorls narrow, convex, with equally spaced bead-like nodes; remainder of whorl sculptured by 2 spiral rows of heavy cords bisecting axial cords of equal strength, form- ing bead-like nodes at intersections and square pits be- Explanation of Figures 1 to 8 Figure 1: Terebra boucheti Bratcher, spec. nov. Holotype MNHN Figure 2: Same specimen as in Figure 7 Figure 3: Terebra troendlei Bratcher, spec. nov. Holotype MNHN X 38 Figure 4: Same specimen as in Figure 3 Figure 5: Zérebra swobodai Bratcher, spec. nov. Holotype LACM no. 1185 X 3¢ Figure 6: Same specimen as in Figure 5 Figure 7: Terebra turschi Bratcher, spec. nov. Holotype LACM no. 1191 X 3¢ Figure 8: Same specimen as in Figure 7 8 01 1 sainsty [aaHoLvag] V ‘ON ‘&% "JOA “AXOITIA THT, Vol. 23; No. 4 tween intersections; body whorl with 2 rows of spiral cords crossing axial ribs, forming strong nodes, and 3 rows of square pits ending at periphery; anterior to periphery axial ribs becoming obsolete, spiral cords continuing to siphonal fasciole; columella gently curved; siphonal fasciole striate, with weak keel. Dimensions: Holotype 24.3 x 4.3mm. Paratypes from 23.7 X 4.1 to 27.2 to 4.9mm. Type Locality: Zamboanga, Mindanao, Philippines, on Xenophora pallidula Reeve, 1842, from net traps. Type Material: Holotype LACM no. 1185. Paratypes, BM(NH) no. 19018 (1)) USNM no. 773510 (1); Bratcher coll.(2); Cernohorsky coll.(1); Swoboda coll. (1). Distribution: Philippines. Discussion: As a gift I received a pair of Xenophora pallidula Reeve, 1842, which had been dredged from deep water in the Philippines. They were decorated with many terebrids, one species of which was strikingly different from any I had previously seen. Examination of other Xeno- phora pallidula dredged from the same area produced sev- eral more of the same species. Subsequent research con- vinced me they are an undescribed species. The most outstanding feature of this species is the large square pits formed by the crossing of heavy spiral and axial cords. The number of spiral cords may vary from 2 to 4. In all specimens examined, the axial and spiral cords are of equal strength. Of the 7 specimens seen (all were on Xenophora pallidula), none had the protoconch intact, though there were intact protoconchs on other terebrid species on the same Xenophora. There is no species with which Terebra swobodai could be confused. Terebra fenestrata Hinds, 1844, often has square pits formed by the crossing of axial and spiral cords, but it has a larger, broader shell, with a double subsutural band and a completely different sculpture pattern. This species is named for Edward Swoboda who pre- sented me with the Xenophora on which the type material was found. Terebra turschi Bratcher, spec. nov. (Figures 7 and 8) Diagnosis: A small turreted brown shell with a light band anterior to the suture, decorated with axial ribs and many fine spiral threads. THE VELIGER Page 331 Description: Shell size small; color, somewhat shiny brown, with a light band anterior to suture; outline of whorls turreted; protoconch of 44 slender conical whorls; axial sculpture of teleoconch of thin, sharp, curved axial ribs from suture to suture, the posterior ends forming weak elongate nodes, 13 on penultimate whorl; interspaces marked with many fine spiral threads, 8 rows on penulti- mate whorl plus 5 on subsutural band; spiral threads faintly crossing ribs; axial ribs and spiral threads contin- uing on body whorl to siphonal fasciole; aperture elongate; columella curved with a heavy, light colored parietal cal- lus; siphonal fasciole striate, with a sharp keel. Dimensions: Holotype 14.1 x 3mm. Paratypes from 11.6 x 2.8 to 14.3 x 3.2mm, Type Locality: Hansa Bay, North Coast of Papua, New Guinea, in 36 meters, mud bottom (04°06’S, 144°22'E). Type Material: Holotype LACM no. 1191. Paratypes AM no. 120657 (1); AMNH no. 181847 (1); ANSP no. 352483 (1); BM(NH) no. 198020 (1); CAS no. 60675 (1); MORG no. 21.277 (1); SDMNH no. 73614 (1); USNM no. 773512 (1); Bratcher coll. (11); Cernohorsky coll. (2); Mabry coll. (1); Tursch coll. (4). Distribution: New Guinea. Discussion: There is little variation in the specimens examined except in size. A few are slightly lighter in color. This species may be separated from Terebra poly- gyrata Deshayes, 1859, which has a broader, heavier shell and a quadrate aperture. It also has wider spaced, thicker ribs. Terebra turschi also somewhat resembles the eastern Pacific T. zola Pilsbry, 1932, which has a small brown shell with many spiral cords between narrow ribs. It lacks the parietal callus, the light band anterior to the suture, and the groove between the ribs marking the subsutural band. This species is named in honor of Dr. Bernard Tursch of Brussels, Belgium, who collected the type material. Abbreviations have been used for a number of institutional collections cited in this paper. They are: AM — Australian Museum AMNH_ — American Museum of Natural History ANSP — Academy of Natural Sciences of Philadelphia BM (NH) — British Museum (Natural History) CAS — California Academy of Sciences LACM -— Los Angeles County Museum of Natural History Page 332 MNHN- — Muséum National D’Histoire Naturelle, Paris, France MORG ~— Museu Oceanografico de Rio Grande, Brasil SDMNH — San Diego Museum of Natural History ACKNOWLEDGMENTS I wish to thank Dr. Philippe Bouchet of the Muséum National D’Histoire Naturelle, Paris and Dr. Joseph Rose- water of the United States National Museum (Smith- sonian Institution) for the loan of material from their insti- tutions for study. For the loan of material I also am in- debted to Brian Parkinson, Jean Tréndle, and Dr. Ber- nard Tursch. To Edward Swoboda who gave me the Xenophora on which Terebra swobodai was discovered, I add my thanks. My appreciation to Dr. A. Myra Keen for the critical reading of the manuscript of this paper. THE VELIGER Vol. 23; No. 4 Literature Cited Apams, ArTHuR & Lovett Aucustus Reeve 1850. The zoology of the voyage of H. M. S. Samarang. prt. 2: 25 -44; plts. 10-17 (May 1850) BraTcHER, Twita L. 1979. A new Indo-Pacific terebrid. The Veliger 29 (1): 65-66 1 text fig. (1 July 1979) BraTcHER, Twila & Rosert Donatp BurcH 1967. A new terebrid species with check list of Terebridae from the Red Sea (Mollusca : Gastropoda). The Veliger 10(1): 7-9; pit @ I 1 Dezsuayes, Gérarp PAuL ee 1859. A general review of the genus Terebra and a description of new species. Proc. Zool. Soc. London for 1859: 270-321 (between July and October 1859) Lamarck, Jean Baptiste Pizrre ANTOINE DE MONET DE 1822. Histoire naturelle des animaux sans vertébres. 7 [mollusques] Paris (“chez Pauteur au jardin du Roi”): 1-711 (August 1822) Pirssry, Henry Aucustus « Herspert Ne~tson Lowe 1932. | West Mexican and Central American mollusks collected by H. N. Lowe 1929-31. Proc. Acad. Nat. Sci. Phila. 84: 33 - 144; 6 figs.; pits. 1-17; 2 photographs (21 May 1932) Reeve, Lover, Aucustus 1842. Descriptions of new species of shells, principally from the col- lection of Hugh Cuming, Esq. Proc. Zool. Soc. London prt. X: 49-50 (November 1842) SatvaT, BERNARD & CLAUDE Rives 1975. Coquillages de Polynesie. SmatH, Epcar ALBERT Pp. 1 - 392 1873. | Remarks on a few species belonging to the family Terebridae and descriptions of several new forms in the collection of the British Museum. Ann. Mag. Nat. Hist. (4) 11: 262-271 (April 1873) Vol. 23; No. 4 THE VELIGER Page 333 Distribution, Activity, and Food Habits of Juvenile Tegula funebralis and Littorina scutulata (Gastropoda : Prosobranchia ) as they Relate to Resource Partitioning JEFFREY T. JENSEN Hopkins Marine Station of Stanford University, Pacific Grove, California 93950 (4 Text figures) INTRODUCTION Tue snaits Tegula funebralis A. Adams, 1853 and Litto- rina scutulata Gould, 1849 are abundant in the mid-tide zone on California rocky shores. Numerous studies have been made on the adults of T. funebralis (see Veliger, 6, suppl., 1964; and Appotr & Haper.iz, 1980), but the juveniles have received comparatively little attention. Littorina scutulata has also been studied (see review in Apsott & HApDERLIE, op. cit.), and the possibility exists that two distinct forms or species are involved (Murray, 1979), but many aspects of the natural history are still in- completely known. No previous studies have focused pri- marily on the juveniles of either T. funebralis or L. scutu- lata, particularly on their relationship to one another in the middle intertidal zone community. The present work examines the possibility of competitive resource partition- ing interactions between the young of these herbivorous gastropods by comparing their distribution, activity pat- terns, and food habits. DISTRIBUTION anp MOVEMENTS For present purposes juvenile snails are defined as those individuals measuring 4mm or less in maximum linear shell dimension. All studies were conducted on Mussel Point, Pacific Grove, California, adjacent to the Hopkins Marine Station, in a region protected from strong wave action. The 4 sites chosen all displayed sloping rocks show- ing marked vertical zonation and a diversity of habitats including bare granite, surfaces covered with barnacles or algae, and some small pools and cracks where sand could accumulate. At each site a vertical transect was extended from a 0.0m level upward, and two 25cm’ samples were taken at each 15 cm increment in height above mean lower low water. Absolute height was determined from a sur- veyed benchmark nearby. At each level the 25 cm* quadrats were placed a variable distance from the middle of the transect on the basis of random numbers. All Littorina and Tegula were inspected in each quadrat, and field records made of the 22 distinct microhabitats occupied by the snails as they were collected. Holdfasts and fronds of algae were removed from the quadrat and examined separately. In all situations where accurate counts could not be made in the field, samples were bagged and examined later under a dissecting microscope. The 4 transects sampled showed consistent trends; pooled data appear in Figure 1. In vertical placements, juvenile Tegula funebralis occurred predominantly below the +1.2m level, while juvenile Littorina scutulata were found mostly above the +0.9m level, the two populations overlapping mainly 0.9-1.2m above MLLW. Figure 1 shows distribution of the snails according to specific micro- habitat, with habitats (A-V) arranged in a sequence to show the shifting relative abundance of the two species. Young Tegula funebralis are seen to occur chiefly in sandy holdfasts of the common macroalgae (e.g., Rhodoglossum affine (Harvey) Kylin, 1928) and in rocky crevices, while Littorina scutulata are more frequently on the fronds of the same macroalgae and in empty barnacle shells. Thus, microhabitat partitioning and zonation sharply limit the possible interactions between juveniles of the two species. These data on vertical placement and habitat of small Page 334 THE VELIGER Vol. 23; No. 4 Vertical Height Above Mean Lower Low Water APacm DME ere aK aN eOMmeE UID 00% UT s[ieus Jo Jaquinny Substrate Figure 1 Low tide distribution of juvenile Tegula funebralis (white bars) and Littorina scutulata (black bars), based on pooled data from 4 transects at Mussel Point, Pacific Grove, California. Numbers indi- cate the numbers of snails taken from the various microhabitats at each level. Letters refer to the following microhabitats: A. Sandy holdfasts of Rhodoglossum affine B. Sandy holdfasts of Gigartina papillata C. Rocky crevices D. Sandy holdfasts of Gigartina agardhiz E. Crustose red algae F Sand G. Sandy holdfasts of Endocladia muricata H. Sandy holdfasts of Gelidium sp. I. Rocky holdfasts of Gigartina papillata J. Sandy holdfasts of Gigartina leptorhynchos Tegula funebralis complement and extend existing infor- mation on the distribution of the species. SEAPY & LITTLER (1979) at Cayucos Point, California, determined the T. funebralis vertical population distribution to lie between 117cm and 27cm above MLLW. Wara & WricHT (1964), working with the occurrence at low tide of specimens over 13mm in length at Pacific Grove, found that the popula- tion density decreased as the amount of the algal cover on the substrate increased. The smaller animals tended to be L. Tidepools N. Fronds of Iridaea sp. P. Pelvetia fastigiata K. Rocky holdfasts of Iridaea sp. M. Crustose coralline algae O. Fronds of Rhodoglossum affine Q. Rocky holdfasts of Endocladia muricata R. Fronds of Gigartina agardhu S. Fronds of Endocladia muricata U. Empty barnacle shells T. Bare Rock V. Fronds of Gigartina papillata higher up and farther inshore. In the present study, adults were more common at lower elevations; they occurred on relatively bare rock surfaces, whereas the juveniles were found in the sandy holdfasts of macroalgae. Juvenile T. funebralis were often commonly on the undersides of rocks in the pools—areas where the larger adults could not take refuge. However, specimens over 6mm in diameter rou- tinely occurred in the same crevices as the larger animals. The tendency toward habitat separation of juveniles from Vol. 23; No. 4 larger animals should tend to reduce intraspecific compe- tition, possibly important in a species where individuals may live as long as 30 years (DarBy, 1964). The studies of CHow (1975), on the distribution of Littorina scutulata at Bodega Head showed that individ- ual size tends to increase with increasing vertical height in the intertidal zone, though juvenile (1-4mm) snails oc- curred over the entire vertical range. Both the vertical range of the population (0.9-3.6m above MLLW) and ver- tical position of the peak in population density (1.86m) in Chow’s study site were higher than those observed at Mus- sel Point, a difference very likely related to stronger surf at Bodega Head. More recent studies by Murray (1979), reveal differ- ences in egg mass shape and penis shape in adult Littorina scutulata,suggesting that two distinct forms or species may exist and even occur together on the West Coast. As only juvenile individuals were dealt with in my study, all L. scutulata were treated as a single population. ACTIVITY Although it was feasible to determine the vertical position and microhabitat distribution at low tide of juvenile Tegula funebralis and Littorina scutulata, it was desirable to supplement this with information on movements of the animals and their distribution at high tide. This proved difficult in the field even in a region of moderate surf. Thus, observations were made under laboratory condi- tions. An artificial tide was created in an aquarium with a constant inflow of seawater at 14-15°C. A cleck was used to control water level; the tip of the outflow hose of the aquarium was attached to a rod extending from the hour hand of the clock (Figure 2), providing an approxi- mately natural cycle of two high and two low tides each 24 hours. A rock collected from the intertidal zone in an area common to both species and placed in the aquarium pro- vided a natural habitat. This rock was visually divided into 3 vertical zones (high, middle, and low), each forming a belt 5cm wide and each with approximately the same proportion of Gigartina papillata (C. Agardh) J. Agardh, 1846 and bare surface. A vertical crevice ran down one side of the rock. The artificial tide was adjusted so the rock was completely covered at high water and completely exposed at low water. A skylight over the aquarium in the laboratory provided a natural light regime. To increase contrast between snails and background the experimental animals were marked with fingernail polish, distinctive colors being used for the two species. Twenty THE VELIGER Page 335 Figure 2 Aquarium used to simulate tidal conditions in the laboratory Hour hand of the clock (A) raises and lowers outflow hose of the aquarium (B). Seawater flow into tank (C) is constant. Rock simulating natural habitat (D) is supported above the bottom on slender pegs (E) marked juveniles of each species were selected, placed on top of the rock in the aquarium, and allowed to move about and acclimate for 24 hours. Thereafter, at 2 hour intervals over a 24 hour tidal cycle, the number of snails of each species in each vertical zone on the rock (high, middle, low) and on each type of substrate (Gigartina papillata fronds, the lower frond/holdfast area, the rock surface, or the rock crevice) was recorded. A dim red light was used to make observations at night. Later the same experiment was repeated, but with the tidal clock shifted by six hours, yielding data under a different phase relation- ship of the diel and tidal cycles. The animals were allowed to adjust to the new tidal regime for 24 hours before obser- vations of movement began. The results of both experiments are shown in Figure 3. As regards vertical zonation on the rock, the Littorina scutulata population was found to occur higher than the Tegula funebralis population under all conditions of light and tide. The greatest overlap between the populations occurred on the middle region of the rock. The T. fune- bralis juveniles, however, displayed greater vertical mobil- ity. Individuals often moved to the high surface of the rock as the water rose, and returned to the lower regions as it fell. When the receding tide occurred at night, fewer snails moved down, and as a result more were left high on the rock at the morning low tide. The large number of Tegula low on the rock at high tide in the dark is contrary to the general trend. Most of these snails, however, were active on the rock surface, and were observed moving up the THE VELIGER Vol. 23; No. 4 Page 336 High Tide vertical position substrate TER iB: Th fa bas: Dusk Dark 4 Low Tide vertical position substrate 1B dhe & 1B ip the & peArasqQ uonemndog jo juao10g Gann CZALAN Vertical Position Sa) Substrate on Rock ah uae high OT rs Gigartina papillata frond medium 4 — lower frond /holdfast low Rock surface —— £3: — Rock Crevice Figure 3 Vertical position and microhabitat choice of juvenile Tegula funeb- ralis and Littorina scutulata on a rock in a laboratory aquarium, under varying conditions of light and tide. The bars indicate the percent of the population observed on the different substrates and at different elevations on the rock. Horizontal rows are arranged in the order of the number of snails of both species on the high zone of the rock at high tide; this number decreases from top to bottom of the graph. Arrows refer to the predominant movement of the populations during the two readings made prior to the condition shown; the left arrow in each column refers to T: funebralis, the right one to L. scutulata. Where no arrow appears, vertical shifts in the population of snails approached zero. With respect to vertical position, the mid-line represents the middle of the rock. The mid-line in the substrate columns divides snails on Gigartina papillata (above the line) from those on rock substrates (below the line) Vol. 23; No. 4 rock. The L. scutulata juveniles showed a slight tendency to move downward on the rock during daylight falling tides. Snails of both species were observed moving away from direct sunlight when completely submerged during a daylight high tide. With regard to the specific substrates on which the animals were found, Littorina scutulata juve- niles tended to remain on Gigartina papillata, moving to the tips of fronds when covered by water, while young Tegula funebralis were observed predominantly on the rock surface, retreating to the crevice, rock bottom and G. papillata holdfasts at low tide. The separation of the two species observed under lab- oratory conditions correlates well with differences in zona- tion and microhabitat distribution presented in Figure 1. Juveniles of Littorina scutulata continue to occupy a higher zone than juvenile Tegula funebralis, despite compres- sion of the 1.8m vertical range found in the field into a 15 cm range in the laboratory tank. The habitat differences of the two species in the field at low tide persist through the tidal cycle; Tegula funebralis juveniles continue to be found mainly on the rock surface and Gigartina papillata holdfasts and young Littorina scutulata predominate on the G. papillata fronds. This continued occupancy of dis- tinct microhabitats supports the idea of a real resource partitioning between juveniles of the two species. DaniELs (1978), studying the activity of adult Tegula funebralis under field and laboratory conditions, found that population movements corresponded to the tidal cycle. However, in the absence of tidal fluctuations (as in outdoor aquaria kept continuously full of water) move- Tegula funebralis Other Dinoflagellates Diatoms Green Algae Detritus 100 90 80 7o 60 50 40 30 20 10 THE VELIGER Page 337 ment occurred according to a diel cycle, with the animals moving up rock surfaces at night, and down to shaded areas in the day. He also observed adult T. funebralis occasionally left high and dry in the field after a receding tide at night, and concluded that light reinforces the down- ward response of the animals. In the present study, juve- nile T. funebralis generally show these same tendencies, but the phototactic response of both adults and juveniles need further investigation. FOOD HABITS Juvenile snails of both species were collected from the field, usually during early morning low tides, when the animals—still wet from the previous high tide—had full stomachs. The substrate on which they were found was noted, and the animals were immediately preserved in Io per cent formalin. In the laboratory the stomachs were removed under a dissecting microscope. Gut contents were mounted on slides in glycerol, and examined at 400X. Dr. Isabella A. Abbott and Mr. William Magruder assisted in the identification of possible food items. Materials in the gut were grouped into five categories: detritus (organic material of unidentifiable origin), green algae, diatoms, dinoflagellates, and other (miscellaneous). Relative abun- dance of the different constituents, as a percentage of the total biomass of the contents, was visually estimated. Figure 4 shows the means and ranges of the categorized gut contents of 10 juveniles of each of the two species. Both Littorina scutulata 10 20 30 40 50 60 70 80 90 100 Figure 4 Diet of juvenile Tegula funebralis and Littorina scutulata as per- centage of the total biomass of stomach contents. Bars shown are the averages based on io snails. Lines on the bars give the range Page 338 species contained much detritus. Littorina scutulata juve- niles contained more green algae and diatoms than did juvenile Tegula funebralis, and the latter showed many small,brown dinoflagellates lacking in the gut of L. scutu- lata. A few cells from encrusting red algae and an occa- sional foraminiferan were found in the stomachs of small T. funebralts. The high concentration of detritus in the guts of both species suggests that they feed in a similar and relatively non-selective manner. The higher percentage of green algae and diatoms consumed by young Littorina scutulata may reflect ingestion of epiphytes, for these are found on the macroalgal fronds frequented by the snails. I saw no evi- dence of feeding on any of the larger macroalgae, such as Gigartina papillata or Rhodoglossum affine. Comparison of these results with the findings of Brest (1964) indicate that the diets of adult and juvenile Tegula funebralis are quite different. Best found the adults fed on a variety of large and small algae, with detritus contrib- uting little bulk. The amount of detritus consumed by juveniles in the present study again suggests a partitioning of resources between different stages in the life history. The investigations of DAHL (1964) and Foster (1964) on the microscopic and macroscopic food sources of adult Littorina scutulata show that macroalgae, particularly Pelvetia fastigiata (J. Ag.) De Toni, 1895 and Cladophora columbiana Coll., 1903, were preferred food sources of snails in the laboratory, although green algae and diatoms contributed significantly. No indication of feeding on detritus was noted, but the stomach contents of animals freshly collected from the field were not