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Full text of "Malacologia"

HARVARD UNIVERSITY 

Library of the 

Museum of 

Comparative Zoology 



VOL. 18 NO. 1-2 1979 



MALACOLOGIA 



PROCEEDINGS of the SIXTH 



EUROPEAN 



MALACOLOGICAL 



CONGRESS 

19 



AMSTERDAM 



Amsterdam 1977 




MUS. COMP, z 
LfSRARY 



MAY 2 



HARVARO 
I RÄJXY 



PROCEEDINGS 

of the 

SIXTH EUROPEAN MALACOLOGICAL CONGRESS 

(Amsterdam, 15-20 August 1977) 



Edited by A. С VAN В RUG G EN, Ph.D. 



Published by the Sixth European Malacological Congress and the Institute 
of Malacology, Ann Arbor, Michigan, U.S.A. 

Philadelphia, 1979 



(Price US $25) 



COMITE D'HONNEUR 

Dr. Vera FRETTER, United Kingdom 
Dr. J. LEVER, Netherlands 
Dr. С P. RAVEN, Netherlands 
Dr. A. RIEDEL, Poland 
Dr. К. M. WILBUR, U.S.A. 



ORGANIZING COMMITTEE 

Dr. A. С VAN BRUGGEN, University Leiden, President 

Dr. E. GITTENBERGER, Rijksmuseum van Natuurlijke Historie, Secretary General 

Dr. С J. STOLL, Free University Amsterdam, Treasurer 

Dr. H. E. COOMANS, University Amsterdam 

Prof. Dr. J. JOOSSE, Free University Amsterdam 

Dr. S. VAN DER SPOEL, University Amsterdam 

Prof. Dr. N. H. VERDONK, University Utrecht 

Prof. Dr. J. LEVER, Free University Amsterdam, Advisory Member 

Mrs. W. H. VAN BRUGGEN-GORTER, Oegstgeest, Companion's Programme 



CONGRESS BUREAU 

P. J. SPITTJE, Free University Amsterdam 
Mrs. M. VAN URK, Free University Amsterdam 



CONTENTS 

Preface vii 

Introduction ix 

Presidential address xi 

Allocution présidentielle, résumé en français xiii 

Anrede des Vorsitzenden, Deutsche Zusammenfassung xiii 

Unites Malacologica Europaea xv 

Proceedings of the Sixth European Malacological Congress (papers arranged alphabetically according to 

authors' names) 
ACHAZI, R. K.: 5-Ht induced accumulation of 3', 5'-AMPand the phosphorylation of paramyosin in 

the ABRM of Mytilus edulis 465 

AIELLO, E.: Nervous and local mediator control of mucociliary transport in a bivalve gill 469 

AJANA, A. M.: Preliminary investigation into some factors affecting the settlement of the larvae of 

the mangrove oyster Crassostrea grasaríAdanson) in the Lagos lagoon 271 

ALTRUP, U., SPECKMANN, E.-J. & CASPERS, H.: Axonal pathways and synaptic inputs of three 

identified neurons in the buccal ganglion of Helix pomatia 473 

ANT, H. & JUNGBLUTH, J. H.: E.I.S.-Beiträge aus der Bundesrepublik Deutschland 185 

ARNAUD, P. M. & PO I Z AT, C: Données écologiques sur des Caecidae (Gastéropodes Prosobranches) 

, du Golfe de Marseille 319 

BABA, K.: Die Sukzession der Schneckenzönosen in den Wäldern des Alföld und die Methoden zum 

Studium der Sukzession 203 

BAR, Z. & MIENIS, H. K.: The malacofauna of Mount Hermon 73 

BENEDECZKY, I.: The fine structural organization of sensory nerve endings in the lip of Helix 

pomatia L 477 

BENJAMIN, P. R.: Electrophysiology of "Yellow Cells," neurosecretory neurones in Lymnaea 483 

BOETERS, H. D.: Species concept of prosobranch freshwater molluscs in western Europe, 1 57 

BOLOGNANI FANTIN, A. M. & BOLOGNANI, L.: The palliai gland of Lithophaga lithophaga (L.): a 

histochemical and biochemical approach of the rock boring problem 587 

BOYLE, P. R., MANGOLD, K. & FROESCH, D.: The organisation of beak movements in Octopus .... 423 
BREURE, A. S. H.: Taxonomical, ecological and zoogeographical research on Bulimulidae (Gastropoda, 

Pulmonata) 107 

BROWN, D. S.: Biogeographical aspects of African freshwater gastropods 79 

COOK, A.: Homing in the Gastropoda 315 

COOMANS, H. E.: Albinism in the genus /4nc/7/a (Gastropoda, Olividae) 157 

CRISP, M.: The effect of activity on the oxygen uptake of Nassarius reticulatus (Gastropoda, 

Prosobranch ia) 445 

CURRY, D. & RAMPAL, J.: Shell microstructure in fossil thecosome pteropods 23 

DENIS, A.: L'utilisation du Microscope Electronique à Balayage dans l'examen des tissus minéralisés 

chez les Lamellibranches 19 

DUPONT, L.: Note on variation in Diacria Gray, 1847, with descriptions of a species new to science, 

Diacria rampali nov. spec, and a forma new to science, Diacria trispinosa forma atlántica nov. 

forma 37 

DUPOUY, J.: Compétition entre Melanopsis (Gastropoda: Prosobranch ia) et Basommatophores en 

Algérie: l'élimination de Bulinus truncatus truncatus 233 

FOURNIE, J.: Formation de la coquille des mollusques: Les problèmes posés par la présence et 

le comportement de cellules libres dans la coquille normale et régénérée chez Agriolimax reticulatus 

(Gastéropode Pulmoné) 543 

FRETTER, V. & KO, B. H.: The specialization of the aplysiid gut 7 

FRIEDL, F. е.: Some aspects of amino acid catabolism in the freshwater pulmonate snail Lymnaea 

stagnalis 595 

GITTENBERGER, E.: On Elona (Pulmonata, Elonidae fam. nov.) . 139 

GOMOT, L. & COURTOT, A. M.: Etude en culture in vitro du contrôle endocrine de la glande à 

albumen chez l'escargot Helix aspersa 361 

GOTTING, K.-J.: Durch Parasiten induzierte Perlbildung bei Mytilus edulis L. (Bivalvia) 563 

GRIFFOND, В.: Evolution des relations entre ovocyte et cellules folliculeuses au cours de l'ovogenèse 

de la paludine Viviparus viviparus (Gastéropode Prosobranche) 369 

HALLERS-TJABBES, С С. TEN: Sexual dimorphism in Buccinum undatum L 13 

HANUMANTE, M. M.. FAROOQUI, U.M., KULKARNI, G. K. & NAGABHUSHANAM, R.: Inhibition of 

hypertonic-saline stimulated neurosecretory changes in the freshwater bivalve Indonaia caeruleus 

(Prashad) by chlorpromazine and reserpine 569 

HEPPELL, D.: Alexander Crosbie and the "Challenger" Teredo 163 

JANSE, C, KITS, K. S. & LEVER, A. J.: The re-formation of connections in the nervous system of 

Lymnaea stagnalis after nerve injury 485 

JELNES, J. E.: Taxonomical studies on Bulinus using isoenzyme electrophoresis with special reference 

to the africanus group on Kano Plain, Kenya 147 

JUNGBLUTH, J. H.: Zur Integration chorologischer und ökologischer Befunde der Malakozoologie in 

die ökologische Landschaftsforschung 197 

KISS, I.: Functional characteristics of an identified pair of neurones in the CNS of the pond snail 

(Lymnaea stagnalis L.) 489 

¡ii 



iv PROC. SIXTH EUROP. MALAC. CONGR. 

KNIPRATH, E.: The functional morphology of the embryonic shell-gland in the conchiferous molluscs. . 549 

KRKAC, N.: Temperature and reproductive cycle relations in Radix peregra O. F. Müller 227 

LEVER,' A. J.: Habituation characteristics of the tentacle contraction reflex of the pond snail 

Lymnaea stagnalis (L.) ^^^ 

LOMTE, V. S.: Thermoregulation in the freshwater iamellibranch Parreysia corrugata ; • • • ^^^ 

MACAROVICI, N.: Sur les mollusques de la limite entre le Pliocène supérieur et le Pleistocene 

inférieur en Roumanie 265 

MANE, и. H., KACHOLE, M. S. & PAWAR, S. S.: Effect of pesticides and narcotants on bivalve 

molluscs ^^' 

MANE, и. H. & NAGABHUSHANAM, R.: Studies on the growth and density of the clam Paphia 

laterisulca at Kalbadevi estuary, Ratnagiri, on the west coast of India 297 

MANGA GONZALEZ, M. Y. & CORDERO DEL CAMPILLO, M.: New malacological records for the 

province of León (N.W. Spain) and percentages of infestation by Trematoda 61 

MARCOS MARTINEZ, M. R.: Cytomorphology and histochemistry of the glandular cells in the foot 

of Cernuella (Xeromagna) cespitum arigonis (Rossmässler) 591 

MEAD, A. R.: Anatomical studies in the African Achatinidae— A preliminary report 133 

MEIER-BROOK, C: The planorbid genus Gyraulus in Eurasia 67 

MORTON, В.: The population dynamics and expression of sexuality in Balcis shaplandi and 

Mucronalia fulvescens (Mollusca: Gastropoda: Aglossa) parasitic upon Archaster typicus (Echino- 

dermata: Asteroidea) 327 

NAGABHUSHANAM, R. & HANUMANTE, M. M.: Experimental evidence for the hormonal control of 

oviposition in the freshwater pulmonate Indoplanorbis exustus 373 

NEWELL, P. F. & APPLETON, T. С: Aestivating snails— the physiology of water regulation in the 

mantle of the terrestrial pulmonate Otala láctea 575 

NIXON, M.: Hole-boring in shells by Octopus vulgaris Cuvier in the Mediterranean 431 

ODÍETE, W. O.: The central nervous control of the adductor behaviour of Iamellibranch molluscs 499 

ÖKLAND, J.: Distribution of environmental factors and fresh-water snails (Gastropoda) in Norway: use 

of European Invertebrate Survey principles 211 

ÖKLAND, К. A.: Sphaeriidae of Norway: a project for studying ecological requirements and geographical 

distribution 223 

PAFORT-VAN lERSEL, T.: The columellar muscle system in Clio pyramidata and Cymbulia peroni 

(Pteropoda, Thecosomata) 31 

PARODIZ, J. J.: Anatomy and taxonomy of Protoglyptus quitensis (Pfeiffer) (Gastropoda, Pulmonata, 

Bulimulidae) 115 

PASIÓ, M.: Effects of ionic environmental changes on the light-evoked depolarization of an identified 

Helix pomatia neuron 507 

PETITJEAN, M.: Différenciation des genres Homalocantha, Jaton et Maxwellia (Gastéropodes, 

famille Muricidae) au moyen de la structure microscopique de leur coquille 151 

PRETORIUS, S. J., DE KOCK, K. N. & VAN EEDEN, J. A.: The population dynamics of the 

pulmonate snail Bulinus (Physopsis) africanus (Krauss) 237 

PUSZTAI, J. & SAFONOVA, T. A.: Microelectrode investigations of learning phenomena in snail 

{Helix pomatia) neurones 453 

RAO, M. В.: Preliminary studies on the natural diet and carbohydrases in the digestive gland of the 

tropical aquatic pulmonate snail Lymnaea luteola Lamarck 421 

RICHARDOT, M.: The limpet Ferrissia wautieri, a model for studies on calcification mechanisms in 

molluscs: some results 553 

RICHARDSON, С A., CRISP, D. J. & RUNHAM, N. W.: Tidally deposited growth bands in the shell 

of the Common Cockle, Cerastoderma edule (L.) 277 

RIEDEL, A.: Verbreitung der Familie Zonitidae 53 

RIGBY, J. E.: The fine structure of the oocyte and follicle cells of Lymnaea stagnalis, with special 

reference to the nutrition of the oocyte 377 

RUDOLPH, P. H.: The strategy of copulation of Stagnicola elodes (Say) (Basommatophora: 

Lymnaeidae) 381 

RUNHAM, N. W. & HOGG, N.: The gonad and its development in Deroceras reticulatum (Pulmonata: 

Limacidae) 391 

SCHMEKEL, L.: Elektronenmikroskopische Untersuchungen zur Regeneration bei Nudibranchiern 413 

SCHRODER, H. и., NEUHOFF, V., PRIGGEMEIER, E. & OSBORNE, N. N.: The influx of 

tryptamine into snail (Helix pomatia) ganglia: comparison with 5-hydroxytrvptamine 517 

SMITH, B. J.: Survey of non-marine molluscs of south-eastern Australia 103 

SOFFE, S. R., SLADE, С T, & BENJAMIN, P. R.: Environmental osmolarity and neurosecretory 

neurones in Lymnaea stagnalis (L.) 583 

SPOEL, S. VAN DER: Strobilation in a pteropod (Gastropoda, Opisthobranchia) 27 

STARMUHLNER, F.: Distribution of freshwater molluscs in mountain streams of tropical Indo-Pacific 

islands (Madagascar, Ceylon, New Caledonia) 245 

STEFFENS, H.: Cytological aspects of different nerve cell somata in the buccal ganglia of Helix 

pomatia L 527 

STOLL, С J.: Peripheral and central photoreception in Aplysia fasciata 459 

UMINSKI, T. & FOCHT, и.: Population dynamics of some land gastropods in a forest habitat in 



Poland 



181 



VALOVIRTA, I.: Primary succession of land molluscs in an uplift archipelago of the Baltic ........ ^69 



CONTENTS V 

VIANEY-LIAUD, M.: Influence du jeûne et de la renutrition sur l'oviposition et les gamétogenèses chez 

le Planorbe Biomphalaria glabrata (Gastéropode Pulmoné Basornmatophore) 401 

VOVELLE, J. & GRASSET, M.: Approche histophysiologique et cytologique du rôle des cellules à 

spherules caldques du repli operculaire chez Pomatias elegans (Müller), Gastéropode Prosobranche. . 557 
WABNITZ, R. W.: Neurogenic contractile activity of the penis retractor nnuscle of Helix pomatia L. ■ . 533 
WÄREBORN, I.: Reproduction of two species of land snails in relation to calcium salts in the foerna 

layer 177 

WATTEZ, C: The control of sexual differentiation by the cephalic complex in the slug Arion 

subfuscus Drap. (Gastropoda Pulmonata) 407 

WIKTOR, A. & LIKHAREV, I. M.: Phylogenetische Probleme bei Nacktschnecken aus den Familien 

Limacidae und Milacidae (Gastropoda, Pulmonata) 123 

WILBUR, К. M. & TOMPA, A. S.: Physiological changes in gastropods during egg shell calcification 

Part II 561 

WILSON, J. G.: What is the function of the shell ornamentation of Tellina fabula Gmelin? 291 

ZIDEK, W. & SPECKMANN, E.-J.: Temperature dependent membrane potential changes in snail 

neurons and their relation to active ion transport 539 

ZUNKE, U.: Feinstruktur des Auges der Bernsteinschnecke Succinea putris (L.) (Gastropoda, Stylom- 

matophora) 1 

List of congress members 605 

Index 609 



PREFACE 



The sixth international congress of Unitas Malacologica Europaea was held in Amsterdam, 
Holland, from 15-20 August 1977. It was attended by ca. 200 malacologists from all over the 
world representing ca. 30 nations; between them they read 11 major and ca. 135 contributed 
papers, and displayed ca. 15 posters. 

Apart from the above, the programme featured an informal get-together in the bar of the 
Alpha Hotel on August 14, a reception organized by the Free University on August 15 
(attended by the rector of the university. Prof. J. de Ruiter), a museum curators meeting under 
the chairmanship of Dr. Van Bruggen after this reception, a reception organized by the 
Zoological Museum of the University of Amsterdam on August 16 (attended by the director. 
Dr. С A. W. Jeekel, and held in the exhibition halls of the museum and in the famous 
aquarium of the Zoo), a European Invertebrate Survey meeting under the chairmanship of Dr. 
Gittenberger on August 18, a congress dinner in the Alpha Hotel on August 19, and the general 
assembly of U.M.E. on August 20. The companion's programme offered an introduction to the 
city of Amsterdam. On Wednesday August 17 there was a choice of 3 excursions, viz. to the 
océanographie research institute (N.I.O.Z.) on the island of Texel, to Zeeland with an 
opportunity to meet Mrs. Dr. Van Benthem Jutting, and to the surroundings of Amsterdam in 
order to collect and study freshwater molluscs. Much to our disappointment the weather was 
not what we expected it to be. 

The Amsterdam congress has featured 2 innovations, viz. 11 invited lectures (which have 
been published separately under the title Pathways in Malacology, editor S. van der Spoel, 
Bohn, Scheltema & Holkema, Utrecht, 1979) and the introduction of posters. Both innovations 
have been well received by the congress participants. 

The 1977 meeting was the last congress of Unitas Malacologica Europaea. On August 20 the 
general assembly decided to convert U.M.E. to a truly worldwide body: Unitas Malacologica. 

Acknowledgments are due to the Free University, Amsterdam, for considerable financial 
assistance and free use of their magnificent congress facilities. 

A. С van Bruggen 



VII 



* 



INTRODUCTION 



The Proceedings of the Sixth European Malacological Congress, Amsterdam, 15-20 August 
1977, as here presented contain 87 papers of varying length, quality and subject matter. A total 
of ca. 135 papers was read and ca. 15 posters were exhibited. The 11 invited lectures have been 
published separately (see Preface) and a number of participants have declined to submit papers 
for the Proceedings. From the beginning it has been our policy that the Proceedings of the 
Amsterdam congress should not contain abstracts, but only papers; we have adhered to this 
rule, although there are a few exceptions. The abstracts have been published in a limited edition 
for congress participants (Abstracts, Sixth European Malacological Congress, Amsterdam, 152 
p.). Congress participants exhibiting posters have also been asked to submit manuscripts if 
desired. Therefore this volume contains both contributed papers and posters. In addition and by 
way of exception 2 papers are published although their authors were unable to attend the 
congress. Editing the proceedings has been a task of some magnitude; on the whole editing has 
been mild and restricted. Some authors have (considerably) overstepped the mark as regards the 
length of their contributions; editing has resulted in some shortening and more modest authors 
have made up the difference in pages. The editor owes a debt of gratitude to many colleagues 
and others who have assisted in getting these Proceedings through the press. Without detracting 
from the valuable contributions by others, there would have been no Proceedings but for the 
help of Dr. George Davis and his editorial staff. Dr. E. Gittenberger, Dr. H. H. Boer, Mrs. 
Wendy van Bruggen, Mrs. J. B. Smit, H. Heijn and A. 't Hooft. The papers have been arranged 
according to subject; in the contents authors names have been enumerated alphabetically. 

Once again we should like to stress our gratitude to the Free University, Amsterdam, for 
generous support in many respects. 

A. С van Bruggen 



IX 



PROC. SIXTH EUROP. MALAC. CONGR. 

PRESIDENTIAL ADDRESS 

A. С van Bruggen 

President of Un ¡tas Malacologica Europaea 

Ladies and Gentlemen, 

I have the honour to welcome you to the Sixth International Malacological Congress 
organized on behalf of Unitas Malacologica Europaea. The preceeding congresses of London 
(1962), Copenhagen (1965), Vienna (1968), Geneva (1971), and Milan (1974) have been a great 
success, each with its own atmosphere and achievements. I do hope the Amsterdam congress 
will be as memorable as the others have been. 

Thanks to co-operation from many sides we have been able to look forward to today 
without undue trepidation. Our acknowledgements are due to the Comité d'Honneur consisting 
of Dr. Vera Fretter and Drs. Lever, Raven, Riedel and Wilbur. I owe a great and sincere debt of 
gratitude to the Organizing Committee consisting of Drs. Coomans, Gittenberger (Secretary- 
General), Joosse, Van der Spoel, Stoll (Treasurer), Verdonk and Dr. Lever as advisory member, 
and in addition Mrs. Van Bruggen. The congress bureau consisting of Mrs. Van Urk and Mr. 
Spittje have done their best to help us for which we are grateful. We have been liberally assisted 
financially by the Free University, indeed without their support there would have been no 
congress at all; further financial assistance has been graciously given by Her Majesty's 
Government (Minister of Education and Sciences) and by Shell Nederland. The Dutch 
malacological society has supported us from the beginning under the leadership of Drs. Joosse, 
past president, and Van der Spoel, the present president. Our thanks are due to all these people 
and institutions. 

Ladies and Gentlemen, this is a long list of acknowledgments, but let me sound a warning 
here: a congress is not effected by organizing talent and money, a congress is made by the 
participants. The Concise Oxford Dictionary defines the word 'congress' as follows: "formal 
meeting of delegates for discussion, esp. of persons engaged in special studies." You will notice 
that in this wording the participants are mentioned twice, viz., as 'delegates' and as 'persons.' 
Let me emphasize that it is up to you all to transform this particular meeting into a real 
congress— we have done our best, now it is your turn. 

As regards congresses the Netherlands are not altogether without experience in the field, 
particularly as regards biological congresses. Ornithologists and entomologists have repeatedly 
convened in our modest country and we have hosted a regular international zoological congress 
as far back as 1895 in Leiden, at a time when congresses were not as fashionable as they are 
today. Of course, there have been thematic meetings on various zoological subjects, but this is 
definitely the first time that a large international gathering of malacologists meets in this 
country. Allow me to recall that at a meeting on the occasion of the 25th anniversary of the 
Dutch malacological society in Amsterdam in 1959 in the presence of a limited number of 
foreign malacologists the idea of European congresses was born. The first congress in London in 
1962 was conceived in this very city where we are convening today. 

Malacology is the science of molluscs in as wide a context as possible and today you are 
honoured guests in a country where malacology has had very early beginnings and where a great 
deal of malacological research is conducted at present. According to Solem (1974) Swammer- 
dam in the mid 1600's was the first person ever to meticulously dissect, describe and depict a 
snail, although his results were not published until almost a hundred years later (Swammerdam, 
1737-1738). Nowadays the Free University is a well-known centre of experimental malacologi- 
cal research and it is therefore fitting that we convene here. Somebody once told me that here 
one finds the highest permanent concentration of malacologists in the world; today their 
numbers have temporarily multiplied. As regards malacology in the Netherlands I may refer to 
the booklet published by the Dutch malacological society on the occasion of our congress, 
which booklet graciously has been made available free to all full members of the congress (Van 

xi 



xii PROC. SIXTH EUROP. MALAC. CONGR. 

Bruggen, 1977). This publication will give you a concise impression of malacological research 
being conducted in our country, at the same time making a lengthy discourse on the subject 
superfluous. Suffice it to say that malacology just now prospers in the Netherlands. 

Every local organizing committee tries to bring something different; we have been guided by 
the principle that more attention should be paid to non-taxonomic malacology than has been 
done before. We have tried to set the themes for this congress by inviting 12 prominent 
malacologists from all over the world, who have been asked to give comprehensive lectures on 
their own particular subjects. Much to our regret Prof. Sakharov of the U.S.S.R. cannot be 
present at our conference. Apart from the main lectures, to be published separately in book 
form (Van der Spoel, 1979) next year, there are the usual contributed papers. These 
contributed papers, more than a hundred in number, reflect the wide diversity of molluscan 
studies on a world-wide basis. The papers have been organized in 3 simultaneous sessions in 
such a way that there are no clashes of interest, we hope. In addition we have introduced 
posters on a much larger scale than before. The response has been gratifying and we are able to 
announce about 15 posters of a very diverse nature. Production of the Proceedings of the 
preceding congress has been consistently dogged by ill-fortune, but these will now be available at 
this congress. I sincerely promise to see to quick publication of the Proceedings of the present 
congress, reason why we have asked you to bring the finalized manuscripts along with you to 
Amsterdam. Apart from invited and contributed papers and posters, the congress will feature 
the now customary meetings of the European Invertebrate Survey and of the museum curators. 

It is somewhat risky to organize a congress in times of economic depression; our financial 
difficulties have been considerable and we regret the absence of potential participants because 
of financial stringency in their respective countries. Mrs. Dr. Van Benthem Jutting, formerly of 
the Amsterdam museum and our senior malacologist, will not attend the congress because it 
would be too much of a strain to her. Nevertheless she is looking forward to meeting the 
participants of the field trip to Zeeland. Also, some of our colleagues have passed away since 
we convened in Milan in 1974. I regret to have to inform you that Dr. Lemche of Copenhagen, 
president of the 1965 congress, has suddenly died very recently. Dr. Lemche will be 
remembered as a great scientist and a powerful force behind the European malacological 
congresses (see Knudsen, 1977). Two others have passed away. Dr. Van Regteren Altena of the 
Netherlands, a former council member of Unitas (Vice-President 1965-1968) and Prof. Caesar 
Boettger of Germany. All in all there are now in Amsterdam about 200 scientific participants 
of which ca. 30 from outside Europe, the total representing ca. 30 nations. 

The time has come to review the position of Unitas. The main function of the U.M.E. has 
been to organize international malacological congresses in Europe. In my opinion this should be 
the paramount aim, next to furthering international projects such as the European Invertebrate 
Survey and world-wide molluscan conservation. Gradually a feeling has developed that working 
in a purely European context is perhaps somewhat restrictive and at the council meeting of 
Unitas in Frankfurt am Main in February 1977 we have decided to propose the conversion of 
U.M.E. into a world-wide international body, Unitas Malacologica, with the stipulation that 
every 3 years a congress will be held in Europe. Unitas has always had ties outside Europe; 
apart from lively participation by our corresponding members from outside Europe (particularly 
the Americans), the international journal Malacologia, based in the United States of America, 
has produced or assisted with the production of our Proceedings right from the beginning and 
we have their promise that they will continue to do so. We feel that the voice of a world-wide 
international body will be heard throughout the world where necessary, which particularly for 
co-operation in the field of conservation has its advantages. Moreover, international bodies may 
be able to obtain funds from United Nations agencies so that our financial position may 
improve, which in turn will place us on a par with other international biological congresses. 
After all, I do not have to remind you that the Mollusca are the second most diverse phylum in 
the animal kingdom. The tremendous economic, medical and veterinary importance of these 
fascinating animals warrants them being considered on an equal footing with groups like birds 
and insects, taxa that have had their own international congresses on a world-wide basis already 
over a considerable period. Our own congresses have always considered the economic 
importance of molluscs and indeed here in Amsterdam various aspects will be discussed in both 
invited and contributed papers. Our ambition is to further malacology, the study of molluscs, 
and we feel that a measure as discussed before would be beneficial to both malacology in 



VAN BRUGGEN xiii 

general and malacologists in particular. Herewith I declare the Sixth International Malacological 
Congress organized on behalf of Unitas Malacologica Europaea open. 

LITERATURE CITED 

BRUGGEN, A. С VAN, ed., 1977, Malacology in the Netherlands. Nederlandse Malacologische Vereniging, 

Leiden, 53 p. 
KNUDSEN, J., 1977, Obituary Henning iVl. Lemche (11 August 1904-4 August ^9^7). Journal of Molluscan 

Studies, 43: 205-207. 
SOLEM, A., 1974, The shell makers/Introducing mollusks. Wiley & Sons, New York/London, etc., 289 p. 
SWAMMERDAM, J., 1737-1738, Bybel der Natuure, ed. by H. Boerhaave. Severinus & Van der Aa, Leiden, 

1034 p. 

ALLOCUTION PRESIDENTIELLE 
Résumé en Français 
Mesdames et Messieurs, 

Je vous souhaite la bienvenue à Amsterdam au sixième congrès international malacologique 
organisé sous les auspices de l'Unitas Malacologica Europaea. L'Université Libre à Amsterdam 
est un centre de la malacologie expérimentale et pour cela nous sommes enchantés de nous 
assembler ici. En outre, l'Université Libre nous a bien aidé en manière de finances; nous 
pouvons dire sans exagération qu'il n'y aurait nullement de congrès sans ce secours en argent. 

Chaque comité d'organisation tend à faire quelque chose nouvelle ou différente. Nous nous 
sommes efforcés d'accentuer un peu plus les aspects non-taxonomiques de la malacologie. On 
retrouve les sujets du congrès dans les 11 conférences principales auquelles nous avons invité des 
malacologistes du monde entier. A coté de cela il y aura environ 100 conférences normales et 
nous présentons aussi environ 15 'posters,' une innovation dont nous vous prions de bien 
prendre acte. En outre le congrès a organisé des séances de t'European Invertebrate Survey et 
des conservateurs malacologiques des musées. 

Malheureusement les comptes rendus du congrès précédent (Milano, 1974) ont été publiés 
avec un tel retard que nous sommes à même de les distribuer au congrès actuel! Pour prévenir 
une répétition de cet événement nous vous avons prié de bien vouloir apporter à Amsterdam 
vos manucrits complets; les conférences des malacologistes invités seront publiées comme un 
livre séparé. 

Je vous prie aussi de bien vouloir penser avec nous sur l'avenir de l'Unitas. Le conseil de 
rU.M.E. a conclu qu'une position internationale soit a préférer à une position européenne, 
d'une part afin que notre voix soit appris dans le monde entier, ce qui est très important au 
point de vue de la protection des mollusques, etc., d'autre part afin que nous soyons à même 
d'obtenir de l'argent des organisations des Nations Unies. Après tout l'U.M.E, a toujours eu une 
interprétation plus ou moins mondiale, vu nos liens cordiaux avec les membres correspondants 
et la publication de nos comptes rendus. Pourtant nous nous faisons un devoir de continuer 
sans interruption la série des congrès en Europe. 

Je vous souhaite un congrès productif. 



ANREDE DES VORSITZENDEN 

Deutsche Zusammenfassung , 

Sehr verehrte Damen und Herren, 

Seien Sie herzlich willkommen beim Sechsten Internationalen Malakologenkongress, organi- 
siert in Amsterdam im Namen der Unitas Malacologica Europaea. Die Freie Universität in 
Amsterdam ist bekannt als Mittelpunkt experimenteller Malakologie und deshalb freuen wir uns 
darüber heute hier zusammenkommen zu können. Ausserdem ist die Freie Universität uns auch 



xiv PROC. SIXTH EUROP. MALAC. CONGR. 

finanziell sehr zu Willen gewesen; man kann ohne Uebertreibung sagen, dass es ohne diese 
Unterstützung überhaupt keinen Kongress in den Niederlanden gegeben hätte. 

Jedes Organisationskomitee bemüht sich etwas Anderes odes Neues zu bringen. Wir haben 
versucht die nicht-taxonomischen Aspekte der Malakologie etwas mehr zu betonen. Die 11 
Hauptvorträge zeigen die Thema's des Kongresses an; zu diesen Hauptvorträgen haben wir 
Malakologen aus der ganzen Welt eingeladen. Daneben gibt es über 100 kleinere Beiträge und 
etwa 15 'Posters,' eine Neuigkeit welche hoffentlich starke Beachtung finden wird. Ausserdem 
gibt es wie immer eine Tagung der Museums-Kustoden und der 'European Invertebrate Survey.' 

Leider sind die Abhandlungen des vorigen Kongresses (Mailand, 1974) so sehr verspätet, dass 
wir diese erst heute austeilen können. Damit sich so etwas nicht wiederholt, wurden die Redner 
gebeten ihre Manuskripte druckfertig nach Amsterdam mitzubringen. Die Hauptvorträge werden 
separat in Buchform veröffentlicht werden. 

Auch möchte ich bitten dem Vorstand der U.M.E. Hilfe zu leisten bei der Politik der 
Zukunft. Der Vorstand hat beschlossen, dass eine internationale Organisation einem europä- 
ischen vorzuziehen ist, einerseits weil wir unsere Stimme weltweit hören lassen möchten (was 
immer wichtig ist, zum Beispiel beim internationalen Molluskenschutz), andererseits weil wir so 
auch finanziell von Organisationen der Vereinigten Nationen unterstützt werden könnten. Die 
Unitas hat immerhin schon seit Jahren mehr oder weniger weltweit gearbeitet, wie sich aus der 
Liste der korrespondierenden Mitglieder und aus unseren Verhandlungen klar ergibt. Man muss 
jedoch Sorge tragen für eine ununterbrochene Fortsetzung der Reihe europäischer Kongresse. 

Ich wünsche Ihnen einen angenehmen und erfolgreichen Kongress. 



UNITAS MALACOLOGICA EUROPAEA 



Unfortunately the Proceedings of the Milan congress did not include reports on U.M.E.; 
these are included in this volume for the sake of continuity. 

Preparations for the Milan congress were initially handicapped by a number of strikes, so 
that circulars and presidential messages had to be distributed mainly by the secretariat (Dr. 0. 
Paget) in Vienna. The congress itself was well organized by the president Dr. Toffoletto and his 
committee and there were no difficulties. Ca. 125 participants took part in lectures and 
excursions. 

During the General Assembly the president. Dr. F. Toffoletto, gave a short summary of the 
congress activities. The secretary. Dr. Paget, deputizing for the treasurer. Dr. Jung, gave a report 
on the financial situation of U.M.E. (summary see below). This report led to vivid discussion as 
the expenses of council meetings were criticized. The small number of members and the modest 
membership fees make it almost impossible to cover the expenses for the necessary meetings of 
the council. In this connection Dr. Paget stated that the expenses of the secretariat (secretary, 
paper, printing, stamps, etc.) and even part of the costs of the circulars were paid by the 
Austrian Ministry of Science and Research. In addition to this $1000 had to be paid (as from 
the Milan congress) by Unitas as well as the congress as a contribution to printing the 
Proceedings. We are grateful for the contribution of Malacologia, but this is a heavy financial 
burden for the small budget of Unitas. A vote decided with a small majority that the 
membership fee should be increased to Sfr. 20 annually for ordinary members and Sfr, 10 for 
corresponding and collective members. This decision, incidentally, has very much improved the 
financial situation of Unitas. 

Dr. Paget unfortunately had to cancel his offer of the Vienna congress (1968) to distribute 
annual lists of publications since almost no response and cooperation could be obtained from 
the European malacologists. 

For the election of a new council and the place of the next congress there were no other 
candidates and suggestions than those proposed by the old council. Therefore the following 
council was elected with only 46 of the 132 members eligible to vote casting their vote: 

President: Dr. A. С van Bruggen 

Vice-president: Dr. J. Gaillard 

Secretary: Dr. O. E. Paget 

Treasurer: Dr. P. Jung 

Member of council: Prof. Dr. A. Grossu 

The new president declared in a first statement that he wanted to strengthen Unitas 
particularly by trying to attract more members. 

At the meetings of the new council in 1974-1977 the basis for a complete reorganisation of 
Unitas was laid. The necessity of internationalisation on a worldwide basis was agreed on, 
particularly with respect to the possibility of raising funds from international organisations to 
improve the financial situation. As this could only be approved by voting at a congress the final 
decisions were postponed until the Amsterdam meeting. 

The secretariat in Vienna contributed both financially and personally as regards the 
Amsterdam congress in order not to burden the budgets of both Unitas and the congress too 
heavily. 

The Amsterdam congress (15-20 August 1977) took place at the Free University and was 
very well organized by the president. Dr. Van Bruggen, his Secretary-General Dr. E. Gitten- 
berger, and the many other members of the committee (see list) and proved to be a great 
success. 

During this congress the proceedings of the Milan congress were received and partially 
distributed. 

XV 



xvi PROC. SIXTH EUROP. MALAC. CONGR. 

A number of changes in the organisation of the congress were initiated in Amsterdam. One 
of these, the 'Poster Sessions/ was very successful indeed and certainly will play an important 
role in future congresses. Furthermore there was a number of invited lectures; these will be 
published in a separate volume available upon payment of an additional sum. The proceedings 
of the Amsterdam congress will be distributed free of charge only to members of Unitas and 
not (as formerly) to all congress participants. This decision caused a considerable number of 
congress participants to join U.M.E. 

Another important decision was the above-mentioned intention to convert Unitas Malaco- 
logica Europaea to Unitas Malacologica on a worldwide rather than purely European basis. All 
corresponding members automatically become ordinary members. In the preliminary new rules 
it was proposed to hold congresses in Europe every 3 years, while in addition congresses outside 
Europe may be held on request in the periods in between. The retiring president should serve 
on the council for another 3 years. This will doubtlessly ensure continuity in the development 
and council of Unitas. The council will be enlarged so as to include a number of members from 
outside Europe. This decision was made to strengthen the international position and to enlarge 
the basis of our society. These important changes will not become effective before October 1, 
1978. All above-mentioned decisions were taken at the final session, the General Assembly of 
Unitas; voting showed large majorities in favour of these changes. 

Voting for the new council was done in the summer of 1977 and the proposals of the old 
council were almost unanimously accepted: 

President: Dr. J. Gaillard 

Vice-President: Prof. Dr. A. Grossu 

Secretary: Dr. 0. E. Paget 

Treasurer: Dr. P. Jung 

Member of council: Prof. Dr. J. Joosse 

Therefore Dr. Gaillard is president of Unitas for the period 1977-1980 and president of the 
next congress to be held in 1980 in France. This time 58 out of 125 members have used their 
right to vote. 

Ca. 200 malacologists from ca. 30 countries attended the Amsterdam congress. A total of ca. 
135 lectures was held and excursions gave the opportunity to see something of the Netherlands. 

At the General Assembly the retiring president. Dr. Van Bruggen, reported on the state of 
Unitas and expressed the expectation that the society will now be able to work even more 
effectively and successfully. Then the treasurer. Dr. Jung, gave his report (see summary below). 
The secretary's report presented by Dr. Paget showed that in August 1977 Unitas had 170 
members in 23 countries (134 ordinary, 26 corresponding, and 10 collective members). Unitas 
mourned the deatb of 3 foundation members (Prof. Dr. С R. Boettger, Dr. С 0. van Regteren 
Altena, and Dr. H. Lemche, the latter president of the 1965 Copenhagen congress). 

Besides supporting the European Invertebrate Survey, one of the main aims of Unitas is the 
worldwide conservation of molluscs. 

Members of Unitas normally receive the proceedings of the European congresses; some other 
projects are in preparation in order to supply members with additional publications at a 
reduced price. Projects on the bibliography of European malacologists and on literature have 
been taken in hand and members will hear about this before the next congress. 

Finally it may be stated that the development of Unitas Malacologica Europaea towards 
Unitas Malacologica on an international (worldwide) basis is without doubt a most important 
step on the way to a successful worldwide cooperation of all malacologists and we all hope that 
existing cooperation will be continued and improved. 

We wish to thank all those who have supported Unitas before and we should like to invite 
all malacologists throughout the world to join us by applying for membership. Please contact 
Dr. 0. E. Paget, Naturhistorisches Museum, Burgring 7, Postfach 417, A-1014 Wien, Austria. 

0. E. Paget 
Secretary 



PAGET xvii 

Nous regrettons que les Comptes rendus du Congrès de Milan ne renferment pas des rapports 
sur rU.M.E.; ceux-ci ont été insérés dans ce tome pour assurer la continuité. 

Au début des grèves ont rendu difficile le travail des personnes chargées de préparer le 
Congrès de Milan: les circulaires et les bulletins du Président ont dû être distribués principale- 
ment par le secrétariat (le dr. O. Paget) à Vienne. Le Congrès lui-même fut bien organisé par le 
President le dr. Toffoletto et son comité. Il n'y a pas eu de difficultés. Environ 125 personnes 
ont participé aux conférences et excursions. 

Pendant l'Assemblée Générale le President le dr. Toffoletto a donné un résumé sommaire des 
activités du Congrès. Le secrétaire le dr. Paget remplaçant le trésorier le dr. Jung a rapporté sur 
la situation financière de l'U.M.E. (voir le résumé ci-après). Une discussion animée s'engagea au 
sujet des dépenses des réunions du Conseil. Le nombre restreint de membres et la modicité des 
cotisations rendent presque impossible de couvrir les frais des réunions du Conseil. En rapport 
avec ce qui précède le dr. Paget mentionna que les dépenses du secrétariat (secrétaire, papier, 
imprimés, timbres, etc.) et même une partie des frais des circulaires ont été payes par le 
Ministère de la Recherche Scientifique de l'Autriche. De plus (à partir du Congrès de Milan) 
rUnitas aussi bien que le Congrès doivent payer $1000 pour la publication des Comptes rendus. 
Nous acceptons avec reconnaissance la contribution de Malacologie mais le budget est trop 
restreint pour faire des frais si élevés. On a décidé à une petite majorité des voix que les 
cotisations s'augmentent à Sfr. 20 par an pour les membres ordinaires et à Sfr. 10 pour les 
membres correspondants et collectifs. Entretemps cette décision a beaucoup amélioré la 
situation financière de l'Unitas. 

Malheureusement le dr. Paget dût révoquer son offre du Congrès de Vienne (1968) de 
distribuer des listes annuelles des publications parce qu'il n'a pas pu obtenir la coopération de la 
part des malacologistes européens. 

En ce qui concerne l'élection du nouveau Conseil et le choix du lieu du congrès prochain on 
s'accorda avec l'ancien Conseil. Ainsi le Conseil suivant fut élu avec seulement 46 des 132 
membres ayant droit de vote: 

Président: Dr. A. С van Bruggen 

Vice-Président: Dr. J. Gaillard 

Secrétaire: Dr. 0. E. Paget 

Trésorier: Dr. P. Jung 

Membre du Conseil: Prof. Dr. A. Grossu 

En premier lieu le nouveau Président déclara qu'il souhaite consolider l'Unitas particulière- 
ment en essayant d'attirer plus de membres. 

Lors des réunions du nouveau Conseil dans la période 1974-1977 la base d'une réorganisation 
complète fut mise. On s'accorda à reconnaître la nécessité de l'internationalisation à base 
mondiale. Ceci en particulier en rapport avec la possibilité de pouvoir obtenir l'appui financier 
de la part des organisations internationales afin d'améliorer la situation financière. Pour pouvoir 
obtenir l'approbation de ces projets il a fallu les mettre aux voix au Congrès. Pour cela on a 
remis les décisions définitives à la réunion d'Amsterdam. 

Au point de vue financier et personnel le secrétariat à Vienne a contribué au Congrès 
d'Amsterdam afin de ne pas trop charger le budget de l'Unitas aussi bien que celui du Congrès. 

Le Congrès d'Amsterdam (du 15 au 20 août 1977) eut lieu à l'Université Libre et fut très 
bien organisé par le Président le dr. Van Bruggen, le Secrétaire Général le dr. E. Gittenberger et 
beaucoup d'autres membres du Comité (voir la liste) et se trouva avoir un grand succès. 

Pendant le Congrès les Comptes rendus du Congrès de Milan ont été repus et distribués en 
partie. 

Un nombre de modifications dans l'organisation du Congrès a été initié à Amsterdam. En 
effet une d'entre elles, les "Poster Sessions," eut un grand succès et jouera sans doute un rôle 
important aux congrès futurs. De plus il y a eu des conférenciers invités; leurs communications 
seront publiés dans un tome à part, qu'on peut obtenir en payant un supplément. Les Comptes 
rendus du Congrès d'Amsterdam ne seront distribués gratuitement qu'aux adhérents de l'Unitas 
et non pas (comme autrefois) à tous ceux qui ont pris part au Congrès. Cette décision a 
persuadé un nombre considérable de congressistes à s'affilier à l'U.M.E. 

Une autre résolution importante fut le projet déjà mentionné de convertir l'U.M.E. en Unitas 
Malacologica à base mondiale plutôt qu'à base purement européenne. Tous les membres 



xviii PROC. SIXTH EUROP. MALAC. CONGR. 

correspondants deviennent automatiquement membres ordinaires. Dans le nouveau règlement 
préliminaire on a proposé de tenir des congrès en Europe tous les 3 ans; en outre— sur 
demande— des congrès hors de l'Europe peuvent être tenus dans les intervalles. Le Président du 
Conseil ne démissionnera pas et restera encore 3 années. Cela assurera sans doute la continuité 
du développement et du Conseil de l'Unitas. Le Conseil sera agrandi de sorte qu'un nombre de 
membres hors de l'Europe peuvent accéder au Conseil. On a pris cette décision pour consolider 
la position internationale de notre société et pour en élargir la base. Les modifications 
importantes n'entreront pas en vigueur avant le premier octobre 1978. Toutes les décisions 
citées plus haut ont été prises à la séance finale, l'Assemblée Générale de l'Unitas. On a voté à 
la majorité des voix en faveur de ces modifications. 

Dans l'été de 1977 on a voté pour l'élection du nouveau conseil; les propositions de l'ancien 
conseil ont été acceptées presqu'à l'unanimité des voix. Le conseil fut ainsi constitué: 

Président: Dr. J. Gaillard 

Vice-Président: Prof. Dr. A. Grossu 

Secrétaire: Dr. 0. E. Paget 

Trésorier: Dr. P. Jung 

Membre du Conseil: Prof. Dr. J. Joosse 

Le dr. Gaillard sera donc Président de l'Unitas pour la période 1977-1980 ainsi que président du 
congrès prochain qui doit avoir lieu en France en 1980. Cette fois 58 des 125 membres ont 
profité de leur voix deliberative. 

A peu près 200 malacologistes d'environ 30 pays ont assisté au Congrès d'Amsterdam. Au 
total environ 135 conférences ont été présentées. Les congressistes ont eu l'occasion de faire des 
excursions en Hollande. 

A l'Assemblée Générale le Président démissionnaire le dr. Van Bruggen rapporta sur la 
position de l'Unitas et exprima son espoir que dès maintenant la société peut fonctionner 
encore plus efficacement. Apres le trésorier le dr. Jung donna un compte rendu (voir ci-après). 
Le rapport du secrétaire présenté par le dr. Paget montra qu'au mois d'août 1977 l'Unitasavait 
170 membres en 23 pays (134 membres ordinaires, 26 membres correspondants et 10 membres 
collectifs). L'Unitas regretta la mort de 3 membres fondateurs (le prof. dr. C. R. Boettger, le dr. 
С 0. van Regteren Altena et le dr. H. Lemche; ce dernier a été président du Congrès à 
Copenhague en 1965). 

Un des principaux buts de l'Unitas— en dehors de l'aide à la cartographie des invertébrés 
européens— est la conservation mondiale des mollusques. 

Normalement les membres de l'Unitas reçoivent les Comptes rendus des congrès européens. 
On est en train de préparer d'autres projets afin de pouvoir procurer aux membres des 
publications complémentaires à prix réduit. Des projets pour composer des bibliographies des 
malacologistes européens et des listes de littérature ont été entrepris. On tiendra au courant les 
membres avant le congrès prochain. 

Pour conclure on peut constater qu'avec le développement de l'U.M.E. pour devenir l'Unitas 
Malacologica à base internationale (mondiale) nous sommes sans doute sur la bonne voie pour 
ce qui est d'une coopération effective et efficace de tous les malacologistes. Nous espérons tous 
que la coopération existante sera continuée et améliorée. 

Nous tenons à remercier tous ceux qui ont soutenu l'Unitas jusqu'à présent et nous aimons à 
inviter tous les malacologistes du monde entier à se faire inscrire comme membre de l'Unitas. 
Prière de s'adresser au dr. 0. E. Paget, Naturhistorisches Museum, Burgring 7, Postfach 417, 
A-1014 Wien, Autriche. 

0. E. Paget 
Secrétaire 

Nachdem durch eine Reihe von unglücklichen Zusammenhängen in den Proceedings des 
Mailänder Kongresses keine Berichte der U.M.E. aufgenommen wurden, sollen (um die 
Kontinuität zu wahren) diese Berichte in diesem Band nachgeholt werden. 

Die Vorbereitung des Mailänder Kongresses war ursprünglich durch eine Reihe von Streiks 
sehr behindert, so dass vom Wiener Sekretariat (Dr. 0. Paget) der Grossteil der Aussendungen 



PAGET xix 

der Rundschreiben und alle Mittellungen des Präsidenten durchgeführt werden mussten. Der 
Kongress selbst war vom Präsidenten Dr. Toffoletto und seinen Mitarbeitern sehr gut vorbereitet 
gewesen und in seiner Durchführung gab es keine Schwierigkeiten. Insgesamt ca. 125 
Teilnehmer aus 25 Ländern nahmen an Vorträgen und einigen Exkursionen teil. 

In der Generalversammlung gab Dr. Toffeletto ein kurzes Resümee des Kongresses und seiner 
Aktivitäten. Anschliessend gab der Sekretär Dr. Paget in Vertretung des Schatzmeisters Dr. Jung 
den Bericht über die finanzielle Situation der U.M.E. (Zusammenfassung siehe unten). Dieser 
Bericht gab Anlass zu Diskussionen, da von einem Teil der anwesenden Mitglieder die Ausgaben 
für die Treffen des Vorstandes kritisiert wurden, da sie (aufgrund der geringen Mitgliederzahl 
und der geringen Beiträge) einen beträchtlichen Teil der Einnahmen ausmachten. In diesem 
Zusammenhang stellte Dr. Paget fest, dass die gesamten Kosten des Sekretariats und selbst ein 
Teil der Aussendungen und Druckkosten ausschliesslich durch das österreichische Bundesminis- 
terium für Wissenschaft und Forschung getragen wurden. Darüber hinaus müssen ab dem 
Mailänder Kongress (diesen eingeschlossen) jeweils $1.000.- sowohl von der Unitas als auch vom 
jeweiligen Kongressbudget zum Druck der Proceedings beigetragen werden. Wenngleich die 
grosse Hilfe von Malacologie anerkannt wird, bedeutet das doch eine schwere Belastung für das 
kleine Budget der Unitas. 

In einer leider knappen Abstimmung wurde dann beschlossen, den jährlichen Mitgliedsbeitrag 
auf sfr. 20.- für Ordentliche aud auf jeweils sfr. 10.- für Korrespondierende und Kollektive 
Mitglieder zu erhöhen. Wie sich in der Zwischenzeit herausgestellt hat, war diese Massnahme 
geeignet, die finanzielle Situation der Unitas bedeutend zu verbessern. 

Dr. Paget musste ferner bekanntgeben, dass es ihm nicht möglich war, die von ihm beim 
Kongress Wien 1968 freiwillig übernommenen Aufgaben der Herausgabe eines jährlichen 
Literaturverzeichnisses durchzuführen, da trotz mehrfacher Aufforderung keine ausreichende 
Beteiligung erreicht werden konnte. 

Bei der Wahl des neuen Vorstandes und des Platzes des kommenden Kongresses konnte 
ausser dem Vorschlag des Vorstandes kein weiterer aus den Reihen der Mitglieder erhalten 
werden. Daraufhin wurde folgender Vorstand für die nächste Periode gewählt: 

Präsident: Dr. A. C. van Bruggen 

Vizepräsident: Dr. J. Gaillard 

Sekretär: Dr. 0. E. Paget 

Schatzmeister: Dr. P. Jung 

Vorstandsmitglied: Prof. Dr. A. Grossu 

Von 132 wahlberechtigten Mitgliedern haben nur 46 von ihrem Wahlrecht Gebrauch gemacht! 

Der neue Präsident erklärte in seiner Antrittsrede, dass er versuchen werde, die Unitas durch 
verstärkte Mrtarbeit zu stärken und auch insbesonders sich bemühen werde, neue Mitglieder zu 
werben. 

Bei den zwischen 1974 und 1977 abgehaltenen Treffen des neuen Vorstandes wurden die 
Grundlagen für eine völlig neue Ordnung der Unitas gelegt. Allgemein wurde festgestellt, dass es 
notwendig wäre, die Unitas auf eine internationale Basis zu stellen, um für ihren Unterhalt auch 
Geldmittel internationaler Gesellschaften erhalten zu können. Da diese Frage jedoch nur durch 
eine Abstimmung der Mitglieder entschieden werden kann, wurden alle Vorbereitungen dafür 
getroffen, dieses Problem in Amsterdam zu lösen. 

Auch bei der Vorbereitung des Amsterdamer Kongresses hat das Sekretariat in Wien sowohl 
in finanzieller als auch arbeitsmässiger Hinsicht beigetragen, das Unitas-Budget und jenes des 
Amsterdamer Kongresses nicht zu sehr zu belasten. 

Der Amsterdamer Kongress (15-20 August 1977) fand in den Räumen der Freien Universität 
statt und war von seinem Präsidenten Dr. Van Bruggen, seinem General-Sekretär Dr. E. 
Gittenberger, sowie zahlreichen anderen Mitarbeitern (siehe Liste) bestens vorbereitet und ein 
voller Erfolg. 

Während des Kongresses trafen die Proceedings des Mailänder Kongresses ein, die teilweise 
gleich verteilt werden konnten. 

Eine Reihe von Änderungen wurde von den Organisatoren des Kongresses eingeführt. Vor 
allem hatten die zahlreichen "Poster-Sessions" grossen Erfolg und werden wohl auch bei 
künftigen Tagungen eine wesentliche Rolle spielen. Ferner gab es eine Reihe von eingeladenen 
Reden, die in einem eigenen Band erscheinen und gegen zusätzliche Bezahlung bezogen werden 
können. Die Proceedings des Amsterdamer Kongresses werden nur Mitglieder der Unitas gratis 



XX PROC. SIXTH EUROP. MALAC. CONGR. 

erhalten, während alle übrigen Teilnehmer des Kongresses hfl. 30.- zu zahlen haben. Für die 
übrigen Bezieher ist der endgültige Preis noch nicht festgelegt. Diese Entscheidung hatte zur 
Folge, dass eine grosse Anzahl von Kongressmitgliedern der Unitas beitrat. 

Ein weiterer wesentlicher Punkt war die schon angeführte Entscheidung, die "Unitas 
Malacologica Europaea" auf eine internationale Basis zu stellen, ihren Namen auf "Unitas 
Malacologica" zu ändern und automatisch alle bisherigen "Korrespondierenden Mitglieder" zu 
"Ordentlichen Mittgliedern" zu machen. In einem Entwurf der neuen Statuten wurde ferner 
festgestellt, dass zwar wie bisher alle 3 Jahre ein Kongress in Europa stattfinden wird, dass aber 
auf Antrag auch zwischen diesen Kongressen ausserhalb Europas weitere abgehalten werden 
können. Ferner wurde beschlossen, dass der scheidende Präsident für eine weitere Periode von 3 
Jahren Mitglied des Vorstandes bleibt, wodurch Zweifellos eine grössere Kontinuität in der 
Entwicklung und Führung der Unitas gewährleistet ist. Darüber hinaus werden in den Vorstand 
der internationalen Organisation auch aussereuropäische Mitglieder aufgenommen werden. Diese 
Entscheidung soll dazu beitragen, die internationale Zusammenarbeit zu fördern und unsere 
Gesellschaft auf eine breitere Basis zu stellen. Um die Umstellung auf diese neue Situation zu 
erleichtern, wurde beschlossen, erst im Oktober 1978 die endgültige Umwandlung vorzunehmen. 
Dieser und alle übrigen Vorschläge wurden in der Abschlusssitzung bzw. in der General- 
versammlung mit grosser Mehrheit angenommen. 

Die in Sommer 1977 durchgeführte Wahl für den neuen Vorstand (zu der neuerlich nur der 
Vorschlag des alten Vorstandes eingebracht wurde) ergab eine fast einstimmige Bestätigung des 
Vorschlages: 

Präsident: Dr. J. Gaillard 

Vizepräsident: Prof. Dr. A. Grossu 

Sekretär: Dr. 0. E. Paget 

Schatzmeister: Dr. P. Jung 

Vorstandsmitglied: Prof. Dr. J. Joosse 

Damit ist Dr. Gaillard Präsident der Unitas Malacologica für 1977-1980 und Präsident des 
Kongresses 1980 in Frankreich. Diesmal haben von 125 Mitgliedern 58 von ihrem Wahlrecht 
Gebrauch gemacht. 

Am Kongress in Amsterdam nahmen insgesamt ca. 200 Malakozoologen aus etwa 30 Ländern 
teil. Es wurden ungefähr 135 Vorträge gehalten und einige Exkursionen durchgeführt. 

Bei der abschliessenden Generalversammlung gab der scheidende Präsident Dr. A. С van 
Bruggen eine Übersicht über die geänderten Verhältnisse der Unitas und gab seiner Hoffnung 
Ausdruck, dass diese Organisation noch wirkungsvoller und erfolgreicher wird arbeiten können. 

Dann gab der Schatzmeister Dr. P. Jung seinen Bericht (Zusammenfassung siehe unten). 

Der Bericht des Sekretärs Dr. 0. Paget ergab dass die Unitas mit I.August 1977 insgesamt 
170 Mitglieder (134 Ordentliche, 26 Korrespondierende, 10 Kollektive Mitglieder) aus 23 
Ländern hatte. Mit grossem Bedauern wurde der Tod von 3 Gründungsmitgliedern der Unitas 
erwähnt (Prof. Dr. C. R. Boettger, Dr. С О. van Regteren Altena und Dr. H. Lemche, wobei 
letzerer Präsident des 2. Kongresses in Kopenhagen 1965 war). 

Neben der Unterstützung des Projektes "European Invertebrate Survey" wird auch dem welt- 
weiten Schutz der Mollusken grössere Bedeutung beigemessen werden müssen. 

Um den Mitgliedern über den Bezug der Proceedings hinaus auch jenen weiterer Publika- 
tionen zu einem reduzierten Preis zu ermöglichen, sind einige Projekte in Vorbereitung. Vor 
allem eine Bibliographie europäischer Malakologen und über Literatur. Sie sollen vor dem 
nächsten Kongress näheres darüber erfahren. 

Abschliessend kann festgestellt werden, dass die Entwicklung der "Unitas Malacologica 
Europaea" zur "Unitas Malacologica" auf weltweiter internationaler Basis zweifellos einen 
bedeutenden Schritt darstellt auf dem Weg zu einer wirkungsvollen weltweiten Zusammenarbeit 
aller Malakologen und wir alle hoffen, dass die bisherige allgemeine gute Zusammenarbeit auf 
diese Weise noch verstärkt werden wird. 

Wir danken allen, die sich bisher so tatkräftig für die U.M.E. eingesetzt haben und laden alle 
Malakologen der Welt ein, durch ihren Beitritt diese Organisation zu stärken. Diesbezügliche 
Anfragen sind an den Sekretär, Dr. O. E. Paget, Naturhistorisches Museum, Burgring 7, Postfach 
417, A-1014 Wien, Österreich, zu richten. 

O. E. Paget 
Sekretär 



SUMMARY OF U.M.E. ACCOUNTS FOR 1971-1974 

Income 

Subscriptions Sfr. 3356.19 

Interest 734.80 

Income tax recovered 75.40 

Reimbursements 1050.00 

Sfr. 5216.39 

Expenditure 

Income tax Sfr. 220.50 

Council meetings 3569.30 

Grants 1108.00 

Sundries 245.30 

Sfr. 5143.10 
Excess of income 73.29 

Sfr. 5216.39 

Balance at 29.VI 1 1. 1974 

Assets Schweizerische Bankverein Sfr. 7093.41 

Balance 26.VIII. 1971 7020.12 

Excess 73.29 

SUMMARY OF U.M.E. ACCOUNTS FOR 1974-1977 

Income 

Subscriptions Sfr. 5336.05 

Interest 645.75 

Income tax recovered 348.50 





Sfr. 6330.30 


Expenditure 




Income tax 


Sfr. 203.40 


Council meeting 


418.10 


Contribution Proceedings Milan Congress 


2525.00 


Sundries 


328.50 




Sfr. 3475.00 


Excess of income 


2855.30 



Sfr. 6330.30 

Balance at 8.VIII. 1977 

Assets Schweizerische Bankverein Sfr. 9948.71 

Balance 29.VI 1 1. 1974 7093.41 

Excess 2855.30 



P. Jung 
Treasurer 



XXI 



MALACOLOGIA, 1979, 18: 1-5 

PROC. SIXTH EUROP. MALAC. CONGR. 

FEINSTRUKTUR DES AUGES DER BERNSTEINSCHNECKE 
SUCCINEA PUTRIS (L.) (GASTROPODA, STYLOMMATOPHORA) 



Ulrich Zunke 



Anatomisches Institut der Universität Würzburg, 
Koellil<erstrasse 6, D-8700 Würzburg, West Germany 



ABSTRACT 

The structure and some aspects of the development of the eye of Succinea putris were 
studied with the aid of the electron microscope. The eye is of the closed vesicle type and 
is composed of retina, cornea, vitreous body, lens and optic nerve. Three different types 
of cell are to be found in the retina: 

(1) the small elongated pigment cell with an avoid nucleus, many pigment granulée 
and short microvilli at the apical end of the cell; 

(2) the sensory cell type I with a large irregular nucleus, long microvilli, which extend 
to under the surface of the lens, a large number of light-cored vesicles, 700 Â in diameter 
and the axon; 

(3) the elongated slender sensory cell type II with many dense cored vesicles, several 
pigment granulae in the distal region of the cell and short irregular microvilli at the apical 
end of the cell. This type is few in number. 

Two results of the study of the embryonic eye are described: the cornea cells differ 
from those in the adult eye in the nucleus-cytoplasm relation and the optic nerve is 
smaller than in the adult eye. 



EINLEITUNG 

Verschiedene Arbeiten befassten sich in der letzten Zeit mit der Feinstruktur der Augen von 
Gastropoden. Dabei wurden bei Helix aspersa (siehe Brandenburger, 1974) u.a. zwei Sehzell- 
typen beschrieben. Der Sehzelltyp II wurde bisher nur durch die Untersuchungen an den Augen 
von Agriolimax californicus (siehe Eakin & Brandenburger, 1975) und Limax flavus (siehe 
Kataoka, 1975) bei den Stylommatophora bestätigt. Es stellt sich die Frage, ob der Sehzelltyp 
II auch bei niederen Stylommatophora zu finden ist. Dieser Frage wird im Rahmen einer 
Beschreibung des Auges der Bernsteinschnecke Succinea putris (Sigmurethra) nachgegangen. Hier 
konnten mit Hilfe lichtmikroskopischer Methoden nur 2 Retinazelltypen differenziert werden 
(Zunke, 1978). Ausserdem werden an den Beispielen des Nervus opticus und der Corneazellen 
eines Embryoauges erstmalig Unterschiede zum adulten Auge belegt. 

MATERIAL UND METHODEN 

Als Material wurden Exemplare der Art Succinea putris (L.) aus dem Gebiet des Vogelsberges/ 
Hessen verwendet. Die adulten Tiere wurden zur Eiablage in einem Terrarium gehalten. Die 
abgelegten Eier wurden datiert, um das Alter der Embryonen angeben zu können. Zwölf Tage 
alte Embryonen wurden wie die Augen der adulten Tiere in 2%-igem Glutaraldehyd 2 Stunden 
fixiert; als Puffer diente 0,05 M Kakodylatpuffer. Die Nachfixierung geschah nach gründlichem 
Auswaschen im Puffer in 1%-igem OSO4. Eingebettet wurde in Vestopal W. Die am Reichert 
Mikrotom OmU2 gewonnenen Dünnschnitte wurden mit Uranylacetat und Bleicitrat kontras- 
tiert. Zur Durchsicht und Fotografie der Dünnschnitte diente ein Zeiss EM 9A. 



^Mit dankenswerter Unterstützung der Deutschen Forschungsgemeinschaft. 

(1) 



PROC. SIXTH EUROP. MALAC. CONGR. 




ЖТ^ЛГ^Г'-'РЗ!? 



^x^ 




ZUNKE 3 

ERGEBNISSE 

Das Auge gehört zum Grundtyp des geschlossenen Blasenauges. Es differenziert sich in die 
Cornea, Retina, Linse und einen Glaskörper. Das Auge wird von einer Bindegewebskapsel 
umschlossen, die sich aus Muskulatur und Kollagenfasern zusammensetzt (Fig. 6). 

RETINA. Drei Zelltypen kann man bei einer Übersicht über die Retina erkennen: die 
Pigmentzellen und 2 unterschiedliche Sehzelltypen (Fig. 3, 4). Weiterhin fallen an der 
Retinabasis Bündel von quergeschnittenen Axonen der beiden Sehzelltypen auf (Fig. 6). 
Sehzelltyp I ist durch folgende charakteristische Merkmale gekennzeichnet: Von einem apikalen, 
bis in den Glaskörper hineinreichenden Zellfortsatz (Fig. 3) aus ragen lange, relativ gleichmässig 
geformte Mikrovilli bis an die Peripherie der Linse heran. Im Querschnitt (Fig. 1) zeigt sich ein 
homogenes Muster. Mitochondrien findet man im distalen Abschnitt der Zelle zwar auch, doch 
zahlreicher sind sie im mittleren Teil der Zelle (Fig. 3, 4). Auffallend sind die Golgi-Apparate 
(Fig. 3, 4), die in unterschiedlich hoher Anzahl vorhanden sind. Der Zellkern ist mindestens 
doppelt so gross wie die Zellkerne der anderen Zelltypen. Er weist starke Einbuchtungen auf 
und ist reich an Chromatin (Fig. 4). Umgeben wird der Kern von einer grossen AnzaW 
gleichgrosser, elektronenlichter Vesikeln, die einen durchschnittlichen Durchmesser von 700 Â 
haben (Fig. 4, 5, 7). Diese Vesikeln findet man in geringerer Anzahl in den übrigen Abschnitten 
der Zelle. 

Diese für den Sehzelltyp I so charakteristischen Vesikeln sind im Sehzelltyp II nicht 
nachzuweisen. Hier fallen im Zytoplasma überwiegend elektronendichte Vesikeln (Fig. 7) neben 
vereinzelt elektronenlichten Vesikeln auf. Alle Vesikeln haben sehr unterschiedliche Durch- 
messer (700 Ä-1200 Ä). Der Zellkern liegt weiter von der Zellbasis entfernt als der Kern des 
Sehzelltyps I. Er ist von schollenförmiger Gestalt und ebenfalls mit Chromatin ausgefüllt. Starke 
Einbuchtungen sind selten (Fig. 4). Das Axon führt bis zur Basis der Retina (Fig. 4). Die 
Mikrovilli sind bei diesem Zelttyp sehr unregelmässig und kürzer als bei dem Sehzelltyp I (Fig. 
2). Verbindungen zwischen einer Pigmentzelle und Sehzelltyp II sind Desmosomen (Fig. 2), Im 
Gegensatz zur Pigmentzelle hat der Sehzelltyp II in diesem apikalen Abschnitt kein Pigment. Es 
liegt im mittleren Bereich und hat den gleichen Durchmesser wie das Pigment der Pigmentzellen, 
ist aber nicht so zahlreich. Der Sehzelltyp II ist im Auge relativ selten vertreten. Die 
Pigmentzellen sind langgestreckt und schmal. Sie senden oft Fortsätze in die umliegenden 
Zellen. Der Kern ist von ovoider Gestalt (Fig. 4) und mit Chromatin angereichert. Starke 
Einbuchtungen fehlen ganz. Die Zelle ist fast vollständig mit Pigmentgranula ausgefüllt. Die 
Mikrovilli sind kurz (Fig. 2) und werden meistens von den Mikrovilli der anderen Retinazell- 
typen verdeckt. 

Die CORNEA (Fig. 9) unterscheidet sich von den übrigen Zellen des Auges durch ein 
besonders elektronenlichtes Zytoplasma. Die birnenförmigen bis kreisrunden Kerne sind nur 
randständig zu finden. Organellen sind im Gegensatz zur embryonalen Corneazelle reduziert. 
Mitochondrien, Golgi-Apparate, Endoplasmatisches Retikulum findet man nur vereinzelt im 
basalen Bereich der Zelle. Zellgrösse und Kernform unterscheiden sich bei adulten Corneazellen 
sehr stark. Manche Corneazellen scheinen kernlos. Die Kern-Plasma Relation ist zugunsten des 
Zytoplasmas verschoben (vergleiche Fig. 8, 9). In Fig. 9 konnte nur der Randbereich der Cornea 
eines adulten Tieres abgebildet werden, Fig. 8 dagegen zeigt die Cornea des Auges eines 12 Tage 
alten Embryos an ihrer breitesten Stelle. Auffallend ist hier die Menge des rauhen und glatten 
Endoplasmatischen Retikulums. Mikrovilli sind nur gering ausgebildet. 

Der everse Charakter dieses Gastropoden-Augentyps wird durch den Austritt der Axone der 
Sehzellen in Form eines Nervus opticus verdeutlicht (Fig. 10, 12). Zur Bildung des Nervus 
opticus muss die Bindegewebskapsel des Auges von den Axonen durchbrochen werden (Fig. 10, 
12). Im Nervus opticus sind unterschiedliche Vesikeln (Fig. 11), die denen in den Axonbündel 
gleichen (Fig. 6) vorhanden. In den Axonen sind Mitochondrien nicht selten. Bemerkenswert 
sind die randständigen Kerne der den Nervus opticus umgebenen Bindegewebshülle (Fig. 12). 

-^ 

FIG. 1-7. Ausschnitte aus der Retina. 1. Mikrovilli des Sehzeiltyps I (X 53.600). 2. Mikrovilli des Sehzelltyps II 
und der Pigmentzelle (X 15.600). 3. Apikaler Abschnitt der 3 Retinazelltypen (Х3.700). 4. Distaler Abschnitt 
der 3 Retinazelltypen (X3.700). Man achte auf das Axon des Sehzeiltyps II und die unterschiedliche 
Kerngrösse der verschiedenen Zelltypen. 5. Elektronenlichte Vesikeln des Sehzeiltyps I (Х53.600). 6. 
Axonbündel, an die Bindegewebskapsel grenzend (Х9.400). 7. Ausschnitt aus Sehzelltyp II, Vesikeln und 
Golgi-Apparat (XI 5.600). 



PROC. SIXTH EUROP. MALAC. CONGR. 




10 Ч^^.%1ч\.>^;^л1П1^ 



ZUNKE 5 

Dieses Merkmal findet man bei den embryonalen, wie auch bei den adulten Augen. Der Nervus 
opticus des embryonalen Auges ist schmaler als der des adulten Auges (Fig. 12), da die Anzahl 
der Axone geringer ¡st. 

DISKUSSION 

Die Untersuchungen am Auge von Succinea putris bestätigen daslVorhandensein eines zweiten 
Sehzelltyps. Er weist die gleichen Strukturen und ähnlich angeordnete Organellen auf, wie der 
Sehzelltyp II nach Brandenburger (1974). Nur konnten im Sehzelltyp II bei Succinea putris 
keine Cilien oder auch nur ein Basalkörper nachgewiesen werden. Weitere Bauelemente des 
Auges von Succinea putris decken sich mit den Untersuchungen von Brandenburger (1974) und 
Eakin & Brandenburger (1975) und Kataoka (1975). Es sind die für die Gastropodenaugen 
schon typischen elektronenlichten Vesikeln im Sehzelltyp I, die von Eakin als "photic vesicles" 
bezeichnet werden. 

Eine geringere Anzahl der Axone im Nervus opticus des embryonalen Auges von Succinea 
putris lässt die Vermutung der Zellvermehrung im Verlaufe des Wachstums des Auges zu. 

Desmosomen findet man bei allen bisher beschriebenen Augen im apikalen Bereich der 
Retina. 



DANKSAGUNG 



Ich danke Herrn Prof. Dr. K. J. Götting und Herrn 
Unterstützung zur Verwirklichung des Posters. 



Dr. С J. Stoll für die freundliche 



LITERATUR 

BRANDENBURGER, J. L., 1974, Two new kinds of retinal cells in the eye of a snail, Helix aspersa. Journal 

of Ultrastructure Research, 50: 216-230. 
EAKIN, R. M. & BRANDENBURGER, J. L., 1975, Retinal differences between light-tolerant and 

light-avoiding slugs (Mollusca: Pulmonata). Journal of Ultrastructure Research, 53: 382-394. 
KATAOKA, S., 1975, Fine structure of the retina of a slug, Limax flavus L. Vision Research, 15: 681-686. 
ZUNKE, U., 1978, Bau und Entwicklung des Auges von Succinea putris (Linné, 1758) (Gastropoda, Stylom- 

matophora), I: Lichtmikroskopische Ergebnisse. Zoologischer Anzeiger, 201: 220-224. 



ABKÜRZUNGEN ZU FIG. 1-12 



Epidermis, Mikrovilli; 
Pigmentzelle, Mikrovilli; 
Nervus opticus; 

Nucleus der Bindegewebshülle des Nervus 
opticus; 

Pigmentzelle, Pigmentgranula; 
Pigmentzelle; 
Pigmentzelle, Nucleus; 
Retina; 
Sehzelltyp I; 
Sehzelltyp 11; 
Sehzelltyp I, Nucleus; 
SZN II Sehzelltyp II, Nucleus; 
Tentakelnerv; 

Sehzelltyp I, elektronenlichte Vesikeln; 
Sehzelltyp II, Vesikeln verschiedener Dichte 
und Grösse. 

^ ■ 

FIG. 8-12. Ausschnitte aus der Cornea und dem Nervus opticus. 8. Corneabereich des Auges eines 12 Tage 
alten Embryos (X3.700). 9. Corneabereich des Auges eines adulten Tieres (X3.700). 10. Nervus opticus eines 
adulten Auges, die Bindegewebskapsel durchbrechend (X3.700). 11. Unterschiedliche Vesikeln im Nervus 
opticus eines adulten Auges (X15.600). 12. Nervus opticus des Auges eines 12 Tage alten Embryos (X4.300). 



A 


Axone der beiden Sehzelltypen mit 


Vesikeln 


MVE 




(V); 




MVP 


AX 


Sehzelltyp II, Axon; 




NO 


В 


Bindegewebskapsel; 




NON 


CO 


Corneazelle; 






CON 


Corneazelle, Nucleus; 




P 


EPN 


Epidermis, Nucleus; 




PZ 


ER 


Endoplasmatisches Retikulum; 




PZN 


G 


Glaskörper; 




RE 


GA 


Golgi-Apparat; 




SZ 1 


GG 


Sehzelltyp 1, Glykogengranula; 




SZ II 


HD 


Hemidesmosomen; 




SZN 1 


L 


Linse; 




SZN 1 


M 


Mitochondrium; 




TN 


MU 


Bindegewebskapsel, Muskulatur; 




VI 


MV 1 


Sehzelltyp 1, Mikrovilli; 




V2 


MV 2 


Sehzelltyp II, Mikrovilli; 







MALACOLOGIA, 1979, 18: 7-11 

PROC. SIXTH EUROP. MALAC. CONGR. 

THE SPECIALIZATION OF THE APLYSIID GUT 



Vera Fretter and Ko Bun Hian 
University of Reading, England 

ABSTRACT 

Members of the subfamilies Aplysiinae and Dolabellinae contain the largest of living 
opisthobranchs. They are essentially herbivorous, ingesting relatively large fragments of a 
variety of algae. The food does not enter the stomach directly, but passes to a gizzard 
where it is triturated by teeth and digested by secretion from the digestive gland. Such 
small fragments as a filter chamber allows to pass and the products of digestion enter the 
stomach; the rest of the food is transferred directly to the intestine. In Ap/ysia punctata 
Cuvier and Dolabella auricularia (Lightfoot) a ciliary sorting mechanism within the 
stomach ensures that the largest particles found there do not enter the ducts of the 
digestive gland, but, together with waste from the gland, are compacted into pellets. The 
pellets, which incorporate the total waste from the stomach, are manufactured and 
routed to the intestine in areas isolated from the sorting areas and the ducts of the 
digestive gland; they retain their identity amongst the rest of the faecal matter, which has 
come from the foregut, and is relatively voluminous and loosely packed. Particles of food 
which will enter the digestive gland are maintained in the lumen of the stomach by 
opposing ciliary currents on folds of the wall, whilst the rejected ones pass along grooves 
between the folds and are directed posteriorly away from the openings ta the gland. The 
successful functioning of the gut is achieved in similar ways in the two species. Posterior 
to the conducting region of the oesophagus are the crop, gizzard and filter chamber 
where there is considerable mechanical activity and which are confined to a ventral part 
of the anterior haemocoel by a septum. The stomach, which may be closed to 
oesophagus and intestine by sphincters and valvular folds, receives ducts of the digestive 
gland ventrally and laterally, whilst dorsally a channel, separated by typhlosoles, leads to 
the intestine. This channel comes from a caecum in the posterior wall where the faecal 
pellets are formed. 



Members of the order Aplysiomorpha are the largest of living opisthobranchs. They are 
herbivorous, eating large fragments of algae, though if weed is not immediately available 
Dolabella auricularia (Lightfoot, 1786) (Bebbington, 1974) eats small invertebrates from sandy 
mud (Ko, 1976). The oesophagus and stomach (Eales, 1921, 1944, 1946) have certain 
characters that are found only in a few other gastropods, ail opisthobranch. The initial part of 
the oesophagus is a tube leading from the buccal cavity to the vicinity of the visceral mass, 
where it opens to a crop followed by a gizzard (Fig. 1). Peristaltic movements of the crop force 
food into the gizzard for trituration by large teeth on the wall. Anterior to these are small 
sharp teeth, elongated and recurved, which are directed forward on dilatation of the gizzard, grip 
the weed passing from the crop and drag it into the gizzard as they are rotated backwards on 
its contraction (at). Crop and gizzard contain a brown digestive fluid from the digestive gland 
which is mixed with the food. The similarity in size of particles in these 2 chambers indicates 
that the food is passed to and fro between them. The backward passage of the food from the 
gizzard is regulated by a filter chamber (Howells, 1942; 'posterior crop' of Eales, 1921, 1944) 
which leads to stomach and intestine. Its epithelium forms setae which are directed forwards 
and extend across the lumen when the chamber is constricted and prevent the escape of large 
particles. Fluid, with the products of digestion and the finest particles, passes through the filter 
to the stomach. The bulk of the food intake, however, is directed from the gizzard to the 
intestine. 

The stomach, a diverticulum arising between filter chamber and intestine, is relatively 
insignificant in size. It receives the broad ducts of the digestive gland (dd) which are long and 
much branched, and extends distal ly into a caecum (ce) which is comma-shaped and exposed 
on the surface of the gland. The walls of the stomach and the ducts are ciliated and have a 

(7) 



8 PROC. SIXTH EUROP. MALAC. CONGR. 

precise arrangement of folds. Along the dorsal gastric wall are two longitudinal typhlosoles (ti , 
t2) which pass into the caecum (though at times they may block its entrance) and subdivide 
the lumen into dorsal (dc) and ventral (vc) channels: the ventral communicates with that part 
of the stomach into which the ducts of the digestive gland open, and the dorsal with the 
channel between the two gastric typhlosoles (tj, t2) which leads to the intestine. The caecum is 
distinguished by its thick muscular coat of mainly circular fibres and by numerous epithelial 
glands in the dorsal channel. This channel is blocked at its inner end by a transverse bridge of 
tissue (tv). 

Details of gut structure are best known for Aplysia punctata (cf. Howells, 1942) and 
Dolabella auricularia (cf. Ko, 1976). Differences between them relate to the number of teeth in 
the gizzard, setae in the filter chamber and valves at the junction of filter chamber, stomach 
and intestine. In Aplysia Howells describes 4 or 5 rows of gizzard teeth (total number 50-60), 
small teeth comprising the 2 anterior rows. In Dolabella there are 6-8 small teeth in a single 
anterior row and an occasional one posterior to 2 rows of massive grinding teeth which total 9 
or 10. The filter chamber of Aplysia has fewer setae (about 24) not arranged in regular rows as 
in Dolabella (Fig. 1, se) where also 2 longitudinal rows are enlarged and directed towards the 
gastric opening. Valves which isolate the stomach from the filter chamber and intestine are 
figured for Dolabella. The 2 gastro-intestinal valves (gv) are present in Aplysia punctata 
('intestinal folds' of Howells), but no gastric valve (gav). In this species the gastric typhlosoles 
are longer, extending between the gastro-intestinal valves to the intestine (Fig, 2B, ti , ta) and 
there are no intestinal valves; in Dolabella these may represent the remains of gastro-intestinal 
typhlosoles (Fig. 1, iv). 

The muscular action of the walls of the gut maintains a constant exchange of material 
between crop and gizzard, a forward flow of digestive fluid which mixes with the food and the 
backward passage of this mixture. The filter chamber and valves at the entrance to the stomach 
ensure that only fluid and finely divided particles enter the stomach. Large pieces are prevented 
from escaping from the crop and gizzard by the filter and, if trapped there, are driven forward 
with digestive fluid giving the possibility of their digestion. Periodically the contents of the 
gizzard are sucked through the distended filter chamber to the anterior intestine. 

It has been concluded (Howells, 1942) that ciliary currents on the gastric walls of Aplysia 
are concerned only with the transfer of waste from the digestive gland to the caecum. A 
re-investigation of these currents shows that they provide a sorting mechanism for particulate 
matter entering the stomach. This results in the larger particles, apparently too big to be 
ingested by cells of the digestive gland, being directed into the caecum. The epithelial folds of 
the lateral and ventral gastric walls (Fig. 2B) are separated by deep troughs which can be widely 
opened over a limited area or closed by subepithelial muscles. The largest and heaviest particles 
(tested by carborundum) coming into contact with the summits of the folds are initially carried 
posteriorly with the smaller ones, but come under the influence of currents directing them into 
the troughs which open and allow them to enter (Fig. 2E). They pass along the troughs which 
lead to the caecal entrance and are joined by waste from the digestive gland. The small particles 
are raised from the surface of the epithelium by opposing ciliary currents at the sides of the 
closed troughs and sucked into the ducts of the gland. In Dolabella diatom frustules and sponge 
spicules are found in the stomach and caecal contents, but there is no evidence that such 
particles are taken up by the cells of the digestive gland. The caecum also contains an 
abundance of brown spherules from the excretory cells of the gland. 

The faecal matter in the stomach passes to the broad entrance to the ventral channel of the 
caecum where it accumulates in the lumen. It is carried posteriorly by ciliary currents and 
muscular activity and transferred to the dorsal channel (Fig. 2A, C, D). Here the contents are 
coated with secretion from epithelial glands and moulded into a faecal rod. Hashimoto et al. 
(1953) regarded this rod as a style with a weak amylase, but its ultimate fate refutes this idea. 
It is passed back into the stomach along the dorsal passage which leads to the intestine and is 
. ^ 

FIG. 1. Dolabella auricularia, gut opened mid ventrally. Scale does not allow longitudinal, epithelial folds of 
stomach and ventral channel of caecum to be indicated, ai, anterior intestine; at, gripping tooth; c, crop; ce, 
caecum; cm, circular muscles of gizzard; dc, dorsal channel; dd, duct of digestive gland; fc, filter chamber; 
gav, gastric valve; gi, gizzard; gt, grinding tooth; gv, gastro-intestinal valve; iv, intestinal valve; o, oesophagus; 
se, seta; sm, sphincter; st, stomach; t, caecal typhlosole; t, , tj , gastric typhlosoles; tv, transverse valve; vc, 
ventral channel. 



FRETTER AND KO 




10 



PROC. SIXTH EUROP. MALAC. CONGR. 




FIG. 2. Aplysia punctata. A, caecum and adjacent areas of stomach opened mid ventrally; arrows indicate 
ciliary currents on gastric typhlosoles and ventral channel of caecum. B, stomach opened mid ventrally; the 
gastric typhlosoles block the entrance to the caecum and intestine (large arrow). C, D, transverse sections of 
caecum at levels indicated by lines; note the thick muscular coat. E, diagram of piece of stomach wall to 
show folds separated by deep troughs, small particles (dots) driven into lumen by opposing ciliary currents 
(arrows), large particles carried into troughs and then towards caecum, f, faecal rod. Other letters as in Fig. 1. 



isolated from the rest of the stomach by the gastric typhlosoles. In the intestine of Dolabella 
rods up to 10 mm long, slightly shorter than the caecum, are found alongside unutilized food 
passed into it by way of the filter chamber. The intestinal contents include strips of Zostera up 
to 12 mm long, retaining their colour since only cells with injured walls are emptied. Similar 
observations have been made for Aplysia feeding on Ulva. 

The herbivore Akera bullata 0. F. Müller regarded by Guiart (1901) and Morton & Holme 



FRETTER AND KO 11 

(1955) as an aplysiomorph, has similar specializations of the gut: a gizzard, filter chamber ('2nd 
gizzard' of Morton & Holme), reduced stomach with a caecum and broad intestine which 
receives the bulk of the food directly from the filter chamber. The presence of plant fragments 
in faecal rods moulded in the caecum, in addition to waste from the digestive gland, indicates 
that there is a ciliary sorting mechanism in the stomach. A remarkably similar gut is also 
present in the closely allied thecosomatous pteropods. They are ciliary feeders taking mainly 
vegetable food, but there is no evidence that cellulose walls are weakened except by the 
crushing action of gizzard plates. The cone-shaped chamber posterior to the gizzard, which 
opens to intestine and stomach, has no filter (Yonge, 1926; Howells, 1936)— an unlikely 
requirement for a ciliary feeder. The gastric caecum has been regarded as a style sac (Morton, 
1954) and its contents as a style (Yonge, 1926; Howells, 1936). However, Howells (1942) 
re-investigated its structure in Cymbulia peronii (Blainville) and concluded that it was similar to 
that of Aplysia and concerned with consolidating faecal waste. Earlier (1936) he had suggested 
that there might be a sorting mechanism in the stomach with unwanted particles being directed 
to the intestine and not to the caecum as has now been shown for aplysiomorphs. 

Herbivorous prosobranchs rasp the plant tissue and ingest small fragments, but aplysiomorphs 
crop larger pieces gripping the weed with the radula and cutting it with jaws. In the absence of 
a cellulase and with a gizzard action which, partly on account of the speedy passage of food 
through the gut, results in poor fragmentation, a very high percentage of food remains 
undigested. This food by-passes the stomach leaving it free to deal with the filtrate of 
semi-digested food from the filter chamber. Certain characteristic functions of the molluscan 
stomach are retained, a ciliary sorting mechanism related to particulate matter and the 
elaboration of waste. Although the gut is wasteful of herbage its success is reflected in the 
speedy growth and size which some animals attain. 

LITERATURE CITED 

BEBBINGTON, A., 1974, Aplysiid species from East Africa with notes on the Indian Ocean Aplysiomorpha 

(Gastropoda: Opisthobranchia). Zoological Journal of the Linnean Society of London, 54: 63-99. 
EALES, N. В., 1921, Aplysia. Liverpool Marine Biology Committee Memoirs, 24: 1-84. 
EALES, N. В., 1944, Aplysiids from the Indian Ocean, with a review of the family Aplysiidae. Proceedings of 

the Malacological Society of London, 26: 1-22. 
EALES, N. В., 1946, The anatomy of Dolabella gigas. Proceedings of the Malacological Society of London, 

27: 109-118. 
GUI ART, J., 1901, Contributions à l'étude des gastéropodes opisthobranches et en particulier des 

cephaiaspides. Mémoires de la Société Zoologique de France, 14: 5-219. 
HASHIMOTO, Y., HIBIYA, T. & IWAI, E., 1953, On the crystalline style of Dolabella scapula. Comparative 

studies on the stomachal plates and crystalline style, 4. Bulletin of the Japanese Society of Scientific 

Fisheries, 19: 67-71. 
HOWELLS, H. H., 1936, The anatomy and histology of the gut of Cymbulia peronii (Blainville). Proceedings 

of the Malacological Society of London, 22: 62-72. 
HOWELLS, H. H., 1942, The structure and function of the alimentary canal of Aplysia punctata. Quarterly 

Journal of Microscopical Science, 83: 357-397. 
KO, В. H., 1976, Studies in the functional anatomy of Dolabella scapula (Martyn, 1786) and Pleurobranchus 

perrieri (Vayssibre, 1896). Ph.D. thesis. University of Reading. 
MORTON, J. E., 1954, The biology of Limacina retroversa. Journal of the Marine Biological Association of 

the United Kingdom, 33: 297-312. 
MORTON, J. E. & HOLME, N. A., 1955, The occurrence at Plymouth of the opisthobranch Akera bullata, 

with notes on its habits and relationships. Journal of the Marine Biological Association of the United 

Kingdom, 34: 101-112. 
YONGE, С M., 1926, Ciliary feeding mechanisms in the thecosomatous pteropods. Journal of the Linnean 

Society of London, Zoology, 36: 417-429. 



MALACOLOGIA, 1979, 18: 13-17 

PROC. SIXTH EUROP. MALAC. CONGR. 

SEXUAL DIMORPHISM IN BUCCINUM UNDATUM L. 

Cato С. ten Hallers-Tjabbes 
Geological Institute, State University, Groningen, the Netíierlands 

ABSTRACT 

The study of the variability in shape of fossil Gastropoda is limited to that of its only 
remnant, the shell. The aim of this study is to determine whether sexual dimorphism 
exists in the shell of Buccinum undatum L. Specimens of Buccinum have been taken 
from living populations. After experimenting on various ways of describing the shell 
shape quantitatively, it was found that discriminant analysis proved a rather successful 
method. This analysis revealed that, within a sample from one locality a high proportion 
(up to 90%) of shells of unknown sex can be classified correctly according to its sex. 
Differences in shape between the shells of different localities do occur and generally 
interfere with the sexual shape characteristics. 

The problem how to interpret shape features in shells, the only fossil remnants of most 
gastropods, is often raised among palaeontologists (Morse, 1876; Klähn, 1920; Pelseneer, 1935; 
Makowski, 1962; Gould, 1966; Raup, 1966; Sohl, 1969). One of the topics in this field is sexual 
dimorphism. It is seldom possible to tell the sex of a mollusc specimen from its shell. Usually 
we need the body in order to determine the sex. It will be shown in this paper, however, that 
from a detailed study of the shape of certain shells using quantitative measurements it is 
possible to determine the sex with surprising reliability. 

A suitable shell for investigations on this matter is Buccinum undatum L., the common 
whelk. Buccinum is large enough to provide measurements of good reliability. Samples of 
animals for this study were collected from the seabed, at various North European localities, 
mainly by scuba diving. The shells were marked according to sex, as determined by examining 
the soft body. 

As there is little and contradictory information on the aspects of the shell which might show 
sexual differentiation, the shape of the shell has to be analysed in as many details as possible, 
and preferably in 3 dimensions. A geometric system naturally suited to describe the shell is a 
cylindrical coordinate system in which the columella is used as zero-axis (see Fig. 1). A 
mechanical measuring device with electronic output was constructed in order to measure the 
following coordinates: ^—Xhe rotation angle in the shell from zero onwards; r— the horizontal 
distance from the zero-axis onwards; z— the vertical distance in the direction of the zero-axis. 
The shell can be turned around its axis to yield ^. Both r and z are measured by a system from 
outside the shell (see Fig. 2). The measuring was performed in points along the frame-pattern of 
the shell, the frame-pattern being a series of lines containing the most characteristic information 
about the shape of the shell (see Fig. 3). Among the shape elements the aperture is regarded as 
a most important feature of the whelk, this being the area where the animals might need 
differences in shape in order to perform their sexual acts. 

The measurement data of the lines were processed by computer. Initially all the measured 
lines were plotted 2-dimensionally and visually inspected to determine whether differences 
could be detected between male and female shells. For this purpose the coordinate system was 
converted into a cartesian one. Differences seemed to exist in the aperture, the aperture of the 
male being slightly longer than that of the female. Also some differences in aperture form 
appeared, although there is a big overlap between the 2 sexes. The other measured tracts did 
not show differences between the sexes. 

The 2-dimensional plots of the aperture in the horizontal and vertical planes suggested that 
differences might become more pronounced if the aperture would be projected onto an oblique 
plane. To investigate this possibility the coordinates were converted into coordinates arranged in 

(13) 



14 



PROC. SIXTH EUROP. MALAC. CONGR. 




FIG. 1. Whelk with coordinate system. 



slanting systems. Projections in 3 of the askew planes show a better pronounced difference 
between nriale and female shells, pointing towards the upper part of the aperture as the area of 
the shell showing most differences. The direction and change of direction in this part of the 
shell is not the same between males and females. 

Now the shells themselves were examined again, in order to see how this shows in the actual shell. 
The direction of the upper part of the aperture and the way of curving of the concave part just be- 
low it seems to differ in males and females. The dominating aspect is that the aperture of the fe- 
male shell has a rounder concave part, which is also located higher up (see Fig. 4). When guessing 
vyhether the shell belonged to a male or a female whelk, on the basis of this information, I guessed 
right 7 or 8 times out of 1 0. When this score is possible by eye there must be a way to teach the com- 
puter to discriminate between the sexes on the base of a method which can be generally applied. 

Because of the shape and the great individual differences a mathematical description of the 
aperture in a way that makes sexing possible is very complicated, if not impossible. Therefore a 
statistical approach was adopted. The most promising method seemed to be discriminant 
analysis, a technique in multivariate statistics in which data of members of groups are analysed 



TEN HALLERS-TJABBES 



15 




FIG.3. The frame-pattern. 



FIG. 2. Measuring equipment. 




16 



PROC. SIXTH EUROP. MALAC. CONGR. 




FIG. 4. The character of the differences between 9 and d. 




FIG. 5. Differences in shape of the shell of 2 populations. 



in order to draw from them discriminatory coefficients. Individuals that belong to one of the 
groups, but of unknown affinity can then be classified using the discriminatory coefficients. 

As direction and change of direction in the aperture seems characteristic of the differences 
between the sexes, the direction must be expressed in the data. In order to get comparable data 
on the aperture 16 points at equal distance were identified. Coordinates of these points were 
obtained by interpolating between the more than 16 measured points. Direction is expressed by 
vectors of unit length along the chords between adjoining points. The projections of these 
vectors in X-, y- and z-direction act as input parameters for the discriminant analysis program, 
together with the height of the aperture and a number indicating the sex of the whelk. 

Two samples of 140 whelks each, from 2 different localities, containing equal numbers of 
male and female shells, were subjected to this analysis. One third of each sample, randomly 
chosen, was not numbered according to sex, these were of "unknown" membership. Two thirds 
were used for the analysing part. All shells were then classified afterwards, applying the thus 
found discriminant coefficient. Of the "unknown" individuals of the two samples 75% and 90% 
was classified correctly. Of the "known" ones classification was correct in 92% and 99% of the 
cases. The better performance in the latter classification is probably due to a sampling effect. It 
is seen that this way of measuring and processing is quite successful. 

When discriminant analysis was applied to the combined samples of 280 whelks, the number 
of. correctly classified cases decreased both for the "unknown" and for the "known" individuals 
to 70% and 90% respectively. As this lower score might be dlje to the different origin of the 
samples, the same method was used to determine whether differences between the 2 samples 



TEN HALLERS-TJABBES 17 

existed. Indeed discrimination, based on factors independent of sexual dimorphism, between the 
2 samples from different localities proved possible, indicating that some effect of microgeo- 
graphical variation had entered the shape of the shell. 

This effect of location on the shell shape, whether genetical or controlled by environmental 
factors, might interfere with the method applied (see Fig. 5). For instance, the slenderness of 
the shell, at least one of the factors in which populations of 2 localities differ, influences the 
dimensions of the aperture. P' and P" (Fig. 5) are comparable points, but their coordinates do 
not show this. I am developing an adjusted computer program, accomodating the influence of 
slenderness on the aperture shape. To do this I concentrate on the upper part of the whelk, 
grown when the animal was sexually immature, and showing no visible differences between the 
sexes. I assume that from this part a measure of shell slenderness can be derived. Using this 
measure, the data of the aperture can be corrected for the effect of general shape of the shell. 

LITERATURE CITED 

GOULD, S. J., 1966, Allometry in Pleistocene land snails from Bermuda: the influence of size upon shape. 

Journal of Paleontology, 40: 1131-1141. 
KLÄHN, H., 1920, Der Wert der Variationsstatistik für die Paläontologie. Berichte der Naturforschenden 

Gesellschaft zu Freiburg im Breisgau, 22: 1-218. 
MAKOWSKI, H., 1962, Problems of sexual dimorphism in ammonites. Paleontología Polonica, 12: 1-92. 
MORSE, E. В., 1876, On a diminutive form of Buccinum undatum male, a case of natural selection. 

Proceedings of the Boston Society of Natural History, 18: 284-288. 
PELSENEER, P., 1935, Essai d'éthologie zoologique, d'après l'étude des mollusques. Académie Royale de 

Belgique, Brussels, 662 p. 
RAUP, D. A., 1966, Geometrical analysis of shell coiling: general prob\err\s. Journal of Pa/eonto/ogy 40: 1178- 

1190. 
SOHL, N. F., 1969, Gastropod dimorphism, in: Westermann, G. E. G., ed.. Sexual dimorphism in fossil 

Metazoa and taxonomic implications: 94-100. E. Schweizerbart'sche Verlagsbuchhandlung, Stuttgart. 



MALACOLOGIA, 1979, 18: 19-21 

PROC. SIXTH EUROP. MALAC. CONGR. 

L'UTILISATION DU MICROSCOPE ELECTRONIQUE À BALAYAGE 

DANS L'EXAMEN DES TISSUS MINÉRALISÉS 

CHEZ LES LAMELLIBRANCHES 

Alain Denis 

Laboratoire de Paléontologie, Bâtiment 504, Université de Paris XI, 91405, Orsay, Cedex 

ABSTRACT 

Mineralized tissues of bivalves were studied with the aid of the Scanning Electron 
Microscope. Bivalve shells have a layered structure underneath the organic periostracum. 
Three structural groups of mineralized tissue may be distinguished: (1) nacro-prismatic 
structures with an external prismatic layer (Fig. 1) and an internal nacreous layer (Fig. 
3), e.g. in Mytilidae and Unionidae; (2) foliated structures (Figs. 2 and 4), e.g. in 
Ostreidae, Pectinidae, Anomiidae, etc.; (3) crossed-lamellar structures (Figs. 5, 6 and 7), e.g. 
in Cardiidae, Glycymeridae, Veneridae, etc. Certain species also exhibit little canals or 
'tubules/ see Fig. 8. Evolutionary trends in the various bivalve families, both Recent and 
fossil, still have to be elucidated. 

Au cours du développement des organismes animaux et végétaux, les matériaux entrant dans 
la formation des parties dures (squelettes, carapaces, tests, etc.) sont toujours composés de 2 
types de substances: une substance minérale et une substance organique. Ces substances existent en 
proportion variable. Leur conservation est possible sous certaines conditions chez les fossiles. 
Les phénomènes biologiques et cytologiques, qui font que la matière minérale se constitue à 
partir de l'activité organique au niveau des tissus épithéliaux, se traduisent dans la microstructure 
des organismes. 

Tandis que chez les vertébrés, la phase organique est principalement constituée de collagène 
et la phase inorganique de СаСОз, les matrices organiques des invertébrés présentent une grande 
variation et les composants inorganiques sont nombreux. 

Les Mollusques possèdent une coquille calcaire sécrétée par le manteau. Le processus de 
formation de la coquille de Lamellibranche consiste essentiellement en un dépôt de cristaux de 
carbonate de calcium sur une matrice organique protéique ou conchyoline. Ces cristaux 
prennent naissance dans des sites de "nucléation" localisés à la surface de la matrice où existent 
des groupements chimiques adéquats aptes à permettre la constitution cristalline. Au cours de 
ce processus, 3 phénomènes dynamiques sont particulièrement remarqués: 

—les réactions métaboliques associées à la formation du carbonate de calcium et la synthèse 
de la matrice organique à partir d'un germe. 

—la sécrétion des constituants de la coquille par le manteau. La coquille est formée à partir 
d'une mince couche de liquide extra-palléal compris entre le manteau et sa surface interne. La 
gaz carbonique nécessaire est puisé soit dans le milieu, soit lors de la decarboxylation du cycle 
de Krebs. 

—la formation des couches cristallines. 

La croissance de la coquille est liée à l'accroissement du manteau en surface, poids et 
épaisseur; cet accroissement est fonction de la quantité de carbonate de calcium et de matrice 
organique. Le carbonate de calcium se dépose sous 3 formes: calcite, aragonite et moins 
fréquemment vatérite. La forme cristalline adoptée par le calcaire, d'origine alimentaire, dépend 
du milieu dans lequel le carbonate se trouve dissous. 

Les coquilles de Lamellibranches ont une disposition stratifiée en couches en dessous d'un 
revêtement superficiel ou periostraceum. Le nombre et la nature de ces couches sont variables; 
on en distingue habituellement 2 ou 3 (externe, moyenne et interne). L'étude fine de ces tissus 
minéralisés (couches) réalisée au Microscope Electronique à Balayage a permis d'observer les 
principales structures suivantes: prismatique, nacrée, foliée, lamellaire-croisée simple ou com- 
plexe. 

(19) 



20 PROC. SIXTH EUROP. MALAC. CONGR. 

L'association de ces types de structures détermine des groupes structuraux: 

(1) Le groupe nacro-prisrnatique a fondamentalement une couche externe prismatique (Fig. 
1), c'est à dire formée de lames de calcaire noyées dans de la conchyoline, et une couche 
interne nacrée (Fig. 3) comme chez les Mytilidés et Unionidés. 

(2) Le groupe folié (Fig. 2 et 4) où l'on observe une distribution tout a fait variable des 
lamelles croisées et des prismes (Ostréidés, Pectinidés, Anomiidés, etc.). Ce groupe est calcitique 
et aragonitique. 

(3) Le groupe lamellaire-croisé (Fig. 5, 6 et 7) a une couche interne lamellaire-croisee 
complexe, c'est à dire dans laquelle des unités primaires plus ou moins prismatiques sont 
constituées de lamelles de 2ème ordre qui s'irradient à partir de l'axe de ces unités primaires et 
une couche externe lamellaire-croisée, c'est à dire une structure où il y a un assemblage de 
lamelles de degrés d'ordre différent (1er, 2ème et 3ème ordre) organisées de telle façon que 2 
lamelles adjacentes de 1er ordre plongent dans 2 directions différentes en faisant un angle entre 
elles (Cardiidés, Glycyméridés, Vénéridés, etc.). Ce groupe a essentiellement une composition 
aragonitique. 

Certaines espèces présentent d'autre part des canaux ou "tubules" à l'intérieur de leur 
structure, la signification biologique de ces éléments restant imprécise (Fig. 8). 

Une étape ultérieure d'étude conduira à l'examen des tendances évolutives qui peuvent 
exister dans les différentes familles de Lamellibranches tant fossiles qu'actuelles. 

LITTERATURE CITEE 

ALLER, R. C, 1974, Préfabrication of shell ornamentation in the bivalve Laternula. Lethaia, 7: 43-56. 
DENIS,' A., 1972, Essai sur la microstructure du test de Lamellibranches. Travaux du Laboratoire de 

Paléontologie, Orsay, 89 p. 
ERBEN, H. K., 1974, On the structure and growth of the nacreous tablets in gastropods. В iomineraiisation, 7: 

14-27. 

GREGOIRE, С, 1961, Sur la structure submicroscopique de la conchyoline associée aux prismes des coquilles 
de mollusques. Bulletins de l'Institut Royal des Sciences Naturelles de Belgique, 37(3): 1-34. 

MUTVEI, H., 1972, Formation of nacreous and prismatic layers in Mytilus edulis. Biomineralisation, 6: 96-100. 

TAYLOR, J. D., KENNEDY, W. J. & HALL, A., 1969, The shell structure and mineralogy of the Bivalvia. 
Introduction, Nuculacea-Trigoniacea. Bulletin of the British Museum (Natural History), Zoology, Supple- 
ment 3: 1-125. 

TAYLOR, J. D., KENNEDY, W. J. & HALL, A., 1973, The shell structure and mineralogy of the Bivalvia II. 
Lucinacea-Clavagellacea, conclusions. Bulletin of the British Museum (Natural History), Zoology, 22: 
253-294. 

TOWE, K. M., 1972, Invertebrate shell structure and the organic matrix concept. Biomineralisation, ^■. 1-14. 

TRAVAUX DU LABORATOIRE DE MICROPALEONTOLOGIE, UNIVERSITE PARIS VI1974, 3, Applica- 
tion du MEB à la paléontologie et à la sédimentologie. 

WATABE, N., 1965, Studies on shell formation. XI. Crystal matrix relationships in the inner layers of 
molluscs shells. Journal of Ultrastructure Research, 12: 351-370. 

WILBUR, K. M. & YONGE, С M., 1964, Physiology of Mollusca. Vol. 1. Academic Press, 473 p. 

WILBUR, K. M. & WATABE, N., 1960, Influence of the organic matrix on crystal of molluscs. Nature, 188: 
334. 

WISE, S. W., 1970, Microarchitecture and mode of formation of nacre (mother-of-pearl) in pelecypods, 
gastropods and cephalopods. Eclogae Geologicae Helvetiae, 63: 778-797. 



FIG. 1. Couche prismatique. Unió, environ X2300. FIG. 2. Structure foliée; on y remarque une couche 
prismatique surmontant une couche lamellaire, Ostrea (Pliocène), environ X750. FIG.3. Structure nacro- 
prismatique, détail des prismes de la couche nacrée chez Mytilus, environ Х2300. FIG. 4. Structure foliée. 
Chama (Lutétien), environ XI 50. FIG. 5. Structure lamellaire-croisée avec lamelles de 1er ordre parallèles les 
unes aux autres chez Cardium, environ X150. FIG. 6. Détail de la structure lamellaire-croisée, Dreissena, 
environ X2300. FIG. 7. Couche externe lamellaire-croisée montrant les 2 directions d'empilement des lamelles 
de 1er ordre, Lima, environ Х250. FIG. 8. Couche externe prismatique avec existence de tubules surmontant 
une couche lamellaire-croisée interne, Spondylus, environ XI 50. 



DENIS 



21 







^"¿Si 




MALACOLOGIA, 1979, 18: 23-25 

PROC. SIXTH EUROP. MALAC. CONGR. 

SHELL MICROSTRUCTURE IN FOSSIL THECOSOME PTEROPODS 

Dennis Curry^ and Jeannine Rampai^ 

'^University College London, London WC1E 6BT, England 

and 
"^Université de Provence, 13331 Marseille Cedex 3, France 

In this preliminary study we have sought to discover whether the shell microstructure of 
living members of various families of the Thecosomata can be matched amongst fossil forms. 

MATERIALS AND METHOD OF STUDY 

Three species, each belonging to a different genus, have been studied. 

—A spirally-coiled form, Spiratella pygmaea (Lamarck), occurring in the Paris and Hampshire 
basins (Middle Eocene). 

—A form with a shell gently coiled in an open helix, Camptoceratops priscum (Godwin- 
Austen), known from the London and Aquitaine basins (Lower Eocene). 

—A form with a straight, bilaterally symmetrical shell, Vaginella depressa Daudin, occurring 
in the Aquitaine basin (Lower Miocene). 

The shell is broken along predetermined directions and the untreated fracture-faces so 
produced are metallised under vacuum with gold-palladium alloy and observed under a scanning 
electron microscope (J.S.M.P. 15, Université de Provence, Marseilles). 

RESULTS 

(1) Spiratella pygmaea (Lamarck) has a prismatic structure resembling that of certain living 
species of the same family (S. inflata, S. trochiformis). The prisms are like fine needles. They 
are mostly straight, but in some regions of the shell are slightly curved and, locally, arranged in 
a chevron pattern (Fig. 1a,b). Depending on their shape, the prisms lie approximately at right 
angles to the shell-surface or obliquely to it. The prismatic layer occupies almost the whole 
thickness of the shell and is normally covered on the outer surface of the shell with a thin layer 
of finely prismatic calcareous material. 

Study of other fossil species referred to the Spiratellidae is in progress to verify whether 
these all have the structural characters described above or whether some possess the crossed- 
lamellar or lamellar/prismatic structure known in certain living species belonging to the family. 

(2) Camptoceratops priscum (Godwin-Austen), whose shell is coiled in an open helix, has a 
spiral internal structure which foreshadows that of living straight-shelled forms. This remarkable 
structure is not known from any other group of the Mollusca (Rampal, 1972, 1975). The 
crystal units are in the form of long fibres which are strongly curved and which appear to 
follow a spiral path which encompasses almost the whole thickness of the shell (Fig. 1c,d). The 
outer surface is covered by a film of prismatic calcareous material of varying thickness. Near to 
the surface of the shell and over about a quarter of its thickness we have observed a pattern 
recalling that produced by the crossed-lamellar structure. Here the crystal elements lie in two 
directions inclined at about 130° and produce a latticed appearance (Fig. Id). As this pattern is 
not found in all layers of the shell, it is unlikely that it represents a special structure; we 
suspect that it is a result of the intermeshing of adjoining spiral fibres. 

(3) Vaginella depressa Daudin, a species with a straight shell, has an internal structure which 
resembles that of living symmetrical forms; that is, a characteristic spiral structure (Fig. 1e,f). 

(23) 



24 



PROC. SIXTH EUROP. MALAC. CONGR. 




FIG. 1. Vertical sections of shells seen under a scanning electron microscope: a-b, Spiratella pygmaea 
(Lamarck); c-d, Camptoceratops priscum (Godwin-Austen); e-f, Vaginella depressa Daudin. 



CURRY AND RAMPAL 25 

The long fibres arising at different levels are aligned diversely but In combination build up the 
total spiral pattern (Fig. If). The layer with spiral structure is overlain by a prismatic zone 
which varies in thickness but is always relatively thin. The above structural pattern has been 
observed also in another species of Vaginella. 

CONCLUSION 

The shells of living representatives of the different families of the Thecosomata are 
characterised by considerable structural diversity. Shells of spiral shape show a prismatic and/or 
crossed-lamellar structure, whilst straight shells have a spiral structure. 

The fossil species with a spiral shell, Spiratella pygmaea, has a prismatic structure resembling 
that of some living shells of the same genus. However, it differs in that the constituent prisms 
are more or less strongly curved. Further study is required to explore whether this peculiarity is 
a specific one or whether it is found in other representatives of the Spiratellidae. 

The 2 straight-shelled forms, Camptoceratops priscum and Vaginella depressa, display the 
spiral structure seen in living straight-shelled members of the Thecosomata. It seems that the 
evolution in that group from spiral to straight shells was reflected at a very early stage in the 
shell microstructure of the fossil forms. 

The difficulty of deciding whether a particular spirally-coiled molluscan shell should be 
referred to the gastropods or the thecosomes is well-known. The principal diagnostic characters 
applied to fossil shells were listed by Curry (1965). However, it seems that a systematic study 
of shell microstructure may provide additional data for the resolution of this problem in cases 
of doubt. 



LITERATURE CITED 

CURRY, D., 1965, The English Palaeogene pteropods. Proceedings of the Malacological Society of London, 

36: 357-371. 
RAMPAL, J., 1974, Structure de la coquille des Ptéropodes au microscope à balayage. Rapports et 

Procès- Verbaux des Réunions, Commission Internationale pour l'Exploration Scientifique de la Mer 

Méditerranée, 22(9) : 133-1 34. 
RAMPAL, J„ 1975. Les Thécosomes (Mollusques pélagiques). Systématique et évolution. Ecologie et 

biogéographie méditerranéennes. Thèse Doctorat d'Etat, Université de Provence, Marseille, CNRS АО. 

11932, 485 p. 



MALACOLOGIA, 1979, 18: 27-30 

PROC. SIXTH EUROP. MALAC. CONGR. 

STROBILATION IN A PTEROPOD (GASTROPODA, OPISTHOBRANCHIA) 

S. van der Spoel 

Institute of Taxonomic Zoology (Zoological Museum), 
Plantage Middenlaan 53, Amsterdam, the Netherlands 



ABSTRACT 

The splitting of individuals of dio pyramidata into 2 new specimens is a type of 
behaviour not expected to occur annongst Mollusca. After Van der Spoel (1973) was 
published, 2 questions were still left unanswered. The first one is "how does the primary 
specimen develop" and the 2nd is "is it real strobilation"? A detailed histological 
investigation of the primary animal after completion of the transversal fission revealed 
that there was no organ system or tissue in a stage of breaking down, while the gonads, 
accessory sexual glands, seminal groove and penis were in a stage of renewed develop- 
ment. Moreover the mantle gland, regarded as a shell secreting organ, was even more 
active than in juveniles with not yet fully developed shells, while the activity of neural 
cells in the pedal ganglia and commissures seems to be comparable with those of specimens 
in an early male phase. Consequently it seems acceptable to consider the primary speci- 
men as again developing into a normal male specimen. Specimens were examined to 
find out whether the fission is perpendicular to the body axis of the animal and whether 
original liver tissue is present in the aberrant stage. These 2 facts are major characters of 
strobilation and both are found to be present in Clio pyramidata so that real strobilation 
seems to occur here. 



INTRODUCTION 

Mollusca are so typical that they share only few special characters with other invertebrate 
phyla. Most clear links with other groups consist of the worm-like trochophore larvae, the 
segmentation as found in Neopilina, the haemocyanine as in Arthropoda and probably the 
coelenterate-like strobilation. It is my opinion that a phenomenon of this last type is found in 
Clio pyramidata Linnaeus, 1767. In this cosmopolitan, oceanic plankton species, vegetative 
reproduction by division of the body into two parts occurs under natural conditions. No 
parasites or external damage have ever been found amongst the more than 100 specimens 
studied histologically or as intact soft parts. The phenomenon of vegetative reproduction has 
been found in all parts of the range of the species, though its frequency seems higher in 
hydrologically instable areas. 

STROBILATION IN COELENTERATA 

Strobilation in Coelenterata is transverse fission of a polyp. "In nature, . . . , polyps undergo a 
segmentation, or strobilation, process, i.e., transverse epidermal constrictions mark off a series 
of segments of the trunk, forming in sequence beginning at the distal end and eventually 
consuming all but the basal part of the polyp" (Berrill, 1971: 162). During this process there is 
no destruction of old tissues, but there occurs metamorphosis and regeneration. The strobilus 
(ephyra) is detached from the oral side, the fission crosses the primary body axis perpendicu- 
larly. It takes place in an area where inducers or inducer-transport, regulating development and 
differentiation, are in equilibrium. At both sides of the fission undifferentiated mesenchymous 
tissues are present. The apical pole of the polyp stays in position, the oral side develops a new 
"oral field." The posterior, detached part, the ephyra, develops a new anterior part. 

If the opisthobranchous pteropod Clio shows real strobilation, exactly the same has to occur. 
In my 1973 paper I suggested that strobilation might be the case and a strobilating Clio was 
described, but proof for strobilation could not be given. 

(27) 



28 PROC. SIXTH EUROP. MALAC. CONGR. 

THE PRIMARY BODY AXIS 

The study of Miss Pafort-van lersel (in this volume) showed that the columellar muscle 
system in Clio is the same as a dorsoventral or septal muscle system, running from apical to 
oral. Here the terminology of Lemche (1971) is followed, being the only adequate one when 
comparing Mollusca with Coelenterata. The course of the columellar muscles thus marks the 
embryonic axis of the species. The fission between the two parts found in Clio is 
perpendicular to this body axis. The separation also crosses the four quadrants (A, B, С and D) 
which are in the upper part of the body, each characterized by a branch of the columellar 
muscle and by septal organs like penis, accessory sexual gland and by the incisions between the 
lobes of the hepatopancreas gland. 

The section which in previous publications I called "aberrant, resting stage or secondary 
animal," thus the part below the split, is comparable to the polyp; the primary specimen or the 
part above the split is comparable to the ephyra or medusa. 

THE SPLITTING 

The incision between this "polyp" and "medusa" does not divide ail organs into two parts. 
Only the skin (ectoderm), the liver (interstitial mesenchymous tissues), a genital tissue 
(meso-ectoderm) and the columellar muscle are split. The epidermal constriction occurs directly 
below the most caudal loop of the intestine so that no part of the endoderm is left in the 
lower part of the body (polyp) after division. 

A new development in the area of epidermal constriction is the body of reserve food, which 
is found on top of the "polyp." Theoretically this mass of reserve tissue can be explained as 
follows. Fission occurs at a place where the concentration of inducers is in equilibrium, which 
permits regeneration and new development at both sides of the fission, differentiation in this 
area is thus ambivalent (Berrill, 1971). Strobilation in Clio is to all probability a slow process, 
because completion of the fission is preceded by development of undifferentiated reserve 
tissues. This reserve food is the only nutrition available to the "polyp" during its first 
development. 

Apart from reserve tissue, parts of the liver are also located in the "polyp," which is very 
important as this type of undifferentiated tissue guarantees the possibility of development of 
new organ systems, which is a major criterion for strobilation. 

THE SPLITTING OF THE COLUMELLAR MUSCLE 

In an earlier paper (1973) I assumed that the anterior part or "polyp" realised a secondary 
fixing to the shell and that detachment preceeded strobilation. If this is correct the soft parts, 
originally developed in the shell, detach and form a bud anteriorly. This bud then can realise 
this secondary attachment, and no strobilation has occurred. 

However, all columellar muscles which lost contact with the shell or those which have 
recently become fixed secondarily, show twisting, or if this is not the case, the body is curled. 
The columellar muscle in the "medusa" or posterior part of the animal is always strongly 
twisted and the body is usually curled. In the anterior or "polyp" part twisting is never found. 
So the "polyp" has to all probability always been fixed to the shell, and the medusa is the only 
part which became detached. This evidently shows that no budding but real strobilation is 
found in these animals. 



DEVELOPMENT OF THE ANTERIOR PART 

The growth of the anterior part or polyp has been described before (Van der Spoel, 1963, 
1967, 1973) but the typical characters of this development were not understood. However, a 
comparison with embryonic development is possible. 

In the "polyp" a completely new gastric invagination takes place. The extremely thick 



V. d. SPOEL 29 



ttttt 

FIG. 1. Strobilation in Clio pyramidata (from left to right) (altered after Van der Spoel, 1973). 



mucus cover of the "polyp" seems to have no function, as it is not concerned in feeding, unless 
one compares it with similar parts in invertebrate blástula and gastrula stages (cf. Berrill, 1971) 
where it contains the factors responsible for the regulation of differentiation and invagination. 

The invagination results in a mouth, which is situated opposite to the attachment of the 
columellar muscle to the shell. This is thus comparable to normal larval invagination (the mouth 
is ontogenetically ventral, though with regard to the shell it is in dorsal position). The position 
of the wings in regard to the mouth in normal Thecosomata (not in Gymnosomata) suggests 
that the wings are a modified velum. If this is correct, the wings of the "polyp" also develop 
like a velum posterior to the mouth. 

Another resemblance with embryos of Gastropoda is the development of the undifferentiated 
liver tissues. These interstitial tissues grow exactly as the mesoderm does in Haliotis embryos, as 
a left and a right band into the anterior body pole. Whether this is an analogy or homology I 
am not sure. 



DEVELOPMENT OF THE POSTERIOR PART 

The upper part or "medusa" attains full development after splitting from the "polyp." This 
could have been suggested already in my 1973 paper, but at that time it was impossible to 
trace gonad, gonoduct and accessory sexual glands. These organs have now been discovered as a 
band of interstitial cells present on the left side of the body between the neck and the place of 
fission. These cells occupy exactly the same place as the initial cells of the genital system in 
juveniles. As penial development and the occurrence of a seminal groove is also evident, it must 
be concluded, that the "medusa" develops again into a functional male specimen. However, it 
has lost its shell. 

The shell secreting glands in the mantle edges on the other hand proved to be active, 
secretory cells being even more numerous than in juveniles. In all probability, a new shell is 
thus formed, but it is out of the question that an embryonic shell is formed by this stage. Thus 
there must exist specimens of Clio pyramidata with embryonic shells (direct development) and 
without embryonic shells (developed through strobilation). Both types of shells are usually 
present in larger samples, but absence of protoconch was usually attributed to damage. 
Probably, however, a number of these "damaged" shells belong to specimens born by strobilation 
and in that case the absence of a protoconch is normal. 

CONCLUSION 

The direction of cleavage and the development of the two separate parts when Clio 
reproduces vegetatively, unmistakably point to the occurrence of strobilation in this opistho- 
branch mollusc. This is a firm support for the theory that Mollusca are related to Coelenterata. 



30 PROC. SIXTH EUROP. MALAC. CONGR. 

The conclusion that pteropods or opisthobranchs thus are a primitive group, however, does not 
hold. Explanation for strobilation in Clio can better be found in the fact that these 
euthecosomatous pteropods are neotenous animals. The structure of the muscle system (cf. 
Pafort-van lersel, this volume) and the foot parts as well as the development of the shell (Van 
der Spoel, 1976) give strong evidence for the fact that the adult Clio is of a juvenile structure. 



LITERATURE CITED 

BERRILL, N. J., 1971, Developmental biology. McGraw-Hill Book Company, New York, 535 p. 

LEMCHE, H., 1971, Phylogeny as elucidated by the basic morphological pattern of metazoans. / Simposio 

Internacional de Zoofilogenia, 1969: 203-208. Universidad de Salamanca. 
PAFORT-VAN I ERSE L, T., 1979, The columellar muscle system in Clio pyramidata and Cymbulia peroni 

(Thecosomata, Pteropoda). Malacologie, 18: 31-35. 
SPOEL, S. VAN DER, 1963, Aberrant forms of the genus Clio Linnaeus, 1767 with a review of the genus 

Proclio Hubendick, 1951. Beaufortia 9(107): 173-200. 
SPOEL, S. VAN DER, 1967, Eu thecosomata, a group with remarkable developmental stages (Gastropoda, 

Pteropoda). Noorduyn, Gorinchem, 375 p. 
SPOEL, S. VAN DER, 1973, Strobilation in a mollusc; the development of aberrant stages in Clio 

pyramidata Linnaeus, 1767 (Gastropoda, Pteropoda). Bijdragen tot de Dierkunde, 43: 202-215. 
SPOEL, S. VAN DER, 1976, Finer sculptures in euthecosomatous shells, and their value for taxonomy 

(Mollusca, Pteropoda). Beaufortia 24(314):105-132. 



MALACOLOGIA, 1979, 18: 31-35 

PROC. SIXTH EUROP. MALAC. CONGR. 

THE COLUMELLAR MUSCLE SYSTEM IN CLIO PYRAMIDATA AND 
CYMBULIA PERONI (PTEROPODA, THECOSOMATA) 

Trudy Pafort-van lersel 
Institute for Taxonomic Zoology (Zoological Museum), University of Amsterdam, the Netherlands 

ABSTRACT 

The presence and stmcture of the columellar muscles in Cfio pyramidata and 
Cymbulia peroni have been investigated. In Clio this muscle is attached to the shell 
aborally; above the diaphragm it splits into 2 branches, besides a branch ramifying to the 
penis. The 2 main columellar muscle branches split off 2 ventral ramifications each, while 
the remaining parts fan out into the wings. In Cymbulia the aboral part of the muscle has 
disappeared, the oral part shows the ramification to the penis, but is otherwise reduced. 
The phylogeny of the genera Clio and Cymbulia is discussed, and a Coelenterata-like 
ancestor is accepted for the whole group of Thecosomata, while it is postulated that Clio 
shows the primitive characters, on which the above conclusion is based, because of the 
fact that its adults, being neotenous, show a "larval stage" of development. 

INTRODUCTION 

The purpose of the present investigation is to explain the phylogenetic relation between Clio 
pyramidata Linnaeus, 1767, and Cymbulia peroni De Blainville, 1818, based on the structure of 
the columellar nriuscle system, and to trace the phylogenetic relations of the Thecosomata. 

The specimens of Clio pyramidata have been taken from different samples of the Ocean Acre 
Project (Bermuda area) and those of Cymbulia peroni from different samples of the Dana 
Expeditions and the collection of the Institute of Taxonomic Zoology (North Western 
Atlantic). Of both species a series of specimens was sectioned (5дт), stained with H.E., 
Crossmon or Azan and used for histological study; other specimens were studied intact, either 
anatomically or after elucidation with transparent light. 

The author is very much indebted to Dr. С F. E. Roper and Dr. J. Knudsen for providing 
material, 

MUSCLE SYSTEM IN CLIO 

The mantle muscles and columellar muscle of Clio pyramidata are of the same histological 
structure and they belong to the same system. Aborally the columellar muscle is found dorsad 
and the mantle muscles ventrad. The origin of these muscles is near the embryonic shell. The 
mantle muscles are attached below the origin of the columellar muscle. In spiralized species this 
is a normal situation (cf. Cylichna in Lemche, 1956) and it points to spiral isation in the 
ancestors of Clio. At the aboral side near the apex, 8 mantle muscles occur, slightly shifted to 
the left side of the mantle. The 2 large ventral mantle muscles are fastened to the shell through 
connective tissue. The origin of the other 6 mantle muscles is not always clear; maybe some of 
them originate from the columellar muscle as is also known for other Opisthobranchia (Brace, 
1977; Lemche, 1956). The muscles in the mantle probably have a retractor function while a 
more transversal course at some places is related to the protection of organs like heart and 
kidney in the mantle cavity. On the other hand it is possible that the mantle muscles promote 
the water current in the mantle cavity (Eales, 1949; Brace, 1977). 

Below the diaphragm, the dorso-anterior part of the strongly developed columellar muscle 
has a retractor function. Due to the straight shell, the retractor part is symmetrically situated 
with regard to body and shell. 

(31) 



32 



PROC. SIXTH EUROP. MALAC. CONGR. 



In the neck region the columellar nnuscle penetrates into the body, where it gives rise to the 
penis retractor and splits asymmetrically into 2 unequal bundles situated slightly to the right. 
There are few features in the anatomy which point to a spiralised origin; the asymmetry of the 
columellar muscle-bundles in the neck is one of them. In the wings and head-parts no sign of 
asymmetry is found. This also corresponds with spiralised species, where the asymmetrical 
organisation of the body does not influence the head-parts (Eales, 1949). 

