pa, od BM a“ АН PA md Sarge ales ET рат ae Jaa hah enews A AW HARVARD UNIVERSITY 09 uf us! LIBRARY OF THE Museum of Comparative Zoology A VOL. 10 NO. 2 DECEMBER 1970 MALACOLOGIA International Journal of Malacology | | Revista Internacional de Malacologia Journal International de Malacologie Международный Журнал Малакологии Internationale Malakologische Zeitschrift PUBLICATION DATES MALACOLOGIA, Vol. 8. No. 1-2: 11 November 1969 MALACOLOGIA, Vol. 9. No. 1: 16 June 1970 20 July 1970, NA ho MALACOLOGIA, Vol. 9, No. MALACOLOGIA, Vol. 10. No. 1: 14 November 1970 NEW NAMES HARVARI UNIVERSITY, GASTROPODA erbsus (Stiliger), Marcus € Marcus, /970, 192 estuarinus (Potamopyrgus), Winterbourn, 1971, 286 isa (Noumeaella). Marcus & Marcus, 1970, 2/2 kirsteueri (Smaragdinella), Marcus & Marcus, 1970. 188 regina (Hypselodoris), Marcus & Marcus, 1970, 199 vreelandae (Elysia). Marcus & Marcus, 1970, 194 PELECYPODA Cumberlandinae, Heard, /97/, 338 Megalonaladinae, Heard, /97/, 338 Popenatadinae, Heard, 1971, 339 MALACOLOGIA, VOL. 10 CONTENTS ABBOTT, В. Г. Eastern manne mollusks: das a De т APLEY, М. Г. Field studies on life history, gonadal cycle and reproductive periodicity in Melampus bidentatus (Pulmonata: Ellobiidae). . . . . . . . . . 381 GEAMPITE P. T. Comparative ecology of the snails Physa gyrina and Physa integra (Basommatophora: Physidae) . . . . . . . Dr Di ras to OS CLARKE, A. H. (editor) Rare and endangered mollusks of North America . . . . . . . . . 1 ELENCH. We. J. Aster land SAS ue ee ee hoe O “= A 1190 CVANCARA, A. M. Mussels (Unionidae) of the Red River Valley in North Dakota and Minnesota WBS TASER день ра О PAR et te a ES GREENE, R. W. Symbiosis in sacoglossan opisthobranchs: Symbiosis with algal CHIOKOPIASIS® ut m An ee ST GREENESR. We Symbiosis in sacoglossan opisthobranchs: Translocation of photo- synthetic products from chloroplast to host tissue. . . . . . . . . 369 HEARD, W. H. Eastern freshwater mollusks. ER The South Atlantic and Gulf AA A E : A E ee HEARD, W. H. and GUCKERT, R. H. A re-evaluation of the recent Unionacea (Pelecypoda) of North America 333 JURBERG, P. The shell structure of Astraea olfersi (Gastropoda: Turbinidae) . . . 415 KEEN, A. M. Westernimarmne molluskSs> a. ее. A ne | KRAEMER, L. R. The mantle flap in three species of Lampsilis (Pelecypoda: Unionidae) 225 12 у ELOYDB DIE. The function of the odour of the Garlic Snail Oxychilus alliarius (Pulmonata: Zonitidae) LEOY DD: D.E: The composition of the odour of the Garlic Snail Oxychilus alliarius (Pulmonata: Zonitidae). MARCUS, E. and MARCUS, E. Some gastropods from Madagascar and West Mexico. McCRAW, B. M. Aspects of the growth of the snail Lymnaea palustris (Muller) . McSWEENY, E. S. Description of the juvenile form of the Antarctic squid Mesony- choteuthis hamiltoni Robson. MORRISON, J. P. E. Brackish-water mollusks MERE А С. Western land snails . STANSBERY, D. H. Eastern freshwater mollusks. (1) The Mississippi and St. Lawrence River systems . EIER SN. : BT: TAYLOR, D. W. Western freshwater mollusks . van der SCHALIE, H. Hermaphroditism among North American freshwater mussels . WILLIAMS, N. V. Studies on aquatic pulmonate snails in Central Africa. I. Field distribution in relation to water chemistry . WILLIAMS, N. V. Studies on aquatic pulmonate snails in Central Africa. II. Experi- mental investigation of field distribution patterns. WINTERBOURN, M. The New Zealand species of Potamopyrgus (Gastropoda: Hydrobiidae) ZISCHKE, J. A., WATABE, N. and WILBUR, K. M. Studies on shell formation: measurement of growth in the gastropod Ampullarius glaucus 441 451 181 399 323 53 39 33 93 153 165 283 423 МАЛАКОЛОГИЯ, TOM 10 ОГЛАВЛЕНИЕ АББОТТ Морские моллюски Востока АПЛИ Полевые исследования по живой истории, гонадный цикл и периодичность размножения Melampus bidentatus (Pulmonata: Ellobiidae) . КЛАМПИТТ Сравнительная экология улиток Physa gyrina и Physa integra (Basommatophora: Physidae) . КЛАРКЕ (редактор) Редкие и вымирающие моллюски Северной Америки КЛЕНЧ Наземные улитки Востока... КВАНКАРА Двустворчатые моллюски (Unionidae) долины Ред Ривер в Северной Дакоте и Миннесоте. США ГРИН Симбиоз у моллюсков Opisthobranchia: Sacoglossa, Симбиоз с хлоропластами водорослей ГРИН Симбиоз y Opisthobranchia: Sacoglossa, Транслокация продуктов фотосинтеза их хлоропластов в тканях хозяев НЕРД Пресноводные моллюски Востока. П. Дренажи Южной Атлантики и Мексиканского Залива . ХЕРД и Р. Х. ГУККЕРТ Ревизия современных Unionacea (Pelecypoda) Северной Америки Born vil | 47 381 113 3 351 369 23 333 R- > la |] tj 01 tu ЮРБЕРГ tg Строение раковины Astraea olfevsi (Gasteopeda:. “Turbinidae)! 2.0 e CR AD See КИН NOperme молнюеки Запада ее м КРЕЙМЕР Мантийный клапан у трех видов Lampsilis (Pelocypoda”.. “Wnionidaay 10 C0 war ees а ION Функция запаха чеесночной улитки Oxychilus alliavius (Pulmonata: Zonitidae) ........... eis A INOVI Состав запаха y чесночной улитки Oxychilus alliarius (Pulmonatas"Zontidaer ое МАРКУС и Е. МАРКУС М. Fr We Некоторые гастроподы Мадагаскара IE Мексики of. ASE to (Nal mee ees р. os МАК ГРОУ Аспекты роста улитки Lymnaea palustris (Müller) . . . . . . МАКСВИНИ Описание ювенильной формы антарктической каракатицы Mesonychoteuthis hamiltoni Робсона . . и... Е. МОРРИСОН Бэзоноватоволные моллюски оо аа СМИТ Наземные MOLNKCKU Jada... a.m... u не Восточные пресноводные моллюски. (1. Системы Миссиссипи и CENAR Лоуренс (RUBE Oia ее Ре viii 415 = 225 441 451 181 399 323 5) 39 X. Дж. У. ТЭЙЛОР Западные пресноводные моллюски... + + ван дер ШЕЛИ Гермафродитизм у Северо Американских пресноводных моллюсков В. ВИЛЬЯМС Изучение водных улиток Pulmonata центральной Африки I Распространение моллюсков в природе в связи с химизмом воды В. ВИЛЬЯМС Изучение водных улиток Pulmonata центральной Африки П. Экспериментальное исследование распределения груп- пировок в естественных условиях ВИНТЕРБУРН Новозеландские виды Potamopyrgus (Gastropoda: Hydrobiidae) А. IMIIKE Формационное исследование раковины: измерение роста у гастроподы Ampullarius glaucus ix 33 93 153 165 283 423 уч mo 424 Shaq sep SER Ты. * O 7 org we zur] 0 5 = : 0) 7 LA : PTE ng | Br = > Y 7 = = à i- un A o tre Aa u. вит aa a u o AS u Е = 7 al Loe | > 7 a, o ' A = I rw р A OL] y yo АЕ и | MUS. COMP. ZOOL, VOL. 10 NO. 1 REN MAY 1970 à NOV 30 1970 à HARVARD UNIVERSITY | MALACOLOGIA Международный Журнал Малакологии Internationale Malakologische Zeitschrift EDITORIAL OFFICES Museum of Zoology 19, Road 12 University of Michigan Maadi, Egypt, U.A.R. Ann Arbor, Michigan 48104 USA A. GISMANN, General Editor Center for Advanced Study in Marine Biology C. J. BAYNE, General Editor Marine Biological Station C. M. PATTERSON, Managing Editor > S. -K. WU, Business Manager ae Novo, Tamilnadu State M. S. GLADSTONE, Secretary J. B. BURCH, Editor-in-Chief R. NATARAJAN, Associate Editor MALACOLOGIA is published by the Institute of Malacology, 1336 Bird Road, Ann Arbor, Michigan, U.S.A. The Sponsor Members of this Institute, also serving as editors, are listed below. N. F. SOHL, President E.G R. ROBERTSON, President-Elect JE J. F. ALLEN, Vice-President M. R. CARRIKER C. R. STASEK, Secretary G. M K. J. BOSS, Treasurer А. а Subscription price of MALACOLOGIA for North American institutions is US#10.00. Subscription prices for all others and addresses for ordering are listed below: US$ 7.00 $ A 6.25 Rs 53.00 Fr. 35.00 MALACOLOGIA MALACOLOGIA MALACOLOGIA MALACOLOGIA Museum of Zoology c/o Australian Museum c/o Marine Biological Sta. c/o Muséum National University of Michigan 6-8 College St. Porto Novo d’Histoire Naturell Ann Arbor, Mich. 48104 Sydney Tamilnadu State 55, Rue de Buffon U.S.A. Australia India Paris V*, France UNITAS MALACOLOGICA EUROPAEA IV European Malacological Congress The Fourth European Malacological Congress will be held in Geneva, Switzerland, from September 7 to 11, 1971. It will follow a one-day meeting of museum curators in charge of Mollusca, devoted to the discussion of curatorial problems and collaboration. The meetings will take place in the new Museum of Natural History and in the University buildings. All malacologists are cordially invited. The Congress fee is S. Fr. 30.- (about US $ 7.00) for members and corres- ponding members of U.M.E., S. Fr. 40.- (about US $ 9.00) for non members, and S. Fr. 15.- (about US $ 3.50) for students and accompanying persons. Accommodation will be arranged by the Tourist office in hotels and the Student hostel. If you are interested and have not received the circulars, please contact the president, Dr. E. Binder, for more detailed information. Address: IV European Malacological Congress Museum of Natural History CH- 1211 Geneva 6, Switzerland MALACOLOGISTS INTERESTED IN AFRICA. --- During the last week in November 1969, a meeting was held at the Musée Royal de l’Afrique Centrale, Tervuren, Belgium, which was attended by various people interested in the study of land and freshwater mollusks of Africa, south of the Tropic of Cancer, including Madagascar (Malagasy), the adjacent islands and part of Arabia. This group decided to issue a newsletter once a year, beginning in the spring of 1970, giving names and addresses of researchers interested in this region, as well as lists of their papers and current researches, notes on the location of African type specimens in museums, proposed expeditions to Africa, specialized bibliographies and addresses for inquiries. This newsletter will be called ACHATINA. Copies of it will be available at no costto bona fide workers who cooperate in this scheme. The terms of reference will be restricted to taxonomy and zoogeography; medical aspects will be outside the area of interest. A long term project is to compile an annotated bibliography of all the papers dealing with non-marine molluscs of this area. Those interested should contact Dr. J.-J. VAN MOL, c/o Section des Invertébrés non Insectes, Musée Royal de l’Afrique Centrale, Tervuren, Belgium. -) + MALACOLOGIA Proceedings of the American Malacological Union Symposium on Rare and Endangered Mollusks PAPERS on the RARE AND ENDANGERED MOLLUSKS OF NORTH AMERICA Edited by Arthur H. Clarke National Museum of Natural Sciences National Museums of Canada Ottawa Based on a Symposium on the Rare and Endangered Mollusks of North America sponsored by the American Malacological Union and presented on July 16, 1968 at Corpus Christi, Texas né u qe Le D $ ha RHUME: март || | "A | SYMPOSIUM: RARE AND ENDANGERED MOLLUSKS 3 FOREWORD The papers presented here document crisis situations which will be of concern to all persons who care about the preservation of our unique North American fauna. Through expanded industrial development, increased water pollution, widespread habitat disruption, and over-collecting, more than 400 native species of mollusks are in imminent danger of extinction. At least 1000 others will soon be endangered if present trends continue. All of the scientists who participatedinthe American Malacological Union's Symposium on Rare andEndangered North American Molluskspossess special knowledge and several of them are among our most distinguished malacolo- gists. All of the assessments, presented here, are therefore authoritative. Excerpts from some of the papers speak for themselves. “We are left with the inescapable conclusion that we are gradually destroy- ing upwards of a thousand endemic species of freshwater mollusks.” (David H. Stansbery). “There is a [large] complex of hydrobiid gill-breathing snails in North American brackish water that is headed for extinction even before the species are scientifically described or named.” (Joseph P. E. Morrison). “About 1953, land clearing and the building of fishing camps and other tourist attractions eliminated just about all of the hammock land [on Lower Matecumbe Key] and, of course, a few more color forms of Liguus peculiar to this key. The same type of destruction has occurred along the entire series of Keys from near Miami to Key West.” (William J. Clench). “Among the [marine] species that are being over-collected in certain limited areas are Strombus gigas, Cassis madagascariensis, Pleuropoca gigantea, Cyrtopleura costata, Cymphoma gibbosum, Melongena corona, and edible clams, scallops and oysters.” (R. Tucker Abbott). “Viewed from the most pessimistic angle, it might be stated that all land mollusks indigenous to the western part of the United States are endangered to some degree.” (Allyn G. Smith). The objectives of the symposium and ofthis publication are to call attention to the present threats to species survival, to make available within a single reference preliminary lists of our rare and endangered mollusks, and to pro- vide some basis for their planned conservation. Corrections and necessary additions to these lists are solicited. Individuals and organizations are urged to do what they can to conserve and protect our endangered native species and to preserve them from destruction. A. H. C. ¡a af a by 15 nn | } DIT Oe | sita! 03 5 Pr 6 La ih HA = р 1 nr a> huy? u. alias м ca | o té TE M > y 0 10. SYMPOSIUM: RARE AND ENDANGERED MOLLUSKS CONTENTS ROLENWOLA ко Die es SA enh ee eas SOM a A 2 ke eee. PRE ee ater sabe бе ие Se ER INET OGUCETON Ewe Re due Sule olor tay wa GHG! con fol ee à sine eels Eastern Freshwater Mollusks. (I) The Mississippi and St. Lawrence River Systems. By DAVID H. STANSBERY......... Discussion, By. ARTHUR IH. СТАВКЕ. Sin ec eels wie ele eee ole Eastern Freshwater Mollusks. (I) The South Atlantic and Gulf Drainages. Ву WILLIAM:H. HEARD. .:. : 220. 2% 2202.08 Discussion. By HERBERT 9. ATHEARN . „0... ata no wei x Western Freshwater Mollusks. By DWIGHT W. TAYLOR (Summary) .... Discussion. Ву НАНОЬО. О... MURRAY. да catas e NOR Eastern, Land Snails.. By WILLIAM J. CLENCH . ».. .. apical: DISCUSSION: By DEE 5. DUNDEE:. +2... Le 8 3.8 ns ds Cole RTS Western Land Snails. Ву. ALLYN С: МИН... .... oe 2000 ен... Eastern Marine Mollusks. Ву В. TUCKER АВВОТТ................ Discussion. By JOSEPH ROSEWATER. ee Lan ее where ot . Western Marine Mollusks. By A. МУКА КЕЕМ................... Discussion. Ву WILLIAM К. EMERSON : 2. 2... 2.00 iii... de ee os Brackish-Water Mollusks. By J. P. E. МОВШЗОМ................. Page de ñ EIERN | @ 2 DÍA 1 Aaa b> Uh tara T € Aa I HAT a. zer art «rl or ева DE ; > NPATUA ло 2108 тай SAG в В A Y] u $ @ Al р b 6 à ¡a A | = o » D | ye, EL в x TULA Ned iis. ААА DARA : TOR aA Ша) EG A A MA e DO $ ‘oy O va Wha AUTM A 08 aslo anit рези М МАНГИ «3 Lamas .5 20 L vd аки че р a зам SYMPOSIUM: RARE AND ENDANGERED MOLLUSKS 7 1. INTRODUCTION The magnificent freshwater mollusk fauna of southeastern North America was dis- covered by C. S. Rafinesque, Thomas Say, Isaac Lea, T. A. Conrad, and other cele- brated naturalists who, between 1816 and 1850, described hundreds of unique new species from that region. Influencedby abenign climate, varying topography, abundant calcium and fortunate geological history, a hundred million years of uninterrupted evolution had produced there the most diverse and luxuriant freshwater molluscan fauna known to exist on earth. As the country became more densely populated streams were dammed; cattle, sewage and industrial wastes poisoned the waterways; and, one after another, rivers became unfit for mollusks and other aquatic animals. During the nineteenth and twentieth centuries most of the rivers became partially or wholly polluted and their mollusk faunas were destroyed (see paper by D. H. Stansbery, this publication). For example the Powell, Clinch, Holston, French Broad and Hiwassee rivers, all major tributaries of the upper Tennessee River, were previously unsurpassed for their rich mollusk populations. By 1950 only the Clinch and portions of the Powell remained unspoiled. On June 10, 1967 a retaining wall collapsed at Carbo, Virginia sending 130 million gallons of toxic industrial waste flooding into the Clinch River. In Virginia alone an estimated 163 million fish were killed. Effects of the poison on the mollusk fauna were then unknown but the worst was feared. Malacologists have long been aware of the gradual depletion of the North American fauna but most had felt, with some justification, that nothing could be done. But the call for action signalled by the Clinch River disaster was too imperative to ignore. On July 31, 1967 an Executive Council of the American Malacological Union appointed the writer as Chairman of a Committee to recommend action for the preservation of the rare and endangered mollusks of North America. Clearly the first assignment of the Committee was to assess the problem and to identify those species of mollusks which are now rare and in danger of extinction. It was decided that a symposium on this subject should be held during the next annual AMU meeting and its results published. During the next few weeks malacologists possessing special knowledge of the survival status of marine, freshwater and terres- trial mollusks of both eastern and western North America were asked to participate. The response was most gratifying. All of the workers who were asked to present papers promptly accepted and most of the invited discussants also agreed to help. The Symposium. took place on July 16, 1968 in Corpus Christi, Texas during the 34th annual meeting of the American Malacological Union. Carefully prepared papers from 14 malacologists were read. Audience participation was enthusiastic and much valuable supplementary information was thereby brought forth. All of the contributed papers which have been released by their authors for publica- tion are presented here. Some have been revised but most are printed essentially as they were delivered. These collected papers constitute the first attempt to enumerate the rare and endangered mollusks of North America or, for that matter, of any con- tinental molluscan fauna. The purpose of this publication is to focus attention on the species mentioned and to stimulate corrective action wherever possible. Every land management agency of national, regional, and local governments is invited and requested to do what it can. “Individuals, organizations, and interested agencies are urged to employ all means available to them toward achieving greater security for all wildlife. Only by united appropriate action will we prevent other species from joining the list of those now extinct.” (1966, United States Department of the Interior, Resource Bulletin, 34: iii). 8 Ale CLARKE It had been hoped that the Symposium might also provide some basis for planned conservation or, if necessary, for propagationofthese species. Fundamental informa- tion of this sort has already been published by the U.S. Department of the Interior’s Bureau of Sport Fisheries and Wildlife (op. cit.) for the rare vertebrates of North America and by the International Union for Conservation of Nature and Natural Resources (1966, the Red Data Books) for rare mammals and birds of the World. We had proposed to use these works as models. It was soon obvious that although the geographical distribution of most rare North American mollusks is reasonably well- known (often to their detriment) we know almost nothing about the ecology, life history or population structure of most of them. Critical areas for research are therefore plainly indicated. Biologists are becoming increasingly convinced that our generation has a profound obligation to conserve our natural environment for the practical and esthetic benefit of future generations of man. Some are also deeply concerned with our moral obliga- tion to preserve rare species for the benefit of the species themselves. Either cause is more than sufficient and it is proper that the American Malacological Union should assume a leading role in fostering the conservation of our North American molluscan fauna. A. H. C. MALACOLOGIA, 1970, 10(1): 9-22 AMERICAN MALACOLOGICAL UNION SYMPOSIUM RARE AND ENDANGERED MOLLUSKS 2. EASTERN FRESHWATER MOLLUSKS (I) THE MISSISSIPPI AND ST. LAWRENCE RIVER SYSTEMS by David H. Stansbery The Ohio State Museum of The Ohio Historical Society Faculty of Population and Environmental Biology of The Ohio State University, Columbus, Ohio 43210, U.S.A. THE EXTENT OF THE FAUNA The conditions for speciation of stream dwelling animals has been nearly ideal in eastern North America for many million years. One of the results has been the origin of what is probably the richest freshwater mollusk fauna in the world. While true of nearly all groups of freshwater mollusks represented, it is especially striking in the stream forms: 1) the river snails of the Family Pleuroceridae and 2) the naiads of the Family Unionidae. Tryon (1873: XXXVII) notes that: “We have, in North America, nearly five hundred recognized species of shells belonging to the various genera of Strepomatidae [= Pleuroceridae]. So consider- able a moiety of these are to be found to be inhabitants of the upper Tennessee River and its branches in East Tennessee and North Alabama, and of the Coosa River in the latter State, that we quite agree with Mr. Lea in regarding that region as the great centre of this kind of animal life.” It should be added that these species are endemic to eastern North America and most probably outnumber the combined melanian species of the rest of the world. The abundance of naiads or “unios” in both species and numbers of individuals proved to be no less spectacular. In his synopsis of the naiads of the world Simpson (1900: 505) recognizes: “about one thousand species and 82 varieties of Unionidae. . . Of these 533 species and 55 varieties belong in North America. . .” Subtracting the few western North American species we find that eastern North America has roughly half the known species of river snails and half the known species of naiads in the world and together they total about a thousand species. With a very few exceptions these species are found nowhere else in the world. A RESUME OF THE POST-COLUMBIAN HISTORY OF THE FAUNA Although the prehistoric North American Indians utilized prodigious quantities of these mollusks (Stansbery, 1966: 42) their harvests apparently had little effect on the survival of these species. A comparison of the shells recovered from prehistoric mounds and midden heaps with pioneer lists reveals that the species composition of our streams had not changed appreciably for at least six to eight thousand years prior to pioneer settlement. The factors which have been responsible for the decimation of our freshwater mol- lusks have increased in both number and intensity as our population has grown. With the initial clearing of the forests and tilling of the soil great quantities of humus-rich topsoil was washed into our streams. This loss to early agriculture was also a loss to stream life through a reduction of dissolved oxygen and an increase in organic acids. The removal of topsoil decreased the ability of the land to hold water, hence (9) 10 D. H. STANSBERY producing greater floods in the wet seasons and dryer droughts in the dry part of the cycle. Each exaggerated extreme took its toll of stream life. Over a century ago Higgins (1858: 550) wrote: “Gentlemen who collected the shells of this vicinity in early times, found many species in great abundance which have at this day either totally disappeared or are represented by occasional straggling specimens, and all species, with but few exceptions, have gradually decreased in numbers, .. This remarkable decrease and extinction among the mollusca, may, to a great degree be accounted for, when we consider the immense change whichthe surface of the country has under- gone. The change of the wilderness into a highly cultivated country, the immense area of forest which has yielded to the plow; the decrease in the volume of the water in our rivers and creeks,. . .” The fine silts and clays which followed the topsoil into our streams may well have had a smothering effect on some species by the simple effect of clogging of gills or stimulating excess mucus secretion. In the early days the rivers were commonly the direct recipients of lumbermill sawdust, brewery slops, and slaughterhouse refuse (Trautman, 1957: 18). With the coming of community sewage systems, raw domestic sewage was added without benefit of treatment. The discovery of new energy resources in the form of coal and petroleum leddirectly to an upsurge of technology and a mush- rooming of industry. Not only didthe mining and drilling operations add new pollutants in increasing amounts to our waters but the industries they supported contributed a whole new spectrum of soluble and insoluble wastes to our already overloaded rivers. Ortmann (1909) was so moved by the wholesale destruction of mollusks and crus- taceans that he wrote a paper on “The destruction of the fresh-water fauna in western Pennsylvania.” In addition to polluting industries of many diverse kinds he also cites the “damming up of certain rivers.” He notes that: “By this process [damming] the rivers, which originally possessed a lively current, with riffles, islands, etc., have been transformed into a series of pools of quiet, stagnant water,... It is most destructive to mussels, most of which require a lively current. Dams also prevent free migration, for instance of fishes, and thus they must be anobstacleto the natural restocking of the rivers...” Ortmann seems to have been the first biologist to correctly diagnose the true effect of impoundments on stream life. It is easy to understand why he, being the first, grossly underestimated the effects damming could have on our stream life. It is to be regretted that many biologists (perhaps most) have yet to recognize that nearly all of the exceedingly rich freshwater fauna of eastern North America evolved in or adjacent to a riffle or shoal habitat. To the extent that we change our streams into long chains of lakes -- to this extent do we eradicate this unique biological heritage. More and more in recent years sand and gravel firms have turned to the alluvial deposits of our stream beds as a source of materials. These operations in addition to the dredging involved in stream channel “improvement” and quarry washing opera- tions have their effect felt for miles downstream. For reasons as yet unknown, a dredged section of stream will not regain a naiad fauna for as much as a decade or more. The advent of the chemical pesticide industry over the past twenty years has given additional cause for concern since the bulk of most of these toxins are washed into our streams. Their precise effects on our freshwater mollusks have yet to be docu- mented in detail. Malacologists over the years have not beenblindto the increasingly damaging effects man has had on our stream environments and the organisms living there. Ortmann followed his work in Pennsylvania (which formed the basis of his 1909 paper cited above) with a survey of the naiads of the upper Tennessee Drainage System. At the SYMPOSIUM: RARE AND ENDANGERED MOLLUSKS 11 conclusion of his paper (Ortmann, 1918: 525) he records: “In view of the gradual, slow but steady, deterioration of the fauna in consequence of stream-pollution, there is great danger that the fauna will largely become de- stroyed, and that it will be impossible, in the future, to duplicate this collection.” I have collected the upper Tennessee with some thoroughness. Ortmann’s fear has been largely realized. The rivers which make up the headwaters of the Tennessee (Powell, Clinch, Holston, Nolichucky, French Broad, Little Tennessee and Hiwassee) are, in large part, destroyed. Where the fauna has not been greatly reduced or elimi- nated by pulp mill liquors, salt plant effluent, wood extracting plants, paper mills, etc., the high dams of the Tennessee Valley Authority have done so. There are still a few streams, however, having something which approaches the original fauna. The Powell and Clinch Rivers just above Norris Reservoir still afford conditions where the in- dustrious collector may take as many as thirty species from a single site. How long these conditions will last cannot be predicted but I suspect not very long. There is already agitation for additional dams on both rivers and concerted efforts are being made to industrialize this section of “Appalachia.” I would not be surprised to witness the eradication of most elements of the Cumberlandian Fauna within the next several decades. We have excellent reason to expect it. In 1924 Ortmann brought the influence of damming on the naiad fauna at Mussel (Muscle) Shoals to the attention of American scientists with an article in Science. He expressed the concern that the richest of all known naiad sites (at least 70 species in 31 genera) was being destroyed. Efforts to assess any changes in that particular fauna since Ortmann’s day have been made (Stansbery, 1964: 25). Extensive collecting produced specimens of less than half of the original fauna. Over the five years since that time Professor Paul Yokley of Florence State College has made every reasonable effort to add to the recent list. His persistent labors with commercial collecting gear and SCUBA equipment have resulted in the recovery of single specimens of four ad- ditional species. Mr. Billy Isom informs me that the original Mussel Shoals lie today beneath 19 feet of muck behind Wilson Dam, at the bottom of Wilson Reservoir. The “glory of the mussel shoals” discovered originally by Conrad (1834: 12) and lamented by Ortmann (1924: 565) has indeed become history. In more recent times Van der Schalie (1938, 1945, 1947, 1958, 1960) has been out- spoken in his criticism of dams and pollution and has cited evidence which abundantly supports his position. The impoundment of the lower Tennessee, known as Kentucky Lake, has been studied by Bates (1962: 232). He found the faunal assemblage of the old river channel to be essentially the sameas the pre-impoundment composition. All individuals so taken were found to be adults (10+ years) with juveniles being absent. It would seem that impounding either stopped effective reproduction or the survival of the young in these populations leaving only the pre-impoundment individuals to live out their life expectancies. More recent collections from the same area support this conclusion. We are left with the inescapable conclusion that we are gradually destroying nearly a thousand endemic species of freshwater mollusks. This fauna was millions of years in coming into being and is in the process of being eliminated in only a century or two. -- And all this before we have even begun to seriously investigate their po- tential value. RARE AND ENDANGERED SPECIES It should be noted at the outset that my knowledge of the status of standing-water Species in general, and non-naiad speciesin particular, is too scant to determine which are either rare or endangeredtoday. Althoughthe stream forms, especially the naiads, 12 D. H. STANSBERY are far better known, the observations offered below are obviously only as valid as the extent of my field experience and that of my several colleagues. A “rare and endangered species” is defined, for the purposes of this paper, as any species which is known living today from only one or a very few populations having a restricted range. Even though a species may be reduced to an estimated 10% or less of its former abundance it is not included unless it fits the above criteria. For some species the time for concern appears to be past. A number of species of the Genus Dysnomia Agassiz (= Epioblasma Rafinesque) have not been collected alive nor have fresh specimens oftheir shells been found in nature for at least half a century despite a concerted effort to find them. They are included here (see Pls. 1 and 2) in order to give a reasonably complete record and with the hope that one or more sur- viving populations may yet be discovered. Such species are, however, presumed ex- tinct and shall be so listed until valid evidence of their continued existence is obtained. CLASS GASTROPODA Subclass PULMONATA Order BASOMMATOPHORA Family PHYSIDAE Family LYMNAEIDAE Family PLANORBIDAE Insufficient data Family ANCYLIDAE for Subclass PROSOBRANCHIA Evaluation of Order MESOGASTROPODA Species Status Family VIVIPARIDAE Family VALVATIDAE Family HYDROBIIDAE Family PLEUROCERIDAE Genus Jo Lea, 1831. Io fluvialis Say, 1825. A few relict populations remain in the Powell, Clinch, and Nolichucky Rivers. It is absent from most of its former range. Genus Lithasia Haldeman, 1840. (Includes Angitrema Hald.) Most of the small stream species still persist in isolated localities. Most of the large river species are either extinct or existing as very small populations in the rapid water below dams. Genus Pleurocera Rafinesque, 1819. Many headwater species still persist although most ofthe species character- istic of large rivers are either greatly reduced or extinct. Genus Goniobasis Lea, 1862. Most of the species of this typical headwater genus still survive. Genus Eurycaelon Lea, 1864. A few populations of at least one species yet survive in the headwaters of the Tennessee River system. Genus Anculosa Say, 1821. (= Leptoxis Raf.) Some species of this genus may still be found in numbers on the rocky riffles of many medium to small streams of the southern part of the Ohio River system in Kentucky, Tennessee and Virginia. Genus Spirodon Anthony, 1873. (= Миаайа Haldeman, 1840, of authors) The few species of this genus still survive in rivers of the east central Atlantic drainage and in the headwaters of the New and Holston rivers of the Mississippi basin. SYMPOSIUM: RARE AND ENDANGERED MOLLUSKS 13 CLASS BIVALVIA Order UNIONOIDIA Family MARGARITIFERIDAE Ortmann, 1911. Cumberlandia monodonta (Say, 1829). Remnants of this species still live in the Powell and Clinch Rivers with scattered individuals in the Tennessee River proper. The Green River of Kentucky has at least one small population but the only population of sub- stantial size presently known is found in the Gasconade River of the Ozark Plateau in Missouri. Family UNIONIDAE (Fleming, 1828) sensu Ortmann, 1911. Subfamily AMBLEMINAE Morrison, 1955. Fusconaia cuneolus (Lea, 1840). A single population remains in the Clinch River in Virginia. Fusconaia edgariana (Lea, 1840). Small relict populations remain in the Clinch and Paint Rock Rivers. The only known population of size is in the Powell while one persisting until 1967 in the lower Elk River, Tennessee, has apparently since been de- stroyed by quarry washings. Quadrula intermedia (Conrad, 1836). A few scattered small populations yet remain in the Powell, Clinch and Duck Rivers. Known until recently from the Elk River, Tennessee. Quadrula sparsa (Lea, 1841). This form stands between Q. metanevra and Q. intermedia but merges with neither. A single population remains in the Powell River in Tennessee. Quadrula cylindrica (Say, 1817). The big river form cylindrica appears tc be reduced to a few populations in the Ouachita Mountains of Arkansas and Oklahoma, but the headwater form strigillata still lives in a number of small headwater populations of the Ohio system. Plethobasus cicatricosus (Say, 1829). Known today from a population in the Tennessee River below Wilson Dam in Alabama. Plethobasus cooperianus (Lea, 1834). Occasional specimens are still taken from the Tennessee River in Tennessee and Alabama. Lexingtonia dolabelloides (Lea, 1840). Individuals rarely taken yet in the Powell, Clinch and Holston Rivers. Duck and Paint Rock Rivers have small local populations. Pleurobema clava (Lamarck, 1819). This once common widespread Ohioan species still remains in several small disjunct headwater populations in Ohio. Occasional specimens are taken in the Wabash River of Indiana and the Green River of Kentucky. Pleurobema pyramidatum (Lea, 1831). In recent years this naiad has been found only in the Green River of Kentucky, the Clinch River above Norris Reservoir, and rarely from the Tennessee River proper. Lastena lata (Rafinesque, 1820). Although extirpated from nearly all its former range this species still lives in the Green River at Munfordville, Kentucky, and the Clinch River above Norris Reservoir. A population in the ElkRiver persisted until 1967. 14 FIG. FIG. FIG. FIG. FIG. FIG. D. H. STANSBERY PLATE 1. Extinct Unionidae Dysnomia flexuosa (Rafinesque, 1820). OSM 10369.1, male, “Ohio River,” 18 ?, length = 58 mm. Dysnomia flexuosa (Rafinesque, 1820). OSM 10369.2, female, “Ohio River,” 18 ?, length = 69 mm. Dysnomia stewardsoni (Lea, 1852). OSM 10371.2, male, “Tuscumbia, Ala. ,” 18 ?, length = 39 mm, from Henry Moores Collection. Dysnomia stewardsoni (Lea, 1852). OSM 10371.4, female, “Tuscum- bia, Ala.,” 18?, length = 35 mm, from Henry Moores Collection. Dysnomia arcaeformis (Lea, 1831). OSM 10364, male, “Tenn. River, Alabama,” 18 ?, length = 35 mm. Dysnomia arcaeformis (Lea, 1831). OSM 10363, female, “Holston River, Tenn.,” 18 ?, length = 38 mm, from Henry Moores Collection. SYMPOSIUM: RARE AND ENDANGERED MOLLUSKS 15 16 FIG. FIG. FIG. FIG. FIG. FIG. D. H. STANSBERY PLATE 2. Extinct Unionidae Dysnomia personata (Say, 1829). OSM 10379.1, male, “Ohio River, Cin., O.,” 18 ?, length = 40 mm, from Henry Moores Collection. Dysnomia personata (Say, 1829). OSM 10370.1, female, “Ohio River,” 18 ?, length = 46 mm, from Henry Moores Collection. Dysnomia lenoir (Lea, 1843). OSM 20208. 4, male, Stones River 1. 2 miles west of Couchville, Davidson Co. , Tenn., 2 Sept. 1965, length = 33-mm. Dysnomia lenoir (Lea, 1843). OSM 20208.1, female, Stones River 1. 2 miles west of Couchville, Davidson Co., Tenn., 2 Sept. 1965, length = 27 mm. Dysnomia propinqua (Lea, 1857). 18 ?, length = 35 mm. Dysnomia sampsoni (Lea, 1861). length = 41 mm. OSM 4078, male, locale unknown, OSM 10395, male, “Wabash,” 18 ?, 17 RARE AND ENDANGERED MOLLUSKS SYMPOSIUM 18 D. H. STANSBERY Subfamily ANODONTINAE (Swainson, 1840) sensu Ortmann, 1910. Pegias fabula (Lea, 1836). Never common, this species has become increasingly rare in recent years. . Its range appears to have been reduced to a few isolated populations in the upper Cumberland River tributaries. Simpsoniconcha ambigua (Say, 1825). A species sporadic in distribution and seldom found in numbers anywhere in recent years. Its habitat in the silt beneath relatively large flat rocks may render its rareness more apparent than real. \ Arkansia wheeleri Ortmann and Walker, 1912. This species of the streams flowing out of the Ouachita Mountains has ap- parently never been found in numbers. The only recent record is from Kiamichi River in Oklahoma. Subfamily LAMPSILINAE (von Ihering, 1901) sensu Ortmann, 1910. Ptychobranchus subtentum (Say, 1825). Remnant populations may still remain in the Rockcastle River of the upper Cumberland and the Duck River of the lower Tennessee. Two substantial populations are today found in the Powell and Clinch Rivers above Norris Reservoir. Cyprogenia aberti (Conrad, 1850). The range of this species has apparently been reduced to the Black and Ouachita Rivers of Arkansas. Dromus dromus (Lea, 1834). Formerly found throughout the Cumberlandian Faunal Region this species is now restricted to the Powelland Clinch Rivers just above Norris Reservoir. Obovaria retusa (Lamarck, 1819). A population still living in the impounded lower Tennessee had apparently not reproduced since impoundment and is expected to die out. The only known breeding population of this once widespread species is a small one in the Green River near Munfordville, Kentucky. Leptodea leptodon (Rafinesque, 1820). This species, rare since its discovery, has now all but disappeared east of the Mississippi River. In the last half century single specimens have been taken from the Green River of Kentucky, the Ohio River near Cincinnati, the Meramec River of Missouri, the Kiamichi River of Oklahoma and several each from the Gasconade River in Missouri and the Saline River of Arkansas. The expression “widespread and everywhere rare” fits this species perfectly. Proptera capax (Green, 1832). Although largely if not entirely gone from the entire Ohio River drainage, this species still survives in the White and St. Francis Rivers of Arkansas. Carunculina glans (Lea, 1831). The typical C. g. glans of the Ohioan Faunal Zone appears on the verge of extinction while its Cumberlandian counterpart C. g. moesta exists in some numbers in several headwater streams of the Cumberland Plateau and the Southern Appalachians. Carunculina cylindrella (Lea, 1868). A population of this exceedingly rare species still lives in the Paint Rock River system of northern Alabama. Conradilla caelata (Conrad, 1834). Originally found throughout the upper Tennessee this rare species is now restricted to several small populations in the Powell, Clinch and Duck Rivers of that region. SYMPOSIUM: RARE AND ENDANGERED MOLLUSKS 19 Villosa trabalis (Conrad, 1834). The typical form У. t. trabalis may still be found in the Cumberland River just below the Cumberland Falls and in the Rockcastle River nearby. The purple nacred У. t. perpurpurea seems restrictedtothe upper Clinch River where it is very rare and to Copper Creek, one of its tributaries. Villosa ortmanni (Walker, 1925). Never known outside the Green River system in the Mammoth Cave region of south central Kentucky. Common today only inthe vicinity of Munfordville. Lampsilis orbiculata (Hildreth, 1828). The typical form Г. 0. orbiculata may still be taken occasionally from the Tennessee River below Wilson Dam and Guntersville Dam and very rarely from its type locality, the Muskingum River in Ohio. The L. o. higginsi is known living today only from the upper Mississippi River. Related forms from the Gasconade, Black and Sabine Rivers of the Ozark-Ouachita are also rare and may constitute a third species or subspecies of this interest- ing complex. Lampsilis virescens (Lea, 1858). Never a common species nor widely distributed, L. virescens is found today only in the Paint Rock River of Alabama. Dredging operations there may render this species extinct within the year. Dysnomia flexuosa (Rafinesque, 1820). Pl. 1, Figs. 1, 2. This species has not been collected since 1900 in spite of repeated efforts to find it. It was apparently a species of shallow riffles in big rivers, a habi- tat which has been totally eliminated. It is presumed extinct. Dysnomia arcaeformis (Lea, 1831). Pl. 1, Figs. 5, 6. The entire range of this species is now under a series of impoundments. It has not been collected in over halfa century and hence is presumed extinct. Dysnomia lenior (Lea, 1843). Pl. 2, Figs. 3, 4. The last known population of this speciesis now covered by the Priest Reser- voir on the Stones River in Tennessee. The only records of this species during the last 50 years were from this site. It is presumed extinct. Dysnomia sulcata (Lea, 1829). The big river D. s. sulcata form having a purple nacre may be extinct but the white nacred D. s. perobliquus is still occasionally found in streams tribu- tary to western Lake Erie or Lake St. Clair. Dysnomia haysiana (Lea, 1834). This rare species is today apparently restricted to that part of the Clinch River from St. Paul to Dungannon, Virginia, a distance of only about ten miles. Dysnomia personata (Say, 1829). Pl. 2, Figs. 1, 2. I know of no collections of this species made in this century. It is an Ohioan species once found in the shallows of the Ohio and a few of its largest tributaries. It is presumed extinct. Dysnomia stewardsoni (Lea, 1852). Pl. 1, Figs. 3, 4. A rare species even before the impoundments and apparently not collected in the last half century. It is presumed extinct. Dysnomia lewisi (Walker, 1910). Recorded from both the Tennessee and Cumberland River Systems up until the construction of Wolf Creek Dam on the Cumberland and the TVA Dams on the Tennessee. It has not been collected in over 20 years and hence is presumed extinct. D. lewisi is figured by Walker, 1910, The Nautilus 24(4): P1.3, Figs. 3-5 and by Neel & Allen, 1964, Malacologia 1(3): 451. 20 D. H. STANSBERY Dysnomia biemarginata (Lea, 1857). The big river D. b. biemarginata form has not been collected during this century and presumably has been extinct for some time. The headwater D. b. turgidula form was recently rediscovered in the Elk River of Ten- nessee but quarry washing operations in the summer of 1967 apparently destroyed most or all of thenaiadsinthis area. It may yet be rediscovered in some undamaged tributary. Dysnomia florentina (Lea, 1857). The form D. f. florentina is apparently gone from the entire Tennessee System except for the South Fork Holston River in Virginia. A closely related species or subspecies, D. f. walkeri, has its range reduced to the lower Stones and Red Rivers of the Cumberland River system. Dysnomia torulosa (Rafinesque, 1820). Typical D. t. torulosa are still occasionally collected in commercial opera- tions on the lower Ohio River (Kentucky-Illinois) (Parmalee, 1967) and from the Nolichucky River near its mouth inwestern Tennessee. It is gone throughout the rest of its previous range. The smooth headwater sub- species, D. t. rangiana, persists as a few populations in smaller streams in the Ohio and lower Great Lakes systems. In the southern Appalachians one may still find an occasional specimen of D. t. gubernaculum but it is apparently restricted to the Clinch River and is rare even there. Dysnomia propinqua (Lea, 1857). Pl. 2, Fig. 5. Never known outside the Tennessee System, this species has not been collected in over half a century. It is similar to both D. torulosa and D. sampsoni but apparently does not merge with either. It is presumed extinct. Dysnomia sampsoni (Lea, 1861). Pl. 2, Fig. 6. A smooth inflated form of the lower Wabash River which appears to merge with D. Е. rangiana and may be simply a variant of that subspecies. It has not been collected for over 50 years and may well be extinct in spite of the relatively good condition of this river. A review of the status of the 103 species of naiads now known from the Ohio River drainage system reveals that 41 readily qualify listing as rare and endangered and, of this latter number, at least 8 species are presumed to be extinct. All 8 species be- lieved to be extinct are members of the Genus Dysnomia Agassiz (= Epioblasma Rafinesque). Species of this genus are characteristic of the riffle (or shoal) habitats of high gradient streams and the 8 extinct forms were recorded, with rare exception, from riffles of our largest rivers. This specific type of habitat has all but disappeared from the Ohio basin and is being further reduced with the construction of new and higher dams. LITERATURE CITED BATES, John M. 1962. The impact of impoundment on the mussel fauna of Kentucky Reservoir, Tennessee River. Amer. Midl. Nat., 68(1): 232-236. CONRAD, Timothy A. 1834. New fresh water shells of the United States with coloured illustrations, and a monograph of the Genus Anculotus of Say; also a synopsis of the American naiades. Judah Dobson, Philadelphia, 76 p, 8 pls. HIGGINS, Frank. 1858. A catalogue ofthe shell-bearing species, inhabiting the vicinity of Columbus, Ohio, with some remarks thereon. Twelfth Ann. Rept. Ohio State Bd. of Agr. for 1857: 548-555. SYMPOSIUM: RARE AND ENDANGERED MOLLUSKS 21 ORTMANN, Arnold E. 1909. The destruction of the fresh-water fauna in western | Pennsylvania. Proc. Amer. Phil. Soc., 47(191): 90-110, 1 map. - ORTMANN, Arnold E. 1918. The nayades (freshwater mussels) of the upper Tennessee | drainage with notes on synonymy and distribution. Proc. Amer. Phil. Soc., 57(6): 521-626, 1 map. ORTMANN, Arnold E. 1924. Mussel Shoals. Science, 60(1564): 565-566. ’РАБМАГЕЕ, Paul W. 1967. The fresh-water mussels of Illinois. Ш. State Mus. Popular Sci., Ser. 8: i-ix, 1-108, 35 pls. SIMPSON, Charles T. 1900. Synopsis of the naiades, or pearly fresh-water mussels. Proc. U.S. Nat. Mus., 22(1205): 501-1044, 1 pl. STANSBERY, David H. 1961. A century of change in the naiad population of the Scioto River system in central Ohio. Amer. Malac. Union Ann. Reps. 1961, 28: 20-22. STANSBERY, David H. 1964. The mussel (muscle) shoals of the Tennessee River revisited. Amer. Malac. Union Ann. Reps. 1964, 31: 25-28. STANSBERY, David H. 1965. The naiad fauna of the Green River at Munfordville, Kentucky. Amer. Malac. Union Ann. Reps. 1965, 32: 13-14. STANSBERY, David H. 1966. Utilization of naiads by prehistoric man in the Ohio valley. Amer. Malac. Union Ann. Reps. 1966, 33: 41-43. STANSBERY, David H. 1967. A provisional classification of the Pleurobema cordatum complex in the Mississippi drainage basin of North America. Ohio State Museum, March 1967, 2 p. TRAUTMAN, Milton B. 1957. The fishes of Ohio. Ohio State Univ. Press, p i-xviii, 1-683, 172 maps, 7 pls., 172 figs. TRYON, George W. 1873. Land and fresh-water shells of North America. Part IV, Strepomatidae (American melanians). Smith Misc. Coll., 253: i-iv, 1-435. van der SCHALIE, Henry. 1938. Contributing factors in the depletion of naiades in eastern United States. Basteria, 3(4): 51-57. van der SCHALIE, Henry. 1939. Additional Notes onthe naiades (fresh-water mussels) of the lower Tennessee River. Amer. Midl. Nat., 22(2): 452-457, 1 table, 1 map. van der SCHALIE, Henry. 1945. What has happened to snails of the Genus Jo? Mollusca, 1: 59-61. van der SCHALIE, Henry. 1947. The ecology of mollusks for the biology teacher. Amer. Biol. Teacher, 9(6): 174-176. van der SCHALIE, Henry. 1958. The effects of thirty years of “progress” on the Huron River in Michigan. The Biologist, 40: 7-10. van der SCHALIE, Henry. 1960. Egypt's new high dam -- asset or liability? The Biologist, 42(3-4): 63-70. Discussion of Dr. Stansbery’s Paper by Arthur H. Clarke The eastern regions not considered by Dr. Stansbery or Dr. Heard, the North Atlantic Watershed and the Canadian Interior Basin, contain mostly widespread species whose ranges extend into undeveloped, sparsely settledregions. Although many local mollusk populations there have been killed by pollution, the species themselves are not yet endangered. A possible exception may be the unionid Alasmidonta heterodon (Lea), a small, rare Species known only from 5 river systems, viz. the Peticodiac in New Brunswick, the Connecticut and the Housatonic in New England, the Delaware in Pennsylvania and the Rappahannock in Virginia. Expansion of industrial pollution could eliminate this 22 A. H. CLARKE species. There are no early records ofits occurrence elsewhere and its discontinuous distribution may indicate that it is becoming extinct through natural causes. According to the literature some species within the Canadian Interior Basin (i.e., the Hudson Bay Watershed combined with the Arctic Watershed) have been taken only at one or a few localities and might be presumed to be rare. Recent work (Clarke, in press) has shown that most of them are not rare and that some are even abundant. For example, Acroloxus coloradensis (Henderson), previously known only from 4 lakes in the Rocky Mountains, has been found in 5 other localities in eastern Canada and may be widely distributed. Physa jennessi jennessi Dall, previously recorded only from its type locality near Bernard Harbour in the Canadian Arctic has now been collected from about 30 localities along the arctic mainland coast and near both sides of Hudson Bay. It appears to be a common arctic species. Physa jennessi skinneri Taylor, another presumably rare taxon, is now known from approximately 100 localities within the Canadian Interior Basin alone and should be considered abundant. Of the 103 species and subspecies now recognized from that region none now appear to be in danger of extinction by man. MALACOLOGIA, 1970, 10(1): 23-31 AMERICAN MALACOLOGICAL UNION SYMPOSIUM RARE AND ENDANGERED MOLLUSKS 3. EASTERN FRESHWATER MOLLUSKS (II) THE SOUTH ATLANTIC AND GULF DRAINAGES by William H. Heard Florida State University, Tallahassee, Florida 32306, U.S.A. INTRODUCTION The eastern United States contains over 50 major drainage systems, as well as many smaller ones, between the St. Croix River on the Maine - New Brunswick, Canada, border and the Rio Grande River on the Texas - Mexico border. In addition, the in- terior drainages contribute to the very extensive Mississippi River and Great Lakes - St. Lawrence River watersheds. The coastal drainages have been designated by Simpson (1900) and H. & A. van der Schalie (1950) as comprising the Atlantic and Apalachicolan, as well as part of the Interior Basin (= Mississippian), faunal regions for unionid mussels. The Atlantic region has been divided into a northern and a southern element, with the Potomac River drainage employed as the demarcation between the 2 parts. This report will cover the freshwater gastropods and bivalves of the South Atlantic Region from the Potomac River in Maryland to the St. Marys River on the Georgia - Florida border, peninsular Florida, the Apalachicolan Region, and the southern-most portion of the Interior Basin (i.e., the Alabama River system west to the Rio Grande drainage in Texas). Unfortunately, there are significant gaps in our knowledge of the taxonomy, phylo- genetic relationships, and geographical and ecological distribution of the mollusks of many of the drainages. Efforts have been made in recent years to correct our igno- rance, and it is hoped that the effect of this symposium will be to stimulate both further and more intensive research in these areas. THE NATURE OF THE FAUNA In general, the streams flowing into the Atlantic Ocean and Gulf of Mexico contain rather endemic mollusk elements. Each region or subregion is characterized by the presence and/or absence of various genera and species, and even within a single region striking differences in the fauna may occur from one stream to another. For example, one-half of the entire mollusk fauna of the Apalachicolan Region is endemic (e.g., Notogillia Pilsbry and Quincuncina Ortmann), about one-quarter also extends to the north and west, and the remaining nearly one-quarter extends south- ward into central Florida (Clench & Turner, 1956). Examining the mussel fauna (Unionidae) separately, one finds that one-fourth of the species are endemic, another quarter are related to eastern (South Atlantic) species, and half of the species have western (Interior Basin) affinities (van der Schalie, 1940). Within this same Apalachicolan Region, different drainages often have different assemblages of mollusks, i.e., vary in the numbers and kinds of species present. In comparing the elements of the whole region, Clench & Turner (1956) clearly point out that the Apalachicola River (with its major tributaries, the Flint, Chattahooche and Chipola rivers) contains the greatest total number of species, the largest number of (23) 24 W. H. HEARD species endemic to the region, and the largest number of species endemic to any single one of the drainage systems. In contrast, the Suwannee River drainage has fewer total species, has a proportionately smaller fauna which is endemic to the region, and altogether lacks species endemic to that drainage. These relationships of endemism (both between and within regions) appear to occur throughout the coastal drainages in the eastern United States, while widespread species typify (in part) the much larger Interior Basin. If one compares freshwater mollusks regionally, however, it becomesimmediately clear that the South Atlantic and Apalachi- colan faunas are depauperate in relation to those of the southern part of the Interior Basin (particularly as concerns the large Alabama River system). THE NATURE OF THE AREA The drainage systems of the South Atlantic Region, peninsular Florida, the Apalachi- colan Region and the southern part of the Interior Basin traverse one or more of the following physiographic provinces (as listed and described by Fenneman, 1938): Appalachian Mountains/Highlands, Valley and Ridge, Blue Ridge, Piedmont Plateau and Coastal Plain (both the Atlantic and Gulf portions). Short streams are usually confined to the Coastal Plain, while larger drainage systems may have tributaries flowing through several provinces. For example, the Coosa River tributary of the Alabama River system originates in the Blue Ridge and flows through the Valley and Ridge Province and the Piedmont Plateau before entering the Alabama River proper in the northern Gulf Coastal Plain. Another tributary, the Tombigbee River, flows largely through the Gulf Coastal Plain (a tributary of its own, the Black Warrior River, originates in the Appalachian Highlands) where it joins the Alabama River proper only about 25 miles from the Gulf of Mexico. Striking differences in the freshwater mollusk fauna(s) occur between and occasion- ally within, different physiographic provinces. The Piedmont Plateau has a very sparse fauna, and most of the species of the rich fauna of the Coosa River occur in the Valley and Ridge Province. And frequently, the Coastal Plain assemblage is quite distinct from the composition found upstream in another province. These phenomena are mentioned here to point out that within a single faunal region distinct elements of the biota may be found in different “zones” of the same drainage. These faunal elements may reflect a variety of circumstances, such as (1) a group which is adapted to living in small stream conditions versus a large river habitat, (2) an area which is comparatively “more favorable” for such factors as type and/or quantity of food or substrate conditions, or (3) preclusion of a part or all of the fauna because of industrial pollution. Such generalities are frequently made to explain the presence or absence of species in/from an area without more specific information. It is particularly common to blame pollution for the absence of some or all biota, and while this conclusion may often be valid it is nearly always based on superficial observation. More detailed in- formation concerning ecological requirements and hazards are in effect lacking, and such data are desirable for all species, and in particular for those which are local- ized in distribution and can be considered rare and/or endangered. CHANGES IN THE FAUNA It should be clear to all that the freshwater mollusk fauna(s) of the eastern United States has been altered and is continuing to change at an amazing rate, often in a disadvantageous direction. The following categories of circumstances and the accompanying specific examples SYMPOSIUM: RARE AND ENDANGERED MOLLUSKS 25 reflect largely personal observations; a few conditions were taken from the literature. Further information is currently being assembled on the freshwater mollusks of peninsular Florida and the drainages of the South Atlantic Region, principally by the workers at Harvard’s Museum of Comparative Zoology. More complete data will be provided when their studies are published. Species of Decreased Abundance /Distribution The natural ranges of many species of plants and animals are diminishing, largely due to human alteration of the environment(s). This circumstance is demonstrated, in part, by the reduced abundance of organisms in an area. Unless at least a few breeding individuals can be maintained, the population will become extinct. And if this course is followed by numerous populations, the species may be summarily re- duced in its geographic distribution and perhaps eventually experience total extinction. Pomacea paludosa Say (Gastropoda: Pilidae) occurs in southern Georgia and Ala- bama and throughout Florida. Because of the activities of the U.S. Army Corps of Engineers, large tracts of the Everglades in southernmost peninsular Florida have been drained. One result of this actionhas been the destruction of this snail’s habitat, and consequently their numbers have decreased in this region. Similarly, the Florida kite, a bird which preys upon P. paludosa in the Everglades, is diminishing in numbers. Another example concerns two unionid clams. In 1963 Anodonta imbecilis Say and A. peggyae Johnson occurred in approximately equal numbers in Lake Talquin (the type locality of A. peggyae!), a reservoir of the Ochlookonee River, Leon-Gadsdon County, Florida. Since that time, however, А. imbecilis has become all but extinct and A. peggyae has become drastically reduced in numbers in the impoundment. This Situation has evidently been wrought principally by the Florida Fresh Water Fish and Game Commission which has administered rotenone to the reservoir to remove a pest fish, the grizzard shad (= Dorosoma cepedianum). After such treatment, the shore is littered with numerous decaying bivalves of several species. Clench & Turner (1956) state that Goniobasis albanyensis Lea (Gastropoda: Pleuro- ceridae) probably formerly occupied the entire Apalachicola River system but that it now is confined to the Flint and Chattahoochee tributaries. Farming and consequent silting is listed as the cause of the decline not only of С. albanyensis but also of G. boykiniana (Lea) which is considered nearly extinct. Notogillia wetherbyi Dall (Gastropoda: Hydrobiidae) is recorded by Clench € Turner (1956) as inhabiting the St. Johns, Suwannee and Apalachincola drainage systems. It has also been discovered as fossil along the McBride’s Slough tributary of the Wakulla River in Wakulla County, Florida. For unknown reasons, it is extinct in that drainage now. Extinct Species Although several fossil species of freshwater mollusks have been described from the South Atlantic and Gulf Coastal drainages, very few have become extinct in com- paratively recent times. Ordinarily, a list of such species would include those of the genus Tulotoma Haldeman (Gastropoda: Viviparidae). However, in the past few years intensive collecting by Mr. Herbert Athearn of Cleveland, Tennessee, has located 1 living population each of 2 Species, T. angulata (Lea) and T. magnifica (Conrad), in the Coosa River tributary of the Alabama River. The Coosa River is crossed by a number of dams, and the atten- dant impoundments as well as silting and pollution have served to drastically alter the original aquatic fauna(s). Consequently, the 2 populations of Tulotoma may represent the last remnants of this genus. Among the pleurocerid snails, Clench & Turner (1956) list Goniobasis catenoides 26 W. H. HEARD (Lea), known only from the Chattahoochee River at Columbus, Georgia, as extinct, “apparently ... exterminated by river silt.” Extinct Communities On occasion, one may find that a habitat previously visited has been destroyed and that the assemblage of mollusks at that site has been eliminated. We are fortunate indeed to have such faunal lists as that prepared by Hinkley (1906) for the Yalobusha River (and other drainages) and that by Frierson (1911) for the Pearl River (in part), bothin Mississippi. The Yalobusha and Pearl drainages present- ly receive substantial industrial effluents, andtheformer faunas at Grenada and Jackson (respectively) have been obliterated. Further downstream, beyond the recovery zone, one may again find elements of the fauna that formerly resided upstream. In the Pearl River at Columbia, Mississippi, approximately 100 miles downstream from Jackson, one can collect over 20 speciesofunionid mussels. But only upstream from the bridge (U.S. Hwy. 98), because immediately under the bridge the stream again receives an odorous contribution, the Columbia sewage. A striking zonation can be observed, and no mussels occur below the source of the effluent. More horrifying still are examples of the extinction of the fauna of nearly entire drainages. A paper mill at Foley, Florida, voids its wastes into the Fenholloway River about 15 miles from the Gulf of Mexico. The entire fauna and flora of the main channel has been totally destroyed, and only remnants remain in the unaffected small tributaries. A similar situation, involving phosphate mining pollution, has effected the decimation of the fauna in the main channel of the Peace River in peninsular Florida. DISCUSSION (THE ENDANGERED FAUNA) The overall changes in the freshwater mollusk fauna(s) of the eastern United States brought about by human activities have been immense, although only a few examples have been cited here. Examination of a drainage map of the United States reveals a paucity of natural lakes in the Atlantic and Gulf coastal states as compared to those of the northern areas which felt the impact of glaciation, one effect of which was to scour out depressions which became lake basins. Evidently the evolution of freshwater gastropods has fol- lowed accordingly. The majority of aquatic pulmonates are in the north, and most prosobranchs occur in the south. Nearly the entire fauna of the south is composed of gilled species, and as such it is more susceptible to disruption of the aquatic environ- ment than the lunged basommatophorans of the northern lakes. Most gilled aquatic mollusks are stream-dwellers, and they are affected if the stream is altered in some way such as by (1) dam construction and impoundment of stream water to provide recreational facilities, better navigation, and/or a source of electric power, (2) industrial pollution which affects the chemical content of the water (by robbing the stream of dissolved oxygen, adding toxic materials, and/or adding normally non-toxic materials intoxic quantities), and/or by (3) extensive farming which through erosion will increase the silt content of streams, a process tending to pro- gressively destroy the aquatic fauna. Although Birmingham, Alabama, lies several hundred miles upstream from the Gulf of Mexico and numerous dams occur along the Alabama-Coosa River waterway, at- tempts have been made to promote this city as a seaport. The aquatic mollusks of the drainage have already been extensively damaged by impoundment-production (as well as by silting and pollution), yet further efforts are underway to construct additional dams (with locks), threatening the remaining species. SYMPOSIUM: RARE AND ENDANGERED MOLLUSKS 27 Industrial plants are continually arising alongside or near streams, and while at- tempts to encourage conservation are everywhere these days there are too few and/or too weak laws to punish or correct violations. Plans for the construction of a paper mill on the Apalachicola River between Bristol and Blountstown, Florida, are now under consideration. Unless measures are taken for adequate treatment of the effluents, we will most certainly lose the mollusks of the main channel, particularly Glebula rotundata (Lamarck) (Pelecypoda: Unionidae), a large stream species which finds its eastward limit in this drainage. The southern states are comparatively agricultural (e.g., cotton, peanuts, tobacco), and soil conservation must be practiced not only for human benefit of continued crops but also for the perpetuation of the aquaticfauna. Silting is often said to affect mollusks by interfering with their respiration and/or feeding, and by altering the substrate dis- advantageously. Specific evidence, particularly of an experimental nature, is largely lacking, however. One can and must conclude that all of our freshwater mollusks, not only those of the eastern United States, are endangered. The factors which have partially or totally destroyed such faunal elements continue to plague us. Particular concern should be afforded not only rare and/or diminishing species (e.g., the unionids Pleurobema collina (Conrad) of the James River, Virginia, and the Tar River, North Carolina; and Elliptio spinosa (Lea) of the Altamaha River drainage in Georgia (Boss & Clench, 1967)), but also those which are greatly restricted in range even though they may be abundant in it (e.g., the unionids Elliptio mcmichaeliClench & Turner and Quincuncina burkei Walker of the Choctawhatchee River system in southern Alabama and the Florida panhandle (Clench & Turner, 1956)). If such streams are sufficiently changed in some way, these endemic forms will vanish. LITERATURE CITED BOSS, K. J. & CLENCH, W. J. 1967. Notes on Pleurobema collina (Conrad) from the James River, Virginia. Occ. Pap. Moll., Harvard Univ. Mus. Comp. Zool., 3: 45-52. CLENCH, W. J. & TURNER, R. D. 1956. Freshwater mollusks of Alabama, Georgia, and Florida from the Escambia to the Suwannee River. Bull. Florida State Mus., 1: 97-239. FENNEMAN, N. M. 1938. Physiography of the Eastern United States. McGraw-Hill Book Co., Inc., New York, 714 p. FRIERSON, L. 5. 1911. A comparison of the Unionidae ofthe Pearl and Sabine rivers. Nautilus, 24: 134-136. HINKLEY, A. A. 1906. Some shells of Mississippi and Alabama. Nautilus, 20: 34-36, 40-44, 52-55. SIMPSON, C. T. 1900. Synopsis of the naiades, or pearly freshwater mussels. Proc. U.S. Nat. Mus., 22: 501-1044. van der SCHALIE, H. 1940. The naiad fauna of the Chipola River, in northwestern Florida. Lloydia, 3: 191-208. van der SCHALIE, H. & vanderSCHALIE, A. 1950. Mussels of the Mississippi River. Amer. Midl. Nat., 44: 448-466. 28 H. D. ATHEARN Discussion of Dr. Heard’s Paper by Herbert D. Athearn Cleveland, Tennessee 37311, U.S.A. My field work on the freshwater mollusks of the Gulf of Mexico drainage region began in 1941 and has been carried on intensively since 1954. During that period collections were made at about 500 stations. Many species were found to be abundant, others are common, and some are rare or very rare and have been found on only one or a few occasions. Other species previously reported from the region have never been collected by me. Some species have apparently become very rare or perhaps even extinct during the past few years because of water pollution, dam construction or other habitat disruption. Dam construction on the Coosa River has eliminated almost all riffle habitats and has been particularly destructive to the rich, endemic fauna which previously flourished there. Several of these now rare and endangered, or possibly extinct, species have already been mentioned by Dr. Heard. Unfortunately an additional large number should also be inserted into the preliminary list. These are as follows: SOUTHERN AND CENTRAL TEXAS DRAINAGES UNIONIDAE Fusconaia friersoni B. H. Wright 1896 Fusconaia lananensis Frierson 1901 Fusconaia ridelli Lea 1861 Quadrula aurea Lea 1859 Lampsilis bracteata Gould 1866 LOWER MISSISSIPPI AND ATCHAFALAYA RIVER TRIBUTARIES PLEUROCERIDAE Lithasia hubrichti Clench 1965 Anculosa arkansensis Hinkley 1915 UNIONIDAE Margaritifera hembeli Conrad 1838 Fusconaia missouriense Marsh 1901 Arkansia wheeleri Walker & Ortmann 1912 Ptychobranchus occidentalis Conrad 1836 Lampsilis streckeri Frierson 1927 Dysnomia florentina curtisi Utterback 1915 Dysnomia lefevrei Utterback 1915 TOMBIGBEE - ALABAMA - COOSA RIVER SYSTEM NERITIDAE Lepyrium showalteri Lea 1861 VIVIPARIDAE Lioplax cyclostomatiformis Lea 1844 SYMPOSIUM: RARE AND ENDANGERED MOLLUSKS AMNICOLIDAE Clappia cahabensis Clench 1965 Clappia clappi Walker 1909 PLEUROCERIDAE Pleurocera foremani Lea 1842 Pleurocera showalteri Lea 1862 Goniobasis alabamensis Lea 1861 Goniobasis bellula Lea 1861 Goniobasis brevis Lea 1842 Goniobasis bullula Lea 1861 Goniobasis caelatura stearnsiana Call 1886 Goniobasis cahawbensis fraterna Lea 1864 Gontobasis capillaris Lea 1861 Goniobasis clausa Lea 1861 Goniobasis crenatella Lea 1860 Goniobasis fusiformis Lea 1861 Goniobasis gibbera H. H. Smith, Goodrich 1936 Goniobasis hartmaniana Lea 1861 Goniobasis haysiana Lea 1842 Goniobasis impressa Lea 1841 Goniobasis jonesi Goodrich 1936 Goniobasis lachryma Anthony, Reeve 1861 Goniobasis laeta Jay 1839 Goniobasis macglameriana Goodrich 1936 Goniobasis olivula Conrad 1834 Goniobasis pilsbryi Goodrich 1927 Goniobasis pupaeformis Lea 1864 Goniobasis pupoidea Anthony 1854 Goniobasis pygmaea H. H. Smith, Goodrich 1936 Goniobasis vanuxemiana Lea 1842 Gyrotoma alabamensis Lea 1860 Gyrotoma amplum Anthony 1860 Gyrotoma cariniferum Anthony 1860 Gyrotoma excisum Lea 1843 Gyrotoma hendersoni H. H. Smith, Goodrich 1924 Gyrotoma incisum Lea 1843 Gyrotoma laciniatum Lea 1845 Gyrotoma lewisi Lea 1869 Gyrotoma pagoda Lea 1845 Gyrotoma pumilum Lea 1860 Gyrotoma pyramidatum Shuttleworth 1845 Gyrotoma spillmani Lea 1861 Gyrotoma walkeri H. H. Smith, Goodrich 1924 Anculosa choccoloccoensis H. H. Smith, Goodrich 1922 Anculosa clipeata H. H. Smith, Goodrich 1922 Anculosa coosaensis Lea 1861 Anculosa foremani Lea 1842 Anculosa formosa Lea 1860 Anculosa griffithiana Lea 1841 Anculosa ligata Anthony 1860 Anculosa melanoides Conrad 1834 Anculosa modesta H. H. Smith, Goodrich 1922 30 H. D. ATHEARN Anculosa picta Lea 1860 Anculosa showalteri Lea 1860 Anculosa taeniata Conrad 1834 Anculosa torrefacta H. H. Smith, Goodrich 1922 Anculosa vittata Lea 1860 ANC YLIDAE Rhodacmea cahawbensis Walker 1904 Rhodacmea filosa Conrad 1834 Rhodacmea gwatkiniana Walker 1917 Rhodacmea rhodacme Walker 1917 Neoplanorbis carinatus Walker 1908 Neoplanorbis smithi Walker 1908 Neoplanorbis tantillus Pilsbry 1904 Neoplanorbis umbilicatus Walker 1908 Amphigyra alabamensis Pilsbry 1906 UNIONIDAE Fusconaia rubidula Frierson 1905 Quadrula archeri Frierson 1905 Quadrula stapes Lea 1831 Pleurobema aldrichianum Lea 1858 Pleurobema altum Conrad 1854 Pleurobema avellana Simpson 1900 Pleurobema concolor Lea 1861 Pleurobema decisum Lea 1831 Pleurobema favosum Lea 1856 Pleurobema fibuloides Lea 1859 Pleurobema furvum Conrad 1834 Pleurobema hagleri Frierson 1900 Pleurobema hanleyanum Lea 1852 Pleurobema hartmanianum Lea 1860 Pleurobema instructum Lea 1861 Pleurobema interventum Lea 1861 Pleurobema irrasum Lea 1861 Pleurobema johannis Lea 1859 Pleurobema lewisi Lea 1861 Pleurobema meredithi Lea 1858 Pleurobema murrayense Lea 1868 Pleurobema perovatum Conrad 1834 Pleurobema rubellum Conrad 1834 Pleurobema simulans Lea 1874 Pleurobema showalteri Lea 1860 Alasmidonta mccordi Athearn 1964 Strophitus alabamensis Lea 1861 Ptychobranchus foremanianum Lea 1842 Ptychobranchus greeni Conrad 1834 Obovaria curta Lea 1859 Plagiola lineolata Rafinesque 1820 (secure elsewhere) Lampsilis altilis Conrad 1834 Lampsilis perovalis Conrad 1834 Lampsilis perpasta Lea 1861 Villosa propria Lea 1865 Dysnomia metastriata Conrad 1840 SYMPOSIUM: RARE AND ENDANGERED MOLLUSKS 31 Dysnomia othcaloogensis Lea 1857 Dysnomia penita Conrad 1834 EASTERN GULF DRAINAGES: ESCAMBIA TO SUWANNEE RIVER UNIONIDAE Margaritifera hembeli Conrad 1838 Quincuncina burkei Walker 1922 Megalonaias boykiniana Lea 1840 Pleurobema pyriforme Lea 1857 Elliptio sloatianus Lea 1840 Alasmidonta triangulata Lea 1858 Medionidus penicillatus Lea 1857 Lampsilis australis Simpson 1900 Lampsilis binominata Simpson 1900 Lampsilis haddletoni Athearn 1964 Lampsilis jonesi van der Schalie 1934 5 7 . E 7 2 | | > | ини die ‘ amore. (le Ñ 7 N 25 ro wid LE pres ons. | {| ао Ве AA Pa OCT o A DEE | ¿o VIS ENSTSAZT а pee ” 1 a | 1) Mo bd бит ‘ PR DEL lO Wiley } | E poe AA = : need al tone ass o cmt os or aa eel ме | YO rt pate a hy E cojas QUA т ¡0 AAN nal ‘ $ iia eae 5 Pans ave her f 1 в. у 2 7 u Do o до Y ve iene A ing | o 1 101 5 2 Ar mn DO pa | y i LOL Wat Mm ye u a ater ys рат. RE vere = + в DS NO MO NA een sj Soa a ШИ es | . o. ) e: ler Din ae 2 Fhe a AP fm, - ~*. °F bie + пи» 6. TS + o | | | ДО > UD) A ha rs SRA A e | ee + + 1004 1 фи MALACOLOGIA, 1970, 10(1): 33-34 AMERICAN MALACOLOGICAL UNION SYMPOSIUM RARE AND ENDANGERED MOLLUSKS 4. WESTERN FRESHWATER MOLLUSKS by Dwight W. Taylor Arizona State University, Tempe, Arizona 85281, U.S.A (Editor’s Summary) Dr. Taylor discussed in detail the nature of the fauna and the changes which are occurring. The full text of his paper is not available for publication but his list of recently extinct and/or rare and endangered species (status uncertain, and only those already named) is as follows: Valvata virens Tryon, 1863. Clear Lake, and a lake near Watsonville, California. Fontelicella idahoensis (Pilsbry, 1933). Snake River, southwestern Idaho. Pyrgulopsis nevadensis (Stearns, 1883), Pyramid Lake, Nevada. Durangonella mariae Morrison, 1945. Valley of Mexico. Durangonella seemanni (Frauenfeld, 1863). Durango City, Mexico. Planorbella traskii (Lea, 1856). Lakes in southern San Joaquin Valley, California. Menetus opercularis (Gould, 1847). Mountain Lake, San Francisco, California. Physa columbiana Hemphill, 1890. Columbia River below The Dalles, Oregon- Washington. Physa humerosa Gould, 1855. Upper Gila River, Arizona-New Mexico. Physa virginea Gould, 1847. Mountain Lake, San Francisco, California. Discussion of Dr. Taylor’s Paper by Harold D. Murray Trinity University, San Antonio, Texas 18212, U.S.A. Dr. Taylor has carefully and accurately analyzed the numerous causes of the changes in the molluscan fauna of Western North America. Perhaps his most succinct state- ment is “...the greatest handicap to evaluating the endangered species is the general lack of knowledge of the fauna.” That statement needs no further elaboration. The definition of “Western North America” used by Dr. Taylor is adequate for the purposes and discussion he presents. This author would be inclined to extend the eastern border of his definition into the Great Plains possibly as far east as longitude 100. This eastward extension is possible not because of faunal similarities to the far western area but because the same factors in faunal changes also apply there. This author is impressed by the vivid references to the rich endemic fauna of Cuatro Cinegas in northeastern Mexico. I wonder how many similar such habitats exist in the vast area of western United States. I disagree with but one of Dr. Taylor’s comments. He states that no field evidence of deleterious effects of introduced species of mollusks have been observed. At present, I know of one example located 30 miles north of San Antonio, Texas. Melan- oides tuberculatus and M. (Thiara) graniferus have invaded the type locality of Goniobasis comalensis Pilsbry 1886 to the extent that G. comalensis is now extremely (33) 34 D. W. TAYLOR difficult to find where it was once common. Furthermore, several other habitats where С. comalensis was once common are now predominately occupied by one or both of the above introduced species. It is possible that either M. tuberculatus or M. graniferus, or both, couldintime findtheir way to some of the localities of endemic native species to which he refers and have serious effects. MALACOLOGIA, 1970, 10(1): 35-37 AMERICAN MALACOLOGICAL UNION SYMPOSIUM RARE AND ENDANGERED MOLLUSKS 5. EASTERN LAND SNAILS by William J. Clench Museum of Comparative Zoology, Harvard University, Cambridge, Massachusetts 02138, U.S.A. The preservation of our land mollusks is an almost impossible task. The allocation of small as well as large areas as National Parks or National and State forests will in a measure preserve some of our species. Other than in a limited number of cases, it would be impossible to prevent the extermination of certain species or races which have a very restricted distribution. What has occurred on the Lower Florida Keys is parallel if not similar to what has taken place over much of North America. Most of the area composing the Lower Florida Keys was and is privately owned and as such is subject to the whims, one way or another, of the owner of the property. A classic example is that of Lower Matecumbe Key, about midway in the Lower Keys. I first saw this key during the winter of 1929. At that time Lower Matecumbe was relatively undisturbed. There was, of course, both the auto road and the Florida East Coast Railroad, both of which had a right-of-way cut through the length of the key. Hammock land was rather extensive and Liguus were abundant. About 1935 a very severe hurricane completely destroyed a group of beach hammocks along with Liguus solidus dohertyi Pflueger, a color form known only from these small hammocks. About 1953, land clearing and the building of fishing camps and other tourist attrac- tions eliminated just about all of the hammock land and, of course, a few more color forms of Liguus peculiar to this Key. This same type of destruction has occurred along the entire series of keys from near Miami to Key West. In general, the loss of our land mollusks is not due to pollution but to land clearing, strip mining, fire and other factors which destroy or completely change the natural habitat. At this time we have but little control over many of these factors. Pesticides and weed killers cause an element of pollution, perhaps only in local areas where they are used, so far as it concerns the land mollusks. Both of these may be far more serious as a pollution problem in our freshwater streams due to surface run-off. In the North, during winter months, tons of salt are used to keep the highways free from ice. This same salt becomes a most important pollutant when carried into our roadside streams and ponds. Even trees and other vegetation along the highways are killed by the salt. With relatively few exceptions most of our eastern land mollusks possess a fairly large distributional range. Asa consequence, many or most of these species will be under “protective custody” in our National and State Parks and Forests. Species and subspecies with a restrictive range or those known from but a single locality are far more difficult to protect. We are probably even unaware of the exis- tence of many unique populations which need protection. Factors given above will also hold for most of the West Indies. Rapid air transpor- tation is making most of these tropical islands easily accessible and shortly these will be subjected to the ever increasing pressure of the tourist. A curious factor which is detrimental to colonies of Cerion in Cuba is the quest for “Sharp” sand for concrete and cement work. Cerion lives only along the upper strand line in Cuba and it is here where this type of commercial sand occurs. As a conse- quence areas along this strand line are completely destroyed. Bulldozers cut down as much as 6 feet into jumble of coral rock and sand, destroying the vegetation of bushes and small trees, and of course the colonies of Cerion. (35) 36 D. S. DUNDEE Discussion of Dr. Clench’s Paper by Dee S. Dundee Department of Biology, Louisiana State University, New Orleans, Louisiana 70122, U.S.A. In considering rare and endangered eastern land snails, several questions come to mind. First, what exactly does rare mean? Does it mean those which once had a wide distribution but now are restricted to a fewplaces? Or does it mean those that always have been restricted to a few places where they continue to maintain the population at a high level? Or does it mean those that have a wide range as a species but have the individuals widely scattered within that range? Or, does it mean all of these? One must resolve these questions before he can set about thinking clearly of the problem at hand. Once a decision is reached about the meaning of rare, one must ask, if it is rare, then is it necessarily endangered? After wrestling with these questions and discussing them with my colleagues, I find that I am still confused. Therefore, I have had arbi- trarily to select, as being rare, those snails which are, for one reason or another, now limited to one area (a State or less). I have decided that, even though they are rare, they are not necessarily endangered. Upon these premises I shall proceed with my comments. Here we should consider some other questions: first, what will cause the extinction of any species? Dr. Clenchhas mentioneda few things: climatic factors such as hurri- canes, the clearing of landby man, strip mining, fire, pesticides. There are, of course, many others such as other types of climatic changes, soil changes, biological intro- ductions, and so on. Second, what generaltypes of snails are most likely to disappear? Assuming that edaphic factors such as climate and soils remain somewhat constant (they never do) in the near future, it would appear, as Dr. Clench has pointed out, that those snails having a restricted range or those from a small locality, or in some cases, the larger, more conspicuous forms would be most likely to disappear. Those ranging widely over much of eastern North America may have their populations depleted by man, but they should survive and most probably will adapt to the new environments created by man (e.g., where did all of those which now live in flower and vegetable gardens and lawns live prior to 1609?). Next we must ask, which of the eastern land snails then are likely to become extinct? Or which, if any, should we protect? Here we must use our arbitrary decisions as to what is rare and, if it is rare, is it en- dangered. I have checked through the land snails of eastern North America and have arrived at the following possibilities. Dr. Clench mentions only one, Liguus, which is truly North American. I believe that others may also be considered. I certainly am not proposing that we include all of these ina list of rare and endangered forms. I only ask that my colleagues consider these in the light of their experiences and help me decide. (After the session various malacologists contributed deletions and additions and the following list is the result.) Pomatiasidae: Opisthosiphon bahamensis (Pfeiffer) Florida Oleacinidae: Varicella gracillima floridana (Pilsbry) Florida Polygyridae: Triodopsis soelneri (Henderson) North Carolina Stenotrema hubrichti Pilsbry Illinois Polygyriscus virginianus (P. R. Burch) Virginia Polygyra hippocrepis (Pfeiffer) Texas SYMPOSIUM: RARE AND ENDANGERED MOLLUSKS 37 Pupillidae: Bothriopupa variolosa (Gould) Florida & Yucatan Sterkia eyriesi rhoadsi (Pilsbry) Florida Sagdidae: Hojeda inaguensis (Weinland) Florida Keys - Bahama Islands Zonitidae: Vitrinizonites uvidermis (Pilsbry) North Carolina, Tennessee Pilsbryana tridens (Morrison) Oklahoma, Texas P. aurea (Baker) Tennessee Paravitrea roundyi (Morrison) Oklahoma P. variabilis (Baker) Tennessee, Oklahoma P. aulacogyra (Pilsbry & Ferriss) Arkansas Clapiella saludensis (Morrison) South Carolina Bulimulidae: Liguus fasciatus (Müller) Florida Orthalicus reses (Say) Florida O. floridensis (Pilsbry) Florida Drymaeus dormani (Binney) Florida D. dominicus (Reeve) Florida Cerionidae: Cerion incanum (Binney) Florida It is very difficult to really decideif some of these are endangered; one really needs to be working with the groups to know for sure. A final question, and one which will be very unpopular, is this: should we worry about our rare species of eastern land snails? When one considers that the molluscs are a very old group dating back 600 million years, one must realize that there surely have been many species which lived and became extinct in that much time. Many of them doubtlessly were as desirable as those about which we now are concerned. In fact, those which concernus now may have taken the places of some of the earlier ones. Perhaps the destruction of these present day forms is merely the next evolutionary step in the scheme of things with man being the evolutionary agent. A prominent ecologist has pointed out that, despite the fact that man is severely changing the land- scape, there ave organisms adapting to those changes and filling the niches of those wiped out by the changes. This whole question is a very philosophical one and has many ramifications but it is one which we should consider. Dr. Clench pointed out in his opening statement that the preservation of land molluscs is an almost impossible task. | я un tre iu wve AV. 7 < E : и « à tnt Er walt С Г ve EN] afd he \ 1 + MO l'A asa NTI y | 4 a АТГ с 7 $ 0 ue РА) m > » mile , “ii = y y Z i ap (Srv A ay 1d i 7 | ы A a Gil LEN : € a ef т » | rte > | 3000 te 9 ¡ey A 4 un Tin 16 y ; via, > sr ee а ao ve úl = € | ect ANNE ha ver 7 . | , „> фо ME 8 2 410 — ES в E caf A ad f ° в ми Qe ® 7 4 te ae oul ns À o MA В $ q las © tt + À 5 4 à . wr Des 10, My м ve "ù E ui $e MALACOLOGIA, 1970, 10(1): 39-46 AMERICAN MALACOLOGICAL UNION SYMPOSIUM RARE AND ENDANGERED MOLLUSKS 6. WESTERN LAND SNAILS by Allyn G. Smith Department of Invertebrate Zoology, California Academy of Sciences, San Francisco, California 94118, U.S.A. INTRODUCTION Viewed from the most pessimistic angle, it might be stated that all land mollusks indigenous to the western part of the United States are endangered to some degree. The rapid growth of the West has been spectacular and indications are that this will be accelerated in the future. While this is particularly true of the States west of the Rocky Mountains, to a much lesser degree has it affected Alaska, western Canada and Mexico, but eveninthese broad areas such growth is beginning to be felt. This massive advance in civilization, brought about by what amountsto a population explosion, brings with it the construction of more and ever wider freeways for motor traffic; bigger and higher dams that cause the flooding of beautiful, scenic cafions; bigger airports and similar projects that take over more and more wild land, scar the countryside and destroy land-snail habitats right and left. Developers are creating new towns and housing projects. The industrial trend is creating a movement from the central cities into outlying areas. This, with the air pollution and garbage disposal problems that result, bodes ill for the future of many western land snails, none of which can survive out of their natural habitats. There area few species of land mollusks that do tolerate the advance of civilization - Helix aspersa, Oxychilus cellarius and several species of slugs to mention a few. But these are European immigrants and are not pertinent to this discussion. The future picture does, however, have some bright spots. The western national, state and local parks provide habitats for many snail species. Those living in these areas are definitely not endangered and hopefully never will be. We are only just be- ginning to wake up to the need topreserve more wild areas for the enjoyment of future generations of people, and public opinion, prodded by an increasing number of con- servation-minded folks, seems to be moving in this direction, however slowly. This augurs well for the extension of the great western park systems, the creation of “green belts,” and the setting aside of wilderness areas safe from the incursion of loggers, miners, cattle men, resort developers and others of like ilk whose interest in the preservation of our natural resources leaves something to be desired. Another bright spot for the future well-being of indigenous land snails is the western “lay of the land,” with its vast mountainous and desert areas. Much of these are so inaccessible and incapable of “improvement,” or the climatic conditions are so ad- verse, that the so-called advance of man and his works is prevented or at least severely limited and will remain so. Land snails that live in such areas will continue to do so without habitat interference. Fortunately, also, the ranges of many western land snail species are sufficiently extensive geographically so that the liklihood of wiping them out completely is remote. There is a danger here, however, for future malacological studies dealing with ecology and with species evolution. The possibility of eliminating certain local races of wide- spread species through habitat destruction is imminent, especially where such races occupy limited areas. (39) 40 A. G. SMITH Again, the relatively few collectors especially interestedinland mollusks at present are not liable to endanger a species; but this may not be so true in the future. There is an ever-present danger from the over-collecting of some forms having an extremely limited distribution or living in micro-habitats not occurring anywhere else. Danger to such forms can and should be minimized in the interests of science. Land snail collectors can reduce this danger if they will operate with discretion, with a weather eye on the need to allow a race or a colony to perpetuate itself. RARE AND ENDANGERED WESTERN LAND SNAILS I can say, at the outset, that at present I know of no western land snail species that is so rare or endangered to the degree that exists, for example, in the case of the California Condor, the California Clapper Railor the Trumpeter Swan. There may well be such but the west is a big country and includes thousands of square miles where I have not done any appreciable amount of collecting. Thus, I can comment only on those areas and those species with which I have had some familiarity starting in the year 1910, with the hope that others will be able to fill in the gaps. Perhaps the most practical way to approach the subject is to use Pilsbry’s two- volume monograph on the Land Mollusks of North America (North of Mexico), 1939- 1948, published by the Academy of Natural Sciencesof Philadelphia, taking the groups, family by family, and commenting on species known to be rare, or that appear to be in some danger of extinction. This, of necessity, will not cover species described since the Pilsbry Monograph was published - one of the gaps mentioned above. For the sake of brevity in the following list, code letters are used, as follows: R - Rare occurrence in nature (not because merely hard to collect); Г - Limited or local in geographic distribution; E - Endangered or possibly endangered for stated reasons, LIST OF SPECIES Family HELMINTHOGLYPTIDAE Monadenia M. fidelis group. Widespread with many localized subspecies. Safe in redwood parks. М. f. celeuthia Berry. В - L. Upper Rogue River valley. M. f. pronotis Berry. В - L. Near Crescent City, Calif. M. f. leonina Berry. В - L. Along Klamath River, Calif. M.f. klamathica Berry. R-L. A high dam on the Klamath River could eliminate this and the preceding subspecies. M. infumata group. Many localized races. Generally safe in redwood parks. М. i. alamedensis Berry. В - L - E, by industrial development and housing expansion along the eastern shore of San Francisco Bay. M. mormonum group. Many local races. Generally safe in mountain areas. М. m. buttoni (Pils.). В - L - E, by construction of both high and low dams causing cafion flooding. M. m. cala (Pils.). L. Safe in Calaveras Big Tree Park. M. m. loweana Pils. R - L. М. m. hirsuta Pils. В - L - E, from possible over-collecting. M. troglodytes Hanna € Smith. В - L. Recently found living. M. circumcarinata (Stearns). В - L. Possibly a relict species nearing*extinction. Not found living in recent years. SYMPOSIUM: RARE AND ENDANGERED MOLLUSKS 41 M. hillebrandi (Newc.) & ssp. yosemitensis (Lowe). R - L. Safe in Yosemite and Kings River National Parks. A high dam across the Merced River below the Yosemite Park boundary could eliminate a local race. Helminthoglypta H. tudiculata series. Fairly widespread. Many local races and subspecies. Generally safe in mountain habitats. Н. t. grippi (Pils.). R - L. H. t. angelena Berry. L - E, by industrial expansion. H. cypreophila series. Widespread, and generally safe in mountain habitats. H. allynsmithi (Pils.). R-L. A high dam across the Merced River Cañon could eliminate this species. H. hertleini Hanna & Smith. R - L. H. nickliniana series. H. californiensis (Lea). L. The typical small form is practically gone from the type locality, a small off-shore islet being destroyed by wave action, but is safe in Pt. Lobos State Park. H. berryi Hanna. В - L-E. Possibly nearing extinction as a relict species. Could be endangered further by over-collecting. H. n. awania (Bartsch). R - L. Safe in Pt. Reyes National Seashore. H. n. bridgesi (Newc.). L - E, by industrial and building expansion. H.n. contracostae (Pils.). L - E, at the type locality from resort expansion or over-collection. The habitat for the race arnheimi on the east side of San Francisco Bay has been completely destroyed by industrial expansion. H. аттоза series. Widespread and generally not endangered. Many local forms, coastal and inland. H. a. holderiana (Cooper). L - E, by industrial expansion on the east side of San Francisco Bay. H. a. miwoka (Bartsch). В - L. Safe in Pt. Reyes National Seashore. H. a. pomoensis A. G. Smith. R - L. Some danger from logging operations. H. a. mailliardi Pils. В - L. H. ayresiana series. Limited to Santa Barbara Channel Islands. E, on San Miguel Id., the type locality, from U.S. Navy operations. The ssp. sanctaecrucis Pils. in no present danger on Santa Cruz Id. H. walkeriana (Hemphill) and ssp. morroensis (Hemphill). R - L. H. dupetithouarsi series. H. dupetithouarsi (Desh.). An unnamed, dwarf race on an offshore islet (type locality of H. californiensis) is probably extinct from wave erosion of its micro-habitat. H. cuyama Hanna & Smith. R - L. H. benitoensis Lowe. В - L. Safe in Pinnacles National Monument. H. sequoicola consors (Berry). L - E, by expansionof farming and industrial operations. H. cuyamacensis series. Mostly in mountain habitats. H. c. lowei (Bartsch). R - L. Н. с. avus Bartsch. В - L. H. с. venturensis (Bartsch). В - L. H. c. paiutensis Willett. R - L. H. callistoderma (Pils. & Ferriss). R-L-E, possibly by a high dam across the lower Kern River Cañon. H. orina Berry. В - L. H. tularensis series. Mountain habitat. R. Mostly safe in Sequoia National Park. H. napaea series. L. Mountain habitat. Safe in national parks. (Mohave desert 42 A. G. SMITH series). R - L. Several species with desert habitat. Not in danger at present. H. traski series. Many subspecies and races. Mostly mountain habitat. H. t. misiona Chace. R - L. H. t. coelata (Bartsch). R - L. H. t. coronadoensis (Bartsch). R-L-E, from over-collecting in island habitat. . t. pacoimensis Gregg. R-L. .t. де Pils. R - L. . t. phlyctaena (Bartsch). R - L. . t. willetti (Berry). В - L - E, possibly by severe forest fires. H. t. tejonis Berry. R - L. . carpenteri (Newc). R - L. Desert habitat. . similans Hanna & Smith. R - L. Desert habitat. . petricola series. Several species and subspecies. В - L. . stageri (Willett). R - L. . inglesi Berry. В - L. . lioderma Berry. В - L. . ferrissi Pils. R - L. A large race safe in Kings Cañon National Park. H. proles series. Mountain habitats. Two subspecies. Generally safe in national parks. H. euomphalodes Berry. В - L. H. tularica (Bartsch). R?-L. A “lost” species. Micrarionta. The southern and Lower California species, of which there are many, are confined to the Santa Barbara Channel Islands or to desert mountain habitats. M. stearnsiana (Gabb) is a mainland species and there are others in Lower Cali- fornia. Most are limited in distribution. Living specimens of desert species are rare and difficult to collect for the most part. Those that might be endangered at present are: M. rufocincta (Newc.) and ssp. beatula Ckll. E, from resort expansion on Santa Catalina Id. M. facta (Newc.). E. May be extinct on San Nicolas Id. M. kelletti (Fbs.). L-E, from possible destruction of its cactus-patch habitat on Santa Catalina ld. M. tryoni carinata Hemphill. R - E, especially on San Nicolas Id. Sonorella. Widely distributed, as a genus, but many species, subspecies and local races have extremely limited distributions. Usually occurringin colonies but living specimens often rare and difficult to collect, asthey are subterranean. Some forms are no doubt in possible danger from over-collecting or other causes. Dr. Walter B. Miller has studied the group recently and is in a better position than I to indicate species that may be endangered. Humboldtiana. Mountain snails confined in the U.S. to the Texas border, extending south at least as far as Mexico City. U.S. species seem to be relatively rare but apparently not in danger. Oreohelix. Mountain snails widespread in the West. Generally colonial and common, with many species, subspecies and local races. As a group, the Oreohelices do not appear to be in any particular danger although some forms having extremely limited distributions may be potentially endangered. O. avalonensis (Hemphill). E, if not already extinct, the single known colony having been wiped out by the original collector many years ago. Polygyrella. Fairly wide distribution in relatively unpopulated country. Ammonitella. A relict genus, possibly on the way to extinction, though common at present, where found. H H H H AAA SYMPOSIUM: RARE AND ENDANGERED MOLLUSKS 43 A. yatesi and ssp. allyni Chace. L - E, from possible over-collecting. The sub- species seems Safe in a national park. Polygyroidea. Possibly another relict genus. Mountain habitat. P. harfordiana (J. G. Cooper). R-L. Safe in Mariposa Big Trees, the type locality, although it appears to be becoming increasingly rare there because of its extremely limited habitat. Also occurs in Merced River Cafion below Yosemite Park, where it could be endangered by a high dam. Glyptostoma. Several southern California species and subspecies, all except С. newberryanum (W. G. B.) being localized and rare. G. gabrielense Pils. L - E, from industrial development in the Dominguez Hills, near Los Angeles, but probably safe in Elysian Park, Los Angeles. Family POLYGYRIDAE Trilobopsis. Generally occurs in a mountainous habitat, in relatively unpopulated areas. T. loricata series. Several subspecies, all more or less limited in distribution but not thought to be endangered. Т. trachypepla Berry. В - L. Т. voperi series. Т. roperi (Pils.). R - L. T. tehamana (Pils.). R - L. T. penitens (Hanna € Rixford) R-L-E, as type locality inundated by Folsom Reservoir. A new locality for this species discovered in 1968, which also may be in trouble from a resort developer. Triodopsts. T. devia (Gld.). E, because of industrial expansion in the Seattle area. May not be in danger elsewhere in its range. T. mullani series. Many subspecies and local races in a mountainous habitat, generallyin unpopulated country. In no present danger, as a group. T. sanburni W.G.B. R-L. Т. populi (Van.). E. A high dam on the Snake River at Hell's Cañon may put this species in danger. Allogona. Western species in no particular danger. Widespread in Pacific Northwest east of the Cascades in U.S. and Canada. A. ptychophova solida (Van.). L-E, from a possible high dam at Hell's Cañon. Vespericola. Many species and subspecies, plus local races, most not being in any present danger although the habitats of some are being restricted. V. columbiana series. У. с. depressa (Pils. & Henderson). В - L. У. hapla (Berry). R - L. Ashmunella. Mountain snails in Arizona and New Mexico. Many species, subspecies and local races. Generally colonial. I am not familiar with their abundance or rarity at the present time. Most seem not in danger, as a group, although some may be in danger from over-collecting. Family SAGDIDAE Thysanophora. Widespread in the Southwest and in Mexico (including Baja California). Microphysula. Fairly widespread distribution. In no present danger. Family BULIMULIDAE Bulimulus. Western species (Pacific Southwest, Mexico and Baja California) occupy mountainous or desert mountain habitats. In no particular danger. 44 A. G. SMITH Family UROCOPTIDAE Holospiva. Numerous species in Arizona and New Mexico. Generally colonial in mountainous terrain. I am not familiar withforms that are presently rare, although some have limited distributions. Probably not endangered at present. Coelocentrum. Several species and subspecies on islands in Gulf of California and in Baja California. Probably not endangered, as most are remote. Family ACHATINIDAE Rumina. Introduced into Arizona and California. Cecilioides. Introduced into California. Family HAPLOTREMATIDAE Haplotrema. Numerous western species and subspecies. Smaller forms usually rare. . duranti (Newc.). Santa Barbara Channel Ids. only. R - E. catalinense (Hemphill). R - L. Santa Catalina Id. only. . keepi (Hemphill). В - L. . transfuga (Hemphill). В - L. voyanum (Newc.). R-L. No typical specimens found in recent years. May be extinct. H. v. humboldtense Pils. R? - L?. Unknown to me. Possibly not related to true H. voyanum. by by y Ku in Family ZONITIDAE Euconulus. Small; widespread. Mountainous habitat. Not in danger. Oxychilus. Several introduced species. Adapts to civilization. Retinella. Small mountain snails. Generally rare and seasonal. Probably not in danger. Pristiloma. Small; seasonal. Numerous western species. Probably not endangered. . stearnsi (Bland). R. . pilsbryi Vanatta. R. . tdahoense Pils. R. . arcticum (Lehnert). R. P. a. crateris Pils. R - L. . lansingi (Bland). R. . johnsoni (Dall). R. nicholsoni H. B. Baker. R - L. . shepardae (Hemphill). R - L. Island distribution only. . orotis (Berry). R - L. . gabrielinum (Berry). В - L. . wascoense (Hemphill). R - L. . subrupicola (Dall). R. Р. $. spelaeum (Dall). В - Г. Not a true cave snail. Hawaiia. Small; widespread. Not in danger. Striatura. Small; widespread. Not endangered. Vitrina. Widespread in mountains at higher elevations. Not in danger. Megomphix. Shells similar to Haplotrema. M. hemphilli (W. G. B.). R. M. lutarius H. B. Baker. R-L. M. californianus A. G. Smith. R - L. oh ae NES Mo la > Ba > a > E fa > E > Be SYMPOSIUM: RARE AND ENDANGERED MOLLUSKS 45 Family ENDODONTIDAE Anguispira. One common western form in Pacific Northwest and British Columbia. Not in danger. Discus. Small mountain snails. Not endangered. D. marmorensis H. B. Baker. R - L. D.? selenitoides (Pils.). R - L. Safe in Yosemite Park. Helicodiscus. H. singleyanus (Pils.). R. H. eigenmanni arizonensis (Pils. & Ferriss). R. H. salmonaceus W.G.B. R-L. Speleodiscoides. S. spirellum A. G. Smith. R-L. Nota cave snail. Found living for the first time in 1967. May not be an endodontid. Punctum. Small; generally widespread. Western species not endangered. Radiodiscus. Small. Mountain habitat. Western species not in danger. Family SUCCINEIDAE Oxyloma. Western species probably not endangered. O. nuttalliana (Lea). R. O. n. chasmodes Pils. R - L. O. haydeni Ranabensis Pils. R - L. O. hawkinsi (Baird). R. Succinea. Western species generally not endangered. S. rusticana Gld. R. S. lutella Gld. R. In Arizona and New Mexico. S. gabbi Tryon. R. S. californica Fischer & Crosse. R. In Baja California. S. oregonensis Lea. An unknown species. Quickella. Western species not worked out taxonomically. Family VALLONIIDAE Vallonia. Western species not endangered. У. gracilicosta Reinhardt. R - L. In western states. V. albula Sterki. R - L. In western states. Planogyra. P. clappi (Pils.). R. Cionella. C. lubrica (Müller). R - L. In western states. Family PUPILLIDAE Gastrocopta Chaenaxis Pupoides Many western species and subspecies, some with limited ranges Pupilla (e.g., Chaenaxis and Sterkia). Not considered to be particularly Vertigo endangered, especially in mountainous and desert habitats. Sterkia Family CARYCHIIDAE Carychium. C. exiguum (Say). R-L. C. occidentale Pils. R. 46 A. G. SMITH Family TRUNCATELLIDAE Truncatella. T. simpson: Stearns. R - L. C. californica Pfeiffer. R - L. The above list is, as stated earlier, far from complete. It omits any detailed mention of species living in western Canada (especially the northern provinces), Alaska and Arctic North America, whose status is not known to me. Similarly, I am not familiar with the extensive land snail fauna of Mexico (south of the Sonora Desert), or of Central America, where little collecting has been done in recent years. For such areas, much of which is largely unexplored conchologically, it probably can be stated categorically that the species living there are in no particular present danger. MALACOLOGIA, 1970, 10(1): 47-49 AMERICAN MALACOLOGICAL UNION SYMPOSIUM RARE AND ENDANGERED MOLLUSKS 7. EASTERN MARINE MOLLUSKS by R. Tucker Abbott du Pont Chair of Malacology, Delaware Museum of Natural History Greenville, Delaware 19807, U.S.A. The survival problems confronting marine species, although somewhat similar to those facing the land and fresh-water forms, are quite different in severity, manner of endangerment and nature of possible remedial measures. Marine mollusks do not appear to be endangered in the same sense as are many birds, mammals and fresh-water mollusks. In my considered judgement, there are few, if any, marine species of mollusk, anywhere in the world, being led to extinction because of the activities of man. This, however, is mainly because the distribution of every species of marine mollusk is either very extensive over many hundreds of linear miles, or, in the case of a few highly endemic species, at least extended over many hundreds of square miles. Furthermore, bathymetric ranges in sublittoral species give additional protection. Although no accurate figures are available, and, indeed, there is need for new studies along these lines, I would not hesitate to say that the well-known high mortality rates of marine mollusks are largely due to natural causes. Probably less than 1% of the annual death rate of all marine mollusks is due to the activities of man. Commercial fisheries would probably account for the greatest cause of man’s reduction of mollusk populations; pollution and other environmental changes made by builders and engineers would probably come second; and shell collectors would make a very poor third. From the distributional records being made by several research fisheries’ boats and by casual dredging samplings by amateur conchologists and commercial shrimp trawlers, it would appear that there is a population band of Macrocallista maculata running from Alabama to central west Florida and from North Carolina to central east Florida, anywhere from 1 to 8 miles in width at depths ranging from 6 to 60 feet. This represents about 6,000 square miles of high density Calico Clam populations. The species, incidentally, extends through the Caribbean to Brazil. One might hazard a guess that about 2 billion bushels of this clam die every 5 years. Old age, fish, “red-tide,” cold water, fungal diseases and shifting bottoms probably account for most of these deaths. Of the 2 billion bushels, I doubt if shell collectors account for more than 1,000 bushels, and most of these would be specimens cast ashore after storms. A similar situation exists for the vast majority of the marine mollusks. Are some marine species being over-collected? Yes. Especially, locally; and especially the larger and edible species. Arethey in danger of becoming extinct? No. Is over-collecting bad? Yes, because it reduces the density of the populations in cer- tain areas to the extent that they are no longer available in commercial quantities (in the case of oysters, scallops, clams and edible whelks) or no longer present in suf- ficient numbers to satisfy the normal, modest requirements of hobby collectors. Among the species that are being over-collectedincertain limited areas are Strombus gigas (the Pink Conch), Cassis madagascariensis (the Helmet Shell), Pleuroploca gigantea (the Horse Conch), Cyrtopleura costata (the Angel Wing), Cyphoma gibbosum (the Flamingo Tongue), Melongena corona (the King’s Crown) and edible clams, scallops and oysters. Of all these species, the first 3 (Strombus, Cassis and Pleuro- (47) 48 В. €. ABBOTT ploca) are the least able to replace their numbers, and are becoming comparatively uncommon, but certainly not extinct. In addition to over-collecting, and I refer mainly to that created by commercial fisheries’ activities and professional shell gatherers who sell to shell dealers, far- reaching and much more serious consequences can descend upon shore mollusks and, of course, other forms of marine life, by major engineering projects of man or by mass pollution of coastal waters by heavy metals, major heat transfers, massive oil Spillage or altered currents. The filling of extensive marsh lands by real estate developers robs the coastal offshore waters of their life-giving source of nutrients. What’s bad for a Melampus marsh snail is bad for a coastal shelf Junonia. What practical protective measures are possible? Space does not permit me to discuss national pollution and conservation problems. Agencies of the United States government and well over 500 private foundations and organizations, such as the National Wildlife Federation and the Welder Wildlife Foundation, are actively working on these matters. Over-collecting can be reduced by shellfishery laws and the dissemination of in- formation among shell collectors. I have studied the shellfishery laws of each state, and in 1961 I published a digest of the laws of 24 of the U.S. states and Canadian provinces that have salt-water coasts (How to Know the American Marine Shells, Signet Key Book, KT 375, New American Library, Inc., N. Y., р 197-203). In this I said, “The laws were not created to annoy tourists or shell collectors or to inter- fere with students of marine life. Unfortunately, the regulations vary from state to state, and in many instances they are ambiguous, scientifically inaccurate, and self- contradictory. We recommend 3 general rules for collectors: cooperate with local wardens; ask local fishermen or ocean-front property owners about local restrictions; don’t collect live oysters at any time. Beware of Sunday “blue law” restrictions, especially in eastern Canada and New Jersey. You may write to the director of fishery agencies for special collecting permits. Most states will issue them cheerfully with- out cost.” Many clubs are encouraging the conservation of mollusks. The Sanibel-Captiva club in Florida was the first to initiate a program of local education by publishing posters, flyers and booklets on “Don’t Be a Pig.” Other clubs have distributed “col- lecting creeds,” urging members to take small samplings, rather than to pick up every specimen seen. Authors of popular articles and books are now urging the general public to collect in moderate numbers. These measures are helpful in local areas. In some good collecting spots you can find a choice specimen only because a thoughtful and courteous collector was there just before your visit. One of the most successful systems of protecting our wildlife was championed by President Theodore Roosevelt, who began our system of National Parks and Wildlife Preserves. This is an ideal mechanism of ensuring reasonable protection to under- sea life in many areas. There are several underwater parks in America, the first being the Key Largo Coral Reef Preserve, openedin Florida in 1960. The Department of Mollusks at the Academy of Natural Sciences has made surveys in such island groups as the Seychelles, Indian Ocean, with a view towards outlining the methods of establishing underwater preserves that will not interfere with the rights and liveli- hood of the local people. Other governments, as in Malaya, British Honduras and the Bahamas, are now taking active steps to protect sea life for future generations. SYMPOSIUM: RARE AND ENDANGERED MOLLUSKS 49 Discussion of Dr. Abbott’s Paper by Joseph Rosewater Division of Mollusks, U.S. National Museum, Washington, D. С. 20560, U.S.A. It is refreshing to learn that in regardto our marine mollusks it is unlikely that any species is endangered due to man’s activities. I should like to make the point, how- ever, that it may not always be possible to make a subjective determination on the probability of the extinction of a species. The fossil record tells us that long before the appearance of man millions of once living species had already ceased to exist. We are relatively sure that this is continuing, and in the case of such cryptic animals as mollusks, probably largely undetected. What causes it? Probably many things, such as unsuccessful competition between species, changes in climate or in other characteristics of the habitat. It may be that there is inherent in each species a sort of evolutionary “time piece” which “runs down” at last. This is an enormous simplification which one day may be elaborated and more fully understood. The “running down,” however, could certainly be hastened or delayed by a multiplicity of factors, many of which man may influence especially in the light of his recent population growth. Persons, such as ourselves, who collect forms of life intensively and specifically may do well to approach the task thoughtfully. It is true that if we did not collect them the individuals would eventually die anyway. But if we collect every visible specimen of a species from a unit area, we may be upsetting the “balance of nature” in that spot. And if we destroy the habitat by turning rocks which we do not replace, etc., we may be sure that we have created havoc in that spot. What can be done? Dr. Abbott has made what are probably the most effective sug- gestions to assure us of a continuing source of enjoyment in our hobby and work. Obey local collecting regulations; collect moderately and intelligently; support conservation efforts. To these I would like to add another suggestion which may appear questionable at first but which may be understandable upon reflection: avoid subjective measures which bring about major changes in the environment or species composition, for these have in the past, and almost certainly will in the future, upset evolution. ua per if had > AAA ns = 48 ee Ч Lows {tem | | | | | MALACOLOGIA, 1970, 10(1): 51-53 AMERICAN MALACOLOGICAL UNION SYMPOSIUM RARE AND ENDANGERED MOLLUSKS 8. WESTERN MARINE MOLLUSKS by A. Myra Keen Department of Geology, Stanford University, Stanford, California 94305, U.S.A. Having contacted several collectors who might know of any West Coast mollusks that are both rare and endangered, I am pleasantly surprised to come up with nearly negative findings. It is true that we have rare species. We also have areas and habi- tats that are threatened. As yet there seem to be few if any species qualifying in both categories. I had thought that perhaps Norrisia norrisi, a trochid snail that feeds on the blades of giant kelp, might be in a precarious state, for the extent of the kelp beds has markedly diminished in southern California; also, commercial harvesting removes much of the annual production. However, Mr. John Fitch reports that although in places where pollution and sea urchins have destroyed the kelp, the snail is rare or missing, around some of the offshore islands and in untainted coastal waters it is still abundant. The great hazard to marine populations on the Pacific Coast is not so much to certain species as it is to the whole ecosystem, especially in the shallow bays. This West Coast, characterized by a steep continental shelf and slope, has only a few bays, and most of the species that have adapted to the bay environment tend to be wide- spread in geographic range. If only part of the bays were threatened, the assemblages might be expected to survive in other areas. However, the pressure of human popula- tions and the obsession on the part of developers to fill or radically modify the few bays that are here is cause enough for alarm. Pollution from industrial wastes, from sewer outfalls, and (most hazardous of all) from agricultural pesticide runoff has already had considerable effect on the marine fauna, and as it increases can cause enormous havoc. The voice of the conservationists is being raised, but here, as else- where in the country, the cry is yet too feeble to influence the expansionist planners. Commercial development of shellfish resources on the West Coast has been limited by several factors. Oysters were introduced into San Francisco Bay nearly a century ago from the Atlantic coast, for the native oyster, which had thrived there, is too small for marketing. Withinafew years pollution had built up so much that the oysters became unsafe for food. The industry continues, however, in a few other sites along the coast, importations now being of spat from Japan. With the oysters came several Atlantic and Japanese molluscan species, accidentally. Some have flourished -- for example, /lyanassa obsoleta -- but so far as I know none has been a special threat to native species as so often happens with introduced forms. Because it is in the inter- ests of the industry to keep bay watersclean, the industry is, on the whole, on the side of conservation. A canning industry, based on such West Coast food clams as the razor clam, Siliqua patula, burgeoned in the 1920’s from Washington to Alaska, but this enterprise soon foundered because the shellfish could not reproduce fast enough to supply the demands the canners were making. Some clam beds have never recovered, but there was a large enough breeding population so that the species have managed to survive. I shall give a review of the situation for the one intertidal species, a littorinid, that comes close to qualifying as endangered. It could easily be wiped out with only a (51) 52 А. М. КЕЕМ slight habitat change. For a time its numbers decreased markedly, and as Ц has a limited range, its condition was precarious. The status of Algamorda newcombiana (Hemphill, 1876) For the following notes on the situation of Algamorda newcombiana (family: Lit- torinidae), I am indebted to Mr. Robert Talmadge, who has been making observations on the species for about thirty years. This small snail is virtually restricted to Humboldt Bay, in northern California. It lives on the lower stems of a marsh succulent, Salicornia, or in the muddy substrate immediately below. Its optimal distribution is at or slightly above mean high tide level, so that it is submerged in sea water only a few hours per year and, because of the heavy rainfall of the region, is more apt to be wetted by fresh than by salt water. In the 1930’s, when Mr. Talmadge’s studies began, the species was distributed over a stretch of about 10 miles along the bay margins, present wherever there was Salicornia but tending to be in uneven clusters of dense populations thinning out later- ally. During the 1940’s and 1950’s several sawmills were actively operating in the area. By 1961 most of the snails were gone, and only a mass of half-burned sawdust could be found blanketing their habitat. Small isolated colonies survived in parts of the bay where the sawdust was less pervasive, but the prospects at this time seemed dim for the species. Upon my recent inquiry as to status of the snail, Mr. Talmadge revisited the bay in February 1968. He found a few colonies doing well in both the south and the north ends of the bay. Some of the sawdust layer has broken up, and mud is again evident in places. Some of the normal associates such as arthropods and the marsh snail Phytia were present again, even where Algamorda was not. It would seem, therefore, that habitat recovery is taking place. Several of the sawmills have been abandoned and others have converted to a type of work not producing sawdust. Thus, the menace to estuarine life here is lessening. Algamorda may again be able to expand to its for- mer extent, barring further pollution factors. Possibly the re-occupation of its range might be hastened by judicious transplanting as soon as the environment, through decay and flushing away of the sawdust, has again returned to normal. Discussion of Dr. Keen’s Paper by William K. Emerson Department of Living Invertebrates, American Museum of Natural History, New York, N. Y. 10024, U.S.A. I concur with Dr. Keen’s conclusion that there are apparently no species of west American marine mollusks facing biological extinction. However, as Dr. Keen has pointed out, it is the basic ecosystem of the shallow water bays, especially those of southern California, that is endangered. The severe modification of these bays by man for commercial and recreational purposes requires that one must look to northern Baja California, Mexico to find an essentially undisturbed bay-fauna of the Californian faunal province. San Quintin Bay, whichis situated some 150 miles south of San Diego, is an example of such an embayment (Gorsline & Stewart, 1962). Fortunately, most of the shallow-water, marine inhabitants of the bays of southern California occur as populations living offshore in shallow water at depths that are below effective wave action. A caseinpoint is the Giant Smooth Cockle, Laevicardium SYMPOSIUM: RARE AND ENDANGERED MOLLUSKS 53 elatum (Sowerby), a southern ranging species that was reported living in San Diego Вау at the turn of the century (Kelsey, 1907). Apparently as a result of man-made changes of the environment of the bays of southern California, this species is now restricted along this coast to quiet offshore waters. Populations of this species are now known to occur between Seal Beach and Huntington Beach, off the California coast (Fitch, 1953). Farther south, this cockle, which ranges from San Pedro to Panama, can be found living in the intertidal zone (Keen, 1958). It appears likely that most of the marine elements of the bays of southern California would be re-populated by the offshore-larvae of the presently missing species. The re-establishment of these species seemingly will occur only when the bays are allowed to return to their former environmental status. Partial success in re-establishing these species by natural faunal succession has apparently been achieved in Mission Bay at San Diego, where the bay environment was modified extensively for recre- ational purposes, but where certain areas are being retained as natural preserves (Morrison, 1957). It is, however, the truly estuarine species, which require brackish water and ex- tensive mud flats, that appear at the present time to be in danger of extinction locally. The destruction of the tidal flats by land fill and the changing of the salinity of the water by the channelling of the runoff of freshwater from the few rivers and streams of the area into unnatural flood control systems has largely eliminated some elements of the brackish water fauna in the larger bays. Although the brackish water element constitutes only a small part of the fauna, we must make an effort to conserve this endemic assemblage by retaining some of the existing natural areas of the bays when we undertake to modify them further for the “benefit” of mankind. LITERATURE CITED FITCH, John E. 1953. Common marine bivalves of California. Calif. Fish Bull., 90: 102 p, 63 figs. GORSLINE, Donn S. & STEWART, Richard A. 1962. Benthic marine exploration of Bahia De San Quintin, Baja California, 1960-61. Marine and Quaternary Geology. Pacific Naturalist, 3(8): 281-319, 17 figs. KEEN, A. Myra. 1958. Sea shells of tropical west America. Marine mollusks from Lower California to Colombia. Stanford Univ. Press, p i-viii, 1-624, illus. KELSEY, F. W. 1907. Mollusks and brachiopods collected in San Diego, California. Trans. San Diego Soc. Nat. Hist., 1(2): 31-55. MORRISON, Roy L. 1957. Molluscan life and collecting in Mission Bay, before and after dredging. [Abstract]. Amer. Malacol. Union Ann. Reps. 1957, 24: 28. MALACOLOGIA, 1970, 10(1): 55 AMERICAN MALACOLOGICAL UNION SYMPOSIUM RARE AND ENDANGERED MOLLUSKS 9. BRACKISH WATER MOLLUSKS by J. P. E. Morrison Division of Mollusks, United States National Museum, Washington, D. C. 20560, U.S.A. Brackish water mollusks may be divided into 2groups. Those with the more primi- tive life histories have a free swimming veliger stage that permits scattering of in- dividuals in each generation to all available and suitable estuarine habitats. The second group has “crawl-away” young. Its species are thereby assured continuation in one- way current-swept localities, but spread of the populationis restricted to immediately contiguous habitats. In North America man continues to unconsciously endanger and to ignorantly exter- minate brackish water species every time a marina is “built,” “dug,” “dredged” or “improved” in an estuary Situation. Inthe same way, today’s real-estate developments with land-fills and dredged or blasted canals, designed to increase the number of water-front lots for: sale, are deadly to estuarine species. Another modern water “conservation” plan to impound fresh waters in lowland reservoirs by damming estu- aries, prevents effective mingling with saline waters, and so narrows or destroys the brackish water habitat. Brackish water mollusks (with pelagic larvae) suchasthe Salt Marsh Snail Melampus bidentatus, the mactrid clam Rangia cuneata and the Virginia Oyster Crassostrea virginica, are not now in danger of extinction. Local populations may be extinct, but Melampus bidentatus still lives from southeastern Quebec to Yucatan. Rangia cuneata is locally abundant from Chesapeake Bay, Marylandtothe Laguna Terminos, Campeche. The Virginia Oyster is still harvested commercially from New Brunswick to Campeche. Some widespread species such as the ovo-viviparous marsh clam Cyrenoida flori- dana and the tiny snail Hydrobia jacksoni may be exterminated locally whenever conditions are arbitrarily changed by man. Such local populations could only be replaced by reintroduction from (relict) undisturbed populations in other areas. There is a complex of hydrobiid gill-breathing snails in North American brackish waters that is headed for extinction evenbefore the species are scientifically described or named. Littoridinops tenuipes is the only named species among hundreds which belong to the group. Some havebeenmade extinct by a single hurricane which changed the salinity of the waters in their restrictedlocal habitat. A pair of species are known to have been wiped out of existence when their brackish water “lake” was filled in the construction of one airport facility in Maryland. Others are so localized in range that a single marina development is known to have made a half dozen species extinct. The direct importance of these minute species (with crawl-away young) to man is nil except in that they form part of the food chain. They serve as food for shrimps, crabs and fishes in these brackish waters. With the extinction of even a small fraction of the food chain the production of sea-foods from the estuaries is modified. Since estuarine and littoral habitats are the greatest proportionate source of sea- foods man must examine critically every “improvement” that modifies and inevitably decreases his own food supply. Note that the Virginia Oyster is today commercially re-seeded or re-planted in many regions in an effort to prevent such a decrease of food resource. In the lagoons of Campeche, the Virginia Oyster has been deliberately replanted into “reefs” for centuries to maintain the harvest. (55) 56 A. H. CLARKE 10. SUMMARY In spite of differences in mode and degree of endangerment of the mollusks within the regions discussed, some features are common to all. In general those species whose survival is most in jeopardy occur only within small geographical areas which are undergoing urbanization, industrialization or other ecological disruption. More- over, numbers of species have recently become extinct or are on the threshold of extinction which were not even suspected of being imperiled. A much larger number will soon follow if effective programs for their protection are not soon initiated. The survival status of large segments of the freshwater molluscan fauna is particu- larly precarious, especially within the southeast and south-central portions of North America. In all, approximately 185 species and subspecies have been cited as rare and endangered. An additional 9 species, 8 Dysnomia (pp 19-20, pl. 1, 2) and 1 Gonio- basis (G. catenoides, p 25), are now almost certainly extinct. These figures do not in- clude the gastropods of the American Interior Basin because their status has not been determined. Scores of Pleuroceridae and many other snails from that region are probably also endangered or recently extinct. Numerous terrestrial species are imperiled. Some 45 species and subspecies, about half in the East and half in the West, are apparently rare and endangered. A much larger number, particularly in the West, are also rare and/or highly localized. Many of these may soon have to be added to the list of endangered taxa. Fortunately marine mollusks are relatively secure. Only Almagorda newcombiana (p 52) is known to be endangered. Some local populations of the more conspicuous species are being over-collected but since most of these also occur in subtidal or other relatively inaccessible regions, or are widely distributed, the species them- selves are still safe. Brackish-water mollusks, like freshwater mollusks, are vulnerable to pollution and habitat disruption. Widespread species are not in danger but hundreds of highly en- demic species, especially Hydrobiidae, are in great danger. Future challenges to species survival may be even more intense. The recent Santa Barbara disaster has shown that massive pollution from oil may menace whole com- munities of species. Effects of pesticides and radioactive waste products may be even more pervasive. Critics of the proposed sea-level canal in or near Panama have even predicted that if unrestricted faunal interchange is permitted between the oceans much of the tropical eastern Pacific fauna may be wiped out from competion with Caribbean species possessing superior adaptive features. Fortunately this problem is now under investigation by a number of workers. Recently Mr. H. D. Athearn has revisited the Clinch River and has found that the rich mollusk fauna there is stillina healthy condition. Miraculously, it was apparently unharmed by the temporary severe pollution in 1967. The recent deaths of millions of fish in the Clinch River was a most regrettable accident. That accident, however, engendered this Symposium. If students are now encouraged to study the endangered mollusks of North America and if heightened general awareness of our obligation to conserve our fauna coupled with suitable remedial action now result, the net effect of that accident will have been supremely beneficial to the preservation of our native molluscan fauna. A. H. Gi we += 4 < E “4 4 2% ae y < = $. = 4 > р ~ ~ > > a Xt » +. MALACOLOGIA, 1970, 10(1): 57-92 MUSSELS (UNIONIDAE) OF THE RED RIVER VALLEY IN NORTH DAKOTA AND MINNESOTA, U. S. A. Alan M. Cvancara Department of Geology University of North Dakota Grand Forks, North Dakota 58201, U.S.A. ABSTRACT Thirteen species of mussels inhabit the Red River of the North and 18 of its tributaries in eastern North Dakota and western Minnesota. These species, in 10 genera, are: Fusconaia flava (Rafinesque), Amblema costata Rafinesque, Quadrula quadrula Rafinesque, Lasmigona compressa (Lea), L. costata Rafin- esque, L. complanata (Barnes), Anodonta grandis Say, Anodontoides ferussaci- anus (Lea), Strophitus rugosus (Swainson), Proptera alata (Say), Ligumia recta latissima (Rafinesque), Lampsilis siliquoides (Barnes) and L. ventricosa (Barnes). Eight mussel species have been collected from the Red River, and 1-13 species from each of its tributaries. The 4 most common species are Lasmigona complanata, Anodonta grandis, Anodontoides ferussacianus and Lampsilis siliquoidea. Five species, Amblema costata, Quadrula quadrula, Proptera alata, Ligumia recta latissima and Lampsilis ventricosa, are general- ly characteristic of the larger rivers in the Red River Valley. Lasmigonia com- pressa and Anodontoides ferussacianus are generally indicative of smaller rivers in the Valley. The mussel fauna of the Red River Valley, which is part of the Hudson Bay drainage, originated from that of the Mississippi River system. The Valley fauna, however, constitutes only 26% of that of the Mississippi. Four ecological factors are presumably of primary importance in restricting the distribution of mussels in the Red River Valley. These are: prolonged lack of river flow, high chloride content, water pollution and possibly high turbidity. INTRODUCTION Previous work and purpose Little but species lists have previously been published for the mussels of the Red River drainage in North Dakota and Minnesota. Owen (1852: 177), during a geological reconnaissance, reported ob- serving very abundant mussels in the Red River, below the mouth of the Red Lake River, in July, 1848. He listed the following species as most common: Unio plicatus [= ? Amblema costata Rafin- esque], U. quadrulus [= Quadrula quad- rula Rafinesque], U. alatus [= Proptera alata (Say)], U. gibbosus [= ? Ligumia recta latissima (Rafinesque)], and U. crassus [= ? Lampsilis siliquoidea (Barnes) ]. (57) In 1858, Lea listed 9 mussel species from the Red River of the North at 50° N. lat.; if the latitude is correct, the locality would be in the vicinity of Winnipeg, Manitoba. Species given by Lea were: Unio rubiginosus Lea [= Fusconaia flava (Rafinesque)], U. undu- latus Barnes [= Amblema costata Rafin- esque], U. asperrimus Lea [= Quadrula quadrula Rafinesque], Anodonta decora Lea [= Anodonta grandis Say], Anodonta ferussaciana Lea [= Anodontoides ferus- sacianus (Lea)], U. alatus Say [= Prop- tera alata (Say)], U. rectus Lamarck [= Ligumia recta latissima (Lamarck)], U. luteolus Lamarck [= Lampsilis sili- quoidea (Barnes)] and U. occidens Lea [= Lampsilis ventricosa (Barnes)]. Daw- son (1875: 350) listed 7 mussel species for the Red River; his species, or the 58 A. M. CVANCARA presumed equivalents of his species names, did not differ from those of Lea (1858), with the exception of Unio spatu- lus Lea [= Ligumia ellipsiformis (Con- rad): = ? Ligumia recta latissima (Lamarck)]. Grant (1885: 115-119) listed and remarked upon 8 species of mussels from the Red River, Wilkin County, Minnesota. His species, or the equiva- lents of his species names, were pre- viously given by Lea (1858) with the ex- ception of Anodonta edentula Say [= Strophitus rugosus (Swainson)]. In ad- dition to those species listed by Lea (1858) and the previously mentioned authors, Dall (1905) noted the following species for the Red River drainage: Quadrula heros (Say) [= Megalonaias gi- gantea (Barnes)], Quadrula plicata (Say) [= Amblema peruviana (Lamarck) |, Sym- phynota complanata (Barnes) [= Lasmi- gona complanata (Barnes)] and Lampsilis gracilis (Barnes) [= Leptodea fragilis Rafinesque]. Wilson € Danglade (1914: 12) listed 10 species of mussels from 5 stations on the Otter Tail River (= “Red River”) in Minnesota. Species not mentioned previously by Owen (1852), Lea (1858) or Dall (1905) were Anodonta pepiniana Lea, Symphynota costata (Rafinesque) [= Lasmigona costata (Rafinesque)] and Quadrula coccinea (Conrad) [= Pleuro- Бета cordatum coccineum (Conrad)]. Coker € Southall (1915: 15), in a survey for commercial mussels, reported 6 species from the Red River at Fargo and 4 species from the Sheyenne River at Lisbon. Only one species listed, Quad- rula pustulosa (Lea) (at Fargo), was dif- ferent from those already cited above by earlier workers. Winslow (1921: 15) listed 5 mussels from North Dakota and only 2, Lampsilis luteola (Lamarck) [= Lampsilis siliquoidea (Barnes)] and Lasmigona compressa (Lea), from a river of the Red River Valley (Sheyenne River). Dawley's (1947: 679) survey of Minnesota aquatic mollusks included a listing of 10 mussel species for the Red River and 11 for the Red Lake River. Tuthill’s (1962, 1963) lists of North Dakota mollusks included mussels of the Red River Valley. Clarke’s (1964) sum- mary of the mollusks of the Hudson Bay Watershed includes all of the species which I have taken from the Valley. Since 1964, my students and I have studied the distribution and ecology of mussels in the Valley (Cvancara & Harrison, 1965; Cvancara, 1966; Cvan- cara, Heetderks & Iljana, 1966; Cvan- cara, 1967 and Norby, 1967. The main purpose of this paper is to present the known mussel fauna and its distribution in the Red River Valley of North Dakota and Minnesota. Also, those ecologic factors presumed to in- hibit the distribution of mussels are evaluated. Geologic setting, climate and river discharge The term “Red River Valley,” asused herein, refers to a glacial lacustrine plain or basin on both sides of the Red River of the North in eastern North Dakota and western Minnesota. Its boundary is defined as the highest strand- line (Herman “beach”) of glacial Lake Agassiz (Fig. 1). The Red River and its tributaries are part of the Hudson Bay FIG. 1. Map of the Red River Valley showing stream discharge at U. S. Geological Survey gaging stations. Discharge values are for the 10 year span from October 1, 1955 to September 30, 1965. The left hand bar portrays the mean discharge for each station whereas the right hand bar shows the minimum discharge. Figures above the bars indicate discharges under 10 cu. ft. 7 sec. that are not readable on the scale; where minimum discharge was zero, figures below the right hand bar indicate the percent of time that zero discharge has occurred. Discharge data were taken from U. S. Geological Survey (1961-1966a, 1961-1966b and 1964c). The highest strandline of glacial Lake Agassiz is from Leverett (1932) and from Colton, Lemke & Lindvall (1963); the deltas of glacial Lake Agassiz are from Upham (1895). DISCHARGE MEAN 3000 2000 MINIMUM 5 - PERCENT ZERO A USGS GAG 540 HIGHEST GLACIAL DELTA LAKE RED RIVER VALLEY MUSSELS 920 Tamarac o = o EN) River 825 GRAND A e FORKS N 790 A CROOKSTON > = e 515 WAHPETON FERGUS FALLS x a? ES oF TIME DISCHARGE ING STATION STRANDLINE OF LAKE AGASSIZ Loke Traverse OF GLACIAL AGASSIZ 20 MILES 59 60 A. M. CVANCARA drainage and drain northward. Only a relatively small part of the maximum extent of glacial Lake Agassiz, which was about 80,000 square miles (Elson, 1967: 37), occupied North Dakota and Minnesota. During the interval of about 12,500-9,000 years ago, 4 or 5 episodes of the lake occurred in the now general Red River Valley area (Elson, 1967: Table 6 and Fig. 6). The geology and geological history of Lake Agassiz in the United States and over its entire extent has been summarized recently by Laird (1965) and Elson (1967), respec- tively. Sediments over much of the RedRiver Valley consist of silt and clay, deposited in lake water perhaps up to 200 - 700 feet deep (Elson, 1967: 45). Marginal to the Valley are linear ridges of sand and gravel, commonly referred to as “beaches.” Sand and gravel bodies in the form of deltas also occur at the ex- treme margins of the Valley, those at the eastern side poorly defined (Fig. 1). Glacial till generally occurs peripherally and beneath the lake-associated sedi- ments. Local relief in the Red River Valley, excepting incised stream valleys, gener- ally is only a few to several feet. In the Grand Forks area (Fig. 1), for example, the local relief is only 1-15 feet per Square mile. Along the axis of the Red River Valley, the regional slope is very low. Using the cities of Wahpeton, Fargo, Grand Forks and Drayton (at the U.S. Geological Survey (USGS) gaging station 920, Fig. 1) as control points, I have calculated the regional slope to be as follows: 1.9 ft/mile (Wahpeton to Fargo), 1.1 ft/mile (Fargo to Grand Forks), and 0.53 ft/mile (Grand Forks to Drayton). The average of these slopes is only 1.2 ft/mile. Visher (1954: 365) has classified the climate of eastern North Dakota and western Minnesota, including the Red River Valley, as “Dry Subhumid.” In this region evaporation is usually in ex- cess of precipitation (Visher, 1954: 364). The average annual runoff in the Valley is only about one inch (Miller, Geraghty & Collins, pl. 10). Temperature and precipitation data for Wahpeton, Fargo, Grand Forks and Pem- bina are givenin Table 1. The average temperature and precipitation for the Valley is 41° F and 20.6 inches, respec- tively, as calculated from data in Table 1. These data also show a temperature range of 144° (-42-102° F) and a pre- cipitation range of 23.4 inches (12.9 - 36.3). The average temperature gradient was calculated as 1.6% F/degree latitude; this gradient, as computed between the 4 cities, appears to decrease northward. Table 4 shows average water temper- atures for selected stations inthe Valley. These data suggest that average water temperatures, as exemplified by those at Grand Forks and Fargo (Tables 1 and 4), are about 10° higher than average air temperatures. Discharge values for many localities are shown in Fig. 1. Ataglance one can see that the principal tributaries of the Red River are the Otter Tail, Sheyenne, Buffalo, Wild Rice (Minnesota), Red Lake and Pembina, listed in a downstream direction. The Red Lake River is the largest tributary, and effectively doubles the discharge of the Red River at Grand Forks. Below Grand Forks, at USGS gaging station 920 (in city of Drayton), the mean discharge of the Red River is nearly 3,000 cu. ft./sec. (Fig. 1). This discharge is appreciable although the gradient is very low. Between Grand Forks and Drayton, I have calculated the river gradient as 0.26 ft/mile; between Grand Forks and Fargo, and Fargo and Wah- peton, the gradients are 0.53 ft/mile and 0.85 ft/mile, respectively. The average of these gradients, from Wahpeton to Drayton, is only 0.55 ft/mile. Gradients of the rivers transverse to the Valley axis, however, are generally consider- ably higher, at least in their upper reaches, Parts of several streams have low minimum discharge values and are also characterized by relatively long periods 61 RED RIVER VALLEY MUSSELS *G96T ‘nesıng IeyyeoOM *S ‘AN pue ‘99GI-GG6I ‘nesang A9UYYE9M *S *f] моду UDALI элэм eyep ПУ ‘SUIHORI элэм SYFUOUI в 103 eyep osneoaq popn]9u1 jou эле BUIQUIG лоу зэптел uorjejidioaad 1e303) pue элпзелэтэз эЗелэле G96T °ULx (sayouJ) NOLLVLIdIDAHA TVLOL (HOYUIIYLA о) IHALVUAANAL AOTTVA 19A1H POU OY} UL SOYTEIO] F ло} (9961-9961) жезер поцезетоола pue ongexoduro uojedyem 03181 SHIOJ риело eurguod uojodyem SM1O0] риелэ eurquied "TAIadVL 62 A. M. CVANCARA of zero discharge. Several gaging stations (Fig. 1) show a minimum dis- charge of 10 cu. ft./sec. or less. A few stations in North Dakota (station 517, 530, 605 and 655) indicate no flow for about half the time. Under the condition of zero discharge, sections of a river are reduced to stagnant, elongate ponds. MATERIALS AND METHODS Field work was done during the sum- mers of 1965 and 1966. Mussels were collected by 2 methods: by hand and with a crowfoot dredge. Hand-picking was by far the most ef- fective method; it was used in all the tributaries and along the banks of the Red River. In water of low turbidity a Turtox Fishscope, which is an aluminum alloy cylinder measuring 24 inches in length by 6 inches in diameter fitted with a glass plate, aided in locating mussels. In turbid waters, mussels were located by feel with hands and feet. With ex- perience, a mussel could often be dis- tinguished from a pebble by the feet, even through thick rubber waders. The length of bottom examined, for each station, was determined by pacing. Usually 1/2-2 hours were spent in hand-picking and all mussels noted were gathered and counted. The numbers were converted to mussels per hour and used in con- structing Fig. 8. Counts were made for each species, and a presumedly repre- sentative series was taken for each. Sex was determined inthe sexually dimorphic species. An 8-foot crowfoot dredge was dragged from a 17-foot canoe for all Red River stations, in addition to hand-picking along the banks. The crowfoot dredge con- sisted of a pipe 2 inchesindiameter with 1 1/2-foot chains spaced at 6-inch inter- vals. Each chain was fitted with 2 back- to-back hooks fashioned from a single piece of heavy wire. On the Red River and 18 of its tribu- taries, 119 stations were checked for mussels (Fig. 2). Generally, about 5 stations were selected for eachtributary, including, where feasible, 1-2 stations just outside of the lake plain. Suchrivers as the Mustinka, Rabbit and Marsh in Minnesota, and the Rush in North Dakota were not sampled. They did not behave like true rivers, for I observed no flow in them during the summer of 1966, a wet year. The water was analyzed by about one dozen chemical tests (see p 16) and also for turbidity, at most stations, in the field, with a Hach Chemical Company portable chemical kit (Model DR-EL). With few exceptions, all tests were made at 3-5 stations for each tributary during the same day. All dissolved oxygen and free carbon dioxide tests were made during daylight hours. Field data also included observations on the bottom (Table 2), width and depth of stream, Shading of banks, associated animal life and aquatic vegetation. Shell measurements were made with vernier calipers on specimens with 4 or more growth annulae. Of the sexually dimorphic species, only shells of the males were measured. Length (L) was taken as the greatest length parallel to the hinge line; height (H) was taken аз Ве greatest dorso-ventral measurement at right angles to the hinge line; and width (W) was the greatest measurement taken across both valves. RESULTS Mussel species A complete taxonomic treatment for each species, including generic and spe- cific descriptions and synonymies, seems unwarranted here. In the diag- noses for the following 13 species, for brevity, generic and specific characters are not differentiated. A diagnosis in- cludes those characters that permit ready distinction of one species from all others in the Red River Valley. FIG. 2. O LIVE MUSSELS O NO LIVE MUSSELS RED RIVER VALLEY MUSSELS 63 CANADA PEWBINA 112 Ne RN 17 ug 4 ae ave O 13 © 96 tomer” GRAND Forks & 31 Rivers af OU o, MOORHEAD ES 30 179 WAHPETON HIGHEST STRANDLINE OF GLACIAL LAKE AGASSIZ Lake Traverse DELTA OF GLACIAL SCALE o 10 20 MILES = | LAKE AGASSIZ Map of mussel stations in the Red River Valley. The explanation of Fig. 1 gives sources for the highest strandline and deltas of glacial Lake Agassiz. Locality descriptions of stations and predominant bottom type at each are given in Table 2. рим Ápues “wed ‘N ‘ртечоэт N TU ф/8 9 ‘uy AIN (£OIV) zz pues (A,qqed) Апелелхо "NEU UN ‘ээпу AS па Z/T9 ‘worden (SOTY) tz [24818 Apues "wed 'N ‘OOlTV MS па < ‘‘H arde (901) 05 pnu 494819 (“UUIA ‘реэчхоой 197099 ммм па ф) "NE ‘М “POOMIBH AS Tu p/€ G ‘Я POU (08IV) 61 pnu 494819 "wed “N ‘Sunstaygp M TU P/E T ‘‘H POTN PIIM (SIIV) 81 рим Aokejo ‘Apues "Ne ‘М ‘WSIMG AN TU p/6 $ ‘Ч POTN рим (--) LT pues ÁPpnia "Ne ‘N ‘uosuryueH N IMF ‘A SOI рим (EIIV) эт pues Appnw “wed ‘М ‘orourpudM MS TU Z/T 9 ‘ ‘H ээ14 рим (==) ST pues ({rqqod) Affoaeayg "wed `М ‘oaseueny N TU 9 ‘ "М DIH РИМ (==) тт pnur Apues (‘uu ‘реза MNM TU p/g I) “APA 'N “901 рим A па 5/11 Upou (68IV) ET i [94813 (atqqed) ‘Аррии ( “UUIJA “UOJADATOM MN TUL I) “HPC ‘м ‘OUTISIAYD я па Z/TZ ‘'upeu «(SZTV) ст о Тэлех8 (914494) ‘Apues ( uuım ‘o8pliuoyooig лэзиэо МММ TU F/T >) "Ява ‘М ‘чозэдчелм лэзиэо N па F/T PF ‘'upeu (LZTV) IT = pues (A1qqad) АПэлелхю "UUIN ‘э8рухиэхоэхя 197099 ASA TU p ‘YU TIBL INO (L6V) от = [94813 (orqqdod) *Apues "УПИ “SWOYXOA MSS MU 9 ‘‘H TIBL 1990 (96V) 6 À [04818 (orqqod) ‘Apues "ЧИП ‘SIIBA SNSIOH 107000 MS TU p/E L ‘‘H из AO (SEY) 8 2 194813 (eTqqed) ‘Apues "ЧИП ‘ST[BA SNSISA 107009 MS FU p/£ T "U TIBLI9NO (81V) L [94813 (o1qqad) “pues "ИА “YI9QBZIA ‘‘H чеоцеа (86V) 9 [948.13 Apues “UU ‘SIA SNGI9A 197099 ANA TU p/E € ‘AU ПВГ, 49330 (11V) S pau 43118 ‘Apueg (‘uu ‘э8ртхиэхоэлхя 197000 $ ца 1) "MEA ‘М ‘uojodyeM 193u99 HS па F/T I ‘ ‘H XNOIS эр Slog (9ZIV) + [9A8a3 (aopnoq 07 914494) Appnur ‘Apues (uu *Treqdueo M ия 3/1 2) “Hed 'N “junowaeg AN TU p/£ $ ‘М XNOIS эр SIOH (9TIV) $ pues (Arqqod) AT[9ABAD (‘uul *319QSIOH M TU с/т) “MU 'N ‘Hoy 9YUM я Tu F/T ‘ "Ч XNOIS эр Slog (STTYV) Z „„pnur Aokejo ‘Apueg (“UU ‘uoyeoyM MSM TU p/T 2) "ea 'N “HOYSOYH AS FU 8 ‘ "Я XNOIS эр Slog «(FIIV) 1 woyog JUBUIMIOP9A AH 00194820] 9013835 > 4989 ye э4Аз 101404 JueurwWopord чим ADT[TVA IOAN poy OY} ur „suoryeIs [JOSSNMN ‘Z ATAVL 65 RED RIVER VALLEY MUSSELS pues Appnn 'yeq ‘м ‘puelyodg N JU 7/1 < ‘ ‘H 98009 Чочета UHON (--). # 104818 (o1qqod) ‘Apues “XeQ ‘м ‘PUeIHOd ММА TU p/€ y ‘Ч 95009 YOUBIZ SIPPIN (66V) Er pau AoAe]o ‘Apues (‘маг ‘реззтен.