Pallial Oviduct Research Articles

Bisphenol A Induces Superfeminization in the Ramshorn Snail (Gastropoda: Prosobranchia) at Environmentally Relevant Concentrations

Previous investigations have shown that bisphenol A (BPA) induces a superfeminization syndrome in the freshwater snail Marisa cornuarietis at concentrations as low as 1 μg/L. Superfemales are characterized by the formation of additional female organs, enlarged accessory sex glands, gross malformations of the pallial oviduct, and a stimulation of egg and clutch production, resulting in increased female mortality. However, these studies were challenged on the basis of incomplete experimentation. Therefore, the objective of the current approach was to bridge several gaps in knowledge by conducting additional experiments. In an initial series of experiments, study results from the reproductive phase of the snails were evaluated in the sub-micrograms per liter range. Before and after the spawning season, superfemale responses were observed [NOEC (no observed effect concentration) 7.9 ng/L, EC10 (effective concentration at 10%) 13.9 ng/L], which were absent during the spawning season. A further experiment investigated the temperature dependence of BPA responses by exposing snails at two temperatures in parallel. The adverse effect of BPA was at least partially masked at 27°C (EC10 998 ng/L) when compared with 20°C (EC10 14.8 ng/L). In M. cornuarietis, BPA acts as an estrogen receptor (ER) agonist, because effects were completely antagonized by a co-exposure to tamoxifen and Faslodex. Antiandrogenic effects of BPA, such as a significant decrease in penis length at 20°C, were also observed. Competitive receptor displacement experiments indicate the presence of androgen- and estrogen-specific binding sites. The affinity for BPA of the estrogen binding sites in M. cornuarietis is higher than that of the ER in aquatic vertebrates. The results emphasize that prosobranchs are affected by BPA at lower concentrations than are other wildlife groups, and the findings also highlight the importance of exposure conditions.

Anatomy of an adaptive radiation: a unique reproductive strategy in the endemic freshwater gastropod Tylomelania (Cerithioidea: Pachychilidae) on Sulawesi, Indonesia and its biogeographical implications

The patterns of adaptive radiations in ancient lakes provide valuable clues to mechanisms of speciation and adaptation. In contrast to vertebrate radiations, for instance in fishes or finches, invertebrate species flocks have been largely neglected. While the increase in molecular data narrows this gap, the anatomical basis for interpreting these data against the background of evolutionary hypotheses is still widely lacking. Here we evaluate anatomical findings in the live-bearing pachychilid freshwater gastropod Tylomelania, which has radiated extensively in ancient lakes in the Indonesian island, Sulawesi; we have aimed at reconciling these data with recently obtained molecular phylogenetic evidence. Discovered more than a century ago, the speciose and phenotypically diverse species flock with 34 currently described taxa was only occasionally cited as an example of adaptive radiation in ancient lakes, while anatomical data were entirely lacking. Our study of anatomical characters reveals very low qualitative variation at the species level. Thus, contrary to earlier views we suggest the existence of a single monophyletic lineage endemic to this island. The most conspicuous feature of Tylomelania is its uterine brooding strategy, i.e. retaining eggs and embryos in the pallial oviduct. This is unique among South-East Asian pachychilids. Within the uterine brood pouch the offspring is surrounded by considerable amounts of nutritive material produced by a very large albumin gland, and the embryos are produced continuously. The shelled juveniles of some species are the largest known so far in viviparous gastropods, measuring almost 2 cm in length when hatching. This combination of reproductive features in Tylomelania, characterized by a high amount of maternal investment, is considered to be ovoviviparous, rendering its brooding strategy unique also among other gastropods. In addition, our data reject a previously assumed close relationship to other South-East Asian pachychilids and instead suggest the North Australian Pseudopotamis as sister group to Tylomelania. These findings have significant consequences for the phylogenetic interpretation of morphological characters of Tylomelania in an evolutionary and biogeographical context, leading to the hypothesis that the common ancestor of both genera originated somewhere on the northern Australian continental margin. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society, 2005, 85, 513–542.

