Most previous studies identifying Panopea generosa and P. globose have used non-rigorous visual methods as well as older shell measurement techniques. Newer mathematical methods based on shell shape variation allow for more accurate identification of clam species, as well as modeling of phenotypic differences due to environmental effects in populations in different sites. Interspecific shell morphology for two Mexican geoduck clam species was analyzed from a total of five sites off both coasts of the Baja California peninsula. In addition, intraspecific analyses of shell morphology were conducted for one of the species, P. globosa, at four sites along its reported distribution. Two approaches were employed for the analyses: a novel approach based on radiating lines to characterize shell outlines, and a more traditional approach using internal shell landmarks. In general, the novel approach afforded greater fidelity in distinguishing inter- and intraspecific variation. Our results from both methods agree with original species descriptions, and showed that Bahía Magdalena geoducks are P. globosa, thus revealing a wider distribution than previous reports for this species. The outline and internal scars were highly discriminant between the two species. Shell shape of P. generosa was also less variable than that of P. globosa. Intraspecific analyses of P. globosa shell shape suggest an adaptive or phenotypic response to environmental conditions at each site. Our results may also be indicative of reproductive isolation between Pacific P. globosa at Bahía Magdalena and conspecifics in the Gulf of California.

The New Zealand mud snail, Potemopyrgus entipoderum (Gray, 1843), is recognized as a successful invader of aquatic environments in Australia, Europe, Japan, North America and western Asia. To date, a long-term survey on the occurrence of P. entipoderum (including its initial dispersal, establishment and integration) both in mining subsidence reservoirs and an adjacent river in Poland has not been carried out. The objectives of this survey were to analyze the environmental factors that influence the occurrence of P. entipoderum in relation to mollusc communities in mining subsidence reservoirs affected by coal mine output in terms of initial dispersal and the establishment of self-sustaining populations in the new habitat, to analyze annual variations in the densities and shell height of P. entipoderum in relation to the different types of substratum, and to determine the number of embryos in the brood pouch per female at the integration stage (phase). During the years 1993–2008, seven mining subsidence reservoirs that have different water sources and a part of the Mleczna River were investigated.

From 1997 to the present, P. entipoderum has been eudominant in mollusc communities both in coal mining subsidence reservoirs, which receive water from the mine dewatering system and in the river. Based on a redundancy analysis (RDA), the conductivity of water and the concentration of nitrates were the parameters most associated with the distribution of mollusc species, including P. entipoderum. The relation between the species and these environmental variables was statistically significant.

These results do not suggest that the integration of P. entipoderum has negatively influenced the occurrence of other mollusc species either in the mining subsidence reservoirs or in the Mleczna River, probably due to smaller densities compared with a survey of the western United States, where P. entipoderum has a strong influence on aquatic ecosystems and restricts the occurrence of native macroinvertebrates. Potemopyrgus entipoderum has established itself in these mining subsidence reservoirs and is integrated into the local biota without any major negative effects (e.g., extirpations) on the communities being invaded.

Pomecee canaliculata is a freshwater snail native to South America that together with some congeners has invaded natural wetlands and paddy fields in several continents, especially in Southern Asia. The high variability in shape, color and thickness of Pomacea shells and the sexual dimorphism in many traits blurs the species limits and hampers taxonomic identification. Ecological characterization of habitat productivity based on shells was previously proposed for P. canaliculata but was never methodically explored. Using full siblings of P. canaliculata, we studied the effects of different chronic levels of food availability (from 100% to 20% of daily ingestion rate) on shell shape, somatic indices and sexual dimorphism at maturity. The eight specific morphometric and somatic indices investigated showed different combinations of the effects of food availability and sex: changes related to food availability but independent of sex (relative aperture width), sexual dimorphism independent of food availability (shell globosity and relative aperture expansion), and changes related to food availability and sex, without a noticeable interaction (organic density); a significant interaction that increases the intersexual differences when food availability increases was detected in some indices (relative operculum weight, overall shell density and relative shell investment). The organic density can be used as a condition index to indicate the actual trophic availability in the field, although it should be estimated separately for males and females. The relative aperture width and the overall shell density can be used as paleo-environmental indicators of productivity, as they can be measured on empty shells. The effect of water alkalinity should be taken into account should the latter be used.

Few studies have documented chiton growth rates, and lifespans for most chiton species remain unknown. This study presents the first size-at-age and longevity estimates for Cryptochiton stelleri and Katharina tunicata, two of the largest known species of chitons. Age estimates were based on growth ring counts obtained by cross-sectioning and polishing valves. This process alone showed clear growth rings in shell plates of K. tunicata. Valves of C. stelleri did not show conspicuous growth rings in cross section, so the acetate peel technique was used to highlight growth bands. Linear growth in terms of body length and shell width approached an asymptote in both species and was described with the von Bertalanffy growth function. Both C. stelleri and K. tunicata displayed indeterminate growth with regard to tissue weight and shell weight, continuing to maintain a steady growth rate throughout their lifespans. The oldest K. tunicata specimen was estimated to be 17 years old. The oldest C. stelleri was estimated to be 40 years old, making it the longest-lived chiton species known.