я Im т) ‘Ува ‘N ‘етаорэтео ASS tw Z/T L ‘Я POU (EEIV) zp ри 40410 ‘Apues ‘UUIN ‘WNAIpUSH N пас “*Y 99H рим (F8V) IP pues “UU ‘UMIPUSH AS ru Z/TL ‘Ч SOTU рим (88%) 07 pues (4A1qqod) Afeaeıg “UUTN ‘PV 197009 ASH тс ‘'HOOIM рим (38V) 6€ 1948.13 (914499) ‘Apues “UU ‘ÂAOIIEA UIML MNM TU p/g S ‘‘H POTN РИМ (08V) 88 184818 (o1qqad) ‘Apues “UU ‘AOIIEA UIML MNN TU p/g T ‘39819 Aneysew (IgV) LE [94813 (э194э9) ‘Apues “UU ‘UNE MS TU p/T “YH 90H рим (64V) 9€ pnur 424819 "xed `М ‘OS[OM ASA tu 4/1 9 “Y UTA (- 38 pnu 494819 ‘Apues (“UUHA “UMOJO3109D MN TU Z/T I) ‘Ява ‘N “OITASNSAY ANA TU p/19 ‘HY peu (IEIV) pe pnur alero ‘Apues "uuim “UMOJO3109D ‘'y отедая (FEV) 88 pues Appnn “UU HA ‘UopuATD MN TU ÿ/I L ‘HOME (e6v) 58 pues (A1qqad) АПелело "um ‘UOpuATD ANA FU Z/1Z ‘'yorepma (z6v) IE 194813 (o1qqod) ‘Apues ‘uu ‘Аэтмен MSS ru p/1E ‘'worepma (I6V) 0€ 194813 (914499) ‘Apues “UU ‘Аэтмен ANA Tu 9/8 с ‘'yorepma (06V) 65 pues AppnW "Ne ‘м “POOMIBH MS Tu p/g $ ‘Ч ouuoAoUS (801V) 85 pues Appnn за ‘м ‘908104 MS MU Z/T I ‘"youuskays (TITY) 22 pues “HG 'N ‘HOOIEM MNM I р ‘‘u ouuoAous (OTIV) 92 pues (A1qqad) АЦелехо за ‘М ‘wypesuy $ Tu т “y ouuoAoYS (601V) SZ 104818 (orqqod) ‘Apues “Ne "N “UOQSIT 107000 ASS ии y /g y ‘'H ouuekeys (LOTV) vz pnur “Lakes ‘Apues за ‘м “urgang ANA TU с/т т ‘Я эти (POTV) ez A A и реек vi A A AAA AAA ЕВЕ ИЕН moyog зивитхорэла u017290'T uo1e]S ВЕ EEE EL (:pzuoo) $ ATAVL pues Á[[9ABID "Ne "N ‘хоче MS TU Z/TZ ‘‘HOIMNL (02V) 99 pues Á[[9ABAIO "Xe ‘М ‘элобихет AN па $ ‘‘HOIMNL (69V) 39 рим Ápues "NBA ‘М ‘тэлиеи ANA ия $/т8 ‘Я рэн (LSV) 99 рим A719 "wed 'N “SALOA PUBID espe М ‘‘H PO (85%) 89 рим АэХето ‘Apues "УзА ‘М “SAIOA PUBLIO “*Y эхет poy ymow 9PIS атеэлдзимор * “Y poy (==) 39 pnur Ápues “UUIJA “SNIOA PUBID ‘A 197499 ASH TU Z/1Z ‘Ч элет peu (19V) 19 pues Affoawan "ЧИП “19YSIA 93P9 M “HU OMUT pou (99V) 09 pues (A1qqad) Affeaway *“UUIA ‘UOJSYOOID ‘тер espe WE21JSUMOP “*H эчет POH (9%) 6S [9At18 Apues ‘UUTN ‘UOJSYOoID 107090 Ч пи P/E $ ‘YU э\ет peu (pg) 8s ES [9A8a3 (o1qqad) ‘Apues "чи ‘SIIBA 9MYT рэч M пи Z/TE ‘"y эхет poy (ТРУ) LS E рим 43$ ‘Apues ('UUTN ‘SHIOH PUBID “| 193U99 $ ии Z/T Z) “Med 'N ‘5улоя риелю ‘улеа ujoour] “YU PO (6SV) 93 2 риш AoÂe[o ‘Apueg (‘ци “19YSIA MSM MU p/T 2) “xed *М “uosdwoysL ASH га g ‘'H рен (ZEIV) SS > pnu AoÁe]o ‘Apues (cUUIA ‘XEWITO M TU Z) “xed 'N ‘чозхаа A та ф/Т IT CUPO (FEIV) ps 5 [9AB.1B Apues "ОП XBUITO MSM TU Z/T ‘ ‘H ПН pues (68v) $5 = pues (Ajqgad) Affoaeay "ЧИП “OTTIASTOIN AN TU p/€ < ‘Я IIIH pues (88V) 56 pues АПэлел3 “Appnia "ци “UB 19g ASA TU Z “Y TH pues = (L8V) IS [94813 (orqqod) ‘Apues "UUIN ‘HA ASA па p/E “Y ИН pues (98v) 06 pues (A1qqod) Afoaeay "ЧИНА ‘Tepury MN I Z/TZ ‘U IIIH pues (G8v) 6F joavas Appnw (‘uur ‘AOTIOUS MN TU p/£ 5) “NCA 'N ‘етаорэтео AN TU Z/TT ‘'HPOU (SETV) sp [90AB13 Ápues ‘Med ‘м ‘этаорэео ‘ "Я 95009 (ZOIV) Lp pues AppnN "Med ‘М “OJOQSTIH ANA Tu p/I & ‘‘H э5009 (TOIV) 9F pues Appnw "УзА ‘М “OXOQSITIH ММА TU Y ‘‘H 95009 (OOTY) Sp woyog Jueuruop9ad 0011890] (014838 “o ("pyuoo) $ ATAVL 67 RED RIVER VALLEY MUSSELS Joavis Apues рита Ápues ‘AJJPABIN [94813 Apues pnur Ápues рим Á3TIS pnu 424819 риа 424219 pues Appn [94813 Ápues pnur A9Â8I9 pues A][9ABID yeaeis Apues ри Apues pnu Apues рита Ápues pues pues АПэлел3 ‘Ayıs pues АПэлелэ pnur Apues pnur Apues pnur 4311$ pues АПэлел8 ‘AppnN 9103409 JUBUTUIOP9IA "Ne "N “19ATH AABA MNM TU F/T с "Y AAV Youesrg ymos (0ФУ) 88 "Ye ‘N ‘этаоон $ па Z/1€ ‘"y улва youeıg SIPPIN (ТРУ) 28 "121 ‘М “YSANQUIPA N па £/Z I ‘ "Ч улеа чочела SIPPHA (--) 98 ( uumm “usyda3s MSM тах Z/T 11) ( uumm ‘0180 э8рэ MN) (UUIN ‘OTSO $$ TU Z/T 1) UO1Je007I "МАПА ‘9944935 MSM TU y /E OT ‘UUIN ‘0150 ANN TU p/g L мати “OPBIBAIY $ MU Z/T I ‘UUIN “UIIBM 93P9 MSM "ЧИП ‘UeTIeM ANA TU Z/T д "ИА ‘21481Y MN TUE ‘ "ЧИП “9]ÁBIY HSH TU p/g + ‘ "e ‘N ‘OJUIN ASA Tu Z/TZ ‘ "xed “N ‘OJUIN MS TU p/1Z ‘ "yeq 'N ‘1935 N TU Z ‘ "Med N ‘эПтархол $ Tu Z/T ‘ € € 6 € “ed “N ‘poomyeo A TU g ‘ “YU рэч (ESv) Se "u eyeug (£9V) 78 "yoyeus (z9v) €8 "yoyeus (T9V) 58 "Я eyeug (2LV) 18 "Я oyeug = (LEV) 08 "Я STPPPIN (09V) 64 "Я OIPPIN (sEeV) 84 "ити ‘UOPIOJMON M IU ст ‘u oIppIm © (9EV) LL “wed ‘М ‘MesıeM AN па 8/5 9 ‘‘'H PO = (FSV) 92 ‘wed ‘N ‘MesıeM ANA TU $ “*Y 389104 Garen "Я IS9IOH (SPV) FL "Я 25элоля (ФРУ) 84 "Я 35элоя (ZrV) ZL "Я ysetog (eV) TL yeq 'N “Puelod ‘AH TU p/£ $ ‘u pow (SS¥) 04 "Ne ‘М “TOAUBIN ANN TU p/g 9 * “YU peu (9S¥) 69 "Ye ‘N “TOAUEIA N IWF ‘"yopuanL (£LV) 89 "Ye ‘М ‘HOUTHON A TU p/g € ‘Ч 9TANL (--) 19 0014835 (*pzuoo) $ ATAVL CVANCARA A. M. 68 pnu AoAe]o ‘Apues pues (414949949) АПелел9 194813 (orqqed) ‘Apues [9Aea3 (orqqed) ‘Apues 194813 (orqqod) ‘Apues pau AJTIS ри 484819 рита 424819 pnur 494819 pnu 49419 pnur A9ÂEI9 [9ABAZ Appn pau Apues (Arqqod) АПэлехо рита Apues (Ajqqed) АПэлелэ pnu Apues ({rqqod) Апэлелхо [94813 Ápues pnu 424819 pnu 404819 ‘Apues pnu Ápues pnur Apues рим Á[[9ABAO) [9AB1B Apues woyog Jueurmop9ad "ОА “YOOTTRH ММА TU Z/T д “STOATY OML "ЧИТА ‘HOOTIEH ASS TU ф/$ $ ‘SIOATY OMY, Чочеха YMOS "ПАГ “19ISB0UB'T MS IU F/T < “SLOATY OMY, YOUBIH YIION "ПИТА ‘HOOITEH Я TU p/£ © ‘SIOATY OML YOURIG этррим *UUIJA ‘UOSUOIg 9NBT 93p9 MS “SISAIH OML YOUBIE 'S "Ne ‘N ‘juousemog AN TU E/T E ‘U peu "Ne ‘М ‘чозАвла ANN TU Z/T p ‘ ‘U рэч (uuım ‘urggoy N u p/€ Т) “Hed 'N ‘чозАвха ANN га 8/5 < ‘u peu yeq ‘N ‘чозАвлха ANA TU Z/T I “YU POH "PU ‘М ‘чозАела ASS tm Z/T & ‘ ‘H POU ‘UUIN ‘9949935 ММА TU p/£ TT ‘ "Я влечет, ‘uu, ‘4944935 МММ TU p/T1 € “ “Y влечет, ‘UUIN ‘usydaIg Ye WEP э8рэ WP91JSUMOP **Y влечет, “UU ‘uoyd93S ASS TU F/T ‘ ‘H DPABUIB,L ‘uu ‘uoydeyg ASS TU y * “Y OBIBUIEL "пати ‘ysınbpuens M TU 9 “Y влечет, ‘xed ‘М ‘роомуео AN TU p/E 8 ‘u peu "yeq ‘М “POOMALO ANA пал ‘'y peu ‘wed ‘М “POOMALO ANA па $ ‘ “Y MAPA “YA ‘м ‘uoyery ANA TU < * “Y ALBA "wed ‘М ‘чозуехо MN TU $ “Y MAP ‘wed ‘М ‘AOAIY NAPA ANA па Z/1S “ "Y ALBA чочела Y mos UO1YBI0T (GTV) OTT (PZ1V) 601 (ezIy) 807 (--) LOT (ссту) 901 (89%) SOT (LEV) pot (OFTV 3 8vV) SOT (6FV) сот (0Sv) тот (=-) 001 (FEV) 66 (SEV) 86 (TEV) 26 (ZEV) 96 (SEV) S6 (ISV) #6 (zsV) €6 (==) À: (9FV) 16 (--) 06 (6ev) 68 101415 (*pquoo) $ HIAVL 69 RED RIVER VALLEY MUSSELS Авто pue JIS Jo posodulod заэтатрэ$ e SI PONIA xx *ejoyed YON Jo Ayısıaarun ‘ÂBSO[OON JO quo -31edog 94) Jo SISQUINU UOISSIDOB эле SISQUINU UOT}e1S BUIMOT[OJ Sosogquored up ‘Z ‘SLI UO UMOYS 9SO0YI 03 puodse1109 SISQUINU UOIFEIS% pues Appnw "wed 'N ‘vulquied MS Tu F/E < ‘YU EUIQUEX (IZIV) 6IT pues "wed *N ‘OYOON я пи Z/1Z SU eUIqMieg (OZIV) SIT pues (414499) АПелел9 "wed °М ‘Аолет м па Z/1 “cu euqueg (6TIV) LIT 194813 (914499) ‘Apues "wed ‘М ‘еПечтем MSS TU F/T I ‘‘H EUIQUEX (8TIV) 9IT [oae13 (914999) ‘Apues “wed 'N “EIBUTEM M TU Z/T 9 ‘‘H eUIqmeg (LITY) SIT pnur Аэхето “wed ‘М ‘oyesyyeg ‘A mu p/e G ‘Ч эп8иот, (LETV) FIT pues (414499) АПелело "ЧЕ 'N “BAY 93p9 MN ‘‘H onduoL (9ETV) ETT pnur AoAe]9 ('UUIN ‘juooutA ‘JS 93p9 MS) “APA "N “Burquiog espe As ‘u peu (8EIV) ZIT pnur 4e4e19 Apues (WUT “9I00YI1ON MSM TU p/g 8) “AeA "N ‘OMPTIOL A пи 97/8 т ‘'H POU (6ETV) TIT woyog зазипаорэл 10148301 0014819 (*pjuoo) $ AIAVL 70 A. M. CVANCARA PLATE 1. (All figures are X 1/2; locality numbers correspond to those shown on Fig. 2 and listed in Table 2. Catalog numbers are those of the paleontological collection of the Department of Geology, University of North Dakota. ) 1. Lasmigona compressa (Lea), Pembina River, locality 115, UND Cat. No. 13001. 2. Quad- rula quadrula Rafinesque, Red Lake River, locality 59, UND Cat. No. 13002. 3. Fusconaia flava (Rafinesque), Buffalo River, locality 30, UND Cat. No. 13003. 4. Lasmigona costata Rafinesque, Red Lake River, locality 57, UND Cat. No. 13004. 5. Anodonta grandis Say, Forest River, locality 71, UND Cat. No. 13005. 6. Lasmigona complanata (Barnes), Sheyenne River, locality 26, UND Cat. No. 13006. 7. Amblema costata Rafinesque, Sheyenne River, locality 24, UND Cat. No. 13007. RED RIVER VALLEY MUSSELS 71 PLATE 2. (All figures are X1/2; locality numbers correspond to those shown on Fig. 2 and listed in Table 2. Catalog numbers are those of the paleontological collection of the Department of Geology, University of North Dakota. ) 1. Anodontoides ferussacianus (Lea), Sand Hill River, locality 49, UND Cat. No. 13008. Strophitus rugosus (Swainson), Pembina River, locality 116, UND Cat. No. 13009. 3. Ligumia 2. recta latissima (Rafinesque), Red River, 9, locality 103, UND Cat. No. 13010. 4. Lampsilis siliquoidea (Barnes), Buffalo River, ©. locality 30, UND Cat. No. 13011. 5. Lampsilis ventri- cosa (Barnes), Red River, С, locality 11, UND Cat. No. 13012. 6. Proptera alata (Say), Red River (not collected alive), locality 105, UND Cat. No. 13013. 72 A. M. CVANCARA Family Unionidae Subfamily Unioninae Fusconaia flava (Rafinesque) “Wabash pig toe” Plate 1, Fig. 3 Diagnosis. Shell subtriangular, smooth; posterior ridge moderately prominent, roundly angled; shallow, radial depression anterior to posterior ridge; beak sculpture of fine to moderate, subconcentric ridges. Hinge complete, of coarse teeth; nacre white or salmon- colored. Measurements. Shells (32) varied in length from 48 to 119 mm (average 78 mm), had H/L ratios of 0.60-0.78 (aver- age 0.68) and W/H ratios of 0.45-0.76 (average 0.59). Remarks. Fusconaia flava was col- lected alive from 7rivers and 13 stations (Table 3; Fig. 3). Its distribution appears to be erratic but related tothe relatively larger rivers in the Valley. This species was usually taken from a firm bottom of Sandy gravel or gravelly sand, but it occurred also on a sandy mud bottom at stations 76 and 111 (Fig. 3). The largest and thickest-shelled specimens were collected at station 8, which included the largest and most thick-shelled specimens of Strophitus vugosus and Ligumia recta latissima. Shells of Amblema costata and Anodonta grandis were also relatively large and thick from this locality. Specimens with a Salmon tinge to the nacre were col- lected from only stations 25 and 39 (Fig. 3). Amblema costata Rafinesque “Three ridge” Plate 1, Fig. 7 Diagnosis. Shell subrhomboidal, may be subovate, with coarse diagonal ridges that may also be present on postero- dorsal area; beak sculpture of fine to moderate, concentric ridges. Hinge complete, with coarse teeth; nacre white, may be purplish or pinkish on posterior part of shell. Measurements. Shells (42) varied from 74 to 145 mm in length (average 110 mm), had H/L ratios of 0.56-0.77 (average 0.64) and W/H ratios of 0.40- 0.72 (average 0.59). Remarks. Amblema costata was col- lected alive from 5riversand 13 stations (Table 3; Fig. 3); it is associated with the larger rivers in the Valley. Greatest numbers of individuals were taken at stations 24, 25, 58 and 59. This species was usually collected from a firm bottom of sandy gravel or gravelly sand, but it occurred also on a mud bottom at stations 54, 101, 103 and 112 (Fig. 3). Ridges on the postero-dorsal area of the shell are either poorly developed or lacking on most “specimens examined from the Valley. Clarke € Clench (1966) have suggested that Amblema plicata is a “stunted ecophenotype” of A. costata, and a senior synonym; therefore, it should take pre- cedence and serve as the type species of Amblema. This approach is subjective and the ruling of Opinion 840 of the International Commission on Zoological Nomenclature (1968: 339) does not spe- cifically suppress A. costata Rafinesque, 1820 for A. plicata (Say), 1817. There- fore, I shall continue to use A. costata for the conspicuously costate mussel in the Valley. Quadrula quadrula Rafinesque “Maple leaf” Plate 1, Fig. 2 Diagnosis. Shell subquadrate to sub- rhomboidal, with many pustules; median, shallow, radial depression; beak sculp- ture of fine, double-looped ridges. Hinge complete, with coarse teeth; nacre white. Measurements. Shells (15) varied from 56 to 97 mm in length (average 72 mm), had H/L ratios of 0.70-0.81 (aver- age 0.76) and W/H ratios of 0.46-0.61 (average 0.54). Remarks: This species was collected alive from only the 2 largest rivers and 7 stations in the lower part of the Valley (Table 3; Fig. 3). Quadrula quadrula was taken from sandy gravel, gravelly sand and mud. It occurred with one or all 73 RED RIVER VALLEY MUSSELS ямы №. Пак. Pembina R., N. Dak. Middle R., Minn. Snake R., Minn. Turtle R., N. Dak. Red Lake R., Minn. Tamarac R., Minn. Park R., N. Dak. Tongue R., N. Dak. Two Rivers, Minn. Forest R. DSOID1AJUGA sınsdwoT vopi0nb1]18 sijisqduvT DULISS1ID] DJDBA mwndıT 01010 DAIBIGOAd AVNTTISINV'I snsogna SNILYGFOAJS 51и112055п49{ SIP10JUOPOUY S1PpUDAS DJUOPOUY DIVUD]MOI VUOSIMSDT 0101509 DUOSIMSDT DSSIAQMOI DUOSIMSD'T a VNILNOGONV vjnıponb vınıpond 2121502 VMIIQUY рар{ DIDUOISNT AVNINOINN Dak. Sand Hill R., Minn. Goose R., N. Dak. Wild Rice R., Minn. Buffalo R., Minn. Maple R., N. Dak. Sheyenne R., N. Dak. Wild RiceR., N. Otter Tail R., Minn. ‘UJIOU 04 YJNOS WOAF рэЗивелле эле “14311 0) 79] mOAF реэл se “SO1IBI -nALIL *(4) S[ISSOJ Se рэзэлалэзит pue эзиэцирэ$ 998119} IOAII WOAF ло ‘(0) $ПэЧ$ Aydws Aq Afuo рэзаэзэлаэл ‘(X) элие pa309]109 se рэзвотрит эле soroadg *SOIIBINQIAJ SJ JO QT PUB A9AIY Pay эЧ3 ит S[OSSNU JO ээцэллпо2о ‘в TIAVL 74 A. M. CVANCARA CANADA rerum EN MINN. 12 MOORHEAD WAHPETON FERGUS —= |] FALLS 4 a EMPTY ALIVE SHELLS e О Fusconaia fiava a O Amblemo costata A А Quadrula quadrula HIGHEST STRANDLINE OF GLACIAL LAKE AGASSIZ Traverse DELTA OF GLACIAL o 20 MILES LAKE AGASSIZ ини ини FIG. 3. Distribution map of Fusconaia flava (Rafinesque), Amblema costata Rafinesque and Quadrula quadrula Rafinesque in the Red River Valley. Stations are as in Fig. 2; for glacial Lake Agassiz features see Fig. 1. EMPTY ALIVE SHELLS e O Lasmigona |] О Lasmigona A А Lasmigona RED RIVER VALLEY MUSSELS CANADA PEMBINA Middle EA MOORHEAD [à 30 BRECKENRIDGE Où S Tail sioux Rob, pois De compressa costata complanata P= ew STRANDLINE OF к“ GLACIAL LAKE AGASSIZ Traverse DELTA OF GLACIAL o 20 MILES CAKE, AGASSIZ — m — 8 River 5 7, D-A ® FERGUS FALLS 75 FIG. 4. Distribution map of Lasmigona compressa (Lea), L. costata Rafinesque and L. com- planata (Barnes) in the Red River Valley. On October 21, 1967, L. compressa was also col- lected alive from the Red Lake River about 8 air miles east-northeast (upstream) of station 57. Stations are as in Fig. 2; for glacial Lake Agassiz features see Fig. 1. 76 A. M. CVANCARA of the species: Amblema costata, Prop- tera alata, Ligumia recta latissima and Lampsilis ventricosa. Subfamily Anodontinae Lasmigona compressa (Lea) Plate 1, Fig. 1 Diagnosis. Shell subrhomboidal, pos- terior margin biangulate, smooth; beak sculpture of fine, irregular, double- looped ridges. Hinge complete, with fine teeth; nacre white or salmon or cream- colored, especially near beaks. Measurements. Shells (6) variedfrom 70 to 96 mm in length (average 82 mm), had H/L ratios of 0.56-0.70 (average 0.60) and W/H ratios of 0.46-0.56 (aver- age, 0.50). Remarks. This species was collected alive during the study from only 3rivers and 4 stations (Fig. 4). Later, it was taken also from the Sheyenne River above station 24 and the Red Lake River above station 57 (Table 3; Fig. 4). Further collecting has revealed its occurrence at several more localities in the Forest River, although not in large numbers. Lasmigona compressa is generally characteristic of smaller rivers or the upper parts of larger riversinthe Valley. It seemed to prefer a gravelly sand or sandy gravel bottom. Lasmigona costata Rafinesque “Fluted shell” Plate 1, Fig. 4 Diagnosis. More elongate than Las- migona compressa, with radial costae or ridges on postero-dorsal part of shell. Moreover, double-looped ridges on beak are coarser, and only moderate pseudo- cardinals (no laterals) are present on hinge. Measurements. Shells (6) varied from 73 to 109 mm in length (average 90 mm), had H/L ratios of 0.52-0.59 (average 0.56) and W/H ratios of 0.48-0.60 (aver- age 0.52). Remarks. This species was collected alive from only the Red Lake River at 1 station (station 57, Fig. 4). Here, the bottom was of sandy pebble gravel. Empty shells of this species were col- lected from 2 other stations on the Red Lake River, and 1 station on the Otter Tail River (station 5). Wilson & Danglade (1914: 12) said Lasmigona costata was one of the 3 principal commercial species of the Otter Tail River. Lasmigona complanata (Barnes) “White heel splitter” Plate 1, Fig. 6 Diagnosis. Larger, higher and with more distinctly double-looped beak ridges than in Lasmigona compressaand L. costata. Also, differs from L. com- pressa in lacking lateral teeth, andfrom L. costata in lacking costae or ridgeson postero-dorsal part of shell. Measurements. Shells (45) varied from 85 to 166 mm in length (average, 122 mm), had H/L ratios of 0.61-0.76 (average 0.69) and W/H ratios of 0.35- 0.61 (average 0.50). Remarks. This species is one of the 4 most common in the Valley (Table 3; Fig. 4), and occurs in both small and large rivers. It seemed to prefer a bottom of sandy gravel and gravelly sand but was found also on sandy mud and mud. The largest and thickest shells were col- lected from stations 24, 25 and 42 (Sheyenne and Red Rivers). Anodonta grandis Say “Floater” Plate 1, Fig. 5 Diagnosis. Shell elongate, subovate, thin, smooth; beak sculpture of fine to moderate, distinctly | double-looped ridges. Hinge teeth lacking; nacre vari- able, white, bluish white, greenish yellow and orange-pink. Measurements. Shells (75) varied from 76 to 160 mm in length (average 116 mm), had H/L ratios of 0.46-0.66 (average, 0.55) and W/H ratios of 0.50- 0.81 (average 0.61). Remarks. This species is the most common in the Valley and was collected alive from all rivers but the Park Table 3; Fig. 5). Consequently, it was taken from all types of bottom, but more RED RIVER VALLEY MUSSELS 77 CANADA EMPTY ALIVE SHELLS A A Anodonta grandis e O Anodontoides ferussacianus |] D Strophitus rugosus =. HIGHEST STRANDLINE OF kT GLACIAL LAKE AGAssiz Traverse DELTA OF GLACIAL SCALE о 10 20 MILES LAKE AGASSIZ Aa] FIG. 5. Distribution map of Anodonta grandis Say, Anodontoides ferussacianus (Lea) and Strophitus rugosus (Swainson) in the Red River Valley. On September 8, 1966, Strophitus rugo- sus was also collected alive from the Forest River about halfway between stations 72 and 73. Stations are as in Fig. 2; for glacial Lake Agassiz features see Fig. 1. 78 A. M. CVANCARA frequently from sandy gravel and gravel- ly sand than from muddy sand or mud. Several specimens of an Anodonta col- lected from the Maple River (stations 21, 22 and 23) were shorter (relative to height) and with more centrally-placed beaks than in typical A. grandis. How- ever, early growth stages showed little deviation from normal A. grandis, and plots of H/L against length and posterior length (beak to posterior margin)/L against length showed overlap of points. Both of these factors suggest that the differences noted are not taxonomic. Perhaps some pathological or parasitic condition inhibited the posterior growth of certain individuals, resulting in shorter specimens with more centrally- placed beaks. Clarke (1966: 25) has placed the Anodonta of the Valley into the subspecies A. grandis grandis. He stated that it extends northward to central Saskatche- wan. Anodontoides ferussacianus (Lea) “Cylindrical paper shell” Plate 2, Fig. 1 Diagnosis. Smaller than Anodonta grandis; beak sculpture of fine, concen- tric ridges. Measurements. Shells (26) varied in length from 48 to 81 mm (average, 63 mm), had H/L ratios of 0.44-0.67 (aver- age 0.54) and W/H ratios of 0.57-0.90 (average 0.68). Remarks. This species is one of the 4 most common in the Valley (Table 3; Fig. 5), and is generally characteristic of smaller rivers or the upper parts of larger rivers. It was collected from a variety of bottom type, but mostly from sandy gravel and gravelly sand. Ano- dontoides ferussacianus occurs com- monly with Anodonta grandis, and in marginal, uppermost stream conditions, either or both of these species are usually the only mussels present. Strophitus rugosus (Swainson) “Squaw foot” Plate 2, Fig. 2 Diagnosis. Shell elongate, subovate to subelliptical, smooth; beak sculpture of coarse, concentric ridges. Hinge incom- plete, only with rudimentary pseudo- cardinals (slight tubercles); nacre white or bluish white, commonly cream or salmon-colored, especially near beaks. Measurements. Shells (5) varied in length from 60 to 109 mm in length (average 81 mm), had H/L ratios of 0.50-0.61 (average 0.55) and W/H ratios of 0.55-0.66 (average 0.61). Remarks. This speciesis not common in the Valley; it was taken alive from 6 rivers but only 7 stations (Table 3; Fig. 5). It seems to be characteristic of the larger tributaries of the Valley, and was not found in the Red River. Strophitus rugosus seemed to prefer a firm bottom of sandy gravel or gravelly sand. Subfamily Lampsilinae Proptera alata (Say) “Pink heel splitter” Plate 2, Fig. 6 Diagnosis. Shell subovate, with promi- nent dorsal wing; sexually dimorphic; smooth; beak sculpture of fine, double- looped ridges. Hinge complete, with moderate teeth; nacre purple or pink. Measurements. Shells (43) varied in length from 97 to 145 mm (average, 119 mm), had H/L ratios of 0.66-0.72 (aver- age 0.70) and W/H ratios of 0.36-0.44 (average 0.39). Remarks. This species was collected alive from only the Red Lake River at 3 stations, although empty shells were taken at several stations on the Red River (Table 3; Fig. 6). It occurred on 3 different types of bottom, sandy gravel, gravelly sand and sandy mud. Ligumia recta latissima “Black sand shell” Plate 2, Fig. 3 Diagnosis. Shell very elongate, sub- elliptical; sexually dimorphic; smooth; periostracum very dark; beak sculpture of fine, double-looped ridges. Hinge complete, of moderate teeth; nacre white or pink to purple. Measurements. Shells (293) varied in RED RIVER VALLEY MUSSELS 79 Rivers Middle But tel, FAR 0 MOORHEAD [à River 7 LJ RECKENR 7 BRECKENRIDGE WAHPETON FERGUS FALLS . « . PS EMPTY ALIVE SHELLS ® O Proptera alata |] О Ligumia recta latissima HIGHEST STRANDLINE OF GLACIAL LAKE AGASSIZ Troverse DELTA OF GLACIAL SCALE o 10 20 MILES LAKE AGASSIZ —— a] FIG. 6. Distribution map of Proptera alata (Say) and Ligumia recta latissima (Rafinesque) in the Red River Valley. Stations are as in Fig. 2; for glacial Lake Agassiz features see Fig. 1. 80 A. M. CVANCARA length from 103 to 127 mm (average, 112 mm), had H/L ratios of 0.38-0.46 (average 0.43) and W/H ratios of 0.50- 0.68 (average 0.57). Remarks. Ligumia recta latissima was collected alive from only 3 rivers at 8 stations (Table 3; Fig. 6). Itis characteristic of the largest rivers in the Valley. This species was taken on bottoms of sandy gravel, gravelly sand, sandy mud and mud. Lampsilis siliquoidea (Barnes) “Fat Mucket” Plate 2, Fig. 4 Diagnosis. Shell elongate, subovate to subelliptical; sexually dimorphic; periostracum yellowish or brownish, commonly with green rays; smooth; beak sculpture of fine, chevron-like (or wavy, double-looped) ridges. Hinge complete, with moderate teeth; nacre white. Measurements. Shells (2539) varied in length from 65 to 120 mm (average, 90 mm), had H/L ratios of 0.40-0.67 (average 0.52) and W/H ratios of 0.48- 0.94 (average 0.65). Remarks. Secondto Anodonta grandis, this species was the most frequently found in the Valley (Table 3; Fig. 7). Consequently, it was taken from both large and small rivers and all types of bottom from gravel to mud; however, it was collected at most stations from sandy gravel, gravelly sand and sandy mud. It occurred commonly and in large numbers along the banks of the Red River, usually associated with Lampsilis ventricosa. Lampsilis ventricosa (Barnes) “Pocketbook” Plate 2, Fig. 5 Diagnosis. Higher than Lampsilis siliquoidea with more elevated beaks; also sexually dimorphic; beak sculpture with coarser, indistinctly double-looped ridges; hinge teeth coarser. Measurements. Shells (383) varied in length from 82 to 130 mm (average 99) had H/L ratios of 0.57-0.71 (average 0.62) and W/H ratios of 0.52-0.74 (aver- age 0.62). Remarks. This species was collected alive from 5 of the largest rivers in the Valley at many stations (Table 3, Fig. 7). It was found most frequently on abottom of sandy mud or mud but also commonly on sandy gravel. Lampsilis ventricosa was commonly associated with L. sili- quoidea along the banks of the Red River but in lesser numbers than that species. Concentrations of mussels An idea of concentrations of mussels in the Valley, all species taken collec- tively, can be gained from Fig. 8. This map might prove useful should com- mercial exploitation of mussels be con- templated there. In the Red River, more individuals appear to occur in the lower reaches near the U.S. - Canada border. Just below the largest city complexes of Fargo- Moorhead and Grand Forks - East Grand Forks, mussels are presumably absent, but concentrations increase generally downstream from them. Few mussels occur above Fargo - Moorhead with the exception of the upper reaches of the Bois De Sioux River where only 1 species was taken alive (Anodonta grandis). Tributaries ofthe Red River commonly show a decrease of mussel individuals downstream. The Park, Forest and Turtle Rivers apparently have no live mussels in their lower reaches. The Wild Rice, Goose and Park Rivers in North Dakota, and the Tamarac, Middle and Snake Rivers in Minnesota are par- ticularly poor in mussels. High in both individuals and species is the Red Lake River, the best tributary for mussels in the Valley. Bottom and turbidity Bottom sediments generally vary from gravel and sand at or near the margins of the lake plain to primarily silt and clay (collectively, mud) at or near the axis of the Valley (Table 2). Bottom type is closely allied with turbidity and gener- ally is directly reflected by it. Turbidity in the tributaries generally increases downstream as the bottom sediment becomes finer (Fig. 9). Values RED RIVER VALLEY MUSSELS 81 0-à GRAND FORKS EMPTY ALIVE SHELLS e О Lampsilis siliquoidea |] О Lampsilis ventricosa Trover Ee HIGHEST STRANDLINE OF 7324 GLACIAL LAKE AGASSIZ te DELTA OF GLACIAL 20 MILES LAKE AGASSIZ ини — пани FIG. 7. Distribution map of Lampsilis siliquoidea (Barnes) and L. ventricosa (Barnes) in the Red River Valley. Stations are as in Fig. 2; for glacial Lake Agassiz features see Fig. 1. 82 A. M. CVANCARA CANADA р. À BRECKENRIDGE WAHPETON FeRous FALLS MUSSELS COLLECTED PER HOUR HAND PICKING HIGHEST STRANDLINE or GLACIAL LAKE AGASSIZ lake Traverse DELTA or GLACIAL о 20 MILES LAKE AGASSIZ а па FIG. 8. Map of the relative abundance of individual mussels in the Red River Valley. The width of each dark band on a river is equivalent to the numbers of mussels collected per hour by hand-picking. Dark bands show breaks where control is lacking and the mussel concentrations are inferred. Stations used for control are shown on Fig. 2. RED RIVER VALLEY MUSSELS 83 STATION STATION 106 117 РЕМВ!МА В. TWO RIVERS 8/3/66 8/4/66 o . 22.51% 7 No . А > MUSSELS . © 724 Ne >) wish ein — TURBIDITY 5.5 20 40 MILES ABOVE MOUTH MILES ABOVE MOUTH STATION STATION 66 67 59 58 TURTLE R. 9 RED LAKE В. 8/27/65 8/20/65 Ten à 20 40 MILES ABOVE MOUTH MILES ABOVE MOUTH STATION STATION 25 26 8 7 SHEYENNE R. OTTER TAIL R. 7/27/66 7/14/66 120 80 40 20 40 MILES ABOVE MOUTH MILES ABOVE MOUTH FIG. 9. Variation with station position of total alkalinity, total chlorides, turbidity and mussel species for 6 tributaries of the Red River, from measurements made in July and August, 1965 and 1966. Chemical values are in ppm and turbidity is in Jackson turbidity units (JTU). Arith- metic scales were used for all factors plotted except total chlorides, which are plotted on a loga- rithmic scale. Station numbers correspond tothose shown on Fig. 2. Arrows point downstream. 84 A. M. CVANCARA (in Jackson turbidity units, JTU) varied from 11 (station 5) to 285 (station 52) with considerable fluctuation. Inthe Red River, turbidity is consistently high with relatively less fluctuation, and values of 65-240 JTU were measured. Secchi disk readings were correspondingly low, from 0.50 to 1.0 ft. Chemical data Generally, chemical factors vary with discharge. Therefore, the Red River, with a relatively high discharge, exhibits relatively less variability in the con- centration of chemical ions. Tributaries of the Red, however, with less and gener- ally more fluctuating discharge, are characterized by greater chemical vari- ability. Total dissolved solids for a few se- lected localities are listed in Table 4. Values range there from 150 to 1,110 ppm (both extremes for the Sheyenne River). The relationship of chemical variability to discharge canbe perceived if one compares extreme values of total dissolved solids and discharge for each of 2 gaging stations on the Red and Sheyenne Rivers. Water was analyzed for dissolved oxygen, free carbon dioxide, pH, total chloride, nitrate and nitrite content, phenolphthalein and total alkalinity, cal- cium and total hardness, andiron. Values obtained during the summers of 1965 and 1966 are summarized below. Dissolved oxygen and free carbon di- oxide, in the Red River, varied from 6.5 (stations 63 and others) to 9.1 ppm (station 11) and from 2.4 (station 62 and others) to 19.2 ppm (station 103), respec- tively. In the tributaries, oxygen and carbon dioxide ranged from 5.3 (station 39 and others) to 14 ppm (station 29) and from O (station 2 and others) to 33 ppm (station 32), respectively. Values of pH in the Red River were from 8.0 (station 34 and others) to 8.3 (station 11). Inthetributaries, pH varied considerably more, from 7.5 (station 6) to >9.2 (station 2). Total chloride values showed rela- tively little variability in the Red River, from 6.5 (station 12) to 37.5 ppm (station 94). In the tributaries, however, marked extremes were present, from 3.5 (station 60) to 2180 ppm (station 68). Variation in chloride content with station is shown for 6 tributaries in Fig. 9. Total chloride is seento increase markedly downstream in the Turtle River. High chloride values were noted also in the lower reaches of the Forest and Park Rivers. Nitrate and nitrite content in the Red River ranged from 0.65 (station 13) to 2.75 ppm (station 104) and from 0.000 (station 12 and others) to 0.014 ppm (station 94), respectively. In the tribu- taries, these same factors varied from 0.00 (station 65) to 5.1 ppm (station 96) and from 0.000 (station 3 and others) to 0.046 ppm (station 17), respectively. Phenolphthalein and total alkalinity in the Red River were from 0 (station 12 and others) to 10 ppm (station 48) and from 188 (station 12) to 300 ppm (station 64 and others), respectively. In the tributaries, these same factors varied from O (station 5 and others) to 60 ppm (station 51 and others) and from 118 (station 2) to 450 ppm (stations 44 and 53), respectively. Phenolphthalein alka- linity, at most mussel stations, was zero. Variation in total alkalinity at different stations is shown for 6 tributaries in Fig. 9; no readily apparent trends are present. Calcium and total hardness values for the Red River ranged from 90 (station 12) to 180 ppm (station 85) and from 230 (station 19 and others) to 330 ppm (station 54), respectively. In the tributaries these factors varied from 65 (station 5) to 600 ppm (station 68) and from 170 (station 58) to 1050 ppm (station 68), respectively. In the Red River, iron values were from 0.38 (stations 62 and 63) to 0.86 ppm (station 93). Iron values in the tributaries varied from 0.07 (stations 44 and 81) to 1.04 ppm (station 52). DISCUSSION AND CONCLUSIONS Thirteen species of mussels, arranged in 10 genera, are presently known to in- 85 RED RIVER VALLEY MUSSELS "0$ 19QUISIASS 07 Т 1940790 WOL xx “(1 SM) 068 0014835 лол} weaıysdn [IU Y ИеЧ $1388 1014815 SUISED “qQ9GT PUB E996T “G96T “AP96T “Ep961 “E96T-0961T ‘APAING [91801089 ‘$ *f] WOAF UAB) элэм LYE ‘I ‘SLA чо UMOYS эле SUOIJEIS 341388 Jo SUOTFEIOT% (99) s9 ‘E9-29 eulquieg (9) 65-88 (110A19S9Y SWWOH) NAPA (885) 39-43 08/175 (s1104 PUBID) peu (Z1) 39-29 0 'S8€T oye] poy (1) 99 9°LZ oremg (F1Z) S9-LS 8°26 suuefoeys (885) 59-96 G ‘0g ouuaÂous (975) 99-98 G "109 (03184) peu ($) s9 ‘19 0 “36% ет, 1990 ee (:99s/:'y no) (dd) эрно$ ¿UOIJ8IS peajossiq Be 3u1389 SISN (SUOIJBALISO (:194y) jo ‘ON) pue ‘due I s1eo **SIBOA DIEM J9JEM OR uUtaIN £9TIBA 19AIH poy OY} Ul „suorye4s 301388 Аэлхиб 1891801099 :S ‘A рэзоэТэз то} ‘э8леЧозтр UBOUL чм ‘зэлизелэ 91 лэзем PUB SPI[OS POAIOSSIP [eJoL “pF AIAVL 86 A. M. CVANCARA habit the rivers and streams of the Red River Valley (Table 3). Dawley (1947: 679) also reported 2 other species, Obli- quaria тейеха and Actinonaias carinata, but I have not been able to verify their occurrence. Later, Dawley (written communication, dated January 20, 1967) indicated that the reported occurrences of these 2 species from the Red River are probably in error. Additions that I have been able to make to Dawley’s list (: 679) areQuadrula quadrula, Lasmigona compressa and Anodontoides ferussaci- anus for the Red Lake River and Lasmi- gona complanata for the Red River. I have not taken Strophitus rugosus and Proptera alata alive from’ the Red River as she reported. Generally, the larger the river, the more mussel species it will contain. Exceptionally, the Red River has 8 species, whereas the Red Lake River, its largest tributary, has yielded the total mussel fauna of 13 species (Table 3). Other tributaries have from 1 (Park River) to 9 species (Sheyenne River). In the lower part of the Sheyenne River, Lasmigona compressa was not observed; however, it has been collected above station 24 (Fig. 2; Norby, 1967: 19) and therefore was included in Table 3. The 4 most common species are Las- migona complanata, Anodonta grandis, Anodontoides ferussacianus and Lamp- silis siliquoidea (Table 3). Two species, Lasmigona costata and Proptera alata, were taken alive from only a single river, the Red Lake (Figs. 4, 6). Quadrula quadrula was collected alive from only the Red and Red Lake Rivers (Fig. 3). The distribution of certain species shows a relation to river size. The species taken usually from the larger rivers in the Valley include Amblema costata, Quadrula quadrula, Proptera alata, Ligumia recta latissima and Lampsilis ventricosa (Figs. 3, 6 and 7). Three of these species, Quadrula quad- уша, Proptera alata and Ligumia recta latissima are common throughout the main mussel-bearing reaches of the Mississippi River (van der Schalie & van der Schalie, 1950: 457). Two species, Lasmigona compressa and Anodontoides ferussacianus, are generally indicative of smaller rivers or the upper parts of larger rivers in the Valley. The Red River Valley mussels repre- sent a modified Mississippi River system fauna in that the 13 species in 10 genera of the Valley are a sharp reduction from the 50 species in 29 genera of the Missis- sippi and its tributaries (determined from van der Schalie € van der Schalie, 1950: 454-456). The Valley fauna is basically one pertaining to the uppermost Mississippi and its tributaries. Only 4 Valley species, Quadrula quadrula, Las- migona complanata, Proptera alata and Ligumia recta latissima are common throughout the main Mississippi River (van der Schalie € van der Schalie, 1950: 457). The causes for the faunal limitation are not clear. Perhapsthe range in size, or maximum size, of water body (river) is a significant factor. Rivers of the Red River Valley are not as large nor as varying in size as those of the Missis- sippi Valley. Consequently, fewer habi- tats are available, resulting ina smaller mussel fauna. Availability of suitable rivers is reflected in part by average annual runoff, which is directly related to the amount of precipitation inanarea. The average annual runoff is 7.2 inches in the Upper Mississippi drainage basin but only 1.6 inches in the part of the Hudson Bay drainage basin concerned in the United States (Miller, et al., 1962, Pl. 9). Mussels must have entered the Valley from the south via its upper reaches during confluence over a divide now separating the present Mississippi and Hudson Bay drainage basins (van der Schalie, 1939: 254; 1945: 359). This migration must have occurred during at least part of the existence of glacial Lake Agassiz via River Warren (its valley presently occupied by the Minnesota River), the southern outlet of the Lake. Dawley (1947: 680) has noted the presence of Amblema costata, Lasmigona com- RED RIVER VALLEY MUSSELS 87 planata, Ligumia recta latissima, Lamp- silis siliquoidea and Г. ventricosa in glacial Lake Agassiz sediments. Whether the 8 remaining mussel species of the Valley migrated into it during glacial or post-glacial time is uncertain. I am presently concerned with the time of first arrival of certain mussel species in the Valley. The study will necessi- tate considerable search for mussels in Lake-associated sediments and species found at known levels will need to be correlated to events at the southern out- let of the Lake (Matsch & Wright, 1967). Transfer of mussels is probably still occurring between the Mississippi system and the Valley. Big Stone Lake, the source of the Minnesota River, and Lake Traverse, the ultimate source of the Red River, are separated by but a few miles. Dawley (1947: 680) has pointed out that these 2 lakes are connected at times of very high water. Restrictive ecological factors Physical. Bottom type seems to have little significant effect in limiting the distribution of mussels. Certain mussels apparently prefer a specific bottom, but most mussels in the Valley have been found on a variety of sediment, indicating a relatively wide tolerance to bottom type. Also, many species seem totoler- ate both firm and soft bottoms (e.g., Lampsilis siliquoidea on gravel or sand in most of the tributaries and in soft mud along the banks of the Red River). A shifting bottom is a different matter. in practically no instance have I taken live mussels from a rippled, moving bottom. High turbidity, correlated with a finer bottom, may be a limiting factor in the lower reaches of several tributaries, where it increases (Fig. 9). This in- crease is commonly associated with a decrease in the number of mussel in- dividuals (Fig. 8) and species (Fig. 9). However, the Red River is highly and consistently turbid and yet harbors large numbers of mussels. River discharge is probably a signifi- cant limiting physical factor. Rivers with higher discharge generally contain more mussel species and those with a low or sporadic discharge generally have fewer (Fig. 1, Table 3). Noflowfor long periods may notably restrict or exclude mussels from certain parts of rivers. This is perhaps true inthe lower reaches of the Tamarac, Middle andSnake Rivers, where flow may be interrupted continu- ously for longer than 7 and 8 months (MacLay, Winter & Pike, 1965). Stagna- tion for long periods is probably also inhibiting in parts of the Wild Rice and Goose Rivers in North Dakota (Fig. 1), where discharge is zero about half the time. Such a Situation may be detri- mental to mussels because of lowered dissolved oxygen, increased concentra- tions of dissolved salts, and increased predation accompanying the lowering of the water level. Chemical. Of the chemical factors measured, a high chloride content ap- pears to restrict significantly the occur- rence of mussels. Relatively high chloride values occur in the lower reaches of the Park, Forest and Turtle Rivers, a high of 2180 ppm having been measured in the Turtle River (Figs. 2, 9). In this region of high chloride values, I have taken no live mussels. The high chloride content is thought to be the result of saline ground water seepage from Cretaceous rocks of the Dakota Group (Upham, 1895: 527). Saline soils in this region also relate to high chloride values of the river water (Cvancara & Harrison, 1965, Figs. 1, 2). The prohibitive effects, if any, of other chemical factors are uncertain. The relatively high total alkalinity and hard- ness of water in the Valley should be 2 chemical factors conducive to the propa- gation of mussels. Biological. Biological factors have been considered only partially in this study, but they may be of as much or more significance than the other factors. Fish hosts may be of prime importance in the distribution of mussels, and have a greater influence than bottom type. 88 A. M. CVANCARA This inference is made from the occur- rence of many species on different types of bottom; I believe that, if other con- ditions are suitable, the bottom probably will not be prohibitive and that mussels occur in a stream not far from where they left the fish host as larvae. After leaving the fish host, they are presumably concentrated or grouped locally, at least in small rivers, into areas of relatively higher water velocity (Cvancara et al., 1966). Food, although not separately evalu- ated, seemed to be generally available. Predation, notably by the raccoon and muskrat, is presumably a biological factor of secondary importance. Pollution. Industrial, municipal or domestic pollution, although not as seri- ous as in many other sections of the United States, appears to restrict mussels in parts of the Valley. I have not taken live mussels just below the urban complexes of Fargo - Moorhead and Grand Forks-East Grand Forks (Fig. 2), and attribute their presumed absence there to pollution. The apparent absence of live mussels at the down- stream edge of Stephen, Minnesota, on the Tamarac River (station 98) and just below Fairmount, North Dakota, on the Bois De Sioux River (station 3) is pre- sumably also the result of poor water quality. An example of recent, possible pollu- tional effects is found just below the American Crystal Sugar Company plant near Drayton, North Dakota. On August 24, 1965, before the plant began opera- tion, an assistant and myself collected from a 312-yard-long strip, 160 yards below the sugar plant effluent channel and along the opposite (right) bank (station 103.) In one hour we picked 351 mussels. One year later (August 19, 1966), after the sugar plant had been operating during the autumn and winter, we collected from exactly the same part of the river, recovering only 97 mussels per hour, which corresponds to a reduc- tion in mussels of approximately 75%. The least polluted part of the Red River is from about Drayton (USGS gaging station 920, Fig. 1) to the Canadian bor- der (Gallagher et al., 1965). The near absence of pollution is apparently re- flected by the greater concentration of mussels in that section of the river (Fig. 8). ACKNOWLEDGMENTS This study was supported inlarge part by the North Dakota Water Resources Research Institute with funds provided by the U.S. Department of Interior, Office of Water Resources Research under Public Law 88-379. Grateful acknowledgment is given to the following persons for their aid in this study: Dr. Wilson M. Laird, Chair- man of the Geology Department at the University of North Dakota, who placed the department’s facilities at my dis- posal; Clifford H. Beeks, Jr. and Akey Chang-Fu Hung, acting as fieldresearch assistants; A. Kirth Erickson, John R. Tinker, Jr. and Dennis N. Nielsen, ser- ving as laboratory research assistants; Mr. George M. Pike, U.S. Geological Survey; Dr. Henry van der Schalie, Mollusk Division, Museum of Zoology, University of Michigan, and Dr. F. D. Holland, Jr., Professor of Geology at the University of North Dakota, for offering useful suggestions. LITERATURE CITED CLARKE, A. H., Jr. 1964. 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Water resources data for North Dakota and South Dakota. U.S. Government Printing Office, Washington. 104 p. U. S. GEOLOGICAL SURVEY. 1966a. Quality of surface waters ofthe United States, 1960-1961. U.S. Geol. Survey Water-Supply Pap., 1743: 275 p; 1883: 311 p. U. S. GEOLOGICAL SURVEY. 1966b. Quality of surface waters ofthe United States, 1963.U.S. Geol. Survey Water- Supply Pap., 1949: 407 p. U. S. WEATHER BUREAU. 1955-1966. Climatological data, North Dakota, 1955-1965. U.S. Govt. Printing Office, Washington. vol. 64-74. U. S. WEATHER BUREAU. 1965. Cli- matic summary of the U. S., supple- ment for 1951through 1960, climatog- тарйу of the Ц. S., No. 86-28, North Dakota. U.S. Govt. Printing Office, Washington. p 1-75. van der SCHALIE, H. 1939. Distribu- tional studies of the naiades as related to geomorphology. J. Geomorphology, 2(3): 251-257. van der SCHALIE, H. 1945. The value of mussel distribution in tracing stream confluence. Pap. Michigan Acad. Sci., Arts & Letters, 30: 355- 373. van der SCHALIE, H. € van der SCHALIE, A. 1950. The mussels of the Missis- sippi River. Amer. Midl. Natur., 44(2): 448-466. VISHER, S. S. 1954. Climatic atlas of the United States. Harvard Univ. Press, Cambridge. 403 p. WILSON, C. B. & DANGLADE, E. 1914. The mussel fauna of central and northern Minnesota. U.S. Comm. Fish. Rep., 1913 (Bur. Fish. Doc. 803): 1-17. WINSLOW, M. L. 1921. Mollusca of North Dakota. Occ. Pap. Mus. Zool. Univ. Michigan, (98): 1-18. RED RIVER VALLEY MUSSELS 91 RESUME MOULES D’EAU DOUCE (UNIONIDAE) DE LA RED RIVER VALLEY DU NORD DAKOTA ET DU MINNESOTA, U. $. A. A. M. Cvancara Treize espéces de Moules d’eau douce habitent la Red River du Nord et 18 ses tributaires du Nord Dakota et de l’Ouest du Minnesota. Ces espèces, appartenant à 10 genres, sont: Fusconaia flava (Rafinesque), Amblema costata Rafinesque, Quadrula quadrula Rafinesque, Lasmigona compressa (Lea), L. costata Rafinesque, L. com- planata (Barnes), Anodonta grandis Say, Anodontoides ferussacianus (Lea), Strophitus rugosus (Swainson), Proptera alata (Say), Ligumia recta latissima (Rafinesque) Lamp- silis siliquoidea (Barnes) et L. ventricosa (Barnes). Huit espéces ont été collectées de la Red River, et 13 espéces de chacun de ses tributaires. Les 4 espéces les plus communes sont Lasmigona complanata, Anodonta grandis, Anodontoides ferussacianus et Lampsilis siliquoidea. Cinq espèces, Amblema costata, Quadrula quadrula, Prop- tera alata, Ligumia recta latissima et Lampsilis ventricosa sont généralement carac- téristiques des plus grandes riviéres, tandis que Lasmigona compressa et Anodonta ferussacianus le sont des plus petites riviéres de la Red River Valley. La faune de moules d’eau douce de la Red River Valley, qui fait partie du drainage de la baie d’Hudson, tire sonorigine de celle du réseau hydrographique du Mississippi. La faune de la Valley, cependant, comporte seulement 26% de celle du Mississippi. Quatre facteurs écologiques sont vraisemblablement de premiére importance dans la restriction de la distribution des espéces dans la Red River Valley. Ce sont: les longues périodes sans courant, la haute teneur en chlorures, la pollution de l’eau et peut-être la forte turbidité. A: RESUMEN ALMEJAS (UNIONIDAE) DEL RED RIVER EN DAKOTA DEL NORTE Y MINNESOTA, E. E. U. U. A. M. Cvancara Trece especies de almejas habitan el Red River del Norte y 18 de sus tributarios, en el este de Dakota del Norte y oeste de Minnesota. Estas especies, pertenecientes a 10 géneros son: Fusconaia flava (Rafinesque), Amblema costata Rafinesque, Quad- rula quadrula Rafinesque, Lasmigona compressa (Lea), L.costata Rafinesque, L. com- planata (Barnes), Anodonta grandis Say, Anodontoides ferussacianus (Lea), Strophitus rugosus (Swainson), Proptera alata (Say), Ligumia recta latissima (Rafinesque), Lamp- silis siliquoidea (Barnes) y L. ventricosa (Barnes). Ocho especies fueron colectadas en el Red River y 13 especies en cada uno de los tributarios. Las cuatro especies mas comunes son Lasmigona complanata, Anodonta grandis, Anodontoides ferussaci- anus, y Lampsilis siliquoidea. Otras cinco, Amblema costata, Quadrula quadrula, Proptera alata, Ligumia recta latissima y Lampsilis ventricosa son generalmente caracteristicas de los grandes rios en el valle del Red River. Lasmigona compressa y Anodontoides ferussacianus generalmente indicadoras de ríos menores. La fauna de almejas en este valle que es parte de cuenca de la Bahia de Hudson, tuvo su origen en aquella del sistema del Rio Mississippi, pero constituye sólo un 26% de la de ese río. Se indican cuatro factores ecológicos, presumiblemente de primera importancia en la restricción de la distribución de las almejas en el valle del Red River, que son: falta prolongada de corriente en el río, alto contenido de cloro, corrupción de las aguas y posiblemente la elevada turbidez. AA Р. 92 A. M. CVANCARA ABCTPAKT МОЛЛЮСКИ (UNIONIDAE) ИЗ ДОЛИНЫ РЕД РИВЕР, СЕВЕРНАЯ ДАКОТА И МИННЕСОТА А. М. КВАНКАРА Тринадцать видов моллюсков известны в Ред Ривер на севере и в 18 ее притоках на востоке Северной Дакоты и западной Миннесоты. Эти виды, от- носящиеся к 10 родам, следующие: Fusconaia flava (Rafinesque), Amblema costata Rafinesque, Quadrula quadrula Rafinesque, Lasmigona compressa (Lea), L. costata Rafinesque, L. complanata (Barnes), Anodonta grandis Say, Anodontoides ferussacianus (Lea) ,Strophitus ru- gosus (Swainson), Proptera alata (Say), Ligumia recta latissima (Rafinesque), Lampsilis siliquo- idea (Barnes), и L. ventricosa (Barnes). Из них 8 видов были собраны в Pen Ривер и от 1 до 13 видов в каждом из ее притоков. Из них 4 вида наиболее обычны, это: Lasmigona complanata, Anodonta grandis, Anodontoides ferussacianus WM Lampsilis siliquoidea. Пять видов: Amblema costata, Quadrula quadrula, Proptera alata, Ligumia recta latissima и Lampsilis ventricosa,-xapaKTePHH для более крупных рек долины Ред Ривер, а 2 вида, Lasmigona compressa и Anodontoides ferussacianus, обычны для мелких речек этого района. Фауна моллюсков долины Ред Ривер, являющейся частью бассейна Гудзоно- ва залива, берет свое начало от малакофауны речной системы Миссисиппи. Фауна моллюсков долины Ред Ривер составляет лишь 26% последней. Четыре экологических фактора имеют, по видимому, основное значение, ограничивающее распространение моллюсков в долине Ред Ривер: протяжен- ность рек, высокое содержание хлоридов, загрязнение воды и, возможно, большая ее мутность. 7. А. В. MALACOLOGIA, 1970, 10(1): 93-112 HERMAPHRODITISM AMONG NORTH AMERICAN FRESHWATER MUSSELS! Henry van der Schalie Museum of Zoology The University of Michigan Ann Arbor, Michigan 48104, U.S.A. ABSTRACT Information on the extent of hermaphroditism among the freshwater mussels of the rich naiad fauna of the U.S.A. is fragmentary. In this study the gonads of 1,871 specimens belonging to 97 species in 32 genera were histologically ex- amined, using the paraffin block technique for sectioning. Only 4 species in 2 unionid subfamilies were shown to be dominantly hermaphroditic (monoecious); 3 in the Anodontinae: Anodonta imbecillis, Lasmigona compressa and a close relative L. subviridis and 1 in the Lampsilinae: Carunculina parva. Sporadic hermaphrodites were found in another 22 species or forms belonging to 17 genera in 2 families. Usually such individuals appear to be predominantly of one sex, with only a small amount of gonad tissue of the opposite sex. One ambisexual specimen was found in the Margaritanidae, in Margaritifera mar- garitifera, among 24 specimens sectioned representing 2 genera and species. In the Unionidae accidentally monoecious individuals occurred in all 3 subfami- lies. Among the Unioninae, with 567 specimens (34 species, 11 genera) examined such individuals were found in 9 species (or forms) of 5 genera, i.e., in Elliptio dilatatus, E. productus, Fusconaia ebenus, F. flava, Gonidea angulata, Pleuro- bema cordatum, Р. с. coccineum, Quadrula quadrula and Tritogonia verrucosa. In the Anodontinae, with a total of 479 specimens (20 species, 5 genera) sectioned, sporadic hermaphrodites were demonstrated in 5 species belonging to 4 genera, of which 2 are the genera also containing the predominantly hermaphroditic species; i.e., they occurred in: Anodonta corpulenta, A. grandis footiana and Lasmigona complanata as well as in Alasmidonta marginata and Strophitis ru- gosus. In the Lampsilinae, with a total of 801 specimens (41 species, 14 genera) sectioned, the condition was detected in7 further species representing 6 genera, i.e., in: Actinonaias ellipsifovmis, Lampsilis cariosa, Leptodea laevissima, Proptera alata, Ptychobranchus fasciolaris, Р. subtentum and Villosa (Micro- mya) tris. This rather extensive survey of American naiades shows that they are gener- ally dioecious. Whether or not hermaphroditism appears in animals confronted with difficult environmental conditions, as has been previously suggested, re- mains an open question. One of the best summary analyses of sexual differentiation among pelecypod mollusks was published by Coe (1943). He indicated that among the 10,000 odd species of bivalves about 400 were known to deviate from the strictly dioecious or unisexual condition and stressed that in these every grade of sexual differenti- ation and of ambisexuality was found. Hermaphroditism could be complete, partial or occasional. Among the nor- mally hermaphroditic (ambisexual, mo- This paper was read at the Second European Malacological Congress, Copenhagen, August, 1965 and abstracted in Malacologia, 1966. It has now been brought up to date in minor details. 94 H. VAN DER SCHALIE noecious) marine species studied, some exhibited alternative sexual phases, in- cluding functional hermaphroditism. Not only could species of the same genus differ considerably in sexuality but there existed variability in different indi- viduals of the same species or in single individuals at different periods of life. Similarly, the distribution of ovogenic and spermatogenic tissues also showed great variation. The observed variability is attributed to the interplay between multiple hereditary sex differentiating mechanisms and environmental factors, though evidence as to the influence of the latter yet needed further and more direct experimental proof. As regards freshwater mussels, the sphaeriids are all known to be her- maphroditic, but relatively little is known about the extent of hermaphroditism in the larger forms. As late as 1926, Pelseneer noted that the number of freshwater mussels investigated in this respect was not great. That the unionid Anodonta may show the condition has been known for a long time. Weisensee (1916), in a scholarly article on the sex of Anodonta, thoroughly reviews the observations made since the time of Leeuwenhoek in 1722: he states (опр 275): “Seit der Arbeit von Lacaze-Duthiers Uber den Genitalapparat der Lamelli- branchiaten wurde die Frage nach der Geschlechtsverteilung bei Anodonta nicht mehr zum Gegenstand einge- henderer Untersuchungen gemacht. Seit diesem Zeitpunkt war man der Ansicht - und diese Ansicht finden wir in fast allen heutigen Lehrbüchern vertreten-dass sowohl Anodonta als auch Unio in der Regel getrennt- geschlechtlich seien. „2 “Translation: “Since Lacaze-Duthiers’ [1894] work on the genital apparatus of the lamelli- branchs, the question of sex distribution in Anodonta has not been made the object of further detailed investigation. The general view held since that time - a view to be found in almost all textbooks today - is that Ano- donta, as well as Unio, are, as a rule, of separate sexes. ” Hermaphroditism in British Anodonta was intensively studied by Bloomer (1930, 1934, 1935, 1939). Pelseneer (1920) quotes Schierholz’s report of Margaritifeva as an occasional her- maphrodite in Germany. In the U.S.A. Sterki (1898) recognized hermaphro- ditism in 3unionids: Anodonta imbecillis, Сатипсийта parva and Fusconaia flava. In the latter 2 genera for the first time Ortmann (1912) noted, however, that most of the Unioninae have separate sexes. The histology of the gonads of Caruncu- lina parva was later studied by Tepe (1943). The aim of the present study was to investigate the extent of hermaphrodit- ism among the numerous species of freshwater mussels (Unionacea) and, if possible, to gain information on factors that may serve to induce hermaphro- ditism. During the past several years material was collected from widely dis- tributed locations, and 1,871 specimens belonging to 97 species (or forms) in 32 genera (Table 1) were histologically ex- amined. The distribution of these species as to family group was as follows: 2 Species in the Margaritanidae; and, in the Unionidae, 34 species in the Uni- oninae, 20 in the Anodontinae and 41 in the Lampsilinae. The specimens were anaesthetized (usually in sodium nembutal) and killed and fixed (mostly in Bouin’s fluid). They were then serially sectioned in paraffin and stained with haematoxylin and eosin. ? RESULTS In the present study, only 4 unionid species have been found to be dominantly hermaphroditic (Tables 1, 2), while spo- radic, sometimes partial hermaphro- dites were found in 22 species distributed in all families and subfamilies (Tables 1, The investigation is continuing. To date an- other 2000 specimens have been quick frozen and sectioned with a cryostat (a microtome designed to cut frozen tissue). So far, no essential differences from the results re- ported in this paper have been found. HERMAPHRODITISM IN NAIADES TABLE 1. North American freshwater mussels sectioned to determine sex (97 species; 32 genera) Species Nos. sectioned MARGARITANIDAE (2 species; 2 genera) Cumberlandia monodonta (Say) 12 *Margaritifera margaritifera (Linnaeus) 12 24 UNIONIDAE (95 species; 30 genera) Unioninae (34 species; 11 genera) Amblema boykiniana (Lea) Amblema costata (Rafinesque) Amblema costata plicata (Say) Amblema neislerii (Lea) Amblema peruviana (Lamarck) Amblema perplicata (Conrad) Cyclonaias tuberculata (Raf. ) Elliptio buckleyi (Lea) Elliptio complanatus (Dillwyn) Elliptio crassidens (Lamarck) *Elliptio dilatatus (Raf. ) Elliptio fraternus (Lea) 8 *Elliptio productus (Conrad) 9 Elliptio sloatianus (Lea) 6 6 6 bo —- я оновгоаям a № 00 Elliptio strigosus (Lea) Elliptio tuomyi (Lea) Fusconaia barnesiana (Lea) 6 *Fusconaia ebenus (Lea) 35 *Fusconaia flava (Raf. ) 68 Fusconaia succissa (Lea) 34 *Gonidea angulata (Lea) 12 Lexingtonia dolabelloides (Lea) 7 Megalonaias gigantea (Barnes) Plethobasus cooperianus (Lea) 1 Plethobasus cyphyus (Raf. ) 1 *Pleurobema cordatum (Raf. ) 38 *Pleurobema cordatum coccineum (Conrad) 35 Pleurobema pyriforme (Lea) 8 Pleurobema strodeanum (B. H. Wright) 7 Quadrula cylindrica (Say) 4 Quadrula pustulosa (Lea) 23 *Quadrula quadrula (Raf. ) 85 Quadrula quadrula speciosa (Lea) 2 * Tritogonia verrucosa (Raf. ) J 567 Anodontinae (20 species; 5 genera) Alasmidonta calceolus (Lea) 86 *Alasmidonta marginata (Say) 48 Alasmidonta undulata (Say) 4 Anodonta couperiana Lea 6 H. VAN DER SCHALIE Table 1 (contd. ) Species Nos. sectioned Anodontinae (contd. ) *Anodonta corpulenta Cooper 35 Anodonta californiensis Lea 6 *Anodonta grandis footiana (Lea) 12 Anodonta cataracta Say 2 Anodonta hallenbeckii Lea 1 **Anodonta imbecillis Say 105 Anodonta marginata Say 6 Anodonta suborbiculata Say 5 Anodontoides ferussacianus (Lea) 38 Arcidens confragosus (Say) 14 *Lasmigona complanata (Barnes) 3 **Lasmigona compressa (Lea) 25 Lasmigona costata (Raf. ) 8 **Lasmigona subviridis (Conrad) 2 *Strophitus rugosus (Swainson) 64 Strophitus undulatus (Say) 19 479 Lampsilinae (41 species; 14 genera) *Actinonaias ellipsiformis (Conrad) 206 Carunculina corvunculus (Lea) 6 **Carunculina parva (Barnes) 14 Carunculina vesicularis (Lea) 15 Dysnomia compacta (Lea) 1 Dysnomia triquetra (Raf. ) 8 Lampsilis anodontoides (Lea) 10 Lampsilis anodontoides floridensis (Lea) 1 *Lampsilis cariosa (Say) 7 Lampsilis claibornensis (Lea) 27 Lampsilis clarkiana (Lea) 1 Lampsilis dolabraeformis (Lea) 5 Lampsilis excavata (Lea) 7 Lampsilis fasciola (Raf. ) 44 Lampsilis hydiana (Lea) 6 Lampsilis siliquoidea (Barnes) 41 Lampsilis siliquoidea rosacea (DeKay) 18 Lampsilis splendida (Lea) ТУ Lampsilis subangulata (Lea) 6 Lampsilis tampicoensis (Lea) 6 Lampsilis ventricosa (Barnes) 20 Lampsilis ventricosa cohongoronta (Ort. ) 8 Leptodea fragilis (Raf. ) 18 *Leptodea laevissima (Lea) 72 Ligumia nasuta (Say) 26 Medionidus simpsonianus Walker 9 Obliquaria reflexa Rafinesque 10 Obovaria subrotunda (Raf. ) 3 Plagiola lineolata (Raf. ) 5 *Proptera alata (Say) 14 HERMAPHRODITISM IN NAIADES Table 1 (contd. ) 97 Species Nos. sectioned Lampsilinae (contd. ) Proptera purpurata (Lamarck) 2 * Ptychobranchus fasciolaris (Raf. ) 22 *Ptychobranchus subtentum (Say) 18 Truncilla donaciformis (Lea) 11 Truncilla truncata (Raf. ) 1 Villosa (Micromya) fabalis (Lea) 4 *Villosa (Micromya) iris (Lea) ui Villosa (Micromya) lienosa (Conrad) ılal Villosa (Micromya) nebulosa (Conrad) 4 Villosa (Micromya) ogeecheensis (Conrad) 9 Villosa (Micromya) vibex (Conrad) ET; 801 В *Occasionally hermaphrodites **Dominantly hermaphrodites 3). Some of these species are discussed in the following. Data illustrating the gonadal picture in 27 specimens belong- ing to 23 species or forms are given in the legends to the figures. I. Margaritanidae Margaritifera margaritifera (Linnaeus) Fig. 4 This long-lived circumpolar pearl producing mussel is interesting in sever- al respects. Comfort (1957) wrote: “If the 100-year estimate of longevity in М. margaritifera (L.) is correct, it is the longest-lived invertebrate known. A life span of this order in the wild would imply an exceedingly low adult mor- tality.” Subsequently Hendelberg (1960) reported that the species could live, at least, 116 years. As already indicated, Schierholz (quoted by Pelseneer, 1920) found 1 hermaphrodite among 80 speci- mens from northern Germany that he sectioned, while Hendelberg (1960) failed to find any in a series of 20 specimens from arctic Sweden. In 1962 I collected Margaritiferafrom Pole Cat Creek in Yellowstone National Park, Wyoming, U.S.A. One of a series of 12 specimens sectioned was her- maphroditic (Fig. 4). II. Unionidae a. Unioninae Paraffin sections were made of 567 specimens of this subfamily, represent- ing 34 species. While none were found to be regularly hermaphroditic, 9 were found to be occasionally so, as detailed in Tables 1 and 3. Ortmann (1912) had already clearly stated that most of the Unioninae had separate sexes. He also noted that the gonadal tissues of these mussels were highly colored, showing various tints of orange, pink or bright crimson. While it has been stated that this coloring is associated with egg pro- duction, Ortmann’s studies (: 244) would indicate that the color may be found in males as well as females. He asserts that there is “no relation of these colors to sex.” My own observations corrobo- rate his statement. 98 H. VAN DER SCHALIE Fusconaia flava (Rafinesque) Figs. 8, 9 So far as I can determine, Sterki (1898) was the first and only one to indi- cate that this species “had a few acini producing ova in the gonad charged with copious sperm.” The distinction, he ex- plained, was particularly easy because of the bright crimson color of the ova. The animal’s visceral mass indeed often shows a striking coloration. Inthe spring of 1962, a large collection of Fusconaia flava was made in the headwaters of the Grand River in Michigan. Some animals in this series were orange, others white. When an equal number of each were sectioned, the proportion of males and females was about equal, which tends to support the view that visceral coloration is not associated with sex. The her- maphroditic individuals figured were taken in 1959 and 1960 from Ore Creek, a tributary in the Saginaw drainage. b. Anodontinae In this subfamily 479 specimens repre- senting 20 species were sectioned (Table 1). Of these, 8 species had hermaphro- ditic gonads: in 3 of these species or forms the condition was found to be dominant (Tables 1, 2); in the 5 others the condition is rare (Tables 1, 3). Four of the species showing hermaphroditism are discussed below. Anodonta imbecillis Say? Fig. 1 Again Sterki (1898) was the first to notice that all of the specimens of Ano- donta imbecillis he examined were gravid. He found “ova and sperma in various proportions.” The species is reported to be dominantly monoecious. It is also of interest that 3 character- istics, i.e., the hermaphroditic state, the lack of elevated umbones and the 4The related species Anodonta henryana Lea and A. gibbosa Say have not been sectioned in this study, but from preliminary examination it would seem that they are not monoecious. supposed metamorphosis without para- sitism, induced F. C. Baker (1927) to establish the genus Utterbackia. How- ever, Mary Tucker (1928) showed clearly that Anodonta imbecillis does have a normal fish host, the green sunfish, Apomotis cyanellus. Many years ago, (1940) I made serial sections of specimens of this species from the Ann Arbor, Michigan, area. It was evident that the acini composing the male elements were characteristically located along the sides of the visceral mass and were not as widely distributed as the acini containing the eggs. More recently I examined animals considered to belong to this same species, from Hillsboro River in Florida. It came somewhat as a surprise to find that the sexes of that population were separate. In a recent paper, Johnson (1965) reports a hitherto unrecognized species of Ano- donta, which he calls A. peggyae, also giving Hillsboro River as one of the localities. This report suggests thatthe difference in the sexual condition ob- served between the northern and southern forms, thought to be one of geographical strain, might even be specific, a moot point. Johnson, incidentally, corrects the spelling of the specific name ¿m- becillis to imbecilis. Anodonta grandis footiana (Lea) Fig. 15 Observations by Boycott and Oldham led Bloomer (1930, 1934, 1935, 1939) to extensively investigate the sex conditions of Anodonta cygnea (L.) in the British isles. From the structure of the gonad he suspected possible sex reversal (1934). Studying the ratios of males, females and hermaphrodites in various populations (1939) he found these constant for, but varying between, populations. His stimulating papers aroused our curi- osity and our interest in Anodonta grandis Say, the most common North American species, about which, in contrast to A. imbecillis, no information was available. As reported by van der Schalie & Locke (1941), gonads of a lake form of this species, A. grandis footiana were sectioned and hermaphroditism was HERMAPHRODITISM IN NAIADES TABLE 2. The only North American naiades in which hermaphro- ditism is the dominant condition Families Species MARGARITANIDAE none UNIONIDAE: Unioninae none Anodontinae Anodonta imbecillis Say (Fig. 1) Lasmigona compressa (Lea) (Fig. 2) Lasmigona subviridis (Conrad) Lampsilinae Carunculina parva (Barnes) (Fig. 3) TABLE 3. Species of North American naiades in which hermaphro- dites were occasionally found MARGARITANIDAE Margaritifera margaritifera (Linn. ) (Fig. 4) UNIONIDAE Unioninae Elliptio dilatatus (Raf.) (Figs. 5, 6) Elliptio productus (Conrad) (Fig. 7) Fusconaia flava (Raf.) (Figs. 8, 9) Fusconaia ebenus (Lea) Gonidea angulata (Lea) (Fig. 17) Pleurobema cordatum (Raf. ) Pleurobema cordatum coccineum (Conrad) (Figs. 10, 11) Quadrula quadrula Raf. Tritogonia verrucosa (Say) (Fig. 12) Anodontinae Alasmidonta marginata (Say) (Figs. 13, 14) Anodonta corpulenta Cooper (Fig. 16) Anodonta grandis footiana (Lea) (Fig. 15) Lasmigona complanata (Barnes) (Fig. 18) Strophitus rugosus (Swainson) (Fig. 19) Lampsilinae Actiononaias ellipsiformis(Conrad) (Figs. 20, 21) Lampsilis cariosa (Say) (Fig. 22) Leptodea laevissima (Lea) (Fig. 23) Proptera alata (Say) (Fig. 24) Ptychobranchus fasciolaris (Raf.) (Fig. 25) Ptychobranchus subtentum (Say) (Fig. 26) Villosa (Micromya) iris (Lea) (Fig. 27) 100 H. VAN DER SCHALIE FIGS. 1-9. Gonadial tissues of some North American naiades showing various degrees of hermaphroditism (stain: haematoxylin and eosin). FIG. 1. Anodonta imbecillis (Say). Huron River, above Ypsilanti, Washtenaw Co., Michigan. May 25, 1940. Henry van der Schalie, Collector. Specimen: 5 years old. Normal hermaphro- dite with male and female tissues separated so that male gonad is found along the upper and outer sides of the visceral mass. (Original photomicrograph taken at X 100). FIG. 2. Lusmigona compressa (Lea). Ore Creek, 5 mi. below Hartland, Michigan. June 9, 1959. Henry van der Schalie, Collector. Specimen: 82 mm long, 5 years old, gravid. A typical and normal hermaphrodite with eggs in one follicle and sperm developed in another. (Taken at x 125). FIG. 3. Carunculina parva (Barnes). Tennessee River, Station 3, near New Johnsonville, Tennessee. October 16, 1964. John M. Bates, Collector. Specimen: 27.5 mm long, 8 years old, not gravid. A normal hermaphrodite with male and female follicles separate. (Taken at X 125). FIG. 4. Margaritifera margaritifera (L.). Pole Cat Creek, just south of Yellowstone Park, Wyoming. August 15, 1962. Henry van der Schalie, Collector. Specimen: 34 mm long, 5 years old, not gravid. Note that male and female follicles are separate. (Taken at X 125). FIG. 5. Elliptio dilatatus (Raf.). Cranberry Creek, Byron, Shiwassee Co. , Michigan. June 5, 1961. Henry van der Schalie, Collector. Specimen: 67 mm long, 8 years old, not gravid. Mainly female, but with male tissue developing in female follicles; eggs seem to be developing normally. (Taken at X 125). FIG. 6. Elliptio dilatatus (Raf.). French Creek, trib. Allegheny River, 5 mi. north of Mead- ville, Pennsylvania. July 17, 1961. MacKenzie Keith, Collector. Specimen: 4 years old, 61 mm long, gravid. Spermatogenesis clearly evident in female follicles. (Taken at X 125). FIG. 7. Elliptio productus (Conrad). Savannah River, above Route 301 bridge, south of Allen- dale, S. Carolina. June 24, 1964. John M. Bates, Collector. Specimen: 59 mm long, 6 years old, not gravid. A small amount of normal female tissue present in a preponderantly male specimen. (Taken at X 125). FIG. 8. Fusconaia flava (Raf.). Ore Creek, 1 mi. northwest of Hartland, Livingston Co. , Michigan. May 22, 1960. Henry van der Schalie, Collector. Specimen: 74 mm long, 12 years old, not gravid. A female with only a small amount of spermatogenesis in wall of follicles. (Taken at X 125). FIG. 9. Fusconaia flava (Raf.). Ore Creek at Clyde Road, below Hartland, Livingston Co. , Michigan. June 25, 1959. Henry van der Schalie, Collector. Specimen: 68 mm, 11 years old, not gravid; predominantly male with only small foci of female tissue and eggs tending to be sup- pressed. (Taken at X 100). HERMAPHRODITISM IN NAIADES 101 102 H. VAN DER SCHALIE FIGS. 10-18. Gonadial tissues of some North American naiades showing vari- ous degrees of hermaphroditism (stain: haematoxylin and eosin). FIG. 10. Pleurobema cordatum coccineum (Conrad). South branch Cranberry Creek at Byron, Shiawassee Co., Michigan. Nov. 21, 1960. Henry van der Schalie, Collector. Specimen: 35 mm long, 3 years old, not gravid; mostly female tissue with only a small amount of discrete male follicles. (Original photomicrograph taken at X 100). FIG. 11. Pleurobema cordatum (Raf.). Tennessee River, above New Johnsonville, Tennessee. Nov. 11, 1963. John M. Bates, Collector. Specimen: 80 mm long, 17 years old, not gravid; appears to be about half male and half female with eggs poorly developed in follicles with sper- matogenesis in walls. (Taken at X 100). FIG. 12. Tritogonia verrucosa (Raf.). Guadalupe River, 1/2 mi. west of Sequin, Guadalupe Co., Texas. August 22, 1962. John M. Bates, Collector. Specimen: 66 mm long, 5 years old, not gravid; mainly female with patches showing spermatogenesis. (Taken at X 125). FIG. 13. Alasmidonta marginata (Say). River Raisin, Sharon Hollow, Washtenaw Co., Michi- gan. July 20, 1962. Henry van der Schalie, Collector. Specimen: 41 mm long, 3 years old, not gravid; evidently a female with patches of sperm developing in walls of follicles; eggs do not seem normal in development. (Taken at X 125). FIG. 14. Alasmidonta marginata (Say). Powell River, at U.S. 25 E, Claiborne Co., Tennes- see. June 23, 1961. B. Dazo and H. van der Schalie, Collectors. Specimen: 62 mm long, 10 years old, not gravid; evidently sex quite mixed so that many egg follicles have spermatogenesis in walls with eggs often suppressed in development. (Taken at X 125). FIG. 15. Anodonta grandis footiana (Lea). Zukey Lake, Lakeland, Livingston Co., Michigan. May 11, 1940. Henry van der Schalie, Collector. Specimen: 7 years old; mostly male with only small amount of female tissue which seems to be normal in development. (Taken at X 125). FIG. 16. Anodonta corpulenta Cooper. Tennessee River, slough along river at mile 97.7, near New Johnsonville, Tennessee. October 16, 1964. John M. Bates, Collector. Specimen: 81 mm long, 5 years old, gravid; eggs do not appear to be developing normally and spermato- genesis appears in walls of some follicles. (Taken at X 125). FIG. 17. Gonidea angulata (Lea). Snake River, near Bliss, Idaho. August 18, 1962. Henry van der Schalie, Collector. Specimen: 117 mm long, 15 years old, not gravid; a typical her- maphrodite with both male and female tissues well developed. (Taken at X 125). FIG. 18. Lasmigona complanata (Barnes). River Rouge, Michigan. October 1, 1962. Carol Geake, Collector. Specimen: 170 mm long, 12 years old, gravid; the gonad appears to be mostly female but with scattered spermatogenesis in the walls of many follicles. (Taken at X 125). HERMAPHRODITISM IN NAIADES 104 H. VAN DER SCHALIE FIGS. 19-27. Gonadial tissues of some North American naiades showing vari- ous degrees of hermaphroditism (stain: haematoxylin and eosin). FIG. 19. Strophitus rugosus (Swainson). Inlet to Zukey Lake, Livingston Co., Michigan. July 14, 1960. Bonifacio Dazo, Collector. Specimen: 56 mm long, 4 years old, gills not clear as to gravid state; mostly male with only a small amount of female tissue. (Original photomicrograph taken at X 125). FIGS. 20 & 21. Actinonaias ellipsiformis (Conrad). Ore Creek, at Clyde Road, near Hartland, Livingston Co., Michigan. Henry van der Schalie, Collector. Specimen: 67 mm long, 10 years old, not gravid; one of most unusual hermaphrodites observed in that male and female tissues quite thoroughly mixed. (Taken at X 125). FIG. 22. Lampsilis cariosa (Say). Potomac River, Point of Rocks, near Frederick, Maryland. September 22, 1962. John M. Bates, Collector. Specimen: 100mm long, 8 years old, not gravid; eggs in poor development but in discrete follicles; some spermatogenesis in walls of poorly de- veloped female follicles. (Taken at X 125). FIG. 23. Leptodea laevissima (Lea). Tennessee River, at mile 97.7 near New Johnsonville, Tennessee. October 16, 1964. John M. Bates, Collector. Specimen: 55 mm long, 3 years old, gravid; mostly female but with small foci of what appears to be developing sperm. (Taken at % 125). FIG. 24. Proptera alata (Say). Lake Erie, at 32 feet depth near Middle Sister Island, Ohio. August 22, 1962. Yarl Hiltunen, Collector. Specimen: 66 mm long, 5 years old, gravid; mainly female tissue but with a hermaphroditic trend shown by an incipient spermatogenesis. (Taken at X 100). FIG. 25. Ptychobranchus fasciolaris (Raf.). Little Portage River, above Toma Road, Wash- tenaw Co., Michigan. Bonifacio Dazo, Collector. Specimen: 69 mm long, 9 years old, gravid; mainly female but with small areas of spermatogenesis scattered throughout the glandular masses. (Taken at X 125). FIG. 26. Ptychobranchus subtentum (Say). Powell River, at U.S. 23 E, Claiborne Co., Ten- nessee. August 23, 1961. B. Dazo and H. van der Schalie, Collectors. Specimen: 82 mm long, 15 years old, not gravid; a female with clear-cut patches of male tissue with follicles showing poor development of eggs. (Taken at X 125). FIG. 27. Villosa (Micromya) iris (Lea). River Raisin, Sharon Hollow, Washtenaw Co., Michi- gan. July 20, 1962. Norman Reigle, Collector. Specimen: 33 mm long, 3 years old; female with gills about spent; mainly female, but with unusually abundant spermatogenesis appearing in walls of many female follicles. (Taken at X 100). HERMAPHRODITISM IN NAIADES 105 106 H. VAN DER SCHALIE demonstrated in 2 out of 14 specimens. Lasmigona compressa (Lea) and L. subviridis (Conrad) Fig. 2 All 25 specimens of Lasmigona com- pressa collected from several creeks in Michigan were hermaphroditic. This species is widespread and unique in that it is able to occupy very minute creeks and streams - places in which often no other mussels are found. A closely related eastern species of similar ecology, L. subviridis, has also been found for the first time to be domin- antly hermaphroditic (2 out of 2 ex- amined). The relationship of these 2 species is uncertain. Strophitus rugosus (Swainson) Fig. 19 Among others, a series of 64 speci- mens was collected in a creek con- necting 2 lakes in Livingston County, Michigan, in every month of the year. The hermaphroditic condition was ob- served in only 1 specimen. There was a clear-cut separation between the male and female tissues. The animal was collected on July 14, 1960, andthere were sufficient eggs in a normal state to indi- cate that the specimen was a functional hermaphrodite. c. Lampsilinae In this subfamily 801 specimens repre- senting 41 species were sectioned (Table 1); 8 species belonging to 7 genera were found to be hermaphroditic; one, Carun- culina parva was regularly ambisexual (Tables 1, 2) and 7 species were oc- casionally so (Tables 1, 3). Carunculina parva (Barnes)? Fig. 3 Hermaphroditism in this species was STwo other species of Carunculina, C. cor- vunculus (Lea) and C. vesicularis (Lea), col- lected in southern states, were not found to be monoecious. reported at an early date (Sterki, 1898). Tepe (1943) carefully studied the his- tology of the gonads. He reported the occasional presence of hermaphroditic acini that contained eggs as well as sperm and made the following statement regarding this condition: “In most instances it was observed that eggs enclosed in male follicles were smaller (20-24 microns) than eggs from strictly female _ follicles (40-100 microns). The eggs in essentially male follicles were free from germinal epithe- lium, and their small size does not seem to indicate immaturity. Both eggs and spermatozoa appeared mature in all the individuals, which would seem to indicate that this hermaphroditic condition does not represent a phase in a periodic sex reversal.” Our studies on 14 individuals from the Tennessee River show essentially the Same conditions. All individuals ex- amined were hermaphrodites; 2 of them also had acini with both eggs and sperm. Actionaias ellipsiformis (Conrad) Figs. 20, 21 In an earlier study (H. € A. van der Schalie, 1963) some 200 specimens of this species were collected over an ex- tended period. It was found that the gonads remained undifferentiated for the first 2 years. All specimens 2 years old or older were either distinctly male or female, except for one hermaphro- dite. This specimen was the largest (68mm) of a series of 25 individuals taken late in June from Ore Creek, Livingston Co., Michigan, of which 13 were gravid and 12 non-gravid. It was originally considered a female because the lower posterior portion of the outer gill showed a small amount of marsupial tissue. At that time the animal was reaching the end of the spring glochidial shedding period, but there was enough gill modification to show it was function- ing as a female. Its hermaphroditic condition was not discovered until the gonads were sectioned, whenit was found HERMAPHRODITISM IN NAIADES that male and female tissue was quite thoroughly mixed.6 This mussel, with 10 annuli on the shell, was the oldest of the series. On the chance that this her- maphroditic condition might be associ- ated with senescence, the other large specimens of this serieS were re- examined, but results were negative. Villosa (Micromya) iris (Lea) Fig. 27 A specimen of this species has also been found to have similarly mixed gonad tissue,® simultaneously producing eggs and sperm. DISCUSSION Hermaphroditism in mollusks is sup- posed to be derived from an originally dioecious condition. Some authors emphasize that the condition tends to appear in situations when the animal is confronted with difficulties in its normal reproductive activity. Hence her- maphroditism might be an adaptive mechanism, giving the species some evolutionary advantage. Now that almost 100 North American naiad species have been studied, it has become evident that among this large and highly evolved group relatively few are regularly hermaphroditic. Es- sentially the situation is similar to that in the marine lamellibranchs in which also there are comparatively few species that are monoecious. Among the naiades, only the Anodontinae andthe Lampsilinae appear to have species in which the con- dition occurs regularly and only 4 species are involved: 3 in the former sub- genus and 1 in the latter. All of the sporadic cases that were detected in 22 species or forms clearly belong to the SThe unusual condition of the gonads of the 2 specimens here quoted has been recently discussed (van der Schalie, 1969). It was stressed that the simultaneous production of eggs and sperm is quite uncommon among freshwater mussels. 107 category that Coe (1943: 156) considered as accidental or developmental ambi- sexuality. Under this heading he stated: “Even in species which are otherwise strictly of separate sexes there may be an occasional individual with functional hermaphroditism. These can allbe con- sidered as resulting from deviations in the developmental processes due to a failure of the sex-differentiating mecha- nism to function normally. The pro- portion of spermatogenic and ovogenic tissues in the gonad is highly variable, some individuals having approximately equal parts of both sexual types, while others are principally one sex, with but few cells characteristic of the opposite sex. This type of sexuality is more common in the pelecypods than in most other groups of animals and it occurs frequently in young individuals at the first reproductive season. In certain local races of oviparous oysters, clams and mussels it is possible to determine whether the initial sexual phase is normal or accidental.” In the present study specimens from species found to be regularly hermaphro- ditic presented a “normal” histological picture, with male and female tissues, resp. acini separate, a situation that was also encountered in Margaritana, Strophitus and Gonidea. The other oc- casional hermaphrodites, however, were as a rule predominantly of one sex, with only some tissue or cells of the other sex developing in or among the follicles of the dominant sex. The various occasional hermaphro- dites detected were certainly not re- stricted to, or prevalent in, young indi- viduals. But Coe does not quote only age as a factor connected with modifi- cation of the sexual state. Temperature, resp. season, and several other factors have also been incriminated. Thus, for instance, nutritional disturbances of the Bombay oyster apparently resulted in an increased proportion of males, where- as in years and locations favoring rapid growth, Virginia oysters had a large proportion of females. Habitat has been 108 H. VAN DER SCHALIE considered to play a role: Weisensee (1916: 292) claimed to have observed that the dioecious condition was normal for Anodonta cygnea living in rivers, while those living in impounded waters tended to be hermaphroditic. In other instances variation is attri- buted to heredity per se: Coe (1943) reports races with different heredity in the Virginia oyster. Bloomer (1939) reports populations of Anodonta cygnea in which hermaphroditism was relatively more common than in others in a con- stant manner. From the findings re- ported in this survey, it appears quite possible that wide-ranging species, such as Anodonta imbecillis, may not be her- maphroditic throughout their whole range, so that northern forms may differ in this respect from the southern repre- sentatives (?A. peggyae). Sucha region- al difference was recently shown to exist (van der Schalie, 1965) in a freshwater gastropod, Campeloma, which in the northern United States is partheno- genetic, no males being known from that region. Though interesting to speculate on, Weisensee’s contention as to a direct influence of the environment would, ac- cording to his own testimony, need much additional investigation before it could be plausibly substantiated. Although a wide cross-section of the North Ameri- can mussel fauna has now been sampled, including mussels living in streams as well as in lakes, it has not been possible so far to demonstrate any environmental factor that would indicate any causal relation with sexuality. The extent of ambisexuality and the mechanisms pro- ducing it still remain open questions. Studies would need to be intensified so as to cover species in greater detail, i.e., at different ages, seasons and locali- ties. Such investigations are not easy because gonad smears or sections must be made to discover hermaphroditism and ample material must be procured. While it would be of interest to explore factors (chemical, physical, etc.) that might perhaps serve to induce sex changes in the naiades, this group un- fortunately does not lend itself readily to laboratory experiments. However, investigations are continuing. Arrange- ments have been made for the procure- ment of Margaritana from the Rocky Mountain regions of the U.S.A. during the active season of the year, anda study to determine the sex ratios of several commercially important mussels is be- ing conducted by the University of Michi- gan in Kentucky Lake, Tennessee, andin the Muskingum River in Ohio. ACKNOWLEDGEMENTS Several of our staff and students as- sisted with preparing the thousands of paraffin blocks and cutting thin sections that made this investigation possible. Some of the sections were made by my wife, Annette; others were made by Khan Tandaraporn, Barbara Peckham, Su- sanne Pauly, Jane Phelps and Paula Levy. Colleagues and students generously con- tributed live specimens for proper fixa- tion and preservation; among them mention should be made especially of John M. Bates, William H. Heard, Boni- facio Dazo and Robert Wakefield. The photographs were made with the assis- tance of Vera Farris, Louis P. Martonyi and Gene K. Lindsay. LITERATURE CITED BLOOMER, H. H. 1930. A note on the sex of Anodonta cygnea. Proc. malac. Soc. London, 19: 10-14. BLOOMER, H. H. 1934. On the sex and modification of the gill, of Anodonta cygnea. Ibid., 21: 21-28. BLOOMER, H. H. 1935. A further note оп the sex of Anodonta cygnea L. Ibid., 21: 304-321. BLOOMER, H. H. 1939. A note on the sex of Pseudanodonta Bourguignat and Anodonta Lamarck. Ibid., 23: 285- 297. BAKER, F. C. 1927. On the division of the Sphaeriidae into two subfamilies and the description of a new genus of HERMAPHRODITISM IN NAIADES 109 Unionidae, with descriptions of new varieties. Amer. Midl. Nat., 10: 220- 223. COE, W.R. 1943. Sexual differentiation in mollusks. I. Pelecypods. Quart. Rev. Biol., 18: 154-164. COMFORT, A. 1957. The duration of life in molluscs. Proc. malac. Soc. London, 32: 212-241. FRETTER, V. & GRAHAM, V. 1964. Reproduction in Physiology of Mollus- ca. Eds. Wilbur, Rm. M., Yonge, С.М. Academic Press, N. Y. Vol. 1: 127- 164. HENDELBERG, J. 1960. The fresh- water pearl mussel; Margaritifera margaritifera (L.). Rep. Inst. freshw. Res., Drottningh., No. 41: 149-171. JOHNSON, В. I. 1965. A higherto over- looked Anodonta (Mollusca: Unionidae) from the Gulf drainage of Florida. Breviora, No. 213: 1-7. LACAZE-DUTHIERS, A. 1854. Re- cherches sur les organes génitaux des Acéphales Lamellibranches. Ann. Sci. Nat. 4 Sér., Zool., Vol. II: 155, Paris. ORTMANN, A. E. 1912. Notes upon the families and genera of the naiades. Ann. Carnegie Mus., 8: 222-365. PELSENEER, P. 1920. Les variations et leur hérédité chez les mollusques. Mem. Acad. Roy. Belg., Brussels, 5: 1-321. PELSENEER, P. 1926. La proportion relative des sexes chez les animaux et particulièrement chez les mol- lusques. Acad. Roy. Belg. Classe Sci. Mem. 8: 34-35. PURCHON, R. D. 1951. Hermaphro- ditism. Reprinted from: Gazette King Edward VII Med. Soc., Univ. Malaya, Vol. II (no pagination). STERKI, V. 1898. Some observations on the genital organs of Unionidae with reference to classification. Nautilus, 12: 18-21: 28-32. TEPE, W. 1943. Hermaphroditism in Carunculina parva, a freshwater mussel. Amer. midl. Nat., 29: 621- 623. TUCKER, M. E. 1928. Studies on the life cycles of two species of fresh- water mussels belonging to the genus Anodonta. Biol. Bull., 54: 117-127. VAN DERSCHALIE,H. 1965. Observa- tions on the sex of Campeloma. Occ. Pap. Mus. Zool., Univ. Mich., 641: 1-15. VAN DER SCHALIE, H. 1966. Her- maphroditism among North American freshwater mussels. Abstracted in: Proc. Second Europ. Malacol. Congr. (Copenhagen, 1965) Malacologia, 5(1): 77-78. VAN DER SCHALIE, H. 1969. Two unusual unionid hermaphrodites. Science, 163: 1333-1334. VAN DER SCHALIE, H. & LOCKE, F. 1941. Hermaphroditism in Anodonta grandis, a freshwater mussel. Ibid., 432: 1-7. VAN DER SCHALIE, H. & VAN DER SCHALIE, A. 1963. The distribution, ecology and life history of the mussel, Actiononaias ellipsiformis (Conrad). Occ. Pap. Mus. Zool., Univ. Mich., 633: 1-17. WIESENSEE, H. 1916. Die Geschlechts- verhältnisse und der Geschlechts- apparat bei Anodonta. Z. wiss. Zool., 115: 262-335. WELLMANN, G. 1939. Untersuchungen über die Flussperlmuschel (Margari- tana margaritifeva L.) und ihren Lebensraum in Báchen der Lüneburger Heide. Z. f. Fischerei u.d. Hilfswiss., 36(1938): 489-603. 110 H. VAN DER SCHALIE RESUME L’HERMAPHRODISME CHEZ LES MOULES D’EAU DOUCE D'AMERIQUE DU NORD H. van der Schalie Les informations sur l’existence de l’hermaphrodisme parmi les moules d’eau douce de la riche faune des U.S.A., sont fragmentaires. Dans cette étude, les gonades de 1871 exemplaires appartenant a 97 espéces et 32 genres ont été examinées histo- logiquement, par la technique des coupes a la paraffine. Seulement 4 espéces parmi 2 subfamilles des unionides se sont montrées essentiellement hermaphrodites (mono- iques); 3 chez les Anodontinae: Anodonta imbecillis, Lasmigona compressa et (espéce toute proche) L. subviridis; 1 chez les Lampsilinae: Carunculina parva. Des hermaphrodites accidentels ont été trouvés chez 22 autres espéces ou formes, appartenant a 17 genres et 2 familles. En général, de tels individus ont généralement un sexe dominant, avec seulement une faible quantité de tissus de l’autre sexe. Un spécimen ambisexué a été trouvé chez les Margaritanidae, chez Margaritifera mar- garitifera, parmi 24 spécimens sectionnés représentant 2 genres et espéces. Chez les Unionidae, des hermaphrodites accidentels se rencontrent dans les 3 subfamilles. Parmi les Unioninae, sur 567 spécimens (34 espéces, 11 genres) examinés, de tels individus ont été trouvés dans 9 espéces (ou formes) et 5 genres, soit: Elliptio dila- tatus, E. productus, Fusconaia ebenus, F. flava, Gonidea angulata, Pleurobema cor- datum, P. c. coccineum, Quadrula quadrula et Tritogonia verrucosa. Parmi les Ano- dontinae, sur un total de 479 spécimens (20 espéces, 5 genres) sectionnés, des her- maphrodites accidentels ont été mis en évidence chez 5 espéces appartenant a 5 genres, dont 2 sont des genres comportant aussi des espéces hermaphrodites; c.a.d. qu’ils se rencontrent chez: Anodonta corpulenta, A. grandis footiana et Lasmigona complanata ainsi que chez Alasmidonta marginata et Strophitus rugosus. Chez les Lampsilinae, avec un total de 801 spécimens (41 espéces, 14 genres) sectionnés, le phénomène a été à nouveau trouvé chez 7 espèces représentant 6 genres, c.a.d. chez: Actinonaias ellipsiformis, Lampsilis cariosa, Leptodea laevissima, Proptera alata, Ptychobranchus fasciolaris, P. subtentum et Villosa (Micromya) iris. Ce relevé, a peu pres complet des moulesd’eau douce américaines, montre qu’elles sont généralement dioiques. La question reste toujours posée de savoir, si oui ou non, l’hermaphrodisme apparait chez des animaux places dans des conditions de milieu difficiles, comme cela a été antérieurement suggéré. AR RESUMEN HERMAFRODITISMO EN ALMEJAS DE AGUA DULCE DE NORTE AMERICA H. van der Schalie La información existente acerca de la amplitud del hermafroditismo en la rica fauna de naiades de U.S.A. es fragmentaria. Para el presente estudio se examinaron las gonadas de 1871 ejemplares pertenecientes a 97 especies de 32 géneros, usando cortes de bloques de parafina. Sólo 4 especies, en dos subfamilias de uniónidos, mostraron ser dominantemente hermafroditas (monoicos); 3 en los Anodontinae: Anodonta imbecillis, Lasmigona compressa y (la estrechamente emparentada) L. sub- viridis, y 1 en los Lampsilinae: Caranculina parva. HERMAPHRODITISM IN NAIADES i En otras 22 especies o formas, pertenecientes a 17 géneros y 2 familias, se en- contraron hermafroditas esporadicos. Usualmente estos individuos parecen ser predominantemente de un sexo, con sólo una pequeña cantidad de tejido gonadal del sexo opuesto. Un ejemplar ambisexual se encontró en Margaritanidae, en Margariti- fera margaritifera, entre 24 ejemplares seccionados que representaban 2 géneros y especies. En los Unioninae, individuos accidentalmente monoicos aparecieron en las 3 subfamilias. Entre los Unioninae con 567 ejemplares (34 especies, 11 géneros) examinados, tales individuos se encontraron en 9 especies (o formas) de 6 géneros: Elliptio di latatus, E. productus, Fusconaia ebenus, F. flava,Gonidea angulata, Pleuro- Бета cordatum, Р. с. coccineum, Quadrula quadrula, y Tritogonia verrucosa. En los Anodontinae, con un total de 479 ejemplares (20 especies, 5 géneros) seccionados, hermafroditas esporádicos se mostraron en 5 especies de 4 géneros, de los cuales 2 géneros son los que también contenian las especies predominantemente hermafroditas; las 5 especis son: Anodonta corpulenta, A. grandis footiana, Lasmigona complanata, Alasmidonta marginata y Strophitus rugosus. En los Lampsilinae con un total de 801 especimenes (41 especies, 14 géneros) seccionados, la condición fue detectada en otras 7 especies representantes de 6 géneros: Actinonaias ellipsiformis, Lampsilis cariosa, Leptodea laevissima, Proptera alata, Ptychobranchus fasciolaris, P. sub- ternum y Villosa (Micromya) iris. Esta inspección de un caracter mas bien extensivo de los naiades americanos, muestra que ellos son generalmente dioicos. Queda aun por resolver la cuestión si el hermafroditismo aparece o no en los animales que confrontan condiciones ambi- entales dificiles. J2J.P. ABCTPAKT ГЕРМАФРОДИТИЗМ Y СЕВЕРО- АМЕРИКАНСКИХ ПРЕСНОВОДНЫХ МОЛЛЮСКОВ Г. ВАН-ДЕР ШЕЙЛИ О гермафролитизме среди пресноводных наялил, фауна которых в США очень богата, известно очень мало. В настоящей статье рассматриваются результаты гистологического изучения гонад этих моллюсков, полученных от 1871 экземпляра 97 видов из 32 родов. Для срезов использовались параффи- новые блоки. Лишь 4 вида из 2 подсемейств унионид были преимущественно TepMahponn- тными (однодомными). Это 3 вида из Anodontinae: Anodonta imbecillis, Lasmigona compressa и близкородственный L. subviridis Y один вид U3 Lampsilinae Carunculina parva. Спорадический гермафродитизм был отмечен у 22 видов или форм, относя- щихся к 17 родам и 2 семействам. Обычно такие особи с виду кажутся одно- полыми, лишь с небольшой частью гонады противоположного пола. Одна дву- полая особь была найдена среди Маргаритинид- Margaritifera margaritifera, из 24 экземпляров, на которых были сделаны срезы, представляют 2 вида и ви- да. Из Unionidae случайно однодомные особи были встречены во всех трех подсемействах. Среди просмотренных 567 экземпляров (34 вида и 11, родов) такие особи были найдены y 9 видов (или форм) из 5 родов. Это: Elliptio dilatatus, E. productus, Fusconaia ebenus, Е. flava, Gonidea angulata, Pleurobema cordatum, P. c. coccineum, Quadrula quadrula u Tritogonia verrucosa. 112 H. VAN DER SCHALIE Из 479 изученных экземпляров Anodontinae (20 видов и 5 родов), cnopa- дический гермафродитизм был отмечен у 5 видов из 4 родов. Из них 2 отно- сились к родам, также имеющим преимущественно гермафродитные виды. Это: Anodonta corpulenta A. grandis footiana и Lasmigona complanata , а также Alasmidonta marginata и Strophitus rugosus. Из Lampsilinae был изучен 801 экземпляр (41 вида из 14 родов); указанные выше особенности отмечены у 7 видов из 6 роцов, а именно: Actinonaias elipsiformis, Lampsilis cariosa, Leptodea laevissima, Proptera alata, Ptychobranchus fasciolaris, P. subtentum u Villosa (Micromya) iris. Эти ловольно экстенсивные исслепования американских наядид показали, что они являются преимущественно раздельнополыми. Вопрос о том, появля- ется ли гермафродитизм у животных в трудных условиях существования, оста- ется пока открытым. 2. A. Е. MALACOLOGIA, 1970, 10(1): 113-151 COMPARATIVE ECOLOGY OF THE SNAILS PHYSA GYRINA AND PHYSA INTEGRA (BASOMMATOPHORA: PHYSIDAE)!>? Philip T. Clampitt Department of Zoology University of Iowa Iowa City, Iowa, U.S.A 3 ABSTRACT A comparative study was made on 2 freshwater pulmonate snails, Physa gy- yina Say and P. integra Haldeman, in the Lake Okoboji area, Dickinson County, Iowa to investigate the local distribution of each species and its causes. P. integra was found to be a characteristic inhabitant of rocky lake shores and of vegetated off-shore areas of lakes to depths of at least 3 meters, but was totally absent from ponds. Dense populations of P. gyrina were found in ponds, in rocky lake shore areas and in habitats of intermediate types, but always in very shallow water. In field populations of both species, growth and reproduc- tive activity was greatest in the spring (April through June), there was consider- able mortality during the summer, and growth was slight during the winter. P. gyrina was consistently the more rapidly growing species infield and laboratory, but laboratory grown P. integra usually reached reproductive maturity slightly sooner (often under 2 months). In the laboratory, both species produced an average of 200-300 eggs per snail per month during the peak period of repro- duction (4 months in P. gyrina, 6 months in P. integra). Stomach analyses and extensive laboratory observations on food preference suggest that both species consume a wide variety of food materials, determined chiefly by what can be scraped loose and ingested; food habits are not apprecia- bly different. Dispersal rates of P. gyrina were significantly higher than those of P. integra in the laboratory and in the field. The 2 species behaved similarly under the following circumstances: in a temperature gradient chamber they moved away from the cold end (11% C) and tended to move toward, but not into, the heated end (380-400 С); both moved freely through a wide range of tempera- tures. When wave action was heavy in rocky shore areas, they moved to the lower or otherwise protected surfaces of the stones. They came to the surface regularly for aerial breathing when in very shallow water. P. integra in deeper water, however, had the mantle cavity filled with water and could remain sub- merged throughout the life cycle. P. gyrina can withstand high temperatures (35% and 400 C), and also the ef- fects of drying, for a significantly longer period of time than can P. integra. Partly for this reason P. integra is excluded from ponds. The large size and rapid growth rate of P. gyrina with the resultant need for atmospheric oxygen, may limit this species in summer to very shallow water, while the smaller, lAdapted from a dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the University of Iowa. 2The work was supported through a National Science Foundation Cooperative Graduate Fellow- ship, 1961-63. Present address: Cranbrook Institute of Science, Bloomfield Hills, Michigan, U.S.A. (113) 114 P. T. CLAMPITT slower-growing P. integra is not so restricted. P. integra may be restricted to the more stable conditions of lakes (as compared with ponds) partly also be- cause of its slower growth rate, a potentially longer period of reproduction, and slower rate of dispersal in response to changing environmental conditions. INTRODUCTION In considering any species of animal in relation to its environment, the fol- lowing questions arise: (1) Where isthe animal found? (2) Why is it found in some habitats and not in others? Comparative studies of closely related species are of value in dealing with these questions, because they lead us to de- termine what factors are limiting for one species but not for another. Where there are differences in geographic or local distribution between related species, explanations can be sought in terms of limiting factors. A compara- tive approach may guide us in choosing what factors to study. Two species of freshwater pulmonate Snails, Physa gyrina Say and Physa in- tegva Haldeman, were chosen for this study with the above considerations in mind. The adults of the 2 species can be distinguished readily from external morphology alone. Both species occupy a wide geographic range centering broadly in the Great Lakes region of North America, and are common species in the Lake Okoboji area of northwest Iowa, where most of the field work for this study was done. In the study area, the 2 species are found together in rocky lake shore habitats. Only P. gyrina is found in ponds, and only P. integra inthe vegetated offshore areas of lakes. The purpose of the investigation was to de- termine as precisely as possible the similarities and differences inlocaldis- tribution in the 2 species, and to attempt to explain these similarities and differences. The methods used include a wide va- riety of field and laboratory techniques. These will be described in some detail under the headings to which they pertain. Very briefly, the methods include: (1) qualitative and quantitative sampling in various habitats; (2) laboratory and field experiments designed to measure the behavior and tolerance of the 2 species in response to specific factors, such as food, temperature and drying; (3) life history studies in the field and the labo- ratory; and (4) observations, in field and laboratory, on locations, orientation and attributes of behavior of the 2 species. The facilities of the lowa Lakeside Laboratory, Milford, Iowa, were used for a large part of the work reported here. THE TWO SPECIES The taxonomy of the large genus Physa, at least in its North American representatives, is at presentina rather doubtful state. The statement of Good- rich € van der Schalie (1939), “No general rules have been laid down as yetthat are helpful toward a certain and confident determination of the species of Physa,” is still valid today. Baker (1928), in his monograph, The Fresh-water Mollusca of Wisconsin, describes some 50 species and varieties of Physella (=Physa). Wurtz (1949) suggests that a large pro- portion of these should be reduced to Synonymy. With the vary large number of names associated with what may be only a relatively few species, the geo- graphic and local distribution of ‘any “species” of Physa is at best uncertain, and the proper label to attach cannot now be determined with certainty. Geographic and Local Distribution Baker (1928) states that Physa gyrina occurs “from the Arctic regions south to Alabama and Texas.” Clench (1926) claims, on the other hand, that the species does not extend south of the Ohio River or southern Missouri. The cata- logue of the mollusk collection at the University of Michigan has some listings for P. gyrina from points as divergent ECOLOGY OF PHYSA as Nova Scotia and Prince Edward Island in the northeast to Florida in the south- east and California in the west. Whether these all represent correct listings is doubtful, but it can be said with some confidence that the species has an ex- tensive geographic range. Baker (1928) cites Crandall (1901) as giving the distribution of P. integra as “from the Great Lakes to the Gulf, occupying a belt from central Arkansas to central Kansas.” He adds that it has not been reported from south of the Ohio River, but is common in several states from New York west to South Dakota. The University of Michigan collection has listings from such divergent areas as Quebec, New York, Alabama, Texas, Colorado, Wyoming, andN. W. Territory, Canada (Great Slave Lake). The limits of the range of this species are again uncertain, but the range is apparently extensive and covers much of the geo- graphic area where P. gyrina may also be found. Baker (1928) says of P. gyrina that “it appears to be characteristic of slow- moving and stagnant bodies of water, in shallow water, usually ona mud bottom.” DeWitt (1955) describes the species as being “a typical inhabitant of temporary and permanent ponds.” Listings for this species in the University of Michigan collection include a large number of entries from creeks, rivers, lakes and ponds. H. B. Baker (1922) gives some useful ecological notes on the speciesas it occurs in Dickinson County, Michigan, noting that it occurred abundantly in several stagnant, muck-bottomed ponds, along the marshy shore of a lake, and also in a stream with a rocky and gravel bottom and with a fairly swift current. Goodrich & van der Schalie (1939) also report on P.gyrina collected from several creeks, brooks, rivers, ponds and a lake, noting that many of the habi- tats were mucky and stagnant and were sometimes filled with aquatic vegetation. The picture that emerges is that this is primarily a pond species, but one which 115 can also live in streams and lakes having a variety of other ecological conditions. P. integra is found, according to Good- rich & van der Schalie (1944) “more often...in streams than in quiet waters.” The same authors (1939) re- port this species from a number of creeks, rivers and brooks, atleast some of these habitats having a stony or a gravel substratum. The University of Michigan collection has listings for P. integra from a large number of rivers, creeks and lakes. Baker (1928) reports it from lakes (including Green Bay, Lake Michigan), on substrata of mud, clay, sand, gravel or boulders, in water ranging from 5 cm to 3m deep. H. В. Baker (1922) found the species on water lilies (Nymphaea advens) in a lake; he also records a “variety” of P. integra as being abundant along the shore of a river, in shallow water with a swift current and a substratum of sandy clay. The impression that emerges here is that this species lives in streams and lakes on a variety of substrata, but that, unlike P. gyrina, it is absent from ponds. Both P. gyrina and P. integra‘ occur in abundance in the lakes area of north- west Iowa (Fig. 1). P. gyrina, at least, is common also in other parts of the state. The 2 species overlap in their distribution in lake habitats; my obser- vations confirm P. gyrina as a charac- teristic pond inhabitant and P. integra as being absent from ponds. A full dis- cussion of the local distribution of the 2 species will be presented under “Habi- tats” (p 130 £f.): 4The latter species is listed in a recent paper by Bovbjerg & Ulmer (1960) as Physa зауй. Examination of numerous specimens, includ- ing the anatomy of the male genitalia, and of much of the relevant literature, has convinced me that this designation (and that of a similar form from Douglas Lake, Michigan, as P. sayii crassa) is in error. P. sayii appears to belong in a subgenus separate from these forms. (See p 119-121). 116 BAT: CLAMPITT LAKES AREA FIG. 1. Lakes area of northwestern Iowa (approximate location indicated on map, upper left)where much of this study was carried out. Several locations from which Physa were studied are: (a) Little Miller’s Bay, West Okoboji Lake, Iowa Lakeside Laboratory; (b) western shore, Center Lake; (c) Big Stoney Point, Spirit Lake; (d) Garlock Slough; (e) Lower Gar Lake. Morphology Because of the confusion surrounding the taxonomy within the genus Physa, some discussion of the morphology of the 2 species is in order. External Characteristics (Figs. 2, 3) Adults of the 2 species differ in size, shape and color of shell and animal body. P. gyrina is the larger species. I have found a few specimens with shells up to 25 mm long, while a P. integra shell 14 mm long can be considered an unusually large one. Fig. 2 shows fairly large shells of adult P. gyrina (14-15 mm long) and P. integra (10-11 mm). In P. integra the ratio of width to length of the shell is greater (see bio- metric analysis below). The body whorl and whorls of the spire are more con- vex and the “shoulder” between the spire and body whorl is also a characteristic difference from the rather smooth tran- sition between these shell parts in P. gyrina. The shell of P. integra is typically paler in color than is that of P. gyrina. The outer lip of the aperture is often thickened and whitish in the former species, and there may be additional white stripes (“rest marks” or varicose bands) running longitudinally elsewhere on the shell. The shell of P. gyrina not only is darker, but the thickenings of the lip of the aperture and elsewhere on the shell are, if present, dark brown. The body of P. integra (Fig. 3), like the shell, is typically light-colored. The foot is often yellowish, and the body light-colored from above, though it often has a dark band over the dorsal part of the mantle which can be seen through the shell. In contrast, P. gyrina is typically quite heavily pigmented, both ventrally on the foot and through the shell dorsally. As these characters are highly variable for both species, they are not in themselves very reliable. The most reliable criteria for dis- tinguishing the 2 species by external morphology relate to width-length ratios, convexity of body whorls and whorls of spire (related to the more deeply im- pressed sutures between whorls in P. integra), and the degree of shouldering between body whorl and spire. Biometric Analysis Although average and maximum sizes were consistently greater for P. gyrina than for P. integra, sizes were too vari- able in both species to yield meaningful statistical comparisons. Data on width- length ratios, however, do provide mean- ingful comparisons.° Table 1 sum- marizes some of these data for the 2 species, along with information on habi- tats, number of snails in the samples, and size range of shells. Snails selected 5Tests of significance referred to in this paper were performed using the t distribution. ECOLOGY OF PHYSA 117 PHYSA INTEGRA FIG. 2. Shells of the 2 species of Physa. Note the differences in size, shell shape, and con- vexity of the body whorl and whorls of the spire. Note also the whitish outer lip of the aperture of P. integra (2nd figure from lower left), and the dark outer lip of P. gyrina (upper extreme right figure). P. INTEGRA P. GYRINA FIG. 3. Live specimens of the 2 species of Physa. Note the darker color, both dorsally and ventrally, of P. gyrina. Approximate shell lengths of snails: upper 1., 10 mm; lower 1., 8 mm; upper r., 12 mm; lower r., 16 mm. 118 PT. CLAMPIPTT TABLE 1. Biometrics Species of Habitats* Sample Shell length Width-length Physa size in mm ratios of shells P. integra 2 Lakes: (Center L. & Spirit L.- 106 re 0.65 + 0. 03** A rocky shore area) W. Okoboji L. (Little Miller’s Bay - 50 ru 0.63 + 0.02 à E X= 6.0 in offshore vegetation) P. gyrina 2 Ponds: 9.6 24. (Clear Creek € 154 = = = : 0.55 + 0.02 Garlock Slough) f Spirit Lake 7.1 > 17.8 = 5 250. (rocky shore area) = x = 2936 0: 595 0508 W. Okoboji Г.. (Little Miller’s Bay - 50 el 0.59 + 0.02 : Х = 11.0 periphery) *See Fig. 1 for locations of these habitats. **In the above table and elsewhere in this paper, the number following the + sign in- dicates the standard deviation of the sample. for measurement were representative samples of adult populations (shell length over 5 mm in P. integra and over 7 mm in P.gyrina) in the selected habitats. Measurements were made to the nearest 0.1 mm, using a vernier caliper. Data are given on 5 samples of snails, 2 of P. integra and 3 of P. gyrina; width- length ratios vary somewhat within as well as between species. Analysis of the data shows a significant difference be- tween species, and likewise between pond and lake populations of the same species in the case of P. gyrina.