An updated scheme of imposex for Cantharus cecillei (Gastropoda: Buccinidae) and a new mechanism leading to the sterilization of imposex-affected females

The morphological expressions of imposex in gastropods have been classified into seven stages (S0–S6) with three types (a, b and c). This typical imposex scheme, however, fails to cover some new findings such as specimens with the proximal vas deferens section passing by the vaginal opening (VDSP) and aborted egg capsules. In the present study, Cantharus cecillei was sampled from the coastal waters of China from May to November in 2003. This species showed all the morphological expressions in the typical imposex scheme with the exception of S1b and S2b. In addition, specimens with VDSP occurred in all stages other than stage 4, and were documented for the first time with scanning electron micrographs or in histological sections. Besides VDSP, which was observed exteriorly, excrescent tissue, e.g. the vas deferens, also originated in the ventral channel or the inner wall of the pallial oviduct was extruded. Based on these new findings, the typical imposex scheme was modified to obtain one valid for C. cecillei. Types a*, b* and c* were added as new types corresponding to types a, b and c, respectively. S4* was also rearranged to correspond to S4; S4*, thus, no longer represented the end of imposex development. The updated scheme was not only valid for describing diverse expressions of imposex development in C. cecillei and Nassarius reticulatus, but could also be generalized to define various forms of VDSP in other species. Histological observation indicated that egg capsules would be blocked by the tissues of the vas deferens section or the extrusion of the pallial oviduct wall. This new mechanism, leading to the sterilization of imposex-affected females, was first conclusively revealed and described in the present scheme.

Observations of the reproduction and population structure of the caenogastropod, Gabbia vertiginosa Frauenfeld, 1862 (Rissooidea : Bithyniidae)

Aspects of the reproduction and population structure of Gabbia vertiginosa (Bithyniidae) in the New England Tablelands, New South Wales, Australia, are described. The pattern of embryo growth from encapsulation in the pallial oviduct, deposition of fully formed embryonic snails in the habitat, to sexual maturity in the adult snail are examined. A three-year population study has shown the reproductive period of G. vertiginosa to commence in December and end in June/July with the possibility of three reproductive events per season.Additional keywords: Bithynia, embryo.

Reproductive cycle and size at sexual maturity of the commercial whelk Buccinum isaotakii in Funka Bay, Hokkaido, Japan

The reproductive cycle and size at sexual maturity of the commercial whelk Buccinum isaotakii in Funka Bay, southern Hokkaido, Japan, was examined using monthly samples of individuals collected from May 1999 until October 2000. Female and male sexual maturity was determined based on reproductive organ sizes and histological examination, and sex ratios did not differ from parity. There were parallel annual cycles in the size of the ovary and pallial oviduct, and an inverse cycle for the digestive gland. The testis and seminal vesicle showed inverse cycles. The peak in seminal vesicle size was at the same time as the peak in ovary and pallial oviduct. The size of the male digestive gland exhibited no evident cycle. Males were mature from May to October 1999 and from April to October 2000, and spent individuals first appeared in September 1999 and then decreased in numbers until June 2000. Sperm content and epithelium in seminal vesicle indicated that the copulating period started in March and lasted until August 2000. Ovarian maturation and oogenesis occurred from October 1999 onwards and peaked in January 2000, with egg laying occurring from May until September. An increase in temperature coincided with the advancement of spermatogenesis and the egg laying while the transfer of the sperm from the testis to the seminal vesicle in males and the maturation of ovaries in females coincided with a decrease in temperature.

REVISION OF THE GENUS BENTHOBIA (CAENOGASTROPODA, PSEUDOLIVIDAE)

A revision of the genus Benthobia Dall, 1889, which inhabits deep waters worldwide, is provided. In addition to B. tryonii, which inhabits the North Atlantic, four new species are described: B. atafona, from southeast Brazil; B. complexirhina from the Tasman Basin, Australia; B. tornatilis, from the Coral Sea, Australia and B. sima, from Madagascar. Species separations are based on conchological and anatomical features. An anatomical diagnosis for the genus is provided, leading to a discussion of the systematics of the family. Distinguishing anatomical characters for the genus include: eyes lacking; posterior furrow in foot sole; horseshoe-shaped attachment to operculum; single, massive, muscular and hollow accessory salivary gland with narrow duct; salivary gland separated into two parts; closed pallial sperm duct; penis with closed penial duct and broad, sub-terminal, dome-shaped papilla; pallial oviduct generally with a posterior seminal receptacle, and terminal, muscular bursa copulatrix positioned between vestibule and pore, partly attached to pallial floor. Most of the remaining features are typical of muricoideans. A discussion on the possible validity of Nux alabaster, from the Atlantic coast of South Africa, is provided; based on conchological, opercular and radular characters, it is concluded that it is closely related to Benthobia.

