Snails exhibit a primary left-right asymmetry that appears during the first cleavages of the eggs, and a secondary asymmetry, related to the coiling of the shell. Most species are constituted by either dextral or sinistral morphs (enantiomorphs) while individuals with reversed primary asymmetry are extremely rare. Freshwater snails of the family Ampullariidae are normally dextral enantiomorphs with planispiral, hyperstrophic or orthostrophic shells. Pomacea canaliculata, a well-studied species because of its invasive status, shows dextral primary asymmetry and orthostrophic growth that results in clock-wise shells. Despite the great number of studies focused on P. canaliculata, only two specimens with reversed asymmetry have been hitherto reported. Here we report the finding of two live snails and three empty shells of P. canaliculata with anti-clockwise coiling that appeared in two populations from the southern Pampas, Argentina. Both anti-clockwise live snails were males that attempted to copulate with clock-wise females in the laboratory but failed to inseminate them. The apex of anti-clockwise shells and the anatomy of the snails revealed that the reversal of coiling was due to an orthostrophic development of sinistral enantiomorphs. Morphological analysis performed through geometric morphometrics did not find other differences with clock-wise snails other than coiling direction. We conclude that these anti-clockwise snails are probably engendered, as in other snails species, when the mother is a recessive homozygote for reversing alleles that show delayed maternal inheritance. The chances of establishment of populations with dimorphic asymmetry are very low because of the reproductive disadvantages of anti-clockwise individuals.

Sex differences in stress responses may be a key factor that determines population structure. Sex ratios of Pomacea canaliculata populations usually average 1:1 at birth, but are often female-biased for adults. Low temperatures and drought are the main abiotic stresses affecting reproductive dispersal and population development. Therefore, we investigated whether Pomacea sp. (mainly P. canaliculata but might include P. maculata) exhibited sex differences in cold hardiness and desiccation tolerance. The results show that more females survived than males during cold-drought stress and overwintering. Following cold-drought stress, 58% of females and 40% of males survived at 3°C drought conditions for 6 days. With the development of cold-drought hardiness, increased amounts of bound water, glycerol and lipids were found in Pomacea sp. along with decreased free water levels. These physiological parameters exhibited sex differences in the snails, except for lipids, and the changes all showed tendencies favoring the survival of females under cold-drought stress. These results suggest that female Pomacea sp. may be more viable than males under cold and dry conditions.

Many species of terrestrial mollusks are small and difficult to find, with poorly known ranges and habitat preferences. Because desiccation is a primary cause of mortality for many terrestrial mollusks, incorporating wetness as a habitat variable may improve survey results for different species. We compared presence and abundance data from terrestrial mollusk surveys in Tillamook Resource Area to two measures of relative wetness: topographic wetness index (TWI) and geomorphic features (landslides, debris-flow channels, etc.). Hurdle Model regression revealed a positive correlation between increased TWI and likelihood of presence or abundance for four species, and a negative correlation for six species. Overall species diversity and total mollusk count were negatively correlated with increased TWI, but the effect size was small (p = 0.02, R²= -0.03). Our Kruskal-Wallis Analysis of Variance of TWI between species was significant (p < 0.001), indicating terrestrial mollusks occupy significantly different wetness regimes – but this relationship was driven entirely by the wetness specialization of Hemphillia glandulosa. Our chi-square analysis of topographic features found significant preferences of different species for different topographic types, which correlated loosely but not precisely to the preferences indicated by TWI. These results show that altering current terrestrial mollusk survey protocol to include geomorphic features, which are simpler and less time-intensive than calculating TWI, would increase detection likelihood of certain species, including Hemphillia glandulosa, a species protected under the Survey and Manage guidelines of the Northwest Forest Plan.

We describe a new helicoidean semi-slug based on morphological and molecular evidence. The new species belongs to the genus Bunnya and is described from a small agricultural area in Zinacantepec, San Juan de las Huertas, México. The genus Bunnya is externally similar to Xanthonyx, another Helicoidea genus; both genera have similar shell and body form, and both have a tail horn. Internally, Bunnya is similar to Humboldtiana, since both have dart-sacs (3 in Bunnya, 3−4 in Humboldtiana) surrounding the vagina, two dart-bulbs associated with each dart sac, and a gland number similar to the dart-sacs number. Four adult specimens of Bunnya metli n. sp. were dissected and compared with the two described species: B. bernardinae from Cuajimalpa, México City, and B. naranjoe from Sierra de Manantlan, Jalisco. Bunnya metli n. sp. is characterized by: very closely-spaced radial riblets (about 23 per mm) crossed by fine spiral wavy threads on the embryonic whorls; unfused glands inserted on the vagina above the dart-sacs and only one dart per sac; a short, swollen penis with a large spherical verge about half the penis size; an elongated bursa copulatrix with a slight constriction in the middle; a long bursa copulatrix duct; and dart sacs with a muscular pad within the vaginal lumen, surrounding the basal part of the genitalia. We performed a phylogenetic analyses using data from fragments of 16S rRNA mtDNA and 28S rRNA genes from one of the collected specimens, as well as other helicoidean sequences from GenBank. Our analyses support the membership of Bunnya metli n. sp. in Xanthonychidae. This suggests that the taxonomic position of Bunnya in Humboldtianidae or Xanthonychidae warrants reevaluation.