® The probability of any of these differences occurring by chance alone is in each case well under 0.001. P. integra samples taken from Center Lake and Spirit Lake (Table 1) were analyzed separately and yielded nearly 6Comparable differences in these ratios in laboratory reared P. gyrina whose parents were collected, respectively, from a pond and from a lake, suggest that the difference in width-length ratio has, within this species, a genetic basis. identical width-length ratios. The same is true of samples of P. gyrina from 2 ponds (Table 1), even though these ponds are nearly 300 miles (480 km) from each other (Clear Creek Pond near Iowa City, Garlock Slough adjacent to Lake Okoboji in northwest Iowa). Also, the width- length ratios of P. gyrina from one of these, Clear Creek Pond, were found to be identical in the following instances: (1) a May 1962 sample of 51 snails averaging 11 mm in length and ranging from 9.6 to 13 mm, and (2) a June 1962 sample of 65 snails averaging 17.5 mm and ranging from 15 to 24 mm in length. These data appear to conflict with DeWitt’s (1954a) observation that, during growth in later life in this species, there is “a change from longitudinal to lateral expansion” of the shell. Two conclusions can be drawn from these data: (1) There are clear-cut differences between the 2 species in width-length ratios, differences that are not only apparent subjectively but can also be revealed statistically. (2) Intra- specific differences in these ratios are also present, especially in P. gyrina. ECOLOGY OF PHYSA 119 Les Pen isices heath. --zretractor - muscles? Vas defienens=—— == MM ----praeputial gland-- = male aperture--__ — FIG. 4. Male genitalia of Physa gyrina and P. integra (anterior portion only), shell lengths 15 mm and 11 mm respectively. Note, in P. gyrina, the much longer penis sheath, composed of 2 distinct portions separated by a constriction, and the characteristic granular appearance of the basal portion. In P. integra, note the constriction and the characteristic kink near the base of the penis sheath. Gross Anatomy of the Male Reproductive System (Fig. 4) Differences in the male genitalia of the 2 species provided a useful criterion for checking identifications made in- itially on the basis of external charac- teristics. These structures can be ex- posed quite easily by making an incision on the left side of the animal behind and above the head. Dissections of the male genitalia of both species were made, from time to time, on more than 100 Snails of all sizes and from various habitats. Although there were variations, especially those associated with dif- ferences in size and reproductive ma- turity, all specimens (except very small ones) could be placed with confidence in either of 2 categories on the basis of differences in length and form of the penis sheath, as illustrated in Fig. 4. In P. gyrina the penis sheath is elongated and has a prominent constriction between lower pigmented and upper portions; that of P. integra lacks the constriction, is Shorter, lacks pigmentation, and typi- cally has a sharp kink at its base. In none of the specimens did there appear to be intermediates between these 2 forms, and the features of external mor- phology and those of the male reproduc- tive system consistently showed the ex- pected correlation. Subgeneric Systematics The male genitalia provide a helpful criterion for species identification in Physa, but their use for this purpose has 120 Р. Т. CLAMPITT definite limitations. A number of species resemble P.gyrina. in having an e- longated penis sheath with a prominent median constriction, while others are similar to P. integra in having a much shorter penis sheath without the con- striction (Fig. 4; & Baker, 1928, Fig. 190). These differences in the length and form of the penis sheath may, how- ever, provide a valid basis for grouping the majority of American species - certainly most of those in the Great Lakes region - into 2 subgenera. P. gyrina and P. integra would be repre- sentative of these subgenera. The idea of subdividing the American Physa into subgenera is not new. Haldeman (1842) proposed names and defined the following subgeneric sections: Physella, “with branchiae, shell globose,” with type P. globosa; Physodon, “columella toothed,” with the type P. microstoma; Diastropha, “shell umbilicated, no fold.” Baker (1926), while dismissing the characters given by Haldeman as trivial, thought it ap- propriate to retain the names Physella and Physodon, which he emended. Baker proposed that the name Physella should replace the name Physa in North America on the grounds that the North American forms differed anatomically from the European. Further, he proposed that the names Physella and Physodon be used also as subgeneric names, under the genus Physella. Hedescribed these sub- genera (see below), and placed all of the Wisconsin species under one or the other of them. Baker's (1926) use of the names Physella and Physodon was declared invalid by Clench (1930),’ who added that there seemed to be no justification ana- tomically, as yet, to split the genus Physa - as represented by most of the European and American forms - “into groups worthy of generic or subgeneric headings.” While granting the validity of the objections to Baker's use of the names Physella and Physodon, 1 believe that what the names designate are real entities. I base this opinion upon: (1) examinations, particularly of the male systems, of snails from some 50 dif- ferent populations, mostly from Michigan and lowa but including other scattered localities in the United States and Canada as well; (2) a study of Baker's (1928) illustrations and descriptions of this organ system. Shell characters as described below are highly variable and may be unreliable; the male genitalia, however, exhibit features which are conservative and, I believe, diagnostic for distinguishing major subgenera. In Baker’s subgenus “Physella,” the male system closely resembles that of P. gyrina (Fig. 4) in having a long penis sheath - often nearly twice the length of the praeputium - with a definite con- striction midway along its length. Baker (1928) describes the group as follows: “Shell large, usually rather thin, the columella twisted and with a plait or ridge; genitalia with the penis sheath having a constriction in the middle dividing it into two parts.” Based on the shells I have examined, I would add that there tends to be a rather smooth transition between body whorl and spire of the shell (Fig. 2, upper figures) and that the apex is often somewhat blunt. Baker (1928) gives descriptions, and in most instances figures, conforming to 7Clench (1930) states that an examination of Haldeman's original specimens of P. globosa - the type of Physella Haldeman, which Baker also selected - show them to be “materially different from any other known American Physa”; thus “the name Physella ... must be retained only for the single species Physa (Physella) globosa, and not be used in the generic sense for many of the North American forms. ... Haldeman's name Physodon (1842, p 39)and its emendation by Baker is untenable for subgeneric use as the main character for which the name was established, on the presence of columellar teeth, is not a con- stant character at all and at best can only be considered of specific value” (Clench, 1930). ECOLOGY OF PHYSA 121 the male genitalia as described above, for the following forms: P. ancillaria Say, P. vinosa Gould, P. зауй Tappan, Р. warreniana Lea, P. chetekensis Baker, P. bayfieldensis Baker, P. ob- vussoides Baker, P. gyrina Say and P. elliptica Lea. I have similar evidence for some of the above plus the following: P. parkeri “Currier” DeCamp,® P. mag- nalacustris (Walker) and P. remingtoni Clench. Whether all of these forms represent valid species may be doubted (Wurtz, 1949). However, the available evidence, particularly that based on the male genitalia, suggests that the forms listed are part of a natural grouping. In the subgenus “Physodon,” as defined by Baker, the male system closely re- sembles that of P. integra (Fig. 4) in that the penis sheath is short - never much longer thanthe praeputium - andis not subdivided into 2 parts by a central constriction. Baker (1928) gives the following description: “Shell small, usually rather thick and solid, the colu- mella smooth without distinct twisted plait; genitalia without constriction in center of penis sheath, which gradually enlarges.” Again from my own observa- tions, I would add that the shell usually has a shouldered appearance, witha very evident angle between body whorl and whorls of the spire, and that the apex of the spire is usually fairly sharp (Fig. 2, lower figures). Baker (1928) gives descriptions and figures conforming to the male system, as described above, for P. integra Haldeman and P. walkeri SExamination of P. parkeri specimens from Douglas Lake, Michigan, suggests a possible error in Baker’s figure (1928, Fig. 186, p 422) of the male genitalia of this species; the penis sheath is actually - in these specimens - of the same basic type as in P. gyrina, rather than like that of P. integra as Baker’s figure indicates. Crandall. I have additional evidence of the same type for P. michiganensis Clench and P. anatina Lea. All of the above forms are evidently representa- tive of a natural grouping which differs in shell characters, and particularly in the male genitalia, from the “Physella” group. In summary, Baker’s (1928) concept of grouping the American species of Physa into 2 major subgenera appears to be basically sound. Further explora- tion of this concept, focussing initially on characters of the male genitalia, should aid us in gaining a better understanding of the systematics of this difficult group. Life History Considerable life history information is available on P. gyrina (DeWitt 1954a, b, c, 1955) and onother species of Physa, notably the European Physa fontinalis (Frömming, 1956; DeWit, 1955; Duncan, 1959; Hunter, 1961а, b). Reproduction, early development and fecundity have also been studied intensively in P.gyrina (DeWitt, 1954a, b, c) and the anatomy and physiology of the reproductive system in P. fontinalis (Duncan, 1958, 1959). No such work is available for P. integra. The aim of this section is twofold: (1) to report, for comparative purposes, the results of life history studies on both field and laboratory populations of P. gyrina and P. integra; and, while doing so, (2) to fill this particular gap in our knowledge concerning P. integra. Scope and Techniques of Investigation Comparative data were collected on times of breeding, length of reproductive periods, size composition of natural populations, growth rates, life spans and fertility (egg production) in the 2 species. For securing field data, snails of both species were collected at monthly inter- 122 PAT CGLAMPITE vals from selected habitats by methods which are described in detail below (p 130). A special effort was made to get representative samples, including all sizes of snails and in representative pro- portions. Also, notes were made on the presence and abundance of egg masses at the sites of these collections each month. To supplement the field data, snails of each species were cultured in small (5 liter) aquaria at room temperatures (averaging 20° -23% С). Green lettuce and dried maple leaves were the usual food source. The aquaria were aerated continuously, and uniform and continuous illumination from overhead fluorescent lights was maintained. All snails were measured with a vernier caliper, those in the laboratory being measured alive and then returned to the aquaria in which they were being cultured. Field Populations Little Miller's Bay P. gyrina and P. integra: Life history studies were made on populations of both species in Little Miller’s Bay, West Okoboji Lake, Dick- inson County, Iowa (Fig. 5). The P. gyrina were from the extreme edge of the bay (station 1), where there was a sand substratum and much allochthonous ma- terial; there was some emergent vegeta- tion, notably Scirpus. The P. integra were from station 5, 60 m from shore, water depth 1.8 m; the snails were on the dense growth of Ceratophyllum demersum and other submerged vascular plants above a substratum of mud (see р 135 for a brief description of the Little Miller’s Bay area). The P. gyrina population (Fig. 6) grew little during the winter, but showed rapid growth from April through June,9 and produced many eggs in May and a new generation in June. There was consider- able mortality among the larger snails, For growth rates of various populations see p 126-130 € Fig. 10. 100 m e sta. 1] / MILLER'S 5 IOWA LAKESIDE LABORATORY a Li MILLER'S BAY sta. — b E | LITTLE MILLER'S BAY CROSS SECTION FIG. 5. a, The Little Miller’s Bay study area in West Okoboji Lake (see Fig. 1 for geo- graphic location). b, In the cross sectional diagram, vertical exaggeration is 2.5 x. P. gyrina was dominant at station 1, along the east shore of the bay. Only P. integra was found at station 5, 60 m from shore, and in all the more central portions of the bay. Miller’s Bay area map after that of D. M. Kelly (un- published). 12 mm or more in length, in July and August. In the P. integra population (Fig: 7) there was slight growth from March to April, but considerable growth from April to June. Egg production occurred in a great burst in May, and young snails (1-2 mm) were present in great numbers in June. There was much mortality of the larger snails, 4-8 mm long, by June, and all of this older generation were dead by July 15. No more eggs were found at that time. Even with warmer water temperatures and continued growth of vegetation, the P. integra did not grow or reproduce as much during the summer as in the spring. However, there was 123 ECOLOGY OF PHYSA ‘ulej100unN SI зэЗаецо uorepndod jo enjeu J08xe uoymM зротлэЯ yuosoider soul] ueyorg ‘(АМ и! yeod) чоцопрола 339 jo poriod aawums pue S3urads oy} pue ‘soanyeaodwus 19JEM 9J0N “IBIÁ ou} Moy3Nn01Y] seSsueyo 9Z1S ATyyuow SUIMOUS ‘971$ [TOYS JO (D эЗиел pue (x) uvow se рэзиэзэла “e Ul se eyep эшеб ‘q :Siequnu эзптозе ul S}[Npe eu; pepesoxe 18] Sunok эчт, '%001 Se yoo “(aut] Тезио7тлоч Aq рэртлтр) Afoyeredos рэзиэзэлаэл эле uoryendod ayy jo syueuoduoo 3pmpe pue 3unoA4 ‘sunp ul ‘ordures xod sjreus jo saoquinu [8707 juosordoi yde13 yoeo jo JUSIA LOMO] OY} 04 (8 pue Z ‘SSL. ит pue элэц) adA] a9e] prod ul SI9QUINN *Z961 1940790 YÍNOA1YI 1961 1940790 WO.AF p9j09]]09 sordures элцезиэзэхаэх WoL]T "WU ISOTBOU OF yysueT [foys ur “S[IBUS pezIs заэлхэтир jo (%) зчотдлодола элиеэч ‘в “Avg S.AMIIN 91911 ‘(с ‘SLI 998) Т UOTIeIS мод] 212448 DSCYF JO 971$ ПЭЧ$ UI SOSUEUO [Jeuoseas *9 “Ol A 2961 1961 "ЗУМ à “NYE ‘230 y “190 113HS H19N31 oS 9 or : Е - SIINIVITWIL YILVM . q 2961 1961 #390120 12 4393831935 yl 15 ПЭПУ sl AINF 61 INNF yl AVW 81 114dv 02 4390120 82 91 8 4 © 113HS H19N31 07 Ov 0z or 07 % Ao) 124 P. T. CLAMPITT some egg production again in August and September, and many very young snails were found in September. Little or no growth occurred between October and February. The small maximum size (4-8 mm) and early mortality of the “adult” snails of this population may be atypical for P. integra. Such atypical features can perhaps be explained onthe basis of peculiarities in the ecology of Little Miller’s Bay, e.g., relative isola- tion of the bay and seasonal succession toward a vegetation-choked pond-like environment which becomes inhospitable for P. integra - particularly for the larger snails - by midsummer. What- ever the peculiarities of this life history pattern, it appears to have survival value for the population as a whole, in that the bay supports and maintains a large population of the species. The life histories of these speciesare Similar here in that both show a peak of growth and reproductive activity in the spring and early summer, suffer con- siderable mortality, particularly among the larger specimens, during the summer, and grow very little during the winter months. They differ in that P. gyrina have much faster growth rates (during the periods when they are ac- tively growing) and attain much larger absolute sizes than do P. integra. An- other difference was the 100% mortality of the older generation of P. integra by the end of June; such mortality did not occur in P. gyrina until July and August. Clear Creek Pond P. gyrina: For comparative purposes, life history data are presented on a pond population of P. gyrina. This pond, about 5 miles (8 km) west of lowa City in Johnson County, lowa, is small (about 50 m long and 30 m wide in the widest part), has a substratum of silt and clay, is bordered on 2 sides by a fairly open woodland, and by a cultivated field and a gravel road on the other 2 sides, and its basin is formed by part of an old ox-bow of Clear Creek; at times of flooding the overflow from the stream enters the pond. Environmental conditions, relating to depth and area covered by the water, temperature, turbidity, amount and character of the vegetation, animal life and other factors are extremely variable, much more so than in lake habitats. In depth, for example, the range was from a maximum of more than 1 m after a 20-cm (8-inch) rainin July 1962, to no water in September and October 1962. More typically, the depth ranged from about 30 to 60 cm, andthe pond contained some water continuously from at least October 1961 to early September 1962. The small size of the pond, its constantly fluctuating conditions, and particularly the fact that the P. gyrina population was a thriving one during most of the period of study, make it desirable to compare the life history here with that in Lake Okoboji. The Clear Creek Pond P. gyrina (Fig. 8) grew slightly during the winter (1961- 62). A tremendous burst of egg produc- tion in early April was followed in turn by a very rapid growth in the previous year’s population. By early May, many tiny young snails of the new spring generation had appeared, and these and the previous year’s crop continued to grow rapidly until June. Egg production ceased sometime before the end of May. During June and July there was con- siderable mortality, and the largest snails were eliminated from the popu- lation. The rate of growth of the spring generation diminished greatly during July and August. A general decline in numbers of snails between June and August indicated high mortality among all size classes. In June, several hundred snails could be collected readily in a few minutes; in August, anhour’s search yielded about 150 snails. A brief period of egg production in August was followed by a gradual drying of the pond. Drying followed by freezing had, by early No- vember, killed most of the snails. Some survived through the winter, for in early April (1963), when water from previously melted snow and ice had refilled the pond, a few live if weather-beaten P. gyrina (along with small numbers of egg masses) 125 ECOLOGY OF PHYSA ‘ulej190uUN SI so3ueygo uorjepndod jo e1n3eu JOoeXe usym Sporiod диэ5элхаэл soul] UeyoIg ‘(Ae ul yeod) a9oquia3das-3sn3ny pue sunf-AeM Ul uorjonpoad 339 jo зротлэЧ pue ‘soanye1adwus} лэдем DION “ABIÁ ou} JNoySno1y} sesueyo 9715 ATyyuow SUIMOUS ‘9ZIS [[OUS JO (4) эЗиел pue (x) uvow se poquoseid ‘в ит Se eJep эшез ‘4 "saaquımu amposqe UI S}[Npe ay} рэрэээхэ 18] Sunok 9YL '%00T Se Човэ ‘(our [ejuoz110y Aq рэртлтр) Afoyeredos рэзиэзэл4эл эле uorjemdod oy} jo squauoduioo }npe pue 3unoA ‘эипр Ul *£961 Алеплаэя ч8полЧ3 Z96T YOLBIA Wor, рэзээПоэ: sOTdues элуезиэзэлаэл mol} ‘итал 4S9IB9U 0} YI3U9] [[9YS Ul “S[IBUS P9ZIS зиэлэдир jo (%) suorzıodoad oaryepoy ‘в ‘Ава SOIT TT ‘(G ‘SLI 995) < UOIJE]S WOT DAS2JUL DSÁYF JO 9715 ЦЭЧ5 ur SeBsuvyo Teuoseag *L “DIA 296] 2961 * 834 “NYE ‘534 “AON ‘190 “das -onv ANT INNF АУМ "dv “Y VW nn ЕЕ ег E у 4 m 9 Z (9) 4 8 ax Я 09 ofl 002 E B92 Biz 002 09 al ww “do - SIUNLVIIAWIL YILVM q AYVNugI4 91 2761 YI9W3D30 | YIGOLDO 12 yaawaldas pl isnonv yl n CAE à m (= y [-= = m 97 Q 8 — Е oy 0z op 0z oy 02 09 oy 0z oy 0% Soe Stud ANT ZI annr El АУМ ZI 1194V 15 Hoyvw zi 6961 N 113HS H19N31 E E O 09 07 02 09 op oz or 02 oy 07 09 op 07 % 126 P. Т. CLAMPITT were collected there. The life history pattern of the pond P. gyrina is similar to that of the Little Miller's Bay P. gyrina in most respects, such as the slight growth during the winter, the great upsurge of growth and reproduction in the spring, andthe heavy mortality during the summer. The patterns differ in that the eggs appeared in the pond a month earlier than in the lake (due perhaps in part to the fact that the ice melted from the pond nearly 3 weeks earlier than from the lake), the spring growth rates were more rapid in the pond, and egg production stopped completely in the pond for a long period during the summer. Also, the maximum size reached by the pond P. gyrina (shells up to 25 mm long in May and June) was greater than in the lake (17 mm in June and July). DeWitt's (1955) study of P. gyrina in a pond (Scio) in Michigan shows a life history pattern basically similar to that described here for the same species. Differences in details, suchasthe timing of reproduction, growth rates and mor- tality patterns, are probably a reflection of differences both in regional climatic factors and in conditions peculiar to the local habitats. Laboratory Populations Fig. 9 shows comparative growth rates in the 2 species during a 3 month period after hatching, from January to April 1963. Parent stock for both these popu- lations was collected from Big Stoney Point on Spirit Lake (see Fig. 1) in late November 1962. The basis for these studies was 130 eggs of P. gyrina and 126 of P. integra. Approximately 32 young snails were grown in each of 8 aquaria during the first 2 months of the study, after which the numbers were reduced to 16 snails per aquarium, a total of 64 snails of each species, repre- sentative of all sizes in the population, being selected for further study. Growth rates of the 2 species (Fig. 9) averaged about the same (up to about 3.2 mm shell length) during the first 30 days. After 2 months P. gyrina were slightly longer on the average (5.4 compared with 5.0) mm) and were considerably so in maximum length (7.8 compared with 6.1 mm); this divergence had widened markedly after 3 months (mean shell lengths: 7.6 mm against 5.9 mm). Growth rates during the first 9 weeks after hatching averaged .69 mm per week in P.gyvina and .54 mm per week in P. integra. By comparison, DeWitt's (1954a) data for P.gyrina reared in isolation reveal a faster average growth rate of 1.60 mm per week for the first 7 weeks after hatching; the rate there- after slowing greatly to .1 mm or less per week. In our populations the vari- ability in size became progressively greater in P. gyrina than in P. integra. Both species had produced some eggs before they were 2 months old. P. integra, which reaches reproductive ma- turity when about 5 mm long, reached this stage slightly earlier than did P. gyrina, which becomes mature when the shell is about 7 mm long (see also DeWitt, 1955). Separate populations of the 2 species, grown over longer periods of time, were also measured at monthly intervals. Portions of the growth curves of these populations are shown in Fig. 10. (1) During a 6-month period (January to June 1962) a laboratory population of 15 P. gyrina (parents collected from Clear Creek Pond) increased in shell length from an average of 2 mm to 12 mm, or by 10 mm in all, with a mean rate of growth of 1.7 mm per month (.39 mm per week). Divided into 2-month inter- vals, the growth rates averaged as follows: first 2 months, 2.6 mm per month; second 2 months, 1.5 mm per month; third 2 months, 0.8 mm per month. (2) During a 10-month period (November 1961 to September 1962) a laboratory population of 13 P. integra (collected as small snails from Big Stoney Point, Spirit Lake) increased in average shell length from 4.3 to 10.5 mm, a total growth of 6.2 mm, and a nearly constant mean rate of 0.62 mm per month (.15 mm per week). These 127 ECOLOGY OF PHYSA “итезлерий $1 sogueyo uoryepndod jo элизеи зовхэ usym sporiod заэзэл4эл saut] ueyorg ‘(пилу ul yeod) 19quiajdos Атлеэ 03 ¿sn3ny oye] pue Av -[lady ul uoljonpoid 339 Jo spotaod pue *sa.myelodulay] 1978M 9J0N «1895 943 Mmoy3no1qy sesueyo 9zıs ATyyuowu ZUIMOUS ‘9715 [[OUS JO (D эЗиел pue (x) ивэш se рэзаэзэла ‘e Ul se eyep oures ‘q ‘SIOQUMU эзпто5зае ul SJNPE oY} рэрэээхэ ле} sunok эчт, "рот Se yoeo ‘(our тезио7ллоч Aq рэртл!р) Атезехедэ$ рэзаэзэлаэл эле uoryepndod ay} jo sqyuouodwuoo ype pue 3unoA ‘49 эмир uo pue Ави Ul ‘Z961 AOqweIdeg y#noiy} 1961 1240790 ол} рэзоэоо So[dues элтуезиезэл4эх сходу ‘wur 389.189 0} qy3u9] [JOYS Ul ‘SIIBUS pazis jueJaj -Jıp Jo (9) suorjaodoxd aargeroy ‘в ‘MOI ‘Ао BMO] ABOU PUOJ Уээло леэто UL DULAÁS VSÉYT JO 971$ ПЭЧ$ ur Sodueya [RBUOSTIS *8 “DIA 7961 1961 H19N31 © \ N \ Xt DS 1 \ 1 an! Ver | \ ' | | RARES | \ | | ae oe | | | | A | | | | \ | ' | | к | ON | \ | | \ \ | | \ \ \ = O mae a < E 3 0z Lc Y 2 zz L 2 vz E E o£Z 60% ol? opl-2t of CUO о? 09! ww Do - SIVUNIVIIIWIL Y3LYM q 2961 1961 "1435 8% ‘Onv pz AF 61| INNF 97 INNF 9 АУМ 6-6 Wudv + JIIWIAON 81 #390120 81 Zn él в | 59 86 Ors fe = = | 77 Sp) u НЧ gs C4: [En] | EJ a [ia] ee у [| [ ] = =z ss 21 == Ss =) [Es] Cl [5 | LI EA 9 Ps] ЕЕ | es u v9 Cl ES ESS) =) 5 a 5 : _ | 822 [re >=] zOz = ur En En = SS =a ol al ea Es a] Sa | = al fea = | E I | “o 2 = Е wen TN = i | u a ES | ES | 81 | | | | [ | | oy oz oz oy oz oz % wo) o a o a o a o a o + o a 128 P. T. CLAMPITT — E P. INTEGRA 0 P. GYRINA > Saul IN MM SHELL LENGTH 30 60 74 88 DAYS AFTER EGGS LAID FIG. 9. Laboratory growth rates of Physa gyrina and P. integra during the first 3 months after hatching, showing mean shell length and range for each species. Parents of both popula- tions were collected from Spirit Lake (Big Stoney Point). ECOLOGY OF PHYSA 129 14 13 Р. GYRINA me (April-May) | field mx. e — me — lab =— == — - = X 2 2 10 b a LAKE (edge) C E 4 (July) X wu x 7 Y > 7 LAB ш 8 / 7 + : 4 =. * z u / 7 > X P. INTEGRA / A Give | lee ee LAKE 0 Peat cates (May-June) => a = »” LAB <———30 DAYS— > FIG. 10. Growth rates of 5 populations of Physa, beginning at 4 mm mean shell length and continuing for a 2-month period. a, Clear Creek Pond P. gyrina, April-May 1962 (see Fig. 8). b, Little Miller’s Bay P. gyrina, July 1962 (see Fig. 6, station 1). c, Laboratory reared popu- lations of 15 P. gyrina; parent stock from Clear Creek Pond. Laboratory temperatures, 20-230 C. d, Little Miller’s Bay P. integra, May-June 1962 (see Fig. 7, station 5). e, Laboratory reared population of 13 P. integra, collected as young snails from Spirit Lake (Big Stoney Point). Laboratory temperatures, 20-230 C. 130 PRE. CLAMPITTI data indicate a much slower but also much more constant growth rate for P. integra than for P. gyrina in these populations. Comparative Growth Rates in Field and Laboratory Fig. 10 shows growth rates, for a 2- month period, of 5 populations (eachdis- cussed previously) of snails representing both species. These data, iftruly repre- sentative, indicate that P. gyrina is a much more rapidly growing species than is P.integra. Particularly striking is the growth of the pond P. gyrina from a mean shell length of 4 mm to nearly 11 mm, a net gain of about 7 mm (1.6 mm per week), during a 30-day period in April. In comparison, the Little Miller’s Bay P. integra, with a net growth of hardly over 1.5 mm (4-5.5 mm, at .35 mm per week) during a 30-day peak period in May, appears to be a slowly growing snail, indeed. Laboratory popu- lations of both species were, in these examples, considerably less rapid in their growth rates than were their field counterparts: laboratory-reared P. gy- yina had a net gain in shell length of slightly over 3 mm in a 30-day period (.7 mm per week), while laboratory- reared P. integra grew very slowly, al- though at a steady rate, with a net gain of 0.7 mm per month (.16 mm per week). Egg Production Fig. 11 shows the monthly egg produc- tion in laboratory populations of 15 P. gyrina (parents from Clear Creek Pond) and 13 P. integra (collected as small snails, Big Stoney Point, Spirit Lake). Both populations were grown under the laboratory conditions described pre- viously (p 122). All egg masses were re- moved at weekly intervals, and the eggs counted throughout the reproductive life of the populations. The data (Fig. 11) show high egg pro- duction in both species, lasting for 6 months (24 weeks) between March and August 1962 in P. gyrina, and for 9 months (36 weeks) between December 1961 and August 1962 in P. integra. Peak production was reached in the P. £yrina population during the 2nd month, and in P. integra during the 3rd month. Half of the eggs had been laid by the P. gyrina population in slightly over 2 months, while in P. integra this halfway point was reached about the middle of the 4th month. Both species produced an average of 200-300 eggs per snail per month through much of the reproduc- tive life of the population. The very high productivity of the last surviving P. gyrina individual during the last month is noteworthy; it suggests that a few highly fecund snails could also have been responsible for most of the egg production earlier. These results on egg production differ from those of DeWitt (1954b, c) chiefly in the greater total number of eggs laid per snail and in the higher proportion of the total life span during which repro- duction occurred. For example, DeWitt (1954c) found that 6 P. gyrina reared together produced an average of 272 eggs per snail during a reproductive period occupying 38% (131 days) of a total life span of 346 days. In the present study, total egg production per snail averaged over 700 in P. gyrina and more than 1000 in P. integra. The total reproduc- tive period of the P. gyrina population was 163 days, or 63% of the maximum life span of 260 days; that of P. integra was 243 days, again over 60% of the (estimated) maximum life span. A few days of unusually hot weather late in August 1962 may have hastened the death - and thereby shortened the post- reproductive period - of the remaining snails of both species. HABITATS The purpose of this section is to dis- cuss in some detail the habitats and microhabitats where each species was located; and, for selected spots, the numbers in which they were found. Qualitative and quantitative samples, and a study of seasonal changes in local dis- tribution, are included. Qualitative Samples in the Field Techniques Qualitative samples of snails were 131 ECOLOGY OF PHYSA "yyuowu 4301 94) Jo pus ou} ye рлбэлиз ‘A 3Se] ayy “uorzonpoad 333 jo yuou yy, eu} Suranp рэтр 2248 *d ISP] ЭЧЛ, *D4S97U1 A Ul yyuow Y) ou} Sulinp pue 21448 *q ul ZurAe]-339 JO YJUOUI рис oY} 1978 P9.LINDD0 $143 FEU} 9J0N ‘рэлетчов useq sey uorjendod ayy jo uorjonpoad 339 [8107 eu} JO Fey чэЧл oul, ayevrxoadde squosaudal (x) YSIIEISY "OFIT элцопролаэл элцие y3no1Y1 ‘24812 A pue puirás vskyd Ynpe jo suoryerndod Axoyexoqe] ur ‘зротхэа (Азр gz) ATYJUOM Zurinp uorgonpoad 884 ‘IT “DIA SHLNOW -12Q SHINOW “1DW 01 6 8 7 ©) S y € С | L 9 б y. E С | STE BÉBÉ EEE = = |A Eu Eu Eu Eu = 005 = 00S 0001 = 0001 Z Z с € ES = LE wm m 0051 = oos! à Е 1ous/s66e ‘ou * Блу le) о al = Qu m [al s66e ‘ou ¡Djo] 0007 о 0002 O © о Ca] м 0087 0082 * 000€ 000€ ViOILNI “d VNIYAO 00S€ 00SE lu a apa" 1 Е : : 5 BLU O alte) Во A BOO PTE №520 MED a SEG UDS a elle Gin Kal SG eZ 11245 uoew S|/DUS эл! г CRE Pig 20) are e, SE ne elle Gi ee 132 P. T. CLAMPITT usually collected by hand from stones, sticks, leaves, green or decaying vegeta- tion or other materials. Inpondhabitats a dip net was also used. In water too deep for wading, a grappling hook or an Ekman dredge was used from a boat, the choice of instrument depending on the substratum characteristics and on the quantity and kind of vegetation present. The same instruments were operated through a hole in the ice during winter. Materials collected by means of these tools were later sorted for snails on shore or in the laboratory. A series of graded screens was used for washing the bottom materials collected with the Ekman dredge. Notes on such factors as depth, distance from shore, substratum, types and density of vegeta- tion, temperature, hardness of the water, and wave action or currents were re- corded, and the snails were usually killed and fixed in formalin (a 10% solution) for future reference. Selected snail samples were relaxed in a nembutal solution, according to a method suggested by van der Schalie (1953), and were then killed and fixed for later anatomical studies. Types of Habitats Samples were taken from a variety of lakes, temporary and permanent ponds, ditches and streams. Most of these habitats were in the region immediately around Lake Okoboji in Dickinson County, Iowa (Fig. 1). In this area there are a large number of lakes and ponds of various sizes and types, but streamsare rather few in number andtype. Alimited amount of sampling was also done from ponds and streams in the area immedi- ately around Iowa City, Johnson Couty, Iowa. Lake habitats sampled were mostly along the shore, and ranged from steep, wave-beaten boulder shores, on one ex- treme, to quiet, stagnant, mud-bottomed, gently sloping pond-like borders of small bays on the other. Intermediate in character were moderately sloping, wave-washed cobble shores, and others with a gravel or sand substratum, some- times grading into mud. Offshore habi- tats included a relatively shallow, mud- bottomed, vegetation-choked bay, areas ranging from gravel to mud with only sparse or no vegetation, and profundal bottom ooze. Pond habitats also varied, though less so than those of lakes. In sizethe ponds ranged from small shallow puddles to large sloughs several hundred acres in extent. Some were transitory wet places, others semi-permanent aquatic habitats. Some were crowded with emergent vege- tation such as Typha or Carex, others had dense growths of submerged Utricu- laria or Ceratophyllum, and in others vascular plants were sparse or lacking. Most were inrather open prairie country, but some were in wooded areas. Some were roadside ditches, others oxbows along streams, still others undrained depressions in otherwise fairly level farm land. Substrata varied, but were usually of silt or clay. The few streams that were sampled were all rather turbid, currents varied from fairly swift to sluggish, and sub- strata were of cobbles, gravel, sand or silt, or of some combination of these materials. Characteristic Species Of the various habitats surveyed inthis study, P. integra was a characteristic species in 2 general types: rocky shores and vegetated offshore areas of lakes. In the shore habitat, the substratum was typically of cobble-sized stones, the slope was usually moderate, there was typically a good growth of algae on the stones, and wave action ranged from slight to heavy. Inthe vegetated offshore areas, the snails were found on the vegetation: mainly Ceratophyllum de- mersum, Myriophyllum exalbescens, Ranunculus longirostis, various Po- tamogeton species, and perhaps other submerged aquatics; the vegetation ranged from dense to fairly sparse; the depth ranged from less than 50 cm to more than 3 m; and the substratum was of sand or mud. Habitats of the Two ECOLOGY OF PHYSA 133 Certain contrasts between these 2 P. integra habitats should be noted. In the shore habitat the snails were on the stones, while in the deeper vegetated habitat they were very largely on the vegetation. Along the shore they had easy access to the surface for air breathing, while in deeper water that access was, at best, more difficult; my failure to find snails on the surface film in these offshore areas suggested that in these habitats they do not come to the surface. A contrast was seen in the P. integra populations themselves: the individuals of the shore-dwelling populations reached a considerably larger size than did those of the offshore populations. All of these differences deserve care- ful attention, particularly as they relate to food, oxygen requirements and be- havior in the species. The types of habitats in which P. integra were not found should also be well noted. Included in this negative category were the zones of lakes too deep to support rooted vegetation, and particularly all types of ponds (see dis- cussion under “Conclusions”). In sharp contrast, P.gyrina is a characteristic and obviously successful pond species. It was found on a variety of materials such as boards, sticks, de- caying weed stems, leaves, filamentous algae, on the substratum itself, and on the surface film. Summer populations of P. gyrina were restricted largely to the edges of these ponds, often in water less than 10 cm deep. On warm, sunny days, water temperatures in these very shallow areas reached high levels, often over 30° and sometimes 35° C. P. gyrina occupied something of a continuum of types of habitat from stag- nant ponds to the wave-washed rocky shores of lakes which latter were also characteristic for P. integra. Inthe lake Shore habitat and in the pond, the snails were within easy reach of the surface for aerial breathing. In most other respects, notably wave action, type of substratum, the relative scarcity of living and particularly of decaying vas- cular plant material, andmore moderate and stable temperature conditions, the lake shore differs greatly from the pond. The P.gyrina of the 2 habitats were themselves different; as has already been noted (p 118), the lake shore P. gyrina had a consistently greater width-length ratio than did the 2 pond populations of the same species; these differences were statistically significant. While P. integra populations can often be found in offshore vegetated areas of lakes in water 3 m or more deep, those of P. gyrina (at least in summer popu- lations) appear to be completely absent from depths greater than 1 m, and are largely restricted to depths of only a few centimeters. In summary, P. gyrina, although a characteristic pond species, may also be found on rocky shores of lakes in company with P. integra, as well as in habitats of an intermediate type. In depth distribution, however, P. integra is considerably less restricted than is P. gyrina. Quantitative Samples Quantitative samples were made in certain selected habitats in order to determine relative densities, and hence perhaps when and where the optimum conditions for survival and reproduction have been reached. Techniques In shallow water (wading depth), quantitative samples were taken using a sheet metal cylinder enclosing an area of 1/4 m2. This “sampling cylinder” was used in lake shore and in pond habitats. The cylinder was placed upon, or if possible pushed into, the substratum; then all materials which it enclosed (stones, weed stems, etc.) were care- fully removed and sorted for the snails which they contained. The snails were later counted and preserved for future study. Where densities of snails were low, a larger area of 1 m2 was sampled. No very satisfactory technique was de- veloped for securing data on densities 134 р. T. CELAMPITT TABLE 2. Depth distribution of Physa integra in Center Lake (West Shore) Depth 0-15 cm Distance from shore 0-.5m Cobbles Substratum (algae-covered) Number of snails / 8 1/4 m2 = Cobbles & gravel 50 cm 100 cm 2m 5m Gravel, some mud 210 46 TABLE 3. Depth Distribution of Physa in Spirit Lake (Big Stoney Point) Depth Distance from shore Substratum Number / 1/4 m2 P. gyrina P. integra in the vegetated offshore zone, although a rough volumetric measure of the quantity of vegetation in a sample was of some value in this connection. Density Related to Depth and Distance from Shore Densities of both physid species were highly variable both spatially and tem- porally. Several factors may be involved in these variations. Most consistent and predictable among these is the fact that densities of both species decrease with depth. Two examples will serve to illustrate this relationship. (1) On the rocky west shore of Center Lake (Fig. 1) in June of 1961, a very dense population of P. integra (but no P. gyrina) could be found. Table 2 summarizes data on density related to depth, distance from shore and sub- stratum characteristics. The rapid de- crease in numbers with increasing depth can readily be seen. Substratum changes may also have been a factor in this density -distribution pattern. (2) At Big Stoney Point on the east shore of Spirit Lake (Fig. 1), both P. gyrina and P. integra could be found, in 0-10 cm 10-35 cm 0-.5 m 2m (Boulders & cobbles throughout) 185 17 50 8 the summer of 1961, in large numbers. This shore again is rocky, with con- siderable exposure to wave action. Table 3 summarizes data collected in July 1961, along one side of Big Stoney Point. Again there was a decided de- crease in density with increased depth and distance from shore, and in this case substratum changes could not have been a factor as there were none. These 2 examples serve to illustrate what appeared to be a general pattern of distribution among all summer popula- tions of P. gyrina and many of P. integra. Comparable results were obtained in other quantitative samples of oneor both species from a variety of lake and pond habitats. These confirm the general impression that populations of both species are concentrated in shallow water close to shore. This distribution pattern is probably related to the sur- facing behavior and respiratory habits of these pulmonate snails, at least as these phenomena apply to the larger adults of the 2 species. Other Factors Associated with Density Substratum, available food and pro- ECOLOGY OF PHYSA 135 tection for the young snails are all factors which may be of importance in explaining the densities of one or both snail species in their various habitats. To these may be tentatively added the factor of light. All are to some degree interrelated, though none could be iso- lated for separate investigation in the field. Dense populations of P. integra are usually associated with the absence of, or an opportunity to avoid, a substratum of sand or silt. In rocky shore areas, such a substratum is absent, and in offshore areas the snails avoid these substrata by clinging to the vegetation. In the rocky shore areas, a dense “Aufwuchs” on the stones also appears to be essential, which inturn is dependent on considerable exposure to sunlight. Young snails must avoid or escape the impact of wave shock, which they can do in rocky shore habitats where there are rock pools or interstices among the stones which afford such protection. Substratum appears not to be critical for P. gyrina. Dense populations of this Species are usually associated with plentiful quantities of food, which may vary greatly with the type of habitat. In a pond, dead and partially decaying plant material, or perhaps fungi or algae associated with them, seem to be es- pecialiy favored (DeWitt, 1955). Ponds heavily shaded with Typha or other large emergent plants, however, contain few P. gyrina. In the rocky lake shore habi- tat, P. gyrina appears to have the same needs, for food and protection for the young, as does P. integra. Seasonal Changes in Local Distribution, Little Miller’s Bay, West Okoboji Lake The desirability of a year-round study on the locations of populations of the 2 physid species in relation to shore is suggested by the work of Cheatum (1934). Cheatum studied seasonal migrations of Snails in Douglas Lake, Michigan, in- cluding 2 species of Physa. He found that as the water temperature declines in the fall, these snails migrate from the littoral zone to deeper water, where they overwinter. As the temperature rises in late spring and early summer, the snails move shoreward from the deeper water. By these seasonal migrations, the snails avoid being trapped in the ice cover in winter, and can easily reach the surface for aerial breathing in the summer; thus this behavior appears to have definite adaptive value. The question therefore arose: do P. gyrina and P. integra, in the Lake Okoboji area, have a similar seasonal migratory behavior? Little Miller’s Bay on West Okoboji Lake (Fig. 5) was chosen as the site for this year-round study. This small bay is mostly surrounded by land and therefore protected from heavy wave action. It is shallow, not more than 2 m deep, has a mud bottom, muddy or in some places sandy shores, and a dense growth of submerged vegetation (Cerato- phyllum dominant; also Myriophyllum, aquatic Ranunculus, and several Po- tamogeton species). It is bordered with trees interspersed with meadow, and this terrestrial vegetation contributes al- lochthonous material to the bay. An interesting pattern of distribution of the 2 Physa species occurred there during 1961 and 1962. P. gyrina popu- lations were concentrated (in summer) around the periphery of the bay where the conditions were essentially pond- like, with emergent vegetation of a variety of kinds, and often much dead and decaying plant material; water was usually quiet, and daytime summer temperatures often reached 30°C or higher. By contrast, P. integra popu- lations were found year-round in the offshore submerged vegetation, where temperatures rarely rose above 25° C. Methods Several stations along a transect, ex- tending from the shore of the sand spit to a point 60 m _ westward into Little Miller’s Bay (see Fig. 5), were sampled for snails at regular monthly intervals, from March 1962 to February 1963. Procedures already described for quali- 136 P. T. CLAMPITT TABLE 4. Little Miller’s Bay transect area* Station Depth Distance from РЕ Su tati No. ae EAN ubstratum mmer vegetation Dead weed stems, leaves 1 0-10 0-0.5 Sand ; a e sticks, debris. 9 50 6 Sand Some green vegetation; debris. Muddy Moderate growth of sub- 3 100 12 Eh merged vegetation; outer edge of emergent zone. 4 150 95 Mud Moderate growth of sub- merged vegetation. 5 180 60 Mud Dense growth of submerged vegetation. *See Fig. 5. tative sampling (p 130) were also fol- lowed here. Findings Table 4 shows the locations of the 5 stations in terms of depth and distance from shore; information on substratum and summer vegetation conditions is also included. Station 5 (see also Fig. 5), 60 m from shore, is essentially similar to much of the central part of the bay, in substratum and vegetation charac- teristics as well as in the character of its snail population. Р. gyrina, whenever found (April through November), was concentrated in the extreme littoral area of the bay (station 1). Water temperatures during this period fluctuated between a low of 6° and a high of 31° C (as measured at times of sampling). No snails of this species were found at any station during the winter period ofice cover (December to April) when the surface was frozen solid to a depth of 50 cm or more. The findings of Cheatum (1934) and DeWitt (1955) suggest, however, that those snails which survived had migrated to depths of 1 m or more. A dense population of P. integra was found throughout the year inthe vegetated offshore zones, where temperatures ranged from 1° C under the ice to a 26° C maximum in the summer. During the winter of 1961-62, green submerged vegetation was scarce to absent within a range of 25 m or more from shore in the transect area, and few P. integra were found there. They were abundant, however, at station 5, 60 m from shore in water 1.8 m deep, on the Cerato- phyllum which was green even under 25 cm of snow and 60 cm of ice; a dis- solved oxygen content of 5 ppm was also present (March 1962). Asthe submerged vegetation near the margin of the bay grew and became progressively denser during the late spring and early summer of 1962, P. integra became more abun- dant also toward the shore, being well represented at station 2 (50 cm deep, 6 m from shore) by June. Although they came close, very few of the snails of this species actually reached the ex- treme littoral, pond-like shore area where P. gyrina were most abundant. During the winter of 1962-63, incontrast to the previous winter, Ceratophyllum remained healthy and abundant at station 3 (1 m deep, 12 m from shore), and P. integra were abundant at this station in a February collection. In summary, it seems likely that there ECOLOGY OF PHYSA 137 are seasonal changes in the distribution pattern of P. gyrina in the Okoboji area; and there was a spread of the P. integra population toward the shore as spring and summer growth of the submerged vegetation progressed, but it did not cul- minate in the arrival of the species in the shore area, or in its disappearance from the vegetated offshore area. For data on seasonal changes in shell size and periods of reproduction in the Little Miller’s Bay populations of P. gyrina and P. integra, see Figs. 6 and. SPECIFIC ANALYSES OF ENVIRONMENTAL FACTORS The purpose of this section is to at- tempt to explain, in terms of food, be- havior and physiological tolerances, why the 2 species are found indifferent kinds of habitats. Food Techniques Two quite different approaches were made to the problem of determining the types of food used by the 2 species. One was an attempt to measure food preferences. Starved snails of each Species were put into an environment containing a choice of materials which might conceivably be used as food, and behavior of the snails was observed. The second approach was an attempt to determine the different kinds and rela- tive amounts of various materials actually consumed by the snails; stomach analyses were performed on a series of Snails which had been killed and fixed shortly after being collected in the field. The second and more fruitful method will be discussed first. Stomach Analyses Analyses were made on the stomachs (i.e., crop plus gizzard) of 23 snails of each species, all from rocky shore habitats in either Spirit Lake or Center Lake. Stomachs of both P. integra and P. gyrina were found to contain a wide variety of materials, many of them recognizable. These included: diatoms, shreds of filamentous algae, other green and blue-green algae; rotifers; small crustaceans such as ostracods and cladocerans; parts of amphipods, Diptera (tendipedid) larvae, and other arthro- pods; chaetae of freshwater oligochaetes; small amounts of vascular plant tissues; and sand grains. An unidentified gelati- nous material (possibly mucus secreted outside the body and later consumed) completely filled the stomachs of several P. gyrina, and formed a substantial part of the stomach contents of other snails of both species. As for relative pro- portions of different foods, the largest part consisted (in these habitats) of detritus, algae of all kinds, and the gelatinous material mentioned above; animal and vascular plant tissues formed only a minor portion. A rather striking difference in the algal flora of the 2 lake habitats was indicated in these analyses: stomachs of Spirit Lake snails of both species tended to contain a pre- ponderance of diatoms; those from Center Lake yielded very few diatoms, but had a very large proportion of colonial bluegreen algae such as Microcystis. The results of these analyses indicate that both species consume a great variety of types of materials, determined chiefly by what is available and can be scraped loose and ingested in any particular habitat where the snails are found. The 2 species apparently do not have ap- preciably different food habits, although the possibility of a difference has not been completely ruled out. Food Preference Experiments When starved snails of either species were introduced into a trough containing stones alternately with and without an algal coating, the majority always ac- cumulated eventually on the stones covered with algae. Table 5 shows the cumulative results of a series of 20 ex- perimental trials in each of which 10 P. gyrina or P. integra - i.e., cumulative total of 100 animals of each species - were released in the center of a small trough. For each replicate of 10 snails, 138 P. T. CLAMPITT the trough contained lake water and 3 barren and 3 algae-covered stones, spaced alternately through the length of the trough. Positions of all snails rela- tive to the stones were recorded at regular time intervals; the data given (Table 5) are the cumulative total number (= %) of snails found on algae-covered stones, barren stones, and elsewhere in the trough, as recorded at intervals during a total time of 60 minutes. The results are essentially the same for the 2 species. The very gradual accumula- tion of the snails on the stones covered with algae suggests random movements which cease when the animals chance to meet favorable environmental conditions (in this instance, food). These findings are similar to those of Bovbjerg (1957, 1965) on the freshwater mussel Lamp- silis siliquoidea and the snail Stagnicola reflexa. That feeding was indeed taking place was indicated by radular motions; later examination of fecal material pro- vided further confirmation. When dead Carex stems from a pond were introduced into a container with starved snails, both species accumulated upon them, much as they hadupon stones with an algal coating. Extensive laboratory observations indicated that when snails of both species were given a “choice” between stones coated with algae and dead weed stems, the choice was neither clear-cut nor consistent for either species. When Ceratophyllum demersum or Myriophyllum exalbescens, vascular plants characteristic of the offshore vegetated habitats of P. integra, were introduced as the “food” material, both species behaved indifferently toward these materials, even though they had been deprived of food previously for a week or longer. A similar indifference to the filamentous alga Cladophora was apparent for both species. Laboratory populations of both P. gyrina and P. integra have been reared successfully using a mixture of dried maple leaves and green lettuce as the primary food sources. Both species accumulate upon and readily consume these materials. In none of these experiments and ob- servations have I been able to establish that there is a difference between the 2 species, even though some materials are quite characteristic of the habitat of one species and not of the other. On the basis of present evidence, therefore, it must be concluded that differences in the local distribution of the 2 species are based upon factors other than food preference and food consumption. Dispersal Behavior and Factors Influencing Dispersal Rates of Dispersal Observations in the field and labora- tory gave the impression that P. gyrina was a considerably more active snail than P. integra. Thinking this feature might have some significance in the dis- tribution pattern of the 2 species, I designed laboratory and field experi- ments in an attempt to compare dis- persal rates of the 2 species. Laboratory experiment: (1) Technique: The experimental chamber was an aluminum trough 68 cm long, 7 cm wide and 4 cm deep. Its length was marked with an 8 cm “release” area in the center, and at 5 cmintervals from this central area toward each end. The trough was filled with lake water to a depth of 2 1/2 cm for each experi- ment. Overhead fluorescent lights pro- vided uniform lighting, and water temperatures ranged from 20° to 23° C. At the beginning of each of 20 replicate experiments, 10 P. gyrina or P. integra were released in the central starting area. Positions of all snails were re- corded, to the nearest 5 cm, after 2, 5, 10, 15 and 20 minutes, and from these positions the mean distribution of each species was calculated for each time interval, to give a comparative measure of dispersal rate. Because some P. gyrina had reached the end of the trough after 5 minutes, useful data are limited to the first 5 minutes, and these alone will be presented below. (2) Results (Fig. 12): Although there ECOLOGY OF PHYSA 139 P. GYRINA IN DISTANCE FROM RELEASE MEAN on 2 MINUTES FIG. 12. Mean dispersal rates of Physa gy- vina and P. integra, in a linear chamber in the laboratory. Data recorded in cmfrom release after 2 and 5 minutes. Based on 20 replicate experiments, using 10 snails in each. After 2 minutes, P< .01. After 5 minutes, P< .05 (for standard deviations, see text). was considerable variability in the dis- persal rates of both species, the average rate of dispersal of P. gyrina was twice that of P. integra. After 2 minutes, P. gyrina had moved 4.2+2.2 cm (standard deviation, SD), while P. integra had moved only 1.7 + 1.1 cm. After 5 min- utes, P. gyrina had moved 10.9+5.5 cm, and P. integra 5.5+3.9 cm. Under these laboratory conditions, P. gyrina dis- perses at a significantly faster rate than does P. integra (P<.01 after 2 minutes, P<.05 after 5 minutes). Field experiment: Snails (130) of each species were marked on the upper surface of the shell with fingernail polish of a conspicuous hue - red for P.gyrina, pink for P. integra. They were then released on a substratum of cobbles near the west shore of Center Lake (July 1962). At intervals the area in the vicinity of re- lease was searched for the marked snails, and their positions, as distances from release, were recorded. The first search took place 2 hours after the time of release; the last took place 3 weeks later. The results of this experiment are summarized briefly in Table 6. They indicate that P. gyrina dispersed much more rapidly, and widely, inthis experi- ment than did P. integra. However, as there was considerable local variability in the environment as to substratum, depth and other conditions, factors in addition to differential rates of move- ment in the 2 species may have been operating to produce these results. Dispersal of both species, under natural conditions, may be passive as well as active. The laboratory experi- ments, and probably the one in the field, involved only active dispersal. Passive dispersal, through wind and wave action in lakes and currents in streams, may play an important role in dispersing snails to new habitats. Other animals (for example, aquatic birds which may carry young snails on their feet) may also play such a role. The exact nature and extent of these roles are not known. Movements in Response to Temperature Changes P. gyrina is often found in ponds and pond-like margins of lakes, where day- time temperatures rise to 30°C or higher during the summer. P. integraisnearly always absent from these habitats. It was therefore thought that behavior in response to temperature (and also toler- ance to high temperature, for whichdata are given on p 144 and in Fig. 14) would help to explain this distribution. Technique: A temperature gradient chamber was set up. It consisted of a horizontally placed glass tube, 4 cm in diameter and 120 cm long, filled half full of water and corked at both ends, and containing 3 thermometers,- one at each end and one in the middle In testing the response of the snails to 140 PB. TUCOLAMPITT TABLE 5. Location of snails in trough containing algae-covered and barren stones* No. (=%) P. gyrina No. (=%) P. integra Minutes after On algae- On On algae- On release Elsewhere Elsewhere covered barren 3 covered barren р in trough in trough stones stones stones stones *See p 137-138 for further details. TABLE 6. Field dispersal experiment, Center Lake, July 1962 Bass Mean Greatest y Species of No. snails distance distance after Physa located* from release from release release m m P. gyrina 40 1207 6.5 : P. integra 44 1.3 3.5 E P. gyrina 34 3.9 18.5 P. integra 25 2.2 6.5 Р. gyrina 18 4.3 12.5 14** e P. integra 15 177 4.5 *130 snails of each species were released at the beginning of the experi- ment. **After 21 days, 8 P. gyrina and 6 P. integra were located, too few to yield meaningful data on mean and maximum distances from release. cold, one end of the gradient was cooled with “Dry Ice” (solid CO.) and the other end warmed above a beaker of hot water. Separate experiments were used to test the response to heat, by heating one end of the gradient strongly above boiling water and cooling the other slightly with ordinary ice. In the first set of experi- ments the cooled end of the gradient averaged 11° C; in the second set the heated end was maintained at 38°-40°C. Fifteen marked snails of each species were introduced into the gradient chamber for each replicated experiment. The positions, to the nearest 10 cm, of all snails of both species, were recorded at least 4 times at 15 minute intervals while the gradient was maintained. The ECOLOGY OF PHYSA 141 4 (or more) readings were averaged to reflect the distribution during the experi- ment as a whole. Seven such experi- ments, involving 105 snails and over 400 position recordings of each species, were done using the cold stimulus, and7 more using the heat stimulus. A series of 10 control experiments were also done; in these, the above procedures were fol- lowed, except that the temperature was kept uniform throughout the chamber. Results: The outcome of the tempera- ture preference experiments is illus- trated in Fig. 13. Both species moved away from the cold end of the gradient (middle figure). They both showed some tendency, though not consistently, to move toward but not into the heated end (at 38° - 40% С). Neither species showed great sensitivity to these differences in temperature; they moved around quite freely through a wide range of tempera- tures. There was no Significant differ- ence between the species in any of this be- havior; on the contrary, they responded in much the same manner (see figure legend for probabilities). Temperature preferences, therefore, cannot be con- sidered a factor controlling the different distributions of the 2 species in nature. During the winter, when ice formed overnight in aquaria kept on a window sill in the laboratory, nearly all snails of both species clustered on the bottom and sides away from the site of ice for- mation. These snails againbecame more randomly distributed after the ice had melted. This adaptive response on the part of both species is suggestive of what probably occurs in nature. Movements by Adult Snails in Response to Wave Shock When wave shock was extremely heavy in the field, as it was frequently at Big Stoney Point on Spirit Lake, few if any Snails could be seen on the upper ex- posed surfaces of stones, but both species could be found readily on the lower or otherwise protected surfaces of boulders and cobbles. When wave action was light or moderate, however, numerous Snails of either species were seenonthe exposed surfaces of the stones. Respiratory Behavior In the laboratory, P. gyrina and P. integva came regularly to the surface for aerial breathing. This also appeared to be true of pond P. gyrina and of shore- dwelling lake populations of both species during the warmer seasons. It seemed doubtful, however, that this surfacing behavior occurred in P. integra in the deeper water (1-3m or more) farther from shore. Hunter (1953), studying offshore populations of Physa fontinalis in Loch Lomond, Scotland, found that in these snails the mantle cavity is invari- ably filled with water. Iapplied Hunter’s method of direct microscopic examina- tion in the field (from a boat), immedi- ately after collection and before the snails had opportunity to come to the surface, in investigating the mantle cavity contents of a summer (August 1964) population of P. integra. This Snail population was located in offshore vegetation (mainly Potamogeton spp) at a depth of 2.5-3 m in Spirit Lake, near Big Stoney Point. Samples of vegetation bearing the snails were pulled up gently from the substratum with a grappling hook, but kept continuously submerged in water in a large plastic container while the snails, a few at a time, were transferred under water to a dish, then immediately examined (before they crawled to the water surface) under a stereoscopic microscope. An air bubble in the mantle cavity, if present, could be detected easily by this method through the thin shell of any of these snails. Some 50 P. integra 4-9 mm long - and many more of smaller size - were col- lected and examined in this manner, and all had the mantle cavity filled with water. Egg masses and many young snails were present in the habitat at the same time. This evidence strongly indi- cates that the P. integra of these off- shore habitats can complete their entire life cycle without coming to the surface and with the mantle cavity remaining filled with water. Respiratory needs would appear to be satisfied by direct 142 PETICLAMPITT DECIMETERS CONTROL COLD TO WARM MEDIUM TO HOT Mean PE GYRINA X 10 CM P. INTEGRA () FIG. 13. Temperature preference of Physa gyrina (x) and P. integra (0). The symbols x and o represent the mean distribution within the temperature gradient chamber of a population of 15 snails ofeach species, in 3 series of experiments. a, Control experiments. Temperatures were kept uniform throughout the “gradient” chamber. Note that the mean distribution of both species | lies, as expected, very near the mid-point in the chamber (for both species, P > .80). b, Re- — sponse to cold temperatures. One end (left) of the gradient was chilled (to 11.00 С average), and HOURS TO 50% MORTALITY (AT 40° C) ECOLOGY OF PHYSA P. gyrina = . integra 16 14 12 10 8 6 4 ; E EXPERIMENT NUMBER ON MT o JA № FIG. 14. Relative tolerance of Physa gyrina (white) and Р. a, Number of hours to 50% mortality in each species, at 40° C, from a series of temperatures: 143 P. gyrina : P. integra EXPERIMENT NUMBER Р < .005 ny o со o DAYS TO 50% MORTALITY (AT 35% C) > nN > III M > D > MMIII integra (shaded) to lethally high 6 experiments, each involving an average of 25 snails of each species, collected from several localities. The difference between species is significant (Р < .01). b, Number of days to 50% mortality, at 35° C, from 6 experiments, each with 20 snails of each species, all collected from Lower Gar Lake. diffusion of gases through the integument. Evidence of comparable behavior in P. gyrina is lacking, and the absence of these snails from deeper water may be tentatively explained (at least in part) on this basis. Tolerances Heat Technique: Experiments were de- Signed to measure tolerance to high, ultimately lethal temperatures. Snails Again, the difference between species is significant (P < .005). of both species were first acclimatized for one week or more to laboratory room temperatures averaging 23-25° C. In one set of 6 experiments, the snails were then placed in an aquarium which was rapidly heated (in about 4 hours) from room temperature to 40°C. The experiment was checked and dead snails (those showing no sign, macroscopically, of muscular activity) were removed at 2-hour intervals, until at least 50% of both species of snails were dead. Each 1 the opposite end (right) warmed (to 27. 4° С average). mean distribution of both species to the right of the mid-point. Difference between species: One end (right) of the gradient was heated (to 38. 8° P < .001. c, Response to heat. ment is significant; doubtful significance. C average) and the opposite end (left) cooled slightly (to 21.49 C average). Note the consistent displacement of the In both species, this displace- .20> P >.10, considered of Note some (not con- sistent) displacement of mean distribution of both species to the right (toward the heated end) of the mid-point. For both species, . 20 > P >.10; considered of doubtful significance. 144 P. T. CLAMPITT of the 6 experiments involved 20 - 30 snails of each species, some 300 snails being tested in all. In a second set of 6 experiments, the aquarium was heated only to 35° C and snail mortality was checked at 8-hour intervals. All of the snails of both species were in this case collected from the same habitat (the rocky west shore of Lower Gar Lake; see Fig. 1). Twenty snails of each species were tested in each experiment, 240 snails in all. Results (Fig. 14): In both sets of experiments, P. gyrina consistently tolerated the hightemperature conditions for a longer period than did P. integra. At 40° C (Fig. 14 a), the range for the former species, until 50% mortality oc- curred, was 7 - 16 hours; for the latter species, only 5-10 hours. Considering the results of each experiment as aunit, the difference between species is sig- nificant (P<.01). At 35°C (Fig. 14 b), both species survived many times longer than at 40° C; 50%mortality was reached in 11 - 13 days (264-312 hours) in P. gyrina and in 5.7 - 8.7 days (136-208 hours) in P. integra. Again, the dif- ference between species is significant (P <.005). Differential tolerance to high temperatures may therefore be a factor helping to explain the presence of P. gyrina in ponds and the absence of P. integva from such habitats. Drying P. gyrina has been reported from temporary as well as from permanent ponds (De Witt, 1955), habitats confirmed in this writer’s experience, while P. integra is apparently absent from both. Because of the possible significance of desiccation in determining the distribu- tion in temporary ponds, experiments were designed to measure the influence of this factor. Technique: The experimental chamber was a large (30x60 cm) aquarium in- verted over slightly moistened cheese- cloth, supported in turn by a heavy screen placed on bricks whose bases stood in water to help maintain slightly humid 80 P. GYRINA % SURVIVAL un o 40 30 INTEGRA Pr PO FIG. 15. Relativetolerance of Physa gyrina and P. integra to desiccation. Percent of sur- vival after 3, 6 and 12 days, from a series of 4 experiments, each using 40 snails of each species. The difference between species is significant (P > .01). conditions in the chamber. At the start of each experiment, 40 adult snails of each species (alive and apparently healthy) were placed at random on the cheesecloth. At 3-day intervals, the aquarium was removed and the snails were all removed to dishes of water. Those still alive nearly always showed signs of activity within a few minutes; these were returned to the experimental chamber. The experiment was continued until at least 50% of both species were dead, Four experiments were performed involving 160 snails of each species, all of which were collected from the rocky west shore of Lower Gar Lake (Fig. 1). Results (Fig. 15): P. gyrina showed considerably greater tolerance to drying than did P. integra. After 3 days, the percentage of survival in P. gyrina was 83 + 11% (SD) while that in P. integra was 44 + 17%; after 6 days: P. gyrina ECOLOGY OF PHYSA 145 73+10% and P. integra 28+12%; and after 12 days: P.gyrina 51 + 14% and P. integra 14+14%. In P. integra, 50% mor- tality was reached in 3 days, but in P. gyrina not until 12 days. These dif- ferences between species are considered significant (P<.01). Limited tolerance to drying is probably, therefore, an im- portant factor helping to explain the absence of P. integra from temporary ponds. Data from a comparable set of experi- ments involving P. integra collected at Big Stoney Point on Spirit Lake and P. gyrina from 2 ponds in the area were more highly variable, but tended to con- firm the above conclusions. They also Suggest that considerable intraspecific variation occurs among populations of both species; in these 50% mortality oc- curred after an average of 10 days in P. integra and 23 days in P. gyrina. Field data: Clear Creek Pond, near Iowa City (also discussed above, p 124), previously well-populated with P. gyrina, gradually dried out during a period of drought during late summer and early fall of. 1962. In late September, at a time when the pond had held no free water for perhaps 2 weeks, an intensive search was made for live P. gyrina. A small number (totalling 19 during a search of at least 1 hour) were finally found. These were nearly all on the flat bottom mud near the center of the pond, the mud having gradually dried and cracked at intervals. These snails were fairly small (5-11 mm long), and all were oriented with the apertures facing down into the mud. The edges of the shell of each snail were buried very slightly below the surface, andthe dorsal side of the shell protruded above the mud. The snail body had in each case retracted well into the shell, and there was usually an epiphragm, i.e., a small layer of dried mucus slightly behind the aperture. When placed in water, these Snails, within a very few minutes, e- merged and became active. A rainy period in early October temporarily im- proved moisture conditions in the pond. More dry weather was in turn succeeded by frost, and by the end of October nearly all of the snails had apparently been killed. An hour’s search on October 29, 1962, yielded 1 live P. gyrina. Mortality at this time was, I believe, the direct result of freezing rather than of drying. That some of the snails survived through the winter has already been mentioned, p 124. A small roadside pond about 3 miles (5 km) southwest of the Iowa Lakeside Laboratory on West Okoboji Lake was the focus of other observations on desiccation and survival in P. gyrina. During a dry period in the summer of 1964, the water gradually receded inthis mud-bottomed pond (a good habitat for P. gyrina) so that by late July practically no standing water remained. OnJuly 29, what was thought to be an intensive search for P. gyrina in the pond - onthe partly dried mud, amongst the stems and leaves of Typha, Carex and other pond plants, and in the little remaining stand- ing water - revealed no live specimens of this species. Then on the night of July 30, a 10-cm rainfall drenched the area. On again visiting the pond, now filled with water, I found rather to my surprise that live P. gyrina of adult size were quite numerous; 75 specimens were collected in less than half an hour. The possibility that these snails burrow in the mud as a temporary pond dries up (affirmed by DeWitt, 1955), tentatively rejected on the basis of the experience at Clear Creek Pond, had to be re- considered. This problem warrants further investigation. CONCLUSIONS Apart from differences in size, there appear to be no morphological dif- ferences between the 2 species which would help to explain their differential distribution. But the size at maturity may be critical. A shell length of 7 mm is about the minimum size at which P. gyrina becomes sexually mature (DeWitt, 1955); 5 mm is the corresponding figure 146 P. T. CLAMPITT for P.integra. The greater absolute size of P. gyrina, and the resulting de- crease in the ratio of surface to volume, coupled with the respiratory needs of the animal, may be important in re- stricting this species, in summer popu- lations, to very shallow water where snails have ready access to the surface for air-breathing. Conversely P. integra is less restricted, and its smaller size may be responsible, for corresponding reasons. In the vegetated offshore areas where this species is plentiful, the mantle cavity is filled with water; respiratory needs would thus appear to be satisfied, through the entire life cycle, by direct diffusion of gases through the integument. This parallels the situation described by Hunter (1953, 1964) for offshore popula- tions of Physa fontinalis in Loch Lomond, Scotland. The available evidence sug- gests that the need for aerial oxygen may be limiting for P. gyrina, but not for P. integra. The slower rate of growth of P. integra, and potentially, the more ex- tended period of reproduction, could mean that this species needs relatively more stable conditions in order to sur- vive and reproduce than does P. gyrina. These include food, temperature, oxygen and permanence of water; a larger body of water, such as a lake, provides such stability to a degree which a pond does not. Because the food of both species is so varied, it is probably not limiting for either species in most habitats where they might otherwise be found. Ap- propriate foods may conceivably be in short supply, however, for P. integra in the vegetated offshore areas; stomach analyses performed on a few P. integra from such a habitat (Little Miller’s Bay) indicate that the food is restricted largely to detritus and algae and that no vascu- lar plant material is consumed. Hunter (1961b) attributed the smaller sizes and poorer reproduction in offshore popula- tions of P. fontinalis in part to poorer feeding conditions inthese areas. Growth rate differences in the 2 species suggest the possibility of a difference in food utilization rate; it is possible that P. gyrina requires a greater quantity of food than does P. integra, but again, a knowledge of the diverse types of food which both species may consume leads to the conclusion that food rarely limits their distribution. The 2 species showed different rates of dispersal, but other behavioral attri- butes that were tested (movements in response to temperature and to wave shock) were not found to be different. Whether the slower rate of dispersal of P. integra serves to limit the distribution of this species is doubtful. However, it seems plausible that withthe more stable conditions of lakes than of ponds, in food supply and in other factors, less of a premium would be placed on mobility. It may be that P. integra finds itself in a suitable microhabitat most often by staying where it is, while P. gyrina in a pond moves about at random and thereby discovers new and suitable microhabitats as they develop and change (see Bovbjerg, 1957). The data on temperature tolerance in- dicate that temperature probably is limiting for P. integra in that it will not survive high environmental tempera- tures. This speciesis probably excluded from ponds, of all types, partly for this reason. The greater tolerance of P. gyrina to lethally high temperatures indi- cates that temperature is less likely to be limiting for this species. Drying also is probably a limiting factor for P. integra, and effectively excludes the species from temporary ponds. Small size may bea disadvantage in this connection, too. P. integra may dry out more rapidly thandoes P. gyrina, eventually to the point of no recovery, partly because of the smaller initial size and therefore greater relative surface area for evaporation. Adults of both species can tolerate fairly heavy wave shock, but the young need protection. Without the success of a new generation, a population ona rocky lake shore cannot long endure. There- ECOLOGY OF PHYSA fore heavy wave shock, in the absence of protection for the young (i.e., without rock pools or interstices among the stones), acts as a limiting factor on populations of both species in rocky, wave-washed, lake shore habitats. Several questions which remain un- answered, or are revealed by this study, include the following: how much genetic plasticity is there in both species, as suggested by morphological differences (width-length ratios) in P. gyrina and size differences in different populations of P. integra? As for O2 requirements, could winter reduction of oxygen tensions in ponds prevent their habitation by P. integra while allowing such habitation by P. gyrina? The tolerance of some P. gyrina to drying followed by freezing in the pond is very striking, and leads to the question: how do they survive? Do those that survive do so primarily because of position or because of their inherent hardiness? What is the migra- tion pattern in winter? This point is no clearer for shore populations of P. in- tegra than for P. gyrina. What in fact prevents the habitation by P. gyrina of the offshore lake habitats where P. ¿n- tegva is common? Is there continuity, and therefore gene flow, between the offshore populations of P. integra and those along the shore, or is there iso- lation, and thus the opportunity for speciation? What are the effects of the intensity and the duration of periods of light on the growth and on the reproduc- tive patterns of the 2 species? What are the effects of predation and para- sitism on their distribution and abun- dance? Finally, is there competition between species in the lake shore habi- tats where the 2 species are found to- gether? These questions await further study. ACKNOWLEDGEMENTS I am deeply grateful to Dr. RichardV. Bovbjerg, of the University of Iowa, for his invaluable advice and encouragement through all stages of this study. I wish 147 also to thank Dr. Henry van der Schalie for making available for my use the mollusk collection and library of the Museum of Zoology at the University of Michigan, and for the loan of specimens. Dr. George M. Davis, formerly of the University of Michigan, andDr. JamesR. Wells, Cranbrook Institute of Science, have kindly read and offered helpful criticisms of the manuscript. LITERATURE CITED BAKER, F. C. 1926. Nomenclatorial notes on Americanfresh water Mollus- ca. Trans. Wisc. Acad. Sci. Arts, Letters, 22: 193-205. BAKER, F. C. 1928. The fresh water Mollusca of Wisconsin, Part 1, Gastro- poda. Wisc. Geol. € Nat. Hist. Surve y Bull., 70(1): 507 p. BAKER, H. B. 1922. The Mollusca of Dickinson County, Michigan. Occ. Papers Mus. Zool. Univ. Mich., No. 111, 44 p. BOVBJERG, R. V. 1957. Feeding re- lated to mussel activity. Proc. Iowa Acad. Sct., 64: 650-653. BOVBJERG, R. V. 1965. Feeding and dispersal in the snail Stagnicola re- flexa (Basommatophora: Lymnaeidae). Malacologia, 2: 199-207. BOVBJERG, R. V. € ULMER, M. J. 1960. An ecological catalog of the Lake Okoboji gastropods. Proc. Iowa Acad. Sci., 67: 569-577. CHEATUM, E. P. 1934. Limnological investigations on respiration, annual migratory cycle, and other related phenomena in fresh-water pulmonate snails. Trans. Amer. microsc. Soc., 53: 348-407. CLENCH, W. J. 1926. Three new species of Physa. Occ. Papers Mus. Zool. Univ. Mich., No. 168, 9 p. CLENCH, W. J. 1930. Notes on Physidae with descriptions of new species. Occ. Papers Boston Soc. Nat. Hist., 5: 301-315. CRANDALL, O.A. 1901. The American Physae. Nautilus, 15: 25-30, 42-45, 54-58, 69-71. 148 P. T. CLAMPITT DeWIT, W. F. 1955. The life cycle and some other biological details of the fresh-water snail Physa fontinalis (L.). Basteria, 19(4): 35-73. DeWITT, R. M. 1954a. Reproduction, embryonic development and growth in the pond snail Physa gyrina Say. Trans. Amer. microsc. Soc. 73(2): 124-137. DeWITT, R. M. 1954b. Reproductive capacity in a pulmonate snail (Physa gyrina Say). Amer. Nat., 88: 159-164. DeWITT, R. M. 1954c. The intrinsic rate of natural increase inapond snail (Physa gyrina Say). Ibid., 88: 353-359. DeWITT, R. M. 1955. The ecology and life history of the pond snail Physa gyrina. Ecology, 36(1): 40-44. DUNCAN, C. J. 1958. The anatomy and physiology of the reproductive system of the fresh-water snail Physa fon- tinalis (L.). Proc. zool. Soc. London 131(1): 55-84. DUNCAN, C. J. 1959. The life cycle and ecology of the fresh-water snail Physa fontinalis (L.). J. anim. Ecol., 28(1): 97-117. FRÖMMING, E. 1956. Biologie der mitteleuropäischen Süsswasser- schnecken. Duncker & Humblot. Berlin. GOODRICH, C. & van der SCHALIE, H. GOODRICH, C. & van der SCHALIE, H. 1944. A revision of the Mollusca of Indiana. Amer. Midl. Nat., 32: 257- 326. HALDEMAN, 5.5. 1842. A monograph of the freshwater univalve Mollusca of the United States. E. G. Dorsey, Philadelphia. HUNTER, W. R. 1953. The condition of the mantle cavity in two pulmonate snails living in Loch Lomond. Proc. Roy. Soc. Edinburgh, 65 B(11): 143- 165. HUNTER, W. R. 1961a. Annual vari- ations in growth and density innatural populations of fresh-water snails in the west of Scotland. Proc. zool. Soc. London 136(2): 219-253. HUNTER, W. R. 1961b. Life cycles of four freshwater snails in limited popu- lations in Loch Lomond, with a dis- cussion of infraspecific variation. Proc. zool. Soc. London, 137 (1): 135-171. HUNTER, W. R. 1964. Physiological aspects of ecology in nonmarine molluscs. In: K. M. Wilbur € C. M. Yonge (eds.), Physiology of Mollusca, 1: 83-126, Academic Press, N. Y. € London. van der SCHALIE, H. 1953. Nembutal as a relaxing agent for mollusks. 1939. Aquatic mollusks of the Upper Amer. Midl. Nat., 50: 511-512. Peninsula of Michigan. Misc. Publ. WURTZ, C. B. 1949. Physa hetero- Univ. Mich. Mus. Zool., No. 43, 45 p. stropha (Say). Nautilus, 63 (1): 20-33. RESUME ECOLOGIE COMPAREE DES GASTROPODES PHYSA GYRINA ET PHYSA INTEGRA (BASOMMATOPHORA: PHYSIDAE) P. T. Clampitt Une étude comparée a été faite sur 2 mollusques pulmonés d’eau douce, Physa gyrina Say et P. integra Haldeman, dans la région du lac Okoboji, Comté de Dickinson, lowa, pour reconnaítre la distribution locale de chaque espéce et ses causes. P. integra a été trouvé comme habitant caractéristique des berges rocheuses du lac et des zones de végétation aquatique jusqu'a des profondeurs de 3 m au moins, mais se trouve totalement absent des mares. Des populations denses de P. gyrina ont été ECOLOGY OF PHYSA 149 trouvées dans les mares, sur les berges rocheuses du lac et dans les habitats de type intermédiaire, mais toujours de faible profondeur d’eau. Dans les populations naturelles des 2 espèces la croissance et l’activité reproductrice est la plus forte au printemps (d’avril a juin); il y a une trés forte mortalité en été et la croissance est faible en hiver. P. gyrina a une croissance notablement plus rapide dans la nature et au laboratoire, mais, élevée en laboratoire, l’espéce P. integra atteint généralement la maturité sexuelle légerement plus tót (souvent moins de 2 mois). Au laboratoire, les 2 espéces produisent.une moyenne de 200-300 oeufs par individu par mois, durant la période de pointe de la reproduction (4 mois chez P. gyrina, 6 mois chez P. integra). Des analyses d’estomac et des expériences poussées au laboratoire sur les préfé- rences alimentaires, font penser que les 2 espèces consomment une large variété de matériaux nutritionnels, dont le choix est surtout dû au fait qu’ils peuvent être désagrégés par ráclage et ingérés. Les taux de.dispersion de P. gyrina sont signifi- cativement plus élevés que ceux de P. integra au laboratoire et dans la nature. Les 2 espèces se comportent de la même manière dans les circonstances suivantes: dans une chambre à gradient thermique, elles se déplacent du pôle froid (11° C) en direction mais non à l’intérieur du pôle chaud (38°-40° C); toutes deux se déplacent librement dans un large champ de températures. Quand l’action des vagues est importante sur les berges, elles se déplacent en profondeur ou à l’abri des pierres. Elles viennent régulièrement en surface pour respirer l’air quand elles sont en eau peu profonde. P. integra cependant, en eau profonde, a la cavité palléale pleine d’eau et peut de- meurer immergée toute sa vie. P. gyrina peut résister à des hautes température (35° et 40° C) et aussi aux effets de sécheresse, pendant une période significativement plus longue que P. integra. En partie pour cette raison, P. integra est exclue des mares. La grande taille et le taux rapide de croissance de P. gyrina a pour résultante un besoin d’oxygene atmosphérique, ce qui limite cette espèce en été aux eaux très peu profondes, tandis que P. integra, plus petite et plus lente de croissance n’est pas aussi limitée. P. integra peut être restreinte aux conditions plus stables des lacs (par rapport aux mares) en partie à cause de sa croissance plus lente, de sa période de reproduction potentiellement plus longue et de son taux de dispersion plus lent en réponse aux changements de con- ditions de milieu. A. L. RESUMEN ECOLOGIA COMPARADA DE PHYSA GYRINA Y PHYSA INTEGRA (BASOMMATOPHORA: PHYSIDAE) P. T. Clampitt Este estudio comparativo, sobre dos caracoles pulmonados Physa gyrina Say y P. integra Haldeman en el area del lago Okoboji, condado de Dickinson, Iowa, fué hecho para investigar la distribución local y sus causas, de cada especie. P. integra resulta ser un habitante caracteristico de las margenes rocosas del lago y de la vegetación sumergida a profundidades 3 metros por lo menos, pero totalemente ausentes en charcos. En cambio, densas poblaciones de P. gyrina se encontraron en charcos, pero también en orillas rocosas o habitats de tipo intermedio, pero siempre en aguas de poca profundidad. En poblaciones silvestres de ambas especies, crecimi- ento y actividad reproductiva fueron mayores en la primavera (de Abril a Junio); hubo mortalidad considerable durante el verano y el crecimiento fué poco notable en in- vierno. P. gyrina fué, consistentemente, la especie de crecimiento más rápido ya en 150 Pre. CEAMPITT el campo o en laboratorio, pero las P. integra desarrolladas en el laboratorio alcan- zaron madurez reproductora un poco antes (con frecuencia a los dos meses). En laboratorio, ambas especies produjeron un término medio de 200-300 huevos por individuo en un mes durante el período culminante de reproducción (4 meses en P. gyrina, y 6 meses en P. integra). Analisis estomacales y observaciones extensivas en el laboratorio sobre las prefer- encias alimenticias, sugieren que ambas especies consumen una amplia variedad de materiales, determinados principalments por lo que puedan escarbar e ingerir al alcance; hábitos alimenticios no mostraron apreciable diferencias. Dispersión de P. gyrina fue significativamente mayor que la rápidez de dispersion en P. integra en el laboratorio como en el campo. Las2 especies tuvieron comportamientos similares bajo las siguientes circunstancias: En una camara de temperatura gradiente se movieron desde el extremo frío (11? C) con tendencia hacia, pero no internandose, en el extremo cálido (38-40 С); ambas se movieron libremente dentro de amplios límites de temperatura. Cuando la acción del oleaje era fuerte en las áreas rocosas se trasladaron a zonas más profundas o bajo la protección de las rocas. Cuando se encuentran en aguas de poca profundidad suben regularmente a la superficie para respirar. Sin embargo, P. integra en aguas hondas, tiene la cavidad paleal llena de agua y puede permanecer sumergida a través de todo el ciclo vital. P. gyrina puede soportar altas temperaturas (35-409 С) y también los efectos de la sequía por un período mucho más largo que P. integra. Por esta razón, particular- mente, P. integra esta excluida de los charcos. El tamaño grande y el crecimiento rápido de P. gyrina con la resultante necesidad de oxígeno atmosférico, puede limitar la especie en verano a aguas muy superficiales, mientras que la más pequeña y de lento crecimiento, P. integra, no esta tan restringida. P. integra puede estar limi- tada sin embargo a las condiciones de lagunas mas estables (en relación a charcos) parcialmente por su menor rapidez de crecimiento, un período de reproducción poten- cialmente más largo, y una rapidez de dispersión menor en respuesta a los cambios ambientales. J. J. Р. ABCTPAKT СРАВНИТЕЛЬНАЯ ЭКОЛОГИЯ МОЛЛЮСКОВ PHYSA GYRINA И РНУЗА INTEGRA (BASOMMATOPHORA, PHYSIDAE) Ф. T. КЛЕМПИТТ В озере Окободжи, Дикинсон, штат Айова, проводилось сравнительное ис- следование двух пресноводных моллюсков из Р. integra Haldeman и Pulmonata -Physa gyrina Say с целью изучить их локальное распространение и причины его обусловливающие. P. integra оказалась характерным обитателем каменис- THX берегов озера и его заросших открытых частей, на глубине до 3M; в прудах полностью отсутствовала. Плотные поселения P. gyrina были найдены в прудах, на каменистых бере- гах озера и в местообитаниях промежуточного характера, но всегда в очень мелких местах. У диких популяций обоих видов рост и репродуктивная активность были наибольшие весной (с апреля по июнь); в течение лета наблюдалось их зна- чительное отмирание, а самый слабый рост был зимой. Р. gyrina-3TO наибо- лее бысторастущий вид, как в полевых, так и в лабораторных условиях. Р. integra, выращенная в лаборатории, обычно достигает половозрелости не- ECOLOGY OF PHYSA 151 много скорее (часто менее, чем через 2 месяца). В лабораторных условиях каждая особь обоих видов продуцирует, в среднем, по 200-300 яиц в месяц в период наиболее интенсивного размножения (4 месяца у Р. gyrina и 6 Me- сяцев у Р. integra). Анализ желудков и обширные лабораторные наблюдения по предпочтению моллюсками той или иной пищи, позволили предположить, что оба вида потребляют самую разнообразную пищу. Ее состав определяется главным образом тем, что может быть легко соскоблено и заглочено. Образ питания у обоих видов сходный. Дисперсность Р. gyrina (как в лаборатории, так и в поле) значительно выше, чем у Р. integra. Оба вида в определенных условиях ведут себя сходным образом. Так, в камере градиентов температуры, они уходят от холодной стороны камеры Gia?) и имеют тенденцию находиться ближе к теплой стороне камеры (38°C- AOC), не входя, однако, в нее. Оба вида свободно двигаются в довольно широких пределах колебаний температуры. При сильном волнении воды у ка- менистых берегов озера, моллюски опускаются по камням ниже или уходят в более защищенные части. На мелководьях они регулярно выходят на поверхность для воздушного дыхания. Однако, у Р. integra, обитающей в более глубоких местах, мантий- ная полость наполнена водой, и они могут оставаться погруженными в Te- чение всего жизненного цикла. P. gyrina может выдерживать высокую темпера- туру (so) и осыхание гораздо дольше, чем P. integra. Частично поэтому Р. gyrina не встречается в прудах. Большие размеры и более быстрый темп роста P. gyrina и, как следствие этого, потребность в атмосферном кисло- роде, возможно, ограничивают распространение этого вида летом, когда он приурочен лишь к очень мелководным районам. Местообитание более мелкой и медленно растущей Р. integra не так сильно ограничено. Она, возможно, ограничена более устойчивыми (по сравнению с прудами) условиями обитания в озерах, частично благодаря ее более медленному росту, потенциально бо- лее длинному периоду размножения и более медленной скорости расселения при изменении условий обитания. Я. Al Y; ny Y JA y Bin ‘i ( à р e 1 6 » р 1 4 an 4 i net Ma т у ine j D dá ¢ { u N N ' 1 WMA < ие, р a Tea { Ls i „Zi ind 1 (4 и > Y mi ($ ná po A pare wry, à, в — УИ, o > VANA MALACOLOGIA, 1970, 10(1): 153-164 STUDIES ON AQUATIC PULMONATE SNAILS IN CENTRAL AFRICA I. FIELD DISTRIBUTION IN RELATION TO WATER CHEMISTRY N. V. Williams University College of Rhodesia ABSTRACT The aim of this study was to determine if there was any relationship be- tween the distribution and relative densities of 5 common aquatic snails and the calcium bicarbonate concentration of the aquatic environment, Four- teen stations were selected within a 50-mile radius of Salisbury, Rhodesia, to cover a wide range of calcium and bicarbonate concentration. These stations were classified as follows: “Soft water” - less than 5 mg/1 Ca and less than 20 mg/1 bicarbonate as CaC0,; “medium water” - 5 to 40 mg/1 Ca and 20 to 200 mg/1 bicarbonate as CaC0:; “hard water” - above 40 mg/1 Ca and above 200 mg/l bicarbonate as CaC0 3. Monthly quantitative snail samples and water analyses were obtained from all stations for at least a 12-month period. Highest snail densities were found in the “medium water” stations; densities in the “soft water” stations were low. Four distributional patterns were found: Gyraulus spp. (mainly G. costu- latus) were found only in soft and medium water; Bulinus (B.) tropicus was restricted to medium water; Biomphalaria pfeifferi was found only in medium and hard water; Bulinus (Physopsis) globosus and Lymnaea natalensis were continuous in their distribution and were found in all water types, although densities were lower in soft water. Much concern has been expressed over the lack of detailed information on the ecology of freshwater snails, par- ticularly those species which act as intermediate hosts of the schistosomes of man (World Health Organization, Tech. Rep., 1957). One of the most important ecological problems is the unexplained irregular distribution of snails in unpolluted aquatic habitats. Many workers have attempted to cor- relate the preference of freshwater snails for particular types of habitats with physical and chemical factors, and to discover the range within which the snails can establish themselves. Ayad (1956), Boycott (1936) and Wat- son (1958) have shown that important factors involved are the amount of avail- able food, penetration of sunlight, cur- rent strength and nature of the sub- stratum. The available data, however, are too scanty for assessment of the individual importance of these factors. Boycott (1936), Andrade (1954), An- drade, Santos & Oliveira (1955), Gohar & El Gindy (1960) and Harry, Crumbie & Martinez de Jesus (1957) have sug- gested that some degree of correlation exists between the distribution of snails in various habitats and the chemistry of the water. In contrast to these views, Alves (1958), De Meillion, Frank & Allanson (1958), Frómming (1938), Mar- rill (1958) and Deschiens (1954, 1957) have all concluded that the distribution lpresent address: Department of Biology, University of Salford, Salford, Lancs, England. (153) 154 N. V. WILLIAMS is independent of the water chemistry. The irregular type of distribution of freshwater snails occurs in the Salis- bury area of Rhodesia, which is typical of high ground in Central Africa. The main species concerned are Biompha- laria pfeifferi (Krauss), the intermediate host of Schistosoma mansoni, Bulinus (Physopsis) globosus (Morelet), the host of Schistosoma haematobium, Lymnaea natalensis (Krauss), the host of Fasciola gigantica, Bulinus (Bulinus) tropicus (Krauss), and Gyraulus spp. Many of the latter were examined by Mr.C.C. Cridland and were all found to be Gyrau- lus costulatus (Krauss); nevertheless, all specimens could not be checked and the possibility remains that other spe- cies were present. In addition species of Ferrissia appeared occasionally in samples, but, as the sampling and han- dling techniques used were not con- sidered suitable for this snail, these records have not been included in this study. METHODS Fourteen field stations were chosen in the Salisbury area covering a wide range of chemical conditions, and month- ly snail and water samples were taken over a period of a year. At some sta- tions collecting began in December, 1961 and at others in January, 1962, or a month or 2 later. At a few stations the water sampling programme was continued for a further year. Biological samples. The samples were taken with a modi- fied drag scoop, Hairston, et al. (1958). This consisted of an elongated aluminum box, with cross section dimensions 30 cm by 30cm, attached to a long handle, open at the proximal end and with the distal end covered with metal gauze of 10 mesh/cm and mesh holes of 0.8 mm across. The lower edge of the scoop was equipped with a cutting hacksaw blade. The scoop was pulled over the substratum, thereby collecting speci- mens clinging to stout aquatic plants, those on and in the top layer of mud, and those floating on the surface in shallow water. It was most effective in fairly loose vegetation, but could not be used in rocky or stony areas. Samples were taken by pulling the scoop a dis- tance of 2 metres through vegetation; this was done twice on each monthly visit. Biological samples were preserved in the field with 4% formalin and later subdivided into 2 parts in the laboratory using a sieve with 8 mesh/cm. The large snails retained by the sieve were removed and sorted by eye and the rest of this portion, the “macrosample”, was scanned for further snails under a dis- secting microscope. The portion passing through the sieve, the “micro-sample”, was retained in a fine net; as it was usually very bulky, it was sub-sampled by the method of Allanson & Kerrich (1961), and juvenile snails were iden- tified and counted under a dissecting microscope. Finally, the results were combined and the composition of the snail fauna was calculated. Water samples. Four litres were collected in poly- thene bottles for chemical analyses fol- lowing the techniques outlined in the American Public Health Association’s Standard Methods (1960). The electri- cal conductivity of the water and the pH values were determined in the field using a “Dionic” conductivity meter and a “Lovibond” comparator respec- tively. The pH values were checked occasionally by glass electrode mea- surements. The alkalinity, acidity, chlo- rides, sulphates, calcium, magnesium, sodium and potassium contents were determined according to Standard Meth- ods (1960). The phosphates and copper were determined by the methods pre- sented by Murphy & Riley (1958) and Somer € Garraway (1957) respectively. Turbid waters during the wet season were centrifuged to remove suspended solids before analyses were made. SNAIL DISTRIBUTION AND WATER CHEMISTRY 155 Field stations. The annual rainfall in the Salisbury area is from 30 to 35 inches and is confined to the warm season extending from about November to April; thus dilution of dissolved substances occurs during this time. The rest of the year is dry, allowing concentration through evaporation. Many small streams, ponds and farm dams dry up completely during this period, but the sampling station for this study were all perennial. The sites were chosen because of their water chemistry and are numbered in the ascending order of the bicarbonate and calcium concentrations. All sampling stations were within a 50-mile radius of Salisbury, Rhodesia, and lay at alti- tudes between 1000 m and 1450 m above sea level, experiencing much the same temperature regimes. Shiff (1964a,b) gives an account of the range of water temperatures in the region. DESCRIPTION OF FIELD STATIONS Stations 1 and 2 (31° 15'E, 17° 35'S) were pools in a small stream running over soils derived from granite for- mations, the depth varying from a few cms in the dry season to 30 cms during the “rains”. Station 3 (1° 14'E, 17° 53'S) was on a quiet backwater of a similar small stream. At these 3 sta- tions, fast flowing water during the rainy season prevented the establish- ment of many aquatic plants in the main stream, but emergent vegetation flourished in the quiet pools and back- waters of the sampling sites. The depth varied from about 30 cm to over 1 metre. Stations 4 and 5 (31° 9'E, 17° 51'S) were on the shore of an old and supplementary reservoir, the lst being at the spillway and the 2nd at the upper reaches of the reservoir where the feeding streams entered; Stations 6 and 7 (31° 30E, 18” 1'S) were situated in a fairly large conservation dam which had its catchment area lying on soils derived from granite formations. Sta- tions 8 and 9 (30° 47'E, 17° 52'S) were on the south shore of Lake McIlwaine, which is the main water supply to Salisbury. The lake is approximately 10 miles long and 2 to 3 miles wide. Station 10 (30° 35'E, 17° 46'S) was a small pool in a perennial stream where a concrete ford crossed the stream. Most of the catchment area was granite, but some basement series formations were included; thus the drainage waters contained more calcium salts than the former stations. The depth of water at this station varied from about 30 cm during the dry season to about 1 metre during the wet season, although flash floods sometimes raised the water level up to 2 metres for short periods. Sta- tion 11 (31° 3'E, 17° 46'S) was in a permanently flooded borrow pit which collected drainage water from the meta- volcanic basement series. Stations 12, 13 and 14 (31° 31'E, 17° 20'S) were small pools in a stream which flowed for a few weeks only, during the middle of the wet season. For the rest of the year it consisted of a series of more or less permanent pools in a swampy area. The catchment was situated in a region characterised by metasedi- mentary rocks with some limestone; the water of this series of pools was the hardest encountered in the area. At all the stations there was much emergent vegetation present, and often submerged aquatic plants as well. RESULTS 1. Water Chemistry. Table 1 summarises the results of the chemical analyses of the water from the field stations over a sampling period of 2 years, and shows the mean values of calcium, magnesium, sodium, potassium and bicarbonates, which are the ions associated with hardness and alkalinity. The salt present in the greatest con- centration and common to all the field stations was calcium bicarbonate, and 156 N. V. WILLIAMS consequently the field stations are ar- ranged in an ascending order of con- centration of this salt in Table 1. The stations were also classified as soft, medium and hard water types according to their calcium bicarbonate content. Soft waters contained <5 mg/1 Cat+ and <20 mg/l HCO3”; medium water, 5 to 40 mg/l Cat+ and 20 to 200 mg/l HCOz”, and hard water > 40 mg/l Са++ and >200 mg/1 НСОз`. Amongst other ions investigated were the phosphates, since they influence algal growth which constitutes part of the snail’s diet; sulphates, because their low concentrations might have limiting effects on the snail distribution; and copper, since it is a known snail poison and is mined in the sampling area. The copper, sulphate, phosphate and chloride concentrations have, however, about the same range of values from Stations 1 to 14. They are thus unlikely to affect the abundance and consequently the distribution of the snails. 2. General distribution of snails The summary analysis of the snails collected from the field stations is shown in Table 2. The next to the last column shows the total catches of snails at each station, and in the final column these catches are shown as percentages of the total snails recovered from all stations. The results are shown graphi- cally in Fig. 1. The ionic concentra- tions increase progressively from Sta- tion 1 to 14, and the ratio of Ca** to HCOs ions is relatively constant at all stations. Any increase in the calcium ion concentration thus has a propor- tional increase in the alkalinity. This graph and the histograms (Fig. 2) relate the field results to the calcium ions only, but similar results would be ob- tained using the bicarbonate concentra- tion. It can be seen from Table 2 and Fig. 1 that when the total of all snail species is considered, numbers were low in soft water, rose to a maximum in medium water, and declined again in hard water; the ratio in the 3 types of water, expressed as a percentage of the total snails, was 11% 67% and 22% respectively. 3. Specific distribution patterns. Table 3 presents the total number of snails of each of the individual species in each of the 3 water types (soft, medium and hard), as a percentage of the total snails of all species collected. This allows a comparison of the abun- dance of each species to be made in the different water types, and also al- lows a comparison of the total abundance of each species throughout the whole range of water chemistry. Fig. 2 presents the number of snails of each individual species found in a particular water hardness range. As there were different numbers of sta- tions per “water type”, figures here have been adjusted as if there were 6 stations in each, and expressed as a percentage of the new total number of snails of that species found throughout the whole area. It can be seen that there are 4 distribution patterns. The first, represented by Gyraulus spp. (probably mostly G. costulatus), is a discontinuous one, for this species was absent from hard waters. Of their total numbers, 94% were recovered from medium water, and the remaining 6% were taken in the soft water range. A 2nd type of distribution pattern, although again discontinuous, is shown by Bulinus (B.) tropicus. This species was even more restricted than Gyraulus spp., and was found only in medium type waters. A 3rd type of distribution pattern, represented by 2 species, Lymnaea natalensis and Bulinus (Ph.) globosus, is of the continuous kind. Both species exist in the 3 types of water; L. natalen- sis attained its maximum population level in the medium water concentra- tions, but also tolerated soft and hard waters. B. (Ph.) globosus showed a 157 SNAIL DISTRIBUTION AND WATER CHEMISTRY ‘UMUIIUIU = "Ulm {UMUIXeU = “XIN xx *U9A1Í3 зэптел ивэш 9} Moog yonw 4олр jou ртр 1894 ayy Jo SYJUOU от лоу pue Атр1Авл Алэл эзол зэптел popls -qns peu spoo]] лэзуу "Zurpoo]j Áaeoy Á[peuoridaoxa Surinp SY99M мэ} e Jo Spotted 10] pa3sisaad suoljzejs Soy} хо} ети MOT AIOA YL x et rennt PIBH pıeH раен UMIP9A UMIP9A WUNIPp9A UMIP9A UMIP9A UMIP9A 0$ yos 31098 э4Аз 1078 а OR TE opt à = I I т т т um OS 1/2w se 0°21 9 v € Z € y z GT 2:2. 26 16 Чи sereuding 07 8 9 L 9 9 6 € _2 g 8 L "хи &0‘0 9000 900° 100 200 20 500 200° E00 10°0 200 Z0'0 ‘UN ng 1/8u se 700 100 £0%0 20 ‘0 50 °0 $0 ‘0 700 S00°0 50`0 20°0 £0"0 #0°0 чееи einge, 600 20 80°0 50 ‘0 70 ‘0 800 800 100 $0`0 20°0 30`0 L0'O жи “Git, 87° oc 60 € = Lo e7z 30 207780 “Ro 920) CON Я 1/2u se 9°8 89 3:3 61 92 т 9“ 80 A O 221.9: 1. Ben rer £'8T 8'Z1 158 67 y's 5 5 т:9 от ER те ez без Onn ОЗ. 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WILLIAMS 158 %001 8Sé‘9T %00T s831 %001 OTEL %00T 9765 %00T 8535 %00T 6831 Гезог, 3 € 9TS E E 90 07 = ES r'6 TEE $ "TT StI ртен УТ 8L 6L21 = == 6'6 1747 Wa =a $ “El 897 0'L 06 PIEH ET SI $75 == a L°0 05 35 a 3 € gel €°s 89 PIEH СТ 3 °6 8SST $ “PE GIE == = Lew GGL 6 "TE Fall == 7 UMIPIAN TT 6 81 580€ L° 38 9°S ОТ? 0 `57 8931 10€ £801 v "33 685 UMIPIA OT 8°9 ITIT sol ТЕТ Ут 558 1'0 € oT 55 Т*2 16 cant pe 6 $ 12 097$ 6 '0% 895 8 OF 8865 ve 66 Der 6€ Ls 99 UMIPIA 8 с ST 6675 8 °SE 09? р “OT G8LT $ `55 186 €°€ STI L'TI IST um pe L €°S $28 9 62 L'E $45 $ “TT 1433 6°G L8T 8°0 I umIpenN 9 LS €9S a == $ °G 68€ r'0 el 60 "0 T FSI 091 3305 5 17 729 =- == v8 r19 30 т 90 `0 & $’? 75 3305 v el 313 == De эт SIT ST 58 == == 87 39 3305 $ от SST == u == => 63 38 == “a v's 02 3305 3 8 *0 LET Fe == sl 06 30 G a == ge ch 1705 I Sno sıs ‘dds A aim cg sco gh A: 118% зу [BIOL IE % SV `& 18107 Пе % sy "7 1870} Пе % sv 18307 re % SY re303 Пе % sy 18307 J9JëM — (014835 тепчау y fenuuy jenuuy [enuuy fenuuy 5 п$эхл р]э Jo sosAyeue Arewuns ‘Z ATAVL SNAIL DISTRIBUTION AND WATER CHEMISTRY 159 O 4 8 12 6 20 24 28 32 36 40 44 48 52 ++ . Ca in mg/l FIG. 1. Distribution of aquatic pulmonates in relation to calcium concentrations. The annual total of snails per station is expressed as a percentage of all snails collected from all stations. 100 TT er un 77 Gyraulus id Y Bulinus (B.) tropicus % 50 as % total 0 7 В. (B) tropicus 100 B.(Ph) glob Е Hm РРР SEN) globosus + = dit % 50 Y as % total 100 % 50 ea) gate: В. feiffer! м = В. pfeifferi SOFT MEDIUM HARD FIG. 2. Distribution of snails in relation to calcium concentrations. Figures have been ad- justed for an equal number of snails per water type. N. V. WILLIAMS 160 L "vv T*8T L'TG 6°L 0°8 % TROL 0°S 118 = = L°S 756 = = (5591 €0E 005 1940 (лэуем рлеч) OF 1940 $ ‘8€ 8835 G LT 2085 0°9T 1092 6°L S831T L’E 86S 005-05 (1978M UMIPET) 07-9 FL тат 6 0 6€1 20 ‘0 € = > vz 88€ 05- ‘0 (1938M OS) S-0 spreus spreus spleus spreus spreus 8% SV Mie Пе % SV en Ie % SV Le Te $ SV me ne % SV bye 18% *[/3m ul "ИЗ ut Be a on) SON 4:89 sısuajpypu *7 dds snjnvaky taaffiafd ‘4 51214044 (*g) ‘4 SnsoQ01$ (‘Yd) ‘4 5912э4$ пис отлэзовлецо 1вэпиэцчо ssoupaey pue A}UI[VY[e 0} UOLJB[9A ur STIBUS [fe Jo чоциатал тр 988JU09194 ‘€ ATAWL SNAIL DISTRIBUTION AND WATER CHEMISTRY 161 more even distribution, but with a ten- dency to fall off in soft water. A 4th and last type of distribution pattern, illustrated by Biomphalaria pfeifferi, was again of the discontinuous kind. This species obviously cannot live successfully under soft water con- ditions; only 3 specimens were collected in these waters during the sampling period. Of the total В. pfeifferi popu- lation, 58% was found in the medium range, but this species can also thrive well in hard water, where the remaining 41% were taken. DISCUSSION Both lentic and lotic habitats were included in the soft and medium water types. The 3 hard water stations were running for a few weeks during the height of the wet season, but at other times they could be considered to be ponds. The general distribution pattern of all snail species, irrespective of the habitat type was: low densities in soft waters and maximum densities in medi- um waters. From the more limited results available from hard water sta- tions, there appeared to be a tendency for densities to be lower than inmedium water. These hard water results are treated with more caution because ofthe close proximity of the stations, and because there were only 3 hard water stations; nevertheless, from other as- pects, they would all have appeared to have been very suitable snail habitats as flood scour during the rainy season was minimal and the pools contained much aquatic vegetation and a rich invertebrate fauna. Harrison & Mason (1967) studied another hard water stream in the-same district, which had been treated with molluscicide; when mol- lusciciding was discontinued a similar snail fauna developed. The specific distribution pattern shows that Lymnaea natalensis was more abundant in soft and medium water concentrations than any of the other 4 species, and it was also the most abundant snail species in the field, forming nearly 45% of the total snail collection. The fact that it is well distributed throughout the whole water hardness range is of economic im- portance, since it is the intermediate host of the liver fluke, Fasciola gigan- tica. Biomphalaria pfeifferi was found to be the 2nd most abundant species in the area, forming 20% of the total snails, but it had a more limited range of distribution, being largely restricted to medium and hard water types, and it was less tolerant of soft water. This species was, however, the most abun- dant snail in the hard water range. Bulinus (Ph.) globosus was found in all types of water, but formed only 8% of the total catch. These results are reflected in epidemiological studies of schistosomiasis, for although Bulinus (Ph.) globosus, the host of Schistosoma haematobium, forms only 8% of the total catch, its wide distribution results in a similar wide distribution of the parasite. On the other hand, Schisto- soma mansoni, found in Biomphalaria pfeiffevi, has a more restricted range, similar to its snail. ACKNOWLEDGEMENTS My grateful thanks are due to Dr. A. D. Harrison for advice during the study and to my wife for enthusiastic assis- tance with the field collections. This research was financed by The Rocke- feller Foundation of New York, U.S.A. LITERATURE CITED ALLANSON, B. R, € KERRICH, J. E., 1961, A statistical method for esti- mating the number of animals in field samples, drawn from polluted rivers. Ver. Int. Ver. Limnol., 14: 491-494, ALVES, W. 1958, Chemical constituents of surface water in S. Rhodesia, with special reference to the mölluscan vectors of Bilharziasis. Bull. Wld. Hlth. Org. 18: 1071. 162 N. V. WILLIAMS American Public Health Association, 1960, Standard methods for the ex- amination of water and waste water. 11th edition. New York. ANDRADE, R. M. de, 1954, Alguns dados hidroquimicos de criadouros de plan- orbideos do Distrito Federal. Rev. bras. Malar.,6: 473-475. ANDRADE, В. M. de, SANTOS, I. N., € OLIVEIRA, R., 1955, Contribucáo para o conhecimento dos criadouros de planorbideos na area do Distrito Federal 1. Variacao de diferentes factores quimicos de ouas agua. Rev. bras. Malar., 7: 103-130. AYAD, -N., 1956, Bull. Wild. Hith. Org. 14, 1. In Abdel-Malek (1958) Factors conditioning the habitat of Bilharzia- sis Intermediate Hosts of the Family Planorbidae. Bull. Wid. НИЙ. Org., 18: 785-818. BOYCOTT, A. E., 1936, The habits of freshwater Mollusca in Britain. J. anim. Ecol., 5: 116-186. DE MEILLION, B., FRANK, G. H., & ALLANSON, B. R., 1958, Some as- pects of snail ecology in S. Africa. Bull. Wid. НИЙ. Org., 18: 771-783. DESCHIENS, R., 1954, Incidence de la mineralisation de l’eau sur les mol- lusques vecteurs des Bilharziasis. Bull. Soc. Path. exot., 47: 915-929. 1957, Les facteur conditionant Vhabitat des mollusques vecteurs. Ann. l'Inst. Pasteur, 92: 93. FRÓMMING, E., 1936, Untersuchungen über den Einfluss der Härte des Wohngngewässers auf das Vorkominen unserer Süsswassermollusken. Int. Rev. Hydrobiol., 36: 531-561. GOHAR, H. A. F., € EL GINDY, H.I., 1960, The ecology of Egyptian snail vectors of bilharziasis and fasciolia- sis. I. Chemical factors. Proc. Egypt. Acad. Sci., 15: 79-86. HAIRSTON, N. G., HUBENDICK, B., WATSON, J. M. € OLIVIER, L. J., 1958, An evaluation of techniques used in estimating snail populations. Bull. Wld. Hlth. Org., 19: 661-672. HARRISON, A. D., € MASON, M. H., 1967, The effects on the fauna of natural waters of surveillance treat- ment with Bayluscide in Rhodesia. Hydrobiol., 29: 149-155. HARRY, H. W., CRUMBIE, В. G., € MARTINEZ DE JESUS, J., 1957, Studies on the qualities of freshwater of Puerto Rico relative to the occur- rance of Australorbis glabratus (Say). Amer. J. trop. Med. Hyg., 6: 313-322. MARRILL, F. G., 1958, Sur les varia- tions de la composition chimique de l’eau et les variations d’abundance de Bulinus truncatus Audoin. Bull. Wld. НИЙ. Org., 18: 1064-1070. MURPHY, J. & RILEY, J. P., 1958, J. marine biol. Ass., 9: 37. SCHIFF,C. J., 1964a, Studies on Bulinus (Physopsis) globosus in S. Rhodesia. I. The influence of temperature on the intrinsic rate of natural increase. Ann. trop. Med. & Parasit., 58: 94- 105. SHIFF, С. J., 1964b, Studies on Bi- omphalaria pfeifferi in S. Rhodesia. I. The influence of temperature on the intrinsic rate of natural increase. Ann. trop. Med. & Parasit., 58: 106- 115, SOMER, E. € GARRAWAY, J. L., 1957, Chem. Ind.: 395. WATSON, J. M., 1958, Ecology and distribution of B. truncatus in the Middle East. Bull. Wid. Hlth. Org. 18: 833-894. World Health Organisation, 1957, Study group on the ecology of intermediate snail hosts of Bilharziasis. Tech. Rep., 120. Geneva. SNAIL DISTRIBUTION AND WATER CHEMISTRY 163 RESUME ETUDES SUR LES MOLLUSQUES PULMONES AQUATIQUES D’AFRIQUE CENTRALE I. DISTRIBUTION NATURELLE EN RELATION AVEC LA NATURE CHIMIQUE DES EAUX N. V. Williams Le but de cette étude est de vérifier s’il y a une relation entre la distribution et la densité relative de 5 pulmonés aquatiques communs d’une part et la concentration du milieu aquatique en carbonate de calcium d’autre part. Quatorze stations ont été sélectionnées a l’interieur d'un rayon de 50 miles autour de Salisbury, Rhodésie, de facon a recouvrir une large échelle de concentration en calcium et bicarbonate. Ces stations ont été classées comme suit: “eaux douces” - moins de 5 mg/l Ca et moins de 20 mg/ 1 de bicarbonate exprimé en CaCO3; “eaux moyennes” - de 5 à 40 mg/l Ca et de 20 a 200 mg/l de bicarbonate exprimé en CaCO3; “eaux dures” - plus de 40 mg/1 Ca et plus de 200 mg/1 de bicarbonate exprimé en CaCO3. Chaque mois des relevés quantitatifs de mollusques et des analyses d’eau ont été faits dans toutes les stations et ceci pendant une période d’au moin 12 mois. Les plus fortes densités de mollusques ont été trouvées dans les stations d’ “eaux moyennes”; les densités dans les stations d’ “eaux douces” étaient faibles. Quatre modes de distribution ont été distingués: Gyraulus spp. (surtout G. costulatus) se trouvent seulement dans les eaux “douces” et “moyennes”; Bulinus (B.) tropicus est cantonné dans les eaux “moyennes”; Biomphalaria pfeifferi ne se rencontre que dans les eaux “moyennes” et “dures”; Bulinus (Physopsis) globosus et Lymnaea natalensis sont constantes dans leur distribution et se rencontrent dans tous les types d’eaux, bien que leurs densités soient plus faibles dans les eaux “douces”. AXE: RESUMEN ESTUDIOS SOBRE PULMONADOS ACUATICOS EN AFRICA CENTRAL I. DISTRIBUCION EN RELACION A LA QUIMICA DEL AGUA N. V. Williams El propósito de este estudio fué el de determinar la posible relación entre la distribución y densidad relativa de población, de 5 cinco especies de caracoles dulceacuícolas comunes, y la concentración de carbonato de calcio en el ambiente. Se eligieron 14 estaciones dentro de un radio de 50 millas de Salisbury, Rodesia, para cubrir un vasto campo de concentración de carbonato de calcio. Las estaciones se clasificaron como sigue: “Aguas blandas” (de menor concentración) con menos de 5 mg/l Ca y menos de 20 mg/l bicarbonato como CaCog; “aguas intermedias”, con Ба 40 mg/l Ca y 20 a 200 mg/l bicarbonato como CaCog; “aguas duras” con mas de mg/l Ca y más de 200 mg/l bicarbonato como CaCog. Muestras cuantitativas mensuales de caracoles y analisis de aguas se sacaron por un periodo de por lo menos 12 meses. La mayor densidad de caracoles se encontró en aguas intermedias; en las aguas blandas la densidad fue la menor. Pudieron establecerse cuatro patrones distribucionales: Gyraulus spp. (princi- palemente G. costulatus) se encontró solamente en aguas blandas y medianas; Bulinus (B.) tropicus restringido a las aguas medianas; Biomphalaria pfeifferi solamente en aguas medias y duras; Bulinus (Physopsis) globosus y Lymnaea natalensis en todos los tipos de agua, aunque la densidad fué más bien menor en las aguas blandas. den) pP. 164 N. V. WILLIAMS ABCTPAKT ИЗУЧЕНИЕ ВОДНЫХ УЛИТОК PULMONATA ИЗ ЦЕНТРАЛЬНОЙ АФРИКИ Г. РАСПРОСТРАНЕНИЕ МОЛЛЮСКОВ В ПРИРОДЕ В СВЯЗИ С ХИМИЗМОМ ВОДЫ Н. В. ВИЛЬЯМС Целью настоящей работы было: определить имеется ли какая-нибудь связь между распространением и относительной плотностью поселений 5 обычных водных моллюсков и концентрацией бикарбоната кальция в воде. Было вы- брано 14 станций в радиусе 50 миль от Солсбери, Родезия, чтобы охватить более широкий диапазон изменений концентраций кальция и бикарбонатов. Эти станции были классифицированы следующим образом: "мягкая вода"-менее 5 мг/л Са и менее 20 мг/л бикарбонатов (CaCO3); "средняя вода"-около 5- 40 мг/л Ca и 20-200 мг/л бикарбонатов (CaCOz); "жесткая вода"-более 40 мг/л Са и более 200 мг/л бикарбонатов. В течение 12 месяцев ежемесячно на всех станциях брались количественные пробы моллюсков и анализы воды. Самая высокая концентрация моллюсков наблюдалась на станциях в "средних водах", а самая низкая-в "мягких водах". Было отмечено 4 типа их распространения: Gyraulus spp. (главным обра- зом, С. сознйа из) были найдены только в мягких и средних водах; Bulinus (B.) tropicus придерживается средних вод; Biomphalaria pfeifferi была найдена толь- ко в средних и жестких водах; Bulinus (Physopsis) globosus и Lymnaea natalensis имели распространение непрерывное и были найдены в водах всех типов, хо- тя плотность их поселений в мягких водах была ниже. Za As MALACOLOGIA, 1970, 10(1): 165-180: STUDIES ON AQUATIC PULMONATE SNAILS IN CENTRAL AFRICA II. EXPERIMENTAL INVESTIGATION OF FIELD DISTRIBUTION PATTERNS N. V. Williams University College of Rhodesia! ABSTRACT These experimental studies followed field studies on the distribution of aquatic snails in the region of Salisbury, Rhodesia, in which the distribution and relative density of 5 species had been shown to bear some relationship to the calcium and bicarbonate concentrations of the aquatic environment. Two species were selected for confirmatory laboratory experiments: Bulinus (Physopsis) globosus, which had been present in waters containing very low concentrations of calcium bicarbonate to waters containing high concentra- tions, and Biomphalaria pfeifferi, which had been shown to be limited to waters with medium to high concentrations of calcium bicarbonate, The 2 species were cultured in the laboratory in media designed to cover a wide range of calcium and bicarbonate concentrations, at a constant temper- ature of 25 C and with other controllable factors kept as constant as possible. Age specific fecundity and survivorship rates were determined for each test culture medium, and the mean generation time (MGT), the finite rate of increase(R) and the intrinsic rate of natural increase (ги) were estimated. The ги values obtained for Biomphalaria pfeifferi showed that there were distinctly higher increase rates of experimental populations at medium coneentrations of bicarbonate and calcium ions than at the upper and lower extremes. In addition, the rm values were directly proportional to the rela- tive density of this species at the different concentrations in the field, sug- gesting that its discontinuous distribution was partly due to its limited toler- ance to the extremes of the calcium bicarbonate concentration range occuring in the Salisbury region, notably the lower extreme. The rm values obtained for Bulinus (Ph.) globosus also indicated that the highest population increase occurred at medium concentrations of calcium bicarbonate. However, the range of r, values, obtained from the lowest to the highest ionic concentrations, was much smaller for this species than for the previous one, and no significant relationship was found between these values and the relative densities found in the field. This suggests that its continuous field distribution is due, in part, to its wider tolerance of calcium bicarbonate concentrations, Field studies on 5 species of aquatic pulmonate snails in the Salisbury region of Rhodesia, Central Africa, have shown that the distribution of at least 3 of them is influenced by the ionic composition of the natural waters. Because of the complicated surface geology of the re- gion, there was great variation in the 1 present address: composition of run-off water and it was found that these could be classified into 3 main types according to the cal- cium and bicarbonate concentrations: “soft” - <5 mg/l Са++ and <20 mg/l HCO;”, as CaCO;; “medium” - 5 to 40 mg/l Ca++ and 20 to 200 mg/l HCO,” as CaCO;; and “hard” - >40 mg/l Cat+ Biology Department, University of Salford, Salford, Lancs, England. (165) 166 N. V. WILLIAMS and >200 mg/l HCO; as CaCOz. The field distribution of some species could be related to the distribution of these water types. The aims of this experiment were to culture the snails in the laboratory in test waters covering these ranges of calcium and bicarbonate concentrations and to determine the effects on the life histories. It was hoped that the results might help to explain the field distri- bution patterns. Two species were cho- sen for the experiment, Biomphalaria pfeifferi (Krauss), the intermediate host of the “human” schistosome, Schisto- soma mansoni, and Bulinus (Physopsis) globsus (Morelet), the intermediate host of Schistosoma haematobium. The field survey had shown that the first snail was restricted to waters of the “me- dium” and “hard” types, and the second had been shown to occur in all three types. METHODS Experimental parameters. It was assumed from the field work that the effects of the different levels of calcium and bicarbonate concentrations on the snail life histories would be a subtle one, so that some parameter more sensitive than growth rate, egg- laying rate or death rate would have to be used. Shiff (1964a) and Shiff & Garnett (1967) were able to demonstrate a relationship between different constant temperature levels in the culture medium and the intrinsic rate of natural increase (the biometric parameter r„) of these 2 species of snails. Since values forr,, are obtained from a formula combining figures for survivorship and fecundity, it was decided to use this concept in the interpretation of these experimental studies. The use of this parameter in ecology derives from Lotka’s (1925) work on human populations. Andrewartha & Birch (1954) emphasize the importance of the biometric parameter r,,, “the innate capacity for increase,” which they de- fine as “the maximal rate of increase attained at any particular combination of temperature, moisture, quality of food, and so on, when the quantity of food, space and other animals of the same kind are kept at an optimum and other organisms of different kinds are excluded from the experiment.” Never- theless, they give sound reasons for introducing Lotka’s concept of “stable age-distribution” into the definition and point out that his “intrinsic rate of natural increase ” is the same as their “innate capacity for increase”. The precise value for r, may be obtained by solving the equation: Le 24120952 sal where x is the time interval con- sidered 1, is survivorship at time x m, is the number of female births at “pivotal age” x e is the base of natural logarithms r, is the intrinsic rate of natural increase. Andrewartha & Birch (1954) point out that r, is a statistic which summarises those physiological qualities of an ani- mal that are related to its capacity for increasing, qualities which are truly “innate” and which make rn as charac- teristic of a species as its morphology. Using the summation rather than the integral, it is possible to use experi- mentally obtained 1,m, data and to ar- rive at a solution for r,. This is ordinarily done by a process of trial and error, as described by Andrewartha and Birch, using the equation: loge 27 lxm, Tm = T T being the mean generation time of the population. The experiments described below were designed to obtain survivorship (1,) and LAB STUDY OF SNAIL DISTRIBUTION 167 fecundity (m,) data for the estimation of rm values at different levels of calcium and bicarbonate concentrations, keeping all other controllable factors as constant and optimal as possible. It should be pointed out that both species of snails are hermaphrodites and are truly female during most of their re- productive lives, thus all births (i.e., fertile eggs) and deaths had to be taken into account. The time intervals, x, used in the experiment were periods of 2 weeks, or a fortnight, and the “pivotal ages,” when 1, and m, values were calculated, were the middle points of these periods, 0.5x, 1.5x etc., to 13.5x. Snail Culture. The composition of the culture media for the 12 experiments carried out is given in Table 1. Natural waters were used for experiments 2 and 7; an en- tirely artifical, calcium-free solution was used for experiment 1; and the rest were built up from natural water 7 by adding deionised water and ana- lytical reagents. To study the effects of different levels of bicarbonates, solutions with values from 0 to 800 mg/l of bicarbonates, as CaCO;, were prepared, this range being greater than the range encountered in natural environments during the field studies. The bicarbonate anions were built up with the sodium, magnesium and potassium salts, keeping these and the calcium levels at values consistent with the values found in the medium and hard waters in the field. In a similar fashion, artifical snail culture solutions of calcium were pre- pared from 0 to 50 mg/l, as Ca, using the sulphate and chloride salts. The bicarbonate values were kept consis- tent with medium water levels in the field. The required amounts of ions for the various levels were theoretically computed, and the solutions analysed every 2 to 3 days to check the concen- trations. Tap water, which had been allowed to mature in a small outside concrete pond to eliminate the chlorine intro- duced by the municipal chlorination pro- cess, was used for the control experi- ments (7). At no time during the experiments were the various ratios of sodium, magnesium, potassium, sul- phates and chlorides in the culture solutions, allowed to exceed the ratio of these salts found in the natural waters. The culture of both Biomphalaria pfeiffevi and Bulinus (Ph.) globosus was essentially similar. The eggs of both species are laid in oval to round capsules, the 1st species having 20 to 30 eggs per capsule and the 2nd having a larger number, usually up to 40 eggs per capsule. Since about 50 individuals are necessary for a suitable sized “co- hort” for the establishment of a life table, 2 to 3 capsules were used per culture. The initial size of the cohorts was between 39 and 68 individuals, but most were between 50 and 60. Individual stock tanks, containing un- parasitised snails originating from in- dividuals netted from Lake McIlwaine near Salisbury, were kept at 25°C + 0.5°C in constant temperature cabinets. This was the temperature at which Shiff (1964a) obtained maximum “r,,” values for these snail species. Both species were kept in separate tanks and laid their egg capsules on the glass walls. These egg capsules were removed with clean razor blades when they were 4 to 5 days old. Those capsules showing live embryos were placed in 500 ml of the various artificial culture solutions contained in small plastic dishes, and were placed in the constant temperature cabinets. Biomphalaria pfeifferi were fed after hatching with small pieces of boiled lettuce leaves. These leaves had been previously boiled and dried, the 2nd boiling ensuring the removal of air and further softening of the plant tis- sues. A small piece about 1 sq. cm was placed on the bottom of each con- tainer in an attempt to ensure that 168 N. V. WILLIAMS searching for food by the young snails was kept to a minimum. Bulinus (Ph.) globosus did not thrive very successfully when fed immediately on lettuce. Faeces from adult snails were therefore introduced into the media during the first week after hatching and the young snails fed on their algal content. When Biomphalaria pfeifferi and В. (Ph.) globosus reached a diam- eter of 1 to 2 mm, they weretransferred to crystalising dishes of 1 litre ca- pacity, and reared in these until they were 6 weeks old. They were finally transferred to large aquaria containing 12 litres of solution. The population of B. pfeifferi was maintained at a density of 1 to 1.5 snails per litre and that of B. (Ph.) globosus at 1 snail per litre of solution. Shiff (1964b) shows that the growth rate of the latter species is retarded at densities in excess of this. The aquaria were maintained in an aquarium room at a constant temper- ature of 25°C + 1.0 C; the room received some daylight which was supplemented during the day with fluorescent light. Faeces and detritus were pipetted out of the aquaria every 2 or 3 days and fresh, dried lettuce was added daily. The culture solutions were tested at the same time as the tanks were cleaned, and their concentrations were adjusted if necessary. Make-up water was added to keep the volume con- stant. A few Ceriodaphnia spp. and Simocephalus spp. were introduced into the tanks to reduce the bacterial growth; this resulted in clear solutions and healthy snails. The survivorship, fecundity and speed of development of the snails was re- corded over a period of 13.5 fortnights (27 weeks) and the data used to cal- culate the values of r„, its natural antilog R (the ratio of increase per unit time) and the mean generationtime, MGT. For Biomphalaria pfeifferi values were obtained for all concentrations, but for Bulinus (Ph.) globosus, the pa- rameters were not obtained at bicarbon- ate concentrations of 600 and 800 mg/l (experiments 11 and 12), or for experi- ments 1 and 2. Experiment 7 was con- sidered to be in the nature of a control, since tap water was used; this water lay in the “medium” range with a bi- carbonate concentration of 35 mg/l as CaC0;. It originated from Lake MclIl- waine, which was also the source of the laboratory colonies of the 2 snail spe- cies. In the calcium experiments, solutions were prepared with concentrations of 0, 2, 12 and 50 mg/l “as Ca "It was found, however, that some of the bi- carbonate experiments had calcium ion levels which could be fitted into this series. RESULTS Bicarbonate concentrations. Biomphalaria pfeifferi: Fig. 1 relates the values obtained after 13.5 fortnights for the experimental parameters, Irn, R and MGT, to the bicarbonate concen- trations of the culture media. This species showed a positive r„ value in all concentrations, but the values varied widely from 0.298 to 0.719, a difference of 0.42. The variation was not hap- hazard, because a pattern emerged in that the highest values were obtained from the “medium” waters, and lower values were obtained from both “soft” and “hard” waters. The mean genera- tion time varied reciprocally. Bulinus (Physopsis) globosus: Fig. 2 gives the results for this species. Al- though similar relationships were found between the parameter values and the bicarbonate concentrations, the range of rm values was less than for the previous species, viz., 0.345 to 0.513, a difference of only 0.17. These re- sults are taken to indicate that B. (Ph.) globosus is tolerant of a wider range of bicarbonate concentrations that Biom- phalaria pfeifferi. Calcium concentrations. Fig. 3 and 4 relate the parameter LAB STUDY OF SNAIL DISTRIBUTION 169 TABLE 1. Ionic composition of experimental culture media Experiments* Tons 1 2 3 4 5 6 7 8 9 10 11 12 Cat+, mg/l as Ca 00 20 24 259.0 105 130 120 51.0 36.0: 39.0 80:0 106 Mg**, mg/l аз Mg >95 2140 ©3103. 