examined. As in Tegula funebralis, the difference in food habits between juveniles and adults may enable larger populations to be supported. Despite the similarity of the gut contents in juveniles of Tegula funebralis and Littorina scutulata, it appears likely that there is little interspecific competition for food. Both field and laboratory studies indicate that the species forage in relatively distinct subhabitats. SUMMARY At Mussel Point, Pacific Grove, California, juveniles (4mm or less in greatest shell dimension) of Tegula fune- bralis and Littorina scutulata occupy largely separate microhabitats. At low tide, juveniles of 7. funebralis occur predominantly in the sandy holdfasts of macroalgae and in rock crevices, less than 1.2m above mean lower low water; juveniles of L. scutulata are found mainly on the fronds THE VELIGER Vol. 23; No. 4 of macroalgae and in empty barnacle shells more than 0.9m above MLLW. Laboratory experiments in aquaria with artificial tides demonstrate a similar partitioning of the habitat by vertical position and microenvironment. Juveniles of both species appear to be mainly relatively non-selective detritivores. Young Littorina scutulata con- sume more green algae and diatoms, probably representing the ingestion of epiphytes; Tegula funebralis contained more dinoflagellates. While juveniles of the two species consume roughly the same food, they obtain it in different places, so competition appears light. ACKNOWLEDGMENTS I wish to thank the entire instructional staff of the Hopkins Marine Station for their help and encouragement through- out the course of this study. I am particularly indebted to Dr. Donald P. Abbott for helpful advice and guidance during all stages of the work. Literature Cited AxssoTT, DoNALD PuTNAM & EuGENE CLINTON HADERLIE 1980. Prosobranchia: Marine Gastropoda. In: R. Morris, D. P Ab- bott a E. C. Haderlie (eds.), Intertidal invertebrates of the California coast. Stanford Univ. Press, Stanford, Calif. xi+690 pp.; 200 plts. (November 1980) Best, BARBARA 1964. Feeding activities of Tegula funebralis (Mollusca : Gastropoda). The Veliger 6 (Supplement): 42-45; 1 text fig. (15 November 1964) Curow, VicToR 1975. | The importance of size in the intertidal distribution of Littorina scutulata (Gastropoda : Prosobranchia). The Veliger 18(1): 69 to 78; 8 text figs. (1 July 1975) DauH1, ARTHUR LYON 1964. Macroscopic algal foods of Littorina planaxis Philippi and Lit- torina scutulata Gould (Gastropoda : Prosobranchiata). The Veli- ger 7 (2): 139-143 (1 October 1964) Danie.Ls, MatTHEW 1978. Rhythmic movement of the marine snail Tegula funebralis (Pro- sobranchia: Trochacea) on intertidal rocks in relation to tidal and diel cycles. Unpubl. stud. reprt. on file at Hopkins Marine Station library, Pacific Grove, Calif;; 12 pp. Darsy, RicHarp L. 1964. On growth and longevity in Tegula funebralis (Mollusca : Gast- ropoda). The Veliger 6 (Supplement): 6-7; pit. 1 (15 Nov. 764) Foster, Micwaet S. 1964. Microscopic algal food of Littorina planaxts Philippi and Lit- torina scutulata Gould (Gastropoda : Prosobranchiata). The Veli- ger 7 (2):149- 152, 152a (1 October 1964) Murray, TALBOT 1979. Evidence for an additional Littorina species and a summary of the reproductive biology of Littorina from California. The Veliger 21 (4): 469-474; 2 text figs. (1 April 1979) Seapy, Rocer R. & Mark M. LITTLER 1978. The distribution, abundance, community structure, and primary productivity of macroorganisms from two central California rocky inter- tidal habitats. Pacif. Sci. 32 (3): 293-314 (July 1979) Wara, WILLIAM M. & BENJAMIN B. WRIGHT 1964. The distribution and movement of Tegula funebralts in the inter- tidal region of Monterey Bay, California (Mollusca ;: Gastropoda). The Veliger 6 (Supplement): 30 - 37; 9 text figs. (15 November 1964) Vol. 23; No. 4 THE VELIGER Page 339 New Species of Fusinus (Gastropoda : Fasciolariidae ) from the Tropical Eastern Pacific BY LEROY H. POORMAN' (1 Plate; 8 Text figures) A RECENT EXAMINATION of molluscan material at the Los Angeles County Museum of Natural History and in several large private collections has revealed 5 previously unrecog- nized species. They are described herein. Current sub-generic grouping within Fusinus is some- what unsatisfactory. Therefore, placement below the genus level will not be attempted. Fusinus Rafinesque, 1815 A new name for Fusus Lamarck, 1799. Type species: Murex colus Linnaeus (by M). Shell large, spindle-shaped; canal long, open; aperture ovate, outer lip lirate within, columella with callus deposit ; sculpture of spiral cords and threads crossing axial ribs. Fusinus consagensis Poorman, spec. nov. (Figures 7, 6 and 10) Shell fusiform, of medium size for the genus. Protoconch blunt, of 14 turns with the tip immersed and with fine axial riblets and spiral threads appearing on the last 4 turn. Early whorls of the teleoconch with about 10 strong, low, rounded axial ribs, interspaces narrow; ribs crossed by 2 strong spiral cords in prominent crests; several fine threads above and below the cords. By the 5 whorl, upper cord dominant and outline of whorl angulate, slightly convex above and below and marked by about 5 spiral threads. Below the suture, a shallow sulcus extends all the way to 1 Mailing address: 15300 Magnolia Street, Space 55, Westminster, CA 92683 Figure 6 Protoconch of Fusinus consagensis Poorman, spec. nov. X 50 the aperture. Body whorl large, axial ribs and peripheral cords weak, obsolete on the gerontic stage. Outer lip thin, flaring, serrated, with numerous weak lirations within. Columellar callus thin, underlying cords visible. Body whorl constricted around the base, pinching in the outer lip opposite a heavy callus deposit on the columella. Canal long, narrowly open to the right, bent strongly to the left, terminating with a distal flexure. Color tan with brown maculations between the ribs, aperture white. Periostra- cum thin, non-fibrous. Radula: 1-R-1. Type locality: off Consag Rock, Gulf of California; 31°07’ N Lat., 114°30' W Long.; 56 specimens dredged in 20-30 m on sand. Holotype: Los Angeles County Museum of Natural History no. 1934. Page 340 0.5 mm Figure 10 Radula of Fusinus consagensis Poorman, spec. nov. X 100 Dimensions of the Holotype: Height 68.7mm, maxi- mum diameter 23.4 mm. Paratypes: 1 paratype is at the American Museum of Natural History, catalogue no. 198963; 1 paratype is at the National Museum of Natural History, Smithsonian Institution, catalogue no. 784586; 35 paratypes are in the Helen DuShane Collection; 2 paratypes are in the Carl and Laura Shy Collection; 16 paratypes are in the Leroy and Forrest Poorman Collection. Numerous lots of Fusinus consagensis have been exam- ined. All were taken from sand in 20-30m in the Gulf of California north of Tiburon Island. Beach specimens are not uncommon from Cholla Bay, Sonora, and San Felipe, Baja California Norte. The specific name is derived from the type locality, Con- sag Rock, in the upper Gulf of California, which in turn was named for Fernando Consag, an early explorer-mis- sionary. Remarks: The protoconch and the radula place this new species near to Fusinus ambustus (Gould, 1853). In both the young and the adult stages, there is 1 more cusp on the lateral tooth of the new species. In other respects, it is unique from any recognized Eastern Pacific fusinid, being easily determined by: the angulate outline of the whorls, THE VELIGER Vol. 23; No. 4 the subdued quality of the sculpture on the later stages, the disproportionately large body whorl, the narrow canal bent to the left, and the pinched-in outer lip at the lower part of the aperture. Fusinus humboldti Poorman, spec. nov. (Figures 2, 7 and 11) Shell small and narrow for the genus, of 7 whorls and a long canal. Height of spire less than aperture plus canal. Protoconch (eroded) small, turbinate, about 3 turns, with a slight basal carina. Whorls rounded, with a constricted wavy suture, and with 7 high, broadly rounded axial ribs aligned up the spire. Ribs crossed by 3 heavy spiral cords in prominent nodes; 5 cords on the body whorl and about 10 lesser threads on the pillar; several very weak threads between the major cords. Aperture oval, outer lip thin, about 10 lirations within. Columellar callus thin, with sev- eral weak plications at the lower part of the aperture. Canal open to the right, extending to the left of the shell axis. Color white. Radula: 1-R-1. Figure 7 Protoconch of Fusinus humboldti Poorman, spec. nov. X 50 Explanation of Figures 1 to 5 Figure 1: Holotype of Fustnus consagensis Poorman, spec. nov. X 1 Figure 2: Holotype of Fusinus humboldti Poorman, spec. nov. X 3 Figure 3: Holotype of Fusinus magnapex Poorman, spec. nov. X 2.8 Figure 4: Holotype of Fusinus paulus Poorman, spec. nov. X 3 Figure 5: Holotype of Fusinus sonorae Poorman, spec. nov. X 1.1 THE VELIGER, Vol. 23, No. 4 [PoorMAN] Figures 1 to 5 Figure 17 Figure 2 Figure 3 Figure 5 a) vi Vol. 23; No. 4 0.5 mm Figure 11 Radula of Fusinus humboldti Poorman, spec. nov. X 100 Type locality: off Duncan Island, Galapagos Islands, Ecuador; 00°35’S Lat., go°40’W Long.; 5 specimens dredged in 400m. Holotype: Los Angeles County Museum of Natural His- tory no. 1935. Dimensions of the Holotype: mum diameter 8.9mm. Height 22.1mm, maxi- Paratypes: 1 paratype is at the American Museum of Natural History, catalogue no. 198964; 2 paratypes are at the Los Angeles County Museum of Natural History, nos. 1943 and 1944; 1 paratype is at the National Museum of Natural History, Smithsonian Institution, catalogue no. 784585. The species is known only from the Galapagos Islands. There is one other record of 2 specimens dredged off Floreana Island. The specific name is in recognition of the German nat- uralist-explorer, Alexander von Humboldt. Remarks: In terms of shell morphology, this species is very close to Fusinus paulus described herein. Fusinus humboldti differs in being more slender and in having a proportionately longer canal. Also, the outer lip is lirate within. The major difference, however, is in radula mor- phology. The angular shoulder of the rachidian tooth and the deep basal cusp of the lateral tooth of F. humboldti are unique in Eastern Pacific Fusinus. THE VELIGER Page 341 Fusinus magnapex Poorman, spec. nov. (Figures 3, 8 and 12) Shell small, fusoid; spire equal to aperture plus canal in height. First turn of protoconch large, sharply tilted, tip immersed; second turn slightly larger, flat-sided. Beginning of adult sculpture eroded. Spire of 6 whorls increasing reg- ularly to a large body whorl. Aperture oval; outer lip sharp and serrated, about 7 lirations within. Columellar wall with light callus but with a heavy deposit before the juncture with the canal. Canal short, broadly open to the right, angling slightly to the left of the shell axis. Axial sculpture of 8 strong rounded ribs equal in width to inter- spaces, aligned up the spire. Spiral sculpture of 7 strong cords overriding the ribs in crested nodes, the 3 at the periphery strongest; weaker threads on the shoulder and down the pillar; with a few intercalary threads between the major cords. Color white; regions above and below the 3 peripheral cords red brown, strongest on the shoulders of the ribs. oor ons ~ Figure 8 Protoconch of Fusinus magnapex Poorman, spec. nov. X 50 Radula: 1-R-1. Type locality: WSW of Todos Santos, outer coast of Baja California Sur, Mexico; 23°20’N Lat., 110°22’W Long.; 4 specimens dredged in 160-220m. Holotype: Los Angeles County Museum of Natural His- tory no. 1936. Dimensions of the Holotype: mum diameter 10.8 mm. Height 25.4mm, maxi- Page 342 Figure 12 Radula of Fusinus magnapex Poorman, spec. nov. X 100 Paratypes: 3 paratypes are at the Los Angeles County Museum of Natural History, nos. 1945, 1946, and 1947. One other lot of 2 specimens has been dredged in 150m some 15km NE of the type locality. The specific name is in reference to the disproportion- ately large protoconch. Remarks: This new species superficially resembles a small specimen of Fusinus ambustus. It differs radically in having such a large protoconch with a tilted first turn, and in being proportionately shorter and stouter. Also, it is unique in having so many cusps on the lateral tooth of such a small animal. Fusinus paulus Poorman, spec. nov. (Figures 4, 13) Shell small, stout, solid, with about 6 whorls; height of the spire equal to the aperture plus the canal. Protoconch eroded (probably turbinate). Adult sculpture begins ab- ruptly with fine axial ribs and spiral cords. Axial sculpture of 8 rounded ribs aligned up the spire. Spiral sculpture of 3, strong cords on the periphery of each rounded whorl, crossing the ribs as high elongated nodes, several weak threads below the suture and between the cords; about 6 smaller cords on the pillar. Aperture ovate, constricted below by columellar callus. Outer lip thin and crenulated, THE VELIGER Vol. 23; No. 4 without internal lirations. A low cord of callus begins on the parietal wall and spirals into the aperture to the left of the suture. Canal short, open, starting left from aperture and curving right to end on shell axis. Animal color (dried) pale yellow; shell color white; fibrous periostracum yellow- beige. Radula: 1-R-1. Figure 13 Radula of Fusinus paulus Poorman, spec. nov. X 100 Type locality: San Jaime Bank, W of Cabo San Lucas, Baja California Sur, Mexico; 22°50’N Lat., 110°15’W Long.; 6 specimens dredged in 150m on rock. Holotype: Los Angeles County Museum of Natural History, no. 1938. Dimensions of the Holotype: Height 19.2 mm (nucleus eroded), maximum diameter 7.7 mm. Paratypes: 4 paratypes are at the Los Angeles County Museum of Natural History, nos. 1939, 1940, 1941, and 1942; I paratype is at the National Museum of Natural History, Smithsonian Institution, catalogue no. 784588. Fusinus paulus is known only from the type locality. The specific name was chosen to call attention to the small size of this stoutly solid shell. Remarks: This new species superficially resembles Fus:- nus humboldti described herein. It differs from the Gala- pagan species in having a broader, more open canal, in radular variations, in being smooth within the outer lip, and in having an internal cord of callus at the top of the aperture. Vol. 23; No. 4 Fusinus sonorae Poorman, spec. nov. (Figures 5, 9) Shell broadly fusoid, of medium size; height of spire equal to aperture plus canal. Protoconch turbinate, 3-whorled, heavy distant ribs on last 4 turn. Whorls of teleoconch shouldered, subsutural region concave, spire somewhat turreted; first few whorls nearly flat-sided, with 2 heavy spiral cords crossing 12 crowded ribs. Beginning with 5 whorl, spiral cords gradually increase to 9 on the body whorl and 9 more on the pillar. Axial ribs decrease in num- ber down the spire, 8 on the body whorl; ribs rounded and Figure 9 Protoconch of Fusinus sonorae Poorman, spec. nov. X 50 strong but weaker near the sutures. Spiral cords cross ribs in crested nodes. Aperture large, ovate, pinched poste- riorly. Outer lip thin, serrated, with 9 irregular lirations within. Columella with heavy callus at lower part of aper- ture. Canal stout, shorter than aperture, broadly open to the right, angled to the left of shell axis. Color cocoa brown, darker on ribs; prominent crests on spiral cords white. Radula: unknown. Type locality: 5km SE of Punta San Antonio, near Guaymas, Sonora, Mexico; 27°54’N Lat., 111°05/W Long.; 7 specimens dredged in 100-120m on sand and dead shell. Holotype: Los Angeles County Museum of Natural His- tory no. 1937. THE VELIGER Page 343 Dimensions of the Holotype: mum diameter 23.3 mm. Height 56.1mm, maxi- Paratypes: 1 paratype is at the National Museum of Natural History, Smithsonian Institution, catalogue no. 784587; 3 paratypes are in the Carl and Laura Shy Col- lection; 2 paratypes are in the Leroy and Forrest Poorman Collection. One additional specimen in the Los Angeles County Museum of Natural History collections was dredged off Isla Partida, Baja California Norte. The specific name refers to the type locality off the Sonoran coast of Mexico and is used as a noun in the genitive case. Remarks: The protoconch is of the same type as Fusinus zacae Strong & Hertlein, 1937; and the shell morphology is similar. However, differences in coloration and the out- lines of the spires readily separate the 2 species. Fusinus sonorae is much stouter and has a turreted spire. The shoulders are high and rounded and the spiral cords are of nearly equal strength from suture to suture. The sub- sutural region is concave and nearly tangent to the whorl above. The spire of F. zacae is sharply angulated by a strong peripheral cord which rises to prominent crests over the ribs. The shoulder is concave and the lower part of the whorl in only slightly convex. The suture is distinct and incised. ACKNOWLEDGMENTS A number of people have contributed significantly to this project. My thanks go to Dr. James McLean for making the large collections at the Los Angeles County Museum of Natural History available for study. Three of the new species came from these collections. Conversations with Dr. S. Stillman Berry and access to his collection and library were most helpful. I am also indebted to Carol Skoglund, Phoenix, Arizona, Helen DuShane, Whittier, California, and Carl & Laura Shy, Westminster, Cali- fornia, for the opportunity to review their collections and for useful suggestions. Mr. Anthony d’Attilio, San Diego Museum of Natural History, made the drawings of the radulae and protoconchs. The holotype (LACMNH no. 1937) and 1 paratype (USNM cat. no. 784587) of Fusinus sonorae were con- tributed by Carl & Laura Shy. The holotype (LACMNH no. 1934) and 1 paratype (AMNH eat. no. 198963) of Fusinus consagensis were contributed by Helen DuShane. Page 344 THE VELIGER Literature Cited GouLp, Aucustus ADDISON 1853. Descriptions of shells from the Gulf of California and the Pacific coasts of Mexico and California. Boston Journ. Nat. Hist. 6: 374-408; plts. 14-16 (October 1853) Keen, A. Myra 1971. Sea shells of tropical West America: marine mollusks from Bafa California to Peru, 204 ed. Stanford Univ. Press, Stanford, Calif ixxiv+ 1064 pp.; ca. 4000 text figs.; 22 col. plts. (¢1 September 1971) RAFINESQUE-SCHMALTZ, CONSTANTINE SAMUEL 1815. Analyse de la nature ou tableau de l’univers et des corps organi- sés. Barravecebia, Palermo. p. 145 [not seen] Strronc, ARCHIBALD McC.iure « Lzo Greorcre HERTLEIN 1937. | The Templeton Crocker expedition of the California Academy of Sciences, 1932. No. 10. Marine Mollusca from Acapulco, Mexico, with notes on other species. Proc. Calif. Acad. Sci. (4) 22 (6): 159 to 178; plts. 94, 35 (31 December 1937) Vol. 23; No. 4 Vol. 23; No. 4 _ THE VELIGER | Page 345 Comments on Two Misunderstood Fusinids (Gastropoda : Fasciolariidae) from the Tropical Eastern Pacific LEROY H. POORMAN' (1 Plate) A LARGE NUMBER of juvenile specimens (10-100mm) of Fusinus has been taken in 60-100m in the vicinity of Guaymas, Sonora, Mexico. These specimens were referred to Fusinus dupetitthouarsi (Kiener, 1840). Close examina- tion has revealed the presence of 2 radically different protoconchs and significant variations in the nepionic whorls and the teleoconchs. The specimens were sorted into groups of A & B on the basis of these differences. Numerous radulae of adult and juvenile specimens of each group were extracted and minor variations were apparent. Recently, the author collected 4 live adult fusinid speci- mens intertidally in sand among rocks near the above location. One of the adult specimens still retained the protoconch, thus providing a complete growth series for group A. Material labeled Fusinus dupetitthouarsi in the collec- tions of the Los Angeles County Museum of Natural His- tory was reviewed and divided into 2 groups based on the criteria established above. This material provided a growth series for group B. There were 29 lots in group A and 100 lots in group B — nearly the same ratio which resulted from the juvenile specimens from Guaymas. Sev- eral large private collections were reviewed with the same result. The genus Fusus has been modified several times by early authors and species have been placed in synonymy and then dropped from the literature. After much search- ing, 3 names have emerged from the literature which must be considered. They are: Fusus turris Valenciennes, 1832; Fusus Dupetit-Thouarsi Kiener, 1840; and Fusus funicu- latus Lesson, 1842. A brief history of each taxon is per- tinent to an understanding of the three. * Mailing address: 15300 Magnolia Street, Space 55, Westminster, CA 92683 Fusus turris was described with Acapulco as type local- ity, but was not figured. Reeve, 1847, illustrated what he assumed to be Fusus dupetitthouarsi; but he did not have the type material. The illustration looks like Fusus turris. CaRPENTER, 1857, mentioned F. turris and compared it to Fusus colus; but CARPENTER, 1864-72, synonymized F. turris with F. dupetitthouarsi. The “Second Report’ in- cludes a discussion of the species. Tryon, 1881, also syn- onymized the 2 species. There seems to be no further men- tion of the taxon in the literature. Fusus Dupetit-Thouarsi was described with the “Coast of California” as the type locality. The species was well- figured. The taxon has endured and emerges today as Fusinus dupetitthouarsi. Fusus funiculatus Lesson, 1842, was described with Acapulco as type locality, but was not figured. Later in the same year, Lesson questioned whether his species was a synonym of Fusus Dupetit-Thouarsii. KEEN, 1971, ac- cepted this synonymy. GRABAU, 1904, discussed the early tendency among workers to consider the form of the shell in characterizing the genus. He emphasized the importance of the proto- conch and early whorls of the teleoconch. He then said that no species which did not have a protoconch similar to Fusus colus, the type of the genus, could be assigned to Fusus. Grabau is the 1*' worker to mention the importance of the protoconch in generic placement. At the request of Dr. James McLean, Los Angeles County Museum of Natural History, Dr. Philippe Bouchet, Paris Muséum National d’Histoire Naturelle, made avail- able for study and comparison the type material consisting of 3 lots. The 1° lot was the holotype of Fusus Dupetit- Thowarsi. The 2™° lot consisted of 5 specimens; and the box contained several labels showing Lesson’s personal name. Also included was a label naming the lot as Fusus Page 346 THE VELIGER Vol. 23; No. 4 turris from Valparaiso. The 3" lot of 2 specimens con- tained a label which said “Fusus turris Val.” ; and on the back was printed TYPE. Lots 2 & 3 are unquestionably conspecific. Dr. Bouchet states that he has searched the collections of the “museums of France” and that these lots constitute all extant original material of the three species. The 2 specimens of lot 3 bear remnants of glue and cardboard as though they had been mounted on a tablet, as was customary in the rgth century. It is almost certain that they represent syntypic material of Fusus turns Val- enciennes, 1832. This is reinforced by the fact that FIscHER-PIETTE & BEIGBEDER, 1944, list 2 syntypes of the species in the collection of the museum. There are several interesting points to be made concern- ing lot 2. The holotype, an adequate description, and an excellent figure of Fusus Dupetit-Thouars were available to Lesson at the time he described Fusus funiculatus. Also, the locality data for lot 2 do not correspond to the type locality for Lesson’s species. It seems logical to accept Les- son’s evaluation of his species and thus leave lot 2 as study material of an unrecognized species. Group B, discussed earlier, corresponds to lot 1; and group A corresponds to lots 2 & 3. The data assembled in this investigation indicate that Fusinus turris and Falsifusus dupetitthouarsi are 2 valid but superficially similar species living in the ratio of 1:3 in the Tropical Eastern Pacific; and that they occur inter- tidally and to a depth of 200m from the head of the Gulf of California to northern Peru. Partial diagnoses and fig- ures of the 2 species are included herein. Fusinus Rafinesque, 