A NEW SPRING SNAIL OF THE GENUS GRAZIANA (CAENOGASTROPODA: HYDROBIIDAE) FROM SWITZERLAND

This paper describes a new species of hydrobiid spring snail, Graziana quadrifoglio, occurring in southern Switzerland and probably also in northern Italy. Populations of this species have been known since the middle of the twentieth century, but they were not recognized as belonging to a separate species. The description of the new species is based on detailed morphological and anatomical investigations, including electron microscopy and computer-aided reconstructions of histological serial sections. The presence of a single, distal seminal receptacle, the course of the bursal duct running between albumen gland and bursa copulatrix, the histology of the pallial oviduct, the shape of the penial lobe, together with the presence of the shield caecum arising from the posterior chamber of the stomach, characterize the new species as a member of Graziana Radoman, 1975. The wide, ovateconical shell shape, the penial lobe pointing anteriorly and the complex coiling of the renal oviduct differentiate G. quadrifoglio from its congeners.

Effects of endocrine disruptors on prosobranch snails (Mollusca: Gastropoda) in the laboratory. Part I: Bisphenol A and octylphenol as xeno-estrogens.

The effects of suspected endocrine disrupting chemicals on freshwater and marine prosobranch species were analysed in laboratory experiments. In this first publication, the responses of the freshwater snail Marisa cornuarietis and of the marine prosobranch Nucella lapillus to the xeno-estrogenic model compounds bisphenol A (BPA) and octylphenol (OP) are presented at nominal concentration ranges between 1 and 100 micrograms/L. Marisa was exposed during 5 months using adult specimens and in a complete life-cycle test for 12 months. In both experiments, the xeno-estrogens induced a complex syndrome of alterations in female Marisa referred to as "superfemales" at the lowest concentrations. Affected specimens were characterised by the formation of additional female organs, an enlargement of the accessory pallial sex glands, gross malformations of the pallial oviduct section resulting in an increased female mortality, and a massive stimulation of oocyte and spawning mass production. The effects of BPA and OP were comparable at the same nominal concentrations. An exposure to OP resulted in inverted U-type concentration response relationships for egg and spawning mass production. Adult Nucella from the field were tested for three months in the laboratory. As in Marisa, superfemales with enlarged accessory pallial sex glands and an enhancement of oocyte production were observed. No oviduct malformations were found probably due to species differences in the gross anatomical structure of the pallial oviduct. A lower percentage of exposed specimens had ripe sperm stored in their vesicula seminalis and additionally male Nucella exhibited a reduced length of penis and prostate gland when compared to the control. Because statistically significant effects were observed at the lowest nominal test concentrations (1 microgram BPA or OP/L), it can be assumed that even lower concentrations may have a negative impact on the snails. The results show that prosobranchs are sensitive to endocrine disruption at environmentally relevant concentrations and that especially M. cornuarietis is a promising candidate for a future organismic invertebrate model to identify endocrine-mimetic test compounds.

Variation and Abnormality of Genital System in Littorina sitkana Philippi (Mollusca, Gastropoda) in Northern Japan

Abstract The anatomy of Littorina sitkana was examined using specimens from nine localities in northern Japan. These localities are known to be genetically clustered into two geographic groups; the first group consists of localities on the northern coast of Hokkaido along the Seas of Japan and Okhotsk and the second one comprises localities on the Pacific coasts of Hokkaido and Honshu. Anatomical surveys revealed that the mean numbers of penial glands differ significantly between the northern and Pacific sites, in correlation with the genetic variation. On the other hand, the mean relative size of the capsule gland within the pallial oviduct was positively correlated with mean sea-surface temperature, almost independently of the genetic difference. In addition, imposex was found for the first time in L. sitkana. Females frequently lacked the capsule gland in the imposex-present populations. The mean relative size of capsule gland to the whole pallial oviduct was significantly smaller there than in the imp...