0 143.372 2:84 2.01 1-68, 40 „21:0, 46.0, 60 Nat, mg/l CAD os 500), 6.0), 4.0 250, 46.0 420 7350 100 Kt, mg/l O 30 (20; 2.0 235% Оо Ао 203 HCO3 , mg/l as 26.0 15.0 30.0 0.0 5.0 15.1 35.0 66.8 150.5 300.0 608.0 829 CaCOg CH. mg/l -- 1.5 0.5 150 150 90 20 360 1.0 10. 0,8% 0:4 $04, mg/l -- 2,0:#0.5 25.0 25.0 260 20 250 20 130 108 0.4 *Experiments 4, 5, 6, 7, 9, 10 and 12 were designed to test bicarbonate concentrations; 1, 2, 3, 7 and 8 formed the “calcium series,” although some of the other experiments fitted in as well. Experiment 7 used matured tap water from Lake McIlwanie and Experiment 2 used water from a naturally soft stream. 170 N. V. WILLIAMS 20 11-6 1-9 R 11-2 1.8 № 10-8 \ (49) \ = N 104 & \ (©) 16 N 10-0 = \ 15 5 96 5 0-9 Хх = 14 \ 92 = 0:7 IN = m 13 < 8-8 2 0:5 te 12 \ 84 0-3 \MGT 1-1 x 80 0:1 \ ee LO Ser 7-6 0 02 04 06 08 10 1.2 14 16 18 20 22 24 26 28 30 BICARBONATE CONCENTRATION (LOG SCALE) FIG. 1. The effect of bicarbonate concentration on rm, R and MGT of Biomphalaria pfeifferi, obtained after 13.5 fortnightly periods. 112 10-8 0 10.4 E © za 1002 S 96 © 92 = E 88 © = 84 8.0 1070240205 08 10 12 14 16 18120 22024 BICARBONATE CONCENTRATION (LOG SCALE) FIG. 2. The effects of bicarbonate concentration on rm, Rand MGT of Bulinus (Physopsis) globosus, obtained after 13. 5 fortnightly periods. LAB STUDY OF SNAIL DISTRIBUTION 171 20 R |-9 В 8 10-8 17 10.4 $ 79) 16 alt GO te F5 ! 96 2 0-9 i fr +4 r Г 92 O 0-7 de =, a r 13 ee Sh г т Fa ser 88 < 0-5 ER | ES E 12 A aoe | 8-4 (5 0-3 > M.G.T. = Г I+ ae due 8-0 -| > BIN OLLO pa git 7.6 QO 0:2. 704, 05 08 IO ЮР 14 16 18 20 CALCIUM CONCENTRATION (LOG SCALE) FIG. 3. The effects of calcium concentration on rm; Rand MGT of Biomphalaria pfeifferi, obtained after 13.5 fortnightly periods. +9 i 18 i 1-2 KX 17 2 10-8 R H \ 16 R / \ Klar, à р 15 м / 10-0 ? / o 1.4 N / 96 2 Je \ ST / = O7 MET ; = 13 dw fk Snel ПЕ os Е = Im 12 - lm à / O | 8-8 0-3 Za à = rl 8.4 = 0-2 LO 8-0 O 02 04 06 08 10 12 14 16 18 20 CALCIUM CONCENTRATION (LOG SCALE) FIG. 4. The effects of calcium concentration on Ги, Rand MGT of Bulinus (Physopsis) glo- bosus, obtained after 13. 5 fortnightly periods. 172 N. V. WILLIAMS values for the 2 species to the calcium concentrations. Again В. pfeifferi showed a greater range of r valuesthan did B. (Ph.) globosus. The latter species is then probably more tolerant of a wider range of calcium concentra- tions. The validity of these experiments hinges, to some extent, on the time period of 13.5 fortnights within which they were carried out. It is possible to keep individuals of both species alive and laying eggs for much longer periods than this. In both species, egg-laying usually started between the 4th and the 6th fortnight, and it might seem neces- sary to run the experiments for more than 13.5 fortnights. Tables 2 and 3 show the values of r,, В and MGT over the last 4 fortnights of the experimental runs for both species. It will be seen that the values for these parameters changed little over this period, so that contributions of further fortnightly periods would be negligible. Fig. 5 summarizes the position re- garding the r,, values obtained for both species in all experiments. Experi- ments 4 to 7 are of particular impor- tance, because the calcium ion concen- trations were very similar whereas the bicarbonate concentrations increased slowly from 0 to 35 mg/1. In these the maximum difference in r, values for Bulinus (Ph.) globosus was only 0.07, while for Biomphalaria pfeifferi it was 0.4, showing the importance of bicar- bonate concentrations (as divorced from differences in calcium) for the latter species. Since the bicarbonate con- centrations must be responsible for the buffering capacity of natural waters, the small differences for B. (Ph.) glo- bosus again indicate that it has a great- er tolerance to changing chemical con- ditions. A comparison of the results of experiments 2 and 3 is interesting. In experiment 2, B. pfeifferi was cul- tured in a “soft” natural stream water with a calcium value similar to that of experiment 3. The main difference was the low bicarbonate concentration in expt. 2, a normal adjunct to low calcium values in the field. The г, value was much lower in 2 than in 3. COMPARISON OF LABORATORY AND FIELD DATA The field results (Williams, 1970) demonstrated that Bulinus (Ph.) glo- bosus has a wide tolerance to chemical conditions and is well distributed throughout the whole range, whilst B. pfeifferi, is restricted to medium and hard ranges of natural water. In the present experimental study, the wide tolerance of Bulinus (Ph.) globosus is suggested by the relatively constant r, values over the whole range of bicarbonate and calcium ion concen- trations, while the more limited toler- ance of Biomphalaria pfeifferi may be due to the wider range of r„ values over the same experimental conditions. The total number of snails of both species recovered at each sampling station was known from the field studies, as was the corresponding average cal- cium ion concentration. The r„ values for both species were known for certain calcium ion concentrations from the experimental results, whilst other val- ues could be interpolated. The 2 sets of data had thus a common factor, the calcium concentrations. In the case of Biomphalaria pfeifferi, the comparison of field and laboratory data by regres- sion analysis (Snedecor, 1962), showed that the relationship between r„ and the log field numbers (Fig. 6) was signifi- cant at the 5% confidence level (P > 0.05 <0.025). The regression of Bulinus (Ph.) globosus numbers on the experi- mental rm values was not significant (P >0.4 < 0.2), the regression line be- ing almost horizontal (Fig. 7). A slight increase in г, values produces a slight increase in field snail numbers, but this is not statistically significant. The significant positive correlation between the field abundance of Biompha- laria pfeifferi and the laboratory de- termined r, values suggest that the 173 *53Ч8тазлоу UL X 93% [eIDAIdy -SJy31U10J [TE лоу 9pew JOU 919M SuolJenofea :8 pue $ ‘с syuowmaadxyq -s339 SUIAR] 910794 рэтр [Te S[IBUS :т JuauridedxH LAB STUDY OF SNAIL DISTRIBUTION EST’Ol EPP'I 29980 G6LL°6 EFT 1998`0 0816 OEF'T LLGE'O S69'8 807°Т 0578`0 088 801 т 2116 ZEC'T 9957`0 0186 959°1 9557`0 896°8 LIST 99197`0 8E9"8 SOS*T 28070 009 ce IT Z26"8 —689°1 EPZG'O 69'S 989'T F2ZS°0 898°`8 089'I 88IS'0 696°4 049°Т 8ZIS"0 008 0F OT pIO'8 SP6*I €$99°0 ZS8°L УР6б°Т 17990 6LG'L IP6G'I Z£99"0 G6LZ°L 9€6"T 9099°0 OST 98 6 PLO‘OT 68S°IT 5897`0 988 °Т 5577'0 99 03 8 COL'L 860° EGIL'O 779, 230° 8814°0 LPE"L — 190°5 ESIL'O P80'L 870°< 8914°`0 SE т L 099°L PIO"Z 1004`0 SES'L ZIO"Z 1669°0 TSE" 110°C 98690 P8T*L 800°% 01690 ST eT 9 O7$°8 G628°I 22090 09£'8 L2Z8'I 9509°0. £€L0'8 28° 0109°0 SEL°L 818°Т 94650 8 01 G OTT'IT SPE'I 9862 0 POS OT SEET TI6Z'0 SIP'OT LIST 5845°0 868°6 PLZT 20720 0 6 v 8888 — 756°Т S6S9'0 0€ vz € 762 8Lp'I 806€ ‘0 GT с Z 95 0 I LOW Y Va LOW Y uta LOW Y u LOW Y a «RG "ET «хо "ZT «XS "TT «XS "OT Es COMORES эзу u О а 90S ‘0 + 9068 Jo эхпзело4 93 yue]ysuoo e ye рэлзэл 1412/12/94 mAamoyduoiZ 103 LOW Pue y ‘т jo sonjeA рэчпихлэзэр Алозелодет ‘5 чтахт, N. 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WILLIAMS 174 *SJY3TUy1OJ Ul X 938 [BJOAId x *JyÍTUJ1OJ YITT Oy} PUOÁ9Q 2AIAINS JOU PIP S[IBUS ‘QT JuswmLıadxy *SJY3TUJ1OJ [fe OJ PEU Jou 919M SUOIJEMOITED :6 pue g ‘g ззаэцихеахя -s339 SUIÁB] элоуэа рэтр Пе SIIBUS :т заэцилеахя PSI°S ZIP‘I 037$ `0 00€ 07 OT OLP'IT I6P'I 9668`0 168`0Т 69P'T 9788 `0 OST 9€ 6 90801 ISSG'T 08Sp'0 99 0S 8 p6C'8 1/19°Т PEIS'O SZE"8 999'T FOIS’O 020°8 €99'I 9808`0 TEL" SS9°T 8EOS'O 8 ZI L $716 IS9°I PIOS'0 800°6 039°Т 800S°0 98S9°8 199°Т €S6P'0 EEE 8 SE9*I 9167`0 GT el 9 790°6 809°Т 8PLP'0 ZE8'8 GO9'T OELP'O — 995°8 PEG'T E99F'0 9€6"L 988°Т EIIF'O S OT G 268 "8 2951 0970 8LZ'S 0951 Lbbb'0 813'8 G6SS°I Iprr'O 890°8 SSS*I 9197`0 0 6 y 29201 9EP'T 8198 `0 0€ т € 95 0 I LOW Y uz LOW Y Ua LOW Y us: LOW Y Er «XS "el, #XG ‘ZT +XG *TT xXG "OT oie eo *1/3u Juowrxodxy ut €QOH UF 4480 93V . - 2.08 ‘0 + 9035 Jo 9anmyexoduroy jueysuoo e ye рэлеэл 57509018 (ya) Snurng лоу LOW pue 4 “a jo зэптел рэциахезер Клозелоде] ‘€ ATAVL LAB STUDY OF SNAIL DISTRIBUTION 175 $01 o—0 HCOZ concentration in mg/L : ++ RR: œ—-0 Са concentration in mg/L MAS U B.pfeifferi o a LS) cal SIL = B.(Ph.) globosus D (J = 2:0 rd о 5 7 SE ie ed O Hal о 0-8 < / © / 0:7 == O ® / 0-6 © CET EN lO ih? я 1 05 r H ay й 7 y 2 u с 27 Y й й Y Y 0-4 = at À A 14 16 14 IG ТАМА ИЯ 05 mn ia ala 14 14 | II] 4 ИЛИ |A И 787 k a |A 14 ИИА И / / у A414 1414 14 12 / a NA A ТИ ei Nate O: A | IA IA IA | or АИ 14 14 14 14 14 Ip 0.0 Eptsol. ем Эыб Jard Sinti, „eo (8 KQaolOreoll ride FIG. 5. Relationship between the intrinsic rate of natural increase (rm) obtained experimen- tally, and calcium and bicarbonate concentrations. Consult Table 1 for actual concentrations. 176 N. V. WILLIAMS abundance of this species inthe field is controlled to some extent by the calcium concentration, in this case mostly cal- cium bicarbonate. It therefore follows that the distribution will also be de- termined in part by the ionic compo- sition of the water. In the case of Bulinus (Ph.) globosus, since no signi- ficant correlation was found between the field abundance and the laboratory determined rates of increase, it appears that the ionic composition of the water does not significantly affect the field abundance, and consequently the dis- tribution, of this species. DISCUSSION In considering the value of the bio- metric parameter r, in laboratory in- vestigations, it is well to consider the ways in which it may be used. First, is the commonly accepted method of using r, aS a means of demonstrating the rate of growth of a population under optimum constant conditions. It has also been used when the effects of survivorship, speed or development and fecundity are combined as a single response to some environmental factor. A 3rd use is the interspecific com- parison of the ability of similar animals to adapt themselves to changes in en- vironmental conditions, thus providing an insight into problems of abundance and distribution in the natural environ- ment. Andrewartha & Birch (1954) state that the intrinsic rate of natural in- crease (r,,), when calculated under ideal conditions, is as characteristic of the species as any distinct morphological feature. It is difficult however to eval- uate experimental conditions in these terms, because it has been shown in this laboratory that slightly different culture techniques produce different estimations of the parameter r„. Opti- mum laboratory conditions of temper- ature, food, space and water chemistry may be approached, but the “ideal con- dition” of Andrewartha & Birch (1954) may not be reached, and in consequence, the experimental r, values may be slightly below the hypothetical “abso- lute” ones for any particular set of environmental conditions. An impor- tant point is that the experimenter may be much more successful in producing near-optimal conditions for one species than for another, so that interspecific comparison of actual r, values will lead to erroneous conclusions. Never- theless, comparable experimental re- gimes will allow optimal value for a variable, such as calcium concentra- tion, to be determined for any one species, irrespective of the fact that the determined r, values may be slight- ly lower than the absolute ones. Any environmental factor which has a quantitative effect on either the speed of development, survivorship or fe- cundity of a species will cause changes in the r, values. In this study, empha- sis has been placed on water chemistry, but it is obvious, however, that the effect of other factors may be studied in this way. It has been possible to compare the values of г, within one species under different conditions, but these values have not been used to compare one species with another. The range of r,, values, however, has been used for this interspecific comparison; the large range of r, values of Biom- phalaria pfeifferi, in contrast to the small range of Bulinus (Ph.) globosus, has been taken to indicate that the former tolerates a narrower range of chemical conditions. This lack oftoler- ance appears to be one of the factors affecting the abundance and distribution of B. pfeifferi in the natural environ- ment. ACKNOWLEDGEMENTS Grateful thanks are due to Dr. A. D. Harrison, now at the University of Wa- terloo, Waterloo, Ontario, Canada for advice and useful criticism during the course of this study, and to my wife for her untiring assistance in the main- LAB STUDY OF SNAIL DISTRIBUTION 177 30 (LOG SCALE) о NUMBER OF SNAILS COLLECTED =) 0-3 0.4 05 0-6 0-7 EXPERIMENTAL rm FIG. 6. Regression of experimental values of r,, on numbers of Biomphalaria pfeifferi col- lected in the field. 3:0 2:0 (LOG SCALE) NUMBER OF SNAILS COLLECTED =) 0:0 0-3 0.4 0-5 EXPERIMENTAL rm FIG. 7. Regression of experimental values of Ty on numbers of Bulinus (Physopsis) globosus collected in the field. 178 N. V. WILLIAMS tenance of the large numbers of snail cultures. This project was financed by the Rockefeller Foundation of New York, U.S.A. LITERATURE CITED ANDREWARTHA, H. G. € BIRCH, L.C., 1954, The distribution and abundance of animals. Chicago. LOTKA, A. J., 1925, Elements of physi- cal biology. Williams € Wilkins. Bal- timore. SHIFF, C. J., 1964a, Studies on Bulinus (Physopsis) globosus in S. Rhodesia. SHIFF, C. J., 1964b, Studies on Bulinus (Physopsis) globosus in S. Rhodesia. Il. Factors influencing the relation- ship between age and growth. Ann. trop. Med. & Parasit., 58: 106-115. SHIFF, C. J. & GARNETT, B., 1967, The influence of temperature on the intrinsic rate of natural increase of the freshwater snail Biomphalaria pfeifferi (Krauss) (Pulmonata: Plan- orbidae). Arch. Hydrobiol., 62(4): 429-438. SNEDECOR, G. W., 1962, Statistical methods. 5th ed. lowa Univ. Press, lowa. 1. The influence of temperature on the intrinsic rate of natural increase. WILLIAMS, N. V., 1970, Studies on pulmonate snails in Central Africa. Ann. trop. Med. € Parasit., 58: 94- I. Field distribution in relation to 105. water chemistry. Malacologia, 10: 153-164. RESUME ETUDES SUR LES MOLLUSQUES PULMONES AQUATIQUES D’AFRIQUE CENTRALE II. ANALYSE EXPERIMENTALE DES MODES DE DISTRIBUTION DANS LA NATURE N. V. Williams Ces experimentations font suite 4 des études dans la nature sur la distribution de mollusques aquatiques dans la region de Salisbury, Rhodesie, dans lesquelles on a montré que la distribution et la densité relative de 5 espéces avaient une certaine relation avec les concentrations en calcium et bicarbonate du milieu aquatique. Deux especes ont été retenues pour confirmation par experimentation: Bulinus (Physopsis) globosus, qui se rencontre aussi biendans les eaux a fortes qu’a faibles concentrations en bicarbonate de calcium, et Biomphalaria pfeifferi quise limite aux eaux a moyennes et fortes concentrations en bicarbonate de calcium. Les deux especes ont été élevées en laboratoire dans des milieux calculés pour recouvrir une large variation de concentrations en calcium et bicarbonate, ceci a une température constante de 250, les autres facteurs contrólables étant maintenus aussi constants que possible. On a determine l’äge spécifique de fécondité et les taux de survivance pour chaque lot de culture, et estimé le temps moyen d’une génération (МСТ), le taux limité d'accroissement(R) et le taux intrinsèque d’accroissement naturel (rm). Les valeurs du ry, obtenues pour Biomphalaria pfeifferi, montrent qu'il y a des taux d’accroissement des populations expérimentales, qui sont plus forts a des con- centrations moyennes d’ions calcium et bicarbonate qu’à des concentrations basses ou élevées. En plus, les valeurs du rm sont directement proportionnelles aux densités relatives de cette espèce selon les différentes concentrations observées dans la nature, ce qui suggère que la distribution discontinue de l’espèce est en partie LAB STUDY OF SNAIL DISTRIBUTION 179 due a sa faible tolérance pour les concentrations extrémes de bicarbonate de calcium existant dans la région de Salisbury, notamment les plus basses. Les valeurs du rm obtenues pour Bulinus (Ph.) globosus indiquent aussi que les plus forts accroissements de populations interviennent pour les concentrations moyennes de bicarbonate de calcium. Cependant, l’échelle des valeurs de r,, obtenues des plus hautes aux plus basses concentrations ioniques, sont plus faibles pour cette espèce que pour la précédente, et l’on n’a pas trouvé de relation significative entre ces valeurs et les densités relatives rencontrées dans la nature. Ceci suggére que sa distribution continue dans la nature est due, en partie, a sa grande tolérance vis-a- vis des concentrations en bicarbonate de calcium. A. L. RESUMEN ESTUDIOS SOBRE PULMONADOS ACUATICOS EN AFRICA CENTRAL II. INVESTIGACION EXPERIMENTAL DE LOS PATRONES NATURALES DE DISTRIBUCION N. V. Williams Estos experimentos continuaron aquellos estudios realizados en el campo, acerca de la distribución y densidad relativa de 5 especies de caracoles de agua dulce en la región de Salisbury, Rodesia, cuya relación con la concentración de carbonato de calcio en el ambiente quedó demostrada. Dos especies se eligieron para experi- mentos confirmatorios en el laboratorio: Bulinus (Physopsis) globosus, presente en aguas que contienen una concentración baja de carbonato de calcio, y Biomphalaria pfeifferi, la cual esta limitada a los ambientes con concentraciones medianas y altas. Las 2 especies fueron cultivadas en el laboratorio en una forma designada a cubrir una considerable latitud en la concentración del carbonato de calcio, a temperaturas constantes de 250 C y conotrosfactores controlables guardados en la forma más cons- tante posible. Edad, fecundidad específica y proporción de sobrevivientes se de- terminaron para cada prueba de cultivo, y se calculó el término medio de generación- tiempo (MGT), la proporción definida.de aumento (R), la proporción intrínsica del aumento natural (rp). Los valores r,, Obtenidos para Biomphalaria pfeifferi distintamente indicaron aumento mayor en las poblaciones experimentales de concentración media de carbonato de calcio, que en los altos obajos extremos. También, los valores rm fueron directa- mente proporcionales a la densidad relativa de la especie con los diferentes tipos de concentración en el campo, sugiriendo que su distribución discontinua se debió en parte a la limitada tolerancia a los extremos de concentración del bicarbonato de calcio que existen en la región de Salisbury, notablemente en el extremo bajo. En Bulinus (PH.) globosus, los valores rm también indicaron que el mayor aumento de población ocurre en concentraciones medias. Sin embargo, la latitud de esos valores, obtenidas desde las más bajas a las más altas concentraciones iónicas, fué más reducida para esta especie que para la precedente, y no se encontró relación significativa entre esos valores y los que se encontraron en el campo. Esto sugiere que su continua distribución natural, se debe, en parte, a su más amplia tolerancia de concentración de carbonato de calcio. JS J. J. 180 N. V. WILLIAMS ABCTPAKT ИЗУЧЕНИЕ ВОДНЫХ УЛИТОК PULMONATA ИЗ ЦЕНТРАЛЬНОЙ АФРИКИ П. ЭКСПЕРИМЕНТАЛЬНОЕ ИССЛЕДОВАНИЕ РАСПРОСТРАНЕНИЯ ГРУППИРОВОК МОЛЛЮСКОВ В ЕСТЕСТВЕННЫХ УСЛОВИЯХ Н. В. ВИЛЬЯМС Эти экспериментальные работы сопровождали полевые исследования водных улиток в районе Солсбери, Родезия по распространению и относительной плотности поселений 5 видов моллюсков в связи с количеством кальция и концентрацией бикарбоната в природных вопах. Два вида были выбраны пля подтверждения этого в лабораторных услови- ях: Bulinus (Physopsis) globosus, обитающий в водах как с низкой концентрацией бикарбоната кальция, так и в водах с высоким его содержанием; второй Bun- Biomphalaria pfeifferi, которая придерживалась вод co CpelHe и высокой концентрацией бикарбоната Са. Эти: лва вида культивировались в лаборатории в водах с широким диапа- зоном концентрации кальция и его бикарбоната, при постоянной температуре 25°C и с другими, возможно более постоянными факторами, поддающимися контролю. Лля кажлой культуры моллюсков определялась возрастная плодовитость, выживаемость и средняя скорость образования генераций 5 (MGT), конеч- ная скорость их увеличения (В) и свойственная им скорость естественного увеличения (rm). Величина Tm для Biomphalaria pfeifferi ‚показала, что наблюдается заметно большая скорость увеличения популяции в эксперименте при.средней концен- трации бикарбоната и ионов кальция, чем при высоких и низких их концент- рациях. Кроме того, величины Гт были прямо пропорциональны относитель- ной плотности поселений данного вида при различных их концентрациях в природных водах, если предположить, что непрерывное распространение этих видов определяется частично их ограниченной выносливостью к крайним ве- личинам бикарбоната кальция, встречающимся в районе Солсбери, особенно к низким. Величины г/у полученные для Bulinus (Ph.) globosus также указывают на то, что самые плотные популяции этих моллюсков наблюдаются при сред- них концентрациях бикарбоната кальция. Однако, колебания величин Гщ, полученных при самых низких и при самых высоких концентрациях этих ио- нов, были гораздо меньше для В. globosus, чем для предыдущего вида; не было найдено значительной связи между этими величинами и относительной плотностью поселений моллюсков в природных условиях. Поэтому можно ду- мать, что его непрерывное распространение частично обуславливается его больщой толерантностью к концентрациям бикарбоната кальция. Zi, Asis MALACOLOGIA, 1970, 10(1): 181-223 SOME GASTROPODS FROM MADAGASCAR AND WEST MEXICO ! Eveline du Bois-Reymond Marcus? and Ernst Marcus? ABSTRACT This paper deals with 43 species of marine gastropods, mostly opistho- branchs (but also 1 lamellariacean and 3 onchidiaceans) from Madagascar and from the Gulf of California. Anatomical descriptions are given for the various species. Three species were recognized to be common to both collections; these represent taxa occurring in circumtropical-warm seas, The following new species are described: Smaragdinella kirsteueri, Stiliger (Stiliger) erbsus, Hypselodoris regina and Noumeaella isa (from Madagascar), and Elysia vreelandae (from West Mexico). The new name Stiliger (S.) raorum substitutes $. (S.) nigrovittatus Rao & Rao, 1963. The opisthobranchs of Mada- gascar belong to the rather homogeneous Indo-Pacific reef fauna, while those from the Gulf of California live in areas largely devoid of coral reefs, but containing an admixture of Panamic and American temperate Pacific faunal elements. INTRODUCTION The present paper treats 30 species from Madagascar as Part XI of the Austrian Indo-west Pacific Expedition 1959/1960, and 13 species from the Gulf of California. Five new species are described, of which 4 are from Mada- gascar. Benthonic animals of shallow water from these regions are separated by Ekman’s East Pacific Barrier (Emer- son, 1967). Only 3 species, which occur in all warm seas, are represented in both collections. Comparative morpho- logical studies of opisthobranchs indi- cate that many species, especially nudi- branchs, have extensive geographical ranges. Several species are known to occur in more than one zoogeographical province and some species of nudi- branchs are apparently circumtropical in distribution. Therefore, a combined publication of zoologically allied, though geographically separate collections, fa- cilitates faunal comparisons. The opis- thobranchs of Madagascar belong to the rather homogeneous Indo-Pacific reef fauna, but those from the Gulf of Cali- fornia live in areas largely devoid of coral reefs. There, species of re- stricted or wide distribution in the Panamic faunal province meet with others of the American temperate Pa- cific fauna. The Panamic province is related to the Caribbean, and the Amer- ican temperate Pacific fauna includes Japanese elements. Although most of the species in the present collections are opisthobranchs, the first species treated belongs to the Lamellariacea. These are traditionally collected and studied together with opis- thobranchs. Our 4 last species are Onchidiacea. Van Mol (1967) re-estab- lished the subclass Pulmonata in a re- cent study of the cerebral ganglion in Basommatophora, Stylommatophora, and lPublished with the cooperation of the Institute of Malacology. 2Address: Caixa Postal 6994, Säo Paulo, Brazil. 3Professor Emeritus of Zoology, University of Säo Paulo. Deceased June 30, 1968. (181) 182 Soleolifera, so the Onchidiacea are sep- arated from the Opisthobranchia again, if one follows that author. The types and some of the other ma- terial in this article are deposited in the Department of Living Invertebrates of The American Museum of Natural History. MATERIALS Collecting stations from Madagascar, 1959 (Ernst Kirsteuer) viii Tanikely, Porites cf, iwayamaensis, 2.5 meters, June 25, ix Tanikely, Seriatopora angulata, 2 meters, June 26, x Tanikely, Porites cf. iwayamaensis, 2.5 meters, June 27, xi Tanikely, Seriatopora angulata, 2.5 meters, June 29, xiii Tanikely, Seriatopora angulata, 2.5 meters, July 1. xiv Tanikely, Seriatopora angulata, 3 meters, July 2. xvi Tanikely, Seriatopora angulata, 4 meters, July 4. xviii Tanikely, tide pool, coarse sand and fragments of coral, under stones, 0.2 meter, June and July. xix Tanikely, Millepora tenella, 4.5 meters, July 8. xxi Tanikely, Acropora corymbosa, 2.5 meters, July 13. xxii Tanikely, Acropora corymbosa, 2 meters, July 14. xxiv Tanikely, Acropora pharaonis, 3 meters, July 16. xxvi Nossi Iranja, southwest coast, un- der stones and dead coral, low in- tertidal zone, Nov. 24, xxvii Tanikely, Acropora pharaonis, 2 meters, Dec. 3. xxviii Tanikely, Acropora corymbosa, 3 meters, Dec. 4. xxix Tanikely, Acropora corymbosa, 2.5 meters, Dec. 5. XXX Tanikely, Seriatopora angulata, 2 meters, Dec, 6. xxxi Tanikely, Seriatopora angulata, 2 meters, Dec. 7. xxxii Tanikely, Millepora tenella, 2 me- ters, Dec. 8. xxxiii Tanikely, Porites cf. iwayamaensis, 3.5 meters, Dec. 10. xxxvi Tanikely, Gracilaria species, 3me- MARCUS AND MARCUS ters, Dec. 13, xxxvii Tanikely, Millepora tenella, 4 me- ters, Dec. 14. xliii Nossi Be, Bay of Ambanoro, in front of the institute, sand under stones, low intertidal zone, Dec. xlv Nossi Be, Bay of Ambanoro, mud with sand, 20 meters, Dec. 29. Collecting stations from Mexico, Gulf of California i Mexico, Sonora, Puerto Pefiasco ii Mexico, Sonora, San Agustin = El Sahuaral iii Mexico, Sonora, Guaymas, latitude 27 59' N, longitude 110° 58' W. iv Mexico, Baja California, Cabo Pulmo, latitude 23° 22' N, longi- tude 109° 28' W. SYSTEMATIC ACCOUNT List of species Prosobranchia, Monotocardia, Mesogastro- poda, Lamellariacea, Lamellariidae 1. Coriocella nigra Blainville 1824 Euthyneura, Opisthobranchia, Cephala- spidea, Bullacea, Atyidae Atys spec, juv. Cephalaspidea, Philinacea, Smaraginelli- dae 2. Lathophthalmus smaragdinus Rüp- pell & F. S. Leuckart 1828 3. Smavagdinella kirsteueri, spec. nov. Philine spec., juv. Cephalaspidea, Philinacea, Aglajidae 4, Chelidonura punctata Eliot 1903 5. Chelidonura inermis (Cooper 1862) Anaspidea, Aplysiidae 6. Aplysia (Pruvotaplysia) parvula Mörch 1863 7. Dolabella auricularia (Solander 1786) 8. Dolabrifera dolabrifera (Rang 1828) 9. Stylocheilus longicauda (Quoy & Gai- mard 1824) Ascoglossa, Elysiacea, Stiligeridae 10. Stiliger (Stiliger) erbsus, spec, nov. Ascoglossa, Elysiacea, Elysiidae 11, Elysia vreelandae, spec. nov. Notaspidea, Pleurobranchacea, Pleuro- branchidae 12. Berthellina cuvieri (Bergh 1898) Doridoidea, Eudoridacea, Cryptobranchia, Dorididae, Conualevinae 13. Conualevia marcusi Collier & Farmer 1964 Doridoidea, Eudoridacea, Cryptobranchia, MADAGASCAN AND MEXICAN GASTROPODS 183 Dorididae, Chromodoridinae 14. Chromodoris quadricolor & Е. 5. Leuckart 1828) 15. Chromodoris norrisi Farmer 1963 16. Hypselodoris regina, spec. nov. Doridoidea, Eudoridacea, Cryptobranchia, Dorididae, Aldisinae 17. Rostanga pulchra MacFarland 1905 Doridoidea, Eudoridacea, Cryptobranchia, Dorididae, Archidoridinae 18, Atagema osseosa (Keelart 1859) 19. Trippa intecta (Keelart 1858) Doridoidea, Eudoridacea, Cryptobranchia, Dorididae, Discodoridinae 20. Taringa aivica timia Marcus 1967 21. Tayuva ketos ketos Marcus 1967 Doridoidea, Eudoridacea, Cryptobranchia, Dorididae, Halgerdinae 22. Asteronotus cespitosus (van Hasselt 1824) Doridoidea, Eudoridacea, Cryptobranchia, Dorididae, Platydoridinae (=Arginae) 23. Platydoris scabra (Cuvier 1804) Doridoidea, Eudoridacea, Phanerobranchia, Nonsuctoria, Gymnodorididae 24. Gymnodoris bicolor (Alder € Han- cock 1864) Doridoidea, Porostomata, Dendrodorididae 25. Dendrodoris nigra (Stimpson 1855) 26. Dendrodoris rubra (Keelart 1858) 27. Dendrodoris pudibunda (Bergh 1879) Doridoidea, Porostomata, Phyllidiidae 28. Phyllidia (Phyllidia) varicosa La- marck 1801 29, Dermatobranchus (Dermatobran- chus) striatus van Hasselt 1824 Eolidoidea, Pleuroprocta, Flabellinidae 30. Coryphellina rubrolineata O’Don- oghue 1929 Eolidacea, Cleioprocta, Favorinidae 31, Favorinus mirabilis Baba 1955 32. Pteraeolidia janthina (Angas 1864) 3. Noumeaella isa, spec. nov. Eolidacea, Cleioprocta, Aeolidiidae 34, Aeolidiella indica, Bergh 1888 Soleolifera, Onchidiacea, Onchidiidae 35. Peronia peronii (Cuvier 1804) 36. Peronia verruculata (Cuvier 1830) 37. Hoffmannola hansi Marcus 1967 38. Onchidella hildae (Hoffmann 1928) (Ruppell Lamellariacea Coriocella nigra Blainville 1824 (Figs. 1-9) Coriocella nigra Blainville, 1824, p 259; 1825, p 466, pl. 42, fig. 1. Range: Mauritius. Collecting station: Madagascar; xxviii, 1 male. Description: In life, the present specimen was 15 to 18 mm long, 8 to 10 mm broad, smooth, and uniformly black with whitish-yellow, granulated tentacles. In the preserved specimen a little pigment is present in the folds of the mantle, near the snout, and from the under side of the mantle onto the back of the foot. The surface of the mantle has about 5 bosses, evidently produced by contraction of the cutaneous muscles. One of the bosses lies over the apex of the shell (ax). The conchinous shell has about 3 whorls; the measurements are: length 10 mm, breadth 6.3 mm, length of aperture 8.5 mm. The blackish calcareous layer of the shell is shivered as generally in preserved Coriocella. The inhalant siphon (er) lies in the middle. The triangular tentacles are smooth, not furrowed. They bear the brown eyes in a knob near the base. The anterior border of the foot is trans- versely grooved (vo). The mantle skirt is thin, its epidermis rich inglandcells. The osphradium (om) has at least 30 leaflets of equal length on either side of the broad rhachis. The food in the gut contains alcyonarian sclerites. The penis is rudimentary, only ahemispher- ical wart, 930 u high and 200 u in di- ameter at its base. The seminal duct (d), 35 u in diameter, courses straight within the muscle layers of the body wall. In Bergh’s much larger snails (1886, p 222, 225) it serpentines. The jaws measure 1.4 by 1 mm. The radula has 48 rows. The left limb of the rhachidian tooth is 230 u long, the right one 155; the cusp is either median or inclined to the right or left. On either side it bears 4 to 6 denticles. The laterals are 380 y high, their cusp has 3 to 6, generally 4, coarse teeth on the inner side, 6 to 12 (sometimes up to 17) finer teeth on the outer side. Remarks: For synonomy and range we limit ourselves to Bergh (1886, p 176) who called the species Chelyonotus tonganus var. mauritiana, and synono- 184 MARCUS AND MARCUS mized Marsenia berghi from Mauritius and Réunion with it. Later (1908b, p 107) he united the latter with C. sem- peri, considered an independent species in 1886 and 1905b. In 1908b Bergh questioned the specifity of C. semperi. Vayssiére’s Chelyonotus niger (1912, p 118) possibly belongs to the present species in which case its distribution would extend to the Gulf of Aden. But the symmetrical rhachidian tooth of Vays- siére’s material differs from that in ours. Whether or not Adam & Leloup’s “? Lamellaria (Coriocella) mauritiana Bergh” (1938, p 141) from the Aru Is- lands belongs to C. nigra cannot be judged. Scaphandracea Atys species, juvenile (Figs. 10-15) Collecting station: Madagascar; xxvii. Description: The living snail was 1.5 to 2 mm long, 1 mm thick. Its narrow head shield was 0.8 mm long and slight- ly notched behind. The parapodia lay to the sides of the head shield and touch a little distance behind it, like in other species of Atys (Ostergaard, 1955, fig. 1; Macnae, 1962b, fig. 1). In the present juvenile only a small part of the shell, as well as the posterior mantle lobe, projected from the parapodia. The liv- ing specimen was bluish-white. On the head shield, parapodia and mantle lobe there were opaque snow-white spots, in the region of the shell brown dots. The light yellowish-brown Hancock’s organs, the gizzard of the same color behind the head shield, and the dark eyes are rec- ognizable in the drawing ofthe collector. In the preserved snail the head shield and parapodia are contracted forward, and the shell stands out behind. In front the jaw plates project from the mouth. The notch of the head shield is deepened. Under the head shield lie the inconspicuous transverse folds of the Hancock’s organs, whose hind ends are united by a fold over the back. On the right side runs the seminal groove; the penis is not developed yet. The sole is not set off from the parapodia; a trans- verse fold in its anterior Y is probably due to contraction. The general color of the preserved snail is brown, the di- gestive glandis green. The shell which lies on the mantle border is completely decalcified. The preserved conchinous layer, 1 mm long, shows a protruding sinistral larval shell of 1 whorl. The following dextral whorl] is widened tothe front and backward; the growth lines run parallel to the border, whose outer lip is slightly concave in the middle. The hind lobe beyond the larval shell is strong. The absence of spiral lines does not permit a judgment of the full grown Shell, in, e.g., Micromelo undata, the structure of the shell changes rather late. From the mantle border a lobe hangs over the mantle opening behind the gill. It corresponds to the “squamiform la- mella” of Acteon and Aplustrum (Per- rier & Fischer, 1911, p 26, 65), but is bigger. The inner side of the lobe bears cilia (zo), 40 u long, which are the be- ginning of the dorsal ciliated ridge, the “raphé supérieur” of Perrier & Fischer. The lower mantle lobe is smaller than in Acteon. The gill (К) is small. The jaw plates, about 100 u by 50 u, are composed of 8 to 10 rows of short pegs whose surfaces bear 3 to 6 short denticles at their broadest sides. The radula has 27 rows of teeth, and in the present young snail there are 4 lateral teeth on either side. The rhachidian tooth has a broad short cusp and a base widened toward the sides. The laterals are hooks without denticles; the inner- most and outermost are shorter thanthe 2 middle ones. The 3 brown gizzard plates measure 300 u by 140 u; they bear at least 21 straight ribs, each with one row of pointed spines. The connec- tives of the nerve ring are short. Remarks: Apart from the limitations of a decalcified shell, a snail so young cannot be classified beyond the genus. In Atys obovatus Bergh (1908a, p 156) the ribs of the gizzard plates bear MADAGASCAN AND MEXICAN GASTROPODS 185 Similar spines as in the present animal, but the ribs form an angle on the crest of the plate. In A. xarifae Marcus (1960a, figs. 9, 10) the ribs are straight and spiny, but less numerous than in the present, smaller specimen. Also, the smooth elements of the jaw plates dis- tinguish A. xarifae. The gizzard plates of A. naucum and A. cylindricus, both without spines, are very different from each other. Philinacea The genera of the Smaragdinellidae The name Ophthalmidae Bergh (1905a, p 35) cannot be applied to this family because this name is not derived from one of the genera of the family. Thiele (1931, p 387) used Cryptophthalminae, but Cryptophthalmus Ehrenberg, 1831, has been replaced by Lathophthalmus (Pruvot-Fol, 1931, p 748). In a list, Thiele (1925, p 265) mentioned Sma- ragdinellinae, and this name appears in Pruvot-Fol (1934, p 29), Habe (1952, p 144), Zilch (1959) and Marcus € Burch (1965, p 236). Pruvot-Fol (1934, p 30) is inclined to unite the 2 genera with internal shell, Lathophthalmus and Phanerophthalmus Adams, 1850. In Smaragdinella Adam & Reeve, 1848, the shell is mainly external (Fischer, 1887, p 557, 565; Pilsbry, 1893-1895, p 258; 1895-1896, p 36). The shell of Nona algiva (Hanley) is similar to that of the type species of Smaragdinella, but as it is internal, Nona cannot be a sub- genus of Smaragdinella. An internal shell may appear to be external, when the mantle is very thin (Eales, 1938, p 82, 83). In Phaneroph- thalmus there is no mantle foramen; the mantle foramen of Lathophthalmus varies in diameter without relation to age; and that of Aplysza varies with age (Eales, 1960, p 280). When it is large (Baba, 1936, p 5), the exposed shell looks like an external shell, partly em- bedded in the mantle (Vayssiére, 1912, p 8). In Ehrenberg’s figure of L. smar- agdinus (Pilsbry, 1895-1896, pl. 6, fig. 30) the mantle foramen shows when the parapodia are spread. Bergh (1901, p 235) examined 2 speci- mens from Ehrenberg’s collection with- out entering into the matter of the position of the shell. Previously (1900a, p 164) and later on (1901, p 301) he united 1 specimen from Mauritius and 1 from Fiji with Ehrenberg’s species and described an external shell over the mantle. These animals do not belong to Lathophthalmus, but possibly to Sma- ragdinella. Some years later Bergh (1905a, p 36, 39) observed the internal shell and the mantle foramen of Lathoph- thalmus, but did not correct his earlier statement. Evidently Thiele (1931, p 387) based his diagnosis of Cryptophthalmus upon Bergh’s first characterization of the genus (1900a). Therefore he called the shell for the most part external, and Hoffmann (1934, p 363) and Zilch (1959, p 44) repeated this. Lathophthalmus smaragdinus (Rüppell & Leuckart 1828) (Figs. 16-22) Lathophthalmus smaragdinus, Marcus, 1960a, p 886-890, figs. 14-25. Range: From the Red Sea to the Ryukyu and Marshall Islands. (The “Lathophthalmus” specimens of Bergh (1901, p 301), cited by Marcus & Burch (1965, p 238), do not belong to this genus.) According to the aforesaid, not Fiji Islands (Marcus & Burch, 1965, p 238). Collecting stations: Madagascar; xviii, xxvii, xxxiii, xliii, 25 snails. Description: The living snails were 20 to 22 mm long, 5 mm broad. The color is yellowish-green with fine dark spots. The rims of the head shield and parapodia are light bluish-green. In a photograph by Dr. Kirsteuer the black eyes and the yellow-brown pharynx are seen. The dark green digestive gland Shines through the integument. .The preserved snails are light olive witha greenish liver. 186 MARCUS AND MARCUS KEY TO LETTERING IN FIGURES ampulla albumen gland male atrium aorta anus ascus allosperm duct apex bursa copulatrix buccal ganglia strand of connective tissue cerebral ganglion head shield ventral ciliated ridge seminal duct pedal ganglion inhalant siphon hermaphrodite duct female aperture common genital opening gastro-oesophageal ganglion Hancock’s organ intestine digestive gland and its ducts inner oviduct gill mouth male aperture foliate stomach mantle foramen gland of mantle border female gland mass kidney nephroproct nidamental duct notal gland pharynx oesophagus oesophageal pouch osphradium opening of notal gland blood space ovotestis penis penial appendage prostate retractormuscle radula rectum rhinophore oral tube salivary gland spermatocyst gland of spine stomach seminal groove spine sac with spine spermatheca buccal gland thin part of male duct sheathed part of male duct blood gland vagina vestibulum anterior border of foot seminal receptacle accessory prostate vestibular gland eye hyponotal glands hyponotal pore perinotal glands transverse fold dorsal ciliated ridge ductule of hyponotal gland MADAGASCAN AND MEXICAN GASTROPODS 187 FIGS. 1-9. Coriocella nigra. Fig. 1, Side view of living snail, from sketch by Dr. E. Kir- steuer. Fig. 2, Dorsal view of preserved snail. Fig. 3, Dorsal view of living snail, from sketch by Dr. E. Kirsteuer. Fig. 4, Ventral view of fore end. Fig. 5, Anterior part of body with opened mantle cavity. Fig. 6, Radular teeth. Fig. 7, Penis and seminal duct. Fig. 8, Jaw plate. Fig. 9, Shell. FIGS. 10-15. Atys species, juvenile. Fig. 10, Living snail, from sketch by Dr. E. Kir- steuer. Fig. 11, Shell. Fig. 12, Jaw elements. Fig. 13, Gizzard plate. Fig. 14, Transverse section of opening of mantle cavity. Fig. 15, Radular teeth. 188 MARCUS AND MARCUS In life the head shield is slightly notched in front and has 2 short lobes behind; the eyes are equally far from the anterior border and from each other, but nearer to the sides. The border of the left parapodium is covered by the right one. The body is narrowest at the beginning of the parapodia, widest near the hind end. The skin is smooth, the sole not set off. In the preserved specimens the bor- ders of the parapodia touch each other. Under the head shield (cs), but standing out behind are the Hancock’s organs (h), which consist of 18 vertical leaves. Their wavy upper borders are united by a transverse fold (zm) behind the head shield. In the anterior part of the back the silky fibers of transverse muscles are seen. The hind part bears the shell, covered by the mantle and decalcified by preservation in Bouin’s fluid. The mantle aperture (mo) is of different widths, generally round, but sometimes triangular. The shell of a 6 mm snail measures 2.4 by 1.5 mm. The some- what curved apex lies to the left near the middle. The growth lines runparal- lel to the right border, whose tip pro- jects into the right mantle lobe. The crescent-shaped jaw plates con- sist of short thick elements whose tips each bear 2 to 3 strong points on their broader sides. The radula has 38 rows of 14.1.14 teeth. The rhachidian tooth has a single cusp and is broadest at its base; all laterals are blunt-ending hooks, the outermost the smallest. The black- ish-brown gizzard plates are 780 u long. They have about 100 ribs, up to 10u broad, bearing a row (sometimes 2 rows) of pointed denticles. From the seminal groove (sr) a closed male duct, more than 12 mm long, runs inwardly. Its innermost glandular tube, the prostate (q), is 2.5 mm long and contains sperm. Outwardly it follows as a sheathed muscular tube (um), which extends to the left until under the shell. A portion only 24 y thick (ui) leads to the penial sac, which is 1.3 mm long and through which the male duct courses as a groove between 2 high folds. Remarks: Only in the original ma- terial (Bergh, 1901, p 235) and in the present specimen are described the thin duct between the penial sac and the inner parts. Dissected reproductive or- gans, clarified ones, and those described by reconstruction from sections often result in rather different descriptions and alone do not justify specific separa- tion. The length of the median cusp of the rhachidian tooth, small (Bergh, 1901, pl. 19, figs. 31-33) or great (Baba, 1936, fig. 1 C, a) depends upon the position on the slide (cf. figs. 18 and 19). The sharp borders of a pit in the base of the rhachidian tooth simulate lateral den- ticles of the cusp (Bergh, 1905a, pl. 10, fig. 12; Marcus, 1960a, fig. 19). The greater size of Ehrenberg’s animals (Pilsbry 1895-1896, p 37) explains the large number of radular teeth (Bergh, 1901, p 236), greater than in Vays- siere's (1912), Baba's (1936), our first (Marcus, 1960a) and the present speci- mens. Smaragdinella kirsteueri, new species (Figs. 23-27) Collecting stations: Madagascar; xxxi, xxxii, 2 specimens. Diagnosis: The dark green-brown animals, up to 40 mm long, differ from the congeneric species by the short, posteriorly notched head shield, the denticulate jaw elements, and details of the radula. Holotype and paratype: AMNH (American Museum of Natural History) 140583. Description: The living snails were 35 to 40 mm long, 9 to 10 mm broad, and uniformly dark green-brown with greyish-yellow shell. The surface of the parapodia of the perserved speci- mens is smooth. The head shield is short, in life slightly notched in front, bilobed behind. The border of the right parapodium covers the left, even when preserved. The large eyes are visible only after dissection; the sole is not set off. The Hancock’s organs consist of MADAGASCAN AND MEXICAN GASTROPODS 189 24 complete and several incomplete folds; they are united behind as in the preceding species. The head shield oc- cupies about '4 of the body length in life, the shell 14. Between both lies a stripe of the back, 6 mm long, with dis- tinct transverse muscle fibers. The shell of the larger specimen is completely decalcified; only in the smaller snail are its size (5 to 3.1mm), position and approximate shape discern- ible. The shell lies free on the roof of the mantle, whose border is thickened by glands. The growth lines are parallel to the right shell border. The border is rolled in slightly near the middle on the left side, and a little wider in front than behind. If it had an inner columel- lar process, this would not be recog- nizable in the decalcified shell. The hind border of the mantle is prolonged into a short lobe on the right. The jaw elements are thick columns, up to 80 y high, with a surface 40 y by 25 u, whose narrow border bears 1 to 3 pointed denticles. The radula of the larger specimen has 57 rows and 37 teeth on either side of the rhachidian tooth. The latter measures 30 u by 30 u, is a little narrower basally, and has a denticle on the sides of the cusp, at least simulated by the structure of the tooth. The bases of the uniform lateral teeth measure 50 u to 60 u and are rough in the inner half of the row. The cusp of the lst tooth is 50 long, the following ones increase to 80 u, out- wardly they decrease to 30u on the outermost tooth. The 3 equal gizzard plates, 2.7 to 1.6 mm long, bear numer- ous ribs, which are 28 y broad, with several rows of knobs. The ribs are angled at the crest andinclined obliquely backwards. The male copulatory organ, 7.2 mm long, extends backwards beyond the nerve ring. From the seminal groove a 2 mm tube courses inwards and widens (p) to a folded sac, 1.5 by 1.0 mm. On the bottom of the sac inserts a thick re- tractor muscle (r); a thin one inserts at the entrance of the tube. Entally to the sac follows a thin connecting tube, 2 mm long, to the glandular prostate (q), 1.7 by 0.65 mm, which contains sperm. The species is named for the collec- tor, Dr. Ernst Kirsteuer. Remarks: The head shield of Sma- vagdinella calyculata (see Marcus & Burch, 1965, p 237), its mandibular rod- lets and male organ are different from the present species. Also the radula (ibid., fig. 4) is different, but cannot be used as distinctive character, if the sy- nonymy (¿bid., р 236) is adopted. Risbec’s Smaragdineila viridis (1951, p 139) differs from S. kirsteueri mainly by the jaw elements, rhachidian tooth, and especially by the large shell; S. andersoni (see Pilsbry, 1893-1895, p 260) differs by the shape of the shell. Pilsbry called the parapodia of this species expansions of the mantle; Habe (1952, p 146) united the species with the unfigured S. sieboldi Adams, 1864. Bergh’s Cryptophthalmus olivaceus (1900a, p 164) from Fouquets Reefs, with an external shell (hence not Ehren- berg’s species, but probably a Smarag- dinella), is similar to S. kirsteueri in the body size, measurements of the Shell, formula of the radula and per- haps jaw platelets. Differences are the indistinct Hancock’s organ and the rounded, hardly notched hind end of the head shield. The rhachidian tooth and the male organ of Bergh’s animals were not described. Philine species, juvenile (Fig. 28) Collecting station: xxvii, 1 snail. Description: The living animal mea- sured 3 by 1 to 1.5 mm andwas whitish- yellow with the brownish liver shining through the skin. The strongly short- ened head shield gives the preserved snail an odd appearance; its shell is decalcified. The radula has 13 rows of 2.1.0.1.2 teeth. The inner lateral tooth has a strong outer process and about 18 pointed denticles on the inner side. The 2 marginals are smooth hooks Madagascar; 190 MARCUS AND MARCUS whose cusp is larger than the base. The outer marginal is smaller than theinner one. There are no gizzard plates; the muscle layer of the gizzardis thickened. A penis is not yet developed. Remarks: We only know Philine cale- donica Risbec (1951, p 134) as an Indo- Pacific species of the genus without gizzard plates and with a radula of the same type as the present specimen. Its inner lateral tooth is, however, much broader (loc. cit., fig. 8) than that shown in our Fig. 28. As our specimen has no shell remaining, we cannot com- pare it with the Atlantic P. (Ossiania) quadrata, also without gizzard plates and with the same radular formula. Chelidonura Adams 1850 The 2 genera of the Aglajidae with elongated head shield and long mantle lobes, Chelidonura and Navanax Pilsbry, 1895, should be united (Bergh, 1905a, p 42). As in Aglaja, the shell can be used only for the separation of the spe- cies. The cephalic sense organs of Chelido- nura and Navanax are of the same type. On either side of the mouth there isa protrusible thickening beset with many tufts of cilia. In most cases the thick- ening is vertically bipartite, so that an outer, sometimes larger knob and an inner one are formed (Marcus, 1955, fig. 8). In preserved slugs the thick- ening is often retracted and hidden under the head shield, so that the bipartition and the size of the knobs are difficult to judge. If they can be analyzed they are useful specific characters. The long and smooth penis papilla, considered as a generic character of Navanax (Marcus, 196la, p 8), occurs also in certain species of Chelidonura. Chelidonura punctata Eliot 1903 (Figs. 29-31) Chelidonura hirundinina var. punctata Eliot, 1903c, p 336, pl. 13, fig. 2. Range: Zanzibar. Collecting station: Madagascar; xxxi, 1 specimen. Description: The living snail was 40 to 45 mm long, 8 to 10 mm broad, bluish-black with scattered brown- orange spots of different size on the head shield, back, parapodia and under side. The head shield, parapodia and caudal lobes have a very narrow white rim. Also the seminal groove is white. The tail lobes are pointed. To the sides of the mouth the inner and outer knobs are beset with tufts of sensory cilia. The Hancock’s organs are only a row of pits. The shell, 7 by 4 mm, is nearly as long as the mantle shield. Its front part is shivered; around the aper- ture it is solid and silvery. The right border of the outer lip penetrates into the right tail lobe. Between the outer lip and the apex there is a deep sinus. The columella has a thick callus which is obliquely furrowed. When the animal is opened ventrally, the foremost organ is the white foot gland, 2 mm long. Its surface is rough, the hind border slightly notched. Dorsal to the foot gland lies the small pharynx, 2.5 by 1.5 mm, with the cerebral ganglia apposed to its hind end. To the right is situated the male organ, 2.2 mm long. The peritoneum is stippled with me- lanophores. The penis corresponds to “type 2” of Aglaja (Marcus, 1966, p 165). The seminal groove enters the atrium. Two slightly lobed prostatic tubes of differ- ent length go out from the bottom of the atrium. Between them there is a small lobe of the large cells. The pointed penial papilla is broad at its base and projects into the atrium. Remarks: Quoy & Gaimard’s original material of Chelidonura hivundinina (1833) was not uniform in color and pat- tern (Pilsbry, 1895-1896, p 35; Pruvot- Fol, 1934, p 29). Therefore, striped and spotted snails were classified as C. hirundinina (Pilsbry, 1895-1896, pl. 2, figs. 31, 32) or called var. elegans and var. punctata (Bergh, 1900b, p 213). The MADAGASCAN AND MEXICAN GASTROPODS 191 penes of the species of Chelidonura should be better known before such combinations can be justified. The penis of C. punctata differs from that of C. elegans, and also from that of west Atlantic animals which we previously determined as hirundinina (due to their agreement with Baba's figures (1949, pl. 2, fig. 4; 1958, frontispiece)). Baba € Abe (1959, p 280) stress the similarity of their Chelidonura tsuru- gensis with C. punctata, but the sole of the Japanese species has no spots, and the parapodia are not rimmed. The short right tail lobe is rounded in all specimens of С. tsurugensis. The head shield bears a triangular white area on either side of the midline (Abe, 1964, ply 2; tig): Chelidonura inermis (Cooper 1862) Navanax inermis, Marcus, 1967, p 149, fig. 11. Range: From Monterey Bay to the Gulf of California. Collecting station: Mexico; iv, Dec. 26, 1966 (Paula Vreeland), 1 specimen. Remarks: Alive the animal was 30 mm long. The bluish-grey under side of the photograph shows golden yellow dots. In part these are still recogniz- able in the preserved specimen, whose back has dark streaks. Anaspidea Aplysia (Pruvotaplysia) parvula Mörch 1863 Aplysia (Pruvotaplysia) parvula, Eales, 1960, p 287-291, figs. 10-11. Range: In all warm and warm-tem- perate seas, from about latitude 40° N to 40° $; not in the Mediterranean. Collecting stations: Madagascar; xxix, 1 specimen. Mexico: ii, Nov. 12, 1966 (Paula Vreeland), algae on rocks in the inter- tidal zone, 1 specimen. Remarks: The living animal from Madagascar was 8 to 10 mm long and 3 to 4 mm broad. It was dark green with whitish-yellow spots and yellow tips of the tentacles and rhinophores, and dark brown rings around the eyes. The para- podia are rimmed with dark brown and joined high up. The specimen from the Gulf was 18 mm long when living, colored reddish- brown with whitish blotches. The para- podia were rimmed with dark blue. The tips of the light outer parts of the ten- tacles and rhinophores were blue. Dolabella auricularia (Solander 1786) (Fig. 35) Dolabella scapula, Engel, 1942, p 199, 207-234, figs. 6-16. Dolabella auricularia, Marcus, 1965, p 266. Dolabella californica, MacFarland, 1966, p 32-37, pl. 6, fig. 14, pl. 8, figs. 26-32, pl. 9, figs. 13, 14. Range: Indo-Pacific, from the Red Sea to Japan, Easter Island, Ecuador and the Gulf of California. Collecting stations: Madagascar; xxvi, 1 specimen. Mexico: iv, Dec. Vreeland), 1 specimen. Remarks: The snail from Madagas- car was 100 mm long alive and 50 to 60 mm broad. It was green-brown with lighter and darker spots and whitish grey, mottled borders of the parapodia. The parapodia are beset with short, pointed papillae. The Californian specimen was 95 mm long and had green spots similar to MacFarland’s specimen 26. 26, 1966 (Paula Dolabrifera dolabrifera (Rang 1828) Dolabrifera dolabrifera, Engel, 1936, р 29-43, fig. 16; Kay, 1964, p 184, 185. Range: Circumtropical and circum- subtropical, but not recorded yet from the American Pacific coast. Collecting station: Madagascar; xviii, 3 specimens. Remarks: The largest specimen was 40 mm long alive, 12 to 15 mm broad. 192 MARCUS AND MARCUS The ground color was a light green- brown, the border of the foot whitish- grey. On the back there were whitish- grey papillae and dark brown spots. Stylocheilus longicauda (Quoy & Gaimard 1824) Stylocheilus longicauda, Engel, 1936, p 57-72, figs, 24-43; Kay, 1964, p 182-184, pl. 8, fig. 4; Marcus, 1967, p 159, figs. 16, 17. Range: Circumtropical. Collecting stations: xxxvi, 5 specimens. Mexico: iv, Dec. Madagascar; 26, 1966 (Paula Vreeland), rocks, intertidal zone, 1 specimen. Remarks: The preserved slugs from Madagascar are up to 22 mmlong. They have wart-shaped and ramified papillae, black streaks and the ocellar spots vis- ible as white dots, as in Engels ma- terial from Barbados Reef (1936, p 61). In the hind gizzard we found only 3 cuticularized warts. The Mexican specimen was 14 mm long, 10 mm high and 9 mm broad when alive. It has the longitudinal streaks and ocellar spots which distinguish the species fromStylocheilus citrinus (Rang, 1828, p 71; Marcus, 1962b, p 16, 1967, p 40). Radula, gizzard plates and penial spines do not furnish clear-cut diagnos- tic characters. Ascoglossa Stiliger (Stiliger) erbsus, new species (Figs. 32-34) Collecting station: xxii, 1 specimen. Diagnosis: Small, whitish-yellow, with green granules in the liver branches, the hind ends of which anastomose. In the cerata the hepatic diverticula are unbranched. Holotype: AMNH 140585. Description: The slug was 3 mm long and 1 mm broad when alive. The main liver stems are slightly ramified. The anterior foot border, lips and rhino- phores are whitish and transparent; on the rhinophores there is а dorsal stripe of graphite-black. Further skin pigments Madagascar; are a dark brown irregular middorsal area, and melanophores between the cerata and the foot border. The preserved animal measures in mm: length 2.5, breadth 0.55, tail 0.4, rhinophores 0.5, longest cerata 0.5, distance between the eyes 0.25; diam- eter of eyes 0.05. The cerata stand ina row on either side, about 12 large and many small ones. The head stands out over the thick lips. The rhinophores are blunt, round in transverse section, and narrowed at the base. The anterior foot border is notched, with short and round lateral angles. Two transverse folds of the sole are probably produced by contraction. The border of the sole is distinctly set off from the sides. The tail is limited by an anastomosis of the liver branches between the hindmost cerata. The blunt cerata contain an un- branched hepatic diverticulum, but no tube of the albumen gland. Large sub- epidermal gland cells, especially near the tip of the cerata, are irregular, not arranged in stripes. The short pharynx lies between the eyes. The anus is situated in the midline in the anterior part of the pericardial eminence, which extends to the middle of the body. The short penial stylet is curved. The radula has about 6 teeth in the ascending limb, 6 in the descending limb, and 4 smaller ones heaped in the ascus. The teeth are 104 u long, the base 39 u; the tip is broad and round. The upper side of the tooth is bipartite by a pit, the borders of the hollow under- side are smooth, even when viewed with high power. Remarks: Stiliger erbsus differs from all other species of the genus. Avoiding a discussion of the synonymy of the European species, we mention only the Indo-Pacific ones. Those of the subgenus Ercolania Trinchese, 1872, differ from the new species by their rhinophores flattened or grooved on the outer side. These species are: S. (E.) akkeshiensis Baba (1935a, p 116); S. (E.) illus Marcus (1965, p 267); S. (E.) MADAGASCAN AND MEXICAN GASTROPODS 193 а 106 20 FIGS. 16-22. Lathophthalmus smaragdinus. Fig. 16, Living snail, from color photo. Fig. 17, Jaw elements. Fig. 18, Radular teeth. Fig. 19, Rhachidian tooth of other specimen. Fig. 20, Ribs of gizzard plate. Fig. 21, Male duct in situ. Fig. 22, Male duct. 25 (VS J соо a = ES, GE FIGS. 23-27. Smaragdinella kirsteueri. Fig. 23, Living snail, from sketch by Dr. E. Kir- steuer. Fig. 24, Jaw elements. Fig. 25, Radular teeth. Fig. 26, Three ribs of the gizzard plate. Fig. 27, Male duct. FIG. 28. Philine species, juvenile. Radular teeth. FIGS. 29-31. Chelidonura punctata. Fig. 29, Living snail, from color photo. Fig. 30, Male duct. Fig. 31, Shell. FIGS. 32-34. Stiliger erbsus. Fig. 32, Preserved slug. Fig. 33, Penial stylet. Fig. 34, Radular teeth. FIG. 35. Dolabella auricularia. Living snail, from sketch by Dr. E. Kirsteuer. 194 MARCUS AND MARCUS noto Baba (1959, p 330); S. (E.) smarag- dinus Baba (1949, р 32, 129); S.(E.)van- couverensis (O’Donoghue, 1924b, p 19); S. (E.) zanzibaricus (Eliot, 1903a, p 256); and S. (E.) zosterae Baba (1959, p 331). Among the Indo-Pacific species with round rhinophores, the following species differ from Stiliger (S.) erbsus by a branched or lobed hepatic diverticulum in the cerata: 5. (S.) boodleae Baba (1938, p 129), S. (S.) evelinae Marcus (1959, р 22), 5. (S.) gopalai Rao (1937, р 435), 5. (S.) nigrovittatus Rao € Rao (1963, р 232), S. (S.) pica Anandale & Prashad (1922, р 700) and $. (S.) varians Eliot (1904, p 290). Stiliger varians, it is true, has longitudinal lines on the cerata (Eliot, 1903b, pl. 32, figs. 9, 10), not hepatic branches. Such lines also distinguish S. (S.) subviridis Baba (1959, p 328) from S. (S.) erbsus. The location of the anus in front of the pericardial hump, or behind it, separates Stiliger (S.) fuscovittatus Lance (1962, р 32) and $. (S.) felinus Hutton (Eliot, 1907, p 330) respectively from S. (S.) erbsus. In Stiliger (S.) berghi Baba (1937, p 222) 7 to 9 large and small cerata al- ternate on either side; in 5. (S.) irregu- lavis Eliot (1904, p 291) and S. (S.) pusillus Baba (1959, p 328) the hindmost cerata are the largest. Stiliger (S.) ornatus Ehrenberg, 1831, (not modestus (Bergh, 1872, p 139; 1878a, p 812)) and S. (S.) viridis (Ke- laart, 1859, p 492; Eliot, 1906, p 686, pl. 46, fig. 3) differ from S. (S.) erbsus by the great number of cerata. Prolonged anterior foot corners occur in Stiliger (S.) formicarius Baba (1959, p 329) [later transferred to Costasiella] and in S. (S.) tentaculatus Eliot (1917, p 179) [ of doubtful generic position]. Stiliger viridis (Kelaart, 1859) has priority over the Mediterranean S. vi- ridis (A. Costa, 1866), whose first syno- nym, nigrovittatus, must replace viridis. Therefore, S. (S.) nigrovittatus Rao € Rao, 1963, must be renamed. There- fore, we introduce the new name, S. (S.) yaovum. Elysia vreelandae, new species (Figs. 36-40) Collecting station: Mexico; ii, Nov. 12, 1966 (Paula Vreeland), on Codium, 4 specimens. Diagnosis: A small, dark olive-green species with lighter borders of the para- podia and blue dots. The hepatic tubes are very thin near the stomach. Epi- thelial tubules form a penial appendage. There is a Single female aperture. Holotype and paratype: AMNH 140586. Description: The animals were about 10 mm long when living; preserved they are up to 8 mm. A preserved animal with almost fully spread parapodia is 7 mm long, 5 mm broad. The color is dark olive-green with lighter borders of the parapodia and the blue dots. A colorless crescent around the posterior border of the pericardial hump lies over the white kidney. Farther behind, the back is yellowish-brown in color. The small hepatic terminations containing the chloroplasts of the alga form a dense pattern on the head, neck and outer side of the parapodia; on the inner side they are coarser and less ramified. The inner side of the rhinophores (ri) and a minute halo around the eyes (y) are white, the sole is only alittle lighter than the outer side of the parapodia. Two longitudinal vessels run along the back. A single melanophore lies on either side of the mouth. The pharynx (nx) is very small, 400 u by 400 u. The radula has 8 teeth in the dorsal limb, 14 in the ventral limb, and many heaped up in the ascus (as). The teeth are up to 120 y long, their furrow is 80 u, the base 34 y; 10 u embrace 6 of the small denticles. The short oesophagus (0) bends to the left, bears a muscular pouch (oc) and passes gradually to the stomach (so). The oesophagus and the cardia are wide dorso-ventrally, andthe stomach is wide antero-posteriorly, even when empty. The epithelium of the oesophagus, pouch, and stomach is cili- ated; the cilia in the stomach are es- MADAGASCAN AND MEXICAN GASTROPODS 195 pecially strong. The digestive gland (ia) has 6 ducts. The foremost duct supplies the head and enters the rhinophores; it opens far in front into the ventral wall of the stomach. The following 3 ducts come from their regions in front and on the right side, bend to the left, and turn to the stomach. The hindmost ducts course over the borders of the sole and open into the stomach from both sides. The hepatic tubes are very thin near the stomach, widen in the middle and de- crease in width, again peripherally where they touch the skin. The stomach narrows gradually into the intestine, which is 100 long. The anus (ar) lies between the right parapodium and the pericardium. The female germ cells occupy the ental half of the hermaphrodite follicles (ov); the male cells occupy the ectal part. The ciliated ampulla (a) lies about in the middle of the hermaphrodite duct (eu). The seminal duct (d) and the inner oviduct (io) receive the more central prostatic (q) and the more lat- eral albumen gland (ag) tubes, respec- tively. The crowded prostatic cells are claviform with homogeneous secretion; their diameter is 15 to 20 u. The al- bumen gland cells measure about 25 u. and contain granules measuring 6 u. The deep male atrium (am) is ¡bent backwards and contains the conical penis (p), 3 times as long as broad. Epithelial tubules form a possibly glan- dular appendage (pg) in front, at the root of the penis. The male aperture (ma) lies under the right rhinophore (ri). Clusters of glands open between the cells of the inner oviduct (io). This part corresponds to a membrane gland (Ghiselin, 1965, p 337). Where the ovi- duct passes into the mucus gland (mu) there are some small pouches (vs) with sperms not fastened to the wall. They correspond to a seminal receptacle. The low epithelium of the mucus gland has long cilia and invaginated saccules of glands which make the surface bram- bly. The vaginal duct leading to the bursa copulatrix (b) goes out from the nidamental duct (ni). The single female aperture (fa) lies 1 mm behind the male pore, the anus (ar) 100 u behind it, and the renal pore (ne) still farther behind and farther dorsal. The species is named for the collec- tor, Mrs. Paula Vreeland. Remarks: The atrial diverticula of Elysia lobata (Marcus, 1958, fig. 40, 3), E. maoria (Reid, 1964, figs. ТА, В, а), and E. hedgpethi (Fig. 41) are farther behind than that in E. vreelandae. Elysia hedgpethi Marcus (1961a, p 13) ranges from the State of Washington to the Gulf of California (Lance, 1966, p 71). It is up to 29 mm long when pre- served. Its penis is twice as long as broad, with a diverticulum near the inner end of the atrium. The openings of the vagina and the oviduct are far apart. Elysia bedeckta MacFarland (1966, p 50) from Monterey to Newport Bay is synonymized to E. hedgpethi by Sphon & Lance (1968: 79) though it dif- fers slightly by the position of the vagi- nal pore close to the male aperture and the anus on the right anterior side ofthe pericardial hump. The teeth of E. be- deckta reach 330 y, those of E. hedgpethi, 170 y. The mentioned characters sepa- rate E. hedgpethi from E. vreelandae. Notaspidea Berthellina cuvieri (Bergh 1898) (Figs. 42-48) Pleurobranchus cuvieri, Bergh, 1898, p 129-131, pl. 11, figs. 19-27. Range: Mauritius; possibly Ceram. Collecting stations: Madagascar; xi, xiii, xiv, xvi, xix, xliii, 7 specimens. Description: The animals were 35 to 40 mm long when alive, 15 to 17 mm broad, and uniformly light orange. The veil, and the membrane which unites the rhinophores at half their length, were transparent. The snails measure 13 to 19 mm when preserved; the longest is 14 mm high and 13 mm broad. The mantle border is rolled in, the foot border wavy. In the smooth, gelatinous 196 MARCUS AND MARCUS notum lie opaque, invaginated epidermal glands (up to 0.5 mm long) in different stages, as in Berthellina granulata (Hill, 1963, fig. 1). We found neither spicules nor organic traces of such; some sponge spicules stuck in the skin. The shell measurements in mm are: 9 by 5.5 (body 13 mm); 5.5 by 2 (body 14 mm); 8.5 by 5 (body 15 mm); 6 by 2.5 (body 16 mm); 6.5 by 2.4 (body 19 mm). The growth lines are distinct. The spiral sculpture consists of rows of dots which do not reach the anterior border; on the shell of snails 13 to 16 mm long, it extends over Y, of the shell, in the 19 mm specimen over /,. The fact that a small snail had the biggest shell is fortuitous. The periostracumis colorless. The furrowed anterior foot border, the veil and the rhinophores show no peculiarities. The last quarter of the gill is free. Animals of 15, 14 and 19 mm have 20, 24 and 26 branchial leaves, respectively. The jaw plates are 3.5 by 1.5 mm (14 mm snail) and 4.5 by 2 mm (15 mm snail). The elements (80 u by 22 ı) are generally unicuspidate, but sometimes they have a secondary point on one or both sides of the cusp. The radulae of a 14 mm and a 15 mm snail measure 3.5 by 3.2 mm and 3.33 by 3.33 mm, re- spectively. They have 80 and 90 rows, 150 and 200 teeth per half-row, respec- tively. The largest teeth are 180 u and 170 u long, respectively. The teeth of both specimens have 12 to 19 denticles; the innermost teeth have the fewest denticles, those in the middle the great- est number of denticles. On the outer teeth the denticles are longest. At the outlet of the long and narrow ampulla (a), filled with sperm, the sperm- oviduct divides into an inner oviduct (io) and a seminal duct, which is glandular at its beginning (q). The acinous pros- tate is apposed to the spermatheca (t). Into the succeeding part of the male duct there opens a coiled, glandular tube, the accessory prostate (xs). The heavily muscular seminal duct (d) enters the male atrium (am), dilated by a strong penial papilla (p). A retractor muscle (r) inserts at the bottom of the atrium. Beside the male aperture (ma) lies the wide opening (fa) in common for vagina (v) and nidamental duct (ni). The vagina leads into the soft spermatheca (t) containing black residues of sperm and prostatic secretion. From the va- gina a thin duct courses to the sperma- tocyst (sc) full of orientated sperm. The wall of the spermatocyst is con- nected with the mucus gland by a strand of connective tissue, whose position cor- responds to an allosperm duct (perhaps it is a rudimentary duct). Remarks: Vayssière’s Berthellina brocki (1896, p 120; 1898, p 256) and Bergh's B. cuvieri are from the same locality and collection, but Vayssiére’s name and description refer also to specimens from Amboina, Java, and New South Wales, Jervis Bay. Later, its range was extended to Easter Island (Odhner, 1921, р 248). The reproductive organs of B. brocki agree with those of our animals, while they are incompletely known for B. cuvieri. The spiral shell sculpture reaches the anterior border in brocki, but not in the present mater- ial. Possibly Vayssiére’s specimens from Jervis Bay are identical with Pleu- robranchus punctatus Quoy € Gaimard, 1832, (Pruvot-Fol, 1934, p 34, 35). Therefore, Macnae (1962a, p 172) called his snails from Madagascar and south- ern Mozanbique Berthellina punctata. The position of the prostate and the allo- sperm duct in Macnae’s figure differ from our Fig. 48. Burn (1962, p 138) united Berthellina brocki, B. punctata and other species with B. citrina (Rúppel € Leuckart, 1828). In living animals of this species the cutaneous glands produce areticula- tion of the notum, but not always, see Gohar & Abul-Ela, 1957, pl. 1. The spiral sculpture reaches the anterior border of the shell. The jaw elements are short and have 1 or several secon- dary cusps (Vayssiére, 1906). The ra- dula comprises 60 rows and up to 140 MADAGASCAN AND MEXICAN GASTROPODS 197 FIGS. 36-40. Elysia vreelandae. Fig. 36, Diagram of digestive tract. Fig. 37, Ramification of liver on back of animal. Fig. 38, Radular tooth. Fig. 39, Ramification of liver on inner side of parapodia. Fig. 40, Diagram of reproductive organs. FIG. 41. Elysia hedgpethi. Penis. 47 FIGS. 42-48. Berthellina curieri. Fig. 42, Head of living snail, from color photo. Fig. 43, Notal skin, preserved. Fig. 44, Shell of 13 mm animal. Fig. 45, Shell of 16 mm animal. Fig. 47, Tips of radular teeth. Fig. 48, Diagram of reproductive organs. 198 MARCUS AND MARCUS teeth per half-row. The teeth are up to 160 u long (Gohar, 1957); their denticles are coarser than in B. brocki (Vays- siére, 1898, p 260). Though the repro- ductive organs of animals called B. citrina (Risbec, 1951, fig. 14, 2; Burn, 1962, fig. 3) agree with our Fig. 48, we consider it premature to use this name for the present specimens. Eudoridacea Conualevia marcusi Collier & Farmer 1964 (Fig. 49) Conualevia marcusi Collier € Farmer, 1964, p 381-383, figs. 1, C-H, pl. 2 on p 386. Range: Gulf of California, west coast of northern part. Collecting station: Mexico; ii, Nov. 12, 1966 (P. Pickens), rocky intertidal, 1 specimen. Descriptive notes: The preserved slug is 8 mm long; alive it was 16 mm long. The body and the rhinophores are white, the 16 unipinnate gills retracted. The notum is finely papillose with opaque glands to the sides of the gills and farther in front. There are no ridges around the rhinophoral and bran- chial pits. The rhinophores are quite smooth, the stout tentacles rectangular. Translucent bundles of muscles produce striae in the hyponotum. No spicules are recognizable. The radula consists of 42 rows and 59 teeth per half-row. The teeth are simple hooks up to 60 u high. Their aspect depends on their position on the slide. For further infor- mation on the alimentary and reproduc- tive organs, we refer to the original paper (Collier & Farmer, 1964). Remarks: The present slug has fewer rows and teeth in the radula than the original diagnosis. But as Collier and Farmer counted only 1 of their speci- mens, the taxonomic value of this dif- ference cannot be judged. Chromodoris quadricolor (Rúppell € Leuckart 1828) (Figs. 50-53) Chromodoris quadricolor, Marcus, 1960a, p 899-901, fig. 42. Glossodoris quadricolor, Engel € van Eeken, 1962, p 23, 24, fig. 1; Engel € Nijssen-Meyer, 1964, p 27-32, figs. 1-5, color plate, figs. 1-3. Range: Red Sea; Indo-west Pacific, from the east coast of Africa to New Caledonia; possibly (Engel € Nijssen- Meyer, 1964) also Japan, Hachijojima and Sagami Bay (Baba, 1949, p 140). Collecting station: Madagascar; xxxi, 1 specimen, together with Hypselodoris regina (Figs. 54-59). Remarks: The living animal was 40 to 50 mm long, 8 to 10 mm broad, orange with 3 bluish-black longitudinal dorsal stripes bordered with whitish- blue, and a white rim around the notum. The tentacles are yellow and the 8 uni- pinnate gills are reddish-orange. On the sides of the foot there are 2 black lines. The salivary glands are long tubes with pointed ends. Our Figs. 52, 53 and 57, 58 show the differences be- tween the labial armatures and the ra- dular teeth of Chromodoris quadricolor and Hypselodoris regina, respectively. Chromodoris norrisi Farmer 1963 Chromodoris norrisi Farmer, 1963, p 81-84, figs. la-le, pl. 1a; Marcus, 1967, p 170, figs. 21-24. Range: Pacific coast of Baja Cali- fornia; Gulf of California, western and eastern coasts. Collecting station: Mexico; iii, July 30, 1966 (A. Kerstitch), rocky inter- tidal, 3 specimens. Remark: The present slugs have the same color pattern as the type speci- mens. MADAGASCAN AND MEXICAN GASTROPODS 199 Hypselodoris regina, new species (Figs. 54-59) Collecting station: Madagascar; xxxi, 1 specimen together with Chromodoris quadricolor (Figs. 50-53). Diagnosis: This is a species of Hyp- selodoris of the H. semperi group with straight stripes, similar to H. nigro- striata (Eliot), whose stripes are сигуеа and branched. Eliot’s species is much smaller than H. regina, has more gills and radular rows, but fewer teeth per half-row. Holotype: AMNH 140582. Description: The living slug had an orange back with 3 bluish-black longi- tudinal stripes bordered with light blue and not raised. The pattern of light blue and black is shown in the Figs. 54- 56; the rhinophores, gills and tip of the tail are orange. Only brown bands and the orange color were retained in the preserved specimen (August 1967). The measurements in mm were: alive, 40 to 50 mm long, 8 to 10 broad, preserved, 22 long, 7 broad, 9 high. The notal border is broad in front, narrow on the sides and behind, and has many globular glands, increasing in size backwards. The tentacles are short and grooved on the outer side. The bilabiate foot bor- der is not notched. The rhinophores have 14 leaves; there are 7 unipinnate gills. The labial rodlets are up to 60 y high, 9 „in diameter, unicuspidate or with 2 slight secondary cusps. The radula has 62 rows, a narrow naked rhachis, and 90 teeth per half-row. The teeth are bicuspidate, the innermost is tricuspi- date by a strong inner and an outer den- ticle. Up to tooth 75, the outer denticle gradually moves downwards; farther to the side the teeth decrease in length, the cusps become blunt and the ventral border nodular. The salivary glands are flat with a broad middle portion and a pointed end. The ampulla (a) is spherical, the spermoviduct is long; the seminal duct begins tubular, then forms a broad, flat, coiled prostate (q) more than twice as” long as the following muscular section (d), which ends with an acrembolic, unarmed penis (p). Beside the penis open the vagina (v) and the nidamental duct (ni) independently; there is no vestibular gland. From the wide vagina 2 canals of equal length go to the spermatheca (t) and the spermatocyst (sc). At the same point begins the long, winding allosperm duct (au). Remarks: According to its teeth, Hypselodoris vegina belongs to Eliot’s first group (1904, p 385), whose species are generally spotted. H. nigrostriata (Eliot 1904, p 394; 1905, p 247) is striped, but differs from HA. regina by color pattern and teeth. Eliot’s Chrom- odoris ?magnifica Quoy € Gaimard, var. (1904, p 397) is not Quoy and Gaimard's species, now united with C. quadricolor (Pruvot-Fol, 1934, p 72), but a Hypselo- 40715. It differs from H. regina by the radular teeth with 3 to 5 denticles under the terminal cusps, as in H. hilaris (Marcus & Burch, 1965, fig. 26). Atagema osseosa (Kelaart 1859) (Figs. 60-64) Doris osseosa Kelaart, 1859, p 298; Alder & Hancock, 1864, p 121, pl. 28, figs. LOI Doris carinata (non Quoy € Gaimard, 1832); Alder & Hancock, 1864, p 122, pl. 29, figs. 5, 6 Sclerodoris osseosa, Eliot, 1903a, p 380; 1908, p 114; 1910, p 420. Range: East Africa; Coetivy (latitude 7° 15' S, longitude 56° 24' E); Ceylon; coast of the Bay of Bengal. Collecting station: Madagascar; xviii, 1 specimen. Description: The living animal was hard, 40 mm long and 30 mm broad, with a folded notal border. The rough surface bears dorsal papillae which stand on a net of ridges. The meshes in between are flat. The papillae are small on the margins of the notum, the rhinophoral sheaths, and on a median ridge. This ridge begins behind the rhinophores and ends in front of the 200 MARCUS AND MARCUS gills. The ground color is ocher, the papillae are white. The meshes are light brown on the sides, dark brown or blackish-green inthe region over the vis- cera; their pigment is traversed by lines of the ground color. The rhinophores are ocher; their high sheaths have finely scalloped borders. The preserved animal is 30 mm long (35 mm when measured over the back) and has a 7 mm broad notum. The ten- tacles are pointed triangles; the rhino- phores have 20 leaves. A hump in the cardiac region was not salient in the living slug. The branchial pit has 3 large anterior and 2 smaller posterior lobes; between these the 5 multipinnate gills and the anal papilla project back- ward. The notum covers the foot, which is 20 mm long. In front, the foot is deeply bilabiate; it is pointed behind. The papillae contain projecting spi- cules and are connected by tracts of spicules. Further tracts run from the dorsal to the ventral side, where they form a coarse net. The spicules are smooth, blunt on both ends, and general- ly straight. The biggest were 700 u long, 35 u thick. Globular melano- phores, 200 u to 30 u in diameter, lie in the connective tissue. The eyes are small; the central nervous system is similar to that of Austrodoris (Odhner, 1934, fig. 27). The blood glands are whitish-yellow. The labial cuticle has no rods or platelets, but bears some colorless soft points. The salivary glands are ribbon- like. The radula, 4.8 by 3 mm, has 17 rows with 30 teeth per half-row. The 6 inner teeth are simple spines, whose size increases from 46y to 210 u. The succeeding teeth are hooks. Their length increases from 300 u to 500 u. From the 24th outwards the size decreases; the 2 outermost teeth are 95y and 60 y long. The stomach lies free over the liver, the caecum on the left. The autosperms in the ampulla and the allosperms in the seminal reser- voirs show that the specimen is mature. The inner oviduct (io) and the seminal duct separate at the exit of the longish ampulla (a). The prostatic part (q) is the dilated inner section of the male duct; the outer one (d) is narrower. It opens without a papilla into a strongly muscular male atrium and functions as an acrembolic penis (p). Between the nidamental duct (ni) and the penis, a short vagina (v) runs to the seminal reservoirs, the large sper- matheca (t) and the small spermatocyst (sc). The spermatheca contains irregu- larly heaped sperms, the spermatocyst parallelly arranged ones. The topog- raphy of the reservoirs and their ducts corresponds to the vaginal type. The allosperm duct (au) leads from the the spermatocyst to the inner region of the female gland mass (mu), where the rising allosperms meet the eggs de- scended through the inner oviduct (io). On the genus Atagema Gray 1850 The holotype of Doris carinata Quoy & Gaimard 1832, from New Zealand has dried (Pruvot-Fol, 1934, p 64). There- fore Bergh’s description of a similar specimen from New Zealand (1904, p39- 41), which he called Atagema carinata (Quoy € Gaimard, 1832), is acceptable to settle the type. Petelodoris Bergh (1882, p 227) and Sclerodoris Eliot (1903a, p 361) cannot be separated from Atagema. The 2 known species of Pero- nodoris Bergh, 1904, however, have a penial stylet. This genus cannot be united with Sclerodoris, as did Thiele (1931, p 435), Allan (1947, p 451) and Iredale & McMichael (1962, p 93), but should be maintained separate (Eliot, 1908, p 113, 114; Odhner, 1926, p 54). The species of Atagema have a hard and rough notum; those of Halgerda Bergh, 1881, a leathery or stiff, jelly- like one. Due to the texture of the notum, Doris apiculata Alder € Han- cock (1864, p 122) was removed from Sclerodoris Eliot (1903a, p 361), i.e., Atagema, to Halgerda (id., 1906, p 645, 1002; 1908, p 113). The strong pros- tate, an internal character of Halgerda, was found in H. apiculata by Eales (1938, p 404). MADAGASCAN AND MEXICAN GASTROPODS 201 FIG. 49. Conualevia marcusi. Radular teeth. FIGS. 50-53. Chromodoris quadricolor. Fig. 50, Dorsal view of preserved slug. Fig. 51, Ventral view of same. Fig. 52, Labial rodlets. Fig. 53, Radular teeth. FIGS. 54-56. Hypselodoris regina. Fig. 54, Living slug, from color photo. Fig. 55, Pre- served slug, dorsal view. Fig. 56, Side view of same. FIGS. 57-59. Hypselodoris regina. Fig. 57, Labial rodlets. . Fig. 58, Radulaf teeth. Fig. 59, Diagram of reproductive organs; prostate laid apart. 202 MARCUS AND MARCUS The range of Atagema comprises the west coast of Africa (Pruvot—Fol, 1953); the Mediterranean (Pruvot-Fol, 1951); the western Indic from the east coast of Africa to the Bay of Bengal; New Zea- land; Japan, Enoshima (latitude 35° 18' N, longitude 139° 22' E); California, San Diego (Collier, 1963). Trippa intecta (Kelaart 1859) (Figs. 65, 66) Doris intecta Kelaart, 1859, p 302. Goniodoris erinaceus Angas, 1864, p 57, pl. 5, fig. 5. Trippa ornata Bergh, 1905a, p 129-131, pl. 1, fig. 6, pl. 15, fig. 37; Risbec 1928, p 97. Trippa affinis Bergh, 1905a, p 131-133, pl. 15, figs. 38, 42, Trippa intecta, Eliot, 1909, p 83-85; Baba, 1949, pl. 24, fig. 89. Yu € Si, 1965, pl. 3, fig. 2. Trippa erinaceus, Allan, 1947, p 450, pl. 42, fig. 8. Range: Ceylon; Malaysia; South China Sea; middle Japan; New South Wales; New Caledonia. Collecting station: Madagascar; xviii, 1 specimen. Description: The slug was 40 to 50 mm long, 30 mm broad when alive; pre- served, it is 30 mm long. The notum, hyponotum and sides were reddish- brown, the sole whitish-grey. The dark middle part of the back bore an ocher- brown stripe in the posterior %. The notum is covered with large tubercles with thin black papillae on their tops. These contain sparse spicules, some of which stand out. On the sides of the foot are small tubercles; larger ones are on its wavy black border. The connection from head to foot (Bergh, 1877a, pl. 58, fig. 3) was not seen, as part of the mantle border had been autotomized. The rhinophores are black with white tips and have about 25 leaves. The 5 tripinnate gills are black. The high rhinophoral sheaths and the borders of the branchial pit bear tubercles and papillae. The anterior foot border is bilabiate and notched. The labial cuticle is smooth. The radula has 24 rows and 40 to 43 teeth per half-row. From the innermost tooth, 100 u high, the succeeding teeth increase rapidly to 280 and remain large till far outwards, where they decrease to 85 u. The large stomach and the caecum are free. The winding ampulla (a) is continued in a short spermoviduct which divides into a seminal duct and inner oviduct (io). The tubular prostate (q) is very long. The muscular portion ofthe semi- nal duct winds in a sheath andis widened in its penial termination (р). From the vestibule the wide vagina (v) leads to a spherical spermatheca (t). Im- mediately beside the entrance of the vagina the allosperm duct (au) leaves the spermatheca and, near its origin, bears the spermatocyst (sc) filled with orientated sperm. The opening of the allosperm duct into the gland mass (mu) is near the entrance of the inner oviduct. The nidamental duct (ni) opens behind the vestibule (ve). Remarks: Narrower inner teeth of the radula (Bergh, 1877a, pl. 58, fig. 5; Baba, 1949, p 64, fig. 78 a) or thicker ones (Bergh, 1905a, pl. 15, fig. 38, a) have no systematic value. Regular dif- ferences of the teeth within the row, as, e.g., in Diaulula hispida (Odhner, 1926, fig. 56), are specific. The light middle stripe or crest of Trippa intecta occurs also in material (Bergh, 1890, p 905) allotted to T. affinis (id. 1905a, p 131). Also the numbers of the rows and teeth of the radula do not furnish clear-cut differences in the descriptions by Bergh, Eliot and Risbec, so that T. affinis cannot be maintained. Trippa monsoni Eliot (1903a, p 371) from the east coast of Zanzibar, prob- ably identical with the Ceylonese T. leoparda (Kelaart, 1859, p 294), differs from T. intecta by characters of color and radula. Rostanga pulchra MacFarland 1905 = Rostanga pulchra, MacFarland, 1966, p 165-169, pl. 25, fig. 7, pl. 29, figs. 7-10, pl. 35, figs. 1-16, MADAGASCAN AND MEXICAN GASTROPODS 203 Range: From the Vancouver Island region to the Gulf of California (Farmer & Collier, 1963, p 62); South Chile, Chiloé. Collecting station: Mexico; i, Oct. 29, 1966 (Mary Anne Hill), rocky inter- tidal on a red sponge, 2 bright red Specimens. Remark: The Indo-west Pacific Ros- tanga arbutus (Angas, 1864) differs from R. pulchra by the radula, but not always by the color (Marcus, 1959, p 36, 37). Taringa aivica timia Marcus 1967 Taringa aivica timia Marcus, 1967, p 189, figs. 47-51. Range: Gulf of California, Sonora. Collecting station: Mexico; i, Oct. 15, 1966 (Mary Anne Hill), rocky intertidal, 1 specimen. Remarks: The specimen was trans- parent light brown with darker rhino- phores and spots on the notum and gills. The latter form 2 circles, the right one with 7 normal plumes and a single mi- nute one, the left with 3 large and 1 Small plume. The pits of both circles are separated by aperineum. The ter- minal section of the intestine bifurcates, so that an anal opening occurs in the center of either circle. Probably the rectal anomaly caused that of the gills. Risbec (1928, p 108) mentioned 2 bran- chial pits in another doridid. Tayuva ketos ketos Marcus 1967 Tayuva ketos Marcus, 1967, p 192, figs. 52-56. Range: Gulf of California, Sonora. Collecting station: Mexico; i, July 18, 1966 (Mary Anne Hill), rocky intertidal, 1 specimen. Remarks: The present animal, about 25 mm long when alive, is young and less intensely colored than the original material. The radula has 21 rows and 25 teeth per half-row. The 2 hindmost plumes of the 6 tripinnate gills are largest. The vestibule, though already wide, does not yet contain the charac- teristic cuticular spicules. Also, the penial papilla is shorter. Two slugs from Curacao differ prin- cipally by a carrot-shaped penial pa- pilla, and will be described under a new subspecific name. Asteronotus cespitosus (van Hasselt 1824) (Figs. 68-70) Asteronotus cespitosus, Bergh, 1890, p 917-921 (synonymy), pl. 86, figs. 7, 8; 1905a, p 141 (synonyms), pl. 1, fig. 5; Baba, 1936, p 32 (references), pl. 1, fig. 2; Kenny, 1960, p 224; Yu & Si, 1965, pl. 3, fig. 9. Asteronotus hemprichii Ehrenberg, 1831; Bergh, 1877b, p 161-173 (including the synonym A. bertrana Bergh), pls. 1, 2; Eliot, 1903a, p 384; 1908, p 116; 1910, p 428; Pruvot-Fol, 1933, p 120, 121, pl. 1, fig. 1; 1934, pl. 1, fig. 19. ? Asteronotus fuscus O’ Donoghue, 1924a, p 551, 552, pl. 28, figs. 12, 13. Asteronotus brassica Allan, 1932, p 93- 95, Figs. 1, 2 (опр 104), pl. 5, figs. 12-14. Range: Red Sea; western and eastern Indic; South China Sea; Ryukyu Islands; ?Western Australia; Queensland; New South Wales; Palau and Fiji Islands; Samoa. Collecting station: Madagascar; xxvi, 1 specimen. Description: The slug was 70 mm long and 40 mm broad when alive. The back and the warts on the notal bulges are blackish-green, the median crest, the bulges, and the rims of the rhino- phoral and branchial pits greenish- brown, the margins of the notum ocher to reddish-brown. Preserved, the dark pigment is visible through the notal border on the under side. Inwards to this dark zone follows a dense light stripe and one with epidermal pigment. Also, the sole is pigmented. The peri- toneum and the vestibule are grey. The rhinophoral sheaths have a median spur. The branchial pit is surrounded by 2 anterior and 3 posterior lobes. The smooth labial cuticle is folded. The radula has 38 rows with 45 smooth, 204 MARCUS AND MARCUS hooked teeth per half-row. Thestomach has thick walls. The hermaphrodite duct forms atubu- lar ampulla (a) at the exit of which the oviduct and the seminal duct separate. The latter begins with a clustered pros- tatic part (q), followed by a smooth, massive one. The winding sperm duct (d) ends with a coil in the muscular penial pouch (p), which opens into the deep, folded vestibule (ve). Opposite to the penial pouch there is a voluminous vestibular gland (sd), the follicles of which have a common muscular duct. This ends with a spine (ss) lodgedina muscular sac. The vagina (v) courses from the vestibule to the spermatheca (t) containing residues of sperm and prostatic secretion. Beside the en- trance of the vagina the allosperm duct (au) leaves the spermatheca. The-duct communicates with the broad lobed spermatocyst (sc) filled with sperm, and joins the inner oviduct at its entrance into the gland mass. The nidamental duct (ni) opens behind the aperture of the vestibule. Remarks: The reproductive organs of our specimen agree with Bergh’s de- scriptions (1878b, p 641-644; 1890, p 920, 921), which refer to animals from Malaysia and the Palau Islands. These organs are somewhat different in Eales’ specimen (1938, p 104, fig. 120) from the Gulf of Aden, which measured 32 mm long preserved and was possibly im- mature. Asteronotus fuscus, listed above, is probably a young А. cespitosus. Mrs. Joyce Allan related A. brassica to A. mabilla (Abraham, 1877, p 249) a Synonym of cespitosus, by a hand- written note in her reprint of 1932, sent in 1954. Asteronotus madrasensis O’ Donoghue (1932, p 158) has considerably more radular teeth than A. cespitosus. As- teronotus sp. (Eales, 1938, р 105-107) is similar to A. madrasensis, but imma- ture. A. wardianus Allan (1932, p 95) does not belong to A. cespitosus. A. (Tumbia) trenberthi Burn (1962, p 161) is not an Asteronotus. Risbec (1928 and later) called Discodoris boholiensis Bergh (1877a, p 519) Asteronotus b., but it is the type species of Discodoris, whose species have labial rodlets. Platydoris scabra (Cuvier 1804) Platydoris scabra, Marcus, 1960a, р 907-911 (synonymy), figs. 55-57; 1965, p ХА Range: Red Sea; Indo-west Pacific, from the east African coast to the Carolines, Marshall and Tonga Islands; Samoa. Collecting station: Madagascar; xxvi, 2 specimens. Descriptive notes: The living animal was 100 mm long, 50 mm broad. The notum is light brown with a broad mar- ginal region of white blotches in its 3 posterior fourths. The rhinophores and the gills are grey; the former have orange-yellow terminal knobs, the latter have dark vessels. The digitiform ten- tacles are flecked with black and tipped with yellow. Also, the rim of the bran- chial pit and the border of the sole are yellow. The sole itself is white; the sides of the foot are rusty brown. The radula has 50 rows of teeth with 98 to 100 teeth per half-row. In some of the innermost teeth the cusp arises from a shoulder-like angle of the base, as in Bergh’s fig. 18 (1884, pl. 2). The salivary glands have narrow fundi, with an inner wide and an outer thin portion of the ducts. Remarks: The salivary glands in the present specimen are as in the animal from the Red Sea (Marcus, 1960a); in other descriptions the terminal narrow part is much longer (Bergh, 1884, pl. 3, fig. 11, a) or the wide middle portion is absent (White, 1950, p 98). As in other species of the genus the ejaculatory duct and the vagina have different cuticular structures. The latter bears thick folds as in most descriptions; only once are prominent rounded bosses mentioned (Bergh, 1905a, p 138). The male duct contains spiny discs. MADAGASCAN AND MEXICAN GASTROPODS 205 ZEISS == OO ЕЕ = FIGS. 60-64. Ategema osseosa. Fig. 60, Dorsal aspect, combined from color photo and preserved slug. Fig. 61, Detail of sculpture. Fig. 62, Radula. Fig. 63, Diagram of repro- ductive organs. Fig. 64, Radular teeth. FIGS. 65-66. Trippa intecta. Fig. 65, Innermost, middle, and outermost teeth. Fig. 66, Diagram of reproductive organs. FIG. 67. Gymnodoris bicolor. Living slug, from sketch by Dr. E. Kirsteuer. FIGS. 68-70. Asteronotus cespitosus. Fig. 68, Dorsal view of living slug, from sketch by Dr. E. Kirsteuer. Fig. 69, Ventral view of preserved slug. Fig. 70, Diagram of reproductive organs. 206 MARCUS AND MARCUS Gymnodoris bicolor (Alder & Hancock 1864) (Fig. 67) Gymnodoris bicolor, Macnae, 1958, p 358 (synonymy); Marcus & Burch, 1965, p 249, 250 (range). Range: Indo-west Pacific, from Zan- zibar and Mozambique to middle Japan, New Caledonia, and Samoa. Collecting station: Madagascar; xxvii, 1 specimen. Remarks: The living animal was 2.5 mm long, yolk-yellow, with small orange spots. The 11 radular rows have 4 to 7 teeth per half-row, of the shape characteristic for the species. Theslug has no gills yet around the anus that lies in the posterior Y, of the back. This was examined in sections which still have yolk in the digestive gland. Porostomata Dendrodoris nigra (Stimpson 1855) (Fig. 74) Dendrodoris nigra, Marcus € Burch, 1965, p 250 (references). Range: Red Sea; Indo-west Pacific to west, south, and east Australia (Burn, 1966, p 349); north to Japan, Mutsu Bay (latitude 41” N.); east to Gilbert Islands and New Caledonia. Collecting stations: Madagascar; xviii, xxii, xxiv, xxxiii, xliii, 5 speci- mens. Remarks: The color of the present specimens is black with small whitish- yellow dots in 2 longitudinal rows or distributed irregularly. A liver-brown ground color with or without dots occurs in this species too. The body shape varies from broad with undulate borders to narrow with nearly smooth borders. Specimens of Dendrodoris nigra with an outermost black line are separated ex- ternally from the west Atlantic and east Pacific D. krebsii Bergh, but a white notal border without black rim occurs also in D. nigra (Baba, 1935b, pl. 6, fig. 2). Such animals differ from D. krebsii by the short penial pouch (Marcus, 1957, fig. 152, ei). The length of the seminal duct between the prostate and the pouch varies in D. krebsii (Marcus, 1967, figs. 62, 63). In the present D. nigra this part is long. A grey or black blood gland charac- terizes Dendrodoris nigra; in D. krebsii it is unpigmented or contains only few pigment granules. The cerebro-buccal connectives are 3 times as long as the diameter of the pharynx in D. krebsii from the Gulf of California; in the pre- sent D. nigra they are quite short. Characters of these two species which differ by degree are the concentration of the central nervous system, higher in D. krebsii, and the more coalesced oral glands in that species. Dendrodoris rubra (Kelaart 1858) (Figs. 71-73) Doriopsis rubra, Alder & Hancock, 1864, p 126, pl. 31, figs. 1, 2; Collingwood, 1881, p 135, pl. 10, fig. 8; Bergh, 1902, p 190, 191, pl. 2, Не. 16: Doridopsis rubra, Eliot, 1904, р 279; 1905, p 255; 1908, p 118, 119; 1909, p 95. Dendrodoris vubra, O’Donoghue, 1929, p 731; White, 1951, p 250, fig. 20, Range: Red Sea; Zanzibar and coast of the mainland; Mozambique, Inhaca Island; west and east coast of India; Ceylon; Singapore; Siam; Viet Nam (Risbec, 1956, p 26). Collecting stations: Madagascar; xxi, xliii, 5 specimens. Description: The living slugs were pink, a little darker in the middle of the back, with red spots. The shaft of the rhinophores was pink, the 16 leaves red, and the knob white. The gills were red. The largest of the preserved slugs is 30 mm long, measured over the back, 15 mm broad and 13 mm high. We dis- sected the most stretched specimen, which measured 12 by 8 mm. The skin is smooth without papillae or spicules. The tentacles are folds between the mouth pore and the anterior foot border, which is furrowed and notched. The hyponotum is folded in front, but the MADAGASCAN AND MEXICAN GASTROPODS 207 aspect varies in the present 5 slugs. The 2 hindmost of the 6 multipinnate gills are the largest, and are bifurcate. The anal papilla lies in the center of the branchial circle. The rhinophoral gan- glia are set off from the cerebral ones (cr). The pigment cups of the eyes (y) are big, 140 u in diameter; the lens is not very large. The buccal gland (uc) consists of 2 roundish lobes and has a short and thick duct. The angled sali- vary glands (sa) are separate and lie behind the buccal ganglia (cc). The fore gut comprises the oral tube (ro), the pharynx (nx), the oesophagus (0), a spherical dilatation, and the digestive gland with a wide lumen, the stomach. The roundish blood gland is composed of small follicles which roughen the surface. The spermoviduct leaves the spher- ical ampulla (a) beside the entrance of the hermaphrodite duct (eu). The short, thin seminal duct (d) is followed by the loop of the prostate (q) and a short muscular portion, 3 mm by 0.19 mm. In a 15-mm slug the penial spines were developed. The short inner oviduct (io) passes to the outer oviduct between the albumen (ag) and mucus gland (mu). In the young dissected slug which had copulated, the gland mass is small and opens into the common vestibule (ve) by a short nidamental duct (ni). Be- tween the penis and the oviduct begins the vagina (v) first wide, then narrow and winding. It enters the longish sper- matheca (t) beside the exit of the allo- sperm duct (au). The globular sper- matocyst (sc) filled with sperm is joined by a short canal to the allosperm duct, which opens into the gland mass near the entrance of the inner oviduct. The 3 examined specimens had no vestibular gland. Remarks: Dendrodoris rubra nigro- maculata, frequent in Japanese seas, and the possible synonyms of D. rubra (Eliot, 1905, p 254; Pruvot-Fol, 1934, p 62), were not considered in the range. The description of D. rosea (Vayssière, 1912, p 82), whose hyponotum bears similar folds, does not allow for iden- tification with D. rubra nor for separa- tion from it. In Bergh’s 18 mm speci- men the seminal duct ectal to the prostate was “thin and highly wound”; in White’s (1951) figure of a 36-mm animal it is short. Dendrodoris pudibunda (Bergh 1879) (Figs. 75-79) Doriopsis pudibunda Bergh, 1879, p 33, 34; 1889a, p 844, 845. Doridopsis pudibunda, Eliot, 1904, p 274. Range: Zanzibar; Mauritius, Fou- quets Reefs; Philippines Sea. Collecting station: Madagascar; xxvi, 1 specimen. Description: The living animal was 80 to 90 mm long, and 30 to 35 mm broad. The color was light brown in the middle of the back, with 6 dark brown spots on either side; the sides of the notum were whitish-grey with yellowish- brown spots near the wavy border. The rhinophores were grey; the gills white with grey plumes. The notal papillae are soft bosses when preserved, smaller and more numerous toward the sides than in the middle. Their tops are covered with high glandular cells. In the big bosses the center of the glandu- lar area is invaginated. The noval con- nective tissue is traversed by many nerves with nerve cells, as noted by Bergh (1879, p 34). There are no spicules. The tentacles are small. The rhino- phores have 25 leaves and smooth bor- dered pits. The circle of the 8 multi- pinnate gills is completed behind by the anal papilla, nearly as high as the gills. The eyes have small pigment cups, 80 u in diameter, and lenses 120 u high. As in all Dendrodoris, the central nervous system is highly concentrated. The cerebral (cr) and pleural ganglia are distinguished by the different size of the nerve cells. The buccal ganglia (cc) lie apposed to the limit of the pharnynx (nx) and oesophagus (0), between the small salivary glands (sa), which coalesce 208 MARCUS AND MARCUS behind them. The mouth tube (ro) pro- jects into the buccal cavity and re- ceives the thin, winding duct of the buccal gland (uc). The 2 lobes of the latter are fused. The mouth tube bends to the left before passing through the nerve ring. Behind this follows the long, muscular pharynx (nx) looping first to the left, then to the middle. Its lumen is triangular. The glandular oesophagus (o) forms a globular dila- tion before entering the stomach. At the beginning of the intestine there is a small caecum. The aorta (ao) courses through the bipartite, coarsely lobed blood gland (us). There is no pigment in the mouth tube, the inner organs, or the peritoneum. The spermoviduct leaves the pear- shaped ampulla (a) some distance from the entrance of the hermaphrodite duct (eu). The seminal duct (d) widens sud- denly to form the prostatic portion (q) and passes abruptly to the following narrow part (ui), 100 u in diameter. This section 'uncoiled would be at least 10 mm long. The short muscular tube, the acrembolic penis (p), is wide and bears a few cuticular spines. Where it opens into the folded common vestibule (ve) inserts a retractor muscle (r), which lodges a small gland among its fibers. There is a long, clustered ves- tibular gland (xv). The inner oviduct (io) enters the gland mass between the albumen gland (ag) and the mucus gland (mu). The short nidamental duct (ni) opens into the vestibule (ve) beside the wide beginning of the vagina (v), and continues as a winding duct to the spherical spermatheca (t). Close to its entrance leaves the long, winding allo- sperm duct (au), to which the spermato- cyst (sc) is connected by a long, straight duct. The spermatocyst contains ori- ented sperms. Remarks: When the species was first mentioned (Bergh, 1876, p 387), it was neither described nor figured. The penial spines are scarse in specimens from the western Indic; in the original animal from the Philippines they were called “as usual.” The thick-walled seminal duct of that slug, 2.5 mm long, does not agree with our specimen. The above mentioned different length of the seminal duct in Dendrodoris rubra shows that this character is systemati- cally useless. Dendrodoris clavulata (Alder € Han- cock, 1864, p 127), not the D. clavicu- lata (Eliot, 1904, p 278) that is widely distributed in the Indo-west Pacific (Risbec, 1953, p 24), has spots on the border of the notum as D. pudibunda, but its colors are brighter and the bosses stronger. Phyllidia (Phyllidia) varicosa Lamarck 1801 Phyllidia (Phyllidia) varicosa, Marcus, 1960a, p 911-913 (references, range), fig. 58; 1965, p 277, 278. Range: Red Sea; tropical Indo-west Pacific, from the east coast of Africa to the Ryukyu Islands and east to Micro- nesia, Gilbert Islands. Collecting station: Madagascar; viii, 4 specimens. Descriptive notes: The living animals are up to 70 mm long and 40 mm broad, black with bluish-grey ridges, yellow papillae, and graphite-grey sides and sole. The connections of the tentacles with the foot (Bergh, 1869, pl. 14, fig. 6; Pruvot-Fol, 1952, fig. 3) are distinct. There are 150 branchial leaves; the genital aperture lies at the level of the 13th gill. The folds of the pericardium, an important feature of the Porostomata (Bergh, 1892b), were drawn in their natural position by Risbec (1956, fig. 85). Remarks: The gastro-oesophageal ganglia (Bergh, 1869, p 380, 401, pl. 16, fig. 4) were confounded with salivary glands in early publications (Bergh, 1889a, p 857; 1892a, p 1126; 1897, pl. 12, fig. 13). This was repeated in Hoffmann’s treatise (1938, p 947). Ris- bec (1956, p 23) described the 2 pairs of ganglia correctly. Risbec’s Fryeria pustulosa from Mad- agascar (1929) is Phyllidia varicosa; in MADAGASCAN AND MEXICAN GASTROPODS 209 FIGS. 71-73. Dendrodoris rubra. Fig. 71, Head of preserved slug. Fig. 72, Anterior part of gut. Fig. 73, Diagram of reproductive organs. FIG. 74. Dendrodoris nigra. Section of penis and vagina. FIGS. 75-79. Dendrodoris pudibunda. Fig. 75, Side view of living slug, from sketch by Dr. E. Kirsteuer. Fig. 76, Skin. Fig. 77, Section of skin. Fig. 78, Dorsal view of living slug, from sketch by Dr. E. Kirsteuer. Fig. 79, Anterior part of gut. 210 MARCUS AND MARCUS his fig. 1 the dorsal anus is seen at the end of the dorsal crest. Arminoidea Dermatobranchus (Dermato- branchus) striatus van Hasselt 1824 Pleuroleura striata, Bergh, 1905a, p 209, 210, pl. 4, fig. 22, pl. 19, figs. 7-9. Dermatobranchus striatus, Baba, 1937, p 316, 317, fig. 12, pl. 2, fig. 1. Dermatobranchus (Dermatobranchus) striatus, Baba, 1949, p. 73, 157, 158, ftg. 83, pl. 29, fig. 109. Range: Malay Archipelago, coasts of Japan. Collecting station: Madagascar; xxi, 2 specimens. Descriptive notes: The slugs were 20 to 25 mm long when living, 5 to 7 mm broad. The ground color was yellow- ocher with whitish-grey ridges and dark brown blotches near the wavy borders. The rhinophores are furrowed longitu- dinally, whitish-grey peppered with black, and have a greenish-yellow top. In the borders of the notum lie the sac- cules, which are not cnidophores. Inthe middle of the notum there are 3 longi- tudinal ridges, which multiply irregu- larly backwards. On the border they run parallel to the contour in one speci- men and fan out in the other. Thenotum is deeply notched in front and covers the pointed tail behind. Ventrally to the anterior border lie the frontal veil and the buccal folds. The foot is bilabiate and notched. The thick edge of the foot is frilled, the sole narrow. The genital opening lies to the right in the anterior third. The notal ridges do not contain diverticula of the digestive gland, con- trary to the lateral lamellae of Armina (Marcus, 1960b, p 172). Nor are the ridges provided with especially numer- ous blood lacunae, so that a respiratory function is not evident. The thin, light brown jaws have den- ticulate masticatory borders. The rad- ula has 32 rows with 16 teeth on either side of the rhachidian. The innermost lateral is much broader than the suc- ceeding ones, as shown in the figures of Bergh (pl. 19, fig. 9) and Baba (1937, fig. 12; 1949, fig. 83). The succeeding laterals are smooth hooks. Remarks: The Red Sea is not in- cluded in the range of Dermatobranchus (D.) striatus, though a specimen from there was published under this name (Eales, 1938, p 111-113). The radular formula, as already noted by the author, and the shape of the central and the innermost lateral teeth (loc. cit., fig. 24) are incompatible with D. (D.) stri- atus. Eales’ species does not agree with any of the 17 species of Dermato- branchus, not even with D. glaber (Eliot, 1908, p 88) from the Red Sea. The genus can be expected to occur in deep water in low latitudes, because 1 species is known from the Arctis. Eolidoidea Coryphellina rubrolineata O’Donoghue 1929 (Fig. 81) Coryphellina rubrolineata O’Donoghue, 1929, p 798-802, fig. 219; Baba, 1955, p 26, 27, 51, figs. 40, 41, pl. 13, fig. 37; Marcus, 1961b, p 224-227, figs. 1-10; Burn, 1962, p 107; Abe, 1964, pl. 30, fig. 107. Range: Suez and entrance of the Canal; Australia, Port Phillip heads; Japan, Sagami Bay, Toyama Bay; Brazil, entrance of the Bay of Santos. Collecting station: Mexico; ii, Nov. 12, 1966 (Paula Vreeland), rocky inter- tidal, 1 specimen. Descriptive notes: The living slug was 13 mm long. Measurements of the preserved specimen are in mm: length 8; tentacles 2.5; rhinophores 2.0; foot corners 1.0; cnidosacs 0.4. The body is pinkish-orange with orange inner organs. Tentacles, rhinophores, foot corners, tail and cerata bear red rings, which were violet in life. The long white tips of the cerata were powdered with yellow. A median line on the pointed tail was silvery white. The shaft of the rhinophores is short. The back of the long club is beset with 12 oblique rows of about 15 high and blunt papillae each. The consistent, MADAGASCAN AND MEXICAN GASTROPODS 211 slender cerata form 11 groups of 3 to 4 cerata each; the 3 first groups of the posterior liver contain 7, 6 and 5 cer- ata. The flange between the back and the side of the body reaches the poster- ior cerata. The genital openings lie under rows 3 and 4, the anus under the flange in the interhepatic space. The masticatory process of the jaws bears several rows of rough denticles. The radula has 34 rows of 1.1.1 teeth. The median tooth has 7 denticles on each side and a longer median cusp beneath them. The lateral teeth have 5 to 7 denticles on the inner side, which leave the tip free. Remarks: The number of the rhino- phoral papillae is highly variable, but the essential characters of the speci- mens from all localities do not evidence clear-cut differences. The zoogeogra- phic aspect of Coryphellina rubrolineata is that of a species recently distributed on ships’ bottoms. The larva of the neighboring Coryphella rufibranchialis, though better adapted for a pelagic life than the larvae of several other Eoli- doidea (Thorson, 1946, p 269, 270), cannot survive long-distance transport by ocean currents (see Thorson, 1961, fig. 3). All previous records are from ports with much traffic. C. rubrolineata was possibly brought to the present Sonoran locality by the Japanese fishing fleet in the area of Guyamas (Steinbeck & Ricketts, 1941, p 247). Favorinus mirabilis Baba 1955 (Figs. 83-85) Favorinus mirabilis Baba, 1955, p 30, 53, fig. 50, pl. 17, fig. 46. Range: Japan, Sagami Bay, 50 to 60 meters. Collecting station: Madagascar; xxix, 1 specimen. Description: The living slug was 5 mm long and 1.2 mm broad. The ground color is transparent light grey with white flecks over the whole body, es- pecially on the pericardial hump. The claviform grey cerata have a subapical brown spot. The head is light greenish- yellow, the tentacles grey; the brown rhinophores bear few yellow spots, be- tween them lies a brown triangle. The preserved specimen is 3.5 mm long. The tentacles are longer than the rhino- phores, the latter longer than the foot corners. The tail is pointed. The rhi- nophores have 8 to 9 leaves. The cerata stand in 8 groups in single rows, the 4 anterior ones are arches with 7, 7, 5 and 4 cerata. In the 5th group there are 2 cerata, the posterior groups eachhave 1 ceras. The genital opening lies under the lst arch, the anus in the 2nd. There are several rows of pointed denticles on the masticatory border of the jaws. The 15 radular teeth have strong cusps and no denticles. Remarks: The type specimen was larger, 15 mm, and had correspondingly more (12) groups of cerata and 21 teeth. Only the lst 3 groups are arches, the rest slanting rows, but our single speci- men does not justify a specific separa- tion. Foliate rhinophores occur also in F. perfoliatus Baba (1949, p 109, 177). It differs from the present species by short foot corners, slender cerata with- out a subapical spot, and only 2 groups of horseshoe-shaped cerata. Pteraeolidia ianthina (Angas 1864) Flabellina ianthina Angas, 1864, p 65, pl. 6, fig. 6. Pteraeolidia semperi (Bergh), Marcus, 1960a, p 921, fig. 77; 1965, p 280. Pteraeolidia ianthina (Angas, 1864), Burn, 1965, p 89, 90. Range: From the Red Sea and the east coast of Africa to middle Japan; New South Wales; east to New Caledonia and Micronesia, Carolines. Collecting station: Madagascar; Tan- ikely, 1 specimen. Remarks: The preserved animal is 40 mm long and has 18 pairs of tufts of cerata. Living slugs up to 75 mm long have been recorded. 212 MARCUS AND MARCUS Noumeaella isa, new species (Figs. 86-89) Collecting station: Madagascar; xxx, 1 specimen. Diagnosis: This first Noumeaella from the western Indic is characterized by an opaque white net all over the body, and the radular tooth whose cusp is flanked by 2 small inner and 4 larger outer denticles. Holotype: AMNH 140854. Description: The living animal was 5 mm long, 2.5 mm broad, semitrans- parent white, with an opaque white net- work over the whole body. Also, the yellowish-white cerata have this net, as well as brownish-yellow granules at their base. The pointed foot cornersare about as long as the tentacles. The pointed rhinophores stand far behind the latter; on their posterior side they havea brush of papillae standing in rows. The small black eyes show at the base of the rhinophores. The slender cerata stand in 5 uniseriate arches. The lst has 8 cerata. The groups following contain 8, 6, 4 and 2 cerata. In the interhepatic space lies the strong genital papilla; the anus lies in the first arch of the right posterior liver. The furrow of the anterior foot border is continued onto the angles. The shape of the jaws is similar to that in Noumeaella curiosa Risbec and N. rehderi Marcus. No denticles were seen on the masticatory border. The radula has 16 horseshoe-shaped teeth with long limbs. The cusp is flanked by 2 small inner and 4 larger outer den- ticles on either side. The male organs are a thin seminal duct which arises at the exit of the ampulla (a), a thick prostatic part (q) curving to the left and connected with the muscular terminal part (p) by a thin duct (d). The thick and long penis bears a cuticular stylet. The bursa (b) con- tains orientated sperm. A vaginal canal (v) isolated from the oviduct lies far inwards, but folds separate the path of the allosperms from the path of the eggs farther outwards. Insemination may be presumed near the opening of the va- ginal canal. Remarks: The 2 other species of the genus (Risbec, 1937, p 163; Risbec, 1953, p 158; Marcus, 1965, p 282) have a single strong median cusp flanked by 6 to 8 smaller denticles. The denticu- late masticatory border of these species contrasts with the probably smooth one of the present species. Aeolidiella indica Bergh 1888 (Figs. 90, 91) Aeolidiella indica Bergh, 1888, p 781- 783, pl. 78, figs. 1, 2. Range: Mauritius. Collecting station: Madagascar; xlv, 1 specimen. Description: The slug was 5 mm long, 1.5 mm broad, both when alive and preserved. Its buccal mass was pressed out. The longest cerata are 0.8 mm with 0.2-mm cnidosacs. The color was whitish-yellow with dark brown spots on the rhinophores, the middle of the back, and the anterior face of the cerata. The eyes are largest in the antero-posterior direction (140 м). The tentacles are longer than the smooth rhinophores. The foot is nar- rower than the body, its furrowed an- terior border has short angles. The tail is short. The claviform cerata are cylindrical and pointed. The liver diverticula are smooth tubes in the present juvenile specimen. The cerata stand in 12 slant- ing rows. The 4 anterior ones bear 7 cerata each, followed with 2 with 5, 3 with 4, 1 with 3, and 2 with 2 cerata. Through the opaque skin the ramifica- tions of the liver are not visible. The anus lies between the 4th and 5th rows. The brownish jaws have growth lines parallel to the border. The radula has 13 light brown teeth. The strong median cusp is sometimes oblique. On either side of it stand 19 to 21 denticles; in the oldest teeth there are 10 to 14 denticles. The breadth of the teeth in micra is as MADAGASCAN AND MEXICAN GASTROPODS 213 follows: 80 in front, 146 behind; the height of the teeth in micra is 52 and 110, respectively, including the den- ticles, which are 20 y and 26 y long. There is only a primordium of the male reproductive organ. Remarks: Aeolidiella faustina Bergh (1900b, p 235; 1904, pl. 1: A. pacifica) has a minute central cusp on the tooth; A. orientalis Bergh (1889b, p 673) has rounded anterior foot corners (Eliot, 1908, p 96). The adult specimen of A. drusilla Bergh (1900b, p 33) has espec- ially short anterior rows of cerata, and its anus lies between the 5th and 6th row. Also the young specimens allotted to A. drusilla with reservation (Bergh, 1905a, p 222) have 3 to 4 cerata in the anterior rows; the tooth has 15 lateral denticles. Our young slug, not com- pletely concordant with the preserved 8 mm long original animals of A. indica, agrees with them regarding the teeth and the numerous cerata in the anterior rows. Onchidiacea Peronia peronii (Cuvier 1804) Ретота (Peronia) ретопй, Marcus, 1960a, p 877-881 (references), figs. 1-5. Range: Red Sea (Labbé, 1934, p 190); Indo-west Pacific, from southern Mo- zambique and Madagascar (Odhner, 1919, p 42) to the west Pacific: Fiji, Tonga Islands, Samoa. Collecting station: Madagascar; xxvi, 1 specimen. Remarks: We consider the genera Peronia Blainville, 1824, and Para- peronia Labbé, 1934, at most as sub- genera, because the definable character (Marcus, 1960a, p 876) of Paraperonia suffers exceptions (Labbé, 1934, p 202), while the other characters (ibid., p 196) are rather vague. The examined slug was 90 by 80 mm when living. Arborescent tubercles oc- cur over the whole notum, and more than 30 of them bear eyes. In life the ground color was a dark green, the tubercles were slightly lighter, brown- ish-green. The copulatory organs are very small, evidently malformed, as re- ported for other Onchidiacea (Plate, 1893, p 180; Labbé, 1934, p 195). The retractor of the penis originates beside the nerve ring, corresponding to Plate’s lst type (1893, р 148, 170, note 1), occurred generally in Peronia peronii (ibid., p 173). Hoffmann (1928, p 105) indicated the 2nd type for P. peronii, an origin beside the pericardium. We found the latter condition in a specimen from the Maldive Islands (Marcus, 1960a, p 480), but in a 2nd animal from there we now noted the 1st type. Peronia verruculata (Cuvier 1830) Onchidium verruculatum, Hoffmann, 1928, p 44, 72, 106 (references, range); Awati & Karandikar, 1948, p1-53 (anatomy, embryology, bionomics); Baba, 1948, p 20, 144, Range: From Suez through the Indic and western Pacific to Hawaii and Japan, Shimoda (latitude 34° 40' N, longitude 138° 55! E). Collecting station: Madagascar; xliii, 1 specimen. Remarks: The living animal was 45 mm long, 20 mm broad, greyish-green above, with a hue of yellow towards the borders, and densely set tubercles of the same color as the back. The hypo- notum is yellow with a slight green tint, the sole yellow-green. About 25 branched tubercles occur in the poster- ior 6th of the strongly contracted pre- served animal. The peritoneum is slightly pigmented, the penial gland large, the penial retractor originates in the posterior angle of the body cavity (i.e., as in Plate’s 3rd type (1893, p 170, note 1)). The intestinal loops are as in Plate’s 2nd type (1893, p 119), uncom- mon in Peronia verruculata, but not unprecedented (Labbé, 1934, p 193). Peronia anomala Labbé (1934, p 195) has the same type of intestine; his spe- cies is probably a synonym of P. ver- ruculata. A further species quite close to P. veruculata is P. branchifera 214 MARCUS AND MARCUS (Plate, 1893, p 183). The papilla of the penial gland of Peronia gaimardi Labbé (1934, p 194, fig. 8) is evidently not a specific character, but an evaginated muscular sac (Marcus, 1960a, fig. 1, es). Therefore, P. gaimardi also might be a synonym of P. verruculata. Hoffmannola hansi Marcus 1967 (Figs. 92, 93) Hoffmannola hansi Marcus, 1967, p 232, figs. 87-95. Range: Gulf of California, San Agus- tin, probably also Angel de la Guarda Island. Collecting station: Mexico; ii, Nov. 12, 1966 (P. Pickens), on rocks, 7 speci- mens. Remarks: The Onchidiacea can be separated into the Onchidiidae with the male pore situated to the left of the right tentacle, and the Onchidellidae with the male pore or pores (Peronina Plate, 1893) to the right of the right tentacle. Watsoniella Hoffmann, 1928, replaced by Hoffmannola Strand, 1932, belongs tothe Onchidiidae, contrary to Labbe’s indica- tion (1934, p 238). Hoffmann’s material of Hoffmannola lesliei (Stearns, 1892) had been collec- ted in 1852 and was histologically de- fective (Hoffmann, 1928, p 57). There- fore he could not understand an “organ of unknown function” (p 64) which lies between the big notal glands (no) and the body cavity. He observed the blood spaces (00) and the hyponotal pores (za) connected with the organ in H. lesliei, and pondered a respiratory function. Thanks to Professor Pickens, who pre- served material of H. hansi for histo- logical purposes, the organ can be de- fined as composed of parcels of glands (z) embedded in diagonal fibers of the body musculature. The secretion is led out by ductules (zu) which unite to wider ducts. These also receive canals from the perinotum which drain clusters of small gland cells (zi). In the outer part of the hyponotum the epidermal cells bear cuticular cones (Fig. 92), and some sensorial knobs, whose aspect and location suggest re- ception of mechanical stimuli. Onchidella hildae (Hoffmann 1928) Onchidella hildae, Marcus, 1967, p 230- 231, figs. 84-86. Range: Ecuador, Puna Island; Pana- ma, Pacific coast; Mexico, Sonora, Puerto Pefiasco. Collecting stations: Mexico; ii, Nov. 12, 1966 (P. Pickens), rocky intertidal, 6 specimens; iv, Dec. 26, 1966 (Paula Vreeland), rocks, 1 specimen. Remarks: Measured over the back, the preserved animals are 8 to 25 mm long. Two specimens have 18 marginal papillae, 4 have 19, and 1 has 20 papil- lae. The slugs of the original material, up to 25 mm long, had 16 papillae. The radula of the smallest specimen has 48 rows of 52 teeth without denticles per half-row. The muscular wall of the efferent duct in its free part equals the diameter of its lumen. The hyponotal line near the foot distinguishes Onchi- della hildae from O. binneyi Stearns, 1893, which occurs also at Puerto Pefiasco (Marcus, 1967, p 227). ACKNOWLEDGMENTS We owe much of our information about the specimens from Madagascar to the collector, Dr. Ernst Kirsteuer of the American Museum of Natural History. He kindly sent us his drawings of the living animals accompanied by notes on colors and sculpture. The material from the Gulf of California was col- lected by Prof. Peter E. Pickens of the University of Arizona and his collabora- tors. Some specimens were illustrated by photographs of the living animals in natural colors, and continue Professor Pickens’ previous collections, published by the Institute of Marine Science, Miami (Marcus, 1967). MADAGASCAN AND MEXICAN GASTROPODS 215 06000090 0 800 9% N) DICO O, 84 SANTA > = NE Wp Uf FIG. 80. Dendrodoris pudibunda. Diagram of reproductive organs. FIG. 81. Coryphellina rubrolineata. Rhinophore of preserved slug. FIG. 82. Phyllidia varicosa. Oesophagus with buccal and gastro-oesophageal ganglia. FIGS. 83-85. Favorinus mirabilis. Fig. 83, Living slug, from sketch by Dr. E. Kirsteuer. Fig. 84, Denticles of masticatory border. Fig. 85, Radular tooth. FIGS. 86-89. Noumeaella isa. Fig. 86. Dorsal and left side view of living slug, from sketches by Dr. E. Kirsteuer. Fig. 87, Preserved slug with partly plucked cerata. Fig. 88, Diagram of reproductive organs. Fig. 89, Radular tooth from above and from the side. FIGS. 90-91. Aeolidiella indica. Fig. 90, Living slug, from sketch by Dr. E. Kirsteuer. Fig. 91, Radular tooth. FIGS. 92-93. Hoffmannola hansi. Fig. 92, Section of outer part of hyponotum. Fig. 93, Section of notal and hyponotal glands. 216 MARCUS AND MARCUS REFERENCES ABE, T., 1964, Opisthobranchia of To- yama Bay and adjacent waters. Ho- kuryu-Kan, Tokyo, p i-ix, 1-99, pls. 1-36, [supervised by Kikutarô Baba]. ABRAHAM, P. S., 1877, Revision of the anthobranchiate nudibranchiate Mol- lusca, with descriptions or notices of forty-one hitherto undescribed spe- cies. Proc. zool. Soc. London, p 196- 269, pls. 27-30. ADAM, W. & LELOUP, E., 1938, Pros- obranchia et Opisthobranchia. Mem. Mus. Roy. Hist. nat. Belgique, hors ser., 2(19): 1-209, pls. 1-8. ALDER, J. & HANCOCK, A., 1864, No- tice on a collection of nudibranchiate Mollusca made in India by Walter Elliol, Esq., with descriptions of sev- eral new genera and species. Trans. zool. Soc.. London, 5: 113-148, pls. 28-33. ALLAN, J. K., 1932, Australian nudi- branchs. 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Lon- don, 28: 93-101, pl 9. 