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

Summary 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.     

Revision of the Genera Thyca, Stilifer, Scalenostoma, Mucronalia and Echineulima (Mollusca, Prosobranchia, Eulimidae)

All species that have been described of the genera mentioned in the title are listed and their systematic position given. The species of Stilifer (with 11 species, including S. inflatus sp.n. and 5. concavus sp.n.) are parasites of starfishes. Scalenostoma (3 species) are parasites of stone corals. Thyca (with 8 species) is removed from Capulidae, and included in Eulimidae. T. hawaiiensis sp.n. is described. The species of Thyca are parasites of starfishes. The species of Mucronalia (including M. trilineata sp.n.) are probably parasites of ophiuroids and Echineulima (with 4–6 species, including E. ponderi sp.n.) are parasites of echinoids. All species are figured, their characteristics are given and their host species and distributions are listed. Keys are given to the species of each genus, except Mucronalia. The genera Stilimella Laseron and Hyperlia Pilsbry are synonymized with Scalenostoma and the genera Kiramodulus Kuroda, Granulithyca Habe and Bessomia Berry are considered subgenera of Thyca.     

Anatomy and affinities of pseudococculinid limpets (Mollusca, Archaeogastropoda)

The anatomy of 12 pseudococculinid species, representing the two subfamilies and 10 (of 11 known) genera, is described in detail. Three new genera are erected, Yaquinabyssia, Copulabyssia and Amphiplica. Subfamilial and generic systematics are reconsidered and additionally based on anatomical characters. Characters defining subfamilies and genera (Pseudoeoeculininae: Pseudococculina, Notocrater, Tentaoculus, Mcsopelex, Bandabyssia, Kurilabyssia; Caymanabyssiinae: Caymanabyssia, Colotrachelus, Yuquinabyssia, Copulabyssia, Amphiplica) are the modifications in shell and radula, the number and arrangement of gill-leaflets, the size of the pedal gland, the degree of eye-reduction and the modifications of the seminal groove and of the copulatory organ. Separation of the Pseudococculinidae Hiekman, 1983 from the Cocculinidae Dall, 1882 at the superfamilial level is confirmed by great differences in their anatomy. Whereas the Cocculinidae are closely related to the Bathysciadiidae (Cocculinoidea). the Lepctcllidae, Pyropeltidae, Pseudococculinidae,? Bathyphytophilidae, Osteopeltidae, Cocculinellidae, Addisoniidae and Choristellidae form a clearly separated supcrfamily (Lepetelloidea). Both superfamilies compose the Cocculiniformia. a primitive but highly specialized arehaeogastropod suborder.     

Anatomy and affinities of cocculinid limpets (Mollusca, Archaeogastropoda)

The anatomy of seven cocculinid species, representing four genera, is described. Two new genera are erected, Paracocculina and Coccocrater, and a comparative account of all cocculinid species so far anatomically investigated is given. Definitions of six genera, mainly based on anatomical data, are presented. Variation at the species level is also discussed. The closest relatives of the Cocculinidae are found in the Bathysciadiidae, sharing a distinct gill type and similar coelomic conditions. Therefore, both families are united as the Cocculinoidea. The Lepetelloidea (Lepetellidae, Pseudococculinidae, Osteopeltidae, Bathyphytophilidae (?), Cocculinellidae, Addisoniidae and Choristellidae) are more distantly related and are classified, together with the Cocculinoidea, within the suborder Cocculiniformia. The Cocculiniformia are regarded as one of the earliest offshoots at the archaeogastropod level of organization, being secondarily modified in several respects.     

On the Anatomy and Systematic Position of the Mathildidae (Mollusca, Allogastropoda)

The anatomy of two mathildid species, Opimilda maoria Powell, 1940 and Gegania valkyrie Powell, 1971 has been investigated using serial sections. The mathildid anatomy strongly resembles that of the Architectonicidae, and therefore both families are included in the superfamily Architectonicoidea. The buccal system of Gegania valkyrie is the most primitive of all Allogastropoda (Architectonicoidea and Pyramidelloidea) so far investigated. Reproductive features within with Architectonicoidea vary. Certain species ( Gegania valkyrie ) are hermaphrodites, whilst others ( Opimilda maoria ) appear to be gonochorists; in these species males also possess a (sperm-filled) receptaculum seminis. Similar genital and reproductive features are found in the prosobranch relict species Campanile symbolicum Iredale, 1917, the systematic position of which is discussed briefly.     