Morphological study on Littorina Flava (King & Broderip) from Brazil (Caenogastropoda, Littorinidae)

A detailed morphological study of the littorinid Littorina flava (King & Broderip), from Venezuelan and Brazilian coasts, is given and commented. a considerable degree of shell characters variation was found, mainly in color and sculpture. The pallial cavity presents normal fashion of mesogastropods, without any detectable morphological modification for the long air-exposure. The digestive system present odontophore muscles very similar to those of the cerithioideans and hydrobioideans; the radula, however, is enormously long; the stomach lacks differentiate style sac. The penis is characteristic in lacking annex glands. The pallial oviduct has no jelly gland, and has a well developed bursa copulatrix and vaginal tube.

TBT effects on the female genital system of Littorina littorea: a possible indicator of tributyltin pollution

Specimens of the prosobranch Littorina littorea (L., 1758) collected along the East Frisian North Sea coast in summer 1993 exhibited alterations of the pallial oviduct termed as intersex in response to tributyltin (TBT) pollution. The range of TBT body burden was between 150.9 and 1289.5 µg as Sn kg−1 (dry wt.). Five stages of intersex development (0–4) could be distinguished and are documented with scanning electron micrographs. In stages 2–4, which can be found in the direct vicinity of harbours and marinas, the morphological malformations of the oviduct inhibit successful copulation and capsule formation, resulting in sterilization. The intersex index (ISI, calculated as the average intersex stage of a population) and the average prostate length of females were used as parameters for the determination of intersex intensities in the populations. Both indices show significant and positive correlations to the TBT body burden of L. littorea and are promising parameters for TBT biomonitoring. A comparison of TBT bioconcentration factors with populations from England and France indicates that the threshold concentration for intersex development is in the range of 15 ng TBT as Sn/l. Morphometric analyses of the midgut gland revealed no significant differences between sampling stations. In the ovary a retardation and blockage of maturation (atresia) was observed in populations close to harbours. Lytic processes in ovary follicles were observed not only at TBT exposed sites but also at reference stations.

The rough tingleOcenebra erinacea (Neogastropoda: muricidae): An exhibitor of imposex in comparison toNucella lapillus

The muricid gastropodOcenebra erinacea exhibits imposex (occurrence of male parts in addition to the female genital duct), a phenomenon which is caused by tributyltin (TBT)-compounds leached from ships’ antifouling paints. Five stages of imposex development (1–5) with two different types at stage 1 can be distinguished and are documented with SEM-photographs for the first time. Four additional alterations of the genital tract are shown. Close to harbours and marinas,O. erinacea females exhibit malformations of the pallial oviduct, which seem to inhibit copulation and capsule formation resulting in sterilization. The TBT accumulation in the whole body and the accumulation pattern in single tissues are described; contrary to other prosobranchs no sexrelated differences were found. The VDS, uncubed RPS and average female penis length of a population were analysed regarding their quality as parameters for TBT biomonitoring. On the background of the ecology of this species the VDS is chosen as the best index. Only in highly polluted areas should the uncubed RPS be used as a secondary parameter. A statistical study, based on the analysis of natural populations ofNucella lapillus andO. erinacea, allows a comparison of the specific TBT sensitivity of the two bioindicators. Dogwhelks exhibit a greater TBT sensitivity, namely at slightly polluted sites, nevertheless even here rough tingles develop obvious imposex characteristics.

