RSA SGEN IL TREE ee mn runter nen иги ге pe) HARVARD UNIVERSITY LIBRARY OF THE Museum of Comparative Zoology RR Bi un | ИЖ |. + wire nm y к yi 7 | И AH ти Ах D us q Ba" aft il, À MER Me IN у COLOGIA y] SORTE u wel Jounal of Мо ко! mis marine qt Ч Malae cr: , be ‘ т я ye Be Ah Es pnd! Imker land) ae ie Ehen и урн N hint a им и 14 № á un 7 UN CT an De RIO yl e ve | a Mena M al alg 7 ia 1 ent N т | PURE: 7 Se OR VOL. 3 1965-1966 MALACOLOGIA International Journal of Malacology Revista Internacional de Malacologia Journal International de Malacologie Международный Журнал Малакологии Internationale Malakologische Zeitschrift MUS. COMP. ZOOL. LIBRARY JUN 21 1966 HAR Va UNIVERSITY DATES OF PUBLICATION At least 50 copies of MALACOLOGIA were mailed to subscribers (including a free copy to the Library of Congress, Washington, D. C.) on the following dates: Vol. II, No. 1 August 31, 1965 Vol. Ш, No. 2 December 9, 1965 Vol. HE No.3 May 31, 1966 iv MALACOLOGIA, VOL. 3 CONTENTS . J. BOSS Symbiotie eryeinaeean Divalves.. . .... еее... . R. CLARKE “Growth rings” in the beaks of the squid Moroteuthis ingens (Oeconsidacs Onychoteuthidae) =. iy. ar... 4 4h Joue, eb e . C. DAZO The morphology and natural history of Pleurocera acuta and Goniobasis livescens (Gastropoda: Cerithiacea: Pleuroceridae) . H. FRANK and A. Н. MEYLING A contribution to the conchometry of Biomphalaria pfeifferi IBasemmatophbora:, Planorbidae) o. be ke ee Zac... . T. GHISELIN Reproductive function and the phylogeny Портосе PaAStrOpods 060 «eae a nt dora cette el, . O. GREGG and D. W. TAYLOR Fontelicella (Prosobranchia: Hydrobiidae), a new genus of west AMERICAN. TreEShwateriSnarlis: не Soc ene bse Reese nies . N. GRUSOV The endoparasitic mollusk Asterophila japonica Randall and Heath (Prosobranchia: Melanellidae) and its relation to the parasitic gastropods .............. . LAURSEN Dhereenus-Myain'the-Aretie region... 2... 20 0 0 LU a aw hee . L. McALESTER Evolutionary and systematic implications of a transitional Ordeyieianzlucinoidäpivalvery. Le as ee eee ee . McCLARY Statocyst function in Pomacea paludosa (Mesogastropodas-Ampullariidae) 71.12. IH 2 ee: . MARCUS Some Opisthobranchia from Micronesia... 2.6. еее. . MARCUS and J. B. BURCH Marine euthyneuran Gastropoda from Eniwetok Atoll, WEST aci cle dence т. MALACOLOGIA, VOL. 3 К. N. NESIS Ecology of Cyrtodaria siliqua and history of the genus Cyrtodaria (Bivalvia: Hiatellidaeht ........ 2... ao ae ee 197 C. M. PATTERSON and J. B. BURCH The chromosome cycle in the land snail Catinella vermeta (Stylommatophora: (Succineidae) aici te una cha Naar Fame oie 309 H. VAN DER SCHALIE and G. M. DAVIS Growth and stunting in Oncomelania (Gastropoda: Hydrobiidae)..... 81 S. K. WU Comparative functional studies of the digestive system of the muricid gastropods Drupa ricina and Morula granulata........ 211 vi Tom 3 МАЛАКОЛЕНИЕ Май 1966 ОГЛАВЛЕНИЕ Страница, К. КЕННЕТ Симбиотические двустоврчатые надсемейства, Еяус ac ea . . . . . . . . . . . . . . . . . . . . . o . . 183 MATES КЛАРЕЗ "Кольца роста" на клюве кальмара Moroteuthis ingens (Oegopsida: Onychoteuthidae). «5 = «5 ее + + + + + te о we COT Б. К. ДАЗО Морфология и история жизни Pleurocera acuta и Goniobasis livescens (Gastropoda: Cerithiacea: Pleuroceridae). ........ 1 Г. X. ФРАНК И A. X. МЕЙЛИНТ Конхометрия пресноводной улитки Biomphalaria pfeifferi (Basemmalophprar Planorbidae) 2 y lie a nm... a 5819 ШТ. гИЗЛИЕ Репродуктивные Функции и Филогения заднежаберных ВЕН О оков «ee Gu. a Da at an QUE ae аъ ae В. 0. ГРЭГГ ИД. В. ТЭЙЛОР Fontelicella (Prosobranchia: Hydrobiidae), новый pol. западно-американских пресноводных улиток. . . „103 ВЕ. ГРУЗОВ Зндопаразитический моллюск Asterophila japonica Randall et Heath (Prosobranchia: Melanellidae) и его связь с паразитическими брюхоногими +. +. + +. + + + .111 Д. ЛАРСОН Примета А i Mlle, По Le ее сб в 9999 А. Ли. МкАЛИСТЕР Эволюционные и систематические проблемы промежуточных люциноидных двустворчатых +. 2 + + + + + + 2433 А. МаккЛЕЙРИ Функционирование статоцистов у пресноводной улитки Ротасеа paludosa (Mesogastropoda: Ampullariidae) . . . . .419 Э. МАРКУС Некоторые заднежаберные моллюски из мкронезии +. +. + + + .263 Ш Э иМАРКУ СТИ. Б.'БЕБУ Морские брюхоногие моллюски подкласса Euthyneura из атолла зниветок западной части великого океана . +. . .235 vii МАЛАКОЛЕНИЕ К. H. НЗЗИС Экология Cyrtodaria siliqua и история жизни рода Cyriodaria (BivalvianHiatelidae). 2. 1. le masa нее м № С. Mo ПАТТЕРСОНИИ Me. Bs БЕРЧ Хромосомные циклы у наземиой улитки Catinella vermeta (Stylommatophora: Succeineidae). „ее 2.0 © 0. in Oe Г. ВАН ДЕР ШАЛЭ И Г. М. ДЭЙВИС Рост и его замедление у Oncomelania (Gastropoda Нуакорнаае) зо о с о RC Mo о ВА Сравнительное исследование пищеварительного процесса у брюхоногих Drupa vicina и Morula granulata . . . . „211 viii MALACOLOGIA, VOL. 3 NEW NAMES GASTROPODA Fontelicella, Gregg & Taylor, 1965, 103 californiensis, (Fontelicella), Gregg & Taylor, 1965, 109 Natricola, Gregg & Taylor, 1965, 108 Microamnicola, Gregg & Taylor, 1965, 109 musetta, (Haminoea), Marcus € Burch, 1965, 239 linda, (Haminoea), Marcus € Burch, 1965, 241 briqua, (Chromodoris), Marcus € Burch, 1965, 245 mietta, (Herviella), Marcus € Burch, 1965, 252 evelinae, (Onchidella), Marcus € Burch, 1965, 253 illus, (Stiliger, Ercolania), Marcus, 1965, 267 bayeri, (Elysia), Marcus, 1965, 270 тата, (Elysia), Marcus, 1965, 270 cuis, (Hypselodoris), Marcus, 1965, 272 lora, (Discodoris), Marcus, 1965, 273 ylva, (Discodoris), Marcus, 1965, 275 lonca, (Catriona), Marcus, 1965, 279 urquisa, (Catriona), Marcus, 1965, 279 rehderi, (Noumeaella), Marcus, 1965, 282 evelinae, (Muessa), Marcus, 1965, 283 Muessa, Marcus, 1965, 282 1% И RT я 5 ei a fad ke: OS A iad PLN DENE a ya Ae Mn ek. Ba. ce ре ik OD | Cu à | er e rue pa ee N a Be y sons ia р to! 19: ato ne gan Ms tate Y AF: CAN do WE A à DA MER PRO АХ ‘ 90: Bet NET, EUR) mo anne? YES AO AA RA Uns ne NL a te) u COUT Mine du “yey tA N MAA a | AR „Ku el к. : ADO 5 an PEN O uy LIE BOs) dew LEN Jon sa fk AS ПЕ. = F404 Caunes RT NE A | PE + мыза ern ET 7 “ee HAG сом A) e E: | oe | id Ore al each. E A лезем” RES EN Bus par Ac LE MBA 0 DANS a a | 7 MR о eT AL: млм РАЯ ra. № En № PE A0 E coudre \ pre is à ТУ РЕ boy эВ MAR MR бою as ROA alt Lore ELLE ia | Cae’. vol OTT RAU O y © | | | } i \ N | | | À D 1 | À | | | ar b В + № № м. в И Е 1 я u |. У у VOL. 3 NO. 1 AUGUST 1965 MALACOLOGIA 1 ’ > a MUS. COMP ZOO! LIBRARY SEP 16 1905 HARVARD ternational Journal of Malacology Revista Internacional de Malacologia Journal International de Malacologie Международный Журнал Малакологии Internationale Malakologische Zeitschrift MALACOLOGIA ANNE GISMANN, General Editor 19, Road 12 + Maadi, Egypt UA. Re J. B. BURCH, Managing Editor Museum of Zoology The University of Michigan Ann Arbor, Mich. 48104, U.S.A. EDITORIAL BOARD SCHRIFTLEITUNGSRAT P. O. AGÓCSY Magyar Nemzeti Múzeum Baross U. 13 Budapest, VIII., Hungary C. R. BOETTGER Technische Hochschule Pockelsstrasse 10a Braunschweig, Germany A. H. CLARKE, JR. National Museum of Canada Ottawa, Ontario Canada C. J. DUNCAN Department of Zoology University of Durham South Rd., Durham, England E. FISCHER-PIETTE Mus. Nat. d’Hist. Natur. 55, rue de Buffon Paris V®, France A. FRANC Faculté des Sciences 55, rue de Buffon Paris V©, France P. GALTSOFF P. O. Box 167 Woods Hole, Mass. U.S.A. T. HABE National Science Museum Ueno Park, Daito-ku Tokyo, Japan A. D. HARRISON University College of Rhodesia & Nyasaland Salisbury, Rhodesia K. HATAI Inst. Geology & Paleontology Tohoku University Sendai, Japan РЕДАКЦИОННАЯ КОЛЛЕГИЯ N. А. HOLME Marine Biological Assoc. U.K. The Laboratory, Citadel Hill Plymouth, Devon, England G. P. KANAKOFF Los Angeles,County Museum 900 Exposition Boulevard Los Angeles, Calif., 90007, U.S.A.. A. M. KEEN Department of Geology Stanford University Stanford, Calif., 94305, U.S.A. Y. KONDO Bernice P. Bishop Museum Honolulu, Hawaii, 96819, U.S. A. H. LEMCHE Universitetets Zool. Museum Universitetsparken 15 Copenhagen ®, Denmark A. LEMMA Faculty of Medicine Haile Sellassie 1 University ° Addis Ababa, Ethiopia N. MACAROVICI Laboratoire de Géologie Université “Al. I. Cuza” Iasi, Romania D. F. McMICHAEL The Australian Museum College Street Sidney, Australia J. E. MORTON Department of Zoology The University of Auckland Auckland, New Zealand У. К. OCKELMANN Marine Biological Laboratory Grönnehave, Helsingór Denmark J. M. HUBER, Associate Editor Museum of Zoology The University of Michigan Ann Arbor, Mich. 48104, U.S.A. CONSEJO EDITORIAL CONSEIL DE REDACTION W. L. PARAENSE Centro Nacional de Pesquisas Malacológicas, C. P. 2113 Belo Horizonte, Brazil J. J. PARODIZ Carnegie Museum Pittsburg, Penn., 15213, К.А, В. О. РОВСНОМ Chelsea College of Science and Technology London, S. W. 3, England S. G. SEGERSTRÄLE Zool. Mus. Helsinki University P. -Rautatiekatu 13 Helsinki, Finland F. STARMÜHLNER Zool. Inst. der Universität Wien Wien 1, Luegerring 1 Austria J. STUARDO Instituto Central de Biologia Universidad de Concepcion Cas. 301, Concepcion, Chile W.S.S. VAN BENTHEM JUTTING Noordweg 10 : Domburg The Netherlands J. A. VAN EEDEN Inst. for Zoological Research Potchefstroom Univ. for C.H.E. Potchefstroom, South Africa C. M. YONGE Department of Zoology The University Glasgow, Scotland A. ZILCH Senckenberg-Anlage 25 6 Frankfurt am Main 1 Germany LS к nn MALACOLOGIA was established with the aid of a grant (NSF-G24250) from the National Science Foundation, Washington, D. C,, U.S. A. MALACOLOGIA wurde unter Beihilfe einer Unterstützung (NSF-G24250) der National Science Foundation, Washington, D. C., U. S. A., gegründet. MALACOLOGIA fut établi avec l’aide d'une subvention (NSF-G24250) de la National Science Foundation, Washington, D. C., U.S. A. MALACOLOGIA fue establecida con la ayuda de una subvencion (NSF-G24250) de la National Science Foundation, Washington, О. C., Ц. 5. A. Журнал МАЛАКОЛОГИЯ был подготовлен к изданию при дарственного научного общества в Вашингтоне, США. помощи субсидии (NSF - 624250) or Tocy- MALACOLOGIA, 3(1):1-80, 1965 THE MORPHOLOGY AND NATURAL HISTORY OF PLEUROCERA ACUTA AND GONJOBASIS LIVESCENS WUS COMP. 7001 (GASTROPODA: CERITHIACEA: PLEUROCERIDAE)!,2 LIBRARY Bonifacio Capili Dazo3 SFP 16 1909 ABSTRACT HARVARD DNIVERSI] Relatively little is known about the Pleuroceridae, a family of freshwater operculate snails common in North America, which comprises, or is related to, medically important melaniid snails in the Far East. Their taxonomy, largely based on shell characteristics, is generally in need of revision. A com- parative study was made of the morphology and biology of 2 species classified in 2 different genera: Pleurocera acuta Rafinesque and Goniobasis livescens (Menke), originating from 4 stations near Ann Arbor, Michigan, and from additional localities in Michigan and Ohio, U. S. A. The shells and opercula of these 2 species differ: however, the similarities not only of their internal anatomy but also in the general pattern of their life history are so striking, that their position in 2 separate genera is open to question. Differences in the shell, though quite marked, are not always present, and were hardly discernible in some intermediate specimens. P. acuta is about twice as large. Although the general form and pigmentation of the body are quite similar, P. acuta has a more elongated snout and head-trunk region, and longer and more tapering tentacles. It has a smaller and more elongate foot which may be an adaptation to its bottom dwelling and burrowing habit, while G.livescens has a rounder and larger foot in relation to the head region, which may be associated with its crawling habit. The mantle and sense organs, the general organization of the nervous system, the morphology of the respiratory, excretory, digestive, circulatory and the muscular systems of both species are quite similar; they differ only in size. In the Pleurocerinae the males have no penis. Females have a deep reproductive pit in the neck between the right tentacle and the base of the foot, and a shallow reproductive groove leading to this pit. Otherwise the general pattern in the reproductive system conforms with that of other prosobranchs. The sexes are separate. In both species the reproductive organs of each sex were almost identical and occu- pied the same position. Spermatozoa were of 2 types: the typical (eupyrene) and the atypical (apyrene) form. The former are transferred to the female in spermatophores. Ecologically, the North American pleurocerids require clean water. Except for Goniobasis they all prefer relatively large habitats. They usually live in sandy or muddy areas in the sheltered portions of streams. Goniobasis lives- cens is found in almost any clean and permanent type of fresh-water environ- ment (springs, swift flowing streams, inland lakes); this species is usually LA dapted from a dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the University of Michigan. 2This investigation was supported (in part) by a research grant, 5 T1 Al 41-05 (2E-41), from the National Institute of Allergy and Infectious Diseases, U. S. Public Health Service. 3Present Address: World Health Organization, Regional Office for the Eastern Mediterranean, Alexandria, Egypt, U. A. R. (1) B. C. DAZO found crawling on rocks and stones. Both the laboratory and field observations indicated that mating takes place during the fall. When the temperature falls below 5°C the animals hibernate. They resume activity and begin to lay eggs in spring. The sand-covered eggs of P. acuta are laid in batches of varying sizes and shapes; the number of eggs per mass varies from 1-19. G. livescens lays eggs singly, sometimes 2-3in a row and several centimeters apart; these are usually covered with a thin layer of soil. P. acuta has a greater egg output than С. livescens (15 eggs snail/day as against 4) but has a shorter period of egg-laying (April to June against April to mid-August). In both species embryonic development lasts about 2 weeks. Growth was most pronounced during the first year (from 0.3 to 10 mm in P. acuta;, 0.3 to 3.8 mm in С. iivescens). When the laboratory-bred snails attained sexual maturity, at 2 years, they were 16.7 and 7 mm long, respec- tively, after which time no appreciable growth occurred. Environmental snails were larger. The normal life span is 3 years but may perhaps extend to 4 years. In P. acuta the sex ratio was about 2:1 in favor of the females; in G. livescens about 5:1. As other prosobranchs, both species feed on red and green algae, desmids, and diatoms. Larval trematodes belonging mainly to the families Azygiidae, Allocreadiidae and Aspidogastridae often heavily para- sitized the liver, gonad, alimentary tract and other organs. CONTENTS Page Page Reproductive System . . 2.200 35 Male Reproductive System ... . 36 INFRODUC TION es sso ule ae are 3 Female Reproductive System . . 38 SYSTEMATIC POSITION AND Muscular System... ооо 40 HISTORICAL REVIEW :2%:..#.1. 40 3 ECOLOGICAL STUDIES... + 782 41 DISTRIBUTION ............... 9 Description of Habitats... se. 41 Geologic Distribution. ......... 9 те — i Geographic Distribution........ 10 Some athe leo eee METHODS AND TECHNIQUES.... 11 Michigan .. ...-. VER 43 Sampling Methods ......... Ses Collecting site in Ohio ....... 44 Limnological Methods ......... 12 Vegetation .. „u. 2... o 46 Maintenance in the Laboratory ... 13 Limnological data. ..... . 0e 46 Preparation of Materials for Influence of Environmental Anatomical Studies ......... 14 Factors.on Shell... ha ee 51 Histological Methods. ......... 16 LIFE HISTORY............... 55 MORPHOLOGICAL STUDIES ...... 16 Mating Habits? i 2). . EEE 55 Shell and’ @perculund . "2... 22... 16 The Egg and Egg-laying PEUR REPIONE AN и. 19 Activities 2.5.0... ete eee 56 senserOrgans it ee, 21 Time of Development in the Egg NEFVOUS SYSTEME 0 elote en. cu 21 and gross Embryology....... 60 Digestive System? 1. codi do 26 Growth. ae CO 60 Alimentary iract 3/24 LL 28 Sexual Maturity and Longevity ... 61 Gtherorsansie.s tin ere 30 Sex: Ratio Hi CA Ce 63 Vascular Systems. 02905420 4 32 Diurnal and Seasonal Excretory System. 4.2: . „u... 34 Activities. oo Sica eee 63 Respiratory System"... ......,. 35 Food and Feeding Habits....... 64 PLEUROCERA AND GONIOBASIS Contents (cont.) Page Parasites and Predators ....... 66 DISCUSSION OF PLEUROCERID RS ES e as er, 71 ACKNOWLEDGEMENTS ......... 13 Pires CURE, CITED ео. 74 INTRODUCTION The melaniid snails of the family Pleuroceridae are common and wide- spread on the North American conti- nent and are the dominant group of fresh-water gastropods in the south- eastern United States. Nevertheless, little attention has been given to the biology of this common prosobranch family. Most of the existing literature pertains to shell descriptions and shell variation and only a few papers deal with aspects of their morphology and natural history. There are several factors which con- tribute to the neglect this family has suffered: (1) Their greatest abundance and the great majority of species occur in the southeastern United States, which has only recently developed research facilities; (2) the great individual and intrapopulation variation in the various Species and the large number of names superficially applied to this variation has resulted in a taxonomic and nomen- clatural confusion which is discouraging to workers interested in working with the group; and (3) there has been a general failure to culture pleurocerid snails successfully in the laboratory. The purpose of this investigation was to study aspects of the biology of Pleurocera acuta Rafinesque and Gonio- basis livescens (Menke). These 2 species were selected because: (1) they are common and readily available in the Surroundings of Ann Arbor, Michigan; (2) little is known of their biology; (3) they are important in that they serve as intermediate hosts for trematode parasites of fresh-water fish and are of interest to parasitologists in that they harbor various other larval flukes; and (4) they are related to medically important melaniids in the Orient4 Also it is hoped that the present work may serve to lay a foundation for further morphology and life history studies on other members of the family and help formulate a new evaluation and a more meaningful revision of the systematics of the Pleuroceridae. SYSTEMATIC POSITION AND HISTORICAL REVIEW The Pleuroceridae belong to the sub- class Prosobranchia which are usually bisexual, operculate snails having the gills in front of the heart and crossed visceral nerve commissures producing an 8-shaped loop. This family belongs to the order Mesogastropoda Thiele, which almost corresponds to the Pectinibranchia of earlier authors or to the Ctenobranchia excluding the Steno- glossa, i.e. to the Taenioglossa. The “taenioglossid” radula has 7 teeth, 3 on each side of the median tooth. The systematic position of Pleurocera acuta and Goniobasis livescens, slightly modified from Thiele (1929), is as follows: Phylum Mollusca Class Gastropoda Cuvier, 1797 Subclass Prosobranchia Milne-Ed- wards, 1848 (Streptoneura Spengel, 1881) Order Mesogastropoda Thiele, 1925 Superfamily Cerithiacea Fleming, 1882 4Semisulcospira libertina end Thiara (Tarebia) granifera, which act as the first intermediate hosts of Paragonimus wester- mani, the human lung fluke, and Melanoides tuberculatus, which carries Clonorchis sinensis, the oriental human liver fluke. B. C. DAZO v E 8 a SUPERIOR MINNESOTA | WISCONSIN ı À y N я $ —- 7 —_- -— A ee caroL!N ORTEN —f o Ч) FLORIDA Q Y) FIG. 1. The distribution of Pleurocera acuta in North America. PLEUROCERA AND GONIOBASIS \ Mo: | NISNOOSIM j ® A VLOS3NNIN FIG. 2. The distribution of Goniobasis livescens in North America. 6 B. C. DAZO FIG. 3. The distribution of Goniobasis livescens in Michigan (From Goodrich, 1945). PLEUROCERA AND GONIOBASIS 1! FIG. 4. The distribution of Pleurocera acuta in Michigan. 8 B. C. DAZO Family Pleuroceridae® Fischer, 1885 Subfamily Pleurocerinae Morrison, 19546 Genus Pleurocera Rafinesque, 1818 Species Pleurocera acuta™ Raf- inesque, 1831 Genus Goniobasis Lea, 1862 Species Goniobasis livescens (Menke), 1830 Morrison (1952, 1954) in an evalua- tion of phylogenetic relationships of old and new world melanians, based on the morphology of the reproductive system and on biological considerations, sug- gested an arrangement in which all freshwater melaniids were grouped in 3 families, each of which is directly related to 3 marine families, as follows: 1) Melanopsidae-Modulidae; 2) Pleuro- ceridae-Cerithiidae; and 3) Thiaridae- Planaxidae. The first 2 groups are SThe earlier family name Strepomatidae Haldeman, 1863, must be rejected because it is not basedon anavailable generic name. A proposal for validation and inclusion in the Official List of both the family Pleuro- ceridae and the genus Pleurocera as its type is now under the consideration of the International Commission of Zoological Nomenclature (Melville, 1960). 6Thiele (1929) listed Pleurocerinae as a subfamily of Melaniidae. ТВу longstanding usage the species acuta has been treated as the type species of the genus Pleurocera, whereas, by strict application of the present rules of nomen- clature, the type species ought to be “P.” verrucosa. However, formal acceptance of verrucosa would entail confusing transfers of names; the snails now placed under Lithasia Haldeman, 1963, would become Pleurocera, while another name would have to be resurrected for those now commonly called Pleurocera. To avoid widespread confusion, a request for the validation of P. acuta as the type has been placed before the I.C.Z.N. (Melville, 1960). dioecious, while no males are present in the third group, in which the females reproduce parthenogenetically. The families all belong in the superfamily Cerithiacea. Rosewater (1960a) con- siders the above proposals interesting but not yet conclusive and believes that some of the various relationships on which it is based need to be further investigated and evaluated before final acceptance. According to Morrison the charac- teristics of the typical subfamily Pleuro- cerinae, to which the North American pleurocerids probably all belong, are: the females, all oviparous, unfailingly have an egg-laying sinus on the right side of the foot; the males have no intromittent organ. Morrison, rejecting the name Pleuro- cera. for the forms grouped under it by Bryant Walker (1918), selected for them the name Oxytrema Rafinesque, 1819, and further combined under this genus, on the basis of egg-laying characters, most species of Goniobasis. He also revived the genus Mudalia Haldeman, 1840 and, placed Goniobasis livescens (Menke) under it. The writer feels that the evidence for this combination and the concomitant transfers is as yet insufficient and prefers to maintain the traditional nomenclature until such a time when more extensive study of the group con- cerned will provide a broader basis for revision. For further details on the subject the reader is referred to the section “Discussion of Pleurocerid Systematics” (p 71). In the following, a brief his- torical review only is given of the early literature pertaining to Pleuroceridae to provide a background. The earliest known pleurocerid records were those by Lister (1770) and Gmelin (1791) on Buccinum (-Goniobasis) virginicum. In the early days all the pleurocerid groups were assigned to the genus Melania Lamarck (1792), which also included all operculate fresh-water gastropods other than those belonging AAA AA A PLEUROCERA AND GONIOBASIS 9 to the Viviparidae and Pilidae, from all parts of the world. In due time the heterogeneous condition within the genus Melania was recognized and various authors provided some relief by splitting the group and introducing new genera. In the following are listed some of the most notable authors of generic names for the pleuroceridgroup of North America and their corres- ponding contributions. C. S. Rafinesque, in 1818, established the genus Pleuro- cera, naming 6 species without giving any descriptions; in 1819 he defined Pleurocera and created the genus Oxy- trema. The following year he described the first recognizable species, Pleuro- cera verrucosa (-Angitrema verrucosa) and at the same time he also described a species from Lake Erie, P. acuta. Rafinesque’s failure to designate a type for the genus Pleurocera has caused contention, not only among his contem- poraries, but also among many of his successors (Walker, 1917) and the ques- tion as to which species will ultimately be accepted as the type species is not yet settled. In 1819 he also named the genus Leptoxis. According to Morrison (1945) Leptoxis is the earlier and valid name for the genus that Thomas Say named Anculosa in 1821. Isaac Lea? later proposed the 3 genera: Jo, in 1831, Goniobasis, in 1862 and Eury- caelon, in 1864; Shuttleworth, in 1845, described the genus Gyrotoma; Halde- man, in 1840, named the genera Muda- lia, and Lithasia; Nitocris was named by H. and A. Adams in 1854. Pilsbry, in 1910, added the genus Lithasiopsis”. H. and A. Adams (1854) established Elimia as a subgenus of Pleurocera 8Lea also introduced Trypanostoma (a syno- nym of Pleurocera) and Strephobasis as one of its sections, but these are not in use to- day. 2The position of this genus is dubious. I share Goodrich’s (1942) opinion that Lithasi- opsis probably is related to Pachy- chilus. and placed in it 16 species including G. livescens; but among these were at least 4 with obviously different kinship (Goodrich, 1945). In 1896, Pilsbry tried to revive Elimia, raising it to generic rank, to take the place of Goniobasis. Later, he decided that Goniobasis should be restored as a genus on the grounds that Elimia was a composite group (Walker, 1918). The earlier synonyms for the genus Pleuro- cera are given in Tryon’s (1873) manual on the Strepomatidae, p 49, while those for the genus Goniobasis are listed on p 138. Among authors that have made valu- able contributions to pleurocerid syste- matics are: Hannibal, Conrad, Anthony, DeKay, Hinds, Gould, Tryon, Menke, C.C. Adams, Goodrich, and others. Their contributions are too numerous to be discussed here; however, Adams’ study on Jo is listed in the references. More detailed data on the literature regarding the 2 species under consid- eration, Pleurocera acuta and Goniobasis livescens, and their close relatives, will be given in the appropriate sections. Unfortunately these records deal mostly with descriptions of the shell and with ecology, while information on the ana- tomy and life history of these snails is scarce. Most important among these are Magruder’s (1935b) studies on the anatomy of Pleurocera canaliculatum undulatum which furnished a valuable basis for the present study and will be extensively quoted below. Worthy of note are also the studies of Rose- water (1959a, 1961) on P. canaliculata, those of the cytologist Woodard (1934, 1935, 1940) on the reproductive system and spermic dimorphism of Goniobasis laqueata and Jewell’s (1920) observa- tions on the reproduction of Goniobasis livescens correcta. DISTRIBUTION Geologic Distribution. Records exist for pleurocerids in 10 B. C. DAZO strata ranging from the Cretaceous to the Pliocene epoch. Although Weatherby (1876) suggested that they appeared as early as the Carboniferous age of the Paleozoic era, or that immediately suc- ceeding it, this has never been cör- roborated. White (1882), Walker (1900), and Adams (1915) were of the opinion that the earliest fossil Pleuroceridae are from the late Mesozoic Laramie formation, while Henderson (1935), in a comprehensive work on the nonmarine Mollusca of North America places them a little earlier. He reported that the oldest known member of this group is Goniobasis multicarinata Russell, which was found in Alberta, and which is believed to have existed during the Lower Cretaceous. He listed other fos- sil pleurocerids as follows: 13 species from the Upper Cretaceous, 10 from the Lower Cretaceous, and 28 from the Cenozoic (Tertiary) era. The species Goniobasis livescens and Pleurocera acutum tvactum were reported by F. C. Baker (1902) from the Pleistocene loess. The oldest fos- sil specimen of G. livescens, according to F. C. Baker (1920), was found in the Toleston deposits of glacial Lake Chicago, whereas the oldest P. acuta (quoted as P. subulare (Lea) were from the Wabash and the Sangamon inter- glacial deposits. Wright (1932) studied post-glacial fossil remains of P. acuta and G. livescens in the Tippecanoe River system of Indiana and his find- ings indicated that they had migrated there from the Kankakee and Iroquois Rivers at the close of the glacialperiod. At present, the Tippecanoe system is a tributary of the Wabash River and a portion of the Ohio River drainage sys- tem, where these snails still flourish. Two conflicting ideas exist with regard to the geographic origin of the living members of this group. The first and more popular theory supports the view that the Pleuroceridae originated from the Laramie formation (probable beds in Colorado, Wyoming, Montana, Alberta, and Saskatchewan). Their surviving des- cendants are believed to have migrated from the west to the Mississippi Valley and southeastern United States together with the Unionidae. This theory was propounded by White (1882) who reasoned that although the large lakes, which existed in the Tertiary and Laramie periods, successively became obliter- ated, it was reasonable to conclude that at least part of the river channels of today have existed as such from earlier geologic times. This applies to some of the present tributaries of the Mis- Sissippi River system that partly coin- cide with former outlets or inlets, or both, of these ancient lakes. It is pos- sible, therefore, to infer that the mol- luscan fauna of the Mississippi River system descended directly from the faunae of those ancient lakes and mi- grated through the river systems in which they constituted lacustrine elements. Simpson (1896) accepted this theory. The opposite view tends to support the idea that pleurocerids originated in the southeastern United States and that they spread westward, as they did during more recent post-glacial migrations (Walker, 1900). Adams (1915) favored this theory, stating that the southeastern streams have been favorable as habi- tats for certain mollusks since the close of the Paleozoic era. The presence of a large number of endemic species which are confined to that region strengthens his view. He postulated that the lack of fossils in the south- east was brought about by the persis- tent adherence of rivers to their ancient channels; it is only in deposits of lacus- trine portions of ancient river systems that these faunal elements have been preserved. Geographic Distribution. Lake Erie is the type locality for Pleurocera acuta. Its general distri- bution (Fig. 1) includes the headwaters of the Ohio River and its tributaries, the Mississippi River westward to eastern Nebraska and Kansas. The PLEUROCERA AND FONIOBASIS 11 species invaded the Erie Canal and en- tered the basin of the Hudson River. According to F. C. Baker (1928a) the easternmost locality record for P. acuta is a tributary of Lake Champlain in Vermont, in the St. Lawrence drain- age; the most northern locality recorded is Lake Superior, Bayfield, Bayfield County, Wisconsin. Some forms, in- distinguishable from P. acuta, have been taken as far south as the branches of the Cumberland and Duck Rivers of Tennessee (Goodrich, 1940) and the tributaries of the Mississippi River in Louisiana and Arkansas. Goniobasis livescens is generally dis- tributed from New York to the Great Lakes region, and from Canada to the Ohio River drainage (Fig. 2). It was named and described by Menke in 1830, from specimens collected from the eastern end of Lake Erie. It is found in the tributaries of the Ohio River, east of the Scioto River in Ohio, the Wabash River and its tributaries west to the Illinois River; it is especially common in the St. Lawrence River basin, including the Great Lakes. G. livescens occurs as far east as Lake Champlain and parts of Quebec. It also invaded the Hudson River Basin by way of the Erie Canal. It has been found in all of the Great Lakes except Lake Superior though it is known to occur in one stream tributary to Lake Superior and within less than a mile of the stream’s discharge; it oc- curs also in the St. Mary’s River con- necting Lakes Superior and Huron. In the Ohio River drainage it occupies small streams of western Pennsylvania and various rivers in Ohio, excepting the Scioto and the Little and Big Miami. Somewhat the same discontinuous dis- tribution is found in Indiana where G. livescens lives in streams flowing into Lake Michigan, in the Lake Erie drain- age and the Wabash River with its northern tributaries; it has not been found in the White River forks, nor in streams to the east of the Wabash, such as the Big Blue and White Water Rivers. Specimens were reported from Des Moines River in Iowa by Goodrich (1940). Baker (1928a) stated that in Wisconsin С. livescens is confined to Lake Michigan and streams emptying ato it: The distribution of G. livescens in Michigan, based on studies by Goodrich (1945), is shown in Fig. 3 and the recorded distribution of P. acuta in Fig. 4. It is evident from these maps that G. livescens has a wider distribution in this state than does P. acuta. Goodrich (1940) further stated that it had a wider distribution in Michigan than any other aquatic mol- lusk, with the possible exception of the pulmonate, Helisoma trivolvis Say). METHODS AND TECHNIQUES Sampling Methods. This investigation was begun with a general survey for areas positive for pleurocerid snails. Various collecting sites were chosen in Michigan (and also Ohio). For ecological and life history studies, 4 permanent stations were designated in 2 rivers and 2 smaller streams near Ann Arbor, Michigan, which are described in detail in the Ecology section (p 41). These stations were visited at least once a month for a period of 1 year. The snails were collected by 2 methods: random sampling outside of the im- mediate station area and quantitative Sampling in staked areas. In this second method, 3 one-meter quadrat samples were taken at each monthly collection, 2 samples on each side of the stream and the third in the middle. In order to avoid col- lecting in the same place, successive monthly samples moved progressively to an up-stream undisturbed portion. The quadrat area was staked by using 4 strips of tin-aluminum metal alloy (each measuring 3 cm by 100 cm), with holes drilled at each end. Iron nails 6 inches long were driven through the holes, marking the square meter 12 B. C. DAZO enclosure. The tin-aluminum alloy is heavy, sinks readily in water, and can be clearly seen. The metal strips also have the advantage of being easily rolled and stored when not in use. All snails visible within the sample area through a glass-bottom viewer, were removed with a pair of forceps. Then the surface sand and gravel were carefully scraped and shoveled into a clean wooden box the bottom of which was lined with fine (about 1 mm) wire mesh for collecting the tiny snails. Occasionally, when the snail density was high only 1/2 or 1/4 of the quadrat was sampled. Most of the snails recovered in the field were taken to the laboratory where they were relaxed and fixed (see p 14- 15). Some were crushed on the spot with a pair of pliers and fixed immedi- ately in Lavdowsky’s Solution (Formalin- Alcohol-Acetic Acid 2:10:1 parts by volume) to preserve the stomach con- tents for a study of the food habits of these snails (see p 64). Shell measurements were made for use in a growth and life history study (p 63 and Table 12). The data re- corded were: (1) maximum length of shell; (2) greatest width perpendicular to the long axis; and (3) the number of whorls present. Larger snails were measured with calipers, whereas an ocu- lar micrometer and a dissecting micro- scope were used on the smaller ones. In all cases, measurements were taken with the aperture of the snail facing the observer. The sex of the snail was also deter- mined (see p 63 and Table 13). Limnological Methods. Just before collecting snails at each permanent station during the monthly sampling, and at other collection sites limnological and other ecological obser- vations were made. The data taken include: free carbon dioxide content of the water, methyl orange alkalinity, dissolved oxygen, pH, water current velocity, water level fluctuations, tur- bidity, and temperature records of both the water and the atmosphere. Lim- nological methods followed are those presented in Welch (1948) and in the “Standard Methods” of the American Public Health Association (1955). Ambient and water temperature were taken with an ordinary mercury ther- mometer. Water level fluctuations were recorded as follows: a wooden post was driven into the stream bed in the middle of the stream and, using this post as reference, the water depth was recorded at each visit. A portable Beckmann pH meter (Model 180) was used for determining the hydrogen-ion concentration of the water. This meter was calibrated from time totime against a standard laboratory apparatus. Water current was determined with the aid of a “pygmy” model current meter (Bat- tery operated, serial number R-318), manufactured by Arline Precision Instruments, Baltimore 29, Maryland, which had been calibrated by the U.S. Bureau of Standards and Measures. The free carbon dioxide content of the water was taken in the field using phenol- phthalein indicator and a N/44 aqueous solution of sodium hydroxide as titrating agent. Methyl orange alkalinity was deter- mined in the laboratory from 2 sam- ples for each station. Two drops of methyl orange indicator were added to a 100 ml sample which was titrated against an aqueous solution of N/50 Sulphuric acid until the water changed from orange to a permanent light pink color. The amount of sulphuric acid used in cu. mm multiplied by 10 gives the methyl orange alkalinity of the water in parts per million (ppm). Two water samples from each station were also used for determining the oxygen content. These samples were “fixed” in the field using the H. Pomeroy-Kirschman- Alsterberg modification method, as fol- lows: 1 ml of potassium fluoride was added to a 200 ml sample and agitated; 2 ml of concentrated sodium iodide and 2 ml of manganese dioxide solutions PLEUROCERA AND GONIOBASIS were added and mixed. A brownish- red precipitate appears but is dissolved by the addition of 1 1/2 ml of con- centrated sulphuric acid. The fixed sample was titrated in the laboratory by means of an aqueous solution of N/100 sodium thiosulphate, until the color of the water sample changed from orange to light pink. The amount of sodium thiosulphate used in ml multiplied by the factor of 1.6 gives the amount of dissolved oxygen of the water in parts per million. Maintenance in the Laboratory. At the beginning of this program it seemed impossible to maintain or cul- ture pleurocerid snailsinthe laboratory. The adults would survive for a few days or weeks and then die out. Only after more than a year of experimenting, was it found that unless exceptionally good oxygenation was supplied and un- less adequate amounts of green algae and diatoms were present, the pleuro- cerids would not thrive. When these two important needs were met, and combined with periodic renewal of the setup, the culture of these snails be- came possible. The pleurocerid snails were success- fully cultured in two ways: in an arti- ficial stream and in aquaria. The artificial stream was made of 2 long wooden troughs each 11 feet long, 12 inches wide and 6 inches deep, con- nected at one end by a short trough (29 inches) to form a U-shaped canal. Leakage was prevented by lining the corners and the bottom with fiberglass. This set of troughs was set on a regu- lar laboratory table with one end higher than the other. The flow system was completed by means of a plexiglass paddle wheel mounted on a short end trough at the lower, open, end of this canal. A small electric motor attached to the wheel served to move the water from the lower end of the trough to the upper, through a fiberglass channel, creating a continuous flow without a water tank or reservoir. Care was taken 13 to use neutral materials and to avoid metal (especially copper) parts since various metal ions are detrimental to the snails. River water, rocks, sand, soil and water plants from the field were placed in this artificial stream, to simulate natural conditions. The troughs were covered with glass to prevent excessive evaporation of water and the water was kept at a fairly constant depth of about 5 inches. After trial maintenance runs, gravid snails were transferred to this indoor station. Oxygenbubblers were connected at several points along the stream to augment the aeration of the water. The temperature of the water fluctuated, but was near that of the outside atmosphere because the windows were kept open throughout the year. Natural light also came from these windows. This artificial stream served well for some time. Later, the wood warped on the side of the paddle wheel, which was replaced by a small Bro-Jo Plastic Pump. It successfully pumped water from the lower to the higher side, and no further difficulties were encountered. Pleurocerid snails were also main- tained and cultured in the laboratory in regular aquarium tanks. These were placed on shelves in front of windows for sufficient lighting. Again water, aquatic plants, rocks, soil, and sand used in these tanks were taken from the field. Oxygen was supplied to the bottom of each tank by the usual aquar- ium air bubblers. Eachtank was covered with a glass lid. The water temperature was 220 to 23° C (72° F) all year round. In both methods the pH was kept within the range of 8.0 to 8.4; the carbon dioxide and dissolved oxygen con- tent of the water in the tanks were checked at least once a month. Loss of water by evaporation was unavoid- able, even with glass covers, and in- creased the salt content of the water. In time, the increasing amount of fecal materials also produced an increase in 14 B. C. DAZO hydrogen-ion concentration. These ten- dencies were offset by adding distilled water. If, however, the pH fell below 8.0 either pond water was added or, to increase alkalinity, calcium in the form of powdered calcium carbonate and calcium sulphate. Adult female specimens ofboth species were collected during spring and early summer. They oviposited in the labora- tory and many young hatched. Although there was a high mortality rate among the juvenile snails, many of them did reach maturity and in turn laid eggs, completing the cycle. The snails were fed regularly with fresh leaf lettuce. Other leafy vege- tables, such as water-cress, spinach, cabbage, etc., were tried but the snails seemed to prefer lettuce. The Lee and Lewer’s (1956) modification of the Stan- den snail food (Cerophyll), which has been used successfully with some planor- bid snails, did not attract pleurocerids. The diet was supplemented with green algae and diatoms by providing rocks and pebbles covered with green algae and diatoms from the normal habitats at least once a month; those previously procured were then removed to avoid overcrowding. Filamentous green algae (Spirogyra) and blue green algae (Ana- baena) often grew profusely and proved to be a nuisance: the former is seldom eaten, the latter is toxic, and both were periodically removed to avoid crowding the containers. Because of the presence of one dead Snail could induce fatalities among the rest of the animals in the tank, dead animals were immediately removed from the culture. When a tank became too dirty, with an overaccumulation of fecal material, with the snails dying and a consequent bacterial content, it was completely reestablished. When conditions in the tanks became unhealthy ostracods would often appear in great numbers and could often be seen observed biting and attacking weak snails. They always swarmed over the decaying animals. A tank in which most of the snails died was always one con- taining a thriving colony of ostracods. Leeches and planarians were often seen within the shells of decaying animals. Care was therefore taken to keep the aquaria fresh and to avoid proliferation of the scavengers. The common aquari- um fish Lebzstes reticulatus (Peters) was not kept in the snail tanks after observing that it would eat the eggs of pleurocerid snails. With the methods outlined above, pleurocerid snail culture in the labo- ratory was very successful and it was now at last possible to initiate studies on egg-laying activities, mating and feeding habits and longevity. Success in culture likewise insured a good supply of normal specimens for basic work in morphology, for most pleurocerid snails collected in the field were heavily para- sitized by larval trematodes and there- fore not considered representative. Preparation of Materials for Anatomical Studies The snails to be studied were placed in finger bowls or white enamel pans containing pond water (usually 150-200 cc). They were relaxed by adding a few menthol crystals. The container was then covered with a glass plate. In this initial stage extreme care must be taken not to shake or move the con- tainer because the animals are very sensitive to such stimuli and contract immediately. Once contracted, they are not apt to relax again. It usually takes about 6-8 hours for the animals to properly distend and relax with menthol. After that time, about 10 cc of 10% veterinary sodium nembutal was added. The total relaxation time was usually about 16 to 18 hours. The animals were then immediately fixed, either with Bouin’s picro-formol solution or with 10% neutralized formalin. This timing is important for obtaining good speci- mens. If fixation is attempted before the snails are completely relaxed, the animals invariably pull back into their shells and are fixed with their opercula PLEUROCERA AND GONIOBASIS 15 closed. If however, the specimens are fixed a few hours after complete relax- ation, the soft parts show tissue wrinkles and partial disintegration. Specimens remained in the fixative for at least 24 hours but never beyond 72 hours. Longer fixation produces tough and hard tissues which are unsuitable for gross dis- section. After fixation, the animals were carefully removed from their shells, transferred to 30%, 50% and finally 70% ethyl alcohol solution. Empty shells and opercula were cleaned with a small brush using soap and water. Shells were dried in air and then stored for measurements. Opercula were also soaked overnight in a weak solution of oxalic acid, rinsed’ and again cleaned with a brush. Later, they were passed through series of alcohol solutions (30%, 50%, 70%, 85%, 95% and 100%). The opercula were cleared with xylene and mounted in Canada balsam. For radular preparations the entire buccal mass, including the radular ribbon, was carefully dissected from relaxed animals and soaked for a few days in a weak solution of sodium hydroxide to dissolve away the tissue. Afterwards, the radular ribbon was re- moved carefully and washed in a 10% acetic acid solution to neutralize the hydroxide. The ribbons were then washed in distilled water and passed through increasing grades of alcohol. Prior to staining and mounting, they were stored in 70% alcohol. Some radulae were stained with Orange G using Roger’s (1924) electrical method. Most of them were stained with chromic acid, borax Carmine, and eosin. The ribbons were transferred from 70% alcohol to the stain. It was found helpful to overstain and then destain slowly in acid alcohol (70% with a few drops of concentrated hydrochloric acid) transferring toa basic alcohol to the desired intensity. After washing the ribbons in a neutral 70% alcohol, they were dehydrated with in- creasing grades of alcohol through 100% and cleared in xylene. They were then carefully flattened on a microscope slide and mounted in Canada balsam or euparal. Some were ripped apart with teasing needles before mounting on the slide to allow a better view of individual teeth. The jaws were carefully dissected from the buccal mass, cleaned and stained with aceto-carmine, prepared in a similar manner and mountedin Canada balsam. Whole mounts were prepared as follows: the newly relaxed and unfixed animals were held between two glass slides. Gentle pressure was applied to the slides and, at the desired thickness they were bound into position with a piece of string. The preparation was then fixed for at least 48 hours in formalin or Bouin’s. According to the fixative used they were either washed in running tap water to remove all traces of formalin or to hasten the removal of excess picric acid in finger bowls to which a small amount of powdered lithium carbonate had been added. The washed specimens were then passed through in- creasing grades of alcohol to 70%. They were stained in borax carmine. Over- stained specimens were slowly destained in acid alcohol as indicated for the radulae. The stained specimens were dehydrated in alcohol and cleared in oil of cloves. The excess oil was removed with xylene. The whole mounts were made with Canada balsam. Pieces of broken glass were used to support thick specimens in these slide preparations. Gross dissection of preserved speci- mens was done under a dissecting micro- scope in dishes partially filled with wax on which the specimens were mounted. The preferred dissecting fluid consisted of equal parts by volume of pure glycerine and 70% alcohol. The fluid made the snail tissues soft and quite pliable. Pliers were necessary for Cracking and re- moving the hard calcareous shell of the animal; jeweler’s or watchmaker’s forceps, scalpels with pointed ends, scissors with curved tips, extra fine insect pins, fine camel hair brushes and 16 B. C. DAZO other standard laboratory supplies were used for detailed dissection. Nervesand delicate membranes were traced by means of a 0.5% aqueous solution of methylene blue dye (Basch, 1958). Formalin (15% solution) was used to remove excess dye in the nerve tissues; a neutral 70% alcohol removes the blue dye completely from all tissues. For vivisection sometimes the snails were first anesthetized in menthol and the shell was then removed with a pair of pliers. Dissection was carried out in physiological salt solution developed by Fraser (Carriker, 1946). Histological Methods Serial sections were made ofthe whole animal as well as of excised organs and organ systems. Most of these prepa- rations were made with animals whose shells had been removed with Bouin’s picro-formol solution; some were of animals carefully extracted from their Shells. The fixed animals were well washed in running tap water to remove excess picric acid. The specimens were then passed up through the alcohol series to absolute alcohol. They were cleared by passing through a solution of 1:1 chloroform andabsolute alcohol and were later transferred to pure chloroform. Wax infiltration began at the half chloro- form and half paraffin stage. After about 30 minutes, the specimens were trans- ferred to pure paraffin for complete embedding. The blocked paraffin tissues were cut at 124. The sections were fixed on the slides with egg albumen and the ribbons were flattened on an electric slide warmer. Paraffin was removed from the slides by immersing them in 2 changes of xylene. The sections were then run through a decreasing series of alcohol to 30% and finally to water. The tissues were stained with hematoxylin (Harris and Ehrlich’s acid hematoxylin) and washed in tap water. After staining, the slides were passed through anincreasing series of alcohol to 95% and counter- stained with 0.5% Eosin for 30 seconds. After washing the slides several times in 95% alcohol, they were dehydrated in absolute alcohol, and cleared in oil of cloves and xylene; mounts were in Canada balsam or euparal. The histological and embryological photographs (Plates VI and VII) were taken with an Exakta VX Ila, a single- lens reflex camera. The morphological drawings were made with the aid of a camera lucida at table height. MORPHOLOGICAL STUDIES Shell and operculum As previously stated, most of the literature available on pleuroceridae deals with the shell and its variations. Little is to be added to the innumerable papers on shell characters. The brief description given here is based on publi- cations by F. C. Baker (1902, 1928a) and Calvin Goodrich (1939c, 1945), both of whom adequately described the dextral shells and the opercula of P. acuta and G. livescens; it is supplemented by observations on the material used in this study. Pleurocera acuta Shell. The shell of this snail is thick and heavy, somewhat conical in shape, and much elongated (Plate I and Fig. 11). The color of the shell varies from pale brownish horn to dark chestnut. Black and pale yellow specimens are also found. In nature, the shell is often coated with mud or algal growth. When cleaned, some have a lustrous surface, while others may appear dull. In river forms, a yellowish band sometimes en- circles the whorls just below the suture. In some lake forms, 2 or 3 brown bands often are clearly visible on the inner and outer side of the body whorl. Oblique lines of growth and prominent scars often appear on that whorl. It is angulate, with or without sharply defined carinae. A double carina or ridge tends to be very distinct in the young. This carinationis usually carried PLEUROCERA AND GONIOBASIS 17 4 PLATE I. Pleurocera acuta andGoniobasis livescens as they appear in the living condition and their opercula (insets). FIGS. 1&2. P. acuta FIGS. 3&4. G. livescens 18 B. C. DAZO only on the first 3 to 6 apical whorls in adult shells, while the later whorls appear smooth. The median ridge or carina is more prominent than the one located near the suture. Occasionally one encounters a shell with 1-3 carinae encircling the base of the body whorl. The shell of an adult is 29.92 mm long on the average and 11.29 mm wide (See Table 13). It usually has 9 to 11 whorls but in unbroken specimens the number may go to 15. The shell aperture is subrhomboidal, white, bluish-white to purple within, angulate, tending to form a canal below (canaliculate). The columella is twisted, with a bluish- white tint. Operculum (Plate I, Fig. 2). The paucispiral operculum is chitinous, thin and reddish-brown in color. There are 3 opercular whorls in the adult. It is somewhat oval in shape with the left margin almost straight and the basal and right margins broad and regularly curved. Its apex is more or less roundly acute. The growth lines are fine and numerous and the rest scars are very well marked by darklines. The nucleus is sunken and located at about a third of the distance from the base to the apex, nearer the left margin. The area of attachment to the columellar muscle of the foot occupies about half the anterior (=nuclear) side. An interesting observation on the oper- culum of P. acuta was made by the writer, which agrees well with those made by Goodrich (1939a) in Pleurocera canali- culatum undulatum and in other pleuro- cerids. In the laboratory some of the animals were noted to lose their oper- cula. This loss seemed to be brought about by encysted parasites (ostracods?) that were often seen occupying the region between the base of the foot and its attachment with the operculum. An entirely new operculum then grows to replace the missing one. At first this new structure was extremely thin, though full size. Within 3-4 months the new operculum attained the normal thickness and texture. Goniobasis livescens Shell. According to Goodrich (1939c) this mollusk shows extreme variations. He reported that the spire may be long or short and loosely or tightly coiled; whorls flattened to rounded; shell shape slender and elongate to ventricose. These extremes in variation were also exhibited among specimens collected from all 4 study stations sampled inthis study. Adult shells of G. livescens are ovately-conic, elongated and often turreted on the upper whorls. They average 18.24 mm in length and 8.79 mm in diameter (See Table 13). The juveniles, on the other hand, are conic or pyramidal and the carinae are promi- nent structures in both spiral and body whorls. Specimens collected at the Zuckey Lake Inlet Station had the fine carinae on the juvenile whorls continued as strongly marked keels on the mature whorls (Plate I and Fig. 11). In the other 3 permanent collecting stations, however, this carination was usually wanting because of the eroded condition of the adult shell. If present, it was found only in the first 2-3 apical whorls. The apex or nucleus is seldom present. The body whorl is usually convex and inclined to be bulbous. The shell is smooth. Its color varies and may be bluish-gray, light or dark brown, plain black, greenish light yellow or flesh color. It is for the “bluish” specimens that Menke (1830) selected the specific name “livescens”: (from (lividus = blue). A greenish or yellow green hue is apparently due to algal growth. Goodrich (1939c) attri- buted the dark brown or black coloration, which is characteristic of most streams of Upper Michigan, to “bog stain”. This dark color contrasts with that of the shells of downstream and lake colonies, which are yellow or light brown. A light yellow band may encircle the whorls just below the suture. Adult shells of G. livescens have 7 to 9 whorls; specimens of the same age PLEUROCERA AND GONIOBASIS 19 appear to have the same number of whorls, although their size varies greatly. Shells taken at the Lake Erie station are nearly twice the size of specimens collected from Zuckey Lake Inlet station (Table 13). The number of whorls serves as an excellent index for comparing snails of various sizes and shapes but evidently belonging to the same age group. The whorls of older specimens are usually flat-sided while those belonging to immature shells are convex, bulbous or rounded. The aperture of С. livescens is large, less angulate than that of P. acuta and without the basal canal. It is ovate or subrhomboidal, somewhat produced at the lower part and in live specimens of a brownish-purple to purple color inside. The peristome is sharp, thin, but thick- ened with a callus within the outer lip, and more or less sinuate. The columella is thick, smooth, not twisted and tinged with blue or purple. Operculum. The operculum of С. livescens is chitinous, thin, ovate, and reddish brown. It has 3 whorls in the adult. Its shape is similar to that of P. acuta except that its apex is more acute (Plate la, Fig. 4). The growth lines are coarse in G. livescens; under a microscope they appear as very fine wavy lines with wrinkled ridges. Growth lines or rest scars are more prominent than in P. acuta. By an analysis of these scars, it might be possible to determine the age of this species with some degree of accuracy. As in P. acuta, the nucleus is sunk; it is located at the lower quarter or third of the long diameter, near the left margin. The area of attachment of the columellar muscle occupies the upper 2/3 of the length of the operculum and the right edge of the ihner side. Trunk Region Head-Foot Region. A general aspect of this region is shown in Plate I and Text Figure 5. Usually an adult P. acuta is about twice the size of С. livescens. My observations lead me to agree, in the main, with the descriptions given by F. C. Baker (1928a) and Good- rich (1945), although some oftheir state- ments, especially those referring to coloration, are not representative and need correction. F. C. Baker (1928a) described P. acuta as follows: “Animals with wide, Short, thick foot, truncated before and rounded behind; color blackish above, yellowish underneath; the top of the rostrum is marked by black transverse bands or spots; side of the body and foot streaked with black; mantle dark gray or blackish; operculigerous lobe conspicuous; head prominent, with large, somewhat elongated proboscis or rostrum, subconical in form, which is capable of considerable extension when the animal is in motion; mouth placed at tip of rostrum, disk-like, and repre- sented by a long longitudinal slit which divides the snout-like end into a double disk; the radula may be plainly seen in the mouth when the animal is feeding; tentacles rather long, tapering, very narrow; eyes black, placed on swelling at the outer base of the tentacles; mantle simple, folded on the right side to form the respiratory cavity; on the right side of the body there is an impressed line which extends along the body in a parallel direction and curves to the margin of the foot behind the right tentacle; gills as usual in this group, the primary gill being very narrow.” I have found that the foot of P.acuta has a yellowish to grayish- orange color; the orange hue becoming more prominent on the margin. As for С. livescens, he stated: “Similar in form to Pleurocera. Body yellowish- white with lines of black; orange or yellowish on neck; rostrum orange near tip, darker on upper part; under side of foot bluish white, flecked with dark spots. The whole body is sometimes lemon-yellow.” However, there is no question but that the head-foot region of G. livescens is muchbroader and shorter than that of P. acuta. Calvin Goodrich (1945), on the other 20 B. C. DAZO large intestine gills stomach digestive gland (liver) small intestine heart kidney PA operculum columellar muscle mantle collar efferent ctenidialsinus right cerebral ganglion tentacle esophagus radular sac salivary gland right pedal ganglion foot FIG. 5. Arrangement of organs in Goniobasis livescens. Lateral view (right side) with shell removed. The osphradium, on the left inner side of the mantle, can not be seen. hand, more appropriately described G. livescens as follows: “The body of the male specimen was rather short and rounded posteriorly and had a blunt wedge-shaped rostrum. The mouth was a narrow, vertical slit. The tentacles were short, thick at the base, and tapering to a blunt termination. Strongly pigmented eyes at the base of the tentacles were conspicuous. The mantle covered about three-fourths of the body; its margins were smooth. Atrench-like line extended from the pallial cavity to the right tentacle. The color in general was grayish to nearly black. A female of the same colony, taken at the same time, differed in showing faint discon- tinuous stripes of tallowish coloration on top, not greatly contrasting with the leaden hue of the body mass. Irregular spots occurred here and there on the sides of the foot. Thetipofthe tentacles was translucent, nearly colorless. In the extended animal, the operculum rested in a fold or pocket, showing only its edges. The edges of the mantle were slightly yellow.” However his statements about sexual differences in coloration and marking cannot be generalized. The rostrum of both species has a pattern of black pigmented stripes against a yellowish-orange background resembling that of a tiger, only in finer detail. These pigmented areas are more prominent near the mouth and diminish into spots near the neck of the mantle region. The portion of the rostrum which forms part of the mouth and comes in contact with the surface of the rocks and gravel when the animal browsing has a bluish-yellow or bluish- white color. Mantle and its cavity. The mantle surrounds the neck and head-foot region of the snail. It protects the neck and PLEUROCERA AND GONIOBASIS 21 the anterior organs, especially the head, foot and sense organs. It also acts as a buffer between the hard calcareous shell and the animal itself, spreading like a cushion throughout the entireinner surface of the body whorl. It is inner- vated by nerves coming from the anterior portion of the cerebral ganglia and is supplied with blood originating from the ctenidia or gill sinuses. It is thin, white and almost transparent. In live speci- mens the mantle may be seen adhering closely to the inner surface of the body whorl. The collar or anterior margin of the mantle is smooth and surrounds the edge of the aperture. The space between the neck, the head- foot region, and the mantle is called the mantle cavity. The gill filaments and the osphradium are located inthis cavity, as well as the termination of the genital laminae and the anus. Sense Organs Eyes. The eyes of P. acuta and G. livescens are located at the outside of the slightly swollen base of the long tentacles (Plate I and Text Figure 5). They are innervated by the optic nerve which originates on each cerebral ganglion. Otocysts (Statocysts). These organs, one on each side of the animal, are located below the pleuropedal commis- sures on the postero-dorsal surface of the pedal ganglia (Plate II, Fig. 3). They appear as white spherical bodies about 0.250 mm in diameter; they are connected to the pedal ganglia by thin connective tissues and minute nerves, and are mainly innervated by the 2 statocyst nerves originating from the cerebral ganglia. Their function is generally thought to concern balance (Tschachotin, 1908). Osphradium. The osphradium (Text Fig. 9 and Plate IV) is found in the pallial cavity to the left ofthe ctenidium. Although it is in the direct path of the respiratory current, it is not thought to have a respiratory function. Lacaze- Duthiers (1859) speculated that this gastropod organ had a sensory role. Spengel (1881) reported that it served to test the physical and chemical properties of the water entering the pallial cavity and that this might possibly aid in food selection. Bernard (1890) supported Spengel’s theory. Copeland (1918) working ontwo marine gastropods proved that the osphradium served as an organ that assisted the process of procuring food. More recently, Magruder (1935b), in Pleurocera, verified that it does not have any respiratory function. Tentacles. In previous reports, the tentacles have not been considered as sense organs. Since they obviously serve as organs of touch, it seems proper to include them here. The tentacles (Plate I and Text Fig. 5) are long and slender extensions from the dorso-lateral portions of the head. They have a yellow or light golden color with black pigmentation scattered to form a striped pattern. The tentacles of P. acuta are much longer and more tapering than those of С. livescens. A longitudinal section of the latter is shown in Plate VIL ЕЕ 5. Nervous System Rosewater (1961) published ob- servations on the nervous system of pleurocerid snails. He found that the central nervous system of 9 species of North American Pleuroceridae differed from each other mainly in the length of the cerebral commissure and of the length of the connective between the left pleural ganglion and the subintestinal ganglion. Since he used only 6 specimens of each species, and since in my opinion none of the specimens were properly relaxed and fixed, it is doubtful whether his data can be considered reliable for detail. Only one reference dealing in detail with the central nervous system of a pleurocerid snail was found in the literature: Magruder’s (1935b) report on Pleurocera canaliculatum undulatum. To facilitate a comparative approach, his terminology is used here for the 22 B. C. DAZO various ganglia10 and nerves, as well as his definition of commissures and connectives, so that the nerves con- necting like ganglia of opposite sides are called commissures, whereas con- nections between unlike ganglia of the same or opposite sides are referred to as connectives. Comparing tue central nervous system of P. acuta and G. livescens with that of P. canaliculatum undulatum (Say) and lo fluvialis (Say), a related pleurocerid whose anatomy will be described and published later, it was found that it is essentially the same and differs mainly in size. The general pattern appears, on the whole, similar to that of other Cerithiacea. These similarities are, for instance, evident from the work of Sunderbrink (1929) ор Melanopsis du- Jourei Férussac and Cerithium vulgatum Bruguiére, snails belonging to the related families Melanopsidae and Cerithiidae respectively. As an example of simi- larity, the subintestinal ganglion in C. vulgatum is also closely associated and connected to the left pleural ganglion, as it is in the melaniid genera Pachy- melania, Potadoma and Cleopatra (Binder, 1959). The position of that ganglion differs, however, in Melanopsis dufourei, where it is located between the right and left pleural ganglia and joined to them by long connectives. Bright’s (1958, 1960) illustration of the nervous system of Cerithidea califor- nica (Haldeman) show that the following features differentiate Cerithiidae from Pleuroceridae: 1) the cerebral commis- sure is lacking; 2)thereis no connection between the subintestinal ganglion and the right mantle nerve; and 3) the visceral ganglion does not form a Y- Shaped structure; instead, a widely split or broad U-shaped connection is formed between the right and the left 10He used the terminology applied to ganglia by Spengel (1881) which is generally ac- cepted. visceral connectives from which 4 smal- ler nerves branch off posteriorly. п: the present work only the main branches of the central nervous system of P. acuta and G. livescens, have been illustrated (Plate II, Figs. 1, 2 and 3). Not only were the smaller nerve rami- fications very difficult to follow but they also vary considerably as to size, number, and their relative position even among individuals of the same species. The central nervous system is com- posed of 4 principal pairs of ganglia, namely: the cerebral, the buccal, the pedal, and the pleural ganglia with their associated connectives. In addition, there are 3 minor and unpaired ganglia; the subintestinal, supraintestinal, and the visceral. The following account applies to both P. acuta and G. livescens. For all paired ganglia except the pleural, a description of only one side will be given since all of the nerves that originate from them are paired and identical. The pleural ganglia differ from one another in size, shape and arrangement of nerves and are discussed separately. Cerebral Ganglia and their Nerves. The most prominent pair of nerve centers in the anterodorsal part of these snails are the cerebral ganglia. They are located on each side of the esophagus and are more or lesstriangular although somewhat flat. Their posterior ends are directly dorsal to the extreme anterior ena of the pleural ganglia. They form a rooflike “canopy” over the esophageal region. A total of 9 pairs of nerves arise from the cerebral ganglia. The anterior end of each ganglion is pointed where it gives off 5 large nerves going to the anterior head region and the buccal mass. Each ganglion gives off 3 lateral nerves, one eachfromits antero- dorsal, anterolateral and posteroventral sides. From the mid-ventral surface of the cerebral ganglion also originates the nerve that forms the corresponding pedal ganglion. Toward their posterior end, the paired cerebral ganglia are connected to each PLEUROCERA AND GONIOBASIS 23 \ À Ey G F 2 ES Е Z Z Е N tentacle = labial nerves À Z tentacular nerve [1 = 4 À [a cerebral ganglion pleuropedal connective left pleural ganglion optic nerve E \ ; À Z N FA left pleural ganglion HO left mantle nerve 7 right pleural ganglion right mantle nerve mantle right pleural ganglion nght mantle nerve subintestinal ganglion. supraintestinal nerve genital nerve Subintestinal nerve mantle Ne supraintestinal ganglion A AWA Mn ks: I \ A > Nun El ; \ N left mantle nerve 0 A KO >. = 7 - - @ right visceral connective Е F . visceral ganglion visceral nerve tentacular nerve 3 mantle supraintestinal nerve Gy optic nerve G a E : 27 à otocyst right pleural ganglion =} у TR GEL FG I cerebral ganglion labial nerves left mantle nerve : <=: | subintestinal nerve =x subintestinal ganglion I, auricle 4 — 4 P” etterent ur ctenidialsinus ricle e vent efferent renal sinus Organs of the mantle region and other miscellaneous structures. 1. The mantle was excised and turned back toward the right to expose its inner side and the various organs it contains. Magnification approximately 35X. Gill leaflet with the blood vessel (right lower side) as it enters the gill. The otocyst and its relation to the pedal ganglion. 2 3 4. The kidney with its many folds. 5. The heart. rectum. Magruder (1935b) described these sinuses in P. canalculatum un- dulatum, and discusses the function as follows: ‘‘Blood from various parts of the body is finally collected into 2 main sinuses - the perivisceral and peri- intestinal sinuses, from which it returns to the heart by one of the 3 general routes: 1) directly to the afferent ctenidial sinus by way of the perirectal and mantle sinuses, and through the ctenidium to the efferent ctenidial sinus, thence to the auricle; 2) through the anterior renal chamber and to the afferent ctenidial sinus to follow the same route; 3) to the posterior renal organ by way of the afferent renal sinus, through the renal plexus to the efferent renal sinus into the auricle without aeration.” Excretory System. In P. acuta, G. livescens and also Io fluvialis, the kidney (Figure 8 (2)) is large, oblong and flat, and opaque white to light gray. It is made up ofa series of leaf-like fused lamellae and covered by a thin layer of connective tissue. It lies on the anterodorsal surface of the proximal portion of the intestine and is in close contact with the anterior part of the stomach. In females it is located immediately behind the posterior region of the genital fold and the seminal receptacle; in males it is found behind the prostate gland. PLEUROCERA AND GONIOBASIS 35 The gills or ctenidia are anterior to the kidney. The pericardial sac containing the heart lies posterior to it. Two openings lead from the kidney: one to the pericardial cavity, and the other to the pallial cavity. It is probable that the only means of eliminating metabolic wastes is through these body cavities. For the circulation of blood in the renal organ see the vascular system (p 32). Histologically (Plate VI, Fig. 1), each leaf appears spongy and vascularized due to the loose arrangement of the glandular cells. These are irregular in shape and may be differentiated from the cells of the gills (Plate VII, Fig. 6) by the absence of cilia. Further information was given by Magruder (1935) in his description of the kidney of P.canaliculatum undulatum which also applies to the species here studied. Respiratory System. The respiratory system consists of a set of gills or ctenidial branchiae (Fig. 8 (1 and 2)). These arise as folds from the mantle and appear to hang from the roof of the pallial cavity. They are arranged in one set or column in the manner of a comb (=pectinibranch). When the snail is held with a pair of forceps and immersed under water, so that the shell aperture faces the observer, these gills are easily seen at the back of the head somewhat on the left side of the anterior part of the inner side of the mantle. The middle gills are more or less triangular in shape, and fairly uniform in structure, although they vary in size. Those located near the anterior and posterior end of the gill column are much smaller and irregular in both size and shape. In Pleurocera acuta there are about 102 to 110 gills in a set and in Gonio- basis livescens 75-87. The middle gills measure 1.80 by 1.53 mm for P. acuta and 1.50 by 1.18 mm for G. livescens. Histological sections of the gills are Shown in Plate VI, Figs. 4 and 6. Reproductive System. The pleurocerids, like the proso- branchs in general, are dioecious. Ex- cept for one subfamily, the males lack external genitalia. For this reason difficulties were encountered in dis- tinguishing the males and females in the Pleurocerinae. Stimpson (1864) was the first to observe a deep pit or sinus in the neck, between the right tentacle and the foot, in the females of 2 species, Mudalia dissimilis and Melania (-Gon1o- basis) virginicall. F. C. Baker (1902, 1928a) did not succeed in differentiating the sexes of Pleurocera subulare @Pleurocera acuta) and Goniobasis livescens on this basis, since he stated that the only wayto determine the sex was to crush the animal and examine it for Ova or spermatozoa under a microscope. Later authors have consistently found this reproductive “ovipositor” pit and some have described a transitional, functional egg-laying groove leading to this pit from the mantle cavity, and the presence of a rudimentary papilla near the pit. Moore (1899) is of the opinion that the reproductive grooves and pouches of the “Melanians” are to be regarded as extremely primitive charac- ters and are to be looked upon as the last remains among existing Proso- branchia of the grooves andintroversible penes of the Opisthobranchia. To strengthen his point, Moore cited the case of the female Littorina and some other forms, such as Strombus, whose part of the accessory reproductive apparatus, the groove, still remains, albeit it appears to have no function. Having examined several thousand pleurocerid snails belonging to 6 genera and 19 species or forms, the writer has also found the sinus a reliable character for differentiating the sexes in this group. These pleurocerids are: Io fluvialis brevis, lo f. lyttonensis, Не regarded the 2 species as identical be- cause of the basic similarity in their anatomy. 36 B. C. DAZO Pleurocera acuta, P. canaliculatum, P. с. undulatum, P. curtum, P. unciale, P. unciale curtatum, P. subulaeforme, Goniobasis livescens, G. clavaeformis, С. arachnoidea, С. proxima, С laqueata, G. mutabilis, G. virginica, Anculosasub- globosa, Eurycaelon anthonyi, and Nito- cris (Anculosa) carinata. The groove was present in live material and in all relaxed females of P. acuta and G. livescens used for dissections. A papilla-like structure in the vicinity of the pit was observed only in a limited number of specimens. Serial sections of the gonads of these 2 species were prepared and examined. No evidence was found to indicate herma- phroditism. The presence of larval trematodes in the gonads was ascer- tained. Data on the reproductive system of Pleurocera and Goniobasis are available in the literature. Jewell (1931) studied serial sections of G. livescens correcta and made observations on reproduction, but did not attempt to describe the general morphology of the reproductive organs. Woodard (1934, 1935, 1940), however, in his work on G. laqueata gave an excellent description of the reproductive system of that animal and described its eggs and egg-laying habits. He also thoroughly discussed the struc- ture and function of typical and atypical Spermatozoa. Magruder (1935b) de- scribed the reproductive system of P. canaliculatum undulatum. In pleurocerids, the genital tract, in both sexes is composed ofa “closed” initial portion and an “open” or laminal terminal portion. Male Reproductive System Excepting for size, the system is identical in P. acuta and G. livescens. It consists, in the closed tract, of: the testis, sperm duct, prostate, cytophore and, in the open tract, lateral (left) lamina, medial (right) lamina, spermato- phore organ and the genital canal or 12Woodard’s (1934) terminology. groove (Text Fig. 9). The sexual products are the sperm and spermatophores (Plate IV). (1) The testis is one of the largest organs in these snails. It occupies most of the shell region above the body whorl and surrounds the digestive gland (liver) excepting for a narrow strip on each side of the genital duct. On the surface, the testis is lobate and com- posed of numerous branched, tubular follicles. The color is a light or pale yellow, which, during the breeding season becomes golden yellow due to the presence of pigmented granules in the ectodermal covering as described by Woodard (1935) for Goniobasis laqueata. Its tiny tubules anastomose to form common tubes, the vasa efferentia. (2) All of them empty into a common duct, the sperm duct. This duct runs along the columellar side of the coiled liver and testis, together with the visceral artery and a nerve from the visceral region, until it reaches the antero-ventral portion of the style- sac or the stomach. It then curves abruptly before it terminates at the pocket-like structure formed by the end portion of the open tract where the medial lamina folds over the lateral lamina. (3) After this end point of the closed genital system and just below the beginning of the open genital canalisa much folded, thin walled structure, which Woodard (1934) called cytophore in Goniobasis laqueata. (4) He also referred to the terminal portion and more dilated area of the sperm duct near the open genital tract, as the prostate. (5) Beyond the prostate, the genital groove extends forward as 2 broad laminae fused dorsally to each other and to the mantle. The ventral margins of the laminae are free, forming a slit- like channel between them, which commu- nicates freely with the mantle cavity. This channel is the only opening in the male tract and the sexual products are discharged freely into the general mantle PLEUROCERA AND GONIOBASIS 37 prostate spermatophore organ gills anus eo : osphradium = mantle ad digestive gland (liver) sperm duct py testis cytophore organ lateral lamina medial lamina rectum oviduct seminal receptacle nidamental gland ee y FIG. 9. The reproductive system of Pleurocera acuta. The head-trunk region was removed and the mantle was cut on the left side and turned back toward the right to expose its inner side. Approximately 20X. cavity. The epithelial lining of theinner wall of the posterior portions of the laminae has numerous folds creating pockets. According to Woodard (1935) the membranous spermatophores (see below) are formed in these pockets around the masses of spermatozoa passing through and he consequently designated this portion of the laminae as the spermatophore organ (Text Fig. 9). It is believed that, in the absence of copulatory organs for direct transfer of sperm, the spermatophore is a pro- tective measure for the preservation 38 B. C. DAZO and storage of sperm. (6) As inG. laqueata and P. canalicul- atum undulatum, the spermatozoa found in P. acuta and G. livescens are of two types (Plate IV, Figs. 1 and 2), namely, the typical “eupyrene” or “hair- shaped” forms and the much larger atypical “apyrene” or “worm-shaped” sperml3, both of which are formed by the primordial spermatogonia. Woodard (1935, 1940) gave anexcellent discussion on the spermic dimorphism in G. laqueata. In the forms he studied (1934), namely: Io, Anculosa, Gyrotoma, Pleurocera, Goniobasis and Lithasia, he stated that “there are no differences to be observed between the typical spermato- zoa, and the same may be said for the atypical.” He indicated that the normal eupyrene spermatozoa are enclosed in spermatophores while still in the male reproductive tract and that the atypical apyrene spermatozoa which make a de- layed appearance in the testis, are never included in these spermatophores (see under 7, below) and hence never reach the females, and suggested that these bodies perhaps did not have a necessary functional relationship to the ova or to the eupyrene spermatozoa. Regarding the chromosomes of G. laqueata, Wood- ard reported a haploid number of 18 in the first maturation division of a typical sperm and the absence of hetero- chromosomes. (7) A spermatophore of G. livescens is shown in Plate IV, Fig. 3. Itis a crescent-shaped hollow sac whose tips are spread out then folded back slightly toward the convex side. Itis 4.5mm long and 1.5 mm at its widest diameter. In the spermatophores the sperm cells do not follow a definite pattern of arrange- ment. Only typical (eupyrene) spermato- zoa were seen in them, as alsoindicated by Woodard (1934, 1935) for Goniobasis laqueata and by Jewell (1931) for G. livescens correcta, although she did not 13Terminology of Woodard (1935, 1940) and Magruder (1935b); however, also used. the term oligopyrene for atypical sperm. mention the presence of both kinds of spermatozoa. She observed that the sperm has a distinctive form, the cylin- drical head bearing a hook-shaped structure. Similarly, Magruder (1935b) reported that the typical sperm of Pleurocera canaliculatum undulatum posess a hook-shaped structure whichis as long as the head. The author did not observe any such structure in stained and fresh preparations of sperm from both P. acuta and G. livescens. Female Reproductive System In many respects, the general mor- phology of the female reproductive system is similar to that of the male (Text Fig. 9). The following organs compose the system: ovary and oviduct in the closed tract and lateral and medial laminae, seminal receptacle, and nidamental gland in the open tract. (1) The ovary, which is red to dark brown, occupies the same position as the testis in the male. (2) The oviduct bear the same relation to the ovary as the sperm duct does to the testis. It follows a similar course and, at the level of the stomach, turns and passes into the body wall. There is, however, no auxiliary structure corresponding to the cytophore in this part of the oviduct. Just before its end, it makes an abrupt U-turn. (3) It then is continued by 2 laminae forming the ‘‘open’’ tract, which corres- ponds to that in the male, and also communicates freely with the mantle cavity. The posterior portion of both the lateral (right) and medial (left) lamina are greatly folded. Seenfrom the mantle cavity these overlapping folds appear as a swollen sac. The inner walls of these folds are lined with epithelial cells into which the spermatozoa, that have entered the female tract, insert their heads and remain embedded for an indefinite time. This sac, therefore, corresponds to the seminal receptacle of other proso- branchs. It is probable that it acts as a reservoir for spermatozoa during the PLEUROCERA AND GONIOBASIS 39 digestive gland sperm duct testis seminal receptacle cytophore organ SE, I prostate nidamental gland spermatophore organ ur lateral lamina lateral lamina medial lamina medial lamina ne RER NO anus 27 anus ) osphradium osphradium elle \ o: gills = E mantle PLATE IV. Sperm of Goniobasis livescens. FIG. 1. Typical, eupyrene spermatozoon, similar to that of Goniobasis laqueata illustrated by Woodard (1935). FIG. 2. Upper portion of a mature apyrene (atypical) spermatozoon drawn from a fresh smear preparation. FIG. 3. Crescent-shaped spermatophore with its tapering ends. 40 B. C. DAZO entire breeding season. (4) In the female, the lateral lamina is thin and narrow but the mediallamina is swollen and glandular. This gland is whitish and probably corresponds to the nidamental gland of other prosobranch snails. It occupies the region between the rectum and the genital groove and extends from the mantle margin to the posterior surface of the seminal receptaele over which it is folded. The nidamental gland is divided into 2 parts, a shorter anterior or lower more gland- ular portion and an upper or posterior less glandular end. The upper portion is supposedly albumen-producing and the lower portion may function as a capsule gland. The entire gland is provided with numerous ducts which open into the open channel between the 2 laminae. This part of the open genital tract seems to be the counterpart of the pallial oviduct in other closely allied amnicolid or hydrobiid prosobranchs such as Pomati- opsis and Oncomelania. The fertilization of the egg has not been studied. It may take place in the posterior portion of the laminae so that, as the ova continue through the open female genital tract, the albumen and the egg capsule material are added after fertilization. According to my observations, the eggs leave the mantle cavity and reach the exterior along a channel formed by the egg-laying groove on the foot and by the mantle. The eggs remain in the pit for a brief period, after which they are pasted to the substrate and finally covered, either with mud or with sand grains, in the case of G. livescens or P. acuta respectively. Details on eggs and egg-output are given under life history (p 137-146). Woodard (1934, 1935) and Magruder (1935b) gave an excellent description of the histology of the reproductive systems of Goniobasis laqueata and Реитосета canaliculatum undulatum, which are corroborated by my ob- servations on P. acuta and G. live- scens. median longitudinal muscle columellar muscle FIG. 10. The muscular system of Goniobasis livescens (simplified). Only the main muscu- lature of the body is given; the columellar muscle has been somewhat exaggerated to clarify its location. Muscular System Only the 3 major muscle complexes are considered here: the columellar, which is the largest and most con- Spicuous, the pedal and the pharyngeo- buccal (Text Fig. 10). (1) The columellar muscle is a broad and rather flat muscle which attaches the animal to its heavy shell, and also serves to retract the operculum, head and foot. It is attached to the shell at the side or base of the columella at the third whorl, always allowing the animal free play in the penultimate and body whorls. Its ramifications insert at various points of the animal, from the operculum to the head and foot and the visceral regions. The median longitudinal muscle in this complex arises from the mid-dorsal part of the columellar muscle, at a point near the bucco-pharyngeal region. This broad and flat muscle extends forward, giving rise to 3 pairs of branches: a) the slender and flat buccal muscles which branch off from the sides of the median longitudinal muscle and are in- serted on the sides of the buccal mass; b) the muscles which branch off from the lateral median side of the buccal mass and insert into the dorso-lateral part of the head region near the point PLEUROCERA AND GONIOBASIS 41 where the tentacular nerve innervates the muscles of the tentacle. These muscles serve to retract the buccal mass or lingual organs and the proboscis; c) the third pair, which arises from the median longitudinal muscles represents the re- maining muscles in the proboscis. They are attached to the ventral wall of the proboscis just behind the mouth and below the buccopharynx and serve to retract the proboscis. After giving rise to a branch going to the operculum the columellar muscle sends off a branch to the foot. It also sends branches to the sides of the head which are almost inconspicuous and form part of the wall of the head and give rise in turn to smaller muscles that retract the tentacles. (2) The foot is made up of a network of transverse, oblique, circular, and longitudinal muscle fibers which are interlaced in all directions to form the floor of the foot musculature. (3) The muscular coat of the buccal mass together with the circular and longitudinal muscle fibers around the pharynx form another intricate muscular system. Connective tissue bands can be seen crossing below the muscles retracting the radula, the proboscis, and the buccal mass. At the same time the bands connect the lateral walls of the head region and serve to hold the an- terior part of the esophagus in place. ECOLOGICAL STUDIES Ecological and limnological data were obtained during the monthly visits to the 4 permanent collecting stations and at various other collecting sites mainly in Michigan, positive for P. acuta and G. livescens. Three visits were made to the Tennessee River Valley (Cumberland Region) where large scale water impoundment has already caused great ecological changes and destroyed many endemic species of mollusks, Thisarea is probably still the richest in pleuro- cerids in the North American continent, More than 300 sites were surveyed out of which about 200 were positive for pleurocerid snails (see p 35 and Table 6). Some of these sites willbe described in detail. A list of the vegetation found on the shores of, and in the collection sites, correlating the common and scientific names of the plants mentioned in the descriptions, will be found in Table 1 (p 45). From my own observations and from the literature (Woodard (1934), Dawley (1917), and Goodrich (1945), it appears that all pleurocerids require clean water. Р. асща and other species belonging to the genus Pleurocera prefer to inhabit relatively larger bodies of water as do most pleurocerids, except Goniobasis. Pleurocerids are usually foundin shallow water, only afewinches deep, though they may also be found at depths up to 3 feet. P. acuta snails occupy quiet and sheltered areas. Generally, they can be regarded as bottom dwellers since they like to burrow under the sand most of the time. They may also burrow under layers of decaying leaves and other organic material. С. livescens on the other hand live in extremely varied habitats, from natural springs to swift flowing rivers and open lakes.14 They are often found clinging or crawling on the sides of rocks and stones although in lake situations they, like P. acuta, also burrow under the sand bottom. The stones frequented by Goniobasis, are often densely covered with algae and diatoms. These habitat selections seemed to in- dicate that P. acuta is more ofa detritus feeder. A discussion of food andfeeding habits is given in a later section (p 64). Description of Habitats The Four Permanent Collecting Sta- tions in Michigan. G.livescens was 144 comprehensive discussion on the habitats of С. livescens was given by Goodrich (1945), who also compiled information from other authors. 42 B. C. DAZO present in all of these stations, but P. acuta only in one, the Portage Creek station. (1) The Huron River Station at Dexter This station located at the northeastern part of the village of Dexter, Washtenaw County, represents the terminal quarter mile of Mill Creek, a tributary to the Huron River; the stream is approxi- mately 2 miles long and about 25 feet wide. .In this region, the stream is well shaded by trees, such as red maple (compare with Table 1), American white birch, scarlet oak and rock elm. Some shrubs, such as gooseberries, winged sumacs and red-osier dogwoods are found on the northern bank of the stream near the collecting site. The stream bottom contains gravel, stones, oc- casional sandy-muddy areas where patches of emergent aquatic plants, mainly water cress, arrow-heads and the submerged tape grass are present. The rocks are usually covered with a thick algal growth largely composed of red algae, during the summer and fall. The water level was observed to fluctuate a great deal especially in the course of seasonal changes. In the spring, when the snow and ice are melting and when the water level reached its peak it was almost impossible to collect snails, for the current was swift and very strong. Conditions re- mained turbid and muddy throughout spring and the summer and fall were best for collecting. During the winter, the stream froze over completely; the animals were then seen lodged under- neath rocks and stones which tended to produce air spaces between themandthe ice cover. Goniobasis livescens was the most plentiful mollusk at this station, though it had a rather spotty distribution. As- sociated mollusks were the limpet Laevapex fuscus, the snails Helisoma anceps, H.trivolvis, Physa gyrina. P. integra, and the mussel Micromya iris. (2) The Portage Creek Station. This collecting site is located at the boundary line of Washtenaw and Livingston Counties, on Toma Road. It is approxi- mately 2 miles north of the University Radar Observation station and about 3 miles directly south of Pinckney. It is a relatively small stream, about 4 miles long, originating from Hi-land Lake in Dexter Township which empties into Little Portage Lake. It is about 25 to 30 feet wide and, during the summer and fall months, it has an average depth of 2 to 3 feet. Although the area freezes over partially during the winter there is a continual current at the bottom through- out the year. In the spring the area is always flooded and muddy, as is that near other streams in this vicinity. This creek is also well shaded by trees and shrubs. Some ofthe additional plants noted were: white oak, pin oak, blackjack oak, mockernut hickory, red pine, Swamp cottonwood, summer grapes, poison sumacs and an abundant growth of poison ivy. The bottom of this stream has gravel, rocks and _ stones with many sandy patches, especially near the sides of the stream where the banks cut the slopes rather abruptly. The common emergent aquatic plants growing there were the sedges, cut-grasses, arrow-heads and water cress; among the submerged vegetation, tape grass, water weeds and pondweeds were noted. This station was the only one of the 4 collecting sites where both Pleurocera acuta and Goniobasis livescens occurred together. However, closer examination showed that these 2 pleurocerids tended to occupy separate and distinct nichesin this stream, P. acuta being located in the sandy patches and those with decaying organic material and С. livescens among the rocks that were covered with algae. At this station the most abundant species of mollusks were P. acuta and G. livescens; freshwater mussels were equally plentiful, especially Micromya ivis, Dysnomia triquetra, Elliptio dilatatus, Strophitus rigosus, Anodonta grandis, and Lampsilis siliquoidea. Other snails present were Campeloma decisum, Аттсоа limosa, Physa PLEUROCERA AND GONIOBASIS 43 integra and P. gyrina. (3) The Kalamazoo River Station. This site is located near Reiger Park in the city of Albion, Calhoun County. The river here is about 20 to 25 feet wide with an average depth of 2 feet during the summer and fall. About 500 yards above the collecting site, the river has been diverted into 3 channels. Dams were built in 2 of these branches to produce electrical power while the third serves as a diversion channel or an out- let for excess water. The Kalamazoo River is one of the longer streams in southwestern Michigan extending across half the lower Pen- insula. It has 2 separate headwater branches, joining just above the city limits of Albion. The main river flows through the city and continues to Lake Michigan as a winding stream. At the collecting site many trees line the banks of the river; among them were: a few scarlet oak, white oak, swamp cottonwood, American white birch and many red maples. Patches of cat- tails and bullrushes grow near the lake formed by the overflow from the dams. _ The bottom of this river is very rocky but has occasional sandy areas. Sub- merged aquatic plants such as tape grasses, water weeds, pondweeds, and stoneworts grow luxuriously in the col- lecting area. The water flows swiftly throughout the year and during the winter months, this stream freezes only along the sides. Goniobasis livescens occurred on rocks, among the water plants andonthe Sides of the concrete wall of the dam site. Associated mollusks were: the snails Physa gyrina, Helisoma trivolvis, Campeloma decisum; the fresh-water limpet Laevapex fuscus; andthe mussels Lampsilis siliquoidea, Micromya iris and Elliptio dilatatus. Because of the tremendous amount of pollution from the city, no mollusks were found down- stream. (4) The Zuckey Lake Inlet Station. This station is located at Lakeland, Livingston County, Michigan. The stream, approximately a quarter mile long and about 4-5 feet wide connects Island Lake to Zuckey Lake. In its upper two-thirds this stream has a higher water level and is surrounded by a marshy area with an abundant growth of cattails and arrowhead; the bottom is muddy and devoid of submerged vegetation. Along the bank are patches of red-osier dogwoods but no trees. Mollusks were found only in the lower third of the stream. G. livescens were extremely abundant and quite evenly distributed over the col- lecting area. The shells of the adult Snails were generally smaller than those from the 3 other stations and most of them retained their carinae in the nuclear whorls unlike the other specimens, which were larger and had smooth whorls. It was noticeable also that G. livescens at this station were very black and were often covered with marl. They were found on the rocky bottom which was thickly covered with aquatic plants such as stoneworts, muskgrasses, arrow- heads, pondweeds and yellow and white water lilies. The larger stones and rocks were often covered with patches of fila- mentous green and with red algae. At the collecting site the water had a depth of about 2 feet or more during spring, but only 4 to 6 inches during summer and fall. Other mollusks found at this site were the snails: Amnicola limosa, Physa gyrina, and the mussels Lambsilis siliquoidea, Micromya iris, and Strophitus rugosus. Some other habitats in Michigan. Pleurocera acuta (1) In western Michigan, an excellent population of Pleurocera acutawas found inhabiting the outlet of Big Pigeon River at Lake Shore Drive, Port Sheldon, Ottawa County. This station was wide and lake-like and the current was hardly noticeable. The depth varied from 1 to several feet and the bottom was sandy- muddy. It supported a dense growth of submerged aquatic plants, such as 44 B. C. DAZO various species ofpondweeds, stonewort, water weeds, hornwort and water milfoil. At the edge of the river there was a marshy area with cattails, arrow heads and water lilies. P. acuta was very abundant in the river outlet where they were collected among the water plants and on the sandy bottom. The shells of these specimens of P. acuta are the largest in my collection. (2) Two living P. acuta were collected in the Huron River at the Zeeb Road bridge in Scio Township, Washtenaw County in southeastern Michigan. The specimens were found crawling on the sandy bottom in the vicinity ofpatches of hornwort. Attempts to find these snails in other parts ofthe river were unsucces- ful, although previous collectors, such as Walker and Beecher (1876) and Good- rich (1943), reported colonies inhabiting the quiet waters of this stream. (3) The colony of P. acuta nearest to the University Museum laboratory was the one at Honey Creek, Scio Township, Washtenaw County. Although both P. acuta and G. livescens live in this small stream, they are rather sparse there. The stream, which originates as the effluent from a group of lakes called the Sister Lakes, is about 2 miles long and located within the Ann Arbor city area. During the summer, the water is only a few inches deep, exposing much of the rocks, gravel and sandy patches that form the stream bottom. Blue-green and filamentous green algae are abun- dant. This station does not appear to be a normal habitat for P. acuta which usu- ally occurs in relatively large streams. Goniobasis livescens In 3 streams in southeastern Michigan (1, 2, 3 below), in which P. acuta was previously reported, they can no longer be found. These streams were, however, positive for G. livescens. These and other habitats were: (1) The Huron River near the outlet from Portage Lake in Washtenaw County. (2) The Kalamazoo River in Calhoun County. (3) The Raisin River in Monroe County. (4) Two collections of G. livescens were made, in depths up to 5 feet in Douglas Lake, Cheboygan County, north- ern Michigan, where, according to H.B. Baker (1912, 1942) these snails were introduced and where they have been a thriving colony up to the present. One lot was taken at Grapevine Point, at the sheltered western shore of the lower end of the lake, on sandy bottom where patches of submerged aquatic plants, consisting mostly of hornwort and water milfoil grow luxuriously. The other collection was made at the Sedge Point area, where the bottom was covered with mud and marl and had a very thick growth of stoneworts and muskgrass. The shells here were covered with marl, thick and massive, in contrast to river specimens, whose shells are much smaller, thin and less bulbous. (5) A collection of G. livescens was also made from the north end of the eastern shore of Burt Lake, Cheboygan County, northern Michigan. This area is very much exposed to wind and wave action. The snails were found crawling on, or buried in, the sandy bottom and sometimes they were seen hiding under- neath decaying driftwood and other vege- tative matter in the shallow portion of the lake. (6) Another batch of G. livescens was taken from the north part of the western shore of Silver Beach, Mullet Lake, Cheboygan County, where the habitat is very Similar to the one at Burt Lake, i.e., open to wind and wave action and devoid of any submerged aquatic plants. Collecting site in Ohio. Goniobasis livescens was collected in Lake Erie, at the Put-in-Bay Biological Station, in front of the Fishery Hatchery building. The snails were clinging to the rocks and gravel near the sheltered shore and in water about 2 to 3 feet deep. The shells were a pale yellow-brown, thick, massive and covered with marl and red algae. PLEUROCERA AND GONIOBASIS 45 TABLE 1. Vegetation near and in pleurocerid habitats in Michigan Common name Latin name Shade plants common on banks: Trees american white birch Betula papyrifera blackjack oak Quercus marilandia mockernut hickory Carya tomentosa pin oak Quercus palustris red maple Acer rubrum red pine Pinus resinosa rock elm Ulmus thomasi scarlet oak Quercus coccinea swamp cottonwood Populus heterophylla white oak Quercus alba Shrubs gooseberry Ribes missouriense poison sumac Rhus vernix red-osier dogwood Cornus stolonifera winged sumac Rhus copallina Other poison ivy Rhus radicans summer grape Vites aestivalis Aquatic plants: e emergent arrow-head Sagittaria latifolia bullrush Scirpus americanus cattail Typha latifolia cut-grass Leersia sp. sedge Carex sp. watercress Nasturtium officinale water lily, yellow Nuphar variegatum water lily, white Nymphaea odorata submerged Algae: - blue green Anabaena sp. - filamentous green Spirogyra sp. - redl5 Batrachospermum vagum muskgrass Nitella flexilis stonewort Chara vulgaris hornwort Ceratophyllum demersum pondweed Potamogeton natans P. praelongus P. richardsonii tape-grass Vallisneria americana water milfoil Myriophyllum tenellum water weed Elodea canadensis 15 These were plentiful at many sites in Michigan and also in the Cumberland region (Virginia and Tenessee) of the southeastern United States. 46 B. C. DAZO Vegetation. See Table 1, page 45. Limnological Data The limnological procedures followed have already been indicated under ma- terials and techniques. Results, in- cluding data on depth of water and current, water analysis, temperatures, and average snail densities from each of the 4 permanent collecting stations are given in tabular form in Tables 2, 3, 4 and 5. Corresponding data, gathered from other positive sites are shown in Table 6 and for 2 negative sites in Table 7. RP Water Levels and Velocities. From the tabulated data it is evident that the water levels at the regular collecting stations, excepting the Kalamazoo River whose flow is controlled by dams, reached a peak during the late winter and spring months (14-38 inches) while the lowest levels occured in the fall (3-9 inches). The melting ice and snow usually causes flooding at the stations, especially early in spring and also results in greater flow and higher velocity readings. The velocities measured ranged from 0.5-2 feet per second. . Water Chemistry. (1) The hydrogen- ion concentration of the water in posi- tive areas ranged from 7.5 to 8.6 (that of the 4 local stations from 7.8 - 8.5). Shoup and Peyton (1940) and Shoup (1943) reported that Goniobasis emeryensis was found in a stream with a pH of 6.2, which is quite unusual, because pleuro- cerids are seldom found when the pH falls below 7.0. Goodrich (1940a), quoting Shoup et al. (1941), reported that a branch of the Obey River, whose pH was above 7.0 in 1939 was “extensively colonized by these mollusks; [whereas] in another fork of the river where the average pH was 6.1 and the lowest was only 2.6, the area was devoid of any pleurocerids.’’ In the laboratory, P. acuta and G. livescens were kept in containers with a hydrogen-ion con- centration range from 7.2 (the pH of the distilled water used) to 8.8, but in tanks with water of a pH lower than 7.8 they survived only about 7 weeks and in containers with a pH higher than 8.5 only 6 weeks. The ideal pH range for these snails seems to fall between 8.0 and 8.4, at which range all cultures were ultimately kept in the laboratory. A low pH, or acidity, is frequently blamed for shell corrosion in mollusks (see influence of environmental factors, р 51. (2) Carbon dioxide is readily soluble in water to form carbonic acid. How- ever, some of it is normally carried in streams as free carbon dioxide. The metabolic processes of plants and ani- mals involves the uptake of oxygen and the production of an appreciable amount of carbon dioxide. Oxidation brought about by certain bacteria (Ruttner, 1953) in the bottom mud or substrate also accounts for variable amounts of carbon dioxide. Under ordinary conditions, water flow and turbulence at rapids and riffles are sufficient for eliminating excess carbon dioxide (Shoup, 1950). However, occasionally the oxygen supply diminishes and the carbon dioxide con- tent of the water may rise to a point detrimental to many fishes and other biological forms. The behavior of carbon dioxide is quite different from that of oxygen and its ecology is not yet well known. It is, therefore, difficult to make general statements as to its role as a limiting factor (Odum, 1959). Shoup (1950) shared this opinion and mentioned that there appeared to be but little accurate information on the true and exact toxic action of carbon dioxide upon aquatic organisms. The amounts of carbon dioxide recorded in this study were rather low, i.e. between O and 15 ppm (See Tables 2-6). Whether these small quantities are a good indication for the presence of pleurocerids in all the places visited is unknown. PLEUROCERA AND GONIOBASIS 47 (3) Total alkalinity was determined by using methyl orange as an indicator and was high (about 110-230 ppm). Evi- dently pleurocerids, especially P. acuta and G. livescens tolerate (or require) high alkalinity. These data are similar to those reported by van der Schalie (1938), who obtained an alkalinity range between 133 and 233 ppm in the Huron River, in Fleming Creek, and in Little Portage River, a tributary of the Huron River, streams that have been and still are positive for G. livescens. Data obtained by the Institute of Fisheries Research (Goodrich 1945) also showed this same high alkalinity for the following places, all positive for pleurocerids: Crystal Lake, Benzie County, 111-120 ppm; Muskegon Lake, Muskegon County, 132 ppm; Van Ettan Lake, Iosco County, 136-148 ppm; Big Platte Lake, Benzie County, 141-156 ppm; Round Lake, Benzie County, 139-150 ppm; and Mus- kegon River, Clare County, 87-89 ppm. Shoup (1943), studying the distribution of fresh-water gastropods in relation to total alkalinity, reported that the range of alkalinity for 25 species of pleuro- cerids was between 5 and 220 ppm. His data reveal that these snails tolerate a wide range of total alkalinity. Shoup, however, also found that the more alkaline streams tend to be more pro- ductive in gastropods, while those with only 2-6 ppm bicarbonate were very unproductive since they contained little or no calcium for shell building. (4) Pleurocerids are known to require a fairly good supply of oxygen. This oxygen need is borne out by the high amount of dissolved oxygen recorded in the course of this study. The lowest reading was 17.63 ppm, taken in Portage Creek; the highest was 53.86 ppm, at the Zuckey Lake Inlet. Prescott (1939) and Goodrich (1945) observed that a massive destruction of pleurocerids was brought about by the depletion of oxygen in lakes by a pro- longed winter ice cover. For fresh-water fishes, the minimum levels of dissolved oxygen were given as 3-4 ppm by Needham (1938) and as 5 ppm by Ellis (1937). As regards pleurocerids, the lower limits of tolerance variously quoted in the liter- ature are 6 ppm (Shoup and Peyton, 1940), 4.3 ppm for P. acuta (Wiebe, 1928) and 7.8 ppm for pleurocerid life in general (Jewell, 1920). But, according to my observations, flourishing colonies of these sensitive snails seem to be associated with 20 ppm of oxygen at least. Beck (1954) considered Gonio- basis to be among the more sensitive forms in that they tolerate no appreciable amount of pollution. Polluted waters seldom have sufficient oxygen content and are usually barren of most life forms. Ortmann (1909), Adams (1915), van der Schalie (1945), and Goodrich (1945) attributed the disappearance of pleuro- cerids and many other aquatic mollusks to a wide variety of man-made sources of pollution brought about by “progress” and by modern industrialization. Temperature tolerances. In this study G. livescens was found to tolerate temperature extremes varying from freezing up to 80° F. The maximum temperature measured in the only P. acuta habitat under regular observation (Portage Creek Station) was 76° F. At the Huron River Station G. livescens was found to survive under the ice with tightly closed apertures, hidden under- neath stones or under layers of decaying organic matter in the manner already described by Goodrich (1945) in un- frozen streams (See Seasonal activities, р 63). During the hot summer months when the water is only a few inches deep they did not seem disturbed by the direct rays of the sun. Regarding heat tolerance, a laboratory experiment was conducted by Nash (1954) to deter- mine the temperature and exposure time necessary to cause death by heat in G. livescens. She established that the critical temperature that wouldkillafter one hour's exposure was 36° С (96.89Е); that, if the temperature was below 369C B. C. 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AYIUTTEATV SUBIO TUI (vdd) (Hd) quoquo эртхота uoryeayus u93AxO 0928) -DU0J UOT POAIOSSIQ 9914 -u9301pAH (u "bs/ ON) (dd) suadsaay ‘2 jo Ayisuoc 988194 uoryeI4s IOATY UOINH ‘SOTJIsusp [Teus PUB дер Teor3ojouwrT (*2э5/ *33) 4719019 A yusamy aoyeMm (-098/ *33) AYLOOTO A qua ano a9yeM (sayour) 1918 M jo yideg O3B19AY "€ HIAV.L (seyout) aayeM jo Ч34эа 9IBIDAY °c WIdVL 15 *00q 63 *AON 95 PO 65 "des 08 "any GT Ane 55 sunf 85 'ady 096T € ‘AON TZ ‘100 6S6T JofeM му jo oyeq aamyeaoduaL 8% “AON ZI ‘390 ОТ “idos ст any Tt Amp GT sunp 83 “ady 096T L *AON 6561 aayeM му jo oyeq amyeaadwuaL 49 PLEUROCERA AND GONIOBASIS (u *bs/ *ON) sua9saaı] °9 jo Ayısusq 9ÍBIDAY LEG SET LST 9yT 9ST З7Т €0T (ut *bs/ *ON) sua9saay °=) jo Aysusq эЗвлэлу (soyour) aoyeMm Jo М jo jo wdoq aanyeaodwaL 93819AV (dd) (Hd) (*2э5/ *33) yuaguo y эртхота uolye1yu9 AYLOOTO A uasAxO U0QAB O -OUu09 UOT queraing p9A]JOSSIA ээля -u930A1pAH aoayeM (vdd) (udd* AYIUTTEAT SUBIO TÁYI9N (014835 JOTUI 9MBT AoyonzZ ‘sorjIsuop [BUS pue eyep JeoTsojouur] “Ss ATAVL (undd) (Hd) yueyuo y эртхота uoryeayua u984X0O uoqIe O -Ou09 UOT P9AIOSSIQ 9911 -ues0.1pAH (sayour) aoyeM jo jo ujdoq sanygeasadwuaL эЗвлэлу (:098/ *y) JON AI AYOOTO A yusaand reyeM (uadd) AyureyIv esueio IA (vdd) uopeIg делу оотеатетем ‘SorjFsuop [reus pue вер [eodojouur] *p ATAVL 08 ‘des Te 'anv La Amp 87 SUNLf + Av 0961 LT ‘320 < “idos 6961 oyeq B. 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Limnological data from two sites negative for pleurocerids at Oakridge, Теппеззее19 Average Depth of Water (inches) Temperature Locality East Fork Branch Poplar Creek Creek #64 Hydrogen- ion Conc- entration (pH) Free Dissolved Methyl Carbon Oxygen Orange Dioxide Content Alkalinity (ppm) (ppm) (ppm) 147.0 19The above data appear to lie within the limits of toleranceand do not explain the absence of pleurocerids. these snails could tolerate longer ex- posures and if it was above 360 С, they tolerated only short exposure times. Snail densities. The procedure fol- lowed in determining snail densities at the permanent collecting stations has been described under sampling methods (p 11-12). The average densities, for each visit, are given in Tables 2, 3, 4 and 5. For localities other than the regular stations (Table 6), the average snail density refers to all of the pleuro- cerid snails inhabiting the area and the number of snails is only an approxi- mation. Among the 4 permanent stations, the Zuckey Lake Inlet station was the richest in G. livescens, with a maximum of 892 snails per square meter area in Sep- tember 1960 and an average of 531. The Portage Creek station had the lowest density, with a corresponding average of only about 38 snails while at the same station P. acuta, was even less numerous, with an average of 24. The limited data available do not allow interpretation in terms of population dynamics. However, the highest records for snail densities in all 4 permanent stations were obtained during summer and fall. Influence of Environmental Factors on Shell. Among the Pleuroceridae, as in many other molluscan groups, both intra- and interspecific variation is common, and in consequence, the taxonomy ofthis group also remains in a very confused state. The extent of shell variation of the species called Goniobasis livescens since Goodrich’s (1945) comprehensive study, is well illustrated by the fact that various authors in the past have believed it to belong to several different species; Walker (1893), originally used 8 names. However, Goodrich (1945) surmised that there were certain basic and constant characters in the internal anatomy of G. livescens to indicate that all of the forms in Michigan represent but one polymorphic species. My observations, based on specimens collected from vari- ous localities in Michigan clearly support this view (Fig. 11 and Table 13). There is evidence that shell, form in mollusks may be influenced by environ- mental factors, such as wave action, current, substratum, etc. For the Pleuroceridae, one of the earliest ob- servations was made by Bartsch (1906) on variations in Goniobasis virginica of the Potomac River, but he did not correlate them with environmental con- ditions. Adams (1900, 1915) intensively studied the pleurocerid genus Jo in Tennessee and clearly showed the occurrence of geographical variation, which corresponds to a clinal variation in the course of a river system. He attributed the variation, in part, to 52 B. C. DAZO 9 10 FIG 11. A. Goniobasis livescens ea 13 14 Shell variation in Goniobasis livescens and Pleurocera acuta fromvarious localities. 1. 1-year old, laboratory bred. Note single carina on whorls. 2. 2-year old, laboratory bred. Note single carina on whorls. 3. Zuckey Lake Inlet Station, Livingston Co. , Michigan. 4. Portage Creek Station, Livingston-Washtenaw Co. Line, Michigan. 5. Kalamazoo River Station, Calhoun Co. , Michigan 6. Huron River Station, Washtenaw Co. , Michigan. 7. Shore of Lake Erie (U. S. Fishery Hatchery Station), Put-in-Bay, Ohio. 8. Grapevine Point, Douglas Lake, Cheboygan Co. , Michigan. B. Pleurocera acuta 9. 1-year old, laboratory bred. Note double carinae in whorls. 10. 2-year old, laboratory bred. Note double carinae in last whorls. 11. Portage Creek Station, Livingston-Washtenaw Co. Line, Michigan. 12. Huron River near Zeeb Road bridge, Scio Township, Washtenaw Co. , Michigan. 13. Honey Creek, Scio Township, Washtenaw Co. , Michigan. 14. Big Pigeon River at Lake Shore Drive, Port Sheldon, Ottawa Co. , Michigan. chemical differences, stating “That there are chemical differences in the differ- ent parts of the river, and further that these influences affect these snails ., that the shells do not abound in waters other than those draining lime- bearing rocks, clearly shows that lime is a limiting factor in their range.” He realized, however, that chemical fac- tors do not suffice to explain variation: “From the standpoint of chemical com- position of the water the presence of mixed communities of shells as near Rogersville, with great extremes from smooth to spinose shell on the same shoal, is particularly confusing, because we cannot believe that in such a situ- ation the agitated waters can show a corresponding chemical diversifica- tion.” The occurrence and variable extent of erosion in Goniobasis was noted by PLEUROCERA AND GONIOBASIS 53 Clench (1926). Since it occurred in locations where the mechanical action of waves or current were not the caus- ative factors, he attributed it to chem- ical action. Reports on the corrosion of snail shells are common; it is usually attributed to the action of acid water or sometimes also to abrasion by other snails in quest of lime. Goodrich (1940a) attributed irregularities in the suture and corrosion of the shell, such that all of the epidermis was removed except on the body whorl or part of it, to the direct effect of low pH. Frómming (1956), however, points out that such corrosions may be present in lime-bearing waters and absent in waters rich in carbon dioxide and humic acids, that frequently not all specimens of a colony are corroded and that both corroded and uncorroded colonies may occur in one and the same lake. He supports the idea that the periostracum of the snails must first be damaged by certain algae, before corrosion can take place. The writer has observed pleurocerid colonies in a stream at Oak Ridge, Tennessee, containing pleurocerids only, where every single snail, young or adult, showed advanced corrosion. Baily, Pearl and Winsor (1932, 1933a, 1933b) studied variations in Goniobasis virginica and Anculosa carinata under natural conditions. They concluded that the variation in the size of the shell was influenced by chlorine, food supply, silt, and other environmental factors. Wiebe (1926) studied variations of G. livescens in several stations in Lake Erie. He showed that the average shell obesity, i.e., the ratio of shell diame- ter to total length, was directly pro- portional to the degree of exposure to wave action. The snails subjected to almost continuous wave action had more bulbous or obese shells, while those that inhabit more sheltered areas pos- sessed long and slender shells. Wiebe thought that snails exposed to wave ac- tion probably develop so slowly that the shell may never develop its full number of whorls or that the direction of growth may be altered altogether; consequently, such shells become short and obese rather than long and slender. A similar increased obesity with wave action is reported by Boettger (1944) for Lymnaea spp. An interesting laboratory experiment by Plaget (1929) has a bearing on shell form in relation to exposure. He had found that in exposed situations in lakes, the shells of Lymnaea siagnalis had relatively short spires and long aper- tures. When these snails were raised in laboratory tanks, the offspring pro- duced longer spires than their progeni- tors. When these long spired forms were raised in a mechanically agitated aquarium, the young produced even shorter spires and longer aperturesthan their wild grandparents. Cheatum and Mouzon (1934) used bio- metry in their study of Goniobasis comalensis Pilsbry. They found that, on the average, pond dwellers had greater length and diameter than the river forms. They also showed that the mean ratio of diameter to length of the shells among river forms was greater than that for pond specimens. Goodrich (1945) re- ported that loose coiling was more characteristic of Goniobasis in sheltered situations; tight coiling was more pre- valent among snails in western Lake Erie in the more open habitats. F. C. Baker (1928b), in his Wis- consin report, recognized 4 forms of G. livescens, according to the habitat occupied by the so-called species, as follows: (1) G. livescens; witha smooth, acute shell characterized by narrow whorls, inhabits bays andrivers entering the Great Lakes; (2) С.1. michigan- ensis, with a bulbous body whorl, a wider spire, and a thick shell and lip, lives on exposed lake shores; (3) G. l. correcta, a small river form with a less elongated spire,6-8 whorls, a narrower, more elongated aperture, and a rounded bulbous body whorl, is found in quiet rivers and their pond-like ex- tensions in Wisconsin; and (4) G. l. B. C. DAZO 54 PLATE V PLEUROCERA AND GONIOBASIS 55 barronensis, characterized by its elon- gated shell with very flat-sided whorls and raised spiral ridges on the body whorl, is found in small, swift flowing rivers. LIFE HISTORY As already mentioned, only few ci- tations dealing with the life history of pleurocerid snails are found in the literature. Mating habits It is shown below (see p 56-60), (Egg laying season and potential) that in Michigan P. acuta and G. livescens begin to oviposit in April as soon as they become active in spring, with a peak of egg laying activities in April and May, and that, having apparently exhausted their egg laying potential, P. acuta will not oviposit after June nor G. livescens after the middle of August. Both species, collected in the field late in the fall and acclimatized in the laboratory, laid eggs on the sides of the containers a few days after they were transferred to thelaboratory. This sequence of events indicates that mating must have taken place sometime earlier in the fall. It is believed that mating is most common in the fall, when these snails are very active in their natural habi- tats though it is possible that copu- lation may also take place during spring. In the laboratory it was very diffi- cult to observe the mating habits, be- cause these snails are without external genitalia. However, they were observed to assume positions suggesting that they copulate like other prosobranchs. When associated individuals were thus sus- pected of copulating they were immedi- ately isolated in separate containers. The presence of spermatophores in the water was then taken to indicate that the couple actually did so, and their absence, that the snails had been crawling inadvertantly over each other. That mating actually occurred in the fall is also borne out by cytological evi- dence (p 64). Jewell (1931) experienced the same difficulties in her studies of! Ga lo correcta. It appears that the female genital sinus, in addition to its function of assisting oviposition by contraction, also functions as a bursa during copulation. A simi- lar opinion was also expressed by Woodard (1934), who stated: “Since Spermatozoa and spermatophore rem- nants are frequently found in the sinus, and since no spermatophores are ever found intact between the laminae in females, and hence, must never be in- troduced there, it must be inferred that the spermatophores are _ shed by the males and collected into the sinus by females.” It would seem that the sperma- tophores break down as soon as they reach the genital sinus. The released Spermatozoa then find their way to the seminal receptacle by way of the gen- ital groove and laminae. Woodard (1934) also suggested that possibly the migra- tion of sperm takes place only when the females are retracted in their shells so that the genital pit, with the shell, PLATE V. FIGS. 1& 2. The egg masses of Pleurocera acuta FIG. 1. Detached egg masses of various shapes; some from the lower side (not coated with sand). 13X. FIG. 2. Recently laid egg clutch with embryos in the second cellular division (trans- mitted light). 30X. FIGS. 3&4. The eggs of Goniobasis livescens FIG. 3. The upper egg has the characteristic coating of soil; the lower one was turned over to show the egg itself. 25X. FIG. 4. Newly laid egg with its covering of soil. 60X. 56 B. C. DAZO forms a duct to insure a safer transit for the immigrating sperm. The Egg and Egg-Laying Activities - Eggs and Egg Clutches, The average diameter of the ovum of P..acuta (from over 500 measurements) is about 300u and, with its membrane, about 350 u. The eggs are encased in clear spherical compartments, whichare surrounded by a transparent, gelatinous matrix. In color the eggs vary from gray tobluish- green; sometimes they appear light yel- low, orange or pink. Within the egg mass or clutch the eggs do not seem to be arranged in any definite pattern. A general description of the eggs of this species as well as of P. lewisii is given by Van Cleave (1932). The eggs are deposited in masses which vary in size (on the average 1.5-2.0 mm) and shape (Plate V, Figs. 1 and 2) and may contain from 1-19 eggs. In side view, each egg mass has a plano-convex shape, the flat side adhering to the solid substratum to which the snail attaches its eggs; the convex upper side is usually coated with minute sand grains which the parent snails place there during the process of egg laying. Van Cleave (1932) describes the clumped eggs with their coating as having the appearance of insect cases. The egg masses of P. acuta are deposited on a wide variety of objects, such as stones, leaves, and discarded empty beer cans and bottles. It is not uncommon to find eggs deposited on the shells of other live specimens. Jewell (1931) gave a good descrip- tion of the egg of Goniobasis livescens correcta (from Illinois): “Eggs always appeared singly or in lines of two or three with no covering except the simple Shell membrane which remained until the time of hatching. Little variation was found in the size of the newly laid eggs. The size most frequently found was 306 „ as the diameter of the egg itself within a membrane of 382 u to 425 u in diameter.” The details of this description also apply to G. live- scens in Michigan, except for minor dif- ferences in size. The eggs of the local G. livescens were smaller, measuring about 280 „ in diameter; with the egg membrane, the average diameter was 330 u (from over 300 measurements) (Plate V, Figs. 3 and 4). Rows for lines) of 2-3 eggs were likewise noted; these were about 3 cm apart from one another. The eggs were quite hard to see; I first observed them on the sides of the aquaria in March, 1959 and I was able to find them only a year later in the field. These eggs, which are also laid on solid objects, lack a sand grain cover, but are coated with a thin layer of soil and blend perfectly with their background. If the thin soil coat is removed, a whitish-gray ovum is exposed that is surrounded by a clear gelatinous membrane. A brief comparison of the spawn of the 2 snails here described with that of other pleurocerids may be found in Table 9, and a discussion of the pos- sible significance of the various types on classification, on p 172. Egg Laying Season and Potential. The combined information obtained for both species in the field and in the laboratory indicates that P. acuta produces eggs during a shorter period (April-June) than does G. livescens (April through mid-August). It should be noted however that P. acuta has a greater egg laying rate (per snail per day) than С. live- scens (15 as compared to 4). The approximate egg-laying potential of P. acuta was determined as follows: 45 adult females were collected at the Portage Creek station on April 20, 1960, a period when eggs usually begin to appear in nature. In that instance, however, the water temperature at the station was only about 50°F and there was no egg-laying yet. The snails were kept at room temperature (72°F). Within a few days the snails began to deposit eggs on the sides of the container and continued to do so over a period of about 4 weeks, after which no more eggs were deposited. Throughout the PLEUROCERA AND GONIOBASIS 97 egg-laying period a daily record was made of the total number of egg masses and the number of eggs per mass. Most of the clutches were laid on the glass sides of the aquarium. These were marked witha red wax pencilas they were laid; the few clutches in other locations were also recorded. From day to day the unmarked clutches represented the newly laid eggs. A total of 2,096 egg masses with 18864 eggs were laid in 256 days. Assuming that all 45 snails were gravid, each female had produced an average of 46.5 egg masses. With an average of 9 eggs per mass, it is calculated that a single female produced a total of 398.7 eggs, or an average of about 15 eggs per day. However, about 80% of the eggs were laid during the first 2 weeks of the egg-laying period. The same procedure was repeated in 2 successive experiments, one beginning June 20, and the other on July 27, 1960. The earlier culture only gave positive results, the snails laying a few eggs, for one week; this clearly indicates that in nature egg-laying does not extend beyond June. _ It was determined among laboratory raised P. acuta that the animals ovi- posited for the first time when they were about 2 years old. The egg-laying activities of 2 age groups, one in their first and the other in their second egg- laying season, were compared by taking 100 egg masses at random from each group and counting the number of eggs (Table 8). It was found that young adults generally laid fewer eggs per mass than did the older group, the average number of eggs per clutch being 2.81 and 6.62 respectively, and that these laboratory bred snails laid smaller egg clutches than did those from the field, with 4.7 eggs per mass against 9. For possible reasons, see stunted growth of cultured animals (p 61). Van Cleave (1932) reported an average of 4-5 eggs per clutch. The egg-laying capacity of G. live- Scens was Similarly studied. Forty adult females, collected on April 19, 1960, TABLE 8. Number of eggs per clutch in laboratory bred Pleurocera acuta of two different age groups. Approximate age of snails 2 years 3 years (beginning of (fully egg-laying) matured) 4 4 DHL 0:5 5 8 Оо 3 4 STAY oe 4 5 бп 6 5 4 PA 5 9 5 21608 1 2 4 4 6 8 5 6 4 4 Ad AA o 1 2 LME NT 5 3 ASIS 7 4 DOS 1 3 Be 3 Val 5 6 ALIAS 2 2 Sie eS 7 5 By ts al 2 1 de ya te A 6 8 DNS ND 4 3 4 1 4 7 7 Dien il 2 тыл 7 4 Ci) 7510235 1 3 22.21 14 4 CAOS 4 2 SAS 71.714 nt 5 5 rl 6 4 8 4 6 3 2 4 3 4 5 6 AO AO 3 il SAS 6 5 OI 3 3 PAN A 275716 1 1 SEL 9 1 ZAS 5 i I Au 6 Би AG 5 3 EC 6019 4 Average number of eggs рег clutch from 100 random clutches: 2.81 6. 62 from the 200 clutches: 4.71 at the Huron River station were main- tained in the laboratory. Over an ob- servational period of 20 days, they produced a total of 3,264 eggs, cor- responding to a mean of 81.6 eggs per female, and an average of 4.08 eggs per day. Two additional series of 40 snails each were observed using snails collected from the Kalamazoo River and the Huron River stations, on July 22 and on August 5, 1960. Since all these snails produced eggs, although fewer in number, another batch was collected on August 18, 1960. These failed to oviposit and it is concluded that eggs 58 B. C. DAZO TABLE 9. Comparison of egg-laying among twelve species of Pleuroceridae Species Egg deposition and average egg output per snail Pleurocera acuta (Dazo: 1-19 eggs/mass; about 15 eggs/day). Pleurocera lewisii Eggs in masses sparsely covered with sand; flat, with gelatinous covering; range 3-15 eggs; avg. 7-8 eggs per mass; egg-laying time per mass 45 min. Eggs in masses with or without a cover of sand grains or soil; range 3-13 eggs; avg. about 9 eggs per mass; diam. of each mass 1-1.7 mm. Pleurocera canaliculata Goniobasis livescens correcta Eggs laid singly, or 2-3 in a row; no sand cover; shell membrane covering alone. Eggs laid singly, or 2-3 ша row about 3 cm apart; covered with thin layer of soil; about 4 eggs per day. Goniobasis livescens Eggs laid singly; with thin soil or detritus covering; no sand grains. Goniobasis clavaeformis Eggs in plano-convex egg-mass, 1-1.7 mmin diam.; sparsely covered with sand; about 4- 16 eggs per capsule. Data confirmed, Dazo. Goniobasis laqueata Eggs in masses with 2-15 eggs or more; eggs spirally arranged, with fairly tough outer mem- branous cover forming septa and dividing mass into compartments; foreign matter attached to egg mass. Goniobasis virginica Eggs laid singly, or 3-6 or more usually in a row; successive capsules connected bya thread-like portion of outer egg membrane; with sand covering. Anculosa carinata Lithasia venusta Eggs laid in pairs opposite each other in a con- tinuous ribbon; diam. of egg mass about linch. Eggs in ribbon-like gelatinous, transparent mass devoid of sand covering; a mass meas- sures on avg. 9.27 by 2.70mm; eggs arranged diagonally with respect to length of mass in rows of 1-5 eggs; 182 eggs per day. Io fluvialis Anculosa (“Leptoxis”) sp. Eggs laid singly. Average Diameter of Egg in Microns 300 285 300 306 275 280 300 (Dazo) No data No data No data 350 700-1000 PLEUROCERA AND GONIOBASIS TABLE 9 (continued) Egg-laying Period Development of and Region Egg in Days April to June Illinois March to April Illinois May Tennessee March to June Illinois April to middle of August Michigan April to June Tennessee January to May Tennessee June Maryland June Maryland January to May Tennessee April to May (laboratory, Ann Arbor, Mich.) No data 15 - 16 (72° F) (Dazo) No data 15 11.5 15 (72° F) No data 15 (72° F) (Dazo) No data No data No data 15 (7225) No data 59 Author and Citation Van Cleave, 1932 Van Cleave, 1932 Rosewater, 1959 Jewell, 1931 Dazo New data. Dazo. Unpublished data. Woodard, 1934 Winsor, 1933 Winsor, 1933 Woodard, 1934 Dazo, 1961 Rosewater, 1960b 60 B. C. DAZO are not deposited in nature beyond the middle of August. Data on the eggs, egg clutches, season of oviposition and length of development for 12 pleurocerid species belonging to 6 genera, have been compiled in Table 9 from the literature and from personal observation. As regards the egg-laying season it appears that pleurocerids in various parts of the United States generally oviposit in spring and early summer, though in Tennessee 2 species are re- ported to start as early as January. My field observations in various streams of Tennessee and Virginia further in- dicate that, in these southeastern parts, there also occurs another reproductive season in the fall. Van Cleave's findings (1932, 1933) that P. acuta oviposits from April to June, in Illinois, are entirely corroborated, for Michigan, by my own. The long egg laying season of G. lives- cens here reported is, however, in con- trast to the data reported for other species. Time of Development in the Egg and Gross Embryology Except for some minor details, the embryonic period of P. acuta and G. livescens is about the same. At room temperature (720F), the young hatch about 2 weeks after oviposition; the developmental process is the same for both species. Hence, only one general outline on the gross embryology isgiven in Table 10. Although 15 days are here given as the time for the develop- ment of the eggs, young may hatch several days beyond the normal period. Fully developed snails were often observed “sitting” within the egg case. Basch (1959), in his account of the basommato- phoran fresh-water limpet Ferrissia shimekii (Pilsbry) reported that the young were often in no hurry to emerge and may remain in the egg capsule for Several weeks without any apparent ill effects. The newly hatched P. acuta were, on the average, 340 y long and 450 y wide; G. livescens were about 270 u long and 380 u wide. At that stage the shells of both species closely resemble figures given by Jewell (1931) and Winsor (1933) for other species of Gonio- basis and Anculosa. Newly hatched Snails were observed to be quite active; they moved continuously on the bottom and sides of the aquaria apparently serching for their first meal. Growth On April 27, 1959 and May 2, 1960, adult female P. acuta from Portage Creek station were brought into the laboratory and on April 30, 1960, speci- mens of С. livescens from the inlet to Zuckey Lake. These snails laid eggs in the indoor tanks a few days after they were collected. The young ob- tained were used for growth studies. The shell of the newly hatched snails has one whorl, but occasionally there may be the beginning of a second whorl. The data given in Tables 11 and 12 represent measurements of laboratory- raised snails of both sexes. In each Species 2 batches belonging to 2 different age groups were measured at intervals. The first series comprises snails less than one year old; it started with groups of about 150 individuals which, however, declined with each subsequent measure- ment, till only a few specimens were left in each case. The second series comprises snails over one year old and covers groups declining from 44-17 individuals in the case of P. acuta and from 300-135 individuals in that of G. livescens. Since growth studies on P. acuta had started earlier it was possible to obtain more data on that Species. Development was more pro- nounced during the first year (from an average length of 0.34-10.8 mm) and growth then continued slowly even after sexual maturity (copulation) at 18 months, when they reach 13.95 mm, to 16.72 mm at 2 years, after which time no appreciable growth occurs. The corresponding figures for G. livescens are 0.27-3.87 mm atone year ofage, 5.15 PLEUROCERA AND GONIOBASIS 61 TABLE 10. General observations on the embryonic development of Pleurocera acuta and Goniobasis livescens, at 72°F. Agein Days 1 Cleavage begins about 2 hours after eggs are laid; development from 4 to 8 cell stage; extrusion of polar bodies observed. 2 Cell division produces many cells (32 to 64); general shape of egg changes from spherical to slightly ovoid. 3 Embryos in blastula stage; some rotate slowly, counterclockwise; others remain in multi- cellular stage. 4 Gastrula stage; more pronounced rutation of embryos; period of organ formation. 5 Trochophore stage; rotation continues. 6 Appearance of velum in some specimens; continues. general shape approaches a veliger; rotation 7 Velum more visible; body begins to be organized with respect to position of head, foot and shell; rotation continues. 8 Velum very prominent; veliger stage reached; rotation slows down. 9 First heartbeat observed in some specimens; foot begins to move; velum remains large. 10 Velum beginning to contract; foot movements and beating of heart more pronounced; ro- tation ceases. 11 Velum much reduced; foot movements and heartbeats very pronounced. 12 Velum disappears; young have formed and move actively; eyes visible at swollen outer base of tentacles; proboscis with lips; shell begins to take shape. 14) 1 3) Fully formed young with shell (one whorl); very active inside capsule. 15 Young begin to hatch, though hatching may be delayed for several days. mm at sexual maturity and 6.96 mm at 2 years of age. The data indicate that the laboratory raised snails (Tables 11 and 12) are much smaller than field specimens (Table 13) having the same number of whorls. P. acuta with 9-11 whorls measured about 16.5 mm in the laboratory and from 26.5-31.5 mm in the field (i.e. 1 1/2 to twice as much) and С. livescens with 7 whorls measured between 6 and 7 mm in the laboratory, while field specimens with 7-9 whorls were twice to 3 times that size (13.76- 22.70 mm). This difference (as also the difference in fertility, see p 144) may have been due to crowding and per- haps to a lack of necessary nutrients in the laboratory tanks. It is also possible that too much handling of the animals might have accounted for the stunted growth of the cultured animals. Sexual Maturity and Longevity Definite information on the life span of the 2 pleurocerid snails under study has not been published before. As already indicated, the laboratory raised snails attain sexual maturity at the age of 18 months and begin to lay eggs at the age of 2 years, at which time the average length of Pleurocera acuta is about 16.7 mm and its width 6.6 mm; the corresponding average measurements for Goniobasis livescens are 7 mm and 4.5 mm. We have also seen (Table 8) that fewer eggs were 62 B. C. DAZO TABLE 11. Size of laboratory bred Pleurocera acuta and their corresponding age Number of Snails used Number of Whorls Average size in mm LIPuNNEOSoS ялревннно?е? in months 12 5. 44 15 5. 41 18 6. 40 21 6. 37 24 6. 31 27 6. 24 30 6. 20 33 6. 1br Number of Snails Used Number of Whorls Average size inmm 0. 0. 1 0. 0. 1.5 132 0. 0. 2 102 0. 0. 3 79 1: if 4 48 its il 4.5 25 2. 2. 5-6 18 3. 2. 5 - 6.5 13 4. 2. D'or in months 12 300 15 280 18 227 21 162 24 PLEUROCERA AND GONIOBASIS TABLE 13. Sizes of adult snails collected at various localities in Michigan and Ohio Average size inmm Pleurocera acuta20 Portage Creek 29.10 11. 28 Big Pigeon River 32.70 12. 91 Honey Creek 26. 62 11.10 Spring Lake 29.70 т Grand River 31.50 125 Bl Total: 149. 62 58. 95 Average: 29.92 Tals TE) Goniobasis livescens21 Zuckey Lake Inlet 13276 elo Kalamazoo River 14. 50 7.88 Portage Creek 15.60 8. 00 Huron River 17. 30 8.41 Honey Creek 21. 03 9. 83 Burt Lake 18. 98 9. 92 Douglas Lake 20. 32 8.49 Mullet Lake 20. 45 9. 49 Lake Erie22 22.20 9.45 Total: 164. 14 79. 08 Average: 18.24 8.79 20Number of whorls 9-11; 669 snails used. 21Number of whorls 7-9; 9261 snails used. 220nly locality in Ohio. laid by P.acuta that had just begun to oviposit than by the older, fully matured snails (2.8 eggs per clutch as compared to 6.2). The field and laboratory data indicate that both P. acuta and G. livescens attain an age of about 3 years. Rose- water (1960) assumed the same longe- vity for P. canaliculata. The life span 63 of the 2 species studied here may ex- tend to 4 years perhaps, depending on the environmental conditions to which the colonies are subjected. In open areas, such as the exposed shores of inland lakes where the animals are con- tinuously exposed to windand wave action during the warmer months and to de- pletion of oxygen in the winter, it is hardly conceivable that these snails can live up to 4 years. On the other hand, colonies occupying sheltered or more protected habitats may have a better chance to live for more than 3 years. Sex Ratio Snails of both species from the per- manent collecting stations and from labo- ratory cultures were examined as to sex. It was found that females outnumbered males both in the field populations and the laboratory colonies, especially so in the latter, and especially for G. livescens, (Table 14), the overall sex ratios being roughly 2:1 for P. acuta and 5:1 for G. livescens. That the laboratory raised specimens of both species showed a much higher ratio in favor of the females than those from the field seems to indicate that the females tolerate artificial conditions better than the males. Diurnal and Seasonal Activities In nature, G. livescens are often ob- served crawling over the sides of rocks, stone and various solid objects, ap- parently scraping off algae and diatoms in the process of feeding. Now and then they pause for a while but usually the restless hunt for food goes on. In contrast, P. acuta is somewhat slug- gish. It slowly plows through the sandy TABLE 14. Ratios of females to males in adult Pleurocera acuta and Goniobasis livescens Speci Laboratory eas bred snails P. acuta G. livescens Field Overall snails ratio Dale 130 1.85 74 6.50 2.42 4.71 318 No. of snails used Lab. bred 64 B. C. DAZO bottom with its rostrum fully extended. F. C. Baker (1928a) described its move- ment as follows: “Its rostrum is like an elephant’s trunk or a hog’s snout waving about from side to side, examing the bottom--this reminds one of a dog on the scent”... “when progressing, the animal glides along for a short distance, then pulls the shell after it, thus advancing by a succession of jerks.” In the laboratory, both P. acuta and G. livescens preferred to stay on the bottom of the glass aquaria in the evening. The former species often re- mained buried halfway in the sand; some protruded their rostrum partly from the shell while their tentacles slowly moved about. G. livescens would simply “sit” on top of or on the sides of rocks or gravel with little or none of the head region visible. As day begins, the animals of both species again ascend the sides of the aquaria. Whether this habit is a direct response to light or associated with feeding is unknown. Goodrich (1945) reported that 5°C was the lowest temperature at which he observed G. livescens on the upper sides of stones in the Huron River. When the temperature had dropped to 1.1°C he (and Jackowski) noticed that all the snails had disappeared. They found the animals hibernating under stones or in gravel and sand, in water flowing too fast to freeze. Their apertures were tightly closed by their opercula; the Shells were covered with a film of white material which they assumed to be gelatinous algae. Goodrich reported May 1, 1943, as the earliest spring date at which he saw the snails active. He realized that the end of hibernation might have occurred earlier but had not been discovered because of high water and the turbidity common during the flood season. I have usually found these snails active at an earlier date, in the second half of April. Egg laying starts in spring when the lake and stream waters begin to warm up. As already discussed, breeding con- tinues through the early part of summer (p 56). In view of their increased activities, summer and fall are the best times for collecting and studying pleurocerids. Many snails crowd to- gether in distinct colonies, and their distribution in the stream or lake is somewhat spotty. The juveniles of both species are often observed floating at the surface of the water with their shell hanging down- ward and the foot adhering to the sur- face film. On closer examination the foot was found to assume a cup-like shape that created a partial vacuum be- tween it and the thin film of water. Another pattern of behavior noted was the habit of these snails to come to the top of the water, where they ex- tended their rostrum above the surface. They would remain in this position for hours. F. C. Baker (1902) observed the same in С. livescens. Michigan pleurocerids are very active in the fall. At this season they can frequently be seen taking up the “mating position.” That laboratory bred snails lay eggs in midwinter, seems to bear out previous mating (p55). Further evidence for fall mating is furnished by the presence of fertilized eggs in gonad sections of P. acuta and G. livescens collected during winter (Plates VI and УП, Figs. 2 and 3). In nature hiber- nation begins immediately with the in- ception of winter conditions and the eggs are laid in spring only. Food and Feeding Habits About 200 P. acuta and 250 G. lives- cens from the permanent and occasional stations were used in this study. They were fixed and preserved in Lavdowsky’s solution (formalin: alcohol: acetic acid 2:10:1 parts per volume). In the laboratory the stomach con- tents were examined microscopically. Algae, including green and red algae, diatoms and desmids, were found to constitute a major part of the diet of both species, which do not differ in this respect from Oncomelania quadrasi snails (Dazo and Moreno, 1962). A PLEUROCERA AND GONIOBASIS 65 PLATE VI. Histological sections of Pleurocera acuta. FIG. FIG. FIG. FIG. FIG. FIG. 1. Cross section of the visceral region showing the position of the 2 chambered heart (H), the much folded structure of the kidney (K), the esophagus (E), the stomach (S), and the intestine (I). Cross section of the ovary (O) of a specimen collected in the winter withripe ova in the. gonad. Note liver (L) pigments in lower left corner. Approx. 