1951, On a collection of mol- luscs, mainly nudibranchs from the Red Sea. Proc. malacol. Soc. London, 28: 241-253. YU, L. G. & SI, T., 1965, Opisthobran- chia from the inter-tidal zone of Hai- nan Island, China. Oceanologia et Limnologia Sinica, (1): 1-20, pls. 1-3. ZILCH, A., 1959-1960, Gastropoda (Eu- thyneura). Jn: Schindewolf, Otto H., Handbuch Paläozool., 6(2): 834 + xiip, 2515 figs. 222 MARCUS AND MARCUS ADDENDUM Since the present paper was completed in 1967, I received some opisthobranchs from Komodo by the kindness of Dr. Brian K. McNab-Gainesville. These were one specimen of Trippa intecta, two of Atagema osseosa, and one of a Gymnodoris with the innermost radular tooth twice the length of the second scriptions of the well-classified G. cit- rina (Bergh, 1877). The brown color of the innermost tooth agrees with that in the material from Eniwetok (Marcus and Burch, 1965: 249), at that time classified as G. bicolor (Alder and Hancock, 1864), later transferred to citrina (Marcus, 1970, Opisthobranchs from the Southern Tropical Pacific. Pacific Science 24: 155-179, on p 169). tooth, hence corresponding to the de- RESUME QUELQUES GASTROPODES DE MADAGASCAR ET DE L’OUEST DU MEXIQUE E. du Bois-Reymond et E. Marcus Cet article traite de 43 espéces de gastropodes marins, surtout Opisthobranches (mais aussi 1 Lamellariacea et 3 Onchidiacea) de Madagascar et du golfe de Cali- fornie. Des descriptions anatomiques sont données pour les diverses espéces. Trois espèces ont été reconnues comme communes dans l’une et l’autre série; elles repré- sentent des taxa qui se rencontrent dans les mers chaudes circumtropicales. Les nouvelles espèces suivantes ont été décrites: Smaragdinella kirsteneri, Stiliger (Stiliger) erbsus, Hypselodoris regina et Noumeaella isa (de Madagascar), et Elysia vreelandae (de 1’Ouest du Mexique). Les Opisthobranches de Madagascar appartiennent a la faune récifale indo-pacifique, qui est assez homogene; au contraire, ceux du golfe de Californie vivent dans des zones largement dépourvues de récifs coralliens, mais contenant un apport d’éléments faunistiques du Pacifique tempéré américain et panaméen. A. L. RESUMEN ALGUNOS GASTROPODOS DE MADAGASCAR Y MEXICO OCCIDENTAL Marcus y Marcus Se tratan 43 especies de gastropodos marinos, la mayoría opistobranquios (pero también 1 lamelariáceo y 3 onquidiacéos) de Madagascar y del Golfo de California. Se da la descripción anatómica para varias de las especies. Se reconocieron 3 especies comunes en ambas colecciones que representan taxa de mares circum- tropicales. Se describen las siguientes especies nuevas: Smaragdinella kirsteureri, Stiliger (Stilliger) erbsus, Hypselodoris regina, y Noumeaella isa( de madagascar), Elysia vreelandae (del oeste de Mexico). Los opistobranquios de Madagascar per- tenecen a una fauna Indo-Pacifica mas bien homogenea, de los arrecifes, mientras que los del Golfo de California viven en areas donde no existen arrecifes de coral, pero que contienen una mezcla de elementos faunisticos de la zonas de Panama y templadas del Pacifico. Ji SAP. MADAGASCAN AND MEXICAN GASTROPODS 223 ABCTPAKT О НЕКОТОРЫХ БРЮХОНОГИХ С МАДАГАСКАРА И ЗАПАДНОЙ МЕЖСИКИ 3. ДЮБУА-РАЙМОН-МАРКУС И 3. МАРКУС В работе рассматривается 43 вида морских брюхоногих моллюсков, глав- ным образом заднежаберных (но также 1 представитель Lamellariacea И 3 пред- ставителя Onchidiacea) с Мадагаскара и из Калифорнийского залива. Приведе- ны анатомические описания различных видов. Три вида оказались общими для обоих мест сборов; они представляют собой таксоны, встречающиеся в цир- кумтропическо-теплых морях. Описаны следующие новые виды: Smavagdinalla kir- steueri, Stiliger (Stiliger) erbsus, Hypselodoris regina и Noumeaella isa (с Мадагаскара) и Elysia vreelandae (из Западной Мексики). Заднежаберники с Мадагаскара принадлежат к более или менее однородной Индо-пацифической рифовой фау- не, в то время как моллюски из Калифорнийского залива живут в областях, в значительной степени лишенных коралловых рифов, но содержащих примесь панамских и американских умеренных пацифических элементов фауны. BASE MALACOLOGIA, 1970, 10(1): 225-282 THE MANTLE FLAP IN THREE SPECIES OF LAMPSILIS (PELECYPODA: UNIONIDAE) Louise Russert Kraemer! Department of Zoology University of Arkansas Fayetteville, Arkansas 72701, U.S.A. ABSTRACT The purpose of this study was to review the morphological and general activity bases of mantle flapping in the North American unionid subfamily Lampsilinae and to explore experimentally some factors that may account for this striking activity: flapping mussels resemble smallswimming fish. Morphological studies (chiefly on preserved material of Lampsilis ventricosa and L. fasciola), oc- casional field studies (in several counties in northwest Arkansas), and prolonged aquarium studies on living L. ventricosa, L. siliquoidea and L. brevicula brittsi were carried out from 1962 to 1965. It was found that the mantle flaps which are an extension of the inner lobe of the mantle edge just anteroventrad to the branchial siphon, are a permanent feature of the mature female. Among the flaps of these 3 species, there exist structural similarities (presence of eyespot, innervation by branches of pallial nerves from the visceral ganglion) as well as differences in shape and pigmentation. Flap movements are initiated by paired pulses which produce contractions starting at. the tail base and move toward the eyespot ends of the flaps. A re- covery phase follows, in which the flaps assume their former position, with the tails floating horizontally. Flapping behavior also involves the coordinated function of foot, marsupia, valves and siphons to such an extent that the supposed normal spatial relation- ships between body and shell are much altered. For different species flapping involves different behavioral complexes as well as different relevant stimuli (in particular light intensity for Lampsilis ventricosa and water waves and jarring of substrate for L. siliquoidea). Flaps occur only in mature female specimens, although juveniles and males have flap rudiments, and flap movements have been seen only in gravid, never in non-gravid females. Flapping occurs. in prolonged periodical spells through- out the summer months and has been seen to accompany the gradual emptying of the ovisacs, and the shedding of conglutinates. Flapping has not been observed after spawning of glochidia. Two earlier hypotheses concerning the function of flap movements in the Lampsilinae, i.e., the roles of the moving flaps as “lures” for host fish to the mussels’ glochidia, and as aerators for the gills and marsupia, seem now to be only partly plausible. Because of the differences in aspect, in speed of flapping and in responsiveness to environmental stimuli among the different species, it is here suggested that these differences are possible adaptations to habits of peculiar host species of fishes. The bellows-like movement created by the paired pulses of all flap movements, regardless of species or of flapping frequency, might help the glochidia to remain suspended in the water for a period of time, and thus facilitate the vitally necessary contact with a host fish. 1a dapted from a dissertation submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy at the University of Michigan. (225) 226 L. R. KRAEMER INTRODUCTION Only a few genera of freshwater mussels, all in the American subfamily Lampsilinae? within the large and world- wide family Unionidae, are known to pos- sess mantle flaps. These flaps (F) are appendages of the mantle, that are lo- cated anteroventrad to the branchial siphon (BS, Fig. 1). During late spring and through the summer months, female animals possessing such well-developed flaps may upend themselves in the sub- strate. Their mantle flaps are then extended (Fig. 2) and moved in a series of rhythmic pulsations. To the human observer they strongly suggest a small fish, complete with pigmented eyespots, stationary in the current and waving its flanks and tail. Ortmann (1911) was the first to record observations of flap movements which he had seen best in Lampsilis ventricosa and L. multivadiata (Г. fasciola). Studies on the natural history of freshwater mussels undertaken early in the century (e.g., Wilson € Clark, 1912; Coker etal., 1921) contain occasional references to lampsilid flap movements. Taxonomic treatments of the Unionidae (e.g., 2The Lampsilinae are the only unionid subfamily entirely confined to North and Central America. ICM FIG. 1. Lampsilis ventricosa (Barnes). Drawing of preserved specimen, seen from the left side. Left valve and most of left mantle removed. Specimen collected from River Raisin, above Sharon Hollow, Washtenaw Co. , Michigan, 1963. (For abbreviations, see р 228). MANTLE FLAP IN LAMPSILIS — I CM FIG. 2. Lampsilis ventricosa (Barnes) in typical “headstand” position (rotated by 90°) during flapping behavior, drawn from the left side. Specimen collected from War Eagle Creek, Benton County, Arkansas, June 14, 1964. (For abbreviations, see p 228). Scammon, 1906; Ortmann, 1911; Simpson, 1914; Walker, 1918) provide brief descriptions of the flaps’ ap- pearance. Some authors (Ortmann, 1911; Howard & Anson, 1922; Welsh, 1933) have specu- lated that the unique lampsilid flaps and flap movements may be involved in fish- host relationships. Welsh (1933) carried out a brief experimental study of the mantle flaps with Lampsilis nasuta (Ligumia nasuta) in which he discovered 227 228 L. R. KRAEMER LIST OF ABBREVIATIONS AA anterior adductor muscle AE “anterior” or eyespot end of flap AS part of mantle modified as anal siphon B base of flap BS part of mantle modified as branchial siphon BT basal tentacle CG conglutinates DEF distal edge of flap DM distal edge of marsupium E eyespot ERF edge of right flap ESH edge of shell ET empty tube F mantle flap FT foot G glochidia H hinge region ISH inner shell layer IG inner gill L ligament LBS location of branchial siphon LF left mantle flap LM left marsupium LP labial palp LT left mantle flap’s “tail” LV left valve a correlation between frequency of flap movements and decreasing light in- tensity. Lack of sufficient live material prevented Welsh from conducting further experiments. The foregoing constitutes the slender bulk of work which has been published to date on lampsilid mantle flaps. The precise nature of the flap movements, their possible role in the mussel’s life history, and in the distribution and speciation of the Lampsilinae, were un- explored. A feeling of some urgency accompanied the present study, because freshwater mussel populations are vanishing at an alarming rate in theU.S. (H. & A. van der Schalie, 1950). Living Lampsilinae are increasingly difficult to find, and may be unobtainable for such studies a decade hence. It is the purpose of this communica- tion (1) to describe flap movements of Lampsilis ventricosa (Barnes), as well M marsupium (modified posterior portion of outer gill) MA mantle OSH outer shell layer ОУ ovisac (water tube) of exposed marsupi- um P line of pigment on inner surface of mantle flap PA posterior adductor muscle PE periostracum PG pedal gape РО pore PS pigment spot RE region which corresponds with location of eyespot on outer surface of right mantle flap RF right mantle flap RM right marsupium RT right mantle flap’s “tail” RV right valve SAS supra-anal-siphon SG secretory groove SP siphonal partition T “tail” of mantle flap TE tentacle U umbo as the species” characteristic “flapping behavior” complex (which is ostensively related to its general behavior inven- tory; (2) to summarize results of experi- mental studies of possibly relevant stimuli to flapping behavior in L. ventri- cosa; (3) to report comparative studies of L. siliquoidea (Barnes) and L. brevi- cula brittsi (Call), which reveal striking differences from L. ventricosa in flap morphology, in flapping behavior, and in stimuli relevant to that behavior; (4) to present evidence in support of certain conclusions which I have reached re- garding the role of flapping behavior in the life history of these species; and (5) to suggest further hypotheses. BACKGROUND 1. Taxonomic position of the Lampsilinae Mantle flaps and flap movements are peculiar to the Lampsilinae, a subfamily MANTLE FLAP IN LAMPSILIS 229 that has long been considered to contain the most advanced forms. As Walker (1917: 10) pointed out, the evolution of the Unionidae “has all been centered around the adaptation of the gills of the female for the care of the eggs until they are hatched.” Evidence for Walker’s generalization is patent in the dis- tinguishing characteristics of the 3 sub- families of the Unionidae: (1) the Unioninae are short-term breeders in which water tubes of all 4 gills serve as containers or ovisacs for glochidia; (2) the Anodontinae are long-term breeders in which only modified midsections of the water tubes of the outer gills serve as ovisacs (Ortmann, 1911); and (3) the Lampsilinae are long-term breeders in which only the posterior portion of each outer gill serves as a marsupium, the ventral borders of the latter extending below the distal edge of the inner gills, and often having a “beaded” appearance. Water tubes which become ovisacs inthe Lampsilinae remain undivided, the whole tube serving as ovisac. Ortmann (1911) believed that the Lampsilinae were the most highly evolved of the unionid subfamilies, not only because of the restriction of the marsupium to part of each outer gill, but also because of the prominent ex- pression of sexual dimorphism in the shell, and the characteristic presence of special structures just in front of the branchial siphon: (1) the distinct, often large, conical papillae (or tentacles) found in Ligumia and Villosa (TE, Fig. 3) and (2) a lamellar keel or ribbonlike flap (the mantle flaps mentioned above), better developed in the female than in the male. 2. Mantle movements in other bivalves Though mantle flap movements have been seen only in the Lampsilinae, generalized rhythmic movements of the mantle, independent of shell movements, occur in other bivalves. Redfield (1917: 233) investigated rhythmic mantle move- ments in at least 9 different species of lamellibranchs, and observed that in Mya arenaria, for example, a wave of con- FIG: 3. left mantle edge, showing tentacles of unknown function anterior to branchial siphon (drawn Villosa (Lampsilinae); posterior from fresh specimen). 2, middle or second fold of-mantle edge; 3, inner or third fold of mantle edge. Scale = lcm. traction is seen to start at the distal end of the extended siphon, and to “move forward ending with the rise and fall of the mantle,” about once a minute, ina freshly collected specimen. Pelseneer (1935) and Franc (1960) contended that such mantle movements favor circula- tion of water in the pallial cavity. 3. Modified mantle structures in other bivalves Though mantle flaps per se are pe- culiar to the Lampsilinae, modified mantle structures are known in other bivalves, and include: eyes whichrim the mantle of pectinid species and stud the Siphonal tentacles of Cardium; a crown of tactile papillae around the branchial siphon (Tapes, Corbula, Poromya); and tactile papillae edging mantle borders (Solenomya, Lepton, Pecten). Among the Unionidae, in the Lampsilinae, there occur modified mantle structures of un- known function near the branchial siphon, such as “caruncles” or fleshy protuber- ances (Carunculina), and conspicuous tentacles and papillae (Ligumia, Villosa). 4. Factors which affect spawning in other bivalves In the present study, the possible re- lationship of flaps, and flap movements of the Lampsilinae, to spawning of 230 L. R. KRAEMER glochidia will be considered. For fresh- water mussels as a whole, direct experi- mental evidence of factors which affect spawning is slight, though some efforts have been made to study them (Utter- back, 1931). For marine bivalves, especially for several commercially valuable species, a number of factors have been implicated (Table 1). 5. Review of general neuroanatomy and sensory structures of Lampsilis Since the present paper deals witha form of bivalve behavior, and since “... an organism’s behavior is an expression principally of the capabilities of its nervous system” (Dethier & Stellar, 1964: 3), there follows a brief review TABLE 1. Presumed spawning factor Condition (“ripeness” of bivalve prior to spawning) Spawning movements (shell) Temperature (above 27% C, spawning appears to be inhibited) Lunar periodicity (uncertain whether light or water pressure is critical factor) Sex of bivalve (differences in latent period between stimulus and spawn- ing: oO are generally more respon- sive to stimulus than 9) Sperm cells in surrounding water Diantlin (an active principle in sperm cells of some bivalves) Thyroxin, theelin (injections followed by emission of sperm) Extracts of Ulva, a green alga, induces shedding of sperm Neurosecretions (as suggested by effects of extirpation of cerebro- pleural and visceral ganglia) Mechanical stimulation (scraping and pulling of byssus; water turbulence) Repeated stimuli (no response to lst application of stimulus but to later ones) Species Mytilus californicus Ostrea (9) Ostrea edulis Crassostrea virginica Ostrea edulis ($) Ostrea Gryphea (= Crassostrea) virginica Mytilus californianus Ostrea (Crassostrea) virginica Oysters Mytilus californianus Tridacna Ostrea gigas (9) Ostrea gigas (0) Mytilus edulis Chlamys varia Mytilus californianus Cumingia tellinoides Mytilus californianus *Spawning refers to emission of sperm or eggs Factors implicated in spawning* in some marine bivalves Investigator Young, 1945 Galtsoff, 1938a Loosanoff & Engle, 1940 Korringa, 1947 Galtsoff, 1938a Nelson & Allison, 1940 Young, 1945 Nelson & Allison, 1940 mentioned by: Fretter & Graham, 1964 Galtsoff, 1940 Miyazaki, 1938 Lubet, 1956 Young, 1945 Grave, 1927 Young, 1945 MANTLE FLAP IN LAMPSILIS 231 of the neuroanatomy of Lampsilis. The organization of the nervous system of Lampsilis closely resembles that of Anodonta (described by Simpson, 1884).3 Members of the genus Lampsilis possess a bilateral nervous system that includes the 3 pairs of ganglia charac- teristic of bivalves. A pair of cerebro- pleural ganglia are located on either side and slightly posterior to the mouth and to the anterior adductor and protractor muscles, where they are embedded inthe tissue of the foot. Nerves from the cerebropleural ganglia extend into the mantle, viscera, anterior muscles, muscles of the foot and to the stato- cysts. A conspicuous connective passes under the esophagus and joins the 2 cerebropleural ganglia. Connectives extend from each cerebropleural ganglion to the fused pedal ganglia, deep in the muscle of the foot. Prominent connectives from each cerebropleural ganglion emerge posteriorly from the visceral mass, and approach each other fused visceral ganglia. The visceral ganglia are closely joined by a wide commissure to form a single large, butterfly-shaped ganglion (here- after referred to as the visceral ganglion), located just under the super- ficial epithelium covering the ventral surface of the posterior adductor muscle. From this ganglionic complex arise many nerves which I have traced into the osphradia, gills, kidneys, pericardial cavity, posterior adductor muscle, rectum, inner and outer surfaces of the mantle in general, and by way of many branches and anastomoses into the siphons and flaps.4 As in other bivalves, sense organs, such as statocysts? and osphradia are found in Lampsilis. The statocysts are 2 tiny spherical cavities (each of which contains a sizeable statolith) at the ends of the statocyst nerves, deep in the foot tissue. The osphradia are 2 small patches of specialized epithelia next to the branchial nerve, just dorsal to the gills and ventral to the visceral ganglion. 6 just behind the posterior retractor muscle, where they shortly join the 3The summary which follows here is based on dissections made for this study, as described in “Materials and Methods,” under “Anatomical Studies” (p 232). No attempt was made in this study to follow nerve fibers through the ganglia. Friedenfelt (1904) described much of the fine structure of the visceral ganglion in Anodonta; but Rawitz (1887) was the only investigator whom I found to have described pathways of nerve fibers through this ganglion (in Mytilus). Since Rawitz’ work was done with primitive techniques, one is inclined to believe, with Bullock & Horridge (1965: 1396) that especially with reference to the cerebro- pleural and pedal ganglia, “the whole matter of pathways. . .must be regarded as requiring in- vestigation de novo. ” SStatocysts have been experimentally implicated as organs of equilibrium (Buddenbrock, 1913, for Chlamys varia). 6The assertion (by Rawitz, 1887; Pelseneer, 1906) that the innervation of the osphradia is by way of connectives from the cerebropleural ganglia through the visceral ganglion, has recently been questioned (Bullock & Horridge, 1965). That osphradia function as chemoreceptors in bi- valves has often been maintained (e.g., Pelseneer, 1906; Allen, 1923); but this claim has not, to my knowledge, been experimentally demonstrated. Bailey & Laverack (1963) reported that action potentials in the branchialnerve ofa snail followed chemical stimulation ofits osphradium. Aiello & Guideri (1964) suggest that regulation of water flow through the mussel (Mytilus edulis) may be due to a possible physiological connection between chemical stimulation of the animal’s osphradia and subsequent nervous control of ciliary activity on the lateral epithelia of the gills. 232 L. R. KRAEMER Specialized photoreceptors have not been identified in the Unionidae, despite the fact that several species (including those of Lampsilis) are light, i.e., “shadow” sensitive (skioptic). Photo- receptors are known in some marine bivalves (reviewed by Franc, 1960).7 Tactile sensitivity in bivalves (noted in Lampsilis, too) is particularly local- ized in the siphonal papillae and in the anterior part of thefoot. The innervation of such papillae has been studied in other species (e.g., by Galtsoff, 1964, in Crassostrea virginica). Franc (1960) reported that the siphons of Mya are sensitive to a pressure of 1 mg per 1 mm2 of siphonal surface (Pieron, 1941) and noted that the foot of the Unionidae orients itself into the weakest of currents, being sensitive to the slightest differences in frictionon either side of the foot. MATERIALS AND METHODS Field Collections: From the summer of 1962 through the summer of 1965, occasional collections were made of Lampsilis ventricosa, L. siliquoidea and Г. brevicula brittsi, chiefly in the White River and its tributaries, in Washington County, northwest Arkansas (see Fig. 4). L. ventricosa exhibiting flapping behavior were ob- served on several occasions in June, 1962, and in June, 1963, in the White River. The best collection site was in that river near the Wyman Community. Very large (over 20 cm long) old speci- mens of L. ventricosa of both sexes were not difficult to find there prior to serious depletion of 2 fine shoals, ap- parently through drought and sewage pol- lution late in the summer of 1963. Other shoals which served as collection sites are now inundated by the backing up of the White River behind Beaver Dam. In no instance were Lampsilis abundant. Several hours of searching would turn up 2-3 gravidfemales. Young individuals were seldom found. Specimens were collected usually on shoals of sand and gravel, in swift and in sluggish currents, in water ranging from clear to very turbid, and from depths of 1-3.5 feet. Anatomical Studies: Dissections were made of fresh specimens of Lampsilis ventricosa, L. siliquoidia, L. brevicula brittsi as they became available, largely in the summer months. The neuro- anatomy of preserved L. ventricosa and L. fasciola and of methylene blue prepa- rations of fresh L. ventricosa was ex- amined in some detail. Preliminary studies of flap and nerve histology were also made. Aquarium Studies: For purposes of observation some mature female Lamp- silis were maintained in aquaria through- out most of the year from the summer of 1962 through the summer of 1965, Individuals were held in aquaria in a variety of environments for as long as 12 months. Female mussels were kept in various ways: solitary, with others of the same sex, with males of the same species, with specimens of other species, and with fish of various kinds, including the black crappie, largemouth bass, and madtom. The aquaria used were of various sizes ranging from 2 to 50 gallons in capacity. Water temperature in some aquaria was allowed to fluctuate with normal room temperatures, but was held constant in others. Light conditions were varied from no daylight with only occasional artificial light (i.e., incan- descent or fluorescent light) to natural daylight only. It was not possible for me to feed the animals adequately. In many instances, algae were allowed to grow on the sides of the tank, and were then periodically suspended in the water TKennedy (1960) was able to demonstrate photoreceptive activity of the pallial nerve in Spisula, although he was not able to identify pertinent photoreceptor pigments there. (Photoreceptive function has not been demonstrated for cytochrome h, the hemoprotein he actually found present in high concentration in the pallial nerve of Spisula). MANTLE FLAP IN LAMPSILIS | \ | | | | | | j | E MA у р р e GR, À n a a a y DENTON = COUNTY a / pa ir < 7% 1 | y SPRINGDALE 4 = . / ee PE ER > ! | SPRINGS a j eS »SONORA / ve ~ ae & / : h Y | f & / À д 1 CM 6 | | (See p 240 for legends to Fig. 6 and Fig. 7). 240 of the valves, whereby the rotundity of the female shell accomodates the mar- supia as well as the thickened posterior mantle edges. In the living, mature female animal, the outer mantle lobe (Fig. 6, 1) is much thickened in the siphonal and flap region, and is almost completely covered by the shell. The middle lobe (2) is very thin at the base of the anal and branchial siphons, but is evident as a rounded pigmented ridge, near the flaps (Figs. 7, 8). The inner lobes (3) not only form the flaps, but their protruding apposition under the flaps “tails” is seen (especially in a rear view of flapping L. ventricosa, Fig. 8, B3) to cause an elevation of the tails. 2. Orientation of Lampsilis ventricosa to the substrate during flapping behavior 9 When the mussel is engaged in flap- ping, its appearance is much altered from “normal” (Figs. 9a, b) by: (1) for- ward tilting of valves (a rotation of about 90°); (2) exaggerated posterior extension of foot; and (3) extreme protrusion of flaps, inner mantle lobes and marsupia (Fig. 9c). Flapping behavior configuration alters not only the position of the animal rela- tive to its substrate, but to the valves of its shell as well. The “anatomical correspondence” areas defined by Stasek (1963) for a number of bivalves, would not apply to L. ventricosa during flap- ping. (See Fig. 10). 9Orientation of animal to substrate only is discussed here. L. R. KRAEMER For the foregoing reasons, convention- al designations of “anterior,” “pos- terior,” “dorsal” and “ventral,” become misleading; and thus terms which are meaningful within the special context of flapping behavior (as shown in Fig. 11) will be used in this paper. A summary contrasting orientation of L. ventricosa to its substrate during flapping behavior and during normal activity is presented in Table 3. The typical position of flapping L. ventricosa illustrated in Fig. 9c is the only one I have noted for this species under natural conditions. Ortmann (1911) and Grier (1926) have presented general descriptions of this position. However, I have often observed that L. ventricosa in aquaria may exhibit flap movements when its valves are tilted up no more than 45° (Fig. 7), although such flap movements are slow, and occur at low light intensities. 3. Analysis of flap movements in Lampsilis ventricosa Ortmann (1911), Wilson & Clark (1912), Grier (1926) and others noted that flap movements are very rhythmic and rapid in L. ventricosa. In the course of pro- longed observations of flapping animals in aquaria during spring and summer months and from analysis of 16 mm moving pictures of some of these ani- mals, I have determined that there are at least 2 principal categories of flap movements: (1) regular movements, observed at high flapping frequencies of Field observations (my own, 1962, 1963, and those of Ortmann, 1911) indicate that the flapping animals may orient themselves into the current. Present studies have not included an investigation of this factor. FIG. 6. Diagram of transverse section of bivalve mantle edge. 1, outer lobe; 2, middle lobe; 3, inner lobe (from Morton, 1960). Scale shown indicates approximate size of a trans- verse sectionthrough posterior mantle edge of Lampsilis ventricosa, Y, in a specimen 15 cm long. FIG. 7. Semi-diagrammatic view of Lamp- silis ventricosa, during slow flap movements in aquarium, from left rear side, indicating lobes of mantle edge. 2, middle lobe; 3, inner lobe and structures arising from it. Note that valves here are tilted by only 45°; the inner mantle lobes are pushed out against each other. MANTLE FLAP IN LAMPSILIS 241 flaps exhibit other types of movements too, though less often. All spontaneous flapping movements involve both mantle flaps. Regular flap movements (Figs. 12, 13): Before the regular movement is begun, the tails of the flaps are spread apart, to float horizontally in the water, inner surface dorsal. The “anterior” ends (see Fig. 11) of the flaps, with white- rimmed black “eyespots”10 on the ex- ternal surface, are held together; or, if the marsupium protrudes, flaps are held close to the sides of the marsupium. 11 The movement starts with aquick strong contraction at the base of the flaps. The tails are thereby turned upward, and often clap together over the exposed edge of the marsupium. Now apulsel2 moves from just in front of each of the tails, cn forward to the anterior, eyespot ends of the flaps. A lateral bulge is thus FIG. 8. Flapping in mature female Lamp- Simultaneously produced in each flap; silis ventricosa. Rear view during flap move- ments. Drawnfromlivinganimal. 2, 3, middle and inner lobes, respectively, of mantle edge. Note that the inner lobes belowthe mantle flaps are pushed tightly together. 60 or more moves per minute, and (2) slow movements, seen at rates of less than 30 moves per minute. The mantle and as the pulse moves along, it in- creases in amplitude and causes each flap to be turned downward and outward. Finally the pulse reaches the eyespot end of each flap, pushing the whole flap-pair forward, and snapping the eyespot ends outward.13 The slower recovery stroke of the regular movement now occurs. The tails relax and float out horizontally, 10The eyespot’s function as a photoreceptor has not been demonstrated. Sufficient material for adequate pigment analysis was not available in this study, but chromatograms made from a couple of eyespots from very large (20cm) specimens showed pink fluorescence above pigment sample, and dark, probably UV absorption spots 5-7 cm above pigment sample (Whatman' #1 paper, butidine solvent). Presence of porphyrins (characteristic for photosensitive pigments) may be indicated. Because no photoreceptive function has yet been demonstrated for the “eye- spot, ”the term is inappropriate. It will be used throughout this study, however, because it is established in the literature, and because many lampsilids possess numerous other pigment spots. llBecause frequently one marsupium only protrudes during flapping behavior, the term “mar- supium” rather than “marsupia” will be used in much of this description, although both of the marsupia protrude from time to time. 124 pulse is a superposition of sine waves of different frequencies, analogous to the motion generated by pushing up, then pulling down on a taut rope’s end - not a wave or undulation, which would advance at a constant speed and amplitude. 13When one observes a flapping L. ventricosa in a turbid stream, the completion of the forward movement of the pulse is striking. On the internal surface of the flaps in this species, at a point corresponding with external location of the eyespots, there is a patch of white. To the human observer, the flash of the white patches is the most eye-catching part of the regular flap movements. 242 L. R. KRAEMER FIG. 9. Flapping in mature female Lampsilis ventricosa. Diagrams showing appearance while anchored in substrate, from the left side, a, during normal activity, flaps withdrawn; b, flaps visible; and c, during flapping behavior, showing “headstand” position with tilted valves, foot as prop, flaps and marsupium broadly protruding. Note “normal” position of marsupium (dotted) under shell in a. FIG. 10. Flapping in mature female Lampsilis ventricosa. Diagrams showing “anatomical correspondence” areas, defined by Stasek (1963) for bivalves, as they might be applied to Lamp- silis ventricosa during: a, “normal” activity, and b, during flapping behavior. A, pedal margins, which extend from anterior limit (AL) of the infra-branchial chamber near the mantle isthmus of the animal to its pedal gape (PG); B, the inhalent aperture, extending from the pedal gape to siphonal partition (SP); and C, the exhalent aperture which extends from the siphonal partition to the limit of the suprabranchial chamber near the hinge (H). MANTLE FLAP IN LAMPSILIS 243 FIG. 11. Flapping in mature female Lamp- silis ventricosa. Diagram of flap region show- ing terminology used in text (p 228) in ana- lyzing movements of mantle flaps during flap- ping behavior. Notethat the distal edge of mar- supium and distal edge of flap is now “dorsal, ” while the eyespot end is “anterior” and the tail of the flap is “posterior. ” the anterior ends move up against each other (or against the protruding mar- supium), and both flaps are simultane- ously pulled back and together. Regular flap movements resemble Swimming motions of a little fish, a resemblance first noted by Coker et al. (1921), and later by Howard & Anson (1922). This resemblance has prompted Welsh (1933) to refer to the flaps as “lures” for possible fish hosts to the mussel’s glochidia. Regular flap move- ments have been observed at frequencies varying from 60 or slightly less to as much as 180 per minute. At 1 per second frequency, each recovery stroke requires about 0.6 seconds. The slow movements (Figs. 14, 15): I have observed slow movements usually at low light intensities, and at frequencies of from 30 per minute down to less than one in 30 minutes. Before the slow movement starts, flaps are spread wide apart, the entire length of each floating out horizontally, inner sides uppermost in the water. The marsupium may not, but more often does, protrude between the flaps. When the movement begins, there is a contraction at the flap base; the tails move up and may touch medially; then a pulse moves forward from infront of the tails, which draws the eyespot ends of the flaps upright, together, and backward. In recovery, first the tails, then gradu- ally the rest of the flaps relax and float out horizontally once more. At the end of the recovery stroke, the flaps have moved forward slightly, again. Whereas it has been speculated that the minnow-like aspect produced by the rapid (“regular”) movements of the flaps might attract possible fish hosts, and that these movements may serve to aerate the glochidia, slow movements of the flaps seem unqualified for either role. The slow movements can go on for hours at very low light intensities and obviously contribute little to aerate glochidia, nor do they give the impression of a swim- ming fish. A prominent feature of the mussel's slow movements is the accompanying, broad exposure of the marsupium. Other flap movement patterns: Other movement patterns noted in this study for L. ventricosa are: “fluttering” move- ments, “weak, regular” movements, and, rarely, “double” movements. The first 2 are described here. Fluttering movements may be ob- served during periods of very low flap- ping frequency. They consist of slight, rapid contractions which course from eyespot to tail and from tail-base to eyespot, and involve just the distal, gray-pigmented parts of the flaps. Their passage along the flap is accompanied by minute darkenings of the pigment, and bendings of delicate papillae which fringe the free surface of each flap. Weak regular movements may be seen during periods of prolonged, high flapping frequency (1 move/sec.). Initial con- tractions at flap-base, and the pulse subsequently generated, are much less strong than in the regular movements. The pulse does not cause the eyespot ends of the flaps to be thrust forward and to snap apart. The recovery stroke does not bring the flap edges upright and together. The effect of these weak regu- lar movements is to producea rhythmic, gentle “waving” of the flaps. 244 L. R. KRAEMER TABLE 3. Orientation of Lampsilis ventricosa during “normal” activity, contrasted with position during flapping behavior (compare with Fig. 9) Body Position during “normal” RE , A : P d structure (non-flapping) activity saition during Seppe poe Valves “Upright, ” i.e., umbones and liga- Tipped (rotated anteriorly), often in Foot Anal siphon Branchial siphon Mantle flaps ment on top (dorsal). Used chiefly during locomotion: foot extended at front, then back, valves then hunching forward. Dorsal and posterior; line ligament - anal siphon nearly parallel with substrate. Posterior, ventral to anal siphon. Distal edges projecting parallel to substrate (papillae may be touching medially). If visible, located ventral to branchial siphon, not extending far from valves. Tails may or may not be hanging free, and ventral to rest of flap. “headstand, ” i.e., umbones are now near substrate, ligament vertically above umbones or even in a line forming an acute angle with substrate in front of the animal. Posterior part of foot much extended to make wedge-shaped prop for animal’s up-tilted valves. Dorsal to anterodorsal. Line liga- ment - anal siphon vertical to substrate. Dorsal, posterior to anal siphon, distal edges may be turned medially, papillae touching. Dorsal, posterior to branchial siphon. Eyespot, “anterior” flap portion just posterior to branchial siphon. Tail, posterior portion, floating free, the whole flap pushed out from valves. Inner lobe Distal edges touching medially, or Distal edges projecting at least 2 cm (3), at base withdrawn between the valves. If from valves (in specimen 10 cm long, of flaps withdrawn, mantle flaps are not touching each other medially at 60° extended or visible. angle to form peak under flap tails (see Fig. 8). Marsupia Ventral to posterior adductor and Pushed out between flaps, protruding (posterior rectum. Kept within pallial cavity. 2 cm; distal edges dorsal. Posterior portion of tubes of marsupium now anterior outer gills) because of 90° rotation of animal. Marsupia may move “up” and “down” between flaps according to light intensity and frequency of movements. 4, Behavior accompanying initiation of flap movements Lampsilis ventricosa often begins flap movements at dawn, with a characteris- tic behavior sequence (Table 4), the con- sequences of which are: (a) mussel has assumed “headstand”; (b) foot is promi- nently displayed as a luminous white heel, or prop, for uptilted valves; (c) flap movements markedly increase in frequency (from 30 moves/5-10 minutes, to 30 moves/30 seconds or less, i.e., they become from 10-30 times as fast, see Fig. 16), and (d) one marsupium or both marsupia protrude between flaps. MANTLE FLAP IN LAMPSILIS 245 FIG. 12. Elements of the regular flap movements of Lampsilis ventricosa, viewed from above (semidiagrammatic). A, position at end of recovery stroke (tails floating out, eyespot ends against sides of marsupium); В, pulse begins near base of tails, outer margins fold over and meet at centerline; C, pulse (bulge) moving toward anterior eyespot end of each flap; D, pulse nearing eyespot ends of flaps; E, pulse at eyespot ends of flaps, pushing them outwards and forward horizontally. TABLE 4. Summary of sequence of events in initiation of flap movements in gravid female of Lampsilis ventricosa Approximate Step Behavioral event duration in minutes il Mussel in normal position (ligament dorsal). -- 2 Flaps are extended, until free edges of tails are exposed. 5-10 3 Flaps hang limply, ventral to branchial siphon. 5 + Fluttering movements occur. 2 5 Pause. 2 6 Animal completely withdraws flaps; mantle lobes in 1 siphonal region are squeezed together; mussel extends foot out and slightly backward in substrate and tips valves forward, toward umbones. 7 Valves open slightly; flaps are re-extended. 2 8 Repetition of steps 4 through 7, approx. 3 times. 20 Whenever flaps are withdrawn, the mar- Supium is moved down into the pallial cavity. The flaps then are re-extended, and move vigorously for 1-2 minutes before marsupium protrudes fully again. Grier (1926) described an increase in flapping frequency in L. ventricosa, but not in the context of the animal’s response to increasing daylight. He observed (:112): “At first the rate is quite slow, as if the creature were ‘warming up’ but rapid acceleration occurs to a maxi- mum rate...” I have found that the rate of acceleration in flapping frequency is not always rapid, and that the “maxi- mum” rate varies with eachanimalfrom 246 L. R. KRAEMER See) - Ру AAN > FIG. 13. Semidiagrammatic view of the regular flapmovements of Lampsilis ventricosa, from the left side. Compare stages with Fig. 12. A, end of recovery phase (tails out, horizontally); B, beginning of “forward” pulse (note that it begins at base of tails); these are then bfought up- ward and seem to clap together medially, over the protruding marsupium; C, pulse moves along each flap, causing a lateral bulge; D, pulse nears “anterior” eyespot end of flaps; E, pulse is at each flap end, pushes them outward and horizontally, also thrusting the flap-pair forward. MANTLE FLAP IN LAMPSILIS 247 FIG. 14. Elements of the slow flapping movements of Lampsilis ventricosa, viewed from above. A, position of flaps at end of recovery stroke (flaps wide apart, floating horizontally, entire inner surfaces uppermost, marsupium widely exposed); B, pulse begins at base of flaps, bringing tails together medially; C, pulse moves forward, bringing mid-portion of flaps up medi- ally; D, pulse nears eyespot ends of flaps, bringing them up close together with their anterior ends pulled back a little; E, end of forward pulse, most of flaps up, together and still backward. === ICM FIG. 15. “Head-on” view of flaps of Lamp- silis ventricosa during slow movements; drawn from an animal in headstand position, looking from branchial siphon toward the flaps. Eye- spot ends of flaps in foreground, free-floating flap-tails in rear. Note widely exposed mar- supium. Only one marsupium is visible, the other one held within the branchial cavity. one day to another (as well as from one time of day to another). Variation in the daily time of onset of flap movements was noted in this study. Occasionally an animal would not initiate flap movements until mid-afternoon, even on a sunny day. Water temperature did not appear to be animmediate stimu- lus for initiation of flap movements. No differences were observed between specimens of L. ventricosa maintained in aquaria at normal, fluctuating tempera- tures, and others kept at a constant temperature of 19° C, in the lengths of their flapping periods, in the daily time of onset, or in behavior at onset of flap movements. 5. Behavior accompanying cessation of flap movements This process may be observed in an undisturbed animal just before sundown (see Fig. 17), in rapidly fading daylight, when the mussel virtually reverses the warming up behavior it exhibited at sun- rise (see Table 4). As the rate of flap- ping decreases from 1 movement/sec. to 1 movement/2 secs., there is a shift from the regular to the slow type of flap movement, the latter broadly exposing the marsupium. Flaps are drawn to- gether, then withdrawn between the valves, as the animal gradually changes its angle of headstand orientation by hunching back down into the substrate. Flaps float out again and movements continue at the reduced rate. After a 248 L. R. KRAEMER ю- 05 | п + = WwW a2 > о Y > r & = { 3 > | = 5 sor | el : TRIALS : Я STARTING TIMES a © 4 Sea TRIALS u L ae u | STARTING TIMES = \ es © A.M. 2 \ RE u 70+ | —= 7:00 =5 \ E pS | ; ——= 655 z \ --—= 6:42 un | RS : = 7:06 a | -—= 650 = о ш 80- | 35 ¡AS = > 1 = 7:00 <0 a 3 o 9061 = 1 < 7 = | a 100 1234567891011 2 13145 6 17 18 1920 ! 234 5 67 8 91011 12 34 516 892 FLAPPING FREQUENCY AT SUNRISE (17) FLAPPING FREQUENCY JUST BEFORE SUNSET FIG. 16, 17. Flapping frequency of Lampsilis ventricosa at sunrise and sunset from 5 trials each, on different days in July and August, 1965. Each trial consisted of up to 20 consecutive counts (given in seconds in Fig. 16; in minutes in Fig. 17). Each of the large black dots repre- sents a count, that is, the time span for 30 flap movements. Note that in 2 of the trials at sunset, movements did not cease, though movements perceptibly slowed in one of them. 4 an 9 MU MU Ne MU De ш = НЕ 533 Ey? zu zu; = =o z=, > z 278 ake Z aa = 35 ri Fa, CET ZO So 3mM92 za” a MD MD i O | O MD [2 3 TES *6 тив а г. 2 3.4 5) 6, 74,8 эт т COUNTS COUNTS FIG. 18, 19. Alteration of flapping frequency (duration in minutes of 30 flap moves) which ac- companies movements of marsupia in Lampsilis ventricosa. Trials comprised of 15, 13 con- secutive counts in Figs. 18, 19 respectively. A count is the duration of 30 flap movements. Trials started at 3:40 p.m. on August 1, 1965 (Fig. 18) and at 10:45 a.m. on July11, 1965 (Fig. 19). MD, marsupia moved down into pallialcavity; MU, marsupia moved up to protrude between flaps. MANTLE FLAP IN LAMPSILIS 249 few minutes, flap withdrawal, valve closure, hunching down and flap re- extension are repeated. Finally, the flaps remain withdrawn, and the animal has assumed a normal siphoning position in the substrate. 6. Behavior accompanying diminution of flapping frequency (see Fig. 17) Often the mussel maintains a headstand while its flap movements decrease in frequency with the oncoming dusk. Flap movements change to the slow pattern; the marsupia continue to protrude; and the flaps are spread more and more widely apart as daylight fades. 14 7. Role of marsupia in flapping behavior of Lampsilis ventricosa The marsupia of L. ventricosa affect flapping behavior in at least 4 ways: (a) As a necessary condition for flap- ping behavior. The marsupia must con- tain glochidia. Among more than 40 living mature female L. ventricosa ob- served at length in this study, flap move- ments were seen only in gravid, though not in all gravid specimens. play. In the course of the 3- to A ‘summer season offlapping, L. ventricosa will, the first few weeks, show one mar- supium or the other (seldom both) pro- truding just slightly between the flaps whereas in later weeks, one or both marsupia project prominently from be- tween the flaps throughout the daily flap- ping periods. 14The animal may remain thus for hours in the dark. periods at night, with a safe-light (a red, 25-Watt bulb). When both marsupia are exposed, one is invariably thrust out more than the other, occupying a position closer to the siphons. The appearance of the 2 marsupia is neither quite side- by-side, nor quite one-behind-the-other (see Figs. 20, 21). (c) In sharply altering frequency of flap movements (Figs. 18 and 19). The marsupia are occasionally | spontaneously moved down into the pallial cavity and subsequently up between the flaps, during flapping movements. The downward movement is accompanied by a slight pause, then an increase in flapping frequency. Re-emergence of the mar- supium is typically accompanied by a noticeable slowing of flap movements. (d) In spawning of glochidia. Toward the end of several months of inter- mittent flapping behavior, a tiny hole appears in the distal margin of each visible ovisac (charged water tube ina marsupium); and within a week or less, the ovisacs are emptied of glochidia, ostensibly through these openings, during lengthened periods of flapping. Alterna- tively, the edge of one (or more) of the ovisacs may rupture, and the entire con- tents are shed as a conglutinate.15 Figs. 20 and 21 show marsupia protruded (in the manner typically observed late in the season of flapping behavior). Loca- tion of pores in the ovisacs is shown in Fig. 22, and the gradual emptying of ovisacs, or spawning, is shown in Fig. 23. Becausetheovisacs are transparent, and because individual ovisacs may have contents of different appearance,16 it is I have watched these movements for long Slowest flapping rate recorded in this context: 30 flap movements in 36 minutes and 18.3 seconds (August 13, 1965). 15 The conglutinate or mass of embryos expelled as a whole still has the shape of the ovisac. Conglutinates of Lampsilis ventricosa are the size, shape and color of a slivered almond. All those examined in this study consisted of well-developed glochidia, each larva usually still surrounded by its own membrane. as some other unionids. splinter-shaped conglutinates within an hour after collection. immature embryos. Lampsilinae do not seem to abort conglutinates as readily Pleurobema, for example, frequently shed many tiny, bright pink, These often consist largely of l6Differences in color and texture of ovisac contents are not as marked in Lampsilis ventricosa as they are in Pleurobema and other unionids (Lefevre € Curtis, 1910) where there can be brightly colored stratification of unfertilized eggs among the glochidia in the tubes of each marsupium. 250 L. R. KRAEMER FIGS. 20-23. Marsupia of gravid female Lampsilis ventricosa. FIG. 20. Protrusion of both marsupia, dorsal view (sketched on August 5, 1964, 10:30p.m. artificial light (75 Watt incandescent bulb). FIG. 21. Protrusion of both marsupia seen from right side (sketched on-August 15, 1964, 8:00 a.m. in natural light). Several water tubes (ovisacs) in left marsupium, near branchial siphon (BS) looked partly empty. 15 141 18 17 16 3121 109 [a AS aed nn ne b ~ 23 FIG. 22a, b, c. Location of pores in ovisacs (water tubes of posterior portion of outer gill). a. “Anterior” part of exposed marsupium, showing “edge-on” view of marsupial border; ovi- sacs empty. Orientation as in Fig. 15. b. Lateral view, slightly tipped to show pores on bor- der. c. Exposed marsupium of flapping animal, sketched from anterior (eyespot) end of flaps. FIG. 23. Spawning. Left mantle flap and exposed right marsupium, seen from left side, on 2 successive days. Ovisacs are numbered to show that between time when upper sketch was made, (6:30 a.m., Sept. 2, 1964) and time of lower sketch (8:30 p.m., Sept. 3, 1964), a number of water tubes (serving as ovisacs) had discharged their glochidia, probably via pores (not sketched here). No conglutinates were shed during that time. MANTLE FLAP IN LAMPSILIS 251 possible to observe the emptying of vari- ous tubes in a marsupium, from day to day (Fig. 23). 8. Characteristic flapping periodicities The times when Lampsilis ventricosa exhibits flapping may be summarily categorized as follows: | (a) Flapping season: extends for about 4 months from late spring on- wards through the summer. I have records for a few Arkansas specimens which exhibited flapping behavior inter- mittently from June through September while in aquaria (see Tables 13 € .4). (b) Flapping period: consists typi- cally of a week or less in which the mussel exhibits flapping behavior at least part of every day. I have observed 6-8 such periods in individual specimens kept in aquaria at normal temperatures throughout a flapping season. A flapping period is frequently preceded by ex- tensive locomotion, i.e., the mussel makes a circuit or two of the aquarium, before tilting up to a headstand (flapping position). Flapping periods are sepa- rated by several days to several weeks or more when no flapping occurs. (c) Flapping day: is a day of flapping activity, which often begins at dawn; the flap movements finally cease or radically diminish in frequency just before sun- down. Table 5 is a record, for one specimen of Lampsilis ventricosa, of 4 flapping periods, including a total of 18 flapping days, during which the animal was checked continually for flap move- ments. These data seem typical for L. ventricosa, in that they indicate the fol- lowing: (1) frequency of flap movements varies throughout the day, and from one day to another; (2) flapping frequency does not increase or decrease uniformly through the day; (3) a flapping day is usually inaugurated at sunrise and tapers off just before sunset (Graph, Fig. 24, taken from Table 5). I have further observed (at controlled and uncontrolled temperatures) that dur - ing any day of a flapping period, Lamp- stlis ventricosa is more likely to exhibit flapping activity at sunrise or just before sunset than at any other times of the 24 hour day. B. EFFECT OF PHOTIC STIMULI ON THE FLAPPING BEHAVIOR OF LAMPSILIS VENTRICOSA Early studies of the general (non- flapping) behavior of Lampsilis ventri- cosa included observation of the marked response of both siphons, but especially of the anal siphon to sudden shadows (skioptic response). Table 6 shows a typical series of responses by the anal siphon of a specimen of (non-flapping) L. ventricosa to repeated shadows. The anal siphon soon becomes “habituated” to the shadow stimulus. That is, the anal siphon shows a waning response to the repeated stimulus, not evidently occasioned by sensory adaptation or muscular fatique, inasmuch as the “habituated” siphon is still responsive to other (e.g., tactile) stimuli. Later studies of the flapping behavior of Lampsilis ventricosa indicated the flapping animal’s evident sensitivity to photic stimuli. Table 7 contrasts the observable responses of mantle flaps to photic stimuli (as well as to tactile stimuli, local water waves, jar of sub- strate, and temperature fluctuations) during flapping behavior, withresponses of siphons during normal activity. The reader is reminded of the fact that both siphons and mantle flaps are part of the third (inner) lobe of the mantle edge, and that both are innervated by nerves from the visceral ganglion. Simple preliminary experiments re- vealed that Lampsilis ventricosa can apparently be induced to increase its flapping frequency in response to light of increasing intensity.17 A series of experiments was then 17Lampsilis ventricosa does alter its flapping frequency in apparent response to sudden, arti- ficial changes in light intensity. The following is taken from notes made on July 7, 1964, re- garding an aquarium specimen maintained at normally fluctuating temperatures: “A hot (100° Е) sunny day. Water temperature up to 33°C. Mussel had been flapping in extreme headstand all through the day. Movements very rapid (up to 10sec. for 30 movements). (Contd. on p 252). 252 L. R. KRAEMER TABLE 5. Average flapping frequency* for one specimen of Lampsilis ventricosa at various times of day in natural light only, at a constant water temperature of 19° C, during 4 flapping periods, from July 2 to August 18, 1965 : Duration in seconds of 30 movements at different hours Flapping | Date periods | 1965 10-12h | 12-14h | 14-16h | 16-18h | 18-20h | 20-22h ae NECE EXEC se CC Pest eat — fe Poste] I | el CC CO O O CS a SEE [m [eee | | | Deere. | ala + *Frequency is er as average Se of 30 Se] nn in a series 20 N counts. In 11 instances fewer counts (10) were made (superscripts in parentheses). 17 (contd. ) Still flapping at 8:00 p.m. Turned on light over aquarium at 9:00 p.m. Mussel had tilted back down toward normal position in substrate. No flap movements. Marsupia with- drawn. 9:30 p.m., animal in headstand, flapping rapidly. (30 movements in 10 seconds).” I later found an evident correlation between the beginning, continuation and termination of a flap- ping period, and the proclivity of a mussel for exhibiting such artificially induced movements. MANTLE FLAP IN LAMPSILIS 253 TABLE 6. Successive responses ofanalsiphon ofagravid Lampsilis ventricosa to a sequence of shadows (1 sec. each). Total time for all trials tabulated, 7 minutes Shadow* Recovery time** Trial Siphon closure a sec. in seconds 1 1 Immediate, complete 26.1 2 1 Immediate, complete 23:5 3 1 Immediate, complete 15.9 4 1 Immediate, complete 23.3 5 al Immediate, complete 30.3 6 it Immediate, complete STO 7 1 Immediate, complete Eu 8 1 Immediate, complete 18.6 9 1! Immediate, partial 8.5 10 1 Immediate, partial 8.1 11 1 Immediate, partial as 12 1(x3) Delayed, partial 16.3 13 1(x3) Delayed, complete 21.1 14 1(x3) Delayed, complete 16.8 15 1(x4) More delayed, partial 11525 16 1(x8) Still more delayed, partial 9.3 17 1(x20) No response. Anal siphon remained open *Shadows were presented more than once (numbers in parentheses) in trials 12-16 before siphon closed. **Recovery time is period between closure of anal siphon in shadow response and re-opening. carried out, (a) to test the assumption that photic stimuli can alter mantle flap behavior in L. ventricosa, and, if photic stimulation could be experimentally demonstrated, (b) to examine certain parameters of the photic response. The experiments covered a consider- able range of light intensities (0.3-22.5 foot candles). They were performed at night, with a single light source (see Materials and Methods), and at a con- stant water temperature of 19°C. Ob- servations included short time checks (10 timed counts or less of 30 movements each), and long ones (20-such trial counts). They were conducted when the animal was in a headstand or almost a headstand position; after days of vigorous flapping, and after days of flapping in- activity; and at the beginning, middle, and end of flapping periods. Pre- conditions of 8 experiments are sum- marized in Table 8. Table 9 is a sum- mary of the results of the 8 experiments. At light intensities greater than 3.7 foot candles, alterations of flapping frequencies in response either to incre- ments or decrements of light were not consistent. In the light intensity interval from 2.3 foot candles to 0.8 foot candles, flapping frequencies were consistently altered, increasing in response to small or large increments of light (Fig. 25), decreasing in response to smallor large decrements of light (Fig. 26). The above experimental results make it seem likely that the “warm-up” and “slow-down” character of flapping behavior typically exhibited by L. ventricosa at sunrise and just before sundown, respectively (com- pare Figs. 16 & 17), isaphotic response. C. COMPARATIVE STUDIES WITHIN THE GENUS LAMPSILIS Comparative studies were made ofthe flapping behavior of Lampsilis sili- quoidea and L. brevicula brittsi inorder 254 L. R. KRAEMER TABLE 7. Comparison of responses to various stimuli of mantle flaps (during flapping behavior) and of siphons (during normal activity) in Lampsilis ventricosa Stimulus Response of Mantle Flaps Response of Siphons Photic a. Repeated shadows (sudden light decrements) b. Gradual decre- ment (as at sundown) c. Darkness d. Gradual incre- ment (as at sunrise) Tactile Stroking of relevant structures with fine probe Local water waves Sudden jarring of substrate Temperature fluctuations Diurnal variations vs. constant temperature Shadow response present, as slight pause (0.1 sec.) in flap movements (some indication that shadow response may be inhibited at a high flapping frequency). * “Headstand” maintained, moves slow, change from “regular” to “slow” pattern, flaps are spread wide apart, marsupia exposed; OR: headstand abandoned, flapping slows, then ceases; flaps and marsupia withdrawn. If flapping, moves are in “slow” pattern, marsupium (-ia) exposed. Assumption of headstand, ex- tension of flaps, onset of flap movements, change from “fluttering” to “slow” to “regular” pattern (the last a protective configuration, i.e., marsupia mostly covered by flaps). Negligible; flapping frequently unaltered, even when moving flaps are touched. No observable response in L. ventricosa (marked response in L. siliquoidea and L. brevicula). Animal may pause and then either continue or withdraw flaps, then siphons, abandon “head- stand” and stop altogether. None noted (although Grier, 1926, claimed temperature response for this species). Shadow response. present, es- pecially for anal siphon, except after repeated responses to shadows (Table 6). No consistent observable response to natural gradual increments or decrements of light intensity. Siphons may be wide open, or closed, in dim or in bright light, day or night. Anal siphon: negligible; branchial siphon: innermost row of papillae in lumen sensitive, siphon may close. No observable response. Siphons may close, then withdraw; foot may also withdraw, and valves may close. None noted. *I have made several observations of L. ventricosa during periods ofvery high flapping frequency (as high as 3movements per second), when the mussel gave no recognizable response to shadows. One such observation was made on June 22, 1963, in the White River near Wyman, Washington County, Arkansas, on a large (20cm long) gravid female, angled in a headstand, into the current, and flapping in full mid-afternoon sun, in approx. 18 in. of water. For more than an hour, I made repeated attempts to induce the shadow reflex in the flapping animal, There was, however, no closure of siphons nor any apparent diminution of flapping frequency. Such observations as these indicate that high flapping frequency may inhibit the siphonal shadow reflex. MANTLE FLAP IN LAMPSILIS 255 to distinguish elements of flapping be- havior common to these 2 species and to L. ventricosa, as well as to determine any flapping characteristics peculiar to one or more of these species. Flaps and Flapping Behavior in Lampsilis siliquoidea 1. Flapping position and gross flap morphology In L. siliquoidea, flapping position in characteristically a rotation of only about 50°; the flaps are heavily pigmented, with less conspicuous eyespots than those of L. ventricosa, and with elaborate de- velopment of flap tail portions (Table 10; Figs. 27, 28). 2. Flap movements in L. siliquoidea These are similar to the “regular” movements of L. ventricosa. The moves begin with contractions at the base of each flap’s tail, and progress as paired pulses toward the eyespot. The pulse pulls the eyespot end of each flap later- ally. Recovery phase of the movement brings first the eyespot ends, then the rest of the flaps together once more. Flap movements in this species differ from those of L. ventricosa as follows: a. There are no movements compar- able in configuration to the “slow” move- ments of L. ventricosa in the flapping behavior repertoire of L. siliquoidea. b. Frequency of flap movements is much lower in L. siliguoidea than in L. ventricosa. I have recorded rates up to 180 per minute for L. ventricosa, com- pared with a maximum for L. siligoidea of 29.7 per minute.18 Г. ventricosa, also, exhibits a much greater range of flapping frequencies. c. Spontaneous flap moves in L. sili- quoidea are preceded by definite, twitch- ing contractions of basal tentacles (BT, Figs. 27, 28) just under the flap tails, followed by a slight pause. d. Spontaneous flap moves typically occur in pairs in L. siliquoidea. Howard € Anson (1922: 71) also noted this charac- teristic of L.siliquoidea flap movements, describing them as “. . .regular undula- tions [sic!] of two rapidly succeeding waves lasting 2 seconds, each taking approximately a second to pass from the anterior ventral lobes to the eyespots. ” 19 e. A single flap movement (i.e., a Simultaneous movement of both flaps) may be readily induced in L. siliquoidea (but not in L. ventricosa) by sudden jar- ring of the substrate or by water waves in the immediate vicinity of the flaps, such as can be caused by fin movements of a fish.20 Such flap responses cannot be induced by stroking the flaps with a fine probe. The single flap movement occurs when the flaps are extended and either moving rhythmically,2! or not moving. These mechanically induced flap movements are thus readily dis- tinguished from spontaneous movements (Table 11). 3. Characteristic flapping periodicities of Lampsilis siliquoidea a. Flapping season lasts through the spring and summer months. My earliest 18 The most extensive recordings of daily flapping frequency for a single specimen of L. sili- quoidea, cover the period from April 25 to July 23, 1963. Average number of movements per minute for 10 minute counts were tabulated several times daily. Average flapping frequency throughout this period was between 4 and 5 moves per minute. 19« Anterior ventral lobes” are the tails of the flaps. The speed these authors record is faster than that I measured for L. siliquoidea. 20An attempt to measure the stimulus causing this response was unsuccessful. Tuning forks (512, 384 and 324 cycles per second) set to vibrating in and near the aquarium containing flap- ping L. siliquoidea did not stimulate the single flap movement response described above. 21+ the single flap move is induced during spontaneous movements, their rhythm is broken. Further, ability of flaps to respond to water waves or to jarring with the single flap movement diminishes with prolonged stimulation, then ceases, so that several minutes must elapse be- fore the single-flap-move response can be induced again. L. R. KRAEMER 256 40 [_] days of observation no. of days when flapping was observed O O SAvQ 30 YSEWNN 35 30 25 20 IS 23456 7 8 9101112 13 1415 16 17 18 19 2021 222324 HRS: HOUR OF OBSERVATION Flapping activity of Lampsilis ventricosa. Times of 24-hour day, during 4 flapping FIG. 24. periods (compare with Table 5), of 190 C. Constant water temperature when flap movements occurred. MANTLE FLAP IN LAMPSILIS 257 0000 —e— e— 90 200° cee o 5 © \ o 60 # | 120 IN SECONDS OF 30 FLAP MOVEMENTS 180 DURATION 00 0:306..0:8:1:01.3..1.7:2.0/2:3:3:71:54:35:7. 748.510 12.2165 22.5 LIGHT INTENSITY IN FOOT CANDLES FIG. 25. Response of mantle flap movements of Lampsilis ventricosa to increasing light in- tensities. Data taken from experiments recorded in Tables 8 and 9. At low light intensities (be- tween 0.8 and 2.3 foot candles) flapping frequency increased in response to light increments (compare with speedup of activities at sunrise, Fig. 16). 258 L. R. KRAEMER © O DURATION IN SECONDS OF 30 FLAP MOVEMENTS m O 225 165221085 74 57 343723217 13 TO SRE LIGHT INTENSITY IN FOOT-CANDLES FIG. 26. Response of mantle flap movements of Lampsilis ventricosa to de- creasing light intensities. Data taken from experiments recorded in Tables 8 and 9. At low light intensities (between 2.3 and 0.8 foot candles) flapping frequency decreased in response to light decrements (compare with slowing or stoppage of activity at sunset, Fig. 17). MANTLE FLAP IN LAMPSILIS 259 BS х “) зиэмэлойт ив pamo]]ojy Ácuanba.1] dematjıed в IOYUPUYM 9789IpUI SMOIIY *Y989 S9AOU (0$ JO SJUNO9 9A1MI9SU09 05 03 dn моду зэ8влэлв эле SISQUMU 94} ‘Spuodes Ul possa1dxa SI 2117 ‘SJUOWOAOU 0$ JO UOIJBANP эЗелэле SE pessoidxe эт Áduanbal Ax L“L3v 9°68 917 >65 — 28 00e 7 > 905 ко 8 32159 ————> 9'108 — > 6'01I>€ "62% L Ch SS free AA VAR SS $ "8413 г. SS 9635221 9 $ "ag Lig, > 0105 — SC On IG 185 CoS. SE = IT TI = ee oe ee eae) OS A VOS ARO VILO O A G°92— В 9 9, — 1'876 ‘$2 <—1 SZ 3 5 *58 Z “OPT 0 “POT т I *8ZL1<0 "895 € 9 "267 < 9 ‘6 <6 HE P'PE —7 ZE - 0 “eS LIE < 9798 — E € "97 —0°SZ Т ‘0€<— 2 LG << Z "9% 8 "9€ I 9 “pTI Go, 9° 8° Ost SAT 2.1 0:5 SZ ics ф 6 АО apo 9'8 00T SET: SOT EIER oa -119dXH (sa]pueo 3003 ur) Aysuoyur 34 3rT SO1JISUOQUI 3431] SNOLIBA Je DSOIIAJUaA sınsdwvT Jo чэтатоэа$ e jo ,Aouonbozy Зита 93RIDAY ‘6 ATAVL MANTLE FLAP IN LAMPSILIS 263 TABLE 10. Comparison of flapping position and gross flap morphology in Lampsilis siliquoidea and L. ventricosa Flapping feature Position valves: branchial siphon: marsupia: Appearance (in flapping animal) tail: eyespot: outer flap surface: inner flap surface: L. siliquoidea typically not a headstand; animal usually tilted (i.e., rotated forward) at 45° angle. (Figs. 27, 28) edges often held horizontally do not protrude prominently between the flaps long, broad, prominently fringed with many basal tentacles raised, dark, not prominent on external surface of flap; visible though smaller on internal surface often dark, reddish brown, with rows of dark brown spots. Prominent dark spots near tail base and on tail a rosy peach, especially in tail region of flap. Line of pigment, extending from eye- spot to tail, may be present L. ventricosa typically a headstand, especially at higher flapping frequencies. Animal tilted (rotated anteriorly) at 90° angle to substrate. Foot serves as prop. (Fig. 2) edges not often held horizontally do protrude prominently between the flaps, especially later in flapping season, at time of regu- lar moves with high flapping frequency, and at times of very “slow” flap movements; marsupia may move up and down with changes in light intensity truncated, with few or no basal tentacles prominent, often raised, dark, and surrounded by white ring; not visible on internal surface of flap uniform, medium-light gray; not spotted. Line of pigment on inner surface shows through pale gold to pink, with prominent black line of pigment extending from just behind area corres- ponding to exterior location of eyespot to tail tip substrate. 2. Flap movements They resemble those of L. siliquoidea, beginning as a pair of pulses at the base of the flap tails, moving simultaneously toward the eyespots, causing the eyespot portions of the flaps to turn laterally. Recovery stroke brings first the eyespot ends, then the rest of the flaps together in apposition once more. Movements occur in groups of 2 or more, the flaps moving at slightly higher frequencies than those of L. siliquoidea. 264 L. R. KRAEMER TABLE 11. Comparison of spontaneous “regular” flap movements with me- chanically induced movements in Lampsilis siliquoidea Spontaneous movements normal flap movements as described for L. ventricosa preceded by twitching of basal tentacles occur typically in pairs (less often triple, rarely single moves) RRE o 6 = № NO. OF DAYS FLAP MOVES OCCU = YN w2 wo m Ist flopping period 2nd flapping period = 3rd flapping period E 4th flopping period O cumulation of 4 flapping periods FIG. 29. Diurnal flapping activity in Lamp- silis siliquoidea. Flap movements may be mechanically induced in L. brevicula brittsi, as they are in L. siliquoidea. The fortuitous observation described below indicates Mechanically induced movements the same aspect for individual move not so preceded are single produced in response to jarring of substrate or to local water waves provokable in absence of spontaneous flapping how flap movements induced mechani- cally (e.g., by water waves) may facili- tate mantle flap activity by L. brevicula britts?. On August 11, 1964, a specimen of L. brevicula brittsi had come to a po- sition not more than 5 cm away from a specimen of L. siliquoidea, in one of my aquaria. At 11:00 a.m., both animals were exhibiting flap movements, almost flap-tail to flap-tail.24 The very regular alternation of movements, first by one animal then the other, caused meto time several flapping sequences of the 2 ani- mals (Table 17). L. brevicula brittsi maintained aflap- ping frequency about twice that of L. siliquoidea throughout. Neither the characteristic twitching of the basal tentacles which precedes spontaneous flapping in L. siliquoidea, nor the typical paired movements were observed at that time. It seemed probable that the move- ments of Г. siliquoidea were being mechanically stimulated by the move- ments (local water waves) of L. brevicula brittsi nearby. L. brevicula brittsi, in turn, may have been responding at least 2470 mature female specimens of Lampsilis ventricosa, at the opposite end of the same aquari- um, exhibited no flap movements at that time. MANTLE FLAP IN LAMPSILIS 265 FIG. 30. Various flapping positions in Lampsilis brevicula brittsi. Specimen collected from War Eagle Creek, Washington County, Arkansas, on July 5, 1964. Sketched: a, August 4, at 7:00 a.m.; b, August 5, at 6:30 a.m.; с, August 1, at 11:00 a.m. 266 L. R. KRAEMER TABLE 12. Diurnal flapping activity of a specimen of Lampsilis siliquoidea at seasonal fluctu- ating temperatures and natural light*, from April 25 to July 2, 1963 Date (1963) Hour of the day T г Re Nome Sl Sal ae ees 7 | Еж | | ] ! И | | | | A Ta a ee eS ee | PA | i i } 1 > т + H u, + ERMA DEE МА Я А | | part of the time to the movements of its 3. Time of flapping activity of L. neighbor. The animals didnotthen seem brevicula brittsi to be maintaining independent spontane- ous mantle flap rhythms. 25 The flapping season lasts through the 25This behavior continued through the day. Another series of 20 minute-count trials was made beginning at 10:30 p.m. on the same date, with results much the same as those recorded in Table 17. MANTLE FLAP IN LAMPSILIS 267 Table 12. (Contd. ) Hour of the day } i a | + 4 $ . t — | | are + | 5 | | р + $ | q : 2 : t ; OS + 4 AN = Bot — | 6 y | | —_ = - } + es + + . . 1 ms | 7 i oe ROUTE * * * I = E A 4 - ds | 5 } i * | $ — ES ; à + + + 5 „ + * * = } 9 A $ 10 y * > E } y > y — Be RB i CN ees et E 12 * жж! * kx a Lu." — E 13 * X xk * * * * > } t ae 2 = _ 14 : * * Же * * * een € } X у eee | 15 * * aie SES sae ‘ Е CE Tr i 17 e + + + * + * ; * * N == - i E | р | 18 | ee agen ae mens “EL ¡ON AAA > en 2 A OY S > ry + nA sn + re - + uud | 19 * * SEE * — — — > TASSE + + A > — 20 | A RAS $ ‘ E a ip 21 = * * * k x * ¡== Е : = > $ ж | + > , > se: 22 à Au a === za = > + 1 > | (en 123 | ‘ $ $ | | 24 i: 4 a * x! ur xT] Ss = == не 2 ; - pa | 25 ee + x ни = = + < 4 + 5 . + - - 26 *' ome * * * и ' | i j AA Y SE ue E } aes } ale | 2 i : i 4 |1 т | * Е | m = + $ = + ER 5 fe a + > re ees 4 + er | 28 i р 7; х | * | * | i i | MER | | = —— === + er 1 - + } . + 4 | 29 ! * E * | | * | Еж | k | | = AE + + + t + — lan Fr \ ! Late р { u + О 4 + peal a | | DT Là I A + | | | + far | Flapping 4010110 2 12/10/10) 7131 3, 3 13 10| 81101121 13] 7, 16115112126] 4 ee Garvin al Ta фаре. р He et я ¡Not flapping mae От, 2 Е 10:30, sols. 7/4 16/10; 6) | 91 9} 12) 6/13/12) 13) 12) | Total 1 [0 [2] 2,3 [22140 [19| 17| 9 10, 7 129 [20] 14116121 | 22] 19[ 22128 | 24/39] 67 + = No flapping occurred. * = Flap movements occurred. x = After dark observations were made with a small penlight. spring and summer months. For a single however, are capable of vigorous flap- specimen my earliest record of flapping ping in the dark (as seen with a 25-Watt activity was June 5, and the latest, safelight). September 3. There is not enoughinfor- mation at the present time for meaning- A Note on Flaps and Flapping Behavior ful comparisons of eventual “flapping in Lampsilis fasciola Rafinesque periods” of L. brevicula brittsi with those of other species. Specimens of L. L. fasciola is of interest, because, as brevicula brittsi, like L. siliquoidea, H. & A. van der Schalie (1963) have | 268 TABLE 13. L. R. KRAEMER Diurnal flapping activityX of a specimen of Lampsilis ventricosa main- tained at seasonal, fluctuating temperatures, from June 29 to September 11, 1964, with some observations in artificial light Date (1964) Hour of the day | j } | | | | | ] | 5678 | 9 [10 11112 13/14 15/16; 17! 18! 19; 20| 21| 22 | 23 | р * \ Ei aS ren E EI EE AE A e SN RE E AAA | | i | 1 | | («conglutinates shed) | | | || y + == * \ * | - lu. [| 111 | |} (conglutinates shed) | | | | XNo observations were made between midnight and 5 a.m. *Flap movements occurred, in natural light (after dark observations were made with a small penlight). “Flap movements did not occur, in natural light. + The same animal as that used in the previous light experiments. X No observations were made between midnight and 6 a.m. ы Flap movements occurred, in natural light (after dark, checks were made with 25-Watt red safelight). “No flap movements occurred, in natural light (after dark, checks were made with 25-Watt red safelight). # Flap movements occurred, in artificial light (incandescent bulb, at different light intensities). IR Flap movements occurred, in dim natural light plus artificial infra-red source. These pre- liminary studies with infra-red light were insufficient to yield conclusive results. 269 MANTLE FLAP IN LAMPSILIS at 19° C under varying conditions of light, from July 2 to August 24, TABLE 14. Flapping activity of a specimen of Lampsilis ventricosa* maintained 1965* Hour of the day Date (1965) AAA ls “Li re cn re a re = el — * 270 L. R. KRAEMER TABLE 15. Characteristics of a flapping day for Lampsilis siliquoidea and for L. ventricosa Flap activity L. siliquoidea L. ventricosa Time of onset any time of day often at dawn Pattern through daylight hours a day starts, stops, starts; often 3 or more times starts, speeds up flap movements at dawn, flaps through day, slows down or stops at dusk Pattern after may show more vigorous dark flap moves (especially if flapping, moves are of slow pattern from 10-11 p.m.) than in daylight Response to experimental light conditions no consistent definite responses noted* consistently, at low illuminations flapping frequency slows in response to light decrements and speeds up with light increments *Limited experimental efforts only were made to check the effect of various light intensities on flap movements of L. siliquoidea (see Table 16). pointed out, it has a curiously circum- scribed distribution in some areas of Michigan. This species exhibits fairly rapid, regular mantle flap movements. I had the opportunity to observe a number of L. fasciola in the River Raisin, up- stream from Sharon Hollow, Washtenaw County, Michigan (see also footnote 40), in August, 1962. The 9 flapping females seen at that time were all clearly visible in the main channel at water depths from 1.5 to 2 feet. Movements of their flaps were such that all must have been in a headstand position. The movements were rapid and regular. In appearance, the flaps (Figs. 5c, d) are similar tothose of L. siliquoidea (Figs. 27, 28), with elaborate pigmentation and many basal tentacles. DISCUSSION AND CONCLUSIONS In the course of this study, it hasbeen found that: (1) Mantle flaps in Lampsilis ventri- cosa, L. siliquoidea, L. brevicula brittsi and L. fasciola have common structural features:26 (a) all are extensions of the third or inner lobe of the posterior mantle edge anteroventrad to the branchial siphon; (b) all possess the same general configuration with a pigmented spot (the eyespot) just posterior to the branchial siphon, anda free-hanging tail; (c) pigmentation of the external flap surface is generally more elaborate and always different from that of the internal surface; (d) innervation of the mantle flaps (examined in Г. ventricosa and 26These morphological characteristics are found also in Lampsilis cariosa, of which a number of preserved specimens were examined for this study. MANTLE FLAP IN LAMPSILIS 271 TABLE 16. Flapping frequency averages (av- erage No. of moves/min. for 10 min.) in dim light and in bright (incandescent) light for Lampsilis siliquoidea Date Time Frequencies/min. April P.M 1964 у dim light bright light 26 8:30 4.4 DS 97 915 6.1 1.3 10:30 13.8 10.8 28 7:30 5.1 5. 4 29 7:10 3.5 335 Yala 11: 0.8 an 9:30 De 2.3 L. fasciola) is by way of branches of pallial nerves extending from the visceral ganglion. (2) Mantle flaps in the above species differ morphologically in (a) external pigmentation, which may be a uniform gray (L. ventricosa), or heavily spotted (L. siliquoidea, L. brevicula brittsi and L. fasciola); (b) development of the tail, which may be truncated and slender, as in L. ventricosa, or broad and elaborately fringed with tentacles, as in the other 3 Species; (c) appearance of the eyespot, which may be prominent, ringed with white, and confined to the external flap surface (L. ventricosa), or inconspicuous and visible on external and internal flap surfaces (as in the other 3 species). (3) Flap movements as studied in L. ventricosa, L. siliquoidea and L. brevic- ula brittsi all comprise (a) paired pulses which are initiated as contractions at each tail base and move toward the eye- spot ends of the flaps; and (b)a recovery phase in which the flaps assume their former position, often with tails floating free and horizontally in the water. (4) Flapping behavior in the above 3 species is not limited to flap movements, but involves the coordinated function of many body structures, to such an extent that the supposed normal relationships between body and shell are muchaltered. (5) Flapping involves different be- havioral complexes in different species, e.g., headstand (upending by 90°), regular and slow flap movements, spontaneous marsupial movements, changes in flap- ping frequencies at dawn and dusk, and diurnal flapping pattern in L. ventri- cosa - contrasted with not so pronounced a headstand (forward rotation of 50°), regular double flap movements, no slow movements, no noticeable spontaneous marsupial movements, crepuscular to nocturnal flapping pattern in Г. siliquoidea. (6) Flapping behavior inthese species involves different stimulus modalities, especially light for L. ventricosa, and water waves and jarring of substratefor L. siliquoidea. (7) The special characteristics of flap movements in the species studied here, fit into the larger context of the total behavior repertoire of the non-flapping animal: (a) mantle movements in- dependent of shell movements do exist in various bivalve genera (as found by Redfield, 1917, for Mya, Modiolus, Mytilus, Solenomya, Ensis, Cumingia and Yoldia); (b) extreme heel formation of the foot, in serving as a prop for some flap- ping lampsilids, can logically be viewed as an exaggeration of a phase of normal bivalve locomotion (the Hakenform and Schwellform of Fraenkel, 1927); (c) alterations of flapping frequency in re- sponse to alterations of light intensity show Similarities to the animal’s general skioptic (Shadow) sense, which mediates siphon withdrawal in many bivalves; (d) marked response of extended or moving mantle flaps of mussels such as L. siliquoidea to jarring of substrate andto water waves is more difficult to identify although bivalves are notoriously sensi- tive to jar, the most widely observed response being siphon withdrawal and valve closure. (8) Despite the fact that mantle flaps respond to different stimuli in different species and that flap movements can occur for a whole season previous to 272 L. R. KRAEMER TABLE 17. Sequence and number of flap movements during 20 1-min. periods for 2 specimens of Lampsilis whose moving flaps were approximately 5cm apart; in aquarium, at natural’ temperatures. Trials started at 11:00 a.m. on August 11, 1964 Trial Spectes* Consecutive fan movements Total flap during 1 minute** movements 1 | eal: eye RN; 4 5 à PS / 7. 2 3 be af A À E / 6 | L.s. / / й 3 iv / PAS Be / 6 i Bas / y / 3 a Leber seit eal O 6 у LS: 7 N 2 5 L fod fp hod, 6 Г Т.Я i / / 3 6 L / ff ME À 5 | L.s / / / / a ы | | ae NE a Pe 6 ES / / 2 В u / hei for 7 6 j is / 7 i 3 nn mt es D SD JE AO 7) 7 j L.s / й / / 4 N L.b / / 2 Ls A i / 3 Spawning, they apparently do accompany Spawning of glochidia in all species in which the movements have been ob- served. The foregoing statement is supported by the following evidence from this study: (a) flaps occur only in mature female specimens, whereas juveniles and males have flap rudiments; (b) flap move- ments have been seen only in gravid, never innon-gravid females (although not all gravid females maintained inaquaria for months showed flap movements); (c) flap movements have been seen in associ- ation with gradual emptying of the ovisacs and with shedding of conglutinates; (d) flap movements have not been observed after shedding of glochidia. * * xk Grier (1926) and Welsh (1933) are the only previous investigators known to me to have undertaken experiments with flapping Lampsilinae. Grier contended he had induced increasing frequency of flap movements in a specimen of Lamp- silis ventricosa by experimentally in- creasing water temperature. My own observations do not support his finding. Welsh (1933) made a brief series of MANTLE FLAP IN LAMPSILIS 273 Table 17. (contd. ) : Е Consecutive flap movements Total flap ieee eo CE during 1 minute** movements ых Tb. W/ Var) if We: т ; us: if 3 Teas / MEN Ve eh 5 ar MU 3 Lbs ji teil i bf: 5 = Ess. / ve 7. 4 L.b i, ea Ou 5 At L.s / 2 L.b / / / 4 15 L.s / ik / 3 Lape ey) ig À / 6 15 Lvs: / / 2 Tb fee} / / 5 al ta et / / 3 O / И 6 L.s / / 2 RE A ИИ / 6 L.s 71 / и / 4 о вай / / 5 = L.s. de 2 *L.b. = Lampsilis brevicula brittsi; L.s. = Lampsilis siliquoidea. **/ = one flap movement. determinations of the time required for 10 flap movements in a specimen of Lampsilis nasuta (Ligumia nasuta) over a range of 9 decreasing light intensities, as a consequence of which he observed (1933: 755) that “.. .light did play an important role in determing’ the frequency of these rhythmical contrac- tions.” Though his graph plotting frequency of flap moves against light intensity (here reproduced as Fig. 31) looks as though the animal had increased its frequency in response to increasing light intensity, it had in fact decreased its flapping frequency in response to decreasing light intensity, the data being arranged in inverse order. His numeri- cal data (:755) are here reproduced (Fig. 32). Welsh found (:756) that the flapping rhythm of his specimen “was interrupted at low light intensities and ceased entirely [sic!] after a short ex- posure to an illumination of about 0.2 foot-candles.” My own prolonged ob- servations of Lampsilis ventricosa would indicate that Ligumia nasuta may actually possess a far more complex response to light than Welsh was able to discover 274 L. R. KRAEMER > о = o =! o 2 re Olio > 00- 107207220 log I FIG. 31. Frequency of flapping in “Lamp- silis” (= Ligumia) nasuta from Welsh (1933: 755-756. Note that exposure was in reverse order, i.e., with decreasing light intensity, as indicated byhis explanation of the graph: “Plot of data showing frequency of movement (number of movements per second) of the mantle flaps of Lampsilis nasuta plotted against the logarithm of the light intensity. Observations were begun at the highest illumination. ” from his more limited opportunity for study. Two hypotheses have been advanced by other investigators concerning the probable functions of flapping in these animals. First, the speculation by Ortmann (1911) and others (e.g., Coker et al., 1921) who followed him, that the flap movements help to aerate the glo- chidia, and second, the hypothesis sub- scribed to by Coker etal. (1921), Howard & Anson (1922), and Welsh (1933), that the moving flaps are in effect mimicking minnows and serve as lures to host fish. The first hypothesis seems, in the light of the study presented here, to be quali- fiedly plausible. Regular movements of Lampsilis ventricosa (carried on inter- mittently for several months during the summer) especially those at high frequencies, do appear to create alively water current over the bulging marsupia, though the slow movements certainly do not. Butin species suchas L. siliquoidea, in which flapping movements are much slower, and the marsupia do not com- monly protrude, the relation of flapping to gill or marsupial aeration would hardly seem to be of much consequence. The second hypothesis is an intriguing idea, but it has many shortcomings. Admittedly, to the human observer watching rapid regular movements of an upended L. ventricosa, particularly on an eye-level with the eyespots of the flaps, the resemblance of the moving flaps to some small fish is striking. However, a flapping Lampsilis ventri- cosa exhibiting slow movements does not present a fish-like appearance, neither does a mussel such as L. siliquoidea, which does not characteristically assume a headstand, does not commonly protrude its marsupia (suggesting the rounded body of a fish), does not flap in a fish- like fashion, and does not have prominent eyespots. It seems most plausible to reason that if host fishes are attracted to the flaps, it would be movements per se, rather than a fish-like appearance which might attract them. All of the species ob- served at length in this study (L. ventri- cosa, L. siliquoidea, L. brevicuia), have been maintained from time to time with possible host fish suchas the largemouth bass (Micropterus salmoides) and the black crappie (Pomixis nigromacula- tum). The crappies upon occasion would make darting movements toward the tails of the moving flaps. At other times, a fish would loiter nearly motionless for hours in the vicinity of the tails of the moving flaps. If the fish were attracted by the flapping (though their presence always seemed merely fortuitous to me) the presence of the fish in the neighbor- hood of the moving flaps would insure their exposure to any glochidia dis- charged. The differences between mussel species inflapping postures, appearance, optimal time of flapping activity 27 and 27Such differences might coincide with periods of activity of potential fish hosts, such as de- scribed by Davis (1962). MANTLE FLAP IN LAMPSILIS 275 Times in Seconds for Ten Movements of the Mantle Flaps of Lampsilis with Their Averages, and the Frequency (Number of Movements per Second) at Each of Several Intensities of Illumination. Temp. 21. 3°C. Intensity (Foot-candles) 0.20 Time (secs. ) for 10 movements 65.0 61.0 62.0 63.5 61.8 . 6 . 9 2 . 2 .0 . 5 . 8 .0 .0 .0 Averages Frequency or Pro» Oo 01 62.66 47.86 33.18 26. 3.6 12.0 23.0 180.0 689.0 22. 22. 22. 22. 21. 22. 23. 23. 23. 23. 21. 20. 21. 21. 21. 21. 21. 21. 21. 21. 21. 20. 20. 20. 20. 20. 21. 20. 20. 21. 20. 20. 20. 20. 20. 20. 20. 19. 20. 20. 20. 20. 20. 20. 20. 19, 19. 19. 20. 19. O w OH Où © M N & u D © 1 ND 01 © 1 # © N D O O © © © © wo FP PORNO PER D © © D I rm PB D © © © for) 59 22.75 21.32 20.84 20.19 19. 0.159 0.210 0.301 0.376 0.439 0.469 0.481 0.495 0.502 FIG. 32. Numerical data from Welsh (1933). the manner in which they respond to environmental stimuli suggests possible adaptations (still in need of much study) to habits of peculiar fish-host species. 28 I would like to suggest another explana- tion for the flapping movements of lamp- silids. A simple if partial hypothesis for the flap movements may be suggested by the diagram (Fig. 33) here. It shows an aquarium which Lefevre & Curtis (1910) constructed for the purpose of infecting host-fish with glochidia. The tank has a cross-hatched arrangement of perforated connecting pipes on the bottom, which were fed by a vertical inlet pipe of similar diameter. The purpose of this apparatus was toprevent glochidia, when introduced into the tank, from settling helplessly on the bottom, and to keep them suspended inthe water, so that they might more readily come into contact with fish-hosts already in the tank. Similarly, I suggest, the bellows-like movement created by the paired pulses of all flap movements, regardless of species or flapping frequency or regularity, would help the glochidia to remain suspended in the water for a period of time, and thus facilitate the vitally necessary contact with a host fish. Regrettably, I did not experiment with the adequacy of flap generated currents to sustain glochidia in a mid-water position. This certainly should be done. Ancillary problems arising from this 28However, Iam loathe to subscribe to anthropomorphic generalizations: what looks like fish to us need not necessarily do so to fish themselves. Further, empirical evidence - some almost paradoxical in the light of earlier hypotheses - should not be ignored. L. ventricosa, flapping at high speed in full sun in the stream or inthe aquarium has never been observed in the course of this study to “attract” any local creatures, any more than any other piece of the scenery. Also, this animal flaps very slowly for long periods in the dark. Under such circumstances, the nature of the “attraction” for a fish-host would be difficult to imagine. Lampsilis sili- quoidea, which flaps in a similar manner day andnight (i.e., with its own characteristic slower but “regular” movements), responds quickly to any.local water movement including the move- ment of a fish’s fin by interrupting its regular flap movements, with no detectable response by the fish. Lampsilis fasciola studied for a week in the River Raisin, July, 1967 repeatedly ceased flapping movements in response to movements of fish or crayfish in the immediate vicinity of the flaps. 276 L. R. KRAEMER FIG. 33. Apparatus designed by Lefevre & Curtis (1910: 166) “for keeping glochidia suspended in water while fish are being exposed to them for gill infections.” The force of the tap water entering at S and issuing in fine jets from perforations in the bottom grid is so regulated as to insure an even distribution of glochidia within the water, while preventing them from rising to the top and escaping with the overflow. study fall into 2 groups, those related to mechanisms within flapping Lamp- silinae, primarily, and those of broader taxonomic ramification such as species distribution, and fish-host relationships. In the first group would be included: (a) The study of microscopic anatomy of the flaps, combined with neuroana- tomical studies of the animal. Such studies, including a search for neuro- secretory material, are in progress. (b) Physiological studies of the mechanism whereby increasing light at low illuminations can increase or induce flapping behavior, and decreasing light at low illuminations can slow down or inhibit flapping behavior, as is the case in Г. ventricosa. Particularly light (shadow) sensitive areas should be searched for in the mantle flaps and in neural entities such as the visceral ganglion or pallial nerve. Relationships between the siphonal shadow reflex and mantle flap response to altered light intensity might be investigated and measured in a single species. Careful efforts could be made to extract pig- ments (especially from eyespots of L. ventricosa) and perhaps to ascertain the reaction spectrum of the mantle flaps. 29 (c) Neurosecretory substances known to control spawning in other organisms could be injected into the mussels, such as the “shedding substance” investigated by Chaet et al., (1964) from radial nerves of starfish, inorder to determine whether flapping behavior could thus be induced in Lampsilis. (d) The mechanism whereby some lampsilids alter their flapping behavior 29Conly-Dillon (1965: 346) in his work on spectral sensitivity of eyes of the scallop Pecten maxi- mus, injects a word of caution into an analysis of his findings: “. . . the possibility is not ex- cluded that other light-sensitive structures, perhaps located directly within the nervous system itself, may be contributing to the spectral sensitivity of the animal. ” MANTLE FLAP IN LAMPSILIS 277 in response to jarring of substrate or to water waves, should be investigated, along with the relationship between this response and the general bivalve re- sponse to jarring. In the second group would be included: (a) Tests of the hypothesis that flap movements help to keep glochidia afloat, employing lighting techniques (Westphal, 1965) to make the glochidia visible, and devising means to collect larvae at vary- ing distances above the flapping animal. (b) Further field studies, perhaps on a species such as Lampsilis fasciola, for which some living material is still available. (c) Systematic fish host studies, especially with a view toward matching the flapping behavior repertoire of a given species of Lampsilis (time of maximum flapping frequency, etc.) with the behavior of the fish species. (d) Further comparative studies among the species here investigated (Lampsilis ventricosa was contrasted with Г. siliquoidea and Г. brevicula brittsi) and other Lampsilinae, to dis- cover the parameters of relevant flap- ping stimuli within the subfamily as a whole. There is urgency in making these studies because of the decline of mussel populations so often noted in American streams. The urgency is accentuated by the need for substantial numbers of experimental and: sacrificial mussels if the experimental analyses are to be adequately replicated in well designed, statistically significant studies. ACKNOWLEDGEMENTS I wish to thank Professor Henry van der Schalie who suggested the study of mantle flaps in Lampsilis, and who sup- plied a number of preserved specimens for this study. Thanks are due also to Profs. Henry van der Schalie, John E. Bardach, Alfred M. Elliot and Karl F. Lagler, for their encouragement and ad- vice and for their helpful criticism of the original manuscript. Acknowledgement is due to Mrs. F. W. Gibsonfor her care in drafting Figs. 1, 2, 5, 8, 12, 13, 14 and 27 from my sketches and preparations. LITERATURE CITED AIELLO, E. & GUIDERI, G. 1964. Nervous control of ciliary activity. Science, 146: 1692-1293. ALLEN, W. R. 1923. Studies of the bi- ology of freshwater mussels. I. The nature and degree of response to certain physical and chemical stimuli. Ohio J. Sci., 23: 57-82. BAILEY, D. F. & LAVERACK, M. F. 1963. Central nervous responses to chemical stimulation of a gastropod osphradium. Nature, 200: 1122-1123. BARNES, G. E. 1955. 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The mussels of the Missis- sippi River. Amer. Midl. Natur. 44: 448-466. van der SCHALIE, H. € van der SCHALIE, A. 1963. The distribution, ecology, and life history of the mussel Actino- nais ellipsiformis (Conrad), in Michi- gan. Occas. Papers Mus. Zool., Univ. Michigan, 633: 1-17. WALKER, B. 1917. The method of evo- lution in the Unionidae. Ibid., 45: 1-10, WALKER, B. 1918. A synopsis of the classification of the Mollusca of North America, north of Mexico, and acata- logue of the more recently described species, with notes. Misc. Publ. Mus. Zool., Univ. Michigan, 6: 1-213. WELSH, J. H. 1933. Photic stimula- tions and rhythmical contractions of the mantle flaps of a lamellibranch. Proc. Acad. Nat. Sci., Philadelphia, 19: 755-757. WENRICH, D. H. 1916. Reactions of bi- valve molluscs to changes in light in- tensity. J. animal Behaviour, 6: 297- 318. WESTPHAL, J. A. 1965. Schlieren technique for studying water flow in marine animals. Science, 149: 1515- 1516. WILSON, C. B. € CLARK, H. W. 1912, The mussel fauna of the Kankakee Basin. Bull. U.S. Bur. Fish., 781:1-63. YOUNG, R. T. 1945. Stimulation of spawning in the mussel, Mytilus cali- fornianus. Ecology, 26: 58-69. 280 L. R. KRAEMER RESUME LE VOILE PALLEAL CHEZ 3 ESPECES DE LAMPSILIS (PELECYPODA, UNIONIDAE) L. R. Kraemer L’objet de cette étude est de passer en revue les bases morphologiques et d’activité générale des battements des voiles palléaux chez les unionides d'Amérique du Nord, de la sous-famille des Lampsilinae, et d’explorer expérimentalement certains facteurs qui peuvent compter pour cette activité frappante: les mollusques battant leurs voiles ressemblent a des poissons en traindenager. Les études morphologiques (principale- ment sur du matériel fixé de Lampsilis ventricosa et de L. fasciola) les études occasionnelles dans la nature (dans plusieurs régions du Nord-Ouest de l’Arkansas), et les études prolongées en aquarium sur L. ventricosa, L. siliquoidea et L. brevicula brittsi ont été menées de 1962 a 1965. On a trouvé que les voiles palléaux, qui sont une extension du bourrelet interne du bord du manteau antéroventral au siphon branchial, sont un fait permanent chez les femelles matures. Parmi les voiles de ces 3 expèces, il existe des similitudes de structure (présence de tâches “oculaires” pigmentées, innervation par les branches des nerfs palléaux en provenance du gang- lion viscéral), aussi bien que des différences dans la forme et la pigmentation. Les mouvements des 2 voiles débutent par des pulsations couplées qui produisent des contractions partant de la base des franges et se propagant vers l’extr@mite où se trouvent les taches pigmentées. Il s’ensuit une phase de repos, pendant laquelle les voiles reprennent leur position initiale, avec les franges flottant horizontalement. Le comportement du battement entraine aussi des fonctions coordonnées du pied, du marsupium, des valves et des siphons, a un point tel que les relations spatiales que l’on peut considérer comme normales entre le corps et la coquille, sont profon- dément altérées. Pour les différentes espéces, lebattement nécessite différents types de comportements de méme que différents stimuli adéquats (en particulier, intensité lumineuse pour Lampsilis ventricosa et agitation de l’eau et tremblement du substrat pour L. siliquoidea). Le voile n’existe que chez les femelles matures, bien que les juvéniles et les mâles en aient des rudiments; les mouvements. du voile n’ont été observés que chez les ex- emplaires gravides, jamais chez les non-gravides. Le battement se produit pério- diquement tout au long des mois d’été et on l’a vu accompagner le vidage graduel des ovisacs et le rejet de larves glochidium conglutinées. Le battement n’a pas été ob- servé après l’émission des larves. Deux anciennes hypothèses concernant la fonction des mouvements du voile en mouvement agissant soit comme leurre pour les poissons qui sont les hôtes des larves glochidium, soit comme aérateurs des branchies et du marsupium, semblent maintenant n’être que partiellement plausibles. Compte-tenu des différences existantes dans l’aspect, dans la vitesse de battement et dans la réponse aux stimuli chez les diverses espèces, on pense pouvoir suggérer que ces différences sont des adaptations possibles aux modes de vie d’espèces particulières de poissons-hôtes. Le mouve- ment de soufflet, créé par des pulsations couplées pour tout battement du voile, quelles que soit les espèces et la fréquence de battement, pourrait aider les larves glochidium à demeurer en suspension dans l’eau pendant un certain temps et ainsi leur faciliter le contact vital nécessaire avec un poisson-hôte. As e MANTLE FLAP IN LAMPSILIS 281 RESUMEN EL REPLIEGUE PALEAL EN LAS ESPECIES DE LAMPSILIS (PELECYPODA: UNIONIDAE) L. R. Kraemer El propósito de este estudio fué revisar las bases morfológicas y de actividad general del repliegue y aleteo del manto enlas especies norteamericanas de uniónidos de la subfamilia Lampsilinae, y explorar experimentalmente algunos factores que pueden contarse en esa actividad: el aleteo del manto simula un pequeño pez nadando. Estudios morfológicos, (principalmente de material conservado de Lampsilis ventri- cosa y L. fasciola), estudios ocasionales en el campo (en algunos condados del noro- este de Arkansas), y prolongados estudios en acuarios sobre individuos vivos de L. ventricosa, L. siliquoidea y L. brevicauda brittsi, se realizaron desde 1962 a 1965. Se comprobó que los repliegues alígeros del manto, que son una expansión del lóbulo interno del borde paleal anteroventral al sifón, constituyen un caracter permanente de las hembras maduras. Entre los repliegues de las 3 mencionadas especies existen similaridades estructurales (presencia de manchas oculares, ramificación de nerva- duras paleales del ganglio visceral) así como diferencias en forma y pigmentación. El aleteo se inicia en pulsaciones pares que producen contracciones, empezando en lo que correspondería a una base caudal y moviéndose hacia la terminación del repliegue con manchas oculares. Sigue una fase de reposo, en la que el repliegue asume su posición anterior, con la cola flotando horizontalmente. El comportamiento envuelve también la función coordinada del pie, marsupia, valvas y sifones en forma tal que las supuestas relaciones espaciales normales entre el cuerpo y la concha estan muy alteradas. En diferentes especies el aleteo implica diferentes complejos de comportamiento, así como tambien los diferentes estímulos pertinentes (en particular intensidad luminosa para Lampsilis ventricosa, y sacudidas del substrato por los movimientos del agua en L. siliquoidea). Los repliegues aparecen solamente en ejemplares de hembras maduras, aunque las juveniles y los machos presentan rudimentos; los movimientos del repliegue se han observado sólo en la hembras grávidas, nunca en las no gravidas. El aleteo ocurre por turnos periódicos durante el verano y se ha visto que acompañan la descarga gradual de los ovisacos y el derrame de conglutinados. No se observaron después de la liberación de las gloquidias. Dos previas hipótesis concerniente a la función de estos movimientos del repliegue paleal de los Lampsilinae, que indicaban ser ya un cebo para peces que hospedan las gloquidias, o un sistema ventilador para las bránquias y marsupia, sólo en parte parecen ser verosímiles. Las diferencias enaspecto, velocidad de aleteo, y respuesta a los estímulos ambientales en diferentes especies, sugiere posible adaptaciones a los hábitos de las especies particulares de peces huéspedes. Los movimientos como de fuelle que se crean en las pulsaciones de los repliegues del manto, sin tener en cuenta especies o frecuencia del aleteo, podrían ayudar a la gloquidia a permanecer sus- pendida en el agua por cierto tiempo, facilitando así el contacto vital necesario con el pez hospedador. Jo JP. 282 L. R. KRAEMER ABCTPAKT МАНТИЙНЫЙ КЛАПАН. У ТРЕХ ВИДОВ LAMPSILLIS (PELECYPODA: UNIONIDAE) ЛУИЗА Р. КРЕМЕР В настоящей статье дается обзор морфологии и деятельности мантийного клапана у северо-американских унионид из семейства Lamsilinae, а также приводятся данные экспериментального исследования некоторых факторов, которые могут объяснить эту интересную активность. Движение мантийного клапана несколько напоминает небольших плавающих рыбок. Морфологические исследования (главным образом на фиксированном мате- риале по Lampsilis ventricosa и Г. fasciola), случайные полевые наблюдения (в некоторых районах северо-западного Арканзаса) и длительное аквариальное изучение живых Г. ventricosa, L. siliquoidea и L. brevicula brittsi проводились в период с 1962 по 1965 гг. Было найдено, что мантийные клапаны моллюсков, которые представляют собой выросты внутренней лопасти края их мантии и находятся антеро-вент- рально от бронхиального сифона, всегда имеются у половозрелых самок. Среди клапанов указанных выше моллюсков, существуют как структурное сходство (наличие глазных пятен, иннервация ветвями мантийных нервов, отходящих от висцерального ганглия), так и различия (в общей форме и пигментации). Движения этих клапанов вызываются парной пульсацией, благодаря их сокращениям, которые начинаются с их хвостовой части и идут вперед, к тем концам клапанов, где имеются глазные пятна. Затем следует обратная фаза, когда клапаны приходят в исходное положение, и концы их распола- гаются горизонтально. Работа клапанов включает также координированные движения ноги, марзу- пиев, створок и сифонов, в той степени, в какой предполагаемое нормаль- ное пространственное отношение между телом и раковиной наиболее выгод- но. Для различных видов колебания клапанов связаны как с различными по- веденческими комплексами у моллюсков, так и стимулами из внешней среды (особенно таких, как интенсивность света для Lampsilis ventricosa и движение воды или вибрация субстрата для L. siliquoidea). Клапаны развиваются только у половозрелых самок, в то время как у мо- лоди и у самцов бывают только их рудименты. Движения клапанов наблюда- ются только у беременных самок. Движение клапанов может происходить дли- тельно в течение всех летних месяцев и сопровождаться постепенным опоро- жнением яйцевых сумок и высеванием конглютинатов. После выхода глохидиев движение клапанов прекращается. Ранее высказанные гипотезы, относительно роли движения клапанов y Lampsilinae, видимо, справедливы лишь отчасти. Так, считалось, что движение клапанов служит "приманкой" для рыб-хозяев глохидиев и что это движение служит для аэрации жабр и марзупиев. Разли- чие в скорости движения клапанов и в отношении. к факторам среды у раз- личных видов моллюсков предполагает возможность существования адаптаций жизнедеятельности моллюсков к особенностям образа жизни различных рыб- хозяев. Движения, напоминающие работу мехов для раздувания, обусловленные парной пульсацией всего аппарата клапанов (вне зависимости от вида мол- люска или от частоты колебаний клапанов), может помогать глохидиям оста- ваться в течение некоторого времени в воде во взвешенном состоянии и таким образом облегчать жизненноважную для них возможность контакта с рыбами-хозяевами. 7. A. Е. VOL. 10 NO. 2 DECEMBER 1970 MUS. COMP, GO". DEC 23 1971 ARVARD UNIVERSITY MALACOLOGIA ternational Journal of Malacology Revista Internacional de Malacologia $ Journal International de Malacologie Международный Журнал Малакологии Internationale Malakologische Zeitschrift x FOUT JAN VOL. 10 NO. 2 DECEMBER 1970 MALACOLOGIA International Journal of Malacology Revista Internacional de Malacologia Journal International de Malacologie Международный Журнал Малакологии Internationale Malakologische Zeitschrift MALACOLOGIA Editor-in- Chief Associate Editor Managing Editor TB. BURGH R. NATARAJAN C. M. PATTERSON General Editors Business Manager ANNE GISMANN С. J. BAYNE эк. Wi EDITORIAL OFFICES Museum of Zoology 19, Road 12 Marine Biological Station The University of Michigan Maadi, Egypt Porto Novo, Tamil Nadu Ann Arbor, Mich. 48104, U.S.A. U.A.R. India SPONSOR MEMBERS OF THE INSTITUTE OF MALACOLOGY N. F. SOHL, President C. R. STASEK, Secretary М. В. CARRIKER К. ROBERTSON, Pres.-Elect K. J. BOSS, Treasurer G. M. DAVIS J. F. ALLEN, Vice-President EG BERRY A. G. SMITH 7. В. BURCH EDITORIAL BOARD P. O. AGOCSY Z. A. FILATOVA A. D. HARRISON Magyar Nemzeti Múzeum Institute of Oceanology Department of Biology Baross U. 13 U.S.S.R. Academy of Sciences University of Waterloo Budapest, VIII., Hungary Moscow, U.S.S.R. Waterloo, Ontario, Canada H. B. BAKER E. FISCHER-PIETTE K. HATAI 11 Chelten Road Mus. Nat. d’Hist. Natur. Inst. Geology and Paleontology Havertown 55, rue de Buffon Tohoku University Pennsylvania 19038, U.S.A. Paris Ve, France Sendai, Japan E. E. BINDER A. FRANC N. A. HOLME Muséum d’Historie Naturelle Faculté des Sciences Marine Biological Assoc. U.K. 1211 Geneva 6 55, rue de Buffon The Laboratory, Citadel Hill Switzerland Paris Ve, France Plymouth, Devon, England C. R. BOETTGER V. FRETTER B. HUBENDICK Technische Universitát Department of Zoology Naturhistoriska Museet Braunschweig University of Reading Goteborg 11 Braunschweig, Germany Reading, England Sweden А. Е. CLARKE, JR. P. GALTSOFF G. P. KANAKOFF National Museum of Canada P.O. Box 167 Los Angeles County Museum Ottawa, Ontario Woods Hole, Mass. 02543 Los Angeles, Calif. 90007, Canada U.S.A. U.S.A. E. S. DEMIAN A. V. GROSSU A. M. KEEN Department of Zoology Facultatea de Biologie Department of Geology Ain Shams Univ.. Abbassia Splaiul Independentei, No. 93 Stanford University Cairo, Egypt, U.A.R. Bucharest, Rumania Stanford, Calif. 94305, U.S.A. <. J. DUNCAN T. HABE M. A. KLAPPENBACH Department of Zoology National Science Museum Museo Nacional Hist. Natural University of Durham Ueno Park, Daito-ku Casilla de Correo 399 South Rd., Durham, England Tokyo, Japan Montevido, Uruguay (Continued on next page) EDITORIAL BOARD (continuea) Y. KONDO Bernice P. Bishop Museum Honolulu, Hawaii 96819 U.S.A. T. KURODA 41, Tanaka Minami-Okubo-cho Sakyo, Kyoto, Japan H. LEMCHE Universitets Zool. Museum Universitetsparken 15 Copenhagen, Denmark AKLILU LEMMA Faculty of Science Haile Sellassie I University Addis Ababa, Ethiopia У. 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POWELL Auckland Institute and Museum Auckland, New Zealand R. D. PURCHON Chelsea College of Science and Technology London, S.W. 3, England C. P. RAVEN Zoölogisch Laboratorium Rijksuniversiteit Utrecht, The Netherlands O. RAVERA Biology Division C.C.R., Euratom 21020 Ispra (Varese), Italy CREME TROPER U.S. National Museum Washington, D.C. 20560, U.S.A. М. W. RUNHAM Zoology Department Univ. College of North Wales Bangor, N. Wales, U.K. S. G. SEGERSTRALE Institute of Marine Research Biological Lab., Bulevardi 9-A Helsinki 12, Finland R. V. SESHAIYA Marine Biological Station Porto Novo, Tamil Nadu India F. STARMUHLNER Zool. Inst. der Universitat Wien Wien 1, Luegerring 1 Austria J. STUARDO Instituto Central de Biologia Universidad de Concepcion Cas. 1367, Concepcion, Chile F. TOFFOLETTO Viale Piceno 39 Milano Italy W. 5. 5. VAN BENTHEM JUTTING Domburgse Weg 6 Domburg, The Netherlands J. A. VAN EEDEN Inst. for Zoological Research Potchefstroom Univ. for C.H.E. 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NATARAJAN Marine Biological Station Porto Novo, Tamil Nadu India Since Vol. 8, each volume of MALACOLOGIA is issued in two numbers. Occasionally, the two numbers will be combined into a single issue (as in Vol. 8). Volumes will no longer contain an issue No. 3. have been issued as follows: Vol. Vol. Vol. Vol. Vol. Vol. Vol. Vol. Vol. Vol. Vol. (Voi. 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Vol. 1—1962--63 Vol. 2—1964 Vol. 3—1965 Vol. 4—1966 Vol. 5—1967 Vol. 6—1968 Vol. 7—1968 Vol. 8—1969 Vol. 9—1969 Vol. 10—1970 Vol. 11—1971 Vol. 12—1971 MALACOLOGIA, 1970, 10(2) : 283-321 THE NEW ZEALAND SPECIES OF POTAMOPYRGUS (GASTROPODA: HYDROBIIDAE) Michael Winterbourn! Department ef Zoology Massey University, Palmerston North New Zealand ABSTRACT In his revision of the genus, Suter (1905) recognized 6 species and 3 subspecies of Potamopyrgus from the 2 main islands of New Zealand, but the present study has shown that only 3 species exist. They are P. antipodarum (Gray, 1843), P. pupoides Hutton, 1882, and a previously unrecognized species P. estuarinus n. sp. Potamopyrgus estuarinus and P. pupoides are oviparous, possess smooth, unornamented shells and are confined to brackish water, whereas P. antipodarum is ovoviviparous, highly variable in shell size, shape and ornamentation, and inhabits both fresh and brackish water. Populations of P. antipodarum may consist entirely of parthenogenetic females or contain varying numbers of sexually functional males. Rearing of P. anti- podarum in the laboratory has shown that snails do not necessarily breed true with respect to shell ornamentation, and that shell shape and ornamentation are not controlled primarily by environmental factors. The shell of P. estuarinus is indistinguishable from shells of some P. antipodarum, but P. pupoides is easily recognized by its small, pupiform shell. The radula, operculum, external morphology, body pigmentation and male repro- ductive system are similar in all species and do not provide useful taxonomic characters. In Potamopyrgus antipodarum the lower section of the female reproductive system is modified to form a brood pouch with the Open sperm groove running along its floor. In P. estuarinus and P. pupoides the lower reproductive tract is dominated by the strongly developed capsule gland which is physically separated from the spermathecal duct below. The diploid chromosome number of all 3 species is 24. Ion-exchange chromatography of shell periostracal protein has disclosed no significant differences in amino acid composition between species, but considerable intraspecific variation is found. Potamopyrgus antipodarum is abundant in permanent freshwaters of all kinds and has been found in water up to 26%, salinity, although experimental work indicates that it is active only in water below 17:5%, salinity. No clear relationship between shell morphology and type of habitat has been found. P. estuarinus is most abundant in tidal estuaries where considerable fluctuations in salinity are found, and where many snails are regularly exposed to the air for part of each tide cycle. P. pupoides occupies a similar habitat, but normally remains fully aquatic at all times. In the laboratory P. estuarinus and P. pupoides remained active at all salinities from fresh to sea water, but they have not been found in fresh water in the field. Laboratory experiments have shown the existence of behavioural differences between ' species, which are associated with the different habitats occupied by them. Potamopyrgus: estuarinus shows pronounced amphibious tendencies not found in P. antipodarum -and was able to survive in a “* dormant *” state when exposed to the air for up to 70 days. The Potamopyrgus antipodarum complex is examined in the light of current concepts of the species, and the high degree of variability found in this species is associated with 1 Current Address: Department of Zoology, University of Canterbury, Christchurch, New Zealand. 283 284 M. WINTERBOURN the occurrences of ovoviviparity and parthenogenesis which allow a high degree of divergent evolution to occur independently in individual populations. A comparison between Potamopyrgus antipodarum and the European species P. jenkinsi (Smith) shows that the 2 cannot be distinguished on anatomical grounds, and many features of their biology and ecology are similar. It therefore seems probable that the 2 are the same species, the European snails having been introduced from New Zealand (or Australia ?) in the 19th century. INTRODUCTION Two genera of Hydrobiidae, Potamo- pyrgus Stimpson 1865 and Opacuincola Ponder 1966 are recognised from New Zealand, the latter containing a single, recently discovered subterranean species (Ponder, 1966). The genus Potamopyrgus was erected for the New Zealand species Melania corolla Gould 1874, and was separated from other hydrobiid genera primarily on the basis of radular struc- ture. This study has confirmed the generic distinctness of Potamopyrgus, but its relationships to other hydrobiid genera remain unclear. Taylor (1966) has sug- gested it may belong in his subfamily Littoridininae in which he places Pyrgo- phorus Ancey 1888, the other genus con- taining ovoviviparous, spiny-shelled snails, although differences in the verge of Pota- mopyrgus suggest that it is not close to the American hydrobiids familiar to him. In 1882, Hutton assigned all the known New Zealand Hydrobiidae to Potamo- pyrgus, and in the most recent revision of the genus, Suter (1905) recognised 6 species and 3 subspecies, which he dis- tinguished primarily on shell characters. Suter’s (1905) revision has remained the definitive systematic work on Potamopyr- gus in New Zealand, but it is now clear that there is much greater variation in shell characteristics than was recognised by him. A thorough investigation of the systematics of Potamopyrgus in New Zea- land has therefore been undertaken. Snails were collected from 128 localities throughout the 2 main islands of New Zealand, and selected morphological, re- productive and biochemical factors, as well as environmental relationships have been examined.” As a result of this study it 1s concluded that only 3 species can be recognised on the 2 main islands of New Zealand. In addition, 2 species, Potamopyrgus dawbini Powell 1955 and (?) P. melvilli (Hedley, 1916) have been described from the Auck- land and Kermadec Islands respectively, and species probably referable to Pora- mopyrgus are found in southern and eastern Australia (Williams, 1968). A single species, P. jenkinsi (Smith) is widely distributed in Britain and Europe, and was probably introduced from Aus- tralasia in the late 19th century (Boettger, 1951; and this paper). North American species formerly referred to Potamopyrgus are now placed in other genera (Morrison, 1939; Taylor, 1966) but the true generic status of central African snails placed in Potamopyrgus by Pilsbry & Bequaert (1927) remains problematical. REVISED DIAGNOSIS OF POTAMOPY RGUS Potamopyrgus Stimpson 1865 Type (Monotypy): Melania corolla Gould, 1847 Shell dextral; height less than 12 mm; shape variable ovateconical-cylindrical; up to eight whorls, ventricose-flat sided, 2 The raw data on which this account is based may be found in the appendices to a thesis by the author deposited in the Massey University Library, Palmerston North, New Zealand. NEW ZEALAND POTAMOPYRGUS 285 smooth with or without shouldering and/ or periostracal spines; body whorl over half height of shell; imperforate; aperture ovoid, continuous (in fully grown shells). Operculum ovate, thin, corneous, sub- spiral, usually possessing a calcareous smear. Radula taenioglossan; central tooth trapezoidal, inferior margin nearly straight, faintly trilobate, basal cups close to lateral margins; lateral tooth denticu- late, shank 2-3 times length of subrhom- boidal body which possesses no basal peg; marginals finely serrate, long and slender, shanks straight, sharply curved (3-5) 1 (3-5). CAES): (7-13): (14-32): (21 48). Animal with long pointed tentacles. Reproduction sexual or parthenogenetic, ovoviviparous or oviparous. Males with long, narrow non-lobate penis containing a single duct, normally coiled beneath the mantle edge and attached to the head on right of mid- dorsal line; vas deferens strongly coiled: prostate imbedded in visceral mass. Ovo- viviparous females possess a thin walled brood pouch, with the sperm channel (=ventral channel) incorporated in its floor; oviparous females with the sper- mathecal duct separated from the acces- sory glands above, and probably func- tioning as the pallial oviduct. Habitat, fresh and brackish water. at free ends; cusp formula Synonymy Until further anatomical information is available the synonymy of other genera with Potamopyrgus must be considered tentative. Such genera may include Aus- tropyrgus Cotton 1942 and Fluviopupa Pilsbry 1911. DIAGNOSTIC CHARACTERS OF THE NEW ZEALAND SPECIES Potamopyrgus antipodarum (Gray, 1843) Amnicola antipodanum, Gray, 1843, in Dieffen- bach, E., Travels in New Zealand, 2: 241 (New Zealand; British Museum). Amnicola antipodarum, Gray, 1844, Rev. Zool., 11.2356: Hydrobia antipodum, von Martens, 1873, Mal. Blätter, 19: 14. Hydrobia antipodum, Smith, 1875, Zool. Voy. “ Erebus ” & “ Terror ”, 2: 3. Bythinella antipoda, Hutton, 1880, Man. N.Z. Moll., р 81. Potamopyrgus antipodum, Hutton, 1882, Trans. N.Z. Inst.. 14: 145. Potamopyrgus antipodarum, Hedley & Suter, 1893, Proc. Linn. Soc. N.S.W., 7: 619. Potamopyrgus antipodum, Suter, 1893, J. Con- chyliol., 41: 221. Potamopyrgus antipodum, Suter, 1905, Trans. N.Z. Inst., 37: 263. Potamopyrgus antipodum zelandiae (Gray, 1843), Suter, 1905, Trans. N.Z. Inst., 37: 263 (New Zealand; in British Museum). Potamopyrgus corolla (Gould, 1847), Suter, 1905, Trans. N.Z. Inst., 37: 260 (New Zealand: U.S. Nat. Museum). Potamopyrgus badia (Gould, 1848), Suter, 1905, Trans. N.Z. Inst., 37: 264 (Banks Peninsula, N.Z.; U.S. Nat. Museum). Potamopyrgus egenus (Gould, 1848), Suter, 1905, Trans. N.Z. Inst., 37: 265 (Banks Peninsula, N.Z.; U.S. Nat. Museum). Potamopyrgus corolla salleana (Fischer, 1860), Suter, 1905, Trans. N.Z. Inst., 37: 262 (New Zealand; collection of J. de Conchyliologie, Paris). Potamopyrgus spelaeus (Frauenfeld, 1862), Suter, 1905. Trans. N.Z. Inst., 37: 266 (caves, Colling- wood, Nelson, N.Z.; К.К. Hofmuseum, Vienna). Potamopyrgus subterraneus, Suter, 1905, Trans. N.Z. Inst., 37: 267 (well, Ashburton, N.Z.; Dominion Museum, Wellington). Holotype.—Deposited in the British Museum (Natural History). Type Locality—New Zealand, in fresh water. A full account of all earlier synonymies and the nomenclatural histories of the species recognized by Suter (1905) is given in his paper and therefore is not repeated here. However, the full nomenclatural history of Suter’s Potamopyrgus antipodum is given, as the valid spelling of the specific name has been in doubt. This is resolved as follows. 286 M. WINTERBOURN In his original description, Gray mis- spelled the specific name antipodanum. This was emended in a second description of the species the following year (Gray, 1844) and was also recognized as “an evident and accidental mis-spelling ” by Hedley & Suter (1893). As Gray’s original spelling was clearly an inadver- tent error it should be corrected to anti- podarum. The emendation of Gray’s name to antipodum is not justified, and this spelling which has been followed by most subsequent authors should not be used. Shell ovate-conic, height fully grown 3-12 mm; shape highly variable, slender and elongate to ventricose; spire long or short, loosely or tightly coiled, whorls 4-8 flattened to rounded, with or without shouldering and variable periostracal spi- nation. Females ovoviviparous, the lower oviduct forming a brood pouch. Repro- duction sexual or parthenogenetic, sex ratio variable. Inhabit: fresh waters of practically every type and also brackish water, throughout New Zealand. Potamopyrgus pupoides Hutton, 1882 Potamopyrgus pupoides, Hutton, 1882, Trans. N.Z. Inst., 14: 146. (Heathcote estuary Christchurch; Canterbury Museum). Potamopyrgus spelaeus pupoides (Hutton, 1882), Suter, 1905, Trans. N.Z. Inst., 37: 266. Holotype.—Deposited in the Canterbury Museum, Christchurch, New Zealand. Type Locality.—Heathcote estuary, near Christchurch, New Zealand. In brack- ish water. Shell height less than 2°5 mm, conic- cylindrical, obtuse in apical region: whorls 5, flat, smooth, never possessing spines or keels, suture often margined below. Re- production sexual, females oviparous. Inhabits the brackish lower reaches of streams and rivers, and tidal estuaries, throuzhout New Zealand. Potamopyrgus estuarinus n. sp. Holotype: Deposited in Dominion Mu- seum, Wellington, New Zealand. Paratypes: Auckland, Dominion and Can- terbury Museums, New Zealand; Natur- historiska Museet, Goteborg, Sweden. Type Locality: Small brackishwater stream, Bell Block, Taranaki, New Zealand. Shell ovate-conic, height up to 7 mm; whorls 6-7, smooth, flattened; never possessing periostracal ornamentation; sutures sometimes margined below; apical whorls frequently eroded. Females ovi- parous, reproduction sexual. Rostral and mantle pigmentation always very dark. The ecological niche of this species is restricted and distinctive, snails inhabiting the lower tidal reaches of rivers, and particularly harbour mud flats adjacent to river mouths, where they are alternately exposed and covered by water of varying salinity. The animals of dried specimens labelled Amnicola antipodarum in the USS. National Museum were examined by Morrison (1939), who reported that the males possessed a long, simple, geniculate verge and the females were oviparous. This description indicates that they were my Potamopyrgus estuarinus. However, examination of a photograph of the holotype of A. antipodarum in the British Museum shows that it is definitely not estuarinus as it possesses a large, heavily built shell unlike that found in the latter and this is confirmed by Dr. R. K. Dell (pers. comm.) who has examined the type. COMPARATIVE SYSTEMATIC ACCOUNT; ; | Methods Shell | Three shell parameters, height, width and height of aperture (Fig; Та)’ were NEW ZEALAND POTAMOPYRGUS 287 ‘measured to the nearest 0-1 mm, with a linear eyepiece micrometer inserted in a stereoscopic microscope at magnifications of x12-5 and x32. For comparative purposes, ratios of shell height to shell width (h/w) and shell height to aperture height (h/ap h) were employed, as well as direct comparisons of measurements. Shells of fully grown snails only were used in comparative studies. The number of snails measured from each population was determined partly by numbers avail- able and in all cases was sufficient to give a thorough indication of the full range of variation found within the population. In most cases 10-20 snails were measured. Whorl counts were made to the nearest complete whorl. Because the apex of many shells was eroded accurate whorl counts could not always be made. Some shell characters such as con- vexity and shouldering of whorls, and degree of ornamentation cannot be ex- pressed conveniently as measurements and so do not lend themselves to bio- metric examination. Comparisons of such characters were made from camera lucida tracings. Embryo shell Embryos were taken from the brood pouches of individuals of Potamopyrgus antipodarum and camera lucida tracings of shell outlines were made at a magni- fication of х 120. From the shell tracings the width of the tip of the apical whorl, and the diameter of the first whorl were measured (Fig. 1b). Operculum Opercula were removed from snails and cleaned in a weak solution of oxalic acid. Permanent mounts were made in polyvinyl alcohol (PVA), and examined with a binocular microscope using both top and bottom lighting. Slides were placed on a dark background so that calcification within the operculum would be visible. FIG. 1. Measurements made in the study of shell variation. a. Fully grown shell. b. Em- bryonic shell. h, shell height; w, shell width; ар В, aperture height; 1, width of tip of apical whorl; 2, diameter of first whorl. Radula Radulae were extracted in boiling 4% KOH, stained in picric acid and perma- nently mounted in PVA. Some radulae were mounted intact, whereas the teeth of others were teased apart. Duplicate counts of cusps, denticles and serrations were made on at least 3 lateral, inner and outer marginal teeth from each radula. All measurements were made with a linear eyepiece micrometer at magnifica- tions of x 100 and x 400. Internal anatomy Anatomy was examined by dissection and serial sections. The most successful dissections were carried out on fresh 288 M. WINTERBOURN material. Snails to be sectioned were fixed in Bouin’s fluid, sections were cut at 5-10 д, stained with Ehrlich’s haema- toxylin and counterstained with eosin. Chromosome numbers Chromosome numbers were determined using a squash technique. Shells of freshly obtained snails were cracked and tissues were examined imme- diately without fixation, or were fixed for 24 hours at 4°C in Carnoy’s fluid (ethyl alcohol: glacial acetic acid: chloroform, 6:1:3, v/v/v), and stored in 70% alcohol in a refrigerator until required. Small pieces of testis and ovary (plus digestive gland) were separated and stained in acetic-orcein (1% orcein in 45% acetic acid) for 10-15 minutes on a cavity slide. Material was transferred to a plain microscope slide in a minimum of stain, gently squashed under a cover slip and examined microscopically using oil immersion at < 1000 magnification. Laboratory rearing of Potamopyrgus anti- podarum Potamopyrgus antipodarum was kept in the laboratory in transparent plastic boxes (14x 11x6 cm) with loose fitting lids. Boxes were half filled with tap water, and each contained several grams of finely sieved pond mud and pieces of Elodea canadensis. No artificial aeration of the water was required. Water levels were maintained and small quantities of pond mud were added at infrequent intervals. Under these conditions growth of snails was continous and fairly rapid (minimum generation time 6 months), and embryos were released by large numbers of adult snails. Amino acid composition of shell perio- stracal protein The method of Ghiselin er al. (1967) was used for preparation and analysis of shell material. Snails were completely removed from their shells, or in some cases the animal was separated after decalcification, and the shells were thoroughly cleaned. Shells were decalci- fied in the presence of 10% trichloracetic acid solution by HCl, and the periostra- cum remaining was removed, washed and hydrolysed with 6N НСТ at 110°C for 24 hours under vacuum. All samples consisted of periostracal material pooled from a number of snails. Amino acids were analysed using a Beckman/Spinco Model 120 amino acid analyser. Salinity relations Snails were kept in the laboratory at 11 salinities, 0, 10, 20—100°% sea water, made up by diluting freshly collected sea water with distilled water. Salinities were checked by titration with silver nitrate. Ten fully-grown individuals of Potamo- pyrgus estuarinus, 10 of P. pupoides and 20 of P. antipodarum, half from fresh- water and half from water of fluctuating salinity, were placed in glass bowls con- taining 200 ml of water, at each salinity. Snails were transferred direct to the experimental salinity from water taken from their natural habitats. All experi- ments were run at 18-20°C for 24 hours. At the end of an experiment all inactivated snails were transferred to water with a salinity of 3-5% and examined again after a further 24 hours. All experiments were run in duplicate. Amphibious behaviour Laboratory experiments were designed to compare the behaviour of Potamopyr- gus antipodarum and P. estuarinus when offered a choice between submerged and exposed substrata. The experimental ap- paratus consisted of a rectangular plastic box (20x10x7 cm) with a cardboard floor covered in a layer of river mud forming a sloping “ramp”. The floor was subdivided into 3 zones, a lower submerged section, an upper zone of NEW ZEALAND POTAMOPYRGUS 289 FIG. 2. Outline tracings of fully grown shells of Potamopyrgus antipodarum from 19 populations showing variations in size and shape. Typical shells of P. estuarinus (e), and P. pupoides (p) included for comparison, 290 M. WINTERBOURN FIG. 3. Outline tracings of fully grown, ornamented shells of Potamopyrgus antipodarum from 20 populations, showing variations in size, shape and form of ornamentation. slightly damp, exposed mud, and a middle the air. One hundred snails were used zone of saturated mud also exposed to in each experimental run. Tap water NEW ZEALAND: POTAMOPYRGUS 291 was employed in experiments on both species and sea water was also used with P. estuarinus. The different salinities did not affect the responses of P. estuarinus in the experimental situation. All experiments were carried out at 18-20°C. Effects of desiccation and starvation (1) To determine the time snails can exist in a dry atmosphere before death occurs, experiments similar to those of van der Schalie & Getz (1963) were carried out. Shells of experimental snails were dried thoroughly with filter paper and placed in open, 9 cm diameter petri dishes which were kept in a desiccator containing calcium chloride as desiccant. The apparatus was maintained at 20-22°C Fifty specimens of Potamopyrgus estua- rinus and P. antipodarum, and 20 of P. pupoides were used in each experiment. Five individuals of each species were removed from the desiccator every hour for the first 3 hours, and then at 6 hour intervals until all were dead. A snail was considered dead if it showed no sign of movement within an hour of being placed in a shallow container of water. (2) A permanently saturated atmos- phere was produced in 9 cm covered petri dishes, by placing 6 thicknesses of water-soaked filter paper on the floor of each dish. As the petri dish lids were loose fitting, they permitted adequate gaseous exchange with the outside atmos- phere. Dishes were kept at 20-25°C. In each experiment 40 individuals of each species were employed. Snails were exa- mined daily to determine whether they were dead or alive, until all had died, or for 56 days in the case of Potamopyrgus estuarinus, and then after 70 days. Death was not easy to determine towards the end of the experiment, as with an increase in time the snails gradually withdrew FIG. 4. Outline tracings of typical shells of a, Potamopyrgus estuarinus (from the type locality) andb, P. pupoides. further into their shells, until in many cases the operculum could no longer be seen. A snail was considered dead when no withdrawal reaction was elicited upon prodding the operculum firmly with a needle, or when signs of putrefying tissue were visible around the aperture of strongly withdrawn individuals. Results Shell Shells of the New Zealand species of Potamopyrgus are small and plain (apart from periostracal ornamentation), and offer few useful taxonomic characters. Shells of P. antipodarum are illustrated in Figs. 2 and 3, and of P. estuarinus and P. pupoides in Fig. 4. Size and shape Shell size, shape and variability within and between populations were examined biometrically by measuring shell height, shell width, aperture height and whorl number. It was reasoned that by com- paring these parameters from a large number of populations, the nature of the shell variation, i.e., whether continuous or discontinuous variation existed, within to NO bh populations of number 4 8 shell height mm FIG. 5. Maximum height of shells in 100 populations of Poramopyrgus antipodarum. the Potamopyrgus complex could be determined. Any discontinuities thus found might be indicative of separate lower taxonomic units which could be investigated further. Maximum shell height in populations of Potamopyrgus antipodarum ranged from 4-11:5 mm. When the frequency of these heights is plotted (Fig. 5), the dis- tribution is approximately normal and possesses a single peak at 6-6-6 mm, 72% of the values lying between 5°5-7°5 mm. By contrast, shells of the other 2 species are more uniform in height, those of P. estuarinus ranging from 5:5-7:5 mm and those of P. pupoides, 2:5-3 mm. Shell ratios (h:aph, h:w) from selected populations of the 3 species are compared in Figs. 6 and 7. The populations are arranged in order of increasing mean h:aph ratios, and little correlation between aperture height and shell width is appa- rent. Mean shell ratios for all popula- tions of Potamopyrgus antipodarum are plotted in Fig. 8, and the range of varia- tion of these ratios within populations is shown in Fig. 9. Although the shells of M. WINTERBOURN some populations of P. antipodarum are so unlike that they could be considered sub-specifically different (Mayr et al. 1953), it is clear that continuous variation in shell shape is found within this species. By comparison, only limited variability is exhibited by the shells of P. estuarinus and P. pupoides. Numbers of whorls in fully-grown shells from 100 populations of Potamo- pyrgus antipodarum are shown in Table 1. Again there is considerable variation between populations but no clear division into discrete groups is found. As a general rule, the taller the shell, the more whorls developed. To summarize, measurement of shell parameters has not provided evidence of clearcut morphological groups existing within the Potamopyrgus antipodarum complex, but rather has shown the exis- tence of continuous variation of size and shape within this species. P. pupoides is distinguished by its small, pupiform shell, but the shell of P. estuarinus is indistin- guishable from those of some forms of P. antipodarum. Ornamentation The presence or absence of spines or keels has been considered important in the separation and identification of the New Zealand species of Potamopyrgus (Suter, 1905). However, field observa- tions made during the course of this study have shown that within the P. antipodarum complex considerable variation in degree and nature of shell ornamentation is found, even, in many cases, within a single population (Fig. 10). Ornamenta- tion is purely periostracal, and no calcium is found in the spines. Potamopyrgus antipodarum was reared in the laboratory in order that shell form and ornamentation of progeny of known parent snails could be examined. Some investigators (Dell, 1953; Hunter, 1961) have considered that much shell variation NEW ZEALAND POTAMOPYRGUS 293 an. 10 Ha > 16 ОН va ве 15 CO 14 ja al 10 is a 16 BE nn a O on 15 Bos on ie 18 ies u 15 = 2 m es us de el. 16 n Me cole Alo = 18 o a a uen um BE’: p eo maa A ciara se 18 q iss oa en es = 16 г Nees on MORE JE 2 een Ee Te Na FIG. 6. Variation in shell height: shell width (h:w) ratio, and shell height: aperture height (h:aph) ratio in 18 populations of Potamopyrgus antipodarum. horizontal bar=range; open rectangle=1 SD; closed rectangle=1 SE; vertical bar=mean; numbers at right are sample sizes. is the result of exposure to different en- vironmental conditions, and this was observed in Lymnaea tomentosa reared in the laboratory under different conditions (Boray & McMichael, 1961). In this study the experimental situation was reversed, and snails taken from differing environments were reared in the laboratory under identical conditions. Experimental populations were main- tained for up to 3 years. In the first series of rearings 711 pro- geny of 32 parthenogenetic snails from 12 populations were examined. Of 14 smooth-shelled parent snails, 9 produced totally smooth young, and 5 both smooth and spiny young. No smooth parent produced only spiny progeny. Of 18 spiny adult snails, however, only 3 pro- duced all spiny young, 3 produced both smooth and spiny young, and 12 pro- duced smooth young. In all cases, snails from natural populations consisting solely of smooth-shelled snails bred true in the laboratory, but this did not always hold for spiny-shelled snails. As snails from different populations were reared under identical laboratory 294 M. WINTERBOURN | = ui 14 Mi u 15 2.0 2.2 2.4 2-0 2-8 1-6 1.8 2-0 h/aph ratio h/w ratio FIG. 7. Variation in shell height: shell width ratio, and shell height: aperture height ratio in populations of Potamopyrgus pupoides (a-d) and P. estuarinus (e-h). = .1 2 3 4 +5 2 shell dimensions mm 15 17 19 21 23 127“ mean shell ratios FIG. 9. Range of variation in shell height: shell width ratio, and shell height: aperture height ratio FIG. 8. Mean shell height : shell width ratios, in 95 populations of Potamopyrgus antipodarum. and mean shell height : aperture height ratios in populations of Potamopyrgus antipodarum. Bro- ken line=h: aph ratio; solid line=h: w_ratio. Broken line=h:aph ratio; solid line=h:w ratio. A minimum of 10 shells were measured in all populations. Erratum The figure shown for Fig. 9 (p 294) is incorrect. The correct figure is shown below. 