In the head a ramifying pattern of 8 columellar muscle bundles is found. Two ramifications 
fan out into each wing, while the other 4 bundles terminate in the posterior foot lobe near the 
mouth (Fig. 1, 2). This division of muscles very strongly resembles the division of muscles over 
4 quadrants as found in coelenterates and worms. 

Besides having a rectractor function, the sections of the muscle in the wing also contribute 
to the swimming movements, while the bundles in the head and posterior foot lobe are 
concerned with food collecting. The subdivision into some smaller bundles in the head region 
increases the mobility in that part of the body (Brace, 1977), which has a positive effect on the 
collecting of food. 

Along its course through the body, anchorage of the columellar muscle is ensured by thin 
muscle filaments, originating from the columellar muscle and terminating in mantle integument, 
body wall and wing wall. In other opisthobranchs like Philine (cf. Brace, 1977) and Cylichna 
(cf. Lemche, 1956) similar structures are found. The anchoring probably has a double purpose: 
all parts of the body become connected with the retractory system by these filaments, and the 
muscle is kept in position. 



PFL 



CMW SC PR CMO TWM 



w- 



D_ 
PR- 



S 

CM 




CMW 



CMLW О P^ CMRW 

CMLP CMRP 



FIGS. 1-2. Clio pyramidata, 1. schematic dorsal view; 2. schematic cross-section near the mouth. 

FIGS. 3-4. Cymbulia peroni, 3. schematic longitudinal section dorsad to the oesophagus; 4. schematic 
cross-section oral to the diaphragm. 

Abbreviations: bm, body muscles; cm, columellar muscle; cmlp, columellar muscle branches in left part of 
posterior foot lobe; cmlw, columellar muscle branches in left wing; сто, columellar muscle branches near the 
oesophagus; cmrp, columellar muscle branches in right part of posterior foot lobe; cmrw, columellar muscle 
branches in right wing; cmw, columellar muscle branch in wing; d, diaphragm; m, mantle; o, oesophagus; p, 
penis; pfl, posterior foot lobe; pr, penis retractor; ps, pseudoconch; s, shell; sc, supporting cell; sew, wall of 
supporting cells; twm, third aboral muscle layer of wing; w, wing. 



PAFORT-VAN lERSEL 33 

The walls of the wings contain 2 layers of strongly developed striated muscles each. In 
opisthobranchs there is a stronger development of body wall musculature than in other 
gastropods, while the importance of the columellar muscle decreases. Especially in pteropods, 
considered to be the best swimming opisthobranchs, the striated musculature of the wing wall is 
very strongly developed (Thompson, 1976). 

The muscles of stomach and oesophagus belong to a common system. The radula muscles are 
probably connected with the columellar muscle system, but the material studied gives no 
certainty. 

One may conclude from the structure of the columellar system that Clio develops without 
metamorphosis. The adult still shows its larval stage. This is supported by the orientation of the 
mantle muscles somewhat to the left of the middle, and of the columellar muscle somewhat to 
the right of the middle in the neck region of the body, and by the place of the origin in the 
shell. The mantle muscles have to be considered as the original right retractor muscle in the 
veli^er of Opisthobranchia (Brown, 1934), which is turned to the left in the Cavoliniidae by the 
180 rotation of the body part (Meisenheimer, 1905; Tesch, 1913; Bonnevie, 1914). In the 
same way the columellar muscle of Clio, orientated slightly to the right, resembles the left 
retractor muscle in the veliger of Opisthobranchia, running to the velum and operculum (into 
the wings and posterior foot lobe respectively). The structure of the shell also points to a direct 
development from a larval stage and to absence of metamorphosis (Van der Spoel, 1976a). The 
fact, that the adult when full-grown is still in a larval stage may be considered a logical 
consequence of the identical pelagic behaviour of larva and adult. 

The asymmetrical orientation of the 2 columellar muscle ramifications in the neck region, 
the origin of the columellar muscle above the fastening of the mantle muscles and the trace of 
spiralisation in the soft parts of the larvae (Van der Spoel, 1967), point to a spiralisation in the 
ancestors of Clio. Therefore, the external symmetry is an adaptation to the pelagic way of life 
and so of a secondary nature. Consequently, there is no reason to doubt the commonly 
accepted theory, that within the Euthecosomata the Limacinidae are the ancestors of the 
Cavoliniidae (Pelseneer, 1892; Tesch, 1904; Meisenheimer, 1905; Bonnevie, 1914; Van der Spoel, 
1967; Minichev, 1967). 

MUSCLE SYSTEM IN CY MBU LI A 

According to Meisenheimer (1905) and Tesch (1913), the muscle plates or body muscles 
laterad to the body of Cymbulia peroni, would be identical with the columellar muscle. The 
present investigations, however, proved the lack of a columellar muscle aboral to the diaphragm. 
In Cymbulia, as is normal in Opisthobranchia, the loss of the shell is coupled with the loss of 
the retractory and attaching part of the columellar muscle (Lang, 1900). The forming of a 
secondary gelatinous shell did involve the forming of secondary attaching muscle systems, the 
muscle plates. These body muscles develop from an outer striated muscle layer of the wing 
wall. They are not attached to the pseudoconch, but terminate in mantle integument 
(Meisenheimer, 1905; Van der Spoel, 1976b). The muscle plates are doubly folded; the median 
parts are situated inside the pseudoconch, the lateral parts outside, in the external mantle 
integument (Fig. 3). 

Oral to the diaphragm a weakly developed part of the columellar muscle system is still 
found. Some bundles run from the diaphragm dorsad along the oesophagus towards the area of 
the mouth as also found in the tectibranch Philine (Brown, 1934; Hurst, 1965; Brace, 1977). 
Like in Clio the penis retractor ramifies from this part of the columellar system. Obviously this 
part of the columellar muscle is functionally related to internal food transport. Connections of 
the collumellar muscle with buccal organs have not been found. 

Part of the columellar muscle runs in the wing lumen between the walls of the wing, where 
small muscle filaments radiate. These muscles contribute to the swimming locomotion of 
Cymbulia. The columellar muscle filaments in the wings are connected with numerous 
supporting cells, between the walls of the wings. The latter maintain the shape of the large wing 
disc (Fig. 3). Two little walls of supporting cells found lateral to the penis, besides having a 
supporting function, probably also have something to do with the evagination of the penis, 
because they have a larger quantity of muscle filaments than other supporting cells. These 



34 PROC. SIXTH EUROP. MALAC. CONGR. 

supporting "walls" and the large supporting cells attach themselves ventrad and laterad on the 
diaphragnn, forming a protecting envelope around oesophagus, ganglia and penis, and they 
separate the wing disc from the rest of the body (Fig. 4). 

As in Clio the circular muscles of stomach and oesophagus form one single system. Only a 
few mantle muscle filaments could be recognised in the mantle; it seems that this system is not 
well developed. 

The strongly developed striated muscles of the wall of the wing disc contain orally 2 layers 
and aborally 3 layers. The body muscles originate from the 3rd aboral layer. 

In CymbuHa a metamorphosis occurs during which, among other changes, the larval shell is 
thrown off (Thiriot-Quiévreux, 1970). There are no indications, that the reduced columellar 
muscle system did develop from a larval system, as supposed for Clio. But for Cymbulia too, 
there is no difference between the pelagic way of life of larva and adult. 

Some features point in the direction of spiralised ancestors: the external symmetry is 
secondary. For example, on the right the mantle cavity penetrates further dorsad (Meisen- 
heimer, 1905); the position of the body muscles is asymmetrical; one osphradium is present on 
the right side; the embryonic shell is ultra-dextral (Pelseneer, 1891). As to the present 
investigations, there is no cause to doubt the commonly accepted theory that the ancestor of 
Cymbulia \s Peraclis (Meisenheimer, 1905; Bonnevie, 1914; Tesch, 1948; McGowan, 1968). 

PHYLOGENY 

The columellar muscle systems of Clio pyramidata and CymbuHa peroni are quite different. 
In Clio the columellar muscle is a strongly developed larval muscle system, whereas in Cymbulia 
the columellar muscle is reduced and many parts have even disappeared. 

It seems that the adaptation to a pelagic behaviour of adults in Thecosomata resulted in Clio 
in the disappearance of a real metamorphosis (neoteny), while in the Cymbuliidae the 
calcareous shell is replaced by a gelatinous pseudoconch, thus increasing the floating capacity, 
while the columellar system is strongly reduced. Clio and Cymbulia belong to different lines of 
development of which the Pseudothecosomata seem to be more adapted to a pelagic life and 
therefore they are the most progressive group of the Thecosomata. The Euthecosomata and 
Pseudothecosomata are supposed to be related through an unknown ancestor which gave rise to 
Limacina and Peraclis respectively (Meisenheimer, 1905; Tesch, 1914, 1948; Van der Spoel, 
1976b). 

In Clio pyramidata 2 facts need special attention. First there is the strobilation as described 
by Van der Spoel (1967, 1973), a process comparable with the strobilation in Annelida and 
Coelenterata. Secondly we see in both mantle and head a pattern of 8 muscles of the 
columellar system. The posterior parts can be divided into 4 ontogenética! quadrants, each with 
2 ramifications of the columellar muscle (right wing, left wing, right part posterior foot lobe, 
left part posterior foot lobe, see Fig. 2). This situation resembles that in Cylichna (Lemche, 
1956) and suggests a phylogenetic relation with Annelida or Coelenterata. The 8 muscles in the 
head perhaps also resemble the 4 parts of larval retractor muscles in the Opisthobranchia. 
According to Lemche (1966), the 8 larval muscles show that the molluscs must be derived from 
a primitive tetracyclomeric type of organism like the Coelenterata and that 'from Molluscan-like 
ancestors Arthropods and Annelids have evolved independently.' 

Summarizing, we may state that in the opisthobranch Clio pyramidata 2 primitive features 
appear, which affirm the possible relation to a Coelenterata-like ancestor. The fact that both 
these primitive features appeared in Clio, may be due to the 'larval stage' of the adult. 

LITERATURE CITED 

BONNEVIE, K., 1914, Remarks on the phylogeny of Pteropods. IXe Congrès International de Zoologie, 

Monaco, 25-30 mars 1913, section 5: 617. Berthüs, Rennes. 
BRACE, R. C, 1977, The functional anatomy of the mantle complex and columellar muscle of tectibranch 

molluscs (Gastropoda, Opisthobranchia), and its bearing on the evolution of opisthobranch organization. 

Philosophical Transactions of the Royal Society of London, B277: 1-56. 
BROWN, H. H., 1934, A study of a tectibranch gastropod mollusc Philine aperta (L.). Transactions of the 

Royal Society of Edinburgh, 58: 179-210. 



PAFORT-VAN lERSEL 35 

EALES, N. В., 1949, Secondary symmetry in gastropods. Proceedings of the Malacological Society of 

London, 28: 185-196. 
HURST, A., 1965, Studies on the structure and function of the feeding apparatus of Philine aperta with a 

comparative consideration of some other opisthobranchs. Malacologia, 2: 281-347. 
LANG, A., 1900, Lehrbucti der Vergleicfienden Anatomie der Wirbellosen Thiere. Mollusca (1). Fischer, Jena 

viii + 509 p. 
LEIVICHE, H., 1956, The anatomy and histology of Cylictina. Spolia Zoológica Musei Hauniensis, 16: 1-278. 
LEMCHE, H., 1966, The place of Mollusca among invertebrates. Malacologia, 5: 7-10. 
MCGOWAN, J. A., 1968, Thecosomata and Gymnosomata. Veliger, 3, supplement: 87-135. 
MEISENHEIMER, J., 1905, Pteropoda. Wissenschaftliche Ergebnisse der Deutschen Tiefsee-Expedition auf 

dem Dampfer "Valdivia" 1898-1899, 9(1): 1-314. 
MINICHEV, Y. S., 1967, Studies on the morphology of the Lower Opisthobranchla (on the evolutionary 

significance of the detorsion-process). Trudy Zoologichesko Institute, Akademiya Nauk U.S.S.R., Lenin- 
grad, 44: 109-182 (in Russian). 
PELSENEER, P., 1891, Sur la dextrosité de certains Gastéropodes dits "sénestres." Comptes Rendus des 

Séances de l'Académie des Sciences, 112: 1015-1017. 
PELSENEER, P., 1892, La classification générale des mollusques. Bulletin Scientifique de la France et de la 

Belgique, 23: 1-27. 
SPOEL, S. VAN DER, 1967, Euthecosomata, a group with remarkable developmental stages (Gastropoda, 

Pteropoda). Noorduijn en Zoon, Gorinchem, 375 p. 
SPOEL, S. VAN DER, 1973, Strobilation in a mollusc; the development of aberrant stages in Clio pyramidata 

Linnaeus 1767 (Gastropoda, Pteropoda). Bijdragen tot de Dierkunde, 43: 202-215. 
SPOEL, S. VAN DER, 1976a, Finer sculptures in euthecosomatous shells and their value for taxonomy 

(Mollusca, Pteropoda). Beaufortia, 24(314): 105-132. 
SPOEL, S. VAN DER, 1976b, Pseudothecosomata, Gymnosomata and Heteropoda (Gastropoda). Bohn, 

Scheltema en Holkema, Utrecht, 484 p. 
TESCH, J. J., 1904, The Thecosomata and Gymnosomata of the Siboga Expedition. Siboga-Expeditie, 52: 

1-92. 
TESCH, J. J., 1913, Pteropoda. In: SCHULZE, T. E., ed.. Das Tierreich. Friedländer, Berlin, 170 p. 
TESCH, J. J., 1948, The Thecosomatous Pteropods II. The Indo Pacific, Dana Report, 5(30): 1-45. 
THIRIOT-QUIEVREUX, C, 1970, Transformations histologiques lors de la métamorphose chez Cymbulia 

peroni de Blainville (Mollusca, Opisthobranchia). Zeitschrift für Morphologie und Ökologie der Tiere, 67: 

106-117. 
THOMPSON, T. E., 1976, Biology of opisthobranch molluscs, \. The Ray Society, London, 151, 207 p. 



MALACOLOGIA, 1979, 18: 37-52 

PROC. SIXTH EUROP. MALAC. CONGR. 

NOTE ON VARIATION IN DIACRIA GRAY, 1847, WITH DESCRIPTIONS 

OF A SPECIES NEW TO SCIENCE, DIACRIA RAMPALI NOV. SPEC, 

AND A FORMA NEW TO SCIENCE, DIACRIA TRISPINOSA 

FORMA ATLÁNTICA NOV. FORMA 

Lydie Dupont 
Institute of Taxonomic Zoology (Zoological Museum), University of Amsterdam, the Netherlands 

ABSTRACT 

Variation of shell shape and colour pattern in the Diacria trispinosa group consisting 
of 3 taxa, D. rampali n. sp., D. trispinosa f. trispinosa and D. trispinosa f. atlántica n.f., 
have been studied. D. trispinosa is distinct in colour pattern and has a shell shape 
somewhat different from that of D. rampali. The difference in shell shape consists chiefly 
of a higher position of the lateral spines; this position is indicated by the l/m ratio. 
Discriminant analysis has been used to separate D. rampali and D. trispinosa. Specimens 
from the Philippine area can be well discriminated but specimens from the Atlantic 
Осеагь can only be separated if one also uses differences in colour pattern. The colour 
patterns of D. rampali and D. trispinosa are distinct and their development is different. In 
the Atlantic north of 30° N D. trispinosa becomes larger with higher latitudes, due to 
adaptation in favour of the floating capacity. The teleoconch becomes fully coloured. 
These North Atlantic populations have been described as D. trispinosa f. atlántica. 
Specimens of D. trispinosa f. trispinosa, living at higher latitudes do not show 
enlargement of the teleoconch. D. trispinosa f. atlántica is restricted in distribution to the 
North Atlantic Ocean. D. major has been found in the North Atlantic and the Pacific 
Ocean. In the material studied, no D. major was found in the Indian, nor in the South 
Atlantic Ocean. D. trispinosa f. trispinosa has been collected in all oceans. D. rampali has 
been found in the Atlantic and the Pacific Oceans. 



INTRODUCTION 

The variability in Diacria has been discussed by various authors (Boas, 1886; Van der Spoel, 
1970; Rampa!, 1975; etc.). Diacria trispinosa (De Blainville, 1821) was considered a monotypic 
species, although its variation is great. The above-mentioned authors considered this variation as 
only ecophenotypic. In this paper it is shown that D. trispinosa can be split up into 3 
taxonomic groups, mainly based on differences in colour pattern, correlated with differences in 
shell shape. One species and one forma, both new to science, has been distinguished besides D. 
trispinosa s.S. 

MATERIAL AND METHODS 

Alcohol-preserved material from the Atlantic Ocean and from West of New Guinea and 
Recent sediment material from the Atlantic and Indo-Pacific Oceans has been studied. Special 
attention was given to the Caribbean Sea, the North Atlantic Ocean and the Philippine area. 
This material has been collected mainly by the United States Bureau of Fisheries and the Dana 
expeditions. Eleven measurements of the shell have been taken, of which B, D, E, I, L, M and 
(see Fig. 1) are accurate up to 0.07 mm and A, G, J and К are accurate up to 0.02 mm. 
Besides, attention was paid to the colour pattern. Material collected by the Dana expeditions in 
the South Atlantic, the Indian and the South Pacific Oceans has not been incorporated in the 
computer programs. Age discrimination was possible by means of histological examination of 
the developmental stage of soft parts. Discriminant analysis has been made to distinguish the 
groups according to size differences apart from colour pattern variation. This multiple 
discriminant analysis was performed using the SPSS subprogram DISCRIM (Nie et al., 1975). 

(37) 



38 



PROC. SIXTH EUROP. MALAC. CONGR. 




FIG. 1. Measurements taken from the shell: 

A width at the membrane (lowest part of the teleoconch) 

В length of the posterior spine 

D length of the teleoconch 

E maximal width (between lateral spines) 

G height of the shell aperture 

I length of protoconch II 

J length of protoconch I 

К width of protoconch I 

L length from the lateral spine to the dorsal rim of the shell aperture 

M length from the lateral spine to the membrane 

О width of the shell aperture 



accuracy (in mm) 

(0.02) 
(0.07) 
(0.07) 
(0.07) 
(0.02) 
(0.07) 
(0.02) 
(0.02) 
(0.07) 
(0.07) 
(0.07) 



DUPONT 39 

ACKNOWLEDGEMENTS 

The author wishes to express her thanks to Dr. С F. E. Roper of the Smithsonian 
Institution, Washington, and to Dr. J. Knudsen from the Universitetets Zoologisk Museum, 
Copenhagen, for making large amounts of material available and to Mr. A. F. de Fluiter for 
technical assistance. 

RESULTS 

In the present study variation of the colour pattern and size is compared. The colour pattern 
variation shows 2 types correlating with 2 types of shell shape. The development of the colour 
pattern has been studied in a series of specimens of different ages (see Fig. 2). The studied 
specimens, preserved in alcohol, have been collected by the Dana expedition 1922 at 16° 06' N 
76° 02' W. The 2 types of colour pattern proved to be distinct throughout the developmental 
stages of the animals. In many samples, from plankton as well as from sediment, representatives 
of both types have been found. The 2 groups differing in colour pattern are sympatric in the 
Atlantic Ocean and the Philippine area. The colour patterns of the sympatric groups are distinct 
and therefore these groups will be considered different species: D. rampali nov. spec, and D. 
tri spin osa. 

Size variation is correlated with variation in coloration and distribution. A group of 
populations of D. trispinosa in the North Atlantic Ocean shows large, dark shells. Intermediates 
between these populations and more southern populations have been found. In the northern 
populations shell size increases with higher latitudes. Therefore the northern populations are 
considered to represent a forma new to science: D. trispinosa forma atlántica nov. forma. 

Diacria rampali nov. spec. (Fig. 3) 

The species name is given in honour of Dr. J. Rampai, who was the first to pay full 
attention to the variation of D. trispinosa and its related forms. 

Holotype: adult specimen in Universitetets Zoologisk Museum, Copenhagen. 

Paratypes: 1 adult specimen, 2 transitional s and 2 minutes in Universitetets Zoologisk 
Museum, Copenhagen, and 2 adults and 6 transitionals in Zoological Museum, Amsterdam. 

Type locality: 16° 06' N 76° 02' W; depth 300 meter wire, Dana expeditions, station 1215 IV; 
27-1-1922. 

This species may be identical with Hyalaea aculeata d'Orbigny, 1846: 687, pi. 7 fig. 1-5. The 
colour pattern of Hyalaea aculeata is the same as that of D. rannpali but shell shapes are 
different. 

Hyalaea trispinosa d'Orbigny, 1836: 106. 

Diacria trispinosa Adams, 1853: I, 52 pi. 6 fig. 2a; Adams, 1859: 45; (in part) Vayssière, 
1915: 58, pi. 1 fig. 14. 

Description. Rather small species; teleoconch slender posterior to the lateral spines, caudal 
spine long, shell aperture small, rim of shell-aperture and the middle of dorsal ribs brown. The 
colour of the ventral lip is connected with a spot on the teleoconch anterior to the lateral 
spines. Lateral spines are white and sometimes lateral ribs are very light brownish. When a 
specimen grows older, the colour becomes more intense. Minute stages and often transitional 
stages lack the brown spot on the teleoconch. In adults the anterior half of the teleoconch 
sometimes becomes fully coloured. Table 1 shows the measurements of the holotype. 

TABLE 1. Measurements (in mm) of the holotype of 
D. rampali. 



A 0.77 


J 0.24 


В 3.88 


К 0.20 


D 5.98 


L 4.49 


E 7.48 


M 4.88 


G 0.59 


2.73 


1 3.64 


L/M 0.92 



40 



PROC. SIXTH EUROP. MALAC. CONGR. 




FIG. 2. Colour pattern development 
paratypes) (left). 



in D. trispinosa f. trispinosa (right) and in D. rampali (holotype and 



DUPONT 



41 




42 



PROC. SIXTH EUROP. MALAC. CONGR. 




FIG. 3. Holotype of D. rampali nov. spec. 



Compared to D. trispinosa the dorsal aperture rim is less curved, the caudal spine is longer, 
the vaulting of the teleoconch is slightly less, the lateral growth of the ventral aperture rim in 
the adult stage is less pronounced. The lateral ribs are white instead of brown as in D. 
trispinosa, and D. rampali lacks the light brown spot present in the adult stage of D. trispinosa 
near the caudal spine. 

Compared to Diacria major (Boas, 1886) the teleoconch is smaller and slender, the lateral 
spines are less curved, the caudal spine is proportionally longer. The colour of D. major ¡s 
restricted to the rims of the shell aperture. 



Diacria trispinosa (ms Lesueur) (De Blainville, 1821) 
forma atlántica nov. forma (Fig. 4) 



Holotype: adult specimen in Universitetets Zoologisk Museum, Copenhagen. 

Paratype: 100 adult specimens in Universitetets Zoologisk Museum, Copenhagen, and 709 
adults and 1 minute in Zoological Museum, Amsterdam. 

Type locality: 39°21'N 21 51 'W; depth 300 meter wire, Dana expeditions, station 1380 IV; 
19-6-1922. 



DUPONT 



43 






>?v- ' 



1- 



%. 



1 MM. 



FIG. 4. Holotype of D. trispinosa f. atlántica nov. forma. 



44 PROC. SIXTH EUROP. MALAC. CONGR. 

Hyalaea trispinosa. Quoy & Gaimard, 1832: 378, (1833) pi. 27 fig. 17-19; (in part) 
Souleyet, 1852a: 45; (in part) Souleyet, 1852b: 161. 

Diacria trispinosa (in part). Gray, 1847: 203; (in part) Vayssière, 1915: 58, pi. 1 fig, 11; 
Tesch, 1907: 195. 

Diacria depressa ? Gray, 1850: 11. 

Diacria trispinosa var. minor (in part) Boas, 1886: 95, 210, pi. 1 fig. 3, pi. 2 fig. 14. 

Description. Shell large, up to 9 mm teleoconch length. Lateral spines rather straight. Caudal 
spine proportionally short, shell aperture wide. The holotype is darkly coloured at the anterior 
part of the teleoconch; the posterior part is light brown and the spines are white. The position 
of the membrane is low in the caudal spine, therefore the teleoconch is long and the caudal 
spine short. Measurements of the holotype are given in Table 2. 



TABLE 2. Measurements (in mm) of the holotype of 
D. trispinosa f . atlántica. 



A 0.85 


J 0.27 


В 3.29 


К 0.21 


D 7.94 


L 6.92 


E 10.52 


M 6.15 


G 0.93 


4.22 


1 3.02 


L/M 1.12 



Shells of the northern populations of this taxon are darker and the teleoconch is completely 
brown with exception of the spines. In the southwestern populations only the ribs of the shell 
and the aperture rim are coloured. Intermediates between these colour patterns are abundant. 
The length of the teleoconch of this forma varies also with latitude. 

Diacria trispinosa (ms Lesueur) (De Blainville, 1821) 
forma trispinosa (ms Lesueur) (De Blainville, 1821) 

Hyalaea trispinosa (ms Lesueur) (in part) De Blainville, 1821a: 82; De Blainville 1821b: 97; 
d'Orbigny, 1836: 106; (in part) Souleyet, 1852a: 45, pi. 3 fig. 1-7; (in part Souleyet, 1852b: 
161, pi. 6 fig. 1-6. 

Hyalaea mucronata (non d'Orbigny, 1836). Quoy & Gaimard, 1827: 231, pi. 8b fig. 1-2. 

Diacria trispinosa (in part). Gray, 1847: 203; (in part) Gray, 1850: 10; Chenu, 1859: 109, 
fig. 4, 65-466. 

Diacria trispinosa var. minor (in part) Boas, 1886: 95, 210. 

Description. Teleoconch length about 6 mm. The teleoconch length does not show variation 
with latitude. The colour pattern of D. trispinosa f. trispinosa is restricted to the ribs of the 
shell and the aperture rims, but sometimes adult specimens get a brown spot on the teleoconch 
posterior to the lateral spines, on the ventral side. The aperture is smaller and the posterior 
spine proportionally longer than in D. trispinosa f. atlántica. 



REMARKS ON VARIATION 

The measurements A, D, E, G, L and M (see Fig. 1) are used to study teleoconch variation. 
In the histograms (Fig. 5) the size of the different taxa may be compared. The ratio L/M (= 
distance from lateral spine to dorsal aperture rim/distance from lateral spine to membrane) is an 
indicator for the position and curving of the lateral spines. For D. rampali and D. trispinosa f. 
trispinosa from the Atlantic Ocean this ratio differs slightly. Most Atlantic and all Philippine 
specimens of D. rampali have a lower L/M ratio; consequently this means a higher position of 
lateral spines compared to D. trispinosa f. trispinosa. Atlantic specimens of D. rampali have 



DUPONT 45 




i-A_i. 












kLj^jL 



I 

■ ATLANTIC 



DIACRIA TRISPINOSA 









FIG. 5. Histograms of parameters of shell shape and size of different taxa in different oceans. 



46 



PROC. SIXTH EUROP. MALAC. CONGR. 



almost the same L/M ratio as D. trispinosa f. atlántica, but the latter is much bigger, as is shown 
by the teleoconch length (D) and the maximal width (E). The length of the teleoconch in 
Atlantic specimens of D. trispinosa f. trispinosa is slightly less than that in D. rampali; in the 
Philippine area the difference is just the reverse. 

The length of the teleoconch of D. trispinosa f. atlántica becomes larger at higher latitudes. 
In Fig. 6 mean and standard deviation of data are plotted against latitude. According to Van der 
Spoei (1970a) this variation is due to adaptation to colder and less saline waters to enlarge the 
floating capacity. Only the mean of the samples from the Sargasso Sea, North of the Azores 
(arrows), does not fit. This is probably due to isolation of these water masses. In Fig. 6 the 
teleoconch length variation of D. major sampled in the Atlantic Ocean is also plotted, which 
shows a comparable phenomenon. 

Discriminant analyses have been made for 4 groups, based on colour pattern: the taxa D. 
rampali, D. major, D. trispinosa f, trispinosa, D. trispinosa f. atlántica. Shell shape differences of 
these groups have been studied. The analyses were carried out with 3 parameters of the shell: 
A = width of the shell at the level of the membrane; L = distance of the lateral spine and the 
dorsal aperture rim; M = distance between the lateral spine and the membrane. These 
parameters have been chosen because they discriminate well and their correlation is limited 
(Table 3). 




5. 



6. 



7 



8. 



9. 



MM. 



FIG. 6. Mean and standard deviation of samples of D. trispinosa f. atlántica (blacl< dots) and of D. major 
(black squares), plotted against latitude. 



DUPONT 



47 



TABLE 3. Correlation matrix of the parameters A, L and M in the taxa D. rampali, D. major, D. trispinosa f. 
trispinosa, D. trispinosa f. atlántica. 





D. rampali 


D. major 


D. 


trispinosa f. trispinosa 


D. trispinosa f. atlántica 




L M 


L M 




L M 


L M 


A 

L 


.19 .01 
X .48 


.37 .47 
X .55 




.01 .03 
X .44 


.24 .16 
X .61 



-7.00 



-4.00 



1.00 




2.00- 



-100 



-4.00 



-700- 



O О 

О о 
ooo о о о 
ооооо 



FIG. 7. 'Plot of single cases' of discriminant analysis for 4 groups: D. rampali (circles), D. major (black dots), 
D. trispinosa f. trispinosa (triangles downward), D. trispinosa f. atlántica (triangles upward), of whicn tne 
cases or specimens were sampled in the Atlantic Ocean. 



48 



PROC. SIXTH EUROP. MALAC. CONGR. 



In Fig. 7 a discriminant analysis of specimens sampled from the Atlantic Ocean is given. Fig. 
7 shows that D. major is easily recognised using the above mentioned parameters. The ranges of 
variability of D. rampa/i and D. trispinosa f. trispinosa overlap but the centroids are distinct. 
With this method it was possible to separate up to 81% of Atlantic specimens of D. rampa/i 
from D. trispinosa f. trispinosa. D. trispinosa f. atlántica and D. rampa/i do not overlap. 
Separation between D. trispinosa f. trispinosa and D. trispinosa f. at/antica is distinct for 89% 
of the specimens. In relation to these data one has to consider that the colour pattern of D. 
rampa/i is distinct from that of D. trispinosa, and that there are intermediates in colour pattern 
between D. trispinosa f. trispinosa and D. trispinosa f. at/antica. In Fig. 8 discriminant analysis 
of specimens sampled from the Philippine area is given. It shows that there is no overlapping of 
D. rampa/i and D. trispinosa f. trispinosa when parameters A, L and M are used for these 
specimens. Separation of D. rampa/i and D. trispinosa f. trispinosa only based on colour pattern 
gives the same groups as the separation based on shell shape. 

Results drawn from the discriminant analyses are identical with the conclusions from the 
histograms. 



5 00 



2.50 



2.50 



5.00 



-2.50 



TT T 

▼ TT T 

T T T T ▼ 

TTTTTTTTTTT 
T T T T 

▼ ▼ ▼ TT ▼ 

▼ TT -rrw rf TT 

TT TT 

TT TT 
T T T T T T 

T T 



о о о 
о 
о о о оо 

о 
о оо ооо о 
оо о ооооо о 
о of 

о о 
о о о 

00 

о 
о 



FIG. 8. 'Plot of single cases' of discriminant analysis for 2 groups: D. rampali (circles) and D. trispinosa f. 
trispinosa (triangles); cases or specimens were sampled in the Philippine area. 



DUPONT 



49 







О 
О ¡i 

SE 



■D S 
a> ce 



» E 

• v> 

11 
If 
:•! 



о га 



•SE 

Id 



S o 
o. °- 



o 2 

° с 

1° 

v> ra 
"O a> 

¿b 

■M • 

Q. a> 

■ (Л 

O) (O 

di 



50 



PROC. SIXTH EUROP. MALAC. CONGR. 







U-OC 



DUPONT 51 

DISTRIBUTION 

The localities of the material studied, measured as well as unmeasured specimens, are 
represented on Figs. 9 and 10. Due to lack of material the North Pacific Ocean has hardly been 
investigated. 

The distribution of D. trispinosa f. atlántica is restricted to the North Atlantic Ocean, 
between 60 N and 30-25° N. At the southern border intermediates with D. trispinosa f. 
trispinosa occur, 

D. trispinosa f. trispinosa has been found in all oceans down to 35° S. It occurs up to 35° N 
in the Atlantic and, according to Van der Spoel (1967), up to 40° N in the Pacific Ocean. In 
most of the studied areas D. trispinosa f. trispinosa is sympatric with D. rampali. 

D. rampali has been collected in the Atlantic Ocean between 30° N and 35° S. In the Pacific 
it has been sampled between 15° N (Philippine area) and 10° S. It is possible that the 
distribution of D. rampali in the Pacific Ocean is wider than given here. 

D. major has been collected in the North Atlantic Ocean up to 30° N and in the Pacific 
Ocean down to 35 S. Among the material investigated no D. major has been found in the South 
Atlantic nor in the Indian Ocean. 

Near the coast off Georgia, in sediment material, D. trispinosa f, trispinosa and D. rampali 
have been found. On the maps (Figs. 9 and 10) this is indicated by an arrow. Neither D. 
rampali nor D. trispinosa f. trispinosa have been collected recently in the same areas, though 
they have been well explored by the Deep Dumpsite Project. So either the 2 taxa are regressing 
in distribution or the waters near Georgia had a higher temperature in the recent geological 
past. The last hypothesis contradicts other paleontological and geological evidence. Therefore it 
is postulated here that D. rampali and D. trispinosa f. trispinosa have had a larger distribution 
in the Atlantic Ocean. 



LITERATURE CITED 

ADAMS, A., 1859, On the synonyms and habitats of Cavolina, Diacria and P/europus. Annals and Magazine 

of Natura/ History (3)3: 44-46. 
ADAMS, H. & ADAMS, A., 1853, The genera of Recent Mollusca, 1 and 3. John van Voorst, London, 256 p. 
BLAINVILLE, M. H. D. DE, 1821a, (ms Lesueur), Dictionnaire des sciences naturelles 22. Paris & Strasbourg, 

570 p. 
BLAINVILLE, M. H. D. DE, 1821b, Mémoire sur le genre Hyale. Journal de Physique, de Chimie et 

d'Histoire Naturelle, 93: 81-97. 
BOAS, J. E. V., 1886, Spolia Atlántica. Bidrag til Pteropodernes. Morfologi og Systematik samt til 

kundskaben от deres geografiske udbredelse. Kongelige Danske Videnskabernes Selskabs Skrifter, 6. 

Raekke, Naturvidenskabelig og Mathematisk Afdeling, 4(1): 1-231. 
CHENU, J. C, 1859, Manuel de Conchyliologie et de Paléontologie conchyliologique. Victor Masson, Paris, 

508 p. 
GRAY, J. E., 1847, A list of the genera of Recent Mollusca, their synonyma and types. Proceedings of the 

Zoological Society of London, (1847) 15: 129-219. 
GRAY, J. E., 1850, Catalogue of the Mollusca in the collection of the British Museum II Pteropoda. E. 

Newman, London, 45 p. 
NIE, N. H., HADLAI HULL, C, JENKINS, J. G., STEINBRENNER, K. & BENT, D. H., 1975, SPSS: 

Statistical Package for Social Sciences. Modified version 65, 26 May 1977. Vogelback Computing Center, 

Northwestern University. McGraw Hill Book Company, New York. 
D'ORBIGNY, A., 1836, Voyage dans l'Amérique méridionale exécuté pendant les années 1826-1833, 

Mollusques, 5(3): 49-184. Bertrand, Paris. 
D'ORBIGNY, A., 1846, Voyage dans l'Amérique méridionale exécuté pendant les années 1826-1833, 

Mollusques, 5(3), Atlas pis. 1-85. Bertrand, Paris. 
QUOY, J. R. С & GAIMARD, J., 1827, Observations zoologiques faites à bord de "l'Astrolabe" en mai 

1826, dans le détroit de Gibraltar: description des genres Biphore, Carinaire, Hyale, Flèche, Cleodore, 

Anatife et Briarée. Annales des Sciences Naturelles, 10: 225-239 + Atlas. 
QUOY, J. R. С & GAIMARD, J., 1832, Voyage de découvertes de "l'Astrolabe," Zoologie, 2. Tastu, Paris, 

686 p. + Atlas (1833). 
RAMPAL, J., 1975, Les Thécosomes (Mollusques pélagiques). Systématique et évolution. Ecologie et 

biogéographie méditerranéennes. Thèse Doctorat d'Etat, Université de Provence, Marseille, CNRS АО. 

11932, 485 p. 



52 PROC. SIXTH EUROP. MALAC. CONGR. 

SOULEYET, F. L. A., 1852a, In: Rang, S. & Souleyet, F. L. A., Histoire naturelle de mollusques ptéropodes. 

Monographie comprenant la description de toutes les espèces: 1-86. J. B. Baillière, Paris. 
SOULEYET, F. L. A., 1852b, In: Eydoux, J. F. T. & Souleyet, F. L. A., Voyage autour du monde exécuté 

pendant les années 1836 et 1837 sur la corvette "La Bonite." Zoologie, 2. Bertrand, Paris, 664 p. + Atlas. 
SOWERBY, G. В., Jr., 1859, Illustrated index of British shells. British supplement to Thesaurus Conchyli- 

orum: 1-15. Simpkin, Marshall & Co., London. 
SPOEL, S. VAN DER, 1967, Euthecosomata, a group with remarkable developmental stages. Noorduyn & 

Zn, Gorinchen, 375 p. 
SPOEL, S. VAN DER, 1970, Morphometric data on Cavoliniidae with notes on a new form of Cuvierina 

columnella (Rang, 1827) (Gastropoda, Pteropoda). Basteria, 34:103-151. 
TESCH, J. J., 1907, Pteropoda of the Leyden Museum. Notes of the Leyden Museum, 29: 181-203. 
VAYSSIERE, A., 1915, Mollusques Euptéropodes (Ptéropodes thécosomes) provenant des campagnes des 

yachts "Hirondelle" et "Princesse Alice" (1885-1913). Résultats des Campagnes Scientifiques accomplies 

sur son yacht par Albert 1er, Prince Souverain de Monaco, 47: 3-226. 



MALACOLOGIA, 1979, 18: 53-55 

PROC. SIXTH EUROP. MALAC. CONGR. 

VERBREITUNG DER FAMILIE ZONITIDAE 

Adolf Riedel 
Polnische Akademie der Wissenschaften, institut für Zoologie, Warszawa, Polen 

ABSTRACT 

The distribution of the Zonitidae is Holarctic . Of the about 550 species and 
subspecies roughly 1/3 live in the Nearctic and 2/3 in the West Palaearctic, only 1 species 
(Zonitoides nitidus) being fully Holarctic. Out of the almost 100 genera and subgenera 
only 2 (Zonitoides and Nesovitrea) are common to the Nearctic and all of the Palaearctic, 
while 2 Nearetic ones (Pristiloma and Hawaiia) enter the East Palaearctic. In the Nearctic 
Region the Appalachians are the main centre of differentiation. Only 1 genus, Pristiloma, 
is exclusively western; in the south zonitids reach into Central America. In the West 
Palaearctic they live mainly in the Mediterranean region sensu lato, i.e., from the Azores 
to N.E. Iran. The southern limit is the desert belt of the Sahara and the Middle East, 
with only 1 genus and species crossing it, Araboxychilus sabaeus (Oxychilini), which is 
endemic in the mountains of the S.W. tip of Arabia. The Central Palaearctic is inhabited by 
only 2 wide-ranging species, which extend to the Far East, there meeting the few species 
of Nearctic origin. Northwards there is a rapid decrease in the number of species, with 
only very few widely distributed forms crossing latitude 50° in America and 52° in 
Europe. 

Die Familie Zonitidae wird hier folgendermassen beschränkt und systennatisch eingeteilt: 
Unterfamilie Gastrodontinae; Unterfamilie Zonitinae mit Triben Vitreini, Zonitini und 
Oxychilini; Unterfamilie Daudebardiinae. Viele Malakologen betrachten jedoch die Daudebardi- 
inae und Schileyko (1972) auch die Gastrodontinae als besondere Familien. Die amerikanischen 
Autoren (H. B. Baker, Pilsbry) rechnen dagegen auch die Vitrinidae als eine Unterfamilie den 
Zonitidae zu. Die Euconulidae, die vorher zu den Zonitidae gezählt wurden, werden heute 
schon allgemein entweder als eine besondere Familie betrachtet oder den Heiicarionidae 
zugerechnet. Als eine abgesonderte Familie nehme ich auch die Trochomorphidae an. Die 
hawaiische Gattung Godwinia, manchmal in eine Unterfamilie Godwiniinae ausgesondert, stelle 
ich gerade in die Zonitinae-Zonitini. 

Die Zonitidae, in meiner Erfassung, sind eine fast ausschliesslich holarktische Gruppe. In der 
Orientalischen und Australischen Region (samt Ozeanien aber ohne Hawaii-Inseln) werden sie 
durch verwandte, aber abgesonderte Familien Heiicarionidae, Euconulidae, Trochomorphidae, in 
der Äthiopischen Region durch schalentragende Urocyclidae ersetzt; in der Neotropischen 
Region fehlen die einheimischen Limacoidea wohl vollständig. 

Die Zonitidae umfassen etwa 520 (-550) "gute" rezente Arten und Unterarten, die zu fast 
100 Gattungen und Untergattungen gehören; aus dieser Zahl fallen etwa 350 Arten auf die (fast 
ausschliesslich westliche) Paläarktis und 170 auf die Nearktis samt Mittelamerika und den 
Hawaii-Inseln. Die Daudebardiinae (ca 30 Arten) und die Oxychilini (ca 160 Arten) leben 
endemisch in der West-Paläarktis. Die Gastrodontinae sind in der Nearktis zahlreicher und mehr 
differenziert; in der West-Paläarktis leben nur 4 Zonitoides- Arten, sowie die kleine endemische 
Gattung Janulus auf Madeira und den Kanaren. Möglicherweise zu Gastrodontinae gehören auch 
die Reliktgattungen Spelaeopatula (5 Arten in Süd-Jugoslawien und Albanien) und Gastranodon 
(eine Art in Nordost-Iran); ihre Anatomie und systematische Stellung bleiben aber bisher 
unbekannt. Im Tertiär waren die Gastrodontinae, wie es scheint, in Europa zahlreicher und 
mehr differenziert als heute. Die Vitreini und die Zonitini sind gleich reichlich, aber durch 
besondere Gattungen, in der Paläarktis und der Nearktis repräsentiert, wobei die Vitreini in der 
Nearktis und die Zonitini in der Paläarktis mehr differenziert sind. 

Es gibt nur eine panholarktische Art der Zonitidae, Zonitoides nitidus, und nur 2 Gattungen 
sind für die ganze Paläarktis und die Nearktis gemeinsam, ZoAí/fo/c^es und Nesovitrea (N.B.: die 

(53) 



54 PROC. SIXTH EUROP. MALAC. CONGR. 

nearktische Glyphyalinia betrachte ich als besondere Gattung und nicht als Untergattung der 
paläarktischen Retinella). Überdies reichen 2 nearktische Gattungen, Hawaiia und Pristiloma, in 
die östlichste Paläarktis (siehe unten). 



VERBREITUNG IN DER NEARKTIS 

Am häufigsten treten die Zonitidae im Osten der Vereinigten Staaten auf, ihr Zentrum der 
Differenzierung liegt im Gebiet der Appalachen (sensu lato). Hauptsächlich hier leben die 
artenreichen Gattungen Mesomphix, Paravitrea, Glyphyalinia, Zonitoides (samt Ventridens); 
zahlreiche Untergattungen sowie die Gattungen Gastrodonta und Vitrinizonites sind für das 
Gebiet endemisch. Im Westen der USA, der pazifischen Küste entlang, kommen nur die grosse 
Gattung Pristiloma, die zweite endemische Gattung Ogaridiscus mit 1-2 Arten, und wenige in 
Amerika weit verbreitete Arten vor. 

Nach Norden (Kanada) nimmt die Anzahl der Zonitidae plötzlich ab, die endemischen Arten 
fehlen fast vollkommen (Ausnahme: manche Pristiloma- Arten im Nordwesten Nordamerikas). 
Nach Süden (Mexico) sinkt die Artenzahl langsamer und hier kommen endemische Arten oder 
sogar höhere Taxa vor: Pycnogyra, Untergattungen Omphalinella, Patulopsis, Zonyalina und 
Moreletia der Gattung Mesomphix. Die Zonitidae dringen im Süden in die Sonorische 
Übergangsregion: über Mexico nach Mittelamerika (Guatemala, Kostarika, Panama) vor. 

Ausser dem nordamerikanischen Kontinent bewohnen die nearktischen Zonitidae die 
Bermuda- (endemische Gattung Poecilozonites der Gastrodontinae) und die Hawaii-Inseln 
(endemische Gattung Godwinia, einige endemische Nesovitrea- und Striatura- Arten, Hawaiia 
minúscula). Die am weitesten verbreitete nearktische Art ist Hawaiia minúscula, die jedoch auf 
manche Inseln des Pazifiks und des Karibischen Meeres sowie nach Südamerika sicher durch 
Menschen eingeschleppt worden ist. 

Der Einfluss der nearktischen Fauna macht sich am östlichsten Rand Asiens geltend. Über 
Alaska und den Aleuten dringt dort die Gattung Pristiloma vor und wird auf Hokkaido, 
Sachalin, den Kurilen und im Süden Kamtschatkas durch eine endemische Art, P. ¡aponicum, 
vertreten. Die einzige in der Ost-Paläarktis endemisch lebende, monotypische Gattung 
Coreovitrea (aus Nord-Korea) steht der nearktischen Gattung Pristiloma näher als irgendwelchen 
westpaläarktischen Zonitiden. Bis nach Primorskij Kraj und Korea reicht Hawaiia minúscula (im 
natürlichen Bereich, nicht vom Menschen eingeschleppt!), bekannt auch aus dem Pleistozän 
Japans. Im Neogen musste die amerikanische Gattung Hawaiia in paläarktischem Asien sehr weit 
verbreitet sein und von dort bis nach Südost-Europa reichen. Als Spuren ihres einstigen Areals 
gelten: die reliktäre, endemische Hawaiia afghana in Afghanistan und ein miozäner Fund der 
Hawaiia antiqua im Kaukasus. 

VERBREITUNG IN DER PALÄARKTIS 

Inder Paläarktis ist das Areal der einheimischen Zonitidae im Grunde auf den westlichen Teil 
der Region, hauptsächlich auf Europa beschränkt. Die Grenze dieses Areals markt der Bereich 
der zahlreichsten Gattung, Oxychilus (ungefähr 150 Arten in über 20 meist eng verbreiteten 
Untergattungen), aus. Die Zonitidae bewohnen ganz Europa, nach Norden aber nimmt ihre 
Anzahl rasch, obwohl allmählich, ab. In Skandinavien kommen nur 9-10 Arten vor und von 
ihnen dringen nur 4-5 nach Island vor; dies sind in der Regel weit oder sehr weit verbreitete 
Arten. In Ost-Europa reichen die Zonitidae bis nach Estland, Lettland, Litauen, Weissrussland 
und der Ukraine und nur ganz wenige nach West-Russland. Östlich der Wolga, in den 
ausgedehnten Gebieten Sibiriens, der Mongolei und der zentralasiatischen Sowjetrepubliken 
treten nur die 2 am weitesten verbreiteten Arten auf: der holarktische Zonitoides nitidus und 
die paläarktische Nesovitrea hammonis, die bis nach Korea und Sachalin reicht. Erst am 
östlichen Rand Asiens erscheinen einige Arten nearktischer Herkunft. An den südöstlichen 
Rändern des Areals der Familie treffen die dort schon nicht mehr zahlreichen Zonitidae die 
Vertreter der verwandten, für die Orientalische Region charakteristischen Familien Helicarion- 
idae und Euconulidae und kommen zusammen mit ihnen vor (z.B. in Afghanistan, Korea, auf 
Hokkaido). 



RIEDEL 55 

Nach Westen reichen die Zonitidae bis auf den Azoren, Madeira und den Kanaren, wo sie 
recht reichlich und durch viele endemische Formen und Gruppen vertreten sind; z.B. auf den 
Azoren 15 Arten, darunter endemisch 9 Arten und 3 Untergattungen, auf Madeira und den 
Kanaren die endemische Gattung Janulus, auf den Kanaren die endemische Untergattung 
Lyrodiscus. 

Die südliche Arealgrenze der Zonitidae in der West-Paläarktis ist sehr scharf, im Gegensatz zu 
der nördlichen und östlichen Grenze. Sie wird durch die Wüsten Afrikas und Vorderasiens oder 
durch die an ihnen vom Norden grenzenden extrem trockenen Gebirgen, z.B. Hoher und 
Saharischer Atlas, ausgemarkt. Die Zonitidae erreichen diese Grenze in einer merkbaren Anzahl 
hauptsächlich endemischer und stark differenzierter Arten. Die Artenzahl nimmt nach Süden 
nicht allmählich ab, sondern das Areal hört plötzlich auf. Den Rand des südlichen Bereiches 
bilden: West- und Nord-Marokko, Nord-Algerien samt Teil-Atlas, Nordwest-Tunesien, Kyrenaika 
in Libyen, Israel, West-Jordanien, Nordwest-Syrien, Süd-Türkei, irakischer Kurdistan und 
Nord-Iran. 

Hauptgebiet des Vorkommens der paläarktischen Zonitidae sind die weit gefassten Mittel- 
meerländer, die sich den Breitenkreisen entlang von den Azoren an bis dem Chorassan und 
Kopet-dag-Gebirge an der Grenze zwischen Iran und der Turkmenischen SSR| ziehen. In diesem 
breiten Gürtel zwischen dem 32° und 45° geographischer Breite befinden sich einige deutliche 
Entwicklungszentren der Zonitidae, die sich mit ihrer spezifischen Fauna aussondern. Unter 
anderen: das kabylische Zentrum (in Nord-Algerien) mit endemischen Gruppen Pseudopolita 
und Allogènes und den verwandten Ox)/c/7/7í7s-Formen; das dinarische (westbalkanische) 
Zentrum— hier leben die meisten Arten der Gattung Aegopis, Paraegopis s.S., die endemischen 
unterirdischen Gattungen Spelaeopatula, Gyralina und Meledella; das ägäische Zentrum, mit 
Zonites (mehrere Arten), Eopolita und Lindbergia s.s., Untergattungen Hiramia, Helicophana 
(ein einziger enger Endemit am östlichen Rand Kretas) und Calloretinella (eine endemische Art 
auf Zypern) der Gattung Oxychilus; das westkaukasische Zentrum, endemische Gattungen 
Vitrinoxychilus und Discoxychilus sowie Untergattungen Conulopolita, Forcartiella, Retowskiella 
und Pontoxychilus (der Gattung Oxychilus), Entwicklungszentrum weiter verbreiteter Unter- 
gattungen Schistophallus und Longiphallus. 

Die nördlichsten Entwicklungszentren der Zonitidae bilden der West-Kaukasus, die Karpaten 
und die Alpen. Dabei sind die Zonitidae in den Karpaten und Alpen weit mehr in den südlichen 
als in nördlichen Teilen dieser Gebirgsmassiven differenziert. Besonders, charakteristisch für die 
Karpaten sind: starke Differenzierung der Daudebardiinae und ihre endemische Gruppe Cibinia; 
Untergattung Riedelius und endemische, monotypische Untergattung Cellariopsis der Gattung 
Oxychilus; monotypische, endemische unterirdische Gattung Troglovitrea. In den Süd-Alpen 
liegt das Zentrum der Differenzierung der Gattung Aegopinella, ebendort und in benachbartem 
Toskanien das Entwicklungszentrum von Oxychilus s.s. und möglicherweise auch Retinella s.s. 

In der Alten Welt ist nur eine Gattung und Art der Zonitidae bekannt, die ausserhalb der 
Grenzen der Paläarktis, in der Äthiopischen Region vorkommt. Dies ist Araboxychilus sabaeus 
der Tribus Oxychilini, der das Gebirge des südwestlichen Randes Arabiens endemisch bewohnt 
und durch eine weite Lücke vom Hauptareal der Familie getrennt wird. Analogisch zu der 
Verbreitung der Familie Vitrinidae zu urteilen, wäre die Entdeckung der Vertreter der Zonitidae 
auch in den Gebirgen Äthiopiens zu erwarten. Araboxychilus sabaeus in Arabien wie auch die 
Vitrinidae ebenda und in den Gebirgen Äthiopiens, sind Relikte aus den pluvialen Perioden des 
Spätneogens oder Pleistozäns, aus der Zeit als der Wüstengürtel, der heute keinen Kontakt und 
Austausch der mesophilen Malakofauna des Mediterranen Raumes mit der Fauna der 
Äthiopischen Region erlaubt, noch nicht existierte. 

In der vorliegenden Besprechung wurden die mehreren Fälle der Verschleppung einzelner 
Arten durch den Menschen und ihres Vorkommens ausserhalb des natürlichen Areals vollständig 
ausgelassen. 



LITERATUR 

SCHILEYKO, A. A., 1972, Grundzüge des Bauplans von Zonitoides nitidus (Müller) im Zusannmenhang nnit 
der Frage der systematischen Rangordnung der Gastrodontinae (Gastropoda, Stylommatophora) (russisch). 
Sbornik Trudov Zoologicheskogo l\/luzeja Mgu, 12: 145-156. 



MALACOLOGIA, 1979, 18: 57-60 

PROC. SIXTH EUROP. MALAC. CONGR. 

SPECIES CONCEPT OF PROSOBRANCH FRESHWATER 
MOLLUSCS IN WESTERN EUROPE, I 

Hans D. Boeters 
Rumfordstrasse 40, D-8000 München 5, Germany (BRD) 

ABSTRACT 

The species concept of prosobranch freshwater snails inhabiting caves and springs is 
discussed. There are basically 2 schools of thought, viz. authors who subscribe to a very 
narrow species concept (all geographically isolated taxa are species: high rate of 
endemism) and those who recognize fewer species with more extensive distribution. The 
isolation of many populations appears to be less strict than generally surmised. Waters 
may be connected underground and aerial dispersal is certainly possible. There are also 
transitions between spring and cave snails. This may be caused by underground water 
connections and is evidenced by reduction of eye pigment. There are 2 possibilities, viz. 
snail species of which the different populations each have a different type of eye 
pigmentation, and snail species of which individuals with and without eye pigment occur 
together in the various populations. Species of Bythinella, Microna, Litthabitella and 
Horatia are cited as examples of these phenomena. 

With respect to the different taxa the evaluation of the specialists in many cases differs 
considerably. Therefore the confusion of other people coming in contact with this field must be 
even greater. For this reason, the species concept and criteria for distinguishing species used in 
this publication are to be clarified. 

At present the situation is that according to one concept a certain number of species having 
a more or less wide distribution must be recognized. According to another concept, however, 
some of these species must be split into several species having much more limited distributions 
(endemism). For example. Binder (1957: 59) and in addition obviously Ant (1962: 71) 
combine the 10 Horatia species described by Bourguignat to one single species, whereas Schutt 
(1961: 69) combines them to 8 species, some of which are said to have separate distribution 
areas (cf. klecakiana, praeclara and servaini according to Schutt). Boeters (1970: 113) discusses 
a distribution of Microna saxati/is from central Portugal to Bosnia-Hercegovina. Radoman 
(1975: 29) reviews the genus for the Balkans; however, he does not mention M. saxati/is 
(Radoman has received from me alcohol material of this form from France). On the contrary, 
he elevates 4 subspecies to species rank (M. croatica, M. fontinalis, M. /<uesteri and M. 
/acheineri, some of which have separate distribution areas, cf. Radoman, 1975: fig. 11). 

BIOLOGICAL SPECIES CONCEPT 

Although both concepts mentioned above lead to different results, it may be assumed that 
the authors who represent them, start from a common theoretical basis. This is, for example, 
obvious for Schutt (1961: 69) and his opponent Ant (1962: 71), since Schutt refers to Mayr 
(1942) from whose relevant theoretical basic concepts Ant also obviously starts. 

Mayr (1975: 31) attributes the following 3 features to a species: (a) the individuals of a 
species form a reproductive community; (b) in addition, the species is an ecological unit; (c) 
finally, the species is a genetic unit of an intercommunicating gene pool. The species definition 
is as follows: species are groups of natural populations which cross with each other and which 
are, with respect to their reproduction, isolated from other such groups. 



(57) 



58 



PROC. SIXTH EUROP. MALAC. CONGR. 
APPLICATION OF THE BIOLOGICAL SPECIES CONCEPT 



An analysis (Tables 1-2) of the arbitrarily selected publication of Jaeckel, Klemnn & Meise 
(1958) shows that endemism appears substantially in so-called spring snails and cave snails 
(crenobionts and troglobionts). This is the classical concept of obvious absence of any 
possibility for gene exchange between comparable neighbouring populations; these authors feel 
that their species concept is confirmed by morphological differences. 

Therefore these 2 groups, spring snails and cave snails, and the variability of aquatic 
prosobranch molluscs will be considered in more detail below. 



THE SPECIES CONCEPT OF SPRING SNAILS 



In the present context snails whose populations are normally restricted to springs are 
designated spring snails. The reason for this restriction to springs consists in the fact that these 
snails reproduce themselves only in water of a relatively constant temperature (for Bythinella 
see Jungbluth, 1973: 1584, 1585; for Microna see Boeters, 1970: 120). 

TABLE 1. Genera having up to 50% endemism (except Lake Ochrid and Lake Prespa; analysis of data of 
Jaeckel, Klemm & Meise, 1958). Genera in this table having no spring and cave species: 88%; genera having 
both spring and cave snails are only Pseudamnicola and Sadleriana. 



Genus 



Total number of species 



'Endemic' species 



number 


% 


7 


35 








5 


42 








1 


50 


1 


25 




















2 


40 














1 


25 
































2 


25 


1 


33 



Cochlostoma 

Pomatias 

Acicala 

Papula 

Renea 

Vivíparas 

Valvata 

Hydrobia 

Marstoniopsis 

Lithoglyphas 

Emmericia 

Truncatella 

Balimus 

Pyrgala 

Micromelania 

Assiminea 

Amphimelania 

Fagot i a 

Pseadamnicola 

Sadleriana 



20 
2 

12 
1 
2 
4 
5 
6 
1 
5 
1 
1 
4 
1 
1 
2 
1 
2 
8 
3 



TABLE 2. Genera having more than 50% endemism (except Lake Ochrid and Lake Prespa; analysis of data of 
Jaeckel, Klemm & Meise, 1958). Genera in this table having spring and cave snails: 91%. 



Genus 



'Endemic' species 



Total number of species 



number 


% 


16 


100 


1 


100 


1 


100 


4 


100 


7 


54 


3 


100 


1 


100 


1 


100 


3 


100 


1 


100 


1 


100 



Paladilhia 

Lartetia 

Costellina 

Plagigeyeria 

Bythinella 

Horatia 

Hadziella 

Microsalpinx 

Lanzaia 

Baglivia 

Hydrocena 



16 
1 
1 
4 

13 
3 
1 
1 
3 
1 
1 



BOETERS 59 

If, exceptionally, a constant temperature is guaranteed to occur in waters other than springs, 
these snails are able to spread in these waters over large distances. For example, Bythinella, 
Microna and Litthabitella are known from subterranean waters (for Bythinella see Vire, 1902: 
606, Locard, 1902: 608, Boettger, 1939: 19, and Boeters, 1968: 762, 764; for Microna see A. 
J. Wagner, 1914: 48, Kuscer, 1928: 50, and H. Wagner, 1935: 35; for Litthabitella see Bole, 1971: 
15); in addition, Bythinella is known from the bottom of lakes (Brehm, 1909: 741, Mahler & 
Sperling, 1955: 3, HadI, 1967: 167). The actual presence in lakes underlines Diluvial records 
according to which Bythinella was at that time accompanied by typical lake forms of the actual 
mollusc fauna (Ehrmann, 1914: 133). 

During Quaternary climate changes the snails actively withdrew into the springs with 
increasing temperature (Jungbluth, 1971: 229). This led to splitting into separate populations; 
this would mean the beginning of a process of speciation if passive distribution could be 
ignored or excluded (Giusti & Pezzoli, 1977: 131), 

POSSIBLE AERIAL DISPERSAL 

For a long time aerial dispersal of small bivalves by insects has been assumed since these 
bivalves are able to occupy very small and isolated waters without any inlet or outlet. This has 
been supported by a number of observations (cf. Kuiper, 1976: 496). Although corresponding 
observations have been made for prosobranch land snails, the possibility of aerial dispersal of 
prosobranch spring snails has not been taken into account until now (forjRenea cf. Rees,1965: 
271; for Pomatias cf. Rees, 1965: 271, and Boeters: in September 1975 a grasshopper, 
Orthoptera, was observed for about 15 minutes when transporting on one of its legs a live 
specimen of Pomatias elegans in France, dépt. Gard, Monteil at Orgnac-l'Aven). From the aerial 
dispersal of prosobranch land snails it is evident that (a) prosobranch molluscs are in principle 
able to close their shells so quickly that they may grab insect legs and, in addition that (b) they 
are able to hold on long enough to be transported. Therefore, it is possible to assume analogous 
conditions for both prosobranch spring snails as well as prosobranch land snails and small 
bivalves. This assumption is underlined by repeated records of Bythinella in wells (Blanchet, 
1911: 356, Boeters, 1968: 762, Stock, 1961: 78). 

For aerial dispersal of prosobranch spring snails the following insects may be taken into 
consideration. Lengerken (1924: 14), for example, mentions several beetles as inhabitants of 
springs (Dytiscidae, Hydrophilidae, Haliplidae) and Engelhardt (1955: 17) reports on various 
species of water beetles and water bugs (Hydrocorisae) which stop for short or longer periods in 
springs during overland flights in autumn. 

To sum up, for the reasons given above the species characteristic of a communicating gene 
pool may be maintained over large distances even today. 

TRANSITIONS BETWEEN SPRING AND CAVE SNAILS 

It is not possible to distinguish sharply between spring snails and cave snails in every case; 
transitions do exist. However, regular records of cave snails in springs do not give evidence for 
such transitions because the animals may be transported by the water to the springs. Transitions 
exist (I) if species, which in certain places are restricted only to springs, have penetrated far 
into the subterranean area (cf. section on spring snails) or (II) if species (as evidenced below) 
show a reduction of their eye pigment. It is possible to distinguish 2 possibilities: 

(1) Populations of one and the same species appear to have different eye pigmentation (4 
examples): 

(a) Bythinella cylindracea in the département Aube (France) has normal eye pigmenta- 
tion in springs and reduced eye pigmentation in interstitial waters (samples ВОЕ 139 
and 141 plus 146, respectively); 

(b) Microna saxatilis with eye pigmentation may be collected regularly in springs and, 
exceptionally, without any eye pigmentation (ВОЕ 362, Fontaine in Arneguy, dépt. 
Basses-Pyrénées); 

(c) according to Bole (1971: 89) subterranean populations of ¿/ff/7ab/'fe//a are 'blind' in 
contrast to surface populations (presumably blind animals are merely albinos, cf. e.g. 
Richards, 1973: 49); 



60 PROC. SIXTH EUROP. MALAC. CONGR. 

(d) Horatia minuta may be collected in neighbouring secondary springs of the Source-de- 
I'Ain with or without eye pigmentation (ВОЕ 75 and 175). 

(2) Different eye pigmentation appears in one and the same population, e.g. Horatia minuta 
in the subterranean waters of the Sour (dépt. Ariege, ВОЕ 769) may be either with or 
without any eye pigmentation. 

LITERATURE CITED 

ANT, H., 1962, Bemerkungen zum Genus Horatia. Archiv fur Molluskenkunde, 91: 71-76. 

BINDER, E., 1957, Position systématique de Valvata minuta Drap., Valvata globulina Palad. et d'autres 

petites espèces attribuées au genre Valvata (Gastropoda, Prosobranchia). Atti délia Société Italiana di 

Scienze Naturali, 105: 371-376. 
BLANCHET, е., 1911, A propos des coquilles terrestres et fluviátiles du bassin du Léman, II. Bulletin de la 

Société Zoologique de Genève, 1(16a): 355-357. 
BOETERS, H. D., 1968, Die Hydrobiidae Badens, der Schweiz und der benachbarten französischen 

Départements. Mitteilungen des Badischen Landesvereins für Naturkunde und Naturschutz, N.F., 9: 

755-778. 
BOETERS, H. D., 1970, Die Gattung Microna Clessin, 1890 (Prosobranchia, Hydrobiidae). Archiv für 

Molluskenkunde, 100: 113-145. 
BOETTGER, С R., 1939, Die subterrane Molluskenfauna Belgiens. Mémoires du Musée Royal d'Histoire 

Naturelle de Belgique, 88: 1-68. 
BOLE, J., 1971, Über Anatomie und Taxonomie der Gattung Litthabitella Boeters, 1970 (Gastropoda, 

Hydrobiidae). Dissertationes Academiae Scientiarum et Artium Slovenica, 14(3): 77-91. 
BREHM, V., 1909, Charakteristik der Fauna des Lunzer Mittersees, Siebente Mitteilung aus der biologischen 

Station in Lunz. Internationale Revue der Gesamten Hydrobiologie und Hydrographie, 2: 741-748. 
EHRMANN, P., 1914, Grundzüge einer Entwicklungsgeschichte der Tierwelt Deutschlands. Voigtländer, 

Leipzig, 213 p. 
ENGELHARDT, W., 1955, I/Vas lebt in Tümpel, Bach und Weiher? Kosmos, Stuttgart, 232 p. 
GIUSTI, F. & PEZZOLI, E., 1977, The genus Bythinella in Italy (Prosobranchia, Hydrobiidae). Malacologia, 

16: 131. 
HADL, G., 1967, Bythinella austriaca als Bewohnerin eines Voralpensees (Prosobranchia: Hydrobiidae). 

Archiv für Molluskenkunde, 96: 167-168. 
JAECKEL, S. H., KLEMM, W. & MEISE, W., 1958, Die Land- und Süsswasser-Mollusken der nördlichen 

Balkanhalbinsel. Abhandlungen und Berichte aus dem Staatlichen Museum für Tierkunde in Dresden, 23: 

141-205. 
JUNGBLUTH, J. H., 1971, Die systematische Stellung von Bythinella compressa montisavium Haas und 

Bythinella compressa (Frauenfeld) (Mollusca: Prosobranchia: Hydrobiidae). Archiv für Molluskenkunde, 

101: 215-235. 
JUNGBLUTH, J. H., 1973, Zur Verbreitung und Ökologie von Bythinella dunkeri compressa (Frauenfeld 

1856) (Mollusca: Prosobranchia). Verhandlungen der Internationalen Vereinigung für Theoretische und 

Angewandte Limnologie, 18: 1576-1585. 
KUIPER, J. G. J., 1976, Gedachten over het soortbegrip in het genus Pisidium en de betekenis van passieve 

verspreiding. Correspondentieblad van de Nederlandse Malacologische Vereniging, 169: 469-512. 
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Borntraeger, Berlin, 38 p. 
LOCARD, A., 1902, Description de mollusques nouveaux appartenant à la faune souterraine de France et 

d'Italie. Bulletin du Muséum National d'Histoire Naturelle, 8: 608-611. 
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Umgebung. Mitteilungen der Naturwissenschaftlichen Arbeitsgemeinschaft vom Haus der Natur, Salzburg 

(Zoologische Arbeitsgruppe), Ъ16 = 1954/55: 3-17. 
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Muséum d'Histoire Naturelle du Pays Serbe, Beigrade, B30: 29-69. 
REES, W. J., 1965, The aerial dispersal of Mollusca. Proceedings of the Malacological Society of London, 36: 

269-282. 
RICHARDS, C. S., 1973, Pigmentation variations in Biomphalaria glabrata and other Planorbidae. Mala- 
cological Review, 6: 49-50. 
SCHUTT, H., 1961, Das Genus Horatia Bourguignat. Archiv für Molluskenkunde, 90: 69-77. 
STOCK, J. H., 1961, Ondergrondse waterdieren in Zuid-Limburg. Natu urhistorisch Maandblad, Maastricht, 

50: 77-85. 
VIRE, A., 1902, La faune et la flore souterraine du puits de Padirac (Lot). Bulletin du Muséum National 

d'Histoire Naturelle, Paris, 8: 601-607. 
WAGNER, A., 1914, Höhlenschnecken aus Süddalmatien und der Hercegovina. Sitzungsberichte der Kaiser- 
lichen Akademie der Wissenschaften, Mathematisch-Naturwissenschaftliche Classe, Wien, 123(1): 33-48. 
WAGNER, H., 1935, Ueber die Mollusken-Fauna der Planina-Hôhle. Mitteilungen über Höhlen- und 

Karstforschung, 11: 35-37. 



MALACOLOGIA, 1979, 18: 61-66 

PROC. SIXTH EUROP. MALAC. CONGR. 

NEW MALACOLOGICAL RECORDS FOR THE PROVINCE OF LEÓN 
(N.W. SPAIN) AND PERCENTAGES OF INFESTATION BY TREMATODA 

M. Y. Manga Gonzalez and M. Cordero del Campillo 
Laboratory of Parasitology, Faculties of Veterinary Medicine and Biology, León, Spain 

The province of León (Fig. 1) is situated in the northwestern part of Spain. According to 
the work "Mapas provinciales de suelos de León" (Provincial soil maps of León) carried out by 
the National Institute for Agrarian Research (Madrid, 1973), León is considered to be divided 
into 5 natural regions: Mountain, Transition, Central, El Bierzo, and La Cabrera. Roughly 
speaking, the first 3 correspond to the upper, mid and lower valleys of the rivers of the Douro 
basin respectively. The material discussed was collected in the period 1972-1975 at ca. 350 
localities; the species forming the subject of this study were found generally in a few places 
only. A total of 761 molluscs was examined for parasites. 

The following species of Helicidae (Gastropoda, Pulmonata), identified with the assistance of 
the Rijksmuseum van Natuurlijke Historie|(Leiden, Holland), were recorded for the first time in 
the province. 

Subfamily Helicellinae 

Candidula intersecta (Poiret, 1801) (Fig. 2), found in 3 different parts of the Mountain- 
Transition border, in the Central region and in La Cabrera at heights of 819-978 m, the soil 
being mainly sandy and the vegetation of the Chenopodio-Scleranthea division; 4.2% of the 24 
specimens studied had trematodes. 

Candidula rocandioi (Ortiz de Zarate, 1950) (Fig. 3) was found in 16 localities within the 
Mountain region and on the Mountain-Transition border, 947-1 199 m, mainly on sandy soils 
and in vegetation types principally of the Chenopodio-Scleranthea division. None of the 65 
specimens studied had parasitic worms. 

Helicella ordunensis (Kobelt, 1882) (Fig. 4) was found in 65 localities in Mountain, 
Mountain-Transition border and Central areas, at heights of 922-1260 m, mainly on alluvial 
terraces and sandy soils, the dominant vegetation type being the Chenopodio-Scleranthea 
division. Of the 316 specimens studied, 4.1% had trematodes in the kidney and 2.5% had 
trematodes in the hepatopancreas. 

Helicella cf. madritensis (Rambur, 1868) (Fig. 5) was found in 15 localities in the Transition 
and Central regions at 736-909 m, mainly on alluvial terraces and clayey soils in the 
Chenopodio-Scleranthea division. Of 85 studied 2.3% had trematodes in the hepatopancreas. 

Subfamily Monachinae 

Monacha (Ashfordia) granulata (Alder, 1830) (Fig. 6) was found in 4 localities in the 
Mountain and Transition regions, at 857-1233 m, mainly on moist open soils, the dominant 
plant being Phragmites communis. Of 34 studied 2.9% had trematodes in the kidney. 

Subfamily Hygromiinae 

Hygromia inchoata (Morelet, 1845) (Fig. 7) was found in 6 localities in the Transition, 
Transition-Central border. Central, El Bierzo and La Cabrera areas, in the last named at heights 
of 380-877 m, chiefly on alluvial terraces and silty soils with an almost pure vegetation of the 
Chenopodio-Scleranthea division. Of 91 studied 38.5% had trematodes in the kidney and 1.1% 
in the hepatopancreas. 

Hygromia (Pyrenaearia) cantábrica cantábrica (Hidalgo, 1873) (Fig. 8) was^ found in 3 
localities within the Mountain region and on the Mountain-Transition border at 1019-1 182 m, 
mainly on sandy soils with vegetation of the Festuco-Bromea division. The specimens studied 
were free of helminths. 

(61) 



62 



PROC. SIXTH EUROP. MALAC. CONGR. 




FIG. 1. Natural regions of the province of León, Spain; the following 5 regions may be distinguished— (1 ) 
Mountain reqion (Zona de Montaña), (2) Transitional region (Zona de Transición), (3) Central region (Zona 
Central), (4) El Bierzo (Zona del Bierzo), (5) La Cabrera (Zona de Cabrera). Please note that longitudes refer 
to the meridian of Madrid and not Greenwich. 



Hygromia (Pyrenaearia) cantábrica covadongae (Ortiz de Zarate, 1956) (Fig. 9) was found in 
1 locality in the Mountain region (Cantabrian side) at 770 m on silty soils. None of the 3 
specinnens studied had trematodes. 

Ponentina ponentina (Morelet, 1845) (Fig. 10) was found in 8 localities in the following 
regions: Mountain-Transition, El Bierzo and the Bierzo-Cabrera border at 380-877 m, on mainly 
silty soils with chiefly Chenopodio-Scleranthea vegetation; 16.2% of 37 specimens studied had 
trematodes in the kidney. 

Euomphalia (l\/lengoana) brigantina (Da Silva Mengo, 1867) (Fig. 11) was found in 6 
localities in the Mountain region at heights of 520 m (Cantabrian side) and 1337 m, on mainly 
open soils with Chenopodio-Scleranthea vegetation; 12.1% of the 66 specimens studied had 
trematodes in the kidney. 

Subfamily Helicodontinae 

Oestophora (Oestophora) barbula (Rossmässler, 1838) (Fig. 12) was found in 7 localities in 
El Bierzo, the Bierzo-Cabrera border and La Cabrera, at 380-900 m, mainly on silty soils with 
chiefly Chenopodio-Scleranthea vegetation. None of the 25 specimens studied had parasites. 

Oestophorella buvinieri (Michaud, 1841) (Fig. 13) was found in 9 localities in the Mountain 
region and on the Mountain-Transition border, between 520 m (Cantabrian side) and 1278 m, 
mainly on sandy soils with a Festuco-Bromea vegetation. None of the 7 studied had trematodes. 



MANGA GONZALEZ AND CORDERO DEL CAMPILLO 63 

ABBREVIATIONS IN THE FIGURES 

a —atrium genitale ga —albumen gland 

ap —appendix gm — glandulae mucosae 

b —bursa of receptaculum seminis mrp— penial retractor muscle 

bd —dart sac ov —oviduct 

cb — pedunculus of receptaculum seminis p —penis 

cd —vas deferens pd —distal part of penis 

ch —hermaphrodite duct pr —prostate 

d -dart pro —proximal part of penis 

ep — epiphallus sod — spermoviduct 

f — flagellum v —vagina 

fd —diaphragm 

LITERATURE CITED 

ALONSO, M. R., 1975, Fauna malacólogica terrestre de la depresión de Granada (España) II. El género 

Helicella Férussac, 1821. Cuadernos de Ciencias Biológicas, 4(1): 11-28. 
ALTIMIRA, С, 1969, Notas malacológicas. XI. Moluscos terrestres y de agua dulce recogidos en la provincia 

de Lugo (Galicia) y Asturias. Publicaciones del Instituto de Biología Aplicado. 46: 107-113. 
BISHOP, M. J., 1976, On the occurrence of Monacha (Ashfordia) granulata (Alder) in Spain. Archiv für 

Molluskenkunde, 107: 111-114. 
CORDERO DEL CAMPILLO, M., ed., 1975, Indice- Catálogo de zooparèsitos ibéricos, I, Protozoos. Il, 

Tremátodos. Instituto Bayer de Terapéutica Experimental, Barcelona, 115 p. 
GITTENBERGER, E., 1968, Zur Systematik der in die Gattung Trissexodon Pilsbry (Helicidae. Helicodonti- 

nae) gerechneten Arten. Zoologische Mededelingen, 43: 165-173. 
GITTENBERGER, E., 1971, Eine nomenklatorische Notiz: Die Veröffentlichungsdaten einiger neuen Taxa, 

verwandt mit Hygromia Risso, 1826. Basteria, 35: 113-114. 
HESSE, P., 1931, Zur Anatomie und Systematik palaearktischer Stylommatophoren. Zoo/og/ca, 31 (1/2, Heft 

81): 1-118. 
HESSE, P., 1934, Zur Anatomie und Systematik palaearktischer Stylommatophoren, Zweiter Teil. Zoológica, 

33 (1, Heft 85): 1-59. 
NAVARRO ANDRES, F., 1974, La vegetación de la Sierra del Aramo y sus estribaciones (Asturias). Revista 

de la Facultad de Ciencias de Oviedo, 15: 1 1 1-243. 
ORTIZ DE ZARATE Y LOPEZ, A., 1943, Observaciones anatómicas y posición sistemática de varios 

Helicidos españoles. Boletín de la Real Sociedad Española de Historia Natural, 41: 61-83. 
ORTIZ DE ZARATE Y LOPEZ, A., 1949, Observaciones sobre la especia conocida con el nombre de Helix 

brigantina Mengo, en el Museo de Madrid. Revista Las Ciencias, Madrid, 16: 285-292. 
ORTIZ DE ZARATE Y LOPEZ, A., 1950, Observaciones anatómicas y posición sistemática de varios 

Helicidos españoles. Especies de los subgéneros Candidula, Helicella s.S., Xerotricha, Xeromagna y 

Pseudoxerotricha nov. subg. Boletín de la Real Sociedad Española de Historia Natural, 48: 21-85. 
ORTIZ DE ZARATE Y LOPEZ, A., 1956, Observaciones anatómicas y posición sistemática de varios 

Helicidos españoles. IV. Género Pyrenaearia. Boletín de la Real Sociedad Española de Historia Natural, 54: 

35-61. 
ORTIZ DE ZARATE Y LOPEZ, A., 1962, Observaciones anatómicas y posición sistemática de varios 

Helicidos españoles. Género Oestophora Hesse, 1907. Boletín de la Real Sociedad Española de Historia 

Natural, (B), 60: 81-104. 
WRIGHT, С. А., 1960, Relationships between trematodes and molluscs. Annals of Tropical Medicine and 

Parasitology, 54: 1-7. 



64 



PROC. SIXTH EUROP. MALAC. CONGR. 




FIG. 2. Candidula intersecta (Poir.), genitalia (scale 1mm) and 2 mandibulae (scale 0.2 mm). FIG. 3. 
Candidula rocandioi (Ortiz de Zar.), genitalia (scale 1 mm) and 2 mandibulae (scale 0.2 mm). FIG. 4. Helicella 
ordunensis (Kob.), genitalia (scale 1 mm) and 3 mandibulae (scale 0.2 mm). FIG. 5. Helicella cf. madritensis 
(Ramb.), genitalia (scale 1 mm) and 2 mandibulae (scale 0.2 mm). 



MANGA GONZALEZ AND CORDERO DEL CAMPILLO 



65 




FIG. 6. Monacha (Ashfordia) granulata (Aider), genitalia (scale 1 mm) and 2 mandibulae (scale 0.2 mm). FIG. 
7. Hygromia inchoata (Mor.), genitalia (scale 1 mm) and 2 mandibulae (scale 0.3 mm). FIG. 8. Hygromia 
(Pyrenaearia) с cantábrica (Hid.), genitalia (scale 1 mm) and 2 mandibulae (scale 0.3 mm). FIG. 9. Hygromia 
(Pyrenaearia) cantábrica covadongae (Ortiz de Zar.), genitalia (scale 1 mm) and 2 mandibulae (scale 0.2 mm). 



66 



PROC. SIXTH EUROP. MALAC. CONGR. 




FIG. 10. Ponentina ponentina (Mor.), genitalia (scale 1mm) and 2 mandibulae (scale 0.2 mm). FIG. 11. 
Euomphalia (Mengoana) brigantina (Da Silva Mengo), genitalia (scale 1 mm) and 2 mandibulae (scale 
0.3 mm). FIG. 12. Oestophora (Oestophora) bartula (Rossm.), genitalia (scale 1 mm) and 2 mandibulae (scale 
0.2 mm). FIG. 13. Oestophorella buvinieri (Mich.), genitalia (scale 1 mm) and 2 mandibulae (scale 0.2 mm). 



MALACOLOGIA, 1979. 18: 67-72 

PROC, SIXTH EUROP. MALAC. CONGR. 

THE PLANORBID GENUS GYRAULUS IN EURASIA 

С Meier-Brook 
Tropenmedizinisches Institut der Universität Tübingen, Federal Republic of Germany 

ABSTRACT 

Within the Planorbis tribe of the family Planorbidae the genus Gyraulus Charpentier is 
defined conchologically: a conspicuous gap in the range of shell variation serves to 
delimit it against Anisus and Bathyomphalus. Anatomical comparison indicates the 
existence of 6 subgenera: Gyraulus s.s. with a wide distribution in North America, 
Eurasia inclusive of N. Africa, and Indonesia, Australia, New Zealand, and the Pacific 
Islands; Torquis Dall in N. America and Europe; Lamorbis Starobogatov in N. and N.E. 
Europe; Caillaudia Bourguignat in Africa S. of the Sahara; Car'mogyraulus Polinksi in 
Lakes Ochrid and Prespa, Macedonia; Choanomphalodes Lindholm in Lake Biwa, Japan. 
Characters suitable for species discrimination are found mainly in the reproductive 
system, but mantle pigmentation and kidney shape have also proven to be more or less 
constant within a species or species group. While anatomical diversity is great in Europe, 
it is relatively low in Asia. From West Asia through the continent south of the high 
mountain chains to the Far East there is a group with characters grading into each other. 
This group is conceived to constitute a 'Rassenkreis' similar to that of Radix auricularia. 
Its oldest species name is Gyraulus chinensis; euphraticus, convex iuscu lus, spirillus, and 
probably some other groups are regarded to be races of G. chinensis. The Malay 
Archipelago harbours a group that is anatomically quite different from the group of 
continental South Asia. The non-planispiral Gyraulus species in Lake Biwa and in the old 
Macedonian lakes appear to have a different origin within the genus, their conchological 
similarities being due to convergence. 

The freshwater snails of the genus Gyraulus Charpentier, 1837, are distributed in all parts of 
the world except South America south of Venezuela. Several revisions in restricted parts of the 
distribution area have increased the number of named "species," because these were exclusively 
based on shell characters. A synoptic review of the genus over a wider area was hitherto not 
available. The parasitologists particularly want clarification as regards which species is or are the 
intermediate hosts of Echinostoma ilocanum and E. lindoense, intestinal flukes of man and 
animals in South East Asia. During the last few years I have therefore attempted to include 
anatomical data in taxonomical studies as far as material was obtainable. The main results are 
presented here. 

The genus is characterized by a small shell with a rounded periphery, often more or less 
angulate or even keeled in its middle, and by the presence of a peculiar stylet on the tip of the 
penis. This latter feature it shares with the genera Anisus, Bathyomphalus, and Armiger, which 
are closely related and can be generically separated on conchological grounds only. 

The European fauna outside that of the old Macedonian lakes consists of 5 species. These 
are conchologically rather dissimilar and easily separated since some corrections had been made 
after anatomical studies (cf. Meier-Brook, 1964). An anatomical comparison has revealed basic 
differences suggesting the separation of some species groups (Fig. 1). The main distinguishing 
characters are found in the male copulatory organ which usually has a club-shaped penis sheath. 
In 2 species, riparius and rossmaessleri, it is reduced in form and size. The penis itself generally 
has a terminal thickening comparable to the mammalian glans penis. The penis pore is situated 
in or near this thickening. This is the situation in the groups to which our species albus, 
acronicus and laevis as well as the species of the Ethiopean region belong. The narrow vas 
deferens is sharply set off against the penis sheath. The prostate gland has a number of 
diverticula which may be regularly and densely arranged as in albus, acronicus, riparius, and 
rossmaessleri, or irregularly and loosely arranged, as in laevis, or greatly reduced as in 
costulatus. The long tubular portion of the kidney may have conspicuously undulate margins 

(67) 



68 



PROC. SIXTH EUROP. MALAC. CONGR. 



Gyraulus s.str. 



Torquis Dall 



Lamorbis Starobogatov 



Caillaudia Bourg. 



male 

copulat. 

organ 







prostate 
gland 





kidney 
{tub. port. 



^ÄZiÖ^^^^^^^^^ 



other 
charact. 



shell often with spiral 
striae, angled periph. 
and fringe of periostr. 



shell surface always 
smooth, neither angled 
nor with fringe of 
periostracum 



ovotestis and seminal 
vesicle unusually big 
(the latter almost as 
large as digest .gland) 



all reproduct. organs 
unusually small and 
delicate 



North America, North 
Africa, Europe, Asia, 
Pacific Islands, 
Australia 



North America, Europe 



North and East Europe 



Africa south of the 
Sahara 



examples 
of spp. 



albus (O.F.Müller), 



acronicus (Fer.), chi- 



parvus (Dall), laevis 



(Alder) 



nensis (Dkr) , piscina - 



riparius (Westerlund) , 
? rossmaessleri (Au- 
erswald) 



costulatus (Krauss) , 



connollyi Brown & van 



rum (Bourguignat) 



FIG. 1. Main distinguishing characters of the widely distributed subgenera of Gyraulus. Kidney: tub. port. = 
tubular portion. 



and large transverse septa, as in laevis, riparius and rossmaessleri, as far as the European fauna is 
concerned. Such a kidney is encountered in North American and European Gyraulus species but 
nowhere in Asia. Here and in Africa, Australia and in the rлajority of European snails of the 
genus the kidney has straight margins with only a few tiny septa. These and other constant 
differences suggest the existence of three subgenera in Europe: Gyraulus s.S., Torquis, and 
Lamorbis. A fourth subgenus, Caillaudia, is confined to Africa south of the Sahara. In the 
whole North Eurasiatic region from N. Scandinavia to Kamchatka G. acronicus is the only 
species according to the scarce material I could examine anatomically. 

The Near East harbours at least 4 species which can be separated not only by anatomical 
characters. They all are members of the nominate subgenus. 

In South and East Asia there is a great variety of shell forms which, during the last decades, 
usually were identified as convexiusculus (type locality in Afghanistan). Anatomical comparison 
revealed a uniformity which is quite surprising in view of the vast area stretching from Iran to 
Korea. The male copulatory organ is of the usual type (Fig. 2), and the penis pore is in the 
terminal thickening. Also variation in other features, such as prostate diverticula numbers (range 
8-24, in contrast with 7-39 in Europe), is small, so that it is justified to unite all these forms in 
one "superspecies" or rather "Rassenkreis," similar to that of the lymnaeid. Radix auricularia 
(L.), as demonstrated by Hubendick (1951). The oldest name available for the South and East 
Asiatic Gyraulus is chinensis (Dunker). In only one case I had to decide to keep a species apart 
despite apparent anatomical resemblance, viz. G. tokyoensis. This extremely large form is 
conchologically very different and, moreover, is sympatric with the eastern race of G. chinensis 
in Japan and Okinawa, where Davis & Yamaguchi (1969) found "no gradation of spirillus into 
G. tokyoensis." They must, consequently, be reproductively isolated from each other. 

The finding of great anatomical uniformity in S. and E. Asiatic Gyraulus snails might suggest 
that this vast area is inhabited only by the races of G. chinensis and its close relative, G. 
tokyoensis. But it must be borne in mind that from China a lot of Gyraulus forms have been 
named, and almost no material could be obtained for this study. The only available alcohol 




FIG. 2. Shape of the penis sheath and penis and positions of the penis pore in Gyraulus samples fronn South 
and East Asia and Indonesia. Equal magnification in all anatomical drawings. 



preserved specirnens, collected by the Sven Hedin Expedition to Inner Mongolia in 1927, 
actually represent a species hitherto unknown. Both anatomical and shell characters place it 
well outside the variability of the chinensis-group. 

The widely distributed Gyraulus forms from Indonesia were so far identified as con- 
vexiusculus, apart from a few species endemic to Sumatra. Shell characters in fact fall 
completely in the range of those of the chinensis races. Anatomically, however, the 2 lots 
examined from Central Java and Bali showed striking aberrations (Fig. 2). The vas deferens is 
much widened over its full | length so that the site of its passing into the penis sheath is nearly 
indiscernible. The penis lacks the terminal thickening, and the penis pore is near the middle or 
even in the upper half of the penis. A penis pore so far from the usual site has been reported 
only once, namely by Hubendick & Radoman (1959) from a species in Lake Ochrid. All other 
specific characters, however, are so different that a convergent development of this one feature 
must be concluded. A 3rd lot showing characters very similar to those In the Indonesian forms 
is from Kuala Lumpur in Malaysia. Now the question arises whether or not the whole Malay 
Archipelago is inhabited exclusively by Gyraulus forms having these aberrant male copulatory 
organs. Any additional material will be greatly appreciated. 

As far as can be judged from the few observations the Malay forms resemble the South 
Asiatic ones in other essential features, including a characteristic "patchy" pigmentation pattern 
on the roof of the mantle (Fig. 3). Such a pattern is never encountered in species indigenous to 
Europe. European species have a weak and diffuse mantle pigmentation; the only exception is 
acronicus, where a certain, but less distinct, pattern is visible. Whenever a conspicuous patchy 
pigmentation is found in Europe, a recent introduction from outside Europe must be suspected. 



70 



PROC. SIXTH EUROP. MALAC. CONGR. 




Gyraulus sp., Malaysia 



chin, spir, Okinawa albus, Germany 



FIG. 3. Pigmentation of the mantle roof in 3 Gyraulus species. 



G. chinensis has, e.g., been found at several places on this continent. A 2nd species introduced 
is G. parvus from North America, which has been collected at 2 German localities. 

When we compare variation in Gyraulus in Europe and Asia we may say that it is high in the 
former and low in the latter. Europe harbours 3 subgenera: Gyraulus s.S., Torquis, and 
Lamorbis. In Asia the 2 latter are certainly absent. Lamorbis is apparently also absent from 
North America, as judged from Baker's studies (1945). There is also no evidence that in North 
America a further subgenus has evolved. This shows that Europe is tue centre of differentiation 
within the genus. Moreover, the related genera, Planorbis, Anisus, Bathyomphalus, and Armiger, 
are also largely confined to Europe, only slightly extending into West Asia. Thus Europe may 
also be regarded to be the centre of differentiation within the whole Planorbis tribe. It is, 
therefore, probable that the genus Gyraulus had its origin in this part of the world as well. 

Finally a brief account must be given of the species living in lakes of Tertiary origin. These 
are the Macedonian lakes Ochrid and Prespa and the Japanese Lake Biwa. Conchologically the 
shells are characterized by non-planispiral and multicarinate shells. These similarly directed 
deviations from the usual shell form have repeatedly caused speculations as to their possible 
common origin. Hubendick & Radoman (1959) were the first to dissect species from the Ochrid 
basin. In 4 of the 5 species they found a striking increase in numbers of prostate diverticula 
which are arranged in several rows (Fig. 4). In the species of the neighbouring Lake Prespa, as 
well as in Lake Biwa in Japan, this increase has not taken place. The radulae (Fig. 5, top and 
middle rows: radula forms of widely distributed taxa for comparison demonstrating great 
uniformity) show similar aberrations in both Macedonian lakes. Four of the 5 Ochridan species 
have elongated and unicuspid central and lateral teeth instead of bi- and tricuspid ones 
respectively. The species examined from Lake Prespa displays intermediary stages of cusp 
reduction with bi- and unicuspid central teeth and a general elongation of teeth together with a 
reduction of ectocones in the lateral teeth. The species from Lake Biwa, on the other hand, has 
adhered to the form usual throughout the genus. There is, thus, no evidence that the Japanese 
and Macedonian endemic species are more closely related within the genus. Most likely 
abandoning planispiral growth and development of carinae are the results of convergent 
evolution in the 2 parts of the world. On the other hand, similarities in radular structure, 
together with conchological affinities and the short distance between the two Macedonian lakes 
support the assumption of a common origin of the Prespan species and the 4 species of the 
Ochrid basin. These can be united in a separate subgenus, Carinogyraulus Polinski, while it 
seems equally justified to accept subgeneric rank for the species endemic to Lake Biwa, viz., 
Choanomphalodes Lindholm. Knowledge of anatomical characters described by Hubendick & 
Radoman (1959) and in the present study enable us to follow the possible course of evolution 
in the subgenus Carinogyraulus. After the non-planispiral and multicarinate shell had been 
developed, initially reduction of cusp numbers in central and lateral teeth took place. In the 



MEIER-BROOK 



71 




L.Ochrid 



FIG. 4. Shell and prostate gland of Gyraulus species from old lakes. A & B, 6. lychnidicus Hesse; C, G. 
crenophilus Hubendick & Radoman; G, G. trapezoides Polinski; E & F, G. stankovici Hadzisce; G, G. 
amplificatus (Mori) (Pidenticai with biwaensisl); H & I, G. biwaensis (Preston). С & D after Hubendick & 
Radoman (1959); G original; all others after Meier-Brook (in press). Scales 1 mm). 




FIG. 5. Radulae of widely distributed Gyraulus species (A to F) compared with those of species endemic to 
old lakes (G to I). A, G. albus (О. F. Müller), Denmark; В, G. parvus (Dali), Iceland; С, G. hebraicus 
(Bourg.), Turkey; D, G. chinensis convex iusculus (Hutton), India; E & F, G. ch. spirillus (Gould), Taiwan and 
Korea; G, G. lychnidicus. Lake Ochrid; H, G. stankovici. Lake Prespa; I, G. biwaensis. Lake Biwa (short scale 
applies to G and H only). 



72 PROC. SIXTH EUROP. MALAC. CONGR. 

Ochrid basin the 2nd step of evolution was done by increasing the number of prostate 

diverticula. A 3rd step of evolution including further reduction of cusp nunnbers in the lateral 
portions of the radula and some minor changes subsequently led to the evolution of the recent 
species. 

I wish to express my gratitude to all the many colleagues and museum authorities who 

provided the material used in these studies, although it is impossible to mention them 
individually. 

LITERATURE CITED 

BAKER, F. C, 1945, The molluscan family Planorbidae. University of Illinois Press, Urbana, xxxvi + 530 p. 
DAVIS, G. M. & YAMAGUCHI, S., 1969, The freshwater Gastropoda of Okinawa. Venus, 28: 137-152. 
HUBENDICK, В., 1951, Recent Lymnaeidae. Their variation, nnorphology, taxonomy, nomenclature, and 

á\5Xr\bui\or\. Kungliga Svenska Vetenskapsakademiens Handlingar, (4), 3(1): 1-222. 
HUBENDICK, B. & RADOMAN, P., 1959, Studies on the Gyraulus species of Lake Ochrid. Morphology. 

Arkiv for zoologi, Serie 2, 1 2: 223-243. 
MEIER-BROOK, C, 1964, Gyraulus acronicus und G. rossmaessleri, ein anatomischer Vergleich (Planorbidae). 

Archiv für Molluskenkunde, 93: 233-242. 
MEIER-BROOK, C, in press. Taxonomía studies on Gyraulus (Gastropoda; Planorbidae). Malacologie. 



NOTE ADDED IN PROOF. Continuing studies have revealed that (a) Armiger must be considered a further 
subgenus of Gyraulus, and that (b) G. euphraticus should be kept separate from the "Rassenkreis" of G. chinensis 
(cf. Meier-Brook, in press). 



MALACOLOGIA, 1979, 18: 73-77 

PROC. SIXTH EUROP. MALAC. CONGR. 

THE MALACOFAUNA OF MOUNT HERMON 

Z. Bar and H. K. Mienis 

M. L. Kinglaan 356, Diemen, Netherlands 

and 

Zoological Museum, Hebrew University of Jerusalem, Israel 



ABSTRACT 

In this preliminary report of the first survey of the malacofauna of Mount Hernnon 
(33°24' N 35°50' E), the outlines are presented of the geographical and altitudinal 
distribution of 33 land molluscan species. From these outlines, a few general patterns 
emerge. 



INTRODUCTION 

The malacofauna of Mount Hermon (33°24' N 35°50' E) has hardly been investigated before 
owing to its isolated position, political restrictions and severe climatic conditions which greatly 
limit the collection of live snails. Here are presented the preliminary results of a survey of all 
the known material collected on the western part of the mountain, Israeli-held since 1967. 



PHYSICAL GEOGRAPHY 

Mount Hermon is the southern continuation of the Anti-Lebanon whose anti-clinal axis runs 
NE-SW. In the east it borders on the Damascus basin, in the south on the basalt table land of 
the Golan, and in the west on the alluvial Hazbani Valley. The length of the ridge is some 
45 km and its greatest width about 25 km. The summit reaches 2814 m. The main substrate is 
hard Jurassic limestone. Mean annual precipitation at the peaks is about 1700 mm, mainly in 
the form of snow and only on the eastern and western slopes as rain. Usually the snow remains 
on the ground for 3-5 months at altitudes above 1500 m. A substantial part of the rain and the 
melting snow quickly percolates through the porous rock, resulting in karstic erosion and an 
almost complete absence of top soil. In summer, when relative humidity is extremely low and 
there is no soil to contain water, dry steppe conditions prevail (Inbar, 1971; Orni, 1972). 

THE SPECIES AND THEIR DISTRIBUTION 

Sommerville (1869) did not only give the first, but so far also the most extensive, list of (7) 
land snails from an unidentified locality, probably situated at the foot of the western part of 
the mountain. Among the species mentioned in this list, Buliminus labrosus (Olivier, 1804), 
Pene sidoniensis (Férussac, 1821), Helix texta (Mousson, 1861), and Sphincterochila cariosa 
(Olivier, 1804) can be identified with certainty. The first slug from Mount Hermon was 
described by Pollonera (1908) as Agriolimax libanoticus (= Deroceras sp.). Recently several land 
snails from the Hermon area have been mentioned in monographic works: Pleurodiscus erdelii 
(Roth, 1839) (Bar, 1974), Pene sidoniensis and P. auriculata (Pallary, 1929) (Heller, 1974), 
Buliminus labrosus (Heller, 1975), Sphincterochila cariosa (Bar, 1975), Xeropicta vestalis 
¡oppensis (Schmidt, 1855) (Forcart, 1976), Lauria cylindracea (Da Costa, 1778) (Mienis, 1976) 
and Monacha crispulata (Mousson, 1861) (Bar, 1976). A complete list of the species found in 
this survey is presented in the table of altitudinal distribution. 

(73) 



74 



PROC. SIXTH EUROP. MALAC. CONGR. 



35°40' 




3320' 



3315 



35 40' 








^P Pene sidoniensis 

1 

m) Pene aurioulata 


С 


^ 


2 








©c c^ 








L €\ i 


чУ / 






• 


/^ 






7 


У-- 


-^U 


vq 





3320 



3315 



FIGS. 1-2. Some typical distribution patterns of land snails on Mt. Hermon; the little lake on the right hand 
bottonn corner of the maps is Birqet Ram. H. Heijn del. 



BAR AND MIENIS 



75 



3540 




3320' 



3540 



3315 



33°20 



^^ Monaoha sp. nov. 
щ\ Monaaha haifaensis 
^^ Monacha syriaaa 




3315 



FIGS. 3-4. Some typical distribution patterns of land snails on Mt. Hernnon; the little lake on the right hand 
bottom corner of the maps is Birqet Ram. H. Heijn del. 



76 



PROC. SIXTH EUROP. MALAC. CONGR. 



In spite of its isolated topographic and ecological position, Mount Hermon seenris to harbour 
only few endemic species. Of these, a montane Monacha species replacing the Mediterranean 
Monacha syriaca (Ehrenberg, 1831) and M. haifaensis (Pallary, 1939) at 1300 m, is so far the 
only one to have been collected alive. Pene auriculata likewise replaces P. sidoniensis at high 
altitudes and has a discontinuous distribution in the Lebanon (Heller, 1974), probably governed 
by a similar hierarchy. Cristataria is a clausiliid genus with a relict distribution from the Taurus to 
the Judean Hills (Nordsieck, 1971, 1977; Bar, 1977). Helix texta, Umax eustrictus (Bourguignat, 
1866), Oxychilus (Hiramia) camelinus (Bourguignat, 1852) and Orculella orientalis (L. Pfeiffer, 
1861) are all species which here reach the southern limit of their distribution. The Lebanese Helix 
texta occurs only on the mild western slopes of the mountain and is elsewhere replaced by 
Helix engaddensis (Bourguignat, 1852). Figs. 1-4 illustrate some typical distribution patterns of 
land snails on Mt. Hermon, 



ALTITUDINAL DISTRIBUTION 

The altitudinal distribution is presented in Table 1. Many species found in the lower zones 
are found at even much lower altitudes in Israel and the Lebanon. Furthermore, some of 



TABLE 1. Altitudinal distribution. 



\^ 






Alpine 


^\^ VEGETATION 




Montane 


traga- 


\v^ 


Mediterranean maquis 


open scrub 


canthic 




E 


E 


Е 


Е 


Ê 


Е 


E 


^\ ALTITUDE 


о 


о 


о 


8 


о 


о 


о 




Ю 


о 


ю 


ю 


о 


ю 




Ю 


со 


о 


СО 


ю 


00 


о 








^ 


г— 


^ 


^ 


CSI 




ó 


ó 


ó 


ó 


ó 


ó 


ó 




о 


in 


о 


ю 


о 


ю 


о 




со 


ю 


00 


о 


со 


ю 


00 


SPECIES ^\^ 








*" 


'" 


*" 


*" 


Pyramidula hierosolymitana (Bgt., 1852). . 


+++++ 


■++++++ 


■+++++++ 


■++++ 








Orculella orientalis (L. Pfr., 1861) 






++++ 


•+++++++■ 


+++++++■ 


-И-+++-И 


+++++ 


Granopupa granum (Drap., 1801) 


+ 














Rupestrella rhodia (Roth, 1839) 


+ 














Lauria cylindracea {Da Costa, M78) .... 


+ 














Pleurodiscus erdelii Roth. 1839) 


+++++• 


•++++++ 


•++++ 










Jaminia borealis (Mousson, 1874) 


+++++ 


•++++++ 


■+++++++ 


•+++++++■ 


■+++++++■ 


++++ 




Ena nov. spec 










++++■ 


■++++++Н 


+++++ 


Paramastus episomus (Bgt., 1857) 


+++++ 


■++++++ 


•++++ 










Buliminus labrosus (Olivier, 1804) 


+++++■ 


■++++++ 


•+++++++ 


■+-1-++ 








Pene auriculata (Pallary, 1929) 








++++■ 


+++++++■ 


++++ 




Pane sidoniensis (Férussac, 1821) 


+++++■ 


•++++++ 


■+++++++■ 


■+++++++■ 


■+++++++■ 


■++++ 




Succinea spec 


+ 














Eopolita protensa jebusitica (Roth, 1855) . 


+ 














Oxychilus camelinus (Bgt., 1852) 


+++++■ 


•++++++ 


•+++++++ 


•+++++++• 


+++++++• 


++++ 




Daudebardia saulcyi (Bgt., 1852) 


+ 














Milax barypus (Bgt., 1866) 


+ 














Umax eustrictus (Bgt., 1866). 


+++++■ 


•++++++ 


■++++ 










Lehmannia flava (L., 1758) 


+ 
+ 














Dereceras berytensis (Bgt., 1852) 




Cristataria hermonensis Nordsieck, 1977 . . 






+ 










Sphincterochila cariosa (Olivier, 1804) . . . 


+++++• 


•++++++ 


•+++++++■ 


■+■1-++ 








Xeropicta vestalis joppensis (Schmidt, 1855) 


+++++■ 


■++++++ 


•+++++++ 


•++++ 








Monacha obstructa (Férussac, 1821). . . . . 


+ 














Monacha haifaensis (PaWary , ЛЭ29) 


+++++■ 


•++++++ 


•+++++++• 


•++++ 








Monacha syriaca {Ehvenberq, 1831) 






++ 










Monacha crispulata (Mousson, 1861) .... 


+++++■ 


++++++ 


■++++ 










Monacha nov. spec 






++++■ 


■+++++++- 


+++++++■ 


■++++++■ 
■++++ 


+++++ 


Metafruticicola nov. spec 




Metafruticicola fourousi (Bgt., 1863) .... 


+ 














Levantina caesareana (Mousson, 1854) . . 


+++++■ 


++++++■ 


(■+++++++■ 


■++++ 








Helix engaddensis Bgt., 1852 


+++++■ 
+++++■ 


++++++■ 
++++++■ 


[-+++++++■ 
h+++++++- 

1 


■+++++++■ 
■+++++++■ 


+++++++■ 
++++ 


++++++■ 


+++++ 


Helix texta Mousson, 1861 









BAR AND MIENIS 77 

these-notably very small species-may yet be found higher up. Some typical Mediterranean 
species enter the montane region. They all hide in cracks {Pene) or under stones (Jaminia, 
Oxychilus). Helix engaddensis is able to span the amazingly wide range of 0-2050 m. It 
aestivates while buried in the little soil that accumulates in a few cracks. In the surrounding 
Mediterranean and desert regions, land snails aestivate during the long, hot and dry summer, 
their activity being limited to the mild rainy winter and short spring. It seems likely that, at 
altitudes above 1300 m where snow covers the ground during severe! months, snails are being 
forced into two periods of dormancy, an unnatural condition for most species adapted to a 
Mediterranean climate. 

Acknowledgments for assistance in completing this paper are due to Messrs. H. Heijn and Dr. 
A. С van Bruggen of Leiden University, Holland. 



LITERATURE CITED 

BAR, Z., 1974, The geographical distribution of Pleurodiscus erdelii (Pulmonata, Pleurodiscidae). Basteria, 

38: 85-91. 
BAR, Z., 1975, Distribution and habitat of the genus Sphincterochila (Gastropoda, Pulmonata) in Israel and 

S\T\a[. Argamon, 5: 1-19. 
BAR, Z., 1976, The geographical distribution of Monacha crispulata (Mousson, 1861). Basteria, 40: 85-88. 
BAR, Z., 1977, Distribution and habitat of the genus Cristataria Vest (Pulmonata, Clausiliidae). /Ал^этол, 6: 

1-16. 
FORCART, L., 1976. Die Cochlicellinae und Helicellinae von Palästina und Sinai. Archiv für Molluskenkunde, 

106: 123-189. 
HELLER, J., 1974, Systematics and distribution of the land snail Pene (Pulmonata: Enidae) in Israel. 

Zoological Journal of the Linnean Society of London, 54: 257-276. 
HELLER, J., 1975, The taxonomy, distribution and fauna! succession of But/minus (Pulmonata: Enidae) in 

Israel. Zoological Journal of the Linnean Society of London, 57: 1-57. 
INBAR, M., 1971, Physiographic units of the Golan. Teva Va'aretz, 13: 158-161 (in Hebrew). 
MIENIS, H. K., 1976, Lauria cylindracea (Da Costa, 1778) in Israel. Levantina, 3: 21-22. 
NORDSIECK, H., 1971, Zur Anatomie und Systematik der Clausilien, X. Zur Kenntnis des Genus Cristataria 

Vest, 1867, \. Archiv für Molluskenkunde, 101: 237-261. 
NORDSIECK, H., 1977, Zur Anatomie und Systematik der Clausilien, XVIII. Neue Taxa rezenter Clausilien. 

Archiv für Molluskenkunde, 108: 73-107. 
ORNI, E., 1972, Entry 'Mt. Hermon' in: Encyclopaedia Judaica, 8: 373-374. Publ. Keter, Jerusalem. 
POLLONERA, C, 1908, Sui Limacidi della Siria e della Palestina. Bollettino dei Musei di Zoología ed 

Anatomía Comparata della R. Universita di Torino, 608: 1-8. 
SCÍMMERVILLE, J. E., 1869, Notes on some land and freshwater shells from Egypt and Palestine. 

Proceedings of the Natural History Society of Glasgow, 1 : 382-384. 



MALACOLOGIA, 1979, 18: 79-102 

PROC. SIXTH EUROP. MALAC. CONGR. 

BIOGEOGRAPHICAL ASPECTS OF AFRICAN FRESHWATER GASTROPODS 

David S. Brown 

Medical Research Council of the U.K.; Zoology Department, 
British Museum (Natural History), London SW7 5BD, England 

ABSTRACT 

To Pilsbry & Bequaert (1927) the outstanding features of the freshwater molluscan 
fauna of the Ethiopian region were its taxonomic poverty and its uniformity over 
immense areas. This view can hardly be maintained having regard to taxonomic and 
distributional data accumulated in recent years largely due to interest in the transmission 
of human schistosomiasis. Various distribution patterns are evident at the levels of the 
species and of the genus, which are of considerable biogeographical interest. About 300 
species of freshwater gastropods are living in Africa of which about one-fifth are endemic 
to certain of the great lakes. Most of the species which are not strictly lacustrine fall into 
two main groups: 

(1) Species having their closest affinities with the fauna of Europe and/or South West 
Asia. These reach their southwestern limits in North Africa and some penetrate to 
Ethiopia. 

(2) Species which are characteristic of Africa south of the Sahara and do not occur in 
North West Africa, though some are present in the lower Nile and a few extend into 
South West Asia. 

Another, smaller, group of alien species can be distinguished of which some obviously 
have been introduced by man. Representative distribution maps are presented, with an 
analysis of species-diversity in relation to the major climatic regions to Africa. 

INTRODUCTION 

To Pilsbry & Bequaert (1927) the outstanding features of the freshwater molluscan fauna of 
the 'Ethiopian Region' were its taxonomic poverty and its uniformity over immense areas. This 
view can hardly be maintained having regard to taxonomic and distributional data accumulated 
in recent years largely through interest in the snail hosts concerned in the transmission of 
human schistosomiasis. Various distribution patterns of biogeographical interest are evident at 
the levels of both genus and species, and are discussed in the context of southern Africa by 
Brown (1978). 

The present maps are based partly on unpublished records from the collections of the 
Experimental Taxonomy Unit, British Museum (Natural History), and the Danish Bilharziasis 
Laboratory. I am grateful to Dr. С A. Wright and Dr. G. Mandahl-Barth for permission to 
include these data, and to the Department of Geography of the University of Chicago for 
permission to reproduce a map from the Goode Base Map Series in Figs. 1-9. The shaded areas 
approximate to the main areas of occurrence, but within these areas distribution may be 
discontinuous, and it is commonly disrupted by the scarcity of aquatic habitats in districts 
receiving comparatively low rainfall. However, a greater order of isolation is evident for some 
populations and these are indicated in the maps by a single spot, or open circles in the case of 
records based only on shells. More or less worn shells have been termed by authors 'sub-fossil' 
and their age is uncertain, though probably North African examples are of late Pleistocene to 
Recent age. 

According to a revised synopsis of gastropods living in the fresh and brackish waters of 
Africa (Brown, in press), there is a total of about 314 species of gastropod (227 prosobranchs 
and 87 pulmonates) living in such waters on the African mainland. This number excludes three 
families which do not penetrate far from strong marine influence (Potamididae, Littorinidae and 
Ellobiidae), and the Hydrobiidae of North Africa which are in outstanding need of revision. 
Further, the ancylid genera Ferrissia and Burnupia are included as single taxa because their 
nominal species are so poorly defined. 

(79) 



80 PROC. SIXTH EUROP. MALAC. CONGR. 

About one-quarter of the African freshwater gastropods are restricted to lakes and these will 
not be considered in the subsequent biogeographical account. This exclusively lacustrine group 
is made up mainly of about 25 species of Thiaridae endemic to Lake Tanganyika, and 
representatives of a number of widespread prosobranch genera, including Bellamya, Gabbiella 
and Melanoides. Amongst pulmonates, the genus Ceratophallus has the highest proportion of 
lacustrine species (most of them described originally as 'Gyraulus'). 

The assemblage of about 235 species which are not exclusively lacustrine (though some may 
live at the edges of lakes) can be divided into 2 main groups based on biogeographical 
considerations, and a small 3rd group of introduced species. 

(1) Palaearctic group. These species have their closest affinities with the fauna of Europe 
and/or South West Asia. These are characteristic of the northern part of Africa which is 
customarily included in the Palaearctic biogeographical region, but some extend into the 
highlands of Ethiopia, and 2 are widespread south of the Sahara (Melanoides tuberculata and 
Lymnaea truncatula). 

(2) Afrotropical group. Most of the species included here are confined to Africa south of 
the Sahara or there occupy the main part of their range. They are thus characteristic of the 
traditional 'Ethiopian' biogeographical region, for which the name Afrotropical Region is 
preferable (Crosskey & White, 1977). Although the occurrence of shells shows that some of 
these species have been widespread in the Sahara, only Bulinus truncatus is known to live in 
North West Africa. Taxonomic problems make it difficult to decide exactly how many of the 
indigenous members of the Afrotropical group occur outside this region; these widespread 
species are comparatively few in number and belong to genera which are associated with 
brackish water or are confined to freshwater habitats near the coast [Neritina, Septaria, Thiara, 
and the Ellobiidae). 

(3) Introduced species. Physa acuta, Lymnaea columella and Helisoma spp. are present in 
both the Afrotropical and the Palaearctic regions of Africa. Their occurrence appears to be 
closely associated with European settlement and probably these snails have been dispersed 
mainly or entirely during the recent historical period. 

THE PALAEARCTIC GROUP 

This group comprises about 20 species (Table 1) of which about 16 occur in North West 
Africa and 10 in Egypt and/or Ethiopia. Only 4 species are known from North West Africa and 
also Egypt. Bithynia and Melanopsis are remarkable in being present in North West Africa and 
in South West Asia, but neither occurs in Egypt (for Bithyniidae see Mandahl-Barth, 1968). 

TABLE 1. The Palaearctic group of freshwater gastropods living in Africa; of these only Melanoides tuberculata 
and Lymnaea truncatula occur south of Ethiopia. 

Species Egypt (E) and/or Ethiopia (ET) North West Africa Both 

Theodoxus fluviatilis — X — 

T. nil oticus E — — 

Valvata nilotica E,ET — — 

Bithynia 2 spp.? — X — 

Melanoides tuberculata E,ET X X 

Melanopsis praemorsa — X — 

Lymnaea truncatula E,ET X X 

L. palustris — X — 

L. peregra — X — 

L. stagnalis E XX 

Planorbis planorbis E XX 

Armiger crista ET XX 

Gyraulus ehrenbergi E — — 

G. sp. — ? — 

Anisus 2 spp.? — X — 

Hippeutis sp. — X — 

Planorbarius metidjensis — X — 

Ancylus fluviatilis ET XX 

A. regularis ET — — 



BROWN 81 

Isolation between the freshwater faunas of North West Africa and Egypt is derлonstrated 
well by Theodoxus (Fig. 1), which does not penetrate south of the Sahara. This genus is 
represented in the northwest by forms related to T. fluviatilis, which belongs to Theodoxus s.s. 
In contrast, T. nilotica of Egypt belongs to the subgenus Neritaea and is closely related to T. 
jordani of South West Asia. The northern limit for the latter subgenus lies in Iraq and Iran. 

Valvata (Fig. 2) presents a more extensive penetration into northeast Africa, being common 
in the highlands of Ethiopia and known as a 'subfossil' from Lake Rudolf. Valvata tilhoi is 
recorded from several localities in the Sahara desert, the most westerly being Fort Flatters in 
Algeria (Fischer-Piette, 1949). The very small shells from Algeria described as new species of 
Valvata by Hagenmüller (1884) seem unlikely to belong to this genus, which is otherwise 
unknown from North West Africa. The absence there of V. piscinalis is surprising but is perhaps 
related to lack of this species in southern Spain (Zilch & Jaeckel, 1962), where the 
southernmost localities appear to be near Valencia and Alicante (Gasull, 1971). The probable 
route of entry into northeast Africa is indicated by the presence of isolated living populations 
of Valvata in the Sinai peninsula (Tchernov, 1971). 

The Lymnaeidae included in Table 1 are confined to North West Africa and/or Egypt with 
the exception of L. truncatula (Fig. 3), which is distributed discontinuously through eastern 
Africa to the Cape Province of South Africa. This snail is restricted to highland areas in the 
tropical region but inhabits a wider altitudinal zone in the southern temperate region; it is 
particularly abundant in Lesotho (Basutoland) (Prinsloo & Van Eeden, 1973). It seems correct 
to accept that L. truncatula has Palaearctic affinities, though its extensive range in Africa seems 
to be long established, as 'subfossil' shells are known from isolated localities which include the 
Ahaggar mountains in southern Algeria (Sparks & Grove, 1961). L. glabra is omitted from Table 
1 although its presence in Algeria is indicated by Hubendick (1951, fig. 332) on the basis of 
shells in the collection of the British Museum (Natural History). I have examined two lots of 
shells from Algeria in this collection, originally identified as L. glabra, but they appear to be 
slender examples of L. palustris. Moreover, since L. glabra is unknown from the Iberian 
peninsula, it would be unlikely to occur in North West Afrrca (see note on p. 84), 

The Planorbidae of North West Africa are almost unknown anatomically and consequently 
the correct taxonomic position of most of the nominal species recorded there is uncertain. 
Planorbis planorbis and Planorbarius metidjensis are widespread in this region. P. planorbis (Fig. 
4) lives also in Egypt and is known from shells obtained at the 2nd Nile Cataract in northern 
Sudan (Martine, 1968), and in the Rift Valley of Ethiopia (Brown, 1965). Armiger crista is 
known in North West Africa and also lives in Ethiopia (Brown, 1967). It appears that the 
Palaearctic genera Anisus and Hippeutis are represented by one or more species in North West 
Africa, but anatomical study is necessary to establish the presence of any species of Gyraulus. 

Ancylus occupies 2 widely separated areas in Africa (Fig. 5), one in North West Africa and 
the other in the Ethiopian highlands. A possible past connection between the Ethiopian populations 
and the main area of distribution in Europe is indicated by isolated localities for -4. fluviatilis 
known in the Arabian peninsula and in Syria. This possible route of dispersal perhaps pre-dates 
the major earth movements which separated the highlands of South West Arabia from those in 
Ethiopia, Support for the view that Ancylus is long established in the Ethiopian highlands is 
provided by the occurrence there, in addition to A. fluviatilis, of 2 endemic species (Brown, 
1965, 1973). 

Melanoides tuberculata has a much greater range than the other species here considered in 
the Palaearctic group. It occurs not only in the southern part of the Palaearctic Region but also 
in the Indomalayan and Afrotropical Regions, and its geographical origins are not known. There 
is one record for Spain (Gasull, 1974), perhaps the result of introduction by man. In Africa M. 
tuberculata is commonest in the eastern part (Fig. 6) and it is known from few localities in 
West Africa, The presence of shells in many localities in the Sahara desert shows that this snail 
has been widespread in North Africa, and isolated living populations occur in Chad, Algeria and 
probably also Morocco, M. tuberculata is practically absent from the Zaire basin where there 
are numerous endemic species belonging to the genus. 



82 



PROC. SIXTH EUROP. MALAC. CONGR. 



AFROTROPICAL GROUP 

The genera comprising this large assemblage can be divided according to their geographical 
range and the extent to which they have evolved species within Africa (Table 2). The most 
cosmopolitan genera, Septaria and Thiara, are represented by few species, which are widespread 
in the Indo-Pacific region. Secondly, there is a group of twelve widely distributed genera, each 
of which has some species endemic to Africa. Thirdly, a group of 28 genera can be regarded as 
strictly Afrotropical, although some species occur in the lower Nile, and some live on 
Madagascar and other islands in the Indian Ocean. 

Considered in terms of geographical range, the most widespread of the Afrotropical genera is 
Bulinus. B. truncatus is present in Iberia and the Mediterranean region, and extends eastwards 
into Iran (Fig. 7). At first sight this large range seems inconsistent with an Afrotropical nature. 
However, since B. truncatus has a tetraploid number of chromosomes its distribution can be 
regarded as a secondary expansion from the area occupied by the ancestral diploid group within 
Africa (Fig. 8). Indeed the only diploid Bulinus known to occur north of Ethiopia belong to the 
B. forskali and B. reticulatus species groups, which are not closely related to B. truncatus. B. 
reticulatus has an extensive range in south and eastern Africa (Fig. 9), and the closely related B. 
wrighti occurs in Arabia penetrating eastwards into Oman. 

Biomphalaria is also present in the eastern Mediterranean region and in South West Asia (Fig. 
10), but is less widespread than Bulinus. However, Biomphalaria is also present in South 

TABLE 2. Genera of freshwater gastropods living in Africa south of the Sahara (Afrotropical Region). 



Widely distributed genera represented by widespread 
species: 

Septaria 
Thiara 

Widely distributed genera with endennic species in 
Africa: 

Neritilia 

Neritina 

Bel I amy a 

Hydrobia 

Potamopyrgus 

Pila 

Assiminea s.l. 

Melanoides 

Lymnaea 

Gyraulus 

Biomphalaria 

Ferrissia 



Strictly Afrotropical genera (E— present in Egypt; 
M— present in Madagascar): 

Hydrobiidae 
Lobogenes 
Soapitia 
Tomichia 

Pilidae 
Afropomus 
Lanistes {E,M) 
Saulea 

Bithyniidae 

Gabbiella (E) 

Incertihydrobia 

Jubaia 

Congodoma 

Funduella 

Liminitesta 

Siérrala 

Assimineidae 
Eussoia 
Pseudogibbula 
Sep tar i el Una 
Valvatorbis 

Thiaridae 
Potad от a 
Cleopatra (E,M) 
Pseudocleopatra 
Potadomoides 
Pachymelania 

Planorbidae 

A f году rus (E,M) 

Ceratophallus 

Len torbis 

Segmentorbis (E,M) 

Bulinus (E,M) 

Ancylidae 
Burnupia 



BROWN 



83 



America and the Caribbean area, and the genus appears to be long established in the 
Neotropical Region. Surprisingly, these snails are absent from North West Africa although shells 
of extinct populations are found in numerous localities in the Sahara. Biomphalaria is absent 
from the coastal region of East Africa, perhaps because of an unfavourable high temperature, 
whereas low temperature is apparently a major factor restricting distribution in the south- 
western part of the continent. In Fig. 10 the range is shown to extend continuously from 
Kenya to Ethiopia, but in fact there is a significant gap of about 400 km between the closest 
localities for B. pfeifferi known in Kenya (Marsabit) and Ethiopia (Lake Margherita). However, 
given suitable bodies of water there can be little doubt that this snail would occur in thé 
intervening area. For some other taxa the isolation of the Ethiopian part of their range appears 
substantially greater, and this area is indicated separately in the maps (Figs. 13, 15, 17). 

Bellamys (Fig. 11) also extends down the Nile into lower Egypt but is practically absent 
from South West Asia. However, this genus is present also in southern Asia. Effective isolation 
between the African and the Asian parts of this range is reflected in the lack of any species 
which lives in both areas. Although Gabbiella (Fig. 12) is also present in the lower Nile, it 
appears to be primarily an Afrotropical group comprising about 30 species mostly restricted to 
central Africa (Mandahl-Barth, 1968). 

The Planorbidae provide many examples of taxa having extensive ranges but which are 
unknown north of the Sahara, including the Bulinus natalensis/tropicus complex (Fig. 8), the B. 
africanus group (Fig. 13), Gyraulus costulatus (Fig. 14) and Ceratophallus (of which many 
species were described originally as Anisus) (Fig. 15). 

Potadoma (Thiaridae) (Fig. 16) has a remarkable distribution pattern comprising 2 separate 
areas, one in the west and another in central Africa. Their habitat, streams flowing through 
forest, is occupied in Madagascar by the closely related genus Melanatria. 

There is one strictly Afrotropical genus of Ancylidae, Bumupia (Fig. 17), reported most 
frequently from eastern Africa though probably widespread also in the streams of central 
Africa. 

Many of the species living in tropical African freshwaters are absent from the southwestern 
part of the continent, which experiences a comparatively dry and cool climate. In the east, 
however, tropical species occur further south in a slender coastal zone termed the 'tropical 
corridor' which extends into the Natal province of South Africa. The general similarity in the 
southern limits for tropical species in this region (Figs. 10, 13, 14) appears to reflect the 
climatic transition between the tropical and the southern temperate climatic zones. Gyraulus 
Connolly! is one of the few freshwater molluscs characteristic of the southern temperate zone 
(Brown & Van Eeden, 1969). This snail is not known to extend north of the Drakensberg ridge 
in eastern Transvaal province, where its lower altitudinal limit is about 1,500 m. 