200X. Cross section of the testis (T) of a specimen collected in the fall, showing the charac- teristically oriented spermatozoa in the gonad. Liver (L) cells with dark stained pig- ments can be seen in lower half. Approx. 200X. Longitudinal section of the mantle region showing cross sections of the gill filaments. The large intestine appears in the lower right corner. ' Approx. 30X. Longitudinal section of the head-trunk region showing mouth (M), pharynx (P) and lingual ribbon or radula (R). Approx. 30X. Cross section of the neck region showing the larval trematode parasites (PA) inside the large intestine; some of the gills (G) from the right side, and in the lower portion, the cross section of the esophagus (E) and columellar muscle (C). Approx. 80X. 66 B. C. DAZO PLATE VII. Histological section of Goniobasis livescens. FIG. 1. Cross section of the buccal mass showing the pharynx (P), the pair of salivary glands (S), the buccal cartilage (BC) and the complicated buccal musculature (BM). 60X. FIG. 2. Cross section of the ovary of a female collected in the winter showing the presence of ripe ova in the gonad. FIG. 3. Close-up of the ovary showing a ripe ovum. Approx. 400X. FIG. 4. Cross section of the stomach (S) showing the entrance of the single duct (D) from the digestive gland (L). Approx. 60X. FIG. 5. Longitudinal section of the tentacle (TE) showing the eye. Approx. 200X. list of these algae is given in Table 15. Bacteria and soil material were also present in the gut of G. livescens. The large quantity of decaying vegeta- tive material and extremely fine sand grains in the stomach of P. acuta clearly indicates that this animal is a substrate feeder. Parasites and Predators The pleurocerid group and especially the genera Pleurocera and Goniobasis have long been known to serve as inter- mediate hosts for a variety of trema- PLEUROCERA AND GONIOBASIS 67 TABLE 15. A systematic list of algae serving as food to Pleurocera acuta and Goniobasis livescens . A. From stomach contents of 200 specimens each of both species, from various localities in Michigan. Division: CHLOROPHYTA Sub-division: Chlorophyceae Order: Tetrasporales Family: Palmellaceae Species: Sphaerocystis schroeteri Chad. Order: Ulotrichales Family: Microsporaceae Species: Microspora floccosa (Vauch.) Thur. Family: Cylindrocapsaceae Species: Cylindrocapsa geminella Wolle. Family: Protococcaceae Species: Protococcus viridis Ag. Order: Chlorococcales Family: Oocystaceae Species: Chlorella variegatus Beij. Dictyosphaerium pulchellum Wood Order: Zygnematales (Conjugales) Family: Desmidiaceae Species: Desmidium grevillii (Kiitz. ) Micrasterias radiata Hassall Staurastrum furcigerum Breb. Division: CHRYSOPHYTA Sub-division: Bacillariophyceae Order: Pennales Family: Fragilariaceae Species: Diatomella balfouriana Grev. Tabellaria fenestra (Lyngb. ) Kiitz. Family: Gomphonemataceae Species: Gomphonema Vibrio Ehr. Family: Cymbellaceae Species: Cymbella cistula (Hempr. and Ehr.) Kirchn. C. lanceolata (Ehr.) Brun. Epithemia turgida (Ehr. ) Kiitz. Rhopalodia gibba (Ehr.) O. Müller Family: Naviculaceae Species: Navicula gracilis Ehr. N. radiosa Kiitz. N. rhyngcocephalaKütz. Pinnularia viridis (Nitzsch. ) Ehr. Anomoeoneis sphaerophora (Kütz.) Pfitz. Stauroneis anceps Ehr. Brebissonia boeckii (Ehr. ) Grun. Gyrosigma kilizingii (Grun.) C1. 68 B. C. DAZO Division: RHODOPHYTA Sub-division: Florideaea Family: Chantransiaceae Species: Batrachospermum vagum (Roth) B. From stomach contents of 50 Goniobasis livescens from Douglas Lake, Cheboygan County, Michigan. 23 Division: CHRYSOPHYTA Sub-division: Bacillariophyceae Order: Centrales Family: Coscinodiscaceae Species: Melosira ambigua (Grun.) O. Müll. M. varians C. A. Ag. Cyclotella bodanica Eulenst. Cyclotella sp. Cyclotella sp. Coscinodiscus lacustris Grun. Order: Pennales Family: Fragilariaceae Species: Tabellaria fenestra (Lyngb. ) Kütz. Fragilaria brevistriata Grun. F. capucina Desmazieres F. construens (Ehr.) Grun. F. construens (Ehr.) Grun. var. subsalina Hust. Synedra ulna (Nitzsch) Ehr. S. vaucheriae Kütz. Family: Achnanthaceae Species: Achnanthes exigua Grun. var. heterovalvata Krasske A. lanceolata Breb. A. minutissima Kütz. A. minutissima Kütz. var. cryptocephala Grun. Cocconeis pediculus Ehr. C. placentula (Ehr.) Family: Gomphonemataceae Species: Gomphonema constrictum Ehr. G. subtile Ehr. Family: Cymbellaceae Species: Cymbella affinis Kütz. C. cymbiformis (Agardh? Kütz.) van Heurck C. delicatula Kütz. C. naviculiformis Auerswald C. prostrata (Berkeley) Cleve C. ventricosa Kütz. Amphora normani Rabh. Family: Epithemiaceae Species: Epithemia zebra (Ehr.) Kütz. Rhopolodia gibba (Ehr.) O. Müller 23Identified by Dr. George M. Davis, Mollusk Division, Museum of Zoology, University of Michigan, Ann Arbor, Michigan. PLEUROCERA AND GONIOBASIS 69 Species: В. parallela (Grun.) O. Müller Family: Nitzschiaceae Species: Nilzschia acicularis W. Smith N. hantzschiana Rabh. N. sinuata (W. Smith) Grun. var. tabellaria Grun. Family: Naviculaceae Species: Mastogloia smithii Thwaites М. smithii Thwaites var. cryptocephala Grun. Amphipleura pellucida. Kiitz. Gyrosigma kützingii (Grun. ) Cleve Stauroneis anceps Ehr. Navicula cryptocephala Kiitz. N. cryptocephala Kütz. var. venela (Kütz.) Grun. N. exigua (Greg.) O. Müller . lacustris Greg. minima Grun. oblonga Kiitz. pupulla Kiitz. radiosa Kiitz. rostella Kiitz. EEE FIT . viridula Kütz. . radiosa Kütz. var. rhynchocephala Kütz. tenella (Breb.) Grun. . tuscula (Ehr.) Grun. . tuscula (Ehr.) Grun. fo. minor Hust. Pinnularia lata (Breb.) W. Smith todes. The numerous records of pleuro- cerids as hosts of larval flukes clearly indicate the significance of pleurocerid biology in the field of parasitology. For a number of larval forms the life histories are not known, to quote only Cercaria aurita (Zetek, 1918), a mono- stome cercaria of the urbanensis type; C.gorgonocephala (Heard, personal com- munication), an interesting cercaria forming colonies by joining tails, both from Goniobasis livescens; as well as a dozen species of virgulate xiphidio- cercariae from P. acuta and G. lives- cens and from Goniobasis sp. (Hall, 1960). The life cycles of certain fish tre- matodes developing in Pleurocera and Goniobasis are, however, knownand data from several important publications re- lating to three families have been as- sembled, and are included, in Table 16. These trematodes of fishes are remarkable in that a number of them have a contracted, modified life cycle in which some step in the development of the digenetic trematodes is sup- pressed, some species being even capable of direct development in the snail without passing through a verte- brate host. Dobrovolny (1939b) showed that G. livescens served as both first and second intermediate host of the allocreadtrema- tode Plagioporus sinitsini, a parasite of cyprinid and other fish. The cer- cariae never leave the sporocyst in which they form but encyst т situ. The sporocysts with mature metacercariae emerge from the snail to be consumed by their definitive host. The aspidogastrid species Cotylo- gastev occidentalis was found to occur in Goniobasis in 2 forms, “immature” and “mature”, the latter containing numerous eggs with viable embryos (miracidia) (Dickerman, 1948). That author further stated that, while it was possible to infect sheephead (Aplodinotus 70 TABLE 16. B. C. DAZO Definitive Host Trematode infections observed in Pleurocera acuta and Goniobasis livescens Parasite Intermediate Snail Host (Vertebrate and Author Invertebrate) Cercaria aurita Goniobasis pulchella (-lives- |No data Zetek, 1918 cens)- Big Vermilion River, Illinois. Plagioporus G. livescens, Oneida Lake, Fishes Baker, E.C., 1916 sinitsini New York Plagioporus G. livescens, Huron River, Cyprinid and other |Dobrovolny, 1939b Sinissini huroni |Washtenaw Co., Michigan fishes Plagioporus G. livescens, Huron River, Centrarchid fishes |Dobrovolny, 1939a lepomis Washt. Co., Mich. 1.25% of No specific trematode given 43,189 snails shed cercaria Pleurocera acuta Outlet of L. Oconomowoc, Wisconsin. (Oconomowoc River) No data Baker, F.C., 1928a Proterometra G. livescens correcta-Des Fishes: Dickerman, 1934 macrostoma Plaines River, Evanston and Crappie, Pomoxis Hickory Creek, New Lenox, Sparoides; blue Illinois gills, Helioperca incisor; sunfish, Eupomotis gibbosus Proterometra Р. acuta and С. livescens from Fishes Dickerman, 1934 macrostoma the Great Lakes Region. Proterometra P. acuta and G. livescens W. Dickerman, 1945 Sagittaria Lake Erie, Sandusky River, Sunfish, Freemont and Maumee River, | Eupomotis gibbosus Ohio Cotylogaster С. livescens-Bass Is. , Lake Fishes: Dickerman, 1948 occidentalis Erie, Ohio. 2% of 7,697 snails} Rock bass, Amblo- infected. plites rupestris; sheephead, Aplo- dinotus grunniens ; clam, Lampsilis luteola Cercaria G. livescens , Douglas Lake, No data Heard (1960) gorgonocephala {Cheboygan Co., Mich. (pers. comm.) virgulale С. livescens and P. acuta fr. | No data Hall, 1960 xiphidiocercariae (12 species) Wabash and Tippecanoe rivers, Indiana, and Goniobasis sp. fr. Marquette river, Michigan possibility of developing within or with- out a vertebrate host, he supported the classification which places the Aspido- gastrea in a trematode subclass distinct grunniens) experimentally by forcible feeding of these eggs, the embryosinthe egg were not dependent upon the fish for continued existence. Because of this PLEUROCERA AND GONIOBASIS 71 from the Digenea. This fluke has also been reported from a clam. Similar conditions seem to prevail among the Azygiidae, whose large cysto- cercous cercariae are known to be eaten. by centrarchid fishes, in which they mature. According to Dickerman (1946) the rediae of Proterometra sagittaria, after discharge of cercariae, also con- tained eggs with mature miracidia, which likewise suggests the possibility of an alternative direct life-cycle. Parallel observations were made for Protero- metra macrostoma by Anderson (1962, personal communication). Parthenitae and cercariae of certain trematodes were frequently encountered in the course of this study in snails from various localities in Michigan. The cercariae of Proterometra macrostoma were found in G. livescens collected in the Ocqueoc River, Presque Isle County, northern Michigan, as well as Portage Creek and Zuckey Lake Inlet, south- eastern Michigan. In the same region this parasite was also found in P. acuta from Portage Creek and Honey Creek. Some P. acuta collected from the Big Pigeon River, Ottawa County, south- western Michigan, shed Cercaria sagit- taria; Plagioporus sinitsini cercariae were shed by G. livescens collected in the Huron River and Kalamazoo River stations. These various parasites were foundin the liver, gonad, alimentary canal (especially the large intestine or rectum) and the mantle region in the vicinity of the laminal folds of the “open” or terminal portion of the reproductive tract of the snail. Information about animals that prey on pleurocerids is rather scarce, but it appears that many pleurocerids are consumed by fishes. For example, Dickerman (1948) examined 22 sheep- heads and found evidence in the stomach of one large fish that it had eaten Goniobasis snails. The fish was also parasitized with 3 specimens of Cotylo- gaster occidentalis, which it may have thus acquired. Goodrich (1945) reported that an examination of the stomach con- tents of brook trout (Salvelinus fontin- alis) yielded the remains of shells of 8 genera of fresh-water mollusks, in- cluding G. livescens and that shells of that species were found in the gizzard of a white-winged scoter shot at Fish Point, Tuscuola County, in 1926. DISCUSSION OF PLEUROCERID SYSTEMATICS While there are some striking differ- ences in the morphology of the she1124 and operculum of P. acuta and G. lives- ‘cens (Summarized in Table 17)andsome distinction in the radular teeth, there is a striking similarity in the internal anatomy of the 2 species. Despite some differences in ecological preferences and in other detail, the general pattern in the life history of both species is almost identical. A consideration of these basic similarities emphasizes that P. acuta. is closely related to G. lives- cens, and indicates that the present systematic arrangement, with each Species under a separate genus is open to question. Evidently the use of shell characters alone in this group, where intra- and inter-specific variation is so common, does not seem to provide a good criterion for intrafamilial classification. While the present systematic arrange- ment appears unsatisfactory, it is not yet possible to submit a better one. The Pleuroceridae have been and will probably continue to be a difficult group to contend with, because few thorough and inclusive morphological and bio- logical studies have yet been made, while such knowledge as we have does indicate great morphological simi- larities of the animals. The system- atic uncertainties exist at all levels and are due in part to unfortunate legacies 24 There were, however, some intermediate specimens from the field in which these differences were hardly discernible. 72 Feature Adult shell Juvenile shell Operculum Radular teeth B. C. DAZO Elongated; whorls flat numbering from 9to 11; no callus thickening on parietal wall; columella twisted; aperture angulate tending to form a canal below. Double carinae prominent on the whorls. In adult shells these ridges are present only in the first 3to 6 whorls; lateral ridge less marked thanthe median; sometimes 3 carinae may be found in some specimens, 1 median and 2 lateral. Small; more elongated and thin; more uniform in shape; spaces between growth scars growth lines narrow; well marked by dark lines. Range of cusps in lst marginal in 2nd marginal TABLE 17. Comparison2° between Pleurocera acuta and Goniobasis livescens Pleurocera acuta Goniobasis livescens Ovately conic; whorls more convex ranging from 7 to 9; parietal wall with callus; columella smooth; aper- ture subrhomboidal, subangular at the base but not canaliculate. Single carina present at the middle of juvenile whorls; this ridge usually disappears in matured specimens but is sometimes retained. Larger and more variable in shape; wide spaces between growth lines which under the microscope appear as very fine spiral lines and are similar to wrinkled ridges as in the sculpture of many fresh-water shells. 6-7 8-12 Teeth, though equal in size, relatively much larger. Lives in almost any kind of clean, permanent type of fresh-water envi- ronment ranging from springs to Ecology Generally inhabits quiet areas in big- ger streams; prefer sandy-muddy bottom presumably because of its burrowing habit. Egg-laying In masses. swift flowing streams and rivers and sheltered areas in lakes; prefers to crawl on rocks or stones. | Singly. 25The difference in size is not considered an essential feature. left by pioneer workers such as Rafin- esque, Lea and many others (Walker, 1917) (see introduction, p 9). Only recently has there been an em- phasis on the value of morphological, as well as life history studies, in evalu- ating the phylogenetic relationships among animals in most molluscan groups, including the pleurocerids. Morrison’s (1954) attempt to regroup the North American pleurocerids according to the characteristics of their egg masses opens interesting possi- bilities. He has assigned the name Oxytrema to those forms whose egg capsules aggregate in clusters and are usually encased in sand grains, and he includes all species hitherto known as Pleurocera and most species known as Goniobasis. The pleurocerid species whose eggs are laid singly or instraight chains (including Goniobasis livescens) he relegated to the genus Mudalia. How- ever, observations do not yet exist for all species and it is not certain whether egg-deposition characteristics will ulti- mately prove to be a valid criterion at the generic level, or perhaps only at PLEUROCERA AND GONIOBASIS 73 the specific level. On the basis of what was known about reproductive features, such as egg- masses and spermatophores, Rosewater (1960a) divided the pleurocerids into 5 categories, which were ‘‘inpart corre- lated with the ecologic niche in which each species is found.” Later, Rose- water (1961) indicated the possible taxonomic implications of the differences he found in the length of the commis- sures and connectives of the central nervous system of 9 species of Pleuro- ceridae. Since the 3 species of pleuro- cerids belonging to 3 genera (Pleuro- cera, Goniobasis and Jo that I have examined in this respect proved to be very closely similar and since ex- amination did not corroborate the differ- ences indicated, this attempt at classi- fication does not appear valid. The information obtained in this study would seem to favor a classification based on the character of the egg masses. As shown in Table 9, information is available at the present time for 12 Species. From these data it is now possible to formulate some tentative group relationships. The groupings here proposed are: (1) Eggs in batches or compound masses; conspicuously cased in sand grains. This group includes Pleurocera and some species of Goniobasis. (2) Eggs laid singly, sometimes con- nected by strands of outer egg- membrane (up to 6 in a row), with shell membrane covering and a thin layer of soil. Anculosa, and the majority of the species of Goniobasis belong in this category. (3) Eggs laid in pairs opposite each other in a continuous ribbon-like mass. Lithasia is the only known member of this group. (4) The eggs are arranged in rows, up to 5 in arow, running diagonally across the elongated gelatinous egg mass. This group includes Jo fluvialis and presumably its forms. It is expected that additional infor- mation about the character of egg deposition of the other genera will enable a more complete and accurate analysis of the value of this feature for deter- mining group relationships. However, such reproductive characters are not sufficient in themselves and must be Supported or supplemented by a variety of other significant biological data. For example, the host specificity indicated by a Similarity in larval trematode in- fection may also prove useful in any attempted reclassification of these snails. Cytological and electrophoretic studies might also throw light on various relationships. But, in the present state of knowledge it is impossible to appreci- ate which combination of features would be most useful in an evaluation of the systematics of the group. It hasbecome increasingly obvious, however, that many more basic studies are needed on the morphology and biology of members of the Pleuroceridae to derive more mean- ingful and concise taxonomic arrange- ment of the genera and species now grouped within this family. ACKNOWLEDGMENTS I wish to express my sincere gratitude to Dr. Henry van der Schalie, whose continued guidance, encouragement and unfailing interest in my work made this study possible. Grateful acknowledge- ment is also made to Dr. J. B. Burch for constant advice and aid during the course of the investigation and for accompanying me on several field trips. I am also indebted to Dr. Nelson G. Hairston, whose kind assistance and constructive criticisms aided me during the formative stages of this work; to Mrs. Anne Gismann who critically edited the manuscript, and to Mr. William L. Brudon and Mrs. Stanlee Lonsdale for their help in the preparation of figures and plates. 74 B. C. DAZO LITERATURE CITED ADAMS, C. C., 1900, Variation in Jo. Proc. Am Assn. Adv. Sci., 49: 280- 225. ‚1915, The variations and eco- logical distribution of the snails of the genus /o. Nat. Acad. Sci. Wash- ington, 2nd Memoir, 12(2): 1-185. ADAMS, H. and ADAMS, A., 1854, The genera of recent mollusca (Fam- ily Melaniidae), 1: 293-311. AMERICAN PUBLIC HEALTH ASSOCIA- TION, INC., 1955, Standard methods for the examination of water, sewage and industrial wastes, p 250-260, 10th ed. ANDERSON, M. G. 1962, Personal communication (New Mexico State Univ., Univ., Univ. Park, New Mexico). BAILY, J. L., PEARL, R. and Winsor, C. P., 1932, Variation in Goniobasis virginica and Anculosa carinata under natural conditions. Pt.I. The prob- lem, material and methods. Biologia Generalis, Bd. VIII, Liefer. 2: 607- 630. , 1933а, Variation in Gonio- basis virginica and Anculosa carinata under natural conditions. Pt. 2. Re- lations between size of the.shells, and environmental factors: Biologia Gen- eralis, Bd. IX, Liefer. 2: 301-336. ‚ 1933b, Variation in Gonio- basis virginica and Anculosa carinata under natural conditions. Pt. 3. Cor- relations, shape of shells, and con- clusions. Biologia Generalis, Bd. IX, 2. Hälfte: 47-69. BAKER, F. C., 1902, The Mollusca of the Chicago Area. Chicago Acad. Sci. Bull. No. Ш, Pt. II of the Nat. Hist. Surv. , 1920, The Life of the Pleis- tocene or Glacial Period. Univ. Ill, Contr. 7, Mus. Nat. Hist., 476 p. , 1916, The relation of mol- lusks to fish in Oneida Lake. N. Y. State College Forestry Techn. Publ., 4: 1-366. , 1927, Molluscan associations of White Lake, Michigan: A study Douglas Lake, Michigan. of a small inland lake from an eco- logical and systematic viewpoint. Eco- logy, 8(3): 353-370. , 1928a, Freshwater mollusca of Wisconsin, Part I, Gastropoda. Wisc. Geol. and Nat. Hist. Surv., Bull. 70. ‚ 1928b, Influence ofa changed environment in the formation of new species and varieties. Ecology, 9(3): 271-283. BAKER, H. B., 1909, Key to the genera of gastropoda of Michigan. 11th Ann. Rept. Michigan Acad. Sci., p 139. , 1912, A few notes on the mollusca of the Douglas Lake Region. IXth Ann. p 209-211. , 1942, Goniobasis livescens in Nautilus, Rept. Mich. Acad. Sci., 56: 33-34. BARTSCH, P., 1906, Variation in the shell of Goniobasis virginica with an outline for breeding experiments (Ab- stract of lecture). Science, 23: 465- 466. BASCH, P. F., 1958, The morphology and biology of Ferrissia fusca (Adams): A comparative study. Doc- toral Thesis, Univ. Mich. On micro- film, No. 58-7678. , 1959, Studies on the develop- ment and reproduction of the fresh- water limpet, Ferrissia shimekii (Pilsbry). Trans. Amer. microsc. Soc., 78(3): 269-276. BECK, W. M. JR., 1954, Studies in stream pollution biology. I. A simpli- fied ecological classification of organ- isms. Quart. J. Fla. Acad. Sci., 17 (4): 211-227. BERNARD, F., 1890, Recherches sur les organes palléaux des gastéropodes Prosobranches. Ann. Sci. nat. Zool., 9(7): 89-404. BINDER, E., 1959, Anatomie et sys- tématique des Mélaniens d’Afrique ocidentale. Rev. suisse Zool., 66(4): 735-759. BOETTGER, C. R., 1944, Tierwelt der Nord-und Ostsee, Basommatophora, 35, Lieferung 9b2, Becker und Erler, PLEUROCERA AND GONIOBASIS 75 Leipzig. BOUVIER, E. L., 1887, Système пег- veux, morphologie générale et classi- fication des Gasteropodes Proso- branches, Ann. Sci. nat. Zool., 3(7): 1-510. BRIGHT, D. B., 1958, Morphology of the common mudflat snail, Cerithidea californica. Bull. So. Calif. Acad. Sci., 57(3): 127-139. | 1960, Same paper, 59(1): 9-18. CARRIKER, M. R., 1946, Observations on the functioning of the alimentary system of the snail Lymnea stag- Ibid. nalis appressa Say. Biol. Bull., 91(1): 88-111. CHEATUM, E. D. and MOUZON, E. D., 1934, Biometrical study of Gonio- basis comalensis Pilsbry from two diverse habitats. Field and Lab., 3(1): 18-23. CLENCH, W. J., 1926, Some notes and list of shells of Rio, Kentucky. Nauti- lus, 40: 7-12. COPELAND, M., 1918, The olfactory reactions and organs of the marine snails Alectrion obsoleta (Say) and ‚ Busycon canaliculatum (Linn.). J. exp. Zool., 25: 177-227. COX, L. R., 1960, Gastropoda. Gen- eral characteristics of Gastropoda. In:. Treatise on Invertebrate Paleon- tology, Part I, Mollusca, Ed. R. C. Moore. Geol. Soc. Amer. and Univ. Kansas Press. CURRIER, A, O., 1868, List of the Shell-bearing mollusca of Michigan. Misc. Publ. Ky. Sci. Inst., p 9. DAWLEY, C., 1947, Distribution of aquatic mollusks in Minnesota. Amer. Midland Naturalist, 38(3): 671-697. DAZO, В. C., 1961, Some studies on the genus Jo. Abstract of paper read at the 28th annual meeting of the Amer. malacoi. Union, June 19-23. DAZO, B. C. and MORENO, R. G., 1962, Studies on the food and feeding habits of Oncomelania quadrasi, the snail intermediate host of Schistosoma japonicum in the Philippines. Trans. Amer. microsc. Soc., 81(4): 341-347. DECAMP, W. H., 1881, List of shell- bearing Mollusca of Michigan. Misc. РЫБ Кубе Inst; 5: 11. DENNIS, С. А., 1928, Aquatic gastro- pods of the Bass Island Region of Lake Erie. The Franz Theodore Stone Laboratory, Contr. No. 8. DICKERMAN, E. E., 1934, Studies on the trematode family Azygiidae. I. The morphology and life cycle of Proterometra macrostoma Horsfall. Trans. Amer. microsc. Soc. 53(1): 8-21. , 1945, Studies on the trema- tode family Azygiidae. II. Parthenitae and cercariae of Proterometramacro- stoma (Faust). Trans. Amer. mic- rosc. Sco. 64(2): 138-144. , 1946, Studies on the trema- tode family Azygiidae. III. The mor- phology and life cycle of Proterometra sagittaria n. sp. Trans. Amer. mic- rosc. Soc., 65(1): 37-44. , 1948, On the life cycle and systematic position of the aspidogas- trid trematode, Cotylogaster occi- dentalis Nickerson, 1902, J. Parasit., 34(2): 164. DOBROVOLNY, C. G., 1939a, The life history of Platioporus lepomis, a new trematode from fishes. J. Parasit., 25: 461-470. , 1939b, Life history of Plagio- porus sSinitsini Meuller and embry- ology of new cotylocercous cercariae (Trematoda). Trans. Amer. microsc. Soc., 58: 121-155. ELLIS, M. M., 1937, Detection and measurement of stream pollution. Bull. 22, U. S. Bur. Fish., 58: 365- 437. FISCHER, P., 1885, Manuel de con- chyliologie et de paleontologie con- chyliologique ou histoire naturelle des mollusques vivants et fossiles. Libr. F. Savy, Paris. FLORKIN, M. and LOZET, F., 1949, Cellulose in Helix. Arch. internatl. Physiol., 57: 201-207. FRÖMMING, E., 1956, Biologie der mit- teleuropäischen Süsswasserschenc- ken. Duncker and Humbolt, Berlin. 76 B. C. DAZO GMELIN, J. F., 1791, Systema Na- turae, ed. 13, Vol. 1, Pt: 6, р 3505, Species 168, (Buccinum virginicum). GOODRICH} EZ, 1928, Strophobasis: A section of Pleurocera. Occ. Pap. Mus. Zool. Univ. Mich., No. 192, 15p. , 1932, The Mollusca of Mich- igan. Mich. HandbookSer. Mus. Zool., Univ. Mich., Ann Arbor, Vol. 5, p 1-120. ty 1939a, New opercula for old. Nautilus, 52: 140. , 1939b, Pleuroceridae of the Mississippi River Basin exclusive of the Ohio River System. Occ. Pap. Mus. Zool. Univ. Mich., No. 406: 1-4. , 1939c, Pleuroceridae of the St. Lawrence River Basin. Occ. Pap. Mus. Zool., Univ. Mich., No. 404: 1-4. , 1940, The Pleuroceridae of the Ohio River Drainage System. Occ. Pap. Mus. Zool., Univ. Mich., No. 417: 1-21. , 1941а, Distribution of the Gastropods of the Cahaba River, Ala- bama. Occ. Pap. Mus. Zool., Univ. Mich., No. 428: 1-30. ‚ 19416, Pleuroceridae of the small streams of the Alabama River System. Occ. Pap. Mus. Zool., Univ. Mich., No. 427: 1-10. , 1941c, Studies of the Gastro- pod Family Pleuroceridae. VIII. Occ. Pap. Mus. Zool., Univ. Mich., No. 447: 1-13. ‚ 1941d, Two new species of ~ Goniobasis. Occ. Pap. Mus. Zool., Univ. Mich., No. 426: 1-4. , 1942, The Pleuroceridae of the Atlantic Coastal Plain. Occ. Pap. Mus. Zool. Univ. Mich., 456: 1-6. , 1943, The Walker-Beecher paper of 1876 on the mollusca of the Ann Arbor area. Occ. Pap. Mus. Zool., Univ. Mich., No. 475: 1-26. ; 1944, A revision of the Mollusca of Indiana. Amer. Midland Naturalist, 32: 257-326. ‚ 1945, Goniobasis livescens of Michigan. Misc. Publ. Mus. Zool., Univ. Mich., No. 64: 1-26. GOODRICH, C. and VAN DER SCHALIE, H., 1939, Aquatic Mollusks of the Upper Peninsula of Michigan. Misc. Pub. Mus. Zool. Univ. Mich., No. 43: 1-45, 2 maps. HALDEMAN, S. S., 1863, On Strepo- matidae aS a name for a family of fluviatile Mollusca usually confounded with Melania. Proc. Acad. Nat. Sci. Phila., (15): 273-274. HALL, J. E., 1960, Studies on virgu- late xiphidiocercariae from Indiana and Michigan. Amer. Midl. Naturalist, 63(1): 226-245. HEARD, W., 1962, Personal communi- cation (Department of Biological Sci- ences, Florida State University, Tala- hassee, Florida). HENDERSON, Junius, 1935, Fossilnon- marine mollusca of North America. Geol. Soc. Amer., Spec. Pap. No. 3. HOWE, S. W., 1930, A study of the variations in the radula of a snail with particular reference to the size of the median teeth. Nautilus, 44: 53-63. , 1938, A study ofthe radulae of snails of the family Pleuroceridae. Amer. Midland Naturalist, 20(3): 549- 561. JEWELL, D. D., 1931, Observations on reproduction in the snail Goniobasis. Nautilus, 44(4): 115-119. JEWELL, M. E., 1920, The quality of water in the Sangamon River. St. of Ill., Dept. Registr. and Educ., St. Water Surv., Urbana, Ill. Bull. No. 16: 230-246. KRECKER, F.H., 1924, Conditions under which Goniobasis livescens occurs in the island region of Lake Erie. Ohio J. Sci., 24(6): 299-310. KRECKER, F. H. and LANCASTER, L. Nas 1933, Bottom shore fauna of Western Lake Erie, Ecology, 14: 79- 93. LACAZE-DUTHIERS, H., oire sur le pourpre. Zool., 12(4): 1-84. LEE, CHANG-LING and LEWERS, R. M., 1956, The maintenance of Schistosoma mansoni in the laboratory. J. infect. 1859, Mem- Ann. Sci. nat. PLEUROCERA AND GONIOBASIS 77 Dis., 99: 15-20. LISTER, M., 1770, Historiae sive synop- sis methodicae chonchylionum et tabu- larum anatomicarum. ed. 2., pl. 113, Pie. ds MAGRUDER, S. R., 1934, Notes on the life history of Pleurocera canalicul- atum undulatum (Say). Natilus, 48(1): 26-28. , 1935a, Record of a crystal- line style in two fresh-water gastro- pods. Nautilus, 48(3):-100-102. ‚ 19356, The anatomy of the fresh-water Prosobranchiate gastro- pod, Pleurocera caniculatum undula- tum (Say). Amer. Midland Naturalist, 16: 883-912. MELVILLE, R. V., 1960, Proposed fur- ther use of the plenary powers in the case of the generic name Pleurocera Rafinesque, 1818 (Class Gastropoda). Z. N. (S.)83. Bull. 2001. nomencl. 17 (pts 6-8): 170-174. MOORE, J. E. S., 1899, On the diver- gent forms at present incorporated in the family Melaniidae. Proc. Malac. Soc. London, 3: 230-235. MORRISON, J. P. E., 1952, World rela- tions of the melanians (an abstract). Amer. Malacol. Union News Bull. and Ann. Rept. 1951, p 6-9. ‚ 1954, The relationships of old and new world melanians. Proc. U. S. Nat. Mus., 103(3325): 357-394. MORTON, J. E., 1958, Molluscs. Hutchinson Univ. Library, London. NASH, Carroll B., 1954, Heat death temperatures and exposure times of Goniobasis livescens. Science, 119: 773-774. NEEDHAM, P.R., 1938, Trout streams: conditions that determine their pro- ductivity and suggestions for stream and lake management. Comstock Publ. Co., Ithaca, N. Y., 1-233. ODUM, EUGENE P., 1959, Fundamen- tals of ecology. W. B. Saunders Co., Philadelphia, p 125. ORTMANN, A. E., 1909, The des- truction of the freshwater faunas in Western Pennsylvania. Proc. Amer. Phila. Soc., 68(191): 90-110. Pleurocera canaliculata PILSBRY, H. A., 1910, Lithasiopsis: A New Mexican Genus of Pleurocera- tidae, Proc. Malac. Soc. London 9(47): 47-50. PILSBRY, H. A. and RHOADS, В. N., 1896, Contributions to the zoology of Tennessee. No. X. Mollusks. Proc. Acad. Nat. Sci. Phila., 48: 487-506. PLAGET, J., 1929, L’adaptation de la Limnaea stagnalis aux milieux lacus- tres de la Suisse romande. Etude biometrique et génétique. Rev. suisse Zool., 36: 263-531. PRESCOTT, G. W., 1939, Some rela- tionships of Phytoplankton to Lim- nology and Aquatic Biology, In Prob- lems of Lake Biology. Publ. Amer. Assn. adv. Sci., 10: 65-78. ROBSON, G. C., 1922, On the style- sac and intestine in Gastropoda and Lamellibranchia. Proc. malacol. Soc., 15(1): 41-46. ROGERS, T. H., 1924, Electrical methods of staining the radulae of Mollusca. J. Roy. microsc. Soc., 44: 295. ROSEWATER, J., 1958, A pleurocerid index to past collecting in the Ohio and Tennessee River basins with some thoughts for the future. Abstract of paper read at the 24th annual meeting of the Amer. Malacol. Union, Sept., 2-6. A 1959, Calvin Goodrich; A bibliography and catalogue of his spe- cies. Occ. Pap. Moll. Mus. Comp. Zool. Harvard Univ., 2(24): 180-208. , 1960a, The egg mass and gross embryology of Pleuroceracana- liculata (Say, 1821). Ann. Rept. Amer. Malacol. Union, 1959. Bull. No. 26, Jan. 1. _, 1960b, Geographic variation of (Mollusca: Prosobranchia) in the Ohio River Basin. Doct. dissert., Harvard Univ., Cambridge, Mass. , 1961, Preliminary observa- tions on the nervous systems of some Pleuroceridae. Abstract of paper read at the 28th annual meeting ofthe Amer. Malacol. Union, June 19-23. 78 B. C. DAZO RUTTNER, F., 1953, Fundamentals of Limnology. Univ. of Toronto Press. SHOUP, C. S., 1940, Biological and chemical characteristics of the drain- age of the Big South Fork of the Cum- berland River in Tennessee. Rept. Peelfoot Lake Biol. Stat. 4: 76-105. , 1943, Distribution of fresh- water gastropods in relation to total alkalinity of streams. Nautilus, 56(4): 130-134. , 1950, Field chemical exam- ination of the waters in Tennessee streams. J. Tenn. Acad. Sci., 25(1): 4-55. SHOUP; CS. and: PEYTON, “J; “E, 1940, Collections from the drainage of the Big South Fork of the Cumberland River in Tennessee. Rept. Peelfoot Lake Biol. Stat. 4: 106-116. SHOUP, C. S., and PEYTON, J. H. and GENTRY, G., 1941, A limited biolo- gical survey of the O’Bey River and adjacent streams in Tennessee. Rept. Peelfoot Lake Biol. Stat. 5: 48-76. SIMPSON, C. T., 1896, The classifi- cation and geographical distribution of the pearly fresh-water mussels. Proc. U. S. Natl. Mus., 18: 295-343. SIMROTH, H., 1896-1907, Bronn’s Klas- sen und Ordnungen des Thier-Reichs., Bd. 3(2), Gastropoda, Prosobranchia. SPENGEL, J. W., 1881, Die Geruch- sorgane und das Nervensystem der Mollusken. Z. Wiss. Zool., 35: 333- 383. STIMPSON, W., 1864, On the structural characters of the so-called Melanians of North America. Amer. J. Sci. and Arts, 37: 41-53. SUNDERBRINK, O., 1929, Zur Frage der Verwandtschaft zwischen Melaniiden und Cerithiiden. Z. Morph. Okol. Tiere, 14: 261-337. THIELE, J., 1929, Handbuch der Sys- tematischen Weichtierkunde, I. Gustav Fischer, Jena. TRYON, GEORGE W. JR., 1873, Land and fresh-water shells of North America. Part IV. Strepomatidae (American Melanians). Smithsonian misc. Coll. 253: 1-435. TSCHACHOTIN, S., 1908, Die Stato- cysten der Heteropoden. Z. wiss. Zool., 90: 343-422. VAN CLEAVE, HARLEY J., 1932, Studies on snails of the genus Pleuro- cera. I. The eggs and egg laying habits. Nautilus, 46(1): 29-34. , 1933, Studies on snails of the genus Pleurocera. II. The young of P. acuta. Nautilus, 47(2): 48-49. , 1934, Length of life span as a factor in regulating populations. Eco- logy, 15(1): 17-23. VAN DER SCHALIE, H., 1938, The naiad fauna of the Huron River in Southeastern Michigan, Misc. Publ. Mus. Zool. Univ. Mich., 40: 1-83. , 1945, The value of mussel distribution in tracing stream con- fluence. Papers of the Mich. Acad. Sci., Arts, and Letters, 30: 355-373. , 1953, Nembutal as a relaxing agent for mollusks. Amer. Midland Naturalist, 50(2): 511-512. VAN DER SCHALIE, H. and DUNDEE, D. S., 1955, The distribution, ecology and life history of Pomatiopsis cin- cinnatiensis (Lea), an amphibious operculate snail. Trans. Amer. microscop. Soc., 74(2): 119-133. E 1956, The morphology of - Pomatiopsis cincinnatiensis (Lea), an amphibious prosobranch snail. Occ. Pap. Mus. Zool., Univ. Mich., (579): 1-17. WALKER, B. and BEECHER, C., 1876, List of land and fresh-water shells found within a circuit of four miles about Ann Arbor, Michigan. Proc. Ann Arbor Sci. Assn., 1: 43. WALKER, BRYANT, 1917, The type of Pleurocera Rafinesque. Occ. Pap. Mus. Zool., Univ. Mich., No. 38: 1-10. , 1918, Synopsis of the clas- sification of the fresh-water Mollusca of North America, North of Mexico. Misc. Publ. Mus. Zool., Univ. Mich., No. 6: 149, 154-162. WEATHERBY, A. G., 1876, Remarkson the variation in form of the family Strepomatidae with descriptions of new PLEUROCERA AND GONIOBASIS 79 species. Proc. of the Cincinnati Soc., Nat. Hist., (1): 1-12. WELCH, P. S., 1948, Limnological methods. The Blakiston Company. Philadelphia, p 381. WHITE, C. A., 1882, Areviewofthe non- marine fossil mollusca of North America. Ann. Rept. U. S. Geol. Surv. 1881-2: 403-550. , 1877, Report upon the inver- tebrate fossils collected in portions of Nevada, Utah, Colorado, New Mexico and Arizona by parties of the expe- ditions of 1871, 1872, 1873, and 1874. Eng. Dept. U. S. Army, U. S. Geol. Surv. West of the 100th Meridian (Wheeler), 4, Paleontology. , 1886, On the relation of the Laramie molluscan fauna to that of the succeeding fresh-water Eocene and other groups. U.S. geol. Surv. Bull. 34. WIEBE, A. H., 1926, Variations in the fresh-water snail Goniobasis lives- cens. Ohio J. Sci., 26(2): 49-68. , 1928, Biological survey ofthe upper Mississippi River with special reference to pollution. Bull. Bur. crystalline style in Oncomelania. Trans. Amer. Microscop. Sco., 78(3): 262-268. WINSOR, C. P., 1933, The eggs of Gonio- basis virginica Gmelin and Anculosa carinata Brugiére. J. Wash. Acad. Sci., 23(1): 34-36. WOODARD, T. M., 1934, Anatomy ofthe reproductive system of Goniobasis laqueata (Say). J. Tenn. Acad. Sci., 9: 243-259. ‚ 1935, Spermic dimorphism in Goniobasis laqueata (Say). J. Morphol., 57(1): 1-23. ‚ 1940, The function of the apyrene spermatozoa of Goniobasis laqueata (Say). I. The behavior ofthe apyrene and eupyrene spermatozoa under natural and artificial conditions. J. exper. Zool., 85(1). WRIGHT, H. P., 1932, Aquatic Mollusca of the Tippecanoe River system. Part I. Post-glacial migration and present distribution of four species of snails. Ecol. Monographs, Durham, N. C., 2(3): 233-251. ZETEK, J., 1918, The Mollusca of Piatt, Champaign, and Vermillion Counties of Fish., 43(2): 137-167. Illinois. Trans. Ill. Acad. Sci., 11: WINKLER, L. R. and WAGNER, E. D., 165. 1959, Filter paper digestion by the RESUMEN HISTORIA NATURAL Y MORFOLOGIA DE PLEUROCERA ACUTA RAFINESQUE Y GONIOBASIS LIVESCENS (MENKE) Relativamente poco es lo que se conoce acerca de los Pleuroceridae, una familia de caracoles fluviales operculados comün en Norte America, la cual comprende, o esta relacionada con, caracoles melanidos de importancia médica en el Lejano Oriente. La taxonomia, principalmente basada en caracteristicas concholögicas, necesita una revision general. Aqui se estudiala morfologia y biologia comparadas de dos especies clasificadas en géneros diferentes: Pleurocera acuta Rafinesque y Goniobasis livescens (Menke) procendentes de cuatro estaciones cerca de Ann Arbor, Michigan, y de otras localidades adicionales en Michigan y en Ohio. Aunque opérculos y concha en estas dos especies son diferentes, las similari- dades encontradas en sus anatomias internas asi como en los modos de vida son tan extraordinarias que su ubicación en géneros diferentes resulta cuestionable. Diferencias conchológicas, a veces muy marcadas, no estan siempre presentes y en algunos especímenes son poco discernibles. P. acuta es doble entamaño; aun- que la forma general y pigmentación del cuerpo son similares, P. acuta tiene la trompa y región anterior del cuerpo más alargados, con tentáculos largos. El pié es más alargado pero en proporción más pequeño lo cual puede ser una adaptación a la vida de fondo y hábitos excavadores, mientras que G. livescens tiene el pié 80 B. C. DAZO mäs redondeado y grande en relaciön a la cabeza, lo que puede asociarse con sus hábitos reptantes. Manto y órganos sensoriales, organización general del sistema nervioso, morfología de los aparatos respiratorio, digestivo, excretor, circulatorio, y el sistema muscular de ambas especies son muy similares, y difieren sólo en tamaño. En los Pleurocerinae, el macho no tiene órgano copulador; las hembras tienen una cavidad reproductiva en el cuello entre el tentáculo derecho y la base del pié, y una hendidura poco profunda que conduce a esa cavidad. En otros aspec- tos el sistema reproductor corresponde en general conel de los demás prosobran- quios. Los sexos son separados. En ambas especies los órganos reproductores de cada sexo son casi idénticos, ocupando la misma posición. Los espermatozoos son de dos tipos: eupirenos, típicos, y los apirenos, atípicos; los últimos se trans- fieren a la hembra mediante espermatoforos. . Ecologicamente los pleuroceridos norteamericanos requieren aguas claras. Ex- ceptuando Goniobasis todos prefieren habitats amplios. Usualmente viven en fondos de arena o barro en áreas al abrigo de las corrientes Goniobasis livescens se encuentra en casi todos los ambientes dulceacuícolas limpios de tipo permanente (manantiales, lagos, rápidos) y con frecuencia se encuentran crepando en rocas. Observaciones en el ambiente natural y en el laboratorio indican que el aparea- miento tiene lugar en otoño. Cuando la temperatura desciende a menos de 5%C los animales invernan, y la actividad es reasumida, comenzando a desovar, en la primavera. Los huevos de P. acuta se depositan en masas cubiertas de arena, de diferente forma y tamaño, y el número de huevos por masa varía entre 1 y 19. G. livescens pone los huevos de uno a uno, algunas veces dos o tres seguidos, pero depositados varios centimetros aparte y generalmente quedan cubiertos con una fina capa del substrato. P.acuta produce más huevos diarios (15) que С. livescens (4), pero tiene un período de puesta más corto, de abril a junio (G. livescens de abril hasta mediados de agosto). El crecimiento es más pronunciado durante el primer año (de 0.3 a 10 mm en P. acuta; 0,3 a 3,8 mm en С. livescens). Cuando los са- racoles criados en el laboratorio alcanzaron madurez sexual a los dos años, el tamaño era de 16,7 y 7 mm de largo respectivamente, despues de lo cual no se observó crecimiento apreciable. Caracoles de ambientes naturales eran más grandes. La duración normal de la vida es tres años, pero quizá pueda extenderse a cuatro. En P.acuta la proporción de sexos es de dos a uno en favor de las hembras, y en G. livescens es de cinco a uno. Como otros prosobranquios, ambas especies de alimentan de algas verdes y rojas, desmidos y diatomeas. Larvas de trematodes, principalmente de Azygiidae, Allocreadiidae y Aspido- gastridae, con frecuencia y abundancia parasitan el hígado, gonada, canal alimenticio y otros órganos. MALACOLOGIA, 3(1): 81-102, 1965. GROWTH AND STUNTING IN ONCOMELANIA (GASTROPODA: HYDROBIIDAE)! Henry van der Schalie and George M. Davis Museum and Department of Zoology University of Michigan, Ann Arbor, Michigan, U. S. A. ABSTRACT These data deal with the problem of raising large numbers of Oncomelania spp. rapidly, efficiently and in a predictable way as a means for facilitating studies of Schistosoma japonicum in the laboratory. Previous reports indicate that the growth rates attained in other laboratories were about 0. 3-0.4 mm per week under conditions that produced excessive mortality (38% in one publication). The culture procedures here described stimulate fairly uniform growth rates of about 0.65 mm per week with a mortality rate below 10%. Optimal growth is obtained when 1 or 2 young newly hatched snails (2. 0-2.5 whorls) are placed in a 9 cm Petri dish. A patty of unsterilized mud, which is alkaline, fine textured and supports the growth of naturally occurring diatoms, is placed in the center of this dish. After the addition of water, the dish is covered and placed under light of about 150 foot candles cycled for about 10 to 12 hours per day. No food additives are used; the temperature is maintained at about 250 3 20C. Increasing the number of snails per culture to 5 and 10 caused stunting,i.e., a distinct decrease in the rate of growth and development. Correlated with stunting was a decrease in the rate of gonadal maturation, a lack of development of the sex organs, and an increased mortality. The shell of the stunted snail is indistinguishable from that of a normal one; consequently, the dwarfed snail can only be identified if one knows its age. ' Optimal growth is dependent on the interaction of the following variables: light, an adequate volume of container, suitable soil and a thriving microflora. When the light and the volume of the container are kept constant, a soil high in calcium and capable of supporting an abundance of green algae and diatoms is most critical. INTRODUCTION Two major difficulties encountered in studying Schistosoma japonicum in laboratories far removed from endemic areas are: 1) the length of time neces- sary for the parasite to mature in the snail; 2) dependable and efficient methods for rearing species of Oncomelania, so that a sufficient supply of snails of uniform age and size for full scale experiments will be assured. Because of these difficulties studies on 5. japonicum have lagged far behind simi- lar investigations involving S. mansoni. The latter matures in Australorbis gla- bratus in about 1 month. Ritchie et al. (1963) have shown that A. glabratus can also be grown from the egg to maturity in one month. In comparison 5. japonicum matures in Oncomelania in 3-4 months and the time reported for growth from egg hatching to maturity for species of Oncomelania is gener- ally in excess of 5 months (DeWitt, 1952). In our program, culture techniques have been developed which enable not 1This work was carried out under the sponsorship of the Commission on Parasitic Diseases, Armed Forces Epidemiological Board; and was supported by the Office of TheSurgeon General, Department of the Army. (81) 82 VAN DER SCHALIE AND DAVIS only a predictable high rate of production but also a means for insuring a rapid rate of growth and maturation with a minimal rate of mortality for the 4 so-called species of Oncomelania. In an attempt to increase efficiency in rearing young snails we increased the density of the young snails per culture. It was found that this crowding caused a pronounced degree of stunting, which was evident not only in terms of a de- creased rate of growth but also in a decreased rate of maturation of the reproductive system. The latter was demonstrated in histological and ana- tomical studies. Dwarfing among various organisms raised under crowded and unsuitable environments has been observedfor well over 100 years. While such stunting has been studied in several aquatic pulmonate snails, the fact that it also occurs in amphibious prosobranchs has not been previously demonstrated. A more comprehensive review of the lit- erature dealing with stunting of aquatic snails can be obtained inthe publications of the following authors: Colton, 1908; Forbes and Crampton, 1942; Chernin and Michelson, 1957 a,b; Wright, 1960; Berrie and Visser, 1963. The purpose of this paper is to demonstrate: (l) the culture conditions which produce optimal growth in young Oncomelania; (2) the effects of crowding on growth and development of O. for- mosana; and (3) the necessity for understanding the relationship between the size and age in species of On- comelania. This informationisprovided to demonstrate that adequate criteria for measuring optimal physiological conditions and normal growth are neces- sary in experiments which involve inter- mediate hosts in the many phases of schistosomiasis research. For example, it should be understood that among stunted snails neither size nor maturity is related to the actual age of those snails. Furthermore, one cannot tell a normal snail from a stunted snail on the basis of its shell alone. These data are designed to provide an ade- quate means for detecting the kinds of environment and the conditions which usually cause stunting. MATERIALS AND METHODS Snails studied Stunting was observedinO, nosophora, O. formosana, and O. hupensis;however, O. formosana only was used for the more intensive studies and experiments. All of the snails were laboratory reared young which were removed from paren- tal cultures at about 1 week of age, when they had 2.0-2.5 whorls. At 2 whorls the height of the shell was about 0.5 mm. The young were then placed in the different types of culture chambers where they were maintained for at least 8 weeks. Culture chambers It has been generally recognized that the young of Oncomelania tend to be aquatic and are usually found submerged in the water provided in their aqua- terraria for at least 2 weeks of their early development. Taking this tendency into consideration, 2 types of cultures were used for rearing the young; a plastic tray culture and a Petri dish culture. The former was modified from the aquaterrarium used by DeWitt (1951, 1952) and closely resembles that developed by Moose and Williams (Moose, personal communication, 1964). This container is a moulded plastic tray often used by florists as planters. The tray is 11” x 7.5” x 2.5” BBicmı 19 cm x 6 cm). The soil used was ob- tained from the habitat of Pomatiopsis cincinnatiensis, a North Americar amphibious snail related to Oncomelania. This soil was alkaline and supported a high level ofalgalproductivity (green algae and diatoms). Its texture varies as follows: sand, 40-69%, silt, 13-42%; clay 7-24% (van der Schalie and Getz, 1962). It was found that the cultures were maintained much better if the soil GROWTH AND STUNTING IN ONCOMELANIA 83 had a minimum of sand. The soil was smoothed into a firm, flat, rectan- gular mass at one end of the tray giving an area of about 45 square inches. The edge of the mass sloped at a 25° angle into the reservoir. The depth of soil was 0.5 - 0.75 inches. This reservoir was filled with about 200 cc of boiled, filtered pond water and the tray was then covered with a sheet of plexiglass. The central area of the cover was bored with 160-170 holes, each 2.5 mm in diameter, which provided for gaseous exchange and the escape of some water vapor. A 1 cm hole was drilled through the lid to provide access to an area over the reservoir. This opening served to accommodate an aeration tube. The reservoir was actively aerated at all times. The culture thus prepared was then heated in an oven at 600 C for 2 hours; this baking eliminated a problem often caused by oligochaetes, without killing the algae. In unheated cultures the worms tended to “tear up” the soil with their burrowing activity so that, within a week, their presence was evident by isolated piles of worm castings. Usually within a month at least 80% of an untreated culture was seriously disrup- ted because of worm activity. The Petri dish culture chamber has an inside diameter of 9 cm and a depth of 1.9 cm. A mound of mud, from the source previously mentioned, was placed in the center of the dish where it was stroked with a spatula to form a smooth and solid surface. This mound was 1.5 cm high and it had a basal diameter of 6 cm. A clear and open space of 1.5 cm was left between the glass wall and the base of the soil mound and it served as a reservoir to which about 40 cc of pond water was added. These cul- tures were not baked since such a small amount of soil does not harbor a sufficient number of worms to cause any appreciable damage to the culture, and since such cultures were used for only 8 weeks. The dish was finally covered with the usual petri dish cover. Active aeration is not necessary. Both types of cultures were illuminated for 10-12 hours daily by a 40 watt, white, ‘‘cool,’’ fluorescent tube with an intensity of 100 to 150 foot candles, suspended 10 inches above the cultures. The radiation from the light maintained the temperature in the Petri dish cul- tures at 25°C + 20; that of the plastic tray cultures at 249 t 20C. EXPERIMENTS The Effect of Light on Growth For all 4 of the so-called species of Oncomelania it was found that growth was fastest when a single young specimen was placed in a Petri dish and the culture was maintained under light. This development is shown in the following experiments with O. formosana. Two experiments (la and 1b) were designed to determine the effect of light on the survival and growth of young O. formosana, which differed only in that one was terminated in 7 weeks, the other in 8. In each case 3 groups of 50 snails each (2.0-2.5 whorls) were arranged, as follows: one group was placed in constant dark (pitch-black), a second in constant light, and the third in normal, natural, room-level light; these snails were maintained singly in Petri dishes. The intensity of the constant light varied from 100to 125 foot candles; the variance depended on the distance of the dish from the light source. Room- level intensity varied from 35 to 45 foot candles during the day and was reduced to about 10 at night. The temperature: for cultures maintained in the dark and room-level light was 24° + 2° С Че. оу 1°C less than those exposed to the radiation warmth of the light. At the end of each ex- periment the snails were removed, their sex determined, weight and length mea- sured, and the percentage of survival 84 VAN DER SCHALIE AND DAVIS calculated. The results are shown in Table 1. The data showed that the most rapid growth occurred in snails maintained under constant light. During the ex- periment lasting 7 weeks, males grew 0.77 mm per week and females 0.80. By the 8th week the logarithmic phase of growth was over and little further increase could be expected. In the ex- periment covering 8 weeks, males main- tained under constant light had grown with a rate of 0.68 mm per week and the females 0.78. Males and females maintained in the dark or at room- level light for the 7 weeks had growth rates of about 0.44 and 0.39 mm per week, respectively. In the experiment lasting 8 weeks, rates of growth were increased only for snails maintained in the dark or room-level light. Males and females in the dark grew with a rate of about 0.49 mm per week while males and females in room-level light grew with rates of about 0.60 mm per week. The increase in growth rate for snails maintained 8 weeks under room-level light over that of snails maintained 7 weeks in the same environment was most likely due to variability in the fluctuation of light in the room-level light situation as well as a slight growth spurt in the 8th week in the second experiment. The relatively high mortality rate of snails reared under constant light was due, in part, to the detrimental effects of algal accumulation in the cultures. Constant light induced algal proliferation with the following negative effects: (1) algae overgrew young snails, hindering movement and causing death; (2) dense algal mats tended to limit the soil sur- faces for browsing; and (3) living snails, which were often covered with algae, were difficult to find. Although growth rates were maximal under full 24-hour illumination, it was concluded that this advantage was offset by disadvantages of too luxuriant a proliferation of fila- mentous algae and that better balance TABLE 1. Differential growth and survival of Oncomelania formosana reared singly in Petri dish cultures under different conditions of lighting Experiment la Sex ration 2/3 Average wt in gm* Average length in mm Percentage survival Experiment 1b Sex ratio Average wt in gm* Average length in mm Percentage survival *including shell o - Standard deviation : Snails reared 7 weeks Snails reared 8 weeks : Dark Constant 1/0.78 1/0. 81 141.3 0. 0062 0. 0054 0. 0208 0. 0068 0. 0059 0. 0227 3. 5(01. 07) 3. 0(01. 20) 5. 9(00. 15) 3. 6(01. 02) 3. 3(00. 29) 6. 1(00. 21) 57 88 76 1/0.55 1/1. 05 1/13 0. 0089 0. 0127 0. 0191 0. 0114 0. 0162 0. 0273 4. 3(01. 35) 5. 2(00. 28) 5. 9(a0. 14) 4. 6(01. 48) 5. 3(60. 39) 6. 7(00. 15) 48 82 64 GROWTH AND STUNTING IN ONCOMELANIA 85 TABLE 2. Mortality in 2 series of Oncome- lania formosana cultured in Petri dishes at varying densities No. snails | tality at used Experiment between development and survival might be obtained by shortening the duration of direct illumination. As will be seen in subsequent experiments where the duration of light was reduced to 10- 12 hours per day, there was a decreased algal growth with a decided decrease in mortality. The data appear to show that increased temperature is correlated with an in- crease in the growth rate. It is not yet possible in this paper to discuss quantitatively how light, temperature, and food supply interact to provide an environment for optimal growth. How- ever, it is already evident that tempera- ture differences per se between 24°C and 26°C were not sufficient to account for the observed differences in growth. The Effect of Population Density on Growth. We were anxious toincrease efficiency by rearing more snails per area; to this end, 2 series of experiments (A and B) were set up. The snails were kept in Petri dishes under equal and optimal environmental conditions (10- 12 hours of light daily), only the number of snails per dish varied. At the end of 8 weeks (1 group at 9 weeks) the snails were removed from culture and the length of shell, sex, and whorl count were recorded for each snail. A sub- sample was chosen at random; the speci- mens were fixed in Bouins, sectioned, and stained with Hematoxylin and Eosin. These sections were then analyzed for degree of gonad development. TABLE 3. Comparative growth of Oncomelania formosana cultured in Petri dishes at varying densities, at 8 weeks pene se $ $ 8 №. snails рег dish 2А 5.8 7.0 0. 65 3.7 5.9 0.40 2.7 5.1 0. 25 5.8 3.8 3.1 - 5.8 6.9 0. 66 4.0 5.7 0. 44 2.7 4.9 0. 28 1 5 10 il 5 10 2B d 2 $ 5 $ 10 2 5 10 Average No. of Growth in Whorls mm/week 6.8 0.56 5 5.9 0. 41 3 5.3 0. 39 86 VAN DER SCHALIE AND DAVIS NUMBER OF SNAILS Ne BE A re, 10 Per Dish .. ..... . 5 Per Dish 1 Per Dish 0 1 2 A S 6 PIS LENGTH OF SHELL IN MM FIG. 1. Histogram showing growth in terms of size distribution among Oncomelania formosana cultured at 1, 5 and 10 per Petri dish for 8 weeks. (Experiment 2A). Experiment 2A. Young snails (2.0- 2.5 whorls) were reared in Petri dishes with 199 reared singly, 340 distributed in groups of 5 per dish, and 450 main- tained at 10 per dish. When the snails were removed from culture after 8 weeks and the data tabulated, the effects of increased density were pronounced. Crowding resulted in increased mor- tality (Table 2). It also produced a distinct decrease in shell size and whorl count. The average length of shell, the whorl counts for the males and females, as well as their average rates of growth for the 8-week period are tabulated in Table 3. The distributions around these mean values are given in Figs. 1 and 2. The average growth rate for snails reared singly was 0.56 mm per week for the males and 0.65 mm per week for the females. Under conditions of crowding this rate was only 0.41 and 0.40 for males and females, respectively, when the animals were reared at 5 snails per dish; and did not exceed 0.39 and 0.25 for males and females, respectively, at a density of 10 per dish. A histological study of the gonads GROWTH AND STUNTING IN ONCOMELANIA 87 10 Per Dish > о w& о 20 NUMBER OF SNAILS 5 Per Dish 1 Per Dish ie Gy ORC a ER Thi N E 7:8 NUMBER OF WHORLS FIG. 2. Stunting as shown by a decrease in the number of whorls of Oncomelania formosana when males and females were maintained for 8 weeks at 1, 5 and 10 per Petri dish (Experiment 2A); size distribution is shown in Fig. 1. in a random series of snails from these 3 groups indicated that the degree of maturation was correlated directly with the size of the snail. For purposes of analysis each serially sectioned snail was assigned a rating into one of the 4 following categories of gonad tissue growth: undifferentiated, differentiated, almost mature, and mature. In the undifferentiated group (Fig. 3A) gonadal tissue was either entirely lacking or the primordia observed could not be positively identified as gonadal tissue. The differentiated series (Figs. 3B, C, D) included those developmental stages ranging from the first recognizable gonad tissue to the initial formation of oocytes or primary spermatocytes. The gonads 88 VAN DER SCHALIE AND DAVIS GROWTH AND STUNTING IN ONCOMELANIA 89 which were almost mature (Figs. 3E, G) contained secondary spermatocytes, spermatids, and a few scattered mature sperm in the male; in the females the oocytes were developed to about half- size. The fully mature gonads (Figs. 3F, H) were usually packed with mature sperm or well developed oocytes. In the case of the males, snails 3 mm or less in length were usually “undifferentiated” or barely “differen- tiated,”, while those 3.0-4.2 mm long were “almost mature;” among those larger than 4.2 mm, some 64% were “mature.” It was of interest to find that some snails were still “almost mature” when they were 6.0 mm in length. In any case, development was distinctly slower in the females; snails 4.4 mm and smaller were “undifferen- tiated” or just “differentiated;” among those measuring 4.5 mm-5.5 mm only 50% were “differentiated;” 33% “almost mature,” and17% “mature.” These data were collected with respect to size only and not by the culture condition in which they were maintained. Correlations of gonadal development with each culture condition are discussed in the next ex- periment. Experiment 2B. While experiment 2A was in progress we noticed that 2 young snails per Petri dish apparently grew as rapidly as 1 per dish. The experiment was then repeated by placing 92 snails at 2 per dish, 100 at 5 per dish, and 100 at 10 per dish. As in the previous experiment, snails were removed from culture at the end of 8 weeks for collect- ing data excepting 16 of the snails reared 2 per dish, which were continued in culture for an extra week. As shown in Table 2 analogous mortality rates occurred in the 2 experiments. Like- wise, the mean lengths and whorl counts for each group of snails (Table 3) were of the same magnitude. The varia- tions around these means are shown graphically in Figs. 4and5. Considering the average growth in mm per week for the 8-week period (Table 3), males reared 2 per dish had a greater rate of growth compared with those 1 per dish, the former being 0.66 and the FIG. 3. Differences in gonad development and maturity of Oncomelania formosana reared under varying conditions of crowding in 8 week old males (A, B, C, E and F) and females (D, G and H). A. Male with an undifferentiated gonad (arrow) which could be either a male ora female (greatest width at middle of whorl 180 u). Differentiated gonad with male tissue just forming in a strip about 25 y wide. C. Male tissue differentiated to form spermatocytes (greatest height of gonadal lobe 40 u). D. Differentiated female gonad with lobes just forming (lower arrow, oocyte 35 u long). The early stages in differentiation in the female appear similar to those for males in B. E. Almost mature male with spermatids and a few scattered sperm in the sections (gonadal tissue 200 и high). F. Fully mature male with spermatids and clusters of sperm; arrow points to a mass of sperm 43 y in diameter. G. Almost mature female gonad with lobes filled with oocytes in early stages of development; some have little yolk (right arrow shows one 28 u in diameter), others have accumulated yolk (left arrow). H. Fully mature female gonad with gonad with eggs full of yolk (arrow indicates an oocyte 78 y long). 90 VAN DER SCHALIE AND DAVIS NUMBER OF SNAILS 10 Per Dish QE 5 Per Dish 2 Per Dish 0 1 Ри A 7 LENGTH OF SHELL IN MM FIG. 4. Histogram showing growth in terms of size distribution among Oncomelania formosana cultured at 2, 5 and 10 per Petri dish for 8 weeks (Experiment 2B). latter 0.56, while the females at this density level had an almost equal rate: 0.66 against 0.65. The rates ofdevelop- ment in the snails reared at greater densities were also quite similar in the 2 experiments. Results of the histological analysis are presented in Table 4. Of the gonads among those snails reared 2 per dish none was “undifferentiated,” 23% were “differentiated,” 45% were “almost mature” and 29% were “fully mature,” The extra week of development for the 16 snails (13 were sectioned) also pro- duced an increase in maturation so that 39% were “almost mature” and 61% “fully mature.” At the end of 8 weeks more than 80% of the snails reared 5 and 10 per dish had “undifferentiated” gonads. It is concluded that a popula- tion of 1-2 snails per 9 cm diameter Petri dish is vastly more favorable in every respect than one of 5 or 10 snails per dish. The Effect of Population Density on Development, in Plastic Tray Cultures The plastic trays had, for a long period of time, proved suitable for maintaining adults; they were also fairly GROWTH AND STUNTING IN ONCOMELANIA 91 Experiment 2 10 Per Dish 5 Per Dish NUMBER OF SNAILS 2 Per Dish DIAZ AB 2487576, 7280) 12.345 7 NUMBER OF WHORLS FIG. 5. Stunting as shown by a decrease in the number of whorls of Oncomelania formosana when males and females were maintained for 8 weeks at 2, 5 and 10 per Petri dish (Experiment 2B); size distribution is shown in Fig. 4. : adequate in encouraging the production area. of young. A tray provides about 8 x To ascertain whether the increased the total area of a Petri dish and, surface area of soil and water would when established, about 19 x as much provide an environment stimulating op- soil surface area above the water line timal growth for a large number of with about 4 x as much water surface young snails, 100 young snails were 92 VAN DER SCHALIE AND DAVIS TABLE 4. Comparison of the effect of different conditions of culture on the gonadal develop- ment of Oncomelania formosana State of Gonad Experi- | Type of Snails |Duration of ment culture per of A Undiffer- | Differ- | Almost eulture culture entiated | entiated | mature Petri dish cad 8 months 6 months & & 3 eZ Petri dish 2 months 8 months TABLE 5. Showing arrested growth and mortality in a group of 100 Oncomelania formosana raised in common, and the favorable effect of subsequent separation and culturing in pairs Petri dishes for last 2 months 6+2 = 8 months (b) Plastic | Plastic Tray Culture = Culture *87 snails split into 2 groups: (a) 43 to a new tray culture; (b) 44 at 2 per dish to Petri dishes. No. snails at end of given period of time Average length (mm) Average whorl count % Mortality 87* 2.7 5. 0 6 FIG. 6. Growth differences in both size and whorlcount among a population of Oncomelania formosana at different times and under different culture conditions (Experiment 3). A. Plot showing growth after 4 months in the Plastic Trays. B. Growth after an additional 2 months. C. Approximately half of the above group was continued another 2 months (a total of 8 months) in a new tray. D. The second half of the group was transferred and reared at 2 per Petri dish for an additional 2 months, (total of 8 months in culture). NUMBER OF SNAILS GROWTH AND STUNTING IN ONCOMELANIA 4 months 6 months 8 months Plastic Tray 8 months Petri Dish ES о SC La OP AN AMEN Иа LENGTH OF SHELL IN MM NUMBER OF WHORLS 93 94 VAN DER SCHALIE AND DAVIS established in such a culture. All of these young were derived from one parental plastic tray culture. Since at the end of 8 weeks little growth was noted, the snails were maintained in culture for an additional 8 weeks. At the end of this period of 4 months all of the snails were removed, meas- ured, and their whorl counts determined. Table 5 and Fig. 6A show that these 4-month-old snails were more stunted than they would have been if they had been placed in groups of 10 per Petri dish (see Fig. 1). The mortality was 8% These snails were then returned to their original tray and observed for an additional 2 months when they were again removed and measured. Another 6% of the snails had died and they showed only little additional growth(Table 5, Fig. 6B). After these 6 months of culture, the snails were divided into 2 groups; 43 were placed in a new tray and returned to culture under light (10-12 hours per day) (Group A); 44 were placed in Petri dishes, with 2 per dish, also under light (10-12hours per day) (Group B). At the end of 8 weeks (the animals were then 8 months in culture) the snails were removed from their cultures and measured. The 43 snails of Group A, in the trays, showed a 16% mortality. Their average length was 3.0 mm and the average whorl count was 5.0 (Table 5; Fig. 6C). The growth of these snails was still less than. that of the snails maintained in groups of 10 per Petri dish for 8 weeks. No young were pro- duced in the plastic tray culture over the 8-month period. An analysis of the gonads of 15 individuals of this group revealed that all of them were in the “undifferentiated” category (Table 4). There was no mortality among the 44 snails of Group B, in the 22 Petri dishes. Their average length was 5.8 mm and the average whorl count was 6.5 (Fig. 6D; Table 5). This growth pattern was equal to that expected for snails reared with 2 per dish for 8 weeks. An analysis of the gonads of 17 individuals in this group revealed 23% “undifferentiated,” 35% “almost mature,” 23% “fully mature” (Table 4). These results, when compared with those of experiment 2B show a lag in the development of some of those snails which had been suppressed in growth and development for 6 months. They were slower in passing from an “un- differentiated” gonadal condition to one of “differentiation.” However, the same magnitude of difference existed among the “mature” or “almost mature” spec- imens found in both experiments. It is concluded that although the plastic trays will maintain adult populations they are not suitable for rearing young snails which show extreme retardation and mortality. Analysis of Stunting and Whorl Count In Oncomelania, the formation of a varix on the shell occurs when the snails have reached a length which can be correlated with gonadal development in the category of “mature” or “almost mature.” The varix is a pronounced thickening of the outer lip and after it is formed little further growth occurs. The following question now arose: is it possible to examine a snail which does not have a varix and determine if it is stunted? In a number of non- related experiments we had collected records on the length of snails grown under optimal conditions and the ac- companying whorl counts. The number of snails measured at each whorl stage, along with the average length per whorl count, is recorded in Table 6. The average length per whorl countis plotted and the standard deviation for the length of shell at each whorl count is recorded in. Fig, 1. The whorls were counted to the nearest half whorl by the following procedure. The snail was held with the apex up and with the outer lip to the right; observations were made under a dissect- ing microscope. The whorl count was GROWTH AND STUNTING IN ONCOMELANIA 95 marked the final whorl. Snails which had been stunted by rearing in groups of 10 were used to compare the average length per whorl count with the normal condition as plot- ted in Fig. 7 and Table 6. From this comparison it can be seen that the num- ber of whorls increases in a regular manner when the snail is in an unfavor- able environment, but the rate of shell formation is decreased. In other words, the size or height of each whorl is not reduced in the stunted snail but the rate of growth and speed of whorl formation is greatly reduced compared with the normal condition. It follows, therefore, that one cannot determine the age of a snail by its size alone. It is thus not о 2 3 7 5 7 = = possible to differentiate a stunted snail WHORLS from a snail grown under optimal con- ditions, if both have the same size or FIG. 7. The relationship between the length Whorl count. We find, in Oncomelania, as THE STANDARD DEVIATION FOR THE LENGTH OF EACH WHORL (mm) LENGTH OF SHELL IN MM of the shell of Oncomelania formo- Ritchie et al. (1963) found for Australor- sana and the whorl count for snails bis glabratus, that shell size is a more grown under optimal conditions. important criterion for maturity thanage. Development of Reproductive Organs in then begun at the edge of the outer lip Relation to Size and progressed up the shell. The posi- tion of the tip of the apical whorl Both normal and stunted snails were TABLE 6. The average length of shell per whorl count for normal and stunted Oncomelania formosana snails Stunted Snails Whorls No. of snails Average No. of snails Average measured length (mm) measured length (mm) =~] — © TAPP AAP Pwo ww py O1 © O1 © 1 © O1 © 1 © 1 © D O1 # W & ND N M Hi © I 96 VAN DER SCHALIE AND DAVIS TABLE 7. A comparison of degree of development of reproductive organs (lengths in mm) among 5 stunted and 1 normal male and female Oncomelania formosana 8 months old 2 months old (stunted) (normal) d Specimen il 2 3 4 5 1 Shell 2.5 6.5 Gaia none 1 ne у found as Prostate 0. 24 И Verge 0. 22 3.4 ? Specimen 1 Shell 6.5 Gonad 2.6 Accessory gland 5.7 — = not measured. used to study the anatomy of the male and female reproductive systems. We found that stunting or suppression of growth hindered the development of the reproductive organs in a pronounced manner. Many organs, such as the gonad, prostate, verge, accessory gland, spermathecal duct, bursa copulatrix, etc., would not develop beyond their rudimentary stages regardless of age if the environment was such as to retard growth. An example of this re- tardation in development is shown in Table 7 where 5 males and 5 females were chosen as representatives of many that were found to be similarly stunted. These snails were taken fromthe plastic tray culture of Experiment 3 when they were 8 months old. The normal indi- viduals were chosen at random from Petri dishes where they had beenreared 2 per dish for 2 months. In the stunted males the verge was just a slight projection rising from the “neck” region behind the tentacles; the gonad was often undetected in gross dissections. In females in their normal state of growth the accessory gland is a thick organ found along the full length of the mantle cavity; it opens beside the anus just posterior to the edge of the mantle collar. In the stunted snails this gland was only a slender thread of tissue extending, in many cases, no further than half way towards the mantle collar from the rear of the mantle cavity. The whole reproductive system tends to remain undeveloped among the animals thich have become stunted in growth. DISCUSSION Culture Chambers. The plastic tray culture in many respects represents a small and sim- plified aquaterrarium compared with that described by Vogel (1948) and DeWitt (1952); it is also similar to the culture chamber used in the 406 Medical Gen- eral Laboratory of the U. S. Army Gen- eral Command, Japan (Moose, 1964). Containers of this type which simulate the natural environment have been used for many years (see Sugiura, 1933). The concept of using a Petri dish as a simplified culture chamber is also not new. Sandground and Moore (1955) used GROWTH AND STUNTING IN ONCOMELANIA 97 10 cm and15 cm diameter Petri dishes; they emphasized the difficulty in main- taining and observing young snails in a large tank-like aquaterrarium. Con- sequently, they constructed an environ- ment in their dishes resembling that in their aquaterrarium, to provide a sloping soil bank and a small reservoir of water. For food they used strips of filter paper impregnated with sodium alginate. Komiya et al. (1959) used a 9 cm Petri dish as a “simple breeding method for Oncomelania...” under vary- ing conditions. They had a sloping soil bank, which they described as good. for adults, and a flattened soil mass covered by a Sheet of water, which they described as good for the young. They recommended putting 8 to10adults in such a container and 16-20 young were not considered too many if they were 3 mm or less in height. Cul- tured diatoms and rice powder were added for food. It should be emphasized that rearing young snails to maturity in the labora- tory is a problem quite different from that of maintaining adults and encour- aging the production of young. Those who previously recommended Petri dish cultures failed to give any quantitative data on the production of young, nor did they give any rates of growth for young snails. The problems relating to the stunting of these snails were not recog- nized so that the slow rates of growth were generally taken for granted. The Petri dish culture method described here was tailored to meet the specific pro- blems of rearing young snails to matur- ity efficiently as well as in a predic- table manner. One cannot rear large numbers of young snailsinanaquaterra- rium without inducing stunting. Rates of Growth and Mortality Table 8 was prepared to show the rates of growth in Oncomelania for- mosana, O. nosophora, and O. hupensis obtained by various workers under both field and laboratory conditions. The rates of growth in this table were calculated from the data presented by these authors and are represented as rates converted to mm per week. It is pertinent to discuss how these rates were induced as compared with conditions that were found to stimulate optimal growth. Since |TABLE 8. Comparison of growth rates for 3 species of Oncomelania, as reported in the literature Growth calculated] Laboratory |Laboratory|Calculated growth per week, in mm light condition O. hupensis O. O. formosana | nosophora (field) (field) (field) (field) (field) 26 (field) | Kojima 0.30 11962, Moose et al. 1965, van der Schalie & Davis, this paper fluctuating 98 VAN DER SCHALIE AND DAVIS O. nosophora, O. hupensis, andO. for- mosana are allrelatively similarinsize, their rates of growth under optimal conditions in the laboratory were ob- served to be about the same magnitude during the first 8 weeks in culture. This basic similarity enables us to make some useful comparisons with the data presented in Table 8. We found that the growth of these species of Oncomelania (starting at 0.5 mm length) under optimal conditions follows a distinct sigmoid curve with a reduction in growth rate at about 6.5 to 7 weeks. Calculations of change in length per time beyond 8 weeks would greatly reduce values of mm growth per week. It is evident that, in 1933, Sugiura provided an accurate estimate of growth for O. nosophora in the field, when the animals were in their logarith- mic phase of growth; these data were later confirmed by Hosaka et al.(1959). The low rate obtained by McMullen et al. (1951) under field conditions re- sulted from measuring the change in mode length when the initial measure- ment involved snails already 4.0-5.0 mm long. Snails of this size are pass- ing out of the ‘‘log phase’’ of growth and the increase in length in mm per week decreases markedly. Li (1953) gave data which can likewise be accounted for in this manner. In the laboratory, it is now evident that rates of growth of only 0.3-0.4 mm per week during the first weeks of life indicate stunting and conditions unsuitable for optimal growth. In the data presented by the Laboratory (406) Report (1962) crowding and the use of room-level light probably accounts for the low rates of growth (0.3-0.5 mm per week). Komiya and Kojima (1961) state that they reared their snails in growth experiments under conditions described by Komiya et al. (1959; dis- cussed above under“Culture Chambers”). They prescribed using room-level light with the avoidance of direct sunlight. They placed a single 2 mm Snail in a 10 cm Petri dish. Temperatures varied from 15°C to 25°C during their ex- periments. These unusually low temp- eratures and the use of room-level light probably account for their low growth rate (0.3mm). They gave no mortality data. Komiya and Kojima (1961) stated that Chi and Wagner (1957) presented no temperature records and that the latter data showed greater growth than that obtained by themselves. Actually, these authors reported that they ran their experiments at 26°C under constant light. Comparing the curves for growth presented by Chi and Wagner with those of Komiya and Kojima during the first 8 weeks of culture, the order of magnitude of growth in mm per week was essentially the same: about 0.3. Chi and Wagner (1957) used constant light from a 20 watt fluorescent (day- light) tube 9-10inches above the cultures. Newly hatched snails were reared at 26° C in a 7 ml pH beaker witha small quantity of mud, a-piece of filter paper, and some spring water. When the snails reached 3.5 whorls they were transferred to a 50 mm Petri dish (1 per dish). They do not state whether the mud was sterilized although in meth- ods prescribed earlier by Wagner and Wong (1956) the soil, sand, and gravel were Sterilized. In spite of the pro- vision of constant light and the 26°C temperature they induced only a low growth rate and they stated that the growth rate “varied greatly between snails of the same age.” The mor- tality was 38%. The variance in growth, low growth rate; and excessive mortal- ity indicate an environment unsuitable for the snails. The poor growth per- haps could be attributed to sterile soil and lack of a proper source of food energy. Mortality serves as an excellent cri- terion for determining whether the lab- oratory environment is optimal. In ex- periment 1 our mortality rates were 24 and 36% for snails reared under con- stant light; this high loss was cor- related with an excessive algal condi- GROWTH AND STUNTING IN ONCOMELANIA 99 tion. As shown in Table 2, by lowering the amount of light, the excessive algal condition was checked and mortality dropped below 10% for snails reared 1 or 2 per dish. Our experience has also shown that in the routine handling of large numbers of young snails mor- tality may increase due to mechanical injury to the snails. Overcrowding Crowding also produces increased mortality in addition to the stunting and Suppression of sexual maturity. Large culture chambers such as the plastic trays become inefficient when only small numbers of snails are reared in them, so as to avoid stunting, because of the necessity for active aeration, their bulk, and increased maintenance. Like- wise, the use of a small 5 cm Petri dish proved unsuitable as a relatively rapid algal growth and soil breakdown lead to suppressed growth andincreased mortality. The interaction of the factors causing stunting were not studied. Such a study would involve a quantitative inves- tigation of the relationships of food supply, the effects of accumulated waste material, and the effect of increased physical interaction between snails ina confined area. We noted that increased mortality for snails reared at higher densities was due, in part, to an increased ten- dency of young (2.5 whorls) snails to climb up on the glass above the water line. At that size they were inconspi- cuous, were easily overlooked, and died from desiccation. This behavior may stem either from their avoidance of accumulated waste or result from in- creased snail interaction. The increased tendency for crowded Snails to climb from their culture cham- ber is related to growth. Pesigan, et al. (1958) found that O. quadrasi continuously ingested food throughout the 24-hour cycle so that the snails changed gut contents every 3-10 hours. We made a 24-hour study in the field on the feeding of Pomatiopsis cincinna- tiensis, a local species closely related to Oncomelania. The North American snails ate continuously and voided in excess of 15 fecal peilets per hour every hour. In crowded cultures the climbing activity of the snails results in a loss of energy to them as they are moving or are dried to the sides of the containers, not feeding. This Significant loss of energy is possibly the cause of reduced growth rates. Conditions Favoring Optimal Growth Optimal conditions for rapid growth and development of Oncomelania are based on the interaction and proper balance of such factors as light, soil, volume of the environment, and food source. It is not yet possible here to discuss quantitatively the many dif- ferent interactions among these vari- ables. Experimental evidence is needed to explain how these several factors combine to produce a favorable environ- ment. If one considers light and the volume of the culture as constant, then soil and its accompanying microflora are the critical variables. Excluding the possible influence of trace elements on growth, we find that a basic soil of fine texture with a high calcium con- tent, and capable of supporting a high proliferation of diatoms is the most suitable for culturing Oncomelania. It is most important that decaying organic material be present as well as the at- tendant bacterial decomposers. Diatoms in large numbers (such as the 10,000- 500,000 per gram of dried soil in the river bank mud we used) provide a constant turnover of decaying matter. In Experiment 1, snails reared on this soil and water in constant dark grew at a rate of about 0.4 mm per week. After 8 weeks in the dark the soil was analyzed and was found to con- tain sparsely scattered algal resting cells and only a very few living diatoms. These snails could survive and they did grow on the organic material present with its accompanying decomposing flora. 100 VAN DER SCHALIE AND DAVIS In a previous study (Davis, 1962) fecal pellets surgicallyiremoved from the intestines of snailsf were; cultured under optimal laboratory conditions. Steriletechniques wereused in removing the pellets. Many species of diatoms and algae were cultured from this fecal material. It is evident that many healthy cells passed through the snail unaffected by its digestive processes. These cir- cumstances suggest that it is the weak- ened, dying, and decaying cells provided by a rich diatom flora which serve as a source of energy for these snails. Davis (1962) provided an experimental model to determine if such a process is operative in terms of energy flow. Studies in the Medical General Lab- oratory 406 (Report for 1955) also note this voiding of undigested algal cells (green and blue-green). The positive value of diatoms as food for Oncomelania in nature was indicated by Mao (1958) and Komiya et al. (1959); Stunkard (1946) also used diatoms as a food additive in rearing snails. Dazo and Moreno (1962) stated that O. quadrasi “appears to be a herbivore; its diet consists mainly of green algae and dia- toms.” They also state that O. quadrasi rarely ingested blue-green algae “al- though these were abundant in the areas studied.” The Medical General Lab- oratory (406) reported (1955) that “as a group the green algae appeared to be more acceptable as food than the blue-green algae.” They found that some blue-green algae appeared to be toxic for young snails; they did not test diatoms. ACKNOWLEDGEMENTS Several technical assistants devoted many hours of arduous work culturing these Oncomelania, measuring them, and gathering data used for this report. For this assistance we are especially indebted to: Berton Roffman, Robert Wakefield and Andrew Bratton. The program itself was sponsored by the Commission on Parasitic Diseases (an affiliate of the Armed Forces Epidem- iological Board); their continued sup- port has made these studies possible. LITERATURE CITED BERRIE, A. D. and VISSER, S. A., 1963, Investigations of a growth- inhibiting substance affecting a natu- ral population of freshwater snails. Physiol. Zool., 36(2): 167-173. CHERNIN, E. and MICHELSON, E. H., 1957a, Studies on the biological con- trol of Schistosome-bearing snails. II. The effects of population density on growth and fecundity in Australorbis glabratus. Amer. J. Hyg.,65(1):57- 70. , 1957b, Studies on the bio- logical control of Schistosome-bearing snails. IV. Further observations on the effects of crowding on growth and fecundity in Australorbis glabra- tus. Amer. J. Hyg., 65(1): 71-80. CHI, L. W. and WAGNER, E. D., 1957, Studies on reproduction and growth of Oncomelania quadrasi,O.nosophora, and O. formosana, snail hosts of Schistosoma japonicum.Amer. J. trop. Med. and Hyg., 6(5): 949-960. COLTON, H. S., 1908, Some effects of environment on the growth of Lym- naea columella Say. Proc. Acad. nat. Sci. Phil., 60(3): 410-448. DAVIS, G. M., 1962, A theoretical model for measuring secondary pro- ductivity in mollusks. Ann. Report, Amer. malacol. Union, 29: 4. DAZO, B. C. and MORENO, R. G., 1962, Studies on the food and feed- ing habits of Oncomelania quadrasi, the snail intermediate host of Schis- tosoma japonicum in the Philippines. Trans. Amer. micr. Soc., 81(4): 341-374. DeWITT, У. В., 1951, Two devices use- ful for maintaining aquaterraria. Tur- tox News, 29: 58-59. , 1952, Pomatiopsis lapidaria, its occurrence in the Washington D. C. area and its laboratory rearing in comparison to that on Oncome- GROWTH AND STUNTING IN ONCOMELANIA 101 lania spp. J. 326. FORBES, B.S. and CRAMPTON, H. E., 1942, The effects of population den- sity upon the growth and size in Lymnaea palustris. Biol. Bull., 83: 283-289. HOSAKA, Y., IJIMA, T., SASAKI, T., HASHIMOTA, I. and TSURUTA, J., 1959, The growth of Oncomelania nos - ophora in the natural habitat. Jap. J. Parasit., 8: 745-748 (text in Jap- anese; English summary). KOMIYA, Y., KOJIMA, K. and KOYAMA, T., 1959, A simple rearing tech- nique of Oncomelania in Petri dish. Jap. J. Parasit., 8: 721-724 (text in Japanese, English summary). KOMIYA, Y. and KOJIMA, K., 1961, The growth difference depending upon the sex of Oncomelania nosophora and O. hupensis, the vector snails of Schistosoma japonicum. Jap. J. med. Sci. and Biol., 14(4):201-204. LI, S. Y., 1953, Studies on schisto- somiasis japonica in Formosa. II. The bionomic of Oncomelania formo- sana, a molluscan intermediate host “of Schistosoma japonicum. Am. J. Hyg., 57: 30-45. MAO, C. P., 1958, Research on schis- tosomiasis japonica in China. Amer. J. trop. Med. and Hyg., 7(1): 58-62. MCMULLEN, D. B., KOMIYAMA, S., and ENDO-ITABASHI, E., 1951, Ob- servations on the habits, ecology, and life cycle of Oncomelania noso- phora, the molluscan intermediate host of Schistosoma japonicum in Japan. Amer. J. Hyg., 54: 402-415. Medical General Laboratory (406), U. S. Army Medical Command, Japan, Profession- al Reports, 1954, 1955, 1962. MOOSE, J. W., WILLIAMS, J. E. and FLESHMAN, P., 1962, Rice cereal as sustenance for rearing oncomelanid snails in the laboratory. J. Parasit., 48(1):68. MOOSE, J. W., 1964, Personal communi- cation concerning the Med. Gen. Lab. (406) Report of 1962. Parasit., 38(4):321- PESIGAN, T. P., HAIRSTON, N. G., JAUREGUI, J. J., GARCIA, E. G., SANTOS, A. T., SANTOS, B. C., BESA, A. A., 1958, Studies on Schis- tosoma japonicum infections in the Philippines. 2. The molluscan host. Bull. Wld Hlth Org. 18: 481-578. RITCHIE, L. S., 1955, The biology and control of the amphibious snails that serve as intermediate hosts for Schis- tosoma japonicum. Amer. J. trop. Med. and Hyg., 4(3): 426-441. RITCHIE, L. S., BERRIOS-DURAN, L. A., and DEWEESE, R., 1963, Biolo- gical potentials of Australorbis gla- bratus: Growth and maturation. Amer. J. trop. Med. and Hyg., 12(2): 264- 268. SANDGROUND, J. H. and MOORE, D. V., 1955, Notes on the rearing of Oncomelania spp. in the:laboratory. J. Parasit., 41(1): 109-113. STUNKARD, H. W., 1946, Possible snail hosts of human schistosomiasis in the United States. J. Parasit., 32: 539-552. SUGIURA, S., 1933, Studies on biology of Oncomelania nosophora (Robson), an intermediate host of Schistosoma japonicum. Mittlgn a. d. path. Inst. d. med. Fakult., Niigata, Japan, 31: 1-18 VAN DER SCHALIE, H. and GETZ, L. 1962, Distribution and Natural History of the snail Pomatiopsis cincinnati- ensis (Lea). Amer. Midland Nat., 68(1): 203-231. . VOGEL, H., 1948, Uber eine Dauerzucht von Oncomelania hupensis und Infek- tionsversuche mit Bilharzia japonica. Z. f. Parasitenkunde, 14: 70-91. WAGNER, E. D. and WONG, L. W., 1956, Some factors influencing egg laying in Oncomelania nosophora and Oncomelania quadrasi, intermediate hosts of Schistosoma japonicum. Amer. J. trop. Med. and Hyg., 5(3): 544- 558. WRIGHT, C. A., 1960, The crowding phenomenon in laboratory colonies of freshwater snails. Ann. trop. Parasitol., 54: 224-232. 102 VAN DER SCHALIE AND DAVIS RESUMEN DESARROLLO NORMAL Y ARRESTADO EN ONCOMELANIA (GASTROPODA, HYDROBIIDAE) Se suministran datos concernientes al problema de la crianza de Oncomelania en grandes cantidades, rapida, eficientemente y de una manera predictable, para facilitar el estudio de Schistosoma japonicum en el laboratorio. Informacion pre- via obtenida en otros laboratorios indica que la proporción de crecimiento era de 0.3 - 0.4 mm por semana, en condiciones que producían gran mortalidad 38% en ciertos casos). El procedimiento de cultivo aqui descripto, estimula un crecimiento uniforme de unos 0.65 mm por semana con una proporción de mortalidad menor del 10%. Crecimiento óptimo se obtiene cuando 1 o 2 caracoles recién nacidos (con 2 a 2.5 vueltas) se aislan en una cápsula de Petri de 9 cm. En el centro de la cápsula se coloca una pequeña masa de tierra de textura fina sin estirilizar, que siendo al- calina favorece el desarrollo de las diatomeas de su natural contenido. Se agrega agua y la cápsula se cubre, ubicándola la luz de 150 bujías en ciclos de 10a 12 horas diarias. La temperatura debe mantenerse entre 25% + 20 C.; no se agrega ningun alimento. El aumento de individuos por cada cultivo a 5 y 10 produjo impedimentos en el desarrollo, correlacionado con reducción en la madurez gonal, falta de desarrollo en los organos sexuales, y mayor mortalidad. La concha de los caracoles asi afectados no se distingue de la de los normales, y en consecuencia el individuo retardado sólo puede identificarse si se conoce su edad. El crecimiento óptimo depende de la interacción de los siguientes variables: luz, adecuado volumen del recipiente, substrato en buenas condiciones y próspera microflora. Cuando luz y volumen se mantienen constantes, un substrato rico en calcio y capaz de mantener algas verdes en abundancia es un factor muy crítico. | MALACOLOGIA, 3(1): 103-110, 1965 FONTELICELLA (PROSOBRANCHIA: HYDROBIIDAE), A NEW GENUS OF WEST AMERICAN FRESHWATER SNAILS! WO: Gregg? and D. W. Taylor Los Angeles, California, 0.5. A. U. 5. Geological Survey Menlo Park, California, U.S. A. ABSTRACT Fontelicella, g. п. , (subfamily Hydrobiinae) includes 3 subgenera: Fonteli- cella s.s. (type F. californiensis, sp. n.), with 8 species, Pliocene to Recent, of western U. S. A. and Baja California, México; Natricola, subg. п. (type Pomatiopsis robusta Walker, 1908), with 3 species living in the Snake River drainage of Idaho and Wyoming, U. S. A.; and Microamnicola, subg. n. (type Amnicola micrococcus Pilsbry, 1893), with 1 species living in the Amargosa River drainage of southern Nevada and southeastern California, U. S. A. Among adequately described species, the most similar is Cincinnatia integra (Say) of eastern U. S. A.; it differs in details of verge, radula, pigmentation, shell, and foot. The described features of Fontelicella spp. include general form, locomotion, behavior, pigmentation, external morphology, radula, verge, eggs, and habitat. Arrangement of melanin and calcareous granules in the head region is a particularly useful source of specific characters that has been generally neglected in previous work on the family. “ The generally small and characterless shells of the Hydrobiidae have rarely been sought by collectors in western North America. There are even less biological data available for this un- popular group than in many others, so from species to family rank their classification is obscure. Our studies have aimed at a partial survey of the western American species, trying to understand their histories and distri- bution, and to fit the known fossil record into a biological framework. Preparation of a detailed, illustrated account of the species will require further work, but our observations so far are comprehensive enough to permit definition of a new genus. We publish this paper to validate use of the names in other papers in progress. DIAGNOSIS Family Hydrobiidae Subfamily Hydrobiinae Fontelicella 3 Gregg and Taylor, new genus Diagnosis. Shell 2.5-8 mm long in adults, rimate or imperforate, narrowly elongate to conic or globose, with 3-6 whorls, the aperture 20-40% of total shell length. No sculpture except for IContribution No. 4, Western American Freshwater Mollusks Program, Institute of Malacology. “Research by Gregg was partially supported by National Science Foundation grant GB-1653. 3Latin fons, fontis, a spring; helix, helicis, a snail, and the feminine diminutive, -ella. Hence, little spring snail. The name refers to a characteristic habitat of the group. (103) 104 GREGG AND TAYLOR minute growth striae. Embryonic shell helicoid, umbilicate, with about 1 1/2 whorls. Verge bifid, with a narrow, melanin-pigmented penis, and a usually wider, virtually unpigmented, ductless accessory process on the left. Ac- cessory process usually with a terminal glandular lobe, subterminal constriction, and additional glandular areas in the form of ridges, lobules or papules. Radula - with formula 15 to 30: 17 to 24: 3 to 6-1-2 to 3: 3 to 7-1-3 to 7 1 from the second marginal to the central tooth. Eggs laid singly in smooth, unornamented capsules 0.3-0.5 mm in diameter, either free in the substratum or appressed to a firm surface. Type. Fontelicella californiensis Gregg and Taylor, new species. Remarks. The names applied most commonly to species here referred to Fontelicella have been Paludestrina lon- ginqua (Gould) and P. stearnsiana Pils- bry. One of these two species might therefore have been selected as type of the genus. Amnicola longinqua is based on fossil shells and may well be com- posite. Although the living Paludestrina stearnsiana is a recognizable Fonteli- cella, no topotype material.can be col- lected because the growth of Oakland and other cities has destroyed the original habitats. We consider F. stearnsiana a valid species on the basis of near- topotypes, but it is more prudent to fix as type species one whose type locality is likely to be available to future students of the group. The assignment of species described from fossil shells (Amnicola longinqua, А. micra, A. pilsbryana, and Hydrobia truckeensis), and of the anatomically unknown Paludestrina cedrosensis and Pomatiopsis intermedia, to the genus is based on shell characters only. Our evaluation of these shell characters is based on knowledge of the anatomy of practically all described western American Hydrobiidae as well as many undescribed forms. DESCRIPTION OF GENUS Study of numerous species (in several genera) of western American Hydrobi- idae has revealed sets of characters that unite the group we establish as Fonteli- cella, and distinguish if from other groups. The more conspicous characters are listed in the generic diagnosis. Less striking features that are commontothe described and undescribed species we have examined are summarized below. General form, locomotion, behavior. The elongate or globosely conic shell 2.5-8 mm long in adults is borne free of the substratum, with the apex directed upward and posteriorly to the right, so that the axis of the shell forms an angle of about 309-450 with the long axis of the foot. In dorsal view when the snails are crawling, the snout, tentacles, and eyes are visible in front of the shell. In different species or in different de- grees of extension the broadly rounded posterior end of the foot and the anter- ior corners of the foot may also be visi- ble. Compared to other Hydrobiidae we have seen the snails crawl relatively rap- idly; they move smoothly and do not show the stepwise gait of the Pomatiopsinae. The tentacles are relatively long and slender, rod-shaped, tapering slightly or imperceptibly to blunt tips, about 2/3- 3/4 as long as the shell aperture. Cilia may occur in definite longitudinal rows, or scattered with no obvious arrangement. The tentacles are borne diverging at an angle of 700-1000 (900 common), and usually are in vertical or horizontal movement. They move both above and below a plane parallel with the substratum, and often touch the substratum as if sensing it. We have seen no rhythm in motion ofthe tentacles in any species examined except F. hen- dersoni, in which the tentacles move up and down alternately. In crawling the snail keeps its snout appressed to the substratum and moves it from side to side. This lateral movement is inconspicuous when the FONTELICELLA G.N. 105 snail is crawling rapidly, but when mov- ing slowly and feeding the whole head turns from side to side. In animals with less heavily pigmented snouts the action of the radula inside can be seen as the animals browse. Both direct observation of living snails, and the worn radular teeth show that the snails rasp food from a hard surface as well as pick up fine particulate matter. Field and laboratory observations, and examination of fecal pellets, suggest that the species of Fontelicella crudely select detritus from soft mud or browse microorganisms from the surface of stones, dead wood, and decaying leaves. When observed under a microscope, specimens of Е. hendersoni showed a positive tropism to the heat or light of the lanp. No other species studied showed this behavior, and it is probably significant that F. hendersoni is the only known Fontelicella of a warm spring habitat. Pigmentation. The externally visible parts of the body are gray to deep purple-black, from a variably dense suffusion of fine melanin granules. No other pigment is known in Fontelicella, in contrast to Lithoglyphus, which has both fine melanin granules and larger, yellow-pigment granules. The other elements of color in Fontelicella are internal organs, ingested food, fecal pellets, algal or other coating on the outside of the shell, and abundant cal- careous granules scattered through most of the head-foot mass and concentrated behind the eyes. The pattern of pigmentation is speci- fically diagnostic in nearly all species of Fontelicella we have examined, and there are even more marked differences between the genera of Hydrobiidae. Our work thus yields results similar to those of Muus (1963), who found differences in pattern between 3 Danish species of Hydrobia. Although each colony of snails may have considerable variability in the density of melanin from one individual to another, in nearly all species the arrangement of melanin and calcareous granules in the head region is distinc- tive. Future work оп Hydrobiidae should include critical attention to these fea- tures as a source of taxonomic char- acters. The externally visible body of species of Fontelicella varies in color from gray to deep purple-black, but generally the melanin is not uniformly diffused. The dorsal and lateral aspects of the snout and the operculigerous lobe are most deeply pigmented, and ends and sides of the foot, and ventral aspect of the snout less pigmented. The tentacles may be pigmented with diffuse melanin granules like the head, or paler in constrast, but lack discrete patches or bands. When the tentacles are deeply pigmented and bear a discrete ciliary tract, the ciliated strip is outlined asa less heavily pigmented area. The eyes are set in swellings on the outer bases of the tentacles, and appear as intense black spots within a clear area. A dense, conspicuous aggregation of white granules adjacent to each eye is characteristic of the genus. These granulose areas often give the appear- ance of eyebrows when they are narrow regions immediately above and behind the eyes. They also may be larger and more diffuse, extending posteriorly on the dorsum of the head, or they may lie in front of the eyes on the lateral aspect of the tentacles. The sole of the foot in ventral and lateral views can be seen to be unpig- mented. When the upper surfaces of the foot are deeply pigmented the color change is abrupt, at a line running around the edge of the foot just above the sole. The lips are lightly pigmented in contrast to the snout. Pigmentation of the mantle, organs in the mantle cavity, and upper head-foot varies considerably from species to species. The mantle may be opaque, or so lightly pigmented that the stomach, intestine, and outlines of the ctenidial lamellae are visible. The density of melanin decreases from the foot upward, so that the body stalk and floor of the 106 GREGG AND TAYLOR mantle cavity are virtually unpigmented. The free portion of the penis is densely suffused with melanin granules and is in contrast to the light, unpigmented accessory process. Head-foot mass. The sole is about 2-3 times as long as wide when the snail is crawling rapidly, but varies in proportions with rate of travel. It is broadly rounded at the hind end, with parallel. sides, and widened by 2 auri- culate lobes at the anterior corners. The anterior border of the sole is straight or slightly concave. An anterior pedal groove traverses the anterior edge of the foot; into this groove the anter- ior mucus glands discharge their se- cretions. Scattered through the connective tissue of the head-foot mass, mantle border, and externally visible walls ofthe pallial cavity are numerous relatively large hyaline granules. These are visible only where there is no dense epithelial suf- fusion of melanin, and likely are spread ‘through all the head-foot mass, except that they are rare in the tentacles. The highly contractile snout is about 1/3 as wide as the foot, flattened-oval in cross-section, and more convex dor- sally. Ordinarily it is appressed to the substratum in front of the foot, but the anterior edge of the foot canbe stretched farther forward than the end ofthe snout. Two fleshy pads at the end of the snout together form a roughly oval area in anterior view, narrower dorsally. They are divided in the median plane by the slit of the mouth, and set off from the more deeply colored snout by a narrow constriction. Mantle cavity. The mantle cavity has the usual organization of hydrobiid snails. From the roof of the cavity the ctenidium hangs down as a Series of triangular lamellae forming a ridge that divides the cavity lengthwise into 2 approximately equal parts. To the left on the mantle lies the osphradium, and to the right close to the junction of the roof and floor of the cavity is the rectum. The pallial oviduct lies between the rectum and right side of the mantle cavity in the female. The large verge fills much of the cavity in the male. Circulation in the mantle cavity is simple, with a fairly strong inhal- ant current on the left side and a perceptibly weaker exhalant current out of the right side. Ciliated epithelium carries particles to be rejected from the floor of the mantle cavity down the right side of the body stalk to the edge of the sole, along which they are carried to the hind end of the foot. This ciliated area has suffi- cient force to carry a fecal pellet up out of the mantle cavity and to the rear of the foot when a snail is held on its back. The exhalant current is usually inadequate to this task. Cil- iated epithelium on the left side also carries particles down the body to the edge of the sole and thence posterior- ly. The ctenidium consists ofabout 14- 30 triangular lamellae hanging down from the mantle intothe mantle cavity. It is nearly colorless and extends from just inside the thickened mantle border to the rear end of the mantle cavity. The fecal pellets are ovoidor spindle- shaped, as in all Hydrobiidae seen, and arranged lengthwise in the rectum. They contrast with the cigar-shaped pellets of Pleuroceridae that are arranged transversely in all but the most distal part of the rectum. Representative measurements of the fecal pellets of Fontelicella are .12 x .28 mm (ЕР. hendersoni) and .11 x .25 mm (F. cali- forniensis). They are composed of vegetable fibres and tiny rock particles, with no evident internal structure. The pellets are voided singly as a rule, but sometimes 2 pass through the anus linked by a strand of mucus and fe- cal material. Verge. The verge is attached to the floor of the mantle cavity, to the right of the midline and behind the right tentacle. It is relatively large compared to other organs in the mantle FONTELICELLA G.N. cavity, and although directed for- ward does not usually protrude from the cavity. The forward direction of the verge is in contrast to that of some other genera, such as Lith- oglyphus and Amnicola, in which the verge curves to the left from its at- tachment and extends through the me- dian plane. The relative size of the accessory process and free portion of the penis vary greatly. In Fontelicella stearnsi- una the accessory process is about 1/4 as long, and slightly narrower than the free penis. In Р. idahoensis it is twice as long and about 6 times as wide as the base of the free part of the penis. Most species of Fontelicella have an accessory process with compli- cated ornament of small discrete glandu- lar areas that appear as lowraised areas, circular or elongate in plan, or as secondary lobes that may reach nearly the size of the rest of the accessory process. The differences in pattern of these glandular areas provide many of the characters used in separation of Species. Radula. The odontophore bears about 55 (50 - 67 observed in adults) rows of 7 teeth each. The central tooth is approximately quadrilateral, about 2/3 as high as wide, and widest at the base between the ventrolateral angles. The reflection of the tooth is serrated into a large, central, lanceolate cusp with 3-7 progressively smaller cuspsoneither Side according to the species. The strong basal ridge of the central tooth has a strong basal denticle at its arch on either side. The basal margin is prolonged in the center into a tongue- Shaped process extending about as far as the ventrolateral angles. The pos- terior surface of the tongue-shaped pro- jection is concave, and successive teeth interlock thereby. The lateral tooth has a broad peduncle, and 6-9 cusps on the reflection. The longest and widest cusp is in the middle; 2-3 are medial and 3-6 lateral according to the species, all becoming smaller 107 toward the sides. The base of the tooth is bowed ventrally so that there is an area convex ventrally, concave dorsally, by which successive teeth of the lateral series interlock. A ridge runsfrom this ventrally concave projection to the dorsal margin of the peduncle. The first marginal tooth is falcate, with a broad peduncle anda blade bearing 17-24 long, slender, sharp-pointed cusps. A ventrally projecting ridge, concave dorsally, extends nearly the whole length of the peduncle and interlocks successive first marginals. The second marginal tooth is slightly narrower, about as long as the first marginal, but lacks an interlocking ridge. The blade of the tooth is shorter, ser- rated into 15-30 cusps that are shorter and more slender than those of the first marginal. Operculum. The operculum is as in most Hydrobiinae seen, corneous, pau- cispiral, with a subcentral nucleus near- er the basocolumellar edge. COMPARISON Cincinnatia is the only genus of ade- quately described Hydrobiidae that shows clear similarities to Fontelicella. Fea- tures common to C. integra (Say) as described by Berry (1943) and to species of Fontelicella are a verge with one duct (vas deferens), a relatively large accessory process, and relatively small penis. Differentia are shown in Table 1. Subgenus Fontelicella s.s., new subgenus Diagnosis. Shell small for the genus (2.5-5 mm long, 3-4 whorls in adults). Accessory process usually a little longer than free penis. Habitat small springs, seepages, or small streams, in soft mud among dense aquatic plants, on rocks or sticks. Eggs laid in capsules usually free, or sometimes appressed to substratum, usually difficult to see be- cause of a coating of foreign matter. Type. Fontelicella (s. s.) californiensis 108 GREGG AND TAYLOR Fontelicella imperforate or narrowly per- forate distinctly auriculate most heavily pigmented part of body. TABLE 1 Shell distinctly umbilicate Foot not auriculate Snout lighter colored than head Penis not heavily pigmented with melanin Accessory process Central tooth Lateral tooth Gregg and Taylor, new species. Distribution. Western United States and northwestern Mexico, in the Great Basin and Pacific drainages. California; Nevada, southeastern Oregon, southeast- ern Idaho, Utah, Arizona, and Baja California. Known from rocks as old as middle and perhaps early Pliocene. This is the most widespread and speci- ose group of west American Hydrobiidae. Referred species. Fontelicella (s. s.) californiensis Gregg and Taylor, new species. Southern California and northwestern Baja Cali- fornia. Fontelicella (s.s.) cedrosensis(Pilsbry), 1927 (Paludestrina). Cedros Island, Baja California. Fontelicella (s. s.) intermedia (Tryon), 1865 (Pomatiopsis). Owyhee River, Malheur County, Oregon. Fontelicella (s. Ss.) longingua (Gould), 1855 (Amnicola) in part. Subfossil, Col- orado Desert, southern California. Fontelicella (s. s.) micra (Yen), 1946 (Amnicola). Pliocene, Salt Lake Group, Bear Lake County, Idaho. Fontelicella (s. s.) pilsbryana (Baily and a) with no terminal lobe set off by subterminal constriction b) about 6 times width of penis base c) lacking glandular tissue heavily pigmented with melanin a) nearly always with terminal lobe set off by subterminal constriction b) 2-6 (usually 2-3) times width of penis base c) with several discrete areas of glandular tissue 3 to 7-1-3 to 7 1-1 2 or 3-1-3t0 6 Baily), 1952 (Amnicola). ¿Amnicola pils - bryi Baily and Baily, 1951, non Walker, 1906). Bear Lake Valley, southeastern Idaho-northeastern Utah. Fontelicella (s.s.) stearnsiana (Pilsbry), 1899 (Paludestrina). San Francisco Bay region eastward to Sierra Nevada foot- hills, California. Fontelicella (s. s.) truckeensis (Yen), 1950 (Hydrobia). Middle or early Plio- cene, Truckee Formation, Churchill County, Nevada. Subgenus Natricola4 Gregg and Taylor, new subgenus Diagnosis. Shell large for the genus (4-8 mm long, 4-6 whorls in adults). Accessory process about twice as long as free penis. Habitat large springs, rivers, or lakes, in mud or sandbottom, on gravel, or onaquatic vegetation. Eggs laid incapsules appressedto substratum. * atin natrix, natricis, a water snake;-cola, inhabitant. From the occurrence of most of the species in the Snake River drainage. FONTELICELLA G.N. Type. Fontelicella (Natricola) robusta (Walker), 1908. Distribution. Snake River drainage of western Wyoming and southern Idaho; Harney Lake Basin, eastern Oregon. Referred species. Fontelicella (Natricola) hendersoni (Pilsbry), 1933 (Amnicola), Harney lake basin, Harney County, Oregon. Fontelicella (Natricola) idahoensis (Pilsbry), 1933 (Amnicola), Snake River, southwestern Idaho. Fontelicella (Natricola) robusta (Walk- er), 1908 (Pomatiopsis), Jackson Lake, Teton County, Wyoming. Subgenus Microamnicola® Gregg and Taylor, new subgenus Diagnosis. Shell small for the genus (1.5-1.7 mm long, 3 1/2 whorls in adults), more nearly ovate. Accessory process beyond fork of verge about half as long as free penis, tapering to a rounded distal end, lacking terminal glandular lobe, subterminal constriction, or other ornamentation. Free penis rod- like, with parallel sides and rounded distal end, heavily pigmented and visible through shell and mantle. Habitat springs, on rocks and aquatic vegetation. Eggs laid in free capsules, less heavily coated with adherent particles than in Fonteli- cella s. s. Type. Fontelicella (Microamnicola) micrococcus (Pilsbry, in Stearns, 1893) (Amnicola). Distribution. Amargosa River drain- age, in southern Nye County, Nevada; eastern Inyo County, and northern San Bernardino County, California. Referred species. Only the type Species is known in this subgenus. Fontelicella (s. s.) californiensis® Gregg and Taylor, n. sp. Diagnosis. Shell about 3-4 mm long 5From the Greek word for small, and Amni- cola. 6Named for the Californias, to which it is restricted. 109 in adults, elongate-ovate, with 4 whorls. Free part of penis moderately pigmented, with a dorsal ridge extending nearly to the tip. Accessory process about as long as free part of penis, and about 3 times as wide at the fork, with a terminal lobe, subterminal constriction, and vari- able ornamentation, usually including a dorsal lobule, 1-5 dorsal longitudinal ridges, and a ventral transverse ridge. Main body of verge with a dorsal trans- verse ridge that may unite with the dorsal ridge on the accessory process or penis. Type. University of Michigan Museum of Zoology catalog number 220000. Campo Creek, San Diego County, Cali- fornia, 0.6 mi. east of Mountain Empire Dam, W 1/2 SW 1/4 sec. 19, Т. 18 $., В. 5 ES. W. O. Gregg, W. В. Miller, 25- III-1962. Distribution. Southern California and adjacent Baja California. From the southern Sierra Nevada (on the western slope only) through the western Trans- verse Ranges and coastal plains to the Laguna Mountains. This species is characteristic of perennial springs and small streams in the mountains. It occurs in both the Pacific Ocean and interior drainages. REFERENCES BAILY, J. L., JR. and BAILY, В. I, 1951, Further observations on the Mollusca of the relict lakes in the Great Basin. Nautilus, 65:46-53, 85- 93, Pl. 4. and 1952, Amni- ~ cola pilsbryana, new name. Nautilus, 65: 144. BERRY, E. G., 1943, The Amnicolidae of Michigan; distribution, ecology, and taxonomy. ‚Misc. Publ. Mus. Zool. TLand in the United States is commonly di- vided into “townships”, each6 miles square, that are numbered according to tier (T.) and range (R.) from standard base lines and meridians. A township is divided into 36 “sections”, each section (sec.) 1 mile square. 110 GREGG AND TAYLOR Univ.Mich., 57: 1-68, Pl. 1-9. GOULD, A. A., 1855, New species ofland and fresh-water shells from western (N.) America. Proc. Boston Soc. Nat. Hist., 5:127-130. MUUS, B. J., 1963, Some Danish Hydro- biidae with the description of a new species, Hydrobia neglecta. Proc. malac. Soc. London, 35:131-138. PILSBRY, H. A., 1899, Catalogue of the Amnicolidae of the western United States. Nautilus, 12:121-127. 1927, Expedition to Guadalupe Island, Mexico, in 1922. Land and freshwater mollusks. Proc. Calif. Acad. Sci., ser 4, 16: 159-203, Pl. 6- 12. 1933, Amnicolidae from Wy- oming and Oregon. Nautilus, 47:9-12, Pl. 2, Fig. 1-10. STEARNS, R. E. C., 1893, Report on the land and fresh-water shells col- lected in California and Nevada by the Death Valley Expedition, including a few additional species obtained by Dr. C. Hart Merriam and assistants in parts of the southwestern United States. N. Am. Fauna, 7:269-283. TRYON, G. W., JR., 1865, Descriptions of new species of Amnicola, Pomatiop- sis, Somatogyrus, Gabbia, Hydrobia, and Rissoa. Am. J. Conch., 1:219- 222, Pl. 22, Fig. 5-13. WALKER, BRYANT, 1908, Pomatiopsis robusta n. sp. Nautilus, 21:97. YEN, T.-C., 1946, Late Tertiary fresh- water mollusks from southeastern Id- aho. J. Paleont., 20:485-494, Pl. 76. 1950, A molluscan fauna from the type section of the Truckee For- mation. Am. J. Sci., 248:180-193, 1 Pi, RESUMEN FONTELICELLA (PROSOBRANQUIA, HYDROBIIDAE) UN NUEVO GENERO DE CARACOL FLUVIAL DEL OESTE AMERICANO Fontelicella g. n. (subfam. Hydrobiinae) incluye 3 subgeneros: Fontelicella s.s. (tipo F. californiensis sp. п.) con ocho especies del Plioceno al Reciente en el oeste de Estados Unidos y Mexico (Baja California); Natricola subg. n. (tipo Po- matiopsis robusta Walker, 1908) con tres especies en el sistema del Rio Snake de Idaho y Wyoming; Microamnicola subg. n. (tipo Amnicola micrococcus Pilsbry, 1893) con su única especie viviente en el sistema del Rio amargosa del sur de Nevada y sureste de California. Entre especies adecuadamente descriptas la mas similar es Cincinnatia integra (Say) del oriente de Estados Unidos; difiere en detalles de la verga, rädula y pigmentaciön, concha y pie. Los aspectos descriptos de Fontelicella incluyen forma general, locomociön, comportamiento, pigmentaciön, morfologia externa, radula, verga, huevos y habitat. El agrupamiento de granulos de melanina y calcio en la region cefalica es de particular utilidad como caracter especifico, y no habia sido tomado en cuenta en previos trabajos sobre esta familia. MALACOLOGIA, 3(1): 111-181, 1965 ЗНДОПАРАЗИТИЧЕСКИЙ МОЛЛЮСК ASTEROPHILA JAPONICA RANDALL ET HEATH (PROSOBRANCHIA: MELANELLIDAE) И ЕГО СВЯЗЬ С ПАРАЗИТИЧЕСКИМИ БРЮХОНОГИМИ Е. Н. Грузов (Зоологический институт АН СССР) Резюме Строение эндопаразитического моллюска Asterophila japonica Randall & Heath подверглось сильному изменению в процес- се приспособления к образу жизни. Существующие сведения об его анатомии во многом не верны, а его систематическое поло- жение осталось невыясненным. | Моллюск обитает в стенке тела ряда морских звезд /puc.1/, распространенных вдоль азиатских берегов Тихого океана. На поверхности женских особей прикрепляются карликовые нео- ‘гтенические самцы /рис. 3, 4 B/, строение которых до сего вре- мени оставалось неисследованным. В теле моллюска удается различить все основные отделы туло- вища брюхоногих : голову, внутренностный мешок и ногу /рис. 6, 9/, олнако это деление сильно замаскировано. Голова лишена щупалец и глаз. У самок она иногда вытянута, в хобот /puc. 3, 14 A/, но чаще этот орган оказывается недо- развитым /рис. 2/ или совсем исчезает /рис. 14 B/, у самцов он всегда отсутствует /рис. 10/. За счет покровов головы образуется прекрасно развитая ложная мантия /рис. 5(4), рис. 6(1)/, целиком окружающая внутренностный мешок и ногу и ограничивающая обширную псевдопаллиальную полость, в кото- рой у самок происходит развитие яиц до стадии велигера. Полость сообщается с внешней средой через отверстие на вен- тральной стороне псевдопаллиума /рис. 2(3), рис. 5 (2)/. Нога /рис. 6, 10, 22/ рудиментарна, лишена крышечки, педальных желез и ползательной поверхности и не Ффункциони- рует. К ноге мужских особей примыкает с правой стороны со- вокупительный орган педального происхождения /рис. 9-10/. У незрелых самцов иногда сохраняется рудимент передней пе- дальной железы /puc. 24(8)/. Внутренностный мешок /рис. 7-11/ утратил раковину и при- обрел почти шаровидную форму, не сохранив следов спиральной закрученности. Мантия и мантийная полость рудиментарны, хотя сохранили примитивное положение слева от ноги /рис. 6(8), рис. 9(3)/. Мантийный комплекс органов распался и в большей части ре- дуцировался. Только почка сохранила нормальное положение и открывается в мантийную полость. Жабра, осфрадий, '"runo- бранхиальная железа и ректум исчезли. Матка вынесена за (111) 112 E. H. ГРУЗОВ пределы полости /рис. 8(1)/ на правую сторону тела. Пищеварительный аппарат начинается ротовым отверстием, ведущим в мускулистую сосательную глотку, имеющую во фрон- тальной плоскости два слепых выпячивания /рис. 14(12)/, ко- торые Рандаль и Хиз (1912) считали рудиментами слюнных же- лез. С другой стороны, можно считать их новообразованиями, отсутствовавшими у анцестральных форм. Характерно, что все представители Melanellidae - Entoconchidae, с которы- ми А. japonica имеет много общего, лишены слюнных желез. Вопрос о природе дивертикулов глотки Asterophila не может ‘быть решен окончательно, и поэтому то или иное толкование этих образований не должно влиять на наше понимание систе- матического положения исследуемой фофмы. Недлинный, лишенный желез пищевод/рис. 25 (4)/ соединяет глотку со слепо замкнутой пищеварительной железой - печенью (2). Челюсти, радула, желудок и задняя кишка отсутствуют. Кровеносная система тоже претерпела значительное вторич- ное упрощение, касающееся главным образом сосудистого аппа- рата. Перикардий сохранил нормальное положение на левой стороне тела рядом с почкой /рис. 8(10), рис. 10(6)/. Рено - перикардиальное отверстие отсутствует. Сердце дву- камерное /рис. 8(8,9)/. Сосуды замещены системсй лакун и синусов /рис. 12, 13/. Почка развита нормально. Респира- ция происходит через поверхность псевдопаллиума.. Центральная нервная система имеет следующий план строе- ния /рис. 31/. Церебральные и плевральные ганглии сливают- ся друг с другом, образуя обширную ганглиозную массу (5,15), лежащую над кишкой. Вентрально к ним примыкают два педаль- ных ганглия (9), лежащих рядом с основанием ноги. Имеется пара статоцистов (8). В глотке присутствуют два буккаль- ных ганглия (1), соединяющиеся друг с другом двумя комис- сурами (2). Висцеральное кольцо разомкнуто. Одна его по- ловина состоит из висцерального (4) и субинтестинального(6) - ганглиев, связанных с левой половиной церебро-плевральной массы(15). Другая половина содержит единственный супраин- тестинальный ганглий (12). Имеется хиастоневрия. Головая система самок /рис. 38/ состоит из яичника и выводных путей, дифференцированных в дистальной части на 3 отдела : дополнительную железу (4), семеприемник (3) u матку (2). Склеенные в кокон яйца откладываются в полость псевдопаллиума /рис. 6/. Семенник /рис. 36(1)/ соединяется с семепроводом, обра- зующим конечное расширение - дополнительную железу (6). Личинка представляет собой типичного велигера с несколь- ко редуцированным парусом /рис. 43-48/. В отличие от ли- чинок Entoconchidae, она обладает перикардием и почкой. Все строение Asterophila свидетельствует о ее близо- сти к Melanellidae - Entoconchidae. так что выделение ее в самостоятельное семейство Asterophilidae, как это делает Thiele (1929), едва ли оправдано. Признаки для раз- деления группы Melanellidae ua отдельные семейства, Melanellidae, Stiliferidae, Pelseneeriidae и Paedophoropodidae) A A A ee ST | ASTEROPHILIA JAPONICA 113 также недостаточны. Правильнее объединять их в одно o6mNp- ное семейство Melanellidae 5. lat., куда естественно войдет и исследуемая Форма. Схема, представленная на рис. 49, иллюсгрирует Ффилогенетические взаимоотношения между представителями данной группы. 1. Введение. Материал и методика. Паразитизм среди брюхоногих моллюсков - явление сравнительно редкое. В настоящее время известно. около 200 видов паразитиче- ских Gastropoda при общем числе видов брюхоногих около 85000. Тем не менее, изучение этих животных представляет большой обще- биологический интерес, так как ни одна другая группа животных, за исключением, может быть, ракообразных (Copepoda, Cirripedia) не дает столь ясной картины процесса эволюции паразитов под влиянием образа жизни. Среди брюхоногих имеются все стадии перехода от свободно- живущих Форм с высокой и совершенной организацией к глубоко спе- циализированным и упрощенным эндопаразитам, представляющим собой едва ли не самых деградированных представителей животного мира. Подобный размах эволюционных изменений при наличии множества переходных Форм позволяет изучить многие законрмерности и детали процесса регрессивной эволюции. Отдельные представители парази- тических Prosobranchia легко могут быть выстроены в ряд, иллю- стрирующий этапы процесса приспособления животного к паразитизму. Нирштрас (Nierstrasz, 1913), Ваней (Vaney, 1913), Иванов (1937a) и др. показали, что подобный ряд весьма близок к филогенетическо- му. Много интересного дает также изучение адаптаций паразити- ческих брюхоногих к конкретным условиям паразитирования, так как в каждом отдельном случае ясны причины изменения тех или иных органов. Изучение паразитических моллюсков интересно и со стороны их биологии, особенно биологии размножения. Увеличение количест- ва продуцируемых яиц, забота о потомстве, ускорение индивидуально- го развития, приспособления, обеспечивающие встречу самцов и са- MOK, - таков далеко не полный перечень вопросов, поддающихся раз- решению на данном материале. Паразитизм среди Prosobranchia возникал по меньшей мере 5-6 раз в самых разнообразных семействах ; родственые связи этих семейств со свободноживущими моллюсками в большинстве случаев ясны. Имеется лишь несколько аберрантных форм с неясным систематическим положением. Одной из таких форм до недавнего времени считалась Asterophila japonica (Randall et Heath, 1912), изучению op- ганизации которой и посвящена данная работа. Сведения об этом своеобразном животном крайне скудны. Моллюск был описан в 1912 г. Рандаль и Хизом (Randall et Heath, 1912). Авторы приводят краткое описание женской особи Asterophila (самцы остались им не u3BeCTHH) и ничего не сообщают о ее систе- матическом положении. 114 BH TEYSOB Нирштрас (Nierstrasz, 1913) ограничивается указанием Ha He- возможность сближения этой формы е Ctenosculum и с другими па- разитическими моллюсками. Ваней (Vaney, 1914), напротив, сближает рассматриваемый вид с Ctenosculum hawaiiense Heath, провизорно помещая оба рода среди Aspidobranchia. В 1929 году Тиле ( Thiele ) выделяет особое семейство Asterophilidae, которое он относит к трибе Lamellariacea, сближая, таким образом, Asterophila се Pseudosacculus и Lamellariidae. Однако основания, которыми OH при этом руко- водствовался, остались не ясными. Наконец, в тридцатых годах исследование этого брюхоногого предпринял А. В. Иванов, обнаруживший карликовых самцов этого ви- да и собравший большой и интересный материал как по анатомии взро- слых форм, так и по их эмбриональному развитию. Однако это иссле- дование не было доведено до конца, и в печати появились только отрывочные сведения, разбросанные по различным работам (Иванов, 1937 a, 1944 1945, 91952 m Ир.) Таким образом, к настоящему моменту большинство фактических сведений о строении Asterophila практически попрежнему нахо- дятся в небольшой работе Рандаль и Хиза, которая основана на изу- чении всего лишь шести женских особей. Естественно, что авторы не смогли избегнуть ряда ошибок, и наши знания об анатомии и о систематическом положении А. japonica в настоящее время совер- шенно недостаточны. Между тем, исследование этого интересного брюхоногого, под- вергшегося сильному изменению в процессе приспособления к пара- зитическому образу жизни, может расширить наши представления не только об его эволюции, но и о морфологических закономерностях эволюции других паразитических гастропод. Учитывая это, проф. А. В. Иванов передал в мое распоряжение все свои матерыалы по Asterophila, содержащие множество фикси- рованных животных, препараты и рисунки, и положил начало данному исследованию. В течение всей работы я много раз пользовался его советами и теперь рад случаю принести ему мою искреннюю благо- дарность. Всего в моем распоряжении имелось около 600 женских особей Asterophila, что позволило судить He только о нормальной aHa- томии животного, но и о наиболее характерных отклонениях в его строении. На многих особях находились прикрепленные карликовые самцы этого вида, организация которых до сего времени оставалась неизвестной. В ложномантийной полости половозрелых самок при- сутствовали личинки на разных стадиях развития. Моллюски были зафиксированы самыми разнообразными Ффиксато- рами : жидкостью Ценкера, сулемой с уксусной кислотой, жидкостью Флемминга, пикриновой кислотой (по Буэну) и др. Сравнительно крупные (до 35мм) размеры животного позволили значительную часть анатомии женских особей исследовать путем вскрытия. Полученные таким образом сведения всегда проверялись и дополнялись при изу- чении серий срезов. Заливка в парафин производилась через н.-бу- тиловый спирт. Срезы окрашивались железным гематоксилином Гей- денгайна с подкрашиванием лихтгрюном и бисмаркбрауном, а также по Маллори и азокармином по Гейденгайну. Последний способ давал ASTEROPHILA JAPONICA 115 наиболее четкие картины. Для выявления слизистых клеток применяласт окраска. тионинсм и толуидинблау. Строение животного восстанавливалось по срезам методом графи- ческих реконструкций. В отдельных случаях, когда это оказывалось необходимым, приходилось прибегать к объемным пластическим реконструкциям. В результате исследования строения Asterophila я пришел к выводу о ее принадлежности к группе моллюсков, связанных с Melanellidae. Поэтому при сопоставлении нашей формы с другими паразитическими моллюсками, упор делается на сравнении с предста- вителями Melanellidae, Stiliferidae, Entoconchidae и -Paedo- phoropodidae. 2. Распространение Asterophila и ee хозяева. Географический ареал А. japonica чрезвычайно широк. Моллюск встречается вдоль всего азиатского побережья северной части Тихого океана от Берингова пролива до Кореи на глубинах от 14 до 700 метров. Вполне вероятно, что действительные границы его ареала еще шире. Такое распространение паразита в значительной степени объяс- няется его малой специфичностью : хозяева Asterophila находятся среди всех отрядов Asteroidea: Phanerozonia, Spinulosa и Forcipulata. Подавляющее большинство особей было добыто из Ctenodiscus crispatus Retzius, и Leptasterias polaris Müller et Troschel. Кроме того, моллюски попадались в Leptychaster Sp., Cribrella sp., Leptasterias groenlandica (Lütken) и Г. arctica (Murdoch). Зараженные звезды обычно легко узнаются по внешнему виду, т. к. моллюски вызывают деформацию стенки тела хозяина. Моллюск находится между соединительной тканью стенки тела звезды и перитонеальным эпителием, выстилающим целомическую по- лость /рис. 1/. Перитонеум над моллюском немного растянут и плот- Разрез через луч звезды. Схема. 1 - стенка тела; 2- полость луча; 3 - перитонеальный эпите- лий звезды; 4 - плас- тинки амбулакрального скелета; 5 - пластин- ки адамбулакрального скелета. Location of male and female Astero- phila japonica in the host. Section through ray of starfish. Diagram- matic. 1- body wall; 2- cavity of Puc. 1. Положение самца и ray; 3 - peritoneal epithelium of FIG. 1. самки Asterophila starfish; 4 - plates of ambulacral japonica в хозяине. skeleton; 5 - plates of adambulacral skeleton. 116 EH. ГРУЗОВ HO прилегает к его ложной мантии. Скелетные элементы участка ко- жи, с которым соприкасается моллюск, сильно деформированы. Стен- ка тела в этом месте образует чашевидное углубление, снаружи вы- ступающее в виде опухоли. Y Leptasterias на дне yr- лубления, в одной из ячеек между скелетными пластинками, заметно очень маленькое сморщенное отверстие, прободающее стенку луча. Моллюск внутри опухоли располагается так, что отверстие в его ложной мантии (наружное половое отверстие) лежит против отверстия в стенке луча и его псевдопаллиальная полость сообщается, таким образом, с внешней средой. У остальных исследованных звезд от- верстие в стенке тела отсутствует, но слой кожи между пластинка- ми скелета бывает чрезвычайно тонким. По всей вероятности, связь паразита с наружной средой, необходимая для выведения.наружу ли- чинок, осуществляется периодически через разрыв истонченного уча- стка кожи, который позднее регенерирует. На дне чашевидного углубления стенки тела морской звезды обычно наблюдается углубление, меньших размеров, в котором поме- щается карликовый самец Asterophila. Самцы встречаются только вместезс самками и сидят на их ложной мантии недалеко от Hapyx- ного полового отверстия. Отверстие в псевдопаллиуме самцов об- ращено к женскому половому отверстию. В тех случаях, когда на самке находится несколько мужских особей Asterophila, под каждой из них стенка тела морской звезды образует небольшие дополнитель- ные углубления. Ротовое отверстие самок А. japonica обращено к стенке тела, хозяина, рот мужских особей обычно погружен в ложную мантию са- мок. Интересно сравнение положения Asterophila внутри хозяина а таковым других паразитических брюхоногих. В семействе Melanellidae наблюдается постепенный переход от форм, паразитирующих на поверхности тела иглокожих,к настоя-- щим эндопаразитам. Первый шаг к глубокому погружению в Cutis хозина делает Megadenus arrhynchus Ivanov, живущий в глубине цистообразного углубления стенки тела морской звезды Anthenoides rugulosus Fisher. Животное Целиком находится внутри цисты, однако его связь с внешней средой еще велика, т. к. циста широко открыта наружу. Ротовое отверстие Megadenus обращено к стенке тела звезды (Иванов, 1952). Bee представители рода Stilifer живут в толще стенок тела хозяина и сообщаются с наружной средой только узким отверстием ложномантийной полости. Хобот этих форм прободает стенку тела и проникает в целомическую полость (P. and Е. Sarasin, 1885; Hirase, 1932; Иванов, 1952 и др.). Наиболее измененный представитель семейства, Gasterosiphon deimatis (Koehler et Vaney) оказывается уже истинным эндопара- зитом. Как сообщают Келер и Ваней ( Koehler et Vaney, 1903), он обитает в полости тела голотурии Deima blakei Theel, прикреп- ляясь хоботом к маргинальному сосуду на кишке хозяина. Связь па- разита с внешней средой поддерживается посредством сифона, откры- вающегося через стенку тела голотурии. Все Ещосопсшаае - настоящие эндопаразиты, обитающие в полости тела различных голотурий, однако способ их прикрепления eee eee TE ee ee ASTEROPHILA JAPONICA 117 несколько варьирует. ÆEntocolax ludwigi Voigt, E. schiemenzi Voigt, E. trochodotae Heding и Етосопсйа mirabilis Braun прикрепляются при помощи сифона к стенке тела голотурии ( Voigt, 1888, 1901; Heding, 1934; Müller, 1852). Остальные вилы Entocolax, a также Enteroxenos и Parenteroxenosl по данным Шванвича (Schwanwitsch, 1917), Бонневи ( Bonnevie, 1902) и ‘Иванова (1945, 1947), прикрепляются к кишке голотупий. Тело Enteroxenos и Parentevoxenos одето перитонеальным эпителием хозяина, отходящим от его кишечника ( Bonnevie, 1902; Иванов, 1947). По способу паразитирования Asterophila занимает mpomexy- точное положение между Stiliferidae и Entoconchidae. Подобно Megadenus arrhynchus, живущему Ha дне чашеобразного углубления стенки тела звезды, ее ротовое отверстие обращено к стенке тела хозяина, откуда моллюск добывает свою пищу. Однако в отличие от всех Stiliferidae (за исключением Gasterosiphon), Asterophila прошла сквозь толщу стенки тела звезды и обитает под перитонеальным эпителием. Подобно примитивным Entoconchidae она сохраняет связь с внешней средой через стенку тела хозяина. 3. Организация взрослых животных 1. Внешний вид Рандаль и Хиз приводят удачное описание внешности типичной самки Asterophila, хотя, имея дело всего с шестью особями, они, естественно, не смогли коснуться вопроса об индивидуальной измен- чивости животных, которая очень велика. Паразитизм наложил на А. japonica глубокий отпечаток, в ре- зультате чего моллюск совершенно утратил облик переднежаберной улитки. Снаружи все тело животного одето ложной мантией, так что при внешнем осмотре животного. видны лишь этот орган и хобот. Часто сквозь тонкие стенки псевдопаллиума просвечивают внутрен- ностный мешок и яйцевой кокон. Рис. 2 передает внешность неполовозрелой самки, ее ложная мантия (1) не растянута и шаровидна. Животное изображено с брюш- ной стороны, которая легко узнается по находящемуся на ней вторич- ному половому отверстию (3). У особей, достигпих половой зрелости, вокруг отверстия сидят самцы /puc.3/. Ложная мантия лишена опорных образоваий и легко растягивается и деформируется, что сильно меняет облик животного. Большинство экземпляров имеют бобовидную форму /рис. 4, 5/; иногда приобре- тают вид гантели, или деформированы в еще большей степени. Внешний вид самцов гораздо более постоянный, чем у самок. По-видимому, нормой и здесь следует признать сферическую Форму те- ла, хотя часто встречаются и экземпляры, имеющие овальные очерта- e lle rindo OIR AIR O RN а Pe a ae (Baer, 1952) предлагает считать Parenteroxenos Ivanov синонимом Thyonicola Mandahl-Barth. Однако описание Мандаль- Барта, ( Mandahl-Barth, 1941) так неполно, что объединять эти формы в настоящий момент преждевременно. 118 Be GH. SEEYSOB PUC ICI Рис. 2. FIG. 2, Asterophila japonica. Aslerophila japonica. Внешний вид неполовозре- лой самки. 1 - ложная мантия; 2 - внутренностный мешок; 3 - отверстие ложной мантии; 4 - ротовое отверстие; 5- хобот. Ventral view of immature female. 1 - pseudopal- lium; 2 - visceral mass; 3 - open- ing ofpseudopallialcavity; 4 - open- ing of mouth; 5 - snout. = Asterophila japonica. Самка и самцы, прикрепив- шиеся вокруг отверстия ложной мантии. Asterophila japonica. Female, and males clustering around the opening of the pseudopallial cavity of the fe- male. ASTEROPHILA JAPONICA 119 2 тт B Puc. 4. Asterophila japonica. Половозрелая самка. A - Вид co FIG. 4. спинной стороны. Б - Вид с брюшной стороны. 1 - внутренностный мешок; 2 - хобот; 3 - ротовое отверстие; 4 - яйцевой кокон; 5 - отверстие ложной мантии. Asterophila japonica. Mature female. A, dorsal view; В, ventral view. 1- visceral mass; 2-snout; 3- opening of mouth; 4- cocoon-like egg mass; 5 - opening of pseudopallial cavity. 120 E. H. ГРУЗОВ ния /рис. 3, 5/. Сквозь стенки псевдопаллиума самцов просвечивает внутренностный мешок и совокупительный орган, который иногда высо- вывается наружу через отверстие ложной мантии /рис. 5/. Рис. 5.Asterophila japonica Y, FIG. 5.Вид с левой стороны (ри- сунок А. В. Иванова). 1 - пенис; 2 - отверстие ложной мантии; 3 - внут- ренностный мешок; 4 - лож- ная мантия. Asterophila japonica d. View from left side (after A. V. Ivanov). 1- penis; 2- opening of pseudopallial cavity; 3- visceral mass; 4 - 0 -5mm pseudopallium. Дополнительной причиной изменчивости внешнего вида моллюска, служит хобот. Большинство особей обладают хоботом, к которому хо- рошо подходит название, данное Рандаль и Хизом:"ротовая папилла". Это невысокий бугорок, закругленный у вершины, где помещается ро- товое отверстие. Иногда, особенно у самцов, он совершенно пропа- лает, иногда же, напротив, приобретает вид массивного цилиндричес- кого образования /рис. 14, A. Размеры тела колеблются в зависимости от возраста в пределах от 2 до 35 мм; диаметр внутренностного мешка не превосходит 15мм. Самцы редко бывают более 2мм. Тело моллюска, по сообщению А. В. Иванова, желтовато-белого цвета. После удаления ложной мантии /рис. 6-11/ становятся заметны внутренностный мешок животного и рудимент ноги, помещающийся у его основания против отверстия псевдопаллиума. К ноге самцов прилега- ет развитый penis /рис. 10 (9)/. Присутствие ноги помогает ус- тановить правильную морфологическую ориентировку тела Asterophila: плоскость, проходящая через ротовое отверстие, вершину внутренност- ного мешка и середину ноги, представляет собой медиальную плоскость, ротовое отверстие находится на переднем конце тела, а нога распо- лагается на брюшной стороне. Подобная ориентировка полностью сов- падает с той, которая была принята Рандаль и Хизом. Внутренностный мешок, лишенный раковины и спиральной закру- ченности, как у самцов, так и у самок имеет шаровидную' Форму и обычно слегка сплюснут с боков или в дорзо-вентральном направлении. Спереди он срастается с основанием псевдопаллиума Ha передней стороне внутренностного мешка слева от ноги тянется Узкая складка мантии /рис.7 (4) и рис. 9 (3)/. Около ее левого края сквозь покровы тела просвечивает перикардий /рис. 8 (10)/ и почка /рис. 8 (7)/. На правой и брюшной поверхности внутренност- ного мешка заметны выводные пути половой системы. У самок /puc.8/ это белковая железа (5), семеприемник (2) и матка (1); у самцов /рис. 9/ - семепровод и дополнительная железа (1). И женское, и ASTEROPHILA JAPONICA 121 Puc. 6. Asterophila japonica Y. FIG. 6. Ложная мантия вскрыта. Вид с брюшной стороны. 1 -- ложная мантия; 2 - яйцевой кокон; 3 - яичник; 4 - печень; 5 - нога; 6 - Asterophila japonica?. Pseudopal- lium opened. Ventral view. 1- pseudopallium; 2 - cocoon-like egg mass; 3-ovary; 4-liver; 5- отверстие ложной мантии; foot; 6 - opening of pseudopallial 7 - хобот; 8 - мантия; 9 - cavity; 7- snout; 8- mantle; 9- перикардий; 10 - сердце. pericardium; 10 - heart. Рис. 7. Aslerophila japonica Y. FIG. 7. Ложная мантия удалена. Вид со спинной стороны. 1 - яичник; 2 - печень; 3 - белковая железа; 4 - Asterophila japonica 2. Pseudopal- lium removed. Dorsal view. 1- ovary; 2 - liver; 3 - albumen gland; мантия; 5 - ложная мантия; 4- mantle; 5 - pseudopallium; 6 - 6 - ротовое отверстие; 7 - opening of mouth; 7- snout; 8 - хобот; 8 - семеприемник; seminal receptacle; 9 - pallial ovi- 9 - MaTKa. duct. 122 Prc. ESPE: REYIOD — 8. Asterophila japonica $. FIG. 8. Ложная мантия удалена. Вид спереди. 1 - матка; 2 - семеприем- ник; 3 - яичник; 4 - пе- чень; 5 - белковая железа; 6 - хобот; 7 - почка; 8 - предсердие; 9 - желудочек; 10 - перикардий; 11 - ро- товое отверстие; 12 - пе- редняя лопасть ноги; 13 - задняя допасть ноги; 14 - ложная мантия; 15 - половое отверстие. Asterophila japonica Y. Pseudopal- lium removed. Anterior view. 1- uterus; 2 - seminal receptacle; 3 - ovary; 4- liver; 5 - albumen gland; 6 - snout; 7- kidney; 8 - auricle; 9 - ventricle; 10 - pericardium; 11 - opening of mouth; 12 - anterior part of foot; 13 - posterior part of foot; 14 - pseudopallium; 15 - gen- ital opening. mm Рис. 9. Asterophila japonica Y. FIG. 9. Ложная мантия удалена. Вид спереди. 1 - дополнительная железа; 2 - половое отверстие; 3 - мантия; 4 - сердце; 5 - перикардий; 6 - ротовое отверстие; 7 - нога; 8 - ложная мантия; 9 - пенис. Asterophila japonica $. Pseudopal- lium removed. Anterior view. 1- accessory gland; 2- genital open- ing; 3- mantle; 4 - heart; 5 - per- icardium; 6 - opening of mouth; 7 - foot; 8 - pseudopallium; 9 - penis. ASTEROPHILA JAPONICA 123 Рис. 10. Asterophila japonica Y. FIG. 10. Ложная мантия удалена. Вид с левой стороны. Asterophila japonica d. Pseudopal- 1 - внутренностный мешок; lium removed. View from left 2 - пенис; 3 - нога; 4 - side. 1 - visceral mass; 2 - penis; ложная мантия; 5 - мантия; 3 - foot; 4 - pseudopallium; 5- 6 - перикардий. mantle; 6 - pericardium. Puc. 11. Asterophila japonica с’. FIG. 11. Ложная мантия удалена. Вид с правой стороны. 1 = пенис; 2 - внутренно- стный мешок; 3 - дополни- тельная железа; 4 - ман- тия; 5 - ложная мантия; 6 - ресничная борозда. Asterophila japonica 9. Pseudo- pallium removed. View from right side. 1 - penis; 2 - visceral mass; 3- accessory gland; 4- mantle; 5 - pseudopallium; 6 - ciliated neHuca. groove of penis. 124 Е. H. ГРУЗОВ Рис. 12. Общий план строения самца ресничная борозда пениса; FIG. 12. Asterophila japonica. Схема. 24 - ложная мантия; 25 - 1 - семенник; 2 - семе- кровеносные лакуны. провод; 3 - дополнитель- ная железа; 4 - крове- HOCHM синус; 5 - виесце- Gross anatomy of male Asterophila ральный ганглий; 6 - поч- japonica. Diagrammatic. 1 - tes- ка; 7 - половое отверстие; tis; 2- уаз deferens; 3- acces- sory gland; 4- blood sinus; 5- visceral ganglion; 6 - kidney; 7 - genital opening; 8- mantle; 9- subintestinal ganglion; 10 - cepha- lic blood sinus; 11 - cerebro-pleu- ral ganglionic mass; 12 - esopha- gus; 13- buccal ganglion; 14- pharynx; 15 - pharyngeal diverti- 8 - мантия; 9 - субинтес- тинальный ганглий; 10 - головной кровеносный си- Hyc; 11 - церебро-плев- ральная ганглиозная мас- са; 12 - пищевод; 13 - буккальный ганглий; 14 - глотка; 15 - дивертикулы culum; 16 - pedal ganglion; 17- глотки; 16 - педальный supraintestinal ganglion; 18 - per- ганглий; 17 - супраинтес- icardium; 19- foot; 20 - liver; тинальный ганглий; 18 - 21 - opening of pseudopallial cavi- перикардий; 19 - Hora; ty; 22 - ciliated groove of penis; 20 - печень; 21 - отвер- 23- penis; 24 - pseudopallium; стие ложной мантии; 22 - 25 - blood lacunae. мужское половые отверстия имеют вид узкой и длинной щели, распола- гающейся справа от ноги /рис. 8 (15); рис. 9 (2)/. В экваториаль- ной части внутренностного мешка находится печень /puc.?7 RATE а вершину занимает ToHana. У женских особей граница между этими органами хорошо заметна снаружи, благодаря тому, что яичник, наполненный яйцами с большим количеством желтка, выделяется своим цветом, а сквозь тонкие стенки печени просвечивают ее многочисленные внутренние складки. Наиболее существенными особенностями наружного строения Asterophila нужно признать следующие: 1) отсутствие раковины Рис. ASTEROPHIA JAPONICA 13. Общий план строения сам- FIG. 13. ки Asterophila japonica. Cxema. 