Molecular systematics of the marine gastropod families Trochidae and Calliostomatidae (Mollusca: Superfamily Trochoidea)

This study is the most extensive molecular study of the gastropod families Trochidae and Calliostomatidae published to date, in terms of both numbers of taxa and of gene sequences. As a result of Bayesian phylogenetic analyses of molecular sequence data from one nuclear gene and three mitochondrial genes, we propose dramatic changes to Trochidae family systematics, present the first molecular phylogeny for Calliostomatidae and include the first published sequence data for the enigmatic subfamily Thysanodontinae. Our phylogeny demonstrates that within the family Trochidae there is strong support for three subfamilies new to traditional classifications: Alcyninae subfam. nov., Fossarininae and Chrysostomatinae subfam. nov. As proposed, Alcyninae consists only of the nominotypical genus Alcyna, which is sister to all other trochids. The subfamily Fossarininae, as defined here, includes Fossarina, Broderipia, Synaptocochlea and “Roya” eximia and probably also Clydonochilus and Minopa. The subfamily Chrysostomatinae comprises the genera Chrysostoma and Chlorodiloma. Additional molecular support is also obtained for recently redefined Trochinae, Monodontinae, and Cantharidinae and for the traditionally recognised subfamilies Umboniinae and Stomatellinae. The subfamily Lirulariinae is not supported by the molecular data, but rather is incorporated into Umboniinae. We also demonstrate that the current concept of the subfamily Margaritinae (previously a trochid subfamily, but recently and provisionally assigned to Turbinidae) is not monophyletic. We provide preliminary evidence that whereas Margarella rosea (previously a member of Margaritinae) belongs in the trochid subfamily Cantharidinae, its presumptive congener M. antarctica is not a trochid, but instead clusters with the thysanodontine genus Carinastele. Based on the phylogenetic placement of C. kristelleae, we agree with previous proposals based on morphological data that Thysanodontinae are more closely related to Calliostomatidae than Trochidae. Both Calliostoma and Carinastele are carnivorous and if a sister relationship can be confirmed between Carinastele and Margarella antarctica it might mean that carnivory evolved twice in Trochoidea. The direction of dietary changes was not investigated in this study, but mapping diet onto the phylogeny suggests that true herbivory is predominantly a derived character. The new classification system also means that five trochid subfamilies are predominantly associated with hard substrata, one with soft substrata (Umboniinae) and two with algae and seagrass (Alcyninae and Cantharidinae). There has been a shift back to hard substrata in one umboniine clade. Two of three clades within Calliostomatidae were predominantly associated with hard substrata, but one Japanese clade is associated with sand. The finding of three new, unidentified species from very deep water means that Trochidae, like Calliostomatidae, now includes species found at bathyal depths. More deep-water species may be found as increased sampling leads to the discovery of new species.     

Revision of the Genera Apicalia A. Adams and Stilapex lredale and Description of Two New Genera (Mollusca, Prosobranchia, Eulimidae)

All species that have been described in Apicalia , except the type-species, are transferred to other eulimid genera. Three species earlier included in other genera and four new species are placed in Apicalia , viz. A. angulata sp.n. A, cicatricosa sp.n. A. echinasteri sp.n. (all three Queensland), and A. habei sp.n. (Japan). Those of which the hosts are known are all ectoparasites of asteroids. Two of the seven species previously included in Stilapex are excluded and four species earlier placed in other genera are transferred to Stilapex . The members of the latter genus are parasites of ophiuroids. Tropiometricola gen.n. is erected to include Stilifer sphaeroconcha Habe, a crinoid parasite. Parvioris gen.n. is described with Eulima fulvescens A. Adams as type species. A list of species described in eulimid genera and fitting Parvioris is given. P. australiensis sp.n. (W. Australia), P. blakeae sp.n. (Mauritius), P. mortoni sp.n. (Hong Kong), and P. noumeae sp.n. (New Caledonia) are described. Those species of which the host is known, are all ectoparasites of starfishes.     

Anatomy and systematics of bathyphytophilid limpets (Mollusca, Archaeogastropoda) from the northeastern Pacific

Bathyphytophilus diegensis sp. n. is described on basis of shell and radula characters. The radula of another species of Bathyphytophilus is illustrated, but the species is not described since the shell is unknown. Both species feed on detached blades of the surfgrass Phyllospadix carried by turbidity currents into continental slope depths in the San Diego Trough. The anatomy of B. diegensis was investigated by means of semithin serial sectioning and graphic reconstruction. ‘The shell is limpet-like; the protoconch resembles that of pseudococculinids and other lepetclloids. The radula is a distinctive, highly modified rhipidoglossate type with close similarities to the lepetellid radula. The anatomy falls well into the lepetelloid bauplan and is in general similar to that of Pseudococculinidae and Pyropcltidae. Apomorphic features are the presence of gill-leaflets at both sides of the pallial roof (shared with certain pseudococculinids), the lack of jaws, and in particular many enigmatic pouches (bacterial chambers?) which open into the postcrior oesophagus. Autapomorphic characters of shell, radula and anatomy confirm the placement of Bathyphytophilus (with Aenigmabonus) in a distinct family, Bathyphytophilidac Moskalev, 1978. As revealed by a cladistic study, the Bathyphytophilidae should be classified within the Lepetelloidea close to the Lepetellidae, Pyropeltidae, and Pseudococculinidae.     