SPECIES DIVERSITY IN RELATION TO LATITUDE 

An analysis limited to genera of freshwater pulmonates provided Hubendick (1962) with no 
evidence for greater faunal diversity in the warm tropics, and he concluded that "neither the 
Ethiopian nor the Neotropical fauna shows any clear increase of diversity from high to low 
southern latitudes." However, recent advances in taxonomy indicate a marked increase in 
diversity towards the equator in the freshwater gastropod fauna in southern Africa (Fig. 18). 
Excluded from the present analysis are species endemic to lakes, the genus Tomichia which 
does not seem truly to belong to the freshwater fauna, and the Ancylidae because their 
taxonomy is so poorly known. 

There is a decline of over 75% from the number of species (65) known in the equatorial 
zone between 0° and 5° South and the total (14) known in the coastal zone of South Africa 
lying between 30° and 35° South. Inclusion of Tomichia and Ancylidae might considerably 
increase the number of species known in southern Cape Province, but almost certainly not to a 
level comparable with the totals for latitudinal zones north of 15°. In these zones major 
contributions to the fauna are made in eastern Zaire by Potadoma and Melanoides, in the lower 
Zaire river by endemic Hydrobiidae and Assimineidae, and in southeastern Zaire by a group of 
local species including the endemic hydrobiid genus Lobogenes. 



84 , PROC. SIXTH EUROP. MALAC. CONGR. 

LITERATURE CITED 

AY AD, N., 1956, Bilharziasis survey in British Somaliland, Eritrea, Ethiopia, ЗоглаМа, Sudan and Yemen. 

Bulletin of the World Health Organisation, 14: 1-117. 
BACCI, G 1951, Element] per una malacofauna dell'Abissinia e della Somalia. Annali del Museo Civico di 

Storia Naturale Giacomo Doria, Genova, 65: 1-144. 
BROWN, D. S., 1965, Freshwater gastropod Mollusca from Ethiopia. Bulletin of the British Museum (Natural 

History), Zoology, 1 2: 37-94. 
BROWN, D. S., 1967, Records of Planorbidae new for Ethiopia. Archiv für Molluskenkunde, 96: 181-185. 
BROWN, D. S., 1973, New species of freshwater Pulmonata from Ethiopia. Proceedings of the Malacological 

Society of London, 40: 369-379. 
BROWN, D. S., 1978, Freshwater molluscs. In: M. J. A. WERGER (ed.), Biogeography and ecology of 

southern Africa: 1153-1180. Junk, The Hague. 
BROWN, D. S., in press, African freshwater snails. Taylor & Francis, London. 
BROWN, D. S. & VAN EEDEN, J. A., 1969, The molluscan genus Gyraulus (Gastropoda: Planorbidae) in 

southern Africa. Zoological Journal of the Linnean Society of London, 48: 305-331. 
CROSSKEY, R. W. & WHITE, G. В., 1977. The Afrotropical region. A recommended term in zoogeography. 

Journal of Natural History, 1 1 : 541-544. 
FISCH ER-PIETTE, E., 1949, Mollusques terrestres et fluviátiles subfossiles récoltés par Th. Monod dans le 

Sahara occidental. Journal de Conchyliologie, 89: 231-239. 
FISCHER-PIETTE, E. & VUKADINOVIC, D., 1973, Sur les mollusques fluviátiles de Madagascar. 

Malacologia, 12: 339-377. 
GASULL, L., 1971, Fauna malacológica de las aguas continentales dulces y salobres del sudeste Ibérico. 

Boletín de la Sociedad de Historia Natural de Baleares, 16: 23-83. 
GASULL, L., 1974, Una interesante localidad con Melanoides tuberculata en la provincia àè Castellón de la 

Plana. Boletín de la Sociedad de Historia Natural de Baleares, 19: 148. 
HAGENMÜLLER, H„ 1884, Clausilie et valvées nouvelles du Nord de l'Afrique. Bulletins de la Société 

Malacologique de France, 1: 209-216. 
HUBENDICK, В., 1951, Recent Lymnaeidae. Kungliga Svenska Vetenskapsakademiens Handiingar, (4) 3(1): 

1-222. 
HUBENDICK, В., 1962, Aspects on the diversity of the freshwater fauna. Oikos, 13: 249-261. 
MANDAHL-BARTH, G., 1968, Revision of the African Bithyniidae (Gastropoda Prosobranchia). Revue de 

Zoologie et Botanique africaines, 78: 129-160. 
MARTINE, F., 1968, Pleistocene mollusks from Sudanese Nubia. In: WENDORF, F. (ed.). The prehistory of 

Nubia, 1: 55-79. Southern Methodist University Press, Dallas. 
PILSBRY, H. A. & BEQUAERT, J., 1927, The aquatic mollusks of the Belgian Congo. With a geographical 

and ecological account of Congo nnalacology. Bulletin of the American Museum of Natural History, 53: 

69-602. 
PRINSLOO, J. F. & VAN EEDEN, J. A., 1973, The distribution of the freshwater molluscs of Lesotho with 

particular reference to the intermediate host of Fasciola hepática. Wetenskaplike Bydraes van die P.U. vir 

С. H. О., В, Natuurwetenskappe, 57: 1-13. 
SPARKS, В. W. & GROVE, A. T., 1961, Some Quaternary fossil non-marine Mollusca from the central 

Sahara. Journal of the Linnean Society of London, Zoology, 44: 355-364. 
TCHERNOV, E., 1971, Freshwater molluscs of the Sinai peninsula. Israel Journal of Zoology, 20: 209-221. 
TCHERNOV, E., 1975, The early Pleistocene molluscs of 'Erg el-Ahmar. Israel Academy of Sciences and 

Humanities, Jerusalem, 36 p. 
WRIGHT, С A., 1971, Bulinus on Aldabra and the subfamily Bulininae in the Indian Ocean area. 

Philosophical Transactions of the Royal Society, London, B, 260: 299-313. 
WRIGHT, W. H., 1973, Geographical distribution of schistosomes and their intermediate hosts. In: N. 

ANSARI (ed.). Epidemiology and control of schistosomiasis (bilharziasis): 32-247. World Health Organiza- 
tion. 
ZILCH, A. & JAECKEL, S. G. A., 1962, Mollusken. In: BROHMER, P., et al., eds.. Die Tierwelt 

Mitteleuropas, 2, 1, Ergänzung: 1-294. Quelle & Meyer, Leipzig. 



NOTE ADDED IN PROOF. Lymnaea glabra (p. 81 ) is reported to occur in the coastal region of northern Spain 
by SANCHEZ, J. A., 1965, Boletín de la Real Sociedad Española de Historia Natural, Secc. Biológica, 63: 9-14. 



BROWN 



85 




FIG. 1. The distribution of Theodoxus in Africa, southern Europe and South West Asia. An isolated locality 
is indicated for 'recent' shells from the 2nd Nile Cataract (Martine, 1968). Unconfirmed reports for Ethiopia 
(cited by Bacci, 1951) are omitted. Theodoxus s.s. is present in Europe and North West Africa, whereas the 
subgenus Neritaea occurs in Egypt and South West Asia. In this and subsequent maps no attempt is made to 
show distribution on all Mediterranean islands. 



86 



PROC. SIXTH EUROP. MALAC. CONGR. 




FIG. 2. The distribution of Valvata in Africa, southern Europe and South West Asia. This genus appears to 
be absent from the southern part of Iberia. Isolated localities are indicated for living populations in the Sinai 
peninsula, and for shells in Africa. 



BROWN 



87 




FIG. 3. The distribution of Lymnaea truncatula in Africa, southern Europe and South West Asia. Isolated 
localities are indicated for living populations and 'subfossil' shells. 



88 



PROC. SIXTH EUROP. MALAC. CONGR. 




FIG. 4. The distribution of Planorbis planorbis in Africa, southern Europe and South West Asia. Isolated 
localities are indicated for living populations and 'subfossil' shells. 



BROWN 



89 




FIG. 5. The distribution of Ancylus in Africa, southern Europe and South West Arabia. Isolated localities are 
indicated, including IVIadeira and Teneriffe for living populations or recently living specimens. There are also 
records for the Cape Verde islands. A. fluviatilis appears to be present almost throughout this range. 



90 



PROC. SIXTH EUROP. MALAC. CONGR. 




FIG. 6. The distribution of Melanoides tuberculata in Africa, southern Europe and South West Asia. The 
range extends eastwards through southern Asia to China, the Pacific islands and Australia. Isolated African 
localities are indicated for living populations and 'subfossil' shells. This snail is connparatively uncommon in 
West Africa. 



BROWN 



91 




FIG. 7. The distribution of Bulinus truncatus and other tetraploid populations of Bulinus (including records 
for 'Isidora contorta'). Further cytological observations are necessary to establish глоге precisely the range in 
central Africa. Isolated localities are indicated for living populations and 'subfossil' shells presumed to belong 
to tetraploid snails. 



92 



PROC. SIXTH EUROP. MALAC. CONGR. 




FIG. 8. The distribution of the diploid Bulinus natalensis/tropicus complex. Further cytological observations 
are necessary to establish more precisely the range in central Africa. Even so, there appears to be little 
overlap with the range of the related tetraploid populations (compare Fig. 7). 



BROWN 



93 




FIG. 9. The distribution of the Bu/inus reticulatus species group. These snails occur in snnall seasonal 
waterbodies and are distributed discontinuously even within the shaded areas. B. reticulatus is present in 
Africa and B. wrighti in Arabia. 



94 



PROC. SIXTH EUROP. MALAC. CONGR. 




CB.H.2IM-Wt.9a4».|>).20l7.IOOO. 4/t3 



FIG. 10. The distribution of Biomphalaria in Africa and Arabia. The genus is present also in the Neotropical 
region. Isolated localities are indicated for living populations and 'subfossil' shells. The locality on the Libyan 



coast (W. H. Wright, 1973) requires confirmation. 



BROWN 



95 



^^^^ 



■^ 







C>.H.2IM.Wt.384».D<l.2OI7-l00O. 4/63 



FIG. 11. The distribution of Bellamya in Africa. Isolated localities are indicated for living populations and 
'subfossil' shells. Confirmation is required of records for Madagascar (Fischer-Piette & Vukadinovic, 1973), 
Yemen (Ayad, 1956) and in the Pleistocene fauna of the Jordan Valley (Tchernov, 1975). 



96 



PROC. SIXTH EUROP. MALAC. CONGR. 




Ce.H.2eM-WL38iW-Dd.30l7. 1000. 4/63 



FIG. 12. The distribution of Gabbiella and related genera (Bithyniidae). Most species are restricted to central 
Africa (Mandahl-Barth, 1968). However, G. adspersa occurs in isolated localities in eastern Ethiopia, and G. 
senaariensis lives in Egypt. The isolated locality shown in Ivory Coast represents 'Bithynia' tournieri Binder 
(1955). 



BROWN 



97 




CB.H.2B«4-WL3&4?9.Dd.2OI7.l00D. 4/63 



FIG. 13. The distribution of the Bulinus africanas group. Isolated localities are indicated for living 
populations and 'subfossil' shells. There is no evidence that this group has penetrated further northwards, 
either in the Sahara or down the Nile. The area indicated in Madagascar represents B. obtusispira which 
shows some relationship with the B. africanus group (C. A. Wright, 1971). 



98 



PROC. SIXTH EUROP. MALAC. CONGR. 




CB.H.2B(4-Wt.384n.Dd.2OI7-10OO- 4№3 



FIG. 14. The distribution of Gyraulus costulatus. Isolated localities are indicated in the Sahara for 'subfossil' 
shells. The genus is represented in Egypt by a different species, G. ehrenbergi, which appears to be related to 
members of this genus living in South West Asia. Gyraulus is unknown in Madagascar, though present in the 
Mascarene islands. 



BROWN 



99 



^^^ ^ 







C>.H.2l»t-Wt.3«4n-Dd.2OI7.l000- 1КЗ 



FIG. 15. The distribution of Ceratophallus natalensis (recorded in earlier literature as 'Anisus"). Isolated 
localities are shown for Lake Chad and in Zaire. Most other members of this genus are confined to lakes in 
East Africa. 



100 



PROC. SIXTH EUROP. MALAC. CONGR. 




CB.H.2e«4.Wt.38499-Dd.20l7. 1000- 4/6Э 



FIG. 16. The distribution of Potadoma and Melanatria. Potadoma lives in streams in two forested areas, one 
between Liberia and Lower Zaire and the other comprising part of northeastern Zaire and the adjacent 
Central African Republic. Melanatria is endemic to Madagascar, and related genera occur in southern Asia and 
on some Indonesian islands. 



BROWN 



101 



^^^^^ ^XJ- 



■^o ^ 






CB.H.2eM-Wt.3e499-Od.aOI7.IOOO- 4/«3 



FIG. 17. The distribution of Burnupia. These ancylids are recorded most frequently from streams in the 
highlands of Ethiopia and in the temperate region of South Africa. Isolated localities for 'subfossil' shells are 
situated in the now semi-arid areas of Botswana and Namibia. Probably Burnupia is more widespread m 
central Africa than available records indicate. 



102 



PROC. SIXTH EUROP. MALAC. CONGR. 



LATITUDE IN 
DEGREES SOUTH 

EQUATOR 



NO» SPECIES 
15 30 4 5 



60 



KINSHASA 



LUANDA 



10 



MOCAMBIQUE 15 



BEIRA 



MAPUTO 



DURBAN 



:o 



25 



30 



CAPE TOWN 



FIG. 18. Numbers of species of freshwater gastropods known in Africa south of the Equator, in latitudinal 
zones of 5 degrees. Excluded are species endemic to lakes, the genus Tomichia and the Ancylidae. Based on 
Brown (1978 and in press). 



MALACOLOGIA, 1979, 18: 103-105 

PROC. SIXTH EUROP. MALAC. CONGR. 

SURVEY OF NON-MARINE MOLLUSCS OF SOUTH-EASTERN AUSTRALIA 

Brian J. Smith 
Invertebrate Department, National Museum of Victoria, Melbourne, Victoria, 3000, Australia 

ABSTRACT 

A survey is undertaken of the non-marine molluscs of south-eastern Australia in 
connection with future land use in this densely populated area with a concentration of 
heavy industry. The area harbours ca. 220 species in 39 families with a very high 
proportion of endemism. 

INTRODUCTION 

It has long been recognised that the flora and fauna of Australia shows distinct regional ity 
(McMichael & Iredale, 1959) with a high incidence of regional endernism. The non-marine 
mollusc fauna can be divided into a number of regional faunal groups, each with its own 
characteristics and each dominated by one generic or family grouping. This dominance, both in 
terms of numbers of species and of individuals, takes the form of a radiation within one group. 

The Euronotian Region, containing the Bassian sub-region, occupies the south-eastern part of 
Australia and consists of Victoria and Tasmania including the Bass Strait Islands and the 
southern parts of South Australia and New South Wales. This area is less than 20% of 
Australia's land surface but contains over 80% of the human population including the Federal 
and four State capitals and much of the heavy industry. The region is therefore the most 
man-modified of any of the faunal regions of Australia, with little completely natural bush or 
unchanged aquatic habitat. However, much of the native mollusc fauna remains, with 
remarkably little change, and new land use studies are producing demand-pressures for detailed 
taxonomic and distributional data of this fauna. 

The present survey is being undertaken to acquire systematic distributional data of the 
non-marine mollusc fauna of south-eastern Australia. The area under study is bounded by the 
33° South line of latitude between the Pacific Ocean and Spencer Gulf, South Australia. The 
area is divided into major grid areas of 1.5 degrees by 1 degree corresponding to the 1:250,000 
standard map sheets. These areas are divided into 54 ten minute grid squares, there being over 
2,500 grid squares in the survey area. It is intended to eventually produce an atlas of dot maps 
of the fauna based on this system. 

Running concurrently with the distributional work is a series of taxonomic revisionary 
studies of various problem groups within the fauna based on the collections made for the survey. 
This is based on the early descriptive work of Iredale (1933 et seq.), Gabriel (1930) and many 
others. 

HABITAT TYPES 

The area is cool temperate to warm temperate, extending from 44 S to 33 S. Terrestrial 
habitats vary from the hot dry mallee regions in the north and west to the true alpine regions 
of the Great Dividing Range in Victoria and New South Wales and the Central Plateau in 
Tasmania. The southern slopes of the Great Divide and the western regions of Tasmania have 
large areas of temperate rain-forest with deep fern gullies and extensive litter and fungal growth. 
Large areas of dry sclerophyll forest occur on the more open slopes where the rainfall is lower. 
Coastal heathland comprises another major terrestrial habitat with extensive salt-marsh areas in 
sheltered embayments. Extensive land clearing has been carried out in all these habitats with 
the land being sown down with introduced pasture grasses or with monoculture of pines, wheat 
or other crops. 

(103) 



104 PROC. SIXTH EUROP. MALAC. CONGR. 

Many major rivers including the Murray, rise in the rnountain areas of the region. Groups of 
isolated freshwater lakes are found in south-western Tasmania while a series of saline lakes 
occurs in western Victoria. However, most non-marine aquatic habitats are subject to regular 
severe drought cycles resulting in a consequent depauperate fauna. The aquatic habitats too 
have been extensively modified with storage and hydroelectric impoundments being constructed 
on many of the major rivers. Artificial connection of previously separate river systems has also 
occurred. Large areas in the northern part of the region are under irrigation with a consequent 
change in flow and salinity regimes. 

FAUNA 

The non-marine mollusc fauna of south-eastern Australia consists of about 220 species in 39 
families (see Appendix). It is intended to produce a field guide to this fauna next year. Brief 
notes are given below to some of the more interesting aspects of the fauna. 

About 30 introduced species have been recorded. Most of these originate in Europe and are 
classed as serious pests, and include 9 species of Helicidae and 9 species of slugs (Altena & 
Smith, 1975). A recent aquatic introduction is Lymnaea columella, an occurrence causing a 
great deal of concern because of its implication with sheep liver fluke. While many of the 
introduced species show wide distribution throughout the region, most of the native species 
have restricted distribution limits. 

Tasmania has several unique faunal features due to its long period of isolation, though it is 
part of the south-eastern faunal region due to the intermittent Bass Strait land bridge. 
Transition zones occur between this region and the two adjacent regions, the central region and 
the east coast region. A high proportion of the fauna (over 60%) is endemic to the region with 
several species having a very restricted distribution. 

The terrestrial fauna is dominated by the endodontoid snails. These are small to minute 
snails, most of which are 3 mm or less in diameter, belonging to the families Charopidae and 
Punctidae. The taxonomic status of many of the species in these families is unsure but it is 
estimated that the fauna contains about 54 species of charopids and 9 species of punctids. Most 
of these are endemic to the region with many of the charopids having very restricted 
distributions, being confined to one range of mountains (Smith, 1977) or area of forest. 
Contrasting with this dominance of the endodontoids are two families of snails, the Camaenidae 
and the Pupillidae, which, while having a widespread and even dominant role in the fauna of 
Australia as a whole, have a diminished role in this region. Nine or ten species of camaenids are 
described for the region but all except 1 or 2 have close affinities with the adjacent regions and 
are restricted to the northern part. No camaenids are found on Tasmania. The pupillids show a 
similar reduction in species numbers in a southerly direction, with only 1 or 2 of the 11 species 
known from the region found in Tasmania. 

Another important element is the group of carnivorous snails belonging to the family 
Rhytididae. Thirteen species of this family, or almost half the Australian fauna, occur in this 
region, almost all being endemic including the endemic genus Victaphanta (Smith & Kershaw, 
1971). The family Caryodidae contains the largest species of the region including two genera, 
Caryodes and Anoglypta, endemic to Tasmania. The genus Bothriembryon, belonging to the 
family Orthalicidae, shows a wide species radiation in the south-western Australian faunal region. 
However, two species occur in the southern and western regions of the south-eastern region 
including one species endemic to Tasmania. The final element of special interest in the 
terrestrial fauna is the group of native slugs belonging to the Cystopeltidae. These are common 
throughout the forest regions of Tasmania, Victoria and southern New South Wales and the 
family extends up as far as southern Queensland. 

The aquatic non-marine fauna includes some supra-littoral marine and salt marsh species 
which can be found associated with terrestrial flora and fauna. It also includes estuarine and 
hyper-saline species as well as freshwater species inhabiting rivers, creeks, swamps and dams. 
The major family of aquatic snails is the Hydrobiidae, species of which are found in estuarine 
creeks, in hyper-saline lakes and in high alpine acid bogs. Of particular interest is the genus 
Coxiella, large populations of which are found in the salt lakes of western Victoria and the 
dune salt lakes of the Victorian, South Australian and Tasmanian coasts. Two species of the 



SMITH 



105 



aberrant hydrobiid genus Glacidorbis are found in acidic alpine bogs of Victoria and Tasmania 
(Meier-Brook & Smith, 1975). 

Two operculate families, the Viviparidae and the Thiaridae, have species found only in the 
River Murray and its tributaries. The family Planorbidae is the most widely distributed aquatic 
group with respect to total area covered. The high-spired forms belonging to the genera Bulinus, 
Physastra and Glyptophysa are to be found in most freshwater habitats. The planispiraí 
planorbids are less common but still make up a significant part of the fauna. The final group 
worthy of mention are the freshwater mussels belonging to the family Hyriidae. Ten species 
occur in the region including a few endemic species with very restricted ranges. 

ACKNOWLEDGEMENTS 

I would like to thank Mr. R. C. Kershaw of Tasmania for his assistance with this work. 
Thanks are also due to the Science and Industry Endowment Fund, to B.H.P. Pty. Ltd., to 
Comaico Australia, and the Council of the National Museum of Victoria for providing funds to 
attend the congress. 

LITERATURE CITED 

ALTENA, С. О. VAN R. & SMITH, В. J., 1975. Notes on introduced slugs of the families Limacidae and 

Milacidae in Australia, with two new records. Journal of the Malacological Society of Australia, 3: 63-80. 
GABRIEL, С J., 1930, Catalogue of the land shells of Victoria. Proceedings of the Royal Society of 

Victoria, 43: 62-88. 
IREDALE, T., 1933, Systematic notes on Australian land shells. Records of the Australian Museum, 19: 

37-59. 
MCMICHAEL, D. F, & IREDALE, T., 1959, The land and freshwater Mollusca of Australia In: KEAST, A., 

CROCKER, R. L. & CHRISTIAN, С S., Biogeography and Ecology in Australia: 224-245. W. Junk, 

Publishers, The Hague. 
MEIER-BROOK, C. & SMITH, B. J., 1975, Glacidorbis Iredale 1943, a genus of freshwater prosobranchs with 

a Tasmanian-Southeast Australian-South Andean distribution. Archiv für Molluskenkunde, 106: 191-198. 
SMITH, В. J., 1977, The non-marine mollusc fauna of the Otway region of Victoria. Proceedings of the 

Royal Society of Victoria, 89: 147-155. 
SMITH, B. J. & KERSHAW, R. C, 1971, Tasmanien snail referred to the genus Victaphanta (Stylommato- 

phora : Paryphantidae). Memoirs of the National Museum of Victoria, 33: 111-1 14. 

APPENDIX 



List of families of non-marine molluscs in south-eastern Australia, with approximate number of 
species in each family (I = contains introduced species; E = contains species endemic to the region). 



Viviparidae 


- 1 


Hydrobiidae 


-18(E) 


Truncatellidae 


- 2 


Bithyniidae 


- 1 


Assimineidae 


- 2 


Thiaridae 


- 1 


Ellobiidae 


- 8 


Amphibolidae 


- 2 


Physidae 


- 1 


Lymnaeidae 


- 4(1) 


Planorbidae 


-11 (i)(E) 


Ancylidae 


- 2(E) 


Onchidiidae 


- 5 


Succineidae 


- 2 


Athoracophoridae 


- 1 


Achatinellidae 


- 1 


Cionellidae 


- 1 (1) 


Pupillidae 


-11 (E) 


Valloniidae 


- 1 (1) 


Ferrussaciidae 


- 1 (1) 



Rhytididae 


-13(E) 


Caryodidae 


- 4(E) 


Orthalicidae 


- 2(E) 


Charopidae 


-54(E) 


Punctidae 


- 9(E) 


Arionidae 


- 3(1) 


Zonitidae 


- 6(1) 


Limacidae 


- 5(1) 


Milacidae 


- 1 (!) 


Cystopeltidae 


- 2(E) 


Euconulidae 


- 3(1) 


Helicarionidae 


- 6(E) 


Testacellidae 


- 1 (1) 


Camaenidae 


- 9(E) 


Bradybaenidae 


- 1 (1) 


Helicidae 


- 9(1) 


Hyriidae 


-10(E) 


Corbiculidae 


- 1 


Sphaeriidae 


- 3 



MALACOLOGIA, 1979, 18: 107-114 

PROC. SIXTH EUROP. MALAC. CONGR. 

TAXONOMICAL, ECOLOGICAL AND ZOOGEOGRAPHICAL RESEARCH ON 
BULIMULIDAE (GASTROPODA, PULMONATA) 

Abraham S. H. Breure 

Department of Systematics and Evolutionary Biology of the University, 
c/o Rijksmuseum van Natuur/ijke Historie, Leiden, Netherlands 

ABSTRACT 

An introduction is given to the land snail family Bulimulidae and the purposes of a 
systematic research project are explained. A phylogenetic system of the family will be 
constructed with the aid of the theory of Hennig. Some preliminary results are given, viz. 
revisions of Bulimulus Leach, 1814 sensu Zilch (1960) and Bothriembryon Pilsbry, 1894. 
The most likely relationships of the latter genus are indicated. Furthermore, some 
ecological data are presented and the theoretical background of the zoogeographical 
analysis is indicated. 



INTRODUCTION 

The Bulimulidae form a relatively large family, mainly confined to the Neotropical Region. 
At present the family includes 144 genera and subgenera. The number of specific and 
subspecific names available is estimated at about 3,000. It is supposed that a critical revision 
might reduce these numbers to about 100 and 1,000 respectively. 

The family is subdivided into five subfamilies, viz. Bulimulinae (the largest subfamily with 
ca. 90 genera and subgenera; mainly in South America, but also found in Central America, the 
West Indies and SW Australia), Amphibuliminae, Odontostominae (both confined to South 
America and the West Indies), Orthalicinae (South and Central America, West Indies) and 
Placostylinae (Melanesia and New Zealand). 

The aim of the present research project is to carry out a revision of the (sub)genera of the 
Bulimulinae and to establish the phylogenetic relationships of these genera and of the five 
subfamilies. The resulting phylogeny and the ecological observations made during field research 
will form the basis for the zoogeographical analysis. 

TAXONOMY 

When constructing a phylogenetic system of this family the theory of Hennig will be used. 
This theory is characterized by the use of monophyletic groups, which are "groups of species 
that arose by species cleavage, ultimately from a common stem species that is the stem species 
only of those species included in the group in question" (Hennig, 1966). Within such a 
monophyletic group one should try to find out which characters belong to one and the same 
phylogenetic transformation series, i.e. which are homologous, and whether they are plesio- 
morphous ("primitive") or apomorphous ("derived"). Only the joint possession of apomorphous 
characters (synapomorphy) corroborates the assumption that the species in question belong to 
the same monophyletic group. As the cleavage of a species ultimately leads to the formation of 
(theoretically not more than) two daughter-species, which each form part of a monophyletic 
group, it follows that each monophyletic group will have one sister-group to which it is more 
closely related. 

The present classification of the Bulimulidae is entirely based on morphological characters of 
the shell. The most important of these characters is the sculpture of the protoconch. Although 
this is certainly a very helpful criterion for classification it does not always lead to an 

(107) 



108 



PROC. SIXTH EUROP. MALAC. CONGR. 




FIG. 1. Protoconch of Bostryx ploegerorum Breure. 

FIG. 2. Protoconch of Naesiotus wolfi (Reibisch). Scales 0.5 mm. 



unambiguous identification, which is shown, e.g., by the case of Naesiotus (Naesiotellus) 
latecolumellaris Weyrauch, 1967. This species, for which the monotypical subgenus Naesiotellus 
Weyrauch, 1967, was created, belongs instead to Bostryx Troschel, 1847; Weyrauch has 
probably been misled by the weak axial riblets of the protoconch sometimes to be found 
among Bostryx species. These riblets, however, are never as strong and regular as those of 
Naesiotus species (Figs. 1-2). 

The following characters will now be used as a base for the phylogeny: (1) the morphology 
of the genitalia; (2) the internal structure of the genitalia, especially of the phallus complex; (3) 
the morphology of the radula and mandíbula; (4) the structure of the protoconch; (5) the 
morphology of the palliai organs; (6) the morphology of the muscle system. 

At present the results have not yet led to the recognition of a complete phylogenetic 
transformation series for any of the above-mentioned characters. But such characters as the 
morphology of the radula and the internal structure of the genitalia show already a certain 
pattern in which parts of a transformation series may be recognized. 

Two examples of the preliminary results will now be given. 

A. The genus Bulimulus Leach, 1814 sensu Zilch (1960) has been revised as follows: the 
nominate subgenus is widespread in the Neotropics and is characterized e.g. by (1) the structure 
of the protoconch (axial wrinkles, often anastomosing on lower part of whorl), (2) the 
morphology of the phallus complex (especially by the club-shaped penis) and (3) the internal 
structure of the phallus complex (penis with parallel tubes and epiphallus penetrating into penis; 
Fig. 3). Rhinus Albers, 1850, is retained as a subgenus of Bulimulus, differing mainly by (1) the 
structure of the protoconch (zigzag wrinkles) and (2) the presence of spiral series of epidermal 
hairs on the shell. The other taxa grouped by Zilch under Bulimulus are now treated as separate 
entities: Rabdotus Albers, 1850, is given generic status on account of, e.g., (1) the structure of 
the protoconch (straight axial riblets) and (2) the internal structure of the phallus complex 
(epiphallus not penetrating into penis; Fig. 4). Leptobyrsus Fischer & Crosse, 1875 (with its 
synonym Puritania Jacobson, 1958) and Plicolumna Cooper, 1895, are considered subgenera of 
Rabdotus. Itaborahia Maury, 1935, is also given generic status. The species of this genus, which 
are known from Miocene deposits in Brazil, also have a pattern of axial riblets on the 
protoconch (Breure, unpublished). Dentaxis Pilsbry, 1902, is transferred to Bostryx Troschel, 
1847, because of the structure of the protoconch and of the anatomy. The anatomy of species 



BREURE 



109 




FIG.3. Schematic reconstruction of the phallus complex in Bulimulus (B.) guadalupensis (Bruguière) 

FIG. 4. Do., Rabdotus (R.) mooreanus (W. G. Binney). EP = epiphallus; FL = flagellum; PD = distal part ot 

penis; PP = proximal part of penis. 



110 



PROC. SIXTH EUROP. MALAC. CONGR. 




FIG. 5. Genitalia of Bothriembryon (B.) indutus (Menke). Scale 1 cm. 

FIG. 6. Genitalia of Bothriembryon (Tasmanembryon) gunnii (Sowerby). Scale 1 cm. 



of Pseudoxychona Pilsbry, 1930, demonstrates that this taxon has to be placed near Leiostracus 
Albers, 1850. Finally, all other subgenera mentioned by Zilch are treated as Naesiotus Albers, 
1850 sensu lato (see Table 1). 

B. The taxonomy of Bothriembryon Pilsbry, 1894, has been revised considerably. Nearly all 
subgenera created by Iredale (1933, 1939) could be synonymized with the nominate subgenus 
on account of the anatomy of their type species; only Tasmanembryon Iredale, 1933, proved to 
be different, viz. by (1) having the spermathecal duct reduced in length (Figs. 5-6) and (2) the 
different structure of the protoconch. Most probably the sister-group of Bothriembryon is 
Plectostylus Beck, 1837, which is found in Chile. The synapomorphic characters of these genera 
are (1) the presence of a single type of glandular tissue in the penis (Figs. 7-8); (2) the absence 
of a penis sheath; (3) a certain type of palliai organs, and (4) a certain type of radula (Figs. 
9-12). This will be fully worked out in the final revision. Related genera are Scuta/us Albers, 
1850, and "Peronaeus (Lissoacme)" from Argentina. 



BREURE 



111 



TABLE 1. Classification of Bulimulus Leach, 1814. 



Zilch, 1960 



Bulimulus (Bulimulus) 
(Rhinus) 
(Den tax is) 
(PItaborahia) 
(Rabdotus) 
(Puritania) 
(Leptobyrsus) 
(Plicolumna) 
(Pseudoxychona) 
(Protoglyptus) 
(Maranhoniellus) 
(Naesiotus) 
(Raphiellus) 
(Granucis) 
(Nuciscus) 
(Reel asta) 
(Adenodia) 
(Stemmodiscus) 
(Olinodia) 
(Saeronia) 
(Ochsneria) 
(Granitza) 
(Granella) 
(Pleuropyrgus) 
(Pelecostoma) 



Breure, 1977 



Bulimulus (Bulimulus) 

B. (Rhinus) 

Botryx 

Itaborahia 

Rabdotus (Rabdotus) 

R. (Leptobyrsus) 

R. (Plicolumna) 

Leiostracus (Pseudoxychona) ? 



Naesiotus s.l. 



ECOLOGY 

Until now the ecology of the Bulimulidae was poorly known. Field research has led to the 
observation of the following generalized habitats: (1) species which are ground-dwellers and 
which are living off detritus found among leaf litter, etc.; (2) do., but only under or in the 
immediate vicinity of (large) stones; (3) species living on rock-faces, where they probably feed 
on mosses and algae; (4) species living on (low) shrubs; (5) species living Ion trees. As a rule 
species (of a certain genus) have been found only in one of these generalized habitats. 

ZOOGEOGRAPHY 

When the phylogenetic relationships have been worked out the analysis of the zoogeographical 
pattern of the Bulimulidae may be undertaken. At this stage of the research I only want to 
point at the theoretical background. 

There are several theories to explain the intra- and intercontinental distribution. The most 
stimulating one is the theory worked out by Croizat; his concept of biogeography is one of a 
dynamic process in time and space, in which the idea of vicariant species (viz., closely related 
species which are geographically isolated) plays an important role. When plotting the distribu- 
tion of a monophyletic group (which will include several vicariant species) one may draw a 
"track" which will connect the disjunct distribution areas. A number of congruent tracks will 
form a generalized track that estimates an ancestral biota that, because of changing geography, 
has become subdivided into descendant biotas. 



ACKNOWLEDGEMENTS 

This research is being supported by grants from the Foundation for the Advancement of 
Tropical Research (WOTRO), for which I am most grateful. Furthermore I am very much 
obliged to Prof. J. T. Wiebes, head of the Department of Systematics and Evolutionary Biology, 
for his continuous and stimulating interest. 



112 



PROC. SIXTH EUROP. MALAC. CONGR. 







\ 




FIG. 7. Schematic reconstruction of the phallus connplex in Bothriembryon (BJ indutus (Menke). 
FIG. 8. Do., Plectostylus peruvianas (Bruguière). 



BREURE 



113 




FIG. 9. Lateral teeth in Bothriembryon (B.) melo (Quoy & Gaimard). Scale 25мпп. 

FIG. 10. Lateral teeth in Bothriembryon (Tasmanembryon) gunnii (Sowerby). Same scale. 

FIG. 11. Lateral teeth in Plectostylus peruvianas (Bruguière). Same scale. 

FIG. 12. Lateral teeth in "Peronaeus (Lissoacme)" aguirrei (Doering). Same scale. 



LITERATURE CITED 



HEIMNIG, W., 1966, Phylogenetic systematics. University of Illinois Press, Urbana, 263 p. 

IREDALE, T., 1933, Systematic notes on Australian land shells. Records of ttie Australian Museum, 19: 

37-59. 
IREDALE, T., 1939, A review of the land Mollusca of western Australia. Journal of the Royal Society of 

Western Australia, 25: 1-88. 
ZILCH, A., 1959-1960, Gastropoda, Euthyneura. In: SCHINDEWOLF, 0. H., ed., Handbuch der Palào- 

zoologie, 6(2): 1-834. Borntraeger, Berlin (part quoted: 1960). 



114 PROC. SIXTH EUROP. MALAC. CONGR. 

RESUMEN 

Investigaciones taxonómicas, ecológicas y zoogeográficas 
sobre Bulimulidae (Gastropoda, Pulmonata) 

Se introduce la familia de caracoles terrestres Bulimulidae indicando los objetos de las 
investigaciones. Se construirá una sistema filogenética de la familia, usando la teoría de 
Hennig. Se presenta algunos resultados provisorios, o sea revisiones de Bulimulus Leach, 
1814 sensu Zilch y Bothriembryon Pilsbry, 1894. Las relaciones más probables del liltimo 
género están indicadas. Además se presenta algunos datos ecológicos y se indica el fondo 
teorético del análisis zoogeográfico. 



MALACOLOGIA, 1979, 18: 115-122 

PROC. SIXTH EUROP. MALAC. CONGR. 

ANATOMY AND TAXONOMY OF PROTOGLYPTUS QUITENSIS (PFEIFFER) 
(GASTROPODA, PULMONATA, BULIMULIDAE) 

J. J. Parodiz 
Carnegie Museum of Natural History, Pittsburgh, Pa., U.S.A. 

ABSTRACT 

The differences between Naesiotus Albers, 1850, and Protoglyptus Pilsbry, 1897, are 
given, based on characters of the shell and the anatonny. Further study is still needed to 
delimit these genera, both morphologically and geographically. After diagnosis of the 3 
subgenera of Protoglyptus, the synonymy and a redescription of Protoglyptus (Rimatula) 
quitensis (Pfeiffer) are given. The radula, maxilla and genitalia of this species are figured. 
An examination of 1,700 specimens from different localities along the interandine plateau 
of Ecuador proved that recognition of subspecies is without taxonomical importance. 

The species originally described as Bui ¡mus quitensis Pfeiffer, 1847, was subsequently placed 
in different genera, or subgenera, of Bulimulus: Scutalus by Martens, 1855; Thaumastus by 
Cousin, 1887; Lissoacme by Pilsbry, first in 1835, and Scutalus in 1897. More recently (1940), 
attending to the embryonic sculpture, Rehder included it in Naesiotus; on this occasion Rehder 
also described several subspecies within its distributional area in Ecuador. This paper discusses 
the genitalia, radula and conchological characteristics of B. quitensis, on account of which it is 
now placed in the genus Protoglyptus. 

Protoglyptus and Naesiotus have similar protoconch structures, consisting of regular and 
well-defined axial riblets, the spaces in between crowded with very fine spiral incisions in 
various degrees of development, sometimes more conspicuous in Naesiotus than in Protoglyptus. 
Such embryonic characteristics have important taxonomic value in Bulimulidae. Attending to 
these features only, it is very difficult to separate not just between the two genera, but also 
with allied groups belonging to the same ancestral stock, as Neopetraeus and Rabdotus. Similar 
difficulty is found in grouping species with smooth protoconchs as in Bostryx and Peronaeus. 

To begin with the shell, Naesiotus has, generally, the surface spirally striated or strongly 
rugose; in many species the columella is twisted inside, with callosities or folds that even may 
develop into well formed teeth, and the last whorl is in many cases somewhat angulate. Such 
features are not found in Protoglyptus. Moreover, the features indicated for Naesiotus are 
shown conspicuously in species of the Galapagos Islands where the genus is endemic. Dall 
(1920) proposed a division for the genus into sections: Granucis, Nuciscus, Reclasta, Adenoida, 
Stemmodiscus, Olinodia, Saeronia, Granitza, Granella. These sections were recognized by Thiele 
(1930), and Zilch (1960) included them as subgenera of Bulimulus. The shell differences among 
the types of such subgenera are considerable in relation to the type of Naesiotus s.s., N. nux 
Broderip. Some of the species, such as Naesiotus (Nuciscus) tanneri Dall, could be easily 
confused with a Neopetraeus. In the genus Protoglyptus on the other hand, shell modification is 
less important, and it appears to be a more natural group, 

MAXILLA. In Protoglyptus quitensis it is characteristic of the genus. It is as strong as in 
Neopetraeus and Scutalus but without a large central plate; the central plates are narrower and 
closer together. The maxilla is 1 mm long and 0.25 mm wide, with ribs or plates cemented on 
to the upper portion (Fig. 4). 

RADULA. Also typical of Protoglyptus, see Figs. 1-3. It has a blunt spine at the top of the 
rachidian tooth, while in Naesiotus (Fig. 5-7) the teeth resemble more those in Neopetraeus. P. 
quitensis has the central cusp shorter, without the additional cusps of Naesiotus, and the 
marginal teeth are not serrated. 

(115) 



116 



PROC. SIXTH EUROP. MALAC. CONGR. 







FIG. 1-4. Protoglyptus quitensis, radula: (1) rachidian, (2) lateral, (3) marginal; (4) maxilla (ca. 40X). 
FIG. 5-7. Naesiotus nux (after Dall), radula: (5) rachidian; (6) lateral; (7) marginal. 



EXTERNAL BUCCAL ORGANS. In Protoglyptus these are of intermediate type with that 
of Scuta/us, with "lips" rounded at the base, curved at the tips. In this it differs from other 
bulimulids. 

GENITALIA. The differences in the genital systems of Protoglyptus and Naesiotus have 
generic significance. In Protoglyptus (Fig. 8) the ovotestis or hermaphroditic gland, is more or 
less spirally enrolled as in Bulimulus and Scutalus, but not racemose as in Neopetraeus. The 
albumen gland, although large, does not show substantial differences as compared to that of 
other genera. The spermoviduct or uterus, is a sizeable organ, wider than in other bulimulids 
and not tortuous except sometimes at its end. The spermatheca or bursa copulatrix, is spheroid, 
united at the entrance of the vagina by a long duct which runs almost attached to the uterus 
wall. The vaginal sac is very short. Penis furnished with a long flagellum, which is broader and 
thicker at the base, into which the vas deferens running from the penis sheath is introduced; 
there is some similarity in this organ to that of Scutalus, but it is smaller and it differs from 
that in other bulimulids. 

Considering the general features of the genitalia in their family affinities, the hermaphroditic 
gland of Protoglyptus is distinguished by not being racemose. The spermatic duct is slender and 
the uterus ends, together with the spermatic duct, nearer to the entrance of the vagina than in 
other genera. 

Compared with the genitalia of the type-species of Naesiotus, N. nux, the differences are 
significant. Dall figured the genitalia of N. nux after Binney's drawings, calling attention to the 
incorrect nature of that figure, because the male and female openings appear separated, instead 
of being united at the atrium which is normal. 

Neither Dall (1896, 1920), who studied most of the species of the Galapagos Islands, nor 



PARODIZ 



117 




FIG. 8. Genitalia of Protoglyptus quitensis (PU.), Pillaro, Tungurahua, Ecuador, ag— albumen gland; ds- 
spermatic duct; f— flagellum; hd— hermaphroditic duct; ot— ovotestis; p— penis; pp— praeputium; sp- 
spermatheca; u— uterus; vd— vas deferens; vs— vaginal sac. 



Pilsbry (1897) when he described the subgenus Protoglyptus, mentioned any anatomical 
differences. Pilsbry merely stated that "Naesiotus and Orthotomium [= Rabdotus?] are 
identical with Protoglyptus in apical sculpture" and that they, apparently, derived from the 
same (primitive) stock. This led subsequent authors to the description of species either as 
Naesiotus or Protoglyptus, without anatomical considerations; most of the species, of course, 
were described on the shell alone. 

In both groups the shells are very variable in size and shape, but not to the extent which 
induced Weyrauch (1956) to describe Naesiotus andivagus and N. pilsbryi as belonging to the 
same genus. Subsequently, with the second species, Weyrauch (1958) created the subgenus 
Maranhoniellus, which Zilch categorized under Bulimulus. I agree with Weyrauch that it is 
advisable to treat Naesiotus as a genus, but so is Protoglyptus. On the other hand, the fact that 
Naesiotus is endemic in the Galapagos Islands, and Protoglyptus is better known in mainland 
South America, does not imply that all species of the Galapagos are Naesiotus or that 
Protoglyptus cannot be found on the islands. A better knowledge of most speices is needed to 
establish the limits, morphological and geographical, of these groups. 

Genus Protoglyptus Pilsbry, 1897 

Manual of Conchology (2)11: 85 (as subgenus of Bulimulus). 

Type-species: Buliminus pilosus Guppy, from Trinidad, West Indies (near Venezuela) 
(American Journal of Conchology, 1871, 6: 310). Subsequent designation by Parodiz, 1946: 



118 PROC. SIXTH EUROP. MALAC. CONGR. 

the first species included by Pilsbry under Protog/yptus. Zilch (1960) made, independently, the 
same designation, but instead of the type species, he illustrated Protog/yptus durus (Spix). 

Pilsbry's brief diagnosis is applicable to a group of species which can be considered as 
Protog/yptus s.S. In 1946 the present author studied a number of species from the northwest 
and southern regions of South America, diagnosing three particular groups: 

(1) Protog/yptus s.S.: P. crepundia (d'Orbigny), P. munster/ (d'Orbigny), and P. punctustr/- 
atus Parodiz. Umbilicus wide and deep. 

(2) Subgenus Rimatu/a Parodiz, 1946: 353. Type P. de/etang/ Parodiz from northern 
Argentina. It includes P. oxy/abr/s (Doering), P. montivagus (d'Orbigny), and P. po//onerae 
(Ancey). This group is characterized by its very narrow umbilicus, partially covered by the 
columellar expansion. 

(3) Subgenus Obstrussus Parodiz, 1946: 354. Type Bu/imus rocayanus d'Orbigny; includes Л 
c/iacoensis (Ancey). Imperforate, with the columellar margin expanded over the umbilicus; base 
of columella with a torsion which projects the end of the aperture to the left; long spire, with 
more whorls than in other Protog/yptus. Such a subgeneric arrangement is for want of 
something better and may be proved to be untenable with increased knowledge of the species. 

Protog/yptus (Rimatu/a) quitensis (Pfeiffer, 1848) 

Bulimus quitensis Pfeiffer, 1848, Proc. zool. Soc. Lond., 1847: 230. — Reeve, 1849, Concti. icon., 5: fig. 

317. - Hidalgo, 1870a, Moluscos del Viaje al Pacifico: 130, pi. 7, fig. 5-8. - Hidalgo, 1870b, 7. Conch. 

Paris, 18: 63. - Pfeiffer, 1877, Monogr. Helic. viv., 8: 157. - Pilsbry, 1895, Man. Conch. (2) 10: 158, pi. 

51, fig. 16-18. [Bulimulus (Bostryx-Lissoacme)] . - Rehder, 1940, Nautilus, 53: 114, fig. 2, 4, 7, 9, 11, 

13, 15, 16, 18, 20 [Naesiotus] . - Weyrauch, 1958, Arch. Moll. 87: 121 [Naesiotus] . 
Bulimus irregularis Pfeiffer, 1848, I.e.: 231. - Reeve, 1849, I.e.: fig. 454. - Martens, 1885, Conch. Mitt., 2: 

162 [Bulimulus (Scutalus)] . - Cousin, 1887, Bull. Soc. zool. Fr., 12: 225 [Thaumastus] . - Pilsbry, 

1897, Man. Conch. (2) 11: 34, pl. 34, fig. 71 [Bulimulus (Scutalus)] . 
Bulimus striatus King sensu Reeve, 1848, I.e.: fig. 139. 
Bulimus caliginosus Reeve, 1849, I.e.: fig. 609. - Hidalgo, 1870a, I.e.: 59; Martens, 1885, I.e.: 161. - 

Cousin, 1887, I.e.: 223 [Thaumastus] . - Pilsbry, 1897, I.e.: 33, pl. 4, fig. 43-45 [Bulimulus (Scutalus)]. 

— Germain, 1910, Mission Serv. gkogr. Amer. Sud, 9: С. 31 [Bulimulus (Scutalus)] . 
Bulimus catlowiae Pfeiffer, 1853, Monogr. Helic. viv. 3: 427. - Pfeiffer, 1854, Proc. zool. Soc. Lond, 1852: 

154. - Hidalgo, 1870a, I.e.: 128, pl. 7, fig. 9-10. - Hidalgo, 1870b, I.e.: 63.- Pfeiffer, 1877, I.e.: 154. 

Miller, 1878, Malak. Bl., 25: 194 [Scutalus]. - Pilsbry, 1897, I.e.: 34, pl. 5, fig. 69-70 [Bulimulus 

(Scutalus)] . 
Bulimus anthisanensis Pfeiffer, 1853, I.e.: 406 [in part]. - Pfeiffer, 1854, I.e.: 155. - Albers, 1860, Die 

Heliceen, 2e Ausg.: 217. - Pilsbry, 1897, I.e.: 32, pl. 4, fig. 41-42 [Bulimulus (Scutalus)]. 
Bulimulus (Scutalus) quitensis rufescens Gernnain, 1910, I.e.: C.35, pl. 4, fig. 1-2. 
Naesiotus quitensis jacksoni Rehder, 1940, I.e.: 116, fig. 1, 5. 
Naesiotus quitensis orinus Rehder, 1940, I.e.: 116, fig. 6, 10. 
Naesiotus quitensis vermiculatus Rehder, 1940, I.e.: 117, fig. 17, 19. 
Naesiotus quitensis ambatensis Rehder, 1940, I.e.: 117, fig. 12, 14. 
Naesiotus quitensis antisana Rehder, 1942, Nautilus, 55: 103. 

Type locality: Quito, Ecuador. 

Pilsbry in his monograph of the Bulimulidae (1895: 159) declared not having seen this 
species, and being not aware of its apical sculpture, placed it in the combination Bostryx- 
Lissoacme, but adding that it may prove to be a Scuta/us. 

Description— Shell of regular bul ¡moid type with large body whorl and short spire (ovate- 
conical), with 6-7 whorls, including the V /г of the protoconch which is axially and obliquely 
ribbed and the spaces between ribs filled with numerous, very fine, spiral striae; the ribs 
become finer and closer near the middle of the second whorl, then disappear altogether; the 
following whorls with irregular creamy-white axial costulae of different width, the spaces 
between of chestnut color, giving the surface a rough appearance of clear and dark streaks. 
Spire with slightly convex whorls; body whorl globose. Aperture ovate-elongate; inside chestnut, 
and sufficiently transluscent to make the external streaks visible. The columella is dark and 
straight, the basal end forming an angle with the lip. Peristome thin and not reflexed. Average 
size 30 mm long and 13-15 mm wide. 

The variations in size, color and shape have led to the description of several species and 
subspecies. 

The examination of 1700 specimens from different localities along the interandine plateau 
of Ecuador (Fig. 9) proved that separation of geographically limited subspecies is not only 



PARODIZ 



119 



MBABURA 



ЮОг 



Tí. 

•A 



CAVAMBE^« COLOMBIA 




FIG. 9. Localities of the studied populations of Protoglyptus quitensis (Pfeiffer). H. Heijn del. 



120 PROC. SIXTH EUROP. MALAC. CONGR. 

extremely difficult but without taxonomic importance. A northern sample, from Cayambe, 
including 171 specimens, shows different types of interpopulation variations: 36 small 
vermiculatus type; 15 small with surface less rugose than in vermiculatus Rehder; 50 larger, 
with distinct brown streaks but with grayish ground color; 12 of medium size with wider 
straw-yellow streaks and chestnut background, as in anthisanensis Pfeiffer or antisana Rehder; 
35 with wide clear and dark areas; 18 larger creamy-white with some chestnut bands as in 
jacksoni Rehder; 5 uniformly brown-colored without streaks; some albino as in orinus Rehder. 
The proportional measurements of these specimens are also variable, ranging from narrow (25 X 
11 mm) to very globose shells (24 X 15 mm). 

More diverse, but not exclusively distinct, is a sample of 67 specimens from Pichincha, 
with paler colors: 23 pure white to straw-yellow with pale brown bands, some with pink- 
ish apexes, interior of the aperture white, showing clearly the external bands, surface wrin- 
kled; 8 smoother with umbilicus diversely opened; 14 larger, fleshy-colored and with strong 
wrinkles, but interior of aperture darker; 1 1 with a combination of the above characteristics. 
The shells are 18-28 mm long and 10-14.5 mm wide. This seems to be a population closer 
to the typical quitensis, but other lots of the same locality, Pichincha and around Quito, 
include many specimens of the darker anthisanensis type, or as rugose as in vermiculatus. 

In the following key to color patterns and size within the species, the "forms" are 
designated according to the specific or subspecific names given by the authors, with their type 
localities. 

1 — Pale colored, with less contrasting streaks; medium to large size 2 

— Darker; small to medium size 3 

2 — Variable populations with yellowish to pale brown streaks P. quitensis quitensis. 

including forms such as 
irregularis Pfeiffer, 
rufescens Germain, 
orinus Rehder 
(Hidalgo's var. b). Quito. 

— Very pale with sometimes flesh-colored streaks 4 

3 — Shell wider (most common form), streaked with very contrasted chestnut 

and pale brown axial bands; various sizes vermiculatus Rehder. 

Tungurahua. 

4 — Longer and slender, very pale, without or with very pale streaks jacksoni Rehder. 

Guaillabamba. 

— Flesh-colored, sometimes purplish, with irregular lighter streaks; small .... catlowiae Pfeiffer. 

ambatensis Rehder. 
Am bato. 

Southern samples from Chimborazo included variation between the typical quitensis and 
vermicu/atus but with predominance of the anthisanensis form. In a large sample from Mount 
Antisana, Chimborazo and Pillaro there is a mixture of all "forms" from 1 to 4. 

When collecting has been unbiased, it is impossible to find any particular form restricted to a 
single locality or zone. All forms are sympatric. 

Protoglyptus quitensis is broken up, not into subspecies or even races, but is a polymorphic 
species with transitional and overlapping forms, which can be summarized in 6 series of basic 
patterns of color and surface structure. 

Series AI to A6, from yellowish-white and light brown to darker specimens, with increasing 
rugosity of the surface: 

Al— Very dark, with a few fine yellow lines and dark apex; 

A2— With more yellow and brown lines; 

A3— Yellow-brown lines very abundant; 

A4— With many grayish-white streaks, aperture chestnut; 

A5— With 2 or 3 of the bands darker, aperture paler; 

A6— Predominance of dark streaks, aperture colored at margin but uncolored inside. 

Series Bl to B5 with progressive darkening of background color and gradual intensification 
of the streaks, including the larger vermicu/atus type: 

Bl— Resembling AI but with the yellow-brown zones wider; 
B2— Intermediate between A2 and A3; 



PARODIZ 121 

ВЗ— Clearer background color and more banded; 

B4— Same as 83 but with diffuse streaks; 

B5-Strong dark streaks well separated by white zones (as fig. 609 in Reeve's caliginosus). 

Series CI to C4 with progressively paler colors, more diffusely streaked: 

CI— Intermediate between B1 and 82; 

C2— Resembling 83 but darker; 

C3— With many diffuse streaks; 

C4— Background very pale brown to whitish with very diffuse streaks. 

Series D1 to D3 from paler many-streaked specimens to some with only 2 or a single streak: 

D1 — Light brown and white zones more evenly divided; 

D2— White with irregular brown streaks; 

D3-White with 1 or 2 conspicuous streaks (as fig. 317 in Reeve). 

Series El and E2, from rugosely streaked to almost white: 
El— Many fine brown lines with rugose surface (as in fig. 454 in Reeve); 
E2— Ashy white or almost white with the streaks reduced to the end of the last whorl; 
streaks on the upper whorls, if present, very weak. 

Fl— Completely white without streaks. 

When these series are compared, all kinds of transitional and individual variations are found; 
thus, D2 can be considered as transitional between C2 and C3, etc. The following diagram 
shows the relationship of any of the intrapopulation variants with others closely associated: 

Fl 

El E2 

D1 D2 D3 

CI C2 C3 C4 

81 82 83 84 85 

Al A2 A3 A4 A5 A6 



DISTRIBUTIONAL FACTORS 

Protoglyptus quitensis is distributed along the interandine plateau of Ecuador, from Cayambe 
to Riobamba. It is abundant at both sides of the watershed of the three main rivers of the area, 
Guiallabamba, Napo and Pastaza. 

The headwaters of the Guiallabamba River, which runs northwest to the Pacific, are 
separated from the headwaters of the Pastaza River (a tributary of the Marañon) by elevations 
of over 18,000 feet. The high plateau on the west side of the Cordillera Oriental is divided into 
2 sections. The type localities for P. quitensis quitensis and P. quitensis jacksoni are in the 
northern section, in the Pichincha province; to the south, Chimborazo is the type locality of P. 
quitensis orinus, and the type localities of P. quitensis ambatensis and P. quitensis vermicu- 
latus are in the Tungurahua province. P. quitensis quitensis is also found in Tungurahua, thus, 
the central elevation of Leon province is not a barrier factor for isolation. With regard to P. 
quitensis anthisanensis {=antisana), its type locality is on the highest eastern part of the plateau, 
on the headwaters of the Napo River (another tributary of the Marañon), which forms the 3rd 
division, but that form is also found elsewhere in the other sections. 

In northern specimens from Cayambe, near the type locality of P. quitensis jac/<soni, all 
other intermediate types of variation occur, as well as in Pichincha (north) and Chimborazo 
(south). There is no allopatry for any of the variations which were described as subspecies. It is 
possible to find a certain degree of differentiation among typical P. q. orinus and P. q. 
vermicu/atus, which vanishes when transitional forms are considered. Furthermore, most of the 
collecting was done in the provinces of Pichincha, Tungurahua and Chimborazo, but almost 
nothing is reported from Leon where, in all probability, all types will be found highly mixed. 

At certain periods of the expansion of the species, different populations of P. quitensis 
probably became isolated geographically, resulting in a rapid development of ecophenotypes, 
but the isolation never was completed in such a manner as to result in allopatric subspecies, and 



122 PROC. SIXTH EUROP. MALAC. CONGR. 

a continuous exchange of genetic material of the populations has resulted in a mosaic of a 
polymorphic species, with gradual and uninterrupted gradient characteristics. Although not 
evident at present, the species may have been, formerly, of a clinal nature. 

Localities of the material examined: (1) Province of Pichincha— Cayambe, Guiallabamba, 
Volcano Pichincha, Quito, Mount Antisana; (2) Province of Tunguraha— Pillaro, Ambato, 
Agoyan on Pastaza River, Agoyan at Baños de Tungurahua; (3) Province of Chimborazo— Mount 
Chimborazo. 



LITERATURE CITED 

DALL, W. H., 1896, Insular landshell faunas, especially as illustrated by the data obtained by Dr. G. Baur 

in the Galapagos Islands. Proceedings of the Academy of Natural Sciences of Pfiiladelpfiia, 1896: 

395-460. 
DALL, W. H., 1920, On the relations of the sectional groups of Bulimulus of the subgenus Naesiotus 

Albers. Journal of the Washington Academy of Sciences, 10: 1 17-122. 
GUPPY, R. J. L., 1871, Notes on some new forms of terrestrial and fluviatile Mollusca found in Trinidad. 

American Journal of Conchology, 6: 306-311. 
PARODIZ, J. J., 1946, Les géneros de los Bulimulinae Argentinos. Revista del Museo de La Plata (n.s.), 

Zoología, 4: 303-371. 
PILSBRY, H. A., 1895-1896, American bulimi and bulimuli. Strophocheilus, Plekocheilus, Auris, Bulimulus. 

Manual of Conchology, (2)10: i-iv, 1-213. Academy of Natural Sciences, Philadelphia. 
PILSBRY, H. A., 1897-1898, American Bulimulidae: Bulimulus, Neopetraeus, Oxychona and South 

American Drymaeus. Manual of Conchology, (2)11: 1-399. Academy of Natural Sciences, Philadelphia. 
REHDER, H. A., 1940, New mollusks of the genus Naesiotus from Ecuador. Nautilus, 53: 111-118. 
TH\ELE, J., ^929-^93^. Handbuch der systematischen Weichtierkunde, 1: i-iv, 1-778. Gustav Fischer, Jena. 
WEYRAUCH, W. K., 1956, The genus Naesiotus, with descriptions of new species and notes on other 

Peruvian Bulimulidae. Proceedings of the Academy of Natural Sciences of Philadelphia, 108: 1-17. 
WEYRAUCH, W. K., 1958, Neue Landschnecken und neue Synonyme aus Südamerika, 1. Archiv für 

Molluskenkunde, 87: 91-139. 
ZILCH, A., 1959-1960, Gastropoda, Euthyneura. In: Schindewolf, H. O., ed., Handbuch der Paläozoologie, 

6(2): i-xii, 1-834. Borntraeger, Berlin-Nikolassee. 



MALACOLOGIA, 1979, 18: 123-131 

PROC. SIXTH EUROP. MALAC. CONGR. 

PHYLOGENETISCHE PROBLEME BEI NACKTSCHNECKEN AUS DEN 

FAMILIEN LIMACIDAE UND MILACIDAE 

(GASTROPODA, PULMONATA) 

Andrzej Wiktor^ und Ilia M. Likharev^ 

ABSTRACT 

As we do not know how to inteфret the scant fossil remnants of slugs, the authors 
had to have their phylogenetic considerations based on Recent animals only. Their 
conclusions are based on an analysis of external characters, anatomy of the alimentary 
canal, palliai complex, and genitalia, as well as geographical distribution and biology. 
Milacidae and Limacidae are undoubtedly of different origin. It seems necessary to 
separate the Boettgerillidae from the Milacidae, and the Agriolimacidae from the 
Limacidae; these should be considered to represent four different families. 

Die Feststellung der verwandschaftlichen Beziehungen ist bei den Nacktschnecken besonders 
schwierig. Bis jetzt sind wir noch nicht im Stande die verkümmerte Schale dieser Tiere für 
systematische Zwecke zu verwenden. Deshalb ist es auch noch nicht möglich fossile Reste zu 
deuten, was für phylogenetische Studien von grosser Bedeutung wäre. Daher können wir uns bei 
Forschungen zur Ermittlung der verwandschaftlichen Beziehungen in dieser Gruppe nur auf 
morphologische Merkmale rezenter Formen stützen, teilweise auch auf Angaben über die 
Bionomie, Ökologie und Verbreitung. Untersuchungen in dieser Richtung haben wir im 
Zusammenhang mit einer monographischen Bearbeitung der Nacktschnecken der UdSSR und 
der angrenzenden Gebiete unternommen, d.h. an Material von einem grossen Teil der Paläarktis. 

Mit der Phylogenese der hier behandelten Familien beschäftigte sich in der letzten Jahrhun- 
dertwende insbesondere Heinrich Simroth (1901)— der sachverständigste Nacktschnecken- 
spezialist der damaligen Zeit. Spätere Aussagen zu diesem Thema, darunter auch jene von Hesse 
(1926) und Wagner (1934, 1935, 1936) sind eigentlich nur als Vervollständigungen oder als 
geringe Modifikationen der bisherigen Erkenntnisse anzusehen. In den letzten 70 Jahren nach 
Simroth's Tätigkeit sammelten sich zahlreiche Informationen an, welche uns neben unseren 
eigenen Forschungsergebnissen zu einer Aktualisierung der Meinung über dieses Thema angeregt 
haben. 

Wir konnten uns überzeugen, dass für die systematische Gruppierung der Familien- und 
Gattungsrangen folgende Merkmale verwendbar sind: 

(a) der Habitus; 

(b) der Bau des Verdauungssystems; 

(c) der Bau des Palialkomplexes; 

(d) der Bau der Schale; 

(e) das Bauschema der Genitalien. 

Diese Merkmale korrespondieren eindeutig mit den entsprechenden Angaben über die 
Bionomie und Verbreitung der Arten. Unter dem Begriff "Nacktschnecken" ist eine heterogene 
Gruppe zu verstehen, deren einziges gemeinsames Merkmal in der verkümmerten Schale besteht. 
Letztere ist gewöhnlich unter dem Mantel verborgen. Die Reduktion der Schale bedingt bei den 
Nacktschnecken einerseits den Verlust einer Schutzvorrichtung, anderseits gelangten diese Tiere 
dadurch zu ganz anderen Bewegungsmöglichkeiten. Die Schale verwandelte sich allmählig in ein 
abgeflachtes Gebilde, wodurch es zu wesentlichen Änderungen im Habitus und zu Verschie- 
bungen der inneren Organe, speziell des Eingeweidesackes, kam. 

1 Naturhistorisches Museum, Universität Wroclaw, Polen. 

^Zoologisches Institut, Akademie der Wissenschaften, Leningrad, USSR. 

(123) 



124 



PROC. SIXTH EUROP. MALAC. CONGR. 





^^ 




FIG. 1. Das Entstehen der 2 verschiedenen Land-Nacktschnecken-Gruppen: Raubnacktschnecken und phyto- 
phage Nacktschnecken (die Pfeilen zeigen die Entwicklung des Cephalopodiums). 



Unter den Land-Nacktschnecken lassen sich zwei verschiedene biomorphologische Gruppen 
unterscheiden. 

(1) Bei der ersten Gruppe ist der vordere Körperabschnitt stark entwickelt d.h. der Schlund- 
Abschnitt und der vordere Teil des Fusses. Gleichzeitig wurde der Mantel nnit dem ganzen 
Pallialkomplex nach hinten verschoben und abgeplattet. Der hinter dem Mantel befindliche 
Körperabschnitt ¡st kurz. Hierher gehöhren verschiedene Raubschnecken, wie z.B. die Vertreter 
der Familien Trigonochlamydidae, Testacellidae, Daudebardiidae usw. (Fig. 1). 

(2) Bei der zweiten Gruppe sind der mittlere und der hintere Teil des Fusses stark 
entwickelt. Der Eingeweidesack dringt sich in das Cephalopodium hinein und reicht bis zu 
seinem Ende. Der Mantel und der Pallialkomplex, oder zumindest der Letzte, befinden sich auf 
der vorderen Körperhälfte. Der hinter dem Mantel liegende Körperabschnitt ist stark verlängert 
und birgt den grössten Teil der inneren Organe. Hierher gehören ursprüglich phytophage 
Schnecken, wie z.B. die Vertreter der Familien Limacidae, Milacidae, Arionidae, Philomycidae 
usw. (Fig. 1). 

Aus unseren Untersuchungen geht hervor, dass sowohl die Milaciden wie auch die Limaeiden 
nach der bisherigen Auffassung als uneinheitliche Gruppen anzusehen sind, wobei von der 
ersten, wie Van Goethem (1972) es bereits suggerierte, die Familie Boettgerillidae abgetrennt 
werden sollte, während von der zweiten die Familie Agriolimacidae abzuspalten wäre. Einen 
ähnlichen Vorschlag in Bezug auf die letzte Gruppe finden wir in den Veröffentlichungen von 
Wagner (1935). Unsere Untersuchungen bestätigen, dass die schon zeitiger bemerkten Eigentüm- 
lichkeiten mancher Merkmale eine neue Einteilung der Nacktschnecken gerechtfertigen. Deshalb 
haben wir die erwähnten Gruppen als selbstständige Familien aufgestellt. 

Alle oben genannten Gruppen unterscheiden sich deutlich im äusserem Habitus. Dies betrifft 
das allgemeine Gepräge und den Muskelbau der Fusssohle. Sowohl die Milaciden wie auch die 
Boettgerilliden besitzen auffällige Mantelfurchen, während den Vertretern der beiden übrigen 
Familien solche Furchen fehlen. Sie unterscheiden sich dagegen untereinander durch das 
vorhandene bzw. fehlende Ring rund dem Pneumostom (Fig. 2). 

Das Verdauungssystem entwickelte sich ebenfalls in verschiedenen Richtungen. Als primär 
dürfte die Anordnung des Darmes mit zwei Schlingen anzusehen sein, denn einen solchen Bau 
weisen fast alle Gehäuseschnecken und die meisten Nacktschnecken auf. Die Ausbildung einer 
dritten Schlinge im Zusammenhang mit der Verlängerung des Darmes, sowie die Entwicklung 
eines Blinddarmes ist als Resultat einer späteren Spezialisierung anzusehen, welche unter den 



WIKTOR UND LIKHAREV 



125 





Mil. 




Agr. 





FIG. 2. Der äussere Habitus. Unten: 
Limacidae, Agr.— Agriolimacidae. 



die Fusssohleoberfläche. Boet.— Boettgerillidae, Mil.— Milacidae, Linn.— 



Gastropoden nur bei ümaciden vorkommt. Von wesentlicher Bedeutung scheint u.a. das 
Verhältnis der Schlingenlängen im Darm zu sein, weiter die Position der Schlingen und der 
Abzweigung des Blinddarmes. Bei allen Limaeiden reicht die erste Schlinge am weitesten nach 
hinten und alle ausser der Gattung Eumilax besitzen 3 Darmschlingen. Die übrigen 3 Familien 
haben nur 2 Darmschlingen, wobei die erste Schlinge weiter vorn liegt als die zweite. Ein 
Blinddarm ist nur bei manchen Limaeiden und Agriolimaciden vorhanden. Im ersten Fall bildet 
der Blinddarm eine Verlängerung der dritten Schlinge, wobei dieser lang ist, dagegen ist dieses 
Organ bei den Agriolimaciden klein, liegt ziemlich entfernt vom Mantel und bildet eine seitliche 
Tasche des Rectum (Fig. 3). 

Der bei systematischen Untersuchungen bisher wenig beachtete Pallialkomplex erwies sich als 
recht brauchbar für die Bestätigung der Selbständigkeit der einzelnen Gruppen. Im Pallial- 
komplex sind besonders die Niere, ferner der Ureter und die hiermit verbundenen Strukturen 



126 



PROC. SIXTH EUROP. MALAC. CONGR. 






Lim. 



Boet. 



Mil. 




Agr. 



FIG. 3. Die 
Agriolimacidae. 



Verdauungssystemen. Boet.— Boettgerillidae, Mil.— Milacidae, Lim.— Linnacidae, Agr. 



eigenartig. Bei den Boettgerilliden ist der Bau der Ausscheidungsorgane besonders charakter- 
istisch. Bei den Agriolimaciden und Milaciden ist ein "Nierenlappen" (Lobus) vorhanden, 
wahrend bei den Limaeiden dieses Merkmal fehlt. Bei den Limaeiden und Agriolimaciden gibt es 
ferner eine Harnblase, welche wiederum bei den Milaciden nicht vorkommt (Fig. 4). 

Die Schale ist so stark reduziert, dass danach nicht einmal Gattungen gedeutet werden 
können. Trotzdem ist es möglich nach diesem Merkmal die verschiedene Herkunft der Milaciden 
einerseits, sowie der Limaeiden und Agriolimaciden andererseits zu erkennen. Bei den Milaciden 
liegt der embryonale Teil der Schale auf der symmetrischen Achse und daraus ist zu schliessen, 
dass der Prototyp dieser Schale ähnlich wie die Schalen der rezenten Daudebardiidae gebaut sein 
konnte. Die asymmetrische Schale der beiden übrigen Familien dagegen musste aus einer 
anderen Schalenform entstanden sein. Bei der Gattung Boettgerilla ist die Schale symmetrisch 
wie bei den Milaciden, aber die hier extrem fortgeschrittene Verkümmerung ist so stark, dass 
es schwierig ist hierfür einen Prototyp ausfindig zu machen (Fig. 5). 

Der Bau der Genitalien ¡st recht gut brauchbar für die systematische Gliederung in Gattungen 
und Arten. Für die Gruppierung in höhere systematischen Einheiten ist besonders die 
Anwesenheit oder das Fehlen von verschiedenen akzessorischen Organen massgebend und zwar 



WIKTOR UND LIKHAREV 



127 




Во et. 




Lim. 





Mil. Agr. 

FIG. 4. Der Pallialkomplex. Boet.— Boettgerillidae, Mil.— Milacidae, Lim.— Limacidae, Agr.— Agriolimacidae. 





Boet. Mil. 





Lim. Agr. 



FIG. 5. Die Schalen, Boet.-Boettgerillidae, Mil.-Milacidae, Lim. -Limacidae. Agr.-Agriolimacidae. 



128 



PROC. SIXTH EUROP. MALAC. GONGR. 




FIG. 6a. Die Verbreitung. Boet.— Boettgerillidae (Achtung ! endemisch für Kaukasus, hier zusammen mit 
Verschleppungsareal), Mil.— Milacidae. 



WIKTOR UND LIKHAREV 



129 




FIG. 6b. Die Verbreitung. Lim.— Lirлac¡dae, Agr.— Agriolimacidae. 



130 PROC. SIXTH EUROP. MALAC. CONGR. 

sowohl im männlichen wie auch im weiblichen Teil des Geschlechtssystems. Wichtig ist auch die 
Verbindung der Bursa copulatrix mit den übrigen Organen. Charakteristisch für die Milaciden ist 
das Vorhandensein eines Epiphallus und der Anhangdrüsen in der Nähe der weiblichen 
Kopulationsorgane oder des Atriums. Die Boettgerilliden zeichnen sich unter den paläarktischen 
Schnecken durch das Spindelorgan (Corpus fusiforme) aus. Die Limaeiden und Agriolimaciden 
besitzen keine deutlichen Trennungsmerkmale, doch fehlen hier gewisse Organe, welche bei den 
vorher erwähnten Familien vorkommen. Die Unterschiede zwischen diesen Familien sind nicht 
so deutlich ausgeprägt und bestehen hauptsächlich in den Ausmassen der Vertreter. Schliesslich 
ist noch zu erwähnen, dass bei den Milaciden und Boettgerilliden die Bursa copulatrix mit den 
weiblichen Kanal, dagegen bei den Agriolimaciden und Limaeiden mit dem Penis, verbunden ist. 

Die hier vorgeschlagene Gruppierung der Nacktschnecken nach morphologischen Merkmalen 
findet auch eine deutliche Unterstützung durch zoogeographische Argumente. Obwohl wir über 
die primären Verbreitungszentren dieser Schnecken wenig wissen, ist bekannt, dass sich die 
Verbreitung der rezenten Vertreter dieser Familien recht unterschiedlich gestaltet. Die Boett- 
gerilliden sind endemischen Formen des Kaukasus, später anthropogen weit in Europa und 
Asien verschleppt. Die Milaciden besiedeln Gebiete mit mildem Meeresklima, d.h. den Mittel- 
meerraum in weiteren Sinne. Die Limaeiden besitzen ein grösseres Verbreitungsareal, welches 
auf die westliche Paläarktis und Tian-Schan Bergsystem begrenzt ¡st. Die Agriolimaciden 
bewohnen die ganze Holarktis, doch kommt die Mehrzahl der Arten in der Paläarktis vor (Fig. 
6). 

Die Verschiedenheit der aufgezählten Familien wird auch durch viele bionomische Merkmale 
bestätigt. So sind beispielweise die Boettgerilliden sehr beweglich und leben im Boden, d.h. 
unterirdisch. Die Milaciden sind wärmeliebend, wiederstandsfähig gegen Trockenheit und wenig 
beweglich, besiedeln die Bodenoberfläche. Die Limaeiden sind mesophil und sehr beweglich. Die 
Agriolimaciden sind am stärksten eurytop und besiedeln offenes Gelände mit starken Klima- 
schwankungen. An solche Verhältnisse haben sich diese Tiere mit kurzen Lebens- und Entwick- 
lungszeiten angepasst, während die übrigen Nacktschnecken bedeutend länger leben. 

Es zeigt sich also nochmals, dass das einzige gemeinsame Merkmal dieser vier Gruppen in 
deren "Nacktheit" besteht, wobei die Körperproportionen charakteristisch für die phytophagen 
Nacktschnecken geblieben sind. 

Zur Vervollständigung unserer Kenntnisse lohnt es sich noch die verwandschaf fliehen 
Beziehungen zwischen den Gattungen der behandelten Gruppen zu analysieren. Die Familie 
Boettgerillidae umfasst nur eine Gattung mit 2 hoch spezialisierten Arten. Die Familie Milacidae 
umfasst rund 50 Arten, welche leicht in 3 gut unterscheidbare Gattungen aufgeteilt werden 
können. Als Trennungsmerkmal ist hier die Lage der Anhangdrüsen und des Stimulators 
massgebend (Fig. 7). Die Familie Limacidae ist sehr stark differenziert und umfasst 10 
Gattungen mit insgesamt 150 Arten. Ausser Genitalien sind zur generischen Gruppierung 
besondere Einzelheiten im Bau des Verdauungssytems verwendbar, wie z.B. die Grösse der 
dritten Darmschlinge und des Blinddarmes. 

Die grössten Schwierigkeiten bereiten die Agriolimaciden. Hierher gehören 5 Gattungen mit 
etwa 110 Arten. Die grösste Gruppe dazwischen bildet die Gattung Deroceras. Eine Einteilung 
in kleinere Gruppen ist hier schwer durchzuführen und kann nur unter Berücksichtigung von 
mehreren morphologischen Merkmalen erfolgen. Es handelt sich hier zumeist um Merkmale, die 
nur bei einer Gattung vorhanden sind und bei den übrigen fehlen. Als Beispiel kann hier das 
Vorhandensein oder Fehlen des Blinddarmes, des Stimulators, des Kieles auf dem Rücken oder 
der Längsfurchen am Fuss erwähnt werden. Die hier behandelte Gruppe bleibt weiterhin am 
wenigsten durchforscht und nach der Ansammlung von weiteren neuen Erkenntnissen dürften 
über diese Artengruppe zukünftig noch rege Diskussionen zu erwarten sein. Es hat den 
Anschein, dass wir hier mit der phylogenetisch jüngsten Gruppe zu tun haben, worauf ihre 
starke Differenzierung hinweist. 

Zusammenfassend weisen wir darauf hin, dass wir die bisher angenommene Meinung, nach 
welcher alle 4 Gruppen gemeinsamer Herkunft sein sollen, nach den dargestellten Überlegungen 
nicht vertreten. Die Milaciden sind zweifellos von anderen Vorfahren abzuleiten als die 
Limaeiden, Agriolimaciden und Boettgerilliden. Darauf deutet der Bau der Schale, des Mantels, 
des Fusses usw. Die Limaeiden und Agriolimaciden wie auch Boettgerilliden seheinen 
miteinander näher verwandt zu sein und es ist möglich, dass diese Familien von einem 
gemeinsamen Zweig unter den Gehäusesehnecken abstammen. Die Boettgerilliden scheinen eine 
hochspezialisierte, unterirdische, in dem Boden lebende Gruppe zu sein. 



WIKTOR UND LIKHAREV 



131 





Boet. 



Lim. 





Mil. ^gr- 

FIG. 7. Die Genitalien. Boet.— Boettgerillidae, Mil.— Milacidae, Lim.— Limacidae, Agr.— Agriolimacidae. 



LITERATUR 

GOETHEM, J. VAN, 1972, Contribution à l'étude de Boettgerilla vermiformis Wiktor, 1959 (Mollusca 
Pulmonata). Bulletins de l'Institut Royal des Sciences Naturelles de Belgique, 48(14): 1-16. 

HESSE, P., 1926, Die Nacktschnecken der palaearktischen Region. Abhandlungen des Archiv für Mollusken- 
kunde, 2(1): 1-152. 

SIMROTH, H., 1901, Die Nacktschneckenfauna des Russischen Reiches. Kaiserliche Akademie der Wissen- 
schaften, St. Petersburg, 321 p. 

WAGNER, J., 1934, Die Nacktschnecken Ungarns, Croatiens und Dalmatiens I. Teil. Annales Musei Nationalis 
Hungariae, 28: 1-30. 

WAGNER, J., 1935, Die Nacktschnecken Ungarns, Croatiens und Dalmatiens II. Teil. Annales Musei 
Nationalis Hungariae, 29: 169-212. 

WAGNER, J., 1936, Die Nacktschnecken Ungarns, Croatiens und Dalmatiens III. Teil. Annales Musei 
Nationalis Hungariae, 30: 67-104. 



MALACOLOGIA, 1979, 18: 133-138 

PROC. SIXTH EUROP. MALAC. CONGR. 

ANATOMICAL STUDIES IN THE AFRICAN ACHATINIDAE-A 
PRELIMINARY REPORT 



Albert R. Mead 

Office of the Dean, Liberal Arts College, Modern Languages Building, Room 347, 
University of Arizona, Tucson, Arizona 85721, U.S.A. 



ABSTRACT 

Basic anatomical patterns of the reproductive system in the Achatinidae are reported. 
Both macro- and microphallate species are found in genus Archachatina and subgenera 
Achatina and Lissachatina in genus Achatina, an interpretation for which is still elusive. 
Good characters are found at the generic, subgeneric and usually specific levels. In some 
closely related species complexes, the anatomies may be very similar. Subspecific 
differences seem to rest entirely in conchological features. Both soft anatomy and shell 
characters are necessary for a better understanding of the phylogeny in this group. Great 
emphasis is placed on the importance of an adequate series of specimens in good 
condition and of variable age. Different methods of expanding, killing, preserving and 
examining are evaluated. 

In 1944 and 1945, my early anatomical studies of the Achatinidae in, then, the Gold Coast 
(Ghana) and Nigeria established the fact that at least some of the species in this family are 
distinct from each other in the anatomy of the genital system. This, in turn, raised the hope 
that a comparative anatomical study would contribute substantially to a better understanding of 
the phylogeny in this popular, taxonomically confused group. With the indispensable concho- 
logical support of Dr. Joseph С Bequaert (1950), such a study was initiated in 1948 at the 
Museum of Comparative Zoology at Harvard under the sponsorship and support of the National 
Research Council-National Academy of Science and the Office of Naval Research (Mead, 1950). 
The principal thrust of that study was to establish through comparative anatomy the identity of 
the "parent" continental African population of the pestiferous /АсЛаГ/ш fúlica Bowdich, which 
had spread widely through the Indo-Pacific region (Mead, 1961), and to distinguish it from its 
related achatinid species. Such a study was judged to be a necessary prelude to an exploration 
for the "natural enemies" of this species in its native hearth as possible biological control agents 
(Williams, 1951). 

Achatina hamillei Petit and A fúlica Bowdich proved to be indistinguishable in the basal 
genital structures but tangibly distinguishable in their conchological features. Bequaert therefore 
placed A. hamillei as a subspecies of A. fúlica and assigned the populations that were not on 
the African mainland, or on Zanzibar and other African coastal islets, to the nominate 
subspecies (1950: 86). This early established the parameter of minimal consistent anatomical 
differences of the soft anatomy at the level of species and the parameter of minimal 
conchological differences at the level of subspecies. In contrast, A. Immaculata Lamarck [= 
panthera (Fer.)] , the only other achatinid to become established outside continental Africa, and 
A. fullea are often so strikingly similar conchologically, particularly in old or worn specimens, 
that they are misidentified in many collections. Anatomically these 2 species manifested extreme 
dissimilarity (Figs. 1,2), leaving no doubt about their validity as distinct species. In further 
contrast, the only 2 grossly reticulate achatinid species, A. reticulata Pfeiffer and A. albopicta 
E. A. Smith, were found to be conchologically so similar, and therefore frequently confused in 
collections, that Bequaert initially decided to place A. albopicta as a subspecies of A. reticulata. 
However, the anatomy of the basal genital structures proved to be so different (Figs. 3,4) that 
the 2 taxa were maintained as separate but closely related species. As a matter of fact, the basal 
genital structures of A fúlica and A. albopicta seem superficially more similar to each other 
than they are to A. Immaculata and A. reticulata, respectively, because they both retain what is 

(133) 



134 PROC. SIXTH EUROP. MALAC. CONGR. 

believed to be the prototypic, diminutive, completely ensheathed penis and the heavily 
muscular basal vagina. All are in Bequaert's subgenus Lissachatina (Bequaert, 1950: 49). It was 
clear at this point that anatomical and conchological features had to be considered in concert to 
understand and interpret better the phylogenetic relationships and to establish a more accurate 
taxonomy in this group. 

These early, encouraging results at Harvard set the stage for more extensive and intensive 
studies of the Achatinidae during the periods October 1974 to June 1975 (Mead, 1976) and 
July to September 1977, principally at the Musée Royal de l'Afrique Centrale in Tervuren, 
Belgium, but also at the following institutions: Institut Royal des Sciences Naturelles in 
Brussels, Rijksmuseum van Natuurlijke Historie in Leiden, Muséum National d'Histoire Naturelle 
in Paris, British Museum (Natural History) in London, Zoologisch Museum in Amsterdam, and 
the Naturhistoriska Museet in Göteborg, Sweden. Whereas the earlier project included mainly 
East African forms, the more recent studies have included to a greater extent the West African 
and South African forms. The present report is intended to be only preliminary, with 
anatomical details and new taxa being fully described elsewhere. 

The species of subgenus Achatina, as in subgenus Lissachatina, were found to fall into 2 
anatomically distinct groups, viz. those with enlarged penes, usually well extended beyond the 
penial sheath (Fig. 5), and those with diminutive, tripartite penes usually entirely embraced by 
the penial sheath (Fig. 6). But the differences are proportionately greater in subgenus /АсЛэГ/пэ. 
Fig. 5, of which Achatina achatina (L.) is typical, shows a large, thick-walled penis; a long, 
bipartite, thick-walled vagina; a short free oviduct; and a spermatheca adjacent to the uterine 
portion of the spermoviduct. In direct contrast, many other species in this group (Fig. 6) have a 
small, tripartite penis entirely enclosed in the penial sheath; a slender, short, thin-walled vagina; 
a long free oviduct; and a spermathecal duct so short that the spermatheca does not reach the 
uterine portion of the spermoviduct. The penes of the macrophallate forms in Lissachatina 
(Fig. 2) are relatively thin-walled and, as in the microphallate forms in that group (Fig. 1), 
there is a thin-walled prepuce (PC) basal to the penial sheath (PS) and apical to the genital 
atrium (GA). A prepuce could not be distinguished in subgenus ЛсЛаг/лэ. The tripartite penis of 
Lissachatina (Fig. 1) has a thick-walled muscular apical penis (AP); an extremely slender, 
tube-like medial penis (MP); and a thin-walled basal penis (BP) that is set off from the 
unensheathed prepuce (PC) by a constriction. The tripartite penis of subgenus Achatina (Fig. 
6), however, has a thick-walled arcuate apical penis; a broad medial penis usually containing a 
pilaster or pilaster-like thickening; and a thin-walled basal penis that is confluent with the 
genital atrium. In contrast to Lissachatina, the tripartite penis of subgenus /Ac/7af/>7a is attached 
throughout its length, and in all directions, to the inner wall of the penial sheath by a thick 
webbing of filamentous muscle strands— so much so in some species that the penis literally has 
to be excavated after the penial sheath has been cut. Heavier muscle strands, apparently 
originating on the outer surface of the basal penial sheath, connect broadly with the basal 
vagina, genital atrial wall, and adjacent portions of the body wall, sometimes considerably 
obscuring these structures. 

The basal genital structures of the 7 examined species in subgenera Archachatina, Calachatina 
and l\/legachatinopsis of genus Archachatina show a remarkable resemblance (Fig. 7) to those of 
the macrophallate species of subgenus Achatina (Fig. 5). The vagina in the macrophallate 
Achatina, however, is bipartite and contrastingly very thick-walled. In both groups there is a 
thick but conspicuous band of muscle fibers, running from the basal vagina to the region of the 
juncture of the free oviduct and the spermathecal duct, originating in the wall of the basal 
female conduit and attaching narrowly to the right body wall along the juncture of the lung 
diaphragm, mantle, and neck. This band probably functions as a vaginal retentor (VR). It is 
tempting to assume a correlation between this and the macrophallate condition; but the absence 
of it in the near-macrophallate Lissachatina (Fig. 4) and the presence of it in 5 examined 
microphallate species of subgenus Tholachatina of Archachatina (Fig. 8) caution against this 
assumption. At least 3 of the 5 South African species of Tholachatina have a longitudinally 
grooved or doubly folded penis (Fig, 8), the expanded condition of which during copulation 
probably produces a formidable intromittent organ (Van Bruggen & Appleton, 1977). This 
would seem to justify the existence or persistence of the retentor muscle. The examination of 
other Tholachatina species is beginning to bridge the gap between the macro- and microphallate 



MEAD 135 

species of Archachatina. In addition, the congeneric or consubgeneric status of some of the 
species currently assigned to Tholachatina is coming into question. 

On the basis of earlier work (Mead, 1950), the species of Limicolaria and the closely related 
Limicolariopsis remain distinctive in that a verge or penis papilla is present. Collaboration 
between this author and Dr. A. С van Bruggen of the Rijksmuseum van Natuurlijke Historie in 
Leiden has shown that some species in Callistoplepa (= Callistopepla) are not congeneric. A 
co-authored taxonomic revision of this genus is currently in progress. Other genera in the 
Achatinidae have revealed so far only tantalizing bits of anatomical information and have yet to 
take a firm place in the taxonomic scheme. 

The question is often asked, "Just how valuable and dependable is the reproductive anatomy 
in determining relationships in the Achatinidae?" At the generic and subgeneric levels it is good, 
although the known anatomies in each of genus Archachatina and subgenera Achatina and 
Lissachatina (and apparently Tholachatina), fall into 2 rather distinct groups, viz. macro- and 
microphallate. An explanation for these parallel anatomical dichotomies is slow in emerging. At 
the level of species, the soft anatomy is generally providing good criteria, although in certain 
groups of closely related species, such as the schweinfurthi-stuh /mann i-tincta-weynsi comp\ex\r\ 
subgenus Achatina, the anatomies understandably tend to be very similar. Differences at the 
subspecific level appear to rest entirely in conchological features. 

What is really needed to establish the true nature of the soft anatomy, and its relative 
taxonomic value, is an adequate series of specimens in good condition and of variable age. 
Through the careful examination of such a series, artifacts of preservation, anomalies, and 
juvenile features can be put into perspective. Regrettably, all too often specimens in wet 
collections are found to be improperly preserved. Dropping alive directly into 70% ethanol 
produces a badly contracted and distorted specimen that usually is so dehydrated that 
protracted soaking in water or, better, 2% trisodium phosphate is required. Even then, the inner 
layers of the body wall may remain so hard that the genital system literally has to be 
excavated. The basal genital structures in such specimens are not infrequently extremely 
attenuated, contracted, or distorted. Putting the specimen directly into unneutralized formalin 
is actually worse because the corrosive action etches and lifts off the periostracum, erodes the 
nepionic whorls beyond recognition, obscures the diagnostic sculpturing of the shell, fuses 
portions of the mantle with the chemically changed nacreous layer, alters the colors (e.g. 
yellows to browns), and causes the shell to become so thin, brittle and chalky that the soft 
parts cannot be removed without shattering it. 

Ideally, the specimen should be narcotized for several hours in a tepid solution of any one 
of several quite good agents (berthanol chloride, propylene phenoxetol, nembutal, chloral 
hydrate, chloretone, etc.) to relax and extend it. In the absence of such agents, either the 
specimen can be drowned for several hours in boiled water or the shell of the live animal can 
be crushed and the specimen examined directly. Protracted drowning, especially where the 
temperature is elevated, often causes a prolapse of the genital atrium and the basal portions of 
the male and female conduits. It is virtually impossible to reconstruct the normal condition of 
the genitalia in such specimens. If the shell is to be saved, the live specimen can be dropped in 
near-boiling water and removed from its shell as soon as the columella muscle will give way (3-5 
minutes). Large series of Achatina fúlica heat killed and dissected in this manner showed 
remarkably little anatomical distortion as compared to most alcohol or formalin preserved 
material. Live dissected material served as a control. 

In the field, when there is no time for dissecting, and where it is important to keep shell and 
soft parts together, the snails should be drowned in boiled water (at room temperature-usually 
warm) overnight (ca. 8 hours) to extend them. Either of the following 2 methods can then be 
used with usually excellent results: The snails are injected and submerged in 4% neutralized 
formalin (no higher percentage!) for no more than 48 hours. They are then removed, washed 
thoroughly in water and preserved in 70% ettianol, usually with another change of solution. Or, 
the snails are put directly into 70% ethanol for 2-3 days, removed, injected with and immersed 
in a new solution of 70% ethanol. I have had relatively little trouble removing all or nearly all 
of the soft parts of such specimens without damaging the shell, and the soft parts remain firm 
and pliable. Where the specimen is small, the soft parts can be removed from the shell with 
strong rat-tooth forceps. In large specimens, a heavy metal probe can be forced through the 



136 



PROC. SIXTH EUROP. MALAC. CONGR. 



All illustrations are diagrammatic and not drawn to scale. The penial retractor, all of the apical vas deferens, 
most of the basal vas deferens, the spermoviduct, and the spermatheca (in species where it is attached to the 
uterine portion of the spermoviduct) have been omitted for simplicity and to emphasize relevant structures. 







FIG. 1, Achatina fúlica Bowdich; FIG. 2, A immaculata Lamarck; FIG. 3, A. albopicta E. A. Smith; FIG. 4, 
A. reticulata Pfeiffer. 



MEAD 



137 



AP-apical penis, AV-apical vagina, BD-basal vas deferens, BP-basal penis, BV-basal vagina, FO-free 
oviduct, GA-genital atriunn, MP-medial penis, PC-penial prepuce, PS-penial sheath, SD-spermathecal duct, 
VR— vaginal retentor. 







FIG. 5, A achatina (L.); FIG. 6, rnicrophallate type, subgenus Achatina: FIG. 7, macrophallate type, genus 
Archachatina; FIG. 8, microphallate type, some species of subgenus Tholachatina. 



138 PROC. SIXTH EUROP. MALAC. CONGR. 

center of the foot and the soft parts can literally be unwound from the shell with the aid of a 
jet of water directed into the shell behind the body mass. The upper part of the digestive gland, 
gonads, hermaphroditic duct, talon, and possibly the albumen gland with adjacent portions of 
the spermoviduct may be lost, but the diagnostic basal genital structures usually remain intact. 
Of course, if the series is large enough, the shell may be sacrificed in selected specimens. 

The greatest impediment in the present study is the paucity of preserved anatomical 
material. The collection in the Musée Royal de l'Afrique Centrale is outstanding and is 
doubtless without equal any place in the world. Collections elsewhere so far have proven to be 
considerably more modest in series or in represented species, or both. With conditions being 
what they are today in many parts of Africa, particularly in Angola where there are a number 
of little known, confused, smaller species o^ Achatina, the outlook is not at all optimistic. Even 
when preserved specimens are available in fair series, conclusions frustratingly may have to 
remain tentative because of the lack of ecological data and the presence of questionable 
characters that could be explained as artifacts of preservation, immaturity of specimens, or 
natural variability. One thing remains clear. As announced earlier (Mead, 1950: 287), both 
conchological and anatomical data are needed as complements. To these emphatically must be 
added ecological data wherever possible. Ultimately, genetics, physiology and histology will 
contribute their part to a better understanding of the phylogenetic relationships and therefore 
taxonomy of the zoogeographically important family Achatinidae. 

ACKNOWLEDGEMENTS 

I wish to express my sincere gratitude to the following who generously made their 
collections, facilities and personal services available for this study: Dr. P. L. G. Benoit of the 
Musée Royal de l'Afrique Centrale in Tervuren, Belgium, Dr. J. L. van Goethem of the Institut 
Royal des Sciences Naturelles de Belgique in Brussels, Dr. A. С van Bruggen of the 
Rijksmuseum van Natuurlijke Historie in Leiden, Dr. P. Bouchet and Dr. S. Tillier of the 
Muséum National d'Histoire Naturelle in Paris, Mr. J. F. Peake of the British Museum (Natural 
History) in London, Dr. B. Hubendick of the Naturhistoriska Museet in Göteborg, and Dr. H. 
E. Coomans of the Zoologisch Museum in Amsterdam. This work was supported in part by a 
grant from the University of Arizona. 

LITERATURE CITED 

BEQUAERT, J. C, 1950, Studies in the Achatininae, a group of African land snails. Bulletin of the Museum 

of Comparative Zoology at Harvard College, 105: 1-216. 
BRUGGEN, A. С VAN & APPLETON, С. С, 1977, Studies on the ecology and systematics of the terrestrial 

molluscs of the Lake Sibaya area of Zululand, South Africa. Zoologische Verhandelingen, Leiden, 154: 

1-44. 
MEAD, A. R., 1950, Comparative genital anatomy of some African Achatinidae (Pulmonata). Bulletin of the 

Museum of Comparative Zoology at Harvard College, 105: 219-291. 
MEAD, A. R., 1961, The giant African snail: a problem in economic malacology. University of Chicago Press, 

Chicago, xi -i- 257 p. 
MEAD, A. R., 1976, Comparative anatomical studies in Europe on the African Achatinidae. Annual Reports 

of the Western Society of Malacologists, 9: 39. 
WILLIAMS, F. X., 1951, Life-history studies of East African Achatina snails. Bulletin of the Museum of 

Comparative Zoology at Harvard College, 105: 295-317. 



MALACOLOGIA, 1979, 18: 139-145 

PROC. SIXTH EUROP. MALAC. CÖNGR. 

ON ELONA (PULMONATA, ELONIDAE FAM. NOV.) 

E. Gittenberger 
Rijksmuseum van Natuurlijke Historie, Leiden, Netíierlands 

ABSTRACT 

The genus E/ona Adams & Adams, 1855, is represented by 2 recent species, E. 
quimpenana (Férussac) and E. pyrenaica (Draparnaud), both living in SW Europe. 
However, while studying the genitalia of these species it became evident that they are 
clearly different from what is usual in the Helicidae. The mucous glands, inserting on the 
upper part of the vagina, are irregularly bulbous. There is a double-walled penis without 
papilla; the inner tube shows longitudinal ridges or papillae in the lumen. E/ona obviously 
does not fit well in any of the known subfamilies or families. Therefore, a new family, 
Elonidae, is proposed. 

E. quimperiana and E. pyrenaica differ in many characters of shell and genitalia. 
Evidently, however, they are more closely related to each other than to any other Recent 
pulmonate snail species, which should be recognized in the nomenclature. The relation to 
Tropidomphalus Pilsbry, 1895, known from the European Oligocene-Pliocene, remains 
unclear. 



The name Elona has been introduced by Adams & Adams (1855: 211) as a nomen novum 
for Sterna Albers, 1850, non Linnaeus, 1758, a name proposed for a single pulmonate snail 
species, E. quimperiana (Férussac, 1821), known from Brittany and, separated from there by a 
500 km gap, also from the northeastern Atlantic coastal area of Spain as far east as the extreme 
SW of France (Fig. 1). E. quimperiana differs conspicuously from all other western Palaearctic 
gastropods in shell shape (Figs. 2-5), somewhat resembling certain tropical Camaenidae, 
especially of the genus Ch/oritis Beck, 1837. The shell is thin and transparent, and has a 
strongly inflated last whorl and an immersed apex. The first ca. 1% whorls show a regular 
pattern of spirally arranged elongated papillae, formed by the calcareous part of the shell and 
accentuated by periostracal, erect (usually deciduous) scales. On the following about 1У2 whorls 
comparatively big and widely spaced round calcareous papillae are developed, forming the bases 
of ca. 0.15 mm long, thick periostracal hairs; additionally, many very fine periostracal papillae 
are found on this part of the shell. On the last whorls only an irregular radial sculpture is seen, 
with very fine, more or less obsolete spiral striae. 

As early as 1855-1856, the brilliant French malacologist Moquin-Tandon published anatomi- 
cal data on E. quimperiana as well as on many other gastropod species represented in France. 
He had discovered that E. quimperiana was not only aberrant in shell shape, but also in having 
club-shaped mucous glands instead of glands of the normal finger-like type. He also had found a 
2nd species with similar mucous glands, known as Helix pyrenaica Draparnaud, 1805. This 
species, which is restricted to a small area in the eastern Pyrenees in France, Andorra and Spain 
(Fig. 1), strongly resembles certain representatives of the European Campylaeinae in shell shape 
(Figs. 4, 5). The shell is less thin than in E. quimperiana, the body-whorl is not strongly 
inflated and the apex is not immersed. The first ca. % whorls show an irregular pattern of 
papillae and wrinkles. On the following Ул-Уг whorls, irregular radial riblets become more 
obvious and vague, spirally elongated papillae are developed, most clearly on the part of the 
whorl adjoining the outer suture; on the opposite part, near the inner suture, the pattern of 
roundish papillae is continued, in some specimens as far as the aperture of the shell. Irregular 
radial riblets and very fine spiral striae are seen on the younger whorls; the striae may be 
obsolete or completely reduced on the body whorl. As all specimens studied were well 
"cleaned", additional periostracal structures have not been observed although these might be 
present, 

Moquin-Tandon (1855-1856: 126) assigned E. quimperiana and E. pyrenaica to a Heiix 

(139) 



140 



PROC. SIXTH EUROP. MALAC. CONGR. 



quimperiana 




FIG. 1. Distribution of Elona quimperiana and E. pyrenaica, after Gernnain (1930: 229-230) and material 
present in the Rijksnnuseum van Natuuriijke Historie, Leiden, Netherlands, and in the Senckenberg Museum, 
Frankfurt am Main, Germany. 



subgenus of their own, characterized by the club-shaped mucous glands. He used the name 
Corneóla Held, 1837, for this taxon, apparently overlooking that Gray (1847: 172) selected 
"Helix cornea" as type-species of Corneóla, in conformity with the ICZN, as Held (1837: 912) 
listed "cornea Drap." under Corneóla. H. cornea is assigned to Chilostoma Fitzinger, 1833, by 
Moquin-Tandon (1855-1856: 134). Later on Hesse (1885) restudied the genitalia of E. 
quimperiana and Ortiz de Zarate (1946: 337-340) did the same for E. pyrenaica. Hesse (1885: 
4) emphasized the isolated position of E. quimperiana, stating that the species most certainly 
does not belong to Campylaea ("alles Andere ... als eine Campylaea"); however, he could not 
suggest any alternative classification. Ortiz de Zarate (1946) confirmed the observations 
published by Moquin-Tandon (1855-1856) and gave some additional information. Zilch (1960 
700) classified Elona among the Campylaeinae, Helicidae, as had been done by Germain (1930 
228), which author only used a different name, Helicigoninae, for the subfamily; Pilsbry (1895 
307) considered Elona even a subgenus of Helicigona Férussac, 1821. 

The present paper deals with two main questions: (1) should E. quimperiana and E. 
pyrenaica be considered congeneric or not, (2) are these 2 species only aberrant amidst the 
many representatives of the Helicidae by the shape of the mucous glands, or are they both 
different in other characters as well. 

The conspicuous differences in shell shape and structure have been mentioned above. The 
genitalia of E. quimperiana and E. pyrenaica are clearly different as well. In E. quimperiana 
(Figs. 10-13) the genital atrium has a thick muscular knob (AK). The vagina consists of a broad 
proximal part (VP) bearing a large dart sac (DS) with a long and slender dart (D) inside, and a 
more slender distal part (VD) around which the about six club-shaped mucous glands (MG) 
insert. In the thick proximal vagina there is a conspicuous dart papilla (DP). The receptaculum 
seminis has a diverticulum (Dl) which is longer than the spermatheca (S) and its duct (SD) 



GITTENBERGER 



141 




FIGS. 2,3. Elona quimperiana, Spain, Santander, Ramales, Español leg.; width 26.8 mnn (RMNH, Leiden). 
FIGS. 4, 5. Elona pyrenaica, Spain, Gerona, Rialp, Queralps, С. Аи1гл1га leg.; width 21.1mm (RMNH, 
Leiden). FIGS. 6, 7. Elona quimperiana, details of the radula (numbers of teeth indicated), France, Finistère, 
between Berrien and Scrignac (SE of Morlaix), J. P. M. Clerx leg.; 6, X550; 7, X525. FIGS. 8, 9. Elona 
pyrenaica, details of the radula (numbers of the teeth indicated), France, Pyrénées-Orientales, Villefranche- 
de-Conflent, D. Aten leg.; 8, X600; 9, XI 275. 



142 



PROC. SIXTH EUROP. MALAC. CONGR. 



together. The penis (P) is slightly longer than the flagellum (F) and more than twice as long as 
the epiphallus (E). The flagellum is widest at its base. From its insertion on the genital atrium 
about 4/5 of the penis is double-walled. The inner tube is subdivided from proximal to distal in 
3 parts according to the surface structure of its lumen, which consists of a few irregular 
longitudinal ridges, many fine papillae and a few longitudinal ridges, respectively. There is no 
penis papilla. On Fig. 10 the albumen gland (AG), the oviduct (O), the ovotestis (ОТ), the 
prostate (PR) and the retractor muscle (R) of the penis, which do not show special characters, 
are indicated as well. 

In E. pyrenaica (Figs. 14, 15) the genital atrium (A) has no knob. The distal part of the 
vagina (VD) has a very thick wall and is, therefore, as thick as the proximal part (VP). The 
club-shaped mucous glands (MG) have shorter stalks (ducts). A dart papilla is absent and the 
small dart sac (DS) contains a very short dart (D) with a broad base. Externally the male part 
of the genitalia differs from that of E. quimperiana in the very long flagellum (F), which is 
more than twice as long as the penis (P), and the epiphallus (E) which equals the penis in 
length. The flagellum is broadest at about the middle of its distal half. The double-walled part 
of the penis, comprising 4/5 of its total length, ends at the insertion of the penis retractor. 
Therefore, in contrast to what is found in E. quimperiana, the most proximal part of the penis 



OT- 



OS. 



10 



11 




FIGS. 10-12. Elona quimperiana, France, Finistère, between Berrien and Scrignac (SE of Morlaix), J. P. M. 
Clerx leg. (RMNH, Leiden); 10, genitalia; 11, detail of the dart papilla; 12, detail showing the position of 
dart papilla and dart. 



GITTENBERGER 



143 




FIG. 13. Elana quimperíana, specimen of Figs. 10-12, detail illustrating the position of the inner tube of the 
penis, with arrows indicating where its 3 parts end (see also the text). 



is simple. The inner tube can be subdivided in only 2 parts, the most proximal one with 
papillae, which are less small than in E. quimperíana, and the distal part with some longitudinal 
ridges. A penis papilla is also absent in E. pyrenaica. There are no conspicuous differences in 
the shape of the receptaculum seminis; the diverticulum may be swollen at the end (Fig. 14). 

In both E. quimperíana and E. pyrenaica the right eye retractor muscle passes between penis 
and vagina. The foot-sole is not subdivided in the first species; this character could not be 
investigated in the other taxon. In E. quimperíana the mantle shows irregular dark spots, visible 
through the transparent shell, and, therefore, causing a kind of mimicry as seen independently 
in various groups of gastropods (cf. e.g. Van Bruggen, 1978: 900, Fig. 10). On the mantle of E. 
pyrenaica, which has an opaque shell, no dark spots were observed. 

Both species have an odontognathous mandíbula. The radulae (Figs. 6-9) are similar. The 
same type of teeth are seen in E. quimperíana and E. pyrenaica, in which the formulae С + 50 
(after one specimen) and С + 45-47 (after 2 specimens) were found respectively. 

Summarizing we may say that E. quimperíana and E. pyrenaica not only differ clearly in 
shell shape and microsculpture, but also in the morphology of the genitalia. The relative 
measurements of many parts are very different in both species. Some structures are found in 
only one of the 2 (atrial knob, dart papilla), others show obvious differences in shape (e.g. 
flagellum, dart, inner surface of the inner penial tube). However, E. quimperíana and E. 
pyrenaica are more closely related to each other than to any other western Palaearctic 
gastropod species known at present. I prefer to demonstrate this relationship in nomenclature, 
rather than to emphasize the many structural differences by introducing a new genus or 
subgenus name. 

Obviously, Elona cannot be assigned to the Campylaeinae, which are characterized by a 
completely different type of genitalia (e.g. Knipper, 1939). A double-walled penis as seen in 
certain Helminthoglyptidae (e.g. Pilsbry, 1939: 67), and mucous glands as in Bradybaenidae 
(e.g. Pilsbry, 1895: xxxvi), inserting, however, on the vagina as in Helicidae, make the 
classification of Elona difficult. Therefore, a new family, Elonidae, is proposed, with some 
hesitation, as much research on the higher pulmonate taxa still has to be done. 

One could pose the question whether fossil representatives of the Elonidae are known. 
Unfortunately, as we have seen before, these might not be clearly distinguishable from the 
Campylaeinae, as only shell characters will be available. Schlickum & Strauch (1972: 79, fig. 4) 
described Elona kowalczyki from the German Upper Pliocene based on a single damaged shell, 
without giving details on the microsculpture. Judging from the description and figure only, it 
remains obscure to me why these authors suppose that this species does not belong to 
Tropidomphalus Pilsbry, 1895. In fact, it would be most interesting to know how the 
representatives of this genus, known from the Oligocène to the Pliocene in Europe, differ from 
the Elona species. Judging from Zilch (1960: 699-700, figs. 2434, 2435) the Tropidomphalus 
species bridge the gap between E. quimperíana and E. pyrenaica, at least in shell shape. Here we 
find another argument against creating a separate genus or subgenus for E. pyrenaica at this 
moment. 



144 



PROC. SIXTH EUROP. MALAC. CONGR. 





FIGS. 14, 15. Elona pyrenaica, France, Pyrénées-Orientales, Villefranche-de-Conflent, D. Aten leg. (RMNH, 
Leiden); 14, genitalia and dart; 15, detail illustrating the position of the inner tube of the penis, with an 
arrow indicating the transition between its 2 parts (see also the text). 



LITERATURE CITED 



ADAMS, H. & ADAMS, A., 1855, The genera of recent Mollusca; arranged according to their organisation, 

2(22): 189-220. John van Voorst, London. 
BRUGGEN, A. С VAN, 1978. Land molluscs. In: WERGER, M. J. A., ed., Biogeography and ecology of 

southern Africa: 877-923. Junk, The Hague. 
GERMAIN, L., 1930, Mollusques terrestres et fluviátiles (prennière partie). Faune de France, 21: 1-477. Paul 

Lechevalier, Paris. 
GRAY, J. E., 1847, A list of the genera of recent Mollusca, their synonyma and types. Proceedings of the 

Zoological Society of London, 15: 129-219. 
HELD, F., 1837, Notizen über die Weichthiere Bayerns. (Fortsetzung). Isis (Oken), 1837(12): 901-919. 
HESSE, P., 1885, Die systematische Stellung von Helix quimperiana Fér. Jahrbücher der Deutschen 

Malakozoologischen Gesellschaft, 12: 45-47. 



GITTENBERGER I45 

KNIPPER, H., 1939, Systematische, anatomische, ökologische und tiergeographische Studien an südost- 

europäischen Heliciden. (Moll. Pulm.). Archiv für Naturgeschichte, N.F., 8: 327-517. 
MOQUIN-TANDON, A., 1855-1856, Histoire naturelle des mollusques terrestres et fluviátiles de France 

2(4-5): 1-368. J.-B. Bailiiere, Paris. 
ORTIZ DE ZARATE, A., 1946. Observaciones anatómicas y posición sistemática de varios heKcidos 

Españoles. Boletín de la Real Sociedad Española de Historia Natural, 44: 337-356. 
PILSBRY, H. A., 1895, Guide to the study of Helices. In: TRYON, G. W. & PILSBRY, H. A., Manual of 

Conchology; structural and systematic, (2)9 (Helicidae, 7): i-xlviii (part 33a) + 161-336 (part 36). Academy 

of Natural Sciences, Philadelphia. 
PILSBRY, H. A., 1939, Land Mollusca of North America (north of Mexico), 1 (1). Monographs, The 

Academy of Natural Sciences of Philadelphia, 3: l-XVII, 1-573, i-ix. 
SCHLICKUM, W. R. & STRAUCH, F., 1972, Vier Beitrage zur neogenen Landschneckenfauna Europas. 

Archiv für Molluskenkunde, 102: 77-84. 
ZILCH, A., 1960. Gastropoda, Teil 2, Euthyneura. In: SCHINDEWOLF, O. H., ed., Handbuch der 

Palàozoologie, 6(2)(4): 601-835, l-XII. 



MALACOLOGIA, 1979, 18: 147-149 

PROC. SIXTH EUROP. MALAC. CONGR. 

TAXONOMICAL STUDIES ON BULINUS USING ISOENZYME 

ELECTROPHORESIS WITH SPECIAL REFERENCE TO THE 

AFRICANUS GROUP ON KANO PLAIN, KENYA 

Jens Erik Jelnes 
Danish Bilharziasis Laboratory, Jaegersborg Alle ID, DK-2920 Charlottenlund, Denmark 

ABSTRACT 

Isoenzyme electrophoresis is shown to be an innportant aid in species discrimination in 
taxonomically difficult groups such as Bulinus. B. africanus and 8. nasutus do not show 
any phosphoglucose isomerase allozyme variation in the Nyanza Province, Kenya, and the 
mobilities of phosphoglucose isomerase are sufficiently different for identification using 
this particular character. 

Species of the planorbid genus Bulinus act as internnediate hosts for a number of 
Schistosoma species causing bilharzia in man and his livestock, while other species are of no 
importance in this context. Due to the great variability of morphological and anatomical 
characters, species of this genus are very difficult to tell apart. Thus at the Danish Bilharziasis 
Laboratory we have initiated a long term programme involving the study of by now up to 20 
enzymes in natural populations of Bulinus in order to improve the species determination. 

On the Kano Plain, Kenya, the distinction between the different species belonging to the 
africanus group is a very difficult matter (Brown, 1975; Southgate & Knowles, 1975, 1977). On 
a morphological basis the latter authors suggest the occurrence of hybrid populations between 
B. africanus and B. nasutus. 

In Fig. 1 the area covered by the samples is shown. In Fig. 2 a representative phospho- 
glucose isomerase zymogram of africanus group species is shown. In the table the mobilities and 
gene frequencies observed in the different samples are given. 

It is seen that the 2 species B. ugandae and B. globosus in Nyanza Province have the same 
mobilities in the phosphoglucose isomerase isoenzymes (Pgi-1.00, Pgi-1.25 and Pgi-1.36). 
However, a significant difference exists in the frequency of the alleles Pgi-1.00 being rare in B. 
ugandae (p = 0.03) and common in B. globosus (p = 0.33). None of the alleles found in these 2 
species have been observed in either B. africanus or B. nasutus from Kenya. B. africanus and B. 
nasutus do not show any phosphoglucose isomerase allozyme variation in the Nyanza Province 
samples and the mobilities of phosphoglucose isomerase observed in the 2 species are so 
different that an identification using this character is easily made. 

The samples which have been available from other areas of Kenya and Tanzania do not show 
any overlap in phosphoglucose isomerase mobilities, thus strongly indicating the usefulness of 
the phosphoglucose isomerase character. However, more live material is needed to clarify this. 
The data on the phosphoglucose isomerase isoenzymes presented here are further supported by 
data on other isoenzymes. 

LITERATURE CITED 

BROWN, D. S., 1975, Distribution of intermediate hosts of Schistosoma on the Kano Plain of Western 

Kenya. East African Medical Journal, 52: 42-51. 
SOUTHGATE, V. R. & KNOWLES, R. J., 1975, The intermediate hosts of Schistosoma bovis in Western 

Kenya. Transactions of the Royal Society of Tropical Medicine and Hygiene, 69: 356-357. 
SOUTHGATE, V. R. & KNOWLES, R. J., 1977, On the intermediate hosts of Schistosoma haematobium 

from Western Kenya. Transactions of the Royal Society of Tropical Medicine and Hygiene, 71: 82-83. 



(147) 



148 



PROC. SIXTH EUROP. MALAC. CONGR. 




500 Km 



FIG. 1. Map of Kenya and Tanzania giving location of towns. 1 Kisumu, 2 Nairobi, 3 Monnbasa, 4 Tanga, 5 
Mwanza, and 6 Iringa. 



+ 



Origin 



FIG. 2. Starch gel phosphoglucose isomerase isoenzyme pattern of whole aninnal extracts. 1 Bulinus ugandae 
Pgi-1.25, 2 B. ugandae Pgi-1.25/1.36, 3 B. africanus Pgi-1.44, and 4 B. nasutus Pgi-1.04. 



JELNES 



149 



TABLE 1. Phosphoglucose isomerase allele frequencies in populations of the fît/Z/nusafr/canus group from Kano 
Plain, Kenya, the Kenyan coast and Tanzania. N = number of wild snails tested. + = allele present in an old 
laboratory stock. 



Species and locality 



1.00 



Pgi alleles 



1.04 



1.25 



1.36 



1.44 



B. ugandae 

Kenya, Nyanza Province, Kisumu 1 
Kenya, Nyanza Province, Dunga 
Kenya, Nyanza Province, Kaloka 
Kenya, Nyanza Province, Aram Market 

B. globosus 

Kenya, Nyanza Province, Kisumu 1 

B. africanus 

Kenya, Nyanza Province, Kisumu 2 
Kenya, Nyanza Province, Kisumu 3 
Kenya, Nyanza Province, Kisumu 4 
Kenya, Nyanza Province, Kisumu 5 
Kenya, Eastern Province, Kinui 
Kenya, Eastern Province, Machakos 
Tanzania, Kalenga at Iringa 
Tanzania, Misungwi at Mwanza 

B. nasutus 

Kenya, Nyanza Province, Kisumu 2 
Kenya, Nyanza Province, Kisumu 3 
Kenya, Nyanza Province, Kisumu 4 
Kenya, Coast Province, Kinango 
Kenya, Coast Province, Tiwi 
Tanzania, Tanga Area, Muheza 
Tanzania, Tanga Area, Magila 
Tanzania, Tanga Area, Amani 
Tanzania, Misungwi at Mwanza 



0.08 
0.09 
0.03 
0.03 

0.33 



1.00 
1.00 
1.00 
1.00 
1.00 

0.83 

+ 
1.00 



0.89 0.03 

0.85 0.07 

0.95 0.02 

0.93 0.04 



0.63 



1.00 
0.17 

+ 



0.04 



18 
23 
39 
38 

12 





1.00 


2 




1.00 


10 




1.00 


2 




1.00 


5 




1.00 


3 




+ 




+ 






+ 







12 

14 

2 

14 

14 

3 

3 



MALACOLOGIA, 1979, 18: 151-156 

PROC. SIXTH EUROP. MALAC. CONGR. 

DIFFERENCIATION DES GENRES HOMALOCANTHA, JATON ET 

MAXWELLIA (GASTEROPODES, FAMILLE MURICIDAE) AU MOYEN 

DE LA STRUCTURE MICROSCOPIQUE DE LEUR COQUILLE 

Michel Petitjean 

Université Paris VII, Laboratoire de Physique des Systèmes Biologiques, 
12 Rue Cuvier, Paris Уте, France 

ABSTRACT 

Results of studies on the microscopical structure and mineralogical nature of the shells 
belonging to the muricid genera Homalocantha, Jaton and Maxwellia lead to taxonomic 
conclusions. The observed structures are consistent on the generic level (primary 
character; presence or absence of a calcitic cortex) or on the subgeneric level (secondary 
characters). Quantitative variation in the relative thickness of the layers, caused by 
ecological factors, does not influence the taxonomical conclusions. The genus Homa- 
locantha is easily distinguished from Jaton and Maxwellia in the shells being entirely 
aragonitic, while Jaton and Maxwellia have a calcitic cortex. On the other hand, there 
appears to be no difference between the species of the latter two genera as regards 
secondary characters (form of the connecting zone cortex-ostracum, relative thickness of 
the cortex, orientation of the leaflets of the first ostracal layer). One may conclude that 
other morphological characters are required to justify separating 7afo/7 and Maxwellia. 

La systématique des Muricidae est encore source de discussion et de problèmes, malgré les 
nombreux travaux qui lui ont été consacrés. Certains genres semblent bien connus, mais, en 
réalité, les espèces qui les constituent changent souvent de position taxonomique avec les 
auteurs. 

Un exemple en est fourni par le groupe d'espèces dont la suture présente à son contact avec 
les varices une série de "puits" assez profonds. Ces espèces sont actuellement réparties entre 
trois genres: Homalocantha Mörch, 1852, Jaton Pusch, 1837 et Maxwellia J. L. Baily jr., 1950, 
mais les avis des auteurs sur cette répartition sont loin d'être concordants. Il apparaît parmi ces 
espèces 2 types morphologiques assez distincts à l'oeil: certaines ont des varices foliacées et 
digitées comme Murex scorpio Linné, d'autres des varices arrondies comme Murex gemma 
Sowerby. Entre ces 2 types extrêmes, on trouve des espèces polymorphes comme Murex 
gibbosus Lamarck, polymorphisme qui peut sans doute être dû à des conditions écologiques 
(profondeur, agitation des eaux), comme cela a déjà été observé chez d'autres espèces. 

Nous avons appliqué à ces espèces les critères de différenciation que nous avons mis en 
évidence dans une précédente étude (Petitjean, 1965): il s'agit de la structure microscopique et 
de la nature minéralogique de la coquille. 

Le premier travail important sur ce sujet est dû à Carpenter (1845, 1848) qui a prouvé (1) 
que l'examen, fut-ce d'un petit fragment, est suffisant pour déterminer la structure de la 
coquille; (2) que la structure est qualitativement la même chez tous les individus d'une espèce; 
(3) que les structures sont indicatrices, à un degré élevé, des affinités zoologiques entre les 
espèces et, même, entre les genres. 

Ces conclusions ont été admises et vérifiées par tous les auteurs qui ont ensuite fait des 
études détaillées de la structure des coquilles, en particulier B<iggild (1930) et Kessel (1933, 
1936). Notre étude de plusieurs centaines d'espèces appartenant à la famille des Muricidae 
aboutissait aux mêmes résultats, à savoir: ou bien la coquille est entièrement aragonitique, ou 
elle est formée d'une couche interne d'aragonite (l'ostracum) et d'une couche externe de calcite 
(le cortex). Toutes les espèces d'un même genre sont du même type. Cette alternative constitue 
ce que nous avons appelé: "caractère primaire." 

Or Lowenstam (1954a, 1954b) prit le contre-pied des opinions admises jusque là. Il estimait 
que la nature minéralogique des coquilles, loin d'être fixée génétiquement, était un caractère 

(151) 



152 PROC. SIXTH EUROP. MALAC. CONGR. 

somatique fonction des seuls facteurs écologiques, surtout la température. Il admettait en 
particulier que l'aragonite pouvait exister seule chez les individus des mers tropicales et pouvait, 
au contraire, disparaître totalement, au bénéfice de la calcite, chez les individus des mers 
boréales. Nous avons déjà critiqué ce point de vue (Petitjean, loc. cit.) mais nous allons le 
refaire ici brièvement. 

Lowenstam n'a fait que des études par diagrammes de Debye et Scherrer in toto, sans jamais 
faire de lame mince de ses échantillons, donc sans voir leur structure microscopique. Il a utilisé 
une méthode "quantitative," mise au point simultanément par Sabatier (1953) et par Chave 
(1954), mais dont les insuffisances ont été mises en évidence ensuite par Davies & Hooper 
(1963). 

Si la théorie de Lowenstam était exacte, les pourcentages d'aragonite devraient varier au sein 
d'une espèce entre 0% et 100%. Si, au contraire, la structure se conserve qualitativement, et que 
les facteurs écologiques fassent seulement varier plus ou moins l'épaisseur relative du cortex et 
de l'ostracum, les valeurs des analyses doivent se placer entre des limites finies. Et c'est bien ce 
qu'on observe si on considère les propres résultats de Lowenstam, dans les cas où le nombre 
d'analyses est suffisant pour être significatif. De plus au sein de certaines espèces comme 
l\/lytilus edulis, Lowenstam lui-même donne des teneurs en aragonite plus faibles pour les 
individus de stations plus chaudes, ce qui est contraire à sa théorie. 

Autre critique: Lowenstam trouve peu d'aragonite dans les espèces boréales de certains 
"genres" et 100% d'aragonite dans les espèces tropicales. Mais il a adopté comme ouvrage de 
systématique celui de Thiele, dont les "genres" sont considérés aujourd'hui par tous les 
taxonomistes comme des super-genres ou des tribus. Si l'on en revient à la conception actuelle 
du genre, l'objection de Lowenstam ne tient plus, notamment en ce qui concerne l'argument 
majeur qu'il tirait de l'étude des Littorinidae: les espèces boréales, appartenant au genre 
Littorina, auraient un cortex calcitique, les espèces tropicales aragonitiques appartiennent à un 
tout autre genre: Melaraphe. 

Ces objections levées, nous pouvons donc appliquer nos critères d'étude dans le cas des 
espèces de Muricidae rapportées aux genres Homalocantha, Jaton et Maxwellia. 

Mörch (1852) a créé le genre Homalocantha pour le Murex scorpio Linné, qu'il prit pour 
espèce-type, mais il ne donna aucune description du genre. 

Pusch (1837) a créé le genre Jaton, en discutant l'hétérogénéité du genre Aquila Montfort, 
qu'il proposait d'écarter de la nomenclature. Il a pris comme espèce-type Murex decussatus 
Gmelin, synonyme de Murex gibbosus Lamarck et de "Le Jatou" d'Adanson. Il lui ajoutait des 
espèces sans affinités, comme Murex miliaris Gmelin qui est un Vitularia. Dans sa description du 
genre, il indique seulement que les espèces possèdent "des côtes transversales avec, entre elles, 
des sillons transverses profonds et un peristome très plissé." 

J. L. Baily jr. (1950) a créé le genre Maxwellia pour Murex gemma Sowerby, Murex 
santarosana Dali, Murex fimbriatus A. Adams et Murex (erinaceoides ?) indentatus Carpenter. Il 
refusait l'association de ces espèces avec Murex festivus Hinds, comme le faisaient Dali (1921) 
et Grant & Gale (1931). Effectivement cette espèce n'a pas de "puits" suturaux. Mais il niait 
aussi leur parenté avec Murex decussatus et le genre Jaton, qui en possèdent, sans en donner de 
raisons. 