1 - яичник; 2 - эпителий внутренностного мешка; 3 - кровеносный синус; 4 - кровеносные лакуны; 5 - яйцевод; 6 - печень; 7 - висцеральный ганглий; 8- белковая железа; 9 - поч- ка; 10 - мантия; 11 - суб- интестинальный ганглий; 12 - церебро-плевральная ганглиозная масса; 13 - пищевод; 14 - глотка; ‘15 - буккальный ганглий; 16 - дивертикулы глотки; 17 - ротовое отверстие; 18 - головной кровеносный си- нус; 19 - педальный ганг- лий; 20 - супраинтести- нальный ганглий; 21 - пе- рикардий; 22 - нога; 23 - отверстие ложной мантии; 24 - самец; 25 - половое отверстие; 26 - матка; 27 - семеприемник; 28 - ложная мантия; 29 - яй- цевой кокон. Gross anatomy of female Astero- phila japonica. Diagrammatic. 1- ovary; 2- epithelium of visceral mass; 3- blood sinus; 4 - blood lacunae; 5 - oviduct; 6 - liver; 7 - visceral ganglion; 8 - albumen gland; 9 - kidney; 10 - mantle; 11 - subintestinal ganglion; 12 - cerebro-pleural ganglionic mass; 13 - esophagus; 14 - pharynx; 17 - opening of mouth; 18 - cephalic blood sinus; 19 - pedal ganglion; 20 - supraintestinal ganglion; 21 - pericardium; 22 - foot; 23 - open- ing of pseudopallial cavity; 24-a male; 25 - genital opening; 26 - pallial oviduct; 27 - seminal re- ceptacle; 28 - pseudopallium; 29 - cocoon-like egg mass. и спиральной закрученности внутренностного мешка, 2) сильную pe- дукцию головного отдела, ноги и органов мантийного комплекса и 3) развитие псевдопаллиума.. Все эти признаки указывают на глу- 125 126 Her ISMTPYSOB pS OD © N ur 3 3 | Las лий; 7 - покровный эпите- oe кольцевые Мышцы; 9 - продольные мышцы; соединительная ткань; 10 - 114 глотка? Ter = глотки; 13 - ротовое от- верстие; 14 - пищевод; 15 - ганглии центральной нервной системы. дивертикулы Asterophila japonica Y. Frontal sections through anterior end of body. Diagrammatic. A - snout developed; В - snout absent. 1- liver; 2- pericardium; 3 - heart; 4- pseudopallium; 5 - cephalic Asterophila japonica 2. Фронтальный разрез через передний конец тела. Схема. A - особь с раз- blood sinus; 6- blood sinus of snout; витым хоботом; Б - особь, 7 - surficial epithelium; 8 - trans- лишенная хобота. verse muscle; 9 - longitudinal mus- 1 - печень; 2 - перикар- cle; 10- connective tissue; 11- дий; 3 - сердце; 4 - лож- pharynx; 12- pharyngeal diverticu- ная мантия; 5 - головной lum; 13- opening of mouth; 14- кровеносный синус; 6 - esophagus; 15 - ganglion of cen- кровеносный синус хобо- tral nervous system. бокую перестройку организации B связи с далеко зашедшим соблением к паразитизму. Отсутствие раковины и связанная с этим деспирализация внут- ренностного мешка сближает нашу форму с паразитическими Ento- conchidae и Paedophoropodidae. Bee Melanellidae и Stiliferidae приспо- ASTEROPHILA JAPONICA 127 обладают высокой закрученной раковиной D)? ASEO OO E Хобот, как указывалось, очень мал и часто совсем не выражен. В наиболее развитом виде он имеет форму закругленного у вершины цилиндра. Его строение видно на продольном срезе, представленном на рис. 14 А. Стенки органа состоят из покровного эпителия (7) и лежащего под ним толстого соединительно-тканного слоя (10). В середине хобота располагается глотка и пищевод, отделенные от стенок пространством кровеносного синуса (6), образующего от- четливо выраженную полость хобота. Никаких рудиментов ретракторов в нем обнаружить не удается. На уровне ложной мантии полость без резких границ переходит в головной кровеносный синус (5). Покровный эпителий состоит из опорных и железистых клеток /рис. 15 (2, 3)/. Поверх него обычно присутствует бесструктурный слой неясного происхождения (1). Расположенная глубже соедини- тельная ткань /рис. 16/ содержит многочисленные мускульные волокна, имеющие по периферии продольную и кольцевую ориентацию, а в глубо- ких слоях лежащие безпорядочно. Обилие мускульных элементов ука- зывает на то, что хобот обладает некоторой способностью к актив- ному движению. * Выше уже отмечалась большая изменчивость хобота. Она касается не только его размеров, но и степени развития кровеносного синуса, мускулатуры и т. д. На рис. 14 А схематически изображен продольный разрез через развитый хобот. Он представляет собой массивный вытянутый орган с обширным кровеносным синусом. Глотка занимает лишь передний участок хобота, почти вплотную прилегая к его стенкам. Полость вокруг нее развита слабо. В центре проксимального конца, хобота прямой трубокой проходит пищевод. Кровеносный синус вокруг него развит сильнее и далее назад сливается с головным, в котором лежат ганглии около пищеводного кольца. На рис. 14 Б представлен продольный разрез через передний конец тела другого экземпляра, совершенно лишенного хобота. Рото- вое отверстие (13) у него лежит на очень небольшом возвышении стенки тела. Глотка (11) расположена на уровне основания мантии (4) в непосредственном соседстве с околопищеводным нервным коль- 1) Среди Stiliferidae описаны две лишенные раковины Формы: Gasterosiphon deimatis (Koehler et Уапеу) и Diacolax cucumariae Mandahl-Barth. Однако сведения O'NEPBOM животном (Koehler et Vaney, 1903) вызывают сомнения, Т.к. моллюск обла- дает спирально закрученным внутренностным мешком. По всей вероят- ности, раковина этого моллюска растворилась при фиксации. Что касается Diacolax, то его без сомнения следует отнес- ти к Entoconchidae, поскольку основной аргумент автора (Mandhal-Barth, 1945 - 46) о разной природе псевдопаллиума у Eulimidae и Entoconchidae ‘`несостоятелен (см. сноску на стр. 132). 128 DB. "E "TEYSOB 0:025mm Puc. 15. Asterophila japonica. Puc. 16. Asterophila japonica, FIG. 15. Наружный покровный эпи- FIG. 16. Участок соединительной телий. Маллори. ткани хобота. Маллори. 1 - бесструктурный слой; 1 - мускульные волокна; 2 - опорные клетки; 2 - клетки веоединитель- 3 - железистые клетки; ной ткани; 4 - базальная мембрана; 3 - основное вещество. 5 - соединительная ткань. Asterophila japonica. External Asterophila japonica. Part of con- surficial epithelium. Stained with nective tissue of snout. Stained Mallory’s. 1 - structureless layer; with Mallory’s. 1- muscle fiber; 2 - supporting cells; 3 - glandular 2 - cell of connective tissue; 3- cells; 4 - basal membrane; 5- ground substance. connective tissue. yom (15). Эпителий пищевода образует несколько складок, что ука- зывает на известное сокращение переднего конца тела, однако оно, по- видимому, невелико и не может объяснить полное исчезновение хобота. Формы, изображенные на рис. 14, являются крайними в ряду из- менчивости хобота и встречаются сравнительно не часто. Подавляю- mee большинство экземпляров Asterophila, как и особи, изученные Рандаль и Хизом, занимают промежуточное положение. У самцов хобот всегда отсутствует или представлен очень невы- сокой ротовой папиллой, к которой название "хобот" применить очень трудно. Крайние различия в степени развития хобота столь существенны, что при отсутствии переходных состояний смогли бы послужить кри- териями для установления самостоятельных видов. Подобный размах ASTEROPHILA JAPONICA 129 изменчивости, указывая Ha направление эволюции хобота в сторону его упрощения, в то же время свидетельствует о TOM, что Формооб- разовательные процессы у Asterophila к настоящему моменту еще не закончились. Редукция хобота происходит у большинства прикрепленных пара- зитических Melanellidae и Stiliferidae. В ряду Мистопайа eburnea Deshayes - Parastiliferl - Megadenus (xpome M. arrhynchus) Stilifer наблюдается постепенное упрощение этого органа. Полость его зарастает соединительной тканью, а ретракторы исчезают ( Nierstrasz, 1913; Schepman und Nierstrasz, 1913; Rosen, 1910; Иванов, 1952). Однако полное исчезновение хобота наблю- дается только у Megadenus arrhynchus, хотя здесь остаются еще рудименты ретракторов (Иванов, 1952), и у высших Entoconchidae (Bonnevie, 1902; Иванов, 1947). Сохранению хобота у Stiliferidae способствует выполнение им Функции прикрепления к хозяину. Возможно, что полная редукция хобота у эктопаразитов становится возможной только при наличии со- сательной глотки (М. arrhynchus, Asterophila ). 3. Ложная мантия Ложная мантия начинается вокруг проксимального конца хобота, и, простираясь назад, одевает все тело животного. Связь моллюска с внешней средой осуществляется через отверстие на брюшной стороне псевдопаллиума, которое представляет собой наружное (вторичное) ‚ половое отверстие: через него происходит копуляция и выходят на- ружу личинки, развивавшиеся в ложномантийной полости. Характерно, что при растяжении ложной мантии расстояние между отверстием псев- допаллиума и половым отверстием остается неизменным. Как у большинства паразитических моллюсков, ложная мантия Asterophila представляет складку покровов хобота. В соответствии с этим гистологически она образована двумя комплексами тканей: наружным и внутренним, представляющими как бы зеркальное отображе- ние друг друга /рис. 17/. Каждый комплекс складывается из TIDK- ровного эпителия и подстилающей его соединительной ткани, содержа- щей мускульные элементы. Наружный покровный эпителий (3) во всем подобен эпителию хо- бота и составляет с ним одно целое. Лежащая под ним соединитель- ная ткань образована некрупными, рыхло лежащими клетками (7), между которыми проходят мускульные волокна, которые в своей совокупности образует два слоя мускулатуры: наружный (5) и вну- тренний (6). Направление волокон в каждом слое. можно уяснить из схемы, приведенной на рис. 18. Наружный слой спереди переходит в слой кольцевых мышц хобота, а внутрений - в слой продольных мышц, так что мускульные волокна покровов, взятые в целом, располагаются 1) Stilifer sibogae Y St. sp. Schepman et Nierstrasz выделены Ивановым (1952) в новый род Parastilifer Ivanov. 130 E. H. ГРУЗОВ. 1 - наружный комплекс тка- ней; 2 - внутренний комп- лекс тканей; 3 - неружный покровный эпителий; 4 - базальная мембрана; 5 - кольцевые мускульные во- = = локна; 6 - продольные мус- SE $ кульные волокна; 7 - клет- ки соединительной ткани; 8 - кровеносная лакуна; 9 - амебоциты; 10 - основ- ное вещество соединитель- ной ткани; 11 - внутренний покровный эпителий. ES Da: PI oS Asterophila japonica. Section through pseudopallium. Stained with Mallory’s. 1 - external tis- sue complex; 2 - internal tissue complex; 3- external surficial epi- thelium; 4 - basal membrane; 5 - 0-0 5 = transverse muscle fiber; 6 - longi- tudinal muscle fiber; 7 - cell of connectivetissue; 8 - blood lacuna; Puc. 17. Asterophila japonica. 9 - amebocyte; 10 - ground sub- FIG. 17. Разрез через ложную мантию. stance of connective tissue; 11- Маллори. internal surficial epithelium. по параллелям и меридианам между двумя полюсами, из которых одним служит ротовое отверстие, а другим - отверстие ложной мантии. В соответствии с асимметричным положением второго отверстия на брюшной стороне тела, нарушается также и радиальная симметрия в расположении мускулатуры ложной мантии, характерная для всех Entoconchidae. Тем не менее гомология наружного слоя слою коль- цевых, а внутреннего - слою продольных мышц псевдопаллиума других моллюсков не вызывает сомнения. У Asterophila продольная ось ложной мантии оказывается изогнутой на брюшную сторону и не сов- падает с передне - задней осью тела животного, и морфологически задний конец этого органа находится не в точке, противоположной ротовому отверстию, а в участке, занимаемом наружным IIOJIOBBIM отверстием. Внутренний комплекс тканей ложной мантии /рис. 17 (2)/ имеет обратное расположение слоев: снаружи, то есть в непосредст- венном соседстве с внешним комплексом, залегает богатая мускулату- рой соединительная ткань, глубже находится внутренний покровный эпителий (11), клетки которого свободными концами обращены внутрь полости ложной мантии. Этот эпителий /рис. 19/ значительно ниже наружного и часто ASTEROPHILA JAPONICA 131 ной мантии. 1 - кольцевые волокна; 2 - продольные волокна; 3 - отверстие ложной И 1 мантии; OI LP Orientation diagram of muscle fi- bers in the pseudopallium. 1 - transverse fibers; 2 - longitudinal Рис. 18. Схема ориентации мус- fibers; 3- opening of pseudopal- FIG. 18. кульных волокон в лож- lial cavity. при сокращении псевдопаллиума становится складчатым. OH образован невысокими цилиндрическими клетками, несущими довольно длинные реснички (1). Изредка в эпителии встречаются вытянутые, ли- шенные ресничек клетки с более густой протоплазмой (2). Их бога- тые хроматином ядра сильно сдавлены и слегка оттеснены к базальной мембране. Секреторная Функция этих клеток не исключена. Мускульные волокна внутреннего комплекса располагаются в два слоя и имеют то же направление, что и во внешнем комплексе /рис. 17/, однако продольные мышцы (6) лежат здесь снаружи от кольцевых (5). Оба слоя, а в особенности слой кольцевых мышц, значительно мощнее соответствующих слоев наружного комплекса. Между слоями продольных и кольцевых мускульных волокон в сое- динительной ткани внутреннего комплекса проходят мощные нервы, от- ’ходящие от церебральных ганглиев /рис. 32 - 35 (13)/. Эти нервы, по три с каждой стороны, прослеживаются на некотором расстоянии в толще ложной мантии, а затем теряются. На границе между комплексами имеются лакуны кровеносной си- стемы. Обилие их во всей ложной мантии свидетельствует о сущест- венной роли этого органа в процессе дыхания животного. В основа- нии псевдопаллиума лакуны вступают в связь с головным кровеносным синусом. Оба комплекса псевдопаллиума послойно переходят друг в друга через отверстие ложной мантии, и при этом кольцевые волокна кон- центрируются вокруг отверстия, образуя его сфинктер. В нормаль- Азокармин по Гейденгайну. 1 - ресничные клетки; 2 - железистые клетки; Internal surficial epithelium of pseudopallium. Stained with Рис. 19. Внутренний покровный Heidenhain’s azocarmin. 1- cili- FIG. 19. эпителий ложной мантии. ated cells; 2 - glandular cells. 132 He th SRPY SOB эпителий; - мускульные волокна; - кровеносные лакуны; основное вещество; - внутренний покровный эпителий. пром 1 mm Section through stretched part of pseudopallium. Stained with ; Heidenhain’s azocarmin. 1- exter- Рис. 20. Разрез через растянутый nal surficial epithelium; 2- muscle FIG. 20. участок ложной мантии. fibers; 3 - blood lacunae; 4- Азокармин no Гейденгайну. ground substance; 5 - internal sur- 1 - наружный покровный ficial epithelium. ном состоянии отверстие закрыто, а его края образуют многочислен- ные морщины. Покровный эпителий этого участка сильно складчатый. Отверстие способно значительно увеличиваться за счет растяжения его стенок. Псевдопаллиум часто сильно растягивается, особенно в своей спинной части. При этом оба покровных эпителия вытягиваются на- столько, что внутренний становится чешуйчатым, и клетки его те- ряют свои реснички /рис. 20/. Все элементы соединительной ткани также истончается и становятся едва различимыми. Правильность в расположении мускульных волокон пропадает. Псевдопаллиум Asterophila бесспорно гомологичен ложной мантии Stiliferidae и Entoconchidae (1и представляет сильно разросшуюся кольцевую складку покровов. Иннервация его внутренних (морфологически задних) частей от церебральных ганглиев свидетель- ствует о головной природе этого образования. Морфологические изменения псевлдопаллиума в процессе эволюции паразитических Melanellidae - Entoconchidae достаточно известны. ( Schiemenz, 1889; Rosen, 1910; Иванов, 1946 и др.). Однако с функциональной стороны этот вопрос требует дополнительного рас- смотрения. Ложная мантия возникает у свободно передвигающихся полупарази- тических Melanellidae (Koehler et Vaney, 1912; Fretter, 1955) в виде небольшой кольцевидной складки вокруг основания хобо- та. Назначение подобного образования заключается в том, что оно изолирует дистальный конец хобота моллюска от внешней среды и предотвращает проникновение воды в ранку и вымывание пищеваритель- ных секретов и соков хозяина. al Теория Мандаль - Барта (Heding and Mandahl-Barth, 1938), по которой выводковая камера и сифон Entocolax представляют дистальный участок гонодукта, покрытый снаружи модифицированной мантией (и, следовательно, эти органы не гомологичны ложной мантии Stiliferidae ) была обсуждена и опровергнута Ивановым (1953). ASTEROPHILA JAPONICA 133 Puc. 21. Мантийный эпителий. Жид- FIG. 21. кость Флемминга, желез- ный гематоксилин Гейден- гайна, тодуидинблау. 1 - базальные ресничные зерна; - ресничные клетки; - включения; железистые клетки; - базальная мембрана; - соединительная ткань; - слизистые клетки. NO 01 & WM 1 Pallial epithelium. Fixed with Flemming’s mixture. Stained with Heidenhain’s iron hematoxylin, toluidine blue. 1— basal granule; 2 - ciliated cells; 3- inclusions; 4 - glandular cells; 5 - basal mem- brane; 6 - connective tissue; 7 - mucus cells. У эктопаразитов, обитающих в стенке тела иглокожих, псевдопал- лиум разрастается и заворачивается назад на раковину ( Megadenus, Stilifer ). Здесь он служит для фиксации паразита на хозяине и одновременно создает полость, соединяющую мантийную полость с внеш- ней средой. Мерцательный эпителий внутренней поверхности ложной мантии создает ток воды, омывающей жабру и выносящей наружу яйца, продукты обмена и экскременты животного. Эта новая Функция - осу- цествленение связи организма с внешней средой - сохраняется за псевдопаллиумом в процессе дальнейшей эволюции и возможно служит причиной того, что орган удерживается даже у крайне деградирован- ных Entoconchidae. y Asterophila 5 результате обитания в глубоких слоях стенки тела хозяина, на ложную мантию возлагается задача газообмена, и при этом утрачивается значение псевдопаллиума как органа, вентили- рующего мантийную полость. Существенно также превращение полости ложной мантии в выводковую камеру, - Функция также сохраняющаяся за псев- допаллиумом на продолжении всей дальнейшей эволюции паразитов, свя- занных с Melanellidae. У Entoconchidae к ложной мантии переходит роль экскреторного органа, a y ЁЕщетохепо$ и Parenteroxenos - также и Функция вса- сывания питательных веществ. Кроме того, у эндопаразитов ложная мантия снова используется для прикрепления к кишечнику хозяина. 4. Мантия и мантийный комплекс органов. Мантия располагается на передней поверхности внутренностного 134 E. H. ГРУЗОВ мешка Ha левой стороне тела /рис. 7, 8, 9/. Она имеет вид узкой, нависающей вперед складки. Ограничиваемая ею мантийная полость невелика, вход в нее, напротив, очень широк. Мантийную складку и всю переднюю поверхность внутренностного мешка одевает железистый эпителий. Строение его весьма характерно Он образован чередующимися ресничными /puc. 21 (2)/u секреторными (4,7) клетками, первые из которых имеют суженный базаль- ный конец и расширенную дистальную часть, а вторые - наоборот. В соответствии с этим ядра клеток располагаются в два отчетливо выраженных ряда: базальный и дистальный. `Железистые клетки, в свою очередь, дифференцированы на два типа. Одни из них (7) окрашиваются бисмаркбрауном в желтый цвет, a толуидинблау - в фиолетовый, T. €. содержат слизистый секрет, оформленный в округлые капли. Клетки другого сорта (4) не содержат слизи, и их секрет собран в мелкие зернышки или капельки, слегка чернящиеся железным гема- токсилином. Кроме такого рода включений, протоплазма этих клеток содержит еще довольно крупные, неправильной Формы глыбки, которые после осмиевой фиксации и окраски железным гематоксилином приобре- тают глубокий черный цвет (3). Описанные клетки чрезвычайно сходны со слизистыми клетками гоно- дукта. Мантийный комплекс органов расвнался и частично редуцировался. Ктенидий, осфрадий, гипобранхиальная железа и ректум исчезли, а по- ловое отверстие вынесено за пределы мантийной полости на правую сторону тела. Только почка сохранила примитивные отношения и от- крывается в глубине мантийной полости. В связи с тем,что внутренностный мещок утратил спиральную закрученность, почка, перикардий иматка испытывают смешение Ha по левой стороне тела, а последний-по правой. левой стороне тела, а последний - по правой. Несмотря на изменение топографии мантийного комплекса органов, основной план строения моллюска не нарушается: почка и перикардий по-прежнему располагаются слева от ноги, а гонодукт - справа от нее. Между Tem, Рандаль и Хиз ( Randall et Heath, 1912) отмечают, что перикардий и почка Asterophila лежат на правой стороне, a ди- стальные части гонодукта - на левой. Такое же взаимное расположе- ние органов изображают они на рис. 1 и 2 таблицы 1. Вопрос о топо- rpadun рассматриваемых органов имеет принципиальное значение, т.к. оказывает существенное влияние на выводы о Ффилогенетических взаимо- отношениях нашего вида с другими моллюсками. Поэтому мною было просмотрено большое число особей Asterophila, и в результате я пришел к убеждению в ошибочности описания Рандаль и Хиза. Редукция мантии у паразитических Gastropoda, повидимому, очень тесно связана с исчезновением раковины. Во всяком случае все Формы с раковиной имеют нормально развитую мантию, а их мантийный комплекс варьирует лишь в деталях. Изменения касаются степени развития жабры, осфрадия и гипобранхиальной железы, причем послед- ние два органа, а также ректум могут совсем исчезнуть. Так, осфра- And: отсутствует у Eulima acutissima Swb. (Risbec, 1954), Megadenus holothuricola Rosen (Rosen, 1910) и несколько недоразвит у M. arrhynchus (Иванов, 1952). У некоторых экземпляров Рата- stilifer sibogae отсутствуют прямая кишка и анальное отверстие ASTEROPHILA JAPONICA 135 (Jonker, 1916). Гипобранхиальная железа недоразвита y Stilifer celebensis (Иванов, 1952) и отсутствует y Eulima equestris (Koehler et Vaney, 1912), E. sp. Risbec E. acutissima (Risbec, 1954) и ap. Однако эти изменения не нарушают об- щего плана строения всего комплекса органов. С другой стороны, даже у самых примитивных из Форм, утратив- ших раковину, мантия всегда рудиментарна, а мантийный комплекс под- вергается перестройкам, сходным с теми, которые произошли у Asterophila. У Molpadicola orientalis Grusov мантийная полость еще сравнительно велика, но в нее открывается лишь почка; органы, располагавшиеся на потолке полости, исчезли; остальные (матка, рек- тум) оказались вынесенными за ее пределы (Грузов, 1957). Небольшой рудимент мантии, прикрывающий только отверстие почки, сохранился также у Paedophoropus (Ivanov, 937). У всех Entoconchidae мантия окончательно исчезает. Из мантийного комплекса, по-видимому, первым исчезает осфра- дий. Гипобранхиальная железа может дегенерировать очень рано, но может сохраняться и у глубоуо измененных паразитов. Редукция жабры происходит, вероятно, одновременно с мантией. Редукция задней киш- ки и анального отверстия сопряжены в большей степени с изменениями пищеварительной системы, чем с мантийным комплексом. Дольше всех удерживает связь с мантийной полостью почка. Условия для редукции раковины и мантии подготовлены всем ходом филогенетического развития паразитов. Обитание в толще сте- нок хозяина и в его внутренних органах делает ненужным сумествование раковины. Также излишней становится защита органов мантийного ком- плекса, главным образом, из-за развития ложной мантии. Едва ли не основной причиной исчезновения мантии можно признать ее топографи- ческое полпжение: складка, направленная свободным краем вперед, оказывается невыгодной при погружении паразита в стенку хозяина, т.к. вход в ограничиваемую ею полость становиться затрудненным. Рис. 22. Нога. Ложная мантия уда- FIG. 22. лена, оставшийся лоскут отогнут. 1 - задняя лопасть ноги; 2 - внутренностный мешок; 3 - ложная мантия; 4 - передняя лопасть ноги. Foot. Pseudopallium removed, ге- mainder folded back. 1 - posterior part of foot; 2 - visceral mass; 3 - pseudopallium; 4 - anterior part of foot. 136 E. Н. ГРУЗОВ 5. Нова. Нога Asterophila низведена до степени небольшого рудимента, расположенного на внутренностном мешке около основания ложной ман- тии /рис. 22/. Глубоким поперечным вдавлением нога разделена на две части и перегнута в этом месте пополам. В результате перегиба передняя, большая лопасть ноги обращена к вершине внутренностного мешка /рис. 6/ и полностью (или почти полностью) прикры- вает небольшую заднюю лопасть. В описании, сделанном Рандаль и Хизом, задняя лопасть не упомянута. Если отогнуть переднюю лопасть вперед /рис. 22/, становится заметной поверхность между обеими лопастями, покрытая многочислен- ными поперечными складками, между которыми проходят не столь глу- бокие продольные морщинки. Морщинистый участок имеет более или менее овальную Форму и вытянут в передне-заднем направлении. Изу- чение срезов показывает, что он состоит из педальной соединитель- ной ткани. Задняя лопасть приподнимается над морщинистым участком в виде небольшого конического бугорка (1). Гомология частей ноги не вызывает сомнения: передняя доля от- вечает проподиуму, задняя - метаподиуму, а складчатая поверхность между ними - подошве других Форм. Нога у самцов развита несколько лучше, чем у самок. Внешне она также поделена глубокой перетяжкой на передний и задний отделы, приблизительно равной величины /рис. 10 (3)/. Морщинистость ноги незначительна. У молодых Форм в переднем отделе есть небольшой рудимент педальной железы, полностью исчезающий с возрастом. BTo- рая педальная железа и крышечка постоянно отсутствуют. Снаружи нога одета ресничным эпителием /рис. 23/. Он состоит из высоких цилиндрических клеток и в большей своей части имеет складчатый характер. IS Рис. 23. Продольный разрез через SA FIG. 23. переднюю лопасть ноги. yy +0 De Азокармин no Гейденгайну. Sue À y 1 - продольные мускульные za aS. волокна; ENDS 2 - соединительная ткань; oF 3 - покровный эпителий; Oe 4 - базальная мембрана; 5 - мускульные волокна. Longitudinal sectionthrough anteri- or part offoot. Stained with Heiden- hain’s azocarmin. 1 - longitudinal muscle fibers; 2 - connective tis- sue; 3- surficial epithelium; 4 - O:5mm_ basal membrane; 5- muscle fibers. ASTEROPHILA JAPONICA 137 O-5mm Рис. 24. Продольный разрез через эпителий; FIG. 24. тело самца. Железный ге- 13 - внутренний покров- матоксилин, лихтгрюн. ный эпителий. 1 - эпителий внутренност- ного мешка; - семенник; - пенис; - ресничная борозда; a Longitudinal section through body 4 5 - ложная мантия; 6 if 8 of male. Stained with iron hema- toxylin, light green. 1 - epithelium of visceral mass; 2- testis; 3- penis; 4- ciliated groove; 5- pseudopallium; 6 - pseudopallium - ложная мантия самки; - педальный ганглий; - рудимент педальной of female; 7 - pedal ganglion; 8 - железы; vestige of pedal gland; 9- foot; 9 - нога; 10 - печень; 10 - liver; 11 - connective tissue; 11 - соединительная ткань; 12 - external surficial epithelium; 12 - наружный покровный 13 - internal surficial epithelium. Вся толща ноги заполнена соединительной тканью /рис. 23 (2)/, в которой проходят мускульные волокна (5), приуроченные главным об- разсм к периферии органа. В центре ноги мускульные элементы немно- гочисленны, что свидетельствует о полной редукции колюмеллярного мускула. Педальная железа молодых мужских особей имеет Форму небольшого круглого пузырька, погруженного в соединительную ткань ноги /рис. 24 (8)/. Образующие железу крупные вакуолизированные клетки плотно прижаты друг к другу и лишены видимого секрета. К переднему краю железы подходит короткий канал, открывающийся наружу между основа- нием передней лопасти ноги и ложной мантией. Положение железы сви- детельствует о ее гомологии с передней (краевой) железой других моллюсков. Как самый факт существования ноги у Asterophila, так и силь- ная ее дегенерация не представляют ничего неожиданного. Редукция 138 Kd Ну MTEYSOB ноги свойственна паразитическим моллюскам при переходе их к сидя- чему образу жизни; однако полное ее исчезновение наблюдается у сильно специализированных Entoconchidae. Процесс редукии иллю- стрируется следующим морфологическим рядом: Melanella - Mucronalia - Megadenus - Stilifer, - Parastilifer - Gasterosiphon - Entoconchidae. Все исключения из этого правила ( Megadenus arrhynchus, Stilifer celebensis Kükenthal, Paedophoropus dicoelobius Ivanov и др. имеют хорошо развитую, хотя и измененную ногу) объясняются тем, что нога приобретает новые, не локомоторные функции ( Ivanov, 1937; Иванов, 1953; Hirase, 1932). По степени редукции ноги Asterophila оказывается Ha одной ступени с Gasterosiphon, хотя характер изменения органа в обоих случаях различен: у Gasterosiphon нога сохраняется в виде боко- вых складочек, у Asterophila - передней и задней. Присутствие у Asterophila — рудимента метаподиума оказывается важным для понимания его систематического положения и эволюции: деление ноги на про - и метаподиум из всех паразитических моллюс- ков наблюдается только у некоторых Melanellidae и низших Stili- feridae; y высших Stiliferidae и Paedophoropodidae oo от- сутствует. Между тем, по уровню общей организации Asterophila бесспорно приближается к последним формам. Подобное несоответствие указывает на особый путь эволюции А. japonica, но не может пре- пятствовать сближению ее с группой Stiliferidae - Entoconchidae, поскольку в эмбриональном развитии Hora представителей этих семейств обнаруживает ясное деление на переднюю и заднюю доли. 6. Пищеварительная система, Пищеварительный анпарат /рис. 25/ состоит из глотки, пищевода и пищаварительной железы, или печени. Рис. 25. Пищеварительная система. FIG. 25. Ложная мантия удалена, стенка тела вскрыта. 1 - яичник; 2 - печень; 3 - яйцевод; 4 - пищевод; 5 - глотка; 6 - дивертику- лы глотки; 7 - ротовое отверстие; ложная мантия; 9 - мантия. 00 | Alimentary system. Pseudopallium removed, body wall opened. 1- ovary; 2- liver; 3- oviduct; 4 - esophagus; 5- pharynx; 6 - pha- ryngeal diverticulum; 7 - opening of mouth; 8 - pseudopallium; 9 - mantle. ASTEROPHILA JAPONICA 139 IO TES Глотка представляет собой овальный в продольном сечении или же цилиндрический орган, полость которого сильно расширена по сравнению с полостью пищевода /рис. 14/. Язык, радула и челюсти в ней отсутствуют. Спереди глотка открывается наружу ро- товым отверстием, а сзади соединяется с пищеводом. На переднем конце органа глоточный эпителий образует два сле- пых кармана глотки, лежащих в толще соединительной ткани BO ŸPOH- тальной плоскости /рис. 25 (6)/. Рандаль и Хиз считают эти обра- зования рудиментами слюнных желез. Они имеют вид небольших пузырь- ков, обычно шаровидной формы, но у некоторых индивидуумов сильно увеличиваются в размерах, и их стенки становягся складчатыми, что соответствует описанию Рандаль и Хиза. Просмотр большого коли- чества экземпляров Asterophila показывает, что складчатость сте- нок этих выпячиваний встречается не часто. С полостью глотки ди- вертикулы связаны каналами /рис. 12, 13/, часто столь короткими, что правильнее говорить о непосредственном соеднении глотки с дивертикулами. Глоточный эпителий /рис. 26/ состоит из невысоких цилиндри- ческих или кубических клеток, несущих реснички, под которыми хо- рошо заметны базальные зерна. Спереди эпителий переходит в покровный эпителий хобота, а сзади - в эпителий пищевода. Ни- каких железистых клеток (ни расположенных среди обычных эпители- альных, ни погруженных под базальную мембрану) в нем обнаружить 1 - клетки соединительной ткани; 2 - продольные мышцы; 3 - ядра мус- кульных клеток; - основное вещество; радиальные мускуль- ные волокна; 6 - коль- цевые мускульные во- локна; 7 - базальная мембрана; 8 - эпителий глотки; 9 - базаль- ные ресничные зерна. or ! Part of anterior section through pharynx. Stained with Heidenhain’s azocarmin. 1 - cell of connective tissue; 2- longitudinal muscle; 3 - nucleus of muscle cell; 4- ground mass; 5- radial muscle fibers; 6 - transverse muscle fi- Puc. 26. Участок поперечного раз- bers; 7 - basalmembrane; 8 - epi- FIG. 26. реза через глотку. Aso- thelium of pharynx; 9 - basal gran- кармин по Гейденгайну. ще. 140 Е. Н. ГРУЗОВ не удалось. Это обстоятельство кажется особенно удивительным, т. к. Рандаль и Хиз ( Randall et Heath, 1912) описали погружен- ные железистые клетки, открывающиеся темно окрашивающимися прото- ками между клетками эпителия. Однако изображения их авторы не при- водят, и решить, с какими именно образованиями они имели дело, не- возможно. Строение глоточного эпителия несколько меняется в области бо- ковых карманов глотки. На протяжении каналов, соединяющих их с полостью глотки, он делается ниже, становясь кубическим и далее - плоским, и теряет реснички. Базальные зерна ресничек рассмотреть в нем не удается. Секреторная Функция этого эпителия категоричес- ки исключается. Снаружи от глоточного эпителия находится слой соединительной ткани, богатой мускульными элементами /рис. 26/. Сразу за базаль- ной мембраной эпителия лежит слой кольцевых мышц (6), а глубокие слои соединительной ткани пронизаны радиальными волокнами (5). Кроме упомянутых мускульных волокон, в стенке глотки присутствуют отдельные, редкие волокна продольного направления (2). Они лежат снаружи от кольцевых и обособленного слоя не составляют. Спереди кольцевые и продольные мышцы глотки продолжаются в стенках хобота.. Обилие радиальных мускульных волокон и отсутствие в глоточном эпителии железистых клеток свидетельствуют о сосательной Функции органа.. Из рис. 26 видно, какое сильное развитие в стенках глотки полу- чает основное вещество соединительной ткани (4). Оно окрашивается по Маллори в синий цвет и слегка подкрашивается бисмаркбрауном. Его волоконца очень нежные и гораздо более тонкие, чем в соедини- тельной ткани других органов. В основном веществе разбросаны мно- гочисленные соединительно-тканные клетки с крупными, бедными хрома- тином ядрами (1); они гораздо обильнее в периферических частях сте- нок глотки, чем в центре. Ядра мускульных клеток, напротив, рас- полагаются ближе к полости органа /рис. 26/. На срезах через стенку глотки встречаются многочисленные нерв- ные волокна, а около боковых выпячиваний располагаются два неболь- ших буккальных ганглия. Чрезвычайно важным для выяснения систематического положения Asterophila оказывается вопрос о природе слепых карманов TIOT- ки. Возможно два решения этого вопроса. Следуя за Рандаль и Хи- зом, можно считать дивертикулы рудиментами слюнных желез. С дру- гой стороны, можно признать их новообразованиями, не находящими себе гомологов у других Gastropoda. Какая из этих возможностей соответствует истине? Бедность рассматриваемых образований морфо- логическими признаками не дает возможности высказаться по этому поводу с полной определенностью. Дивертикулы, несмотря на сильную редукцию, обнаруживают харак- терное деление на собственно "железу" и ее проток. У некоторых индивидуумов Asterophila карманы имеют складчатые стенки и по внешнему виду напоминают слюнные железы брюхоногих. Положение этих образований в латеральной плоскости, в передней части глотки,- соответствует месту впадения протоков слюнных желез. Эти факты, как будто, говорят в пользу представлений Рандаль и Хиза. | | | | | | ASTEROPHILA JAPONICA 141 зерна; базальная мембрана; 3 - кольцевые мускульные волокна; 4 - продольные мускульные волокна. D р Part of anterior section through esophagus. Stained with Mallory’s. 1 - basal granule; 2 - basal mem- Рис. 27. Участок поперечного разре- brane; 3 - transverse muscle fi- FIG. 27. за через пищевод. Маллори. bers; 4- longitudinal muscle fi- 1 - базальные ресничные bers. С другой стороны, полное погружение дивертикулов в ткани глот- ки совсем необычно для слюнных желез брюхоногих. Полное отсутствие секреторной деятельности также представляет аргумент в защиту про- тивоположной точки зрения. Весьма существенно, что все моллюски (как паразитические, так и свободноживущие) группы Melanellidae - Entoconchidae , с ко- торыми Asterophila обнаруживает много общего во всех чертах сво- его строения, лишены слюнных желез или их рудиментов. Это застав- ляет нас рассматривать гипотезу Рандаль и Хиза, по крайней мере, как спорную. Б. Пищевод От заднего конца глотки берет начало пищевод, который тонкой трубкой с нешироким просветом без каких-либо расширений проходит во внутренностный мешок и впадает в печень. Стенки его образованы кубическим ресничным эпителием /рис. 27/. Снаружи пищевод одет слоем кольцевых (3), а затем продольных (4) мускульных волокон глотки. Постоянных, встречающихся у всех особей, изгибов пищевода и, тем более, петель нет. Однако часто на уровне основания ложной мантии наблюдается его искривление и отклонение от прямого курса, что объясняется неравномерным растяжением ложной мантии и связан- ным с этим смещением ротового отверстия в сторону. Именно такая особь изображена Рандаль и Хизом ( Randall et Heath, 1912) Ha Fig. 1 nu их работы. Кроме того, часто эпителий пищевода стано- вится складчатым, что указывает на некоторое сокращение переднего конца тела животного. В. Пищеварительная железа. . Объемистая пищеварительная железа, печень, у женских особей занимает всю центральную часть внутренностного мешка /рис. 25/. У половозрелых особей спинная стенка пищеварительной железы по всей длине образует чрезвычайно глубокую складку, вдающуюся внутрь органа (3). В глубине сладки вдоль центральной продольной оси тела проходит яйцевод. Впячивание стенок делит полостьоргана, на две лопасти, 142 Bu Ш. ATEVSOB охватывающие яйцевод со всех сторон и соприкасающиеся друг с Apy- гом на спинной стороне тела. В результате печень приобретает вид баранки, и создается обманчивое впечатление, что женский гонодукт прободает пищеварительную железу. У самцов и молодых самок подоб- ное вдавление отсутствует, и гонодукт проходит рядом с боковой стенкой органа. Кроме дорзальной складки, имеется целый ряд менее глубоко вдающихся в полость печени складок. Отграничиваемые ими дольки соединяются друг с другом и, в конце концов, открываются в централь- ный просвет пищеварительной железы /puc. 13/. Внутрь печени ведет единственное отверстие, лежащее на ее пе- редней стороне, через которое орган соединяется с пищеводом. Задняя кишка отсутствует. Гистологическое строение печени сходно у самцов и у самок /рис. 28/. Стенка органа состоит из типичного для брюхоногих од- нослойного эпителия, содержащего клетки двух сортов. Основную массу составляют крупные цилиндрические клетки (2) с вакуолизи- ровакной протоплазмой, почти не окрашивающейся никакими красите- лями. Клетки содержат сферические жировые включения (1), приоб- ретающие после осмиевых фиксаций черный цвет. От дистальных кон- цов клеток внутрь полости печени отходят какие-то нити, несколько напоминающие реснички /рис. 28/. Базальные зерна под ними обна- Рис. 28. Эпителий печени. Жид- 6 - капли секрета; FIG. 28. кость Флемминга. Желез- 7 - железистые клетки. ng er en Epithelium of liver. Fixed with и Flemming’s mixture. Stained with 1 - включения; Heidenhain’s iron hematoxylin. 1- 2 - пищеварительные клет- inclusions; 2- digestive cell; 3- ки; 3 - базальная basal membrane; 4 - muscle MeMOpaHa; fibers; 5- connective tissue; 6 - 4 - мускульные волокна; droplets of secretion; 7 - glandular 5 - соединительная ткань; cells. ASTEROPHILA JAPONICA 143 ружить не удалось. Возможно, что они представляют собой струйки секрета, выдавленные из клеток при Фиксации животного. Во всяком случае, отсутствие базальных зерен, не вполне типичный вид самых "ресничек", а также отсутствие мерцательных элементов в печени дру- гих паразитических брюхоногих не позволяют считать эти образования ресничками. Заметим, кстати, что их окраска и окраска плазмы в дистальном конце клеток совершенно одинаковы. Клетки другого сорта (7) отличаются меньшей шириной и более темной плазмой, в которой видны округлые, темные капли какого-то секрета. Их плазма сильно окрашивается железным гематоксилином. Строение эпителия печени одинаково на всем протяжении органа. Никаких намеков на исчезнувший желудок нет. По строению пищеварительного аппарата Asterophila o6Hapyxu- вает много общего с паразитическими Melanellidae - Entoconchidae. Большинство Melanellidae и Stiliferidae обладают глоткой в общем сходного с Asterophila строения. Существенно, что во всех случаях она лишена челюстей, языка, радулы и слюнных желез. Глоточные выпячивания в области глотки известны лишь у Megadenus holothuricola (Rosen, 1910) u M. voeltzkowi (Schepman et Nierstrasz, 1913). У обоих видов непарная железа ле- жит вентрально около переднего конца глотки и погружена в ее стенки. Проводить гомологию этих образований с какими бы то ни было орга- нами других Gastropoda едва ли возможно. Пищевод А. japonica , выстланный мерцательным эпителием, на- поминает соответствующий орган Pelseneeria stylifera (Turton) и Entocolax ludwigi (Rosen, 1910; Voigt, 1888). Y остальных паразитических моллюсков эпителий пищевода He имеет ресничек. Пищевод Entocolax rimsky - korsakovi Iwanow снабжен многочислен- ными мешковидными железами (Иванов, 1953). Пример Megadenus holothuricola, М. voelizkovi и Entocolax rimsky - korsakovi показывает возможность появления новообразований в районе перед- ней кишки. Редукция желудка, задней кишки и изменения печени у Astero- phila ue представляют ничего неожиданного. Процесс деградации желудка и субституции его печенью подробно освещен в литературе (Graham, 1949; Rosen, 1910; Иванов, 1945 u ap.). Asterophila занимает промежуточное положение между Stiliferidae и низшими Entoconchidae, более приближаясь к последним. 7. Кровеносная система и органы дыхания. Кровеносная система Asterophila претерпела сильное вторич- ное упрощение, касающееся главным образом сосудистого аппарата. Сердце находится в обширной, выстланной плоским' перитонеальным эпителием перикардиальной полости, лежащей под левым краем мантии. Оно состоит из предсердия и желудочка, расположенных так, что BHem- ний конец предсердия лежит в заднем наружном углу перикардиальной полости и сообщается с околопочечным CUHYCOM, а желудок подходит к внутренней стенке перикардия и находится, следовательно, справа и немного впереди предсердия /рис. 8, 10/. Клапанов между отдела- ми сердца нет. Стенки как желудочка, так и предсердия весьма мус- 144 Prc. L 3 ou» E. Н.. ГРУЗОВ 0-25 тт 29. Фронтальный разрез через тело самца. матоксилин, Железный ге- лихтгрюн. наружный покровный эпителий;2 - семенник; эпителий внутренност- ного мешка; ложная мантия; соединительная пищевод; дополнительная железа; церебро-плевральная ганглиозная масса; буккальные ганглии; дивертикулы глотки; глотка; 12 - ротовое отверстие; 13 - лож- ная мантия самки; субинтестинальный ткань; ганглий; 15 - печень; 16 - внутренний покров- ный эпителий. Frontal section through body of male. Stained with iron hematoxy- lin, light green. 1- external sur- ficial epithelium; 2- testis; 3- epithelium of visceral mass; 4- pseudopallium; 5 - connective tis- sue; 6 - esophagus; 7 - accessory gland; 8 - cerebro-pleural gangli- onic mass; 9- buccal ganglion; 10 - pharyngeal diverticulum; 11 - pharynx; 12- opening of mouth; 13 - pseudopallium of female; 14 - subintestinal ganglion; 15 - liver; 16 - internal surficial epithelium. кулисты и образуют множество продольных складок /рис. 8/. Сосудистая система Функционально заменена, системой кровенос- ных синусов и лакун /рис. 12, 13 /. отходящая от желудочка короткая аорта, внутрь висцерального мешка и скоро впадающая в обширный головной синус. Из сосудов сохранилась только направляющаяся вперед и Кровь в нем омывает ганглии центральной нервной системы и прилежащие органы. Спереди синус связан с полостью хобота /рис.14/. Сзади он продолжается в то, CUHYCOM: что может быть названо висцеральным систему лакун, простирающихся вдоль по гонодукту, между ASTEROPHILA JAPONICA 145 внутренними дольками печени и среди яйцевых фолликулов, где лакуны наиболее обширны /рис. 13 /. У самцов кровеносный синус вокруг ce- менника также весьма объемист /рис. 12 /. Венозная кровь собирается в предсердие из широкого синуса на поверхности гонады и печени, и при этом часть ее проходит через кровеносные лакуны почки, особенно многочисленные около ее Hapyx- ной стенки и в трабекулах. Циркуляция крови осуществляется, по- видимому, не только работой сердца, но и сокращением мускулатуры всего тела. Специальных органов дыхания нет. Респирация происходит в сильно разветвленных лакунах ложной мантии, связанных с головным кровеносным синусом. Кровеносная система, нормально развитая у ряда эктопаразити- ческих Stiliferidae, с углублением паразитизма редуцируется. Вероятно, существует тесная связь между редукцией кровеносной си- стемы и жабры; во всяком случае, все Формы, утратившие ктенидий, обнаруживают значительную редукцию сосудов, замещаемых лакунами первичной полости тела. Хорошей иллюстрацией этого положения слу- жит Molpadicola orientalis, органы внутренностного мешка кото- рой почти не подверглись редукции, и потому отсутствие сосудов y этой формы может быть связано только с исчезновением жабры (Гру- зов, 1957). Сосуды отсутствуют также у Paedophoropus (Ivanov, 1837), Gasterosiphon (Koehler et Vaney ,1903)u всех Entoconchi - dae (Bonnevie , 1902; Schwanwitsch, 1917; Иванов, 1947, 1953). Последние из перечисленных Форм лишены также и сердца. 8. Выделительная система, Почка, Asterophila представляет обширный орган /рис. 12, 13/, граничащий с перикардием, лежащим несколько вентральнее. PeHo- перикардиальное отверстие и нефридиальная железа отсутствуют. Передний конец почки находится в области мантийной полости, куда, она открывается небольшим отверстием. Мочеточник отсутствует. Расширяющей или суживающей отверстие мускулатуры нет. Стенки органа образуют многочисленные вдающиеся внутрь склад- ки (трабекулы), анастомозирующие друг с другом и местами образую- щие губчатую ткань, заполняющую большую часть внутреннего прос- вета органа. Трабекулы могут отходить от всех стенок почки, но наружная стенка всегда несет большее их число, и сами складки здесь крупнее; кроме Toro, трабекулы на наружной стенке появляются в OH- тогенезе, по-видимому, раньше, чем на внутренней. Количество Tpa- бекул у самцов меньше, чем у самок. Однослойный почечный эпителий /рис. Зо/ образован невысокими цилиндрическими, кубическими или же неправильной Формы многоуголь- ными клетками, лишенными ресничек. В каждой клетке имеется нес- колько крупных и большое число мелких вакуолей (2), содержащих раз- личного размера включения (3), имеющие естественный буровато-серый цвет и окрашивающиеся по Маллори в синий цвет, а также чернящиеся железным гематоксилином. Включения, бесспорно, представляют собой продукты выделения животного. Таким образом, почка А. japonica мало изменена по сравнению 146 | Е. H. ГРУЗОВ со свободноживущими Gastropoda. То же можно сказать относи- тельно этого органа у других паразитических моллюсков Melanell - idae, Stiliferidael и Paedophoropodidae. Характерно, что почечные трабекулы здесь располагаюся только на наружной стенке ODrFAHS MY Entoconchidae почки нет. Рис. 30. Эпителий почки. Железный FIG. 30. гематоксилин Гейденгайна. 1 - базальная мембрана; 2 - вакуоли; 3 - конкреции. Epithelium of kidney. Stained with Heidenhain’s iron hematoxylin. 1 - basal membrane; 2 - vacuoles; 3 - concretions. 9. Нервная система. А. А. Центральная нервная система. Центральная нервная система Asterophila имеет следующий план строения /рис. 31/. Церебральные и плевральные ганглии сли- ваются друг с другом, образуя общую ганглиозную массу (5, 15), ле- жащую над кишкой. Вентрально к ним примыкают два педальных ганг- лия (9), лежащие рядом с основанием ноги. Имеется пара статоциетов (8), занимающих нормальное положение. В области глотки находятся два буккальных ганглия (1), прилегающих к боковым дивертикулам киш- ки и соединяющихся друг с другом комиссурами (2), проходящими над и под глоткой. По-видимому, имеется соединение буккаьных ганглиев с церебральными при помощи церебро-буккальных коннективов (3). Висцеральное нервное кольцо разомкнуто. Одна его половина состоит из висцерального (4) и субинтестинального (6) ганглиев, связанных с левой половиной церебро-плевральной ганглиозной массы коннекти- вом (7), проходящим под кишкой. Другая половина висцерального кольца содержит единственный супраинтестинальный ганглий (12); коннектив, соединяющий его с левой половиной церебро-плевральной массы (14), огибает кишку сверху. Таким образом, наблюдается пе- рекрест нервных стволов, направляющихся во внутренностный мешок, т.е. хиастоневрия. От описанного плана строения имеются много- численные отступления, связанные с изменчивостью топографического положения отдельных органов, и главным образом, большей или меньшей изогнутостью пищевода. 1) у Gasterosiphon deimatis почка отсутствует ( Koehler et Vaney, 1903). ASTEROPHILA JAPONICA 147 ный коннектив; 8 - cTa- тоцист; Y - педальные ганглии; 10 - педальная комиссура; 11 - нерв ста- тоциста; 12 - супраинтес- тинальный ганглий; 13 - нервы ложной мантии; 14 - плевро-супраинтести- нальный коннектив; 15 - левая половина цереб- ро-плевральной ганг- лиозной массы. lig Diagram of central nervous system. Posterior view. 1- buccal gang- lion; 2 - buccal commissures; 3 - cerebro-buccal connectives; 4 - visceral ganglion; 5 - right por- Puc. 31. Схема строения централь- FIG. 31. ной нервной системы. Вид сзади. Е $ ce + : tion of cerebro-pleural ganglionic ? mass; 6 - subintestinal ganglion; 3 - церебро-буккальные 7- pleuro-subintestinal connective; коннективы; à £ 8 - statocysts; 9- pedal ganglia; 4 - висцеральный ганглий; 10 - pedal commissure; 11 - nerve 5 - правая половина цереб- of statocyst; 12- supraintestinal ро-плевральной гангли- ganglion; 13- pseudopallial nerves; озной массы; 6 - субин- 14 - pleuro-spuraintestinal connec- тестинальный ганглий; tive; 15 - left portion of cerebro- 7 - плевро-субинтестиналь- pleural ganglionic mass. У особи, изображенной на puc. 32, плевро-супраинтестинальный коннектив плотно прижимается к левой половине церебро-плевральной массы и в одном месте сливается с ней (16), так что на срезах ви- ден переход волокон из нервного тяжа в ганглий. В другом случае /рис. 33 Б/ этот коннектив полностью сли- вается с церебро-плевральной массой и выступает лишь как валик на ее поверхности. Часто наблюдается большая концентрация центральной нервной системы, чем это описано выше. У экземпляра, изображенного на рис. 34, субинтестинальный (6) и висцеральный (4) ганглии слиты вместе и отделяются только легкой перетяжкой; кроме того, субин- тестинальный ганглий частично сливается с правой половиной церебро- плевральной массы. Таким образом, у данного экземпляра оказывают- ся слитыми в общую массу шесть ганглиев: два церебральных, два плевральных, один париетальный и висцеральный. Обращает на себя внимание сильное развитие части нервной си- стемы, расположенной в хоботе (16) и образующей плексус симпати- ческой нервной системы вокруг глотки. Наконец, в одном случае /рис. 35/ субинтестинальный ганглий (6) соединяется с правым плевральным (5), но висцеральный (4) да- леко отстоит от него. Коннектив (7), соединяющий его с париеталь- 148 By H. “EPYSO0OB Центральная нервная си- crema. А - вид спереди; Б - вид сзади. Пласти- ческая реконструкция. 16 - место соединения плевро-супраинтестиналь- ного коннектива с левой половиной церебро-плев- ральной массы. Остальные обозначения как Ha puc.31. Central nervous system. А, an- terior view; В, posterior view. Plastic reconstruction. 16 - point of fusion of pleuro-supraintestinal connective with left portion of cere- bropleural mass. Other numbers as in Fig. 31. Центральная нервная си- стема. А - вид спереди; Б - вид сзади. Пласти- ческая реконструкция. Обазначения как на рис.31. Central nervous system. А, ап- terior view; B, posterior view. Plastic reconstruction. Numbers as in Fig. 31. ASTEROPHILA JAPONICA 149 Puc. 34. Центральная нервная систе- FIG. 34. ma. А - вид спереди; B - вид сзади. Пластическая ив Central nervous system. А, an- 16 - нервный плексус глот- terior view; В, posterior view. ки; 17 - педальный нерв; Plastic reconstruction. 16 - 18 - висцеральный нерв; nerves of pharyngeal plexus; 17 - 19 - церебро-плевро-пе- pedal nerve; 18 - visceral nerve; дальный коннектив. Осталь- 19- cerebro-pleuro-pedal соппес- ные обозначения как Ha tive. Other numbers as in Fig. Brei... 31; 31. ным ганглием, проходит неподалеку от второго плевропариетального коннектива (14), и между ними устанавливается связь при помощи короткого нервного тяжа (16). Отмеченная пластичность строения центральной нервной системы иллюстрирует ход и направление ее эволюции в сторону увеличения концентрации ганглиев. У мужских особей концентрация несколько меньшая /рис. 29, 36/. Органы чувств представлены парой статоцистов, лежащих рядом с педальными ганглиями /рис. 34, Б (8)/. Глаза и щупальцы от- сутствуют. Б. Периферическая нервная система. Наиболее мощные нервы отходят от латеральных частей церебро- плевральной массы, по три с каждой стороны. Они направляются в ложную мантию /рис. 31-35/, проходят во внутреннем комплексе тка- 150 Ш. «Не. TPYSOB 1 0-25mm A 0-25mm B — Рис. 35. Центральная нервная си- FIG. 35. стема. А - вид спереди; Б - вид сзади. Пласти- ческая реконструкция. 16 - место ‘соединения субинтестинального ган- глия с плевро-супраинтес- тинальным коннективом; 17 - педальный нерв; 18 - нерв субинтестиналь- ного ганглия. Остальные обозначения как на рис.31. Central nervous system. А, an- terior view; В, posterior view. Plastic reconstruction. 16 - point of fusion of subintestinal ganglion with pleuro-supraintestinal con- nective; 17 - pedal nerve; 18 - nerves of subintestinal ganglion. Other numbers as in Fig. 31. ней этого органа и легко прослеживаются на значительном протяжении. Кроме того, от церебро-плевральной ганглиозной массы отходят два нерва к статоцистам /рис. 34/. Педальные ганглии /рис. 34/ посылают по два коротких нерва в ногу (17). У самцов от правого педального ганглия отходит мощный нерв в основание совокупительного органа. Пара тонких нервов отходит от супраинтестинального ганглия и очень скоро теряется в соединительной ткани внутренностного мешка, в области мантии, перикардия и почки /рис. 33/. Проследить область иннервации субинтестинального ганглия не удалось, хотя на некоторых препаратах заметны несколько отходящих от него тонких нервов /рис. 34/. Около висцерального ганглия на- блюдался единственный нерв /puc. 33/, проходящий вдоль гонодукта ASTEROPHILA JAPONICA 151 и вскоре исчезающий. Нервы, иннервирующие глотку, были описаны выше. Большинство Melanellidae и Stiliferidae обладают высоко- развитой центральной нервной системой обычного для Taenioglossa типа. Она состоит из парных церебральных, плевральных и педальных ганглиев, соединяющихся друг с другом, а также двух париетальных и, по-видимому, всегда единственного висцерального гангпия. MHo- гие представители этой группы ( Melanella polita (Linnaeus), Balcis devians (Monterosato);, B.alba (Da Costa) Megadenus arrhynchus, Stilifer celebensis и Gasterosiphon) имеют, кроме того, парные буккальные ганглии, расположенные в хоботе по соседству с глоткой и соединяющиеся с церебральными длинными коннективами. Уже у примитивных форм проявляется тенденция к концентрации церебральных, плевральных и педальных ганглиев, выражающаяся в их сильном сближении и укорочении соответствующих коннективов и ко- миссур, однако ганглии при этом остаются еще вполне раздельными. Таково строение нервной системы Melanella equestris (Koehler et Vaney, 1912), Megadenus cysticola Koehler et Vaney и М. arrhynchus ( Koehler et Vaney, 1912; Иванов, 1952), всех Pelseneeria (Rosen, 1910), ряда видов Stilifer (Risbec, 1954; Иванов, 1952) и др. Так как подобная степень концентрации известна еще и у многих свободноживущих Taenioglossa, то весь- ма вероятно, что она явилась исходным состоянием для всех более специализированных паразитов, для которых характерно слияние от- дельных ганглиев друг с другом. При этом оказывается, что плев- ральные ганглии имеют тенденцию сливаться с церебральными, а це- ребральные друг с другом. Педальные ганглии обычно остаются само- стоятельными, но тесно прижимаются к церебральны`. и плевральным, ‚’ а соответствующие коннективы значительно укорачиваются (Иванов, 1952). Изменения висцерального нервного кольца у Stiliferidae выражаются в исчезновении осфрадиального ганглия и редукции ряда ганглиев. Нервное кольцо часто оказывается разомкнутым. По уровню концентрации нервной системы Asterophila обнару- живает много общего с Paedophoropus dicoelobius и с некоторы- ми представителями Stiliferidae . Редукция центральной нервной системы у Entoconchidae зашла значительно дальше, и только y Entocolax schwanwitschi сохраняется рудиментарный церебральный ганглий (Schwanwitsch, 1917). Женские и гермафродитные особи остальных Entoconchidae полностью лишены нервной системы. В то же время у самцов некото- рых Entoconchidae, например Entocolax trochodotae, нервная система развита несколько лучше (Heding, 1934), что стоит в свя- зи с неотеническим характером этих организмов. 10. Половая система А. Мужская половая система Семенник представляет собой обширный мешковидный орган, зани- мающий большую часть внутренностного мешка, не исключая и вершины 152 E "Ho "EPYSOD 0-25mm 7 Puc. 36. Фронтальный разрез через чень; 17 - эпителий FIG. 36. тело самца. Железный ге- внутренностного мешка. матоксилин, лихтгрюн. 1 - семенник; 2 - висце- ральный ганглий; 3 - на- ружный покровный эпителий; 4 - соединительная ткань; 5 - внутренний покровный эпителий; 6 - дополнитель- ная железа половой системы; 7 - мантийная полость; 8 - ложная мантия; 9 - мантия; 10 - ресничная борозда пениса; 11 - ди- Frontal section through body of male. Stained with iron hematoxy- lin, light green. 1- testis; 2- visceral ganglion, 3- external surficial epithelium; 4- connec- tive tissue; 5 - internal surficial epithelium; 6- accessory gland of reproductive system; 7 - mantle cavity; 8- pseudopallium; 9 - mantle; 10- ciliated groove of вертикулы глотки; 12 - ro- penis; 11 - pharyngeal diverti- ловной кровеносный синус; culum; 12 - cephalic blood sinus; 13 - педальный ганглий; 13 - pedal ganglion; 14 - pseudo- 14 - ложная мантия самки; pallium of female; 15 - suprain- 15 - супраинтестиналь- testinal ganglion; 16 - Пуег; 17- ный ганглий; 16 - ne- epithelium of visceral mass. /рис. 36/. Спереди он граничит с пищеварительной железой, пери- кардием, почкой и гонодуктом; вся остальная поверхность органа при- легает к покровам внутренностного мешка, местами отделяясь от них кровеносными синусами. Снаружи семенник покрыт тонкой соединитель- но-тканной мембраной. На срезах через семенник видны картины интенсивного спермато- генеза. Зародышевые клетки занимают пристеночное положение, а бли- же к центру органа располагаются сперматоциты на разных стадиях созревания и зрелые сперматозоиды. У молодых неполовозрелых осо- бей семенник целиком заполнен половыми клетками и лишен внутреннего ASTEROPHILA JAPONICA Рис. 37. Разрез через выводные пути FIG. 37. мужской половой системы. Кислый гемалаун Мейера, бисмаркбраун. 1 - сперматозоиды; Sr A Section through vas deferens. 3 - эпителий семепровода; Stained with Mayer’s acid haema- 4 - железистые клетки; lum, Bismarck brown. 1- sper- 9 - опорные клетки; matozoa; 2-testis; 3- epithe- 6 - эпителий внутренност- lium of vas deferens; 4 - glandu- ного мешка; lar cells; 5- supporting cells; 7 - дополнительная железа; 6 - epithelium of visceral mass; 8 - соединительная ткань; 7 - accessory gland; 8 - connec- 9 - семепровод. tive tissue; 9 - vas deferens. просвета. У старых самцов слой сперматоцитов и сперматогониев очень TOHOK, и орган имеет обширную внутреннюю полость, в которой группами и поодиночке разбросаны сперматозоиды. Часть стенок семенника‘в районе отверстия семепровода образо- вана кубическим, лишенным ресничек эпителем, переходящим в эпите- лий гонодукта /puc. 37/. Семенник соединяется с очень коротким семепроводом, залегаю- щим под покровами внутренностного мешка на правой стороне тела, /рис. 37 (9)/. Семепровод представляет собой прямой узкий канал, который, по всей вероятности, может несколько растягиваться массой спермы. Его стенки образованы кубическим или цилиндрическим без- ресничным эпителием (3), клетки которого не содержат никакого сек- рета. Их округлые ядра занимают центральное положение. Снаружи базальной мембраны, подстилающей эпителий семепровода, без опреде- ленной ориентации проходят редкие мышечные волокна. 153 154 Е. Н. ГРУЗОВ Дистальный участок мужского гонодукта резко выделяется своим строением, образуя хорошо ограниченную дополнительную железу поло- вой системы. Спереди она открывается узким щелевидным половым от- верстием, расположенным на передней поверхности внутренностного мешка, немного впереди свободного края мантийной складки /рис. 9 Е Толстые стенки железы образованы высоким эпителием из непра- вильно чередующихся железистых и опорных клеток /рис. 37/. Желе- зистые клетки (4) имеют крупные размеры, широкое основание и су- женный дистальный конец, через который их секрет поступает в по- лость железы. Протоплазма сильно вакуолизирована и интенсивно ок- рашивается бисмаркбрауном, так как содержит большое количество слизистого секрета. Некоторое количество выделившейся слизи всег- да присутствует и в полости органа. Опорные клетки (5) значительно уже железистых и равной с ними высоты. Обычно они располагаются между железистыми клетками, и тогда их дистальные концы расширяются, а клетки в целом приобре- тают вид урночек с тонкими стебельками. Ядра находятся в расши- ренных частях клеток. В тех случаях, когда опорные клетки собраны группами, они имеют более или менее правильную цилиндрическую форму, а ядра занимают центральное положение. Снаружи железа одета тонким слоем мускульных волокон. Относительно Функции железы можно строить лишь предположения. Возможно, что выделяемая ею слизь служит той средой, в которой жи- вут сперматозоиды. На передней стороне тела справа от ноги помещается penis животного /рис. 10/. Он представляет собой более или менее цилин- дрический, пальцеобразный вырост, превосходящий по своей длине вы- соту внутренностного мешка. Диаметр его постепенно уменьшается от основания к вершине, а самый конец мягко закруглен. Вдоль дорзальной стороны органа проходит глубокий желобок, по которому стекает сперма. Penis способен к значительным мышечным сокрацще- ниям и может сильно вытягиваться при копуляции. В спокойном со- стоянии он лежит в ложномантийной полости, прилегая к внутренност- ному мешку. Многочисленные морщины на его поверхности и значитель- ная толщина органа при сравнительно небольшой длине указывают на его сильное сокращение. При копуляции совокупительный орган вытя- гивается и высовывается через отверстие в ложной мантии; конец его вводится в наружное половое отверстие самки и, вероятно, проникает также и в отверстие матки, так как сперма в ложномантийной полости самок никогда не наблюдалась. Гистологическое строение органа видно из рис. 24. Складчатый покровный эпителий образован цилиндрическими, лишенными секрета клетками с хорошо развитыми ресничками. Около дистального края клеток присутствует полоска базальных ресничных зерен. Овальные, небогатые хроматином ядра располагаются в центре клеток. В районе ресничной борозды (4), проходящей вдоль совокупительного органа, реснички мерцательных клеток становятся более густыми и длинными. Специальные железистые клетки нигде не были обнаружены. Снизу эпителий подстилается базальной мембраной, под которой залегает соединительная ткань и мускулатура органа. Мускульные волокна проходят только в продольном направлении и образуют ясно Puc. 38. Женская половая система. ЕТа. 38. Вид ИЕ O O1 > WwW | ASTEROPHILA JAPONICA 155 спереди. женское половое от- верстие; 2 - матка; семеприемник; белковая железа; яйцевод; яичник. выраженный мускульный слой. Соединительная ткань представлена, мало отличающимися от клеток педальной Female reproductive system. An- terior view. 1- female genital opening; 2- pallial oviduct; 3 - seminal receptacle; 4- albumen gland; 5- oviduct; 6 - ovary. неправильной Формы клетками, соединительной ткани. Обращает на себя внимание сильное развитие в совокупительном opra- не кровеносных лакун, веносным синусом. эрекцию органа, ного эпителия. В толще соединительной ткани проходят нервные волокна, OTXO- дящие от правого педального ганглия. соединяющихся, в конце концов, с головным кро- Наполнение лакун кровью может вызвать сильную о чем свидетельствует также складчатость покров- Таким образом, педальное происхождение пениса не вызывает сомнений. Б. Женская половая система Женский половой аппарат /рис. 38/ состоит из яичника (6) и яйцевода (5), дистальный конец которого подразделяется на три раз- личных участка: дополнительную, белковую железу (4), семеприемник (3) и железистую матку (2). Форма, размеры и положение яичника, естественно, сильно ме- HAWTCA с возрастом животного. У самых молодых исследованных эк- земпляров, далеко не достигших еще половой зрелости, он представ- ляет небольшую трубку, спинной стороны внутренностного мешка, залегающую непосредственно под покровами правее медиальной линии. У более сформированных, но не перешедших еще к половой активности 156 fs) Ho ЕРУЗОВ животных, яичник ветвится так, что боковые отростки отходят в обе стороны от основного ствола, хорошо заметного, благодаря большим размерам /рис. 39/. Орган достигает вершины внутренностного меш- ка и при дальнейшем росте заворачивается на брюшную сторону. Эта стадия позволяет ясно судить о характере расчленения органа. Ee самой замечательной особенностью следует признать отхождение боко- вых ветвей яичника в обе стороны от центрального ствола - черта, свидетельствующая о глубокой перестройке организма, утратившего всякие следы спиральной закрученности органов внутренностного меш- ка даже на ранних стадиях онтогенеза.. о У животных, находящихся в разгаре репродуктивной деятельности, яичник достигает больших размеров, заполняя вся вершину висцераль- ного мешка и оттесняя печень вперед. Увеличение его размеров про- исходит за счет многократного ветвления как главного ствола, так и боковых ветвей, что приводит к образованию многочисленных долек органа и к исчезновению разницы в размерах между основным и побоч- ными его стволами. Рисунок 38 передает Форму яичника на такой стадии развития. Характерно, что отдельные дольки нигде не ана- стомозируют, хотя на наружной поверхности яичника они оказываются тесно прижатыми друг к другу. Сквозь эпителий яичника просвечи- вают яйца и крупные овоциты, наполненные желтком. Картины овоге- неза очень напоминают соответствующие стадии овогенеза у Enterox - enos, описанные Бонневи ( Bonnevie, 1906). OT переднего конца яичника, из того места, где все трубки этого органа соединяются воедино, отходят яйцевод. На всем своем протяжении он проходит в глубокой дорзальной складке печени, так что при поверхностном изучении создается впечатление того, что он прободает пищеварительную железу. Иногда яйцевод образует несколь- ко искривлений, но чаще представляет прямую, сравнительно короткую трубку с узким просветом. Стенки его лишены внутренних складок, но тем не менее могут несколько растягиваться во время прохождения яиц. Около передней поверхности тела он резко вздувается, образуя добавочную железу, лежащую на спинной стороне /рис. 38/. Железа имеет яйцевидную форму, и ее расширенная часть сообщается с маткой и семеприемником. Яйцевод подходит к задней (внутренней) поверх- ности железы и открывается в нее небольшим отверстием, лежащим ближе к вентральной стороне органа. Левая часть железы имеет вид слепо замкнутого мешка. y Рис. 39. Яичник и выводные пути FIG. 39. неполовозрелой самки. 1 - яичник; 2 - яйцевод; 3 - дистальная часть гонодукта.. Ovary and oviduct of immature fe- male. 1- ovary; 2- oviduct; 3 - distal part of gonoduct. ASTEROPHILA JAPONICA 157 Рис. 40. Эпителий дополнительной FIG. 40. (белковой) железы женской половой системы. Азокар- мин по Гейденгайну. 1. - базалвные ресничные зерна; 2 - ресничные клетки; 3 - железистые клетки; 4 - базальная мембрана. Epithelium of accessory (albumen) gland of female genital system. Stained with Heidenhain’s azocar- min. 1- basal ciliated granule; 0-025 2 - ciliated cells; 3 - glandular mm cells; 4 - basal membrane. Sas S Рис. 41. Эпителий семеприемника. FIG. 41. Азокармин по Гейденгайну. Epithelium of seminal receptacle. 1 - ресничные клетки; Stained with Heidenhain’s azocar- 2 - сперматозоиды; min. 1- ciliated cells; 2 - sper- 3 - базальная мембрана. matozoa; 3 - basal membrane. 158 | Е. H. ГРУЗОВ Рис. 42. Эпителий матки. Азокар- FIG. 42. мин по Гейденгайну. 1 - базальные ресничные зерна; ресничные клетки; - железистые клетки; базальная мембрана; мускульные волокна. oF wm 1 Epithelium of pallial oviduct. Stained with Heidenhain’s azocar- O-O5mm min. 1- basal ciliated granule; 2 - ciliated cells; 3 - glandular cells; 4- basal membrane; 5- muscle fibers. Tuctonoruueckn яйцевод и железа имеют сходное строение /рис. 40/. Их эпителий образован чередующимися мерцательными (2) и железисты- ми (3) клетками, окрашивающимися по Маллори в голубой цвет и, по- видимому, секретирующими слизистые вещества. Семеприемник представляет собой выпячивание спинной стенки гонодукта на границе между дополнительной железой и маткой /рис. 38/. Стенки его имеют многочисленные внутренние складки /рис. 41/, выстланные мерцательным эпителием. В полости органа постоянно находится сперма. Матка расположена на правой стороне передней поверхности внутренностногомешка, и ее дистальный конец доходит почти до ноги, а левый край находится на линии соединения внутренностного мешка. с ложной мантией. Расширенным проксимальным концом она соединяется с дополнительной железой и семеприемником, а к дистальному концу постепенно сужается, заостряясь на вершине. В поперечном сечении орган имеет форму сильно вытянутого эллипса, так как наружная и внутренняя стенки близко прилегают друг к другу. Длинным и узким щелевидным отверстием матка открывается в полость ложной мантии около основания псевдопаллиума. Рандаль и Хиз (Randall et Heath, 1912) правильно описали положение полового отверстия на правой стороне тела, но на рисунках (Fig. 1-2) изобразили его лежащим слева. Толстые стенки органа образованы высоким цилиндрическим эпи- телием, составленным правильно чередующимися железистыми (слизи- стыми) и мерцательными клетками /рис. 42/. Неодинаковая высота клеток в разных участках органа вызывает появление морщин и скла- док, общее число которых обычно невелико. Протоплазма железистых клеток наполнена сферическими каплями или зернами секрета, приобретающего после окраски по Маллори ин- тенсивно синий цвет. Эти же включения метахроматически окрашивают- ся толуидинблау в фиолетовый цвет, что указывает на слизистую при- ASTEROPHILA JAPONICA 159 роду секрета. Ha дистальном конце клетки сужаются и открываются наружу узкими протоками, проходящими между мерцательными клетками. Клеточные границы всегда хорошо различимы. Не все железистые клетки наполнены секретом, многие из них оказываются порожними. В таком случае в протоплазме присутствует большое число вакуолей, содержащих лишь отдельные капли секрета, и они окрашиваются по Маллори в голубой цвет, теряя способность краситься бисмаркбрауном и толуидинблау. Матка длинной щелью открывается наружу на правую сторону вис- церального мешка справа от ноги. Откладываемые яйца склеиваются в кокон, насчитывающий несколько сотен яиц. Кокон помещается в псевдопаллиальной полости. и По строению половой системы Asterophila обнаруживает много общего с раздельнополыми представителями Stiliferidae и Ento- conchidae, особенно с некоторыми видами Megadenus, обладающими дополнительными придатками половой системы. Выработавшиеся у Asterophila приспособления, обеспечивающие оплодотворение яиц, т. е. обитание самца на поверхности самки, боль- mag длина совокупительного органа и др., также находят себе анало- гию в этой группе паразитических моллюсков. У раздельнополых па- разитов, обитающих неподвижно в коже хозяина, самцы прикрепляются всегда рядом с самками, при этом они обычно ок%зываются меньших размеров ( Возеп, 1910; Иванов, 1941). У многих Entoconchidae крошечные мужские особи обитают внутри ложномантийной полости са- мок ( Schwanwitsch, 1917; Иванов, 1953). Вместе с уменьшением размеров тела самцов происходит процесс их морфологического упрощения, протекающий параллельно процессу деградации женских особей. Скорости этих процессов у представите- лей разных полов, как правило, не совпадают. Самцы крайне спе- циализированных эндопаразитов ( Entocolax schwanwitschi, Ento- concha) упрощены сильнее самок. Тело мужских особей Ento- concha, первоначально ошибочно описанных Мюллером под названием "семенные капсулы", состоит только из покровов и семенника, все остальные органы, даже семепровод, исчезли ( Müller , 1852). В To же время самцы менее специализированных паразитов (Asterophila, Entocolax trochodotae и др.) во многих отношениях примитивнее самок. Это выражается или в присутствии у них некоторых органов, исчезнувших у женских особей того же вида, или же, наоборот, в от- сутствии или меньшей выраженности признаков, развитых у самок зна- чительно сильнее. Существенно, что органы первой категории, например рудимент ноги Entocolax, отсутствующий у самок, или нервная система Asterophila, менее концентрированная y самцов, как правило, ис- чезают в процессе эволюции, а органы второй категории, недоразви- тые у самцов (ложная мантия, слюнные железы Capulidae и др.), представляют образования, с углублением паразитизма развивающиеся прогрессивно. В данном случае характер отличий между особями раз- ных полов ясно свидетельствует о том, что большинство органов у мужских особей остановилось на более ранней стадии онтогенетичес- кого развития, чем у женских. Подобная неотеничность самцов, по- видимому, характерна для некоторых Stiliferidae, Paedophoropod- idae u A. japonica. 160 E Ha, DPY30B Что касается Entoconchidae, To у них для объяснения различий в уровне организации разных полов недостаточно одного явления нео- тении. Метаморфоз E. schwanwitschi показывает, что здесь сов- падают только самые начальные этапы постларвального развития сам- цов и самок. Дальнейшее развитие самцов сводится к дегенерации большинства личиночных органов и развитию одной лишь половой сис- темы, тогда как у самок происходит прогрессивное развитие и ряда соматических органов: ложной мантии, кишечника и др. Процесс де- генерации личиночных органов самцов у остальных раздельнополых Entoconchidae, по-видимому, заходит еще дальше (Шванвич, 1946). Способ развития полового диморфизма дает некоторые указания и на возможные причины этого процесса. Выпадение конечных стадий метаморфоза у примитивных Форм и крайняя простота метаморфоза у форм редуцированных одинаково ведут к ускорению процесса развития. Известно, что метаморФоз личинки во взрослого самца начинается только с момента проникновения ее в самку, которая к этому времени проделала уже большую часть своего постларвального развития (Schwanwitsch, 1917). Ускоренное развитие самца, на наш взгляд, позволяет особям разного пола достигнуть половой зрелости в одно и то же время и этим повышает плодовитость животного. в 1У. Организация личинки. Как уже отмечалось выше, склеенные в кокон яйца развиваются в ложномантийной полости женских особей до стадии ве- лигера. К моменту полного сформирования личинок кокон разрушается и 7 Рис. 43. Внешний вид велигера. FIG. 43. A - вид с брюшной стороны; Б - вид слева. 1 - парус; 2 - щупальца; Ventralviews of veliger. A, view 3 - ротовое отверстие; of ventral surface; В, view from = SS left. 1- velar lobes; 2 - tenta- HOM железы; cles; 3- opening of mouth; 4- 5 - задняя лопать ноги; opening of gland of sole; 5 - pos- 6 - крышечка; terior part of foot; 6-operculum; 7 - раковина; 7 - shell; 8 - anterior part of 8 - передняя лопасть ноги. foot. ASTEROPHILA JAPONICA 161 велигеры свободно плавают в жидкости псевдопаллиальной полости. Выпускание личинок наружу через отверстие ложной мантии, вероятно, производится поодиночке. 1. Внешний вид Рисунки 43 Аи Б передают внешний вид сформированной личинки. Тело личинки поделено на три отдела: голову, ногу и внутренностный мешок. Голова плоло отграничена от остального туловища. На передней поверхности она несет пару коротких округлых щупалец (2), имеющих сравнительно крупные размеры. Позади них находится парус (1), со- стоящий из двух уховидных, не соединяющихся друг с другом лопастей, очень нежных и прозрачных. Каждая лопасть по периферии ограничена, непрозрачной белой каемкой высокого эпителия, который несет длин- ные и грубые реснички, уменьшающиеся в размерах по направлению от середины к краям. Между щупальцами и ногой на небольшом возвышении лежит хоро- шо заметное снаружи ротовое отверстие (3). Нога /рис. 43/ глубокой поперечной складкой разделена на два отдела: передний (8) и залний (5) - и несет крышечку (6). При рассматривании личинки со стороны устья раковины виден широкий вход в объемистую мантийную полость /рис. 43 A. Сквозь тонкую раковину частично просвечивает внутренностный мешок, однако детали его строения удается рассмотреть только после растворения раковины путем декальцинации слабо подкисленным спир- том /рис. 45 A, B /. Сохраняющаяся при этом очень тонкая пленочка органического вещества не мешает наблюдению. Передняя часть внутренностного мешка прикрыта снаружи мантией (4), различные участки которой вследствие неравномерной толщины обладают неодинаковой прозрачностью. С правой стороны тела мантия толста и делает невидимыми лежащие под ней органы; с левой стороны /рис. 45, А /. непрозрачны лишь два участка, выделяющиеся белыми матовыми пятнами на ŸOHE нежной стенки этого органа. Первый, He- большой участок, округлых очертаний, соответствует супраинтести- нальному ганглию (3), расположенному на потолке мантийной полости, около ее вентрального края. Другой участок (5), серповидной Формы, начинается в виде узкой полоски в глубине мантийной полости и далее, загибаясь вперед и постепенно расширяясь, тянется до самого входа в нее. Непрозрачность его объясняется тем, что по внутренней по- верхности мантии проходит ресничная полоска, образованная высоким мерцательным эпителием. Остальная часть мантии с левой стороны прозрачна, и сквозь нее просвечивает задняя часть эктодермальной кишки. Вершина раковины занята эктодермальной средней кишкой (7), ко- торая отчетливо заметна, благодаря большому количеству содержащих- ся в ней нерассосавшихся желточных зерен, имеющих характерный жел- то-оранжевый цвет. На правой стороне тела, в месте, соответствую- щем концу шовной линии раковины, на фоне кишки выделяется белый овальный половой зачаток /рис. 45 Б. (10). Несколько впереди рас- сматриваемого участка энтодермальная кишка соприкасается с эктодер- 162 UCA AG ul Pie, 45: EH. РРУЗОВ 0-25mm A д = с вершины раковины; Раковина личинки. вид Б - вид со стороны устья. 1 - шовная линия; а Viel bes 3 - париетальная мозоль. Aslerophila japonica. FIG. 45. Личинка с декальцинирован: ной раковиной. А - вид слева, Б - со спинной стороны. 1 - парус; 2 - раковина; 3 - супраинтестинальный ганглий; 4 - мантия; 5 - ресничная борозда мантийной полости; 6 - перикардий; 7 - энто- дермальная кишка; 8 - нога; 9 - щупальце; О:25тт В Larval shell. A, apical view; В, apertural view. 1- suture; 2- aperture; 3 - parietal calius. 10 - половой зачаток; 11 - почка. Asterophila japonica. Larva with decalcified shell. A, left side; В, dorsal view. 1- velar lobe; 2- shell; 3- supraintestinal ganglion; 4 - mantle; 5 - ciliated groove of mantle cavity; 6- pericardium; 7 - entodermal gut; 8 - foot; 9 - tentacles; 10 - gonadal rudiment; 11 - kidney. ASTEROPHILA JAPONICA 163 мальной, и здесь же проходит задняя граница мантийной полости. В непосредственном соседстве с последней, на спинной стороне тела, на- ходятся зачатки почки (11) и перикардия (6) с сердцем, слабо про- свечивающим сквозь его стенки. Почка лежит несколько впереди и ле- вее сердца. По словам А. В. Иванова, наблюдавшего личинок А. japonica в живом состоянии, большая часть их тела бесцветна и только верши- на внутренностного мешка окрашена в желто-оранжевый цвет вследствие наличия в ней желточных зерен. 2. Раковина и крышечка. Низкая выпуклая раковина личинки, изображенная на рис. 44 А,Б, асимметрична и геликоидно закручена вправо. Весь ее завиток обра- зует немногим более одного оборота, вследствие чего мягко закруг- ленная вершина (арех) располагается недалеко от устья, и высота ра- ковины оказывается меньше ее ширины. На верхней поверхности рако- вины заметна неглубокая короткая шовная линия (1). Устье /puc. 44, B (2)/ имеет в общем овальную Форму, но на участке, прилегающем к начальному обороту завитка, TAM, где Hapyx- ная губа устья переходит во внутреннюю, образуется сглаженный у вершины апикальный угол. Перистом на рассматриваемом участке обра- зует небольшую париетальную мозоль (3). Края устья несколько отог- нуты наружу. Высота раковины колеблется от O, 27 мм до O, 31 мм, наибольшая ширина равна O, 57 MM. Крышечка, расположенная на задней лопасти ноги, в общем повто- ряет Форму устья. Она состоит из рогоподобного вещества, сохраняет- ся при кислых фиксациях, совершенно прозрачна, имеет мелкую попереч- ную исчерченность и обычно плохо заметна. По Форме раковина личинки Asterophila чрезвычайно сходна с таковой Entocolax schwanwitschi (Schwanwitsch, 1917). Она также напоминает раковину только что вылупившихся личинок Balcis alba, В. devians и Pelseneeria stylifera (=Stilifer stylifer), описанных Лебур ( Lebour, 1932, 1935) и Торсоном (Thorson, 1946). Однако поздние личиночные стадии этих моллюсков уже существенно отличаются от личинок Asterophila тем, что их раковина приобре- тает башневидную Форму и имеет около пяти оборотов. Личинки А. japonica вплоть до начала метаморфоза сохраняют раковину, свой- ственную ранним велигерам. Стадия, соответствующая позднему вели- repy Melanellidae, вымала из онтогенеза исследуемой формы. 3. Нога и педальные железы. Колюмеллярный мускул. Нога личинки Asterophila представляет самый мускулистый ор- ган тела. Помимо собственной мускулатуры, она содержит волокна, прекрасно развитого колюмеллярного мускула /puc. 46/, который сво- им задним концом прикрепляется к столбику раковины, а спереди, за- гибаясь в соответствии со спиральной закрученностью внутренностно- го мешка, входит в толщу соединительной ткани ноги позади педаль- BE... EFYS0B Puc. 46. Сагиттальный разрез через личинку. Маллори. FIG. 46. 1 - парус; 2 - церебральный ганглий; 3 - плевральный ганглий; 4 - эпителий внутренностного мешка; 5 - ман- тия; 6 - эктодермальная кишка; 7 - мантийная железа; 8 - мантийная полость; 9 - сердце; 10 - раковина; 11 - перикардий; 12 - энтодермальная кишка; 13 - жел- точные зерна; 14 - соединительная ткань; 15 - колю- меллярный мускул; 16 - крышечка; 17 - задняя лопасть ноги; 18 - эпителий ноги; 19 - отверстие подошвенной железы; 20 - железистые клетки; 21 - передняя лопасть ноги; 22 - педальный ганглий; 23 - отверстие краевой железы; 24 - щупальце; 25 - краевая железа; 26 - по- дошвенная железа. Sagittal section through larva. Stained with Mallory’s. 1 - velar lobe; 2 - cerebral ganglion; 3- pleural ganglion; 4- epithelium of visceral mass; 5 - mantle; 6 - ectodermal gut; 7 - pallial gland; 8 - mantle cavity; 9- heart; 10 - shell; 11- pericardium; 12 - entodermal gut; 13 - yolk granules; 14 - connective tissue; 15 - columellar muscle; 16 - operculum; 17 - posterior part of foot; 18 - epithelium of foot; 19 - opening of gland of sole; 20 - glandular cells; 21 - anterior part of foot; 22 - pedal ganglion; 23 - opening of glandular area; 24 - tentacle; 25 - glandular area; 26 - gland of sole. ного ганглия. Здесь OH разбивается на два равных пучка, один из которых подходит к задней, несущей оперкулюм, стороне ноги, а дру- гой проходит между педальными железами к ее брюшной поверхности, соответствующей ползательной подошве других моллюсков. Сокраще- нием колюмеллярного мускула личинка может втягиваться внутрь рако- вины и прикрывать устье крышечкой, причем действие переднего пуч- ка мускульных волокон вызывает складывание ноги попалам и появле- ASTEROPHILA JAPONICA 165 ние глубокой поперечной щели, делящей ногу на две лопасти. Передняя лопасть ноги имеет овальные очертания и очень выпук- ла /рис. 46 (21)/. Ee длина примерно в два раза меньше ширины. На границе этой лопасти с головой, на медиальной линии тела, нахо- дится небольшое отверстие передней педальной железы (23). Вторая лопасть более массивная, прямоугольная, со слегка за- кругленным задним краем и уплощенной брюшной поверхностью. Ee сво- бодная спинная сторона, которая при складывании ноги обращена назад, несет operculum. В толще этого отдела залегает задняя педальная железа /рис. 46 /, открывающаяся широким отверстием на линии пере- гиба ноги (19). Вся поверхность ноги, за исключением оперкулярной области, покрыта мерцательным цилиндрическим эпителием обычного строения. На подошве среди мерцательных клеток встречаются отдельные крупные железистые клетки, строение которых рассматривается ниже. Эпителий оперкулярной области невысокий, почти кубический, нерезко переходит в плоский эпителий брюшной поверхности внутрен- ностного мешка. Железистые и мерцательные элементы в нем отсут- ствуют. Большая часть ноги занята педальными железами. Наружное отверстие передней железы ведет в короткий, неширо- кий канал, образованный впячиванием покровов, которые в рассматри- ваемом участке состоят из кубического или плоского мерцательного эпителия. На задней стенке канала клетки несколько выше, чем на передней, и реснички на них развиты лучше /рис. 47 (23) /. Часто на передней стенке реснички вовсе отсутствуют. Канал направляется косо назад и в самой глубине его клетки испытывают железистое перерождение: размеры их резко возрастают, а базальные концы расширяются и погружаются в толщу ноги и головной лопасти. Замечательно, что все железистые клетки располагаются по одну сторону канала - черта, свойственная взрослым моллюскам Stiliferidae. Эти клетки образуют компактную массу и, благо- даря этому, сильно деформируются. Их расширенные базальные концы содержат интенсивно окрашивающиеся, богатые хроматином ядра, от- тесненные к периферии железы /рис. 47 /. У многих особей железа, переполнена зернистым секретом, имеющим слизистую природу и мета- хроматически окрашивающимся гематоксилином в фиолетовый цвет /рис. 47 (25)/. Кроме того, в протоплазме присутствует несколько круп- ных округлых вакуолей, содержимое которых вымывалось при обработ- ке препарата. Плазма клеток слегка окрашивается бисмаркбрауном, что указывает на присутствие слизи, равномерно распределенной в клетке. Вторая педальная железа /рис. 46 (26)/, примерно такой же величины, что и первая, располагается непосредственно позади нее. По ее передней и задней поверхностям тянутся волокна колюмелляр- ного мускула. Она также является производной покровного эпителия ноги и образована инвагинацией части’ клеток вглубь тела личинки. На рис. 46 (19) отчетливо видна щель впячивания. Неправильной формы железистые клетки имеют очень большие размеры. Так же как у клеток передней железы, их базальные концы расширены и содержат чрезвычайно деформированные ядра, оттесненные к периферии /рис. 46/. Специальный выводной канал отсутствует. 166 ных зерен. Сами реснички могут отсутствовать. Протоплазма наполнена неоформленным секретом слизистой приро- ды. Он интенсивно окрашивается бисмаркбрауном и по Маллори, но герматоксилин не воспринимает. Многочисленные вакуоли не содер- жат видимого секрета. Без резких границ железистое впячивание переходит в эпителий подошвы. По периферии отверстия железы, среди мерцательных кле- ток покровов присутствуют отдельные крупные железистые клетки /рис. 46 (20)/, отличающиеся от клеток железистого впячивания 1 только меньшими размерами и тем, что их ядра почти не деформиро- } ваны. Клетки открываются наружу в промежутках между ресничными | клетками. В переднем отделе ноги подобные клетки расположены гу- ще, чем в заднем. Судя по расположению, структуре и характеру секрета, железа соответствует подошвенной железе Melanellidae и других брюхо- | HOTUX моллюсков. Подобную железу имеют личинки всех исследованных Entoconch- idae и Paedophoropodidae. Личинки Melanellidae и Stilifer- idae, к сожалению, остаются до сих пор He изученными. Е РОВ Под наружной поверхностью клеток находится слой базальных реснич- | 5 4. Мантия Хорошо развитая мантийная полость доходит почти до вершины внутренностного мешка и слегка асимметрична. Мантийная складка, /рис. 46 (5)/ состоит из двух слоев эпителия, переходящих по краю один в другой. Наружный прилегает к раковине и образован крайне уплощенными клетками с чешуевидными ядрами. Сзади он переходит в такой же эпителий внутренностного мешка. Правая сторона мантийной складки дифференцирована в виде ман- тийной железы (7), образованной клетками двух родов. Одни из них невысокие, цилиндрические, лишенные ресничек, с протоплазмой, со- держащей множество мелких прозрачных вакуолей. У отдельных, глав- ным образом, молодых экземпляров внутри вакулей можно наблюдать массу капель или зерен секрета, который после сулемовых фиксаций и окраски железным гематоксилином с лихтгрюном приобретает глубо- кий зеленовато-серый цвет. Клетки этого сорта располагаются в са- мой глубине мантийной полости. Ближе к выходу из нее подобные клетки сменяются другими, тоже железистыми и лишенными ресничек, но с гомогенным секретом, собранным внутри одной-двух (реже трех) круп- ных вакуолей. После окраски азокармином по Гейденгайну секрет приобретает светло-желтый или розоватый оттенок, а железный гема- токсилин им почти не воспринимается. У самого края мантии располагаются низкие клетки, лишенные сек- реторной функции. Приблизительно по медиальной линии мантии проходит ресничная полоска /рис. 45 А (5)/, отделяющая мантийную железу от правого прозрачного района мантии. Мерцательные клетки кубические, с длин- ными ресничками и хорошо развитыми базальными зернами /рис. 48 (26)/. Между обоими слоями мантийного эпителия могут присутствовать редкие, рыхло лежащие соединительнотканные клетки, хотя обычно оба ASTEROPHILA JAPONICA 167 O-Imm Рис. 47. Сагиттальный разрез ue- FIG. 47. рез личинку. Маллори. 26.— статоциет; el -WIOU- Sagittal section through larva. ка; 28 - подошвенная же- Stained with Mallory’s. 26- sta- леза; 29 - ротовое отверстие; tocyst; 27- kidney; 28 - gland остальные обозначения как of sole; 29 - opening of mouth. Ha puc. 46. Other numbers as in Fig. 46. слоя TECHO сближены. Кровеносные лакуны развиты незначительно. 5. Кишечник Расположенное на вершине небольшого возвышения головы ротовое отверстие ведет прямо в полость эктодермальной передней кишки, ко- торая представляет неширокую трубку, имеющую на всем протяжении одинаковое строение и не разделенную на отделы. Задний конец киш- ки образует слепо замкнутый мешок, входящий в завиток внутренност- ного мешка и прилегающий к энтодермальному отделу кишечника. Стенки кишки состоят из невысокого цилиндрического, лишенного ресничек эпителия с крупными овальными ядрами /рис. 46 (6) /. Ка- кие-либо железистые участки и отдельные железистые клетки во всем эпителии отсутствуют. Протоплазма клеток гомогенная и не содержит включений. Полость кишки лишена пищевого KoMKa. Замкнутая с обоих концов средняя кишка энтодермального проис- хождения /рис. 46-48 (12)/ занимает всю вершину внутренностного мешка. Просвет кишки очень невелик. Стенки образованы крупными клетками с неровными границами и чрезвычайно прозрачной плазмой. Круглые или овальные ядра с ядрышком обычно оттеснены к периферии, поскольку вся протоплазма наполнена нерассосавшимися желточными зернами. EH. MPYSOB Задней кишки и анального отверстия HET. По строению кишечника личинка Asterophila не отличается от известных личинок Entoconchidae (Schwanwitsch, 1917; Иванов, 1953; и др.), a также Paedophoropodidae (Ivanov, 1937). Кишечник личинок Melanellidae имеет, вероятно, более слож- ное строение ( Thorson, 1946). 6. Перикардий и сердце В заднем отделе внутренностного мешка, на границе передней и средней кишок, находится перикардий с зачатком сердца. Эпителиальные стенки перикардия образованы чрезвычайно упло- щенными клетками, столь тесно прижатыми к покровам внутренностного мешка и пограничным органам, что по большей части делаются неви- димыми. Небольшая перикардиальная полость содержит трубковидный 3aua- ток сердца, пересекающий ее от спинной стенки до брюшной. В сред- ней части трубка имеет легкую перетяжку, а оба конца ее вздуты и соответствуют предсердию и желудочку /рис. 46 (9)/. Мускульные волокна в стенке сердца отсутствуют. Мне не удалось обнаружить никаких сосудов, связанных с серд- цем; по-видимому, их нет. Но в различных районах тела между клет- ками соединительной ткани сохраняются полости кровеносных синусов или лакун. Значительного развития они, впрочем, тоже не получают. У всех изученных личинок Entoconchidae и Paedophoropodidae нет ни перикардия, ни сердца. Сведения о личинках Stiliferidae и Melanellidae отсутствуют. 1. TOURS Рядом с перикардием на спинной стороне тела лежит небольшой пузыревидный орган, стенки которого состоят из одного ряда клеток, ограниченных снаружи тонкой мембраной /рис. 47 (27)/. Дистальные концы клеток языками вдаются в полость органа. Округлые ядра за- нимают центральное положение или слегка прижаты к базальной мем- бране. Грубозернистая протополазма содержит многочисленные вакуо- ли, лишенные конкреций. С левой стороны орган вплотную примыкает к перикардию, но не соединяется с ним. Положение, форма и строе- ние органа не оставляют сомнения в том, что это - зачаток почки. Выделительное отверстие отсутствует. Интересно, что у личинки Paedophoropus dicoelobius иванов (Ivanov, 1937) встретил орган, сходно расположенный в левой части внутрен- ностного мешка. Этот орган в существенных чертах напоминает почку личинки нашего моллюска, чем подтверждается предположение Иванова, о природе данного образования. У личинок всех Entoconchidae зачаток почки отсутствует. 8. Нервная система, В переднем отделе личинки, под эктодермальной кишкой, распо- ASTEROPHILA JAPONICA 169 лагаются три пары TECHO сближенных ганглиев /puc. 46 (2, 3, 22)/. Самые крупные из них, церебральные (2), лежат впереди и ox- ватывают кишку с боков. OT каждого из них вперед к щупальцам отхо- дит тяж нервных клеток, сопровождающих нервные волокна, заходящие в щупалвце. Сзади церебральные ганглии соединяются с небольшими плевральными (3). Под этими ганглиями, заходя нижними концами в ткани ноги, располагается пара педальных ганглиев (22), соединенных друг с другом короткой комиссурой. К их задней поверхности приле- гают статоцисты /рис. 47 (26)/. Педальные ганглии при помощи це- ребро- педальных коннективов связаны с церебральными, а посредст- вом другой пары коннективов (плевро-педальных) - с плевральными ганглиями. Оба коннектива столь коротки и толсты, что, вероятно, было бы правильнее говорить о слиянии ганглиев в общую массу /рис. Aegean (2. 3, 122) И Последний, непарный ганглий /рис. 48 (28) / лежит на левой стороне тела, внутри мантийной складки около ее основания. Он имеет приблизительно округлую Форму, невелик и не соединяется с передней частью центральной нервной системы. Его положение воз- ле перикардия соответствует положению супраинтестинального ганглия y взрослых форм, хотя там он находится целиком во внутренностном мешке, не заходя в мантию. По-видимому, это обстоятельство объяс- няется сильной редукцией мантийной складки у взрослых женских осо- бей Asterophila. Органы чувств представлены парой небольших округлых щупалец и статоцистами с единственным статолитом. Глаза отсутствуют. Центральная нервная система личинок всех изученных паразити- ческих брюхоногих не подверглась существенным изменениям. В ином ‘ положении оказываются органы чувств. У личинок примитивных моллюс- ков, вроде Balcis alba, В. devians и Pelseneeria stylifera, имеются хорошо выраженные, заостренные Ha конце щупальца, Ha расши- Рис. 48. Поперечный разрез через FIG. 48. личинку на уровне поло- вого зачатка. Кислый ге- малаун Мейера, лихтгрюн. 26 - ресничная борозда мантийной попости; 27 - половой зачаток; 28 - супраинтестинальный ганглий. Остальные обоз- начения как на рис. 46. Anterior sectionthrough larva at the level of the gonadal rudiment. Stained with Mayer’s acid haema- lum, light green. 26 - ciliated groove of mantle cavity; 27- go- nadal rudiment. 28- supraintes- tinal ganglion. Other numbers as in Fig. 46. 170 EX. TEYSOB ренных базальных частях которых располагаются глаза ( Lebour, 1932, 1935; Thorson, 1946). У личинок Paedophoropodidae и низших Entoconchidae щупальца в значительной мере упрощены, a глаза вовсе отсутствуют ( (Ivanov, 1937; Иванов, 1953; Schwanwitsch, ISE Наконец, y личинок Ратещетохепо$ нет ни щупалец, ни глаз (Иванов, 1949). У Parenteroxenos исчезают также и статоцисты, присутствующие у личинок всех остальных паразитических брюхоногих. 9. Половой зачаток. В вершине внутренностного мешка на уровне конца шовной линии раковины располагается половой зачаток. Он находится на правой стороне тела, непосредственно под покровами, соприкасается с энто- дермальной кишкой /рис. 48 (27)/ и представляет собой лепешковид- ное образование, состоящее из крупных, недифференцированных клеток с большими округлыми ядрами, каждое из которых содержит по единст- венному ядрышку. Протоплазма клеток окрашивается гематоксилином. | В общем, половой зачаток Asterophila очень напоминает соот- ветствующие органы личинок Entocolax schwanwitschi, Е. rimsky- korsakovi, Paedophoropus и Parenteroxenos (Schwanwitsch, 1917; Ivanov, 1937; Иванов, 1949 a, 1953). Сведения о половом зачатке личинок Melanellidae и Stiliferidae отсутствуют. Подводя итоги, можно сказать, что по уровню организации ли- чинка Asterophila стоит ближе всего к личинкам примитивных Entoconchidae. Однако отдельные черты ее строения, и, в первую очередь, присутствие рудиментов перикардия и почки, свидетельству- ют о большей примитивности исследуемой формы. Сравнение с личинками Melanellidae и Stiliferidae крайне затруднено из-за их плохой изученности. Однако имеющиеся данные позволяют заключить, что личинки Asterophila во многом. упрощены по сравнению с личинками примитивных паразитических брю- хоногих. В филогенезе подобное упрощение, вероятно, происходило как путем редукции определенных органов, т.е. полного исчезновения каких-либо их зачатков, так и путем отрицательной анаболии (Беуег- cov , 1931), т.е. выпадения конечных стадий развития. Отсутствие глаз у личинки нашего вида, по всей вероятности, есть следствие первого процесса; рудиментарный характер раковины, щупалец и не- которых других образований - результат недоразвития соответствую- щих органов. rte D EE У. Систематическое положение Asterophila u ee филогенети- ческие взаимоотношения с другими паразитическими брюхоногими Во всей организации А. japonica наблюдается сочетание при- митивных, унаследованных от отдаленных предков черт строения с признаками далеко идущей специализации. Интересно проанализиро- вать строение животного под этим углом зрения. К числу признаков первой категории относятся: расчленение тела на голову, внутренностный мешок и ногу; присутствие у некото- ASTEROPHILA JAPONICA 21 рых экземпляров рудимента хобота; наличие рудимента ноги; сохране- ние рудиментарной мантии, расположенной на левой стороне тела; нор- мальное развитие перикардия с двукамерным сердцем; наличие почки и ее положение рядом с перикардием, расположение почечных трабекул исключительно на наружной стороне органа; строение нервной системы и наличие хиастоневрии; раздельнополость, строение половой системы, открывающейся наружу щелевидным половым отверстием, положение со- вокупительного органа справа от ноги; откладка яиц в коконах; ор- ганизация личинок, обладающих спирально закрученной дексиотропной раковиной. Вторая категория признаков: наличие ложной мантии головного происхождения; редукция головы, глаз и щупалец; отсутствие хобота у некоторых экземпляров и сильная его редукция у остальных; руди- ментарный характер ноги, лишенной крышечки и педальных желез; утра- та раковины и спиральной закрученности внутренностного мешка; ре- дукция мантии и мантийной полости, исчезновение жабры, осфрадия и гипобранхиальной железы; утрата колюмеллярного мускула и редукция мускулатуры тела; субституция желудка печенью и ее смещение в се- редину внутренностного мешка, исчезновение задних отделов кишечни- ка; смещение перикардия на брюшную сторону, положение предсердия впереди желудочка; резкий половой диморфизм, прикрепление самцов к Псевдопаллиуму самок; вынашивание яиц под защитой ложной мантии. Многие из примитивных признаков указывают на положение Astero- phila 5 пределах Prosobranchia Monotocardia, в частности среди Taenioglossa. Известно, что паразитизм внутри этого от- ряда возникал многократно и независимо друг от друга. В настоящее время известно (если не считать саму Asterophila ) шесть групп паразитических моллюсков, берущих начало от разных семейств свобод- ноживущих брюхоногих (Ivanov , 1937; Иванов, 1941): Capulidae, Pseudosacculidae, Ctenosculidae, паразитические Pyramidellidae, паразитические Melanellidae - Stiliferidae - Entoconchidae, происходящие OT свободноживущих Melanellidae, и Paedophoropodidae, происходящие также oT Melanellidae. Последние три группы вместе со свободноживущими Aclididae Тиле (Thiele, 1929) относит к трибе Aglossa. Попытаемся теперь сравнить Asterophila с паразитическими моллюсками, т. к. его родственные связи естественно искать именно здесь. При этом Pseudosacculidae и Ctenosculidae сразу выпадут из круга рассматриваемых форм, т.к. ряд глубоких различий разобща- ет их с Asterophila (Heath, 1910; Hirase, 1927). Нельзя сближать наш вид также с паразитическими Capulidae, несмотря на ряд общих черт их строения, поскольку сходство распро- страняется либо на признаки, вообще часто встречающиеся среди Prosobranchia (концентрация нервной системы; строение полового аппарата), либо на признаки, конвергентно возникакщие у многих па- разитов (ложная мантия, редукция пищеварительной системы и др.). Некоторые черты строения Asterophila, бесспорно унаследо- ванные ею от своих предков, резко отличают ее от СариПаае. Наиболее важным является, пожалуй, положение совокупительного ор- гана самцов A.japonica на правой стороне тела, в то время как y Thyca он расположен слева от ноги. Положение мантии Asterophila на левой стороне тела также отличает ее от Capulidae (Adam, 1933, 1934). 172 E. H. ГРУЗОВ Прежде чем перейти к сравнению Asterophila с паразитически- ми моллюсками трибы Aglossa, остановимся вкратце на взаимоотно- шениях между представителями этой группы. В анатомическом отноше- нии все относящиеся сюда семейства, за исключением Pyramidellidae, нечетко отграничены друг от друга. В особенности это касается семейства Melanellidae и Stiliferidae, морфологические отли- чия между которыми попросту отсутствуют. По степени развития лож- ной мантии, редукции ноги, изменениям в пищеварительной системе и концентрации нервной системы различные представители Melanellidae часто оказываются более специализированными, чем примитивные Stiliferidae. Строение остальных органов, по-видимому, одинаково в обоих семействах. Также и конхиологический критерий оказывается недостаточным для разделения Melanellidae и Stiliferidae, на что указывал еще Нирштрас ( Nierstrasz, 1913). Естественно поэтому объединять всех представителей рассматриваемых семейств в одно семейство Melanellidae. Едва ли заслуживают выделение в отдельное семейство виды Pelseneeria. Единственное отличие этих животных от Melanellidae касается природы ложной мантии, представляющей у Melanellidae разрастание покровов головы, a у Pelseneeriidae - ноги. Однако разнообразие строения истинных Melanellidae касается не менее важных признаков, а Филогенетическая неоднородность этого семейст- ва так велика, что позволяет включить в Hero и Pelseneeria. В частности, y Stilifer celebensis Y Megadenus arrhynchus нога претерпевает существенную перестройку в связи с приспособле- нием к новым функциям /Hirase, 193247 B Melanellidae s. lat. можно включить и Paedophoropodidae, описанное Ивановым (Ivanov, 1937) после исследования единственного вида Paedophoropus dicoelobius. Главным его отличием oT Stiliferidae автор считает отсутствие ложной мантии головного происхождения, своеобразное строение ноги и отсутствие резкого полового диморфиз- ма. Однако описанная позднее (Грузов, 1957) Molpadicola orient- alis в известной мере заполняет пробел между Paedophoropodidae и Melanellidae. Строение ноги этой формы, дифференцированной на центральную часть с ползательной подошвой и боковые лопасти, позволяет видеть примитивное состояние этого органа. Боковые ло- пасти по форме напоминают ложную мантию Pelseneeria и имеют одинаковую с ней педальную природу. Сильная специализация ноги Paedophoropus стоит в связи с превращением ее в инкубационный орган. Не следует придавать также слишком большое значение слабой редукции самцов относительно самок. Известное несоответствие меж- ду уровнем общей редукции животного и степенью полового диморфФиз- ма наблюдается, по-видимому, и у Stiliferidae. Таким образом, различия между Paedophoropodidae и Melanellidae не столь Cy” щественны, чтобы противопоставлять их друг другу в систематичес- ком отношении. Эволюция Paedophoropodidae, как и Pelseneeriidae происходила, конечно, особым путем, однако и Stiliferidae не представляют однородной группы. Помимо типичных видов, эволюция которых шла от свободноживущих форм через эктопаразитов к эндопа- A En ae ASTEROPHILA JAPONICA 173 разитическим Entoconchidae, семейство Stiliferidae включает в себя также такие формы, как Mucronalia variabilis и Рата- stilifer, которые занимают совершенно обособленное положение и, ве- роятно, независимо происходят от свободноживущих моллюсков, близ- ких к современным Melanellidae (Иванов, 1952). Типичные Stiliferidae (Mucronalia, Megadenus, Stilifer и Gasterosiphon) также не представляют единой линии развития, хотя их различия He столь существенные (Nierstrasz, 1913). Таким образом, моллюски, происходящие от Melanellidae, образуют целый пучок Форм, расходящийся в разные стороны. При этом различия крайних членов разных эволюционных направлений ока- зываются иногда весьма существенны. Однако эти формы через прими- тивных представителей связаны друг с другом, и поэтому деление груп- пы на ряд семейств кажется нам недостаточно обоснованным. Гораздо естественнее в настоящее время относить их к одному обширному се- мейству, за которым лучше всего сохранить название Melanellidae. К этому семейству тесно примыкает Entoconchidae, представляющее собой наиболее ‘деградированных паразитических гастропод. Несмотря на то, что филогенетическая связь обоих семейств не вызывает ника- ких сомнений, оснований для объединения их воедино пока что недо- статочно. Правда, можно надеяться, что новые находки окончательно заполнят пробел между этими группами. Сходство А. japonica c представителями Melanellidae и Entoconchidae подчеркивалось на протяжении всей работы. OHO pac- пространяется прежде всего на признаки, унаследованные от свободно- подвижных предков, такие как состав центральной нервной системы, строение почки и полового аппарата и, особенно, организация личин- ки Asterophila. Далее, процессы редукции органов у A.japonica и Melanellidae протекают сходным образом: раковина редуцируется, пищеваритель- ная система упрощается и т. д. Даже такая своеобразная особен- ность, как почти полное исчезновение хобота, встечается у Megadenus arrhynchus. Исчезновение спиральной закрученности внутренностного мешка и связанное с этим смещение перикардия на брюшную сторону, а также изменение в положении сердца сходным образом, хотя и конвергентно, осуществлены у Paedophoropus и Molpadicola. Одинаково про- исходила редукция мантийного комплекса органов, в результате чего половое отверстие оказалось вынесенным за пределы мантийной полос- ти. В то же время левый край половой щели у Asterophila лежит y самого входа в мантийную полость, что до некоторой степени сбли- жает е с примитивными Melanellidae. Наконец, немногочисленные случаи прогрессивного развития от- дельных органов (например ложной мантии) указывают на идентич- ность и этих процессов у А. japonica и Melanellidae - Entoconch- idae. При таком положении вещей He имеет смысла сохранять самостоя- тельность семейства Asterophilidae, как это было сделано Thiele (1929) на основании данных Рандаль и Хиза. Если исходить из этих данных, то наиболее замечательными особенностями строения Astero- phila нужно было бы признать следующие: 1/ Положение перикардия и почки на правой стороне тела, а гонодукта - на левой и 2/ нали- 174 E... : ГРУЗОВ une рудиментов слюнных желез. Однако, как нам удалось показать, топография’ мантийного комплекса у исследуемой формы не отличается от нормы, присущей Taenioglossa. Что же касается слепых карма- нов глотки, то бедность этих образований морфологическими призна- ками не позволяет установить их гомологию со слюнными железами других гастропод, и, следовательно, точка зрения Рандаль и Хиза оказывается по меньшей мере недоказанной. Толкование природы этих образований оказывается всецело зависящим от нашего понимания Qu- логенетических связей Asterophila c другими моллюсками. Все остальное строение нашего вида не выходит за пределы мно- гообразия, наблюдаемого внутри Melanellidae. Поэтому нам ка- жется правильнее относить А. japonica к этому семейству на правах самостоятельного рода. При этом приходится признать, что диверти- кулы глотки возникли у нее как новообразования в связи с переходом к обитанию в новых условиях. Аналогичные образования передней час- ти кишечника появились также у Megadenus holothuricola, М. voeltzkovi и Entocolax rimsky-korsakovi. Особенная близость обнаруживается между A.japonica и Mega- denus arrhynchus. Так, обе рассматриваемые формы практически ли- шены хобота, - особенность, указывающая на особый путь их эволюции. Вместе с тем, Megadenus сохранил еще рудименты ретракторов хобота, полностью исчезнувшие у нашего вида. Другая характерная черта Megadenus состоит в неравномерном развитии ложной мантии на правой и левой сторонах тела. Это объяс- няется особенностями паразитирования данной Формы, сидящей как бы боком в чашеобразном углублении стенки тела морской звезды. Наблю- даемая у Asterophila неравномерность в развитии вентрального и дорзального участков псевдопаллиума, выражающаяся в асимметричном положении вторичного женского полового отверстия на брюшной стороне ложной мантии, вероятно, вызвана аналогичными условиями паразити- рования ее предков. В соответствии с меньшей специализацией Megadenus, его ложная мантия развита значительно слабее, чем y Ha- шего вида. Наиболее существенные различия во внешней морфологии между сравниваемыми видами касаются формы внутренностного мешка, степени развития мантии, мантийного комплекса органов и строения ноги. Все перечисленные органы, кроме ноги, у Megadenus мало отличаются от соответствующих образований у свободноживущих брюхо- ногих. Нога испытывает прогрессивное развитие в связи с приобрете- нием новой Функции обновления воды в мантийной naiocTu. У Astero- phila эти органы подверглись сильной редукции, HO, тем не менее, сохранили свое первоначальное положение. Пищеварительная система рассматриваемых видов в принципе сход- Ha, HO y Megadenus несколько примитивнее и открывается наружу анальным отверстием. Желудок у обоих видов отсутствует, как, впро- чем, и у большинства паразитических брюхоногих. Сравнение кровеносной и выделительной систем Megadenus и Asterophila He дает подтверждений их родства, хотя и не противо- речит ему. Почка в обоих случаях несет трабекулы только на своей наружной стороне и открывается почечным отверстием в глубине ман- тийной полости.’ Редукция кровеносной системы зашла у А. japonica дальше и привела к полному исчезновению сосудов, хорошо выраженных у Megadenus arrhynchus. ASTEROPHILA JAPONICA 175 Enteroxenos Parenteroxenos ' Entoconcha Entocolax Diacolax (Entoconchidae) Asterophila Paedophoropus' | Asterophilidae Molpadicola Gasterosiphon Ah (Paedophoropodidae) Stilifer В Parastilifer р Odostomia М. arrhynchus- —- Megadenus Mucrona lia/ Pelseneeria Turbonilla (Pelseneeriidae) (Pyramidellidae) Mucronalia variabilis (Stiliferidae) Melanella, Balcis n sp. (Melanellidae) Puc. 49. Схема Ффилогенетических взаимоотношений паразитиче- FIG. 49. ских моллюсков трибы Aglossa. Diagram of phylogenetic interrelations of parasitic mollusks of the tribe Aglossa. Центральная нервная система М. arrhynchus состоит из тех же ганглиев, что и у Asterophila, однако гораздо менее концен- трирована. Плевральные ганглии вполне обособлены от церебральных. Висцеральное кольцо замкнуто, хотя имеется только один висцераль- ный ганглий. Много общего имеется в строении буккального отдела нервной системы. Буккальные ганглии Megadenus соединяются при помощи буккальной и лабиальной комиссур над и под кишкой. Имеется пара мелких лабиальных ганглиев, возможно, гомологичных небольшим нервным узелкам в глотке Asterophila. Женская половая система сравниваемых видов одинаково харак- теризуется наличием дополнительной белковой железы, несвойственной большинству Melanellidae. Дополнительная железа сходного с Asterophila строения имеется также и в составе мужского полового аппарата Megadenus. Самцы обоих видов обладают совокупительным органом, позволяющим им копулировать с самками, находясь на неко- тором удалении от них, снаружи ложной мантии. Из сказанного ясно, что М. arrhynchus по своей организации должен быть весьма сходен с предками Asterophila, и в системе паразитических гастропод эти формы необлодимо располагать побли- зости друг от друга. Однако непосредственно выводить А. japonica oT Megadenus невозможно, т.к. оба вида обладают чертами глубокой специализации. 176 E. НЧ. ГРУЗОВ Филогенетические взаимоотношения между моллюсками трибы Aglossa можно представить в виде следующей схемы /рис. 49/. Вид- но, что Asterophila есть представитель боковой ветви эволюцион- ного ряда Melanellidae - Entoconchidae и филогенетически He предшествует последним. Это доказывается наличием у не некото- рых специфических особенностей, прежде всего, сильной редукцией хобота и своеобразным строением ложной мантии: положение отверстия псевдопаллиума у Asterophila не соответствует положению сифона, У Entoconchidae. С этим, по-видимому, связано и другое существен- ное различие между ними, а именно, меньшая редукция самцов у наше- го вида. Близость отверстия в ложной мантии к первичному половому отверстию позволяет самцам, прикрепленным к наружной поверхности органа, копулировать с самками. У Entoconchidae отверстие сифо- на помещается на заднем конце тела, и их самцы, вероятно, с самого начала располагались во внутренней полости псевдопаллиума. Это могло создать условия для их редукции и, в частности, для утраты ими совокупительного органа. Таким образом, сходство Asterophila с Entoconchidae не представляет собой результата их непосредственного родства, а объяс- няетсяих происхождением от общих предков и дальнейшей параллельной эволюцией под влиянием сходных условий существования. Подобный параллелизм - явление весьма частое у паразитических гастропод. ЛИТЕРАТУРА ГРУЗОВ, Е. Н., 1957, Новый эндопаразитический моллюск Molpadicola orientalis, gen.n., sp.n. (семейство Paedophoropodidae ). 3001. журн., 36(6): 852-863. ИВАНОВ, A.B., (IVANOV, A. W.), 1937, Die Organisation und die Lebensweise der parasitischen Molluske Paedophoropus dicoelobius A. Ivanov. Acta Zool., 18: 111-208. » 1937a, Морфологические адаптации к паразитическому образу жизни. Уч.зап. ЛГУ, 13, Cep. биол., 3(4): 53-94. » 1941, Половые отношения у паразитических Gastropoda. Тр. Лен. Общ. естествоисп., 68(4): 61-80. » 1945, Морфологические адаптации пищеварительной си- стемы у паразитических Gastropoda. Уч. зап. ЛГУ, 75, cep. биол 5119. » 1946, О путях проникновения паразитических брюхоногих в хозяев. Тр. Лен. Общ. естествоисп., 69(4): 88-91. » 1947, Строение и развитие зндопаразитического брюхо- Hororo моллюска Parenteroxenos dogieli A. Ivanov (сем. Entoconchidae ). Сообщение 1. Организация взрослого животного. Изв. АН СССР, сер. биол., 1: 3-28. » 1949, Строение и развитие зндопаразитического брюхо- Hororo моллюска Parenteroxenos dogieli А. Ivanov (сем. Entoconchidae ). Сообщение 2. Организация личинки и постларвальный метаморфоз. Изв. АН CCCP, сер. биол., 2: 109-134. ASTEROPHILA JAPONICA ит > 1949а, Строение и развитие зндопаразитического брю- xoHororo моллюоска Parenteroxenos dogieli A.Ivanov (сем. Entoconchidae ). Сообщение 3. O взаимоотношениях между родами Entoconchidae. Изв. AH CCCP, cep. биол., PASS LS , 1952, Строение эктопаразитических брюхоногих Stilifer - idae как результат их образа жизни. Tp. Лен. Общ. естествоисп., 71(4): 86-140. , 1953, Строение эндопаразитического брюхоногого мол- люска Entocolax rimsky-korsakovi A. Ivanov Tp. 3001. инст. ВЕ ECOLS LS IESO. ШВАНВИЧ, B. H., (SCHWANWITSCH, В. N.), 1917, Observations sur la female et le male rudimentaire d’Entocolax ludwigi Voigt. u. Russe Zool., 2. » 1946, О метаморфозе самки паразитического моллюска Entocolax. Homa. ЗАНИСССВ, Salt): 99395. ADAM, W., 1933, Note préliminaire sur le male de Thyca crystallina Gould. Bull. Mus. Hist. nat. Belg., 9(39): 1-5. , 1934, Prosobranches parasites. Mém. Mus. Hist. nat. Belg. Res. sci. Voyage Ind. Orient. Neerl., 2(14): 87-115. BAER, J. G., 1952, Ecology of animal parasites. Urbana: 1-244. BONNEVIE, K., 1902, Enteroxenos dstergreni, ein neuer, in Holothurien schmarotzender Gastropode. Zool. Jahrb., Abt. Anatomie, 15: 731-792. , 1906, Untersuchungen tiber Keimzellen. I Beobachtungen an den Keimzellen von Enteroxenos östergreni. Jena. Zeitschr. Naturwiss., 41: 229-428. FRETTER, V., 1955, Observations on Balcis devians (Monterosato) and Balcis alba (Da Costa). Proc. malac. Soc. London, 31: 137-144. GRAHAM, A., 1949, The molluscan stomach. Trans. roy. Soc. Edinb., 61(3): 737-779. HEATH, H., 1910, A new genus of parasitic Gastropods (Ctenosculum). Biol. Bull. mar. biol. Labor. Woods Hole, 18: 99-108. HEDING, S., 1934, Entocolax trochodotae n. sp. A new endoparasitic Gastro- pod. Vidensk. Medd. naturh. Foren. Kgbenhavn, 98: 207-214. et MANDAHL-BARTH, G., 1938, Investigations on the anatomy and systematic position of the parasitic snail Entocolax Voigt. Medd. Grönland, 108(5): 1-40. HIRASE, S., 1932. The adaptive modification of the gastropod Stilifer cele- bensis Kük., parasitic on the starfish Certonardoa semiregularis (Müll. & Trosch.). Proc. malac. Soc. London, 20: 73-76. JONKER, A., 1916, Uber den Bau und die Verwandschaft der parasitischen Gastropoden. Tijdschr. Ned. dierk. Vereen., (2), 15(1): 17-89. KOEHLER, R., et VANEY, C., 1903, Entosiphon deimatis, nouveau Mollusque parasite d’une Holothurie abissale. Rev. Suisse Zool., 11: 23-41. et , 1912, Nouvelles formes des gastéropodes ecto- parasites. Bull. sci. Fr. Belg., Paris, ser. 7, 46: 191-217. LEBOUR, M., 1932, The eggs and early larvae of two commensal gastropods, Stilifer stylifer and Odostomia eulimoides. J. mar. biol. Ass., 18: 117-122. , 1935, The larval stages of Balcis alba and B. devians. J. mar. biol. Ass., 19: 65-69. 178 Е. H. ГРУЗОВ MANDAHL-BARTH, G., 1941, Thyonicola mortenseni п. gen., п. sp., eine neue parasitische Schnecke. Vidensk. Medd. naturch. Foren., Köbenhavn, 104: 341-351. , 1945-46, Diacolax cucumariae n. gen., n. sp., a new parasitic snail. Vidensk. Medd. naturch. Foren. Kébenhavn, Bd. 109: 55-68. MULLER, J., 1852, Uber die Erzeugung von Schnecken in Holothurien. Arch. Anat. Physiol.: 1-37. NIERSTRASZ, H., 1913, Die parasitische Gastropoden. Erg. Fortschr. Zool., 3: 534-593. RANDALL, J. et HEATH, H., 1912, Asterophila, a new genus of parasitic gastropods. Biol. Bull. mar. biol. Lab. Woods Hole, 22: 98-106. RISBEC, J., 1954, Observations sur les Eulimidae (Gastéropodes) de Nouvelle-Caledonie. Bull. Mus. Hist. nat., Paris, ser. 2, 26: 109- LY fe ROSEN, N., 1910, Zur Kenntnis der parasitischen Schnecken. Acta Univ. Lund., N.F., Afd. 2, 6(4): 1-67. SARASIN, P. et F., 1885, Ueber zwei parasitische Schnecken. Zool. Anz., 9: 19-21. SCHEPMAN, M. et NIERSTRASZ, H., 1913, Parasitische und kommen- salistische Mollusken aus Holothurien. Voeltzkow Reise Ostafrica 1903-1905, 4: 383-416. SCHIEMENZ, P., 1889, Parasitischen Schnecken. Biol. Centralbl., 9: 567- 574, 585-594. SEVERCOV, A. N., 1931, Morphologische Gesetzmässigkeiten der Evolution. Jena: 1-371. THIELE, J., 1929, Handbuch der systematischen Weichtierkunde. 1: 1-376. THORSON, G., 1946, Reproduction and larval development of Danish marine bottom invertebrates. Medd. Komm. Havundersfg Kgbenhavn, ser. plankton, 4(1): 1-523. VANEY, C., 1913, L’adaptation des Gastropodes au parasitisme. Bull. sci. Fr. Belg., 47: 1-87. , 1914, Morphologie comparée des Gastropodes parasites. IX-e Congrés international de zoologie, tenu a Monaco: 486-491. VOIGT, W., 1888, Entocolax ludwigi, ein neuer seltsamer Parasit aus einer Holoturie. Zeitschr. wiss. Zool., 47: 658-688. ‚1901, Entocolax schiemenzi, n. sp. Zool. Anz., 24: 285-292. ABSTRACT THE ENDOPARASITIC MOLLUSK ASTEROPHILA JAPONICA RANDALL AND HEATH (PROSOBRANCHIA: MELANELLIDAE) AND ITS RELATION TO THE PARASITIC GASTROPODS E. N. Grusov The anatomy of the endoparasitic mollusk Asterophila japonica Randall & Heath has undergone severe modifications in the process of adaptation to its mode of life. Previous information aboutits anatomy is in many waysincorrect, and its systematic position has been uncertain. The mollusk lives inthe body wall of starfishes (Fig. 1) found along the Asiatic coast of the Pacific ocean. On the surface of the female mollusks are ASTEROPHILA JAPONICA attached the tiny neotenic males (Figs. 3, 4B), whose structure has not been studied previously. All the main subdivisions of the gastropod body were found; head, visceral mass, and foot (Figs. 6, 9), although these subdivisions were strongly masked. The head lacks tentacles and eyes. In the female it is sometimes prolonged into a snout (Fig. 3, 14A), but usually this structure has developed incompletely (Fig. 2) or disappeared completely (Fig. 14B); in the males it is always absent (Fig. 10). From the surface of the head has originated an enormously developed pseudopallium (Fig. 5-4; Fig. 6-1) enclosing the visceral mass, foot, and an extensive pseudopallial cavity, where in the females the eggs develop into veligers. The cavity communicates externally through an opening on the ventral side of the pseudopallium (Fig. 2-3; Fig. 5-2). The foot (Figs. 6, 10, 22) is vestigial; it lacks operculum, pedal glands, and creeping surface, and is nonfunctional. The male copulatory organ originates on the right side of the foot (Figs. 9, 10). In immature males there is some- times the vestige of an anterior pedal gland (Fig. 24-8). The visceral mass (Figs. 7, 8, 9, 10) has lost the shell and acquired an al- most spherical form; it does not retain traces of spiral coiling. The mantle and mantle cavity are vestigial, although they have retained the primitive position to the left of the foot (Fig. 6-8); Fig. 9-3). The complex of pallial organs has been dispersed and mostly reduced. Only the kidney has retained its normal position and opens into the mantle cavity. Ctenidium, osphradium, hypobranchial gland, and rectum have disappeared. The pallial oviduct opens outside the mantle cavity (Fig. 8-1) on the right side of the body. The digestive system begins with the oral opening, leading into a muscular, sucking pharynx that has 2 blind diverticula inthe frontal plane (Figs. 14A, B-12); Randall and Heath (1912) interpreted these as vestigial salivary glands. On the other hand they can be interpreted as new structures, absent in the ancestral forms. Characteristically all Melanellidae - Entoconchidae, with which Astero- phila japonica has much in common, lack salivary glands. The nature of the pharyngeal diverticula of Asterophila cannot be resolved conclusively, and therefore one or another interpretation of these structures should not be in- volved in our evaluation of the systematic position of the animal. The short, glandless esophagus (Fig. 25-4) connects the pharynx with the blind digestive gland or liver (Fig. 25-2). Jaws, radula, and lower intestine are absent. The circulatory system has also undergone a remarkable secondary simpli- fication, affecting mainly the vascular apparatus. The pericardium retains a normal position on the left side of the body next to the kidney (Fig. 8-10; Fig. 10-6). A renopericardial opening is absent. The heart is two-chambered (Fig. 8-8, 9). The vessels have been replaced by a system of lacunae and sinuses (Figs. 12, 13). The kidney is normally developed. Respiration takes place through the surface of the pseudopallium. The central nervous system has the following plan (Fig. 31): the cerebral and pleural ganglia are fused, forming an extensive ganglionic mass (5, 15), lying on the esophagus. Ventral to these ganglia are 2 pedal ganglia (9), lying next to the base of the foot. There are a pair of statocysts (8). On the pharynx are 2 buccal ganglia (1), connected with each other by 2 commissures (2). Thevisceral loop is incomplete. One of its portions consists of visceral (4) and subintestinal (6) ganglia, connected tothe left part of the cerebro-pleural mass (16). The other portion consists ofa single supraintestinal ganglion (12). There is chiastoneury. The female reproductive system (Fig. 38) consists of ovary and oviduct, differentiated distally into 3 parts: accessory gland (4), seminal receptacle, and pallial oviduct. Adhering in a cocoon-like mass the eggs lie in the pseudopallial cavity (Fig. 6). 179 180 E. Н. ГРУЗОВ The testis (Fig. 36-1) is connected by the vas deferens to a terminal énlarge- ment, the accessory gland (6). The larva is a typical veliger with slightly reduced lobes (Figs. 43 to 48). In contrast to the larva of Entoconchidae it has a pericardium and kidney. The whole anatomy of Asterophila indicates its closeness to Melanellidae - Entoconchidae, so that allocating it to an independent family Asterophilidae, as did Thiele (1929), is hardly justified. The characters for dividing the Melanell- idae into separate families Melanellidae, Stiliferidae, Pelseneeriidae and Paedophoropodidae are also inadequate. It is more correct to unite them into a single broad family, Melanellidae s. 1., where the form under investigation ‘certainly belongs also. Fig. 49 illustrates the phylogenetic interrelations be- tween representatives of this group. RESUMEN ASTEROPHILA JAPONICA La anatomia del molusco endoparasito Asterophila japonica Randall & Heath ha sufrido severas modificaciones en el proceso de adaptación. La información previa sobre su anatomia es muchas veces incorrecta y la posición sistemática incierta. El molusco vive en las paredes del cuerpo de estrellas de mar (Fig. 1), en la costa asiática del Pacífico. Adheridos superficialmente al las hembras se encuentran machos nototenicos (Figs. 3, 4B), cuya estructura no habia sido aun estudiada. Aunque no claramente distinguibles, pueden apreciarse las principales regiones del cuerpo gastrópodo: cabeza, masa visceral y pié (Figs. 6, 9). En la cabeza faltan los tentáculos y Ojos, y en la hembra esta se prolonga en una trompa (Fig. 3, 14A), incompletamente desarrollada (Fig. 2), o que desaparece por completo (Fig. 14B); en los machos esta siempre ausente (Fig. 10). De la superficie cefálica se origina un enorme seudopalio (Fig. 5-4; Fig. 6-1), envolviendo la masa visceral, pié, y en la extensa cavidad seudopalial de las hembras se desarrollan los huevos en larvas veligeras. Esta cavidad se comunica al exterior por un orificio ventral (Fig. 2-3; Fig. 5-2). Del pié (Figs. 6, 10, 22) sólo hay vestigios; no tiene opérculo, glandula pedal ni superficie de reptación, siendo inactivo. El órgano copulador masculino sale por el lado derecho del pié (Figs. 9, 10). En machos inmaduros hay algunas vestigios de una glandula pedal anterior (Fig. 24-8). No poseen concha y la masa visceral es casi esférica, sin presentar rasgos de arrollamiento (Figs. 7, 8, 9, 10). Del manto y su cavidad sólo hay vagos rasgos, aunque ha retenido su primitiva posición a la izquierda del pié (Fig. 6-8; Fig. 9-3). El complejo de órganos paleales está disperso y reducido. 5010 el rifñión ha mantenido su posición normal y se abre en la cavidad paleal. Branquias, osfradios, glandula hipobranquial y el recto han desaparecido. El oviducto se abre al exterior sobre el lado derecho (Fig. 8-1). La boca conduce a una faringe muscular, succionadora, con dos diverticulos ciegos en el plano frontal (Figs. 14A, B-12); Randall € Heath interpretan esto como un vestigio de glandulas salivares. Por otra parte también pueden interpretarse como estructuras nuevas, ausente en las formas ancestrales. Todos los Melanellidae - Entoconchidae con los cuales Asterophila japonica tiene mucho de común, se carac- terizan por la falta de glandulas salivares. La naturaleza de los diverticulos faringeos de Asterophila no puede resolverse conclusivamente, y su interpretación no debe incluirse en valuaciones sistemáticas. El esófago, corto y sin glandulas (Fig. 25-4) conecta la faringe con la glandula digestiva ciega o hígado (Fig. 25-2). Mandibula, rádula e intestino inferior estan ausentes. El sistema circulatorio ofrece también una gran simplificación que afecta principal- mente al aparato vascular. El pericardio tiene posición normal sobre la izquierda cerca del hígado (Fig. 8-10; Fig. 10-6). Abertura renopericardial ausente. Corazón ASTEROPHILA JAPONICA con dos cämaras (Fig. 8-8, 9). Vasos remplazados por un sistema lacunar y senos (Fig. 12-13). Riñón normal. Та respiracion se opera a traves del seudopalio. El sistema nervioso tiene elplan siguiente (Fig. 31): ganglios cerebrales y pleurales fusionados en una gran masa (5, 15) encima del esófago. En posición ventral a esos ganglios hay 2 ganglios pedales (9), cerca de la base del pié. Hay un par de estatocistos (8). Sobre la faringe hay dos ganglios bucales (1) conectados por comisuras (2). El arco visceral es incompleto; una porción consiste de ganglios viscerales (4) y sub- intestinales (6), conectados a la parte izquierda de la masa cerebro-pleural (16); la otra porción consiste de un simple ganglio supraintestinal (12). El sistema reproductor femenino (Fig. 38) consiste de ovario y oviducto diferenciado distalmente en tres partes: glandulas accesorias (4), receptaculo seminal y oviducto paleal. Masas ovigeras en forma de capullo yacen en la cavidad seudopalial (Fig. 6). El testículo (Fig. 36-1) se conecta por el vas deferens a un terminal agrandado, la glandula accesoria (6). Larva veligera típica con lóbulos algo reducidos (Figs. 43 a 48), la cual, en contraste con las de los Entoconchidae, tiene un riñón y pericardio. La completa anatomía de Asterophila indica su afinidad con Melanellidae - Entoconchidae, de modo que no justifica su ubicación por Thiele (1929), en una familia diferente. Los caracteres que se han usado para dividir los Melanellidae, Stilliferidae, Pelseneeridae y Paedophoropodidae son inadecuados. Es más correcta la unión en una misma, amplia, familia Melanellidae, a la que pertenece la forma aquí investigada. Figura 49 ilustra las relaciones filogenéticas entre los representates de este grupo. 181 DIRECTIONS TO AUTHORS Malacologia will publish original monographs and longer papers devoted primarily or exclusively to the study of mollusks. It aims to provide a common medium for such different aspects of malacology as anatomy, ecology, medical malacology, paleontology, physiology and taxonomy. The journal will try to combine scholarly standards with prompt publication. All manuscripts will be reviewed by at least two editors. 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VAN EEDEN Inst. for Zoological Research Potchefstroom Univ. for C.H.E. Potchefstroom, South Africa C. M. YONGE Department of Zoology The University Glasgow, Scotland A. ZILCH Senckenberg-Anlage 25 6 Frankfurt am Main 1 Germany 1 fl peuvent être envoyés à l’un de ] франков. Подпиеку Е. FISCHER-PIETTE A Mus. Nat. d'Histoire Naturelle 55, rue de Buffon $ « Paris V®, France 0 arty Waele ung a оо ни р url mu rid Y ‚AR; at Age N = i р р 4 Hs nd 14% у wits DET X te À pay: var ño AAA в № Cherie. ws altri hs ‘ =. Be AE Wen DATE REN, Dee ne Ken rele CIEL ELITE mh ` у hig Ms hs Л (Ni 2 р Г a PAEr Me nl ROR AR er di oe | | u tue er (eli Be Lk Lon Le Pus у BT. | 4 ue") ld PL ESA у Er id ‘(LA Wii LA N у 7 ee Г £ IA | Fr № АЯ к NER Г - - t Е : N =? MA и u Sara | т vi ste car Y a | | | SANS Mr WT ROS oe № d LA у | | = Ba = 2$ \ U 2 u } rie ALT LOT м Lente de h i | | \ a E Y e LU E В my ; ad 4 4 E fe nr } + | Pr. méme 2 rate } ae hat | N, ehem Ly + В er tin р ` iy + (Fae 67 xl eg Behr (pea В E a ИВ uf ¿ADOS ' - р Li oo ] HE 2 i ri i off: A i ve i у A i y À к. où o y \ pr Г à re oes “a = DR 1 24 à J N + ? h 0 MATACOLOGTA, 1965, 3(2): 183-195 f a36b:% NE SYMBIOTIC ERYCINACEAN BIVALVES LIBRARY, Kenneth J. Boss VOU AV Ichthyological Laboratory EU TS Bureau of Commercial Fisheries, Fish and Wildlife Service UNIV Nal A Department of the Interior, Washington 25, D. C., U.S. A. ABSTRACT This paper is a summary of the occurrence of symbiotic behavior among rep- resentatives of the eulamellibranch superfamily Erycinacea. Individual cases of commensalistic, mutualistic, or even ectoparasitic and seemingly endopara- sitic habits are presented and documentationis provided. The mollusks are dis- cussed in relationto their hosts, and brief remarks are appended concerning the general causal nature of these associations. INTRODUCTION During the preparation of a paper on a bivalve living attached to the stomatopod crustacean Lysiosquilla (Boss, 1965), I had occasion to consult the literature on commensal and para- sitic lamellibranchs. The occurrence of these bivalves is widely document- ed in diverse publications, and it is the primary purpose of this paper to present a résumé of the scattered lit- erature. In documenting the many known examples of commensalism and para- sitism in the Bivalvia, I have limited the scope of this review to those in- volving the eulamellibranch superfamily Erycinacea. Cases of inquilinism, such as mytilids inhabiting sponges and as- Cidians or pectinids associated with corals, examples of specialized boring habits, such as Lithophaga or Clavagella in corals, or instances of true parasitism, such as the glochidium in the Unionidae, have been omitted. Further, no discussion of the defi- nitions! of parasitism, mutualism, or commensalism will be made since the divisions among the phenomena are arbitrary and commonly’ the exact 1Definitions of the terms relating to symbio- tic phenomena may be found in Pennak (1964). biological relationships between the bivalve and its host or hosts are unknown. Most of the species of bivalves with known patterns of commensal or para- sitic behavior appear to have a high degree of specificity. This specificity may be illusory, occasioned by the lack of detailed study or experimental ob- servation. Thus, in a well-known spe- cies, Mysella bidentata (Montagu), range of hosts, including annelids, si- punculids, and ophiuroids, has been docu- mented, whereas in the majority of Species only a single host has been mentioned. The relationships between the bivalves and their hosts are not well known. It appears that the water currents generated by the host are usually utilized by the mollusk in feed- ing. Further, some of the associa- tions might well prove to be the means of efficient dispersal for the mollusks. In most examples it is difficult to detect what benefit, if any, is derived by the host animals. Pelseneer (1909) has discussed the evolution of 2 diverse phylogenetic branches in the Erycinacea. The con- chological studies of Chavan (1960) in- clude a discussion of the evolution of hinge mechanisms in the Erycinacea, and considerations of anatomy have been (183) 184 K. J. BOSS presented by Pelseneer (1911), Kaspar (1913), Popham (1939; 1940), and Old- field (1955; 1961; 1964) as well as numerous other authors who have dis- cussed anatomical characters in their descriptions of new genera and species. The definitions of genera and, for that matter, of families and subfamilies in the superfamily are not precise. For this reason, the generic placement of some commensals has changed fre- quently. Information on the anatomy of those type-species, which are otherwise known only conchologically, is greatly needed in order to establish a more sound taxonomic foundation. In this review, each major group of hosts is considered. Original sources are included in the bibliography. The following is an alphabetical list of the erycinacean genera here discussed and the sections in which they are men- tioned. Achasmea Echiuroidea Aligena Annelida Ceratobornia Annelida, Arthropoda Cycladella Mollusca Cycladoconcha Echinodermata Devonia Echinodermata Divariscintilla Arthropoda . Entovalva Echinodermata Ephippodonta Porifera, Coelenterata, Arthropoda Fronsella Sipunculoidea Galeomma Coelenterata Jousseaumiella Coelenterata, Sipunculoi- dea Kellia Porifera, Bryozoa, Mol- lusca, Echinodermata, Arthropoda Lasaea Mollusca, Echinoder- mata Lepton Annelida, Echinoder- mata, Arthropoda Libratula Coelenterata Marikellia Porifera, Mollusca Montacuta Sipunculoidea, Bryozoa, Echinodermata Mylitta Echinodermata Mysella Sipunculoidea, Annelida, Mollusca, Echinodermata Nipponomontacuta Coelenterata Parabornia Arthropoda Peregrinamor Arthropoda Phlyctaenachlamys Arthropoda Potidoma Sipunculoidea, Annelida Pseudopythina Annelida, Arthropoda Rochelfortia Sipunculoidea, Arthropoda Scintillona Echinodermata Scioberetia Echinodermata Serridens Mollusca Sphaerumbonella Coelenterata Synapticola Echinodermata Thyreopsis Coelenterata Vasconiella Arthropoda PORIFERA Cotton and Godfrey (1938) recorded Marikellia vincentensis 4 from the Gulf of St. Vincent, Australia, in the hollows of an unnamed sponge. Three species of Ephippodonta, from Australia: E. macdougalli Tate, E. lunata Tate, and Е. turnbullae Buick and Bowden, live in association with an unnamed, orange- colored sponge at the opening of the muddy burrows of the shrimp Axius (Tate, 1889; Matthews, 1893; Buick and Bowden, 1951). COELENTERATA From unnamed corals, Adams (1868) described Thyreopsis coralliophila from Mauritius and Pease (1865) named Li- bratula plana from the Central Pacific. These species have been cited by Franc (1960) as members of the genus Galeom- ma. Yamamoto and Habe (1961) established Nipponomontacuta actinariophila, which was found on an unnamed sea anemone off Honshu, Japan. Coen (1933) des- cribed a new genus andspecies,Sphaer- umbonella brunelli, as occurring in a burrow, which was thought to be that of an annelid, at the base of a mad- reporarian coral at Massaua, Eritrea, on the Red Sea. Kuroda (1946) figured and described Ephippodonta murakamii from Japan, and 2Dell (1964) included Marikellia Iredale in the synonymy of Kellia Turton. SYMBIOTIC ERYCINACEAN BIVALVES 185 Arakawa (1960) presented ecological data which indicate that this species of Ephip- pondonta, unlike the Australian species, lives attached to the deep sea coral Dendrophyllia cribosa Milne-Edwards and Haime. From the Ceylon coast in the Gulf of Manaar, Bourne (1906) named 2 spe- cies of the genus Jousseaumia, later renamed Jousseaumiella (Bourne, 1907). The 2 species, J. heteropsammiae and J. heterocyathi, live in the burrows of the sipunculid Aspidosiphon, in the corals Heteropsammia michelini Milne-Ed- wards and Haime and Heterocyathus aequicostatus Milne-Edwards and Haime, respectively. To one of these species of Jousseaumiella, Bouvier (1894; 1895) applied the name Kellia deshayesii and Shipley (1903) referred to them as unknown species of Mysella. SIPUNCULOIDEA Pelseneer (1928) listed some ex- amples of the symbiotic relationships between sipunculids and mollusks. Mon- tacuta (Litigiella) glabra (Fischer), which according to Pelseneer (1911) is synonymous with Erycina сиепой Lamy and Montacuta perezi Pelseneer, has been found on Sipunculus nudus Linnaeus at Arcachon, France (Pelsen- eer, 1909; Franc, 1960). In Japan, Fronsella ohshimai Habe may attach on the skin near the anus of S. nudus (Habe, 1964). Species associated with Golfingia vulgare (de Blainville) on the coast of France include Mysella bidentata and Potidoma clarkiae (Clark) (Pelsen- eer, 1925). Deroux (1961) placed Lep- ton clarkiae in the genus Potidoma. In England, M. bidentata and P. clarkiae have been reported in association with Phascolosoma pellucidum (Orton, 1923; Winckworth, 1924a) and with P. elon- gatum Keferstein (Gardiner, 1928; Sal- isbury, 1932; Popham, 1940). A more complex commensal relation occurs among the species of Jousseau- miella. Two species of this genus have been recorded in association with the corals Heteropsammia and Heterocy- athus in the Gulf of Manaar by Bourne (1906) where they live in the burrows of Aspidosiphon, sometimes imbedded in the skin of the posterior portions of the sipunculid. From Indonesian waters, Knudsen (1944) described Jous - seaumiella concharum, a protandric her- maphrodite with brood protection, which attaches to the Mitra shell used by species of Aspidosiphon or Phascolion. In Europe, Phascolion strombi (Mon- tagu) is the center of a complex etho- logical relationship (Perez, 1924; 1925). This sipunculid inhabits discarded shells of gastropods including Nassarius, Mur- ex, and Aporrhais. In the example given by Perez, P. strombi lived in the shells of Turritella communis Risso and Zi- zyphinus |=Calliostoma] conuloides La- marck. The bivalve Montacuta phas- colionis Dautzenberg was attached atthe orifice where the sipunculids generated water currents. In addition, the small ectoparasitic gastropodOdostomia (Auri- stomia) perezi Dautzenberg, a syllid polychaete, Langerhansia cornuta (Rath- ke), and the endoproct bryozoan Loxo- soma may also be in the association. In the western Atlantic, Phascolion strombi lives in the empty shells of Nassarius trivittatus (Say) and Eupleura caudata (Say). Hampson (1964) showed that Rochefortia (Pythinella) cuneata (Verrill and Bush) lives in association with this sipunculid, much as Monta- cuta phascolionis does in Europe. ECHIUROIDEA Habe (1962) described and figured Achasmea thalassemicola, attached to the body and proboscis of the echiu- roid Thalassema mucosum Ikeda, from the intertidal zone of Tomoe Bay, Tom- ioka, Japan. BRYOZOA Madsen (1949) recorded an associa- tion between Kellia rubra (Montagu) and an unnamed bryozoan in Iceland. 