The diagnosis and geographical distribution of the genus Hypselartemon Wenz, 1947, which was originally proposed as a subgenus of Rectartemon Baker, 1925, were re-examined based on preserved material, including type specimens, collected since the nineteenth century and deposited in scientific institutions. The comparative morphology of shell, radula, and soft body parts, when available, of Hypselartemon alveus (Dunker, 1845), H. contusulus (Férussac, 1827), H. deshayesianus (Crosse, 1863), and H. paivanus (Pfeiffer, 1867) were analyzed in order to redescribe and to highlight characters that can be used for species identification. Examination of the reproductive organs revealed significant differences among the species, all of which are endemic to the state of Rio de Janeiro, Brazil, and do not occur in Colombia as originally suggested. These results seem useful in examining the taxonomy and systematics of the Neotropical Streptaxidae.

A comparative histological study was undertaken to reveal the morphological diversity and systematic characters of a radula-supporting organ of gastropods. Observations on 33 species, all from different families, revealed six major morphological characters: (1) the number of odontophoral cartilages or radular bolsters: 0, 1 (fused), 2, 4, 5, 6 and 10; (2) histology categorized into 6 types based on the properties of cartilage matrix and cells; (3) the presence or absence of an enclosing membrane of the cartilages or radular bolsters; (4) the presence or absence of overlapping of the right and left cartilages or radular bolsters; (5) the closest position of the cartilages or radular bolsters to each other in cross section at ventral or dorsal side; and (6) the insertion areas of the ventral approximator muscle connecting the cartilages or radular bolsters – ventral, medial, or outer lateral area. Outgroup and ingroup comparisons based on recent phylogenetic hypotheses suggest the following evolutionary scenario for gastropod radula-supporting organs: the ancestral gastropod is assumed to have possessed two pairs of odontophoral cartilages with a thick matrix and ventrally connected by the approximator muscle. The cartilages have possibly independently increased in number in patellogastropods and Neritimorpha, decreased into a one pair, single piece or lost in Caenogastropoda, and replaced by connective tissue and muscle fibers in Heterobranchia. Some taxa such as Cypraeidae have gained a unique histology. The cartilages or radular bolsters are closest ventrally in cross section in the majority of gastropods but closest dorsally in part of the taenioglossate Caenogastropoda. The diversification of these character states in gastropods seems to be phylogenetically constrained, not ecologically.

This paper lists the species and the distribution of the bivalves collected from the deep-sea expeditions undertaken by American, British and French research vessels in the Atlantic over a period of twelve years. Samples were taken from eleven basins, and the analysis is resticted to samples taken with the epibenthic sled from depths ranging from 500 m to 5,000 m. A preliminary analysis is made of the changing distribution with depth and discussion as to why some genera and families are either restricted to or are more dominant in the deep sea as compared with those found at shelf-sea depths. It provides a baseline of information against which future deep-sea sampling can be compared.

Dwight Willard Taylor (1932–2006) was a malacologist and paleontologist whose research on the systematics and biogeography of freshwater gastropods, particularly the Hydrobiidae and Physidae, resulted in numerous taxonomic innovations and led to extensive research by others. His biogeographical analyses of the distribution of freshwater mollusks, particularly from western North America, were provocative and stimulating. His research on endangered or threatened species was influential in the conservation of those species and their habitats. He published 65 papers and 9 abstracts, and authored numerous internal reports to federal and state agencies, primarily for the U.S. Geological Survey and the U.S. Fish and Wildlife Service. He described 132 taxa, comprising 12 family-level taxa, 31 genus-level taxa, and 89 species; most of his taxa were in the Hydrobiidae (54) and Physidae (39), and he was involved in the founding and early development of Malacologia.

This paper reviews the new taxa made available by Gray in the Griffith & Pidgeon (1833–1834) English translation of Cuvier's famous Le règne animal 1830, as well as the taxa attributed, correctly or incorrectly, to Gray in this work. We discuss various complications concerning the dating and authorship of these taxa, and some new information is provided about their type material.

Six generic names date from this work, five of them now considered valid. Sixty-five species names were made available, of which 44 are now considered valid, although some of these have not been recognized in recent literature, and one is a nomen dubium; 21 are placed in synonymy because they are junior synonyms, preoccupied homonyms, or unused senior synonyms that have been or should be suppressed.

Ultastructural studies of the development and degeneration of the oocytes and follicle cells in female Chlamys (Azumapecten) farreri farreri (Jones & Preston, 1904) are described for scallops collected from Daehuksando, Jeollanam-do, Korea. Vitellogenesis occurred by way of endogenous autosynthesis and exogenous heterosynthesis. Auto-synthesis involved the combined activity of the Golgi complex, mitochondria, and rough endoplasmic reticulum, whereas heterosynthesis involved endocytotic incorporation of extraovarian precursors at the basal region of the early vitellogenic oocytes prior to the formation of the vitelline coat. Auxiliary cells were involved in the development of the previtellogenic and early vitellogenic oocytes and appear to play an integral role in vitellogenesis and oocyte degeneration by assimilating products originating from the degenerated oocytes, thus allowed the transfer of yolk precursors needed for vitellogenesis. Auxiliary cells presumably have a lysosomal system for breakdown products of oocyte degeneration. The reproductive cycle in females was classified into five stages: Stage I: early active stage (January to March), Stage II: late active stage (March to April), Stage III: ripe stage (April to August), Stage IV: partially spawned stage (June to August), and Stage V: spent/inactive stage (August to January). The spawning period continued from June to August, with a peak between July and August when the seawater temperature was exceeded 22°C. The percentage of first sexual maturity was 59.3% in individuals of 50.1–60.0 mm in shell height, and 100% in those > 70.1 mm in shell height.