Les auteurs de monographies des Muricidae, postérieurs à Mörch ont adopté des répartitions 
des espèces qui ne coincident pas entre elles, ni avec celles des auteurs précédents. G. B. 
Sowerby jr. met dans sa section IV: Murex festivus; V: Murex linguavervecina Chemnitz = M. 
lingua Dillwyn avec des espèces aujourd'hui placées dans le genre Cerostoma Conrad; VI: M. 
scorpio Linné, M. rota Sowerby, M. secundus Lamarck, M. varicosus Sowerby, M. digitatus 
Sowerby, M. fenestratus Chemnitz, M. gemma Sowerby et M. fimbriatus A. Adams (coquilles 
pyriformes avec des "puits" à la suture). 

Tryon (1880) reconnaissait le genre Homalocantha. Il y plapait les mêmes espèces que 
Sowerby sauf M. gemma et M. fimbriatus, mais faisait de cette dernière espèce un Phyllonotus, 
et de M. gemma un membre d'une section á'Ocenebra, où il l'unissait à M. tetragonus 
Broderip. Il plapait M. gibbosus dans une section de Pterynotus. Enfin, pour lui M. indentatus 
était synonyme de M. californicus Carpenter et de M. trialatus Sowerby, donc un Cerostoma. 

Enfin, dans sa monographie des Muricidae, Maxwell Smith (1953) adopte la répartition 
suivante: dans Homalocantha, les mêmes espèces que Tryon; dans Pterynotus: M. lingua et M. 
santarosana; dans "Muricidea"(l): Maxwellia gemma; dans Cerostoma, M. festivus. Enfin M. 
fimbriatus devenait un Typhisl 



PETITJEAN 153 

L'étude de la littérature rnontre donc une très grande confusion. Seul des 3 genres, 
Maxwellia a fait l'objet d'une description détaillée. La question reste donc entière, quant à la 
validité zoologique de ces genres; y en a-t-il 1, 2 ou 3? et, quelle est la bonne répartition des 
espèces entre les genres? 

Nous avons donc abordé le problème par notre méthode habituelle: dans chaque coquille, 
nous avons découpé des fragments de 5-8 mm de long, les uns parallèles aux stries d'accroisse- 
ment, les autres perpendiculaires à elles; ces fragments ont été meules pour en faire des lames 
minces que l'on a observées au microscope polarisant. En raison de la taille des cristaux, la 
calcite se distingue d'emblée de l'aragonite. Elle montre de plages d'extinction franche du blanc 
au noir, alors que l'aragonite présente des couleurs de polarisation et la structure bien connue 
en couches prismatiques et entrecroisées. La vérification de la nature minéralogique des couches 
séparées les unes des autres a été faite par des diagrammes de Debye et Scherrer, qui ont 
toujours confirmé l'observation optique. 

Nous n'avons pu, faute d'échantillons, étudier toutes les espèces supposées appartenir à ces 3 
genres. Nous avons examiné M. scorpio, M. rota, M. digitatus, M. fenestratus, M. heptagonatus 
pauli Tournoue (qui avait été placée de façon erronée dans le genre Favartia par Cossmann & 
Peyrot, 1924), M. gibbosus, M. lingua, M. gemma, M. santarosana, M. festivus, M. californicus. 
Ces échantillons provenaient des doubles des collections du Museum National d'Histoire 
Naturelle de Paris, comme la collection Jousseaume. Leur lieu de récolte est donc moins précis 
que ce à quoi l'on est habitué pour les récoltes actuelles. M. scorpio provient des Philippines, M. 
rota de la Mer Rouge, M. gibbosus et M. lingua du Sénégal, M. festivus, M. gemma, M. 
santarosana et M. californicus de Californie, M. heptagonatus pauli du Tertiaire d'Aquitaine. 

Résultats: les espèces rattachées habituellement au genre Homalocantha (M. scorpio, M. rota, 
M. heptagonatus pauli, M. digitatus, M. fenestratus) sont entièrement aragonitiques (Fig. 1). 

Par opposition avec ce groupe d'espèces, toutes les autres possèdent un cortex calcifique 
(Fig. 2). Le critère primaire (présence ou absence d'un cortex calcifique) nous conduit donc à 
une différenciation entre: d'une part Homalocantha, aragonitique; d'autre part Jaton et 
Maxwellia, à cortex calcifique. 

A côté du caractère primaire, nous avions observé que des distinctions étaient parfois 
possibles, dans les genres à cortex, entre genres différents ou sous-genres, sur la base des 
caractères secondaires: forme de la zone de jonction entre cortex et ostracum, importance 
relative du cortex par rapport à l'ostracum, orientation des lames de la couche externe de 
l'ostracum, etc. Nous avons donc étudié chez les espèces de Jaton et de Maxwellia ces 
caractères secondaires, pour y détecter les différences éventuelles. 

La zone de jonction entre le cortex et l'ostracum est souvent bien visible car elle est 
marquée en général par un dépôt de conchioline. Chez M. gibbosus (Fig. 3) et M. lingua, elle 
suit exactement les ornementations de la surface externe de la coquille. Il en est de même chez 
M. festivus. Chez M. gemma, la zone de jonction est plus régulière, plus aplatie, et suit de plus 
loin les ornementations externes. Chez M. santarosana (Fig. 4), la zone de jonction présente des 
ondulations dont la "longueur d'onde" et l'amplitude sont une sorte de "négatif" de la surface 
externe: l'amplitude diminue et la "longueur d'onde" augmente au niveau des ornementations 
en relief; c'est le contraire dans les zones plus lisses de la coquille. Ceci a pour effet de donner 
au cortex une épaisseur irrégulière: il est plus épais au niveau des tubercules ornementaux; il est 
plus mince et plus "tourmenté" entre ceux-ci. Cependant, s'il existe bien certaines différences 
entre les espèces étudiées, il ne semble pas qu'elles soient assez marquées pour justifier une 
distinction générique. 

L'importance du cortex est à peu près la même dans les 5 espèces. Il forme le 1/5 ou le 1/6 
de l'épaisseur totale de la coquille. 

L'ostracum est formé de 3 couches (4 chez un M. gibbosus, mais nous savons qu'au delà de 
3 couches, ceci peut-être un phénomène d'épaississement individuel). Les feuillets formant la 
couche la plus externe sont dans les 5 espèces perpendiculaires aux stries d'accroissement. 

Donc, aucun des caractères structuraux secondaires ne permet de justifier la séparation des 
Jaton et des Maxwellia en genres distincts. Il faudrait, pour le faire, se référer à d'autres critères 
morphologiques. L'opercule, figuré par Vokes (1964) ^our Maxwellia a un nucleus sub-basal qui 
paraît peu différent de certains opercules purpuroides, où la latéralité du nucleus est peu 
marqué. L'opercule des espèces de Jaton n'a jamais été figuré. 

Les différences entre les deux genres reposent actuellement sur leur répartition géographique 



154 



PROC. SIXTH EUROP. MALAC. CONGR. 




FIG. 1. Structure de la coquille dans le genre Homalocantha: H. heptagonatus pauli. Coupe parallèle aux 
stries d'accroissement, X50. 




FIG. 2. Structure de la coquille dans le 'genre' Maxwellia: M. gemma. Coupe parallèle aux stries d'accroisse- 
ment, X375. 



PETITJEAN 



155 




FIG.3. Structure de la coquille dans le 'genre' Jaton: J. gibbosus. Coupe perpendiculaire aux stries 
d'accroissement, X50. 




FIG. 4. Structure de la coquille dans le 'genre' Maxwe/lia: 
d'accroissement, X100. 



M. santarosana. Coupe perpendiculaire aux stries 



156 PROC. SIXTH EUROP. MALAC. CONGR. 

(Jaton, en Afrique, Maxwellia dans le Pacifique américain) et le nombre des varices assez 
nombreuses chez les Maxwellia, alors qu'il n'y en a que 3 chez Jaton. 

On séparera M. festivas de ces 2 genres, si on considère que les "puits" de la suture en sont 
une caractéristique. Cette espèce pourrait alors, soit être rattachée au genre Ocenebra (bien que 
les espèces américaines pacifiques du genre aient en général une orientation des feuillets de la 
première couche de l'ostracum, parallèles aux stries d'accroissement), soit laissée incertae sedis 
pour le moment, conclusion qui paraît moins hasardeuse. 

Conclusions: En tenant compte, à la fois, des travaux des autres auteurs et de nos propres 
études sur la structure microscopique et la nature minéralogique de la coquille des Muricidae, 
nous arrivons à la répartition suivante des espèces: 

—dans le genre Homalocantha (entièrement aragonitique): M. scorpio, M. rota, M. digitatus, 
M. fenestratus, M. heptagonatus pauli; 

—dans le genre (?) Jaton (à cortex calcitique): M. gibbosus, M. lingua; 

—dans le genre (?) Maxwellia (à cortex calcitique): M. gemma, M. santarosana; 

—incertae sedis: M. festivus. 

LITERATURE CITEE 

BAILY, J. L., 1950, Maxwellia, genus novum of Muricidae. Nautilus, 64: 9-14. 

BQÍGGILD, о., 1930, The shell structure of the mollusks. Kongelige Danske Videnskabernes Selskabs Skrifter, 

(9)2: 231-326. 
CARPENTER, W., 1845, On the nnicroscopic structure of shells. Report of the British Association for the 

Advancement of Science, 14: 1-24. 
CARPENTER, W., 1848, Report on the microscopic structure of shells. Report of the British Association for 

the Advancement of Science, 17: 93-134. 
CHAVE, К., 1954, Aspects of biogeochemistry of magnesium. 1) Calcareous marine organisms. Journal of 

Geology, Chicago, 62: 266-283. 
COSSMANN, M. & PEYROT, A., 1924, Conchologie neogénique de l'Aquitaine, t.lV, Gastéropodes. Actes de 

la Société Linnéenne de Bordeaux, 75: 193-318. 
DALL, W. H., 1921, Summary of the marine shellbearing mollusks of the north-west coast of America, from 

San Diego, California, to the Polar Sea, mostly contained in the collection of the United States National 

Museum, with illustrations of hitherto unfigured species. Bulletin of the United States National Museum, 

112: 1-217. 
DAVIES, T. & HOOPER, P., 1963, The determination of calcite: aragonite ratio in mollusc shells by X-Ray 

diffraction. Mineralogical Magazine, 33: 608-612. 
GRANT, U. S. & GALE, H. R., 1931, Catalogue of the marine Pliocene and Pleistocene Mollusca of 

California and adjacent regions . . . together with a summary of the stratigraphie relations of the 

formations involved. Memoirs of the San Diego Society of Natural History, 1: 1-1036. 
KESSEL, E. VON, 1933, Über die Schale von Viviparus viviparus L. und Viviparus fasciatus Müll. Ein Beitrag 

zum Strukturproblem der Gastropodenschale. Zeitschrift für Morphologie und Oekologie der Tiere, 27: 

129-198. 
KESSEL, E. VON, 1936, Über den Bau der Haliotisscba\e. Zoologischer Anzeiger, 113: 290-299. 
LOWENSTAM, H., 1954a, Environmental relations of modification compositions of certain carbonate 

secreting marine invertebrates. Proceedings of the National Academy of Sciences of the U.S.A., 40: 39-48. 
LOWENSTAM, H., 1954b, Factors affecting the aragonite: calcite ratios in carbonate secreting marine 

organisms. Journal of Geology, Chicago, 62: 294-332. 
MORCH, O. A. L., 1852, Catalogus conchyliorum quae reliquit D. Alphonso d'Aguirra & Gadea, comes de 

Yoldi. Copenhague, 2 fascicules, 172 + 76 p. 
PETITJEAN, M., 1965, Structures microscopiques, nature minéralogique et composition chimique de la 

coquille des Muricidés (Gastéropodes, Prosobranches). Importance systématique de ces caractères. Thèse de 

Doctorat d'Etat-ès-Sciences Naturelles, 02.04.1965, Paris, Série A, no. 4493, no. d'ordre 5340, 128 p. 
PUSCH, G. G., 1837, Polens Paläontologie oder Abbildung und Beschreibung der vorzüglichsten und der 

noch unbeschriebenen Petrefacten aus den Gebirgsformationen in Polen, Volhynien und den Karpathen. 

Stuttgart, 218 p. 
SABATIER, G., 1953, Application de la diffraction des Rayons-X à l'étude des coquilles de mollusques. 

Cahiers des Naturalistes (Bulletin des Naturalistes Parisiens), N.S., 8: 97-102. 
SMITH, M., 1953, An illustrated catalog of the recent species of tJie Rock Shells, Muricidae, Thaisidae and 

Coralliophilidae. Edwards Brothers, 84 p. 
SOWERBY, G. В., 1880, Thesaurus Conchyliorum or monographs of genera of shells, Л, Murex, 1st division: 

26-27; 2nd division: 31-32. Sowerby, London. 
TRYON, G. W., jr., \ZZO, Manual of Conchology, structural and systematic, (1)2, Muricidae, Purpuridae: 1-289. 

Tryon, Philadelphia. 
VOKES, E. H., 1964, Supraspecific groups in the subfamilies Muricinae and Tritonaliinae (Gastropoda: 

Muricidae). Malacologia, 2: 1-41. 



MALACOLOGIA, 1979, 18; 157-161 

PROC. SIXTH EUROP. MALAC. CONGR. 

ALBINISM IN THE GENUS ANC/ LLA (GASTROPODA, OLIVIDAE) 

Henry E. Coomans 
Zoological Museum, Amsterdam, the Netherlands 

ABSTRACT 

In the shell of molluscs a great variability in colour forms can often be observed. Two 
forms have received special names: black is called melanism, white {= the lack of any 
colour) is called albinism. Partial albinism is also known. In the Cypraeidae melanism is 
known from a number of species. Albinism is rare, but seems scattered throughout all 
groups of the gastropods. However, albinism seems to occur more often in Ancilla. The 
genus Ancilla (fam. Olividae) contains about one hundred recent species; more than ten 
subgenera can be recognized. They are living in marine tropical and subtropical waters. 
The shell is mostly coloured yellow-orange-brown. From the collection of the Zoological 
Museum in Amsterdam and from the literature at least ten species are known to have 
(partial) albinistic forms. Some of these albinos were originally described as distinct 
species, like Ancilla candida (Lamarck) and A. nivea (Swainson). 

INTRODUCTION 

Colour variation of molluscan shells has always attracted the attention of malacologists. In 
many species these colour forms received names. In older literature they were described as 
varieties, like var. alba, aurea, nigra, rubra, viridis, etc. In modern literature they are considered 
to be colour forms, forma rubra, etc. 

General terms are being used for two colour forms: black colouration is called melanism, 
white is known as albinism. These 2 terms are not only used for shells, they are valid in all 
groups of animals. Within the gastropods melanism is known from several species of Cypraeidae 
(Cernohorsky, 1963). The reference list in Old (1964) comprises the literature on melanistic 
Cypraeidae. Black specimens of Cypraea are known in particular from New Caledonia, like 
Cypraea arabica niger, C. stolida crossei, С caurica thema, and C. eglantina. Some metals, found 
on New Caledonia and in the waters around this island, are thought to have caused these 
melanistic shells. It is therefore considered an ecological factor. 

Albinism is the lack of any colour. It is known from most classes of the animal kingdom. 
When both parents are albino, their offspring is albinistic as well. Therefore albinism is 
hereditary, and caused by mutation.' In "partial albinism" the animal is only partially white. 

Not all white shells should be regarded as albinos. Sometimes the natural colour of the shell 
is white, as in many Epitonium species and in the Lucinidae. In collections the original colour 
of the shells may have faded through the influence of daylight. Shells found on the beach are 
often bleached by sunlight. Many fossil shells have become white in time. 

Albinos are sometimes described as formae of the normal shell, usually with the indication 
alba (= white), candida (= shiny white), nivea (= snow white), or virgínea (= virgin-like). 

Albinism is rare; in gastropods it is known from a very limited number of species only. Mrs. 
Waverley H. Harmon of New York has a special interest in albino shells, and has collected them 
for about 15 years. Her albino collection now contains a little over 100 species, both 
gastropods and bivalves, from a number of families, including land, marine and freshwater 
molluscs. It is therefore obvious that albinism is rare, and scattered throughout all taxa of the 
gastropods. However, from literature and the collection of the Zoological Museum, Amsterdam 
(= ZMA), it appears that albinism occurs more often in shells of the qenus Ancilla. 



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158 PROC. SIXTH EUROP. MALAC. CONGR. 

ALBINISM IN ANCILLA 

The genus Ancilla Lamarck, 1799 (syn. Ancillaria Lamarck, 1811) belongs to the family 
Olividae of the Prosobranchia. About 100 Recent species are known, which are placed in ten 
subgenera. The species of Ancilla are living in (sub)tropical marine waters. Most of them are 
found in the Indopacific area, some subgenera having a limited distribution, such as Sparella 
from the Red Sea to the Persian Gulf, and Anolacia around Madagascar and Mauritius. The 
subgenus Eburna occurs from the southern Caribbean Sea to the coast of Brazil. Furthermore 
species of Ancilla are found around South Africa, South Australia, and New Zealand. Recent 
species of Ancilla are not known from the tropical eastern Pacific, nor from the Mediterranean 
Sea and West Africa. However, fossil Ancilla are known from Europe and North America. 

The shell of Ancilla is elongate to fusiform, and solid; length 1-10 cm; the surface is smooth 
and glossy; spire high and conical; aperture rather wide, often with parietal callus, columella 
twisted and grooved; colour yellow, orange, brown, and white; operculum small. 

Albinistic specimens are known from the following species. 

Subgenus Ancilla s.s. 

Ancilla ampia (Gmelin, 1791) from the Indian Ocean is yellow coloured (Fig. la). One 
albino shell from Ceylon (Fig. lb) is present in the collection of ZMA. Evidently albinism is 
not rare within this species, as the albino form was described as Ancillaria candida Lamarck, 
1811. Albinistic specimens were also figured by Sowerby II (1859, pi. 212, fig. 29) and Reeve 
(1864, pi. 8, fig. 27a). 

Subgenus /4/7c/7/iys Montfort, 1810 

Ancilla muscae Pilsbry, 1926. This is a new name for Ancillaria elongata Gray, 1847, non 
Deshayes, 1830. The species is living in Australia, the shell is white. Normally the upper part of 
the spire is covered with a brown periostracum (Fig, 2a). When the periostracum is removed, a 
white shell (Fig. 2b) remains, giving the impression of an albino. This is an example of 
pseudo-albinism. Sowerby II (1859, pi. 213, figs. 52-53) also figured a white specimen next to 
one with the brown periostracum. 

Subgenus Spare//a Gray, 1857 

Ancilla fulva (Swainson, 1825) from the Red Sea is cream to light brown (Fig. 3a). One 
albino (Fig. 3b) is in the collection of ZMA. Sowerby II (1859, pi. 214, fig. 75) also figured an 
albino. 

Ancilla cinnamomea Lamarck, 1801, is from the Red Sea and Persian Gulf area. The shell is 
brown, the spire has brown and white bands (Fig. 4a). The ZMA collection contains some 
partial albino shells (Fig. 4b), which have the spire banded, but the last whorl is completely 
white. Ancilla tronsoni (Sowerby II, 1859) is considered a synonym of A. cinnamomea by 
Burch & Burch (1960). As A. tronsoni is pure white (Sowerby II, 1859: 58, pi. 212, figs. 20-21) 
it must be the albino form of cinnamomea. 

Ancilla castanea (Sowerby I, 1830) is a chestnut coloured species from the Red Sea. Ati 
albino is figured by Sowerby II (1859, pi. 214, fig. 76). 

Subgenus /4A7o/ac/a Gray, 1857 

Ancilla mauritiana (Sowerby I, 1830), syn. A. torosa (Sowerby II, 1859), is found around 
Madagascar and Mauritius. It is the only species in this subgenus. Next to the brown coloured 
shells (Fig. 5a) albinos are often seen in collections (Fig. 5b). The albinistic form is also known 
in literature (Sowerby II, 1859, pi. 212, fig. 31). The coloured juveniles of this species were 
named Ancilla aperta (Sowerby I, 1825), and juvenile albinos were described and figured by 
Sowerby II (1859: 58, pi. 212, figs. 37-38) as Ancillaria scaphella. 

Subgenus Ebiyrna Lamarck, 1801 

Ancilla glabrata (Linné, 1758) has a very limited range in the southern Caribbean. The island 
of Aruba seems to be the centre of its distribution. It is one of the largest species of the genus 
Ancilla; the ZMA collection contains a specimen of 75 mm length. The shell is yellow (Fig. 6a). 



COOMANS 



159 




F\G. ^. Ancil/a (Ancilla) ampia (Gmelin). a. Yellow, length 23.1mm, Ceylon, b. Albino = A. candida 

(Lamarck), length 29.4 mm, Ceylon. 

FIG. 2. Ancilla (Ancillus) muscae Pilsbry. a. White with brown spire, length 43.5 mm, W. Australia, Exmouth 

Gulf. b. Pseudo-albino, length 36.7 mm, Australia, Torres Strait. 

FIG.3. Ancilla (Sparella) fulva (Swainson). a. Cream coloured, length 31.6 mm, Red Sea. b. Albino, length 

29.8 mm, Saudi Arabia, Jubail. 

FIG. 4. Ancilla (Sparella) cinnamomea Lamarck, a. Brown, length 26.1, mm Persian Gulf. b. Partial albino, 

white with brown band around the suture, length 27.4 mm, Persian Gulf. 

(Specimens in collection Zoological Museum, Amsterdam, photographs by L. A. van der Laan). 



160 



PROC. SIXTH EUROP. MALAC. CONGR. 




FIG. 5. Ancilla (Anolacia) mauritiana (Sowerby I) a. Brown, length 41.7 mm, Madagascar, b. Albino, length 

41.8 mm, Madagascar. 

FIG. 6. Ancilla (Eburna) glabrata (Linné), a. Yellow, length 71.8 mm, Aruba. b. Albino, length 71.9 mm, 

Aruba. 

FIG. 7. Ancilla (Eburna) balteata (Swainson). a. Yellow, length 39.5 mm, West Indies, b. Albino = A. nivea 

(Swainson), length 50.3 mm, Antilles. 

FIG. 8. Ancilla (Eburna) lienardi (Bernardi). Yellowish-brown, length 31.2 mm, Brazil, Acaraù, Cearà. 

FIG. 9. Ancilla (Eburna) tankervillei (Swainson). Yellow, length 56.5 mm. Venezuela, Isl. Margarita. 

(Specimens in collection Zoological Museum, Amsterdam, photographs by L. A. van der Laan). 



COOMANS 161 

The figured albino (Fig. 6b) is very large too. Albino specimens are also known from the 
literature (Sowerby II, 1859, pi. 213, fig. 63). 

Ancilla balteata (Swainson, 1825) is known from the same area as the former species. 
However, in literature and in old collections it is mentioned from Ceylon. This species is 
closely related to A. glabrata, but smaller and with a shouldered shell (Fig. 7a). The colour is 
orange-yellow. Albino specimens (Fig. 7b) were described as Ancillaria nivea Swainson, 1825. 
Sowerby II (1859: 66) considered A. balteata and A. nivea to be distinct species, both from 
"Ceylon." Reeve (1864, spec. 49) already recognized the synonymy, he mentioned the relation 
with A. glabrata, and gave A. balteata a West Indian distribution, i.e. "probably Gulf of 
Mexico." 

Ancilla lienardi (Bernardi, 1858) from the coast of Brazil has a yellowish-brown to 
reddish-orange shell (Fig. 8). We have not seen any albino of this species; however, Reeve 
(1864, spec. 50) figured an albino (pi. 12, figs. 50c-d) next to a coloured specimen (figs. 
50a-b). 

Ancilla tankervillei (Swainson, 1825) is known from Venezuela (Isl. Margarita) and the north 
coast of Brazil. The shell is coloured yellow (Fig. 9). The collection of ZMA does not have any 
albino, but a white specimen is figured by Sowerby II (1859, pi. 211, fig. 5). 

DISCUSSION 

Although albinism is very rare in the Gastropoda, it is remarkable that in the genus Ancilla, 
with about 100 species, albinos are known from at least 9 species. In most of these 9 species, 
albino specimens are not rare at all, so we may conclude that albinism is rather common in 
Ancilla. Albinism in Ancilla occurs in a number of subgenera, and is not connected with any 
zoogeographical province. Albino Ancilla species are known from the Indian Ocean, Red Sea, 
and the West Indies. 

LITERATURE CITED 

BURCH, J. Q. & BURCH, R. L., 1960, Catalogue of Recent and fossil Olives. Minutes of the Conchological 

Club of Southern California, 196: 1-46. 
CERNOHORSKY, W. O., 1963, Rostration and melanism in Cypraea. The Cowry, 1: 70-72. 
OLD, W., 1964, Status of Cypraea arabica niger. The Cowry, 1: 97-99. 

REEVE, L. A., 1864, Monograph of the genus /4пс///ал/э. Conchologia ¡cónica, 15, pis. 1-12. London. 
SOWERBY, G. B. (I), 1830, Monograph of the genus /4nc/7/ar/a. Species Conchyliorum, 1(1): 1-10, 3 pis. 

London. 
SOWERBY, G. B. (II), 1859, Monograph of the genus Ancillaria, Lamk. Thesaurus Conchyliorum, 3: 57-67, 

pis. 211-214, London. 



MALACOLOGIA, 1979, 18: 163-167 

PROC. SIXTH EUROP. MALAC. CONGR. 

ALEXANDER CROSBIE AND THE "CHALLENGER" TEREDO 

David Heppell 
Royal Scottish Museum, Edinburgh, Scotland 

ABSTRACT 

Alexander Crosbie was staff-surgeon aboard HMS "Challenger" during her circum- 
global expedition of 1873-76. His private collection of shells in the Royal Scottish 
Museum, Edinburgh, contains 4 shells labelled "Xylophaga dorsalis from fruit of screw 
pine (palm) [Pandanus] . 1400 fms. 29/8/7A" ["Challenger" station 184, off Cape York, 
Queensland]. No Xylophaga from this or any other station appears in the "Challenger" 
report on the Lamellibranchiata (Smith, 1885), but a juvenile specimen of an unnamed 
species of Teredo is recorded from this station. Moseley (1895), quoted in the summary 
of results of the expedition, writes: "The trawl brought up half a dozen large palm 
fruits . . . the husks were bored by the young of a Terec/o-like bivalve." Examination of 
the "Challenger" material at the British Museum (Natural History) showed that there are 
actually 2 specimens, preserved in spirit, both very damaged and very small but 
undoubtedly Xylophaga and conspecific with Crosbie's specimens. The wide-spread 
occurrence of deep-water species of Xylophaga was not known until Knudsen (1961) 
described 17 species taken from depths greater than 900 m by the "Galathea" expedition 
of 1950-52. Comparison of Crosbie's specimens and Knudsen's descriptions and figures 
identifies them as X. wolffi, previously known only from the 2 "Galathea" specimens 
taken from 5050 m in the Sulu Sea. 



In the "Challenger" Report on the Lannel I ¡branch lata (Smith, 1885: 27) the first species, 
under the heading Teredo sp., is described as follows: "A single very small specimen, all that 
was obtained, may possibly be the young state of the Teredo mentioned in the Report of the 
collections made during the Voyage of HMS "Alert" in Torres Strait. The striae on the anterior 
part of the valves are, however, rather coarser. Although from Station 184, to which a depth of 
1400 fathoms is assigned, it seems probable that this shell, which contained the animal, got into 
the trawl near the surface, during the process of hauling in. This, however, is not certain, for 
water-logged wood might be found at that depth into which it might bore." 

Smith's uncertainty as to the provenance of this species was resolved by Moseley (in Murray, 
1895: 681) who observed that at Station 184, off Cape York, Queensland: "The trawl brought 
up half a dozen large palm fruits ... the husks were bored by the young of a Teredo-like 
bivalve." No mention of this material was made by Turner (1966: 55-56) in her account of the 
occurrence of Teredinidae in deep water, and the identity of the "Oiallenger" Teredo might 
have remained conjectural had it not been for new evidence from an unexpected quarter. 

Late in 1971, in preparation for an exhibition at the Royal Scottish Museum to mark the 
"Challenger" centenary, the Crosbie collection of shells was examined as a possible source of 
specimens for display. Alexander Crosbie (Fig. 1) was staff-surgeon aboard HMS "Challenger" 
during her circumglobal expedition of 1873-76. His interest in natural history was considerable, 
and he took the opportunity afforded by the voyage to add to his collection of shells, which 
was presented to the Royal Scottish Museum in 1927. Amongst his "Challenger" material was a 
box labelled: "Xylophaga dorsalis from fruit of screw pine (palm). 1400 fms. 29/8/74." The 
date of collection and the depth identified the locality of Station 184, but the identity of the 
specimens was obviously incorrect, as X. dorsalis (Turton, 1819) is a coastal species of the NE 
Atlantic and Mediterranean. 

Within the box, apart from 4 specimens of a Xylophaga, were 6 specimens of Myrina 
coppingeri Smith, 1885, a mytilacean described from Station 184 as a new species as yet 
unreported from any other locality, and three specimens of a small, unidentified and possibly 
undescribed gastropod. Of the 4 specimens of Xylophaga (RSMNH 1927.120.128) 3 are 

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164 



PROC. SIXTH EUROP. MALAC. CONGR. 




FIG. 1. Alexander Crosbie, Surgeon, R.N. 



complete; the valves are attached, being held together by the dried remains of mantle tissue still 
adhering to the shell, and the accessory plates are in place although some distortion of their 
position has occurred in the smallest specimen. In the 4th specimen the valves have separated 
and the accessory plates have been lost. 

Comparison of these specimens with the descriptions and illustrations of bathyal and abyssal 
Xylophaga collected by the "Galathea" expedition and reported by Knudsen (1961) established 
their identity with X. wolffi Knudsen, 1961, known only from 2 "Galathea" specimens with 
adhering juveniles taken from 5050 m in the Sulu Sea. The dimensions (in mm) of the largest 
of the RSM specimens are: length 12.2, height 11.2, breadth 12.5; the umbonal area is eroded 
as in the "Galathea" specimens (Knudsen, 1961: 187, fig. 29). The figured specimen (Figs. 2-3) 
is free from erosion; its dimensions are 11.2, 11.0, 11.7mm. For comparison, the dimensions of 
Knudsen's type are 8.5, 8.9, 8.9 mm. 

Although the Crosbie collection provided evidence that the "Challenger" had obtained 
specimens of X. wolffi from off Cape York it remained to discover whether the specimen 
described by Smith was the same. Turner (1966: 56) mentioned the occurrence of living 
Teredothyra smithi (Bartsch) from the same "Galathea" station as yielded X. wolffi, so the 
co-existence of a Xylophaga and a teredinid in deep water was a possibility. Investigation of the 
"Challenger" material at the British Museum (Natural History) revealed that there are in fact 2 
specimens, preserved in alcohol (BMNH 1889.11.11.153), both very small and very damaged. 

The larger specimen (Figs. 4, 5, 8, 9) is 6.9 mm long. The right valve is fragmentary, and 
only the disc and part of the anterior slope of the left valve remain. Fortunately the contracted 
incurrent siphon and the aperture of the excurrent siphon with 6-7 small tentacles on each side 
and a larger tentacle posterior to the aperture can be distinguished. The form of the siphons is 
an important taxonomic character in the Xylophaginae, and there is a close correspondence 



HEPPELL 



165 





FIGS. 2-3. Xylophaga wolffi Knudsen, RSMNH 1927.120.128. 



between the siphons visible in this specimen and those of X. и /o/ff/ figured by Knudsen (1961: 
188, fig. 30b). 

The smaller specimen (Figs. 6, 7, 10, 11) is 2.5 mm long. The right valve is fragmentary but 
the left valve is more or less intact. The siphons are not visible but sufficient characters remain 
to establish that it is a Xylophaga and not a teredinid: the adhesive surface of the foot is 
surrounded by a pedal ridge, the anterior fold of the mantle (exposed by the missing mesoplax) 
is visible in the anterior incision overlaying the anterior adductor muscles, and the umbonal- 



166 



PROC. SIXTH EUROP. MALAC. CONGR. 







FIGS. 4-7. "Teredo" sp., BMNH 1889.11.11.153. Damage to the shells has resulted in the mantle and visceral 
mass being squeezed out around the broken edges of the valves. 



ventral ridge of the right valve (corresponding on the inner surface of the shell to the 
umbonal-ventral sulcus of the outer surface) is visible where a broken fragment of that valve has 
been displaced away from the mantle. The sculpture on the anterior slope and beak of the left 
valve corresponds closely to that on the Crosbie specimens. Diagrams have been provided (Figs. 
8-11) to aid in the interpretation of the damaged specimens (Figs. 4-7); the terminology used in 
the diagrams and elsewhere in this paper is based on that established by Purchon (1941) and 
Turner (1955). 

It was concluded from the above investigation that the "Teredo sp." of the "Challenger" 
Report is Xylophaga wolffi Knudsen, 1961. The "Alert" Teredo from Torres Strait was also 
examined (BMNH 1881.11.10.174-5). Only a single right valve was present in the box. The 
presence of a apophysis and the lack of an umbonal-ventral ridge indicated that this specimen is 
a teredinid and not a Xylophaga. 



HEPPELL 



167 




AM 






FIGS. 8-1 1. Diagrams of the specimens illustrated in Figs. 4-7. A = anterior slope; AM = anterior mantle fold; 
В = beak; D = disc; ES = excurrent siphon; F = foot; IS = incurrent siphon; LV = left valve; M = mantle 
edge; P = stained area of periostracum; PR = pedal ridge; R = umbonal-ventral ridge; RV = right valve; S = 
umbonal-ventral sulcus; U = eroded area adjacent to umbo. 



LITERATURE CITED 



KNUDSEN, J., 1961, The bathyal and abyssal Xylophaga (Pholadidae, Bivalvia). Galathea Report. 5: 

163-209. 
MURRAY, J., 1895, A summary of the scientific results obtained at the sounding, dredging, and trawling 

stations of H.M.S. Challenger. Report of the Scientific Results of the Voyage of H.I\4.S. Challenger 

1873-76 (Summary), 1: 1-796. 
PURCHON, R. D., 1941, On the biology and relationships of the lamellibranch Xylophaga dorsalis (Turton). 

Journal of the marine biological Association of the United Kingdom, (N.S.) 25: 1-39. 
SMITH. E. A., 1885, Report on the Lamellibranchiata collected by H.M.S. Challenger during the years 

1873-76. Report of the Scientific Results of the Voyage of H.M.S. Challenger 1873-76 (Zoology), 13(35): 

1-341. 
TURNER, R. D., 1955, The family Pholadidae in the western Atlantic and the eastern Pacific. Part 

II— Martesiinae, Jouannetiinae and Xylophaginae. Johnsonia, 3(34): 65-160. 
TURNER, R. D., 1966, A survey and illustrated catalogue of the Teredinidae (Mollusca: Bivalvia). Museum of 

Comparative Zoology, Cambridge, Massachusetts, 265 p. 



MALACOLOGIA, 1979, 18: 169-176 

PROC. SIXTH EUROP. MALAC. CONGR. 

PRIMARY SUCCESSION OF LAND MOLLUSCS IN AN 
UPLIFT ARCHIPELAGO OF THE BALTIC 

llmari Valovirta 

Zoological Museum, University of Helsinki, 
P. Rautatiekatu 13, SF-00100 Helsinki 10, Finland 

ABSTRACT 

In the archipelago of Quarken, Gulf of Bothnia, primary succession is controlled by 
land uplift. The successional changes of both vegetation and land mollusc malacocenosis 
is best demonstrated on islets of less than 10 ha. The age of the islands can be calculated 
according to the altitude above sea level, but besides age, also isolation, area and 
ecological factors have a considerable effect on the mollusc fauna. The number of land 
mollusc species found on the islands reflects the succession: islands of the first stage are 
inhabited by 1-6 species, the 2nd stage by 7-12 species, and the last stage by more than 
12 species. On the outer uplift archipelago there are 5 typical pioneer species, viz. 
Vallonia pulchella, Deroceras agreste, Oxyloma pfeifferi, Deroceras laeve, and Vertigo 
alpestris. Moreover, there are some species which can be considered as species of a late 
successional stage and many species from in between these stages. Whether studying 
primary succession on whole islands or in different habitats the results will be very 
similar as regards pioneer species and also species of later successional stages. The species 
diversity derived from Shannon's measure of diversity H' and the evenness J' will increase 
with succession. 

INTRODUCTION 

Primary succession is a dynamic phenomenon. In the area studied it is controlled by land 
uplift. The sequence of biocenoses goes from somewhat grassy shores (open meadows), thickets 
to forests. Primary succession is usually connected with time-consuming changes in the 
composition of the malacocenosis. In the extreme conditions pioneer communities may persist 
for a fairly long time. 

Of the many aspects which are more or less significant for primary succession, e.g. biomass, 
production, diversity, uniformity and stability, I shall deal with the factors controlling speed of 
the primary succession, changes within species composition, pioneer species and successional 
order of species in different biotopes. Moreover, I will deal with species diversity, since 
variations in the diversity are positively correlated with stability of various biotic and abiotic 
components of ecosystems (Leigh, 1965; Margalef, 1968; Slobodkin & Sanders, 1969; 
Whittaker, 1975). 

THE STUDY AREA AND THE AGE OF ISLANDS 

The study area, the Quarken archipelago, is at the centre of the land uplift area in the 

northern Baltic (63°N, 22°E). The earth's crust is rising at a rate of 0.8 m per century. Within 

the last 9000 years the Quarken region has risen about 250 m (Kääriäinen, 1953). The age of 

an island of known height has been calculated according to the formula (see Okko, 1967; 

Kukkamäki, 1971) 

. ,. PH 
In (1 +^) 

ln(1+P) 
T = the age of the island 
H = height of island (m) 
V = recent relative uplift (0.8 m/century) 
P = magnitude of retardation (about 1.6%/century) 

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170 



PROC. SIXTH EUROP. MALAC. CONGR. 



Because the land is flat, especially on the Finnish side of the Quarken archipelago, new islets 
continuously appear and the area of the existing islands enlarges. Thus, the area is extremely 
suitable for studying primary succession. I have studied 95 islets younger than 430 years (height 
^350 m), 88 islands older than that (3,51-25 m), and 36 "islands" on the mainland. 



HEIGHT CLASSES (m) AND MAX. AGE {YEARS) 



species 



mainland 
-6000 



CLA. DUB. 
LEU. MAR. 
VER. LIL. 
CLA. riRU. 
LIM. TEN. 

CGC. LAM. 
ARL SIL. 
BRA. FRU. 
sue. SAR. 
PUP. MUS. 
BAL. PER. 

ARI. CIR. 
ART. FAS. 
TRI. HIS. 
DER. RET. 
ARI. ARB. 
COL. EDE. 

VAL. COS. 
VAL. SUB. 
VER. PUS. 

PUN. PYG. 
VER. ALP. 



ZON . NIT. 
SUC. PUT. 

ZOO. HAR. 
ARI. SUB. 
VER. RON . 
COL. ASP. 
DIS. RUn. 

CLA. BID. 
VIT. PEL. 

DER. LAE. 
COC. LUB. 
NES. H Л M. 

EUC. FUL. 

VAL. PUL. 

DER. AGR. 

OXY. PFE. 




37 


30 


20 


23 


32 


13 


36 


28 


28 


24 


24 


27 


20 


37 


0.9 


2 


17 


Ю 


240 


1300 





Na of islands 19 
No. of species 17 
Area Ji. (ha) o,3 

FIG. 1. Constancies of the species recorded from islands of 7 height/age classes. Constant species = black 
(const. > 50%); accessory species = coarse dots (const, less than 50%, but statistically different from 0); 
accidental species = fine dots (const, does not differ statistically from 0). Asterisks denote the statistical 
significance between classes at the 0.05 (*), 0.01 (*') and 0.001 (***) probability level. 



VALOVIRTA 
AGE OF ISLANDS AS A CRITERION OF SUCCESSION 



171 



Of the 39 indigenous species found in the study area, 34 also live on the archipelago. The 
number of species can be considered as some kind of criterion for the succession of this uplift 
area. Fig. 1 shows the species recorded from islands of 7 age classes and from the mainland. In 
the classes where islands are older than 125 years the number of species (24-29) does not 
increase with time. On the young and small islets there are 17 species and 37 species can be 
found on the mainland, which is the species pool. 

It is typical for an uplift archipelago that once a type of biotope has appeared, it exists on 
each island throughout the succession, but its location changes according to altitude from the 
sea level. However, the proportional area of these pioneer biotopes will diminish greatly on the 
islands of the sub-climax stage. This is why the species of young islets also occur on the older 
ones. 

The large number of species in the classes of islets of 125-250 and 250-430 years old show 
that the effects of age, height and area are not the only factors involved, but the effectiveness 
of isolation and certain ecological factors should also be considered. 

Moreover, the stage of primary succession does not depend on the age of the island alone. 
Especially on small islets the area is important. Waves and movements of ice considerably affect 
accumulation of soil and primary succession may thus progress very slowly. On the other hand, 
2 islands of very different size (even though the one is a 100 times as large as the other) may 
be at the same stage of land mollusc succession, if the larger is effectively isolated, but the 
smaller one is not. 

On islands of equal age and size differences in the numbers of species between isolated and 
non-isolated islands are greater on smaller islets, and will diminish towards larger ones (Fig. 2), 
For instance, increase of size from 0.1 to 10 ha will increase the number of species from 9 to 
13 in non-isolated islands (grouping effect greater than 75%) but from 2 to 10 in isolated 
islands (grouping effect less than 75%) (Fig. 2). 




0.1 



1.00 
In AREA Cha) 



10.0 



/oao 



FIG. 2. Number of land mollusc species on isolated (grouping effect ^75%) and non-isolated (grouping effect 
over 75%) islands. 



172 



PROC. SIXTH EUROP. MALAC. CONGR. 



40 



20. 




>Q.<* 



> • < 50 



12 3557 11 m 

FIG. 3. The amount of constant (^ 60%), accessory (> *, < 50%) and accidental (> 0, < *) species as a 
function of the height/age of islands. 

However, age alone can give only a rough suœessional trend of land molluscs. The islands 
will reach stability with constant, accessory and accidental species after ca. 600 years (Fig. 3). 
The proportion of constant species (constancy > 50%) will increase from 20 to 60%, the 
accidental species (constancy value does not differ statistically from 0, according to Fisher's 
exact probability test) will decrease from 60 to 30% and the accessory species between these 2 
groups, will decrease from 20 to 10% (Figs. 1 and 3). 



PIONEER SPECIES AND THE SUCCESSIONAL ORDER OF THE SPECIES 

It is very difficult to compare islands of different age, area, isolation and vegetation. 
Therefore I have grouped together all islands with 1-6, 7-12, and 13-21 species in order to trace 
typical pioneer species of the outer archipelagoes and to find the order in which the species will 
occupy the islands (Fig. 4). 

Islands with 1-6 species are usually treeless, grassy skerries with sparse thickets. According to 
the vegetation they are at the early successional stages. The constancy values of 5 species, viz. 
Vallonia pulchella (O.F. Müller) (^Q) , Deroceras agreste (L.) (38) , Ox y/oma pfeif feri (Rossm.) (14), 
Deroceras laeve (0. F. Müller) (36), and Vertigo alpestris Alder (7) do not differ statistically 
from the corresponding constancies on islands with 7-12 or 13-21 species (cf. Valovirta, 1977). 
These pioneer species can be considered so-called r-strategists (MacArthur & Wilson, 1967; 
Horn, 1974; Pianka, 1974). They are easily dispersed and colonize nearly all the archipelagoes in 
the study area. Pioneers are also prolific and not particular about their habitat on low islets. 

Islands with 7-12 species are at an intermediate stage of succession. The biotopes are variable 
and there are already trees of moderate size. Five common species, Euconulus fulvus (0. F. 
Müller) (40), Nesovitrea hammonis (Ström) (24), Vitrina pellucida (О. F. Müller) (23), Clausilia 
bidentata (Ström) (42), and Succinea putris (L.) (13) reach their maximum constancies at this 
stage. However, the constancies do not differ statistically from those on islands with 13-21 
species. The other species of this stage, viz. Cochlicopa lubrica (0. F. Müller) (1), Columella 
áspera Waiden (3), Discus ruderatus (Férussac) (17), Vertigo ronnebyensis (Westerlund) (8), 
Arion subfuscus (Draparnaud) (20), and Zoogenetes harpa (Say) (12) are more constant on 
islands with 13-21 species, and can be considered as species of later successional stages (Fig. 4). 

Islands with 13-21 species are large, less isolated and the forests are usually in the sub-climax 
stage. Typical species of the late successional stage are Nesovitrea petronella (L. Pfeiffer) (25), 
Punctum pygmaeum (Draparnaud) (16), Vertigo pusilla O. F. Müller (4), and Columella 
edentula (Draparnaud) (2). These species are the last ones to occupy islands on the outer 
archipelagoes of the study area (Fig. 4). 

Study of the primary succession in different biotopes gives very similar results as when 
studying the succession on islands as a whole, both as regards pioneer species and species of 



VALOVIRTA 
OUTER ARCHIPELAGOES 



173 



constancy 



uu 
80 










1-6 species 


60 








N = 26 


40 
















20 










Ф 






« 














10"38^14^36^ 7^ 

k. ^k. Лк. J^ ^k. ^ 


ф||ЭП-^ l—h-n— 1 Í— > 




1 . ' 


* 
* 






80 












« 


♦ « 


















• 


* 7-12 species 




















♦ N=48 
























♦ 
























« 


40 








1 
















* 
















1 






















* 














* 




с ^k. ^k. ^k. ^k. ^ 




40^24^23^^2^13" 
k. ^k. ^k. ^k. ^k. ^ 




' 


3 17 8 20 12^ 

к. J^ ^k. ^k. ^w ^ 


1 1— r— , 


^^ n 




1 


1 


1 


1 1 


« 


* 


* 


80 










* 
* 




* * 


1 
1 — 




1 






















» 


^ ^ji 13 - 21 species 


































* ♦ N = 14 


. 


































» ♦ 






1 




-L 










« 


40- 










1 
































♦ « 
















































♦ * 




























































1 1^>A 




10 ,38 14 ,36^^ 7 


k<°.J^.Jlk«.J3. 


^:лл.в..2о^л 


25: 16' 4 2 

k. ^W ^k. ^k. ^ 


48 , 6 28 11 ,45 
к ^k. ^k. ^k. ^k. 


> 



FIG. 4. The number of land mollusc species found on the islands of the outer archipelagoes reflecting the 
succession. Pioneer species are constant on islets with 1-6 species. The species of an intermediate stage of 
succession reach their maximum constancies on the islands with 7-12 species; the species of later successional 
stages occur mainly on islands with 13-21 species (cf. text). Numbers inside the black circles are the codes of 
the species. Asterisks denote the statistical significance as in Fig. 1. 



later successional stages. Fig. 5 shows a successional series of biotopes 1гогл open beach meadows 
to shore thickets and to forests in the middle of islands. The intermediate biotopes have also been 
included. According to the constancy values the order of the first 10 species of the open grassy 
skerries has been marked on the left side of the diagram. The first 3 species are the same as in Fig. 
4. However, during the successional series of biotopes these 3 pioneer species will disappear from 



174 



open 

shore 

n = 26 



PROC. SIXTH EUROP. MALAC. CONGR. 

sfi^^hickets thickets forest 

n = 43 n=42 n 43 



forest 
n 65 




FIG. 5. The order (numbers) of land mollusc species on the successional series of biotopes from open shore 
meadows (grassy skerries) to forest, including the intermediate biotopes. 



the group of the 10 first species before the sub-climax stage. Species which belong to the group of 
the 10 species which occur only in forests or in mixed biotopes of forest and thicket are 
Columella áspera. Vertigo ronnebyensis, Arion subfuscus, and Zoogenetes harpa. These are also 
the species of later successional stages in Fig. 4. 



SPECIES DIVERSITY 

Since the variations in species diversity are positively correlated with the stability of various 
biotic and abiotic components of ecosystems, diversity is significant in the study of succession 
(Whittaker, 1975). In Fig. 6 the species diversity has been derived from Shannon's measure of 
diversity (H') corrected according to Hutcheson (1970), 

H' = -S Pjln p¡, 

where Pj is the proportion of the total number of individuals (H|nd) or the abundance frequency 
(individuals/litre) of the ith species (Hg^^^) in the studied biotope or successional stage. 

In Fig. 6 the successional stages of the islands in the outer archipelagoes have been arranged 
according to vegetation, and the biotopes represent the oldest stage of maturity on every island. 
The average ages of the first successional stages do not differ greatly because of the effective 
compensation of the other island factors (see above). However, on the uplift islands the 
diversity will increase with island maturity (cf. Väisänen & Järvinen, 1977). 

Differences in diversity (HJnd) from 1,65 to 2.45, imply that at the early stages of 
succession of the grassy skerries (1) the number of "equal common species" exp(H|nd) will be 



VALOVIRTA 



175 



H' 



2.60 



2,40 



2.20 - 



H 

ел 

tí 2.00 

H 
> 



1.80 . 



1.60 _ 




H ind 



H'abu 



200 400 600 

TIME ( X ) 



800 



1000 YEARS 



FIG. 6. Diversity of land mollusc species as a function of average age of islands grouped in 5 successional 
stages according to vegetation. H'jnd = individual-based diversity, Н'аЬи = abundance-based diversity, 1 = shore 
meadows, 2 = shore meadows/shore thickets, 3 = shore thickets, 4 = shore thickets/forests, 5 = forests. 



5.2 and that it will increase up to 8.8 in thickets (3) and 11.6 in forests of the late sub-climax 
stage (5). 

Tramer (1969, 1975) has suggested that Н' values for taxa in unstable environments should 
vary as a function of evenness (cf. Pielou, 1966). Therefore, the evenness has been measured 
according to the formula j' = HÍnd'/'n S, where S is the number of species at the stage of 
succession, in this material 10, 14, 17, 17, and 21 respectively. Evenness will increase first from 
0.72 (1) to 0.85 (4). After that it differs from the function of H-nci and decreases to 0.81 (5). 
Correlation between H|nd and J' is 0.913 and the coefficient of determination (R^) will be 
83.3% (see Järvinen & Sammalisto, 1973). 

Fig. 6 shows that the 500-600 years old islands which are at the thicket/forest stage (4), 
have reached some kind of stability according to the diversity (H|nci) values, which is nearly the 
same as on the islands of sub-climax forests (cf. Fig. 3). By using abundancy-based diversity 
(Hgbu) the diversity will increase continuously from 1.51 (1) to the value of 2.24 of the 
sub-climax stage. 

ACKNOWLEDGEMENTS 

I wish to thank Miss Sirpa Mäkelä, Miss Barbro Elgert and Mr. Matti Tolvanen who have 
worked as technical assistants. The work has been supported by a grant from the Fmnish 
Cultural Foundation. 



176 PROC. SIXTH EUROP. MALAC. CONGR. 

LITERATURE CITED 

HORN, H. S., 1974, The ecology of secondary succession. Annual Review of Ecology and Systematics, 5: 

25-37. 
HUTCHESON, K., 1970, A test for comparing diversities based on the Shannon formula. Journal of 

Theoretical Biology, 29: 151-154. 
JÄRVINEN, 0. & SAMMALISTO, L., 1973, Indices of community structure in incomplete bird censuses 

when all species are equally detectable. Ornis Scandinavica, 4: 127-143. 
KUKKAMÄKI, T. J., 1971, Fennoscandian sub-commission. Finland. Symposium on recent movements of the 

crust. Moscow, 5 p. (roneoed). 
KÄÄRIÄINEN, E., 1953, On the recent uplift of the earth's crust in Finland. Fennia, 11: 1-106. 
LEIGH, E. G., Jr. 1965, On the relation between the productivity, biomass, diversity, and stability of a 

community. Proceedings of the National Academy of Sciences of the U.S.A., 53: 111-183. 
MacARTHUR, R. & WILSON, E. O., 1967, The theory of island biogeography. Princeton University Press, 

Princeton, 203 p. 
MARGALEF, R., 1968, Perspectives in ecological theory. Chicago University Press, Chicago, 112 p. 
OKKO, M., 1967, The relation between raised shores and present land uplift in Finland during the past 8000 

years. Annales Academiae Scientiarum Fennicae, (A3), 93: 1-59. 
PIANKA, E. R., 1974, Evolutionary ecology. Harper and Row, New York, 356 p. 
PIE LOU, E. C, 1966, Species diversity and pattern diversity in the study of ecological succession. Journal of 

Theoretical Biology, 13: 131-144. 
SLOBODKIN, L. & SANDERS, H., 1969, On the contribution of environmental predictability to species 

diversity. Brookhaven Symposia in Biology, 22: 82-95. 
TRAMER, E. J., 1964, Bird species diversity, components of Shannon's formula. Ecology, 50: 927-929. 
TRAMER, E. J., 1975, The regulation of plant species diversity on an early successional old-field. Ecology, 

56: 905-914. 
VALOVIRTA, I., 1977, The Baltic island survey, a malacological cooperation between Scotland and Finland 

1974. Malacologia, 16: 21\-211. 
VÄISÄNEN, R. & JARVINEN, 0., 1977, Quantitative structure and primary succession of bird communities 

in a Finnish archipelago. Ornis Scandinavica, 8: 47-60. 
WHITTAKER, R. H., 1975, Communities and ecosystems. Macmillan, New York, 162 p. 



MALACOLOGIA, 1979, 18: 177-180 

PROC. SIXTH EUROP. MALAC. CONGR. 

REPRODUCTION OF TWO SPECIES OF LAND SNAILS IN 
RELATION TO CALCIUM SALTS IN THE FOERNA LAYER 

Ingvar Wäreborn 
Department of Animal Ecology, University of Lund, Sweden 

ABSTRACT 

In culture experiments with Cochlicopa lubrica (Müll.) and Discus rotundatus (Müll.) 
addition of calcium citrate and calcium oxalate to the substrate were demonstrated to 
have a positive influence on reproduction. The number of young produced in the culture 
boxes could also be increased by sodium carbonate additions, from which one may infer 
that both the calcium content and the pH-increasing action of the calcium compounds in 
the foerna are important. Ca citrate was significantly betteijthan Ca oxalate. To facilitate 
comparisons with conditions in nature a small biometrical study of C. lubrica was made. 
Length of the reproductive season, young production and yearling growth were studied. 
Leaves of oak and beech are rich in oxalate-bound calcium, while in ash, lime, maple and 
elm more soluble Ca compounds (e.g. citrate) are dominating. This may be related to 
mollusc fauna differences between different types of deciduous woods on non-calcareous 
bedrock. 

INTRODUCTION 

In 1966-76 snails of two species, Cochlicopa lubrica (Müll.) and Discus rotundatus (Müll.), 
were cultured in plexiglass boxes under semi-natural outdoor conditions (cf. Wäreborn, 1970: 290, 
the few experiments with D. rotundatus are described in that paper). In this study the effect of 
calcium citrate and calcium oxalate additions to the substrate on the reproduction of C. lubrica 
is discussed. A calcium-deficient beach litter was used as substrate in all boxes. Besides this, 
there was one series, where pH was increased without Ca additions. Sodium carbonate was used 
instead. In order to kill predators, the litter was boiled for 5 minutes in distilled water (or in 
sodium carbonate solution) before it was placed in the boxes. In the 2 Ca salt series, the salt 
additions correspond to an increase of calcium of 1.5% of the dry weight of the substrate. 
Before addition it contained 1.0% Ca. The boxes were moistened with distilled water or in the 
sodium carbonate series with a dilute soda solution during dry weather periods. The 
experiments were started in the middle of June and lasted for about 17 weeks. During the 10 
years when the experiments were conducted, there was a normal variation between dry and 
rainy summers. 

There were different pH changes in the different box series. When no calcium salt was 
added, pH increased about one unit during the culture period (from about 5.0 to 6.2). Ca 
citrate had an immediate increasing effect (from 5.0 to about 7.3). Ca oxalate addition gave a 
rise about a month after the start of the experiments (from 5.3 to about 7.5). With sodium 
carbonate thé pH was kept between 7.0 and 7.8 during the whole culture period. 

Differences in effect on molluscs of different calcium salts naturally occurring in plants have 
not been presented by other authors. Voelker (1959) describes growth experiments with 
Achatina fúlica Bowd. including pH increase with sodium carbonate. There was, however, no 
positive effect of the soda additions. 

As a complement to the study, sift collections of С lubrica from 9 localities in southern 
Sweden were biometrically studied in order to get an understanding of the life history of the 
species. Thereby it was revealed, that more or less distinct "winter lines" may be distinguished 
in the shells. 



(177) 



178 PROC. SIXTH EUROP. MALAC. CONGR. 

TABLE 1. Reproduction of Cochlicopa lubrica (Müll.): culture results. Culture experiments with different 
substrates: A, beech litter without calcium salts added; B, as A, but watered with sodium carbonate solution; 
C, beech litter mixed with Ca citrate; D, beech litter with Ca oxalate. Significance has been calculated on the 
mean differences between young numbers in paired samples of culture boxes. 

















Md = mean of differences 


Substrate category 




Culture 


results: 


number 


of young 




Significance 


С (with citrate) 


15 


38 


28 


38 


29 


36 






A (no Ca added) 





6 


10 


17 


7 


9 


Md = 22.50 


t = 8.96 


Differences 


15 


32 


18 


21 


22 


27 


p < 0.001 




D (with oxalate) 


13 


21 


19 


17 


25 


28 






A (no Ca added) 


6 


10 


7 


1 


17 


7 


Md = 12.50 


t = 5.84 


Differences 


7 


11 


12 


16 


8 


21 


p < 0.005 




С (with citrate) 


38 


17 


13 


28 


38 


29 






D (with oxalate) 


13 


9 


6 


21 


28 


25 


Md = 10.17 


t = 3.31 


Differences 


25 


8 


7 


7 


10 


4 


p < 0.03 




В (soda watered) 


7 


15 


13 


9 


9 


8 






A (no Ca added) 


4 


9 


10 


7 


1 


4 


Md = 4.33 


t = 4.71 


Differences 


3 


6 


3 


2 


8 


4 


p < 0.01 





RESULTS OF THE CULTURE EXPERIMENTS 

The culture results with C. lubrica are presented in Table 1. Eight culture experiments with 
Discus rotundatus have also been made (Wäreborn, 1970); the results are in accordance with the 
above. The significance tests are based upon pairing of the experiments (Snedecor & Cochran, 
1967: 93). Thereby pairs were formed of experiments from the same year. If more than one 
pair in a series could be formed per year, boxes placed close to or near each other were 
designed to form the pairs. It would have been desirable to have more pairs in every series; this 
kind of work is, however, very time-consuming. 



BIOMETRICAL STUDIES 

In a small series of complete sift collections of С lubrica the following measurements were 
taken: length and width of the shell and height of the aperture. The number of whorls were 
counted (Ehrmann, 1956: 21). The collections (belonging to the Natural History Museum of 
Gothenburg) were from the end of the months of May to October. Three samples from October 
and one sample from each of the other months were measured. A total of 177 adults and 851 
juveniles was studied biometrically. The latter were sorted into different year classes, mainly on 
the basis of winter lines. These are distinct in young specimens and may still be discernible in 
about two thirds of the adult shells. Drought may produce lines in the shells and so do various 
types of repaired damage; the latter cannot, however, be mistaken for winter lines. With 
increasing experience most of the drought lines can also be sorted out. As the lines penetrate to 
the surface of the shell, they cannot be caused by inside epiphragms. C. lubrica has a long 
reproduction season from (May) June to October (November) and a rather rapid elimination of 
juveniles. It does not seem possible to discern year classes only on the basis of length 
measurements or whorl counting. Results from this small biométrie study are presented in Table 
2. The collections are from rather different wood habitats. There are great variations in the rate 
of elimination of the juveniles. 



CONCLUSIONS 

From the biometrical study and from the study of winter lines in the shelfs one may infer 
that young production in the culture boxes, where calcium salts were added, was within the 
natural variation of reproduction in good Cochlicopa lubrica localities in the area. Yearling 



i 



WÄREBORN 179 

TABLE 2. Biometrical results and results from a study of winter lines in the shells of Cochlicopa lubrica. 
Locality type No. 1 = oligotrophic, 2 = mesotropic, 3 = eutrophic. The distribution of juveniles in year 
classes is mainly based on winter lines. 









Maximum 


Maximum 




Number 


of juv. 




Numbei 


r of juv. 




Type of 

1 _ __i :*. . 


length 
of shell 


growth 
of year- 


Number 


year 


No. 




per 10 adults 




locar 


iiiy 












Collection 






in year- 


lings 


of 


year- 






2nd 


year- 


date 


No. 


PH 


lings mm 


(whorls) 


adults 


lings II 


Ill 


IV 


year 


lings 


21.5.1967 


3 


6.5 


0.84 


0.1 


38 


1 58 


12 


11 


15.3 




26.6.1971 


2+ 


6.5 


0.87 


0.2 


9 


4 41 


12 


1 


45.6 




28.7.1971 


3 


6.0 


1.19 


0.6 


13 


11 18 


1 


— 


13.8 




19.8.1965 


3 


7.0 


1.37 


0.8 


14 


31 1 


1 


3 




22.1 


29.9.1963 


2 


5.7 


2.02 


1.6 


14 


16 36 


15 


2 




11.4 


25.10.1973 


3 


7.5 


2.42 


1.9 


21 


283 18 


17 


2 




135.0 


31.10.1973 


2 


6.0 


1.72 


1.2 


23 


33 8 


9 


4 




14.4 


31.10.1970 


3- 


7.7 


2.39 


2.0 


45 


200 3 


5 


— 




44.4 



growth in these boxes has also been within natural variation (0.0-0.8 whorls in boxes with Ca 
citrate and 0.0-0.9 with Ca oxalate). Both young production and growth was less in boxes with 
no Ca salt additions (growth in boxes moistened with distilled water and in soda moistened 
boxes was 0.0-0.5 whorls). The juveniles may need 3-4 years to reach adult size. 

Reproduction is increased by additions of calcium citrate and calcium oxalate. The former is 
significantly better than the latter. This is interesting, because in nature leaves of ash, lime, 
maple and elm are rich in rather soluble calcium compounds (e.g. Ca citrate), while in leaves of 
oak and beech calcium occurs mainly as Ca oxalate (Mattson & Koutler-Andersson, 1946). 
Litter from the 2 latter tree species contains more tannic acid and other acid substances 
(Edwards & Heath, 1975) than that from the citrate-rich trees. Calcium oxalate needs months 
in the foerna to be disintegrated, and until then it has no neutralizing effect upon acids. The 
mollusc faunas of woods on soils without calcium carbonate (e.g. on bedrock of granite, gneiss 
or greenstones) seem to depend upon citrate-rich trees, and where such trees occur the faunas 
are as a rule much richer both in individuals and in number of species (Wäreborn, 1969). It is 
probable that the effect of the calcium salts depends both on their Ca content and their 
pH-increasing action (cf. the soda experiment series. Table 1). In the surface of the soils of oak 
and beech woods on non-calcareous bedrock pH is about one unit lower than in woods with 
ash, lime, maple or elm upon the same type of bedrock substratum (Wäreborn, 1969). 

ACKNOWLEDGEMENTS 

Prof. Per Brinck, Department of Animal Ecology, Lund University, has taken a continuous 
interest during more than a decade in this work and has given valuable advice. The same can be 
stated for Dr. Henrik Waiden, Natural History Museum of Gothenburg, who also kindly has 
contributed material to the biométrie study from collections made by himself and belonging to 
the museum. Thanks are also due to Dr. B. Hubendick, head of the Gothenburg Museum, who 
agreed to lending the material. Assistance in the work has in various ways been given by 
mesdames G. and A. Wäreborn. 



LITERATURE CITED 

EDWARDS, С A. & HEATH, G. W., 1975, Studies in leaf litter breakdown III. The influence of leaf age. 

Pedobiologia, 15: 348-354. 
ERHMANN, P., 1956, Mollusca. In: Brohmer, P., Ehrmann, P. & Ulmer, G., eds., Tierwelt Mittel-Europas, 

2(1). Quelle 8e Meyer, Leipzig, 264 p. 
MATTSON, S. & KOUTLER-ANDERSSON. E., 1946, The acid-base condition in vegetation, litter and humus 

IX. Forms of bases. Annals of the Royal Agricultural College of Sweden, 13: 153-178. 
SNEDECOR, G. W. & COCHRAN, W. G.. 1967, Statistical Methods. Iowa State University Press, Ames. Iowa, 

xiv + 593 p. 



180 PROC. SIXTH EUROP. MALAC. CONGR. 

VOELKER, J., 1959, Der chemische Einfluss von Kalziumkarbonat auf Wachstum, Entwicklung und 

Gehäusebau von Achatina fúlica Bowd. (Pulmonata). Mitteilungen aus dem Hamburgischen Zoologischen 

Museum und Institut, 57: 37-78. 
WÄREBORN, I., 1969, Land molluscs and their environments in an oligotrophic area in southern Sweden. 

Oik os. 20: 461-479. 
WÄREBORN, I., 1970, Environmental factors influencing the distribution of land molluscs of an oligotrophic 

area in southern Sweden. Oikos, 21: 285-291. 

NOTE ADDED IN PROOF. A recent work dealing with winter lines in snail shells should be included in the list 
of references: 

POLLARD, E., COOKE, A. S. & WELCH, J. M., 1977, The use of shell features in age determination of juvenile 
and adult Roman snails Helix pomatia. Journal of Zoology, 183: 269-280. 



MALACOLOGIA, 1979, 18: 181-184 

PROC. SIXTH EUROP. MALAC. C0NGR.1 

POPULATION DYNAMICS OF SOME LAND GASTROPODS IN 
A FOREST HABITAT IN POLAND 



Tomasz Umiriski and Urszula Focht 

Instytut Zoologii, Uniwersytet Warszawski, Krakowskie Przedmiescie 26/28, 
00-927/1 Warszawa, Poland 



ABSTRACT 

In the Hel peninsula (Poland) litter and the surface of the soil of an old AInus forest 
were square-frame sampled 4 times a year. All the 10 snail species were numerous in 
spring and autumn. In July and August a dramatic drop in numbers was noted. 
Presumably the snails escape the summer drought, digging themselves into the soil. 
Vitrina pellucida has a one-year life cycle; they hatch in the spring, with a shell diameter 
of 0.8 mm, reach full size and maturity in late autumn, then lay eggs and die. Only a few 
survive until next April. Cochlicopa lubrica needs approximately 22 months to attain 
maturity; adults live over 1 year. Euconulus fulvus is probably also slow-growing, 
long-lived, and the young lead a largely subterranean life. 

In order to understand the place of gastropods in the structure and function of terrestrial 
ecosystems, more information is needed on their life cycles and population dynamics. 

STUDY AREA, METHODS, MATERIAL 

The study area was in the Hel peninsula (Baltic coast), 1 km NW of the summer resort 
Kuznica. It is an old AInus forest, covering a sand flat among dunes, 2 m above sea level. The 
lower layer was formed by Sorbus aucuparia and Sambucus nigra, the still lower stratum by 
Rubus (Eubatus) sp. with some Ribes sp. The litter and top 2 cm of soil were hand-sampled 4 
times a year in 1970-1972 and again in 1976, using a square-frame of 1/16 m^. Each sample 
consisted in principle of 16 frames. It is assumed, that the disturbance by sampling itself was 
negligible. The collected material comprised 1399 live specimens and 2261 shells of: Vitrina 
pellucida (Müller) (47.5%), Euconulus fulvus (Müller) (28.0%), Cochlicopa lubrica (Müller) 
(12.3%), Punctum pygmaeum (Draparnaud), Nesovitrea hammonis (Ström), Vertigo pusilla 
Müller, Cepaea hortensis (Müller), Helicigona arbustorum (L.), Vallonia pulchella (Müller), and 
Arion subfuscus (Draparnaud). 



DENSITY 

All 10 species show at least one common regularity— in July and August their density is 
extremely low. Most are fairly numerous in spring and autumn. Data on the 3 dominant species 
are summarized in Fig. 1. In Vitrina pellucida these changes in density are vividly pronounced— 
in July 1972 and 1976 not a single living individual was found— but the other species clearly 
follow the same pattern. This summer disappearance is not due to mortality, because the 
animals found in autumn unquestionably represent the same age class which was found in May 
or June, as will be shown later. Migration is obviously out of the question. The snails must dig 
themselves into the sandy soil, escaping the summer drought. Hence what is shown here is not 
the actual population density, but density of animals obtained by the procedure adopted. 

"•Or. Umirfski has been unable to attend the Amsterdam congress; as an exception hisj paper is published in these 
Proceedings. 

(181) 



182 

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FIG. 1. Yearly changes in density. Mean density calculated where at least 3 values were available. July and 
August data combined. 



Vitrina pell и ci da (Müller) 



SIZE DISTRIBUTION 



Yearly changes in size distribution as shown in Fig. 2 indicate a clear-cut one-year life cycle. 
In spring and early summer there are only very small individuals, bigger ones in September and 
really big ones in November. We conclude that they hatch about April with a shell diameter of 
0.8 mm, reach their final size in November, then lay eggs and die. Occasionally some may hatch 
in autumn, as witnessed by single, very small individuals, collected in November 1970 and 
September and November 1972. These may hibernate, as undoubtedly did the 2 specimens of 
May 1971; these had shell diameters of 2.5 and 2.9 mm and were both at the stage juvenile I 
(Uminski, 1975a), their genital systems barely visible strands of tissue. Snails of 2.9 mm shell 



UMINSKI AND FOCHT 



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184 PROC. SIXTH EUROP. MALAC. CONGR. 

diameter, taken in November 1970 and 1971 were mature II, i.e. after copulation, ready to lay 
eggs, their genital systems occupying something like % of the whole specimen's bulk. This 
relative independence of size and maturity is in keeping with data on populations of the Tatra 
Mountains, with a 2-year life cycle (Uminski, 1975b). Hibernation of full-sized adults was noted 
in April 1973. Thus the postembryonic life span here would be 8-12 months. It is most 
striking, that growth is largely arrested during summer. Over the period June-September in 1971 
and May-September in 1972 and 1976 mean shell diameter of this population increased by 0.4, 
0.45 and 0.1 mm per month respectively. In sharp contrast, this increase during October- 
November 1970 and September-November 1971, 1972 and 1976 amounted to 0.8, 0.8, 0.7 and 
0.8 mm respectively. No such thing was ever found in the Tatra populations. Drought is the 
probable cause. It seems, that the snails, when in hiding, are not active, possibly close to 
anabiosis. Data on empty shells here are not as instructive as they were in the Tatras. All 
samples of July, August and even of September comprise a fair proportion of shells of animals 
which, judging from their size, must have died not later than April. In other words. Vitrina 
shells persist here for at least 3-5 months of the snow-free season, while in the Tatras they 
disintegrate completely in less than 2 months, serving as a precise measure of mortality in the 
preceding month. Still, comparison of number and size of animals and shells, collected 
simultaneously suggest that mortality is about the same for all age size groups, quite low until 
late autumn. 

Cochlicopa lubrica (Müller) 

As in this population 98.3% of animals and shells with an incrassate labial margin are larger 
than 4.5 mm (shell length) this value was taken as a "maturity line" (Fig. 2). In all samples, 
regardless of season, there is always a well-defined group of adults. The young are usually few 
and, with the exception of those of May 1972, differ from mature ones in size by being 
1-3 mm shorter. The group, which can be reasonably presumed to represent one age class, was 
first noted in October 1970, with a shell length of 0.9-1.8 mm. It could be followed (dotted 
line) in all subsequent samples until May 1972, when it began to merge with the grown-ups. 
The very small specimens of May, September and November 1972 could represent the next age 
class. Hence С lubrica needs 21-24 months to attain finalsize and maturity. Adults must live at 
least for 1 year to account for their constant presence. The remarkably low number of young 
as compared to that of adults would imply even higher longevity of the latter, as well as a 
balance based on low natality and low mortality. It seems that breeding is possible at any time; 
the most successful hatching must have been in September. 

Eu CO nul us fulvus (Müller) 

Shell size distribution (Fig. 2) resembles that of C. lubrica in that a relatively numerous 
group of big individuals is present almost constantly, indicating longevity of adults. The young 
were fairly numerous, but their occurrence did not show any orderly pattern. Not a single age 
class could be traced the way it was with C. lubrica. Very small young of under 1 mm diameter 
were remarkably scarce, particularly so, as similarly small specimens of other species, including 
Punctum pygmaeum, were more numerous. This whole picture could be accounted for if young 
E. fulvus: (a) were similarly slow-growing as C. lubrica, (b) led a largely subterranean life, (c) 
emerged onto the soil surface only during temporary favourable weather conditions. 

LITERATURE CITED 

UMINSKI, T., 1975a, Reproductive maturity in some Vitrinidae (Mollusca, Gastropoda) from Poland. Annales 

Zqologici, 32: 357-374. 
UMINSKI, T., 1975b, Life cycles in some Vitrinidae (Mollusca, Gastropoda) from Poland. Annales Zoologie!, 

33: 17-34. 



MALACOLOGIA, 1979, 18: 185-195 

PROC. SIXTH EUROP. MALAC. CONGR. 

E.I.S.-BEITRÄGE AUS DER BUNDESREPUBLIK DEUTSCHLAND 
H. Ant^ und J. H. Jungbluth2 

ABSTRACT 

This is a summary of European Invertebrate Survey (E.I.S.) contributions in the 
Federal Republic of Germany (BRD) with examples of local distribution of selected 
species (Figs. 1-6) and graphical presentation (Figs. 8-9). Fig. 7 shows the areas covered 
with the respective numbers of species. 

VORBEMERKUNG 

Auf die noch ausstehende, zeitgemässe malako-faunistische Erforschung der BRD hat Waiden 
(1963) in einem Aufsatz hingewiesen, auf den Ant (1963a) geantwortet hat. Bis zu diesenn 
Zeitpunkt lagen nur lokale oder höchstens regionale Teilbearbeitungen von Molluskenfaunen 
vor. Für die Untersuchungsräunne wurden Faunenlisten erstellt und die Fundorte benannt; die 
kartographische Darstellung in der Form von Punktkarten war eine Ausnahme. Den ersten 
umfassenderen Kartenbeitrag legte Ant (1963b) vor, wenn von den Najaden-Bearbeitungen von 
H. Modell einmal abgesehen wird, die sich jeweils mit einem Flussystem befassten. 

Die Organisationsstrukturen für eine bundesdeutsche Beteiligung am E.I.S.-Programm wurden 
erst nach dem Symposium 1972 in Saarbrücken geschaffen. Am dortigen Schwerpunkt für 
Biogeographie wurde schliesslich das nationale Kartierungszentrum (Prof. Dr. P. Müller) 
geschaffen. Die Einrichtung und finanzielle Sicherung zogen sich jedoch über mehrere Jahre hin, 
so dass bis heute erst ein Verbreitungsatlas für Lepidopteren publiziert werden konnte. Nach 
dessen Erscheinen im Jahre 1976 sind weitere, abgeschlossene Kartierungs-Beiträge im Druck 
und werden wahrscheinlich noch 1977 erscheinen, so auch der erste Molluskenatlas (Jungbluth, 
1978). 

PROBLEME 

Der Fortschritt der Kartierung wird im wesentlichen von zwei Faktoren bedingt: 

(a) die Ausstattung der Mitarbeiter mit dem erforderlichen Grundkartenmaterial. Die U.T. M.- 
Karten sind nicht in jedem gewünschtem Masstab frei im Handel erhältlich, 

(b) der rasche Druck der abgeschlossenen Kartierungsbeiträge. In Saarbrücken wurden 
inzwischen die UTM-Gitternetz-Karten für die Bundesländer und auch für kleinere Gebiete 
erstellt, so dass dieses Problem zumindest teilweise gelöst ist. Weiter wurde ein Computer-System 
zur Erstellung von Fundortkarten für die BRD codiert (Klomdat, s. Klomann & Müller, 1975). 

Abschliessend ist noch auf das Problem von Zeitaufwand und Mitarbeitern einzugehen. Die 
Erfahrungen der eigenen Arbeitsgruppen haben gezeigt, dass die Verwendung der Einzelbeleg- 
Karten für kleine Teams entschieden zu zeitaufwendig ist und nicht bewältigt werden kann, dies 
auch unter dem Gesichtspunkt, dass z.Z. eine sofortige Einspeisung der Daten in den Computer 
noch nicht möglich ist. Wir erfassen daher die Daten in Karteien auf Fundortsammeikarten bzw. 
in Registern mit Fundortsammelblättern, auf denen jeweils grosse Anzahlen von Daten je Art 
gesammelt werden können. 

Vom Zeitaufwand her ist die blosse Anfertigung von Grid-Verbreitungskarten nicht 
vertretbar, so dass hier weitere Daten in das Kartenbild eingehen müssen. In der BRD wird 
versucht, über die reinen Artverbreitungskarten hinaus Organismen-Kataster für kleinere und 
grössere Räume zu erstellen (Klomann & Müller, 1975). 

"•4700 Hamm, Dahlienstrasse 38; F.R.G. 

^Zoologisches Institut I der Universität, 6900 Heidelberg, Im Neuenheimer Feld 230; F.R.G. 

(185) 



186 PROC. SIXTH EUROP. MALAC. CONGR. 

KARTIERUNGSBEITRÄGE 

Erste Erfahrungen wurden in der BRD bei der Kartierung der Mollusken des Vogelsberges 
nach der E.I.S.-Methode gesammelt (Jungbluth, 1975a). Für die eigenen Arbeitsgruppen hat sich 
gezeigt, dass entweder kleine Gebiete (s. Fig. 2) insgesamt bearbeitet werden können oder 
bei grossräumigen Kartierungen eine geringe Artenzahl ausgewählt werden muss. Für die 
Beurteilung von Standort- und Raumqualitäten durch Zeigerarten oder -gesellschaften muss ein 
kleines Grid-Raster gewählt werden (z.B. 1 X 1 km). 

Bislang wurden folgende Kartierungen abgeschlossen: 

1. Vogelsberg, 131 Arten; 2,5 X 2,5 km (Jungbluth, 1975a) 

2. Odenwald, 170 Arten; 1 X 1 km (Ritter, 1974) 

3. Heidelberg und Umgebung, 151 Arten; 1 X 1 km (Kirchesch, 1976) 

4. Hessen, 204 Arten; 10 X 10 km (Jungbluth, 1978) 

5. Nordrhein-Westfalen, 54 Arten; 10 X 10 km (Ant) 

Darüber hinaus liegen die Verbreitungskarten von Bythinella bavarica (H. Boeters),^ Bythinella 
dunkeri (J, H. Jungbluth)! und Margaritifera margaritifera (J. H. Jungbluth) für die BRD vor. 

AUSBLICK 

Für die weiteren Kartierungen liegen die Kartierungsanweisungen (Ant, 1973) vor. Die 
Anfertigung weiterer U.T.M.— Gitternetz-Karten ist auf der Basis des vorhandenen Karten- 
materiales (auch im Massstab 1:50.000) möglich. Die Mitglieder der Deutschen Malako- 
zoologischen Gesellschaft wurden zur Mitarbeit aufgerufen (Jungbluth, 1975b) und ein 
Überblick über die bisherigen Kartierungsbeiträge an anderer Stelle gegeben (Jungbluth, 1976). 

LITERATUR 

ANT, H., 1963a, Die zukünftige malakofaunistische Erforschung Deutschlands. Mitteilungen der Deutschen 

Malal<ozoologischen Gesellschaft, 1 : 43-44. 
ANT, H., 1963b, Faunistische, ökologische und tiergeographische Untersuchungen zur Verbreitung der 

Landschnecken in Nordwestdeutschland. Abhandlungen aus dem Landesmuseum für Naturkunde zu 

Münster in Westfalen, 25: 1-125. 
ANT, H., 1973, Erfassung der Europäischen Wirbellosen. Kartierungsanweisungen. Hamm, 23 S. 
JUNGBLUTH, J. H., 1975a, Die Molluskenfauna des Vogelsberges unter besonderer Berücksichtigung 

biogeographischer Aspekte. Biogeographica, 5; 1-138. 
JUNGBLUTH, J. H., 1975b, (jber die Kartierung der Mollusken von Hessen. Mitteilungen der Deutschen 

Malakozoologischen Gesellschaft, 3: 232-240. 
JUNGBLUTH, J. H., 1976. Hessische Beiträge zum EDV-unterstützten Programm der "Erfassung der 

Europäischen Wirbellosen" (E.E.W.). Jahresberichte der Wetterauer Gesellschaft für die gesamte Naturkunde, 

125-128:2740. 
JUNGBLUTH, J. H., 1978, Prodromus zu einem Atlas der Mollusken von Hessen. Saarbrücken, 165 S. 
JUNGBLUTH, J. H. & BOETERS, H. D., 1977, Zur Artabgrenzung bei Bythinella dunkeri und bavarica 

(Prosobranchia). Malacologia, 16: 143-147. 
KIRCHESCH, M., 1976, Die Molluskenfauna Heidelbergs— ein Beitrag zur Kartierung der westpalaeark- 

tischen Evertebraten. Heidelberg. 
KLOMANN, U., & MÜLLER, P., 1975, Ökologischer Informationskataster für das Saarland. Mitteilungen aus 

der Biogeographischen Abteilung des Geographischen Instituts der Universität des Saarlandes, 7, 24 S. 
RITTER, H., 1974, Die Mollusken des Odenwaldes unter besonderer Berücksichtigung ihrer Zoogeographie. 

Heidelberg, Staatsexamensarbeit. 
WALDÉN, H. W., 1963, Wie wird sich die malakofaunistische Durchforschung Deutschlands in der Zukunft 

gestalten? Mitteilungen der Deutschen Malakozoologischen Gesellschaft, 1: 41-42. 



1 (Jungbluth & Boeters, 1977) 



ANT UND JUNGBLUTH 



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FIG.3. Pomatias elegans (G. F. Müller, 1774) am westlichen Odenwaldabhang. Diese substratgebundene Art 
ist entlang der naturräumlichen Einheit Bergstrasse verbreitet. Sie besiedelt hier das westlich an den Odenwald 
anschliessende Gebiet, das durch Lössauflagen einen entsprechenden Mindestkai kgehalt im Boden aufweist. (1 
X 1 km; Punkt: Funde nach I960; halber Punkt: Funde vor 1960; Stern: Literaturangaben; Bearbeiter: 
Helmut Ritter). 



190 



PROC. SIXTH EUROP. MALAC. CONGR. 



DEUTSCHLAND 

HESSEN 

E. E. W. 

(ERFASSUNG DER EURO- 
PÄISCHEN WIRBELLOSEN) 
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FIG. 4. Limax flavus Linnaeus, 1758, in Hessen. Das Kartenbild zeigt, dass neuere Fundnachweise fehlen. 
Dies ist offensichtlich auf die für die Art veränderte ökologische Situation in Mitteleuropa zurückzuführen. 
Hier kann L. flavus früher in den feuchten, nnit Lehmböden ausgestatteten Kellern vor, die heute nur noch 
ausnahmsweise vorhanden sind. (10 X 10 km; halber Punkt: Funde vor 1960; Stern: Literaturangaben). 



ANT UND JUNGBLUTH 



191 





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FIG. 5. Unió pictorum (Linnaeus, 1758) in Hessen. Die Art ist nicht in denn Masse an grosse Fliessgewässer 
sowie deren Altwässer wie U. tumidus gebunden und weist so eine weitere Verbreitung auf. (10 X 10 km; die 
naturräumlichen Einheiten sind eingezeichnet; Punkt: Funde nach 1960; halber Punkt: Funde vor 1960; 
Stern: Literaturangaben). 



192 



PROC. SIXTH EUROP. MALAC. CONGR. 




Margaritifera mavgavitifeva (LINNAEUS 1758) 



FIG. 6. Margaritifera margaritifera (Linnaeus, 1758) in der BRD. Die Flussperlnnuschel hat in den letzten 
Jahrzehnten erhebliche Teile ihres Areales in Mitteleuropa verloren und ist heute meist nur noch in 
schwachen Populationen vertreten. (Computer-Karte der BRD, jede Signatur entspricht einem 10 X 10 km 
Quadrat; Punkte: Funde aus dem Zeitraum 1950-1975; Kreise: Funde vor 1950; Dreieck: Literaturangaben). 



ANT UND JUNGBLUTH 



193 




FIG. 7. Karte der BRD mit malakozoologisch bearbeiteten Gebieten. In die Gitternetzkarte der BRD sind die 
bearbeiteten Gebieten eingezeichnet: 1 = Nordrheinwestfalen; H. Ant; 60 Arten, 1977; 2 = Hessen; J. H. 
Jungbluth; 204 Arten, 1978; 3 = Vogelsberg; J. H. Jungbluth; 131 Arten, 1975 (publiziert, s. Literatur); 
4 = Odenwald; H. Ritter; 170 Arten, 1974; 5 = Heidelberg; M. Kirchesch; 151 Arten, 1976. 



194 



PROC. SIXTH EUROP. MALAC. CONGR. 




FIG 8 Verbreitung von Candidula unifasciata (Poiret. 1801) in Nordwestdeutschland, dargestellt als 
PunkS^erbrertungskarte ohne Gitternetz (aus Ant. 1963b). Diese Art der Darstellung .st heute überholt und 
sollte nicht mehr verwendet werden. 



ANT UND JUNGBLUTH 



195 



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CANDI DULA UN I PASC I ATA 
H.ANT/HAMM 



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9 

8 

7 
6 



57 



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56 



FIG. 9. Verbreitung von Candidula unifasciata (Poiret, 1801) in Nordrtieinwestfalen. (10 X 10 km; Punkt: 
rezentes Vorkomnnen, Kreuz: Genistfund). 



MALACOLOGIA, 1979, 18: 197-201 

PROC. SIXTH EUROP. MALAC. CONGR. 

ZUR INTEGRATION CHOROLOGISCHER UND ÖKOLOGISCHER BEFUNDE 

DER MALAKOZOOLOGIE IN DIE ÖKOLOGISCHE 

LANDSCHAFTSFORSCHUNG 



Jürgen H. Jungbluth 

Zoologisches Institut I der Universität, 
Im Neuenheimer Feld 230, 6900 Heidelberg, F.R.G. 

ABSTRACT 

Until recently ecological studies of the landscape have only been carried out by 
geographers; zoological data have hardly been taken into consideration. The following 
remarks, based on zoogeographlcal and ecological results from malacological work in 
Hessen (West Germany), partially using the UTM grid, are the first zoological contribu- 
tions to this branch of science. An ecological study of the landscape should try to record 
all facts of importance, both biotic and abiotic, in order to characterize a certain type of 
landscape. This may be done by an elementary analysis, deductive (cf. the division of 
natural regions in West Germany) as well as inductive (cf. the nature-conditioned 
landscapes in East Germany). According to the size of the areas under discussion, it is 
possible to use chorological results for the larger ones, and ecological results for smaller 
areas, the so-called topes in a topological dimension. Freshwater molluscs characterize 
their biotopes (habitats) by special coenoses and in addition they indicate the quality of 
the water. Therefore they may be used to classify the natural region where such waters 
occur. The ecology of land gastropods shows that the species belong to certain coenoses 
and biotopes (habitats). The most important factors here are geological formation, soil, 
humidity, temperature, etc. With regard to the above it is possible to find the same 
species and coenoses in topes of equal abiotic and biotic arrangement in a topological 
dimension. 

Die ökologische Landsciiaftsforschung hat sich die Erfassung der Landschaft in ihrer 
Gesamtheit (Alexander von Humboldt: "Charakter einer Erdgegend," vgl. Schmithüsen, 1976) 
zum Ziel gesetzt. Zur Verwirklichung dieses Anspruches in ganzheitlicher Sicht bedient sie sich 
der Elementaranalyse und der Komplexanalyse (Neef, 1965). Die unterschiedlichen Wege, 
dieses Ziel zu erreichen, fanden in der "naturräumlichen Gliederung" der BRD (Schmithüsen, 
1953 u.a.) als deduktivem und in den "naturbedingten Landschaften" der DDR (Schultze, 1955 
u.a.) als induktivem Ergebnis ihren Niederschlag, um nur zwei Beispiele zu nennen. Beide 
Konzeptionen sind als methodisch einander ergänzend und nicht als konträr anzusehen. In der 
topologischen Dimension finden sie heute mit verfeinerten Feld- und Laboranalysen in den 
Untersuchungen zur "naturräumlichen Ordnung" (Haase, 1964; Richter, 1967) ihre Fortsetzung. 
In dieser räumlichen Dimension werden die Daten zur Charakterisierung und Bilanzierung der 
kleinsten Einheiten, der Tope, erhoben. Nach ihren stabilen bzw. labilen Merkmalen oder ihrer 
"ökologischen Varianz" abgegrenzt, werden diese Räume nach dem sie prägenden Geofaktor 
bezeichnet. Wir sprechen von Morpho-, Pedo-, Klima- und Hydrotopen bzw. Phyto- und 
Zootopen (Fig. 1). Der Physiotop (site) umfasst alle Daten der abiotischen Kategorie und gilt 
als Zentral begriff der komplexen physischen Geographie (Neef, Schmidt & Lauckner, 1961). 
Seine biotische Entsprechung sind Flora und Fauna (cover) als die Summe der Geofaktoren der 
vitalen/biotischen Kategorie. Die Integration der Biota (Phytotop + Zootop) und Abiota (d.h. 
der zum Physiotop vereinigten abiotischen Tope) spiegelt über den Ökotop hinaus auch das 
Ökosystem wieder. 

Trotz der engen Verknüpfung der Biota mit der ökologischen Landschaftsforschung seit 
Alexander von Humboldt und ihrer bereits früh erkannten Zeigereigenschaften wurde zumeist 
nur die Flora berücksichtigt, was zweifellos auf methodische Probleme zurückzuführen ist. 
Klink (1966) und Haase (1967) haben auf die vordringliche Berücksichtigung und Untersuchung 

(197) 



198 



PROC. SIXTH EUROP. MALAC. CONGR. 



к о t о p 



^ 



Synthese 



analytisch • 



^ 



Geofaktoren der anorganischen 
Kategorie 

A Ъ i о t a 



Physiotop 
( site ) 



Relief 



'Wasser 



•haushält 



< \ Boden I * 



Klima 



Geofaktoren der vitalen 
Kategorie 

В i ota 



Z о о t о p 
+ 
Phytotop 
( cover ) 



Abbild 



Integration Faktoren Integration 



Abbild 



FIG. 1. Verknüpfungen und Betrachtungsweisen innerhalb der topologischen Dimension (in Anlehnung an 
Neef und Schultze). 

der Tierwelt (und hier insbesondere auf die der ortssteten Kleinlebewesen) hingewiesen. Durch 
in der topologischen Dimension erhobene Befunde wird eine Beurteilung enger Korrelationen 
zwischen Unnwelt/Organismus und Umwelt/Coenose möglich, die zur Erhellung kausaler Zusam- 
menhänge innerhalb des Geokomplexes (funktionell: Ökosystem) beiträgt. Für eine 
entsprechende Berücksichtigung der Fauna in der ökologischen Landschaftsforschung erscheint 
ein multipler Ansatz notwendig: 

(I) zur Integration in die bereits vorliegenden Landschaftsbearbeitungen der naturräumlichen 
Gliederung in der BRD bieten sich besonders chorologische (biogeographische) Methoden und 
damit grossräumig gewonnene Ergebnisse an; 

(II) in den Rahmen der Gesamtbilanzierung und -Charakterisierung kleinster Räume (Tope) in 
der topologischen Dimension scheinen sich mit tierökologischen Methoden erzielte Daten am 
ehesten einzufügen. 

Eine Synthese beider Ansätze wird über die Eigenschaft der Biota als Zeigerarten und 
-gesellschaften,— d.h. als Bioindikatoren—, zur Beurteilung von Raum- bzw. Standortqualitäten 
führen. Auf diesem Wege wäre über die Integration der Daten aller Tope der anorganischen 
(abiotischen) und vitalen (biotischen) Kategorien eine Charakterisierung und Bilanzierung und 
damit die Erfassung der Landschaft in Sinne Alexander von Humboldt's möglich. 

Direkte Beiträge zur ökologischen Landschaftsforschung liegen im Augenblick nur 
ansatzweise vor, da zumeist das zoologische Objekt im Vordergrund stand. Am ehesten ist hier 
noch die Arbeit von Mörzer Bruijns, Van Regteren Altena & Butot (1959) zu nennen oder auch 
die von Koepcke (1961). Weitere Untersuchungen beschäftigen sich mit verschiedenen Tiergrup- 
pen in landschaftsökologisch abgegrenzten Räumen, jedoch mehr aus chorologischer Sicht. 



MATERIAL UND METHODE 

Für die Prüfung einer möglichen Integration chorologischer Daten aus dem Bereich der 
Malakozoologie wurden verschiedene Gebiete in der BRD (Vogelsberg, Odenwald, Hessen) nach 



JUNGBLUTH 199 

der Methode des European Invertebrate Survey auf UTM-Gitternetz-Karten mit unterschiedlichen 
Quadratgrössen (1X1 km; 2,5 X 2,5 km; 10X10 km) bearbeitet. Dabei wurden alle erreichbaren 
Sammlungsdaten und Literaturangaben für Land- und Wassermollusken erfasst; die 
Sammlungsdaten wurden nach Zeiträumen (vor und nach 1960) aufgeschlüsselt in den Karten 
markiert. Für den Vogelsberg wurden z.B. für 131 Molluskenarten insgesamt 1.281 Angaben 
kartiert (2,5 X 2,5 km) und für Hessen von 204 Arten nahezu 19.000 (10 X 10 km). Obwohl nur 
für einige Arten flächendeckende Kartierungen vorliegen, ermöglichen die gesammelten Daten 
erste Aussagen über das malakozoologische Inventar verschiedener Naturräume. 

Unter ganz anderem Aspekt sind in dieser Beziehung die ökologischen Ergebnisse zu sehen und 
zu werten. Diese wurden nach den herkömmlichen Methoden (siehe z.B. Jungbluth, 1976) 
kleinräumig für einzelne Arten (autökologisch) oder für einzelne Gesellschaften (synökologisch) 
ermittelt. Eine Integration in die ökologische Landschaftsforschung scheint hier in enger 
Beziehung mit pflanzensoziologischen Befunden am sinnvollsten möglich zu sein; allerdings fehlen 
hierzu noch weitere Daten bzw. eine entsprechende Kooperation. Am Rande ist darauf 
hinzuweisen, dass für den Bereich der Zoologie bislang kaum synökologische Kartierungen 
vorliegen. Ökologische Untersuchungen wurden an Land-und Wassermollusken im Vogelsberg und 
im Odenwald durchgeführt. 

ERGEBNISSE 

I. Tiergeographische Ergebnisse 

Bei der Auswertung der Verbreitungsmuster und deren Bedeutung für eine 
landschaftsökologische Berücksichtigung müssen die Wasser- und Landmollusken getrennt 
betrachtet werden, da die Ausbreitung und die Areale der zuerst genannten Gruppe durch das 
Gewässernetz vorgegeben sind. Die Wassermollusken sind über ihre autozoische Dimension 
Bestandteil der Naturräume, in denen die entsprechenden Wohngewässer vorhanden sind. 
Trotzdem können sie mit ihrem Areal Naturräume charakterisieren und von angrenzenden, in 
denen die von der Art bevorzugten Gewässertypen fehlen, abheben. Für Bythinella dunkeri 
compressa haben wir dies an anderer Stelle bereits dargelegt (Jungbluth, 1976). Bithynia leachii 
gilt als palaearktisch sehr lückenhaft verbreitet und bewohnt gewöhnlich Pflanzenreiche Tümpel 
und Gräben. In unserem Untersuchungsgebiet ist ihr Vorkommen auf die Naturräume des 
Rhein-Main-Tieflandes (Fig. 2) begrenzt und strahlt lediglich noch in das Rheintal ein. Galba 
glabra, eine Art mit sehr ähnlichen Biotopansprüchen, weist eine vergleichbare Bindung an die 
genannten Naturräume auf und erreicht hier in flächenhafter Verbreitung ihre südliche Arealgrenze 
in Deutschland (Fig. 2). Bei den Landschnecken gelten Feuchtigkeit, Temperatur und 
Substrateigenschaften als verbreitungslimitierende Faktoren. Diese können in den naturräumlichen 
Einheiten punkthaft ein Milieu bedingen, das die Voraussetzungen für das Vorkommen einzelner 
Arten ist, ohne dass hier ein Bezug zum grösseren Naturraum evident wird. An dieser Stelle führen 
die kleinräumig ermittelten ökologischen Daten zur weiteren Klärung: so konnte für Pomatias 
elegans, einer caiciphilen Art, in der Verbreitung eine gute Übereinstimmung mit entsprechenden 
Pflanzengesellschaften und über diese mit den zugehörigen Bodentypen (Pedotopen) gefunden 
werden. Im Untersuchungsgebiet fällt die Hauptverbreitung dieser Art mit der naturräumlichen 
Einheit Bergstrasse zusammen, die durch Lössauflagen am westlichen Odenwaldhang und das 
Gunstklima des nördlichen Oberrheintieflandes gekennzeichnet ist und so grossräumig die 
Bedingungen für das Auftreten dieser substratgebundenen Art schafft. Die chorologischen 
Ergebnisse für hygrophile Arten oder aber auch südliche und östliche Arten lassen ähnliche 
Übereinstimmungen mit naturräumlichen Einheiten im Untersuchungsgebiet erkennen (Jungbluth, 
1976). 

II. Tierökologische Ergebnisse 

Die Landschnecken erscheinen von der Anlehnung ihrer Coenosen an die Vegetationsformationen 
her gut geeignet, um als zoologische Komponente in der ökologischen Landschaftsforschung 
Berücksichtigung finden zu können; wie bereits erwähnt wurden jedoch noch keine speziellen 
Untersuchungen unter diesem Aspekt durchgeführt. In der topologischen Dimension ergeben sich 



200 



PROC. SIXTH EUROP. MALAC. CONGR. 





FIG. 2. Die Verbreitung von Bythinia leachii (linl<s) und Galba glabra (rechts) 
Ordnungsstufen nummeriert) von Hessen. 



in den Naturräumen (nach 



hier gute Übereinstimmungen zwischen Tier- und Pflanzengesellschaft sowie dem Physiotop in der 
Ausdehnung. Die Untersuchung der Helicella itala-Zebrina detrita-Coenose am Weinberg, einem 
Kalkhang im südlichen Vogelsberg, sei hierfür beispielhaft genannt (Fischer, 1972). Der|Hang bei 
Kressenbach kann wegen seiner gleichartigen morphograph ¡sehen Eigenschaften als Morphotop 
aufgefasst werden, der zwei verschiedene Pflanzenassoziationen aufweist. Die Zweiteilung der 
Phytocoenose spiegelt sich auch in den Schneckengesellschaften wieder. Der grösste Teil des 
südexponierten Hanges ist von Mesobrometum bestanden, seitlich schliesst sich ein an 
Rosengewächsen und Hasel reich bestandenes Gebüsch an. In diesem waren vier Waldschnecken 
nachzuweisen, wahrend sonst subthermophile und thermophile Arten den Hang besiedelten. Die 
Waldarten Cochlodina laminata und Laciniaria biplicata waren auch an schattigen Stellen der sonst 
offenen Fläche des Mesobrometums zu finden während die Leitarten der Coenose Helicella ¡tala 
und Zebrina nicht in den Bereich der Hecke eindrangen. Schneckengesellschaft und 
Vegetationsformation wiesen in ihrer Bindung an den Morphotop des südexponierten Kalkhanges 
gute Übereinstimmung auf. Ähnliche Beobachtungen konnten auch bei Untersuchungen einer 
Schneckengesellschaft des Arrhenaterions an einem südlichen Hang des West-Odenwaldes bzw. 
eines feucht-kühlen Bruchwaldes auf Pseudegley im nördlichen Hohen Vogelsberg gemacht 
werden. 



LITERATUR 



FISCHER, В., 1972, Die Gastropodengeselischaft eines xerothermen Kalkhanges im südlichen Vogelsberg. 

Staatsexamensarbeit Giessen. 
HAASE, G., 1964, Landschaftsökologische Detailuntersuchung und naturräumliche Gliederung. Petermann's 

Geographische Mitteilungen, 108: 8-30. 
HAASE, G., 1967, Zur Methodik grossmassstäbiger landschaftsökologischer und naturräumlicher Erkundung. 

Wissenschaftliche Abhandlungen der Geographischen Gesellschaft der D.D.R., 5: 35-1 28. 



JUNGBLUTH 201 

JUNGBLUTH, J. H., 1976, Der zoologische Partialkomplex in der öl<ologischen Landschaftsforschung: 

malal<ozoologische Beiträge zur naturräumlichen Gliederung. Dissertation Saarbrücken. 
KLINK, H.-J., 1966, Naturräumliche Gliederung des Ith-Hils-Berglandes. Art und Anordung der Physiotope. 

Forschungen zur deutschen Landeskunde, 159: 1-257. 
KOEPCKE, H.-W., 1961, Synökologische Studien an der Westseite der peruanischen Anden. Bonner 

Geographische Abhandlungen, 29: 1-320. 
MÖRZER BRUIJNS, M. F., VAN REGTEREN ALTENA, С О. & BUTOT, L. J. M., 1959, The Netherlands as 

an environment for land Mollusca. Basteria, 23, Supplement: 132-162. 
NEEF, E., SCHMIDT, G. & LAUCKNER, M., 1961, Landschaftsökologische Untersuchungen an verschiedenen 

Physiotopen in Nordwestsachsen. Abhandlungen der sachsischen Akademie der Wissenschaften, 

Mathematisch-Naturwissenschaftliche Klasse, 47(1): 1-112. 
RICHTER, H., 1967, Naturräumliche Ordnung. Wissenschaftliche Abhandlungen der Geographischen 

Gesellschaft der D.D.R., 5: 1 29-160. 
SCHMITHÜSEN, J., 1953, Grundsätzliches und Methodisches. Einleitung. In: MEYNEN, E. & SCHMITHÜSEN, 

J., Hrsg., Handbuch der naturräumlichen Gliederung Deutschlands, 1 : 1-44. Bad Godesberg. 
SCHMITHÜSEN, J., 1976, Allgemeine Geosynenergetik. In: OBST, E., Hrsg., Lehrbuch der Allgemeinen 

Geographie, 1. Berlin. 
SCHULTZE, J., 1955, Über Landschaften und ihre Gliederung. Grundlegung und Arbeitsverfahren.' In: 

SCHULTZE, J. et al.. Hrsg., Die Naturbedingten Landschaften der Deutschen Demokratischen Republik. 

Ergänzungshefte zu Petermann 's Geographische Mitteilungen, 257: 1-64. 



MALACOLOGIA, 1979, 18: 203-210 

PROC. SIXTH EUROP. MALAC. CONGR. 

DIE SUKZESSION DER SCHNECKENZÖNOSEN IN DEN WÄLDERN 
DES ALFÖLD UND DIE METHODEN ZUM STUDIUM DER SUKZESSION 

K. Baba 
Zoologischer Lehrstuhl der Pädagogischen Hochschule "Gyula Juhasz," Szeged, Ungarn 

ABSTRACT 

The role of river-transported land snails in primary stocking of flooded shores was 
studied in the lowlands of Hungary. Eight Recent and fossil samples studied (Table 1) 
show differences on the basis of the order of succession of the species carried (Table 2) 
and on the basis of accidental elements. The composition of the floating fauna carried is 
determined, as already expected, by the climatic potentialities of the country adjoining 
the rivers. The difference in composition of the Recent and Pleistocene alluvial samples 
may be attributed to different climatic conditions. The composition of the alluvial fauna 
may therefore also be used in climate reconstruction analysis (Table 3). The frequency 
distribution of the snails of the Tisza Salicetum is close to the order of succession of the 
river-carried fauna of the Tisza river. The living snails carried to the banks of the river 
downstream may become adapted to local conditions and through organogenic succession 
may become naturalized elements or accidental elements in other types of vegetation 
(Fig. 1) in accordance with local environmental conditions. 

EINLEITUNG 

Im Laufe meiner sich auf rund 20 Jahre erstreckenden Studien der Schnecken des 
Ungarischen Alföld (Tiefebene) habe ich in den Waldassoziationen des Alföld das Ineinan- 
derübergehen der Schneckenzönosen, d.h. den Prozess ihrer Sukzession, untersucht und dabei 
die Sukzession der Seh necken bestände parallel mit der Vegetationssukzession, vornehmlich in 
Naturschutzgebieten bzw. in den noch vorhandenen Wäldern mit natürlicher Erneuerung, 
studiert. In der vorliegenden Studie wird untersucht, welche Rolle den vom Flusswasser 
getragenen Schnecken in der primären Besiedlung der Wälder entlang den Flussläufen zukommt. 

UNTERSUCHUNGSMETHODIK, ZIELSETZUNG 

Anhand von Probenentnahmen nach der Qu ad rat- Methode habe ich annähernd 400, 
insgesamt 13 Waldtypen angehörende, Waldassoziationen untersucht (Baba, 1977). Die unter- 
suchten Waldtypen gehören 3 Vegetationssukzessionsreihen an. Studiert habe ich die Verteilung 
der Zahl der festgestellten Arten in den Wäldern der 3 Vegetationssukzessionsreihen. 

Um zu einer Entscheidung hinsichtlich der faunentransportierenden Rolle des Flusswassers zu 
kommen, habe ich 24 den Forderungen der zufälligen Probenentnahme entsprechende Fluss- 
geschiebeproben analysiert. Neben den Flüssen des Alföld habe ich vergleichsweise auch 
Geschiebeproben von einem Bach im Ungarischen Mittelgebirge, sowie auch aus dem Oberen 
und Unteren Pleistozän stammende Flussgeschiebeproben mituntersucht. In den rezenten und 
den Pleistozän-Proben kamen 36,290 Individuen von insgesammt 108 Arten vor (Tabelle 1). 
Weitere 9, für die Geschiebefauna neue Arten kamen im Laufe der Einsammlungen von Baba 
(Vásárhelyi, 1962 in Baba et al., 1962) entlang der Theiss zum Vorschein. Diese sind: Acme 
similis Reinhardt, Cecilioides petitiana (Benoit) (Horváth, 1962), Arion subfuscus (Drap.) 
(Baba), Oxychilus glaber striarius (West.), 0. orientalis (Cless.) (Vásárhelyi, 1958 in Bereczk et 
al., 1958), Deroceras agreste (L.), D. laeve (O. F. Müller) (Baba), Trichia villosula (Rm.), T. 
unidentata (Drap.), Hygromia transsylvanica (West.) (Vásárhelyi, 1958 in Bereczk et al., 1958), 
Helix lutescens Rm. (Baba). 

Dies bedeutet einen Anstieg der aus Geschiebeproben zum Vorschein gekommenen Arten 
bis auf 117. Die aus dem Flussbett herausgespülten fossilen Schalen und ausgeblichenen 

(203) 



204 PROC. SIXTH EUROP. MALAC. CONGR. 

subfossilen Schalen wurden bei der Analyse der rezenten Flussgeschiebeproben unberücksichtigt 
gelassen. Unter Zugrundelegung der Dominanzwerte der in den einzelnen Proben vorkommenden 
Arten habe ich eine Rangordnungsskala betreffs der Tragehäufigkeit der Arten aufgestellt. Eine 
Rangliste habe ich auch aufgrund der Schneckenarten der das erste Stadium der organogenen 
Sukzession bildenden (Salicetum) Weidenbestände angefertigt. Die Geschiebe- bzw. Tragungs- 
ausdehnung \der von den verschiedenen Flüssen transportierten gleichen Arten habe ich 
aufgrund der Häufigkeitskonfidenzintervall-Berechung verglichen. 

Bei der Analyse der Flussgeschiebeproben strebte ich nicht eine faunistische Analyse an, wie 
die früheren Autoren (Czógler & Rotarides, 1938), sondern trachtete zu klären, ob die 
Flusswasser-getragene Fauna gemeinsame qualitative und quantitative Züge aufweist, ob hinsicht- 
lich der einzelnen Flussabschnitte und ihres Charakters Abweichungen im Transport bestehen 
und ob zeitliche Gesichtspunkte des Transports beantwortet werden können. Die Möglichkeit 
hierzu war gegeben, da die Proben aus den Jahren 1922, 1958 und 1975 stammen. 

Die Fundorte der Geschiebeproben waren: 1, Bükk-Gebirge, Szalajka-Bach, VII. 1963, leg. A. 
Horváth; 2-3, Dorogpuszta, Dorogháza-Ujtelep, VI. 1976; 4-6, Zagyva, Pásztó, lll-IV. 1975, IV. 
1976, leg. A. Varga; 7-12, Theiss (von Norden nach Süden): Tiszavid, VII. 1966, Vásárosna- 
mény-Bagiszeg, X. 1958, Kisköre, VII. 1975, Hódmezovásárhely-Szeged, 1922; 11-12, Szeged, 
1938, 1975, leg. G. Kolosváry, A. Horváth, К. Baba, M. Rotarides, К. Czógler, und К. Baba; 
13, Marosch, 2km oberhalb der Flussmündung, VII. 1975, leg. K. Baba; 14-19, Donau: 
Esztergomsziget, Pilismarót, Esztergom: Wasserwerk-Ferenceskert-Kenyermezö, V-Vll. 1965, leg. 
L Pinter; 20, Szabadhidvég: Unteres Pleistozän; 21-23, Koröshegy: Obere Phase des Unteren 
Pleistozän; 24, Hódmezovásárhely: Oberes Pleistozän, leg. E. Krolopp. 

Den Herren Kollegen Krolopp, Pinter und Varga entbiete ich für die Überlassung der Proben 
auf diesem Wege meinen Dank. 

Die Artenliste der Geschiebeproben enthält Tabelle 1, vereinfacht auf Fundorte bezogen. Bei 
den Proben ist nur das Vorkommen vermerkt. Die Proben der gleichen Flüsse sind durch 
Addieren vereinfacht; die Ziffern bedeuten die Häufigkeit des Vorkommens. 

DIE VERTEILUNG DER IN DEN WALDSUKZESSIONEN 
GEFUNDENEN ARTEN 

49% der im Alföld gefundenen 72 Arten (Baba, 1977) sind waldbewohnende, feuchtigkeits- 
liebende Elemente. 

Solche mit höheren Feuchtigkeitsansprüchen sind: Acicula polita, Pomatias rivulare, 
Aegopinella pura, Oxychilus glaber, O. inopinatus, Arion circumscriptus, Limax cinereoniger, 
Cochlodina laminata, Clausilia pumila, Laciniaria plicata, L. bi plicata, Ruthenica filograna. 
Discus rotundatus, Perforatella bidentata, P. dibothrion, P. incamata, P. vicina, Helicigona 
banatica, H. arbustorum, Trichia hispida und 7". unidentata. 

Über niedrige Feuchtigkeitsansprüche verfügen: Columella edentula. Punctum pygmaeum, 
Arion subfuscus. Vitrea crystallina, Nesovitrea hammonis, Limax nyctelius, Aegopinella minor, 
Bradybaena fruticum, Hygromia kovacsi und Euomphalia strigella. 

Auffallend ist, dass diese Arten in den mit fliessenden Wässern reichlicher versehenen, 
waldigen Anteilen anzutreffen sind. Die Zahl der Arten mit höhern Feuchtigkeitsansprüchen 
wird mit zunehmender Entfernung von den Flüssen geringer. Auch die Gesamtartenzahl lässt 
nach, und zwar je nach den Vegetationssukzessionsreihen in unterschiedlicher Weise. Die 
Verteilung der Gesamtartenzahl in den 3 Vegetationssukzessionsreihen veranschaulicht Fig. 1. Es 
¡st festzustellen, dass die grössten Artenzahlen nahe den fliessenden Gewässern in der 
organogenen Sukzessionsreihe erscheinen. 

Die Mehrzahl der Arten mit höheren Feuchtigkeitsansprüchen sind in niedriger Individuen- 
zahl vorkommende, akzidentelle Elemente (Vorkommenshäufigkeit 0-10%); andere werden in 
den Inundationswäldern zu konstant-dominanten Elementen. Die Erklärung der Erscheinung: 
der Reichtum der Schneckenfauna des Ungarischen Alföld an waldbewohnenden Arten ist das 
Resultat der ständigen faunentransportierenden Wirkung der fliessenden Gewässer, was für eine 
Bevölkerung der Malakofauna des Alföld von den Gebirgsgegenden her spricht. Dies beweist der 
Umstand, dass, mit der Entfernung von den Flüssen, in den Waldtypen der Waldsukzessions- 
reihen Waldbewohner selten sind. Ebenfalls gering ist die Zahl der waldbewohnenden 
Schnecken in dem an Wasserläufen armen südlichen Alföld und im nördlichen Teil des Alföld 



BABA 
MINEPALOGENE SUKZESSION 



205 



AUFFÜLLUNG 



TROCKNUNG 



Calamagostrís -Salicet-um cinereae (23%) Salid pen^andnae-ße^ulehJm (25%) 
Dyophericli-Alnel'um(l5%) Fraxino pannonicae-Alnehum (39%) 



ORGANOGENE SUKZESSION 



AUFFÜLLUNG 



TCOCkNUNG 



HUMIFIZIE- 
RUNG 



Salice^um (41%) »^ Fraxino pannonicae -Ulmet-um (67%) 

p . .^. - . /,^„/^ Querco roboris-Carpinehum (35%") 

Fesmcopseudovinae-Quercel-um (16%) 4. 

(bnvallario-Quercetum (24%") 



VON SANDßASEN AUSGEHENDE SUKZESSION 



BEFEUCHTUNG 



Bromehum j-ectorum (5%) 
Fesf'ucehum vaginal'ae(l't%). 



Junipero-Populeiumalbae (15%) 
Fesiuco-Quercehum roboris (25%) 



FIG. 1. Veranschaulichung der Artenzahl-Verteilung der Schnecken in den verschiedenen Vegetations- 
Sukzessionsreihen. 

am Fusse des Bükk- und des Matra-Gebirges. In den dem Alföld zugekehrten Anteil dieser 
Gebirge gibt es sehr wenig fliessende Gewässer. 



AUS DER ANALYSE DER GESCHIEBEFAUNA SICH 
ERGEBENDE LEHREN 

Aufgrund der aus den Flüssen stammenden 24 Geschiebeproben können qualitative und 
quantitative Feststellungen getroffen werden. Die qualitative Zusammensetzung der getragenen 
Schneckenfauna zeigt, dass die hochmontanen Arten aus dem Geschiebe sowohl der Theiss als 
auch der Donau nur sporadisch zum Vorschein kommen (was die Feststellungen von Czógler & 
Rotarides, 1938, bekräfticht). Dies bedeutet, dass das getragene Material des Geschiebes nicht 
aus den Hochgebirgen, sondern von den schmalen Zonen der niedrigen, mittelgebirgigen und 
hügeligen Bachufer der Wassersammeigebiete der Flüsse stammen kann. 

Zwischen den untersuchten, aus 3 Zeitepochen stammenden Sammlungen entlang der Theiss 
besteht hinsichtlich der qualitativen und quantitativen Verhältnisse der Arten kein wesentlicher 
Unterschied. 

Nach dem Vergleich der von den einzelnen Flussabschnitten zum Vorschein gekommenen 
Proben und dem Vergleich der von der gleichen Donaustrecke stammenden Proben der Donau 
ist zu sagen, dass hinsichtlich der qualitativen Zusammensetzung der akzidentellen Elemente 
Abweichungen möglich sind. Die Geschiebe, bzw. Trage-Ausdennung, der Arten zeigt, von 
einigen Arten angesehen, streckenweise Unterschiede, doch decken die Tragungsintervalle auch 
hier einander häufig. 

Die einzelnen Flüsse lassen sich auch anhand der von dem betreffenden Fluss getragenen 
akzidentellen Arten kennzeichnen. Die akzidentellen Arten zeigen die zoogeographischen 
Unterschiedlichkeiten der Wassersammeigebiete auf und machen auf die Wichtigkeit der 
Erforschung der Geschiebefauna der Nebenflüsse aufmerksam. 

Die differenzierenden, kolorierenden Elemente der Geschiebefauna der einzelnen Flüsse sind: 

Zagyva: Helicodiscus singleyanus, Oxychilus gl aber, Daubedardia rufa. 

Theiss: Pomatias rivulare, Cochlodina transsy/vanica, С orthostoma, Ruthenica filograna, 
Laciniaria plicata, Iphigena latestriata, I. túmida. Vitrea transsylvanica, Perforatella dibothrion, 
P. vicina, Trichia bieizi euconulus, T. villosula, Isognomostoma isognomostoma und Helix 
lutescens (aus der Theiss und dem nördlichen Nebenfluss der Theiss, der Zagyva, kamen zum 
Vorschein: Ena obscura, Iphigena ventricosa, Clausilia pumila, Oxychilus inopinatus, Perforatella 
bidentata, P. vicina, Hygromia transsylvanica und Discus perspectivus). 

Marosch (Nebenfluss der Theiss im Süden): Chondrula tridens albolimata, Cecilioides 



206 PROC. SIXTH EUROP. MALAC. CONGR. 

petitiana, Trichia sericea, Helicigona faustina, H. banatica (aus der Theiss und auch aus der 
Marosch kamen Aghardia parreysi, A. bieizi und A. truncatella zum Vorschein). 

Donau: Vertigo alpestris, Trichia strio/ata danubialis, T. unidentata, T. hispida, Helicigona 
arbustorum und Cepaea hortensis (die beiden Orcula- und die Zebrina-AxX werden ausser von 
der Donau auch von der Zagyva und der Marosch transportiert). 

Die Zahl der akzidentellen Arten (30%) der Theiss liegt höher als die in der Donau 
anzutreffende (21%), was auf den Unterschied zwischen den Wassersammeigebieten hindeutet 
(Tabelle 2). 

In quantitativer Hinsicht noch interessanter ist es, wenn man die in den gesamten Proben 
vorkommenden Arten untersucht. Es waren 23 Arten auffindbar, die in den Geschiebeproben 
der Theiss, der Donau und des Oberen Pleistozän gleichermassen vorkommen (Tabelle 3). 

Von den Werten der Trageausdehnung der Theiss und der Donau gleichermassen verschieden 
sind jene des Tragebereichs im Pleistozän. Von den Arten waren die Granaria-, 2 Va/Ionia-, die 
Succinea-, Chondrula- und Trichia- Arten nach der Ansicht von Lozek die Schnecken der 
Lösz-Steppen. All dies deutet darauf hin, dass die quantitative Zusammensetzung der Geschiebe- 
fauna sich dem durchschnittlichen Klimazustand der Epoche anzupassen scheint. Dies bedeutet 
auch, dass die Flüsse auf ihren Flussabschnitt im Alföld ab ovo in einem solchen prozentuellen 
Verhältnis Schneckenarten tragen inklusive auch die selteneren Waldbewohner, in welchem prozen- 
tuellen Verhältnis sie vom Wasser aus den Bergen heruntergespült werden. Bei den klima- 
empfindlichen Schnecken hängt dieses Verhältnis vom Klimazustand der Wassersammeigebiete ab. 

Das in Mittel-Europa herrschende, teils kontinentale, Klima schafft auf weiten Gebieten 
gleiche Bedingungen. Daher stehen das Tragungsausmass der von der Theiss und der Donau 
transportierten Schnecken einander näher. Die Wassersammeigebiete der einzelnen Flüsse sind 
aber meso-und mikroklimatisch verschieden, daher kommt es, dass die einzelnen Flüsse sich in 
der Transporthäufigkeit der transportierten Arten, d.h. in ihrer Rangordnung, voneinander 
unterscheiden. An der Rangordnung-Skala an Tabelle 2 sind die ersten 10 Arten eingetragen. Die 
Ziffern in den einzelnen Kolumnen geben auf den Fluss bezogen die Rangordnungsreihenfolge 
des Tragens an. Der Unterschied zwischen den Flüssen betreffs der Trage-Rangordnung der 
Schnecken entspricht den mesoklimatischen Unterschieden der Wassersammeigebiete. Die an der 
Rangordnung-Skala der Geschiebeschnecken der Donau eingetragenen Arten Zeigen aufgrund 
ihrer klimatischen Ansprüche den kühleren, feuchteren Charakter der Alpen, während die Inder 
Rangordnung-Skala der Theiss verzeichneten Arten einen warmen, feuchten Charakter vertreten. 
Ebenso differieren auch die Pleistozän-Proben. So tragen von den Proben aus dem Unteren 
Pleistozän die ersten einen glazialen, die zweiten und die aus dem Oberen Pleistozän 
stammenden aber interglazialen Charakter zur Schau. Aufgrund der Rangordnung-Skala wird 
eine Rekonstruierung der Klimaabweichungen möglich. 

Die letzte Kolumne in Tabelle 2 zeigt die Rangordnung-Skala der aus den Weidenbeständen 
entlang der Theiss zum Vorschein gekommenen konstant-dominanten Arten, Von beweisendem 
Wert ist der Vergleich mit der Rangordnungs-Skala der Geschiebefauna der Theiss. Die 
Gegenüberstellung der Rangliste der vom Flusse getragenen Arten und der Arten aus den 
Wäldern entlang den Flussufern beweist hinsichtlich der ersten 6 Stellen die aktive Faunen- 
transportierende Rolle des Flusses. 

AUSWERTUNG DER BEFUNDE 

Die Bevölkerung der organogenen Vegetationssukzessionsreihen mit Schnecken geschieht 
folgendermassen. Das Wasser trägt die Schnecken lebend herunter. In den niedrig gelegenen, 
alljährlich mehrmals von Überschwemmungen heimgesuchten Weiden beständen vermögen nur 
wenige Arten zu leben und sich zu vermehren, wie z.B. die Arianta arbustorum im Donau-Tal. 
In die höher gelegenen Orte, z.B. Auwälder, gelangt, gehen nur jene Arten nicht zugrunde, 
deren Toleranz die gegebene Umwelt entspricht. In den Auwäldern lassen sich diejenigen Arten 
dauerhaft nieder, die gemäss dem Charakter der lichtreichen Wälder auch massig oligotherm 
sind. Aus den Auwäldern gelangen sie infolge der Vegetationssukzession in andere, von 
den Flüssen entfernt gelegene Waldtypen. Von den Buschweiden an ändern sich in den 
einzelnen Waldtypen auf immer höher gelegenen Terrains die Zusammensetzung und die 
quantitativen Verhältnisse der Schneckenfauna. Entsprechend den veränderten Umweltverhält- 
nissen kommt es bereits in den Weidenbeständen (Salicetum) zur Adaptation der auf dem 
Wasserwege eintreffenden Schneckenarten. Daher stimmt die Rangordnungsliste der Weiden- 



BABA 



207 



bestände nicht vollkommen mit jener der eintreffenden Geschiebefauna überein. Die 
Wahrscheinlichkeit der Ansiedlung und des Nachschubes sichern die zeitlich konstant wirksamen 
erneuten Überschwemmungen. Die im Flusslauf aufscheinenden regionalen quantitativ- 
qualitativen Abweichungen sind den regional verschiedenen Trage- bzw. Geschiebeausdehnungen 
zu verdanken. Aus diesem Umstand und den Transportunterschieden der Nebenflüsse erklärt 
sich zoogeographisch der in den verschiedenen Landschaften des Alfeld zu beobachtende 
Unterschied in den Schneckenzönosen. Die Realität des Prozesses unterstützt auch, dass in den 
Auwäldern die meisten Waldbewohner akzessorische Elemente mit Konstanzwerten von 10-20% 
sind. In den verschiedenen Landschaftseinheiten können die Waldbewohner abweichende sein. In 
den Hainbuchen- und Maiglöckchen-Eichenwäldern, die von den Flüssen schon lange 
abgeschlossen sind, kommen wenig waldbewohnende Elemente vor. 

Bemerkt sei, dass auch im Falle eines kontinuierlichen Zusammenhanges von Alföld- und 
Gebirgswäldern die Verbreitung einiger montaner Arten im Alföld zu beobachten ist, so z.B. die 
Perforatella dibothrion im Nordöstlichen Alföld. Heute ist diese Verbreitungsweise wegen des 
Aufhörens der zusammenhängenden Waldungen selten. 

TABELLE 1. Die Artenliste der Geschiebeproben bezüglich der einzelnen rezenten und Pleistozän-Flüsse (die 
Proben der Gleichen Flüsse durch Addition vereinfacht). 



No. 



Arten 






ел 

=o 



> 

N 

E- 



1 . Poma ti as г i vu I a re E i с h w . 

2. Paladilhia oshanovae Pinter 

3. Acicula banatica Rossm. 

4. Carychium minimum O. F. Müll. 

5. Carychium tridentatum Risso 

6. Cochlicopa lubrica О. F. Müll. 

7. Cochlicopa lubricella Porro 

8. Columella edén tu la Drap. 

9. Truncatellina cylindrica Fér. 
10 Vertigo angustiar Jeffr. 

1 1 . Vertigo parcedentata A. Braun 

1 2 . Vertigo genesii G red I . 