186 K. J. BOSS Perez (1924) showed that the endoproct Loxosoma may be involved in the com- plex commensal relationship between Montacuta phascolionis and Phascolion strombi. ANNELIDA Stimpson (1855) described Lepton [Ceratobornia] longipes from South Car- olina and noted that it lived in “holes of marine worms and fossorial crus- taceans.” Lepton squamosum (Montagu) and an unnamed species of Kellia were listed from annelid burrows by Fischer (1887). The occurrence of Mysella bidentata in the burrows of Nereis has been reported by Winckworth (1923) and Orton (1923). Anthony (1916) cited an unnamed species of Montacuta in the tubes of Eunereis longissima (Johnston) at Boulogne. In the eastern Pacific, Pseudopythina rugifera (Carpenter), well-known as an ectoparasite of the crustacean Upogebia, lives attached by its byssus to the ventral surface of the polychaete worm, or sea mouse, Aph- rodite (Oldroyd, 1924; MacGinitie and MacGinitie, 1949). For the European species, Lepton subtrigonum Jeffreys, Deroux (1961) established the genus Potidoma, which also includes Lepton clarkiae, a commensal of sipunculids. Potidoma subtrigona attaches byssally to the medial segments of the ventral surface of the polychaete Polydontes maxillosus (Ranzani). In Barnstable Harbor, Massachusetts, Aligena elevata Stimpson has been found attached to the lower end of Clymenella torquata(Leidy) (Sanders et al., 1962). MOLLUSCA AMPHINEURA. Kelsey (1902) found Serridens oblonga (Carpenter) nestling under the mantle or clinging to the shell of /schnochiton conspicuus (Car- penter) at Point Loma and Pacific Beach, California. In adding [schnochiton mag- dalenensis Hinds to the list of known hosts for S. oblonga, Burch and Burch (1944) confirmed the observations of Kelsey and noted that the commensals could also be found among the gills and on the bottom of the foot of the chitons. In their study on the fauna of Monterey Bay, California, Smith and Gordon (1948) recorded S. oblonga on Ischnochiton heathiana (Berry). GASTROPODA. Lasaea scalaris Philippi has been found attached to the aperture of Turricula teresiae Ten- ison-Woods in South Australia by Verco (1913), who suggested that a possible commensal relationship existed between the 2 species. Kellia rubra (Montagu) has been found among the tubes of Vermetus corallinaceus Tomlin at Oude- krall, South Africa (Barnard, 1964). Mysella bidentata (Montagu) has been associated with Akera nana Jeffreys and A. bullata Müller (Winckworth, 1923). BIVALVIA. Members of the genus Lasaea often nestle among the byssi of mytilids (Keen, 1938). Haas (1942) reported a specificity in these habits within Г. cistula Keen and Г. subviri- dis Dall. Both species preferably live in the shell or within the byssal strands of Brachidontes (Hormomya) multi- formis Carpenter in California, and are not found in the byssus of Mytilus californianus Conrad. North of Point Conception, at the end of the range of B. multiformis, both species of Lasaea occur in the byssus of М. californianus. Haas also reported that in Peru, L. miliaris Philippi lives in the byssus of Brachidontes granulatus Hanley. A Similar situation obtains among the spe- cies of Marikellia [=Kellia] in Australia where Laseron (1956) has reported that certain species are found among the byssus of the mussel Trichomya hir- suta (Lamarck). Carpenter (1865) recorded a number of species, including those of his genus Cycladella on the shells of Chama and Spondylus. The species were nestlers and no indication of commensal rela- tionships was evident. Packard (1918) found Kellza laperousii Deshayes in pholadid borings in San SYMBIOTIC ERYCINACEAN BIVALVES Francisco Bay, and Pelseneer (1922) found Mysella bidentata on Barnea can- dida (Linnaeus) in Europe. ECHINODERMATA ECHINOIDEA. Many reports in the literature document the occurrence of Montacuta substriata (Montagu) and M. ferruginosa (Montagu) with various echi- noids. Jeffreys (1863) and Pelseneer (1925) listed the species of echinoids upon which M. substriata could be found. Among them were: Spatangus purpureus Miiller (=S. meridionalis Risso), Cidaris cidaris (Linnaeus), Echinocardium fla- vescens (Müller), Brissopsis lyrifera (Forbes), and Echinus esculentus Lin- naeus. M. substriata attaches itself by 2 or 3 byssal threads to the oral spines of S. purpureus. This behavior has been reported from numerous Eur- opean localities (Brusina, 1865; Norman, 1891a; Grieg, 1896; Madsen, 1949; Pop- ham, 1940; Pelseneer, 1925; Deroux, 1961). Also, Vayssiére (1920) found Lasaea rubra on Spatangus. Certainly the most remarkable situa- tion which involves the commensals of S. purpureus is that reported by Marshall (1891). When both Montacuta substriata and M. ferruginosa live at- tached to the urchin, the specimens of M. substriata attach only to the spines on the ventral region of the host where- as individuals of M. ferruginosa are on the dorsal spines. Outside the range of M. substriata, M. ferruginosa is found on both oral and aboral regions of its host. This example is a fine illus- tration of Gause’s law of competitive exclusion. As early as 1848, Lovén recorded the occurrence of M. ferruginosa on Bris- sopsis lyrifeva in Sweden, and Giard (1886) found it on Echinocardium cor- datum (Pennant) on the French coast. Marshall (1891) noted M. ferruginosa living in the burrow of E. cordatum at Torbay, England, while in another popu- lation he discovered the bivalves attached to the spines of the urchin. The larger 187 or more adult specimens of M. ferrug- inosa live opposite the anal siphon ofthe urchin but younger individuals are at- tached to the urchin’s oral spines (Allen and Todd, 1900; Salisbury, 1932; Winck- worth, 1924a; Moore, 1933; Popham, 1940; Deroux, 1961; Morton, 1962). Similarly, at Port Philipp, Victoria, Aus- tralia, Montacuta semiradiata Tate lives on the spines oí Е. cordatum (Tate, 1889; Cotton and Godfrey, 1938; Franc, 1960). In Japan, Montacuta echinocardio- phila has recently been described by Habe (1964) as attaching to E. cordatum. The Antarctic spatangoid, Abatus ca- vernosus (Philippi), previously referred to such genera as Spatangus, Tripylus, and Hemiaster, is host to a number of commensals. Dall (1876) described the first of these asLepton parasiticumfrom the ambulacra or the surface of the test of an unnamed species of spa- tangoid dredged in Royal Sound, Ker- guelen Island. Smith (1877) substan- tiated Dall’s discovery andindicated that the host species is A. cavernosus, Later Bernard (1896) described the curious Scioberetia australis which lives com- mensally in the brood pouches of A. cavernosus, and then Grieg (1929) named Montacuta christenseni, another com- mensal bivalve living attached to the Spines around the peristome on the ventral side of the sea urchin. Morten- sen (1936; 1951) mentioned an unnamed Lepton, attaching in great numbers to A. cavernosus and filling up the petals and apical system of the urchin. Ac- cording to him, this species is not the L. parasiticum of Dall. Soot-Ryen (1959) referred a species of Lepton to parasiticum of Dall which was found living on Tripylaster philip- pi Gray in southern Chile. Dell (1964) has indicated that the species found by Soot-Ryen could not be the same as L. parasiticum. HOLOTHUROIDEA. Semper (1868) made early mention of the occurrence of ectocommensal bivalves on synaptids when he recorded but did not describe a small pelecypod living on Protankyra 188 similis (Semper) in the Philippines. The first documented case of “para- sitism” of bivalves in holothurians was presented by Voeltzkow (1890) who named and described Entovalva mirabilis, a species living in the oesophagus of Synapta [Leptos ynapta] ooplax von Mar- enzeller 3. Schepman and Nierstrasz (1913) added to the original description and gave ecological data on E. mira- bilis. Entovalva (Devonia) perrieri was des- cribed by Malard (1903), who found the ectoparasite on the posterior portions of the body of the synaptid Leptosyn- apta inhaerens (Müller) at Saint-Vaast- la-Hougue, France. He erected the genus Synapticola for the species but since this name was preoccupied in the Crus- tacea, Winckworth (1930) proposed De- vonia. Anthony (1916) studied the mor- phology of E. perrieri in detail, noted its relationship to Е. mirabilis, and considered the species a member of Entovalva. He found that the small bivalve was usually attached to the pos- terior portions of the body of the syn- aptid but occasionally was found at the base of the tentacles of its host. He also indicated that the glochidial-type larval form found by Herpin (1915) at Cherbourg may be a stage in the life history of Е. perrieri. Clench and Aguayo (1931) recorded E. perrieri at Woods Hole, Massachusetts, on Z. inhaerens and thus extended the known range of the ectoparasite to the western Atlantic. In England, Popham (1940) discussed some aspects of the mor- phology of the mollusk and noted that it attached to and progressed over the surface of the holothurian by means of its foot. Another species of Entovalva, E. sem- peri Ohshima, occurs in the Pacific Ocean and was reported by Ohshima 3Spärck (1931) has indicated that the holothur- ian in which E. mirabilis lives is Patinapta crosslandi (Heding) not Synapta ooplax von Marenzeller. K. J. BOSS (1929; 1930; 1931) from Kyushu, Japan. This species infests 2 apodous holo- thurians, Leptosynapta inhaerens, the usual host for Entovalva, and Protankyra bidentata (Woodward and Barrett). From Isigaki Island in the Ryukyu Islands, Kawahara (1942) found another Devonia, E. (D.) ohshimai attached to the body wall of Leptosynapta ooplax (von Mar- enzeller). A fifth species of Entovalva, E. major, was described by Bruun (1938) from the Biological Station at Ghardaga, Egypt, on the Red Sea. This species was associated with the aspidochiroten Mer- tensiothuria fuscocineria (Jaeger) |=Holothuria curiosa (Ludwig)]. On the basis of circumstantial evidence, Bruun suggested that E. major probably lives in the cloaca of the holothurian. Spirck (1931) established the new genus and species, Cycladoconcha am- boinensis, from Indonesian waters, where it lives in small pouches in the oesophagus of the apodous holothurian Patinapta laevis (Bedford). This pe- culiar endoparasitic relationship is very similar to that of Entovalva mirabilis in the oesophagus of Patinapta cross- landi mentioned previously. Cyclado- concha is closely related to Entovalva. Montacuta donacina (Wood) and M. percompressa Dall have been found on Leptosynapta inhaerens (Bateson, 1923; Gray, 1933; М. donacina has also been found on Labidoplax digitata (Montagu) (Franc, 1960). Morton (1957) discussed the mor- phology and parasitic habits of Scintil- lona zelandica (Odhner) on the synaptid Trochodota dendyi Mortensen, in New Zealand. OPHIUROIDEA. At Salcombe, Eng- land, Mysella bidentata (Montagu) lives in association with the brittle stars Ophiocnida brachiata (Montagu) andAm- Рита filiformis (Müller) (Winckworth, 1923). At Plymouth, Orton (1923) found M. bidentata in the vicinity of the disc of O. brachiata and reported a third organism in this commensalistic asso- ciation, namely, the polynoid polychaete SYMBIOTIC ERYCINACEAN BIVALVES 189 Harmothoé lunulata (delle Chiaje). Pop- ham (1940), in her study of the mantle cavity of the Erycinacea, noted that M. bidentata does not attach itself to its ophiuroid host. ARTHROPODA DECAPODA. Living along the muddy burrows of the shrimp Axzus plecto- rhychus (Strahl), are the 3 Australian species of Ephippodonta: E. macdougalli Tate, E. lunata Tate, and Е. turnbullae Buick and Bowden (Tate, 1889; Buick and Bowden, 1951). A sponge may also live along with these species in the burrow. In addition to the species of Ephip- podonta, 3 species of Mylitta: М. tas- manica Tenison-Woods, М. gemmata Tate, M. deshayesiana d’Orbigny, as well as an unnamed species of Kellia, may also be found in the burrows of Axzus (Matthews, 1893; Cotton and Godfrey, 1938). The morphology of Ephippodonta has been discussed by Woodward (1893). In England, Lepton squamosum (Mon- tagu) lives in the burrows of Upogebia deltaura (Leach) and U. stellata (Mon- tagu) (Norman, 1891а; Winckworth, 1924 a and b; Salisbury, 1932), and in France, Lepton nitidum Turton has been found attached by its byssus to U. deltaura (Pelseneer, 1925). One of the best known cases of a bivalve attached to a crustacean is that of Pseudopythina rugifera (Carpenter) which affixes by means of it byssus to the ventral portions of the abdominal segments of the blue mud shrimp of western North America, Upogebia puget- tensis (Dana). Stimpson (1857) first noted this relationship; it was subsequently reported by, among others, Norman (1891b), Harrington and Griffin (1898) and Dall (1899), who pictured the at- tached bivalve. The Lepton rude des- cribed by Whiteaves (1880) is synony- mous with P. rugifera. MacGinitie and MacGinitie (1949) reported that P; rugifera may also be encountered on the venter of the sea mouse Aph- rodite even more often than on the mud shrimp. From Japan, Shöji (1938) des- cribed Peregrinamor ohshimai,a gale- ommatid commensal, which attaches by its byssus tothe ventral portion and along the median line of the cephalothorax of the burrowing shrimp Upogebia major (de Haan). Stimpson (1855) discovered Lepton longipes, which he noted living in the “holes of marine worms and fossorial crustaceans” in South Carolina. Nor- man (1891a) identified some of the hosts of Г. longipes as Callianassa major Say and Upogebia affinis (Say). Dall (1899) placed Г. longipes in the genus Ceratobornia. Oldroyd (1924) added that both Pseudopythina compressa Dall and P. myaciformis Dall were also com- mensal with crustaceans. Rochefortia pedroana Dall attaches to the hairs of the legs and the ventral regions among the gills of the large sand crab, Ble- pharipoda occidentalis Randall in Cal- ifornia (Burch and Burch, 1944; Emer- son, 1944). Incidentally, the nonerycina- cean bivalves Mytilus edulis Linnaeus and Cerastoderma edule (Linnaeus) have been found attached to the abdomen of Carcinides maenas (Linnaeus) (Fischer, 1930; Wolff, 1959). STOMATOPODA. Kuroda (1937) illus- trated Pseudopythina subsinuata (Lis- chke) attached by its byssus to the first abdominal segment of Squilla oratoria de Haan from Japan. From the area of the Great Barrier Reef in Australia, Popham (1939) described Phlyctaena- chlamys lysiosquillina which lives com- mensally in the burrows of Lysiosquilla maculata (Fabricius). Powell (in Mor- ton, 1957) suggested that Divariscintilla maoria Powell of New Zealand, which is conchologically similar to Vasconiella of the eastern Atlantic (Kisch, 1958), may live attached to a species of Ly- siosquilla. Moore (1961) noted the pre- sence of a small bivalve, which he ten- tatively referred to as Lepion, on Ly- siosquilla scabricauda (Lamarck) in Mississippi; Boss (1965) has described this species as Parabornia squillina 190 K. J. BOSS found attached to the ventral surface of the abdomen and thorax of L. sca- bricauda from the Caribbean coast of Panama. CONCLUSION Some general principles may be stated from even a casual analysis of the ex- tensive list of individual commensals and their hosts. The hosts are ex- clusively invertebrates, and certain groups of invertebrates are preferred. Two common ecological or behavioral factors may be responsible for these associations. Most of the hosts are slow moving, almost sessile forms, which burrow in sandy or muddy bottoms, and further, most of them obtain their food by filter feeding. The relative immobility of the hosts facilitates sim- ple attachment or association by the commensal and the currents created by the processes of filter feeding generate a favorable environment for the small mollusks, which are themselves filter feeders. Natant or more mobile hosts, such as the higher crustaceans, carry the small bivalves attached ventrally in a relatively protected position. The re- lationships between erycinacean bivalves and their hosts appear to be predomi- nantly commensalistic, and no evidence exists of deleterious or pathologic ef- fects on the hosts, even when the mol- lusks live inside the host or attach directly to its epidermis. In assuming a commensalistic existence, the erycina- ceans have evolved toward highly specialized habits with concomitant mor- phological adaptations, including the en- closure of the shell by the mantle and the reduction of the shell. ACKNOWLEDGMENTS R. B. Manning, D. L. Pawson, and M. E. Jones, of the U. S. National Museum read and criticized the manu- script in regard to their specialized areas of study. J. Rosewater, Division of Mollusks, U. S. National Museum, R. Robertson, Department of Mollusks, Academy of Natural Sciences, Phila- delphia, A. H. Clarke, National Museum of Canada, Ottawa, B. Collette, Ichthyo- logical Laboratory, Burean of Commer- cial Fisheries, Washington, D. C., and A. S. Merrill, Bureau of Commercial Fisheries, Oxford, Maryland, offered suggestions and criticisms. LITERATURE CITED ADAMS, H., 1868, Further descriptions of new species of shells collected at Mauritius by Geoffrey Nevill, Esq. Proc. zool. Soc. London, pt. 1, p 12- 14, pl. 4. ALLEN, E. J. and E. A. TODD, 1900, The fauna of the Salcombe Estuary. J. mar. biol. Ass. U. В.о 317. ANTHONY, R., 1916, Contribution 4 étude de l’Entovalva (Synapticola) perrieri Malard, mollusque acéphale commensal des synaptes. Arch. Zool. exper. et générale, 55: 375-391,pls. 6-7, 8 text-figs. ARAKAWA, K. Y., 1960, Ecological ob- servations on an aberrant lamelli- branch, Ephippodonta murakamii Kur - oda. Venus, 21: 50-60, pls. 7-8. BARNARD, K. H., 1964, Contributions to the knowledge of South African marine Mollusca. Part 5. Lamelli- branchiata. Ann. S. Afr. Mus., 47: 361-593, 39 figs. BATESON, G., 1923, [no title]. Proc. malac. Soc. London, 15: 266-267. BERNARD, F., 1896, Scioberetia aus- tralis, type nouveau des lamelli- branches. Bull. Sci. France et Bel- gique, 27: 364-395, pls. 13-15. BOSS, K. J., 1965. A new mollusk (Bivalvia, Erycinidae) commensal on the stomatopod crustacean Lysio- squilla. American Museum Novitates, no. 2215, 11pp., 3 figs. BOURNE, С. C., 1906, On Jousseaumia. A new genus of eulamellibranches commensal with the corals Hetero- cyanthus and Heteropsammia. In Herdman, W. A., ed. Rept. Pearl ile Sit eile SYMBIOTIC ERYCINACEAN BIVALVES 191 Oyster Fisheries ofthe Gulf of Manaar. 37th Suppl. Rep., Part 5, 243-266, 3 pls. , 1907, Note to correct the name Jousseaumia, Proc. malac. Soc. London, 7: 260. BOUVIER, E. L., 1894, Un nouveau cas de commensalisme: association de vers du genre Aspidosiphon avec des polypes madréporaires et un mol- lusque bivalve. СН. vAcads, Sel Paris, 119: 96-98. , 1895, Le commensalisme chez certains polypes madréporaires. Ann. Sen nat: Zool., ‚ser. 7, 20: 1-32, 1 pl., 25 figs. BRUSINA, S., 1865, Conchiglie dalmati inedite. Verhandl. zool. bot. Ge- sellschaft, Wien, 15: 1-42. BRUUN, A. F., 1938, A new entocom- mensalistic bivalve, Entovalva major n. sp., from the Red Sea. Vidensk. Medd. Dansk Naturh. Foren., 102: 163-167, 1 fig. BUICK, W. G. and W. M. BOWDEN, 1951, A new Australian shell. S. Aust. Nat., 26: 5-6, 1 fig. BURCH, J. Q. and T. BURCH, 1944, [no title]. Minutes, Conchol. Club S. Calif., (40): 15-16. CARPENTER, P. P., 1865, Diagnoses of new species and a new genus from the Reigen Mazatlan collection. Proc. zool. Soc. London, pt. 3, p 268-273. CHAVAN, A., 1960, Remarques sur la charnière des Erycinacea et des Cyamiacea. Bull. Soc. Geol. France, Bera Ty 1:0712=718; CLENCH, W. J. and C. G. AGUAYO, 1931, Entovalva (Devonia) perrieri (Malard) in the western Atlantic. Occ. Paps. Boston Soc. nat. Hist., 8: 5-8. COEN, G., 1933, Un nuovo lamellibranco eritreo. Boll. di pesca, di pisci- coltura e di idrobiologia, Roma, 9: 206-208, 1 pl. COTTON, B. C. and F. K. GODFREY, 1938, The Mollusca of South Australia. Pt. 1. The Pelecypoda, 314 p, 340 figs. DALL, W. H., 1876, Contributions to the natural history of Kerguelen Island. Bull. U.S. Nat: 'Mus., 3: 42-48. , 1899, Synopsis of the Recent and Tertiary Leptonacea of North America and the West Indies. Proc. U. S. Nat. Mus., 21: 873-897, pls. 87-88. DELL, R. K., 1964, Antarctic and sub- antarctic mollusca: Amphineura, Scaphopoda and Bivalvia. Discovery Rept., 33: 93-250, 6 pls. DEROUX, G., 1961, Rapports taxono- miques d'un leptonacé non décrit “Lepton subtrigonum” Jeffreys (nomen nudum - 1873). Cahiers Biologie Marine, Roscoff, 2: 99-153, 1 pl., 18 figs. EMERSON, W. K., 1944, [no title]. Min- utes, Conchol. Club S. Calif., (41): 20. FISCHER, P., 1887, Manuel de Conchyli- ologie. Paris, 1369 р, 23 pls., 1158 figs. FISCHER, P. H., 1930, Lamellibranches fixés sous l’abdomen d’un crabe. J. Conchyl., 74: 39-41, 4 figs. FRANC, A., 1960, Classe des Bivalves. In Grassé, Traité de Zoologie, 5: 1845-2133. GARDINER, A., 1928, Notes on British Mollusca. J. Conchol., 18: 245-250. GIARD, A., 1886, Les habitants d’une plage sablonneuse. Bull. Sci. Nord. France, sér. 2, 17: 187-196. GRAY, G. M., 1933, Observations on Montacuta percompressa Dall. Nauti- lus, 46: 76-79. GRIEG, J. A., 1896, Bidrag til Kund- skaben om Vestlandets mollusker. Bergens Mus. Aarbog, (10): 14. , 1929, Echinodermata from the Palmer Archipelago, South Shetlands, South Georgia and the Bouvet Islands. Det Norske Videnskaps-Akad. Oslo, Sci. Results Norwegian Antarctic Exp., 1927-1928, 1928-1929, (2): 16 p. HAAS, F., 1942, The habits of life of some west coast bivalves. Nautilus, 56: 30-33. HABE, T., 1962, Achasmea thalassemi- cola sp. nov., a new commensal bi- valve found in an echiuroid, Thalas- sema mucosum Ikeda. Venus, 22: 117- 119, figs. 1-3. 192 K. J. BOSS , 1964, Two commensal bivalves from the west coast of Kyushu, Japan. Venus, 23 (3): 137-139, pl. 8. HAMPSON, G. R., 1964, Redescription of a commensal pelecypod, Roche- fortia cuneata, with notes on ecology. Nautilus, 77: 125-128, fig. 1 a-f. HARRINGTON, N. R. andB. B. GRIFFIN, 1898, Notes upon the distribution and habits of several Puget Soundinverte- brates. Trans. New York Acad. Sci., 16: 152-165. HERPIN, R., 1915, Un mollusque én- igmatique commensal des synaptes. Bull. Inst. Océanogr., Monaco, (302): 1-5. JEFFREYS, J. G., 1863, British Conch- ology. Van Voorst, London, Vol. 2, 465 p, 8 pls. KASPAR, J., 1913,Beitrage zur Kennt- nis der Familie der Eryciniden und Carditiden. Zool. Jahrb., (Suppl. 13), 4: 545-625. KAWAHARA, T., 1942, On Devonia oh- shimai sp. nov., a commensal bivalve attached to the synaptid Leptos ynapta ooplax. Venus, 11: 153-164, figs. 1-2. KEEN, A. M., 1938, New pelecypod species of the genera Lasaea and Crassinella, Proc. malac. Soc. Lon- don, 23: 18-32, pl. 2. KELSEY, F. W., 1902, [no title]. Nauti- lus, 15: 144. KISCH, B. S., 1958, Vasconiella jef- freysiana (P. Fischer). Proc. malac. Soc. London, 33: 21-24, pl. 3. KNUDSEN, J., 1944, Agephyrean, apoly- chaete and a bivalve (Jousseaumiella concharum nov. sp.) living together (commensalistically) in the Indo-Ma- layan seas. Vidensk. Medd. Dansk Naturh. Foren., 108: 15-24, 6 figs. KURODA, T., 1937, The habit of “Kellia” subsinuata Lischke [in Japanese]. Venus, 7: 188-189, 2 figs. , 1946, [no title; in Japanese]. Venus, 14: 39-41. LASERON, C. T., 1956, A revision of the New South Wales Leptonidae. Rec. Aus. Mus., 24: 7-22, figs. 1-27. LOVEN, S., 1848, Bidrag till Känne- domen om Utvecklingen af Mollusca Acephala Lamellibranchiata. K. Vetensk. Akad. Handl., 2: 329-435, pls. 10-15. MacGINITIE, G. E. and N. MacGINITIE, 1949, Natural history of marine ani- mals. McGraw-Hill, New York, 473p, 282 figs. MADSEN, F. J., 1949, Marine Bivalvia. The Zoology of Iceland, 4: 116 p, 12 figs. MALARD, A. E., 1903, Sur un lamelli- branche nouveau, parasite des synap- tes. Bull. Mus. Hist. nat. Paris, 9: 342-346. MARSHALL, J. T., 1891, The habitat of Montacuta ferruginosa. Jour. Conchol., 6: 399-404. MATTHEWS, E. H., 1893, On the habit of the genus Ephippodonta (Tate). Conchologist, 2: 144-145. MOORE, D. R., 1961, The marine and brackish water Mollusca of the state of Mississippi. Gulf Research Re- ports, 1 (1): 1-58. к MOORE, Н. G., 1933, А comparison of the sand fauna of Port Erin Bay in 1900 and in 1933. Proc. malac. Soc. London, 20: 285-294. MORTENSEN, T., 1936, Echinoidea and Ophiuroidea. Discovery Rept., 12: 199-348, 9 pls. , 1951, Monograph of the Echi- noidea. Spatangoida Il. Copenhagen, 593 p, 286 figs., 64 pls. MORTON, J. E., 1957, The habits of Scintillona zelandica (Odhner) 1924 (Lamellibranchia: Galeommatidae). Proc. malac. Soc. London, 32: 185- 188. , 1962, Habit and orientation in the small commensal bivalve mollusc, Montacuta ferruginosa. Anim. Behav., 10: 126-133. NORMAN, A. M., 1891a, Lepton squa- mosum (Montagu), a commensal, Ann. Mag. nat. Hist., ser. 6,7: 276-278. , 1891b, Additional notes on the mollusks Lepton as a commensal and on the crustacean genus Bathynectes. Ann. Mag. nat. Hist., ser. 6,7: 387-388. OHSHIMA, H., 1929, On a rare bivalve, Entovalva semperi n. sp. creeping on SYMBIOTIC ERYCINACEAN BIVALVES 193 the body surface of apodous holothu- rians [in Japanese]. Dobutsug. Zasshi, Tokyo, 42: 364-366. , 1930, Preliminary note on Entovalva semperi sp. nov., a com- mensal bivalve living attached to the body of a synaptid. Annot. Zool. Japan, 13: 25-27, pl. 2. , 1931, On Entovalva semperi ~ Ohshima, an aberrant commensal bi- valve. Venus, 2: 161-177, pls. 5-6. OLDFIELD, E., 1955, Observations on the anatomy and mode of life of Lasaea rubra (Montagu) and Turtonia minuta (Fabricius). Proc. malac. Soc. London, 31: 226-249. , 1961, The functional morphol- ogy of Kellia suborbicularis (Montagu), Montacuta ferruginosa (Montagu) and M. substriata (Montagu), (Mollusca, Lamellibranchiata). Proc. malac. Soc. London, 34: 255-295. , 1964, The reproduction and de- velopment of some members of the Erycinidae and Montacutidae (Mol- lusca, Eulamellibranchiata). Proc. malac. Soc. London, 36: 79-120, 21 figs. OLDROYD, I. S., 1924, Marine shells of Puget Sound and vicinity. Publ. Puget Sound biol. Stat., 4: 272 p, 49 pls. ORTON, J. H., 1923, Some new com- mensals in the Plymouth district. Nature, 112: 861, 1 fig. PACKARD, E. L., 1918, Molluscan fauna from San Francisco Bay. Univ. Calif. Publ. Zool. (Berkeley), 14: 199-452, pls. 14-60. PEASE, W. H., 1865, Description of new genera and species of marine shells from the islands of the Central Pacific. Proe. Zool. “Soc. London “pt02,° р 512-517. PELSENEER, P., 1909, Phylogenie des Lamellibranches commensaux. Bull. Acad. Belg. (Sci.), (12): 1144-1150. ‚ 1911, Les lamellibranches de l’expedition du Siboga. Partie Ana- tomique. Siboga-Exped., Monogr. 53a, 125 p, 26 pls. E , 1922, [no title]. Ann. Soc. Roy. Zool. Malac. Belgique, 52: 149. , 1925, Un Lamellibranche com- mensal de Lamellibranche et quelques autres Lamellibranches commensaux. Wimereux Trav. Stat. Zool., 9: 164- 182. , 1928, Les parasites des mol- ” lusques parasites. Bull. Soc. Zool. Fr., 53: 158-189. PENNAK, R. W., 1964, Collegiate Dic- tionary of Zoology. Ronald Press, New York, 583 p. PEREZ, C., 1924, Le complexe étho- logique de la Turritelle et du Phas- colion strombi. Bull. Soc. Zool. Fr., 49: 341-343. , 1925, Sur le complexe étho- ~ logique du Phascolion strombi. Bull. Soc. Zool. Fr., 50: 74-76, 3 figs. POPHAM, M. L., 1939, On Phlyctaena- chlamys lysiosquillina gen. and sp. nov. a lamellibranch commensal in the burrows of Lysiosquilla maculata. Sci. Rep., Great Barrier Reef Exp., 6: 61-84. , 1940, The mantle cavity of some of the Erycinidae, Montacutidae, and Galeommatidae with special refer- ence to the ciliary mechanisms. J. mar. biol. Ass. U. K., 24: 549-586. SALISBURY, A. E., 1932, On Lepton squamosum (Montagu) and Montacuta ferruginosa (Montagu) and some other molluscs observed at the Salcombe estuary, Devon. Proc. malac. Soc. London, 20: 100-103, pl. 9b. SANDERS, H. L., GOUDSMIT, E. M., MILLS, R. L., and G. E. HAMPSON, 1962, A study of the intertidal fauna of Barnstable Harbor, Massachusetts. Limn. and Oceanogr., 7 (1): 63-79. SCHEPMAN, M. M. and H. F. NIER- STRASZ, 1913, Parasitische undkom- mensalistische Mollusken aus Holo- thurien. т Voeltzkow, Reise in Osta- frika in den Jahren 1903-1905, 4: 384-416, pls. 27-30. SEMPER, G., 1868, Reisen im Archipel der Philippinen. ЦП. Teil. 1. Die Holothurien. Leipzig. 288 р. SHIPLEY, A. E., 1903, Report on the Gephyrea collected by Professor Herdman at Ceylon in 1902. In 194 K. J. BOSS Herdman, W. A. ed. Rept. Pearl Oys- ter Fisheries of the Gulf of Manaar. Part 1, p 169-176, 1 pl. SHÖJI, K., 1938, A new commensal bi- valve attached to a burrowing shrimp. Venus, 8: 119-128, pls. 3-4. SMITH, A. G. and M. GORDON, 1948, The marine mollusks and brachiopods of Monterey Bay, California, and vi- cinity. Proc. Calif. Acad. Sci., ser. 4, 26: 147-245, pls. 3-4, 4 figs. SMITH, E. A., 1877, Mollusca. Transit of Venus Expedition, 1874-1875. Phil. Trans. Roy. Soc. London, 168: 167- 192, pl. 9. SOOT-RYEN, T., 1959, Reports of the Lund University Chile Expedition 1948-59. Pelecypoda. Lunds Uni- versitets Arsskrift, 55:.1-86, 4 pls. SPARCK, R., 1931, Cycladoconcha am- boinensis n. gen. n. Sp., a commen- salistic lamellibranch. Vidensk. Medd. Dansk Naturh. Foren., 91: 227- 239, pl. 2. STIMPSON, W., 1855, On some remark- able marine invertebrates inhabiting the shores of South Carolina. Proc. Boston Soc. nat. Hist., 5: 110-117. , 1857, On the Crustacea and Echinodermata of the Pacific shores of North America. Pt. I. Crustacea. J. Boston Soc. nat. Hist., 6: 444-531, pls. 18-23. TATE, R., 1889, Description of some new species of marine Mollusca from South Australia and Victoria. Trans. Proc. Rept. Roy. Soc. South Australia (Adelaide), 11: 60-66, pl. 11. VAYSSIERE, A., 1920, Étude sur la faune marine de la cöte occidentale du Golfe de Marseille. Ann. Mus. Hist. nat., Marseille (Zool.), 17: 93- Note added in press: Two recently discovered cases of commensalism have been reported from New Zealand by Ponder (1965, The biology of the genus Arthritica. Trans. Roy. Soc. New Zealand, Zoology, 6(8): 75-86). Arthritica crassiformis Powell 110; VERCO, J. C., 1913, Note on Lasaea scalaris Philippi. Trans. Roy. Soc. South Australia (Adelaide), 37: 448- 449. VOELTZKOW, A., 1890, Entovalva mi- rabilis, eine schmarotzende Muschel aus dem Darm einer Holothurie. Zool. Jahrb. (Abt. Syst. Geogr. Biol.), 5: 619-628, pl. 42. WHITEAVES, J. F., 1880, On some marine invertebrates from the Queen Charlotte Islands. Rept. Progress Geol. Survey Canada, 1878-1879. 16 p., 2 text-figs. WINCKWORTH, R., 1923, Montacuta bidentata (Montagu). J. Conchol., 17: 86. , 1924a, Specimens of molluscs and other animals associated with them found in a day's digging at Salcombe. Proc. malac. Soc. London, 18:1; ‚ 1924b, Lepton squamosum (Mtg.), J. Conchol., 17: 158. , 1930, Notes on nomenclature 5. Some new names for British marine bivalves. Proc. malac. Soc. London, 19: 14-15. WOLFF, T., 1959, Epifauna on certain decapod Crustacea. Proc. Int. Congr. Zool., 15: 1060-1061. WOODWARD, M. F., 1893, On the anatomy of Ephippodonta macdougulli. Proc. malac. Soc. London, 1: 20- 26, pl. 2. YAMAMOTO, T. and T. HABE, 1961, Nipponomontacuta actinariophila gen. et sp. nov., a new commensal bi- valve of the sea anemone. Publ. Seto mar. biol. Lab., 9: 265-266, 2 text-figs. lives attached to the external surface of the rock-boring pholad bivalve, Ancho- masa similis (Gray), and a closely re- lated species, Arthritica hulmei Ponder lives attached by its byssus to the inner surface of the elytra of the annelid sea mouse, Aphrodita australis Baird. SYMBIOTIC ERYCINACEAN BIVALVES RESUMEN BIVALVOS ERYNACEOS SIMBIOTICOS Este trabajo sumariza la ocurrencia de comportamiento simbiötico entre repre- sentantes de los eulamelibranquios de la superfamilia Erycinacea. Casos indivi- duales de comensalismo, mutualismo, o hasta ectoparasitismo y tambien aparente endoparasitismo, se presentan documentados. Los moluscos se discuten en relacion a sus huéspedes con breves anotaciones concernientes a la causa general de esas asociaciones. 195 MALACOLOGIA, 1965, 3(2): 197-210 ECOLOGY OF CYRTODARIA SILIQUA AND HISTORY OF THE GENUS CYRTODARIA (BIVALVIA: HIATELLIDAE) K. N. Nesis Polar Research Institute of Marine Fisheries and Oceanography (PINRO) Murmansk, USSR ABSTRACT Cyrtodaria siliqua (Spengler) is distributed from the northern extremity of the Great Newfoundland Bank to the Georges Bank; it inhabits fine sand bottoms down to 500m, but mainly at depths of 50-150m, and is found below 250m only in the areas of intensive downward movements of water; it was observed at tem- peratures of -1.0 to +5. 7°C and at salinities of 32.3 to 34. 2° /00. The species is a mobile suspension feeder of incoherent bottoms. Its require- ments of depth and substrate are connected with its type of feeding. It probably cannot breed at constant low temperatures, for which reason it does not pene- trate north of the Great Newfoundland Bank. In its range C. siliqua is a West- Atlantic north-boreal species, and in its thermal requirements a low-arctic- boreal one. The genus Cyrtodaria Daudin is of Atlantic origin. It was formed during the transition of the Paleogene to the Neogene, its ancestors possibly living in the seas of the South-Russian geosyncline during the Paleogene; by the end of the Neogene it spread to the shoals of the North Atlantic and the Arctic and broke up into a number of closely related species. Due to the pleistocene glaciations these ‚ species died out off the shores of Europe, and the West-Atlantic С. siliqua was driven to the south. In the period of the postglacial climatic optimum it spread as far as northwestern Greenland, but due to the increased depth of the Denmark Strait it could not again penetrate to Iceland where it hadlived in preglacial times (Nesis, 1961). C. kurriana, the second living species of the genus, is a circumpolar high- arctic species inhabiting only brackish waters of the coastal shallows; it origi- nated in the Arctic at the beginning of the Pleistocene. Its ancestors were rela- tively warmth-loving and lived at normal sea water salinities. Due to the re- peated drying of the shelves in the periods of eustatic regressions, it was driven into the brackish water areas. At the beginning of the postglacial, or in one of the interglacials, it migrated southward as far as the Amur estuary, but during subsequent warming and rise in salinity of the coastal waters of the Far Eastern Seas it died out in the intervening areas. The present warming of the Barents Sea may also lead to a further decrease in the range of this species. The genus Cyrtodaria demonstrates the 2 main trends of species formation; the “linear or chain” and “bouquet” types of E. F. Gurjanova (1951). The evo- lution of Cyrtodaria according to the “linear” type resulted in the transformation of ancestors requiring higher temperatures (a comparatively rare example of high-arctic species of Atlantic origin) into the Artic species C. kurriana, each species of the chain retaining the morphophysiological adaptations toa definite type of feeding. INTRODUCTION tioned very rarely in scientific litera- ture and are familiar only to taxono- Cyrtodaria Daudin, 1799 is one of the mists. The genus consists of only 2 little-studied genera which are men- living species: С. siliqua (Spengler, (197) 198 К. N. МЕБ 1793)1 and С. kurriana Dunker, 1862 which for a long time were united erroneously (Dautzenberg and Fischer, 1912; Lamy, 1925). We have some data, though very limited, on the ecology of C. kurriana, but little was known of С. siliqua, whose distribution even was not quite clear, although the species is known since the 18th century. This lack of information is especially strange because this species is one of the most frequent bottom organisms on the Great Newfoundland Bank andthe favourite food of cod 2 haddock 3 yellowtail American dab® and other fishes. The frequency of Cyrtodaria in the food of cod sometimes reaches 20% (by weight even more). Taking into account that millions of people indifferent countries from Canada to Africa and from England to Brazil have been eating Newfoundland cod for aimost 6 centuries, we can say that to a certain extent, people have been eating transformed Cyrtodaria. It is the abundance of benthos there that provides the great abundance of cod and haddock on the Newfoundland Banks which has attracted fishermen into this area as far back as Pre-Columbian times. The present data on the distribution and ecology of C. siliqua were obtained from the study of the collections made by PINRO expeditions in the period 1954-1960, from 2 research vessels: the “Sevastopol” (Cruise I, inApril-May 1954, collection by A. D. Starostin; Cruise 14, in July-August 1959, col- lection by the author; Cruise 16, in March-April 1960, collection by K. P. Yanulov, A. A. Georgiev and others; Cruise 17, in July-August 1960, col- lection by the author) and the “Odessa” (Cruise 1, in March-April 1958, col- INorthern propeller clam, or banks clam. 2Gadus morhua L. 3Melanogrammus aeglefinus (L.). 4Limanda ferruginea (Storer). 9 Hippoglossoides platessoides (Fabricius). lection by Mrs. I. N. Sidorenko). The collections were gatheredby commercial trawl, by the Sigsbee trawl and the bottom grab “Ocean 50”. Investigations were carried out in the northwestern Atlantic, on the shallow water banks of the outer shelf and the upper bathyal waters of a rather extensive area from the northern extremity of Labrador to the central part of Nova Scotia. С. sili- qua was encountered at more than 70 stations (Fig. 1). According to the data available in the literature (Packard, 1867; Gould, 1870; Verrill, 1880; Whiteaves, 1901), this species is to be found throughout the shallow water area of the Gulf of St. Lawrence right up to the Strait of Belle Isle, on the Newfoundland Banks, off Nova Scotia, in the Gulf of Maine and on the Georges Bank. The southern boundary of its range runs south-west of Cape Cod. It is worth noting that we never found С. siliqua on the outer shelf north of the Great Newfoundland Bank. Neither was it encountered on the Flemish Cap Bank where we collected more than 100 samples. Judging from its area of distribution, С. siliqua is a West Atlantic north-boreal species. Cyrtodaria siliqua The outward appearance of this mol- lusk is rather peculiar. It can reacha rather big size; up to 8-10cmin length. The shell sits on the body of the mol- lusk like a tight coat on a fat man, gaping in front, from below and from behind and the valves closing only near the beak. The mantle lobes are grown together almost throughout the whole body length, leaving an opening for the foot only in front, and are also grown tightly to the shell. On the ventral side of the body that portion of the man- tle which is free from the shell, is especially fat and fleshy. The entirely united siphons are also rather fleshy. The internal structure of the mollusk is typical of Hiatellidae (Woodward, 1875). The banks clam, Cyrtodaria siliqua, completely buries itself into the ground ECOLOGY OF CYRTODARIA 199 70 65 60 55 ‚50 45 50 45 FIG. 1. Distribution of Cyrtodaria siliqua on the outer shelf and shallow banks off Newfoundland and Nova Scotia as revealedby the PINRO expeditions in the period, 1954-1960 (depth in fathoms). 1. Great Newfoundland Bank, 2. Flemish Cap Bank, 3. Banquereau Bank, 4. Gulf of St. Law- rence, 5. Georges Bank. 200 K. N. NESIS (Brunel, 1960), but not very deeply: the depth can hardly exceed a few cm as its siphons cannot extend greatly, in view of the small size of the pallial sinus, and since the foot is small and weak. It is quite clear that this mollusk can easily become a prey of various fishes. Fishes usually swallow the whole of the mollusk, but sometimes cod bites off only the siphons and the ven- tral part. On the Great Newfoundland Bank this clam is more common in the food of cod than any other mollusk, probably because cod cannot take clams which bury themselves very deeply into the ground; further, cod evidently avoid preying upon organisms whose body is completely covered by the shell. Had- dock also readily eat banks clams (Ho- mans and Needler, 1946). The whole structure of С. siliqua shows that this organism is a typical filter feeder of the near-bottom water layer. According to A. I. Savilov’s classification (1961), it must be placed with the mobile suspension feeders of the incoherent bottoms. The requirements of this mollusk regarding depth and type of bottom are closely connected with its manner of feeding, С. siliqua is common at depths down to 500m: from 51-472m (Verill, 1885), 9-90m (Johnson, 1934), 4-165m (Bousfield, 1960), 38-500m (our observations); but it obviously prefers the depths of 50-150m, at which depths 2/3 of all our collections were taken. This organism is rarely found at less than 50m (Fig. 2). Our data reveal that 125 m is the average depth of its distribution. The species shows marked restriction to certain depths: the stan- dard ratio of factorial and random de- viates calculated by the one-factor com- plex corresponds to a probability ex- ceeding 0.999. Of the various factors conditioning the distribution of the spe- cies, depth is assigned 40% of the total influence. In fact, the influence of depth is even more pronounced, since below 250 m C. siliqua was found only on the eastern slope of the Great Newfoundland Bank, in the area of the intensive des- % 50 0 50 100 150 200 250 300 350 400 450 500 FIG. 2. Bathymetrical distribution of Cyrto- daria siliqua (depth in meters). cending movements of waters. There, at 250-500 m, there prevail the conditions characteristic of shallow waters. С. siliqua lives mainly in fine sand, avoiding the coarse-sand bottoms in the shallowest parts of the banks. The distribution of С. szliqua in the Northwest Atlantic, both horizontal and vertical, coincides almost entirely with that of the sand dollar Echinarachnius parma Lamarck (Nesis, 1962), which is extremely abundant in that area. This sea urchin is also a suspension feeder of the near-bottom water layer (Sokolova and Kuznetsov, 1960). The zone where mobile suspension feeders of the inco- herent bottoms live is limited by the upper and middle parts of the broad platform shelves (Neiman, 1961) with fine-sand bottoms and considerable de- position of suspended matter. Above and below this zone the quantity of sus- pended matter in the near-bottomlayers decreases: in the zone of development of the coastal epifauna the particles of detritus are suspended by reason of the intensive water movements and are car- ried above the bottom; on the other hand, the lower sublittoral and bathyal areas are located farther from the shore, which is the main source of food materials for the benthos. С. siliqua avoids the shallowest depths because of the de- crease in the amount of food available for buried mollusks and because of hard bottoms which are unfavourable for them. In the Newfoundland area the Atlantic waters wash the continental slope, while ECOLOGY OF CYRTODARIA 201 the shallows are covered with arcticand local water masses of lower salinity and sharp seasonal and year-to-year temperature fluctuations (Schott, 1942; Elizarov, 1961). Evidently, the banks clam, an inhabitant of shallow water areas, can withstand considerable de- crease in temperature and salinity. We found Cyrtodaria at temperatures from -1.0°C to 5.7°C (+1.15°C on the average) and salinities from 32.30/00 to 34.29/00 (33.29/00 on the average). The fact that С. siliqua occurs more frequently in shallow waters explains why it is absent from the Flemish Cap Bank: the waters of the cold Labrador Current do not approach the bank, and the strait separating the Flemish Cap Bank from the Great Newfoundland Bank is too deep (1200 m) for Cyrtodaria to cross it. Why does С. siliqua not occur to the north of the Great Newfoundland Bank? Presumably this absence is connected with the reproductive postulates of this species, since it is well known that re- production and the early stages of de- velopment are the most “vulnerable” periods in the life cycle of aquatic organ- isms. The reproductive habits of the banks clam are unknown, therefore we can only draw an analogy with the before- mentioned Echinarachnius parma. The northern part of the Great Newfoundland Bank is the boundary of the boreal zone, the limit of distribution of a number of boreal and north-boreal species and of one of the most important north-boreal communities, the Echinarachnius parma community. The causes of this pheno- menon are more fully discussed in an- other article (Nesis, 1962). Here, it is merely pointed out that, in our opinion, the distribution of these animals to the north is restricted by the narrow tem- perature range within which they can reproduce. Adult specimens of north-boreal spe- cies are usually highly eurythermic, but cannot breed at temperatures below a certain limit, particularly at negative temperatures (Runnström, 1927; Thor- son, 1952). The short duration of the period of mass development of phyto- plankton in the Labrador waters is of great importance for species with plank- tonotrophic larvae. As a rule, boreal species of animals are not found at temperatures below 1-30 C (Blacker, 1957), but the banks clam can withstand negative tempera- tures as well. From its limits of tolerance it is therefore to be regarded as a low-arctic-boreal species. Thus, it can be concluded that feeding type and reaction to temperature during the reproductive period are the main factors influencing the distribution of С. siliqua. Cyrtodaria kurriana The second species ofthe genus differs from С. siliqua by a number of charac- teristics such as shape, proportions, colour of the shell, and especially by its small size, usually up to 2 cm, some- times 3-4 cm long. This circumpolar high-arctic species inhabits only the diluted coastal shallow waters (though it never entered the fresh waters). It is scarcely found below 50 m, its usual depth being 10-20 m. Valves of dead mollusks are, however, carried with ice down to even the abyssal depths of 2-3 km. С. kurriana is common (Fig. 3) off the coasts of West and East Greenland, Jan-Mayen, Spitsbergen, Franz Joseph Land, Novaya Zemlya (chiefly off the eastern coast), in the south-eastern part of the Barents Sea (Petchora estuary), in the Kara and Laptev Seas, East Siberian Sea, where it is especially abundant, off Wrangel Island, along the northern shore of the Chukchi Peninsula, in the Anadyr es- tuary, in the weakly diluted part of the Amur estuary (single findings), in the Norton Sound, on the northern shores of America east of Point Barrow, in Baffin Bay, Hudson Bay, Hudson Strait, and Ungava Bay (Derjugin, 1925; Mess- jatzev, 1931; Gorbunov, 1946, 1952; Uschakov, 1953; Filatova, 1957; Dall, 1919; Madsen, 1949; Thorson, 1951; La Rocque, 1953; Ockelmann, 1958; Hiilse- К. N. NESIS 202 “MOU рэллэзао *"SISUQUIPUIDI * ‘9 304 SI YSN][OW $141 919UM SEITE Ul DUDIA ‘avassiual ‘I ‘5 -Any *) JO soaTeA Aydute Jo soueTANDINO ‘OI *Dnb111S *) [ISSO} JO SQUIAMIDO *p *DILÍSDISUDA à ‘D ‘6 *2т1Ь1]1$ *y jo a3uea JUoSEI “€ °202]2AQnauU ‘D '8 *DUDIAANY *D TISSOJ JO 9DUATAINIIO *Z *D]SNSUD *D ‘L *DUDIAANY *D JO OBUEI даэзэла "I “quosoid pue 3sed ou} Ul D14Dpoya 7 smusd ou} jo Sseloods Jo UOIMAITISIO ‘€ “DIA ECOLOGY OF CYRTODARIA 203 mann, 1962). The feeding habits of this species are similar to those of С. siliqua, but С. kurriana belongs to the high-arctic communities of the con- tinental runoff area where bivalve mol- lusks prevail, i.e. the Portlandia aes- tuariorum community in the Kara Sea (Filatova and Zenkevitch, 1957) and the Gomphina (Liocyma) fluctuosa com- munity off East Greenland(Ockelmann, 1958). History of the genus Cyrtodaria Five fossil species of this genus have been described. However, the oldest of them, C. transcaspica Korobkov and Mironova, 1955, from the Paleogene (upper Eocene-lower Oligocene) of the Transcaspian area (Mangyshlak, Ustj- Urt, northern part of the Aral region, Turgai, probably Fergana Valley), so strongly differs, judging by its des- cription (Iljina, 1955), from all other representatives of Cyrtodaria by the al- most central position of its beaks and the absence of a pallial sinus, that it cannot belong to the genus Cyrtodaria. ‚ The other 4 species are recorded in the Neogene -Anthropogene® ofthe North- Atlantic basin and the Arctic (Fig. 3): C. neuvillei (Cossmann and Peyrot, 1909) from the lower Miocene (Burdigalian) in the vicinity of Bordeaux (Cossmann and Peyrot, 1909); C. angusta (Nyst and Westendorp, 1843) = C. vagina (Wood, 1857) from the middle Miocene-Pleis- tocene of eastern England, the Nether- lands and Belgium” (Wood, 1857; Cogels, 1874; Bell, 1918; Glibert, 1958); C. camdenensis Dall, 1920, from the Plio- cene of northern Alaska (Dall, 1920); C. jenisseae Sachs, 1953, from the Ple- istocene (chiefly early-and middle-Qua- ternary sediments) of the Soviet Arctic, from the Kolgujew Island to the Kha- tanga River (Sachs, 1953; Strelkovetal., 6 Anthropogene =the Quaternary Period. A A. I. Korobkov also mentioned this species from the middle Oligocene of the Transcas- pian area. 1959). Both recent species of Cyrto- caria are found only in the Plio-Pleis- tocene. As V. N. Sachs (1953) points out, C. jenisseae is intermediate in shell form between C. angusta and C. siliqua. Judging by the pictures, these 3 species are rather closely related to each other and are very near in their form to C. neuvillei, whereas C. cam- denensis more resembles C. kurriana. Both the general paleoclimatic data and the zoogeographical characteristics of the other mollusks found in associa- tion with the forms of Cyrtodaria ex- amined give a rough idea of the thermal tolerances of these fossil forms. Only one recent form has been found together with C. neuvillei: it is the world-wide Hiatella arctica (s.l.) (Cossmann and Peyrot, 1909). Paleoclimatic data in- dicate that the climate of the Lower Miocene in the vicinity of Bordeaux was subtropical (Termier, 1952; Schwarz- bach, 1950). In eastern England C. angusta occurs more frequently in the sediments of the Coralline Crag and in the layers immediately underlying these sediments. At that time the climate was a little bit warmer than now (south- boreal). The latest records of C. angusta belong to layers which corres- pond to the boreal climate (Reid, 1890). In Belgium C. angusta has been found together with boreal mollusks which are now living in the North Sea and the Eng- lish Channel (Glibert, 1958). Evidently, this species was typically boreal, i.e. lived in south-boreal as well as north- boreal waters. Together with C. cam- denensis other molluscan forms were found which are very nearly related to the recent arctic-boreal species Yol- diella frigida (Torell), Natica clausa (Broderip and Sowerby), Amauropsis islandica (Gmelin) and also represen- tatives of the genera Caecum, Cadulus and Dentalium (Dall, 1920). Now these 3 genera are completely absent from the Arctic, but are to be found in the northernmost parts of the boreal zone. Apparently, C. camdenensis was a north- boreal or low-arctic boreal species. 204 K. N. NESIS According to V. N. Sachs (1953), C. jenisseae is a sub-arctic species, i.e. according to our terminology, a low-arctic-boreal Species. The fossil specimens of C. siliqua have been found in northern Iceland, eastern Canada, and in northwestern Greenland. In northern Iceland the old- est layers with C. siliqua (Upper Plio- cene or’ Eopleistocene® ) were formed under climatic conditions which appar- ently corresponded to the present cli- mate of the English coasts, and the youngest layers with C. siliqua (Lower Pleistocene) under the climate prevailing now off western Iceland. Whenthe water temperature off the shores of northern Iceland dropped to the present level (now arctic species greatly predominate there), С. siliqua disappeared (Bärdar- son, 1925). In eastern Canada it has been found in the postglacial sediments of the area where it now lives (Packard, 1867; Richards, 1962). C. siliqua in- habited the area off the shores of Green- land only during the period of the post- glacial climatic optimum (Laursen, 1944, 1950) when the water temperature was about 2°C above that observed now, a fact which, incidentally, confirms the idea that the distribution of С. siliqua in the northern direction is limited by the water temperature. С. kurriana is recorded in Pleistocene and Holocene sediments in the Soviet Arctic from the Polar Urals to the Chukchi Peninsula and in Alaska under conditions roughly similar tothe present (Merklin et al., 1962; Merklin et al., 1964; Principles of Paleontology, 1960; Dall, 1919; Sachs, 1953; Strelkov et al., 1959). The above information enables us to draw the following conclusions con- cerning the history of the genus Cyrto- daria. Having originated in the eastern Atlantic some time during the transi- tion between the Paleogene and the Neo- 8 Eopleistocene =the early Pleistocene until the Mindel glaciation. gene, from ancestors which, in the Paleogene, inhabited the seas of the South-Russian geosyncline,—derivatives of the old Tethys—the genus Cyrtodaria, by the end of the Neogene, had widely spread in the shallow water areas or the North Atlantic and the Arctic, which was warm at that time, where it broke up into a number of closely related Species. The existence of a chain of shallow-water shoals between Norway and Greenland during the late Pliocene promoted the penetration of Cyrtodaria into the Northwest Atlantic (Nesis, 1961). The species of Cyrtodaria required relatively warm temperatures, being boreal or low-arctic boreal, lived at the normal salinity of sea water andreached a size of 8-10 cm. During the Ple- istocene glaciations they gradually died out in the Arctic and East Atlantic, while West Atlantic С. siliqua retreated somewhere to the south, to the shores of New England. During the postglacial period С. siliqua rapidly spread to the north and at the period of climatic optimum it appeared off the coasts of Greenland. After the end of the warmer period it moved back to Newfoundland. It could not reach Iceland again as it now had to overcome the increased depth of the Denmark Strait and the strong contrary East-Greenland current. С. siliqua has not been found in the post- glacial deposits of Iceland (Bardarson, 1911; Pjetursson and Jensen, 1905). C. kurriana, which is probably the off- shoot of C. camdenensis, formed in the Arctic at the beginning of the Pleisto- cene period. The ecology of this spe- cies is to a considerable extent asso- ciated with the repeated drying of shelves as a result of the Pleistocene eustatic regressions. In the periods of regres- sions the marine fauna could survive in 2 situations only: either at great depths, in bathyal and abyssal waters, or in the brackish and fresh waters (Zenkevitch, 1933; Gurjanova, 1939). The descent of a shallow-water filter feeder down to great depths being apparently not possible, C. kurriana adapted to low ECOLOGY OF CYRTODARIA 205 temperatures and salinities. An in- herent eurythermy andeuryhalinity inits ancestors must have made this adapta- tion somewhat easier. It is possible that the small size of this species, un- usual for the genus in question, can be explained by the influence of Arctic conditions of existence or of freshening, as the decrease in size of animals of marine origin in the brackish waters is well known (Zenkevitch, 1963). Not so very long ago the distribution of this species was evidently wider than it is now. It is possible that 8,000- 10,000 years ago, at the very beginning of the postglacial period when the Bering Strait was formed, but when the coastal waters were still very cold and diluted, C. kurriana together with Portlandia aestuariorum penetrated into the Pacific Ocean and spread to the south down to the Amur estuary, where these species have been recorded by P. V. Uschakov (1953; P. aestuariorum is doubtful). This penetration might also have oc- curred at the beginning of one of the interglacial transgressions. With the increase of salinity and rise in the ‘temperature of coastal waters C. kur- riana perished and could survive only in such places as the Amur and Anadyr estuaries. The area of C. kurriana distribution in the Barents Sea is probably decreasing due to the present warming. I. I. Mess- jatzev (1931) found living specimens of this species which, inhis opinion, is dying out in the Barents Sea, onlyinthe coldest parts of the western shore of Novaya Zemlya: in the Zabludyashchaya and Krestovaya inlets (north-west of the Northern and south of the Southern Islands). He found empty valves also in the warmer areas of Novaya Zemlya (Mityushikha and Belush’ya inlets), inthe Kanin and Petchora regions of the Sea. The collections at the Zoological Insti- tute of the Academy of Sciences of the USSR contain rather fresh valves of this Species from the Teriberskaya inlet on the Murman coast (collection of S. M. Herzenstein, 1887), but now it is not observed in this area (Uschakov, 1948; Miloslavskaya, 1954). During our in- vestigations in the southern and eastern parts of the Barents Sea we also did not observe С. kurriana beyond the limits of the Petchora estuary, where it was first recorded by K. M. Derjugin (1925) and is abundant up to now. What is the general conclusion from the foregoing history of the genus Cyrto- daria? First of all, C. kurrianais one of the rather rare Arctic species of Atlantic origin. Analysis of the paleontological data confirmed the supposition of G. P. Gorbunov (1952) about the Atlantic origin of C. kurriana, which he made from the study of its distribution area. Secondly, we can see that, in the process of evolu- tion of the genus, there occurred a gradual adaptation of individual species to the low temperatures: from sub- tropical through boreal and low- arctic-boreal to arctic conditions. This adaptation was simultaneous with the general cooling of the seas in the Northern Hemisphere during the Neo- gene-Anthropogene(Schwarzbach, 1950). This type of species formation is very near to the “linear, or chain type of Species formation” proposed by E. F. Gurjanova (1951). At the same time the morphophysiological adaptation of spe- cies to a certain feeding type remained unchanged in all the species of Cyrto- daria entering the chain and consequently they were still restricted to shallow water grounds. When the ancestral form of Cyrto- daria broke up into several closely re- lated species during its initial spread in the Atlantic and Arctic, the main ecological peculiarities were retained. This latter type of species formation can be compared with the “bouquet” type usually observed when animals first appear in new areas. Thus, 2 main ways of species evolution can be observed in this small genus. ACKNOWLEDGMENTS I should like to express my apprecia- 206 K. N. NESIS tion: toy Dr. Re Г. Merklin, Dr. Yack Starobogatov and Prof. P. V. Uschakov for their help and valuable remarks. This paper is a modified text of the report submitted to the 1st meeting on the investigation of mollusks held in the Zoological Institute of the Academy of Sciences of the USSR, Leningrad, at the end of 1961. It was published in Rus- sian in the book “Mollusks. The prob- lems of theoretical and applied mala- cology” (Moscow-Leningrad, 1964). The Russian text was kindly translated into English by Mrs. Г. P. Mokhan'ko and Mrs. I. P. Penina. REFERENCES BARDARSON, G. G., 1911, Maerker efter klima-og niveauforandringer ved Hünaflöi i Nord-Island. Vid. Medd. for 1910. ; 1925, A stratigraphical survey of the pliocene deposits at Tjörnes, in Northern Iceland. Det Kgl. Danske Vid. Selsk. Biol. Med- delelser, 4:5. BELL, A., 1918, The Suffolk boxstones and their probable age. Geol. Mag., 6 Dec., 5:1. BLACKER, R. V., 1957, Benthic animals as indicators of hydrographic condi- tions and climatic change in Svalbard waters. Fish. Investig., Ser. 2, 20:10. BOUSFIELD, E. L., 1960, Canadian Atlantic Sea Shells. Ottawa. BRUNEL, P., 1960, De la diatomée- a la morue. Les invertébrés du fond. Actualités marines, 4:2. COGELS, P., 1874, Observations géo- logiques et paléontologiques sur les différents dépots rencontrés à Anvers. Ann. Soc. malacol. Belgique, Vol. 9. COSSMANN, M. and PEYROT, A., 1909, Conchologie néogènique de l’Aquitaine. Actes Soc. Linnéenne, Bordeaux, Vol. 63. DALL, W. H., 1919, Mollusks, recent and Pleistocene. Rep. Canadian Arc- tic Exp. 1913-18, 8,A. , 1920, Pliocene and Pleisto- cene fossils from the Arctic coast of Alaska and the auriferous beaches of Nome, Norton Sound, Alaska. U. S. geol. Survey Prof. Pap., 125-C. DAUTZENBERG, P. and FISCHER, H., 1912, Mollusques provenant des cam- pagnes de 1’ “Hirondelle” et de la “Princesse-Alice” dans les mers du Nord. Rés. Camp. Sci. Monaco, Vol., Sik DERJUGIN, K. M., 1925, Explorations of the Barents and White Seas and the Novaya Zemlya 1921-1924. (In Rus- sian) Izd. Archangel. obshch; kraeved., Archangelsk. ELIZAROV, A. A., 1961, Brief charac- terization of the hydrological condi- tions of the Northwestern part of the North Atlantic. In: У... В. Travian: Fishery in the Northwest Atlantic areas. (In Russian) Murmanskoye Knizhnoye izd-vo, Murmansk. FILATOVA, Z. A., 1957, General as- pect of the marine bivalves fauna of the northern seas of the USSR (In Russian). Trudy Inst. Okeanol. AN SSSR, 20. and ZENKEVITCH L. A., 1957, Quantitative distribution of the bottom fauna of the Kara Sea. (In Russian). Trudy vsesojuzn. gidrobiol.. Obshch., 8. GLIBERT, M., 1958, Tableau strati- graphique des mollusques du néogéne de la Belgique. Bull. Inst. roy. Sci. natur., 34:32. GORBUNOV, G. P., 1946, Bottom life of the Novosiberian shoalwaters and the central part of the Arctic Ocean. (In Russian, English summary). Trudy dreifuyushchei Ekspeditsii Glavsev- morputi na 1/p “G. Sedov” 1937- 1940 gg; 3. ‚ 1952, Bivalve mollusks of the Chukchi Sea and the Bering Strait. (In Russian). In: Krainii Severo- Vostok Sojuza SSR, 2. GOULD, A., 1870, Report on the In- vertebrata of Massachusetts. 2. ed. Boston. GURJANOVA, E. F., 1939, Contributions to the origin and history of the fauna of the Polar basin. (On the base of ECOLOGY OF CYRTODARIA the study of the Crustacea-Amphi- pods and Isopods). (In Russian, Eng- lish summary). Bull. Acad. Sci. USSR, Ser. biol., 5. , 1951, The amphipods of the seas of the USSR and the adjacent seas. (In Russian). Izd-vo Acad. Nauk SSSR, Moscow-Leningrad. HOMANS, R. E. S. and NEEDLER, A. W. H., 1946, Food of the haddock. Proc. Nova Scotian Inst. Sci., 21:2. HULSEMANN, K., 1962, Marine Pele- cypoda form the north Alaskan Coast. Veliger, 5:2. ILJINA, A. P., 1955, Paleogene Mol- lusks of north Ustj-Urt. (In Rus- sian). Trudy Vsesoiuz. neftianoi nau- chno-issl. geologorazved. Inst., Nov. ser., 89. JOHNSON, C. W., 1934, List of marine Mollusca of the Atlantic coast from Labrador to Texas. Proc. Boston Soc. nat. Hist., 40:1. KOROBKOV, A. I., 1962, Recent data on the faunal character and geologic age of the Ashcheiryk series of north Ustjurt. (In Russian). Doklady Akad. Nauk SSSR, 144 (2). LAMY, E., 1925, Révision des Saxi- cavidae vivants du Muséum national d'histoire naturelle de Paris. J. Conchyl., 68:34. LA ROCQUE, A., 1953, Catalogue of the recent Mollusca of Canada. Bull. nat. Mus. Canada, 129. LAURSEN, D., 1944, Contribution to the Quaternary geology of northern West Greenland especially the raised marine deposits. Medd. om Grón- land, 135:8. , 1950, The stratigraphy of the marine quaternary deposits in West Greenland. Medd. om Grönland, 151: 16 MADSEN, F. J., 1949, Marine Bivalvia. The Zoology of Iceland, IV, 63. MERKLIN, R. L., PETROV,O. M. and AMITROV, O. V., 1962, Atlas for the identification of the mollusks in the quaternary deposits of the Chuk- chi Peninsula. (In Russian). Izd- vo Acad. Nauk SSSR, Moscow. 207 MERKLIN, В. L., PETROV, O. M. HOPKINS, D. M. and MacNEIL, F. S., 1964, An attempt of correlation to be made for the late Cenozoic marine deposits from Chukotka, north- eastern Siberia and western Alaska. (In Russian). Izv. Acad. Nauk SSSR, ser. geol., 10. MESSJATZEV, I. I., 1931, Mollusken des Barentsmeeres. Peels «(e Russian). Trudy Gosud. okeanograf. Inst., 1 (1). MILOSLAVSKAYA, N. M., 1954, On the distribution of bivalve mollusks of East Murman in relation to the tem- perature fluctuations in the environ- ment. (In Russian). Doklady Acad. Nauk SSSR, 99 (4). NEIMAN, A. A., 1961, «Some general laws concerned with the quantitative distribution of benthos in the Bering Sea. (In Russian). Okeanologiya, NESIS, K. N., 1961, The routes, and the periods of formation of the inter- rupted area of distribution of amphi- boreal species of marine bottom an- imals. (In Russian). Okeanologiya, 1 (5). English Transl.: Deep-Sea Res., 10 (4), 1963. , 1962, Pacific elements in Northwest Atlantic benthos. (In Rus- sian). In: Soviet Fisheries Investi- gations in the Northwest Atlantic. Moscow. English Transl.: Isr. Progr. Sci. Transl., Jerusalem, 1963. OCKELMANN, W. K., 1958, Marine Lamellibranchiata. The Zoology of East Greenland. Medd. om Gren- land, 122:4. PACKARD, A. S., 1867, Observations on the glacial phenomena of Labrador and Maine, with a view of the recent invertebrate fauna of Labrador. Mem. Boston Soc. nat. Hist. 1:2. PJETURSSON, H. (and JENSEN, A. S.), 1905, Om forekomsten af skalfp- rende skurstensler i Bülandshöfdi, Snaefellsnes, Island, med bemaerknin- ger om molluskenfaunaen af Ad. S. Jensen. Oversigt over det Kgl. Danske Vid. Selsk. Forhandlinger for 1904, 208 K. N. NESIS 6. PRINCIPLES OF PALEONTOLOGY, 1960, Mollusca: Loricata, Bivalvia, Scaphopoda. (In Russian). Izd-vo Acad. Nauk SSSR, Moscow. REID, C., 1890, The Pliocene deposits of Great Britain. Mem. geol. Sur- vey U. K., London. RICHARDS, H. G., 1962, Studies on the marine Pleistocene. Trans. Amer. philos. Soc., 52:3. A RUNNSTRÓM, S., 1927, Uber die Ther- mopathie der Fortpflanzung und Ent- wicklung mariner Tiere in Beziehung zu ihrer geographischen Verbreitung. Bergens Mus. Arbok, naturvid. rekke, 2. SACHS, V. N., 1953, The Quaternary period in the Soviet Arctic. (In Russian). Trudy nauchno-issl. inst. geologii Arktiki, 77. SAVILOV, A. I., 1961, Ecologic charac- teristics of the bottom communities of invertebrates in the Okhotsk Sea. (In Russian). Trudy Inst. Okeanol. AN SSSR, 46. SCHOTT, G., 1942, Geographie des Atlantischen Ozeans. Hamburg. SCHWARZBACH, M., 1950, Das Klima der Vorzeit; Eine Einführung in die Paläoklimatologie. Stuttgart. SOKOLOVA, M. N. and KUZNETSOV, A. P., 1960, On the feeding charac- ter and on the role played by trophic factor in the distribution of the flat sea urchin Echinarachnius parma La- marck. (In Russian, English sum- mary). Zoolog. Zhurn., 39 (8). STRELKOV, S.A. "DIBNER. VS D., ZAGORSKAYA, N. G. et al., 1959, Quaternary deposits of the Soviet Arc- tic. (In Russian). Trudy nauchno- issl. inst. geologii Arktiki, 91. TERMIER, H. and G., 1952, Histoire geologique de la biosphére. Paris. THORSON, G., 1951, Scaphopoda, Placo- The God- Medd. om phora, Solenogastres etc. thaab-Expedition 1928. Grgnland, 81,2. , 1952, Zur jetzigen Lage der marinen Bodentier -Okologie. Zool. Anz., 16. Suppl.-Bd. USCHAKOV, P. V., 1948, Murman Biological Station of the Academy of Sciences of the USSR in Dalne-Ze- lenetsky Bay and its first scientific works. (In Russian). Trudy Mur- man. Biol. St., 1. , 1953, The fauna of the Sea of Okhotsk and its conditions for existence. (In Russian). Izd-vo Akad. Nauk SSSR, Moscow-Leningrad. VERRILL, A. E., 1880, Notice on the remarkable marine fauna occupying the outer banks off the southern coast of New England, I. Am. J. Sci., 20 (120):119. , 1885, Results of the ex- plorations made by the steamer “Al- batross” off the northern coast of the United States, in 1883. Rep. U. S. Comm. Fish and Fisheries, 11. WHITEAVES, J. F., 1901, Catalogue of the marine Invertebrata of Eastern Canada. Geol. Survey Canada, Ottawa. WOOD, S. V., 1857, A monograph of the Crag Mollusca with descriptions of shells from the upper Tertiaries of the BritishIsles, 2, Bivalves. Palaeon- togr. Soc., 9. WOODWARD, S. P., 1875, A manual to the Mollusca, being a treatise of recent and fossil shells. London. ZENKEVITCH, L. A., 1933, Beiträge zur Zoogeographie des nördlichen Po- larbassins im Zusammenhang mit der Frage über dessen paläogeographische Vergangenheit. (In Russian, German summary). Zoolog. Zhurn., 12(4). ‚1963, Biology of the Seas of the USSR Interscience (Wiley), New York. ECOLOGY OF CYRTODARIA ZUSAMMENFASSUNG ÖKOLOGIE DER CYRTODARIA SILIQUA UND DIE GESCHICHTE DER GATTUNG CYRTODARIA (BIVALVIA: HIATELLIDAE) Cyrtodaria siliqua (Spengler) ist von dem nördlichen Ausläufer der Grossen Neufundland-Bank bis zu der Georges-Bank verbreitet und lebt auf feinem Sand in Tiefen bis zu 500 m, vorzugsweise von 50 bis 150 m (tiefer als 250 m nur in den Gebieten mächtiger Wassersenken). Sie wurde von uns bei Temperaturen von 1,0 bis +5,70 und bei einem Salzgehalt von 32,3 bis 34,2°/oo angetroffen. Diese Art ist ein beweglicher Sestonophag der losen Böden, dessen Bedürfnisse in Bezug auf Tiefenlage und Beschaffenheit des Grundes mit seiner Ernährungsweise verbunden ist. Wahrscheinlich kann sich diese Art bei konstant niedrigen Temperatu- ren nicht vermehren, infolgedessen fehlt sie nördlich der Grossen Neufundland-Bank. Nach dem Charakter ihres Areals ist C. siliqua eine nord-boreale westatlantische Art, nach ihren thermischen Ansprüchen eine niederarktisch-boreale Art. Die Gattung Cyrtodaria Daudin hat eine atlantische Herkunft. Sie bildete sich um die Zeit des Übergangs vom Paläogen zum Neogen (ihre Ahnen lebten möglicherweise im Paläogen in den Meeren der südrussischen Geosynklinale), siedelte sich gegen das Ende des Neogens in den nordatlantischen und arktischen Untiefen an und zerfiel in eine Reihe nahe verwandter Arten. In der Folge der Pleistozänvereisungen starben diese Arten an den europäischen Küsten aus, und die westatlantische С. siliqua wurde nach Süden zurückgedrängt. In der Periode des postglazialen Klimaoptimums ver- breitete sie sich nach Norden bis zu den nordöstlichen Küsten Grönlands, konnte aber nach Island, wo sie in der präglazialen Zeit lebte, infolge der Vertiefung der Däne- markstrasse, nicht mehr zurück (Nesis, 1961). Die zweite rezente Art der Gattung, C. kurriana, eine zirkumpolare hocharktische, an die entsalzten Küstenuntiefen streng gebundene Art, entstand gegen das Pleistozän in der Arktis. Ihre Ahnen waren ziemlich wärmeliebend und lebten bei normalem ozeanischen Salzgehalt. In die entsalzten Gebiete war sie durch die mehrmaligen Entwässerungen der Schelfe infolge der eustatischen Pleistozänregressionen “hineingetrieben”. Am Anfang der Postglazialzeit (oder in einer der Interglazial- perioden) verbreitete sie sich nach Süden bis zum Amurliman, starb jedoch in den Verbreitungs-Mittelpunkten während der nachfolgenden Steigerung der Temperatur und des Salzgehaltes der Küstengewässer der fernöstlichen Meere aus. Die gegenwärtige Erwärmung verringert wahrscheinlich ihr Verbreitungsgebiet auch in der Barentssee. Am Beispiel der Gattung Cyrtodaria kann man zwei Grundwege der Speziation beobachten: den “Linear- oder Kettentypus” und den “Boukett-Typus” (nach E. F. Gurjanova, 1951). Die Evolution der Cyrtodaria nach dem “Kettentypus” führte zur Entstehung der arktischen Art C. kurriana, von wärmeliebenderen Ahnen abstammend (ein ziemlich seltenes Beispiel einer hocharktischen Art atlantischer Herkunft), wobei bei allen in der Kette eingereihten Arten die morpho-physiologische Adaptation an einen bestimmten Nahrungstypus erhalten blieb. RESUMEN ECOLOGIA DE CYRTODARIA Cyrtodaria siliqua (Spengler) se distribuye desde el extremo norte del Gran Banco de Terranova al Banco Georges, sobre fondos de arena fina hasta 500 m de profun- didad, pero principalmente entre los 50 y 150 m, y debajo de los 250 m solo se en- cuentra en areas donde las aguas descienden intensivamente; se ha observado a temperaturas de -1.0 a -5.7°C y salinidades de 32.3 a 34.2 0/00. Los requerimientos de profundidad y substrato en esta especie se relacionan con su tipo de alimentación de substancias móbiles en suspensión. Probablemente no se repro- duce cuando las temperaturas bajas son constantes, razón por la cual no pasa al norte del Banco de Terranova. La especie es nor-boreal, del Atlantico occidental y 209 210 К. М. NESIS sus demandas térmicas del bajo-artico-boreal. El género Cyrtodaria Daudin es de origen Atlantico. Evolucionö durante la tran- sición del Paleogeno al Neogeno, de antecesores que vivían principalmente en el geosinclinal sudprusiano durante el Paleogeno; al final del Eogeno se extendió a los bajíos del Atlantico Norte y Artico, dividiéndos en un número de especies muy rela- cionadas. Durante las glaciaciones pleistocénicas las especies desaparecieron de las costas europeas, y en el Atlantico occidental C. siliqua fue arrastrada hacia el sur. En el periodo de clima postglacial óptimo se propagó hasta Groenlandia pero debido al creciente ahondamiento del Estrecho de Dinamarca no pudo esta vez alcanzar Is- landia, donde ya habia vivido en tiempos preglaciales (Nesis 1961). La segunda especie viviente, C. kurriana, es circumpolar alto-artica, habitando sólo las aguas salobres de los bajíos costeros; se originó el Artico al principio del Pleistoceno. Sus antecesores eran de aguas relativamente cálidas y salinidad nor- mal. Debido a las repetidas secas de la plataforma durante los periodos de regre- sión estática, fue acarreado a las aguas salobres. Al principio del postglacial, o en uno de los interglaciales emigró hacia el Sur tan lejos como el estuario de Amur, pero en el subsecuente calentamiento y aumento de salinidad de las aguas costeras de los mares del Lejano Oriente se extinguió en lasareas intermedias. El presente aumento de temperatura enel Mar de Barents puede también producir eventualmente una reduc- ción en las distribución de la especie. El género Cyrtodaria muestra los dos principales tipos en la formación de especies indicados por E. F. Gurjanova (1951): la “linear o en cadena” y de “ramillete”. La evolución de Cyrtodaria de acuerdo al tipo “linear” resultó en la transformación de antecesores que requerian más altas temperaturas (un ejemplo comparativamente raro de especies Articas de origen Atlantico), en la especie Artica C. kurriana, con cada especie de la cadena reteniendo las adaptaciones morfofisiolögicas a un tipo definido de alimentación. MALACOLOGIA, 1965, 3(2): 211-233 COMPARATIVE FUNCTIONAL STUDIES OF THE DIGESTIVE SYSTEM OF THE MURICID GASTROPODS DRUPA RICINA AND MORULA GRANULATA1 Shi-Kuei Wu2 Department of Zoology University of Hawaii Honolulu, Hawaii, U. $. A. ABSTRACT In the Hawaiian Islands Drupa ricina (L.) occurs in a luxuriant algal environ- ment, with holothurians and sponges. Morula granulata (Duclos) lives in areas with less algal growth and occurs with the bivalve Jsognomon and sponges. The anatomy and histology of the digestive system of D. ricina is described in detail and compared with that of M. granulata. They are, in general, similar except with respect to the radula, gland-gut complex, stomach and rectal gland. D. ricina has 5-cusped rachidian teeth with unindented bases while those of М. granulata have 3 cusps and an indented rachidian base. Two significant differ- ences are associated with the gland-gut complex: in D. ricina a pair of sym- metrically developed accessory salivary glands are free from the mass of the salivary glands while, in M. granulata, the larger left accessory salivary gland is completely embedded inthe salivary mass and the right, smaller one, remains free. The stomachs differ externally: both are essentially a U-shaped sac, but the stomach of D. ricina has a pouch at the esophageal side, while that of M. granulata has none. The rectal gland of D. ricina is light yellow and its outline is obscure, while that of M. granulata is black and easily distinguishable ex- e ternally. The functional aspects of the digestive system of D. ricina and М. granulata are discussed. The buccal cavity, salivary glands and their accessory glands are associated with lubrication during feeding. Ciliary currents occur through- out the entire digestive system except in the buccal cavity. Morula was observed to drill bivalves, though it preferred carrion, while Drupa is not thought to be a typical predator of hard-shelled mollusks, but to subsist on live prey, such as sponges and holothurians, or carrion. The feeding habits and dietary differences are placed in relation with the structural differ- ences in the digestive system. Comparison of the feeding habits and stomach patterns of Drupa and Morula with that of carnivorous Mesogastropoda and other Stenoglossa seems to indicate that Drupa and Morula represent the basal or primitive features of the Stenoglossa, reflecting their mesogastropod ancestory. INTRODUCTION well known for their predatory habits. Despite numerous studies on various The muricid gastropods (superfamily aspects of the digestive system (radula: Muricacea, suborder Stenoglossa) are Cooke, 1919; Arakawa, 1957, 1958, Lrhesis submitted to the Department of Zoology of the University of Hawaii in partial fulfilment of the requirements for the degree of Master of Science. 2Present address: Institute of Zoology, Academia Sinica, Nankang, Taipei, Taiwan, Republic | of China. (211) 212 5. К. WU 1962а; proboscis: Herrick, 1906; Carriker, 1943; esophagus.and stomach: Graham, 1941, 1949; mid-gut gland: Nakajima, 1956; and fecal pellets: Arakawa, 1962b) there is no compre- hensive functional study of the digestive system of any muricid. The purpose of this paper is to report on a compara- tive functional study of the digestive system of 2 muricids: Drupa ricina (L.) and Morula granulata (Duclos). D. ricina and M. granulata are both readily available in the littoral zone of the Hawaiian Islands. Previous work on Drupa and Morula is limited to the taxonomic studies by Burch (1955), Dall (1923, 1924), Hedley (1913) and Hertlein (1960), the report on spawning and development of Morula by Ostergaard (1950), and the radular study by Cooke (1919). MATERIAL AND METHODS Specimens of р. ricina and М. granu- lata were collected at Black Point, Waikiki, and Kewalo, Oahu, and dissected both alive and after preservation. For histological studies the digestive system of the snails was cut into the following parts: 1) proboscis, 2) gland-gut com- plex (including the organ of Leiblein3, nerve ring, mid-esophagus, salivary gland and its accessory gland) and the gland of Leiblein, 3) stomach and di- gestive gland, and 4) intestine and rectum. Fixatives for histological preparations included Bouin’s, 5% neutral formalin and Flemming-without- acetic-acid. Paraffin sections were cut at 5 - 8 и. Three staining methods: Delafield’s hematoxylin and eosin, Mal- lory’s triple stain, and Heidenhain’s iron-hematoxylin, were utilized for specimens fixedin Bouin’s and 5%neutral formalin. Mallory’s triple stain was The term is combined from “pharynx of Leiblein” and “pyriform organ” (Graham, 1941) and “valve of Leiblein” (Fretter & Graham, 1962). especially useful for descriptions ofboth nuclear and cytoplasmic structures. Tissues fixed with Flemming-without- acetic-acid were stained in safranin and light green, a technique utilized by Millot (1937). Radulae were fixed and flattened in 70% ethyl alcohol, dehydrated and mounted in Euparal. Observations of ciliary currents were made by the direct method of injecting fine particles of either carmine or India- ink on to the excised gut, and by the indirect method of examininghistological preparations, as adopted and discussed by Millot (1937). FUNCTIONAL MORPHOLOGY OF THE DIGESTIVE SYSTEM OF DRUPA RICINA (L.) Habitat and external features D. ста (Pl. I, Fig: 1) occurs if the inter-tidal zone of the rocky shore, or of a sand shore studded with rocks, where Ulva fasciata and other algae grow abundantly. The snails cling to the undersurfaces and sides of large rocks which have relatively smooth surfaces. Associated with D. ricina are a holothurian, Holothuria atra, and the mollusks Cypraea caputserpentis, Aplysia juliana and, with minor eco- logical differences, Morula granulata and М. nodus. D. vicina is readily distinguished by its solid, biconical, low-spired shell, the surface of which is tuberculated. The shell itself is primarily yellow- green but is usually covered with vari- ously colored calcareous algae and may be white or purple red. The head and foot of D. ricina are different shades of green, mottled with white or black. The 2 long tentacles and the anterior siphon are seen when the snail is moving about. The foot is more or less lanceolate, somewhat bi- lobed in front, angulated at each corner, and rounded or bluntly pointed behind. The ventral creeping surface is milky- DIGESTIVE SYSTEMS OF TWO MURICIDS green and is grooved medially. Im- mediately behind the anterior margin of the foot is a transverse groove in the anterior 1/6th of the foot. A horny operculum rests on the posterior end of the dorsal surface of the foot. The operculum has an eccentric nucleus and is of the lamellate type. Anatomy and histology of the digestive system The buccal region. The mouth (M) lies at the summit of a long pleur- embolic proboscis (PR). Itis oval with two-fold lips and immediately at the inner border of the lip the dorsal and ventral jaws are distinguishable. The dorsal jaw or “sclerite” (Carriker, 1943) is a beak-like structure. The transverse section of the dorsal jaw (DJ) shows 2 prominent lateral elevations (LE) and a low central elevation (CE) (Pl. I, Fig. 1). The central elevation rapidly vanishes posteriorly, where a central depression forms a dorsal groove (DG) between the 2 lateral elevations (Pl. III, Fig. 4).* The ventral jaw (VJ) is rec- tangular, with its long axis in antero- posterior direction; it also has2lateral elevations (LE) and a concave surface between these elevations. Furrows (FU) are present (Carriker, 1943)between the lateral walls of the buccal cavity and the lateral elevations of the dorsal and ventral jaws (Pl. II, Fig. 1). The odontophore (O) is composed of the retractor muscles, 2 cartilagenous rods (CR) and the radular sac (RS). The latter, together with its membrane, covers these 2 complex masses of muscles and cartilage projecting an- teriorly into the buccal cavity (BC). Posteriorly the radular sac runs below the anterior esophagus (AE); it has a coiled free blind end. The buccal cavity is lined with a “Since the anatomy of D. ricina and M. granu- lata, are, in general, very similar, sections of the latter species are occasionally quoted to illustrate features discussed in the former. 213 columnar epithelium, the cells of which have oval nuclei located in the center of the cell. The dorsal wall is dis- tinguished by a pair of dorsal folds (DF) equipped, especially medially, with long cilia which beat toward the dorsal groove (DG) (Pl. III, Fig. 4). The ventral wall is formed by the ventraljaw. The lateral walls are covered by a thin cuticle (LCU) which is continuous with the dorsal and ventral jaws. The ducts of the salivary glands open into the buccal cavity at the lateral side of the ventral jaw (VJ). An extremely small, single duct of the accessory salivary glands opens mid-ventrally to the outer surface of the lip. The radula is of the rachiglossate type usually formulated as 1-C-1 (Pl. I, Fig. 2). The rachidian or central tooth (RT) possesses 5 main cusps, of which the central cusp (CC) is the longest one. Each of the 2 lateral cusps (LC) has denticles (MD, LD) medially and later- ally. The marginal cusps (MCU) are less than half the length of the lateral cusps (LC). The tips of all cusps are sharply pointed. The anterior margin of base (В) of the rachidian is concave, but projects slightly at the median, thus forming 2 waves. Thelateraltooth (LT)istypically sickle-shaped with a thick, broad base and an extremely long process which reaches half way over the next tooth in the radular row. All the teeth rest on a membrane of connective tissue. The esophageal region. The esopha- geal region is extremely long and compli- cated. Itis most conveniently divided into 3 parts: the anterior, mid-, and pos- terior esophagus (Graham, 1941). The anterior esophagus (AE, Pl. I) begins above the opening of the radular sac and ends before the organ of Leiblein. Its dorsal folds (DF) are the contin- uations of the prominent dorsal folds of the walls of the buccal cavity (BC, Pl. Ш, Fig. 4). The tract between the folds is the food channel (FC), the outline of which is transversely H-shaped (Pl. II, Fig. 4b). As the anterior esophagus terminates, the dorsal folds diminish and several 214 S. K. WU JD wn x ot eee Ts y ------ = = > TU FIG. 1. Drupa ricina; apertural view of shell. FIG. 2. Drupa ricina; dorsal view of the digestive system. FIG. 3. Drupa ricina; dorsal view of the digestive system, except for proboscis and convoluted portion of mid-esophagus, which are shown laterally, with the glandular structures removed. Lower-case letters a-k refer to transverse sections on Pl. II, Fig. 4. DIGESTIVE SYSTEMS OF TWO MURICIDS equally developed, more or less sym- metrical folds appear (Pl. II, Fig. 4c). Histologically the anterior esophagus is lined with ciliated columnar cells with central, oval nuclei. 215 The cytoplasm of the distal ends of the cells stains deeply with eosin. The cilia are especially well developed on the dorsal folds. KEY TO LETTERING IN PLATES anus anterior aperture of the digestive duct almost circular fold anterior esophagus aperture of LGD ampulla of the gland of Leiblein accessory salivary gland artificial space base of the rachidian tooth buccal cavity cilia central cusp cilia cell central elevation connective tissue and muscle convoluted portion cartilaginous rod connective tissue denticle “digestive” cell dorsal fold dorsal groove digestive gland dorsal jaw esophageal region of stomach major fold of stomach minor fold of stomach food channel food groove furrow gonad granules glandular epithelium of the organ of Leiblein gastric shield region inner epithelial layer intestinal groove intestine lumen left accessory salivary gland lateral cusp lateral cuticle lateral denticles of the lateral cusp lateral elevation the gland of Leiblein duct of the gland of Leiblein the organ of Leiblein lateral tooth mouth mucoid cell marginal cusp medial denticle middle muscular layer mucous pad mucus nucleus nucleus of cilia cell nucleus of epithelial cell nucleus of mucoid cell nerve-ring portion odontophore outer glandular layer pouch posterior aperture of the digestive duct posterior esophagus phagocyte proboscis rectum right accessory salivary gland rectal gland radular sac rachidian tooth “secretory” cell salivary duct salivary gland style sac region stomach major typhlosole minor typhlosole ventral cleft of the organ of Leiblein ventral fold ventral groove ventral jaw 216 FIG. 1. FIG. 2. FIG. 3. See WU PLATE I Drupa ricina; a transverse section through the anterior portion of the buccal cavity. Drupa ricina; radula. Drupa ricina; a series of semidiagrammatic frontal sections through the organ of Leiblein at the points a, b, c, marked by arrow-heads in Pl. II, Fig. 4d. DIGESTIVE SYSTEMS OF TWO MURICIDS 217 Scattered among the ciliated cells are mucus cells. The esophagus is sur- rounded by circular musclesin which the ducts of the salivary glandare embedded. The mid-esophagus begins with the organ of Leiblein (LO) and extends to the point of entrance of the duct of the gland of Leiblein (LGD). The mid-esophagus can be subdivided into 3 portions on the basis of prominent structural differ- ences: the organ of Leiblein (LO), the nerve-ring portion (NRP), and the con- voluted portion (CP, Pl. I, Fig. 3). The organ of Leiblein is a markedly pear- shaped expansion of the esophageal tract, the apex of which points posteriorly and ventrally, because of the ventrally located nerve ring which has pulled down on the digestive tract. The organ of Leiblein is opaque white except for a dark streak curving around the organ. It starts at the midventral line on its an- terior side and comes to lie on the right Side at the posterior end of the organ. The streak is dueto an extremely narrow cleft (V) in the tissue of the wall, ex- panding into a hernia-like protrusion of the lumen (Pl. II, Figs. 4d € 4e). Because of the extreme thinness of the glandular epithelium (GE) at this point, the cavity oí the esophagus can be seen through it as a shadow (Graham, 1941). An almost circular mucus pad (MP) lies in the wall of the organ, excepting at the midventral cleft (У) (Pl. II, Figs. 4d € 3a) and forms the base of an almost circular fold (ACF), the ciliated lip or valve of Graham's (1941) terminology, projecting into its cavity (Pl. II, Figs. 3b, 3c and 4d). The right side of the mucus pad is located slightly anterior to the left one (Pl. II, Fig. 3a), a con- figuration probably due to torsion. His- tologically, 2 types of cells are present (Pl. II, Fig. 3). One type consists of mucoid cells (MC) which have round or oval nuclei (NM) placed closely against the basement membrane. The second type includes those cells bearing cilia (CCE) which have elongated nuclei (NC) located 1/3 of the distance from the apical end of the cells. The base of the cells is thread-like, reaching the base- ment membrane. The apical end of the cytoplasm stains slightly andis striated; this striation connects with the cilium of each cell. The anterior side of the almost circular fold is lined with ex- tremely long ciliated, columnar epi- thelial cells and the posterior side is lined with columnar cells which stain lightly. The remaining portion of the organ of Leiblein consists of glandular epithelium (GE, Pl. II, Fig. 3) which stains deep blue with Mallory’s triple stain. Here there are also 2 types of cells similar to those of the mucus pad except that the cytoplasm stains much more densely. The bottom of the narrow, hernia-like cleft is lined with squamous Cells without cilia. The lateral wall is lined with ciliated columnar cells which decrease both in height and in length of cilia as they approach the bottom of the cleft. The organ of Leiblein is coated by fibrous connective tissue which contains a layer of muscle fibers. Posterior to the organ of Leiblein the mid-esophagus becomes extremely narrow and curves slightly to the left side of the medial axis where it is sur- rounded by the nerve-ring and can thus be referred to as the nerve-ring portion FIG. 4. Drupa ricina; a series of diagrammatic transverse sections through the digestive canal at the points a-k marked by arrow-heads in Pl. I, Fig. 3. a. Through the junction of the buccal cavity and the anterior-esophagus. B. Through the anterior part of the anterior esophagus. c. Through the posterior part of the an- terior esophagus. d. Through the anterior part of the organ of Leiblein. e. Through the posterior part of the organ of Leiblein. f. Through the nerve ring portion of the mid-esophagus. g. Through the convoluted portion of the mid-esophagus. h. Through the posterior esophagus. i. Through the duct of the gland of Leiblein. j. "Through the intestine. k. Through the rectum. 218 5. К. WU (NRP, Pl. I, Fig. 3). The epithelium of this region is folded into longitudinal ridges and grooves. The dorsal side is greatly modified as the dorsal fold (DF, Pl. I, Fig. 4f) in which the epithelial cells are mainly mucoid (MC, Pl. V, Fig. 1) staining light blue in Mallory’s triple stain. Numerous phagocytes are between the mucoid cells. The ventral side of the tract consists of ridges and grooves. These are lined with ciliated columnar epithelial cells, the apical ends of which stain more deeply than the basal ends. The nucleus is round and centrally located. The nerve-ring portion is coated with fibrous connective tissue which con- tains embedded muscle fibers. Posterior to the nerve-ring portion, the mid-esophagus gradually shifts to the right side of the medial axis of the animal and upwards, at the same time expanding into a large tube greater in diameter than any other part of the esophagus; this is due to the expansion and convolution of the dorsal wall (the “median unpaired fore-gut gland” of Haller [1888], the “glande framboisée” of Amaudrut [1898], or the “convolution” of Graham[ 1941]. The convoluted portion (CP) is completely hidden under the gland of Leiblein (LG, Pl. I, Fig. 2)and extends as far back as the point at which the duct of the gland of Leiblein enters on the right side. The histology of this portion is similar to that in the nerve- ring portion, except that the dorsal fold is much more developed than formerly. The degree of modification of this portion varies with individual specimens. The convoluted portion is coated, as is the former portion, with fibrous connective tissue containing embedded muscle fibers; these fibers are thicker than formerly, averaging 30 „ in thickness. The posterior esophagus (PE, Pl. I, Figs. 2 & 3) is slender and long. In cross section (Pl. II, Fig. 4h) about 10 equally developed longitudinal folds can be observed. Histologically the posterior esophagus is similar to the nerve-ring portion of the mid-esophagus. Three glands are associated with the esophagus; the paired salivary and accessory salivary glands (SG, ASG), which open into the buccal cavity, and the unpaired gland of Leiblein, which opens into the mid-esophagus. The salivary glands. The salivary glands area white mass, which surrounds the organ of Leiblein and is overlapped by the gland of Leiblein on the dorso- posterior side. The mass cannot be macroscopically recognized as a bi- lobed structure, but when the branching system of ductules is traced, it is evi- dent that it is acutally composed of 2 closely approximated lobes. Each lobe is of the compound acinous type. The cells of the terminal portion are of 2 types (Pl. IV, Fig. 1). Mucoid cells (MC) are most numerous. The oval nucleus (N) is centrally located; and the cytoplasm stains blue with Mallory’s triple stain. “Secretory” cells (SC) are less numerous than mucoid cells; they are triangular in shape, with an oval nucleus located basally; the cytoplasm is filled with equal-sized granules which stain red with Mallory’s triple stain. The duct system of the salivary gland is of the dichotomous branching type. The ductules are approximately 30 - 40 у in diameter. The ductules of each gland finally converge into a single duct which leaves the gland near the anterior region of the organ of Leiblein and runs an- teriorly along the dorsal folds of the anterior esophagus (SD, Pl. II, Figs. 4b & 4c). At the junction of the anterior esophagus and the buccal cavity the duct descends and penetrates the ventro- lateral walls of the buccal cavity. The diameter of the duct averages 75 y. It is lined with low epithelial cells, 7 „ in height (Pl. IV, Fig. 2), whose oval nuclei (NEC) possess clear nucleoli and whose cytoplasm stains lightly with eosin. The cilia (C) are long and form bundle-like structures, whose origins are concen- trated near the nucleus. The accessory salivary glands. The accessory Salivary glands (ASG, Pl. I, Fig. 2) are a pair of tubular structures which are located laterally to the nerve DIGESTIVE SYSTEMS OF TWO MURICIDS 219 ring. The terminal portion of the left gland swells posteriorly, while that of the right gland swells anteriorly. A transverse section of the gland shows that it is divided into 3 layers (Pl. IV, Fig. 3). The outer layer (OGL), which is the thickest of the 3, consists entirely of mucoid cells. These cells are tall columnar cells with long necks which penetrate the next 2 layers and open into the lumen (L) of the gland (not shown in figure). The nuclei of these mucoid cells are small, round, and centrally located; the cytoplasm stains homo- geneously deep-blue with Mallory’s triple stain and pink with eosin. The middle layer (ММГ) consists of circular muscle fibers, between which inter- penetrate the necks of the mucoid cells mentioned above, and some connective tissue. The inner layer (IEL), which lines the lumen, is composed of low columnar epithelial cells with round or oval nuclei. These cells surround the terminal necks of the mucoid cells. The proximal portion of each tubular gland is coiled and gradually decreases in diameter. The proximal tubes from right and left join anterior to the nerve- ring, forming an extremely fine duct which runs below the hemocoel of the proboscis. The duct is lined with cuboidal cells, having oval nuclei, dis- tinct nucleoli and lightly staining cyto- plasm. The duct opens to the outer margin of the inner lip. The diameter of the duct near the opening is about 25 u. The gland of Leiblein. The gland of Leiblein (LG, Pl. I, Fig. 2)is a single, large, brown or yellow mass which lies immediately behind the salivary gland mass and overlapsthe convoluted portion (CP) of the mid-esophagus. It is tall and triangular with a terminal position ampulla (AM). The left side of the gland has 2 anterior-oblique incisions. The gland is of the monopodial branching type. Each terminal portion consists of 2 types of cells: “granular” and mucoid (Pl. IV, Fig. 4). The “sranular” cellsare columnar cells with round or oval nuclei which appear in the basal portion of the cell in hematoxylin- eosin stained material. The nucleus is not visible when using Mallory’s triple stain because of the presence of gran- ules. At the proximal portion of the cell the granules (GR) are smaller and stain red to orange, while in the distal half of the cell the granules are larger, stain blue to green, and are surrounded by vacuoles. Mucoid cells (MC) are scattered among the “granular” celis. Each lobule of the gland has a ventral fold and groove which convergestowards the single duct of the gland. The duct is short (about 1 - 2 mm) and opens into the mid-esophagus from the dorsal side. The duct wall on the oral side of the duct is formed by the continuation of the convoluted portion of the mid- esophagus. However, as it approaches the gland of Leiblein, the glandular cells are greatly reduced in number and the epithelium is formed of a cuboidal cell layer. The opposite wall, which is lined with tall ciliated columnar cells, bears the ventral folds of the duct (VF, Pl. II, Fig. 4i) Here the apical ends of the cell stain deeply. A deep groove is formed between the folds, the cells of which stain lightly. The stomach. The stomach (ST) is a U-shaped sac with a distinct pouch (P) at the esophageal end of the base of U (Pl. I, Figs. 2 & 3). In surface view the dorsal side of the stomach is visible; the major portion of the stomach is covered by the other viscera, such as the kidney, digestive gland (DGL) and gonad (G). The long posterior esophagus opens into the esophageal region of the stomach (ER, Pl. V, Fig. 4); the intestine leaves the stomach from the right angle of the U-sac. Internally, the stomach (Pl. V, Fig. 4) is a simple sac with 2 longitudinal folds more or less continuous with the typhlo- soles of the intestine. These separate the intestinal groove (IG) from the stomach proper. The major fold (F1) bordering this groove, arises at the junction of the posterior esophagus and 220 5. К. WU PLATE Ш FIG. 1. Morula granulata; apertural view of shell. FIG. 2. Morula granulata; dorsal view of the digestive system. FIG. 3. Drupa ricina; a part of the mucus pad and the glandular epithelium of the organ of Leiblein. FIG. 4. Morula granulata; atransverse sectionthrough the position region of the buccal cavity. FIG. 5. Morula granulata; radula. DIGESTIVE SYSTEMS OF TWO MURICIDS 221 the stomach; it follows the curve of the stomach, flattening out andbecoming less distinct posteriorly. In the style sac region it is continued by the typhlo- sole (T1). The minor longitudinal stomach fold (F2) similarly arises and runs parallel to the major fold, finally continuing as the minor typhlosole (T2) in the style sac region. The stomach proper can be divided topographically into an anterior esopha- geal region (ER), a “gastric shield” region (GSR) and a posterior style sac region (SSR) (Pl. V, Fig. 4). In the esophageal region a series oftransverse parallel ridges and grooves runs across the stomach at right angles to the major fold. The region just before the pos- terior end of the style sac is smooth- walled, and the major fold is less prominent than in the esophageal region. Although neither a gastric shield, suchas occurs in the stenoglossans (e.g. Cyclope neritea; Morton, 1960), nor a cuticular epithelium indicating its remnant, were observed; this distinct region is here called the gastric shield region for reasons of analogy. The style sac region (SSR) commences near the posterior aperture of the digestive duct (PAD) and ends at the intestine (INT). In the style sac region the typhlosoles (T1 and T2) meeting the stomach folds become distinct. The wall here shows weak ridges and grooves which are Set at right angle to the typhlosoles. In dis- secting one living specimen, a “proto- style” or mucus rod (Graham, 1939) was obtained in the style sac region.% The intestinal groove (IG), a de- pression in the floor of the stomach, runs, at first between the major and the minor stomach folds and later between the typhlosoles, from the esophageal angle of the stomach to the intestine. Two apertures of the di- gestive gland open into this groove: the anterior aperture (AAD) opens at the esophageal angle of the stomach, the posterior aperture (PAD) opens at the SThat a protostyle was found only once may perhaps be due to rapid dissolution before dissection. height of the “gastric shield” region. The stomach is lined by a ciliated columnar epithelium the cells of which average 40 y in height. The epithelium of the longitudinal gastric folds and of the transverse ridges of the esophageal region of the stomach have especially tall columnar cells. The height of the cells in these regions averages 90 u. In all the epithelial cells there are elongate nuclei which are centrally located. The cytoplasm stains homo- geneously except for the apical end of the cells where it stains somewhat more densely. The cilia are 10 „ in length throughout the stomach epithelium. Mucus cells are scattered among the columnar epithelial cells. At the base of the epithelial cells there are infiltrated phagocytes which possess oval or round nuclei that stain red with Mallory’s triple stain. Below the epithelium are dense fibers which stain deep blue with Mallory’s triple stain. Embedded in the connective tissue are blood cells, fibroblasts and muscle fibers. Blood spaces are located between the digestive gland and the stomach. The digestive gland. The digestive gland (DGL, Pl. I, Fig. 2) is a brown mass which surrounds all ofthe stomach except for its dorsal surface. It coils in a counterclockwise direction together with the stomach and the gonad. The digestive gland is of the compound acinous type. Two types of cells are present: “digestive” and “secretory”. The “digestive” cells (DC, Pl. IV, Figs. 5 & 6) are more numerous and are columnar epithelial cells. Their nuclei are round or oval and are located in the basal portion of the cells. Thecyto- plasm is filled with granules which stain red, yellow-green and blue with Mallory’s triple stain. The red granules occur inthe proximal portion, the yellow- green in the middle, andthe blue granules in the distal portion of the cells. The blue granules are surrounded by a vacuole. All the granules stain black in Heidenhain’s iron-hematoxylin. The “secretory” cells (SC) are tri- angular in a longitudinal section with a broad surface along the base of the 222 5. К. WU epithelium. They taper to a fine point (Pl. IV, Fig. 6) where they reach the lumen of the tubule. The “secretory” cells tend to occur in groups at the distal ends of tubules where the cells face the visceral hemocoel. The nuclei are round or oval and are relatively smaller than those of the “digestive” cells. The cytoplasm stains densely. The terminal portion of the gland is coated withathin connective tissue mem- brane. The space among the tubules is usually filled with blood corpuscles which are oval and which have round or oval nuclei. The duct of the digestive gland is of the dichotomous branching type and opens into the stomach by way ofthe 2 apertures discussed above. The duct is a con- tinuation of the stomach epithelium, and is histologically identical with that of the stomach walls, consisting of a lining of ciliated columnar cells. The intestine. The intestine (INT, Pl. I, Figs. 2 & 3) leaves the stomach at the end of the style sac region. It runs parallel to the posterior esophagus as far as the region of the heart and then continues ventrally to the heart, shifts laterally and dorsally under the kidney, and eventually leads into the dorso-ventrally compressed rectum. The intestinal wall is rather smooth, bearing the major and minor typhlosoles leading out from the stomach. These are prominent in the proximal portion óf the intestine only and gradually disappear (Pl. I, Fig. 4j). The intestine is lined with a ciliated columnar epithelium. The nuclei are ovaland more or less centrally located; the cytoplasm stains deeply at the apical end of the cells. Mucoidcells are scattered among the epithelial cells but are not numerous. The intestine is coated with thin connective tissue. The rectum. The rectum (R, Pl. I) begins where the intestine is dorso- ventrally flattened. The wall of the rectum (Pl. II, Fig. 4k) is longitudinally folded; the folds are conspicuously better developed than in the intestinal wall. The histology is similar to that of the intestine. The anus (A) opens into the right corner of the mantle cavity and termi- nates in a papilla-like projection, about 7 mm from the mantle margin. The wall of the anus is distinctly folded into ridges and grooves. The rectal gland. The rectal oranal gland (RG, Pl. I, Fig. 2) which is wedged between the rectum, the mantle and the hypobranchial gland, is а _ branching tubular structure which opens into the rectum near the anus. It is not well- developed, very pale yellow in color and is usually difficult to perceive in dis- section. Feeding and ciliary currents Feeding. Unfortunately field and the laboratory observations failed to eluci- date the feeding habits of D. ricina. Examination of the stomach contents revealed: the complete exoskeleton of young shrimp, a young holothurian, sponge spicules, flagellates, andseveral kinds of algae (mainly diatoms and fila- mentous green algae). These obser- vations seem to indicate that D. уста is not a typically mollusk-drilling, predatory species but rather that it subsists on a varied diet, perhaps in- cluding carrion. Though neither feeding habits nor the feeding mechanism have been determined, the stomach contents suggest that sucking may possibly be involved in the feeding mechanism. The hypothesis that sucking may play a part in feeding is given further weight by observation of some ciliary currents in the buccal cavity in livingexcised speci- mens. Althoughtransference ofparticles falling on the tip of the proboscis and the ventral wall of the buccal cavity to the esophagus was almost negligible in the buccal cavity proper, distinguishable ciliary currents were noted at the junction of the buccal cavity and the anterior esophagus. Ciliary currents. Ciliary currents in the anterior esophagus result largely from ciliary action of cells onthe dorsal folds (DF, Pl. V, Fig. 3). The particles DIGESTIVE SYSTEMS OF TWO MURICIDS 223 are entangled by mucus secreted by the mucoid cells. Within a few seconds the particles and mucus form a fine string, the food bolus, which is slowly moulded and transported posteriorly. Weak peristaltic contraction initiating from the anterior end of the esophagus and spreading posteriorly may aid in the movement of the food materials. At the end of the anterior esophagus the food bolus is passed through the canal of the almost circular fold to the main cavity of the organ of Leiblein. The particles moving toward the canal situated below the narrow cleft (V, Pl. Il, Fig. 4d) are lifted upward and in- corporated into the food bolus. In the organ of Leiblein the cilia of the almost circular folds move back and forth in the excised specimens. The particles falling on the glandular epithelium (GE) of the organ of Leiblein move down to the ventral medial food groove (FG) (Pl. II, Fig. 4e;, see also Pl. V, Fig. 3). Histological studies also indicate that the cilia of the glandular epithelial cells move toward the ventral Side, as does the occurence of mucus in the cavity. The epithelial cells around the groove stain light blue in Mallory’s triple stain and may be an interesting feature of the mucus secretion phase. The narrow hernia-like cleft was free from food at all times; its function was not determined. The food string moves from the organ of Leiblein posteriorly into the nerve-ring portion of the esopha- gus. While it moves along the ventral surface of the tube, particles which fall into the dorsal groove are re- jected and swept obliquely-laterally over the fold and to the. sides where they move posteriorly. In the convoluted portion the ciliary currents are similar to those in the nerve-ring portion. In the posterior esophagus the food bolus is passed posteriorly and receives the string-like secretion of the gland of Leiblein (Pl. V, Fig. 3). This latter is incorporated into the food bolus, Spiralling into the bolus in a clockwise direction (anterior view). The ciliary currents in the stomach (Pl. V, Fig. 4) move the food in a clockwise spiral fashion in the stomach proper (i.e. not into the intestinal grove). A fewgrooves which run parallel to the major gastric fold move it pos- teriorly toward the “gastric shield region”. Thus the food bolus in the stomach is formed by the rotatory move- ment of the cilia of the stomach epitheli- um. Particles falling into the intestinal groove are rejected by way of the tiny ridges and grooves in the intestinal groove itself. Some particles move along the inner edge of the minor stomach fold together with secretions from the digestive gland and go into the intestine. Particle movement in the intestinal groove is especially rapid. The food bolus in the stomach proper is gradually passed over to the gastric Shield region. Rotation is also ina clockwise direction. The particles move Slowly here. A complete holothurian was found in this region. The foodbolus passes eventually into the style sac region, and the bolus is further mixed with the secretion of the epithelial cells here. In the intestine the food bolus is rotated and mixed with the secretions of the digestive gland which are intro- duced by way of the intestinal groove. Once the food bolus has reached the rectum, movement is slowed down and the ciliary currents here indicate that the food bolus and stray particles are moved back and forth in the same position. The feces are formed at the distal end of the rectum and finally are passed outside through the anus. The feces contain many kinds of diatoms, filamentous green algae, sponge spicules and different sizes of sand grains. FUNCTIONAL MORPHOLOGY OF THE DIGESTIVE SYSTEM OF MORULA GRANULATA (DUCLOS) Habitat and external features М. granulata occurs in the intertidal 224 S. K. WU PLATE IV FIG. 1. Morula granulata; a portion of transverse section of the tubules of the salivary gland. FIG. Morula granulata; a transverse section of the duct of the salivary gland. FIG. 3. Morula granulata; a portion of transverse section of the accessory salivary gland; semi-diagrammatic: shown are the 3 layers, but not the fact that the mucoid cells of the first layer penetrate the 2 other layers. FIG. 4. Drupa ricina; a portion of the epithelium of the gland of Leiblein. FIG. Drupa ricina; a portion of transverse section of the tubule of the digestive gland. FIG. 6. Morula granulata; a portion of longitudinal section of the distal end of the digestive gland tubule. The scales of Figs. 1, 4, 5 and 6 are at Fig. 5. D A DIGESTIVE SYSTEMS OF TWO MURICIDS zone of the sand-rocky shore and on coral reef flats. Those snails which live along the sand-rocky shore wedge themselves in crevices and between boulders. Those snails which live on the reef flat occur on the undersurface of rather smooth coral fragments or rock. There M. granulata occurs with /sognomon, а lamellibranch which is attached to the coral blocks by byssal filaments. Numerous empty /sognomon shells were observed near specimens of M. granu- lata. The shell of М. granulata (Pl. Ш, Fig. 1) is solid and biconical, and its surface is granulated. The shell is black but it is usually encrusted with variously colored calcareous algae. The head and body of M. granulata are similar to those of D. ricina except for coloration: the exposed soft parts are black. Anatomy and histology of the digestive system The anatomy andhistology of M. granu- lata are, in general, similar to those of р. vicina. In the following account attention will be focused chiefly on differences of detail, especially with respect to the radula, gland-gut com- plex, stomach and rectal gland. The radula formula is also 1-C-1. The rachidian tooth (RT, Pl. Ш, Fig. 5) possesses 3 main cusps of which the central cusp (CC) is the longest. The central cusp is sharply pointed while the lateral cusps (LC) have a strong medially placed denticle (D) which is free from the lateral cusp. There are 2 blunt denticles or rather wrinkles lateral to the lateral cusps. The angles of the margins are somewhat raised but do not form cusps. The base (B) of the rachidian is rectangular and has an indentation or pit on the posterior side, which serves to anchor the cusps. The lateral teeth (LT) are typically sickle- shaped, like those of D. vicina, but much more slender and smaller in size. The left accessory salivary gland is completely embedded in the salivary 225 gland while the right accessory salivary gland is free from it. The pair is asymmetrically developed, the right accessory Salivary gland being smaller than the left one. In spite of the difference in development, the histo- logical structure of the accessory sali- vary gland is similar to that of D. уста. The stomach of M. granulatais almost entirely embedded in the digestive gland (DG) except for a portion which, in dorsal view, shows externally as a U- shaped tube (Pl. Ш, Fig. 2). Asin D. vicina the stomach is a U-shaped sac, but it lacks the pouch at the base of the U. Its internal structure (Pl. V, Fig. 5) is similar to that of D. rzcina. The epithelial folds of the intestine are slightly less developed in M. granulata. The location of the rectal gland corre- sponds to that in D. vicina, but it is well developed and can be easily seen by its black coloration. It isabranching type of gland from whose main trunk long branches emerge laterally and short branches emerge medially (Pl. III, Fig. 2). Histologically the transverse sec- tions of the trunk and branches of the rectal gland (Pl. V, Fig. 2) are lined with ciliated, low columnar cells. The nuclei (N) are round or oval and centrally located. The cells mainly contain large brown to black granules (GR) which give rise to the black color of the gland. The cytoplasm is homogeneously and lightly stained. The apical ends of the cells stain light blue in Mallory?s stain. The rectal gland is coated by a thin fibrous membrane and some muscle fibers are attached to the membrane. It is also surrounded by fatty tissue, as is the rectum. Feeding and ciliary currents Feeding. In both the field and the laboratory М. granulata clings to 2 species of /sognomon, I. incisum and J. costellatum, and feeds on them, either by actually boring or by projecting the proboscis through the slit between the valves of the lamellibranch. M. granu- lata may also prey on holothurians and 226 S.:K: "WU feeds on fragments of Turbo, the flesh of which is made available by ophiuroids. М. granulata was successfully kept in the laboratory with Jsognomon and Ostrea. The species exhibits 3 interesting characteristics: it shows a preference for Ostrea rather than for Isognomon; the species is gregarious when feeding, and it has a tendency to “prefer” feeding on deadorganisms when both living and dead organisms are available. The proboscis performs a prominent role in feeding. It first appears in “searching” for the prey and “selects” an acceptable drilling site. When fully extended the proboscis is equal inlength to the height of the shell. It is very flexible and able to rotate in any di- rection. Examination of shells on which М. granulata had preyed indicated that the snail drilled only the thinnest portion of the shell of the prey. The proboscis also plays a role in the mechanical drilling of the shells of Isognomon and Ostrea. Drilling involves the radula, the musculature of the pro- boscis, and the buccal mass, all of which work together; it is alsocorrelated with the presence of an accessory boring organ (Carriker, 1961) or pedal gland (Fretter, 1941) located in a sac, opening into the sole of the foot near its anterior end. It is concluded from behavioral studies that the accessory boring organ secretes a shell-softening substance (Carriker, 1943, 1961). A detailed account of drilling by muricids has been given by Carriker (1943). In M. granu- lata some rasping strokes were observed but the detailed phases of drilling were not observed. Ciliary currents. Ciliary currents were not apparent in the buccal cavity. Those in the esophageal region (Pl. V, Fig. 3), the stomach (Pl. V, Fig. 5), the intestine and the rectum are similar to those of D. ricina. The fecal pellets which were obtained near the anus are black, pointed at both ends and slightly twisted. They are composed of fine black granules (2 - 3 u in diameter), various kinds of diatoms, filamentous green algae and sponge spicules. The feces are surrounded by a thin, trans- parent film of mucus. COMPARATIVE FUNCTIONAL MORPHOLOGY OF THE DIGESTIVE SYSTEM OF D. RICINA AND M. GRANULATA Although D, vicina and М. granulata differ from one another in certain features of their anatomy, the functional morphology of the digestive system in both species can be most fruitfully ex- plored by way of a comparative dis- cussion of the feeding habits, structure and function of the digestive system of the 2 species, and by a comparison of those with previous descriptions of the muricid digestive system. D. vicina and M. granulata, living in distinct ecological niches, also have different feeding habits. Although the feeding habits of D. vicina were not observed, it is inferredfrom the associ- ated plants and animals, the radula and stomach contents, that D. ricina is apparently not a boring gastropod but probably feeds on carrion, deposits and /or living sponges and holothurians. М. granulata, on the other hand, was ob- served to bore actively into bivalves such as /sognomon and Ostrea, although it preferred feeding on carrion even in the presence of both living bivalves. The buccal cavities of D. ricina and М. gvanulata are similar to that of Urosal- pinx cinerea (Carriker, 1943). The walls of the buccal cavity are modified in association with the movement of the odontophore during feeding. The ventral jaw, forming a concave surface which is lubricated by the secretion of the salivary gland, provides space against which the odontophore slides back and forth, and the lateral furrow of the wall can expand allowing for the extrusion of the odonto- phore. The distinctive “drupid” and “morulid” radular patterns displayed by each species may possibly be associated with the feeding habits of each species. In D. vicina, where there are 5 cusps, of which the laterals are clearly denticu- lated medially and laterally and where the a a OA ae oe FIG. FIG. FIG. FIG. FIG. w № DIGESTIVE SYSTEMS OF TWO MURICIDS 227 PLATE V 5 Drupa ricina; a portion of transverse section of the dorsal fold of the nerve-ring portion of the mid-esophagus. Morula granulata; a portion of transverse section of the rectal gland. Drupa vicina; esophageal region, incised from the dorsal side at anterior half and lateral side at posterior half of the figure, showing both internal surface and ciliary currents (arrows). Drupa ricina; the stomach, incised from the dorsal side, showing both structure and ciliary currents(arrows). Morula granulata; the stomach, incised from the dorsal side, showing both structure and ciliary currents (arrows). 228 S. K. WU rachidian base is not indented, the radula is apparently a functional rasping organ. In M. granulata where there are 3 smooth cusps with a free denticle between the central and the lateral cusps, 2 wrinkles rather than denticles lateral to the lateral cusps, and a rachidian base with an indentation or pit in which sit all the cusps, the radula functions in both boring and rasping. Architecturally this kind of a rachidian tooth would seem to have great advantages in boring, the pit forming a firm base for any boring activity of the cusps. In the formative portion of the radula the lateral teeth overlap the rachidian, forming a long, narrow band. The tips of all the teeth point backward except when the odontophore is protruded, at which time the rachidian cusps are oriented anteriorly and the tip of the lateral teeth antero-laterally. In re- traction the movement of the radula is reversed and the teeth are again oriented posteriorly. This motion makes it possible for the central elevation of the dorsal jaw to function as a surface which aids in the removal of food and shell particles from the radula. In the organ of Leiblein, the almost circular fold perhaps not only acts asa valve, preventing the regurgitation of food into the anterior-esophagus (Graham, 1941) but might also create a negative pressure by means of the vibration of the long cilia which rim the edges of the fold. The structure responds to the forward thrust of the proboscis during the feeding stroke. The dorsal folds of the mid-esopha- gus, developing after the organ of Leib- lein in the region of the nerve-ring and the convoluted portion, function in the rejection of food particles. The dorsal folds are rich in mucoid cells and in- filtrated with phagocytes. The presence of phagocytes among the mucoid cells Suggests that the phagocytes may enter the mid-esophagus at this point and that some phagocytosis may occur inthis area of the digestive tract. The dorsal folds fade away immediately after curving into the duct of the gland of Leiblein. The wall of the dorsal groove of the mid- esophagus is lined by simple cuboidal cells, their structure suggesting that no secretions are produced in the dorsal groove. The function of the salivary gland is apparently that of lubrication. Although the aperture of the duct of the salivary gland has been described as opening into the dorsal part of the cavity above the tip of the odontophore in some muricids (Graham, 1941; Carriker, 1943), in D, ricina and M.granulata the duct descends from the dorsal fold and opens into the buccal cavity through the ventro-lateral wall, near the lateral side of the ventral jaw. Thus, the function of the salivary gland apparently is associated with the movement of the ventral jaw during the outward and inward movement of the odontophore in the feeding stroke, and it is reasonable to assume that the secretion is a lubricant. A proteolytic enzyme was suggested by Mansour-Bek (1934) to be secreted by the salivary gland in Murex and by Mendel and Bradley (1905) to occur in Busycon. The function of the accessory salivary glands in the muricids remains unknown. As already described, there are 2 signifi- cant differences in the accessory. sali- vary glands of D, vicina and M. granu- lata. The first difference relates to the position of the accessory salivary gland with respect to the salivary mass. InD, vicina a pair ofaccessory salivary glands is located ventro-laterally andfree from the salivary gland. In M. granulata the left accessory salivary gland is com- pletely embedded in the salivary mass while the right accessory salivary gland remains free. The second difference involves the accessory salivary glandit- self. In D. ricinia there is a symmetri- cally developed pair of accessory sali- vary glands while in M. granulata the pair of glands is not symmetrically developed, the right accessory salivary gland being smaller than the left one. The asymmetrically developed ac- cessory salivary gland in М. granulata, DIGESTIVE SYSTEMS OF TWO MURICIDS the absence of accessory salivary glands in Murex pomum and their extremely small size in Bedeva hanleyi, Murex fulvescens, and M. fulvescens arenarius (Carriker, 1961) deprecate the possible role of these glands in the boring process - as does the fact, reported by Graham (1941), that the secretion of the accessory salivary gland of Nucella lapillus has a pH of 6 and does not etch shell or dissolve shell flakes. That the function of the accessory salivary gland may be that of lubri- cation, particulary associated with the raking food habit, is suggested by the position of the duct opening, and the contrasting development nfthe accessory salivary gland in D. ricina and M. granu- lata. The epithelial cells of the tubules of the gland of Leiblein are club-shaped cells as described by Graham (1941) for Nucella lapillus. There are 2 types of epithelial cells: mucoid and “granular”. During secretion the round apical end is nipped off. The secretion in the lumen consists of granules, mucus and phago- cytes. The secretionis moved away from the lumen in a spiral string by the ventral fold of the duct of the gland of Leiblein to the posterior esophagus (Pl. V, Fig. 3). It has been suggested that the secretion of the gland of Leiblein probably contains enzymes which split protein molecules (Mansour-Bek, 1934). The stomachs of D. ricina and M. granulata differ externally. In D. ricina the esophagus leads straight into the center of the stomach which is a U- shaped structure with a pouch at left side of the esophageal opening. In M. gvanulata the stomach is also U-shaped but it does not possess this pouch. In- ternally the stomach surface of both species is identical, showing the structural landmarks of the stomach of a generalized prosobranch, as described by Graham (1949). The stomach is also to be interpreted in the light of the particular feeding habits of the 2 species. In D. ста the pouch at the base of the U is remi- 229 niscent of some ofthe omnivorous meso- gastropods and of a style-bearing steno- glossan neogastropod, Cyclope neritea, which is both a carrion and deposit feeder (Morton, 1960). In M. granulata. the typical U-sac is reminiscent of the stomach of Trivia (Mesogastropoda) which feeds on ascidian zooids (Fretter, 1951) and of Murex, which is typically an active predator (Carriker, 1961). The function of the stomach in both Species is that of mechanically rotating and moulding the food bolus. A sorting mechanism such as was described for some of the carnivorous mesogastropods (Graham, 1949) was not observed. Parti- cles in the intestinal groove were not observed to enter either aperture of the digestive gland, but to be drawn out, all particles being rejected by ciliary currents. The digestive gland is mainly composed of “digestive” cells but at the terminal end of each tubule there are also grouped “secretory” cells (Fretter & Graham, 1962). The “digestive” cells are filled with granules which stain variously, indicating that a number of complicated chemical changes occur within these cells. The function of these cells, whether absorptive or se- cretory, has not been determined. How- ever, the rejection of particles by the intestinal groove, and the club-shaped apical end of the “digestive” cells suggest that secretion is probably the principal activity of the digestive gland. The “secretory” cells, with their triangular bases facing the visceral hemocoel, may take up materials from the blood and elaborate these materials into some secretion which is then shed into the lumen of the tubule (Fretter & Graham, 1962). The intestine of р. ricinaandM. granu- lata differs slightly in the development of the epithelial folds, those of D, уста being more developed than those in M. gvanulata. The surface of the intestinal epithelium of M. granulata is smooth, interrupted on occasion by notches. The more folded intestine of D, vicina offering 230 S. K. WU a greater surface, might perhaps be associated with an omnivorous diet. The notches in the epithelium in M. granulata might permit the infiltration of phago- cytes from surrounding tissues. The rectum shows considerable longi- tudinal folding and again there are a large number of phagocytes in the lumen of both species. The rectum is sur- rounded by blood spaces. The presence of phagocytes again suggests a site where absorption occurs. In addition, the rectum dehydrates the feces, which becomes more solid towards the anal end, and also molds it. The occurrence of large numbers of undigested diatoms and algae in the feces indicates that no enzymes are present which can digest these sub- stances. The rectal glands of D. vicina and M. granulata are significantly different: in the latter species it is black and is easily distinguishable externally, while in the former it is light yellow and has an obscure outline. The function of the rectal gland, according to Fretter (1946) is that of abstracting excretory matter from the blood. A well-developed rectal gland thus would be advantageous to carnivorous snails whose food contains much nitrogeneous material. DISCUSSION The muricid genera Drupa and Morula have long been considered closely re- lated conchologically, and in fact are separated only on the basis of size (Morula including the smaller, ovate species), sculpture (Drupa with spines and Morula with nodules), shape (Drupa with a low spire and Morula with a high spire) and the teeth of the outer lip (Drupa with grouped teeth and Morula with single teeth). Cooke (1919) pointed out that the radulae of the 2 genera are distinct. The results of the comparative studies of the digestive system of one species in each genus also indicate that Drupa and Morula are deserving of generic separation. The 2 species representing the genera not only live in distinct ecological niches, but also apparently have different feedinghabits. Correlated with their feeding habits are the structural differences in the digestive system described above. The Muricacea, although well known for their predatory habits, have recently been considered to be the most primitive of the stenoglossan gastropods (Fretter & Graham, 1962). From the point of view of the digestive system the Steno- glossa as a suborder are characterized, in general, by a narrow band of radula, a long pleurembolic type of proboscis, the gland of Leiblein, frequently a simpli- fied stomach, a short intestine and sometimes, a rectal gland. In the Muricacea the organ of Leiblein is well developed and the effects of torsion are apparent anterior to the nerve-ring. The dorsal fold can be traced throughout the length of the esophagus. The gland of Leiblein is bulky. The accessory salivary gland, the accessory boring organ and the rectal gland are present. These features are to be contrasted with those of the other 2 superfamilies of the Stenoglossa, the Buccinacea and the Volutacea where the organ of Leib- lein is not well developed, and the effects of torsion are apparent posterior to the nerve-ring. The dorsal folds of the mid-esophagus are less obvious. The gland of Leiblein is less developed, and both the accessory salivary glandand the accessory boring organ are lacking. Within the Muricacea, assuming the D, vicina and М. granulata are representa- tive species of their respective genera, both Drupa and Morula exhibit clearly primitive features from the standpoint of the evolution of gastropod feeding habits and stomach structure. The primitive features of Drupa and Morula are not reflected inthe proboscis, radula, or esophagus, all of which show striking similarities to those which have been previously described for muricids (Carriker, 1943; Graham, 1941), but in DIGESTIVE SYSTEMS OF TWO MURICIDS 231 the stomach pattern. The stomach of both D. ricina and M. granulata differs significantly from the simplified stomach of Nucella lapillus described by Graham (1949) in that it still shows a definite style sac region, “gastric shield” region, and, on occasion, a protostyle. The difference between Drupa and Morula on the one hand and Nucella on the other is further emphasized by the presence of 2 apertures of the digestive gland in the former 2 species, contrasting with the Single aperture described by Graham (1949) in Nucella. Two apertures of the digestive gland, however, have been described for Murex erinaceus (Sim- roth, 1896-1907), a higher carnivorous form. The stomach patterns of both р. vicina and M. granulata closely resemble that of Trivia (Graham, 1949), a carnivorous member of the Mesogastropoda, the sub- order from which the Stenoglossa are currently thought to have originated. Among the Stenoglossa, the stomach patterns of D. ricina and М. granulata resemble most closely that of the nas- sariid, Cyclope neritea, a member of the Buccinacea (Morton, 1960). Morton has pointed out that the style sac, gastric Shield, and protostyle of this species are evidence for its primitive status within the Buccinacea, and he suggested that deposit feeding and primitive stomach patterns, which are generally characteristic of the Prosobranchia, may be retained among the lower members of the generally more advanced Steno- glossa. The feeding habits and stomach patterns of Drupa and Morula may thus be interpreted as representing the basal or primitive features of the Stenoglossa, reflecting their mesogastropod an- cestry. ACKNOWLEDGMENTS This work was carried out in the Department of Zoology, University of Hawaii under the guidance of Dr. E. A. Kay, to whom I am very grateful for stimulating and fostering my interest in the Muricacea. Thanks are also grate- fully extended to Dr. D. C. Matthews of the University of Hawaii for his advice and attention regarding the manuscript; to Dr. Yoshio Kondo, Department of Mollusks, Bernice P. Bishop Museum, Honolulu, for allowing and encouraging me to study the museum specimens; and to Dr. M. R. Carriker, Marine Biological Laboratory, Woods Hole and Dr. K. Y. Arakawa, Miyajima Aquarium, Hiroshima, Japan who have taken time to answer my questions. LITERATURE CITED AMAUDRUT, A., 1898, La partie an- térieure du tube digestive et la torsion chez les mollusques gastéropodes. Ann. Sci. Nat. Zool., ser. 7, 8: 1-291. (vide GRAHAM, 1941). ARAKAWA, К. Y., 1957, On the re- markable sexual dimorphism of the radula of Drupella. Venus, 19: 206- 214. , 1958, Some notes on the radulae of Purpura echinulata Lamarck. Venus, 20: 67-75. , 1962a, A study on the radulae of the Japanese Muricidae. (1) The genera Purpura, Thais and Mancinella. Venus, 22: 70-78. , 1962b, A coprological study on the molluscan faeces. Venus, 22: 151-172. BURCH, J. Q., 1955, A systematic out- line of the Muricacea in the Eastern Pacific. Min. Conch. Club. S. Calif., 149: 3-13. CARRIKER, M. R., 1943, On the struc- ture and function of the proboscis in common oyster drill, Urosalpinx cinerea (Say). J. Morph., 73: 441- 498. , 1955, Critical review of biology and control of oyster drills Urosalpinx and Eupleura. Spec. Sci. Rep. U. S., Dept. Inst. Fish., 148: 1-150. , 1959, Comparative functional morphology of the drilling mechanism in Urosalpinx and Eupleura (muricid 232 5. К. WU gastropods). Proc. XVth int. Cong. Zool. London, 373-376. | , 1961, Comparative functional morphology of boring mechanism in gastropods. Amer. Zool., 1: 263-266. COOKE, A. H., 1919, The radula in Thais, Drupa, Morula, Concholepus, Cronia, Iopas and the allied genera. Proc. malac. Soc. London, 13: 90-110. DARIN, .W. J., 1912, Buccinum. L.M. B.C. Memoir, 20. Williams & Norgate, London. DALL, W. H., 1923, Notes on Drupaand Morula. Proc. Acad. nat. Sci. Phila- delphia, 75: 303-306. , 1924, The marine shell bearing Mollusca and Brachiopoda of Hawaiian and Palmyra Island. (unpub. ms.). , BARTSCH, P. and REHDER, H. A., 1938, A manual of the recent and fossil pelecypod mollusks of the Hawaiian Islands. Bernice P. Bishop Mus. Bull., 153. FRETTER, V., 1941, The genital ducts of some British stenoglossan Proso- branchs. J. Mar. biol. Ass. U. K., 25: 173-211. , 1946, The pedal sucker and anal gland of some British Stenoglossa. Proc. malac. Soc. London, 27: 126- 130. , 1951, Some observations on the British cypraeids. Proc. malac. Soc. London, 29: 14-20. , and GRAHAM, A., 1962, British Prosobranch molluscs; their functional anatomy and ecology. Ray Soc., London. GRAHAM, A., 1939, On the structure of the alimentary canal of style- bearing Prosobranchs. Proc. zool. Soc. London., Ser. B., 109: 75-112. , 1941, The oesophagus of the stenoglossan Prosobranchs. Proc. Roy. Soc. Edinburgh, 61: 1-32. , 1949, The molluscan stomach. Trans. Roy. Soc. Edinburgh, 61: 737- 761: , 1955, Molluscan diets. Proc. malac. Soc. London, 31: 144-157. HALLER, B., 1888, Die Morphologie der Prosobranchier I. Morph. Jb., 14: 54-169. (vide GRAHAM, 1941). HEDLEY, C., 1913, Onthe nomenclature of Drupa. Nautilus, 27: 79-80. HERRICK, J. C., 1906, Mechanism of the odontophoral apparatus in Sycoty- pus canaliculatus. Amer. Nat., 40: 707-737. HERTLEIN, L. G., 1961, The subfamily Drupinae (Gastropoda) in the eastern Pacific. Veliger, 3: 7-8. HIRSCH, G. C., 1924, Der Weg des resorbierten Eisens und des phago- cytierten Carmins bei Murex trun- culus. Z. vergl. Physiol., 2: 1-22. KAY, A., 1960, The functional mor- phology of Cypraea caputserpentis L. and an interpretation of the relation- ships among Cypraeacea. Int. Revue. ges. Hydrobiol., 45: 175-196. KEEN, A. M., 1958, Sea shells of tropical West America. Stanford Uni- versity Press, Stanford, Calif. MANSOUR-BEK, J. J., 1934, Uber die proteolytischen Enzymen von Murex anguliferus Lamk. Z. vergl. Physiol., 20: 343-369. MENDEL, L. B. and BRADLEY, H. C., 1905, Experimental studies in the physiology of the molluscs. Amer. J. Physiol., 13: 17-29 (vide GRAHAM, 1941). MILLOT, N., 1937, On the morphology of the alimentary canal, process of feeding and physiology of digestion of the nudibranchiate mollusc, Jorunna tomentosa (Cuvier). Phil. Trans. Roy. Soc. B., 228: 173-217. MORTON, J. E., 1952, The role of the crystalline style. Proc. malac. Soc. London, 29: 85-92. , 1953, The function of the gastropod stomach. Proc. Linn. Soc. London, 164: 240-246. , 1955a, The functional mor- phology of the British Ellobiidae (Gastropoda Pulmonata) with special reference to the digestive and repro- ductive system. Phil. Trans. Roy. Soc. London, B., 239: 89-160. , 1955b, The structure and function of the stomach and sorting DIGESTIVE SYSTEMS OF TWO MURICIDS caecum in Lunella samraga (Martyn) (Turbinidae). Proc. malac. Soc. London, 31: 123-137. ‚ 1960, The habits of Cyclope neritea, a style-bearing stenoglossan gastropod. Proc. malac. Soc. London, 34: 96-105. NAKAJIMA, M., 1956, On the structure and function of the midgut-gland of mollusca, with a general consideration of the feeding habits and systematic relations. Jap. J. Zool., 11: 469-556. OSTERGAARD, F. M., 1950, Spawning and development of some Hawaiian marine gastropods. Pacific Sci., 4: 75- 115. OWEN, G., 1958, Observations on the stomach and digestive gland of Scutus breviculus (Blainville). Proc. malac. Soc. London, 33: 103-114. - RISBEC, J., 1955, Consideration sur l’anatomie comparée et la classi- fication des gasteropodes proso- 233 branches. J. Conchyl., 95: 45-82. SIMROTH, H., 1896-1907, Bronn’s Klassen und Ordnungen des Tier- reichs. Vol. 3, Leipzig. TAYLOR, D. W. and SOHL, N. F., 1962, An outline of gastropod classification. Malacologia, 1: 7-32. THIELE, J., 1931, Handbuch der Sys- tematischen Weichtierkunde. 2 Vols. G. Fischer, Jena. WEEL, P. B. V., 1949, Contribution to the physiology of the glandula media intestini of the African Giant snail, Achatina fulica Fer., during the first hours of digestion. Monographiae Biologicae, 2: 1-19. ‚1961, Thecomparative physi- ology of digestion in molluscs. Amer. Zool., 1: 245-252. WHITAKER, M. B., 1951, Onthehomol- ogies of the oesophageal gland of Theodoxus fluviatilis (L.). Proc. malac. Soc. London, 29: 21-34. RESUMEN y SISTEMA DIGESTIVO DE DOS MURICIDOS En las Islas Hawaii Drupa ricina (L.) habita un lujuriante ambiente algológico, con holoturias y esponjas. Morula granulata (Duclos) vive en áreas con menor desarrollo de algas, junto con el bivalvo Isognomon y esponjas. La anatomía e histología del aparato digestivo de D. ricina se describe en detalle y en comparación con M. granulata. En general son similares, excepto en sus rádulas, complejo glándular, estómago y glándulas rectales. D. ricina tiene dientes raquídeos con 5 cúspides sin base hueca, mientras que M. granulata tiene 3 cúspides y base hueca. Dos diferencias significativas se asocian con el complejo glandular: en D, ricina un par de glándulas salivares accesorias estan desarrolladas simetricamente y separadas de la masa glandular salivar, y en M. granulata la glándula accesoria izquierda, más grande, esta completamente incluída en la masa, y la derecha que es. más pequeña, permanece libre. EI estómago difiere externalmente: en ambas es como un saco en forma de U pero en D. ricina tiene una bolsa sobre el lado faríngeo, que falta en М. granulata. La glándula rectal en D. ricina es amarillo-clara y de con- tornos no definidos, mientras en M. granulata es negra y bien distinguible externa- mente. Se discuten los aspectos funcionales del sistema. Cavidad bucal, glándulas sali- vares y sus accesorias estan relacionadas con la lubricación durante la alimentación. Corrientes ciliares existen en el sistema entero, excepto en la cavidad bucal. Se observó que Morula taladra los bivalvos, aunque prefiere carnes muertas, mientras que Drupa no parece ser un enemigotipico de los moluscos con concha dura, sino que subsiste sobre una variedad de presas eomo holoturias y esponjas. Los hábitos alimenticios y diferencias dietarias se ubican en relación a las diferencias es- tructurales; comparación de estos aspectos y de los estómagos de Drupa y Morula con la de los Mesogastropodos carnívoros y otros Estenoglosos, pueden indicar que ambos géneros representan las caracteristicas primitivas de los Estenoglosos, reflejando su ascendencia mesogastropoda. nu 1 L Neal BIER | q pd 1 $ РИ à > | ie un IR р y r D ro LA | KIN At 4 De и р | à ah M Ky < р Lo won BUIN yl N : ME 4 ny rib eA р | ' m Уи urn № NE 4 . | Mu ' № А 1 y vr at | 41 В | i : y { . MALACOLOGIA, 1965, 3(2): 235-262 MARINE EUTHYNEURAN GASTROPODA FROM ENIWETOK ATOLL, WESTERN PACIFIC] Ernst Marcus2 and J. В. Burch? ABSTRACT This study is based on a collection of marine euthyneuran mollusks made by the second author at Eniwetok Atoll, Marshall Islands, during February-April, 1960. Seventeen species were collected, of which 5 are described in this paper as new species. The new species are: Haminoea musetta, H. linda, Chromo- doris briqua, Herviella mietta and Onchidella evelinae. Of the other 12 species, the distribution of 7 of them extends eastward from the western Indian Ocean (2 also occur in the Red Sea) to Eniwetok or farther east; 2 species are circum- tropical or circumsubtropical; 2 species are known only from the western Pacific; and 1 species occurs from Eniwetok westwards into the eastern Indian Ocean. The relative uniformity of the western Indopacific reef fauna is indicated by the fact that 9 (or over 50%) of our species are known to range from the western edge of the Indian Ocean to the western or central Pacific. The genus Herviella seems to be confined to the western Pacific. Thenotogaeic occurrence of an Onchidella with a ventral recurrent limb of the kidney and a cuticular stylet in the diverticulum of the penial pouch is remarkable. Eniwetok Atoll comprises a group of some 30-odd coral islands inthe western Pacific. Eniwetok is one of several such atolls which make up the Marshall Islands of Micronesia. During the months of February-April, 1960, the second author and Dr. William H. Heard collected mollusks on 4 islands of Eniwetok Atoll. The present report is based on the 17 species of euthyneuran gastropods col- lected at that time. All specimens, except representative series sent to the University of Hawaii and the University of Säo Paulo, are now in the collections of the Museum of Zoology, University of Michigan. Grateful acknowledgement is made to the United States Atomic Energy Commission for supporting the study of the second author at Eniwetok by pro- viding travel funds, logistical support and use of the facilities of the Eniwetok Marine Biological Laboratory. The cooperation of the U.S. A. E. С. Eniwetok Field Office, Task Group 7.1, and Holmes and Narver, Inc., greatly facilitated the field collecting. A note of gratitude is due to Dr. I. Eugene Wallen, U.S.A.E.C., Dr. Robert W. Hiatt, University of Hawaii, and Prof. Henry van der Schalie, University of Michigan, for promoting these studies, and to Dr. William H. Heard, Florida State University, for assistance while at Eniwetok. Acknow- ledgement is also due Mrs. Eveline du Bois-Reymond Marcus for assistance to the senior author and for preparing the illustrations. MATERIALS AND METHODS The animals reported on here were lThe field work for this investigation was supported by the Division of Biology and Medicine, U. S. Atomic Energy Commission. 2University of Säo Paulo, Brazil. 3Museum and Department of Zoology, University of Michigan, Ann Arbor, Michigan, U. S. A. Supported (in part) by a Public Health Service research career program award (number 5 K3-AI-19, 451) and by research grant 5 T1 AI 41-07 from the National Institute of Allergy and Infectious Diseases, U. S. Public Health Service. | (235) 236 MARCUS AND BURCH collected from various localities on 4 islands of Eniwetok Atoll: "Eniwetok I., Parry I., Japtan I. and Annaianni I. Most of the specimens were anesthetized before being fixed and preserved. A number of different anesthetizing re- agents were used: chlorotone, chloral hydrate, menthol, magnesium chloride, nembutal and propylene phenoxetol. Three different fluids were used for fixing the specimens: Bouin’s fluid, AFA (alcohol-formalin-acetic acid) and 10% neutralized formalin. The animals were preserved in either 5% formalin, 1% propylene phenoxetol or 70% ethanol. The most satisfactory technique for preserving nudibranchs was a modifi- cation of the method of Hanna (1955). The living animals were frozen in sea water in a freezer; the ice was then melted with 10% formalin and the animals were transferred to 1% propylene phenoxetol. Sketches and color photographs were made of the living animals, accompanied by notes of external characters, colors, measurements, etc. SYSTEMATICS AND DISTRIBUTION A systematic list of species of Euthy- neura collected at Eniwetok during the field study are listed below. The species are treated individually in consecutive order in the section following the list. Cephalaspidea, Philinacea, Smaragdi- nellidae 1. Smaragdinella calyculata (Brod- erip and Sowerby, 1829) 2. Lathophthalmus smaragdinus (Rüppell and F. S. Leuckart, 1828) Cephalaspidea, Bullacea, Atyidae 3. Haminoea musetta, new species 4, Haminoea linda, new species 9. Lamprohaminoea cymbalum (Quoy and Gaimard, 1833) Anaspidea, Aplysiidae, Dolabriferinae 6. Dolabrifera dolabrifera (Rang, 1828) Anaspidea, Aplysiidae, Notarchinae 7. Stylocheilus longicauda (Quoy and Gaimard, 1824) Doridoidea, Eudoridacea, Crypto- branchia, Dorididae, Chromodoridinae 8. Chromodoris fidelis (Kelaart, 1859) 9. Chromodoris briqua, new species 10. Hypselodoris hilaris (Bergh, 1890) Doridoidea, Eudoridacea, Phanero- branchia, Nonsuctoria, Gymnodorid- idae 11. Gymnodoris bicolor (Alder and Hancock, 1864) Doridoidea, Porostomata, Dendro- dorididae 12. Dendrodoris nigra (Stimpson, 1855) 13. Dendrodoris erubescens (Bergh, 1905) Eolidoidea, Cleioprocta, Favorinidae, Favorininae 14, Herviella claror Burn, 1963 15. Herviella mietta, new species Soleolifera, Onchidiacea, Onchidiidae 16. Onchidella evelinae, new species Basommatophora, Siphonariacea, Siphonariidae 17; Siphonaria (Sacculosiphonaria) guamensis (Quoy and Gaimard, 1833) 1. Smaragdinella calyculata (Broderip and Sowerby, 1829) (Figs. 1-5) Pilsbry, 1895, p 258 (viridis), pl. 33, figs. 42, 45-53 (viridis and glauca); Bergh, 1901, p 228, pl. 19, figs. 39-45 (viridis); Habe, 1952, p 144, 146, pl. 20, fig. 07e pls 2194122726: Occurrence: In lagoon at north end of Eniwetok Island. Further distribution: Southern Indian Ocean, Reunion and Mauritius; Java (Adam and Leloup, 1938, p 199); middle Japan, Seven Islands off Izu; southern Japan, ShikokuIsland, Amami and Ryukyu Groups; Mariana Islands, Guam; Hawaiian Islands; Pitcairn Island; PACIFIC EUTHYNEURA 237 FIGS. 1-5. Smaragdinella calyculata. Fig. Fig. 5. Male genital structures; A, atrium; Hancock’s organ; . Living animal dorsal view, drawn from Kodachrome transparency. Fig. 2. Right side viewof anterior part. Fig. 3. Inner side of shell. Fig. 4. Radular teeth. CS, cephalic shield; E, eye; GO, genital opening; HaO, M, mouth; MD, male duct; MV, muscular vesicle; Pa, parapodia; PM, posterior mantle lobe; Pr, prostate; RMu, retractor muscle; SG, seminal groove; Sh, shell; SV, seminal vesicle. Easter Island (Odhner, 1921), p 248; not Dall, 1908, as Odhner’s asterisk indicates). The shell is mainly external, solid, the one measured was 6 mm long, 3.8 mm broad. The shell’s apexis concealed. The outer lip of the aperture is angular posteriorly without a thickening in the Shell examined. The columellar border runs out into a cup-shaped process pro- jecting forward into the aperture. In living animals the shell is diaphanous yellow; inpreserved animals itis opaque white, green on the inner side and witha transparent periostracum. A large snail was 14 mm long and 8.5 mm broad when crawling; 4 preserved Specimens measured 11, 9.5, 7.5 and 6 mm in length. The body in life is pale green with many opaque white spots and a somewhat smaller number of scattered small black spots. White spots occur in patches along the colorless edge of the foot and on the posterior lobe of the mantle. White marks occur onthe para- podia and also on the cephalic shield, where they are less numerous. The small black eyes (Fig. 1, E) are situated farther from the mid-line than from the sides. There is an opaque white oval area at the hind end of the cephalic shield (CS), followed by many rather uniformly spaced black spots which show through the shell (Sh). These spots are larger than the ones previously men- tioned. Farther backward growth lines of the shell can be seen between the parapodia (Pa). The cephalic shield is nearly straight in front. In living animals it extends to the middle of the body and ends with a blunt point. In preserved specimens 238 MARCUS AND BURCH the posterior terminus of the cephalic shield is slightly bilobed and located near the anterior border of the shell. Hancock’s organ has only dorsal pinnae and it lies under the cephalic shield, dorsal to the seminal groove (Fig. 2, SG). The end of the foot does not ex- tend beyond the visceral hump. The jaw elements are rod-shaped. The radula (Fig. 4) is light yellow, consisting of 30 rows with 19, rarely 20, teeth per half-row. The rhachidian plate is 47 micra high, more slender than in Habe’s (1952) figure (pl. 21, fig. 26), with a central cusp, but without lateral denticles, so that it agrees with Habe’s figure and differs from Bergh’s (1901) S. glauca (p 240, pl. 19, figs. 47, 48). The lateral plates have long, hook-shaped cusps. The 5-6 outermost lateral plates lack cusps. The cusp of the innermost lateral tooth measured 57 micra in length; the cusp of the next lateral tooth measured 65 micra. The length of the cusps increased to 72 micra in the middle of the row and decreased out- ward. The bases of the 8 outer teeth are broad; the bases of the 5-6 inner ones have basal striae, as also occur in several species of Haminoea. The gizzard plates are conchinous, black in front, ivory behind, with a median crest and many ridges on either side. The common genital opening (Fig. 2, GO) is located far in front, in front of the posterior end of the cephalic shield (CS). The seminal groove (SG) is straight, its aperture at the level of the anterior end of Hancock’s organ (HaO) as in Haminoea. The male atrium (Fig. 5, A) is wide, with a folded epithelium and a muscular wall. The male duct (MD) has a terminal seminal vesicle (SV), a bilobed prostate (Pr), and a second muscular vesicle (MV). One bundle of the retractor muscle (RMu) inserts on this vesicle; some fibers insert on the loop of the male duct and on its straight section between loop and atrium. Discussion of Smaragdinella calyculata Pilsbry (1895, p 259) and Pruvot-Fol (1934, р 24) consider $. viridis, now known as 5. calyculata, and S. glauca, whose type-specimens are lost, as one and the same species. If thisis correct, the shape of the inner process of the Shell, like a lancet in Zilch’s specimen (1959, fig. 144), like a cup in Risbec’s material from New Caledonia (1951, fig. VII, 3), is systematically insignificant. In fact, shells such as those drawn by Pilsbry (1893-95, pl. 33, fig. 47), Thiele, (1931, fig. 487), and Habe (1952, fig. 7) are intergrades between the mentioned extremes. Bergh’s diagnoses of S, viridis and S. glauca, whichhe separates, do not reveal palpable differences; his description of the male organ is in- complete. Risbec’s figure of the living animal (pl. 8, fig. 9) hardly represents a Smaragdinella. In his anatomical record only the size of the lateral gizzard plates is a little smaller than the central one, and the shape ofthe latter disagrees with what is known of $. calyculata. If Risbec’s animal is another species, it must be renamed; he published it as Smaragdinella viridis, n. sp. 2. Lathophthalmus smaragdinus (Riippel and F. S. Leuckart, 1828) Marcus, 1960a, p 884-890, figs. 14-21 (bibliography and description). Occurrence: Very abundant at Eni- wetok Atoll during March, 1960. Col- lected at the south end of Parry Island, under stones on seaward tide flat; March 15, 1960. Further distribution: Indo-West Pa- cific Ocean, from the Red Sea to southern Ryukyu and Fiji Islands. The living animals measure up to 35 mm in length when extended. Two pre- served specimens measured 19 x 8.5 and 16 x 7 mm. Correspondingly, their cephalic shields were 6 x 5 and 3.8 x 3 mm. The Hancock's organ had 15 leaves in the larger of the 2 animals, and 20 leaves in the smaller one. The position of the eyes in relation to the Hancock's organ is the same in both specimens. The mantle foramen which leaves part of the shell free is the best distinguishing PACIFIC EUTHYNEURA 239 FIGS. 6-11. Haminoea musetta, n. Sp. Fig. 10. Diagram of male genital structures. Fig. 6. Living snail, drawn from Kodachrome transparency dorsal view. Fig. 7. Radula, central and first lateral teeth. Fig. 8. Right Hancock’s organ. Fig. 9. Shell. Fig. 11. Detail of penial papilla; A, atrium; AS, atrial sheath; CS, cephalic shield; E, eye; Fu, fundus of atrium; Ma, mantle under shell; MP, male duct; Pa, parapodia; PM, posterior mantle lobe; Pr, prostate; RMu, retractor muscle; SG, seminal groove; SV, seminal vesicle. character of Lathophthalmus, Pruvot- Fol, 1931 (p 748) separating it from Phanerophthalmus A. Adams, 1850; but the distinction is not easy (Pruvot-Fol, 1934, p 30). 