1815 A new name for Fusus Lamarck, 1799. Type species: Murex colus Linnaeus (by monotypy). Shell large, spindle-shaped; canal long, open; aperture ovate, outer lip lirate within, columella with callus deposit; sculpture of spiral cords and threads crossing axial ribs. Fusinus turris (Valenciennes, 1832) (group A) Fusus turris VALENCIENNES, 1832, Coq. univalves de l’Amér- ique Equinoxiale, vol. 2, p. 287. Illustrations by subsequent authors: REEVE, 1847, Conch. Icon., vol. 4, plt. II, fig. 9 (as Fusus Dupetit-Thouarst). Tryon, 1881, Man. Conch., vol. 3, plt. 36, fig. 134 (as var. Dupetitthouarsit). GRABAU, 1904, Smithsonian Misc. Col., vol. 44, no. 1417, plt. V, fig. 5 (as Fusus dupetit-thouarst). KEEN, 1971, Seashells of Tropical West America, p. 615, no. 1340, left fig. only (as Fusinus dupetitthouarsi) . Shell fusiform, turreted; protoconch of 14 turns with tip immersed, last 4 turn with fine axial ribs, ending in a thickened rib; whorls rounded on the teleoconch; axial ribs broad and low, obsolete on the gerontic stage; spiral sculp- ture of numerous cords of nearly equal strength through- out; aperture ovate, outer lip lirate within; heavy callus on the columella and along the short thick canal, with a chink behind. Falsifusus Grabau, 1904 Type species: Fusus meyeri Aldrich, 1886 (an Eocene fossil) Shell fusiform; protoconch of 34-4 turns, the 1°** minute, gradually increasing in size to form a narrow cone, last 2-3 turns with narrow, crowded, axial ribs, and with a thread- like basal carina on the ribbed portion. Falsifusus dupetitthouarsi (Kiener, 1840) (group B) Fusus Dupetit-Thouarsi Kiener, 1840, Spéc. gén. et icon. des cog. viv., pt. 1 (Fusus), p. 15, plt. 11. ?Fusus funiculatus Lesson, 1842, Rev. Zool. (Soc. Cuv.), vol. 5, P. 104. Fusus dupetit-thouarsti, Grabau, 1904, plt. V, figs. 1-4. Explanation of Figures 1 to 4 Figure 1: Syntype of Fusus turris Valenciennes, 1832 Figure 2: Holotype of Fusus Dupetit-Thouarsi Kiener, 1840 Figure 3: Protoconch of Fusus turris Valenciennes, 1832 (Guaymas) Figure 4: Protoconch of Falsifusus dupetitthouarsi (Kiener, 1840) (Guaymas) [PoorMAN] Figures 1 to 4 THE VELIGER, Vol. 23, No. 4 Vol. 23; No. 4 THE VELIGER Page 347 Fusinus dupetitthouarsi, Keen, 1971, p. 615, no. 1340, left fig. only. Shell fusiform; protoconch of 4 turns, the 1*' minute, gradually increasing, the last 3 turns with narrow, crowded axial ribs and a fine basal carina, last turn slightly angu- lated at the periphery; by the 4 whorl of the teleoconch, 2 peripheral cords dominant and upper cords reduced to threads, whorls beginning to sag; by the 6" whorl, periph- eral cords reduced to 1, outline of the whorl sharply angu- lated, nearly flat above and below; on the gerontic stage, spiral cords of equal strength, with a single stronger periph- eral cord marked by nearly obsolete axial ribs as low nodes. ACKNOWLEDGMENTS A word of appreciation is due Dr. James McLean and Dr. Philippe Bouchet, without whose cooperation this project could not have been completed. I also wish to acknowledge the contributions of Dr. S. Stillman Berry and his library. Literature Cited Carpenter, Poitier PEARSALL 1857. Report on the present state of our knowledge with regard to the Mollusca of the west coast of North America. Reprt. Brit. Assoc. Adv. Sci. for 1856: 159 - 368; plts. 6-9 (before 22 April 1857) 1864. Supplementary report on the present state of our knowledge Reprt. Brit. Assoc. Adv. Sci., 33 (for 1863): 517 - 686 (post 1 Rprt. Brit. Assoc. Adv. Sci., 33 (for 1863): 517-686 (post 1 August 1864) (reprint: 1872, Smithson. Misc. Coll. 10 (252): 1-172; original pagination at top of page]) FIsCHER-PigeTTE, E. & J. BEIGBEDER 1944. Catalogue des types de gastropodes marins conservés au labora- toire de Malacologie. IV Fusidae, Buccinidae. Bull. Mus. Nat'l. Hist. Nat. (2) 16(1): 70-77 (Jan.-Feb. 1944) Grasau, AMADEUS W. 1904. Phylogeny of Fusus and its allies. 44 (1417): ilit+192 pp.; 23 text figs.; 18 plts. Keen, A. Myra 1971. Sea shells of tropical West America: marine mollusks from Baje California to Peru, 2nd ed. Stanford Univ. Press, Stanford, Calif. i-xiv+1064 pp.; ca. 4000 text figs.; 22 col. plts. (21 September 1971) Kiener, Louis CHARLES 1840. Spécies général et iconographie des coquilles vivantes. Genre Fuseau. Paris; 5: 1 - 593 30 pits. Lesson, RENE PRIMVERE 1842. Mollusques recueillis dans la mer du Sud et Océan Atlantique, par M. Adolphe Lesson. Rev. Zool. Soc. Cuvier. 5: 104, 212, 213 RAFINESQUE-SCHMALTZ, CONSTANTINE SAMUEL Smithson. Misc. Coll 1815. | Analyse de la nature ou tableau de l’univers et des corps organi- sés. Barravecebia, Palermo. p. 145 {not seen] REEVE, LOVELL AUGUSTUS 1847. Conchologia Iconica: or illustrations of the shells of molluscous animals. Genus Fusus. London, 4: plt. 11 (November 1847) Tryon, GzorGE WASHINGTON, Jr. 1881. Manual of Conchology. VALENCIENNES, ACHILLE 1832. Coquilles marines univalves de TAmérique équinoxiale, re cueillies pendant le voyage de MM. de Humboldt et Bonpland. In: FE H. A. von Humboldt « A. J. A. Bonpland, Voyage aux régions équinoxiales du nouveau continent. 2: 262 - 339; plts. 53-57 (1) 3: 58, 278; plt. 36 Page 348 THE VELIGER Vol. 23; No. 4 The Littoral Polyplacophora of Shell Beach, San Luis Obispo County, California BY BARRY FOLSOM PUTMAN Moss Landing Marine Laboratories, Moss Landing, California 95039 INTRODUCTION AFTER APPROXIMATELY SIX YEARS (1974-1980) of collect- ing and observing littoral mollusks in San Luis Obispo County, California, a considerable sampling of the indi- genous species of Polyplacophora has been collected. The intent of this paper is to present the species of littoral poly- placophoran mollusks found by the author at Shell Beach along with their approximate zonation, habitat, and abundance. SITE LOCALITY anp ECOLOGICAL NOTES Shell Beach is a small, Pacific-front community located in San Luis Obispo County at Latitude 35°11'N, Longi- tude 120°51’W on U.S. Highway 101, approximately 18 km south of the city of San Luis Obispo. Overlooking the Pacific atop rocky cliffs, beach access is possible in two areas via stairs that conveniently divide the location into a northern area and a southern area. North Shell Beach is a characteristic semi-protected, rocky outer coast, receiving almost directly the force of the northwesterly winds from the Pacific, the direct force being broken by Point San Luis. South Shell Beach, on the other hand, is a fully pro- tected, rocky outer coast. Here the direct force of the Pacific is not only broken somewhat by Point San Luis but is also lessened by the presence of several, slightly offshore rocks that provide a rather good chiton habitat. TERMINOLOGY Zonation: When dealing with the intertidal zonation of Shell Beach, I use a system superficially resembling that proposed by Ricketts & CaLvin (1968) in that the terms “Zone 1” through “Zone 4” are used. However within the system used in this paper, “Zone 1” extends from the splash zone down to, but not including, the Pollicipes- Mytilus zone; “Zone 2” begins with the Pollicipes-Mytilus zone and extends down to a point roughly half-way be- tween this and the mean lower low water; “Zone 3” covers the remaining half of the habitat to mean lower low water, and “Zone 4” is identical to that of Ricketts and Calvin in that it covers the portion of the littoral zone only ex- posed during minus tides. This particular system is un- usually well suited to most, if not all, of San Luis Obispo County’s rock intertidal areas. Habitat: ‘Two notations will generally be given for hab- itat: One for physical habitat and one for biological habitat. 1. Physical Habitat: Defined by 4 terms: a. Exposed Nip: A small impression within solid rock that is generally open to direct sunlight. Exposed Shelf: An unrecessed, relatively flat sub- stratum generally open to direct sunlight. c. Protected Shelf: An unrecessed, relatively flat substratum not exposed to the light, as habitats under ledges and dark areas on the sides of tidal troughs. Under Rock: A substratum beneath a movable stone or boulder, generally positioned on a gravel or sand/mud bottom. b. XS) Biological Habitat: That habitat characterized by the organisms found in association with the animal. Since the primary purpose of this paper is one of systematics, only brief, random notations shall be given for some of the species. Abundance: Due to the arbitrary nature of this term, abundance shall be expressed using the terms “very com- mon,” “common,” “uncommon,” and “rare.” Within the parameters of these terms, a “very common” chiton is a species that would always be found on any given day; whereas a “rare” animal is one that was found by the author only once, and only singularly. Vol. 23; No. 4 SYSTEMATIC ACCOUNT North Shell Beach Cyanoplax dentiens dentiens (Gould, 1846). Zone 2, ex- posed shelf ; uncommon. Cyanoplax hartwegii (Carpenter, 1855). Zone 2, exposed shelf; very common. Found under drapes of Pelvetia. Lepidozona cooperi (Dall, 1878). Zone 3, under rock; common. Mopalia lignosa (Gould, 1846). Zone 4, exposed shelf; un- common. Mopalia muscosa (Gould, 1847). Zone 3, exposed shelf; common. Nuttallina californica (Reeve, 1847). Zone 1, exposed nip; very common. Zone 2, exposed shelf; common. Stenoplax heathiana Berry, 1946. Zone 3, under rocl:; common. Tonicella lineata (Wood, 1815). Zone 3, protected shelf; uncommon. On lower zone Lithothamnium. SYSTEMATIC ACCOUNT South Shell Beach Cryptochiton stelleri (Middendorff, 1847). Zone 4, exposed shelf; rare. Cyanoplax hartwegii (Carpenter, 1855). Zone 2, exposed shelf; very common. Found in aggregations under drapes of Pelvetia. Zone 3, exposed shelf, uncommon. Zone 4, protected shelf, rare. Lepidozona cooperi (Dall, 1878). Zone 3, under rock; com- mon. Zone 4, under rock; common. Lepidozona mertensii (Middendorff, 1847). Zone 4, ex- posed shelf; uncommon. Mopalia hindsi hindsi (Reeve, 1847). Zone 3, exposed shelf ; uncommon. THE VELIGER Page 349 Mopalia lignosa (Gould, 1846). Zone 3, exposed shelf; un- common. Zone 4, under rock; common. Mopalia muscosa (Gould, 1847). Zone 2, exposed shelf; common. Zone 3, under rock; uncommon. Nuttallina californica (Reeve, 1847). Zone 2, exposed nip; very common. Zone 3, exposed shelf; uncommon. Stenoplax heathiana Berry, 1946. Zone 4, under rock; common. Tonicella lineata (Wood, 1815). Zone 4, protected shelf; common. DISCUSSION Within the waters of San Luis Obispo County, some 47 species of polyplacophoran mollusks have been noted (PuTMAN, 1980). Of these 47 species, 8 have been found to eccur within the littoral zone of north Shell Beach, 10 within the littoral zone of south Shell Beach. Excluding sublittoral forms, of likely occurrence within the littoral part of the Shell Beach area, due to their occurrence in littoral areas to the north or to the south, or both, are the following species: Lepidopleurus rugatus (Pilsbry, 1892), Ischnochiton regularis (Carpenter, 1855), I. interstinctus (Gould, 1846), Stenoplax fallax (Pilsbry, 1892), Lepido- zona sinudentata (Pilsbry, 1892), Basiliochiton heathii (Pilsbry, 1898), Katharina tunicata (Wood, 1815), Placi- phorella velata Dall, 1878, Chaetopleura gemma Pils- bry, 1892, and Mopalia ciliata (Sowerby, 1840). Literature Cited PutMAN, Barry Fotsom 1980. Taxonomic identification key to the described species of polypla- cophoran mollusks of the west coast of North America (north of Mexico). Pacif. Gas Electr. Co., Dept. Engineer. Res. Reprt. 411- 79.342. Pacif. Gas Electr. Co. Biol. Labor., Avila Beach, Calif. Ricketts, Epwarp FE & Jack CaLviN 1968. Between Pacific tides. 4th ed. rev. by Joel W. Hedgpeth. xiv+ 614 pp.; illus. Stanford Univ. Press, Stanford, Calif. Page 350 THE VELIGER. Vol. 23; No. 4 Neustonic Feeding in Early Larvae of Octopus dofleint (Wilker) JEFFREY B. MARLIAVE Vancouver Public Aquarium, P O. Box 3232, Vancouver, British Columbia, Canada V6B 3X8 (1 Plate) INTRODUCTION IN THE LABORATORY, early larval stages of the giant Pacific octopus, Octopus dofleini (WULKER, 1910), were observed to exhibit a distinctly neustonic behavioral pattern; that is, an association with the surface tension film. This observa- tion is the first evidence for evolved neustonic behavior in planktonic larvae of an octopodid species, although near- surface occurrence has been documented in other ceph- alopods (Davin, 1965; HARTMANN, 1970). This behavior bears relevance to the trophic relationships of larval Octo- pus dofleini. MATERIALS anp METHODS The present observations were conducted on octopus lar- vae which hatched on October 31, 1978 and were reared in four 1000 L tanks with through-flowing seawater (10° C, 29%.) toa maximum of 87 days. Two to three thousand larvae were placed in each tank at hatching (numbers determined from mortality records). The groups of larvae in each of 4 different tanks were fed different diets: live adult and naupliar Artemiasalina; frozen krill (Euphausia pacifica); frozen krill supplemented with larval cottid fish (Hemilepidotus hemile pidotus) ; and all of these foods, plus trout micropellets, in the last group. The frozen krill was shaved onto the water surface where it floated briefly. RESULTS Newly hatched larvae were offered adult Artemia, which they fed on immediately after its introduction. At 1-day age, frozen krill was offered to and accepted by larvae. Larvae at 2-days age grasped pieces of krill within a few seconds of introduction of the food and a majority of lar- vae had filled guts, indicated by the pink color of krill, within 10-15 minutes. By 6-days age, a pattern of neustonic feeding on floating krill became evident. Larvae contacting floating pieces of krill with their mantles would turn over and adhere to the surface tension film in an inverted pos- ture (Figure 1). They would use their siphon to move lat- erally, their weight supported by the surface tension film. Upon contacting floating krill with the tentacles, the lar- vae would seize the krill and leave the surface to feed on it. Only a few larvae would be seen in this inverted posture prior to a feeding, but within minutes of food introduc- tion a significant fraction, numbering at least a thousand individuals, would be clinging to the surface. With filled Explanation of Figure 1 Larval Octopus dofleini adhering to surface film in inverted posture (upper night) and larva in normal swimming posture holding piece of krill (lower left). Reflected glare reveals attachment of suckers to surface and depression of surface tension film. THE VELIGER, Vol. 23, No. 4 [MarutAve] Figure 1 Vol. 23; No. 4 THE VELIGER Page 351 guts, this behavior would be abandoned, usually within one half hour of the start of feeding. By 28-days age, the tendency to adhere to the surface was reduced. This be- havior disappeared shortly thereafter when larvae had grown to an average 4mm interocular width (defined as distance between outermost points of the eyes, in Rosson, 1929) compared to 3mm at hatching. By 43-days age, the larvae visually oriented toward and darted at food items in the manner of larval and adult squid (HuRLEy, 1976). Thus, this neustonic feeding behavior appears to be char- acteristic of recently hatched larvae only, as is the case with many marine fish species (MARLIAVE, 1977). That the larvae grew and developed beyond the stage of this mode of behavior suggests that it can occur normally in the field, as morbidity would be expected if this phenomenon were an artifact of unnatural laboratory conditions. The Octopus dofleint larvae seemed capable of display- ing food preferences. The action of grasping a food item was always preceded by brief contact with the item by ten- tacle tips. All items would be touched, then acceptable food items grasped for feeding. In a choice situation with roughly equal food sizes and densities, krill was absolutely preferred to adult Artemia. Survival on krill was longer (no = 1800, max. 87-days, 50% dead at 16-days) than on Artemia alone (no = 2600, max. 22-days, 50% dead at 5- days). Fish larvae were not available until the octopuses were 21-days old, at which time a strong preference for krill was evident. Fish larvae were usually eaten only at times of day when krill was unavailable. The occurrence of food selection, together with the sequence of touching objects with the arm tips prior to grasping and eating, suggests a chemotactile discrimina- tory function, as has been demonstrated for adult Octopus vulgaris (WELLS, 1963; WELLS, et al., 1965; Nixon & Ditty, 1977). Adult octopuses have more sensory cilia tufts on their suckers than do squids, probably as a basis for chemosensation (Nixon & Ditty, 1977). Squid larvae (Loligo opalescens) reared in the laboratory displayed the adult mode of visually oriented feeding from hatching on- ward (HurLEy, 1976). DISCUSSION Strictly planktonic larvae of octopodids have the poten- tial to exhibit coordinated benthic crawling if placed on a microscope slide, although they rarely adhere to sub- strates in the laboratory (BoLETzKy, 1977). This paradox- ical ability has been hypothesized by Boletzky to indicate a gradual transition from the plankton to the benthos. The present observations suggest an alternative explanation, that this potential evolved to permit exploitation of neus- tonic food sources by means of adhering to the surface tension film and moving the arms in a coordinated fashion to detect floating prey. Field studies on neuston patchiness, especially of potential prey which can rest on the surface film (epineuston), may clarify the significance of this neus- tonic feeding behavior to the survival of early larval stages of octopuses. Literature Cited BOLETZEY, SIGURD V. 1977. Post-hatching behaviour and mode of life in cephalopods. Symp. zool. Soc. London 38: 557 - 567 Dav, P M. 1965. The surface fauna of the ocean. Hartmann, J. 1970. Diurnal vertical migration and vertical microdistribution of cephalopods of the neuston west of Madeira. Ber. deutsch. wissen. Komm. Meeresforsch. 21: 494 - 499 Huruey, A. C. 1976. Feeding behavior, food consumption, growth, and respiration of the squid Loligo opalescens raised in the laboratory. Fish. Bull. U. S. 74: 176 - 182 MaruiAveE, JEFFREY B. 1977. Development of behavior in marine fish. Sci. Res. Lab. Tech. Reprt. 20: 240 - 267 Nrxon, M. « PN. Ditty 1977. Sucker surfaces and prey capture. 38: 447-511 Rosson, Guy Copurn 1929. A monograph of the Recent Cephalopoda. Part I. Octopodinae. Clay & Sons, Bungay, Suffolk, 263 pp.; 7 plts. WELLs, M. J. 1963. Taste by touch: some experiments with Octopus. Biol. 40: 187 - 193 WELts, M. J., N. H. Frezman & M. ASHBURNER 1965. Some experiments on the chemotactile sense of octopuses. Journ. exp. Biol. 43: 553 - 563 Endeavour 24: 95 - 100 Mem. Univ. Mar. Symp. zool. Soc. London Journ. exp. Page 352 THE VELIGER Vol. 23; No. 4 Casmaria atlantica Clench (Mollusca : Gastropoda): Thoughts on its Evolution J. GIBSON-SMITH anp W. GIBSON-SMITH Escuela de Geologia, Minas y Petrofisica, Universidad Central de Venezuela, Apartado 47.351, Caracas 1041 A, Venezuela (2 Text figures) THE ONLY RECORD OF Casmaria atlantica Clench in the southern Caribbean appears to be that of BAYER (1935: 112) as Phalium erinaceum var. vibex (Linnaeus) from “near Caracas” (ABBOTT, 1968: 201). The acquisition of a specimen of this rare species to add to our collection of the Venezuelan Recent gave rise to the ensuing thoughts. It is the only representative of the genus in the Western Atlan- tic; in the Indo-Pacific there are two species with sub- species and a single subspecies in the Panamic Province. In a list of circumtropical, prosobranch gastropod spe- cies EMERSON (1978: 98, table 2) excluded, “tropical superspecies with allopatric populations in the western and eastern Pacific and the Western Atlantic that are presently recognised as distinct species, ¢. g., Casmaria erinaceus (Linnaeus), C. vibexmexicana (Stearns) and C. atlantica Clench,” a statement perhaps implying that they might be considered synonymous. Earlier, ABBoTT (1968: 201) made C. atlantica a subspecies of C. ponderosa (Gmelin, 1791) noting that, “This rare Caribbean subspecies is scarcely differentiated from C. ponderosa form cernica Sowerby, 1888, from the Indian Ocean.” Nevertheless, for our part, we have great difficulty in accepting these proposed close relationships between C. atlantica and its Indo-Pacific and Panamic congeners and suggest, somewhat tentatively, an altogether different relationship. Casmaria atlantica Clench, 1944 (Figures 1, 2) Description: The Venezuelan specimen is thin shelled and of medium size, the bodywhorl comprising 2 of the shell. Protoconch of 44 smooth whorls, last 1 whorls large and bulbous, first 2 whorls with a thin brown line at the suture. Teleoconch of 44 whorls, the first 14 whorls weakly reticulate with 5 fine spiral threads crossed by exaggerated growth striae; remainder with crowded microscopic spiral and growth scratches only, appearing smooth except for 2 distinct spiral threads adjacent to the siphonal canal. Outer lip thickened and flaring, no previous varices, and having 6 minute denticles adjacent to the anal canal and 5, weak denticles on the outer face of the lower part. Colu- mella truncated by a strong ridge forming the border of the short, strongly recurved anterior canal; above and on the parietal wall are g fine, subequal plicae. Parietal area and columella covered in a thin, microscopically pitted glaze. Colour translucent cream to tan, darker over the dorsum; darker patches subsuturally and 8 along the back of the outer lip; obsolescent (faded?) spirals of darker patches scarcely visible. Height 33.1mm, diameter 19.1 mm. Remarks: The specimen comes from Tucacas, Falcén State, an area of coral reefs, lagoons and mangroves. It was found by Michael Osborn, SCUBA diving at about 30m. Figure 1 Casmaria atlantica Clench, 1944 Ventral view Vol. 23; No. 4 Figure 2 Casmaria atlantica Clench, 1944 Dorsal view Comparisons: It differs from the northern Caribbean form as described by CLENcH (1944: 2) in having weak reticulate sculpture on the early whorls, in having 6 minute denticles on the outer lip bordering the anal canal and in having more plicae on the inner lip. However, the two forms are otherwise so closely similar that these differences can be accepted as due to variation. Evolution: The more accentuated sculpture of the Venezuelan specimen places it marginally closer to another Western Atlantic cassid: Phalium (Tylocassis) ctcatrico- sum (Gmelin, 1791) of which a specimen (smooth form) is to hand from Barbados. Although placed in the synonymy of P. (T.) granulatum (Born, 1780) by AsBotT (1974: 161), P. cicatricosum (smooth form) lies morphologically somewhere between P. granulatum and Casmaria atlantica as the table shows: Diameter: Sculpture Height Height P. granulatum very strong 10oomm 70% P. cicatricosum ~— weak 60mm 67% C. atlantica very weak 40mm 5770 In one respect only does the above sequence not apply: the protoconch of P. cicatricosum, to judge from one spec- imen only, is a little wider than either that of P. granu- latum or C. atlantica: 2.4mm versus 2.0mm. In the Indo- Pacific it is Casmaria which occurs in a nodulose and a smooth form but, here, it is Phalium cicatricosum which is said to occur in the two forms. CLENcH (1944: 9) notes that, “In regard to certain of the synonyms [of cicatrico- THE VELIGER Page 353 sum], the names abbreviatum Gmelin, lactea Kiener and peristephes Pils. and McG. all refer to the small and nodu- lose specimens” and the two he illustrates have heights of only 30mm and 36mm, suggesting that they may represent a nodulose form of C’.. atlantica rather than of P. cicatri- cosum. Alternatively, they may be more properly identified as P. abbreviatum Gmelin. Parenthetically, it can be noted here that Abbott (1968: 201) says that P. granulatum lacks the brown sutural line of the protoconch of C. atlantica; it is our observation that it is present in both P. granulatum and P. cicatricosum; it is a feature also of Casmaria in the Indo-Pacific. Discussing the paleogeography of the Indo-Pacific and Panamic gastropod faunas Emerson (1978: 92) has this to say, “The small