Sex Change in the Female Dog-Whelk,Nucella Lapillus, Induced by Tributyltin from Antifouling Paints

Imposex, the development of a penis and vas deferens in the female (Smith, 1971) is known to occur in over 30 species of marine gastropods but, to date, in only one species has this syndrome been demonstrated to have a serious deleterious effect. This species is the dog-whelk,Nucella lapillusL. Both field and laboratory observations have provided conclusive evidence that imposex inN. lapillusis initiated by tributyltin (TBT), used as a biocide in antifouling paints, at concentrations in water of less than 1 ng Sn/1. This feature is manifest in the widespread occurrence of imposex even in areas far removed from centres of boating activity (see Bryanet al.1986). Imposex appears to have little effect on the reproductive biology ofN. lapillusuntil this syndrome is developed to its fullest extent when it sterilises the female because the pallial oviduct becomes occluded by vas deferens tissue thus preventing expulsion of the egg capsules (Gibbs & Bryan, 1986). Laboratory experiments have indicated that this condition, found in females close to harbours and marinas, may prevail after prolonged exposure during the first few years of life to TBT levels as low as 2 ng Sn/1 (Gibbset al.1987). Of six organotin compounds tested by Bryan, Gibbs & Burt (1988), tributyltin chloride proved the most effective in promoting imposex inN. lapillus.

Anatomy of Afropomus balanoideus (Mollusca, Gastropoda, Ampullariidae) and its implications for phylogeny and ecology

The hitherto unknown anatomy of Afropomus balanoideus is described. Its systematic position within the Ampullariidae is indicated by the possession of the following autapomorphic characters of the Ampullariidae: presence of a lung sac, an ampulla-shaped aorta anterior, a bipartite copulatory organ of pallial origin, a left-sided zygoneur nervous system, a bipartite kidney, a lamellate osphradium, labial tentacles, an ingestion and an egestion sipho and a radula with strong teeth. The pallial vas deferens is completely closed, while the pallial oviduct is anatomically open in its distal part but functionally closed, because it is embedded in the surrounding mantle tissue. The copulatory organ is of pallial origin and innervated by the right pleural ganglion. The plesiomorphic states of some characters indicate that Afropomus balanoideus might represent the adelphotaxon of the remaining Ampullariidae. The morphological structures show that this species is adapted to an amphibious mode of life and to aestivation, as has been shown for other species of Ampullariidae.

The genera Bembicium and Risellopsis (Gastropoda: Littorinidae) in Australia and New Zealand

The taxonomy of the Australasian littorinid genera Bembicium and Risellopsis is revised. Five Recent species of Bembicium are recognised: auratum, nanum, melanostoma, vittatum and flavescens, the first four of which occur on the Australian mainland, the last on Norfolk and Lord Howe Islands. B. melanostoma, B. vittatum and B. flavescens are sibling species which have been synonymised as B. melanostoma in recent systematic accounts, and are shown to be allopatric and distinguished mainly by characters of the penis. At least three fossil species of Bembicium are known, of which one is described as new, and the fossil record extends back to the late Oligocene or early Miocene. The genus is endemic to Australasia and presently extinct in New Zealand and the Kermadec Islands. The genus Risellopsis is monotypic, represented only, by R. varia in New Zealand, and has no fossil record before the Pleistocene. Systematic descriptions of the shell and animal and details of habitat and distribution are given for each species. These genera are abundant in the intertidal zone and the rather large literature on their biology and ecology is reviewed. Relationships with other littorinacean taxa are discussed. It is suggested that Bembicium and Risellopsis together form a monophyletic group, defined by synapomorphies of anterior salivary glands, anterior position of the junction of the duct of the seminal receptacle with the pallial oviduct, longitudinal division of the jelly gland and trochoidal shell shape. The littorinid genus Peasiella is superficially similar in shell characters, but anatomical features show that it is not closely related to Bembicium and Risellopsis. Interesting features of Bembicium include the type of development (the hatching of planktotrophic veligers from benthic egg masses recorded in two species is rare in the family) and the extreme intraspecific variability in the form of the radular teeth.