40 populations number of shell ratio range FIG. 9. Range of variation in shell height : shell width ratio, and shell height : aperture height ratio in 95 populations of Potamopyrgus antipodarum. Broken line=h:aph ratio; solid line=h:w ratio. A minimum of 10 shells were measured in all populations. The figure shown for Fig. 19 (p 315) is incorrect. The correct figure is shown below, antipodarum pupoides estuarinus continuing genetic divergence elimination of males obligatory parthenogenesis reduction in numbers of males (facultative parthenogenesis ?) aquatic amphibious sexual reproduction : tendencies development of shell ornamentation and ovovivipary shell smooth oviparous sexual reproduction invasion of freshwater invasion of brackish water ANCESTOR marine shell smooth oviparous sexual reproduction FIG. 19. Postulated steps in the evolution of the New Zealand species of Potamopyrgus. je | o we 4 м быв ror e ar 2 » à u I = : | =A 4 A u < « ÿ si " р ь s = a > > e =" À E | р ES ~ MY ~ ay + a a > © Ts eel | à aay LAN OP TE L av a = я at À DE Zu ss AU AIN DAA + . > terms Thi E EE u À am de i es $ зд ALP р u A 3 TED VE 4 . Саи Y IN e : IE Le: ve К > = | hem RARE ani ue te ve ond mit, cl À 3% . > e, à or >» one Se we +e wh lie К = La р o р FE ng NEW ZEALAND POTAMOPYRGUS 295 TABLE 1. Numbers of whorls in fully-grown shells from 100 populations of Potamopyrgus antipodarum. po - a | No. of Whorls | Shell height ; Totals um 4 5 6 7 8 3-3-9 | 13 | 44:9 ОВ 30 | 54 55:9 | 4 15 2 22 6-6-9 5 7 11-9 | | 8-8-9 | | Totals 2 41 52 4 vee 100 TABLE 2. Results of rearings from parthenogenetic individuals of Potamopyrgus antipodarum obtained from a pond at Massey University. Е Е, | Е, p,* P,* | P, IA | Smooth Spiny Smooth | Spiny Smooth | Spiny E | L р к Smooth 4 1 Smooth 35 0 sae = Smooth 0 37 Spiny 2 3 Spiny 0 10 Spiny 0 22 Smooth 43 0 Spiny 4 20 Spiny 0 33 Spiny 0 10 Spiny 0 16 Spiny 21 20 Smooth 43 0 Smooth 12 0 | Smooth 5 0 | | Smooth 6 0 - Smooth 20 0 Spiny | 56 | 3 Smootht 92 0 Smooth 25 0 Smooth 11 | 0 Smooth 24 0 Smooth 35 0 Smooth 27 0 Smooth 20 0 Smooth 8 0 *P—parent; F=offspring. 14 snails kept together. M. WINTERBOURN 296 NEW ZEALAND POTAMOPYRGUS 297 conditions, it is impossible to infer environ- mental influences as the only factors deter- mining shell ornamentation. This must therefore have a genetic basis. A longer term experiment was carried out using parthenogenetic snails taken from a pond at Massey University, Pal- merston North, in which smooth and spiny shelled snails were present in approximately equal numbers. All gene- rations were kept under identical experi- mental conditions but again a consider- able amount of variation in shell orna- mentations was found between the pro- geny of siblings, and between generations (Table 2). A possible genetic basis for shell poly- morphism in Potamopyrgus jenkinsi and P. antipodarum is suggested as follows. Ornamentation may be under polygenic control rather than determined by a single pair of alleles, and the expression of different degrees of shell ornamentation could result from interaction between environmental factors and the genomes of shell secreting cells in the mantle. Characteristically, only a part of a cell’s genome is manifest at any one time, and environmental changes could modify and direct gene function producing pheno- typic differences, e.g., inducing spine development, when the correct genes were active. Such a mechanism could account for the intra-specific variation in shell ornamentation which is frequently found and which cannot be explained in simple Mendelian terms or as solely environmentally controlled changes of the phenotype. In contrast to shell ornamentation, the shell shape, height, whorl convexity and ratios of shell parameters of progeny in all laboratory populations closely resem- bled those of the parent. Range of shell variation between daughter snails was 60 50 40 = = > = $ 30 © E 20 Е 10 10 14 18 -22 -26 -30 shell dimensions mm FIG. 11. Whorl measurements of 136 embryonic shells from 19 populations of Potamopyrgus antipodarum. Broken line=diameter of first whorl; solid line==width of tip of apical whorl. slight, and less than that found in samples of randomly selected adult snails from the original habitats. Embryonic shell The shells of embryos contained in the brood pouch of Potamopyrgus antipoda- rum are semi-transparent and possess no ornamentation, although transverse growth rings are visible (Fig. 12 c-e). The embryonic shell possesses 1°5 whorls when released from the brood pouch, and in older snails these whorls cannot be differentiated from later developed shell. The width of the tip of the apical whorl and the diameter of the first whorl of 136 embryonic shells from 19 populations of Potamopyrgus antipodarum are plotted in Fig. 11. No indication of the presence of distinct size groups is found. FIG. 10. Variation in shell shape and ornamentation in 6 populations of Potamopyrgus antipodarum 1, a-c; 2, d Е; 3, g-i; 4, ]-1; 5, m-o; 6, p-s. 298 M. WINTERBOURN || | 1 \ lh eS | | | | | | FIG. 12. Externals and radula of Potamopyrgus antipodarum. a, Radular teeth. b, Operculum (outer side). се, Embryonic shells from brood pouch. f, Animal extended (ventral). g, Head pigmenta- tion. c¢—central; |—lateral; im—inner marginal; om--outer marginal; ca —calcareous smear; cl=clear area; t=tentacle; т -mouth lobe; mg=mucous groove; ap—aperture; g—granule; op—position of operculum. NEW ZEALAND POTAMOPYRGUS 299 TABLE 3. Variation in whorl dimensions of embryonic shells from 4 populations of Potamopyrgus antipodarum. Locality No. of shells measured Lake Rotoiti | 10 Lake Pupuke | 10 Mt. Wharite 10 Lindis Pass | 10 The range of variation in whorl mea- surements found in embryonic shells from 4 populations is given in Table 3. Clearly intrapopulation size variations can be almost as great as variations between populations. Operculum Stimpson (1865) described the oper- culum of Potamopyrgus simply as cor- neous, and Suter (1913) did not elaborate further. The following more detailed description is based on an examination of opercula from 30 populations of P. antipodarum, 3 of P. estuarinus and 3 of P. pupoides. The ovoid operculum (Fig. 12b) is semi-transparent, its colour ranging from yellow to brown. The nucleus is sub- central, subspiral growth lines are clearly visible and there is no distinct marginal area. The muscle insertion area is indis- tinct but a narrow, clear, quasicrescentic area extending over half the length of the operculum is present close to the inner margin. The clarity of this area is some- what variable. А small, irregularly shaped, calcareous smear is usually pre- sent to the right of the nucleus. The extent and degree of calcification is also variable but is clearly visible when the operculum is viewed with top lighting 2 Width of apical Diameter of Ist tip (mm) whorl (mm) 0-10—0-13 0-21—0-23 0-11—0-16 | 0-21—0-23 0-09—0:16 0-20—0-27 0-13—0-16 0-25—0-31 against a dark background. The oper- culum is of no value in distinguishing the New Zealand species of Potamopyrgus. Radula The radula of Potamopyrgus is taenio- glossan. No important differences in general tooth shape are found between species, and representative teeth are illus- trated in Fig. 12a. Within populations, slight variations may be found in the positions of the teeth on the radular ribbon with respect to one another. Some individuals have a clear space between the central and lateral teeth, but in others, no gap is found. Radular length generally increases with snail size (Fig: 13). In all 3 species radulae of fully grown individuals examined possessed 62-93 rows of teeth. The rows are closer together in Potamopyrgus pupoides than in P. antipodarum or P. estuarinus (Fig. 14). Cusp formulae for the 3 species are given below. These are based on an examination of snails from 28 populations of Potamopyrgus antipodarum, 3 of P. pupoides and 3 of P. estuarinus. P. pupoides ons) 01 2112509 80 (4-5) — (4-5) 300 M. WINTERBOURN 14 о © radula length mm O 06 0 2 4 6 8 Shell height mm FIG. 13. Radular length plotted against shell height in 14 populations of Potamopyrgus. p =P. pupoides; e =P. estuarinus ; other points— P. anitpodarum. P. estuarinus G-4—-G-4) 3 — 3 : 8- 9: 14-19: 21-35 P. antipodarum (3-5) 165) ss : 7-13: 15-32: 24-48 (3-5) — (3-5) Results of a study of cusp variation in 3 populations of Potamopyrgus antipoda- rum are presented in Table 4. Cusp formulae vary considerably and in P. anti- podarum this variation appears to be independent of variations in shell charac- teristics. P. pupoides can be distinguished using radular characters, (smaller, and the rows of teeth are closer together), but P. estuarinus and P. antipodarum possess sufficient variability in shape, cusp formulae and radula length: shell length ratios to prevent specific differences from being defined. Hutton’s (1882) cusp formulae for 4 New Zealand ‘“ species ” cannot be given the diagnostic importance he gave them. 12 bh O radulae number of h 50 45 100 125 150 rows of teeth per mm FIG. 14. Numbers of rows of teeth per mm of radular ribbon in the 3 species of Potamopyrgus. Broken line=P. estuarinus; solid line—P. antipodarum; solid histogram — P. pupoides. The minor variations in tooth shape shown in his figures appear to have been produced by orientation of the radulae for illustration rather than by true struc- tural differences and the dimensions he provided are far too large. Ponder’s (1967) figure of the radula of ** Potamo- pyrgus antipodum ” (actually P. estuarinus; Ponder, pers. comm.) is also inaccurate. Externals of animal The external appearance of the 3 species is identical (Fig. 12 f, g) except for dif- ferences in size and intensity of head and mantle pigmentation. The following des- cription therefore applies to all 3 species. The tentacles are long and _ slender, clear, with black pigment distributed as in Fig. 12g. The eyes have prominent pigment cups and are located in bulges at the bases of the tentacles. They are not borne on prominent tubercles as described by Morrison (1939). Rostru pigment is distributed in fine transverse NEW ZEALAND POTAMOPYRGUS 301 TABLE 4. Variation in numbers of cusps, denticles and serrations on the radular teeth of Potamopyrgus antipodarum from 3 populations.* Locality Central Massey (4-5)-1-(4-5) University | E A | (3-4)-(3-4) Tiritea 5-1-5 Stream (3-4)-(3-4) Makara (4-5)-1-(4-5) | | (3-4) (3 4) | | } Inner Outer Lateral Marginal Marginal 9-11 20-25 31-47 9-11 | 25-35 32-45 9-11 | 21-29 32-42 * Examination of 12 snails per population making duplicate counts of cusps, denticles and serrations on at least 3 teeth per row per radula. bands, is dark and evenly dispersed in Potamopyrgus pupoides and P. estuarinus, but is often lighter and more variable in P. antipodarum. The mouth lobes are white and normally have grey, crescentic markings dorsally. Pigmentation of the head behind the level of the eyes is always dark and the buccal mass is often visible dorsally near the base of the rostrum. The broad, grey foot has a stippled appearance, is rounded posteriorly and truncated anteriorly. The anterior margin is nearly straight, and the antero-lateral angles are somewhat auriculated. The anterior mucus slit is prominent and extends the width of the foot. The mantle skirt is black, with a well defined, pale, anterior margin. Large numbers of shiny white ** granules ” are found in the foot and mantle edge, and frequently in the mouth lobes and tentacles close to the eyes. Although both Fretter & Graham (1962) and Muus (1963) consider that head pigmentation is distinctive in different species of European Hydrobiidae, and a useful aid in identification, no consistent differences in pigment distri- bution have been found between the New Zealand species of Potamopyrgus. Also, no correlation has been found between pigment intensity and shell form in P. antipodarum as has been suggested may occur in P. jenkinsi (Warwick, 1952). Reproduction Sex ratio Morrison (1939) found that the speci- mens of “ Amnicola antipodarum” he examined possessed sexual reproduction and were oviparous, and he assumed that all the New Zealand species of Potamopyrgus reproduced in this way. Later writers, however, apparently un- aware of Morrison’s study, have assumed them all to be viviparous (Marples, 1962; Dell, 1969), and apart from P. pupoides, parthenogenetic (Ponder, 1966). The present investigation has shown that none of the New Zealand species consists solely of parthenogenetic females, and that males are relatively common ir all 3 species. 302 M. WINTERBOURN rs od sdu en mn — _ ee —- sg FIG. 15. Reproductive system. a, diagramatic representation of male system. b, penis. e, dia- gramatic representation of female system of Potamopyrgus estuarinus and P. pupoides. d, diagramatic representation of female system of P. antipodarum. e, arrangement of ducts in region of the bursa in P. estuarinus. №, Transverse section of empty brood pouch of P. antipodarum showing position of sperm groove. p=penis; pr=prostate; t—testis; v=vas deferens; ag—albumen gland; ap—female opening to pallial cavity; be =bursa copulatrix; bp=brood pouch; cp=capsule gland; od=oviduct; rs =recepta- culum seminis; $4 =spermathecal duct; sdu =sperm duct; sg=sperm groove. NEW ZEALAND POTAMOPYRGUS 303 TABLE 5. Dimensions of sperms of New Zealand species of Potamopyrgus compared with those of 2 species of European Hydrobiidae. Total length Species (microns) 5 3 P. antipodarum 110 P. estuarinus 140 P. pupoides 110-129 P. jenkinsi 40 Hydrobia ulvae 100 Head length (microns) Reference 3) | Present study 3 Present study 3 Present study 4-6 Patil (1958) % | Patil (1958) An initial investigation into the occur- rence of males was made by examining 6-10 individuals from each of 63 popu- lations of Potamopyrgus antipodarum, 5 of P. estuarinus and 3 of P. pupoides. Males were found in all populations of the 2 latter species and in 24% of P. antipo- darum populations. In a more comprehensive study, 50-200 snails were examined from selected popu- lations. Males were found in 9 out of 24 populations of Potamopyrgus anti- podarum, and in 7 of these they constituted less than half of the total sample. (In populations in which males occurred they represented 2-52%, mean=29%, of snails examined.) In P. estuarinus 36-58% of population samples were males, and in P. pupoides males constituted 10-28% of population numbers. Male reproductive system The gross anatomy of the male repro- ductive system is identical in all 3 species (Fig. 15a) and closely resembles that of Potamopyrgus jenkinsi as described by Patil (1958). The testis lies in the upper whorls of the shell on the columella side, and from it arises the vas deferens, a narrow, highly convoluted tube with a thin, muscular wall. It passes through a large prostate gland embedded in the tissues of the visceral mass at the posterior end of the body whorl, and finally runs forward on the head, close to the skin, to the penis, opening at its tip. No proximal dilation of the vas deferens, as described in P. jenkinsi by Patil, was found. In all 3 species the vas deferens of mature individuals is normally packed with living sperm throughout its entire length and consequently has a conspicuous white appearance. Sperms have slender, conical heads and long, lash-like tails, and are all of the one kind. Their dimensions (living) are given in Table 5 in which comparisons are made with the sperm of Potamopyrgus jenkinsi and Hydrobia ulvae. The sperms of the New Zealand species are comparable in length to those of Hydrobia ulvae but are 2-4 times as long as those described for P. jenkinsi. As the sperm of P. jenkinsi was observed in sectioned material, however, it is possible that the dimensions given are not a good indication of their length in life. The penis (Fig. 15b) is situated on the right side of the head beneath the mantle edge. It is simple in form, tapering at its tip and bears no accessory lobes. In Jife 304 M. WINTERBOURN it is colourless and semi-translucent, the vas deferens being visible within. It is capable of considerable contraction and expansion, and when contracted the walls near its base have a telescopic appearance. In preserved specimens the shape and orientation of the penis tend to vary considerably, and usually it becomes somewhat coiled, especially towards the tip. The penis is of no value as a taxonomic character for differentiating between New Zealand species of Potamopyrgus. Female reproductive system The structure of the female reproduc- tive system divides the New Zealand species of Potamopyrgus into 2 distinct groups which possess major differences in the form of the lower section of the oviduct, and its associated glands. (1) Potamopyrgus antipodarum (Fig. 15d) The ovary is situated on the columellar side of the digestive gland in the apical whorls, and reaches almost to the tip of the spire. It has a white, rather lumpy appearance when mature, and contrasts strongly in colour with the brownish digestive gland which has a stippled appearance. The oviduct leading from it is slender and thin walled, but its walls become greatly thickened in the region of the bursa copulatrix and receptaculum seminis. Anteriorly, the reproductive sys- tem consists of the pallial oviduct which has a prominent, clearly demarcated groove, the sperm channel, on its ventral surface (Fig. 15f). In immature indi- viduals the thin walled lower oviduct is circular in cross section but in mature snails it becomes greatly enlarged and distended to form a brood pouch within which over 100 embryos in various stages of development may be found. The sperm channel leads directly to the very large bursa copulatrix and via the sperm duct to the smaller receptaculum seminis, Both normally function to store sperm (Fretter & Graham, 1962), but must have lost this function in parthenogenetic individuals. Fretter and Graham have suggested that the well developed bursa copulatrix of Potamopyrgus jenkinsi may act as a waste dump for excess egg capsule secretions. Surrounding the posterior wall of the brood pouch are a prominent albumen gland and a mucus (shell) gland. The single opening of the pallial oviduct is situated close to its anterior extremity. The condition found in P. antipodarum agrees well with that described for P. jenkinsi by Patil (1958), and Fretter & Graham. (2) Potamopyrgus estuarinus and P. pu- poides (Fig. 15c) In these 2 species the form of the female system is identical and differs markedly from that of Potamopyrgus antipodarum in the structure and function of the lower section which is dominated by the strongly developed capsule gland. The ovary, oviduct, bursa copulatrix and recepta- culum scminis are similar in size, shape and position to those of P. antipodarum, and in fertilized individuals the recepta- culum seminis has a vivid, white appea- rance, given to it by masses of sperm packed inside. Both the diverticulae com- municate with the spermathecal duct, a straight tube with a muscular wall, which opens to the anterior of the mantle cavity and is completely separate from the capsule gland above. This is unlike the condition found in Hydrobia, where the capsule gland forms the pallial oviduct, with the spermathecal duct running along its ventral surface only partially separated by longitudinal folds of tissue. Immedi- ately in front of the bursa copulatrix is the albumen gland whose lumen is con- tinuous with that of the capsule gland. Although the exact course of the eggs through the system has not been estab- lished it seems probable that the capsule NEW ZEALAND POTAMOPYRGUS 305 gland does not function as a pallial ovi- duct. Evidence from dissections and serial sections indicates that it has no anterior opening to the mantle cavity, nor any major connection with the sper- mathecal duct or oviduct (Fig. 15e) and developing eggs have never been found in its lumen. It is assumed, therefore, that eggs pass into the spermathecal duct which would act as the pallial oviduct as proposed by van der Schalie & Getz (1962) for Pomatiopsis cincinnatiensis. The eggs of Potamopyrgus estuarinus and P. pupoides are spherical with a gra- nular appearance, possess а thick (15 4), striated shell, have no organs of attach- ment, and are laid singly. Eggs of P. estuarinus have a diameter of about 200 «, whereas those of P. pupoides are larger, with a diameter of about 370 a. Gametogenesis has been observed in collections of Potamopyrgus estuarinus made in January, May, August, Septem- ber and December and it seems probable therefore that it occurs throughout the year. Less is known regarding P. pupoides but females containing developing ova have been observed in spring and summer. Chromosome numbers Squashes of male and female gonads from the 3 species, including Potamopyr- gus antipodarum from parthenogenetic and sexually reproducing populations, were examined to determine chromosome numbers. Interpretation of ovarian matc- rial was difficult but testis squashes in- cluded cells at various stages of spermato- genesis and could be readily interpreted. Chromosomes could be distinguished with some difficulty in early prophase and were most clearly counted in late pro- phase and metaphase. In all 3 species the diploid number 2n=24 was found and male gametes possessed the hap!oid com- plement n=12. As a rule, chromosome numbers in the Prosobranchia tend to be conservative (Patterson, 1967), and this is clearly the case in Potamopyrgus. Amino Acid Composition of Shell Perio- stracal Protein The use of amino acids from molluscan shell protein for phylogenetic and taxo- nomic purposes is a very recent develop- ment, and preliminary studies have indi- cated that it could be a useful taxonomic technique (Degens, 1967; Ghiselin et al., 1967). The molluscan shell is produced by secretion of precursors from the epi- thelial tissue in specialized areas of the mantle, and may consist of several layers. The outer layer or periostracum is not calcified and consists of over 95%, protein (Degens, 1967). The inner layers of the shell are calcareous and include a pro- teinaceous matrix which represents less than 1% of the mineralized shell layers in the Gastropoda (Hare & Abelson, 1965). As a species is defined, in part, by its distinct genetic composition differing from that of other species, and as proteins are genetically determined, genetic divergence between species will be displayed by dif- ferences in protein composition. In this investigation, amino acid analyses of periostracal protein have been made using ion exchange chromatography. Perio- stracum was chosen for two main reasons: (a) It is easy to obtain relatively large quantities of material compared with minimal amounts of matrix protein. (b) Shell ornamentation is periostracal, and comparisons of amino acid composi- tion of smooth and spiny shells is of interest. Snails from 2 populations of Potamo- pyrgus estuarinus, 1 of P. pupoides and 4 of P. antipodarum were examined (Table 6) and the results of analyses are presented in Table 7. Reproducibility of results was tested on 2 samples of P. estuarinus 306 M. WINTERBOURN TABLE 6. Material used for shell protein analysis. Sample Species 1 Р. pupoides 2a P. estuarinus 2 bye | Р. estuarinus 3 | P. estuarinus 4 P. antipodarum 5 P. antipodarum 6 | P. antipodarum | 7 | P. antipodarum 8 P. antipodarum * B—brackish water. from Huia (Table 7, 2a, 2b, 2c). When 2 identical runs were made on the sample (2b, 2c) the mean variation between amino acid values was 0°26% (range 0:01-0:63%,). The mean variation between the same amino acids from 2 different samples from the same locality (2a, 2b) was 0-71% (range 0-11-2-8%). This variation incorporates differences between specimens, and errors introduced by decalcification, chromatography and data handling. Marked differences in amino acid con- centrations were found between Huia and Heathcote samples of Potamopyrgus estua- rinus, glycine, proline, tyrosine and pheny- lalanine being greatly reduced in the latter, whereas most others showed cor- responding increases in proportions. Values for P. pupoides corresponded closely to those of P. estuarinus from Huia, apart from a lower proportion of tyrosine. A wide range of variation was found in P. antipodarum, and no relation- ship between amino acid concentration Locality Shell form Wananaki B* Smooth Huia B Smooth Huia B Smooth Heathcote B Smooth Dannevirke Smooth Lake Pupuke | Spiny Whangarei Smooth & spiny Lake Tutira Smooth Lake Tutira | Spiny and shell ornamentation was apparent. This is clearly demonstrated by comparing the extreme shell forms represented by Lake Pupuke and Dannevirke samples. In these, with the exception of tyrosine, relative proportions of amino acids are of a similar order. The presence of increased tyrosine in spiny shells is probably of no significance however, as high concentra- tions are also found in the smooth shells of P. estuarinus. Clearly, the New Zea- land species cannot be distinguished by comparing the proportions of amino acids in shell periostracum as a high degree of intra-specific variation is found, parallel- ing the wide range of variation in macros- copic shell morphology. The presence of considerable variation in the proportions of amino acids in the periostracum of Potamopyrgus species reinforces similar findings obtained in other studies. Hare (1963) found that periostracum showed more variation in amino acid composition than any other Structural unit of the shell, and showed NEW ZEALAND POTAMOPYRGUS 307 TABLE 7. Ratios of periostracal amino acids in the 3 species of Potamopyrgus, expressed as percent total amino acids. | P. pupoides _ Amino acid | | | | — Aspartic acid Threonine Serine | Glutamic acid Proline Glycine Alanine 1/2 Cystine Valine Methionine Isoleucine Leucine Tyrosine Phenylalanine Lysine Histidine Arginine > RON SAN EN SE nue où un NNR Li N Yu J — > USO ALES Sy o =] Cac Ca Gy cS US) = SES We HY WS SG) ба t WBONUNANOARHAAYANA J U B ND I] JJOO Un \ | DS D © SD PR = % >» 5 ESS ty Ug EN EN ФА ST trace: that samples from the growing edge, around the periphery of a single specimen of Mytilus californianus may vary 10-15% in numbers of residues of many amino acids. Clearlv defined differences in amino acid composition of periostracum between individuals of the brachiopod Laqueus californianus have also been demonstrated by Jope (1967). An important source of amino acid variation may be protein heterogeneity, i.e., more than | protein may contribute to the periostracum as suggested by Hare (1963), Degens et al. (1967) and Jope (1967). Ghiselin et al. (1967) found that environmentally controlled variation in the amino acid composition of periostra- cum is sufficient to mask genetic differ- ences in many cascs. Recently, Hare & Meenakshi (1968) have reported that changes occurred in the proportions of periostracal amino acids of Potamopyrgus P. estuarinus BOAÁ==nu P. antipodarum Mac se 9 5 6 7 8 | | | | 10-9 14-9) 13-3: 12.7 | 11.52 211-7 99 7 3.2 DAS WEA.G | 4.4132 48155 ADN A SO 6:7 6.40 326 | 27240 7156 IS 2 || 355 58 222. 022 23| 36| 451 54 34-2 | 26-6 | 31-9 | 28-9 | 40-1 | 26-9 | 20-5 32 727.0 AA ETA | 91| 8.7 ВО Tol т ili 14T т 0605-61 5-0 3-91 424 62 0.5 09| 0-8 | 0-6 | 02| 0.51 №0 В 3-0 SET 545-815-790 55 56.0 Tel BASA 2 AAA 5.40 SO A 5-51 A 4:3 ad 32| 2.9215 3024|, 4:4 | 3-7 0:22 0-1 0:6 0-20-70 3.3 Ia 39 Эа PSS 37 jenkinsi raised in the laboratory at dif- ferent salinities. In particular they found an increase in the ratio of glycine to the acidic amino acids with decreasing salinity. However, no similar relationship was evident when the brackish water species P. estuarinus and P. pupoides were com- pared with P. antipodarum from fresh water. Environmental Relationships Distribution and general ccology (1) Potamopyrgus estuarinus. Potamopyrgus estuarinus has a clearly circumscribed habitat, and is confined to brackish water. Commonly it is found near the mouths of streams and rivers entering harbours, where the water is of fluctuating salinity. Frequently, the snails live a semi-terrestrial existence on mud flats or muddy banks adjacent to river 308 M. WINTERBOURN ditch 50 | 50 ЧА. [erie о stream 50 50 0 BLM Fa, 10) N 5 river = = 50 Bae wi O a О 0 [e] = ond 5 100 г 50 о [ol 0 0 lake 50 50 ih Seed : 1 27374755 shell height mm ornamentation FIG. 16. Relationship between shell size, orna- mentation and habitat in 97 populations of Pota- mopyrgus antipodarum. Key to shell ornamen- tation classes: 1—all snails smooth shelled; 2— most smooth; 3—half smooth, half spiny; 4— most spiny; 5—all spiny. channels, or in harbour backwaters and salt swamps. In these situations they may lie exposed to the air for over half a tide cycle, and for the other half live in water of high salinity. The snails are inactive when exposed on mud flats, and may lie on the surface of the mud, be partially buried, or be grouped grega- riously alongside or under stones, wood, etc. Snail densities of up to 884,000 per m? have been recorded in the Heathcote estuary. Other snails remain immersed through- out the tide cycle, and may occupy various substrates including sand, mud, the upper and lower surfaces of stones, and clumps of weed. In river estuaries, snails are normally most abundant towards the sea- ward end, where salinities remain high. Many past reports of the finding of Potamopyrgus antipodarum in brackish water undoubtedly refer to P. estuarinus. (2) Potamopyrgus pupoides. Potamopyrgus pupoides is confined to brackish water, and is frequently found in association with P. estuarinus in river estuaries, but is less frequently found on mud flats where it would be exposed to the air for regular periods of time. P. pupoides exhibits no marked substrate preferences and is found on stones, mud, and among living and decaying vegetation. Frequently, it is abundant in estuaries on a substrate of smooth, clean sand. (3) Potamopyrgus antipodarum. Potamopyrgus antipodarum occurs throughout New Zealand in a wide variety of habitats, including lowland rivers, stony streams, creeks, ditches, estuaries, ponds, lakes, springs, wells and permanent seepage. One of the few freshwater habitats it seems unable to colonize is the temporary pond as the snails apparently lack resistant stages capable of carrying them over long dry seasons. Within the Potamopyrgus antipodarum complex a number of relationships be- tween particular shell forms and geo- graphical or ecological distribution are evident, but none of these relationships appears to be so well circumscribed, or clearly defined, as to warrant taxonomic recognition of the populations concerned. The main trends found are: (a) Many snails at high altitudes, and/ or in relatively oligotrophic waters, have a much smaller adult size than most low- NEW ZEALAND POTAMOPYRGUS 309 TABLE 8. Salinity ranges at which the 3 species of Potamopyrgus have been found living. | Salinity 0/00 | Species Maximum P. antipodarum | 26-4 | P. pupoides | 303 P. estuarinus | 34:8 land populations. These snails are ргс- dominantly smooth shelled. (6) Snails in many, but not all, popu- lations north of Auckland attain a very large size, their shells sometimes exceed- ing 10 mm in height. This size increase is produced by an increase in the number of whorls, rather than by an increase in size of the whorls. (c) There is a tendency for the shells of spiny shelled snails in many lakes and rivers to be more slender and strongly shouldered in the South Island than in the North. Although laboratory rearing work has indicated that shell form is not a simple phenotypic response to environment, in some instances small size may be the result of reduced growth at low temperatures, or under poor food conditions. Conversely, higher temperatures may permit an increase in the rate and amount of growth, resulting in the attainment of large size. No clear relationship between shell height or ornamentation, and different habitat types was found (Fig. 16), although many lake populations tend to consist predominantly of spiny snails, whereas smooth shelled snails are more abundant in running water. Salinity relations All 3 species of Potamopyrgus are found over a wide range of salinities, but Maximum Diurnal Range Minimum h — only P. antipodarum is found in fresh water (Table 8). In order to determine the range of salinities tolerated by cach species, the responses of snails kept in water at 11 different salinities ranging from 033%. salinity, were examined in the laboratory. After 24 hours in the experimental situation all individuals of Potamopyrgus estuarinus and P. pupoides exhibited nor- mal acitivity at all experimental salinities, 0-33%. salinity, and P. antipodarum from fresh and brackish waters was active at up to 17-5% salinity. Some reduced movement of P. antipodarum was found at 21%. salinity but in more saline water all snails withdrew completely into their shells, their opercula acting as physical barriers to exclude the water. After a further 24 hours in water of 3:5%. salinity, all previously inactivated snails resumed normal activity. In the field, the highest salinity at which Potamopyrgus antipodarum has been found living is 26:4%., slightly higher than the greatest salinity at which activity occurred under experimental conditions. It is possible that some intraspecific variation is found in P. antipodarı:m with respect to salinity tolerance as was found in P. jenkinsi by Duncan & Klekowski (1967). Although P. estuarinus and P. pupoides have not been found in fresh water in the field, they were able to exist 310 M. WINTERBOURN in it for several months in the laboratory. Perhaps they are unable to reproduce or develop in freshwater. The ability to tolerate a wide range of Salinities is clearly advantageous to all 3 species, as rapid changes in salinity are regularly encountered in the estuarine reaches of rivers frequently inhabited by them. Amphibious behaviour Apart from inhabiting waters of dif- ferent salinities, Potamopyrgus antipoda- гит and P. estuarinus are frequently found in contrasting physical environ- ments. P. estuarinus is often abundant on high-tidal mud flats bordering streams where snails may be exposed to the air for an appreciable period of each tide cycle, whereas P. antipodarum always remains in the water. Laboratory experi- ments were carried out to compare the behaviour of the 2 species when a choice of 3 substrata, submerged mud, exposed water saturated mud, and slightly damp mud, was offered to them. Results of experiments are shown in Fig. 17. In Experiment 1 snails were distributed cvenly throughout the box at the start of the experimental period and a single examination of their subsequent distribution was made after 17 hours. In Experiment 2 all snails were placed in the submerged section of the box on commencing the experiment, and their distribution was examined after 1, 2, 24 and 72 hours. Similar results were ob- tained in both studies. A clear be- havioural difference between the 2 species was apparent, the majority of Potamo- pyrgus estuarinus finally selecting the driest substrate, whereas almost all P. antipodarum remained in the water, or were buried in the water-saturated mud of the middle zone. Movement of P. estuarinus from the water to the dry upper zone is clearly shown in Experi- ment 2 (Fig. 17). antipodarum estuarinus Exp 1 Lo. Exp2 100 Ihr 50 | E 2hrs D Е 24hrs = = Е À pu IE a FIG. 17. Selection of submerged and exposed substrata by Potamopyrgus estuarinus and P. antipodarum in laboratory experiments. Expt. 1, snails initially distributed throughout box; examined after 17 hours; Expt. 2, all snails initially submerged. Substrata: a=damp, ex- posed mud; b=saturated mud; c=submerged mud. The relatively large numbers of Pota- mopyrgus antipodarum occupying the mid- dle zone of water-saturated mud, is probably explained by the presence of favourable respiratory conditions at the air-water interface in this zone. A similar situation is regularly found in still water laboratory cultures lacking vegetation, in which the majority of snails move up the sides of the containers and settle imme- diately beneath the surface film. Although in the experimental situation most Potamopyrgus estuarinus remained NEW ZEALAND POTAMOPYRGUS 31 TABLE 9. Time survived by snails in a still, dry atmosphere, and on a dry substratum. re | All alive P (hours) P. antipodarum | 0-6 P. estuarinus 0-6 P. pupoides 0-6 permanently in the dry zone and exhibited no active movement back to the water, in their natural habitat they do not nor- mally remain exposed to the air for more than a few hours at a time, as tidal move- ments ensure they will be covered at regular intervals. It is essential that the habitat should be submerged regularly as snails cannot move about and feed when the substrate is dry. One consequence of this positive movement out of water could be to prevent colonization of per- manent river channels, and so effectively isolate populations of P. estuarinus and P. antipodarum in many areas where their ranges Overlap. Effect of desiccation and starvation Associated with the colonization of a non-aquatic habitat is the problem of preventing desiccation. This is likely to be of considerable importance to a pri- marily aquatic species such as Potamo- pyrgus estuarinus which is periodically exposed to the air. P. antipodarum al- though strictly aquatic, sometimes inha- bits bodies of fresh water with fluctuating water levels, or which can be drained by natural or artificial means. In such situations, if the snails are unable to withstand exposure to air, whole popu- lations may be quickly destroyed. Laboratory experiments were designed to examine the effect of desiccation and First death All dead occurs (hours) (hours) | 6-12 30 6-12 | 42 ] | 6-12 | 24 | starvation on the 3 species, (a) in dry air and on a dry substratum, and (6) on a damp substratum in moisture saturated alr. The time survived by the 3 species in a still, dry atmosphere is shown in Table 9. Similar responses were obtained from all species. Survival times of snails in a moisture- saturated atmosphere, and on a damp substrate is shown in Fig. 18. Direct observations indicated that snail tissues did not become rapidly desiccated under these conditions, and that at all times some moisture was maintained within the shells of the snails. On a damp, but non-submerged substrate, how- ever, movement, and consequently feed- ing, cannot occur and therefore death probably results from starvation com- bined with desiccation. Deaths of Pota- mopyrgus antipodarum and P. pupoides are therefore attributed to the combined effects of desiccation and starvation. However, the situation was very differcnt for P. estuarinus which apparently entered a state of dormancy or aestivation, and had a high survival rate over a long period. Individuals which remained dormant up to 50 days resumed activity when transferred to a vessel of water. Little is known about aestivation in the Prosobranchia although short term aesti- vation does occur in some Pomatiasidae tw 159) 100 80 living oO O > о per cent 20 0 10 20 30 days M. WINTERBOURN 40 50 60 70 FIG. 18. Survival time of snails on a damp substratum at 20-25" С. Circles — Potamopyrgus pupoides: squares =P. antipodarum; triangles and broken line=P. estuarinus. (all resumed activity). (Hunter, 1964) and Hydrobiidae (Dundee, 1957). Quick (1920) found that Hydrobia spp. could withstand long periods of exposure and survive in an apparently desiccated state, and Dundee (1957) has noted that dormancy occurs in the amphi- bious Pomatiopsis lapidaria in very cold or hot and dry weather. This evidently ensues when there is a lack of sufficient available moisture, the snails lying with their opercula inserted well into the shell apertures during the inactive period, and becoming reactivated with the onset of rain. Clearly the ability to withstand long periods of exposure out of water is advantageous to snails such as P. lapidaria and P. estuarinus which possess an amphi- bious way of life, and may suffer pro- longed periods of exposure. DISCUSSION The species problem As a result of this study, 3 species of Potamopyrgus are now recognized in X-10 snails placed in water New Zealand. Two of these, P. pupoides and P. estuarinus, are clearly distinguished using morphological, reproductive, and ecological evidence, but P. antipodarum contains a heterogeneous assemblage of forms embracing all the purely freshwater populations. It includes a wide range of morphological variants, as well as differ- ing reproductive forms, and is found under diverse environmental conditions. In the past, many of the forms included in this species have been considered mor- phologically distinct enough to be recog- nized as separate species, or to have had restricted geographical distributions allow- ing them subspecific recognition. This study has shown that continuous mor- phological variation exists within the complex, and that discrete geographical distributions of taxonomic subgroups, consistent with the definition of the sub- species (Mayr, et al., 1953) are difficult to find. A gradation in reproductive forms, through populations with few males, to total parthenogenesis is also NEW ZEALAND POTAMOPYRGUS 313 found, and the possession of these dif- ferent states, apparently unassociated with particular morphological forms, or the occupation of particular habitats adds further to the difficulty of discriminating distinct taxonomic units within the com- plex. The possession of а parthenogenetic mode of reproduction by a large propor- tion of the populations of Potamopyrgus antipodarum is perhaps the major factor responsible for so much of the taxonomic uncertainty that has occurred in the past, and it has permitted the formation of many reproductively isolated clones in which divergent evolution has been able to occur. Furthermore, Struhsaker (1968) in a discussion of shell variation in Litto- rina spp. suggested that species which are viviparous could be expected to have more intra-specific variation because of decreased distribution (dispersal) and re- stricted mating. This would result in isolated populations, whereas strictly ovi- parous populations with widespread larvae should be least variable. This contention is supported by the findings in the present study, the 2 oviparous species, P. estua- rinus and P. pupoides possessing limited morphological variability compared with the extreme plasticity of the ovovivi- parous P. antipodarum. Reproduction by parthenogenesis also poses nomenclatural problems. The bio- logical species definition (e.g. Mayr, 1963, ‘* Species are groups of actually or poten- tially interbreeding natural populations which are reproductively isolated from other such groups”), applies only to sexually reproducing organisms, and it is generally accepted that the taxonomy of obligatory parthenogens therefore must be arbitrary. In the past it has been based primarily on morphological, eco- logical and biogeographic evidence. The occurrence of sexual reproduction and parthenogenesis in the Potamopyrgus anti- podarum complex poses further problems. White (1954) and Mayr (1963) have pointed out that it is illogical to recognize parthenogenetic and bisexual ** races ” of the same species, irrespective of the mor- phological resemblances between the geno- types, and they considered that such forms were better recognized as sibling species, if they were indistinguishable by ordinary taxonomic criteria. On the other hand, Mayr et al., (1953) have agreed that it is unjustifiable to give nomenclatural recog- nition to forms with temporary or facul- tative parthenogenesis. In P. antipoda- rum, sexually reproducing and partheno- genetic forms are connected by inter- mediates possessing limited numbers of males, and it seems likely that in such populations both parthenogenesis and sexual reproduction may occur. In view of this lack of a sharp division between reproductive types, and the pre- sence of continuous morphological varia- tion within the complex, it seems most sensible to consider the whole range of intergrading populations as a single species. The suitability of an evolutionary spe- cles concept such as that of Simpson (1961); “Ап evolutionary species is a lineage evolving separately from others and with its own unitary evolutionary role and tendencies ”, which is not ham- pered by the static restrictions of genetical (biological) definitions, is evident in a situation of this kind. Parthenogenesis and evolution in Pota- mopyrgus Parthenogenesis was first discovered in molluscs by Boycott (1919), in Potamo- pyrgus jenkinsi, and later in the American viviparids Campeloma rufum and C. deci- sum by van Cleave & Altringer (1937) and Medcof (1940), and in 4 species of Melaniidae by Jacob (1957). Partheno- genesis in all these species is thelytokous (female diploid parthenogenesis) and of the apomictic type, (i.e., it is ameiotic and 314 M. WINTERBOURN neither chromosome reduction nor fusion of nuclei takes place in the egg). In many animals, parthenogenesis is fre- quently accompanied by polyploidy (Suo- malainen, 1950), and of the molluscs examined, 3 species of Melanoides are polyploid and 1 species is diploid (Jacob, 1957). It has been stated that P. jenkinsi exists as 2 distinct genotypes, a diploid race in Europe (2n=20-22) and a tetra- ploid race in Great Britain (2n—36 44) (Sanderson, 1940), but Suomalainen (1950) and Patterson (1967) consider that this needs reinvestigation. In the Melanoides species, partheno- genesis is obligatory, although small numbers of sexually non-functional males are found in 2 species (0°01-3°0% of populations). Obligatory parthenogenesis has been considered the rule in P. jenkinsi also, although a single male has been found by Patil (1958). Males occur sporadically in populations of C. rufum (about 1%) and are scarce or rare in 3 other species of Campeloma about whose reproduction little is known (Mattox, 1938: van der Schalie, 1965). In Potamopyrgus antipodarum partheno- genesis is apomictic (2n=24) and poly- ploidy has not been observed in any snails examined. In populations where males are present, they are always sexually functional and male gametes possess the haploid chromosome number (n=12). Circumstantial evidence therefore sug- gests that parthenogenesis is not neces- sarily obligatory in all populations of P. antipodarum, and that where it is not, and fertilization occurs, a reduction in the chromosome number of ova must occur, so as to maintain the diploid number and not produce a triploid form. Perhaps the stimulus bringing about meio- sis in the developing egg is the occurrence of copulation, or the presence of the sperm in the female system. A situation closely paralleling that found in P. anti- podarum has been described by Robertson (1966) in chrysomelid beetles of the genus Calligrapha. These possess extremely variable sex ratios, ranging from 1:1, to all female populations, and partheno- genesis in at least one species, C. scalaris, is facultative. The origin of parthenogenesis in all cases examined is considered to be from sexually reproducing forms, i.e. it is a secondarily derived condition (Mayr, 1963; Suomalainen, 1961), and Mayr has stated, that with the apparent exception of the bdelloid Rotifera, virtually every case of parthenogenesis in the animal kingdom is probably of very recent origin. A recent origin for parthenogenesis in Pota- mopyrgus antipodarum is indicated by the continued presence today of bisexual as well as parthenogenetic populations, and by the retention of the sperm channel, bursa copulatrix and receptaculum seminis in the reproductive system of partheno- genetic females. A parallel situation is found in parthenogenetic species of Calli- grapha which retain a non-functioning spermatheca (Robertson, 1966). The advantages parthenogenesis gives to a species have been discussed by several workers (White, 1954; Mayr, 1963; Tomlinson, 1966), who have concluded that it is particularly advantageous to animals inhabiting temporary or mar- ginally suitable habitats where population densities are often low. In these situa- tions it permits a single individual to commence breeding without requiring a mate and the reproductive capacity of the clone will be doubled as all individuals will be egg producing females. Thus, parthenogenesis increases productivity by allowing rapid build up of populations, and therefore it can be of definite, short term advantage to forms possessing it. Because no exchange of genes is possible, a parthenogenetic species frequently will continue to diverge as different mutations establish in different lines of descent. Thus, a high degree of variability will NEW ZEALAND POTAMOPYRGUS 315 ultimately result within many partheno- genetic species, variability which will not necessarily be correlated with geographic distribution in the same way as in a sexually reproducing form. This is what is found in Potamopyrgus antipodarum. Suomalainen (1961, 1962) has speculated on the ways in which mutations may be expressed in apomictic parthenogenetic animals, and his theoretical mechanism could possibly apply in the present situa- tion. He argues that increasing heterozy- gosity will occur between more and more gene pairs (because elimination of reces- sive mutations by natural selection is impossible) until the 2 chromosome sets can no longer be considered diploid or polyploid in a genetic sense. This will reduce obstacles to the expression of the mutations present in them, and may thus, in part, even allow the formation of mor- phologically divergent biotypes. Further, with a continuous increase in the degree of heterozygosity, an apomictically par- thenogenetic form gets an ever increasing chance to benefit from heterosis (hybrid vigour). This may therefore provide the basis for the apparently great adaptive- ness and dispersive ability of many parthenogenetic forms (e.g., P. antipoda- rum), although it is in direct contrast with the widely held view that parthenogenesis leads to a lack of adaptability, and long term disadvantage (White, 1954). Probable steps in the evolution of Potamopyrgus are shown in Fig. 19. P. estuarinus and P. pupoides possess the primitive features, smooth shell, sexual reproduction and oviparity, and are con- fined to brackish water, whereas in P. antipodarum shell ornamentation, parthe- nogenesis and ovoviviparity have develop- ed,probably concurrently with the invasion of fresh water. Further divergent evolu- tion has occurred and is occurring within isolated parthenogenetic populations of P. antipodarum, resulting in a high degree of genetic and phenotypic variability. 3 > о [a] о number of populations 5 о 3 ‘5 7 Shell ratio range FIG. 19. Postulated steps in the evolution of the New Zealand species of Potamopyrgus. The relationship of Potamopyrgus anti- podarum to the European species P. jenkinsi Potamopyrgus jenkinsi made a sudden appearance in Europe, first being de- scribed by E. A. Smith in 1889, although it may have been present as early as 1859. Its origin is uncertain and has been the subject of considerable speculation which has been reviewed by Adam (1942), Bondeson & Kaiser (1949) and Fretter & Graham (1962). The subsequent distri- bution of P. jenkinsi through Europe has also been discussed by these authors and others, e.g., Hubendick (1950). Attempts to explain the sudden appea- rance of Potamopyrgus jenkinsi in Europe have been made by various authors, and 2 possible explanations have been sug- gested; (a) that it arose by mutation (Steusloff, 1927; Boettger, 1949), and (5) that it had been introduced from elsewhere. Bondeson & Kaiser (1949) have hypothesized a possible Australian origin on account of the close resemblance to the Australian species (?) P. pattisoni, and Boettger (1951) has suggested a New Zealand origin for P. jenkinsi as he con- sidered its shell characters identical with those of P. badia (=P. antipodarum) from the South Island of New Zealand. 316 M. WINTERBOURN As a result of the present study on the New Zealand species of Potamopyrgus, it is possible to make a more critical com- parison with P. jenkinsi than has been possible in the past. In doing this, infor- mation contained in the literature has been evaluated, and in addition, living and preserved material of P. jenkinsi from Scotland has been examined. The shells of Potamopyrgus jenkinsi are variable in shape, size and ornamentation, although not as variable as those of P. antipodarum (T. Warwick, pers comm.), and cannot be differentiated from those of some P. antipodarum. Ornamentation is purely periostracal, and exists in many degrees of strength, from a faint line to a well marked spinous keel (Warwick, 1944; Fretter & Graham, 1962). Rearing experiments (Boycott, 1929; Robson, 1926; Warwick, 1944), have shown that as in P. antipodarum shell ornamentation of progeny does not necessarily follow that of the parent, but despite consider- able speculation the mechanism control- ling shell ornamentation remains unknown (Warwick, 1944; 1952; Bondeson & Kaiser, 1949). The radula of Potamopyrgus jenkinsi has been described by Woodward (1892) and Krull (1935), and new material has been examined in this study. The shape of the teeth, cusp formulae, radular length, and number of rows of teeth lie within the ranges found in P. antipodarum. Potamopyrgus jenkinsi exhibits consi- derable variability in colour and pigmen- tation of the head and mantle (Robson, 1920), and it cannot be separated from P. antipodarum on this basis, or on the structure of the operculum, or the form of the female reproductive system. Both species are ovoviviparous, and P. jenkinsi is considered to be parthenogenetic like many populations of P. antipodarum. A single male of P. jenkinsi has been de- scribed by Patil (1958), and it is possible that a situation similar to that found in P. antipodarum in which variable numbers of males occur in some populations, also exists in P. jenkinsi. The anatomy of the male reproductive system in the solitary male P. jenkinsi was identical to that of P. antipodarum, apart from one minor difference, the presence of a small swelling in the upper vas deferens, described as the seminal vesicle by Patil. No such swell- ing has been found in P. antipodarum. Both species reproduce throughout the year, an unusual condition in freshwater Mollusca (Fretter & Graham, 1962), and although a maximum of only 35-40 embryos has been recorded in the brood pouch of P. jenkinsi, compared with over 100 in some individuals of P. antipodarum, this is unlikely to be of systematic signi- ficance. Rather, it 1s probably a func- tion of the size of the snail (and therefore the brood pouch) as P. jenkinsi rarely exceeds about 5 mm in shell height, whereas P. antipodarum may attain a height greater than 10 mm. Considerable variation in ecology is also found in the 2 species. Potamopyrgus jenkinsi was initially found in brackish water (1889) and has since colonized inland waters throughout Europe and the British Isles, first having been recorded in fresh water in England in 1893 (Hunter & Warwick, 1957). P. antipodarum, simi- larly, is found in fresh and brackish water, although it is primarily a freshwater species and has certainly been established in that environment for a much longer period than has P. jenkinsi. Salinity records and experimental work have shown that both species possess a high degree of euryhalinity and can tolerate considerable and rapid changes in salinity. Maximum salinities at which P. jenkinsi can reproduce, 12-18%, (Duncan & Klekowski, 1967) correspond closely to the value of 17:5%., obtained in this study at which normal activity of P. antipodarum ceases and the snails withdraw into their shells. Both species tolerate waters with NEW ZEALAND POTAMOPYRGUS 317 high and low calcium content, and live in a variety of still, and running water habitats, on hard and soft substrates, and amongst vegetation. To conclude, no significant morpho- logical or biological differences between the 2 nominal species have been found to date, and the evidence available therefore suggests that they are the same. How- ever, the systematics of the Australian hydrobiids, some of which are or have been placed in Potamopyrgus and related genera, are not clear at present and their relationship to the New Zealand species and to P. jenkinsi cannot be clarified until after comprehensive morphological and biological studies have been carried out on them. The presence of related genera and species in Australia (Williams, 1968) and in the South Pacific (Hubendick, 1952), indicates that New Zealand is near the centre of Potamopyrgus evolution, however, and it seems most likely that the European snails have been introduced from the Australasian region. ACKNOWLEDGEMENTS I wish to thank Dr. Tim Brown, Dr. W. C. Clark and Mr. L. Gurr of Massey University, and Drs. R. K. Dell and W. F. Ponder of the Dominion Museum, Wellington for their assistance and interest during the course of this work. The help of Dr. G. G. Midwinter with the biochemical analyses, Miss Pauline Campbell who did much of the sectioning of snails, and Mr. Tom Warwick who sent me living specimens of P. jenkinsi from Scotland has been greatly appreciated. LITERATURE CITED ADAM, W., 1942, Notes sur les Gastéropodes. XI. Sur la répartition et la biologie de Hydrobia jenkinsi Smith en Belgique. Bull. Mus. roy. d Hist. nat. Belg., 18: 1-18. BOETTGER, C. 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D., 1954, Animal cytology and evolution. Cambridge University Press, 3178) 10% WILLIAMS, W. D., 1968, Australian freshwater life. The invertebrates of Australian inland waters. Sun Books, Melbourne, 262 p. WOODWARD, B. B., 1892, On the radula of Paludestrina jenkinsi Smith, and that of P. ven- trosa Mont. Ann. Mag. nat. Hist., (6) 9: 376-378. RESUME LES ESPECES DE POTAMOPYRGUS DE NOUVELLE-ZELANDE (Gastropoda: Hydrobiidae) M. Winterbourn Dans sa revision du genre, Suter (1905) reconnait 6 especes et 3 sousespeces de Potamopyrgus dans les deux principales îles de Nouvelle-Zélande, mais l'étude présente a mis en évidence qu’il n’y a seulement que 3 espèces. Ce sont: P. antipodarum (Gray 1843), P. pupoides Hutton 1882 et une espèce précédemment non reconnue P. estuarinus n. sp. Potamopyrgus estuarinus et P. pupoides sont ovipares, possédant des coquilles lisses non ornementées et se confinent aux eaux saumátres, tandis que P. antipodarum est ovovivipare, a une coquille extrêmement variable par sa taille, sa forme et son ornemen- tation et habite aussi bien les eaux douces que saumátres. Les populations de P. antipodarum peuvent comprendre uniquement des femelles parthénogénétiques Ou contenir un pourcentage variable de mâles sexuellement fonctionnels. L'élevage de P. antipodarum au laboratoire a montié que les individus ne conservent pas forcément d’une génération à l’autre les caractères ornementaux de la coquille et que la forme et l’ornementation de la coquille ne dépendent pas à l’origine des facteurs du milieu. La coquille de P. estuarinus est indistingable de certaines coquilles de P. antipodarum, mais P. pupoides est facilement reconnaissable par sa petite coquille pupiforme, 3 0 M. WINTERBOURN La radula, l'opercule, la morphologie externe, la pigmentation du corps et l'appareil reproducteur male sont semblables dans toutes les espéces et n’apportent pas de caractéres taxonomiques utilisables. Chez Potamopyrgus antipodarum la section inférieure de l'appareil reproducteur femelle est modifié pour former une poche incubatrice, sur le plancher de laquelle s'étend le sillon spermatique ouvert. Chez P. estuarinus et P. pupoides la partie inférieure du tractus génital est domiré par la glande nidamentaire fortement développés qui est effectivement séparée du conduit spermatique situé au-dessus. Le nombre diploïde de chromosomes est de 24 pour les trois espèces. La chromatographie des protéines du périostracum de la coquille n’a pas permis de distinguer de différences significatives entre les espèces en ce qui concerne la composition en amino-acides, mais a mis en évidence de considérables variations intraspécifiques. Potamopyrgus antipodarum est abondant dans les eaux douces permanentes de toutes sortes et a été trouvé dans une eau atteignant 26%, de salinité, bien que les expérimenta- tions montrent qu'il n’est actif que dans une eau de salinité inférieure à 17,5%,. On n’a pas établi une nette relation entre la morphologie de la coquille et le type d’habitat; P. estuarinus est surtout abondant dans les estuaires de marézs où existent d'importantes fluctuations de la salinité et où beaucoup d'individus sont régulièrement exposés a l’emersion entre chaque maré2. P. pupoides occupe un habitat semblable, mais nor- malement demeure toujours immergé. Au laboratoire P. estuarinus et P. pupoides demeurent actifs à toutes les salinités, depuis l’eau douce jusqu'à l’eau de mer, mais ils n'ont pas été trouvés en eau douce dans la rature. Des expériences de laboratoire ont montré l’existence de différence le comportement entre les espéces, qui sont en relation avec leurs différences d'habitat. Potamopyrgus estuarinus montre des tendances amphibies prononcées qui n’existent pas chez P. anti- podarum et se révèle capable de survivre dans un état * dormant ’’ quand il est exposé à l’air pendant 76 jours. Le complexe Potamopyrgus antipodarum est examiné à la lumière des conceptions actuelles sur la notion d'espèce, et le haut degré de variabilité qu’on a trouvé dans cette espèce est à mettre en relation avec l'existence de l’ovoviviparite et de la parthénogénèse qui permettent à un haut degré d'évolution divergente d’apparaitre indépendamment dans des populations individuelles. Une comparaison entre Potamopyrgus antipodarum et l'espèce européenne P. jenkinsi (Smith) montre que les deux ne peuvent être distinguées sur des bases anatomiques et que de nombreux faits de leur biologie et de leur écologie sont semblables. Il semble par conséquent probable que les deux sont la même espéce, les spécimens éuropéens ayant été introduits de Nouvelle-Zélande (ou d'Australie?) au cours du 19 eme siècle. A. L. NEW ZEALAND POTAMOPYRGUS ABCTPAKT НОВОЗЕЛАНЛСКИЕ ВИДЫ POTAMOPYRGUS (GASTROPODA: HYDROBIIDAE) M. ВИНТЕРБОУРН В своей ревизии рода Potamopyrgus, Suter (1905) различал в нем 6 видов и 3 подвида, обитающих на двух основных островах Новой Зеландии; однако в настоящей работе указывается, что имеется лишь три вида: Р. antipodum (Gray 1843), Р. pupoides (Hutton 1882) и ранее неизвестный вид- P. estuarinus n.sp. Р. estuarinus и P. pupoides откладывают яйца, имеют гладкую без узоров ра- ковину и связаны в своем обитании с солоноватыми водами, в то время как Р. antipodum является яйцекладуще-живородящей, сильно изменчивой по разме- рам, очертаниям и орнаментации раковины и живет как в пресной воде так и в солоноватой. Популяции P. antipodum могут состоять только из партеногене- тических самок или содержать различное количество особей, функционирующих как самцы. Разведение P. antipodum в лабораторных условиях показало, что эти моллюски не обязательно дают орнаментированные раковины и что форма раковины и ее орнамент не зависят от факторов среды. Раковина Р. estuarinus He отличима от раковин некоторых P. antipodum, однако P. pupoides легко от- личается от них своей маленькой раковиной. Радула, крышечка, наружная морфология, пигментация тела и половая система самцов сходны у всех видов и не имеют таксономического значения. УР. antipodum нижняя часть женской половой системы модифицирована в выводковую камеру с открытым желобком для спермы, проходящим по ее дну. УР. estuarinus и P. pupoides нижний репродуктивный проток имеет вид сильно развитой капсульной железы, отделенной от лежащего ниже протока спермате-. ки. Диплоидное число хромосом у всех трех видов равно 24. При помощи ион- но-обменной хроматографии белков из периострака раковины не было устано- влено различий в составе аминокислот у всех видов, однако отмечена его внутривидовая изменчивость. Р. antipodum изобилует в постоянно-пресных водах всех типов и был найден также при солености 26%, хотя эксперименты показывают, что эти моллюски активны лишь при солености ниже 17,5%.Не было найдено никакой ясной кор- реляции между морфологией раковины и характером их местообитания. P. estuarinus наиболее обилен в эстуариях литоральной зоны, где наблюда- ются значительные колебания солености и где многие брюхоногие моллюски регулярно подвергаются осушению во время приливно-отливного цикла. P. pupoides занимает сходное местообитание, но обычно всегда находится под водой.В лабораторных условиях Р. estuarinus и Р. pupoides остаются актив- ными при разной солености, начиная от пресной воды до морской, однако в природе они в пресных водах до сих пор не встречались. Лабораторные опыты указывают на существование различий в поведении различных видов, которые связаны с различиями в условиях их обитания. P. estuarinus имеет ясно выраженную тенденцию к амфибионтности (чего не наблюдается yP. antipodum) 1 может выживать на воздухе в "сонном" состоянии в течение 70 дней. Комплекс P. antipodum исследовался в свете современных теорий о виде; высокая степень изменчивости этого вида связана с наличием у него то от- кладки яиц и живорождения, то партогенеза, которые сопровождаются высо- кой степенью дивергентной эволюции и наблюдается независимо у различных популяций. Сравнение между Р. antipodum и европейским видом Р. jenkinsi (Smith) пока- зывает, что они не могут быть отличимы по анатомическим признакам и что многие черты их биологии и экологии сходны. Поэтому кажется вполне веро- ятным, что оба они являются одним и тем же видом, поскольку европейские улитки были интродуцированы из Новой Зеландии (или Австралии?) в X1X столетии. | ZA ER 321 MALACOLOGIA, 1970, 10(2) : 323-332 DESCRIPTION OF THE JUVENILE FORM OF THE ANTARCTIC SQUID MESONYCHOTEUTHIS HAMILTONI ROBSON! Edward S. McSweeny Institute of Marine Sciences University of Miami, Miami, Florida, U.S.A. ABSTRACT The juvenile form of Mesonychoteuthis hamiltoni Robson is fully described and figured from 4 specimens captured by the U.S. Naval Ship ELTANIN in Antarctic waters. Measurements and indices are given. This constitutes the first full description of the species. The validity of the genus is reaffirmed, but relationships to other genera within the family Cranchiidae are not yet clear. In 1925 Robson described a new species of squid, Mesonychoteuthis hamiltoni, from 2 large brachial crowns taken from the stomach of a sperm whale captured near the South Shetland Islands. He was un- certain of the systematic position of the species represented by these fragments, but tentatively placed it between the Ony- choteuthidae and Enoploteuthidae (Rob- son, 1925: 272). The principal features mentioned by Robson in this paper were the presence of hooks in the central por- tion of the arms, and the supposedly dis- tinctive structure of the tentacular hooks. Clarke (1966) includes the species in his systematic review, with the statement “М. hamiltoni is a taonine cranchiid which attains giant size ”” (Clarke, 1966: 240). Clarke further states that the genus Mesonychoteuthis is monotypic and is “ characterized by hooded hooks in the middle of each arm.” The only other reference to the genus found in the litera- ture is Clarke’s (1962) discussion of the mandibles. Among the Antarctic cephalopod col- lections made by the National Science Foundation’s research ship ELTANIN are 4 small cranchiid squids which bear hooded hooks in the central portion of the arms, and must be referred to Rob- son’s species. The following description of these juvenile specimens constitutes the first full description of the species. The writer would like to thank Dr. G. L. Voss of the Institute of Marine Sciences for his comments and criticisms of the manuscript. Dr. R. E. Young of the Department of Oceanography, Univer- sity of Hawaii, materially aided the writer by offering many helpful sugges- tions and critically read the manuscript. The specimens on which the description is based were collected by the University of Southern California’s biological sampl- ing program aboard the U.S.N.S. ELTA- NIN. The terminology used in describ- ing the mandibles is after Clarke (1962) and Mangold & Fioroni (1966). The illustrations were executed by my wire Constance. This work was supported by National Science Foundation grants GA 103, GA 709, and GA 1493, Dr. G. L. Voss, principal investigator. This support is gratefully acknowledged. ? Contribution No. 1272 from the Institute of Marine Sciences, University of Miami, Florida, U.S.A. 324 E. S. McSWEENY Mesonychoteuthis hamiltoni Robson, 1925 Figs. 1-3 Mesonychoteuthis hamiltoni Robson, 1925, p. 272, figs. 1, 2. Material examined: | Specimen, mantle length 86 mm. ELTANIN Sta. 142. 60045, 65°15'\ № Aug: 1962. Эт |КМТ, 0-1850 m. Specimen, mantle length 68 mm. ELTANIN Sta. 929. 10°12°S; 110 17%. 19 Jan. 1964. Эт IKMT, 0-1098 m. Specimen, mantle length 59 mm. ELTANIN Sta. 941. 69°56°S, 98°31’W. 23 Jan. 1964. 3 m IKMT, 0-2562 m. Specimen, mantle length 59 mm. ELTANIN Sta. 946. 67°39°S, 90°27 W. 26 Jan. 1964. 3 m IKMT, 0-1711 m. — — — Description The mantle is short and wide (MWI= 35°0), tapering smoothly to the middle of the fins, where it abruptly narrows to closely sheath the gladius. Only the integument continues over the conus. The mantle is thin and leathery, and is fused to the head at the dorsal midline and ventrally to each side of the funnel. At each ventral fusion there is a 5 or 6- pointed cartilaginous tubercle, and at the dorsal fusion point there is a single small, conical tubercle. The gladius is distinctly visible through the integument along the dorsal midline. The fins measure 20-30% of the mantle length and are almost semi- circular (FLI, FWI=21:0). The funnel is broad at the base and tapers rapidly, extending nearly to the base of the ventral arms. It is fused to the head dorsally. The dorsal member of the funnel organ has the shape of a rounded, inverted V, with the two legs of the V directed slightly outward at the tips. At the apex there is a long conical tubercle surmounted by a narrow flap of tissue. The height of this tubercle is 4 to 1 the total length of the dorsal member. At the posterior end of each leg of the V, there is a smaller, rounded tubercle. The ventral pads are fanshaped, with the apex directed antero- medially. There is no trace of a funnel valve. The head is small, with large globular eyes. The total width, including the eyes, is less than the mantle width (HWI=25:0). The eyes are directed outward at an angle of about 45° from the longitudinal axis. The eyes have a large, wide, crescent- shaped light organ applied to the ventral surface, and extending upward almost half the circumference. A smaller, oblong light organ lies inside the concavity of the crescent, close to the pupil. There is a very small anterior notch in the rim of the eye opening. The stalk of the “ olfac- tory papilla ” is very short, and the organ is closely applied to the posterior surface of the eye capsule, well below the midline. The arms range from 20-30% of the mantle length in smaller specimens and from 30-40%, in the larger specimens. They are round in cross section, with the formula 4.3.2.1. Protective membranes and trabeculae are fairly well developed on the ventral side of all the arms, and consist of a low, scalloped fringe on the dorsal side. A weak swimming keel is present on the third arms, and a stronger lateral keel on the ventral arms. The suckers are arranged in 2 rows with small suckers proximally, becoming larger to about the mid-point of the arms, where they are replaced by prominent hooks. On the largest specimen, these hooks are initially much larger than any of the suckers, becoming the same size distally. On the smaller specimens, the proximal hooks are about equal in size to the pre- ceding suckers. The distal portion of the arms again bears suckers, the most prox- imal of these being slightly smaller than 325 JUVENILE SQUID MESONYCHOTEUTHIS Mesonychoteuthis hamiltoni Robson. Mantle length 86 mm (ELTANIN Sta. 142). A. Ventral B. Dorsal view. FIG #1. C. Tentacular club. VIEW. 326 ES S. McSWEENY TABLE 1. Measurements (in mm) of 4 juvenile specimens of Mesonychoteuthis hamiltoni Robson. Cher ELTANIN ELTANIN ELTANIN ELTANIN Sta. 142 Sta. 929 Sta. 941 Sta. 946 Mantle length 86 68 | 59 59 Head width 27 17 15 15 Eye diameter 15 10 8 | 8 Fin length 22 14 11 | 11 Fin width | 21 14 11 | 11 Arm length: 1 | 25 13 11 10 Il 29 18 13 11 Ш 31 20 16 14 IV | 33 24 18 | 16 Tentacle length | 60 44 46 37 Club length 15 12 10 9 the last sucker proximal to the hooks. Table 3 lists the numbers of proximal suckers and hooks. The number of suckers distal to the hooks ranges from 8-10 in the smaller specimens to 25-30 in the largest specimen. Dentition is apparent on the first few suckers distal to the hooks. This consists of incisions in the most distal quarter of the inner ring to form | to 5 irregular teeth. The tentacles are moderately long and slender, oval in cross section and slightly flattened on the oral surface. The dia- meter is nearly constant, with the club tapering evenly to the tip. The only demarcation between the stalk and club is a slight constriction across the aboral surface. The club comprises one-quarter of the total tentacle length and is bor- dered by a very low and indistinct pro- tective membrane on either side. There is a very small dorsal keel at the extreme tip. The club bears 4 longitudinal rows of suckers, with from 22 (dorsal row) to 24 (ventral row) suckers. The first 6 to 8 suckers in the two central rows are modi- fied into hooks. The suckers of these rows, distal to the hooks, decrease in diameter toward the tip, while those of the marginal rows are small suckers of nearly constant diameter throughout. The club suckers are armed with small teeth around the inner circumference, with those in the distal quarter better developed. The carpal apparatus consists of 10 suckers, without teeth, and 10 pads on each tentacle. The stalk carries 22 to 23 pairs of small suckers, alternating with pads, and extending almost to the base of the tentacle. The buccal membrane has 7 lappets. The connectives attach dorsally to arms I and II, and ventrally to arms TIT and IV. JUVENILE SQUID MESONYCHOTEUTHIS 327 FIG. 2. Mesonychoteuthis hamiltoni Robson. (A-K, M-O, ELTANIN Sta. 142. L, ELTANIN Sta. 929). A. Vertral, and В. Lateral view of eye capsule, showing light organs. С. Left arms I-IV. D. Funnel organ. E, Е. Hook, arm Ш. С. Hook, arm IV. H. Ist sucker proximal to hooks, arm III I. Ist sucker distal to hooks, arm III. J. Ist sucker proximal to hooks, arm IV. К. 2nd sucker distal tc hooks, arm If. L. 2nd sucker distal to hooks, arm I. M. Tentacular hook. N. Dactylus sucker. O. Cartilaginous tubercles at mantle-funnel fusion points. McSWEENY S. Bs JUVENILE SQUID MESONYCHOTEUTHIS 329 TABLE 2. Indices of bodily proportions of 4 juvenile specimens of Mesonychoteuthis hamiltoni Robson. All indices are the indicated measurement expressed as a percentage of the mantle length. | ELTANIN Character | VO Mantle width index (MWI) 35-0 Head width index (HWI) 31-0 Fin length index (FLI) 26:0 Fin width index (FWI) | 26-0 Arm length index (ALI): 1 | 29-0 II 34-0 II | 36-0 IV 38-0 Club length index (CLI) | 17-0 The hood of the upper mandible is slightly flattened dorsally and forms rounded angles dorso-laterally. These dorso-lateral angles join near the tip of the rostrum to form a dorsal ridge. The line of the inner edge of the rostrum continues posteriorly across the wing as a distinct ridge. Above this ridge, the lateral surfaces of the hood are slightly concave. The wings extend downward to the lower angle of the lateral wall. There is a wide area of fusion between the lateral wall and the wing, forming a slightly projecting shoulder. The jaw angle is about 90°, and is somewhat recessed. The hood length is approxi- mately 3 of the crest length. The lower mandible has the obtuse jaw angle partially obscured by an overlapping lateral bulge of the wing. The wing ex- ELTANIN ELTANIN ELTANIN Sta. 929 Sta. 941 Sta. 946 31-0 34-0 36-0 25-0 25-0 25-0 21-0 19-0 19-0 21-0 19-0 20-0 19-0 19-0 17-0 26-0 24-0 20-0 29-0 30-0 26-0 35-0 32-0 27-0 18-0 17-0 17-0 tends downward beyond the lower margin of the lateral wall. The hood length is slightly more than 1 the crest length. The radula has a tricuspid rachidian tooth with a long median and small outer cusps. The first lateral tooth has a broad base, with a moderately long inner cusp and a small outer cusp. The second lateral is simple, broad and thick at the base, and somewhat longer than the first lateral. The third lateral is simple, strongly curved, and longer than the other teeth. The marginals are very small, unarmed plates. The gladius is narrow, with the vanes bordering the posterior third of the rachis. The anterior $ of the rachis is very narrow, of nearly uniform width, and slightly concave ventrally. In the region of the vanes, it is thickened and FIG. 3. Mesonychoteuthis hamiltoni Robson (A, B, D, E, F, ELTANIN Sta. 142;) C, ELTANIN Sta. 946). A, Radula. mandible. B, Gladius. С, Conus of gladius; ventral view D, E, Upper mandible. F, Lower 330 E. S. McSWEENY TABLE 3. Numbers of proximal suckers and hooks on arms of juvenile specimens of Mesonychoteuthis hamiltoni. | ELTANIN haracte Character ARM Sta. 142 Proximal | 13/14 Suckers (Right/Left) II 15/14 Il 17/17 IV 20/20 | 6/6 Hooks (Right/Left) II 7/8 Il 10/9 IV 16/16 steeply ridged along the midline. At the posterior tip the vanes overlap ventrally, but are not fused. This portion of the gladius of a 59 mm specimen (ELT 946) is illustrated in Fig. 3C. All others had the vanes broken away in this region. DISCUSSION It is difficult to compare the present material with Robson's original descrip- tion, even without considering the dis- parity in size. Some of the features which he mentioned as being charac- teristic were most probably the result of the action of the digestive process. How- ever, some conclusions can be drawn. The arms present the feature of greatest interest, namely the series of hooks in the central portion. As Mesonychoteuthis is the only cranchiid known to _ possess hooks on the arms, it is not surprising that this armament, coupled with the tentacular hooks, led Robson to ally the species with the enoploteuthids and Question marks indicate missing hooks at end of series. ELTANIN ELTANIN | ELTANIN Sta. 929 Sta. 941 Sta. 946 | | Reet: 13/13 14/15 14/14 13/13 15/15 15/15 16/16 19/19 18/18 19/20 22/22 22/21 6/5 7/7 | 5/5 8/7 82/92 6/6 9/9 10/10 7/8 13/14 10+/122 8/7 onychoteuthids. The presence of the hooks in these juvenile specimens is of utmost importance, as it accentuates the value of this feature as a generic char- acter. This character makes Mesony- choteuthis easily separable from Galiteu- this, which it resembles in the possession of tentacular hooks. The writer has examined a mature specimen of Galiteu- this and found well developed suckers present along the full length of the arms. In Robson’s specimens, the suckers were missing in the distal portion of the arms, with the stumps remaining. He considered that this was the result of atrophy rather than accident (Robson, 1925: 273). The fact that in the present material the suckers extend to the tips of the arms indicates that in Robson’s speci- mens these suckers were probably lost accidentally or through digestion. Robson considered the “‘ swivel-move- ment’ of the tentacular hooks to be a feature characteristic of only a few species (1925: 275). After an examination of JUVENILE SQUID MESONYCHOTEUTHIS 331 specimens of most of the genera which have tentacular hooks, it is apparent that all are capable of some degree of swivel- motion, probably much more so in life than is indicated in preserved animals. The principal difference between species seems to be in the degree of freedom of movement, although differences are not really great. It is doubtful that this feature has particular significance in Mesonychoteuthis. The tentacular club of Robson's specimen was probably broken, as he mentions a ‘ very short hand ” and states that it lacked suckers (1925: 275). It is possible that the pro- portions of the club change with growth. but it seems probable that the extreme condition reported by Robson was the result of damage or digestion, or both. The lack of differentiation between the tentacular stalk and the comparatively long club is a distinctive feature of the specimens described above. Robson described the row of suckers and pads on the tentacular stalk as being “ unique among these forms ” (1925: 276). What is meant by “ these forms ” is un- clear, but this conformation is common among cranchiid squids, while it does not occur in either of the families to which he supposed Mesonychoteuthis was most closely related. The eyes are completely sessile in the present material, giving no indication of a stalked condition, although it is very likely that younger forms pass through such a stage. This has been shown to be the case in Desmoteuthis (= Megalocran- chia) by Muus (1956), and has been ob- served by the writer in specimens of Taonius and Galiteuthis. No features observed in the present material could be considered larval characters. The light organs of the eye, although well-formed in the largest specimen, are probably not completely developed. In the smaller specimens, the small light organ at the inside of the ventral crescentic 4 organ is only partially formed, consisting of a narrow, thickened ridge. In the larger specimens, this ridge is bordered by an area of thin, dark tissue. These organs may in time become crescent- shaped also, or oval. The mandibles show some differences from Clarke’s (1962) description of a much larger example. The significance of these differences cannot be determined without a series bridging the gap in size. The principal differences are in the concave lateral surfaces of the hocd, and the ridge across the midpoint of the wing. The radula shows a considerable dif- ference from Robson’s illustration (1925, fig. 1), but the differences can protatly be explained by both the difference in size of the specimens and the angle at which the drawings were made. In Rob- son’s figure, the third lateral tooth is shown as nearly straight, although Rob- son states (1925: 276) that it is slightly curved. This indicates that the drawing was made without flattening the ritton, which could account for other differences. as in the relative height of the cusps. Robson also overlooked the marginal plates, which are extremely small. These specimens show similarities to other genera in some respects, notably to Megalocranchia in general appearance, and to Galiteuthis in possession of tenta- cular hooks. However, this resemblance is only superficial, as is shown by most of the principal characters. It would be premature at this time to speculate on relationships within the family. LITERATURE CITED CLARKE, M. R., 1962, The identification of cephalopod “beaks” and the relationships between beak size and total body weight. Bull. Br. Mus. nat. Hist. Zool., 810): 419-480. CLARKE, М. R., 1966, A review of the syste- matics and ecology of oceanic squids. Adv. mar. Biol.. 4: 91-300. 332 E. S. McSWEENY MANGOLD, K. & FIORONI, P., 1966, Mor- Cranchiidae. Meddr. Danm. Fisk.- og Havun- phologie et biometrie des mandibules de quel- ders., N.S., 1(15): 1-15. ques cephalopodes mediterraneens. Vie et ROBSON, G. C., 1925, On Mesonychoteuthis, Milieu (Ser. A) 17(3A): 1139-1196. a new genus of Oegopsid Cephalopoda. Ann. MUUS, B. J., 1956, Development and distribu- Mag. nat. Hist., (9) 16(XXXIX): 272-277. tion of a North Atlantic pelagic squid, family RESUME DESCRIPTION DE LA FORME JUVENILE DU CALMAR ANTARCTIQUE MESONYCHOTEUTHIS HAMILTONI ROBSON E.S. McSweeny La forme juvénile de Mesonychoteuthis hamiltoni Robson est entierement décrite et figurée a partir de quatre spécimens capturés par le U.S.N.S. Eltanin dans les mers antarctiques. Des mensurations et des indices sont donnés. Cela constitu: la premiére description complete de l’espece. La validité du genre est réaffirmée, mais la relation avec les autres genres de la famille des Cranchiidae n'est pas encore claire. A. L. RESUMEN DESCRIPCION DE LA FORMA JUVENIL DEL CALAMAR ANTARTICO MESONYCHOTEUTHIS HAMILTONI ROBSON Е. 5. McSweeney La forma juvenil de Mesonychoteuthis hamiltoni Robson, se describe en forma completa y se ilustra con 4 ejemplares que fueron capturados por el U.S.N.S. ELTANIN en aguas antarticas. - Todo esto constituye la primera descripción total de la especie. Se confirma | la validez del género Mesonychoteuthis, aunque su relación con otros en la familia Cranchiidae no resulta todavía muy clara. Y. TAB: ABCTPAKT ОПИСАНИЕ ЮВЕНИЛЬНОЙ ФОРМЫ АНТАРКТИЧЕСКО ГО а, MESONY CHOTEUTHIS HAMIL TONI ROBSON 9. С. МЭКСВИНИ Ювенильные Формы Mesonychoteuthis hamiltoni Robson описаны и изображены по 4 экземплярам, пойманным на корабле "Илтенин" в водах Антарктики. Приво- дятся данные измерений и индексы, что дополняет первое полное описание этого вида. Подтверждается валидность рода, однако его взаимоотношения внутри семейства Cranchiidae еще не ясны. 7. A. F. MALACOLOGIA, 1970, 10(2): 333-355 - A RE-EVALUATION OF THE RECENT UNIONACEA (PELECYPODA) OF NORTH AMERICA William H. Heard and Richard H. Guckert Florida State University, Tallahassee, Florida 32306, U.S.A. ABSTRACT Recent higher classifications of freshwater mussels, based principally on shell characters, do not reflect the phylogenetic relationships of these animals which may be interpreted from reproductive features. Although these 2 types of characters are not consistently mutually exclusive, there is comparatively little overlap. Shell characters have received emphasis in the classification of naiades on a world-wide basis because of convenience of study and because they can be employed in investigations of fossil material. Unfor- tunately, too little information on reproductive morphology and habits is presently available to permit a wide-scale classification based on these features, and it may prove difficult to relate fossil forms to such a scheme should one eventually be proposed. The choice of one system (i.e., either shell or soft-parts) demonstrates parallel evolution of characters in the other system. It is considered here that a system based on aspects of reproduction, with parallelism in the shell features, more accurately reflects natural, evolutionary affinities than does a system which reverses the emphasis. In order to stimulate further investigation (particularly of non-Nearctic groups), a revised system of affinities of North American naiades at the familial and subfamilial levels, derived from anatomical and related aspects of reproduction, is presented here. This system concerns such features as (a) the number of marsupial demibranchs (4 or 2), (b) the location of the marsupial demibranchs (only the inner 2, or only the outer 2), (c) specific regions of the marsupial demibranchs which incubate the developing larvae (the entire demibranchs, only the posterior portion, only the central portion, efc.), (d) the morphology of the marsupial demibranchs (simple or subdivided septa and water- tubes; continuous or interrupted septa and water-tubes), (e) the duration of incubation of the larvae (short- or long-term), (f) the nature of the glochidial shell (hooked or hookless), and (g) other anatomical aspects more subtly related to reproduction in terms of water currents (completeness and composition of the diaphragm; — presence/ absence of a supra-anal opening). : These characters indicate that Recent representatives of the Margaritiferidae, Amblemidae and Unionidae occur in North America. A fourth family, the Hyriidae, is known from the Nearctic Region only in fossil form; living species are presently con- fined to South America and Australasia. Nearctic subfamilies and their characters are delineated for these 3 Recent families, and the North American genera of each group are listed. Three new subfamilies are proposed: Cumberlandinae (Margaritiferidae), Megalonaiadinae (Amblemidae) and Popenaiadinae (Unionidae). Notes on related unionacean groups in the Neotropical, Palearctic, Ethiopian, Oriental and Australasian regions are provided. A suggested relationship of the Mutelacea to the Unionacea is included, and phylo- genetic affinities of the families and subfamilies of Nearctic unionaceans are interpreted - from reproductive data. The presently-Holarctic Margaritiferidae, the most primitive group of unionaceans, is considered to have independently given rise to the hyriid- mutelacean stock and to the Amblemidae. The Amblemidae, present in all areas but South America and the Australasian Region, in turn is described as ancestral to the Unionidae. The unionids have reached greatest diversification in North America and comprise the vast majority of Nearctic mussels. The more primitive Pleurobeminae (presently confined to North and Central America) is suggested to have given rise inde- 333 334 HEARD AND GUCKERT pendently to (a) the Popenaiadinae of the southern United States, Mexico and Central Amzrica, (b) the Anodontinae of the Northern Hemisphere, and (с) the Lampsilinae of North and Central Aiaerica. The Unioninae s.s. of Eurasia is thought to have been derived from anodontine stock. The Pleurobeminae is considered to be ancestral to the primitive lampsiline stock which subsequently diverged along several lines through specializations of the marsupial demibranchs. The evolutionary trends in advancement and/or specialization of the Nearctic unionaceans include (a) reduction from 4 to 2 (principally the outer pair) marsupial demibranchs, with greatest diversification occurring in present groups in the Northern Hemisphere, (b) development of coatinuous interlamellar septa and water-tubes, (c) morphological adaptations of the marsupial demibranchs which reach greatest specializa- tion by restricted regionalization of ovisacs in the unionid Lampsilinae, (4) a tendency toward a complete diaphragm formed entirely by the ctenidia, and (e) a general change from short-term to long-term incubation of the larvae. Most unionaceans possess hook- less glochidia, and the hooked larvae are considered to have evolved independently in the hyriids and in the unionine-anodontine stock. INTRODUCTION Modell (1942, 1949, 1964), Morrison (1955, 1966, 1967). McMichael & Hiscock (1958), and Haas (1969a, 1969b) have altered the taxonomic treatment and presented new impressions of the phylogenetic affinities (?) of freshwater mussels of the families Margaritiferidae, Mutelidae and Unionidae as formerly interpreted by Simpson (1896, 1900a, 1914), Ortmann (1910a, 191la, 1912a, 1921a) and Frierson (1927). However, the work of Parodiz & Bonetto (1963) has demonstrated the necessity of a re-evaluation of these other recent reports and has consequently prompted this extension of their findings. Modell originally (1942) emphasized beak sculpture-as the principal character which he considered to reflect phylo- genetic relationships; other shell charac- ters (e.g., form and hinge aspects), anatom- ical features, and larval type were relegated to secondary importance. Later (1949), Modell fruitlessly attempted to support his concepts with morphological informa- tion. His most recent report (1964) shows few digressions from his previous considerations. 1 This taxon was first employed by Hannibal in 1912, While Ortmann’s (1910a) system of the “ Unionidae,” widely followed by North American workers, consists of but 3 subfamilies (viz., Unioninae, Anodontinae and Lampsilinae), Modell’s latest (1964) scheme includes the following higher taxa which include Nearctic repre- sentatives: Family Elliptionidae Modell, 1942 Subfamily Pleurobeminae! Modell, 1942 Subfamily Elliptioninae Modell, 1942 Subfamily Ambleminae? Modell, 1942 Subfamily Alasmidontinae? Frier- son, 1927 Subfamily Lampsilinae von Ihering, 1901 Family Unionidae? Fleming, 1828 Subfamily Quadrulinae von Ihering, 1901 Subfamily Rectidentinae Modell, 1942 Subfamily Anodontinae? Swainson, 1840 Morrison (1955) restored Modell’s Ambleminae to familial rank (as Refinesque, 1820, employed it) and included in it the subfamilies Ambleminae 2 These taxa were Originally proposed by Rafinesque in 1820, NORTH AMERICAN UNIONACEA 335 s.s. and Lampsilinae. As Morrison (1967) also pointed out, the family Quadrulidae Hannibal, 1912, and its subfamily Quad- rulinae von Ihering, 1901, are synonyms of the Amblemidae and Ambleminae. respectively. McMichael & Hiscock (1958) recog- nized the importance of soft-part and reproductive features, but they persisted in subscribing to Modell’s scheme based principally on shell characters. Haas (1969a, 1969b) presents more conservative systems which include the Recent North American unionaceans in the Margaritiferidae and Unionidae (and its subfamilies Unioninae s.s., Quadruli- nae, Anodontinae, Alasmidontinae, Lampsilinae and Hyriinae). In our opinion most classifications of freshwater mussels have (1) over- emphasized shell sculpture, paleontological data and seemingly zoogeographic rela- tionships, and (2) only superficially inter- preted anatomical features. While Frierson (1909, р 107) stated that *‘ beak sculpture and manner of carrying ova in the gills are not correlated,” he pre- ferred to use shell features as the basis of classification. However, as Hannibal (1912, p 117) and Ortmann (1912a, p 230) have pointed out, respectively, shell characters are of “‘ secondary importance in the recognition of groups more compre- hensive than genera,” and are “ unfit to be used for the distinction of the larger groups.” Modell’s (1942, р 164) suggestion that most anatomical charac- ters “ gehen Hand in Hand mit Umbil- dungen der Schale ” would be considered by Hannibal and Ortmann (and by us) to be fallacious. A number of different schemes of classification of freshwater mussels have been proposed (see McMichael & Hiscock, 1958), each seeming to stress a different combination of characters and/or re- arranging the member groups. Van der Schalie (1952) has provided a most informative paper which reviews (1) some of the systems that earlier workers devised, and (2) the personalities of several of these taxonomists/systematists. Sterki (1898, 1903) indicated that the classification of these mollusks should include their reproductive features, e.g., the number and location of the marsupial demibranchs, the regions of these demi- branchs which incubate the developing larvae, the morphology of the marsupial demibranchs, the duration of gravid periods (= “ breeding season ” of authors), and the nature of the glochidial larvae. Simpson (1900a) created a number of divisions (based upon distinctive marsu- pial demibranch features) within the subfamilies of the “ Unionidae.” Ortmann subsequently subscribed to the initial findings of Sterki and Simpson and extended their work in more detail. In viewing Modell’s most recent phylogenetic scheme (1964, figure on p 122), one can immediately detect the composite nature of the families Ellip- tionidae and Unionidae. In the Elliptio- nidae (comprising elements of Ortmann's 19104 Unioninae, Anodontinae and Lampsilinae!) are the Lampsilinae and Alasmidontinae which are for the most part bradytietier (.е long-term breeders,” retaining developing glochidial larvae except in the Nearctic summer), while others are tachytictic (1.e., ** short- term breeders,” carrying glochidia only in the Nearctic summer: Pleurobeminae, Elliptioninae and Ambleminae). The Alasmidontinae contains species with hooked glochidia, while the other mem- bers of this family Elliptionidae possess hookless larvae. Animals of the Ellip- tionidae have seven different marsupial gill conditions which Simpson (1900a) termed tetragenae, homogenae, diagenae, heterogenae, mesogenae, eschatigenae and ptychogenae. Modell also included in the “family Unionidae” groups with (1) the tetragenous condition, short-term 336 HEARD AND GUCKERT breeding and hookless glochidia, and (2) the homogenous condition, long-term breeding and hooked glochidia. Further- more, groups with hooked glochidia, the homogenous condition and long-term breeding were placed in 2 different unionid subfamilies (Rectidentinae and Anodontinae), and genera with these same features were included in the Alasmidontinae of the Elliptionidae. Finally, Modell’s Rectidentinae con- tains (1) Rectidens Simpson which is tetragenous and has hookless glochidia, and (2) Arnoldina Hannibal, Utterbackia Baker and Pyganodon Crosse & Fischer” which have the homogenous condition and hooked glochidia. These few exam- ples should suffice to demonstrate the shortcomings of Modell’s classification. Hass (1969a. 1969b) has provided the most recent conchological systems, and he lists 6 subfamilies (compared to Modell’s 12), inthe Unionidae: Unioninae, Quadrulinae, Anodontinae, Alasmidon- tinae, Lampsilinae and Hyriinae. How- ever, his scheme (1) does not consistently separate tetragenous and homogenous groups, (2) maintains a distinction between the Anodontinae and the Alasmi- dontinae, and (3), like Modell, retains the Hyriinae* in the Unionidae. In these previous examples we have attempted to show the limited value of using principally (or entirely) shell charac- ters in the classification of freshwater mussels. Ortmann’s work remains today as a model of the anatomical/reproductive approach. He recognized, however, that his provisional interpretations could be subject to change in the light of additional information. In addition, he was inte- rested in the natural relationships of these mussels, not just in their nomencla- nn == ture. We will attempt to follow Ortmann’s lead and hopefully extend our knowledge of the evolution of this large and diverse group of animals. To do so, however, requires a re-evalua- tion of his concept of the unionid sub- families, particularly the Unioninae (see Ortmann, 1910a, 1912a). His considera- tion of this group includes several genera with 4 marsupial demibranchs as well as others with only the outer 2 demibranchs marsupial (although all except Megalonaias Utterback (tetragenae) and Popenaias Frierson (homogenae) are short-term breeders, and all North American groups possess hookless glochidia). His (1910a) Anodontinae (s.l.) encompasses the Alas- midontinae (s.s.) as defined by Rafinesque (1820), Swainson (1840), Frierson (1927), Modell (1942, 1949, 1964) and Haas (1969a, 1969b). Since all species of these 2 groups possess marsupial demi- branchs (homogenae in all genera but Strophitus, which has the diagenous condi- tion) with secondary interlamellar septa- and secondary water-tubes, they are more correctly considered as a single group unlike any other subfamily. Ortmann's (1910a) Lampsilinae (an exten- sion of von Ihering’s 1901 taxon) is retained by Modell (1942, 1949, 1964) and Morrison (1955), but is removed to the Elliptionidae and Amblemidae, respec- tively. It appears to us that the aforementioned reproductive characters are more signifi- cant than Modell, Morrison, McMichael & Hiscock, and Haas have considered, and we find their systems artificial and untenable. Consequently, we recommend a consideration of what we feel are more distinctive features, and we offer here a revised higher classification of the North 3 These 3 -taxa are actually subgenera of Anodonta Lamarck which Modell correctly places in the Anodontinae. 4 McMichael & Hiscock (1958) included the Hyriinae in the Mutelidae (Mutelacea), but Parodiz & Bonetto, (1963)-correctly restored it to familia rank and placed it in-the Unionacea: NORTH AMERICAN UNIONACEA 337; American naiades. Unlike numerical taxonomists who use all characters and give them equal weight, we have subjec- tively elected to ignore one entire array of characters (i.e., conchological features) and to suggest soft-part anatomy and reproductive habits as pre-eminent in describing phylogenies. There is regre- tably little specific evidence to support our contention that shell features are the less conservative characteristics. However, ecophenotypic variation in the shell is well documented, and it is difficult (if not impossible) to interpret the possible genetic adaptation(s) of different forms of beak and disc sculpture. Besides, although the shell features of these mussels are indeed convenient, they have not adequately been demonstrated to be more conservative than any other set of characters. Consequently, we have pre- ferred to emphasize reproductive aspects in the manner that systematic botanists favor flowers (1.e., reproductive organs) to such vegetative characters as leaves. Nevertheless, it is hoped that when more information on naiades from other regions becomes available the shell and reproduc- tive features can be correlated into a more meaningful system which more accurately defines the parallel evolution in either or both set(s) of characters on a worldwide basis. The anatomy and reproductive habits of mussels of the Ethiopian, Oriental and Australasian Regions are still poorly known. While we have provided notes on some species/genera from these areas, we cannot at this time adequately interpret their characters in terms of our proposed system. Future investigations of nalades in these areas will provide information which may well modify the views and concepts presented here. Our objective is to present a format to which future studies (hopefully. to be stimulated by this paper) may be compared, We have listed in this paper the. commonly-used generic designations of the different families and subfamilies of the Nearctic unionaceans. However, we wish to stress that a critical re-evalua- tion of these alleged genera is needed. This is indicated in particular by the presence of some 18 monotypic genera among the 48 genera listed for North America. Superscript numbers in the following section refer to corresponding comments under Notes, which appear at the end of this paper (p 345). CLASSIFICATION SUPERFAMILY UNIONACEA (Fleming, 1828) Thiele, 1935 Freshwater pelecypods. with schizodont hinge dentition; ovoviviparous animals, the larvae (= glochidia!) being incubated in all 4 or in only some (either the inner or the outer pair) of the demibranchs; glochidia of most species temporarily parasitic on the gills or fins of fishes?; for additional features see Thiele (1935, p 815). Family 1. MARGARITIFERIDAE Haas, 19403 Type genus: Margaritifera Schumacher, 18164 (type species: Mya margaritifera Linnaeus, 1758). All 4 demibranchs mar- supial; glochidia hookless but with irregular small teeth at ventral margin of the valves (Ortmann, 1912a, p 232); interlamellar connections of demibranchs irregularly scattered or forming irregular oblique rows, or incomplete septa which run obliquely to the direction of the gill filaments; ctenidia lacking water- tubes; posterior margins of mantle not united, lacking even a tendency to form anal and branchial siphons; supra-anal opening lacking; diaphragm separating branchial and. suprabranchial cavities 338 HEARD AND GUCKERT incomplete, formed only by the ctenidia: bradytictic. Present distribution: North America and Eurasia. Subfamily Margaritiferinae s.s. (Modell, 1942°) Type: same as for the family. Inter- lamellar connections discontinuous. irregularly scattered or falling into oblique rows. Represented in the United States by Margaritifera margaritifera (Linnaeus), M. falcata (Gould) and M. hembeli (Conrad). Subfamily Cumberlandinae, new subfamily Type genus : Cumberlandia Ortmann, 1912b (for Unio monodonta Say, 1829). Interlamellar connections of the demibranchs scattered and in interrupted rows, but developed as continuous septa which run obliquely forward. The mono- type, Cumberlandia monodonta (Say), 1s confined to the Tennessee, Cumberland and Ohio River systems in the United States. Family 2. AMBLEMIDAE Rafinesque, 1820 Type genus: Amblema Refinesque, 1820 [type species: Amblema costata Rafines- que, 1820 = A. plicata (Say, 1817). All 4 demibranchs marsupial (= tetra- genae); glochidia hookless*; interlamellar connections usually developed as conti- nuous septa (interrupted in Gonidea). parallel to the gill filaments: undivided water-tubes present, either continuous or interrupted (Gonidea), but always parallel to the gill filaments; posterior margins of mantle not united but drawn together by the diaphragm, thus separating the branchial and anal siphons; anal siphon closed above, leaving a separate supra- anal. opening; diaphragm complete, formed entirely by the ctenidia; princi- pally tachytictic (except in the Megalo- naladinae). Present distribution in the Nearctic Region”: principally in the United States, a few species ranging into southern Canada. Subfamily Gonideinae Ortmann, 1916 Type genus: Gonidea Conrad, 1853, for Anodonta angulata Lea, 1838. Septa incomplete, interrupted and perforated by subcircular holes so that the water- tubes communicate with each other?; tachytictic. The monotype, Gonidea angulata (Lea), is presently found in western North America from southern British Columbia into southern Cali- fornia. Subfamily Ambleminae s.s. [=Quadrulinae (von Ihering, 1901) Hannibal, 1912] Type: same as for the family. Septa and water-tubes well-developed and con- tinuous, not perforated; tachytictic. Re- cent genera in the Nearctic Region are: Amblema Rafinesque, 1820 Elliptoideus Frierson, 1927 Fusconaia Simpson, 1900a Plectomerus Conrad, 1853 Quadrula Rafinesque, 1820* Quincuncina Ortmann, 1922 Tritogonia Agassiz, 1852 Subfamily Megalonaiadinae, new subfamily Type genus: Megalonaias Utterback. 1915, for Unio crassus var. giganteus Barnes. 1823. Septa and water-tubes well- developed and continuous; bradytictic. Megalonaias Utterback currently ranges from north-central United States into Central America. NORTH AMERICAN UNIONACEA 339 Family 3. HYRIIDAE (Swainson, 1840) Parodiz & Bonetto, 1963 Type genus: Prisodon Schumacher. 1817, for Prisodon obliquus Schumacher. 1817. Only the 2 inner demibranchs mar- supial; glochidia with hooks; marsupial demibranchs with septa-like, interrupted interlamellar connections forming incom- plete (discontinuous) water-tubes which run parallel to the gill filaments; distinct branchial and anal openings present, but lacking a separate supra-anal opening; diaphragm complete: anterior part formed by the ctenidia (perforated), posterior part formed by union of the posterior mantle margins; duration of larval incubation little known!®. Recent species are con- fined to South America and Australasia. although Diplodon is known from the Triassic of Texas and Pennsylvania in the United States (Parodiz & Bonetto. 1963). Family 4. UNIONIDAE Rafinesque. 1820 2 Type genus: Unio Philipsson. 1788 !? (type species: Mya pictorum Linnaeus. 1758). Only the 2 outer demibranchs marsupial; glochidia hooked or hook- less; interlamellar connections devel- oped as continuous septa; water-tubes usually uninterrupted ** (but divided in the Anodontinae s.l.); septa and water- tubes parallel to gill filaments except in Strophitus (Anodontinae): posterior mar- gins of mantle not united but drawn together by the diaphragm, thus separat- ing the branchial and anal siphons: anal siphon closed above, leaving a separate supra-anal opening: diaphragm com- plete, formed entirely by the ctenidia: tachytictic or bradytictic. Recent species occur in the Nearctic, Neotropical, Pale- arctic, Ethiopian, Oriental and Australa- sian Regions. Subfamily Unioninae s.s.!* Type: same as for the family. Mar- supial demibranchs: homogenae (entire outer demibranchs forming smooth pads externally); glochidia usually with hooks!’; septa and water-tubes (parallel to the gill filaments) undivided, lacking secondary septa and secondary water-tubes; tachy- tictic. Ortmann (1912a, p 273) suggests that Unio of Europe is not equivalent to the similar forms (i.e., Pleurobeminae) of North America, principally because of the presence of hooked giochidia and differences in beak sculpture. Present dis- tribution: Palearctic, Ethiopian, Oriental, and Australasian Regions; absent from the Nearctic and Neotropical Regions. Subfamily Pleurobeminae (Hannibal, 1912) Modell, 1942 Type genus: Pleurobema Rafinesque, 1820 (type species: Pleurobema mytiloides Rafinesque, 1820= Unio clava Lamarck, 1819). Marsupial demibranchs: homo- genae; glochidia lacking hooks; septa and water-tubes (parallel to gill filaments) undivided, lacking secondary septa and secondary water-tubes; tachytictic. Recent genera are known from southern Canada and the United States (listed below), and the northern Neotropical Region (Central Americas), Cyclonaias Pilsbry, 1922 Elliptio Rafinesque, 1820 Hemistena Rafinesque, 1820 Lexingtonia Ortmann, 1914 Plethobasus Simpson, 1900a Pleurobema Rafinesque, 1820 Uniomerus Conrad, 1853 Subfamily Popenaiadinae, new subfamily 1° Type genus: Popenaias Frierson, 1927 (type species: Unio popei Lea, 1843). 340 HEARD AND Marsupial demibranchs: homogenae; glo- chidia lacking hooks; septa and water- tubes (parallel to gill filaments) undivided, lacking secondary septa and secondary water-tubes; bradytictic. Presently known only from peninsular Florida (P. buckleyi (Lea)) and Texas (P. popei (Lea)) in the United States: Mexico and Central America. Popenaias Frierson, 1927 Cyrtonaias Crosse & Fischer, 1893, in Central America Subfamily Anodontinae (Rafinesque, 1820) Ortmann, 1910a Type genus : Anodonta Lamarck, 1799, for Mytilus cygneus Linnaeus, 1758. Mar- supial demibranchs: homogenae, or dia- genae (in Strophitus only: marsupia filling the entire outer 2 demibranchs, with ovisacs subdivided into compartments which are transverse to the demibranchs); glochidia hooked; septa divided from front to rear by secondary septa, pro- ducing secondary water-tubes which are parallel to the demibranchs (except in Strophitus); bradytictic.2° Principally North American forms, but also occurring in Central America, Eurasia and the Oriental Region. Alasmidonta Say, 1818 Anodonta Lamarck, 1799 ?' Anodontoides Simpson, 1898 Arcidens Simpson, 1900a Arkansia Ortmann & Walker, 1912 Lasmigona Rafinesque, 1831 Simpsoniconcha Frierson, 1914 Strophitus Rafinesque, 1820 Subfamily Lampsilinae ?? (von Ihering, 1901) Ortmann, 1910a Type genus: Lampsilis Rafinesque, 1820 (type species: Unio ovatus Say, 1817). GUCKERT Marsupia represented by ovisacs confined to varying restricted regions of the outer 2 demibranchs: (a) longenae=ventral part of entire demibranchs, (6) hetero- genae=posterior part, (c) mesogenae= central part, (d) eschatigenae=lower part of posterior region, demibranchs not folded, and (e) ptychogenae=lower part of demibranchs which are composed of vertical folds; ovisacs marked externally by sulci, marsupia not forming smooth pads as in tetragenae, homogenae and diagenae; glochidia hookless, or axe-head shaped (Proptera); septa and water-tubes undivided, both running parallel to the gill filaments; bradytictic, except Obli- quaria which is tachytictic; widespread sexual dimorphism in the shell? and in the development (in females) of flaps, papillae or caruncles in the mantle below the branchial opening. Recent genera, confined to North and Central America, ane: heterogenae: Actinonaias Crosse & Fischer, 1893 Carunculina Simpson, 1898 Dysnomia Agassiz, 1852 Ellipsaria Rafinesque, 1820 *4 Glebula Conrad, 1853 Lampsilis Rafinesque, 1820 Lemiox Rafinesque, 1831 ”° Leptodea Rafinesque, 1820 Ligumia Swainson, 1840 Medionidus Simpson, 1900b Obovaria Rafinesque, 1819 Pachynaias Crosse & Fischer, 1893 Proptera Rafinesque, 1819 Truncilla Rafinesque, 1819 Villosa Frierson, 1927 mesogenae: Cyprogenia Agassiz, 1852 Obliquaria Rafinesque, 1820 eschatigenae: Dromus Simpson, 1900a *° . NORTH. AMERICAN : UNIONACEA 341 ptychogenae: Ptychobranchus Simpson, 1900a longenae: ?” Friersonia Ortmann, 1912a DISCUSSION Hannibal (1912), Ortmann (1912a) and Walker (1917) have concluded that the primitive condition of the freshwater mussels is the tetragenous marsupial condition in which all 4 demibranchs incubate the developing glochidial larvae for a short (1.е., tachytictic) duration. Of the 2 groups which exhibit this feature, the Amblemidae is more advanced than the Margaritiferidae because of the typical presence in the former of (a) continuous interlamellar septa and water-tubes, (b) distinct branchial, anal and supra-anal openings (=“ siphons ”), and (с) a com- plete diaphragm. While Hannibal and Ortmann derive the Mutelidae and Unio- nidae (both sensu lato) from the Mar- garitiferidae, Modell (1964) has proposed that the Mutelidae (i.e., his opinion of the superfamily Mutelacea) gave rise independently to the composite Unionidae and to the Margaritiferidae, from which the composite Elliptionidae evolved. It seems more probable that the tetra- genous condition of the Margaritiferidae gave rise to the tetragenous condition of the Amblemidae, and through the loss of the marsupial function of the outer demi- branchs also gave rise to the unionacean Hyriidae and to the Mutelacea (Fig. 1). The nature of such a divergence is obscure, particularly concerning the larvae (glo- chidia in the Unionacea, lasidial forms in Mutelacea). Indeed, our conjecture is in contrast to the view of Parodiz & Bonetto (1963, p-185) that ‘ The two different types of larvae, i.e., glochidium and lasidium, cannot be considered to be derived from any hypothetical direct ancestry.” Through loss of the marsupial function of the inner demibranchs, the tachytictic Amblemidae could account for the origin of the tachytictic Unionidae which could have independently given rise to the sub- families Unioninae s.s., Anodontinae and Pleurobeminae by adaptations in the larvae (some developing hooks), a ten- dency toward a bradytictic habit, and morphological changes in the marsupial demibranchs (Anodontinae). The Lamp- silinae 1s considered here to have evolved from the Pleurobeminae through a change in the duration of incubation and in the morphological specialization of the mar- supial demibranchs (Fig. 2). Our sug- gested relationships within the Lampsi- linae are outlined in Fig. 3. Gonidea angulata (Lea) has usually been associated with the family Unionidae sensu lato: in the Unioninae s.l., by Ortmann (1916), Frierson (1927), Thiele (1935) and Haas (1969a, 1969b); in the Anodontinae s.l. by Hannibal (1912). Modell (1964), however, saw fit to place it in the margaritiferid subfamily Pseudo- dontinae Frierson, 1927, which in turn Thiele (1935) considered part of the Unionidae (Unioninae sensu lato). Ort- mann (1916) investigated the anatomy of this monotypic genus and found some features suggesting the Margaritiferidae (interlamellar septa and water-tubes pre- sent, but not continuous) and some recall- ing the Amblemidae (complete diaphragm ; supra-anal opening present), while other aspects were common to both groups (tetragenous gill condition; data suggest- ing a tachytictic habit). We consider Ortmann’s subfamily Gonideinae a valid taxon and place it in the Amblemidae below the more advanced Ambleminae (SE ie D: ji Lys A number of other peculiarities and exceptions have been previously men- tioned (e.g., the bradytictic Megalonaias and Popenaias, the allegedly ultra-tachy- tictic Anodonta imbecilis, and the tachy- 342 HEARD AND GUCKERT K UNIONACEA Hyriidae Unionidae (1+22),4,6,8,11,13,15+16 1+2,5,6,9,12,14,15+16 \ MUTELACEA \ 1r.,22),4,.7,9,.11,13 - \ \ N \ Megalonaiadinae ES \ 2,3,6,9,12,14,15 N \ y x Amblemidae N \ Se Ambleminae N \ 1, 3,6, 9. 12.14.15 = Gonideinae \ 1,3,6,8,12,14,15 \ ?\ Margaritiferidae 153, 6, S 10:13, 5 FIG. 1. Proposed affinities of the families of the Unionacea, and the suggested relationship of the Mutelacea to the Unionacea. 1, tachytictic (short-term incubation); 2, bradytictic (long-term incubation); 3, tetragenae (all 4 demibranchs marsupial); 4, only the inner 2 demibranchs marsupial; 5, only the outer 2 demibranchs marsupial; 6, possessing glochidial larvae; 7, possessing lasidial or lasidial-like larvae; 8, interlamellar septa and water-tubes interrupted; 9, interlamellar septa and water-tubes continuous; 10, diaphragm incomplete; 11, diaphragm complete, composed of gill and mantle tissues; 12, diaphragm complete, formed by gills only; 13, supra-anal opening absent; 14, supra-anal opening present; 15, glochidia hookless; 16, glochidia with hooks. NORTH AMERICAN UNIONACEA 343 Lampsilinae 1+2, 3+5, 9 (see Fig. 3) Strophitus 2,4,8 Anodontinae 240 ? — Anodonta imbecilis (see Note 20) Popenaiadinae CSST . . * au Unioninae — —? i,4,7 Pleurobeminae 1,3,7 FIG. 2. Proposed affinities of the subfamilies of the Unionidae. *For the Unioninae Ortmann (1912a, p 273), however, suggests that (a) Unio and the Pleurobeminae arose independently from a tetragenous marsupial condition, and (b) the subtriangular hooked glochidium ‘ somewhere near Unio was the starting point for the development of the subfamily Anodontinae.” 1, tachytictic; 2, bradytictic; 3, glochidia hookless, semielliptical; 4, glochidia hooked, subtriangular; 5, glochidia hookless, axe-head shaped; 6, tetragenae; 7, homogenae; 8, diagenae; 9, marsupial demibranchs other than tetragenae, homogenae or diagenae. tictic Obliquaria). Our interpretation of The taxonomy and relationships of their phylogenetic affinities is shown in most freshwater mussels is still poorly Figs. 2 and 3. known. Of the 54 genera of the Unio- ~ HEARD AND GUCKERT 344 heterogenous groups 2,3+4,8 Cyprogenia* anh Ptychobranchus 2.510 x 2 . ce Dromus — — Obliquaria LTS ISS Friersonia' 2.316 м o RR Pleurobeminae ел ©, FIG. 3. Possible relationships in the unionid subfamily Lampsilinae. *Cyprogenia, Dromus, Friersonia 2, bradytictic; 3, glochidia semielliptical; 4, and Obliquaria are monotypic genera. 1, tachytictic; 2, glochidia axe-head shaped (in Proptera); 5, homogenae; 6, longenae; 7, mesogenae; 8, heterogenae; 9, eschatigenae; 10, ptychogenae. NORTH AMERICAN UNIONACEA 345 ninae sensu lato discussed by Thiele (1935), 24 are listed as ** Tier unbekannt; ” and of the morphological accounts avail- able, many are superficial. Thiele was able to provide only inconsistent infor- mation from the previous literature in his review of the Unioninae. Such infor- mation, because it is incomplete, is con- fusing and at present it is impossible to relate it adequately to our classification. In our system of the Nearctic fresh- water mussels we have attempted to employ with consistency what we feel are the most pertinent features which characterize the various groups. The superfamilies are distinguished principally according to the larval type produced. The families of the Unionacea are sepa- rated primarily on the basis of (a) the number and location of the marsupial demibranchs, and (6) the morphology of these demibranchs. The subfamilies have been characterized largely by the (a) mor- phology of the marsupial demibranchs (1.e., the anatomical conditions of the ovisacs), (b) hooked/hookless nature of the glochidia,? and (с) duration of larval incubation. Although further studies of soft-part morphology are desirable, continued in- vestigation of the shell features (e.g., beak and disc sculpturing, hinge dentition) and their critical evaluation in the definition of genera, subgenera and species (and their geographic and temporal distribu- tion) is also needed. Chromosome and electrophoretic studies on the Nearctic unionaceans are currently underway in several laboratories, and it is hoped that these approaches will also provide greater insight into a natural classification of these freshwater mussels and allow a better understanding of their evolutionary relationships. NOTES ! The superfamily Mutelacea Parodiz & Bonetto (1963) is characterized prin- cipally by the production of lasidial (Mycetopodidae Gray, 1840) or lasidial- like (Mutelidae Gray, 1847) larvae which (like the unionacean Hyriidae) are incu- bated in the inner two demibranchs. ?In the Unionidae s.s., Anodonta imbecilis Say and Strophitus undulatus (Say) (both Anodontinae s.l.) nave been reported to undergo direct development in the marsupia without a parasitic stage (Howard, 1914, and Lefevre & Curtis, 1911, respectively). However, Tucker (1927, 1928) has shown that the glochidia ot A. imbecilis are facultatively parasitic, utilizing the fish Lepomis cyanellus Rafi- nesque as the host. Simpsoniconcha ambigua (Say), also in the Anodontinae s.l., utilizes a salamander | Necturus macu- losus (Rafinesque)] as the glochidial host. In the hyriid genus Diplodon Spix, the subgenus Diplodon s.s. possesses parasitic glochidia while the larvae of the subgenus Rhipidonta Morch undergo direct develop- ment (Parodiz & Bonetto, 1963). 3 Official List Name No. 202 (see Flemming, 1958а); =Margaritanidae Ort- mann, 19 la. 4 Official List Name No. 1236 (see Flemming, 1958b); — Margaritana Schu- macher, 1817 (Official Index Name No, 1082; see Flemming, 1958c). 5 Margaritiferinae Modell, 1942 = Margaritaninae Ortmann, 1910a (Official Index Name No. 233; see Flemming, 1958d). 5 The number of species of Unio Philipsson with glochidia possessing/lacking hooks is presently unknown. If the number of species with hooked glochidia is small in relation to the number lacking hooks, the provisional distinction of the subfamilies Unioninae s.s. and Pleurobeminae would seem artificial. If further investigations demonstrate this possibility, the Pleurobeminae might best be considered synony- mous with the Unioninae s.s. 346 HEARD AND * Thiele (1935) cites Rectidens Simp- son (southeast Oriental Region) as having tuberculated glochidia. “According to Bloomer (193la, 1931b, 1932, 1933, 1946, 1949), Haas (1924, 1954), von Martens (1900), Morri- son (1967), Ortmann (1910b, 1911b, 1917), Prashad (1918, 1919a, 1919b) and Thiele (1935), additional tetragenous species occur in Central America and in the southern Palearctic, Ethiopian and/or Oriental Regions: Balwantia Prashad, Brazzaea Bourguignat, Caelatura Conrad, Contradens Haas, Ensidens Frierson, Indo- naia Prashad, ? Lamellidens Simpson, Lamprotula Simpson, Nitia Pallary, Par- reysia Conrad, Potomida Swainson, Pseud- odon Gould, Psilunio Stefanescu, Rhomb- unio Germain, Rectidens Simpson and Trapezoideus Simpson. However, several discrepancies and/or unusual features may be noted: (1) Bloomer (193la) reported that Brazzaea anceyi Bourguignat from Africa is tetra- genous, has a distinct supra-anal opening, and has continuous but perforated septa (except in the inner demibranchs of males). He consequently suggested re- moving the genus Brazzaea from the Mutelidae (Haas, 1969a, nevertheless re- tained it there as a subgenus of Aspatharia Bourguignat; he later, 1969b, removed it to the Unioninae s.l. as a subgenus of Caelatura Conrad) and placing it in Ortmann’s Unionidae/Unioninae. This taxon would appear to belong to our concept of the amblemid subfamily Goni- deinae. (2) Contradens cambojensis (Sowerby) from Siam had previously been grouped in the Unionidae s.l. by Ortmann (1917). (3) Lamellidens Simpson was cited by Thiele (1935) as containing embryos either in all 4 or only the outer 2 demibranchs, although Prashad (1918, 1919a) and Bloomer (1931b) found that in L. marginalis (Lamarck) from India only the outer demibranchs were marsupial. Bloomer (1931b) also noted discontinuous, GUCKERT perforated septa in this species. Lamelli- dens consobrinus (Lea) from India was previously grouped in the Unionidae s.l. by Ortmann (1911b). (4) Thiele (1935) placed Potomida Swainson in the Mar- garitiferidae as a subgenus of “ Margari- tana,” although Haas (1969a, 1969b) considers Potomida to be a member of the Quadrulinae of the Unionidae s.l. (5) Pseudodon salwenianus (Gould) was reported by Prashad (1919a) to be tetra- genous, to lack a separate supra-anal opening, and to possess a complete dia- phragm formed by the ctenidia only. These features suggest that this species is an amblemid which has secondarily lost the supra-anal opening. (6) “ Psilunio ” sinuata (Lamarck), which Haas (1940) listed in the unionid Quadrulinae, was previously demonstrated by Ortmann (1912b) to be a margaritiferid. Haas, (1969a, 1969b) eventually concurred and placed this species (as Pseudunio sinuata) in a subgenus of Margaritifera. Although no living species of the Amblemidae (?) possessing radial beak sculpture are currently found in North America, a variety of presumably related fossil forms (Proparreysia Pilsbry, 1921) have been reported from Cretaceous deposits in Wyoming, Montana, Colorado and New Mexico in the United States. Henderson (1935) placed this group in the subfamily Parrevsiinae of the Unio- nidae s.l. * Perforated marsupial septa are also known in Brazzaea anceyi Bourguignat (Bloomer, 193la), Caelatura aegyptiaca (Cailliaud) (Bloomer, 1932, 1949) and Parreysia acuminata (H. Adams), P. bakeri (H. Adams), P. ruellani (Bourguignat) and P. stuhlmanni (von Martens) (see Bloomer, 1932), all in the Amblemidae; in Contradens cambojensis (Sowerby) and Hyriopsis Conrad (see Ortmann, 1917) and Lamellidens thwaitesii (Lea) (Bloomer, 1931b), all in the unionid Pleurobeminae (7); and even in Grandidieria burtoni NORTH AMERICAN UNIONACEA 347 (Woodward) in the Mutelidae (Bloomer, 1933). ® Frierson (1927) listed a number of seemingly meaningless subgeneric namcs for Quadrula Rafinesque and described additional new ones. Morrison (1966) elevated several of these taxa to generic rank. 10 The 4 Australasian subfamilies of the alleged Mutelidae listed by McMichael & Hiscock (1958) were relocated on ana- tomical grounds in the family Hyriidae by Parodiz & Bonetto (1963). These groups should be re-examined. and per- haps re-defined, however, particularly in terms of (a) the characteristic portion(s) of the inner demibranchs which are mar- supial, and (4) the gravid periods. И is of special interest that among members of Hyridella Swainson (Hyridellinae Ire- dale) “* Breeding apparently seasonal, from spring through summer ” (McMichael & Hiscock, 1958, p 439). This time would correspond to the Nearctic fall and winter. Dr Juan. J, Parodiz (of. the Carnegie Museum, Pittsburgh, Pennsylvania, U.S.A.) has kindly provided us with unpublished data from his observations on South American hyriids (pers. comm., 1969): “ Diplodon charruanus (d’Orb.) begins [incubation] in summer (Dec., Jan.); maturation in fall (May) to early spring (Sept... D. rhuacoicus (d’Orb.), the same as in charruanus. D. burroughianus (Lea), spring and sum- mer (Sept. to Feb.), sometimes continves until next fall (May). D. hylaeus (d’Orb.), spring and summer (Oct. to Jan.), lasts all winter; maturation next spring. This species lives in rather warmer areas than the others mentioned. D. delodontus (Lam.), begins in summer, maturation in fall to next spring and cont.; probably all year around.” п Unionidae Fleming, 1828 =Official List Name No. 201 (see Flemming, 1958a). However, as Bowden and Heppell (1968, Note 48, p 250) pointed out, Rafinesque 5 should receive authorship through pre- vious usage. 12 Official List Name No. 1235 (see Flemming, 1958b). Unio Philipsson, 1788 =“ Unio Retzius, 1788” (see Simp- son, 1900a, p 679). 13 Morrison (1955) erroneously listed hooked glochidia, as well as divided water-tubes. as a feature of the entire family Unionidae. Acuticcsta Simpson from China was cited by Thiele (1935) as having tuberculated glochidia. Min Lamellidens consobrinus (Lea) (Pleurobeminae) from India most marsu- pial septa are continuous, although some are incomplete (temporarily, becoming continuous during gravidity?) (Ortmann, 191 1b). 5 The supra-anal opening is secon- darily lost in Cyclonaias tuberculara Rafi- nesque (Pleurobeminae) and in Carun- culina parva (Barnes) (Lampsilinae). A similar condition occurs in Mutela kame- runensis (Walker) (Mutelidae) and in Pseudodon salwenianus (Gould) (Amble- midae). 16Ortmann’s, 1910a, Unioninae s.l. encompasses the subfamilies Unioninae s.s. and Pleurobeminae of the Unionidae as well as the entire family Amblemidae as employed here. “Ortmann (1918) reported the ab- sence of hooks on the glochidia of Unio caffer Krauss from Africa. However, Ortmann’s material may have been com- paratively immature. McMichael & His- cock (1958) have demonstrated that Veles- unio ambiguus (Philippi) from Australia does indeed possess hooked glochidia (the hooks appear only late in larval development), although this species was considered earlier by Hiscock (1951) to have hookless larvae. A re-examination of U. caffer Krauss (the type of Simpson’s, 1900a, Section Cafferia which Modell, 1964, considered to be a genus in the unionid subfamily Rectidentinae; Haas, 1969a and 1969b, placed it in the Unio- 348 ninae s.l.) in terminal stages of larval incubation is therefore desirable. !SThe Central American “ genera ” Cinicula Swainson, Psoronaias Crosse & Fischer and Sintoxia Rafinesque, which Morrison (1967) listed in the Amble- midae, may belong to the Pleurobeminae. 19 Ortmann (1912a) noted that ** Elliptio” popei (Lea) from Mexico is gravid in December and January, and Frierson (1913) observed that “ Unio (Nephronaias) ^^ ortmanni Frierson from Guatemala is gravid in February. Ort- mann (1921c) further reported that 3 other species from Guatemala (viz., “* Elliptio ^^ * calamitarum (Morélet), E. : vyZahulensis (Crosse & Fischer) and Е. ravistellus (Morelet)) are gravid in January and/or February. Finally, Morrison (1967) has indicated that “ Elliptio ” opacatus (Crosse & Fischer) and an unidentified species of Barynaias Crosse & Fischer from Mexico are gravid in December, and he further suggested that “ Cyrtonaias mussels may also have a short breeding season in the cool summer months.” Ortmann (1912a: 272) stated for E. popei that “ Here we would have a so- called summer breeder which breeds in mid-winter. But we know now, that not the season of the year, but the shortness of the breeding season is important, and according to а! analogies, E. popei should be a form with a short breeding season’ (i.e., tachytictic). However, recent inves- tigations have confirmed | species with the homogenae type of marsupial demi- branchs to be bradytictic, and circum- stantial evidence suggests that other such species in Texas, Mexico and Central America undergo winter breeding. HEARD AND GUCKERT In 1965 six bi-monthly collections of what is commonly known as Elliptio buckleyi (Lea) (+=Unio buckleyi Теа, 1843), endemic to the Florida peninsula, were made by the senior author from the Myakka River at the Myakka River State Park, 17 Sarasota Co., Florida. The January, March, May, September and November collections contained gravid females; gravid animals were lacking in the July collection (each collection contained more than 100 animals). Although Ortmann (1912a) implied that Е. popei is tachy- tictic, it is probable that this species, as well ‘as E. ortmanni, E. calamitarum, "E. opacatus, E. yzabalensis and E. ravistellus (and conceivably others), does not exhibit latitudinal, seasonal variation from the more northern summer-breeding groups but is also bradytictic. “ Elliptio” buckleyi, E. calamitarum, E. ortmanni, E. popei, E. ravistellus and E. yzabalensis display the homogenae structure which is found in the species of miles southeast of Sarasota. the pleurobeme genera previously listed.’ The extended (— winter) breeding habit is the principal character which ‘distin- guishes this group from the related tachy- tictic species of the Pleurobeminae. The occurrence of bradyticy in this group warrants providing these species with a generic designation distinct from those given to their tachytictic allies.’ The only available name for any of these species is Popenaas Frierson, 1927 (p 38).” This taxon was originally proposed as a sub- genus of Elliptio Rafinesque; the type is P. popei (Lea) by original designation (p 10). Future taxonomic re-evaluation may necessitate the’ inclusion of other $ Ortmann considered all Central American naiades with the anatomy of Elliptio to belong to that genus. 7 Haas (1969a, 1969b) considers Popenaias (homogenae, bradytictic) to be a subgenus of Nephronaia. Crosse & Fischer, but the anatomy and breeding habits of the type of Nephronaias (Ито plicatulus Charpentier) are entirely unknown. Although Haas originally (1969a) placed Elliptoideus (tetragenae, tachytictic) as a subgenus of, Elliptio (homogenae, tachytictic), he later (1969b) included it as a subgenus of Nephronaias. This example again demonstrates the misleading value of shell characters. y NORTH AMERICAN UNIONACEA 349 species and/or genera in this bradytictic- homogenae group of unionids. This group of bradytictic, subtropical and tropical, homogenae-unionids with undivided septa and water-tubes is more advanced than the related species oí the Pleurobeminae and js here placed in a new subfamily, the Popenaiadinae, which is characterized by long-term gravidity. 20 Allen (1924) has postulated a very short (3-week), repetitive reproductive habit in Anodonta imbecilis Say. 21 Anodonta Lamarck has been divid- ed into several subgenera, one of which (Arnoldina Hannibal, 1912) Modell (1964) placed as a genus in the subfamily Recti- dentinae, family Unionidae. The type, Rectidens Simpson, 1900a, was placed in the Unioninae s.l. by Thiele (1935), who stated that all 4 demibranchs contain glochidia, and by Haas (1969a, 1969b). 22 Hannibal (1912): raised the Lamp- silinae to familial rank, including in it only some of the typical lampsiline genera. 23 Sexual dimorphism in the shell 15 noted among the other subfamilies only in Tritogonia verrucosa (Rafinesque) of the Ambleminae (Amblemidae). 2 Ellipsaria Rafinesque, 1820 =Pla- giolopsis Thiele, 1935 —Plagiola Rafines- que, 1819 (see Baker, 1964). 25 Lemiox Rafinesque, 1831 =Conra- dilla Ortmann, 1921b, fide Thiele (1935). 26 Conchodromus Haas, 1930 = Dro- mus Simpson, 1900a, fide Baker (1964b). 27 Longenae isa new term (consistent with Simpson’s, 1900a, terminology) to describe the nature of the comparatively primitive marsupial demibranchs of Frier- sonia Ortmann, 1912a. LITERATURE CITED AGASSIZ, L., 1852, Uber die Gatturgen unter den nordamerikanischen Najaden. Arch. Naturg., 18: 41-52. 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(ed.), 1958a, Official list of family group names in zoology. First installment: Names 1-236. Metcalfe & Cooper Ltd. London, xvili+ 38 р. FLEMMING, F. (ed.), 1958b, Official list of generic names in zoology. First installment: Names 1-1274. Ibid., xxxvi+200 р. FLEMMING, F. (ed.), 1958c, Official index of rejected and invalid generic names in zoology. First installment: Names 1-1169. Ibid.,xii+-132p, 350 HEARD AND FLEMMING, F. (ed.), 1958d, Official index of rejected and invalid family-group names т zoology. First installment: Names 1-273. Ibid.. xii+-38 р. FRIERSON, L. S., 1909, Remarks on the sub- families Hyriinae and Unioninae. Nautilus, 22: 106-107. FRIERSON, L. S., 1913, Unio (Nephronaias) ortmanni, n. sp. Ibid., 27: 14-15. FRIERSON, L. S., 1914, Some observations on the genus Symphynota Lea. Ibid., 28 : 40. FRIERSON, L. S., 1927, A classified and anno- tated check list of the North American naiades. Baylor Univ. Press, Waco, Texas, p 1-111. GRAY, J. E., 1840, Synopsis of the contents of the British Museum. Ed. 42, London. GRAY, J. E., 1847, A list of the genera of Recent Mollusca, their synonyms and types. Proc. zool. Soc. London, 15: 129-219. HAAS, F., 1924, Anatomische Untersuchungen an europäischen Najaden. 1. Arch. Moll, 56: 66-82, Taf. IV. HAAS, F., 1930, Uber nord- und mittelamerika- nische Najaden. Senckenbergiana, 12: 317-330. HAAS, F., 1940, A tentative classification of the Palearctic unionids. Field Mus. Publ. Zool., 24: 115-141. HAAS, F., 1954, Zur Anatomie und Entwick- lungsgeschichte einiger athiopischer und süd- amerikanischer Unionazeen. Arch. Moll., 83: 89-90. HAAS, F., 1969a, Superfamilia Unionacea. In: Das Tierreich. Eine Zusammenstellung und Kennzeichnung der rezenten Tierformen, Lief. 88: i-x, 1-663. W. de Gruyter & Co., Berlin. HAAS, F., 1969b, Superfamily Unionacea. In: Treatise on Invertebrate Paleontology (R. C. Moore, ed.). Part N. Mollusca, 6; Vol. 1 (of 3): Bivalvia. Unionacea: N411-N470. HANNIBAL, H., 1912, A synopsis of the Recent and Tertiary freshwater Mollusca of the Cali- fornian Province, based upon an ontogenetic classification. Proc. malacol. Soc. London, 10: 112-211, pls. У-УШ. HENDERSON, J., 1935, Fossil non-marine Mollusca of North America. Spec. Pap. No. 3, Geol. Soc. Amer., 313 p. HISCOCK, I. D., 1951, A note on the life history of the Australian freshwater mussel, Hyridella australis Lam. Trans. Roy. Soc. S. Australia, 74: 146-148. HOWARD, A. D., 1914, A second case of meta- morphosis without parasitism in the Unionidae. Science, 51: 353-355. HOWARD, A. D., 1915, Some exceptional cases of breeding among the Unionidae. Nautilus, 29: 4-11. GUCKERT IHERING, H. VON, 1901, The Unionidae of North America. Nautilus, 15: 37-39, 50-53. LAMARCK, J. B. P. A. de M., 1799, Prodrome d'une nouvelle classification des coquilles. Mem. Soc. Hist. nat. Paris, 1: 63-91. LAMARCK, J. B. P. A. de M., 1819, Historie naturelle des animaux sans vertébres, 6. A. Lanoe, Paris. LEA, 1., 1838, Description of new fresh-water and land shells. Trans. Amer. philos. Soc., 6(N.S.): 1-154, pls. I-XXIV. LEA, I., 1843, On new fresh-water shells. Ab- stract published privately by the author (see Proc. Amer. philos. Soc., 4 (1843): 8, 11) LEFEVRE, G., & CURTIS, W. C., 1911, Meta- morphosis without parasitism in the Unionidae. Science, 33 : 863-865. LINNAEUS, C., 1758, Systema Naturae, per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis locis. Ed.10. Laurentii Salvii, Holmiae. MARTENS, E. Von, 1890-1901, Land and fresh- water Mollusca. Biologia Centrali- Americana. Taylor and Francis, London, 706 p, 44 pls. (1900: 473-608, 1901: 609-706; Unionidae s.l.: 478-539 and 647-654 in the Supple- ment). McMICHAEL, D.F. & HISCOCK, I. D., 1958, A monograph of the freshwater mussels (Mollusca: Pelecypoda) of the Australian Region. Australian J. mar. frwtr. Res., 9: 372-503, pls. 1-19. MODELL, H., 1942, Das natúrliche System der Najaden. Arch. Moll., 74: 161-191. MODELL, H., 1949, Das nattirliche System der Najaden. 2. Ibid., 78: 29-48. MODELL, H., 1964, Das natürliche System der Najaden. 3. Ibid., 93: 71-126. MORRISON, J. P. E., 1955, Family relationships in the North American freshwater mussels. Amer. malacol. Union Ann. Rpts. 1955, p 16-17. MORRISON, J. P. E., 1966, Zoogeography of the family Amblemidae. /bid., р 43-45. MORRISON, J. P. E., 1967, Collecting Mexican freshwater mussels. Jbid., р 50-51. ORTMANN, A. E., 1910a, A new system of the Unionidae. Nautilus, 23: 114-120. ORTMANN, A. E., 1910b, The soft parts of Spatha kamerunensis Walker. Ibid., 24: 39-42. ORTMANN, A. E., 1911a, Monograph of the najades of Pennsylvania. Parts I and II. Mem. Carnegie Mus., 4: 279-347, pls. 86-89. ORTMANN, A. E., 1911b, The anatomical struc- ture of certain exotic naiades compared with that of the North American forms. Nautilus, 24: 103-108, 127-131 and pls. 6, 7. NORTH AMERICAN UNIONACEA 351 ORTMANN, A. E., 1912a, Notes upon the fami- lies and genera of the najades. Ann. Carnegie Mus., 8: 222-365, pls. 18-20. ORTMANN, A. E., 1912b, Cumberlandia, a new genus of naiades. Nautilus, 26: 13-14. ORTMANN, A. E., 1913-1916, Studies in najades. Ibid., 27: 88-91 (1913); 28: 20-22, 28-34, 41-47, 65-69 (1914); 28: 129-131, 141-143 (1915); 29: 63-67 (1915); 30: 54-57 (1916). ORTMANN, A. E., 1916, The anatomical struc- ture of Gonidea angulata (Lea). Ibid., 30: 50-53. ORTMANN, A. E., 1917, The anatomy of Contradens cambojensis (Sow.) (Nayades). Ibid., 30: 106-108. ORTMANN, A. E., 1918, The anatomy of two African nayades, Unio caffer and Spatha wahlbergi. Ibid., 31: 75-78. ORTMANN, A. E., 192la, South American naides; a contribution to the knowledge of the freshwater mussels of South America. Mem. Carnegie Mus., 8: 451-668, pls. 34-48. ORTMANN, A. E., 1921b, The anatomy of certain mussels from the upper Tennessee. Nautilus, 34: 81-91. ORTMANN, A. 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AMES, The first American edition of the British Encyclopedia or dictionary of arts and sciences, comprisirg an accurate and popular view of the present improved state of human knowledge. Philadelphia, 2: no pagination. SAY, T., 1818, Account of two new genera, and several new species, of fresh water and land shells. J. Acad. nat. Sci. Phila., 1: 276-284. SAY, T, 1829, Descriptions of new terrestrial and fluviatile shells of North America. New Harmony Dissem. Useful Know., 2: 291-293, 308-309, 323-324, 339-341, 355-356. SCHUMACHER, F. C., 1816, Overs. K. Dansk Vidensk. Selsk. Forhandl. Kjobenhavn, 7: 7. SCHUMACHER, F. C., 1817, Essai d'un nouveau systeme des habitations des vers testacés. Copenhague, p 1-287, pls. 1-22. SIMPSON. C. T., 1896, The classification and geographical distribution of the pearly fresh- water mussels. Proc. U.S. Natl. Mus., 18: 295-343. SIMPSON, C. T., 1898, In: BAKER, F. C., The Mollusca of the Chicago area. Part I, Bull. nat. Hist. Surv., Chicago Acad. 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E., 1927, Morphology of the glochidium and juvenile of the mussel Anodonta imbecilis. Trans. Amer. micros. Soc., 46: 286-293. TUCKER, М. E., 1928, Studies on the life cycles of two species of fresh-water mussels belonging to the genus Arodonta. Biol. Bull., 54: 117-127. UTTERBACK, W. I., 1915-1916, The naiades of Missouri. Amer. Midl. Nat., 4: 41-53, 97-152, 182-204, 244-273 (1915); 311-327, 339-354, 387-400, 432-464 (1916); pls. 1-27. van der SCHALIE, H., 1952, An old problem in naiad nomenclature. Nautilus, 65: 93-99, WALKER, B., 1917, The method of evolution in the Unionidae. Occ. Pap. Mus. Zool., Univ. Michigan, No. 45, p 1-10. RESUME UNE REEVALUATION DES UNIONACES (PELECYPODA) ACTUELS D’AMERIQUE DU NORD W. H. Heard et В.Н. Guckert Les principales classifications récentes des bivalves d’eau douce, basées essentiellement sur le caractére de la coquille, ne refletent pas les relations phylogénetiques de ces animaux, alors que ces relations peuvent étre interprétées á partir de caractéristiques de reproduction. Bien que ces 2 types de caracteres ne soient pas en toute logique mutuelle- ment exclusifs, ils se recoupent relativement peu souvent. Les caracteres de la coquille ont été exagérés dans la classification des moules d'eau douce dans l’ensemble du monde, d'une part parce qu'ils peuvent étre employés dans les recherches sur matériel possible, d'autre part a cause de la facilité d'étude. Malheureusement il y a trop peu d'informa- tions sur le fonctionnement et la morphologie de l’appareil reproducteur pour permettre d'établir, a l'échelle mondiale, une classification basée sur ces caractéristiques, et il serait difficile de mettre en évidence les relations des formes fossiles avec un tel systéme si jamais on le proposait. Le choix d'un systeme unique (c.a.d. soit la coquille, soit les parties molles) montre une évolution parallèle des caractères dans l’autre système. D'où l’on considère qu'un systeme basé sur les aspects de la reproduction, en parallèle avec les caractéristiques de la coquille, reflète les affinites naturelles et évolutives avec plus de précision que ne le ferait un système qui se limiterait à exagérer un autre caractère. Dans le but de stimuler de nouvelles investigations (en particulier pour les groupes non-Néoarctiques) on présente ci-aprés un systéme revisé des affinités des moules d’eau douce d'Amérique du Nord, en le situant au niveau des families et sous-familles et en le basant sur l’anatomie et les aspects de la reproduction. Ce système tient compte de caractéristiques telles que (a) le nombre de chambres marsupiales (4 ou 2), (b) la localisa- tion des chambres marsupiales (seulement les 2 internes ou seulement les 2 externes), (c) les régions spécifiques de la chambre interbranchiale qui sert 4 l’incubation des larves (la chambre entiére, ou seulement la portion centrale etc. . .) (d) la morphologie des chambres marsupiales (septa et canaux simples Ou subdivisés, septa et canaux continus ou interrompus), (e) la durée de l’incubation des larves, (f) la nature de la coquille du glochidium (avec ou sans crochet), et (g) les autres aspects anatomiques plus subtilement en relation avec la reproduction en matière de courant d’eau (forme et composition du diaphragme, présence/absence d’une Guverture supra-anale). Ces caractères indiquent que les représentants actuels des Margaritiferidae, Amblemidae et Unionidae se rencontrent en Amérique du Nord, Une 4ème famille, les Hyriidae, NORTH AMERICAN UNIONACEA est connue de la région Néoarctique seulement sous forme fossile, les espèces vivantes actuelles sont actuellement confinées à l’Amérique du Sud et l’Australie. Les sous- familles Neoarctiques ont été caractérisées pour ces"3 familles et la liste des genres de chaque groupe a été établie. Trois nouvelles sous-fammilles sont proposées: Cumber- landinae (Margaritiferidae), Megalonaiadinae (Amblemidae) et Popenaiadinae (Unioni- dae). Des indications sur less roupes d’Unionacés ont été fournies pour les régions Néotropicales, Paléarctiques, Ethiopiennes, Orientales et Autralasiennes. Un parenté des Mutelacea aux Unionacea a été suggéré: et les affinités phylogénétiques des familles et sons-familles d’Unionaces Néoarctiques sont interprétées d'aprés des données de la reproduction. Les Margaritiferidae Holarctiques actuels, le plus primitif des groupes d’Unionacés, est considéré comme ayant donné naissance independamment d'une part au stock mutelacés-hyriidés, d'autre part aux Amblemidae. Les Amblemidae, présents dans toutes les aires sauf de Sud-Amérique et d'Australasie, sont á leur tour décrits comme ancétres des Unionidae. Les Unionides ont atteint leur plus grande diver- sification en Amérique du Nord et comprennent la grande maiorité des moules d'eau douce Néoarctiques. Les plus primitifs Pleurobeminae (actuellement confinés a l’Amerique du Nord et du Centre) ont, pense-t-on, donné naissance indépendamment (a) aux Popenaiadinae du Sud des U.S.A., du Mexique et de l'Amérique Centrale, (b) aux Anodontinae de l'hemisphere Nord et (с) aux Lampsilinae d’Amerique du Nord et du Centre. Les Unioninae $. $. d’Eurasie ont, semble-t-il, dérivé du stock des Anodontinae. Les Pleurobeminae sont considérés comme les ancétres du stock primitif des Lampsilinae qui, en conséquence, se separent en plusieurs lignees selon la specialisation du marsupium. Les tendances évolutives dons la progression et/ou la spécialisation des Unionacés Néoarctiques comprend (a) la réduction de 4 a 2 (surtout la paire externe) chambres marsupiales, avec la plus grande diversification apparaissant dans les groupes actuels de l’hémisphère Nord, (b) le développement de septa et canaux interlamellaires continus, (c) les adaptations morphologiques des marsupiums qui atteignent la plus grande spéciali- sation par restriction spaciale des ovisacs chez les Lampsilinae, (d) une tendance à avoir un diaphragme complet formé entièrement par les cténidies et (e) un passage général d’une incubation des larves du court terme au long terme. La plupart des Unionacés possèdent des larves glochidium sans pointes, et les larves à pointes sont considérées comme ayant évolué indépendamment d’une part chez les Hyriidae et d’autre part chez les Unioninae-Anodontinae. Ave: 353 354 HEARD AND GUCKERT ABCTPAKT РЕВИЗИЯ СОВРЕМЕННЫХ UNIONACEA (PELECYPODA) СЕВЕРНОЙ АМЕРИКИ В. ХЕРД и Р. ГУККЕРТ Современные классификации пресноводных моллюсков на уровне высоких таксонов, основанные, главным образом, Ha характере строения раковины, не отражают Филогенетических отнощений этих моллюсков, которые могут быть освещены при учете характера их размножения. Хотя эти два типа особенно- стей моллюсков не исключают друг друга, но они перекрываются сравнитель- но мало. На характер раковины особенно обращается внимание в классифика- ции наядид. Эти признаки широко известны, благодаря удобству их примене- ния как на живых, так и на. ископаемых раковинах. К сожалению, имеется слишком мало данных по морфологии размножения и по образу жизни личинок, чтобы можно было создать крупно-масштабную классификацию, основанную точно на этих признаках. Если бы такая схема и была предложена, возника- ют трудности установления родственных связей между современными и иско - паемыми формами. При выборе какой-нибудь одной системы (т.е. по морфоло- гии раковины или по морфологии мягких частей тела) выяснилось бы наличие параллельной эволюции признаков. Авторы считают, что система, основанная на характере размножения, с параллельным учетом признаков строения раковины, точнее отражает естест- венную эволюцию и близость форм, чем любая другая система. Чтобы стимулировать дальнейшие исследования (особенно среди не-неоар- ктических групп), в настоящей статье авторы представляют пересмотренную систему признаков северо-американских наядид на уровне семейств и подсе- мейств, учитывая анатомические признаки и родственные черты в характере размножения. Эта система охватывает такие признаки, как: а) количество полужабр с марзупиями (4 или 2); 6) расположение полужабр с марзупиями (только 2 внутренних или только 2 внешних); в) особые места, где инкубируются раз- вивающиеся личинки (вся полужабра, или лишь задняя ее часть, или только центральная и т.д.); T) морфология марзупиальной полужабры (простая или разделенная септа и водяные трубки, непрерывная или прерывистая септа и зодяные трубки); д) продолжительность инкубации личинок (кратко- или долговременная); e) природа раковины глохидия (с крючками или без них); ж) другие анатомические аспекты, более тонко связанные с характером раз- множения, например, токи воды (полнота и строение диафрагмы, наличие или отсутствие супра-анального отверстия). Эти признаки указывают на то, что современные представители семейств Margaritiferidae, Amblemidae и Unionidae встречаются в Северной Америке. Чет- вертое семейство-НугИдае, известно из неоарктического района лишь в иско- паемом виде. Современные же приурочены к Южной Америке и к австрало-ази- атскому` району. Для этих трех современных семейств устанавливаются нео- арктические подсемейства и указываются их признаки, а также даются спис- ки северо-американских родов для каждой группы. Предлагаются три новых подсемейства: Cumberlandinae (Margaritiferidae), Megalonaiinae (Amblemidae) и Рорепайпае (Unionidae). Приводятся замечания о родственных группах унионид в неотропическом, палеарктическом, эфиопском, восточном и австрало-ази- атском районах. Рассматриваются предполагаемые родственные связи между Mutelacea и Unionacea, 3 также Ффилогенетическая близость семейств и подсе- мейств неоарктических унионид, которые интерпретируются исходя из осо- бенностей их размножения. Margaritiferidae (самая примитивная группа из унионид), являющаяся в настоящее время холарктической, рассматривается как представляющая собой независимую ветвь отНугИдае-Мшеасеа к Amblemidae. Последние, распространенные во всех областях, кроме Южной Америки и ав- NORTH AMERICAN UNIONACEA страло-азиатского района, рассматриваются в свою очередь как предки уни- онид, которые достигли наибольшего разнообразия в Северной Америке и co- ставляют большую часть неоарктических моллюсков. Предполагается, что наиболее примитивные Pleurobeminae (в настоящее время приуроченные к Северной и Центральной Америке) восходят непосред- ственно к а) Popenaiinae из южных районов США, Мексики и Центральной Аме- рики; 6) к Anodontinae северного полушария и в) к Lampsilinae Северной и Це- итральной Америки. Считается, что Unioninae s.str. Евразии произошли от Anodontinae. Pleurobemi- пае рассматриваются как предки примитивных лампсилин, которые постепенно разделились на несколько линий путем специализации марзупиальных полу- жабр. Эволюционные тенденции в развитии и/или в специализации неоаркти- ческих унионид включает: а) редукцию с четырех до двух (главным образом, на внешней паре) марзупиальных полужабр, при этом самое большое разно- образие встречается у современных форм в северном полушарии; 6) развитие непрерывной интерламеллярной септы и водяных трубок; в) морфологическую адаптацию марзупиальных полужабр, достигающую наибольшей специализации путем усиления локализации яйцевых мешков у Lampsillinae; г) тенденцию к эбразованию полной диафрагмы, целиком за счет ктенидиев; д) общее изме- нение периода инкубации личинок с кратковременной на долговременную. Большинство унионид имеют глохидий без крючков, а крючконосые личинки рассматриваются как возникшие независимо у Hyriidae и у унионид-анодонтид. ZAR. 355 MALACOLOGIA, 1970, 10(2): 357-368 SYMBIOSIS IN SACOGLOSSAN OPISTHOBRANCHS: SYMBIOSIS WITH ALGAL CHLOROPLASTS Richard W. Greene! Department of Zoology, University of California Los Angeles, California 90024, U.S.A. ABSTRACT The green bodies responsible for the color of 4 species of sacoglossan opisthobranchs (Mollusca: Gastropoda) were investigated and were found to be chloroplasts derived from the animals’ algal food. The chloroplasts were invariably restricted to digestive cells of the digestive diverticula in each species. Chloroplasts in the tissues of Elysia hedgpethi and Placida dendritica are derived either from Codium fragile or Bryopsis corticulans. The plastids in the tissues of Placobranchus ianthobapsus are derived from an unidentified siphonaceous green alga. In the 3 cases above, the chloroplasts were found to be retained in the animals in a symbiotic condition. The 4th species investigated, Hermaeina smithi, was found to ingest chloroplasts of Chaetomorpha aerea and Cladophora trichotoma, but the plastids are apparently rapidly degraded. It is suggested that symbiosis between algal chloroplasts and sea slugs of the Order Sacoglossa may be the rule rather than the exception. INTRODUCTION Unicellular algae living in symbiotic associations with a variety of animal hosts have been known since the 19th century. Since that time much work has been done on relationships of algae symbiotic with protozoans, coelenterates and platyhelminths, but comparatively little has been done on molluscs (see reviews by Droop, 1963; McLaughlin & Zahl, 1966; and Yonge, 1957). As early as 1895, it was known through the work of Hecht that opisthobranch molluscs could exist in symbiotic relationships with unicellular algae, specifically zooxan- thellae. Naville (1926) showed that the nudibranch Aeolidiella alderi contained zooxanthellae intracellularly in its diges- tive gland. He further showed that the zooxanthellae were derived from the tissues of the actinian, Heliactis bellis, upon which the nudibranch fed. It was Naville’s belief that the zooxanthellae reproduced within the nudibranch’s tissues, but Graham (1938) was unable to observe this. Buchner (1965) listed 5° species of nudibranchs which reportedly contained zooxanthellae in their tissues. Those species are: Aeolis glauca, Favorinus albus, Melibe rangii, Phyllirhoe sp. and Spurilla neapolitana which contain zooxanthellae within the cells of the digestive gland in the dorsal appendages, and Doridoeides gardineri which apparently contains zoo- chlorellae, or green algae. It is supposed that in all cases, the algal cells are ingested along with the food. Yonge & Nicholas (1940) described 1 Present address : Department of Biology, University of Notre Dame, Notre Dame, Indiana 46556, U.S,A, 357 358 R. W. GREENE zooxanthellae in the tissues of Tridachia crispata, a sacoglossan opisthobranch from Jamaica. This statement was, how- ever, ultimately retracted for lack of evidence (Yonge, 1966). Kawaguti (1941) reported that another sacoglossan, Placobranchus ocellatus from Palao, contained unicellular green algae in its body. He demonstrated that when maintained in the light, the animal/algal association produced more oxygen than it consumed. In 1965, Kawaguti, Yama- moto & Kamishima reported a similar association in P. ianthobapsus from Hawaii. On the basis of pigment extracts and observations with the electron micros- cope, the green bodies were interpreted as unicellular blue-green algae living within the cells of the animal’s digestive gland. The present study presents evi- dence to show that these bodies are not unicellular algae, but algal chloroplasts. In the same year, Kawaguti & Yamasu (1965) identified the green bodies in the digestive gland cells of Elysia atroviridis as chloroplasts of the alga, Codium fragile, on the basis of structural similari- ties revealed with the electron microscope. Taylor (1967) reported finding chloro- plasts in the digestive gland cells of five additional sacoglossan slugs: Elysia viridis, Hermaea bifida, H. dendritica, Acteonia senestra and Limapontia capitata. In a more complete report, Taylor (1968) demonstrated the similarity between the chloroplasts found in the tissues of Elysia viridis and those from the alga, Codium tomentosum, upon which the animal feeds. The tentative identity of the chloroplasts was established by use of the electron microscope and compari- sons of plant pigment extracts. By incu- bating animals in sea water containing 4CO, and doing radio-autography, he was able to establish that the chloroplasts within the animal’s cells fix **C in the light. More recently, Trench, Greene & Bystrom (1969) have re-examined Trida- chia crispata (see also Trench, 1969) and, in addition, have investigated Trida- chiella diomedea from the Gulf of Cali- fornia and Placobranchus ianthobapsus from Hawai. Chloroplasts have been found in the cells of the digestive diverti- cula in all 3 species. Exposure of the animals to "CO, in the light, with subsequent radioautography of the animal tissue has revealed **C in the chloroplasts. It is now evident that the occurrence of algal chloroplasts within the tissues of sacoglossan opisthobranchs is a wide- spread phenomenon. In the present study, the green bodies in the digestive gland cells of Placo- branchus have been examined in detail and evidence will be offered to establish their identity not as _ blue-green algae, but as algal chloroplasts. In addition, chloroplast-animal symbioses are des- cribed in two species of sacoglossans from southern California: Elysia hedgpethi and Placida dendritica. A third saco- glossan from California, Hermaeina smithi, was also investigated and was found to lack chloroplast symbionts in its tissues. MATERIALS AND METHODS Experimental animals Four species of anımals were used in the present study, and all belong to the Order Sacoglossa (Mollusca: Opistho- branchia). Elysia hedgpethi Marcus was collected at Flat Rock, Palos Verdes, Los Angeles County, California. Elysia was found on fronds of Codium fragile Hariot or on filaments of Bryopsis corticulans Setchell along with another sacoglossan, Placida dendritica Alder & Hancock. Collections were made from low intertidal to about 5 m below low water neaps. Hermaeina smithi Marcus was collected at Leo Carillo Beach State Park, Los Angeles County, California, This species SACOGLOSSAN SYMBIOSIS 359 was found in the mid-tide region in the rocky tide pools containing either Clado- phora trichotoma Kützing, or more com- monly, Chaetomorpha aerea Kiitzing. Hermaeina was not observed on any other algal substrate. Placobranchus ianthobapsus Gould was collected from reef-flats in Kaneohe Bay, Oahu, Hawaii. The animals were invariably found crawling in the silty white sand which makes up the sediment on the reef-flat. No animal was ever collected from, or obServed on, an alga in the field, although the red alga, Acantho- phora sp., was abundant at the collecting site. Most specimens used in this study were collected from water about | m in depth. Species from California were main- tained in large holding tanks in the recirculating sea water system at the Zoology Department of the University of California at Los Angeles. The tempe- rature was maintained at 13°C. The local species were given constant access to their natural algal food. Placobranchus was maintained in plastic tubs (27 x 32 x 13 cm) at room temperature (about 22°C). Since the algal food of this species is not known, the animals were not fed in the laboratory. Histology Whole animals were fixed in Clark’s fixative, Bouin's solution made up in sea water, or Fleming’s fixatives with and without acetic acid (see Weesner, 1960). Best results were achieved with Clark’s and Bouin’s fixatives. Fixation times ranged between I and 24 hours after which the tissues were transferred directly to 70% ethanol. All animals were de- hydrated through serial dilutions of ethanol (1 hour in each solution), cleared in xylene, and embedded in paraffin (56-58°C). Sections were cut at 7 or 10 4 and were stained with Ehrlich’s haematoxylin and eosin Y, Mallory triple stain, toluidine blue (Weesner, 1960) or periodic acid-Schiff (PAS) (Lillie, 1965). Materials fixed in Fleming’s fixatives were left unstained. Electron microscopy Small pieces of tissue (1 mm?) were fixed in 3%, glutaraldehyde (with glucose and monosodium phosphate) for 1 hour at 25°C. They were rinsed completely in 3°4°%, sodium chloride solution and were post-fixed in 1%, osmium tetroxide (with glucose and monosodium phosphate) for, hour at 25°C (7. Lauritis, pers, comm.). The tissues were then dehydra- ted through a series of ethanol concentra- tions and were embedded in Araldite (Luft, 1961). Sections were cut on a Porter-Blum MT-2 ultra-microtome, then stained with uranyl acetate and lead citrate, and viewed and photographed with an Hitachi 11B electron microscope. Plant pigment analysis (F.T. Haxo, pers, comm.) Photosynthetic pigments were extracted from the various plant and animal tissues in the cold (3-4°C) under nitrogen gas with absolute methanol. The pigments in the methanolic extract were transferred to diethyl ether in a separatory funnel and 10% sodium chloride was added to effect phase separation. The diethyl ether phase was further washed with the salt solution to remove any remaining metha- nol. Petroleum ether (b.p. 60-80°C) was added to the diethyl ether, and was washed with distilled water. The resul- ting petroleum ether-diethyl ether extract was transferred to a small flask and the remaining traces of water removed by the addition of anhydrous sodium sulfate. The extract was then concentrated by evaporation under nitrogen gas. All extraction procedures were conducted in a darkened room, and the flasks containing 360 R. W. GREENE the pigments were wrapped in aluminum foil to shield the extracts from direct light. The dried extracts were taken back into solution in diethyl ether and were spotted on precoated silica-gel sheets (Eastman Chromagram, Type K30IR2). The thin layer sheets were then developed in the dark with 15%, petroleum ether in diethyl ether. Comparisons were made between whole extracts from the animals and plants, as well as between separate pigment bands eluted from the thin layer chromato- grams. Absorption spectra were read on a Cary 15 Recording Spectrophotometer in diethyl ether unless otherwise specified. RESULTS Gross anatomy A diagrammatic representation of a typical sacoglossan gut appears in Fig. 1. A short oral tube leads from the mouth to the muscular buccal mass which houses the radula. The esophagus runs posteriorly from the buccal mass to the stomach, an outpocketing at the junction of the esophagus and intestine. The stomach receives tubules from the diges- tive diverticula which branch extensively throughout the body. It is the character of the cells of the digestive diverticula which is of interest in the present study. Histology of the digestive diverticula In Elysioid sacoglossans (Elysia and Placobranchus) the digestive diverticula ramify throughout the entire body of the animal. Sections taken at random through the animals invariably include many sections through digestive tubules (see Fig. 2).. In cross-section, the tubules are composed of 5 or 6 cells surrounding a central. lumen. These cells, -in the living animal, are dark green in color. They stain darkly in tissues fixed in solutions containing osmium tetroxide, FIGE generalized sacoglossan gut. a, anus; b.m., buccal mass; d.g., digestive gland; int , intestine; m.. mouth; s.g., salivary gland; st., stomach. Diagrammatic representation of a indicating the presence of lipid. Such cells appear granular when observed under the light microscope (Fig. 3). The granular bodies, 2 3 4 in diameter and roughly spherical, seem similar to the `` Spherules ” described in the diges- tive cells of Elysia viridis by Fretter (1941) and Taylor (1968). The spherical bodies are strongly eosinophilic. Evi- dence presented below will establish these bodies in Placobranchus as algal chloroplasts. Eolidiform sacoglossans (Placida and Hermaeina) show a slight variation on the pattern described above. The sto- mach in species of this group is a large, thin-walled sac. The digestive gland sends branches into each of the cerata and is generally less branched than in the elysioid forms. In Placida, the diges- tive diverticula extending into the cerata are very similar in appearance to the digestive tubules in elysioid sacoglossans. The lumen is small compared with the size of the diverticulum. The cells sur- rounding the lumen are large and rounded. In _ stained preparations the 2-3 # spherules are inside the cells. In Hermaeina, on the other hand, the SACOGLOSSAN SYMBIOSIS 361 EIG.4 ENS FIG. 2. Photomicrograph of transverse section through the middle of the body of Placobranchus. Clark’s fixative, stained with hematoxylin and eosin Y. Arrows indicate digestive gland tubules. 50X. FIG. 3. Photomicrograph. of digestive gland cells of Placobranchus showing 2-3 и granules. Tissue was fixed in Fleming’s fixative with acetic acid, and was left unstained. 125X. FIG. 4. Electron micrograph showing chloroplasts (arrows) within digestive gland cells of Placobranchus. 36,500X. FIG. 5. Electron micrograph showing chloroplasts in cells of Placobranchuy 75,000X. Animal cell nucleus is designated by “N ”. 362 RW GREENE cells lining the diverticulum are long and narrow. The lumen in this species is large compared with the diameter of the diverticulum, and granules are not visible within the gland cells. The egg masses and veliger larvae of Elysia, Placida (= Hermaea) and Her- maeina have been described elsewhere (Greene. 1968), as have those of Placo- branchus (Ostergaard, 1950). In no case has it been possible to identify bodies resembling the 2-3 4 plastids described above in the eggs or larvae. This implies that the plastids are not transmitted via eggs or sperm, but are newly acquired by each individual sometime after the late veliger stage. Electron microscopy Symbiosis with algal chloroplasts has already been described for species of Elysia (Kawaguti & Yamasu, 1965; Tay- lor, 1967, 1968) and for Placida (= Her- maea) (Taylor, loc. cit.). In the preceding reports, the symbionts have been likened to chloroplasts of species of Codium, the alga upon which the animals feed. The spherical bodies within the digestive cells of Placobranchus, however, have been previously identified as unicellular green algae (Kawaguti, 1941) and blue- green algae (Kawaguti ef al., 1965). Fig. 4 is an electron micrograph showing lamellar bodies within the cells of the digestive gland of Placobranchus. The same bodies appear in Fig. 5 at still higher magnification. The interior of these bodies is almost completely occupied by lamellae formed of varying numbers of thin membranes. There is no nuclear material in evidence and no cell wall. The bodies are always intracellular and are present only in the digestive cells of the diverticulae. Plasto- globuli are commonly found within the lamellar system of the bodies and are highly osmiophilic. Sa =. © carotenes O O Orne O D O ch b 6 sipnonein OO vidlaxanthin neoxanthin A las) SON a ao, an OO Siphonaxanthin Origin Elysia hedgpethi Placida dendritica lanthobapsus Codium fragile Placobranchus FIG. 6. Thin-layer chromatogram comparing methanolic extracts of Elysia, Placida and Placo- branchus with pigments of the alga, Codium fragile. These lamellar bodies are identical with the granular bodies described in the previous section and have now been identified as algal chloroplasts on the basis of the above observations and the following information on pigment extracts. Pigment analyses The results of the various pigment analyses appear in Figs. 6 and 7. The animals which normally feed on species of siphonaceous algae (i.e., Elysia, Placida and Placobranchus) are shown together with pigments extracted from Codium fragile, the algal substrate of Elysia and Placida. Each pigment band corres- ponds to a band in each of the other extracts (Fig. 6). The unique feature of all of these pigment extracts is the presence of siphonein (A, maxima т petroleum ether, 450 and 475 nm) and siphonaxanthin (A, maxima in petroleum SACOGLOSSAN SYMBIOSIS 363 Solvent Front e © O chi. a 8 eles В 0 O carotenes ADE DS DADO DEAD) 010 Origin 2 ro Oo Cm ov Wes ОФ с Ес = > Om с мо 3 ee ES le DE vo ©) Se aE FIG. 7. Thin-layer chromatogram of methano- lic extracts of Hermaeina (fed and 24 hr.-starved) and its algal food, Chaetomorpha aerea. ether, 450 and 480 nm), 2 pigments characteristic of siphonaceous green algae (Strain, 1965). Although Placobranchus has not been observed feeding on algae in the field, the pigment extract conformed to the pattern characteristic of a siphon- aceous alga. Thus, on the basis of the pigment analysis, it may be concluded that the chloroplasts in the tissues of Placobranchus are derived from an alga belonging to the Order Siphonales. A similar conclusion was drawn from investi- gations on Tridachia crispata, a sacoglossan opisthobranch from Jamaica (Trench, 1969; Trench, Greene & Bystrom, 1969). Pigment extracts from the animal and the siphonaceous alga, Caulerpa racemosa, were identical, suggesting that the chloro- 6 plasts were originally derived from some species of siphonaceous alga. No attempt has been made in either case to identify the alga. Pigment extracts of Hermaeina smithi were compared with extracts from Chaeto- morpha aerea (Order Cladophorales), the alga upon which the animal is found. The results are found in Fig. 7. In animals starved one day prior to extrac- tion, the carotenoid pigments show the same mobility as those from the algal food, while the chlorophylls do not. The latter effect may be due to pigment degradation by the animal. In freshly fed animals, extracted pigments were indistinguishable from pigments from Chaetomorpha. DISCUSSION All of the data presented in the previous section are consistent with the interpre- tation that the green bodies in the digestive gland cells of Placobranchus ianthobapsus are algal chloroplasts. Furthermore, in- formation derived from the separation of the plastid pigments permits the assignment of the chloroplasts to an alga belonging to the Order Siphonales (Chloro- phyta). Unfortunately, it is not possible to identify the source of the plastids more completely, since the animals have not been found in close association with any species of alga in the field. Kawaguti et al. (1965) identified the bodies in Placobranchus as blue-green algae. How- ever, my pigment data (Fig. 6) do not support this interpretation. The pre- sence of chlorophylls a and b and the xanthophylls, siphonein and siphonaxan- thin in the extract establish the symbiont’s identity among the siphonaceous green algae (Strain, 1965). If the bodies were blue-green algae, chlorophyll b would not be present in the pigment extracts. Chloroplasts symbiotic with digestive gland cells of species of the genus Elysia 364 В. W. GREENE have already been described. Kawaguti & Yamasu (1965) found chloroplasts in the tissues of E. atroviridis from Japan. In this case the chloroplasts were derived from the green alga, Codium fragile. In 1968, Taylor reported finding chloro- plasts of Codium tomentosum within the digestive cells of Е. viridis from Great Britain. The present report extends these accounts to include £. hedgpethi from California. This species obtains its chloroplasts from either Codium fragile or Bryopsis corticulans, both siphonaceous green algae. Another species of sacoglossan which has been discussed in this regard is Placida dendritica (Taylor, 1967, 1968). Placida from the coast of California has now also been found to contain chloroplasts. Again, the chloroplast source is either Codium or Bryopsis. whichever happens to be abundant. A close relative of Placida, Hermaeina smithi, differs from the other sacoglossans studied. Hermaeina shows no sign of chloroplasts within the cells of the diges- tive gland. Indeed, pigment separations from this species indicate that chloro- plasts are ingested, but are rapidly degraded (digested?). In animals starved for very short periods, it can be deter- mined that the chlorophyll pigment from the plastids has been destroyed (Fig. 7). Preliminary studies involving incorpora- tion of H“CO, show that Hermaeina is incapable of fixing any more carbon in the light than it can in the dark, inferring that the chloroplasts are no longer photosynthetic. Thus, it must be concluded that a symbiotic association does not exist in the case of Hermaeina. Functional aspects of the chloroplasts symbiotic in Elysia, Placida and Placo- branchus will be presented elsewhere (Greene, in prep.). The occurrence of chloroplasts in animal cells raises many questions. Symbiosis between sacoglossan opisthobranchs and algal chloroplasts is an example of an hereditary symbiosis in which the symbiont is not transmitted from one generation to the next through the egg (as in ane- mones and corals). Each generation must acquire its chloroplasts anew and most hosts must be assured a continuous supply of new chloroplasts to maintain their association (Greene, 1968, and in prep.). In other hosts, the chloroplasts may replicate. The actual mode of primary infection of the animal by the chloroplasts remains unknown, though it seems logical that they are acquired through feeding by the adult and enter the cells of the digestive gland by phago- cytosis. The highly specialized feeding habits exhibited by the Sacoglossa (Fretter, 1941) have generally limited each species within the group to a single species of alga which can be used for food. Some sacoglossans, however, may feed on 2 or 3 species of closely related algae (e.g.. Elysia on Codium or Bryopsis). Table 1 shows the results of a food preference survey of 38 sacoglossan species from all over the world. It is significant that 56%, of the slugs surveyed fed exclusively on green algae of the Order Siphonales. The question immediately arises as to the nature of the attractant quality of the algae involved in these associations. Evans (1953) and Kay (1968) have men- tioned the possible importance of the chemical nature of the food, while MacNae (1954) was more concerned with the structural peculiarities of the algae in question. It is difficult to assess the former possibility since appropriate infor- mation on the metabolism of marine algae is unavailable. The idea that the structure of the algal species is an impor- tant factor is more easily examined. First, it is necessary to consider whether or not the animal will be capable of feeding on the alga considering the modified nature of the buccal apparatus. SACOGLOSSAN SYMBIOSIS TABLE 1.* Algae commonly taken as food by sacoglossan opisthobranchs. Algae** Per cent of tota! plant species Division Clorophyta Order Cladophorales Chaetomorpha Cladophora Rhizoclonium Urospora Unspecified Cladophorales Order Siphonales Boodlea Bryopsis Caulerpa Codium Halimeda Division Xanthophyta Order Vaucheriales Vaucheria Division Phaeophyta Order Dictyotales Dictyota Padina Order Fucales Sargassum Division Rhodophyta Order Ceramiales Delesseria Griffithsia Laurencia Polysiphonia Order Gigartinales Gracilaria Gracilariopsis (14- © D D OO NV = NNN WN 00 ыы * Data compiled from а review of the literature. ** Classification follows the scheme of Dawson (1966). The algal species best suited for the animals would be those with large cells that could be easily punctured by the radular teeth. Indeed, the algal genera listed in Table 1 reflect this requirement for the most part, and are characterized by having large cells. Algae in the Order Siphonales (Chlorophyta) are coeno- cytic, or “ acellular’, and would, there- fore, yield large amounts of cell sap to an animal exerting little energy in feeding. The other point is the ability of the animals involved to ingest the chloroplasts of the various algal species. Once again LE] 366 К. \. GREENE > the genera in Table 1 show a general similarity with regard to their chloro- plasts. With the exception of the mem- bers of the Order Cladophorales. the algal species fed upon have large numbers of small chloroplasts in their cells. In the Cladophorales each cell contains a single, reticulate chloroplast of large size, which at first would seem impossible for a liquid feeder to ingest. However, under certain conditions this type of chloroplast does fragment into numerous discoid pieces (Smith, 1951), especially after mechanical disruption of the cells. It is these pieces which are ingested by Hermaeina smithi (pers. obsery.). It was pointed out above that Hermaeina did not possess functional chloroplast sym- bionts since the latter did not fix CQ,. It was assumed that the chloroplasts were degraded shortly after ingestion. My preliminary experiments show that the fragments from disrupted Chaeto- morpha and Cladophora are quite capable of photosynthetic fixation of "CO, (Greene, unpubl.). The probability is great that chloroplast- sacoglossan symbiosis is a widespread phenomenon. Of 86 sacoglossan species surveyed for body color, 82% were described as green. Those species that were not green had been collected from non-green algal species, and Taylor (1967) has already shown that at least two of these contain plastids from red algae in their tissues. Thus, it appears that sym- biosis with algal chloroplasts may be nearly universal among the Sacoglossa. In light of information now available, it would seem that Kay’s (1968) hypo- thesis regarding the evolution of feeding habits among sacoglossans must be re- evaluated. The hypothesis, as it stands, states that primitive forms fed on species of Caulerpa which supplied a nutrient not available in other algal genera. Then, drawing on the older literature describing symbionts in various saco- glossans as zooxanthellae and zoochlo- rellae, it is assumed by Kay that the presence of algal symbionts freed the slugs from the Caulerpa ‘ habit ”. Since, in all cases investigated, the symbionts are now known to be chloroplasts derived from the animal’s algal food, the Saco- glossa must now be even more firmly associated with those algal species whose chloroplasts they bear. ACKNOWLEDGEMENTS ! wish to thank Drs. Leonard Muscatine and Austin J. MacInnis for their aid in the prepara- tion of this manuscript. Support for this study was provided by grants from the National Science Foundation (Nos. 6438 and 11940) and a trainee- ship for Protozoology and Parasitology from the United States Public Health Service. LITERATURE CITED BUCHNER, P., 1965, Endosymbiosis of animals with plant micro-organisms. Interscience, N.Y., 909 p. DAWSON, E. Y. 1966, Marine botany—an introduction. Holt, Rinehart and Winston, Гос. №... Эр» DROOP, M., 1963, Algae and invertebrates in symbiosis. /n: Symbiotic Associations. Soc. Gen. Microbiol. Symp. No. 13. В. Mosse and P. Nutman, Eds. Cambridge, 356 p. EVANS, T. J., 1953, The alimentary and vascular systems of Alderia modesta (Lovén) in relation to its ecology. Proc. malacol. Soc. Lond., 29: 249-258. FRETTER, V., 1941, On the structure of the gut of the sacoglossan nudibranchs. Proc zool. Soc., B, 110: 185-198. GRAHAM, A., 1938, The structure and function of the alimentary canal of aeolid molluscs, with a discussion on their nematocysts. Trans. Roy. Soc. Edin.. 59: 267-307. GREENE, R. W., 1968, The egg masses and veligers of southern California sacoglossan opisthobranchs. Veliger, 11: 100-104. GREENE. R. W., 1970, Symbiosis in sacoglossan opisthobranchs: Translocation of photosynthe- tic products from chloroplast to host tissue. Malacologia, 10: 369-380. GREENE. R. W. & MUSCATINE. L.. Sym- biosis in sacoglossan opisthobranchs : Photosyn- thetic products of the chloroplasts. (in prep.). HECHT, E., 1895, Contribution à l'étude des nudibranches. Mém. Soc. zool. France. 8: 539-711. SACOGLOSSAN SYMBIOSIS 367 KAWAGUTI, S., 1941, Study on the inverte- brates associating unicellular algae. I. Placo- branchus ocellatus von Hasselt, a nudibranch. Palao Trop. Biol. Sta. Studies, 2: 307-308. KAWAGUTI, S., YAMAMOTO, M. & KAMI- SHIMA, Y., 1965, Electron microscopy on the symbiosis between blue-green algae and an opisthobranch, Placobranchus. Proc. Japan Acad., 41: 614-617. KAWAGUTI, S. & YAMASU, T., 1965, Elec- tron microscopy on the symbiosis between an elysioid gastropod and chloroplasts of a green alga. Biol. J. Okayama Univ., 11: 57-65. KAY, E. A., 1968, A review of the bivalved gastropods and a discussion of evolution within the Sacoglossa. Jn: Studies in the structure, physiology and ecology of molluscs. У. Breiten Ede Symp zool. Soc, Lond... 22: 109-134. LILLIE, R. D., 1965, Histopathologic technique and practical histochemistry. McGraw-Hill, N.Y., 715 p. LUFT, J. H., 1961, Improvements in epoxy resin embedding methods. J. Biophys. Bio- chem. Cytol., 9: 409-414. MacNAE, W., 1954, On four sacoglossan mol- luscs new to South Africa. Ann. Natal Mus., 13: 51-64. McLAUGHLIN, J. J. A. & ZAHL, P., 1966, Endozoic Algae. In Symbiosis. 5. M. Henry, Ed. Vol. 1. Academic Press, N.Y., 478 р. NAVILLE, A., 1926, Notes sur les eolidiens—un eolidien d’eau Saumatre. Origine des nemato- cystes. Zooxanthelles et homochromie. Rev. Suisse Zool., 33: 251-289. OSTERGAARD, J. M., 1950, Spawning and development of some Hawaiian marine gas- tropods. Pac. Sci., 4: 75-115. SMITH, G. M., 1951, Marine algae of the Mon- terey Peninsula. Stanford University Press, Stanford. 622 p. STRAIN, H. H., 1965, Chloroplast pigments and the classification of some siphonalean green algae of Australia. Biol. Bull., 129: 366-370. TAYLOR, D. L., 1967, The occurrence and significance Of endosymbiotic chloroplasts in the digestive glands of herbivorous opistho- branchs. J. Phycology, 3: 234-235. TAYLOR, D. L., 1968, Chloroplasts as symbiotic organelles in the digestive gland of Elysia viridis (Gastropoda: Opisthobranchia). J. mar. Biol. Ass. U.K., 48: 1-15. TRENCH, R. K., 1969, Chloroplasts as func- tional endosymbionts in the mollusc Tridachia crispata (Bergh), (Opisthobrarchia, Sacoglossa). Nature, 222: 1071-1072. TRENCH, R. K., GREENE, R. W. & BYS- TROM, B. G. 1969, Chloroplasts as func- tional organelles in animal tissues. J. Cell Biol., 42: 404-417. WEESNER, P. M., 1960, General zoological microtechniques. Williams & Wilkens Co., Baltimore. 230 p. YONGE, C. M., 1957, Symbiosis. In: Treatise on Marine Ecology and Paleoecology. 1. J. Hedgpeth, Ed. Geol. Soc. Amer. Mem., 67. 1296 p. YONGE, C. M., 1966, Symbiosis with unicellular algae. In: Physiology of Mollusca. K. M. Wil- bur and С. M. Yonge, Eds. Vol. 2. Academic Press NEY. (6451p: YONGE, C. M. & NICHOLAS, H. M., 1940, Structure and function of the gut and symbiosis with zooxanthellae in Tridachia crispata (Oerst Bgh. Pap. Tortugas Lab., 32: 287-301. RESUME SYMBIOSE CHEZ DES OPISTHOBRANCHES SACOGLOSSES SYMBIOSE AVEC DES CHLOROPLASTES D’ALGUES К. W. Greene Les corpuscules verts responsables de la couleur de quatre especes d’Opisthobranches Sacoglosses (Mollusca; Gastropoda) ont été étudiés et Pon a trouvé que les chloroplastes dérivent de l’alimentation en algues de l’animal. Les chloroplastes sont invariablement limités aux cellules des diverticules digestifs dans chaque espéce. Les chloroplastes des tissus d'Elysia hedgpethi et Placida dendritica dérivent soit de Codium fragile soit de Bryopsis corticulans. Les plastes des tissus de Placobranchus ianthobapsus dérivent d’une algue verte siphonée non identifiée. Dans les trois cas précédents, on a trouvé que les chloroplastes sont maintenus dans l’animal dans les conditions de symbiose, 368 К. W. GREENE La quatrieme espece étudiée, Hermaeina smithi, ingere des chloroplastes de Chaeto- morpha aerea et Cladophora trichotoma, mais les plastes sont apparemment vite dégradés. On pense que la symbiose entre les chloroplastes d'algues et les Opisthobranches de l’ordre des Sacoglosses est peut-étre la regle, plutót que l’exception. A! RESUMEN SIMBIOSIS EN OPISTOBRANQUIOS SACOGLOSOS: SIMBIOSIS CON CLOROPLASTOS ALGACEOS R. W. Greene Se investigaron los cuerpos verdes causantes de ese color en cuatro especies de opistobranquios sacoglosos, descubriendo que son cloroplastos derivados de la alimen- tación algácea del molusco, y estan invariablemente restringidos a los divertículos digestivos en cada especie. Cloroplastos en los tejidos de Elysia hedgpethi y Placida dendritica, derivan de Codium fragile odde Bryopsis corticulans. En los tejidos de Placobranchus ianthobapsus derivan de un alga sifonácea verde de especie no identificada. En esos tres casos los cloroplastos estaban retenidos por los animales en condición simbiótica. La cuarta especie investigada, Hermaeina smithi, demostró haber ingerido cloroplastoa de Chaetomorpha aerea y Cladophora trichotoma, pero aparentemente los plástidos degradaron muy rápido. Se sugiere que la simbiosis entre cloroplastos algáceos y esas ** babosas marinas ” del orden Sacoglossa pueda ser la regla en vez de la excepcion. EUA ABCTPAKT СИМБИОЗ У МОЛЛЮСКОВ SACOGLOSSAN OPISTHOBRANCHS: СИМБИОЗ С ХЛОРОПЛАСТАМИ ВОДОРОСЛЕЙ Р. ГРИН Были изучены зеленые тельца, создающие окраску тела у четы- рех видов Sacoglossa (Mollusca, Gastropoda, Opisthobranchia). Оказалось, что происхождение у них этих хлоропластов связано с питанием моллю- сков водорослями. Хлоропласты всегда располагались в пищеваритель- ных клетках пищеварительных дивертикул всех видов моллюсков. Хлоропласты в тканях Elysia hedgpethi и Раса dendritica происходили или от Codium fragile или от Bryopsis corticulans. Пластиды в тканях Placobranchus ianthobapsus были связаны с неопределенной зеленой водорослью из Siphonacea. В трех случаях, из указанных выше, хлоропласты находились‘ в животных как симбионты. Чет- вертый из изученных видов- Hermaeina зтй получил хлоропласты от загло- ченных ею Chaetomorpha aerea и Cladophora trichotoma, но пластиды, видимо, бы- стро деградировали. Предполагается, что симбиоз между хлоропластами водорослей и морски- ми моллюсками из отряда Sacoglossa может быть скорее правилом, чем исклю- чением, Z,A,F, MALACOLOGIA, 1970, 10(2): 369-380 SYMBIOSIS IN SACOGLOSSAN OPISTHOBRANCHS: TRANSLOCATION OF PHOTOSYNTHETIC PRODUCTS FROM. CHLOROPLAST TO HOST TISSUE Richard W. Greene? Department of Zoology, University of California, Los Angeles, California 90024, U.S.A. ABSTRACT Two species of sacoglossan slugs, Elysia hedgpethi and Placobranchus ianthobapsus (Mollusca: Opisthobranchia), were studied in order to determine whether or not the chloroplasts present in their tissues were leaking organic compounds to the animal tissues. Animals were incubated with H!!COz in the light and dark for varying periods of time. Radioautographs of tissue sections indicated rapid translocation of C-labeled material to the animals’ mucus glands, and renopericardial tissue. Separation of chloroplast- bearing from chloroplast-free tissues in Placobranchus afforded an independent assay for translocation, and showed that after 36 hrs., over 20% of the total 4C fixed by the chloroplasts was leaked to the animal tissue. Chloroplasts isolated from Codium fragile, Elysia’s algal food, were incubated with H4COs and the suspending medium was analysed by radiochromatography. A single leakage product was found in the medium which was identified as glycolic acid and which accounted for about 16% of the total carbon -14 fixed. INTRODUCTION strated the translocation of materials produced by the algal symbiont to the One of the most frequently discussed features of symbiotic relationships be- tween autotrophs and heterotrophs isthe question of translocation of nutrient sub- stances from the symbiont to the host. Muscatine & Hand (1958) presented the first radioautographic evidence for the translocation of **C-labeled materials from zooxanthellae to their sea anemone host, Anthopleura elegantissima. Since that time studies have been carried out on a variety of organisms harboring algal symbionts in their tissues in an attempt to establish translocation of materials (Goreau, Goreau & Yonge, 1965; von Holt & von Holt, 1968; Muscatine & Lenhoff, 1963). These studies all demon- tissues of an animal host. More recently, attention has focused on in vitro studies of symbiotic algal strains in order to elucidate the nature of compounds being excreted to the external medium. Work in this area has been reviewed by Smith, Muscatine & Lewis (1969). The carbohydrates most com- monly released by symbiotic algae to their animal hosts are glycerol, glucose or mal- tose depending on the association investi- gated. Algal symbionts in lichens have also been studied and have been found to release sorbitol, ribitol, erythritol and glucose (Smith et al., 1969). Similar questions have now been raised concerning symbioses between algal chlo- 1 Present address : Department of Biology, University of Notre Dame, Notre Dame, Indiana 46556, U.S.A: 370 в. №. GREENE roplasts and sacoglossan opisthobranchs. Since the first report of this phenomenon (Kawaguti & Yamasu, 1965), it has become apparent that animal-chloroplast associations are widely distributed (Tay- lor, 1967, 1968; Greene, 1968, 1970; Trench, 1969; Trench, Greene & Bystrom, 1969). The papers of Taylor (1968), Trench (1969) and Trench et al. (1969) all present radioautographic evidence for the translocation of C-labeled materials from symbiotic chloroplasts to host animal tissue. The present study gives evidence for the translocation of material in 2 species of chloroplast-bearing sacoglossan slugs, using !!C as a tracer. Studies on the algal chloroplasts in vitro show that glycolic acid is excreted to the external medium under the experimental condi- tions. MATERIALS AND METHODS 1. Experimental Organisms (a) Animals. Two species of sacoglos- sans (Mollusca: Opisthobranchia) were used. Elysia hedgpethi Marcus was col- lected from Flat Rock, Palos Verdes, Los Angeles County, California. The specimens were obtained intertidally on the green alga, Codium, which is abundant in the collecting area. The other species, Placobranchus ianthobapsus Gould, was collected from reef-flats in Kaneohe Bay, Oahu, Hawaii, at a depth of about | m. Specimens of Elysia were maintained in large holding tanks in the recirculating sea water system in the Zoology Depart- ment at the University of California at Los Angeles. The animals were kept in constant light, and water temperature was maintained at 13°C. While in cap- tivity, Elysia was supplied with fresh Codium continuously. Placobranchus was kept in plastic tubs (27 x 32x 13 cm) containing sea water at room temperature (about 22°C) and in constant light. Since the algal food of this species is unknown, the animals were not fed in captivity. Experimental ani- mals were used within 5 days of their collection in Hawaii. (b) Algae. The alga used in this study was Codium fragile Hariot (Chlorophyta: Siphonales). It was obtained at Flat Rock, Palos Verdes, Los Angeles County, California, intertidally. The alga was maintained in holding tanks with recir- culating sea water at 13°C in constant light. 2. Experimental Procedures (a) Incubation of Animals with MC. Animals were incubated in 25 ml Erlen- meyer flasks containing Millipore-filtered sea water (porosity 0:45 и) to which had been added NaH'*CO, (Calbiochem, sp. act. 35 mc/mM) to achieve an initial specific activity of 10 zc/ml. Experi- mental animals were placed in the light from 15 minutes to 5 hours for Elysia and to 60 hours for Placobranchus. The light source consisted of 4 photoflood lamps (C.E. 150W., 115V.) controlled by a rheostat. Light intensity was main- tained at 500 foot candles measured at the bottom of the incubation flasks (Weston Illumination Meter, Model 756). Temperature was maintained constant during incubations by immersing the flasks in a running water bath (14°C for Elysia, 22°C for Placobranchus). Follow- ing incubation, animals were rinsed twice with about 5 ml fresh Millipore-filtered sea water to remove excess isotope prior to further analysis. (b) Radioautography. Whole animals incubated as in (a) above were fixed in Clark’s fixative for 1 hour. Specimens were transferred directly into 70%, ethanol and were dehydrated through a series of ethanol solutions. Tissues were cleared in xylene, and embedded in paraffin SACOGLOSSAN SYMBIOSIS 371 Chloroplast- ALB) bearing tissue —> >’ Chloroplast - free tissue EIG. 1. EN VE mee Diagrammatic representation of the tissue separation technique as applied to samples of Placo- branchus showing the appearance of the tissue cylinders (see Methods). (т.р. 56-58°C). Sections were cut at 7 4 and were mounted on glass microscope slides. Slides were dipped in Kodak nuclear track emulsion (Type NTB2), and sections were allowed to expose for 1-2 weeks. Dark control animal tissues were treated similarly. Development was car- ried out according to the manufacturer's directions. (c) Tissue Separations. This technique was only possible with specimens of Placobranchus. Animals were incubated with isotope as described above, and 4 specimens were sampled at each 12 hour interval up to 60 hours. The animals were frozen on dry ice in an extended position, and cylindrical sections were cut from the animals’ parapodia by use of a 3/16” diameter cork borer. The frozen cylinders which resulted contained an upper region of chloroplast-bearing tissue, and a lower region of chloroplast- free tissue (see Fig. 1). By careful trim- ing with a sharp blade, the 2 layers could be separated and assayed for radio- activity. Separated tissues were ground with a glass rod in hot IN NH,OH to produce a homogeneous suspension. Ali- quots of 0:1 ml were plated on pre- weighed planchets, acidified with 1-ON HCI to drive off unbound 'CO,, and dried under an infrared lamp. The planchets were weighed again to deter- mine the weight of tissue deposited, and radioactivity was assayed by counting with a transistorized Nuclear Supplies scaler (Type SA-250) with a thin end- window G.M. tube (LND Inc., No. 733). (d) Isolation of Chloroplasts. Approxi- mately 10 g fresh Codium were placed in a Waring Blender with a serological head. Fifty ml of Millipore-filtered sea water (O°C) were added and the material was blended for 5 seconds. The suspension was immediately poured through glass wool into tubes for centrifugation. The material was centrifuged for 50 seconds at high speed (International Clinical Cen- trifuge, Model CL) and the supernatant removed. The pellets were resuspended in fresh Millipore-filtered sea water and then recentrifuged. This washing process was repeated 3 times. Observation of the pellets with an oil immersion lens (930X) showed particulate contamination by algal cell nuclei and unidentifiable material. In proportion to the chloro- plasts in the preparation, the contami- nation was judged to be negligible. (e) Incubation of Chloroplasts. Chloro- plasts were incubated as in section (a) except that the initial specific activity used was 20 “c/ml, and the incubation period was shortened to 10 minutes. The chloroplasts were centrifuged, the medium was saved, and alcohol soluble materials were extracted from the pellet in a series of hot ethanol dilutions. (f) Paper Chromatography. Materials to be analyzed by paper chromatography 372 R. W. GREENE RIOS SACOGLOSSAN SYMBIOSIS were first desalted by evaporation to dryness in vacuo (Rotary Evapomix), and resuspension in dry absolute ethanol. The material was placed at the origin on Whatman No. 4 chromatography paper (46x57 cm) and was developed in 2 dimensions. The solvent in the first dimension was phenol-water (100:39, w/v) (PW), and in the second dimension was n-butanol: propionic acid: water (142:71: 100, v/v/v) (BPAW). Radioactive spots were located by exposing the paper to Kodak single-coated, blue-sensitive medi- sal X-ray film (Bassham & Calvin, 1957). Films were developed according to the manufacturer’s specifications. (g) Identification of Unknowns. Radio- active spots were cut from chromato- grams, and the compounds were eluted with a small volume of distilled water. In the present study, glycolic acid was tentatively identified in the following manner. The unknown material was co- chromatographed in 2 dimensions (PW: BPAW) with authentic glycolic acid (Calbiochem). Tolbert & Zill (1956) report that no other acid moves with the Rf values (39, 63) in the PW:BPAW solvent system. The unknown was also co-chromatographed with authentic material in a single dimension developed with ethyl acetate - acetic acid - water (3:3:1, v/v/v). Specific identifications of other compounds of less importance will be discussed elsewhere (Greene & Muscatine, in prep.). ¡99 — Ww RESULTS 1. Radioautography In order to detect the translocation of '4C-labeled materials from chloroplast- bearing tissues to chloroplast-free tissues of sacoglossans, animals were incubated in NaHCO, for varying periods of time, sectioned and exposed to liquid nuclear- track emulsion. Fig. 2 shows a section through a specimen of Elysia which was incubated in isotope for 15 minutes in the light. The exposed silver grains are generally limited to areas directly over the tubules of the digestive gland which contain the symbiotic chloroplasts. In specimens incubated with 14C for 60 minutes in the light (Fig. 3), labeled material appears in the mucus glands. At the same time, the number of exposed silver grains lying over digestive gland has increased markedly. After 90 minutes incubation in the light, the digestive diverticula and mucus glands appear heavily labeled (Fig. 4). The reno-pericardial complex also shows, signs of high activity. In general, reduced silver grains appear over all parts of the tissue. Control animals incubated in the dark for 90 minutes elicited very little silver grain reduction (Fig. 5). That radio- activity which is present could be the result of heterotrophic fixation by the animal tissue. It must be remembered FIG. 2. Radioautograph of tissue of Elysia following incubation in НИСОз in the light for 15 minutes. The tissue was unstained. 50X. FIG. 3. Radioautograph of tissue of Elvsia following incubation in H!*CO3 in the light for 60 minutes. The tissue was unstained. SOX. FIG. 4. Radioautograph of tissue of Elysiafollowing incubation in H4CO3 in the light for 90 minutes. The tissue was unstained. 50X. FIG. 5. Radioautograph of tissue of Elysia following incubation in HC™“Os in the dark for 90 minutes. The tissue was unstained. SOX, 374 R. W. GREENE FIG. 6. Radioautograph of tissue of Placobran- chus following incubation in H*CO3 in the light for 180 minutes. The tissue was unstained. 50X. that in the above procedure, only radio- active materials in the animal tissue which are not soluble in water, alcohol or xylene are detected. It has been previously demonstrated that a minimum of 39%, of the total “С fixed is extracted from a sea slug during dehydration and embed- ding (Trench ef al., 1969). Comparable extraction values were obtained during the present study. Studies involving specimens of Placo- branchus ianthobapsus incubated in NaH "CO, follow the same pattern of labelling as in Elysia. Fig. 6 shows a radio- autograph of an animal incubated with isotope for 180 minutes in the light. in which the animal tissue is nearly uni- formly labeled. Reduced silver grains are especially abundant over the digestive W O 01,14 С. Translocation O 12 24 36 48 60 Incubation Time (hrs) FIG. 7. Translocation of “C-labeled photosyn- thate from chloroplast-bearing tissues to chloro- plast-free tissues Of Placobranchus. The values were derived from the tissue-separation experi- ment and are expressed as %, of total “С fixed present in the chloroplast-free fraction. gland tubules which contain the chloro- plasts and over the mucus glands. Dark- control specimens of Placobranchus showed negligible silver grain reduct- ion. The appearance of reduced silver grains over chloroplast-free regions of tissue in Elysia and Placobranchus indicates that there has been translocation of "C- labeled material from the symbiotic chlo- roplasts to the animal tissue. Since animals incubated with isotope in the dark showed negligible radioactivity in their tissues, 1t may be concluded that the observed '*C in the tissues of light incubated animals is mainly the result of photosynthesis by the chloroplasts. 2. Assay of Translocation by Tissue Separation Since chloroplast-bearing and chloro- plast-free tissues may be separated rela- tively easily in Placobranchus, an inde- pendent assay for translocation of 11C- photosynthate was possible. Animals were incubated with NaHCO, in the light and dark for varying periods of time. Tissues were then frozen, sepa- SACOGLOSSAN SYMBIOSIS SR) TABLE 1. Tissue separation data showing the translocation of “C-labeled photosynthate from chloro- plast-bearing tissues to chloroplast-free tissues of Placobranchus. dry weight. LIGHT Sample chloroplast- | chloroplast- | bearing free | (cpm) (cpm) shee а 8966 | 12577 b A 2135 24h. a A 654 b ae aaa 761521 Bohr а 831 396 b 7475 1219 48h. a 4012 1320 b 5314 1024 60h. a 4702 | 1433 b 3792 | 1229 * see Results section. rated and assayed as described above. Table 1 shows the data derived from the tissue separations. This information shows that considerable radioactive mate- rial was found in the chloroplast-free tissue at every sampling time. Data for animals incubated in the dark show that small amounts of “С are heterotrophi- cally fixed by the animal tissue. The values for translocation occurring in dark- incubated animals are presented for com- parison of **C-distribution only, since the activity was probably fixed in situ in these tissues rather than translocated from the chloroplast-bearing tissue. Fig. 7 shows the percentage of the total 1*C fixed by the animal in the light which appeared in the chloroplast-free tissue fraction. The data are averages from the 2 groups of animals incubated (see Table 1). These values must all be considered to be mini- Data represent cpm/mg DARK trans- chloroplast- chloroplast- | trans- located bearing free located * (%) (cpm) (cpm) (%) 12.2 97 36 27.0 23.0 187 59 23.9 16:9 144 93 39.2 26:4 137 93 | 40-4 | 32-2 104 50 | 32-4 14-0 61 40 39:6 DASS 84 5 | 50-2 16-1 51 2 | 38-5 | 2353 59 | 90 | 60-4 A Е ne mum values since, unavoidably, there is chloroplast-free tissue assayed with the chloroplast-bearing tissue. From the data presented above, it is evident that after 36 hours of exposure to isotope in the light, over 20% of the total 14C fixed by the animal has been passed to the chloroplast-free tissue. It is significant to note that all of the activity found in the animal tissue is insoluble in water and hot ethanol. 3. Release of C-labeled Products by Chloroplasts in vitro To determine the identity of the com- pound(s) released to the animal tissues in the previous experiments, chloroplasts isolated from the alga, Codium fragile, were incubated with NaH'™CO, in the light, and the suspending medium was 376 В № ¡(GREENE FIG. 8. Radiochromatogram of the aqueous medium in which isolated chloroplasts of Codium were incubated with H!!COs for 10 minutes in the light. The solvent system used was phenol- water (1) and n-butanol-propionic acid-water (2). The (O) shows the position of the origin. Alanine »* FIG. 9. Radiochromatogram of an ethanol extract of isolated chloroplasts of Codium follow- ing 10 minutes incubation with НИСОз in the light. Solvents as in Fig. 8. The notation (Glu/Gal) indicates the presence of both glucose and galactose, inseparable in these solvents. analyzed by paper chromatography. Fig. 8 is a radiochromatogram of this material showing that a single radioactive com- pound was leaked to the medium by the chloroplasts under the experimental con- ditions. In order to demonstrate that the compound in Fig. 8 was not the result of chloroplast disruption, the incubated chloroplasts were extracted with ethanol and the resultant material was chromato- graphed (Fig. 9). If plastid disruption had occurred during the isolation proce- dure or incubation, the radiochromato- grams would be identical. The material released from the chloro- plasts under the experimental conditions previously described has been provision- ally identified as glycolic acid. This, presumably, is the compound leaked to the animal tissues during photosynthesis by the plastids. The amount of glycolic acid excreted represents about 16% of the total “С fixed by the chloroplasts in the light, while the glycolic acid within the chloroplasts accounts for 26% of the total radioactivity extracted, DISCUSSION In the present study radioautographic evidence was presented to establish trans- location of "C-labeled photosynthetic material from symbiotic chloroplasts to the tissues of the sacoglossan slugs, Elysia hedgpethi and Placobranchus iantho- bapsus. In both species the mucus glands and renopericardial tissues became rapidly labeled. In very short incubations with isotope, only the areas associated with digestive diverticula show evidence of radioactivity. This was to be expected since the chloroplasts occur solely within the cells of the diverticula. In dark- incubated controls, reduction of silver grains over animal tissue was negligible. The material released by chloroplasts of Codium fragile incubated in vitro was identified as glycolic acid. It is well known that algae symbiotic with a variety of invertebrate hosts are capable of selectively releasing compounds derived from photosynthesis to the host tissue. Muscatine & Lenhoff (1963), SACOGLOSSAN SYMBIOSIS 377 working with green hydra, showed that between 10-12% of the photosynthetically- fixed “С was translocated to the host tissues, and that about half of this mate- rial was incorporated into protein. In 1965, Goreau, Goreau & Yonge demon- strated that when the giant clam, Tridacna, was incubated with '*CO,, label rapidly appeared in the mucus glands, crystalline style and pericardium. Von Holt & von Holt (1968) showed that after 3 hours of photosynthesis by the symbionts of various coelenterates, 24.40% of the total photo- synthate was found in the tissues of the animals. In 1968, Taylor presented electron radio- autographic evidence for the translocation of "C-labeled photosynthate from chloro- plast symbionts to the tissues of the saco- glossan slug, Elysia_ viridis. Trench, Greene & Bystrom (1969) used light radioautography to demonstrate the move- ment of labeled photosynthate from the chloroplasts symbiotic with Tridachia cris- pata, to the animal tissues. Carbon-14 labeled material appeared in the pedal mucus gland, the reno-pericardium and in the sheath associated with the cerebral ganglia. The occurrence of labeled material in the mucus glands and pericardial tissue of Elysia and Placobranchus is consistent with the findings of Goreau et al., (1965) and Trench er al. (1969). In both cases the regions may be assumed to have high metabolic requirements, and, in the case of the mucus glands, a high turnover rate of materials due to secretory activity. The excretion of glycolic acid by intact algae to the suspending medium both in vivo and in vitro is well known. Allen (1956) reported the excretion of glycolic acid into the medium by species of Chlamydomonas. Nalewajko, Chowdhuri & Fogg (1963) showed that planktonic Chlorella liberated glycolic acid, and they discussed some aspects of glycolate in aquatic habitats. In 1965, Fogg. Nale- wajko & Watt surveyed phytoplankton samples and again demonstrated the excretion of glycolic acid to the surround- ing waters. Hellebust (1965) studied 22 species of marine algae and was able to show glycolate excretion by most species, albeit in small amounts. Among species of algae found in sym- biotic relationships, glycolic acid is com- monly found to be excreted to the medium when incubations are carried out in vitro (Muscatine, 1965; Muscatine, Karaka- shian & Karakashian, 1967). Excretion of glycolic acid has also been reported from studies on isolated chloroplasts (Jensen & Bassham, 1966; Bassham, Kirk & Jensen, 1968). In the present study 16% of the total MC incorporated by the chloroplasts was released to the suspending sea water as glycolic acid. This value is well within the limits described in the foregoing papers dealing with intact algal cells. In contrast to the work of Bassham et al. (1968), however, glycolic acid was the sole product excreted by Codium chloro- plasts under the experimental conditions. The chloroplasts from spinach (Bassham et al., 1968) `` leaked ” several compounds to the medium. Muscatine (1965) has already suggested the `` adventitious utilization ” of excreted glycolic acid by an animal acting as host to algal symbionts. Glycolic acid may easily enter the tricarboxylic acid cycle through glyoxylic acid and then combina- tion with succinic acid to form isocitric acid (Bassham & Calvin, 1957). From this point, it is able to enter the metabolic pathways of the animal cell. It should be noted that excretion by the chloroplasts in vitro does not neces- sarily represent the in vivo situation. Although the chloroplasts isolated from Codium leaked glycolic acid into the sus- pending medium, one cannot be certain that the same occurs when the plastids are in the tissues of Elysia. 378 В W. ACKNOWLEDGEMENTS I wish to thank Dr. Leonard Muscatine for his assistance in the preparation of this manu- script, and Dr. Robert Veomett for taking the phase contrast photomicrographs. Financial assistance for this study came from grants from the National Science Foundation (GB-6438 and 11940) and a United States Public Health Service Training Grant in Parasitology and Protozoology. LITERATURE CITED ALLEN, M. B., 1956, Excretion of organic compounds by Chlamydomonas. Arch. Mikro- biol., 24: 163-168. BASSHAM, J. A. & CALVIN, M., 1957, The Path of Carbon in Photosynthesis. Prentice- Hall, Inc. Englewood Cliffs, N.J. 104 p. BASSHAM, J. A., KIRK, M. & JENSEN, R. G., 1968, Photosynthesis by isolated chloroplasts. I. Diffusion of labeled photosynthetic inter- mediates between isolated chloroplasts and suspending medium. Biochim. Biophys. Acta, 153: 211-218. FOGG, С. E., 1962, Extracellular products. Jn: Physiology and Biochemistry of Algae. R. A. Lewin, Ed. Academic Press, New York, p. 475-489. FOGG, С. E., NALEWAJKO, C., & WATT, W. D., 1965, Extracellular products of phyto- plankton photosynthesis. Proc. Roy. Soc., B. 162: 517-534. GOREAU, T. F., GOREAU, N. I. & YONGE, C. M. 1965, Evidence for a soluble algal factor produced by the zooxanthellae of Tridacna elongata (Bivalvia, Tridacniidae). Abst. paper presented to International Con- ference on Tropical Oceanography, 18 Novem- ber, 1965. GREENE, R. W. 1968, The egg masses and veligers of southern California sacoglossan opisthobranchs. Veliger, 11: 100-104. GREENE, R. W., 1970, Symbiosis in sacoglossan opisthobranchs: Symbiosis with algal chloro- plasts. Malacologia, 10: 357-368. GREENE, R. W. & MUSCATINE, L., Sym- biosis in sacoglossan opisthobranchs: Photosyn- thetic products of the chloroplasts. (in prep.). HELLEBUST. J. A.. 1965. Excretion of some organic compounds by marine phytoplankton. Limnol. Ocean., 10: 192-206. GREENE JENSEN, R. G. & BASSHAM, J. A.. 1966, Photosynthesis by isolated chloroplasts. Proc. nat. Acad. Sci., 56: 1095-1101. KAWAGUTI, S. & YAMASU, T., 1965, Elec- tron microscopy on the symbiosis between an elysioid gastropod and chloroplasts of a green alga. Biol. J. Okayama Univ., 11: 57-65. MUSCATINE, L., 1965, Symbiosis of hydra and Algae. III. Extracellular products of the algae. Comp. Biochem. Physiol., 16: 77-92. MUSCATINE, L. & HAND, C., 1958, Direct evidence for transfer of materials from symbio- tic algae to the tissues of a coelenterate. Proc. nat. Acad. Sci., 44: 259-1263. MUSCATINE, L., KARAKASHIAN, S., & KARAKASHIAN, M., 1967, Soluble extra- cellular products of algae symbiotic with a ciliate, a sponge and a mutant hydra. Comp. Biochem. Physiol., 20: 1-12. MUSCATINE, L. & LENHOFF, H. M., 1963; Symbiosis of Hydra with Algae. J. gen. Microbiol., 32: vi. NALEWAJKO, C., CHOWDHURI, N. & FOGG, С. E., 1963, Excretion of glycollic acid and the growth of a planktonic Chlorella. Microalgae and Photosynthetic Bacteria, 171- 183 (1963). SMITH, D. L., MUSCATINE, L. & LEWIS, D., 1969, Carbohydrate movement from auto- trophs to heterotrophs in parasitic and mutual- istic symbiosis. Biol. Rev., 44: 17-90. TAYLOR, D. L., 1967, The occurrence and significance of endosymbiotic chloroplasts in the digestive glands of herbivorous opistho- branchs. J. Phycol., 3: 234-235. TAYLOR, D. L., 1968, Chloroplasts as symbictic organelles in the digestive gland of Elysia viridis (Gastropoda: Opisthobranchia). J. Mar. biol. Ass. U.K., 48: 1-15. TOLBERT, N. Е. & ZILE, Г. Р., 1956: MBXcCIe> tion of glycolic acid by algae during photo- synthesis. J. biol. Chem., 222: 895-906. TRENCH, R. K., 1969, Chloroplasts as func- tional endosymbionts in the mollusc Tridachia crispata (Bergh), (Opisthobranchia, Sacoglossa). Nature, Lond., 222: 1071-1072. TRENCH, В. K., GREENE, R. W. & BY TROM. В. G., 1969, Chloroplasts as functional organelles in animal tissues. J. Cell Biol., 42: 404-417. Von HOLT. C. & Von HOLT, M., 1968, Transfer of photosynthetic products from zooxanthellae to coelenterate hosts. Comp. Biochem. Physiol. 24: 73-81. SACOGLOSSAN SYMBIOSIS RESUME SYMBIOSE CHEZ LES OPISTHOBRANCHES SACOGLOSSES: TRANSFERT DES PRODUITS DE PHOTOSYNTHESE DU CHLOROPLASTE AU TISSU DE L’HOTE R. W. Greene Deux especes de Sacoglosses, Elysia hedgpethi et Placobranchus ianthobapsus (Mollusca: Opisthobranchia), ont été étudiés afin de déterminer si oui Ou non les chloroplastes pré- sents dans leurs tissus cédent des composés organiques aux tissus animaux. On a inoculé aux animaux du H **CO;- pendant des temps variables, en lumière et à l'obscurité. La radioautographie des coupes de tissus ont montré un transfert rapide du **C marqué2 dans les glandes á mucus de l’animal et dans le tissu péricardique. La séparation des tissus porteurs de chloroplastes des tissus non porteurs chez Placobranchus, a permis de réaliser un test de transfert et a montré qu'apres 36 heures, plus de 20% du **C total fixé par les chloroplastes avait migré dans les tissus de l’animal. Des chloroplastes isolés de Codium fragile, nourriture algale d'Elysia, ont été mis au contact de H '!CO,-, puis le milieu de suspension a été analysé par radiochromatographie. Un seul produit migran ta été mis en évidence dans le milieu; on l’a identifié comme étant un acide glycolique qui correspond a environ 16% du total de carbone 14 fixé. ALE. RESUMEN SIMBIOSIS EN OPISTOBRANQUIOS SACOGLOSOS: TRANSPOSICIÓN DE PRODUCTOS FOTOSINTÉTICOS, DE CLOROPLASTOS A TEJIDOS HUÉSPEDES R. W. Greene Se estudiaron dos especies de moluscos opistobranquios sacoglosos, las “ babosas marinas ” Elysia hedgpethi y Placobranchus ianthobapsus, para determinar si los cloro- plastos presentes en los tejidos, eran o no productos de derrame de los compuestos organicos.’’ Los animales fuer on incubados con H!!CO-, a la luz y en la obscuridad por varios periodos. Radioautografías de cortes histólogicos indicaron cambios rápidos en la ubicación de los materiales marcados como **C a las glándulas mucosas y reno- pericardicas del animal. Separación de los tejidos, conteniendo cloroplastos y otros sin ellos, en Placobranchus, permitieron probar la transposición independiente, mostrando también que despues de 36 horas, más del 20% del total del **C de los cloroplastos habia entrado por derrame al tejido animal. Cloroplastos aislados de Codium fragile, que es el alimento algófilo de Elysia, se incubaron con НЧСО-, y el medio de suspensión fue analizado por radiocromatografia. Un producto único de derrame se encontró en el medio, el cual fué identificado como ácido glicólico, e importaba a un 16% del total fijo de Carbón 14. VITA: 379 380 В. W. GREENE ABCTPAKT СИМБИОЗ У SACOGLOSSA OPISTHOBRANCHIA: ТРАНСЛОКАЦИЯ ПРОДУКТОВ ФОТОСИНТЕЗА ИХ ХЛОРОПЛАСТОВ В ТКАНЯХ ХОЗЯЕВ Р. ГРИН У двух видов улиток Sacoglossa- Elysia hedgpethi и Placobranchus ianthobapsus (Mollusca, Opisthobranchia)Bb5ACHMAJOCb, имеются ли хлоропласты в их тканях M отдают ли последние органические соединения в ткани животного. Моллюски инкубировались при H14¢03 на свету и в темноте в течение различного Bpe- мени'. Радиоаутография срезов тканей показала быстрый перенос помеченных clé веществ к выделяющим слизь железам моллюсков и к почечно-перикар- дильным тканям. Разделение несущих хлоропласты тканей от тканей без них у Placobranchus при независимых попытках выяснить перенос показало, что после 36 часов более 20% общего количества 614, связанного хлоропластами проникало в ткани моллюсков; хлоропласты, выделенные U3 Codium fragile (растительная пища Elysia) инкубирсвались при н1“соз, после чего среда анализировалась при помощи радиохроматографии. Единично попавшие туда вещества были определены как гликогеновые кислоты, составляющие около 16% от общего количества веществ, помеченных c14, MALACOLOGIA, 1970, 10(2): 381-397 FIELD STUDIES ON LIFE HISTORY, GONADAL CYCLE AND REPRODUCTIVE PERIODICITY IN MELAMPUS BIDENTATUS (PULMONATA: ELLOBIIDAE)! Martyn L. Apley? Department of Zoology Syracuse University and Department of Invertebrate Zoology Marine Biological Laboratory, Woods Hole, Mass. 02543, U.S.A. ABSTRACT Melampus bidentatus is found in the high littoral zone of semi-enclosed salt marshes along the Atlantic Coast from New Brunswick, Canada, to Texas, U.S.A. Observations and work from 1964 through 1968 on a population inhabiting Little Sippewisset Marsh, Falmcuth, Massachusetts, U.S.A., emphasizes ecological and physiological aspects of life-cycle, gonadal cycle, and reproductive periodicity. A 3 to 4 year life-cycle is evident in this population, with usual maximum shell length of about 10°5 mm. Reproductive maturity (when gametogenesis first Occurs) is reached at a size of approximately 5 mm shell length with individuals from 2 age groups participating in annual reproductive periods. The winter growth rate is only one-fifth of the spring-summer growth rate which in turn is nearly twice the growth rate of snails during the breeding season. Annual reproductive periods last 6 weeks sometime during late May, June, and early July each year. Each annual period consists of 3 cycles of oviposition at 2 week (semilunar) intervals correlated with spring tides. A consistently predictable pattern of behavior during these semilunar cycles of reproduction involving aggregation, copulation, oviposi- tion and dispersion exists throughout the population. Egg masses are small, gelatinous, and without a tough outer envelope, each containing a mean of 850 eggs. Free-swimming veligers hatch after 13 days if egg masses are covered by water at that time. Veligers then spend a period of 2 to 6 weeks as planktonic larvae. Settled spat have been found no earlier than 6 weeks following hatching. Using measures such as total organic carbon Or tissue dry weight, it was found that growth extends through nearly 6 orders of magnitude during the 3 to 4 year life span. M. bidentatus is a true simultaneous hermaphrodite in contrast to all reports or assumptions of protandry throughout the family Ellobiidae. Assessments of gonad volume showed an 11-fold increase in volume from wintering to breeding snails, with a tripling of volume during the week preceding the first cycle of oviposition. Systematic decreases in gonad volume, oocyte numbers, and relative sperm content of gonads were found to coincide with periodicity of copulation and oviposition throughout the breeding cycles. A mean of 39 egg masses (850 eggs/mass) per individual per breeding season corresponds to 33,150 eggs per standard snail per year. This indicates a selection ratio of about 50,000:1 assuming any individual need replace itself only once during its lifetime. Adaptations of M. bidentatus to survive the alternating exposure to marine and to nearly terrestrial conditions include a unique combination of physiological and behavioral factors. Of particular importance is the semilunar correlated occurrence of oviposition, hatching, and settlement with spring tides, as is manifested in the Sippewisset population. 1 Supported in part by a grant from the National Institutes of Health, GM 11693, to W. D. Russell-Hunter, and subsequently by a predoctoral fellowship from Syracuse University to the author. Some of this material forms one part of a Ph.D. Dissertation accepted by Syracuse University. Observations during 1968 were made while on a postdoctoral fellowship from the Biology Department, GZ 259, Woods Hole Oceanographic Institution, Woods Hole, Mass.. U.S.A. 2 Present address: Dept. of Biology, Brooklyn College, Brooklyn, М. Y. 11210. 381 382 ML. “ABLEY INTRODUCTION The salt marsh snail, Melampus biden- tatus Say, is a member of the family Ellobiidae, order Basommatophora, and has been regarded as one of the more primitive living pulmonates. The habitat of M. bidentatus is primarily that of semi-enclosed salt marshes from New Brunswick, Canada, to the gulf coast of Texas, U.S.A. These snails inhabit the high littoral zone of salt marshes and consequently are exposed to a unique combination of terrestrial and marine conditions. Frequent exposure to both has resulted in a reproductive facies essentially characteristic of marine forms but adapted for accommodation of the rigors of a semi-terrestrial environment. Although Melampus bidentatus occurs frequently on the Atlantic seaboard and in many salt marshes as the dominant organism, surprisingly little work has been done on its physiology or ecology. Observations of life-cycle and life history of M. bidentatus have been made by Hausman (1932, 1936), Holle & Dineen (1957), and Morrison (1958). Morton (1955b) includes a consideration of M. bidentatus within an evolutionary study of the ellobiids. Russell-Hunter & Apley (1966) and Apley, et al. (1967) have reported preliminary work involving as- pects of life history and reproductive turnover in a population of M. bidentatus. The work and observations reported herein involves the same population of snails in Little Sippewisset Marsh, Fal- mouth, Massachusetts, U.S.A. (41° 35’ N 70° 40’ W). OBSERVATIONS AND RESULTS Only in a few instances have individuals with a shell length greater than 11-5 mm been observed in the Sippewisset Marsh population. The more typical maximum size is about 10-5 mm. The usual mini- mum reproductive size (at time of onset of first gametogensis) is at a shell length of approximately 5 mm, which the major- ity of snails reach before or during their second spring. This population of Melam- pus bidentatus is represented in Fig. 1 in terms of generations on the ground through a representative year. As shown in this figure, the life span of M. bidentatus extends over a period of 3 to 4 years. Included within Fig. | are generation mean size, standard deviation, size range, and growth. The data in Fig. 1 are for the year 1966, including data from 22 samples taken through the year (bi- monthly, for the most part). Regular samples were collected (all snails in any l area were collected until a total of approximately 150 was reached), shell length determined, and number of indi- viduals per class mark of 0:1 mm ex- pressed as per cent of sample. Generations were apparent upon expressing the above data as histogram percentages showing frequency per class mark. In some in- stances observations of shell crosion and growth lines were used to verify genera- tion divisions. The samples are a part of a continuous sampling program extend- ing from 1964 to 1967. Some notes have already appeared (Russell-Hunter & Apley, 1966; Apley, et al., 1967) reporting attempts to express these growth rates as measures of actual organic biomass. As noted elsewhere (Russell-Hunter, er al., 1968), the ash-free dry weight (or tissue dry weight without shell) in Melampus is closely related to the total organic carbon, and thus to calorific value. The mean size measurements (see Fig. 1) for different samples of the ‘ 1964 ” generation at Sippewisset can be converted to mean wet weights and then to ash-free dry weights. Typical values are: 1900 ug (June 28, 1965), 5400 ug (October 18, 1965), 6600 ug (March 9, 1966), 9200 ug (May 9, 1966), and 10,300 ug (June 28, 1966). This generation of FIELD STUDIES ON MELAMPUS 383 SHELL LENGTH IN MM FIG. 1. Shell ‘lengths’? of Melampus bidentatus in Sippewisset Marsh throughout 1966 (mostly bimonthly samples). Means e, ranges I, and standard deviations [ | are shown for samples of each generation with egg-laying cycles represented at bottom of figure. Generations are labelled according to the year of their hatching. The growth rate is indicated by the gradually increasing means within generations. Occurrence of new individuals (66 generation) and dying out of older individuals (63 generation) is also apparent. The means shown for the 1965 generation from January through May are not representative and should be treated with caution. Biased sampling resulted in disproportionately small numbers of lower-size groups being collected in these months. Additional information concerning this figure is given in Table 1 and in the text. snails is the principal contributor (Apley, 1967) to the 1966 reproductive period which was most closely studied. When the increments of dry weights are made proportional to the elapsed times involved, the following rates can be expressed as increment per year (in mg dry weight): 11-4 (late summer), 3-08 (winter), 15-6 (spring-summer) and 8-03 (reproductive period in late May-early July), and with an annual average value of 8-4. Thus it can be seen that the growth rate (expressed in biomass terms) is reduced nearly two- fold during the reproductive period, but is still 2-6 times the overwinter growth rate, These rates will be discussed below in relation to measures of the reproductive output. Oviposition occurs in cycles varying from year to year between late May and the first part of July. Egg masses mea- sure from | to 2 mm in diameter (appro- ximately 0-5 mm thick in the center) and appear as convex gelatinous mounds. Deposition of the masses occurs most commonly upon the ground surface, where they are soon covered by detritus and suspended material due to the action of tides. Egg masses may also be depo- sited on grass stems or leaves and have been observed on the shells of M. biden- tatus. Counts of individual egg masses 384 M. TABLE 1. Quantitative aspects of eggs, veligers, spat and adults of Melampus bidentatus. Shell-length | Wet weights Individual eggs 4-72 Lg Veligers 127 # 494 nano-g Spat (newly settled —ca. 6 weeks after hatching) 383 4 14:6 Lg Spat 675 4 | 65-0 Lg | Adult 5.8 mm 36-1 mg Adult 10-1 mm | 176-0 mg Adult 12-3 mm 312-0 mg (indiv. value) (indiv. value) revealed a mean number of 850 eggs per mass. Observations of egg masses, main- tained on moist filter paper in petri dishes at a room temperature comparable to a field temperature, indicated that eggs hatch in 13 days, but only if they are submerged in water at that time. Newly hatched veligers measure 127 # (mean length), are free-swimming, and assume a planktonic existence. Veligers were col- lected on outgoing tides at times of hatch- ing with a small plankton net in the tidal inlet area. The veligers are planktonic for at least 2 but almost certainly not more than 6 weeks. The earliest that newly settled spat were found in the adult habitat was 6 weeks after oviposition. These spat had a mean length of 383 u. Spat snails frequently occur around the bases of grass stems, in cavities of the plant, organic matter, and surface soil matrix. Before their first winter, most young snails reach a length between 1-0 Dry weights (mean values) (mean values) (mean values) 354 nano-g + ABLEY Tissue dry weight (ash free) (mean values) Shell calcium Organic carbonate | carbon (mean values) (mean values) 109 nano-g 129 nano-g ca. 116 <13 nano-g 33:4 nano-g nano-g 6-0 Lg 1-8 Lg 4-3 Lg | 23-2 lg 11-3 4g 11-9 Lg | 5:03 4g 17-4 mg 4-3 mg 13-1 mg | 1-86 mg 81-0 mg 18-2mg | 62-8 mg 7:4 mg 14-6 mg (пу. value) and 2:0 mm. The life-cycle then follows the pattern already discussed (see Fig. 1). Russell-Hunter & Apley (1966) provide a more quantitative approach to the life history of M. bidentatus, and their data on biemass values for eggs, veligers and spat are relevant to consideration of fecun- dity. These data plus corresponding data for adult snails are presented in Table 1. The ratio of organic carbon in #g per mg wet weight changes from 23-1 (egg), 67-6 (veliger), 77:4 (spat) to 51-5 through 42-1 (in adult growth). In Melampus, using any real measure such as total organic C or TDW (total dry weight), growth extends through 3 orders of magnitude in the first 3 months of life, and through nearly 6 orders of magnitude in the 3- to 4-year life span. In contrast, most freshwater or land pulmonates hatch from relatively large eggs and increase only 2 to 3 orders of magnitude in their life span (e.g., Physa FIELD STUDIES ON MELAMPUS 385 heterostropha from 36 ug to 5:3 mg С; Russell-Hunter, unpublished). The adults in the population studied live in the upper 1/3 of the littoral zone of a semi-enclosed salt marsh. This is mainly in the zone of growth for the sedge, Juncus gerardi, and the grass, Distichlis spicata, with some Spartina alterniflora in lower regions. The marsh at this level is normally flooded for 14-3 hours at times of spring tides and may remain dry for a few days during neap tides in each lunar cycle. Snail activity is normally at a maximum preceding the rising tides. Such populations of M. bidentatus are generally found to be inactive through periods of high tempera- ture during the day in summer, and over a period of a few months during low winter temperatures. Snails may be found in groups and partially buried in moist sand during the summer when temperatures reach a daily and seasonal maximum. At this time they are fre- quently in whatever shade may be avail- able and are usually inactive. Over- wintering specimens of M. bidentatus are found especially accumulated in the holes of fiddler crabs at the same tidal level. Studies of the genital tracts of ellobiids have been infrequent, and those that exist are inadequate in some aspects. The only work specifically referring to Melam- pus bidentatus is that of Morton (1955b), which is based only on fixed specimens and is somewhat limited. Koslowsky (1933) reported on the genital system of the European M. boholensis. In work on M. coffeus collected in Brazil, Marcus & Marcus (1965) briefly discuss the repro- ductive tract. Berry, et al., (1967) re- ported on the genital systems of 3 ello- biids, Pythia, Cassidula, and Auricula, all collected from Malayan mangrove swamps. As in all pulmonate snails, the repro- ductive system in Melampus is hermaphro- ditic with a single gonad or ovotestis and largely distinct male and female duct systems. The present studies have shown that unlike other ellobiids, M. bidentatus is a true simultaneous hermaphrodite, 1.е., with ova and spermatozoa produced in the ovotestis synchronously. The ovo- testis, shaped as a flattened hollow cone, overlies the digestive gland posteriorly and fits under the apex of the shell (see Fig. 2). Considerable increases in gonad volume occur just before and during the reproductive period (see Fig. 4). The ovotestis consists of many acini (which produce both ova and sperm), some of which anastomose, but are basically radial in orientation. At times the lumina of the acini were observed to be distended by densely packed sperm (ova were not observed in this location). Acinar walls vary in thickness, depending on the num- ber and size of oocytes produced and retained. The lesser or little hermaphro- ditic duct extends from the center of the underside of the ovotestis to the albumen gland. This duct is opaque-white in color, highly convoluted and varies con- siderably in diameter depending on the stage of the reproductive period. It is packed with masses of sperm at times during each reproductive cycle. At times other than the reproductive period it is empty, and its lumen is of 5-10% its capacity during the reproductive phase. The lumen is enlarged distally and receives the centripetal lumina of the acini of the ovotestis. The greater hermaphroditic duct runs from the albumen gland to the mucous gland at which point it is joined by the duct of the bursa copulatrix. In contrast to most other ellobiids the greater hermaphroditic duct is short and is not glandular (see Morton, 1955b). This duct is incompletely divided into male and female ducts by a longitudinal fold. The albumen gland and mucous gland are separate diverticula of the genital tract, although in M. bidentatus they are in much closer proximity to co ON = — E-CAPLEY OVOTESTIS TEE HERMAPHRODITIC DUCT MUCOUS GLAND BURSA COPULATRIX ALBUMEN GLAND FERTILIZATION POUCH PENIAL RETRACTOR MUSCLE VAS DEFERENS VAGINA PREPUTIUM FEMALE APERTURE MALE APERTURE > я ey р р ; 4 ; FIG. 2. The reproductive tract of Melampus bidentatus as drawn from dissection and from histological observations, proportionately enlarged. FIELD STUDIES ON MELAMPUS 387 than in most pulmonates. The gametes follow separate pathways after leaving the lesser hermaphroditic duct. Sper- matozoa are evidently passed directly into the vas deferens which branches from the anterior portion of the lesser hermaphroditic duct. Foreign sperm are stored in the bursa copulatrix following copulation. Presumably, fertilization occurs in this vicinity. However, foreign sperm have not been positively identified as such in any of the sections studied. In this same region a duct from the albumen gland unites with the greater hermaphro- ditic duct. Morton (1955b) suggests that the material within the egg capsule is supplied by the albumen gland at this point in the reproductive tract of most ellobiids. This is supported by the work of Berry, et al. (1967) on Pythia, Cassidula and Auricula. These authors also suggest that the mucous gland or glands then produces the egg capsule itself and at least some of the embedding mucous. Histological sections of the single mucous gland in M. bidentatus reveal a channel, parts of which are ciliated, running through the gland. The lumen of this channel is also visible in the mucous gland of entire genital tracts cleared and lightly stained for low power observation. This would suggest that the ova traverse the mucous gland during the process of egg formation. Berry, et al. (1967) have also proposed this in Pythia, Cassidula and Auricula as being the actual pathway. Marcus & Marcus (1965) believed that the pathway of eggs was through the mucous gland in their work on M. coffeus. In the present work (and in all these other cases) the evidence is circumstantial, and in no case have the eggs been observed on their way through the mucous gland in any ellobiid. It seems most likely that Morton (1955b) was in error in hisdeduc- tion that, in Melampus, the mucous- secreting region is not traversed by sexual products. No one suggests that the albumen gland is so traversed. From the base of the mucous gland the oviduct transports the eggs to the vagina and to the female genital aperture laterally located on the right side of the foot, roughly above the transverse pedal groove. Prior to egg-laying, the intromittent organ of the copulatory partner is introduced through the vaginal opening and into the vagina. The vas deferens, with a con- siderably smaller lumen, runs parallel to the vagina as far as the vaginal opening, and then turns anteriorally to the male aperture. From here it loops back into the body cavity and into the distal portion of the preputium at the point of attach- ment of the penial retractor muscle. The male aperture is located below and behind the right tentacle. A true retractile penis is not present in M. bidentatus. At copu- lation, the relatively undifferentiated intro- mittent organ consists of the everted muscular wall of the preputium. Oviposi- tion occurs soon after copulation. In contrast to more random behaviour at non-reproductive times (or throughout most of the rest of the year), the days preceding, during, and just following egg- laying in Melampus bidentatus are be- haviorally patterned. A pronounced re- productive or sexual aggregation of the snails occurs, starting 2 to 3 days prior to copulation. At this time, aggregations of snails may frequently cover areas totalling up to 1/3 of a square meter, with densities (counted per 10 cm? plots) reaching 124. It is worth noting here that non-aggregated snails generally avoid contact with each other. Within these reproductive aggregations snails are gener- ally active and do not exhibit this usual avoidance reaction. Egg masses have always been found within | day of the first observation of copulation in both field and laboratory populations. In approximately 90%, of the instances where copulating pairs were observed and separated, copulation was 388 NEA -ABFEY DISPERSED AGGREGATION COPULATION OVIPOSITION -DISPERSION O JUNE 3— DISPERSED AGGREGATION COPULATION — OVIPOSITION | |-DISPERSION O JUNE le— DISPERSED AGGREGATION COPULATION — OVIPOSITION | |-DISPERSION DEA 2 @ JULY 18 FIG. 3. Sequence and duration of behavioral phases of reproductive cycles as observed during 1966. See text for further discussion. found to be unilateral rather than reci- procal. Frequency of copulating pairs is highest during the first to second day of egg-laying. It seems probable that copu- lation occurs randomly and more than once, with each individual acting as both male and female at some time during the reproductive cycle. However. it remains possible that only one effective sperm transfer is involved. Frequency of con- tact with other individuals increases pre- ceding copulation. Tentacles and oral lobes are involved in an exploration of the head and anterior pedal portions by opposite members of the potential copu- latory pair. Subsequently the pair be- comes orientated with right frontal body regions in contact with each other (1.е., with the male genital opening of each animal opposite the vaginal opening of the other). The whole process requires minutes rather than hours. However, successful entrance of the intromittent organ does not always follow exploration and orientation of a pre-copulatory pair. The highest rate of egg-laying occurs late the second day or early the third day after the onset of copulation. Egg-laying is usually completed within 4 days. Dis- persion of the aggregations begins to occur about the fourth day of egg-laying and is complete by the seventh to eighth day following the beginning of copulation. These observations have been repeated and found to be consistent over the 4 summers of 1965-68. These behavioral aspects of the reproductive cycle are presented in Fig. 3. Observations on the field population during the years 1965 through 1968 re- vealed a definite semilunar periodicity in reproduction. The behavioral sequence, as defined in the preceding section, is repeated in phase with the spring tides in late May, June or the first part of July. Not only are oviposition and related behavior patterned to the diurnal and lunar sequence, but also the annual repro- ductive period covers parallel weeks in May, June, or July from year to year. GONAD VOLUME FIELD STUDIES ON MELAMPUS DUAL 53.0 MM3/ INDI N о о 0.0 J E M A M 389 EGG-LAYING J A S O N D FIG. 4. Changes in mean gonad volume per individual (lower graph) and changes in mean gonad volume related to shell-length (upper graph) at intervals in 1966. Times of egg-laying are represented. Lunar changes preceding egg-laying are shown by © for full moon and @ for new moon. in gonadal volume occurs with progression through the breeding period as shown in the graphs. General decrease Also shown is the volume increase just before or early into egg-laying. The data for 1966 are most complete with Oviposition occurring at times related to spring tides around June 3, June 18, and July 2 (see Fig. 3). During the summer of 1967, oviposition was again correlated with the spring tides, this time around June 8, June 22, and July 7. In 1968, May 27, June 10, and June 25 were times at which oviposition was correlated with occurrence of spring tides. Oviposition at Sippewisset Marsh in 1965 was noted twice, at times corresponding with spring tides of June 14 and July 13. Examination of histologically-fixed collections taken for growth studies indicated that there was also oviposition in conjunction with the spring tides of June 29, 1965. Gonad volume for individuals through- out the year was assessed. Simple gross dissections of fixed specimens demonstrate a rather rapid increase in gonad size pre- ceding egg-laying, as well as a rapid size decrease that accompanies and follows egg-laying (Fig. 4). Individuals were selected at size ranges within each mature generation and fixed in neutral formalin at 2- to 5-day intervals throughout the reproductive period in 1966. Shell lengths were recorded and used as an indication of age and as the basis for comparison of results. The shell was then carefully removed by cracking through gradual application of pressure with a screw clamp and the ovotestis separated from the rest of the snail by first peeling away the mantle and then loosening the ovo- 390 M: «E. АРЕБУ testis around the edges and lifting it away. Each ovotestis was serially sectioned working from the posterior to the anterior at 9 micra and stained by Masson’s hema- toxylin. Each tenth section was marked, starting with the fifth section in which gonad material appeared. Each marked section was projected at a known magni- fication using an ocular prism. The pro- jected image was traced in outline and the area was estimated in terms of a sys- tem of grid squares calibrated to the magnification. A set of about 15 to 17 tracings of area were then converted to give the estimated gonad volume. These volumes are plotted with reference to annual life-cycle in Fig. 3. In general there is an 11-fold increase in gonad volume from wintering to breeding snails. An approximate tripling of gonad volume occurs within the week just prior to the first egg-laying. A nearly 10-fold decrease in gonad volume occurs over the six weeks which follow the first oviposition. Apley, et al. (1967) noted that biomass values for gonads show systematic decreases during this period. Values were obtained imme- diately before breeding started (A), after the first cycle of egg-laying (B), and after the third cycle had concluded the annual reproductive period (C). Mean wet weights of individual gonads change from 6:32 mg (A) to 6:95 mg (В) and to 1:09 mg. (C). Dry weights are less variable, as are the organic carbon values, mean carbon being 698 wg С (A), 845 ug С (В) and 151 #g С (С). Depletion of organic nitrogen is pronounced and uniform with mean values falling from 110 ag (A) and 114 ~2(B) to 10 из (С) In 1966, observed groups totalling 244 snails laid 219 10% eggs, then 345x 10? eggs, and finally 254104 eggs. Therefore, the overall fecundity totalled 818 10? eggs, corres- ponding to 33,150 eggs per standard snail per year. (The standard snail of 8-5 mm shell length was calculated from all data used in work on ovotestis volume and contents. This was done to eliminate any small variations involved due to differences in the mean size for each sample group.) Mean biomass values for individual eggs are dry weight=354 nano-g and organic C=109 nano-g. This average total egg output per individual corresponds to 7:3 mg of dry organic material annually, while mean depletion of “ standing bio- mass ” in the gonads corresponds to 99-8 ug N or 920 ис of dry organic mate- rial. These values can be related to the mean growth increments for M. biden- tatus presented earlier. It would appear that 87%, of the non-respired assimilation (N-RA) was directed to reproduction during the reproductive period. This corresponds to 46%, of the total N-RA, or to 32% N-RA if spring pre-breeding growth rates could be sustained through- out the year (Apley er al., 1967). Total oocyte numbers (all developing oocytes and ova visible under 100 < magnification) were determined from the same serial sec- tions used for ovotestis volume. Oocytes were individually counted in 3 marked sections for each specimen, one centrally located and one evenly spaced on each side. Oocyte counts were made over the entire section at 100 magnification. Results are presented in Fig. 5 in terms of total oocytes per mm? of gonad per standard snail, and are plotted for time and stage in the reproductive cycle (the actual data on oocyte counts were pre- sented in Appendix A in Apley, 1967). By measuring each individual oocyte with an ocular micrometer, in a number of sections of specimens at different repro- ductive stages, a natural discontinuity in size of oocytes was evident, usually at an approximate volume between 1 X 10°” and 1x10* mm? As total oocyte counts were made, each oocyte was included in l of the 2 size categories so defined (although no attempt was made to classify these according to the various stages of oogensis), and total numbers are shown FIELD STUDIES ON MELAMPUS 391 8 EHEGG-LAYING 6 J Larce Q sMaLL 4 n u = One O O uw | а И 2 UNNNANN My a untl! NN NE N 3 NY ANNO HE + SA | Ц N N h N N à N \ N N 4 ù (] A M J J A FIG. 5. Oocytes (all potential female gametes visible with 100X magnification) per mm? of gonad per standard snail (see text) in field collected specimens for times during the breeding period of 1966. Numbers of small oocytes are represented below the midline and numbers of large oocytes are shown above the line. Changes in the ratio of large to small oocytes occur in the progression of each breeding cycle. See text and Fig. 4 for further information in relation to changes illustrated. in Fig. 5. The relation of size distribu- tion in terms of time and reproductive cycle is obvious and these results can be correlated with the total fecundity. Changes in the amount and distribution of spermatozoa in gonads are much more difficult to quantitify than are similar assessments of oocytes. Of several approaches tried, quantitative changes of spermatozoa (assessed relative to overall gonad volume) primarily related to thick- ness of acinar walls yielded reproducible results. The lumina or spaces within the acini of the gonad of Melampus biden- tatus are the regions where sperm accu- mulate when they reach maturity. Cate- gories were devised on the basis of changes in the proportional width of the lumina as compared to the double thickness of the acinar walls. The same slides of gonads used for other studies of the natural reproductive cycle were used heres At Sune: 4. June 19 ава July 3 (times just preceding copulation) the acinar walls were distended by dense masses of sperm in the lumina (specific data are presented in Apley, 1967; see Appendix A and Figs. 8-13, 16). There is a considerable decrease in the relative amounts of mature sperm free in the gonad during the subsequent part of each of the 3 reproductive cycles following copulation. There is an increase in thickness of acinar walls, reflecting an increase in the production and retention of oocytes just preceding egg-laying. The cyclic activities of copulation and oviposition at 2 week (semilunar) intervals through the normal breeding period of about 7 weeks are thus again reflected in the changing relationship of lumina width to acinar wall thickness. DISCUSSION The life-cycle of Melampus bidentatus is of 3 to 4 years with annual reproductive periods from late May or early June into the first part of July, and with a semilunar reproductive periodicity involving pat- terned behavioral responses. The corre- lation of egg-laying, hatching, and settle- ment with the incidence of spring tides is clearly adaptively significant. Sequence of patterned behavior and of gonadal changes in experimental specimens maintained in the laboratory and within field collected specimens was closely comparable. An account of experimental work demon- strating controls of reproductive period and cycles depending on day length and 392 М. т. APLEY semilunar changes is given elsewhere (Apley, 1971). Melampus bidentatus is a simultaneous hermaphrodite and not a protandrous hermaphrodite as are other ellobiids which have been investigated and from which the assumption (Morton, 1955b) of protandry in all ellobiids was evidently derived. Contrary to the early assumption of a biennial cycle being general in pulmonates (Pelseneer, 1906, Baker, 1911) or to the annual cycles reported by Russell-Hunter (1957, 1961), a 3 to 4 year life-cycle is evident at Sippewisset (Fig. 1; and Russell-Hunter & Apley, 1966; Apley, et al., 1967). Such a life-cycle is much more common in marine and nonmarine littoral prosobranchs such as Littorina littorea (Moore, 1940) and Viviparus contectoides (Van Cleave, 1934). The usual minimum reproductive size lies between 5 and 6 mm shell length. Two reproduc- tively mature generations are therefore present in the population through the June and early July reproductive period. The participation of 2 different genera- tions of snails during the annual repro- ductive period is advantageous to the population. This would buffer the popu- lation against lasting effects resulting from | reproductively unsuccessful year. The habitat occupied by Melampus bidentatus is probably close to that in which the family has evolved (as the Sub- class Pulmonata itself has). This habitat in the high littoral or intertidal zone offers a number of advantages and dis- advantages. Essentially, M. bidentatus 1$ an amphibious organism, capable of living either terrestrially or submerged (for at least short periods of time), as are other pulmonates of similar habitats (Lymnaea truncatula, and Succinea pfeifferi, both of which drown if kept continuously sub- merged, see Russell-Hunter. 1953 and 1964, respectively). Regarding respira- tion, M. bidentatus is a true land pulmo- nate with pneumostome and air-filled mantle cavity. From the viewpoint of reproductive physiology, M. bidentatus is a primitive aquatic gastropod, producing large numbers of small unprotected eggs. Such animals living in the high littoral zone can either lay eggs only during the short periods when water is present, or migrate into deeper water at their repro- ductive periods. Of course, a number of littoral animals have internal fertilization and subsequently lay small numbers of large eggs with more-or-less direct develop- ment to the adult. In the majority of littoral animals a number of larval stages intervene betweea hatching and the as- sumption of the adult forms and habitat. Melampus falls in the latter category, producing large numbers of small eggs which hatch directly as veliger larvae. However, there is no migration into deeper water. The problem of ensuring survival of gelatinous egg masses without resistant outer cases and containing many small eggs (mean of 850 eggs/mass) is overcome very effectively and in some respects quite simply. Throughout the course of these investigations (1965-68) a semi-lunar perio- dicity of egg production has been observed. Eggs are laid only through 4 days at the time of spring tides. This helps prevent immediate desiccation of freshly laid egg masses, but more impor- tantly, it covers the egg masses with detri- tus and organic debris which collect and maintain moisture through the ensuing neap tides. In the field the detritus helps maintain better conditions for the survival and development of eggs through the period of nonsubmersion until the next spring tide occurs. At this time, approx- imately 13 days later, veligers have developed, ready to break from the egg masses, and take up a temporary plank- tonic existence. Eclosion is triggered by submersion in sea water. This was seen in all observations of egg masses kept in FIELD STUDIES ON MELAMPUS 393 moist conditions as well as in those obser- vations of desiccated egg masses. (These were egg masses which appeared to be completely dried out, but from which veligers emerged when covered by sea water. These eggs were all relatively far along in development before desiccation occurred. ) Thus in the field, the eggs hatch only upon the inundation by the spring tides, approximately 13 days after being depo- sited. The free-swimming veligers which emerge are, of course, aquatic animals moving by ciliary means. Since both eggs and larvae are highly water-depen- dent, reproduction is made possible in these semi-terrestrial conditions by this significant semi-lunar correlation of egg- laying and hatching with the occurrence of spring tides. The time of settlement of larvae back into terrestrial marsh conditions is not yet clear, but must occur after 2 but before 6 weeks of planktonic life. Settled spat have not yet been observed earlier than 6 weeks after hatch- ing. Partially successful laboratory rear- ing of larvae of M. bidentatus indicate that the veligers have at least 2 weeks of normal planktonic life. Settlement appears to be correlated with the time of spring tides, the only time at which spat snails would be capable of reaching habitat conditions similar to those of their parental stock. This semi- lunar synchrony of egg-laying, hatching and settlement of spat is of primary im- portance for the survival of these high littoral populations. It is not difficult to conceive of the kinds of selection pressures which would create and fix these rhythms of behavior and reproduction. The occur- rence of more than one egg-laying cycle is significant, especially in terms of species survival and distribution. The density of newly settled spat at times following appropriate spring tides varies, and this reflects the extent or success of settlement corresponding to each reproductive cycle. The slight variations observed in intensity of egg-laying with each reproductive cycle could not alone account for the much greater variation in density at spatfall. Multiple periods of intensive oviposition increase the likelihood of adequate spatfall. Egg masses of Melampus have been reported at different times along the Atlantic coast of North America. Holle & Dineen (1957) reported egg masses on June 20 in 3 marsh areas north of Cape Cod. This compares with the May, June or early July periodicity reported for snails of Sippewisset Marsh by Russell-Hunter & Apley (1966), Apley, et al. (1967), and within the present report. Morrison (1958) reports egg masses by August 20 in the vicinity of Cape Hatteras, North Carolina. At the time of the observa- tions of Holle & Dineen (1957) and Morrison (1958), there was no apprecia- tion of a semilunar periodicity of repro- duction as was briefly discussed in Russell- Hunter & Apley (1966), Apley, et al. (1967), and amplified in Apley (1971) and herein. Such reproductive dates cited before 1966 may be isolated observations of only a single reproductive cycle in each case, other cycles of that year’s reproduc- tive period not having been observed or suspected. There was no regularity of field observations in these earlier studies, and their extent is unknown. Holle & Dineen (1957) did report egg-laying in specimens which they took into the labo- ratory during late spring and early summer of 1955. Examination of their reported dates show no simple correlation of egg- laying with lunar cycles. Scattered individual observations by Morrison (1958) suggested a progression of egg-laying dates from north to south through the summer, which he regarded as in ‘apparent anticipation of winter seasons.” Observations of a population of Melampus bidentatus at Fort Macon, North Carolina (34° 43’ N 76° 41’ W), during the summer of 1968 revealed 3 394 М. Е. APEEY periods of oviposition with a semi-lunar periodicity during the last part of August and in September. Through the year a progressively later onset of reproduction as one moves northward is most usual in marine littoral animals (see Hutchins, 1947, and Jenner, 1956). Experimental work reported elsewhere (Apley, 1971) suggests that there may be several alter- native explanations of these data. The possibility exists of a greater number of egg-laying cycles extended over a longer period of time in some more southern populations. The occurrence of physio- logical races in mollusks has been reported and/or hypothesized in a number of instances. These include Korringa (1957), Loosanoff (1960), Russell-Hunter (1961), and Russell-Hunter, er al. (1967). Exis- tence of physiological races of M. biden- tatus is quite possible (and perhaps even probable). As stated, eggs produced by Melampus bidentatus are small and numerous. Counts of egg masses from groups of snails main- tained in the laboratory indicate a mean of 39 egg masses per individual per breed- ing period, corresponding to 3-3 x 10? eggs (derived from data in Apley, 1967). Esti- mates of egg numbers in M. bidentatus compare with approximate egg numbers reported by Fretter & Graham (1964) of 4х 103 in Littorina littorea, 13x 10° in Nassarius reticulatus, both examples of marine prosobranchs. This figure for M. bidentatus can be compared with egg numbers of 100-130 in Lymnaea stagnalis ;* 20-42 in Pianorbarius corneus;? 60-90 in Helix pomatia* (all from Fretter & Gra- ham, 1964); and 150 in Achatina fulica* (Mead, 1961), all of which are non-marine pulmonates. Assuming no great differ- ences within natural populations of M. bidentatus over periods of several years, 2 Aquatic. + Terrestrial. 5 ** Amphibious ”. one would conclude that only a small percentage of the eggs produced resulted in settled spat and an even smaller percent in adults. Since it is likely that each adult snail need only replace itself during its lifetime, the ratio of selection would therefore be about 50,000:1 in M. biden- tatus. This would compare with selection ratios reported by Russell-Hunter (1957) of 1,400:1 in Lymnaea peregra and 46:1 in Ancylus fluviatilis, both of which are freshwater pulmonate snails. No data concerning overall fecundity in other ellobiid pulmonates are available, and there are few such data for other snails. Thorson (1950) reports egg num- bers ranging from a few thousand to several hundred thousand per female per breeding season in marine bottom inverte- brates with planktonic larvae. Marcus & Marcus (1965) report egg masses in M. coffeus similar in form and number of eggs to M. bidentatus, but no overall figures. Egg masses enclosed in protec- tive cases with smaller numbers of eggs than in Melampus have been reported by Morton (1955a, 1955c) for Leucophytia,° Ovatella? and Carychium The most complete adaptation to terrestrial life is shown by the large eggs with calcareous shells found in Strophocheilus (Russell- Hunter, 1955) or Achatina (Mead, 1961), which are physiologically cleidoic and resemble those of higher vertebrates. Thus, Melampus, though a genus of air breathers with appropriate behavioral responses for life in the semiterrestrial conditions of the highest littoral, has an egg size (and total number) closely cor- responding to true marine snails. Many of the peculiarities herein reported of ecology and physiology in M. bidentatus are related to this * amphibian” pattern of aquatic reproduction. FIELD STUDIES ON MELAMPUS 395 ACKNOWLEDGEMENTS The author would like to express his gratitude to Dr. W. D. Russell-Hunter for his advice and concern throughout this work. Appreciation is also extended to Dr. David C. Grant who kindly made regular collections during many of the winter months, to Jay Shiro Tashiro for his assistance in numerous ways, including many calculations and measurements, and to Eric W. Lindgren for his observations and collection of samples of a North Carolina population. PITERATURE CITED APLEY, M. L., 1967, Field and experimental studies on pattern and control of repreduction in Melampus b:dontatus (Say). Ph.D. Dissert., Syracuse Univ. (Available from University Microfilms, Ann Arbor, Michigan, U.S.A.) APLEY, M. L., 1971, Experimental studies on pattern and control of reproduction in Melam- pus bidentatus (Say). (In prep.). APLEY, M. L., RUSSELL-HUNTER, W. D. & AVOLIZI, R. J., 1967, Annual reproductive turnover in the salt-marsh pulmonate snail, Meiampus bidentatus (Say). Biol. Bull., 133: 455-456. BAKER, F. C., 1911, The Lymnaeidae of North and Middle America, recent and fossil. Spec. Publ., No. 3., Chicago Acad. Sci., 539 p. BERRY, А. J., LOONG, 5. С. & THUM, H. H., 1967, Genital systems of Pythia, Cassidula, and Auricula (Ellobiidae, Pulmonata) from Malayan mangrove swamps. Proc. malacol. Soc. Lond., 37: 325-337. FRETTER, V. & GRAHAM, A., 1964, Repro- duction. In: Physiology of Mollusca, Vol. 1, р 127-164. Eds. К. М. Wilbur & С. M. Yonge. Academic Press, New York. HAUSMAN, S. A., 1932, A contribution to the ecology of the salt marsh snail (Melampus bidentatus). Amer. Nat., 66: 541-545. HAUSMAN, S. A., 1936, Food and feeding activities Of the salt marsh snail (Melampus bidentatus). Anat. Record, 67: 127. HOLLE, P. A. & DINEEN, C. F., 1957, Life history of the salt-marsh snail, Melampus bidentatus (Say). Nautilus, 70: 91-95. HUTCHINS, L. W., 1947, The bases for tem- perature zonation in geographical distribution. Ecol. Monogr., 17: 325-335. JENNER, C. E., 1956, The timing of reproduc- tive cessation in geographically separated populations of Nassarius obsoletus. Biol. Bull., 111: 292, 8 KORRINGA, P., 1947, Relations between the moon and periodicity in the breeding of marine animals. Ecol. Monogr., 17: 347-381. KOSLOWSKY, F., 1933, Zur Anatomie der Auriculidae Melampus boholensis H. and A. Adams. Jena. Z. Naturw., 68: 117-192. LOOSANOFF, V. L., 1960, Challenging prob- lems in shellfish biology. In: Perspectives in Marine Biology, р 483-496. Ed., Buzzati Traverso. Univ. California Press, Berkeley. MARCUS, E. & MARCUS, E., 1965, On Bra- zilian supratidal and estuarine snails. Bol. Fac. Fil., Cien Letr. Univ. S. Paulo, n 287, Zoologia n 25, p 19-82. MEAD, A. R., 1961, The Giant African Snail: A Problem in Economic Malacology. Univ. Chicago Press, Chicago, 257 p. MOORE, H. B., 1940, The biology of Lirtorina littorea. Part II. Zonation in relation to other gastropods on stony and muddy shores. J. mar. biol. Assoc. U.K., 24: 227-237. MORRISON, J. P. E., 1958, The primitive life history of some salt marsh snails. Amer. malacol. Union Ann. Report, 11: 25-26. MORTON, J. E., 1955a, The functional morph- ology of the British Ellobiidae (Gastropoda, Pulmonata) with special reference to the digestive and reproductive systems. Phil. Trans. Roy. Soc. London, B, 239: 89-160. MORTON, J. E., 1955b, The evolution of the Ellobiidae with a discussion on the origin of Pulmonata. Proc. zool. Soc. London, 125: 127-168. MORTON, J. E., 1955c, Notes on the ecology and annual cycle of Carychium tridentatum at Box Hill. Proc. malacol. Soc. London, 31: 30-46. PELSENEER, P., 1906, Mollusca. Jn: Treatise on Zoology, Part 5, Ed., E. Ray Lankester. Adam and Charles Black, London, 355 p. RUSSELL-HUNTER, W. D., 1953, A note on the amphibious snail Succinea pfeifferi Ross- massler, in a previously undescribed habitat. Glasg. Nat., 17: 91. RUSSELL-HUNTER, W. D., 1955, Endemicism in the snails of Jamaica. Glasg. Nat., 17: 173-183. RUSSELL-HUNTER, W. D., 1957, Studies on freshwater snails at Loch Lomond. Glasgow Univ. Publ., Stud. Loch Lomond, 1: 56-95. RUSSELL-HUNTER, W. D., 1961, Life cycles of four freshwater snails in limited populations in Loch Lomond, with a discussion of infra- specific variation. Proc. zool. Soc. Lond., 137: 135-171. RUSSELL-HUNTER, W. D., 1964, Physiological aspects of ecology in non-marine mollusks 396 MAL APEEY In: Physiology of Mollusca, Vol. 1, p 83-126 RUSSELL-HUNTER, W. D., MEADOWS, Edited by K. M. Wilbur & C. M. Yonge В. T., APLEY, M. L., & BURKY, A. J., 1968, Academic Press, New York. 645 p. On the use of a “ wet-oxidation ‘’ method for RUSSELL-HUNTER, W. D. & APLEY, M. L., estimates of total organic carbon in mollusk 1966, Quantitative aspects of early life history growth studies. Proc. malacol. Soc. London in the salt-marsh snail, Melampus bidentatus, 38: 1-11 > and their evolutionary significance. Biol Bull. : AE E ie THORSON, G., 1950, Reproductive and larval RUSSELL-HUNTER, W. D., APLEY, M. L.. a a D pi bottom invertebrates. Biol. ev., 25: 1-45. BURKY, A. J. & MEADOWS. В. T., 1967, Interpopulation variations in calcium meta- bolism in the stream limpet, Ferrissia rivularis Say. Science, 155: 338-340. 