Indo-Pacific faunal element in the Panamic Province . . . is generally believed to have been the result of rather recent introductions, whereas the minor element of essentially circumtropical species . . . in the west American tropical waters is thought to represent relict elements dating from the late Tethyan faunas. . Unfortunately there is little direct evidence to substantiate these biogeographical conclusions. The only Recent Indo- Pacific species recognised as fossils in the west American deposits are Cypraea cernica Sowerby in Pleistocene ter- race deposits on Guadalupe Island . . . and possibly Conus tessulatus Born . . . from the late Pliocene of Imperial County, California.” Taken together with his earlier quoted statement it seems that Emerson would regard both Casmaria atlantica and C. vibexmexicana as Tethyan relict elements. According to Eames (in Davies 1971: 346) Casmaria had already evolved by Eocene times in the Indo-Pacific and he made it a subgenus of Semicassis which, he says, occurs also in Europe. The latter, therefore, is likely to be ancestral to P. granulatum and its homologue P. granu- latum centiquadratum Valenciennes of the Western Atlan- tic and Panamic Provinces, respectively. In passing, it may be said that it is unfortunate that there is little agreement between authors for this line at the generic and subgeneric levels: Wooprinc (1959: 199) prefers Semicassis (Tylo- cassis), KEEN (1971: 501) Cassis (Semicassis) and ABBOTT (1974: 161) Phalium (Tylocassis). As Casmaria evolved in the Indo-Pacific in pre-Eocene times it is unlikely to have appeared in the Western Atlan- tic at Tethyan times and its absence, to date, from the rich fossil record of the region supports, even if it does not con- firm, this view. Thus, our difficulty in accepting a close relationship between Casmaria ponderosa atlantica and the Indo-Pacific, or even the Panamic, forms. Nor is Phalium cicatricosum known as a fossil, only the ancestors Page 354 THE VELIGER Vol. 23; No. 4 of P. granulatum and P. centiquadratum are present in the region. Furthermore, had C’. atlantica evolved from a Tethyan ancestor, a close relative could have been ex- pected also in the Panamic Province; instead, there is only C. vibexmexicana which bears little resemblance and which, in any case, has been made a subspecies of C. erina- ceus rather than of C. ponderosa (ABBotT 1974: 161). Nor in the Panamic Province is there a cicatricosum-like form of P. centiquadratum. The situation, therefore, in the Western Atlantic vis-a-vis the Panamic is totally distinct. Records of the precursors of Phalium granulatum, under several names, are too numerous to discuss in detail. They can be traced back to at least three, widespread early Miocene localities as P. aldrichi Dall (Chipola Formation, Florida) or as cf. P. aldrichi Dall (Culebra Fermation, Panama, and Cantaure Formation, Venezuela). The im- portant point is that, up to the Pliocene, all are less than 50mm in height. In the early Pliocene Punta Gavilan For- mation, Venezuela, P. senni Rutsch, a somewhat aberrant (attenuated) form, reaches 68 mm (specimen from our col- lections) whilst for the youngest Tertiary record from the late Pliocene Mare Formation, Venezuela, the height of P. granulatum is still only 55mm. Recent specimens of P. granulatum, however, show an almost explosive increase to reach 1oomm whereas P. centiquadratum, be it noted, remains a pedestrian 55m in height. The present day situation in the Western Atlantic vis-a- vis the Panamic can be said to be “dynamic” as witnessed by the significant increase in height of Phalium granu- latum and the evolvement of P. cicatricosum, P. abbrevi- atum and “Casmaria” atlantica. Our interpretation of the situation is that we are wit- nessing a delayed response by Phalium granulatum to the change in environment brought about by the emergence of the Isthmus of Panama in the late Miocene and early Pliocene, a change which, as is well known, decimated the Caribbean fauna in general (WooprtNnG, 1966). Need we be surprised that this delayed response to the changed eco- logical conditions emulates an evolutionary event which occurred in the Indo-Pacific Eocene some fifty million years ago? Just how Rcicatricosum and “Casmaria” atlan- tica relate to one another is conjectural; the fact that the former seems to have the larger protoconch : uggests that the two lines stem directly from P. granulatum, in which case, with two mutations, or possibly three including P. abbreviatum, is P. granulatum approaching extinction? The placing of the Western Atlantic “Casmaria” within inverted commas is simply to draw attention to the like- lihood that it is a pseudo-Casmaria rather than true Casmaria. Although made a subspecies of C’. ponderosa, as mentioned earlier, the fact is that C. atlantica has a larger protoconch than either of the Indo-Pacific species C. ponderosa or C. erinaceus (AsBott 1968: 189, 176), the former, indeed, having the smallest of the three. Finally, as Casmaria can no longer be considered as cir- cumtropical in distribution and as no Tethyan relict ele- ments of it exist in the fossil record of the region, C. erina- ceus vibexmexicana must be added to the list of recent introductions into the Panamic Province from the Western Pacific. SUMMARY Casmaria, of pre-Eocene origin in the Indo-Pacific, is presently regarded as a Tethyan relict element with a circumtropical distribution. It is suggested, however, that C. atlantica Clench from the Western Atlantic is not a true Casmaria having evolved, since the late Pliocene, as a delayed response to the changed ecological conditions in the Caribbean attendant upon the emergence of the Isth- mus of Panama. It is also suggested that C. erinaceus vibexmexicana (Stearns) of the Panamic Province, in the absence of any fossil record of the genus in the region, must be regarded as a relatively recent arrival from the Western Pacific. Literature Cited AsBoTT, RopertT TUCKER 1968. Indo-Pacific Mollusca. 2 (9) 1974. American seashells. aod ed., 663 pp.; 24 ool. pits. Van Nostrand Reinhold, New York Bayer, C. 1935. Catalogue of the Cassididae in the Rijksmuseum van Natuur- lijke Historie. Zool. Meded. Rijksmus. Nat. Hist. Leiden 18: 93 - 120 CLENCcH, WILLIAM JAMES 1944. The genera Casmaria, Galeodea, Phalium and Cassts in the west- ern Atlantic. Johnsonia 1 (16): 16 pp.; 8 plts. Eames, FE. (in A. Morley Davies) 1971. Tertiary faunas. and ed., vol. 1: 571 pp.; George Allen & Unwin, London EMERSON, WILLIAM KgitH 1978. Mollusks with Indo-Pacific faunal affinities in the Eastern Par cific Ocean. The Nautilus 92 (2): 91-96 (27 April 1978) Gipson-SmiTH, J. « W. Gipson-SmrtrH 1979. The genus Arcinella (Mollusca: Bivalvia) in Venezuela and some associated faunas. Geos No. 24: 11-32:1-3 Keen, A. Myra 1971. Sea shells of tropical West America: marine mollusks from Baja California to Peru, 2d ed. Stanford Univ. Press, Stanford, Calif. i-xiv+ 1064 pp.; ca. 4000 text figs.; 22 col. plts. (21 September 1971) Rutscu, R. FE 1934. Die Gastropoden aus dem Neogen der Punta Gavilan in Nord- \ Venezuela. Abh. Schweiz. Palaeont. Gesell. 54-55: 169 pp.; 9 pits. WEIsBorRD, NoRMAN EDWARD 1962. Late Cenozoic gastropods from northern Venezuela. Bull. Amer. Paleont. 42 (193): 1-672; plts. 1-48 Wooprinc, WENDELL PHILLIPS 1959. Geology and paleontology of Canal Zone and adjoining parts of Panama. Geology and descriptions of Tertiary mollusks (Gastropoda: Trochidae to Turritellidae). U. S. Geol. Surv. Prof. Paper 306-B: 147 - 239; plts. 24 - 38 1966. The Panama land bridge as a sea barrier. Phil. Soc. 110 (6): 425 - 433 Proc. Amer. Vol. 23; No. 4 THE VELIGER Page 355 The Status of Pholadomya candida G. B. Sowerby, I, 1863 BY J. GIBSON-SMITH ann W. GIBSON-SMITH Escuela de Geologia, Minas y Petrofisica, Universidad Central de Venezuela, Apartado 47.351, Caracas 1041 A, Venezuela (1 Text figure) IN A RECENT REPORT by Bruce RUNNEGAR (1979: 17!) entitled, “Pholadomya candida Sowerby: The Last Ca- daver Unearthed,” the statement is made that, “A few live specimens of the deep-burrowing bivalve Pholadomya candida were collected in the Virgin Islands during the last century, but the species now appears to be extinct.” Hence the title of his report. In this opinion, however, the author is mistaken: the species still survives! Otsson (1964: 72) notes that, “P. candida, the type of the genus, occurs in the southern section of the Caribbean and its shell is often cast up onto the beach after severe storms. A dead specimen retaining both valves was dredged by Mr. Jay Weber of North Miami at Water Island in the Virgin Island group in comparatively shallow water; a figure of this shell is shown on Plate 5, figure 4 [not 2 as stated]. As a fossil in Neogene formations, Phola- domya is rare as its thin delicate shell does not lend itself to good preservation and most specimens are known only in the form of molds or casts... .” In our Venezuelan collection a left valve (length 60.6 mm, height 38.5mm) and a right valve with beak of left valve attached (length 45.4mm, height 29.0mm) were collected close inshore at a depth of 1m on coral sand at Borburata, State of Carabobo. This locality is a partially artificial small bay with narrow entrance through fringing reefs. At one side is an oil tank-farm and several years ago the entrance and bay were dredged to a depth of some 14m to accommodate tankers of greater draught. Thus, a few metres from where the specimens were picked up, the bottom slopes steeply down to this depth. Furthermore, the bay is unaffected by storms. It may be, therefore, that the animals were retrieved from this deeper water, possibly by the octopuses which are present. In the private collection of a SCUBA diver (Mrs. Joan d’Esposito, Puerta La Cruz, State of Sucre) are a left valve (length 104.8mm, height 65.0mm) and a right valve (length 97.5mm, height 65.0 mm); the depths were not recorded but were, in any case, less than 40m. Finally, in a third private collection (Sr. G. Ferrato, Cardon, Paraguana Peninsula) is a large single valve (length 120 mm, height 78 mm) which was picked up on a beach on the west coast of the Peninsula fronting the Gulf of Venezuela whose average depth is some 22 m (Fig- ure 1). No live specimens have been found, but the Bor- burata material, retaining ligament and _ periostracum, was obviously not long dead. All the above specimens were collected within the last 17 years. Thus, Pholadomya candida is by no means extinct, al- though a perusal of recent literature leads one to wonder: amongst others, WARMKE & ABsBoTT (1961) and Axssott (1974) make no mention of it, whilst DANcE (1972: 98) says, “known from a few specimens collected many years ago.” Part of the confusion concerning Pholadomya candida may be taxonomic as explained by Cox «& NEWELL (in Moore 1969: N827): “Although several Recent species from various parts of the world have been described under Pholadomya, the type species is the only one resembling Figure 1 Pholadomya candida from El! Pico Beach, Venezuela. Length 120 mm; height 78mm; thickness (one valve only) 25 mm. Photograph provided by Sr. G. Ferrato, Cardon, Venezuela. Page 356 THE VELIGER Vol. 23; No. 4 the numerous fossil forms in size and shape (our italics). The remainder are relatively small shells, some of which belong to the genus Panacca Dall, while some others, par- ticularly certain very small forms from the Antarctic, should probably be included in one or more new genera. All known Recent Pholadomyidae are moderately deep- to deep-water forms, whereas the Mesozoic species of the family are found commonly in shallow-water sediments. No satisfactory subgeneric classification of the numerous species of Pholadomya has yet been achieved and a thor- ough revision of the genus would result in the recognition of any more subgeneric groups than those here distin- guished.” Although they then give the range of Phola- domya s.s. as, “Upper Trias to Recent, cosmopolitan,” it appears that P. candida is the only survivor of the nomi- nate subgenus. More recently, in a review of the genus in the Tertiary of California, ZINSMEISTER (1978: 232) records 3 species pertaining to Pholadomya s.s. and two to the only other subgenus, P. (Buccardiomya), with the statement that, “Most of the California species appear to have lived in fairly deep water, but the occurrence of P. nasuta Gabb [Paleocene] with the shallow water assemblages in the Simi Hills indicates that the genus was not restricted ex- clusively to deep water habitats during the Tertiary.” We would go further: this shallow water, Paleocene ancestor of P. (P.) candida strengthens our view that throughout the Tertiary, as during the Mesozoic, the forms of Phola- domya s.s. were also confined to shallow water. In the fossil record of the southern Caribbean all representatives of the genus pertain to Pholadomya s.s. and all are associated with shallow water faunas; these include: P. walli Maury, 1925, early Miocene (Machapoorie beds), Trinidad. P. sawkinsi Maury, 1925, early Miocene (Machapoorie beds), Trinidad. P. falconensis F. & H. Hodson, 1927, middle to late Mio- cene, Venezuela. P. candida dalli Olsson, 1964, upper Neogene, SW Colombia. P. cf. candida Sowerby, early Pliocene, El Hato Member, Paraguana Formation, Venezuela (our collections, unpub- lished). Pholadomya sp., early Pliocene, Springvale Formation, Trinidad (H. E. Vokes 1938: 17). P. cf. candida Sowerby, late Pliocene Mare Formation, Cabo Blanco, Venezuela (our collections, unpublished). P. cf. candida Sowerby, late Pliocene (Pleistocene?) Playa Grande Formation, Cabo Blanco, Venezuela (WeIsBorD 1964: 411). P. candida Sowerby, Pleistocene, Aruba (WEISBORD 1964: 413). In a brief review of the Pholadomya candida line, WeIs- BORD (1964: 412) notes that, “There are only a few speci- mens of any of the late Cenozoic species of Pholadomya from tropical America, and none of them is perfect. Fur- thermore, the illustrations of P. candida by authors sug- gest that there is considerable variation in details of sculpture, so that all the known fossil species are similar to one variant or another of the Recent P. candida.” - a statement implying a likely degree of synonymy with which one would not wish to argue. Finally, two details can be added to the morphological description of Pholadomya candida from the Recent: the pustulose decoration, absent from the type specimen and usually absent from the fossil, is arranged in microscopic radial lines with as many as 6 lines on either flank of the radial ribs. Secondly, the thin, tan periostracum is in the form of a filamentous mat with the filaments gathered along the crests of the radial ribs, and along the axes of the attendant interspaces, into a fine thread. SUMMARY Some erroneous impressions concerning Pholadomya s.s. are corrected, namely, that since the Mesozoic it has lived only in deep water, that it is rare and that it is now extinct. The evidence presented shows that in the Cenozoic (Neo- gene at least) it was a not uncommon inhabitant of shallow water shelf areas where it still lives today in the form of Pholadomya candida Sowerby, in both the north and south Caribbean, at depths as shallow as 1 to 14m. Literature Cited Apsort, Rossrt Tvoxer 1974. American Seashells. and ed., Van Nostrand Reinhold Ga, New York; 663 pp., 4000+ text figs.; 24 plts. (in color) Dance, STANLEY PEER 1972. Shells and shell collecting. Moore, Raymonp C. 1969. Treatise on Invertebrate Paleontology, Part N, vol. 2, Mollusca 6, Bivalvia, pp. Nagi - Ng52; text figs. Geol. Soc. Amer. Inc. & Univ. Kansas Ousson, Axe, ADOLF 1964. Neogene mollusks from northwestern Ecuador. Paleo. Res. Inst., Ithaca, New York. 256 pp.; 38 plts. (28 October 1964) Runwneoar, Bruce 1979. Pholadomya candida Sowerby: The last cadaver unearthed. The Veliger 22 (2): 171-172; 1 plt.; 1 text fig. (1 October 1979) Voxes, Harotp Ernest 1938. Upper Miocene Mollusca from Springvale, Trinidad, British West Hamlyn Publ. Group, London Indies. Amer. Mus Novit. No. 988: 1 - 28; 29 figs. Warmke, Germaine L. & Ropert Tucker ABBOTT 1961. Caribbean scashells. pp. 1-348; 44 plts.; 34 text figs. Livingston Publ. Co. Narberth, Pa. Werssorp, Norman Epwarp 1964. Late Cenozoic pelecypods from northern Venezuela. Bull. Amer. Paleont. 45 (204): 1-564; 59 plts. ZINSMEISTER, WILLIAM JOHN 1978. Review of the bivalve genus Pholadomya from the Tertiary of California and the description of two new species. The Veliger a1 (2): 292-235; 1 pit. (1 October 1978) Vol. 23; No. 4 THE VELIGER Page 357 Biting as a Defense in Gastropods of the Genus Busycon (Prosobranchia : Melongenidae) PAUL J. WELDON Department of Zoology, University of Tennessee, Knoxville, Tennessee 37916 (1 Plate) INTRODUCTION SOME PROSOBRANCH GASTROPODS ward off predatory sea stars or gastropods through what can best be described as a biting response (see Discussion for species); female Fust- triton oregonensis (Redfield, 1848) do so presumably to protect their eggs against intruding conspecifics and echi- noderms (Eaton, 1972). By far the most notorious of the biting gastropods are those of the genus Conus, which will, when handled, inflict venomous bites on man (Konn, 1963) and octopod molluscs (CuMMINGs, 1936). Whether this behavior ordinarily occurs as a mode of defense in these snails, however, is not known. My observations in the field and laboratory indicate that the whelks Busycon contraritum (Conrad, 1840) and B. spiratum (Say, 1822) extend their proboscides to the side or over the dorsal part of their shell and bite, sometimes repeatedly, the feet of the molluscivorous gastropods Fasciolaria tulipa (Linnaeus, 1758) and Pleuroploca gigan- tea (Kiener, 1840) when attacked. Conspecifics (also dis- covered by B. Kent, pers. comm.), congeners, and the gastropods Melongena corona (Gmelin, 1791) and Poli- nices duplicatus (Say, 1822) also are bitten when placed on or against the shell of Busycon. It is unclear whether biting by whelks involves the use of the jaws, the radula, or both, but it clearly represents an aversive stimulus for the gas- tropods bitten. In most of the encounters observed in this study, gastropods contacted by the tip of the defender’s proboscis instantly retract their foot and withdraw into their shell, or they rapidly crawl away. This study was designed primarily to determine the nature of the stimuli that elicit biting in Busycon. Aside from Pratt’s (1974) inconclusive observations on the slipper shell, Crepidula fornicata Linnaeus, 1758, no at- tempts have been made to systematically delineate the stimulus control of gastropod biting of predators or, as it occurs with some, in bouts with conspecifics (GHISELIN & Witson, 1966; Epwarps, 1969; EATON, 1972; FISHLYN & PHILLIPS, 1980). TESTS anp RESULTS Twenty Busycon contrarium (shell length ey 5.7; 11.0- 22.5 cm) were used in these experiments. All animals were collected in waters around the Gulf coast of northem Florida and had been in captivity from 1 week to 4 months at the time of testing. They were maintained in 360L holding tanks (salinity 32-36%; temp. =15.0-17.5° C) with open recirculating sea water systems. In the first experiment the importance of chemical stim- uli from predators in the elicitation of proboscis extension was tested. Twelve whelks, isolated from other gastropod species for at least 24 hrs, were placed individually into a 5 L aquarium which, for 30 min, had contained three Fasciolaria tulipa (9 cm each). Each Busycon was observed for 15 min. The test tank was freshly conditioned for each test. Ten Busycon were tested in the same fashion in a 38L tank which had contained a Pleuroploca gigantea (32cm). None of the Busycon extended their proboscides during these experiments. To test the importance of tactile stimuli in eliciting bit- ing, a glass probe was rubbed gently against just the feet of twelve Busycon for 15 min each as they crawled in their home tank. A water-filled “balloon,” which might have more closely simulated the texture of a gastropod’s foot, was used in the same way with 8 snails. In no case was a proboscis everted. The importance of persistent contact-pressure cues on the shell in the elicitation of biting was revealed by holding a glass probe on the dorsoposterior crown of the shell of the whelks as they crawled (Figure 1). Manual force, suffi- Page 358 THE VELIGER Vol. 23; No. 4 cient to impede the snails’ normal pace, was applied con- tinuously for 30min. Both the number of proboscis ever- sions and the latency for each were recorded. Eleven of the 13 gastropods tested extended their proboscides out from under either side of the shell. The 9 which did so more than once during a test exhibited a shorter latency before everting the proboscis the second time than they did for the first protrusion (Table 1). In another experiment with 10 snails, contact-pressure similarly applied to the dorsal surface of the tip of the siphonal canal failed to elicit an extension of the proboscis. To obtain results from under more natural conditions, a Pleuroploca (32 cm) was positioned up against the poste- rior of either the columellar or outer side of the shell of 7 whelks in a counterbalanced experimental design. Here the Pleuroploca occasionally fell off the whelks and had to be positioned as before. Since the Pleuroploca suffered through few bouts of biting before withdrawing into its shell, in most cases it was necessary to terminate a trial within 10 min; one session lasted 29 min. Because of these procedural irregularities, a comparison of the results from the glass probe experiment with those from this one is not in order. All 7 snails bit. Twenty-four of the proboscis extensions occurring while the Pleuroploca was in contact with the whelks were directed to the side on which the snails were stimulated and two occurred on the contralateral side (x’?, P <.001). Both male and female Busycon were found to bite. DISCUSSION While water-borne chemicals from molluscan prey induce anteriorly projecting proboscis and siphonal extensions in Busycon (CopELAND, 1918; RAEIHLE, cited in PETtiTT, 1975), such stimuli from predators evidently are not suffi- cient for the elicitation of proboscis eversion. Other inves- tigators have found that chemicals alone fail to elicit defensive biting in other species (PRATT, 1974; FISHLYN & Puituips, 1980), and that, in encounters, biting occurs when the snails are contacted by predators (MaRGOLIN, 1975; FISHLYN & PHILLIPS, 1980; KENT, 1981). Housrick & FRETTER (1969) report that Cymatium spp. and Bursa spp. protrude their proboscides and eject a clear fluid on an attacker (unspecified), and that treating the shell roughly will elicit this response. It has been noted as well by several investigators that contact by sea stars or predatory gastro- pods, perhaps in conjunction with chemical cues, will elicit shell covering by podial flaps (MarcoLin, 1964) or the most extreme forms of escape among prosobranch gastro- pods (e. g., PHmtuips, 1977; WELDON & HoFFMAN, 1979). Table 1 The latency of the first proboscis eversion is greater than that of the second eversion for both glass probe (P < 0.005) and Pleuroploca contact (P < 0.10) (one-tailed Wilcoxon matched-pairs test). X latency for first proboscis X latency for second proboscis extension SD; range (sec) No. tested (No. observed) Glass probe contact 13 311.2 + 345.4 77 - 1240 (11) Pleuroploca contact 7 421.1 + 528.1 36 - 1577 (7) X total no. of proboscis extension SD; range (sec) extensions SD; range (No. observed) (No. biting) 69.1 + 72.3 3.2 + 1.7 15 - 287 1-6 (9) (11) 70.8 + 110.1 3.9 + 23 6 - 267 1-7 (5) (7) Explanation of Figures 1 and 2 Figure 1: Busycon contraritum (12cm long) being stimulated with a glass probe and extending its proboscis out (indicated by arrow) on the siphonal side of its shell Figure 2: Pleuroploca gigantea (32cm long) inverted to show how Busycon contrarium is held prior to feeding THE VELIGER, Vol. 23, No. 4 [Wetpvon] Figures 7 and 2 Vol. 23; No. 4 THE VELIGER Page 359 Obviously, actual contact by a predator denotes greater urgency for potential prey than do other types of stimuli alone. For the elicitation of