1 3 . Vertigo pusilla O.F.Müll. 

14. Vertigo an tivertigo Drap. 

15. Vertigo moulinsiana Dupuy 

16. Vertigo pygmaea Drap. 

17. Vertigo alpestris A\öer 

1 8. Vertigo subs tria ta Jeffr. 

19. Argna bieizi Rossm. 

20. Argna parreyssi Pf r. 

2 1 . Orcula jetschini Kim . 

22. Orcula doliolum В rug. 

23. Orcula dolium Drap. 

24. Granarla f rumen tum Drap. 

25. Gastrocopta moravica Peubok 

26. Pupilla loessica Lozek 

27 . Pupilla sterri Vo i th 

28. Pupilla muscorum densegyrata Lozek 

29. Pupilla muscorum L. 

30. Pupilla triplicate Stud. 

31 . Vallonia pulchella O. F. Müll. 

32. Vallonia costata O. F. Müll 

33. Vallonia tenuilabris A. Braun 

34. Acanthinula aculeata O. F. Müll. 

35. Chondrula tridens O. F. Müll. 

36. Chondrula tridens albolimbata Pfr. 

37. Mastus venerabais L. Pfr. 

38. Ena obscura О. F. Müll. 

39. Zebrina de tri ta О. F. Müll. 

40. Cochlodina orthostoma Menke 
41 Cochlodina cerata Rossm. 

42. Cochlodina laminate Montagu 

43. Cochlodina commutata Rossm. 



- 


2 


2 


- 


1 
1 
5 


- 


- 


- 


- 


2 


4 
2 


+ 


+ 
+ 


3 


+ 


+ 


5 


5 


+ 
+ 
+ 


6 


+ 


3 


+ 
+ 


- 


- 


4 


- 


- 


- 


2 


+ 


^■ 


5 


5 


+ 


6 


+ 


3 


+ 


- 


5 


4 


+ 


4 


+ 


3 
2 


+ 
+ 


- 


3 
4 


6 


+ 


1 
6 


+ 


3 


+ 


- 


- 


4 


+ 


: 


— 


— 


+ 


- 


1 


1 
2 


+ 


1 


- 


- 


- 


^■ 


1 


2 
4 


_ 


1 


— 


— 


_ 


— 


- 


1 


- 


- 


— 


— 


— 



208 PROC. SIXTH EUROP. MALAC. CONGR. 

TABELLE 1. (fortgesetzt) 






No. Arten ,Й г5 f 5 п ,5? ^ Il 



■S ' 



44. Ruthenica filograna Rossm. 

45. Iphigena ven tricosa Drap. 

46. Iphigena la tes tria ta A. Schm. 

47. Iphigena túmida Rossm. 

48. Clausilia dubia Drap. 

49. Clausilia pumila С Pfr. 

50. Laciniaria plicata Drap. 

51. Laciniaria biplicata Montagu 

52. Laciniaria vetusta Rossm. 

53. Pseudalinda guio E. /K. B\e\z 

54. Alopia bieizi Pfr. 

55. Clausilia sp. 

56. Succinea oblonga Drap. 

57. Succinea e legan s Risse 

58. Succinea putris L. 

59; Cecilioides acicula O. F. Mû M. 

60. Punctum pygmaeum Drap. 

6 1 . Helicodiscus sing ley an us P i I s b . 

62. Discus ruderatus Hartm. 

63. Discus rotunda tus О. F. Müll. 

64 . Discus perspec ti vus M ü h I f . 

65. Vitrina pellucida О. F. Müll. 

66. Zonitoides nitidus O. F. Müll. 

67. Vitrea diaphana Studer 

68. Vitrea subrimata Re\nh. 

69. Vitrea crystallina O. F. Müll. 

70. Vitrea contracta West. 

71. Wfrea franss//i/a/7/ca Cless. 

72. Aegopinella pura Alder 

73. Aegopinella minor StabUe 

74. Nesovitrea hammonis Ström 

75. Oxychilus cellarius A. J. Wagner 

76. Oxychilus draparnaudi Beck 

77 . Oxychilus glaber striarius West. 

78. Oxychilus inopinatus U\\cr\\ 

79. Daudebardia rufa Drap. 

80. Limax sp. 

81. Deroceras laeve O. F. Müll. 

82. Deroceras agreste L. 

83. Euconulus fulvus O. F. Müll. 

84. Bradybaena fruticum O. F. Müll. 

85. Helicella obvia Hartm. 

86. Helicopsis striata O. F. Müll. 

87. Helicopsis cereof lava Rossm. 

88. Monacha cartusiana O. F. Müll. 

89. Perforatella bidentata Grr\. 

90 . Per fora te IIa di bo thrion M . Kim. 

91. Perforatella rubiginosa A. Schmidt 

92. Perforatella incarnata O. F. Müll. 

93. Perforatella viel na Rossm. 

94. Trichia bakowskii ?o\\r\sk\ 

95. Trichia unidentata Drap. 

96. Trichia striolata danubialis Clessin 

97. Trichia hispida L. 

98. Trichia sericea Drap. 

99. Trichia bieizi euconulus Polinski 

100. Trichia sp. 

101. Euomphalia s tr ige IIa Drap. 

102. Helicigona banatica Rossrr\. 

103. Helicigona faustina Rossm. 

104. Helicigona arbustorum L. 

105. Isognomostoma isognomostoma Schröter 

106. Cepaea vindobonensis Fér. 

107. Cepaea hortensis O. F. Müll. 

108. Helix pomatia L. 



- 


2 


- 


- 


- 


3 


_ 


2 


3 
3 
1 
2 
4 


~ 


~ 


~ 


~ 


— 


1 


- 


4 


+ 


1 


- 


3 


5 


+ 


- 


_ 


1 


_ 


2 


2 
1 
1 
1 


- 


1 


- 


~ 


~ 


- 


- 


- 


- 


3 


+ 


4 


3 


- 


5 


+ 


3 


+ 


2 


2 


+ 


3 


- 


2 


_ 


3 


3 


- 


3 


- 


- 


- 


5 


1 


+ 


6 


- 


- 


- 


4 
2 


1 


+ 


4 


+ 


3 

1 


+ 
+ 


1 
4 


1 


- 


1 


- 


1 


- 


5 


6 


+ 


5 


- 


_ 


+ 


2 


2 


- 


- 


- 


- 


- 


5 


5 
3 
1 


+ 


4 
1 


_ 


2 


+ 


2 


+ 


2 


- 


- 


- 


1 


1 
1 
1 

2 


+ 


- 


~ 


2 


+ 


1 
5 
1 


- 


- 


- 


- 


- 


- 


- 


1 


+ 


2 


- 


2 


2 
1 


+ 


3 


- 


2 


+ 


2 


4 


- 


4 


+ 


2 


_ 


2 


3 


- 


6 


- 


- 


- 


- 


- 


- 


1 


+ 


3 


+ 


- 


2 


+ 


- 


- 


_ 


_ 


5 


4 


+ 


5 


- 


- 


- 


- 


5 
1 
6 


- 


- 


+ 


3 


+ 


5 


+ 


5 


_ 


_ 


+ 


3 


2 
4 
1 


- 


4 


- 


- 


- 


5 


2 


+ 


2 
1 
6 


- 


3 


+ 


- 


2 


+ 


- 


- 


- 


- 


- 


2 


- 


- 


+ 
+ 


- 


- 


5 


4 
3 


- 


- 


1 


- 


= 


2 
3 

1 
4 


+ 


3 


"" 


- 


+ 


2 


- 


4 
4 
3 


+ 


3 


- 


5 


2 


- 


- 


1 


- 



BABA 



209 



TABELLE 2. Rangordnung der Schneckenarten 
Salicetum-Pflanzenassoziation. 



in den Geschiebeproben und in der 

















чо 
















> 

О) 

ш 


> 
=о 

N 


Е 




> 


СЯ 


<л 


3 


'S О) 


.с 


С =" 


3 




> 
O) 


'5 


о 


го 

с 


Et 


'2 


^ .С 


о 




ro 


£ 


ГО 


о 


N "^ 


ÎO 


-о ^ 


— 


No. Arten 


N 


H 


2 


Q 


СО !с 


•^ 


х-Я 


го 
(Л 


1 . Carychium minimum 


10 


9 


10 


7 


_ 


2 


_ 


_ 


2. Coctilicopa lubrica 


3 


2 


- 


4 


4 


7 


4 


5 


3. Cochlicopa lubricella 


- 


- 


- 


9 


_ 


_ 


- 


_ 


4. Columella edén tu la 


_ 


_ 


- 


_ 


_ 


_ 


_ 


_ 


5. Truncatellina cylindrica 


5 


10 


- 


6 


_ 


5 


_ 


_ 


6. Vertigo pygmaea 


6 


7 


- 


5 


3 


5 


2 


_ 


7 . Vertigo an t i vert i go 


- 


- 


- 


- 


- 


- 


- 


- 


8. Granaría f rumen tum 


- 


6 


- 


— 


_ 


1 


_ 


_ 


9. Pupil la triplicate 


- 


- 


- 


- 


6 


- 


6 


- 


10. Pupilla muscorum 


9 


5 


3 


2 


1 


_ 


1 


_ 


1 1 . Vallonia pulchella 


1 


1 


2 


1 


2 


3 


3 


4 


1 2 . Vallonia cos ta ta 


8 


5 


_ 


5 


_ 


3 


1 


8 


13. Chondrula tridens 


9 


6 


- 


_ 


8 


8 


8 




14. Mastus venerabilis 


_ 


_ 


_ 


_ 


_ 




9 


_ 


1 5 . Cochlodina laminate 


_ 


9 


_ 


_ 


_ 


_ 




_ 


16. Ruthenice filograna 


- 


- 


- 


- 


_ 


5 


_ 


_ 


17. Iph ige ne ven tricóse 


- 


7 


- 


- 


- 


- 


- 


_ 


18. Cleusilie pumile 


- 


10 


- 


- 


7 


_ 


7 


_ 


1 9 . Lecinierie plicata 


- 


7 


- 


- 


- 


- 


_ 


- 


20. Suce i nee oblonga 


- 


- 


- 


8 


- 


6 


- 


3 


2 1 . Suce i nee elegens 


- 


- 


4 


- 


- 


- 


- 


5 


22. Succinea putris 


4 


_ 


— 


_ 


_ 


_ 


_ 


6 


23. Cecil ioides acicule 


5 


_ 


_ 


_ 


_ 


_ 


_ 




24. Punctum pygmeeum 




_ 


- 


- 


_ 


3 


_ 


_ 


25. Discus ruderetus 


_ 


_ 


_ 


_ 


_ 


3 


_ 


_ 


26. Zonitoides nitidus 


2 


4 


1 


10 


_ 


5 


_ 


2 


27. Vitrée crystallina 


- 


8 


8 


3 


- 




_ 


_ 


28. Nesovitrea hammonis 


- 


5 


7 


- 


- 


- 


_ 


8 


29. De roce res egreste 


- 


_ 


_ 


- 


_ 


_ 


_ 


6 


30. Deroceres leeve 


_ 


_ 


- 


_ 


_ 


_ 


_ 


8 


31. Bredybeene fruticum 


- 


7 


- 


- 


- 


- 


_ 


7 


32 . Helicopsis s trie te 


- 


- 


- 


- 


- 


3 


_ 


- 


33. Perforetella bidentete 


_ 


7 


_ 


_ 


9 


9 


_ 


_ 


34. Perforetelle rubiginosa 


7 


3 


6 


- 


10 


- 


_ 


1 


35. Perforetelle vicine 


- 


10 


_ 


_ 


_ 


_ 


_ 


_ 


36. Trichie hispide 


10 


7 


g 


7 


5 


10 


_ 


_ 


37. Trichie sericee 


_ 


_ 


5 


_ 


_ 


_ 


_ 


_ 


38. Helicigone erbustorum 


_ 


_ 


_ 


_ 


_ 


_ 


5 


_ 


39. Cepeee vindobonensis 


- 


6 


_ 


_ 


_ 


4 




- 


40. Helix pometie 


10 


- 


- 


_ 


_ 


— 


- 


_ 


41 . Яе//х lutescens 


- 


- 


- 


- 


- 


- 


- 


9 



210 



PROC. SIXTH EUROP. MALAC. CONGR. 



TABELLE 3. Häufigkeits-Verhältniskonfidenz Intervalle (Geschiebe-Ausdehnungen). 



No. 



Arten 







F. der. 0- 


Recenten-Fl 


üsse 


Pleistocäne 


Theiss 


Donau 


Köröshegy 


- 0,33- 0,41 


- 3,03- 4,19 


- 2,74- 7,46 


- 8,37- 9,16 


- 4,82- 6,23 


- 0.73- 1,99 


- 1,05- 1,36 


- 0,64- 1,24 


- 


- 0,29- 0,47 


- 2,46- 3,52 


0,08- 2,02 


- 0,31- 0,49 


- 0,07- 0,36 


- 0,36- 3,21 


- 1,71- 2,09 


- 4,09- 5,42 


- 0,02- 2,35 


- 1,65- 2,03 


- 0,73- 1,38 


-31,21-41,55 


- 4,77- 5,39 


-13,11-15,29 


- 0,17- 1,71 


-17,82-18,90 


-38,92-41,98 


-10,76-18,33 


- 3,13- 3,63 


- 1,79- 4,18 


-10,82-18,42 


- 4,98- 8,42 


- 1,46- 2,31 


- 2,04- 6,34 


- 0,20- 0,35 


- 0,54- 1,08 


- 1.73- 6,18 


- 0,08- 0,19 


- 0,61- 1,19 


- 0,62- 1,22 


- 6,71- 7,42 


- 1,55- 2,41 


- 1,47- 5,39 


- 2,39- 2,83 


- 4,18- 5,52 


0,21- 1,51 


- 1,64- 2,01 


- 0,07- 0,35 


0,24- 1.42 


- 0,17- 0,30 


- 1,62- 2,51 


- 


- 1,62- 1,99 


- 


- 0,57- 3,66 


- 9,15- 9,97 


- 3,04- 4,21 


- 


- 0,41- 0,61 


0,00- 0,19 


- 


- 1,67- 2,05 


- 0,86- 1,53 


0.27- 1,19 


- 2,52- 2,98 


- 0,19- 0,56 


- 1.43- 5,30 


- 0,04- 0,11 


0.02- 0,14 


0,29- 0,93 



1 . Carychium minimum 

2. Cochlicopa lubrica 

3. Cochlicopa lubricella 

4. Truncatellina cylindrica 
Vertigo antivert igo 
Vertigo pygmaea 
Granarla frumentum 
Pupilla muscorum 
Vallonia pulchella 
Vallonia costata 
Chondrula tridens 
Succinea oblonga 



5. 

6. 

7. 

8. 

9. 
10. 
11. 
12. 

13. Punctum pygmaeum 

14. Zonitoides nitidus 

15. Vitrea crystallina 

16. Bradybaena fruticum 

17. Helicella obvia 

18. Perforatella bidentata 

19. Perforatella rubiginosa 

20. Perforatella incarna ta 

2 1 . Trichia hispida 

22. Cepaea vindobonensis 

23. Helix pomatia 



LITERATUR 



BABA, К.. 1969a, Malakozönologische Untersuchung einiger Sand-Pusztenrasen und Wälder im Zwischen- 
stromgebiet zwischen Duna und Tisza (Die Sukzession der Schneckenzönosen). Szegedi Tanèrkèpzo 
, Fóiskola Tudomànyos Közlemenyeiböl II: 83-92. 
BABA, К., 1969b, Zönologische Untersuchungen der an der Flussbettkante der Tisza und ihrer Nebenflüsse 

Jebenden Schnecken. Tiscia, Szeged, 5: 107-119. 
BABA, К., 1972, The snail coenoses of the willow groves in the Middle Tisza region. Tiscia, Szeged, 7: 

, 101-102. 
BABA. К., 1973 Die Sukzession der kontinentalen Molluskensynusien in den Ungarischen Eschen-Erlen- 

, Mooren. Szegedi Tankrkkpzü Föiskola Tudomànyos Közlemenyeiböl II: 43-50. 
BABA. К., 1974, Quantitative conditions of the molluscs in the oakwoods of various states at Csévharaszt. 

, Abstracta Botánica, 2: 71-76. Budapest. 
BABA, К.. 1975, Möglichkeiten zur Qualifizierung des Zustandes von Wäldern mit Hilfe des quantitativen 
Veränderungsindexes der Schneckenbestände. Juhèsz Gyula Tanàrképzo Föiskola Tudomànyos 
Közlemenyeiböl, II: 37-51. 
BABA, К., 1977, Die kontinentalen Schneckenbestände der Eichen-Ulmen-Eschen-Auwäldern (Fraxino- 

, Pannonicae-Ulmetupi pannonicum Soó) in der L^ngarischen Tiefebene. Malacologia, 16: 51-57. 

BABA, К., KOLOSVARY. G., STERBETZ, I.. VASARHELYI, I. & ZILALI-SEBESS, G., 1962, Das Leben 

der Tisza. XVII. Zoologische Ergebnisse der Vierten Tisza-Expedition. Fortsetzung. Acta Biológica, 

Szeged, N.S., 8: 203-215. 

BERECZK. P., CSONGOR, G., HORVÁTH, A.. KOLOSVÁRY, G. & VÁSÁRHELYI, I., 1958, Das Leben der 

Tisza I. Über die Tierwelt der Tisza und ihrer Inundationsgebiete. Acta Universitatis Szegediensis, N.S., 4: 



216-226. 
^G 



CZOGLER, K. & RQTARIDES. M.. 1938, Analyse einer vom Wasser geschwemmten Molluskenfauna. Die 
Ausyvürfe der Maros und der Tisza bei Szeged. Magyar Biológiai Kutató Intézet Munkai, 1: 8-44. 

HQRVATH, A., 1962, Kurzbericht über die Molluskenfauna der zwei Tisza-Expeditionen im Jahre 1958. 
Opjjscula Zoológica, Budapest, 5: 77-83. 

PINTER, L.. 1974, Katalog der rezenten Mollusken Ungarns. Folia Historico-Naturalia Musei Matraensis, 2: 
123-148. 

SV AB. J,. 1973, Biometriai módszerek a kutatàsban. Mezôgazdasagi Kiadó, Budapest. 517 p. 



MALACOLOGIA, 1979, 18: 211-222 

PROC. SIXTH EUROP. MALAC. CONGR. 

DISTRIBUTION OF ENVIRONMENTAL FACTORS AND 

FRESH-WATER SNAILS (GASTROPODA) IN NORWAY: 

USE OF EUROPEAN INVERTEBRATE SURVEY PRINCIPLES 

Jan Ökland 

Department of Marine Biology and Limnology, Section of Limnology, 
University of Oslo, P.O. Box 1027, В I Indern, Oslo 3, Norway 

ABSTRACT 

This article is a preliminary report on some of the new results arrived at in a study 
comprising the distribution, ecology, and morphology of the fresh-water snails of 
Norway, including aspects of regional limnology. Emphasis has been on subjects related 
to the European Invertebrate Survey (EIS). The base map for Norway comprises 189 
modified 50 km squares. This map is used for both national and international projects. 
ElS-principles have been used for mapping environmental factors and distribution of 
species and population densities. 

Mapping environmental factors. Maps have been made showing (1) elevation above sea 
level, (2) geology, (3) vegetation in the surroundings of habitats, (4) macrovegetation 
along the shores of lakes, (5) substratum, (6) wave exposure in lakes, (7) hydrogen-ion 
concentration (pH), (8) calcium concentration, (9) water colour, and (10) water tempera- 
ture. A selection of maps is presented. Primary data: 1,498 fresh-water habitats in 
Norway (mostly lakes) investigated 1953-1973 during 819 days of field work. 

Mapping of the 27 Norwegian species of fresh-water Gastropoda. Maps have been 
made showing (1) geographical distribution of each species, (2) total number of species in 
each square, (3) average number of species per lake, (4) number of lakes with given 
number of species, (5) number of individuals collected per half-hour (time-catch 
abundance) for each species, and total of all species. A selection of maps is presented. 
Primary data: 73,000 individuals collected in habitats with ecological data (cf. above), 
some 34,000 specimens in museums etc., and literature records. 

Correlation studies. Comments are given on single and multiple factor analyses. 

A preliminary report of some of the results arrived at in a study comprising the distribution, 
ecology, and morphology of the fresh-water snails of Norway, including aspects of regional 
limnology, was given at the 3rd European Malacological Congress in Vienna in 1968 (Okland, 
1969). Since then the study has proceeded. The present communication will give a short outline 
of some of the new results which still have a preliminary character. 

Emphasis will be put on subjects related to the European Invertebrate Survey (EIS), 
particularly with regard to mapping. For the mapping projects a base map of Norway has been 
constructed (Fig. lA). The location of the national squares in relation to the remaining parts of 
Europe, with special reference to the joint EIS dot map surveys, is shown in Fig. IB. 

Construction of maps for both environmental factors and distribution of species is only a 
part of the study which basically has an ecological approach. The major aim is to elucidate the 
importance of various environmental factors for the geographical distribution of the species. 

SOME REMARKS ON THE TOPOGRAPHY OF NORWAY 

Norway forms the north-western border of the European continent. It covers more degrees 
east-west and is longer and narrower than any other European country. It borders Sweden, 
Finland, and the Soviet Union. 

The number of lakes is estimated at 250,000 and their surface area at about 15,000 km^, i.e. 
more than the arable land in Norway. Among the lakes are those located at the highest latitude 
on the European continent (Fig. 2A), that is about 71°N, in the North Cape area. The lakes 

(211) 



212 



PROC. SIXTH EUROP. MALAC. CONGR. 




'70° N 



FIG. 1A. Base map of Norway, consisting of modified 50 km squares for use in European Invertebrate 
Survey. Total: 189 squares. B. From a base map of Europe at 1:10 million. Dots represent 189 modified 
50 km squares completely or partly located in Norway. From Ökland, 1976. 



with the highest elevation in North Europe are also located in Norway (Fig. 2B), as well as the 
4 deepest lakes in Europe (Fig. 2C shows the deepest one). 

Owing to great variation in climate and geology Norway is well suited for regional ecological 
studies. In south-eastern Norway the gradient from lowland districts to high mountain areas, up 
to more than 2,000 m above sea level, is of great ecological significance. In the lowland part of 
south-eastern Norway we find the region which geologically is called the Oslo Region. This 
fairly small geographical area has an unusually wide variety of bedrock and Quaternary deposits 
which greatly influence hydrochemical and biological factors in its numerous water bodies. Both 
rich eutrophic lakes (Fig. 2D), dystrophic lakes with bordering Sphagnum mires (Fig. 2E) and 
poor oligotrophic lakes (Fig. 2F) are present in great numbers within a restricted area. 




FiG. 2. A selection of photographs of the variety of fresh-water habitats in Norway. A. The lake located at 
the highest latitude on the European continent is nameless, and lies near North Cape (shown in the 
background). B. The lake with highest elevation in North Europe (Lake Gjuvvatn, 1,837 m above sea level); 
the glacier descending into the lake is shown in the background. C. The deepest lake in Europe (Lake 
Hornindalsvatn, 514 m deep). In south-eastern Norway a wide variety of lake types is present within a small 
geographical area, such as D. A rich eutrophic lake (Lake Borrevatn), E. A dystrophic lake surrounded by a 
Sphagnum bog (Lake Âsentjern), and F. A poor oligotrophic lake (Lake Eikeren). The latter 3 lakes are 
located west of Oslo Fjord, in the county of Vestfold. 



GASTROPODA-ENVIRONMENT AND SPECIES 



A field study of the 27 species of fresh-water gastropods in Norway was undertaken in 
1953-1973. A total of 1,498 habitats-among them about 1,000 lakes-was investigated. Fig. ЗА 
shows the number of investigated habitats in each square. A total of 819 days was used for 



214 



PROC. SIXTH EUROP. MALAC. CONGR. 



Ш SQUARES WITH 
AREAS ADDED 
TO NEIGHBOURING 
SQUARE 




TOTAL NUMBER 
OF HABITATS 
INVESTIGATED 




FIG. ЗА. Division of North and South Norway according to modified 50 km squares. The map shows number 
of investigated fresh-water habitats with data on environment. Total: 1,498 habitats investigated 1953-1973 
during 819 days of field work. B. • = Squares with data on both environment and Gastropoda, о = Squares 
with data on Gastropoda only. 



field work. In all habitats environmental factors were recorded and gastropods searched for, 
using a time-catch method for estimating population density. 

In Fig. 3B the dots show squares with data on both environment and Gastropoda. Rings 
mark the squares from which only data on Gastropoda (from other sources) were available. 

The habitat was the smallest unit investigated in the field. Usually only one habitat was 
investigated in each lake or river. The habitat may be defined as a place where gastropods were 
obtained and certain ecological factors measured and classified. In lakes and rivers the habitat 
consists of a certain stretch of shores— usually about 200 m— defined by special ecological 
characteristics. The average investigation time per habitat in lakes and rivers was 1 hour. For 
the smaller water bodies like ponds and puddles, the entire water body was investigated and 
considered as one habitat. 

Mapping environmental factors. Using the ElS-system, maps have been made showing 10 
different sets of environmental parameters: (1) elevation above sea level, (2) geology, (3) 
vegetation in the surroundings of habitats, (4) macrovegetation along the shore of lakes, (5) 
substratum, (6) wave exposure in lakes, (7) hydrogen-ion concentration (pH), (8) calcium 
concentration, (9) water colour, and (10) water temperature. 

In this communication only a few examples of such maps will be given. First we shall 
consider 4 maps based on average values within squares. 



J. ÖKLAND 



215 



ELEVATION ABOVE 

SEA LEVEL 

Average values for 
50 km squares 




• : Square With 
no data 



В 



FIG.4A. Elevation above sea level for investigated lakes. B. Observed surface water temperature in summer 
in investigated lakes. 



Fig. 4A shows elevation above sea level for investigated lakes. The highest average values are 
found in the central part of South Norway. 

Fig. 4B shows water temperature in lakes at the time of investigation, i.e. during summer. 
Two points are worth mentioning: (1) low temperatures are prominent in the central part of 
South Norway, and (2) high temperatures are found in coastal districts in South Norway as well 
as in many parts of North Norway, 

Fig. 5A shows calcium concentration (as total hardness) in investigated lakes, expressed as 
average values for summer surface water. We note that large areas in the western part of South 
Norway are very poor in lime salts. Since there is generally a correlation between calcium 
concentration and the buffer capacity of the water, we understand that the lakes in large parts 
of South Norway are but poorly suited to neutralize acid substances from precipitation or from 
the terrestrial environment surrounding the lakes. 

Finally, Fig. 5B shows hydrogen-ion concentration (pH) in investigated lakes, expressed as 
average values for summer surface water. Areas with acid lakes are more widely distributed in 
South Norway as compared with North Norway. In South Norway areas with acid lakes are 
found especially in the southern and western parts as well as in districts along the border with 
Sweden. 

A more detailed way of illustrating environmental parameters within squares is to indicate 
per cent of habitats belonging to a certain category. Maps of this type show that within a given 
square there are usually many types of habitat. 

Fig. 6 shows such a map. The area is south-eastern Norway, built up of a total of 40 
modified 50 km squares. This area has been especially closely studied. The map indicates 
geology in the surroundings of investigated lakes, expressed as percentage of lakes belonging to 
one of 4 possible categories. In south-eastern Norway lakes influenced by geological categories 



216 



PROC. SIXTH EUROP. MALAC. CONGR. 



TOTAL HAR DNESS (°dH) 
Tdl 




HYDROGEN-ION CONCENTRATION 




^pH 



^ ^9-59 
ffl 6 0-66 
^ 67-73 

Ш ''-''^ 

While No dalQ 



m\mm^mii\B 






A В 

FIG. 5A. Calcium concentration (as total hardness) in investigated lakes. Average values for summer surface 
water. B. Hydrogen-ion concentration (pH) in investigated lakes. Average values for summer surface water. 



П 
Ш 

DC 
D 
D 
D 



GEOLOGY 
IN THE SURROUNDINGS 



DDD 
DED 



OF LAKES 




TOTAL: 
560 LAKES 



SOUTH-EASTERN 



NORWAY 

KEY TO SQUARE NO 
(EIS-SVSTEM) 




FIG. 6. South-eastern Norway is represented by 40 modified 50 km squares. For each of these squares this 
map shows geology in the surroundings of investigated lakes, expressed as percentage of lakes belonging to 
one of 4 possible categories: (1) unaltered Cambro-Silurian rocks, rich in lime, (2) marine clay, (3) strongly 
altered Cambro-Silurian rocks, Eocambrian rocks, etc., (4) Pre-Eocambrian rocks, and Permian plutonic and 
effusive rocks of the Oslo Region. 



J. ÔKLAND 



217 



Nos. 1 (bed rock rich in lime) and 2 (nnarine clay) are especially favourable for fresh-water 
gastropods. 

Mapping distribution and population density of fresh-water Gastropoda. The material for this 
mapping consists of 3 parts: (1) 73,000 individuals from 1,498 habitats with ecological data, 
(2) 34,000 individuals in museums, etc., and (3) records from literature. 

Using the ElS-system, maps have been made showing (1) geographical distribution of each 
species, (2) total number of species in each square, (3) average number of species per lake, (4) 
number of lakes with given number of species, (5) number of individuals collected per half-hour 
(time-catch abundance) for each species, and total for all species. 

A few examples of such maps will be shown. The 4 maps in Fig. 7 show distribution 
patterns for 4 of tfie 27 species of fresh-water gastropods in Norway, i.e. (A) Lymnaea peregra 
(Müll.), a widely distributed species with great ecological amplitude, (B) Acroloxus lacustris 
(L.), mainly restricted to more eutrophic habitats in the southern part of South Norway, (C) 
Potamopyrgus jenkinsi (Smith), a recent immigrant to Norway, restricted to fresh and brackish 
water localities in the southern part of South Norway, and (D) Valvata sibirica Middendorff, a 
species with a northern range. 

Fig. 8A shows the total number of species in each square. This map accentuates a common 
feature for many groups of fresh-water invertebrates in Norway: the highest number of species 
occurs in the south-eastern part of South Norway. The communities may also be fairly rich in 
species in other parts of South Norway and in the interior eastern part of North Norway. 



LYMNAEA 

PEREGRA (Müll.) 



ACROLOXUS 

LACUSTRIS (L.) 



POTAMOPYRGUS 
JENKINSI (Smith) 



VALVATA 

SIBIRICA Middendorff 




FIG. 7. Geographical distribution of some fresh-water snails in Norway. A. A widely distributed species. B. A 
species restricted to the southern part of South Norway. С A recent immigrant to Norway (first record: 
1954), also restricted to the southern part of South Norway. This species also occurs in brackish water. D. A 
northern species. 



218 



PROC. SIXTH EUROP. MALAC. CONGR. 




DDaaD 



FRESH-WATER GASTROPODS 
NUMBER OF LAKES WITH GIVEN 
=1 NUMBER OF SPECIES 



2 SPECIES 



a л 



TOTAL 
584 LAKES 



SOUTH-EASTERN 

NORWAY 

KEV TO SQUARE NO 

(EIS-SVSTEM) 




A В 

FIG.8A. Total number of species of fresh-water gastropods in the various 50 km squares in Norway. B. 
Percentage of lakes with given number of species in 50 km squares in south-eastern Norway. 




Average 12 1 



В 



J. ÖKLAND 



219 



LYMNAEA PEREGRA 




Average КЗ 



FRESH-WATER GASTROPODS 
ALL SPECIES 

Average number of 
individuals collected 
per half - hour 
TOTAL 1,498 
HABITATS 




Average 37 6 



A В 

FIG. IDA. Tinne4;atch abundance for Lymnaea peregra (Müll.) indicates that in the south-eastern part of 
Norway none of the squares has the highest category of abundance. This is the area with the highest number 
of species of fresh-water gastropods in Norway (cf. Fiq. 7 A). The reduced population density in this area is 
possibly due to competition with more specialized species. B. Number of individuals collected per half-hour 
(all 27 species treated together). 

Fig. 8B shows the number of lakes with a given number of species for south-eastern Norway. 
We note that in a large proportion of the investigated lakes only 0-2 species were detected. 
Especially in the southern and central part of South Norway a fair proportion of the 
investigated lakes contained 5-12 species. 

Let us now consider 4 maps (Figs. 9-10) dealing with population density, expressed as 
time-catch abundance (based on number of individuals collected per half-hour). Only major 
trends of population density can be shown by such a rough method, and the results obtained 
should be used with caution. 

Fig, 9 shows results for Lymnaea truncatu/a (Müll.). Since this species is known to prefer 
small water bodies like ponds and ditches (Boycott, 1936; Hubendick, 1947; Ökland, 1964), it 
is not surprising that average population density in small water bodies is higher (12 individuals 
collected per half-hour, cf. Fig. 98) as compared with the density in lake habitats (6 individuals 
collected per half-hour, cf. Fig. 9A). 

Fig. 10A shows results for Lymnaea peregra in lakes. This species has a fairly low density in 
the south-eastern part of Norway, which is very rich in species (cf. Fig. 8A). This may be 
explained by competition with more specialized species which are better adapted for a life in 
south-eastern Norway. 

Average time-catch abundance for Lymnaea peregra in lakes was 14 individuals collected per 
half-hour (Fig. 10A), i.e. a higher value than observed for L. truncatu/a in lake habitats (cf. Fig. 
9A). 



FIG. 9. A time-catch method was used to obtain a rough estimate of population density for the various 
species of fresh-water gastropods. These maps show densities for Lymnaea truncatu/a (Müll.), A for lake 
habitats (average 6 specimens collected per half-hour), В representing small water bodies such as ponds and 
ditches (average 12 specimens collected per half -hour). 



220 



PROC. SIXTH EUROP. MALAC. CONGR. 



Treating all species of fresh-water gastropods together. Fig. 10B summarizes population 
density in Norway. Although many parts of North Norway have rather few species (cf. Fig. 
8A), the total number of individuals belonging to the gastropod fauna may be fairly large. Since 
gastropods are important fish-food organisms, this implies that biomass of fish-food may be 
large although number of species is small. 

Correlation studies. In order to point out some general trends in the correlation between 
major factors of environment and the occurrence of fresh-water gastropods in Norway, single 
factor analyses of 10 environmental parameters have been performed. An example is given in 
Fig. 11 which indicates how the frequency of the 14 commonest species in south-eastern 



FREQUENCY DEVIATIONS IN RELATION TO 
MACROVEGETATION ALONG THE SHORE 



GYRAULUS 
ACRONICUS 
N = 417 




ZERO: EXPECTED VALUE IN RANDOM DISTRIBUTION 

^m INCREASED FREQUENCY ШШ DECREASED FREQUENCY 



RICH (QUANTITATIVELY AND QUALITATIVELY) 



A: 
B: 

С POOR MACROVEGETATION 
D: SPHAGNUM BOG 



LYMNAEA 
TRUNCATULA 
N=107 



BATHYOMPHALUS 
CONTORTUS 
N = 218 




LYMNAEA 


PHYSA 


LYMNAEA 


PALUSTRIS 


FONTINALIS 


STAGNALIS 


N = 22 


N = 50 


N = 69 



VALVATA 
PISCINALIS 
N = 56 




LYMNAEA 


VALVATA 


ACROLOXUS 


APLEXA 


GYRAULUS 


HIPPEUTIS 


GLABRA 


CRISTATA 


LACUSTRIS 


HYPNORUM 


CRISTA 


COMPLANATUS 


N = 24 


N = 63 


N = 48 


N = 11 


N = 52 


N = 54 



FIG. 11. Occurrence of 14 species of fresh-water gastropods in south-eastern Norway in lakes with different 
types of macrovegetation along the shore. Material: 541 lakes investigated 1953-57. For each species is 
indicated the frequency in 4 different groups of nnacrovegetation (A-D). Increased frequency is indicated by 
black bars, decreased frequency by shaded ones. The zero level represents expected frequency in random 
distribution. Stars indicate deviations significantly different from zero. 



J. OKLAND 



221 



TOPOGRAPHICAL FACTORS 



FACTORS IN THE WATER 



SPECIES 



TOPOGRAPHICAL 
WATER TVPE 
(LAKE. MIRE, ETC) 




GEOLOGV 

IN THE 

DRAINAGE AREA 



VEGETATION 

IN THE 

SURROUNDINGS 



STRONG DIRECT INFLUENCE 
ON GASTROPODS 



WEAK DIRECT INFLUENCE 
^..l-L ON GASTROPODS 



ГЦ 



NO DIRECT INFLUENCE 
ON GASTROPODS 



INFLUENCES 



STRONG ( DIRECT ON 
GASTROPODS) 



>• STRONG (BETWEEN FACTORS) 

> О WEAK 



FIG. 12. Main relations between environmental factors and fresh-water gastropods. The effect of a given 
factor is considered as direct when the action does not necessarily involve a step through any of the other 
factors. Note how the factor "macrovegetation" is hit by many "ecological cannon balls," i.e. this factor 
reflects a multitude of environmental parameters and has a strong direct influence on the gastropod fauna. 
The effect of a given factor varies according to the development of other factors. The relative importance of 
each factor is to be elucidated by multiple regression analyses. 

Norway is influenced by quantity and quality of nnacrovegetation along the shore of lakes. For 
each species frequency deviations are indicated in relation to a zero value obtained in randonn 
distribution. Most species have a significantly increased frequency in lakes where the macro- 
vegetation belongs to category A or B, i.e. rich vegetation either both quantitatively and 
qualitatively, or only quantitatively. Generally the species have a decreased frequency where 
macrovegetation is poorly developed (category C) or consists of a Sphagnum bog (category D). 

The relative importance of each environmental factor is to be elucidated by multiple 
regression analyses. Fig. 12 shows the main relations between environmental factors and 
fresh-water gastropods. The effect of an environmental factor is considered as direct when the 
action does not necessarily involve a step through any of the other factors here mentioned. 

The picture is more complicated than shown on this figure. We know, for instance, that the 
effect of a given factor varies according to the development of other factors. For example: the 
effect of the hydrogen-ion concentration (pH) of the water increases with decreasing calcium 
concentration (total hardness). 



LITERATURE CITED 



BOYCOTT, A. E., 1936, The habitats of fresh-water Mollusca in Britain. Journal of Anima/ Ecology, 5: 

116-186. 
HUBENDICK, В., 1947, Die Verbreitungsverhältnisse der limnischen Gastropoden in Südschweden. 

Zoologiska Bidrag fran Uppsala, 24: 419-559. 
ÖKLAND, J., 1964, The eutrophic lake Borrevann (Norway)— an ecological study on shore and bottom fauna 

with special reference to gastropods, including a hydrographie survey. Folia limnologica scandinavica, 13: 

1-337. 



222 PROC. SIXTH EUROP. MALAC. CONGR. 

ÖKLAND, J., 1969, Distribution and ecology of the fresh-water snails (Gastropoda) of Norway. Malacologia, 

9: 143-151. 
ÖKLAND, J., 1976, Utbredelsen av noen ferskvannsmuslinger i Norge, og litt om European Invertebrate 

Survey'. Summary in English: Distribution of some freshwater mussels in Norway, with remarks on 

European Invertebrate Survey. Fauna (Oslo), 29: 29-40. 
ÖKLAND, J., (in preparation). Fresh-water snails (Gastropoda) of Norway. Their distribution, ecology, and 

morphology, including aspects of regional limnology (provisional title). 



I 



MALACOLOGIA, 1979, 18: 223-226 

PROC. SIXTH EUROP. MALAC. CONGR. 

SPHAERIIDAE OF NORWAY: A PROJECT FOR STUDYING ECOLOGICAL 
REQUIREMENTS AND GEOGRAPHICAL DISTRIBUTION 

Karen Anna Ökland 

Department of Marine Biology and Limnology, Section of Limnology, 
University of Oslo, P.O. Box 1027, Bl Indern, Oslo 3, Norway 

ABSTRACT 

The рифозе of the project is to study the pH tolerance in the field of the 20 species 
of Sphaeriidae in Norway and to elucidate whether they live in low-buffered lakes with 
pH values near their lower tolerance limit, in areas threatened by acidification. Using the 
European Invertebrate Survey base map of Norway, preliminary distribution maps for 
Pisidium casertanum, P. conventus, Sphaerium corneum, and S. nitidum are presented. 
The small Bivalvia are important fish food organisms and the project is part of the 
Norwegian interdisciplinary research project "Acid Precipitation— Effects on Forest and 
Fish"-the SNSF-project. A few results of the SNSF-project are outlined, especially those 
concerning fish kill due to acidification. 




pH>6.0 6,0-5.5 5.5-5.0 5.0-4.5 4.5-4.0 pH<4.0 

FIG. 1. Maps showing areal distribution of pH values in yearly precipitation over Europe (Oden, 1971). 

(223) 



224 



PROC. SIXTH EUROP. MALAC. CONGR. 



In the 1960s measurements indicated that the precipitation in Europe was becoming 
increasingly acid. A central area with highly acid precipitation was extending from year to year, 
as illustrated in Fig. 1. Recent results are given by Tollan (1977) in a map illustrating mean pH 
values, based on daily measurements of precipitation in Europe between July 1972 and March 
1975. This is constructed from data collected by the Norwegian Institute for Air Research 
(Schaug, 1975, 1976). It was suspected that increasing emission of sulphur dioxide from the 
combustion of fossil fuels is the main cause of this acidification. 

In Norway acid precipitation was seen as the possible cause of increasing acidity of the 
watercourses in the southern part of the country and of the gradual disappearance of trout and 
salmon from many lakes and rivers. It was also feared that the input of acid might reduce 




100 KM 



Noticeable problems 
Severe problems 



FIG. 2. Fish status in lakes of Norway south of 63°. The map is based on data from more than 2,000 lakes. 
"Severely affected" areas are those where a majority of lakes have lost their fish populations. In "noticeably 
affected" areas at least some of the lakes have had reduced population density in recent years (modified from 
Leivestad et al„ 1976). 



к. А. ÖKLAND 



225 



forest growth through increased leaching of nutrient elennents from the soil. Widespread concern 
about these matters led to the organization of the interdisciplinary research project "Acid 
Precipitation-Effects on Forest and Fish"-(SNSF-project) early in 1972 (Braekke, 1976). 

Information on past and present status of the trout populations in more than 2,000 lakes 
has been collected and the "problem" areas have been mapped by the SNSF-project (Fig. 2). 
Lakes which have lost their trout populations are clearly more frequent in those parts of the 
country where the influx of acid pollution is high. 

First affected are small, high altitude lakes with low buffer capacity in the catchment area, 
the bedrock being highly resistant, mainly granitic. Originally, many of these lakes were densely 
populated, harbouring stocks of relatively small, slow-growing fish. The first symptom of acid 
stress is usually a decrease in population density, with the remaining fish showing faster growth. 
This is a result of recruitment failure and test-fishing shows a shortage of the younger age 
classes (Jensen & Snekvik, 1972; Leivestad et al., 1976). 

The disappearance of fish is easily observed, but the distribution of the small invertebrates 
which serve as food for the fish is mostly so poorly known in Norway that a possible 
disappearance is hardly noticed. Therefore, within the SNSF-project a sub-project has been 
launched on selected invertebrate groups. This sub-project started in January 1977 and will last 
for 3 years. 

In a preliminary survey on gastropod ecology in Norway ecological data from about 1,500 
freshwater habitats are presented (J. Ökland, 1979). The same data will be used for studying 
ecological requirements of other groups of animals that were collected or observed together 
with the gastropods. The 20 species of small Bivalvia were chosen for 2 reasons: they are 
important as food for fish, and there are reasons to believe that low pH values in the waters are 
important limiting factors for their distribution in Norway. 




В 



FIG. 3. Preliminary maps of the distribution of 4 species of Sphaeriidae in Norway. A. Pisidium casertanum, 
B. P. conventus, С Sphaerium corneum, D. S. nitidum. 



226 PROC. SIXTH EUROP. MALAC. CONGR. 

The first step is to find the pH tolerance of each of the species in natural habitats, as 
previously done for the freshwater shrimp Gammarus lacustris Sars (K. A. Ökland, 1969). The 
next step is to find out if some of the species live in low-buffered lakes, with pH values near 
their lower tolerance limit, in areas threatened by acidification. 

Fig. 3 shows preliminary distribution maps of 4 species of Sphaeriidae, constructed on the 
European Invertebrate Survey base map of Norway (J. Ökland, 1979). Pisidium casertanum 
(Poli) is probably the species found in most localities in Norway. P. conventus Clessin is a cold 
water species found in many lakes in the north. In the south it mainly occurs in deeper water 
or in high altitude lakes. Sphaerium corneum (L.) is found in many parts of the country, but 
most records are from the south-east. S. nitidum Clessin is a more northern species, in the 
south found mostly in high mountains. 

The work on the Sphaeriidae is made possible by the valuable contribution of Mr. J. G. J. 
Kuiper, Paris. He has kindly identified our samples and is also responsible for the revision of 
the Norwegian museum collections. 

This is SNSF-contribution FA 24/78. 



LITERATURE CITED 

BRAEKKE, F. H., ed., 1976, Impact of acid precipitation on forest and freshwater ecosystenns in Norway. 

Summary report on the research results from phase I (1972-1975) of the SNSF-project. S/VSF-pros/e/rfer 

FR, 6/76: 1-111. 
JENSEN, K. W. & SNEKVIK, E., 1972, Low pH levels wipe out salmon and trout populations in southern 

Norway. /4mb/o, 1: 223-225. 
LEIVESTAD, H., HENDREY, G., MUNIZ, I. P. & SNEKVIK, E., 1976, Effects of acid precipitation on 

freshwater organisms. In F. H, BRAEKKE (ed.). Impact of acid precipitation on forest and freshwater 

ecosystems in Norway. SNSF-prosjektet FR, QllQ: 97-111. 
ODEN, S., 1971, Nederbördens försurning— ett genereilt hot mot ekosystemen. In I. MYSTERUD (ed.), 

Forurensning og biologisk miljövern: 63-98. Universitetsforlaget, Oslo. 
ÖKLAND, J., 1979, Distribution of environmental factors and fresh-water snails (Gastropoda) in Norway: use 

of European Invertebrate Survey principles. Malacologia, 18: 211-222. 
ÖKLAND, К. A., 1969, On the distribution and ecology of Gammarus lacustris G. O. Sars in Norway, with 

notes on its morphology and biology. Nytt Magasin for Zoologi, 17: 111-152. 
SCHAUG, J., 1975, LRTAP ground sampling stations— monthly precipitation and mean concentration values 

July 1972 — December 1973. Norwegian Institute for Air Research, Kjeller, Norway, Report LRTAP, 

МП5: 1-109. 
SCHAUG, J,, 1976, LRTAP ground sampling stations— monthly precipitation and mean concentration values 

January 1974— March 1975. Norwegian Institute for Air Research, Kjeller, Norway, Report LRTAP, 3/76: 

1-91. 
TOLLAN, A., ed., 1977, Sur nedb'ór од noen alternative kilder som aarsak til forsuring av vassdrag. Prosjektet 

"Sur nedbOrs virkning paa skog og fisk"— SNSF-prosjektet. Oslo— Aas, 156 + 12 p. 



MALACOLOGIA, 1979, 18: 227-232 

PROC. SIXTH EUROP. MALAC. CONGR. 

TEMPERATURE AND REPRODUCTIVE CYCLE RELATIONS IN 
RADIX PEREGRA O.P. MÜLLER 

Nevenka Krkac 
Zoologijski zavod PMF, Rooseveltov trg 6, Zagreb, Jugoslavia 

ABSTRACT 

Oviposition as a consequence of reproductive activity of Radix peregra O.F. Müller 
was researched both under laboratory conditions and outdoors. An earlier supposition 
(MeStrov & Krkac, 1970, Krkac & Mestrov, 1970) that oviposition in Radix peregra living 
in habitats with distinct seasonal temperature variations occurs after a rapid rise of water 
temperature in the spring, was corroborated by research in the spring region in Bijela 
Rijeka (Jugoslavia). The population in the basin of non-captive water of Tuheljske 
Toplice (thermal springs) lays eggs continuously throughout the year regardless of 
seasons. Here the temperature of the water varies from 29-32. 1°C. When migrating to the 
compact layer of algae spread over the surface of the warm water the animals are 
exposed to a sudden change of temperature. The air temperature near the surface of the 
algal layer is considerably lower than that of the water, regardless of season. So, the 
temperature gradient produces a permanent incentive to egg-laying throughout the year. 
Laboratory experiments support the outdoor data. Animals with no possibility of 
changing their temperature zone do not lay eggs. The frequency of egg-laying depends on 
an average (breeding) temperature and its fluctuation. 

INTRODUCTION 

Temperature has been shown by many authors to be one of the factors regulating the 
reproductive cycle of Gastropoda (Duncan, 1959; iVIichelson, 1961; Smith, 1967; Van der 
Steen, 1967; Timmermans, 1959;Wolda, 1967). 

The eurythermic species Radix peregra inhabits a very large area including biotopes with 
very different thermal conditions. In Jugoslavia it was found in Tuheljske Toplice (thermal 
springs) at a temperature of 32.4°C and in Stubicke Toplice at 42.2°C (Matonickin, 1957), as 
well as in the subterranean cave waters of Rakov Skocijan (Bole, 1966). Subterranean cave 
waters characteristically have a relatively low and almost constant temperature throughout the 
year. 

Outdoor research (Krkac & Mestrov, 1970) suggested that a thermic jump (an abrupt 
temperature rise in the spring) was followed by egg-laying. A similar reaction was caused by a 
sudden change of temperature zone (Krkac, 1973). Special attention was paid to the relation 
between the temperature regime of the habitat and the reproductive cycle in the context of 
research on the population dynamics of Radix peregra (Krkac, 1975). Outdoor data were 
supplemented by laboratory experiments. 

MATERIAL AND METHODS 

The phenomenon of egg-laying was taken as a parameter of relationship between the 
temperature of the natural or artificial habitat and the reproductive cycle. 

Outdoors, oviposition was studied in the spring region of Bijela Rijeka, where temperature 
variations are distinctive, as well as in the non-captive basin of Tuheljske Toplice which has high 
and almost unvarying temperatures throughout the year. Outdoor studies were performed in 
both localities every month from October 1970 to November 1971 and in Tuheljske Toplice in 
1972, 1973 and 1974. Certain physico-chemical factors such as temperature of the water, 
quantity of dissolved oxygen, acidity (pH), were registered at the same time, always before 
noon. 

(227) 



228 



PROC. SIXTH EUROP. MALAC. CONGR. 



TABLE 1. Oviposition and physico-chemical factors in periods of research in the spring area of Bijela Rijeka. 
Egg-nnass: ++, plenty; +, present. 



Date of 




Water temp. 




Alkalinity 


Hardness 


COj 


0, 


0, 


sampling 


Egg-mass 


°C 


PH 


mval/l 


°d 


mg/l 


mg/l 


% of saturation 


27 .X.I 970 




7.5 


6.8 


5.20 


14.57 


9.84 


10.6 


88.11 


24. XI. 1970 




7.0 


6.6 


5.30 


14.51 


8.74 


11.8 


100.34 


17. XII. 1970 




7.5 


6.8 


5.30 


14.85 


9.84 


10.3 


88.71 


26.1.1971 




7.0 


7.0 


5.91 


16.56 


10.09 


10.5 


89.28 


24.11.1971 




8.0 


6.8 


5.70 


15.96 


— 


10.6 


92.41 


25.111.1971 




6.0 


7.0 


5.30 


14.84 


4.4 


11.3 


93.69 


27. IV. 1971 




8.0 


— 


7.20 


20.16 


22.0 


10.9 


95.03 


26. V. 1971 


++ 


15.5 


7.1 


5.30 


14.92 


29.39 


12.5 


129.39 


24. VI. 1971 


++ 


17.0 


7.1 


5.33 


14.93 


— 


12.2 


130.20 


3.VIII.1971 


+ 


18.0 


7.1 


6.17 


17.73 


10.87 


7.5 


81.69 


5. IX. 1971 




14.0 


— 


5.01 


14.05 


3.20 


10.2 


102.20 


12.x. 1971 




10.0 


6.7 


5.12 


14.34 


0.44 


10.6 


97.06 



TABLE 2. Oviposition and physico-chemical factors in period of research in the non-captive basin of Tuheljske 
Toplice. Egg-mass: +, present; ++, plenty; +++, abundant. 



Date of 




Water temp. 




Alkalinity 


Hardness 


CO2 


0, 


Oa 


sampling 


Egg-mass 


°C 


pH 


mval/l 


°d 


mg/l 


mg/l 


% of saturation 


29.x. 1970 


-1- 


31.0 


7.0 


6.52 


18.27 


22.96 


3.3 


44.47 


26. XI. 1970 


-f- 


29.0 


7.0 


7.03 


19.70 


38.26 


1.6 


20.94 


21.XII.1970 


-1- 


29.5 


7.5 


7.5 


21.42 


31.70 


2.7 


35.62 


28.1.1971 


+ 


30.0 


7.1 


6.63 


18.56 


33.84 


2.1 


27.88 


23.11.1971 


+++ 


30.1 


6.4 


7.10 


19.88 


30.84 


1.4 


18.61 


30.111.1971 


+++ 


30.2 


7.2 


6.70 


18.76 


30.84 


1.5 


19.97 


24. IV. 1971 


4-t- 


31.0 


6.7 


7.10 


19.88 


26.4 


1.1 


14.82 


27. V. 1971 


-f- 


31.0 


7.3 


6.48 


18.14 


29.92 


1.0 


13.47 


30.VI.1971 


-1- 


31.2 


7.2 


6.69 


18.73 


31.71 


1.6 


21.62 


5. VIII. 1971 


+ 


32.1 


7.1 


6.43 


18.00 


31.16 


1.0 


13.67 


8. IX. 1971 


+ 


31.0 


_ 


6.37 


17.85 


24.73 


3.4 


45.82 


4.x. 1971 


+ 


30.9 


7.0 


6.19 


17.27 


19.26 


3.2 


43.06 


4.III.1972 


+++ 


31.2 


7.0 


6.10 


17.08 


39.16 


1.4 


18.91 


2. IV. 1972 


+++ 


_ 


_ 


_ 


_ 


_ 


_ 


_ 


9. VIII. 1972 


+ 


_ 


_ 


_ 


_ 


_ 


_ 


_ 


12.IX.1972 


+ 


31.2 


— 


— 


_ 


— 


— 


_ 


5. XII. 1972 


+ 


30.9 


_ 


_ 


_ 


_ 








26.11.1973 


+++ 


31.1 


_ 


_ 


_ 


_ 


_ 





24.V.1973 


+ 


_ 


_ 


_ 


_ 


_ 


_ 





5. VIM. 1973 


+ 


32.1 


_ 





_ 


_ 


_ 





29.x. 1973 


+ 


31.5 


_ 


_ 


_ 





_ 


_ 


25.1.1974 


+ 


30.5 


_ 


_ 


_ 


_ 


_ 





23. IV. 1974 


+++ 


31.0 


- 


- 


- 


- 


- 


- 



The material was collected with a benthos net from all parts of the water, i.e. the bottom, 
from among rooted aquatic plants, from leaves on the bottom and from the layer of algae on 
the surface. Considering the specific water regime of Bijela Rijeka, sampling was not performed 
in a quantitative sense. Therefore, the presence of egg-masses was defined in both localities by 
relative frequency in a sample. When the egg-masses were found all over aquatic plants, leaves 
on the bottom, bits of wood submerged for a long time, the sample was indicated as 
"abundant" and marked by 3 symbols (+++) (Tables 1 and 2); when egg-masses were found 
easily in the same places, sampling was defined as "plenty" (-I-+), and when possible only by use 
of the benthos net, sampling was called "present" {+). 

Studies of the first oviposition and the frequency of egg-laying were performed with animals 
of 2nd and 3rd generations raised in the laboratory from the population of Tuheljske Toplice. 
Since many authorities claim that parthenogenetic reproduction is common in the Lymnaeidae 
(Crabb, 1928; Colton & Pennypacker, 1934; Hubendick, 1951; Cain, 1956), the animals were 
maintained separate in laboratory vessels filled with 200 cc of water from the natural habitat. 



KRKAC 



229 



Water was changed every 14 days and the vessels cleaned. When required, the animals were fed 
with lettuce. The emergence of egg-masses and the frequency of egg-laying were registered daily 
in 3 or 4 temperature zones. The animals of the 1st group (Table 3) were maintained in water 
of varying temperature (28-31°C), i.e. within the limits of the temperature fluctuations of the 
original population's habitat. The vessels with the animals were submerged in water constantly 
warmed by a heater connected with a thermoregulator. The animals contacted the layer of air 
above the water when emerging and taking in fresh air, being always in the same temperature 
zone. 

The 2nd group of animals (II, Table 3) was kept at a room temperature varying from 
17-25 С This group was a control since all experimental animals were raised at the same 
temperature. 

The 3rd group (III, Table 3) was maintained at an average experimental temperature of 
13.9 С (9-22 С). The temperature of the water in the experimental containers of the 2nd and 
3rd groups was gradually changing, following the temperature variations of the surrounding air. 
Daily fluctuations of up to 5°C were recorded. 

Series of experiments, indicated as A in Table 3, were repeated under the same conditions 
with animals of the 3rd generation (B, Table 3), raised in the laboratory with a slightly 
different temperature regime. Another temperature zone (group IV, Table 3) with a smaller 
interval of variation (13-17.5°C) and a higher average temperature (less than 1°C higher than 
the average temperature in the 3rd group) was added to the experiments already mentioned. 

TABLE 3. Quantity of egg-laying at experimental temperatures defined by average number of eggs per day and 
per animal. Significance of the size differences among the animals at first oviposition was checked with the F-test. 





















Temperature 






















variations 






















in°C 


Temperature 




Shell-length 




( 


Quantity of egg-lay 


ing in 30 day 


Average 


during 120 


variations 


Experi- 


at first 


P 




periods from first 


oviposition 


exper. 


days after 
first 


in°C 
during 


oviposition 












temp. 


ment 


(mm) 


value 


0-30 


31-60 


61-90 


91-120 


121-240 


in°C 


oviposition 


experiment 


1 A 


_ 




_ 





_ 


_ 


_ 


29.5 





28-31 


1 В 


— 




— 


— 


— 


— 


— 


29.8 


— 


28-31 


IIA 


10.9±0.9 


>0.05 


1.1 


1.3 


1.2 


1.4 


0.7 


20.5 


19-25 


17-25 


Il В 


11.1+0.8 


>0.05 


1.4 


1.3 


1.1 


0.9 


0.4 


20.3 


18-22 


18-22 


III А 


10.5±0.9 


>0.05 


1.6 


2.6 


1.2 


0.1 


0.1 


13.9 


15-22 


9-22 


III В 


10.8±0.7 


<0.05 


0.5 


0.3 


0.5 


0.4 


0.4 


14.1 


15-20 


12-22 


ÍV 


13.9±0.9 




0.2 


0.1 


0.01 


0.2 


0.1 


15.0 


14.5-17 


13-17.5 



RESULTS AND DISCUSSION 



The population from the spring region of Bijela Rijeka commences oviposition late in the 
spring (Table 1) when the difference of the water temperature between two successive 
recordings attains 7.5°C. At the beginning of the reproductive season egg-laying is intensive but 
it gradually diminishes towards the end of the season. The period of oviposition is limited to 
2-3 months, as is in accordance with our earlier studies on Radix peregra in a small basin not 
far from the centre of Zagreb (Krkac & Mestrov, 1970). Egg-laying in that locality with distinct 
seasonal temperature fluctuations was also recorded after the thermic jump in the spring. 
Egg-laying continues for the next 2-3 months at a higher and unvarying temperature. The onset 
of oviposition depends on the temperature conditions of a certain year. 

The population living in warm, non-captive springs of Tuheljske Toplice with temperatures 
from 29-32.1 C, lays eggs continuously regardless of the season. However, oviposition is more 
intensive in February, March and April (Table 2). Literature data point out (Wesen berg- Lund, 



230 PROC. SIXTH EUROP. MALAC. CONGR. 

1939; Hubendick, 1951; Clench, 1959) that Lymnaeidae lay eggs in spring or summer. 
Considering such recordings the population of Tuheljske Toplice is quite specific in its 
reproductive characteristics. It appears that the supposed effect of a thermal jump, supported 
by research in the spring region of Bijela Rijeka, could not be applied to the present 
population. Particular behaviour of these animals, i.e. emerging and staying for a considerable 
time on the surface of a compact layer of algae spread over the basin of the thermal spring, was 
an incentive to study that phenomenon (Krkac, 1973). 

The experiment shows that the migration to the surface layer of algae is not regular with 
regard to the time of the day. When migrating, the animals are subjected to various temperature 
shocks due to the time of day or season. The abrupt temperature change produces a permanent 
stimulus to oviposition. 

In fact, these results are in accordance with Van der Steen (1967) indicating that the 
beginning of breeding of Lymnaea stagnalis is a consequence of certain natural temperature 
conditions. So a sudden rise of temperature stimulates the egg-laying, though not at the very 
beginning, while a decrease in temperature inhibits it. The stimulative effect of the temperature 
rise from 20 С to 25-28 С was demonstrated in an experiment of Timmermans (1959), in 
which 50% of Planorbis corneus specimens were laying eggs almost simultaneously in the course 
of 3 hours. 

Studies on the influence of temperature and its variations on first oviposition and the 
frequency of egg-laying were performed in the laboratory. 

The quantity of the egg-mass was defined as the average number of eggs per animal per day 
(Table 3). It should be noted that the reproductive potential of the experimental animals raised 
in the laboratory was deficient when compared to that of the animals collected and transferred 
to the laboratory and maintained in groups in vessels. The animals of the 1st experimental 
group (lA and IB, Table 3) kept under a temperature regime of 28-31°C and deprived of 
changing the temperature zone, did not produce a single egg-mass. 

Like a rise in temperature, a change in the amount of oxygen also stimulates oviposition in 
Lymnaea stagnalis (Lever, 1946; Timmermans, 1959; Joosse, 1972). Outdoor observations on 
emerging and staying out of the water of specimens of the Tuhelj population suggest the same 
effect in Radix peregra. Considering the same period, the saturation of oxygen in the spring 
region of Bijela Rijeka recorded was never less than 81.69% compared to 45.82% in Tuheljske 
Toplice. Emergence of animals out of the water in the spring area of Bijela Rijeka was never 
noticed. The experiment in which animals were separately maintained at a temperature from 
28-31 С refuted such a possibility for Radix peregra. The animals in the experiment were often 
leaving the water just like those from Tuheljske Toplice. By emerging, the animals contacted an 
environment rich in oxygen but of the same temperature, since the water in which the 
containers with the animals were submerged, warmed the layer of air over the vessels. Although 
the animals could reach an environment abundant in oxygen, they never produced a single 
egg-mass. The experiment serves as a contribution to the conclusion that a change of the 
temperature experienced when the snails emerge out of the water, proves to be a significant 
factor in oviposition. 

Group IIA maintained at temperatures from 19-25°C laid eggs in greatest quantities in a 
period of 240 days but only a small number of egg-masses was normally shaped. The term 
'egg-mass' is used indiscriminately whether the empty gel masses were laid with the size of a 
normal egg-mass (see a. Fig. 1), or shaped like a long irregular ribbon (b and c) or whether an 
egg-mass contained a normal (d), excessive (e) or small (f) number of eggs. The quantity of 
egg-laying in experiment IIB was somewhat lower but shape and size of the egg-mass was the 
same as in experiment A. Average temperatures at which the animals were maintained during 
experiments A and В in group II differed only 0.2°C, while variations in temperature during the 
process of egg-laying in group A were 6°C and in experiment В 4° С. 

Considerable differences in amount of egg-laying in group III appeared in the 1st (A) and 
2nd (B) experiments. The animals of experiment A laid a larger number of eggs in the initial 
period of 120 days after laying the 1st egg-mass; the amount of egg-laying in experiment В was 
1/3 of that in experiment A regardless of whether recordings of egg-laying continued for 120 or 
240 days of experiment. The temperature fluctuations in experiment A were 7°C and in В 5° С. 

The quantity of egg-laying in the 4th group was only 0.1 in the 1st and 2nd periods of 120 
days, i.e. less than in other groups. A number of empty gel masses, shaped like ribbons or 



KRKAC 



231 




FIG. 1. Egg-masses of Radix peregra, group IIA (see text); a, empty gel mass with normal size; b, empty gel 
mass shaped like a long, irregular ribbon; c, another abnormal empty gel mass; d, egg-mass with normal 
number of eggs; e, egg-mass with excessive number of eggs; f, egg-mass with small number of eggs 
(approximately natural size, scale 1 cm). 

sometimes like small balls exceeded egg-masses normal in shape and number of eggs. Some of 
the animals of the 4th group produced egg-masses containing more than the usual number of 
eggs. The temperature variations for these according to outdoor observations, supposed to act as 
a stimulus for egg-laying, are here almost half (2.5°C) the smallest variation recorded in 
experiment II В (4 С). 

An analysis of the results of the experiments suggests that the quantity of egg-laying depends 
on both the amplitude of temperature variation and on the average ambient temperature. 

The animals of the 2nd and 3rd group are not particularly distinctive considering the 
shell-length at the beginning of oviposition. The animals of the 4th group laid eggs considerably 
later, after having attained greater shell-length than those of the 2nd and 3rd groups. 

CONCLUSION 

Onset of oviposition in habitats with distinct seasonal temperature fluctuations is caused by 
a raise of the water temperature in the spring. 

Permanent egg-laying of the population of the non-captive basin of Tuheljske Toplice is 
conditioned by the stimulative effect of the change in temperature, to which the members of 
the population are exposed all the year round when migrating to the surface layer of algae. 

Quantity of egg-laying in an experiment depends on the amplitude of the temperature 
variations and on the average temperature conditions. 

Specimens raised at high temperatures (29.5°C and 29.8°C), and deprived of possibilities to 
change the temperature zone, laid no eggs at all. 

LITERATURE CITED 



BOLE, J., 1966, Mehkuzci in zoogeografski polozaj Rakovega Skocijana. Varstvo narave, 5: 129-137. 
CAIN, G. H., 1956, Studies on cross-fertilization and self-fertilization in Lymnaea stagnalis appressa Say. 
Biological Bulletin, 1 1 1 : 45-52. 



232 PROC. SIXTH EUROP. MALAC. CONGR. 

CLENCH, W. J., 1959, Mollusca. In: WARD, H. В., WHIPPLE, G. С & EDMONDSON, W. T., Fresh-water 

biology, 2nd ed.: 1117-1160. Chapman & Hall, London. 
COLTON, H. S. & PENNYPACKER, M., 1934, The results of twenty years of self-fertilization in the pond 

snail, Lymnaea columella Say. American Naturalist, 68: 126-136. 
CRABB, C., 1928, Self-fertilization in the pond snail Lymnaea palustris. Transactions of the American 

Microscopical Society, 47: 82-88. 
DUNCAN, С J., 1959, The life cycle and ecology of the fresh water snail Physa fontinalis. Journal of 

Animal Ecology, 28: 97-117. 
HUBENDICK, В., 1951, Recent Lymnaeidae. Their variation, morphology, taxonomy, nomenclature and 

distribution. Kungliga Svenska Vetenskapsakademiens Handlingar, (4) 3(1): 1-223. 
JOOSSE, J., 1972, Endocrinology of reproduction in Mollusca. General and Comparative Endocrinology, 

supplement 3: 591^601. 
KRKAC, N. & MESTROV, M., 1970, Etude de la neurosecretion chez Radix peregra O.F. Müller 

(Gasteropode, Pulmoné). Bulletin de la Société Zoologique de France, 95: 627-644. 
KRKAC, N., 1973, Promjena temperaturne zone-stimulans za odiaganje jaja vrste Radix peregra O. F. Müller. 

Ekologija, 8: 131-138. 
KRKAC, N., 1975, Dinamika populacija, ciklus reproduktivne i neurosekretorne aktivnosti vrste Radix 

peregra O.F. Müller (Gastropoda, Pulmonata) и razlicitim termickim uvjetima. Thesis, University Zagreb. 
LEVER, J., 1957, Some remarks on neurosecretory phénomènes in Ferrissia sp. (Gastropoda, Pulmonata). 

Proceedings of the Koninklijke Nederlandse Akademie van Wetenschappen, C, 60: 510-522. 
MATONIOKIN, I., 1957, Ekoloîèka istrazivanja faune termalnih voda Hrvatskog zagorja. RadJAZU, 312: 

1.39-206. 
MESTROV, M. & KRKAÔ, N., 1970, Data on neurosecretion of the aquatic lung-gastropod Radix peregra 

O.F. Müller. Bulletin Scientifique, Conseil des Académies de la RSF de Yougoslavie, (A) 15: 6-7. 
MICHELSON, E. H., 1961, The effect of temperature on growth and reproduction oi Australorbis glabratus 

in the laboratory. American Journal of Hygiene, 73: 66-74. 
SMITH, B. J., 1967, Correlation between neurosecretory changes and maturation of the reproductive tract of 

Arion ater (Stylommatophora: Arionidae). Malacologia, 5: 285-298. 
STEEN, W. J. VAN DER, 1967, The influence of environmental factors on the oviposition of Lymnaea 

stagnalis (L.) under laboratory conditions. Archives Néerlandaises de Zoologie, 17: 403-468. 
TIMMERMANS, L. P. M., 1959, Stimulation of oviposition in some land and freshwater snails. Proceedings of 

the Koninklijke Nederlandse Akademie van Wetenschappen, С 63: 363-372. 
WESENBERG-LUND, C, 1939, Biologie der Süsswassertiere/Wirbellose Tiere. Julius Springer, Wien, 817 p. 
WOLDA, H., 1967, The effect of temperature on reproduction in some morphs of the land snail Cepaea 

nemoralis (L.). Evolution, 21: 117-129. 



\ 



MALACOLOGIA, 1979, 18: 233-236 

PROC. SIXTH EUROP. MALAC. CONGR. 

COMPETITION ENTRE /l^£¿/\/VOPS/S (GASTROPODA: PROSOBRANCHIA) 

ET BASOMMATOPHORES EN ALGERIE: L'ELIMINATION DE 

BU LI NUS TRUNCATUS TRUNCATUS 



Jacques Dupouy 

Faculté des Sciences, Université de Yaounde, Cameroun et 
Centre Universitaire de Perpignan, France 

ABSTRACT 

A 3-year study in Algeria has revealed that there is marked competition between species 
of the genus Melanopsis and Basommatophora, particularly Bulinus t. truncatus. Melanopsis 
praemorsa appears to be generally more resistant and prolific than Planorbarius metidjensis 
and Physa acuta and tends to replace these in most habitats of both the low-lying and higher 
plateaus of Tell. It even starts to invade the semi-arid zone of the tablelands of the Atlas 
Mts. In areas of oases Melanopsis dufouri progressively eliminates Bulinus t. truncatus in 
irrigation canals. A reduction in the number of foci of schistosomiasis in the region 
coincides with this phenomenon. Melanopsis praemorsa s.l. has a very wide 
circummediterranean distribution (North Africa, Asia Minor, etc.) and is therefore obviously 
well adapted to arid conditions. This species may be of potential value in combatting 
schistosomiasis and experiments in this line are certainly called for. 

INTRODUCTION 

En Algérie, l'existence de la bilharziose et de son vecteur privilégié, Bulinus truncatus truncatus 
(Audouin), a été signalée à diverses reprises par Sergent (1939), Pallary (1939), Mandoul & 
Jacquemin (1953) et Sinnonet (1959), Sur ce ter r\to\re, Planorbarius metidjensis (Forbes) peut être 
aussi considéré comme hôte potentiel äe Schistosoma haematobium (cf. Mandahl-Barth, 1958). 

Cependant, en 1965, Davadie & Metge font état de la régression d'un foyer de bilharziose au 
Sahara sans, toutefois, en préciser l'origine exacte. 

Or, dans la nature, des agents biologiques multiples, étroitement impliqués dans l'équilibre des 
biocénoses, peuvent agir comme facteurs de régulation démographique des Gastéropodes vecteurs 
de la bilharziose (Michelson, 1957; Wright, 1966); mais leur efficacité reste limitée dans la majorité 
des cas. Toutefois, la compétition entre des Gastéropodes vecteurs et non vecteurs, ayant 
simultanément des exigences écologiques identiques, peut être très sélective. 

En Algérie, précisément, un Prosobranche Thiaridae du genre Melanopsis Férussac, non vecteur, 
tend à éliminer ses concurrents vecteurs, Bulinus t. truncatus ou Planorbarius metidjensis, de leurs 
biotopes sahariens ou oranais. 

BASOMMATOPHORES ET MELANOPSIS EN ORANIE 

La faune des Basommatophores en Oranie est représentée par 5 espèces paléarctiques: Galba 
truncatula {MüWer) , Physa acuta Draparnaud, Planorbarius metidjensis (F orbes) , Anisus vortex (L.) 
etAncylusfluviatilis (Müller). 

Cet inventaire diffère nettement de celui de Pallary^ recensant une trentaine de 
Basommatophores en Algérie non saharienne (1901-1939). Depuis le Pliocène, il ne semble pasque 
sa composition ait sensiblement évolué (Flamand, 1911; Pallary, 1901, 1926), les conditions 
paléoclimatiques elles-mêmes n'ayant guère fluctué depuis le début du quaternaire, dans le Tell et 
l'Atlas. Les Basommatophores fossiles et subfossiles, par contre, avaient une distribution beaucoup 

' De nombreuses espèces admises par Pallary n'ont pas été reconnues valides ultérieurement. 

(233) 



234 PROC. SIXTH EUROP. MALAC. CONGR. 

plus vaste que de nos jours et leur aire de dispersion couvrait les basses et hautes plaines telliennes 
ainsi que certains secteurs du Sahara septentrional (Chevallier, 1969). 

Actuellement, ils végètent dans les Monts de TIemcen et sur les hauts plateaux de Sebdou (Fig. 
1), à une altitude connprise entre 700 et 1000 mètres, à l'exception, cependant, des Ancyles qui 
fréquentent aussi les oueds des basses et hautes plaines telliennes. Ils occupent une aire beaucoup 
plus restreinte qu'au début du quaternaire, située entre les isothermes С et 3°C, à climat 
sub-humide ou semi-aride (Ouled Mimoun, Sebdou), la pluviosité estivale moyenne étant comprise 
entre 25 et 35 mm ou bien 25 et 31 mm, selon Alcaraz (1969). Pour les Basommatophores oranais 
et plus spécialement Planorbarius metidjensis, ce milieu montagnard, au sens large, est un milieu 
refuge en limite d'aire, ayant surtout l'inconvénient d'amoindrir leur potentiel évolutif. Leur 
capacité de reproduction, comparativement à celle de Me/anopsis praemorsa (L.), reste faible et ils 
s'isolent en groupements relictuels, composés d'écotypes non différenciés, dans des points d'eau à 
pH nettement acide (6.5, 6.6) moins favorables à leur croissance que les eaux alcalines (7.1-8.4) 
des plaines telliennes. 

Cet isolement écologique peut s'expliquer par l'action combinée de 3 facteurs: 

(1) en premier lieu, par l'action des facteurs anthropozoogènes sur les conditions édaphiques. 
En effet, il faut tenir compte de l'intensification de la viticulture depuis plus d'un siècle dans les 
basses et hautes plaines telliennes, de la deforestation abusive, de la pratique de l'incendie et du 
surpâturage; 

(2) en second lieu, par l'influence d'un facteur biologique intrinsèque en rapport avec la 
moindre résistance des Basommatophores à la sécheresse estivale étalée sur une période de 5 mois; 

(3) enfin et surtout, par l'action du facteur de compétition malacologique en rapport avec la 
similitude des exigences écologiques des Basommatophores et de Me/anopsis praemorsa. 

Me/anopsis praemorsa est une espèce euryèce, prolifique, adaptée à tous les degrés d'aridité 
relative, aux variations thermiques de grande amplitude, et capable de résister à l'inanition. 
Toutefois, sa tolérance thermique ne lui permet pas de supporter une minimale moyenne inférieure 
à С et sa pénétration géographique ne paraît pas dépasser l'isotherme 0°C vers le sud. Son aire de 
dispersion est beaucoup plus étendue que celle des Basommatophores et couvre tous les étages 
bioclimatiques entre Oran et Sebdou (Fig. 1). Leur fécondité est comparable d'un étage 
bioclimatique à un autre et leur reproduction n'est interrompue que pendant les 2 mois les plus 
chauds de l'année (juillet, août). En outre, la castration parasitaire par les Digènes est toujours 
nettement circonscrite et elle n'affecte pas la progression démographique globale de cette espèce, 
au demeurant très polymorphe. 

Moeurs amphibies, résistance prolongée à la déshydration des sols, solidité du test operculé, très 
forte fécondité et très forte densité de population (25/100 cm ), réversibilité des régimes 
alimentaires ont favorisé la conquête des nîches écologiques de P/anorbarius metidjensis et des 
autres principaux Basommatophores par Me/anopsis praemorsa, en Oranie. 

BU LINS ET MELANOPS/S DANS LA VALLEE DE LA SAOURA 

La régression d'un foyer de bilharziose dans la vallée de la Saoura a été signalée en 1965 par 
Davadie & Metge, alors que, selon Simonet, différents foyers de la maladie étaient encore très 
actifs en 1959. 

Or, l'enquête effectuée dans les oasis d'EI Aouatta, Hanefid et Agdal, dépendant du secteur de 
Béni Abbès, de 1 972 à 1 974, a révélé qu'il n'y avait jamais eu de traitement des puits infectés par 
un molluscicide ni de contrôle thérapeutique systématique des populations locales. 

L'enquête malacologique, par contre, a montré que l'espèce concurrente de Bu/inus t. 
truncatus, Me/anopsis dufouri Férussac s.l., a colonisé tous les biotopes où se trouvait le Bulin, il y 
a encore une dizaine d'années. L'élimination du Bulin de la majorité des points d'eau de la vallée 
de la Saoura, dans le secteur de Béni Abbès, a fortement contribué à faire régresser l'endémie. 

CONCLUSIONS 

L'aire géographique de Me/anopsis praemorsa et de ses formes vicariantes couvre le bloc 
hispano-mauresque (Pérès, 1939, 1943-1945), la Palestine, la Syrie (Germain, 1921), la Grèce, les 



DUPOUY 



235 



5ш 




»- (0 



a> 



. CO f^ 

— oj .r 
U. ТЭОТ 



236 PROC. SIXTH EUROP. MALAC. CONGR. 

régions méridionales de la Russie (Zhadin, 1952) et se morcelle au niveau du Sahara. Son extension 
déborde, au nord-est de l'Asie Mineure, l'aire de dispersion de Bulinus t. truncatus, hôte 
intermédiaire de la bilharziose hématurique, comme Planorbarius metidjensis. 

L'élimination de Bulinus t. truncatus dans le bassin de la Saoura et la régression des nîches à 
Planorbarius metidjensis en Oranie, incitent à l'utilisation du taxon Melanopsis dans la lutte 
biologique contre les Basommatophores responsables de la transmission de la bilharziose 
hématurique dans la zone circumméditerranéenne. 

LITERATURE CITEE 

ALCARAZ, J.-CI., 1969, Etude géobotanique du pin d'Alep en Oranie. These de spécialité de l'Université de 

Mon tpellier. 
CHEVALLIER, H., 1969, Mollusques subfossiles récoltés par Mr. H. Lhote dans le Sud Oranais et le Sahara. 

Bulletin du Muséum National d'Histoire Naturelle, Paris, 41 : 266-294. 
DAVADIE, J. A. & METGE, R., 1965, Régression d'un foyer de bilharziose au Sahara. Bulletin de la Société de 

Pathologie Exotique, 58: 81-88. 
FLAMAND, G. B. M., 1911, Recherches géologiques et géographiques sur le Haut Pays de l'Oranie et sur le 

Sahara (Algérie et Territoires du sud): 122-111 . 941-950. Lyon. 
GERMAIN, L., 1921 , Mollusques terrestres et fluviátiles de Syrie, 1 . J. B. Baillière, Paris, 523 p. 
MANDAHL-BARTH, G., 1958, Intermediate hosts of Schistosoma. African Biomphalaria and Bulinus. World 

Health Organisation Monograph Series, 37: 1-132. 
MANDOUL, R. & JACQUEMIN, P., 1953, Enquête sur la Bilharziose au Tassili. Institut de Recherches 

Sahariennes de l'Université d'Alger, 1: 95-103. 
MICHELSON, E. H., 1957, Studies on the biological control of Sc/j/ífosoma-bearing %na\\%. Parasitology, 47: 

413-426. 
PALLAR Y, P., 1901, Mémoire sur les Mollusques fossiles terrestres, fluviátiles et saumâtres de l'Algérie. 

Mémoires de la Société Géologique de France, Paléontologie, 22: 176-180. 
PALLARY, P., 1921, Faune malacologique du Grand Atlas. Journal de Conchyliologie, 66: 87-154. 
PALLARY, P., 1926-1927, Complément à la faune malacologique de la Berbérie. Journal de Conchyliologie, 70: 

1-50,71: 197-277. 
PALLARY, P., 1926, Sur une faunule aquatique pliocènique d'Oran. Bulletin de la Société d'Histoire Naturelle 

de l'Afrique du Nord, 1 7(9): 284-289. 
PALLARY, P., 1939, Prospection des eaux magnésiennes de l'oued Rirh au point de vue de l'existence de Bulins 

et de Planorbes. Archives de l'Institut Pasteur d'Algérie, 1 7: 604-612. 
PERES, J. M., 1939, Contribution à l'étude de quelques Melanopsis du Maroc. Journal de Conchyliologie, 83: 

129-162. 
PERES, J. M., 1943-1945, Contribution à l'étude du genre Melanopsis. Journal de Conchyliologie, 86(3): 

109-136,86(4): 137-174. 
SERGENT, E., 1939, Enquête sur l'existence en Algérie des Bulins et des Planorbes, hôtes intermédiaires de 

Schistosoma haematobium. Archives de l'Institut Pasteur d'Algérie, 17: 601-603. 
SIMONET, Ph., 1959, Pathologie de l'annexe de la Saoura. Archives de l'Institut Pasteur d'Algérie, 30: 136-143. 
WRIGHT, С A., 1966, The pathogenesis of helminths in the Mollusca. Helm in thological Abstracts, 35: 207-224. 
ZHADIN, V. I., 1 952, Mollusks of fresh and brackish waters of the USSR. Moscou, 368 p. 



MALACOLOGIA, 1979, 18: 237-243 

PROC. SIXTH EUROP. MALAC. CONGR. 

THE POPULATION DYNAMICS OF THE PULMONATE SNAIL 
BULINUS (PHYSOPSIS) AFRICANOS (KRAUSS) 

The influence of temperature on mass increase and survival 

Sarel J. Pretorius, Kenne N. de Коек and Jacobus A. van Eeden 

Snail Research Unit of the Medical Research Council, Potchefstroom University for C.H.E., 

Potchefstroom, South Africa 

ABSTRACT 

Cohorts of the freshwater snail Bulinus (Physopsis) africanus, an intermediate host for 
human schistosomes, were reared in a series of aquaria at different constant temperatures. 
Records of their increase in mass and their mortality were kept. Mathematical functions 
reflecting the mass increase and survival at any age at different constant temperatures, were 
developed. From these a model, expressing thebiomass increase at any temperature regime, 
was formulated. 

INTRODUCTION 

In South Africa Bulinus (Physopsis) africanus acts as an intermediate host of the flukes 
Schistosoma haematobium (Bilharz) and S. mattheei Veglia & Roux, both of which parasitise man 
(Wright, 1971). This snail species is distributed mainly in the temperate to tropical climatic regions 
of South Africa in a strip along the eastern seaboard and bordering through the Lovweld and the 
mid-Transvaal highveld regions (Van Eeden et al., 1965). The health hazard associated with its 
presence makes it imperative that its ecology be studied in detail. 

One of our principal objectives in the study on the dynamics of this snail species is to 
understand how various environmental factors determine and regulate the size and age 
composition of the population. It is hoped that, eventually, it might be possible to predict 
accurately changes in tfie population variables, using information on changes in environmental 
factors. The present paper concerns only a part of this broader objective and a mathematical 
model is formulated whereby the biomass of a cohort of snails under any given temperature regime 
can be estimated. 

MATERIALS AND METHODS 

Thirty-five eggs laid overnight by snails collected from a natural habitat were kept at a constant 
temperature in an experimental aquarium, where they hatched and lived for the duration of their 
natural life. Six such cohorts of snails were maintained simultaneously under similar environmental 
conditions except that the temperatures were rigidly controlled at different levels viz. 17, 20, 23, 
26, 29 and 32°C. The details of the aquaria and the daily feeding and maintenance procedures are 
given by De Коек (1 973). Apart from the daily recording of the age and mortality of the snails we 
measured the mass increase of the cohort, or what remained alive of it, every 14 days by means of 
a procedure described by De Коек (1973). In order to reduce the physical disturbance of the snails 
to a minimum it was decided not to weigh the snails individually. The total mass was divided by 
the number of snails still alive at each weighing to obtain a mean mass value for the individuals of 
the cohort at the successive ages. The mean mass values obtained towards the end of the 
experiment were disregarded in this analysis as these were based on too few snails and are 
therefore unreliable. 



(237) 



238 



PROC. SIXTH EUROP. MALAC. CONGR. 






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PRETORIUS, DE КОСК AND VAN EEDEN 239 

RESULTS 

At only 3 of the temperatures (20, 23 and 26°C) the snails hatched and grew satisfactorily. At 
the other temperatures they either failed to hatch or the few that did, failed to grow at all and 
died within a short period after hatching. Obviously, these temperatures (17, 29 and 32°C) were 
outside their tolerance range both for hatching and growth. In Fig. 1 the mean mass is plotted 
against their relevant ages for the temperatures at which measurable mass increases occurred. In 
the same figure the proportion surviving (1^ = snails alive/35 at age x days) is similarly given. 

THE MATHEMATICAL MODEL AT CONSTANT TEMPERATURES 

The data in Fig. 1 reveal that the increase in mass roughly follows the sigmoid pattern found for 
most animals. This is particularly evident for the snails reared at 23°C. In an attempt, therefore, to 
find an empirical description for our results, it was decided to fit to the data a logistic equation of 
the form 

rrix =K/(l + exp. (b-ax)) (1) 

in which m^ ^ the mean mass per specimen of the snails at any given age (x), К = the upper 
asymptote of mass and a and b represent coefficients of the curve (Fig. 1). The relation between 
mean mass and temperature seems to be such that as the temperature increases, it initially 
promotes growth up to a maximum after which further temperature increases inhibits growth. 
Such a relation might be described by a downward opening parabola. A parabolic function 
between temperature (T) as the independent and the coefficients K, a and b of the growth curve as 
the dependent variables yielded the following results: 

K(T) = -0,0096 T^ + 0,4456 T -4,8928 
a(T) = - 0,0046 T^ + 0,21 1 2 T - 2,31 68 
b(T) = -0,0969 T^ + 4,4299 T -45,9878 

If, in equation (1), the coefficients be replaced by these functions of temperature, then an 
empirical description of the influence of a life-long constant temperature on the mean mass 
increase is obtained, 

mx = K(T)/(1 + exp. (b(T) - a(T)x)). (2) 

The survival (Ix) of the snails can be described empirically by a model of the form 

Ix = q - pinx. (3) 

The coefficients q and p of this equation were estimated from the data and are given in Fig. 1. 
Once again, because of the trend of change of the coefficients from the lower to the higher 
temperatures, parabolic functions between the coefficients and temperature were calculated: 

q(T) = 89,7092 - 5,5970 T + 0,0876 T^ 
p(T) =-17,9578+ 1,1486 T- 0,0186 T^ 

Substituting these coefficients as functions of temperature into equation (3) the following 
survival model dependent on temperature is obtained: 

U = q(T) - p(T) Inx. (4) 

The mean mass will increase indefinitely as no provision is made for the eventual mortality of 
the snails in equation (3). To account for this eventually equations (2) and (4) must be 
combined in some way. To do this, consider the equation for the increase in numbers of a 
population with a stable age distribution in a limitless environment (Birch, 1948). 

Nx = No exp. (rx) (5) 

where Nx = the number of animals with age x, and r = intrinsic rate of natural increase. 

Separating the birth and survival components of this equation and converting it to biomass 
by multiplying the number of animals by their mean mass (mx)> an expression is obtained for 
the biomass (B^) of the population. 



240 PROC. SIXTH EUROP. MALAC. CONGR. 

Bx = rñxNo exp. (bx) exp. (-dx). (6) 

This equation evidently proportions the пиглЬег of animals (Nq) between births (exp. (bx)) and 
survival (exp. (-dx)) in terms of mass. If a fixed number of animals, say 100, of the same age is 
surmised for the population and we postulate that there are no births (exp. (bx) = 1) and 
substituting our symbol Ix for the proportion surviving, the equation becomes a means whereby 
the biomass changes in a cohort of animals may be traced as they become progressively older 

Bx = 100 mxlx- (7) 

By substituting our formulations for mass increase (equation (2)) and survival (equation (4)) 
into equation (7) the combination we set out to do is completed, 

Bx = 100(K(T)/(1 +exp. (b(T)-a(T)x))) (q(T)-p(T)lnx)). (8) 

The function K(T) determines the upper asymptote for mass increase and represents, so to 
speak, the maximum mass to which any individual snail can grow at the particular temperature. 
It is obvious that negative values for K(T) have no meaning in that an animal cannot grow 
smaller. The mass increase factor of equation (8) is, therefore, only applicable when K(T) is 
positive. In addition, the proportion survival can only lie between and 1. As formulated in 
equation (8) it can extend beyond these values. The survival factor of equation (8) must, 
therefore, be limited to these values which occur at the ages 

q(T) - p(T)lnx - 1 

lnx= (q(T)-1)/p(T)) 
x = exp. ((q(T)-1)/p(T))) (9) 

and q(T) - p(T)lnx = 

Inx = q(T)/p(T) 
x = exp. (q(T)/p(T)). (10) 

With all these constraints the model finally becomes 

K(T) < о 

(no mass increases) 

( Bx iff x< exp. ((q(T)-1)/p(T)) 
Bx + 1 = \ Bxlx iff exp. ((q(T)-1)/p(T))<x<exp. (q(T)/p(T)) 
( о iff X > exp. (q(T)/p(T)) 

K(T) > о 
(mass increases) 

( Nomx iffx<exp. ((q(T)-1)/p(T)) 
Bx + i = { NoFiixlx iffexp. ((q(T)-l)/p(T))<x<exp. (q(T)/p(T)) 

(o iff X >exp. (q(T)/p(T)). (11) 

With this model the biomass of a cohort of snails reared life-long at a constant temperature can 
be calculated at any age provided that temperature is the only governing factor (Fig. 2). Some 
insight can be gained into the effect of temperature on survival and mass increase of B. (P.) 
africanus if the restraints of the model are plotted as in Fig. 3. In this figure the shaded area 
represents the zone in which mortalities may be expected to occur in accordance with the 
equation given in the shaded area. To the left of the shaded area there should be no mortalities 
dx = 1) and to the right of the shaded area there should be no survivors (Ix = 0). In addition a 
zone is demarcated in which the prevailing temperatures (in this case 18 to 28 C) will permit 
mass increases to take place in accordance with the equations given on the right hand side of 
the figure. The most striking feature of this figure, however, is the fact that the longest lived 
cohort, before any deaths occur, is to be expected towards the lower temperatures whereas the 
longest lived individuals of a cohort should be found at approximately halfway between 18 and 
28 C. It, therefore, seems that the temperature optimally suited for the survival of an entire 
cohort is lower than the temperature optimally suited for growing to a larger size by an 
individual specimen in a cohort. 



PRETORIUS, DE КОСК AND VAN EEDEN 



241 



20°C 







X Idaysl 200 



FIG. 2. The biomass (Bx) of a cohort of a 100 snails generated by the model given in the text in one day age (x) 
intervals. 



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temperatures (T). 



242 PROC. SIXTH EUROP. MALAC. CONGR. 

The model presented and described so far was constructed from results obtained at only 3 
temperatures viz. 20, 23 and 26°C and it is particularly significant that it predicts that no 
growth is to be expected at constant temperatures of 17, 29 and 32°C. These predictions are in 
full agreement with our experimental findings at the latter temperatures. This circumstance 
might be taken to testify to the reliability of the model. 

A MODEL AT CONSTANTLY CHANGING TEMPERATURES 

The model developed so far is, of course, only valid for those instances where the 
temperatures are kept constant for the duration of the animal's life. In nature, however, the 
snails are subjected to constantly changing temperatures not only diurnally but also seasonally. 

One is, consequently, confronted with the problem of having to use the information 
obtained at constant temperatures to predict what would happen if the temperatures were 
constantly changing. To do this we can, fortunately, resort to a well established mathematical 
procedure in which the biomass at the beginning of any time period together with the slope of 
the biomass curve during that period is used to calculate the biomass at the end of the period 
as follows: 

Bx + Дх = Bx + (ЭВх/Эх) Ax. (12) 

To find the slope of the biomass curve (ЬВ^/дх) one may proceed as follows: 

Bx + Дх = Bx + (ЭВх/Эх) Дх 

= Вх + По Om^lx/ôx) Ах 

= Вх + No (тхЭ1х/Эх + 1хЭтх/Эх) Ах 

- Вх + No {mx(-p(T)/x) + Ixmxa(T) (1-mx/K(T))) Ax. (13) 

An important assumption in this formulation is that the temperature remained constant during 
the period selected for the change in age (Ax). Obviously, the shorter the period Ax, the more 
reliable is the assumption that the temperature remained constant during this time. For 
instance, the biomass estimate would be more reliable on the basis of an hourly change (Ax = 
1/24) than on the basis of a daily change (Ax = 1) because the hourly change of water 
temperature in a natural habitat is negligible compared to the diurnal change. 

Again, certain parts of the model operate only between certain limits as explained for 
equation (11). In addition it may happen that at any given time the biomass exceeds the value 
which the model predicts {K(T) < rñx) for the temperature prevailing at that time. This 
suggests a decrease of biomass which, of course, is impossible except, amongst others, through 
the effect of mortality, egg production and erosion of the shell. 

A model dependent on the age of the snail (x), the change in their age (Ax) and any 
temperature (T) regime can, therefore, formally be written as: 

1. K(T) < о and/or K(T)< nix 

1.1 Bx + Дх "^ Bx 

iffx<exp. ((q(T)-1)/p(T)) 

1.2 Bx + Дх = Bx + Bx (9lx/9x) Ax 

= Bx + Bx {-p(T)/x) Ax 
iff exp. ((a{T)- 1)p(T)) < X < exp. (q(T)/p(T)) 

1.3 Bx + Дх = о 

iff x> exp. (q{T)/p(T)) 

2. K(T)>oandK(T)>mx 

2.1 Bx + Дх = Bx + (ЭгЛх/Эх) Ax _ 

= Bx + Nonnx a(T)(1-mx/K(T)) Ax 
iffx<exp. ((q(T)-l)/p(T)) 

2.2 Bx + Дх = Bx + No (mx(-p(T)/x) + lxmxa(T)(1-mx/K(T))) Ax 

iff exp. ((a(T)-1)/p(T))<x<exp. (q(T)/p(T)) 

2.3 Bx + Дх = о 

iffx>exp. (q(T)/p(T)). (14) 



PRETORIUS, DE КОСК AND VAN BEDEN 243 

The model is only valid for snails of the sanne age and predicts the average trend only. In a 
natural habitat, however, snails with a whole range of different ages can be found at any time. 
Obviously, therefore, births as a function of temperature must also be incorporated into a 
model of this kind. If this could be done the restriction that the model can be applied only to 
a single cohort of snails would fall away. The model could be made still more powerful if a 
measurement of the variability of the mass in snails of the same age as reported by Prinsloo & 
Van Eeden (1973) could be incorporated into it. 



ACKNOWLEDGEMENTS 

We thank Dr. H. S. Steyn, from the Statistics Department, Potchefstroom University for 
C.H.E., for his valuable assistance with the mathematics and the South African Medical 
Research Council for their financial support. 

LITERATURE CITED 

BIRCH, L. C, 1948, The intrinsic rate of natural increase of an insect population. Journal of Animal 

Ecology, 17: 15-26. 
VAN EEDEN, J. A., BROWN, D. S. & OBERHOLZER, G., 1965, The distribution of freshwater molluscs of 

medical and veterinary importance in south-eastern Africa. Annals of Tropical Medicine and Parasitology, 

59: 413-424. 
DE КОСК, К. N., 1973, Die bevolkingsdinamika van vyf medies en veeartseny kundig belangrike varswater- 

slakspesies onder toestande van beheerde temperatuur. D.Sc. thesis, Potchefstroom University for C.H.E., 

South Africa, 388 p. 
PRINSLOO, J. F. & VAN EEDEN, J. A., 1973, The influence of temperature on the growth rate of Bulinus 

(Bulinus) tropicus (Krauss) and Lymnaea natalensis Krauss (Mollusca: Basommatophora). Malacologia, 14: 

81-88. 
WRIGHT, С A., 1971, Flukes and snails. George Alien and Unwin Ltd., London, 182 p. 



MALACOLOGIA, 1979. 18: 245-255 

PROC. SIXTH EUROP. MALAC. CONGR. 

DISTRIBUTION OF FRESHWATER MOLLUSCS IN 

MOUNTAIN STREAMS OF TROPICAL INDO-PACIFIC ISLANDS 

(MADAGASCAR, CEYLON, NEW CALEDONIA) 

Ferdinand Starmühlner 
7. Zoologisches Institut der Universität Wien, Dr. Karl Lueger-Ring 1, A-1010 Wien, Austria 

ABSTRACT 

The distribution of freshwater molluscs between the head-waters and the rлouths of 
mountain streams of the tropical continental islands of Madagascar, Ceylon and New 
Caledonia is discussed. The occurrence of the species of typical freshwater families in the 
different parts of running waters of the different Indo-Pacific islands is compared. 

During several hydrobiologicai missions to tropical, high-elevated continental islands in the 
Indo-Pacific (Starmühlner, 1962, 1968, 1969, 1970, 1973, 1977; Costa & Starmühlner, 1972) 
the distribution of freshwater molluscs between the head-waters and mouths of mountain 
streams was studied. Collections were made qualitatively and quantitatively (1/16 m^-1 m^) at 
selected points of the streams. In connection with the collections ecological factors of the 
habitat, such as velocity of the current, temperature of the water, bottom material (mud, sand, 
gravel, boulders, rocks), aquatic vegetation, and chemistry of the water [hardness, pH, 
SBV(alkalinity), electrolytic conductivity, etc.] were studied (Weninger, 1968, 1972). 

MADAGASCAR (Fig. 1) 

The old continental island of Madagascar consists of a Precambrian granitic socle in the 
centre, interrupted by later volcanic eruptions. On the east coast the central highland slopes in 
a steep gradient to the Indian Ocean. This part is covered with the last remnant of primary rain 
forest. On the west coast adjacent to the Mozambique Channel, the slope is less steep and the 
coast consists of sediments originating from the Triassic to the Tertiary or Quaternary. The 
mountains in the Precambrian centre reach up to 2656 m, the high plateau is about 1000 to 
1500 m high and today shows a steppe-like landscape. The former subtropical woods were 
destroyed by burning and clearing over the last centuries. 

(A) Head-waters in the central mountains (2500-1500 m). 

Torrents originate in mountain forests, partly flowing through open landscapes with 
mountain shrubs and bushes. The bottom contains rocks and boulders, near the margins and 
pools between cascades it contains sand, mud and vegetable debris; water temperature between 
11° and 16°C; current 50 cm /sec- m о re than 1-2m/sec; chemistry, SBV 0.3-0.4, pH 6. Species 
found: Afrogyrus nov.sp. (below flat stones near the margin). 

(B) Highland streams (1500-1000 m). 

Flowing through highland steppes, partly cultivated land with paddy fjelds. Bottom: muddy 
stones, sand, mud, vegetable debris; water temperature between 20 and 23 C; current 
10-50 cm/sec; chemistry, hardness 0.14°dH to 0.7°dH, SBV 0.20-0.70, pH 6-7. Species found: 
Pila cecillei, Melanoides tuberculata (only in waters with a hardness of more than 1 dH), 
Lymnaea (Radix) natalensis hovarum, Bulinus liratus, Afrogyrus crassilabrum, Biomphalaria 
madagascariensis, Ferrissia (Pettancylus) modestus. All species found also occur in still waters; 
Ferrissia (Pettancylus) modestus is found exclusively on the lower surface of floating water- 
plants, wood etc. in a slow current of 30 cm /sec. In the mountain and highland streams no 
forms typical of running waters were found. 

(245) 



246 



PROC. SIXTH EUROP. MALAC. CONGR. 




STARMÜHLNER 247 

(C) Torrents and cascade streanns of the steep slope of the N.W. and E. coast (1000-100 m). 

Flowing in waterfalls and cascades through primary rainforest; between the steplike cascades, 
occasional deep pools. Bottom: rocks, boulders; near the margins and in the pools: sand with 
vegetable debris; water temperature between 23 and 25°C; current: 1 m/sec-more than 2 m /sec 
(near the margin: 30-50 cm/sec, in pools: 0-20 cm/sec); chemistry, hardness 0.3-0.6°dH, SBV 
0.25-0.7, pH 6. Species found: (a) on rocks and boulders (1-2m/sec), Melanatria fluminea, 
Cleopatra spp. (such as madagascariensis, colbeaui, grandidieri), mostly behind and below the 
boulders, protected against the strong current; (b) near the margins and in the pools between 
cascade zones (10-30 cm/sec). Pila cecillei, Melanoides tuberculata (if the hardness is more than 
1°dH), Lymnaea (Radix) natalensis hovarum, Bulinus liratus, A f году rus crassilabrum, 
Biomphalaria madagascariensis. 

(D) Lower courses of streams near the N.W. and E. coast (100-1 m). 

Flowing through primary and secondary forests, partly through cultivated land. Bottom: 
boulders, gravel, near the margins and in the pools between cascade zones: sand, mud, vegetable 
debris; water temperature 26-27°C; current 50cm-1 m/sec; chemistry, hardness up to 7-8 dH, 
SBV up to 2.5, pH 6.5-7. Species found: on the surface of the boulders, Septaria borbónica; on 
the sides of and below the boulders, Neritina (Vittina) gagates, Neritina pulligera knorri. 

(E) Transition between lower courses and the mouths of the streams, partly under influence 
of brackish water during high tide (10-0 m). 

Flowing through cultivated areas and near the coast in connection with the mangrove zone. 
Bottom: rarely boulders, gravel, sandy-mud, sometimes near the coast dead coral blocks; water 
temperature 27-28°C; current 50 cm /sec, near the margins 0-20 cm/sec; chemistry, during high 
tide slightly brackish, during low tide the same as in the lower courses of the streams. Species 
found: Clithon spiniperda, Clithon coronata (^ longispina), Neritina (Neripteron) auriculata 
(below stones), Thiara amarula. 

(F) Transition region of the mouths In the littoral zone of the sea (Om). 

Ecological factors as in (E), except that brackish water also occurs during low tide; many 
marine animals occur here. Species found: Cerithidea decollata. 

CEYLON (Fig. 2) 

The island is a detached part of the continental Deccan plateau of ancient Precambrian 
crystalline rocks. The southern mountains with a general elevation of 1400-1800 m, are 
surrounded by 2 peneplains, the upland from 700/500 m to about 150 m, and the lowland 
from 150/100 m to the coastal zone. Due to their relatively short courses the running waters of 
the highlands have steep falls. These cause high current velocities of between 1 to more than 
2 m/sec. 

(A) Head-waters in the central mountains (2000-1500 m). 

Head-water torrents flowing through foggy mountain forests, very much shaded. Bottom: 
granitic rocks, boulders, gravel, near the margins and in the pools between the cascades: sandy 
with vegetable debris; water temperature 15-19°C; current 1 m/sec-more than 2 m/sec, except 
near the margins and in the pools between cascades below 50 cm/sec; chemistry, conductivity 
8-1 7 A/ Siemens, hardness 0.6-2.35°dH, pH 6.5-6.8 (if hardness below O.TdH molluscs are 
absent). Species found: Paludomus (Philopotamis) nigricans. 

^ ■ — — _— ^^^__^_^-^.^— 

FIG. 1. Cross section of the east coast of Madagascar with distribution of the freshwater gastropods: (1) 
Afrogyrus n.sp., (2) Pila cecillei, (3) Lymnaea (Radix) natalensis hovarum, (4) Bulinus liratus, (5) Melanoides 
tuberculata, (6) Afrogyrus crassilabrum, (7) Biomphalaria madagascariensis, (8) Ferrissia (Pettancylus) 
modestus, (9) Melanatria fluminea, (10) Cleopatra madagascariensis, (11) Neritina (Vittina) gagates, (12) 
Neritina pulligera knorri, (13) Septaria borbónica, (14) Clithon spiniperda, (15) Thiara amarula, (16) Neritina 
(Neripteron) auriculata, (17) Cerithidea decollata. 



248 



PROC. SIXTH EUROP. MALAC. CONGR. 




STARMÜHLNER 249 

(B) Upper courses of the mountain streams (1500-800 m). 

Flowing through primary or secondary rain forests, which are partly cleared with tea estates 
covering the slopes. In such cases the direct sunshine is reflected by higher water temperatures. 
Bottom: granitic rocks, boulders, gravel; near the margins sandy banks, also in the pools 
between the cascade zones; in forest areas thick layers of vegetable debris; water temperature 
19-21°C; current 1 m/sec-more than 2 m /sec, near the margins and in the pools between the 
step-like cascades below 50 cm/sec; chemistry, conductivity 17-21 д Siemens, hardness 2.3- 
9.2°dH, pH 6.5-7. Species found Paludomus (Tanalia) neritoides, and rarely Paludomus 
(Philopotamis) sulcatus, Paludomus (Philopotamis) regal is, Tricula montana. 

(C) Middle courses of the mountain streams (800-200/150 m). 

The valleys and hills of the upland are covered with secondary rain forest and cultivated 
areas (tea estates in the higher parts, rubber plantations in the lower parts, paddy fields in the 
valleys— influence of fertilizer and sewage from the densely populated villages and towns). 
Bottom: sometimes granitic rocks, but mostly boulders and gravel, near the margins sandy and 
muddy with vegetable debris, near settlements laundry places and polluted areas; water 
temperature 21-24 C; current 50cm-1m/sec, in longer sections and near the margins the 
current is slower than 50 cm/sec; chemistry, conductivity 35-300 /i Siemens, hardness 9-13°dH, 
pH 6.5-7. Species found: (a) parts with fast currents, Paludomus (Tanalia) loricatus; (b) near 
the margins and in parts with a slight current, Thiara (Plotia) scabra, Melanoides tuberculata 
and Stillwater forms, such as Bithynia (=Bulimus) stenothyroides and Indoplanorbis exustus. 

(D) Lower courses of the mountain streams (200/150-50/10 m). 

In the low country the running waters cross partly secondary forest, plantations and paddy 
fields. Longer stretches of the streams are sometimes highly polluted as a consequence of 
running through cultivated areas with a high population density. Bottom: rarely boulders, more 
gravel and sand, near the margins sometimes thick layers of organic mud, dense vegetation of 
submerged water plants; water temperature 25-26°C; current 30-50 cm/sec, near the margins 
and longer stretches in the middle of the stream 10-20 cm/sec; chemistry, conductivity 
300-600 /i Siemens, hardness 13-20 dH, pH 7. Species found: (a) parts with moderate current, 
Paludomus (Tanalia) loricatus; (b) parts with a slow current and near the margins, Paludomus 
(Paludomus) species, such as P. chilinoides, rarely P. bicinctus, P. decussatus, P. inflatus (in N. 
Ceylon also P. tanschauricus s.s. and subspecies nasutus), Thiara (Plotia) scabra, Melanoides 
tuberculata and Stillwater forms such as Bithynia (=Bulimus) inconspicua and Indoplanorbis 
exustus. 

(E) Transition of lower courses to the mouths of the lowland streams, upstream of the limit 
of brackish water during high tide (50/10-0 m). 

The coastal region of the lowlands is very densely populated in southwestern Ceylon, but 
only sparsely in the north and east. The villages are surrounded by paddy fields, plantations of 
tropical fruits and particularly coconut palms. The streams carry muddy sediments and near the 
settlements they are polluted with organic material. The margins have a dense vegetation of 
submerged plants. Bottom: gravel, but mostly sandy-muddy, in creeks thick layers of vegetable 
debris are deposited; water temperature 26-28°C; current 10-30 cm/sec, almost no current near 
the margins with the creeks; chemistry, conductivity 600 /n Siemens (and more), hardness 
13-1 5°dH, pH 7-7.5. Species found: (a) moderate current, Septaria lineata, Paludomus 
(Paludomus) species, such as P. chilinoides and in N. Ceylon P. tanschauricus, and the mussels 
Lamellidens lamellatus, L. testudinarius and Parreysia corrugata; (b) slow current or stagnant 
water in creeks near the margins, Thiara (Plotia) scabra, Melanoides tuberculata and Stillwater 
forms such as Bithynia (=Bulimus) inconspicua and Indoplanorbis exustus, sometimes also 
mussels as listed above. 



FIG. 2. Diagram showing temperature, hardness and conductivity of the water correlated with the distribu- 
tion of the gastropods and bivalves between the head-waters and mouths of the mountain streams of southern 
Ceylon (temperature in °C; hardness in °dH; conductivity, Eij^, in м Siemens). 



250 



PROC. SIXTH EUROP. MALAC. CONGR. 




STARMÜHLNER 251 

(F) Mouth region with influence of brackish water during high tide (0 m). 

During high tide the back flow of brackish water reaches the mangrove areas in the mouth 
region of the streams and the inhabitants of this habitat are covered with brackish water during 
this period. At low tide fresh water is running down to the sea. In these areas there are many 
immigrants from the sea such as marine bivalves and snails, hermit crabs, shrimps, Peri- 
ophthalmus, etc. Bottom: gravel and sand, mostly stones mixed with dead coral and empty 
shells, rich vegetation of filamentous algae adapted to brackish water; water temperature 28°C; 
current during low tide 30-50 cm/sec, near the margins 0-10 cm/sec, back current of 
10-20 cm/sec during high tide; chemistry, conductivity during high tide under the influence of 
brackish water up to more than 2000-3000 ju Siemens, hardness up to 20°dH and more, pH 7-8. 
Species found: (a) moderate current, Neritina (Neripteron) auriculata, under stones; (b) slow 
current, Melanoides (Stenomelania) torulosa (with free living veliger larvae), Faunus ater, in N. 
Ceylon also Gangetia burmanica, Syncera (^Assiminea) species; (c) in muddy sand of bigger 
streams, Polymesoda bengalensis (=ceylanica). 

NEW CALEDONIA (Figs. 3, 4) 

This continental island between eastern Australia, New Guinea and New Zealand is an old 
continental socle superimposed by sediment deposits, metamorphic rocks and volcanic effusion 
material, such as peridotite, basalt and serpentine. The island is about 400 km long, but has a 
maximum width of only ca. 50 km. The central mountain range along the spine of the island 
reaches up to 1600 m. The eastern slopes are very steep, whereas on the western slopes the 
gradient is less marked. The remnants of primary forest are only recently protected in the 
higher ranges of the central mountains. The major part of these forests was cleared for nickel 
mining and in the valleys for plantations and pasture. 

(A) Head-waters and upper courses in the central mountains (1000-500 m). 

The head-waters have their sources in the remnants of the primary forest or in the bush 
steppe of the cleared slopes in the areas of nickel mining. In the shady parts of the forest the 
temperature of the running water is lower than in the open landscape of the secondary bush 
steppe and savanna of Niaouli. Bottom: rocks, boulders, gravel, near the margins and in the 
pools between the cascades, sand and vegetable debris; water temperature from 13 С (sources, 
in shady forests of 800-1 000 m) to 15 С (upper reaches in shady forests, 500-800 m ) and 
17.5°C (upper reaches in open landscape, sunny, 500-800 m); current 50 cm /sec to more than 
1 m/sec, except near the banks and in the pools where it is less than 30 cm/sec; chemistry, 
conductivity 34-50 /i Siemens (depends on the bottom, such as peridotite, basalt, grauwacken, 
schists and, only rarely, limestone), hardness 0.5-2.7°dH, pH 5.3-7 (if the hardness is slower 
than 0.5°dH and the pH lower than 6 there are no gastropods). Species found: Melanopsis 
frustulum f. macu latus. 

(B) Transition from the upper to the middle courses of mountain streams (500-100 m. Fig. 
4-1). 

In part the streams cross secondary forest, plantations, pastures and the Niaouli savanna. 
Bottom: boulders, gravel, near the margins and in the pools between the cascades, sandy and 
muddy, vegetable debris; water temperature 17-20°C; current 50 cm /sec to more than 1 m/sec, 
near the banks and in the pools 0-30 cm/sec; chemistry, conductivity 50-1 50 ju Siemens 
(depends on the bottom, see above), hardness 3-4.5°dH, pH ca. 7, Species found: (a) parts with 
moderate current, Melanopsis frustulum f. maculatus (in the serpentine macchia of the south: 
M. mariei), Fluviopupa sp. (and Hemistomia cf. caledonica); (b) under floating water plants, 
stones, Ferrissia (Pettancylus) noumeensis; (c) near the banks and in pools, Melanoides 
tu bereu lata, Phy sastra nasuta. 



FIG. 3. Diagram showing temperature, hardness and conductivity of the water correlated with the distribu- 
tion of the gastropods and bivalves between the head-waters and mouths of the mountain streams of New 
Caledonia (for details see Fig. 2). 



252 



PROC. SIXTH EUROP. MALAC. CONGR. 
3 _ 4 _ /^ 5 







/ ^/ , y / / , . 




2 ;::::^; 




-л-л::-.^ 



STARMÜHLNER 253 

(C) Transition of the middle courses to the lower courses of the mountain streams 
(100-10 m, Fig. 4-2). 

Flowing through plantations, pastures and Niaouli savanna, open landscape without much 
shade. Bottom: gravel, sand, near the banks partly muddy, dense vegetation of submerged water 
plants; water temperature 21-23 C; current 50-75 cm/sec, longer sections with 30-50 cm/sec, 
near the banks and in pools 0-20 cm/sec; chemistry, conductivity 150)и Siemens, hardness 
4-5°dH, pH 7. Species found: (a) parts with moderate current, Septaria porcellana depressa 
(found up to 1 m/sec over short distances such as small cascades), Melanopsis frustulum f. 
multistriatus, Nerit'ma pulligera; (b) under floating water plants, stones, Ferrissia (Pettancylus) 
noumeensis; (c) near the banks and in pools, Melanoides tuberculata, Thiara amarula (and 
Ph у sastra nasuta). 

(D) Lower courses near the back flow of brackish water during high tide (10-0 m. Fig. 4-3). 

Flowing through plantations (mostly coconut) and pastures, banks bordered by Pandanus 
species. Bottom: gravel, sand, banks with muddy sand and dense vegetation of submerged water 
plants; water temperature 23-25°C; current 30-50 cm/sec, near the banks 0-10 cm/sec; chem- 
istry, back flow of brackish water during high tide (see sub E), low tide conditions like С 
Species found: (a) parts with moderate current, on top of stones, Melanopsis frustulum f. 
fasciatus, Clithon nucleolus, Neritina (Vittina) variegata; below the stones, Neritina (Neripteron) 
auriculata s.s. and f. lecontei; (b) near the banks, Melanoides (Stenomelania) arthurii; (c) in the 
sand, Polymesoda bengalensis sublobata. 

(E) Mouth region under the influence of the brackish water (0 m). 

Bordered upstream by Pandanus and transition to the typical mangrove zone on level parts 
of the coast; many marine animals occur here. Bottom: gravel, sand, dead coral, empty shells of 
marine molluscs; water temperature 25°C; current 30-50 cm/sec, near the banks 0-10 cm/sec; 
chemistry, conductivity up to 1 8,000 ju Siemens, hardness up to 14 dH, pH 7.5-8. Species 
found: (a) on stones and dead coral, Syncera (=Assiminea) savesi, Paludinella hidalgoi, 
Melanopsis frustulum f. fasciatus and f. fuscus; (b) attached to stones and dead coral. Modiolus 
bourailensis, Brachyodontes cf. ramosus; (c) near the banks, Truncatella cerea, Cassidula 
intuscarinata. 

CONCLUSIONS 

A comparison of the distribution of the freshwater molluscs in mountain streams of the 3 
continental islands of the Indo- Pacific leads to the following conclusions. 

In the isolated parts of the mountains where the head-waters and upper and middle course 
of the running waters show a strong or moderate current (rocky-stony bottom) old faunistic 
elements of the family Thiaridae (=Melaniidae) dominate with endemic genera, subgenera and 
species (in New Caledonia also species of the family Hydrobiidae, respectively ?Rissoidae): 

MADAGASCAR CEYLON NEW CALEDONIA 

Melanatria species Paludomus (Tanalia) species Melanopsis species 

Cleopatra species Paludomus (Philopotamis) species (Fluviopupa sp., Hemistomia) 

Only in New Caledonia does Melanopsis (a genus with brackish water affinity) also occur in the 
lower parts and the region of the mouth of the stream, which contains brackish water during 
high tide (back flow). The lower courses of the mountain streams upstream of the back flow of 
brackish water and with a strong to moderate current are characterized by species of the 
families Neritidae and Thiaridae (^Melaniidae): 



FIG. 4. Distribution of freshwater gastropods in the various parts of the mountain rivers of New Caledonia, 
viz., (1) head-waters to upper and middle course of the rivers, (2) middle course, (3) lower course to the 
mouth. Gastropod species: (1) Fluviopupa sp., (2) Melanopsis frustulum maculatus, Ш Ferrissia (Pettancylus) 
noumeensis, (4) Melanoides tuberculata, (5) Physastra nasuta, (6) Melanoides tuberculata, (7) Neritina 
pulligera, (8) Septaria porcellana depressa, (9) Melanopsis frustulum multistriatus, (10) Thiara amarula, (11) 
Melanoides (Stenomelania) arthurii, (12) Neritina (Neripteron) auriculata lecontei, (13) Clithon nucleolus, 
(14) Melanopsis frustulum fasciatus, (15) Neritina (Vittina) variegata. 



254 



PROC. SIXTH EUROP. MALAC. CONGR. 



MADAGASCAR 

Sep tar i a borbónica 
Neritina (Vittina) gaga tes 
Neritina pulligera knorri 



CEYLON 

Sep tar i a linea ta 



NEW CALEDONIA 

Septaria porcellana depressa 
Neritina (Vittina) variegata 
Neritina pulligera 



Paludomus (Paludomus) species 
Lamellidens lamella tu s 
Lamellidens testudinarius 
Parreysia cor ru gata 

In the region of the mouths of the streams in the area where there is a temporary influence of 
the brackish water because of the back flow of sea water during high tide and where there is a 
strong to moderate current, the genus Clithon and the subgenus Neripteron of the genus 
Neritina (both Neritidae) and furthermore some Thiaridae (=Melaniidae) and the bivalve 
Polymesoda bengalensis occur typically: 



MADAGASCAR 

Clithon spiniperda 
Clithon corona ta (= 

longispina) 
Neritina (Neripteron) 

auriculata 
Thiara amarula 



CEYLON 



Neritina {Neripteron) 
auriculata 

Melanoides (Stenomelania) 

torulosa 
Faunus a ter 

Polymesoda bengalensis s.s. 



NEW CALEDONIA 

Clithon nucleolus, C. bicolor, 
С. corona 

Neritina (Neripteron) auricu- 

culata s.S. and lecontei 
Thiara amarula 
Melanoides (Stenomelania) 

arthurii 
Melanopsis frustulum f. fasci- 

atus 
Polymesoda bengalensis f. 

su bio bata 



It should be noted that species of the subgenus Stenomelania of the viviparous genus 
Melanoides, living exclusively in the mouth region with temporary influence of brackish water 
during high tide, possess free living veliger larvae. All other species of Melanoides (subgenus 
Melanoides s.s.) live in purely fresh water and pass the veliger stage in the brood pouch of the 
female; young crawling snails leave the opening of the brood pouch later on. 

The outer part of the mouth of the streams in transition to the mangrove or the littoral 
marine zones of the coast is also under the influence of brackish water during low tide. These 
brackish water species are mixed with typically marine forms such as Mytilidae, Ostreidae or 
species of the genus Nerita: 



MADAGASCAR 

Cerithidea decollata 
Syncera (=Assiminea) species 



CEYLON 

Cerithidea cingulata 
Syncera (=Assiminea) species 
Gangetia burmanica 
Faunus a ter 



NEW CALEDONIA 

Syncera (=Assiminea) savesi 
Paludinella hidalgoi 
Melanopsis frustulum f . 
fasciatus and f. fuscus 
Mangrove species: 
Truncatella cerea, Cassi- 
dula intuscarinata. 
Modiolus bourailensis, 
Brachyodontes cf. 
ramosus 



STARMÜHLNER 255 

LITERATURE CITED 

COSTA, H. H. & STARMÜHLNER, F., 1972, Results of the Austrian-Ceylonese Hydrobiological Mission 

1970 of the 1st Zoological Institute of the University of Vienna (Austria) and the Department of Zoology 

of the Vidyalankara University of Ceylon, Kelaniya. Part I: РгеИгл1пагу report: Introduction and 

description of the stations. Bulletin of the Fisheries Research Station, Sri Lanka (Ceylon), 23: 43-76. 
HADL, G., 1974, Results of the Austrian-Ceylonese Hydrobiological Mission 1970 of the 1st Zoological 

Institute of the University of Vienna (Austria) and the Department of Zoology of the Vidyalankara 

University of Sri Lanka, Kelaniya. Part XVIII: Freshwater mussels, Bivalvia. Bulletin of the Fisheries 

Research Station, Sri Lanka (Ceylon), 25: 183-188. 
STARMÜHLNER, F., 1962, Voyage d'études hydrobiologiques à Madagascar, 1958. Naturaliste Malgache, 13: 

53-83. 
STARMÜHLNER, F., 1968, Etudes hydrobiologiques en Nouvelle Calédonie (Mission 1965 du Premier 

Institut de Zoologie de l'Université de Vienne) I. Généralités et descriptions des stations. Cahiers 

O.R.S.T.O.M., Série Hydrobiologique, 2(1): 3-27. 
STARMÜHLNER, F., 1969, Die Gastropoden der madagassischen Binnengewässer. Malacologia, 8: 1-434. 
STARMÜHLNER, F., 1970, Etudes hydrobiologiques en Nouvelle Calédonie (Mission 1965 du Premier 

Institut de Zoologie de l'Université de Vienne) X. Die Mollusken der neukaledonischen Binnengewässer. 

Cahiers O.R.S.T.O.M., Série Hydrobiologique, 4(3/4): 3-127. 
STARMÜHLNER, F., 1973, Die Gattung Melanopsis auf Neukaledonien. Malacologia, 14: 242. 
STARMÜHLNER, F., 1974, Results of the Austrian-Ceylonese Hydrobiological Mission 1970 of the 1st 

Zoological Institute of the University of Vienna (Austria) and the Department of Zoology of the 

Vidyalankara University of Sri Lanka, Kelaniya. Part XVII: The freshwater gastropods of Ceylon. Bulletin 

of the Fisheries Research Station, Sri Lanka (Ceylon), 25: 97-181. 
STARMÜHLNER, F., 1977, The genus Paludomus in Cey\or\. Malacologia, 16: 261-264. 
WENINGER, G., 1968, Etudes hydrobiologiques en Nouvelle Calédonie (Mission 1965 du Premier Institut de 

Zoologie de l'Université de Vienne) II. Beiträge zum Chemismus der Gewässer von Neukaledonien 

(SW-Pazifik). Cahiers O.R.S.T.O.M., Série Hydrobiologique, 2(1): 35-55. 
WENINGER, G., 1972, Results of the Austrian-Ceylonese Hydrobiological Mission 1970 of the 1st Zoological 

Institute of the University of Vienna (Austria) and the Department of Zoology of the Vidyalankara 

University of Ceylon, Kelaniya. Part II: Hydrochemical studies on mountain-streams in Ceylon. Bulletin of 

the Fisheries Research Station, Sri Lanka (Ceylon), 23: 77-100. 



I 



I 



MALACOLOGIA, 1979, 18: 257-263 

PROC. SIXTH EUROP. MALAC. CONGR. 