New archaeogastropod limpets from hydrothermal vents; Superfamily Lepetodrilacea. II. Anatomy

The anatomy of nine species (two genera) of lepetodrilacean limpets is described and the mode of life deduced therefrom. The unique action of the odontophore sets them apart from all prosobranchs yet known: its initial ventral movement is all but suppressed and the dorsal movement, before withdrawal, exaggerated. This action is facilitated by the freedom of the odontophore from the restraining action of the snout which is controlled by special cephalic levator and retractor muscles. Evidence indicates that the jaws are used as scrubbers, loosening particles from the substratum over the animal’s head which are then collected by the specialized rhipidoglossate radula. This is the only method of feeding in the more primitive of the two genera, Gorgoleptis , in which the possession of a metapodium with an operculum indicates that the transformation to the limpet form is incomplete. All members of the superfamily have a single left gill typically bilamellate and with a pectiniform skeleton. The dorsal (left) lamellae are reduced in number and size, particularly in Lepetodrilus (lost in Lepetodrilus ovalis ), and the ventral (right) ones exaggerated and their numbers increased with the enlargement of the mantle cavity. Although the ciliary bands on the lamellae of Lepetodrilus are as in other prosobranchs, at the tips of the lamellae the frontals and abfrontals expand to form pads and the laterals encircle the tips between them. This unusual modification relates to suspension feeding: the two methods of feeding may proceed concurrently. The nervous system has a high degree of fusion of the postcephalic ganglia. The pedal ganglia are large, their short commissure continuous with a pleural commissure, and the supra- and suboesophageal ganglia are contiguous with the right and left pleurals respectively. Nerves to the mantle and foot are compound. The epipodium is well developed, confined to the region of the foot in Gorgoleptis and with elongated tentacles, but spreading on to the head and forming a fold surrounding the base of each cephalic tentacle in Lepetodrilus , which has shorter tentacles round the foot; cilia on the right cephalic fold pass particulate matter from the mantle cavity to the mouth. The penis of Lepetodrilus is also of epipodial origin as opposed to its development from the left side of the snout in Gorgoleptis. In both genera a right pallial tentacle is associated with the exhalant passage from the mantle cavity, though this is greatly reduced in Lepetodrilus . The shell of Gorgoleptis species indicates that these limpets have followed a different evolutionary course from that of Lepetodrilus in that the columellar lip remains as an integral part of the peristome. In species of both genera the mantle edge has two folds, the inner probably represents the fusion of the inner and middle folds of zeugobranch limpets: the remoteness of the periostracal and shell secreting areas results in an inturned band of periostracum particularly broad in Lepetodrilus species. In each, the shell muscle is approximately bilaterally symmetrical, but details of its constituent parts, pedal and pallial, differ. In addition to the bilamellate gill and epipodium, the alimentary, circulatory, nervous and excretory systems indicate that relationships are at the archaeogastropod level. Although similar to the trochaceans, these limpets differ from them in a number of respects. The reproductive system approaches that of monotocardians in the length of the gonadial duct, which in the male is a vesicula seminalis; in the separation of that part of the right kidney through which gametes pass to the urinogenital opening; in the presence of a prostate and penis in the male, and in the female Lepetodrilus of a receptaculum seminis. The female has no hypertrophied pallial oviduct, and eggs with no secondary investments are apparently fertilized in the mantle cavity, and then shed. Although the anatomy of Neomphalus indicates that it had a different origin and evolution from the more conservative lepetodrilaceans, all these prosobranchs share a common characteristic in the attainment of the limpet form by having a narrow section between the enlarged head and the visceral mass marked by the end of the oesophageal pouches and tight chiastoneury.

Copper, Zinc, and Organotin as Long-Term Factors Governing the Distribution of Organisms in the Fal Estuary in Southwest England

