The successive stages of oogenesis and the changes involved in the oocyte degeneration process in the penshell Atrina maura were examined using light and transmission electron microscopy. The ovarian maturation process is asynchronous, as oocytes at different developmental stages can be found simultaneously. Oocytes develop from oogonia and then undergo three distinct stages of oogenesis: previtellogenesis, vitellogenesis and postvitellogenesis with mature oocytes. Atrina maura displays a solitary oogenesis type, in which follicular cells become associated with oocytes from the earliest stages of development and seem to play an integral role in vitellogenesis. The cytoplasm of vitellogenic oocytes contains numerous whorls of rough endoplasmic reticulum and Golgi bodies, suggesting that auto-synthetic vitellogenesis may occur in this species. In addition, the degeneration process of postvitellogenic oocytes triggered by a seasonal increase in water temperature (> 25°C) is described.

This is the first published documentation of the land snails from Kosrae Island (eastern Caroline Islands, Micronesia; ∼ 5.3°N, 163°E). Timed hand collecting in leaf litter and emergent vegetation over the course of five days yielded 15 species in 13 gastropod families, including important collections of Delos oualanensis (Rhytididae) and Sinployea kusaieana (Charopidae), which had not been collected since the last survey of Kosrae in the 1930s. We did not recover evidence for in situ diversification in Kosrae — rather, the fauna seems to be a subset of the general Micronesian fauna (especially that of Pohnpei), with endemic species most likely having sister species off-island. An exotic veronicellid slug, and several snails that are widespread and possibly introduced were found, but no giant African land snails (Achatina fulica) were found. Due to its position as the eastern-most high island in Micronesia, Kosrae is an important part of our understanding of both the pre-anthropogenic assembly of Pacific island faunae, and the ongoing homogenization of same. We recommend that future land snail surveys of Kosrae focus on higher elevations and collection methods that preferentially target partulids and leaf-litter microsnails.

The obsolescence of radial sculpture on the last whorl of the land snail Ancotrema hybridum (Ancey, 1888) has been used to separate it from A. sportella (Gould, 1846), but shells are sometimes difficult to assign to one species or the other, prompting questions about their species status. Factor analysis of shell characters of 311 specimens of Ancotrema Baker, 1931, including characters of surface sculpture strength, shell size and rib density, revealed continuous variation of these characters without bimodality. Radial sculpture begins obsolescing at about whorl five, so shells that stopped growing near whorl five have A. sportella-like morphology, while those that continued growing after whorl five have A. hybridum-like morphology. We saw no meaningful differences in the genital anatomy that would suggest different species. The obsolescence of sculpture beginning about whorl five regardless of ultimate whorl number, lack of bimodality of shell characters, and lack of anatomical differences lead us to conclude that the two forms are a single species. Ancotrema hybridum is a junior synonym of A. sportella.

Temperature is a major environmental factor that influences all aquatic organisms. Our objective was to expose individuals of Lymnaea stagnalis from an Eastern Siberian population to wide temperature gradients to determine whether they express a thermal stress response and what mechanisms are involved in this process. Several parameters of the cellular mechanisms of thermal resistance were tested under the experimental conditions: the level of lipid peroxidation, the synthesis of heat shock protein HSP70, the activities of antioxidative enzymes and changes in the content of energy-associated metabolites.

The results of this study show that the temperature at which the cellular and biochemical stress-response is activated in the L. stagnalis from Eastern Siberian lakes directly corresponds to environmental temperature within the range of 3 to 15°C. The exposure of the gastropods to temperatures outside this range resulted in the activation of HSP70 synthesis, changes in the activities of antioxidative enzymes and glycogenic metabolism. These conditions can be considered to be stressful to the tested gastropods. Because L. stagnalis is a common species that inhabits a wide range of lakes with temperatures higher than 15°C, we suggest that the limitation established by this study can be considered to be the result of a local temperature adaption of the Eastern Siberian population. This diversity of temperature adaptation among different populations of L. stagnalis contributes to the common environmental variation and plasticity of the species, which is strongly reflected at the levels of cellular and biochemical processes and the gastropods' stress reactions.

The shell microstructure of 30 species belonging to 14 genera and nine families of protobranchs were newly described using scanning electron microscopy. As a result, 13 microstructures were recognized. The shell microstructural composition of protobranchia is conservative at a superfamily level among the Recent species, whereas this trend is not necessarily apply to that of fossil protobranchs. Greater diversity of the shell microstructure was revealed in protobranchs than previously known. (1) Nuculoidea commonly have outer prismatic and middle/inner nacreous structures. The outer prismatic layer is newly classified into five types in Nuculidae. In particular, the irregular fibrous prismatic structure was first observed in Nuculoidea. The interspecific variability of outer prismatic layers seems to provide crucial criteria for phylogenetic grouping in this superfamily. (2) Nuculanoidea have non-nacreous structures including the homogeneous, fibrous prismatic and fine complex crossed lamellar structures. Sareptidae, which should presumably be reclassified from Nuculoidea to Nuculanoidea also follows this pattern. (3) Manzanelloidea have microstructural components similar to those of Nuculanoidea. These features strongly suggest the shell microstructure of protobranchs provide useful bases for higher systematics.