biting, contact cues seem befitting since this defense would be effective only when an attacker falls within the limited range of extension of the proboscis tip of the biter. However, the possibilities that defensive biting is potentiated by water-borne chemicai stimuli, and that contact cues peculiar to predators are more efficacious in eliciting this response, need to be examined. In the way of ecological studies, Paring (1963) showed that Busycon contrarium and B. spiratum are taken as prey by Pleuroploca in a proportion about equal to the relative abundance of Busycon in shallow waters around northern Florida. He stated (op. cit.: 67) that “this suggests that Pleuroploca feeds on other gastropods as it encounters them, and that no selection is exercised.” This might also be construed as suggesting that biting, against this pred- atory gastropod at least, affords little protection for these whelks. However, a defensive response can be effective and result in prey being taken in proportion to their abundance in nature if the prey are highly preferred by the predator. My observations on the predatory behavior of some large Pleuroploca (25-32 cm) indicate that, in some cases, they are able to handle whelks in such a fashion as to pre- vent the proboscis from repeatedly contacting their foot. During a bout of biting, the lip of the outer (left) side of the shell of Busycon contrarium is positioned against the inside contour of Pleuroploca’s shell aperture (Figure 2). With the whelk’s aperture facing away, Pleuroploca main- tains its grasp on the shell and out of reach of the whelk’s proboscis. Attempts at biting having ceased, Pleuroploca envelops its victim and commences feeding. Now whether Pleuroploca routinely deals with Busycon spp. in this way, or whether other molluscivorous gastropods are capable of contending with biting gastropods in a similar fashion, is not known. Why do some prosobranchs bite in defending themselves against carnivorous gastropods and echinoderms, whereas many others exhibit only an escape response or shell cover- ing by podial flaps to these particular classes of predators? Pratt (1974) suggested that the occurrence of biting as opposed to escape in the suspension-feeding Crepidula for- nicata may be related to its small size and nearly sessile mode of existence, factors which might compromise the ability to execute an effective flight response. Alia carinata (Hinds, 1844) and Amphissa columbiana Dall, 1916, a couple of other snails which bite (FIsSHtYN & PHILLIPS, 1980; Kent, 1981) are relatively small as well (ca. 10 mm). For other species, possibly, the possession of an elongate proboscis for feeding may have been one positive factor leading to the evolution cf defensive biting. The majority of those now known to bite either gastropods (indicated by *) or echinoderms — Natica millepunctata Lamarck, 1822 (MarRGOLIN, 1975), *Fusitriton oregonensis (EATON, 1972), *Busycon spp., and *Cypraecassis testiculus Lin- naeus, 1758 (pers. observ.) — possess a proboscis used to attack, drill and/or insert into prey. Alternatively, these gastropods may be constrained for other modes of defense or favored for biting by other factors. Further documenta- tions and comparisons, then, are necessary for a more com- prehensive picture of this type of defense to emerge. ACKNOWLEDGMENTS I wish to thank Anne, Florence, and Jack Rudloe; the staff of the Gulf Specimen Co., Panacea, Florida; and Robert Brown, Little Torch Key, Florida for courtesies extended to me in the course of this study. Daniel L. Hoffman kindly assisted with observations on the biting behavior of Cypraecassis testiculus. D. L. Hoffman, Bretton W. Kent, and Alan J. Kohn made helpful comments on an earlier draft of this paper, and Joseph Rosewater provided infor- mation on some of the species’ descriptions. This study was supported, in part, by an NSF research grant (BNS-78- 14196) to Gordon M. Burghardt. Literature Cited CopeLanp, Manton 1918. The olfactory reactions and organs of the marine snails Alectrior obsoleta (Say) and Busycon canaliculatum (Linn.). Journ. exp. Zool. 25: 177 - 227 Cummincs, Bruce 1936. Encounter between cone shell and octopus. North Queens- Id. Nat. 4: 42 Eaton, Cuarites MitcHeti 1972. The reproductive and feeding biology of the prosobranch gastro- pod Fusitriton oregonensis (Redfield) (Fam. Cymatiidae). Master's thesis, Univ. Washingt., Seattle, WA. 40 pp. Epwarps, Dacias Craic 1969. Predators on Olivella biplicata, including a species-specific pred- ator avoidance response. The Veliger 11 (4): 326-333; plt. 51; 1 text fig. (1 April 1969) FisHtyn, Dessay A. & Davip W. PuHILLIps 1980. Chemical camouflaging and behavioral defenses against a pred- atory seastar by three species of gastropods from the surfgrass Phyllo- spadix community. Biol. Bull. 158: 34 - 48 Gutsevin, MicHarL TENANT & Barry R. WILSON 1966. On the anatomy, natural history, and reproduction of Cyphoma, a marine prosobranch gastropod. Bull. mar. Sci. 16: 132-140 Houerick, Joseru R. & Vera Fretrer 1969. Some aspects of the functional anatomy and biology of Cymattum and Bursa. Proc. malac. Soc. London 38: 415 - 429 Kent, Bretton W. 1981. Behavior of the gastropod Amphissa columbiana (Prosobranchia: Columbellidae). The Veliger 23 (3): 275-276 (1 January 1981) Page 360 THE VELIGER Vol. 23; No. 4 Kon, ALAN JAcogs 1963. | Venomous marine snails of the genus Conus. In: Keegan, H. L. & W. V. MacFarlane (eds.): Venomous and poisonous animals and noxious plants of the Pacific area, pp. 83 - 96; 2 plts.; 2 text figs. Per- gamon Press, New York Marco in, ABRAHAM STANLEY 1964. | The mantle response of Diodora aspera. Anim. Behav. 12(1): 187 - ¥94 1975. Responses to sea stars by three naticid gastropods. Ophelia 14: 85 - 92 PaInE, Rospert TREAT 1963. Trophic relationships of 8 sympatric predatory gastropods. Ecology 44: 63 - 73 PertTitT, CHARLES 1975- A review of the predators of Littortna, especially those of L. saxatilis (Olivi) (Gastropoda : Prosobranchia). Journ. Conch. 28: 343 - 357 Puinuirs, Davin W. 1977- Avoidance and escape responses of the gastropod mollusc Olivella biplicata (Sowerby) to predatory asteroids. Journ. exp. mar. Biol. Ecol. 28: 77 - 86 Pratt, Davin M. 1974. Behavioral defenses of Crepidula fornicata against attack by Urosalpinx cinerea. Marine Biol. 27: 47 - 49 WELpon, Pau J. & Danie, L. HorrmMan 1979. Kick and thrust foot movements in the righting and escape be- havior of marine prosobranch gastropods. (Mollusca: Gastropoda). Zeitschr. f. Tierpsychol. 50: 387 - 398 Vol. 23; No. 4 THE VELIGER Page 361 Chaetogaster limnaer (Oligochaeta : Naididae) Inhabiting the Mantle Cavity of the Asiatic Clam, Corbicula fluminea, in Barkley Lake, Kentucky JAMES B. SICKEL anp MARK B. LYLES Department of Biological Sciences, Murray State University, Murray, Kentucky 42071 DurRING A TWO YEAR SAMPLING program in which the Asiatic clam, Corbicula fluminea (Miller, 1774), was being collected from Barkley Lake (Cumberland River), Trigg County, Kentucky, a naidid oligochaete, Chacto- gaster limnaei von Baer, 1827, was discovered living on the gills within the mantle cavity of the clams during a brief two month period in late spring. ENc (1976) first reported C. limnaei in the Asiatic clam from California and indi- cated that infestation was seasonal with the highest prev- alence (87%) occurring from March through May. He noted no evidence of parasitism and reported a low inten- sity of symbionts within their host (several worms per clam). Chaetogaster limnaei was first noticed in Corbicula from Barkley Lake (Cumberland River Mile 67.0) on 21 May 1980 when 4 clams were being examined to determine their reproductive condition and were found to contain many worms. The clams were in poor condition,evidenced by their light weight and emaciated appearance. Clams were collected again on 4 June, and one was found to con- tain between 40 and 50 worms crawling on the gills, foot and mantle surface. Dissection of the clam revealed no worms internally, but there were a number of unidentified hyaline spheres in the gonads along with deteriorating clam eggs. Those clams in poorest physical condition, which generally had a high intensity of C. limnaei, pos- sessed nodules or calcareous concretions on the inner shell surface producing a chalky appearance. Clams kept in aquaria died within a few days and floated to the surface. No C. limnaei were found in dead clams or in aquarium water putrefied by dead clams. Clams were collected again on 6, 17, and 24 June and the prevalence of infection was greater than 80% with the highest intensity in one clam being 167 worms. On 15 August many floaters, floating dead clams with closed shells, were observed in Barkley Lake. Twelve live and 8 dead Corbicula were examined and no C. limnaez were found. Over half of the clams in the bed at Cumberland River Mile 67.0 were dead. Most of those still alive showed signs of stress—emaciated body, separating gill filaments, and rough inner surface of shell. The effect of Chaetogaster limnaei on Corbicula is un- certain. In one clam, worms were observed between the mantle and shell. However, mantle tissue of clams in poor condition was very thin and easily torn. It is not known whether the worms penetrated the mantle on their own or crawled through the lesions caused by some other agent. Chaetogaster limnaei has been characterized as either parasitic or commensal on snails (BRINKHURST & JAMIE- SON, 1971). GRUFFYDD (1965) provided evidence that two forms of Chaetogaster limnaei exist, one commensal on Lymnaea pereger, C. limnaei limnaei, and the other C. limnaei vaghini Gruffydd, 1965, parasitic in the kidney of L. pereger. GAMBLE & FriED (1976) reported C. I. limnaei feeding on subepithelial tissue of Physa acuta. Chaetogas- ter limnaei has been reported also from fingernail clams, Sphaerium (BarBour, 1977) and mussels, Unionidae, (CoKER et al., 1921). Although more Chaetogaster limnaei were found in clams in poor condition than in healthy clams, there was no conclusive evidence indicating parasitism. The relation- ship between C. limnaez and Corbicula fluminea is uncer- tain and needs further investigation. ACKNOWLEDGMENTS The authors thank Jarl K. Hiltunen, Great Lakes Fishery Laboratory, for confirming the identification of Chaeto- gaster limnaei and Murray State University students Mark A. Young and Michael L. Russell for assistance in collect- ing and examining clams. Page 362 THE VELIGER Vol. 23; No. 4 Literature Cited Barsour, MicHae T. 1977. Chaetogaster limnaet limnaei (Oligochaeta: Naididae) inhabit- ing the mantle cavity of the pill clam Sphaerium. Trans. Amer. Mi- crosc. Soc. 96(1): 141-142 Brinkuurst, R. O. « B. G. M. JamMizson 1971. Aquatic Oligochaeta of the world. Univ. Toronto Press; 860 pp. Coxer, R. E., A. E Suira, H. W. Crarx « A. D. Howarp 1921. Natural history and propagation of fresh-water mussels. Bull. U. S. Bur. Fish., 37: 77 - 181 Ene, Larry L. 1976. A note on the occurrence of a symbiotic oligochaete, Chaeto- gaster limnaei, in the mantle cavity of the Asiatic clam, Corbicula manilensis. The Veliger 19 (2): 208 (1 October 1976) Gamstez, H. Ray « BERNARD FRIED 1976. Experimental evidence for parasitism in the relationship between Chaetogaster limnaet limnaet (Oligochaeta) and Physa acuta (Gastro- poda). The Veliger 18 (4): 393-395; 1 plt. (1 April 1976) Grurrypp, Lu. D. 1965. Evidence for the existence of a new subspecies of Chaetogaster limnaeit (Oligochaeta) in Britain. Journ. Zool. 146: 175-196 Vol. 23; No. 4 THE VELIGER Page 363 A Comparison of Fijian Forms of Conus coronatus and Conus aristophanes C. RP LEWIS (4 Text figures) INTRODUCTION THE SPECIES KNOWN as Conus coronatus Gmelin, 1791 and C. aristophanes Sowerby, 1857 are common in Fiji. However, differentiating one from the other can be difh- cult. CERNOHORSKY (1964) presents criteria for separating these two species. They are listed in Table 1. While these criteria are more definitive than others that have been published, and while they are generally satisfactory, they do not always permit identification of individual Fijian were observed in their native habitat and in a home aquarium. The cleaned shells were then examined with the intent of elaborating on the criteria suggested by Cer- nohorsky and of exploring and defining additional char- acteristics that might be useful in discriminating between these two closely related species. Upon gross examination, live animals of Conus coro- natus could not be distinguished from those of C. aristo- phanes. Except for pale crawling surfaces and a bright touch of color at the tip of the siphons, the visible fleshy parts of both species were a translucent grayish white to Table 1 Descriptive criteria for distinguishing between Conus coronatus and Conus aristophanes as given by Cernohorsky (1964). Conus coronatus Conus aristophanes 1. Shape ventricose conical Greatest width below shoulder at shoulder Aperture wide, flaring narrow 2. Spire height elevated depressed 3. Spiral ridges 5 to 7, fine 1 or 2, coarse 4. Coronations sharply cut, rarely obsolete nodulose, often obsolete 5. Pattern: Blotches present, brown absent Waist/shoulder bands (not stated) present 6. Basal ridges strong, interrupted strong, continuous specimens. Not infrequently, a shell may be classified as Conus coronatus by some of the Cernohorsky criteria, but as C. aristophanes by others. It was difficulty in using these criteria that prompted the present study. Specimens tentatively identified as Conus coronatus and C. aristophanes were collected in Fiji. Living animals * Current address: Fiji School of Medicine, Suva, Fiji tan dusted to varying degrees with small, irregular points of reddish purple to black pigment. The tip of the siphons varied from a pale red or orange in lighter colored indi- viduals to a deep purplish-red in darker specimens. Vari- ations in the degree of pigmentation were striking within both species. Attempts to distinguish between the two on the basis of color, pattern or form of the live animal were unsuccessful. Page 364 Attention to habitat proved more revealing. Although the two species occasionally are found together on the main barrier reef, Conus coronatus seems to prefer a harder substrate, clearer water and a higher energy en- vironment. It frequently is found just behind the reef’s edge in heavily washed pockets or stretches of coarse sand. Only occasional specimens of C. aristophanes are found amongst the C. coronatus in such a habitat. On the other hand, C. aristophanes generally is found farther back on the reef in broad stretches of finer sand or mud that are protected from the pounding sea. At this kind of site, most specimens found were C. aristophanes. The preference of Conus aristophanes for quieter wa- ter and finer sand or mud was observed at numerous locations along the southern Viti Levu coast. Mudflats extending from the mangroves out into the lagoon were often found to be populated by pure colonies of C. aristo- phanes. Live C. coronatus were never collected from this type of environment. Details of the study of conchological features are pre- sented below. MATERIALS A series of 50 specimens tentatively identified as Conus coronatus, and a second series of 50 tentatively identified as C. aristophanes were selected for conchological study. These were designated as the C-Group and the A-Group, respectively. Preliminary identifications were based on the criteria given by CERNoHORSKY (1964) with particular attention given to shape, the number of spiral striae and color. Although Cernohorsky did not list color as a cri- terion, he did note that the color of the body whorl of C. coronatus was fawn or pale brown while that of C. aristo- phanes was gray to greenish gray, and such seemed to be a reasonably constant characteristic. After gaining familiarity with these two species, assignment to the C-Group or A-Group was reasonably certain for about 90% of the specimens, but little more than a guess in other instances. Specimens were selected from several localities to help lessen the possibility of undue influence by a peculiarity in any one colony. Members of the C-Group were from various reef locations around Suva and from the island of Nayau which lies in the Lau Group 240km to the east of Viti Levu. Specimens in the A-Group were from the reefs around Suva and from Suva Point. The latter is a rather polluted rocky mudflat with few weeds and little coral. THE VELIGER Vol. 23; No. 4 It is next to shore and immediately adjacent to the city of Suva. An extensive pure colony of Conus aristophanes lives there. Only mature shells, or reasonably mature shells 20mm or more in length, were accepted into the two study Groups. Only shells in good condition were selected for inclusion. No shell eroded to the extent that a potentially useful conchological character might be obscured was admitted into either group. METHODS Cleaned shells were examined grossly and with the aid of a hand-lens. Measurements were made with the aid of calipers modified by “rhinoplasty” as per KoHN & Rices (1975). Numerous differences between shells of the C-Group and the A-Group were apparent, but not a single feature could be called exclusive to either Group. Rather, it was observed that a characteristic would be more or less frequent in one Group than in the other. When a character was perceived to be common in one Group but rare in the other, it was carefully defined with reference to typical specimens from the two Groups. Then each of the 100 shells was classified individually by that definition. In this way, each specimen was designated as belonging to the C-Group or the A-Group on the basis of that one characteristic. Assuming the original placement of shells was correct, or nearly correct, the number of shells mistakenly assigned to the wrong Group gave a measure of the number of errors generated by that defini- tion. In no case was a defined character deemed accept- able as a criterion for distinguishing between Fijian Conus coronatus and C. aristophanes unless fewer than 5% of the shells were misassigned when applying it. In the case of every definition posed, some shells were atypical. Either they could not be evaluated (e. g., blotch color when there was no blotch), or they were midway between the more typical members of the two Groups. Such shells could not be clearly identified as belonging to either to the C-Group or the A-Group. To accommodate these specimens, a third, “Indeterminate,” category was established for each definition. A large percentage of in- determinate specimens detracted from the usefulness of a criterion. Hence, any character which could not be evaluated with certainty in 50% or more of the specimens was not considered useful enough to pursue further. Vol. 23; No. 4 RESULTS Acceptable Criteria Of the various conchological characters examined dur- ing this study, 7 were found to be highly specific. These were characters which, when they could be evaluated, identified a specimen in hand as either a member of the C-Group or the A-Group with a greater than 95% cer- tainty. That is, using any one of these as a criterion, less than one evaluated Conus coronatus in 20 was misidenti- fied as C. aristophanes, or vice versa. The 7 strong 95%- criteria are presented below. Results are summarized in Table 2. THE VELIGER Page 365 This criterion, essentially the same as Number 1 of Cernohorsky, was often difficult to apply to a shell in isolation. However, comparing the shell in silhouette with specimens of typical shape (see Figure 1) nearly al- ways permitted identification. Of the 95 shells which could be evaluated, 93 were correctly identified. Upon gaining some familiarity with shape as criterion, it was one of the most accurate means for distinguishing between Fijian forms of Conus coronatus and C. aristophanes. 2. WwTH Conus coronatus: Broad with ratio of width to height of body whorl equal to 0.87 or more. Table 2 Data establishing strong (95%) criteria for distinguishing between Fijian Conus coronatus and Conus aristophanes (see text). The “+” column gives the number of specimens identified as Conus coronatus by the listed character. The “—” column gives the number of specimens identified as Conus aristophanes. The “0” column shows indeterminate specimens. Conchological character 1. Shape 2. Width 48 0 3. Spire height 28 21 4. Spiral striae 48 2 5. Blotch color 43 7 6. Pits 39 10 7. Line count 1 1 2 2 4 43 1 1 21 27 0 1 5 43 0 1 14 34 1 1 9 39 1 1 1Group includes one specimen ultimately scored as Conus aristophanes. This specimen contributes three of the six “—” scores. 2Group contains 49 specimens rather than the original 50. One shell, a Conus coronatus mistakenly included in the Group, has been omitted. 1. SHAPE Conus coronatus: Inflated conical with sides of body whorl uniformly convex in outline from shoulder to angu- lar constriction near anterior tip. Sharply angular at shoul- der with coronation generally pointing slightly inward. Maximum diameter below shoulder. Aperture wide and flaring. Conus aristophanes: Conical with sides of body whorl slightly convex, flattened or nearly straight. Slightly rounded at shoulder with coronations vertically oriented. Maximum diameter usually at or near shoulder. Aper- ture narrow and straight. Indeterminate: Shape intermediate between above (4% of specimens in present series) . Conus aristophanes: Narrow with ratio of width to height of body whorl equal to 0.84 or less. Indeterminate: 0.85 or 0.86 (4%). The width of each specimen was measured at its broad- est diameter. The height of the body whorl was measured from the most anterior tip to the base of the first and second coronations at the shoulder in a line parallel to the axis of the shell’s greatest length. This height repre- sented the vertical projection of the lateral aspect of the body whorl and excluded the posterior portion of the last whorl. The latter was taken as spire. The width/height ratios within the C-Group varied from 0.82 to 0.96. Only 2 shells had a ratio of less than 0.85. Ratios within the A-Group varied from 0.77 to 0.88 Page 366 THE VELIGER Vol. 23; No. 4 with 2 specimens above 0.86. The C-Group averaged 0.90 (standard deviation: +0.025); the A-Group averaged 0.82 (s. d.: +0.02). Considering the normal range of typical Conus corona- . tus as 0.85 to 0.95, and of typical C. aristophanes as 0.78 to 0.86 (average +2 s. d. units), ratios of 0.85 and 0.86 were common to both. These ratios, where the ranges overlapped, were designated as indeterminate. The relative width of a specimen was not readily dis- cernable by simple visual inspection. The eye had difficul- ty ignoring shape and spire and distinguishing between the lower limits of “broad” and the upper limits of “narrow.” Careful measurements with modified calipers were required for correct assessment by this criterion. 3. Spre HEIGHT Conus coronatus: Elevated spire with ratio of height of spire to height of body whorl equal to 0.39 or more. Conus aristophanes: Relatively low spire with ratio of height of spire to height of body whorl equal to 0.30 or less. Indeterminate: 0.31 to 0.38 (42%). This criterion is a quantified version of the Cernohors- ky criterion Number 2 in Table 1. The height of the body whorl was measured as described above. The height of the spire of each specimen was determined by subtracting the height of the body whorl from overall length. Spire height/body height ratios within the C-Group varied from 0.30 to 0.46 with an average of 0.39 (s. d.: + 0.04). Only one shell had a ratio less than 0.32. With- in the A-Group, ratios varied from 0.18 to 0.42 with an average of 0.29 (s. d.: + 0.045). Only one specimen fell below 0.22 and only one was above 0.38. Taking the normal range of typical Conus coronatus as 0.31 to 0.47, and of typical C. aristophanes as 0.20 to 0.38 (average + 2s. d. units), ratios of 0.31 to 0.38 were common to both species and thus indeterminate. Since this broad indeterminate range covered most of the region between the 2 averages, nearly half of the specimens (42 out of 100) could not be evaluated. Of those shells which could be evaluated, 55 out 57 were properly identified. Specimens with deeply eroded spires could not have been accurately measured; they were excluded at the onset of the present investigation. And, as in the case of width, relative spire height was often not readily ap- parent upon simple visual inspection. The use of this criterion also required careful measurements with modi- fied calipers. 