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.     

Genetic and morphological variability of the gastropod mollusk Nucella heyseana (Mollusca, Gastropoda) in the environmental optimum and pessimum

Genotypic variability at six allozyme loci and six morphological shell characters was examined in 450 individuals (four samples) of mollusk Nucella heysana from the Vrangel' Bight (Nakhodka Bay) and the Vostok Bay (Peter the Great Gulf, Sea of Japan). An analysis of variation in allele frequencies showed that each of the two localities (Vostok and Nakhodka bays) in the analyzed region is inhabited by a single, albeit genetically heterogeneous, population. A canonical analysis and an analysis of variance of individual heterozygosity (Ho) and morphological variation indicate an association between Ho and morphological variation depending on habitat (interaction) in settlements in the Vrangel' Bight and, to a lesser extent, in the Vostok Bay. These results indicate that, in extreme environmental conditions, allozyme phenotypes may be selected either themselves or as markers of genes linked with them.     

Potamopyrgus antipodarum(Mollusca:Hydrobiidae) in continental aquatic gastropod communities: impact of salinity and trematode parasitism

The structure of gastropod communities was examined from January to June 1999 in four sites of the streams of Mont Saint-Michel Bay along a gradient of salinity, and the occurrence of larval trematodes infecting snails was studied. Abundance and species richness of gastropods increased from polyhaline (95 snails, 1 species) to oligohaline waters (6672 snails, 6 species). Whatever the salinity, the most abundant species was Potamopyrgus antipodarum, an invasive non-indigenous species that represented 80% of the gastropods. Only one male was found in P. antipodarum populations suggesting a predominantly parthenogenetic mode of reproduction. Among 7218 gastropods collected, 1.2% were infected by larval trematodes: 5 species in Lymnaea peregra (4.4%), 4 species in Planorbis planorbis (12.0%), one echinostome in Physa acuta (0.2%), and a new species of Sanguinicola in P. antipodarum (0.5%). This is the first record of infected P. antipodarum in Europe. No parasites were found in polyhaline waters. The prevalence per host population varied from 0 to 100% depending on time of collection, salinity and host species. In the lowest-salinity site, abundance of gastropods and prevalence of trematodes were negatively correlated. The dominance of P. antipodarum in the gastropod communities is discussed in relation with euryhalinity, parthenogenesis and weak rate of parasitism.     

Dynamics and ecology of an Indo-Pacific conch, Conomurex persicus (Mollusca: Gastropoda) in southeastern Turkey

Conomurex persicus, one of the tropical conchs, has been introduced to one of the subtropical regions, the northeastern Mediterranean Sea, and invaded sandy bottoms between 1 and 10 m deep. Population dynamics were studied from specimens collected with a standard dredge (60 x 15 cm mouth opening, 0.5 x 0.5 cm eye opening of net). Samples of C persicus were collected monthly along the 5 and 10 m depth contours off Erdemli, Mersin, Turkey, in February and May 2000. Intra-annual density depended on salinity levels, while inter-annual density was correlated with bottom water temperature. Specimens underwent spring emergences and winter burial and sheltering (disappearance). Emergence took place in March when temperatures rose and the disappearance occurred in October-November when temperatures dropped. Adults live at 10 m, juveniles are recruited at a 5 m depth. Recruitment began in April and continued for the next 6 months. In contrast to shell width or shell lip thickness, shell length was not a convenient index for estimation of growth parameters. Annual production and mortality were calculated to be 7.86 g m(-2) and 3.80 g m(-2), respectively, in April-November.     