Evidence of long-term metal pollution in the Fal Estuary is provided by analyses of Cu in oyster (Ostrea edulis) communities extending over more than 120 yr and by analyses of Cu and Zn in sediments dating back to 1921. Indications are that levels of Cu pollution from mining have declined very slowly but that Zn pollution has not. In Restronguet Creek, the most heavily polluted area, metal levels in waters and sediments are elevated by orders of magnitude. The invertebrate fauna of the creek is limited, but far richer than might be predicted from laboratory toxicity data. The cockleCerastoderma edule exemplifies organisms that are excluded from the creek owing to the toxicity of dissolved Cu, whereasOstrea edulis, by virtue of its innate tolerance to Cu and Zn, grown in the Iower reaches. On the other hand, the population of the ragwornNereis diversicolor, which penetrates into the most heavily polluted areas, is demonstrably far more tolerant of Cu and Zn than population from clean areas and appears to be a tolerant strain. To a considerable degree, therefore, the distribution of species is dependent not only on the innate ability of some species to tolerate Cu and Zn, but on the capacities of other populations to develop metal resistance and thereby maintain their original range of distribution. Present-day problems in the Fal Estuary appear to stem not only from mining wastes but also from the increased usage of tributyltins in antifouling paints. In the dogwhelkNucella lapillus, the incidence of imposex (the appearance of a penis and other male characters in females) is virtually 100% at sites along the English Channel coast of southwest England. The degree of imposex is related to the body concentration of hexane-extractable organotin, which includes both tributyltin and dibutyltin fractions. The highest degree of imposex, where the female penis approaches that of the male in size, occurs in the Fal Estuary; also, in some males the penis becomes deformed. Populations of dogwhelks have declined dramatically in this estuary, and are also characterised by the presence of relatively fewer females and by the absence of juveniles and egg capsules. Reproductive failure in females is now known to be caused by blockage of the pallial oviduct during the development of imposex.

Reproductive Failure in Populations of the Dog-Whelk, Nucella Lapillus, Caused by Imposex Induced by Tributyltin from Antifouling Paints

The development of male characters, notably a penis and a vas deferens, on the female (the phenomenon of ‘imposex’) of the dog-whelk, Nucella lapillus, is described. Three stages are recognized: an ‘early’ stage involving the formation of a vas deferens and a small penis, an ‘intermediate’ stage characterized by the enlargement of the female penis to a size approaching that of the male and a ‘late’ stage during which the female opening (vulva) is occluded by overgrowth of vas deferens tissue. This blockage of the pallial oviduct prevents the release of egg capsules and renders the female sterile. The extent and cause of such reproductive failure is evident from the high incidence of females containing aborted capsules in declining populations close to sources of tributyltin (TBT) contamination. These same populations comprise fewer females than expected and it would appear that the accumulation of aborted capsules within the pallial oviduct eventually causes the premature death of the female.

Reproductive cycle and seasonal feeding activity of the neogastropod Buccinum undatum

The whelk Buccinum undatum L. in the northern Gulf of St. Lawrence has a distinct annual reproductive cycle. The ovary and pallial oviduct of the female, and the seminal vesicle of the male, show parallel development, whereas the testis has an inverse cycle. Thus, at the end of winter when the ovary, pallial oviduct and seminal vesicle reach maximal size, the testis is small and undeveloped, whereas the reverse situation occurs in summer. This is the first report of a totally inverse relationship between the ovary and testis for a marine invertebrate. This unusual pattern is due to the long-term storage of sperm in the seminal vesicle of the male prior to copulation. There is no resting period at the end of oogenesis, but rather renewed ovarian development starts shortly after gamete release. By contrast, in the testis after transfer of sperm to the seminal vesicle at the end of spermatogenesis, there is a distinct period of phagocytosis. Mating begins in mid-May, reaches a peak during June and terminates prior to July. Egg laying begins in late May, reaches a peak in mid-June to mid-July and can continue until late August. Examination of the incidence of individuals with food in their stomachs showed that feeding activity is maximal in late autumn through to early spring and decreases sharply coincident with the onset of breeding in late May.

An Anatomical Description of Eulima bilineata Alder with Remarks on and a Revision of Pyramidelloides Nevill (Mollusca, Prosobranchia, Eulimidae)

The anatomy and biology of Eulima bilineata Alder is described and compared with PyramidelIoides miranda (A. Adams) and P. angusta (Hedley). All the species are parasitic on ophiuroids, have a ptenoglossate radula, an acrembolic proboscis with a pair of salivary glands close to the buccal mass and a reduced stomach with two histologically different digestive glands. The males have a well developed penis, the female a partly open or closed pallial oviduct. The central nervous system is concentrated. The sub‐ and supraoesophageal ganglia are completely integrated in the nerve ring. In Eulima, the supraoesophageal ganglion is split into two parts. Few differences were found between the species investigated, and it is concluded that Pyramidelloides should be classified in Eilimidae, not in Rissoidae where it has been placed previously.