4. SPIRAL STRIAE Conus coronatus: 5 or more ridges or grooves per spire whorl. Conus aristophanes: 3 or fewer ridges or grooves per spire whorl. Indeterminate: 4 ridges or grooves (7%). This criterion is similar to the Cernohorsky criterion listed third in Table 1. Magnification was required to accurately count the number of spiral striae. They were not always distinct or continuous, even along a single whorl, and in many speci- mens the number of striae varied slightly from whorl to whorl. In examining shells of the present series, the entire spire of each specimen was scanned to find the maximum number of deep striae whether they were on the outer- most whorl or on one of the smaller inner ones. Only distinct ridges or grooves were counted so that there would be little question that a shell had at least the number of spiral striae recorded. In the C-Group, 45 of the specimens were found to have 5, 6 or 7 striations per whorl. Eight was the maxi- mum observed. Two specimens had only 4 striae; none had fewer. On the other hand, 43 of the members of the A-Group had only 2 or 3 striations per whorl. No shell had zero striations; 5 specimens had 4 and one had 5 dis- tinct striae. Four striations were taken as indeterminate. A simple count of spiral striae had the advantage of being being a reasonably objective process which did not require calipers. By this criterion, 92 of the specimens were identified either as Conus striatus or Conus aristo- phanes with but 2 errors (the Conus aristophanes men- tioned above with 5 striae, and a shell ultimately scored as Conus aristophanes which had 6 striae and was mis- takenly included in the C-Group). 5. BLorcH CoLor Conus coronatus: Blotches pure brown with no gray or green. Conus aristophanes: Blotches gray, olive or green. May have brown or tan undertones, but gray or green pre- dominates. Indeterminate: Blotches absent or blotches colored other than above; e. g., brown with undertones of gray or green (21%). While neither the color of the body whorl nor the pres- ence or absence of blotches turned out to be adequately diagnostic in these Fijian specimens, blotch color did. In all specimens of the C-Group, blotches were brown when Vol. 23; No. 4 present. Shades varied from a delicate and translucent golden to dark and opaque. Occasionally, grayish or greenish undertones were present. When blotches were present in members of the A- Group, they were nearly always gray or olive. However, the blotches of many specimens in this Group were tinted with brown or tan. The shades of color were subtle and attempting to distinguish between a pure olive-green and a green tinted with brown was not practical. Consequent- ly, a trace of brown was accepted as a standard feature for Conus aristophanes. Several specimens, especially of the C-Group, had blot- ches which ran together to give an encircling dark band. In such instances the color of the band was taken as the “blotch color.” Specimens rich in brown but showing some gray or green were designated indeterminate. Shells with- out blotches were also designated as indeterminate. Blotch color proved accurate in 77 of the 78 specimens which could be evaluated by this criterion. However, some care had to be taken in application. Very dark or very light shades of olive sometimes appeared brown upon casual observation. But with a hand-lens, and in good lighting, the green became apparent. Moreover, the green pigment is the first to be lost in sun-bleached shells. This criterion was only applied to fresh specimens with live colors. 6. Prrs Conus coronatus: Rows of pits to shoulder of body whorl. Conus aristophanes: Pits completely absent. Indeterminate: Pits present on body whorl but not ex- tending posteriorly as far as shoulder (20%). As the criterion listed 6" in Table 1, Cernohorsky de- scribed the sculpturing of the body whorl of Conus coro- natus and C. aristophanes in terms of interrupted vs. con- tinuous basal ridges. But, in addition to ridges, these shells also were found to have separate and distinct grooves running immediately posterior to the ridges. In the C- Group, these grooves were frequently pitted by small, close-set punctate depressions. In fact, toward the shoul- der of most shells in this Group, grooves were absent, and the only sculpturing was parallel spiral rows of tiny but distinct pits. Many specimens of the A-Group lacked grooves and most lacked pits. When grooves or pits were present in members of this Group, they were generally confined to the anterior half of the body whorl. Only rarely did grooves or pits extend to as far as the shoulder. The presence or absence of pits could be determined with greater certainty than the presence or absence of THE VELIGER Page 367 grooves, and pits were more diagnostically characteristic than grooves. Hence, the presence or absence of pits (rather than grooves) was taken as the criterion. Of 40 shells pitted all the way to the shoulder, 39 were Conus coronatus. And of 40 shells found completely lacking in pits, 39 were C. aristophanes. The remaining members of both species were pitted, but the pits did not reach to as far as the shoulder; these were classed as indeterminate. 7. Line Count Conus coronatus: 17 or more primary lines encircling body whorl. Conus aristophanes: 14 or fewer primary lines encirc- ling body whorl. Indeterminate: 15 or 16 lines (45%). Parallel lines of alternating white and dark brown dots or dashes encircled the body whorl of every specimen. These lines were superimposed on the elevated ridges, when ridges were present. They were immediately ante- rior, in a one-to-one relationship, to the grooves or rows of pits. Weaker secondary lines, between the main ones and not in proper relationship to the sculpturing, were sometimes seen in large specimens. In the A-Group the brown of the lines was usually arranged in relatively long and uniform dashes (84%), while in the C-Group the pigmentation tended to be broken into smaller and more irregularly spaced dust- like points (86%). This difference in the nature of the lines was helpful in distinguishing between members of the 2 Groups, but it was not constant enough to serve as a criterion. However, in the C-Group the lines were gen- erally more closely spaced, hence more numerous. Within each Group small shells had as many lines as large ones, and a count of the number of primary lines did provide an acceptable criterion. Shells in the C-Group averaged 16.7 (s. d.: + 1.0) primary lines per shell with a range of 14 to 18. In the A-Group the average was 14.8 (s. d.:+ 1.0) with a range of 12 to 17. Setting the indeterminate region at 15 and 16 to cover most of the overlapping zone encom- passed nearly half the specimens, but only 2 cases of mistaken identity resulted among the 54 shells which could be evaluated. Rejected Criteria Several conchological characteristics were examined and rejected as criteria for distinguishing between shells of the C-Group and A-Group. These were character- istics which were not the near-exclusive property of either Group. Any reliance upon them individually would have Page 368 THE VELIGER Vol. 23; No. 4 produced an unacceptably high incidence of misidentifi- cations among the specimens under study. Seven of the more visible of these are noted below. Nature oF Coronations (Cernohorsky Criterion Num- ber 4) While members of the C-Group generally had high and sharply-cut coronations on the spire, and those of the A- Group had lower and more nodulose ones, such was often not the case. In the C-Group, 14% of the shells had low or nodulose (or both) coronations; in the A- Group, 20% had high and sharply-cut ones. In addition, about 4 of the shells in each Group were intermediate and could not be clearly designated as either high or low, sharply-cut or nodulose. CoroNATION CouNT It appeared that shells of the C-Group had a greater number of tubercles on the spire than those of the A- Group. However, a count of coronated elevations on the body whorls failed to reveal a definable difference be- tween the 2 Groups. Kon «& Riccs (1975) also reported no difference in this parameter among ‘Tahitian speci- mens of Conus coronatus and C. aristophanes. PRESENCE OR ABSENCE OF BiotcH (Cernohorsky Crite- rion Number 5, in part) Eighty-two % of the specimens in the C-Group had distinct, dark blotching on the body whorl. In 12% the blotching was diffuse or indistinct, and in the remaining 6% there was no blotch. But many of the A-Group also had blotches. In this Group, 28% were distinctly blotched and another 58% had suggestions of blotches such that they had to be classified as indeterminate. In only 14% were blotches completely and unquestionably absent. Waist/SHOULDER BANDS (Cermohorsky Criterion Num- ber 5, in part) Light colored bands encircling the body whorl at waist and shoulder were features Cernohorsky related to Conus aristophanes. And, in fact, 94% of the shells of the A- Group did have such bands. However, so did most of the shells of the C-Group; 52% of the latter had distinct bands, and in another 40% there were hints of bands such that they had to be called indeterminate. Waist/ shoulder banding was completely undetectable in only 8% of the members of the C-Group. Nature oF Basat Rwces (Cernohorsky Criterion Num- ber 6) Most specimens (92%) of the C-Group possessed spi- ral rows of discrete white beads or granulations over the anterior portion of the body whorl. This produced the strong but interrupted basal ridges of Conus coronatus pointed out by Cernohorsky. In fact, in some specimens these rows of granulations covered the entire body whorl. On the other hand, sculpturing in the A-Group was more subdued. Some specimens completely lacked ridges. Oth- ers, as per Cernohorsky, had irregular to smooth con- tinuous basal ridges. But many (36%), especially those from the main barrier reef, had distinctly beaded or inter- rupted ridges. This latter type of sculpturing could not be distinguished from that of typical members of the C- Group. Bopy Cotor — ExcLupinc BLoTCcHES As noted by CERNoHORSKyY (1964), specimens of the A-Group were usually gray or olive-green while those of the C-Group were generally brown, tan or yellow over most of the body whorl. Both were occasionally tinted with pink. The gray/green vs. brown/yellow difference in body color was a good criterion for distinguishing be- tween the 2 Groups. However, when applied to individual specimens, reliance upon color as a criterion, excluding the color of blotches, was singularly misleading. Several shells were misassigned at the onset of the present study when body color was used for preliminary placement into Groups. Specimens of Conus coronatus with a pure gray body color were encountered (10% in present series), and a green or olive tint was not uncommon (46%) somewhere on the body whorl of this species. Shells of the A-Group exhibited less variation in body color. Those from muddy inshore locations were generally darker than those from the barrier reef, but in both habitats they were almost always pure gray or olive (96%). Nevertheless, variabili- ty within the C-Group precluded using body color as a differentiating character. Waite AXIAL STREAKS Numerous short, irregular, white axial streaks were present in most specimens of the C-Group and in many specimens of the A-Group. They appeared to be more frequent, intense and irregular in the C-Group, but at- tempts to quantify differences or otherwise define the streaks so as to frame them as a meaningful criterion did not meet with success. THE VELIGER Page 369 Figure 1 Characteristic shapes of Conus coronatus (left) and Conus aristophanes (right) Analysis Each shell was evaluated on the basis of the 7 Accept- able Criteria described above. Specimens were scored +1 for each Conus coronatus character, o when indeter- minate and —1 for each C’. aristophanes character. Thus, Figure 2 Forms of Fijian Conus coronatus. Shell at upper left is most typical form scores ranged from +7 when a shell was evaluated as C. coronatus by all criteria, to —-7 when evaluated as C. aristophanes by all criteria. A plot of this Net Character Score vs. number of specimens resulted in a clearly bi- modal distribution with no overlap (see Figure 4). Shells scoring as C’. aristophanes gave a somewhat lower average and broader distribution because shells in the A-Group more often had to be judged as indeterminate. Figure 3 Forms of Fijian Conus aristophanes. Most common forms at right Except for truncation at the extreme, distribution with- in each of the 2 Groups approximated a Gaussian curve. Considering each as such, and considering the Net Char- acter Score as a parametric continuum, normal statistical procedures were applied. Specimens with a positive score averaged -+-5.7 with a standard deviation of + 1.0. Those scoring negatively averaged —4.9 with a standard devia- tion of +1.4. Thus, assuming the 7 criteria to be inde- pendent of each other, about 95% of the specimens scor- ing as Conus coronatus were expected to have scores ranging from +-4 to +7, and about 95% of the specimens scoring as C. aristophanes should have had scores from —2 to —7. Agreement between actual and expected values proved satisfactory. DISCUSSION The criteria proposed by CERNoHoRSKY (1964) distin- guish between typical Fijian specimens of Conus corona- tus and C. aristophanes. But these 2 species are so closely related to each other, and so variable in form, sculpture and pattern, that one or another of his criteria often fail, or identify a specimen wrongly. To use the Cernohorsky criteria with success, one has to examine a large number of shells to learn which criteria deserve the most cre- dence and which may be disregarded when a specimen has some C’. coronatus and some C. aristophanes charac- ters. From the data presented here, it may be seen that the first 3 of the Cernohorsky criteria listed in Table 1 Page 370 Number of Specimens aia ie Semen LIne SWIC) Wo Conus aristophanes (-) THE VELIGER Vol. 23; No. 4 Cine Pate RCM an Laar a ye oe! Conus coronatus (+) Net Character Score Figure 4 Plot of number of specimens vs. Net Character Score revealing Conus coronatus and Conus aristophanes as separate population groups. Bar graph shows observed number of specimens plotted are sound ones if interpreted with care, but the last 3 merit little reliance. In this paper, and in the Cernohorsky publication, the shape of the body whorl is defined descriptively. This pro- against Net Character Scores. Curve shows theoretical distribu- tions within each group as calculated from the 8 individual pheno- typic frequencies vides a rapid and satisfactory means for distinguishing between Fijian forms of Conus coronatus and C. aristo- phanes, but a more objective system would be desirable. Koun « Riccs (1975) have developed a simplified model Vol. 23; No. 4 THE VELIGER Page 371 ——————————_—_—_—_<_<_<$§<«—[/“<—_._._._.aeaeeaaaaaLaL—————SSSSS for quantifying certain morphometric parameters, and they have applied their methods to specimens of C’. coro- natus and C. aristophanes from Tahiti. One of the para- meters by which they found the Tahitian species to differ from each other was in “shape of generating curve.” This measurement reflects the wide and flaring aperture of C. coronatus as compared to C. aristophanes. However, other differences in shape (e. g., the more posterior posi- tion of the maximum diameter in C. aristophanes, the more angular constriction near the anterior tip in C. coro- natus, etc.) either were not found to differ or were not evaluated by the Kohn and Riggs model. Such differences are slight, and they will probably be difficult to quantify with sufficient sensitivity, but the eye can usually discern them in Fijian specimens. Relative width was not mentioned by Cernohorsky, but it was one of the morphometric parameters which Kohn and Riggs found to differ in Tahitian specimens. As “relative diameter,” they found Conus coronatus and C. aristophanes to average 0.75 and 0.71, respectively. Aside from the possibility that Tahitian and Fijian speci- mens might differ, these values are lower and not as widely separated as reported in the present study because of a slight difference in the method of calculation. As denominator, Kohn and Riggs took the entire body whorl (“aperture height”), which includes both the lateral and posterior aspects of the final whorl. Here, the body whorl is measured only to the external shoulder with the poste- rior portion of the last whorl being considered as spire. Since the spire of these 2 species does differ ( C. coronatus is high, C. aristophanes is low), including the posterior aspect of the last whorl in the denominator decreases the width to height ratio by only a little in the case of C. aristophanes, but by more in C. coronatus. For comparative purposes, the relative widths of the Fijian specimens studied here may be calculated in 3 ways: 1. Denominator equal to body whorl to shoulder (as in this study) ; 2. Denominator equal to entire body whorl (as per Kohn and Riggs) ; 3. Denominator equal to total shell length. Respective values, with those of Conus coronatus given first, are:1. 0.90+0.03 vs. 0.82 +0.02; 2. 0.82+0.03 vs. 0.77+0.02; 3. 0.65+0.02 vs. 0.63 + 0.03. As may be seen, differences between the 2 species become less as more spire is included in the de- nominator until including all of the spire negates the usefulness of relative width as a meaningful parameter. From the second set of values, it appears that Fijian speci- mens are somewhat broader than their Tahitian counter- parts. Spire height is a sound criterion when carefully quanti- fied. Cernohorsky simply stated that Conus coronatus has a higher spire than C. aristophanes, and this is generally true; but, without actual morphometry, this is often not a criterion which can be applied with any degree of con- fidence. As far as Fijian specimens are concerned, relative spire height can only be used as a criterion for distin- guishing between these 2 variable species when measure- ment shows it to be equal to or greater than the average for C. coronatus, or equal to or less than the average for C. aristophanes. Kohn & Riggs did not measure relative spire height, per se. One of their parameters, “relative whorl height” (height of the penultimate whorl /aperture height), might correlate with the relative spire heights recorded here, but their measurements revealed no difference between Tahitian specimens of Conus coronatus and C. aristopha- nes. The number of spiral striae is also a sound criterion when properly quantified, but Cernohorsky did not tell one what to do when there were 3 or 4 striae. The data presented herein alleviate this problem with respect to Fijian specimens. Kohn and Riggs used the number of spiral striae as a single criterion for specifying a shell as Conus coronatus (> 5) or C. aristophanes (<5), hence a difference in their values for this parameter was pre- determined. In their Tahitian material they found the former averaged 5.8 striae and the latter 2.9 striae per whorl. The Fijian specimens of the present study aver- aged 6.0 and 2.9 striae per whorl, respectively. Blotch color, the presence or absence of pits, and line count are criteria not addressed by either Cernohorsky or Kohn and Riggs. Cernohorsky did mention that the blotches were brown in Conus coronatus, and this is in agreement with the findings of the present study, but he did not specify blotches in C. aristophanes. Each of these 3 criteria appears to be as accurate and reliable as any other for distinguishing between Fijian specimens of C. coronatus and C. aristophanes. All 7 acceptable criteria have an accuracy of at least 957%. Thus, all are considered equally credible. But, since none is 100% reliable, it is inevitable that an occasional specimen will have one or more characters of the wrong species. The question which arises is: How should speci- mens with mixed results be considered? A shell with one Conus coronatus character, one C. aristophanes character and 5 indeterminate evaluations cannot be identified as either species because neither character may be disregarded in favor of the other. On the basis of the given criteria, it can not be separated from a shell with 7 indeterminate evaluations. Any shell with an equal number of C.. coronatus and C. aristophanes characters can no more be designated as one species or Page 372 THE VELIGER Vol. 23; No. 4 the other than a shell with 7 indeterminate evaluations. To accommodate this situation, and give equal weight to all criteria when scoring a shell, the number of Conus aristophanes characters is simply subtracted from the number of C. coronatus characters. This results in a Net Character Score for each specimen with typical C. coro- natus scoring positively and typical C. aristophanes scoring negatively. This procedure also establishes a scale, ranging from +7 to — 7, which facilitates graphic display of data (Figure 4) and permits a parametric type of analysis on the overall results. It must be noted that the Net Character Score derived in this way does not unequivocally identify a specimen. On rare occasion a Conus aristophanes may be scored as a C. coronatus, or vice versa. Rather, it gives a tentative identification to specimens with those furthest removed from zero being the ones most convincingly documented. There are two essential assumptions inherent in this model for discriminate analysis. First, it is assumed that the observed phenotypic characters are independent of each other. Second, it is assumed that there are two, and only two, species present in this Conus-complex. Data are very limited, but it would appear that the first assumption is probably valid. As may be seen from Table 2, out of the total of 693 evaluations, there are only 14 instances of mistaken identity. The 8 in the A-Group are spread over all 7 criteria, and the 6 in the C-Group are spread over 5 criteria. Such scatter seems random. How- ever, the data are far too few to document independence of these characters within either Group. The acceptable criteria are diverse in type: 3 are morphological, 2 re- flect sculpture, and 2 are based on pigmentation or pat- tern. Until more data are available, it would not seem unreasonable to continue to assume such characters are independent. From the data, as presented in Figure 4, the second assumption has also not been discredited. No third peak is seen. If there is a third species present, it must either be occurring at low frequency, or the criteria are inade- quate to separate it from one of the two recognized species. Additionally, if hybridization is occurring, it must also be at low frequency. One would expect hybrids to score intermediate between the two species, but there is no obvious cluster of specimens scoring in the neighbor- hood of zero. Finally, habitat can also influence form, sculpture, pat- tern and color. This is particularly true in the case of Conus aristophanes. This species can inhabit any environ- ment from inshore mudflats to the outer barrier reef. Specimens from the barrier reef more closely resemble C. coronatus. They are generally a lighter shade of gray or green, more heavily granulated, slightly broader and slightly higher in the spire than specimens from inshore muddy areas. Nevertheless, specimens from both habitats score well to the negative side of zero by the Net Charac- ter Score. CONCLUSION The shells of 50 specimens of Conus coronatus and 50 specimens of C. aristophanes collected in Fiji have been examined for differences in form, sculpture, color and pattern. Seven criteria which distinguish between these two closely related species have been isolated. Each is greater than 95% accurate. Considered together, these criteria permit identification of individual Fijian speci- mens of C. coronatus or C. aristophanes with a high degree of certainty. They separate Fijian specimens into two distinct and non-overlapping population groups, thereby providing evidence in support of the CERNOHORS- KY (1964) conclusion that C. coronatus and C. aristo- phanes are distinct and separate species. Literature Cited Cernonorsky, WALTER OLIVER 1964. The Conidae of Fiji (Mollusca: Gastropoda). 