The taxonomy of subulinid snails in Myanmar has been evaluated, resulting in the recognition of 40 species and subspecies across nine genera: Allopeas, Bacillum, Curvella, Glessula, Opeas, Paropeas, Rishetia, Tortaxis, and Zootecus. Nine species are re-described based on recently collected specimens, and two new species, Glessulamandalayensis Man & Panha, sp. nov. from Mandalay Region and Tortaxiscylindropsis Man & Panha, sp. nov. from Shan State are introduced. The genitalia and radula of Zootecuspullus was studied for the first time. This study also presents a comprehensive list of all subulinid species recorded to date from Myanmar. The type specimens and authenticated museum specimens have been illustrated with accompanying taxonomic remarks and nine species formerly assigned in Glessula are now placed in Rishetia: R.akouktoungensis, R.baculina, R.basseinensis, R.burrailensismaxwelli, R.kentungensis, R.limborgi, R.nathiana, R.pertenuis, and R.pertenuismajor.

Behavior is predicted to be a primary determinant of the success of the invasion process during the early phases of colonization. Comparing invaders with sympatric native species may provide a good approach to unravel behavioral traits involved in an invasion process. In this study, we carried out an experimental simulation of the introduction and the acclimatization phase into a new environment and assessed the expression of activity, alertness, and habituation in an invasive Mediterranean population of the South African nudibranch Godiva quadricolor comparing its profiles with those of the sympatric Mediterranean native nudibranchs Cratena peregrina and Caloria quatrefagesi. Individuals of these 3 species were subjected to 3 behavioral tests: spontaneous activity, carried out in the introduction phase (immediately after sampling) and after a week of acclimatization; alert test, in which a potential threat was simulated by means of a tactile stimulus, and habituation test, in which the same alert test stimulus was repeated 5 times at 30-min intervals. The invasive G. quadricolor showed higher levels of exploration activity, thigmotaxis, alertness, and sensitization than the native species. These behavioral traits may represent pivotal drivers of the ongoing invasion process.

Studies of morphology and developmental patterning in adult stages of many invertebrates are hindered by opaque structures, such as shells, skeletal elements, and pigment granules that block or refract light and necessitate sectioning for observation of internal features. An inherent challenge in studies relying on surgical approaches is that cutting tissue is semi-destructive, and delicate structures, such as axonal processes within neural networks, are computationally challenging to reconstruct once disrupted. To address this problem, we developed See-Star, a hydrogel-based tissue clearing protocol to render the bodies of opaque and calcified invertebrates optically transparent while preserving their anatomy in an unperturbed state, facilitating molecular labeling and observation of intact organ systems. The resulting protocol can clear large (> 1 cm3) specimens to enable deep-tissue imaging, and is compatible with molecular techniques, such as immunohistochemistry and in situ hybridization to visualize protein and mRNA localization. To test the utility of this method, we performed a whole-mount imaging study of intact nervous systems in juvenile echinoderms and molluscs and demonstrate that See-Star allows for comparative studies to be extended far into development, facilitating insights into the anatomy of juveniles and adults that are usually not amenable to whole-mount imaging.

Roundup®, a prominent glyphosate-based herbicide (GBH), holds a significant position in the global market. However, studies of its effects on aquatic invertebrates, including molluscs are limited. Pomacea canaliculata, a large freshwater snail naturally thrives in agricultural environments where GBH is extensively employed. Our investigation involved assessing the impact of two concentrations of GBH (at concentrations of 19.98 mg/L and 59.94 mg/L, corresponding to 6 mg/L and 18 mg/L glyphosate) during a 96 h exposure experiment on the intestinal bacterial composition and metabolites of P. canaliculata. Analysis of the 16 S rRNA gene demonstrated a notable reduction in the alpha diversity of intestinal bacteria due to GBH exposure. Higher GBH concentration caused a significant shift in the relative abundance of dominant bacteria, such as Bacteroides and Paludibacter. We employed widely-targeted metabolomics analysis to analyze alterations in the hepatopancreatic metabolic profile as a consequence of GBH exposure. The shifts in metabolites primarily affected lipid, amino acid, and glucose metabolism, resulting in compromised immune and adaptive capacities in P. canaliculata. These results suggested that exposure to varying GBH concentrations perpetuates adverse effects on intestinal and hepatopancreatic health of P. canaliculata. This study provides an understanding of the negative effects of GBH on P. canaliculata and may sheds light on its potential implications for other molluscs.

Pesticides threat marine organisms worldwide. Among them, the Pacific oyster is a bivalve mollusc model in marine ecotoxicology. A large body of literature already stated on the multiple-scale effects pesticides can trigger in the Pacific oyster, throughout its life cycle and in a delayed manner. In particular, reproductive toxicity is of major concern because of its influence on population dynamics. However, past studies mostly investigated pesticide reprotoxicity as a direct effect of exposure during gametogenesis or directly on gametes and little is known about the influence of an early embryo exposure on the breed capacity. Therefore, we studied delayed and multigenerational consequences through gametogenesis features (i.e. sex ratio, glycogen content, gene expression) and reproductive success in two consecutive oyster generations (F0 and F1) exposed to an environmentally-relevant pesticide mixture (sum nominal concentration: 2.85 μg.L-1) during embryo-larval development (0-48 h post fertilization, hpf). In the first generation, glycogen content increased in exposed individuals and the expression of some gametogenesis target genes was modified. The reproductive success measured 48 hpf was higher in exposed individuals. A multigenerational influence was observed in the second generation, with feminisation, acceleration of gametogenesis processes and the sex-specific modification of glycogen metabolism in individuals from exposed parents. This study is the first to highlight the delayed effects on reproduction induced by an early exposure to pesticides, and its multigenerational implications in the Pacific oyster. It suggests that environmental pesticide contamination can have impacts on the recruitment and the dynamics of natural oyster populations exposed during their embryo-larval phase.