THERMOREGULATION IN THE FRESHWATER LAMELLIBRANCH 
PARRE YS/A COR RUG ATA 

V. S. Lorn te 
Department of Zoology, Marathwada University, Aurangabad— 431004, India 

ABSTRACT 

Thermal relations of the freshwater lamellibranch Parreysia corrugata were studied. 
The mussels, maintained at a laboratory temperature of 26°-28°C, could not survive for 
24 hours at 37° С and 8°C. Their 24 hour median heat tolerance limit was 36.2° С and 
13.5°C at the upper and lower ranges respectively. In warm acclimated mussels (33.0°C) 
the 24 hour median tolerance limit was raised from 36.2°C to 39.5° C. In cold acclimated 
mussels (16.0°C) the 24 hour median tolerance limit fell from 36.2°C to 35.5°C. 
Younger mussels could withstand more heat than the adults. The protein and fat levels 
increased with the increase in temperature but the glycogen level decreased when the 
temperature was raised. A sudden rise of temperature (10.0°C) maintained for an hour 
resulted in an emptying of the neurosecretory cells of the cerebral ganglion while a fall of 
temperature is followed by a significant increase in the secretion products of the same 
cells. 

INTRODUCTION 

Temperature is one of the most important environmental factors which limits the distribu- 
tion of animals and determines their rate of activity. Experiments in which animals were 
maintained at constant temperatures for a period of time provided a more accurate determina- 
tion of lethal temperatures as well as allowed comparison among the species. In such 
experiments either time to death or % survival at intervals was noted (Spoor, 1955; Brett, 1956; 
Fry, 1967; McWhinnie, 1967). 

On the basis of laboratory acclimation, season, microgeography and latitude, acclimation to 
low and high temperatures has been demonstrated in many animals. Acclimation has been 
demonstrated by a higher rate of function at any intermediate temperature when low 
temperature acclimated animals are compared with high acclimated ones. In the periwinkle 
Nodilittorina granulans Oshawa & Tsukuda (1956) found seasonal acclimation in response to 
temperature. Acclimation to higher temperature in the winter snails is established more rapidly 
than the acclimation to lower temperature in the summer snails. Microgeographical acclimation 
has been demonstrated in the limpet Acmaea limatula; Segal (1956) found that samples taken 
from lower intertidal levels had a higher rate of heart beat than those from higher levels. 

Acclimation has its effect on the temperature tolerance of a species. Warm acclimation is 
known to raise the thermal resistance while cold acclimation decreases the tolerance to high 
temperature. A few investigators have studied the influence of warm and cold acclimation on 
median heat tolerance limit of molluscs (Read, 1967; Nagabhushanam & Kulkarni, 1970; 
Kennedy & Mihursky, 1971; Mantale, 1971; Waugh & Garside, 1971; Waugh, 1972). 

Effect of size on the temperature tolerance of the animals varies with the species. Belehradek 
(1955) stated that resistance to heat diminished as the size increased. Contrary evidence has 
been reported by Mcleese (1956) and Diaz (1973). 

Biochemical changes in molluscs following acclimation to high and low temperatures seem to 
have received little attention. Rao & Ramchandra (1961) in Lamellidens and Mantale (1971) in 
Cryptozona have made some useful contributions. Effect of thermal stress on neurosecretory 
activity of molluscs has been studied only by a few workers (Nagabhushanam, 1955; Khatib, 
1975). 

Relatively little work has been done on the temperature relations o^ Parreysia corrugata. The 
present investigation was therefore undertaken to study in detail the thermal relations of 

(257) 



258 PROC. SIXTH EUROP. MALAC. CONGR. 

Parreysia. The investigation provides information on the thermal relations of Parreysia in 
connection with the heat tolerance limit, size of the mussel, biochemical changes and 
neurosecretory changes. 

MATERIAL AND METHODS 

The freshwater mussels, Parreysia corrugata, were collected from the Kham river near 
Aurangabad. At the time of collection, the river temperature varied from 26-30°C. The mussels 
were maintained in the laboratory in shallow glass aquaria containing tap water with a 
temperature range of between 26-28 С Water in the aquaria was changed every day and it was 
aerated to keep the animals in good health. Groups of 30-50 animals were taken at random 
from stock aquaria and maintained in well aerated glass aquaria at acclimation temperatures of 
33 ± 0.5 С and 16 ± 0.5 С The mussels remaining in the stock aquaria were used \as controls. 

The heat tolerance of control and experimental animals was studied by testing their survival 
for 24 hours at different temperatures. The warming period lasted for 1-2 hours according to 
the difference between acclimation and test temperatures. The mussels were brought from the 
acclimation temperature to the test temperature slowly rather than abruptly. 

To find out the effect of size on heat tolerance, 2 groups of mussels were taken. One group 
of mussels ranging in length from 2 to 2.5 cm and the other group from 6 to 6.5 cm were 
tested for their heat tolerance. 

To study the biochemical changes associated with heat tolerance the mussels were acclimated 
to temperatures of 16 С 28 С and 33 С. The water percentage was calculated by drying up 
the mussel tissue at 100 С Glycogen was estimated by the method of Kemp et al. (1954). 
Total nitrogen was estimated by Microkjeldahl method (Hawk et al., 1954). The amount of 
protein was calculated by multiplying the nitrogen value by the factor 6.25. Fat was extracted 
from the tissue powder in Soxhiet apparatus. 

For studying the influence of temperature on neurosecretory activity, the mussels were kept 
at 2 different temperatures, a low temperature of 16°C and a high temperature of 36°C for one 
hour. The ganglia were then preserved in Bouin's fluid for observation of the neurosecretory 
cells. 



RESULTS 

Heat tolerance of control animals 

The mussels were acclimated to the laboratory temperature for one week and their 24 hour 
survival at different temperatures was recorded. In no experiment could the mussels tolerate 
temperatures of 8 С and 37 С and 100% mortality was observed at these temperatures. Fig. 1 
shows that the 24 hour median heat tolerance limit at the upper and lower ranges of 
temperature where 50% mortality was recorded lies at 36.2°C and 13.5°C respectively. 

Effect of warm and cold acclimation on heat tolerance limit 

Groups of mussels were acclimated for a week to a high temperature of 33°C ± 0.5°C and a 
low temperature of 16°C ± 0.5°C with control animals maintained at 28°C laboratory 
temperature. ^hese niussels were then tested for survival at the higher temperature of 34°, 35°, 
36°, 37°, 38° and 39°C (Fig. 2). At the lowest temperature of 34 С there was 100% survival of 
the warm acclimated and control mussels, whereas the survival of cold acclimated mussels at 
this temperature was 72%. At a temperature of 37° C, the survival of warm acclimated, control 
and cold acclimated mussels was 72, 10 and 0% respectively. The warm acclimated mussels 
could tolerate still higher temperatures. In these mussels there was 50% survival at a 
temperature of 39.5°C and almost 0% survival at 40.0°C. It is interesting to note that the 
percent survival of the mussels increased with the increasing temperature of acclimation 
resulting in the increase of a median tolerance limit from 36.2°C to 39.5°C in warm acclimated 
mussels, but there is a decrease in the median tolerance limit from 36.2°C to 35.5°C in cold 



LOMTE 



259 




10 



20 30 

TEMPERATURE "C 



FIG. 1. Percent survival of Parreysia corrugata at different temperatures. 



acclimated mussels. Thus the increase in the acclimation temperature from 28 to 33 C, i.e. 
5°C, has resulted in the increase of the median tolerance limit by 3,3° C, while a decrease in the 
acclimation temperature from 28°C to 16°C has resulted in a decrease by 1.3°C. These results 
indicate that there is some gain in the heat tolerance limit when the mussels are acclimated to 
higher temperatures and much less when acclimated to lower temperatures. 

Effect of size on the temperature tolerance 

Mussels of 2 different size groups were selected to test the effect of size on the temperature 
tolerance. The results are shown in Fig. 3. The mussels of 2-2.5 cm size group have shown a 
median tolerance limit at 37.5°C and the mussels of 6-6.5 cm size group have shown a median 
tolerance limit at 36.0°C. Thus the younger mussels are more heat tolerant than the adults. 

Biochemical changes associated with thermal acclimation 

To find out the changes in biochemical composition due to thermal acclimation the mussels 
were acclimated at temperatures of 16° C, 28°C and 33°C for 7 days. The results are shown in 
Table 1. 



260 



PROC. SIXTH EUROP. MALAC. CONGR. 



100 



> 

(Л 



50 



Ш 

о 
or 

Ш 
CL 



0- 



A- warm acclimated 

В - control 

С - cold acclimated 




TEMPERATURE С 

FIG. 2. Heat tolerance of warm and cold acclimated Parreysia corrugate. 



TABLE 1. Biochemical changes associated with thermal acclimation in Parreysia corrugata. 

Biochemical constituent 
Water 

Protein 

Glycogen 

Fat 



Control 
28° С 


Warm acclimation 
33° С 


Cold acclimation 
16°C 


70.90 
±0.018 


75.45 
±0.007 


71.10 
±0.001 


38.74 
±0.007 


41.30 
±0.090 


37.13 
±0.018 


5.25 
±0.003 


3.90 
±0.020 


5.92 
±0.013 


3.10 
±0.010 


4.70 
±0.015 


2.90 
±0.310 



Water œntent of the mussels increased when they were subjected to higher temperatures 
Percentage of water increased to 75.45% at 33°C and it dropped to 71.10% at 16°C. Protein 
and fat contents increased at higher temperature whereas glycogen content decreased when the 
temperature was raised. 



LOMTE 



261 



О 
о 

Ш 
(Г 

< 

о: 
ш 

CL 

ш 





А- Small 




В— Large 




А 


до 






Е 


Î 




" 


г 


\ 


M 


20 


- 


\ 




- 








Z. 






У 




_ 










- 






¿. 


ш П 


^ 



SIZE 



FIG. 3. Effect of size on temperature tolerance of Parreysia corrugata. 



Effect of thermal stress on neurosecretion 

The effect of a sudden rise in temperature on the neurosecretory activity of Parreysia was 
studied. The mussels were subjected to a sudden rise of temperature (IOC) for an hour and the 
cerebral ganglia of the mussels were observed for stainable neurosecretory cells. It was found on 
observation that there was an emptying of the neurosecretory products in the stressed animals. 
When the mussels were subjected to a low temperature it was observed that there was a 
significant increase in the secretion product of the cells (Fig. 4). 



DISCUSSION 

Physiological adaptation to environmental stress is one of the recurring themes in the 
biological literature (Bullock, 1955; Prosser, 1955). The literature on thermal tolerance of 
poikilotherms is sufficiently convincing to prove that median heat tolerance is dependent on the 
acclimation temperature. The lethal effect has been worked out in more detail in Poikilothermie 
vertebrates (Fry, 1967) than in invertebrates. However, some data are available for^Mollusca. 

Parreysia corrugata could not survive well beyond the thermal range of 8 C-37 С The 
median heat tolerance limit was found to be at 36.2°C when the laboratory temperature ranged 
between 26°-28°C. The median tolerance limit of Lamellidens corrianus was 37.4 С when the 
laboratory temperature was 30°C ± 1°C (Lohagaonkar, 1974) and the tolerance limit of 
Corbicula regularis was 21.'Í'Q, when the laboratory temperature was 27° ± 2 С (Mudkhede, 
1974). In Indonaia caeruleus the median tolerance limit was 36.5°C when the temperature 



262 PROC. SIXTH EUROP. MALAC. CONGR. 





FIG. 4. Effect of thermal stress on neurosecretion of Parreysia corrugata. Experirnent on the left, control on 
the right. 

range in the laboratory was 27°-29 С (Khatib, 1975). Heat tolerance limit varies according to 
variation in the environmental temperature (Brett, 1956). 

In Parreysia it was found that the upper median tolerance limit was increased due to an 
increase in acclimation temperature and vice versa. When acclimated at the warm temperature 
of 33°C ± 0.5°C the mussels have elevated their upper tolerance limit to 39.5 С and when 
acclimated at 16° ± 0.5°C the heat tolerance limit was dropped to 35.5°C. Fry et al. (1942) 
stated that for every 3 С rise in temperature the upper tolerance limit was increased by l"C 
and the lower limit by 2 С in the fish Carassius auratus. In a bivalve, Indonaia caeruleus, the 
heat tolerance limit was raised to 37.1 С from 36.5 С when acclimated at 32 С and it dropped 
to 34.6°C from 36.5°C when acclimated at 18°C (Khatib, 1975). In warm acclimated (32°C) 
Melanoides tuberculatus the tolerance limit was elevated from 36.4° to 39.0°C and in cold 
acclimated snails it fell from 36.4°C to 33.0°C (Khot, 1977). 

Young Parreysia were more heat resistant than the adults. Kennedy & Mihursky (1971) 
stated that at all acclimation temperatures smaller clams were more heat resistant and adults 
were more sensitive to high temperatures. Young snails of l\/lelanoides tuberculatus could 
tolerate more heat than the adults (Khot, 1977). 

McWhinnie (1967) stated that the biochemical changes provide a molecular basis for 
thermogenesis essential to account for activity and synthesis at suboptimum temperature as well 
as survival and homeostasis at superoptimum temperature. 

In Parreysia corrugata protein level was increased at high temperature. In Lymnaea protein 
level was increased as the temperature was raised (Azmatunnissa, 1974). Khot (1977) also 
reported an increase in protein level in Melanoides tuberculatus. Decrease in glycogen content 
was reported in warm acclimated Indonaia (Khatib, 1975). Similar results were obtained in 
Parreysia corrugata. The fat content was found to be increased slightly in warm acclimated 
mussels. In Melanoides there was also a slight increase in fat. Water percentage was related to 
the acclimation temperature. 

Increased water and decreased glycogen content in the warm acclimated mussels probably 
suggest the increased oxidation of carbohydrates consequent to the increased metabolic 
activities at this higher temperature. During cold acclimation, fat content decreased and 
glycogen increased. This suggests retardation of physiological activities due to cold stress. 

Influence of temperature on the neurosecretory activity in Parreysia indicates that at high 
temperatures there was depletion of the secretory material while at low temperatures there was 
accumulation of the secretory material. Nagabhushanam (1964) found that there was emptying 
of the secretory product when the animals were subjected to thermal stress. Khatib (1975) 
reported that there was depletion of the neurosecretory material at high temperatures, while the 
neurosecretory material was accumulated at low temperatures. 



LOMTE 263 

ACKNOWLEDGEMENT 

The author is grateful to Prof. R. Nagabhushanam, Head of the Department of Zoology, 
Marathwada University, Aurangabad, for kindly providing facilities to carry out the work. 

LITERATURE CITED 

AZMATUNNISA, Q., 1974, Biological studies in Indian Pulmonate snail, Lymnaea sp. Ph.D. thesis, 

Marathwada University, Aurangabad, India. 
BELEHRADEK, J., 1955, Temperature and living matter. Protoplasma— Monographien, 8. Borntraeger, Berlin, 

229 p. 
BRETT, J. R., 1956, Some principles in the thermal requirements of fishes. Quarterly Review of Biology, 31: 

75-87. 
BULLOCK, T. H., 1955, Compensation for temperature in the metabolism and activity of poikilotherms. 

Biological Review, 30: 311-342. 
DIAZ, R. J., 1973, Effect of brief temperature increase on larvae of the American oyster (Crassostrea 

virginica). Journal of the Fisheries Research Board of Canada, 30: 991-993. 
FRY, F. E. J., 1967, Responses of vertebrate poikilotherms to temperature. In: ROSE, A. H., ed., 

Thermobiology: 375-409. Academic Press, London/New York. 
FRY, F. E. J., BRETT, J. R. & GLAWSON, G. H., 1942, Lethal limits of temperature for young goldfish. 

Revue Canadienne de Biologie, 1: 50-56. 
HAWK, P. В., OSER, В. L. & SUMMERSON, W. H., 1954, Practical physiological chemistry. McGraw-Hill 

Book Co., New York. 
KEMP, A., & KITS VAN HENNINGEN, A. J. M., 1954, A colorimetric micro-method for determination of 

glycogen in tissues. Biochemical Journal, 56: 646-648. 
KENNEDY, V. S. & MIHURSKY, J. A., 1971, Upper temperature tolerance of some estuarine bivalves. 

Chesapeake Science, 1 2: 1 93-204. 
KHATIB, S., 1975, Some aspects of physiology of Indonaia caeruleus. Ph.D. thesis, Marathwada University, 

Aurangabad, India. 
KHOT, R. P., 1977, Studies on some physiological aspects and control of the snail, Melanoides tuberculatus. 

Ph.D. thesis, Marathwada University, Aurangabad, India. 
LOHAGAONKAR, A. L., 1974, Biological study on the clam, Lamellidens corrianus, Ph.D. thesis, 

Marathwada University, Aurangabad, India. 
MANTALE, B. M., 1971, Studies on the temperature tolerance in snail. Cryptozona semi rugata, Marathwada 

University Journal of Science, 10 (Section 3): 155-163. 
IVICLEESE, D. W., 1956, Effect of temperature, salinity and oxygen on the survival of the American lobster. 

Journal of the Fisheries Research Board of Canada, 13: 247-272. 
MCWHINNIE, M. A., 1967, The heat response of invertebrates. In: ROSE, A. H., ed., Thermobiology: 

535-553. Academic Press, London/New York. 
MUDKHEDE, L. M., 1974, Some biological aspects of the clam, Corbicuia regularis, Ph.D. thesis, Marathwada 

University, Aurangabad, India. 
NAGABHUSHANAM, R., 1964, Neurosecretory changes in the nervous system of the oyster, Crassostrea 

virginica induced by various experimental conditions. Indian Journal of Experimental Biology, 2: 1-4. 
NAGABHUSHANAM, R. & KULKARNI, A. В., 1970, Studies on the temperature tolerance in the slug, 

Laevicaulis alte. Marathwada University Journal of Science, 9: 77-81. 
OSHAWA, W. & TSUKUDA, H., 1956, The seasonal variation in the temperature response relations and 

temperature tolerance of the periwinkle, Nodilittorina granulans. Journal of the Institute of Polytechnics, 

Osaka City University, D, 7: 173-188. 
PROSSER, С L., 1955, Physiological variation in animals. Biological Review, 30: 229-262. 
RAO, K. P. & RAMACHANDRA, R., 1961, Effect of acclimation to high temperature on the blood chloride, 

free amino acids and osmotic pressure in the freshwater field crab, Paratelphusa sp., and the freshwater 

mussel, Lamellidens marginalis.. Journal of Experimental Biology, 38: 29-34. 
READ, K. R. H., 1967, Thermal tolerance of the bivalve mollusc Lima scabra Born, in relation to 

environmental temperature. Proceedings of the Malacological Society of London, 37: 233-241. 
SEGAL, E., 1956, Microgeograph ic variation as thermal acclimation in an intertidal mollusc. Biological 

Bulletin, 111: 129-152. 
SPOOR, W. A., 1955, Loss and gain of heat tolerance by the crayfish. Biological Bulletin, 108: 77-87. 
WAUGH, D. L., 1972, Upper lethal temperatures of the pelecypod. Modiolus demissus, in relation to 

declining environmental temperature. Canadian Journal of Zoology, 50: 523-527. 
WAUGH, D. L. & GARRIDE, E. T., 1971, Upper lethal temperature in relation to osmotic stress in the 

ribbed mussel. Modiolus demissus. Journal of the Fisheries Research Board of Canada, 28: 527-532. 



i 



MALACOLOGIA, 1979, 18: 265-270 

PROC. SIXTH EUROP. MALAC. CONGR. 



SUR LES MOLLUSQUES DE LA LIMITE ENTRE LE PLIOCÈNE 
SUPÉRIEUR ET LE PLEISTOCENE INFÉRIEUR EN ROUMANIE^ 



N. Macarovici 
Laboratoire de Géologie, Université "Al. I. Cuza" laçi, Roumanie 

ABSTRACT 

The border line between Pliocene and Pleistocene deposits in Rumania has tradi- 
tionally been based on data derived from fossil mammals. However, recent research has 
shown that a large number of Pliocene molluscs, accompanied by mammals considered to 
be of Pleistocene age, penetrates into the Lower Pleistocene. Therefore the border line 
between the Upper Pliocene and the Lower Pleistocene in Rumania cannot be based on 
molluscan data. This is fully discussed in the present paper. 



Sur la base de la faune de mammifères fossiles, nous pouvons fixer, pour la Roumanie, la 
limite entre le Pliocène et le Pleistocene au moment où apparaît le genre Elephas (ses formes 
primitives), comme c'est le cas à Tuluce^ti (distr. Gala^i) et à Cernáte^ti (à Dealul Calului), au 
N0. de Craiova (distr. Dolj). Ainsi, à Tuiuce^ti, Elephas planifrons Falc. (Athanasiu, 1915) 
apparaît à côté de Anancus arvernensis Cr. & Job., Cervus (Elaphus) issidorensis Cr, & Job. et 
une molaire de Mastodon borsoni Hays. A cette liste Ghenea & Râdulescu (1964) ajoutent une 
mandibule de Camelus alutinensis Stef. et un métacarpien de Hippotigris stenonis Cocchi. 

Très proche de la faune de Tuluceßti est celle de Dealul Calului de Cernâte^ti (Dolj), d'où 
Schoverth et al. (1963) décrivent des couches moyennes sablonneuses de "Cîndeçti" 
(Stefanescu, 1897) à Unionides, des molaires de Anancus arvernensis Cr. & Job., Elephas 
(Archidiskodon) meridionalis Nesti (très probablement, d'après nous, E. planifrons Falc); 
Rhinoceros cf. etruscus Falc, Equus sp. et une molaire de Mastodon borsoni Hays. 

Il est très important que cette faune de mammifères, incontestablement du pleistocene 
inférieur, se trouve dans les dépôts moyens de sables et graviers à Unionides, nommés "Couches 
de Cînde^ti" (Stefanescu, 1897), de l'Olténie et de l'ouest de la Munténie, connus de Bucovat (à 
l'Ouest de Craiova), Cernäte?ti, Amärä^ti, Urdade-Jos, Valea Muerei et autres localités de 
l'Olténie (Fig. 1). Cette faune est considérée par Stefanescu (1897) comme "levantine." A 
présent, à cause des mammifères cités plus haut, elle est attribuée au Pleistocene inférieur, ne 
restant comme Pliocène supérieur que l'horizon inférieur pélitique (marno-argileux) des 
"Couches de Cînde^ti," qui contiennent: Unio lenticularis Sabba, Psilunio recurvus Sabba, 
Vivipare dezmaniana var. altercarinata Brus., V. bifarcinata var. stricturata Neum., Melanopsis 
pterochila var. breastensis Brus. Valvata sibinensis Neum., et qui constitue le seul horizon 
appartenant au "Levantin" (Bandrabur, 1971). 

Au-dessus suivent les couches moyennes de "Cînde^ti" à Unionides, formées par sables et 
graviers, d'où Schoverth et al. (1963) cite la faune de mammifères mentionnée plus haut, de 
même qu'une faune de mollusques de ces couches à Bucovàj et les autres localités mentionnées 
(Cernàte^ti, Amàra^ti, etc.). 

D'après Stefanescu (1897), Schoverth et al. (1963), Bandrabur (1971) et d'autres auteurs 
antérieurs, cette faune est constituée surtout des espèces suivantes: 



IProf. Macarovici has been unable to attend the Amsterdam congress; nevertheless, by way of exception, his 
paper is published in the Proceedings. 

(265) 



266 



PROC. SIXTH EUROP. MALAC. CONGR. 



»— 

Ф 


LU 


_J 


— 


< 


z 


о 


< 


UJ 

ID 


2 


a 


Э 




MACAROVICI 



267 



Unió (pristinus Bielz) 

Unió procumbens Fuchs 

Unió davilai Por. 

Unió porumbarui Той m. 

Unió (Sca/enaria) bielzi Czek. 

Psilunio sculptus Brus. 

Psi I unió berbestiensis Font. 

Psilunio condai Por. 

Psilunio brandzae Sabba 

Psilunio doljensis Sabba 

Viviparus craiovensis Tourn. 

Viviparus mammatus Sabba 

Viviparus bifarcinatus Bielz 

Viviparus (rudis) rudis Neum. 

Viviparus (rudis) strossmayerianus Brus. 



Viviparus (turgidus) pilari Brus. 

Viviparus (turgidus) turgidus Bielz 

Melanopsis rumana Tourn. 

Melanopsis narzolina Siesm. 

Melanopsis onusta Sabba 

Melanopsis (Canthidomus) soubcirani Por, 

Melanopsis (Canthidomus) porumbarui Brus. 

Melanopsis (Canthidomus) hybostoma Neum. 

Theodoxus quadrifasciatus Bielz 

Theodoxus licherdopuli Sabba 

Theodoxus scriptus Sabba 

Valva ta (Cincinna) piscinalis Müll. 

Emmericia rumana Tourn. 

Emmericia candida Neum, etc. 

Bulimus vukutinovici Brus. 



II faut remarquer (Schoverth et al., 1963) que les valves des Unionides sculptés et des 
Vivipares ornamentes de cette liste sont très érodées, ce qui indiquerait qu'une grande partie de 
cette faune a été remaniée, son dépôt ayant, d'après Schoverth et al. (1963), le caractère 
"torrentiel." 

Mais Schoverth et al. (1963), Macarovici (1965), Liteanu et al. (1957, 1960, 1961, 1967) et 
Bandrabur (1971) attribuent les "couches moyennes de Cînde^ti" au Villafranchien s.str., donc 
à la base du Pleistocene. Elles sont connues également de la Dépression Gétique et de la Plaine 
Roumaine. Une faune semblable à celle des couches moyennes de Cîndejti a été décrite par 
Botez (1916), de Moreni (Dîmbovija) et par Barbu & Barbu (1953) de la rive nord du lac de 
Greaca (au S. de Bucarest); ces dépôts se trouvent donc aussi dans la Plaine Roumaine. 

Au-dessus de l'horizon moyen des couches de Cînde^ti on trouve l'horizon supérieur de ces 
couches dans lequel les restes de Mastodon deviennent de plus en plus rares, tandis qu'on 
rencontre fréquemment celles de Elephas (Archidiskodon) meridionalis Nesti, signalées aussi par 
Stefánescu (1897). 

Les couches (marno-argileuses) supérieures de Cînde^ti contiennent une faune de mollusques 
dont la liste est, en général, constituée par les espèces suivantes: 



Unio sculptus Brus. 
Unio iconomianus Tourn. 
Unio stefanescui Tourn. 
Unio porumbarui Tourn, 
Unio herjeui Porumb. 
Seal en aria bielzi Czek, 
Psilunio craiovensis Tourn. 



Viviparus mammatus Sabba 
Viviparus (rudis) rudis Neum. 
Viviparus plicatus Sabba 
Bythinia vukotinovici Brus. 
Theodoxus semiplicata Neum. 
Theodoxus scripta Sabba 
Melanopsis narzolina Siesm., etc. 

Au-dessus suivent les couches de Frâte^ti qui constituent la fin du Pleistocene inférieur de 
rOlténie et de la Plaine Roumaine. 

Ce que nous avons exposé jusqu'ici sur les mollusques des couches de Cînde^ti, ne nous 
permet pas de préciser la limite entre le Pliocène et le Pleistocene dans la Dépression Gétique 
(en OIténie). La cause en est (d'après Bandrabur, 1971: 53) que, au-dessous de l'horizon 
inférieur marneux à Unio lenticularis Sabba, suit une autre succession de sables et graviers, 
alternant avec des intercalations d'argiles, caractérisées du point de vue paléontologique par des 
Unionides sculptés et Vivipares ornamentes, présentant des espèces qui se rencontrent également 
dans les couches moyennes et supérieures de Cînde^ti, Mais l'auteur ne nous donne pas la liste 
de la faune rencontrée plus bas que l'horizon à U. lenticularis Sabba ce qui abaisserait la limite 
entre le Pliocène et le Pleistocene au-dessous de la cote de О m (de beaucoup au-dessous du 
niveau d'érosion du Jiul), Ainsi la limite entre le Pliocène et le Pleistocene doit être établie, 
toujours d'après les mammifères, dans les limites des couches moyennes de Cînde^ti. 

Au-dessus des couches supérieures de Cînde^ti suivent (comme nous l'avons déjà dit), dans la 
Plaine Roumaine entre le Jiu et l'Argeç, les couches de Frateçti, formées par des sables avec des 
graviers et des blocs vers la base. 

Les couches de Frâtejti ne sont que rarement fossilifères; d'après Bandrabur (1971), à 



268 PROC. SIXTH EUROP. MALAC. CONGR. 

Drägänejti-Olt elles contiennent les nnollusques suivants: Planorbis umbilicatus Müll., P. 
planorbis L., Valvata sulekiana Müll., V. piscina/is Müll., Bulimus vukotinovici Brus., Pisidium 
amnicum Müll., Sphaerium rivicola Leach et des exemplaires de Unio sp. roulés. 

A côté de ces mollusques (qui ne donnent pas des précisions sur l'âge) on trouve, dans les 
couches de Frátejti, très souvent des molaires et parfois aussi des défenses de Archidiskodon 
meridionalis Nesti, pas associées aux restes de Mastodon. La continuité de sédimentation qui 
existe entre les couches de Cînde^ti et celles de Fräteßti (Bandrabur, 1971) montrerait que les 
couches de Fràte^ti achèvent la Pleistocene inférieur de la Plaine Roumaine. 

Dans le sud de la Moldavie, à Tuluce^ti (Galafi), dans le ravin Rîpa Bäläei (sous les couches 
qui contiennent les mammifères que nous avons attribués au Pleistocene inférieur), on trouve un 
dépôt sableux comprenant une faune d'Unionides, citée par Grigorovici-Berezovski (1915) et par 
Macarovici (1960) et formée par les espèces: Uniosandbergeri Neum.,L/. sibinens'isPen., il. wetzieri 
flabellatiformis Mikh. Ces sables s'étendent tant au nord (sur la vallée de la Horincea) que à 
l'ouest de Tuluce^ti, où (par exemple à Slobozia Conachi) ils contiennent: Unio wetzieri 
flabellatiformis Mikh., U. aff. stoliczkai Neum., U. zelebori Hörn., U. sandbergeri Neum., 
Viviparus aff. turgidus Bieiz. 

Ces dépôts à Unionides s'étendent aussi vers l'est, sur le versant gauche de la vallée du Prut 
(dans la R. S. S. Moldave), où Grigorovici Berezovski (1915) a distingué 2 horizons de faune, à 
savoir: (1) Un horizon inférieur, présent aux villages Brînza, Slobozia Mare et Cîjliia, contenant 
les espèces: Unio stoliczkai Neum., U. beyrichi Neum., U. moldaviensis Hörn., U. cf. zelebori 
Hörn., U. cf. nicolaianus Brus., U. sibinensis Pen., U. sandbergeri Neum., U. bogatschevi Mikh., 
U. wetzieri flabellatiformis Mikh., U. lenticularis Sabba. Grigorovici-Berezovski compare cet 
horizon avec la partie supérieure des dépôts moyens à Paludina de Slavonie et avec l'horizon 
inférieur "des dépôts levantins de Craiova" (c'est-à-dire avec l'horizon inférieur des couches de 
"Cmde^ti"). 

(2) Le second horizon de la faune du versant gauche du Prut, établi par Grigorovici- 
Berezovski, est celui de Giurgiulegti-Reni, caractérisé par: Unio procumbens Fuchs, U. davilai 
Por., U. porumbarui Tourn., U. doijiensis Sabba, U. bieizi Czek., Vivípara bifarcinata Bielz, V. 
rudis Neum., etc. L'auteur parallelise cet horizon avec la partie inférieure des couches 
supérieures à Paludines de Slavonie (l'horizon à Paludina sturi Neum. et P. hoernesi Neum.), de 
même qu'avec les couches moyennes ("levantines") de Cmdejti de Bucovaf-Craiova. 

Ces dépôts à Unionides, de la côté gauche de Prut, ont été attribués par Macarovici (1940) 
au "Levantin supérieur" (Pliocène supérieur). Il faut pourtant observer que ces dépôts pliocenes 
supérieurs ne sont, en fait, représentés que partiellement au confluent Prut-Danube, puisque tant 
Grigorovici-Berezovski (1915) que Macarovici (1940) signalent, sur la rive orientale du lac de CahuI, 
des valves remaniées de Unio sturi Hörn., dans les sables contenant la faune pleistocene de 
Babele. Donc, les dépôts qui les contennaient ont été erodes. Pourtant, Bogaîchev (d'après 
Eberzin, 1957) figure des valves intactes provenant des dépôts pliocenes de la vallée du Sal, de la 
région du Don. Le même auteur signale Unio sturi dans les dépôts ap^eroniens (fin du 
Pliocène) de la Transcaucasie de l'est. Eberzin (1957) cite (d'après Bogatchev) des exemplaires 
de U. sturi du Pliocène supérieur de la rivière Kutchurgan (dans le Sud de l'Ucraïne). Bogatchev 
figure aussi une valve de U. sturi de la 5-ème terrasse (fin du Pliocène) du Dniestre à Boçernita 
(près de Rezina). 

Donc, à la fin du Pliocène, U. sturi a eu une grande extension sur le territoire de l'Union 
Soviétique, depuis l'embouchure du Prut jusqu'en Transcaucasie. Dépôts à Unio sturi sont 
connus aussi en Roumanie (valves intactes) à Uzunu et Stroejti (au S. de Bucarest), les dépôts 
étant d'âge Pleistocene inférieur (Macarovici & Cotei, 1962). Nous admettons cet âge parce que 
les couches à Unio sturi de Uzunu (S. de Bucarest) gisent, à ce qu'il paraît (mais sans certitude), 
au-dessus des "couches de Frateçti" (comme le montre les 2 auteurs, 1962). Pour le moment, 
nous ne pouvons pas leur attribuer une position ¿ûre pour la Roumanie. 

Mais Eberzin (1957) affirme que les couches à U. sturi seraient les couches par lesquelles se 
termine le "Levantin supérieur" (le Pliocène supérieur) en Union Soviétique; mais ces couches 
ont été très souvent érodées. 

Eberzin (1959) toujours, ayant en vue la présence de certaines espèces d'Unionides {U. 
flabellatiformis) qui se trouvent dans les dépôts du Pliocène supérieur du confluent du Prut avec 
le Danube, de même que dans le Sud de la Moldavie (mais sont absentes dans les dépôts de 
Bucovaj-Craiova), utilise le terme stratigraphique de Poratien inférieur et supérieur pour les 2 



MACAROVICI 269 

horizons à Unionides du Prut. Mais par l'utilisation du nom de "Poratien," la limite inférieure 
du Pleistocene continue de rester indécise. Sur la base des mollusques, Eberzin (1959) équivaut 
le Poratien (sur lequel il place les couches à U. sturi) à l'Apçeronien, sous-étage par lequel se 
termine le Pliocène supérieur dans l'échelle stratigraphique de l'Union Soviétique. 

Pour la Roumanie, nous le répétons, nous ne pouvous pas préciser, sur la base de la faune de 
mollusques, la limite entre le Pliocène et le Pleistocene. Cette limite peut être tracée, d'une 
manière approximative, seulement après l'apparition de la faune à Elephas, comme nous l'avons 
déjà dit. 

Même la faune de mollusques décrite par Jekelius (1932) dans les dépôts pliocenes du bassin 
de Bra^ov, ne peut pas nous offrir une indication sûre quant à la limite entre le Pliocène 
supérieur et le Pleistocene inférieur. Des 85 espèces décrites par Jekelius (1932) 64 ont été 
décrites par cet auteur pour la première fois dans la littérature comme provenant du bassin de 
Braçov; 12 formes seulement sont connues aussi dans d'autres dépôts pliocenes, où elles 
constituent des éléments, ordinaires; 6 autres formes sont récentes et 3 formes ne sont décrites 
que génériquement. 

Jekelius dit que cette faune considérée en entier "fait l'impression d'être endémique." Elle 
commence, probablement, au Dacien, puisque à Capeni on a trouvé, dans le lignite, des molaires 
de Mastodon borsoni Hays et de Mastodon arvernensis Cr. & Job., à côté des valves de 
Limnocardium fuchsi Neum. La partie supérieure des dépôts pliocenes du bassin de Braßov est 
attribué par Jekelius aux Levantin et Quaternaire, sans pouvoir nous donner, sur la base de 
mollusques, la limite entre ces 2 formations. Cette limite a été tracée par Ràdulescu & Samson 
(1969) au moment où apparaît, dans la faune de mammifères, Archidiskodon meridionalis Nesti, 
dans l'horizon faunique III de Baraolt. 

En conclusion, d'après ce que nous avons exposé plus haut, nous pouvons dire que la faune 
de mollusques pliocenes connue en Roumanie ne nous offre d'indications sûres pour tracer la 
limite entre le Pliocène supérieur et le Pleistocene inférieur. Cette limite ne peut être mise en 
liaison qu' avec l'apparition de la faune de mammifères à Elephas, qui indique le Pleistocene 
inférieur— sans pourtant pouvoir associer, avec précision, le commencement de celui-ci avec un 
certain horizon. 

LITTÉRATURE 

ALEXEEVA, I. L., 1961, Dreivneisai fauna miecopitaiuscih antropoghene jugo evropeiscoi ciasti S.S.S.R. 

Voprosî gheologhii antropoghena, VI Congres INQUA, Varsovie. 
ATHANASIU, S., 1915, Fauna de mamifere pliocen-superioare de la Tuiuceçti-Covurlui. Anuar Institutul 

Geologic al Romàniei, 6 (1912), Bucurejti. 
BARBU, V. & BARBU, Z. I., 1953, Asupra faunei levantine de la Greaca. Dèri de Seamâ, ComitetuI Geologic 

al Romàniei, 37 (1949-50), Bucuresti. 
BANDRABUR, T., 1971, Geología Crmpiei Dunärene dintre Jiu $1 Oit. InstitutuI Geologie al Romàniei, Studii 

tehnice fi economice, seria J. Stratigrafie, 9, Bucuregti. 
BOTEZ, G., 1916, Asupra faunei de molußte levantine de la Moreni. Däri de Seamâ, InstitutuI Geologie al 

Romàniei, 5 (1913-14), Bucurejti. ^ 

EBERZIN, G. A., 1948, Neogen Moldavskoi S.S.S. Noucinie Zapiski Moldavskoi Naucino—lssledov. Bazî, 

Akademie Nauk S.S.S.R., 1. 
EBERZIN, G. A., 1957, Depozitele eu Unio sturi M. Hörn, ji importanja acestei faune pentru stratigrafia 

Pliocenului din R.S.S. Ukraina $i R.S.S. Moldoveneascá. Analele Româno-Sovietice, Geologie-Geografie, an, 

11, seria III, Nr. 1 (1957), Editura Academiei Rep. Soc. Romania. 
EBERZIN, G. A., 1959, Shenna stratigrafii neogenovfh otiojenii lugo S.S.R. Akademia Nauk Azerbaïdjan 

S.S.R., Geologiskii Institut, Baku. 
GHENEA, С & RADULESCU, C, 1964, Contribujii la cunoajterea unei faune villafranchiene m Podijul 

Moldovenesc. Dàri de Seamâ ComitetuI Geologic R.S. Romania, 50, Bucuregti. 
GRIGOROVICI-BEREZOVSKI, N., 1915, Les dépots levantins de la Bessarabie et de la Moldavie. Mémoires 

de l'Université de Varsovie. 
JEKELIUS, E., 1932, Die Molluskenfauna der Dazischen Stufe des Beckens von Brajov. Memoriile /nstitutului 

Geologie al Romàniei, II, Bucuresti. 
KONSTANTINOVA, A., 1967, Antropogen iujnoi Moldavii i ingozadnoi Ukrainî. Akademie Nauk S.S.S.R., 

Geologiskii Institut, Trudi 1 73, Moskva. 
LITEANU, E., 1960, Despre problema limitei superioare a terjiarului din Depresiunea Valahä. Academia 

República Populare Romane, Studii ßi Cercetari de Geologie, 5, Bucurejti. 
LITEANU, E., 1967, Pietrijuri de Cîndejti sau strate de CÍnde?ti. Comitet. Geologie, Studii tehnice ßi 

economice, seria E, 3, Bucuresti. 
LITEANU, E. & BANDRABUR, T., 1957, Geologia СГтр1е1 Getice méridionale dintre Jiu ci Oit. Anuarul 

Comitetului Geologie al Romàniei, 30, Bucureçti. 



270 PROC. SIXTH EUROP. MALAC. CONGR. 

LITEANU, E. & BANDRABUR, T., 1960, Géologie de la Plaine Gétique Méridionale d'entre le Jiu et l'Oit. 

Annuaire du Comité Géologique, 29-30 (résumés), Bucureçti. 
LITEANU, E., MIHAILA, N. & BANDRABUR, T., 1962, Contribupi la studiul Cuaternarului din Bazinul 

nnijlociu al OItului (Bazinul Baraolt). Academia República Socialiste Romania, Studii $i Cercetàri de 

Geologie, 7 Nr. 3-4, Editura Académie! R.S. Romania. 
MACAROVICI, N., 1940, Recherches géologiques et paléontologiques dans la Bessarabie méridionale— URSS. 

Annales scientifiques de l'Université de Jassy, 2-éme section, 26, fascicule 1, laçi. 
MACAROVICI, N., 1960, Contributions à la connaissance de la géologie de la Moldavie Méridionale. Analele 

ßtiinfifice ale Universitàfii "Al. I. Cuza" la$i, secjia II (St. Naturale), 6, fascicule 4, la?i. 
MACAROVICI, N. & COTET, P., 1962, La présence des couches à Unio sturi M. Hoernes et des couches de 

Barboji-Babele dans la Plaine Roumaine. Analele ftiinfifice aie Universitàfii "Al. I. Cuza" la$i, secjia il. St. 

naturale— b. Geologie-Geografie, 8. 
MACAROVICI, N., 1976, Sur la limite entre le Pliocène supérieur et le Pleistocene inférieur en Roumanie, 

établie d'après le critère des mammifères fossiles continentaux. AnuaruI Muzeului de St. Naturale, Piatra 

Neamt, seria Geologie-Geografie, 3, P. Neam^. 
NIKIFOROVA, V. K. & ALEKSEEVA, I. L., 1961, О granije Neogene i Antropogene v sveazi 5 voprosem о 

rascilenenii Pliocene. Material! sovet p о izuceniu cevertici подо péri oda, I. Moskva. 
PAVLOV, P. A., 1925, Dépôts néogènes et quaternaires de l'Europe méridionale et orientale. Stratigraphie 

comparées d'eau douce. Mémoires de la Section Géologique de la Société des Amis de Sciences Naturelles, 

Anthropologie et Ethnographie, Moskva, 1925. 
RADULESCU, C, SAMSON P., MIHAILA, N. & KOVACI. AL., 1965, Contributions à la connaissance des 

faunes de mammifères pleistocenes de la Dépression de Brajov-Roumanie. Eiszeitalter und Gegenwart, 16, 

Öhringen-Württemberg, Dezember 1965. 
SCHOVERT, E., FERU, M. et al., 1963, Cercetàri geologice în zona centrale din vestul Cîmpiei Getice. 

Comitetul Geologic, Institutul Geologic. Studii tehnice ßi economice, seria E, Hidrogeologie, Nr. 6, 

Bucuregti. , 

STEFANESCU, SABBA, 1897, Etudes sur les terrains tertiaires de la Roumanie. Contributions a l'étude 

stratigraphique, Lille. 



MALACOLOGIA, 1979. 18: 271-275 

PROC. SIXTH EUROP. MALAC. CONOR. 

PRELIMINARY INVESTIGATION INTO SOME FACTORS AFFECTING 

THE SETTLEMENT OF THE LARVAE OF THE MANGROVE OYSTER 

CRASSOSTREA GASAR (ADANSON) IN THE LAGOS LAGOON 



A. M. Ajana 

Nigerian Institute for Oceanography and Marine Research, 
P.M.B. 12729, Victoria Island, Lagos, Nigeria 



ABSTRACT 

The settlement of the larvae of Crassostrea gasar on different types of collectors 
(asbestos, hardwood and oyster shells) at varying water depths, in light or shade was 
investigated. Results indicate that shaded collectors, particularly the hardwood, had the 
best spat concentration. There was no statistical difference in spat settlement between 
upper and lower surfaces of the various collectors. Optimum settlement occurred on 
collectors placed between 70 and 120 cm below the water surface. There was marked 
difference in spatfall on stationary and floating collectors, stationary collectors being 
preferred. 



INTRODUCTION 

The mangrove oyster, Crassostrea gasar, is one of the commercially important bivalves used 
extensively as food by the people along the mangrove swamps in the coastal areas of West 
Africa (Nickiès, 1950). It is commonly found in clusters attached to stilt roots and the lower 
branches of the mangrove tree Rhizophora racemosa which lines the edges of the creeks, 
estuaries and lagoons of Nigeria. The per caput consumption of animal protein in Nigeria is 
23 kg of which 11 kg is fish. Fish produced from all sources is ca. 663,000 metric tons whjie the 
actual fish demand is 869,000 tons leaving a deficit of 206,000 tons. With a growth of 2.5% 
per annum, this deficit is estimated to be more by 1985. The fish demand by 1985 is estimated 
at 1.8 million tons. This deficit is unlikely to be met by capture fishery alone, hence the 
importance of shellfish culture (with special emphasis on oyster culture) can not be over- 
emphasized. The present investigation is geared towards bridging this gap. 

A review of the literature shows that very little has been written on the biology of С gasar 
in the Lagos lagoon system. Sandison & Hill (1966) gave an account of its distribution in 
relation to salinity in Lagos harbour and adjacent creeks. They indicated that in Kuramo Water 
and Badagri Creek (Fig, 1) spatfall was at its peak during February and early April and again 
during the short break in the rains in August and September. Sandison (1966) gave an account 
of the effect of salinity fluctuations on the species. 

Although much work has been carried out on the American oyster, Crassostrea virginica, the 
Pacific oyster, Crassostrea gigas, and the European oyster, Ostrea edulis, little has been published 
on the settling behaviour and culture techniques of the spat of C. gasar. A marketable size of 
about 10.0 cm is attainable by the European oyster O. edulis in 4-5 years whereas the mangrove 
oyster C. gasar is found to attain 6.4 cm in about 6 months. This study is therefore aimed at 
establishing a method of spat collection which might be useful for culturing the species. Factors 
investigated in the study include: (1) Settlement on various types of collectors (asbestos, 
hardwood, oyster shell); (2) Larval preference for under-surface or top-surface of collectors; (3) 
Larval preference for collectors in shade or light for settlement; (4) Depth preference for larval 
settlement; (5) Preference for floating and stationary collectors for larval settlement. 

The present investigation was carried out at Kuramo Water (Fig. 1) which is a shallow 
(maximum depth 3.7 m) sheltered lagoon where the spat occur throughout the year (Sandison 
& Hill, 1966). 

(271) 



272 



PROC. SIXTH EUROP. MALAC. CONGR. 



LAGOS LAGOON 




•FIVE COWRIE CREEK 
KUR AMO CREEK 
-06*25-9'n. 

-06°25-2'N. 
KURAMO WATER 
BADAGRY CREEK 



LONG. 03**25 6E: 03 26 

FIG. 1. Map of Lagos Lagoon (Nigeria) showing the position of Kuramo Water. 



Other animals found alongside C. gasar on the stilt roots are Chthamalus aestuarii, Balanus 
pallidus, Mercierella enigmática. Hydroides uncinata and various unidentified sea anennones, 
hydroids and sponges. Mercierella enigmática and Balanus compete with C. gasar for food and 
space. They also settle on the shells. 



MATERIALS AND METHODS 

(a) The collectors. Although the spat of С gasar settle naturally on mangrove stems and 
roots, these are unsuitable for culture purposes as they cannot resist decay and are liable to rot 
before the spat reach maturity. Studies were therefore initiated to find alternative collectors. 
The following substrates were used: (1) asbestos sheets, (2) hardwood (rectangular mahogany 
planks), and (3) old oyster shells. The choice of collectors was based on availability and cost. 

(b) Stringing of collectors. Ten of the rectangular collectors (asbestos sheets 17.0 X 10.2 X 
0.4 cm and hardwood 17 X 10.2 X 1.8 cm) had holes bored through them on opposite ends 
and were strung onto 2 nylon cords (Fig. 2). Paired knots along each cord kept the rectangular 
collectors about 15 cm from one another. 

In the case of the dead oyster shells, a hole was drilled in the middle and these shells were 
strung in batches of ten with 15 cm spacing. Heavy pieces of discarded metal were used as 
anchors for each string of collectors to prevent floating and drifting. 

Strings of various types of collectors were tied to the underside of bamboo rafts (Fig. 3) 
held in place by means of 4 stakes in such a way that the raft may move up and down on the 
stakes with the tide. Two sets of such rectangular rafts were set up 21 m apart; one in the light 
and the other was shaded with palm tree fronds. Strings of the various types of collectors were 
also tied to fixed horizontal beams on the stakes so that the top collectors on each string were 
exposed at low tide. 



AJANA 



273 



^-h 



-NYLON CORD 



/j JA ASBESTOS SHEET 

/^ ^/ OR HARDWOOD 

tí- 



SINKER 



FIG. 2. Experimental strung collector. 



ROKO WOOD 

NDIAN BAMBOO 
90c:m LONG 




FIG. 3. Experimental raft used in the study. 



274 



PROC. SIXTH EUROP. MALAC. CONGR. 



At weekly intervals each string of collectors was taken out of the water and the total 
number of both dead and living spat on each surface was counted and recorded. Remains of 
dead spat were scraped off the collectors at each visit. 

RESULTS AND DISCUSSION 

The number of spat settling on the various types of collectors and under different conditions 
was expressed as number of spat per 500 sq. cm of surface area of collector. Figs. 4a-d show a 
summary of the results obtained during this study. 

(a) Collector preference. The results of the present study indicate that the larvae of C. gasar 
prefer hardwood for settlement. There was, however, no appreciable difference in the number 
of spat settling on the two other types of collectors used. Apart from the relatively rougher 



Î 60 



40 



20 




15 2 за 4 608 

WA,TER 



712 
DEPTH 



Ю1 6 
IN CM- 



I520 



100 




I 



152 304 608 

VATER 



912 
DEPTH 



121 6 
IN CM 



I520 




152 ЭО-4 608 712 ICH 6 

VATER DEPTH IN CM 



152 О 



lKEY^ 



• • 



X — X- 



HARDWCЮD 

SHELL 
ASBESTOS 



ЮО 




121 6 

N CM 



152 О 



FIG. 4. Settlement of oyster spat on various collectors. A. Floating unshaded collectors. B. Floating shaded 
collectors. С Stationary unshaded collectors. D. Stationary shaded collectors. 



AJANA 275 

nature of the two surfaces of the hardwood, which could stimulate the settling process whereby 
the larvae fix themselves by an adhesive secretion to the surface, no other explanation can be 
advanced for the preference for hardwood. Perhaps as suggested by Cole & Knight-Jones 
(1939), Knight-Jones & Stephenson (1950), and Knight-Jones (1953 a,b) for O. edulis, the 
planktonic larvae of C. gasar exhibit certain preferences for settlement surfaces. Although the 
hardwood proved most successful of the 3 collectors tested, however, in commercial practice 
the use of hardwood is not feasible. An alternative material from which spat can be easily 
flicked off is being tried. 

The present study offered an opportunity for comparing the mortality of spat on the 
different collector types. More deaths were recorded on the shells and asbestos than on the 
hardwood. This in itself can be responsible for the higher density of spat observed on the 
hardwood. 

(b) Spat settlement under light/shade. Differences in settlement of larvae under shade and 
unshaded environments were more striking. Figs. 4B-D show that the shaded environment seems 
more conducive to settlement. As has been shown for many sessile marine animals, the 
concentration of settlement of the larvae of C. gasar on the lower rather than top surfaces of 
collectors may be due to their avoidance of light. Nelson (1921) found that the "eyed" larvae 
of С virginica are stimulated by light and continue to move until they reach a shaded place 
where they become quiescent. It therefore seems that, as in the case of C. gigas and O. edulis 
(Walne & Helm, 1974), light is an important factor affecting settlement of the larvae of С 
gasar. 

(c) Settlement in relation to depth. The present investigations show that settlement was 
intense in the middle column of the water but less dense on the collectors at the top and 
bottom of the water column. Less settlement on the top collectors can be attributed to the 
avoidance of direct sunlight while the presence of debris at the bottom may be responsible for 
the scanty spatfall on the collectors there. Davis (1960) claimed that silt is inimical to the 
larvae of C. virginica. 

(d) Settlement in relation to stationary and floating collectors. A comparison of Figs. 4A-B and 
4C-D shows that there were more larvae settling on the various types of stationary collectors than 
on the floating collectors, especially on the collectors in the central region of the water column. 
The low settlement recorded on the stationary collectors placed 15 cm below the surface may 
be correlated with the fact that they were exposed at low tides. The few larvae settling on 
these collectors were found dead and therefore not recorded. 



ACKNOWLEDGEMENTS 

I wish to express my gratitude to Mr. M, 0. Okpanefe who helped in the statistical analysis 
and to Dr. V. Yoloye for his suggestions in writing the manuscript. 

LITERATURE CITED 

COLE, H. A. & KNIGHT-JONES, E. W., 1939, Some observations and experiments on the setting behaviour 

of larvae of Ostrea edulis. Journal du Conseil Permanent International pour l'Exploration de la Mer, 14: 

86-1 05. 
DAVIS, H. C, 1960, Effects of turbidity producing materials in sea water on eggs and larvae of the clam 

Venus mercenaria. Biological Bulletin, 118: 48-54. 
KNIGHT-JONES, E. W. & STEVENSON, J. P., 1960, Gregariousness during settlement in the barnacle 

Elminius modestus Darwin. Journal of the Marine Biological Association of the U.K., 29: 281-297. 
NELSON, T. C, 1921, Aids to successful oyster culture. 1 Procuring the seed. Bulletin of the New Jersey 

Agricultural Experiment Station, 351: 1-59. 
NICKLÈS, M., 1950, Mollusques testacés marins de la côte occidentale d'Afrique. Manuels Ouest-Africains, 2: 

1-269. 
SANDISON, E. E. & HILL, M. В., 1966, The distribution of Balanus pallidus stutsbury i Darwin. Gryphaea 

gasar [(Adanson) Dautzenberg] , Mercierella enigmática Fauve! and Hydroides uncinata (Philipp!) in 

relation to salinity in Lagos harbour and adjacent creeks. Journal of Animal Ecology, 35: 235-250. 
SANDISON, E. E., 1966, The effect of salinity fluctuation on the life-cycle of Gryphaea gasar [(Adanson) 

Dautzenberg] in Lagos Harbour, N\geña. Journal of Animal Ecology, 35: 379-389. 
WALNE, P. R. & HELM, H. M., 1974, Routine culture of the Pacific oyster Crassostrea gigas at Conway 

during 1973. Shellfish Information Leaflet, Fisheries Laboratory, Burnham, 32. 



MALACOLOGIA, 1979, 18: 277-290 

PROC. SIXTH EUROP. MALAC. CONGR. 

TIDALLY DEPOSITED GROWTH BANDS IN THE SHELL OF THE COMMON 
COCKLE, CERASTODERMA EDULE (L.) 

С A. Richardson,'' D. J. Crisp2 and N. W. Runham^ 

ABSTRACT 

Specimens of the intertidal bivalve Cerastoderma edule were nnarked by treatment 
with a cold shock and allowed to grow under different environmental conditions. In 
animals kept in an intertidal environment the number of growth bands deposited 
coincided with the number of tidal emersions. Similarly, in the laboratory, individuals 
grown in a simulated semi-diurnal tidal regime of 8 hours high tide and 4 hours low tide 
under 3 different artificial light regimes, 12 hours light: 12 hours dark, continuous dark 
and continuous light deposited a number of growth bands which coincided with the 
number of tidal emersions. However, the number of bands deposited was independent of 
any change in the light regimes. Individuals continuously immersed in the laboratory and 
in the field showed ill defined growth bands, which however approximate to a 
semidiurnal frequency. It is suggested that the bands are formed during emersion, and are 
thicker when conditions cause the animals to close for longer periods. A lunar cycle with 
periodic alternation of thin and thick bands is thus produced. There is a possibility that 
an endogenous rhythm exists which is entrained in intertidal animals by periods of 
emersion, but which persists when the animals are kept continuously immersed. 



INTRODUCTION 

The calcareous skeletons of many living marine animals show evidence of periodic deposition 
in the form of regular external growth ridges or internal banding. Corals (Wells, 1963), some 
limpets (Kenny, 1977) and pectinids (Clark, 1968, 1975; Wheeler et al., 1975) exemplify the 
former, the bivalves Cerastoderma edule (cf. House & Farrow, 1968), Clinocardium nuttalli (cf. 
Evans, 1972, 1975) and Mercenaria mercenaria (cf. Pannella, 1975) and the barnacles Balanus 
balanoides (cf. Bourget & Crisp, 1975 a,b) and Elminius modestas (cf. Crisp & Richardson, 
1975) exemplify the latter. 

The periodicity of deposition is of great interest since it has been put forward as the basis 
for the interpretation of similar ridges and bands in fossil shells and skeletons, and thereby to 
formulate the daily and lunar components of the primaeval calendar (Runcorn, 1964). Much of 
the geological literature attempts to analyse the periodicities observed into tidal, daily or lunar 
components (House & Farrow, 1968; Dolman, 1975; Whyte, 1975) by reference to regularities 
in the relative distinctness of the bands and spacings within the patterns themselves. A 
necessary check on the supposed correlation of these periodic patterns with astronomical events 
is through direct experiments on living animals. Essential to this approach is the exact dating of 
2 or more bands or ridges. 

Bourget & Crisp (1975b) and Crisp & Richardson (1975) dated the internal growth bands in 
the shells of 2 species of intertidal barnacle by allowing them to grow for short periods in 
calcium enhanced sea water, thereby forming an abnormally thick increment. They were thus 
able to show that normally each shell increment corresponds to a single, semidiurnal period of 
tidal immersion. Fewer but thicker increments were laid down in simulated tidal regimes of 
greater than normal duration. 

Experiments on living bivalves have not as yet allowed any consistent interpretation, nor 
have they concurred with the once prevalent view amongst geologists and others that the bands 
are laid down once daily (Davenport, 1938; Petersen, 1958; Barker, 1964; House & Farrow, 

1 Department of Zoology, The Brambell Laboratories, University College of North Wales, Bangor, Gwynedd 
LL57 2UW, United Kingdom. 

2n.E.R.C. Unit of Marine Invertebrate Biology, Marine Science Laboratories, Menai Bridge, Anglesey, 
Gwynedd LL59 5EH, United Kingdom. 

(277) 



278 PROC. SIXTH EUROP. MALAC. CONGR. 

1968). Dolman (1975), on the basis of 24 hour experiments, concluded that the bands were 
tidal, but Whyte (1975), from 3-hourly sampling during neap tides, appeared to conclude that 
the increment is laid down only at night and therefore formed once per 24 hours. Neither 
experiment, as reported, carries conviction. Evans (1972, 1975) working on another cockle 
from east Pacific shores, where the tidal regime has a strong diurnal component, offers good 
evidence that each growth increment correlates with the period of immersion, and the 
intervening bands with times of low water. 

A similar confusion exists regarding other bivalves. Pannella & MacClintock (1968) marked 
shells of Mercenaria mercenaria and withdrew them 2 years later. They found 1 growth band 
per day, though they also stated that daily increments were further divided into 2 parts. Later, 
Rhoads & Pannella (1970) found more strongly marked bands in intertidal transplants of the 
same species, which Bourget & Crisp (1975b) suggested would be more consistent with tidally 
produced bands. Pannella (1975) has now reached the same conclusion, but from animals in 
Puerto Rico where there is a strong diurnal tide. Clark (1968) described daily bands in juvenile 
Pectén diegensis growing continuously submerged. 

It can thus be seen that in intertidal bivalves at least, the view that growth bands are laid 
down daily is giving way to the view that they are produced tidally. The series of experiments 
described below were designed to clinch this matter for the European cockle Cerastoderma 
edule. 



MATERIALS AND METHODS 

Shells of experimentally grown cockles were briefly cleaned in 10% sodium hypochlorite 
solution to remove organic debris. The right valve of the shell was dried and embedded in resin 
(Metaserv s.w. resin 137/12742) and radial sections were cut in a plane from the umbo to the 
growing point. Sections were ground on successively finer grit, wet and dry "Trimite" paper, 
polished with a cloth soaked in Brasso for 30 sec and etched for a period of 20-25 min with 
cold 0.01 normal HCl. Acetate peel replicas of the polished and etched surfaces were prepared 
by allowing small strips of replicating material (Polaron Equipment Ltd.) to become almost 
molten after 30 sec in ethyl acetate. The strips were applied to the etched shell surface and 
after 5 min when the ethyl acetate had evaporated the peel could be removed and attached to a 
glass slide for microscopical examination. 

Attempts were made to mark the shell internally at a given date. Various concentrations of 
the fluorescent dye tetracycline hydrochloride were not successful, and though Alizarin Red S 
could be incorporated into the shells it was considered unsatisfactory since it adversely affected 
the deposition of the shell. Finally it was found possible during the summer to mark the shells 
by maintaining them for 3 days in moist air at a temperature of 4 С Analysis of replicas of 
shells returned to the natural environment showed that the shells were always notched by the 3 
day shock. Fig. 1 illustrates the appearance of the peel in the region of the cold shock. A 
depression, sometimes shallow but frequently in the form of a deep cleft, (D) can be seen 
which is sometimes associated with the development of a spine (Sp) in the immediate 
post-shock region of the shell. The first few growth bands formed after the cold shock are 
relatively thin, but the subsequent acceleration of growth can be seen to the right of the figure 
from the increasing width of the growth bands. 

Three types of experiments were undertaken to obtain peels of animals maintained for 
known periods under different conditions. 

(1). Intertidal experiments. 

Cockles were given an identification mark and treatment by cold shock before being set out 
at defined levels on the mud flats of the south shore of the Menai Straits at Gorad y Gyt at the 
eastern end (May, 1976) and in sandy substrata at Traeth Melynog, Abermenai Point at the 
western end of the Straits (July, 1976, April, 1977). Animals were recovered after various 
intervals of time and some in the first experiment were marked on the 2nd occasion by cold 
shock treatment and returned to the shore. These experiments were designed to investigate the 
effect of tidal level on shell growth band pattern. Due to losses, not all levels could be 
investigated in each experiment. 



RICHARDSON, CRISP AND RUNHAM 



279 




FIG. 1. Acetate peel showing the cleft (D) in the peripheral layer (PI) of Cerastoderma edule produced by the 
discontinuity of growth after a 3-day cold shock treatment. The associated spine (Sp) can be seen to the 
right of the cleft. Arrows indicate the band at which growth is assumed to have restarted after the cold 
shock. Note that for several days after treatment growth bands can be seen to be closer than they are to the 
right of the figure at the time that normal growth has presumably restarted. This animal was kept under 
simulated tidal conditions in the laboratory during April 1976. CI— crosslamellar layer. 



(2). Raft experiments. 

Cockles, similarly prepared, were placed in a continuously submerged box on a raft in the 
Menai Straits. One half of the box, the "dark box," consisted of a light tight chamber, while the 
other half, the light box," was identical in every respect except that a perspex lid and sides 
replaced the opaque panelling. The passage of water was regulated and light kept out by a series 
of baffles at the entrance and the exit. This experiment was designed to test the effect of 
continuous immersion, natural photoperiod and continuous darkness on shell growth band 
pattern. 

(3). Laboratory experiments. 

Cockles were kept successfully in the laboratory without natural substrata, at a temperature 
of 16 ± ГС, in light controlled tanks with a facility for simple tidal fluctuations, in which 
running sea water was supplied to a depth of 10.5 cm for 8 hours of the simulated high tide, 
and the tanks drained for 4 hours of simulated low tide. Alternatively, the cockles could be 
kept continuously submerged. As there was a possibility that the temperature might rise at 
simulated low tide with no water protecting the animals from the lamps, the tank lids were 
specially designed with baffles to allow heat but not light to escape. Both illuminated and 
non-illuminated tanks were provided with similar lids and lights but the lids of the former had 
perspex panels to allow the light to pass, while those of the latter had opaque panels to exclude 



280 



PROC. SIXTH EUROP. MALAC. CONGR. 



light. In this way both tanks would have been sinnilarly heated during the "lights on" period. 
The cocl<les did not put on appreciable shell growth unless well fed. Seven to 8 litres of algal 
suspension at 2 X 10^ cells Г"" were added to the header tank supplying the 4 experimental 
tanks at every high tide. The initial concentration achieved was approxinriately 10* cells Г'' . 
Appreciable growth would not take place during winter, even if the animals were fed, hence the 
majority of experiments were restricted to the season of natural growth between April and 
September. 

The laboratory experiments were designed to investigate the effect on shell growth band 
pattern of tidal and non-tidal conditions combined with equinoctial photoperiod, continuous 
darkness and continuous light. 

At the end of each of the above experiments, as many cockles as could be recovered were 
sectioned and peels prepared for examination in a projection microscope. Photographs were 
taken of typical peels. The number of growth bands was counted and the average thickness of 
the increments estimated from the total shell growth as measured by a calibrated eyepiece 
micrometer. Three counts were made of the numbers of bands, both in the peripheral layer (Fig. 
2 PI) and in the crosslamellar layer (Fig. 2 CI) of each shell between the position of one cold 
shock cleft and the next, and/or to the growing end of the shell. The total number of bands for 
each shell layer was averaged over ail shells and standard errors calculated. To quantify 
differences seen in the relative distinctiveness of the bands each band was assessed compara- 
tively in each shell layer, and assigned to 1 of the 3 categories "strong," "intermediate," or 
"weak" and the number of each class averaged over all shells. Finally the presence of alternate 
strong and weak bands and the regularity of the increments was noted but not quantified. 

RESULTS 

(1). Intertidal experiments. 

Fig. 2 illustrates the appearance of an acetate peel taken from a radial section of a cockle 
grown at low water neap tide level. The cleft D marks the beginning of the experiment period 
from which 54 growth bands can be counted up to the growing edge of the shell on the right. 
The peel replicates 3 layers; the outermost is a thin, uncalcified periostracum showing as a thin 
dark line extending over the upper surface including the spines, Sp. Next is the peripheral layer, 
PI, of the calcified shell in which the growth banding runs approximately parallel to the 
truncated region at the growing point of the shell. The innermost is the crosslamellar layer, CI, 
with the bands running approximately parallel to the inner surface of the shell. The 
crosslamellar bands join the peripheral bands at a sharp change in angle, corresponding to the 
acutely pointed growing tip. 




FIG. 2. Acetate peel from Cerastoderma edule grown at low water neap tide level at Abermenai Point, 
marked by cold shock on 15 July 1976 and removed from the environment at 19.00 on 12 August 1976. 
Note the cleft at D from which 54 bands can be counted. From a knowledge of the time of removal, the last 
visible band must have been laid down at approximately 19.00 on 12 August 1976 and the last increment 
took place during the ensuing period of daylight. ST— maximum spring tide; NT— maximum neap tide; 
PI— peripheral layer; CI— crosslamellar layer; Sp-spines. 



RICHARDSON, CRISP AND RUNHAM 281 

The banding appears as thin dark lines with thicker, more transparent, regions between. The 
former will be referred to as growth bands, and the distance separating the centres of the 
growth bands as growth increments. It is evident that the growth increment is not constant but 
varies with position along the growth band and with the angle at which it is measured. Since 
the growth increments relate to growth rates rather than to the origin of the pattern, they will 
be dealt with in a separate paper. The growth bands in the peripheral layer are further apart but 
those in the crosslamellar layer are generally more distinct. Each band can usually be identified, 
but sometimes very faint bands are difficult to make out and may be restricted to one shell 
layer. Therefore counts of peripheral and crosslamellar bands were separately assessed and 
averaged; the conformity in the counts of the 2 layers being a good criterion of reliability. 
Occasionally bands were obscured by defects in grinding. Occasionally, late in the season or in 
shells from high water, little growth had taken place, making counting very difficult. Where 
considerable uncertainty existed the counts were excluded from analysis. 

Fig. 2 shows an alternation in the thickness of the bands which appears periodically. From 
the dating of this shell it can be seen that strongly marked alternations coincided with or 
slightly preceded spring tide maxima, while the fainter banding with less evident alternations, 
corresponded with the neap tide period. Furthermore, the last band deposited was a thin one, 
and the penultimate a thick one. Since the shell was collected on the evening low tide, the last, 
fainter line, assuming tidal periodicity, must have been laid down during the morning, and the 
earlier thick line during the previous evening and so on. Other shells sampled from the same 
collection show consistency in the pattern of alternation of the bands indicating that the 
pattern relates to the environment rather than to a particular individual. 

Table 1 records the band counts made from some 70 animals grown in 2 habitats at various 
shore levels in which the exposure of every individual was accurately known in relation to 
dated bands. Therefore the band frequency could be related to the number of light and dark 
periods and to the number of tidal cycles of immersion and emersion. Columns 5 and 6 show 
clearly that the number of bands tend to coincide with the number of tidal cycles, and not the 
number of days. In 4 of the 6 experiments (rows 1, 2, 4 and 6) the agreement is within 2% of 
expectation, and entirely within the 5% confidence limits (approximately 2 x Standard Error) 
for rows 1, 2 and 4. The counts are significantly below expectation for the high water neap and 
mean tide level samples at Traeth Melynog. In the higher shore samples the growth increments 
are smaller and the closer banding makes them harder to read, especially in the crosslamellar 
layer where the bands approach most closely. An underestimate of band frequencies is therefore 
more likely at these tidal levels. 

It will also be noted from Table 1 that very few of the bands were weak, nearly all being 
classified as strong or intermediate. This feature is evident from a cursory inspection of the 
peels, the striped light and dark pattern in all intertidal exposures being very clear. 

(2). Raft experiments. 

When the peels of cockles which had been transferred from an intertidal habitat to the raft 
were examined, a sudden change in the appearance of the pattern of banding could be seen, 
starting at a point corresponding to the cleft induced in the shell surface by cold shock 
treatment (Fig. 3). In place of the clearly marked darker and lighter stripes of the intertidal 
pattern were fainter more widely spaced and less regular bands. The fainter bands produced 
while continuously submerged were slightly less obscure in the peripheral layer than in the 
crosslamellar layer of the shell. Furthermore many of the bands were very faint indeed. 
Immediately after being placed under continuous submersion, there was, in many shells, a zone 
of almost continuous deposition without any bands being clearly identifiable. Later, a series of 
bands were re-established. These never fully resembled the intertidal banding pattern however. 

Table 2 records the number of bands counted in the region of the shell corresponding to the 
45 days and 87 tidal periods of this experiment. The table indicates 2 of the features 
mentioned above, the high proportion of weak growth bands observed and the larger number of 
bands seen in the prismatic layer. The difficulty in reading these peels, or possibly a real 
variation in band number, leads to a much larger standard error as well as a significant 
difference between the 2 shell layers. Nevertheless when the results are averaged out the 
number of bands fits better to the number of tidal cycles than to the number of daily periods 
of light and dark. Moreover, having regard to the large standard errors, there is no significant 



282 



PROC. SIXTH EUROP. MALAC. CONGR. 



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283 




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FIG.3. Acetate peel from an experiment where Cerastoderma edule was transferred from the ¡ntertidal zone 
to a raft with continuously submerged conditions and natural photoperiod. Arrow marks transition. Very 
distinct and narrow growth bands laid down intertidally are seen to the left, sharply demarcated from the 
broader and less distinct bands laid down on the raft where continuous feeding was possible. PI— peripheral 
layer; CI— crosslamellar layer. 



difference in the number of bands in either layer between those animals exposed to submarine 
daylight and those kept in the dark box. 

(3). Laboratory experiments. 

The appearance of the peels from the laboratory experiments in essence confirmed those 
from the field and the raft. Fig. 4 clearly illustrates the effect of tidal conditions on the growth 
bands of laboratory grown animals and parallels Fig. 3. In this particular experiment the inlet 
valve, which closes at simulated low tide and thus prevents the inflow of water, failed to close 
for 32 hours, which included 2 presumptive low waters. As a result, the animals were kept 
beneath a depth of flowing sea water throughout. The valves were then reactivated, producing 4- 
hour periods of emersion once again. As can be seen from the photograph, well defined bands 
were produced under both periods of tidal conditions, but only weak bands were formed when 
the animals were immersed. The graph to the right of the photo illustrates how growth rates 
can be measured off the peels and indicates that a higher rate of growth took place when the 
cockle was kept immersed. The peels of animals which were given simulated tides generally 
produced more distinct and regular bands than those continuously immersed, though the 
banding was less stark than that of animals from the intertidal zone itself. Moreover, as can be 
seen from Fig. 5, there was little evidence of alternation between thin and thick bands which so 
clearly characterised the shells of intertidally grown cockles. Nor did the cockles exposed to 12 
hours light and 12 hours darkness in the laboratory show any appreciable alternation in 
banding. 

Table 3 lists the counts taken from peels of cockles kept under the 6 possible combinations 
of illumination and tidal conditions offered in this experiment. The numbers of growth bands 



284 



PROC. SIXTH EUROP. MALAC. CONGR. 




12 



I PI 




1000- 



500- 




4 8 

_ TIDAL PERIODS (12 HOURS) 

FIG. 4. Left: panel írüín an experiment conducted during September-October 1976, the conditions under 
which Cerastoderma edule was growing were changed from a simulated tidal regime to a continuously 
immersed regime for 32 hours between 2 and 4 October 1976 and then returned to tidal conditions. Note 
the loss of definition of the growth bands and the greatly enhanced width of the bands when continuously 
submerged. Right: Plot of growth against time using data from the peel and assuming each band represents 
one tidal period. Growth rates can be measured from the slope of the graph. 



RICHARDSON, CRISP AND RUNHAM 



285 



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FIG. 5. Acetate peels from laboratory experiment 1 conducted in continuous darkness. The upper figure 
shows a peel from a cockle given tidal emersion every 4 hours in 12, the lower figure shows a peel from a 
continuously immersed cockle. Note the clearer definition and greater regularity of the bands in the cockle 
from the tidal regime. Gb— growth bands; Gb'— narrowing of increments corresponding to an occasion when 
the algal food was not replenished; PI— peripheral layer; CI— crosslamellar layer. 



286 



PROC. SIXTH EUROP. MALAC. CONGR. 



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RICHARDSON, CRISP AND RUNHAM 287 

of the tidally immersed group gave a precise fit to the number of tidal emersions, all falling 
within the expected confidence limits that P < .05. The numbers of bands seen in the peripheral 
layer usually exceeded those in the crosslamellar layer, but the difference was very small, 
generally less than ±2% of the numbers expected. Few of the bands were classified as weak. 
There was no obvious influence of illumination. In the group of cockles fed from the same 
source but continuously immersed, the standard errors between counts were somewhat greater 
than in the tidal group. However, the main difference was in the discrepancy between counts in 
the peripheral layer and in the crosslamellar layer. Whereas the former exceeded, the latter fell 
short of the number of tidal periods experienced, in both cases the differences being usually 
significant. Also the number of weak bands recorded was greater and the number of strong 
bands less than in the tidally emersed group. Otherwise no differences within the continuously 
immersed group could be discerned, illumination again being without apparent effect. 

DISCUSSION 

Table 4 summarises the results of all experiments in a form which makes them comparable. 
The numbers of growth bands are expressed as a percentage of the expected numbers, assuming 
that they each represent a single tidal period. 

All cockles exposed to tidal conditions, whether natural or simulated, gave counts in both 
shell layers which were very close to expectation. The only exceptions were the cockles exposed 
at high water neap tide where growth was small. Another group of cockles exposed very late in 
the season (October) gave deficient numbers of bands compared with expectation, no doubt 
because growth rates were so small that the bands could not reliably be distinguished. It is 
possible that the small number of bands counted by Farrow (1971) in Thames estuary cockles, 
which he ascribed to daily growth, could have been underestimated because he included winter 
periods of virtually no deposition in the counts. Moreover, cockles which were living at the high 
water of neap tides would only just be covered at high tide, or might even remain uncovered in 
the absence of waves or swell during the smallest tides. The underestimate might therefore be 
real, representing a failure to deposit any increment unless immersed and able to feed for a 
certain period of time. As a result, 2 or more consecutive emersion bands might coincide. It 
must follow therefore that Cerastoderma edule, like the intertidal barnac\es Ba/anus ba/anoides 
and Elminius modestus, lays down 1 growth band per tide when growing over most of its 
intertidal range. However, as in barnacles, bands may be missed under circumstances where 
growth does not take place. It is not fully justifiable therefore to equate band numbers to tidal 
periods in individual fossil shells where the conditions of growth cannot be assumed. The 
maximum number of bands are however likely to coincide with tidal frequency. 

There are 2 other features of growth banding which accord with this conclusion. First, the 
clarity and definition of tidally formed bands are greatest in intertidal cockles, intermediate in 
laboratory simulated tidal animals, but dubiously present in shells of continuously immersed 
animals. In Table 4 the entries 3 and 4 represent this last group and are quite similar, showing 
an excess of bands (over 100%) in the peripheral and a deficit in the crosslamellar, due mainly 
to a large number of weak bands being counted in the former. 

Secondly, the occurrence of an alternation of strong and weak bands in naturally growing 
intertidal cockles, was found by dating to have a lunar periodicity coinciding with spring tides. 
During these highest and lowest tides, the animals will be exposed to the air for longer periods, 
presumably thereby forming stronger bands. At neap tides they will be exposed only briefly 
causing the formation of a series of weaker bands. However, the reason for alternation of band 
strength must still be explained. 

Table 4 allows comparison between the shells of cockles grown under natural photoperiod 
on the shore, under artificial photoperiod in the laboratory, and under submarine illumination 
on the raft to be compared with cockles grown in continuous darkness on the raft or in 
continuous light and darkness in the laboratory. All comparisons between different regimes of 
illumination but otherwise similar conditions show that illumination exercises no appreciable 
effect on the growth bands. Not only does this result further refute any lingering claim that the 
banding itself reflects a daily cycle of light and dark, but it also throws doubt on the possibility 
that a light-dark diurnal influence interacts with a semi-diurnal tidal periodicity to produce 



288 



PROC. SIXTH EUROP. MALAC. CONGR. 



TABLE 4. Summary of growth band data, expressed as mean number of bands and calculated as percentage of 
expectation if tidally produced. P: peripheral, C: crosslamellar layers. 





Condition 


Total no. & 
standard error 


Strong 


Inter- 
mediate 


Weak 


1. 


Intertidal Zone 
HWN 


(P) 89.0 ± 2.4 
(C) 81.6 ±2.3 


Too с 
Too с 


ose for assessment 
ose for assessment 






MTL 


(P) 96.2 ±2.2 
(C) 95.1 ± 1.5 


50.7 
46.5 


38.8 
42.1 


6.8 
6.5 




LWN 


(P) 98.7 ±1.2 
(C) 97.0 ± 0.9 


47.3 
41.3 


44.0 
47.6 


7.4 
8.8 


2. 


Laboratory tidal simula- 
tion (8 h. immersed, 
4 h. emersed) 












12 h. light, 12 h. dark 


(P) 100.3 ±2.1 
(C) 96.7 ± 1.1 


49.7 
53.0 


29.8 
31.0 


20.5 
12.6 




Continuous darkness 


(P) 99.5 ± 3.0 
(C) 94.0 ±2.4 


54.4 
58.7 


30.0 
23.0 


15.2 
12.3 




Continuous light 


(P) 104.9 ± 2.8 
(C) 96.7 ± 3.0 


66.5 
70.5 


26.7 
21.1 


11.9 
5.1 


3. 


Raft exposure 












Natural photoperiod 


(P) 114.1 ± 3.4 
(C) 81.7 ±4.4 


41.7 
34.5 


29.3 
19.2 


43.1 
28.0 




Continuous darkness 


(P) 128.9 ± 8.0 
(C) 83.8 ± 4.0 


56.2 
41.1 


38.5 
20.2 


34.2 
22.5 


4. 


Laboratory 












Continuously immersed 
12 h. light, 12 h. dark 


(P) 121.8 ±3.9 
(C) 79.5 ±3.3 


36.4 
31.8 


20.5 
20.0 


54.4 
27.7 




Continuous darkness 


(P) 109.0 ± 6.4 
(C) 87.7 ±4.3 


38.5 
41.5 


31.9 
22.1 


38.6 
24.0 




Continuous light 


(P) 100.2 ±6.0 
(C) 79.8 ± 3.5 


31.4 
38.6 


31.4 
22.6 


37.4 
18.6 


5. 


Mean and S.D. of all bands 
from both layers 












Intertidal 
Simulated intertidal 


92.9 ± 6.5 
98.6 ± 3.65 


46.4 ± 3.9 

58.5 ± 8.1 


43.1 ± 3.7 
26.9 ± 4.1 


7.3 ± 0.8 
12.9 ± 5.0 




Raft exposed 
Laboratory immersed 


102.1 ±23.2 
96.3 ± 17.1 


43.3 ± 9.2 

36.4 ± 4.0 


26.8 ± 9.0 
27.4 ± 7.6 


32.0 ± 8.8 
33.5 ± 12.8 



lunar periodic alternations. If some other diurnal factor which is known to influence banding 
can be found, it would be a more likely candidate. 

Intertidal cockles whose peels successfully included the most recently deposited band at the 
delicate growing point of the shell offered strong evidence that the thinner, weaker bands were 
formed on the early morning spring ebb, and the alternating stronger and darker bands on the 
afternoon ebb. It is likely that during and after the heat of a summer day the stress of high 
temperature and potential desiccation will cause the shells to close more firmly and for longer 
than in the cool of the morning. If shell closure were the proximate cause of the formation of 
shell bands in bivalves, as has been demonstrated in barnacles (Bourget & Crisp, 1975 a,b), one 
would expect the broader band to be formed on the afternoon ebb. During the spring tides, 
when alternations are observed in shell banding, the morning ebb occurs between 0400 and 
0700 and the evening between 1600 and 1900 hours. Thus in summer it is light at both ebbs. 
The neap tides occur at 1000 to 1300 and 2200 to 0100 hours, and these have been shown to 
correspond with more uniform and weaker banding. Though the cockles will be exposed to the 
air and high temperature only briefly at neap tides, they will receive a much greater difference 
in illumination than they will at spring tides. Hence illumination itself appears not to be a 



RICHARDSON, CRISP AND RUNHAM 289 

factor causing difference in band thickness. We suggest rather a combination of insolation and 
duration of emersion. In North Wales, the conditions producing the difference would be 
greatest in the period preceding the spring tide maximum when a reasonably long low water 
occurs either in the heat of the early afternoon, or at dawn. This view is supported by the 
experiments under laboratory simulated tidal regimes with light and dark conditions. A 
temperature differential was carefully excluded and very regular band thicknesses were observed 
without any alternations. 

The experiments conducted on the raft and under constant immersion in the laboratory 
ought not, on the above theory, to have produced any growth bands. True, the banding was 
less distinct and regular, but some bands did appear. Furthermore, although the 2 shell layers 
gave different results, the average agreed very well with the number of tidal periods. This 
average included a very high variability between counts (Table 4, Section 5, see standard 
deviations) whereas the band counts of all cockles under tidal conditions showed little 
variability. 

The tidally periodic influences which are possibly at work in all fully immersed experiments 
would be (1) gravitational force and (2) food availability. The former cannot be ruled out, but 
seems intuitively an unlikely 'Zeitgeber.' The latter would certainly be present in all laboratory 
experiments, because the cockles were pulse fed at each simulated high tide. The algal food 
would be gradually filtered and diminish in concentration until the next high tide when its 
concentration would be restored abruptly. On the raft, a tidal periodicity in the food supply is less 
likely, but possible. The abundance of algal food might vary within water mass oscillating up 
and down the Menai Straits. Also, water current, by renewing the supply of food adjacent to 
the inhalant siphon, is known to influence the intake of food in bivalves and hence their 
growth rate. However, the maximum tidal flux is roughly quadri-, not semi-diurnal, though ebb 
and flood currents are not always equal, especially near shore in narrow channels where counter 
eddies are frequent 

A 3rd possibility exists, namely that a persistent endogenous rhythm causes regular phases of 
growth and rest in the activity of the shell secreting epithelium. In the intertidal zone these 
phases might normally be entrained by periods of emersion, but when continuously immersed, 
they might display their own innate rhythm. Such a theory would explain the persistence of 
regular banding in shells from low water mark. 

It is interesting that a similar persistence of weak growth bands was found by Bourget & 
Crisp (1975b) in barnacles grown on a raft or under continuous immersion in the laboratory. 
These authors also were forced to entertain the possibility of an endogenous rhythm in shell 
growth. 

ACKNOWLEDGEMENTS 

We thank the workshop staff. Marine Science Laboratories and the Zoology Department, 
U.C.N.W., for constructing the apparatus, and Mr. D. Williams for preparing the photo- 
micrographs for publication. Dr. LI.D. Gruffydd, Mr, A. R. Beaumont, Messrs. J. Pratt and M. 
Budd of the NERC Unit gave help and advice and supplied large quantities of algal cultures to 
maintain the animals. Dr. Howells, Deputy Regional Officer, Nature Conservancy Council, 
North Wales, kindly granted access to Traeth Melynog. One of us (CR.) worked under a post- 
graduate studentship from Science Research Council. 

LITERATURE CITED 

BARKER, R. M., 1964, Microtextural variation in pelecypod shells. Malacologia, 2: 69-86. 

BOURGET, E. & CRISP, D. J., 1975a, Factors affecting deposition of the shell in Balanus balanoides (L.). 

Journal of the Marine Biological Association of the United Kingdom, 55: 231-249. 
BOURGET, E. & CRISP, D. J., 1975b, An analysis of the growth bands and ridges of barnacles shell plates. 

Journal of the Marine Biological Association of the United Kingdom, 55: 439-461. 
CLARK, G. R. II, 1968, Mollusk shell: daily growth lines. Science, 161: 800-802. 
CLARK, G. R. II, 1975, Periodic growth and biological rhythms in experimentally grown bivalves. In: 

ROSENBERG, G. D. & RUNCORN, S. K., Growth rhythms and the history of the earth's rotation: 

103-117. John Wiley & Sons, London. 



290 PROC. SIXTH EUROP. MALAC. CONGR 

CRISP, D. J. & RICHARDSON, C. A., 1975, Tidally produced internal bands in the shell of Elminius 

modestus (Darwin). Marine Biology, 33: 155-160. 
DAVENPORT, С В., 1938, Growth lines in fossil pectens as indicators of past clirлates. Journal of 

Paleontology, 12: 514-515. 
DOLMAN, J., 1975, A technique for the extraction of environmental and geophysical infoгrлation from 

growth records in invertebrates and stromatolites. In: ROSENBERG, G. D. & RUNCORN, S. K., Growth 

rhythms and the history of the earth's rotation: 191-222. John Wiley & Sons, London. 
EVANS, J. W., 1972, Tidal growth increments in the cockle Clinocardium nuttalli. Science, 176: 416-417. 
EVANS, J. W., 1975, Growth and micromorphology of two bivalves exhibiting non-daily gorwth lines. In: 

ROSENBERG, C. D. & RUNCORN, S. K., Growth rhythms and the history of the earth's rotation: 

119-134. John Wiley & Sons, London. 
FARROW, G. E., 1971, Periodicity structures in the bivalve shell: experiments to establish growth controls in 

Cerastoderma edule from the Thames estuary. Palaeontology, 14: 571-588. 
HOUSE, M. R. & FARROW, G. W., 1968, Daily growth banding in the shell of the cockle, Cardium edule. 

Nature, 219: 1384-1386. 
KENNY, R., 1977, Growth studies of the tropical intertidal limpet Acmaea antillarum. Marine Biology, 39: 

161-170. 
PANNELLA, G., 1975, Palaeontological clocks and the history of the Earth's rotation. In: ROSENBERG, G. 

D. & RUNCORN, S. K., Growth rhythms and the history of the earth's rotation: 253-283. John Wiley & 

Sons, London. 
PANNELLA, G. & MACCLINTOCK, С, 1968, Biological and environmental rhythms reflected in molluscan 

shell growth. Journal of Paleontology Memoirs, 42: 64-80. 
PETERSEN, G. H., 1958, Notes on the growth and biology of different Cardium species in Danish brackish 

water areas. Meddelelser fra Danmarks Fiskeri- og Havundersdgelser, N. S., 2, 22: 1-31. 
RHOADS, D. C. & PANNELLA, G., 1970, The use of molluscan shell growth patterns in ecology and 

paleoecology. /.егЛэ/э, 3: 143-161. 
RUNCORN, S. K., 1964, Changes in the earth's moment of inertia. Nature, 204: 823-825. 
WELLS, J. W., 1964, Coral growth and geochronometry. Nature, 197: 948-950. 
WHEELER, A. P., BLACKWELDER, P. L. & WILBUR, K. M., 1975, Shell growth in the scaWop A rgopecten 

irradians. I. Isotope incorporation with reference to diurnal growth. Biological Bulletin, 148: 472-482. 
WHYTE, M. A., 1975, Time, tide and the cockle. In: ROSENBERG, G. D. & RUNCORN, S. K., Growth 

rhythms and the history of the earth's rotation: 177-189. John Wiley & Sons, London. 



MALACOLOGIA, 1979, 18: 291-296 

PROC. SIXTH EUROP. MALAC. CONGR. 

WHAT IS THE FUNCTION OF THE SHELL ORNAMENTATION OF 
TELLINA FABULA GMELIN? 



James G. Wilson 

Zoology Department, The University, Glasgow G 12 8QQ, Scotland; 
present address Zoology Department, Trinity College, Dublin 2, Ireland 

ABSTRACT 

Tellina fabula Gmelin is unique amongst the European Tellinidae in the possession of 
diagonal striae on the surface of the right valve only. What purpose this ornamentation 
serves is unclear. Scanning electron micrographs revealed that the striae consist of a series 
of flat ridges overlapping from anterior to posterior. They were not observed on the early 
stages of the shell and became prominent only after the first growth ring. The striae 
appeared to originate from the concentric rings on the shell and there was a significant 
correlation between the number of striae and the length of the valve. However, there was 
no correlation between the number of striae and the weight or the thickness of the valve. 
There was no significant difference in the weight of right and left valves. It is unlikely, in 
view of the burrowing behaviour and life position adopted by T. fabula that the striae 
assist directly in burrowing, but it is possible that they strengthen the right valve against 
the stresses set up by the contraction of the pedal musculature. Other possible 
explanations of the presence of striae such as predator deterring, animal orientation in a 
current, or retention of a primitive ancestral condition, are also discussed. 

INTRODUCTION 

The possession of oblique striae on the valves is by no means common in the Tellinidae 
(Table 1). Exceptions to this rule occur in tropical members of the subgenus Scissula and the 
genus Strigilla in which most species have striations on both valves (Moore, 1969; Stanley, 
1970; Keen, 1971). 

Tellina fabula is exceptional in that not only is it the sole British tellin with striae (Tebble, 
1966) but also the striae occur on one valve, the right valve, only. What purpose this 
ornamentation could serve was unclear, so this present study was set up to investigate the 
morphology of the striae by means of the scanning electron microscope (SEM) and to attempt 
to relate morphology to possible function. 

METHODS 

Specimens were obtained from a site 6.0 m below Chart Datum in Kames Bay, Millport, 
Scotland. The valves were cleaned by removing the flesh in boiling NaOH solution (Rees, 1950) 
and washing in distilled water. 

TABLE 1 . Number of tellinid species with or without diagonal striae on one or both valves. 
Number with striae Number without striae References 



1* 9 Wood (1848-1882) 

!• 3 Br(¿gger (1901) 

3 23 Allan (1950) 

1« 11 Heering(1950) 

4 Ockelmann (1958) 

1» 8 Tebble (1966) 

14 73 Moore (1969) 

3 15 Stanley (1970) 

14 60 Keen (1971) 

»r. fabula 

(291) 



292 PROC. SIXTH EUROP. MALAC. CONGR. 

For the SEM 12 valves (1 left valve and 11 right valves, of varying sizes) were nnounted on a 
metal stub and shadowed with gold. 

A further 28 specimens were chosen for size and weight analysis. The left and right valves 
were weighed on a microbalance, and the length (L) and breadth (B) of the right valve only was 
noted. The number of striae on the right valve were counted at the extreme edge of the valve. 
An estimation of the thickness (T) of the right valve was obtained in the following way. The 
valve was assumed to be elliptical in shape and of density (D) of 2.80 g/ml (Taylor & Hayman, 
1972; Currey, 1975). Then, since 

Weight (W) = D X 5^ LB X T 1 



T = 



4 
4W 



2.80 n LB 



The T values obtained approximated to the "mean" thickness obtained by direct measurement 
by Trueman (1942) for the closely related Tellina tenuis. 

Least squares regression analysis (Bailey, 1959) was used to test for correlation between the 
number of striae and the length of the valve; number of striae and logio weight of the valve; 
and number of striae and thickness of the valve. The Sign Test (Siegel, 1956) was used to 
compare the weights of right and left valves. 

RESULTS 

Figs. 1 and 2 are the left and right valves respectively of the same specimen of T. fabula: 
the diagonal striae on the right valve can be clearly seen. 

At higher magnification (Fig. 3), the striae are revealed as a series of flat ridges of constant 
height, overlapping from anterior to posterior. The striae did not seem to be present on the 
early stages of the valve. They became prominent only after the 1st growth ring, and appeared 
to originate from the concentric rings (Fig. 4). Occasionally they did not originate from a 
concentric ring (Fig. 5) or they disappeared at a growth ring (Fig. 6). The angle of approach of 
the striae to the edge of the shell was altered not only at the edge itself (Fig. 2), but also at 
the growth rings (Fig. 6), although the striae subsequently resumed their previous angle after 
each ring. There was also evidence of distortion of the striae around areas of damage (Fig. 7). 

Size and weight analysis (Table 2) revealed that there was a significant correlation between 
the number of striae and the length of the valve (Fig. 8, Table 3), although there may be 
appreciable variation in the number of striae on valves of the same length (Table 2, animal no. 
8 and animal no. 10). However, there was no significant correlation between the number of 
striae and the logio weight of the valve or the number of striae and the thickness of the valve 
(Table 3). There was no significant difference [P = 0.38 (Siegel, 1956)] in the weight of left 
and right valves (Table 2). 

DISCUSSION 

The ridges of the striae have their edges aligned roughly at an angle of 45° to the 
anterior/posterior axis, and are consequently at right angles to the line of penetration when the 
animal is burrowing (Trueman et al., 1966). This results in a "ratchet" profile being presented 
to the sand. The striae of Tellina similis, of similar shape and orientation to those of T. fabula 
but present on both valves, are thought to aid the animals' burrowing by the "ratchet" 
alternately gripping and sliding through the sediment (Stanley, 1970). In theory, then, the right 
valve of T. fabula should go down faster than the left, until the animal lies horizontal in the 
sand on its right valve. In fact, like most of the Tellinidae, T. fabula burrows at an angle with 
the right valve uppermost, and eventually lies in the sand in a near horizontal position on its 
left valve (Holme, 1961). 

This preference for burrowing at an angle may result in an unequal stress on the valves, and 
the striae are therefore required to strengthen the right valve. It has been suggested by other 
workers that the ribs on mollusc shells provide strength with economy of material (Stanley, 



WILSON 



293 






7 .^«á 




FIGS. 1-7. ТеШпа fabula. 1. Left valve, ca. X17. 2. Right valve, showing striae, ca. X17. 3. Close-up of 
striae, showing shape, ca. X560. 4. Origin of striae (arrowed), ca. X68. 5. Origin of a stria between concentric 
rings (arrowed), ca. XI 40. 6. Disappearance of striae at growth rings (arrowed) showing also change of angle, 
ca. X68. 7. Distortion of striae around an area of damage, ca. X34. 



294 



PROC. SIXTH EUROP. MALAC. CONGR. 



50- 



CO 



30 



10- 



4.0 



6.0 



8.0 1 0.0 

LENGTH (mm) 



12.0 



FIG. 8. Tellina fabula, number of striae versus length of right valve. For equation of line see Table 3. 



TABLE 2. T. fabula. Number of striae, length (L) and breadth (B) of right valve, weight of left (LV) and 
right (RV) valves and thickness (T) of right valve. 



Animal 


Number of 
striae 


L (mm) 


В (mm) 




W(m) 




number 


LV 


RV 


Т(дт) 


1 


24 


12.3 


7.8 


29.35 


28.97 


137.24 


2 


36 


10.5 


6.4 


17.27 


17.90 


121.08 


3 


39 


9.6 


6.1 


12.28 


12.40 


96.34 


4 


34 


9.0 


5.5 


11.14 


11.49 


105.28 


5 


33 


9.0 


5.7 


10.48 


10.58 


93.64 


6 


35 


8.7 


5.3 


9.33 


9.02 


88.92 


7 


29 


8.7 


5.6 


8.90 


9.01 


84.04 


8 


48 


8.5 


5.2 


9.58 


9.46 


97.28 


9 


36 


8.5 


5.3 


8.59 


8.49 


85.68 


10 


24 


8.5 


5.3 


8.61 


8.57 


86.48 


11 


42 


8.3 


5.1 


8.46 


8.38 


90.00 


12 


26 


8.2 


5.0 


7.54 


7.61 


84.36 


13 


42 


8.1 


5.0 


8.29 


8.58 


96.28 


14 


39 


8.1 


5.2 


8.65 


8.56 


91.72 


15 


38 


8.0 


5.0 


8.29 


8.75 


99.44 


16 


33 


8.0 


5.1 


9.38 


8.09 


90.12 


17 


36 


7.9 


4.8 


7.01 


7.10 


85.12 


18 


40 


7.9 


5.0 


8.24 


7.58 


87.24 


19 


36 


7.8 


45 


6.75 


6.81 


81.00 


20 


29 


7.8 


4.9 


7.42 


7.43 


86.00 


21 


43 


7.2 


4.7 


5.66 


5.85 


78.60 


22 


28 


7.1 


4.4 


5.80 


5.64 


82.08 


23 


36 


7.1 


4.5 


5.30 


5.60 


79.68 


24 


29 


6.9 


4.4 


4.69 


4.74 


70.96 


25 


33 


6.6 


4.1 


4.76 


4.76 


79.96 


26 


32 


6.5 


4.1 


4.38 


4.24 


72.32 


27 


28 


6.0 


3.6 


3.44 


3.56 


74.92 


28 


21 


4.0 


2.8 


1.14 


1.16 


47.08 



WILSON 295 

TABLE 3. T. fabula. Regression analysis (Bailey, 1959) of number of striae versus: (a) length of right valve; 
(b) logj weight of right valve; (c) thickness of right valve. 

Plot r t P Equation 

V = 21.64 + 1.63x 



a 


0.40 


2.68 


0.01 


b 


0.27 


1.44 


0.16 


с 


0.22 


1.13 


0.27 



1970; Boltovskoy, 1974). However, there is no direct evidence to suggest that the striae are 
compensating for lack of strength in the right valve. In addition, it is unlikely that the stress on 
the right valve would be so much greater than on the left (Wainwright, 1969), and nothing 
similar has been reported in other asymmetric Tellinidae which burrow in the same manner 
(Holme, 1961). Lever (1958), from the evidence of differential sorting of right and left valves 
of T. fabula on the beach, postulated that the striae made the right valve more solid than the 
left and that the valves differed in weight. However, Table 2 shows that this is not so, and the 
differential sorting may be due to the respective left- and right-handedness of the valves or to 
the effect of the striae on the movement of the right valve in a current. 

The possibility that the ornamentation affects the transport and subsequent orientation of a 
live animal into a favourable position for rapid re-burrowing, for example if it had been washed 
out of the sand by wave or current action, is remote. Firstly, the sublittoral habitat of T. 
fabula is not one which is exposed to strong current or wave action, and secondly, the 
orientation of T. fabula within the sediment is completely random, which one might not expect 
had the animals been lined up by a current. 

The texture of the shell does not appear to affect prédation by gastropods which manipulate 
the bivalve in their foot before boring. Ansell (1960), working in Kames Bay itself, reported no 
selection by Natica alder! either for or against T. fabula compared to other bivalves. 

The striations do not seem to be a retention of a primitive or ancestral characteristic in 
which striations present on both valves aided burrowing. Firstly, there is no evidence to suggest 
that the condition was any more common in the past than in the present (Wood, 1848-1882; 
Heering, 1950; Moore, 1969) and secondly one is still faced with the problem as to why the 
striae should have been lost from one valve only. 

Wigham (1975) correlated the shell form of Rissoa parva with environmental conditions, but, 
in assessing the extent of environmental influence on the forms of the right valve of T. fabula, 
it must be remembered that animals of the same size (and presumably age) from the same 
square metre of a homogenous environment, had a 2-fold difference in the number of striae. 
The absence of striae from the early stages of the shell does not necessarily mean that they 
were not present in the young T. fabula. The umbonal region of all the specimens was 
considerably worn, that is the striae may have been rubbed off and the fine detail of the larval 
shell lost (Fretter & Pilkington, 1971). Nevertheless, neither Rees (1950) nor Newell & Newell 
(1963) mention striae on the larval T. fabula shell. In other bivalves, such as Donax (A. D. Ansell, 
Dunstaffnage Marine Research Laboratory, personal communication) or Cardium (Van Benthem 
Jutting, 1943), the ornamentation does not develop until the adult shell is deposited. It was 
also noticeable that the striae altered shape at the growth rings, that is under conditions of slow 
or nil growth and that they were considerably distorted around previously damaged areas. It is 
therefore suggested that the deposition of the striae and the main shell are interlinked. 

ACKNOWLEDGEMENTS 

The work was carried out at the Zoology Department, University of Glasgow, during the 
tenure of a Robert Donaldson Scholarship and a Faculty of Science Research Grant. I should 
like to thank Dr. P. E. P. Norton and Mr. P. S. Meadows for much helpful advice and criticism 
and Miss С O'Byrne for typing the manuscript. 



296 PROC. SIXTH EUROP. MALAC. CONGR. 

SUMMARY 

(1) The striae are a series of oblique flat ridges running toward the posterior end of the 
animal. Their numbers increase roughly with size, but they are not visible on the early 
prodissoconch stages of the valve. It is suggested that deposition of the striae is under the same 
control as overall shell growth and hence may be subject to environmental influence. 

(2) The function of the striae is unclear, but they do not seem to aid directly in burrowing, 
or to facilitate reburrowing by affecting the animal's orientation if washed out of the sand, or 
to deter predators, or to be a retention of an ancestral character. The most reasonable 
hypothesis is that they may strengthen the valve against the stresses set up in burrowing. 

LITERATURE CITED 

ALLAN, J., 1950, Australian shells. Georgian House Ltd., Melbourne, 470 p. 

ANSELL, A. D., 1960, Observations on prédation of Venus striatula (Da Costa) by Natica aider! (Forbes). 

Proceedings of the Malacological Society of London, 34: 157-164. 
BAILEY, N. T. J., 1959, Statistical methods in biology. Universities Press Ltd., London, 200 p. 
BOLTOVSKOY, D., 1974, Study of surface-shell features in Thecosomata (Pteropoda: Mollusca) by means of 

the scanning electron microscope. Marine Biology, 27: 165-180. 
BROGGER, W. C, 1901, Om de senglaciale og postglaciale nivaforandringer i Kristianiafeitet (Mollusk- 

faunan). Norges Geologiske Unders'ógelse, 31: 1-731. 
CURREY, J. D., 1975, A comparison of the strength of echinoderm spines and mollusc shells. Journal of the 

Marine Biological Association of the United Kingdom, 55: 419-424. 
FRETTER, V. & PILKINGTON, M. C, 1971, The larval shell of some Prosobranch gastropods. Journal of 

the Marine Biological Association of the United Kingdom, 51: 49-62. 
HEERING, J., 1950, Pelecypoda (and Scaphopoda) of the Pliocene and older Pleistocene deposits of the 

Netherlands. Mededelingen van de Geologische Stichting, (С), IV-I, 9: 1-225. 
HOLME, N. A., 1961, Notes on the mode of life of the Tellinidae (Lamellibranchia). Journal of the Marine 

Biological Association of the United Kingdom, 41: 699-703. 
KEEN, A. M., 1971, Sea shells of tropical West America. Stanford University Press, California, 1064 p. 
LEVER, J., 1958, Quantitative beach research. 1. The "left-right phenomenon": sorting of lamellibranch 

valves on sandy beaches. Basteria, 22: 21-51. 
MOORE, R. C, ed., 1970 sqq., Treatise on Invertebrate Paleontology. Geological Society of America and 

University of Kansas Press, Lawrence, Kansas, 8 vols. 
NEWELL, G. E. & NEWELL, R. C, 1963, Marine Plankton. A practical guide. Hutchinson Educational Ltd., 

London, 221 p. 
OCKELMANN, K. W., 1958, The zoology of East Greenland. Marine Lamellibranchiata. Meddelelser от 

Grönland, 122(4): 1-257. 
REES, С. В., 1950, The identification and classification of bivalve larvae. Hull Bulletins of Marine Ecology, 

3: 73-104. 
SIEGEL, S., 1956, Non-parametric statistics for the behavioural sciences. McGraw-Hill Kogakusha Ltd., 

Tokyo, 312 p. 
STANLEY, S. M., 1970, Relation of shell form to life habits of the Bivalvia (Mollusca). Memoirs of the 

Geological Society of America, 125: 1-296. 
TAYLOR, J. D. & LAYMAN, M., 1972, The mechanical properties of bivalve (Mollusca) shell structures. 

Palaeontology, 15: 73-87. 
TEBBLE, N., 1966, British bivalve seashells. Trustees of the British Museum (Natural History), London, 212 p. 
TRUEMAN, E. R., 1942, The structure and deposition of the shell of Tellina tenuis. Journal of the Royal 

Microscopical Society, 62: 69-92. 
TRUEMAN, E. R., BRAND, A. R. & DAVIS, P., 1966, The effect of substrate and shell shape on the 

burrowing of some common bivalves. Proceedings of the Malacological Society of London, 37: 93-109. 
VAN BENTHEM JUTTING, T., 1943. Mollusca (I). С. Lamellibranchia. Fauna van Nederland, 12: 1-477. 
WAINWRIGHT, S. A., 1969, Stress and design in bivalved mollusc shells. Nature, London, 224: 111-11^. 
WIGHAM, G. D., 1975, Environmental influences on the expression of shell form in Rissoa parva. Journal of 

the Marine Biological Association of the United Kingdom, 55: 425-438. 
WOOD, S. v., 1848-1882, A monograph of the Crag Mollusca. Palaeontographical Society, London, 4 vols. 



MALACOLOGIA, 1979, 18: 297-313 

PROC. SIXTH EUROP. MALAC. CONGR. 

STUDIES ON THE GROWTH AND DENSITY OF THE CLAM 

PAPHIA LATERISULCA AT KALBADEVI ESTUARY, 

RATNAGIRI, ON THE WEST COAST OF INDIA 

U. H, Mane and R. Nagabhushanam 
Department of Zoology, Marathwada University, Aurangabad-431004, India 

ABSTRACT 

Age and growth of the bivalve Paphia laterisulca have been studied by the size 
frequency method from August 1973 to July 1974. The clams measure 23, 38, 47 and 
50 mm at the end of 1, 2, 3 and ЗУг years of life respectively. Length-breadth, 
length-width and length-weight ratios have been studied. Monsoon checks in the form of 
annual rings were also used in determining age. Growth is retarded during the monsoon 
due to very low salinity whereas rapid growth is observed when the salinity rises again. 
Temperature seems to have no effect on the growth rate. Baby clams reach sexual 
maturity after attaining a length of 16-18 mm. The clams appear to breed from 
September to March with 2 peaks: November and March. Spawning intensity appears to 
slow down from December to February. The density of zero age clams (under 1 year old) 
is less in late summer than post monsoon. The density is high in between mid and low 
water marks. A marked decrease in zero age and marketable sized (over 37 mm shell 
length) clams is observed in the monsoon and is due to unfavourable environment. The 
density of marketable clams is high at the western side and less so at the eastern side of 
the estuary; it is also high in the middle part of mid and low water marks with a 
considerable decrease towards high water mark. Preference for intertidal substratum is 
muddy rather than sandy. Comparisons are made with other shellfish from the Indian 
coast. 

INTRODUCTION 

Though nnany species of commercially important bivalves occur along the Indian coast, little 
attention was paid by past workers to various aspects of growth, despite the fact that this field 
offers a large number of unanswered problems. Amongst these species of bivalves, clams have 
received some attention for the study of growth (Durve, 1970; Deshmukh, 1972; Mane, 1973). 
None of the observations made thus far was directed to the study of the growth and density of 
populations during each month of the year of the clam Paphia laterisulca. 

P. laterisulca is an estuarine bivalve of considerable commercial importance and occurs 
abundantly on the west coast of India. Any biological study of this species will therefore be of 
interest from a scientific and also a fisheries point of view. In several markets of the coastal 
towns and villages of the Ratnagiri district this clam finds a ready sale, as the people there have 
developed a taste for them, unlike those of most other regions of India. This clam is also in 
great demand as fish bait for long lines and this demand is no less important than that of 
human food. Kalbadevi, one of the estuaries along Ratnagiri (3 km northwest of the city) has 
been a clam fishing centre for many years and as it is within reach of several economically 
important shellfish beds, it was chosen as a suitable location to carry out the work (Fig. 1). The 
study was undertaken with a view to understanding the biology of the species in the hope that 
a fuller knowledge will be of help in the development and conservation of this valuable clam 
fishery, 

MATERIALS AND METHODS 

Growth rate 

Beach screenings to determine the time of settling of baby clams, the size and growth of the 
various year classes were carried out throughout the year from August 1973 to July 1974. The 
rate of growth was determined by the size frequency method. The length of the clam was used 

(297) 



298 



PROC. SIXTH EUROP. MALAC. CONGR. 




FIG. 1. Sketch map of the Ratnagiri coast showing Kalbadevi estuary. Scalloped lines indicate location of 
clam beds {Paphia laterisulca). 

as a standard measure for determining the age. The data were arranged in size groups at class 
intervals of 3 mm. The 2 fortnightly samples were combined and converted into percent 
frequencies and represented separately for the monthly samples. The shifting of the mode 
values of different groups for each month formed the basis for interpretation of growth rate of 
different year classes. 

Relationships 

From October, 1973 to January, 1974 the clams of all size ranges from 15 to 56 mm were 
collected and preserved in 5% formalin in sea water. These were then grouped at 3 mm 
intervals. All the linear dimensions such as length, breadth and width were measured following 
the method adapted by Abraham (1953). Length-breadth, length-width and length-weight ratios 
of 1979 clams were determined. For length-weight ratios, the preserved clams were dried on 
blotting paper and weighed. The larger clams were individually weighed but the smaller clams 
from the same length groups were weighed together and the average weight of the individual 
was calculated. 



MANE AND NAGABHUSHANAM 



299 



Growth rings 

The study on the growth rings was based on the method used by Weymouth et al. (1925), 
At Kalbadevi estuary, the clams show pronounced annual monsoon checks and regular sampling 
has shown that they can be considered as annuli. Those clams with rings which were difficult to 
read amounted to less than 10% of the samples and were discarded. The clams of population 
estimates of 1973-74 were retained and the distance between the monsoon rings measured to 
the nearest mm. 

Size at sexual maturity 

Periodic collections of clams of up to 24 mm shell length were made at Kalbadevi estuary 
and the clams were divided into 2 mm shell length groups. The gonads were removed, preserved 
in aqueous Bouin's fluid in sea water and histological slides prepared from the centre of the 
gonad were studied for stages. 

Time of spawning 

Adult clams were collected from the estuary in each month during the year August 
1973-July 1974. The 'heel' section of the gonad was preserved in 10% formalin in sea water 
and the stage of the gonad development was determined from examination of smears. 

Hydrographie conditions 

Salinity and temperature of the sea water over the clam bed were recorded monthly at 10 
day intervals during the study period. As these observations were based on mean monthly 
samples they could give only a general idea of the hydrographie conditions over the clam bed. 



H.W.M 



l5Ft 
l¿Ft 

15Ft 

15Ft 

-*- 
I 



30 Ft 

t 
I 
I 



-•-•■ 



M 

-о 



• • 



• • 



V 

3 Ft 



О 

I 
I 



I 
I 

I 

г 

lb 

о 

4 



L.W. 

-4 



S. 



FIG. 2. Schematic diagram of transects used to assess zero age clam populations in the clam beds 
Kalbadevi estuary. 



300 



PROC. SIXTH EUROP. MALAC. CONGR. 



Density of zero age clams 

Beach screenings to determine the strength of the incoming year classes were carried out in 
November and December 1973 and April, May, July and August 1974 at the western part of 
the estuary. Samples were taken randomly from the sections of transects established to estimate 
the population size of the clams on the clam bed as established in the schematic diagram (Fig. 
2). Each time screening was undertaken and samples were taken at regular intervals along the 
transects from low water tide line to the mid-intertidal zone. Almost no samples were taken 
above the mid-intertidal zone since no clams of zero age occur there. All samples were washed 
through 1 mm mesh screen, the small clams were separated and their lengths were measured to 
the nearest mm. 

Density of adult clams (above 37 mm shell length) 

Beach screenings as shown in Fig. 2 to measure the density of 2nd and 3rd year classes were 
carried out in July, August, October and November 1973 and January, February, April and 
May 1974. The collections were made with a 'Sand Pipper' (Fig. 3) which samples an area of 
116 sq. cm to a depth of 20 cm. The number of sand pipper samplings (4) was kept constant 
irrespective to the density of the clams on the clam bed. At every time of sampling, the 
samples were taken from the transect established vertically in 15 ft width of the western part 
of the estuary and the sampling was done at a 5 ft interval from the low water mark vertically 
up. In October and November some additional sampling was done throughout the estuary from 
the middle part of the mid and low water mark at 15 ft width (Fig. 4) at intervals of 20 ft. 



RESULTS 



Growth rate 



Spawning in P. laterisulca at Kalbadevi estuary starts by mid-September and lasts to the end 
of March, as revealed by the successive examinations of the gonadial conditions in the adult 




A o- 



WEST 
SEA 

SIDE 




ÍTT|Í№ 

III l|ll|le 

i|iil|i|r 

It 



HW.M 



EAST 

RIVER 
SIDE 



J M^M 



11 II III l|î 



illiilüi! 



т 
I 

_i t-wm 



FIG.3. Sand Pipper for clam FIG. 4. Schematic diagram of transects used to assess adult clam populations in 
digging. the clam beds in Kalbadevi estuary. 



MANE AND NAGABHUSHANAM 301 

groups of clams. This spawning has 2 peaks— in November and in March. Juvenile clams 
appeared in December and May. As the spawning in this clam occurs for бУг months, there 
appears to be a lot of masking effect on the adult groups of clams growing in different months 
and hence for the interpretation of different modes throughout the year. It was therefore 
necessary to follow separately the growth of clams born during the peak spawning periods, 
'November born' and 'March born' clams. For the sake of convenience to express the rate of 
growth of the different year classes of clams, the different modes in the graph are denoted by 
A, B, C, D and a, b, c, d, e for November and March born clams respectively as was done by 
Mane (1973) for Katelysia opima. The letters used in the present study belong to the following 
year classes. 

A— November born 1970 a- March born 1970 

B— November born 1971 b— March born 1971 

C- November born 1972 c- March born 1972 

D-November born 1973 d-March born 1973 

e— March born 1974 

In August 1973 seven modes appeared. The mode at 8 mm represents the year class 'd/ the 
mode at 20 mm represents the year class 'C,' the mode at 26 mm represents the year class 'c,' 
the mode at 32 mm represents the year class 'B,' the mode at 41 mm represents the year class 
'b,' the mode at 44 mm represents the year class 'A' and the mode at 50 mm represents the 
year class 'a.' In September 1973 seven modes appeared at 11 mm, 20 mm, 26 mm, 32 mm, 
41 mm, 44 mm, and 50 mm. Thus except for the growth of year class 'd' all other year classes 
persisted at the same modes showing no growth. In October 1973 also 7 modes appeared, 
wherein only the modes of year classes 'c,' 'B' and 'A' have shifted to 29 mm, 35 mm, and 
50 mm, respectively. In the year classes 'd,' 'C,' 'b' and 'A' showed no growth. The year class 
'd' has now completed 6 months of life showing a growth of 11 mm and the year class 'a' at 
50 mm has now completed ЗУ2 years of life. In November 1973 the year class 'd' has shifted to 
14 mm, 'B' has shifted to 38 mm and 'A' has shifted to 47 mm. The rest of the year classes 
showed no growth. The year class 'C has completed its 1 year age and has grown to 23 mm 
whereas the year classes 'B' and 'A' have completed their 2nd and 3rd year of life, respectively 
showing growth of 38 mm and 47 mm, In December 1973 year class 'D' has made its 
appearance for the first time at 5 mm mode which was born in the post monsoon of 1973, The 
year classes 'C,' 'c' and 'b' have now grown to 26 mm, 32 mm and 44 mm, respectively. The 
year class 'A' showed no growth. In January 1974 the year class 'D' has shifted to 8 mm and 
the mode of year class 'D' reappeared at 17 mm. The year classes 'C,' 'c' and 'B' have appeared 
at 29 mm, 35 mm and 41 mm modes, respectively. No growth took place in the year classes 'b' 
and 'A.' In February 1974 only the young clams of the year classes 'D' and 'd' have shown a 
growth and appeared at 1 1 mm and 20 mm, respectively whereas the year classes 'C,' 'c,' 'B,' 'b' 
and 'A' showed no growth. In March 1974 five modes appeared at 11 mm, 23 mm, 38 mm, 
41 mm and 47 mm. Thus, year classes 'd,' 'c' and 'b' showed a growth of 3 mm within a month 
and have now completed their 1st, 2nd and 3rd year of life, respectively and appeared at the 
modes 23 mm, 38 mm and 47 mm, respectively. These are the clams born in the early summer 
spawnings of 1973, 1972 and 1971, respectively. The year classes 'D' and 'B' showed no 
growth. In April 1974 the clams of the year classes 'D,' 'B' and 'A' appeared at modes 14 mm, 
44 mm and 50 mm, respectively. No growth occurred in the year classes 'C and 'c' In May 
1974 newly born clams of the year class 'e' appeared at 5 mm mode which have been born in 
the early summer of 1974. A growth of 3 mm has now taken place in the year class 'd' 
appeared at the mode of 26 mm and the year classes 'D' and 'c' appeared at the modes of 
17 mm and 41 mm, respectively. The modes of the year classes 'C,' 'B' and 'A' remained at 
29 mm, 44 mm and 50 mm, respectively. Thus, it can be seen that the year class 'A' has now 
completed ЗУ2 years of life by appearing at the mode of 50 mm. In June 1974 young clams of 
year classes 'e' and 'D' have now grown to 8 mm and 20 mm, respectively. The year class 'C 
appeared at the mode of 32 mm. No growth occurred in the year classes 'd,' 'c,' 'B' and 'A.' In 
July 1974 no growth occurred in the young clams of the year classes 'e' and 'D.' The year 
classes 'd,' 'C/ 'c' and 'A' also showed no growth and persisted at the same modes (Fig. 5). 

Thus, from the foregoing it appears that P. laterisulca spawns from post monsoon to early 
summer, the peak being in November and March. The growth of post monsoon and early 



302 



PROC. SIXTH EUROP. MALAC. CONGR. 




15 30 

LENGTH IN MM 



FIG. 5. Frequency distribution of clams. 



MANE AND NAGABHUSHANAM 



303 








ILàl 






^¡^^ß 











FIG. 6. Paphia laterísulca of 12-47 mm shell length. 

summer born clams in the 1st, 2nd and 3rd and also ЗУ2 years Is similar and sizes attained are 
23 mm, 38 mm, 47 mm and 50 mm respectively. However, the growth in the first 6 months of 
post monsoon born clams (17 mm) is more than the growth of early summer born clams 
(11 mm) giving a difference of 6 mm. From this study it can be inferred that the clams born in 
early summer are faced with a period of comparatively retarded growth in the monsoon and 
therefore grow only to 1 1 mm, but growth in the later periods becomes accelerated and in the 
next 6 months they complete their 1st year of life representing a growth of 23 mm. However, 
the clams born in the post monsoon are initially favoured with a period of active growth; much 
rapid growth occurs before the monsoon and they grow to a size of 17 mm in the first 6 
months but thereafter for the next 6 months growth takes place at a slow rate representing a 
growth of 23 mm during the 1st year of life. The clams of the various sizes ranging from 
12 mm to 50 mm are shown in Fig. 6. 

Linear relationships 

In Fig. 7 the observed and calculated values of breadth and width are plotted against their 
respective lengths. All points for the breadth and width are more or less closely located near 
the fitted lines of regression. Equation for the regression line was used for the expression of 
length-breadth and length-width relationships in terms of calculated values i.e. Y = a + bX 
where X = length, Y = greadth or width and a and b are constants. Using this equation the 
following relationships were established— for length-breadth Y = 1.682 + 0.6636X and for 
length-width Y = -1.299 + 0.5237X. 

The observed and calculated weights of the clams against their respective lengths are plotted 
in Fig. 8. The points closely agree with the calculated weights. Using the formula W = aLb the 
following relationships was established — W = 0.0003758L2 853 or log W = -3.224 + 2.724 log L. 

Annuli (rings) measurements 

Use of this method to determine age and growth of clams depends upon whether annuli are 
formed and whether they are distinguished on the surface of the shell. Most of the clams from 
Kalbadevi estuary have pronounced annuli. Evidence to support the view that they were indeed 



304 



PROC. SIXTH EUROP. MALAC. CONGR. 




40 
SHELL LENGTH 



IN MM 



FIG. 7. Length-breadth and length-width relationships of the clam. 



annuli was obtained by measuring the dominant year classes which settled during 1970-73. 
From the data presented in Table 1 it is clear that the occurrence of rings over the shells 
determine the age of the clams. The distance from first ring to umbo is more or less uniform in 
2 and 3 year old clams. Similarly these distances between the 2nd ring and umbo and 3rd ring 
and umbo are correspondingly uniform in 2 and 3 year old clams. In the clams between 47 mm 
and 51 mm length 3 rings are present. From the evidence of size frequency figures the clams of 
this size have completed 3 years of life. The clams from 38 mm to 42 mm in length have 2 
rings and are over 2 years old but have not completed 3 years age. The clams from 23 mm to 
29 mm in length have only 1 ring and are over 1 year old but have not completed their 2nd 
year of life. The respective distances from 1st, 2nd and 3rd ring from the umbo are 16 mm, 
26 mm and 32 mm, i.e. these rings were formed when the clams were 16 mm, 26 mm and 
32 mm in breadth. From the fitted regression line of the length-breadth curve, it can be seen 
that at breadth of 16 mm, 26 mm and 32 mm, the lengths of the shells are 22 mm, 37 mm 
and 46 mm, respectively. These lengths nearly correspond to the year class ages of the clams. It 
has already been shown that the growth in the monsoon is arrested in all year classes. Thus the 
results show that the annuli are formed during the monsoon every year; they may be called 
'monsoon checks' or 'monsoon annuli.' 

Growth of the clams is faster in post monsoon born clams than early summer born clams 
but the formation of annuli 1 to 3 is similar for all classes in post monsoon and early summer 
born clams. 



MANE AND NAGABHUSHANAM 



305 




40 
LENGTH IN MM 

FIG, 8. Length-weight relationship of the clams. 



Size at sexual maturity 

This study determined tine size at which the clams become sexually mature for the first 
time. Three categories were used to describe the stage of sexual maturity based on histological 
preparations. Stage I is undifferentiated, wherein there is no differentiation of sex and the 
gonad contains only loose vesicular connective tissue. Stage II is differentiated, wherein the 
gonad is in immature stage with well developed connective tissue and ramification of the 
follicles with ciliated ducts is seen. Some primary germ cells on the follicle wall are also 
observed. Stage III is developing and maturing eggs and sperm are seen. 

The data are somewhat limited and unfortunately most of the collections were made in the 
period when the gonads of most of the adult clams are in inactive or in early part of active 
stage. It would have been more advantageous to have taken samples in December and to have 
sampled a single set as it developed to maturity. However, the data give an indication of the 
size at which the clams became sexually mature (Table 2). Clams up to 10 mm in shell length 
were in stage I and it was impossible to sex these clams. Gonads of the clams in the size group 
10 mm to 14 mm were in stage II. Only 3 clams of 14 mm to 16 mm in length were in stage II 
whereas all others were in stage III. All the clams of 17 mm and larger were in stage III. 

From the data it was concluded that the clams become sexually mature when they are 
about 16 mm to 18 mm in shell length. 



306 



PROC. SIXTH EUROP. MALAC. CONGR. 



TABLE 1. Size of P. laterisulca with position and number of rings. 