The number of non-native species has dramatically increased over the last decades in many aquatic habitats of central Europe. Although the spreading of alien mollusc species can poses a serious threat to many native species, no attempt has been made to assemble and analyse an extensive dataset collected over a long time span. So far, eight non-native species of aquatic molluscs — five gastropods and three bivalves — have been recorded in the wild in the Czech Republic in central Europe. We assembled a dataset consisting of 1,783 sites with the presence of these non-native species recorded between 1891 and 2014. We aimed to explore the time course and spatial pattern of the invasions and to define some of the gross predictors of the occurrence of these species by categorizing their sites based on habitat type, elevation and distance from the nearest large river. We found that most of these species expressed affinities to non-natural standing waters and large rivers. The most invaded parts of the Czech Republic were large lowlands, especially the Elbe River basin. In contrast, hilly and mountain areas were notably less invaded as the number of records sharply decreased towards higher elevations for all studied species except Gyraulus parvus. The highest invasion rate was documented for Physella acuta and Potamopyrgus antipodarum, in contrast to two modern invaders (Menetus dilatatus and Corbicula fluminea) that had a much lower rate of colonisation. However, the other four species showing an intermediate rate of spreading were recorded for the first time both 70 years ago (Dreissena polymorpha and Ferrissia fragilis) and less than 20 years ago (Gyraulus parvus and Sinanodonta woodiana). Large rivers serve as the most important corridors for the spreading of non-native species, with a significant association between the number of non-native species recorded and the distance from the 8^th- and 9^th-order rivers.

This study describes the growth of individuals in a population of Buccinanops cochlidium (Nassariidae) through the identification of the best-fitting growth model based on field tag-recaptured experimental data. A total of 48 individuals (8.6% of total tagged snails) were recaptured after 2 to 25 months, representing a remarkable proportion for a field experiment with infaunal organisms. The sex ratio was not different from 1:1. Males measured between 63.4 and 89.0 mm (n = 25), while females measured between 50.9 and 103.2 mm (n = 23) in shell length. The maximum annual length increment obtained was 35.74 mm, mean annual length increment was 4.51 and 8.43 mm for females and males, respectively. Because no statistically significant differences were found between male and female growth increments, a single growth model was fitted to the entire data set.

Regarding individual growth modeling, the inverse Logistic (iLog) model adequately described the pattern in the data, but showed heteroscedasticity. A refitting of iLog using weighted least squares, weighted inverse Logistic (iLog*), better fit the data (and agrees with biological knowledge of B. cochlidium) than the inverse Logistic (iLog), exponential (Exp), von Bertalanffy (vB) and Gompertz (Gz) models. Estimated parameters for the iLog* model were MaxΔL: 27.83, L₅₀: 69.89, L₉₅: 93.36. The results of this study are valuable for assessment of snail fisheries in Patagonia and suggest fisheries management policies for a sustainable future of this potential stock prior to extensive exploitation.

A taxonomic revision of the family Anatomidae from Brazil led to the discovery of nine species, four of which are new. This contrasts with only two species previously recorded: Anatoma aedonia (Watson, 1886) and Anatoma proxima (Dall, 1927). The lectotype designation for A. aedonia by Geiger (2012) has clarified the identity of this taxon, which is now considered a rare species, mainly from deep waters. The holotype of A. proxima is lost (Geiger, 2012), and some very similar taxa occur sympatrically in the western Atlantic; accordingly, we designate here a neotype for Scissurella proxima and redescribe it, re-evaluating its shell variability and radula morphology. The review of a large amount of shells in malacological collections in Brazil, including material from recent dredging along the southeastern coast, revealed the occurrence of seven additional species: Anatoma americana Bandel, 1998, synonymized under A. proxima by Geiger (2012), is herein considered a valid species; Anatoma atlantica (Bandel, 1998); and Anatoma alternatisculpta Geiger & McLean, 2010. Those three species were only known form the Caribbean region and are now recorded from Brazil. Four new species are described: Anatoma espiritosantense, n. sp., diagnosed by a trochiform to globose shell with irregularly distributed axial ribs over the shoulder, is restricted to the southeastern coast of Brazil; Anatoma campense, n. sp., characterized by a biconical shell, a well projecting keel of the selenizone, and a strong spiral cord on teleoconch I, is rare, restricted to the south-southeastern coast of Brazil; Anatoma brychia, n. sp., the deepest species from Brazil (∼ 1,900 m), is diagnosed by its longer teleoconch I, with 1.25 whorls and tiny sculpture; Anatoma copiosa, n. sp., is abundant, with several records from the southeastern coast of Brazil; it is distinguished from A. atlantica by the very faint axial ribs on the base of the shell. An eleventh likely undescribed taxon, Anatoma sp., is recorded based on a single shell, distinguished by a globose shell, faint spiral sculpture, and long teleoconch I.

Among the multifaceted environmental factors, the bacterial community ingested with soil and food might play an important role in physiological processes of terrestrial gastropods, with consequences on population dynamics and species distribution patterns. Therefore, we investigated the bacterial gut community structure and seasonal dynamic in three populations of the protected endangered land snail Helix pomatia. The PCR-DGGE fingerprinting analysis followed by Nonmetric Multidimensional Scaling (NMDS) showed that Gamma-and Alphaproteobacteria were common to all populations, while Mollicutes and Betaproteobacteria were population specific. Allochthonous strains might be transiently abundant in the gut of foraging snails with respect to habitat conditions. Autochthonous strains were permanently present in the gut, even after expulsion of the gut content at hibernation beginning. Some of these permanent strains are known to have ice-nucleating activity, which is consistent with the limited cold hardiness in this species. Snails that did not enter hibernation despite being exposed to winter conditions had a poor bacterial community. In conclusion, the bacterial community structure differed between habitats and physiological states, and might be important for physiological processes and survival. Further studies should focus on the individual variation in bacterial community and investigate how it is affected by environmental changes.