3. Haminoea musetta, new species (Figs. 6-11) Occurrence: North (collection A) and middle (collection B) parts of Parry Island on seaward tide flats; March 25 and April 2, 1960. Shells (collection A): 8-9 mm high, 5-6 mm wide; greatest breadth about in the middle of the shell or slightly anterior of the middle; (collection B): 6.5-7.2 x 4.3-5.5 mm, greatest breadth in the middle of the shell. Ratios of dia- meter to height are 1:1.31 to 1:1.50. Shell shape (Fig. 9) swollen, ovoid. Shell with 11/2 whorls, rather fragile, shining, slightly narrowed posteriorly. The axial growth lines are more or less distinct; the spiral striae are extremely fine. The outer lip of the shell is convex and well-curved. It covers the apex slightly, rising to the right of the sunken spire. The apex may have a small perforation (collection A) or it may be imperforate (collection B). The columella is deeply concave, its base reflected. The colu- mellar callus is separated from the body whorl by a furrow; its enamel layer extends farther posteriorly in the smallest shell of collection A than inthe largest one of collection B. Living snails measure up to 15 mm when crawling (Fig. 6); a preserved extended animal of collection A measured 11 mm; specimens of collection B were all retracted into their shells. Colors in life (collection A): ground color very pale green; mantle (Ma) speckled with dark green and black spots, and green ones with black centers, and a few blank areas without pigment showing 240 MARCUS AND BURCH through the shell. On the cephalic shield (CS) and the parapodia (Pa) the spots are confluent, producing a mottled aspect. In collection B the green spots are less numerous, and the cephalic shield and parapodia are spotted like the rest of the animal, not mottled as on the specimens of collection A. White spots occur everywhere on the animals in clusters, which show through the shell. There are also a number ofbrown spots, except under the center of the dorsal part of the shell. The cephalic shield is slightly notched in front, with two long flaps behind; the parapodia in living specimens reachhalf the length of the shell; in preserved snails (collection A) they are relatively longer. Hancock’s organ (Fig. 8) is pinnate, the dorsal pinnae being longer than the ventral ones. The ends of the dorsal pinnae are often covered by a fold. The jaws are semicircular with pris- matic rodlets which are about 50-100 mi¢cra high: "and 10x 18: паста. in diameter. The radula contains 25-35 rows of teeth with 9-10 laterals per half-row. The rhachidian tooth (Fig. 7) is smooth with a rough base and strong median and short lateral cusps. The lateral teeth are all without denticles; the cusps are longest in the middle of each half-row. The gizzard plates are brown with 17 smooth ridges. Like in all Haminoeas, the male aperture is at the anterior end of the right Hancock’s organ, where the cutaneous seminal groove (Fig. 10, SG) enters the male atrium(A). Inthe present species the latter is a long, muscular tube within a thin sheath (AS). The fundus of the atrium (Fu) has 2 pointed epithelial, not cuticularized, lobes (Fig. 11). The male duct (MP) begins with a small vesicle, then continues as a narrow and winding tube without any spines. The penial retractor muscle (RMu) inserts near the middle of the male duct. The succeeding coils of the duct leadinto a slightly lobed, nearly globular, pros- trate gland (Pr). The walls of the prostate are glandular; its lumen (SV) frequently (collection B) contains sperm masses. There is no separate seminal vesicle. The female organs are system- atically insignificant. The name of this species is derived from “musette” = cornemuse, bagpipe. Discussion of Haminoea musetta The slight differences between the shells and the colors of the soft parts of collection A and B are taxonomically insignificant, because the labial arm- ature, the radula, andthe male copulatory organs of the 2 collections are similar. In classifying the Haminoea of the present collection we went through the same difficulties as Pilsbry (1921, p 368) and Macnae (1962, p 187). The shell of H. musetta is similar to that of the type species of Haloa, H.crocata Pease, (1860a, b, p 19, 432). Pilsbry (1921, p 367) introduced Haloa as a section of Haminoea; Zilch (1959, p 42) called ita Subgenus; and Habe (1952, p 148) con- sidered it as a genus. Habe indicated that the first lateral tooth in Haloa had 2 cusps (actually an inner denticle in addition to the cusp). Since Habe (p 150) considered Vitrohaminoea, without such denticle, as a subgenus of Haloa, the denticle cannot be a generic character. Therefore, we have to compare dH, musetta with other Indo-West Pacific Species without giving any consideration to the radula. The species with a shell most similar to Haminoea musetta is that of H. nigro- punctata Pease, 1868 (Pilsbry, 1895, p 365), but its soft parts differ by the longer and more pointed flaps of the cephalic Shield and the “rather posterior” para- podia. Only black pigment spots were described for H. nigropunctata. Hi binotata Pilsbry, 1895 (1896, р 231) has a much less developed callus (Habe, 1952, pl. 21, fig. 30) than H. musetta and, in addition, peculiar color marks on the shell. In its variety H. b. japonica Pilsbry, 1895 (1896, p 232), today given specific rank (Habe, 1961, p 11), the columellar callus is adnate to the body whorl. This character does not agree therefore PACIFIC EUTHYNEURA 241 with the original diagnosis of Haloa. Pilsbry’s (1895, p 363, pl. 40, fig. 3) first specimen of Haminoea crocata had a “moderately concave” columella. Later (1921, p 367, text fig. 6) he described and figured a deeply concave columella, such as occurs in A. musetta. The outer lip rising at the apex is shown in both of Pilsbry’s figures, and it is described indirectly in his text. This elevation of the outer lip distinguishes Н. crocata and also H. callosa Preston, 1908 (p 189) from H. musetta. More- over, the base ofthe columella is straight in the figure of H. callosa (pl. 15, fig. 31). Probably Pease’s description ofthe body color of H. crocata as “cinereous, pellucid” and hence without any Spots, is not systematically significant, because Pease described preserved material, and the pigment spots of Haminoea fade out in the preserving liquids in contrast to those of several other opisthobranchs. In any case, the dark green color “with large orange hieroglyphs” and the characteristic shape of the foot of speci- mens that Ostergaard called Н. crocata (1955, p 112) showthat it actually belongs tó H. simillima Pease, 1868 (Pilsbry, 1895, p 366; Eliot, 1906b, p 310). The shell of Haminoea galba Pease (1860 a, b, p 20, 432) is considered to be hardly distinguishable from that of H. crocata. It is, however, “perceptibly less swolien” (Pilsbry, 1921, p 368) and different from that of A. musetta. The columella of H. galba bears a fold in Sowerby’s figure (1868, fig. 23), reproduced by Pilsbry (1895, pl. 40, fig. 1); in H. musetta the columella has no fold. The epithelial lobes in the fundus of the male atrium of H. musetta which correspond to a penial papilla, “glans” (Bergh) or “mamelon” (Guiart, 1901, p 145) may be compared with some earlier descriptions, namely those of Bergh (1900, p 162; 1901, p 227, 229, 233), Si (1931, p 56), and Marcus (1958b, p 37; 1961, p 6). 4. Haminoea linda, new species (Figs. 12-16) Occurrence: Parry Island, in sand, in about 2 m depth, in lagoon, about 17 m from shore; March 31, 1960. Shell 10 mm high, 7.5 mm wide; greatest breadth in the middle. The ratio of the shell diameter to the shell height is 1:1.33. The shell (Fig. 14) is swollen, ovoid, with 1 1/2 whorls, very fragile, whitish, slightly shining, narrowed anteriorly and posteriorly. Under a magnifying lens fine growth lines can be seen, but no spiral striae. The outer lip is a little convex, covering the minutely perforate apex. The columella is deeply concave, its base reflected but adnate to the body whorl. The very low, broad callus extends to the apex. The length of a measured crawling snail was about 17 mm; one of the larger preserved animals measured 11 mm in length. The ground color of the animal is pale green with small orange and maroon spots. Onthe cephalic shield and parapodia the larger orange spots are bordered with white. Very large white spots with orange centers occur under the shell. Confluent white patches occur on the tail. The foot is spotted much the same way as the cephalic shield and parapodia. The various pigment spots are of rather diverse size and density. The cephalic shield of Haminoea linda is slightly notched in front, bilobed be- hind. The parapodia cover somewhat less than one-half the length ofthe shell. Hancock’s organ (Fig. 15) is only a simple ridge, hence different from that known in other species of Haminoea (Guiart, 1901, p 104-105; Hoffmann, 1935, p 608). ' The jaws are weak, their rodlets soft, and measure 4-5 micra in diameter. The radula contains about 25 rows, each row with 8 teeth per half-row. The rhachidian tooth (Fig. 13) is tripartite 242 MARCUS AND BURCH FIGS. 12-16. Haminoea linda, n. sp. FIGS. 17-20. Lamprohaminoea cymbalum. Fig. 12. Living snail of Н. linda, drawn from Kodachrome transparency, dorsal view. Fig. 13. Radula, central, 1st and 2nd lateral teeth. Fig. 14. Shell. Fig. 15. Right Hancock’s organ. Fig. 16A. Diagram of male genital struc- tures. B. Detail of penis. Fig. 17. Right Hancock’s organ of L. cymbalum, Fig. 18. Radula, central and lst lateral teeth. Fig. 19. Diagram of male copulatory organ; 1 mm of atrium omitted. Fig. 20. Detail of penis; A, atrium; AS, atrial sheath; CS, cephalic shield; E, eye; Fu, fundus of atrium; MD, male duct; Pa, parapodia; Pe, penis; PM, posterior mantle lobe; Pr, prostate; RMu, retractor muscle; Sh, shell; SV, seminal vesicle. PACIFIC EUTHYNEURA 243 in front, its base is roughened, and its median cusp has lateral denticles. The lateral cusps of the rhachidian tooth are broad, blunt, smaller than the median cusp. The first lateral tooth has about 5 denticles on its inner side, which is quite uncommon in Haminoea. The remaining lateral teeth resemble those found in other species of the genus. The gizzard plates are greenish-brown with 17 smooth ridges. The male atrium (Fig. 16A) in Haminoea linda is a long muscular tube (A) with a thin sheath (AS). The seminal groove becomes a narrow Closed tube at the fundus of the atrium. The duct forms a short, conical dilatation with 6 cuticular spines at the entrance into this dilatation and 9 longer ones at its fundus (Fig. 16B (Fu)). Farther inward the duct (MD) continues as anarrowtube for a short way, then becomes embedded in fibers of the penial retractor muscle (RMu) and bends again toward the fundus of the atrium. Some fibers of the penial retractor muscle connect the duct and the atrium. The duct is also surrounded by the penial retractor muscle in its Succeeding inward course, emerging from the muscle near its middle. The following free section of the duct is lined by a high, vacuolated epithelium. The duct opens into an acinous, nearly globose prostate gland (Pr), which is united entally with a clustery seminal vesicle (SV). The name of this species is the female form of “lindo” = pretty (Portuguese). Discussion of Haminoea linda The color pattern of the new species is similar to that of Haminoea ovalis Pease, 1868 (Pilsbry, 1895, p 365, pl. 40, fig. 94; pl. 43, figs. 9-10, 17), and H. aperta Pease, 1868. However, the Shell of H. ovalis is shorter, and that of H.aperta is longer. The shells of H. vitrea (A. Adams, 1850) (see Pilsbry, 1895, pl. 40, fig. 83) and of H.rotundata (Pilsbry, 1895, pl. 41, fig. 16) approach that of H. linda, but their radulae are quite different (Habe, 1952, pl. 21, figs. 28, 24). In addition to the radula, the male copulatory organ of Haminoea linda also differs considerably from the corre- sponding structures known in other species of Haminoea. The Hancock’s organ of H. linda is similar to that of Lamprohaminoea cymbalum (Fig. 17). 5. Lamprohaminoea cymbalum (Quoy and Gaimard, 1833) (Figs. 17-20) Pilsbry, 1895, p 367, pl. 40, figs. 6, 7; Bergh, 1901, p 230-231, pl. 19, figs. 6- 8; Pruvot-Fol, 1934, p 25; Habe, 1952, publ; pl 20, figs 153) Zilch; 1959, Up 43, fig. 141. Occurrence: Reef on South end of Parry Island. Part of our specimens were collected by Prof. H. van der Schalie. Further distribution: Kerimba Is- lands, northern Mozambique; Reunion; Mauritius; Port Lincoln, South Aus- tralia; Nagasaki, southern Japan; Guam, Mariana Islands (original locality); New Caledonia. The height of our shells measured up to 12 mm and the greatest breadth, Slightly anterior to the middle part ofthe shell, was 7.2 mm. The shell has 1 1/2 whorls, is subglobose, fragile, pellucid, white and narrowed posteriorly. Growth lines are distinct in some shells, but may not be developed in others. The aperture is wide in front, narrowed behind. The outer lip is slightly con- vex, overtops the apex, rising from the center of the sunken spire. The columella is deeply concave; its basal callus forms a narrow reflection over the inner lip. The length of preserved, well an- esthetized adult animals is about 18 mm, their breadth 9 mm. Their color in life is bright green with bright orange spots. The mantle of preserved snails when removed from their shells shows large light spots and small brown and orange ones. The cephalic shield is 244 MARCUS AND BURCH notched in front, bilobed behind. The parapodia are scarcely halfas long as the shell. Hancock’s organ (Fig. 17) is a simple undulated ridge, as in the pre- ceding species. The jaws of Lamprohaminoea cym- balum consist of rodlets which measure 6 micra in diameter. The radula studied (Fig. 18) comprises 36 rows and 14 lateral teeth per half-row. The rhachidian tooth is high, with a smooth base and a long median cusp flanked by two smaller ones. The lateral teeth are rather uniform; all lateral teeth, including the first lateral, lack denticles on their cusps. The cusp is longest in the middle of the half-row. The gizzard plates are chestnutbrown, with 17 smooth ridges. The atrium in Lamprohaminoea cym- balum (Fig. 19, A) is long, muscular and without a special sheath. The fibers of the penial retractor muscle (RMu) insert on the inner end of the atrium. Entally to the atrium the male duct has a spiny, strongly muscular section (Fig. 20, Pe) and farther inward a smooth, thin-walled section (MD). For a part of its course this thin section is em- bedded in the retractor fibers (RMu); it opens into the prostatic gland (Pr). The prostate gland is sausage-shaped, entirely glandular, undivided and without a separate seminal vesicle. Discussion of Lamprohaminoea cymbalum This species approaches Haminoea linda in the similarity of its simple Hancock’s organ and the absence of a penial papilla. Both species have a Spinous loop in the male duct. In dH. elegans there are many rows of spines on the penial papilla (Marcus, 1958b, figs. 18-20). 6. Dolabrifera dolabrifera (Rang, 1828) Marcus, 1963, p 10 (bibliography). Occurrence: Under rock on seaward tide flat at the north end of Parry Island, March 25, 1960. Further distribution: Circumtropical and circumsubtropical, but not yet recorded from the American Pacific coast. According to Engel’s revision (1936, p 29-43) only Dolabrifera nicaraguana Pilsbry, 1896 (p 124) from the west coast of CentralAmericaand D. varie- gata (Risbec, 1928b, p 54) from New Caledonia are valid species of the genus besides D. dolabrifera. Pruvot-Fol (1954, p 13) considers the subequal prongs of the lateral radular teeth of her material from Tahiti, Society Is- lands, a distinction separating it from D, dolabrifera, but Eales (1944, p 7-8, fig. 9A) shows similar characters to occur also in D. dolabrifera. Farran’s (1905) maillardi Deshayes, 1863, whose name Pruvot-Fol uses, was united with D. dolabrifera by Engel (p 39). The shell and male copulatory organ of the material from Eniwetok agree with D. dolabrifera, and the lateral teeth of the radula have subequal prongs. 7. Stylocheilus longicauda (Quoy and Gaimard, 1824) Engel, 1927, p 105-107, figs. 17-25; 1936, p 55-72, figs. 24-43; Marcus, 1963, p 11-15, figs. 10-21. Occurrence: In tide flats of Eniwetok Island, March 4, 1960. Further distribution: Circumtropical; not yet recorded from the west coast of America. Preserved specimens measure about 35 mm in length. Living animals exhibit long tails andarborescent papillae. They are brownish with fine dark longitudinal striae, white spots, and a few blue ocelli. This color pattern andthe spines of the penis are characteristic of Stylo- cheilus longicauda. 8. Chromodoris fidelis (Kelaart, 1859) (Fig. 21) PACIFIC EUTHYNEURA 245 Doris fidelis Kelaart, 1859, p 295. Chromodoris flammulata Bergh, 1905, DOI Ё52. ipl. 4, 15-9, pl. 16, figs: 16-19; Risbec, 1928a, p 137, fig. 35, pl. 8, fig. 8. Chromodoris lactea Bergh, 1905, p 159-160, pl. 16, figs. 40-43. Chromodoris fidelis Eliot, 1906a, p 642-643, pl. 42, fig. 2; 1909, p 91-92. Glossodoris fidelis Risbec, 1953, p 66; Baba, 1953, p 208, figs. 4, 6, H-I. Occurrence: Under rock at about 3 m depth on lagoon side near shore of Eniwetok Island; collected by Mr. Richard Willis, March 27, 1960. Further distribution: Ceylon (original locality); Malay Archipelago, East coast of Sumbawa and Kwandang Bay, North coast of Celebes; Seto, Kii Peninsula, Japan; New Caledonia. The living animal extends to 30 mm, and at such a length has a width of 6 mm. The broad fore end is nearly straight. The short triangular tail pro- trudes from under the mantle. The border of the mantle is slightly wavy; its front and sides are somwhat broader than the body. ‘The notum and underside of Chromo- doris fidelis are pale creamy white. The edge of the back is yellow with about 20 maroon projections of different lengths entering the creamy notum. The maroon projections are edged by a fine thread of opaque white. The tentacles are short and digitiform. The rhinophores are about 4 mm high, with 15-16 dark orange lamellae which are lighter toward the tip of the rhino- phore. The stalks of the rhinophores are rather transparent, but opaque whitish on the inside. There are 5 uni- pinnate, whitish gills, the front one shorter than the others. The foot of Chromodoris fidelis has acute lateral angles in front; it is widened in the posterior third, lanceolate behind. The labial armature consists of short, | bifid and bent rods which stand in rows. The radula contains 45 rows with 42 teeth | in the half-row. The rhachis is naked, | without thickenings or false plates. The eggs in the spawn show dark yellow caps directed towards the beginning of the egg string on larger light yellow spheres. Discussion of Chromodoris fidelis The synonymy given above is that presumed by Eliot (1909) and maintained in Pruvot-Fol’s (1951, p 103, 104, 114) revision. The unusual appearance ofthe labial armature occurs in Eliot’s material from the original locality and in our material from Eniwetok. This character has not been mentioned by Bergh, Risbec or Baba. Eliot’s material from Ceylon had traces of triangular thickenings on the rhachis. In C. flam- mulata the rhachis is naked as it is in our material. In C. lactea and in Baba’s Specimens there is a small, though dis- tinct, rhachidian tooth. Risbec did not describe the rhachis. Pruvot-Fol (1951, p 77-78) considers the presence or absence of radular elements on the rhachis as systematically insignificant; therefore, her synonymy was adopted here, though with some doubt. Doris preciosa Kelaart, 1858 (year according to O’Donoghue, 1933, p 226) is systematically near Chromodoris fidelis. The rhinophores and gills of С. preciosa are red or black (Eliot, 1909, p 92) and evidently the color of these organs varies also in C. fidelis. They were described as black or dark violet, but are dark orange in our material. C. lata Risbec, 1928, which, as Pruvot- Fol indicates, approaches C. fidelis in characters, is maintained as a distinct species by Risbec (1953, p 74). 9. Chromodoris briqua, new species (Figs. 22-24) Occurrence: Eniwetok Atoll; collected by Mr. Richard Willis, March 27, 1960. The animal is broadly elliptic, evenly rounded in front and behind (Fig. 24). Length of living, but not crawling, slug is about 32 mm, its breadth 16mm. The free mantle border is 4 mm broad on either side, covering the head and hind 246 MARCUS AND BURCH FIG. 21. Chromodoris fidelis. FIGS. 22-24. Chromodoris briqua, п. sp. FIGS. 25-27. Hypselodoris © hilaris. Fig. 21. C. fidelis, living snail drawn from Kodachrome transparency, side view. Fig. 22. Radular teeth of C. briqua. Fig. 23. Labial rods. Fig. 24. Ventral view, from living animal. Fig. 25. Dorsal view of crawling slug of H. hilaris, drawn from Kodachrome transparency. Fig. 26. Radular teeth. Fig. 27. Labial armature. end of the foot when the animal is at The notum is smooth, without spicules rest. The outline of the mantle is in the animal put directly into 70% ethyl slightly fringed, the undulation more alcohol. The general color of the living pronounced in the preserved specimen. animal is yellowish-orange (actually a PACIFIC EUTHYNEURA 247 yellow background with red spots). The notal margin has a narrow outer, light blue stripe accompanied by a broader inner, deep purple one. The underside of the mantle and the sole are yellow; in addition to the blue and purple lines noted above, the underside of the mantle has a third, narrow, innermost maroon one. The tentacles are orange, digitiform; the rhinophores maroon, speckled with white, their 28-30 lamellae disposed horizontally in the preserved specimen. There are about 10 unipinnate gills, on one side of which are some Secondary, probably regenerated, plumes. The an- terior border of the branchial pocket is raised; the color of its membrane and center is yellow. The gill leaves are maroon ringed with white. The anal papilla has 4 rings of white spots. The foot is evenly rounded in front and behind in the living quiescent slug; in the preserved specimen a blunt tail protrudes from under the mantle. The anterior pedal border is transversely grooved, without a notch. The lateral pedal corners are rounded, not expanded. ‘The labial cuticle of Chromodoris briqua has a _ dorsally interrupted grasping ring constituted of dark red curved rods (Fig. 23) with a simple, exceptionally bifid, tip. The radula (Fig. 22) has 54 rows, each row witha rhachidian tooth and 63-64 teeth per half- row. The central tooth is rather strong, 50 micra high, with abroadly triangular, wavy edged cusp measuring 13 micra. The innermost lateral tooth is about 80 micra high, its short cusp having 2 broad inner and 5 small outer denticles. The second lateral tooth is a little higher and with a longer cusp and without inner denticles. The cusp grows successively longer onthe outer lateralteethandbears up to 8 outer denticles. The height of the base attains 104 micra in the 12th lateral tooth. High, hook-shaped lateral teeth continue outwards; the outermost 10 teeth decrease in height and length of cusp, becoming laminar with a den- ticulate edge. The gonad appears as a cap on the front of the intestinal gland; itsampulla is distended by sperm. The male duct has a proximal, much convoluted, soft prostatic part and a straighter distal one. It appears silky, due toits muscular sheath. The spherical spermatheca and the pyriform spermatocyst are attached to one another at the proximal end ofthe vagina. Near this point the fertilizing (uterine) duct leaves the vagina. The male and vaginal apertures are united on the genital papilla, with the nidamental opening immediately behind it. A vesti- bular gland, an organ not constantly occuring in Chromodoris (see Odhner, 1934, p 250-251) was not found. Between the epidermis and the body- wall musculature are soft white and red spherules, probably glands, and a white, fibrous network. The name of the species is derived from “brique” = brick. Discussion of Chromodoris briqua The specimen was compared with all species of Pruvot-Fol’s revision (1951) and with the Indo-Pacific ones later described by Baba (1953), Burn (1957; 1961; 1962), Farmer (1963), Gohar and Aboul-Ela (1957), Pruvot-Fol (1954) and Risbec (1956). The Chromodoridinae have either a naked rhachis, a thickening of the cuticle, or a dwarf central tooth with or without a cusp. Chromodoris briqua has a dwarf central tooth with a cusp. Species in which the rhachidian tooth is of normal or nearly normal height, and has a pro- jecting cusp (genera Cadlinella, Lisso- doris and Risbecia; see Odhner, 1934, p 247-249), and those species in which the cups of the rhachidian tooth is split into subequal denticles, are nowexcluded from the genus Chromodoris (Pruvot- Fol, 1951, p 77). However, a subfamiliar separation between a projecting cusp (in Cadlinellinae) and a subdivided one (in Chromodoridinae) is not recommendable (Marcus, 1959, p 33). The difference between an entire cusp (C. amoena Cheeseman, see Odhner, 1934, text fig. 248 MARCUS AND BURCH 14) and a denticulate one (С. juvenca Bergh, 1898, pl. 31, fig. 7) is reducedby the wavy edge of the rhachidian cusp in C. briqua. The presence or absence of a tooth- like structure on the rhachis is in many cases a specific character. A contrary conclusion may be inferredfrom White’s discussion (1951, p 244) of C. runcinata Bergh, but actually she slipped into O’Donoghue’s description (1929, p 820) of С. inornata Pease. There are only a few species of Chromodoris with a dwarf, cusp-bearing rhachidian tooth and we will mention several examples: C. alderi Collingwood, 1881; C. amoena Cheeseman, 1886; andC.aureopurpurea Collingwood, 1881, and refer to Baba (1949, text figs. 52, 54) and Odhner (1934, fig. 14) for their radulae. Bergh (1892, p 1110) united C. alderi with C. reticu- lata (Pease, 1866). He was followed by Eliot (1904, p 386), Farran (1905, p 341), Baba (1933, p 169), and Allan (1947, p 444), though not by Pruvot-Fol (1951, Species nos. 11 and 168). The combination of the radula with the labial armature and the broad mantle having a bicolored border warrant a Specific distinction for Chromodoris briqua. According to Haefelfinger (1959) the color marks seem to be even more specific than is frequently assumed. The above-mentioned subcutaneous spher- ules also occur in other Chromodoridinae (Pruvot-Fol, 1954, p 25-26). 10. Hypselodoris hilaris (Bergh, 1890) (Figs. 25-27) Chromodoris hilaris Bergh, 1890, р 935-9375 ple 865 fies. 11-155) ©: hr var. Eliot, 1904, p 396. Chromodoris lineata Eliot, 396-397, pl. 24, fig. 7. Glossodoris hilaris Baba, 1953, р 210- 211, figs. 5, 6, J-K; Risbec, 1956, p 9. 1904, p Occurrence: Eniwetok Atoll, Annai- anni Island, in water about 2 m deep, on the edge of a large stone in lagoon about 7 m from shore. Further distribution: Zanzibar; Bay of Suot, Nhatrang, Vietnam; Ambon (original locality); Seto, Kii Peninsula, Japan. The animal (Fig. 25) measures 40mm in length and 5 mm in width when stretched out and crawling. Itis rounded and sometimes broadly expanded in front, pointed behind. The free border of the mantle is a little broader than the foot; it covers the head of the crawling slug, leaving the tapering tail free. The color is white with 5 reddish- purple longitudinal lines on the notum and one around the margin. These lines are united by irregular transverse connections. In the living and the pre- served specimen the white areas between the dark meshes are a little raised. The color markings of the head, tail, and the post-branchial area are shown in Fig. 25. The notum contains small papillae which are probably outlets of glands. As in many Chromodoridinae (see Marcus, 1955, p 126), there are 3 rows of light glands on the hyponotum. There is a lavender band on the edge of the foot which shows through in ventral view. The tentacles of Hypselodoris hilaris are digitiform and white with lavender bases. The same lavender pigment occurs along the anterior border of the foot. The rhinophores are 4 mm high, with 15 lamellae, and deep orange in color, except at the tips, where they are white. In front of the rhinophores, where the eyespots show through, the pigment is lighter. There are 10 uni- pinnate gills; their afferent (inner) sides are white, their efferent (outer) sides are orange. The foot has a transversely grooved anterior border, without a notch. The lateral angles of the foot are marked, though not projecting. The labial cuticle (Fig. 27) is strengthened in 2 lateral areas which are connected by a thinner median zone, that bears simple scale-like platelets. The same type of platelets occur also PACIFIC EUTHYNEURA on the low marginal parts of the thickened areas. The tips of the central rods are subdivided into a long cuspand2 smaller ones, one of which is stronger than the other. The radula (Fig. 26) comprises about 72 rows, with about 55 teeth per half-row. The rhachis is naked. Most of the teeth are bicuspidate, with the upper cusp longer than the lower one. The innermost tooth of each half-row has up to 4 inner and 6 outer denticles. The other teeth have only outer denticles. About 5 of the marginalteethare laminar and have a single cusp followed by some denticles. Discussion of Hypselodoris hilaris The present material differs from Chromodoris briqua inhaving more color marks on the tail and stronger con- nections between the longitudinal lines of the notum. The type has only 4 longitudinal lines on the notum, 2 on either side of the middle. Eliot’s above-mentioned Chromodoris lineata (1904) is H. hilaris (Baba, 1953). Later, Eliot (1910, p 430) pointed out the resemblance of Doris magnifica Quoy and Gaimard, 1832, and D. lineata Eydoux and Souleyet, 1841, to H. hilaris. The former is identical with Chromodoris quadricolor (Rüppell and F. S. Leuckart, 1828) (see Pruvot-Fol, 1934, p 71-72). The 5 violet lines on the back of С. lineata are raised (see Barnard, 1927, p 183). The labial armature and the radulae of the original specimens were not described. Therefore, the name lineata cannot replace hilaris. Pruvot-Fol (1951, p 84) thinks that Chromodoris alderi Collingwood, 1881, might be the full-grown stage of H. hilaris, but C. alderi has unicuspidate radular teeth, hence is a Chromodoris as defined by Odhner (1957), not a Hypselodoris. 11. Gymnodoris bicolor (Alder and Hancock, 1864) Trevelyana bicolor Alder and Hancock, 1864, p 440, pl. 29, figs. 11, 12. 249 Gymnodoris bicolor Macnae, 1958, p 358-359 (full synonymy; add: Trevelyana bicolor ? Eliot, 1904, p 89, pl. 4, figs. 1a-c). Occurrences: (1) Under stone on the seaward tide flat at the central part of Parry Island; March 23, 1960; (2) on north end of Japtan Island, March 28, 1960. Further distribution: Inhaca, Delagoa Bay, Mozambique; Zanzibar; Ceylon; near Madras (original locality); Viet- nam; Japan, from Sagami Bay to southern Kyushu; Palau Islands; New Caledonia; Samoa (Eliot, 1899, p 520). One of the larger specimens was 15 mm long and 4 mm broad when crawling, stretching out attimesto19x3mm. The back is orange or yellow with tiny bump- like or spike-like papillae which have orange tips. Subepidermal yellow glands also occur on the back. The frontal veil is broadly rounded, its edge has a dozen short languettes of different sizes. The tail is pointed. The tentacles are short but extensible and are inserted on the oral disc which is connected with the anterior border of the foot. The rhinophores have about 15 lamellae and are yellow with orange tips. There are black eyespots between the posterior borders ofthe rhinophorial pockets. One specimen had coalesced rhinophores (see also Hoffmann, 1933, p 216-217). The genital papilla is at the level of the anterior border of the branchial pocket. There are 10gills, the anterior ones slightly larger than those flanking the anus. Our specimens of Gymnodoris bicolor had no labial plates. The radula of the examined specimen had 20 rows of teeth with about 25 teeth per half-row. The rhachis was naked. The innermost lateral tooth is brown, bigger than the following colorless teeth. The cusp ofthe second tooth is a short sharp point rising from a wide base as figured by Bergh (1877, pl. 56, figs. 19-23) and Baba (1949, text fig. 35). The bases of the following teeth are narrower than the 250 MARCUS AND BURCH base of the second, but they are also strong. Their cusps are long, nearly straight and slightly curved at the tip. A few outermost teeth are smaller. The smaller slug (from Parry Island) was observed biting the larger one (from Japtan Island) in the genital region. The latter specimen was preserved with everted penis. Risbec (1928a, p 188- 189, text fig. 57 bis) interpreted an identical observation of the same Species as an attempt of the animal inthe female phase to squeeze sperm out of the gonad of the slug in the male phase. Risbec found non-synchronous development of oögenesis and spermatogenesis as well as simultaneous hermaphroditism in Gymnodoris bicolor. Discussion of Gymnodoris bicolor The only originally described species of Gymnodoris Stimpson (1855, p 379) had 9 gills. It is certainly a Trevelyana Kelaart, 1858, as understood by Alder and Hancock (1864) and Bergh (1877; 1905). The types of the closely related genera, Nembrotha Bergh, 1877, p 450; Paliolla Burn, 1958, p 7; and Tambja Burn, 1962, p 98, have fewer gills. Vayssiére (1912, p 8) suggested a subgeneric separation of Trevelyana striata Eliot, (1908, p 100) and Risbec (1928a, p 193) separated this species from Gymnodoris by its color marks as Analogium, a genus with 10 gills. Macnae (1958, p 355) doubted whether Risbec’s genus was necessary. Stimpson’s Species, Gymnodoris maculata, from the Ryukyu Islands can- not be defined without knowledge of its radula. Therefore, the substitution of Gymnodoris for Trevelyana (O’Donog- hue, 1929, р 733) is debatable. But since the most recent publications (Risbec, 1956; Маспае, 1958; Baba, 1960a; Burn, 1962) all use Gymnodoris, their example is followed here. 12. Dendrodoris nigra (Stimpson, 1855) Doris nigra Stimpson, 1855, p 380. Doridopsis nigra Alder and Hancock, 1864, p 128, pl. 31, figs. 13-16. Doridopsis arborescens Collingwood, 1881, p 134-135, pl. 10, figs. 15-17. Doriopsis nigra + nigra var. + nigra var. luteopunctata Bergh, 1905, p 169- 172, pl. 24 ties. 13-14. Dendrodoris nigra Baba, 1935, p 348- 349, text fig. 12, pl. 6, fig. 2; 1949, p 69, 154-155, pl. 26, figs. 98-99. Occurrences: (1) Central part of Parry Island; and (2) under stones at the north end of Japtan Island. A total of 13 specimens were collected from March 23 until April 8, 1960. Further distribution: Indo-West Pacific Ocean from the Red Sea, Zanzi- bar, and Mozambique to the Abrolhos Islands, West Australia; Sydney (D. melaena Allan, 1932, p 98; name corrected by hand in the copy received in 1954 from Mrs. Allan), and Japan (from the Ryukyu Islands to Mutsu Bay, Lat. 40° 52’ N). Also from the Gilbert Islands (material of the U. S. Nat. Mus., seen by E. Marcus) and New Caledonia. Length of the animal is 8-35 mm. The color of the notum is black with white spots occurring singly or in clusters. There is an inner red and an outer black border in some specimens. The tips of the rhinophores are white, the border of the foot reddish. The anal papilla is in the mid-line, a little behind the circle of gills. A spiral egg-ribbon, faint yellow, 2 mm high, 10 mm in diameter, was spawned by a 25 mm-long slug. 13. Dendrodoris erubescens (Bergh, 1905) Doriopsis erubescens Bergh, 1905, p 173-174, pl. 3, fig. 15. Dendrodoris communis Risbec, 1928a, p 67-69, text fig. 7, pl. A2 (p 114), pl. 1, fig. 6. Dendrodoris erubescens Risbec, 1953, p 22-23, figs. 2 d-i, fig. 4; 1956, p 26- Ре Occurrence: Japtan Island, under | PACIFIC EUTHYNEURA rock, seaward tide flat, 1 specimen, collected by Dr. William H. Heard on March 8, 1960. Further distribution: Vietnam; Sala- jar Island, Flores Sea (originallocality); New Caledonia. This is a small species, our speci- men measuring 8.5 mm in length. The notum is pale pink, the central area darker, more orange. There are about 10 raised spots on the notum, which were colored orange with white centers. The anal papilla completes the circle of gills, which comprises 2 branchial buds and 6 brownish gills. The gillsare unipinnate, although one of them is beginning to develope secondary pinnules. D. erubescens is similar to D. rubra (Kelaart, 1858) which ranges from the Red Sea to Japan and is mentioned in most reports from the Indian Ocean, e.g. by Alder and Hancock (1864, p 126, pl. 31, figs. 1-2); frequently D. rubra is described and figured as somewhat spotted. Since Bergh (1905, p 176), as well as Risbec (1956, p 22), both of whom failed to refer to this similarity in color, classified D. rubra as well as D. erubescens, these two species are probably distinct. 14. Herviella claror Burn, 1963 (Figs. 28-30) Burn, 1963, p 18-19, figs. 11-15. Occurrence: North end of Eniwetok Island on the lagoon side, under sub- merged rocks in about 10 cm of water at low tide. The 3 specimens were collected by Dr. William H. Heard, April 2-12, 1960. Further distribution: Woody Head, north of Clarence River Heads, north- ern New South Wales. The length of the adult living animal is about 8 mm. The body is slender, ending in a long pointed tail (Fig. 28). The general color is light yellow; the back is speckled with single large 251 melanophores. There are white trans- verse bands between the rows of cerata. The rhinophores and the basal 2/3 of the tentacles are speckled with black; the tips of the tentacles have opaque white granules. The cerata are white with an orange ring in the upper third. The yellowish-gray diverticula of the intestinal gland shine through the cerata. The tentacles and rhinophores of Her- viella claror are smooth, of about equal length. The foot is rounded in front, bilabiate, broader than the head. The cerata are fusiform, forming 4 rows, the foremost of which belong to the right and the left anterior “liver.” The rows contain 3, 4,2 and2cerata, respectively, from front to rear. The genital aperture is under the first row of cerata, the anus close behind the second row. The jaw (Fig. 30) is oval in shape and horn-colored. The masticatory process is short with 6 big, inclined denticles. There are 11 horseshoe-shaped radular teeth; each has a broad median cusp and 3-4 strong denticles on either side (Fig. 29). Discussion of Herviella claror The type species of Herviella Baba, 1949 (p 107, 180), is H. yatsui (Baba, 1930 1937. р 328. pl. 2, fie. .2) from the Pacific coasts of middle and southern Japan. Other species are Н. affinis Baba (1960b, p 81) from the Sea of Japan (Toyama Bay) and the Pacific coast (Osaka Bay) of Japan, H. exigua (Risbec, 1928a, p 245; 1953, p 134) from New Caledonia, and H.claror Burn, 1963, from the east coast of Australia (290 20’ S). H. exigua differs from the other species by lateral denticles of equal length on the radular tooth. dH. yatsui and H. affinis have more slender cerata than the Australian H.claror and the Eniwetok specimens; the proportion of length to breadth of their jaws is 5:4 against 7:4 in H. claror including our Specimens from Eniwetok. The number of denticles on the masticatory process is 7-12 in H. yatsui and 12 in A. affinis in contrast to 6 in H. claror, including 252 MARCUS AND BURCH y 29 yc / 35 FIGS. 28-30. Herviella claror. FIGS. 31-35. Herviella mietta, n. sp. Fig. 28. Living slug of H. claror, drawn from Kodachrome transparency, dorsal view. Fig. 29. Radular tooth. Fig. 30. Jaw and masticatory denticles. and from living animal. Radular tooth. our specimens. Therefore, the identi- fication of the species from Eniwetok with the geographically most distant one is unavoidable. 15. Herviella mietta, new species (Figs. 31-35) Occurrence: North end of Eniwetok Island on the lagoon side, in about 10 cm of water at low tide, under sub- merged rocks (13 specimens), and Annai- anni Island (3 specimens collected by Dr. William H. Heard; April 2-12, 1960). Fig. 31. Dorsal view of living slug of H. mietta, n. sp., drawn from Kodachrome transparency Fig. 32. Right rows of cerata. Fig. 33. Penial stylet. Fig. 34. Jaw. Fig. 35. Living animals measure 7-11 mm. Their bodies are slender with pointed tails (Fig. 31). Two color types are represented in our material. The first type is light and transparent, the back is covered with white granules, the head has a black pattern, there is a black band on the rhinophores, some black pigment on the tentacles, and the yellow diverticula of the intestinal gland may be seen in the cerata (which also have white cnidosacs and, in their basal third, brown pigment). The second color type is dark, the back and the upper part of the sides of the foot are black, the rest of the foot and sole are white, PACIFIC EUTHYNEURA the tentacles have a narrow black longi- tudinal stripe, there is a black band on the rhinophores, there are light halos around the eyes and between the tentacles, and the cerata are black, with a white cnidosac andthe yellowintestinal gland showing through. The smooth tentacles of Herviella mietta are 1/3 of the body length. The rhinophores are also smooth and a little shorter. The foot is rounded in front and bilabiate. The cerata are long and fusiform, thinner than those of H. claror, caducous, and arranged in 5-6 rows on each side (Fig. 32). The first ceras of each row is the smallest. The hind- most cerata of one row cover the fore- most cerata of the following row. All rows of cerata are slightly curved, al- though not arched in a horseshoe shape. The first row (with 5-6 cerata) oneither side represents the anterior liver. The posterior liver branches have 6-3 cerata. The genital opening is under the first row and the anus is at the end of the second row. In 1 specimen the brown penial stylet (Fig. 33) projected from the genital aperture. This stylet measured 84 micra in length. The jaw is dark, long and expanded dorsally (Fig. 34). The masticatory process bears 18 smooth denticles, the hindmost of which is the largest. The radular teeth (Fig. 35) are horseshoe- shaped, 18 in number, with very strong central cusps flanked on either side by 8-9 thin, pointed denticles. The denticles first decrease and then increase in length. The tips of the longest, outer- most denticles curve slightly inward. The name of this species is derived from “miette” = trifle, crumb. Discussion of Herviella mietta The jaw resembles that of Caloria (Facelinidae) or of Dondice (Favorinidae, Facalaninae) andthe radular teeth, whose long lateral denticles are somewhat Similar to those of the pectinate tooth of Cerberilla, are quite peculiar charac- ters of the new species. It belongs to those Favorinidae which have single 253 rows of cerata on the liver branches, i.e., to the Favorininae (Marcus, 1958a, p 59). Among the genera of this sub- family (Marcus, 1960a, p 922, 924) only Cratena Bergh, 1864 (according to Lemche, 1964, Rizzolia), or Herviella Baba, 1949, can perhaps receive the present species. Its simple anterior liver branches and the armed penis show that it is better included in Herviella than in Cratena, as defined by Macnae (1954, p 29). From the lateral view of the radular tooth of Herviella yatsui (Baba, 1949, text fig. 146B) it seems that in that species also the outermost denticle is longer than the inner ones. Moreover, the general color of H. yatsui is also extremely variable (Baba, 1937, pl. 2, fig. 2; 1949, pl. 47, figs. 159-161). 16. Onchidella evelinae, new species (Figs. 36-39) Occurrence: In cracks in coral slabs above water line (at low tide) on the lagoon side at the north end of Eniwetok Island, April 5, 1960. The average length of the adult living slugs (Fig. 36) is 6 mm, their breadth 4mm. Ina preserved animal4mm long the sole is 2.5 mm broad; the hyponotum of one side measures 1 mm. The mantle is strewn with little raised warts, which coalesce in part and contain glands. Small nodules can be seen between the warts. The general color of the notum is yellowish, with the underlying dark greenish intestinal gland showing through the central part. The border of the notum is lightly colored. There is dark pig- ment particularly around the bases of the warts, but their tops have very little or no pigment. There are 16-20 pigment- free marginal papillae. The hyponotum and sole are whitish, the latter with dark pigment in one specimen. The hyponotal line is 0.6 mm from the edge. Between the edge and the hyponotal line are small glandular papillae. The skin between the hyponotal line and the sole 254 MARCUS AND BURCH is smooth. The opening of the mantle cavity is covered by the tip of the foot. The female aperture is located to the right of the mantle cavity opening. The dis- tance of the pneumostome from the border is about 1/4 of the breadth of the hyponotum. The peritoneum is not pigmented. The jaw of a preserved 4 mm specimen is 0.2 mm broad, yellowish, and shaped like that of other species, e.g., Onchidella patelloides figured by Wissel (1904, fig. 77). The radula comprises 50-60 rows with 40-48 teeth per half-row (Fig. 38). The rhachidian tooth is tricuspid, its median cusp the largest. Theinnermost pleural tooth measured 16 micra high; the one following it is 26. micra high. The other pleural teeth are all nearly the same size, decreasing gradually toward the outside of the radula. The terminations of the mesocones are pointed; the points are worn in the oldest 1/3 of the radula. The intestine is like that of Plate’s (1893, p 121) 4th type, but the descending limb is still farther to the right than thatin O, celtica (pl. 8, fig. 32). A sectioned slug, about 3 mm in length after preservation, has a smooth lung. The right and left halves of the kidney are symmetrical, without lamellae. The recurrent limb of the kidney runs ventrally to the right half. The above sectioned animal was inthe male phase (Fig. 37). Sperms were present in the ovotestis (o) and ampulla (x) of the hermaphrodite duct (h). There is no caecum (see Fretter, 1943, p 699) in this species. The albumen glands (k) and the mucus gland (m) are still small. The vesicle of the bursa (b)is spherical, its duct (s) long and winding. The lining of the vagina (w) is folded. The ectal section of the vagina is not widened in comparison with the oviduct (u). The prostate (q) is large, nearly cylindrical and its lumen smooth, not folded. The efferent duct approaches the skin to the right of the female aperture. It then courses forward along the right side of the body. Under the right tentacle the duct curves backward into the body cavity, descending straight (d) along the penis (Fig. 39). The wall of the duct is muscular; its rather thick layer of connective tissue contains vesicular cells. The penis of a 4 mm slug measured 2 mm in length and 0.1 mm in diameter. The penial retractor muscle (r) is about 0.6 mm and inserts at the fundus of the penial pouch. It originates a little behind the peri- cardium (in Fig. 39 the retractor is bent forward to save space). The penial pouch contains the efferent duct (z), which ends on the long (0.17 mm in length) muscular papilla (p), and a long diverticulum. The epithelium of the diverticulum produces a solid cuticular structure (t). This stylet, about 1.2 mm in length and 80 micra in diameter near its inner end, is cylindrical, lamellate below, and becomes semilunar in transverse section farther in front. Its axial thickenings and flat shape at the level of the penial papilla are shown in transverse sections in Fig. 39. Con- spicuous vesicular cells can be seen in the conjunctive tissue in the ectal third of the penial pouch (y). The species is namedfor Mrs. Eveline du Bois-Reymond Marcus. Discussion of Onchidella evelinae Following a recent record (Solem, 1959, p 37), Taylor and Sohl (1962, p 13) indicate one family of the Onchidiacea with 6 genera and subgenera, but actually there are 2 families with a total of 15 genera and subgenera (Marcus, 1960a, p 876). The present species is defined as belonging to the Onchidellidae and to Onchidella Gray, 1850, by the position of the male opening to the right of the right tentacle, and the hyponotal line, respectively. Hoffmann (1929, p269) sub- divided Onchidella into Onchidella and Occidentella according to the position of the recurrent renal limb, ventral to the kidney in the first and dorsal to it in the second subgenus. Two notogaeic Species, O.obscura (Plate, 1893), a PACIFIC EUTHYNEURA 255 FIGS. 36-39. Onchidella evelinae, п. sp. FIGS. 40-43. Siphonaria guamensis. Fig. 36. Dorsal view of living slug of O. evelinae, drawn from Kodachrome transparency. Fig. 37. Diagram of reproductive organs, ventral view. Fig. 38. Radular teeth. Fig. 39. Male copulatory organ and sections of stylet; b, bursa; d, efferent duct; h, hermaphrodite duct; k, albumen gland; m, female gland mass; o, ovotestis; p, penial papilla; q, prostate; r, retractor; s, spermathecal duct; t, cuticular stylet; u, oviduct; w, vagina; x, ampulla; y, penial pouch; z, efferent duct within penis. Fig. 40. Jaw of S. guamensis. Fig. 41. Reproductive organs. Fig. 42. Elements of jaw. Fig. 43. Radular teeth; a, atrial thickening; f, flagellum; g, gland of epiphallus; h, hermaphrodite duct; m, female gland mass; о, ovotestis; $, spermathecal duct; у, seminal vesicle. 256 MARCUS AND BURCH synonym ofnigricans (Quoy and Gaimard, 1833), and O. reticulata (Semper, 1882) have a dorsal recurrent limb (Plate, 1893, p 132, 205, 208), and therefore Hoffmann (l.c.) called Occidentella an Australian group. The dorsal limb dis- tinguishes them from О. evelinae, a typical Onchidella. Of 2 other West Pacific species, O. patelloides (Quoy and Gaimard, 1833) and O. flavescens (Wissel, 1904), the anatomy of the kidney is not known. The first differs from O. evelinae by its black peritoneum (Hoff- mann, 1928, p 90), and the second by its narrow sole (Wissel, 1904, p 668), whose breadth is equal to that of the hyponotum of one side. In his recordofO. maculata (Plate, 1893) from New Guinea, Labbé (1934, p 78) did not give details of the kidney. If his specimen really was O. maculata, previously known from the coast of Southwest Africa, it would have a ventral recurrent renal limb, like O. evelinae. But in Labbé's and Plate's maculata the unarmed penis contains calcareous concretions, absent in O. evelinae which has a cuticular stylet. The male copulatory organ furnishes the principal elements for the specific classification of Onchidella, hence specimens in the mature male phase should be examined. On the other hand, it is advisable to section small slugs with incompletely developed female glands. In big animals these are the bulkiest organs of the genital system, and often render the reconstruction difficult. The absence of folds in the lung (Marcus, 1956, p 79) of small Specimens cannot be used for differ- entiating species. 17. Stphonaria (Sacculosiphonaria) guamensis Quoy and Gaimard, 1833 (Figs. 40-43) Hubendick, 1945, p 25-27, fig. 33; 1946, p 41, pl. 6, figs. 30-32. Occurrence: Southend of Parry Island, on rocks in the intertidal zone of the lagoon. Further distribution: Billiton, Java Sea; Guam, Mariana Islands (original locality). The shells of this species measure up to 12 mm in length, 9.1 mm in width, and 5 mm in height. The shells are rather symmetrical. The apex isbehind the middle, very slightly recurved, and worn in our specimens. There are 20- 26 principal ribs, low, slightly un- dulating, with a secondary rib sometimes between the two principal ones. Our specimens exhibit considerable variation in size. In all shells the ribs are white, their interspaces dark gray. The apex is light in many of these speci- mens, and the remaining parts of the surface are darker. Four of the shells, however, have a dark apex and quite light borders; 3 are more or less uniformly dark, except for the ribs. The body appears grayish when preserved in formalin, not yellow as in Hubendick’s (1945) material. The siphon cannot be seen from the back. The jaw (Figs. 40, 42)is semicircular; its scaly elements are renewed from time to time. The radula (Fig. 43) comprises about 110 rows, the older of which are procoelous, the younger ones straight. The basal plate of the rhachidian tooth is relatively broad and terminates concavely or is nearly split. Its short cusp is simple. There are up to 36 teeth per half-row. The inner- most has the usual strong socket anda long cusp and is bifid at its tip. The length of these points varies; frequently the inner one is a little longer. The basal plate is asymmetrical, prolonged outward. The other lateral teeth are Similar and decrease gradually in size toward the outside of the radula. An ectocone appears on the 13-15th tooth, and an entocone appears on the 19th. The 2 mesocones coalesce, forming a rectangular plate in the outer half of the half-row. The outermost or marginal teeth are low and simplified. The kidney is similar to Hubendick’s PACIFIC EUTHYNEURA 257 (1945, p 35, fig. 61) B-type. The repro- ductive organs (Fig. 41) are like those shown by Hubendick (1945, fig. 33). Minor differences are athickening ofthe genital atrium (a) near the entrance of the spermathecal duct (s), a slightly longer, curved flagellum (f), and a more bulky epiphallus gland (g). The black seminal vesicle (v), not yet recorded for S. guamensis, lies at the entrance of the hermaphroditic duct (h) into the female gland mass (m), as in the other species of Siphonaria (Hubendick, 1945, p 11). The receptacle and the filiform part of the spermatophore are easily dis- tinguishable from one another; thelatter has no barbs. Discussion of Siphonaria guamensis The shape of the radular teeth and their number are of restricted value in the systematics of Siphonaria. The kidney of the present species is ex- ceptional in the subgenus Sacculosiphon- avia, the other known species of which have the C-type (Hubendick, 1945, p 35; 1946, p 41-42). The reproductive organs are, together with the general charac- ters of the shell, decisive for the classification in this subgenus. The jaw of S. guamensis differs widely from that of S. cochleariformis (Hubendick, 1945, fig. 86) of the same subgenus. LITERATURE CITED MADAM, W. and LELOUP, E., 1938, Prosobranchia et Opisthobranchia. Mem. Mus. Nat. Hist. Nat. Belg. Hors série, 2(18): 1-209, pls. 1-8. ALDER, J. and HANCOCK, A., 1864, Notice on a collection of nudibranch- iate Mollusca made in India by Walter Elliot, Esq., with descriptions of several new genera and species. Trans. zool. Soc., 5(3): 113-148, Pls. 28-33. ALLAN, J. K., 1932, Australian nudi- branchs. Austral. Zoologist, 7(2): 87-105, pls. 4-5. , 1947, Nudibranchia from the | Clarence River Heads, North Coast, New South Wales. Rec Austral. Mus., 21(8): 433-463, pls. 41-43. BABA, K., 1930, Studies on Japanese Nudibranchs. (3). A. Phyllidiidae. B. Aeolididae. Venus, Jap. J. Malacol., 2(3): 117-125, pl. 4. , 1933, Preliminary note on the Nudibranchia collected in the vicinity of the Amakusa biological laboratory. Annot. Zool. Japon., 14: 165-179. , 1935, Nudibranchia of Mutsu Bay. Sci. Repts. Tohoku Univ., ser. 4, biol., 10: 331-360, pls. 5-7. , 1937, Opisthobranchia of Japan (I). J. Dept. Agr. Kyushu Imp. Univ. Fukuoka, 5(7): 289-344, pls. 1-2. , 1949, Opisthobranchia of Sagami Bay. 4+2+194+7 p, 50 pls. Tokyo, Iwanami Shoten. , 1953, Three new species and two new records of the genus Glosso- doris from Japan. Publ. Seto marine biol. Laborat., 3(2): 205-211. , 1960a, The genera Gymno- doris and Nembrotha from Japan. Publ. Seto marine biol. Laborat., 8(1): 11-74; pled: , 1960b, The genus Herviella and a new species, Н. affinis, from Japan. Publ. Seto marine biol. Laborat., 8(2): 303-305. BARNARD, K. H., 1927, South African nudibranch Mollusca, with de- scriptions of new species, and a note on some specimens from Tristan d’ Acunha. Ann. South African Mus., 25 (art. 6): 171-215, pls. 19-20. BERGH, R., 1877, Malacologische Untersuchungen, Heft 11. In: SEMPER, C., Reisen im Archipel der Philip- pinen. Wissenschaft. Resultate, 2. Theil, 2: 429-494, pls. 54-57. , 1890, Die Nudibranchien des Sunda-Meeres. Malacologische Unter- suchungen, Heft 17. In: SEMPER, C., Reisen im Archipel der Philippinen. Wissenschaftl. Resultate, 2. Theil, 3: 873-991, pls. 85-89. , 1892, Malacologische Unter- suchungen, Heft 18. System der nudi- branchiaten Gasteropoden. In: 258 BURN, R., 1957, Opisthobranchia. DALL, W. H., 1908, SEMPER, C., Reisen im Archipel der Philippinen. Wissenschaftl. Resultate, 2. Theil, 3: 995-1165. , 1898, Die Opisthobranchier der Sammlung Plate. Zool. Jb., Suppl. 4 (Fauna Chilensis, 1): 481-582, pls. 28-33. , 1900, Malacologische Unter- suchungen, 5. In: SEMPER, C., Reisen im Archipel der Philippinen. Wissenschaftliche Resultate, 7,4. Abt., Abschn. 1. Liefrg.: 159-208, pls. 13- 16. ‚1901, Malacologische Unter- suchungen, 5. In: SEMPER, C., Reisen im Archipel der Philippinen. Wissenschaftl. Resultate, 7, 4, Abt., 3. Abschn. (Bullacea), Liefrg. 1 & 2: 209-312, pls. 17-24. ‚ 1905, Die Opisthobranchiata der Siboga Expedition. Siboga Exped., 50: 1-248, pls. 1-20. On some Opistho- branchia from Victoria. J. malacol. Soc. Australia, 1: 11-29, pls. 1-3. , 1958, Further Victorian J. malacol. Soc. Australia, 2: 20-36, pls. 6-7. , 1951, A new doridid nudi- branch from Torquay, Victoria. The Veliger, 4(2): 55-56, pl. 15. , 1962, Notes on a collection of Nudibranchia (Gastropoda: Dorid- idae and Dendrodorididae) from South Australia with remarks on the species of Basedow and Hedley, 1905. Mem. Nat. Mus. Melbourne, 25: 149-171, pli ‚ 1963, Descriptions of Aus- tralian Eolidacea (1. The genera Catriona and Herviella). J. malacol. Soc. Australia, 7: 12-20. COLLINGWOOD, C., 1881, Onsome new species of nudibranchiate Mollusca from the eastern seas. Trans. Linn. Soc. Lond. Zool., 2(2): 123-140, pls. 9-10. Reports on the dredging operations off the west coast of Central America to the Galapagos, to the west coast of Mexico, and in the Gulf of California. XIV. . The MARCUS AND BURCH Mollusca and Brachiopoda. Bull. Mus. comp. Zool., Harvard, 43(6): 205-487, pls. 1-22. EALES, N. B., 1944, Aplysiids from the Indian Ocean, with a review of the family Aplysiidae. Proc. malacol. Soc. Lond., 26(1): 1-22. ELIOT, C. N. E., 1899, Notes on tecti- branchs and naked molluscs from Samoa. Proc. Acad. nat. Sci. Phila- delphia, 1899: 512-523, pl. 19. , 1904, On some nudibranchs from East Africa and Zanzibar, parts 4 and 5. Proc. zool. Soc. Lond., 1904 (1): 380-406, pls. 23-24; 1904(2): 83- 105, pls. 3-4. , 1906a, On the nudibranchs of Southern India and Ceylon. Proc. zool. Soc. Lond. 1906: 636-691, 999- 1008, pls. 42-47. ‚ 1906b, Nudibranchs and tecti- branchs from the Indo-Pacific: II. J. Conchol., 11: 298-315, pl. 5. , 1908, Notes on a collection of nudibranchs from the Red Sea. J. Linn. Soc. Lond. Zool., 31(204): 86- 122. , 1909, Notes on a collection of nudibranchs from Ceylon. Spolia zeylan., 6(23): 79-95. , 1910, Nudibranchs collected by Mr. Stanley Gardiner from the Indian Ocean in H. M. S. Sealark. Trans. Linn. Soc. Lond. Zool., 2. ser., 13(3): 411-438, pl. 25. ENGEL, H., 1927, Westindische opistho- branchiate Mollusken. II. Bijdr. Dierk., 25: 83-122. , 1936, (unter Mitwirkung von P. WAGENAAR HUMMELINCK), Uber westindische Aplysiidae und Ver- wandte anderer Gebiete. Capita Zoologica, 8(1): 1-75. FARMER, W. M., 1963, Two new opistho- branch mollusks from Baja California. Trans. San Diego Soc. nat. Hist., 13 (6): 81-84, pl. 1. FARRAN, G. P., 1905, Report on the opisthobranchiate Mollusca. In: HERDMAN, У. A., Report to the Government of Ceylon on the Pearl Oyster Fisheries of the Gulf of Manaar. PACIFIC EUTHYNEURA London, 3, suppl. rept. 21: 329-364, pls. 1-6. FRETTER, V., 1943, Studies in the functional morphology and embryology of Onchidella celtica. J. Marine biol. Assoc. United Kingdom, n. ser., 25(4): 685-720. GOHAR, H. A. F. and ABOUL-ELA, I. A., 1957, The development of three chromodorids with the description ofa new species. Publ. Marine biol. Stat. Al-Ghardaqa, Red Sea, 9: 203- 228, pls. 1-5. GUIART,J., 1901, Contributions à l’étude des gastéropodes opisthobranches et en particulier des céphalaspides. Mém. Soc. zool. France, 14: 5-219, pls. 1-7. HABE, T., 1952, Atyidae in Japan. In: Tokubei Kuroda, illustr. catal. Japan. shells, 20: 137-152, pls. 20- 21. , 1961, Fauna of shell-bearing mollusks of the sea around the Shiri- kishinai marine station. Part 2. Gastropoda. In: Fauna and Flora around Shirikishinai Marine Stat., 3: ‚1-11, pls. 1-5. HAEFELFINGER, H.-R., 1959, Remar- ques sur le développement du dessin de quelques Glossodoridiens. Rev. suisse Zool., 66(2): 309-315. HANNA, G. D., 1955, Preparation of Nudibranchiata. Nautilus, 68(3): 105- 106. HOFFMANN, H., 1928, der Oncidiiden. I. 55: 29-118, pls. 2-4. , 1929, Zur Kenntnis der Oncididen. I. Zool. Jb. Syst., 57: 253-302, 1 map. ‚ 1932-40, Opisthobranchia. Bronn’s Klassen..., 3: Mollusca: Abt. I: Gastropoda; Buch 3. Teil.I: XI + 1247 р, 1 pl. Teil Il: 90 p. Leipzig, Akadem. Verlagsges. HUBENDICK, B., 1945, Phylogenie und Tiergeographie der Siphonariidae. Zool. Bidr. Uppsala, 24(1947): 1-216. , 1946, Systematic monograph of the Patelliformia. Kgl. Svenska Akad. Handl., ser. 3, 23(5): 1-93, Zur Kenntnis Zool. Jb. Syst., from Southern Africa. branchia. Opisthobranchia. from California. 259 pls. 1-6. KELAART, E. F., 1859, Descriptions of new and little-known species of Ceylonese nudibranchiate mollusks. Ann. Mag. nat. Hist., ser. 3, 3: 291- 304, 488-496. LABBE, A., 1934, Opisthobranches et silicodermes (Oncidiadés). Res. Sci. Voy. Indes Orient. Néerld. Mém. Mus. Roy. Hist. Nat. Belg., hors ser., 2(14): 1-83, pl. 1. LEMCHE, H., 1964, Proposed suppres- sion under the plenary powers of the generic name Cratena Bergh, inorder to validate the generic name Rizzolia Trinchese, 1877 (Class Gastropoda). Z. N. (S.) 1105. Bull. zool. Nomencl., 21(1): 50-51. MACNAE, W., 1954, On some eoli- dacean nudibranchiate molluscs from South Africa. Ann. Natal Mus., 13 (1): 1-50, pls. 1-2. ‚ 1958, The families Poly- ceridae and Goniodorididae in Southern Africa. Trans. Soc. South Africa, 35(4): 341-372, pls. 17-18. , 1962, Tectibranch molluscs Ann. Natal Mus., 15(16): 183-199. MARCUS, E., 1955, Opisthobranchia from Brazil. Bol. Fac. Filos. Cienc. Univ. S. Paulo, Zoologia, 20: 89-262, pls. 1-30. , 1958a, On western Atlantic opisthobranchiate gastropods. Amer. Mus. Novit., 1906: 1-82. , 1958b, Notes on Opistho- Bol. Inst. Oceanogr. S. Paulo, 7(1-2): 31-79, pls. 1-8. , 1959; Lamellariacea und Lunds Univ. Aarskr., N. F., Avd. 2, 55(9): 1-135. , 1961, Opisthobranch mollusks The Veliger, 3 (Suppl. 1): 1-85, pls. 1-10. MARCUS, EV. and ER., 1956, Zwei atlantische Onchidellen. Kieler Mee- resforsch., 12(1): 76-84, pls. 23-25. , 1960a, Opisthobranchia aus dem Roten Meer und von den Male- diven. Akad. Wiss. Lit. Mainz, Math.- Nat. Kl., 1959(12): 871-934. 260 MARCUS AND BURCH , 1960b, On Siphonaria hispida. Bol. Fac. Filos. Cienc. Univ. 5. Paulo, Zoologia, 23: 107-140, pls. 1-4. , 1963, Opisthobranchs from the Lesser Antilles. Studies on the Fauna of Curacao and other Caribbean is- lands, 19: 1-76. ODHNER, N. H., 1921, Mollusca of Juan Fernandez and Easter Island. In: C. SKOTTSBERG, The natural history of Juan Fernandez and Easter Island, 3(2): 219-254, pls. 8-9. , 1934, The Nudibranchiata. Brit. Antarct. Terra Nova Exped., Zoology 7(5): 229-309, pls. 1-3. , 1957, Chromodoris contra Glossodoris. A systematic-nomen- clatorial controversy. Proc. malacol. Soc. Lond., 32(6): 250-253. O’DONOGHUE, C. H., 1929, Report on the Opisthobranchiata. Res. Cam- bridge Exped. Suez Canal 1924. Trans. Soc. Zool. Lond., 22(6): 713-841. , 1933, Kelaart’s work on the Nudibranchiata ofCeylon. Proc. mala- col. Soc. Lond., 20(4): 221-226, pl. 19. OSTERGAARD, J. M., 1955, Some opisthobranchiate Mollusca from Ha- waii. Pacific Science, 9: 110-136, pls. 1-2. : PEASE, W. H., 1860a, Description of new species of Mollusca from the Sandwich Islands in the collection of Hugh Cuming. Proc. zool. Soc. Lond., 28: 18-36. , 1860b, Descriptions of forty- seven new species of shells from the Sandwich Islands in the collection of Hugh Cuming. Proc. zool. Soc. Lond., 28: 431-438. PILSBRY, H. A., 1893-95, Manual of Conchology, 15: 436 p, 61 pls. , 1895-96, Manual of Conch- ology, 16: VII + 262p, 75 pls. , 1921, Marine mollusks of ” Hawaii XIV, XV. Proc. Acad. nat. Sci. Philadelphia, 72: 360-382. PLATE, L., 1893, Studien über opistho- pneumone Lungenschnecken. II. Die Oncidiiden. Zool. Jb. Anat., 7(1): 93-234, pls. 7-12. | PRESTON, H. B., 1908, Description of new species of land, marine andfresh- water shells from the Andaman islands. Rec. Ind. Mus., 2(2): 187- 210, pls. 14-17. PRUVOT-FOL, A., 1931, Notes de systematique sur les Opisthobranches (suite). Bull. Mus. Hist. Natur. Paris, ser. 2, 3(8): 746-755. ‚ 1934, Les Opisthobranches de Quoy et Gaimard. Arch. Mus. Hist. natur. Paris, ser. 6, 11: 13-92, pl. 1. , 1951, Revision du Genre — Glossodoris Ehrenberg. J. Con- chyliol., 91: 76-164. , 1954, Etude d’une petite col- lection d’Opisthobranches d’Océanie Francaise. J. Conchyliol., 94: 3-30. RISBEC, J., 1928a, Contribution a l’étude des Nudibranches Néo- Calédoniens. Faune Colon. Franc., 2: 1-328, pls. A-D, 1-12. , 1928b, Etude anatomique des Gasteropodes Tectibranches de la presqu’ile de Nouméa avec description de cing espéces nouvelles. Arch. Mus. Hist. natur. Paris, sér. 6, 3: 37-68. , 1951, Notes sur les Tecti- branches de Nouvelle-Calédonie. J. Soc. Océanistes, 7(7): 123-158, pl. 8. , 1953, Mollusques Nudi- branches de la Nouvelle-Calédonie. Faune de l’Union Franc., 15: 1-189. , 1956, Nudibranches du Viet- Nam. Arch. Mus. Hist. natur. Paris, ser. Ч. 41-34 "pis "1-222 SEMPER, C., 1880; 1882, Dritte Familie: Onchidiidae. In: SEMPER, C., Reisen im Archipel der Philip- pinen. II. Theil, 3(5): 251-264, pls. 19-20, 22-23; 3(6): 265-290, pl. 21. SI, T., 1931, Contribution a l’etude des Mollusques Opisthobranches de la cóte Provencale. These du Laborat. Zool. Fac. Sci. Lyon et Stat. Marit. Biol. Tamaris, 221 p, 8 pls. Trevoux (Rhóne). SOLEM, A., 1959, Systematics of the land and fresh-water Mollusca of the New Hebrides. Fieldiana, Zoology: 43: 1-238, pls. 1-34. SOWERBY, G. B., 1868, Haminea in: REEVE, LOVELL, Conchologia << EEE EEE PACIFIC EUTHYNEURA 261 Iconica, 16, 5 pls. STIMPSON, W., 1855, Descriptions of some of the new marine Invertebrata from the Chinese and Japanese Seas. Proc. Acad. nat. Sci. Philadelphia, 7. (10): 375-384; Nudibranchiata: 388- 389. TAYLOR, D. W. and SOHL, N. F., 1962, An outline of gastropod classification. Malacologia, 1(1): 7-32. VAYSSIERE, A., 1912, Recherches zoologiques et anatomiques sur les Opisthobranches de la Mer Rouge et WHITE, K. M., 1951, On a collection of molluscs, mainly nudibranchs from the Red Sea. Proc. malacol. Soc. Lond., 28(6): 241-253. WISSEL,..C. Vos 1904, Pacifische Chitonen der Sammlungen von Schauinsland und Thilenius nebst einem Anhang über neuseeländische Species der Gattung Oncidiella. Zool. Jb. Syst., 20(6): 591-676, pls. 21-25. ZILCH, A., 1959-60, Gastropoda, Teil 2, Euthyneura. In: Schindewolf, Handb. d. Paläozool., 6: XII + 834 p, 2515 EUTHYNEURE MEERESGASTROPODEN VOM ENIWETOK ATOLL, WESTPAZIFIK Die Arbeit beruht auf einer Sammlung euthyneurer Meeresschnecken des zweiten Verfassers vom Eniwetok Atoll, Marshall Inseln. Vom Februar bis April 1960 wurden 17 Arten gesammelt, von denen 5 als neue Arten in dieser Arbeit beschrieben werden. Die neuen Arten sind: Haminoea musetta, H. linda, Chromodoris briqua, Herviella mietta und Onchidella evelinae. Von den übrigen 12 Arten erstreckt sich die Ver- breitung von 7 vom westlichen Indischen Ozean (2 kommen auch im Roten Meer vor) ostwärts bis Eniwetok oder noch weiter nach Osten; 2 Arten sind zirkumtropisch oder zirkumsubtropisch, 2 Arten kennt man nur aus dem Westpazifik, und 1 Art ist von Eniwetok westwärts bis in den östlichen Indischen Ozean verbreitet. Eine gewisse Einförmigkeit der indowestpazifischen Riff-Fauna zeigt sich darin, dass 9 (oder mehr als 50%) unserer Arten von der westlichen Grenze des Indischen Ozeans bis zum westlichen oder zentralen Pazifik vorkommen. Die Gattung Herviella scheint auf den Westpazifik beschränkt zu sein. Das notogäische Vorkommen einer Onchidella mit ventral vom Hauptteil gelegenem rückläufigem Nierenschenkel ist bemerkenswert, wie auch das kutikulare Stilett in einem Blindsack der Penis-Scheide. RESUMEN GASTROPODOS EUTINEUROS MARINOS DEL ATOLL ENIWETOK, PACIFICO OCCIDENTAL Este estudio se basa en una colecciön de Eutineuros marinos hecha por el segundo autor en el Atoll Eniwetok, Islas Marshall, durante febrero-abril de 1960. Se colectaron 17 especies, de las cuales las cinco siguientes se describen como nuevas: Haminoea musetta, H. linda, Chromodoris briqua, Herviella mietta, y Onchidella evelinae. De las otras 12 especies, 7 extienden su distribuciön hacia el este desde el Océano Indico occidental (2 también aparecen en el Mar Rojo) a Eniwetok o mas hacia el este; 2 especies son circumtropicales o circumsubtropicales; 2 se conocen del Pacifico occidental solamente; y 1 se distribuye desde Eniwetok hacia el oeste, dentro del Océano Indico oriental. La relativa uniformidad de la fauna de los arre- cifes del Indopacifico occidental, está indicada por el hecho de que 9 (más del 50%) de nuestras especies se conocen distribuidas desde el margen oriental del Océano du Golfe d’Aden, 2me partie (suite et text-figs. | Berlin-Nikolassee, Gebr. fin). Ann. Fac. Sci. Marseille, 20 Borntraeger. (1911, Suppl.): 5-158, pls. 1-11. ZUSAMMENFASSUNG 262 MARCUS AND BURCH Indico al Pacifico occidental o central. La presencia notogeica de una Onchidella con un limbo ventral recurrente del riñón y un estilete cuticular en el divertículo de la cámara penial es müy notable. RESUMO EUTINEUROS GASTRÓPODOS MARINHOS DO ATOLL ENIWETOK, PACÍFICO OCIDENTAL O presente estudo baseia-se numa colecdo de moluscos marinhos eutineuros feita pelo segundo autor no atoll de Eniwetok, nas Ilhas de Marshall, em fevereiro-abril de 1960. Foram coletadas 17 espécies das quais 5 зао descritas como novas no presente trabalho. As novas espécies sao: Haminoea musetta, H. linda, Chromodoris briqua, Herviella mietta, Onchidella evelinae. Das 12 espécies restantes, a distri- buigao de 7 estende-se do Indico ocidental (2 ocorrem também no Mar Vermelho) até Eniwetok ou mais para o leste; 2 espécies зао circumtropicais ou circumsub- tropicais; 2 espécies conhecem-se sömente do Pacífico ocidental, e 1 espécie осогге de Eniwetok para o oeste, até ao Indico oriental. Certa uniformidade da fauna dos recifes do Indico e Pacífico ocidental depreende-se do fato de se conhecerem 9 (mais que 50%) das nossas espécies como ocorrentes das costas ocidentais do Oceano Indico até ao Pacífico ocidental ou central. Aocorréncia, na Notogea, de uma Onchidella com ramo renal recorrente ventral é estranha; a espécie tem estilete cuticular num divertículo da bolsa penial, incomum no género. MALACOLOGIA, 1965, 3(2): 263-286 1 SOME OPISTHOBRANCHIA FROM MICRONESIA Ernst Marcus Faculdade de Filosofia, Ciéncias e Letras Universidade de Sao Paulo Sao Paulo, Brasil ABSTRACT A Micronesian collection of 130 opisthobranchs belonging to the U. S. National Museum contained 53 species. less than 5 mm in length. Only 10 of them are new, and half of these are These small numbers show the uniformity of the opisthobranch fauna on the reefs in the Indo-West Pacific Ocean, most of whose bigger species are already known. The following new species are described: Stiliger (Ercolania) illus, Elysia bayeri, Elysia ratna, Hypselodoris cuis, Dis- codoris lora, Discodoris ylva, Catriona lonca, Catriona urquisa, Noumeaella rehderi, and Muessa evelinae, the type-species of a new genus of the Favorini- dae, allied to Herviella. Some time ago, Dr. Harald A. Rehder of the Smithsonian Institution, Washing- ton, D.C., U.S.A., sent me for identifi- cation a collection of 130 lots of opis- thobranch mollusks from Micronesia. All of this material was collected in recent years by biologists and geolo- gists sent out on surveys of islands in several of the groups making up this region of the central western Pacific. Of the 53 species identified in this sending, 10 are new, 5 of them being less than 5 mm in length. The recog- nized uniformity of the Indo-West Pacific reef fauna, and the relatively advanced state of exploration account for the small percentage (18.9) of new species. Inour first collection from the little known coast of Brazil, 71.8% were new species. My thanks are due to Dr. Harald A. Rehder for having gone over the manu- script, and to Dr. F. M. Bayer, of the Marine Institute in Miami, Florida, for having furnished many of the color notes used inthe description of the new species. SYSTEMATICS AND DISTRIBUTION A systematic list of species of Euthy- neura collected in Micronesia during the field study are listed below. The species are treated individually in consecutive order in the section following the list. Soleolifera, Onchidiacea, Onchidiidae 1. Peronia (Peronia) peronii (Cuv- ier) Cephalaspidea, Bullacea, Retusidae 2. Retusa sp. Cephalaspidea, Philinacea, Phanero- phthalmidae 3. Phanerophthalmus luteus (Quoy and Gaimard) Cephalaspidea, Philinacea, Aglajidae 4. Aglaja splendida Risbec 5. Chelidonura inornata Baba 6. Chelidonura hirundinina elegans Bergh Anaspidea, Aplysiidae, Aplysiinae 7. Aplysia (Varria) dactylomela Rang 8. Aplysia (Varria) pulmonica Gould 9. Aplysia (Pruvotaplysia) parvula Morch Anaspidea, Aplysiidae, Dolabellinae 10. Dolabella auricularia (Solander) Anaspidea, Aplysiidae, Dolabriferinae 11. Dolabrifera dolabrifera (Rang) lPublished with the cooperation of the Institute of Malacology. (263) 264 12. Petalifera (Bergh) Anaspidea, Aplysiidae, Notarchinae 13. Stylocheilus longicauda (Quoy and Gaimard) Sacoglossa, Elysiacea, Stiligeridae 14. Stiliger (Ercolania) illus, spec. nov. Sacoglossa, Elysiacea, Phyllobran- chillidae 15. Phyllobranchillus (Bergh) 16. Cyerce nigra Bergh Sacoglossa, Elysiacea, Plakobranchi- dae 17. Plakobranchus ocellatus van Has- selt Sacoglossa, Elysiacea, Elysiidae 18. Elysia thysanopoda Bergh 19. Elysia marginata (Pease) 20. Elysia bayeri spec. nov. 21. Elysia тата spec. nov. Notaspidea, Pleurobranchacea, Pleurobranchidae 22. Pleurobranchus peronii Cuvier 23. Pleurobranchus cf. lugubris (Bergh) 24. Berthella grisea (Bergh) 25. Berthellina citrina (Rüppell and Leuckart) i Nudibranchia, Doridoidea, Crypto- branchia, Hexabranchidae 26. Hexabranchus marginatus (Quoy and Gaimard) Nudibranchia, Doridoidea, Crypto- branchia, Dorididae, Chromodoridinae 27. Chromodoris lineolata (van Has- selt) 28. Chromodoris venusta (Bergh) 29. Hypselodoris cuis spec. nov. 30. Hallaxa decorata (Bergh) Nudibranchia, Doridoidea, Crypto- branchia, Dorididae, Miamirinae 31. Casella atromarginata (Cuvier) 32. Casella rufomarginata Bergh Nudibranchia, Doridoidea, Crypto- branchia, Dorididae, Discodorinae 33. Discodoris lora spec. nov. 34. Discodoris ylva spec. nov. 35. Kentrodoris funebris (Kelaart) Nudibranchia, Doridoidea, Crypto- branchia, Dorididae, Asteronotinae petalifera pacifica prasinus E. MARCUS 36. Halgerda elegans Bergh Nudibranchia, Doridoidea, Crypto- branchia, Dorididae, Platydoridinae 37. Platydoris scabra (Cuvier) 38. Platydovis cruenta (Quoy and Gaimard) 39. Platydoris cf. flammulata Bergh Nudibranchia, Doridoidea, Phanero- branchia, Nonsuctoria, Gymnodoridi- dae : 40. Nembrotha nigerrima Bergh Nudibranchia, Doridoidea, Porosto- mata, Dendrodorididae 41. Dendrodoris nigra Stimpson Nudibranchia, Doridoidea, Porosto- mata, Phyllidiidae 42. Phyllidia (Phyllidia) varicosa Lamarck 43. Phyllidia (Phyllidiella) pustulosa Cuvier 44. Phyllidia (Phyllidiella) nobilis (Bergh) 45. Fryeria rüppelli Bergh Nudibranchia, Doridoidea, Dendro- notoidea, Bornellidae 46. Bornella digitata (Adams and Reeve) Nudibranchia, Doridoidea, Dendrono- toidea, Dotoidae 47. Doto cf. albida Baba Nudibranchia, Doridoidea, Eolidoidea, Acleioprocta, Cuthonidae 48. Catriona lonca spec. nov. 49. Catriona urquisa Spec. nov. Nudibranchia, Doridoidea, Cleio- procta, Favorinidae, Favorininae 50. Pteraeolidia semperi (Bergh) 51. Phyllodesmium hyalinum Ehren- berg 52. Noumeaella rehderi spec. nov. Muessa, (gen. nov.) 93. Muessa evelinae spec. nov. Order Soleolifera Superfamily Onchidiacea Family Onchidiidae 1. Peronia (Peronia) peronii (Cuvier, 1804) Mariana Islands: Saipan: from 1/2 ton block of dead coral taken off anchor, MICRONESIAN OPISTHOBRANCHIA 265 lagoon on west coast. Sta. loc. No. 2. Е Ш Cloud, Jr., and J. .H.:O*Mara coll, May 2, 1949. One specimen (USNM 574622).2 Palau Islands: high tide line along fringing reef on west shore of Abappao- mogon Island (Ngermeiaus), about 1 1/2 miles west of Eil Malk, Sta. No. 260. F. M. Bayer and R. R. Rofen coll., November 3, 1955. One specimen (USNM 575678). Marshall Islands: Bikini Atoll: inter- tidal. M. W. Johnson coll., April-May, 1946. Two specimens (USNM 574232). Marshall Islands: Eniwetok Atoll: Rujoru Id., on north outer side. Sta. No. 4598. Jy Tracey: Jr; com June 3, 1946. Two specimens (USNM 574235). Marshall Islands: Eniwetok Atoll: east side of south end of Eniwetok Id. Sta. No. 4454. M. W. Johnson coll., May 20, 1946. One specimen (USNM 574234). Marshall Islands: Eniwetok Atoll: on exposed cobble’ rock flats, intertidal zone, south ocean side at west end of Igurin Id. Sta. No. 4472. J. P.E. Morrison coll., May 22, 1946. One specimen (USNM 574231). Marshall Islands: Arno Atoll: reef flat at Ine anchorage. Sta. No. 55. J. W. Wells coll., June-August, 1950. One specimen (USNM 574686). Gilbert Islands: Onotoa Atoll: A. H. Banner coll., August 15, 1951. One speci- men (USNM 574925). Order Cephalaspidea Superfamily Bullacea Family Retusidae 2. Retusa sp. Marshall Islands: Bikini Atoll: under coral head, outer reef, Bikini Island. Sta. No. 65-1. F. M. Bayer coll., July 25, 1947. Color sketch made. Fragments of one specimen (USNM 574440), in which the absence of the radula was stated. | 2U. $. National Museum Catalog Number. Superfamily Philinacea Family Phanerophthalmidae 3. Phanerophthalmus luteus (Quoy and Gaimard, 1832) Caroline Islands: Ifaluk Atoll: from eel grass beds, south shore of lagoon, Rauau district, north of Katelu benjo, Falarik Id. Sta. No. 548. FM: Bayer coll., October 8, 1953. Two specimens (USNM 574970). Family Aglajidae 4. Aglaja splendida Risbec, 1951 Palau Islands: Koror Island; in eel grass in Geruherugairu Pass, between Kaibakku Island and Kogai-hantó, Au- luptagel Island. Sta. No. 30. F. M. Bayer, coll., July 22, 1955. Black with brilliant blue border. Two specimens (USNM 575680). 5. Chelidonura inornata Baba, 1949 Caroline Islands: Ifaluk Atoll: la- goon reef at Katelu benjo, near “Izzie” and “Barbara” reefs, Rolong canoe house. Sta. No. 724. F. M. Bayer, coll., October 22, 1953. One specimen (USNM 574979). Color: velvety black with fine white flecks. 6. Chelidonura hirundinina elegans Bergh, 1900 Marshall Islands: Bikini Atoll: creep- ing on surface of rocks, outer reef flats, Bikini Island. Sta. No.6. F.M. Bayer, coll., August 5, 1947. Six speci- mens (USNM 574439). Order Anaspidea Family Aplysiidae Subfamily Aplysiinae 7. Aplysia (Varria) dactylomela Rang, 1828 Palau Islands: Urukthapel Island: 266 E. MARCUS lagoon margin of reef on live coral and coral rubble, with abundant Caulerpa and Halimeda, north of east point(Nagareme- diu). Sta. No. 69. Е. M. Bayer, coll., August 5, 1955. One specimen (USNM 575669). Gilbert Islands: Onotoa Atoll: from green algal veneers on dead coral rock, NW corner of atoll. Sta. No. GOC-41. P. E. Cloud, coll., August 21, 1951. Two specimens (USNM 575058), identi- fied by Dr. N. B. Eales. 8. Aplysia (Varria) pulmonica Gould, 1852 Marshall Islands: lagoon reef south of causeway be- tween Lidilbut and Elangelap Islands. Sta. No. 1514. H.S. Ladd, M. Russell, and R. C. Townsend coll., May 11, 1952. One specimen (USNM 574922), identified by Dr. N. B. Eales as prob- ably representing this species. 9. Aplysia (Pruvotaplysia) parvula Mörch, 1863 Gilbert Islands: Onotoa: on algae, ocean side of reef flat. E. Moul, coll., August 6, 1951. The single specimen (USNM 575371) collected represents the variety nigrocincta von Martens, 1880. Subfamily Dolabellinae 10. Dolabella auricularia (Solander,1786) Mariana Islands: Guam: J.L. Gres- sitt, coll., October, 1945. One specimen (USNM 574206). Palau Islands: Iwayama Bay: shallow area in Geruherugairu Pass between Kaibakku Island and Kogai-hentó, Aulu- ptagel Island; in 5-6 feet on coral and sand bottom with eel grass, Halimeda and Padina. Sta. No. 85. Е. М. Bayer et al. coll., August 12, 1955. Two speci- mens (USNM 575683). | Palau Islands: same as above, in 4-5 feet. Sta. No. 140. Е. M. Bayer et al. Eniwetok Atoll: coll., August 30, 1955. Two specimens (USNM 575713). Caroline Islands: Kapingamarangi Atoll: lagoon reef, Hare Island Sta. No. 291. C. Hand coll., July 20, 1954. One specimen (USNM 575712). Dr. Harald A. Rehder called my attention to the fact that the name Dolabella scapula Martyn, 1784, by which this species has gener- ally been known, is invalid, since Martyn’s work “The Universal Con- chologist” has been rejected for nomenclatorial purposes by the International Commission on Zoolo- gical Nomenclature (Opinion 456- 1956). Subfamily Dolabriferinae 11. Dolabrifera dolabrifera (Rang, 1828) Palau Islands: reef flat on outer barrier reef, about 2 miles SSW of Ngaremediu District, east of Urukthapel Island. Sta. No. 111. F. M. Bayer et al. coll., August 19, 1955. Two specimens in about 1 foot on alga-encrusted coral rock (USNM 575684). Caroline Islands: Ifaluk Atoll: sea- ward reef at Fan-ni-wa canoe-house trail, middle of Falarik Island. Sta. No. 443. F. M. Bayer coll., October 1, 1953. Two specimens (USNM 574966 and 574967). Caroline Islands: Ifaluk Atoll: on rocks in sand flats, lagoon side, at south end of Falarik Island. Sta. No. 738. F. M. Bayer coll., October 26, 1953. Two specimens (USNM 574981). Caroline Islands: Kapingamarangi Atoll: on rock pile, lagoon, Hare Island, Sta. No. 604. C. Hand coll., August 6, 1954. Three specimens (USNM 575689). Caroline Islands: Kapingamarangi Atoll: inner reef flat, Touhou Island. Sta. No.67. C. Hand coll., June 25, 1954. One specimen (USNM 575690). Marshall Islands: Bikini Atoll: Inner reef under rocks, Bikini Island. Sta. No. 278. F. M. Bayer coll., August 24, MICRONESIAN OPISTHOBRANCHIA 267 1947. Two specimens (USNM 574441). Gilbert Islands: Onotoa Atoll: in two feet, tide pool, Heliopora reef flat. A. H. Banner coll., August 1, 1951. Two specimens (USNM 575374). 12. Petalifera petalifera pacifica (Bergh, 1900) Caroline Islands: Ifaluk Atoll: from eel grass, south lagoon shore, Rauau district, N of Katelu benjo. Sta. No. 549. Е. М. Bayer coll., October 8, 1953. Ten specimens (USNM 574972 and 574969). Subfamily Notarchinae 13. Stylocheilus longicauda (Quoy and Gaimard, 1825) Caroline Islands: Ifaluk Atoll: north end, Transect C, Falarik Island. Sta. No. 446. F. M. Bayer coll. One speci- men and one radula slide (USNM 574968). Caroline Islands: Ifaluk Atoll: from eel grass beds, south lagoon shore, Rauau district, north of Katelu benjo. Sta. No. 548 and 549. F. M. Bayer coll., October 8, 1953. Two specimens (USNM 574971 and 574974). Caroline Islands: Ulithi Atoll: Asor Island. Stars No. il. Fi Ne? Young coll., May, 1945. One specimen (USNM 574471). Marshall Islands: Bikini Atoll: boat - Cradle anchored off Bikini Island. Sta. No. 4. Е. М. Bayer and Е. С. Zimmer- man coll. August 28, 1947. Four speci- mens (USNM 574437). Order Sacoglossa Superfamily Elysiacea Family Stiligeridae 14. Stiliger (Ercolania) illus, spec. nov. (figs. 1-4) Material: Caroline Islands: Ifaluk Atoll: on large flabellate alga, lagoon reef south of Elangelap, western rim of atoll. Sta. No. 41. R. R. Rofen coll., October 10, 1953. One specimen. Description: Length 2.5 mm, dark brown with light tips of cerata. Head with big black eyes close together in front between rhinophores. These flat- tened on outside, with an auriculate lobe at basal third, similar to Ercolania pancerii Trinchese (Vayssiére, 1888: 126, pl. 6,f. 108). No labial tentacles. Foot anteriorly rounded, without elon- gated corners. Cerata in irregular rows, leaving middle of back free, total number 21, several having fallen off; largest cerata medial, smaller ones lateral. Base of cerata narrow, tip mamillary, middle swollen and almost knobbed due to racemose diverticula of digestive gland. No branches of albumen gland in cerata. Long penis (0.45 mm), completely retracted into male atrium; no stylet. Radula consisting of 8 teeth in ascen- ding, 7 in descending limb, several in ascus. Total length of tooth 54 y, incl. 20 y long base; cusp a slender lowblade, its height in the middle (7.5 п) gradually tapering towards the tip; cutting edge smooth. Holotype: the slug and one slide with radula and penis (USNM 574960). Discussion: The generic position of the present species is Somewhat doubt- ful. The absence of a penial stylet seems certain and can hardly be con- sidered tohave been torn off after mating, as has been observed in St. (St.) vossi Marcus (1960a: 146) whose copulatory organ was found everted in the 3 ex- amined slugs. The diameter and posi- tion of the eyes suggest Costasiella Pru- vot-Fol (1951a: 73), but the type-species has tentacle-like projections at the angles of the foot, and these are also somewhat elongated in C. ocellifera (Simroth, 1895: 168) and C. nonatoi Marcus (1960a: f. 26). The cerata of the latter, the only anatomically known Costasiella, contain branches of the al- bumen gland along with those of the di- gestive gland. The surveys of Ercolania (Pruvot- Fol, 1954a: 191; Marcus, 1956: 7; Baba, MICRONESIAN OPISTHOBRANCHIA 269 1959: 327) include 3 more or less dark species: E. trinchesei Pruvot-Fol (1951a: 71) with bright yellow basal half of the cerata, E. akkeshiensis Baba (1935: 116) whose radular teeth are high, not tapering toward the tip, and E. noto Baba (1959: 330) with broad labial tentacles. I maintain Ercolania Trinchese, 1872, as a subgenus of Stiliger Ehrenberg, 1831 (Marcus, 1956: 6). Family Phyllobranchillidae Genus Phyllobranchillus Pruvot-Fol, 1933 In a recent paper (Marcus and Mar- cus, 1963, p. 17) we used Polybranchia Pease, 1860. Because, however, thetype species P. pellucida Pease is a “species inquirenda” we now consider Pease’s genus as a doubtful one. FIGS. 1-4. Stiliger (Ercolania) illus, sp. n. Two radular teeth. FIG. 4. Penis. 15. Phyllobranchillus prasinus (Bergh, 1871) Caroline Islands: Ifaluk Atoll: on coral rocks on sand flats, lagoon side of south end, Falarik Island. Sta. No. 735. РЕ. М. Bayer coll., October 26, 1953. One specimen and radula slide (USNM 574980). P. orientalis Kelaart, 1858, may be the same species. 16. Cyerce nigra Bergh, 1871 Caroline Islands: Ifaluk Atoll: from algae in 6 feet, sandy bottom, lagoon shelf near margin of the west reef, between Elangelap and Falarik Islands. Sta. No. 138-E-3. D. P. Abbott coll., October 20, 1953. One specimen (USNM 575700). Caroline Islands: Ifaluk Atoll: from FIG. 1. Dorsal view. FIG. 2. Ceras. FIG. 3. ‚ FIGS. 5-6. Elysia bayeri, sp.n. FIG. 5. A. Creeping slug from a drawing by Dr. F. М. Bayer. B. Slug with opened parapodia from a painting by Dr. F. M. Bayer. FIG. 6. Radular tooth. FIGS. 7-8. Elysia ratna, sp. n. FIG. 7. Dorsal view. FIG. 8. Radular tooth. FIGS. 9-13. Hypselodoris cuis, sp. n. armature near margin; FIG. 9. Dorsal view. left side, surface focussed; FIG. 10. Elements of labial right side, bottom focussed. FIG. 11. Labial armature near centre. FIG. 12. One labial platelet, side view. FIG. 13. Radular teeth. Three innermost and one 2nd tooth; one from middle of row; one outermost. FIGS. 14-17. Discodoris lora, sp. n. FIG. 14. Dorsal view. FIG. 15. Sculpture of notum. FIG. 16. Rodlet of labial cuticle. FIG. 17. One radular tooth from middle ofrow and the 2 outer- most teeth. Abbreviations used in Figs. 1-41 а - ampulla am - common atrium ar - anus с - spermatocyst ce - base of plucked ceras d - ejaculatory duct e - sheathed part of efferent duct eu - female duct f - female gland mass g - genital aperture h - hermaphrodite duct ma - male atrium ne - cnidosac ni - nidamental duct oi - inner oviduct p - penis q - prostate s - spermatheca se - efferent duct so - spermoviduct sr - sphincter u - fertilizing (uterine) duct у - vagina 270 E. MARCUS algae in 12 feet, sandy bottom lagoon shelf, north of center of Ella (=Elange- lap) Island. Sta. No. 158-159. R. R. Ro- fen and Yaniseiman coll., October 24, 1953. Two specimens (USNM 575699). Family Plakobranchidae 17. Plakobranchus ocellatus van Hasselt, 1824 Palau Islands: on alga-encrusted coral rocks, reef flat on outer barrier reef about 2 miles SSW of Ngaremediu District, east of Urukthapel Island. Sta. No. 111. F. M. Bayeretal.coll., August 19, 1955. One specimen and radula slide (USNM 575662). Family Elysiidae 18. Elysia thysanopoda Bergh, 1905 Palau Islands: in 2-3 1/2 feet, coral and sand bottom, with eel grass, Hali- meda and Padina, shallow area in Geruherugairu Pass, between Kaibakku Island and Kogai-hantô, Auluptagel Island. Sta. No. 85А. Е.М. Bayer et al. coll., August 12, 1955. Two specimens (USNM 575674). | 19. Elysia marginata (Pease, 1871) Palau Islands: in 3-10 feet, fringing reef on west shore of Abappaomogon Island (Ngermeiaus) about 1 1/2 miles west of Eil Malk. Sta. No. 260. F. M. Bayer and R.R. Rofen coll., November 3, 1955. Three specimens (USNM 575677). Marshall Islands: Bikini Atoll: on alga-covered rocks, lagoon reef of Bikini Island. Sta. No. 278. F. M.Bayer coll., August 24, 1947. Five specimens and radula slide (USNM 574442). 20. Elysia bayeri spec. nov. (Figs. 5-6) Material: Marshall Islands: Bikini Atoll: outer reef, Bikini Island. Sta. No. 65B. F. M. Bayer coll., July 29, 1947. One specimen. Description: Living slug 12 mm long. According to Dr. Bayer’s painting, back of head, rhinophores and pericardial eminence with black and white stripes, tips of rhinophores orange with white stripes. Two longish blue spots in mid- line of head and neck. Dorsal surface dark green, outwards a band of lighter green, followed by a broad black and a broad bright orange margin. Under surface of parapodial border with blackish brown blotches alternating with light orange. Ventral side black with longitudinal narrow white stripes; near parapodial border broad blue dashes, corresponding to orange portions of brim. Preserved specimen 6 mm long, 4mm broad. Back of head and body black except white edging of rhinophores, para- podia and anus; latter situated between mid-line and front edge of right para- podium. Ventral surface light; border of parapodia with black blotches alter- nating with light intervals and running out into gray triangles towards foot. Radula comprising about 15 free teeth and several in ascus. Base and cusp each 25 yu long, tip of cusp a curved point; cutting edge with 15 blunt denti- cles; groove on outer surface long, shallow. Named for Dr. Frederick M. Bayer. Holotype: slug and radula slide (USNM 574438). Discussion: The color, not quite un- like that of E. ornata (Pease, 1860; see Bergh, 1905: 84), characterizes the species well. Also the nature of the radular tooth is uncommon in Elysia, though not unique, as E. livida Baba (1955: f. 13) has a similar tooth. 21. Elysia ratna spec. nov. (Figs. 7-8) Material: Palau Islands: Iwayama Bay: in 0-10 feet, in cave formed by west arm of Kogai-hantó, Auluptagelld., near islets XXXII and XXXIV. Sta. No. 47. F. M. Bayer et al. coll., July 28, MICRONESIAN OPISTHOBRANCHI 271 1955. One specimen. Description: Length 14 mm, breadth 8 mm. Head covered by rhinophores, these black on sides, light, in pre- served specimen cream, in middle. From black margins several spike-like pigmented stripes project towards light area, subdividing it. Dorsal side ofbody and parapodia black with light, now yellowish margin. Pericardial eminence with light longitudinal stripes. Ventral side with light and dark longitudinal stripes, these more numerous and darker on sole than on underside of parapodia. Foot with light borders, concave in front. Radula containing 20 free teeth and about Same number in ascus. Base 22, cusp 28 u long, tip hooked, cutting edge with about 18 pointed denticles; furrow on outer surface deep. Holotype: slug andradula slide (USNM 575705). Discussion: Inthe discussion of Elysia latipes (Marcus,1960b: 899) the literature of the Indo-west-pacific species of Elysza was brought together. The new species differs from all those described in these papers by the great extent of black pig- ment, quite rare in Elysia. Furthermore, in the markedly dark forms of Bergh (1905: 85-87) the color is not arranged as it is in Е. тата. The stripes on rhinophores, pericardial eminence and underside are similar to those of E. bayeri, but the shape of the radular tooth is very different. Order Notaspidea Superfamily Pleurobranchacea Family Pleurobranchidae 22. Pleurobranchus peronii Cuvier, 1804 (Vayssiére, 1898, emend.) Palau Islands: in 0-4 feet on lagoon margin of reef, north of east point (Ngaremediu) of Urukthapel Island. Sta. No. 69. F. M. Bayer et al. coll., August 8, 1955. Two specimens and Slide with radula and jaws (USNM 575667). Oscaniella purpurea Bergh, 1897, 1905, is a synonym. 23. Pleurobranchus cf. lugubris (Bergh, 1905) Palau Islands: Iwayama Bay: in 3-20 feet on coral shelf along west shore of SE peninsula of Koror Island, at mouth of Kaki Suidó (Oyster Pass). Sta. No. 236. H. A. Fehlman, S. Pierce, R. R. Rofen coll. One specimen and slide with radula and jaws (USNM 575670). Palau Islands: Iwayama Bay: in 0- 3 feet, eel-grass, sand, and coral flat in Geruherugairu-suido, between Kai- bakku Island, and Kogai-hantô of Auluptagel Island. Sta. No. 30. Е. М. Bayer et al. coll., July 22, 1955. One specimen (USNM 575681). 24. Berthella grisea (Bergh, 1905) Palau Islands: Iwayama Bay: 0-15 feet, “Bay of the Dragon Palace,”west side of Kogai Peninsula, Auluptagel Island, between USA and Tai Islands. Sta. No. 100. F. M. Bayer etal. coll., August 16, 1955. One specimen and slide with radula and jaws (USNM 575676). 25. Berthellina citrina (Rüppell and Leuckart, 1828) Palau Islands: in 0-1 feet onreefflat, on outer barrier reef, about 2 milesSSW of Ngaremediu district, east of Urukthapel Island. Sta. No. 111. Е. М. Bayer et al. coll., August 19, 1955. One specimen and slide with radula and jaws (USNM 575664). Order Nudibranchia Suborder Doridoidea Infraorder Cryptobranchia Family Hexabranchidae 26. Hexabranchus marginatus (Quoy and Gaimard, 1832) Caroline Islands: Ifaluk Atoll: lagoon shore, Rauau, Falarik Island (taken from Golden Plover). Sta. No. 593. F. M. 272 E. MARCUS Bayer coll., October 15, 1953. One specimen and slide with radula and jaws (USNM 574975). Marshall Islands: Eniwetok Atoll: north of Rigoru Island. Sta. No. 4592. J. P. E. Morrison coll., June 2, 1946. One specimen (USNM 57422). Family Dorididae Subfamily Chromodoridinae 27. Chromodoris lineolata (van Hasselt, 1824) Palau Islands: Iwayama Bay: on eel grass, sand and coral flat in Geruherugairu Pass, between Kaibakku Id. and Kogai-hantó, Auluptagel Id. Sta. No. 30, F. M. Bayer et al. coll., July 22, 1955. One specimen (USNM 575679). Palau Islands: Iwayama Bay: on eel grass, sand and coral flat in Geruheru- gairu Pass, between Kaibakku Id. and Kogai-hantó, Auluptagel Id. Sta. No. 85A. Е. M. Bayer et al. coll., August 12, 1955. One specimen (USNM 575675). Palau Islands: Iwayama Bay: Sandy flat and fringing reef at south end of Gua-zima (Island XV); Abe’s traverse XIII. Sta. No. 92. Е. M. Bayer et al. coll., August 14, 1955. One specimen (USNM 575666). Palau Islands: Koror Island: in Madalai District, extreme west end of Koror Island, shore at S end of Arakabesan-Madalai causeway, man- grove shore grading into mud and sand flat. Sta. No. 12. F. M. Bayer etal. coll., July 9, 1955. One specimen (USNM 575685): black with longitudinal lines, anastomosing here and there; margins of mantle sepia; branchial plumes sepia with white flecks; rhinophores dark sepia with white flecks; sole of foot grayish; tips of tentacles brownish yellow. 28. Chromodoris cf. venusta Bergh, 1905 Palau Islands: Iwayama Bay: east side of mouth of Kaki-suidö (Oyster Pass), between Island XXIX and SE endof Koror Id. Sta. No. 220A. Е. М. Bayer et al. coll., October 12, 1955. One specimen and slide of radula and jaws. (USNM 575702). 29. Hypselodoris cuis, spec. nov. (Figs. 9-13) Material: Caroline Islands: Kapinga- marangi Atoll: Polim reef flat, near Tipongowarakam Pass, Greenwich (Ship) Pass. Sta. No. 723. С. Hand сова August 12, 1954. One specimen. Description: Length 6.5, breadth 3, height 3.5 mm. Light brownish with lighter opaque knots, which are subepi- dermal, longish, more or less sym- metrically disposed in about 10 rows on notum and hyponotum. Skin smooth; brim of notum hardly salient. Tentacles grooved on outer side. Rhinophores nearer to border than to one another. Nine unipinnate gills. Foot narrower than notum; anterior border bilabiate, not notched in middle; tail projecting behind. Labial cuticle forming two triangular areas of pleurobranchid-like platelets. Their prolonged either simple or split tips (Figs. 10-12) lie like scales over bases of following platelets. Radula with 52 rows of 35.0.35 teeth; no rhachidian thickening. Teeth with two principal cusps. Innermost tooth with 2 denticles on inner and 3 on outer side; following teeth with 3-5 denticles, only on outer side and number decreasing outwards. Holotype: slug and slide of radula and labial armature (USNM 575708). Discussion: As recently exposed (Marcus, 1960b: 901), I follow Odhner (1957) in suppressing Glossodoris Ehrenberg, 1831, and using Chromo- doris Alder and Hancock, 1855, for species with unicuspidate teeth, Hypselo- doris Stimpson, 1855, for those with bicuspidate ones. While the labial armature of this sub- family generally consists of rodlets, straight or ending with a bifid hook, a number of species of Hypselodoris have MICRONESIAN OPISTHOBRANCHIA scale-like platelets as labial elements. According to Basedow and Hedley (1905: 141) Bergh’s first Chromodoris crossei (1884: 648) is identical with the type- species of Hypselodoris, Goniodoris ? obscura Stimpson (1855: 388-389). Hence simple labial hooklets combined withbi- cuspidate teeth (Bergh, 1883: pl. 7, 8) occur in the type-species. H. runcin- ata (Bergh, 1877: 479) and H. maren- zelleri (Bergh, 1882: 219) are further examples. Some species of Hypselodoris with platelets are: H. crossei (Angas, 1864; Bergh, 1905: 146), H. semperi (Bergh, 1877: 482; 1905: 147), H.hilaris (Bergh, 1890: 935; Baba 1953: 210), H. nigro- striata (Eliot, 1904: 394; 1905: 247), H. tenuilinearis (Farran, 1905: 342; Eliot, 1905: 246, 248), and H. ransoni (Pruvot-Fol, 1954b: 18). Though some of these species are evidently identical with one another (Eliot, 1. c.; Pruvot- Fol, 1951b), the labial armature should not be disregarded; a list of synonyms as that given by Risbec (1953: 66) for H. diardii cannot be accepted. Н. cuis comes closest to H. ransoni from French Oceania and especially to H. hilaris from Amboina and the Kii Peninsula. NH. тапзот has less outer denticles on the middle teeth than cuis, and its marginal teeth have no cusps. Moreover the labial armature of H. vansoni consists of four separate areas. The specimen of H. hilavis from Amboina has narrower labial platelets than cuis; in the variety from Middle Japan they do not differ, nor does the radula, but the back has 5 longitudinal bright purple lines which can hardly be assumed to have faded out into light knots. 30. Hallaxa decorata (Bergh, 1878) Caroline Islands: Kapingamarangi Atoll: Polim reef flat, near Tipongo- wasakam Pass in Greenwich (ship) Pass. Sta. No. 722. C. Hand coll., August 12, 1954. One specimen and slide with radula and jaws (USNM 575694). 273 Subfamily Miamirinae 31. Casella atromarginata (Cuvier, 1804) Marshall Islands: Bikini Atoll: in 28 fms., 4 miles south of west end of Bikini Id. Sta. No. R4356. J. P. E. Morrison coll., April 25, 1946. One specimen and slide with radula and jaws (USNM 574227). 32. Casella rufomarginata Bergh, 1890 Palau Islands: in shallow water on reef flat on outer barrier reef about 2 miles SSW of Ngaremediu District, east of Urukthapel Island. Sta. No. 111. F. M. Bayer et al. coll., August 19, 1955. One specimen and slide with radula and jaws (USNM 575673). Palau Islands: on reef flat, Ngadarak Reef, north of mouth of Malakal pass. Sta. No. 106. F. M. Bayer et al. coll., August 17, 1955. One specimen and slide with radula and jaws (USNM 575672). Subfamily Discodorinae 33. Discodoris lora spec. nov. (Figs. 14-18) Material: Caroline Islands: Ifaluk Atoll: washed from algae, algal edge exposed at low tide, reef east of south end of Falarik islet, just north of Tran- sect A. Sta. No. 26. D. P. Abbott coll., September 4, 1953. One specimen. Description: Length 12 mm, breadth 6.5 mm, height 3 mm, hence rather flat. Yellowish with black dots on notum, concentrated around the larger of the numerous round, unequal warts. Spicules not found. Tentacles rather large, outer side grooved; rhinophores less distant from borders than from one another; rim of their pockets smooth; clubs with about 12 leaves. Six tri- pinnate gills; rim of their pocket smooth; anal region bulged out in the E. MARCUS 274 MICRONESIAN OPISTHOBRANCHIA 275 preserved specimen, possibly thereby anus removed from centre. Hyponotum smooth, its transverse striation due to muscle fibres showing through epi- dermis. Foot nearly 4 mm broad, an- terior border withtransverse groove and median notch of upper lip; hind end round, not projecting beyond notum. Labial cuticle yellow with up to 80, high, 12-15 „ thick rodlets, consisting of superposed discs. Pharynxbig, 4 mm long. Radula narrow, long, pro- jecting beyond hind end of pharyngeal bulb; 50 rows of 12.0.12 teeth. These hamate, smooth; innermost tooth 60 u high, teeth in the middle 120 y, outer- most tooth shortest, 50 y. The latter with long base and short cusp. Hermaphrodite duct (h) dilated into sausage-shaped ampulla (a) whose out- let coincides with separation of male and female ducts. Efferent duct begins with voluminous prostate (q), continues (d) with simple musculature, followed by ciliate part surrounded by special mus- cle sheath (e), ending with pleurembolic penis (p), “glans” of Bergh’s termino- logy, in male atrium (m) or “prae- putium”. Narrow vagina (v) between latter and nidamental duct (ni), leading to spermatheca (s). Uterine duct (u) begins immediately beside entrance of vagina. Spermatocyst (c) intercalary in uterine duct which enters female gland mass (f) far in front. Holotype: Slug and slide with radula and labial rodlets (USNM 575709). Discussion: The majority of the about 40 species of Discodoris is known from the Indo-West Pacific Ocean. Only the following 6 species with a similar narrow radula must be compared with D. lora. D. indecora Bergh, 1881, from the Mediterranean Sea and the Cape Verde Islands is olivaceous with light dots, and its rhinophores have 15-20 perfoliations. D. dubia Bergh, 1904, dubia var., and D. egena Bergh, 1904, all from the NW coast of Tasmania, differ from D. lora by shape of the outer- most radular tooth and number of rhino- phorial leaves. D. egena is generically uncertain, as a prostate could not be found. The geographically closest Dis- codoris with narrow radula, D. liturata Bergh, 1905, N of Sumbawa, has black notum with few white blots, transversely striped notal margin set off from centre, and distally curved labial rodlets. D. pallida Baba, 1937, from the W coast of Kyushu, has 9 gills and 15 radular rows. The geographically far distant D. erythraeensis Vayssiére, 1912, from the Red Sea, is morphologically nearest to D. lora, but differs by its upright outermost radular tooth, whose base is quite short, and by black spots also on the sole. 34. Discodoris ylva spec. nov. (Figs. 19-22) Material: Gilbert Islands: Onota Atoll: tide pool on Нейорота flat, 60 cm deep. A. H. Banner coll., August 1, 1951. One specimen. Description: Length 11 mm, breadth 8 mm, rather flat. Yellowish, sprinkled with fine black dots on notum, concen- trated in many bigger spots. Back with caryophyllidia which contain pigment Specks, are bigger in middle, smaller towards borders. Spicules numerous, thin,. some of them stand out from tip of caryophyllidia. Border of notum in- complete, probably due toautotomy. Hy- FIG. 18. Discodoris lora, sp. n. Diagram of reproductive organs, from dissection. FIGS. 19-22. Discodoris ylva, sp. n. productive organs, from dissection. FIGS. 23-26. Catriona lonca, sp. n. FIG. 19. Dorsal view. and from above. FIG. 21. Innermost and 5 outermost teeth of radula. FIG. 20. Tentacle from below FIG. 22. Diagram of re- FIG. 23. Right side view. FIG. 24. Jaw and denticles of masticatory process. FIG. 25. Radular tooth. FIG. 26. Penial stylet. FIGS. 27-30. Catriona urquisa, sp. п. FIG. 27. Right side view. FIG. 28. Jaw and denticles of masticatory process. FIG. 29. Smallest radular tooth. FIG. 30. Middle-sized radular tooth. FIG. 31. Noumeaella rehderi, sp. п. Left rhinophore. 276 E. MARCUS ponotum spiculate, transparent, showing spicules forming spikes around bases of caryophyllidia. Tentacles hidden in concavity in front of fore end of foot, triangular with outer side thrown into 5 or 6 transverse folds. Rhinophores about as far from one ano- ther as from edges of notum, clubs with 14 leaves. Rim of rhinophorial pocket bordered with caryophyllidia. So is border of gill-cavity which is empty; gills probably bitten off. Anterior bor- der of foot transversely grooved, upper lip notched; hind end of foot damaged. Labial cuticle with two areas of yellow- ish, stratified 50 » high rodlets. Radula with 21 rows and 30 teeth on either side of rhachis. Length of teeth, in micra: innermost 34, in middle 120, 26th to 30th 90, 80, 70, 60, 50: Most teeth simple hooks, of the outermost ones most frequently 2, exceptionally 1 or 3, with 1-5, generally 1 or 2, accessory cusps. Base of outermost tooth short. Hermaphrodite duct (в) widens to form slender ampulla (a) whose outlet divides into male and female (oi) ducts. Male duct merges into massive white prostate (q). Following tubular duct first brown and glandular, then white, muscular (d). Soft pleurembolic penis (p) hangs into male atrium. Vagina (v) begins broad, narrows internally. Spermatheca (s) contains brownish masses. Uterine duct goes out from vagina, leads to sperma- tocyst (c) filled with silky white orien- tated sperm and is connected with female gland mass (f) by short insemination duct (u). Holotype: Slug and two slides, one with radula and labial rodlets, and one with genital ducts (USNM 575377). Discussion: The peculiar oral tenta- cles resemble those of Tyrinna Bergh, 1898, a widely distant genus related with Cadlina (Marcus, 1959: 29). Digitiform tentacles are common in Discodoris (Eliot, 1903: 553). If these are long and conspicuous as in D, palma Allan (1933: 448) from Pussy-cat Bay near Sydney, they might contract in such a way that outer folds are brought about. However, in the descriptions of preserved speci- mens of numerous species of Discodoris transversely folded tentacles were never mentioned. In the type-species of the genus, D, boholiensis Berg (1877: 519) and the 7 other species published together with it the cusps of all teeth are simple hooks. Species whose outer teeth have split cusps are D, erubescens Bergh (1884: 662), D. lutescens Bergh (1905: 103; misprint in title line), and D. pallida Baba (1937: 305). Together with D. ylva they could possibly constitute an own taxon and reduce the genus Discodoris which is difficult to follow in the present state. But the occurrence of split cusps is not sufficiently constant (Baba, 1937: 306) for a clear cut differentiating character. Onthe other hand this charac- ter cannot be neglected, and the other- wise similar D. labifera (Abraham, 1877; Farran, 1905: 335) must be held apart from D. ylva by reason of the simple hooks of its radular teeth. D. erubescens has pointed villi on the notum, D. lutescens tuberculiform tenta- cles, and D. pallida 14-17 teeth in the half-row of the radula. 35. Kentrodoris funebris (Kelaart, 1859) Palau Islands: Iwayama Bay: sandy flat and fringing reef at south end of Gua-zima (Island XV), Abe’s Traverse XIII. Sta. No. 92. Е. M. Bayer et al. coll., August 14, 1955. Two specimens and one radula slide (USNM 575665). Caroline Islands: Kapingamarangi Atoll: Lagoon reef, Hare Island Sta. No. 606, C. Hand coll., August 6, 1954. One specimen (USNM 575686). Caroline Islands: Kapingamarangi Atoll: Thokataman Is., poisoned along with fish by rotenone. C. Hand coll., July 12, 1953. One specimen (USNM 575687). K. annuligera Bergh, synonym. 1876, is a Subfamily Asteronotinae 36. Halgerda elegans Bergh, 1905 Marshall Islands: Rongelap Atoll: lagoon. Lt. Kaley coll., June 20, 1946. |: 5 MICRONESIAN OPISTHOBRANCHIA One specimen and radula slide (USNM 574165). Color: deep purple with white ring-like markings. Subfamily Platydoridinae 37. Platydoris scabra (Cuvier, 1804) Caroline Islands: Kapingamarangi Atoll: lagoon reef under coral boulder, Tiatua Id. Sta. No. 157. C. Hand coll., July 13, 1954. One specimen and slide of radula and labial cuticle (USNM 575693). Marshall Islands: Bikini Atoll: south half of Enyu Island. Sta. No. R 4028. J. P. E. Morrison coll., March 5, 1946. One specimen (USNM 574228). 38. Platydoris cruenta (Quoy and Gaimard, 1832) Mariana Islands: Guam. J. L. Gres- sitt coll., October, 1945. One specimen and slide with radula and labial cuticle (USNM 574207). Caroline Islands: Ifaluk Atoll: under rocks middle of reef flat, north end of Transect C. Falarik Id. Sta. No. 439. F. M. Bayer coll., October 1, 1953. Two specimens and slide with radula and labial cuticle (USNM 574965). Caroline Islands: Ifaluk Atoll: from rocks and boulders of elang, south end of Falarik Id. Sta. No. 799. F. M. Bayer coll., October 31, 1953. One specimen (USNM 574983). Gilbert Islands: Onotoa Atoll: in tide pool, 1 foot deep, on Heliopora flat. A. H. Banner coll., August 1, 1951. One specimen (USNM 575373). 39. Platydoris cf. flammulata Bergh, 1905 Caroline Islands: Ifaluk Atoll: from beneath boulders, outer elang of Elange- lap Id. Sta. No. 351. F. M. Bayer coll., September 20, 1953. One specimen (USNM 574961). Infraorder Phanerobranchia 277 Superfamily Nonsuctoria Family Gymnodorididae 40. Nembrotha nigerrima Bergh, 1877 Palau Islands: reef flat of Ngada- rak Reef, north of mouth of Malakal pass. Sta. No. 106. F. M. Bayer etal. coll., August 17, 1955. One specimen and slide with radula and labial cuticle (USNM 575671). Palau Islands: lagoon margin of reef, north of east point(Ngaremediu)of Uruk- thapel Id. Sta. No. 69. F.M. Bayer et al. coll., August 8, 1955. Two speci- mens (USNM 575668). Infraorder Porostomata Family Dendrodorididae 41. Dendrodoris nigra (Stimpson, 1855) Gilbert Islands: Onotoa Atoll: Sta. АТ-Ш. D. W. Strasburg coll., July 16, 1951. One specimen (USNM 575369). Gilbert Islands: Onotoa Atoll: reef flat, ocean side. J. E. Randall coll., September 9, 1951. One specimen (USNM 575370). Gilbert Islands: Onotoa Atoll: Sta. No. A-5. А. H. Banner coll., July 25, 1951: One specimen (USNM 575376). Family Phyllidiidae 42. Phyllidia (Phyllidia) varicosa Lamarck, 1801 Mariana Islands: Saipan: lagoon west side of Saipan. Sta. No. c-7-a. P.E. Cloud, Jr. coll., April 10, 1949. One specimen (USNM 574620). Mariana Islands: Guam: Oca Point. Sta. №. 102 :(255) .(Namru:2) ШО. Н. Johnson coll.; May, 1945. One speci- men (USNM 574210). Mariana Islands: Guam: small pools at zero tide, near Oca Point, D. G. Frey coll., November 20, 1954, One specimen (USNM 574353). Palau Islands: inner margin of reef, SW of Ngarduis, SE coast of Babel- 278 E. MARCUS thuap. Sta. No. 262. F. M. Bayer coll., November 4, 1955. Two specimens (USNM 575714). Caroline Islands: Ifaluk Atoll: Helio- pora zone south of Elangelap Id. Sta. No. 713. F. M. Bayer coll., October 23, 1953. One specimen (USNM 574977). Caroline Islands: [Ifaluk Atoll: in 20 feet in main pass. Sta. No. 742. Yaniseiman coll., October 25, 1953. One specimen (USNM 574982). Caroline Islands: Ifaluk Atoll: Elangelap Island. Sta. No. 626. R. R. Rofen coll., 1953. One specimen (USNM 574976). Marshall Islands: Bikini Atoll: tidal pools at tip of sand spit, western end of atoll. Sta. No. S-42-564. 1e ei Schultz and V. E. Brock coll., August 18, 1947. One specimen (USNM 574443). Gilbert Islands: Onotoa Atoll: In outer lagoon, slightly less than 4 miles north of and 85° west of Aiaki, Ma- neba. Sta. No. GOC 28. P. E. Cloud, Jr. coll., July 30, 1951. One speci- men (USNM 574933). Gilbert Islands: Onotoa Atoll: SE end of reef area known as Rakai Ati, south side of big windward point of reef, near center of atoll. Sta. No. GOC 36. PR. Cloud “Jr. coll.” August 20, 1951. One specimen (USNM 575372). 43. Phyllidia (Phyllidiella) pustulosa Cuvier, 1804 Palau Islands: north side of Uruk- thapel Island: in 0-7 ft. in shallow pass between Butottoribo Id. and next island to south, Sta. No. 27. Е. М. Bayer et al. coll., July 20, 1955. One specimen (USNM 575651). Palau Islands: Iwayama Bay: in 2-3 feet on reef flat, south shore of Island II, between shore and deep reef pool. Sta. No. 133. F. M. Bayer et al. coll., August 28, 1955. One specimen (USNM 575653). Caroline Islands: Kapingamarangi Atoll: lagoon reef at Ringutoro Island. Sta. No. 689. С. Handcoll., August 11, 1954. 575656). Caroline Islands: Kapingamarangi Atoll: Polim reef flat near Tipongowa- karam Pass, Greenwich (Ship) Pass. Sta. No. 724. C. Hand coll., August 12, 1954. One specimen (USNM 575654). Caroline Islands: Kapingamarangi Atoll: lagoon reef, Tapatuaitu Island. Sta. No. 862. С. Hand coll., August 21, 1954. One specimen (USNM 575- 655). Caroline Islands: Kapingamarangi Atoll: under boulder, lagoon side of emergent area, Tapatuaitu Island. Sta. No. 297. C. Hand coll., July 21, 1954. One specimen (USNM 575657): dark green in color with white pimples. Caroline Islands: Kapingamarangi Atoll: lagoon reef, Tapatuaitu Id. Sta. No. 862. C. Hand coll., August 21, 1954. One specimen in the collections of the U. 5. National Museum. Two specimens (USNM 44. Phyllidia (Phyllidiella) nobilis (Bergh, 1869) Caroline Islands: Ifaluk Atoll: under rocks, reef flat half way between Elange- lap and NW end of Falarik Island. Sta. No. 378. Е. М. Bayer coll., September 21, 1953. One specimen (USNM 574- 962). Caroline Islands: Ifaluk Atoll: from clump of Stylophora, in 2 1/2 feet of water at low tide, reef flat south of Elangelap Island. Sta. No. 382. F. M. Bayer coll., September 23, 1953. One specimen (USNM 574963). Caroline Islands: Ifaluk Atoll: be- neath rocks, Heliopora zone, between Elangelap and Ella Islands. Sta. No. 386. F. M. Bayer coll., September 23, 1953. Two specimens (USNM 574- 964). Caroline Islands: Ifaluk Atoll: in Heliopora zone, south of Elangelap Id. Sta. No. 713. F. M. Bayer coll., October 23, 1953. Two specimens (USNM 574- 978). Caroline Islands: Ifaluk Atoll: inl PR oe re AL = MICRONESIAN OPISTHOBRANCHIA fathom on reef flat, 800 feet from shore, west of northern end of Falarik Id. Sta. No. 802 (R. R. Rofen Sta. 146). Bakal, Tachim, Yarof, ©. Yark'call,, October 29, 1953. Two specimens (USNM 574984). Marshall Islands: Rongelap Atoll: intertidal at Naen Id. M. W. Johnson coll., July 17, 1946. One specimen (USNM 574230). 45. Fryeria rüppelli Bergh, 1869 Caroline Islands: Ifaluk Atoll: be- neath rocks, in Heliopova zone, reef between Elangelap and Ella Islands. Sta. No. 386. Е. М. Bayer coll., September 23, 1953. One specimen (USNM 574- 964). Caroline Islands: Kapingamarangi Atoll: north pass, Saratokmalei Reef, near Teawaitua Ship Pass. Sta. No. 784. C. Hand coll., August 14, 1954. One specimen (USNM 575692). Suborder Dendronotoidea Family Bornellidae 46. Bornella digitata (Adams and Reeve, 1848) Caroline Islands: Kapingamarangi Atoll: “microatoll”, Touhou Id. Sta. No. 88. C. Hand coll., July 2, 1954. One specimen (USNM 575691). Caroline Islands: Kapingamarangi Atoll: Sta. No.(173.)) CC. Hand. coll., One specimen (USNM 575695). Family Dotoidae 47. Doto cf. albida Baba, 1955 Palau Islands: Urukthapel Island: in 2-4 feet, outer reef at eastern end. Sta. No. 28. РЕ. M. Bayer et al. coll., July 21, 1955. One specimen and 1 radula slide (USNM 575673). Suborder Eolidoidea Infraorder Acleioprocta Family Cuthonidae 279 48. Catriona lonca spec. nov. (Figs. 23-26) Material: Palau Islands: Ngemelis Islands: 1 1/2 to 6 ft. on seaward reef flat at south end of Ngemelis Id. Sta. No. 61. F. M. Bayer et al. coll., August 6, 1955. One specimen. Description: Colorless: 1.5 mm long. Rhinophores andtentacles smooth, former twice as long as latter. Right rhinophore small, in regeneration; left tentacle wanting. Foot rounded in front, corners not elongated; tail pointed. Ce- rata fusiform, cnidosacs (ne) distinct. One anterior branch of digestive gland with 2 cerata; interhepatic space con- taining common genital aperture (g) and anus (ar); posterior liver with 4groups of cerata, the two first with 2 cerata each, the two hinder each with one ceras. Masticatory process of mandible with Single series of numerous high denti- cles. Radula consists of about 40 rows. Tooth low, median cusp receded from cutting edge due to its insertion lying farther back than bases of lateral den- ticles. Number of these 5-8; size varied. Alternate position of bigger and smaller denticles in succeeding teeth produces slanting rows along radula as in Doto (Marcus, 1959, f. 158; 1960a: 168), Miesea evelinae (Marcus, 1957: 466), and Catriona maua (id., 1960a:. 179). Penis bulbar, with cuticular, 40 u long stylet. Holotype: slug and slide with radula, jaw, and penial stylet (USNM 575707). 49. Catriona urquisa, spec. nov. (Figs. 27-30) Material: Caroline Islands: Ifaluk Atoll: washed from algae or sponge, from 1-3 feet, patch reefon lagoon shelf, about 75 feet from shore, Katelu area, SW Falarik Id. Sta. No. 144-E-7. D. P. Abbott coll., October 21, 1953. One Specimen. Description: Colorless: length 2 mm. Tentacles and rhinophores smooth and of equal size. Foot rounded in front, 280 E. MARCUS without lengthened corners; tail pointed. Cerata short, blunt, cnidosacs (ne) one third of their length. Anterior liver one horseshoe with 5 cerata, posterior diges- tive gland with 3 rows of 3, 3 and 2 ce- rata. Anal papilla (ar) in interhepatic space, near first group of posterior liver. Genital aperture (g) between limbs of an- terior horseshoe. Masticatory process of jaw with about 60 saw-like denticles. Radula of 21 teeth. Smallest, oldest tooth 22 u high and broad, newest one 50 y high and broad. First with receded median cusp and 3 lateral denticles on each side. In later developed teeth recession of middle cusp less pronounced; 4-5 lateral denticles, lower and thicker than older ones. Minute cuticular stylet of penis and absence of accessory penial gland observed in sections. Holotype: hind end of slug and two slides: one with radula and jaw, one with transverse sections of anterior part (USNM 575710). Discussion of Catriona lonca and C. urquisa: My reason for the use of the generic names Catriona and Cratena was recently published (Marcus, 1960c: 258). Only few species of Catriona have less than 3 rows of cerata on the right digestive gland. C. bylgia (Bergh, 1870: 4) differs by broadened jaws from the present species; C. cucullata (Bergh, 1905: 230) by black color marks, still present in preserved slugs. С. susa Marcus (1960b: 916) whose tooth is similar in shape to that of urquisa has 36 teeth with the same body length and 32 denticles on the masticatory process. Further Indo-West Pacific cuthonids which must be compared are En- noia briareus Bergh (1896: 393) and Myja longicornis Bergh (1896: 391). The first has 2 anterior liver FIGS. 32-36. Noumeaella rehderi, sp. n. and denticles of masticatory process. smooth masticatory border, the second, one group as lonca, but groups, and unarmed penis; right liver no stylet. Two West Atlantic species of Catriona with 1-2 ducts of the anterior digestive gland (Marcus, 1957: 459; 1958: 45) differ from lonca and urquisa by man- dibles and radulae. The Indo-West Pacific eolidaceans whose position of the anus and rami- fication of the anterior liver have not been described were compared with Catriona lonca and C. urquisa according to the pharyngeal armature. Infraorder Cleioprocta Family Favorinidae Subfamily Favorininae 50. Pteraeolidia semperi (Bergh, 1870) Palau Islands: Iwayama Bay: craw- ling on rocks among hydroids, coral shelf, west shore of SE peninsula of Ko- ror Id., mouth of Kakisuidó (Oyster Pass) between Islands XXIX and east end of Koror. Sta. No. 236 A. Е. М. Bayer, R. R. Rofen, Rikrik coll., October 18, 1955. Three specimens and 1 slide with radula and jaws (USNM 575658). These animals were of a pale violet color. Palau Islands: in 2 1/2-3 1/2 ft., at night on reef flats south of Ngaremediu (Raeldil) Sta. No. 254. F. M. Bayer et al. coll., October 27, 1955. One specimen (USNM 575659). Caroline Islands: Kapingamarangi Atoll: lagoon edge of lagoon reef, Tiatua Island. Sta. No. 173. C. Hand coll., July 13, 1954. (USNM 575660). Two specimens 51. Phyllodesmium hyalinum Ehrenberg, 1831 FIG. 32. Rhinophores from behind. FIG. 33. Jaw FIG. 34. Radular tooth. FIG. 35. Diagram of repro- ductive organs, reconstructed from serial sections. FIG. 36. Right side view. FIGS. 37-41. Muessa evelinae, g.n., Sp.n. FIG. 39. Radular tooth. FIG. 40. Penial stylet. masticatory denticles. FIG. 37. Right side view. FIG. 38. Jaw and FIG. 41. Diagram of reproductive organs, reconstructed from serial sections. MICRONESIAN OPISTHOBRANCHIA 281 282 E. MARCUS Palau Islands: in 0-1 feet, reef flat on outer barrier reef about 2 miles SSW of Ngaremediu District, east of Urukthapel Id. Sta. No. 111. F. M. Bayer et al. coll., August 19, 1955. One specimen and slide with radula and jaws. (USNM 575650). 52. Noumeaella rehderi spec. nov. (Figs. 31-36) Material: Palau Islands: Ngemelis Islands: in 1 1/2-6 ft., seaward reef flat at south end of Ngemelis Island. Sta. No. 61. F. M. Bayer et al. coll., August 6, 1955. One specimen. Description: Colorless; length3.5 mm, cerata 1 mm, cnidosacs 0.15 mm. Head broad, widened laterally; tentacles short; rhinophores with thick cluster of papil- lae on hind side, smooth in front. Foot projecting along body sides, anterior border grooved, groove accompanies projecting corners. Body tapering back- wards. Cerata slender, in widely spaced groups. Anterior liver a horseshoe whose cerata are inserted in one series, inter- hepatic space broad, containing genital aperture (g). Posterior liver with 4 groups of cerata, the first a horseshoe, the 3 following ones slanting rows. Number of cerata on right (left) side: 10 (6); 9 (6), 4 (4), 2 (2), 2 (1). Anus behind anterior limb of first group of posterior liver. Masticatory border of jaw with single series of about 40 rough denticles. Ra- dula with 18 rows, central cusp pointed, 6-7 rather short, sharp lateral denticles on each side. Hermaphrodite duct (h) enters short, bag-shaped ampulla (a). Spermoviduct (so) bifurcates some distance from outlet of ampulla. Male duct first simple (se) continues prostatic (q) for most of its length; muscles of ejaculatory duct (d) thickened to bulbar penis (p) ending with smooth stylet. Inner oviduct (oi) enters voluminous lobed spermatheca (s) where sperms lie withheads attached to wall. Vagina (v) narrow. Outlet of gland mass (f) or nidamental duct (ni) passes into common atrium (am) with enormous sphincter (sr). Named for Dr. Harald A. Rehder. Holotype: fore and hind end of slug in vial, and two slides: one with radula and jaw, one with transverse serial sections of region of gonopore (USNM 575706). Discussion: Similar rhinopores as in the present species occur in Berghia Trinchese, 1877, and Baeolidia Bergh, 1888, both with pectinate radular teeth. Among the Eolidacea with cuspidate teeth these rhinopores are known in Moridilla Bergh, 1888, and Noumeaella Risbec, 1937. As Moridilla belongs to the Facelinidae and has an unarmed penis, it cannot receive the present species. Noumeaella curiosa Risbec (1937: 163; 1953: 159) has the same type of rhino- phores, an armed penis, a very similar- shaped jaw with one row of denticles, first and second groups of cerata as horseshoes, identical position of the gonopore, and similar number (16) of radular teeth with 8 denticles on each side. Hence I infer that Noumeaella curiosa belongs to the Cleioprocta, though this is not evidenced in Risbec’s system (1953: 120). N. curiosa differs from N. rehderi by still shorter lateral denticles of the radular tooth and spine-like irregular tubercles of the penial stylet. Muessa, gen. nov. Cleioproct Eolidacea with cuspidate radular tooth (against Aeolidiidae), a single branch of the right digestive gland (liver) and its left counterpart (Favor- inidae) and a single row of cerata on it (Favorininae). Cerata ovoid, all in short rows. Jaws oblong, masticatory border with one series of few broad denticles with rough edge. Large middle cusp of radular tooth accompanied by strong denticles. Penis with cuticular stylet. Type-species: Muessa evelinae, spec. nov. The annulate tentacles and rhinophores of the type-species are not included in the diagnosis of the genus, because the MICRONESIAN OPISTHOBRANCHIA 283 shape, at least ofthe rhinophores, cannot be utilized for generic distinctions in Facelinidae and Favorinidae (Marcus, 1957: 474; 1958: 60; 1960b: 924). Never- theless, annulate tentacles are excep- tional even in preserved specimens of these families. I considered allocating the new species to Herviella Baba (1949: 107, 180), a favorinine genus with seriate cerata. However, the jaw and the Globiferina- like cerata of the present species differ widely from the type-species of Her- viella, H. yatsui Baba, 1949 (l. c.) whose penial armature was not des- cribed. In Globiferina noumeae Risbec (1937: 163; 1953: 157) the penis is unarmed, and the anus lies in the interhepatic space, hence the species is acleioproct. A singularly dentate jaw occurs also in Phyllodesmium, but its denticles are unlike those of the present species. Phyllodesmium Ehrenberg, 1831, must be added tothe Favorininae whose genera were mentioned recently (Marcus, 1960b: 922). Its type-species, P. hyalinum, is represented in the present collection by a specimen from the Palau Islands. 33: Е 7: 1937: pl. 2, 8515) gave good figures of this Species. Ennoia longicirrha Bergh (1905: 234) is cleioproct and may be a Cratena, though the absence of penial armature was not stated; evidently it belongs to the Favorininae. Its anterior liver and the 2 first branches of the posterior digestive gland are horseshoes. The acleioproct type-species of Ennoia is mentioned here in the discussion of the 2 species of Catriona. 53. Muessa evelinae spec. nov. (Figs. 37-41) Material: Caroline Islands: Ifaluk Atoll: washed from algae, intertidal “fossil reef”, at junction of outer and inner reef flats, east of south end of Falarik Id., Sta. No. 83-0-4. D. P. Abbott coll., September 29, 1953. One specimen. Description: Yellowish, as if it was preserved in picric liquid; minute black rings, principally subepidermal, onhead, cephalic appendages, back, and some on sides of body. Length, when extended, 3 mm, breadth 0.8 mm, cerata 0.6 mm. Tentacles and rhinophores annulate, for- mer longer than latter. Foot rounded in front; tail long, pointed. Cerata egg- shaped, cnidosacs (ne) broad. Anterior liver one group of 3 cerata, posterior liver with 3 groups of 3, 2 and 1 ceras. Genital aperture (g) behind anterior group, anus (ar) below cerata of second. Buccal cavity with sculptured cuti- cle. Mandible as described in diag- nosis of genus. Radula with 14 dark brown teeth; middle cusp broad, prom- inent, 2-5, generally 3-4, strong den- ticles on each side. Hermaphrodite duct (h) dilated into oblong ampulla (a) containing sperm. Male (se) and female (oi) duct separate at outlet of ampulla. Efferent duct muscular in central, prostatic (q) in peripheral course;, penis (p) ends with 70 uy long cuticular stylet. Male atrium (ma) glandular, entering common atrium (am) together with wide female duct (eu). Vagina and nidamental duct united. Dilatation. of female duct between gland mass (f) and constriction of female duct may be spermatheca, but no sperms found in it. Named for Mrs. Eveline du Bois- Reymond Marcus. Holotype: hind end of slug and two slides: one with radula and jaws, one with transverse serial sections of anterior part, (USNM 575711). LITERATURE CITED ALLAN, J., 1933, Opisthobranchs from Australia. Rec. Austral. Mus., 18 (9): 443-450, pl. 56. BABA, K., 1933, Supplementary note on the Nudibranchia collected in the vi- cinity of the Amakusa marine biologi- cal laboratory. Annot. Zool. Jap., 14 (2): 273-283, 8 figs. , 1935, The fauna of Akkeshi 284 pan. I. from Japan. Bay. I. Opisthobranchia. Journ. Fac. Sci. Hokkaido Univ., Ser. 6, Zool. 4: 115-125, pl. 7-8. , 1937, Opisthobranchia of Ja- Journ. Dept. Agriculture Kyushu Univ. Fukuoka, 5: 289-344, pl. 1-2. , 1949, Opisthobranchia of Sagami Bay. Tokyo, Iwanami Shoten, 194 + 7p, 50 pls. , 1953, Three new species and two new records of the genus Glos- sodoris from Japan. Publ. Seto mar. biol. Labs 3 (2): 205-211)" 6 figs: 19090; Opisthobranchia of Sagami Bay. Supplement. Tokyo, Iwanami Shoten, 59 p, 20 pls. ‚1959, The family Stiligeridae Publ. Seto Mar. Biol. Lab., 7 (3): 327-334, pl. 27-28. BASEDOW, H. and HEDLEY, C., 1905, South Australian nudibranchs, and enumeration of the known Australian species. Tr: "Dr. Rep» Roy. “Soc: South Austr., 29: 134-160, pl. 1-12. BERGH, R., 1870, Malacologische Un- tersuchungen, Jn Semper, C. (ed.), Reisen im Archipel der Philippinen. 2. Theil. Wissenschaftliche Resultate. Wiesbaden, 1 (1): 1-30, pls. 1-8. , 1877, Ibid., 2 (11-12): 429- 546, pls. 54-61. , 1882, Beiträge zur Kennt- niss der japanischen Nudibranchien. II. Verh. Zool. Bot. Ges. Wien (1881), 31: 219-254, pl. 6-10. ‚1883, Beiträge zu einer Monographie der Polyceraden. IH. Verh. Zool. Bot. Ges. Wien, 33: 135- 180, pl. 6-10. , 1884, Malacologische Un- tersuchungen, In Semper, C. (ed.), Reisen in Archipel der Philippinen. 2. Theil. Wissenschaftliche Resultate. Wiesbaden, 3 (15): 647-754, pl. 69-76. ‚ 1890, Ibid., (17): 873-991, pl. 85-89. , 1896, Eolidiens d’Amboine. Rev. Suisse Zool., 4: 385-394, pl. 16. , 1904, Malacologische Un- tersuchungen, Jn Semper, C. (ed.), Reisen im Archipel der Philippinen. ELIOT; C::N2, 71903: E. MARCUS 2. Theil. Wissenschaftliche Resultate. Wiesbaden, (see 1870), 6 (1): 1-55, pl. 1-4. , 1905, Die Opisthobranchiata der Stboga-Expedition. т Weber, M. (ed.), Siboga-Expedition, Monogr. 50, 248 p, 20 pls. Nudibranchiata with some remarks on the families and genera and description of a new genus Doridomorpha. In Gardiner, J. St., The fauna and geography of the Maldive and Laccadive Archipelagoes, 2: 540-573, pl. 32. Cambridge. , 1904, On some nudibranchs from East Africa and Zanzibar. Pt. 4. Proc. zool. Soc. London 1904, 1: 380-406, pl. 23-24. , 1905, Nudibranchs from the Indo-Pacific: I. J. Conch., 11: 237- 256. FARRAN, G. P., 1905, Report on the opisthobranchiata Mollusca. Jn Herd- man, W. A. (ed.), Ceylon pearl oyster fisheries, 3 suppl. rep. No. 21, Lon- don (Royal Soc.), p 329-364, pl. 1-6. MARCUS, E., 1957, On Opisthobran- chia from Brazil (2). J. Linn. Soc. London, Zool., 43 (292): 390-486, 246 figs. , 1958, On Western Atlantic opisthobranchiate gastropods. -Amer. Mus. Novit., (1906): 1-82, 111 figs. + 1950 Lamellariacea und Opisthobranchia. Lunds Univ. Arsskr. N. F. Avd. 2, 55 (6): 1-133, 196 figs. MARCUS, E. and MARCUS, E., 1956, On two sacoglossan slugs from Bra- zil. Amer. Mus. Novit., (1796): 1- 21, 23 figs. , 1960a, Opisthobranchs from American Atlantic warm waters. Bull. Mar. Sci. Gulf and Caribbean, 10 (2): 129-203, 97 figs. , 1960b, Opisthobranchia aus dem Roten Meer und von den Male- diven. Akad. Wiss. Lit. Mainz, Math.- Natur. Kl. Jahrg. 1959, (12): 871-934, 86 figs. , 1960c, Some opisthobranchs from the Northwestern Gulf of Mexico. Publ. Inst. Mar. Sci. Univ. Texas, MICRONESIAN OPISTHOBRANCHIA 6 (1959): 251-264, 19 figs. , 1963, Opisthobranchs from the Lesser Antilles. Stud. Fauna Curacao, 19 (79): 1-76, 68 figs. ODHNER, N. H., 1957, Chromodoris contra Glossodoris. A systematic- nomenclatorial controversy. Proc. malacol. Soc. London, 32: 250-253, 2 figs. S PRUVOT-FOL, A., 195la, Etudes des nudibranches de la Méditerranée (2). Arch Zool. Exp. Gen., 88: 1-80, pls. 1-4. ‚ 19516, Révision du genre Glossodoris Ehrenberg, J. Conchyl., 91: 76-164. , 1954a, Mollusques opistho- branches. Faune de France, No. 58. Paris, Paul Lechevalier, 460 p, 173 figs., 1 pl. В ‚ 19545, Etude d’une petite collection d’opisthobranches d’Océ- anie Francaise. J. Conchyl., 94: 3- 30, 37 figs. RISBEC, J., 1937, Note préliminaire au sujet de nudibranches Néo-Calé- et anatomiques sur 285 branches de la Nouvelle-Calédonie. Faune de l’Union Française, No. 15, Paris, Librairie Larose, 189 p, 126 figs. SIMROTH, H., 1895, Die Gastropoden der Plankton Expedition. /n Ergebn. Plankt. Exped. Humboldt-Stiftg., 2 (F. d.): 206, 22 pls. STIMPSON, W., 1855, Descriptions of some new marine Invertebrata. Nudi- branchiata. Pr. Acad. Nat.Sci. Phila- delphia, 7 (10): 388-389. VAYSSIERE, A., 1888, Recherches zoologiques et anatomiques sur les mollusques opisthobranches du Golfe de Marseille. II. Nudibranches (cir- robranches) et ascoglosses. Ann. Mus. Hist. nat. Marseille, Zool., 3: mem. 4, 1-160, pl. 1-7. , 1898, Monographie de la fa- mille des Pleurobranchides. Ann. Sci. Nat., Ser. 8, Zool., 8: 209-402, pl. 13-28. , 1912, Recherches zoologiques les opistho- branches de la Mer Rouge et du Golfe doniens. Bull. Mus. natl. Hist. nat. d’Aden. II. Ann. Fac. Sci. Marseille, ’ Paris, Ser. 2, 9: 159-164. (1911, Suppl.) 20: 5-158, pl. 1-11. ‚ 1953, Mollusques nudi- ZUSAMMENFASSUNG UBER EINIGE MIRKONESISCHE OPISTHOBRANCHIER Eine Sammlung des U. S. National Museums von 130 Opisthobranchiern aus Mikro- nesien enthielt 53 Arten. Nur 10 Arten sind neu und 5 von diesen unter 5 mm lang. Diese niedrigen Zahlen zeigen die Einheitlichkeit der indo-westpazifischen Riff- Fauna, deren grössere Hinterkiemenschnecken grossenteils schon bekannt sind. Die hier beschriebenen neuen Arten sind: Stiliger (Ercolania) illus, Elysia bayeri, Elysia тата, Hypselodoris cuis, Discodoris lora, Discodoris ylva, Catriona lonca, Catriona urquisa, Noumeaella rehderi, und Muessa evelinae, der Gattungstyp einer neuen Gattung der Favorinidae, verwandt mit Herviella. RESUMEN SOBRE ALGUNOS OPISTOBRANQUIOS DE MICRONESIA De una coleccion de 130 especimenes de opistobranquios de Micronesia pertene- ciente al Museo Nacional de Estados Unidos, y compuesta de 53 especies, sólo 10 eran neuvas y la mitad de estas de longitudes menores a 5 mm. Esta pequeña cantidad señala la uniformidad de los opistobranquios en los arrecifes del Océano 286 E. MARCUS Indo-Pacifico occidental, cuyas especies de mayor tamafio son en su mayoria cono- cidas. Se describen las siguientes especies: Stiliger (Ercolania) illus, Elysia bayeri, Elysia ratna, Hypselodoris cuis, Discodoris lora, Discodoris ylva, Catriona urquisa, Noumeaella rehderi, y Muessa evelinae especie tipo de un género nuevo de Favorin- idae, afin to Herviella. RESUMO SOBRE ALGUNS OPISTHOBRANQUIOS DA MICRONESIA Entre 130 lotes de opistobranquios da Micronésia, pertencentes ao U.S. National Museum, houve 53 especies das quais apenas 10 s4o novas. O comprimento da metade das últimas é aquém de 5 mm. Estes números baixos mostram a uni- formidade da fauna dos opistobránquios dos recifes no Indo-pacífico ocidental,cujas especies maiores ja se conhecem, em grande parte. As novas espécies aqui des- critas s4o: Stiliger (Erocolania) illus, Elysia bayeri, Elysia тата, Hypselodoris cuis, Discodoris lora, Discodoris ylva, Catriona lonca, Catriona urquisa, Noumeaella rehderi, e Muessa evelinae, o tipo dum novo género das Favorinidae, parente de Herviella. MALACOLOGIA, 1965, 3(2): 287-307 “GROWTH RINGS” IN THE BEAKS OF THE SQUID 1 MOROTEUTHIS INGENS (OEGOPSIDA: ONYCHOTEUTHIDAE) Malcolm R. Clarke National Institute of Oceanography, Wormley, Godalming, Surrey, England ABSTRACT The present work, which describes cycles of growth lines (microrings) in the lower beaks of Moroteuthis ingens, intends to draw attention to the possibilities of relating cycle formation and time of growth of the squid. The study is based опа large sample of beaks collected from stomachs of sperm whales caught at Durban. Features used in identification (Fig. 1) are described. On the medial surfaces of the lateral walls of these beaks 4 features are visible (Fig. 2): ridges radiate from the rostral tip to the free edge and, running parallel with the free edge, there are minute steps or microrings, undulations and “lines” of varying transparency. Microrings constitute a record of the extension of the la- teral wall during growth. Cycles of microring width between the rostral tip and the free edge can be recognised. Variation in the form of cycles in 50 beaks is described and it is shown that the first 3-4 cycles usually follow a definite pat- tern while later cycles vary considerably (Fig. 3). Very little wear of the ros- tral tip takes place during life in the size range studied (rostral length 0. 7-2.0 cm). Frequency histograms and means of the number of microrings in each cycle show that cycles cannot be formed by random fluctuations of secretion 5 alone even if such fluctuations were biased by later cycles being narrower than earlier cycles. Beak growth can be conveniently expressed as increase in wall length, which is the distance from the rostral tip to the anterior and inner cor- ner of the lateral wall (Fig. 2). Since the history of the growth in wall length is recorded by the distance of the microrings from the rostral tip, growth may be “back-calculated”. Increase in beak size with increase in the number of cycles has been plotted, as well as a back-calculated curve not subject to any bias due to selection by the whale (Fig. 8). Back-calculated wall lengths from older beaks (more cycles) give lower values than those from younger beaks probably because the more slowly growing squids survive longer. The relationship between wall length and the size of the squids has been plotted (Fig. 10, 11). Thetimetakenfor a cycle to be secreted has not been established, but tentative reasoning, based en previous studies of other cephalopods, suggests 6 or 12 months. INTRODUCTION groups or the analysis is complicated by migrations. However, growth has Little information is available on the been studied in several cephalopods growth of cephalopods: they dc not which are found on the continental shelf live for long in aquaria and field sam- at some time during the year, notably ples are either too small to show age in the loliginids Loligo vulgaris, by 1 This paper is based on part of a talk given at the “Symposium on the Mollusca” of the Zoologi- cal Society of London, on the 5th of March, 1964. (287) 288 M. R. CLARKE A INNER wing medial surface of wing fold of hood-wing structure rostral edge rostral tip rostrum hood OUTER medial surface of right lateral wall inner edge of left lateral wall free edges posterior edge of left lateral wall POSTERIOR lateral surface of left lateral wall fold of lateral wall FIG. 1. A diagram of the lower beak of Moroteuthis ingens to show the terms used in the text. Terms underlined describe features characteristic of onychoteuthid beaks. Large arrows indi- cate surfaces upon which material is deposited during growth. Small open arrows indicate the growing edges. Tinbergen and Verwey (1945), and Lo- ligo opalescens by Fields (1950, 1963); the ommastrephids Шех illecebrosus by Squires (1957), Ommastrephes sloanei by Katoh (1959), and Todarodes sagit- tatus by Fredriksson (1943); and the octopod Eledone cirrosa by Wirz (1963). Growth in these species has been studied by examining the size groups in the pop- ulation and by finding the shift in the mean size through the year. Both these methods have disadvantages which would be avoided if some method of age determination, similar to scale or otolith reading in fish, could be dis- covered. Such a method has been found in some species of Sepiidae, as pointed out by Yagi (1960) and Choe (1963), who have shown the average number of days in which a growth “stripe line” in the cuttle bone is secreted. In order to find a method of age determination Tinbergen and Verwey (1945) examined the beaks of Loligo vulgaris and Wirz (1963) examined beaks and radulas of various cephalopods: no method was discovered. The present work describes cycles of growth indicated by “growth lines” or microrings on the lower beak of Moro- teuthis ingens. It has not proved pos- sible so far to identify these with time of growth. Similar cycles are present in beaks of many species and this des- cription is intended to draw attention to them so that a correlation between time and cycle formation can be investi- gated in species at present being studied by other workers. DESCRIPTION AND MATERIAL The descriptive terms used in this paper are evident from Figs. 1 and 2. GROWTH RINGS IN BEAKS OF MOROTEUTHIS 289 Most of these have already been defined (Clarke, 1962) but it has been necessary to introduce several new terms for the present purposes. Surfaces facing the sagittal plane of the beak and animal are termed medial, those facing away from the sagittal plane are lateral; the inner side is that which lies towards the upper beak when in situ andthe outer side is that which lies away from it. The lower beak is bilaterally symme- trical with each half consisting of several thin chitinous sheets: a lateral wall is fused along its anterior border to a hood with an inward extension beyond the la- teral wall termed the wing. A small trapezoid or triangular sheet of chitin joins the lateral wallatits inner anterior corner to the wing and this has been called the medial surface of the wing. The jaw angle is the angle between the medial surface of the wing and the ros- tral edge formed by the fusion of the lateral wall and the hood. The rostrum is a term derived by analogy with the upper beak in which its limits are dis- tinct and here it is used generally to mean the part of the beak from the jaw angle to the rostral tip including the hood and the anterior part of the lateral wall. The wall length is the distance from the rostral tip to the inner anterior corner of the lateral wall (Fig. 2). The present study is based on beaks, identified by the author as those of Moroteuthis ingens, taken from the sto- machs of 14 sperm whales caught off Durban, South Africa in 1962 and 1963. Of these, sub-samples of the beaks collected from a whale killed in June 1962 and another killed in September 1962 were selected for a more detailed examination. All the beaks were not Suitable for all parts of the study and fewer beaks were necessary for certain purposes. A maximum of 292 anda minimum of 39 beaks were used for various parts of the detailed morpholo- gical work. The beaks of 2 other onychoteuthid Species, Moroteuthis robsoni and Tetronychoteuthis sp., were also present in the stomachs. While the beaks of these latter species were associated with flesh, those of M. ingens were entirely devoid of flesh and this may suggest that they had been ingested some time pre- viously in the Antarctic, where the spe- cies is found intact in whale stomachs. For identification, lower beaks from the Durban whales were compared with beaks from complete specimens ofthese 3 species as well as with beaks of 2 other onychoteuthid species. Features distinguishing the beaks of the family Onychoteuthidae (underlined in Fig. 1) are briefly: a clearly de- fined fold of the lateral wall; an obtuse jaw angle; a jaw angle which is hidden from the side by the forward protrusion of the hood-wing structure; a slight step between the medial surface of the wing and the anterior end of the lateral wall due to the fact that the inner end of the rostral edge lies inside and medial to the point where the shoulder is inserted into the rostrum; and the hood is short from front to back compared with the crest. Moroteuthis beaks are further charac- terised by having a fold of the lateral wall which intersects the posterior edge at about half way between the crest and the inner edge of the wall (also noted in Clarke 1962). Moroteuthis ingens and M.robsoniare the only species of this genus known to occur in Antarctic or South African waters and this supports the identifi- cations. If the lower beak of Moroteuthis in- gens is cut on the left side ofthe rostral tip and the medial surface of the lateral wall so exposed is viewed by oblique reflected light, 3 features can be seen (Fig. 2, A). Ridges radiate from the ros- tral tip to the inner and posterior, free edges of the wall, while 2 other features which may be described as undulations and microrings run roughly parallel with these free edges. The latter 2 features are diagrammatically represented in Fig. 2, B. In addition, “lines” of varying colour or transparency, which corres- 290 M. R. CLARKE Icm eee radiating ridges undulations microrings one microring ES, variation in transparency QA A undulation FIG. 2. A. The medial surface of the right lateral wall exposed to show the microrings, undula- tions and radiating ridges. The limits of 7 cycles are indicated by numbers in white areas. Cycle 3 contains the stable region. Limits of the wall length and rostral length are shown. B. A short section of the lateral wall cut along a radiating ridge adjacent to the free edge. It is not to scale and merely illustrates the terms “microring”, “undulation” and “variations in trans- parency”. GROWTH RINGS IN BEAKS OF MOROTEUTHIS 291 pond in position to the microrings, are visible by transmitted light near the free edge of the lateral wallin this species. The microrings constitute a record of the extension of the lateral wall during the growth of the beak. The beak is secreted by an epithelium which adds chitinous material on the pos- terior side of the hood and wings and on the lateral side of the lateral wall (sur- faces indicated by large arrows in Fig. 1). As growth proceeds, the secreting area expands so that the chitinous ma- terial overlaps the edges of the growing surface (edges indicated by small open arrows in Fig. 1). This overlapping gives rise to the microrings on the me- dial surface of the lateral wall, which are really minute steps suggesting that growth is not a steady, continuous pro- cess. In surface view the flat part of each step (microring) is limited by 2 thin “lines”, the vertical components of adjacent steps. The width of the micro- rings varies and the variations occur in a series of cycles running from the rostral tip to the free edges of the la- teral wall (Fig. 2). This cyclic arrange- ment is indistinct in some regions of nearly every beak, but by careful examination, it has proved possible to find cycles along the lengths of over 99% of the beaks examined. The ar- bitrary limit of each cycle has been taken as the posterior margin of the broadest microring in that cycle (Fig. 3). The mean width of the cycles gradu- ally decreases from the rostral tip to the free edges of the lateral wall. Be- Sides this decline, which is not usually regular, there are several possible variations in the microring composition of the cycles (Fig. 3). Table 1 sum- marizes the results of examining the cycles of 50 beaks and provides infor- mation for a rough general outline of the “usual” course of growth inthe beak. It must be stressed that all possible intermediates exist between these forms ¡and their grouping is, therefore, rather | subjective. N y ЕЕ IA Е ee ; y АДД ААА АПУ у = PET TT TIM TT TTT (i to ge oe e y LITE DDN EEC нев FIG. 3. Diagrams to illustrate different types of cycle. The upper figures represent a sur- face view and the lower figures indicate the increasing or decreasing fluctuations in width of the microrings. Cycle limits are indicated with arrows. A. Two cycles showing agra- dual increase and then a sharp decrease at the onset of the next cycle. B. Two cycles show- ing a steady decrease and then a steady in- crease. C. Twocycles showing a steady de- crease followed by a sharp increase at the on- set of the next cycle. D. Two cycles showing little change except for a marked increase at the last microring. Often, the 2 earliest cycles (i. e., nearest the rostral tip) do not have step-like microrings but only undula- tions. However, these undulations may be considered as microrings for our purposes because, in some beaks, both undulations and microrings are present and they coincide very closely in ar- rangement and position. From the first (earliest) one visible, the microrings gradually increase in width to the end of the first cycle. This type of cycle 292 M. R. CLARKE 30 25 20 n м < a at 15 O o z 10 5 O N° OF MICRORINGS FROM LAST BROADEST TO EDGE o o) 30 25 (= a x nz O вое ww ud Zw gas 12 < gb 10 (0) 6 10 “8 o < Ô 5 o 4 75 2 O O EO. Fl 12:3 1:4: 15 1:6 [7 1-8 [9 20 сем | 2'3'4'5'6'7'8. 