Anatomy and ultrastructure of the excretory system of a heart-bearing and a heart-less sacoglossan gastropod (Opisthobranchia, Sacoglossa)

The microanatomy and ultrastructure of the excretory system of the Sacoglossa have been investigated from two species by means of semithin serial sections, reconstructions and transmission electron microscopy. Whereas Bosellia mimetica shows a functional metanephridial system consisting of a heart with ventricle and auricle in a pericardium and a single kidney, Alderia modesta lacks heart and pericardium, possessing only several haemocoelic sinuses and a very long kidney. In B. mimetica podocytes as the site of ultrafiltration could be detected in the pericardial epithelium lining the auricular wall. The flat epithelium of the kidney with extensive basal infoldings and a dense microvillous border towards the luminal surface serves to modify the ultrafiltrate. In A. modesta podocytes are absent. Solitary rhogocytes (pore cells), the fine structure of which strongly resembles podocytes (meandering slits with diaphragms covered by extracellular matrix), occur in B. mimetica and A. modesta, representing additional loci of ultrafiltration. The presence of podocytes situated in the epicardial wall of the auricle is regarded as plesiomorphic for the Mollusca and confirmed for the Sacoglossa in this study, contradicting earlier assumptions of the loss of the primary site of ultrafiltration in the ancestors of the Opisthobranchia. In contrast to the likewise heart-less Rhodopidae with a pseudoprotonephridial ultrafiltration system, A. modesta shows no further modifications of the excretory system. Accepted: 7 May 2001     

Antarctic associations: the parasitic relationship between the gastropod <Emphasis Type="Italic">Bathycrinicola tumidula</Emphasis> (Thiele, 1912) (Ptenoglossa: Eulimidae) and the comatulid <Emphasis Type="Italic">Notocrinus virilis</Emphasis> Mortensen, 1917 (Crinoidea: Notocrinidae) in the Ross Sea

The first case of parasitic association between an eulimid mollusc (Gastropoda, Ptenoglossa) and a comatulid (Echinodermata: Crinoidea) is reported for Antarctica. The mollusc involved in the association is Eulima tumidula Thiele, 1912, which has now been ascribed to the genus Bathycrinicola Bouchet & Warén, 1986, never recognized before in Antarctica. This genus is present only in the NE Atlantic Ocean and the Mediterranean Sea, and encompass species which are specific parasites of the sessile stalked crinoids of the family Bathycrinidae. However, in Antarctica, Bathycrinicola tumidula (Thiele, 1912) exploits the endemic vagile comatulid Notocrinus virilis Mortensen, 1917, and attains the largest known dimensions (∼1 cm) for a Bathycrinicola species. The absence of suitable Bathycrinidae host in modern Antarctic benthic assemblages, as well as the long paleontological history of the genus Notocrinus in Antarctica, suggest a possible ‘host-switch’ phenomenon. This event could reasonably have occurred when many species underwent considerable bathymetric shifts, during the dramatic climatic changes that affected Antarctica.     

Studies on the ecology of Haemaphysalis silacea Robinson 1912 (Acarina: Ixodidae).

Haemaphysalis silacea Robinson is known to be established only in the Eastern Cape Province of South Africa, in localized areas of Fish River Bush in the river valleys and in the coastal bush complex. In the Kowie River valley, it was shown that the distribution of larvae is limited by microclimatic conditions. The humid leaf litter zone in the dense vegetation on the river banks and along minor tributaries is the focus of the larval population. Nymphs are most numerous in drier microhabitats on the wooded, river floodplain. Larvae are active during the humid conditions of autumn and early winter, nymphs during late winter and spring, and adults during the hot, dry summer months. The main hosts of H. silacea are artiodactyls, which are numerous in the dense Fish River Bush. The host/tick interaction occurs as a result of the daily movements and feeding habits of the hosts.     

Population genetics of Haminoea (Haloa) japonica Pilsbry, 1895, a widespread non-indigenous sea slug (Mollusca: Opisthobranchia) in North America and Europe

Haminoea japonica is an opisthobranch mollusk with a large non-indigenous range. This species is a vector for a parasite that causes the human skin disease cercarial dermatitis, and may have negative effects on populations of native species. Molecular evidence from the mitochondrial cytochrome c oxidase I gene and the histone 3 nuclear gene indicates that previously published morphology-based hypotheses on the spread of H. japonica out of Japan are correct. The most likely explanation for the current range of the species, which includes Japan, Korea, France, Spain, Italy, Canada and the USA is a recent, human-mediated dispersal from Japanese populations. The highest levels of nucleotide and haplotype diversity are found in Japan. Non-indigenous populations have low levels of genetic diversity (indicating bottlenecking). Haplotypes that were detected in the non-indigenous range of H. japonica have only been found in two localities in the native range; these two localities are in north-eastern Japan. In addition, the haplotype network structure and Spatial Analysis of Molecular Variance results confirm the origins of non-indigenous populations most likely trace to north-eastern Japan, which is where most Pacific oyster exports to North America also originated. Because there are no major shipping ports in north-eastern Japan, ballast water is less likely to be the mechanism of dispersal. The results of this study provide important data for the development of policies and regulations aimed to prevent further spread of this species in non-indigenous ranges.