Because harvesting clams less than 50.1 mm in shell height could potentially cause a drastic reduction in recruitment, a measure indicating a prohibitory fishing size should be enacted for adequate fisheries management.

This study examined the relative importance of environmental factors and geographic isolation on the distribution of apple snails in Hong Kong two decades after their invasion from South America. A survey of 61 sites was conducted to collect apple snails and measure 18 environmental parameters known to influence mollusk distribution. Identification of specimens collected in our study was aided by analysis of DNA sequences, and all apple snails collected in Hong Kong were identified as Pomacea canaliculata. Since its initial introduction in the early 1980s, the distribution of this invasive snail has only expanded slightly. Principal component analysis showed that the environmental characteristics of the study sites varied with habitat. Streams were quite homogenous in chemical characteristics and contained little dissolved minerals, whereas ponds, abandoned wet farmlands and drainage channels all showed great variations in nutrient loading. Discriminant function analysis (DFA) revealed that the inhabited sites typically had high levels of phosphate and alkalinity, but the snail was also occasionally found in streams where dissolved ion concentrations and nutrient levels were low. Most of the inhabitable wetlands in New Territories have already been occupied by P. canaliculata. Because of its unsuitable hydrology, Hong Kong Island remains uninhabited by this species. Lantau Island has habitable sites for this species, and thus is susceptible for invasion in the future.

Lampsiline bivalves typically are considered a tribe within the Unionidae (Ambleminae: Lampsilini), and they display extraordinary morphological adaptations for reproduction. Recent studies have weakly corroborated the monophyly of the Lampsilini, but evolutionary relationships within the tribe and its sister lineage have yet to be elucidated convincingly. However, these determinations are necessary to better understand the evolution of the spectacular morphological diversity present in lampsilines, as well as the specific circumstances surrounding the group's origin. To clarify these matters, phylogenetic analyses were carried out on 2,310 nucleotide and 770 amino acid position matrices containing sequences from five protein coding gene regions on the F and M mitochondrial genomes from 21 amblemine species. Nodal support values on the best Bayesian inference tree robustly confirm the monophyly of lampsilines and a clade containing the following well-supported relationships: (((lampsilines, Popenaias) Plectomerus) Amblema). Furthermore, a maximum likelihood estimate of ancestral character states indicates that the ectobranchy observed in lampsilines Popenaias is homologous and was derived from a tetragenous ancestral lineage. The sister taxon status of P. popeii to the traditional lampsiline taxa and the occasional use of the inner demibranchs for brooding suggest that this species could still retain character states of the lampsiline ancestral lineage. Therefore, additional studies of morphology, reproduction, phylogeography and ecology for Popenaias, Amblema, Plectomerus, and other taxa within the Amblemini could clarify the circumstances surrounding the origin of the lampsiline bivalves.

The Chilinidae comprises 16 species currently cited for Argentina, mostly distributed in Patagonia. All original descriptions of these species have been based on shell characters, and their internal anatomy is poorly known. Here a new species, Chilina iguazuensis, is described, including shell, radula, and reproductive and nervous systems. This species, found in Iguazú National Park, Misiones Province, Argentina, in the Upper Iguazú River rapids, has the following distinctive characteristics: aperture length equal to last whorl length; central radular tooth asymmetric and bicuspid, with both cusps serrated; and prepuce length 60% of penis sheath length. Chilina iguazuensis is endemic in Iguazú National Park, along with Chilina megastoma, which inhabits waterfalls in the same river.

We document a case of shell convergence in sympatric freshwater cerithioidean gastropods that has caused confusion in traditional classifications emphasizing shell features. Based on the comparative study of the operculum, radula, and embryonic shell obtained from dry remains of soft bodies, we present evidence that “Melania” pisum is not a thiarid species closely related to Balanocochlis glans (Busch, 1842), as has been supposed with respect to the very similar shells of both species. The species is transferred to the family Pachychilidae, because it shows various typical character states for the family. It is tentatively placed within the genus Sulcospira, which is endemic to Java. We assume that a similar shell shape has evolved in both species of not closely related gastropods through convergence, which once more reveals that purely shell-based classifications are particularly problematic.

The Eastern mudsnail, Ilyanassa obsoleta, was attracted to, consumed, and digested resting cysts of the dinoflagellate Scrippsiella lachrymosa when cysts were presented in grazing experiments. Twenty snails were observed individually for one hour in petri dishes divided into four parts wherein cysts were present in one quadrant, sediment particles of the same size range were in another quadrant, and two quadrants were free of particles. Actively foraging snails were nearly twice as likely to be found in quadrants containing S. lachrymosa cysts as in the other quadrants until cysts were consumed. Microscope observations of fecal pellets from snails feeding on cysts revealed digestive destruction of the cysts. These findings indicate that deposit-feeding grazers can actively seek dinoflagellate cysts as a food item, thereby influencing distribution of cysts and subsequent germination of dinoflagellate vegetative cells.

Three species of apple snails (Ampullariidae) have been introduced to Hawaii. In order to clarify their identities, determine their geographic origins, and evaluate their mtDNA diversity in Hawaii, we sequenced the COI and ND6 mtDNA markers from 103 snails collected on the six main Hawaiian islands. Our samples included Pila conica and Pomacea canaliculata, whose identities were confirmed by phylogenetic analysis that included other ampullariid species. The third species, Pomacea diffusa, known to have been present in the past, was not found. Neither species exhibited any variation at either marker. Both species may have been introduced to Hawaii as single introductions, possibly from the Philippines.