9 IO LOWER ROSTRAL LENGTH N® OF MICRORINGS IN STABLE REGION FIG. 4. A. Frequency histograms to show the number of microrings between the limit of the last full cycle and the free edge of the lateral wall. A sample of 53 beaks taken in September (hatched) and a sample of 175 beaks taken in June are shown; mean values are indicated by ar- rows. B. A plot of the number of microrings between the rostral tip and the first microring of the “stable” region against the rostral length in a sample of 39 beaks. The mean number of mi- crorings to the start of the “stable” region is indicated by an arrow. C. Frequency histogram showing the number of microrings in the “stable” region. The mean value is indicated by an arrow. GROWTH RINGS IN BEAKS OF MOROTEUTHIS 293 and a rough indication of changes in growth of the microrings is shown in Fig. 3, A. The second cycle is in general, similar in form to the first. In the second or third cycle a num- ber of microrings have a very uniform width and in 80% of (46) beaks there are 3-12 microrings which are equal in width (Fig. 4, C). The position of the first microring of this “stable” region varies from the 7th to the 34th microring counted from the rostral tip in the sample (39 beaks) examined (Fig. 4, B). Following this “stable” region, there is nearly always a cycle which varies from beak to beak but is characterised by having some extremely narrow, in- conspicuous microrings. Up to this point the undulations have more or less coincided with the. microrings but from here onwards undulations very roughly approximate to the cycles in position. This cycle, which is usually the fourth (but is sometimes the third), is easily recognised because it consists of a broad undulation with very minute micro- rings on it. It, and the following (later) cycles can all take any of the forms shown in Fig. 3, A-D or intermediate forms but there is a tendency towards type D in the later cycles of the older beaks (Table 1). WEAR OF THE BEAK Clearly, if the lateral wall is worn away at the rostral tip to any appre- ciable extent,the cycles cannot be uti- lised for age studies. Fortunately, in the size range examined (lower ros- tral length 0.7-2.0 cm), wear is not appreciable. If microrings did dis- appear by wear, there would be a nega- tive correlation between the number of microrings between the rostral tip and the stabla region and the size of the beak (as shown by rostral length) and such a correlation is not found (Fig. 4, B based on 39 beaks). Nor is such a negative correlation found when the distance from the rostral tip to the end TABLE 1. Types of cycles observed in 50* lower beaks of Moroteuthis ingens Position of cycle from rostral tip Totals2 2Totals are not 50 for all cycles given in this table because some cycles were too indistinct to recognise which type of microring con- figuration was present. 3Types as in Fig. 3. of the first cycle is plotted against the rostral length. Further evidence sug- gesting the loss of few if any micro- rings is that the microrings curve away from the rostral tip just prior to meeting the jaw edge (Fig. 2, A) and, although the distance between the inflection and the jaw edge does decrease towards the ros- tral tip, only the few microrings nearest the tip have lost the inflection altogether. Thus, if loss of microrings does occur, few are involved and we can be con- fident that no complete cycles are lost during the growth of the beak in the size range examined here. How many early cycles are not represented in these beaks is not known. MICRORINGS IN EACH CYCLE The number of microrings in each cycle were counted and the means, standard deviations and standard errors were found for each cycle counting from the tip to the free or growing edge (Table 2; Fig. 5). To avoid subjec- tivity, the limits of cycles were always marked with white ink before micro- rings were counted. Frequency histo- 294 M. R. CLARKE 16 218 140 139 126 Ю 95 86 62 38 2! 2 6 2 | D о №. ОЕ MICRORINGS œ o) 2 4 6 8 10 12 14 CYCLE No FIG. 5. Number of microrings in successive cycles. Means (circles), standard deviations (lines) and the number of beaks are indicated. grams (Fig. 6) of these same counts show a great range with peaks at from 12 in the 1st cycle to about 8 in the 11th cycle; their means are between 8 and 12 (Fig. 5) and they are not conspicuously skewed in either direction. These 3 properties of the histograms (i.e. mode at 8-12, mean at 8-12 and lack of any definite skewness) enable us to see whether the cyclic pattern could arise merely by random fluctuations in se- cretion or if we must look for some other reason for their existence. Ifran- dom fluctuations of secretion produced the cycles, each microring would have an equal opportunity of being either broader or narrower than the previous microring formed. One would then expect a large number of cycles to consist of only 2 microrings because, from the definition of a cycle, a new cycle is started when a narrower microring follows a broader microring. One would not expect every cycle to consist of 2 microrings; but, if the number of microrings in each cycle were plotted as a histogram, one would expect a number of cycles with 2 microrings andthena decreasing number with 3, 4, 5 etc., microrings, i.e., a positively skewed distribution with a mode at 2. Further, if the mean num- ber of “microrings” in each“cycle”is calculated for this skewed distribution, it is found to be about 4 “microrings” per “cycle”. (This was checked by tossing a coin, taking ‘obverse’ to re- present broader than the previous micro- ring and ‘reverse’ to represent narrower than the previous microring. Every time the reverse followed the obverse a “cycle” was commenced and the number of tosses in each “cycle” gave the num- ber of “microrings”). Thus, the dis- tributions derived by counting the num- ber of microrings in each cycle of the beaks have a different mode, mean and skewness to any cyclic pattern which could arise from unbiased random fluc- tuations in secretion. The cycles which are first formedare broader than the later cycles. This may be seen by reference to Fig. 8 in which the back-calculated mean wall lengths are plotted. The latter are found by measuring from the rostral tip to suc- cessive cycles. It will be seen that a line drawn through the means, curves downwards towards the cycles formed more recently, i.e., cycles secreted early in life are broader than those se- creted later. This fact. suggests that there may be a bias during microring formation and this could result incycles having more microrings. If such a bias Operated and a microring was more likely to be narrower than the previous microring secreted, one would expect many cycles to consist of microrings steadily decreasing in size until the last one, which would be larger, i.e., FIG. 6. Frequency histograms showing the number of microrings in successive cycles. The left hand black arrow indicates the mean if chance alone was operating; the right hand arrow, the mean. The broken line shows the simulated distribution with a mean of 11-12 (see text). a Fe „a FREQUENCY NO GROWTH RINGS IN BEAKS OF MOROTEUTHIS 295 EE И 10 20 20 20 40 30 7 = ERES | 52076. 232% AOS ISA 20 22223 24 No. OF MICRORINGS IN EACH CYCLE 296 M. R. CLARKE TABLE 2. The number of microrings in the various cycles No. of beaks in samples (N) Mean No. of micro- rings (x) Cycle as in Fig. 3, C. Because such a pat- tern is not found in the beaks (Table 1), we can be fairly confident that the cycles do not arise in this way. How- ever, recognition of the types of cycle is rather subjective and additional evi- dence is desirable. To test whether bias can give a normal-type distribution with a mean similar to that obtained when frequency histograms of the num- ber of microrings in a cycle are plotted (Fig. 6), a simple experiment was con- ducted. Bricks of 2 colours were drawn from a bag in which sufficient were present to overcome any effect due to removal of the sample. In the trials the bricks were present in different ratios and the minority colour was taken to repre- sent the event of a microring being broader than its predecessor and the majority colour was taken to represent the event of it being narrower. By trial and error it was found that when the bricks were in a ratio of 9.5:1 the mean number of “microrings” per cycle was very similar to that in cycle 1 of the beak, i.e., between 11 and 12. The shape of the distribution, however, was very positively skewed (Fig. 6) and this shows that bias alone cannot be the main factor in producing cycles in the beaks. Standard Varlahee Standard error of 9 deviation mean (s ) (s) (sz) en Bo D IN Go go po go go co go go oO NN I © © =] © J © © CYCLES AND WALL LENGTH Wall length has the advantage over other dimensions of the beak, that the history of its growth is recorded by the position of the microrings near the ros- tral edge. Thus, by measuring the dis- tance from the rostral tip to succeeding cycle limits, the increase in wall length during particular cycles can be found. Frequency distributions of wall lengths, separated according to the total number of cycles in the beaks, show the increase in size with increase in the number of cycles (Fig. 7). The means of these distributions are plotted as crosses in Fig. 8 (Table 3). These means are affected by non-randomness of the sampling. If the whale selectsthe larger young squids, one would expect the curve to be flattened because the means of wall lengths of the younger beaks with fewer cycles would be higher than the means of the population. That such a bias is involved is suggested by comparing the crosses with the back- calculated growth curve (circles, lower curve Fig. 8, Table 4) which is not subject to such a bias. The back- calculated curve is found by measuring from the rostral tip to the limits of every cycle in every beak (150 beaks) and then calculating the mean position GROWTH RINGS IN BEAKS OF MOROTEUTHIS 297 ye 23 CYCLE ae del 40 Où he 45 9.150 ve 50 8 20 5 >= O 40- 28 9 O 37 20 O œ U 40 = 6 30 40 26 ? 201 40 23 + 201- 40 19 50 КОРЕЕ а 2176777:87 52:07 2:27 724772672830 3-2 3-4 WALL LENGTH (in cm) FIG. 7. Frequency histograms showing the wall length in beaks with different numbers of cycles. The number of beaks in each sample is given to the right of the figure. 298 M. R. CLARKE TABLE 3. Wall length and the total number of cycles in 292 beaks Standard Variance Standard error of deviation mean (s) (sz) TABLE 4. Back-calculated? wall lengths Mean wall No. of length at beaks in each cycle sample in cm (N) ® (s°) Variance Standard deviation (s) Cycle D D 0 ND M M M RP RB A 4The back-calculated wall lengths are found by measuring from the rostral tip to every cycle li- mit in each beak means GROWTH RINGS IN BEAKS OF MOROTEUTHIS WALL LENGTH HION37 37LNVN 71VSHOQ о.5 CYCLE Мо FIG. 8. Growth curves of Moroteuthis ingens derivedin different ways from the lower beaks. Crosses show the mean values of wall length plotted against the total number of cycles in the beak. Open circles show the means derived by measuring the distance from the rostral tip to each successive cycle in 161 beaks i.e., the circles show the back-calculated length at suc- cessive cycles (Table 4). Standard deviations are represented by vertical lines. Dorsal man- tle length values (right ordinate in cm) were found from the relationship between wall length and dorsal mantle length given in Fig. 10. for each cycle limit. The position of this curve depends to some extent on the composition of the sample because back-calculated wall lengths from older beaks (more cycles) give lower values than from younger beaks (Table 5 and Fig. 12). The same situation was found by Lee (1912) when fish scale size was back-calculated. It is accounted for by the fact that the fish which grow more Slowly survive longer and the same explanation probably holds good for squids. Frequency histograms of the back- calculated wall lengths at each cycle are given in Fig. 9. A difference in size of the 2 sexes could account for 299 the bimodality of the histogram for cycle 1. BEAK AND SQUID GROWTH Growth of the beak is of only very limited interest unless it can be related to growth of the animal. Fig. 10 shows the relationship between the wall length and the dorsal mantle length (roughly about half the total length) based on the only available data for the family. The line is drawn in to suggest the likely course of growth of Moroteuthis ingens which is represented by the black circles. The 3 open circles which lie well off the curve represent M. robsoni which has a very pointed (i.e. long) mantle. More specimens are required to verify the curve suggested. A double loga- rithmic plot of the weight of the squid against the wall length reveals a linear relationship (Fig. 11). By direct com- parison, therefore, it is possible to find the lengths or weights of squid at dif- ferent beak sizes and a dorsal mantle length scale has been added to the right of Fig. 8. TIME AND GROWTH Clearly, the length of time taken for the beak to grow through one cycle could be established if the increase in microrings between 2 samples taken a few months apart could be found. To this end, the microrings between the limit of the last cycle and the free edge of the lateral wall were counted in beaks taken from a whale caught in June and a whale caught in September of the same year (1962). The counts of the 2 sam- ples were then compared to find any increment in the number of microrings over the 3 months period (Fig. 4, A). Means for these counts were 7.7 and 7.5 for the June and September samples respectively. The samples were not significantly different. However, from frequency histograms (Fig. 13) there is evidence that the size composition of the population sampled differed in the 300 M. R. CLARKE 20 25 CYCLE 10 10 20 42 Ня го 20 See 20 го O S- 20 > ui m0 FL Ш =) Gi rd mu 20 117 5 4 134 3 149 2 149 148 | 192 Pre oe le i Nordea ia sere a UU 1 23 45 6 7 8 9 WH 1213 14 5 K I7 18 19 2021 22 23 24 25 BACK CALCULATED WALL LENGTH (in cm) FIG. 9. Frequency histograms (%) showing the back-calculated wall lengtns at each cycle. The number of beaks in each sample is given to the right of the figure. GROWTH RINGS IN BEAKS OF MOROTEUTHIS 301 TABLE 5. The mean distance in mm from the rostral tip to each successive cycle in each age group (67 beaks) Total number of cycles and number of beaks in sample (N)? . e а | ee .79 к . 59 .95 я . 68 (12) . 14 $ . 50(10) . 14(13) . 28 (12) 5In those few instances where means were based on a different number of beaks, is given in parentheses after the wall length. 2 months and this fact, coupled with the extreme difficulty in counting the very narrow microrings on the edge, probably accounts for this failure to find any increment. cm © 90 80 70 60 50 DORSAL MANTLE LENGTH 0 1-0 2:0 3-0 cm WALL LENGTH FIG. 10. Relationship between wall length of the beak and dorsal mantle length of onycho- teuthids determined by removing beaks from Black circles are Moroteu- identified squids. this ingens. Line drawn in by eye (see text). the value of N DISCUSSION If we consider other methods of study- ing growth several disadvantages are at once apparent. Most previous work on cephalopods has depended on finding the change in the mean size of the popu- lation through the year. If the mean size becomes larger, then there is a temptation to interpret the shift as growth; but it must be remembered that this could equally well be due to mi- gration of larger individuals into the area or smaller individuals out of the area towards the end of the period sampled. Another method employed in studying growth is Petersen’s method of finding the peaks, which may represent age groups in a population sampled over a brief part of the year. This method has also been used to study cephalo- pods (Wirz, 1963; Fields, 1963) but, as pointed out by Wirz, the animals so stu- died must have a rather brief breeding season so that successive broods are easily distinguished by the size and all ages must be present in the sample. Age determination from laminations of some kind would overcome these difficulties. 302 M. R. CLARKE 20,000 10,000 1,000 WEIGHT IN GRAMS 100 ‘| A LS 5.18910 2:0 30 40 WALL LENGTH FIG. 11. Logarithmic plot showing the relationship between wall length of the beak and total weight of onychoteuthids determined by removing beaks from identified squids. Line drawn in by | eye. 303 GROWTH RINGS IN BEAKS OF MOROTEUTHIS TABLE 6. Increment in mantle length during the first 3 years of life of cephalopods previously studied and also the deduced increment in the mantle length of Moroteuthis ingens, estimated from the back-calculated curve of the beaks, assuming 1 cycle on the beak to represent varying spans of time in the life of the squid Increment in mantle length alcala” mantle length in cm Tinbergen 25. 0 Fields 16.5 3 Author 2nd year % of max. 3rd year cm % of max. Species Loligo vulgaris с’ Loligo opalescens & Loligo opalescens & Fields 15.0 3 Illex illecebrosus с’ Squires 2 Illex illecebrosus Y Squires 2 Eledone cirrosa Wirz 255 Moroteuthis ingens (10 cycles) If 1 cycle were formed in 1 month If 1 cycle were formed in 4 months If 1 cycle were formed in 6 months If 1 cycle were formed in 12 months i.e. the mean value of the oldest “age group” given in the papers quoted. i.e. the age of the oldest group given in the papers quoted. Possibly less than a year’s growth. 6 7 8 9 From squid caught in May but probably from a second year age group. 10From 2 squids caught in May but probably from a second year age group. 304 M. R. CLARKE cm и (3) О 2-0 ; У: cas e ой 7 974) / = J oo / 5(14)x/ - 1-5 “8 4 3(4) : и Е I xs / z = = = КО < tu = 0-5 CYCLE N® FIG. 12. Back-calculated mean wall lengths for each cyclefound by examining separately beaks with 3, 5, 7, 9 or 11 cycles on the lateral wall. This figure shows that back-calculation from older beaks (with more cycles) suggests a slower growth than back-calculation from younger beaks and illustrates part of the data given in Table 4. The number of beaks meas- ured is given in brackets for each curve. The present study has not shown the time taken for a microring or a cycle to form, but some of the possible al- ternatives seem unlikely on the basis of work previously done on other species. It seems likely that the microrings are secreted in a discrete time inter- val and vary in width according to some environmental influence such as food supply or temperature. Table 6 summarises the increment in mantle length of the species of squid previously studied in detail as well as the increment estimated from the back- calculated curve of Moroteuthis ingens beaks, if we assume a cycle to be se- creted in 1, 4, 6 or 12 months res- pectively. It will be seen from the table that, if a cycle only takes 1 month to form, the growth would have to be about 4 times the maximum growth known in squids and the largest M. ingens would be less than a year old. This seems unlikely. If a cycle is secreted in 4 months, the annual increment in size would be about twice as much as that of Loligo vulgaris; the largest M. ingens would take 3 years to grow and we know that L. opalescens does survive that long. It is, however, difficult to envisage what environmental influence could operate over 4 months although a combination of factors could possibly do so. It is easier to picture environ- mental influences affecting the growth over 6 months or a year. If a cycle is secreted in a year the annual incre- ment in size would be similar to that met in L. vulgaris males, but this would mean that M. ingens survives for at least 10 years. When the increment in length for each year is expressed as.a percentage of the mean length of the oldest age group found (underlined, Table 6), the species previously studied show certain simi- larities to one another. The growth during the first year amounts to 39- 62% and that of the second year to 32- 41% of the length reached in the final year. In Moroteuthis ingens, if a cycle represented 4 or 6 months, the first year’s growth would be similar to that of the other species (53% or 40% res- pectively) but the 2nd year’s growth would be much less than that ofthe other species (21% instead of 32-41%). In fact, whether 1 cycle represents 1, 4, 6 or 12 months’ growth, it is clear that Moroteuthis ingens is rather dissimilar in this respect from the other species. Certain cycles are very similar in different beaks. The first 2 cycles usually have the type A (Fig. 3) form, and this may suggest more regular feeding or environmental fluctuations than are found in later cycles. The “stable” region mentioned (2nd or 3rd cycle) may suggest stable feeding or con- ditions for the period of its formation. GROWTH RINGS IN BEAKS OF MOROTEUTHIS 305 10 1X (3) 20 10 Vu (2) SO so 40 Vil 30 (4) 20 n 10 ul о == 78 (2 WZ 3 2,100 œ u 90 80 70 60 VI (3) SO 40 30 20 10 == = 20 У 10 (2) 7 -8 9 1O 1-1 12 13 14 1-5 1-6 17 +8 19 20 cm LOWER ROSTRAL LENGTH. FIG. 13. Frequency distributions to show the rostral length of the lower beaks of Moroteuthis ingens taken from stomachs of sperm whales caught off Durban between May and September 1962 and 1963. The months are indicated by Roman numerals and the number of whales from which samples were removed in each month is given in brackets. 306 M. R. CLARKE An interesting point not mentioned so far is that very few of the beaks have undarkened wings and, if such darkening is correlated with attainment of sexual maturity as it is in the Ommastrephidae (Clarke, 1962), the sample would consist of mature squids almost entirely. ACKNOWLEDGMENTS The author is very grateful to Dr. A. Bidder and Mr. R. I. Currie for helpful criticism of the manuscript and Mr. J. Bannister and Mr. R. Gamble who went to considerable trouble in collecting the squid beaks used in this work. REFERENCES CHOE, S., 1963, Daily age markings on the shell of cuttlefishes. Nature, Lond., 197: 306-307. CLARKE, M. R., 1962, The identi- fication of cephalopod “beaks” and the relationship between beak size and total body weight. Bull. Brit. Mus. (nat. Hist.) (Zool.), 8 (10): 421- 480. FIELDS, W. G., 1950, A preliminary report on the fishery and on the bi- ology of the squid, Loligo opalescens. lescens. Proc. XVI International Con- gress of Zoology, 1: 72. FREDRIKSSON, A., 1943, Remarks on the age and the growth of the squid. Greinar, 2: 2-4. KATOH, G., 1959, A few comments on the biological grouping of the common squid derived from its ecological as- pect-1. Rep. Japan Sea reg. Fish. Res. Lab., 5: 1-17. LEE, R. M., 1912, An investigation into the methods of growth deter- mination in fishes. Publ. Circ. Cons. Explor. Mer, 63: 1-35. SASAKI, M., 1921, On the life history of an economic cuttlefish of Japan, Ommastrephes sloani pacificus. Trans. Wagner Free Inst. Sci. Philad., 9 (2): 1-25. SQUIRES, H. J., 1957, Squid, Illex illecebrosus (Le Sueur) in the New- foundland fishing area. J. Fish. Res. Bd. Can., 14: 693-728. TINBERGEN, L. and VERWEY, J., 1945, Zur Biologie von Loligo vulgaris Lam. Arch. neerl. Zool., 7 (1 et 2): 213- 286. WIRZ, K. M., 1963, Biologie des Cé- phalopodes benthiques et nectoniques de la Mer Catalane. Vie et Milieu, Suppl., (13): 1-285. YAGI, T., 1960, On the growth of the shell in Sepia esculenta Hoyle caught Calif. Fish & Game, 36: 365-377. ‚ 1963, Biology of Loligo opa- Fish., 26 (7): 646-652. RESUMEN ANILLOS DE CRECIMIENTO EN LAS MANDIBULAS DE MOROTEUTHIS El presente trabajo, que describe los ciclos de lineas de crecimiento (micro- anillos) en la mandibula inferior de Moroteuthis ingens, intenta llamar la atenciön sobre la posibilidad de relacionar la formación cíclica con el tiempo de crecimiento del calamar. El estudio se basa еп un gran número de muestras de los picos obtenidos del estomago de cachalotes cazados en Durban. ‘Se describen los rasgos usados en la clasificación (Fig. 1). Sobre la superficie media de la pared lateral.en los picos hay 4 caracteres visibles (Fig. 2): costillas que irradian desde la punta rostral al borde libre, y diminutos microanillos, ondulaciones y “lineas” de transparencia variable que corren paralelas a ese borde. Los microanillos constituyen un registro de la exten- sión de las paredes laterales durante el crecimiento. Pueden reconocerce ciclos en el ancho de los anillos entre la punta rostral y el borde libre. En 50 picos observados la variación de los ciclos muestra que los 3-4 primeros ciclos generalmente siguen un patrón definido mientras que los últimos varían considerablemente (Fig. 3). Durante in Tokyo Bay. Bull. Jap. Soc. scient. GROWTH RINGS IN BEAKS OF MOROTEUTHIS la vida del calamar hay muy poco desgaste de la punta rostral en las serie de tama- fios estudiados (longitud rostral 0.7-2.0 cm). Los histogramas de frecuencia y las medidas del nümero de microanillos en cada ciclo muestran que estos no pueden formarse por fortuitas fluctuaciones de secreción, aún cuando esas fluctuaciones representaran la influencia de ciclostardios que son mäs estrechos que los tempranos. El crecimiento del pico puede ser expresado convenientemente como un aumento en la longitud de la pared, que es la distancia desde la punta rostral al ängulo antero- interior de la pared lateral (Fig. 2). Desde que la historia del crecimento se registra por la distancia que separa los microanillos desde la punta rostral, esta puede calcu- larse retroactivamente. Aumento en tamafio del pico junto con al aumento en el numero de ciclos ha sido diagramada, asi como la curva del calculo retractivo no sujeta a ninguna parcialidad selectiva por el cachalote, (Fig. 8). El calculo de la longitud de las paredes de los picos de mucha edad da valores mas bajos que los de los jóvenes, probablemente porque los calamares de desarrollo más lento sobreviven más tiempo. La relación entre la longitud de la pares y tamaño del calamar también se ha diagramado (Fig. 10,11). El tiempoque toma la secreción de un ciclo no ha sido establecida, pero ensayos basados en previos estudios sobre otros cefalópodos, sugiere de 6 a 12 meses. 307 DIRECTIONS TO AUTHORS Malacologia will publish original monographs and longer papers devoted primarily or exclusively tothe study of mollusks. It aims to provide a common medium for such different aspects of malacology as anatomy, ecology, medical malacology, paleontology, physiology and taxonomy. The journal will try to combine scholarly standards withprompt publication. All manuscripts will be reviewed by at least two editors, Manuscripts (for the time being) may be in English, French, German, Russian or Spanish. They must contain a concise but adequate abstract for trans- lation into the other languages. Manuscripts should be typewritten and double-spaced and are to be submitted in duplicate (carbon copy on thin paper). Figures should be carefully executed and with figure numbers and labels large enough to be read easily after reduction. Style will be changed as little as possible, and then mainly in places of possible ambiguity or where economy of space may be achieved. 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ZOOL. № - М 236.2. LIBRARY JUN 2 1 1066 НАКУАЖЫ MALACOLOGIA | |. р x La i de International Journal of Malacology Revista Internacional de Malacologia Journal International de Malacologie Международный Журнал Малакологии Internationale Malakologische Zeitschrift Подписку и MALACOLOGIA ANNE GISMANN, General Editor 19, Road 12 J. B. BURCH, Associate Editor Museum of Zoology The University of Michigan Ann Arbor, Mich. 48104, U.S.A. РЕДАКЦИОННАЯ КОЛЛЕГИЯ Inst. Geology & Paleontology Maadi, Egypt U. А. В. EDITORIAL BOARD SCHRIFTLEITUNGSRAT P. O. AGÖCSY K. HATAI Magyar Nemzeti Müzeum Baross U. 13 Budapest, УШ., Hungary C. R. BOETTGER Technische Hochschule Pockelsstrasse 10a Braunschweig, Germany A. H. CLARKE, JR. National Museum of Canada Ottawa, Ontario Canada G. M. DAVIS 406th Medical Laboratory Tsurauma, Sagamihara City Kanagawa Pref., Japan C. J. DUNCAN Department of Zoology University of Durham South Rd., Durham, England Z. A. FILATOVA Institute of Oceanology U.S.S.R. 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ABSTRACT At least 3 members of the genus Catinella are unique among the Stylommato- phora because of their low chromosome numbers (C. rotundata of Hawaii, n=5 (2n=10); С. vermeta and С. texana, n=6 (2n=12)). Because of this low number and relatively large size of the chromosomes, C. vermeta is particularly well suited for a study of the chromosome cycle during spermatogenesis. The cycle does not differ, in general, from that found in other animals, and especially resembles the cycle we have observed in other euthyneuran snails. De- tails, however, are much clearer, the various stages more easily recognized, and those not detected with certainty before are now clearly evident. The de- tailed description of the chromosome cycle of C. vermeta gives a clear concept of the meiotic process in euthyneuran gastropods and expands greatly on infor- mation contained in any previous report. Early mitotic chromosomes appear as fuzzy, diffuse strands which condense to form mid-prophase chromosomes, the coilednature of which is evident; the centromeres appear as lightly stained or nonstained areas. Further contraction results in metaphase chromosomes that stain more densely, have smooth margins and centromeres indicated only by constrictions. Anaphase chromo- somes are similar but somewhat smaller. The first meiotic prophase nucleus is formed after the last pre-meiotic di- vision. The leptotene chromosomes appear as lightly stained, long, single strands with chromomeres along their length. The free ends show the polari- zation characteristic of the “bouquet stage”. Zygotene pairing begins at the polarized ends and appears to be chromomere-by-chromomere along the length of the homologous strands. Pachytene chromosomes are shorter and more densely stained. Homologues begin to “repel” one another, causing a separation that produces open areas along early diplotene chromosomes. As diplonema progresses, the chromosomes become diffuse and poorly stained. Chiasmata terminalize and contraction continues as the chromosomes form the ring, rod, cross or multiple loop-shaped figures characteristic of diakinesis. Metaphase I bivalents are very condensed ring, half-ring or rod-shaped figures in polar view. Homologous centromeres, with their chromatids, separate at Anaphase I, forming dyad chromosomes about 1/2 the size of Metaphase I bivalents. Fol- lowing cytokinesis, the chromosomes enter the 2nd meiotic division without an observable period of interkinesis. Prometaphase II dyads, before alignment in the equatorial plane, look like later Metaphase II chromosomes, which are greatly contracted, densely stained 1 Contribution from the University of Michigan Biological Station. 2 This investigation was supported (in part) by research grants GB 787 from the National Science Foundation, Washington, D.C., U. S. A., 5 T1 AI 41-07 from the National Institute of Allergy and Infectious Diseases, U.S. Public Health Service, and by a Public Health Service research career program award (number 5-K3-AI-19, 451-03) to the second author. (309) 310 PATTERSON AND BURCH and “dumb-bell” shaped. During Anaphase II, each dyad separates to form 2 monads, which pass to opposite poles, where Telophase II is initiated and sub- sequent cytokinesis takes place. Young spermatids are then formed, each having a conspicuous nuclear membrane. During spermiogenesis, thechromatin becomes disorganized and nuclear condensation takes place to form the mature spermatozoa. INTRODUCTION Land snails of the genus Catinella have recently evoked considerable interest from the cytological point of view because of the unusually low chromosome numbers of at least 3 of its species (n=5, 2n=10 in C. rotundata (Gould) of Hawaii and n=6, 2n=12 inC. vermeta (Say) and C. texana Hubricht of continental U. S. A.) (Burch, 1964a, b; Burch & Patterson, 1965). Having such low numbers, these species are particu- larly well suited for a complete study of the chromosome cycle. The present paper deals with the cytological aspects of C. vermeta and includes an analysis of the chromatin throughout the chromo- some cycle during spermatogenesis and spermiogenesis as well as a description of several chromosomal anomalies sometimes occurring during the cycle. The description ofthe chromosome cycle in C. vermeta gives a clear. Concept of the meiotic process in euthyneuran gastropods and expands greatly on in- formation contained in any previous reports. Catinella vermeta is common to much of the United States. Its generalized distribution, as currently known, is shown in Fig. 1. Its actual distribution may well cover the entire continental U.S. А., but lack of collecting in certain geographical areas and the past nomen- clatural and taxonomic confusion in regard to succineid snails makes accurate tabulations from the literature difficult. The species that is now understood to be Catinella vermeta (Say, 1824b) has been commonly known in the past as C. (or “Succinea”) vagans (Pilsbry) (see Pilsbry, 1948; Miles, 1958; Burch, 1962). Hubricht (1961) found that the FIG. 1. Distribution of Catinella vermeta. type lot of Succinea campestris vagans Pilsbry, 1900, contained a mixture of 2 species which, on shell characters, could not be distinguished from S. campestris Say and C. vermeta (Say). The original description of S. vagans was based on the shells of S. campestris. In addition, the species which until recently has been referred to as “C. (or Succinea) avara (Say)” is probably none other than C. vermeta. Say’s (1824a) type speci- men for “Succinea avara” is animmature shell and unidentifiable (Hubricht, 1958). Catinella vermeta inhabits moist places, usually near bodies of fresh- water, and can be found crawling on the surface of the ground, or resting under wood, leaves or stones. Its shell is characteristically covered with moist mud. C. vermeta may be distinguished from neighboring succineids of the genera Succinea and Oxyloma partly by characters of its shell, but more surely by the lack of a penial sheath, which is present in the other 2 genera. So far as known, species of Succinea and Oxy- CHROMOSOME CYCLE IN CATINELLA 311 loma all have higher chromosome numbers (n=15 or more), which makes them less ideal for a study of the chromo- some cycle. LITERATURE REVIEW The maincomprehensive publications on chromosomes of euthyneuran Gastro- poda are those of J.-L. Perrot (1930), M. Perrot (1938), Inaba (1959a, b), Husted & Burch (1946) and Burch (1960a, b). These and other papers dealing with cytology in Euthyneura are summarized by Burch (1965). J.-L. Perrot (1930) studied the formation of germinal cells and the chromosome cycle during spermatogenesis in a basommatophoran and a stylommatophoran snail; he also studied the “heterochromosomes” in several Stylommatophora and discussed chromosome numbers reported in pul- monate snails. M. Perrot (1938) deter- mined the chromosome numbers in 17 species of Stylommatophora and dis- cussed snail taxonomy in relation to those numbers. Inaba (1959a) studied the chromosomes of 29 species of the Stylommatophora and related these num- bers to present systematics. He also determined the chromosome numbers of 19 species of opisthobranchiate mol- lusks (1959b), discussing higher system- atics in relation to his observations. Husted & Burch (1946) examined the chromosomes of 18 species and sub- Species of the stylommatophoran family Polygyridae; they studied 1 populationin particular regard to varying chromo- some numbers and heteromorphic biva- lents, and discussed chromosome num- bers of the “Pulmonata” in general. Burch (1960a) studied the mitotic chro- mosomes in 5 families of the Basomma- tophora and discussed the value of karyo- type analysis and chromosome numbers to snail systematics. He further in- vestigated the chromosomes of 36 spe- cies and subspecies of basommatophoran snails, reviewed all previous work on that group, discussed taxonomy in relationto chromosomes, and studied formation of germ cells and the chromosome cycle during spermatogenesis of 1 species (Burch, 1960b). Previous authors that have discussed within the last 25 years the chromosome cycle of euthyneuran gastropods are J.-L. Perrot (1930: Lymnaea stagnalis, Lehmannia marginata; 1937: Helx pomatia), Pennypacker (1930: Polygyra [=Mesodon] appressa), Hickman (1931: Succinea ovalis), Whitney (1941: Vallon- ia pulchella), Tuzet (1951: Physa acuta), and Burch (1960b: Stagnicola emar- ата). All of the observations by those authors, with the exception of the description on 5. emarginata, were from sectioned material, a method which is inferior to the squash technique. Because of its much higher chromosome number (n=18), S. emarginata is not as satis- factory an animal to study as Catinella vermeta (n=6), the species used in this paper. Previous papers which have treated in one way or another the chromosomes of Succineidae, to which Catinella ver- meta belongs, are those by Hickman (1931), M. Perrot (1937, 1938), Inaba (1945, 1950, 1959a), Husted & Burch (1946), Koyama (1955), Burch (1964a, b) and Burch & Patterson (1965). Hick- man’s paper deals with the spermio- genesis of Succinea ovalis from the U. S. A., including formation of germ cells, the chromosome cycle, cyto- plasmic inclusions and sperm formation. Perrot gave the haploid chromosome number of S. putris (n=22). Inaba (1945, 1950) gave the haploid and diploid numbers of $. horticola (n=17, 2n=34) and in (1959a) described the mitotic and meiotic metaphase chromosomes of that species. In the latter paper he also discussed aspects of cytotaxonomy in the Succineidae. Husted & Burch, in a footnote to their polygyrid paper, gave the chromosome number of S. ova- lis (n=21) from Virginia, U. S. A., and noted that their findings differed from Hickman’s (n=20) report for the same Species from Maine and New Jersey. Koyama gave the haploid and diploid numbers of S. hirasei and 5. kwansae (both with n=17, 2n=34), briefly described 312 PATTERSON AND BURCH ’ us bo Pr. DAA + q 7 FIGS. 2-7. Mitotic and meiotic chromosomes of spermatogenesis in Catinella vermeta. FIG. 2. Spermatogonial early prophase. Arrow indicates proper cell. FIG. 3. Spermatogonial mid- prophase. Arrows denote centromeric regions. FIG. 4. Spermatogonial metaphase. 4a is greatly magnified as shown by measurement line. The inset figure (4b) has the same magnifica- tion as Figs. 2, 3, 5-7. The arrow points to a secondary constriction in one arm of one of the largest chromosomes. FIG. 5. Spermatogonial anaphase. The arrows point to secondary con- strictions in thelagging sister chromosome arms. FIG. 6. Pre-leptotene nucleus. FIG. 7. Four leptotene nuclei. All figures except 4a are magnified as shown in FIG. 5. their meiotic and mitotic metaphase chromosome data were available. Burch chromosomes and discussed cyto- (1964a, b) gave the chromosome numbers taxonomy of succineid snails for which of Catinella vermeta (n=6, 2n=12) and CHROMOSOME CYCLE IN CATINELLA 313 C. rotundata (n=5, 2n=10) and discussed systematics in the family Succineidae in the light of chromosome numbers. Burch & Patterson (1965) pointed out that the genus Catinella affords excellent cytological material for demonstrating and studying the chromosome cycle in an animal. MATERIALS AND METHODS The specimens of Catinella vermeta used in this study were collected from 4 locations in Michigan: the border of a woods pool in central Washtenaw County; a damp, marshy area adjacent to the Raisin River near Clinton, northern Lenawee County; the edge of the Raisin River near Tecumseh, northern Lenawee County; and the shore of Douglas Lake, Cheboygan County. The specimens were killed, fixed and preserved in New- comer’s (1953) fluid prior to cytological examination. Tissue of the ovotestis was prepared for chromosome studies by the acetic-orcein squash technique (La Cour, 1941). Observations were made with Nikon compound microscopes using 100X (n.a. 1.25) oil immersion objectives and 10X and 30X oculars. The chromosomes were drawn with the aid of a camera lucida and reproduced at a table top magnification of 5340X. Photomicrographs were taken using a 10X ocular, oil immersion objective, a Kodak Wratten 57A (green) filter and Kodak High Contrast Copy film. OBSERVATIONS Spermatogenesis in Catinella vermeta consists of a number of spermatogonial (mitotic) divisions of germ cells prior to the maturational (meiotic) divisions. The spermatogonial mitoses of C. ver- meta appear to be characteristic of normal somatic mitoses as they occur in other animals with the diploid number (2n) of chromosomes visible during the divisions. The chromosomes of early mitotic prophase appear as rather fuzzy, diffuse strands with extremely irregular mar- gins (Fig. 2). The strands are long with slightly darker staining sections along their length. The 12 mitotic chromosomes can be seen as distinct entities and actually can be counted at this early stage in favorable prepara- tions. The mid-prophase chromosomes (Fig. 3) are somewhat shorter, more deeply stained and have smoother mar- gins than those of early prophase as a result of increased chromosome con- traction. The coiled nature of the strands is particularly evident at this stage. The area of the centromere ap- pears as a lightly stained or non-stained portion of each strand and this area produces the primary constriction ofthe chromosome. All 12 chromosomes can easily be counted. In late prophase (Fig. 8), the chromosomes are even more condensed, deeply stained, shorter and have smoother margins than those of mid-prophase. The coiled nature of the strands and the differential staining of the centromeric regions are not as apparent because of the increased con- traction. However, constrictions can be ¿> Le D | FIG. 8. Spermatogonial late prophase chromo- somes. PATTERSON AND BURCH У? 2> 32 >> ]) >> 10 u FIG. 9. Spermatogonial metaphase chromosomes. The homologous pairs have been arranged in decreasing order of length. seen to indicate the centric area in some chromosomes. The 12 chromo- somes can be distinguished with par- ticular ease in this stage. Metaphase chromosomes are greatly contracted, deeply stained, have smooth margins (Fig. 4a,b) and show no evidence of coiled structure as they do in pro- phase. The centromeric regions are indicated only by constrictions which are located at the “bend” of the chromo- somes, where the centromereisattached to the bi-polar spindle apparatus. The karyotype of C. vermeta includes 1 pair of conspicuously large chromosomes, 4 pairs which are intermediate in size and 1 smaller pair (Fig. 9). All of the chromosomes appear to be almost medianly constricted (metacentric) but several may be submedianly constricted to a slight degree. A secondary con- striction is clearly evident near the end of an arm of one of the large chromo- somes; it is probably present in its homologue, but is not always as clear. Spermatogonial metaphase chromo- somes range in length from 5.6 u for the largest pair to 3 y for the smallest pair. Anaphase chromosomes have much the same shape and density of stain asthose of the preceeding metaphase, but are usually somewhat smaller. The chromo- somes of the 2 anaphasic groups are pulled from their centromeres toward opposite poles and sometimes sister chromosome arms may encounter diffi- culty in separating and lag behind the other chromosomes in the complement (Fig. 5). The secondary constriction on one of the largest chromosomes is usually again evident in sister chromo- some arms that lag in anaphase. During telophase, the chromosomes become more tightly grouped within the nucleus and resemble a rather solidball of chromatin. Cytokinesis follows and results in the formation of 2 equivalent daughter nuclei each with the diploid complement of chromosomes. After the last pre-meiotic division, the nucleus enlarges to form the first meiotic prophase nucleus. The pre- leptotene nucleus (Fig. 6) contains localized accumulations of chromatin that are rather “granular” in appearance and only partially formed into chromatin strands. In leptonema (Fig. 7) the chromosomes appear aS maximally ex- tended single strands, which are lightly stained, with more darkly stained bead- like chromomeres along their length. In late leptonema, the free ends of the chromosomes’ are polarized, i.e., associated at one side of the nucleus, forming the “bouquet stage”. The pairing (synapsis) of homologous chromosomes begins in zygonema. The chromosomes begin to synapse at the polarized ends, while the remainder of the strands are yet unpaired in the “bouquet” formation (Fig. 10). The zygotene chromosomes appear to be somewhat more contracted and darkly stained than leptotene chromosomes and the chromomeres are still clearly evi- dent. Pairing of homologous strands is com- pleted in zygonema forming pachytene chromosomes of double thickness and haploid in number. The “bouquet” per- sists into early pachynema and the separate homologues can still be dis- cerned (Fig. 11). Pairing seems to be CHROMOSOME CYCLE IN CATINELLA 315 FIGS. 10-15. Meiotic prophase chromosomes of spermatogenesis in Catinella vermeta. FIG. 10. Zygonema. The arrows indicate synapsis at the polarized ends, while most of the rest of the strands are not yet paired. FIG. 11. Pachytene bivalents. FIG. 12. Late pachytene bi- valents. FIG. 13. Early diplonema. Arrows indicate places where the chromosomes are be- ginning to “open out”. FIG. 14. Diplonema (diffuse stage). FIG. 15. Late diplonema. All figures are magnified as shown in FIG. 13. chromomere-by-chromomere along the creased contraction ofthe strands, which length of the homologous strands. Late begins in leptonema and continues pachytene chromosomes (bivalents) (Fig. throughout Prophase I. In favorable 12) are much shorter than leptotene or preparations, the 6 bivalents can be zygotene chromosomes, due to the in- counted in late pachynema. 316 PATTERSON AND BURCH 10yu FIG. 16. Camera lucida drawing of the paired ends of 6 of the zygotene chromosomes shown in the photograph to the left and in Fig. 10. Strands partly or wholly out of the optical plane are not shown. In early diplonema (Fig. 13), the homologues begin to “repel” one another, causing the chromosomes to separate slightly; but since they remain connected at the points of crossing-over (chias- mata), open areas or loops are formed along their length. Early diplotene chromosomes still stain rather deeply; however, the chromosomes of mid to late diplonema appear more diffuse, poorly stained and with irregularly characterized margins (Figs. 14, 15). As terminalization of chiasmata begins and contraction continues, the chromo- somes soon form the ring, rod, cross or multiple loop-shaped figures charac- teristic of diakinesis (Figs. 17, 18). In early diakinesis, the chromosomes are still quite diffuse and have irregular margins (Fig. 17). Due to the increased contraction, mid to late diakinetic chromosomes are smaller, more deeply stained and have somewhat smoother margins (Fig. 18). The shapes of the various diakinesis bivalents that have been observed in C. vermeta are shown in Fig. 21 with arrows indicating positions of the chiasmata. Cells in which the 6 bivalents form 6 ring-shaped figures (Fig. 21a, b, c) or 5 ring and 1 rod-shaped figure (Fig. 21d) occur in about equal frequency and are most common. Less frequently, 4 ring and 2 rod-shaped figures are observed and occasionally cross and multiple loop- shaped bivalents (Figs. 21е, resp. 211) are present. Ring-shaped bivalents have 2 remaining chiasmata and rod- shaped figures presumably have 1 terminal chiasma remaining. Of the other figures observed, the cross has 1 non-terminal chiasma and the multiple loop has 3 remaining chiasmata, pro- ducing 2 loops. The continued contraction throughout Prophase I forms Metaphase I bivalents that are very condensed with deep stain and smooth marginal outlines. The bivalents form either ring, half-ring or rod-shaped figures in polar view, de- pending upon the number and location of remaining chiasmata. Cells with 6 rings or those with 5 rings and 1 half- ring are most frequently observed. Six bivalents that range in size from 3.2- 2.3 u, measured at the greatest dimen- Sion, are shown in Fig. 19. Homologous centromeres, with their chromatids of varying genic constitution, separate at Anaphase I and the dyads move toward opposite poles. Fig. 20 clearly shows the monocentric nature of CHROMOSOME CYCLE IN CATINELLA 19 < 4 20 FIGS. 17-20. Meiotic chromosomes of spermatogenesis in Catinella vermeta. FIG. 17. Early diakinesis bivalents. FIG. 18. Late diakinesis showing 6 ring-shaped bivalents. FIG. 20. Metaphase-Anaphase I bivalents in side view. phase I bivalents. FIG. 19. Meta- All figures are at the magnification shown in Fig. 18. the chromosomes as the 2 halves of each bivalent are just beginning to be pulled apart. The chromosomes in each anaphasic group are about 1/2 the size of Metaphase I bivalents, but density of stain and smoothness in outline are much the same. The centromeric regions of the dyads can be seen as constrictions in some chromosomes and may appear more lightly stained. Two dyad members of a bivalent are some- times late in separating and they there- fore lag in the center of the cell after the other dyads have passed to their respective poles. A cell in this con- dition is shown in Fig. 22. Cytokinesis follows and spindle formation takes place as the chromosomes seem to immediately enter the second meiotic division without undergoing an obser- vable period of interkinesis (Fig. 23). During Prometaphase II spindle for- mation is completed and the dyads begin to move toward the equator of the cell (Fig. 23). The dyads appear to be just as highly contracted, or even more so, as in the previous anaphase. Cen- tromeric regions are indicated only by constrictions, with no evidence of dif- ferential staining. Fig. 24 shows Meta- phase П dyads which appear as single or double “dumb-bell” shaped figures with the centromeric constrictions clearly evident. The chromosomes of Metaphase I are highly contracted, deeply stained and have smooth mar- ginal outlines. Six dyads are easily counted, with the largest and smallest of the complement measuring 2.6 u and 2.1 y respectively in length, thus 318 PATTERSON AND BURCH oa 3 * + еее 10 u FIG. 21. Diakinesis bivalents of Catinella vermeta. 21a-c, Ring-shaped bivalents, each with 2 chiasmata. 21d, Rod-shaped bivalent with 1 terminal chiasma. 21е, Cross-shaped bivalent with 1 non-terminal chiasma. 21f, Multiple loop-shaped bivalent with 3 chiasmata. Arrows in- dicate positions of chiasmata. being smaller than the Metaphase I bi- valents. In Anaphase Il, each dyad separates to form 2 monads or daughter chromo- somes, which pass to opposite poles. The Anaphase II chromosomes often appear to have slightly more irregular margins than Metaphase II dyads. The 6 separating dyads of early Anaphase II are easily counted in Fig. 25, where 1 dyad can be seen to be noticeably larger. When the chromosomes reach their respective poles, Telophase I is ini- tiated and cytokinesis begins to take place (Fig. 26). Thehaploid complement now consists of 1 large chromosome and 5 smaller chromosomes randomly oriented within the nucleus. In late Telophase II (Fig. 27), the chromosomes are often grouped together near the pole, appearing as a solid mass of chromatin. Upon completion of Telophase II and cyto- kinesis, the chromosomes pass into an interphasic-like state, the chromatin characteristically becoming somewhat diffuse and irregular in shape. Thus begins the formation of young sperma- tids, each with its conspicuous nuclear membrane (Fig. 28). All 6 irregularly Shaped chromatin masses can still be clearly discerned in some of the young CHROMOSOME CYCLE IN CATINELLA 319 26 | 27. * FIGS. 22-27. Meiotic chromosomes of spermatogenesis in Catinella vermeta. FIG. 22. Late Anaphase I. Two dyads, both from the same bivalent, are at the center of the cell; they ap- parently had difficulty in terminalizing, and therefore lagged behind the other dyads in their anaphasic movement. FIG. 23. Prometaphase II dyads in 2 sister cells. FIG. 24. Metaphase II dyads (note spindle fibers). FIG. 25. Metaphase-Anaphase II dyads. FIG. 26. Telophase II monads in 2 sister cells. FIG. 27. Late Telophase II. All figures are at the magnification shown in Fig. 25. spermatids. During spermiogenesis, the deeply stained, nearly mature sperm chromatin becomes progressively more cells are formed (Fig. 31). 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CARTES CPL (0 DT ad 103 AN ‘ ще | A er He de dr roll co HAT A дозора Ne Amen х ‚ый at ' с ара “le ROH их SOUS FT + PAUL ‘ tone ¿us HT г. № 3} ум 57 ) { $ ¥ i in NA DA é el aes : a N > er a A Ст ah y Г ‘ LE 6 04440 RX ЗВ y er ‘ae oat ot as DOTA А: 5 CRAN ITS à À RN. a ST TE ESE lirio avers 34 q dl Live hee: y | x й vv ; ha N BR ng ras ih pen 6 la Ве Кио de ds a ore Fee ae ae ee ibs DE rats x HE vs т OPT» Re A ЭМ № ; | BR dies a s eT: une р. Sajak? to!) ee aie ae , BE DR Phat By ten a a A saone lca ий ho Ve Are + ul GARCIA À >. A A Mile Se ai Y Eee vet À (très y Bas | ty . N Résa sn WE QU EME SOTA | RITA р hé «e MY. de ЦАР и оно «y MALACOLOGIA, 1965, 3(3): 327-378 REPRODUCTIVE FUNCTION AND THE PHYLOGENY OF OPISTHOBRANCH GASTROPODS Michael T. Ghiselinl ABSTRACT The comparative and functional anatomy of the reproductive system through- out the subclass Opisthobranchia is treated critically to provide a sounder basis for phylogenetic studies. Original observations are combined with detailed dis- cussions of older work. Emphasis is given to possible functional explanations for morphological and physiological variations, in order to allow a phylogenetic theory which has a causal theoretical basis. Functional analysis is employed, involving the avoidance of features likely to be convergent, and emphasizing comparison based on complex functional divergences. Homologies of the parts are treated in detail, and some changes in nomen- clature are suggested. The formation of egg masses and the homologies of the glands which secrete them are discussed and clarified by histochemistry and ex- perimental observations. Possible reasons for evolutionary changes are considered. Functional dis- advantages of the ancestral, undivided gonoduct have been overcome in different ways, and these divergences form the basis of hypothetical clades which are evaluated in terms of other evidence. The study considers older systematic work, chromosome numbers, feeding . specializations and other properties of the digestive system, and spermatozoon morphology as auxiliary evidence in adiscussion of phylogenetic problems. The phylogenetic arguments incorporate critical consideration of parallelism and convergence. The reproductive system in the Onchidiidae supports pulmonate affinities.v The Acteonidae have a modified reproductive system and are not ancestral to most other opisthobranchs; the reproductive system and some other structures imply a close relationship to the Hydatinidae; the histology of the ampulla suggests a possible affinity to the Acoela. The premises on which arguments for abiphyletic origin of pteropods have been based are rejected; a monophyletic origin is consistent with the morphology of the reproductive system; both groups resemble the Anaspidea and Sacoglossa in spermatozoon morphology. The re- productive systems of Anaspidea, Sacoglossa, Diaphanidae and Cylindrobullidae can be compared to a hypothetical common ancestor with a divided gonoduct, and may be related. The Retusidae, Philinoglossidae, Bullidae, Atyidae and Runcin- idae may be grouped together onthe basis of a copulatory apparatus which stores sperm and forms spermatophores; herbivorous members of this group have an oesophageal diverticulum and similarities in the gizzard. Correlations between larval shell types and the triaulic condition in aeolid nudibranchs suggest some need for systematic revision. The study supports the naturalness of many groups. INTRODUCTION there being no wholly satisfactory, natural system of classification. Recent The relationships within the subclass work has provided new evidence bearing Opisthobranchia are most uncertain, on systematic problems, but there has lHopkins Marine Station of Stanford University, Pacific Grove, California; present address: Museum of Comparative Zoology, Harvard University, Cambridge 38, Massachusetts, U. S. A. (327) 328 been no adequate, comprehensive syn- thesis. This study aims ata contribution to such a synthesis, and at a recon- sideration of older phylogenetic ideas in the light of more modern evolutionary concepts. Ideally, a phylogenetic study should treat all the relevant evidence; but this is difficult, and attempts to do so often lead to superficial comparisons. Therefore a particular organ system is here treated in detail, and phylogenetic hypotheses are formulated on the basis of this comparison. An effort is then made to see how well the hypotheses agree with inferences made from other kinds of evidence, especially with the re- sults of recent work. Like any other phy- logenetic study, this body oftheory is de- signed to serve as abasis for further re- search by providing hypotheses which may be tested by critical work, especially on other systems. Itis not intended as the final word on relationships, but only as the implications of a particular, limited perspective, which may be interestingto those who desire to further our under- standing of opisthobranch phylogeny. This study has been based on a tech- nique which departs somewhat from the usual approach, and some discussion is essential to an understanding of the argu- ments which follow. Functional analysis has been applied in order to take the causes of evolutionary change into account in reconstructing the sequences of modification. The comparison is organized in terms of physiology in the broad sense, since this approach allows the selection of properties of the organism for comparison on the basis of biological significance rather than con- spicuousness or convenience. I reject the purely morphological approach, since it is likely to confuse non-adaptive characteristics with those the adaptive Significance of which is not known, and rather choose to begin with con- Siderations of adaptive significance. This approach has value too, in the light it casts on physiology, in that morphological variations may suggest correlated physiological ones. M. T. GHISELIN The difficulty in classifying opistho- branchs results in part from extreme modification, and also. from the great amount of parallelism and convergence which characterizes the group аз a whole. The opisthobranchs are in the process of losing the shell. Correlated with this loss of the shell are various other changes in structure, including the re- organization of the body into a slug- like organism with a modified respira- tory apparatus, concentrated nervous system and bilateral symmetry. Morton (1963) refers to this reorganization and the shifts of adaptive zone which it allows as a “program” evolution, and points out that the changes are poly- phyletic. In order to avoid being led astray by parallelism and convergence, I have incorporated a consideration of the possible causes of these compli- cations into the theoretical perspective which is used. In this work I shall refer to a selective influence as any cause of selection pressure. Itake Ц аз axiomatic that parallelism and convergence are caused, fundamentally, by the action of the same selective influence, and that wherever the same selective influence acts on organisms, parallelism and con- vergence are likely. (The difference between parallel and convergent evo- lution is largely a matter of degree, the distinction simply emphasizing the greater propensity of closely-related organisms to undergo particular kinds of changes under the same conditions.) In study of long-term evolutionary change especially, it is desirable to base com- parison on changes which have an un- equivocal functional advantage, since to do so allows reasonable grounds for assuming that evolution has tended to proceed in a particular direction. But just because of such advantage, parallel- ism is likely in closely-related forms. Therefore, in evaluating phylogenetic hypotheses, I avoid drawing the con- clusion that organisms showing identical structure are related if that similarity can readily be explained in terms of convergence resulting from such in- PHYLOGENY OF OPISTHOBRANCHS 329 fluences as may reasonably be supposed to have produced them. Rather, the attempt is made to erect a coherent system of relationships based as much as possible on differences which have explanatory value as divergent adap- tations to the same selective influence. These differences, which Bock (1959) speaks of as multiple pathways of adap- tation, are indications of earlier con- ditions in which a particular functional problem still existed. Although it is not strictly true, it is here assumed, with reservations, that the reproductive system evolves relatively independently of other systems, hence that its own convergences and parallelisms are in- dependent of those of other systems, and that independent correlation should obviate some of the problems of paral- lelism. Further, in a complex organ system it seems reasonable to assume that identical complex structures are not convergent if a variety of functional arrangements can provide improvement over antecedent conditions; however, there are numerous logical pitfalls in the evaluation of phylogenetic hypotheses in this light. For instance, it is very easy to confuse lack of evidence for a hypothesis with evidence against it, as when there has been a secondary loss of a structure. Such practical compli- cations of reasoning must be dealt with individually. A causal phylogenetic system is an attempt at explanation which, because it does explain, may be evaluated by the implications of the explanations it gives. It is argued in this study that some of the variations of the reproductive system are understandable in terms of physiology. Of course, our ability to go so far as to make precise predictions of the course of evolution is made im- possible by unknown selective influences, random changes and pleiotropy. Butthis does not mean that we cannot use our understanding of physiology or evolution- ary mechanisms as evidence for or against a particular relationship. Itis one thing to make a prediction con- cerning the course of evolution, another to recognize that its regularities impose restrictions and tendencies upon evo- lutionary history such that certainhypo- thesis are more credible than others. Thus, ifa particular phylogenetic scheme places the various forms in a pattern of sequences such that the transitions have explanatory value as adaptations and the changes are by gradual, adaptive steps, then the system is supported. Similarly, a system in which the changes can only be explained by macromutations or ad hoc rationalizations is relatively un- satisfactory. One cannot, by comparative anatomy alone, prove that phylogenetic theories are true. However, one can disprove them in a sense by forming hypotheses based on independent struc- tures and rejecting the hypotheses when they contradict each other. Thus a phylogenetic system is not alone that which is best supported, but that which best withstands criticism. The particular kinds of selective in- fluences which are thought to act upon a group and the conditions which are hypothesized as ancestral, determine the kind of arguments which are valid in support of a particular system. For instance, Boettger (1954) erected a phylogenetic system of the euthyneurous gastropods on the degree of development of the following: (1) detorsion of the visceral loop, (2) shortening of visceral connectives, (3) fusion of ganglia, (4) position of the pharyngeal nerve ring relative to the pharynx, (5) loss of the shell, (6) loss of the operculum. As stated above, I agree with Morton (1963), and with Pelseneer (1894), Fretter & Graham (1962) and others in believing that these changes tend to be polyphyletic. There can be no reasonable doubt that loss of the shell has occurred inde- pendently within numerous clades (Hoffmann, 1932-40). Loss of the oper- culum probably results from loss of protective significance ofthe shell. Con- centration of the nervous system and detorsion correlate to a considerable degree with the loss of the shell, andare 330 M. T. GHISELIN also known to be polyphyletic. I demon- strate below that Boettger’s inferred relationships are not valid unless some parallelism is admitted. From the poly- phyletic nature of these changes it follows that there is no way to determine at what stage of their evolution the various lines of descent diverged, except toinfer that the common ancestor ofa particular group was as primitive in the develop- ment of a trend as the most primitive known member. Therefore Boettger’s criteria are such that they are likely to result in Stufenreihe rather than Ahnen- reihe. I do, however, accept Boettger’s criteria in so far as they employ divergences inthe nervous system rather than stages in trends. Therelationships suggested by this study are supportedby such differences. Another problem of convergence re- sults from small size. The convergences of small organisms are well known (Rensch, 1960). They may be under- stood by consideration of their adaptive Significance. In general, organisms undergo changes during the reduction of body size which result in a saving of space, such as simplification of compli- cated structures, loss of less essential parts, and concentration of.the nervous system. They also show such changes as development of ciliary locomotion and reduction in the relative surface of the gill which have an obvious physiological explanation. Such superficial conver- gences are compensated for as a matter of course; however, sometimes the adap- tive significance of a particular modifi- cation is overlooked. For instance, protandry may be advantageous in small opisthobranchs because it saves space; but it also may be primitive in the group; in a small, protandrous form, it may be hard to tell whether the protandry is primitive or secondary. From such considerations, one may avoid being led astray by convergence simply by avoiding conclusions from Similarities which, within a given con- text, are particularly likely to be con- vergent. This study has involved a detailed critique of the literature, as well as observations on the organisms them- selves. Particular emphasis is given to physiology as the basis of comparison. It has been necessary to evaluate the literature, particularly where conflicts and lacunae exist. Various uncertain- ties must, of course, be resolved by new research before the results of this study can be properly tested. I have tried to give proper credit to those who have originated the ideas which are developed here; however, this has been complicated by the fact that the advancement of phylo- genetic knowledge comes more from cor- relating and evaluating the data than from unearthing similarities and differences. Therefore, it may be that adequate cre- dit has not been given to everyone whose work has been useful. I have attempted to cover the relevant literature, although this should not be considered an exhaustive review, as only matters relevant to the discussion are treated here. For the older literature Keferstein’s “Bronn” (1862-66) is useful, and Pruvot-Fol (1960) discusses some aspects of the reproductive system throughout the group. The general anatomy of the opisthobranchs is re- viewed in Hoffmann’s “Bronn” (1932- 40), but this work does not include the reproductive system. To avoid involvement in nomenclatural problems, the most widely-used names are given. On the whole I have followed the usage of Taylor & Sohl (1962), except that the Acoela of Thiele (1929- 35) are retained. METHODS For dissection, animals were anaes- thetized in aqueous magnesium chloride solution isotonic with seawater. Egg masses were fixed in buffered seawater formalin to avoid hydrolysis of the carbohydrates. Tissues used in histo- logical and microanatomical work were fixed in seawater Bouin’s solution, im- bedded in paraffin and sectioned at a PHYLOGENY OF OPISTHOBRANCHS 331 thickness of ca. 10 micra. The staining techniques used, with their standard abbreviations, were as follows: Alcian Blue 8GX (AB) by the method of Steedman (Pearse, 1961). Azure A by the method of Kramer & Windrum (1955). Delafield’s acid haematoxylin. Dimethylaminobenzaldehyde-nitrite (DMAB) method of Adams for tryptophan (Pearse, 1961). Eosin Y in 95% ethanol. Hale’s dialysed iron method for acid mucopolysaccharides (Pearse, 1961). Lasky’s Mucihaematin (Casselman, 1959). The Mercury-Bromphenol Blue (HgBPB) method of Mazia, Brewer & Alfert (1953), using an aqueous solution, for proteins. Millon’s reaction (Bensley and Gersh modification) for tyrosine (Pearse, 1961). Periodic acid-Schiff (PAS) reaction by the method of McManus (Pearse, 1961). GENERAL STRUCTURE, HOMOLOGIES AND NOMENCLATURE The following is a description of an idealized, gonochoric reproductive sys- tem of such a structure that it may serve as an hypothetical ancestral form; it incorporates a uniform terminology and a discussion of criteria of homolgy. The variations will be discussed in later sections. An attempt is made to utilize terms which are consistent with Hyman’s (1951) nomenclature for the Bilateria in general, and with that of Fretter € Graham (1962) for the Prosobranchia. The functional morphology of the repro- ductive system in the Prosobranchia, from which the Opisthobranchia are thought to be descended, has been dis- cussed at length by Fretter & Graham (1962), and such material will not be repeated here. Such an idealized, gonochoric system is diagrammed in Figs. 1A and 1B. In both the male and the female systems, 2 parts, the gonad and the gonoduct may be distinguished. The male also has a group of accessory structures. The gonoduct (go) is divisible in both sexes into 2 portions, the coelomic gonoduct (co) and the pallial gonoduct (pl), terms derived from the evident homologies of these parts (Fretter & Graham, 1962). Although the coelomic gonoduct in the female is simple, and needs no further terminology, that of the male is compli- cated by the presence of a swelling, the ampulla (am), which stores sperm before they are transferred to the partner in copulation. The term “hermaphroditic ampulla” will not be used here because it would be redundant. The ampulla is often called the “seminal vesicle,” but as this term is applied to a variety of structures, its use is likely to be con- fusing. When it is necessary to dis- tinguish between the part of the coelomic gonoduct lying between the gonad andthe ampulla and that between the ampulla and the pallial gonoduct, I will use the terms pre-ampullar coelomic gonoduct (pa) and post-ampullar coelomic gono- duct (po) respectively. The use of such terms as “hermaphroditic duct,” “little hermaphroditic duct” and “largeherma- phroditic duct” is avoided because of their imprecision. The pallial gonoduct in the male con- sists of the prostate (pr) only. This structure evidently plays some role in the transfer of sperm, but its function is poorly known. Chambers (1934) says that it forms a kind of spermatophore, and spermatophore formation by this struc- ture is known in Haminoea (Perrier & Fischer, 1914) and in Runcina (Ghiselin, 1963). A characteristic type of se- cretory cell, the presence of which seems to be a fundamental character of the opisthobranch and pulmonate system, occurs in the prostate of a wide variety of euthyneurous gastropods. These cells seem to have originally been pallial in position, but they may be displaced to the base of the penisinmanyforms. The secretion of this cell may be recognized by its corpuscular structure, and by its staining reactions; in the literature, 332, 1 М. T. GHISELIN go FIG. 1. Idealized diagrams showing terminology. A, male system ina gonochoric form; B, female system ina gonochoric form; C, hermaphroditic system suggestive of conditions in the opisthobranch common ancestor. al, “albumen” gland; am, ampulla; bc, bursa copulatrix; ca, copulatory apparatus; cg, common genital opening; co, coelomic portion of the gonoduct; gd, gonad; go, gonoduct; me, membrane gland; mu, mucous gland; ov, ovary; pa, pre-ampullar portion of the coelomic gonoduct; pl, pallial portion of the gonoduct; po, post-ampullar portion of the coelomic gono- duct; pr, prostate; rs, receptaculum seminis; sg, seminal groove; te, testis. PHYLOGENY OF OPISTHOBRANCHS 333 the strong eosinophily of the secretion is frequently noted. The eosinophilic secretion may be accompanied by other kinds of secretion. In order to extend our knowledge of the chemical nature of this secretion, I subjected formalin- fixed sections of the prostate of a dorid nudibranch, Triopha carpenteri Stearns, and of a thecosomatous pteropod, Creseis virgula Rang, toa series of histochemical tests. The corpuscular secretion stained deeply with eosin and very weakly with haematoxylin; it did not stain at all with AB or PAS; the DMAB reaction was positive. Thus the secretion is probably largely protein, and contains little, ifany, carbohydrate. The prostate is probably homologous throughout the group, but more work is desirable. The copulatory apparatus (ca) consists of a penis with a ciliated groove which extends to the pallial gonoduct. This ciliated groove, or seminal groove (sg) transports the sperm. Numerous modi- fications of the copulatory apparatus have been described. Where the open Seminal groove has been converted into a closed tube, it is called the vas deferens. That portion of the vas deferens which serves to transfer sperm through the penis may be called the ejaculatory duct. A swelling of the vas deferens which forces sperm through the ejaculatory duct will be called the ejaculatory vesicle, The copulatory apparatus may include a structure which stores sperma- tozoa and which, in some forms atleast, is associated with the production of packets of sperm called spermatophores. Although this structure is often called a “male seminal vesicle,” this term may be confused with any of several other “seminal vesicles” and for this reason the term spermatic bulb will be used. The penis is often enclosed in a pro- tective penial sac. In the female, the pallial gonoduct in- cludes sperm-containing structures and secretory organs. There are usually 2 sperm-containing structures in the pallial gonoduct. One of these, the bursa copulatrix (bc) ordinarily receives the sperm at copulation. The other, the receptaculum seminis (rs), stores sperm for longer periods. Common synonyms for these structures are, respectively, “spermatheca” and “spermatocyst.” The most reliable criterion for distinguishing between them is thatinthe receptaculum seminis sperm may be found with their heads attached to the epithelium (Fretter & Graham, 1962; Pruvot-Fol, 1960). Usually, but by no means always, the receptaculum seminis occupies a proximal position in the pallial gonoduct, near the end of the coelomic gonoduct, while the bursa copulatrix opens near the opening of the pallial gonoduct to the exterior. The contents of the various sperm-containing organs are usually given such circumlocutory or obscure designations as “the animal’s own Sperm”, or “ ‘foreign’ sperm.” The terms endogenous and exogenous seem preferable, since their meaning is clear from the etymology. In prosobranchs (Fretter & Graham, 1962), the receptaculum seminis and bursa copulatrix are somewhat more variable in structure and function than in opisthobranchs, but generally the bursa copulatrix receives the sperm and the receptaculum seminis stores it. Occasionally there is also an ingesting gland which absorbs sperm; no homo- logue of this structure has been re- ported from the opisthobranchs. The prosobranch receptaculum seminis (Fretter € Graham, 1962) agrees with that of the opisthobranchs (Lloyd, 1952) in having an epithelium in which the heads of the sperm become imbedded. Fretter and Graham point out that “orien- tation” of the sperm may occur ша variety of parts of the gonoduct. The bursa copulatrix ofprosobranchsis often found to contain sperm and prostatic secretion, but in some, the receptacu- lum seminis is thought to also contain both sperm and prostatic secretion (Fretter & Graham, 1962). The bursa copulatrix in prosobranchs is secre- tory, and amoebocytes may ingest ma- terials (Fretter € Graham, 1962); it is 334 M. T. GHISELIN likewise secretory in opisthobranchs (Foderä, 1915). Lloyd (1952) suggests that the bursa copulatrix is fairly uni- form in histology among opisthobranchs. The uptake of materials by amoebocytes in the bursa copulatrix is known in prosobranchs (Fretter & Graham, 1962) and Lemche (1956) thinks that the sole function of the bursa copulatrixin Cylich- na, a cephalaspidean, is the resorption of prostatic secretion and materials which go astray inthe reproductive tract. Lemche’s interpretation is based partly on his finding eggs in the bursa copula- trix, partly by comparison with the ex- perimental demonstration of Eales (1921) that the exogenous sperm in Aplysia are not deposited in the bursa copulatrix, but rather near the base of the duct of the receptaculum seminis. But this has not been established by direct evidence. In Aglaja and Runcina (Ghiselin, 1963) I have observed that sperm are de- posited just inside the common genital opening; in neither case does the penis penetrate as far as the bursa copula- trix. In a number of dorid nudibranchs, the arrangement of ducts is such that the sperm must pass through the bursa copulatrix. Thus it seems that the re- ceptaculum seminis and bursa copulatrix may each receive sperm, and although their functions are not absolutely uni- form, and although their positions vary somewhat, a comparison between these structures in opisthobranchs and proso- branchs shows that they agree fairly well in histology, function and position. Among the opisthobranchs with an un- divided pallial gonoduct and also possessing both of these structures, the receptaculum seminis is proximal, and the bursa copulatrix is near the common genital opening. When, in the forms with a pallial gonoduct which has a Single, internal division (Anaspidea, Cylindro- bulla), the receptaculum seminis is somewhat displaced toward the genital opening, it is clear that the division of the duct makes this possible. In the Acoela, the arrangement of the bursa copulatrix andthe receptaculum seminis, which is here considered primitive, is supported by a good series of inter- mediate forms (Figs. 3,4). It is pri- marialy among such forms as Acteon, aeolid nudibranchs, pyramidellids and pteropods, in which only one organ which contains exogenous sperm is present, that the criterion of position does not hold strictly true and only the function and structure are available to identify these parts; but in these forms, the systems display a greater similarity to other forms in which the conditions here considered primitive are present than to each other. Again, inthe Sacoglossa, the position, function and form of the struc- tures which contain exogenous sperm are highly variable; yet there isa good series of interconnecting forms (Cylindrobulla, Berthelinia) which allows a derivation from the typical conditions, and the atypical sacoglossan reproductive sys- tems display no particular similarities to those of any other group of mollusks. Thus, while some other interpretations are possible on the basis of part of the evidence, those givenhere are more con- Sistent with the comparative anatomy of the system throughout the group. The terminology and homologies of the secretory portions ofthe pallial gonoduct have long been confused. In opistho- branchs, these structures are usually called the “albumen gland” and the “mucous gland,” according to the parts of the egg mass which they are thought to lay down. However, as Pruvot-Fol (1960) has pointed out, this classification fails to account for all the parts of the egg-mass. Because the establishment of the homologies and functions of these secretory structures is essential to any application of them in a comparative study, I have studied them throughout the order, and compared them with their possible equivalents in the prosobranchs. It has been demonstrated experimentally (e.g., Kawaguti & Yamasu, 1961) that the secretory structures form layers of material around the eggs. The egg masses formed by this process show many features in common, differing mostly in their proportions, and the parts are readily comparable. Several PHYLOGENY OF OPISTHOBRANCHS 335 studies have been published which relate particular layers to the structures which produce them. Further, the egg masses have a structure such that the layers must be laid down in sequence, and the order of the secretory areas suggests their probable functions. The secretory areas in different groups show similari- ties in histology and staining reaction which likewise suggest homologies. However, some variations in staining reaction, and the absence of one of the layers in many forms makes the estab- lishment of homologies difficult. There- fore, additional studies, aimed at com- paring the detailed structure of the layers and relating these layers to specific secretory areas have been carried out. The egg masses of opisthobranchs con- sist, essentially, of eggs surrounded by 3 layers of protective and nutritive materials. Comparable layers exist in those of pulmonates and prosobranchs. These layers willbe called, from interior to exterior, the “albumen”, the membrane, and the mucus. The “al- bumen” has a nutritive function (Fretter & Graham, 1962), and consists largely of galactogen, sometimes mixed with protein (Grainger & Shillitoe, 1952; Horstmann, 1959). Around the “albumen” is a thin layer whichI call the membrane; this corresponds to the “coque intérieure” of Pelsencer (1914), and to the “egg covering” of Fretter & Graham (1962). Outside of the membrane is a layer or series of layers of a substance called mucus. These layers will be spoken of collectively as nidamental layers, and the glands which secrete them as nidamental glands. Variations on this basic structure are numerous, although the opisthobranch egg mass is usually very simple. Any of the nidamental layers may be absent. The number of eggs contained in each mem- brane varies considerably. The mem- brane may have 2 or more twisted por- tions, the chalazae, having no function; they result fortuitously from the manner in which the membrane is formed. In some pulmonates and prosobranchs, one or more additional layers, the capsule, may be formed around the mucus. The most recent general review onthe structure of gastropod egg masses may be found in the treatise of Fretter & Graham (1962), which refers to older works. Gabe (1962) has reviewed the histochemistry of the nidamental glands in the Mesogastropoda and provided evidence for the structural and functional uniformity of these parts. Besides a large number of scattered references to the egg masses of various opistho- branchs, the general structure is well treated by Thorson (1946) andina series of papers by Baba and Hamatani (e.g.: Hamatani, 1962). The presence of a membrane seems to be almost universal among opisthobranchs (cf. Eliot, 1910). Lloyd (1952) seems to have overlooked the membrane. Bolot (1886) describes how the mucus may be separated from the membrane by acid hydrolysis, and gives a fairly detailed description of the egg mass. Trinchese (1884) gives a detailed drawing of the egg mass of an aeolid nudibranch, showing the mem- brane and chalaza. Trinchese’s (1893) observation that the egg masses of aeolid nudibranchs lack an “albumen” layer has been overlooked. Owing to the confused condition of the literature, and to the fact that different staining methods have been used to com- pare the nidamental glands in different animals, it was found expedient to carry out a series of histochemical tests and staining reactions ona variety of opistho- branch egg masses. The results of these follow. Dendrodoris (Doriopsila) albopunctata (Cooper, 1863) gave the best general results. The mucus portion stained metachromatically with Azure A, strongly with haematoxylin and muci- haematin, weakly with AB, and weakly, but positively with Hale’s test; the PAS reaction was very weak, while the DMAB and Millon’s tests for protein were negative; HgBPB gave only weak, back- ground staining. These results strongly suggest that the mucus is made up of a sulfated, acid mucopolysaccharid con- taining little or no protein. The mem- 336 М. T. GHISELIN brane stained orthochromatically with Azure A, gave only weak, background staining with mucihaematin and AB, and stained less intensely with haematoxylin than did the mucus; the PAS reaction was very strong; Hale’s test was weak, as was eosin Staining; the DMAB, HgBPB and Millon’s reactions were all positive. These results are consistent with the interpretation that the membrane consists either of a neutral mucopoly- saccharide mixed with protein, or ofa mucoprotein. The “albumen” stained very weakly and orthochromatically with Azure A, and gave only background staining with mucihaematin, AB, Hale’s test and haematoxylin; it was stained strongly by eosin, and gave a strongly positive reaction with PAS; DMAB and Millon’s tests were negative, andHgBPB gave a weak background stain. Thus the “albumen” consists of a neutral carbo- hydrate, very likely, as in pulmonates, galactogen (cf. Grainger & Shilitoe, 1952). Egg masses of Hermissenda crassi- cornis (Eschscholtz, 1831) were tested with haematoxylin, eosin, mucihaematin, Azure A, AB, PAS, and DMAB. Although an “albumen” layer is not present inthis form, and although the material did not stain readily, the results were roughly comparable with those on Dendrodoris, except that with Azure A some of the mucus did not show metachromasia and the membrane showed a weak meta- chromasia. Egg masses of Hermaeina smithi Marcus, 1961, were tested with Azure A, mucihaematin, AB, haematoxylin, eosin, PAS, DMAB, and HgBPB. The staining reactions were similar to those with Dendrodoris, but some differences were noted. Mucihaematin, haema- toxylin, and AB allowed a less-pro- nounced distinction between the mem- brane and the mucus; this would agree with the results of Gascoigne (1956), who worked with histochemically non- Specific stains, on other sacoglossans. The “albumen” showed distinctly positive reactions with DMAB and HgBPB and had some affinity for haematoxylin; the “albumen” evidently contains some pro- tein. It would seem that the carbohydrate of the membrane in Hermaeina, and « probably in other Sacoglossa as well, differs somewhat from that of Dendro- doris, but since the PAS and protein reactions are all positive, it appears that the difference lies mainly in the degree of sulfation of the carbohydrate in the membrane, as is suggested by the fact that in H. smithi the membrane shows a weak metachromasia with Azure A. Egg masses of Acteon punctocaelatus (Carpenter, 1864) were tested with muci- haematin, haematoxylin, eosin, PAS, AB, Azure A, DMAB and HgBPB. A layer of “albumen,” if present, was too dilute to be detected. The mucus stained to varying degrees in the different parts of the egg mass with AB, mucihaematin and haematoxylin; only the outermost layer showed metachromasia with Azure A. Texts on the mucus with PAS, DMAB and HgBPB were negative. The mem- brane showed positive reactions with HgBPB, DMAB and PAS; it stained weakly with AB, mucihaematin, eosin and haematoxylin; weak metachromasia with Azure A suggests, again, some sulfation. The above results demonstrate that a basic chemical uniformity exists in the egg mass, but there is enough variation that the parts cannot easily be dis- tinguished on the basis of histochemical tests alone; older work based on histo- chemically non-specific staining re- actions must be viewed with scepticism. The nidamental glands should be given names corresponding to the layers which they secrete. As is shown in Fig. 1, these are the “albumen” gland (al), the membrane gland (me), and the mucous gland (mu). The quotation marks around the term “albumen” are given to dis- tinguish it from a similar term used by different authors, and to avoid the implication that the secretion is pro- teinaceous. Theterm “membrane gland” is new, this structure usually having been confused with either the “albumen” gland PHYLOGENY OF OPISTHOBRANCHS 337 or the mucous gland; it corresponds to the “winding gland” of the Anaspidea (Eales, 1921). The mucous glandis often called the “shell gland” in works dealing with pteropods. Several criteria allow the identification of these parts. The most reliable of these is the dissection or sectioning of an animal killed in the process of laying eggs. The staining reactions noted above may also allow a distinction, but their reliability varies. In general, the “albumen” andmembrane are secreted in smaller droplets than the mucus. The relative position of the glands may indicate their function, since the parts of the egg mass must be laid down successively. The structure of the membrane is such that it must be laid down at the point of secretion; therefore the membrane gland must be so constructed that the eggs can pass through it. In various opisthobranchs the eggs do not traverse the cavity of the “albumen” gland. Rather, a specialization has occurred in the gland such that there is an area where the “albumen” is secreted, and another, outside the gland itself, where it is deposited around the eggs. Such a modification has been demon- strated conclusively only in the Anaspidea (Eales, 1921) and Sacoglossa (e.g.: Kawaguti & Yamasu, 1961). Evi- dently this change allows a more rapid and efficient deposition of “albumen” and may prevent misdirection of materials into the gland. Invariably, the membrane gland con- sists of tissue containing gland cells interspersed with ciliated cells. For functional reasons it never has a separation into secretory and depo- sitional areas. The membrane is a thin film, which must be laid down ina sheet, and any movement over a distance would simply wad it into a tangled mass. The cilia are necessary in the area of the gland cells to insure the precise move- ments of the membrane substance and eggs. The eggs are moved through the membrane gland and covered with a sheet of this material (Gascoigne, 1956; McGowan & Pratt, 1954). This process has been described by Linke (1933) for Littorina, a prosobranch. I have also observed it in live Hermissenda crassi- cornis, an aeolid nudibranch, and, with less success, in various dorid nudi- branchs. In H. crassicornis the eggs are moved in series through the folds, and sheets of membrane are secreted around the series of eggs. The whole series of eggs, along with its coverings, is rotated, so that the eggs, either in- dividually or in groups, are surrounded by a sheet of membrane material. The eggs, with their coverings, continue to be rotated, andare separated into packets of one or more eggs. After the membrane has been laid down, the eggs shrink, giving rise to a space which may easily be mistaken for “albumen.” The process in other opisthobranchs appears to be essentially the same, although the details vary. A peice of twisted membrane (chalaza) often marks the spot where the packets were twisted apart. The number of eggs in a single membrane varies considerably within the group, as does the presence or absence of “albumen.” On the basis of Lloyd’s (1952) study of Philine and Scaphander, and of their own work on Acteon, Fretter & Graham (1954) have concluded that in these forms the eggs do nottraverse the cavity of the so-called albumen gland. Although it is impossible to disprove this view at present, I disagree on the foilowing grouds: 1. Fretter & Graham fail to explain the mechanism of formation of the mem- brane. 2. Lloyd overlooked the membrane. 3. What Fretter & Graham regard as tubules in the so-called albumen gland of Acteon tornatilis, Johansson (1954) has described as folds. My own obser- vations on A. punctocaelatus bear out Johansson’s interpretation. 4. The apparent absence of a layer of “albumen” in egg masses of Acteon punctocaelatus (see above) suggests that what Fretter & Graham call the albumen 338 — М. Т. GHISELIN gland may be а membrane gland. 5. The conclusion that the eggs do not enter the gland is based solely on the observation of ciliary currentsinanaes- thetized animals which were not laying eggs. One may question the validity of these experiments on the basis of the fact that ciliary actionis readily modified by chemical and nervous activity (Hillenius, 1960). Fretter € Graham (1954) have suggested that in Acteon tornatilis the eggs, with their membranes, are forced into a pre-existing mass of mucus by ciliary action. In A. punctocaelatus my sections of egg masses show that the eggs are arranged in a Series inside a long tube of mucus of distinctly laminar structure. This long tube is arranged in a coil inside another layer of mucus, forming an egg mass identical to that described by Fretter & Graham for A. tornatilis, and clearly similar to the egg masses of other cephalaspideans. The orderly arrangement of eggs within the egg mass and the laminar structure of the mucus’ throughout the Opistho- branchia make it clear that the mucus is secreted in layers as the egg mass is moved through the gland. This process has been demonstrated by means of sections in sacoglossans (e.g.: Kawaguti & Yamasu, 1961). By means of dis- sections on animals in the process of laying eggs, I have been able to demon- strate that the mucus is laid down in layers in a dorid nudibranch, Anisodoris nobilis (MacFarland, 1905), and in an aeolid nudibranch, Hermissenda crassi- cornis, (cf. Mazzarelli, 1891; Thomp- son, 1961b). In euthyneurous gastropods generally, the male and female systems are, or have been, united into a common system with a single, undivided gonoduct. The pallial gonoduct may become divided into Separate ducts. For an undivided pallial gonoduct the term monaulic is used. In diaulic and triaulic systems, the pallial gonoduct has been divided into 2 and 3 ducts, respectively. As the etymology suggests (aúdós, a pipe), these terms should not be used to denote the number of genital openings. Some confusion of terminology has arisen because the division of the ducts may be only partial. It seems reasonable to base these dis- tinctions solely on whether or not the endogenous sperm, the exogenous sperm, and the eggs have separate ducts (Eliot, 1910), especially since the extent of division varies considerably. For the separated ducts, the terms vas deferens, vaginal duct and oviduct will be used. The diaulic condition is formed by the separation of either a vas deferens or an oviduct. Because of the importance of the distinction between the 2 kinds of diaulic systems, Iintroduce the following terminology. Androdiaulic: having a separate vas deferens and an otherwise undivided gonoduct (Fig. 2A), asin Acteon (Fig. 2B; Fretter & Graham, 1954). Oödiaulic: having a separate oviduct and an otherwise undivided pallial gono- duct (Fig. 2C), as in Aplysia (Fig. 2D; Eales, 1921). A discussion of the synonymies of the terms used to describe the reproductive system has been given by Pruvot-Fol (1960); see also subsequent sections. THE FUNCTIONAL BASIS OF EVOLUTIONARY CHANGE It has been maintained (e.g.: Lloyd, 1952) that the hermaphroditic repro- ductive system in opisthobranchs arose from the superimposing ofa male repro- ductive system on a female one. There is no way to test this hypothesis directly. However, it provides a simple, gradual, adaptive transition between conditions in prosobranchs and those in opistho- branchs. Further, the system resulting from such a union provides a consistent starting point for the derivation of the various reproductive systems which exist in the different groups of opistho- branchs. The sudden superimposing of the male and female system would produce a highly inefficient structure in the sense that the various functions of the gonoduct might interfere with PHYLOGENY OF OPISTHOBRANCHS 339 va pr ae rs AS ve a -ca pr al bc A Aller ” ca me т ом В FIG. 2. Diagrams showing major variations. an example of an androdiaulic system (simplified); C, idealized oödiaulic system; D, Apylsia as an example of an oödiaulic system (after Eales, 1921, but simplified). A, idealized androdiaulic system; B, Acteon as al, “albumen” gland; membrane gland; seminis; am, ampulla; bc, bursa copulatrix; ca, copulatory apparatus; me, mu, mucous gland; ni, nidamental glands; pr, prostate; rs, receptaculum sg, seminal groove; va, vas deferens; arrows, direction of movement of the eggs. each other so much as to make the change to hermaphroditism adaptively deleterious. It seems reasonable to assume that the union took place gradually, with intermediate stages in which the animals were protandrous hermaphrodites rather than simul- taneous ones. The selective advantage of hermaphroditism has been discussed by Tomlinson (1963), who argues that it allows a low population density. A hermaphroditic reproductive system, formed by the superimposing of a male system upon a female one, is diagrammed in Fig. 1C. Such a re- productive system, from which those of all opisthobranchs may be derived, has a number of inefficient features, and in terms of these features one may explain the major modifications and evolutionary trends which occur in opisthobranch reproductive systems. A list of what appear to be the most important ofthese inefficient features follows. 1. Storage of endogenous sperm inthe ampulla interferes with the passage of eggs through the ampulla, and the move- ment of eggs through the ampulla could eject the sperm stored there. 2. Since the endogenous sperm, exo- 820” М. Т. GHISELIN genous sperm, and eggs must all move through the undivided gonoduct, guided at most by ciliary currents and by grooves, the various elements could easily be misdirected. Similarly, sperm may be lost during transfer along the open, external seminal groove. 3. The transfer of sperm by ciliary action is slow. The simplest solution to all of these inefficiencies is the formation of 3 closed, separate ducts, one for each of the 3 major functions of the original, undivided duct. A complete division of the male tract from the female, embracing the gonad, coelomic gonoduct and pallial gonoduct, appears never to have evolved, but the pallial gonoduct has developed a complete separation more than once. In addition, a number of other adaptations provide at least partial obviation of the various inef- ficiencies. A discussion of these adap- tations follows, along with a more de- tailed treatment of division. 1. The following mechanisms may be considered adaptations which have helped to alleviate interference between sperm and eggs in the ampulla. a. Sequential hermaphroditism. This may represent the original con- dition. It would not be a solution to the problem where simultaneous hermaphroditism is advantageous, although combined with the storage of exogenous sperm it would allow the organism to function as a simul- taneous hermaphrodite. b. Emptying the ampulla when the eggs pass through. This mechanism has been reported (Mazzarelli, 1891) for Aplysia, and may have been an adaptation allowing simultaneous hermaphroditism, but it has the obvious disadvantage of wasting sperm. Perhaps such wastage of sperm is partly compensated for by digestion of spermatozoa in the bursa copulatrix; Lemche (1956) has suggested that absorption of misdirected materials may be the major function of the bursa copula- trix, but little precise information in available. c. Formation of separate coelomic ducts for eggs andsperm. Such an adaptation has been reported in a nudibranch by Agersborg (1923), but Odhner (1936) disagrees. Al- though the ampulla has occasionally been said to be partly divided, there is no major group of opisthobranchs which is demonstrably charac- terized by such division; therefore, such divisions, whether or not they really exist, are primarily of theoretical interest, in that they illustrate one of many possible adaptations. а. Bypassing of the ampulla by the eggs. In certain sacoglossans (Pelseneer, 1894) the ampulla is a diverticulum of the coelomic gono- duct rather than a swelling, andthe eggs do not enter it. e. Formation of a ciliated tract which moves the eggs around the sperm, This adaptation is known in effective form in nudibranchs. f. Formation of a sperm-storage organ in the male part of the system. This modification has been reported from some pyramidellids and cephalaspideans (see below). 2. The following mechanisms prevent misdirection of the sperm and eggs in the pallial gonoduct. a. Division of the duct. The pallial gonoduct is often divided into a system of separate tubes through which individual materials pass in a single direction. b. Shortening of open grooves and un- divided ducts. In many forms, such as the Philinidae, the pallial gonoduct as a whole has shortened. As a result of this shortening, the genital products have a shorter distance to travel in the undivided gonoduct, and therefore there is a decreased likelihood that the differ - ent functions will interfere with one another or that the products willbe misdirected out of the grooves 3. PHYLOGENY OF OPISTHOBRANCHS 341 which conduct them. . Simplification. The inefficiencies of a structure may be overcome by its loss. The structures most commonly lost in opisthobranch reproductive systems are those the function of which may be discharged by another structure. For instance, of the 3 nidamental layers it is the “albumen” layer which is most often absent; the disadvantages of aloss of nutritive “albumen” could readily be compensated for by an increase in the amount of yolk. Since the bursa copulatrix and receptaculum seminis both may contain exoge- nous sperm, they are functionally equivalent to some degree, and often one or the other of these parts is absent. In those forms which lack a receptaculum seminis (Acteon- idae) the bursa copulatrix occupies the position characteristic of the receptaculum seminis (Fig. 2B), while in those forms which lack a bursa copulatrix (aeolid nudi- branchs) the receptaculum seminis often is located in the position characteristic of the bursa copul- atrix (Fig. 4). In some instances the receptaculum seminis and the bursa copulatrix appear to have fused into a single organ. The following mechanisms hasten the transfer of sperm. a. b. Shortening of grooves. The short- ening of the pallial gonoduct in such forms as the Philinidae has the advantage that the sperm have less distance to travel from the ampulla to the copulatory appa- ratus. This is particularly signi- ficant where the transport is by ciliary action rather than by muscular movement. Prostate. Prostatic cells seem to have been present in the common ancestor of the Opisthobranchia. They were probably present in the pallial gonoduct and functioned in forming a unitary mass ofsperma- tozoa which could effectively be moved through the open grooves by ciliary action. In androdiaulic and triaulic forms the movement of sperm is largely by muscular action, but the function of con- gealing the sperm into a more or less unitary mass is retained by the prostate. c. A separate, closed ejaculatory duct or vas deferens. Such a modi- fication may be only partial, asin Philine (Pruvot-Fol, 1930) and Cylindrobulla (Marcus & Marcus, 1956b), or it may be complete from the beginning of the pallial gono- duct to the end of the penis, asin androdiaulic and triaulic forms. d. Storage of sperm in the copulatory apparatus, This adaptation allows rapid copulation, since the sperm may be transported slowly to the copulatory apparatus along the seminal groove when the animal is not copulating, and stored there, allowing rapid copulation at a later time. e. Reciprocal copulation. Where copulation is reciprocal it should, theoretically, take place twice as fast as where the animals alternate in the male and female roles. Reciprocal copulation seems to be largely restricted to the triaulic and androiaulic forms (cf. Pruvot- Fol, 1960), since the presence of a penis in the gonoduct of a monaulic or oödiaulic form would obviously interfere with the passage of sperm. However, as anaspideans (which are oddiaulic) copulate in chains or reciprocally (Fischer, 1869; Mc- Cauley, 1960), it seems that a separate vas deferens is not abso- lutely essential. As may be seen from the above dis- cussion, the ancestral form of the opisthobranch reproductive system can be modified in a variety of ways such that its inherent inefficiencies no longer exist, or at least such that the effects of these inefficiencies are decreased. In- dependent lines of descent tend to under- 342 M. T. GHISELIN go different adaptations which overcome the same inefficiency. A change from one kind of adaptation to a particular inefficiency to another is not likely, since once the inefficiency has been overcome, there should be no selection pressure to produce such a change. For example, a change from an androdiaulic to an oödiaulic type of reproductive system is not to be expected, since it would have no particular advantage; on the other hand, a change from a diaulic to a triaulic arrangement would con- stitute a functional improvement, and would be expected. The existence of partial or imperfect adaptations to a particular selective influence does not prohibit the use of such partial or imperfect adaptations, but only causes a greater element of uncertainty to enter into the interpretation. Given an adequate understanding of the manner in which the reproductive system functions, it becomes clear that certain sorts of change are clearly deleterious, and may be rejected. For instance, there is no reason to expect a triaulic reproductive system to revert to the monaulic con- dition with all its inefficiencies. With an understanding of the manner in which the parts function, it may be possible to infer from peculiarities of the reproductive system some of the conditions under which the earlier stages of evolution took place. Some of the features of the reproductive systems which occur in the Sacoglossa, as, for example, the short duct which bypasses the membrane gland in Limapontia (Fig. 5E, *), are best explicable in terms of a specific kind of historical accident which took place in their phylogeny, and cannot be understood unless the manner of function of the parts is known. Like- wise, the diversity of imperfect solutions to the fundamental inefficiencies of the ancestral reproductive system (such as Simplifications and the shortening of grooves), which result in asystem which functions far less well than a triaulic one, can only be understood in terms of their derivation from such an ancestral form. In addition, certain changes which may be considered irreversible are of some value in ascertaining relationships. In Spite of the fact that the loss of a part is easily produced, it can serve as a sign of possible relationship; loss is also useful in that any phylogenetic derivation which requires the loss and reconstruction of a complex part may be considered dubious. Further, the loss in different groups of different parts which show some overlap in function, such as the bursa copulatrix and receptaculum seminis, may be in- terpreted as divergent adaptations to the same selective influence, suggesting that both of the parts were present in the common ancestor of the 2 groups. In such reasoning, the possibility of convergence is, of course, always present. It follows that it is best to minimize the possibility of being led astray by convergence by the selection of characters for comparison which are more complicated than simple loss of parts as well as relatively irreversible; if this is done, convergence is improbable and detectable. In the present work, an attempt is made to reconstruct the sequence of evolution of the reproductive system throughout the group in such a manner that the sequence of forms is consistent with the structural and functional po- tentialities of the system, and with the lines of reasoning outlined above. The possibility of convergence in particular features is fully admitted. However, once the more likely courses of evo- lution are hypothesized, it becomes possible to evaluate other lines of evi- dence in an attempt to reconstruct a phylogeny which is consistent with the structure and function of the reproductive system, with evolutionary theory, and also with analogous conceptions of the changes of other structures and systems. Any such study as this can only give a partial contribution to the problem at hand, and the ultimate criterion of the truth of its findings can only be the PHYLOGENY OF OPISTHOBRANCHS 343 degree to which it allows useful general- ization. A RECONSTRUCTION OF THE PHYLOGENY OF THE REPRODUCTIVE SYSTEM The Opisthobranchia and Pulmonata are often united on the basis of simi- larities in the nervous system and other structures into a single subclass, the Euthyneura. The structure of the re- productive system fully bears out this interpretation, as the reproductive system of all the Euthyneura can be derived from an ancestral form very much like that suggested below for the opisthobranchs. Indeed, it appears that one of the few characteristics which occur throughout the Euthyneura, but never in the Prosobranchia, is the peculiar spermatozoon, which has a Spiral filament wrapped around the head and mid-piece, giving it a pronounced screw-like appearance (Franzen, 1955). A detailed discussion ofthe reproductive system in the Pulmonata will not be given here. The somewhat aberrant ‘Pyramidellidae, which are often con- sidered prosobranchs, are included be- cause their reproductive system is comparable to that of the more typical opisthobranchs. The Reproductive System of the Common Ancestor of the Opisthobranchia The ancestral opisthobranch probably had an hermaphroditic reproductive system somewhat like that diagrammed in Fig. 1C. The degree to which it was protandrous cannot be established, since subsequent forms have evidently tended to evolve in the direction of simultaneous hermaphroditism. Those forms in which protandry is most pro- nounced, the pteropods, may have reverted to this condition because of their small size, whichhas the advantage in pelagic organisms of retarding sinking. The common practice of designating certain opisthobranchs as protandrous hermaphrodites simply because the male gametes begin to mature before the female is misleading. These so-called protandrous her- maphrodites probably function as simul- taneous hermaphrodites since, by the time they are able to function as males, they are capable of storing exogenous sperm in the viable condition until the eggs ripen. It may be that the eggs begin to ripen later simply because the exogenous Sperm can be stored. The pallial gonoduct included a re- ceptaculum seminis, a bursa copulatrix, and “albumen,” membrane and mucous glands. In the primitive condition the receptaculum seminis was situated at the most interior part of the pallial gono- duct and the bursa copulatrix near the common genital opening. Such an arrangement makes Zunctional sense, since the receptaculum seminis should have its duct in a position where the Spermatozoa can be conducted to the eggs before the latter receive their coverings. It is a little more difficult to justify the position of the bursa copulatrix near the common genital opening on purely functional grounds. For dealing with waste materials, the more distal position seems reasonable, and the reception of the sperm mixed with prostatic secretion by the bursa copulatrix might most easily be ac- complished by a bursa copulatrix having a duct in a position where it can readily receive the tip of the penis. But there is no obvious reason why the spermato- zoa Should not be deposited in the pallial gonoduct near its opening and transferred to a bursa copulatrix near the beginning of the pallial gonoduct. The experi- mental demonstration of Eales (1921) that in Aplysia the sperm are deposited in the pallial gonoduct suggests that the deposition of the sperm in the bursa copulatrix is not always necessary. Perhaps the transfer of spermatozoa through the pallial gonoduct is favored by their prior removal from the prostatic secretion. It may be that the distal position is in part the result of ante- 344 M. T. GHISELIN cedent historical conditions in which the reception of the penis in the bursa copulatrix was necessary. However this may be, the position of the bursa copula- trix near the common genital opening is very commonin prosobranchs (Fretter & Graham, 1962). In those opistho- branchs with an elongate, undivided gono- duct the bursa copulatrix is in this same position, and where it is more in- ternally located (Acteon, some sacoglos- sans), the configuration of the system is such that this condition can scarcely be considered primitive. The variations which occur within the group may be explained in terms of the difficulty of transferring sperm from the bursa copu- latrix to the receptaculum seminis. In all such deviant forms, there are one or more special modifications, such as those discussed in the preceding section, which overcome the inefficiency of the long, open duct with ciliated grooves, which primitively connects these struc- tures in mesogastropods and many opisthobranchs. The argument must be rejected that a condition in which the bursa copulatrix and receptaculum semi- nis are close together is primitive in monaulic forms. The shortening of the system as a whole provides a plausible transition from conditions which occur in mesogastropods, and has obvious func- tional advantage in that it decreases the distance which materials must traverse in open grooves within the undivided gonoduct, while the reverse change has no such explanatory value. Polyphyle- tic shortening of the pallial gonoduct accompanied by an approximation of the bursa copulatrix and receptaculum semi- nis may be seen in such monaulic groups as the family Aglajidae (cf. Guiart, 1901; Marcus, 1955, 1961b; Pruvot-Fol, 1954; Vayssiere, 1880; White, 1945, 1946). The above lines of reasoning do not necessarily conflict with Johansson’s (1957) argument that the bursa copula- trix of prosobranchs primitively occu- pied a position near the beginning of the pallial gonoduct, since he hypothesizes different functional conditions among early prosobranchs. The nidamental glands were all folds of tissue, composed of gland cells inter- spersed with ciliated cells. The eggs passed over the surfaces of these tis- Sues, moved by the action of the cilia, and the contents of the gland cells were deposited over them. Such a condition is known in certain Mesogastropoda (Linke, 1933), and persists in such opisthobranchs as the Doridacea (McGowan & Pratt, 1954). It is diffi- cult to establish which groups have been modified by developing a condition in which the eggs do not traverse the cavity of the “albumen” gland, since this struc- ture is often absent. If the nidamental layers originated from the secretion of gland cells in the ciliated epithelium of the mantle, originally deposited as the eggs passed over the epithelium, then it would be more reasonable to assume that the type of “albumen” gland which is traversed by the eggs is primitive. If one assumes that the condition in which the eggs do not enter the gland is primi- tive, one runs into difficulties in trying to explain how such conditions were evolved by natural selection. A change from an arrangement in which the eggs pass through the cavity of the gland to one in which the area of secretion is separated from the area of deposition could easily be produced by a gradual development of a tendency for the gland to secrete into the nonglandular portion of the gonoduct. The reverse change, even if it should for some reason be functionally advantageous, is less likely, since unless the “albumen” gland were completely and suddenly rearranged, with not only a mechanism for moving the eggs into the “albumen” gland and out of it, but also for moving the eggs across the secretory epithelium, the change would have no adaptive signifi- cance; in other words, the change can go only one way without something like a macromutation. The mucous gland was primitively a tube, perhaps folded to some degree. A system in which the mucous gland PHYLOGENY OF OPISTHOBRANCHS 345 has developed specialized secretory and depositional areas is known only in the Anaspidea (Mazzarelli, 1891); this condi- tion may be the result of the large size of the animal. Probably a prostate was presentinthe pallial gonoduct of the ancestral form. Although the prostate tends to occupy a position as part of the copulatory appa- ratus, this was evidently not the original location. The prostate is generally pallial in the Prosobranchia (Fretter & Graham, 1962); the Acteonidae include members in which the prostate is closely associated with the pallial gonoduct, while in the closely related Hydatinidae the prostate is part of the copulatory apparatus; the prostate of the Pyrami- dellidae is pallial. Evidently the pros- tate facilitated the movement of sperm in the open grooves. The opening of the pallial gonoduct was probably inside the mantle cavity, as is the case with prosobranchs, and with those opisthobranchs which retain a more or less unmodified mantle cavity. The penis was a projection on the side of the head, and was connected to the common genital opening by the open seminal groove, which extended to the tip of the penis. Sperm were con- ducted along the groove by ciliary action. Such an arrangement of the copulatory apparatus is retained relatively unmodi- fied in the Anaspidea (Eales, 1921), and agrees well with that which occurs in Mesogastropoda (Fretter & Graham, 1962). The position of the penis at a distance from the common genital opening was evidently a result of ances- tral conditions in which the shell blocked access to the pallial gonoduct. Probably the penis was contractile, but lackeda Sheath into which it could be withdrawn. Some protection for the penis would seem advantageous in burrowing gastro- pods, and in most opisthobranchs this protection takes the form of a penial Sheath. In Acteon, as in some proso- branchs, the shell gives protection to the penis, and it seems reasonable to infer that development of a sheath has followed reduction of the shell. Sucha Sheath could easily be evolved by in- vagination of the body wall, and may very well be polyphyletic. Similarities in the Reproductive Systems of the Acoela and the Acteonidae and Related Forms A number of similarities inthe repro- ductive systems of the cephalaspidean family Acteonidae and of the Acoela (Notaspidea and Nudibranchia) suggest that the groups may be related. The evidence is rather tenuous, but the possibility is real enough that it should be considered in further research. The reproductive system ofthe Acteo- nidae shares with that of the Nudi- branchia the possession of a particular kind of ciliated strip in the ampulla which moves the eggs around the sperm. In Acteon, Fretter & Graham (1954) describe a ciliated strip extending along the wall of the ampulla; to each side of this strip is a ridge of long cilia and gland cells which evidently restrict the eggs to the strip. I have sectioned the ampulla of Triopha carpenteri (Stearns, 1873), a dorid nudibranch, and found that the strip agrees very closely with the description given by Fretter & Graham of the ciliated strip in Acteon. Thompson (196lb) notes the presence of a ciliated strip in the ampulla of Tri- tonia hombergi, a nudibranch of the sub- order Dendronotacea, and describes how the strip moves the eggs around the sperm. Baudelot (1863) made a similar observation on the movement of eggs through the ampulla in Aeolidia papil- losa, a nudibranch of the suborder Eoli- diacea. I have observed transport of eggs by the ciliated strip in Dendro- doris albopunctata and in Hermissenda crassicornis; in each case, the eggs moved through the ampulla without be- coming mixed with sperm. It should be emphasized that more work on the structure and function of the ampulla is necessary, especially in smaller forms such as Embletonia (cf. Chambers, 1934), in which the ampulla seems to be some- 346 M. T. GHISELIN what divergent in structure. In subse- quent sections of this paper I show that the ciliation in the ampulla of a variety of opisthobranchs has been overlooked or misinterpreted; furthermore the vari- ation of the ciliated strip with physio- logical condition, as described by Fretter & Graham (1954), makes its interpre- tation difficult. Be this as it may, the ciliated strip shows some potential as an indication of relationship since: (1) it is fairly complex, (2) its adaptive Significance is known, (3) there are numerous other adaptations which can and do produce the same effect of getting the eggs past the sperm, and (4) it seems not to vary much within the Acoela. A possibility exists that all the Acoela and Acteonidae possess a pallial gono- duct which is either androdiaulic or else triaulic and hence derivable from the androdiaulic condition. In so far as I have been able to establish, there are only 2 possible exceptions reported in the literature, Rhodope (Marcus & Marcus, 1952)and Umbraculum (Moquin- Tandon, 1870). There is no reason for considering Rhodope, which is minute and aberrant, a member of the Acoela, other than its concentrated nervous system and lack of a shell. Riedl (1960) has shown that the nervous sys- tem of Rhodope is quite unlike that of nudibranchs; he argues that the embry- ology of the excretory system is closest to that of the pulmonates. Umbraculum should be reinvestigated by means of serial sections; Eliot (1910: 91) states clearly that Umbraculum has aninternal vas deferens, although he gives no sup- port for this statement. Similarly, Pelseneer (1906) states that the Nota- spidea are diaulic in the sense used here. The Reproductive Systems of the Hydatinidae, Acteonidae and Ringiculidae The cephalaspidean families Acteoni- dae (Bergh, 1901; Fretter & Graham, 1954; Johansson, 1954) and Hydatinidae (Bergh, 1901) are characterized by a closed vas deferens, and by having only one structure containing exogenous sperm (Fig. 2B). This sperm-containing structure is located in the position usually occupied by the receptaculum seminis, but Johansson (1954) has shown it to be a bursa copulatrix. Complete separation of the vas deferens from the pallial gonoduct in Hydatina has not been demonstrated conclusively, but it seems reasonable in the light of Bergh’s illus- trations. The prostate in Acteon (Fretter & Graham, 1954; Johansson, 1954) is surrounded by the mucous gland, and it appears that the only conspicuous difference between the reproductive sys- tems of the Acteonidae and of the Hyda- tinidae is that in the latter family the prostate has been displaced to the base of the penis. In Ringicula, whichis generally thought to be related to the Acteonidae, Fretter (1960) found that both bursa copulatrix and receptaculum seminis are present in the usual position, but was unable either to find the vas deferens noted by Pelseneer (1925) or to locate an exter- nal seminal groove. In view of these uncertainties, it is difficult to establish the systematic position of the Ringicu- lidae on the basis of the reproductive system. Reproductive Systems of the Notaspidea From an ancestral form such as that shown in Fig. 3A, I should derive all the reproductive systems which may be found in the Notaspidea and other Acoela, with the possible exception of Umbraculum. The evolutionary trends which occur in the nudibranch reproductive systems may also be seen in the Notaspidea. The configuration shown in Fig. 3A is, as discussed above, ineffecient in lacking a separation between the nidamental glands and the channel along which sperm is transported from the bursa copulatrix to the receptaculum seminis. The most effective adaptation which would over- come this inefficiency is the triaulic condition (Fig. 3B), which occurs in PHYLOGENY OF OPISTHOBRANCHS 347 va bc rs Va bc ya wa bc ni Se a va bc er FIG. 3. Diagrams showing variations in the arrangement of parts in the Notaspidea. Config- urations shownare known from at least some members of the following taxa (see text); A, hypo- thetical ancestor; B, Berthella; C, Pleurobranchaea; D, Berthelinia E, “Bourvieria” (sensu Vayssiere). am, ampulla; bc, bursa copulatrix; ni, nidamental glands; rs, receptaculum seminis; va, vas deferens. 348 M. T. GHISELIN such notaspideans as Berthella (Marcus € Marcus, 1955a) and in almost all dorid nudibranchs. Most pleurobranchs, how- ever, seem to have evolved different, and less effective solutions. Isolation of the nidamental glands, as occurs in Pleurobranchaea (cf. Bergh, 1897-98), prevents misdirection of sperm into the nidamental glands (Fig. 3C). Subsequent approximation ofthe receptaculum semi- nis and bursa copulatrix (Fig. 3D) makes two-way transport of materials in the gonoduct unnecessary; such a configura- tion is known in Berthelinia (cf. Lacaze- Duthiers, 1859). According to Marcus & Marcus (1959), Pleurobranchaea hamva has a configu- ration of the oviduct essentially like that shown in Fig. 3A, except that the bursa copulatrix has been lost. Absence of the bursa copulatrix seems to be a universal characteristic of the aeolid nudibranchs, in which the receptaculum seminis tends to occupy a position near the mouth of the oviduct, and a variety of pleurobranchs (Vayssiére, 1898, 1901) seem to manifest this same tendency toward a more external location of the receptaculum seminis. A configuration (Fig. 3E) has been reported in certain notaspideans, e.g., in what Vayssiere (1898) calls “Bouvieria ocellata”, in which it appears that the spermatozoa must be passed up the undivided ovi- duct while the eggs are being laid; it would seem that the movement of the receptaculum seminis to the mouth ofthe oviduct results in a functional disadvan- tage. Yet most, if not all, work on the reproductive system of notaspideans in question deals primarily with superficial configuration, and not enough is known of function and internal structure to exclude the possibility that the nidamen- tal glands are actually quite isolated, as in Fig. 3D. A possible explanation for the movement of the receptaculum semi- nis to the exterior in both notaspideans and aeolid nudibranchs is a shift in function as a result of which the sperm are deposited in the oviduct, or evenin the duct of the receptaculum seminis, rather than in the duct of the bursa copulatrix. There is evidence that such a functional shift has taken place in Pleurobranchaea meckeli (cf. Bergh, 1897-98). The result of such a shift in function would be that a movement of the receptaculum seminis towardthe ex- terior would allowa more effective depo- sition of sperm. One might object that the position of the receptaculum seminis at the mouth of the oviduct is primi- tive; but this assumption does not ex- plain such configurations as that shownin Fig. 3C, and it provides a less satis- factory transition from conditions which occur in other groups. Reproductive Systems of Dorid Nudibranchs The anatomy, histology and function of the reproductive system in dorid nudi- branchs have been exhaustively des- cribed by Baudelot (1863), Bolot (1886), Pohl (1905), Eliot (1910), Behrentz (1931), Lloyd (1952) and McGowan & Pratt (1954). The taxonomic literature includes descriptions ofthe arrangement of parts in large numbers of species. In so far as reliable information is avail- able, it appears that the reproductive system of all dorid nudibranchs except Bathydoris is triaulic. In contrast to the aeolid nudibranchs, a bursa copu- latrix is almost always present, and the existence of an “albumen” gland has been demonstrated (McGowan & Pratt, 1954). Bathydoris appears to be the only di- aulic dorid nudibranch (Evans, 1914). Odhner (1934) has described a repro- ductive system from Cadlina affinis which, superficially at least, appears to be diaulic, but the internal structure seems not to have been studied. C. affinis is one of many dorid nudibranchs which are thought to have an imperfect separation of the vaginal tract from the oviducal tract. Odhner (1926) has sug- gested that the degree of separation of the 2 tracts may have systematic signi- ficance, and postulates a series of changes with the receptaculum seminis PHYLOGENY OF OPISTHOBRANCHS 349 and bursa copulatrix both initially opening near the vaginal orifice, a de- velopment of a Separate vaginal duct, and the gradual extension of the division toward the coelomic gonoduct. However, this sequence may be based largely on superficial appearances. For instance, MacFarland (1909) demonstrated that in Discodoris voniheringi the vaginal and oviducal tracts, which externally appear only partly separated, are completely separate within the glandular mass. Odhner (1926) has discussed the func- tional basis of some evolutionary trends which he has observed in the mutual re- lationships between the receptaculum seminis and the bursa copulatrix. How- ever, these trends are polyphyletic and unidirectional, not showing any obvious divergences, and therefore cannot serve as a basis for the establishment of clades. Unlike the reproductive system in, say, sacoglossans or aeolid nudi- branchs, that of the dorid nudibranchs has not been shown to vary greatly in the division of ducts or the manner of function of the parts; such differences form the basis of comparison inthe pre- sent work. The differences within the Doridacea are mostly a matter of pro- portions of the parts and other minor variations such as occur quite generally in complex reproductive systems, but which apparently have insufficient adap- tive significance to allow their arrange- ment in divergent series of adaptive modifications. This lack of variation within the Doridacea is perhaps the best support for the functional arguments used in the present study, since no evolu- tionary change is expected where no functional cause exists for it. I refer the reader to the work of Pruvot-Fol (1960) for a further discussion of some variations of the reproductive system in dorid nudibranchs. The Reproductive System in Aeolid Nudibranchs The term “aeolid nudibranch” will, in conformity with common usage, be applied in the present discussion as a collective term for organisms belonging to the suborders Dendronotacea, Armin- acea, and Aeolidiaceaof Odhner (1939). The anatomy and histology of the repro- ductive system in these forms have been described in detail by Chambers (1934), Lloyd (1952), and Thompson (1961b), and further material is available in the taxonomic literature. Before beginning a discussion of the range of variation and evolutionary history of the repro- ductive system within the group, I will comment on some uncertainties, contra- dictions and misconceptions which exist in the literature. A prostate is occasionally said to be absent (Odhner, 1939: 42); however, the prostatic cells are usually, ifnotalways, present (Thompson, 1961b), although the prostate sometimes cannot be seen ex- ternally. Similarly, Odhner’s (1936: 1068-1071) series of stages of the sepa- ration of the male and female parts of the pallial gonoduct of the Dendro- notacea, including one in whichthe pros- tate is not separate from the female glands, reflects superficial appearances only (MacFarland, 1923; Marcus, 1961b; Thompson, 1961b). If attachment of spermatozoa to the wall of an organ which contains exogenous spermatozoa is sufficient evidence ofits homology to the receptaculum seminis of other opisthobranchs, then no sound evidence exists that any aeolid nudi- branch has a bursa copulatrix. Odhner (1939) states that the aeolid nudibranchs have only one “vesicula seminalis.” Attachment of spermatozoa in this struc- ture has been reported by Trinchese (1884) and various other workers. Whether the receptaculum seminis was located primitively near the opening of the oviduct to the exterior (external position, Fig. 4B), or in a more interior position (internal position, Fig. 4A) has been subject to inconclusive discussion. Odhner (1939) suggests that the “bursa” (i.e. the receptaculum seminis) hasbeen displaced to the interior in some aeolid nudibranchs, and points outthatthe posi- tion of this organ may vary within a 350 M. T. GHISELIN к ni am—— B ni Va Any ie rs ae D FIG. 4. Diagrams showing variations in the arrangement of parts in aeolid nudibranchs. Con- figurations shown are known from at least some members of the following taxa (see text): A, Hancockia californica; В, Tritonia (and numerous other forms); С, Doto; D, Armina. am, ampulla; fc, fertilization chamber; va, vas deferens. single genus (Odhner, 1936: 1068). Func- tional considerations make it seem more likely that the receptaculum seminis was internal in the common ancestor of the aeolid nudibranchs; comparison with other groups of opisthobranchs likewise makes this seem reasonable. The ten- dency for the receptaculum seminis to become external in position is probably polyphyletic, and this change is compen- sated for by a variety of mechanisms which allow the change. MacFarland (1923) found that in Hancockia califor- nica, a member of the Dendronotacea, the receptaculum seminis is in- ternal, and the nidamental glands are only partially isolated from the rest of the oviduct (Fig. 4A). According to ni, nidamental glands; rs, receptaculum seminis; Odhner (1936), the receptaculum seminis in other species is external, and the nidamental glands are more isolated (Fig. 4B). H. californica represents the ancestral condition if one reasons that the nidamental glands have become iso- lated because sperm tended to be mis- directed into them in the ancestral condi- tion, and that the receptaculum seminis migrated to the exterior because sperm were more easily deposited init andtwo- way transport of materials in the un- divided gonoduct became unnecessary in the modified form. The reverse trans- formation would have no adaptive basis, unless one assumes that the nidamental glands were completely unisolated from the oviduct; in this case we should have PHYLOGENY OF OPISTHOBRANCHS 351 to account for the original migration of the receptaculum seminis to the mouth of the oviduct. Such an alternative interpretation, while possible, does not explain such configurations as occur in some species of Doto (Fig. 4C; cf. Marcus, 1961b). Thearrangement shown in Fig. 4B also occurs in Tritonia (Thompson, 1961b), and its derivation from a form in which the receptaculum seminis occupied a more internal posi- tion is strongly supported by embryo- logical evidence (Thompson, 1962). The conditions which are found in some species of Doto (Marcus, 1961b) may be considered an intermediate stage (Fig. 4С). Odhner’s (1936) embryo- logical evidence suggests that the tri- aulic condition was evolved after the receptaculum seminis in Dendronotus became external, but tells us nothing about the original conditions in aeolid nudibranchs. In certain species of Ar- mina (Marcus & Marcus, 1960b) the nidamental glands remain opentothe rest of the oviduct, the receptaculum seminis is external, and a fertilization chamber has developed in the position usually occupied by the receptaculum seminis (Fig. 4D). Apparently, the transfer of sperm to the fertilization chamber occurs prior to the descent of the eggs. An analogous fertilization chamber exists in such Aeolidiacea as Coryphel- lina (Marcus, 1961a). Evans (1922) des- cribes a fold in the oviduct of Calma which allows the spermatozoa to pass up the oviduct to the point of fertili- zation while the eggspassthrough. These varied modifications may easily be understood as different adaptations to the loss of the bursa copulatrix; they allow the receptaculum seminis tobe external. The internal position of the receptacu- lum seminis in a number of aeolid nudi- branchs bears out this interpretation, if we assume that these forms have happened not to develop a new mechan- nism for getting the eggs past the sperm to the point of fertilization while the eggs are being laid. The triaulic condition shows some pro- mise as indicative of relationships, since it would seem unlikely that such a con- dition, once gained, would be lost. How- ever, it is clear that the triaulic con- dition has arisen polyphyletically, at least once in the Dendronotacea and in the Arminacea, and at least twice in the Aeolidiacea. Some possible phylogenetic inferences are suggested ina subsequent section on the basis of attempts to group triaulic forms together; however, these are most uncertain not only because of polyphyletic origin, but also because the triaulic condition can easily be over- looked. The following is a list of the forms which have been reported in the literature to be triaulic. Dendronotacea Dendronotus frondosus (Odhner, 1936) Arminacea Antiopella muloc (Marcus, 1958) Janolus comis (Marcus, 1958) Aeolidiacea Pseudovermis spp. (Marcus & Marcus, 1955b) Miesea evelinae (Marcus, 1961a) Embletonia fuscata (Chambers, 1934) E. pallida (Marcus & Marcus, 1955b) Dondice banyluensis (Portmann & Sandmeier, 1960) Aeolidia papillosa (Eliot, 1910) Berghia coerulescens (Marcus, 1957) Spurilla neapolitana (Marcus, 1957) I have omitted Doto uva from the above list, since the structure which Marcus (1957) calls the fertilizing duct opens near the mouth of the oviduct, and the “vagina” opens into the penial sac; this part is probably not a functional ferti- lizing duct. Reproductive Systems of the Pyramidellidae Almost all of our knowledge of the reproductive system in pyramidellids is due to the work of Fretter & Graham (1949, 1962) and Fretter (1953). The system is clearly monaulic, a sperm- 352 M. T. GHISELIN containing organ is associated with the copulatory apparatus, and the prostate is pallial. In some pyramidellids the seminal groove is not completely closed to form a vas deferens or ejaculatory duct (Fretter, 1953); it would appear that a closure of the duct has arisen within the group, since a closed duct should be more effective in the trans- ference of sperm. Although protandry has been recorded, Fretter & Graham (1949) have reported that sperm are pre- sent in the ampulla when the eggs pass through it; the mechanism which allows the eggs to pass the sperm in the am- pulla has not been discussed in the literature. The presence of “albumen,” membrane and mucous glands has been demonstrated, and their functions deter- mined (Fretter & Graham, 1949); these glands are somewhat isolated from the rest of the gonoduct, and communicate with it by narrow ducts. Abursa copula- trix is absent, and the receptaculum seminis is quite distant from the common genital opening; the ducts of the recep- taculum seminis and of the various nidamental glands are located quite close together (Fretter & Graham, 1949). Such a system could readily be derived from the ancestral type suggested’ above for the opisthobranchs; but the specializa- tions of the copulatory apparatus, the loss of the bursa copulatrix, and the concen- tration of the nidamental glands makes this system difficult to compare with that of any other opisthobranch except in the most general way. Not enough is known of the reproductive system with- in the Pyramidellidae to infer much about evolution within the group. The Oddiaulic Type This type is a variation of the ances- tral form in which the nidamental glands have, to a greater or less degree, acquired a separate, closed channel by a division of the pallial gonoduct (Fig. 2C, D). Such a system, or one which may be derived from it, probably exists in all the Anaspidea, Sacoglossa and Cephalaspidea of the family Diaphanidae which have been sufficiently well studied to allow a decision on this matter. The oödiaulic system appears to be restricted to these groups, and the thesis is here maintained that it is monophyletic. Pos- sibly, some pteropods, if not all, are also oddiaulic. Odhner (1926) has reviewed the struc- ture of the reproductive system in the Diaphanidae, and compares it to that of the Anaspidea, not only on the basis of the lack of a prostate associated with the penis, but also because of the general arrangement of ducts and grooves. If Odhner’s “Spivalkanal” is homologous to the “winding gland” in the anaspidean Aplysia (Eales, 1921), then the reproductive system in both groups is essentially that shown in Fig. 2D. However, a receptaculum seminis is apparently absent in the Diaphanidae which Odhner describes, andthe division of the duct in Aplysza is more extensive than that of the Diaphanidae. Differences in the gross appearance of the repro- ductive systems of the 2 groups are easily explained by differences in size; the proportions of the parts, the extent of the division of the duct and the way in which the system is contracted into a compact mass may vary to some degree. That the “winding gland” of anaspideans is the usual membrane gland is clear from its position (Eales, 1921), and also from its histology (Mazzarelli, 1891), the “winding gland” being the only nidamental gland which has an arrangement of secretory cells inter- spersed with ciliated cells such that it can secrete a membrane as the eggs pass through it. There is also a good agreement in the folded appearance and in staining reaction (Inigier, 1907; Odhner, 1926). Guiart (1901) states that the winding gland forms the membrane in the Anaspidea. Evidence that the Sacoglossa were primitively oödiaulic is somewhat more tenuous, but Cylindrobulla, which is ap- parently oödiaulic (Marcus & Marcus, 1956b), forms a good transition between the Diaphanidae and such triaulic Saco- PHYLOGENY OF OPISTHOBRANCHS 353 glossa as Berthelinia (Kawaguti € Yamasu, 1961). Certain Sacoglossa are said to be androdiaulic. However, a critical review of the literature, dis- cussed in detail below, has convinced me that such views are either unfounded or erroneous, or else are based on the study of forms in which the diaulic condition is clearly secondary. Inevery study of the reproductive system in sacoglossans which has involved a study of serial sections of animals killed in the process of laying eggs (Lloyd, 1952; Gascoigne, 1956; Kawaguti € Yamasu, 1961), the animals studied were found to be triaulic. The study of the repro- ductive system in the Sacoglossa is ex- ceedingly difficult, especially since the function of the parts has only been re- cently worked out. The parts are highly complicated, and the division of the ducts may extend over only a very short dis- tance (Brüel, 1904) As Pelseneer (1894) has pointed out, the division of the ducts may occur very late in ontogeny. Thus the theory that the Sacoglossa were primitively oödiaulic remains somewhat speculative, but there appears to be some evidence for it. The Anaspidea and Sacoglossa, in so far as it is known, show a further point of resemblance in having an “al- bumen” gland of the type in which the eggs do not enter the cavity of the gland. No information is available on this point for the Diaphanidae. In Aplysia (Eales, 1921) the “albumen” is applied in a fertilization chamber, and an “al- bumen pouch” having this function has been described for Berthelinia, a saco- glossan (Kawaguti & Yamasu, 1961). The fact that the bursa copulatrix serves mostly as an organ which deals with dead spermatozoa and other waste materials, and not in receiving the exogenous spermatozoa was demon- strated experimentally for Aplysia by Eales (1921); evidently, the duct of the receptaculum seminis receives the exo- genous sperm. The location ofthe bursa copulatrix in some of the more modi- fied sacoglossans at a point where it cannot receive sperm directly at copu- lation (cf. Gascoigne, 1956) suggests a similar function throughout the oödiaulic forms and those derived from them; it may explain the proximity of the recep- taculum seminis to the bursa copulatrix in Cylindrobulla (Marcus & Marcus, 1956b) and other shelled sacoglossans. The mechanism by means of which the eggs were moved past the sperm in the ampullae of the common ances- tors of the Anaspidea and Sacoglossa is difficult to determine. Nothing is known about the histology or functional anatomy of the ampulla in the Diaphan- idae. In Aplysia, Mazzarelli (1891) notes the presence of cilia in the am- pulla, and observes that the eggs pass through the ampulla and force a quantity of sperm through with them. Eales (1921) states that cilia are not pre- sent in the ampulla of Aplysia, but Marcus & Marcus (1957) do report the presence of cilia in the ampulla, as does Hirase (1929) for Dolabella. Becker (1960) found that in the sacoglossan Bosellia mimetica the eggs are able to pass by the sperm in the ampulla. Kawaguti & Yamasu (1961) say that when the eggs pass through the ampulla of Berthelinia, the bivalved sacoglossan, they carry endogenous sperm with them. In various species of Elysia (Pelseneer, 1894; Marcus, 1955) the ampulla is a separate, blind pouch through which the eggs do not pass. Ihave sectioned the ampulla of Hermaeina smithi, and have found that it contains a ciliated strip in the form of a single, irregular ridge of ciliated cells; it is quite unlike the strip which occurs in Acteon or in the Acoela. In addition to the ciliated strip, the ampulla of H. smithi con- tains numerous, tall secretory cells; gland cells are said to be absent in the ampulla of Limapontia and Alderia (Lloyd, 1952). , From the above it seems, in so far as information is available, that in both the Anaspidea and Sacoglossa the ampulla is far more variable than in the Acoela, suggesting that adaptation to the problem 354 M. T. GHISELIN of getting eggs past the sperm has taken place within both the Anaspidea and Saco- glossa. Direct observational evidence is available to show that, at least in some forms, this adaptation is only par- tial. The homologies of the various ciliated strips are hard to assess, but it is possible that the common ancestor of the opisthobranchs had some kind of ciliated strip in the ampulla. However, the available evidence suggests that the ciliated strip is fully effective only in the Acoela and perhaps the Acteonidae. Evolution within the Sacoglossa The only sacoglossan which does not have avas deferens completely separated from the pallial gonoduct is Cylindro- bulla (Marcus & Marcus, 1956b), which retains a large number. of primitive features. Caliphylla (Brüel, 1904) is said to have a short division of the oviduct (Fig. 5A). In Berthelinia (Kawaguti & Yamasu, 1961) this split is far more extensive (Fig. 5B). In Lima- pontia, Gascoigne (1956) and Lloyd (1952) have described an arrangement which on superficial examination looks very dif- ferent from that of other sacoglossans (Fig. 5E). In thiskindofsystemthe eggs pass out of the coelomic gonoduct into the pallial oviduct and pass to one end of the membrane gland (Fig. 5E, *). In- stead of entering the membrane gland, however, they pass into a peculiar loop (1) which conveys them to the other end of the membrane gland, where they are fertilized by spermatozoa from a kind of modified receptaculum seminis (rs+), and receive the “albumen” from the “albumen” gland (al). They are then covered by a membrane and pass to the mucous gland (mu) where the egg mass is completed. This configuration can hardly be considered an effective mech- anism for producing masses of fertilized eggs, for one would think that a simple triaulic system would function much better. Probably the unusual configura- tion is a result of historical accident. Figures 5C and 5D show hypothetical intermediate steps by which the condi- tions in Limapontia (Fig. 5E) could be derived from an arrangement similar to that of Caliphylla (Fig. 5A). In Fig. 5C a second split has developed in the ovi- duct; such a split is known in various sacoglossans. In Fig. 5D, the vaginal duct (vd) has shortened, and the recep- taculum seminis has fused with another vaginal duct to form a complex struc- ture (rs+). To allow a transition from the configuration shown in Fig. 5D to that shown in Fig. 5E, all that would be necessary would be an extension of the second split to the area of the duct of the albumen gland. The somewhat un- usual position of the bursa copulatrix becomes readily understandable when it is realized that in these forms this organ has ceased to receive sperm at copula- tion and functions as a receptacle for dead sperm and other materials (Lloyd, 1952). Lloyd (1952), on finding that Alderia modesta has a reproductive system such as is diagrammed in Fig. 5F, reasoned that it was derived from a system like that of Limapontia (Fig. 5E) by loss of the bursa copulatrix and the communi- cation between the undivided portion of the oviduct and the membrane gland (Fig. 5E, *). However, the arrange- ment which exists in Alderia could just as well have arisen by a modification of a system with only one split in the oviduct. Some comments follow on the litera- ture concerning reproduction in the saco- glossans. The reproductive system of these animals has been misinterpreted largely because the membrane glandhas been overlooked. Gascoigne (1956) and Kawaguti & Yamasu (1961) have identi- fied this structure. The staining reac- tions of the membrane material are such that the membrane gland is easily con- fused with a part of the mucous gland; the interpretations given here (Fig. 5) are reinterpretations of older accounts in the light of recent work on the mem- brane gland. An attempt is here made to group the sacoglossans according to the number of splits in the oviduct and PHYLOGENY OF OPISTHOBRANCHS 355 mu va am € vd ) Irs al Me va bc am va al | | SEE nay ==> PS+ GS de mA mu F me mu E FIG. 5. Diagrams showing variations and hypothetical intermediate stages in the evolution ot reproductive systems in the Sacoglossa. A, Caliphylla; B, Juliidae; C,D, hypothetical inter- mediate stages; E, Limapontia; F, Alderia. al, “albumen” gland; am, ampulla; be, bursa copulatrix; 1, loop; me, membrane gland; mu, mucous gland; r, receptaculum seminis?; rs, receptaculum seminis; rs+, compound structure including the receptaculum seminis; va, vas deferens; vd, vaginal duct. Arrows show the path of the eggs; the asterisk indicates the short duct bypassing the membrane gland. 