7 (2): 61-94; 7 plts.; 3 text figs. Koun, ALAN Jacoss « Avan C. Rices 1975. Morphometry of the Conus shells. 346- 359 The Veliger (1 October 1964) Systematic Zoology 24: Vol. 23; No. 4 NOTES & NEWS Notes on the Status and Distribution of Littorina flava King & Broderip, 1832 BY DANIEL PRINCZ Estacién de Investigaciones Marinas de Margarita Box 144, Porlamar, Isla Margarita, Venezuela SEVERAL APPROACHES have been made on the status and distribution of Littorina flava (King & Broderip, 1832) (sens. lat.). A definite tendency to consider this taxon as a species, and not as a subspecies, might give us a clue on the determination of its exact distribution pattern along the littoral West Atlantic. Sharpness of the ridges on the whorls and thickness of the shell were the most distinct criteria on which identi- fication was based. But Littorina flava shows a wide vari- ation on these characteristics among the specimens of its extensive latitudinal distribution. When it exhibits sharp ridges and a thin shell, it seems difficult to distinguish it from L. nebulosa Lamarck. Aguayo (personal communication) suggested that these characteristics may be related to the exposure of the an- imal to rough or calm waters. Today, modern investiga- tions propose Littorina flava as a good species, as sufficient anatomical evidence has been compiled (FLorEs, 1973; BANDEL, 1974; ALTENA, 1975). The species has been reported as far south as Uruguay, and is abundant in Brazil, the Guianas, Trinidad and Venezuela. Several specimens from Cuba and Guadaloupe were collected by Aguayo and C. B. Adams respectively (BEQUAERT, 1943). Both of these constituted the only rec- ords until the present in the Antilles, seldom suggested to be introduced by man. I have collected a living adult in the intertidal rocky shore at the south-west coast of Puerto Rico, at the supra- littoral level with rough sea. The specimen shows a very thick shell and weak ridges. Thus, it would seem that the distribution of this specics to the antillean latitudes is made through the Lesser Antilles, as to my knowledge no records have been re- ported from Central America and Mexico. The presence THE VELIGER Page 373 of Littorina flava in Puerto Rico marks an intermediate point between the antillean localities, confirming the pos- sible passage of the species from south to north in the Caribbean Sea. Literature Cited ALTENA, Conrap O. VAN REGTEREN 1975. The marine mollusca of Suriname (Dutch Guiana), Holocene and Recent. Part III. Gastropoda and Cephalopoda Zool. Verhdl. 139: 1 - 104 BANDEL, Kiaus 1974. Studies on Littorinidae from the Atlantic. (2): 92-114; 5 plts.; 22 text figs. BEQuagERT, JosEPH CHARLES 1943. The genus Littorina in the Western Atlantic. (7): 1-27 Fiorzs, C. 1973- La familia Littorinidae (Mollusca: Mesogastropoda) en las aguas costeras de Venezuela. Bol. Inst. Ocean. Univ. Oriente 12 (1): 9-22 The Veliger 17 (1 October 1974) Johnsonia 1 Recent Changes in the Department of Invertebrate Zoology, California Academy of Sciences BY DAPHNE FAUTIN DUNN Department of Invertebrate Zoology California Academy of Sciences Golden Gate Park, San Francisco, CA 94118 On 1 JuLy, 1980, the size of both collection and staff of the Department of Invertebrate Zoology (IZ), California Academy of Sciences (CAS), increased significantly. Re- sponsibility for the dry collection of Recent mollusks was shifted to IZ from the CAS Department of Geology, al- though location of the collection did not change. Dr. Barry Roth, Senior Scientific Assistant in charge of that col- lection, was simultaneously transferred from Geology to Invertebrate Zoology. The rationale for Geology’s custo- dianship of the dry mollusks was that hard parts, such as shells and radulae that are most frequently preserved and therefore are the subjects of paleontological research, should be housed together with fossil material to facilitate Page 374 THE VELIGER Vol. 23; No. 4 comparisons. In practice, this sometimes resulted in depo- sition of the shell of an individual mollusk in the Depart- ment of Geology and the body in IZ. Moreover, IZ holds dry specimens of many non-molluscan phyla such as Cnidaria, Ectoprocta, and Echinodermata. As recatalog- ing of the shells into IZ format and with IZ numbers proceeds, soft and hard parts of an individual will be reunited, and will bear a single catalog number. At the same time, Dr. Roth is designing new cases and drawers to improve access to and protection of the shells and their labels. The wet mollusk collection, for which Dr. Roth has also assumed responsibility, is being moved into the recently renovated Franz B. Steiner Room, which doubles the shelf space of the IZ wet collection. A second addition to the Department of Invertebrate Zoology staff was Assistant Curator Dr. Daphne Fautin Dunn. Primarily a student of coelenterates, her responsi- bilities include the type collection. Until the mid-1970’s, when the general invertebrate collection began to be cata- loged, the only IZ specimens to be designated by catalog numbers were types (before establishment of IZ in 1963, all non-insect and non-arachnid invertebrate types were the property of the Department of Geology, pre- viously called the Department of Paleontology). Thus, for the past five or six years, two independent numbering systems and their card catalogs have coexisted, type spec- imen numbers being distinguished in publication by the prefix “type series” or “TY.” Additional numbering sys- tems were maintained for color transparencies and type microscope slides. A specimen of which photographs and from which microscope slides (histological sections, radu- la mount, etc.) had been made bore several unrelated numbers, one for the specimen, one for each photograph, and one for each microscope slide. Dr. Dunn, after consul- tation with members of the CAS staff as well as those of other such archival institutions, determined that data retrieval could be facilitated if all objects relating to a particular specimen or lot of specimens bore a single number. Thus, the catalog of specimens will serve for photographs and microscope slides as well. Moreover, it was decided to incorporate type specimens into the gener- al IZ catalog; a separate, more detailed type catalog will be maintained as well. Readers of “The Veliger” will notice henceforth that type material in the Department of Invertebrate Zoology is designated by a six digit number that bears no nota- tion distinguishing it as type. Microscope slides and color transparencies, if any, will be referred to by the same number. Only primary types and neotypes will be part of the type collection; so-called hypotypes, now referred to as “voucher specimens,” will be housed in the general collection, although a file of separate documentation will be maintained for them as well. The many hundreds of type and voucher specimens cataloged heretofore are being recataloged with standard IZ six digit numbers (specimens that had originally been cataloged in the general collection and were only later recognized or desig- nated as types already bear such numbers). Cards for them, flagged by colored signals, are being entered in the col- lection files. A reprint/separate of every paper describing a species any type material of which is housed in IZ is kept in the departmental library; catalog numbers of the specimens referred to are being written in the margin beside the description. Blue flags/notations refer to holo- types, syntypes, lectotypes, and neotypes, whereas red indicates paratypes. The lid of each bottle bears a signal dot of the appropriate color. Once all type specimens in IZ have been recataloged, the dry mollusk types will be dealt with similarly, and will be moved from their present location in the Department of Geology to the IZ type cabinets. A register is being as- sembled concurrent with recataloging so that specimens requested by a published number (IZ type series, CAS Geology, or, in some cases, Stanford University numbers) can be located immediately in the new system. It is antici- pated that a catalog of IZ type holdings, including cross- references by published numbers, will be issued when the task is complete, within several years. Active scientists who have deposited type specimens in IZ will be notified of the new catalog numbers as soon as all of their types are reprocessed so that they can use them in future pub- lications, as occasion arises. Another Generous Donation from the Conchological Club of Southern California The Conchological Club of Southern California has again sent a very generous contribution to “The Veliger,” which is added to the Veliger Endowment Fund, where it will continue to yield an income which is used to help keep the membership dues at the lowest possible level. Thus, the thoughtful gift benefits a large number of people. Be- cause this donation arrived after our January issue was already collated and stapled, we were unable to express our thanks publicly to our friends in the CCSC before this. Vol. 23; No. 4 CORRECTION On January 10, 1981, we received the following letter from Mr. Wesley M. Farmer which we assume he wishes us to publish: “The San Diego Museum of Natural History brought to my attention a need for an errata in the Veliger Vol 20(4):pg 378 paragraph 4, SDSNH 63052 should read SDSNH 63053; and on page 379 the bottom line, SDSNH 63053 should read SDSNH 63056.” IMPORTANT NOTICE If the address sheet of this issue is PINK, it is to indicate that your dues remittance had not arrived at the time the mailing was prepared (7..e., by March 1, 1981). We wish to take this opportunity to remind our Members that a reinstatement fee of one dollar becomes due if member- ship renewals have not been received by C.M.S., Inc. by April 15, 1981. However, in view of the unreliability of the postal service, members should not be alarmed by this notice as their remittances may be received between the first of March and the date of mailing this issue on April r. 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Thus, all payments henceforth must be in U. S. funds. At the same meeting it was also decided to keep the membership dues at the same level as for volume 23, with the mailing charges for domestic addresses at $1.50 and those for ALL foreign addresses increased to US$5.-. Because of some irregularities that have occurred in the recent past, we must stress that membership renewals with the correct amount must reach us on or before April 15 each year; if payment is received after that date, a re-instatement fee of $1.- is required. From the foregoing it should be evident that we make a strong effort to combat inflation. But we must ask for cooperation by all our members and subscribers. CALIFORNIA MALACOZOOLOGICAL SociETyY, Inc. is a non-profit educational corporation (Articles of In- corporation No. 463389 were filed January 6, 1964 in the office of the Secretary of State). The Society publishes a scientific quarterly, the VELIGER. Donations to the Society are used to pay a part of the production costs and thus to keep the subscription rate at a minimum. Donors may designate the Fund to which their contribution is to be credited: Operating Fund (available for current production) ; Savings Fund (available only for specified purposes, such as publication of especially long and signi- ficant papers); Endowment Fund (the income from which is available. The principal is irrevocably dedicated to scientific and educational piwposes). Unassigned dona- tions will be used according to greatest need. Contributions to the C. M.S., Inc. are deductible by donors as provided in section 170 of the Internal Revenue Code (for Federal income tax purposes). Bequests, lega- cies, gifts, devises are deductible for Federal estate and gift tax purposes under section 2055, 2106, and 2522 of the Code. The Treasurer of the C. M. 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Box 730, Oakhurst, CA(alifornia) 93644. The same applies to the supple- Vol. 23; No. 4 ments still in print with certain exceptions (see below). Prices of available items may be obtained by applying to Mr. West at the address given above. Volumes 1 through 8 and ro through 12 are out of print. Supplements not available from Mr. West are as fol- lows: Supplements to vol. 7 (Glossary) and 15 (Ovulidae) are sold by ‘The Shell Cabinet, P O. Box 29, Falls Church, VI(rginia) 22046; supplement to vol. 18 (Chitons) is available from “The Secretary,’ Hopkins Marine Station, Pacific Grove, CA(lifornia) 93950. Supplements Supplement to Volume 3: [Part 1: Opisthobranch Mollusks of California by Prof. Ernst Marcus; Part 2: The Anaspidea of California by Prof. R. Beeman, and The Thecosomata and Gymnosomata of the Cali- fornia Current by Prof. John A. McGowan] Supplement to Volume 6: out of print. Supplement to Volume 7: available again; see announce- ment elsewhere in this issue. Supplement to Volume 11: [The Biology of Acmaea by Prof. D. P. Aszorrt et al., ed.] Supplement to Volume 14: [The Northwest American Tellinidae by Dr. E. V. Coan] Supplement to Volume 16: [The Panamic-Galapagan Epitoniidae by Mrs. Helen DuShane] [Growth Rates, Depth Preference and Ecological Succes- sion of Some Sessile Marine Invertebrates in Monterey Harbor by Dr. E. C. Haderlie] Supplement to Volume 17: Our stock of this supplement is exhausted. Copies may be obtained by applying to Dr. E. C. Haderlie, U. S. Naval Post-Graduate School, Mon- terey, CA (lifornia) 93940. WE ARE PLEASED to announce that an agreement has been entered into by the California Malacozoological Society, Inc. with Mr. Steven J. Long for the production and sale of microfiche reproductions of all out-of-print editions of the publications of the Society. The microfiches are available as negative films (printed matter ap- pearing white on black background), 105mm X 148mm and can be supplied immediately. The following is a list of items now ready: Volume 1 through Volume 6: $9.00 each. Volume 7 through Volume 12: $12.00 each. Supplement to Volume 6: $3.00; to Volume 18: $6.00 THE VELIGER Page 377 California residents please add the appropriate amount for sales tax to the prices indicated. Please, send your order, with check payable to Opistho- branch Newsletter, to Mr. Steven J. Long, 359 Roycroft Avenue, Long Beach, California 90814. Volumes and Supplements not listed as available in microfiche form are still available in original edition from Mr. Arthur C. West, P.O. Box 730, Oakhurst, CA(lifornia) 93644. Orders should be sent directly to Mr. West. Single Copies of “The Veliger”: We have on hand some individual copies of earlier issues of our journal and are preparing a list of the various issues available with the prices. Some issues are present in only one or two copies, while others may be present in 10 or more copies. As we are anxious to make room, we will offer these numbers at an exceptionally low price. This list may be obtained by sending a self-addressed, stamped envelope to the Veliger, 1584 Milvia Street, Berkeley, CA (lifornia) 94709. Foreign correspondents should en- close one international postal reply coupon. Requests for the list, for which return postage is not provided, will be ignored. Membership open to individuals only - no institutional or society memberships. Please send for membership ap- plication forms to the Manager or the Editor. Membership renewals are due on or before April 15 each year. If renewal payments are made after April 15 but before March 15 of the following year, there will be a re-instatement fee of $1.-. Members whose dues pay- ments (including the re-instatement fee) have not been received by the latter date, will be dropped from the rolls of the Society. They may rejoin by paying a new initiation fee. The volume(s) published during the time 2 member was in arrears may be purchased, if still available, at the regular full volume price plus applicable handling charges. Backnumbers of the current volume will be mailed to new subscribers, as well as to those who renew late, on the first postal working day of the month following receipt of the remittance. The same policy applies to new members. THE VELIGER is not available on exchange from the Cali- fornia Malacozoological Society, Inc. Requests for re- prints should be addressed directly to the authors con- cerned. We do not maintain stocks of reprints and also cannot undertake to forward requests for reprints to the author(s) concerned. Page 378 _ THE VELIGER Vol. 23; No. 4 WE CALL THE ATTENTION or our foreign correspondents to the fact that bank drafts or checks on banks other than American banks are subject to a collection charge and that such remittances cannot be accepted as payment in full, unless sufficient overage is provided. 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Since we will absolutely not publish a paper unless the galley proofs have been corrected and returned by the authors, the slow surface mail service (a minimum of 6 weeks from European countries, 8 to 12 weeks from India and Africa) may make a delay in publication inevitable. We strongly urge that authors who have submitted papers to the Veli- ger make all necessary arrangements for expeditious read- ing of the proofs when received (we mail all proofs by air mail) and their prompt return by air mail also. Since we conscientiously reply to all letters we actually receive, and since we experience a constant loss in insured and registered mail pieces, we have come to the conclusion that if a correspondent does not receive an answer from us, this is due to the loss of either the inquiry or the reply. We have adopted the habit of repeating our inquiries if we do not receive a reply within a reasonable time, that is 6 weeks longer than fairly normal postal service might be expected to accomplish the routine work. But we can not reply if we have never received the inquiry. Because of some distressing experiences with the Postal Service in recent years, we now urge authors who wish to submit manuscripts to our journal to mail them as insured parcels, with insurance high enough to cover the complete replacement costs. Authors must be prepared to document these costs. If the replacement costs exceed $400.-, the manuscript should be sent by registered mail with additional insurance coverage (the maximum limit of insurance on parcel post is, at present, $400.-). We are unable to advise prospective authors in foreign countries and would urge them to make the necessary inquiries at their local post offices. 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Vol. 23; No. 4 THE VELIGER Page 379 General Notice Because of an increasing number of strange occurrences your editor deems it important to clarify our policy with respect to correspondence. 1. We never reply to letters that do not reach us. Since the U. S. postal service no longer forwards mail pieces that are not franked properly, correspondents waiting for our reply might consider the possibility that their letter falls into this category. 2. We do not acknowledge the receipt of a manuscript unless a self-addressed, stamped envelope is enclosed. 3. We do not reply to complaints regarding the non-ar- rival of our journal, if these complaints are made at a time when the claimed issue could not possibly have reached its destination. In view of the poor postal ser- vice throughout the world, it is unrealistic to expect, for example, the July issue in a shorter period than from 2 to 3 weeks in the United States, in less than 4 to 6 weeks in Europe, and in less than 2 to 4 months in other areas of the world; South American countries, in par- ticular, have to expect maximum delays. It should be obvious that we are not responsible for the postal ser- vice. 4. We particularly object to complaints about non-receipt of issues which are scheduled to be published as much as 6 months after the complaint was sent! A little con- sideration of what is possible and what is absurd should help to obviate such untimely complaints. 5. We are receiving an increasing number of requests for our list of individual back numbers that are still avail- able, as well as for our suggestions to prospective au- thors. These requests state that a self-addressed stamped envelope is enclosed — but somehow the writer must have forgotten to do so. These requests also are not answered by us. We consider that our policy is justified for several reasons: the requirement for self-addressed, stamped en- velopes has been stated in every issue of the Veliger for the past several years. Since we are a non-profit organiza- tion, we prefer to reserve our energy and our resources for productive purposes. However, we do conscientiously, and usually exhaustively, reply to all correspondence that we consider legitimate. Moreover, such correspondence is usually answered the same day as received, with the reply posted the next morning at the main post office in Berke- ley. What happens afterwards is beyond our control. Policy Regarding Reprints It seems necessary to bring the following points to the notice of prospective authors: All manuscripts submitted for inclusion in The Veliger are subject to review by at least two scientists; acceptance is entirely on the basis of merit of the manuscript. Al- though many scientific journals assess page charges, the Executive Board of our Society, for the time being at least, wishes to avoid this possible financial handicap to the younger contributors. However, because of the high cost of halftone plates, a suitable contribution to reimburse the Society must be sought. Similarly, while it was hoped at the “birth” of The Veliger, that a modest number of reprints could be sup- plied to authors free of charge, this has not as yet become possible. We supply reprints at cost. Unfortunately, in recent years it has become “fashionable” for some authors and some institutions to ignore paying for reprints ordered and supplied in good faith or to delay payment for a year or more. This causes financial losses to the Society since our debts are paid promptly. Since the Society is in fact not making any profit, it is necessary to introduce a policy which, it is hoped, will protect us against negli- gence or possible dishonesty. In the case of manuscripts from sources outside of the United States, if a manuscript is accepted, we will inform the author of the estimated cost of reprints and require a deposit in U.S. funds to cover these costs. If such a deposit is not made, we will not supply any reprints. In the case of non-payment by domes- tic authors or institutions, we will pursue legal recourses, Page 380 BOOKS, PERIODICALS, PAMPHLETS The Marine Mollusks of Easter Island (Isla de Pascua) and Sala y Gomez. by Haratp A. REHDER. Smithsonian Contributions to Zoology, No. 289: 158 pp.; illust. 5, August 1980 Harald Rehder’s monograph of the molluscan fauna of Easter Island and Sala y Gémez fills a major gap in our knowledge of the Indo-Pacific fauna. He has increased the number of species recorded from the two islands by 95 %, described 3 new genera and 40 new species, and docu- mented molluscan endemicity at a remarkable 42%. The study is based on examination of more than 7000 speci- mens, the majority of which were collected by the Rehders in 1974. Easter Island has always seemed particularly exotic to me because of its isolation and the incongruity of an “In- do-Pacific island” that is that is situated east of San Francisco. The biogeographic affinities of the fauna only serve to underscore its uniqueness. The molluscan fauna of this volcanic outpost on the East Pacific Rise bears a strange dual affinity with islands strung out along the extreme southern margin of the tropical Pacific (Pitcairn, Rapa, and the Kermadec Islands) on one hand, and the Hawaiian Province on the other. Carole S. Hickman, Department of Paleontology, University of California, Berkeley Classification and Systematic Relationships of the Abyssochrysidae, a Relict Family of Bathyal Snails (Prosobranchia: Gastropoda) by RicHarp S. Housrick. Smithsonian Contribution to Zoology, No. 290: pp. 1-20; illust. 