Length (mnn) 


Height (mm) 


No. of rings 


Distance of the ring from 


umbo (mm) 


Year classes 


1st ring 


2nd ring 


3rd ring 


1st 


15 


12 





_ 


_ 


_ 




17 


13 





— 


— 


— 




19 


14 





— 


— 


— 




20 


16 





— 


— 


— 




22 


16 





— 


— 


— 




23 


17 




15.5 


— 


— 




25 


18 




15.5 


— 


— 




26 


17 




16.0 


— 


— 




28 


20 




16.5 


— 


— 




29 


21 




16.5 


- 


- 


2nd 


38 


27 


2 


15.5 


25.0 


_ 




39 


27 


2 


16.0 


25.0 


— 




39 


27 


2 


16.0 


25.5 


— 




40 


28 


2 


15.5 


26.0 


— 




40 


28 


2 


15.5 


26.5 


_ 




41 


29 


2 


16.0 


26.5 


— 




42 


30 


2 


16.0 


26.5 


— 




42 


30 


2 


16.5 


26.0 


" - 


3rd 


47 


33 


3 


15.5 


25.5 


31.5 




48 


34 


3 


16.5 


25.5 


31.5 




48 


34 


3 


16.5 


26.0 


32.5 




49 


34 


3 


16.0 


26.0 


32.0 




50 


35 


3 


16.0 


26.5 


32.5 




50 


35 


3 


16.5 


26.5 


32.0 




51 


36 


3 


16.0 


26.0 


32.5 



TABLE 2. Stages of gonadal development of P. laterisulca collected at Kalbadevi, 1973-74. 





Date of collection 


No. of clams 




No. of clams in 




Size (mm) 


Stage 1 


Stage II 


Stage III 


0- 2 


2-12-'73 


16 


16 








2- 4 


4-12-'73 


14 


14 








4- 6 


8-12-'73 


11 


11 








6- 8 


5-1 -'74 


8 


8 








8-10 


8-1-74 


19 


19 








10-12 


10-4-'74 


31 





31 





12-14 


21-5-'74 


25 





25 





14-16 


28-5-'74 


10 





3 


49 3d 


16-18 


28-5-74 


17 








99 8c5 


18-20 


3-6-74 


22 








109 12d 


20-22 


8-6-74 


17 








129 5d 


22-24 


15-6-74 


13 








79 6d 



Time of spawning 

The results of the gonad smear observations of the clams are summarized in Table 3. In 
December and May, gonads were maturing and the sexes were easily distinguished. In August, 
all clams were ripe and ready to spawn. In September, many clams were ripe and some 
spawning was observed in a few clams. This spawning reached its peak in November and the 
majority of the clams spawned. From December onwards spawning intensity was lowered and 
the regeneration in the gonad started in many clams. In January the maturation process started 
and by February many clams were in ripe condition. Few clams showed acceleration in 
spawning intensity and by March it reached its 2nd peak. In April the majority of the clams 
were recovering and it was difficult to sex them. In May the sexes were identifiable and in June 
the maturation process occurred in the majority of the clams. In July the majority of the clams 
showed mature eggs and sperm which are to be released in the next season which is favourable 



MANE AND NAGABHUSHANAM 
TABLE 3. Seasonal variation in the gonadal stages of P. laterisulca during 1973-74. 



307 



















Stage 


IV: 








Stage 


II: 


Stage 


Ill 


gor 


lad almost or completely 




Stage 


1: 


gonad ripe and ready 


some spaw 


ning has 


spawned, some 


regeneration 


Date of 
collection 


gonad filling 


to spawn 


taken place 




has taken place 


9 


d 


9 


à 


9 


d 




9 


d 


12-8-'73 


1 


_ 


17 


12 


_ 


_ 










15-9-'73 


— 


— 


15 


10 


4 


2 




— 


— 


13-10-'73 


— 


— 


3 


2 


6 


1 




16 


11 


10-11 -'73 


— 


— 


— 


— 


— 


— 




18 


15 


14-12-'73 


2 


2 


— 


— 


3 


1 




9 


6 


17-1 -'74 


8 


6 


— 


— 


— 


— 




3 


2 


12-2-'74 


— 


— 


10 


7 


4 


2 




1 


— 


11-3-'74 


— 


— 


— 


— 


1 


— 




13 


9 


14-4-'74 


2 


1 


— 


— 


1 


— 




7 


4 


13-5-'74 


11 


9 


— 


— 


— 


— 




2 


— 


15-6-'74 


8 


7 


3 


2 


— 


— 




— 


— 


14-7-'74 


2 


1 


13 


11 


- 


- 




- 


- 



for spawning. Thus in Kalbadevi this clam spawns from September to March with 2 
peaks— November and March. The intensity of spawning was lowered in the winter season. 

Hydrographie conditions 

The data for salinity and temperature of sea water at Kalbadevi over the clam beds are 
shown in Fig. 9 with the fluctuations at its upper and lower limits. Salinity and temperature 
were measured at 10 day intervals during each month. Salinity considerably decreased in the 
monsoon season (June-September) due to the southwest monsoon. In 1974 the rainfall started 
at the end of June and as such there was no marked drop in salinity in this month compared to 




D J F 
MONTHS 

FIG. 9. Variation in salinity and temperature of the sea water over the clam beds August 1973 to August 
1974. 



308 



PROC. SIXTH EUROP. MALAC. CONGR. 



TABLE 4. Density and mean shell length of zero age clams at Kalbadevi, 1973-74. 





November 2-5 


Decembe 


r 12-15 


April 7-9 


May 


10-13 


July 20-23 


August 10-13 


Distance 


























from mid 




Mean 




Mean 




Mean 




Mean 




Mean 




Mean 


water 


No. of 


shell 


No. of 


shell 


No. of 


shell 


No. of 


shell 


No. of 


shell 


No. of 


shell 


mark 


clams 


length 


clams 


length 


clams 


length 


clams 


length 


clams 


length 


clams 


length 


(ft) 


/sq. ft 


(mm) 


/sq. ft 


(mm) 


/sq.ft 


(mm) 


/sq. ft 


(mm) 


/sq. ft 


(mm) 


/sq. ft 


(mm) 


10 


4 


10.5 


7 


14.5 


1 


18.0 


_ 


_ 


_ 


_ 


1 


19.0 


15 


8 


13.5 


5 


15.5 


2 


16.0 


4 


17.0 


4 


16.0 


2 


17.5 


20 


9 


12.0 


8 


11.0 


3 


13.5 


6 


15.0 


2 


17.5 


— 


— 


25 


7 


10.5 


9 


10.0 


4 


10.0 


3 


9.5 


4 


12.0 


— 


— 


30 


6 


9.5 


11 


8.5 


7 


3.0 


5 


6.0 


5 


6.5 


4 


8.5 


40 


15 


3.5 


16 


9.0 


10 


4.5 


7 


5.5 


3 


7.0 


5 


5.0 


45 


11 


4.5 


18 


6.5 


16 


8.0 


9 


12.5 


9 


5.0 


2 


7.5 


50 


20 


7.0 


17 


3.5 


11 


7.5 


17 


16.5 


5 


8.5 


6 


9.5 


55 


28 


9.5 


22 


3.0 


13 


13.5 


18 


17.5 


6 


15.0 


3 


12.0 


60 


13 


14.5 


12 


6.0 


16 


17.0 


2 


19.5 


8 


18.0 


7 


13.0 


70 


17 


14.0 


14 


12.5 


3 


14.5 


9 


18.0 


1 


16.5 


— 


_ 


75 


4 


17.0 


9 


16.0 


— 


— 


3 


13.0 


1 


14.0 


2 


17.5 


80 


10 


15.5 


— 


— 


5 


19.0 


5 


19.0 


_ 


_ 


_ 


_ 


85 


8 


18.0 


4 


18.5 


3 


16.5 


1 


15.5 


— 


_ 


_ 


_ 


90 


3 


16.5 


2 


19.5 


— 


- 


- 


- 


— 


- 


- 


- 



July. A maximum of 36%o was recorded in May and a minimum of 4.1 %o in August. There was 
a steady rise in salinity from September to May i.e. from the end of the monsoon to the 
summer. The highest temperature was recorded in May (33°C) and the lowest in December 
(21.5°). 

Density of zero age clams 

Density of zero age clams has been expressed as number of clams per square foot in Table 
4. The density of clams decreased in July and August, whereas the density was largest in 
November and December and ranged from to 28. In April and May the density was from to 
18 and in July and August from to 9. Very few small clams were found near the mid water 
mark and at the low water mark. The density of small clams was high in between these 2 
marks. The noticeable decrease in the clam population during the monsoon probably was due 
to changes in turbidity and salinity of the sea water caused by the influx of river water in the 
estuary which produced a drastic alteration of conditions over the clam bed. Few zero age 
clams have been found in the screenings worked out during April and May, whereas during 
November and December the density was largest indicating that settlement in April and May is 
generally sparse and sporadic. This low abundance probably resulted in part from poor 
settlement and also from poor survival of the juveniles. 

Density of the adult clams (above 37 mm) 

Clams of 37 mm to 49 mm shell length have a very local distribution. Virtually the entire 
set occurred on the western zone of the estuary. Extremely high clam densities were recorded, 
particularly in October and November; in November it was higher than in October. Further- 
more, the largest clam densities were found in the middle part of the mid and low water marks. 
Few clams did occur above mid water mark but mostly suffered mortality during the late 
summer. In the monsoon the clam density decreased at low water mark (Table 5). This decrease 
in July and August was probably due to survival factors principal among which are lethal 
salinity on the clam bed and low food abundance. This sharp decrease in the density during the 
monsoon coincided with the onset of monsoon storms and the mortality probably resulted 
from the large amount of fresh water brought by the Ratnagiri river which often causes severe 
alteration in the conformation of the clam beds. This agrees with the statement made by 
Tegelberg. & Magoon (1969) who postulated that survival of juveniles is a function of size 
reached before the winter storms strike. A similar statement was made by Bourne & Quayle 
(1970) for Siliqua patula and by Mane (1973) for Katelysia opima. Vertical distribution of 
clams and their densities showed a striking difference in the choice of substratum and it was 
observed that high density occurred in the muddy parts at the area between mid and low water 
marks. 



MANE AND NAGABHUSHANAM 



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310 PROC. SIXTH EUROP. MALAC. CONGR. 

TABLE 6. Distribution of clams at the middle part of mid and low water marks in Kalbadevi estuary. 

Distance from west to east in ft. 

(see 300 ft line in Fig. 4) No. of clams in October 1974 No. of clams in November 1974 

20 25 15 

40 39 27 

60 57 53 

80 70 64 

100 75 71 

1 20 46 49 

140 32 39 

160 53 44 

180 26 19 

200 23 11 

220 18 17 

240 7 2 

260 3 - 

280 - - 

300 - 



In order to assess the density of the clams at the middle part of mid and low water marks 
of the entire estuary, a survey was made in October and November which revealed that the 
greatest clam densities occurred at the western side (i.e. towards the sea side of the estuary), 
whereas at the eastern side (i.e. towards the river side of the estuary) the population was very 
sparse (Table 6). Increase in density of the clams towards the sea side confirms the marine 
habitat of the clam and also probably suggests an abundance of food from marine plankton. 

DISCUSSION 

From Indian waters the majority of the published data on growth show that very young 
specimens of clams grow rapidly in size and that this rate then decreases as the clams become 
older. The first report on the growth of commercially important species of clams by Rao 
(1951) on Katelysia opima from Madras showed that by the end of the 1st year the clams grew 
to 22.5 mm in length, whereas by the 2nd and 3rd year they grew to 31.5 mm and 40.5 mm. 
Another species of clam from the same area [Meretrix casta) showed a growth of 15 mm shell 
length within 2 months and 29.5 mm within 7 months (Abraham, 1953). Nayar (1955) showed 
that Donax cuneatus at Palk Bay on the east coast grew to a length of 14 mm within 10 
months, 19 mm within 2 years and then it dies. On the other hand, D. faba from the east coast 
attained a length of 19.5 mm by the 1st year and 22.5 mm by the 2nd year of its life 
(Alagarswami, 1966). On the west coast of India Solen kempi at Ratnagiri grew to 37.5 mm 
within the first 6 months and attained a length of 47.5-52.5 mm and 66 mm by the end of the 
1st and 2nd years of its life, respectively (Rao et al., 1962). At Ratnagiri Mane (1973) showed 
that K. opima attained a size of 22 mm, 31 mm and 43 mm in shell length by the end of the 
1st, 2nd and 3rd year of its life in Kalbadevi estuary. Talikhedkar et al. (1978) showed that D. 
cuneatus at Ratnagiri grew to 13-14 mm, 21-22 mm and 22-23 mm within the 1st, 2nd and 3rd 
year of life. It can be seen that the growth of P. laterisulca at Kalbadevi estuary at Ratnagiri is 
faster than \n K. opima which occurs in the same estuary. P. laterisulca in the present study 
was found to attain a length of 23 mm in the 1st year and 38 mm and 47 mm in the 2nd and 
3rd years of its life, respectively. 

P. laterisulca in Kalbadevi grew to a size of 17 mm and 11 mm in the first 6 months when 
born in the post monsoon and early summer of the year, respectively. This difference in growth 
of the clams born from 2 spawning peaks is due to a widely fluctuating environment during the 
monsoon. The salinity over the clam bed in the monsoon lowered considerably and attained a 
minimum of 4%o in August which resulted in the closing of the shell valves of the clams for 
most of the time and thereby retarded feeding activity of the younger clams. The clams born in 
the post monsoon are not influenced by this unfavourable environment at the early stages of 
growth, but the clams born in early summer have to face this environment at the early stages of 
growth which leads to retardation of the rate of growth. But the clams of both spawning peaks 



MANE AND NAGABHUSHANAM 311 

attained a length of 23 mm by the end of the 1st year. Thus, it can be said that the growth in 
the early summer born clams is accelerated only after the monsoon. In the entire collection 
during the study period, few clams of 56 mm shell length were observed during November, 
1973; there were only 4 in a total of 327. This probably suggests that the maximum age of the 
clam is ЗУ2 years after which they die. The growth in this clam is accelerated with the rising 
salinity during the post monsoon season. A similar statement has been made by workers while 
studying the growth of marine and estuarine bivalves from the Indian coast (Nayar, 1955; 
Mane, 1973; Deshmukh, 1972). It has been suggested by these workers that in tropical waters 
changes in temperature are negligible and therefore salinity of the water plays an important role 
in the growth of bivalve molluscs. In the present study also there appears to be no correlation 
of temperature changes and rate of growth. 

The linear relationship between length-breadth and length-width in P. laterisulca is in 
accordance with earlier findings (Nayar, 1955; Mane, 1973; Talikhedkar et al., 1978). The 
proportional increase in breadth of this clam indicates the general form to be more or less the 
same throughout life. The relationship between the weight and shell length followed a cube law 
and is close to the slope value of 3.6618. At 49 mm shell length (clams of this size are 
abundant throughout the year) the weight is about 20.1 g inclusive of the shell. Approximately 
40% of the whole weight is usable meat; a 49 mm clam would have 8 g of marketable meat. To 
obtain maximum marketable meat yield from P. laterisulca the commercial harvest would 
probably be limited to summer and early monsoon when the gonads are rapidly filling or are 
full just prior to spawning. Since this period coincides with major efforts in the fishing of other 
important species, harvesting of P. laterisulca can be limited during the spawning periods. Thus 
this edible clam resource can be utilised for fishery management. 

The use of annual shell rings as a means of establishing age has been employed in a variety 
of lamellibranchs: Cerastoderma edule, Orton (1926); Tivela stultorum, Weymouth (1923); 
Venerupis pullastra, Quayle (1952); Anodonta anatina and Unio balthica, Negus (1966); Tellina 
tenuis, Mclntyre (1970); Meretrix meretrix, Deshmukh (1972); Katelysia opima. Mane (1973); 
Donax cuneatus, Talikhedkar et al. (1978). During unfavourable conditions the mantle edges of 
bivalve molluscs are withdrawn from the shell margin causing a cessation of growth. However, 
the innermost nacreous layer is continuously deposited (Seed, 1969). Thus, when growth is 
resumed, old and new regions of the shell are not continuous, resulting in an obvious ring. In P. 
laterisulca, similar formation of rings takes place in the monsoon season. It has been observed 
that during the entire life span of this clam, 3 such rings are laid down at shell lengths of 
22 mm, 37 mm and 46 mm. 

Recently, Quayle & Bourne (1972) stated that sexual maturity in bivalves appears to depend 
on size rather than age. The observations of this study are in close agreement with the findings 
of Nayar (1955), Mane (1973) and Talikhedkar et al. (1978). In the present study it has been 
observed that P. laterisulca at Kalbadevi estuary attained sexual maturity at 16 mm to 18 mm 
in shell length. This length is attained when the clams are 7-8 months old when born in the 
post monsoon whereas maturity is attained in summer born clams when they are 10-11 months 
old. 

Considerable variation in spawning has been reported for different clam populations along 
the east and west coasts of India. Hornell (1922) believed that the normal spawning season in 
Meretrix casta was in April-May and again in September whereas Rai (1932) observed Meretrix 
to spawn from March to June at the Bombay coast. On the other hand, M. casta at Adyar 
estuary, Madras, spawned in July-August, October-November and March-April or May 
(Abraham, 1953). The wedge clam, Donax faba, from Mandapam beach spawns from November 
to June (Alagarswami, 1953), whereas D. cuneatus at Madras showed prolonged spawning from 
January to June. The spawning of D. cuneatus at Ratnagiri coast was from October to January 
with a peak in November and December (Talikhedkar et al., 1978). There was only one 
spawning period in K. opima from Adyar estuary (Rao, 1951) in contrast to the population of 
the same species from Kalbadevi at Ratnagiri (Mane, 1973), which has 2 distinct spawning 
periods in a year, a major one from October to November and a minor one from March to 
April. The present study revealed that P. laterisulca in Kalbadevi spawns from September to the 
end of March with 2 peaks— one in November and the other in March; these spawning peaks 
coincide with the spawning period of K. opima in the same estuary. 

There are no reports from the Indian coast on clam density. Significant differences are 



312 PROC. SIXTH EUROP. MALAC. CONGR. 

evident between the clam populations at the sea side and at the river side in the Kalbadevi 
estuary which show that the clams prefer the bed at the sea side as the environment most 
suitable to them. Simitar observations for the razor clam, Siliqua patula, were made by Bourne 
& Quay le (1970) on the north and south beaches at Masset, B.C. They stated that recruitment 
was consistent in each year on the north beach but very low on the south beach. Clam 
populations on Horseshoe Beach appeared to be intermediate between the 2 beaches indicating 
a possible gradient of environmental factors from west to east. Tegelberg (1964) reported a 
similar variation on Washington State beaches; recruitment was most consistent and growth 
fastest on Capolis beach, the most northerly of the 3 main beaches. He postulated that the 
slower growth on the southern beaches may be due to greater influence of water from the 
Columbia river. Salinities are lower on the southern beach, particularly during the spring 
discharge. The sand is coarsest in the south and finer in the north. Similar océanographie 
conditions might have affected clam distribution and growth in Kalbadevi estuary. During the 
period of maximum runoff fresh water coming into the estuary undoubtedly reduces salinity 
and turbidity increases considerably in the monsoon period. This water mass probably has a 
greater influence on the low density and growth of zero age clams and also the marketable size 
of the clam. 

Extensive digging has taken place in Kalbadevi estuary which has resulted in fluctuation of 
sampling in the middle part of the vertical zone at the sea side over the clam beds. Diggers have 
frequently preferred digging at this area because of the abundance of the clams. 

When analyzing the distribution of the clams at the vertical zone over the western part of 
the estuary, it can be seen that clams are abundant in the middle part of the mid and low 
water marks and rare above mid water mark. The reason is that clams generally prefer to settle 
in muddy parts of the intertidal zone rather than in the sandy area. The area above mid water 
mark at Kalbadevi is covered with sand and the area below it is muddy. 

ACKNOWLEDGEMENT 

The authors wish to acknowledge the efforts of Dhamne K.P.— ex-research fellow of the 
Marine Research Laboratory of Marathwada University, Aurangabad, who has faithfully assisted 
in the work of yearly placement and retrieval of the clams. 

LITERATURE CITED 

ABRAHAM, K. C, 1953. Observations on the biology of Meretrix meretrix. Journal of the Zoological 

Society of India, 5: 169-190. 
ALAGARSWAMI, K., 1966, Studies on some aspects of biology of the wedge clam, Donax faba, from 

Mandapam coast in the Gulf of Mannar. Journal of the Marine Biological Association of India, 8: 56-57. 
BOURNE, N. & OUAYLE, D. В., 1970, Breeding and growth of razor clams in British Columbia. Technical 

Report of the Fisheries Research Board of Canada, 232: 1-42. 
DESHMUKH, R. S., 1972, Some aspects on the biology of the clam, Meretrix meretrix. Ph.D. Thesis, 

Marathwada University, Aurangabad, India. 
DURVE, V. S., 1970, On the growth of the clam, Meretrix casta from the marine fish farm. Journal of the 

Marine Biological Association of India, 12: 125-135. 
HORNELL, J., 1922, The common molluscs of South India. Madras Fisheries Bulletin, 14: 97-215. 
MCINTYRE, A. D., 1970. The range of biomass in intertidal sands with special reference to the bivalve, 

Tellina tenuis. Journal of the Marine Biological Association of the United Kingdom, 50: 561-576. 
MANE, U. H., 1973, Study on the biology of marine clam, Katelysia opima. Ph.D. Thesis, Marathwada 

University, Aurangabad, India, 52 p. 
NAY AR, К. N., 1955, Studies on the growth of wedge clam, Donax cuneatus. Indian Journal of Fisheries, 2: 

325-348. 
NEGUS, С L., 1966, A quantitative study of growth and production of unionid mussels in the river Thames 

at Reading. Journal of Animal Ecology, 35: 513-532. 
ORTON, J. H., 1926, On the rate of growth of Cardium edu/e. Part I. Experimental observations. Journal of 

the Marine Biological Association of the United Kingdom, 14: 239-279. 
OUAYLE, D. В., 1952, The rate of growth of Venerupis pullastra at Millport, Scotland. Proceedings of the 

Royal Society of Edinburgh, B64: 384-406. 
OUAYLE, D. B. & BOURNE, N., 1972, The clam fisheries of British Columbia. Bulletin of the Fisheries 

Research Board of Canada, 179: 1-70. 



MANE AND NAGABHUSHANAM 313 

RAI, H. S., 1932, The shellfisheries of the Bombay Presidency. Journal of the Bombay Natural Historv 

Society, 32: 826-847. 
RAO, K. v., 1951, Studies on the growth of Katelysia opima. Proceedings of the Indo-Pacific Fisheries 

Council. Section 2: 94-102. 
RAO, K. v., NARASIMHAM, K. S. & ALAGARSWAMI, K., 1962, A preliminary account of the biology and 

fishery of the razor shell, Solen kempi from Ratnagiri in Maharashtra State. Indian Journal of Fisheries 9- 

524-579. 
SEED, R., 1969, The ecology of Mytilus edulis (Lamellibranchiata) on exposed rocky shores. II. Growth and 

mortality. Oeco logia, 3: 317-350. 
TALIKHEDKAR, P. M„ MANE, U. H. & NAGABHUSHANAM, R., 1978, Growth rate of the wedge clam, 

Donax cuneatus at Mirya Bay, Ratnagiri on the west coast of India. Indian Journal of Fisheries (in press)! 
TEGELBERG, H. С, 1964, Growth and ring formation of Washington razor clams. Fisheries Research Paper, 

Washington Department of Fisheries, 2(3): 69-103. 
TEGELBERG, H. С. & MAGOON, С. D., 1969, Growth, survival and some effects of a dense razor clam set 

in Washington. Proceedings of the National Shellfish Association, 59: 126-135. 
WEYMOUTH, F. W., 1923, The life history and growth of the Pismo clam (Tivela stultorum Mawe). Fish 

Bulletin, California Fish and Game Commission, 7: 1-120. 
WEYMOUTH, F., MCMILLIN, H. С & HOLMES, H. В., 1925, Growth and age at maturity of the Pacific 

razor clam, Siliqua patula. Bulletin of the United States Bureau of Fisheries, 41: 201-236. 



MALACOLOGIA, 1979, 18: 315-318 

PROC. SIXTH EUROP. MALAC. CONGR. 

HOMING IN THE GASTROPODA 

Anthony Cook 
New University of Ulster, Coleraine, Northern Ireland 

ABSTRACT 

In 1950 Edelstam & Palmer suggested that the most plausible guiding senses used by 
gastropods to home were "smell (for terrestrial forms) and touch (for marine forms)." 
Since that time more information has become available, though the range of species 
examined has not been significantly extended. Homing gastropods may be classified into 
two types: those which only home in air such as Helix pomatia, Onchidium floridanum 
and Limax maximus and those which can home underwater like Patella vulgata and 
Siphonaria spp. The following results are from my own experiments with Limax grossui 
Lupu. Under laboratory conditions the slugs consistently home without trail following. 
Trails emanating from the home site are an adequate stimulus for 'homing' in the absence 
of the home itself, though trail following need not be involved. Failure to find a home 
often results in a period of trail following. The sensory sites for distant chemoreception 
and trail following are anatomically separate. L. grossui homes therefore, using an 
olfactory beacon with a, normally reserved, trail following capacity. This type of 
hypothesis can be extended to encompass the observed features of limpet homing where 
the prime mechanism is trail following with the olfactory beacon normally reserved. The 
dual nature of the mechanism is illustrated by the work of Davis. If the olfactory beacon 
is removed by treatment with boiling water but the trail following pheromone is 
unaffected then Davis' results (held to support the concept of a topographic memory) 
can also be interpreted in pheromonal terms. This dual pheromone mechanism may have 
wide relevance to the solution of gastropod homing problems. Both pheromones are in 
the mucus: one serves as an olfactory beacon and the second is perceived only on 
contact. The beauty of pheromonal homing mechanisms in the gastropods is that they 
depend only on sensory and nervous mechanisms known to be within the capacities of 
soft bodied animals. The alternatives of topographic and kinaesthetic memories both 
involve the precise measurement of angles and distances and the use of a detailed 
memory, none of which have yet been demonstrated in gastropods. 

Honning is a widespread phenonnenon in the Gastropoda; it has been described from the 
prosobranchs and the pulmonates in both aquatic and terrestrial habitats and in both shelled 
and shell-less fornns. The features of homing have been the subject of a great deal of research 
over the last 100 years (Funke, 1968) but there has been little agreement over the methods 
used by these animals to get home. 

Homing gastropods may be classified into 2 types: those that home only in air and those 
that can home underwater (limpets). In 1950 Edelstam & Palmer suggested that the most 
plausible guiding senses for homing were smell for terrestrial forms and topographic memory for 
marine forms. More recently Willows (1973) supported this view. It is my contention that the 
persistence in the literature of the involvement of memory in gastropod homing is a result of 
the failure of chemoreception to account for all the known features of homing and this in turn 
is a result of incorrect assumptions concerning the nature of the guiding chemicals. 

Terrestrial homing has been demonstrated in Deroceras (=Agriolimax) reticulatum, Cepaea 
nemoralis (both Newall, 1966), Helix aspersa (cf. Step, 1960), Limax flavus (cf. Taylor, 1903; 
South, 1965) and has been examined in depth in Helix pomatia (cf. Edelstam & Palmer, 1950), 
Limax maximus (cf. Gelperin, 1974) and Onchidium floridanum (cf. Arey & Crozier, 1921). 
The dominant feature of homing in all these animals is probably the distant chemoreception of 
home, but no critical experiments have been performed to determine whether any other factors 
are involved. 

I have been investigating the relevance of the subsidiary factors of trail following and 
memory in the homing behaviour of Limax grossui Lupu. '^ Five animals were placed in a tank 
0.58 X 1.15 X 0.15 m, the bottom of which was covered by a field of 24 glazed ceramic tiles 

^The Irish populations of 'Limax grossui' have now been renamed Limax pseudoflavus Evans, 1978 (Irish 
Naturalists' Journal, 19: 173). 

(315) 



316 



PROC. SIXTH EUROP. MALAC. CONGR. 



(porous side up). A holed brick provided the only home. Food, on a tray, was always available 
in the same position. L. grossui is strictly nocturnal and so movements were viewed under 
extremely dim red light with a silicon tube T.V. camera and recorded every minute on a time 
lapse video-tape recorder. The conclusions reached here are based on 50 nights of observations 
(equivalent to 3000 slug hrs of movement). Some further trail following experiments were 
performed using the methods of Cook (1977). 

These observations indicate that strange slugs placed in an established tank can find the 
'home' brick, as can strange slugs placed in a clean tank with an established 'home' brick. 
Finding the brick in these experiments cannot involve memory and must be based on olfaction. 
An excursion of a slug in an established tank rarely involves the retracing of the outward path. 
When the excursions of several slugs over several days are superimposed, however, definite 
patterns of movement emerge (Fig. 1). This pattern of movement is based on trails since the 
transposition of some of the tiles and the removal of the home, result in the pattern of 
movement changing with the position of the tiles (Fig. 2). The dependence on the trails may 
reflect the slugs tending to stay in an area of high trail density rather than accurate and definite 
trail following. Failure to find a home after its removal often results in a period of accurate 
trail following (Fig, 3). 




FIG. 1. The superimposed positions of 5 slugs re- 
corded every 5 minutes for four days. Only changes 
in position are recorded. Scale— the home is 20 cm 
long. 



FIG. 2. The nearest row of tiles was reversed so that 
the former edge now runs along the dotted line and 
the home removed. The return track of the slug, 
normally along the near edge of the tank, is now 
influenced by the trails on the reoriented tiles along 
the dotted line. *home removed and tiles reversed 
when the slug first reached the food. Scale— the 
home is 20 cm long. 



COOK 



317 




FIG. 3. The established home was replaced by a clean brick. On its return the slug searched the 'home' and 
the area at the base before moving back and forth along part of its return trail. 



Slugs on the feeding tray of an established tank were moved to an identical but clean tank 
and were not able to home to the clean brick, thus demonstrating that neither topographic nor 
kinaesthetic memories are involved. 

Removal of the optic tentacles results in a dramatic fall in homing and also a significant fall 
in the frequency of trail following. It has no effect on the accuracy with which a slug can stay 
on a trail. Removal of the anterior tentacles on the other hand, does not affect homing, nor the 
frequency of trail following but does significantly impair the trail tracking ability of the slug. 
On removal of both pairs of tentacles the animals refuse to move at all. 

These results indicate that the optic tentacles are essential for homing but that they share 
the control of trail following with the anterior tentacles: the former having a role in the 
identification of the mucus and the latter being concerned with the close tracking of the trails. 
Distant chemoreception and trail following therefore, probably have separate sensory 
mechanisms. 

From all these observations of Umax grossui it may be concluded that it homes using both 
an olfactory beacon based at home and the trails which emanate from home, and also a 
capacity to follow trails home: that is, it is a dual chemosensory mechanism, probably involving at 
least two pheromones, one for distant chemoreception and another for trail following. The 
features described here are compatible with all the experimental evidence for other terrestrial 
homing species. 

In 1968 Funke postulated a dual trail following/distance chemoreception explanation for the 
homing of the limpet Patella vulgata but with the emphasis on the trail following. Limpets can 
home at all states of tide (Cook et al., 1969) and it is in this group of potentially submarine 
homing gastropods that most uncertainty arises concerning mechanisms. As well as Patella, 
Siphonaria (cf. Cook, 1969) and probably Acmaea (cf. Breen, 1971) home using trails. Most 
experiments aimed at removing trails however, do not prevent homing. Since these trails are 
normally not visible the only reliable way of inferring their presence is to follow the behaviour 
of the animals on them. A treatment which does not prevent homing therefore, could be 
interpreted as ineffectively removing the trails rather than requiring some further mechanism. 

Davis (1970) treated rocks with boiling water and the limpets subsequently did not find 
home, though 50% of them got within 2 cm of home. This can either be interpreted as evidence 
for a topographic memory or as evidence that whilst the chemical information on the home was 
destroyed by boiling water, the chemical information on the trail was not. Davis' second series 
of experiments involved various degrees of chipping of the rock around the home. Severe 
chipping prevented homing whilst mild chipping failed to have this effect. The volcanic rocks of 
Skokholm where this work was conducted are extremely hard and it is questionable whether 
mild chipping would be adequate to remove all the original surface of the rock. The evidence 
for a topographic memory is therefore, equivocal. 



318 PROC. SIXTH EUROP. MALAC. CONGR. 

TABLE 1. The effect of treating rock with IN NaOH and displacing limpets 15 cm from home. Homing is sig- 
nificantly reduced (x^ = 4.74, p < .05) and there is no marked tendency to move towards home. The control 
group differed only in the rock not being chemically treated. 

Total Survivors At home Within 10 cm of home 

Experiment 51 38 8 3 

Control 50 38 18 2 

If topographic information is used to home then no chemical treatment of the rock should 
be sufficient to prevent limpets returning to their home area. Cook et al. (1969) performed an 
experiment in which the rock was treated with 0.75N NaOH, but reported this as unsuccessful. 
Reanalysis of this data using x^ shows that this treatment did in fact significantly reduce 
homing, but the distance of the non-homing limpets from their homes was not recorded. I have 
recently repeated this experiment. Limpets were removed from the rock after having numbered 
both animals and their homes. The rock was washed with IN NaOH for 15 min, IN HCl for 5 
min and then thoroughly dowsed with water. The limpets were replaced on the rock 15 cm 
from home and their positions recorded after 24 hrs (Table 1). It is clear that homing is 
significantly reduced (x = 4.74, p < .05) and that limpets did not return to a "home area." 
These results are not compatible with the concept of a topographic memory. The other 
memory mechanism generally considered is a kinaesthetic one, i.e. the use of past movements 
to compute the future course home. Funke (1968) describes one occasion on which a moving 
limpet ('Patella caerulea') was carefully displaced 30 cm. It then moved as if the home had also 
been displaced for a similar distance in the same direction. However, this was a single 
occurrence and limpets were normally disorientated by such a displacement. Further experi- 
ments (Funke, 1968) were inconclusive, though 3 limpets (out of 7) whose trails were 
artificially lengthened stopped moving before reaching the new home position. Many limpets 
reach home with only minutes to spare before being covered by the tide (Cook et al., 1969) 
and it may be that time is the important factor in such experiments rather than a memory of 
distance. 

In conclusion it can be seen that a dual pheromone mechanism is adequate to' account for all 
the features of homing in gastropods if these criticisms of experiments are well founded. In 
support of this mechanism is a consideration of the sensory and mental capacities of 
gastropods. Their prime senses appear to be chemical, no soft bodied animal is known to store 
muscular information and finally it is only recently that they have been shown to be capable of 
simple associative learning (Gelperin, 1974a-b), let alone the complex processes of information 
storage and computing required for kinaesthetic or topographic memory. 

LITERATURE CITED 

AREY, L. B. & CROZIER, W. J., 1921, On the natural history of Onchidium. Journal of Experimental 

Zoology, 32: 443-502. 
BREEN, P. A„ 1971, Homing behaviour and population regulation in the limpet Acmaea digitalis. The 

Veliger, 14: 177-183. 
COOK, A., 1977, Mucus trail following by the slug Umax grossui. Animal Behaviour, 25: 774-781. 
COOK, A., BAMFORD, O. S., FREEMAN, J. D. B. & TEIDEMAN, D. J., 1969, A study of the homing habit 

of the limpet. Animal Behaviour, 17: 330-339. 
COOK, S. В., 1969, Experiments on homing in the limpet Siphonaria normalis. Animal Behaviour, 17: 

679-682. 
DAVIS, J. W. F., 1970, Topographic memory in limpets (Patella). Revue du Comportement animal, 4: 42-45. 
EDELSTAM, С & PALMER, C, 1950, Homing behaviour in gastropods. Oikos, 2: 259-270. 
FUNKE, W., 1968. Heimfindevermogen und Ortstreue bei Patella L. Oecologia 2: 19-142. 
GELPERIN, A., 1974a, Olfactory basis of homing behaviour in the Giant Garden Slug, Limax maximus. 

Proceedings of the National Academy of Sciences of the U.S.A., 71 : 966-970. 
GELPERIN, A., 1974b, One trial food aversion learning by a terrestrial mollusk. Science, 189: 567. 
NEWALL, P. F., 1966, The nocturnal behaviour of slugs. Medical and Biological Illustration, 16: 146-159. 
SOUTH, A., 1965, Biology and Ecology of Agriolimax reticulatus Mull, and other slugs: Spatial distribution. 

Journal of Animal Ecology, 34: 403-417. 
STEP, E.. 1960, Shell life. Warne, London, 443 p. 
TAYLOR, J. W., 1903, Monograph of the land and freshwater Mollusca of the British Isles, 9: 53-104. Taylor, 

Leeds. 
WILLOWS, A. O. D.. 1973, Learning in gastropod mollusks. In: CORNING, W. C, DYAL, J. A. & WILLOWS, 

A. O. D., Invertebrate Learning, 2, Arthropods and gastropod mollusks: 187-274. Plenum Press, New York. 



MALACOLOGIA, 1979, 18: 319-326 

PROC. SIXTH EUROP. MALAC. CONGR. 

DONNEES ECOLOGIQUES SUR DES CAECIDAE (GASTEROPODES 
PROSOBRANCHES) DU GOLFE DE MARSEILLE 

Patrick M. Arnaud'' et Claude Poizat^ 

ABSTRACT 

Seasonal samples of sand from 11 sublittoral stations (11 to 45 m) between Marseille 
and Cassis (Meditterranean coast of France) made it possible to obtain for the first time 
a very abundant material of caecid gastropods. Three species are involved: Caecum 
subannulatum, С auriculatum and C. trachea. Analysis of sedimentary and hydrological 
parameters explains the distribution of these molluscs and shows that the first two 
species are more abundant in stations exposed to strong hydrodynamism. Comparisons 
are made with mesopsammic opisthobranchs and the whole mesopsammon. Vertical 
migrations inside the sediment as a result of increased temperature or in relation with 
trophic or reproductive phenomena are shown to exist in С subannulatum and С 
auriculatum. Reproductive periods are stated. 



INTRODUCTION 

La famille des Caecidae est très mal connue dans le monde. Le matériel en est difficile à 
obtenir, compte tenu des dimensions très faibles et des conditions de vie des membres de cette 
famille et on doit généralement se contenter d'examiner un petit nombre d'individus. 

Ceci avait toujours fait obstacle à toute approche écologique de cette famille, tandis que le 
développement à stades multiples, unique chez les Gastéropodes, rendait sa systématique des 
plus difficiles. Le traitement de divers sédiments sableux du golfe de Marseille par une méthode 
récemment adaptée par l'un de nous (Poizat, 1975) a permis d'obtenir pour la première fois un 
matériel aussi abondant que représentatif de trois espèces de cette famille. La révision 
systématique de ces espèces et de leurs divers stades de croissance fera l'objet d'un autre travail: 
ici ne sont présentés que les résultats écologiques. 

MATERIEL ET METHODES 

Les stations étudiées, suivies depuis plusieurs années (Poizat, 1972, 1975) sont réparties entre 
Marseille et Cassis (Fig. 1). Dans 3 d'entre elles (Nos. 1, 2 et 4), la recherche des Caecidae a été 
faite pendant 6 mois à 1 an, en vue d'étudier leur cycle annuel. Les 8 autres stations (Nos. 3 et 

5 à 11) avaient pour but l'étude des effets de l'hydrodynamisme marin sur la répartition des 
Caecum. 

Les caractéristiques sédimentologiques et hydrologiques de ces 1 1 stations au moment des 
prélèvements, et le détail des Caecidae pris à chacune d'elles sont rassemblés dans le Tableau 1. 

Les sédiments ont été prélevés à la drague Charcot (Picard, 1965) dont la profondeur de 
pénétration dans les sables étudiés atteint environ 12 cm, ou à l'aide de la drague "spatangue," 
dont le cadre métallique en forme de Spatangus (échinide irrégulier) ne fait qu'écrémer les 5 ou 

6 cm superficiels du sédiment. 

Les Caecidae, partie intégrante du mesopsammon, ont été séparés du sédiment par la 
technique de Uhlig (Uhlig et al., 1973) adaptée par Poizat (1975) et permettant le traitement 
de 8 litres de sédiment à la fois: on laisse fondre de la glace d'eau douce au-dessus du sédiment 
placé dans un dispositif spécialement construit à cet effet. Le mesopsammon vagile se concentre 
par ses propres mouvements à la base du dispositif, dans un cristallisoir rempli d'eau de mer. 

^Station marine d'Endoume, 13007 Marseille, France. 

^Faculté des Sciences de Marseille St. Jérôme, 13013 Marseille, France. 

(319) 



320 



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FIG. 1. Stations étudiées dans le golfe de Marseille. Д— hydrodynannisme faible; *— hydrodynamisme moyen; 
*— hydrodynamisme élevé. 

Il a été possible de classer l'ensemble des spécimens de Caecidae en 3 espèces: 2 espèces 
communes, Caecum auriculatum Polin, 1867, et С subannulatum Polin, 1869, et une espèce 
plus rarement récoltée, C. trachea (Montagu, 1803), chacune représentée par divers stades de 
développement (Tableau 1). Disons seulement que ces stades, qui feront l'objet d'une 
publication descriptive particulière, sont appelés ici stade 1 (protoconque avec ou sans 
prolongement), stade 2 et stade 3 (adulte), correspondant respectivement au "premier âge," 
"deuxième âge" et "troisième âge" définis par Polin (1875). 

Les Prosobranches (Caecidae compris) et Opisthobranches sont ainsi triés in vivo après légère 
coloration au rouge neutre. Le reste du mesopsammon (Copépodes, Annélides, Nematodes, etc.) 
est décompté ultérieurement après fixation à l'alcool 70% et coloration au rose Bengale. Tous 
les résultats sont exprimés en fonction d'un volume sédimentaire de 48 litres (par multiplication 
de nos comptages par 6), chiffre voisin du "volume minimum" défini par Picard (1965) pour les 
études de macrobenthos en Méditerranée (50 litres). 

Des mesures sédimentologiques et de température de l'eau de mer apportent des informations 
sur les conditions hydrodynamiques et leurs variations saisonnières dans les stations. Les 
sédiments sont définis ici (Tableau 1) par leur pourcentage de vase (proportion de la fraction 
infé rieure à 50 jum), leur mode (classe dimensionnelle dominante) et l'indice de tri de Trask (So 
= vQa/Qi-" Q3 et Qi étant des paramètres traduisant les dimensions atteintes par 25 et 75% 
des particules). 



ANALYSE DES RESULTATS PAR STATION 

Le sédiment enregistre plus ou moins selon les stations les fluctuations de l'état de la mer 
liées à la météorologie. La tendance générale est à une augmentation de la granulométrie durant 
la mauvaise saison, de novembre à mars (hydrodynamisme marin plus élevé); au contraire, il y a 



ARNAUD ET POIZAT 323 

affinement des sédiments et augmentation de leur hétérogénéité durant la belle saison, de mars 
à octobre. Mais cette réponse du sédiment est modulée par la situation géographique de chaque 
station par rapport aux deux vents dominants du golfe de Marseille: le vent d'Est et celui de 
NNW ou "mistral" (Poizat, 1972). 

On peut classer les 11 stations étudiées en 3 ensembles selon l'intensité de l'hydro- 
dynamisme: hydrodynamisme élevé (stations 1 à 3), moyen (stations 4 à 7) ou faible (stations 8 
à 11). 

Caecum trachea étant peu représenté dans nos récoltes, les commentaires suivants ne 
concernent, sauf exception, que les deux autres espèces. 

Stations à hydrodynamisme élevé 

— station 1 (débouché de la calanque de Port Miou). 

Son orientation l'expose aux vents d'Est alors que l'influence du mistral y est beaucoup plus 
modeste. La rareté exceptionnelle du vent d'Est pendant la période d'étude a entraîné un 
hydrodynamisme plus faible que d'habitude, d'où affinement très important du sédiment (mode 
passant de 2,8 à 1,4 mm) sans augmentation notable d'hétérogénéité (indice de tri assez 
stable). Les circulations d'eau sur ce fond, bien que diminuées, n'ont donc pas cessé, assurant 
une bonne oxygénation du sable et interdisant le dépôt de particules fines (envasement nul). 

L'importance numérique des Opisthobranches a augmenté bien que le mesopsammon ait 
accusé un léger affaiblissement au milieu de l'été (août 1976). 

Cette station s'est montrée remarquablement riche en Caecum auriculatum à tous les stades 
de croissance (traduisant une abondante reproduction); C. subannulatum, quoique beaucoup 
moins abondant, y a toujours été bien représenté. Néanmoins, comme pour le mesopsammon, 
une diminution numérique des deux espèces s'est manifestée en période estivale. 

— station 2 (dans la passe entre les îles Plane et Riou) (Fig. 2). 

Station sous l'influence à la fois des vents d'Est (renforçant le courant marin général d'Est) 
et du mistral (qui perturbe cet écoulement en créant souvent de puissants remous). Mais la 
station est située dans la partie occidentale de cette passe, dont les profondeurs augmentent vers 
l'Ouest: aussi le courant d'Est n'a-t-il qu'un effet moyen de lessivage des sédiments, en tout cas 
plus faible qu'à la station 1, malgré une bathymétrie légèrement moindre. Le schéma de 
variation saisonnière de la granulométrie reste donc le même qu'à la station 1 (mode 2,25 mm 
en hiver et 1,25 mm au début de l'été). 

Les Opisthobranches mésopsammiques et le reste du mesopsammon passent par un maximum 
numérique en mai, puis accusent (moins cependant qu'aux autres stations) un minimum 
numérique estival (juin 1976). Une baisse de la température de l'eau, l'augmentation du mode 
et de la maille sédimentaire, une meilleure oxygénation des interstices sableux entraînent un 
second maximum du mesopsammon, à l'exception des Opisthobranches qui décroissent vers leur 
minimum hivernal. 

Comme la station 1, cette station est très favorable à C. auriculatum et C. subannulatum qui 
y vivent en abondance, s'y reproduisent et montrent un net minimum en juin (comme le 
mesopsammon total, Opisthobranches compris). Chez C. subannulatum, ce minimum est suivi 
d'une remarquable phase de reproduction en octobre. On note (par comparison drague 
Charcot/drague spatangue) une concentration de C. subannulatum et C. auriculatum dans le film 
sédimentaire au moment du maximum thermique estival, suivie d'une phase de reproduction des 
deux espèces. Ce phénomène se manifeste aussi pour les Opisthobranches et le reste du 
mesopsammon, au printemps puis en été. 

— station 3 (calanque de l'Oule). 

Cette station semble représenter l'extrême degré d'hydrodynamisme compatible avec la vie 
des mollusques mésopsammiques. La maille sédimentaire est très vaste; le sédiment, très grossier, 
est très violemment remanié sur une grande épaisseur, ce qui crée un milieu défavorable à un 
riche mesopsammon. Le seul prélèvement qui y a été fait a cependant montré une abondance 
notable de C. auriculatum et C, subannulatum, et l'absence de C, trachea. 



324 



PROC. SIXTH EUROP. MALAC. CONGR. 




HYDRO DYNAMIS M E 



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FIG. 2. Variations saisonnières des paramètres sédimentaires ( ) at thermiques (- 



-) et de l'abondance 



numérique (. — . — .: Drague Charcot; . . . .: Drague spatangue) de Caecum auriculatum et de C. sub- 
annulatum, des Opisthobranches et du reste du mesopsammon, en fonction des 3 degrés d'hydrodynamisme. 



ARNAUD ET POIZAT 325 

Stations à hydrodynamisme moyen 

— station 4 (dans la passe entre les îles If et Ratonneau) (Fjg. 2). 

Station protégée du mistral par l'île Ratonneau et du vent d'Est par l'île d'If. Les eaux y 
sont chaudes, peu oxygénées et polluées. Par suite des températures estivales plus élevées 
qu'ailleurs (28°C en surface et 23°C au fond, fin juin 1976) et de la stratification thermique, 
l'oxygène disponible diminue; corrélativement la granulométrie du sédiment s'affaiblit (mode 
passant de 0,7 mm en hiver à 0,5 mm au début de l'été). 

Il y a un effondrement quantitatif du mesopsammon, Opisthobranches compris, et dispari- 
tion totale des 3 espèces de Caecidae (moins abondantes qu'en hydrodynamisme élevé) qui 
avaient montré cependant une nette phase de reproduction (présence de stades 1 et 2). Notons 
que, depuis la fin de l'hiver, les individus de С auriculatum et C. su ban nu latum s'étaient 
concentrés dans le film sédimentaire superficiel avant cette disparition. 

— stations 5 (calanque d'En Vau), 6 (calanque de Port Pin) et 7 (plateau des Chèvres). 

Malgré une bathymétrie notable, l'hydrodynamisme des stations 5 et 6 est sous l'influence de 
courants de décharge (undertows) en régime de vent d'Est, auquel font face ces deux stations. 
De même, la station 7 est abritée par les mattes d'herbiers de Posidonies qui atténuent 
localement les puissants courants de fond, d'azimut Est, de règle dans cette zone. La maille 
sédimentaire est assez vaste, pratiquement jamais colmatée par les fractions fines. 

Dans ces 3 stations, le mesopsammon (Opisthobranches compris) est très riche. Comme à la 
station 4, les Caecidae (sauf С trachea) se reproduisent normalement (et même intensivement 
pour C. auriculatum) puis disparaissent totalement en début d'été (sauf pour C. subannulatum à 
la station 7). 

Stations à hydrodynamisme faible 

A cette catégorie appartiennent la station 8 (Est de l'île Plane), abritée par les herbiers de 
Posidonies et les récifs de la pointe Est de l'île Plane, et les stations 9 (Riou), 10 (Sormiou) et 
11 (Morgiou), à hydrodynamisme faible (Fig. 2) du fait de leur profondeur plus grande 
(30-37 m). Les sédiments de ces stations sont "moyens" ou "peu grossiers," avec un 
pourcentage de vase atteignant parfois 5 à 8% (stations 10 et 11). Le mesopsammon 
(Opisthobranches non compris) montre des variations analogues à celles observées en hydro- 
dynamisme moyen (cf. Fig. 2, station 4). 

Les Caecidae sont présents en nombre moindre qu'en hydrodynamisme élevé, mais analogue 
à ce qui a été observé en hydrodynamisme moyen. Seule de ces stations la station 9 a fourni 
des stades jeunes, y compris pour C. trachea, mais ce recrutement ne semble pas y être suivi 
d'un maintien durable. Les conditions de milieu (exiguïté et colmatage du milieu interstitiel) de 
ces stations et probablement leurs conditions trophiques sont évidemment à la limite de la 
survie des 3 espèces de Caecum. 

On note pour C. subannulatum et C. auriculatum une migration vers le film sédimentaire, à 
la fin de l'hiver (février), suivie d'une prolifération. Lors du maximum thermique estival, il y a 
décroissance des deux espèces; mais, contrairement à ce que l'on observe en hydrodynamisme 
élevé et moyen, leur maximum numérique coincide avec le maximum thermique estival. Ce 
maximum numérique est suivi d'une diminution brutale de C. subannulatum et de la disparition 
de C. auriculatum. 



CONCLUSIONS 

(1) Caecum trachea n'est pas abondant dans les milieux sableux analysés et ne s'y reproduit 
guère. Cette espèce est peut être inféodée aux herbiers de Posidonies. 

(2) Du point de vue écologique, C. subannulatum et C. auriculatum se distinguent 
difficilement et sont généralement observés dans les mêmes milieux. Leur répartition bathy- 
métrique est analogue dans les limites des stations étudiées entre 11 et 45 mètres de 
profondeur, 

(3) C. subannulatum et C. auriculatum prolifèrent particulièrement bien dans des milieux 



326 PROC. SIXTH EUROP. MALAC. CONGR. 

sableux non envasés, liés à un hydrodynamisnrie élevé et où sédinnentent des sables grossiers à 
très grossiers ("sables à amphioxus"). Dans ce type de biotope, il y a abondante reproduction et 
maintien des 2 espèces toute l'année, malgré un net appauvrissement au moment du maximum 
thermique (exemple: station 2). 

Dans les milieux à hydrodynamisme moyen, caractérisés par des sables plus ou moins 
grossiers ("sables détritiques côtiers") la reproduction des 2 espèces est normale mais il peut y 
avoir localement (station 4) destruction de toute la population au moment du maximum 
thermique, paraissant liée à la diminution d'oxygène de l'eau interstitielle. 

Dans les milieux à hydrodynamisme faible ou très faible et où sédimentent des sables 
moyens à peu grossiers renfermant parfois une certaine proportion de vase, les 2 espèces de 
Caecum sont moins abondantes qu'en hydrodynamisme élevé (elles sont même en état de survie 
précaire à la station 8), du fait soit de l'exiguité de la maille sedimentaire, soit d'un début de 
colmatage de celle-ci. 

(4) Des migrations verticales ascendantes amènent les 2 espèces de Caecum à se concentrer 
plus ou moins dans le film sedimentaire superficiel. Elles semblent de 2 types: 

— Migrations "printanières," qui s'observent dans les 3 intensités d'hydrodynamisme, et sont 
généralement suivies d'une prolifération des Caecum, des Opisthobranches et du reste du 
mesopsammon. Ces migrations semblent être des migrations trophiques et reproductrices. 

— Migrations "estivales," En hydrodynamisme élevé, la concentration des 2 espèces dans le 
film est suivie d'une nouvelle phase de reproduction. En hydrodynamisme moyen, les 2 espèces 
de Caecum disparaissent lors du maximum thermique; enfin, en hydrodynamisme faible, on 
observe soit la disparition des 2 espèces (station 8), soit la disparition de C. auriculatum (station 
9). ^ 

Ce deuxième type de migration doit être relié, dans les 3 catégories d'hydrodynamisme, à un 
déficit en oxygène dissous dans la sous-strate sedimentaire. 



TRAVAUX CITES 

FOLIN, L. DE, 1875, Monographie de la famille des Caecidae. A. Lamaignère, Bayonne, 31 p. 

PICARD, J., 1965, Recherches qualitatives sur les biocoenoses marines des substrats meubles dragables de la 

région marseillaise. Recueil de Travaux de la Station marine d'Endoume, Marseille, 52 (Bull. 36): 1-160. 
POIZAT, C, 1972, Etude préliminaire des Gastéropodes Opisthobranches de quelques sables marins du golfe 

de Marseille. Téthys, 3(1971): 875-896. 
POIZAT, C, 1975, Technique de concentration des Gastéropodes Opisthobranches mésopsammiques marins 

en vue d'études quantitatives. Cahiers de Biologie marine, 16: 475-481. 
UHLIG, G., THIEL, H. & GRAY, J. S., 1973, The quantitative separation of meiofauna. A comparison of 

methods. Helgolânder Wissenschaftliche Meeresuntersuchungen, 25: 173-195. 



MALACOLOGIA, 1979, 18: 327-346 

PROC. SIXTH EUROP. MALAC. CONGR. 

THE POPULATION DYNAMICS AND EXPRESSION OF SEXUALITY 
IN BALCISSHAPLANDI AND MUCRONALIA FULVESCENS 
(MOLLUSCA: GASTROPODA: AG LOSSA) PARASITIC UPON 
ARCHASTER TYPICUS (ECHINODERMATA: ASTEROIDEA) 

Brian Morton 
Department of Zoology, University of Hong Kong 

ABSTRACT 

In Hong Kong the intertidal starfish Archaster typicus (Müller & Troschel) is parasitised 
by two aglossan gastropods, Mucronalia fulvescens (A. Adams) (Stiliferidae) and Balcis 
shaplandi Melvill (Eulinnidae). The population dynamics of the starfish and its parasites have 
been studied for a period of 2 years from April 1973 to March 1975 inclusive. The starfish 
population at Tai Tam Bay, Hong Kong, comprises 4 age classes with new recruits arriving in 
the population in late summer and old individuals dying each winter when the population of 
starfish as a whole lies buried in the sand. A. typicus breeds in early summer (April-June); a 
form of "copulation" takes place with males overlying females, with arms alternating. Both 
parasites are protandrous consecutive hermaphrodites which leave the host in the late 
summer months. At other times the parasites are on the starfish but are spatially separated 
from each other— ß, shaplandi on the aboral, M. fulvescens on the oral surfaces (Morton, 
1976). When on the host (i.e. September-June), both parasites occur in discrete clusters 
which comprise 2 age classes; typically a single large female is surrounded by a variable 
number of smaller males. Copulation takes place first in the spring (April-May). Following 
egg laying (in saucer shaped capsules) the older females die and the young males undergo a 
process of sexual change (with transitional phases recognisable) to become female. These in 
turn are fertilised in a 2nd reproductive phase in autumn (September-November) by their 
now hatched and growing (male) progeny. Both species thus complete their cycle in 
approximately 15 months, but the pattern of 2 breeding seasons per annum ensures a safety 
margin essential for species maintenance. 

The male and female reproductive systems of both species are very similar. The male 
system comprises a vas deferens emptying into a seminal vesicle which in turn discharges 
into a seminal groove surrounded by a postrate gland. Only B. shaplandi possesses a penis. 
The female system comprises an oviduct that discharges into a seminal receptacle via the 
intermediary of an albumen gland. The seminal receptacle opens into a palliai oviduct. The 
egg capsule of both species is thought to be secreted by a large modified hypobranchial 
gland that occurs only in the female. The gametogenic cycle of both species is described 
including the hermaphroditic transitional stage. 

INTRODUCTION 

Little is known of the life cycle of the parasitic aglossan gastropods. Thus Vaney (1913) and 
Fretter (1955) were only able to find females of Eu / ima equestr is anä Balcis devians respectively. 
Hoskin & Cheng (1969) noted that in general terms females of Mucronalia nitidula were larger 
than the males. This, however, was based on an examination of 10 specimens only. Lützen (1972) 
and Gooding & Lützen (1973) have described how Stilifer linckiae and Robillardia cernica are 
probably protandric consecutive hermaphrodites. 

Megadenus cantharelloides (Humphreys & Lützen, 1972) does not exhibit sexual dimorphism 
because the female has to attach egg capsules to the shell of the male whereas species of 
Paramegadenus exhibit a pronounced male dwarfism. Male dwarfism is also found in Enteroxenos 
oestergreni (cf. Lützen, 1968) where the pygmy male is implanted in the wall of the pseudopallial 
cavity of the female. The same author also argued that this was probably also the case in the 
supposedly hermaphrodite Thyonicola, Entoconcha and Entocolax (though male dwarfism had 
been recognised in the latter genus much earlier: Ivanov, 1945). 

Male drawfism might be regarded as an evolutionary indicator of a highly specialised obligate 
endoparasite, typically occurring in few numbers. How such an adaptation arose in the Aglossa, 

(327) 



328 PROC. SIXTH EUROP. MALAC. CONGR. 

however, might be revealed by an understanding of the sexual cycle in less specialised ectoparasitic 
relatives. In Hong Kong the very common intertidal sandy shore starfish Archaster typicus (Müller 
& Troschel) is parasitized by two parasitic aglossans, Balcis shaplandi \bl\eW\\\ and Mucronalia 
fulvescens (A. Adams). The former is a member of the Eulimidae, the latter a member of the 
Stiliferidae. On the host the 2 parasites are spatially separated. B. shaplandi occurs on the aboral 
surface and feeds on the coelomic fluids, M. fulvescens occurs on the oral surface and feeds on the 
fluids of the water vascular system (Morton, 1976). Preliminary studies of these 2 parasites 
suggested that they occurred on the host in variable numbers and often in what appeared to be 
sex-paired clusters. A long term study of the 2 parasites was therefore initiated with the following 
aims: (1), to elucidate the structure of the reproductive systems; (2), to determine the sexual 
cycle; (3), to investigate the population dynamics of the parasites and the host; (4), to elucidate 
the relationships of the parasites, one with the other and with their common host. 

MATERIALS AND METHODS 

Commencing April 1973 for a period of 2 years, 100 specimens of Archaster typicus were 
collected every month from the shallow intertidal sand flats of Tai Tarn Bay, Hong Kong Island. 
Each starfish was carefully examined, on site, for parasites and where these were found they were 
removed and placed in labelled tubes. A record was kept as to whether or not the individuals of 
each species were solitary or were in clusters of two or more. Upon return to the laboratory the 
parasites were measured along their greatest length to the nearest 0.5 mm and, following fixation 
in Bouin's fluid, were sectioned at Gjurn and stained in either Mallory's triple stain, Heidenhain's 
haematoxylin or periodic acid-Schiff (PAS). 

Each month length-frequency histograms of the population of each species of parasite were 
constructed and each parasite, from an examination of the sectioned material, sexed. The sexual 
cycle of both males and females were divided into 5 phases. These were: (1), initial stage; (2), 
developing stage (1); (3), developing stage (2); (4), ripe stage; [Ъ) , spawned stage. The sections 
were also closely examined for transitional stages. 

Every 3 months for a period of one year a much larger sample of Archaster typicus was 
collected and each member of this sample was measured from the tip of one arm to the 
inter-radius of the opposite two arms. From these data length-frequency histograms have been 
constructed which have been analysed using a Walford plot (Walford, 1946; Ricker, 1958). 

Archaster typicus is unusual in that sex pairs are established during the breeding season with 
males overlying females (demente & Anicete, 1949). A record was kept each month of when 
"copulation" was taking place in the majority of the sample i.e. when numbers exceeded 50% of 
the monthly sample of 100 individuals. Records were also kept of the occurrence of newly settled 
and adult starfish in poor condition. 

RESULTS (l)-THE HOST 

In December 1974 the length-frequency histograms of the sample oi Arch aster typicus from Tai 
Tam suggested that the population comprised 4 age classes which could have respectively settled in 
1971, 1972, 1973 and 1974 if breeding and larval settlement takes place but once a year (Fig. 1). 
By March 1975 the same 4 age classes were recognisable with the smallest age class present in 
relatively greater numbers. By June 1975 the oldest age class (i.e. that which was presumed to have 
settled in 1971) was no longer present in the sample and the youngest age class accounted for a 
much greater percentage of the total. This age class had grown from an arm-disc length of 40 mm 
in March to 50 mm in June. Similarly both 1972 and 1973 age classes had grown. In September 
1975 a new age class of length 15 mm appeared in the sample. The 1974 age class had grown by 
this time to 55 mm whilst the 1972 age class was possibly overshadowed by the 1973 age class. 

This analysis of the population structure of A. typicus at Tai Tam suggests that breeding and 
larval settlement takes place but once a year. This fits in well with associated data on the biology 
of A. typicus at Tai Tam. From April to June each year the starfish population as a whole grouped 
itself into sexed pairs with males overlying females (demente & Anicete, 1949). The products of 
this union were collected as young starfish later on in the year; in this case in September 1974. 



MORTON 



329 



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Length (лил ) 

FIG.l. Length frequency histograms showing the composition of samples of the population of Archaster 
typicus inhabiting Tai Tarn bay, Hong Kong. The dates above individual peaks represent the dates at which these 
particular year classes settled. 



330 



PROC. SIXTH EUROP. MALAC. CONGR. 



During the reproductive phase the pairs are occasionally partially buried in the sand though more 
often they lie on the sand surface. This behaviour is not true "copulation" since no copulatory 
organs are possessed by either partner, but proximity may increase the chance of fertilisation 
especially if the release of eggs from gravid females stimulates the release of sperm by the male. 
During the autumn and winter months the starfish lie buried in the sand. Large, presumably old, 
specimens collected at this time were often in a bad condition with broken arms and damaged 
external surfaces. It is probable that old individuals die at this time, as is evidenced in some 
measure by Fig. 1 where by June the oldest (i.e. the 1971 age class) components of the population 
had all died. 

t 



I П I S 




FIG. 2. (A) Walford plot for Archaster typicus from Tai Tarn in which for each year grouping the average length 
(Lt) has been plotted against the average length a year later (Lt + 1). Trial values of Lq have been used to give 
the best fitting line for a plot of loge (Lq - Ц) against t. The slope К obtained from (B) has been used to 
calculate k. The Walford plot has then been drawn in (A) with a broken line using the calculated values of к and 
Lq. For log (Loc-Lt) read loge(l-a - Ц'- 



MORTON 331 

The structure of the population of A. typicus from Tai Tarn has been analysed using a Walford 
plot (Walford, 1946; Ricker, 1958). Fig. 2A shows that the arm-disc length of the 4 age classes of 
the starfish comprising the March 1975 sample approach the 45° line as expected if growth fits the 
Bertalanffy formula Ц = Lad - e-^ít-to)) (Bertalanffy, 1938) where L = length, t = age. La = 
maximum theoretical length and К = a growth constant. For this range of ages loge(La~Lt) has 
been plotted against age (t) (Fig. 2B) to determine by trial the best value of La and the slope of K. 
The best value of La has been shown to be 135 mm and the regression for the slope of the Walford 
plot (k) has been calculated as у = 47.1 + 0.65x (broken line in Fig. 2A). Such an analysis suggests 
that the population picture of A. typicus at Tai Tam as revealed in the samples is a true one and 
that the species can live for approximately 5 years. 

RESULTS (ll)-THE PARASITES 
The reproductive systems 

Mucronalia fulvescens 

At an average length of 3.0 mm the greatest percentage of individuals of this species are male 
(Fig. ЗА). The testis (Fig. 4A, T) occupies a dorsal position in each body whorl being enveloped by 
the digestive diverticula (DD). It is divided into several lobules all of which ultimately discharge 
into a short vas deferens which expands into a seminal vesicle (SV) 400 jum in diameter with an 
epithelium composed of cells 10 дт tall possessing nuclei 4jum in diameter (Fig. 6A). The lumen 
of the seminal vesicle contains unoriented spermatozoa, some of which were also seen with their 
heads embedded in the epithelial wall. A short duct connects the seminal vesicle with the mantle 
cavity. The duct (Fig. 4A), ultimately forming the seminal groove (SG) has a diameter of 
50)Lim and comprises a ciliated cuboidal epithelium 6jum in height (Fig. 6B). The seminal duct is 
encompassed by the prostate gland (PG) which is some 350 )um in diameter and comprises a matrix 
of lightly staining cells interspersed between which are granular secretory cells. These open into 
the seminal duct. There is no penis as in M. nitidula (cf. Hoskin & Cheng, 1969). 

At a length of approximately 3.5 mm M. fulvescens changes sex. Fig. 4B is a diagrammatic 
representation of this transitional stage. As noted by Liitzen (1972) for Stilifer linckiae sex 
reversal must take place extremely rapidly because in only one or 2 specimens out of the many 
hundreds sectioned, was this change at all in evidence. The testis after discharging sperm is spent. 
The tissues begin to break down accompanied by a degeneration of the reproductive tract except 
for, most importantly, the seminal duct and surrounding glandular mass. From a dorsal position in 
each body whorl the primordial cells of the ovary begin to develop and, growing rapidly, occupy 
the space left by the degenerating testis. The female ducts develop; it is not known if they 
represent new structures or if they develop from broken down but restructured male ducts. 

At a length of between 4.0-5.0 mm most specimens of M, fulvescens are female (Fig. ЗА). 

The female reproductive tract is simple and comprises an oviduct which connects up with a 
seminal receptacle (Figs. 4D, SR) via the intermediary of an albumen gland. The albumen gland 
(Fig. 6C) comprises a darkly staining columnar epithelium composed of cells 60 /xm tall possessing 
short cilia (5)um long) and a basally located nucleus 5//m in diameter. The gland has overall 
dimensions of 450 X 150 /urn with a narrow lumen. The seminal receptacle (Fig. 6D) has a 
diameter of 230 //m and comprises a densely ciliated epithelium composed of cells 55/L£m tall each 
possessing a basal nucleus 5jum in diameter. After copulation the seminal receptacle is packed with 
spermatozoa (S) each oriented outwards with its head embedded in the epithelial lining. From the 
seminal receptacle arises a duct that opens into the mantle cavity as the palliai oviduct (Fig. 
4, GD), The palliai oviduct (Fig. 6E) has the same structure as the male seminal duct (Fig. 6B) 
except that the prostate gland cells of the tissue surrounding the duct are not present. Into the 
mantle cavity opens the capsule gland which arises as 2 histologically differentiated regions of a 
single structure [Fig. 4D, CG(1); CG(2)] formed on the dorsal region of the mantle. Proximally 
the gland comprises cells [CG(1)] ЮОдт tall densely staining in Heidenhain's haematoxylin. 
Distally the gland comprises lightly staining cells [CG(2)] some 250 дт tall. Both components of 
the gland, however, possess a similar structure (Fig. 6F) in that elongate secretory cells (SC) with a 
basal nucleus Sjum in diameter are interspersed with inversely conical "supporting" cells (SU) each 
possessing cilia 5-7 /um long and an apically located nucleus 4jum in diameter. Both components of 



332 



PROC. SIXTH EUROP. MALAC. CONGR. 



FEMALE C> 



MALE ° 




SHELL LENGTH (mm) 



FIG.3. Size-frequency analysis of (A) Mucronada fulvescens and (B) Balcis shaplandi showing the relative 
incidence of immature, male and female individuals. 



MORTON 



333 




FIG. 4. Mucronalia fulvescens. Sections through (A), male phase (3.0 mm shell length); (B), transitional stage 
(3.5 mm shell length); (C), female phase (4.0 mm shell length) and (D), female phase (5.0 mm shell length), 
showing a full seminal receptacle (for abbrevations see text). 




FIG. 5. Balds shaplandi. Sections through (A), male phase (2.0 mm shell length); (B), transitional stage (2.5 mm 
shell length) and (C), female phase (3.5 mm shell length) (for abbreviations see text). 



334 



PROC. SIXTH EUROP. MALAC. CONGR. 




FIG. 6. Mucronatia fulvescens. Sections through (A), seminal vesicle; (B), seminal groove and surrounding 
prostate gland; (C), albumen gland; (D), seminal receptacle; (E), palliai oviduct (modified seminal groove) and 
(F) capsule gland (modified hypobranchial gland) (for abbreviations see text). Scales— B, E: ЮОмт; С, F: 
бОдт; A, D: 25 дт. 




FIG. 7. Baicis shaplandi. Sections through (A), seminal vesicle; (В), seminal groove and surrounding prostate 
gland; (C), albumen gland; (D), seminal receptacle; (E), palliai oviduct (modified seminal groove) and (F) capsule 
gland (modified hypobranchial gland) (for abbreviations see text). Scales— A: 25 дт; C-F: 50^m;B: 75 дт. 
A and В should be transposed in the figure. 



MORTON 335 

the gland open via a common aperture into the mantle cavity where the fertilised eggs are 
enveloped within a capsule. The capsule of M. fulvescens (and B. shaplandi) is in the form of an 
inverted saucer and is similar to that of Littorina littorea (cf. Fretter & Graham, 1962). Sometimes 
capsules were found attached to the shell of a male. 

Balds shaplandi 

At an average length of between 2.0-2.5 mm the greatest percentage of individuals of Balcis 
shaplandi are male (Fig. 3B). As with M. fulvescens, the testis (Fig. 5A) occupies a dorsal posi- 
tion within each whorl other than the first, being enveloped by the digestive diverticula (DD). 
The testis discharges into the vas deferens which in turn empties into a large and much convoluted 
seminal vesicle (SV) some IGO^m in diameter and made up of a cuboidal epithelium 5)Ltm tall 
(Fig. 7A). Each cell possesses a small (Sjum) nucleus. The vesicle lumen contains a mass of un- 
orientated spermatozoa and connects up by a long narrow duct with the seminal duct (Fig. 5A,SD) 
which opens into the mantle cavity (MC). As in M. fulvescens the seminal duct and groove is 
surrounded by the swollen mass of the prostate gland. The seminal duct (Fig. 7B) is some 75 дт in 
diameter and comprises an epithelium composed of densely ciliated cells бдт in height, each 
possessing a nucleus 3.5 /im in diameter. The encompassing prostate gland (PG) has dimensions of 
250 X 170ium and comprises a matrix of lightly staining cells interspersed with glandular masses 
which open into the seminal duct. As in B. alba and B. devians (Fretter, 1955), B. shaplandi 
possesses a penis. 

At a length of approximately 2.5-3.0 mm B. shaplandi undergoes a change of sex which as in M. 
fulvescens must take place very quickly. Fig. 5B is a diagrammatic representation of this 
transitional stage. Once spent, the testis and the associated duct system degenerate and from the 
dorsal surface of each whorl the primordial cells of the ovary begin to descend and to occupy the 
space left by the testis. The female reproductive tract that develops is very similar to that of M. 
fulvescens. Females occur in the population over a wide length range i.e. from 1.5-5.0 mm though 
they are most numerous at a length of 3 mm (Fig. 38). 

The female reproductive tract (Fig. 5C) comprises an oviduct which connects up with a seminal 
receptacle via the intermediary of an albumen gland (AG). The albumen gland (Fig. 7C) is 
some 230 /Lim in diameter and comprises a darkly staining columnar epithelium (SC) composed of 
cells 70 /im tall each possessing cilia (C) 5jum long and a basal nucleus 4/im in diameter. The 
seminal receptacle (Fig. 7D) has a diameter of 110/Ltm and comprises cells approximately 12 /tm 
tall with a nucleus 6/im in diameter. The cells are densely ciliated (C) and following copulation 
the receptacle lumen is densely packed with spermatozoa (S) each orientated outwards with its 
head embedded in the epithelium. The receptacle gives rise to a duct that opens into the mantle 
cavity as the palliai oviduct (Fig. 5C, GD). The palliai oviduct (Fig. 7E) is 65jum in diameter and 
comprises cells 15мт tall with long (15/im) cilia and a nucleus 4/Ltm in diameter. As in M. 
fulvescens, the duct is surrounded by the same structure as in the male except that the prostate 
gland cells are not present. Into the mantle cavity of the female opens the capsule gland (Fig. 5C). 
As in M. fulvescens the gland is differentiated histologically into two regions [CG(1); CG(2)] , but 
in B. shaplandi their position is reversed. Thus the darkly staining component of the gland [CG(1 )] 
is located distally and comprises an epithelium QOjum tall. The lightly staining component [CG(2)] 
is located proximally and comprises an epithelium 75 /tm tall. The cilia of this region of the gland 
are somewhat shorter (7 jum) than those of the former (9/im). Both components of the capsule 
gland, however, possess a similar structure (Fig. 7F) and comprise elongate secretory cells (SO 
with a basal nucleus 5 /im in diameter interspersed between ciliated inversely conical "support- 
ing" cells (SU) with an apically located nucleus 3/im in diameter. Both components of the gland 
open into the mantle cavity where the fertilised eggs are encapsulated as in M. fulvescens. 

Gametogenesis 

The gametogenetic cycle in Mucronalia fulvescens and Balcis shaplandi is very similar. The 
following is therefore an account of spermatogenesis and oogenesis! that is applicable to both 
species. 

The acini of the testis (Figs. 8 and 9) are the sites of spermatogenesis. At first (Stage 1) each 
acinus (Figs. 8 and 9A) comprises a small cluster of darkly staining cells which subsequently 



336 



PROC. SIXTH EUROP. MALAC. CONGR. 



-<^ 








^c"- 














N **., 







\-. :. 







FIG. 8. Mucronalia fulvescens. Gametogenetic cycle (A— E = male sequence; F, transitional phase; G— К, female 
sequence) (for abbreviations see text). 

develop into distinct tubules (Stage 2), each epithelial lining possessing a layer of spernnatogonia 
(Figs. 8 and 9B). The tubule walls later enlarge and here can be found primary spernnatocytes with 
nuclei smaller than those of the spermatogonia. Among the primary spermatocytes can later be 
found secondary spermatocytes (Figs. 8 and 9C) which give rise by meiosis to spermatids (Stage 
3). Often arranged in clumps the spermatids eventually give rise to spermatozoa whose flagella 
densely fill the lumina of the acini. The spermatozoa remain attached to the Sertoli cells (Figs. 8 
and 9D) until they are discharged into the seminal vesicle for storage until required during 



MORTON 



337 



igt.-.- ' i.J; * •• ' » t ,' ' -sj 



f 



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\t' . ^ 



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FIG. 9. Balds shaplandi. Gametogenetic cycle 
sequence) (for abbreviations see text). 



(A— E = male sequence; F, transitional phase; G— K, female 



copulation. At this Stage 4 the testis is mature. Once copulation has taken place the acini of the 
testis break down. In spawned individuals (Figs. 8 and 9E) (Stage 5) the acini lumina possess few 
sex cells whilst later the testis becomes a mass of degenerating cells. At this time the volume of the 
testis decreases as in Stilifer (Lützen, 1972) and its place is taken up in the visceral mass by the 
developing ovary (Figs. 8 and 9F). At this time both species are transitional with degenerating 
testis (DT) and developing ovaries (DO). 

The ovary develops from the same position in the visceral mass as the testis, i.e. the dorsal 



338 



PROC. SIXTH EUROP. MALAC. CONGR. 



region of each body whorl. The ovary is first seen (Figs. 8 and 9G) (Stage 1) as a cluster of large, 
lightly staining primordial cells lying above the degenerating testis. Later (Figs. 8 and 9H) (Stage 2) 
a distinct alveolus forms, often with oogonia, which grows downwards into the visceral mass. The 
follicle walls progressively thicken and contain many darkly staining inclusions (probably 
glycogen) which stain positively in Heidenhain's haematoxylin and PAS. The number and size of 
the developing oocytes increases and at this stage are still attached basally to the follicle wall (Figs. 
8 and 91) (Stage 3). Later the oocytes are released into the follicle lumen and ovaries at this stage 
were considered ripe (Figs. 8 and 9J) (Stage 4). At this time the seminal receptacle was observed in 
some specimens to be full of spermatozoa. Few totally spawned individuals were found (Figs. 8 
and 9K) (Stage 5). More common were partially spawned females with a thin follicle wall 
possessing few oogoonia and oocytes and a lumen containing but a few oocytes. At this stage, once 
egg laying has been completed, death ensues and the rarity of totally spawned individuals of both 
species might thus be a consequence of natural mortality. 

Population dynamics 

Balics shaplandi occurs on the aboral surface oi Archaster typicus (Morton, 1976) in extremely 
variable numbers. From Fig. 10 it can be seen that the total number of individuals occurring on 
the 100 starfish (expressed as a % of the total number of individuals of this species collected over a 
12 month period) changes quite considerably from month to month. Thus in April 1973 a large 
number of parasites were collected, but this number declined to in August and remained 
relatively low for the months of September and October. Thereafter the number increased to a 
peak in January 1974. Subsequently numbers again declined (though remaining at an average 
frequency of 9%) with the approach of summer and very few individuals were collected in the 
months of May, July and September. Again numbers increased to reach a peak in February 1975. 
From this data it would thus seem that B. shaplandi is to be found on the host in greater numbers 
in the winter months from October/November to May and in fewer numbers in summer from June 
to September. 

Mucronalia fulvescens occurs on the oral surface of Archaster typicus typically within the axis 
of the arms or within the ambulacral grooves (Morton, 1976). 

As with B. shaplandi, the first sample of M. fulvescens collected in April 1973 registered a large 
number of individuals. This number declined as the year progressed to a few individuals only in 
November and then rose again to a small peak in February followed by a much larger peak in April 
and May 1974. This relatively high incidence of M. fulvescens was followed by a gradual decline to 
low numbers in October-November 1974. A final high incidence of parasites was recorded in 
February 1975. Thus the pattern of occurrence earlier seen in B. shaplandi ^as approximately 



"^ 1 Bolcis shoDlondi 



1973-74 Mucronolio fulvescens 




FIG. 10. The frequency of occurrence of individuals of Balcis shaplandi and Mucronalia fulvescens upon 
Archaster typicus for the years April 1973-March 1974 and April 1974-March 1975. Each monthly total is 
expressed as a percentage of the yearly total. 



MORTON 



339 




FIG. 11. The frequency of occurrence of individuals of Bald's shaplandi and Mucronalia fulvescens upon 
Archaster typicus clustered together in groups of two or more for the year April 1974-March 1975. 



repeated by M. fulvescens with this species occurring on the host in greater numbers in the winter 
months from December/January to May and in fewer numbers in the late summer, i.e. from 
September to November. 

For one year only the % number of individuals occurring in clustered groups of 2 or more 
individuals has been plotted as Fig. 11. In July, August and September when few specimens of ß, 
shaplandi were on the host, the number occurring in clusters was few. Conversely from October to 
February or April, the parasites that were on the host occurred in clusters with in November and 
January more than 50% of the individuals so disposed. Typically at this time a single large (female) 
individual was associated with 1-8 smaller males. 

M. fulvescens exhibited a similar pattern of behaviour. From June to September all individuals 
were solitary. At other times, however, corresponding to the winter months when the parasites are 
on the host, they occurred with greater frequency in clusters of 2, 3 or 4 with a peak in January. 

As with B. Lapland!, a single large (female) individual was clustered with typically 1 or 2 
smaller males. 

The monthly samples of B. shaplandi (Fig. 12) have been sexed to determine first if they were 
either male, female or immature. In April 1973 the population comprised 2 peaks with smaller 
individuals being mature males and larger individuals mature females. In May 1973 a larger % of 
the population comprised very small immature individuals and a number of males, with only 1% of 
the population female. A similar pattern emerged in June but by July few individuals were 
immature, all clearly being either (generally) smaller males or larger females. From August to 
October few B. shaplandi were found on the host but by November the population again 
comprised 2 small peaks of smaller males and larger females. Small immature individuals were 
again recorded from December 1973 to February 1974. By April 1974, however, the sexes were 
once again clearly separated into smaller males and larger females. Few parasites were collected in 
May 1974 but immature individuals occurred on the host from June to August. In September and 
October 1974 the population comprised relatively well defined peaks of smaller males and larger 
females. Immature individuals again occurred from November 1974 until January 1975 these 
superimposing themselves onto an established population of small males and larger females. By 
February all immature individuals had sexually matured and in March the population settled down 
to comprise small males and larger females. 

From April to June 1973 2 peaks of individuals comprised the monthly population samples of 
M. fulvescens on the starfish (Fig. 13). These were larger females and smaller males. From July to 
October, however, smaller individuals appeared in the population which, unlike juvenile B. 
shaplandi, were nearly always clearly recognisable as males. Few individuals were recorded from 
September 1973 to February 1974 but even so a clear size distinction between smaller males and 
larger females was often apparent. Small individuals also appeared in the population in March 1974 



340 



PROC. SIXTH EUROP. MALAC. CONGR. 



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342 PROC. SIXTH EUROP. MALAC. CONGR. 

and these again were clearly male. In May and June 1974 the population was again approxinnately 
divisible into 2 peaks respectively connprising smaller males and larger females. Young individuals 
(again male) appeared in the population in July and August 1974 and finally again in October and 
November 1974. At all times these young individuals superimposed themselves onto an adult 
population which typically comprised small males and older larger females. 

Each individual of both M. fulvescens and B. shaplandi comprising each monthly sample has 
been graded according to its state of sexual maturity earlier defined (Stages 1-5 for each sex) and 
shown in Figs. 8 and 9 (A-K). Figure 14 records the sexual stage (either Ajmmature; i !,male;0, 
female) that the greatest number of individuals of each age class of each species had attained in 
that month. Amplifying Fig. 14 it can be seen that young immature individuals arriving in the 
population of B. shaplandi in November-December and in the population of M. fulvescens in 
October-February grow rapidly and mature into males. Copulation with the larger females takes 
place in April in B. shaplandi and in May in M. fulvescens. Following copulation the males undergo 
a sexual change to become females. These females of both species grow further and mature and are 
fertilised in October-November in B. shaplandi and in September in M. fulvescens. Following egg 
laying these individuals die, having completed their life cycle in approximately 15 months. There 
are thus 2 phases of reproduction in both species each year with the products of one phase of 
reproduction maturing into males and in turn fertilising the formerly male but subsequently 
female parent. The resulting progeny of this fertilisation carry the process on. 



DISCUSSION 

The life cycle of the detritivorous starfish Archaster typicus is apparently straightforward. 
Young individuals enter the population in late summer following a phase of reproductive activity 
in the early summer. The species lives for approximately 4.5 years with the oldest individuals 
dying in the winter months of their 4th/5th year. Calculations show that it would be theoretically 
possible for the species to attain a disc/arm length of 135 mm and it is thus further possible that 1 
or 2 individuals may survive into their 5th year. Within each age class the sexes are in the 
approximate ratio of 1 to 1 (demente & Anicete, 1949) and the species is thus dioecious. The 
same authors could not differentiate between the sexes on a size basis and it is thus safe to 
conclude that the size frequency peaks seen in these samples of A. typicus from Hong Kong do 
represent age classes and not a sexual dimorphism. 

Two features of the life history are, however, unusual. First, during breeding, a form of 
"copulation" takes place, males overlying females with arms alternating. Thus during the early 
summer (April-June) in Hong Kong (and in the Philippines) sex-paired starfish closely dot the 
lower shore. This phase of reproductive activity coincides with the time when sea water 
temperatures in Hong Kong are rising (Morton & Wu, 1975) typically to a maximum of 30°C in 
July. Each year also the oldest age class dies, typically in the winter months when sea water 
temperatures are low (13 С in February). Second, following reproduction, the starfish tend to 
bury themselves with the approach of autumn and damaged and dying starfish were collected in 
the winter months. They are replaced in the population by the new recruits. These 2 factors, it is 
here suggested, influence the life cycle of both parasites. 

Thus during the time of "copulation" in A. typicus, Mucronalia fulvescens is to be found on the 
host, but in declining numbers from April to June. A similar generalisation holds true for Balcis 
shaplandi. In April-May the gonads of both parasites are mature and copulation and egg laying 
takes place. It thus appears that following copulation both parasites leave the host and from 
July-September few parasites of either species were obtained. This may be partially explained by 
the fact that the females of both species, having once completed egg laying, probably die. 
Furthermore the "copulatory" activity of the starfish may physically dislodge some of the 
parasites. Finally, following reproduction, the oldest starfish die as the air and sea temperatures 
begin to fall. New recruits to the starfish population are, however, arriving at this time and it seems 
likely that a percentage of small male and immature, newly hatched parasites of both species, leave 
the host at this time, probably to find a new host. By October both parasites were recorded from 
the starfish in relatively small numbers but it is significant that at this time those that were on the 
host were in clusters and that these individuals were sexually mature. Thus in the late autumn 



MORTON 



343 



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FIG. 14. Average length of each age class in the monthly samples of Mucronalia fulvescens and Balcis shaplandi. 
The dates represent the dates at which each age class hatched. A = immature individuals; j = males; 0- females. 
The number within each of these symbols (1-5) represents the sexual stage (either male or female) attained by a 
majority of the individuals comprising this age class and can be correlated with letters A-E (males) and G-K 
(female) of Figs. 8 and 9. The times of copulation, hatching and death are also indicated. Finally the occurrence 
of each parasite upon the host is correlated with the "copulatory" activity and time of death of the host. 



344 PROC. SIXTH EUROP. MALAC. CONGR. 

(around October for both species) the maturing progeny of the spring (April/May) sexual union 
have grown sufficiently and are mature enough to mate with the sex-changed individuals who were 
their fathers in the spring reproductive phase but who have subsequently become female. After 
this second, autumn phase of reproduction and egg laying the spent females die and the young 
males and immature juveniles remain on the starfish typically in large numbers and in clusters for 
the whole winter period i.e. from October-March. At this time of year the starfish are typically 
buried in the sand (at least during the period of low tide when these samples were collected) and 
because the parasites remain on the host in relatively large numbers it is here suggested that this is 
the time when they are feeding, ensuring that over the cold winter months they have an adequate 
supply of food to see them into the next phase of reproduction that will begin again in the 
following spring. Thus in any one year both M. fulvescens and B. shaplandi undergo 2 phases of 
reproduction, one in spring, the other in autumn. This is essential because both species live for but 
one year during which time they are first male and then female; the females being fertilised by 
their own progeny. Fig. 14 sets out the sexual cycle of both parasites related (1), to the observed 
changes in the gametogenic cycle of each age class of each species; (2), to the recorded occurrence 
of the parasites upon the host, and (3), to important aspects of the biology of >4. typicus. Though 
both species, in general terms, breed in spring (April/May) and in autumn (September/November) 
there are slight differences in the time each species undertakes these activities. This may suggest 
that a partial temporal separation of the 2 parasites on the host occurs, though these data clearly 
indicate that this mechanism of segregation is nowhere near as important as the hitherto described 
selective site segregation, typical of these two parasites (Morton, 1976), that subdivides the host 
into 2 niches. 

There are only slight differences in the structure of the reproductive organs of M. fulvescens 
and B. shaplandi. Thus M. fulvescens does not possess a penis (like M. nitidula, see Hoskin & 
Cheng, 1969). 8. shaplandi (and B. alba, see Fretter, 1955) does possess a penis in the male phase 
that is reduced to a vestige in the female. Otherwise the reproductive tract of both species is very 
similar with a short vas deferens leading into a capacious seminal vesicle that in turn leads into a 
seminal groove surrounded by the prostate gland as possibly in Natica catena (cf. Fretter & 
Graham, 1962). At a length of approximately 3.5 mm in M. fulvescens and of 2.5-3.0 mm in B. 
shaplandi both species undergo a change of sex (following copulation and egg laying) and become 
female. This process involves the degeneration and resorption of the testis and the male 
reproductive system, except for the seminal groove (which now becomes the palliai oviduct) and 
the surrounding prostate gland, which is retained except for the glandular portion of this structure 
which is lost. Lützen (1972) has suggested for Stilifer linckiae (which is similarly a protandric 
consecutive hermaphrodite) that the entire female system develops anew and not from a reformed 
broken down male system. This cannot be verified from the results of this study, but it is 
significant that the female system of both M. fulvescens and B. shaplandi is also simple with 
the oviduct enlarging to form an albumen gland and a seminal receptacle. Fertilisation is thus 
internal in both species though copulation in neither has been observed. In the mantle cavity of 
females of both species develops a large gland, divisible into two histologically distinct components 
that possibly secrete the chemical constituents of egg capsules, once the eggs are released into the 
mantle cavity. This gland is not seen in the male phase and has the general structure of the 
molluscan hypobranchial gland earlier described for Diodora apertura and Emarginula reticulata 
(cf. Fretter & Graham, 1962) and for a number of bivalves (Morton, 1977). In all of these molluscs 
the gland comprises large secretory cells interspersed with inversely flask-shaped, (often termed) 
"supporting cells," that in Solemya are rich in lipids and are possibly absorptive. In Tricolia 
(Fretter & Graham, 1962) a secretion from the lips of the urinogenital aperture of the female is 
augmented by a secretion from the hypobranchial gland and is used to entangle the egg stream 
within the mantle cavity. Similarly a secretion from the hypobranchial gland of Gibbula (Gersch, 
1936) is copiously produced during the breeding season and possibly provides an embedding 
medium for the egg masses. In the bivalve A/aciy /a the hypobranchial gland produces a secretion 
which furnishes nearly all the material from which brood sacs are formed (Drew, 1901). It is 
significant that this structure only occurs in the females of both M. fulvescens and B. shaplandi 
and it would appear that in both its prime function is to produce the material from which the egg 
capsules are formed. 

Hoskin & Cheng (1969) have described the reproductive system of M nitidula and found it (in 
both male and female) to be remarkably simple, the vas deferens developing into a sperm duct, the 



MORTON 345 

oviduct into the uterus. In neither sex were associated glands described. The reproductive system 
of B. devians (Fretter, 1955) is more complex with for example in the female the oviduct 
debouching into a receptaculum seminis with "staining reactions suggest{ing) that the albumen is 
secreted by the inner closed end of the oviduct adjacent to the opening of the receptaculum 
seminis, and that the thick wall of the capsule is a product of the palliai region of the duct." The 
reproductive systems of 3 other parasitic prosobranchs i.e. Stilifer, Megadenus and Robillardia 
have been described by Lützen (1972), Humphreys & Lützen (1972) and Gooding & Lützen 
(1973) respectively. In these aglossans there is a consistency of structure with for example in the 
males a vas deferens leading into a seminal vesicle which in turn discharges into a seminal groove 
via the intermediary of a prostrate gland. In the females an oviduct empties into the seminal 
receptacle (often also with a bursa copulatrix) which in turn releases fertilised eggs into the mantle 
via the genital pore. An albumen gland is located between oviduct and seminal receptacle, whilst 
the capsule gland is found on the mantle (similarly a modified hypobranchial gland?). The 
reproductive organs of both M. fulvescens and B. shaplandi conform to this general plan though 
for neither has it been possible to histologically separate a bursa copulatrix from the seminal 
receptacle. Moreover the prostrate gland of both species is located around the seminal groove. 

Within the prosobranch mesogastropods consecutive hermaphroditism has been recorded in the 
families Calyptraeidae (Orton, 1909), lanthinidae (Ankel, 1926), Scalidae (Ankel, 1936) and the 
Capulidae (Graham, 1954). It has also been long suspected to occur in the ectoparasitic aglossan 
parasites, so that Hoskin & Cheng (1969) noted for Mucronalia nitidula that there were small 
males and large females. Lützen (1972) and Gooding & Lützen (1973) have shown how Stilifer 
and Robillardia are protandric consecutive hermaphrodites. This study of M. fulvescens and B. 
shaplandi similarly demonstrates protandric consecutive hermaphroditism in these 2 species and 
further describes how the population of both species is maintained. Lützen (1972) suggested for 
Stilifer that the oogonia appear by transformation of spermatogonia; this is clearly not the case in 
the species here under consideration. Both gonads develop from the dorsal edge of each whorl 
other than the first. This region of the body obviously comprises primordial cells which in a 
normal sequence give rise first to the testis and later to the ovary. 

Franc (1968) claimed that the Eulimidae and the Stiliferidae are characterised by separate 
sexes. Mucronalia fulvescens (Stiliferidae) and Balcis shaplandi (Eulimidae) are protandric 
consecutive hermaphrodites. Such an adaptation possibly ultimately gave rise to the dwarf males in 
more specialised endoparasitic aglossans e.g. Paramegadenus (Humphreys & Lützen, 1972) and 
Enteroxenos (Lützen, 1968), A. typicus is not simply a source of food for B. shaplandi and M. 
fulvescens. On the host the reproductive activities of both parasites are co-ordinated and their life 
cycle is intimately bound up with the life cycle of the starfish. Because both starfish and parasites 
are so common, this association is an ideal one in which to investigate further the host/parasite 
relationship, especially since so little is known of parasitic molluscs. 



ACKNOWLEDGEMENTS 

I am grateful to my research assistants Miss May Yipp and Mrs. Paula Scott for much practical 
help in this study and to Mr. Davidson Chi for histological assistance. The species here reported 
upon were kindly identified by Dr. John Taylor of the British Museum (Natural History). 

LITERATURE CITED 

ANKEL, W. E., 1926, Spermiozeugmenbildung durch atypische (apyrene) und typische Spermien bei Sca/a und 

Janthina. Verhandlungen der Deutschen Zoologischen Gesellschaft, 31: 193-202. 
ANKEL, W. E., 1936, Prosobranchia. In: GRIMPE, G. & WAGLER, E.,eds., Die Tierwelt der Nord- und Ostsee, 

IX b I. Akademische Verlagsgesellschaft, Leipzig, 240 p. 
BERTALANFFY, L. VON, 1938, A quantitative theory of organic growth. Human Biology, 10: 181-213. 
CLEMENTE, L. S. & ANICETE, B. Z., 1949, Studies on sex-ratio, sexual dimorphism and early development of 

the common starfish, Archaster typicus Müller and Troschel (family Archasteridae). Natural and Applied 

Science Bulletin, Manila, 9: 297-318. 
DREW, G, A., 1901, The life history of Nucula delphinodonta (Mighels). Quarterly Journal of Microscopical 

Science, 44: 313-391, 
FRANC, A„ ed., 1968, Mollusques Gastéropodes et Scaphopodes. In: GRASSE, P.-P., ed., Traité de Zoologie, 

5(3), Masson et Cie, Paris, 1083 p. 



346 PROC. SIXTH EUROP. MALAC. CONGR. 

FRETTER, v., 1955, Observations on Bald's deviens (Mon te го sato) and Balcis alba (Da Costa). Proceedings of 

the Malacological Society of London, 31 : 1 37-144. 
FRETTER, V. & GRAHAM, A., 1962, British prosobranch molluscs. Ray Society, London, 755 p. 
GERSCH, M., 1936, Der Genitalapparat und die Sexualbiologie der Nordeseetrochiden. Zeitschrift für 

Morphologie und Ökologie der Tiere, 31: 106-150. 
GOODING, R. U. & LÜTZEN,J., 1973, Studies on parasitic gastropods from echinoderms III. A description of 

Robillardia cernica Smith 1889, parasitic in the sea urchin Echinometra Meuschen, with notes on its biology. 

Det Kongelige Danske Videnskabernes Selskab Biologiske Skrifter, 20(4): 1-22. 
GRAHAM, A., 1954, The anatomy of the prosobranch Trichotropis borealis Broderip and Sowerby, and the 

systematic position of the Capul idae. Journal of the Marine Biological Association of the United Kingdom, 

33: 129-144. 
HOSKIN, G. P. & CHENG, T. C, 1969, On the ecology and microanatomy of the parasitic marine prosobranch 

Mucronalia nitidula (Pease, 1860). Symposium on Mollusca, Marine Biological Association of India, 1: 

780-798. 
HUMPHREYS, W. F. & LÜTZEN, J., 1972, Studies on parasitic gastropods from echinoderms I. On the structure 

and biology of the parasitic gastropod Megadenus cantharelloides n.sp., with comparisons on Paramegadenus 

n.Q. Det Kongelige Danske Videnskabernes Selskab Biologiske Skrifter, 19(1): 1-27. 
IVANOV, A. v., 1945, A new endoparasitic mollusk, Parenteroxenos dogieli, nov.gen., nov.sp. Doklady of the 

Academy of Sciences of the USSR, Zoology Section, 48: 450-452. 
LÜTZEN, J., 1968, Unisexuality in the parasitic family Entoconchidae (Gastropoda: Prosobranchia). 

Malacologie, 7: 7-15. 
LÜTZEN, J., 1972, Studies on parasitic gastropods from echinoderms. II. On Stilifer Broderip, with special 

reference to the structure of the sexual apparatus and the reproduction. Det Kongelige Danske 

Viderskabernes Selskab Biologiske Skrifter, 19(6): 1-18. 
MORTON, B. S., 1976, Selective site segregation in Mucronalia fulvescens and Balcis shaplandi (Mollusca: 

Gastropoda: Aglossa) parasitic upon Archaster typicus (Echinodermata: Asteroidea). Malacological Review, 

9: 55-61. 
MORTON, B. S., 1977, The hypobranchial gland in the Bivalvia. Canadian Journal of Zoology, 55: 1225-1234. 
MORTON, B. S. & WU, S. S., 1975, The hydrology of the coastal waters of Hong Kong. Environmental 

Research, 10: 319-347. 
ORTON, J. H., 1909, On the occurrence of protandric hermaphroditism in the mollusc Crepidula fornicata. 

Proceedings of the Royal Society, B81: 468-484. 
RICKER, W. E., 1958, Handbook of computations for biological statistics of fish populations. Bulletin of the 

Fisheries Research Board of Canada, 119: 1-300. 
VANEY, C, 1913, La pénétration des gastéropodes parasites dans leur hôte. Comptes Rendus des Séances de la 

Société de Biologie, Paris, 74: 598-601. 
WALFORD, L. A., 1946, A new graphie method of describing growth of animals. Biological Bulletin, 90: 

141-147. 



ABBREVIATIONS USED IN THE FIGURES 



AG 


Albumen gland 


MC 


Mantle cavity 


С 


Cilia 





Ovary 


CG(1) 


Lightly staining component of the 


P 


Proboscis 




capsule gland 


PG 


Prostate gland 


CG{2) 


Darkly staining component of the 


S 


Spermatozoa 




capsule gland 


SC 


Secretory cell 


CM 


Columella muscle 


SD 


Seminal duct 


DD 


Digestive diverticula 


SG 


Seminal groove 


DO 


Developing ovary 


SR 


Seminal receptacle 


DT 


Degenerating testis 


SU 


Supporting cell 


GD 


Genital duct 


SV 


Seminal vesicle 


1 


Intestine 


T 


Testis 



Kidney VM Visceral mass 



MALACOLOGIA, 1979, 18: 347-360 

PROC. SIXTH EUROP. MALAC. CONGR. 

EFFECT OF PESTICIDES AND NARCOTANTS ON BIVALVE MOLLUSCSi 



U. H. Mane, M. S. Kachole and S. S. Pawar 

Dept. of Zoology and Dept. of ßiocfiemistry, Marathwada University, 
Aurangabad-431002, India 



ABSTRACT 

The reactions of the marine bivalves Katelysia opima and Donax cuneatus (both 
connmercially important species in India) to various pesticides and narcotants were 
studied under laboratory conditions. Reactions varied, but thiometon and malathion were 
found to have the least effect on K. opima and D. cuneatus respectively, while malathion 
and DDT were found to be more toxic to K. opima and D. cuneatus respectively. D. 
cuneatus was little affected by the narcotics phénobarbital sodium and hexobarbital 
sodium, but K. opima was affected by phénobarbital sodium. The commercially 
important freshwater bivalve Indonaia caeruleus was studied in detail as regards the 
influence of polluting substances on the neurosecretory cells, the digestive gland and the 
intestine. All organs were affected in different ways. The narcotics affected the 
neurosecretory cells and the secretory material considerably. The effect of narcotics on 
the hepatopancreas was not pronounced, but it was marked on the intestine. Pesticides 
considerably affected the hepatopancreas and intestine. 



INTRODUCTION 

The increasing use of pesticides in modern land and water management has posed a potential 
hazard not only to human beings and wildlife but also to marine organisms of economic 
importance as these pollutants ultimately find their way into the sea. Experiments were planned 
to study the effect of some pesticides and narcotants on the survival and some physiological 
functioning of the estuarine bivalve Katelysia opima and the marine bivalve Donax cuneatus, 
both commercially important shellfish in India. Phénobarbital sodium and hexobarbital sodium, 
commonly used narcotics, were also tested for their effect. Nervous transmission is a suitable 
target for pesticides since it is the basis of a coordination system without which the animal 
cannot live. Also, the effect of pesticides on the liver and alimentary tract have not been 
studied extensively in lower animals. The present study has been undertaken in order to 
understand the effect, if any, on the neurosecretory cells in cerebral and visceral ganglia, on the 
digestive gland and on the intestine passing through the visceral mass in a commercially 
important freshwater bivalve, Indonaia caeruleus. 

MATERIALS AND METH0DS2 

Adult K. opima (25-30 mm) and D. cuneatus (20-25 mm) were collected in the Kalbadevi 
estuary and White Sea area respectively, at Ratnagiri on the west coast of India. In the 
laboratory they were placed in sea water which was changed twice a day (acclimation period: 
24 h). Vital specimens were used only and no food was given. All experiments were conducted 
in early summer 1976. Salinity and temperature were recorded during all experiments. After 
acclimation the rate of particle filtration, rate of oxygen consumption and rate of ciliary beat 
were determined. Both species were then grouped in 8 batches. Each batch was exposed to 
narcotics (phénobarbital sodium: 120 K. opima, 150 D. cuneatus; hexobarbital sodium: 120 

lThis is a condensed version of the original manuscript (Ed.). 

2Apparatus for determining oxygen uptake cf. Galtsoff & Whipple (1930); apparatus for determining rate of 

particle filtration of. Cole & Hepper (1954). 

(347) 



348 PROC. SIXTH EUROP. MALAC. CONGR. 

K. opima, 156 D. cuneatus) and pesticides (endrin, DDT, thiometon, malathion, all in ab- 
solute alcohol: 160 K. opima, 160 D. cuneatus). Apart from these, a batch in absolute al- 
cohol and a control in sea water were also run (in all cases 160 of each species). Narcotics, 
pesticides and alcohol were at a concentration of 1 ppm; the water of each batch was changed 
3 times a day. Rate of mortality expressed as percent mortality was recorded during all 
experiments. Similar sets of both species (25 individuals each) were used for determining 
physiological functioning. 

The oxygen consumed by the clams is expressed as the amount of oxygen consumed by a 
clam per gram wet weight per hour per litre. The rate of particle filtration readings were 
converted to percent concentrations by the use of a calibration curve. All experiments in this 
respect were conducted on 10 individuals and average results are used for expression of data. 
Studies of isolated gill tissue were made to evaluate survival and activity of (a) isolated gill 
material suddenly transferred to narcotics and pesticides, and (b) gill material obtained from 
specimens under experimental conditions. In the first series of experiments 80 specimens were 
carefully removed from their shells; 4-5 mm wide pieces of gill tissue were taken (one from 
each clam) by cutting along the gill filaments. Eight batches of such gill fragments (10 in each) 
were exposed to 50 ml of saline solution of narcotants and pesticides. Under the microscope 
the terminal cilia could be readily observed in action. At 15-20 min intervals ciliary activity and 
survival of each bit of gill tissue were noted. For the 2nd series of experiments clams that had 
been exposed to various pollutants were removed periodically and gill preparations made as 
described above. Ciliary beat activity was rated in 3 categories: 3, normal activity; 2, somewhat 
reduced activity, some cilia may have stopped beating; 1, greatly reduced activity, most of the 
cilia have stopped beating. In these experiments the averages of each gill tissue's rate of ciliary 
activity and survival time are taken into consideration (cf. Vernberg et al., 1963). 

Adults of the freshwater species /. caeruleus (55-65 mm) were obtained from the Kham 
River at Aurangabad and were kept in running water for a day. Healthy adults, scrubbed clean, 
were grouped in 8 batches of 50 each and placed in separate Plexiglas aquaria with river water. 
The 1st batch acted as control, whereas in the 2nd and 3rd batches phénobarbital sodium and 
hexobarbital sodium were added respectively, so as to reach a concentration of 1 ppm. To the 
batches 4-7 endrin, thiometon, malathion, and DDT were added, dissolved in alcohol (concen- 
tration 1 ppm). The 8th group received the same volume of alcohol as a control for the above. 
Water in all groups was changed 3 times a day. Mortality was recorded every time. 

A similar set of 8 groups (50 clams each) was used for determining histological changes at 
LT50. When this was reached the clams were removed from their shells and fixed in Bouin's 
fluid. Control specimens were fixed after 96 h. Cerebral and visceral ganglia were removed, 
hepatopancreas and intestine were dissected out, dehydrated in alcohol, cleared in xylol and 
stained with Gomori's chromhaematoxylin phloxine (CHP) for ganglia and with Mallory's triple 
stain for hepatopancreas and intestine. 



RESULTS 

(1) Tolerance of narcotics and pesticides (33.5%o, 31°C). 

K. opima was kept under observation for 80 h, D. cuneatus for 216 h. The solution wherein 
survival was 50% (and more) after 80 and 216 h respectively was regarded as tolerating range. 
The rate of mortality of K. opima increased with increasing exposure (Fig. 1): 

100% mortality in malathion after 80 h 
50% mortality in malathion after 29 h 
50% mortality in endrin after 36 h 
50% mortality in DDT after 27 h 

In .endrin and DDT 92.5 and 85% mortality occurred after 80 h exposure. Mortality was 
considerably less in thiometon; it progressively increased up to 42 h and 40% mortality 
occurred, but only an additional 5% mortality was registered after 80 h. In alcohol there was a 
gradual increase in mortality up to 68.63% after 41 h. In narcotants 90 and 72.5% mortality 
occurred in phénobarbital and hexobarbital sodium respectively after 80 h; 50% mortality in 
these 2 batches was registered after 26 and 44 h respectively. Mortality in phénobarbital 



MANE, KACHOLE AND PAWAR 



349 



100> 



о 

Z 



u 

as 




TIME IN HOURS 



FIG. 1. Percentage of mortality of Katelysia opima in 1 ppm concentrations of narcotics (A— alcohol; 
H— hexobarbital sod¡urл; P— phénobarbital sodium) and pesticides (D— DDT; E— endrin; M— malathion; T— 
thiometon); C— control. 



350 



PROC. SIXTH EUROP. MALAC. CONGR. 



increased rapidly between 24 and 42 h, whereas in hexobarbital mortality steadily increased up 
to 42 h; after 48 h mortality increased suddenly. In the control there was 5% mortality after 
18 h, which later increased to 7.5% after 48 h. 

In all pesticides (except maiathion) mortality of D. cuneatus increased with increase in time 
of exposure (Fig. 2): 



100% mortal 

50% mortal 

97.09% mortal 

97.09% mortal 

8.75% mortal 

50% mortal 

50% mortal 



ty in DDT 
ty in DDT 
ty in endrin 
ty in thiometon 
ty in maiathion 
ty in endrin 
ty in thiometon 



after 21 6 h 
after 92 h 
after 216 h 
after 21 6 h 
after 21 6 h 
after 1 36 h 
after 1 36 h 



There was a sudden increase in mortality after 132 h in both endrin and thiometon. Mortality 
in maiathion was comparatively less and increased only after 167 h. In alcohol there was 
87.78% mortality after 21 6 h and 50% after 149 h. There was a sudden rise in mortality after 




100 130 160 190 азо 

TIME IN HOURS 

w^h^" Г^uTÎ^^^^°^ mortality of Donax cuneatus in 1 ppm concentrations of narcotics (A-alcohol; 
H-hexobarbjtal sodium; P-phenobarbital sodium) and pesticides (D-DDT; E-endrin; M-malathion; T- 
thiometon); C— control. 



MANE, KACHOLE AND PAWAR 351 

132 h in this batch. Mortality in the narcotants was low. Only 2.66 and 14.08% were registered 
after 216 h in phénobarbital and hexobarbital respectively. Mortality in hexobarbital increased 
from 144 h onwards. In the control there was 6.65% mortality after 216 h. Surprisingly, 
mortality in the control was therefore higher than in phénobarbital. 

Behaviour with regard to siphon extension and accumulation of faecal matter was different 
with respect to the kind of water pollution. K. opima was completely relaxed in narcotants 
after ca. 42 h; complete relaxation results in a slight swelling of the body and a high rate of 
mortality. D. cuneatus was completely relaxed after 92 h without any side effects. In alcohol 
both species showed an increase in faecal discharge and siphon extension. 

K. opima is obviously able to tolerate thiometon and D. cuneatus malathion. Both were least 
tolerant to endrin and DDT. In malathion, endrin and DDT, the siphons of K. opima were only 
extended to 3/4 of the length of those of the controls, whereas D. cuneatus did so in endrin, 
thiometon and DDT, The accumulation of faeces and pseudofaeces was more than in the 
alcohol batch. 

(2) Oxygen consumption of specimens subjected to narcotics and pesticides (33%°, 29°C). 

The normal rate of oxygen consumption of K. opima averaged 0.076 ml/g/h/l (measured for 
72 h). In both narcotants the clams used more oxygen in the first 24 h, but later the rate 
decreased. After 72 h the rate decreased more in phénobarbital than in hexobarbital. In the 
alcohol batch the clams used more oxygen after 24 h , but after 72 h the rate decreased below 
that of the control specimens. In endrin and DDT the specimens showed a more or less similar 
trend in oxygen consumption; it did not markedly alter for 28 h, but after 32 h it decreased. 
This decrease was more than in the alcohol batch; decrease in DDT was more than in endrin. In 
malathion the rate up to 24 h was more or less the same as that of the controls, but then 
sharply decreased after 72 h. This decrease was more than in both endrin and DDT. Thiometon 
was the only pesticide that did not much affect oxygen consumption; for the first 32 h it 
remained more or less at the level of the controls, but after that showed a decrease. 

The normal rate of oxygen consumption of D. cuneatus averaged 0.069 ml/g/h/l (measured 
for 192 h ). In both narcotants the clams used more oxygen over 24 h, but then the rate slowly 
decreased; after 192 h it reached more or less the level of the controls. In both narcotants it 
did not fall below the normal rate. In alcohol there was an increase over 24 h; after that it 
remained steady up to 96 h and then gradually decreased. After 192 h oxygen consumption fell 
below the normal rate. In all pesticides (except malathion) oxygen consumption was consider- 
ably altered. After 24 h more oxygen was used, but the rate then decreased more than in the 
alcohol batch after 192 h. In malathion the rate increased up to the first 72 h, but later 
decreased and more or less reached the level of the alcohol batch after 192 h. In thiometon and 
endrin oxygen consumption fell below the rate of the controls (96 h) and later fell even lower. 
In DDT it fell below the rate of the controls at 72 h and further decreased below that of 
specimens in thiometon and endrin after 192 h. 

The above shows that there are marked differences in the 2 species as regards their reactions 
to these narcotants and pesticides. 

(3) Rate of particle filtration of specimens subjected to narcotics and pesticides (31.5%o, 
29.5°C) (Tables 1,2). 

K. opima controls filtered 58% of neutral red solution^ after 72 h (limits 57-59%). In 
hexobarbital the rate of filtration was least affected: 55% after 72 h. In phénobarbital it was 
altered after 48 h and decreased below the rate in phénobarbital. Filtration in the alcohol batch 
remained more or less constant up to 24 h and then decreased to 48% after 72 h. Pesticides had 
a marked effect, except for thiometon, where the rate was similar to that of the alcohol batch. 
In DDT filtration decreased from 20 h onwards, whereas in endrin and malathion from 24 h 
onwards; in these pesticides filtration decreased considerably after 72 h. This was more marked 
in malathion than in endrin and DDT. 

D. cuneatus controls filtered 47%/h after 192 h (limits 4749%). In both narcotants the rate 
of filtration was more or less similar and little affected. In alcohol there was no change for 
120 h, but from 144 h onwards filtration decreased; after 192 h the rate was 39%. In the 
pesticides (except malathion) there was a noticeable change. The rate in malathion was more or 
less the same as that of the alcohol batch. For the first 96 h in endrin, thiometon and DDT the 



352 PROC. SIXTH EUROP. MALAC. CONGR. 

TABLE 1. Rate of particle filtration in Katelysia opima when subjected to various narcotants and pesticides, ex- 
pressed as percentage of neutral red removed within one hour. 

Pheno- Hexo- 

Hrs Control Alcohol barbital barbital Malathion Thionneton Endrin DDT 

6 58 ± 3 59 ± 4 59 ± 4 58 ± 4 58 ± 2 58 ± 3 58 ± 4 58 ± 2 



18 


58 ± 3 


60 + 4 


59 ± 3 


58 ± 3 


58 ±4 


58 ±3 


59 ± 4 


57 ±3 


20 


59 ± 3 


60 ±4 


57 ± 3 


59 ± 3 


56 ±4 


60 ±3 


56 + 4 


53 + 3 


24 


58 ±3 


58 ± 4 


54 + 3 


52 ± 3 


53 ±4 


59 ±3 


53 ± 4 


55 ±4 


28 


57 ± 3 


55 ±4 


56 + 4 


54 ±3 


51 ± 3 


57 ± 3 


51 ±4 


52 ±4 


32 


59 ±3 


53 + 4 


55 ±4 


53 ±3 


49 + 3 


54 + 3 


52 ±4 


50 ±4 



42 58 ± 3 50 ± 3 55 ± 3 54 + 4 43 ± 4 51+3 49 ± 4 47 + 4 

48 58 ± 2 48 ± 4 55 + 3 54 ± 3 40 ± 4 49 ± 3 46 ± 3 44 ± 3 

54 57 ± 3 48 ± 1 49 ± 2 55 ± 3 34 ± 3 46 + 4 42 + 4 42 ± 4 

63 58 ±2 49 ±3 46 ±4 55 + 3 30 ± 1 47 + 4 38 + 4 41 ± 2 

72 58 + 3 48 ± 4 45 + 3 55 ± 1 28 + 4 46 ± 3 37 ± 4 39 ± 3 



TABLE 2. Rate of particle filtration in Donax cuneatus when subjected to various narcotants and pesticides, 
expressed as percentage of neutral red removed within one hour. 









Phéno- 


Hexo- 










Hrs 


Control 


Alcohol 


barbital 


barbital 


Malathion 


Thiometon 


Endrin 


DDT 


24 


48 ± 2 


49 + 3 


47 ± 2 


48 ±3 


47 ± 2 


47 + 2 


46 ±3 


46 ± 1 


48 


47+ 1 


48+2 


48 ±2 


48 ±3 


47+ 1 


47 ± 2 


46 ± 2 


46 + 2 


72 


47 ± 2 


47 ± 3 


48 ±3 


47 + 3 


46 ± 3 


47 + 3 


45 ± 1 


45 ±2 


96 


49 ± 2 


47 ±2 


48 + 3 


48 ±3 


46 + 2 


46 ±2 


45 ± 4 


45+ 1 


120 


49 ± 2 


48 ± 2 


48 + 2 


48 ±4 


44 ± 3 


42 + 2 


41 + 3 


40 ± 2 


144 


48 ±3 


44 ± 2 


47 ± 2 


48 ±3 


44 ±4 


39 ±3 


38 ± 1 


36 ± 1 


168 


47 ± 1 


41 ±3 


47 ± 2 


45 ±3 


34 ±2 


37 ± 1 


34 ±3 


30 ± 1 


192 


47 ± 1 


39+2 


44 ± 3 


47 ±4 


41 ± 1 


34 ±3 


30 ± 1 


28 ± 4 



rate was not affected, but after that the DDT batch filtered at a much lower rate than in 
endrin and thiometon. In these 2 the rate decreased below that of the alcohol batch after 
192 h. 

Again there are marked differences in reaction of the 2 species. 

(4) Resistance of isolated gill tissue subjected to narcotics and pesticides (32.5%o, 30.3°C) 
(Tables 3, 4). 

Controls of K. opima isolated gill tissue were considered to represent category 3; survival 
time up to 308 min. In phénobarbital ciliary activity and survival were reduced more than in 
hexobarbital. In the alcohol batch activity and survival were reduced more than in the controls. 
Ciliary activity and survival of the pesticide batches show that in endrin, malathion and DDT 
gill tissue was considerably affected as compared to the alcohol batch. In thiometon ciliary 
activity and survival was more or less like that of the alcohol batch. In endrin, malathion and 
DDT ciliary activity was rated in categories 1.9, 1.7 and 2.1 respectively; survival time 140, 123 
and 155 min respectively. Comparing activity and survival of isolated gill tissue obtained after 
6, 24, 48 and 72 h of exposure to narcotics and pesticides shows that activity and survival 
decreased gradually; in phénobarbital, endrin, DDT and malathion the gill tissue was consider- 
ably affected. In the control batch ciliary activity remained the same as that of the control 
batch on sudden transfer, but survival time decreased after 72 h hjecause of the increase in time 
of the experiments. In phénobarbital activity and survival were considerably more reduced than 
in hexobarbital and also than the same batch on sudden transfer. Ciliary activity in 
phénobarbital was rated 1.8; survival time 125 min after 72 h. In the alcohol batch ciliary 
activity was rated very close to that of the same batch on sudden transfer; survival was reduced 
to 212 min after 72 h. In the thiometon batch ciliary activity was the same as that after the 
sudden transfer of the same batch, but survival was similar to that of the alcohol batch after 
72 h. In endrin, malathion and DDT ciliary activity and survival time were reduced more than 
in those suddenly transferred. After 72 h there was a more severe effect of DDT than of endrin 



MANE, KACHOLE AND PAWAR 353 

TABLE 3. Resistance of isolated gill tissue of Katelysia opima subjected to various narcotants and oesticides. 
Upper figures: rate of ciliary beating (average of 10 observations). Lower figures: survival time in minutes. 



Hrs 


Control 


Alcohol 


Phéno- 
barbital 


Hexo- 
barbital 


Malathion 


Thiometon 


Endrin 


DDT 





3.0 

308 ± 18 


2.7 

270 ± 24 


1.5 
190 ± 11 


2.4 

220 ± 14 


1.7 

123 ± 15 


2.6 

195 ± 13 


1.9 
140+ 29 


2.1 

155 ±22 


6 


3.0 
299 ± 21 


2.8 
265 ± 32 


2.8 
240 ± 27 


2.9 

253 ± 16 


2.8 
265 ± 21 


2.9 

280 ± 28 


2.8 
270 ± 24 


2.9 

280 + 25 


24 


3.0 

297 ± 27 


2.9 
239 ± 23 


2.7 
235 ± 1 1 


2.9 

250 ± 10 


2.3 

240 ± 27 


2.9 
255 ± 24 


2.6 
210± 17 


2.5 

250 + 30 


48 


2.9 
292 ± 18 


2.7 
218± 19 


2.2 

205+ 13 


2.8 
215± 18 


2.0 

160 ± 37 


2.7 

230 ± 31 


2.3 

185 + 23 


2.3 

217 ± 15 


72 


3.0 
218 ± 29 


2.8 
212± 17 


1.8 

125 ± 30 


2.6 

198 ± 26 


1.2 

85 + 24 


2.6 

212 ± 22 


1.5 
110± 27 


1.9 
160+ 24 



TABLE 4. Resistance of isolated gill tissues of Donax cuneatus subjected to various narcotants and pesticides. 
Upper figures: rate of ciliary beating (average of 10 observations). Lower figures: survival time in minutes. 









Phéno- 


Hexo- 










Hrs 


Control 


Alcohol 


barbital 


barbital 


Malathion 


Thiometon 


Endrin 


DDT 





3.0 


2.6 


2.8 


2.8 


2.5 


1.7 


1.7 


1.7 




260+ 18 


210±21 


245 + 19 


230 ± 17 


250 ± 18 


190+ 19 


185 ± 22 


170 ±23 


48 


3.0 


3.0 


3.0 


3.0 


3.0 


2.8 


2.9 


2.8 




258 ± 20 


235+ 16 


253 ± 14 


250 ± 19 


240 ± 26 


238 ± 17 


230 ± 11 


245 ± 21 


96 


3.0 


2.8 


2.8 


2.7 


2.7 


2.6 


2.8 


2.2 




252 ± 15 


220 + 1 2 


244 ± 19 


238 ± 21 


230 ± 29 


185 ± 18 


193 ± 22 


170+ 15 


144 


3.0 


2.7 


2.8 


2.7 


2.4 


1.9 


2.0 


1.6 




248 ± 23 


203 ± 22 


237 ± 12 


217 ±27 


215132 


163 + 24 


142 ± 23 


115± 18 


192 


3.0 


2.7 


2.8 


2.6 


2.3 


1.6 


1.4 


1.2 




248 ± 26 


195 i 16 


220 ± 23 


205 ± 24 


210 ± 33 


115± 29 


100 ± 26 


93 ± 12 



and malathion. Ciliary activity and survival in these pesticides were considerably more reduced 
than in thiometon, which obviously has the least effect on gill tissue. 

Controls of D. cuneatus isolated gill tissue were considered to represent category 3; survival 
time 260 min. In both narcotics ciliary activity was rated 2.8 with survival times of 245 and 
230 min respectively. Survival time in hexobarbital was more reduced than in phénobarbital. In 
the alcohol batch ciliary activity was reduced to 2.6; survival time 210 min. In endrin, 
thiometon and DDT ciliary activity was considerably more reduced than in alcohol, i.e. to 1.7 
with a considerably lower survival time. In DDT survival time was lower than in both endrin 
and thiometon. In malathion ciliary activity was more or less the same as that in alcohol, but 
survival time was longer. Obviously, malathion least affected gill tissue among these clams. 
Comparing ciliary activity and survival of isolated gill tissue after 48, 96, 144 and 192 h of 
exposure to narcotics and pesticides shows that activity and survival decreased considerably 
with increased exposure time; in the controls activity was not affected, but survival time 
decreased somewhat. Activity and survival in the narcotants were lower than in the controls and 
the effect was more marked after 192 h. Endrin, thiometon and DDT affected activity and 
survival more than in the same batches on sudden transfer; the effect of DDT was even more 
marked after 192 h. On the other hand, in malathion ciliary activity and survival time were 
least affected as compared to the other pesticides, but were reduced when compared to the 
same batch on sudden transfer. Activity in malathion was reduced more than in the alcohol 
batch after 192 h, but survival time was longer. 

Once more there are considerable differences in reaction of the 2 species under discussion, 
e.g. in K. opima malathion severely affected isolated gill tissue and in D. cuneatus DDT did so. 



354 PROC. SIXTH EUROP. MALAC. CONGR. 

TABLE 5. LT50 values of Indonaia caeruleus when subjected to various narcotants and pesticides. 

Batch l-Tjo (hours) Dead/total 

Control — 

Phénobarbital 85 34/70 

Hexobarbital 96 36/70 

Alcohol 85 32/60 

Endrin 85 33/70 

DDT 72 37/70 

Thiometon 96 29/60 

Malathion 85 31/60 



(5) LT50 values of the freshwater mussel Indonaia caeruleus when subjected to narcotics 
and pesticides (29.5-31 .7°C) (Table 5). 

In hexobarbital LTso has higher values than in phénobarbital; in the pesticides survival was 
highest in thiometon. Survival in alcohol equalled that in phénobarbital, endrin and malathion. 
DDT showed the lowest values of all. Mortality in the control batch amounted to 20% after 
96 h. 

(6) Changes in neurosecretory cells from cerebral and visceral ganglia of /. caeruleus 
subjected to narcotics and pesticides. 

In /, caeruleus 3 types of neurosecretory cells are located on the dorsal and lateral sides of 
cerebral and visceral ganglia. Type I are pyriform (20-25 jum) with a long axon and are directed 
towards the central core of the ganglia. The nucleus (diameter 8-12 jum) is round or oval, 
centrally or eccentrically placed. These cells are less numerous in the ganglia than the other 
types. Type II are oval in shape (diameter ca. 30-35 jum); the large nucleus (15-25мт) is oval 
and peripheral. Vacuoles in the cytoplasm vary in number from 2-5. Type II cells are smaller 
than type II cells (ca. lOjum diameter) and are generally oval, round or sometimes tapering at 
the ends, but the size remains constant. The nucleus (5-6 Atm) is round or oval and placed 
centrally or eccentrally. Vacuoles are rarely seen. In all these cells neurosecretory material is 
seen accumulated in the cytoplasm in the form of droplets (Figs. 3a, 4a). 