15: 17-23. VAN CLEAVE, H. J., 1934, Length of life span as a factor in regulating populations. Ecology, RESUME ETUDES DANS LA NATURE SUR LE MODE DE VIE, LE CYCLE SEXUEL ET LA PERIODE DE REPRODUCTION CHEZ MELAMPUS BIDENTATUS (PULMONATA: ELLOBIIDAE) M. L. Apley Melampus bidentatus (Ellobiidae, Pulmonata) se rencontre dans la zone supralittorale de lagunes saumátres á demi fermées le long de la cóte atlantique depuis le Nouveau Brunswick, Canada, jusqu'au Texas, U.S.A. Des observations ct des études qui ont duré de 1964 á 1968 sur une population habitant la lagune de Little Sippewisset, Falmouth, Massachusetts, U.S.A., a montré les aspects écologiques et physiologiques du cycle vital, du cycle sexuel ct de la période de reproduction. C'est Pévidence que, dans cette population, le cycle vital dure 3 á 4 ans, avec généralement une longueur maxi- male de la coquille d'environ 10,5 mm. La maturité sexuelle (quand la gamétogenese a lieu pour la premiere fois) est atteinte quand la taille de la coquille est d'environ 5 mm chez des individus qui appartiennent á deux groupes d'áge. Le taux de croissance hivernal est sculement le 1/5 du taux de printemps-é:é qui est lui-méme le double de celui des mollusques pendant la saison de reproduction. La période annuelle de reproduction dure quelque fois 6 semaines, en fin mai, juin, début juillet. Chaque période annuelle de reproduction comporte 3 cycles de ponte a intervalle de 2 semaines (semilunaires) en corrélation avec les marées de vives eaux. Il y a, dans cette population, toute une gamme de comportements bien prévisibles pendant ces cycles semilunaires de reprc- duction comprenant les rassemblements sexuels, la copulation, la ponte et la dispersion. Les pontes sont petites, gélatineuses, et dépourvues d'une enveloppe externe dure; chacune contient une moyenne de 850 oeufs. Les véligéres nageuses éclosent apres 13 jours si les pontes sont couvertes d’eau à ce moment là. Ensuite les veligeres sont planc- toniques pendant 2 à 6 semaines. On n’a pas trouvé de larves benthiques plus tôt que 6 semaines après l’éclosion. En utilisant des mesures de carbone organique total ou de poids secs des tissus On a trouvé que la croissance couvre presque 6 ordres de grandeur pendant la durée de vie de 3-4 ans. M. bidentatus est un véritable hermaphrodite simultané contrairement aux observations ou présomptions de protandrie qui ont été faites dans la famille des Ellobiidae. Les valeurs du volume de la gonade augmerte de 11 fois quand on passe du mollusque hiver- nant au mollusque en reproduction, avec un triplement du volume pendant la semaine précédent le premier cycle de ponte. Les diminutions systématiques du volume de la gonade, du ncmbre d’occytes et de la quantité relative de sperme des gonades se sont trouvées étre en coincidence avec les périodes de copulation et de ponte tout au long des FIELD STUDIES ON MELAMPUS cycles sexuels. Une moyenne de 39 pontes (180 oeufs par pontes) par individu par saison de reproduction correspond a 33.150 oeufs par mollusque standard, par an. Ceci montre un taux de sélection d’environ 50,000-1 assurant le remplacement de tout individu une fois seulement au cours de sa vie. Les adaptations de M. bidentatus pour survivre au fait d'étre exposé alternativement a des conditions tantót marines et tantót presque terrestres, sont le résultat d'une com- binaison unique de facteurs physiologiques et éthologiques. Les périodes semilunaires de ponte, d'éclosion et de passage á la vie benthique, en corrélation avec les marées de vives eaux sont á ce propos d'une toute particuliere importance, comme on le voit dans la population de Sippewisset. ABCTPAKT ПОЛЕВЫЕ ИССЛЕДОВАНИЯ ЦИКЛА РАЗВИТИЯ ГОНАЛ И ПЕРИОДИЧНОСТИ РАЗМНОЖЕНИЯ У MELAMPUS BIDENTATUS (PULMONATA: ELLOBIDAE) М. Л. ЭПЛИ Melampus bidentatus (Ellobiidae, Pulmonata) был найден в верхней части лито- ральной зоны в полузамкнутых районах соленых болот, вдоль берегов Атлан - тики от Нью-Брунсвика, Канада до Техаса, США. В наблюдениях и исследова- ниях, проводившихся в 1964-1968 гг. не популяциях этих моллюсков, обита- ющих в болотах Литтл Сиппивиссет, Фальмут, Массачусетс, США, обращалось внимание на экологический и физический аспекты жизненного цикла, на цик- личность в развитии гонад и периодичность размножения моллюсков. Для этой популяции установлено 3-4-х годичный цикл при наиболее обычной ма- ксимальной длине раковины около 10,5 мм. Половозрелость (когда. впервые наблюдается гаметогенез) наступает при длине раковины около 5 MM y ин- дивидуумов из двух возрастных групп, принимающих участие в годовом пе- риоде размножения. Зимняя скорость роста составляет лишь 1/5 от весенне- летней скорости роста, которая в свою очередь почти в 2 раза больше, чем темп роста моллюсков во время периода размножения. Годовой период раз- множения длится 6 недель, захватывая конец мая, июнь и начало июля еже- годно. Каждый годовой период состоит из 3 циклов откладки яиц с 2-х не- дельным интервалом (половина лунного месяца) и коррелируется с сизигий- ными приливами. Устойчивые, предсказуемые особенности поведения моллю- сков в течение этих полумесячных циклов размножения (включая их агрега- ции, копуляцию, откладку яиц и дисперсию) наблюдаются у всех популяций. Яйцевые пачки небольшие, слизистые, без плотной внешней оболочки; каждая из них содержит в среднем 850 яиц. Свободно плавающие личинки-ве- лигер выходят через 13 дней, если яйца в это время покрыты водой. Затем в течение 2-3 недель велигеры ведут планктонный образ жизни. Осевшие ли- чинки (спат) были отмечены не ранее, чем через 6 недель после выклева. При помощи определения количества органического углерода или сухого веса тканей было найдено, что в течение первых 3-4 лет жизни моллюсков наблю- дается их прирост почти в 6 раз. М. bidentatus- настоящий одновременный гермафродит, в противоположность представлениям о протандрии всего семейства Ellobiidae. Измерение объема гонад показало их увеличение в 11 раз у размножающихся моллюсков, по сравнению с зимующими; объем гонад увеличивается в 3 раза в течение не- дели перед первым циклом откладки яиц. Систематическое уменьшение объема гонад, количества ооцитов и относительного содержания спермы в гонадах совпадает с периодичностью копуляции и откладки яиц в течение цикла раз- множения. В среднем 39 пачек яиц (из 850) на одну особь за сезон размно- жения соответствует 33 150 яйцам на стандартного моллюска в год. Это указывает на скорость отбора примерно в отношении 50 000:1, допуская, что каждая особь должна сменить себя 1 раз за свою жизнь. Адаптация М. bidentatus к выживанию при смене морских условий на почти сухопутные включает единую комбинацию Физиологических факторов и условий среды. Особое значение имеет полумесячная корреляция откладки яиц, вы- клева и оседания личинок с сизигийными приливами, как это было установ- лено на популяциях моллюсков из Сиппевиссета. и. А. В: 397 MALACOLOGIA, 1970, (10)2: 399-413 ASPECTS OF THE GROWTH OF THE SNAIL LYMNAEA PALUSTRIS (MULLER) Bruce M. McCraw Department of Pathology Ontario Veterinary College University of Guelph Guelph, Ontario, Canada ABSTRACT Analysis of weekly population samples of overwintering Lymnaea palustris (Müller) revealed that the spring and early summer growth of this snail was rapid, following an almost linear pattern, but that little growth occurred befcre April 15 or after early July. There was no cOncentrated spring egg-laying activity in Arkell pond, although some spring-hatched snails were present in Pond 2. Smaller L. palustris overwintered best, and in Arkell pond almost all the spring and summer population is derived from snails ovipositing the previous year, in late summer or autumn. Unlike some pulmonates, no spring population turnover was Observed. Up to maturity, the reproductive system is slender and shows no pronounced change in general form, but after maturity it under- goes great expansion. The growth rate (k) of the reproductive system is not constant, but gradually declines with age. After a shell length of 11 or 12 mm, growth of individual reproductive organs (albumen gland, oóthecal gland, uterus and muciparous gland, and prostate) in relation to shell length, is linear. Beyond 8 mm the same is true for gizzard growth. All these structures develop very slowly during the first few millimeters of shell growth. Great fluctuation in size occurs with the albumen gland, and this is probably related to reproductive activity. The growth rate of the oóthecal gland is fastest and that of the prostate slowest. INTRODUCTION Detailed life histories of many gastro- pods are already well known, although it is only in recent years that some have been investigated extensively. Among the basommatophoran pulmonates it has been found, at least in temperate climates, that a number of them have a life span of around | year, with oviposition and hatching of young particularly evident in the spring and early summer months. Growth is most rapid during a period lasting from spring until late fall. With the onset of winter temperatures, the growth velocity of all snails decreases, and weeks or months may pass when sampling methods reveal little or no 399 change (excepting possibly for deaths) in population structure (Duncan, 1959; McCraw, 1961). After a rise in tempe- rature following winter conditions, growth resumes, often resulting in a quickly changing population picture and sometimes even an almost complete population turnover (Hunter, 1953; DeWitt, 1955; Geldiay, 1956; McCraw, 1961). It is the purpose of the present study to investigate closely the spring and early summer growth of the pulmonate, Lymnaea palustris (Müller). As little work has been carried out on the growth of internal organs that accompanies an increase in “shell "size, it “seemed desirable to follow also the development 400 B. M. McCRAW i A | АРВ. 17 JUNE 10 | В | A APR. 29 JUNE 17 | B | д MAYI4 JUNE 24 B MAY 21 JULY 3 | ld ры MAA A MAY 27 | JULY 9 JUNE 3 | A0 Allen TH 20 — || 5 10 5 20 25 5 10 15 20 25 SHELL LENGTH (MM) FIG. 1. Collections of L. palustris from Arkell pond plotted according to the number falling within mm size classes. GROWTH OF LYMNAEA 401 of some of these internal structures, especially the reproductive system, during this spring and early summer period. MATERIALS AND METHODS Collections of Lymnaea _ palustris were made at approximately weekly intervals from 2 small semi-permanent ponds near Guelph, Ontario, Canada. Shell dimensions of smaller — snails were measured with an ocular micro- meter calibrated to a stereoscopic micros- cope; for larger snails calipers were used. Snails used for growth analysis of internal organs were relaxed in nembutal and meathol (McCraw, 1958) and fixed in 10% formaldehyde. The various organs were weighed on a B. T. L. “* Empire ” aperiodic projection balance. The combined weight of the following structures, taken while still unseparated from one another, was measured: the albumen gland, prostate, uterus and muciparous gland, oöthecal gland and vagina. This measurement will be re- ferred to as the total weight of the repro- ductive system. However, it excludes the male copulatory organ, ovotestis and the seminal receptacle. The weight of the latter structure in mature snails depended largely upon the amount of sperm present in it. The ovotestis is thoroughly embedded in the digestive gland making a clean dissection exceed- ingly difficult. The following organs were weighed individually: the gizzard, albumen gland, oöthecal gland and pro- state gland. Structures to be weighed were dissected from snails stored in formaldehyde and whose shells were decalcified (in 10%, formaldehyde contain- ing 10%, hydrochloric acid) just before dissection. To remove excess surface moisture immediately before weighing, each organ was gently rolled over on filter paper several times until no more moisture was absorbed. Growth data were analyzed by computer to determine the predicted weight of the reproductive system, as well as the weights of various organs of the reproductive system from shell length (Snedecor & Cochran, 1967). RESULTS AND DISCUSSION Fig. 1 shows the results of approxi- mately weekly samples of Lymnaea palustris taken from Arkell pond between April 17 and July 9, 1959. On May 6 snails were very difficult to find, and the number collected on that date was too small to warrant plotting. Before April 17 no snails were observed, probably because of low water temperatures. As only slight movement of L. palustris is observed in water temperatures between 7° and 9-5°C, it is likely that these snails were inactive until about April 13 when the water temperature first reached 10°C. The sample of April 17 was unimodal, and the shift in this mode was relatively easy to follow in frequency plots until June 3 ( A’ in Fig. 1). On June 10 a new mode was detected (* B”) and this one could be followed until July 3. From July 9 on, throughout the remaining summer weeks little change in the popula- tion picture was evident. The spring and early summer growth of this snail is more clearly revealed by plotting modes (Fig. 2). Shifts in the first mode ( A’) resulted in a striking linearity for the spring growth of L. palustris. In a second pond, Pond 2, where both Aplexa hypnorum (L.) and L. palustris were present, structural changes in the population of both these snails were followed for comparison. Unfortunately, with L. palustris distinct modes which could be followed at weekly intervals were not present. However, clearly de- fined modes for A, hypnorum were found 402 B. M. McCRAW 20 LENGTH (MM) oO nn ss oc 0 SHELL œ TIME FIG. 2. of L. palustris in Arkell pond. (Fig. 3) and these also displayed a re- markably linear pattern for the spring growth of this snail (Fig. 4). These observations are consistent with the growth pattern of laboratory-reared PAysa gyrina Say, which increases in size quickly Ю 20 30 40 50 60 70 80 90 100.110 1207159739228 x LJ E > © 302. => 20 ns 10 X— SINGLE READING °C ® - МАХ TEMP = O— MIN. TEMP °F ul LJ > > > (©) Ant 50 ER Jo я = > > => => < DAYS Plots of modes, labelled A and B in Fig. 1, to illustrate the spring and early summer growth Broken lines indicate estimated growth. during the first few weeks after hatching (12:0 mm at 8th week; 13-6 at 52nd week) (DeWitt, 1954). Similar results were obtained by Chernin & Michelson (1957a; 1957b) for the growth of Austra- lorbis (= Biomphalaria) glabratus raised GROWTH OF 1 С 2 | C JUNE 3 | = | MAY 6 (С | JUNE 10 MAY 14 E ree ee (0 С Marzı TUNE 17 | 20- | A MON 14016 р MAY 27 colt... SHELL LENGTH (MM) POND 2 FIG. 3. Collections of A. hypnorum from Pond 2 plotted according to the number falling within mm size classes. in aquaria. In addition, these authors found that the growth velocity of A. glabratus was markedly influenced by crowding which, when severe, effected considerable retardation. There was probably very little growth of snails in both of these ponds prior to the middle of April. According to Vaughn (1953) Lymnaea stagnalis appressa Say will develop and hatch at a tempera- ture as low as 9-9°C and growth of young occurs between 11°C and 28-2°С. Oviposition (and presumably growth) in Physa gyrina Say does not occur below water temperatures of 10 or 12°C (DeWitt, 1955), while Duncan (1959) found that Physa fontinalis (L.) resumed growth at a slightly lower water temperature (7°C). An estimate of the amount of growth of L. palustris before April 17 is shown in Fig. 2. Plots of the second mode "B’ (Fig. 1) which could be followed in 4 consecutive samples showed a decline in growth velocity (Fig. 2). After July 9, the population structure stabilized, and, except for an accumulation of 22 and 23 mm size classes, the sample of LYMNAEA 403 SHELL LENGTH (MM) 10 20 30 40 50 60 TIME DAYS FIG. 4. Plots of modes, labelled C in Fig. 3, to illustrate the spring growth of A. hypnorum. Broken line indicates estimated growth. August 12 was little changed from that of July 9 (Fig. 1). These findings suggest, therefore, that after about June 15 an inhibiting phase of growth set in with a gradual levelling of the growth curve occurring throughout the summer (Fig. 2). No snails were observed in Pond 2 before May 6. On June 24, 1959 this pond was beginning to dry with the snail fauna clustered into an isolated pocket and a slight decline in growth velocity of Aplexa hypnorum was evident beginning June 17 (Fig. 4). Ritchie et al. (1963) showed that size at the onset of laying of Australorbis glabratus varied with the growth rate, 1.e., a rapidly growing snail would reach a larger size before laying than one that grew slowly. On the other hand, stunting is known to be accompanied by a decrease in the rate of gonadal maturation. Re- duced growth of Oncomelania spp. results in a lack of development of sex organs as 404 B. M. McCRAW uJ œ = < = x 20 40 60 80 100 DAYS FIG. 5. The increase in the percent mature L.palustris in Arkell pond during spring and early summer. well as an increase in mortality (van der Schalie & Davis, 1965). However, Ritchie et al. (1963) concluded that when a near-maximum growth rate occurs, both size and age correlate well with the onset of oviposition; otherwise size is a better criterion of maturity. There was no field evidence that Lymnaea _ palustris was not growing normally and the smallest field-collected snail to oviposit in the laboratory was 14-85 mm in shell length; of a series of snails collected and observed in aquaria, the mean shell length at which oviposition began was 16-25 mm. Fig. 5 illustrates the rapid rise in the per cent of mature animals (16-25 mm and over) present in samples taken from Arkell pond during spring and early summer, 1959. The increase was especially great between May 15 and June 15, From these facts, a burst of egg-laying might have been expected toward the end of May with the appea- rance of large numbers of young by June 15 (based on a 10-day hatching period for most egg masses in aquaria). No recently hatched young were seen at that time and no rapidly growing juveniles were found on successive collec- ting days (Fig. 1). A check on this observation was made the following year (1960) in Arkell pond, and on June | only one L. palustris as small as 4-5 mm was found; the smallest found on June 9 was 7 mm, on June 17 and 23, 8 mm, and on June 30, 9 mm. On the other hand, larger forms were abundant during this time. Although some spring egg-laying must occur (one 4:5 mm snail taken on June 1), the results of two years observation have indicated that in Arkell pond concentrated egg production does not occur in the spring months. Some spring-hatched L. palustris were present in Pond 2, but again there was no pronounced burst of spring reproduc- tive activity. This behavior is in sharp contrast to that of the amphibious L. humilis Say which produces great numbers of eggs during several weeks in spring, as soon as water and air temperatures are favorable, resulting in a large new population of spring juveniles (McCraw, 1961). A similar spring juvenile popula- tion was found for Physa gyrina (DeWitt, 1955), and during the month of May, Duncan (1959) observed many egg capsules of P. fontinalis with a corresponding abundance of young (up to 5 mm) the following month. A remarkable feature of the snails in both ponds studied was that the smaller ones survived winter conditions in greatest numbers. In Arkell pond at the time the water temperature first permitted the resumption of growth the majority cf over-wintering Lymnaea palustris would have been somewhat less than 7 mm in length (Fig. 1), These findings GROWTH OF LYMNAEA 405 are consis- tent with the fact that smaller L. humilis were found to withstand the change from autumn to winter condi- tions better than larger ones (McCraw, 1961). While no eggs were found in spring and early summer in Arkell pond, they were present by mid-summer (August 12). Spring growth of snails which were very small in the middle of April conti- nued in a linear fashion until a shell length of 20 or 21 mm was attained (Fig. 2). To account for the 19 to 21 mm groups of August 12 (assuming a linear growth velocity) one might have expected size classes of 10 to 13 mm or smaller to be present on or about July 9 (Fig. 1). The absence of those size classes on July 9 suggests that the 19 to 21 mm snails of August were not late spring broods, but groups which had over-wintered either as very small snails or perhaps as larval forms in egg masses. While it may be difficult not to include some contribution to the late-summer Lymnaea palustris population of Arkell pond from egg masses laid in spring or early summer, analysis of weekly samples would indicate that the bulk of adult molluscs of 1 year is derived from the previous year. Since very few dead snails were observed in July and August, the molluscs of this over-wintering population must normally live throughout the summer, glving a life span for L. palustris of about | year. Unlike what has been observed with Lymnaea palustris in Arkell pond, recent life cycle studies of several other pulmo- nates have shown that a spring population turnover of these snails is a common occurrence. Results of a study of DeWitt (1955) showed that in April nearly all Physa gyrina were mature, and that most of this generation died during this month after a period of active egg-laying. During May the population was com- posed almost exclusively of newly-hatched snails. Similar findings are recorded for P. fontinalis (Duncan, 1959) and Ancylus fluviatilis Muller (Hunter, 1953). Follo- wing continuous egg-laying for at least 6 weeks, over-wintering L. humilis popula- tions, which were composed of 95% mature snails in April, were found to die off promptly in late May or early June (McCraw, 1961). However, rapid onset of senility followed by death is evidently not a sequel to the spring reproduction of the lymnaeid Acella haldemani (** Desh.” Binney), which lives until mid summer (Morrison, 1932). Fig. 6-11 show the changes that occur in the size and shape of the repro- ductive system of Lymnaea palustris with shell lengths of 23.0, 16:3 and 10:8 mm. Marked differences in appearance are evident between the slender reproductive system of the juvenile (10:8 mm) and the bulky organs of a large mature animal (23-0 mm). The oöthecal, muci- parous and albumen glands displayed great expansion with age, particularly after the onset of maturity. However, up to the time of maturity, there was no pronounced change in the general form of the male and female reproductive tracts. An interesting relationship was observed between growth of snails in the field and sexual maturity. The inhibiting phase of snail growth (June 15 onwards, Fig. 2) corresponded to a time at which approxi- mately 85 per cent of Lymnaea palustris were mature (Fig. 5) suggesting that a decline in growth velocity is related to sexual maturity. It has long been appreciated that the different parts of an organism do not always grow at the same rate. Although several approaches to the problem of growth analysis have been followed (Clark & Medawar, 1945), perhaps one of the most widely used is that proposed by Huxley (1924, 1932). According to this approach, the relation between the size 406 B. M. McCRAW 6 и ] H.G.D. PD 7 SHELL LENGTH 23 MM. MG о Na PR 7 0.6. 10 vo ae I 1 ь FIG. 6, 7, 8, 9, 10 and 11. Changes in the size and morphology of the reproductive system of L. palustis with an increase in shell length. Figs. 6 and 7 from a snail with a shell length of 23 mm, Figs. 8 and 9 from one of 16.3 mm shell length, and Figs. 10 and 11 from one of 10°8 mm shell length. Abbreviations : ALB. G.. albumen gland; H.G.D., hermaphrodite gland duct; L.P.G., lower prostate gland; M.G., muciparous gland; O.G., cóthecal gland; S.R., seminal receptacle; S.R.D., duct of seminal receptacle; U.P.G., upper prostate gland; UT., uterus; VA., vagina; V.D., vas deferens. GROWTH OF LYMNAEA 407 of the whole organism (x) and that of some part of it (y) can often be described by the equation ЗИ == bx*. This equation is usually referred to as the allometry equation; however, other terminologies have been applied to des- cribe growth when k is greater or less than unity, or merely unequal to | (Richards & Kavanagh, 1945). The para- meter b is the value of y when x is o and the value of this parameter in turn depends on the measuring scales used (Richards & Kavanagh, 1945). These authors attri- bute no biological significance to it and even consider comparisons between values of b extremely hazardous. The value k is the slope of the line when the equation is in the form log y = log b + k log x or the ratio of the 2 specific growth rates, dy/ydt : dx/xdt. The exponent k may be a true constant, or as Richards & Kavanagh (1945) point out, it may not actually be one but may remain so while the specific growth rates are themselves changing in such a manner as not to affect their ratio. On the other hand, k may show a gradual change in slope reflecting a continuous or nearly contin- uous adjustment of this value. Such a changing value of k was found for a plot of the total weight of the reproductive system against shell length of Lymnaea palustris (Fig. 12). Using the data of Miller & Hoy (1939), Richards & Kava- nagh (1945) found a similar relationship between the length of the second antenna and body width in the isopod Asellus californicus. A gradual decline in the ratio of the specific growth rates of reproductive system and shell of Г. palustris was evident, with the tendency more pronounced in larger animals. Since few living snails were found over 25 mm in length, this more rapid decline in larger animals is probably indicative of (GM) 6:00 LN. TOTAL WT OF REPRODUCTIVE SYSTEM | | | 120] | | | | — T Sm mm — 2207724052605 28052 SOUS 20510 LN. SHELL LENGTH (MM) FIG. 12. A changing value of the exponent k in the relationship between the growth of the repro- ductive system and shell length of L. palustris. Broken line indicates the onset of maturity (16:25 mm). (Ln. Y =—51:'97+34:43 (Ln. X_)— 5°14 (Ln. X,)?. senile changes. It is therefore clear that although the form of the reproductive system of a juvenile is not in general the same as that of an adult (Fig. 6, 7, 10, 11), there is certainly no sudden change in the ratio of the specific growth rates of this system and shell length that can be attributed to any biological phenomenon, such as the onset or cessa- tion of reproduction. While the allometry formula describes the relationship between the reproductive system as a unit and shell length, the growth activities of separate organs or regions and shell length followed a linear relationship within the limits of the measurements made (Fig. 14-17). The same situation also prevailed for gizzard size (Fig. 13). All these organs, especially the reproductive structures, develop very slowly during the first few mm of shell growth. In Lymnaea (GM) WT, ZARD GIZ Te ЗН 6 8 10 I2 14 16 18 20 22 24 26 28 SHELL LENGTH (MM) FIG. 13. The relationship between gizzard weight and shell length of L. palustris. (Y ="0005X— ‘0044; 1?=874). palustris smaller than 10 mm, the albumen’ oöthecal and prostate glands each weighed much less than .0001 g while in a 25 mm animal these glands weighed .0099, .0134 and .0056 g respectively. Moreover, the mean weight of the entire reproductive system of six L. palustris averaging 9.60 mm was only .0001 g whereas in a 25 mm or larger snail this figure may reach well over .0250 g. For the mean shell length at which oviposition began (16.25 mm), the predicted total weight of this system is .0055 g. Beyond a shell length of about 10 mm various parts of the reproductive system undergo a sudden increment in growth velocity (Fig. 14-17). McCRAW The albumen gland showed great variation in weight (г? =-618). Very often in a snail of 20 mm it may be no larger than in a snail of 12 mm (Fig. 14). In addition, its % weight (relative to the total weight ot the reproductive system) showed no consistent change with an increase in shell length (Table 1). These findings indicate that the size of this organ is dependent not only upon overall animal size, but to a large measure upon the reproductive state of an indivi- dual snail. With the prosobranch Rissoa parva Da Costa, Gostan (1958) stated that there was not always correspondence between the development of the reproduc- tive system and growth of the shell, and she suggested seasonal factors, espe- cially temperature, as a possible reason. With the exception of the albumen gland, correspondence between these 2 parts in Lymnaea palustris was for the most part good, and only one animal with a stunted reproductive system was observed. Duncan (1958) observed that the albumen gland of Physa fontinalis (L.) varied seasonally and was small and difficult to detect during the period October to February. Berrie (1966) noted a similar seasonal reduction in the size of the albumen gland of £. stagnalis (L.). The variation recorded here for L. palustris occurred during late spring and early summer. Fluctuations in the magnitude of the albumen gland of L. palustris were especially noticeable around the time of maturity. A closer relationship was found between the growth of the remaining structures of the reproductive system and shell length than for the albumen gland and shell length (г = -92 and above; r? = -851 and above) (Fig. 15-17). The %, weights 1 Snedecor & Cochran (1967) state that “ r? may be described as the proportion of the variance cf Y that can be attributed to its linear regression on X. When r is 0.5 or less, Only a minor proportion of the variation in Y can be attributed to its linear regression on X. At r=0.7. about half the variance of Y is associated with X, and at r=0.9, about 80%. LE] GROWTH OF LYMNAEA 409 ‘0090 + . ‘0080 ‘0070 (GM) WT OF ALBUMEN GLAND . О fo) С . O A O 6 8 10 12 14 6 18 20 22 24 26 SHELL LENGTH (MM) FIG. 14. The relationship between albumen gland weight and shell length of L. palustris. Brokenire indicates the onset of maturity (16.25 mm). (Y=.0005X—.0069; 1?=.618). :0140 (GM.) ‘0120 0100 ‘0080 ‘0060 ‘0040 WT. OF OOTHECAL GLAND ‘0020 6 8 10 12 14 16 18 20 22 24 26 SHELL LENGTH (MM) FIG. 16. The relationship between the weight of the oôthecal gland (including the vagina) and shell length of L. palustris. Broken line indicates the onset of maturity (16.25 mm). (Y=.0008X —.0100; r?=.856). (GM) o © @ о МТ OF UTERUS AND MUCIPAROUS GLAND 6 8 0 12 14 16 18 20 22 24 26 SHELL LENGTH (MM) FIG. 15. The relationship between the weight of the uterus (including the oviduct) and muci- parous gland, and shell length of L. palustris. Broken line indicates the onset of maturity (1625 mm). (Y=.0006X—.0082; r?=.891). -0045 -0040 ) > ‘0035 (GM -0030 -0020 WT OF PROSTATE GLAND O O oO O о о -0005 6 8 10 12 14 16 18 20 22 24 26 SHELL LENGTH (MM) FIG. 17. The relationship between the weight of the prostate gland and shell length of Г. palustris. Broken line indicates the onset of maturity (16.25 mm). (Y=.0003X—.0031; r?=,851). 410 B. M. McCRAW TABLE 1. Weights of various parts of the reproductive system of L. palustris expressed as per cents of the total weight of the reproductive system. Data arranged accordingto increasing shell length. Total Wt. of Shell à Albumen Gland Reproductive Length System* Per cent (mm) Total Wt. (g) 117 -0010 10-0 12-0 -0014 28-6 13-5 -0010 10-0 14-9 -0014 14-3 14-9 -0032 12-5 14-9 -0045 8-8 15-6 -0073 20-5 15-7 -0059 11-9 16:7 0069 | 27 17-1 -0112 | 22-3 17-9 -0103 18-4 20-0 -0091 4-4 20-3 -0141 24-1 21-1 -0210 24-8 22-9 -0193 13-5 23-7 -0246 31-3 24-0 -0199 18-6 25-0 -0376 26:3 25.8 -0269 22-3 Range % 4-4-31-3 Oviduct, Uterus, Oothecal Gland | Prostate Gland Muciparous | a E Gland Per cent т = ae À er cent Total Wt. otal Wt. otal Wt. 0 35:7 | 35.7 20-0 40-0 30-0 0 42-8 | 42-8 15-6 ES | 34-4 20.2 28-8 42.2 17.8 42-5 19-2 16-9 | 35-6 | 35-6 ee 36: 17:9 15:6 40-8 25 9 19.8 вв 15-2 39-5 | 20.5 26.9 42-0 17-6 30-7 30-7 20-1 23.2 33.6 14-9 | Range % Range % | Range % 0-30-7 | 28-8-43-3 12-8-42-8 | *Includes only those values from which percents are calculated. of the oviduct-uterus muciparous gland complex, oóthecal and prostate glands are shown in Table 1. The phase of initial slow growth is more prolonged for the reproductive organs than in the case of gizzard growth. In the former it lasts until a shell length of 11 or 12 mm is attained, 5 or 6 mm before oviposition begins. After the phase of rapid growth has set in, there is no spectacular difference in the ratios of the absolute growth rates for gizzard growth on the one hand (Fig. 13), and the glandu- lar structures on the other (Fig. 14-17). However, of the individual organs it is worth noting that the growth rate of the oöthecal gland is fastest and that of the prostate slowest. These 2 rates may refiect a difference in glandular activity or in the nature of the secretions of these structures. The oöthecal gland is to a large degree mucus-secreting, while secretory droplets are a prominent feature of the prostate follicles (Holm, 1946; Duncan, 1958). ACKNOWLEDGEMENTS It is a pleasure to express my appreciation to Dr. Gordon C. Ashton, Statistician, Department of Mathematics and Statistics, University of Guelph, for his advice on statistical methods and critical reading of the manuscript, as well as for making available the services of the Statistical Laboratory. GROWTH OF LYMNAEA 411 REFERENCES BERRIE, A. D., 1966, Growth and seasonal changes in the reproductive organs of Lymnaea stagnalis (L.). Proc. malacol. Soc. London, 37: 83-92, CHERNIN, E. & MICHELSON, E. H., 1957a, Studies on the biological control of schisto- some-bearing snails. III. The effects of popu- lation density on growth and fecundity in Australorbis glabratus. Amer. J. Hyg., 65: 57-70. CHERNIN. E. & MICHELSON, E. H., 1957b, Studies on the biological control of schisto- some-bearing snails. IV. Further observa- tions on the effects of crowding on growth and fecundity in Australorbis glabratus. Amer. J. Hyg., 65: 71-80. CLARK, W. E. Le Gros & MEDAWAR, P. В. (Ed.), 1945, Essays on growth and form. i-viii, 408 p. Oxford at the Clarendon Press. DeWITT, R. M., 1954, Reproduction, embryonic development, and growth in the pond snail, Physa gyrina Say. Trans. Amer. microsc. Soc., 73: 124-137. DeWITT, R. M., 1955, The ecology and life history of the pond snail Physa gyrina. Ecology, 36: 40-44, DUNCAN, C. J., 1958, The anatomy and phy- siology of the reproductive system of the freshwater snail Physa fontinalis (L.). Proc. zool. Soc. London, 131: 55-84. DUNCAN, C. J., 1959, The life cycle and ecology of the freshwater snail Physa fontinalis (L.). J. animal Ecol., 28: 97-117. GELDIAY, R., 1956, Studies on local popula- tions of the freshwater limpet Ancylus fluviatilis Miiller. J. animal Ecol., 25: 389-402, GOSTAN, G., 1958, Corrélation entre la crois- sance de la coquille d'un Prosobranche (Rissoa parva Da Costa) et le développment des organes internes. C.R. Acad. Sci. Paris, 247: 2193-- 2195. HOLM, L. W., 1946, Histological and functional studies On the genital tract of Lymnaea stagnalis appressa Say. Trans. Amer. microsc. Soc., 65: 45-68. HUNTER, W. RUSSELL, 1953, On the growth of the fresh-water limpet, Ancylus fluviatilis Muller. Proc. zool. Soc. London, 123: 623-636. HUXLEY, J. S., 1924, Constant differential growth-ratios and their significance. Nature, London, 114: 895-896. HUXLEY, J. S., 1932, Problems of relative growth. i-xix, 276 р. Lincoln MacVeagh, Dial Press, New York. McCRAW, B. M., 1958, Relaxation of snails before fixation. Nature, London, 181: 575. McCRAW, B. M., 1961, Life history and growth of the snail Lymnaea humilis Say. Trans Amer. microsc. Soc., 80: 16-27. MILLER, M. A. & HOY, E. A., 1939, Differen- tial growth and evolution in a subterranean isopod. Amer. Naturalist, 73: 347-364. MORRISON, J. P. E., 1932, Studies on the life history of Acella haldemani: (* Desh. ” Binney). Trans. Wisconsin Acad. Sci., 27: 397-414. RICHARDS, O. W. & KAVANAGH, A. J., 1945, The analysis of growing form. In: Essays on Growth and Form, W. E. Le Gros Clark and P. B. Medawar (ed.). Oxford at the Clarendon Press. RITCHIE, L. S., BERRIOS-DURAN, L. A. & DEWEESE, R., 1963, Biological potentials of Australorbis glabratus: Growth and matura- tion. Amer. J. trop. Med. Hyg., 12: 264-268. SNEDECOR, а. W. & COCHRAN, W. G., 1967, Statistical methods. ¡-xiv, 593 р. 6th ed. The Iowa State University Press, Ames, lowa. van der SCHALIE, H. & DAVIS, G. M., 1965, Growth and stunting in Oncomelania (Gastro- poda: Hydrobiidae). Malacologia, 3: 81-102. VAUGHN, C. M., 1953, Effects of temperature on hatching and growth of Lymnaea stagnalis appressa Say. Amer. Midland Naturalist, 49: 214-228. ~ B. M. McCRAW RESUME ASPECT DE LA CROISSANCE CHEZ LYMNAEA PALUSTRIS (MULLER) B. M. McCraw L'analyse d'échantillons hebdomadaires d'une population posthivernale de Lymnaea palustris (Müller) a révé.é que la croissance de printemps et du début d'été a été rapide suivant une courbe presque linéaire, mais qu'il n'y a eu qu'une faible croissance avant le 15 avril et aprè; le début juillet. Ii n’y a pas eu une activité de ponte de printemps intense dans Vetang d'Arkell, bien que quelques lymnées nézs du printemps aient été présentes dans l'Etang 2. Les plus petits L. palustris hivernent bienet dans l’étang d’Arkell presque toute la population de printemps et d'été dérivait d'animaux nes l’année précédente en fin d’é.é ou d’automne. Certrairement à certains pulmones, il n'y a pas eu ren0uvellement de la population au printemps. Jusqu'à la maturité, l’appareil repro- ducieur est mince et ne montre pas de changement notable dans sa forme générale, mais aprés maturité il subit une grande extension. Le taux de croissance (А) de l’appareil reproducteur n’est pas constant, mais décline graduellement avec l’âge. Apres une taille de coquille de 11 ou 12 mm, la croissance de chaque organe reproducteur (glande de l’albumen, oothèque, utèrus et glande nidamentaire, et prostate) en relation avec la longueur de la coquille, est linéaire. Au-dessous de 8 mm la méme chose est vraie pour le gesier. Toutes ces structures se developpent tres lentement pendant les premiers milli- metres de croissance de la coquille. Une grande fluctuation de taille se manifeste pour la glande a albumen, ce qui est probablement en relation avec l’activité reproductrice. Le taux de croissance de l’ootheque est le plus rapide et celui de la prostate le plus lent. Aas RESUMEN ASPECTOS DEL CRECIMIENTO DEL CARACOL LYMNAEA PALUSTRIS (MULLER) B. M. McCraw Analisis semanales de muestras de poblaciones de Lymnaea palustris (Müller) después de invernada, revelaron que en primavera y principio del verano el crecimiento de los caracoles fué más rávido, pero antes del 15 de Abril o después del principio de Julio no se registro crecimiento. No hubo desove concentrado en la pequeña laguna Arkell,- aunque algunos caracoles que habian hecho eclosión en primavera estaban presentes en la laguna 2. Caracoles pequeños invernaron mejor, y en Arkell toda la población de primavera-verano derivó de individuos que desovaron el año anterior al fin del verano о en otoño. Antes de alcanzar madurez, el sistema reproductor és delgado sin mostrar cambio pronunciado en la forma general, pero después experimenta gran expansión. El crecimiento del sistema reproductor no és constante sino que declina con la edad. Despues que la concha alcanza a 11 o 12 mm, el crecimiento individual de los organos reproductores (glándula albuminoidea, ooteca, útero, glándula mucipora y prostata) es linear en relación a la longitud de la concha. Desde los 8 mm, lo mismo ocurre en el crecimiento del estómago. La glándula albumimoidea ofrece gran fluctuación en el crecimiento y esto probablemente está relacionado a la actividad reproductiva. El crecimiento más rápido se observé en la glandula ootecal y el más lento en la prostata. If de 12: GROWTH OF LYMNAEA ABCTPAKT О POCTE РАКОВИНЫ УЛИТКИ LYMNAEA PALUSTRIS (MULLER) Б. МЭКРОУ Изучение еженедельных проб популяций перезимовавших Lymnaea palustris (Muller) указывает на то, что рост этих моллюсков весной и в раннее летнес время происходит быстро, сопровождаясь линейными отметками. Ослабленный рост наблюдается вплоть до 15 апреля или даже до начала июля. Концентрированная весенняя кладка яиц в пруде Аркелл отсутствова- ла, хотя молодь улиток весеннего выклева наблюдалась в пруде N 2. Лучше всех перезимовывали более мелкие Г. palustris; в пруду Аркелл почти все улитки весенней популяции происходили от особей, отложивших яйца в пре- дыдущем году-в конце лета или осенью. Не в пример некоторым Pulmonata y них не наблюдалось круговорота весенней популяции. Вплоть до наступления половозрелости, их репродуктивная система была развита слабо и в ней eue не наблюдалось заметных изменений общей формы; после наступления полово- зрелости гонады заметно увеличиваются. Темп роста, (К) половой системы не постоянен, но постепенно затухает с возрастом, и после увеличения размера раковины до 11-12 мм у отдельных особей рост половой системы (альбуминовой железы, оотеки, матки, слизи- стой железы и простаты) по отношению к длине раковины происходит линей- но. У особей менее 8 мм тоже самое верно в отношении роста желудка. Все эти структуры развиваются очень медленно при росте раковины на первые несколько мм. Большие колебания размера наблюдаются также у альбуминовой железы, что может быть связано с размножением. Темп роста железы оотеки наиболее быстрый, а у простаты-самый медленный. 413 MALACOLOGIA, 1970, 10(2): 415-421 THE SHELL STRUCTURE OF ASTRAEA OLFERSI (GASTROPODA: TURBINIDAE)! Pedro Jurberg Instituto Oswaldo Cruz, Caixa Postal 926, Guanabara, Brazil ABSTRACT A study of 30 shells of Astraea olfersi Troschel in Philippi, 1846, concerned especially with their structural design and crystallographic arrangement, shows the presence of 2 layers: an outer one, with homogeneous-foliate structure consisting of aragonite and traces of calcites and an inner One, with nacreous structure consisting of aragonite only. After corrosion, the structural design is foliate in both layers. A review of the literature shows that several Recent and Tertiary species of Turbo and Astraea possess this type of aragonite structure. Examination of a polished section of a molluscan shell often shows that the external and internal parts of a layer seem to have the same appearance. This may be observed in the crossed lamellar and prismatic structures. In some instances, on the contrary, the 2 parts are quite different. This happens in the nacreous structure, the external part of which is iridescent, whereas the internal one shows sinuous superposed lines without irides- cence after exposure to corrosion. Based on this fact, and adopting Böggild’s (1930) terminology, | introduce the expression ““ structural design ” to signify the figure produced by any weak corrosion process. The results obtained are expected to be of use in studies of systematics and paleon- tology, as they bring additional details to the description of structural components of shells and to the comparison between Recent and fossil forms. MATERIAL AND METHODS - The’shell of the turbinid prosobranch Astraea olfersi Troschel in Philippi, 1846, was studied by means of corrosion of surfaces, replicas in polyester (Araldite- Ciba), staining with alizarin, Phloxin, cotton blue in acetic acid (Ranson, 1952), ultra-violet examination (Jurberg & Barth, 1964) and X-ray diffraction (Swamy Rama, 1935). The diagrams were made by the powder method, ina Norelco diffractometer. The powder was obtained by scraping off separately each layer of the shell. The specimens were collected alive and left to die in jars at room temperature so as to allow decomposition of the organic mate- rial to take place. This procedure prevents aragonite from turning into calcite during the preparation of the material, as pointed out by Davies & Hooper (1963). About 30 specimens were used in this study: They were collected from calm sea between the middle:littoral and the infralittoral zones (Pérés, 1961), at Arraial do Cabo, Praia do Forno, State of’ Rio de Janeiro, Brazil. y IWork carried out in the Instituto Oswaldo Cruz and the Instituto de Pesquisas de Marinha, and supported by a grant from the Conselho Nacional de Pesquisas, Brazil, 416 P. JURBERG FIG. 1. Section longitudinal to the columellar axis, showing the distribution of the homo- geneous (HL) and nacreous (NL) layers. THE SHELL OF -ASTRAEA OLFERSI The shell of Astraea olfersi shows 2 clearly visible layers, even with macro- scopic observation (Figs. 1-2). The most careful examination did not reveal any periostracal layer, even in specimens col- lected alive. A thick polished section of the outer- most layer shows no textural arrangement and, on this account, it should be con- sidered a * homogeneous structure ””. However, after corrosion its structural design was disclosed as a foliate pattern of sinuous superposed lines (Fig. 3). It could be regarded as a transition from the homogeneous to the foliate structure, and this is why I find it appropriate to name it, with Böggild (1930), the ‘ homo- geneous-foliate structure”. This outer layer spreads all over the external surface of the shell and extends beneath some inclusions into the underlying layer. It did not take the above-mentioned dyes and showed no fluorescence under ultra- lem FIG. 2. Same section seen from the opposite side. violet light, owing probably to its low content of organic material. The pres- ence of calcite in this layer seems difficult to understand. Theories on the deter- minism of CaCO, formation in the molluscan shell are still contradictory as pointed out by Wilbur (1964). The innermost layer has a nacreous aspect and covers all the internal surface of the shell. After corrosion it shows a foliate structure (Fig. 4) much more con- spicuous than that in the outer layer. Excellent corrosion images were obtained with cotton blue acetic acid. This layer also differs from the outer one in taking comparatively well some dyes such as picric acid, phloxin and alizarin. Micro- scopical observation showed, however, that the stain was not evenly distributed throughout the section surface, owing perhaps to the action of the dyes on the organic material largely found in the nacreous layer. Under ultraviolet light the shell sections displayed an intense green fluorescence confined to the inner layer and similar to that observed in the outer surface of shells that have a super- SHELL STRUCTURE OF ASTRAEA 417 FIG. 3. Cross section showing the corrosion figure in the outer layer and: the sinuous lines NL, nacreous layer; HL, homogenous layer. FIG. 4. Cross section showing the corrosion figure and the sinuous lines of the nacreous (inner) layer. FIG. 5. Cross section showing the cement (C) between two contiguous whorls. FIG. 6. Longitudinal section of the apex, showing the first whorls filled with material similar to that of the outer layer. HLR=homogeneous layer reinforcement. ficial conchiolin layer, such as Thais haemastoma (Linné, 1767) and Olivancil- laria brasiliana (Lamarck, 1811). This property may be attributed to the large quantity of organic material in the 4 nacreous layer. X-ray diffraction showed that the inner layer is made up of arago- nite distributed in lamellae parallel to the basal plane. This lamellar arrangement о was evidenced by the reflection 2-85 А 418 P. JURBERG TABLE 1. Forms of CaCO; crystallization in Recent and fossil Turbinidae, as shown by the X-ray powder diffraction method. Arago- Calcite Е nite Species Turbo rhectogrammicus Dall Astraea of C. A, phoebia Roding Turbo marmoratus L. Turbo sp. Turbo sp. Turbo sp. Turbo sp. Geologic Pliocene Locality Authors age Florida, USA | Grandjean, Gregoire & Lutts 1964. Pleistocene? | Florida, USA | Idem. | | | Recent | Roche, Ranson & Eys- seric-Lafon 1951. | Swamy 1935. Gregoire 1957. | Lutts, Grandjean & Grégoire 1960. | Grégoire 1961. (Muller's index 002), which revealed greater intensity than did the ASTM 50453 standard reflection; the corrosion figures confirmed the lamellar structure showed by the diffraction process. Taking into account the external iridescent aspect of this layer, its structural design and the form of its CaCO, crystals, it can be considered a “ nacreous structure”, fol- lowing Böggild’s terminology. At the points of connection between 2 contiguous whorls there forms a layer of moderate thickness surrounded by the homogeneous outer layer which is reflected over it (Fig. 5). It seems to be a cement of organic origin, because it stains much more intensely than the other 2 layers with the same dyes, A section longitudinal to the columellar axis shows, near the apex of the shell, a homogeneous layer which stains less intensely than the outer layer (Fig. 6). Its material makes up the bulk of the apical whorls, and its function seems to be to reinforce the walls of those whorls. The structural design just described is the same for each layer in all parts of the shell, and may be observed whatever the angle of section through the shell. DISCUSSION Those who have studied shell structure in Recent and fossil Turbinidae have confined themselves either to the external appearance, or to the structural design, SHELL STRUCTURE OF ASTRAEA 419 or to the crystallographic arrangement of CaCO,, without considering such aspects together. Gray (1833), Carpenter (1848) and Böggild (1930) agreed that the Turbinidae possess a nacreous layer. Gray (1833) observed that the Haliotidae and Turbi- nidae have a “foliate structure”. As concerns the Turbinidae, | cannot be sure that Böggild’s (1930) foliate structure is equivalent to Grégoire’s (1957) calcio- stracum. Such a doubt arises from the fact that Böggild (1930) described 2 ana- logous structures—the foliate and the nacreous structures—the former differing from the latter in having calcite instead of aragonite (common to the nacreous structure), and in being less iridescent. Both structures show the same design, namely, superposed sinuous lines. Böggild (1930) examined Recent and Tertiary species of Turbo, stating that “the lower layer is nacreous and the upper one homogeneous and at the same time irregularly prismatic or grained ”. Grégoire et al. (1955) studied the pro- tein network in nacre and referred to the following species of Turbinidae as possess- ing a nacreous structure: Turbo canalicu- latus Gmelin. T. cidaris Gmelin, T. chry- sostomus Linné, T. tessellatus Kiener, T. setosus Gmelin, T. coronatus Gmelin, T. undulatus Martyn, Astraea unguis (Wood), A. rugosa (Linné) and A. olivacea (Wood). Table | shows the different forms under which CaCO, crystallizes in the Turbi- nidae, according to the data from several authors, in some cases without species identification. The only references to calcite in the Turbinidae are those by Lutts ef al. (1960) and Grégoire (1961), in undetermined species of Turbo. Grégoire (1961) noticed this discrepancy and tried to explain it in Böggild’s (1930) words: ‘‘calcite may occur quite unexpectedly in one or a few mem- bers of a genus otherwise consisting entirely of aragonite’. The possibility of a wrong taxonomic identification should be considered, since Lutts ef al. (1960) and Grégoire (1961) referred to the occurrence of prisms in a genus in which, according to the literature, they otherwise are lacking. CONCLUSIONS 1. The expression “* structural design” is introduced to signify the figures ob- tained by weak corrosion, a method that permits a more complete study of shell structure. 2. The shell of Astraea olfersi consists of 2 layers: an outer one, with an appa- rently homogeneous structure, and an inner one, with a typical nacreous struc- ture. The structural design of the outer layer shows a homogeneous foliate struc- ture (following Béggild’s terminology) con- sisting of aragonite and traces of calcite, without iridescence. The inner layer, as revealed by corrosion, is made up of aragonite in superposed sinuous lines, with interposed organic material. 3. Other species of Astraea and Turbo are said to be similar in structure. How- ever, the systematic value of shell structure in the Turbinidae will be settled only after examination of more specimens of dif- ferent species at different stages of development. 4. Recent and Tertiary turbinid shells are made up of aragonite, the only excep- tions being pointed out in the text. ACKNOWLEDGMENTS I am indebted to Prof. Walter da Silva Curvelo of the Museu Nacional for the encouragement he has given throughout the course of this study; to Prof. Augusto Batista of the Segao de Cristalo- grafia. Departmento de Exploragao Mineral. Comissao Nacional de Energia Nuclear, for the diffractograms and their interpretation; and to Mr. Newton de Azevedo for the photomicro- graphs, 420 P, JURBERG LITERATURE. CITED BÓGGILD, O. B., 1930, The shell structure of the moliusks. et Kongelige Danske Videnska- bernes Selskabs Skrifter, 9: 233-325. CARPENTER, W., 1848, Report on the struc- ture of shells. Part Il. Rept. 7th Meeting British Assoc. Advancement Sci., 17: 93-134. DAVIES) № Pca HOOPBR РВ 1963 lhe determination of the calcite : aragonite ratio in molluse shells by X-ray diffraction Mineral. Mag., 33: 608-612. GRANDJEAN, J., GREGOIRE, C. & LUTTS? A., 1964, On the mineral components and the remnants of the organic structures in shells of fossil molluscs. Bull. Glasse Sci., Acad. Roy. Belgique, 50: 562-595. GRAY, J. E., 1883, Some observations of mol- luscous animals and on the structure of their shells. Phil. Trans. Roy. Soc., London, Part II: 771-819. GRÉGOIRE, C., 1957, Topography of the organic components in mother-of-pearl. J. Biophys. Biochem. Cytol., 3: 797-808. GREGOIRE, G., 1961, Sur la structure sub- microscopique de la conchioline associée aux prismes des coquilles de mollusques. Bull. Inst. Roy. Sci. Nat., Belgique, 37: 1-34. GREGOIRE, C., DUCHATEAU, G. & FLOR- KIN, M., 1965, La trame protidique des nacres et des perles. Ann. Inst. Océanog., 31: 1-36. JURBERG, P. & BARTH, R., 1964, Técnicas para O estudo de estrutura de conchas de moluscos e suas possiveis ap'icaçoes. Notas Téc. Inst. Pesquisas Marinha, 17-64: 121. LUTTS, A., GRANDJEAN, J. & GREGOIRE, C., 1960, X-ray diffraction patterns from the prisms Of mollusk shell:. Arch. Intern, Physiol. Biochem., 68: 829-831. PERES, J. M., 1961, Océanographie biologique et biologie marine, 1, vii 542 р. RANSON, G., 1952, Les huitres et le calcaire. Calcaire et substratum organique chez les mollusques et autres invertébrés marins. C.R. Acad. Sci., Paris, 234: 1485-1487. ROCHE, J., RANSON, G. & EYSSERIC- LAFON, M., 1951, Sur la composition des escléroproteines des coquilles des mollusques (conchiolines). C.R. Soc. Biol., Paris, 145: 1474-1477, SWAMY RAMA, S., 1935, X-ray analysis of the structure of iridescent shell. Proc. Indian Acad. Sci., (А): 871-878. THIELE, J., 1931, Handbuch der systematischeng Weichtierkunde, vi4+-778 р. Jena. WILBUR, К. M., 1964, Shell formation and regeneration. In: Physiology of Mollusca, 1: 243-282. Eds., K. M. Wilbur & C. M. Yonge. Academic Press, New York. RÉSUMÉ LA STRUCTURE DE LA COQUILLE DE ASTRAEA OLFERSI (GASTROPODA: TURBINIDAE) P. Jurberg L'étude de 30 coquilles d'Astraea olfersi Troschel in Philippi, 1846, concernant leur agencement structural et leurs caracteres cristallographiques, montre la présence de deux couches: une externe, á structure homogene feuilletée constituée d'aragonite el de traces de calcite et une interne, á structure nacrée constituée d'aragonite seulement. Après corrosion, l’agencement structural est feuillet dans les deux couches. Une revue de la littérature montre que plusieurs especes de Turbo et d’Astraea, actuelles et du Tertiaire, possedent ce type de structure avec aragonite, SHELL STRUCTURE OF ASTRAEA RESUMEN ESTUDIO CONCHOLOGICO ESTRUCTURAL DE ASTRAEA OLFERS! TROSCHEL (GASTROPODA, TURBINIDAE) P. Jurberg El estudio de la estructura y composición cristalografica en 30 cjemplares, de la concha de Astraea olfersi Troschel in Philippi, 1846, most:6 la presencia de dos capas una externa homogenea y foliada consistente de aragonita y trozos de calcita, y otra interna, nacarífera, con aragonita solamente. Cuando corroidas, ambas capas son foliadas. Una revisión de la literatura al respecto reve!ó que varias especies del Terciario y Reciente, de Turbo y Astraea, poseen este tipo estructural de aragonita. Vode 1 ABCTPAKT СТРУКТУРА РАКОВИНЫ ASTRAEA OLFERSI (GASTROPODA: TURBINIDAE) II. ЮБЕРГ Исследование 30 раковин Asrtaea olfersi Troschel (в Philippi, 1846), касающе- еся их структуры и кристаллографического строения, показало наличие двух слоев: наружного, гомогенно-листоватой структуры, состоящего из арагони- та и следов кальцита, и внутреннего, перламутрового, состоящего только из арагонита. При коррозии строение обоих слоев становится листоватым. Просмотр литературы показал, что некоторые современные и третичные виды Turbo и Astraea обладают таким же типом арагонитовой структуры раковины. Z.A.F. 421 MALACOLOGIA, 1970, 10(2): 423-439 STUDIES ON SHELL FORMATION: MEASUREMENT OF GROWTH IN THE GASTROPOD AMPULLARIUS GLAUCUS! James A. Zischke?, Norimitsu Watabe® and Karl M. Wilburt Escuela de Biologia, Universidad Central, Caracas, Venezuela, and Department of Zoology, Duke University, Durham, North Carolina ABSTRACT Calcium deposition in various shell regions of Ampullarius glaucus was Measured Over periods of 4-24 hours using Са. The rate of calcium deposition was highest near the shell aperture (7 х 10 *mg/em?/hr) and decreased very markedly and progressively with increasing distance from the aperture within the body whorl. The calcium deposition rate decreased with increasing shell weight. The relation between linear growth rate of the mantle and calcium deposition rate by different mantle areas results in an increasing shell thickness as the whorls develop. After 10 days without food, the mean calcium deposition rate decreased 50%. In darkness, mean linear growth was reduced sharply, whereas the reduction of calcium deposition rate was not significant. The shell has a cross lamellar structure in which the crystals are made up of crystallites 500 A—600 Аш thickness. In rapidly growing snails, 36 layers may be deposited each day. INTRODUCTION Shell growth in molluscs has commonly been studied by following linear or weight changes over weeks or months (Wilbur & Owen, 1964). Other methods permit growth measurements during — shorter periods. These include fluorescent shell marking following tetracycline injection (Nakahara, 1961); incorporation of Са“? into the shell (Wilbur & Jodrey, 1952); external shell marking with later micro- scopic examination (Kenny, unpub.); and measurements of distances between daily growth lines (Choe, 1963; Clark, 1968). Two of these methods—Ca” deposition and external shell marking with micro- scopic observations—have been employed in the present study with the purpose of examining their usefulness in growth studies of very short periods in gastropods. The rate of calcium deposition occurring in several hours in the snail Ampullarius glaucus was found to be easily measurable using Ca”. This method was then used to measure the rate of calcium deposition (1) in various shell regions, (2) as a func- tion of size, (3) in the absence of food, and (4) in the absence of light. As a complement to the Ca* method, shell marking with microscopic obser- 1 Supported by grants from the Office of Naval Research, Oceanic Sciences, Nonr 1181 (06) and №00014— 67-A-0251-0004, the Ford Foundation, and Public Health Service Research Grant No. DE-01382-09 from National Institute of Dental Research, U.S.A. ? Present Address: Biology Department, St. Olaf College, Northfield, Minnesota 55057, U.S.A. 3 Present Address: Electron Microscope Laboratory, Le Conte Building, University of South Carolina, Columbia, South Carolina 29208, U.S.A. 4 Present Address: Department of Zoology, Duke University, Durham, North Carolina 27706, U.S.A, 424 ZISCHKE, vation was used to measure linear growth over short periods. With the information gained from the 2 methods, it has been possible to analyze certain aspects of calcium deposition and shell morphology as the animal increases in size. Observations of the growing shell edge with the light microscope and the scan- ning electron microscope demonstrated that Ampullarius glaucus forms shell by depositing alternating layers differing in crystal orientation. During active growth a large number of crystal layers is formed each day. MATERIALS AND METHODS Animals and maintenance Specimens of Ampullarius glaucus were collected from Laguna Campoma, appro- ximately 85 km east of Cumana, Vene- zuela. They were maintained in aquaria 52 cm x 29 cm x 27 cm containing 15 liters of aerated tap water and fed lettuce every other day. Laboratory lighting during daylight hours was natural and fluorescent illumination. There was no lighting at night except during the course of occa- sional experiments. Isotope procedures Prior to exposure to radioactive solu- tions, the animals were cleaned, dried, and coated with nail polish to prevent uptake of Ca* by the outer shell surface (Wilbur & Jodrey, 1952). They were then returned to tap water for several hours to remove all traces of solvent. Single snails were placed in 250 ml of tap water in plastic boxes 6 cm x 8 cm» 8 cm without food. Although certain plastics may have a toxic effect on snails, no evidence for this was found in the present study in snails reared in plastic boxes up to 3 months. When movements were observed to be normal, the tap water WATABE AND WILBUR was exchanged for Ca*-—tap water with an activity of 3x10% counts per minute per liter. The Са was carrier- free and thus did not appreciably increase the total calcium content of the water. The temperature throughout the experimental period ranged from 24-5° to 2 At the end of the exposure periods of 4 hours to 24 hours in Саар water, snails were removed trem the shell with forceps after cutting the columellar muscle. Pieces of shell 5 mmx5 mm were cut from various regions (Fig. |, insert) with a Dremel power tool with a steel cutting blade and washed with a stream of dis- tilled water from a wash bottle to remove adhering radioactive material. Radioactivity was measured with a gas flow counter with a window thickness of 1-5 mg/cm?. The amount of calcium deposited on the inner shell surface was calculated from the following relation (Wilbur & Jodrey, 1952): AER А» ^ D= Œ where D 15 mg/Ca deposited/cm?; Ae is counts/min/cm? of shell; Aw is counts/ min/liter medium; and C is mg Ca/liter tap water. Calcium content of the tap water ranged from 22 to 26 mg per liter during the experimental period. To estimate radioactivity due to ex- change, empty shells were exposed to radioactive solutions under the same conditions used for living animals. The values obtained for living animals were corrected for exchange in each case. Methodology relating to the use of isotopes for measuring shell growth in molluscs has been discussed previously (Wilbur & Jodrey, 1952). Starvation experiments In studies of the effects of starvation, snails were maintained as described above SHELL FORMATION but no food was given. After various periods up to 10 days the animals were exposed for 16 hours to Ca**—tap water with an activity of 3x 10% c/min/l. The rate of calcium deposition was determined near the shell aperture (Fig. I, insert, A). Light-dark experiments Individual snails were placed in Ca*-— tap water in plastic boxes without food as described under isotope procedures. Some animals were maintained in com- plete darkness. Others were exposed to constant illumination from a 40-watt incandescent lamp at a distance of appro- ximately 2 feet. Alt experiments were started between 8:00 and 9:00 a.m. At the end of a 24-hour period in Ca”, the deposition of Ca* near the shell aperture was measured. The effect of light on linear growth was studied on groups of 15 snails of similar size range placed in each of three plastic tanks containing 28 liters of aerated water. One tank was kept dark by means of black cloth. Two other tanks were each supplied with two 20-watt fluores- cent lamps, 60 cm in length, placed appro- ximately 30 cm above the water. The light intensity at water level was 1500 lux in the center, with minimum intensities of 875 and 950 lux at the edges of the two tanks. One tank was illuminated con- tinuously. The other tank was exposed to a 12-hour light—12-hour dark cycle regulated automatically. The maximum temperature variation in the three tanks was 22.3°—25.0°С. The experiments ran for 5 days and 6 days. The consumption of lettuce by each group of snails was determined by pro- viding weighed amounts of carefully blotted lettuce and reweighing the lettuce after each 24-hour period. Measurements of linear growth For measuring linear growth, the edge IN AMPULLARIUS 425 of the shell aperture was very carefully ringed with nail polish or India ink (Pelican Brand) and the snails returned to aquaria. After various intervals, a random group of snails was removed and a piece of the newly deposited shell 5 mm wide was carefully cut out with a fine- tooth triangular file. The pieces were mounted in water between a slide and coverslip and growth rings were counted using transmitted light with a stereo- microscope at magnifications of 250 and 500 diameters. Linear growth was mea- sured with compass-type calipers. Handling of the animals and addition of nail polish quite possibly retarded growth temporarily. Any initial dis- turbance of growth was minimized by maintaining the animals for growth periods of 5 to 30 days without handling. Transmission electron microscopy Pieces of shell edge were dehydrated in a series of concentrations of ethanol (3 changes, 5 minutes each in 50%, 70%, and 90%; 4 changes, 15 minutes each in 100%), rinsed in 1:1 mixture of propylene oxide and 100%, ethanol, and soaked in two changes of propylene oxide, 30 minutes each. They were left overnight in 1:1 mixture of propylene oxide and Vestopal H in a vacuum desiccator, fol- lowed by constant agitation for 2 hours in Vestopal H. They were then placed in gelatin capsules with fresh Vestopal H and left in an oven at 60°C for 2 days. Thin sections were cut with a diamond knife and observed with an Hitachi HU-11 electron microscope operated at 75 KV. Some sections were decalcified in 1% aqueous solution of uranyl acetate for the observation of organic matrix. Scanning electron microscopy Shell fragments were treated with 5:25% sodium hypochlorite for a few seconds to remove the organic covering of the shell 426 ZISCHKE, WATABE AND WILBUR Ca Deposited - mg X 10°/ cm? Shell 0 4 8 12 16 20 24 Hours т Ca” Solution FIG. 1. Calcium deposition in 3 areas of the shell of Ampullarius glaucus. Insert shows regions where measurements were made. Areas D and E are on the opposite side of the shell from A, B and C. Vertical lines represent range, horizontal lines the means, and vertical bars the standard deviations of the amounts of calcium deposited by 15 snails 20-25 mm long (from tip of spire to base of body whorl) at each time interval. SHELL FORMATION and washed in distilled water. They were mounted on specimen holders, coated with gold under vacuum, and observed with a Stereoscan Scanning Electron Microscope. RESULTS Calcium deposition The rate of shell formation as indicated by deposition of Ca was measured in normal specimens of Ampullarius near the aperture (Fig. |, insert, A) and at various distances from the aperture (B, C, D, E). The amount of deposition in regions A, B, and C after various periods of immersion in Ca is given in Fig. |, curves A, В, and C. Each horizontal bar through the curves represents the mean of 15 speci- mens. The deposition rates of two other areas, D and E (Fig. 1, insert), have also been measured, but are not included in Fig. 1. The relative rates of deposition for the 5 areas measured over 24 hours Were AMAS В--27. © 10: D=0:35 and E—0:1. The values show that the rate of calcium deposition was highest at the mantle periphery corresponding to region A and decreased markedly and progressively centrally. Calcium deposition increased linearly with time after the first 4 hours. The linear nature of curve A (area near aper- ture) demonstrated that the deposition of Ca’ reflected total calcium deposition even at the highest deposition rate. As deposition continued to increase, the radioactivity first deposited would be absorbed by overlying layers of CaCO, and the slope of the curve would be expected to decrease due to self-absorp- tion. This did not occur during a 24-hour period. The mean rate of calcium deposi- tion in the aperture region was 0-7 х 10° mg/cm?/hr. The range in individual cal- cium deposition rates was great (Fig. 1, vertical bars and lines), a finding com- 10 IN AMPULLARIUS 427 monly observed in molluscan growth studies (see, for example, Wilbur & Jodrey, 1952). Extrapolation of the curves in Fig. | toward zero time indicates a change in rate of deposition during the first 4 hours. This is not surprising since time would be required for the Ca* of the medium to come into equilibrium with the mantle. The time for mantle equilibrium in the fresh-water bivalves Anodonta lauta and Hyriopsis schlegelii has been estimated at 24 hours and 40 hours respectively (Kadc, 1960). Obviously, equilibrium is more rapid in Ampullarius. In addition to the time for calcium equilibrium, an initial disturbance of growth probably resulted from changing solutions at the beginning of the experiment. Exchange between the radioactive solu- tion and empty shell was low and amount- ed to 0:81%, of the mean deposition rate at the aperture as measured at 24 hours and 0:69%, and 0-78%, in areas В and С, respectively. Exchange in vivo may not be the same as in the case of empty shells because of differences in conditions at the crystal surfaces in the 2 situations. The extent of exchange in the living animal could be evaluated only if the composition of the extrapallial fluid in contact with the shell surface in the living animal were known, and this has not been studied. Calcium deposition rate and shell size The rate of calcium deposition (mg Ca/cm?/hr) decreased with increasing shell weight (Fig. 2). The decrease was marked as small animals grew to a medium size; and the change was less as the animals attained larger size. The total decrease in calcium deposition rate was some four-fold over the size range studied. Although the rate of calcium deposition decreases as the animal becomes larger, 428 ZISCHKE, WATABE AND WILBUR Ca Deposited-mg X 10/ cm? Shell / hr 0 1,0 2.0 4.0 5.0 6.0 Shell Weight - y FIG. 2. Rates of calcium deposition as a function of shell weight in Ampullarius glaucus. Animals were exposed to Ca** for 24 hours. Measurements were made adjacent to the outer edge of the aperture (area A, see Fig. 1, insert). the thickness of the shell increases. This was shown by measuring shell thickness in 2 areas (Fig. 1, insert, A and C). Thickness increased linearly with shell length (Fig. 3). Older snails may form thickened ridges in the shell, as shown by the points falling well above the line. Linear increase in shell thickness with size was also found in another gastropod Marisa cornuarietis (Fig. 4). In this species, thickness was measured at 6 points along the whorls and plotted as a function of the diameter at the point of measurement (see Fig. 4, insert). Calcium deposition in starved animals The rate of calcium deposition was measured in specimens of Ampullarius maintained for various periods without food (Fig. 5). After 6 days, the mean Shell SHELL FORMATION Thickness - mm 25 Snail FIG. 3. from tip of spire to base of body whorl. (area A, Fig. 1, (area C). decrease in calcium deposition rate was 10%. After 10 days starvation, the rate had decreased to 50%, of that of feeding animals. A more rapid and more marked decrease in rate with starvation has been observed in the marine snail Purpura patula (Zischke, unpub.). Shell thickness as a function of shell length in Ampullarius glaucus. Squares represent the measurements at edge of aperture insert); circles represent the measurement approximately midway around body whorl Line, drawn by inspection, shows the trend of majority of points. IN AMPULLARIUS 429 40 45 Length - mm Length is the distance Calcium deposition in light and darkness Measurements of rates of calcium depo- sition in the marine gastropod Purpura indicated decreased deposition in darkness (Zischke, unpub.). Comparable measure- ments have been carried out with Ampul- 430 Thickness - mm Shell ZISCHKE, WATABE AND WILBUR 1007 — 90 à ‚ 80 £ 9 = 70 о o 2 60 DO U 50 40 30 20 0 2 49 4 Days larius by measuring Ca*” deposition under constant illumination and darkness over a 24-hour period. The mean deposition rate in darkness was 82%, that with illu- mination. Because of the spread of values for individual animals, this difference was not significant statistically (P<0-1). The general form of the curve of deposition as afunction of time in darkness resembled Figs |, Ar Linear growth The experiments described to this point have related to shell growth as measured by calcium deposition per unit area. We now will consider shell growth in terms 6 8 10 Starved 5 SHELL FORMATION IN AMPULLARIUS 431 Growth Rate — % increment / 30 Days Shell Length - mm FIG. 6. Linear growth rate as a function of shell size. Linear growth of the shell at the aperture was measured in marked animals. Shell length was measured from the tip of the spire to the base of the body whorl. of linear increase. Linear growth was measured in snails differing in size. The growth rate de- creased with increasing size (Fig. 6). It will be seen that a snail 18 mm in length than one 35 mm in length. The variation in growth rate between individuals of similar size was considerable, as observed with calcium deposition. Linear growth rate was also studied may grow 10 or 15 times more rapidly under 3 conditions of illumination: con- a FIG. 4. Shell thickness in Marisa cornuarietis. Thirteen snails having diameters between 31 and 37 mm were each cut in two along a mid-sagittal plane. Measurements were made to the nearest 0:5 mm at the 6 points indicated in the sketch and plotted as a function of the diameter at that point. FIG. 5. Rate of calcium deposition during starvation. The rate is expressed as percentage of rate in feeding snails. Horizontal lines represent means, and vertical bars show standard deviations of the rates of calcium deposition in 15 snails 20-25 mm long (from tip of spire to base of body whorl). Animals were exposed to Ca* for 16 hours. AND WILBUR De ve nee té en < E = cl dá = Y 2 N SHELL FORMATION IN AMPULLARIUS 433 TABLE 1. Linear growth in Ampullarius glaucus under different light conditions. I II Ш | Size Exp. Conditions | Duration Range | (mm) LN APA 1 ei Г 24 hr. light 5 days | 11-0—20-0 24 hradark | 5 10:-4—17-7 12 hr. light- 12 hr. dark 5 12-0—19-3 2) 24 hr. light 6 days 11-1—20-0 24 hr. dark | 6 11-0—19-0 12 hr. light- 12 hr. dark 6 10-6—20-8 DV ER; Vile NI Mean | Food Growth Proba- Double * | Consumed (mm) bility | Bands/mm (gm) aft = een E re 2:8+1:8 | 43-4+ 7:3 0-39 < (51 1.41.7 43-3:Е 3-8 0-27 < 027 ПЕ ilies) 41:4+ 8-3 0-39 1-3+0:9 43-3+ 6:5 —- | < 0-01 0-5+0-7 34.2= 9-3 — <0-1 1-1+1-0 37:1+11-0 — * Based on growing specimens stant light, constant darkness, and a cycle of 12-hours light—12-hours darkness. The size range for the 3 groups was similar (Table 1, column III). The rate was reduced in darkness as compared with constant illumination (Table 1, column IV). The difference was statistic- ally significant in | experiment and border- line in the other (column V). Whereas 7°%, of the snails failed to grow in con- stant light and with a light-dark cycle, 28%, showed no growth in darkness. The mean food consumption was somewhat less in animals maintained in darkness (Table 1, column VII). The growth rate under the light-dark cycle was interme- diate between that in constant light and constant darkness. The difference in rate between animals on the light-dark cycle and those in darkness was not FIG. 7. Outer surface of a shell edge of Ampullarius glaucus showing light and dark bands. Photomicrograph. 160. FIG. 8. Ground section of a shell edge. The Outer layer (vertical structure in the picture) has a cross lamellar structure composed of alternating bands of crystals differing in orientation. The bands cor- respond to those shown in Fig. 7 (see also Fig. 9). Crossed nicols. Photomicrograph, 500, A portion of the second layer is seen at the bottom, 434 ZISCHKE, WATABE AND WILBUR SHELL FOMARTION statistically significant in one experiment and of border line significance in a second experiment (Table 1, column V). Band formation The shell surface at the growing edge is seen under the light microscope to be made up of alternating light and dark bands (Fig. 7). The width of the bands was similar throughout the body whorl and averaged about 12 microns, or about 40 double bands per mm, in snails of medium size. In animals less than 15 mm in length, the band width was less. The band width may remain constant with changes in linear growth (Table I, Exp. 1, column VI) or it may be altered (Table 1, Exp. 2, column VI). Ground sections and fracture surfaces showed an outer shell layer at the growing edge which was underlain proximally by a second layer (Fig. 8, bottom). The outer layer was composed of alternating bands of crystals differing in orientation (Fig. 8). The crystal bands correspond to the bands seen on the shell surface (Fig. 7). Fig. 9 shows 4 bands as seen in a fracture surface with the scanning electron microscope. In the 2 vertical bands, crystals made up of elongate units are shown. In the other bands, the fractured ends of similar crystals oriented differently and composed of smaller units are seen. Thin sections viewed in the transmission electron microscope show that the crystals consist of rows of crystal- lites 500 A—600 Á thick (Fig. 10). A crystal band 12 microns in width would comprise more than 200 rows of small IN AMPULLARIUS 435 FIG. 11. Schematic drawing of the cross lamel- lar structure in Ampullarius glaucus showing 3 bands of crystals with alternating directions of orientation. crystallites. The presence of organic matrix throughout the crystalline material was observed in decalcified sections. In summary, 3 orders of crystals are evident in the outer shell layer: large crystals which are the width of the band and arranged in cross-lamellar structure (Fig. 11); elongate units of which the large crystals are composed; and small erystallites arranged in rows. Since the crystals of alternate bands are oriented at a different angle, the difference in light refraction produces light and dark bands as seen in the light microscope. The second shell layer is also cross- lamellar in structure. In contrast to the outer layer, the bands are tapered, giving an appearance of interdigitation. The structural details of this layer have not been studied. DISCUSSION Shell formation can be viewed in terms of 2 activities of the mantle: /inear growth, which governs the increase in Shell area, and secretion, which results in both mineral and organic shell deposition. 2222 FIG. 9. Scanning electron micrograph of a vertical fracture surface of the outer layer. The 2 vertical bands are crystals made up of elongated units. In the horizontal structure, the fractured ends of crystals Oriented differently are seen. 3,500. FIG. 10. Transmission electron micrograph of a thin section of the outer layer. to the horizontal structure seen in Fig. 9, and shows rows of crystallites 500 A—600 A thick. The area corresponds x 65,000. 436 ZISCHKE, WATABE AND WILBUR Units of shell growth Linear growth and the increase in shell area in Ampullarius are represented by bands composed of crystals. The bands can be considered growth units. Whether the mantle which forms the shell growth units also grows in units, we do not know. From the rate of linear growth and the number of bands formed per millimeter, one can calculate that a rapidly growing snail forms a band about every 40 minutes on the average. The actual time required to form the band may be less than this, of course. The thickness of the individual crystal layers is quite uniform, indicating a well controlled mechanism of deposi- tion. The crystals have 2 orientations which alternate as successive bands are formed. The mechanisms which deter- mine layer thickness and crystal orienta- tion are largely unknown, although possi- ble factors have been suggested (Wilbur & Simkiss, 1968; Bevelander & Nakahara, 1969). Banding and cross lamellar structure ‚ similar to that in Ampullarius have been described by MacClintock (1967). How- ever, the crystallites of 500 A to 600 A in width which make up the crystals in Ampullarius (Fig. 10) and in bivalves (Watabe, 1965) were not detectable by MacClintock and others who have studied cross lamellar structure with optical microscopes. Shell thickness The thickness of the shell in any region _ will depend upon the rate and period that inorganic ions and organic material pass from the mantle to the site of shell deposi- tion. From the data on Ca* deposition, it is clear that the deposition rate depends upon the mantle region and the size of the animal. Shell thickness, which in- creases as the animal becomes larger, will also depend upon a third factor —therate of linear mantle growth. Each of these factors will now be considered briefly. In our discussion it will be convenient to imagine the spiral shell stretched to a straight tube whose wall thickness in- creases as it increases in length and diameter. The rate of calcium deposition was highest near the aperture and decreased progressively centrally. For shell of medium size, the difference in deposition rate within the body whorl was more than 100-fold. Because of an extremely low deposition rate in the older shell regions, the shell does not become markedly thickened, even though the time factor would favor increase in thickness. The rate of calcium deposition was found to decrease with increasing size, the decrease being 4 or 5-fold over the size range examined. While the quanti- tative relation between size and age is not known, older individuals certainly deposit calcium less efficiently than younger ani- mals (see also Wilbur & Owen, 1964). As the shell grows forward, each shell region becomes displaced centrally rela- tive to the more recently formed portions. As an animal becomes larger, any given shell region will increase in thickness at a decreasing rate both from the regional effect and the age effect. The relation between shell thickness and linear mantle growth rate can be illustrated in terms of the mantle peri- phery, which is the part most active in deposition. As the mantle grows for- ward, the total amount of calcium depo- sited will obviously depend in part upon the length of time that the mantle peri- phery covers a particular shell region. If the mantle grows forward rapidly, there will be less shell thickening at any given deposition rate than with slow forward growth. Now linear growth becomes slower as the size of the animal increases (Fig. 6), favoring an increased thickness SHELL FORMATION of shell in the aperture region. The thick ridges seen insome shells, particularly in large specimens, may indicate that the ratio of shell deposition to mantle growth rate was temporarily increased in those shell areas. In summary: 1. The decrease in calcium deposition rate with increasing size will favor a decreased shell thickness toward the aperture. The decreased linear mantle growth rate with increasing size will favor an increased shell thickness toward the aperture. The effect of these factors acting together and integrated over the age of each shell region is to increase shell thickness as the animal becomes larger. In other species the resultant of the 2 factors may be different, as in some bivalves in which shell thickness remains essentially uniform with increasing size. No Starvation Starvation reduced the calcium depo- sition rate. A possible cause may be a less active movement of calcium into the animal and through the mantle to the site of deposition. We cannot say whether a deficiency of organic material secreted by mantle occurs and also reduces the deposition of calcium carbonate. The effects of starvation on calcium movement and secretions of organic material could be determined using Са? and _ labelled compounds, respectively. Light and linear growth Linear growth was reduced in darkness as compared with continuous illumina- tion. The effect was clearcut in | experi- ment and of borderline statistical signi- ficance in another (Table 1). R. Kenny (per. comm.) observed that shell growth in the limpet Acmaea was essentially stopped in the absence of light. The IN AMPUL: ARIUS 437 somewhat decreased food consumption in Ampullarius in darkness does not appear a probable explanation. The inhibitory effect of darkness on linear growth appeared to be greater than on calcium deposition. Since the linear growth measurements were carried out over 5-6 days and calcium deposition over | day, a strict comparison cannot be made. ACKNOWLEDGEMENTS We thank Mr. Freddy Losada and Miss Julia K. Hiott for technical assistance, Mr. Rafael Martinez for aid in collecting specimens and Dr. Mary E. Rice and Dr. William Banta for preparing thin sections of shells. Dr. Ernesto Medina kindly furnished counting equipment. We are grateful to the Engis Equipment Com- pany, Morton Grove, Illinois for the use of the Stereoscan Scanning Electron Microscope and to Miss Donna Letzring for taking photographs with this instrument. LTEERATURE-CIFED BEVELANDER, G. & NAKAHARA, H., 1969, An electron microscope study of the formation of the nacreous layer in the shell of certain bivalve molluscs. Calc. Tiss. Res., 3: 84-92. CHOE, S., 1963, Daily age markings of the shell of cuttlefishes. Nature. 197: 306-307. CLARK II, G. R., 1968, Mollusk shell: daily growth lines. Science, 161: 800-802. KADO, Y., 1960, Studies on shell formation in Mollusca. J. Sci. Hiroshima Univ., Ser. B1, 19: 163-210. MacCLINTOCK, C., 1967, Shell structure of patelloid and bellerophontoid gastropods (Mollusca). Peabody Museum of Natural His- tory, Yale University, Bull., 22: 1-139. NAKAHARA, H., 1961, Determination of growth rates of nacreous layer by the administration of tetracycline. Bull. Natl. Pearl Research Lab., 6: 607-614. WATABE, N., 1965, Studies on shell formation. XI. Crystal-matrix relationships in the inner layers of mollusk shells. J. Ultrastruct. Res., 12: 351-370. WIE BUR К. М & ТОВЕУ ES Hr 1952 Studies on shell formation. I. Measurement of the rate of shell formation using Ca#%. Biol, Bull,, 103: 269-276, 438 ZISCHKE, WATABE AND WILBUR WILBUR, K. M. & OWEN, G., 1964, Growth. WILBUR, К. M. & SIMKISS, K., 1968, Calci- In: Physiology of Mollusca, 1, Wilbur, K. M. & fied Shells. In: Comprehensive Biochemistry, Yonge, C. M., Eds., Academic Press, New Eds., Florkin, M., & Stotz, E. H.. Elsevier, York, p 211-242. Amsterdam, 26(A): 229-295, RESUME ETUDES SUR LA FORMATION DE LA COQUILLE: MESURE DE LA CROISSANCE CHEZ LE GASTROPODE AMPULLARIUS GLAUCUS J. A. Zischke, N. Watabe F. Losada et K. M. Wilbur Le dépót de calcium dans divers endroits de la coquille d’Ampullarius glaucus a été mesuré sur des périodes de 4 à 24 heures, par utilisation du Са. Le taux de dépôt de calcium est le plus élevé près de l’ouverture de la coquille (7 x 10°* mg/cm?/h) et decroit progressivement et notablement depuis l'ouverture jusqu'aux tours de spires. Le taux de dépôt de calcium décroit quand le poids de la coquille augments. La relation entre le taux de croissance linéaire du manteau et le taux de dépót de calcium par différents secteurs du manteau a pour résultat une augmentation de l’Epaisseur de la coquille a mesure que les tours de spire se développent. Aprés 10 jours sans nourriture, le taux moyen de depöt de calcium décroit de 50%. Dans Pobscurité, la croissance linéaire moyenne est réduite brusquement, tandis que la réduction du taux de dépót de calcium n’est pas significative. La coquille a une structure transversale lamellaire dans laquelle les cristaux sont cons- titués de cristallites de 500 A a 600 A d’épaisseur. Chez les mollusques a croissance rapide, il peut y avoir dépót de 36 couches par jour. JN HE RESUMEN ESTUDIOS SOBRE LA FORMACION DE LA CONCHA: MEDIDAS DE CRECIMIENTO EN EL GASTROPODO AMPULLARIUS GLAUCUS J. A. Zischke, N. Watabe y K. M. Wilbur La deposición de calcio en varias regiones de la concha de Ampullarius glaucus fue medida durante períodos de 4 a 24 horas usando Ca*. La tasa de deposición de calcio fue mayor cerca de la abertura (7х 10°* mg/cm?/hr), decreciendo muy marcada у progresivamente a medida que en una determinada región de una espira del cuerpo, aumenta la distancia de la abertura. También hubo disminución de esta tasa en relación con el aumento del peso de la concha. La relación entre la tasa de crecimiento linear del manto y la tasa de deposición de calcio para diferentes areas del manto resulta en un engrosamiento de la concha a medida que la espira se desarrolla. Despues de 10 días sin alimento, la tasa de deposición de calcio decreció, 2n promedio, en un 50%. En la obscuridad, el crecimiento linear promedio se redujo marcadamente, mientras que no hubo disminución significativa en la tasa de deposición de calcio. La concha tiene una estructura laminar cruzada en la cual los cristales están formados o o de cristales muy pequeños con un grosor de 500 A—600 A. En caracoles que crecen rápidamente pueden depositarse 36 capas por día. Е. LOSADA SHELL FORMATION IN AMPULLARIUS ABCTPAKT ИССЛЕДОВАНИЕ ОБРАЗОВАНИЯ РАКОВИНЫ: ИЗМЕРЕНИЕ РОСТА РАКОВИНЫ AMPULLARIUS GLAUCUS (GASTROPODA) Дж. ЦИШКЕ, H. ВАТАБЕ и К. ВИЛЬБУР Измерялось отложение кальция в различных частях раковины Ampullarius glaucus; измерения длились в течение 4-24 часов с помощью Са’°. Скорость отложения кальция была наибольшей в области устья раковины (7x107 4mr/em /час), заметно и постепенно уменьшаясь по мере увеличения расстояния OT устья раковины к ее завиткам. Скорость отложения кальция уменьшается по мере увеличения веса раковины. Соотношение между линейной скоростью рос- та мантии и скоростью отложения кальция различными участками мантии вы- ражается в увеличении толщины раковины по мере развития ее оборотов. При отсутствии пищи в течение 10 дней, средняя величина отложения кальция падает на 50%. В темноте средний линейный прирост раковины резко умень- шается, в то время как редукция скорости отложения кальция незначитель- на. Раковина имеет поперечно-пластинчатую структуру, в которой кристаллы состоят из кристалликов 500-600А толщиной. У быстро растущих моллюсков в раковине ежедневно могут образовываться 36 слоев. Tbs IN ES 439 MALACOLOGIA, 1970, 10(2): 441-449 THE FUNCTION OF THE ODOUR OF THE GARLIC SNAIL OXYCHILUS ALLIARIUS (PULMONATA: ZONITIDAE) DEC+Eloyd Department of Zoology, University College of North Wales Bangor, U.K.! ABSTRACT The pungent garlic odour of Oxychilus alliarius has been investigated. It had been presumed by previous authors to be a defensive adaptation. The possibilities of a sex attractant or antibiotic have been shown to be very unlikely. An experiment with hedgehogs as predators showed that the garlic snail was statistically significantly rejected, the 3 other British species of Oxychilus being favoured. INTRODUCTION The garlic snail Oxychilus alliarius (Miller) is characterised, as its name suggests, by the production of a pungent odour indistinguishable from that of garlic. This feature has been noted many times by naturalists; for example Macgillivray (1843) states that the odour from a very small specimen is so strong that it may be noted from a distance of several feet. The snail emits the odour on irritation throughout the year. There appears to be no particular season for its production, nor any time of increased pungency. The odour is even produced in newly hatched animals. Some authors (Step, 1945; Rimmer, 1880; Taylor, 1914) state that the posses- sion of a garlic odour is not characteristic of O. alliarius, but is also found in related species. It is possible that this is a result of misidentification, as there has been considerable confusion in the identifica- tion and taxonomy of these very similar snails. Recent authors (Janus, 1965; Frömming, 1954) attribute the garlic odour only to O. alliarius and I am in complete agreement with this. Garlic odour is recorded from 1 other group in the Animal Kingdom. Perkins (1919) notes that 3 species of solitary bees produce such an odour, but no work appears to have been done on it. Much work has in contrast been performed on the various odours and extracts from the genus Allium, especially those from garlic and onion. These plants have well docu- mented antibiotic properties which are linked, in part, to volatile tissue com- ponents (Hatfield, Walker & Owen, 1948). Fischer (1948) has suggested that the slime from some snails is antiseptic, and Campion (1961) performed experiments to see whether this is so in Helix aspersa. She obtained clearly negative results. An antibiotic has been shown to be secreted by the stomach and salivary glands of O. cellarius by Tercafs (1960), working with a cavernicolus population which catches and preys upon Lepidoptera. 1 Present Address: Department of Zoology and Comparative Anatomy, University College, Cardiff, U.K. 442 D.C BEOND The function of the antibiotic here is to prevent fungal and bacterial decomposi- tion of half-eaten prey. In this laboratory it was noted that the appearance of the odour was coincidental with the production of a characteristic viscous, brown mucus from the mantle region. On separation from the snail this mucus continued to emit the garlic odour for several hours. Step (1945) concluded that the odour of Oxychilus alliarius is most probably a defensive secretion as it is only produced on irrita- tion of the snail. Urbanski (1937) sug- gests that it may well be a defense mecha- nism against the predatory O. draparnaldi, although Frómming (1954) criticises this, saying that O. draparnaldi does not prey on O. alliarius but rather on O. cellarius. Taylor (1914) notes that O. alliarius is the only mollusc to be found alive in the vicinity of wood ants’ nests. Peculiar odours and distasteful secre- tions arefound in many species of molluscs. Kjerschow-Agersborg (1921) has described the odour of Melibe leonina as being like that of oil of bergamont and he presumed it to have a defensive function. André (1900) noted that the North African snail Hyalinia (—Oxychilus) cheliella, produced a very strong characteristic odour on irritation. the caterpillar of Cossus ligniperda. Thempson (1959, 1960a, b) has shown that the acidic defensive secretions of a number of marine opisthobranchs cause them to be distasteful to fish, and Edmunds (1968) has described similar secretions in several species of Doridacea. Binot (1965) has worked on the histology and histo- chemistry of repugnatory glands in Onci- diella celtica, and Renault (1966) has described a defensive gland in the mantle of Cassidula labrella. Experiments to determine the possible sex-attractant, anti- biotic or defensive function of the odour of Oxychilus alliarius are described in the present paper. He likened it to the odour of MATERIALS AND METHODS Sex Attraction A semi-circular, air-tight, wooden box (90 x 45 6 cm) with a glass lid was lined with moist filter paper. Air was extracted from the centre of the base of the box by a vacuum pump. Air was allowed to enter at 5 points on the circumference (Fig. 1). The sucked-in air first had to pass through the small chambe:s (a) before entering the main box (р). In 1 of these chambers, chosen at random, 10 stimulated snails were placed so that the draught picked up the garlic odour. in the main body of the box were placed 100 snails, and the air current was maintained for 5-6 hours. The experiment was repeated several times, each with fresh snails, in both day- light and total darkness. The air current was also varied by altering the strength of the vacuum pump. Anttbiotic Experiments with mucus were per- formed similar to those described by Cam- pion (1961) on Helix aspersa. Mucus was taken from O. alliarius and also from O. cellarius. The latter does not produce a garlic odour and was used as a control. Sterile Petri dishes’ of nutrient agar (Oxoid) were streaked with slime as follows: (a) O. alliarius mucus; (b) O. cellarius mucus; (c) Mucus from both species. An identical series was streaked and then innoculated with Neurospora, and finally a third series was streaked onto plates already carpeted with Neurospora. All plates were incubated at 28° C for 3-4 days. Defense A laboratory experiment was performed to ascertain whether hedgehogs (Erinaceus europaeus), when feeding, exhibited any GARLIC SNAIL ODOUR: FUNCTION air in Y DS ST {/ {/ Y Y y L/ 7 [/ y [/ a 8 L Н И Й H 0 Y O N 4 air out © 443 y pe р ù a N O SE N N N À b N à \ Y O Y Y , у $ $ Ô К) ‘ A 4 # A 4 i (SRS SSeS SSS SSS ооо ооо ОО О ЧЕ ЗЧ ЧЕ ЧЕ ЧЕ ЧЕ < О < оч BEL AAA EIGEN: b=main box. discrimination between the 4 British Oxychilus species. An enclosure of approximately 30 sq. feet was erected in the laboratory and on the floor were fixed 16 plastic Petri dishes arranged in 4 rows of 4. One snail was placed in each dish, 4 specimens of each species being used in each test. To over- come the possibility that the hedgehogs might learn the distribution of the snail species, the positions of the various species were frequently altered during the course of the experiment. In order to randomise the snails’ distributions the 4 rows of 4 latin square patterns of Fisher & Yates (1953) were adopted. The observations, 15 in all, were carried out on 4 successive nights, using 3 hedge- hogs which had been previously exercised for 2-3 hours. The feeding hedgehogs were filmed by time lapse ciné-photo- II Apparatus to test for the possible attractive function of the garlic odour. a=small chambers; graphy. By using a wide aperture it was possible to photograph with flashlights at half-strength. It soon became apparent that the flashes did not affect the hedge- hogs; they continued walking and eating uninterrupted. The photographs were taken at 15 second intervals over a period of 15 minutes. At the end of the experi- ment the remaining snails were noted. The developed film was viewed through a microscope and the positions of the hedgehogs every 15 seconds was noted. RESULTS Sex Attraction The positions of the 100 unstimulated snails at the end of each run was noted. It was found that on each occasion they were randomly distributed all over the DAC ILEOYD 444 "ззиэциазахо ay) Jo (X ST) UONLITTANP ay} JO MALA ur JUEOUIUSISUI IQ оз PALAPISUOI SI рээпроци! 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O. alliarius | O. helveticus | О. cellarius | O. draparnaldi | Total Observed 16 50 Expected (total/4) | 37 37 OLE 2] | 13 | | (O—E)? | 441 | i69 | (O—E)? | ——- ÉD "4557 E moistened floor of the box. Some ap- peared to have moved only about 5 cm or less, whilst others had wandered to the circumference of the box. However, no obvious migration towards the source of odour was observed. Antibiotic In all cases a negative result was obtained, and no distinction could be observed between the effects of the slime from the 2 species. In the first set of plates bacterial colonies developed, pre- sumably derived from the bacteria already present in the snails’ slime. In the second and third series no inhibition of germina- tion or of growth of the fungus was observed. Defense It was first decided to perform a simple X? test on the total of each species taken during the entire experiment (Table 1). The null hypothesis assumed was that there was no difference in the predation on the 4 snail species. The results of this analysis are shown in Table 2. In the tables of the distribution of X? (Fisher & Yates, 1953) with 3 degrees of freedom X?=16.266 at a probability of p=0.001. In the above experiment the 39 43 148 | 37 37 148 Pets 6 4 36 - 571 ОО O OT az: calculated Х2==17.571. "This means that if all the species were equally preferred (null hypothesis) one could expect such a large deviation of the observed from the expected ш less. than 01% оЁ cases: Therefore there is quite clearly a signi- ficant difference between the 4 species, and the greatest contribution (11.92) to this comes from O. alliarius. A “t” test was then performed on the numbers taken per visit for each species. Comparing pairs of species: alliarius with helveticus ROS alliarius with cellarius > alliarius with draparnaldi “Е”= 5.17 cellarius with helveticus TE al 0G6 helveticus with draparnaldi “t"— 1.42 cellarius with draparnaldi “1”= 1.70 In the tables of the distribution of “tt” (Fisher & Yates, 1953) with 28 degrees of freedom (2n-2), “t”=3.674 at a proba- bility of p=0.001. In the comparisons between the non-odourous species the calculated “*t”” is less than the tabular “Е”, whilst comparing the garlic snail with the others in each case the calculated ite exceeds themtabular 7 t = Thereiere at the 0.1% level there is no significant difference between the means of the non- odourous species, whilst the mean value obtained for O. alliarius differs signi- ficantly from the others and this difference 446 DP ese LOYD cannot be accounted for by random chance. The conclusion is that there is a definite rejection of O. alliarius in favour of the other species. DISCUSSION Odourous pheromones are sometimes used in the Animal Kingdom as a means of sexual attraction. Thus it was neces- sary to perform an experiment to see whether this might be the function of the garlic snail odour. There is no clearly defined breeding season in this snail. Rigby (1963) states that the breeding time in O. cellarius is from January to August, and whilst no record has been found in the literature, personal observa- tion in the field indicates a similar dura- tion in the case of O. alliarius. These experiments were performed in the early springtime. The results tend to disprove an attrac- tant function for the garlic odour, al- though they do not rule out an aphrodisiac function acting when the snails are in contact. There are a number of reasons why both of these possibilities are un- likely. Firstly, the odour is produced all the year round, and there appears to be no correlation with any breeding cycle. The odour is only emitted on irritation of the snail, and whilst this would not rule out contact attraction, it would certainly argue against attraction from a distance. Finally the odour is produced even by the very newly hatched snails well before they have reached sexual maturity. The negative results for the antibiotic experiment confirm those obtained by Campion (1961) for Helix aspersa. Cam- pion in fact obtained increased growth of microorganisms on and around the slime. She suggested 3 possible explana- tions; the stickiness of the mucus retained spores settling on it, or the mucus offered extra nutrients to the microorganisms, or thirdly there was the possibility of growth- promoting substances in the mucus. The general conclusions that may be drawn from the preceding experiments are that the odour does not seem to be a sex attractant, nor is it concerned with antibiotic activity, but that it seems most probably to be a defensive adaptation. This confirms the subjective opinions of several previous authors (Taylor, 1914; Urbanski, 1937: Step, 1945). The predators of terrestrial snails such as the oxychilids are quite numerous. The major predators are probably other molluscs, various insects, such as glow worm larvae and carabid beetles, birds and small mammals. When the possible defensive function of the garlic snails’ odour was considered it seemed that small mammals would be the best subjects for experiment. They are predators which hunt, partly at least, by sense of smell. Hedgehogs were chosen as experimental subjects, chiefly because they are probably the easiest of the available small mammals to keep in captivity, and most amenable to the rigours of laboratory experiments. Dimelow (1963a. b) has described the best way to keep hedgehogs in captivity, and has also determined their food pre- ferences within a large range of common invertebrates. She found that whilst they ate most of the animals which she off- ered, they consistently selected some species. Dimelow (1963b) and previous workers (Brockie, 1959, Rothschild, 1961) have shown that hedgehogs are affected considerably by odours emitted by their prey. The odours either repel the hedge- hogs, as in the case of the ladybird, Adalia, (Rothschild, 1961), or aid the hedgehog in finding prey such as certain millipedes (Brockie, 1959). Brockie even found that hedgehogs persistently nosed leaves which had been partly eaten by odourous milli- pedes since removed. With molluscs Dimelow (1963b) found that copious slime GARLIC SNAIL ODOUR: FUNCTION 447 did not deter hedgehogs from readily eating the slugs Milax budapestensis and Arion hortensis. They tended to reject Arion ater, A. fasciatus and A. subfuscus, a possible deterrent here being the tough skin, and the thick-shelled snails Helix sp.. Cepaea sp., Discus rotundatus, Pomatias elegans and Hygromia striolata. With oxy- chilids Dimelow (1963b) found that O. draparnaldi was most strongly preferred, although she notes that O. alliarius was also taken despite its garlic odour. In the filmed tests with hedgehogs, Oxychilus alliarius was also taken, but the statistical analysis shows that it was the least favoured. The “t” tests, however, show no significant difference between the remaining 3 species. Dimelow (1963b) mentions that the relative sizes of the prey may play a part in determining the hedgehogs’ preference. This was allowed for in the present experiment by using half-grown specimens of the non-odourous species which were more or less equal in size to the adult garlic snails. This experiment was limited in that hedgehogs were the only snail predators used. Most certainly there are many more common predators of oxychilids, and it is expected that experiments with some of these would confirm the defensive advantage of Oxychilus alliarius odour. Previous authors have remarked upon the degree of immunity from attack which O. alliarius seems to possess against certain predators, e.g., wood ants (Taylor, 1914), and О. draparnaldi (Urbanski, 1937, Frómming, 1954). Experiments with these 2 predators would be a useful extension of the hedgehog experiment. Unfortunately very little is known of the general ecology of oxychilids. Often one finds within a local woodland a small area dominated by just I or 2 of the species, whilst other species dominate adjacent areas. Alternatively one may find all 4 species in seemingly equal numbers within the same area, even under the same stone or log. This creates an anomalous situation when the marked defensive advantage which Oxychilus alliarius seems to possess over the other species in laboratory experiments is con- sidered. The predator/prey relationships are obviously very complex, and an ecolo- logical investigation of them would be of considerable value. ACKNOWLEDGEMENTS I gratefully acknowledge the considerable aid and criticism of Dr. N. W. Runham, who intro- duced me to this group. I am indebted to Professor F. W. Rogers Brambell, C.B.E., SC.D, F.R.S., in whose department the study was carried Out. Ihave been in tenure of an S.R.C. Research Studentship grant. LITERATURE CITED ANDRÉ, E., 1900, Organes de défense tégumen- taires des Hyalinia. Rev. suisse Zool., 8: 425-433. BINOT, D., 1965, Histologie, histochemie, cyto- logie de quelques formations glandulaires d’ Onchidiella celtica (Cuv.) (Gastéropode, Pulmoné). Cah. Biol. mar., 6: 325-346. BROCKIE. R. E., 1959. Observations on tke food of the hedgehog (Erinaceus europaeus L.) in New Zealand. New Zealand J. Sci., 2: 121. CAMPION. M., 1961, The structure and func- tion of the cutaneous glands in Helix aspersa. Quart. J. micros. Sci., 102(2): 195-216. DIMELOW, E. J., 1963a, The behaviour of the hedgehog (Erinaceus europaeus L.) in the routine of life in captivity. Proc. zool. Soc. London, 141(2): 281-289. DIMELOW, E. J., 1963b, Observations on the feeding of the hedgehog (Erinaceus europaeus L.) Proc. zool. Soc. London, 1412): 291-309. EDMUNDS, M., 1968, Acid secretion in some species of Doridacea (Mollusca, Nudibranchia). Proc. malac. Soc. London, 38: 121-133. FISCHER, P. H., 1948, Données sur la résitance et la vitalité des mollusques. J. Conchyliol, 88: 100. FISHER, R. A. & YATES, F., 1953, Statistical Tables. Oliver and Boyd, London. 126 p. FROMMING, E., 1954, Biologie der Mitteleuro- päischen Landgastropoden. Duncker and Hum- blot, Berlin. 404 p. 448 р. С. HATFIELD, У. C., WALKER, J. С. & OWEN, J. H., 1948, Antibiotic substances in onion in relation to disease resistance. J. agric. Res., 77(4): 115-135. JANUS, H., 1965, Molluscs. Burke, London. 180 p. KJERSCHOW-AGERSBORG, H. P. von W., 1921, Contribution to the knowledge of the nudibranch mollusk Melibe leonina (Gould). Amer. Nat., 55: 222-253. MACGILLIVRAY, W., 1843, A history of the molluscous animals of the counties of Aberdeen, Kincardine and Banff. Cunningham and Mor- timer, London. 372 p. PERKINGS, R. C. L., 1919, The British species of Andrena and Nomada. Trans. R. ent. Soc. London, 1919: 218-317. RENAULT, L., 1966, Existance d'une glande intrapalléale et d'une branchie anale chez Cassidula labrella (Deshayes). С.К. Acad. Sci., Paris, 262, D: 2243-2254, RIGBY, J. E., 1963, Alimentary and reproductive systems of Oxychilus cellarius (Muller) (Stylom- matophora). Proc. zool. Soc. London, 141(2): 311-359. LLOYD RIMMER, R., 1880, Land and freshwater snails of the British Isles. Bogue, London. 208 p. ROTHSCHILD, M., 1961, Defensive odours and müllerian mimicry among insects. Trans. R. ent. Soc. London., 113: 101. STEP, E., 1945, Shell Life—An introduction to the British Mollusca. Warne, London. 443 p. TAYLOR, J. W., 1914, Monograph of the land and freshwater Mollusca of the British Isles. Vol. 3 (Zonitidae, Endodontidae and Helicidae). Taylor, Leeds. 522 p. TERCAFS, В. R., 1960, Oxychilus cellarius MI, un mollusque cavernicole se nourissant de lépidopterea vivants. Rassegna Speleol. Ital., 4: 191-201. THOMPSON, T. E., 1959, Defensive acid-secre- tion in some marine gastropods. Nature, London, 184: 1162. THOMPSON, T. E., 1960a, Defensive acid-secre- tion in marine gastropods. J. Mar. biol. Assoc. U.K., 39: 115-122, THOMPSON, T. E., 1960b, Defensive adapta- tions in opisthobranchs. /bid., 39: 123-134. URBANSKI, J., 1937, Bemerkenswerte Weich- tierfunde aus Polen. Fragm. faun. Zool. Pol., 3: 11220; RÉSUMÉ LA FONCTION DE L’ODEUR D’AIL DU GASTROPODE OXYCHILUS ALLIARIUS (MILLER) (PULMONATA: ZONITIDAE) D.C. Lloyd La violente odeur d’ail de l'Oxychilus alliarius a été analysée. Des auteurs précédents avaient présumé de son adaptation à la défense. On a montré qu'il n’était pas possible de la considérer comme ayant un rôle d’attirance sexuelle ou d’antibiotique. Une expérience avec des hérissons comme prédateurs a montré que les mollusques à odeur d’ail étaient statistiquement significativement rejetés; les trois autres espéces britanniques d'Oxychilus étant préférées. А. E. RESUMEN LA FUNCION ODORIFERA EN EL CARACOL DE AJO OXYCHILLUS ALLIARIUS (MULLER) (PULMONATA: ZONITIDAE) D.C. Lloyd El pungente olor a ajo de Oxychillus alliarius, habia sido indicado por previos autores como una adaptación defensiva. La investigación demuestra que las posibilidades de que sea un atractivo sexual о antibiotico son muy remotas. Experimentos hechos con el predator puercoespin resultaron en el rechazo, estadisticamente significante, de los caracoles: otras especies britanicas de Oxychillus fueron acceptadas por el animal. UI a GARLIC SNAIL ODOUR: FUNCTION 449 ABCTPAKT ФУНКЦИЯ ЗАПАХА Y ЧЕСНОЧНОЙ УЛИТКИ OXYCHILUS ALLIARIUS (MILLER), (PULMONATA: ZONITIDAE) I. К. ЛЛОЙЛ Был исследован острый чесночный запах y улитки Oxychilus alliarius. Рабо- ты ряда прежних авторов показали, что этот запах представляет собой за- щитную адаптацию моллюска. Возможность привлечения моллюсков другого по- ла или наличие антибиотиков кажутся маловероятными. Эксперименты с ежа- ми, как хишниками, статистически показали, что чесночные улитки ими обычно отбрасываются, три же других вида Oxychilus предпочитаются. И.А. Ш. MALACOLOGIA, 1970, 10(2): 451-455 THE COMPOSITION OF THE ODOUR OF THE GARLIC SNAIL OXYCHILUS ALLIARIUS (PULMONATA: ZONITIDAE) D. C. Lloyd Zoology Department, University College of North Wales Bangor, U.K.) ABSTRACT Direct injection into a gas liquid chromatograph shows that the principal volatile compound produced by Oxychilus alliarius (Miller), on irritation, is n-propyl mercaptan. This is probably responsible for the pungent garlic-like odour peculiar to this species. INTRODUCTION The garlic-like odour produced by Oxychilus alliarius when it is irritated is a marked feature of this snail. It has been shown that it is a defense mechanism (Lloyd, 1970), and originates from a small group of cells in the mantle close to the pneumostome. The obvious point at which to begin an attempt at identifying a garlic-like odour is to look at what causes the odour of the garlic and onion plants. The chemistry of the odourous compounds from Allium spp. has been studied in considerable detail (Jones & Mann, 1963). Garlic, Allium sativum, contains an odour- less water soluble amino acid called alliin which is acted upon, on injury, by the enzyme allinase to yield allicin, the cha- racteristic, sulphur containing, antibac- terial, odourous compound of freshly crushed garlic tissue. This is however unstable and breaks down to yield the odourous constituents of garlic oil. Whilst garlic oil contains mainly allyl sulphur compounds, onion oil, Allium cepa, yields methyl and propyl compounds, and this probably explains the difference in aroma and flavour between garlic and onion. Semmler (1892) reported that onion oil consisted mainly of allyl-n-propyl disul- phide, and this finding was accepted for many years. In 1949 Challenger & Green- wood demonstrated n-propyl mercaptan, and Niegisch & Stahl (1956) using mass spectrometry also identified n-propyl mer- captan and a trace of n-propyl disulphide. No allylic disulphides were demonstrated. Carson & Wong (1961) have analysed the volatile components of onions by gas chromatography. They tried 2 methods of isolation; carbon adsorption followed by Soxhlet extraction in ether, and iso- pentane extraction of steam distillates. Their work yielded a variety of volatile constituents including several methyl and propyl disulphides, trisulphides and mer- captans. Thus it seems clear that in Allium spp. the characteristic odours are the result of the liberation, especially on injury, of a variety of volatile sulphur derivities of the lower alcohols. It is most likely that similar chemicals are concerned in the odour of Oxychilus alliarius. There are a few records in the literature of similar volatile sulphur compounds Present Address: Department of Zoology and Comparative Anatomy, University College, Cardiff, U.K. 452 DICH LLOYD occurring in animals. The odour of the North American skunks consists princi- pally of butyl mercaptan (Blackburn & Challenger, 1938). Ronald & Thomson (1964) identified dimethyl sulphide as being responsible for the odour of fresh Pacific oysters Crassostrea gigas. Here it is possible that the odour is the result of bacterial action. Bacterial decompo- sition of these oysters certainly results in an increase of dimethyl sulphide and also the production of a variety of other vola- tile sulphur compounds. Motohiro (1962) has shown that the “ petroleum odour” of tinned Pacific chum salmon is mainly dimethyl sulphide liberated on cooking from dimethyl-8-propiothetin (DMPT). This compound has been traced through the food chain. It is first found in the phytoplankton (Ackman, Tocher € Mc- Lachlan, 1966). DMPT appears in abnormally high concentrations in the pteropod Limacina helicina, which is the principal food of the salmon at the time of year when the petroleum odour is noticed. Dimethyl sulphide is also respon- sible for the ** blackberry ” problem in the atlantic salmon (Sipos & Ackman, 1964), although the links in the food chain are unknown. DMPT has also been found in penguins’ stomachs, derived from krill, which in turn grazes on the phytoplankton. The purpose of this paper is to identify the chemical(s) responsible for the very interesting defensive odour of the garlic snail. MATERIALS AND METHODS 1. Grote test for disulphide and sulphy- dryl compounds (Walsh & Merritt, 1960). Adult snails were obtained from wood- land in the Bangor (Caern., U.K.) area. Air was passed over 100 snails stimulated by agitation of their container, and bub- bled through a mixture of 10 drops of 95%, ethanol plus 2 drops of a mixture of 5%, potassium cyanide and 1%, sodium hydroxide. Then 5 drops of 1% sodium nitroprusside were added and any colour change noted. 2. Carbon adsorption. Air was passed over 100 stimulated snails and through a tube of activated charcoal. This was then Soxhlet ex- tracted with diethyl ether for several hours. The solvent was then gently evaporated in a warm water bath down to about | ml, and an aliquot injected into a gas liquid chromatography column. 3. Gas liquid chromatography. Nitrogen was passed over about 50 snails. They were stimulated by repeated agitation of their container and the vola- tiles which they produced were condensed ina liquid nitrogen trap. After one hour’s collection the contents of the trap were introduced into a Pye series 104 gas chromatograph via a Pye gas sampling valve. The carrier gas was nitrogen, flowing at a rate of 40 ml per minute. Five foot columns packed with 10%, polyethylene glycol adipate adsorbed onto 60-80 celite were used. The separations were carried out at 80°C, and the frac- tions detected by hydrogen flame ioniza- tion. Some difficulty was encountered with the gas sampling valve. On allowing the volatiles to warm up preparatory to injection into the carrier gas stream there was an increase in pressure in the collect- ing coil so that when the valve to the column was opened the detector flame was snuffed out. Thus it became neces- sary to add to the sampling valve a second collecting tube which remained uncooled and took up most of this increased pressure. Glass and stainless steel apparatus was used throughout in the collecting and injection system. On the completion of each run the system was flushed with GARLIC SNAIL ODOUR: FUNCTION 453 nitrogen for an hour and then a blank collection was made, 1.e., with nothing in the snail chamber. Only when this col- lection resulted in a blank record from the chromatograph was the next experi- mental run performed. Reference chro- matograms were also produced under the same conditions with as many alkyl sulphides, disulphides and mercaptans as were commercially available. Finally for confirmation the nitrogen stream from the snail chamber was bubbled through a trap containing either mercuric chloride or mercuric cyanide solutions before being condensed in the liquid nitrogen trap. Identical runs were performed with 3 other species of Oxychilus which are non-odourous. RESULTS AND DISCUSSION The Grote test, although it is sensitive to 50 ug of these compounds, did not show the red colour indicating disulphide and sulphydryl compounds. This would suggest that any such compounds, if present, occur in minute quantities. Skunk odour, butyl mercaptan, is detectable by man down to a concentration of | part in 100. This perhaps gives some indica- tion of the sensitivity of mammals to these sulphurous compounds and may explain why the apparently pungent odour from Oxychilus alliarius was nevertheless not detected by this fairly sensitive Grote test. The carbon adsorption and solvent extraction also yielded nothing. Carson & Wong (1961) needed about 140 pounds of onions to produce 8-7 gm. of distillate of onion oil, representing 75 parts per million of the fresh weight. Probably therefore any attempt to concentrate such com- pounds from Oxychilus alliarius odour after solvent extraction would result in the loss of the majority of these volatile compounds if they were only present in minute amounts. Further attempts at solvent extraction methods were therefore abandoned. It was decided that only by direct injection into a highly sensitive instrument such as a gas liquid chro- matograph would it be possible to demon- strate the presence of specific components in the odour. Fig. 1 shows the traces obtained from this investigation. Chro- matograms of O. alliarius odour are characterised by a large peak which has a short retention time. The time cor- responds to that of n-propyl mercaptan. This peak is absent from chromatograms obtained from the other 3 species. There were several smaller peaks obtained whose retention times did not correspond with any of the available reference compounds. Whether these in fact contain sulphur groups could only be demonstrated for certain by mass spectrometry. И is quite clear that the major peak obtained from O. alliarius 1$ n-propyl mercaptan and that any other volatiles present are in very small amounts. Folkard & Joyce (1963) have shown that if disulphides are passed through 3% aqueous mercuric chloride solution they form complexes whilst mercaptans are unaffected, and vice versa with 4% aqueous mercuric cyanide. Prior passage of the Oxychilus alliarius vapour through these solutions showed that mercuric cyanide removed the main peak whilst mercuric chloride did not. This is con- firmation that the peak is mercaptan. Challenger (1959) gives the following formula for the complex produced when propyl mercaptan is passed through mercuric cyanide: Hs (CNA ECH: CH, CES Hg (S - CH, : CH, : CH) „+2HCN (mercury di-thio-n-propoxide) All the peaks from extracts of non- garlic species of Oxychilus, plus the minor peaks in O. alliarius, were removed in both the cyanide and chloride solutions; this would suggest that they are neither disulphides nor mercaptans. 454 DC: ACKNOWLEDGEMENTS The author wishes to thank Dr. N. W. Runham for considerable advice and criticism, and Dr. J. Turvey for his patient aid and advice in the gas chromatographic work. Acknowledgement is also due to Professor F. W. Rogers Brambell, C.B.E., SC.D., F.R.S., in whose department part of the study was carried out. The work was sup- ported by an S.R.C. Research Studentship grant. EITERATUREZCITED ACKMAN,R. G., TOCHER, C.S. & McLACH- LAN, J., 1966, Occurrance of dimethyl-B-pro- piothetin in marine phytoplankton. J. Fish. Res. Board Canada, 23(3): 357-364. BLACKBURN. 5. & CHALLENGER, F., 1938, The formation of organometalloidal and similar compounds by micro-organisms. J. Chem. Soc., 2: 1872-1878. CARSON, J. F. & WONG, F. F., 1961, The volatile flavour components of onions. J. agric. Fd. Chem., 9(2): 140-143. CHALLENGER, F., 1959, Aspects of the organic chemistry of sulfur. Butterworths, London. 253°): CHALLENGER, F. & GREENWOOD, D., 1949, Sulphur compounds of the genus Allium. Biochem. J., 44: 87-91. FLOYD FOLKARD, A. R. & JOYCE, A. E., 1963, The collection and identification of thiols and disulphides. J. Sci. Fd. Agric., 14(7): 510-514. JONES, Н.А. & MANN, Г. К. , 1963, Onions and their allies. Interscience, New York. 286 p. LLOYD, D. C., 1970, The function of the odour of the garlic snail Oxychilus alliarius. Mala- cologia, 10: 441-449. MOTOHIRO, T., 1962, Studies on the petroleum odour in canned chum salmon. Mem. Fac. Fish. Hokkaido Univ. 10(1): 1-65. NIEGISCH, W. D. & STAHL, W. H., 1956, The onion: gaseous emanation products. Fd. Res., 21: 657-665. RONALD, A. R. & THOMSON, W. A. B., 1964, The volatile sulphur compounds of oysters. J. Fish. Res. Board Can., 21(6): 1481-1487. SEMMLER, F. W., 1892, Uber das atherische Ol des Knoblauches (Allium sativium). Arch. Pharm. Berl., 230(6): 434-443. SIPOS, J. C. & ACKMAN, R. G., 1964, Asso- ciation of dimethyl sulphide with the ‘ black- berry ” problem in cod from the Labrador area. J. Fish. Res. Board Canada, 21(2): 423-425, WALSH, J. T. & MERRITT, C., 1960, Qualita- tive functional group analysis of gas chro- matographic effluents. Anal. Chem., 32: 1378—1381. RESUME LA COMPOSITION CHIMIQUE DE L’ODEUR D’AIL DU MOLLUSQUE OXYCHILUS ALLIARIUS (MILLER) (PULMONATA: ZONITIDAE) Ю.С; Lloyd Par la méthode de chromatographie en phase gazeuse On a montré que le principal produit volatile émis par Oxychilus alliarius, en état @ irritation, est le n-propyl mer- captan. C’est probablement lui qui est responsable de la violente odeur d’ail particuliére a cette espece. А. E. RESUMEN LA COMPOSICIÓN DEL OLOR DEL “CARACOL DEL AJO ” OXYCHILUS ALLIARIUS (MILLER), (PULMONATA: ZONITIDAE) D. C. Lloyd La principal esencia volátil producida por Oxychilus alliarius, cuando es irritado, es n-propyl mercaptan. A esto probablemente se debe el penetrante olor a ajo peculiar de esta especie. ERP GARLIC SNAIL ODOUR: FUNCTION 455 ABCTPAKT СОСТАВ ЗАПАХА Y ЧЕСНОЧНОЙ УЛИТКИ OXYCHILUS ALLIARIUS (MILLER), (PULMONATA: ZONITIDAE) A. К. ЛЛОЙЛ Прямая инъекция в газово-жидкостной хромотограф показала, что главное летучее вещество, продуцирующееся при раздражении Oxychilus alliarius, явля- ется п-пропилмеркаптаном. Возможно, он дает тот острый запах, столь Xa- рактерный для этого вида моллюска. ИА: Е. 70 70 70 60 60 ь 60 О. draparnaldi О. helveticus О. cellarius 50 50 40 Lao 30 130 20 20 10 10 у 30 20 10 20) 10 20 10 90 90 90 0: eye . cellarius 80 80 80 O. draparnaldi 20 HgClo trap 70 70 70 60 60 60 205110 propyl 50 O. alliarius 50 O. alliarius 50 O. alliarius mercaptan HgClg trap O. cellarius O. draparnaldi 40 40 40 O. helveticus 20 Hg(CN), trap 30 30 30 20 20 20 10 10 10 y у 20 10 30 20 10 20 10 FIG. 1. Gas liquid chromatographs of n-propyl mercaptan and Oxychilus spp. volatiles, injected directly, and also after having been passed through mercuric chloride or cyanide traps. The injec- tion point is marked by an arrow. 454 DE: ACKNOWLEDGEMENTS The author wishes to thank Dr. N. W. Runham for considerable advice and criticism, and Dr. J. Turvey for his patient aid and advice in the gas chromatographic work. Acknowledgement 1$ also due to Professor F. W. Rogers Brambell, C.B.E., SC.D., F.R.S., in whose department part of the study was carried Out. The work was sup- ported by an S.R.C. Research Studentship grant. ETTERATURE*CITED ACKMAN, К. G., ТОСНЕК, С. 5. & McLACH- LEOYD FOLKARD, A. R. & JOYCE, A. E., 1963, The collection and identification of thiols and disulphides. J. Sci. Fd. Agric., 14(7): 510-514. JONES, Н.А. & MANN, Г. К. , 1963, Onions and their allies. Interscience, New York. 286 p. LLOYD, D. C., 1970, The function of the odour of the garlic snail Oxychilus alliarius. Mala- cologia, 10: 441-449. MOTOHIRO, T., 1962, Studies on the petroleum odour in canned chum salmon. Mem. Fac. Fish. Hokkaido Univ. 10(1): 1-65. NIEGISCH, W. D. & STAHL, У. H., 1956; The onion: gaseous emanation products. Fd. GARLIC SNAIL ODOUR: FUNCTION 455 ABCTPAKT СОСТАВ ЗАПАХА У ЧЕСНОЧНОЙ УЛИТКИ OXYCHILUS ALLIARIUS (MILLER), (PULMONATA: ZONITIDAE) A. К. ЛЛОЙЛ Прямая инъекция в газово-жидкостной хромотограф показала, что главное летучее вещество, продуцирующееся при раздражении Oxychilus alliarius, явля- ется п-пропилмеркаптаном. Возможно, он дает тот острый запах, столь ха- рактерный для этого вида моллюска. АВ «Ne me INDEX TO SCIENTIFIC NAMES aberti, Cyprogenia, 18 Acanthophora, 359 Acella, 405 haldemani, 405 Achatina, 394 fulica, 394 Achatir.idae, 44 Acmaea, 437 Acroloxus, 22 coloradensis, 22 Acropora, 182 corymbosa, 182 Pharaonis, 182 Acteon, 184 Acteonia, 358 senestra, 358 Actinonaias, 86, 93, 96, 99, 104, 106, 279, 340 carinata, 86 ellipsiformis, 93, 96, 99, 104, 106, 279 acuminata, Parreysia, 346 Acuticosta, 347 Adalia, 416 adrens, Nymphaea, 115 aegyptiaca, Caelatura, 346 Aeolidiella, 183, 187, 212-213, 357 alderi, 357 drucilla, 213 faustina, 213 indica, 183, 187, 212 orientalis, 213 pacifica, 213 Aeolidiidae, 183 Aeolis, 357 glauca, 357 aerea, Chaetomorpha, 357-358, 363, 367-368 ajfinis, Trippa, 202 Aglaia, 190 Aglajidae, 182 aivica timia, Taringa, 183, 203 akkeshiensis, Stiliger (Stiliger), 192 alabamensis, Amphigyra, 30 alabamensis, Goniobasis, 29 alabamensis, Gyrotoma, 29 alabamensis, Strophitus, 30 alamedensis, Monadenia infumata, 40 Alasmidonta, 21, 30, 31, 93. 95, 99, 102, 340 calceolus, 95 heterodon, 21 marginata, 93, 95, 99, 102, 110-112 mccordi, 30 triangulata, 31 undulata, 95 Alasmidontinae 334-336 alata, Proptera, 57, 70, 73, 76, 78, 79, 86, 91, 92, 93, 96, 99, 104, 110-112 457 alatus, Unio, 57 albanyensis, Goniobasis, 25 albula, Vallonia, 45 albus, Favorinus, 357 alderi, Aeolidiella, 357 Aldisinae, 183 aldrichianum, Pleurobema, 30 Algamorda, 52 newcombiana, 52 algira, Nona, 185 alliarius, Oxychilus, 441-454 Allium, 441, 451 cepa, sativum. 451 Allogona, 43 ptychophora solida, 43 allyni, Ammonitella yatesi, 43 allynsmithi, Helminthoglypta, 41 Almaguorda, 56 newcombiana, 56 alterniflora, Spartina, 385 altilis, Lampsilis, 30. altum, Pleurobema, 30 ambigua, Simpsoniconcha, 18, 345 ambiguus, Velesunio, 347 Amblema, 57, 58, 70, 72-74, 76, 86, 338 costata, 57, 10, 72, 73, 74, 76, 86-338 peruviana, 58 plicata, 72, 338 Amblemidae, 333-349 Ambleminae, 13, 334, 335, 338, 341, 342, 349 Ammonitella, 42, 43 yatesi, 43 y. allyni, 43 Amnicola, 285 antipodanum, 285 antipodarum, 285, 301 Amnicolidae, 29 Amphigyra, 30 alabamensis, 30 amplum, Gyrotoma, 29 Ampullarius, 423-439 glaucus, 423-439 Anaspidea, 182, 191 anatina, Physa, 121 ancillaria, Physa, 121 anceyi, Brazzaea, 436 Anculosa, 12, 28, 29 - arkansensis, 28 choccoloccoensis, 29 clipeata, 29 coosaensis, 29 foremani, 29 formosa, 29 griffithiana, 29 458 INDEX TO SCIENTIFIC NAMES ligata, 29 melanoides, 29 modesta, 29 picta, 29 showatteri, 29 tacniata, 29 torrefacta, 29 vittata, 29 Ancylidae, 12, 30 Ancylus, 394, 405 fluviatilis, 394, 405 andersoni, Smarcgdinella, 189 Angitrema, 12 Anguispira, 45 angulata, Anodonta, 338 argulata, Gonidea, 93, 95, 99, 102, 338. 341 argulata, Seriatophora, 182 argulata, Tulotoma, 25 Arodonta, 25, 57, 58, 70, 72, 73, 76-78, 80, 86, 91-96, 98-100, 102, 108, 231, 236, 238, 336, 340, 427 angulata, 338 californiensis, 96 cataracta, 96 corpulenta, 93, 96, 99, 102, 110-112 couperiana, 95 cygnea, 98, 108, 236, 277 cygneus, 340 decora, 57 edentula, 58 ferussaciana, 57, 96 ftuviatilus, 279 gibbosa, 98 grandis, 57, 70, 72, 73, 76-78, 80, 86, 91, 92 96-99, 102, 109-112 f. footiana, 96-99, 102, 110-112 f. grandis, 78 hallenbeckii, 96 henryana, 98 imbecillis, 25, 93, 94, 96, 98-100, 341, 343, 345, lauta, 427 [349 ma. ginaia, 96 p DREAROUEESS Ш, № eo. pe | у у. | i? ча) u | iat 1 u A LU по o | ur! в в NI ni VA Ñ р | u в | Le ] y Nc NL ON | vo и $ o La 5 Db: JM AS ma В $ re a | TORRES | | 7 | u = are | | | LL | A ao | an = Fi y] О Г re CUT mh) к Cu | que wi | u UN y | N У 7 — , |. e р y Y LES do a 7 u u "1 af | 4 | у o Der A we POS | 7 | р | ie; | | e A 7 ~~ 1 у т y 11 u 7 В . n y Г | ‘1 в Dr L j IN | т | 7 a. 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