1979 Although abyssochrysid snails presumably know what to do with the unusual large process projecting from the right edge of the mantle, they have fooled malacologists, who have not been certain whether it is a penis or a large THE VELIGER Vol. 23; No. 4 oviduct. Although Joe Houbrick has not discovered exact- ly what it is either (after much debate he decides to call it a “penis-like” organ), he has put together a number of lines of evidence to suggest that these deep-sea snails are Loxonemataceans, a predominantly Paleozoic group thought to be extinct since the Late Jurassic. If he is correct, they have been doing something right with it, whatever it is, for at least 450 million years. Carole S. Hickman Scanning Electron Microscopy of Shell and Mantle in the Order Arcoida (Mollusca Bivalvia) by Tuomas R. WALLER. Smithsonian Contributions to Zoology, No. 313: 56 pp.; illust. 16 June 1980 This elegant and meticulous piece of research by T. R. Waller stands out scientifically against a background of voluminous molluscan literature of the past decade that is dominated by traditional descriptive systematics on one hand and an increasing number of highly speculative but data-thin tests of theory on the other. It stands out because Waller understands bivalves as real organisms and is making the best use of modern technology to study and illustrate details of morphology and anatomy. It also stands out because he is working in a well-defined evolu- tionary context, critically addressing difficult but funda- mental questions of bivalve phylogeny. There are literally too many important findings to summarize comprehensively here; one of the most im- portant is the clear contradiction in Arcoid bivalves of the traditional threefold view of the bivalve mantle edge and of the traditional functions ascribed to the folds. The mantle-shell fabric relationships and details of the cellular structure of the mantle itself shed light on problems of mantle and shell development and evolution. The photo- receptive mantle curtain and compound eyes in arcoids are unique and further separate the order from the mainstream of bivalve evolution. I can only refer you to the excellent scanning electron micrographs for full ap- preciation of the data presented in the text. The Smithsonian Institution is to be commended for encouraging and supporting this kind of research in the face of a trend in American institutions to value quantity more highly than quality. The quality of this contribution is certainly unmistakable. Carole S. Hickman Vol. 23; No. 4 Review of the Deep-Sea Argyropeza (Gastropoda: Prosobranchia: Cerithiidae) by RicHarp S. Housrick. Smithsonian Contribution to Zoology, No. 321: 28 pp.; illust. 23 July 1980 Good systematic research does not always require field work, although we are all eager to get out there and make new collections. R. S. Houbrick’s review of the deep-sea genus Argyropeza attests to the existence of treasure- troves of unexamined material in our major museums and demonstrates care and resourcefulness in extracting a wealth of information from shells containing dried ani- mals. Specimens dredged by the U. S. Fisheries Steamer Albatross at the beginning of the century have provided a variety of characters for statistical analysis and evalua- tion of phyletic relationships of species as well as evalua- tion of the position of the genus within the Cerithiacea. Carole S. Hickman Intertidal Invertebrates of California by Rosert H. Morris, Donap P. Asgort, and EUGENE C. Haveruie. Stanford University Press, xiv + 690 pp.; 200 color plates. $30.-. 24 November 1980 All who have peered into tide-pools have wished for a convenient pocket manual that would help in recog- nizing the organisms there. This book is too bulky for that — it weighs over 6 pounds and measures 9 X11 X3 inches — but it does supply answers not only to the “What is it?” questions but also to others more basic. It is a reference work that will be frequently consulted by the collector after returning home, and its well-written text will stimulate needed further research. (The arrangement of the book is primarily systematic, some 31 contributors having provided pertinent data on all the phyla represented on our coast, from Protozoa (Foraminifera) to Arthropoda (Insecta). Salient mor- phologic characteristics are given for each of the species treated; bibliographic references, especially to studies on the biology of the organisms, point the way toward further needed work. Also, reference sections at the end of each chapter supply additional titles, more than 5 500 altogether. The species in each chapter are numbered sequentially, the same numbers being used on the plates and in the index. Illustrations are color photographs in the main, done at a scale large enough for ready recog- nition of small forms. Imaginative use of backgrounds and skillful lighting make the color figures interesting both as THE VELIGER Page 381 artistic designs and as scientific records. With very minor exceptions, the color plates come out well. This is a reference work to be repeatedly savored and enjoyed. It integrates much unavailable or hitherto scat- tered information about the structure and functions of the invertebrate animals — how and where they live, their food, their enemies, and their role in the marine economy. The authors are to be congratulated on having carried through so effectively a design that combines biologic information of a sort rarely available to the lay- man with illustrations that make the often-nondescript invertebrates seem to come alive. Myra Keen [Editor’s note: The price of $30.- for this book is extra- ordinarily low, especially in today’s market. This low price, made possible through a generous gift, will enable just about everybody interested in marine biology to ac- quire a copy of this truly magnificent work. ] Common Intertidal Invertebrates of the Gulf of California Second Edition. 1980. RicHarp C. Brusca. University of Arizona Press, Tucson, Arizona. xx + 513 pp.; 14 plts.; 702 text-figs.; 1 map. $26.95 The revised and expanded edition of Dr. Brusca’s hand- book — thicker and larger in every dimension — _rep- resents a significant improvement over the earlier version, and it is now a volume that West Coast malacologists may want for their bookshelves. Admittedly incomplete because many invertebrate groups are as yet poorly known in the Panamic fauna, the book will help stimulate additional research. The intro- ductory material contains a strong plea for conservation, as well as a stimulating commentary on the geological evolution of the Gulf of California, biogeography and intertidal zonation. Particularly well prepared are the chapters on the Crustacea and the Bryozoa, and of spe- cial interest are the precedent-setting chapters on the Insecta and the Arachnida. It is for the non-molluscan invertebrates in particular that malacologists will want the book for reference. The chapter on the Mollusca, while undeniably more com- plete than that in the first edition, is not up to the stand- ard set by the coverage of the Crustacea, leaving out many common intertidal species while including many forms that occur primarily offshore. With a straight- jacketed format, this treatment ignores material pub- lished since the 1971 edition of “Sea Shells of Tropical Page 382 West America” and the now-significant literature on the biology of the molluscan fauna of the Gulf of California (an exception is the subchapter on the Cephalopoda by Fred Hochberg). Eugene V. Coan Fine Dissection of Ascoglossans by T. GascoicneE, Conchological Society of Great Britain; 31 pp.; 11 figs.; 2 plts. 1980 This booklet contains much highly useful information on collection, relaxation, preservation, staining, and dis- section of ascoglossan (== sacoglossan) slugs, together with information on anatomy of the circulatory, diges- tive, reproductive, and nervous systems of ascoglossans. Figures clearly summarize critical anatomical features. Dissection of these animals is quite difficult because of their small size (<(1cm) and soft texture, but quite necessary for accurate taxonomic study. Thus, this guide will be very useful to both novice workers and estab- lished investigators. The dissection techniques should be equally useful with other opisthobranchs (and other small, soft-bodied animals). Gascoigne’s suggestions for stain- ing of viscera and for staging dissections over periods of several days are particularly useful. The booklet is available from the author (16 York Grove, London SE15 2NY, England), at a cost of £1 including postage; profits will go to the Conchological Society. Kerry B. Clark A Selected Bibliography of Worldwide Oyster Literature by Linpa L. BreiscH and Victor S. KeENNeEDy. Univer- sity of Maryland Sea Grant Program Publication Number UM-SG-TS-80-11. 309 pp. Available at $8.00 from the Communications Program, Maryland Sea Grant Program, University of Maryland, College Park, MD 20742. This work is divided into 4 parts: the first part lists a total of 2837 publications of “Primary Literature,” ar- ranged alphabetically and numbered consecutively. This list is followed by the “Primary Literature Index,” in which the various articles are listed by number under a large number of subject headings, geographical areas, species names, and many others. This cross-index should be particularly helpful to many specialists in molluscan THE VELIGER Vol. 23; No. 4 biology, as it enables the worker to select those articles on oysters that concern his special interests. The third part lists 810 “Reports,” followed by an “Reports Index.” This index is organized as is the first index. A list of 134 theses follows and the ‘““Theses Index” concludes the work. It should be noted that this work updates earlier work by Joyce and Baughman and covers the period from the early 1800's to 1980. R. Stohler Catalogo dei Molluschi Conchiferi Viventi nel Mediterraneo by Prero Pant. Boll. Malacologico 16 (5-6): 113-224; May-June 1980 The malacofauna of the Mediterranean Sea, in recent years, has received considerable attention. Along the coasts of Europe and Asia Minor are several marine sta- tions, the best known of which is that at Naples. The present work is a compilation of data derived from the literature, although there is no formal, complete list of bibliographic sources. An apparently complete list of species reported from the area is given in systematic order; type species of genera and subgenera are distin- guished with an *; a Y indicates uncertainty regarding the occurrence of the listed taxon in the Mediterranean Sea and an X signifies uncertainty about the validity of the listed name. Many synonyms are listed in about 200 footnotes. A systematic and an alphabetic index close the work. Shell collectors will find this list very useful as a check list, while the biogeographer may wish that there were at least brief notes on the actual ranges of the various species. R. Stohler Index to the Species of Mollusca Introduced from 1850 to 1870 by Fiorence A. Ruuorr. Smithsonian Contributions to Zoology Number 294. 640 pp. 9g December 1980. The abstract preceding this work states: “A compila- tion, alphabetically arranged, of the names of species of Mollusca introduced during the years 1850-1870, includ- ing a bibliography of molluscan literature written at that time. A taxonomic list, alphabetically arranged by genera, is included.” Vol. 23; No. 4 THE VELIGER Page 383 This succinct statement cannot — and is not intended to — convey the enormous value of this work. It is intended to bridge the gap between the Index Animalium which covers the period from the “official” Linnean be- ginning in 1758 to the year 1850 and the Zoological Record from 1864 to the present. The slight overlap in the periods covered is no disadvantage. Florence Ruhoff is known to taxonomists through sev- eral bibliographic compilations, either as an author or as a co-author. Best known among these are the two dealing with the works of William Healey Dall and Paul Bartsch. It is impossible to exaggerate the value of this latest (and, probably, last) contribution by Ms. Ruhoff as a guide to the information produced during the years covered by her work. What we are about to add is not meant as criticism, as it applies not only to the present work but to all compilations of any type. It is impossible to produce such works totally free of errors, typographical or factual. Nobody is more painfully aware of this fact than this reviewer who has tried for 23 years to produce at least one issue of “The Veliger” totally free of typo- graphical errors from the first line on the frontcover to the last line on the backcover — a dream still unfulfilled. The sources for errors are many: insufficient knowledge of the many foreign languages encountered in a compila- tion as the present one, misreading of words for similar ones of totally different meaning, and last, but unfor- tunately in today’s world not least, the vagaries of type- setters. In a way, it is rather unexpected to find that the Government Printing Plant does not have proofreaders familiar with the grammar of various foreign languages to avoid hyphenations of words in a manner that destroys the sense of the particular term. We have noted quite a few such examples. What we wish to emphasize is simply that the work is a guide that should be fol- lowed, not blindly copied. It should be the required re- sponsibility of the user of this work to check the reference needed against the original publication. Unfortunately, it is so much easier to copy a title out of a compilation than to go to the library and hunt for the original. We will show what we mean by this “diatribe.” On page 67, we find the following citation: Leuckart, R. 1852. Ueber das Vorkommen und die Ver- breitung des Chitons bei den wirbellosen Thieren. In checking the original, we found that the citation should have read: Leuckart, R. 1852. Ueber das Vorkommen und die Ver- breitung des Chitins bei den wirbellosen Thieren. This paper has nothing to do with chitons per se, al- though it does mention the occurrence of chitin in the various classes of the mollusks. However, as indicated above, under pressure it is too easy to misread some words. Yet a good proofreader would at least have queried the correctness of the word sequence “des Chitons” and thus the error might have been avoided. Blindly accepting all citations as totally reliable can lead to a spreading of errors through the literature — as happens too often in text books where sometimes errors are accepted as the true facts and where it can be extremely difficult to substitute the actual true facts. We repeat: all this is not meant to detract from the tremendous work of Florence Ruhoff who has rendered an immeasurably valuable service to malacologists with this work. R. Stohler Sea-Slug Gastropods by WESLEY FarMER. 177 pp.; illust. 1980 This is a very strange book! Reading the preface, one is tempted to assume that the book is intended as a some- what advanced coloring book for children; the tone of the preface - aside from misspellings and improper sentence structure - is of the “Look; Jane, look” variety; and the drawings are color-coded with numbers keyed to the color pencils of a set of 62 (a brochure for the pencils is enclosed !). However, when the text is examined, it becomes ob- vious that a higher ambition motivated the author. His intention is, apparently, to make the study of opistho- branchs easier. To this end he provides good drawings of all species discussed. According to the preface, some of these figures are drawn from transparencies of some of the outstanding workers in this field. Other figures are, by inference, created by the author. Since no clear distinc- tion is made between the two “sources,” the first principle of truly scientific work is violated. The work has, however; other strange features, which, in themselves, would not be totally reprehensible, if they did not stop short of completion, or if they were merely additions to the normal features. For example: Mr. Far- mer lists, in many cases, up to 4 references in inverse chronological order; in some cases, the lists include the original description, but, unfortunately, not in all cases. This lack is particularly disturbing in cases where Mr. Farmer lists only references in which a particular species is discussed under a name that Mr. Farmer apparently considers a synonym; but no indication is given why he uses a different name. A novel approach to an index is also perhaps more interesting than useful. The various species are listed alphabetically under the name of the author! Page 384 Since there is apparently little consistency in the spelling of names (example: p. 97: Conualevia; p. 98: Conulevia; p- 174: Conualeveia) the work becomes an unfortunately rich source for [sic]s in the works of competent authors. The most horrible mistake that caught our eye is the name listed for a species described in 1962 by James R. Lance. Lance called the colorful nudibranch Phidiana pugnax. On page 117, Farmer discusses “Phidiana hiltoni (Lance, 1962)” (the quotation marks are added by us). This entry lists 6 references, all of which we checked. In none of these is the species name other than Phidiana pugnax. To the best of our knowledge, Mr. Lance has never pub- lished the name hiz/tonz in connection with any nudibranch nor in his work on Tigriopus (a crustacean tidepool dwel- ler). It is therefore incorrect to cite Lance’s name, either in parentheses or out of them; if Farmer has evidence that Phidiana pugnax is indeed a junior synonym of a species THE VELIGER Vol. 23; No. 4 described as somethingorother hiltoni, he should cite the work in which that species was described and should give either a citation to a paper in which P pugnax was synonymized or give his scientific reasons for doing so in this book. The only excuse we can offer for our spending a con- siderable amount of time, and valuable space in this issue, reviewing this publication is the hope that Mr. Farmer will undertake a complete revision of the present work, issue a list of corrections, and that he will seek competent help doing so and especially if and when he produces the second half of the work, as stated in the preface. As it is, Mr. Farmer has failed to render the good service he in- tended, service to present and future students (even those of tender age) of nudibranchs. R. Stohler THE VELIGER is open to original papers pertaining to any problem concerned with mollusks. This is meant to make facilities available for publication of original articles from a wide field of endeavor. Papers dealing with anatomical, cytological, distributional, ecological, histological, morphological, phys- iological, taxonomic, etc., aspects of marine, freshwater or terrestrial mollusks from any region, will be considered. Even topics only indi- rectly concerned with mollusks may be acceptable. In the unlikely event that space considerations make limitations necessary, papers dealing with mollusks from the Pacific region will be given priority. However, in this case the term “Pacific region” is to be most liberally interpreted. It is the editorial policy to preserve the individualistic writing style of the author; therefore any editorial changes in a manuscript will be sub- mitted to the author for his approval, before going to press. Short articles containing descriptions of new species or lesser taxa will be given preferential treatment in the speed of publication provided that arrangements have been made by the author for depositing the holotype with a recognized public Museum. Museum numbers of the type specimens must be included in the manuscript. Type localities must be defined as accurately as possible, with geographical longitudes and latitudes added. Short original papers, not exceeding 500 words, will be published in the column “NOTES & NEWS”; in this column will also appear notices of meetings of the American Malacological Union, as well as news items which are deemed of interest to our subscribers in general. Articles on “METHODS & TECHNIQUES” will be considered for publication in another column, provided that the information is complete and tech- niques and methods are capable of duplication by anyone carefully fol- lowing the description given. Such articles should be mainly original and deal with collecting, preparing, maintaining, studying, photo- graphing, etc., of mollusks or other invertebrates. A third column, en- titled “INFORMATION DESK,” will contain articles dealing with any problem pertaining to collecting, identifying, etc., in short, problems encountered by our readers. In contrast to other contributions, articles in this column do not necessarily contain new and original materials. Questions to the editor, which can be answered in this column, are in- vited. The column “BOOKS, PERIODICALS, PAMPHLETS?” will attempt to bring reviews of new publications to the attention of our readers. Also, new timely articles may be listed by title only, if this is deemed expedient. Manuscripts should be typed in final form on a high grade white paper, 812” by 11”, double spaced and accompanied by a carbon copy. A pamphlet with detailed suggestions for preparing manuscripts intended for publication in THE VELIGER is available to authors upon request. A self-addressed envelope, sufficiently large to accom- modate the pamphlet (which measures 51/2” by 8/2”), with double first class postage, should be sent with the request to the Editor. EDITORIAL BOARD Dr. Donan P. Apsott, Professor of Biology Hopkins Marine Station of Stanford University Dr. Warren O. AppicottT, Research Geologist, U.S. Geological Survey, Menlo Park, California, and Consulting Professor of Paleontology, Stanford University Dr. Hans Bertscn, Scientific Education Advisor, Waikiki Aquarium, Honolulu, Hawaii Dr. Jerry Dononue, Professor of Chemistry, University of Pennsylvania, Philadelphia, and Research Associate in the Allan Hancock Foundation University of Southern California, Los Angeles Dr. J. Wyatr Duruaw, Professor of Paleontology, Emeritus University of California, Berkeley, California Dr. Capet Hanp, Professor of Zoology and Director, Bodega Marine Laboratory University of California, Berkeley, California Dr. Carore S. Hickman, Assistant Professor of Paleontology University of California, Berkeley, California Dr. A. Myra KEEN, Professor of Paleontology and Curator of Malacology, Emerita Stanford University, Stanford, California Dr. Victor Loosanorr, Senior Biologist, Emeritus U.S. National Marine Fisheries Service EDITOR-IN-CHIEF Dr. Rupotr SToHLER, Research Zoologist, Emeritus University of California, Berkeley, California Dr. Frank A. PiTELKA, Professor of Zoology University of California, Berkeley, California Dr. Rosert Rosertson, Pilsbry Chair of Melecolaes Department of Malacology Academy of Natural Sciences of Philadelphia Dr. PETER U. Roppa, Chairman and Curator Department of Geology, California Academy of Sciences, San Francisco Dr. Crype FE. Roper, Curator Department of Invertebrate Zoology (Mollusca) National Museum of Natural History Washington, D. C. Dr. JupirH Terry SmitH, Visiting Scholar Department of Geology, Stanford University Stanford, California Dr. Racpu I. Smiru, Professor of Zoology University of California, Berkeley, California Dr. Cuartes R. Stasek, Bodega Bay Institute Bodega Bay, California Dr. T. E. Tuompson, Reader in Zoology University of Bristol, England Dr. ALEX Tompa, Curator of Molluscs Museum of Zoology and Division of Biological Sciences, University of Michigan, Ann Arbor ASSOCIATE EDITOR Mrs. JEAN M. 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