(6a) Neurosecretory cells from cerebral ganglia (Fig. 3). 

In both narcotics neurosecretory material was released from the cytoplasm and there was no 
change in the morphological characters of cell types I and II. Material from type III cells did 
not show any change. Neurosecretory material from hexobarbital specimens was released more 
abundantly from both types when compared to phénobarbital specimens. There were no 
morphological changes in the alcohol batch, but in type I neurosecretory material was traced in 
the axonal part and not in the cytoplasm, whereas secretory material in type II disappeared 
from the cytoplasm; there was no change in type III. In thiometon secretory material 
disappeared from all types of cells, though traces were recorded in a few type II cells. There 
was some shrinkage in type I (16-20jum), whereas type II measured 24-29 )um. Nuclear diameter 
decreased to 6-9 jum (type I) and 11-23jum (type II). Type III cells were not affected. In 
malathion and endrin the effect was more or less similar to that of thiometon, but the degree 
of shrinkage was more in endrin than in malathion. In both pesticides neurosecretory material 
had not completely disappeared from cell types I and II and there appeared to be a 
considerable shrinkage in the size of all 3 cell types: 

type I 14-1 7 jum, nucleus 4-8 /um 
type II 20-26 jum, nucleus 9-1 9 дт 
type III ca. 7)um, nucleus 3-4 /im 

In DDT shrinkage was more than in any other group of pesticides: 

type I 11 -16 jum, nucleus 3-5 дт 
type II 16-22 jum, nucleus 7-1 5 jum 
tVDe III 4 um. nucleus 2-4 um 



ly I^C II l\J £.£. fJLlll, llUUICUa / lUJUIII 

type III 4 jum, nucleus 2-4 /um 



MANE, KACHOLE AND PAWAR 



355 



^■1И 


HHI 


-Ш^ 


щ 


4 

1^ 


4 




^ 




FIG. 3. Effect of narcotics and pesticides on the neurosecretory cells of cerebral ganglia of Indonaia caeruleus 
(a-controi; b-phenobarbital sodium; c-hexobarbital sodiurл; d-alcohol; e-thiometon; f-malathion; g- 
endrin; h-DDT). Cell types I, II and III indicated in Fig. 3a. All figures ca. 600X. 



356 PROC. SIXTH EUROP. MALAC. CONGR. 

In DDT neurosecretory material was only traced along the periphery of the nucleus in types I 
and II. 

Obviously DDT has a considerable effect on the neurosecretory cells in the cerebral ganglia. 

(6b) Neurosecretory cells fronn visceral ganglia (Fig. 4). 

In hexobarbital neurosecretory nriaterial from many of the type I and II cells had 
disappeared, whereas there was no effect on cells of type III. On the other hand, there was 
accumulation of material in types I and II in phénobarbital, which was also shown by some 
type III cells. In the alcohol batch neurosecretory material from all cell types was released and 
there was no effect on cell and nuclear dimensions. Thiometon and malathion did not influence 
nuclear dimension, but there was a considerable change in cell shape. The neurosecretory 
material from all types had disappeared in thiometon, whereas in malathion it remained in the 
cytoplasm. Cell dimensions in thiometon were as follows: type I, 18-23 /im; type II, 27-33 jtxm; 
type III, 8jum. Cells in the malathion batch became irregular in shape and proved difficult to 
measure. In endrin the neurosecretory material from all types had disappeared and cells of type 
I lost their shape: 17-23ium, nucleus 7-10 дт. In DDT the material of all types disappeared and 
the cells lost their shape: 

type I 16-1 8 Mm, nucleus 4-7 jum 
type II 23-27 jum, nucleus ll-20jum 
type III 8-1 1 jum, nucleus 4дт 

DDT once again has a greater effect on the neurosecretory cells of the visceral ganglia than 
other pesticides. 

(7) Changes in the hepatopancreas of /. caeruleus subjected to narcotics and pesticides (Fig. 
5). 

The hepatopancreas consists of ducts and digestive tubules which are grouped in the form of 
small lobules indistinctly separated and connected by interlobular connective tissue consisting of 
Leydig cells and collagenous fibres. 

In the present study attention has been paid to the digestive tubules of the hepatopancreas 
to see whether narcotics and pesticides had any effect. The cells in the digestive diverticula 
accept particles of filtered food and are responsible for absorption and intracellular digestion. 
The lumen is very small as compared to the size of the tubules. Smooth muscle fibres around 
each lobule effect changes in the volume of the tubule. Each tubule consists of large, lightly 
staining vacuolated secretory and absorptive cells and darkly staining generative cells (Fig. 5a). 
In both narcotants the interlobular connective tissue lost its original shape and the muscle fibres 
were relaxed to such an extent that the volume of the lobules increased and thereby affected 
the digestive cells. The pesticides (except malathion) considerably affected the digestive cells 
and the darkly staining cells, but the effect on the connective tissue was not severe. Of all 
pesticides malathion had the least effect, an effect similar to that of alcohol. These chemicals 
influenced the vacuolated and secretory cells which lost their shape to become irregular. There 
was shrinkage in the small darkly staining cells. The lumen of the lobules was shortened and 
sometimes became invisible. Thiometon, endrin and DDT severely affected the tubules; the 
lumen completely disappeared and the muscle fibres lost their connection with the lobules. The 
vacuolated cells completely lost their shape and vacuoles appeared in large numbers. The darkly 
staining cells also lost their shape while showing a considerable shrinkage. 

(8) Changes in the intestine of /. caeruleus subjected to narcotics and pesticides (Fig. 6). 

Secretory cells of the goblet type are interspersed amongst the ciliated cells in the intestine. 
Some of these are actively secreting mucous cells, while others are apparently regenerating. 
Wandering phagocytic cells occur in variable numbers in the lumen amongst the epithelial cells 
and in the surrounding connective tissue (Fig. 6a). In the narcotants mucous cells and muscle 
fibers were affected; shrinkage of the mucous cells was considerable, while the muscle fibers 
became relaxed and the ciliated cells appear irregular in shape. In alcohol the mucous cells lost 
their shape and exhibited shrinkage, whereas the phagocytic cells appeared to have increased in 
size. The connective tissue became irregular. In all pesticides mucous and ciliated cells were 



-#. 



MANE, KACHOLE AND PAWAR 

a 



357 



'it 



~-'-^\ 



it- 






-III 






'^^ \ 



'C^'% 




FIG. 4. Effect of narcotics and pesticides on the neurosecretory cells of visceral ganglia of Indonaia caeruleus 
(a— control; b— hexobarbital sodium; c— phénobarbital sodium; d— alcohol; e— thiometon; f— malathion; g— 
endrin; h-DDT). Cell types I, II and III indicated in Fig. 4a. All figures ca. 600X. 



358 



PROC. SIXTH EUROP. MALAC. CONGR. 









FIG. 5. Effect of narcotics and pesticides on the iiepatopancreas of /лс/олэ/э caert//et/s (a— control; b— phéno- 
barbital and hexobarbital sodiunn; c— alcohol and malathion; d— thiometon; e— endrin and DDT). Shown in 
Fig. 5a: 1— muscle fibres; 2— lightly staining vacuolated cells; 3— interlobular connective tissue; 4— darkly 
staining cells; 5— lumen of lobule. All figures highly enlarged. 



MANE, KACHOLE AND PAWAR 



359 






FIG. 6. Effect of narcotics and pesticides on the intestine of Indonaia caeruleus (a-control; b-phenobarbital 
and hexobarbital sodium; c-alcohol; d-endrin and malathion; e-thiometon; f-DDT). Shown m Fig. 6a: 
1-ciliated cells; 2-secretory cells (mucous cells); 3-phagocvtic cells; 4-muscle fibres; 5-connective tissue. 



360 PROC. SIXTH EUROP. MALAC. CONGR. 

affected; these cells lost their connection with the muscle fibers and the mucous cells were 
reduced in size. Again, the connective tissue became irregular. Phagocytic cells in connective 
tissue appeared in larger numbers in DDT and thiometon. 

DISCUSSION 

In general young organisms are more suitable for toxic studies than adults because they have 
a higher metabolic rate per unit biomass. This is even more important when the pollutants 
under study are of low toxicity and are applied in low concentrations. In the present study 
experiments to observe mortality, filtration and oxygen uptake along with survival and ciliary 
activity of isolated gill tissue were conducted in the summer season when the temperature of 
the seawater is at an optimum value for the bivalves in question. All experiments were 
conducted over a number of days with respect to mortality rates. Hence, the results have given 
a good indication of the effect of various pesticides and narcotics on the physiological activities 
of the clams. 

Literature data indicate that shell growth may be greatly influenced by chlorinated 
hydrocarbon pesticides, even at low concentrations (0.007 to 0.05 ppm). In the present study 
all pesticides and narcotics were applied at a concentration of 1 ppm. It has been observed that 
with increase in exposure time different effective reaction occurred. Thiometon and malathion 
were found to have the least effect on K. opima and D. cuneatus respectively. Malathion and 
DDT were found to be more toxic to K. opima and D. cuneatus respectively. Both narcotics 
little affected D. cuneatus, but phénobarbital sodium did affect K. opima. It would be 
interesting to study and evaluate further the effect of pesticides by giving pretreatment with 
either of these narcotants as inducers to these clams. Furthermore, individual evaluation of each 
pollutant is of importance, because closely related pesticides often have widely divergent effects 
on the same species of animal. 

Preliminary studies of the effect of pollutants on neurosecretory activity and digestive tract 
of /. caeruleus have shown the different reactions of the organism. Bivalves are filter feeders 
and pollutants are therefore able to penetrate the viscera of the animals. It is shown that the 
narcotics affected the neurosecretory material in the ganglia, whereas the pesticides affected 
both the neurosecretory cells and material considerably. The effect of narcotics on the 
hepatopancreas was not pronounced, but it was marked on the intestine. Pesticides considerably 
affected both hepatopancreas and intestine. 



LITERATURE CITED 

COLE, H. A, & HEPPER, B. T., 1954, The use of neutral red solution for the comparative study of filtration 

rates of lamellibranchs. Journal du Conseil Permanent International pour l'Exploration de la Mer, 10: 

197-204. 
GALTSOFF, P. S. & WHIPPLE, D. V., 1930, Oxygen consumption in normal and green oysters. Biological 

Bulletin, 46: 489-508. 
VERNBERG, F. J„ SCHLIEPER, С & SCHNEIDER, D. E., 1963, The influence of temperature and salinity 

on ciliary activity of excised gill tissue of molluscs from North Carolina. Comparative Biochemistry and 

Physiology, 8: 271-285. 



MALACOLOGIA, 1979, 18: 361-367 

PROC. SIXTH EUROP. MALAC. CONGR. 

ETUDE EN CULTURE IN VITRO DU CONTROLE ENDOCRINE DE LA 
GLANDE A ALBUMEN CHEZ L'ESCARGOT HELIX ASPERSA 

L. Gomot et A. M. Courtot 

Laboratoire de Zoologie Embryologie, ERA, CNRS no 229, 
Faculté des Sciences, Université de Besançon, France 

ABSTRACT 

The direct effects of the hermaphrodite gland, the brain and the eye tentacle on the 
albumen gland of the snail Helix aspersa were studied using organ cultures. Fragments of 
albumen gland were explanted onto a solid defined culture medium at one of 2 
developmental stages, organogenesis (stage of acini formation, or presecretory stage) or 
the beginning of secretory activity. Individually cultured acini survive for about one week 
at the presecretory stage, but necrotic cells are noted thereafter. When, however, the 
gland has already begun its secretory activity, its initial aspect is retained in culture. 
When cultured together with a fragment of the hermaphrodite gland, there is no increased 
survival in vitro of the albumen gland cells which lack secretion granules. If secretion has 
already begun, there is a slight stimulation of further secretion. When the albumen gland 
at the end of organogenesis is cultured together with cerebral ganglia from active snails, 
the gland is maintained in a highly satisfactory state for one week and numerous mitotic 
figures are seen. If secretory activity has begun before the explantation, the secretory cells 
are quite significantly stimulated by the cerebral ganglia. This stimulation is shown by the 
formation of endoplasmic reticulum cisternae and by the emission of numerous golgi 
vésicules in the neighbourhood of the secretion globules which fill the acini. The presence 
of the eye tentacle leads to a reduction in the size of the acini and volume of 
mesenchymatous interstitial tissue at the presecretory stage and inhibits secretory 
processes in glands where they have already begun. These results demonstrate a 
stimulatory activity of cerebral ganglia and an inhibitory action of the eye tentacle on 
acinar organogenesis and on the secretory activity of the gland. The gonad has a weak 
direct action only after the onset of secretion. 

INTRODUCTION 

Les observations et recherches expérimentales réalisées chez les Mollusques Gastéropodes 
Pulmones ont conduit à considérer que le développement et le fonctionnement de l'appareil 
reproducteur sont conditionnés par des mécanismes neuro-humoraux et hormonaux. L'influence 
de la gonade sur le tractus génital est celle qui a été la première envisagée. En effet des 
escargots Helix aspersa présentant une castration parasitaire (Garnault, 1889; Chalaux, 1935) 
ont des conduits génitaux et une glande à albumen atrophiés. De même chez quelques 
exemplaires á'Helix pomatia sans glande hermaphrodite (Boulange, 1914; Geigy, 1925) le reste 
de l'appareil génital demeure infantile. 

Le conditionnement vraisemblablement hormonal des caractères sexuels secondaires du 
tractus génital par la gonade a été mis en évidence par des castrations chez Helix pomatia 
(Filhol, 1938) et chez Limax maximus (Abeloos, 1943). Les corrélations entre la gonade et les 
voies génitales et leurs glandes annexes ont été précisées par des expériences de castration et de 
transplantation chez des Limacidés et des Arionidés (Laviolette, 1954). En particulier la glande 
à albumen de jeunes Arion rufus implantée avec le reste du tractus chez un hôte adulte de 
l'espèce Mesarion subfuscus augmente 100 fois son volume en 30 jours. Cette glande réagit donc 
aux stimuli contenus dans l'hémolymphe de l'hôte. Dans ce contrôle de la croissance et de 
l'activité fonctionnelle de la glande à albumen la gonade a un rôle dominant car l'implantation 
d'une gonade adulte chez un animal impubère déclenche une différenciation précoce et rapide 
des annexes glandulaires du tractus génital. Ainsi la gonade semble agir par une substance 
hormonale qu'elle libère dans l'hémolymphe lorsqu'elle est en pleine gamétogenèse car la greffe 
d'une gonade juvénile est inefficace. D'autre part les organes effecteurs présentent une période 

(361) 



362 PROC. SIXTH EUROP. MALAC. CONGR. 

d'insensibilité au facteur gonadique au début de leur formation car la greffe d'une gonade 
adulte chez un hôte infantile est sans effet sur le tractus. 

L'état du tractus génital n'est probablement pas contrôlé exclusivement par la glande 
hermaphrodite. Lusis (1961) suppose une certaine indépendance du tractus vis à vis de la 
gonade chez Arion. Des expériences combinées d'implantation de gonade et de ganglions 
cérébraux, de castration et d'ablation de la glande à albumen, indiquent à Gottfried et al. 
(1967) que le contrôle de la croissance de la glande à albumen á'Ariolimax calif ornicus se fait 
par l'intermédiaire des ganglions cérébraux et que la gonade en développement joue un rôle 
principal en modulant la libération et/ou la synthèse d'un inhibiteur de la glande à albumen 
dans le tissu cérébral. 

A la suite des travaux de Pelluet & Lane (1961) et de Pelluet (1964) qui montrent que le 
cerveau et les tentacules optiques influencent la production d'oeufs des limaces, Meenakshi & 
Scheer (1969) constatent que l'ablation des tentacules optiques chez A rio/ imex columbianus est 
suivie d'une augmentation du poids de la glande à albumine et de la synthèse de galactogène. 
D'après ces auteurs le facteur tentaculaire agirait par l'intermédiaire de la gonade car l'extrait de 
tentacules inhibe la synthèse de galactogène in vivo mais il est inactif in vitro. 

Des expériences comparables à celles de Laviolette (1954) réalisées par Runham et al. (1973) 
chez Agriolimax reticulatus confirment les résultats du premier auteur et les étendent car elles 
montrent l'existence de deux hormones sécrétées successivement. L'une responsable de la 
maturation de la prostate est émise pendant la Spermiogenese, l'autre contrôle les glandes de 
l'oviducte aux stades d'ovogenèse. L'origine des hormones est inconnue. Par la méthode des 
cultures d'organe Bailey (1973) n'observe aucun signe de maturation dans les cellules du tractus 
génital &A. reticulatus cultivé en association avec la gonade ou avec le complexe cerveau/ 
tentacule. Cependant l'association de la glande hermaphrodite et du complexe cerveau/tentacule 
avec le conduit du même animal agit sur la différenciation de la prostate. Ces résultats 
conduisent Runham et al. (1973) à supposer que les facteurs produits par la gonade déclenchent 
la production des hormones prostatiques et oviductaires par le cerveau. 

Récemment Goudsmit (1975) obtient une activation de la synthèse de galactogène dans des 
explants de glande à albumen à' Helix pomatia en hibernation cultivés en présence du collier 
périoesophagien d'escargot en reproduction. Mais des expériences comparables de culture in 
vitro de glande à albumen de Biomphalaria glabrata et Lymnaea stagnalis en association avec le 
système nerveux central et ou avec l'ovotestis n'ont pas permis à De Jong-Brink et al. (1976) de 
démontrer de synthèse de galactogène. Aussi ces auteurs supposent qu'il y aurait nécessité d'un 
stimulus de nature nerveuse supprimé dans les explants dénervés. 

Il apparaît ainsi que 3 sortes d'organes (gonade, cerveau, tentacules) interviennent directe- 
ment ou indirectement dans le système endocrine des Gastéropodes Pulmones qui contrôle le 
développement et la fonction des organes accessoires de l'appareil génital. 

Pour notre part nous avons étudié les effets directs de ces organes sur la glande à albumen de 
jeunes escargots par la méthode des cultures in vitro. 

■ ► 

FIG. 1. Culture d'un fragment isolé de glande à albumen au stade de formation des acini (escargot de 2,1 cm 
de diamètre). Au bout de 8 jours on observe des vacuoles et quelques figures de nécrose (flèches) dans les 
cellules de la glande. 

FIG. 2. Explant de glande à albumen au stade tubulaire composé (escargot de 2,1 cm de diamètre) cultivé 8 
jours en association avec le tentacule oculaire d'un escargot' en activité. Le tissu mésenchymateux interacineux 
est en régression et des cellules glandulaires meurent. 

FIG. 3. Glande h albumen au stade tubulaire composé (escargot de 2,1 cm de diamètre) associée à l'ovotestis 
d'un escargot en activité et cultivée 8 jours. L'évolution de la glande n'est pas meilleure qu'en culture isolée. 

FIG. 4. Culture de glande è albumen au stade tubulaire composé (escargot de 2,1cm de diamètre) en 
association avec les ganglions cérébraux d'un escargot en activité. La glande survit très bien et on note 
l'apparition de nombreuses mitoses (flèches). 

FIG. 5. Glande à albumen au stade sécrétoire (escargot de 2,3 cm de diamètre) cultivée pendant 8 jours. La 
survie est très bonne. 

FIG. 6. Fragment de la glande è albumen qui a fourni l'expiant de la Fig. 5. Après culture pendant 8 jours 
en association avec des ganglions cérébraux homologues la quantité de globules de sécrétion a nettement 
augmenté. 



GOMOT ET COURTOT 



363 




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364 PROC. SIXTH EUROP. MALAC. CONGR. 

MATERIEL ET METHODE 

Pour les associations autologues, des escargots juvéniles (Helix aspersa) ont été choisis aux 
stades fin d'organogenèse ou présécrétion (animaux de 1,8 à 2,1 cm de diamètre) et début de 
sécrétion (de 2,1 à 2,4 cm) de la glande à albumen définis par Courtot (1977). Des escargots 
adultes ont fourni les tentacules, le cerveau et l'ovotestis pour les associations homologues 
hétérochroniques. 

Les cultures d'organes ont été faites selon la technique de Wolff & Haffen (1952) sur milieu 
gélose adaptée par Gomot (1973) à la culture d'organes d'escargots. 

Les organes témoins et cultivés sont fixés 1 h 30 dans le mélange (glutaraldéhyde à 200 
mOsm: 1 vol; tampon cacodylate à 200 mOsm; 1 vol; NaCI à 300 mOsm: 1 vol) puis rincés dans 
la solution (tampon cacodylate à 200 mOsm: 1 vol; NaCI à 300 mOsm: 1 vol). Le lavage est 
suivi d'une post fixation à l'acide osmique dans le tampon cacodylate à 250 mOsm. Après 
déshydratation selon la technique de Luft (1961) les pièces sont incluses dans l'épon 812 ou 
dans l'ERL 4206 selon Spurr (1969). 

Les coupes semi-fines de 1 jum d'épaisseur sont colorées au bleu de toluidine selon la 
méthode de Trump et al. (1961). Les coupes ultrafines sont contrastées à l'acétate d'uranyle à 
3% dans l'alcool éthylique à 50% puis au citrate de plomb selon Reynolds (1963). 

RESULTATS 

(1) Culture de fragments de glande a albumen isolés 

Pendant les stades d'organogenèse la glande à albumen survit bien pendant les premiers jours 
de culture mais au bout de 8 jours on observe quelques figures de nécrose (Fig. 1). 

Lorsque la sécrétion a commencé, les cellules de la glande à albumen conservent leur 
structure initiale (Fig. 5) pendant les 8 jours de culture. 

(2) Culture de la glande à albumen en association avec le tentacule oculaire 

Dans les associations de glandes à albumen en Organogenese avec le tentacule oculaire du 
même animal ou avec le tentacule d'un escargot adulte en activité on note une réduction 
importante du tissu mésenchymateux qui entoure les acini et de nombreuses cellules meurent 
(Fig. 2). 

Dans les explants provenant de glandes en phase sécrétoire cultivés en présence d'un 
tentacule autologue on note une diminution du volume des acini et l'augmentation des espaces 
interacineux. En association avec le tentacule d'un adulte en activité on observe au contraire 
une augmentation du volume des acini et un changement d'aspect des noyaux qui suggère un 
phénomène de dédifférenciation cellulaire. Dans les 2 cas le processus sécrétoire est arrêté. 

(3) Association de fragments de glande à albumen et de glande hermaphrodite 

La culture d'associations autologues de glande à albumen en phase d'organogenèse avec la 
gonade donne des résultats identiques à ceux obtenus dans les explants de glande cultivée 
isolément (Fig. 3). 

Par contre lorsque les cellules contiennent des grains de sécrétion la survie est très bonne et 
l'action de la gonade (juvénile ou d'adulte en activité) augmente légèrement l'activité' sécrétrice. 



FIG. 7. Aspect du cytoplasme d'une cellule sécrétrice de glande à albumen au moment de l'explantation 
(escargot de 2,3 cm de diamètre qui a fournit les explants des cultures représentées Fig. 5 et Fig. 6). On 
observe la formation de vésicules aux extrémités des saccules concentriques de l'appareil de Golgi (g) et des 
grains de sécrétion (GS). 

FIG. 8. Micrographie électronique d'une cellule sécrétrice d'un explant de la glande à albumen représentée à 
la Fig. 7 cultivé 8 jours en association avec des ganglions cérébroïdes (Fig. 6). La conformation des 
dictyosomes s'est modifiée; les saccules golgiens (g) nombreux au voisinage du noyau (N) sont rectilignes et 
émettent de nombreuses vésicules à proximité des globules de sécrétion (GS). L'ergastoplasme (e) se présente 
sous forme de citernes circonvoluant dans le hyaloplasme. 



GOMOT ET COURTOT 



365 




366 PROC. SIXTH EUROP. MALAC. CONGR. 

(4) Culture de la glande à albumen en association avec les ganglions cérébraux 

Les associations autologues et homologues ont les mêmes effets. 

Dans les glandes en Organogenese, la survie est très bonne et de nombreuses mitoses 
apparaissent (Fig. 4). 

Au stade sécrétoire l'activité de la glande est nettement stimulée, les cellules des acini se 
remplissent de globules de sécrétion et les noyaux sont comprimés contre la paroi des acini 
(Fig. 6). Le rapport de la surface des grains de sécrétion (dans 5 acini pris au hasard sur une 
coupe) à la surface totale des acini est de 61% tandis qu'il est de 45% dans les acini du 
fragment témoin fixé à l 'explantation. Le rapport entre la surface des sections de noyaux et la 
surface des acini reste le même (8%). A l'examen en microscopie électronique l'augmentation 
de l'activité de synthèse des cellules se traduit au niveau de l'appareil de Golgi qui constitue des 
dictyosomes avec des saccules plus nombreux (Fig. 7 et 8). L'ergastoplasme se développe en 
formant des plages où de longues citernes circonvoluent dans le hyaloplasme (Fig. 8). 

Dans le cas d'associations triples (glande à albumen, ganglions cérébraux, gonade) le résultat 
est le même que celui observé avec les ganglions cérébraux. 

DISCUSSION-CONCLUSION 

La culture de la glande à albumen isolée nous apporte des renseignements sur I 'Organogenese 
et sur le fonctionnement de cette glande. 

La différenciation de la glande à albumen en Organogenese ne se poursuit pas en culture 
isolée. 

Parmi les organes associés, seuls les ganglions cérébraux ont une action directe et induisent 
une multiplication des cellules. A ce stade la glande hermaphrodite juvénile ou adulte est sans 
effet tandis que les tentacules oculaires sont inhibiteurs. 

Au stade sécrétoire les cellules glandulaires ont une autonomie de survie que l'on peut 
attribuer à la présence de réserves dans les grains de sécrétion ou à une imprégnation plus forte 
en facteurs endocrines. La gonade exerce alors une stimulation effective mais modérée tandis 
que les ganglions cérébraux ont une action directe très nette et augmentent le nombre des 
globules de sécrétion dans les acini. 

Le rôle du cerveau comme organe endocrine est ainsi démontré et les résultats obtenus 
concordent avec ceux de Goudsmit (1975) en les précisant car cet auteur associait l'ensemble 
du collier périoesophagien tandis que nous avons seulement explanté les ganglions cérébraux. 
Cependant ceux-ci sont mis en culture avec leur gaine conjonctive et les corps dorsaux. Il est 
donc possible que l'action mise en évidence soit due à la sécrétion hormonale des corps dorsaux 
qui sont attachés aux parois des ganglions cérébraux de tous les Gastéropodes (Joosse, 1972) et 
dont le rôle dans la différenciation des organes sexuels accessoires femelles a été démontré par 
Geraerts & Joosse (1975) et Geraerts & Algera (1976) chez Lymnaea stagnalis et par Wijdenes 
& Runham (1976) chez Agriolimax reticulatus. 

Il est maintenant nécessaire d'isoler les corps dorsaux et d'étudier leur action sur la glande à 
albumen. 

Comme d'autres auteurs cités en introduction nous avons montré que la glande à albumen 
est sous contrôle hormonal. De plus il apparaît que l'action directe des organes endocrines varie 
avec le stade de développement de l'organe considéré. Si le rôle du système nerveux apparaît 
nettement aux stades de développement et de fonctionnement celui de la gonade est plus 
énigmatique. On peut se demander si elle agit comme intermédiaire entre les tentacules et le 
système nerveux d'une part et la glande à albumen d'autre part ou comme un agent stimulateur 
des deux organes régulateurs précédemment évoqués. De nouvelles expériences doivent être 
entreprises pour élucider les interactions entre les organes dont l'action directe sans connection 
nerveuse vient d'être démontrée. 



GOMOT ET COURTOT 367 

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ABELOOS, M., 1943, Effets de la castration chez un mollusque Limax maximus. Comptes Rendus de 

l'Académie des Sciences, Paris, 21 6: 90-92. 
BAILEY, T. G., 1973, The />? i// fro culture of reproductive organs of the slug Agriolimax reticulatus (Müll.). 

Nettierlands Journal of Zoology, 23: 72-85. 
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Jeunes Naturalistes, 44: 165. 
CHALAUX, J., 1935, Sporocystes d'un Brachylemus dujardini, chez Helix aspersa Müller. Bulletin de la 

Société Scientifique de Bretagne, 12: 53-57. 
COURTOT, A. M„ 1977, Etude cytologique et expérimentale de la différenciation et de la sécrétion de la 

glande a albumine de l'escargot Helix aspersa Müll. Thèse 3è cycle Sciences Biologiques, Université de 

Besançon, 59 p. 
FILHOL, J., 1938, Recherches sur la nature des lépidosomes et les phénomènes cytologiques de la sécrétion 

chez les Gastéropodes Pulmones. Archives cfAnatomie Microscopique et de Morphologie Expérimentale, 

34: 155-439. 
GARNAULT, P., 1889, La castration parasitaire chez Helix aspersa. Bulletin Scientifique de la France et de la 

Belgique, 20: 137-141. 
GEIGY, R., 1925, Anomalies de l'appareil génital chez Helix pomatia. Revue Suisse de Zoologie, 32: 

207-213. 
GERAERTS, W. P. M. & ALGERA, L. H., 1976, The stimulating effect of the dorsal body hormone on cell 

differentiation in the female accessory sex organs of the hermaphrodite freshwater snail Lymnaea 

stagnai is. General and Comparative Endocrinology, 29: 109-118. 
GERAERTS, W. P. M. & JOOSSE, J., 1975, Control of vitellogenesis and of growth of female accessory sex 

organs by the dorsal body hormone (DBH) in the hermaphroditic freshwater snail Lymnaea stagnalis. 

General and Comparative Endocrinology, 27: 450-464. 
GOMOT, L., 1973, Etude du fonctionnement de l'appareil génital de l'escargot Helix aspersa par la méthode 

des cultures d'organes. Archives d'Anatomie, d'Histologie et d'Embryologie Normale et Experimentale, 56: 

131-160. 
GOTTFRIED. H., DORFMAN, R. L, FORCHIELLI, E. & WALL, P. E., 1967. Aspects of the reproductive 

endocrinology of the giant land slug Ariolimax californicus (Stylommatophora: Gastropoda). General and 

Comparative Endocrinology, 9: 454. 
GOUDSMIT, E. M., 1975, Neurosecretory stimulation of galactogen synthesis within the Helix pomatia 

albumen gland during organ culture. Journal of Experimental Zoology, 191: 193-198. 
JONG-BRINK, M. DE. KOOP, H. M., KRAAL. G. & VAN WINGERDEN, В., 1976, The regulation of 

secretory processes in the albumen gland, one of the accessory sex glands of pulmonale snails. General 

and Comparative Endocrinology, 29: 298. 
JOOSE. J., 1972, Endocrinology of reproduction in molluscs. General and Comparative Endocrinology, 

Supplement 3: 591-601. 
LAVIOLETTE. P., 1954, Rôle de la gonade dans le déterminisme humoral de la maturité glandulaire du 

tractus génital chez les Gastéropodes Arionidae et Limacidae. Bulletin Biologique de la France et de la 

Belgique, 88: 310-332. 
LUFT. J. H., 1961, Improvements in expoxy resin embedding methods. Journal of Biophysical and 

Biochemical Cytology, 9:409-414. 
LUSIS, O., 1961. Post embryonic changes in the reproductive system of the %\uq Arion rufus. Proceedings of 

the Zoological Society of London, 137: 433-468. 
MEENAKSHI. V. R. & SCHEER. B. T.. 1969. Regulation of galactogen synthesis in the slug Ariolimax 

columbianus. Comparative Biochemistry and Physiology, 29: 841-845. 
PELLUET. D.. 1964, On the hormonal control of cell differentiation in the ovotestis of slugs (Gasteropoda, 

Pulmonata). Canadian Journal of Zoology, 42: 195-199. 
PELLUET. D. & LANE, N. J., 1961, The relation between neurosecretion and cell differentiation in the 

ovotestis of slugs. Canadian Journal of Zoology, 39: 789-805. 
REYNOLDS. E. S.. 1963. The use of lead citrate at high pH as an electron opaque stain in electron 

microscopy. Journal of Cell Biology, 17: 208-212. 
RUNHAM, N, W., BAILEY. T. G. & LARYEA. A. A.. 1973, Studies of the endocrine control of the 

reproductive tract of the grey field slug Agriolimax reticulatus. Malacologia, 14: 135-142. 
SPURR, A. R., 1969, A low viscosity epoxy resin embedding medium for electron microscopy. Journal of 

Ultrastructure Research, 26: 31-43. 
TRUMP. B. F.. SMUCKER, E. A. & BENDITT. E. P., 1961, A method for staining epoxy sections for light 

microscopy. Journal of Ultrastructure Research, 5: 343. 
WIJDENES, J. & RUNHAM. N. W.. 1976, Studies on the function of the dorsal bodies of Agriolimax 

reticulatus (Mollusca. Pulmonata). General and Comparative Endocrinology, 29: 545-551. 
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Reports in Biology and Medicine, 1 0: 463-472. 



MALACOLOGIA, 1979, 18: 369-372 

PROC. SIXTH EUROP. MALAC. CONGR. 

EVOLUTION DES RELATIONS ENTRE OVOCYTE ET CELLULES 

FOLLICULEUSES AU COURS DE L'OVOGENESE DE LA PALUDINE 

VIVIPARUS VIVIPARUS (GASTEROPODE PROSOBRANCHE) 

B. Griffond 

Laboratoire de Zoologie Embryologie, ERA CNRS n° 229, 
Faculté des Sciences, Université de Besançon, France 

ABSTRACT 

The ovary of Viviparus vmparus was studied ultrastructu rally. Follicle cells are linked 
by septate junctions and surround the oogonia and young oocytes. The relations between 
oocytes and follicle cells are progressively modified during oogenesis: 

—The prenneiotic and previtellogenic phases are characterized by a narrow space 
between follicle cells and oocyte. 

—At the beginning of vitellogenesis, the follicle envelope gradually extends next to the 
basal lamina, where lacunar spaces come into existence. Laterally the intercellular spaces 
become enlarged whereas a follicle cap persists at the apical zone of the oocyte. 

—Next the follicular cells are pushed aside by the increase in size of the oocyte, which 
acquires a certain amount of autonomy, obtaining nutrient elements direct from the 
hemolymph. At this stage septate junctions arrange themselves in such a way as to assure 
the anchorage of the oocyte to the neighbouring follicle cells. 

Feu de travaux ont été jusqu'à présent consacrés à l'étude de l'ovogenèse chez les différentes 
espèces de Paludines. Chez Viviparus viviparus l'évolution de la lignée germinale femelle et 
l'ovogenèse sont décrites brièvement dès 1907 par Popoff puis en 1923 par Ankel. En 1957 
Yasuzumi & Tanaka recherchent à l'aide du microscope électronique l'origine du vitellus dans 
les ovocytes de Cipangopaludina nrtalleata tandis qu'en 1972 et 1973 Bottke publie une 
description ultrastructurale de la morphologie de l'ovaire de Viviparus contectus, s'intéressant 
plus spécialement aux stades prévitellogénétique et vitellogénétique ainsi qu'aux cellules 
folliculeuses de l'ovaire adulte. Dans le cadre d'un travail expérimental visant à la compréhen- 
sion des mécanismes qui règlent le fonctionnement des gonades de Paludines, j'ai été amenée à 
m'intéresser à l'ovogenèse de l'espèce Viviparus viviparus et j'ai pu constater des modifications 
progressives des relations entre ovocyte et cellules folliculeuses au cours du déroulement de la 
gamétogenèse. 

MATERIEL ET METHODES 

Pour les études cytologiques, l'ovaire de Paludines femelles adultes est prélevé par dissection 
et fixé à la glutaraldéhyde à 1% pendant 2 heures. Après lavage, il subit une postfixation d'I 
heure dans l'acide osmique à 2%. Le tampon utilisé est le cacodylate de sodium et la pression 
osmotique des différents liquides est ajustée à 125m0sm. Les inclusions sont réalisées à l'Epon 
ou dans l'ERL 4206 (Spurr, 1969). Les coupes semi-fines sont colorées au bleu de toluidine 
selon la méthode de Trump et al. (1961). Les coupes ultrafines contrastées à l'acétate d'uranyle 
puis au citrate de plomb selon Reynolds (1963) sont observées sur microscope électronique 
"Hitachi ни 12." 

Pour la mise en évidence des espaces extracellulaires, des fragments d'ovaire de femelles 
adultes sont incubés pendant des durées variant de 5 min à 1 heure dans du liquide de 
Holtfreter enrichi de 5% de Peroxydase (Sigma Chemical Company). Après fixation à la 
glutaraldéhyde à 1%, la visualisation de la Peroxydase par la 3-3' diamino-benzidine est réalisée 
selon la technique de Graham & Karnovsky (1966). Après postfixation par l'acide osmique à 2% 
puis inclusion dans l'ERL 4206, le résultat de la réaction est observé sur coupes non 
contrastées. 

(369) 



370 PROC. SIXTH EUROP. MALAC. CONGR. 

RESULTATS 

Chez Viviparus viviparus, l'ovaire est un tubule tapissé par un epithelium au sein duquel sont 
reconnaissables des cellules germinales et des cellules fol Meuleuses. Les cellules folliculeuses sont 
des cellules hautes, orientées perpendiculairement à la lame basale. Leur extrémité apicale est 
ornée de microvillosités tandis que leur région basale émet de longs prolongements pseudo- 
podiaux qui s'enchevêtrent et épousent fidèlement les contours de la lame basale. Latéralement, 
dans leur zone apicale, les cellules folliculeuses sont toujours réunies les unes aux autres par des 
jonctions septées dans le prolongement desquelles s'observent souvent des jonctions inter- 
médiaires ainsi que des desmosomes apicaux. Au contraire les ovogonies et les ovocytes jeunes 
évoluent isolément, n'établissant pas de contacts jonctionnels avec les cellules qui les entourent. 

L'ovogenèse peut être subdivisée en un certain nombre d'étapes en fonction de la taille des 
ovocytes, de la structure des organites ovocytaires et des interrelations ovocytes-cel Iules 
folliculeuses. En effet durant la préméiose puis la prévitellogenèse, plusieurs cellules folliculeuses 
forment un revêtement continu autour de chaque ovocyte dont elles ne sont séparées que par 
un espace étroit et qu'elles isolent totalement. Quelquefois cependant la base de l'ovocyte est 
directement en contact avec la lame basale, au niveau de surfaces réduites. 

La vitellogenèse, marquée par une perte de basophilie du cytoplasme et par un fort 
accroissement de l'ovocyte, peut elle-même être décomposée en plusieurs stades: 

La première phase vitellogénétique ou phase folliculaire, qui intéresse des ovocytes de 25 à 
35 дт de diamètre environ, se déroule à l'intérieur de la barrière constituée par les cellules 
folliculeuses mais les espaces intercellulaires s'élargissent peu à peu sur les côtés et à la base de 
l'ovocyte. Durant ce stade, les gouttelettes lipidiques sont de plus en plus nombreuses, les plages 
polysaccharidiques de plus en plus étendues tandis qu'apparaissent les premières inclusions 
vitellines. 

La seconde phase vitellogénétique, caractérisée par une synthèse particulièrement active des 
globules vitellins, est marquée par une profonde modification des relations entre les cellules 
folliculeuses et l'ovocyte et par un changement de la physiologie de l'ovocyte qui se libère 
progressivement de son enveloppe folliculeuse. Durant cette étape de paroxysme vitellogénétique 
la dilatation des espaces intercellulaires s'accentue, si bien qu'un ovocyte en fin de vitellogenèse 
n'a plus latéralement de rapports avec les cellules folliculeuses qu'au niveau de quelques courts 
processus. A la base se crée un système d'espaces lacuneux qui permet un contact direct entre 
l'ovocyte et l'hémolymphe et au niveau duquel de très nombreuses vésicules de pinocytose sont 
parfois visibles. A l'apex, les cellules folliculeuses sont rejetées sur les côtés par la croissance de 
l'ovocyte qui atteint un diamètre de 60 à 65 дт et dont le pôle fait saillie dans la lumière 
ovarienne où s'accumulent les résidus de nombreux ovocytes en dégénérescence. Latéralement, 
dans sa partie supérieure, l'ovocyte établit alors avec les cellules voisines des jonctions septées 
qui semblent avoir pour principal rôle d'assurer l'ancrage de l'ovocyte que rien ne retiendrait 
plus désormais contre la paroi ovarienne. 



DISCUSSION-CONCLUSION 

Dételles modifications topographiques, schématisées sur la Fig. 1, reflètent vraisemblablement 
des transformations profondes de la physiologie ovocytaire. 

Durant les premiers stades de l'ovogenèse, l'ovocyte apparaît isolé à l'intérieur de son 
enveloppe folliculeuse. Tous ses échanges sont réglés par les cellules folliculeuses qui jouent le 
rôle d'intermédiaires entre la cellule germinale et les tissus voisins. Comme chez l'espèce 
Viviparus contectus (Bottke, 1972 et 1973), chez Viviparus viviparus divers arguments tels que 
l'abondance de l'appareil de Golgi dans les cellules folliculeuses, leur richesse en glycogène, 
vacuoles et corps multivésiculaires ... suggèrent que ces cellules jouent un rôle dans le 
catabolisme du matériel dégénéré dans la lumière ovarienne et dans le stockage de réserves 
nutritives utilisables par l'ovocyte. La rareté des vésicules de pinocytose dans les zones de 
contact entre ovocyte et cellules folliculeuses laisse supposer que les échanges intéressent 
surtout des éléments de faible poids moléculaire, transférés à l'ovocyte sous une forme soluble. 

Ensuite, au cours du paroxysme vitellogénétique, l'enveloppe folliculeuse éclate; l'ovocyte 
semble alors acquérir une certaine autonomie, puisant directement dans l'hémolymphe les 



GRIFFOND 



371 



prévit el logené se 



phase folliculaire 




I 



N noyau 

n nucléole 

't;^ vésicule ergastoplasmique 

Gy mitochondrie 
dictyosomes 
glycogéne 

corps multivèsiculaîre 
globule lipidique 
vitellus protéïque 
membrane basale 






paroxysme" vîtëllôgenique 



cellule 
folliculeuse 




maturation de l'ovocyte 

FIG. 1. Schema des modifications topographiques de l'ovocyte de Viviparus viviparus et de son enveloppe 
folliculeuse. Membrane basale est lame basale. 



372 PROC. SIXTH EUROP. MALAC. CONGR. 

substances dont il a besoin et absorbant peut-être aussi du matériel dégénéré dans la lumière 
ovarienne, au niveau des villosités qui ornent sa surface. 

L'apparition, après éclatement du follicule, de vésicules de pinocytose et de très nombreuses 
inclusions vitellines suggérait la possibilité d'une arrivée massive de produits exogènes véhiculés 
par l 'hémolymphe et captés par I 'ovocyte. La participation de facteurs exogènes, synthétisés 
dans des régions extra-ovariennes, à la constitution des plaquettes vitellines est en effet connue 
chez les Vertébrés, Insectes, Crustacés ... et récemment Hill & Bowen (1976) qui ont observé 
des tubules de pinocytose dans les ovocytes de la limace Agriolimax reticulatus ont émis 
l'hypothèse de la présence de composants auto- et hétérosynthétiques dans le vitellus de ce 
Gastéropode. Pour tenter d'évaluer l'importance du phénomène d'endocytose dans l'ovocyte de 
Viviparus viviparus, j'ai fait appel à la technique de Graham & Karnovsky (1966), dans laquelle 
la Peroxydase sert de traceur pour la mise en évidence des espaces extracellulaires et des 
phénomènes d'endocytose. Les premiers résultats font apparaître une double origine du vitellus, 
constitué: 

—d'une part de matériaux synthétisés par l'ovocyte lui-même avec la participation de la 
plupart des organites cellulaires (appareil de Golgi et mitochondries en particulier), 

—d'autre part de matériaux synthétisés en dehors de l'ovocyte et captés par pinocytose 
uniquement à la fin de la vitellogenèse. 

LITTERATURE CITEE 

ANKEL, W. E., 1923, Zur Befruchtungsfrage bei Viviparus viviparus L. Nebst Bemerkungen über die erste 

Reifungsteilung des Eies. Sencl<enbergiana, 5: 37-54. 
BOTTKE, W., 1972, Zur Morphologie des Ovars von Viviparus contectus (Millet 1813) (Gastropoda 

Prosobranchia). I. Die Follikelzellen. Ze/fsc/7r/Yf für Zellforschung, 133: 108-118. 
BOTTKE, W., 1973, Zur Ultrastruktur des Ovars von Viviparus coritectus (Millet 1813) (Gastropoda 

Prosobranchia). II. Die OocyXen. Zeitsctirift für Zeilforschiung, 138: 239-259. 
GRAHAM, R. С & KARNOVSKY, M. J., 1966, The early stages of absorption of injected horseradish 

Peroxydase in the proximal tubules of mouse kidney: Ultrastructural cytochemistry by a new technique. 

Journal for Histochemistry and Cytochemistry, 14: 291-302. 
HILL, R. S. & BOWEN, I. D., 1976, Studies on the ovotestis of the slug Agriolimax reticulatus (Müller). Cell 

and Tissue Research, 173: 465-482. 
POPOFF, M., 1907, Eibildung bei Paludina vivípara und Chromidien bei Paladina und Helix. Zu der Frage 

nach dem Spermatozoendimorphismus bei Paludina vivípara. Archiv für Mikroskopische Anatomie und 

Entwicklungsgeschichte, 70: 43-129. 
REYNOLDS, E. S., 1963, The use of lead citrate at high pH as an electron opaque stain in electron 

microscopy. Journal of Cell Biology, 17: 208-212. 
SPURR, A. R., 1969, A low viscosity epoxy resin embedding medium for electron microscopy. Journal of 

Ultrastructure Research, 26: 31-43. 
TRUMP, B. F., SMUCKLER, E. A. & BENDITT, E. P., 1961, A method for staining epoxy sections for light 

microscopy. Journal of Ultrastructure Research, 5: 343-345. 
YASUZUMI, G. & TANAKA, H., 1957, Electron microscope studies on the fine structure of the ovary, i. 

Studies on the origin of yolk. Experimental Cell Research, 12: 681-685. 



MALACOLOGIA, 1979, 18: 373-376 

PROC. SIXTH EUROP. MALAC. CONGR. 

EXPERIMENTAL EVIDENCE FOR THE HORMONAL CONTROL 

OF OVIPOSITION IN THE FRESHWATER PULMONATE 

INDOPLANORBIS EXUSTUS 

R. Nagabhushanam and M. M. Hanumante 
Department of Zoology, Marathwada University, Aurangabad-431004, India 

ABSTRACT 

Injection of blood or crude CNS extract from juvenile snails into intact, mature 
Indoplanorbis exustus elicits no egg-laying, whereas administration of blood or crude CNS 
extract from mature adults into the mature snails induces oviposition within 2 hours. 
Boiled extracts of CNS and crude homogenate of foot muscles from mature snails are 
unable to stimulate egg-laying in mature /. exustus. Thus it is hypothesized that a 
blood-borne agent which is possibly proteinaceous in nature, hormonal in character, and 
originating in the CNS of mature /. exustus, may be involved in controlling its oviposition. 

INTRODUCTION 

Egg-laying in the gastropod Pleurobranchaea californica (cf. Davis et al., 1974), which 
occupies a more dominant position in its behavioural hierarchy, is controlled by CNS 
hormone(s). In the opisthobranch Aplysia californica (cf. Arch, 1976) egg-laying is induced by 
its abdominal ganglion bag cell neurohormone. Recently, Ram (1977) has documented that in 
Busycon too, laying of egg capsules can be caused by extracts of the nervous system. 
Oviposition in the pond snail Lymnaea stagnalis is suppressed by the ablation of dorsal body 
and resumption of oviposition can be stimulated by dorsal body implants (Geraerts & Joosse, 
1975). However, stimulation of oviposition by dorsal body hormone is due to reinitiation of 
vitellogenesis. It has been implicitly established that Caudo-Dorsal Cells (CDC) from cerebral 
ganglia of L. stagnalis produce ovulation and oviposition-stimulating hormone and that circadian 
rhythmicity in oviposition in this snail appears to be because of diurnal rhythmic release of 
ovulation-provoking CDC neurohormone (see Roubos, 1976). Interestingly, Indoplanorbis 
exustus of tropical freshwater also exhibits a diurnal rhythm of oviposition (unpublished data) 
which hinted at the possibility of occurrence of some regulatory mechanism, probably 
hormonal by analogy with the pulmonate brethren L. stagnalis. Preliminary evidence is 
forwarded in the present paper substantiating the above possibility by analysing the effect of 
CNS homogenate and blood from juvenile and mature snails on oviposition in adult /. exustus. 

MATERIAL AND METHODS 

Locally collected, healthy snails of /. exustus were adapted to laboratory conditions (23 ± 
2.5° C, 12D:12L) for 7 days before experimentation. Adults (average length, i.e. distance 
between top of the shell and lowest body whorl, 17-20 mm) and juveniles (average length 
5-7 mm) were selected for the treatment. The blood from the snails was collected by breaking 
the shell and withdrawing the blood from the heart by tuberculin syringe. Blood from 20 to 30 
snails was pooled. CNS (cerebral, pleural, pedal, parietal and visceral ganglia) was quickly 
dissected out in chilled saline (0.7%) and homogenised with glass mortar and pestle. Similarly, 
foot muscles were separated, weighed and homogenised. The supernatant after centrifugation 
(3,000 r.p.m. for 10 min) was used for administration. To test the stability of the CNS factor 
responsible for oviposition, the CNS extract was boiled for 15 minutes and after boiling it was 
centrifuged. All injections were given directly into the foot using a 28-gauge needle. Each snail 
received 0.1 ml of blood or tissue extract. 

(373) 



374 



PROC. SIXTH EUROP. MALAC. CONGR. 



TABLE 1. Effect of blood and CNS extract from juvenile snails on egg-laying in mature L. exustus 2 hrs after 
injection. 



Injection 



No. of snails oviposited/ 
No. of snails injected 



No. of 
clutches laid 



1. Blood 

(0.1 ml/snail) 

2. CNS homogenate 

(0.1 ml containing 2 CNS/snail) 

3. Control 

(0.1 ml saline/snail) 



0/21 
1/19 
0/19 



TABLE 2. Effect of blood, CNS and foot muscle homogenate from adult snails on mature /. exustus 2 hrs 
after injection. 



Injection 



No. oviposited/ 
No. injected 



No. of 
clutches laid 



1. Blood 

(0.1 ml/snail) 

2. CNS homogenate 

(0.1 ml containing 2 CNS/snail) 

3. Boiled CNS homogenate 

(0.1 ml containing 2 CNS/snail) 

4. Foot muscle homogenate 

(0.1 ml containing 55 дд muscle/snail) 

5. Control 

(0.1 ml of saline/snail) 



15/15 

19/19 

0/21 

0/12 

2/19 



19 

28 





2 



Preliminary investigations indicated that the egg-clutches are laid 110 to 120 min after CNS 
extract administration. As such the number of egg-clutches deposited was counted 2 hours after 
the injections. The present experiments were carried out in August 1976 between 9:00 a.m. and 
12 p.m. 

RESULTS 

Injections of blood and CNS homogenate from juvenile snails stimulated no egg-laying (only 
one snail laid a single egg-clutch in CNS homogenate-injected snail) 2 hours after injections in 
mature Indoplanorbis (Table 1), whereas blood and CNS extract from mature snails initiated 
egg deposition in all the injected adults after 2 hours. There was no egg-laying in boiled CNS 
extract and foot muscle homogenate treated adults (Table 2). 



DISCUSSION 

The furnished data give evidence that the CNS of mature /. exustus contains a substance 
which can be liberated by homogenisation and which, when administered into other mature but 
intact /. exustus, can stimulate oviposition. Furthermore it is proposed that this oviposition- 
initiating substance is a blood-borne agent, i.e. a hormone which is not heat-stable and the 
release of which normally initiates egg-laying in this freshwater pulmonate. 

/. exustus, however, is an acyclic breeder; breeding attains a peak during the monsoon, i.e. 
June-September (Chintawar, 1974). Micromorphological studies of the neurosecretory system 
have revealed the occurrence of 2 types of neurosecretory cells (A and В cells) throughout the 
CNS (Chintawar, 1974). Of these the В neurosecretory cells from the cerebral ganglia show 
activity correlated with reproduction. Moreover, in /, exustus which are infected with larval 



NAGABHUSHANAM AND HANUMANTE 375 

trematodes, oviposition is dramatically curtailed (unpublished data) and at the same time В cells 
from cerebral ganglia display aberrations (Hanumante et al., 1977), 

The failure of blood or CNS homogenate (if a single exception is ignored) of immature but 
not from mature snails to stimulate egg-laying in adults points out that the elements concerned 
with the production of egg-laying substance are either inactive or absent in juvenile snails. That 
these elements control the egg-laying not through neural impulses but through a vascular 
hormonal channel is indicated by induction of oviposition following blood and CNS injections 
from adult snails and not by foot muscle extract. The inability of boiled CNS extract to 
provoke egg-laying indicates that the egg-laying hormone is not heat-stable and as such may be 
proteinaceous in nature (polypeptide?). Incidentally, Aplysia egg-laying hormone is of a 
polypeptide nature (Arch, 1976). 

The diurnal rhythmic ovipository behaviour of /. exustus (unpublished data) suggests that 
the cells producing egg-laying hormone must also be undergoing rhythmic changes in its 
secretory kinetics as has been demonstrated for CDC from cerebral ganglia of L. stagnalis (see 
Roubos, 1976). However, further extensive experimentation is needed to confirm this hypothe- 
sis and also to know the exact residence of egg-laying hormone. If L. stagnalis is taken as a 
model of pulmonate neuroendocrinology and on the basis of our unpublished data, the cerebral 
ganglia of /. exustus also, appear to be most promising candidates. 

It is intriguing to note that a latent period of about 2 hours is required before the onset of 
oviposition in Indoplanorbis after CNS homogenate or blood injection. It is pertinent to record 
that in the female echinoderm, Echinaster modestus (cf. Turner, 1976) too, a mean latent period of 
163 minutes has to elapse before ova can be released after intracoelomic injection of 
1-methyladenine. In Aplysia also egg-laying is stimulated approximately 50 to 75 minutes after 
administration of a crude bag cell extract into the haemocoel (Arch, 1976). Arch is of the 
opinion that, even though the gonad is immediately triggered by the hormone to extrude eggs, 
approximately 60 minutes are required for the string to be assembled and traverse the distance 
down the genital tract to the exterior in Aplysia. Perhaps even more time is consumed by 
Indoplanorbis to complete these preovipository rituals. However, more evidence is needed to 
draw the firm conclusion as to how the injected homogenate might have acted either directly 
on the gonads or via CNS by provoking the secretory activity of intact egg-laying neuro- 
hormonal cells. Further experiments have been planned to clarify this issue. 

Thus it looks quite apparent that like the lymnaeid pulmonate, L. stagnalis (see Roubos, 
1976) the planorbid, /. exustus, may also join the marine gastropods Pleurobranchaea (Davis et 
al., 1974), Aplysia (Arch, 1976) and Busyœn (Ram, 1977) wherein the presence of an 
ovipository hormone has been established. 

ACKNOWLEDGEMENTS 

The authors are thankful to PL-480 authorities for partial financial support through grant 
A7-ADP-39 and to Mrs. Mariamma Abraham for typing the manuscript. 

LITERATURE CITED 

ARCH, S., 1976, Neuroendocrine regulation of egg laying in Aplysia californica. American Zoologist, 16: 

167-175. 
CHINTAWAR, B. C, 1974, Studies on the biology of Indoplanorbis exustus. Ph.D. thesis, Marathwada 

University, Aurangabad, India. 
DAVIS, W. J., MPITSOS, G. J. & PINNEO, J. M., 1974, The behavioural hierarchy of the mollusk 

Pleurobranchaea II. Hormonal suppression of feeding associated with egg-laying. Journal of Comparative 

Physiology, 90: 225-243. 
GERAERTS, W. P. M. & JOOSSE, J., 1975, Control of viteilogenesis and of growth of female accessory sex 

organs by the dorsal body hormone in the hermaphroditic freshwater snail Lymnaea stagnalis. General and 

Comparative Endocrinology, 27: 450-464. 
HANUMANTE, M. M., VAIDYA, D. P. & NAGABHUSHANAM, R., 1977, Changes in the neurosecretory 

cells of the freshwater pulmonate Indoplanorbis exustus (Deshayes) infected with larval trematodes. Indian 

Journal of Experimental Biology, 15: 413-414. 
RAM, J. L., 1977, Hormonal control of reproduction in Busycon. Laying of egg capsule caused by nervous 

system extracts. Biological Bulletin, 152: 221-232. 



376 PROC. SIXTH EUROP. MALAC. CONGR. 

ROUBOS E W., 1976, Neuronal and non-neuronal control of the neurosecretory caudo-dorsal cells of the 
freshwater snail, Lymnaea stagnai is. Cell and Tissue Research, 168: 11-31. , ,. . 

TURNER R L Í976 Sexual differences in latent period of spawning following injection of the hornnone 
"methyladenine in Echinaster (Echinodermata: Asteroidea). General and Comparative Endocrinology, 28: 
109-112. 



MALACOLOGIA, 1979. 18: 377-380 

PROC. SIXTH EUROP. MALAC. CONGR. 

THE FINE STRUCTURE OF THE OOCYTE AND FOLLICLE CELLS OF 

LYMNAEA STAGNALIS, WITH SPECIAL REFERENCE TO THE 

NUTRITION OF THE OOCYTE 



Joyce E. Rigby 

Department of Biology, Queen Elizabeth College, 
University of London, W8, United Kingdom 

ABSTRACT 

A description is given of the configuration of the surface membrane in the 3 zones of the 
polarised system of oocyte and follicle cells. Thus the cell contacts and relationships 
between these cells are considered and speculation on the significance of surface 
morphology in the passage of substances into the enlarging oocyte, is included. 

Studies on the fine structure of the follicle cells and the oocytes in the gonad of Lymnaea 
stagnalis, show a well defined sequence of developmental phases of the follicle cells adjacent to 
the oocyte, and a high degree of differentiation and polarisation of these cells. The zones thus 
established in the follicle cells coincide with distinctive areas of the oocyte, particularly with 
the configuration of the margin of the oocyte (Rigby, in press). 

Thus three broad zones are recognised in the well grown oocyte of 90-105 дт diameter, and 
also in their follicle cells. Raven (1963, 1967) showed that only 6 inner follicle cells surround 
each oocyte. It is suggested that the striking morphological differences between these areas may 
be associated with the provision of different pathways for transfer of differing substances into 
the growing oocyte. 

As the oocyte separates, first from the lamellate zone of the follicle cells in the apical area 
of the oocyte (the future animal pole) so microvilli, 0.3-0.5 jum in height, are established from 
the surface of the oocyte (Fig. la). These microvilli are shorter and more sparse in distribution 
than those reported in Spisula (Rebhun, 1962), Barnea (Pasteéis & De Harven, 1962), Triturus 
(Hope, Humphries & Bourne, 1963) etc., but as in all these species, the microvilli are embedded 
in the vitelline envelope, pinocytotic vesicles form near their base and occasionally macrovilli 
from the follicle cells traverse the intercellular gap passing between the microvilli to fuse with 
the oocyte. Occasionally pores of the endoplasmic reticulum are also found between the 
microvilli (Fig. lb) and in some material it is indeed difficult to decide whether vesicles in the 
superficial cortical layer are pinocytotic vesicles or transversely cut channels of endoplasmic 
reticulum. The wide range in the degree of distension of channels of the endoplasmic reticulum 
in the apical cytoplasm of the oocyte recorded in this work, implies fluid uptake for the 
expansion of the oocyte through the pores of this system. 

Brummett & Dumont (1976) following investigations on the role of microvilli and 
endocytotic pits in the developing oocytes of Xenopus, stated that "microvilli with their 
negatively charged sialic acid moieties may be the sites of cation exchange (and perhaps small 
molecule uptake?)" and that evidence of the uptake of the main precursor of yolk through the 
mechanism of endocytosis has been obtained. These functions seem also possible in Lymnaea. 

The lateral band succeeds the microvillar surface and extends to the base of the oocyte and 
it equates with the zone between the nucleus and the basal processes of the follicle cells. The 
band is characterised by tight junctions, gap junctions and desmosomes alternating with deeper 
intercellular spaces that contain translucent material or electron-dense floccular material 
between the oocyte and follicle cells (Fig. 2a). Abundant distended vesicles of the endoplasmic 
reticulum and Golgi stacks occur in this part of the follicle cells and suggest high proteinaceous 
and carbohydrate metabolism. Some very large vesicles that seem to extend from the 
endoplasmic reticulum may be discharging their proteinaceous contents to the intercellular 

(377) 



378 



PROC. SIXTH EUROP. MALAC. CONGR. 




щ,ж 



of 



Ш 



Ш 




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pr-v 












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*«^ 






Яй 




i^' 11!" -•■*. 



'*•%--,-.. 



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er 



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FIG. 1. (a) Apical portion of an oocyte with inner follicle cells showing their interlocking lamellae, outer 
follicle cells, and differentiating sperm with Sertoli cells beyond, (b) Pore of the endoplasmic reticulum, in an 
oocyte. Abbreviations: a-amoebocyte cell; d-desmosome; er-endoplasmic reticulum; gj-gap junction; 
if-inner follicle cell; im-intercellular matrix; is-intercellular space; l-lamella; mv-microvillus; n-nucleus; 
nm-nuclear membrane; of-outer follicle cell; o-oocyte; p-pore; s-spermatozoon; tj-tight junction; 
V— vesicle; ve— vitelline envelope; y— yolk granule. 



RIGBY 



379 





0-3}im 



.Ш 



2b 



FIG. 2. (a) Portion of the lateral border of the oocyte and follicle cell, (b) Basal processes of the follicle cells 
and an amoebocyte cell, alongside the base of the oocyte. For explanation of lettering see Fig. 1. 



380 PROC. SIXTH EUROP. MALAC. CONGR. 

spaces. Small vesicles may occur along both the follicular border and the oocyte border of the 
intercellular spaces. In some instances cytoplasmic projections from the follicle cells penetrate 
the oocyte and appear to be nipped off. Are some larger molecules of glycoprotein and nuclear 
protein conveyed directly by such portions of cytoplasm into the oocyte, whilst nucleotides, 
sugar phosphates and choline phosphates pass through gap junctions (Pitts, 1976) into the 
oocyte? 

The growing oocyte rests on the basement membrane of the gonad which merges with the 
intercellular matrix between the digestive gland and the gonad. It is in this matrix that 
'rhizoids,' slender projections from the base of the oocyte (the future vegetative pole), make 
tight junctions, gap junctions and desmosomes with elaborately branching processes which 
ramify through the tissue from the base of the follicle cells; the amoebocyte cells also found in 
the matrix, make cell contacts with the base of the follicle cells and occasionally with the 
oocyte (Fig. 2b). In the deep cups or capsules formed by some processes of the follicle cells, 
secretions aggregate and seem to be taken up by structurally different processes that penetrate 
into the capsule. Small vesicles are frequent along the base of the oocyte. 

It is close to this basal border that the most substantial accumulation of lipid globules is 
found in the oocyte, these inclusions becoming membrane-bound and their contents more 
electron-dense. This certainly appears to be a nutritionally active area, not merely a passive 
anchoring region and these features link with the observations of Joosse & Reitz (1969) that 
yolkKîontaining oocytes are confined "to those parts of the wall of the acini which are apposed 
to the lobes of the digestive gland." 

The question arises whether there is direct transfer of digested food substances across the 
intercellular matrix from the digestive gland to the rhizoids and pinocytotic vesicles at the base 
of the oocyte, whether amoebocytes facilitate the transport of substances to the oocyte and 
follicle cells, or whether some products of the follicle cells are discharged into capsules and 
taken up by processes of the oocyte. Probably all these pathways are used by some substances 
entering the oocyte but there are many problems to contend with to undertake feeding 
experiments with labelled material to resolve these points. These observations on the fine 
structure nevertheless indicate, how the special cytoplasmic differentiation of the mosaic egg of 
Lymnaea stagnalis (cf. Raven, 1967) may arise. 

ACKNOWLEDGEMENTS 

This work was commenced during a sabbatical year spent in the Zoological Laboratory, 
University of Utrecht, and I am pleased to thank Prof. Chr. P. Raven for his kind hospitality 
and interest in the work. I also thank Dr. R. H. Nisbet for his help and for facilities in the E. 
M. Unit, Physiology Department, Royal Veterinary College, London NWl, and Mr. John Расу 
(QEC) for preparation of the plates. 

LITERATURE CITED 

HOPE, J., HUMPHRIES (Jr.), A. A. & BOURNE, G. H., 1963, Ultrastructural studies on developing oocytes 

of the salamander Triturus viridescens. 1. The relationship between follicle cells and developing oocytes. 

Journal of Ultrastructure Research, 9: 302-324. 
JOOSSE, J. & REITZ, D., 1969, Functional anatomical aspects of the ovotestis of Lymnaea stagnalis. 

Malacologia, 9: 101-109. 
PASTEELS, J. J. & DE HARVEN, E., 1962, Etude au microscope électronique du cortex de l'oeuf de Barnea 

candida (mollusque bivalve), et son evolution au moment de la fécondation, de la maturation, et de la 

segmentation. Archives de Biologie, 73: 465-490. 
PITTS, J. D., 1976, Junctions as channels of direct communication between cells. In: GRAHAM, G. F. & 

WAREING, P. F., eds., The developmental biology of plants and animals: 96-110. Blackwell Scientific 

Publications, Oxford. 
RAVEN, Chr. P., 1963, The nature and origin of the cortical morphogenetic field in Limnaea. Developmental 

Biology, 7: 130-143. 
RAVEN, Chr. P., 1967, The distribution of special cytoplasmic differentiations of the egg during early 

cleavage in Limnaea stagnalis. Developmental Biology, 16: 407-437. 
REBHUN, L., 1962, Electron microscope studies on the vitelline membrane of the surf clam, Spisula 

solidissima. Journal of Ultrastructure Reasearch, 6: 107-122. 
RIGBY, J, E., in press. The fine structure of the oocyte and follicle cells of Lymnaea stagnalis. 



MALACOLOGIA, 1979, 18: 381-389 

PROC. SIXTH EUROP. MALAC. CONGR. 

THE STRATEGY OF COPULATION OF STAGN/COLA ELODES (SAY) 
(BASOMMATOPHORA: LYMNAEIDAE)1 -2 



Paul H. Rudolph 

Museum of Zoology, The University of l\/lichigan, 
Ann Arbor, Michigan 48109, U.S.A. 



ABSTRACT 

The copulation of Stagnicola elodes, a North American lymnaeid, is effected by the 
male from a position at the right margin of the female shell. The mode of copulation is 
immediately successively reciprocal, both members of a pair acting as male and female 
during a single meeting. During the first male to female activity, the female becomes 
stimulated, before the male has finished, to copulate in the reciprocal direction. The 
copulatory stimulus can be carried through a 3rd, 4th, etc., snail by placing the 
stimulated female on the shell of a snail other than the male. Females forcibly restrained 
from reciprocating, isolated and then reunited with the male can lose the copulatory 
stimulus. The female can remain stimulated to copulate up to at least 1 hour of isolation. 
Male activity takes approximately 2 hours, and in a reciprocating pair both snails are 
occupied for 4 hours. The ejaculated sperm is in the posterior part of the vagina when 
observed immediately after copulation. Males ejaculate most or all of their stored sperm 
in one copulation. Prostatic secretions are greatly depleted following copulation. Refilling 
of the hermaphroditic duct begins between the first and 2nd day following copulation. 
Two days following copulation, the duct is approximately % to Уг full. A copulatory 
plug, with a probable effective existence of 2 to 3 hours, is formed in the female at the 
area of juncture of the spermathecal duct and vagina. The plug is composed of secretions 
from the male reproductive tract of the male. Two roles are suggested here for the 
secretions of the male reproductive system, i.e., the formation of a copulatory plug and 
implication in the stimulus of male activity in the female. 



INTRODUCTION 

Members of the higher limnic Basomrnatophora are hermaphroditic, and many such snails are 
capable of self-fertilization as well as cross-fertilization. A hermaphroditic animal capable of 
self-fertilization must be prepared for either eventuality, mating when possible and self- 
fertilizing when mating is not possible. Therefore, mating is a major strategy in the reproductive 
biology of these animals. A major difference between the two types of reproduction is the 
origin of the sperm. In self-fertilization, all reproductive materials, sperm included, are provided 
by one animal. In cross-fertilization, the provision of the sperm, and possibly other materials, is 
undertaken by an animal other than the one which lays the eggs. 

However, the mechanism of mating has further implications than a simple transfer of sperm. 
It has been shown that freshwater pulmonates will use foreign sperm in preference to 
autosperm (e.g.. Boycott et al., 1930; Cain, 1956; Wu, 1972). Some planorbids (DeWitt & 
Sloan, 1959; Lo, 1967) and Ancylus fluviatilis (Bondesen, 1950) will not reproduce normally 
without cross-fertilization. It also appears that paired snails begin laying eggs earlier in life than 
isolated snails (Boycott et al., 1930; Noland & Carriker, 1946; DeWitt, 1954; Horstmann, 1955; 
DeWitt & Sloan, 1958, 1959). The stimulus for an earlier initiation of oviposition by snails 
which have mated is ascribed to a sperm factor resorbed from the spermatheca following 
copulation (Horstmann, 1955). 

Although freshwater pulmonates can be induced to mate, the physiological basis for mating 

"• Adapted from a dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of 
Philosophy at The University of Michigan, December 1976. 

2This investigation was supported, in part, by research grant 5T1 AI41 from the National Institute of 
Allergy and Infectious Diseases, U.S. Public Health Service. 

(381) 



382 PROC. SIXTH EUROP. MALAC. CONGR. 

is not explained. Snails reunited after isolation will often copulate (Noland & Carriker, 1946; 
Duncan, 1959); Lymnaea stagnalis appressa copulates readily when the food supply has recently 
been depleted (Noland & Carriker, 1946) and Helisoma trivolvis pseudotrivolvis and Physa 
gyrina "brought fronn lower (below 10°C) to higher tennperatures" will copulate and lay eggs 
within 36 to 48 hours (Roney, 1943). Duncan (1959) has also shown that Physa fontinalis, 
when brought into the laboratory from the field, goes through a period of intense mating 
activity, presumably due to the change of environment. 

The types of pairing during the copulation of freshwater pulmonates are varied. Unilateral, 
chain and reciprocal mating have been described as primary modes of mating among members 
of the Planorbidae (e.g., Hazay, 1881; Precht, 1936; De Larambergue, 1939; Boettger, 1944; 
Maiek, 1952; Paraense & Deslandes, 1956; Pace, 1971). The primary means of mating in 
members of the Lymnaeidae, Physidae and Ancylidae are unilateral or in chains (Karsch, 1846; 
De Lacaze-Duthiers, 1899; Boettger, 1944; Noland & Carriker, 1946; Barraud, 1957; Duncan, 
1959; Marcus & Marcus, 1962; and others). Occasional reports of reciprocal mating among the 
Lymnaeidae exist (Karsch, 1846; Kunkel, 1908; Noland & Carriker, 1946; Barraud, 1957), but 
reciprocal mating is not reported to be a primary means of mating in these three families. Thus, 
among the members of the higher freshwater pulmonates, differences exist in mating behavior, 
even within the same family. 

Phenomena of mating in the North American lymnaeid Stagnicola elodes (Say) will be 
described in this report in order to more clearly delineate the mating mechanism of this snail. 

MATERIALS AND METHODS 

Stagnicola elodes adults were collected from a roadside pond on Liberty Road, 2.2 miles west of Zeeb 
Road, Ann Arbor, Washtenaw County, Michigan. Snails used in this study were laboratory raised descendants 
from the field collected snails. Snails were maintained in 5-gallon aquaria containing aerated tap water and an 
aquarium filter, and fed with lettuce throughout the period of study. 

Sexually mature snails were isolated for 48 hours in plastic drinking glasses containing 50-100 ml of 
previously aerated tap water. Lettuce was added to each covered dish. After 48 hours, the snails were placed 
in pairs in the same water in which they had been isolated and were allowed to copulate. Occasional 
observations were made on non-isolated snails taken directly from the stock tanks. 

Reproductive tracts used for histological sectioning were fixed in Heidenhain's Susa. The reproductive 
tracts were severed posterior to the spermatheca and the anterior portion embedded in Paraplast (melting 
point 56 C), following dehydration in a graded series of ethyl alcohol and clearing in dioxane or xylene. 
Sections were prepared at Q цп\ and stained with methyl blue-picric acid-hematoxylin (Lillie's Allochrome 
without periodic acid-Schiff, Lillie, 1965), hematoxylin-eosin, bromphenol blue or Alcian blue 8GX (pH 
2.5)-eosin. 

Voucher specimens from the laboratory populations are in the Museum of Zoology, University of 
Michigan (UMMZ): shells UMMZ 246000, alcohol specimens UMMZ 246001. 

RESULTS 

Spontaneous male copulatory activity 

When the snails were placed in pairs after the isolation period, 8 experiments showed that 28 
of a total of 98 pairs exhibited spontaneous male activity. If spontaneous male activity was not 
initiated within approximately 2 hours of placing the snails in pairs, it seldom occurred during 
the period of observation (usually 8-12 hours). 

Prior to copulation, the 2 snails move about the dish. The male-acting animal (hereafter 
referred to as the male) crawls upon the shell of the female-acting animal (the female). The 
male continues to crawl around on the shell of the female until it reaches a position on the 
right margin of the shell. During this time, the male gonopore region of the male becomes 
slightly dilated and appears as a white dot, in contrast to the barely visible male gonopore 
observable in a non-copulating animal. The white area is often visible before the male has 
crawled upon the shell of the female. The white area enlarges and the penial complex becomes 
partially everted. The male everts the penis and probes under the shell of the female in search 
of the female gonopore. During the period of male probing, the female apparently does not 
change its behaviour and moves about the dish and may continue to feed. The female suddenly 



RUDOLPH 383 

withdraws the right side of the body partially into the shell. This withdrawal is only temporary, 
and the fennale returns from the withdrawn position and copulation proceeds. It is thought that 
this withdrawal by the female represents the time of insertion of the male penis. Both snails 
remain motionless for some time after the female partial withdrawal and return. The male is 
tightly attached to the shell, and its tentacles are laid against its body. 

Reciprocation and stimulation of male copulatory 
activity in females 

Reciprocation begins with the female becoming active approximately 90 minutes from the 
beginning of copulatory activity, while the penis is still inserted into the female gonopore. The 
female at this time starts to act as a male. The penial movement and characteristics are similar 
to those observed when the male originated copulation. The female moves its body in such a 
way that the anterior region is attached to the shell of the male at the right anterior margin of 
the shell, and begins probing with its penis. During this time the male penis is still inserted into 
the gonopore of the female and the male is still tightly attached to the right margin of the 
female's shell. The female continues to move upon the shell of the male until the female 
switches places with the male. 

The actual point of removal of the male penis was not observed, but it was noted that the 
male penis occasionally was still inserted after the female had assumed the mating position. The 
male penis was not observed to remain in the female vagina during reciprocation. To do so 
would create problems due to the positions of the respective gonopores. Copulation then 
proceeds in the reciprocal direction. Following the reciprocation, the pair separates. The male 
does not recopulate. 

The male copulatory activity of the female can be directed towards a 3rd snail, rather than 
towards the male. The female was prevented from copulating with the male by placing the 
stimulated female, with the male still attached, in contact with the shell of a 3rd snail. The 
female quickly attaches to this shell and begins to copulate with the 3rd snail rather than with 
the male. After the original male ends its activity, it moves off the original female and shows 
no further interest in the remaining two snails. 

The original female, now acting as male, continues to copulate with the 3rd snail. The 3rd 
snail becomes stimulated to act as a male in the same manner as the first female became 
stimulated. By placing the 3rd snail in contact with the shell of a 4th snail, the 3rd snail begins 
copulatory activity with the 4th. The original female finishes its male copulatory activity and 
departs. The male activity in females can probably be carried on through a large number of 
snails. In one experiment, the activity was shown through 5 snails, all females assuming male 
activity in turn before the experiment was terminated. 

Male copulatory activity in the female occurred in nearly every case observed (40 of 42). 
Two females did not respond and were found upon dissection to contain no sperm in the 
hermaphroditic duct. Time of day apparently was not important, for observations of male 
activity in females were recorded throughout the day and evening. 

The average male activity for 45 copulations was 123 minutes. This includes all male 
activity, i.e., spontaneous, reciprocations and male activity induced through 3 or more snails. 

Status of the female reproductive tract 
subsequent to copulation 

Dissection and/or sectioning of the reproductive tract immediately following copulation 
showed that the vaginal region, spermathecal duct and spermatheca are very dilated. The walls 
are extremely thin, and the above organs are fluid filled. The fluid contains small patches of 
material other than sperm, but the composition of the material was not determined. The 
posterior portion of the vagina and the anterior portion of the oöthecal gland contain the 
ejaculated sperm. Peristalsis of the dilated vagina and spermathecal duct was observed. 

A white mass of material fills the vaginal lumen and sticks to the wall of the vagina at the 
junction of the vagina and spermathecal duct. Snails fixed and sectioned immediately following 
copulation showed the material to consist of areas of granules, areas of homogeneous-appearing 
material and areas which have a coagulated appearance (Fig. 1). Sperm were not observed to be 



384 PROC. SIXTH EUROP. MALAC. CONGR. 

mixed with the mass. The granules stain bright yellow to yellow-green with methyl blue-picric 
acid. The granular material and most of the other material is protein as indicated with 
bromphenol blue. Mucopolysaccharides, indicated with Alcian blue 8GX (pH 2.5), are present 
in small amounts. 

Snails fixed and sectioned 2 hours after acting as females showed that the granular 
appearance is somewhat reduced. By 3 hours after acting as females the mass of material 
appears to have decreased in size and is not tightly bound to the vaginal wall (Fig. 2). Four to 
5 hours after acting as females, the material was usually displaced. The material was identified 
in the spermathecal duct and spermatheca (Fig. 3). Some animals observed from 4 to 5 hours 
after acting as females still had the mass in place but it was easily removed. 

In one instance the male was interrupted before completing copulation. The female 
contained sperm but no mass, indicating that this material is passed to the female after 
ejaculation of the sperm. 

Duration of the copulatory stimulus in 
activated females 

Females were forcibly restrained from reciprocating until the male had finished and 
departed. The females were then isolated for 15 or 30 minutes and reunited with the male. If 
copulatory activity by the female after reunion with the male was observed, the female was 
re-isolated and again reunited. This procedure was repeated until no copulatory activity by the 
female was observed (Table 1 ). 



TABLE 1. Duration of male copulatory activity in nine stimulated females isolated after male had finished 
copulation. 

Time of isolation. Time to attempt copulation 

Snail minutes after reunion, minutes Comments 

No copulatory activity 

10 Attempted copulation. 

Re-isolated 

No copulatory activity 

20 Attempted copulation. 

Re-isolated 



1-3 


15 


4 


15 




15 


5 


15 




15 


6 


30 


7 


30 


8 


15 



No copulatory activity 

Attached to partner, then moved off. 
No copulation 



25 Copulated with partner 

15 Attempted copulation. 

Re-isolated 

15 10 Attempted copulation. 

Re-isolated 

30 No copulatory activity 

15 50 Attempted copulation. 

Re-isolated 

15 10 Attemptedd copulation. 

Re-isolated 

15 10 Attempted copulation. 

Re-isolated 

15 15 Attempted copulation. 

Re-isolated 

15 No copulatory activity 



RUDOLPH 



385 





FIG. 1. Copulatory plug shortly after copulation. (1) Vaginal wall; (2) note the close adhesion to the wall 
(3) granular areas; (4) gap probably due to fixation. Methyl blue-picric acid, hematoxylin. 

FIG. 2. Copulatory plug in vagina, 3 hours following copulation. Bromphenol blue. 

FIG. 3. Copulatory plug in spermathecal duct, 5 hours following copulation. Spermathecal duct is stil 
somewhat dilated. Bromphenol blue. 

FIG. 4. Prostate after 48 hours of isolation. Methyl blue-picric acid, hematoxylin. 

FIG. 5. Prostate immediately following copulation. Methyl blue-picric acid, hematoxylin. 



386 PROC. SIXTH EUROP. MALAC. CONGR. 

Status of the prostate and hermaphroditic duct 
in males following copulation 

Following copulation, the prostate of males is flaccid looking, in contrast to a turgid-appear- 
ing prostate prior to copulation. The secretory products of the prostate are depleted in most 
areas (Figs. 4, 5), although some prostates retained a substantial amount of secretory material 
following copulation. It appears that, often, copulation following 2 days of isolation nearly 
empties the prostate. The variation in amount of secretion remaining after copulation is 
presumably dependent on that present prior to copulation. 

Prostates sectioned 1 day following copulation, in animals that had acted only as males, 
showed that the prostate contained more secretory products than those immediately following 
copulation. Sections of prostate made 2 days following copulation, in animals which had acted 
only as males, showed secretory products approximating the amount seen prior to copulation. 

Hermaphroditic ducts from 26 snails were checked by dissection within 2 hours after 
completion of male activity. Of these 26 ducts, 19 were empty and 7 were depleted but were 
not empty. Thus, the duct may retain sperm in relatively large amounts but, more often than 
not, most or all of the sperm is passed during a single copulatory act. The amount of sperm 
remaining after copulation may depend upon how much was present prior to copulation. 

Five animals which had acted only as males were isolated for 24 hours and 5 were isolated 
for 48 hours following copulation, and the contents of the hermaphroditic duct were checked 
by dissection. Animals isolated for 24 hours had little or no sperm in the hermaphroditic duct. 
Animals isolated for 48 hours had more sperm, and the duct was about % to Vi full. 



DISCUSSION 

Since members of the Lymnaeidae, Physidae, Planorbidae and Ancylidae are generally 
simultaneously hermaphroditic, copulation can occur in various manners. It is deemed desirable 
to define terms for the various types of pairing which can occur among pulmonale snails. 

Copulation: sexual intercourse between 2 snails. Copulation will thus be defined to include 
all male activity which occurs during the sexual intercourse of two snails. 

Unilateral couplation: one member acts as male and the other member acts as female. A 
special case of unilateral copulation occurs in chain formation. Chain copulation is actually a 
series of unilateral copulations, since between any 2 members of the chain, copulation is 
unilateral. 

Reciprocal copulation: both members act as male and female with each other. 

(a) Simultaneously reciprocal copulation: both members act as male and female at the same 
time. 

(b) Successively reciprocal copulation: both members act as male and female, in turn. 

(1) Immediately successive reciprocal copulation: the pair does not separate before recipro- 
cation occurs. 

(2) Delayed successive reciprocal copulation: the pair separates before reciprocation occurs. 

These categories may serve to describe any type of copulation which could conceivably occur 
between members of a pair. 

The copulation of Stagnicola elodes, in snails which have been isolated for 48 hours and 
therefore have not copulated for that period of time at least, is nearly always an immediately 
successive reciprocation. The initial male to female behavior is very similar to the unilateral 
copulatory behavior described by Barraud (1957) for Lymnaea stagnalis. 

Reciprocation occurs by the stimulation of the female to act as male. In the 2 instances in 
which the female failed to respond, it was observed that the hermaphroditic duct of the female 
contained no sperm. The same stimulation can be used to form chain, i.e., multiple unilateral, 
copulations. 

It has been occasionally noted that immediately successive reciprocal copulation occurs in 
lymnaeids (Karsch, 1846; Kunkel, 1908; Boettger, 1944; Noland & Carriker, 1946; Barraud, 
1957). Except for Kunkel (1908), the reports state that lymnaeids copulate unilaterally, with 
only occasional reciprocation. 



RUDOLPH 387 

It is probable that stimulation of male copulatory activity in the female occurs in other 
lymnaeids as well, as evidenced by the occasional reports mentioned above. Also, Barraud's 
(1957) description of multiple copulation in Lymnaea stagnalis indicates that stimulation of 
copulatory activity in the female had occurred, since the same type of chain formation was 
easily performed in this study by preventing reciprocation by the female and placing the female 
in contact with the shell of a 3rd snail. 

The stimulus for male activity, both spontaneous and by stimulation, may be hormonal. This 
is indicated by the fact that (1) although male activity is originally spontaneous, male activity 
in the female is not, and (2) a male is not restimulated to male activity after a female has 
reciprocated. The male had not acted as female prior to its acting as male and could 
conceivably be receptive to a mechanical stimulation, if the stimulation to male activity in the 
female was solely dependent upon mechanical stimulation from the male penis. A hormonal 
transmitter would probably be depleted in the male after male activity. Whether such a 
hormone would be released in the female due to mechanical stimulation or by a secretion 
passed from the male, or both, is not known. The stimulus to copulate could be hormonally 
mediated via the brain, much as oviposition is stimulated in Lymnaea stagnalis (see Geraerts & 
Bohlken, 1976). 

A component of the male secretions may stimulate male copulatory activity in female snails. 
It may do so directly or it may stimulate the release of some substance by the female which 
would then stimulate male activity. This would indicate that male copulatory activity can be 
stimulated in different ways. Spontaneous male activity is stimulated by unknown factors and 
induced male activity by factors which may include secretions from the male. 

Since the female of spontaneously copulating pairs had also been isolated for 48 hours, it is 
possible that the male copulatory activity by the female was spontaneous rather than 
stimulated. However, isolated animals would act as females and assume male activity, even 
though they did not show spontaneous male activity, and 97% (40 of 42) of all females 
assumed male activity. These 2 facts speak in favor of a stimulation of male activity in the 
female. 

Although it was not determined how long an interval after copulation is necessary before a 
snail can be stimulated to copulate again, the facts that a male is not stimulated to recopulate 
after reciprocation, that the hermaphroditic duct is usually severely depleted of sperm and that 
the prostate secretions are greatly depleted after copulation indicate that copulation cannot be 
restimulated to occur except after some time. In spontaneously male acting snails isolated after 
copulation, the hermaphroditic duct had filled enough after 2 days for copulation to occur 
again. However, 1 day after copulation the prostate contains secretory products, and it is 
possible that the prostate had recovered sufficiently for copulation to occur again. Also, not all 
snails passed all sperm in one copulation and these could conceivably copulate again without 
refilling of the hermaphroditic duct. 

Whether or not the stimulation of copulatory activity in the female is mediated by secretions 
of the male reproductive system, the white mass in the vagina of the female is formed from 
male secretions. Proteins are a major constituent of the mass. The secretions of the male 
reproductive tract in Stagnicola elodes are overwhelmingly proteins (Rudolph, 1976), and the 
granules of the mass stain similarly to those of the prostate with methyl blue-picric acid. There 
is little doubt that the major part of the material comes from the prostate, although the rest of 
the male reproductive tract may also contribute to the mass. The proteinaceous mass in the 
vagina of the female is interpreted here as a copulatory plug. A coagulum formed from prostate 
secretions and situated at the junction of the vagina and the spermathecal duct in Lymnaea 
stagnalis was recognized by Horstmann (1955), and he suggested that it prevented the outflow 
of sperm. The materials which made up the coagulum in Lymnaea stagnalis were passed to the 
female after the ejaculation of the sperm. De Larambergue (1939) described, in Bulinus 
œntortus (= truncatus), a "coagulum" which contained sperm and was thought to contain secre- 
tion from the prostate. 

The plug in Stagnicola elodes contains no sperm and is neither the remains of a sperma- 
tophore nor used to hold the penis in place during copulation. One female was seen to con- 
tain sperm but no plug, and the penis of Stagnicola elodes possesses a penial knot which, in 
cooperation with the vaginal sphincter muscle, serves as a holdfast mechanism during copulation 
(Walter, 1969). 



388 PROC. SIXTH EUROP. MALAC. CONGR. 

Although the formation of a copulatory plug is known from rats (Mann, 1964), insects 
(Parker, 1970) and snakes (Devine, 1975), it has not been interpreted as such in basommato- 
phorans. The copulatory plug has a counterpart in other gastropods in the form of spermato- 
phores. These are common in slugs and other Stylommatophora. Spermatophores are also 
present in prosobranchs (Hyman, 1967), opisthobranchs (Tardy, 1966), the lower basommato- 
phoran families Chilinidae (Harry, 1964) and Siphonariidae (Abe, 1940; Hubendick, 1944; 
Sumikawa & Onizuka, 1973), but not in the Lymnaeidae, Physidae, Planorbidae or Ancylidae. 
According to Parker (1970), a spermatophore can function in the same manner as a copulatory 
plug. 

Two possible functions of a copulatory plug (Parker, 1970) include prevention of sperm 
leakage following copulation and the prevention of a second successive copulation by another 
male and subsequent competition between the sperm of two males to fertilize the eggs of the 
female. Neither of these possibilities can be ruled out in Stagnicola elodes. During and 
immediately following copulation, the vagina, spermatheca and spermathecal duct are greatly 
dilated, transparent, fluid filled and turgid. It appears that a pressure builds up in the female 
tract and plug formation could aid in keeping this system intact. However, the gonopore region 
of Stagnicola elodes is heavily muscularized (Walter, 1969) and appears able to prevent sperm 
leakage. 

The solidity of the plug and its adherence to the wall of the vagina immediately following 
copulation indicate that the plug could prevent a 2nd male from copulating following the first, 
at least for 2 or possibly 3 hours. This may be a critical period since, in Lymnaea stagnalis, 
sperm destined to fertilize the eggs move through the oviduct to the hermaphroditic duct in the 
first 2 to 3 hours following copulation (Horstmann, 1955). During the period of reciprocation 
in Stagnicola elodes, approximately 2 hours, the sperm from the first mating is probably 
moving up the female reproductive tract and the original female is very quiet. The original 
female is vulnerable to a 2nd mating when quiet, probably more so than when actively moving. 
The copulatory plug is in position during this time, however, and a copulation by another male 
would be prevented. The plug has a relatively short effective existence, however, since 3 hours 
following copulation the structure of the plug has changed and by 4 to 5 hours following 
copulation the plug is often displaced. 

The combination of the 2 mechanisms, the stimulation of male copulatory activity in the 
female and the formation of a copulatory plug would insure insemination of both partners 
during the same mating by reciprocation and yet prevent competition from other males mating 
with either of the two reciprocating snails. This would be most effective when there are 
numerous spontaneous copulations occurring at the same time and in a restricted area. The 
arrival of conditions favorable to a burst of mating, such as during spring or precipitation after 
a dry spell, could constitute such a period. 

The combination of these 2 mechanisms also suggests a way in which a copulatory stimulus 
could be passed through part of a population even though relatively few animals start to 
copulate spontaneously. If the snails were in close proximity to each other, it is possible that a 
female would copulate with a 3rd snail rather than reciprocate with the male. The presence of 
the plug in the female could prevent the 3rd snail from reciprocating and force it to move on 
to a 4th snail, etc. The stimulus could be maintained through a number of snails until either all 
had copulated, the stimulus was lost or until a snail was encountered which had acted as male 
but not female, and the cycle would stop. 

ACKNOWLEDGEMENTS 

I thank Dr. J. B. Burch for continued support throughout this study, H. Wurzinger and A. 
Gismann for reading the manuscript, and G, Borgia and M. Devine for stimulating and helpful 
discussions. 

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MALACOLOGIA, 1979, 18: 391-399 

PROC. SIXTH EUROP. MALAC. CONGR. 

THE GONAD AND ITS DEVELOPMENT IN DEROGERAS RETICULATUM 

(PULMONATA: LIMACIDAE) 

N. W. Runham and N. Hogg 

Zoology Department, University College of North Wales, 
Bangor, Gwynedd (Wales), United Kingdom 

ABSTRACT 

At hatching the gonad of Dereceras reticulatum consists of 1-3 acini and during the 
undifferentiated stage of the gonad this number increases to 70 to 180. In later stages the 
acini increase in size and often become lobed. The first formed acini consist of a lining 
epithelium of gonadal stem cells that are continuous with the epithelium in the ductule 
and a small group of cells filling the lumen. As the cells divide the acinus swells and cells 
similar to those in the lumen appear under the epithelium. The cells in the lumen 
differentiate into sperm, those under the epithelium into oocytes and follicle cells and 
the epithelial cells differentiate into Sertoli cells. Around the entry of the ductule into 
the acinus the gonadal stem cells persist as the germinal epithelium. Further follicle cells 
and oocytes appear to differentiate from the edge of the germinal epithelium. Following 
castration, in young animals, complete and rapid regeneration from the hermaphrodite 
duct occurs and this parallels closely the early development of the gonad. 

INTRODUCTION 

Numerous studies have been undertaken on many aspects of the pulmonate gonad, however, 
as emphasised by recent reviews (Gomot, 1971; Luchtel, 1972), we are still far from 
understanding gametogenesis and the other functions of this organ. Gomot (1971) has clearly 
distinguished 3 fundamental processes that are involved in gametogenesis: the segregation of the 
germinal cells, the entry of germinal cells into gametogenesis, and the orientation of 
gametogenesis to either spermatogenesis or oogenesis. As yet none of these processes has been 
clarified. The authors wishing to study the endocrine relationships of the gonad of Deroceras 
reticulatum required a baseline study of its morphology and normal mode of functioning. The 
present paper is a preliminary report of our findings. 

MATERIALS AND METHODS 

Deroceras reticulatum, collected in the Bangor area, were fixed for light microscope studies 
in Susa fixative, embedded in Fibrowax, sectioned at 7jLtm and the sections stained in Azan. 
For studies in the electron microscope tissues were fixed in a mixture of osmium tetroxide and 
glutaraldehyde (Hirsch & Fedorko, 1968) and embedded in either Epon 812 or Araldite. 
Semi-thin sections were stained in toluidine blue and thin sections in lead citrate and uranyl 
acetate. 

Scale models of acini were prepared from vinyl linoleum. Serial sections were photographed, 
enlarged and tracings made on the lineoleum. These were then cut and glued together with 
Thixofix contact adhesive. After painting, the location and dimensions of the germinal 
epithelium and oocytes were marked on their surfaces. 

RESULTS 

Origin and initial development of the gonad 

During the first few weeks after hatching the reproductive system is difficult to study as it is 
extremely thin. At hatching it consists of a simple blind ending duct opening to the exterior at 

(391) 



392 



PROC. SIXTH EUROP. MALAC. CONGR. 



the genital pore. The cells lining the tract are cuboidal to columnar in shape and contain a basal 
nucleus with dense aggregations of chromatin in a granular matrix (Fig. 1). Within their 
cytoplasm numerous free ribosomes, clear vesicles and multivesicular bodies are present. From 
the luminal surface project microvilli and most cells possess 1 or 2 cilia, indicative of primary 
ciliogenesis. After about 7 days the majority of cells have developed accumulations of granules 
resembling glycogen. The closed end of the duct differentiates into the gonad. This is first seen 
as a slight swelling at the tip, and in some animals this is the state of the gonad at hatching. 
The swelling forms a terminal acinus. In other animals one or two tubular outgrowths close to 
the terminal acinus are also present at this time and acini develop at their tips. 

Histologically it can be seen that the early acini are lined by an epithelium continuous with 
that in the remainder of the duct (Fig. 2). It is proposed to term the cells of the lining 
epithelium in the gonad region gonadal stem cells (G.S.C.) as they appear to differentiate into 
all of the cell types found in the mature gonad. Within the developing acinus proliferation of 



]ШШ^ 




FIG. 1. Transverse section of hermaphrodite ductule from animal at hatching (osmium/glutaraldehyde 
fixation, lead citrate-uranyl acetate staining), L-lumen with sections of cilia, G— gonadal stem cells. 



RUNHAM AND HOGG 



393 



В 




.vT.. I ._:^~ , ■ ■ I . f Y i I ■ . I *- 



.Gonadal stem eel 



шиэирии 





Spermatogonium 

^^ Germinal epithelium 



щтшЁШШшш 




Oocyte 



Sertoli cell 



FIG. 2. Diagrams illustrating the early development of the acinus A. Closed end °fj"^^ "'%^^^ \ fhfst^ 
only been Ln in the regenerating gonad. B. Tip of ductule swollen ^'*^ P^° f ^ "^ ^^'J^^,- T^^^Vn and ?he 
of acinus development found at hatching. С Further prol.ferat.on oL.«;« J''''"9 j ^з"^ wiTh develop ng 
appearance of cells beneath the epithelium. D. Spermatocyte stage acmus. The '"^en s f.Med with developing 
sperm and under the continuous layer of Sertoli cells are developing oocytes and tomcie cens. 



394 



PROC. SIXTH EUROP. MALAC. CONGR. 



cells from the G.S.C. layer leads to an accumulation of cells in the lunnen (Fig. 2 and 4). These 
cells are irregular in outline with low numbers of ribosomes and a clear nucleus (Fig. 3). Similar 
cells appear beneath the G.S.C, layer and are accompanied by a few very small cells. The G.S.C. 
persist in the ductules and as an epithelial layer around the neck of the acinus termed the 
germinal epithelium, but the remaining G.S.C's lining the majority of the acinus differentiate 
into Sertoli cells. The cells filling the lumen of the gland differentiate into spermatogonia while 
those between the Sertoli cell layer and basement membrane evolve into oocytes and follicle 
cells. 

Further development of the gonad 

In a previous study it was shown that the relative proportion and arrangement of gametes 
varies throughout the life of the animal (Runham & Laryea, 1968). The development of the 




FIG.3. Section of wall of acinus from newly hatched animal (osmium/glutaraldehyde fixation, lead 
citrate-uranyl acetate staining). G— gonadal stem cells. S— cells in lumen of acinus which will differentiate into 
sperm. 



RUNHAM AND HOGG 



395 




FIG. 4. Longitudinal section of acinus from animal at hatching (osmium/glutaraldehyde fixation, 1 дт 
section stained toluidine blue). G— gonadal stem cells, S— cells in lumen of acinus which will differentiate into 
sperm. 



gonad was therefore subdivided into 8 stages: (a) undifferentiated, (b) spermatocyte, (c) 
spermatid, (d) early spermatozoon, (g) late spermatozoon, (f) early oocyte, (g) late oocyte, and 
(h) post reproductive. During (a) it now appears that processes leading to proliferation of acini 
predominate leading to formation of between 70 and 180 acini of the typical gonad structure. 
Enlargement of the acini continues during (b) to (e) stages largely because of the predominance 
of spermatogenesis. By the (f) stage the acinus starts to empty of sperm and many mature 
oocytes are present. 

From examination of random sections of the gonad it is difficult to understand how cells are 
arranged within the acinus, so scale models of acini were constructed (Fig. 5). From these it 
was evident that the smallest oocytes were located close to the edge of the germinal epithelium 
(the germinal ring) and that oocyte size increased with distance from the epithelium. The 
largest oocytes were therefore always located at the base of the acinus opposite the ductule 
opening. When degenerating oocytes were present they were situated between the large oocytes. 

Gamete maturation 



Oogenesis appears to continue throughout the life of the animal, but mature oocytes first 
appear towards the end of the late spermatozoon stage and are present in large numbers 
throughout the oocyte stages. A study of oogenesis and vitellogenesis has been completed and 
will be published elsewhere, but in outline they are very similar to the processes described for 
Biomphalaria glabrata (De Jong-Brink et al., 1976). Spermatogenesis is also very similar to that 
reported in other pulmonates (e.g.. De Jong-Brink et al., 1977). 



396 



PROC. SIXTH EUROP. MALAC. CONGR. 




FIG. 5. Reconstruction of two acini from an early spermatozoan stage gonad, a. Top of the acini, b. Bottom 
of the acini. E— germinal epithelium around entry of the hermaphrodite duct. O— oocytes. 



RUNHAM AND HOGG 
Regeneration of the gonad 



397 



While studying the effects of castration on the development of the reproductive tract 
(Runham, 1976 and unpublished) it was found that very rapid regeneration of the gonad 
occurred during the undifferentiated and spermatocyte stages, but was slow during the 
spermatid stage and largely absent from all older animals. In some spermatozoon stage animals 
1 or 2 minute acini had formed after 5 months. 

A short time after castration muscular contraction in the wall resulted in sealing of the 
hermaphrodite duct. Proliferation of connective tissue elements led to the formation of a mass 
of tissue around the wound. Subsequently, the duct cells dedifferentiated. Outgrowths of the 
duct into the surrounding mass of connective tissue were at first tubular and then acini 
developed at their tips. The sequence of differentiation within these regenerated acini closely 
mirrored the development of normal acini during the undifferentiated stage (Fig. 6). The reason 
for the lack of regeneration in the older animals is as yet unknown, but it may be significant 
that during the early spermatozoon stage the lining epithelium normally differentiates; the cells 
becoming either ciliated or non-ciliated cells. 




FIG. 6. Longitudinal section of regenerated acinus (osmium/glutaraldehyde fixation, ^ цт section stained 
toluidine blue). G— gonadal stem cells, S— cells in lumen which will differentiate into sperm. 



398 PROC. SIXTH EUROP. MALAC. CONGR. 

DISCUSSION 

The embryological origins of the gonad and reproductive tract in pulmonates has proved very 
difficult to study (Martoja, 1964). Much misinterpretation may be due to poor fixation 
resulting in difficulties in differentiating it from the accompanying blood vessels and nerves. 

Our observations indicate that the reproductive system has a single origin and as the simple 
tube is continuous with the skin of the animal we presume it is ectodermal in origin. The gonad 
originates from the closed end of this tube and apparently only the cells of the lining 
epithelium participate in the formation of the acinar contents. We are therefore essentially in 
agreement with Laviolette (1954) and Luchtel (1972a). 

Luchtel (1972a and b) denied the existence of a germinal epithelium in Arion circum- 
scriptus, A. ater rufus and Deroceras reticulatum. This study provides strong evidence for its 
existence in D. reticulatum: firstly, all the cells of the gonad including the germ cells derive 
from the G.S.C. which forms the germinal epithelium in the fully formed acinus; secondly, 
mapping of oocytes indicates a clear size gradient, the smallest being next to the epithelium and 
the largest furthest away from it; lastly, despite the absence of a pool of indeterminate germ 
cells regeneration of the gonad can occur from the severed hermaphrodite duct. 

As the cells lining the hermaphrodite duct are gonadal stem cells, it is not surprising that 
development of the regenerated gonad is so similar to the gonad's initial development. The 
stages of regeneration reported here are similar to the three stages described by Laviolette 
(1954); namely, (1), wound nodule formation; (2), digitation; (3), appearance of crypts (acini). 
Laviolette also reported that the germ cells arose from dedifferentiated epithelial cells. Our 
results are in accord with this view. The reduced ability to regenerate in older animals may be 
related to the state of differentiation of the hermaphrodite duct as reported above, or to the 
levels of reproductive hormones in the circulation. 

In their description of the gonad of Lymnaea stagnalis Joosse & Reitz (1969) state that 
there is active migration of gametes around the wall of the acinus from the germinal ring where 
they are first formed to the base of the acinus. While such a process may be necessary in 
Lymnaea with its very extended period of reproduction, particularly in the laboratory, it is not 
necessarily present in D. reticulatum. The enlargement of the acini through the spermatocyte 
to the spermatozoon stages is so great that this could account for the observed distribution in 
size of the oocytes, the largest oocytes arising when the acinus was small and remaining at the 
base of the acinus without any active movement. At the moment it is not possible to 
distinguish between these 2 possibilities. 

All recent work appears to indicate that the acinus is subdivided into 2 compartments; the 
developing sperm being located towards the centre, and the oocytes around the outside against 
the basement membrane. The 2 groups are separated by a layer of Sertoli and follicle cells. How 
the 2 gametes become distributed in this way is not yet clear, but it is possible that 
proliferation of the G.S.C. leads to delamination, the most basal layer forming the oocytes. 

The remarkable similarity between oogenesis in B. glabrata and D. reticulatum makes it 
likely that the processes involved are similar in other pulmonates. Hill & Bowen (1976) and Hill 
(1977) have reported their studies on the oocytes of D. reticulatum and the role of the 
accessory cells. They describe a process of extensive yolk sequestration by vacuolation and a 
Sertoli cell oocyte relationship involving thin cytoplasmic bridges and large intercellular spaces. 
We have never observed such features in well-fixed material. 

We are grateful to Miss Carole Roberts for making the reconstructions. 

LITERATURE CITED 

GOMOT, L., 1971, Nature endocrine des substances réglant la sexualisation de la gonade et son fonctionne- 
ment chez les mollusques gonochoriques et hermaphrodites. Haliotis, 1: 167-183. 

HILL, R. S., 1977, Studies on the ovotestis of the slug Agriolimax reticulatus. 2. The epithelia. Cell and 
Tissue Research, 183: 131-141. 

HILL, R. S. & BOWEN, I. D., 1976, Studies on the ovotestis of the slug Agriolimax reticulatus. 1. The 
oocyte. Cell and Tissue Research, 173: 465-482. 

HIRSCH, J. G. & FEDORKO, M. E., 1968, Ultrastructure of human leukocytes after simultaneous fixation 
with glutaraldehyde and osmium tetroxide and "postfixation" in uranyl acetate. Journal of Cell Biology, 
38: 615-627. 



RUNHAM AND HOGG 399 

DE JONG-BRINK, M., DE WIT, A., KRAAL, G. & BOER, H. H., 1976, A light and electron microscope 

study on oogenesis in the fresh water pulmonate snail Biomphalaria glabrata. Cell and Tissue Research, 

171: 195-219. 
DE JONG-BRINK, M., BOER, H. H., HAMMES, T. G., & KODDE, A., 1977, Spermatogenesis and the role 

of Sertoli cells in the freshwater snail Biomphalaria glabrata. Cell and Tissue Research, 181: 37-58. 
JOOSSE, J. & REITZ, D., 1969, Functional anatomical aspects of the ovotestis of Lymnaea stagnalis. 

Malacologia, 9: 101-109, 
LAVIOLETTE, P., 1954, Etude cytologique et expérimentale de la régénération germinale après castration 

chez Arion rufus (Gastéropode Pulmoné). Annales des Sciences Naturelles, Zoologie, (11)16: 427-530. 
LUCHTEL, D., 1972a, Gonadal development and sex determination in pulmonate molluscs. I, Arion 

circumscriptus. Zeitschrift für Zellforschung, 130: 279-301. 
LUCHTEL, D., 1972b, Gonadal development and sex determination in pulmonate molluscs. 2. Arion ater 

rufus and Deroceras reticulatum. Zeitschrift für Zellforschung, 130: 302-311. 
MARTOJA, M., 1964, Développement de l'appareil reproducteur chez les gastéropodes pulmones. Année 

Biologique, (4)3: 199-232. 
RUNHAM, N. W., 1976, The effects of castration on maturation of the reproductive tract of the pulmonate 

slug Agriolimax reticulatus. General and Comparative Endocrinology, 29: 293-294. 
RUNHAM, N. W. & LARYEA, A. A., 1968, Studies on the maturation of the reproductive system of 

Agriolimax reticulatus (Pulmonata: Limacidae). /Halacologia, 7: 93-108. 



MALACOLOGIA. 1979, 18: 401-406 

PROC. SIXTH EUROP. MALAC. CONGR. 

INFLUENCE DU JEÛNE ET DE LA RENUTRITION SUR L'OVIPOSITION 

ET LES GAMÉTOGENÈSES CHEZ LE PLANORBE BIOMPHALARIA 

GLABRATA (GASTÉROPODE PULMONÉ BASOMMATOPHORE) 

Marc Vianey-Liaud 

Laboratoire d' Ichthyologie et Parasitologie Générale, Université des Sciences et 
Techniques du Languedoc, Place Eugène-Bataillon, F -34060 Montpellier Cedex, France 

ABSTRACT 

In the planorbid Biomphalaria glabrata (Pulmonata, Basommatophora) starvation 
causes a progressive decrease in the number of egg masses and eggs produced by the 
animals; however, the average number of eggs per egg mass does not change. Ten to 12 
days starvation are necessary to stop oviposition completely. In the ovotestis starvation 
causes the terminal stages of spermatogenesis and ovogenesis to disappear. As soon as the 
animals are being fed again they start depositing progressively more egg masses and eggs. 
First oviposition after resumed feeding depends on the length of the period of starvation, 
i.e. occurs earlier after shorter periods of starvation. Male and female gametogenesis will 
again run their normal course and the process is completed simultaneously. 

INTRODUCTION 

Chez le Planorbe Biomphalaria glabrata, si la privation de nourriture dure suffisamment 
longtemps, I'oviposition est bloquée. S'ils sont ultérieurement renourris, les animaux peuvent à 
nouveau pondre et donc se reproduire. 

Le présent travail a pour but de: 

—suivre la diminution de la fécondité lorsque les animaux jeûnent; 
—suivre la restauration du pouvoir reproducteur après renutrition; 

—préciser les conséquences du jeûne puis de la renutrition sur les gamétogenèses mâle et 
femelle. 

MATÉRIEL ET TECHNIQUES 

J'ai utilisé des Biomphalaria glabrata de souche brésilienne, sexuellement mûrs. Les expéri- 
ences ont été organisées de la façon suivante: 

—Première expérience 

Première partie 

Soixante Planorbes féconds sont répartis en 6 groupes numérotés 1 à 6, de 10 individus 
chacun; chaque animal est élevé isolément dans 600 ml d'eau. Avant le début de l'expérience 
tous les individus sont nourris. 

Au temps de l'expérience, les animaux du groupe 1 sont soumis au jeûne, les autres 
continuant à recevoir de la nourriture. Au bout de 5 jours, les Planorbes du groupe 2 sont à 
leur tour privés de nourriture, ceux du groupe 1 le demeurant. Chaque 5 jours un nouveau 
groupe est soumis au jeûne. Cette première partie de l'expérience dure 25 jours. On dispose 
alors de 6 groupes numérotés 1, 2, 3, 4, 5 et 6 qui ont jeûné respectivement 25, 20, 15, 10, 5 
et jours. 

Durant cette première partie de l'expérience, la fécondité est enregistrée pour chaque animal 
tous les 5 jours. Pour caractériser la fécondité, 3 valeurs sont utilisées: (a) nombre moyen de 
pontes par animal; (b) nombre moyen d'oeufs par animal; (c) nombre moyen d'oeufs par ponte. 

(401) 



402 



PROC. SIXTH EUROP. MALAC. CONGR. 



Deuxième partie 

Au bout de 25 jours, les animaux des 6 groupes reçoivent tous de la nourriture. La 
fécondité est enregistrée, non plus chaque 5 jours mais journellement. 

Une 2ème expérience a été réalisée. Elle est comparable à celle qui vient d'être décrite mais 
chaque groupe est constitué par 10 Planorbes élevés dans un même bac et non plus isolés les 
uns des autres. 

Les résultats obtenus sont soumis à une analyse statistique. La méthode principalement 
utilisée est l'analyse de variance. A l'intérieur d'un ensemble de moyennes, la comparaison des 
moyennes 2 à 2 est réalisée selon les cas par la décomposition orthogonale partielle ou, le plus 
souvent, par le test de Tukey (1949). 



RESULTATS 

Dans la première expérience, on connaît la fécondité de chaque animal. Pour chaque période, 
la fécondité d'un groupe peut donc être exprimée par une moyenne et un écart-type, ce qui 
permet ultérieurement d'effectuer des tests statistiques. Ce sont donc essentiellement les 
résultats de cette expérience qui seront exposés. 

Première partie 

(1 ) On constate que 25 jours de jeûne n'entraînent aucune mortalité. 

(2) Dans chaque groupe, après l'instauration du jeûne, on assiste à une diminution 
progressive du nombre de pontes par animal et d'oeufs par animal. Si le jeûne a une durée 
suffisante (de 10 à 20 jours selon les groupes), la réduction de la fécondité peut aller jusqu' à un 
blocage total de l'oviposition, la fécondité étant alors nulle. 

(3) La diminution du nombre de pontes est significative dès le 5ème jour de jeûne. Quelle 
que soit la période considérée, entre et 5 jours mais aussi entre 5 et 10 jours de jeûne, on a 
des différences statistiquement significatives (Tableau 1). Au delà du lOème jour, les moyennes 
ne diffèrent plus. Ceci ne signifie pas que le jeûne est devenu sans effet sur la fécondité mais au 



TABLEAU 1. Comparaison, tous les 5 jours, des nombres moyens de pontes par animal. Le signe < indique 
une différence statistiquement significative, tandis que le signe = en indique l'absence. La virgule placée entre 
deux moyennes indique que la comparaison n'est pas autorisée. Pour chaque moyenne, le chiffre placé en 
indice correspond au numéro du groupe. Les moyennes situées dans une même bande diagonale corres- 
pondent à un jeûne de même durée, m: nombre moyen de pontes par animal pour une durée de 5 jours; 
Gr.: groupe. 





Gr.l 


Gr. 2 


Gr.3 


Gr. А 


Gr. 5 


Gr. 6 




à 5 


nn\< 


m2 


, тз , Шц 


ms 
^5 


416 




5 à 10 


mi\^< 


í Шз 


mi, 


mg 




10 à 15 


mK = 




ГОц , 


ms , 

1 

™5 


П16 


15 à 20 


m\^= 


m2 T шзЧ. < тц \< 


1 

1 


20 à 25 


m¡4 = 


ms ^< mg 

IN 


durée du 
jeûne 




^4 


2С^ 


\ 


1о\ 








VIANEY-LIAUD 



403 



TABLEAU 2. Comparaison, tous les 5 jours, des nombres moyens d'oeufs par animal. Mêmes explications 
que pour le Tableau 1, mais m: nombre moyen d'oeufs par animal pour une période de 5 jours. 



à 



5 à 10 



¿0 à 25 



Gr. 1 



Gr.2 



Gr.3 



Gr, 



Gr.5 Gr.6 



"M \ 7 ™2 " ™3 " ™U = "'s = ni6 



n\< m2\<| 



тз 



mi, 



mg 




Щ 



ni2\^| тз\^| mi, XI mj N^l 



durée du 
j eûne 



XI .XI з\1 



contraire que le nombre de pontes est très réduit voire nul et qu'il en est ainsi tant que les 
animaux sont privés de nourriture. D'ailleurs, au 25ème jour, si l'on compare les nombres 
totaux de pontes déposées depuis le début de l'expérience, on constate qu'entre et 25 jours, 5 
jours de jeûne entraînent des différences significatives. Cinq jours de jeûne provoquent une 
différence significative du nombre d'oeufs par animal sauf pour la période à 5 jours. Comme 
pour les pontes, l'action du jeûne continue à se faire sentir après 10 jours. La fécondité qui est 
IFortement réduite ou même nulle, le demeure tant que le jeûne ne cesse pas (Tableau 2). 

(4) Au terme de la première partie, les nombres totaux de pontes et d'oeufs de chaque 
groupe montrent une corrélation linéaire hautement significative avec la durée du jeûne: pour 
les pontes, on a r = 0,97 et pour les oeufs, on a r = 0,96 alors que dans les 2 cas on a Гд oi ^ 
0,92. Les animaux produisent d'autant moins de pontes et d'oeufs que le jeûne subi a été long 
(cf. Fig. 1). 

On obtient un résultat comparable avec les animaux groupés de la 2ème expérience. Les 
nombres totaux de pontes et d'oeufs sont supérieurs à ceux de l'expérience 1 car dans ce 
dernier cas, on a un léger effet inhibiteur de la fécondité dû à l'isolement (Vianey-Liaud, 1976). 

(5) Le jeûne entraîne une diminution du nombre de pontes et d'oeufs. Une analyse 
statistique révèle qu'en revanche le nombre moyen d'oeufs par ponte n'est pas affecté par la 
privation de nourriture. Au fur et à mesure que le jeûne se prolonge, le nombre d'oeufs par 
ponte correspond à des nombres de pontes et d'oeufs de plus en plus réduits, mais il n'est pas 
lui-même modifié. 

Deuxième partie 

(1) Après renutrition, on enregistre une mortalité non négligeable puisqu'elle atteint 32% des 
animaux en 25 jours. 

(2) La renutrition est suivie d'un retour à la situation d'origine. Les animaux qui avaient 
présenté une réduction du nombre de pontes et d'oeufs, voient ces nombres augmenter 
progressivement. Ils déposent de plus en plus de pontes et produisent de plus en plus d'oeufs. 
La fécondité du groupe 6 qui n'a jamais jeûné demeure sensiblement constante. 

(3) Si l'on procède aux même analyses statistiques que durant le jeûne, on constate que les 
différences alors mises en évidence se maintiennent au plus 20 jours; 25 jours après la 
renutrition, les effets du jeûne sur le dépôt des pontes et la production des oeufs ont disparu. 
Ces nombres ne redeviennent cependant pas semblables à ce qu'ils étaient au début de 
l'expérience. Ceci est la conséquence de l'isolement des animaux (Vianey-Liaud, 1976). 



404 



PROC. SIXTH EUROP. MALAC. CONGR. 



P.t.iO.t. 

i5000 



200 



150 



• oeufs • 
■ pontes ■ 




100 



FIG. 1. Fécondité totale des Planorbes de chaque groupe, h la fin de la première partie de l'expérience. Pour 
les oeufs et les pontes, est donnée l'équation de la droite de régression. J.: durée du jeûne, exprimée en jours; 
O.t.: nombre total d'oeufs produits; P. t.: nombre total de pontes déposées; г.: coefficient de corrélation 
linéaire. 




FIG. 2. Délai séparant la renutrition de la première oviposition, en fonction de la durée du jeûne préalable. 
Les chiffres inscrits dans un cercle correspondent au numéro du groupe. Les limites de l'intervalle de 
confiance sont calculées pour la probabilité P = 0,05. J: durée du jeûne, exprimée en jours; 1ère P.: délai 
séparant la renutrition du dépôt de la première ponte, exprimé en jours. 



D'ailleurs dans la 2ème expérience, la fécondité redevient très proche de ce qu'elle était avant le 
jeûne. 

(4) Le comptage journalier des pontes et des oeufs permet de savoir, pour chaque animal, 
combien de jours après la renutrition apparaît la première ponte. Ces résultats sont présentés 
dans la Fig. 2. 



VIANEY-LIAUD 405 

Les données numériques servent à effectuer une analyse de variance portant sur la régression. 
Il ressort de cette étude que la durée du jeûne préalable a un effet significatif sur le délai qui 
sépare la renutrition de la première ponte et qu'entre et 25 jours ces 2 durées sont 
proportionnelles. Cinq jours de jeûne préalable entraînent un retard compris statistiquement 
entre 2,1 et 4,3 jours. Plus le jeûne a été long, plus les animaux tardent à pondre après renutri- 
tion. 

J'ai effectué une étude histologique de l'ovotestis des Planorbes durant le jeûne et après 
renutrition. 

La gonade d'un animal qui a jeûné au moins 25 jours diffère sensiblement de celle d'un 
témoin. Elle renferme les stades initiaux des gamétogenèses mâle et femelle. Sont présents: les 
spermatogonies et les spermatocytes 1 en prophase de méiose ainsi que les ovocytes de 50 ßn\ 
de diamètre (taille maximum des ovocytes: 100 /zm) qui n'ont pas achevé leur vitellogenèse. Les 
stades plus évolués (spermatocytes 1 en métaphase et anaphase, spermatocytes 2, spermatides, 
ovocytes de plus de 50 /xm) manquent. Ceci crée l'aspect "vide" de l'ovotestis d'un Planorbe 
sous alimenté. Il arrive que soient présents des spermatozoïdes, d'ailleurs jamais très abondants; 
ils ont été formés avant le jeûne et n'ont pas encore été évacués. 

L'ovotestis d'un Planorbe qui jeûne est donc une gonade active dans laquelle Spermatogenese 
et ovogenèse n'aboutissent pas à la production de cellules sexuelles mûres. 

Après la renutrition, les stades manquants des gamétogenèses mâle et femelle apparaissent à 
nouveau tandis que des cellules sexuelles jeunes continuent d'être élaborées. Il n'y a pas de 
décalage dans la restauration de la Spermatogenese et de l'ovogenèse. En une dizaine de jours, les 2 
gamétogenèses sont intégralement représentées dans la gonade. 

DISCUSSION 

Chez Biomphalaria glabrata, Christie et al. (1974) par une étude biochimique et Jong-Brink 
(1973) par une étude histochimique et ultrastructurale, montrent que la privation de nourriture 
retentit profondément sur le fonctionnement des tractus génitaux. 

Le jeûne provoque une diminution du nombre de pontes et d'oeufs produits. Si sa durée est 
suffisante, l'oviposition est complètement bloquée. 

Les calculs statistiques que j'ai effectué témoignent bien de l'influence du jeûne, à la fois sur 
le nombre d'oeufs produits et sur la quantité de pontes déposées. Le jeûne agit à 2 niveaux: 

—sur l'ovotestis (qui produit les oeufs), 

—sur les tractus (qui produisent dans la ponte tout ce qui n'est pas le zygote). 

Ces 2 points d'impact de la privation de nourriture sont relativement indépendants l'un de 
l'autre. En effet: 

-l'action du jeûne sur les tractus génitaux (nombre de pontes) précède celle sur l'ovotestis 
(nombre d'oeufs). D'ailleurs, l'étude histologique de l'ovotestis au bout de 5 jours ne révèle pas 
de changement notoire alors que le nombre de pontes a déjà chuté significativement. 

-si le jeûne n'agissait que sur l'ovotestis, on pourrait obtenir des pontes stériles, sans oeuf 
(phénomène possible chez Biomphalaria), ce qui n'est jamais le cas dans les présentes 
expériences. 

-10 jours après renutrition, alors que la totalité des gamétogenèses est rétablie dans 
l'ovotestis, si le jeûne a été long (au moins 25 jours), les animaux ne déposent aucune ponte. La 
première oviposition survient au moins une semaine après la restauration des gamétogenèses. 

Ceci montre donc que le jeûne agit d'abord sur les tractus génitaux et plus tardivement sur 
l'ovotestis. A l'inverse, après renutrition, c'est sur l'ovotestis que les effets cessent en premier; 
ils persistent plus longtemps sur les tractus génitaux. 

L'ovotestis et les tractus génitaux fonctionnent donc de façon relativement indépendante. Le 
jeûne agit cependant sur les 2 organes, ce qui réduit ou même bloque totalement la 
reproduction. 



406 PROC. SIXTH EUROP. MALAC. CONGR. 

LITTERATURE CITÉE 

CHRISTIE, J. D., FOSTER, W. B. & STAUBER, L. A., 1974, The effect of parasitism and starvation on 
carbohydrate reserves of Biomphalaria glabrata. Journal of Invertebrate Pathology, 23: 55-62. 

JONG-BRINK, M. DE, 1973, The effects of desiccation and starvation upon the weight, histology and 
ultrastructure of the reproductive tract of Biomphalaria glabrata, internnediate host of Schistosoma 
mansoni. Zeitschrift für Zellforschung und Mikrokopische Anatomie, 136: 229-262. 

TUKEY, J. W., 1969, Comparing individual means in the analysis of variance. Biometrics, 5: 99-114. 

VIANEY-LIAUD, M.', 1976, Influence de l'isolement et de la taille sur la fécondité du Planorbe Australorbis 
glabratus (Gas'téro'pode Pulmoné). Bulletin Biologique de la France et de la Belgique, 1 10: 5-29. 



MALACOLOGIA, 1979, 18: 407-411 

PROC. SIXTH EUROP. MALAC. CONGR. 

THE CONTROL OF SEXUAL DIFFERENTIATION BY THE CEPHALIC 

COMPLEX IN THE SLUG ARION SUBFUSCUS DRAP. 

(GASTROPODA PULMONATA) 

Christian Wattez 

Laboratoire de Biologie Animale, Université des Sciences et Techniques de Lille I, 

B.P. n°36, 59650 Villeneuve-d'-Ascq, France, et Laboratoire Associé au C.N.R.S. n°148: 

"Endocrinologie comparée des Invertébrés" 

ABSTRACT 

The problem of determination of sexual differentiation in the slug Arion subfuscus 
has been approached through the organ culture method. Cultures concern young gonads 
obtained from animals 8-10 days old, i.e. at the earlier post-embryonic stage. A 
cytological study of these infantile gonads has been made at light and electron 
microscope levels. Three different cell types are distinguished: (a) at the periphery of the 
gonad, a cortical layer whose nuclei (3-4 jum diameter) are rich in chromatin, uniformly 
distributed in coarse masses. These are stock cells, (b) Some of these cortical nuclei 
show an increase in diameter (4-5 дт) and correlatively their chromatin scatters. They 
represent the protogonia. (c) Centrally positioned are cells (6-8 дт diameter) with a 
pale-staining nucleus in which chromatin is scarce and peripherally located. They have the 
characteristics of spermatogonia. Our results indicate: (1) When cultured in isolation, in 
an anhormonal medium, there is a tendency for an infantile gonad to progress towards 
the female line. (2) Cultures of gonadial material associated with autologous or 
heterologous cephalic complexes demonstrate the part of this complex in se