356 M. T. GHISELIN the arrangement of the parts. Berthelinia certainly has one splitand only one (Kawaguti & Yamasu, 1961). Pelseneer’s (1894) work on the shelled Lobiger did not deal with the details of internal structure of the pallial gono- duct, and Marcus (1957) did not discuss this question. According to Brüel (1904) Caliphylla mediterranea has a small internal division (Fig. 5A) which Marcus (1958), who does not cite Brüel’s work, may have overlooked. Gonor (1961) gives a detailed description of a repro- ductive system in Hermaeina in which the division of the oviduct is single, and Lloyd (1952) has described sucha system in Alderia. Von Ihering (1892) demon- strated that the reproductive system in the shelled Oxynoe is triaulic, with a well developed division, of the duct. The doubly-divided oviduct certainly exists in the Limapontiidae (Gascoigne, 1956; Lloyd, 1952; Pelseneer, 1894), and in at least one species of Stiliger (Rao, 1937). It has also been described in Elysia (Pelseneer, 1894; Marcus & Marcus, 1959). Pelseneer (1894) des- cribes a system in Elysia viridis in which the oviduct is doubly-divided, and in which the duct of the bursa copula- trix also shows a division; this may be considered a variation. Becker (1960) illustrates a system of Bosellia in which there appear to be 2 splits in the ovi- duct, suggestive of conditions to be found in Elysia. Among these forms, the type of reproductive system which occurs in the Limapontiidae has also been found in Hermaea dendritica (Pelseneer, 1894) and in Stiliger (Rao, 1937). From the fact that, according to Pelseneer (1894) the opening of the va- ginal duct occurs late in ontogeny, or, according to Gascoigne (1956), never at all in some modified forms, I question the view of Marcus (1955, 1958) that Elysia is sometimes diaulic. Similarly inconclusive are a number of interpre- tations of Marcus (1957, 1958) and of Marcus € Marcus (19564) of several species of Stzliger in which the “albumen” gland is depicted as entering the so- called mucous gland at a point which probably corresponds to the transition between the division between the mem- brane and mucous glands, because such an arrangement would not function; how- ever, they describe these animals as triaulic, if somewhat different from the form described by Rao (1937). Marcus & Marcus (1960b) argue that Tridachia crispata is diaulic, because they found no separate vaginal opening. But since they say that the female germ cells were immature, since the entrance of the “albumen” gland into the gonoduct before the latter bifurcates may be taken as a sign of immaturity, and since a partial bifurcation, such as occurs in Caliphylla may have been overlooked or have been still unformed, their inter- pretation is open to question. Conditions in the genus Hermaea are most uncertain. Pelseneer’s (1894) account of Hermaea dendritica shows that a system of the Limapontia type (Fig. 5E) is present in at least some members of the genus. Pelseneer (1894) states that H. bifida is diaulic, and Marcus (1955) likewise considers the oviduct of H, coivala to be undivided. Again, a con- nection may have been overlooked, es- pecially since the membrane and mucous glands have not been studied in detail. Briiel (1904) argued that H. bifida does not fit well into the genus Hermaea, and if the genus is artificial, then the deviant condition of the reproductive sys- tem might well be explained. Derivation of the Limapontia type of reproductive system from that which occurs in the allegedly diaulic Hermaea species seems improbable; either the Limapontia type would have to be biphyletic, which, owing to the complexity of the system is un- likely, or else the continuity which Ihave shown between the various sacoglossan reproductive systems is erroneous, which is admittedly a possibility. If H. bifida and H. coirala are actually diaulic, the reproductive system is still some- what atypical, and probably modified, since the bursa copulatrix is quite in- PHYLOGENY OF OPISTHOBRANCHS 357 ternal. It may be that this system has arisen through a secondary simplifi- cation of a Limapontia type of repro- ductive system. Such a simplification may be advantageous in a highly compli- cated system, and would not constitute an exception to the general rule that a triaulic system does not revert to the diaulic condition, since the Limapontia type is doubly triaulic and probably de- rived from one in which the triaulic condition was only partial. Simplifi- cation of function is known in the form of hypodermic impregnation by way of the haemocoel in Alderia (Hand & Steinberg, 1955), and analogous simplification may explain many anomalies in the construc- tion of the sacoglossan reproductive sys- tem. Further research on the anatomy of sacoglossan reproductive systems is necessary to clear up the uncertainties mentioned above. My interpretations and criticisms must be considered hypothe- tical, especially in the light of the great apparent variability of the system within the group, which makes any comparative interpretation highly speculative. Brüel (1904) argued that the reproductive sys- tem in the sacoglossans was primitively triaulic, suggesting that the division of the oviduct has become less extensive secondarily. I am inclined to argue that the reproductive system in sacoglos- sans was primitively oddiaulic (as in Cylindrobulla) and later became triaulic, since this assumption allows a transition from other groups of opisthobranchs to such forms as Berthelinia which have a system differing very little from the usual opisthobranch arrangement; fur- ther, it allows a consistent derivation of the reproductive systems of those saco- glossans in which the reproductive sys- tem is best known. But polyphyletic increase in the extent of the division of the duct seems to me more reason- able in terms of functional advantage. Reproductive Systems of the Acochlidiacea The Acochlidiacea are, in general, small, mesopsammal organisms, and show various kinds of reduction which obscure their relationships. Gonochor- ism, loss of the penis, and formation of spermatophores may be taken as secondary simplifications resulting from small size in the Microhedylidae (cf. Kowalevsky, 1901; Marcus, 1953; Marcus & Marcus, 1954), since other groups of acochlidiaceans show a more typical reproductive system, and reconvergence is not likely. The reproductive system of the Hedylopsidae has been treated by Odhner (1937) who shows that the seminal groove is open, although a closed ejacu- latory duct associated with what he calls a “vesicula seminalis” is present. The copulatory apparatus in the Hedylopsidae has also been described by Kiithe (1935); the copulatory apparatus would appear, at least superficially, to resemble that of the Pyramidellidae, if Odhner’s term for the appendage of the ejaculatory duct actually corresponds toits function. In so far as I have been able to tell from published accounts, there is no internal division of the pallial gonoduct in the Microhedylidae or Hedylopsidae, and it would appear that this condition was primitive in the group, although reduction due to small size cannot be excluded. In view of Odhner’s (1937) suggestion of a possible relationship be- tween the Acochlidiacea and the Dia- phanidae, further work should be di- rected toward attempting to establish whether or not such a division exists. At present there is no good evidence in the structure of the reproductive system in the Acochlidiacea which sug- gests an affinity to any other order of opisthobranchs, beyond those features clearly derived from the common an- cestor of the Opisthobranchia. A Comparison of the Reproductive Systems of the Remaining Cephalaspidea and of the Pteropods All of the cephalaspideans not dis- cussed so far (Scaphandridae, Philinidae, Aglajidae, Gastropteridae, Bullidae, Runcinidae, Atyidae, Retusidae and 358 — M. T. GHISELIN Philinoglossidae) are monaulic, and re- semble the pteropods in having a pros- tate associated with the copulatory ap- paratus. The degree to which this simi- larity may be taken as an indication of relationship cannot be determined at present. The monaulic condition indi- cates only that these animals are not descended from diaulic forms; likewise the prostate could easily have attained its present position polyphyletically. Nonetheless, a clear relationship does seem to exist between many of these forms, and they will be treated together for convenience. As the pallial and coelomic gonoducts do not seem to vary greatly in these forms, the relation- ships must be determined largely on the basis of the copulatory apparatus. Diagrams of a number. of copulatory apparatuses are given in Fig. 6; among these, the most primitive type would be that which has an open seminal groove extending to the tip of the penis, and a prostate secreting into the seminal groove (Fig. 6A). Such a copulatory apparatus has been reported from the Gymnosomata (Morton, 1958), and from a variety of cephalaspideans. The funda- mental inefficiency of this kind of copu- latory apparatus lies in the transfer of Sperm by open grooves during copulation; Sperm would be expected to leak out of the groove and to be moved only slowly by ciliary action. The inefficiency of Open grooves in general is especially great in the copulatory apparatus; ob- viously, when the penis is thrust into the vagina, transfer along the open groove on the penis is particularly dif- ficult owing to mechanical deformation. The most obvious improvement over the primitive arrangement would be the formation of a closed ejaculatory duct (Fig. 6C, E); this modification seems to have arisen separately within several natural groups but is usually not ac- companied by formation of a completely closed vas deferens. This frequency of only partial modification suggests that the closure of the seminal groove in the copulatory apparatus itself has particu- larly great functional advantage. Other modifications of the copulatory apparatus can produce the effect of hastening the transfer of sperm and preventing the loss of sperm from open grooves. One of these modifications (Fig. 6B) involves the development of a sperm storage organ (spermatic bulb) as a part of the copulatory apparatus; sperm are transferred to the copulatory apparatus before copulation. These differing adap- tations which overcome the same inef- ficiency cannot readily be derived from each other, and therefore can be looked upon as divergences, hence as good signs of lack of relationship; as indi- cations of natural groups their useful- ness is somewhat more limited, owing to the relative simplicity of their struc- ture and the probability of convergence. Cephalaspideans with a Spermatic Bulb, and Possibly-Related Forms In a number of cephalaspideans the copulatory apparatus is so modified that it contains a sperm-storage organ, the spermatic bulb (Fig. 6B). In at least some of these forms the prostate has taken on the function of pro- ducing spermatophores. The duct of the prostate functions as an ejacula- tory duct. A penis may be present, but usually the everted penial sac-serves this function, especially in the smaller forms. This kind of copulatory appa- ratus occurs in the families Atyidae (Marcus & Marcus, 1959), Bullidae (Marcus, 1957), Runcinidae (Ghiselin, 1963), Philinoglossidae (Marcus, 1953), and Retusidae (Marcus & Marcus, 1960b). It also occurs in Tornatina (Marcus, 1956), which has been variously placed in the Retusidae and Scaphandridae. This type of copulatory apparatus ap- pears to be somewhat variable in mor- phology, especially in the form of the prostate; hence its fundamental uni- formity in physiology has tended to be overlooked. Spermatophores have been observed in Haminoea (Perrier € Fischer, 1914), and in Runcina (Ghiselin, 1963). Marcus & Marcus (1960) say PHYLOGENY OF OPISTHOBRANCHS 359 FIG. 6. Simplified diagrams showing the arrangement of parts in the copulatory apparatus of certain cephalaspideans. A, ancestral form; B, Atyidae, etc.; C, Philine aperta; D, Philine alba; E, Scaphander lignarius. at, attachment of prostate to penial sac; dp, duct of prostate; ds, seminal duct; ed, ejacula- tory duct; o, opening to seminal duct; op, opening of the prostate; pe, penis; pr, prostate; ps, penial sac; sb, spermatic bulb; sg, seminal groove. 360 that Rhizorus may produce a spermato- phore. Although Perrier & Fischer (1914) searched in vain for spermato- phores in Bulla, this negative evidence is hardly conclusive, since in Runcina spermatophores are only occasionally present (Ghiselin, 1963). This modified copulatory apparatus is quite distinctive, in spite of its varia- bility in some forms. The evidence that it exists in all members of the families and genera mentioned above is, admittedly, somewhat ambiguous. Odhner (1924) did not find a spermatic bulb in Runcinella, but his animals may have been immature. Burn (1963) states that a spermatic bulb is absent in some of the Runcinidae, but it is clear from his drawings that the copulatory appara- tus is very similar to that of other mem- bers of the family in which a sper- matic bulb is present. Marcus (1961b) notes that a spermatic bulb is some- times said to be absent in Bulla gould- tana; Specimens which I have examined vary in its development, suggesting that the spermatic bulb is only present in ani- mals which are in breeding condition. I have not been able to obtain specimens of В. gouldiana in which the presumed spermatic bulb is well developed. Sections of the copulatory apparatus in which the presumed spermatic bulb was quite small did not reveal the presence of spermatozoa, although the lumen was full of the usual eosinophilic, corpuscular secretion. It appears that the tubular structure mentioned by Marcus (1957, 1961b) is homologous to the prostate of other cephalaspideans. Reproductive Systems in the Scaphandridae, Philinidae, Aglajidae and Gastropteridae As Pruvot-Fol (1954) observes, the systematic interrelationships between these families are very much in doubt. The Scaphandridae would appear to be a highly diverse group of forms which are united mainly on the basis of their ex- ternal shell and relatively unmodified digestive system; these are primitive M. T. GHISELIN characteristics not likely to reveal re- lationships. Some forms with a sperm- atic bulb are often placed in the Scaphan- idae, and it seems likely that anadaptive radiation took place at a grade of evo- lution attained by the more primitive members of the family, leading toforms with a spermatic bulb on the one hand, and to a clade including Scaphander, the Philinidae, the Aglajidae andthe Gastro- pteridae on the other. The difficulty of placing these forms in a systematic arrangement results, if this postulated adaptive radiation did occur, from subsequent parallel and convergent changes. The clade which includes the Philinidae is fairly generally recognized, although its precise interrelationships remain obscure (cf. Pruvot-Fol, 1954; Boettger, 1954). There appears to beatrend with- in the group for a reduction of the shell and radula. In Scaphander the shell is external, and the radula formula is I-1-I; in Philine and the Gastropteridae the shell is internal, and the radula formula is I-O-I or n-I-O-I-n; in the Aglajidae the shell is internal and the radula is absent; in certain Philinidae, all Aglaj- idae and the Gastropteridae, the gizzard plates have been reduced or lost (Pruvot- Fol, 1954). Pruvot-Fol (1954) has commented on the difficulties of deciding whether certain exotic forms should be placed in Scaphander or in Philine. Such uncertainties and the general tendency for a loss of the shell and of the hard parts of the gut make it appear likely that parallel developments have taken place. A consideration of the implications of the reproductive system for the evolution of the group follows, because of its theoretical interest and because it clarifies some questions raised in the literature (Pruvot-Fol, 1960). More definite conclusions as to the relationships between the various groups must await the accumulation of additional evidence. The coelomic gonoduct of certain Scaphandridae and related forms has a section in which there are numerous POOP Sw PHYLOGENY OF OPISTHOBRANCHS 361 secretory cells of unknown function. The histology of this secretory area has been described for Cylichna by Lemche (1956), and for Philine and Scaphander by Lloyd (1952). The probable homologue of this structure may be seen in Guiart’s (1901) diagrams of the reproductive systems of Aglaja and Gastropteron. The ampulla of Cylichna has been reduced, evidently because of the small size of this form (Lemche, 1956). In Philine alba my sections show the presence of a ciliated band which extends through the length of the ampulla. A series of secretory cells and long cilia, such as may be found in Acteon and the nudibranchs, was not observed, although the possibility that the animal studied was not in breeding condition cannot definitely be excluded. In the Aglajidae, a closed ejaculatory duct is sometimes present, but in a number of forms the seminal groove extends to the tip of the penis (Marcus, 1961b). A prostate is present, often in the form of a pair of lobes. The copulatory apparatus in this family has not been studied in sufficient detail to allow a detailed comparison with other forms. The copulatory apparatus of Philine aperta (Fig. 6C) has been described by Pruvot-Fol (1930) and studied in detail by Lloyd (1952). The seminal groove (sg) enters the penial sheath, where it communicates with the opening (o) of a sperm duct (ds). This sperm duct joins with the duct of the prostate (dp) toform a divided tube with a common muscular sheath, but with a distinct partition be- tween the 2 ducts. Inside the penis (pe), the 2 separate ducts unite to form a single ejaculatory duct (ed). The prostate (pr) is a very long, closed tube which is attached by a strand of tissue to the penial sheath. According to Pruvot-Fol (1960) this type of copulatory apparatus probably exists in a number of species of Philine, but not in all. Lloyd (1952) has studied a somewhat different copulatory apparatus in Scaph- ander lignarius (Fig. 6E), in which the seminal groove communicates with the ejaculatory duct (ed) through a pore (о) at the base of the penis. The prostate (pr), in the form of a bulb with secretory tubules, communicates with the ejacula- tory duct (ed) via a short duct. Mattox (1958) has described a copula- tory apparatus in Philine alba which resembles that of Scaphander lignarius except that there is an open seminal groove instead of a closed ejaculatory duct (Fig. 6D). By means of serial sections I have been able to verify and Supplement Mattox’s observations. The seminal groove (sg) enters the opening of the duct of the prostate (dp). The surface of the prostate is increased by a folded projection of one of the walls, not by tubules as in Scaphander. The prostate and its duct are surrounded by a layer of circular muscles, which Suggests that the prostate functions as an ejaculatory vesicle. The epithelium of the prostate secretes the usual cor- puscular, eosinophilic substance. Lloyd (1952) suggests that the copula- tory apparatus of Scaphander lignarius (Fig. 6E) arose from one like that of Philine aperta (Fig. 6C) by concentration of the prostate and shortening of the ducts. If this interpretation is correct, and if the kind of copulatory apparatus found in P. aperta is not polyphyletic, then it follows that the genus Philine has been derived from Scaphander at least twice. Lloyd's suggestion would demand a cladogenesis between P. aperta and S. lignarius before the shell became internal and the rachidian tooth was lost, or else a complex reconvergence in a direction opposite to the usual trend with no functional advantage. Other alternatives are possible, but in any case, it is difficult to rationalize a monophyletic origin of Philine with a monophyletic origin of the ejaculatory duct. In view of the imperfect present state of knowledge, it would seem most reasonable to assume that the repro- ductive systems with ejaculatory ducts are derived polyphyletically froma form without an ejaculatory duct, since the 362 M. T. GHISELIN details of structure in the copulatory apparatus of the 3 forms described above are only generally comparable. Likewise the Aglajidae would appear to have developed from forms in which the seminal groove was open along the penis, and do not show clear relation- ships to any of those Scaphandridae or Philinidae in which the copulatory apparatus has been studied in detail. About all that is known of the copula- tory apparatus in the Gastropteridae is that the prostate is elongate and a closed ejaculatory duct is present (Guiart, 1901). Hence, a derivation of the copulatory apparatus of the Gastropteridae from the kind of copulatory apparatus which occurs in Philine aperta cannot be excluded. But if the conditions in P. aperta and the Gastropteridae did arise monophy- letically, then the Aglajidae and Gastro- pteridae cannot be derived as a Single clade from the Philinidae, as Boettger (1954) suggests. Reproductive Systems of Pteropods Because of their relatively small size, the animals placed in the orders of pteropods, Gymnosomata and Theco- somata, display a fairly simple struc- ture in most features of their anatomy. Both groups are so highly modified that their relationships are most uncertain. They have often been considered biphy- letic (Pelseneer, 1888). The similari- ties in the reproductive systems of the 2 groups make it expedient to treatthem together, whether or not these simi- larities reflect a monophyletic deriva- tion. Recent work of Morton (1954, 1958) on the thecosomatous pteropod Spiratella and on the gymnosomatous pteropod Clione agrees fairly well with most older work in suggesting that the reproduc- tive system is monaulic. Yet in neither of these works does Morton take issue with the findings of Meisenheimer (1905) who, in several systematically isolated forms within each order, found a kind of bifurcation in the pallial gonoduct, which suggests that the system is oödiaulic. This discrepancy could mean that the oddiaulic condition has arisen several times, or it could mean thata connection has been overlooked. The secretory structures are rather intri- cately folded, and an inner connection could easily be overlooked, especially if its presence is not anticipated. Minichev (1963) has specifically dis- puted the view of Meisenheimer (1905) that the pallial gonoduct of Hydromyles globulosa, the most “primitive” gymno- somatous pteropod, is divided into 2 tubes. Yet Minichev’s opinion is some- what questionable, in view of the fact that he only studied the male stage of this protandrous, viviparous form. Certain Thecosomata show, ifweac- cept Meisenheimer’s (1905) interpreta- tion, a close agreement with the Dia- phanidae in the structure of the pallial gonoduct. What Meisenheimer (1905) and Morton (1954) call the albumen gland is, from the staining reactions of Hsiao (1939) and its position, a membrane gland. An “albumen” gland is, at least in some forms, absent, and the mem- brane gland is drawn out into a spiral. The “Schalendrüse” corresponds to the mucous gland. The histological details of the nida- mental glands given by Meisenheimer (1905) likewise allow an establishment of homologies in some gymnosomatous pteropods. In Pneumoderma what he calls the albumen gland has a single opening and was found to be full of secretion; it thus shows, as is borne out by its histology, a resemblance to the “albumen” gland of anaspideans. The “Schalendrüse” in both Clionopsis and Pneumoderma includes 2 secretory areas differing in the kind of secretion, which, from their position and their histology, correspond to the membrane and mucous glands of other opistho- branchs. In both groups, only one sperm-con- taining organ is associated with the pallial gonoduct, but Pruvot-Fol (1954) notes that in some forms it is bifurcated PHYLOGENY OF OPISTHOBRANCHS 363 and suggests that it may be homologous to both the bursa copulatrix and the receptaculum seminis of other opistho- branchs. In Spiratella, a thecosomatous pteropod, Hsiao (1939) has described a two-part “receptaculum seminis” in which there are 2 kinds of epithelium; in one part the spermatozoa were found to be normal, and in the other they were degenerating. The inference seems not unreasonable that the reproductive sys- tem in both these groups has been simpli- fied by the union of the receptaculum seminis with the bursa copulatrix. Whe- ther this similarity is only superficial, is due to convergence, or reflects common ancestry is hard to judge; certainly it is unusual. The copulatory apparatus in both groups includes a prostate such as may be found in many Cephalaspidea but not in Anaspidea. The seminal groove may be partly closed off to form an ejacula- tory duct in some members of both groups, but in others it is open (Meisen- heimer, 1905; Morton, 1954,1958). A variety of complications and speciali- zations of the copulatory apparatus are known in both groups, but these have no particular parallel in other opistho- branchs (cf. Bonnevie, 1916; Tesch, 1950; Pruvot-Fol, 1960). Until the above-mentioned conflict in the literature is resolved, a com- parison between the reproductive sys- tems of pteropods and other opistho- branchs must be highly speculative. Yet it would appear that a fairly soundargu- ment can be made for a monophyletic derivation of the pteropod reproductive system. Further, if an affinity between the Gymnosomata and Anaspidea is main- tained, a similar affinity should be sup- ported for the Thecosomata. PHYLOGENETIC INFERENCES In the previous discussion an attempt has been made to compare the repro- ductive systems of the opisthobranchs and to arrange them in probable evolu- tionary sequences. A number of gener- alizations, many of which are rather speculative, and some of which may turn out to be over-simplifications, have been made. Probably, some of the changes treated as if they were mono- phyletic will turn out, on closer exami- nation, to have been polyphyletic. On the other hand, even if these changes are polyphyletic, they are most likely to occur in closely related forms, and the trends may be expected to be inde- pendent of those convergent or parallel trends in other systems which confuse the study of relationships. For these reasons it is expedient to use, with discretion, such a perhaps over-sim- plified concept of the evolution of the reproductive system within the group for comparison of other lines of evi- dence. It is hoped that the use of these other lines of evidence will compensate for the uncertainty and imperfection of some of the lines of reasoning developed above, and for any improbable evolution- ary events (convergences) which may have occurred. Four such kinds of evidence will be used for consideration of the validity of hypothetical relation- ships suggested by the structure and function of the reproductive system. The first of these independent lines of evidence is provided by previous syste- matic work. A number of interrela- tionships are well supported by inter- mediate forms and by a large number of agreements in details of structure, and will be accepted. However, a number of taxa have been erected only for convenience, or are of disputed re- lationship, especially those which are highly modified and lack intermediate forms, or have been based on simi- larities likely to be convergent. There- fore, an attempt has been made to draw a “conservative” phylogenetic tree, em- phasizing the placement of controver- Sial groups only. The second line of evidence willbe the chromosome numbers, which, in spite of our very imperfect knowledge, do suggest some probable relationships. Burch (1962) has noted that the chromo- 364 M. T. GHISELIN some numbers of opisthobranchs are quite constant in well-defined groups. Inaba (1959), who reviews older work, suggests a considerable divergence be- tween the Acoela on the one hand, and the Anaspidea, Sacoglossa and certain Cephalaspidea on the other. He found that in one species of Pleurobranchaea the haploid chromosome number is 12, while in 10 species of dorid nudibranchs and 3 of aeolid nudibranchs, the haploid chromosome number is 13; in the single species which he examined in each of the genera Aglaja, Philine, Petalifera, Notarchus and Elysia, the haploid number is 17. It is difficult to evaluate Zarnik’s (1911) study of chromosomes in several thecosomatous pteropods, since Inaba (1959) found that most older counts are inaccurate. Zarnik reports a haploid number of 10 in one species, 12 in 2 others, and higher counts in various other species. Equally difficult to evaluate is the available information on Haminoea; for one species Small- wood (1904) gives a haploid number of 16, while Dupouy (1964) says that it is 12 in a species with abnormal meiosis. The study of Franzen (1955) on the morphology of the spermatozoon pro- vides further evidence. He finds that some opisthobranchs have spermatozoa with long heads, while in others they are short, the latter condition evidently being primitive. Burch (1962) has ob- served that Boettger’s (1954) phyloge- netic tree is not consistent with the sperm types. It appears that the phylo- genetic relationships inferred in the present study agree fairly well with the oligophyletic origin of the long-headed spermatozoon. The findings of Franzen, supplemented by a few from the litera- ture and some originalobservations, are listed below. Taxon Cephalaspidea Acteonidae Acteon tornatilis Philinidae Philine aperta P. scabra P. alba Aglajidae Aglaja. sp. Atyidae Haminoea navicula H. solitaria Bullidae Bulla gouldiana Scaphandridae Acteocina exima Cylichna cylindracea Diaphanidae Diaphana minuta Anaspidea Akeratidae Akera bullata Aplysiidae Aplysia punctata Sacoglossa Oxynoacea Oxynoidae Oxynoe sp. Spermatozoa Reference Franzén, 1955 Franzén, 1955 Franzén, 1955 original original Dupouy, 1964 Smallwood, 1904 original original Franzén, 1955 Franzén, 1955 Franzén, 1955 Franzén, 1955 original PHYLOGENY OF OPISTHOBRANCHS 365 Taxon Elysiacea Elysiidae Elysia hedgpethi Limapontiidae Limapontia capitata Stiligeridae Hermaeina smithi Thecosomata Spiratellidae Spiratella retroversa Cavolinidae Creseis virgula Gymnosomata Pneumodermatidae Pneumoderma mediterraneum Cliopsidae Cliopsis grandis Acochlidiacea Hedylopsidae Hedylopsis suecica Entomotaeniata Pyramidellidae Partulida spiralis Brachystomia ambigua Nudibranchia Doridacea Onchidorididae Onchidoris muricata Dorididae Archidoris tuburculata Dendronotacea Dendronotidae Dendronotus frondosus Tritoniidae Tritonia hombergi The phylogenetic arrangement used here tends to put forms with similar spermatoxoon morphology together, and the same may be said of the chromo- some numbers. However, it is impos- sible to arrange the forms in such a manner that the 2 criteria are com- pletely consistent. It follows that suf- ficient data are not yet available to allow a complete synthesis, although the results are encouraging. A final line of evidence is speciali- zation in diet. A number of opistho- branchs are quite stenophagous andhave a highly specialized feeding mechanism or an unusual type of food. For example, Spermatozoa long Reference x original x Franzén, 1955 x original x Hsiao, 1939 X original X Meisenheimer, 1905 X Meisenheimer, 1905 Franzén, 1955 Franzén, 1955 Franzén, 1955 Franzén, 1955 Franzén, 1955 Franzén, 1955 Franzén, 1955 the pyramidellids are all ectoparasitic, the aeolid nudibranchs feed mostly on hydroids, and all anaspideans and saco- glossans are herbivores. A specialized feeding mechanism may be considered a complicated adaptive character com- plex, which is not likely to be modified into another specialized mechanism, and, relatively speaking, is an irreversible change. It is more reasonable to de- rive organisms with different specialized feeding mechanisms separately from omnivorous or otherwise more gener- alized feeders. The fact that unusual exceptions exist to this general rule does not invalidate the method, since 366 M. T. GHISELIN E APLYSIIDAE ELYSIACEA RUNCINIDA 11 OXYNOACEA ATYIDAE AKERATIDAE 9 JULIACEA a 8 10 BULLIDAE : CYLINDROBULLIDAE ACOCHLIDIACEA —7 6 14 | 13 12 re DIAPHANIDAE 4 15 = > PULMONA 1148 * THECOSOMATA (INCLUDING PHILINO- ONCHIDIIDAE) 3 ACTEON- GLOSSIDAE IDAE GYMNOSOMATA PYRAMIDEL- Е RETUSIDAE LIDAE 2 An 19 7 UMBRACULIDAE 16 5 20 AEOLIDIACEA Е Lee Kat PLEUROBRANCHIDAE 21 (POLYPHYLETIC) SCAPHANDRIDAE He DORIDACEA AGLAJIDAE ) RS DENDRONOTACEA ARMINACEA GASTROPTERIDAE FIG. 7. Phylogenetic tree showing inferred relationships in the opisthobranchs. Numbers refer to discussion in text. the hypothetical groups are considered speculative unless supported by cor- relation with other, independent lines of evidence. The results of an attempt to evaluate the implications of the foregoing obser- vations on opisthobranch reproductive systems in the light of other lines of evidence are given in the form of a phylogenetic tree (Fig. 7), the numbers on which refer to the discussions given below. The diagram represents only the inferred order of cladogenesis. Differ- ent degrees of certainty are attached to the various inferred relationships, those which are most speculative being accompanied by a question mark. In view of the incomplete and sometimes ambiguous evidence some rather arbi- trary judgements have been made; hence, somewhat different interpretations of the phylogeny of the group could be ad- vanced which are reasonably consis- tent with the evidence. 1. Little else may be said about the structure of the common ancestor of the Euthyneura except that it had the typi- cal euthyneuran spermatozoon, and that it retained a number of “primitive” fea- tures, such as an undivided gonoduct and a streptoneurous nervous system. Whe- ther or not to consider the common an- cestor of the Euthyneura a member of the Acteonidae is a matter of the defini- tion of terms, but the presently existing Acteonidae must be treated asa special- ized branch which are not ancestral to most other groups of opisthobranchs. 2. The Pyramidellidae show no par- ticular similarities in the structure of the reproductive system to any other group of opisthobranchs, except that their reproductive system can readily be derived from the ancestral form of the opisthobranchs in general. The rela- tionship suggested here is based essen- tially on the lack of evidence for an affinity to other groups andis, of course, PHYLOGENY OF OPISTHOBRANCHS 367 provisional. The theory of Boettger (1954) that the pyramidellids are re- lated to the Thecosomata finds no sup- port in the structure of the reproductive system; the presence of a shell and an operculum in both groups is probably due to the retention of primitive cha- racteristics, or perhaps to neoteny in the Thecosomata (cf. Lemche, 1948). 3. I agree with Solem (1959) in re- jecting the notion of Fretter (1943) that the Onchidiidae are opisthobranchs. Fretter’s arguments are based onhighly questionable premises, and anenumera- tion of these follows. Her argument that the Opisthobranchia and the Onchidiidae agree in the loss of the shell and in the reduction in size of the visceral hump is beside the point, since such a reduction in the shell and visceral hump occurs in both pulmonates and opisthobranchs. The posterior posi- tion of the mantle cavity and the posi- tion of the auricle behind the ventricle in Onchidella could very easily result from a posterior displacement of the respiratory apparatus; there is no rea- son for ascribing this displacement to -opisthobranch affinities. Reduction of the ganglia of the visceral loop in Onchidella to 3 is not a sign of relation- Ship to the opisthobranchs, since sucha configuration occurs in such pulmonates as Amphibola. The Onchidiidae can scarcely be classified among the opistho- branchs on the basis of their posses- sion of 3 “liver” lobes, considering the presence of a tripartite digestive gland in Siphonaria, а marine pulmonate (Marcus & Marcus, 1960a). Fretter’s statement that the “general disposition of the reproductive organs” in Onchi- della agrees with that of opisthobranchs is erroneous; the similarities to the opisthobranch system are only of the most general kind, such as would be expected from both belonging to the Euthyneura. The reproductive system of the Onchidiidae agrees in general plan with that of the Pulmonata (cf. Duncan, 1961), especially in the compact gonad, the separation of the sperm-storing por- tion of the ampulla from the conducting part, the reduction of the receptaculum seminis, the type of prostate, and the only partial separation of the vas defe- rens from the pallial gonoduct. The presence in Onchidella of aveliger larva is fully consistent with its pulmonate affinities, since a veliger larva is pre- sent in such pulmonates as Siphonaria (Marcus & Marcus, 1960a). Arguments that the lung is not homologous to that of pulmonates are highly speculative and questionable, because they are based on a lack of embryological evidence; direct development is highly likely, since the lung develops late in ontogeny, and the morphological position of the lung is such that it could well have been derived from a portion of the mantle cavity. A comparison of the gastral plates and tentacle-borne eyes to those of prosobranchs is beside the point; such a comparison, being based on simi- larities which are not due to common descent from an ancestor which posses- sed these structures, does not do away with the problem of a greater similarity between the Onchidiidae and the Pul- monata than between the Onchidiidae and the Opisthobranchia. Iagree with Fretter that the shortness of the visceral loop, the closed vas deferens and the number of lateral teeth on the radula are not germane to the argument. Bergh’s (1884) placement of the Onchidiidae in the Pulmonata was based on a large number of detailed agreements in the structure of the nervous and digestive systems in both groups. Boettger (1954) related the Onchidiidae, in which the gan- glia of the central nervous system tend to fuse below the oesophagus, to the pleurobranchs, in which the ganglia tend to fuse above the oesophagus. On the basis of his own criteria, it would seem more consistent to relate the Onchi- diidae to the pulmonates, in which the ganglia show the same tendency to fuse below the oesophagus, Ifthe Onchidiidae are considered early derivatives of the primitive Pulmonata, their similarities to opisthobranchs are readily under- 368 M. T. GHISELIN stood. 4. On the basis of the chromosome evidence it seems reasonable to regard the Thecosomata as a systematically isolated group, but I see more sound evidence for relating the Thecosomata to the Gymnosomata than for relating either group to any other opisthobranchs. Pelseneer (1888) is largely responsible for the prevalent opinion that the Gymno- somata are derived from highly-special- ized Anaspidea and the Thecosomata from some unspecified group of Cepha- laspidea. The reason for relating the Thecosomata to the Cephalaspidea was the retention of numerous characteris- tics, such as a relatively unconcentrated nervous system, gizzard plates and the like, which characterize the cephalaspi- deans; yet he gave no evidence to show that the Gymnosomata were not derived from such a cephalaspidean, or that the modern pteropods were not derived from a commonancestor which was a pteropod. Pelseneer did manage to find some characteristics in common between the Gymnosomata and Anaspidea. Inthe first place, the nervous system shows the same kind of concentration; yet the ner- vous system is concentrated only in the most highly modified anaspideans, so one must reason either that the simi- larity is convergent and beside the point, or that an exceedingly specialized, mo- dern form gave rise, directly, to the order Gymnosomata. One cannot, as did Boettger (1954), derive the gymnoso- matous pteropods from the primitive an- aspideans and support this relationship on the basis of the structure of the nervous system. The other significant similarity is the supposed homology be- tween the pharyngeal hooks of the anas- pideans and the hook-sacs of the gymno- somatous pteropods, a homology open to question and also referable to a common ancestry between the 2 groups at a much earlier stage than that envisioned by Pelseneer. Morton (1958) rejects this homology, but only on the lack of de- tailed agreement; a more sound, but not compelling, argument is the complete absence of either of these cuticular structures in such “primitive” forms as Hydromyles, a discrepancy which Hoffmann (1932-40) rationalizes as secondary. On the basis of similarities between the tentacles of both orders of ptero- pods, in which the posterior pair of tentacles bears an eye, Hoffmann (1932- 40) denied a homology between the ten- tacles of gymnosomatous pteropods and anaspideans, and suggested relating both groups of pteropods to an early pre- cursor of the Anaspidea. Again, if such an inference is made, then the similari- ties in nervous systems no longer apply. Meisenheimer (1905) affirmed the homo- logy between the “wings” inthe 2 groups; this homology may be supported on the basis of conditions which occur in the “primitive” gymnosomatous pteropod Hydromyles, which resembles the theco- somatous pteropods more than most other members of its order (cf. Tesch, 1950). It is very difficult to derive the “wings” of gymnosomatous pteropods from the reduced epipodia of higher anaspideans. Of some interest is the theory that the Thecosomata are neotenous Cepha- laspidea, a theory supported by the sin- istrality (hyperstrophy) of the larval shell among Opisthobranchs in general, some of the Basommatophora, and in some adult Thecosomata. Neoteny would provide a simple means of reducing the size of the body in adaptation to the pelagic habitat, and has been re- ported in some Gymnosomata (Danforth, 1907). Their manner of origin, how- ever, reveals little concerning their relationships. Minichev (1963), after studying the central nervous system of Hydromyles, has concluded that the similarities it bears to that of the higher Anaspidea are due to convergence; this conclusion seems reasonable in view of the de- tailed structure. He derives the Gymno- somata from the Akeratidae and the Akeratidae from the Acteonidae, while treating the Thecosomata as separately PHYLOGENY OF OPISTHOBRANCHS 369 derived from the Acteonidae. Yet he gives no compelling reason for sepa- rating the 2 groups, although he does point out that there are many differences between them and that convergence could account for the similarities. His notion that either group could be derived from the Acteonidae is not supported by argu- ments, and he gives no explicit reasons for relating the Gymnosomata to the An- aspidea. Nor does he provide any argu- ments against the possiblity that the 2 orders are related, but diverged at an early stage in their evolution. Aside from the inconclusive chromo- some evidence, the most consistent in- terpretation would be to consider the pteropods monophyletic and members of the same clade as the Anaspidea, but by no means derived from them. This intepretation is supported by the evidence from spermatozoon morphology. The hook-sacs, tentacles and reproductive systems would then be explained, and differences between the 2 orders of pteropods would make sense as diver- gences largely related to different feeding mechanisms. 9. The placement of Anaspidea, Saco- glossa and the more typical Cephalas- pidea in a single clade rests largely on the admittedly incomplete chromo- some evidence mentioned above. There is no compelling morphological evidence for this relationship, but neitheristhere any against it. 6. This clade (Sacoglossa, Anaspidea, Diaphanidae and perhaps the Acochli- diacea) is based on the tendency for the prostate to remain pallial and the gono- duct to be oddiaulic. It appears that the absence of well-developed gizzard plates in this group is a primitive trait, since the projections in the gizzard of anaspideans show similarities to the cuticularizations found in that of the Diaphanidae (Odhner, 1926), rather than to the well-developed, opposed plates found in such forms as Haminoea and Scaphander. The pteropods likewise appear to have diverged at a stage when the gizzard plates were not well de- veloped. 7. In the absence of clear-cut evi- dence to the contrary, I accept Odhner’s (1952) idea that the Acochlidiacea are related to the Diaphanidae, with the reservation that small size, convergence and the retention of primitive traits might easily lead one to infer that these forms are more closely related than is actually the case. Indeed, the pre- sence of elongate spermatozoon heads in the Diaphanidae, Sacoglossa and Anas- pidea, rather than short ones as in the Acochlidiacea (Franzén, 1955) strongly suggests that the Acochlididacea are not closely related to the Diaphanidae, and such an interpretation would be consis- tent with the anatomy of the repro- ductive system. 8. Not enough is known of the inter- nal structure of the Diaphanidae and their close relatives to determine their exact relationships, especially since some ap- pear to be rather reduced in size. The nervous system in the Diaphanidae is highly primitive, and nothing in its structure would preclude such a type serving as an ancestral form for the other members of the clade, such as the Acochlidiacea, Anaspidea or Saco- glossa (cf. Odhner, 1926). Odhner (1926) was the first to suggest a unity of these forms on the basis of the structure of the pallial gonoduct. Marcus & Marcus (1956b) have shown that Cylindrobulla shows characteristics suggestive ofboth the Anaspidea and the Sacoglossa. The major distinction between the reproduc- tive systems of the anaspideans and the sacoglossans is that of the copulatory ap- paratus, which does not include a closed ejaculatory duct in the Anaspidea; the absence of such a closed ejaculatory duct in Colobocephalus suggests that the Diaphanidae may well have been an- cestral to the Anaspidea. Of great interest is the fact that both the Saco- glossa and the Anaspidea are herbivo- rous, and this similarity may well have resulted from descent from an herbi- vorous common ancestor. 9. The placement of the Akeratidae 370 M. T. GHISELIN among the Anaspidea (Guiart, 1901) is well supported by the structure of the reproductive system, as well as by nu- merous other similarities, and is no longer disputed. 10. Cylindrobulla is here considered a sacoglossan. Its ejaculatory duct may be looked upon as an early stage in the complete separation of the vas deferens of higher sacoglossans. The uniserial radula, which admittedly may be convergent due to small size, is a characteristic feature of the Sacoglossa. Marcus & Marcus (1956b) have shown some similarities in the radula of Cylin- drobulla to that of the Diaphanidae. 11. The polyphyletic derivation of the shell-less sacoglossans from the shelled ones as suggested by Boettger (1954) appears likely. However, I follow Baba (1961) in assuming that the Oxynoidae and Juliidae are closely related forms which are not ancestral to the shell- less sacoglossans; they could easily be derived from other shelled sacoglossans. The single split in the oviduct is an ancestral characteristic of the Saco- glossa, and therefore a poor indication of the relationships within the group; however, in future studies it may be of value to consider the possibility of a relationship between Hermaeina and Alderia, in which there is only a single split. The similarity in pattern of the first split in the oviduct of Elysia to the single one in Caliphylla likewise suggests a possible relationship. The peculiar construction ofthe reproductive system in Limapontia and a number of other forms can easily be derived from conditions found in Elysia, and a re- lationship is at least possible. Aproper conception ofthe relationship between the various groups of sacoglossans must await precise knowledge of the details of the reproductive system in other forms. However, sufficient evidence is available to show that the repro- ductive system throughout the group has the same fundamental organization, and the suggestion of Gascoigne (1956) that the Sacoglossa are polyphyletic must be considered quite dubious. 12. All members of the Cephalas- pidea except those allied to the Acteoni- dae or to the Diaphanidae are here united in a single clade. The pre- sence of well-developed gizzard plates, few in number and opposed to each other, is wide-spread among these forms, and probably represents an in- heritance from the common ancestor of the clade. The gizzard plates seem to be absent mostly in forms with a specialized feeding mechanism, or in those which are minute (e.g. Philino- glossa). The reproductive system, es- pecially the copulatory apparatus, is derivable from a common type. Simi- larities in general structure between some Scaphandridae and Retusidae like- wise suggest an affinity (cf. Lemche, 1948). 13. This clade, (Retusidae, Philino- glossidae, Bullidae, Atyidae and Run- cinidae) which may be polyphyletic to some degree, includes all forms in which the copulatory apparatus includes a prostate and stores sperm. 14. The Bullidae, Atyidae and Run- cinidae are united partly on the basis of their herbivorous habits (Pruvot-Fol, 1954; Guiart, 1901; Ghiselin, 1963). They all, with the possible exception of Ham- inoea, possess an oesophageal diverti- culum which is probably homologous within the group, but the significance of which has been overlooked (cf. Hoffmann, 1932-40). This diverticulum is present in Bulla (Pelseneer, 1894), Phanerophthalmus (Eales, 1938), and Runcina (Ghiselin, 1963). I have found no record of an equivalent structure in the Anaspidea, pteropods, Scaphandridae or Philinidae. But since a similar structure is present in Diaphanidae and Sacoglossa, this diverticulum may be a primitive trait which is retainedin some herbivorous forms; the possibility that it is homologous to the oesophageal glands of prosobranchs, thought to be absent in opisthobranchs (Fretter & Graham, 1962) should be investigated. The Bullidae are more primitive than PHYLOGENY OF OPISTHOBRANCHS 371 other members of this groupin degree of loss of the shell, of development of nervous concentration and of integration of the gizzard apparatus, and may have diverged early. Boettger’s (1954) idea that the development of a posterior posi- tion of the nerve ring in the Atyidae and Runcinidae is convergent, however true the idea itself may be, was in- consistent with his own phylogenetic method. Marcus (1957) has shown that a derivation of the nervous system in the Runcinidae and Atyidae from that of the Bullidae is fully consistent with the conditions of the nervous system in Bulla. Yet he used this sequence to show that the nervous system is not a good source of indications of relationships, since he was unable to see any reasons for re- lating these forms. Resemblances of Випста to the Notaspidea are, as Pelseneer (1894) demonstrated, super- ficial only. 15. The relationships between the Retusidae and Philinoglossidae are un- clear. I agree with Boettger (1954) in relating the Retusidae (including Rhi- zorus) to the Bullidae and Atyidae, but ‘the groups are so ill defined as to scarcely warrant precise statements as to their relationships. The peculiarities of the Philinoglossidae, however much they make relationships uncertain, are clearly due to reduced size, and do not necessitate the erection of a new order as proposed by Odhner (1952). Simi- larly, any relationship to the Acochli- diacea, as suggested by Pruvot-Fol (1954), must also be rejected as based on convergence, as Pruvot-Fol herself implies. 16. The structure of the reproductive system bears out the concensus of workers in the field that the Philinidae, Scaphandridae, Aglajidae and Gastrop- teridae are interrelated. I use the term Scaphandridae to include the genera Scaphander, Cylichna, Cylichnella, Ac- teocina, and doubtless some other forms which cannot yet be placed, since their anatomy is poorly known. It seems more prudent to consider the Philini- dae, Aglajidae, and Gastropteridae as independent derivatives from a primi- tive stock than to attempt to relate any of these families to one another, since a considerable amount of parallel evolution has evidently taken place. 17. If we accept the authority of Eliot (1910) on the structure of the reproductive system in Umbraculum, then all members of this clade possess a reproductive system which is andro- diaulic or else is derived from sucha one. The similarity between the am- pullae is at least suggestive. Eliot (1910) notes a number of other simi- larities which imply that there is an affinity between the Acoela and the Hydatinidae and Acteonidae, although the degree of divergence since clado- genesis would appear to have hindered the acceptance of his interpretation. Likewise a typological outlook would tend to require the placement of Acteon as it presently exists at the base of the evolutionary tree ofthe Opisthobranchia. If one thinks of the Acoela as related to one group of somewhat aberrant forms bearing a close resemblance to those Acteon-like forms which evidently gave rise to other opisthobranchs, then there is nothing unreasonable about the rela- tionship which Eliot suggested. 18. The unique features of the repro- ductive system which set the Acteonidae and Hydatinidae off from the rest of the opisthobranchs can scarcely be at- tributed to convergence alone. Thus cladogenesis between these 2 families took place after they acquired these features, and an isolated position for them is essential. These families are rather similar in general anatomy, and it appears that both the Acteonidae and Hydatinidae are specialized feeders on annelids (Eales, 1938; Marcus, 1956). Boettger’s (1954) placement of the Hy- datinidae and Acteonidae, with the Ac- teonidae ancestral to all Euthyneura and the Hydatinidae related to the Diaphani- dae, is not consistent with the fact that in both the Acteonidae and Hydatinidae, the cerebral and pleural ganglia are 372 M. T. GHISELIN intimately fused. 19. The Umbraculidae are here treated as a specialized side branch within the Notaspidea; not enough is known of their reproductive systems to allow precise placement, and it may well be that their conchological similarities are con- vergent. Boettger (1954) considered the Umbraculidae ancestral to the Nudi- branchia, and the Pleurobranchidae an early, unrelated offshoot, reasoning on the basis of the somewhat more con- centrated nervous system in the Um- braculidae, but parallelism easily ex- plains this. 20. Relationships between the various notaspideans will not be discussed here. A sufficient range of variation in the anatomy of the reproductive and nervous systems exists in the pleurobranchs to allow the derivation of the nudibranchs from them. The idea of Boettger (1954) that the Dendronotacea are more closely related to the Doridacea than to the Aeolidiacea and Arminacea should be rejected as based on the common re- tention of a number of primitive charac- teristics inherited from the pleurobranch common ancestor of the Nudibranchia. The Dendronotacea show numerous fea- tures of their anatomy which link them closely to the Arminacea and Aeolidi- acea. It seems, however, that many fea- tures held in common by aeolid nudi- branchs, particularly those of the diges- tive system, are due to parallel adapta- tions to the same kind of food, i.e. to coe- lentrates. But the correlation between diet and the details of structure of the reproductive system strongly suggests the unity of the aeolid nudibranchs as a Single clade, although the common an- cestor of the group may well have been a pleurobranch. 21. The most widely accepted division of the aeolid nudibranchs into systematic groups is that of Odhner (1934, 1936, 1939), who has distinguished the Dendro- notacea, Arminacea and Aeolidiacea on the basis of external morphology andthe tendencies of differentiation of the gut. The Dendronotacea are thought to be the most primitive of the aeolid nudibranchs, some of them possessing a number of characteristics, such as a velum, back margin and only partially divided diges- tive gland, which are thought to be de- rived from notaspidean ancestors (Odhner, 1939: 24). The Aeolidiaceaare characterized by a gradual loss of notas- pidean characteristics, with progressive development of several evolutionary trends. These trends include: (1) rami- fication of the digestive gland, (2) de- velopment of cerata, (3) loss of the velum and its transformation into tentacles, (4) reduction of rhinophore sheaths, (5) shortening of optic nerves, (6) displace- ment of the anus toward the dorsal surface. These trends also occur in the Arminacea and Dendronotacea. Odhner has based his classification in part on the degree of development of such changes and in part on various diver- gences in structure which can be re- lated to them. His system is widely accepted, and does seem to reflect relationships. However, the present study suggests some possible improve- ments. Thompson (1961a) has pointed out the importance of the larval shell in the classification of the aeolid nudi- branchs. It would seem that the only member of the Dendronotacea which has a larval shell of type two, Dendronotus, is the only member of the Dendrono- tacea which has a triaulic reproductive system. Unlike all other Aeolidiacea, the Acleioprocta have a larval shell of type two. The Acleioprocta include some forms which are evidently diaulic, such as Eubranchus (Lloyd, 1952) and Calma (Evans, 1922), but a number of others are triaulic, such as Pseudovermis (Marcus & Marcus, 1955b), Miesea (Marcus, 1961a), and Embletonia (Marcus, 1957; Chambers, 1934; Marcus & Marcus, 1955b). The fact that these triaulic forms are small and aberrant and do not fit well into Odhner’s scheme of classification (Embletonia has afron- tal veil) deserves careful consideration by systematists, for it strongly suggests that the Aeolidiacea are polyphyletic. PHYLOGENY OF OPISTHOBRANCHS 373 ACKNOWLEDGEMENTS I wish to express my deepest grati- tude to Dr. Donald P. Abbott for his inspiration, assistance and direction during the course of this study. For providing some of the specimens used, I thank Drs. L. R. Blinks, J. A. McGowan, J. H. McLean and J. H. Dearborn. Support during the period of research was provided, in part, by United States Public Health Service Training Grant 5-TI-GM -647. LITERATURE CITED AGERSBORG, H. P. K., 1923, The mor- phology of the nudibranchiate mollusc Melibe (syn. Chioraera) leonina (Gould). Quart. J. microscop. Sci., (2)67: 507-592. BABA, K., 1961, On the identification and affinity of Tamanovala limax, a bivalved sacoglossan mollusc in Japan. Publ. Seto mar. Biol. Lab., 9: 37-62. BAUDELOT, M., 1863, Recherches sur l’appareil générateur des mollusques gastéropodes. Ann. Sci. nat., Zool., (4)19: 135-222, 268-294. BECKER, R., 1960, Bau und Funktion des Genitalsystems von Bosellia mi- metica Trinchese. Rev. Suisse Zool., 67: 194-201. BEHRENTZ, A., 1931, Trekkav Lamel- lidoris muricata’s biologi of av den generasjions-organers bygning. Nyt Mag. Naturvidensk., 70: 1-25. BERGH, R., 1884, Report on the Nudi- branchiata dredged by Н. М. 5. Challenger during the years 1873-76. Voyage of H. М. 5. Challenger, Zool., 10: 1-154. , 1897-98, Die Pleurobran- chiden. In: Semper, C., Reisen im Archipel der Philippinen, Wiss. Result., 7(Abt. 4, Abschn. 1): 1-155. , 1901, Bullacea. In: Semper, C., Reisen imArchipelder Philippin- en, Wiss. Result., 7(Abt. 4, Abschn. 2): 209-338. BOCK, W. J., 1959, Preadaptation and multiple evolutionary pathways. Evo- lution, 13: 194-211. BOETTGER, C. R., 1954, Die Syste- matik der euthyneuren Schnecken. Verh. Dtsch. zool. Ges., (Suppl. 18): 253-280. BOLOT, E., 1886. Sur la ponte des Doris, C. R. Acad. Aci. Paris, 102: 829-831. BONNEVIE, K., 1916, Mitteilungen tiber Pteropoden. 1. Beobachtungen tiber den Geschlechtsapparat von Cuvieria columnella Rang. Jena. Z. Naturw., 54: 245-276. BRUEL, L., 1904, Uber die Gesch- lechts- und Verdauungsorgane von Ca- liphylla mediterranea Costa: ihr morphologischer Wert, undihre physi- physiologische Leistung. Thesis, Halle. BURCH, J. B., 1962, Cytotaxonomic studies of freshwater limpets (Gastro- poda: Basommatophora) I. The Euro- pean lake limpet, Acroloxus lacus- tris, Malacologia, 1: 55-72. BURN, R., 1963, Australian Runcinacea (Mollusca: Gastropoda). Australian Zoologist, 13: 9-22. CASSELMAN, W. G. B., 1959, Histo- chemical Technique. London: Methuen. CHAMBERS, L. A., 1934, Studies on the organs of reproduction in the nudibranchiate mollusks. Bull. Amer. Mus. nat. Hist., 66: 599-641. DANFORTH, C. H., 1907, A new ptero- pod from New England. Proc. Boston Soc. nat. Hist., 34: 1-19. DUNCAN, C. J., 1961, The evolution of the pulmonate genital system. Proc. zool. Soc. Lond., 134: 601-609. DUPOUY, J., 1964, La tératogénése germinale male des Gastéropodes et ses rapports avec l’oogénèse atypique et la formation des oeufs nourriciers. Arch. Zool. exper. gén., 103: 217-368. EALES, N. B., 1921, 1921, Aplysza. Liverpool Marine Biology Committee, Mem. (24): 1-84. , 1938, A systematic and ana- tomical account of the Opistho- branchia. John Murray Exped. Sci. Rep., 5: 77-122. 374 M. T. GHISELIN ELIOT, C., 1910, The British nudi- branchiate Mollusca. 8(Suppl.): 1-198. London: Ray Society. EVANS, I. J., 1914, The anatomy ofa new species of Bathydoris, and the affinities of the genus. Trans. Roy. Soc. Edinb., 50: 191-209. ‚ 1922, Calma glaucoides, a study in adaptation. Quart. J. micro- scop. Sci., 66: 439-455. FISCHER, P., 1869, Sur l’accouple- ment et la ponte des Aplysiens. C.R. Acad. Sci. Paris, 69: 1095-1097. FODERA, E., 1915, Sulla funzione di secrezione dell’epitelio ghiandolare della vesicola di Swammerdam in Doris verrucosa L. Monit. zool. Ital., 26: 112-113. FRANZEN, A., 1955, Comparative mor- phological investigations into the sper- miogenesis among Mollusca. Zool. Bidr. Uppsala, 30: 399-456. FRETTER, V., 1943, Studies in the functional morphology and embryology of Onchidella celtica (Forbes and Hanley). J. mar. biol. Assoc., U. K., (2)25: 685-720. ‚ 1953, The transference of sperm from male to female proso- branch, with reference, also, to the pyramidellids. Proc. Linn. Soc. Lond., 164: 217-224. , 1960, Observations on the tectibranch Ringicula buccinea (Brocchi). Proc. zool. Soc. Lond., 135: 537-549. FRETTER, V. & GRAHAM, A., 1949, The structure and mode of life of the Pyramidellidae, parasitic opistho- branchs. J. mar. biol. Assoc., U. K., (2) 28: 493-532. , 1954, Observations on the opisthobranch mollusc Acteon torna- tilis (L.). J. mar. biol. Assoc., U.K., (2)33: 565-583. , 1962, British Prosobranch Molluscs. London: Ray Society. GABE, M., 1962, Résultats de 1'his- tochimie des polysaccharides: In- vertébrés. In: GRAUMANN, W. & NEUMANN, K., Handbuch der Histo- chemie. Stuttgart: Fischer. GASCOIGNE, T., 1956, Feeding and reproduction in the Limapontiidae. Trans. Roy. Soc. Edinburgh, 63: 129- 151. GHISELIN, M. T., 1963, On the func- tional and comparative anatomy of Runcina setoensis Baba, an opistho- branch gastropod. Publ. Seto mar. biol. Lab., 11: 219-228. GONOR, J. J., 1961, Observations onthe biology of Hermaeina smithi, a saco- glossan opisthobranch from the West Coast of North America. Veliger, 4: 85-98. GRAINGER, J. N.R. & SHILLITOE, A. J., 1952, Histochemical observations on glactogen. Stain Techn., 27: 81-85. GUIART, J., 1901, Contribution à 1'étude des Gastéropodes Opisthobranches et en particulier des Céphalaspides. Thesis, Paris. HAMATANI, I., 1962, Notes on veligers of Japanese opisthobranchs (5). Publ. Seto mar. Biol. Lab., 10: 283-292. HAND, C. & STEINBERG, J., 1955, On the occurrence of the nudibranch Alderia modesta (Lovén, 1844) on the central Californian coast. Nautilus, 69: 22-28. HILLENIUS, D., 1960, Ciliary reversal in Metridium under nervous control. Arch. Néerland. Zool., 13: 624-626. HIRASE, S., 1929, Eiablage von Dola- bella. Arch. Moll.-kunde, 61: 105- 114. HOFFMANN, H., 1932-40, Opisthobran- chia. Jn: Bronn, Klassen und Ordnun- gen des Tierreichs, 3(2:3:1,2): 1337p. HORSTMANN, H. J., 1959, Untersuchun- gen über Polysaccharide aus Eiern einiger Mollusken. Pubbl. Staz. zool. Napoli, 31: 308-319. HIASO, S. С. T., 1939, | The repros ductive system and spermatogenesis of Limacina (Spivatella) retroversa (Flem.). Biol. Bull., 76: 7-25. HYMAN, L. H., 1951, The Inverte- brates: Platyhelminthes and Rhyncho- coela. Vol. 2. New York: McGraw Hill. IHERING, H. von., 1892, Zur Kennt- niss der Sacoglossen. Nova Acta Ksl. Leop.-Carol. Deutsch, Akademie PHYLOGENY OF OPISTHOBRANCHS d. Naturforscher, 58: 363-435. INABA, A., 1959, Cytological studies in molluscs II. A chromosome study in opisthobranchiate Gastropoda. Annot. Zool. Jap., 32: 81-88. INIGER, A., 1907, Über den Bau der Genitalorgane von Acera bullata. Arch. Math. Nat. Kristiania, 28: 2-18. JOHANNSON, J., 1954, On the pallial gonoduct of Actaeon tornatilis. Zool. Bidr. Uppsala, 30: 223-231. , 1957, Notes on the littorina- cean and stenoglossan genital organs, and a comparison with the Rissoacea. Zool. Bidr. Uppsala, 32: 81-91. KAWAGUTI, S. & YAMASU, T., 1961, Self-fertilization in the bivalvedgas- tropod, with special references to the reproductive organs. Biol. J. Okayama Univ., 7: 213-224. KEFERSTEIN, W., 1862-66, Kopftra- gende Weichtiere (Malacozoa Cephal- ophora). In: Bronn, Klassen und Ordungen des Tierreichs, 3: 667-808. KOWALEVSKY, A., 1901, Les Hedy- lides. Etude anatomique. Mém. Acad. Imp. Sci. St. Petersbourg, 12: 1-32. KRAMER, H. & WINDRUM, G. M., 1955, ‚ The metachromatic staining reaction. J. Histochem. Cytochem., 3: 227-237. KUTHE, P., 1935, Organisation und systematische Stellung des Acochli- dium paradoxum Strubell. Zool. Jb., Abt. Syst., 66: 514-540. LACAZE-DUTHIERS, H., 1859, Histoire anatomique et physiologique du Pleurobranche orange. Ann. Sci. nat., Zool., (4)11: 199-302. LEMCHE, H., 1948, Northernandarctic tectibranch gastropods. Kgl. Danske Vidensk. Selskab, 5(3): 1-136. , 1956, The anatomy and his- tology of Cylichna (Gastropoda Tecti- branchia). Spolia Zool. Musei Hauniensis, 16: 1-278. LINKE, O:,, 1933, Morphologie und Physiologie des Genitalapparates der Nordseelittorinen. Wiss. Meeresun- tersuch. Abt. Helgoland, 19: 3-52. LLOYD, H. M., 1952, A study of the reproductive systems of some opistho- branchiate molluscs. Thesis, London. nudibranch 375 MACFARLAND, F. M., 1909, The opis- thobranchiate Mollusca of the Branner-Agassiz Expedition to Brazil. Leland Stanford Jr. Univ. Publ., Univ. Ser., (2): 1-104. , 1923, The morphology of the genus Hancockia. J. Morphol., 38: 65-102. McCAULEY, J. E., 1960, The morph- ology of Phyllaplysia zostericola, new species. Proc. Calif. Acad. Sci., (4) 29: 549-576. McGOWAN, J. A. & PRATT, I., 1954, The reproductive system and early embryology of the nudibranch Archi- doris montereyensis (Cooper). Bull. Mus. comp. Zool. Harvard Coll., 111: 261-276. MARCUS, E., 1953, Three Brazilian sand-opisthobranchia. Bol. Fac. Fil. Ci. Letr. Univ. S. Paulo, Zoologia, (18): 165-203. , 1955, Opisthobranchia from Brazil. Bol. Fac oil wer, Tetr: Univ. S. Paulo, Zoologia, (20): 89-200. , 1956, Notes on Opisthobran- chia. Univ. 'S. Paulo Bol. Inst. Oceanogr., 7: 31-79. , 1957, On Opisthobranchia from Brazil (2). J. Linn. Soc. Lond., 43: 390-486. , 1958, On Western Atlantic opisthobranchiate gastropods. Amer. Mus. Novitates, (1906): 1-82. , 1959; Lamellariacea und Opisthobranchia. Lunds Univ. Arss- krift. N. F. Avd. 2, 55: 132p. , 1961a, Opisthobranchia from “ North Carolina. J. Elisha Mitchell Sci. Soc., 77: 141-151. , 1961b, Opisthobranch mol- lusks from California. Veliger, 3 (Suppl.): 1-85. MARCUS, E. & MARCUS, E., 1952, The nudibranch Rhodope from South America. Montivideo Mus. Hist. nat. Communic. Zool., 4(68): 1-8. , 1954, Uber Philinoglossacea und Acochlidiacea. Kieler Meeres- forsch., 10: 215-223, , 1955a, Sea-hares and side- gilled slugs from Brazil. Univ. S. 376 M. T. GHISELIN Paulo Bol. Inst. Oceanogr., 6: 3-48. , 1955b, Uber Sand-Opistho- branchia. Kieler Meeresforch., 11: 230-243. , 1956a, On two sacoglossan slugs from Brazil. Amer. Mus. No- vitates, (1796): 1-21. , 1956b, On the tectibranch gastropod Cylindrobulla. Acad. Bra- sil. Ci. An., 28: 119-128. LOST, Notes on Aplysia. Univ. S. Paulo Bol. Inst. Oceanogr., 8: 3-21. ‚ 1959, Opisthobranchia aus dem Roten Meer und von den Male- diven. Akad. Wiss. Lit. Mainz, Abh. Math.-Naturwiss. Klasse. (12): 873- 933. , 1960a, On Siphonaria hispida. Bol. Fac. Fil. Univ. S. Paulo, Zool., (23): 107-139. , 1960b, Opisthobranchs from American Atlantic warm waters. Bull. Mar. Sci. Gulf and Caribbean, 10: 129-203. MATTOX, N. T., 1958, Studies on the Opisthobranchiata: II. A new tecti- branch of the genus Philine. Bull. Southern Calif. Acad. Sci., 57: 98-104. MAZIA, D., BREWER, Р.А. & ALFERT, M., 1953, The cytochemical staining and measurement of protein with mer- curic bromphenol blue. Biol. Bull., 104: 57-67. MAZZARELLI, G., 1891, Richerche sulla morfologia e fisiologia dell’ apparato riproduttore nelle aplysiae del Golfo di Napoli. Mem. R. Accad. Sci. fis. e mat. Napoli, (2)4(5): 1-50. MEISENHEIMER, J., 1905, Pteropoda. Wiss. Ergebn. d. Dtsch. Tiefsee- Exped., “Valdivia” 1898-1899, 9(1): 1-314. MINICHEV, YU. S., 1963, Anatomy of Anopsia gaudichaudii (Souleyet) and systematic position of Gymnosomata (Opisthobranchia). (In Russian) Zool. Zhurn., 42: 1317-1328. MOQUIN-TANDON, G., 1870, Re- cherches zoologiques et anatomiques sur l’ombrelle de la Méditerranée. Ann “Sci. nats Zool. °()14:> 7235p. sp. und die MORTON, J. E., 1954, The pelagic Mollusca of the Benguela Current (first survey, R. R. S. William Scoresby), with an account of the reproductive system and sexual cycle of Limacina bulimoides. Discovery Reports, 27: 163-200. , 1958, Observations on the gymnosomatous pteropod Clione lima- cina (Phipps). J. mar. biol. Assoc., U. K., (2)37: 287-297. , 1963, The molluscan pattern: evolutionary trends in a modern clas- sification. Proc. Linn. Soc. Lond., 174: 53-72. ODHNER, N. H., 1924, New Zealand Mollusca. Vidensk. Meddel. Dansk. Naturh. Foren., 77: 1-90. , 1926, Die Opisthobranchien. Further Zool. Results, Swedish Ant- arctic Exped. 1901-1903, 2: 1-100. , 1934, The Nudibranchiata. Brit. Antarctic (“Terra Nova”) Exped. 1910. Nat. Hist. Rep. Zool., 7: 229-310. , 1936, Nudibranchia Dendro- notacea, a revision of the system. Mém. Mus. Roy. Hist. nat. Belgique, 3: 1057-1128. ‚ 1937, Hedylopsis suecica п. Naktschneckengruppe Acochlidiacea (Hedylacea). Zool. Anz., 120: 51-64. , 1939, Opisthobranchiate Mol- lusca from the western and northern coasts of Norway. Kgl. Norske Vidensk. Selskabs Skrifter 1939: 1-93. , 1952, Petits opisthobranches peu connus de la céte Méditerranénne de France. Vie et Milieu, 3: 136-147. PEARSE, A. С. E., 1961, Histo- chemistry, Theoretical and Applied. Second ed. London: J. € A. Churchill. PELSENEER, P., 1888, Report on the Pteropoda collected by H. M. S. Chal- lenger during the years 1873-76. Part III.--Anatomy. Voyage of H. М. $. Challenger, Zool., 23: 97p. , 1894, Recherches sur divers opisthobranches. Mém. Cour. Cl. Sci. Nat. Acad. Roy. Belgique, 53: 160p. , 1906, Mollusca. Jn: Lan- kester, A Treatise on Zoology, 5: 1- PHYLOGENY OF OPISTHOBRANCHS 377 355. , 1914, Ethologie de quelques Odostomia et d’un monstrillide para- site de l’un d'eux. Bull. Sci. France, Belgique, 48: 1-14. , 1925, Organization et porition systematique du genre Ringicula. Ann. Soc. Zool. Malacol. Belg., 55: 53-58. PERRIER, R. & FISCHER, H., 1914, Sur l’existence des spermatophores chez quelques Opisthobranches. C. R. Acad. Sci. Paris, 158: 1366-1369. POHL, H., 1905, Uber den feinern Bau des Genitalsystems von Polycera qua- drilineata. Zool. Jb., Abt. Anat., 21: 427-452. PORTMANN, A. & SANDMEIER, E., 1960, Dondice banyulensis, sp. nov., un éolidien nouveau de la Méiter- ranée. Revue Suisse Zool., 67: 159- 168. PRUVOT-FOL, A., 1930, L’appareil copulateur de la Philine et du Notar- chus. Arch. Zool. exper. gén., 70: 45-51. ‚ 1954, Mollusques opistho- branches. Faune de France, 58: 1-460. , 1960, Les organes génitaux des Opisthpbranches. Arch. Zool. exper. gén., 99: 135-223. RAO, K. V., 1937, Structure, habits and early development of a new spe- cies of Stiliger Ehrenberg. Rec. Ind. Mus., 39: 435-464. RENSCH, B., 1960, Evolution above the Species Level. New York: Colum- bia University Press. RIEDL, R., 1960, Beiträge zur Kennt- nis der Rhodope veranii, Teil Il. Entwicklung. Z. wiss. Zool., 163: 237- 316. SMALLWOOD, W. M., 1904, The matu- ration, fertilization, and early clea- vage of Haminea solitaria (Say). Bull. Mus. comp. Zool. Harvard Coll., 45: 261-318. SOLEM, A., 1959, Systematics and zoogeography of the land and fresh- water Mollusca of the New Hebrides. Fieldiana: Zool., 43: 1-359. TAYLOR, D. W. & SOHL, N. F., 1962, An outline of gastropod classification. Malacologia, 1: 7-32. TESCH, J. J., 1950, The Gymnosomata II. Dana-Report, (30): 1-55. THIELE, JOHANNES, 1929-35, Hand- buch der systematischen Weichtier- kunde. 2 vols. Jena: Gustav Fischer. THOMPSON, T. E., 1961a, The impor- tance of the larval shell in the classi- fication of the Sacoglossa andthe Aco- ela (Gastropoda Opisthobranchia). Proc. malacol. Soc. Lond., 34: 233- 238. , 1961b, The structure and mode of functioning of the reproductive or- gans of Tritonia homhergi (Gastropoda Opisthobranchia). Quart. J. micro- scop. Sci., (2) 102: 1-14. ‚ 1962, Studies on the onto- geny of Tritonia hombergi Cuvier (Gastropoda Opisthobranchia). Phil. Trans. Roy. Soc. London, (B)245: 171- 218. THORSON, G., 1946, Reproduction and larval development of Danish marine bottom invertebrates. Medd. Komm. Havunders¢g., (Plankton)4: 1-523. TOMLINSON, J., 1963, Personal com- munication. TRINCHESE, S., 1884, Per la fauna marittima italiana. Aeolididae e fa- miglie affini. Atti. R. Accad. Lincei, Mem. Cl. fis. nat., 11: 1-142. ‚ 1893, Nuove osservazioni sulla Placida viridis. Mem. Accad. Sci. Ist. Bologna, 3: 237-245. VAYSSIERE, A., 1880, Recherches ana- tomiques sur les mollusques de la famille des Bullidés. Ann. Sci. nat., Zool., (6)9: 1-123. ‚ 1898, Monographie de la famille des Pleurobranchidés. Ann, Sci. nat., Zool., (8)8: 209-402. 1901, Monographie de la famille des Pleurobranchides. (Deux- ieme et derniere partie.) Ann, Sci. nat:, Zool., (8)12: 1-85, WHITE, K. M., 1945, On two species of Aglaja from the Andaman Islands, Proc. malacol. Soc. Lond., 25: 91-102, , 1946, On a new species of Aglaja from Ceylon. Proc, malacol. 378 M. T. GHISELIN Soc. Lond., 26: 167-142. somencyclus bei Pteropoden. ZARNIK, B., 1911, Uber den Chromo- Dtsch. zool. Ges., 20: 205-215. RESUMEN FUNCION REPORDUCTORA Y FILOGENIA DE GASTROPODOS OPISTOBRANQUIOS La anatomia comparativa y funcional del sistema reproductor en toda la subclase Opistobranchia se trata criticamente con la finalidad de proveer una base mas sölida para estudios filogenéticos. Observaciones originales se combinan con discusiones detalladas de otros trabajos, dando especial importancia a posibles explicaciones funcionales de las variaciones morfolögicas y fisiolögicas, que conduzcan a una teoria filogenética con base causal. En el analisis de las funciones se evita la consideración de aspectos que tienen la posibilidad de ser convergentes, destacando la comparación basada en complejas divergencias funcionales. La homología de las partes es tratada en detalle y se sugieren algunos cambios en nomenclatura. La formación de masas ovígeras y las homologías de las glándulas que las producen, se discuten y clarifican por observaciones experimentales e histo- química. Se consideran las posibles razones de los cambios evolutivos. Desventajas fun- cionales de los gonoductos de caracter ancestral, no divididos, se han superado en diferentes maneras, y tales divergencias dan base para hipótesis que se evaluan en términos de otras evidencias. También se consideran trabajos sistemáticos anteriores, numero de cromosomas, especialización alimenticia y otras propiedades del sistema digestivo, y la morfo- logía espermatozoica, como evidencia auxiliar en la discusión de problemas filo- genéticos, los cuales incluyen consideración crítica de paralelismo y convergencia. El sistema reproductor de los Ochidiidae mantiene afinidades con pulmonados. Los Acteonidae tienen un sistema reproductor modificado y no son ancestrales a la mayoria de otros opistobranquios, y aquel, asi como otras estructuras implican una estrocha relación con los Hydatinidae; la histología de la ampolla sugiere posible afinidad con los Acoela. Se rechazan otras premisas sobre las cuales se habian basado argumentos para un origen bifiletico de los Pterópodos; su origen monofiletico es consistente con la morfología del sistema reproductor; ambos grupos se asemejan a los Anaspidea y Sacoglossa en morfología espermatozoica. El sistema reproductor de Anaspidea, Sacoglossa, Diaphanidae y Cylindrobullidae pueden compararse a un ап- tecesor común hipotético con un gonoducto dividido, y pueden estar relacionados. Los Retusidae, Philinoglossidae, Bullidae, Atyidae y Runcinidae pueden agruparse juntos en base al aparato copulador el cual almacena esperma y forma espermatóforos; miembros herbívoros de este grupo tienen un divertículo esofágico y similaridades en la molleja. Correlaciones entre tipos de concha larval y la condición triáulica en nudibranquios aeolidos sugieren una necesidad de revisión sistemática. El estudio soporta la naturalidad de muchos grupos. Verh. MALACOLOGIA, 1966, 3(3): 379-398 A CONTRIBUTION TO THE CONCHOMETRY OF BIOMPHALARIA PFEIFFERI (BASOMMATOPHORA: PLANORBIDAE) G. H. Frank and A. H. Meyling Council for Scientific and Industrial Research Pretoria, Republic of South Africa ABSTRACT The shell of Biomphalaria pfeifferi, in common with many molluscs, is in the form of a logarithmic spiral, its idealized shape being close to its actual shape. Equations based on this fact were used to calculate its surface area and its weight per square millimeter. As a check, estimationsby a more direct method were done and found to be in substantial agreement. Results based on shells from natural and artificial habitats suggest that the average weight per square millimeter increases with age and with increase of soluble calcium in the medium. This increase apparently takes place equally in all parts of the shell, i.e. the weight per square millimeter for any part is approximately equal to the average measurement for the whole shell. It would appear that the valuekj (radius of whorl/radius of spiral at that point), or its equivalent ratio, shell height to maximum shell diameter, decreases with age and with an increase in the aggressive carbon dioxide of the habitat. If, as the results of this limited investigation suggest, the shell of Biomphalaria always approximates the ideal- ized shell form, detailed conchometry by conventional methods is unnecessary. Full mathematical analysis would only be required if it were found that the rate (1) at which the whorls recede from the centre and the aperture diameter (re- lated to тф ) in similar size groups were significantly different. INTRODUCTION It is now well established that the mineral substances for shell formation in aquatic molluscs may be derived directly from the water of the natural habitat (Galtsoff, 1934; Robertson, 1941; Raven, 1958; Jodrey, 1953). Anadequate concentration of these saltsinthe habitat is therefore of some importance to the snail. As a preliminary towards a better understanding of the role of dis- solved calcium in the biology of Biom- phalaria pfeifferi (Krauss), it was con- sidered of value to discover whether variation in the concentration of this salt in the water of the natural habitat had any direct and easily detectable influence on the shape and thickness of the shell. An attempt was made to measure thickness directly with an eyepiece micrometer after grinding the shell into thin sections, but, due to the sculpturing of the shell surface and the difficulty of orientating the edge to be measured accurately, the technique was found im- practical at the high magnifications re- quired. Since the shell was found to be considerably thicker in the immediate vicinity of the sutures, a large number of measurements would also have been required to arrive at a satisfactory average value. In addition none of these measurements would have revealed any variations in the form of the shell. Because of these difficulties a mathe- matical analysis of shell-form was attempted in order to calculate the sur- face area and, from it and the total weight of the shell, to derive an average value for the weight per unit area. As far back as 1838, Moseley had demon- strated that the shell of Nautilus was a logarithmic spiral, and soon after- wards, that this was also true of all (379) 380 FRANK AND MEYLING TABLE 1. No. of determinations done Colour (APHA units) Turbidity (ppm SiO») pH Conductivity (micromhos) Alkalinity (ppm CaCOg) Calcium (ppm CaCO,) Magnesium (ppm CaCO3) Iron (ppm Fe) Manganese (ppm Mn) Chloride (ppm Cl) Sulphate (ppm SO4) Silica (ppm $105) Ammonia (ppm N) Albuminoid amm. (ppm N) Nitrites (ppm N) Nitrates (ppm N) Phosphates (ppm PO,) Oxygen absorbed (4 hrs, ppm 0) Aggressive CO, (ppm СО5) Na and K (calculated) spiral ammontoid and gastropod Mol- lusca (from d’Arcy Thompson, 1917). His ideas were taken up and elaborated by Blake in 1878 and d’Arcy Thompson early in the present century. Subse- quently Huxley (1932) was able to show that, in simple accretionary growth such as that of the molluscan shell, a regular gradient in the growth-rate across the shell-forming organ (i.e., mantle edge) must of necessity produce a structure which is basically of a logarithmic spiral form. He was also able to show that these gradients in growth-rate per- meated the entire organism (so-called cortical field) and varied regularly not only antero-posteriorly but also later- ally, but expressed themselves only in certain competent areas. Thus, in the veliger of Haliotis, although the shell is Physico-Chemical analysis of waters from 5 habitats C4 © {= © © 4 SS un B етлепру 100pmoO ymadsjojma ymadstjom3n 7.83 at first cup-shaped, asymmetry is al- ready present in the neighbouring soft parts (e.g. liver) and it is this asym- metry of the soft parts which determines the shape of the shell (Eales, 1950). A purely speculative suggestion based on Huxley’s theory of growth gradients is that the almost bilaterally symmetrical shell of Biomphalaria must be looked upon as arising from a mantle edge which is primarily median in position with its growth gradient diminishing antero- posteriorly. The turbinate spiral shell of Bulinus on the other hand is formed by a laterally situated mantle edge with its growth gradient diminishing not only antero-posteriorly but also laterally, the latter gradient being responsible for the ‘shear’ in the shell spiral. That a laterally situated mantle edge (brought EEE CONCHOMETRY OF BIOMPHALARIA 381 about by the process of torsion) will produce this particular type of shell is indirectly supported by Raven’s re- mark (1958) that when “coilingby unequal growth of the shell begins before torsion it takes place according to the plane of symmetry” (e.g. in Trochus) and that the asymmetrical coiled shell forms only after torsion has taken place (e.g. in Haliotis). Torsion of the rapid type brought about by the contraction of the velar retractor muscle (e.g. early tor- sion in Haliotis or later torsion in Acmaea) apparently does not affect this bilateral symmetry. ORIGIN OF MATERIAL Wild Snails. Four widely separated habitats, in which the average dissolved calcium content ranged from approxi- mately 5-115 ppm were chosen and a single graded series (from about 2-10 mm) of 20 undamaged shells was selected from each. In addition 20 shells from snails bred in outdoor aquaria at the laboratory were also used. Collections were not made at the same time of the year. The physico-chemical characteristics of these 5 waters are given in Table 1. However, as Macan (1950) has shown, such general analyses seldom give more than a rough picture of actual conditions in the microhabitat. Joubert’s Dam is a small catchment reservoir in a moun- tainous, soft-water area. Shiya-lo- Ngubu Dam is similarly situated but is far larger and about 1,000 ft higher. Both Buffelspruit and Ngwetispruit are hard-water streams (Schutte & Frank, 1964) flowing off the Jamestown Igneous Complex. Shells from Joubert’s Dam often showed severe erosion of the inner whorls, probably due to the action of aggressive carbon dioxide which was found to be over 8 ppm there. The Shells selected for this investigation were, however, relatively undamaged. Most of the total hardness of the waters of this area is due to magnesium (expressed as CaCO3 in Table 1). Mag- nesium carbonate, which is much more soluble than the Ca salt, is not likely to contribute to shell structure (Frank, 1963) and has therefore been ignored in our evaluations. Laboratory Snails. Because it is quite probable that the snails from these 5 habitats, although nominally all of the same species, had very different genotypes (Paraense, 1956), andbecause it was also impossible to separate the effect of the aggressive carbon dioxide in the natural habitat from that of calcium, it was thought advisable to breed snails in the laboratory under varying experimental conditions. Four groups of eggs, all originating from the same inbred laboratory stock, were therefore exposed to 4 different com- binations of calcium carbonate and aggressive (free) carbon dioxide, pro- ducing variable amounts of dissolved calcium bicarbonate. Upon hatching, the young snails were cultured in these media for a further 15 weeks under con- ditions very similar to those described in a previous paper (Frank, 1963). Ten snails were kept in one litre of medium, with 4 aquaria to each of the 4 different media. But, as difficulty had been experienced before on bubbling air through the aquaria, it was not attempted, this time, to pass the experimental gaseous mixtures through the culture aquaria directly. The different experi- mental media were prepared separately; they were brought to equilibrium with their air-carbon dioxide mixtures for 24 hours before being siphoned, with a minimum of agitation, into the aquaria. The media were changed daily and the snails fed freshly scalded lettuce and lucerne. Conditioned tap water, the same as that used in the outdoor aquaria (Table 2) but slightly diluted with glass distilled water, was used to make up the experi- mental media. Excess calcium carbon- ate (approx. 2 g/l) was added to 2 of the experimental media (C and D). Air from which the carbon dioxide had been partially removed, was passed through 382 FRANK AND MEYLING TABLE 2. Mean and range of conditions* to which snails were exposed in experimental media. Aquarium conditions Reduzdd Mean 24.5 ppm co Max. 32.3 ppm 34. 2 Min. 21.2 ppm Exa Mean 24.7 ppm co Max. 34.0 ppm 2 Min. 20.8 ppm No free CaCO3 *From 9 determinations 2 media, A and C, (the latter with and the former without excess calcium car- bonate) until equilibrium was reached. Another stream of air, enriched with carbon dioxide, was passed through the other 2 media (B and D) also until equilibrium had been reached. The air with reduced carbon dioxide content was simply prepared by passing it through a column of soda-lime. To make a COo-enriched air mixture of а reasonably stable composition, a stream of air was first dried in a silica gel column and then passed through a 25% constant boiling mixture of water and hydrochloric acid kept at roughly 30°C in a water bath. This acidified air was then passed through a saturated solution of sodium bicarbonate, where it became neutralized and picked up CO». Since a constant boiling hydrochloric acid-water mixture evaporates (at constant temper- ature) at afixed rate, an air-COy mixture of constant proportions can thus be pro- duced. By holding the acid at a higher or lower temperature more or less carbon dioxide can be produced. Calcium concentration at beginning h er 24 rs 24.2 19.6 23.3 35.6 16.8 52.8 69. 2 44.6 E Rediiéed Mean 33.1 ppm 2 Max. 40.8 ppm Et | CO2 1 Mo N Min. 29.2 ppm an Ф 7 Extra Mean 89.6 ppm 107.7 El 60 Max. 119.2 ppm | 157.0 - Min. 55.2 ppm 68.4 Aggressive CO, concentration hrs Overall mean 2.9 7.3 4.6 9.5 24 ppm 5.1 ppm 10 5.0 8.9 qos 12.0 329 24 ppm 8.4 ppm 5:1 6.3 0. 85 2.5 5.3 4. 6 43 ppm 0.0 0.5 98 ppm No attempt was made to measure the concentrations of carbon dioxide in the mixtures directly as this was relatively unimportant in the context. Although the media were renewed every day, the content of aggressive carbon dioxide and dissolved calcium was determined weekly for the first 9 weeks only. In all 9 pairs of determinations were done: one immediately before addition of the media to the aquaria and another 24 hours later, i.e. just before they were discarded. The results are summarized in Table 2. The aggressive carbon dioxide in the samples was determined by agitating the sample at intervals, for 24 hours, out of contact with the air, with an excess of calcium carbon- ate: the concentration of aggressive carbon dioxide was then calculated from the increase in soluble calcium bicar- bonate found. All calcium determin- ations were done by the well-known versenate method. The following should be noted in regard to Table 2. (1) Media poor in calcium carbonate. CONCHOMETRY OF BIOMPHALARIA 383 Since there was little calcium in medium A to act as buffer, aggressive conditions developed as soon as the carbon dioxide from the snail metabolism found its way into the water. The carbon dioxide mixture passed through medium B made it very aggressive indeed, butthisinitial condition slowly abated after the medium was placed in the aquaria and the excess carbon dioxide was able to diffuse away. (2) Media with excess calcium carbonate. Medium D and especially C never had much aggressive carbon dioxide present, since it was immediately taken up by the free calcium carbonate which was then converted to the more soluble cal- cium bicarbonate. The concentration of soluble calcium rose steadily during the period the snails were in the medium. (3) Presence of carbon dioxide in soda- lime treated air. As a litre of water at room temperature will only dissolve about 14 mg of cal- cium carbonate without the assistance of carbon dioxide and as the initial mean content of soluble calcium in medium C was about 33 ppm and that of medium A was 24.5 ppm, we must conclude that the soda-lime columns failed to remove ali the carbon dioxide from the air streams conditioning these 2 media. Although the limited facilities avail- able did not enable us to maintain rigidly constant conditions, the results of their effect on shell growth were sufficiently significant to confirm and further illus- trate our field findings. METHOD In any individual adult shell of Biom- phalaria pfeifferi it may be shown, by comparing the ratios of the diameters of each whorl with its successor, that it is in the form of a logarithmic spiral. Unfortunately, because there is a slight, almost regular increase in the ratios as the apex of the shell is approached, the idealized form upon which the equation is based is not valid for the very young snail. Waddington (1929) founda similar condition in Ammonites and worked out a BIG. val sagittal section to show how the 3 largest diameters (a, b and c) were measured (in mm). Shell of Biomphalaria pfeifferi in correction factor for it. Because the innermost whorls were difficult to measure accurately and since it could be shown mathematically (Appendix 2) that the surface area of the last whorl of the shell was approximately 4 times greater than that of the rest of the shell, it was decided there was little loss in accuracy when the mean of only 2 ratios (derived from the last 3 whorl diameters) was used in the subsequent calculations. The equation for shell form and the reasoning which led to its formulation is given in Appendix 1. All shells were carefully cleaned in a very weak solution of caustic potash to clear them of residual organic matter. After thorough drying they were immer- sed and cleared in toluol. This makes it possible to take measurements of the internal structure without destroying the shell. With a low-power eyepiece micrometer the 3 largest spiral dia- meters lying on a line passing through the centre of the shell and the outer edge of the aperture (Fig. 1) plus the average of 3 readings of the diameter of the aperture (taken at right angles 384 FRANK AND MEYLING NCGWETISPRUIT 114 ppm Ca 2130 Е OUTDOOR AQUARIA x 37 ppm Ca 5 я a SHIA-LO-NGUBU DAM & 5 ppm Са a > < x 20 = BUFFELSPRUIT 3 82 ppm Ca = m JOUBERTS DAM 4 ppm Ca —— 4 6 8 10 12 Q - MAXIMUM DIAMETER IN MM FIG. 2. Relationship between shell size and its average weight per square millimeter in different natural habitats. to the walls) were determined. A summary of the calculations per- formed to arrive at the average weight per square millimeter in an individual shell may be found in Appendices 1 and 3. RESULTS Average weight per square millimeter. On calculating the average weight per square millimeter for each individual shell in each natural habitat group it was found that this dimension gradually increased with an increase in the size of the shell. For each habitat the most probable curve (by least squares) repre- senting this increase was found to be, Joubert’s Dam: у = 0.0960 + 0.00489a + 0. 00096322 Shiya-lo-Ngubu Dam: У = 0.0415 + 0.0157a + 0. 000420a2 Outdoor Aquaria: y = 0.0985 - 0.006582 + 0. 00234a2 Buffelspruit: y = 0.0465 + 0.0104a + 0. 000314а2 Ngwetispruit: у = -0. 235 + 0. 0751а - 0. 0021322 where у is the average mg/mm2and а is the maximum diameter of the shell in mm. These curves are shown in Fig. 2. Despite a 23-fold difference in the cal- cium content of the habitats the average weight per square millimeter of the shells increases only 1.2 times (10 mm CONCHOMETRY OF BIOMPHALARIA shells from Shiya-lo-Ngubu Dam and Ngwetispruit). This low rate ofincrease tends to confirmthe theory of Waddington (1953), Warburton (1956) and others that the development of these molluscs in common with other organisms is con- trolled by a cybernetic type of system, which ensures that, within certain limits, a phenotypically normal organism develops despite variations in its geno- type and developmental milieu. However, the results for Shiya-lo-Ngubu Dam, Outdoor Aquaria and Ngwetispruit (Fig. 2) imply that the higher calcium content of the latter 2 habitats does tend to give rise in the larger shells to a slight increase in the shell weight. Boycott (1936) found an appreciable strengthen- ing of the shell in races of thin-shelled Lymnaea bred in hard water. That the concentration of calcium is not the only factor involvedis shown by the anomalous positions of the curves for Joubert’s Dam and Buffelspruit and the confused relationships between the curves at small diameters. It is suspected from un- published data that, in the absorbtion of calcium by the snail, the role of other ions is not inconsiderable and that the concentration of these ions relative to the calcium, especially in the case of Joubert’s Dam, could have been respon- sible for the slightly heavier shells from the latter habitat. The extremely low position of the Buffelspruit curve is not understood. A second set of 20 shells collected and measured more thana year later confirmed the unusually low weight per square millimeter for shells from this hard-water stream. To the unaided eye they do not appear in any way differ- ent to shells from other habitats. Now Buffelspruit as a habitat and also physico-chemically is very similar and lies almost adjacent to Boundary Creek (Schutte & Frank, 1964). It was from this creek that Schutte & van Eeden (1959) reported that a certain proportion of the shells showed an “irregularity in the coiling of the whorls although the rest of the shell ... was typically that of B. pfeifferi” and they put it down to 385 ols 24 ppm Ca MILLIGRAMS PER SQUARE MM m A 24 ppm Ca y - 9 5 6 7 Я - MAXIMUM DIAMETER IN MM FIG. 3. Relationship between shell size and its average weight per square millimeter in different artificial conditions. environmental factors. The results for the snails grown under artifical conditions are es- sentially similar. Unfortunately, due to high mortality under the more un- favourable conditions and lack of space for more extensive cultures, only a few snails were available, and only 10 snails from each group were used for com- parative calculations. In view of this low number there seemed no justification for calculating more than 1st degree curves. These are shown in Fig. 3 and were calculated as follows (у being the average weight in mg/mm2 and a the 386 maximum diameter of the shell in mm): :0. 0795 + 0. 00864a 0.00789 + 0.0213a 0.0789 + 0. 0289a 0.0397 + 0.0397a ou ot Saum ? *The values for assumed secondary deposition, ог the reverse, were calculated according to appendices 3 and 4 resp. Those for direct analysis are based onthe average of 3determinations. example: With secondary deposition: 5 = 0.0415 + 0.0157a + 0.000420a2 No secondary deposition: y = 0.0415 + 0.0315a + 0.00126a2 They are plotted in Fig. 4. To test whether secondary deposition did in fact take place, the weight per square millimeter of the shell at the aperture was found by a more direct method. The surface area of small chips from the mouth of the shell was estimated by drawing them greatly magnified on paper with the aid of a camera lucida. These irregularly shaped outlines were cut out and their weight compared with that of a piece of known area. After dissolving the chips in hydrochloric acid and evapor- ating to dryness, their salts were dis- solved in a known volume of water. The conductivity of this solution was then compared directly with that of a known calcium chloride solution and the weight per square millimeter of the chips estimated on the assumption that they consisted of pure calcium carbonate. The results by this method for shells from Shiya-lo-Ngubu Dam are also plotted in Fig. 4. All 8 values lie below the line given for a shell in which second- ary deposition in the inner whorls has been assumed to have taken place, showing that there was no greater average weight at the aperture, as would be the case if growth was concentrated there. A similar procedure wasfollowed 388 — FRANK AND MEYLING FIG. 5. A diagrammatic cross section of portion of a shell of Biomphalaria pfeifferi showing the various mathematical relationships discussed. for shells from Ngwetispruit and the Outdoor Aquaria. A comparison of the corresponding data, for the 3 habitats, is presented in Table 3. The figures for the direct measurements are based on the average of 3 samples taken from the aperture of each shell. The values obtained by the direct method were found to be either below or at least nearest the curve calculated on the assumption that secondary deposition had taken place. The values would have been slightly higher if (1) allowance had been made for the fact that approximately 4% of the weight of the shell was con- tributed by substances other than calcium carbonate (unpublished data) and (2) the area in the vicinity of the sutures had been sampled more frequently. There was some indication that, in waters as hard as Ngwetispruit there was a tendency for the weight per square milli- meter of the shell at the aperture to be greater than the average weight per square millimeter for the whole shell. Five of the 7 determinations for this habitat show values for the aperture greater than the calculated average for the whole shell, but still closer to the latter than toa shell which, theoretically, had no secondary deposition. Shell Shape. Referring to Appendix 1, rd = radius of whorl ur Rg radius of spiral 1 and, from Fig. 5, k, =sine of = РОО] Thus should kj, supposedly a constant, become greater, < DOOy will also be- CONCHOMETRY OF BIOMPHALARIA IGWETISPRUIT 0 ppm CO» HIYA-LO-NGUBU DAM 3.7 ppm CO2 09 a 08 < EE m =) =) + no. er OUTDOOR AQUARIA 2% 4.5 ppm CO» = 06 OS 389 8 10 l2 A - MAXIMUM DIAMETER IN MM FIG. 6. Relationship between shell size and kj (radius of whorl/radius of spiral at that point) in different natural habitats. come greater; or the average radius of the whorl at the aperature relative to the rest of the shell will increase. Actually, since A (the rate at which the whorls recede from the centre, Appendix 1) remains almost constant (equal to tan a, Fig. 8, Appendix 1) the radius of the aperture cannot easily become greater in the plane of the spiral but only vertical to it. Thusin any particular Shell, while the radius of the aperture in the plane of the spiral will be found to be near its theoretical value, the radii vertical to it may be greater, giving an overall increase inthe average radius. This condition, commonly seen in small shells, makes the aperture appear elliptical. The greatly in- creased average diameter of the aper- ture in these small shells at a con- stant À is probably the fundamental reason why the equation failed in these size groups. We may take kj therefore as an indi- cator of any changes in the relationships of the basic elements of the shell. The most probable curves for kj (by least squares) as the maximum diameter of the shell, a, increases are, in shells from a soft, medium and hard-water habitat: Shiya-lo-Ngubu Dam: К] = 1.448 - 0.193a + 0.0098a2 Outdoor Aquaria: К] = 1.341 - 0.198a + 0.0115a2 Ngwetispruit: k, = 2.265 - 0.325a + 0.0145a2 390 FRANK AND MEYLING They are plotted in Fig. 6. Withgrowth, kı tended to change more rapidly in the hard than it did in the softer waters, but the differences became less as the shells grew larger until they all had very nearly the same value for kıata maximum shell diameter of about 9mm. The relatively greater values found for k] in small shells from Ngwetispruit (the difference disappeared as the shells grew larger) may be taken to indicate that not only was the aperture more elliptical in these hardwater snails but that the whorls must have overlapped more, for, the larger К] is, the greater will be the overlap of one whorl over the preceeding one. As Huxley (1932) points out, this lends greater strength tothe shell. Since for a given perimeter (in this case shell wall) a circle circumscribes a greater area than an ellipse, and since the less overlap there is, the less the earlier whorls protrude into the later whorls, a small soft-water shell will have a greater internal volume and can thus contain a larger snail than a hard-water shell of the same average radius of aperture. Put another way: in early life soft-water snails with their more nearly circular shell whorls and less compact structure tend to use their calcium carbonate more “economically” than their hard-water counterparts. This implies that in a given time, hard-water snails, if their soft-parts are to occupy the same volume, must produce a greater number of whorls than their soft-water counterparts of equivalent age. If water-hardness (Table 1) alone is taken into consideration as a factor influencing shell “shape” (a decrease in К] denoting greater relative flattening) then it would be expected that the curve (Fig. 6) for Outdoor Aquaria (37 ppm CaCO3) should lie between the other two (Ngwetispruit: 114 ppm; Shiya- lo-Ngubu: 5ppm). However, ifaggressive carbon dioxide should be the overriding factor for control it will be seen thatthe curves lieinalogical sequence, Ngwetis- pruit with the lowest value for aggressive carbon dioxide (0 ppm) having the highest values for ky in any size group and Outdoor Aquaria with the highest value for carbon dioxide (4.5 ppm) having the lowest values for k, in equivalent size groups. Furthermore, the results for artifical media, would on the whole, seem to confirm this suggestion, the least aggressive condition having the greatest values for kj in equivalent size groups. The most probable curves (again lst degree in view of the small number of Shells) are plotted in Fig. 7 and are calculated as follows: А: k, = 0.755 - 0.0367a В: kj = 0.669 - 0.0258a С: К, = 0.868 - 0.0526a D: К; = 0.800 - 0. 0533а However, the fact that the values for kj in shells from the hardest artifical medium (D, 98 ppm CaCO3) do not fit this scheme, and, as mentioned before, that anomalies exist in the weight/mm2 relationships of shells from Buffelspruit and Joubert's Dam, give reason to suspect that there are factors, other than the concentration of calcium and carbon dioxide, which affect shell growth and shape, especially where the concen- tration of calcium relative to the other ions in solution is disproportionate. DISCUSSION It is unfortunate that the collections used in the present study were not ob- tained from exactly the same sites as those of Schutte € van Eeden (1959) in their work on the shell of Biomphalaria pfeifferi. It is also regretted that no physico-chemical data are available from their collecting sites. Neverthe- less, it is thought that the habitat con- ditions were sufficiently similar in the 2 studies for a useful comparison of the 2 methods of attack and their results to be made. (a) Our work has confirmed Schutte and van Eeden’s suggestion that only equivalent size groups should be com- pared and not mean values from CONCHOMETRY OF BIOMPHALARIA 391 O6 0.55 D 2.9 ppm COz SHELL SHAPE А, - о ua 5 6 B 8.4 ppm СО2 7 8 а MAXIMUM DIAMETER IN MM FIG. 7. Relationship between shell size and kı (radius of whorl/radius of spiral at that point) under different artificial conditions. measurements of random samples, since, in our case, kj (radius of aperture to that of the spiral) and in theirs the related, though inverse ratio D/H (greatest shell diameter to shell height) changes as the shell grows larger. (b) The marked convergence of values for К] or “shape” (Figs. 6 and 7) and to a lesser extent for Y or average weight/ mm? (Fig. 2) for shells between 8 and 9 mm in diameter is paralleled in Schutte and van Eeden’s results. Their related D/H ratios for samples from various habitats, also differ more from one another in the greater (10-12 mm) than in the smaller (8-10 mm) groups. Un- fortunately they list only 2 samples in the 6-8 mm size group, but both of these have (statistically) highly significant differences. They also state in general for their material and ratios that “samples usually differ more from one another in the greater thaninthe smaller size groups”. (c) Using ground cross-sections of Shells Schutte and van Eeden measured the greatest distance (their “major dia- meter”) across each whorl. This “major diameter” usually lies approximately at right angles to the plane of the spiral (see their Fig. 5). Our data suggest that (1) because kj is not constant (Fig. 6) the relative size of the aperture proba- bly varies, but that near a maximum shell diameter of 9 mm the change becomes slight and is similar for snails from different localities and that (2) the whorl radii, vertical to the plane of the 392 — FRANK AND MEYLING spiral, are exaggerated in the earlier parts of the shell. Schutte and van Eeden's figures also show that over the range 8.5-10.5 mm the ratios the “major diameter” of the penultimate to ultimate and the pre-penultimate to penultimate whorls were constant, but that the ratio for the inner whorls was higher than for the outer. The present work suggests, however, that the outer whorls have the greater ratio. The discrepancy is probably due to the fact that our conclusions were based on an average diameter whereas theirs were based on the “major diameter”. Al- though the ratio of the ultimate to pen- ultimate whorls is virtually constant over the range 8-10 mm, Schutte and van Eeden contradict their figures by saying that these ratios do not vary with the age of the shell. (d) It is clear from Figs. 6 and 7 that К] varies a great deal during the life of the snail and that its rate of change for specimens from different habitats is different. The data further suggest that the alteration in the rate of change in К] is brought about not by the calcium but by the aggressive carbon dioxide of the water. Thus it is very doubtful whether either k (the radius of the whorl relative to the radius of the spiral at that point) or the measurement of shell angles (Schutte & van Eeden, 1959, Fig. 5, = EQF and Calculation of Н$ From Fig. 1 and Appendix 1 Il p Rp + kiRÿ + Rór + k¡Ró-7r Вф + гф + Вф-т + тф-т ll p Ro + Rór = —*— 1-k R pr But as Dem = AO IN = RN AN R-7 Ce®- TÍA e-TA Вф-т = Re ™ or according to (7) Rg [ka and substituting in the above equation a Rg (1 + fk,) = Я er, a Te Ky) (1 + Jk) AN Calculation of k; T or according to (8) bis ky ua AA) Calculation of Bo From Fig. 5 rg = h2 + x? "hon =h* + (y-x)2 rg - та = x2- y2 + 2yx - x2 = 2yx-y 2 But “y = Rg - R-27 r$- $27 = 2(Rg- Rg_o7)X - Rg - Rp- 2m)? $ Thon) + Rp- Rp-2m2 2Rg-Rg am) De CosBo = 1 i _ gran * Rp Вот 2rp(Rá - Вф-2т) According to (6) and (1) Eb k¡Rg: Rg oy =KoRps tp9,=kyRo-27=k1XkgxRo „RO? - Слов? + Rp-kong)? a Gé TES) kı(l + k 1-k ee es i 2 2k, 398 FRANK AND MEYLING APPENDIX 4 meter at the aperture of a shell in which no secondary depo- The equation for the weight per unit sition occurs. area of the shell at the aperture when no secondary deposition takes place or substituting values for shells from Let y and y then [yaa = ay Shiya-lo-Ngubu Dam = shell weight per square milli- meter at the aperture of a shell in which secondary deposition and differentiating to a occurs (same as the average к уда = (0. 04154а + 0.01573 x 2ada + weight/sq mm). = shell weight per square milli- у = 0.0415 + 0.03146a + 0. 0012594a2 RESUMEN CONTRIBUCION A LA CONCHOMETRIA DE BIOMPHALARIA PFEIFFERI (BASOMMATOPHORA: PLANORBIDAE) En comün con muchos moluscos, la concha de Biomphalaria pfeifferi forma una espiral logaritmica. La forma real de esta espiral es cercana a la ideal. Ecuaciones basadas en este aspecto, se usaron para calcular el ärea superficial y su peso por mm2. Como control, se hicieron estimaciones por un metodo mas directo, encon- trandose substancial concordancia. Resultados tomados de conchas de ambientes naturales y artificiales, sugieren que el peso medio por mm2, crece con la edad y el aumento del calcio soluble en el medio ambiente. Este crecimiento tiene lugar, aparentemente, en todas las partes de la concha por ejemplo, el peso por mm2 de una parte es aproximadamente igual a la medida media de la concha entera. Pareceria que el valor Ky(radio del anfracto/radio de la espiral a ese punto) o su proporciön equivalente, altura a diametro maximo, decrece con la edad y con el aumento del agresivo carbon diöxido del habitat. Si, como el resultado de esta limitada investi- gación sugiere, la concha de Biomphalaria siempre se aproxima a la forma ideal, conchometría detallada por métodos convencionales es innecesaria. Análisis mate- mático completo se requerirá solo si se encuentra que la valuación (A) de recesión de las vueltas desde el centro y el diametro de la abertura (relacionado con rg) en grupos de tamaño similar, es significativamente diferente. | уда = а(0. 0415 + 0.015734a + 0. 0004198a2) 0. 0004198 x 3a2da) MALACOLOGIA, 1966, 3(3): 399-418 THE GENUS MYA IN THE ARCTIC REGION Dan Laursen Department of Biology and Earth Science Jackson County Community College Jackson, Michigan, U. 5. A. ABSTRACT The present account was written to clarify a misconception about Arctic spe- cies of Mya. Jensen (1900) has pointed out (in Danish) that all the then existing records of М. arenaria Linnaeus from the Arctic were erroneous and dealt, in fact, with a form of M. truncata Linnaeus which he named ovata. The most re- liable distinguishing marks between the almost similar shells of the 2 species lie in the cartilage plate of the left valve and the corresponding cartilage pit of the right valve. However, because Jensen’s publication is not widely known in the English speaking world, М. arenaria, a boreal species, is still being re- ported from the Arctic. Furthermore, Schlesch (1931) arbitrarily elevated the form ovata, which Jensen himself considered at most to be an infrasubspecies, to species rank, and renamed it M. pseudoarenaria, a name that should not be used. In this paper, the distribution, Recent and fossil, of 3 forms of Mya truncata: M. truncata forma typica Linnaeus, M. truncata f. uddevallensis Forbes andM. truncata f. ovata Jensen, as well as that of M. arenaria is given, as far as it could be ascertained. The lists are not complete. Scientists working with M. truncata are entreated to give more details regarding forms in future papers. Some new records of M.arenaria from within the Arctic regions are dis- INTRODUCTION In 1900, Adolf S. Jensen, the now deceased Professor Zoologiae at the University of Copenhagen, published a paper entitled: “Studier over nordiske Mollusker. I. Mya.” (Studies of Nordic Molluses. I. Mya.), in which he demon- strated that all the specimens from the Arctic Region collected prior to 1900 and identified as Mya arenaria Linnaeus are a variety of Mya truncata, which he named ovata. The paper was written in Danish and, unfortunately, very few malacologists outside of Scandinavian countries benefited from it. H.Schlesch (1931) treated the topic in German. Jensen was occasionally quoted in the English language malacological liter- ature and recently Foster (1946) treated the genus and the problems associated with it in his paper dealing with Mya in cussed, all of which deal with M. truncata f. ovata. the Western Atlantic. Every now and then, however, the old confusion and misconception about the Arctic species of Mya turns up again in papers written in the English speaking parts of the World, even though Jensen clarified the issue more than 60 years ago. This paper is an attempt to prevent the perpetuation of this error. There follows a summary of Jensen’s (1900) paper supplemented by some later information, a revision of more recent records, distribution lists and a dis- cussion. JENSEN’S CONTRIBUTION The melting of the Great European Ice Cap caused an immediate sub- mergence of low level areas in southern Scandinavia. Further deglaciation, how- ever, caused an isostatic uplift of the (399) 400 D. LAURSEN same area whereby the original Baltic basin was turned intothe Baltic Ice Lake, a freshwater lake fed by the meltwater from the still existing ice and drained through the straits and sounds now con- necting the Baltic Sea and the North Sea. Because of a new depression of the earth’s crust, salt water entered the Baltic basin, forming the Yoldia Sea, which is named for its dominant inhabit- ant, the high-arctic bivalve Yoldia arctica Gray (=Portlandia arctica (Gray)). A new uplift again raised the Baltic area, and the sea was converted into a freshwater lake, the Ancylus Lake, named after its characteristic species Ancylus fluviatilis Müller. The steady eustatic rise of sea level caused by the still melting ice again gradually submerged the basin with its associated sounds and belts. The An- cylus Lake became part of the water body called the Littorina Sea (named for the gastropod Littorina littorea Linn- aeus). This lake finally became the present Baltic Sea. During the last quarter of the 19th century the post-glacial deposits of northern Europe were studied in- tensively. Little by little the migration patterns of the present inhabitants of the North Sea and the Baltic Sea were revealed. One fact, however, puzzled interested scientists. Mya arenaria, which now occurs regularly along the coasts of Denmark and southern Sweden, did not occur at all as a fossil in the layers investigated. Nathorst (1872) was the first to direct attention to this fact and it was later confirmed by Petersen (1892). In the older deposits Petersen found several genera (Tapes and Ostrea) which do not occur in the area today. The Tapes deposits are contemporary with extensive kitchen middens where Mya arenaria is absent. It must have immigrated later. This is also the situation in northwest Germany (Berendt, 1867; Mendthal, 1889), in Got- land and Oland in Sweden (Lindström, 1868), in Norway (M. Sars, 1865) andin Belgium (Raeymaekers, 1895). The question which then arose was: where did Mya arenaria live before its immigration to these regions and from where did it emigrate? The answer seemed very easy. From the available distribution records of this species it had to be: from the north. All con- temporary authors dealing with the dis- tribution agreed in classifying M. aren- aria as an Arctic, circumpolar species occurring in Labrador, Greenland, Spits- bergen, the Kara Sea, along the Siberian coast and in the Bering Strait. At the same time, however, aninvestigation of the distribution during the Glacial Period showed the species to be absent from Denmark (Johnstrup, 1882; Jessen, 1899) and the Scandinavian peninsula (M. Sars, 1865; Thudén, 1886). This appeared contradictory to Jensen. He felt that a species now living through- out the entire Arctic zone would certainly have lived in northern waters with the arctic climate prevailed during the Glacial Period. He began an investi- gation of the problem and proved that the classification of Mya arenaria asa high-arctic species was due to a wide- spread misconception. He examined every specimen mentioned in the liter- ature and an overwhelming amount of material available in museums and private collections, and was able to demonstrate that all statements about the presence of M. arenaria in high- arctic regions were due to misidentifi- cation. Jensen gave a detailed account of the differences between Mya arenaria and M. truncata that are useful for identifica- tion. The most reliable distinguishing marks are found in the chondrophores of the left and right valves: the cartilage plate of the left valve and the corres- ponding cartilage pit of the right valve. He also mentioned the diagnostic im- portance of the umbones of the left valve. For a complete, detailed description see Foster (1946). Jensen used these characteristics ina revision of the high-arctic specimens earlier identified as Mya arenaria, which ARCTIC MYA he recognized as a special form of M. truncata that he named forma ovata. He then critically evaluated all literature records of “M. arenaria” from the high- arctic regions. The specimens from Greenland reported by Fabricius (1780), Möller (1842), Mórch (1857), Posselt (1898), Traustedt (1883), Nordenskiöld (1870) and Bay (1895) were all found to be M. truncata forma ovata, andaccord- ingly M. arenaria must be withdrawn from the list of Recent and fossil bi- valves of that island. The same applies to the records of M. arenaria from Ice- land (Mohr, 1786; Mprch, 1868 and Posselt, 1898); from Spitsbergen (Kröyer (unpublished; see Jensen; specimens in the Zoological Museum, Copenhagen); Meyer & Möbius, 1872; Friele,1879); from the KaraSea (Leche, 1883; Collin, 1886); and from the Siberian Sea (Leche, 1878). The occurrence of Mya arenaria in Labrador, both Recent and fossil is mentioned by Packard (1867). A collection of American shells, donated by Packard, is in the Zoological Museum in Copenhagen. Some shells from the Pleistocene of Maine, identified by Packard as M.arenaria are actually M. truncata forma ovata, and no doubt some of the specimens cited by Packard elsewhere are also forma ovata. Packard also sent shells from Maine, the Mari- time Provinces and Labrador to the University Museum, Oslo, Norway. Brégger (1900/01) gives the information, that the specimens from the southern- most locality, identified by Packard as M. arenaria, are true M. arenaria, but those from the northern localities are partly M. arenaria and partly M. trun- cata forma ovata. Otherwise Вгфосег agrees with Jensen’s interpretation of the American shell material. Krause (1885) has stated that very young Mya arenaria are present in the Bering Strait. Jensen demonstrates that in many instances such young speci- mens of M. truncata are misidentified, as they have not yet developed the trun- cate posterior end. The Bering Strait’s 401 specimens are similar and all records of M. arenaria from this locality must be considered erroneous. Jensen finally gave the distributions of the species as known at the turn of the century. Their presently known distributions will be given below. NEW REVISIONS AND RECORDS Baker (1911), Wilson (1904) and Mc- Innes (1904) record Mya arenaria from the Pleistocene of James Bay, Canada. Richards (1936), who later investigated the same area, did not find M. arenaria in the deposits. Probably the 3 first mentioned scientists were influenced by the old idea that M. arenaria was an Arctic species and had no knowledge of Jensen’s paper. It was possible to find the shell col- lected by McInnes at Winisk River. It is an unbroken left valve with an al- most rounded but still recognizable trun- cate posterior end. It has a chondro- phore of the truncata type and also the pallial sinus is truncata-like. The shell must therefore be identified as Mya truncata (Canadian Geological Survey cat. no. 66355). Nichols (1936a), while with the Eastern Arctic Expedition during 1935, collected Shells from the raised terraces in the Hudson Bay area. The shells were identified by A. LaRocque. Mya arenaria is recorded from the following localities: Sugluk, Quebec, Elevation 224 ft. Port Harrison, Quebec. Elevation 110 at. Port Harrison, Quebec. Locality 2. Elevation 20-42 ft. Port Harrison, Quebec, Elevation 124 ft. Port Harrison, Quebec. About 1 mile south. Elevation 162 ft. Shells were also collected at Eric Cove, Wolstenholme, Quebec. Elevations 233 and 345 ft. From the Geological Survey of Canada, I received some samples of Mya shells in addition to the one collected by McInnes. These samples are listed and 402 D. LAURSEN discussed below. Sample 1. Locality: Clyde River, Baffin Island. Alt.: 40-180ft (13.3-60m). Collected by: D. A. Nichols, 1937. Canadian Geol. Surv. cat. no. 66353, The sample consists of 1 large, un- broken left valve, 1 large and 1 small unbroken right valve, plus several frag- ments, some of them with chondrophore and/or-pallial sinus. Mya truncata forma ovata. Two large shells. For the dimensions of these shells and the following see Table 1. Mya truncata forma typica. One small shell and several fragments. Sample 2. Locality: Port Harrison, Quebec. Col- lected by: D. A. Nichols. Canadian Geol. Surv. cat. no. 66352. The sample consists of 4 unbroken Shells: 2 large left and 1 small left valve, and 1 large right valve plus a fragment. Allthe shells are Mya trun- cata forma ovata. Sample 3. Locality: Eric Cove, Quebec. Alt.: 12-32 ft (4-11m). Collected by: D. A. Nichols, 1936(?). cat. no. 66354. The sample consists of 1 whole speci- men, 4 unbroken valves, and several large fragments, most of them with chondrophore. Mya truncata forma typica. One speci- men, 2 unbroken right valves and several fragments. Mya truncata forma ovata. Two valves, a left one and a right one. Sample 4. Mya arenaria ? Locality: Fort Albany, Ontario. North side of Albany River in clay beds. Col- lected by: Fritz Johansen, July 8, 1920. Canadian Geol. Surv. cat. no. 66351. The sample consists of 1 unbroken shell and a large fragment. Mya truncata forma typica. One large fragment. Mya truncata forma ovata. valve. As can be seen from the above, the Canadian Geol. Surv. One left old identification of Mya arenaria at Port Harrison is not correct. The sample I have checked has no record of elevation, but if M. truncata forma ovata was misidentified from one ele- vation, I think this would also happen to the forma ovata shells from the other elevations. For the same reason I also believe that the Mya specimens from Sugluk and Wakeham Bay identified as M. arenaria really are М. truncata forma ovata Jensen. Strangely enough, the only Mya specimens recorded from Eric Cove are all M. truncata forma uddeval- lensis Forbes, whereas forma typicaand forma ovata, present in the sample I got, are not recorded at all by Nichols (1936a,b). However, the sample might be from 1937 and therefore not included in the report. Richards (1940b), records 1 specimen of Mya arenaria from the west coast of Hudson Bay near the north side of Dawson Inlet, about 60 miles north of Eskimo Point. Upon my request Dr. Richards was kind enough to reexamine the speci- men. He informed me that upon further examination he finds it such a young specimen that it should be identified merely as Mya sp. Since all traceable specimens of Mya avenaria recorded from the Hudson Bay area turned out to be M. truncata forma ovata, M. arenaria must be omitted from the faunal lists of that region. Elton & Baden-Powell (1931) record the presence of M. arenaria in raised beaches from Spitsbergen. Feyling- Hanssen & Jgrstad (1950) point out the mistake and identify the specimen found as M. truncata forma ovata. In a paper by Davies, Krinsley & Nicol (1963, p 51-52), it is stated that Mya arenaria was collected on the beach at Narssarssuk, about 20 km southwest of Dundas Airbase, Thule District, North Greenland. It is not indicated whether the shells are Recent or subfossil. They are compared with shells collectedfrom raised beaches, which may indicate that the authors consider the shells from the present beach as Recent. However, M. ARCTIC MYA arenaria does not live and presumably never did live in Greenland waters. The shells were identified by Dr. Harald A. Rehder, Smithsonian Institution. I asked Dr. Rehder to reexamine the specimens but unfortunately they were thrown away, and there is no other record of the identification than the one in the above cited paper. Dr. Rehder has therefore stated that he regards the record of Mya arenaria from the Thule District as a doubtful one. I consider that the record of M. arenaria in the faunal list of Davies et al. is incorrect. If the shells were found in North Star Bay, the harbor of Dundas Airbase, it is just possible that the species could have been transported from a warmer latitude. However, even if the number of ships calling at North Star Bay were greatly increased, the chances for such transport seem to me extremely remote, especially when considering the normal habitat of Mya arenaria. A subsequent migration of the species from the bay to Nars- sarssuk is unthinkable under the circum- stances. It seems to me that there is no doubt about the specimens from Thule being either very young Mya truncata forma typica or M. truncata forma ovata. The temperature of the water in North Star Bay and Wolstenholme Sound is much too low for M. arenaria, being about 20C at the surface in August and 1%C at 10m depth (Riis-Carstensen, 1936). Gener- ally, the species occurs in shallow water (0-6 m), occasionally to a depth of 25 m. The average temperature for the coldest month (February) of the northern locali - ties where true Mya arenaria is recor- ded, ranges from about 0°C (Okhotsk Sea) (Krümmel, 1911) to 6°C (southern Nor- way) (Helland-Hansen & Nansen, 1909). For the southern localities, the average temperature of the coldest month ranges from about 10-110C (France, Japan) to about 15°C (Cape Hatteras). The average temperature for the warmest month (August) ranges from about 5°C (Labrador) to about 10-119C (Akutan Island, Kamchatka, northern Norway). 403 The temperature for the warmest month in the southern localities ranges from about 15°C (California) and 21°C (south- ern France) to about 25°C (Cape Hatteras, Japan). The temperatures above are taken from: Sverdrup, Johnson & Fleming (1961); publications of The Hydrographic Office, Washington D. C.; Department of Transport, Ottawa; Det danske Meteorologiske Institut, Copenhagen; Norsk Polarinstitut, Oslo and Seewarte, Hamburg. Spawning of Mya arenaria takes place in May-June off Japan (Yoshida, 1938), and in June in Danish waters (Barker- Jórgensen, 1946) and off Labrador (Stafford, 1912). The larvae of M. truncata occurred in Danish waters from October to March with a maximum occurrence in November-January (Bar- ker-Jörgensen, 1946). In northeast Greenland Thorson (1936) found M. trun- cata spawning from June to September, reaching amaximumin July. The surface temperature of the Danish waters during the season the veliger of M. truncata is abundant is about 5°C —the same temper- ature found in east Greenland waters when M. truncata veligers are abundant (Spärck, 1933). It seems as if Mya arenaria in its veliger stage needs a temperature of about 12-15°C, and that Labrador is an exception. A calculation based upon available temperatures in the reports from the various institutions mentioned above, from 1946-1956, gives tempera- tures’ of 5°C, 79C’ and 6°C ‘for July, August and September (respectively) in the area supposed to be the northern limit of M. arenaria. However, the temperatures are taken outside the area where M. arenaria generally is found. In the actual area the surface tempera- ture may be a few degrees higher. The lowest observed surface summer temperature off Nain, Labrador, was about 30°C (July 1952) and the highest 11.70C (August 1954). Besides, these temperatures were obtained in navi- gable water. No doubt there are years with a temperature high enough for 404 D. LAURSEN TABLE 1. Dimensions of Mya shells, revised or newly-recorded, from Canada Locality Winisk River, James Bay Clyde River Alt. 40’-180°, Baffin Island 22 Port Harrison, Quebec Eric Cove, Quebec left shell right shell Mya truncata forma typica DEN: Mya truncata forma ovata 62 Fort Albany, Ontario + : д Height x 100 Index renee veligers to survive. Unfortunately we do not know as much as we would like about Mya arenaria on the Canadian coast. М. arenaria, a boreal species, must be considered a key species. Its presence as a Pleisto- cene fossil in the coastal areas of Hudson Bay would give valid proof of a warmer period during part of the Pleistocene, than that which presently exists. An indication of such a warmer period in Canada, as demonstrated earlier in Greenland (Jensen & Harder, 1910; Harder et al., 1949), is givenby Laursen (1946 p 43-46), but more convincing proof is needed, such as actual demon- stration of the presence of Mya aren- aria in raised beaches north of its present northern occurrence. DISTRIBUTION Soot-Ryen (1932), in a paper on the Norwegian “Maud” Expedition, uses the term “true circumarctic” to designate speciesthat arefound continuously along the coasts of the Arctic Ocean and “circumarctic” for those only occurring sporadically along the coast. The old term “circumpolar” is, according to Soot-Ryen, used for species occurring in the northern Pacific and the northern Atlantic, even if they are missing on the arctic coasts of Eurasia and America. As a temporary aid, the terms proposed by Soot-Ryen are used here. In most papers where Mya truncata is mentioned, no sharp distinction is made between forma typica, forma ud- devallensis and forma ovata. This may be adequate when dealing with small areas, but where the coasts of large regions or even continents are involved it is insufficient. Papers available to the present author too often give insuf- ficient information as to the presence or absence of the 2 extreme forms. In the following discussion, vague infor- mation has been disregarded. The fact that animals are not recorded from a specific area, does not mean ARCTIC MYA 405 FIG. 1. Geographical distribution of Mya truncata forma typica Linnaeus. O = living O = fossil The signs only in- dicate the geographical unit (sea, island group, region, etc.) from where the speci- mens are recorded. that they are absent. On expeditions in the arctic seas, scientists very often are obliged to use ahand bottom sampler and hand dredge, which are ineffective in collecting deep-burrowing species such as those of the genus Mya. Intro- duction of new gear, and especially heavier gear, can give better results than have been. obtained earlier (see also Soot-Ryen, 1951). It is often very difficult to determine if a species really lives in the area from where the shells are recorded. In many regions the shells may originate from extensive submerged Pleistocene shell banks. If there is no indication 406 D. LAURSEN whether the collected specimens were entire animals or only empty shells, a decision is difficult. And even when information is on record it may be incorrect because recent shells may look very old, due to corrosion, where- as subfossil (Pleistocene) shells often look very fresh indeed. To give a complete list of all records of both recent and fossil Mya arenaria and M. truncata shells is a time-con- Suming project. At the time Jensen made his studies, more than 350 papers would have had to be examined just to give the Recent distribution, and at least another 200 for the fossil shells. During the more than 60 intervening years, several thousand papers dealing with the Mya family have been published. Moreover, scores of museums all over the world have collections about which nothing has been published. The following indications of distri- bution are therefore far from precise or complete and perhaps the attempt should not have been made. The present object is, however, to encourage zoolo- gists, geologists and malacologists to give as much information as possible in future papers in which Mya arenaria and M. truncata are discussed. Recent Distribution Mya truncata forma typica Linnaeus (Fig. 1) (True circumarctic) North Greenland: Port Foulke (Jeffreys, 1880); West Greenland (Fabricius, 1780); East Greenland: Jórgen Brónlund Fjord- Qegertatsiaq (Ockelmann, 1958); Jan Mayen (Becher, 1886); Spitsbergen (Torrell, 1859); Franz Joseph Land (Cattie, 1886); Novaya Zemlya (Leche, 1878); Barents Sea (Norman, 1881); Norwegian Finmark (Sars, 1878); Mur- man Coast, Murman Sea (Middendorff, 1849); White Sea (Leche, 1883); Kara Sea (Leche, 1883); Laptev Sea (Leche, 1883); East Siberian Sea (Middendorff, 1851); Chukchee Sea (Middendorff, 1851); Bering Strait, BeringSea (Krause, 1885); Kamchatka Peninsula (Middendorff, 1851); Sea of Okhotsk (Middendorff, 1851); Kuril Island (Lamy, 1926); Hako- dadi, Japan (Lamy, 1926); Alaska (Dall, 1924); British Columbia; Port Orchard, Puget Sound, Washington (Foster, 1946); Beaufort Sea (Hägg, 1904); Canadian Arctic Archipelago (Hägg, 1904); Labra- dor, Newfoundland, Massachusetts: Nan- tucket (Foster, 1946). Iceland (Öskars- son, 1952); Faroe Islands (Posselt, 1898); Between Jan Mayen and northern Norway (Sars, 1878); Norway (Sars, 1878); southwestern Sweden (Hägg, 1904); Denmark (Petersen, 1888); Baltic Sea, western part (Meyer & Möbius, 1872); North Sea (Jeffreys, 1865); British Isles (Jeffreys, 1865); Germany (Jaeckel, 1952); Netherlands, Belgium, France south to La Rochelle (Dautzen- berg, 1913); Rockall (a rock in the Atlantic west of Scotland) [dead shells] (Johansen, 1902). Mya truncata forma ovata Jensen (Fig. 2) (Circumarctic) West Greenland (Jensen, 1900); East Greenland (Jensen, 1900); Iceland (Jensen, 1900); Spitsbergen (Jensen, 1900); Franz Joseph Land (Feyling- Hanssen, 1955); Novaya Zemlya (Jensen, 1900); Kara Sea (Jensen, 1900); Bering Sea (Jensen, 1900); Sea of Okhotsk (Middendorff, 1849); Alaska (Midden- dorff, 1849); Labrador (@yen, 1915); Newfoundland (Whiteaves, 1901). Mya truncata forma uddevallensis Forbes (Fig. 3) (Circumarctic ?) North Greenland: Port Foulke (Jeffreys, 1880); West Greenland (Posselt, 1898); East Greenland (Jenser, 1905); Jan Mayen (Hägg, 1904); Iceland (Torrell, 1859); Spitsbergen (Hägg, 1904); Franz Joseph Land (Hägg, 1904); Novaya Zem- lya (Sars, 1878); Barents Sea (Sars, 1878); Ponds Inlet (Laursen, 1946); Baffin Island (Hägg, 1904); Hudson Strait (Hägg, 1904); Labrador (Hägg, 1904); Gulf of St. Lawrence (Forbes, 1846); ARCTIC MYA 407 O = living @ = fossil FIG. 2. Geographical distribution of Mya truncata forma ovata Jensen. Norway (Sars, 1878). Mya arenaria Linnaeus (Fig. 4) Eastern Atlantic: West Coast of Nor- way (Sars, 1878); southern Sweden, Denmark (Petersen, 1888); the Balticto 62036' N. Lat. (Petersen, 1888); west coast of Germany (Jaeckel, 1952); the Netherlands, Belgium (Raeymaekers, 1895); France to the Bay of Biscay south to Arcachon (Dautzenberg, 1913). Western Atlantic: Nain, Labrador to Virginia Beach and Chesapeake Bay (Foster, 1946). Dead valves recorded from Beaufort, North Carolina (Foster, 1946). Eastern Pacific: Akutan Island, Alaska; Puget Sound, Washington; Mon- terey, California (Foster, 194%) 408 D. LAURSEN O = living O = fossill FIG. 3. Geographical distribution of Mya truncata forma uddevallensis Forbes. Western Pacific: From the southern part of Kamchatka Peninsula and the Sea of Okhotsk and across the Tartar Strait to the mainland and south to Nagasaki, the east coast of Sakhalin included (Lamy, 1926); east coast of China (Yent’ai) (Crosse & Debeaux, 1863). Fossil Distribution Mya truncata forma typica Linnaeus (Fig. 1) West Greenland (Posselt, 1898); East Greenland (Jensen, 1905); North Green- land (Jensen, 1917); Jan Mayen, Iceland (Thoroddsen, 1892); Spitsbergen (Fey- ARCTIC MYA 409 O = living @ = fossil FIG. 4. Geographical distribution of Mya arenaria Linnaeus. ling-Hanssen, 1955); Novaya Zemlya (Knipowitsch, 1900); Murman Coast and the north coast of Siberia as far east as Cape Chelyuskin (Grgnlie, 1928), San Pedro, California (Clark, 1931). North- west Territory, Canada (Washburn, 1947); Victoria Island (Washburn, 1947); Baffin Island (author); Hudson Bay, James Bay, Labrador, Newfoundland, Rivière du Loup, Montreal and St. Lawrence Valley, New Brunswick, Main (Richards, 1940a,b). Dredged off Bear Island and Rockall (Johansen, 1902); Norway (Brögger, 1900/01); southwest coast of Sweden (Hessland, 1943); Den- mark (Nordmann & Madsen, 1928); Ice- land (Thoroddson, 1892); The Nether- lands (Nordmann, 1928); Scotland 410 D. LAURSEN (Munthe, 1897). Pliocene: Iceland, England (Schlesch, 1924). | Mya truncata forma ovata Jensen (Fig. 2) West Greenland (Jensen, 1900); East Greenland (Jensen, 1905); Iceland (Jen- sen, 1900); Spitsbergen (Jensen, 1900); Franz Joseph Land (Feyling-Hanssen, 1955); - Novaya Zemlya (Jensen, 1900); Mouth of Yenisey River, Siberia (Schmidt, 1872). Canada: Vansittart Is- land (Laursen, 1946); Northwest Territo- ries (Craig & Fyles, 1960; Craig, 1961); Port Harrison, Quebec; Eric Cove, Que- bec; Fort Albany, Ontario (author); La- brador (Jensen, 1900); Maine (Brógger, 1900/10). Norway (Soot-Ryen, 1951). Pliocene: Iceland (Schlesch, 1924). Mya truncata forma uddevallensis Forbes (Fig. 3) West Greenland (Laursen, 1944); East Greenland (Laursen, 1954); Iceland (Bar- darson, 1921); Norway (Brögger 1900/ 01); southwestern Sweden (Hessland, 1943); Denmark (Petersen, 1888); Spits- bergen (Feyling-Hanssen, 1955); Mouth of Yenisey River (Schmidt, 1872). Cana- da: Kuwatin, northern district, Northwest Territories (Craig, 1961); Baffin Island, southern part (Nichols, 1936b); northern part (Laursen, 1946); Vansittart Island (Laursen, 1946); White Island (Laursen, 1946); Sugluk, Quebec (Nichols, 1936b); Port Harrison, Quebec (Nichols, 1936b); Churchill, Manitoba (Nichols, 1936b). Mya arenaria Linnaeus (Fig. 4) North America: St. Lawrence Valley, Champlain Valley, Massachusetts to New Jersey (Richards, 1940a,b). Europe: Pliocene: Red Crag and Norwich Crag, England (Schlesch, 1924). DISCUSSION Jensen’s paper did not cause contro- versy within the contemporary mala- cological world, as his arguments were generally accepted. Not until 30 years later did the discussion start. Schlesch (1931: 136-137) considered Mya truncata forma ovata a valid species and renamed it M. pseudoarenaria. Schlesch, however, does not support his decision with evidence, nor does he in- form us why he recognizes M. truncata forma ovata Jensen as a specifically “good” species (eine spezifisch “gute” Art). His description fits M. arenaria except for the cartilage tooth which he describes as resembling that of M. trun- cata, a fact already pointed out by Jensen. It would seem that his only point is that: “M. ovata Jensen homonym mit Donovan (1802, pl. 122) (=Unio tumidus Retz.) ist and daher durch einen neuen Namen ersetzt werden muss”. But even here it is difficult to follow Schlesch; first of all because Jensen himself never con- sidered M. truncata forma ovata a Species or even a subspecies and never called it “М. ovata”, as quoted by Schlesch. For that reason the change of name is irrelevant. What Schlesch really did was toarbitrarily raiseaform to species level, without proofs, and then change its name. The present author worked with Jensen for a number of years. We discussed the taxonomy of Mya truncata forma ovata on several occasions. It was Jensen’s opinion that forma ovata could not be more than an infrasubspecies. As work proceeded (Harder, Jensen & Laursen, 1949) and evidence was col- lected of the intergradation between M. truncata f. uddevallensis and M. truncata f. typica on the one hand, and of M. trun- cata f. ovata and M. truncata f. typica on the other, the validity of Jensen’s opinion was further corroborated. Schlesch (1931: 137) quotes Brégger (1900/01: 608) as stating (in Norwegian) (with regard to the form ovata): “It is a specific form closest to M. truncata.” Schlesch, however, picks out only part of Brégger’s statement (р 607-608), which, translated from the Norwegian, runs as follows: “Mya arenaria was until now generally considered anArctic ARCTIC MYA 411 species; however in a paper recently published, Ad. S. Jensen demonstrated that the Mya specimens from Arctic coasts, recorded earlier as Mya aren- aria, actually do not belong to that species, but are a specific form related to Mya truncata, if anything, and by Jensen indicated as Mya truncata forma ovata, whereas Mya arenaria turns out to be a typical boreal form . ..”. Brog- ger then gives information about the distribution of M.arenaria. As can be seen, Brógger merely quotes Jensen— and agrees with him. Since Schlesch wrote his paper, some malacologists have accepted the name M. pseudoaren- aria without hesitation whereas others have discussed the problem before they decided which name to use. Hessland (1943) does not deal with the problem, but has some interesting observations concerning Mya truncata, which are worth mentioning here be- cause they settle the arguments about range and distribution of thick and thin- shelled Mya truncata forma typica and Mya truncata forma uddevallensis. During field work for his doctor’s thesis on the Pleistocene in southwestern Sweden, he came upon a very well pre- served Mya-biotope in clay in which both the typical form and the udde- vallensis form were present in great numbers. The shells-showed a complete series of intermediate forms between typical M. truncata and forma uddeval- lensis. Furthermore, Hessland observed that the supposedly southern, protracted, thin-shelled form occurred abundantly with the thick-shelled, truncated, typical form and with forma uddevallensis, both believed to indicate a relatively cold water temperature. This author (Laursen, 1944, 1945, 1950, 1954), in examining large col- lections of fossil shells from West Greenland and some from Canada, found a complete transition between M. trun- cata and its 2 extreme forms. The new material dealt with in this paper also indicates the same trend, even if the number of shells concerned is limited. A reexamination of shell material avail- able in Scandinavian museums from localities in the Eastern hemisphere did not give evidence for the correctness of establishing forma ovata as a distinct Species. In my opinion the differences in the shells of the 2 forms are not enough to establish a new species. Foster (1946) mentions the ovata form but refers to it as Mya pseudoarenaria Schlesch. Apparently, he did not in- vestigate the problem. He thinks of “Mya pseudoarenaria” as the Arctic counterpart of М. arenaria, which is not correct. Soot-Ryen (1951) thinks Schlesch is correct in his assumption, although the Species of Mya are polymorphic and a thorough revision is needed of the vari- ous forms, both living and fossil, in the Northern Pacific. Feyling-Hanssen (1955a), in his ex- cellent paper on the marine Late- Pleistocene of West Spitsbergen, in- vestigated a great number of Mya trun- cata shells including both forma ovata Jensen and forma uddevallensis Forbes. He maintains (p 150) the classification set forth by Jensen because of the transitions occurring between the typical and extreme forms. The transitions are shown in 3 diagrams. Ockelmann (1958), in an extensive and excellent paper, has examined the large collection of recent Mya shells from East Greenland kept in the Zoological Museum of Copenhagen. He (p 148) arrives at the same results as do Feyling-Hanssen and the author: “Be- tween f. ovata and the typical M. trun- cata all grades of transitional stages occur”. Ockelmann also has his doubts about forma ovata being a subspecies. Until further proof is given I suggest that the name Mya pseudoarenaria Schlesch not be used. ACKNOWLEDGMENTS The author is indebted to Dr. Frances J. E. Wagner of the Geological Survey of Canada, to Dr. D. J. McLaren, Head 412 D. LAURSEN of the Palaeontology Section and to Dr. J. F. Calez, Chief of the Division of Fuel and Stratigraphy for lending him the new material used for this paper. I especially want to thank Dr. Wagner, Dr. D. F. Hewitt, Senior Geologist of the Department of Mines, Toronto, On- tario, and Dr. L. G. Berry of Queen’s University, Kingston, Ontario, for their valuable help in tracing the old col- lection from the Hudson Bay Area. I am very grateful to Dr. Horace G. Richards, Academy of Natural Science of Philadelphia, and Dr. Harald A. Rehder, U. S. National Museum, Washington, D. C., because they took time to reexamine and review earlier identifications. Dr. Rolf Feyling-Hanssen, Palæon- tologisk Museum, Oslo, Norway, confirmed, on my request, that the data from Norway and Spitsbergen were un- changed; he and Mr. Jgrgen Knudsen, M.Sc., Zoologisk Museum, Copenhagen, Denmark, provided me with shell material for comparisons. Their help is highly appreciated. REFERENCES More than 600 papers have been con- sulted. Only those quoted in the text and some other important ones, used to confirm distributions, are listed here. BAKER, M. B., 1911, Iron and lignite in the Mattagami basin. Rept. Ontario Bur. Mines, 20(1): 214-246. BARDARSON, G., 1910, Maerker efter Klima- og Niveauforandringer ved Hunafloi i Nord-Island. Vid. Medd. Nat. Foren. Kgbenhavn. p 35-79. BARKER-JORGENSEN, C., 1946, Lamellibranchia. ‘In: G. THORSON: Reproduction and larval developement of Danish marine bottom Invertebra- tes. Medd. Komm. f. Danm. Fiskeri- og Havunders. Serie: Plankton, 4(1): 277-311. BAY, E., 1895, Geologi. Grgnl., 19(6): 172. BECHER, E., 1886, Mollusken. Oster- Medd. om reichische Polarexpedition nach Jan Mayen 1882-83. K. Akad. d. Wissen- sch. 3(6G): 67-82. Wien. BERENDT, G., 1867, physik. Ges. zu Königsberg, 8:70. BROGGER, W. C., 1900/01, Om de senglaciale og postglaciale niväfor- andringer i Kristianiafeltet (Mollusk- faunaen). Norges geol. Unders., 31: 1-731. CATTIE, J. T., 1886, Les Lamelli- branches recueillis dans les courses du “Willem Barents”, durant les mois de mai à septembre 1880 et 1881. Bijdragen tot de Dierkunde uitgegiven doot Natura ortis magistra, 13(4): 1-48. CLARK, A., 1931, The cool-water Timms Point Pleistocene horizon at San Pedro, California. Trans. San Diego Soc. nat. Hist., 7(4): 25-42. COLLIN, J., 1886, Brachiopoder, Mus- linger og Snegle fra Kara Havet. Dijmphna-Togtets zoologisk-botan- iske Udbytte, Kgbenhavn. p 441-472. CRAIG, B. G., 1961, Surficial geology of Northern District of Keewatin, Northwest Territories. Palaeonto- logical remarks on shells collected by F. J. E. WAGNER. Canada geol. Surv. Paper, 61-5: 1-8. CRAIG, B. G., & FYLES, J. G., 1960, Pleistocene geology of Arctic Canada. Coronation Gulf. N. W. Victoria Schr. d. kgl. Island. Canada geol. Surv. Paper, 60-10: 1-21. CROSSE, H. & DEBEAUX, O., 1863, Note sur quelque espèces nouvelles ou peu connues du littoral de l’empire chinois. J. Conchyl., 3: 253-265. DALL, W. H., 1873-74, Catalogue of shells from Bering Strait. Proc. Calif. Acad. Sci., 5: 246-253. , 1919, The Mollusca of the Arctic coast of America collected by the Canadian Arctic Expedition west from Bathurst Inlet with an appended report on a collection of Pleistocene fossil Mollusca. In: Rep. Canad. Arct. Exp., 1913-18, 8(A): 3-29. , 1920, Pliocene and Pleisto- cene fossils from the Arctic coast ARCTIC MYA 413 of Alaska and the auriferous beaches of Nome, Norton Sound, Alaska. U.S. geol. Surv. prof. Paper, 125: 23-24. , 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 illus- trations of hitherto unfigured species. U. S. Nat. Mus. Bull., 112: 1-217. , 1924a, Supplement to the report of the Canadian Arctic Expedi- tion, 1913-18, Volume VII, Part A, Mollusks, Recent and Pleistocene (1919). In: Rep. Canad. Arct. Exp., 1913-18, 8(A): 31-35 (Suppl. Rep.). , 1924b, Report on Tertiary and Quaternary fossils from the Canadian Arctic Coast, In: O’NEILL, Pt. A, The geology ofthe Arctic Coast of Canada west of the Kent Peninsula. Rep. Canad. Arct. Exp. 1913-18., 11: 27-33. DAUTZENBERG, P., 1913, Coquilles des Cötes de France. Paris. Libraire des Sciences naturelle, Leon Lhomme. 