The study on natural radionuclides in edible bivalves from the Cochin backwater lagoon, Kerala, employing alpha spectrometry, revealed higher concentrations of 210Po and 210Pb compared to 238U and 232Th. The annual committed effective dose (ACED) for the adult coastal population was calculated at a range of 1494.9 to 5783.4 μSv y-1, with 210Po being the predominant contributor, responsible for about 85 % of the dose. This highlighted significant health risks, underscored by a calculated cumulative mortality and morbidity risk range between 5.23 × 10-3 and 2.02 × 10-2. These findings emphasized the need for further research and the development of regulatory measures to mitigate exposure risks.

A sample of phosphatized, originally calcareous, mollusk shells from the Katian age uppermost Mójcza Limestone at its type locality yielded a few hundred polyplacophoran plates. The chelodids are very rare among them. Three septemchitonid species dominate. They represent a gradation from underived steep roof-like plates to almost cylindrical ones, leaving only a narrow ventral slit for the foot. Apparently, this represents the first step toward the extremely derived \'segmented clam\' Bauplan of the Silurian Carnicoleus, with plates completely closed at the venter except for the mouth and anal openings. To enable growth, the plates became thinner and more flexible (or perhaps resorbed) along the dorsum. The tendency toward reduction of the ventral gap of the plates in the early Paleozoic septemchitonid polyplacophorans implies their lack of ability to cling to the substrate with a muscular foot. In compensation, their plates changed toward a more efficient protective function, covering the animal body sides more and more completely. This may explain the origin of the ventral furrow of extant solenogasters hiding the rudimentary foot. An opposite route was chosen by the coeval Acaenoplax lineage, in which the plates did not contact each other, exposing much of the soft body on the dorsum. In both cases the animals appeared to be worm-like, perhaps representing different ways of evolution from the Paleozoic chitons to the extant aplacophorans.

Molluscs have undergone many transitions between separate sexes and hermaphroditism, which is of interest in studying the evolution of sex determination and differentiation. Here, we combined multi-locus genotypes obtained from restriction site-associated DNA (RAD) sequencing with anatomical observations of the gonads of three deep-sea hydrothermal vent gastropods of the genus Alviniconcha living in the southwest Pacific. We found that all three species (Alviniconcha boucheti, Alviniconcha strummeri, and Alviniconcha kojimai) share the same male-heterogametic XY sex-determination system but that the gonads of XX A. kojimai individuals are invaded by a variable proportion of male reproductive tissue. The identification of Y-specific RAD loci (found only in A. boucheti) and the phylogenetic analysis of three sex-linked loci shared by all species suggested that X-Y recombination has evolved differently within each species. This situation of three species showing variation in gonadal development around a common sex-determination system provides new insights into the reproductive mode of poorly known deep-sea species and opens up an opportunity to study the evolution of recombination suppression on sex chromosomes and its association with mixed or transitory sexual systems.

Small non-coding RNAs (sncRNAs) are non-coding RNA molecules that play various roles in metazoans. Among the sncRNAs, microRNAs (miRNAs) guide post-translational gene regulation during cellular development, proliferation, apoptosis, and differentiation, while PIWI-interacting RNAs (piRNAs) suppress transposon activity to safeguard the genome from detrimental insertion mutagenesis. While an increasing number of piRNAs are being identified in the soma and germlines of various organisms, they are scarcely reported in molluscs. To unravel the small RNA (sRNA) expression patterns and genomic function in molluscs, we generated a comprehensive sRNA dataset by sRNA sequencing (sRNA-seq) of eight mollusc species. Abundant miRNAs were identified and characterized in all investigated molluscs, and ubiquitous piRNAs were discovered in both somatic and gonadal tissues in six of the investigated molluscs, which are more closely associated with transposon silencing. Tens of piRNA clusters were also identified based on the genomic mapping results, which varied among different tissues and species. Our dataset serves as important reference data for future genomic and genetic studies on sRNAs in these molluscs and related species, especially in elucidating the ancestral state of piRNAs in bilaterians.

Marine microdebris (MD) seem to be widespread in benthic invertebrates, even in the most remote areas of the planet such as Antarctica, although the information available is still very scarce. Here we provide a detailed quantification and characterization of the MD found on three common bivalve species (Aequiyoldia eightsii, Thracia cf. meridionalis, and Cyclocardia astartoides) inhabiting shallow areas in Johnsons\' Bay, Livingston Island (South Shetland Islands, Antarctica) as a snapshot of the MD present. On average, these bivalves contained 0.71 ± 0.89 items per individual and 1.49 ± 2.35 items per gram, being comparable to the few previous existing studies in other Antarctic areas. Nearly half of the organisms analysed here (45.6 %), contained at least one item. No significant differences were found in the three bivalve species. As far as we know, this is the first study to analyse and compare MD in three bivalve species in the Antarctic Peninsula. Although our results indicate bivalves are as not as polluted as in other areas of the planet, this is remarkable since this is considered one of the last pristine areas of the world. Our results point to local activities as the main source of MD pollution in Livingston Island, although global pollution cannot be discarded. We believe this research provides a useful baseline for future studies and will contribute to develop policies and strategies to preserve Antarctic marine ecosystems from MD pollution.