No introduced marine pests, also known as invasive marine species, were detected in a dry season survey in August 1998 in Darwin Harbour, Northern Territory, Australia. A postwet-season survey in March 1999 found extensive populations of the false mussel Mytilopsis sallei (Récluz, 1849) in the Cullen Bay Marina. An environmental emergency was declared and M. sallei were eliminated. The present paper examines possible reasons for the failure of M. sallei to establish outside Cullen Bay. Mytilopsis sallei is a fresh/brackish water species that naturally lives in low salinities. It is hypothesized that the osmotic shock of rapid movement from low salinity water in Cullen Bay to much higher salinities outside the marina killed the veligers when they were discharged through the entrance lock when it was opened to allow vessel movements. If it entered the harbour, M. sallei could possibly have established in low salinity water in the arms leading into the harbour and possibly have spread in northern Australia.

This paper provides a biography, bibliography and taxonomic catalog for John Clarkson Jay (1808–1891), emphasizing his malacological research based upon his sizable collection and his contributions to the growth and expansion of the New York Lyceum of Natural History, the predecessor to the American Museum of Natural History. Jay described one new genus and 49 new species of molluscs; type specimens are known for 34 of them. He also published but did not describe 76 manuscript names mostly from material collected by Nuttall, of which 28 were made available by later authors (mostly by either Reeve or Carpenter). His collection and sizable library of rare books formed the nucleus of the malacological collection and the rare book library of the American Museum of Natural History. This paper summarizes his life, the growth of his collection, his publications, his new taxa, and his broader role in 19th-century New York professional life.

Double hectocotylization in octopods has only been reported for some individuals of a few species, often affecting arms of the same pair. We herein report several cases of non-bilateral double hectocotylization in a single species collected in different locations of the Mexican Pacific coast. The octopuses were identified by morphological and molecular criteria as Hubb's octopus, Octopus hubbsorum. The “regular” and “accessory” hectocotyli were examined by histological analysis; in the latter, the calamus was present and no ligula was detected. Double hectocotylization can be an intrinsic character of the species.

The date mussel Lithophaga lithophaga is a chemical borer that uses pallial gland secretions to bore holes in the substrate. Calcium-binding proteins are generally considered to be responsible for the chemical dissolution of the calcareous substrate. The aim of this study was to investigate the relative expression of five candidate genes – ANXB9, SCP, CALR, PLA2 and V-ATPase – in four different tissues, with the hypothesis that the expression profile of the candidate genes in the pallial gland would differ from the rest. The results from gene expression analysis revealed that CALR, PLA2 and SCP were up-regulated in the pallial gland. Two of the candidate genes (ANXB9 and V-ATPase) had the same expression profile in all four investigated tissues, indicating that they are not directly involved in the chemical boring mechanism. The results of this study shed light on the genetic background of the chemical boring mechanism in date mussel. This set of candidate genes could be used in future research studies of chemical boring in the date mussel and other marine or freshwater borers.

The Oriental region is among the world's biologically most diverse regions, but also among the most biotically threatened, especially with regard to freshwater biota. The Cerithioidea comprise several families and are a major component of the freshwater gastropod fauna in the Oriental region. Among these, the Paludomidae include numerous taxa mostly described in the 19^thcentury that are in many cases badly in need of revision. As an initial step towards a better understanding of the evolutionary systematics of the family, we here review the genus-group taxonomy and nomenclature of Asian Paludomidae. We show that Paludomus Swainson, 1840, Philopotamis Layard, 1855, GangaLayard, 1855, and OdontochasmaTomlin, 1930, are available names for morphology-based genus-group taxa of Asian Paludomidae. By selection of Melania modicella I. Lea & H. C. Lea, 1851, as type species of Rivulina I. Lea & H. C. Lea, 1851, and by the designation of a neotype for Paludomus (Hemimitra) retusa Swainson, 1840, Rivulina and Hemimitra Swainson, 1840, can both be regarded as synonyms of Paludomus s. str. By selection of Paludomus sulcatus Reeve, 1847, as its type species, Heteropoma Benson, 1856, becomes an objective junior synonym of Philopotamis Layard, 1855. Furthermore, we show that the type species of TanaliaGray, 1847, which has often been used for a subdivision of Paludomus or as a distinct genus, belongs to the Neritidae and that Odontochasma Tomlin, 1930, has been validly proposed as a replacement name for the preoccupied name Stomatodon Benson, 1862. Finally, we revise Paludomus (Odontochasma) stomatodon Benson, 1862, on the basis of available type material, describe its radula for the first time, and compare it with published data on radulae of other Asian paludomids. Taxonomic redundancy in the genus-group in Asian Paludomidae is estimated to be 50% and may be as high as 88% depending on taxonomic opinion.

Freshwater bivalves in the family Unionidae are one of the most endangered groups of animals in North America. In Texas, where over 60% of unionids are rare or very rare, 15 species have been added to the state's list of threatened species, and 10 are under consideration for federal listing. Due to insufficient survey efforts in the past decades, however, primary data on current distribution and habitat requirement for most of these rare species are lacking, thus challenging their protection and management. Although the species are listed as valid, there was no genetic confirmation to test for the possibility of ecophenotypes, which complicates conservation efforts. In this paper, we present genetic and distributional data for two rare Texas species, Truncilla macrodon and Truncilla cognata, and we suggest appropriate conservation measures. Tests of genetic affinities of these species using three gene regions, cox1, nad1 and ITS1, supported recognition of T. cognata and T. macrodon as full species. Analysis of historic and current species distribution showed that both these regional endemics are particularly vulnerable, and their distribution range has been reduced in the last 80 years.