152 p. DAUTZENBERG, P., & FISHER, H., 1911, Mollusques et Brachiopodes recueillis en 1908 par la mission Benard dans le mers du Nord. J. Conchyl., 59: 1-51. , 1912, Mollusques provenant des campagnes de l’Hirondelle et de la Princesse-Alice dans les mers du Nord. Res. Camp. Sci. Albert I de Monaco, 37: 1-25. DAVIES, W. E., KRINSLEY, D. B. € NICOL, A. H., 1963, Geology of the North Star Bugt Area, Northwest Greenland. Medd. om Grgnl., 162(12): 1-68. DONS, C., 1937, Norges Strandfauna XIX. Muslinger 7. Kgl. Norsk. Vid. Selsk. Forh., 10(14): 1-4. DONOVAN, E., 1802, The Natural His- tory of British Shells, 4. London. ELTON, C. S. & BADEN-POWELL, D. Es W.,. 1981; On a collection of raised beach fossils from Spitsbergen. Geol. Mag., 68: 9. FABRICIUS, O., 1780, Fauna Groen- landica, systematice sistens Animalia Groenlandiae occidentalis hactenus in- dagata . .. maximaque parte secundum proprias observationes O. Fabricii... J. G. Rothe, Kgbenhavn & Leipzig. Ed. 1, xvi + 452 p (p 405). FEILDEN, H. W., 1877a, Arctic mol- luscan fauna. Zoologist, 3: 435-440. , 1877b. The Post-Tertiary beds of Grinnell Land and North Green- land. Ann. Mag. nat. Hist., ser. 4, 20: 483-494. FEYLING-HANSSEN, R. W., 1955, Stratigraphy of the Marine Late-Plei- stocene of Billefjorden, Vestspits- bergen. Norsk Polarinst, 107: 1-186. FEYLING-HANSSEN, В. У. € JÖRSTAD, F. A., 1950, Quaternary fossils from the Sassen-Area in Isfjorden, West Spitsbergen. Norsk Polarinst., 94: 1-85. FORBES, E., 1846, On the connexion between the distribution of the existing Fauna and Flora of the British Isles, and the geological changes which have affected their area, especially during the epoch of the Northern Drift. Mem. Geol. Surv. Great Britain, Mus. Econ. Geol., 1: 407. FOSTER, R. W., 1946, The genus Mya in the Western Atlantic. Johnsonia, 2(20): 29-35. FRIELE, H., 1879, Catalog der auf der norwegischen Nordmeer-Expedi- tion bei Spitsbergen gefundenen Mol- lusken. J. Malak. Ges., 6: 264-286. GROOM, G. E. & SWEETING, M. M., 1958, Valleys and raised beaches in Bunzow Land, Central Vestspits- bergen. Norsk Polarinst., 115: 1-18. GRONLIE, O. T., 1924, Contribution to the Quaternary geology of Novaya Zemlya. Rep. Sci. Res. Norw. Exp. to Novaya Zemlya 1921, 21: 1-124. , 1928, Fossil and subfossil Shells from “Maud-Havn” and en- virons. Norw. North Polar Exp. “Maud” 1918-1925. Sci. Res., 5(20): ID: HÄGG, R., 1904, Mollusca und Brachio- poda gesammelt von der schwedischen 414 D. LAURSEN zoologischen Polarexpedition nach Spitzbergen, dem nordöstlichen Grön- land und Jan Mayen im Jahre 1900. I. Brachiopoda und Lamellibranch- iata. Arkivf. Zool., Stockholm, 2(2): 1-66. HARDER, P., JENSEN, A. S. & LAURSEN, D., 1949, The marine Quaternary sediments in Disko Bugt. Medd. om Grgnl., 149(1): 1-85. HELLAND-HANSEN, B. & NANSEN, F., 1909, The Norwegian Sea. Norw. Fishery € Marine Invest. Rep., pt. 1, 2(2): 1-390. HESSLAND, I., 1943, ablagerungen Nord-Bohusläns. geol. Inst. Uppsala, 31: 1-348. , 1946, On the Quaternary Mya period in Europe. Arkiv. f. Zool., Stockholm, 37(2), no. 8: 51 p. JAECKEL, S. H., 1952, Die Muscheln und Schnecken der deutschen Meeres- küsten. Akad. Verlags. Geest & Portig K.-G., 67 р. JEFFREYS, J. G., 1962, British con- chology. I. Land andfreshwater shells. John Van Voorst, London. 341 p. , 1865, British conchology. Ш. Marine _ Shells, comprising the remaining Conchifera, the Soleno- conchia, and Gastropoda as far as Littorina. John van Voorst, London. 393 p. ‚ 1877, The post-Tertiary fossils procured in the late Arctic expedition, with notes on some of the recent or living Mollusca from the same expedition. Ann. Mag. nat. Hist., ser. 4, 20: 229-242. , 1880, Onsome of the Mollusca procured during the Arctic expedition of the “Fox” 1858, 1859. Sci. Proc. Roy. Dublin Soc., newser., 2: 125-128. JENSEN, A. S., 1900, Studier over nordiske Mollusker. I. Mya. Vidensk. Marine Schalen- Bull. Medd. Nat. Foren. Kgbenhavn., 52 (2/2): 133-158. , 1905, On the Mollusca of East-Greenland. I. Lamellibranch- iata. With an introduction on Green- land’s fossil Mollusc-Fauna from the Quaternary time. Medd. om Grgnl., 27(9): 289-362. , 1917, Quaternary Fossils collected by the Danmark Ekspedition. Medd. om Grgnl., 43(21): 621-632. JENSEN, A. S. & HARDER, P., 1910, Post-Glacial changes of climate in Arctic regions as revealed by investi- gations on marine deposits. Post- glaziale Klimaveränderungen. II. in- ternat. Geologkongr., Stockholm. p 399-407. JESSEN, A., 1899, Beskrivelse til Geologisk Kort over Danmark. Danm. geol. Unders. Ser. I, 3: 1-368. JOHANSEN, A. C., 1902, On the hy- potheses on the sinking of sea-beds based on the occurrence of dead shallow-water shells at great depths in the sea. Vidensk. Medd. Nat. Foren. Kgbenhavn. p 393-435. JOHNSTRUP, F., 1882, Om de geo- logiske Forhold i den nordlige Del af Vendsyssel. Universitetsprogram. Kobenhavn. KNIPOWITSCH, N., 1900, Zur Kennt- nis der geologischen Geschichte der Fauna des Weissen und des Murman Meeres. Verhdl. d. Russ. Kaiserl. mineralog. Ges. St. Petersburg. ser. 2, 38: 1-169. à 1901-1903, Zoologische Ergebnisse der Russischen Expedition nach Spitzbergen. I-IV. Ann. Mus. Zool. Acad. Imp. Sci. St.-Petersbourg, 6: 435-558; 7: 355-459; 8: 56-83. , 1904a, Ueber die Postplio- caenen Meeres-Mollusken auf der Insel Kolgnjew. Verhdl. d. Russ. Kaiserl. mineralog. Ges. St. Peters- burg, 41. , 1904b, Neue Fundorte von Meeres-Mollusken und Balaniden in den Ablagerungen der borealen Trans- gression. Verhdl. d. Russ. Kaiserl. mineralog. Ges. St. Petersburg, 41. KRAUSE, A., 1885, Ein Beitrag zur Kenntnis der Mollusken-Fauna des Beringmeeres. I. Brachiopoda et Lamellibranchiata, Arch. f. Natur- gesch., 51(1): 14-40 (p 39). KRUMMEL, O., 1911, Handbuch der Ozeanographie. Engelhorn, Stuttgart, ARCTIC MYA 415 2: 1-764. LAMY, E., 1926, Revision des Myidae vivants du Museum National d’Histoire Naturelle de Paris. J. Conchyl., 70: 151-185. LA ROCQUE, A., 1949, Post Pliocene connection between James Bay andthe Gulf of St. Lawrence. Bull. geol. Soc. Amer., 60: 363-380. ‚1953, Catalogue of the Recent Mollusca of Canada. Bull. nat. Mus. Canada, 129: 1-406 + i-ix. LAURSEN, D., 1944, Contribution tothe Quaternary Geology of Northern West Greenland. Especially the raised marine deposits. Medd. om Grgnl., 135(8): 125 p. , 1945, Marinkvartaere skaller fra Utorgait, Vest Grgnland. Medd. Dansk geol. Foren., 10(5): 591-593. , 1946, Quaternary shells col- lected by the Fifth Thule Expedition 1921-24. Rep. Fifth Thule Exp. 1921- 24, 1(7): 1-60. , 1950, The Stratigraphy of the Marine Quaternary Deposits in West Greenland. Medd. om Grgnl. 151(1): 1-152. , 1954, Emerged pleistocene marine deposits of Peary Land (North Greenland). Medd. om Grgnl., 127(5): 1-26. LECHE, W., 1878, Ofversigt öfver de af Svenska Expeditionen till Novaja Zemlja och Jenissej 1875 och 1876 innsamlade Hafs-Mollusker. Kgl. Sv. Vet. Akad. Handl., 16(2): 1-86 (p 10). , 1883, Summary of arctic marine mollusca collected by the “Vega” -Expedition. I. Lamellibranch- iata. Vega Exp. Vet. laktt., 3: 433- 529 (p 437). LINDSTROM, G., 1868, Om Gottlands nutida Mollusker. Stockholm. McINNES, W., 1904, The Winisk river, Keewatin district. Canada geol. Surv. Summ. Rep. 1903, (A): 100-108. MADSEN, F. J., 1949, Marine Bivalvia. The Zoology of Iceland, 4(63): 1-116. MENDTHAL, M., 1889, Untersuchungen über die Mollusken und Anneliden des frischen Haffs. (Inaug. Diss.), 5. MEYER, H. A. & MÖBIUS, K., 1872, Fauna der Kieler Bucht, 2: 119. Leip- zig. MIDDENDORFF, A. T. v., 1849, Beit- räge zu einer Malacozoologia Rossi- ca. Mem. Acad. Imper. Sci., St. Pe- tersbourg. 6(2): 329-516. ‚1851, Reise in den äusser- sten Norden und Osten Sibiriens wäh- rend... 1843 and 1844... . 2(1): 163- 464, 505-508. St. Petersburg. MOHR, N., 1786, Forsgg til en Islands Naturhistorie, 128. Kgbenhavn. MÖLLER, H. P. O., 1842, Index Mol- luscorum Groenlandiae. Nat. Tidskr., 4: 21. MORCH, O. A. L., 1857, Fortegnelse over Grgnlands Blgddyr. т: RINK: Grgnland geographisk og statistisk beskrevet. Copenhagen. 2(4): 75-100 (p 89). , 1868, Faunula Molluscorum Islandiae. Vidensk. Medd. Nat. Foren. Kgbenhavn, 218. , 1869, Catalogue des mol- lusques du Spitzbergen recueillis par le Dr. H. Krpyer pendant le voyage de la corvette La Recherche en juin 1838. Mem. Soc. malacol. Belgique, 4: 7-32. MUNTHE, H., 1897, On the interglacial submergence of Great Britain. Bull. Geol. Inst. Uppsala, No. 6, 3(2): 369- 411. NATHORST, A. G., 1872, Om Skanes nivaforandringer. Geol. Fören. Stock- holms Förh., 1872-74, 1: 281. NEWTON, E. T., 1899, Notes on a collection of rocks and fossils from Franz Josef Land, made by the Jackson-Harmsworth Polar Expe- dition during 1894-1896. Appendix Jn: JACKSON: A thousand days in the Arctic, 2. New York & London. p 477-519. NICHOLS, D. A., 1936a, Physiographic studies in the western Arctic. Canada geol. Surv. 5(10): 2-7. , 1936Ъ, Post-pleistocene fossils of the uplifted beaches of the eastern arctic regions of Canada. Can. Field Naturalist, 50(8): 127-129. 416 NORDENSKIÖLD, A. E., 1870, Redogö- relse för en Expedition till Grönland Ar 1870. Ofvers. Kgl. Vet.-Akad. Förh. 27(10): 1018. NORDMANN, V., 1928, La position stratigraphique des depöts d’Eem. Danm. сео]. Unders., II (47). 81 p + 4 pl. NORDMANN, V & MADSEN, V., 1928, Oversigt over Danmarks Geologi. Danm. geol. Unders., Ser. V, 4: 1-208. NORMAN, D. v. H., 1881, Die Lamelli- branchiaten gesammelt wärend der Fahrten des “Willem Barents” 1878 und 1879. Niederländ. Arch. f. Zool., Suppl. Bd. 1: 10. OCKELMANN, W. K., Lamellibranchiata. East Greenland. 122(4): 1-256. | O’NEILL, J. J., 1924, The geology of the arctic coast of Canada west of the Kent peninsula. Rep. Canad. Arct. Exp. 1913-1918, 11(A): 1-107. OSKARSSON, I., 1952. Skeldyrafäna Islands. I. Lamellibranchia. Reykja- vik. 119 p. ÖYEN, P. A., 1909, Kvartaergeologiske Streiftog omkring den indre del af Bun- defjorden. Arch. Mat. Nat. Vid., 30(3): 1-51. ; 1910, Kvartaer-studier i Trondhjemsfeltet I. Kgl. Norske Vid. Selsk. Skr. 1909, 4: 1-102. ‚ 1911, Kvartaer-studier 1 Trondhjemsfeltet Il. Kgl. Norske Vid. Selsk. Skr. 1910, 6: 1-189. ‚ 1915, Kvartær-studier i Trondhjemsfeltet Ш. Kgl. Norske Vid. Selsk. Skr. 1914, 6: 1-126. PACKARD, A. S., 1867, Observations on the glacial phenomena of Labrador and Maine, with a view of the recent invertebrate fauna of Labrador. Mem. 1958, Marine The Zoology of Medd. om Grgnl., Boston Soc. nat. Hist., 1: 210-303. PETERSEN, C. G. J., 1888, Om de skalbaerende Molluskers Udbred- ningsforhold i de danske Have indenfor Skagen. Doctoral Thesis, Kgbenhavn. 163 p. “141892; In: Saltvandsalluviet i K. RORDAM: det nordgstlige fossils from Newfoundland. from D. LAURSEN Sjaelland. 106-111. POSSELT, H. J., 1895, Ostgrgnlandske Mollusker. Medd. om Grönl. 19(2): 61-94. , 1898, Grgnlands Brachiopoder og Bléddyr. Medd. om Grgnl. 23, pt. 3(1): 1-298. RAEYMAEKERS, D., 1895, Epoque a laquelle Mya arenaria a disparu de la région du Bas-Escaut, Belge, Ann. Soc. Roy. Malacol. de Belgique, 30: V. RICHARDS, H. G., 1936, Recent and pleistocene marine shells of James Bay. Amer. Midl. Nat., 17(2): 528- 545. Danm. geol. Unders., 2: , 1940a, Marine pleistocene Bull. geol. Soc. Amer., 51: 1781-1788. , 1940b, Pleistocene fossils the Belcher Island in Hud- son Bay. Ann. Carnegie Mus., 28: 47-52. , 1941, Post-Wisconsin Fossils from the west coast of Hudson Bay. Notulae Naturae, Acad. nat. Sci. Phil., 84: 1-10. RIIS-CARSTENSEN, E., 1936, The Godt- haab Expedition. The hydrographic work and material. Medd. om Grönl., 78(3): 1-101. SARS, G. O., 1878, arcticae norvegiae. tiania. 466 p. SARS, M., 1865, Om de i Norge fore- kommende fossile Dyrelevninger fra Qvartaerperioden. 106. Christiania. SCHLESCH, H., 1925, Zur Kenntnis der pliocänen Cragformation von Hall- bjarnarstadur, Tjúrnes, Nordisland und ihre Molluskenfauna. Arch. f. Moll.-k., 57: 45-48. , 1931, Kleine Mitteilungen УП. 1. Beitrag zur Kenntnis der marinen Molluskenfauna Islands; 2. Studien über Mya-Arten. Arch. f. Moll.-k. 63: 133-149. SCHMIDT, F., 1872, Wissenschaftlische Resultate der zur Aufsuchung eines angekündigten Mammutcadavers von der Kaiserlichen Akademie der Wis- senschaften an den unteren Jenissei Mollusca regiones Blóddyr. Chris- AAA ARCTIC MYA ausgesandten Expedition. Mem. Akad. Imp. Sci. St.-Petersbourg. Ser. 7, 18(1): 1-168. SOOT-RYEN, T, 1925, Notes on some mollusca and brachiopoda from Spitz- bergen. Tromsg Mus. Arsh., 47: 1-10. , 1932, Pelecypoda, with adis- cussion of possible immigrations of Arctic pelecypods in Tertiary times. Norw. North Polar Exp. “Maud”, 1918- 1925. Sci. Results, 5(12): 1-35. , 1939, Some pelecypods from Franz Josef Land, Victoriagya, and Hopen collected on the Norwegian Scientific Expedition 1930. Medd. Norges Svalb. Ish.-Unders., (43): 1-22 +1 pl. , 1951, New records onthe dis- tribution of marine Mollusca in northern Norway. Astarte, 1: 11 p. SPARCK, R, 1933, Contribution to ani- mal ecology of the Franz Joseph Fjord and adjacent East Greenland wa- ters. I-II. Medd. om Grgnl. 100(1): 1-38. STAFFORD, J., 1912, On the recogni- tion of bivalve larvae in plancton col- ‘ lections. Contr. Canad. Biol. 1906- 1910, p 221-242. SVERDRUP, H. V., JOHNSON, M. W., & FLEMING, R. H., 1942, The oceans, their physics, chemistry, and general biology. 10th print., 1961. Prentice- Hall, Inc., Englewood Cliffs, N. J. 1087 p. THORODDSEN, T., 1892, Postglaciale marine Aflejringer, Kystterrasser og Strandlinier i Island. Geogr. Tidsskr., Kgbenhavn, 1891/92. 1-17. THORSON, G., 1934, Investigations on shallow water animal communities in 417 the Franz Joseph Fjord (East Green- land) and adjacent waters. Medd. om Grgnl., 100 (3): 1-68. , 1936, The larval development, growth, and metabolism of Arctic ma- rine bottom invertebrates. Medd. om Grgnl., 100(6): 1-155. THUDEN, C. J. A., 1866, Om de i Bohusläns postpliocena eller glaciala formation förekommande mollusker. Göteborg. TORRELL, O., 1859, Bidrag till Spits- bergens Molluskfauna I, jemte en all- män ôfversikt af Arktiska regionens naturförhällenden och forntida ytbred- ning. Doctoral dissertation, Stock- holm. 154 p. TRAUSTEDT, A., 1883, In: К. J. У. STEENSTRUP: Bidrag til Kjendskab til de geognostiske og geografiske Forhold i en Del af Nord Grgnland. Medd. om Grgnl. 4(5): 235. WASHBURN, A. L., 1947, Reconnais- sance geology of portions of Victoria Island and adjacent regions arctic Ca- nada. Geol. Soc. Amer. Mem., 22: 1-142. WHITEAVES, J. F., 1901, Catalogue of the marine Invertebrata of eastern Canada. Surv. Canada Geol., Ottawa. Publ. No. 772, 272 p. WILSON, W. J., 1904, Reconnaissance survey of four rivers southwest of James Bay. Can. geol. Surv. Summ. Rep. for 1903, (A): 222-243. WOODWARD, S. P., 1860, Appendix 2 to: JAMES LAMONT: Notes about Spitzbergen in 1859. Quart. J. geol. Soc. London, 16: 428-444, YOSHIDA, H., 1938, Notes on the veli- gers and the young shells of Mya arenaria japonica. Venus, 8: 13-21. EL GENERO MYA EN LA REGION ARTICA El presente trabajo tiene por objeto clarificar conceptos erröneos acerca de las especies articas de Mya. Jensen sefialö (1900, en dinamarqués) que todas las refer- encias hasta entonces existentes de M. arenaria Linnaeus para el Artico eran equivo- cadas, y correspondian en realidad a una forma de M. truncata Linnaeus, que el llamó ovata. La distinción más notable entre las conchas, casi similares, de las dos especies, se encuentra en los cartilagos de la placa en la valva izquierda y la fosa, correspond- iente al cartilago, de la valva derecha. Sin embargo, como la publicaciön de Jensen 418 D. LAURSEN es poco conocida en el mundo de habla inglesa, M. arenaria, una especie boreal, se sigue señalando para al Artico. Además, Schlesch (1931) elevó arbitrariamente ovata, la cual Jensen consideraba cuando más una infrasubspecie, a la categoria de especie, y la redenominó M. pseudoarenaria, nombre que no debe ser usado. Se da aquí la distribución, Reciente y fósil, de tres formas de M. truncata: forma typica Linnaeus, M. truncata forma uddevallensis Forbes, y M. truncata forma ovata Jensen. La distribución de M. arenaria también se da hasta donde es conocida. Las listas no son completas. A los investigadores que trabajan con M. truncata se les solicita dar más detalles en el futuro acerca de las formas. Se discuten algunas nuevas localidades dadas para M. arenaria, dentro de la región Artica, todas las cuales corresponden a M. truncata f. ovata. age MALACOLOGIA, 1966, 3(3): 419-431 STATOCYST FUNCTION IN POMACEA PALUDOSAl (MESOGASTROPODA: AMPULLARIIDAE) Andrew McClary Department of Natural Science Michigan State University East Lansing, Michigan, U.S.A. ABSTRACT Two groups of snails were studied. Group I consisted of 15 snails from which the left statocyst had been removed, 15 sham-operated snails in which the left statocyst had been exposed by operation but left intact, and 15 unoperated con- trols. Group II consisted of 8 snails from which both statocysts had been re- moved, 8 doubly-sham-operated snails and 8 controls. Prior to operation, snails were anesthetized by submersion for approximately 1 hour in . 25g/liter of MS 222. Wound closure was rapid, and snails became active within an hour after operation. Later autopsy gave no indication of statocyst regeneration. Studies were made of the following behavior patterns: rate and direction of movement, activity level, position when at rest, ability to right after inversion, ciliary feeding and surface inspiration. During these studies, some GroupII operated and sham-operated snails showed an abnormal sagging of the shell. During the activity level studies on Group I, operated and sham-operated snails were less active and less ableto rest on ver- tical surfaces than controls. The above changes were considered due to opera- tive incision. During activity level studies on Group II, operated snails were less able to rest on vertical surfaces than sham-operated or control snails, and this was interpre- ted as due to statocyst removal. Other than the above, no significant behavioral differences occurred between operated and sham-operated snails and their controls. Snails lacking both statocysts showed no loss in ability to move to the water’s surface to inspire. Among the potential factors governing direction to the surface in the absence of statocysts, overhead light and oxygen gradients were presumably eliminated by lateral light and circulation of water. Limited experiments suggested that ten- sion induced by the pendant shell did not provide a cue, as twisting the shells of moving snails failed to divert their upward movement. Potential cues which re- mained were pressure gradients and lung buoyancy. INTRODUCTION died (Carthy, 1958; Fraenkel & Gunn, 1961), experimental work on the func- Although the role of statocysts in tion of gastropod statocysts is limited. other invertebrates has been amply stu- A few workers have shown that stato- i cae Me Е This investigation was supported by National Science Foundation grant NSF-G-19373. I wish to thank Richard Herrmann, now at the School of Medicine, University of Wisconsin-Madison, for his invaluable help as a project assistant during the course of this work. (419) 420 A. McCLARY | cysts function in the static orientation and horizontal movement of snails. Thus, removal of a statocyst from the hetero- pod Pterotrachea resultedinatemporary rolling on the longitudinal axis and a loss of tonus (Tschachotin, 1908; Fried- rich, 1932). Interruption of a single statocyst nerve of the tectibranch Aply- sia caused a circus movement; interrup- tion of both, a general loss of equili- bration (Pelseneer, 1935). Removal of one pedal ganglion with its associated statocyst from the pteropod Cymbulia caused irregular movement towards the operated side and a similar effect was obtained with Helix pomatia (Pelseneer, 1935). Although light (Kanda, 1916a, b; Fraen- kel, 1927; Crabb, 1929) and muscle ten- sion (Davenport & Perkins 1897; Frand- sen, 1901; Kanda, 1916a; Cole, 1925; Crozier & Navez 1930; Hoaglund & Cro- zier 1931; Bower, 1962) have commonly been considered to direct the movements of gastropods on vertical surfaces or slopes, statocysts may also function in this way. Thus, in a study of down- ward motion on an inclined plane, Lever & Geuze (1965) have recently demon- strated disorientation of the aquatic pul- monate snail Lymnaea stagnalis after bi- lateral statocyst extirpation, and, after unilateral extirpation, some deviation towards the side of the remaining stato- cyst. The present paper reports the effect of statocyst removal on certain behav- ioral patterns of the prosobranch Po- macea paludosa. This species was chosen FIG. 1. Method of extension of animal for stato- cyst removal. Arrow indicates approximate location and size of incision. for study as it is easily maintained in the laboratory, possesses statocysts acces- sible to operative removal (McClary, 1963) and has been the subject of stud- ies on behavioral patterns suspect of statocyst control (Johnson, 1952; McClary, 1964). GENERAL METHODS A laboratory population of marked snails was maintained in glass aquaria with charcoal filtered, continuously cir- culating tap water at about 260 С+2, as previously described (McClary, 1964). The animals were 170 days old and weighed an average of 5.6 g at initia- tion of studies. The behavior of 2 TABLE 1. Post-operation survival rates of Pomacea paludosa 4 days after removal or exposure of statocysts Category I unilaterally operated II bilaterally operated Removed Sham operated Removed Sham operated 16 15 15 15 11 8 10 8 % recovery 94 100 73 80 STATOCYST FUNCTION IN POMACEA groups was studied. Group I consisted of 15 snails from which the left stato- cyst had been removed, 15 sham- operated snails, and 15 controls. Group II consisted of 8 (later 7, after death of one) snails lacking both statocysts, 8 doubly sham-operated snails, and 8 controls. Operations were performed as follows: subjects were anesthetized by immersion in .25 g/liter of MS 2222 until animals could be extended manually from their Shells, though still exhibiting some mus- cle tension. Required immersion time averaged one hour. One worker then held the anesthetized snail by its shell and pulled the oper- culum down toward the shell apex. This forced the animal to partially extend from the shell. A second worker made a shallow lateral incision on the left side of the body wall (Fig. 1). A suc- cessful incision exposed the statocyst, which lies approximately 2 mm below the surface and is easily identified by its refractile statoliths. The statocyst was then removed with fine forceps and checked under a dissecting microscope. Whenever a statocyst was broken, or carried adherent tissue, the snail was discarded. If removal was successful, the snail was placed in a 20 gallon recovery tank, and normally became ac- tive within an hour. Wound repair was typically rapid and without complica- tions, the incision being completely healed after a week. When both stato- cysts were scheduled for removal, an operation was performed successively on each side of the snail. Insham-operated snails statocysts were exposed as above but not removed. This was done so that effects of simple incision could be RA methanesulphonate, available from Sandoz Pharmaceuticals, Hanover, U. S. A. I wish to thank Profs. H. van der Schalie for suggesting MS 222 as a suitable anesthetic, and J. Lever for advice regarding its use. МЫ; 421 FIG. 2. Surface inspiration Бу Pomacea palu- dosa, as viewed through aquarium wall. Typi- cal posture is shown at A, detail of head and siphon at B. distinguished from effects of statocyst removal. Table 1 gives data on opera- tions. After operations, snails were allowed to recover for at least 4 days. The behavior patterns which follow were then studied. (The time lapse between opera- tion and study commencement is in pa- renthesis): surface inspiration (GpI, 12- 14 days; Gp I, 14-20 days), ciliary feeding (Gp I, 19 days; Gp II, 9 days), activity level (Gp I, 4-6 days; Gp II, 8-9 days), rate and direction of move- ment (Gp I, 10 days; Gp II, 10 days), ability to upright themselves after in- version (Gp II, 14 days). At completion of the studies, all snails were killed and examined for statocysts. No evi- dence of regeneration was found inthose Snails from which statocysts had been removed. 422 A. McCLARY RESULTS OF STUDIES Surface Inspiration Impending surface inspiration can usually be anticipated, for prior to it, and while still moving upward to the wa- ter’s surface, P.paludosa will commonly form its left mantle lobe into a long, tubular siphon. Upon reaching the sur- face, the snail normally first contacts the air-water interface with its left ten- tacle. - The siphon is then brought into contact with the interface, and air is pumped by a series of body contrac- tions to a lung situated in the mantle cavity (Fig. 2). After inspiring, P. paludosa typically turns down toits right and either drops or crawls to the bottom of the container (McClary, 1964). Surface inspiration was studied in 2 oilcloth wrapped glass cylinders meas- uring 46 x 21 cm which contained aerated circulating water at 26°C, as described for control cylinders in my previous (1964) work, except that lateral rather than overhead illumination was used, light entering through slits in the oilcloth. Snails of Groups I and II were studied in separate cylinders. For any one observation, 4-5 snails of each cate- gory were placed in a cylinder at 09:30 and watched for 2 hours. All snails of Group I were observed twice; those of Group Il, 6 times. During observations, the following data were recorded: TABLE 2. Structure first contacting surface* Left aie Si Total No. of inspira- tions Category (15 each) Left statocyst removed Sham operated Control 1. All surface inspirations. On oc- casion a snail remained at the wa- ter’s surface between inspirations. When this happened, the second in- spiration was not added to the data, for frequency of surface inspiration was intended to serve as ameasure of the snail’s ability to move up- wards to the surface. 2. The number and location, at 10 minute intervals of all inactive snails. 3. The behavior of snails of Group I during surface inspiration. 4. Tracks made prior to inspiration by several snails of Group II. Records were begun when a snail was in the lower half of a cylinder and were made by observing the snail’s move- ment from above the cylinder and pressing a mark into the oilcloth so as to record the snail’s track. Table 2 summarizes the behavior of Group I during surface inspiration. In all 3 categories of this group, behavior of snails was similar to that observed in the previous study. No data were taken on behavior of Group П during surface inspiration. However, informal observations suggested that the behavior of this group was normal except that 2 operated and 2 sham-operated snails had apparently lost some control over their Shells; for the latter tended to sag away Behavior of 15 Group I snails during surface inspiration Direction Average Behavior A turned contractions after after As per : ce ИЕ turning : AR inspiration* inspiration *indicates that data are not available for all inspirations STATOCYST FUNCTION IN POMACEA TABLE 3. 423 Frequency of surface inspirations in Pomacea paludosa after statocyst removal. * Snails of Group I were observed a total of 4 hours, those of Group П, 12 hours. t values insignificant at . 05 level of rejection All Average Number of Standard Student’s x Total number of IR Group Category snails и. SEE deviation T-test inspirations | inspirations observed Г (3) (t) per snail Removed y : Sham unilaterally Я operated P Control Removed I bilaterally F m d operated P Control *measures frequency of motion towards surface from the body, particularly when a snail was moving on a cylinder wall. As indicated in Table 3, the inspira- tion frequency of operated and sham- operated snails in each group did not differ significantly from that of con- trols. Snails of both groups remained inactive for extended periods, and the over-all frequency of surface inspiration was markedly lower than that found in my earlier study (McClary, 1964). No attempt was made to analyze the cause for this, although it is suspected that seasonal differences between the studies may have been a Contributing factor. The tracks (Fig. 3) made by snails of 0.0 Group II prior to inspiration suggested a directed rather than a random move- ment to the surface. To test this, drawings of each track were placed on а 1 cm2 grid, and the number of ver- tical vs. horizontal line crossings com- pared. Chi square analysis of the data is shown in Table 4. As indicated by the table, operated snails showed a di- rected movement tothe surface, although both statocysts had been removed. As cylinder water was in circulation during all observations, the possibility that an oxygen gradient acted as the necessary cue to this movement was eliminated. Since lateral light was used, TABLE 4. Analysis of surface directed tracks, made by Group II snails, superimposed on a 2 . cm# grid Number of tracks Category lines Both statocysts removed Sham operated Control Horizontal crossed Vertical Total lines lines 2* X crossed crossed 8.82 *All X2 values significant at . 05 level of rejection, i.e. , movement is directed 424 A. McCLARY N OPERATED 17 SHAM OPERATED \ CONTROL 5cm FIG. 3. Typical upward tracks made by snails of Group I prior to surface inspiration. which entered each cylinder approxi- mately halfway from the topthrough slits in the oilcloth, it seemed unlikely that light could have acted as a cue. Various workers (Frandsen, 1901; Kanda, 1916a; Cole, 1925; Crozier & Navez, 1930; Hoaglund & Crozier, 1931) have suggested that shell muscle tension acts to direct vertical movement in gastropods. Thus, Crozier & Navez (1930) found that Liguus, a tree snail which normally moves vertically, could be diverted from upward movement by twisting the shell out of alighment with the body. When this was done, Liguus would change its path of travel from the vertical until shell and body were again aligned and shell muscle tension was equal on both sides. If shell muscle tension guided Pomacea upward, it was thought that a similar diversion would result from twisting the shell. Accor- dingly, threads were affixed to the shell apices of several Group II snails. When a snail moved upward, and signaled in- tent to inspire by siphon extension, its shell was pulled out of alignment with the body. As shown in Fig. 4, twisting the shell of these snails failed to di- vert them from their upward travel. Thus, limited experiments failed to sup- port the possibility that shell muscle tension provided the stimuli for the ver- tical movement of P. paludosa. Ciliary Feeding In the presence of particulate food on the water’s surface, P. paludosa will shape the anterior region of its foot into a funnel and, by means of ciliary ac- tion, collect the food contained in the surface film. The aggregated food, mixed with mucus, is then concentrated under the rear portion of the foot and ingested at intervals (Johnson, 1952; McClary, 1964). Typical feeding posture is shown in Fig. 5. The effect of statocyst removalon cil- iary feeding posture was studied by pla- cing snails in 5-gallon aquaria that were illuminated laterally and half filled with filtered tap water at 26°C, and by adding a small amount of particulate food tothe surface. STATOCYST FUNCTION IN POMACEA 3cm i FA for * A | Ni : Ся / ‘à ! Mi has! - i a : \ : 47 i Ir OPERATED SHAM CONTROL OPERATED FIG. 4. Typical results of twisting shells during movementto surface. Tracks selected from approximately 5 records for each cate- gory. All snails from Group II. Arrows in- dicate directionin which shell apex was pulled; dotted line, period during which pull was ex- erted. Shells were twisted approximately 300 from body axis. In 3 operated and 2 sham-operated snails of Group II, a tendency existed for the shell to sag away from the aquarium wall while the snail was feeding. Two of the 3 operated snails had showna similar behavior while rising to inspire. Apart from these, all snails showed a normal posture during ciliary feeding. Activity Level The general procedure for studying activity level was similar to that of previous work (McClary, 1964). Two plastic dishes approximately 10 cmdeep were used. Each contained 3,200 cc of filtered water at 26°C and was illumi- nated by overhead fluorescent light. In the study of GroupI, 15 snails were placed in each dish; for Group II this number was reduced to 12. In each case, dishes contained approximately equal numbers of operated, sham-operated and control snails. All snails were watched for 2 two-hour periods, during which a record was made at 5 minute intervals of all inactive snails and their position in 425 dishes. In addition to the results of this study, data on number and location of inactive snails were available from that on sur- face inspiration. Tables 5 and 6 show results of these studies. During the activity level study on Group I, operated and sham-operated Snails showed a significant decrease in activity, and in ability to rest on verti- cal surfaces. During both activity level and surface inspiration studies on Group II, operated snails showed a significant loss of ability to rest on vertical sur- faces. Rate and Direction of Movement Snails were tested in 3,000 cc plastic dishes containing filtered tap water at 26°C. Illumination was by overhead fluorescent light. Each snail (7-10from each category) was tested singly for 5 FIG. 5. Typical posture assumed by Pomacea paludosa during ciliary feeding. Animal as viewed through aquarium wall. Arrow indi- cates food-mucus aggregate under posterior of foot. 426 A. McCLARY TABLE 5. Activity level of Pomacea paludosa after statocyst removal, recorded at 5-10 min- ute intervals 4 Number snails used Group Study Category Removed Activity Sham level operated I Control unilaterally Removed operated Surface Sham inspiration | operated Control Removed Sham operated Activity level A Control bilaterally Removed operated Surface Sham inspiration | operated Control Number of |Average No. of | Standard | Student’s observations per snail observations | deviation as inactive (t) 0. 38 2.08 1.61 *indicates significant difference from control at . 05 level of rejection minutes and its track onthe bottom ofthe dish, which was transparent and marked with a grid, was recorded as previously described (McClary, 1964). Each snail was observed once. Typical tracks are shown in Fig. 6A € В. Table 7 indicates that there was no significant difference in rate of movement amongthe categories of each group. Although some increase in turning Was present in tracks of Group I operated snails (Fig. 6A, Table 7), there was no conclusive evidence of any true circus movement. Three operated and 2 sham-operated snails of Group II tended to move with their shells sagging to the right. These were the snails which showed a similar behavior in the ciliary feeding study. Ability to turn over when inverted Limited observations were made to determine whether snails of Group II could right themselves. Snails were placed individually, operculum upwards, in water-filled finger bowls. An initial test employed lateral fluorescent lights. Snails were observed for 1 hour. At the end of this period, 4 of 7 operated, 2 of 8 sham-operated, and 1 of 8 con- trol snails had succeeded in righting themselves as a result of the animal’s efforts while extending from the shell. In addition, 3 sham-operated and 3 con- trol snails remained retracted, but rolled over. In a second test, similar to the first, except that it was conducted in complete darkness, the following number of ani- mals were found to have righted them- selves after 1 hour: operated, 5 of 7; sham-operated, 8 of 8; control, 6 of 6. Thus, there was no indication that loss of statocysts caused any significant de- crease in ability to right, either in light STATOCYST FUNCTION IN POMACEA 427 TABLE 6. Number snails Group Study Category used Removed Sham operated Activity level 1 Control unilaterally R operated =e Sham operated Surface inspiration Control Removed Sham operated Activity level 2 Control bilaterally R ‚ operated о. Surface Sham inspiration] operated Control observations when snails Position of inactive snails, indicating reduced ability to rest on vertical surfaces after bilateral statocyst removal Position when observed On On vertical horizontal surface surface Total inactive *indicates significant difference from control at . 05 level of rejection or darkness. DISCUSSION Previous studies which have involved experimental extirpation or neutraliza- tion of statocysts (Tschachotin, 1908; Friedrich, 1932; Pelseneer, 1935; Lever & Geuze, 1965) demonstrated a disrup- tion of normal behavior. In contrast, the present study pro- duced no evidence that statocysts are necessary for the maintenance ofnormal behavioral patterns in P. paludosa, al- though the data can only be regarded as tentative duetothe small population used. The only behavioral change in the pre- sent work which appeared to relate to statocyst loss was the decreased ability of Group II bilaterally operated snails to rest on vertical surfaces. The decrease in activity and in ability to rest on ver- tical surfaces shown by GroupI operated snails of the activity level study was probably due to operative incision rather than to statocyst loss, since a similar reduced capability also occurred with sham-operated snails. Asthis study was the first to be conducted, and began only 4 days after operations were concluded, it seems likely that the reduction in activity and in ability to rest on verti- cal surfaces was due to incomplete wound healing. The sagging of shells found 428 A. McCLARY SNE OPERATED rt roe SHAM OPERATED (695 CONTROL A 5cm 5 $ $ ES = OPERATED LAG SHAM OPERATED Сре CONTROL 5 ст В in both operated and sham-operated snails of several studies was presum- ably a result of a similar but longer lived damage from operation. It is suggested that the discrepancy in results between the present and previous studies may be due to several factors. In some earlier studies, behavioral ab- normalities may have resulted from ge- neralised operative damage. This would seem particularly likely in the case of those experiments on Cymbulia and He- lix (Pelseneer, 1935) in which the entire pedal ganglion was removed. In other experiments such as those onheteropods (Friedrich, 1932), observed abnormali- ties apparently were transient in nature. This suggests that similar transient be- havior patterns may appear when stato- cysts are removed from Pomacea, but were missed in the present study due to the time lapse between operation and observation. The differences between the results of Lever and Gauze (1965) with Lymnaea and those ofthe writer with Po- macea may be a reflection of the numbers of Pomacea studied, differences in time lapse between operation and experiment, or possibly real differences relative to the species used. In Pomacea, normal behavior with res- pect to substrate orientation, horizontal movement, feeding posture and surface inspiration could presumably have been maintained despite the absence of stato- cysts through contact and visual stimuli. With respect to vertical movement, a number of cues to direction other than those provided by statocysts could have been used. Some of the more likely are as follows: 1.) Gravity acting on shell muscle. As suggested by Crozier and others (Crozier & Navez, 1930), vertical move- ment of gastropods may result from an adjustment of position until shell muscle tension on both sides of the body is FIG. 6. Typical horizontal tracks made by snails during study of rate and direction of movement. А =GroupI, В = Group П. S in- dicates start of 5-minute run. STATOCYST FUNCTION IN POMACEA 429 TABLE 7. Rate and direction of movement on horizontal surface Group Category Left statocyst removed Sham operated Control Both statocysts removed Sham operated II Control *All t values insignificant at . 05 level of rejection equal, as would occur when shell and body are aligned on a vertical axis. However, various workers have criti- cized the studies on whichthisidea rests (Hunter, 1931; Fraenkel & Gunn, 1961), and the “string and apex” tests of the present study also argue against it as a means of orientation for Pomacea. 2.) Weight of the shell. As suggested by Fraenkel & Gunn, the upward move- ment of gastropods may be passive in nature; the weight of shell forcing the body to orient vertically. However, it is again difficult to reconcile the string and apex experiments of the present study with this idea, and at least one gastropod, Physa integra, is able to carry out directed vertical movement when suspended in a viscous medium which presumably eliminates any weight effect (McClary, 1961). 3.) Light. Although, in the present work, Group II snails moved vertically in the absence of overhead light, it is possible that the lateral light used pro- duced refraction patterns either on the cylinder walls or air-water interface, and that these served as cues to up- ward movement. Average distance traveled per snail (in cm) Total number of 360° turns Student’s T-test (t)* Standard deviation (s) To left To right 4.) Pressure of the ambient medium. Although theoretically valid, the minute pressure differences to be found along an animal of the size of Pomacea coupled with the apparent lack of any pressure receptors, makes this mode of detection rather unlikely. 5.) Gas in the lung. The location of the lung within the mantle cavity of Po- macea is such that its buoyancy could tend to cause snails to travel upward on a vertical surface. Although lung gas is reduced prior to surface inspira- tion (McClary, 1964), it is conceivable that enough buoyancy still remains to produce such an effect. REFERENCES BOWER, D. R, 1962, A new method of determining the accuracy of geotactic orientation of the snail Helix aspersa Müller. Veliger, 4(4): 181-184. CARTHY, J. D., 1958, An introduction to the behavior of invertebrates. The Macmillan Co. New "York, N.'Y. COLE, W. H., 1925, Geotropism and muscle tension in Helix. J. gen. Physiol., 8: 253-263. 430 A. McCLARY CRABB, E. D., 1929, Egg laying and birth of young in three species of Viviparidae. Nautilus, 42(4): 125-129. CROZIER, W. J. & NAVEZ, A. E., 1930, The geotropic orientation of gastro- pods. J. gen. Psychol., 3: 3-37. DAVENPORT, C. B. & PERKINS, H., 1897, A contribution to the study of geotaxis in higher animals. J. Physiol. 22: 99-110. FRAENKEL, G., 1927, Beiträge zur geotaxis und phototaxis von Littorina. Z. vergl. Physiol., 5: 585-597. & GUNN, D. L., 1961, The orientation of animals. Dover Publ. New York, N. Y. FRANDSEN, P., 1901, Studies on the reactions of Limax maximus to di- rective stiumli. Proc. Amer. Acad. Arts Sci., 37: 185-227. FRIEDRICH, H., 1932, Studien tiber die Gleichgewichtserhaltung und Beweg- ungsphysiologie Pterotrachea. Z. vergl. Physiol., 16: 345-361. HOAGLUND, H. & CROZIER, W. J., 1931, Geotropic excitation in Helix. J. gen. Physiol., 15(1): 15-28. HUNTER, W. S., 1931, The mecha- nisms involved in the behavior of white rats on the inclined plane. J. gen. Psychol. 5: 295-310. JOHNSON, В. M., 1952, Ciliary feeding fresh-water snails. Jbid. in Pomacea paludosa. 1-5. KANDA, S., 1916a, Studies on the geo- tropism at the marine snail Littorina littorea. Biol. Bull., 30: 57-85. , 1916b, The geotropism of 30: 85- Nautilus, 66: 97. LEVER, J. € GEUZE, J. J., 1965, Some effects of statocyst extripations in Lymnaea stagnalis. Malacologia, 2(3): 275-280. McCLARY, A., 1961, Apparent geotac- tic behavior in Physa. Nautilus, 75 (2): 75-79. , 1963, Statolith formation in Pomacea paludosa (Say). Amer. malacol. Union. Ann. Repts., 30: 20- 21. , 1964, Surface inspiration and ciliary feeding in Pomacea paludosa (Prosobranchia: Mesogastropoda: Ampullariidae). Malacologia, 2(1): 87-104. PELSENEER, P., 1935, Essai d’Eth- ologie zoologique d’apres. l’étude des mollusques. Publ. Fond. Agnathon Potter, No. 1. Palais des Acadé- mies. Bruxelles. TSCHACHOTIN, S., 1908, cyste der Heteropoden. Zool., 90: 343-422. Die Stato- Z. wiss. RESUMEN FUNCION DEL ESTATOCISTO EN POMACEA PALUDOSA (AMPULLARIDAE) Se estudiaron dos grupos de caracoles. El grupo I consistió de 15 ejemplares a los cuales se les extirpó el estatocisto izquierdo, otros 15 en los que se efectuó una pseudo-operaciön para exponer el estatocisto izquierdo sin extirparlo, y final- mente 15 quedaron sin ser operados para control. En el grupo Па 8 caracoles se le extirparon ambos estatocistos, 8 fueron pseudo-operados, y 8 de control. Los caracoles fueron anestesiados, por sumersión aproximadamente de una hora, en 25g/litro de MS 222. El cierre de la incisión fué rápido, y los caracoles reasum- ieron actividad dentro de una hora después de la operación. Autopsia posterior no indicó regeneración de estatocistos. Se estudiaron los siguientes comportamientos: velocidad y direcion del movimiento, nivel de actividad, posición de descanso, habilidad correctiva despues de la inversión, alimentación ciliar e inspiración superficial. Algunos ejemplares operados y pseudoperados del grupo II mostraron abollamiento normal de la concha. El nivel de actividad de los caracoles del grupo I fué menor, e incapaces de descansar, comos los controles, sobre superficies verticales. Estos STATOCYST FUNCTION IN POMACEA cambios deben considerarse como causados por la incisión operativa. La extir- pación de estatocistos en el grupo II causó el mismo efecto que en el I. Otras diferencias observadas en el comportamiento entre los operados y los controles no fueron significativas. Caracoles desprovistos de ambos estatocistos no mostraron disminucion en la habilidad para trasladarse e inspirar en la superficie del agua. Entre los factores potenciales que gobierna la dirección a la superficie y la ausencia de estatocistos, luz desde arriba y gradientes de oxígeno fueron presumiblemente eliminados por luz lateral y circulación del agua. 431 wi у en phi À ALL DT Sy how PTE APT A da | ¡ati At м NEN DT AR КА ri oe if it PT dt ER higo di) i ANN х ih N Na ake eh AN a | м N Ne N hp И IAN M ene i o ЛО И А ONT e ju Co A TILL UE PTT 4 DCE EAU az PA LÉ а VA ham EN RN OY a Maa THON tage RN DA HEN, De AT АЯ и A E M a ‘im m Sat Para ЗИ MIR He oT ONE Wü À ut Kur \ Bot IN O IN O RA AN EG RIRE | ABS RER E А LA A yd ine À AN “ IN EN In EU is г il ale | o Aia Pi; Ey р tax | E (e; \ I er a d у № | ALT iy Ir Я MAL | A] le: И y y! у 4 aed f fe à R i i INNE ERICA e tat } Ву м у И R u Ay р 4 и | RP N RL y l vy ми nus | LCI р у Leda AS AA NW, À | № , A A AS N Am vi A LAN | A Y 4 ; ‘ er р В si m $ | г 127 1 И a ‘ / № a р Lt р at, iA 4 dvi hia ПА у ha + ' i ’ rt { | h т é a nr A CE | « Ly à у ' i у } } : Rah р ы y A a y Ni т N 1 1 ) it ы Г и Me nl À Г | Г N ‘ у AR Я у 1 у 4 van MA ) у | | h Pate Mts nu } | и $ M Ban NM A N r ran Wu} ye Meg у и AA MALACOLOGIA, 1966, 3(3): 433-439 EVOLUTIONARY AND SYSTEMATIC IMPLICATIONS OF A TRANSITIONAL ORDOVICIAN LUCINOID BIVALVE A. Lee McAlester Department of Geology, Yale University New Haven, Connecticut, U. 5. A. ABSTRACT Stratigraphic and morphologic evidence indicate that the rare Ordovician bi- valve Babinka is an evolutionary transition between the bivalve superfamily Lucinacea and some monoplacophora-like ancestral mollusc. Paleontologic evi- dence and comparative functional studies of recent forms suggest that the Lucin- acea, Leptonacea and Babinka represent an independent evolutionary lineage which has maintained unique adaptive features since early Paleozoic time. This lineage should probably be treated as a separate bivalve taxon of the highest rank. Lucinoids do not appear to have given rise to other major groups of bi- valves and are probably unrelated to most other “heterodont” forms with which they are commonly associated. The independent origin of lucinoid bivalves suggests that the Bivalvia had a polyphyletic origin from non-bivalved ancestral molluscs. INTRODUCTION Since the recognition of the signifi- cance of the multiple muscle scars in early fossil representatives of the class Monoplacophora, andthe subsequent dra- matic discovery of the living monoplaco- phoran Neopilina, there has been a search by paleontologists for other early fossil molluscs with multiple muscle scars which might indicate a relationship to the Monoplacophora. Of particular Significance would be the discovery of fossils representing the transition be- tween some monoplacophora-like an- cestor and any of the other molluscan classes, but as yet the search for such transitional fossils has yielded few re- sults. One fossil which has attracted wide attention as a possible transitional form is the rare bivalve genus Babinka, which was first described by Barrande in 1881. The genus is known primarily from about a 100 specimens found in lowest Middle Ordovician (Llanvirn) rocks of the Bohemian Basin near Prague, Czechoslovakia. Barrande’s original figures showed that these speci- mens have a peculiar series of elongate muscle-scar impressions on the dorsal region of the valve interiors, and this pattern led Vokes (1954) to suggest that Babinka might be a transition between the Bivalvia and a monoplacophora-like ancestral mollusc. Vokes’ suggestion was quickly taken up by other students of bivalve phylogeny, and the genus has been widely regarded an an ancestral bivalve (Cox, 1959, 1960; Ruzicka & Prantl, 1960; Horny, 1960; Vogel, 1962; Merklin, 1962). A recent restudy of all available speci- mens of Babinka (McAlester, 1965) has documented the morphologic details of the genus and has confirmed Vokes’ suggestion that Babinka shows a primi- tive muscle pattern, although the nature and interpretation of that pattern proved to be more complex than had been pre- viously suspected. Babinka was found to have 8 pairs of pedal muscle scars and a unique series of much smaller scars which probably represent the site of gill muscle attachment. The combined pedal-gill muscle scar patternin Babinka is almost identical to the pattern of (433) 434 A. McALESTER pedal and gill muscle attachmentin Neo- pilina and in some early fossil mono- placophorans. This close similarity strongly suggests that the pattern in Babinka is an inheritance from some monoplacophora-like ancestor. The re- study has also shown that in all features except the pedal and gill muscle scars, Babinka is a typical lucinoid bivalve. Among the features which are indicative of lucinoid affinities are the character- istic shape, elongate anterior adductor scar, non-sinuate pallialline, andtypical lucinoid hinge, dentition and ligament. Babinka is known only from lowest Middle Ordovician rocks and is one of the first bivalves to appear in the fossil record. The first undoubted lucinoid bivalves appear abruptly about one period later, in Middle Silurian deposits, and thus Babinka shows the proper strati- graphic positiontohave beenanancestral lucinoid bivalve. The stratigraphic and morphologic evidence combine to in- dicate that Babinka represents a tran- sition between the large, successful, Silurian to recent superfamily, Lucin- acea, and some monoplacophora-like ancestor. Babinka provides the first direct evi- dence of a transition between the Bi- valvia and a more primitive ancestral form, and the genus is therefore of extraordinary evolutionary significance. This paper has been prepared to call attention to the broader evolutionary CLP d'acte no? 5 . . ie. a } FIG. 1. Life position of recent lucinacean bivalves (modified from Allen, 1958). Nutrient-laden water is brought into the mantle cavity through a mucus-lined anterior inhalent tube constructed by the foot. In some genera the posterior exhalent current discharges directly into the sediment, in others it is channeled to the surface through a retractable posterior siphon. The anterior face of the elongate anterior adductor muscle is covered with cilia and acts as a preliminary sorting area for incoming food particles. ORDOVICIAN LUCINOID BIVALVE 435 implications of this unique fossil, and to provide a preliminary revision of the higher classification of lucinoid bi- valves in the light of the phylogenetic position of Babinka. The systematics of Babinka and the detailed evidence for its transitional evolutionary position have been treatedelsewhere (McAlester, 1965). HABITS AND EARLY GEOLOGIC HISTORY OF LUCINOID BIVALVES Allen’s functional studies of recent Lucinacea (1958, 1960) have shown that all members of the group share unique adaptations for life as deeply buried suspension feeders. Unlike most bi- valves adapted for such a life, lucinoids do not have a posterior siphon through which nutrient-laden water is drawn into the mantle cavity. Instead, the Lucin- acea have the peculiar ability to use the foot not only for burrowing and locomotion, but also for the construction of a mucus-lined, anterior inhalent tube which connects the front edge of the mantle cavity with the surface of the sediment (Fig. 1). The foot is long and cylindrical and may be extended from 3-10 times the shell height, thus per- mitting the animal to live buried at a considerable depth. After burial, the animals tend to remain in one position for long periods, but if disturbed or uncovered, they can readily burrow into the sediment and construct a new in- halent tube. Various morphologic features of the Lucinacea are corre- lated with this specialized mode of life. In particular, the characteristic elongate anterior adductor muscle and anteriorly expanded shell shape serve to facilitate preliminary ciliary sorting of food particles brought in by the anterior in- halent current. If we accept the reasonable assumption that fossil lucinoids shared the adap- tations for infaunal filter feeding found in all recent Lucinacea, then the develop- ment of these adaptations had particular evolutionary significance because lucin- oid bivalves appear in the geologic record long before the first appearance of more typical siphonate infaunal bivalves. The first undoubted lucinoid forms appear fully developed in Middle Silurian deposits, whereas the first strongly Siphonate bivalves (other than the Specialized, deposit-feeding Nuculan- idae) do not appear before the Carbon- iferous, and do not become really common until Mesozoic time. The fossil record therefore indicates that the lucin- oid anterior inhalent tube was an ex- tremely early specialization for a deeply buried suspension feeding mode of life. Lucinoid forms appear to have been the only major group of bivalves with adap- tations for occupying this ecologic niche throughout much of Paleozoic time. If Babinka represents an ancestral lucinoid form, then lucinoids, along with the nu- culoids and some other problematic groups, are among the first bivalves to appear in the fossil record. Lucinoids thus appear to represent a major adap- tive branch of the Bivalvia with distinc- tive specializations and habits that origi- nated in the initial Paleozoic evolutionary radiation of the Class. Like the nucu- loids, lucinoids have survived since the early Paleozoic and are still a diverse and successful group in modern oceans. PROBABLE POLYPHYLETIC ORIGIN OF THE BIVALVIA This extremely early evolutionary differentiation of the Lucinacea and the transitional evolutionary position of Bab- inka suggest that lucinoid bivalves arose independently from some monoplaco- phora-like, non-bivalved ancestor. With perhaps a single exception, there is as yet no compelling paleontologic or zoologic evidence to support a hypothesis that Babinka and later lucinoid forms are themselves ancestral to other major groups of bivalves. Apparently the lucinoid mode of life has persisted in- dependently since the early Paleozoic and has given rise to few, if any, other major bivalve adaptations. Lucinoid 436 A. McALESTER bivalves are probably a separate and distinctive evolutionary branch of mol- luscs which arose independently from a more primitive ancestral form. This suggests that other distinctive groups of the Bivalvia may also have evolved independently from non-bivalved mol- luscan ancestors. Complete restudy of the earliest Paleozoic fossil bivalves will be necessary to work out the details, but there is now enough evidence to predict that the Bivalvia are similar to the Mammalia and other major animal groups in having a “polyphyletic” origin from more primitive ancestral forms. PRELIMINARY REVISION OF LUCINOID HIGHER CLASSIFICATION The independent origin and separate development of lucinoid bivalves suggest some major revisions in the traditional higher classification of the group. With- in the Bivalvia, the superfamily Lucin- acea is usually assigned to a suborder or order “Heterodonta”, which normally includes such diverse groups as the astartaceans, carditaceans, glossa- ceans, cardiaceans, veneraceans, mac- traceans and tellinaceans. This associ- ation of many unlike and ‘divergently adapted superfamilies into a larger “heterodont” taxon has been justified primarily on the basis of vaguely similar patterns of dentition. The fossil record of lucinoid bivalves, combined with Allen’s recent discoveries concerning the unique adaptations of the group, indicates that the Lucinacea represent a separate branch of the Bivalvia which are probably unrelated to most “hetero- dont” bivalves with which they are tra- ditionally associated. Among the 15 or so superfamilies normally assigned to the “Heterodonta”, only the Leptonacea [=Erycinacea] show morphologic and adaptive features which clearly suggest an evolutionary relationship to the Lucin- acea (Popham, 1940; Morton et al., 1957; Oldfield, 1955, 1961). The Lepton- acea are first clearly recognizable in the fossil record in the early Paleogene, and they may represent a late evo- lutionary offspring of the Lucinacea. Continued association of the Lucinacea with other “heterodont” superfamilies cannot now be supported from the fossil record nor from the morphology and adaptations of recent forms. Within the Lucinacea, 3 distinctive families are universally recognized, and an additional 4 families are sometimes assigned to the superfamily on less con- vincing evidence. These families and their approximate known geologic ranges are: Assignment to Lucinacea certain: Lucinidae - Silurian to recent Thyasiridae - Cretaceous to re- cent Diplodontidae (=Ungulinidae)- Cretaceous to recent Assignment to Lucinacea question- able: Mactromyidae (=Unicardiidae)- Triassic to Cretaceous Tancrediidae - Triassic to Creta- eous Fimbriidae (=Corbidae) - Trias- sic to recent Cyrenoididae - recent only Allen’s detailed comparative study of recent lucinoids (1958) treated the 3 characteristic families Lucinidae, Thya- siridae and Diplodontidae. His work suggested that these families exhibit an evolutionary series from the more “primitive” Diplodontidae, through the Thyasiridae, to the more “specialized” Lucinidae. The Diplodontidae were con- sidered to be primitive because they are morphologically and adaptively the most similar to typical heterodont, eula- mellibranchiate bivalves, from which the Lucinacea were presumed to have evolved. In particular, the Diplodont- idae show a weaker anterior inhalent current and more complex gill pattern than do the Lucinidae. In the Lucinidae these features were considered to be the result of secondary specialization. The fossil record shows that the an- terior inhalent current is in fact an extremely early specialization for an ORDOVICIAN LUCINOID BIVALVE 437 it Шут Diplodontidae > y i ф | | - Ze ES ) CAEN AO © LEE Cretaceous Jurassic М Е ОДО iC Lucinidae Triassic Carb-Perm. LUCINACEA Ordovician ancestral mollusc Cambrian FIG. 2. Proposed evolutionary relations of Babinkacea, Lucinacea and Leptonacea. The width of the shaded areas is approximately proportional to the generic diversity of the taxa. 438 A. McALESTER infaunal suspension feeding mode of life and is not a secondary specialization from some more “typical” bivalve pattern. This suggests that Allen’s inferred evolutionary series of the 3 families is actually reversed, and that the similarities between the “primitive” Diplodontidae and typical “heterodont” bivalves is the result of convergent evolution from basically different ances- tral forms. This possibility is further suggested by the late geological appear- ance of representatives ofthe Diplodont- idae and Thyasiridae, both of which are unknown before the Cretaceous (Fig. 2). The independent evolutionary develop- ment of lucinoid bivalves suggests that the entire group should be assigned to a separate bivalve taxon of the highest rank. The Leptonacea have most probably evolved from the Lucinacea and can reasonably be assigned to the same higher taxon. There now appears to be no sound phylogenetic basis for associating other major bivalve groups with the lucinoids and leptonoids. Babinka is most closely related to the Lucinacea, but its unique evolutionary position can best be represented by assignment to a separate superfamily under a larger sub-taxon which also includes the Lucinacea. Within the Lucinacea, the Lucinidae probably represent the ancestral stock from which the other familiesarose. These relation- ships are shown in Fig. 2. Additional anatomical and morphological data will be necessary before the families Mactro- myidae, Tancrediidae, Fimbriidae and Cyrenoididae can be unequivocally assigned to the Lucinacea. These suggestions are summarized in the following tentative scheme of lucin- oid higher classification. To avoid nomenclatural conflicts with the forth- coming bivalve volume of the “Treatise on Invertebrate Paleontology”, noformal names are given to those higher cate- gories which are suggested here for the first time. LUCINOID SUBCLASS OR ORDER Lucinid Order or Suborder Superfamily Babinkacea Family Babinkidae Superfamily Lucinacea Family Lucinidae Family Thyasiridae Family Diplodontidae [? Family Mactromyidae] [? Family Tancrediidae] [? Family Fimbriidae] [? Family Cyrenoididae] Leptonid Order or Suborder Superfamily Leptonacea [Families omitted] ACKNOWLEDGMENTS I am most grateful to Drs. Copeland MacClintock, N. D. Newell and J. H. Ostrom for reading the manuscript and offering many helpful suggestions, and to Miss Martha Dimock for preparing the text figures. The restudy of Babinka which led to these conclusions was supported in part by grant No. G19961 from the National Science Foundation, and in part by the Charles Schuchert Fund of the Peabody Museum, Yale University. REFERENCES ALLEN, J. A., 1958, On the basic form and adaptations to habitat in the Lucinacea (Eulamellibranchia). Phil. Trans. Roy. Soc. London, B, 241: 421-484. ‚ 1960, The ligament of the Lucinacea (Eulamellibranchia). Quart. J. microsc. Sci. 101: 25-36, BARRANDE, J., 1881, Classe des Mol- lusques, ordre des Acephales: vol. 6 of Systeme silurien du centre de la Bohéme, premiere partie [Recherches paleontologiques]. Prague and Paris, 342 p, 361 pls. [in 4 vols.]. COX, L. R., 1959, The geological his- tory of the Protobranchia and the dual origin of taxodont Lamellibranchia. ORDOVICIAN LUCINOID BIVALVE 439 Proc. malacol. Soc. London, 33: 200- 209. ‚1960, Thoughts on the classi- fication ofthe Bivalvia. Proc. Malacol. Soc. London, 34: 60-88. HORNY, R., 1960, On the phylogeny of the earliest pelecypods (Mollusca). Véstn. geol. Ust. Gsl., 35: 479-482. McALESTER, A. L., 1965, Systematics, affinities, and life habits of Babinka, a transitional Ordovician lucinoid bi- valve. Palaeontology 8: 231-246. MERKLIN, R. L., 1962, Ob odnoy novoy sisteme dvustvorchatykh mollyuskov. Byulletin’ Imperatorskago Moskov- skago Obshchestva Ispytateley Pri- rody, otdel geologicheskiy, 37(3): 136. MORTON, J. E., BONEY, A. D. € CORNER, E. D. S., 1957, The adap- tations of Lasaea rubra (Montagu), a small intertidal lamellibranch. J. marine Biol. Ass. U.K. 36: 383-405. OLDFIELD, E., 1955, Observations on the anatomy and mode of life of Lasaea rubra (Montagu) and Turtonia minuta (Fabricius). Proc. malacol. Soc. London, 31: 226-249. , 1961, The functional morpho- logy of Kellia suborbicularis (Monta- gu), Montacuta ferruginosa (Montagu) and M. substriata (Montagu), (Mol- lusca, Lamellibranchiata). Proc. ma- lacol. Soc. London, 34: 255-295. POPHAM, M. L., 1940, The mantle cavity of some of the Erycinidae, Montacutidae and Galeommatidae with special reference to the ciliary mech- anisms. J. marine Biol. Ass. U. K. 24: 549-587. RUZICKA, B. & PRANTL, F., 1960, Types of some Barrande’s pelecy- pods (Barrandian). Zvlästni Otisk Casopisu Narodniho Musea, oddil pri- rodovedny, (1): 48-55. [in Czech with English Summary]. VOGEL, K., 1962, Muscheln mit Schlos- szähnen aus dem spanischen Kam- brium und ihre Bedeutung fiir die Evolution der Lamellibranchiaten. Akad. Wiss. Mainz, Abh. math.- naturw. Kl., Jg. 1962, no. 4, 52p, 5 pls. VOKES, H. E., 1954, Some primitive fossil pelecypods and their possible significance. J. Washington Acad. Sci. 44: 233-236. RESUMEN IMPLICACIONES SISTEMATICAS Y EVOLUTIVAS DE UN BIVALVO TRANSICIONAL LUCINOIDE DEL ORDOVICIANO Evidencia morfolögica y estratigräfica indica que el raro bivalvo del Ordoviciano Babinkia es una transición evolutiva entre la superfamilia Lucinacea y algunos moluscos ancestrales de tipo monoplacöforo. Evidencia paleontolögica, y estudios comparativos funcionales de formas recientes, sugieren que los Lucinacea, Lepton- acea y Babinkia representan un linaje evolutivo independiente que ha mantenido caracteres adaptivos únicos desde el Paleozoico antiguo. Este linaje probablemente deberá ser tratado como un taxon separado, de bivalvos de alta categoria. Los Lucinoidea no parecen haber dado origen a otros grupos mayores de bivalvos y probablemente no estan relacionados a la mayoría de otras formas “heterodontas” con las cuales se asociaban comunmente. El origen independiente de los lucinoideos sugiere que la clase Bivalvia tuvo un origen polifilético de otros moluscos ancestrales no bivalvos. * виа в chante im yt 1741 BLA pets à: AUX | EUR pencas # | En A un PAC ere DRAP UT ET Ken) од мА Re A Su sy TN RASE otha 4 AM ol 4 stati y AS я (ng K4 À ¿MIN THE) rei Sipe senti YM ORTE DENE us ax | er vera | RM BM} HRS?” MTL Gal ROT rl ip apra Ki в MY ann № ie wart 1 it ern р ети ABR À HOT BUN мы: ‚ивр AM: ere FERN rt "ec net: Re ae ме oo > E er | er at ya) IGN м INDEX TO SCIENTIFIC NAMES Abatus, 187 cavernosus, 187 Acer, 45 rubrum, 45 Achnanthes, 68 exigna heterovalvata, 68 lanceolata, 68 minutissima, 68 minutissima cryptocephala, 68 Achasmea, 184, 185 thalassemicola, 185 acicularis, Nitzschia, 69 Acleioprocta, 264, 279, 372 Aclididae, 171 Acmaea, 381 Acochlidiacea, 357, 365, 366, 369, 371 Acoela, 327, 330, 334, 345, 346, 353, 354, 364, 371 acuta, Physa, 311 acuta, Pleurocera, 1-80 acutissima, Eulima, 134, 135 acutum tractum, Pleurocera, 10 Acteocina, 364, 371 exima, 364 Acteon, 334, 336-339, 344, 345, 353, 361, 371 punctocaelatus, 336, 337, 338 tornatilis, 337, 338 Acteonidae, 345, 346, 354, 364, 366, 368, 369, 370, 371 actinariophila, Nipponomontacuta, 184 aeglefinis, Melanogrammus, 198 Aeolidia, 345, 351 papillosa, 345, 351 Aeolidiacea, 349, 351, 366, 372 aequicostatus, Heterocyathus, 185 aestivalis, Vites, 45 aestuariorum, Portlandia, affinis, Cadlina, 348 affinis, Cymbella, 68 affinis, Herviella, 251 affinis, Upogebia, 189 Aglaja, 263, 264, 334, 361, 364 splendida, 263, 264 Aglajidae, 263, 265, 344, 357, 360, 361, 364, 366, 371 205 Aglossa, Akera, 186, 364 bullata, 186, 364 nana, 186 Akeratidae, akkeshiensis, Ercolania, 171, 172 364, 366, 368, 369 269 441 akkeshiensis, Stiliger, 269 alba, Balcis, 151, 163, 169 alba, Philine, 359, 361, 364 alba, Quercus, 45 albida, Doto, 264, 279 albopunctata, Dendrodoris, 335, 345 Alderia, 353, 354, 355, 356, 357, 370 modesta, 354 Aligena, 184, 186 elevata, 186 Amauropsis, 203 islandica, 203 ambigua, Brachystomia, 365 ambrigua, Melosira, 68 amboinensis, Cycladoconcha, 188 Ambloplites, 10 rupestris, 10 americana, Vallisneria, 45 americanus, Scirpus, 45 amoena, Chromodoris, 247, 248 Amnicola, 42, 43, 103, 107-109 hendersoni, 109 idahoensis, 109 limosa, 42, 43 longinqua, 104, 108 micra, 104, 108 micrococcus, 103, 109 pilsbryana, 104, 108 pilsbryi, 108 Amphibia, 323 Amphibola, 367 Amphineura, 186 Amphipleura, 69 pellucida, 69 Amphiura, 188 filiformis, 188 Amphora, 68 normani, 68 Ampullariidae, 419 Anabaena, 14, 45 Analogium, 250 236, 265, 327, 334, 337, 345, 352-354, 363-370 anceps, Helisoma, 42 Anaspidea, anceps, Stauroneis, 67, 69 Anculosa, 9, 36, 38, 53, 58, 60 carinata, 36, 53, 58 subglobosa, 36 Ancylus, 400 fluviatilis, 400 Angitrema, 9 verrucosa, 9 442 MALACOLOGIA angusta, Cyrtodaria, 202, 203 Anisodoris, 338 nobilis, 338 Annelida, 184, 186 Anodonta, 42 grandis, 42 Anomoeoneis, 67 sphaerophora, 67 Anthenoides, 116 rugulosus, 116 anthonyi, Eurycaelon, 36 Antiopella, 351 muloc, 351 aperta, Haminoea, 243 aperta, Philine, 359, 361, 362, 364 Aphrodite, 186, 189 Aplodinotus, 69 grunniens, 10 Aplysia, 212, 263, 265, 266, 334, 338- 343, 352, 353, 364, 420 dactylomela, 263, 265 juliana, 212 parvula, 263, 266 parvula nigrocincta, 266 pulmonica, 263, 266 punctata, 364 Aplysiidae, 236, 263, 265, 364, 366 Aplysiinae, 263, 265 Aporrhais, 185 appressa, Mesodon, 311 appressa, Polygyra, 311 avachnoidea, Goniobasis, 36 arborescens, Doridopsis, 250 Archidoris, 365 tuburculata, 365 arctica, Hiatella, 203 arctica, Portlandia, 400 arctica, Yoldia, 400 arenarius, Murex fulvescens, 229 Armina, 350, 351 Arminacea, 349, 351, 366, 372 arrhynchus, Megadenus, 116, 129, 134, 151, 172, 173, 174, 175 Arthropoda, 184, 189 Aspidobranchia, 114 Aspidosiphon, 185 Asteroidea, 115 Asteronotinae, 264, 276 Asterophila, 111-181 japonica, 111-181 Asterophilidae, 112, 114, 175 atra, Holothuria, 212 atromarginata, Casella, 264, 273 Atyidae, 236, 327, 357-359, 364, 366, 370, 371 auricularia, Dolabella, 263, 266 Auristomia, 185 perezi, 185 aurita, Cercaria, 69 australis, Scioberetia, 187 Australorbis, 81, 95. glabratus, 81, 95 avara, Catinella, 310 avara, Succinea, 310 Axius, 184, 189 plectorhychus, 189 Babinka, 419-425 Babinkacea, 423, 424 Babinkidae, 424 Baeolidia, 282 Balcis, 151, 163, 169, 175 alba, 151, 163, 169 devians, 151, 163, 169 balfouriana, Diatomella, 67 banyluensis, Dondice, 351 Barnea, 187 candida, 187 barronensis, Goniobasis livescens, 55 Basommatophora, 236, 311, 368, 379 Bathydoris, 348 Batrachospermum, 45, 68 vugum, 45, 68 bayeri, Elysia, 263, 264, 270, 271 Bedeva, 229 hanleyi, 229 Bellevalia, 323 Berghia, 282, 351 coerulescens, 351 Berthella, 264, 271, 347, 348 grisea, 264, 271 Berthelinia 264, 271, 334, 347-357 citrina, 264, 271 Betula, 45 papyrifera, 45 bicolor, Gymnodoris, 236, 249, 250 bicolor, Trevelyana, 249 bidentata, Mysella, 183, 185, 186, 187 188, 189 bifida, Hermaea, 356 Bilateria, 331 binotata, Haminoea, 240 binotata japonica, Haminoea, 240 Biomphalaria, 379-398 pfeifferi, 379-398 INDEX, VOL. Ш Bivalvia, 183, 186, 197, 419-425 blakei, Deima, 116 Blepharipoda, 189 occidentalis, 189 bodanica, Cyclotella, 68 boeckii, Brebissonia, 67 boholiensis, Discodoris, 276 Bornella, 264, 279 digitata, 264, 279 Bornellidae, 264, 279 Bosellia, 353, 356 mimetica, 353 Bourvieria, 347, 348 ocellata, 348 brachiata, Ophiocnida, 188 Brachidontes, 186 granulatus, 186 multiformis, 186 Brachystomia, 365 ambigua, 365 Brebissonia, 67 boeckii, 67 brevis, Io fluvialis, 35 brevistriata, Fragilaria, 68 briareus, Ennoia, 280 briqua, Chromodoris, 236, 245-249 Brissopsis, 187 lyrifera, 187 brunelli, Sphaerumbonella, 184 Bryozoa, 184, 185 Buccinacea, 230, 231 Buccinum, 8 virginicum, 8 Bulinus, 380 Bulla, 360, 364, 370, 371 gouldiana, 360, 364 Bullacea, 236, 263, 265 bullata, Akera, 186, 364 Bullidae, 327, 357, 358, 364, 366, 370, 371 Busycon, 228 bylgia, Catriona, 280 Cadlina, 276, 348 affinis, 348 Cadlinella, 247 Cadlinellinae, 247 Cadulus, 203 Caecum, 203 californica, Cerithidea, 22 californica, Hancockia, 350 californianus, Mytilus, 186 californiensis, Fontelicella, 103-109 Caliphylla, 354, 355, 356, 370 mediterranea, 356 Callianassa, 189 major, 189 Calliostoma, 185 conuloides, 185 callosa, Haminoea, 241 Calma, 351, 372 Caloria, 253 calyculata, Smaragdinella, 236, 237, 238 camdenensis, Cyrtodaria, 202, 203, 204 Campeloma, 42, 43 decisum, 42, 43 campestris, Succinea, 310 campestris vagans, Succinea, 310 canadensis, Elodea, 45 canaliculata, Pleurocera, 9, 36, 58, 63 canaliculatum undulatum, Pleurocera, 9, 18, 21, 22, 25, 30-40 candida, Barnea, 187 capitata, Limapontia, 365 capucina, Fragilaria, 68 Capulidae, 159, 171 caputserpentis, Cypraea, 212 Carcinides, 189 maenas, 189 Carex, 45 carinata, Nitocris, 36, 53, 58 carpenteri, Triopha, 333, 345 Carya, 45 tomentosa, 45 Casella, 264, 273 atromarginata, 264, 273 rufomarginata, 264, 273 Catinella, 309-325 avara, 310 rotundata, 309, 310, 313, 321 texana, 309, 310, 321 vagans, 310 vermeta, 309-325 Catriona, 263, 264, 274-280 bylgia, 280 cucullata, 280 lonca, 263, 264, 274-280 maua, 279 susa, 280 urquisa, 263, 264, 274-280 caudata, Eupleura, 185 Caulerpa, 266 cavernosus, Abatus, 187 Cavolinidae, 365 443 444 MALACOLOGIA Cerastoderma, 189 edule, 189 Ceratobornia, longipes, 186 cedrosensis, Fontelicella, 108 cedrosensis, Paludestrina, 104, 108 celebensis, Stilifer, 135, 138, 151, 172 celtica, Onchidella, 254 Cephalaspidea, 236, 263, 265, 352, 357, 363-370 184, 186, 189 Cerberilla, 253 Ceratophyllum, 45 demersum, 45 Cercaria, 69, 70, 71 aurita, 69, 70 gorgonocephala, 69, 70 sagittavia, 1 Cerithidea, 22 californica, 22 Cerithium, 22 vulgatum, 22 Chama, 186 Chara, 45 vulgaris, 45 Chelidonura, 263, 265 hirundinina, 263, 265 inornata, 263, 265 Chlorella, 67 variegatus, 67 christenseni, Montacuta, 187 Chromodoridinae, 236, 247, 248, 264, 272 236, 244-249, 264, 272, 273 Chromodoris, alderi, 248, 249 amoena, 247, 248 aureopurpurea, 248 briqua, 236, 245-249 crossei, 273 fidelis, 236, 244-246 flammulata, 245 hilaris, 248 tnornata, 248 juvenca, 248 lactea, 245 lata, 245 lineata, 248, 249 lineolata, 264, 272 quadricolor, 249 reticulata, 248 vuncinata, 248 venusta, 264, 272 Cidaris, 187 cidaris, 187 cidaris, Cidaris, 187 Cincinnatia, 103, 107, 108 integra, 103, 107 cincinnatiensis, Pomatiopsis, cinerea, Urosalpinx, 226 Cirripedia, 113 cistula, Cymbella, 67 cistula, Lasaea, 186 citrina, Berthelinia, claror, Herviella, Clavagella, 183 clavaeformis, Goniobasis, clarkiae, Lepton, 185, 186 clarkiae, Potidoma, 185 Clione, 362 Clionopsis, 362, 365 grandis, 365 Cleopatra, 22 Cliopsidae, 365 Cleioprocta, 236, 280, 282 Clonorchis, 3 sinensis, 3 clausa, Natica, 203 Clymenella, 186 torquata, 186 coccinea, Quercus, 45 Cocconeis, 68 pediculus, 68 placentula, 68 cochleariformis, Sacculosiphonaria, 257 cochleariformis, Siphonaria, 257 Coelenterata, 184 coerulescens, Berghia, 351 coivala, Hermaea, 356 Colobocephalus, 369 comalensis, Goniobasis, 53 comis, Janolus, 351 communis, Dendrodoris, 250 communis, Turritella, 185 compressa, Pseudopythina, 189 concharum, Jousseaumiella, 185 conspicuus, Ischnochiton, 186 constrictum, Gomphonema, 68 construens, Fragilaria, 68 construens subsalina, Fragilaria, 68 conuloides, Calliostoma, 185 conuloides, Zizyphinus, 185 copallina, Rhus, 45 Copepoda, 113 corallinaceus, Vermetus, 186 29, 82, 99 264, 271 235, 251-253 36, 58 INDEX, VOL. III coralliophila, Thyreopsis, 184 Corbidae, 422 cordatum, Echinocardium, 187 Cornus, 45 stolonifera, 45 cornuta, Langerhansia, 185 correcta, Goniobasis livescens, 9, 36, 38, 53, 55, 56, 70 Coryphellina, 351 Coscinodiscus, 68 lacustris, 68 Costasiella, 267 ocellifera, 267 nonatoi, 267 costellatum, Isognomon, 225 Cotylogaster, 69, 70, 71 occidentalis, 69, 70, 71 crassicornis, Hermissenda, 336-338, 345 Cratena, 253, 280, 283 Creseis, 333, 365 virgula, 333, 365 cribosa, Dendrophyllia, 185 Cribrella, 115 crispata, Tridachia, 356 crispatus, Ctenodiscus, 115 crocata, Haminoea, 240, 241 crossei, Chromodoris, 273 crossei, Hypselodoris, 273 crosslandi, Patinapta, 188 cruenta, Platydoris, 264, 277 Cryptobranchia, 236, 264, 271 cryptocephala, Achnanthes minutissima, 68 cryptocephala, Mastogloia smithü, 69 cryptocephala, Navicula, 69 cryptocephala veneta, Navicula, 69 cucullata, Catriona, 280 cucumariae, Diacolax, 127 cuenoti, Erycina, 185 cuis, Hypselodoris, 263, 269, 272, 273 cuneata, Pythinella, 185 cuneata, Rochelfortia, 185 curiosa, Holothuria, 188 curiosa, Noumeaella, 282 curtatum, Pleurocera unciale, 36 curtum, Pleurocera, 36 Cuthonidae, 264, 279 Ctenodiscus, 115 crispatus, 115 Ctenosculidae, 171 Ctenosculum, 114 445 hawatiense, 114 Cycladella, 184 Cycladoconcha, 184, 188 amboinensis, 188 Cyclope, 221, 229 neritea, 221, 229 Cyclotella, 68 bodanica, 68 Cyerce, 264, 269 nigra, 264, 269 Cylichna, 334, 361, 364, 371 cylindracea, 364 Cylichnella, 371 cylindracea, Cylichna, 364 Cylindrobulla, 334, 341, 352, 353, 357, 369, 370 Cylindrobullidae, Cylindrocapsa, 67 geminella, 67 cymbalum, Lamprohaminoea, 327, 366 236, 242- 244 Cymbella, 67 cistula, 67 cymbiformis, 68 delicatula, 68 lanceolata, 67 naviculiformis, 68 prostrata, 68 ventricosa, 68 cymbiformis, Cymbella, 68 Cymbulia, 420, 428 Cypraea, 212 caputserpentis, 212 Cyrenoididae, 422, 424 Cyrtodaria, 197-210 angusta, 202, 203 camdenensis, 202, 203, 204 jenisseae, 202, 203, 204 kurriana, 197-205 neuvillei, 202, 203 siliqua, 197-210 transcaspica, 202, 203 vagina, 203 cysticola, Megadenus, 151 dactylomela, Aplysia, 263, 265 dactylomela, Verria, 263, 265 Decapoda, 189 decisum, Campeloma, 42, 43 decorata, Hallaxa, 264, 273 Deima, 116 blakei, 116 deimatis, Gasterosiphon, 116, 127, 146 446 MALACOLOGIA delicatula, Cymbella, 68 erubescens, 276 deltaura, Upogebia, 189 indecora, 275 demersum, Ceratophyllum, 45 labifera, 276 dendritica, Hermaea, 356 liturata, 275 Dendrodoris, 236, 250, 251, 264, 277, lora, 263, 268, 269, 273-275 335, 336, 345 lutescens, 276 albopunctata, 335, 345 pallida, 275, 276 communis, 250 palma, 276 erubescens, 236, 250, 251 voniheringi, 349 melaena, 250 ylva, 263, 274-276 nigra, 236, 250, 264, 277 Divariscintilla, 184, 189 rubra, 250 maoria, 189 Dendrodorididae, 236, 264, 277 Dolabella, 263, 266, 353 Dendronotacea, 349, 351, 365, 366, 372 auricularia, 263, 266 Dendronotoidea, 264, 279, 365 scapula, 266 Dendronotus, 351, 365, 372 Dolabellinae, 263, 266 frondosus, 351, 365 Dolabrifera, 236, 244, 263, 266 Dendrophyllia, 185 dolabrifera, 236, 244, 263, 266 cribosa, 185 maillardi, 244 dendyi, Trochodota, 188 nicaraguana, 244 Dentalium, 203 variegata, 244 deshayesiana, Mylitta, 189 dolabrifera, Dolabrifera, 236, 244, 263, deshayesii, Kellia, 185 266 Desmidium, 67 Dolabriferinae, 236, 263 grevillii, 67 donacina, Montacuta, 188 devians, Balcis, 151, 163, 169 Dondice, 253, 351 Devonia, 184, 188 banyluensis, 351 ohshimai, 188 Doridacea, 344, 349, 365, 366, 372 perrieri, 188 Dorididae, 236, 264, 272, 365 Diacolax, 127, 175 Doridoidea, 236, 264, 271 cucumariae, 127 Doridopsis, 250 Diaphana, 364 arborescens, 250 minuta, 364 erubescens, 250 Diaphanidae, 327, 352, 353, 357-371 nigra, 250 diardii, Hypselodoris, 273 nigra luteopunctata, 250 Diatomella, 67 Doriopsila, 335 balfouriana, 67 Doris, 245, 249, 250 dicoelobius, Paedophoropus, 138, 151, fidelis, 245 168, 172 magnifica, 249 Dictyosphaerium, 67 nigra, 250 pulchellum, 67 preciosa, 245 digitata, Libidoplax, 188 Doto, 264, 279, 350, 351 digitata, Bornella, 264, 279 albida, 264, 279 dilatatus, Elliptio, 42, 43 uva, 351 Diplodontidae, 422, 424 Dotoidae, 264, 279 dissimilis, Mudalia, 35 Drupa, 211-233 Discodorinae, 264, 273 vicina, 211-233 Discodoris, 263, 268, 269, 273-276, 349 dubia, Discodoris, 275 boholiensis, 276 dufourei, Melanopsis, 22 dubia, 275 Dysnomia, 42 egena, 275 triquetra, 42 erythraeensis, 275 eburnea, Mucronalia, 129 INDEX, VOL. II Echinarachnius, 200, 201 parma, 200, 201 echinocardiophila, Montacuta, 187 Echinocardium, 187 cordatum, 187 flavescens, 187 Echinodermata, 184, 187 Echinoidea, 187 Echinus, 187 esculentus, 187 Echiuroidea, 184, 185 edule, Cerastoderma, 189 edulis, Mytilus, 189 egena, Discodoris, 275 Eledone, 288, 303 cirrosa, 288, 303 elegans, Halgerda, 264, 276 elegans, Haminoea, 244 elevata, Aligena, 186 Elimia, 9 Elliptio, 42, 43 dilatatus, 42, 43 Elodea, 45 canadensis, 45 elongatum, Phascolosoma, 185 Elysia, 263-271, 353, 356, 364, 365, 370 bayeri, 263, 264, 270, 271 ‘hedgpethi, 365 latipes, 271 livida, 270 marginata, ornata, 270 тата, 263, 264, 268-271 264, 270 thysanopoda, 264, 270 viridis, 356 Elysiacea, 264, 267, 365 Elysiidae, 264, 270, 365, 366 emarginata, Stagnicola, 311 Embletonia, 351, 345, 372 fuscata, 351 pallida, 351 emeryensis, Goniobasis, 46 Ennoia, 280, 283 briareus, 280 longicirrha, 283 Enteroxenos, 117, 133, 156, 175 Entocolax, 170-175 ludwigi, 117, 143 rimsky-korsakovi, schiemenzi, 117 143, 170, 174 117, 132, 143, 151, 159-163, schwanwitschi, trochodotae, 117, 151, 159 Entoconcha, 117, 159, 175 mirabilis, 117 Entoconchidae, 112-181 Entomotaeniata, 365 Entovalva, 184, 188 major, 188 mirabilis, 188 ohshimai, 188 perrieri, 188 semperi, 188 Eolidacea, 282 151, 159-163, 170 Eolidoidea, 236, 264, 279 Ephippodonta, 184, 185, 189 lunata, 184, 189 macdougalli, 184, 189 muvakamii, 184 turnbullae, 184, 189 Epithemia, 67, 68 turgida, 67 zebra, 68 equestris, Eulima, 135 equestris, Melanella, 151 Ercolania, 264, 267-269 akkeshiensis, 269 illus, 264, 267, 269 noto, 269 pancerii, 267 trinchesei, 269 erinaceus, Murex, 231 erubescens, Dendrodoris, erubescens, Discodoris, 276 erubescens, Doridopsis, 250 Erycina, 185 cuenoli,, 185 Erycinacea, 183-195, 422 erythraeensis, Discodoris, 275 esculentus, Echinus, 187 Eubranchus, 372 Eudoridacea, 236 Eulima, 134, 135 acutissima, 134, 135 equestris, 135 Eulimidae, 127 Eunereis, 186 longissima, 186 Eupleura, 185 caudata, 185 Eupomotis, 10 gibbosus, 10 Eurycaelon, 9, 36 236, 250, 251 448 anthonyi, 36 Euthyneura, 263, 320, 343, 366, 367, | - 371 exigua, Herviella, 251 exigua heterovalvata, Achnanthes, 68 exigua, Navicula, 69 exima, Acteocina, 364 evelinae, Miesea, 279, 351 evelinae, Muessa, 263, 264, 280-283 evelinae, Onchidella, 235, 253, 255, 256 Facalaninae, 253 Facelinidae, 253, 282, 283 fasciata, Ulva, 212 Favorinidae, 236, 253, 263, 264, 270, 282, 283 Favorininae, 236, 253, 264, 270, 282, 283 fenestra, Tabellaria, 67, 68 Ferrissia, 60 shimekii, 60 ferruginea, Limanda, 198 ferruginosa, Montacuta, 187 fidelis, Chromodoris, 236, 244-246 fidelis, Doris, 245 fidelis, Glossodoris, filiformis, Amphiura, Fimbriidae, 422, 424 flammulata, Chromodoris, flammulata, Platydoris, flavescens, Echinocardium, flavescens, Onchidella, 256 flexilis, Nitella, 45 floccosa, Microspora, 67 fluvialis, Io, 22, 26, 34, 58, 73 fluvialis brevis, Io, 35 fluvialis lyttonensis, Io, 35 245 188 245 264, 277 187 fluviatilis, Ancylus, 400 Fontelicella, 103-110 californiensis, 103-109 cedrosensis, 108 hendersoni, 104-109 idahoensis, 107-109 intermedia, 108 longinqua, 108 micrococcus, 109 pilsbryana, 108 robusta, 109, stearnsiana, 107, 108 truckeensis, 108 fontinalis, Salvelinus, 11 Forcipulata, 115 formosana, Oncomelania, 81-102 MALACOLOGIA Fragilaria, 68 brevistriata, 68 capucina, 68 construens, 68 construens subsalina, 68 frigida, Yoldiella, 203 frondosus, Dendronotus, Fronsella, 184, 185 ohshimai, 185 Fryeria, 264, 279 rüppelli, 264, 279 fulvescens arenarius, Murex, 229 funebris, Kentrodoris, 264, 276 furcigerum, Staurastrum, 67 fuscata, Embletonia, 351 fuscus, Laevapex, 42, 43 fuscocineria, Mertensiothuria, Gadus, 198 morhua, 198 galba, Haminoea, Galeomma, 184 Gasterosiphon, 351, 365 188 241 116, 127, 138, 145, 146, 151, 173, 175 116, 127, 146 81, 113, 134, 140, 143, 146, 186, 235 Gastropteridae, 357, 360, 362, 366, 371 Gastropteron, 361 geminella, Cylindrocapsa, 67 gemmata, Mylitta, 189 gibba, Rhopalodia, 67, 68 gibbosus, Eupomotis, 10 glabra, Litigiella, 185 glabra, Montacuta, 185 glabratus, Australorbis, glauca, Smaragdinella, Globiferina, 283 noumeae, 283 globulosa, Hydromyles, 362 Glossodoris, 245, 248, 272, 273 fidelis, 245 hilaris, 248 obscura, 273 Golfingia, 185 vulgare, 185 Gomphonema, 67, 68 constrictum, 68 subtile, 68 vibrio, 67 Goniobasis, 1-80 avachnoidea, 36 clavaeformis, 36, 58 deimatis, Gastropoda, 81, 95 236, 238 INDEX, VOL. Ш 449 comalensis, 53 emeryensis, 46 laqueata, 9, 36, 38, 40, 58 livescens, 1-80 livescens barronensis, 53 livescens correcta, 9, 38, 53, 55, 56, 70 livescens michiganensis, 53 multicarinata, 10 mutabilis, 36 proxima, 36 pulchella, 70 virginicum, 8, 35, 36, 51, 53, 58 gorgonocephala, Cercaria, 69 gouldiana, Bulla, 360, 364 gracilis, Navicula, 67 grandis, Anodonta, 42 grandis, Cliopsis, 365 granifera, Thiara, 3 granulata, Morula, 211-233 gvanulatus, Brachidontes, 186 grevillii, Desmidium, 67 grisea, Berthella, 264, 271 groenlandica, Leptasterias, 115 grunniens, Aplodinotus, “0 guamensis, Sacculosiphonaria, 236, 256, 257 guamensis, Siphonaria, 236, 255-257 Gymnodorididae, 236, 264, 277 Gymnodoris, 236, 249, 250 bicolor, 236, 249, 250 maculata, 250 Gymnosomata, 358, 362, 363, 365, 366, 368, 369 gyrina, Physa, 42, 43 Gyrosigma, 67, 69 kútzingii, 67, 69 Gyrotoma, 9, 38 Halgerda, 264, 276 elegans, 264, 276 Halimeda, 266, 270 Haliotis, 380, 381 Hallaxa, 264, 273 decorata, 264, 273 Haloa, 240 Haminoea, 235-243, 331, 358, 364, 369, 370 aperta, 243 binotata, 240 binotata japonica, 240 callosa, 241 crocata, 240, 241 elegans, 244 galba, 241 linda, 235, 236, 241-244 musetta, 235, 236, 239, 241 navicula, 364 nigro punctata, 240 ovalis, 243 rotundata, 243 simillima, 241 solitaria, 364 vitrea, 243 hamva, Pleurobranchaea, 348 Hancockia, 350 californica, 350 hanleyi, Bedeva, 229 hantzschiana, Nitzschia, 69 Harmothoé, 189 lunulata, 189 hawaiiense, Ctenosculum, 114 heathiana, Ischnochiton, 186 hedgpethi, Elysia, 365 Hedylopsidae, 357, 365 Hedylopsis, 365 suecica, 365 Helioperca, 10 incisor, 10 Heliopora, 267, 275, 277, 278 Helisoma, 11, 42 anceps, 42 trivolvis, 11, 42, 43 Helix, 311, 386, 420, 428 pomatia, 311, 420 Hemiaster, 187 hendersoni, Amnicola, 109 hendersoni, Fontelicella, 104-106 Hermaea, 356 bifida, 356 coivala, 356 dendritica, 356 Hermaeina, 336, 353, 356, 365, 370 smithi, 336, 353, 365 Hermissenda, 336-338, 345 crassicornis, 336-338, 345 Herviella, 235, 251-253, 263, 283 affinis, 251 claror, 235, 251-253 exigua, 251 mietta, 235, 252, 253 yatsui, 251, 253, 283 heterocyathi, Jousseaumiella, 185 Heterocyathus, 185 aequicostatus, 185 450 MALACOLOGIA Heterodonta, 442 heterophylla, Populus, 45 Heteropsammia, 185 michelini, 185 heteropsammiae, Jousseaumiella, 185 heterovalvata, Achnanthes exigua, 68 Hexabranchidae, 264, 271 Hexabranchus, 264, 271 marginatus, 264, 271 Hiatella, 203 arctica, 203 Hiatellidae, 197, 198 hilaris, Glossodoris, 248 hilaris, Hypselodoris, 236, 246, 248, 249, 273 Hippoglossoides, 198 platessoides, 198 hirasei, Succinea, 311, 321 hirsuta, Trichomya, 186 hirundinina, Chelidonura, Holothuria, 188,212 | atra, 212 curiosa, 188 holothuricola, Megadenus, Holothuroidea, 187 263, 265 hombergi, Tritonia, 345, 365 Hormomya, 186 multiformis, 186 horticola, Succinea, 311, 321 hupensis, Oncomelania, 82, 97, 98 huroni, Plagioporus sinitsini, 70 hyalinum, Phyllodesmium, 264, 280, 283 Hydatina, 346 Hydatinidae, 327, 345, 346, 366, 371 Hydrobia, 104, 105 truckeensis, 104 Hydrobiidae, 81, 103-106 Hydrobiinae, 103 Hydromyles, 362, 368 globulosa, 362 Hypselodoris, 236, 246-249, 263, 268, 272, 273 crossei, 273 cuis, 263, 269, 272, 273 diardii, 273 hilaris, 236, 246-249, 273 marenzelleri, 273 nigrostriata, 273 vansoni, 273 runcinata, 273 semperi, 273 tenuilinearis, 273 134, 143, 173 idahoensis, Amnicola, 109 idahoensis, Fontelicella, 107, 109 illus, Stiliger, 263, 264, 267-269 Io, 22, 26, 34, 35, 38, 73 fluvialis, 22, 26, 34, 58, 73 fluvialis brevis, 35 fluvialis lyttonensis, 35 Illex, 288, 303 illecebrosus, 288, 303 illus, Ercolania, 264, 267-269 indecora, Discodoris, 275 incisor, Helioperca, 70 incisum, Isognomon, 225 inhaerens, Leptosynapta, 188 inornata, Chelidonura, 263, 265 integra, Physa, 42, 43, 429 intermedia, Fontelicella, 108 intermedia, Pomatiopsis, 104, 108 iris, Micromya, 42, 43 Ischnochiton, 186 conspicuus, 186 heathiana, 186 magdalenensis, 186 islandica, Amauropsis, 203 Isognomon, 225, 226 costellatum, 225 incisum, 225 Janolus, 351 comis, 351 japonica, Asterophila, 111-181 japonica, Haminoea binotata, 240 japonicum, Schistosoma, 81 jenisseae, Cyrtodaria, 202-204. Jousseaumia, 185 Jousseaumiella, 184 concharum, 185 heterocyathi, 185 heteropsammiae, 185 Juliacea, 366 juliana, Aplysia, 212 Juliidae, 355, 370 juvenca, Chroonodoris, 248 Kellia, 184-186, 189 deshayesii, 185 laperousii, 186 rubra, 185, 186 Kentrodoris, 264, 276 funebris, 264, 276 kurriana, Cyrtodaria, kiitzingii, Gyrosigma, kwansae, Succinea, Labidoplax, 188 digitata, 188 197-205 67, 69 311/381 INDEX, VOL. III 451 labifera, Discodoris, 276 lactea, Chromodoris, 245 lacustris, Coscinodiscus, 68 lacustris, Navicula, 69 Laevapex, 42, 43 fuscus, 42, 43 laevis, Patinapta, 188 Lamprohaminoea, 236, 242-244 cymbalum, 236, 242-244 Lampsilis, 42, 43, 70 luteola, 10 siliquoidea, 42, 43 Lamellariidae, 114 lanceolata, Achnanthes, 68 lanceolata, Cymbella, 67 Langerhansia, 185 cornuta, 185 laperousii, Kellia, 186 lapillus, Nucella, 229, 231 laqueata, Goniobasis, 9, 36, 38, 40, 58 Lasaea, 184, 186, 187 cistula, 186 miliaris, 186 vubra, 187 scalaris, 186 subviridis, 186 lata, Chromodoris, 245 lata, Pinnularia, 69 Lathophthalmus, 236, 238, 239 smaragdinus, 236, 238 latifolia, Sagittaria, 45 latifolia, Typha, 45 latipes, Elysia, 271 Lebistes, 14 reticulatus, 14 Leersia, 45 Lehmannia, 311 marginata, 311 Leptasterias, 115, 116 polaris, 115 groenlandica, 115 Lepton, 184-189 clarkiae, 185, 186 longipes, 186, 189 nitidum, 189 parasiticum, 187 rude, 189 squamosum, 186, 189 subtrigonum, 186 Leptonacea, 419, 423, 424 Leptosynapta, 188 inhaerens, 188 ooplax, 188 Leptoxis, 9, 58 Leptychaster, 115 lepomis, Plagioporus, 10 lewisii, Pleurocera, 56, 58 libertina, Semisulcospira, 3 Libratula, 184 plana, 184 lignarius, Scaphander, 359, 361 Liguus, 424 Limanda, 198 ferruginea, 198 Limapontia, 342, 353-357, 365, 370 capitata, 365 Limapontiidae, 365 limosa, Amnicola, linda, Haminoea, lineolata, Chromodoris, Lissodoris, 247 Lithasia, 8, 9, 38, 58, 73 venusta, 58 Lithasiopsis, 9 Lithoglyphus, 105, 107 Lithophaga, 183 Litigiella, 185 glabra, 185 liturata, Discodoris, 275 Littorina, 35, 337, 400 littorea, 400 livescens barronensis, Goniobasis, 55 livescens correcta, Goniobasis, 9, 36, 38, 53, 55, 56 livescens, Goniobasis, 1-80 livescens michiganensis, Goniobasis, 53 42, 43 235, 236, 241-244 264, 272 livida, Elysia, 270 Lobiger, 356 Loligo, 287, 288, 303, 304 opalescens, 288, 303, 304 vulgaris, 287, 288, 303, 304 lonca, Catriona, 263, 264, 274, 275, 279, 280 236, 244, 264, 267 longicauda, Stylocheilus, longicirrha, Ennoia, 283 longicornis, Myja, 280 longinqua, Amnicola, 104, 108 longinqua, Paludestrina, 104 longinqua, Fontelicella, 108 longipes, Ceratobornia, 186 longipes, Lepton, 186, 189 longissima, Eunereis, 186 lora, Discodoris, 263, 268, 269, 273- 275 452 Loxosoma, 185, 186 Lucinacea, 419-425 Lucinidae, 422, 424 ludwigi, Entocolax, 117, 143 lugubris, Pleurobranchus, 264, 271 lunata, Ephippodonta, 184, 189 lunulata, Harmothoé, 189 luteola, Lampsilis, 10 luteopunctata, Doridopsis nigra, 250 lutescens, Discodoris, 276 luteus, Phanerophthalmus, 263, 264 53, 311, 385, 420, 428 stagnalis, 53, 311, 420 lyrifera, Brissopsis, 187 Lysiosquilla, 183, 189 maculata, 189 scabricauda, 189 lysiosquillina, Phlyctaenachlamys, lyttonensis, Io fluvialis, 35 macdougalli, Ephippodonta, macrostoma, Proterometra, Mactromyidae, 422, 424 maculata, Gymnodoris, maculata, Lysiosquilla, maculata, Onchidella, 256 maenas, Carcinides, 189 magdalenensis, Ischnochiton, magnifica, Doris, 249 maillardi, Dolabrifera, major, Entovalva, 188 major, Callianassa, 189 major, Upogebia, 189 maoria, Divariscintilla, 189 marenzelleri, Hypselodoris, marginata, Elysia, 264, 270 marginata, Lehmannia, 311 marginatus, Hexabranchus, Marikellia, 184, 186 vincentensis, 184 mavrilandia, Quercus, Mastogloia, 69 smithü, 69 smithii cryptocephala, maua, Catriona, 279 maxillosus, Polydontes, 186 meckelii, Pleurobranchaea, 348 mediterranea, Caliphylla, 356 mediterraneum, Pneumoderma, Lymnaea, 189 184, 189 70, 71 250 189 186 244 273 264, 271 45 69 365 Megadenus, 116, 129, 134, 138, 143, 151, 172-175 arrhynchus, 116, 129, 134, 151, 172- 175 MALACOLOGIA holothuricola, voeltzkowi, 143, 173 cysticola, 151 melaena, Dendrodoris, 250 Melanella, 138, 151, 175 equestris, 151 polita, 151 Melanellidae, Melania, 8,9 virginica, 35 Melanogrammus, aeglefinis, 198 Melanoides, 1 tuberculatus, 1 Melanopsis, 22 dufourei, 22 Melosira, 68 ambigua, 68 varians, 68 meridionalis, Spatangus, Mertensiothuria, 188 fuscocineria, 188 Mesodon, 311 appressa, 311 Mesogastropoda, 229, 231, 335, 344, 345 Miamirinae, 264, 273 michelini, Heteropsammia, 185 michiganensis, Goniobasis livescens, micra, Amnicola, 104, 108 micra, Fontelicella, 108 Micrasterias, 67 radiata, 67 Microamnicola, 103, 109 micrococcus, Amnicola, micrococcus, Fontelicella, Microhedylidae, 357 Micromya, 42, 43 iris, 42, 43 Microspora, floccosa, Miesea, evelinae, mietta, Herviella, miliaris, Lasaea, mimetica, Bosellia, 353 minima, Navicula, 69 minor, Navicula tuscula, minuta, Diaphana, 364 minutissima cryptocephala, Achnanthes, 68 134, 143, 174 111-181 198 187 53 103, 109 109 67 67 279, 351, 372 279, 351 235, 252, 253 186 69 68 117 minutissima, Achnanthes, mirabilis, Entoconcha, INDEX, VOL. II mirabilis, Entovalva, 188 missouriense, Ribes, 45 Mitra, 185 modesta, Alderia, 354 Mollusca, 184, 186 Molpadicola, 135, 145, 172-175 orientalis, 135, 145, 172 Monoplacophora, 419 Monotocardia, 171 Montacuta, 184-187 christenseni, 187 donacina, 188 echinocardiophila, 187 ferruginosa, 187 glabra, 185 percompressa, 188 perezi, 185 phascolionis, 185, 186 semiradiata, 187 substriata, 187 morhua, Gadus, 198 Moridilla, 282 Morula, 211-233 granulata, 211-233 nodus, 212 Moroteuthis, 287-307 ingens, 287-307 robsoni, 289, 299 mucosum, Thalassema, 185 Mucronalia, 129, 138, 173, 175 eburnea, 129 variabilis, 173, 175 Muessa, 263, 264, 280-283 evelinae, 263, 264, 280-283 Mudalia, 8, 9, 35, 72 dissimilis, 35 muloc, Antiopella, 351 multicarinata, Goniobasis, 10 multiformis, Brachidontes, 186 multiformis, Hormomya, 186 murakamii, Ephippodonta, 184 Murex, 185, 228, 229 erinaceus, 231 fulvescens arenarius, 229 pomum, 229 Muricacea, 211, 230 muricata, Onchidoris, 365 musetta, Haminoea, 235, 236, 239, 241 mutabilis, Goniobasis, 36 Mya, 399-418 avenaria, 399-418 truncata, 399-418 truncata ovata, 399-418 pseudoarenaria, 399-418 truncata typica, 399-418 truncata uddevallensis, 399-418 myaciformis, Pseudopythina, 189 Myja, 280 longicornis, 280 Mylitta, 184, 189 deshayesiana, 189 gemmata, 189 tasmanica, 189 Myriophyllum, 45 tenellum, 45 Mysella, 183-189 bidentata, 183-189 Mytilus, 186, 189 californianus, 186 edulis, 189 nana, Akera, 186 Nassarius, 185 trivattatus, 185 Natica, 203 clausa, 203 Nasturtium, 45 officinale, 45 natans, Potamogeton, 45 Natricola, 103, 108, 109 Nautilus, 379 Navicula, 67, 69 cryptocephala, 69 cryptocephala veneta, 69 exigua, 69 gractlis, 67 lacustris, 69 minima, 69 oblonga, 69 pupulla, 69 vadiosa, 67, 69 radiosa tenella, 69 rhynococephala, 67, 69 rostella, 69 tuscula, 69 tuscula minor, 69 viridula, 69 navicula, Haminoea, 364 naviculiformis, Cymbella, 68 neapolitana, Spurilla, 351 Nembrotha, 250, 264, 277 nigerrima, 264, 277 Neopilina, 419, 420 Nereis, 186 neritea, Cyclope, 221, 229 neuvillei, Cyrtodaria, 202, 203 nicaraguana, Dolabrifera, 244 453 454 nigerrima, Nembrotha, 264, 277 nigra, Cyerce, 264, 269 nigra, Dendrodoris, 236, 250, 264, 277 nigva, Doris, 250 nigra luteopunctata, Doridopsis, 250 nigricans, Onchidella, 256 nigricans, Occidentella, 256 nigrocincta, Aplysia parvula, 266 nigrocincta, Pruvotaplysia parvula, 266 nigropunctata, Haminoea, 240 nigrostriata, Hypselodoris, 273 Nipponomontacuta, 184 actinariophila, 184 Nitella, 45 flexilis, 45 nitidum, Lepton, Nitocris, 9, 36 carinata, 36 Nitzschia, 69 acicularis, 69 hantzschiana, 69 sinuata, 69 nobilis, Anisodoris, nobilis, Phyllidia, nobilis, Phyllidiella, nodus, Morula, 212 nonatoi, Costasiella, 267 Nonsuctoria, 236, 264, 277 normani, Cymbella, 68 nosophora, Oncomelania, Notarchus, 364 Notarchinae, 236, 264, 267 Notaspidea, 264, 271, 345, 346, 371, 372 noto, Ercolania, 269 noto, Stiliger, 269 noumeae, Globiferina, 283 Noumeaella, 263, 264, 274, 275, 280- 282 189 338 264, 278 264, 278 82, 97, 98 282 263, 264, 274, 275, 280-282 229, 231, 386 229, 231 421 264, 271, 345, 365, 372 185 curiosa, rehderi, Nucella, lapillus, Nuculanidae, Nudibranchia, nudus, Sipunculus, Nuphar, 45 variegatum, 45 Numphaea, 45 odorata, 45 oblonga, Navicula, 69 oblonga, Serridens, 186 obscura, Glossodoris, 273 MALACOLOGIA obscura, Occidentella, 254 obscura, Onchidella, 254 occidentalis, Blepharipoda, occidentalis, Cotylogaster, Occidentella, 254, 256 nigricans, 256 obscura, 254 reticulata, 256 ocellata, Bouvieria, 348 ocellatus, Plakobranchus, ocellifera, Costasiella, odorata, Nymphaea, 45 Odostomia, 175, 185 perezi, 185 Oegopsida, 287 officinale, Nasturtium, 45 ohshimai, Entovalva, 188 ohshimai, Fronsella, 185 ohshimai, Peregrinamor, Ommastrephes, 288 sloanei, 288 Onchidella, 235, 253, 255, 256, 367 celtica, 254 evelinae, 235, 253, 255, 256 flavescens, 256 maculata, 256 nigricans, 256 obscura, 254 palelloides, 254, 256 reticulata, 256 Onchidellidae, 254 Onchidiacea, 236, 254, 263, 264 Onchidiidae, 236, 263, 264, 327, 366, 367 189 69, 70, 72 264, 270 267 189 Onchidorididae, Onchidoris, 365 muricata, 365 Oncomelania, 29, 40, 60, 81-102 formosana, 81-102 hupensis, 82, 97, 98 nosophora, 82, 97, 98 quadrasi, 60, 99, 100 Onychoteuthidae, 287, 289 ooplax, Synapta, 188 365 ooplax, Leptosynapta, 188 Ophiocnida, 188 brachiata, 188 Ophiuroidea, 88 Opisthobranchia, 327-378 oratoria, Squilla, 189 135, 145, 172 269 orientalis, Molpadicola, orientalis, Phyllobranchillus, INDEX, VOL. Ш ornata, Elysia, 270 Oscaniella, 271 purpurea, 271 Ostrea, 226, 400 ovalis, Haminoea, 243 ovalis, Succinea, 311, 322 Oxyloma, 310 Oxynoacea, 364, 366 Oxynoe, 356, 364 Oxynoidae, 364, 370 Oxytrema, 8, 71 Pachychilus, 9 Pachymania, 22 pacifica, Petalifera petalifera, 264, 267 Padina, 266, 270 Paedophoropodidae, 112, 115, 126, 138, 146, 159, 166-175 Paedophoropus, 135, 138, 145, 151, 168, 170-175 dicoelobius, 138, 151, 168, 172 Paliolla, 250 pallida, Discodoris, 275, 276 pallida, Embletonia, 351 palma, Discodoris, 276 Paludestrina, 104, 108 cedrosensis, 104, 108 longinqua, 104 stearnsiana, 104 paludosa, Pomacea, 419-431 palustris, Quercus, 45 pancerii, Ercolania, 267 pancerii, Stiliger, 267 papillosa, Aeolidia, 345, 351 papyrifera, Betula, 45 Parabornia, 184, 189 squillina, 189 Paragonimus, 3 westermani, 3 parallela, Rhopolodia, 69 parasiticum, Lepton, 187 Parastilifer, 129, 134, 138, 173, 175 sibogae, 134 Parenteroxenos, 117, 133, 170, 175 parma, Echinarachnius, 200, 201 Partulida, 365 spiralis, 365 parvula, Aplysia, 263, 266 parvula nigrocincta, Aplysia, 266 parvula nigrocincta, Pruvotaplysia, parvula, Pruvotaplysia, 263, 266 patelloides, Onchidella, 254, 256 266 455 188 188 Patinapta, crosslandi, laevis, 188 pediculus, Cocconeis, 68 pedroana, Rochefortia, 189 pellucida, Amphipleura, 69 pellucida, Polybranchia, 269 pellucidum, Phascolosoma, 185 Pelseneeria, 143,151, 163, 169, 172, 175 stylifera, 143, 163, 169 Pelseneeriidae, 112, 172, 175 percompressa, Montacuta, 188 Peregrinamor, 184, 189 ohshimai, 189 perezi, Auristomia, perezi, Montacuta, perezi, Odostomia, Peronia, 263, 264 peronii, 263, 264 peronii, Peronia, 263, 264 peronii, Pleurobranchus, 264, 271 perrieri, Devonia, 188 perrieri, Entovalva, 188 petalifera pacifica, Petalifera, Petalifeva, 264, 267, 364 petalifera pacifica, 264, 267 pfeifferi, Biomphalaria, 379-398 Phanerozonia, 115 pilsbryana, Amnicola, pilsbryana, Fontelicella, pilsbryi, Amnicola, 108 Pinnularia, 67, 69 lata, 69 viridis, 67 Pinus, 45 vesinosa, 45 Phanerobranchia, Phanerophthalmidae, Phanerophthalmus, luteus, 263, 264 Phascolion, 185, 186 strombi, 185, 186 phascolionis, Montacuta, Phascolosoma, 185 elongatum, 185 pellucidum, 185 Philinacea, 236, 263, 265 Philine, 337, 341, 359-364 alba, 359, 361 aperta, 359, 361, 362 scabra, 364 185 185 185 264, 267 104, 108 108 236, 264, 277 263, 265 239, 263, 264, 370 185, 186 456 | MALACOLOGIA Philinidae, 340, 341, 357, 360-371 Philinoglossa, 370 Philinoglossidae, 327, 358, 366, 370, 371 philippi, Tripylaster, 187 Phlyctaenachlamys, 184, 189 lysiosquillina, 189 Phyllidia, 264, 277, 278 nobilis, 264, 278 pustulosa, 264, 278 varicosa, 264, 277 Phyllidiella, 264, 278 nobilis, 264, 278 pustulosa, 264, 278 Phyllidiidae, 264, 277 Phyllobranchillidae, 264, 269 Phyllobranchillus, 264, 269 orientalis, 269 prasinus, 269 Phyllodesmium, 264, 280, 283 hyalinum, 264, 280, 283 Physa, 42, 43, 311, 429 acuta, 311, gyrina, 42, 43 integra, 42, 43, 429 placentula, Cocconeis, 68 plactorhychus, Axius, 189 Plagioporus, 69, 70 lepomis, 10 sinitsini, 69, 70 sinitsini huroni, 10 Plakobranchidae, 264, 270 Plakobranchus, 264, 270 ocellatus, 264, 270 plana, Libratula, 184 Planorbidae, 379 platessoides, Hippoglossoides, 198 Platydoridinae, 264, 277 Platydoris, 264, 277 cruenta, 264 flammulata, 264, 277 scabra, 264, 277 Pleurobranchacea, Pleurobranchaea, hamva, 348 meckelii, 348 Pleurobranchidae, 264, 271, 366, 372 Pleurobranchus, 264, 271 lugubris, 264, 271 peronii, 264, 271 Pleurocera, 1-80 acuta, 1-80 264, 271 347, 348, 364 acutum tractum, 10 canaliculata, 9, 36, 58, 63 canaliculatum undulatum, curtum, 36 lewisii, 56, 58 subulare, 10, 35 subulareforme, 36 unciale, 36 unciale curtatum, 36 verrucosa, 8,9 Pleuroceridae, 106 Pneumoderma, 362, 365 mediterraneum, 365 Pneumodermatidae, 365 polaris, Leptasterias, 115 polita, Melanella, 151 Polybranchia, 269 pellucida, 269 Polydontes, 186 maxillosus, 186 Polygyra, 311 appressa, 311 Polygyridae, 311 Pomacea, 419-431 paludosa, 419-431 pomatia, Helix, 311, 420 Pomatiopsinae, 104 9, 18-40 Pomatiopsis, 29, 40, 82, 99, 103, 108, 109 cincinnatiensis, 29, 82, 99 intermedia, 104, 108 robusta, 103, 109 Pomatogeton, 45 natans, 45 praelongus, 45 vichardsonii, 45 Pomoxis, 10 sparoides, 70 pomum, Murex, 229 Populus, 45 heterophylla, 45 Porifera, 184 Porostomata, 236, 264, 277 Portlandia, 205, 400 aestuariorum, 205 arctica, 400 Potadoma, 22 Potidoma, 184-186 clarkiae, 185 subtrigona, 186 praelongus, Pomatogeton, 45 prasinus, Phyllobranchillus, 269 INDEX, VOL. II 245 103571225113, 171, 231, 331, 343, 345 prostrata, Cymbella, 68 Protankyra, 187 bidentata, 188 similis, 188 Proterometra, macrostoma, ‘10, 71 sagittaria, “0, 71 Protococcus, 67 viridis, 67 Pruvotaplysia, 263, 266 parvula, 263, 266 parvula nigrocincta, 266 proxima, Goniobasis, 36 Pseudopythina, 184, 186, 189 compressa, 189 myaciformis, 189 rugifera, 186, 189 subsinuata, 189 Pseudosacculidae, Pseudosacculus, Pseudovermis, Pteraeolidia, semperi, 264, 280 Pterotrachea, 420 pugettensis, Upogebia, 189 pulchella, Goniobasis, 70 pulchella, Vallonia, 311 pulchellum, Dictyosphaerium, 67 Pulmonata, 311, 343, 366, 367 pulmonica, Aplysia, 263, 266 pulmonica, Varria, 263, 266 punctata, Aplysia, 364 preciosa, Doris, Prosobranchia, 70, 71 171 114 351, 372 264, 280 punctocaelatus, Acteon, 336-338 pupulla, Navicula, 69 purpurea, Oscaniella, 271 purpureus, Spatangus, 187 pustulosa, Phyllidia, 264, 278 pustulosa, Phyllidiella, 264, 278 putris, Succinea, 311 Pyramidellidae, 171, 172, 175, 343, 345, 351, 352, 357, 365, 366 Pythinella, 185 cuneata, 185 quadrasi, Oncomelania, 99, 100 Quercus, 45 alba, 45 coccinea, 45 marilandia, 45 palustris, 45 457 radiata, Micrasterias, 67 vadicans, Rhus, 45 vradiosa, Navicula, 67, 69 radiosa tenella, Navicula, 69 vansoni, Hypselodoris, 273 тата, Elysia, 263, 264, 268-271 rehderi, Noumeaella, 263, 264, 275, 280- 282 vesinosa, Pinus, 45 veticulatus, Lebistes, 14 reticulata, Occidentella, reticulata, Onchidella, retroversa, Spiratella, Retusa, 263, 264 Retusidae, 263, 265, 327, 357, 358, 366, 370, 371 256 256 365 Rhizorus, Rhodope, 346 Rhopalodia, 67, 68 gibba, 67, 68 parallela, 69 Rhus, 45 copallina, 45 vadicans, 45 vernix, 45 rhynococephala, Navicula, Ribes, 45 missouriense, 45 richardsonii, Pomatogeton, 45 vicina, Drupa, 211-233 rimsky-korsakovi, Entocolax, 360, 371 67, 69 143, 170, 174 346 346 Ringicula, Ringiculidae, Risbecia, 247 Rizzolia, 253 robusta, Fontelicella, robusta, Pomatiopsis, Rochefortia, 189 pedroana, 189 Rochelfortia, 184, 185 cuneata, 185 vostella, Navicula, 69 rotundata, Catinella, 309, 310, 313, 321 109 103, 109 rotundata, Haminoea, 243 rubra, Dendrodoris, 250 rubra, Kellia, 185, 186 rubra, Lasaea, 187 rubrum, Acer, 45 rude, Lepton, 189 rufomarginata, Casella, 264, 273 vugifeva, Pseudopythina, 186, 189 458 MALACOLOGIA rugosus, Strophitus, 42, 43 siliqua, Cyrtodaria, 197-210 rugulosus, Anthenoides, 116 siliquoidea, Lampsilis, 42, 43 Runcina, 331, 334, 358, 360, 370, 371 simillima, Haminoea, 241 runcinata, Chromodoris, 248 sinensis, Clonorchis, 3 runcinata, Hypselodoris, 273 sinitsini huroni, Plagioporus, 69, 70 Runcinella, 360 sinitsini, Plagioporus, 69, 70, 71 Runcinidae, 327, 358, 360, 366, 370, 371 sinuata, Nitzschia, 69 rupestris, Ambloplites, “0 Siphonaria, 236, 256, 257, 367 rüppelli, Fryeria, 264, 279 cochleariformis, 257 Sacculosiphonaria, 236, 256, 257 guamensis, 236, 255, 256, 257 cochleariformis, 257 Siphonariacea, 236 guamensis, 236, 256, 257 Siphonariidae, 236 Sacoglossa, 264, 267, 327, 337, 352- Sipuculus, 185 354, 364, 369, 370 nudus, 185 Sagittaria, 45 Sipunculoidea, 184, 185 latifolia, 45 Smaragdinella, 236-238 sagittavia, Cercaria, 1 calyculata, 236-238 sagittavia, Proterometra, ‘0, 71 glauca, 236, 238 Salvelinus, 171 viridis, 236, 238 fontinalis, 71 | Smaragdinellidae, 236 scabra, Philine, 364 smaragdinus, Lathophthalmus, 236, 238 scabra, Platydoris, 264, 277 smithii cryptocephala, Mastogloia, 69 scabricauda, Lysiosquilla, 189 smithii, Mastogloia, 69 scalaris, Lasaea, 186 smithi, Hermaeina, 336, 353, 365 Scaphander, 337,359, 360, 361, 369, 371 Soleolifera, 236, 263, 264 lignarius, 359, 361 solitaria, Haminoea, 364 Scaphandridae, 357-371 sparoides, Pomoxis, 10 scapula, Dolabella, 266 Spatangus, 187 schiemenzi, Entocolax, 117 mevidionalis, 187 Schistosoma, 81 purpureus, 187 japonicum, 81 Sphaerocystis, 67 schroeteri, Sphaerocystis, 67 schroeteri, 67 schwanwitschi, Entocolax, 151, 159, 160, sphaerophora, Anomoeoneis, 67. 163, 170 Spinulosa, 115 Scintillona, 184, 188 spiralis, Partulida, 365 zelandica, 188 Spiratella, 362, 363, 365 Scioberetia, 184, 187 retroversa, 365 australis, 187 Spiratellidae, 365 Scirpus, 45 Sphaerumbonella, 184 americanus, 45 brunelli, 184 semiradiata, Montacuta, 187 splendida, Aglaja, 263, 264 Semisulcospira, 3 Spondylus, 186 libertina, 3 Spurilla, 351 semperi, Entovalva, 188 neapolitana, 351 semperi, Hypselodoris, 273 Spyrogyra, 14, 45 semperi, Pteraeolidia, 264, 280 stagnalis, Lymnaea, 53, 311, 420 Sepiidae, 288 Stagnicola, 311 Serridens, 184, 186 emarginata, 311 oblonga, 186 Staurastrum, 67 shimekii, Ferrissia, 60 furcigerum, 67 sibogae, Parastilifer, 134 Stauroneis, 67, 69 sibogae, Stilifer, 129 anceps, 67, 69 stearnsiana, Fontelicella, stearnsiana, Paludestrina, 104 stellata, Upogebia, 189 Stenoglossa, 211, 230, 231 Stiliferidae, 112-181 Stilifer, 116, 129, 135, 138, 151, 163, 172, 173, 175 celebensis, 135, 138, 151, 172 sibogae, 129 stylifer, 163 Stiligeridae, 264, 267, 365 Stiliger, 263, 264, 267-269, 356 akkeshiensis, 269 illus, 263, 264, 267-269, noto, 269 pancerii, 267 trinchesei, 269 stolonifera, Cornus, 45 Stomatopoda, 189 Strephobasis, 9 striata, Trevelyana, 250 strombi, Phascolion, 185, 186 Strombus, 35 Strophitus, 42, 43 rugosus, 42, 43 stylifera, Pelseneeria, stylifer, Stilifer, 163 Stylocheilus, 236, 244, 264, 267 ‚ longicauda, 236, 244, 264, 267 Stylommatophora, 309, 311 Stylophora, 278 subglobosa, Anculosa, 36 subsalina, Fragilaria construens, subsinuata, Pseudopythina, 189 substriata, Monacuta, 187 subtile, Gomphonema, 68 subtrigona, Potidoma, 186 subulaeforme, Pleurocera, 36 subulare, Pleurocera, 10, 35 subtrigonum, Lepton, 186 subviridis, Lasaea, 186 Succinea, 310 avara, 310 campestris vagans, 310 hivasei, 311, 321 horticola, 311, 321 kwansae, 311, 321 ovalis, 311, 321, 322 putris, 311, 321 vagans, 310 Succineidae, 309, 311, 321 suecica, Hedylopsis, 365 INDEX, VOL. II 107, 108 143, 163, 169 68 susa, Catriona, 280 squamosum, Lepton, Squilla, 189 oratoria, 189 squillina, Pavabornia, 189 Synapta, 188 186, 189 ooplax, 188 Synapticola, 184, 188 Synedra, 68 ulna, 68 vaucheriae, 68 Tabellaria, 67, 68 fenestra, 67, 68 Taenioglossa, 151, 171, 174 Tambja, 250 Tancrediidae, 422, 424 Tapes, 400 Tarebia, 3 tasmanica, Mylitta, 189 tenella, Navicula radiosa, 69 tenellum, Myriophyllum, 45 tenuilinearis, Hypselodoris, 273 teresiae, Turricula, 186 Tetronychoteuthis, 289 texana, Cateinella, 309, 310, 321 Thaira, 3 granifera, 3 Thalassema, 185 mucosum, 185 thalassemicola, Achasmea, 185 Thecosomata, 362-368 thomasi, Ulmus, 45 Thyasiridae, 422, 424 Thyonicola, 117 Thyreopsis, 184 coralliophila, 184 thysanopoda, Elysia, Todarodes, 288 sagittatus, 288 tomentosa, Carya, 45 tornatilis, Acteon, 337, 338 Tornatina, 358 torquata, Clymenella, 186 tractum, Pleurocera acutum, 10 transcaspica, Cyrtodaria, Trevelyana, 249, 250 bicolor, 249 striata, 250 Trichomya, 186 hirsuta, 186 Tridachia, 356 crispata, 356 264, 270 202, 203 459 460 MALACOLOGIA Triopha, 333, 345 carpenteri, 333, 345 trinchesei, Ercolania, 269 trinchesei, Stiliger, 269 Tripylaster, 187 philippi, 187 Tripylus, 187 triquetra, Dysnomia, 42 Tritonia, 345, 350, 351, 365 hombergi, 345, 365 Tritoniidae, 365 Trivia, 229, 231 trivittatus, Nassarius, 185 trivolvis, Helisoma, 11, 42, 43 Trochodota, 188 dendyi, 188 trochodotae, Entocolax, 117, 151, 159 Trochus, 381 truckeensis, Fontelicella, 108 truckeensis, Hydrobia, 104 Trypanostoma, 9 tuburculata, Archidoris, 365 tuberculatus, Melanoides, 3 tumidus, Unio, 410 Turbo, 226 Turbonilla, 175 turgida, Epithemia, 67 turnbullae, Ephippodonta, 184, 189 Turricula, 186 teresiae, 186 Turritella, 185 communis, 185 tuscula minor, Navicula, 69 tuscula, Navicula, 69 Typha, 45 latifolia, 45 Tyrinna, 276 Ulmus, 45 thomasi, 45 ulna, Synedra, 68 Ulva, 212 fasciata, 212 Umbraculidae, 366, 372 Unbraculum, 346, 371 unciale curtatum, Pleurocera, 36 unciale, Pleurocera, 36 undulatum, Pleurocera canaliculatum, 9, 18, 21-40 Ungulinidae, 422 Unicardiidae, 422 Unio, 410 tumidus, 410 Unionidae, 183 Upogebia, 186, 189 affinis, 189 deltaura, 189 major, 189 pugettensis, 189 stellata, 189 Urosalpinx, 226 cinerea, 226 urquisa, Catriona, 263, 264, 274, 275, 279, 280 uva, Doto, 351 vagans, Catinella, 310 vagans, Succinea, 310 vagina, Cyrtodaria, 203 vagum, Batrachospermum, 45, 68 Vallisneria, 45 americana, 45 Vallonia, 311 pulchella, 311 variabilis, Mucronalia, 173, 175 varians, Melosiva, 68 varicosa, Phyllidia, 264, 277 variegata, Dolabrifera, 244 variegatus, Chlorella, 67 variegatum, Nuphar, 45 Varria, 263, 265, 266 dactylomela, 263, 265 pulmonica, 263, 266 Vasconiella, 184, 189 vaucheriae, Synedra, 68 veneta, Navicula cryptocephala, 69 ventricosa, Cymbella, 68 . venusta, Chromodoris, 264, 272 venusta, Lithasia, 58 vermeta, Catinella, 309-325 Vermetus, 186 corallinaceus, 186 vernix, Rhus, 45 verrucosa, Angitrema, 9 verrucosa, Pleurocera, 8 vibrio, Gomphonema, 67 vincentensis, Marikellia, 184 virginicum, Buccinun, 8 virginicum, Goniobasis, 8, 35, 36, 51, , vivgula, Creseis, 333, 365 Virgulate, 10 xiphidiocercariae, 70 viridis, Elysia, 356 viridula, Navicula, 69 viridis, Pinnularia, 67 eg = INDEX, VOL. Ш viridis, Protococcus, 67 westermani, Paragonimus, 3 viridis, Smaragdinella, 236, 238 xiphidiocercariae, Virgulate, 70 Vites, 45 yatsui, Herviella, 251, 253, 283 aestivalis, 45 ylva, Discodoris, 263, 274-276 vitrea, Haminoea, 243 Yoldia, 400 Vitrohaminoea, 240 arctica, 400 voeltzkowi, Megadenus, 143, 173 Yoldiella, 203 Volutacea, 230 frigida, 203 voniheringi, Discodoris, 349 zebra, Epithemia, 68 vulgare, Golfingia, 184 zelandica, Scintillona, 188 vulgaris, Chara, 45 Zizyphinus, 185 vulgatum, Cerithium, 22 conuloides, 185 46 RA au [LA PER om y Г Y a, ` chy 56 “ 1 1 o Nu AUS LUTTE CP dde zu $ Xx A r Sa a i wiley ' Wa Y MALACOLOGIA 463 ABCTPAKT СИМБИОТИЧЕСКИЕ ДВУСТВОРЧАТЫЕ НАДСЕМЕЙСТВА ERYCINACEA Кеннет Босс Эта работа суммирует случаи симбиотического поведения между пред- ставителями пластинчатожаберных моллюсков надсемейства Erycinacea. Отдельные случаи комменсализма, мутуализма, даже эктопаразитизма, и, Ka- жется, эндопаразитизма представлены со всеми данными. Моллюски тут рас- сматриваются с точки зрения их отношений к хозяевам и в конце приложены некоторые замечания относительно причин таких симбиотических сожительств. АБСТРАКТ "КОЛЬЦА РОСТА" НА КЛЮВЕ КАЛЬМАРА MOROTEUTHIS INGENS) (OEGOSIDA: ONYCHOTEUTHIDAE) Мальколвм P. Кларкз Настоящая работа, с описанием циклов линий наростания на нижней мандибуле у Moroteuthis ingens, предлагается с целью обратить внима- ние на возможную связь циклами развития и временем роста кальмара. Это исследование основано на большом отборе клювов, добытых из желудков Ka- шелотов, пойманных у Дурбана. Тут описаны характерные особенности, KOTO- рые были использованы для определения (см. фиг. 1). В средней части бо- ковой поверхности стенок этих клювов заметны 4 особенности (фиг. 2): бороз- ды расходятся радиусами от кончика клюва до свободного края и параллельно ему, мелкие порожки или микрокольца и волнистые линии различной прозрач- ности. Микрокольца являются конечным пределом во время роста боковых стенок. Циклы ширины микроколец между кончиком и свободным краем ясно за- метны. Варианты формы циклов в 50 клювах описаны и покано, что первые 3- 4 цикла обыкновенно следуют по определенному рисунку, в то время как после- дующие значительно рознятся (фиг. 3). В продолжение жизни животного кон- чик клюва претерпевает очень мало изнашивания (ростральная длина колеб- лется между 0.7 и 2.0 см). Частота гистограми и среднее количество ми- кроколец каждого цикла указывают, что эти циклы не являются произвольными колебаниями только одной секреции, если бы даже эти колебания были диаго- нальными по отношению к последующим циклам и более узкими, чем предыдущие циклы. Рост клюва может быть выражен как увлечение длины стенок, т.е. расстояние между кончиком клюва и передним и внутренним углом боковой стенки (фиг. 2). Так как процесс роста длины стенки регистрируется рас- стоянием микроколец от конца клюва, то рост можно высчитать в обратном порядке. Увеличение размеров клюва с увеличением числа циклов было про- эктировано, также как расчет кривой в обратном порядке, зависит не от от- бора автора, а от выбора пищи кашелотов (фиг. 8). Обратный расчет длины стенки среди клювов постарше (с большим количеством циклов) выражен был более низкими цифрами, чем среди более молодых, вероятно, потому что мед- 464 MALACOLOGIA леннее растущие особи кальмаров живут дольше. Было проэктировано COOT- ношение длины стенки с размерами кальмаров (фиг. 10, 11). Время, Heo6xo-. димое для образования одного цикла, установлено не было, HO на основании | прежних исследований других головоногих можно предложить, ‘что этот период. может быть от 6 U до 12 месяцев. АБСТРАКТ МОРФОЛОГИЯ И ИСТОРИЯ ЖИЗНИ PLEUROCERA ACUTA И GONIOBASIS LIVESCENS (GASTROPODA: CERITHIACEA: PLEUROCERIDAE) Бонифаций Капили Дазо Сравнительно мало известно о семействе пресноводных крышечных ули- ток Pleuroceridae распространенных в Северной Америке, охватывающих или же родственных чернушкам, которые важны для паразтологии Дальнего Востока. Систематика их основана главным образом на характере раковины и нуждается в пересмотре. Произведены исследования 2-х видов, отнесен- ных к 2-м различным родам: Pleurocera acuta Rafinesque и Goniobasis livescens (Menke), взятые из 4-х участков в районе Анн Ap6op, штата Мичиган и из других мест в штатах Мичиган и Охайо, в США. Раковины и крышечки этих 2-х видов различны, но их анатомия и образ жизни настолько значительно близки, что их принадлежность к 2-м отдель- ным родам становится сомнительной. Различия в строении их раковин, хотя и вполне заметны, но не яв- ляются постоянными и почти незаметны в некоторых промежуточных особях. Pleurocera acuta приблизительно вдвое больше С. livescens. Хотя общая форма и пигментация тела очень сходны, но P. acuta OTIANMUaAET- ся более продолговатыми головой и хоботом и более длинными и более кону- сообразными щупальцами. У Р. асша нога меньше и более удлиненной формы, что, возможно, является приспособлением к жизни на дне и к рытью, в TO время как у С. livescens нога больше и круглее в сравнении с передней частью тела, что можно связать с привычным ползанием. Мантия и органы чувств, общая нервная система, морфология.дыхательной, выдели- тельной, кровеносной и мускульной систем у обоих видов очень сходны; раз- нятся они только размерами. У подсемейства Pleurocerinae y самцов от- сутствует пенис. У самок глубокое углубление в шее между правым щупаль- цем и подошвой ноги, а также мелкая канавка, ведущая к этому углублению, служат как органы размножения. В остальном общая схема органов размно- жения совпадает с таковыми у других переднежаберных моллюсков. Эти мол- люски раздельно - полые. В обоих видах органы размножения у каждого пола почти идентичны и находятся в том же положении. Сперма у них 2х типов: типичная эупиренная и ненормальная апиренная Формы. Эупренная сперма пе- редается самке в сперматофорах. к Северо-американские переднежаберные нуждаюся в чистой воде... За исключением рода Goniobasis они предпочитают сравнительно более просторные места. Обыкновенно они в песчанных или илистых частях про- точной воды под прикрытием. С. livescens живет почти везде в чисто и проточной пресной воде (будь то ручей, быстрая река или озеро), этот вид обыкновенно наблюдается ползающим по камням. MALACOLOGIA 465 Оба наблюдения, как в природе, так и в лаборатории, указывают, что спаривание происходит осенью. Когда температура падает ‘ниже 50 граду- сов, улитки начинают зимнюю спячку. Весной они возвращаются к актив- ности и кладут яйца. Яйца P. acuta покрытые песком кладутся в массах различного размера и формы, количество яиц в каждой массе колеблется между 1 и 19. С. livescens кладет яйца по одиночке или по 2 - Зв ряд с промежутком в несколько CM., они обыкновенно покрываются тонким слоем ила. Р. асша кладет больше яиц (15 яиц на самку в день), чем С. livescens (около 4-х), но у нее этот период короче (от апреля до июня), тогда как С. livescens кладет яйца от апреля до половины августа. У обоих видов эмбриональное развитие продолжается 2 недели. Во время первого года жизни происходит наиболее заметный рост (от Crna HO LO MM y AP. acuta; oT 0.3 до 0.8 мм УС. livescens). Когда выросшие в лаборатории улитки достигают половой зрелости, в 2 года они были в 16.7 ив 7.0 мм в диаметре, после чего рост их был незначительным. Продолжительность их жизни в нормальных условиях - 3, может быть, 4 года. У Р. acuta количество самцов к количеству самок равно 1:2, а у С. livescens -1:5. Как и другие виды переднежаберных, самцы и самки обоих видов питаются красными, зелеными, десмидиевыми и диатомными водо- рослями. В печени, пищеводе и других органах зачастую паразитируют ли- чинки сосальщиков, главным образом из семейств Azygiidae, Allocreadiidae, Aspidogastridae. ABCTPAKT , КОНХОМЕТРИЯ ПРЕСНОВОДНОЙ УЛИТКИ BIOMPHALARIA PFEIFFERI (BASOMMATOPHORA: PLANORBIDAE) Г. X. Франк и A. X. Мейлинт Раковина у Biomphalaria pfeifferi имеет Форму логарифмической спирали, как и многих моллюсков и ее действительная Форма близка гео- метрической. Чтобы вычислить ее поверхность и вес на квадратный мили- метр, были использованы уравнения, основанные на этом факте. Вычисле- ния, сделанные прямым путем для проверки этого факта, в общем были со- гласны с первыми. Результаты этих вычислений, основанные на естествен- ных и искуственных популяциях, указывают, что средний их вес на квадрат- ный милиметр увеличивается с возрастом и с увеличением в них количества растворимого кальция. Вероятно это увеличение происходит в одинаковой пропорции во всех частях раковины, Т.е. вес каждой части на кв. мм. при- близительно равен среднему размеру всей раковины. По всей вероятности, величина К. (радиус оборота / радиус спирали в той точке), или подобная тому пропорция; высота раковины к максимальному ее диаметру, уменьшается с возрастом и накоплением углекислоты в окружающей среде. Если ракови- на у вида B.pfeifferi всегда близка к идеально геометрической форме, как то подсказывает настоящее ограниченное исследование, то привычная детальная конхометрия станет ненужной. Если будет найдено, что скорость удаления от центра (3) и диаметр устья (относящийся к ?) в группах оди- накового размера значительно отличаются, то только полный математичес- кий анализ будет достаточным. 466 MALACOLOGIA ABCTPAKT РЕПРОДУКТИВНЫЕ ФУНКЦИИ И ФИЛОГЕНИЯ ЗАДНЕЖАБЕРНЫХ БРЮХОНОГИХ МОЛЛЮСКОВ Михаил Т. Гизлин Чтобы дать более особенную базу для Филогенетических исследований, сравнительная и Функциональная анатомия репродуктивной системы была кри- тически рассмотрена у всего подкласса заднежаберных моллюсков. Новые наблюдения были соединены с детальным обсуждением прежних работ. Особое внимание уделено возможности найти Функциональные объяснения для морфо- логических и физиологических вариантов, чтобы предложить филогенетичес- кую теорию, как основу, которая до сих пор имела случайный характер. При функциональном анализе особенности конвергенционного характера были опущены и особое внимание было уделено сравнению, основанному на комплекс фуекциональных дивергенций. Детально рассмотрены гомологии отдельных частей репродуктивного трактаи предложены некоторые изменения в систематике. Образование яич- ных масс и гомологии желез их выделяющих обсуждаются и выясняются на ос- новании гистологических, химических и эспериментальных наблюдений. Обсуждены возможные причины эволюционных изменений. Функциональные затруднения предков из за нераздельного полового протока были устранены различными путями и эти дивергенции составляют основу для предполагае- мых кладов, которые расцениваются другими данными. В настоящей работе были приняты во внимание и прежние работы, коли- чество хромосом, образ питания и другие особенности пищеварительной си- стемы, как и морфология сперматозоидов, как добавочный признак при обсуж- дении филогенетических проблем. При критическом рассмотрении паралле- лизма или конвергенции, были приняты во внимание филогенетические до- воды. , Система органов размножения семейства Onchidiidae указывает Ha родственность легочным. Семейство Acteonidae имеет измененную систе- му органов размножения и оно является родственным большинству других заднежаберных; однако его репродуктивная система и другие особенности указывают на его близкое родство семейству Hydatinidae; гистология Te- нитальной ампулы допускает возможное родство роду Acoela. Предпо- сылки, на основании которых предполагалось бифилетичное происхождение крылоногих моллюсков, признаны негодными; монофилетичное происхождение их согласуется с морфологией системы репродуктивных органов; морфология сперматозоидов обеих групп напоминает таковые у Anaspidea и Sacoglossa. Репродуктивные системы у Anaspidea, Sacoglossa, Diaphanidae и Cylindrobullidae можно сравнить с предлогаемым общим предком с раздельным половым прото- ком и предложить, что они все родственны. Семейства Retusidae, Philinoglossidae, Bullidae, Atyidae n Runcinidae могут быть сгруппирова- ны вместе на основании строения UX совокупительного аппарата, который откладывает сперму и выделяет сперматофоры; у траввоядных родов этой группы имеется пищеводный дивертикул и также сходства в строении желудка. Взаимозависимость между личиночными стадиями ракушечных и триаулитическими. В сверхсемействе голожаберных, аэолидация указывает на необходимость пересмотра их систематики. Это исследование подтверждает естественную классификацию многих групп. MALACOLOGIA 467 ABCTPAKT FONTELICELLA (PROSOBRANCHIA: HYDROBIDAE) НОВЫЙ РОД 3AMANHO- АМЕРИКАНСКИХ ПРЕСНОВОДНЫХ УЛИТОК ВОО Е jipsrt mu Ne BIMESAIGE Fontelicella, gen. nov. (подсемейства Hydrobiinae ) состоит из 3-х подродов: Fontelicella s. s. (тип Fontelicella californiensis sp. nov.) C 8 видами oT Плиоцена до настоящего времени, в западных США и Нижней Калифорнии, Мексике, Natricola, subg. nov. (тип Poma- tiopsis robusta Walker, 1908) с 3 видами в бассейне Снэйк Ривер в штатах Айдаго и Вайоминг, США, и Microamnicola, subg. nov. (тип Amnicola micrococcus Pilsbry, 1893), с 1 видом, живущим в бассейне реки Amap- госса, в южной части штата Невада и в южной Калифорнии, США. Между хо- polo описанными видами, ближайшим является Cincinnatia integra (Say), живущая в восточных штатах США, этот вид отличается OT остальных строе- нием совокупительного органа, пигментацией тела, Формой раковины и ноги. Между описанными особенностями видов Fontelicella являются общая Dop- ма, спосб передвижения, поведение, пигментация, наружная морфология, ра- дула, семепровод, яйца и экология. Устройство меланина и зерен в облас- ти головы, является особенно полезным указателем видовых характеристик, на которые не было обращено должного внимания в предыдущих работах об этом семействе. АБСТРАКТ АРКТИЧЕСКИЙ РОД МУА Дан Ларсон Настоящий доклад имеет целью внести ясность в ошибочное представ- ление об арктическом роде Муа. Дженсен (1900) указал (на датском языке), что все тогдашние сведения о виде Myaarenaria Linnaeus из Арктики были ошибочны и относились Фактически к виду Mya truncata Linnaeus, который он назвал М. ovata. Самая надежная отличительная черта между эти- ми двумя почти одинаковыми раковинами заключается в хрящевой пластинке левой створки и в соответствующей ямке правой створки. Так как работа Дженсена не является широко известной среди говорящего по английски ми- pa, то северный вид Mya атепата до сих пор продолжает упоминаться из Арктики. Позже Шлеш (1931) условно повысил форму М. ovata (которую сам Дженсен считал заслуживающей полпжения не выше подвида) до положения ви- да под именем М. pseudoarenaria, которым не следует пользоваться. В этой работе даны ареалы живущих и вымерших трех Форм вида, М. truncata: M. truncata forma typica, Linnaeus, М. truncata forma uddevallensis Forbes и М. truncata forma ovata Jensen, a также и ареал вида М. arenaria, насколько это удалось установить. Эти списки не полны. Исследователей, работающих с видом Mya truncata, убедительно просят добыть больше дан- ных о его формах в будущих работах. Некоторые из новых свидательств о виде M. атепата из полярного круга, тут обсуждены, во всех случаях они относятся к виду М. truncata forma ovata. 468 MALACOLOGIA ABCTPAKT ЭВОЛЮЦИОННЫЕ И СИСТЕМАТИЧЕСКИЕ ПРОБЛЕМЫ ПРОМЕЖУТОЧНЫХ ЛЮЦИНОИДНЫХ ДВУСТВОРЧАТЫХ А. Ли МкАлистер Стратиграфические и морфологические данные указывают, что редкая ордовикская двустворчатая раковина Babinka является иереходным звеном между хвустворчатыми сверхсемейства Lucinacea и некоторыми их предка- ми, напоминающими моноплакофоры. Данные палеонтологии и исследования функций живущих видов указывают, что возможно, что надсемейства Lucinacea, Leptonacea и род Babinka являются отдельной эволюционной вет- BEN, сохранив - особые адаптивные признаки с ранней палеозойской эры. Эту ветвь, вероятно, следует рассматривать, как отдельную систематичес- кую группу (таксон), высокого развития. МЛюциноиды, очевидно, не дали от себя какую нибудь другую группу двустворчатых и, по всей вероятности, не родственны ни одной из таксодонтных групп, с которыми они обычно обобщаются. Совершенно независимое происхождение люциноидных двуствор- ватых подсказывает, что Bivalvia суть полифилетического происхождения от недвустворчатых моллюсков. АБСТРАКТ ФУНКЦИОНИРОВАНИЕ СТАТОЦИСТОВ У ПРЕСНОВОДНОЙ УЛИТКИ РОМАСЕА PALUDOSA (AMPULIRIDAE) Андрей МакКлейри Две группы улиток были исследованы. В группе 1 было 15 улиток, y которых был удален левый статоцист, 15 улиток, у которых статоцист был обнажен, но не удален, и 15 - контрольных нетронутых. В группе Il, было 8 улиток, у которых были удалены оба статоциста, 8 улиток с обнаженным статоцистом с обеих сторон, и 8 - контрольных. Перед операцией улитки были анастеаированы погружением в раствор MS 222 (0.25 гр / литр), при- близительно на час. Ранки были быстро закрыты и улитки стали активными через час после операции. После вскрытия никаких признаков регенерации обнаружено не было. Следующие особенности поведения были исследованы: быстрота и на- правление их движений, степень активности, положение тела при отдыхе, способность вернуться к нормальному положению, после того как животное было перевернуто, ресничное питание и поверхностное дыхание. Во время этих исследований, у некоторых особей из группы П, как оперированных, так и надрезанных, появился ненормальный прогиб в рако- вине. Наблюдения над степенью активности группы I, оперированных и надрезанных улиток, показали, что они были менее активны и не могли от- дыхать на вертикальной поверхности, как то делали улитки контрольные. И те и другие признаки были признаны результатом операционных надрезов. Наблюдения над активностью улиток группы П показали, что опери- MALACOLOGIA 469 рованным улиткам было труднее оставаться на вертикальной поверхности, чем тем, что были только надрезаны или контрольные; и это было понято как результат удаления статоцистов. За исключением вышеописанных наблюдений, значительной разницы меж- ду поведением оперированных, надрезанных и контрольных не наблюдалось. Улитки, у которых были удалены оба статоциста, не потеряли способ- ности подниматься на поверхность воды для дыхания. Между возможными факторами, регулирующими чувство направления вверх, с удалением статоцистов, свет сверху и градиент кислорода, вероятно ан- нулировали свет сбоку и циркуляцию воды. В границах описанных эксперимен- тов, есть указания, что перемещение улитки не лишает ее способности дви- гаться вверх. Есть также указания на градиент давления и плавучесть. легких. АБСТРАКТ НЕКОТОРЫЕ ЗАДНЕЖАБЕРНЫЕ МОЛЛЮСКИ ИЗ МКРОНЕЗИИ Эрнест Маркус Коллекция из 130 заднежаберных моллсков из Микронезии, принадлежа- щая Национальному музею США, содержит 53 вида. Только 10 видов являются новыми и половина из них размерами не превышает 5 мм в длину. Эти нем- ногие экземпляры отличаются однобразием фауны коралловых рифов западного Великого океана, большинство же более крупных видов уже известно. Опи- саны следующие новые виды: Stiliger (Ercolania) illus, Elysia bayeri, Elysia тата, Hypselodoris cuis, Discodoris lora, Discodoris ylva, Catriona lonca, Catriona urquisa, Noumeaella rehderi и Muessa evelinae генотип нового pola ce- мейства Favorinidae, родственного роду Herviella. ABCTPAKT МОРСКИЕ БРЮХОНОГИЕ МОЛЛЮСКИ ПОДКЛАССА EUTHYNEURA ИЗ АТОЛЛА ЗНИВЕТОК ЗАПАДНОЙ ЧАСТИ ВЕЛИКОГО ОКЕАНА Э. Марку и Иван Б. Бёрч Настоящая работа является следствием изучения морских моллюсков подкласса Euthyneura, собранных вторым автором на атолле Эниветок, группы Маршаловых островов, в Феврале - Апреле 1960 года. Было собрано 17 видов, из которых 5 описаны в настоящей работе, как новые виды: Haminoea тизейа, H. linda, Chromodoris briqua, Herviella mietta и Onchidella evelinae. Из остальных 12 видов 7 распространены к востоку от западной части Ин- дейского океана (2 из них также находятся в Красном море) от этого атол- Ja , 2 вида являются общетропическими или общеподтропическими, 2 вида 470 | MALACOLOGIA известны исключительно только в западной части Великого океана. Срав- нительная однородность фауны рифов западного Индопасифика видна из Pak- та, 9 видов (т.е. более 50 процентов) из общего числа известны от за- падного края Индийского океана и до середины Великого. Род Herviella, повидимому, ограничен распространением только в западной части Великого океана. Замечательными являются рецидивная вентральная конечность ноч- ки и оболочка стилета в дивертикуле пенисного мешка у Onchidella. в районе Австралии, Новой Зеландии и прилежащих осровах. АБСТРАКТ ЭКОЛОГИЯ CYRTODARIA SILIQUA И ИСТОРИЯ ЖИЗНИ РОДА CYRTODARIA (BIVALVIA: HIATELLIDAE) Во Hr Sana Cyrtodaria siliqua (Spengler) распространена от северного края отмелей острова Большого Ньюфаундленд и до отмелей Джорджа, она Bcpeua- ется на дне из мелкого песка, на глубине в 500 м, но главным образом, на глубинах от 50 и ло 150 м, а также и на глубинах более 250 м, но только там, где находится сильный приток воды направленный вниз, она наблюда- лась при температурах от -1.0 и до +5.7 и при солености от 32.3 и до 34.2 процентов. Этот подвижной вид питается планктоном, находящемся в суспензии и предпочитает рыхлое дно. Способ его питания определяет глубину и харак- тер субстрата. Вероятно он не может размножаться при постоянной низкой температуре, почему он не распространяется на север от отмелей Ньюфаунд- ленда. По своему ареалу С. siliqua - западно-атлантический северный вид, а по температурным требованиями, он относится к нижне-арктической северной фауне. Род Cyrtodaria Daudin атлантического происхождения. Он образо- вался в промежуточный период между Палеогеном и Неогеном, а предки его, возможно, жили в морях Южно-Прусской геосинклинали в Палеогене: к концу Неогена они распространились по мелям Северного Атлантического океана и Арктики и разбились на несколько родственных видов. Благодаря пост-пли- осеновому оледенению, эти виды вымерли по берегам Европы и в западном Атлантическом океане. С. siliqua была оттеснена на юг. После ледни- кового периода, она распространилась на северо-запад до Гренландии, но из за больших глубин у проливов Дании, она не смогла продвинуться до Исландии, где она обитала ранее, в доледниковое время (Нэзис, 1961). С. kurriana - другой живущий вид этого рода является циркумполярным ви- дом, обитающим исключительно в солоноватых прибрежных отмелях, он берет свое начало в Арктике в начале Плеистоцена. Его предки предпочитали бо- лее теплую воду нормальной солености. Благодаря повторным высыханиям мелей во время эвстатических регресий, он был отеснен в соленоватые воды. В насале после-ледникового периода, или же в межледниковое время, он мигрировал к югу, до устья реки Амура, но после потепления и повышения солености в прибрежных водах дальневосточных морей, он там вымер. Настоя- MALACOLOGIA 471 mee потепление Баренцева моря может еще сократить ареал этого вида. Род Cyrtodaria указывает Ha 2 главных тенденции видообразования: "линейную или цепную" и "букетную", типа Е.Ф. (по Гурджановой, 1951 г.). Эволюция этого рода по "линейному" типу привела в результате к транс- формации предков, требовавших более высокие температуры (сравнительно редкий случай арктического вида Атлантики) в арктический вид С. Rurriana, где каждый вид цепи сохранил морфофизиологическую адаптацию к определенному типу питания. АБСТРАКТ ХРОМОСОМНЫЕ ЦИКЛЫ У НАЗЕМНОЙ УЛИТКИ CATINELLA VERMETA (STYLOMMATOPHORA: SUCCINEIDAE) С. М. Паттерсон и Иван B. Бёрч Между стебельчатоглазыми рода Catinella по крайней мере три вида отличаются от остальных малым количеством хромосов Catinella rotundata с Гавайских островов, n=5 (2n=10); С. vermeta и С. texana, п=6 (2n=12). С. vermeta в особенности заслуживает исследования хромосомных циклов ее сперматогенезиса, из за малого количества хромосом и их большой вели- чины. В общем циклы ее не отличаются от таковых у других животных и особен- но напоминают циклы, наблюдаемые у подкласса Euthyneura. Но детали развития гораздо заметнее, и различные стадии его легко отличимы и те, что не были выяснены ранее, стали вполне ясными. Детальное описание хромосомных циклов У С. vermeta дает ясное представление о мейотическом процессе у этой группы брюхоногих и значительно расширяет сведения, дан- ные в предыдущих работах. Ранние мейотические хромосомы выглядят пушистыми, распространяют нити, затвердевающие в промежуточные профазные хромосомы, ясно обозна- ченной сиральной формы; центромеры выглядят как слегка окрашенные и не- окрашенные пятна. Следующее уплотнение делает метафазные хромосомы гуще окрашенными, они образуют гладкие края и центромеры обозначатся только сжатием. Анафазные хромосомы похожи на них, но они меньше размерами. Первое мейотическое профазное ядро образуется после последнего пред- мейотического деления. Лептотенные хромосомы выглядят как длинные, OT- дельные нити, слегка окрашенные с хромомерами во всю их длину. Свобод- ные их концы указывают на поляризацию, характерную для "букетной стадии". Парование зиготен начинается у поляризованных концов и выглядит как хро- момер за хромомером соединяются по длине гомологичных нитей. XPOMOCOM- ные пахитены короче и гуще окрашены. Гомологи начинают "отталкивать" друг друга, образуя разделения по линии ранних диплотен хромосомов. По мере развития диплонемы, хромосомы рассеиваются и выглядят слабо окра- шенными. Хиазмы стремятся к концам нитей и уплотнение продолжается, ког- да хромосомы образуют кольца, палочки и кресты или же светлые петлевид- ные фигуры, характерные для диакинеза. В метафазе I биваленты образуют плотное кольцо, дугу или фигуру вроде палочки. Гомологичные центромеры, со своими хроматидами разделяются в стадии анафаз I, образуя сдвоенные 472 | МАГАСОГОСТА хромосомы (диады), приблизительно вдвое меньше чем в метафазе I, бива- ленты. Во время последующего далее цитокинеза, хромосомы начинают вто- рое мейотическое деление без заметного периода интеркинеза. Диады прометафазы Il, прежде чем выстроиться в экваториальном плане, напоминают позние хромосомы метафазы II, толвко сильно сжаты и густо окрашенные, в форме "гантели". Во время анафазы П, каждый диаи отделяется и образует две гонады, которые движутся к противоположным по- люсам, где начинается телофаза Il, после Aero следует цитокинез. Молодые сперматиды образуются после, каждая с заметной ядерной оболочкой. В период спермиогенеза хроматин разлагается и уплотненное ядро превра- щается в зрелого сперматозоида. АБСТРАКТ РОСТ И ЕГО ЗАМЕДЛЕНИЕ У ONCOMELANIA | (GASTROPODA: HYDROBIIDAE) Генрих ван дер llano и Георгий М. Дэйвис Эти данные относятся к проблеме быстрого и аккуратного выращивания лабораторным путем в больших количествах моллюсков вида Oncomelania для исполвзования их при изучении паразита Schistosoma japonicum . Предыду- щие работы указывают на скорость роста этих улиток, достигнутую в других лабораториях - от 0.3 до O. 4 мм в неделю, где их смертность в одном слу- чае достигала 38 процентов. Описанный тут способ’ выращивания культуры дает регулярный рост в 0.65 мм в неделю со смертностью ниже 10 процентов. Самый быстрый рост получается когда 1 или 2 улитки, только-что вылупившиеся из яйца (в 2.0 или 2.5 оборота), помещаются в блюдце Пэтри диаметром в 9 см. В центре блюдца помещается лепешка из алкалического нестерилизованного пресновод- ного ила с нормальным содержанием диатомовой водоросли. Прибавив воды, блюдце прикрывают и ставят под лампу в 150 футо-свечей на 10 - 12 часов в сутки. Без прибавки питания, температура поддерживается в 25, - 2 гра- дуса (по Цельсию). Когда число улиток в каждой культуре было увеличено до 5 и до 10, в результате были получены карликовые формы, т.е. заметное замедление и в их росте и развитии. В соответствии с замедлением роста наблюдалось и замедление в развитии гонад, отсутствие развития половых органов и повы- шенная смертность. Так как наружно карликовая раковина не отлична от нормальной, то ее можно опознать только зная ее возраст. Максимальный рост улитки зависит от суммы следующих данных: свет, достаточный объем сосуда подходящая почва со здоровой микрофауной. Самыми критическими требованиями успешной культуры являются постоянство } в свете и размер сосуда, ил с высоким содержанием кальция и способный nu" тать обильную микрофауну зеленых и диатомовых водорослей. { MALACOLOGIA 473 ABCTPAKT СРАВНИТЕЛЬНОЕ ИССЛЕДОВАНИЕ ПИЩЕВАРИТЕЛЬНОГО ПРОЦЕССА У БРЮХОНОГИХ DRUPA RICINA И MORULA GRANULATA Ши - Квей By На Гавайских островах среди пышной растительности морских водорос- лей, вместе с голотуриями и губками, встречается брюхоногий моллюск Drupa vicina (L.) В сообществе с двустворчатым моллюском Isognomon, губками и меньшим количеством водорослей встречается другой брюхоногий хищный моллюск Morula granulata (Duclos). Описывается анатомия и гистология пищеварительной системы y D. ricina сравнительно с таковым у М. granulata. В общем они довольно сходны, 34 исключением радулы, комплекса кишечника, желудка и ректальной железы. У D. vicina радула имеет 5 зубцов без полого основания, а М. granulata имеет радулу с 3 зубцами и полое основание в центре. Это значительное различие находится в тесной связи с комплексом желез и кишечника: у D. vicina 2 симметрично развытые вспомогательные железы совершенно свобод- ны от главной их массы, ау М. granulata большая из слюнных желез це- ликом погружена в массе остальных, а правая поменьше размерами остается свободной. Желудки обоих видов в общем имеют вид подковообразного меш- ка, но желудок D. vicina снабжен дивертикулой со стороны пищевода, а желудок М. granulata таковой не имеет. Ректальная железа у D. ricina желтого цвета и неопределенных очертаний, ау М. granulata она черна и легко отличима по внешнему виду. Обсуждены Функциональные аспекты пищеварительной системы обоих ви- дов. Во время питания, ротовое отверстие, слюнные и вспомогательные же- лезы смачиваются совместно. За исключением ротового отверстия ресничные волны проходят через всю систему пищеварения. Наблюдалось, что Morula может сверлить двустворчатые, но предпо- читает падаль, а Drupa, не считается типичным хищником моллюсков с жесткой раковиной, но питается живыми губками, голотуриями и падалью. Манера питания и разница в диете находятся в связи с различиями в строе- нии пищеварительной системы. Сравнение методов питания и структуры же- лудков у этих видов с теми же особенностями у других хищных месогастро- под, возможно, что указывает на принадлежность Drupa и Morula к ca- мым основным и примитивным группам стеноглоссовых, отражая их происхож- дение от месоглоссовых предков. ik MALACOLOGIA 475 ERRATA MALACOLOGIA regrets the occurrence of a number of errors and inconsistencies in the first article of Vol. 3 (Dazo, B. C., p 1-80). The more important of these, in particular irregularities relating to figures, tablesor numbers, are herewith corrected. p 12, left column, 4th paragraph, line 3: “Table 12” should. read “Table 13”. 5thparagraph: “Table 13” should read “Table 14”. p 21, left column, 3rd paragraph, under Eyes, line 4: delete “Text Figure 5” and substitute “PLATE Ш, Fig. 1; Text Figure 7”; right column, 2nd paragraph, under Tentacles, line 6: instead of “Text Figure 5” read “PLATE Ш, Fig. 1 and Text Figure 7”. р 23, PLATE Il: The upper left unnumbered figure is Fig. 1. р 27, PLATE Ш: The center unnumbered figure ofthe complete snail is Fig. 1. In Fig. 4, “crystalline roa” should read ”crystalline rod”: р 28, left column, line 9: “PLATE IV” should read “PLATE Ш”. p 29, left column, 2nd paragraph, line 6: “Figure 8(1)” should read “PLATE VI, Fig. 1”. right column, 2nd paragraph, line 2: insert “a” to read “ ... surrounded by a bell-shaped . . .” p 30, left column, 2nd paragraph, last line: “Figure 8(6)” should read “PLATE II, Fig. 1; PLATE VI, Fig. 5”. Last paragraph, lines 1 and 2: “Figure 8(1)” should read “PLATE VI, Fig. 1”. p 31, right column, line 2: “later teeth” should read “lateral teeth”. p 32, FIG. 6: The upper unnumbered set of jaws and radular teeth is 1. The jaws and radular teeth of both species are drawn to the same scale. right column, last paragraph, line 2: “PLATE VII” should read “PLATE VI”. p 34, right column, line 5: “Figure 8(2)” should read “Fig. 8(4)”. p 39, PLATE IV: The unnumbered figure on the left is Fig. 1. The legends are incorrect and should read: FIG. 1. Male reproductive system of Goniobasis livescens. 28X. FIG. 2. Female reproductive system of Goniobasis livescens. 28X. FIG. 3. Typical, eupyrene spermatozoon, similar to that of Goniobasis laqueata illustrated by Woodard (1935). FIG. 4. Upper portion of a mature apyrene (atypical) spermato- zoon drawn from a fresh smear preparation. 3570X. FIG. 5. Crescent-shaped spermatophore with its tapering ends. 53X. p 40, left column, 4th paragraph: “p 137-146” should read “p 55-60”. p 50, TABLE 6, Footnote 18: “p 88” should read “p 35-36”. р 52, FIG. 11: The magnification (not given) of all shells is .82X. 476 p 54, p 57, p 60, p 61, p 62, MALACOLOGIA PLATE V: The legends should read: FIGS. 1 & 2. The egg masses of Pleurocera acuta. FIG. 1. Drawing of detached egg masses of various shapes; some are turned over showing the underside of the mass with exposed eggs. 13X. FIG. 2. Drawing of recently laid egg clutch with embryos in the second cellular division as seen by transmitted light. The opaqueness of the embryos makes them appear black. 30X. FIGS. 3 & 4. The eggs of Goniobasis livescens. FIG. 3. Drawing of 2 detached eggs on their substratum. 25X. FIG. 4. Drawing of newly laideggwith its adhering covering of soil as seen by transmitted light. The opaqueness of the egg makes it appear black. 60X. right column, lines 7-8: “Rows for lines) of 2-3 eggs were likewise noted”, should read: “Rows (or lines) of 2-3 eggs were likewise noted;” second paragraph, last line: “p 172” should read “p 73”. left column, line 11: “in 256 days” should read “in 26 days”. right column, 15 paragraph, last line: for “serching” read “searching”; last paragraph, last line: instead of “0.27-3.87 mm” read “0.27-3.82 mm”. left column, line 15: “p 144” should read “p 57”. TABLE 11: 154 line under the heading Number of Whorls: “1-10” should read “1”. PLATE VI: The legend to Fig. 4 should read: “Longitudinal section of the mantel region, showing cross-sections of the gill filaments (G). The large intestine (I) appears on the lower right corner. Approx. 30X. PLATE VII: The legend should read: “Histological sections of Goniobasis livescens”. TABLE 16: “Plagioporus sinissini huroni” should read “Plagio- porus sinitsini huroni”. nr } | ры hi ren И М BOUND SEPT 1979 ET 3 2044 072 160 2