The anatomy and evolution of the radular apparatus in predatory marine gastropods of the superfamily Conoidea is reconstructed on the basis of a molecular phylogeny, based on three mitochondrial genes (COI, 12S and 16S) for 102 species. A unique feeding mechanism involving use of individual marginal radular teeth at the proboscis tip for stabbing and poisoning of prey is here assumed to appear at the earliest stages of evolution of the group. The initial major evolutionary event in Conoidea was the divergence to two main branches. One is characterized by mostly hypodermic marginal teeth and absence of an odontophore, while the other possesses a radula with primarily duplex marginal teeth, a strong subradular membrane and retains a fully functional odontophore. The radular types that have previously been considered most ancestral, “prototypic” for the group (flat marginal teeth; multicuspid lateral teeth of Drilliidae; solid recurved teeth of Pseudomelatoma and Duplicaria), were found to be derived conditions. Solid recurved teeth appeared twice, independently, in Conoidea — in Pseudomelatomidae and Terebridae. The Terebridae, the sister group of Turridae, are characterized by very high radular variability, and the transformation of the marginal radular teeth within this single clade repeats the evolution of the radular apparatus across the entire Conoidea.

By traditional classification, there are five Cyclotus taivanus subspecies in the low mountainous area of Taiwan and Okinawa: C. taivanus adamsi, C. t. dilatus, C. t. diminutus, C. t. peraffinis, and C. t. taivanus. The molecular phylogenetic relationships of this group have never been discussed. In order to investigate the relationships between C. taivanus ssp., we sequenced part of the mitochondrial COI and the 16S rRNA gene from 26 sampling sites. We also measured 9 shell traits for morphological analysis. Even though morphological PCA analysis revealed a more or less continuous distribution of individuals in morph-space, the two highly divergent haplotype clades in molecular analysis indicated the presence of two independently evolving lineages. Our results indicated that the sequence divergence between the two independent clades was almost as high as that among other Cyclophoridae species found previously. Therefore, from the viewpoint of taxonomy, C. t. adamsi should be considered a valid species, and we here raise the current taxon to a full species: C. adamsi. By environmental analysis, temperature was found to be a limiting factor in the distribution of C. adamsi and the C. taivanus group (C. t. dilatus, C. t. diminutus, C. t. peraffinis, and C. t. taivanus). The ecological divergence is probably a rule of speciation in our case. The PLS (Partial least square) analysis results indicate that phenotypic plasticity may be a key element of the variable shell in the C. taivanus group. The speciation process is not complete among the C. taivanus group, and the adaptation to climatic pressure continues to be a rule of the speciation process.

Seventeen species of ancylids occur in southern South America, seven in Argentina. Anancylus rosanae, n. gen. et sp., is described based on characters of the shell, radula, jaw and reproductive system. This new genus, found in the upper Iguazú River rapids, Iguazú National Park, Misiones Province, Argentina, has the following distinctive features: patelliform shell, usually low, with a circular apex located at the anterior end of the shell; three adductor muscles: large posterior (twice the length of the anterior muscles) and two tear-shaped anterior; adhesive epithelium between the two anterior muscular insertions; no difference between the plates of the jaw.

The family Chilinidae in Argentina has been thought to include 17 species, most being found in Patagonia. All the original descriptions were based mainly on shell characteristics. The present work contains information about the shells, the radulae, and the reproductive and nervous systems in Chilinidae species from northwestern region, along with the description of a new species. This new species from Tucumán Province is characterized by the shell and a penial morphology that includes pustules and transverse lamellae with irregular contours and longitudinal folds. The taxonomic position of Chilina tucumanensis is also reviewed and a redescription of Chilina portillensis is provided. Additional information is provided on their habitats and distributions. These records in northwestern Argentina now increase the total number of species of Chilina inhabiting Argentina to 19.

Recent molecular studies on dreissenid species in southern Europe found that Dreissena blanci (Westerlund, 1890) resides in several lakes where previous studies identified it as Dreissena polymorpha (Pallas, 1771). Because D. blanci seems to constitute a “new record” in the Balkans, the present study provides novel information on the biology and ecology of its planktonic larvae in four natural lakes and one reservoir located in western Greece. Dreissena blend larvae were present in all lakes and their abundance varied between 3.4 and 440 ind. I-1. The larvae were present all year round, having greater abundance in spring and summer and lesser in winter. The species seems to have an extended reproductive period from early spring until late summer. The larvae are distributed mainly in the upper 20 m of the deep lakes Amvrakia and Trichonis, while are aggregated close to or within the thermocline layer in the latter lake. A size-specific depth distribution was observed, with larger larvae residing in deeper strata during the stratification period. Temperature appears to be the most important parameter affecting the abundance variation of the larvae in the natural lakes, while water retention time is the major parameter in Stratos reservoir. In contrast, the soft, muddy substratum of Lake Lysimachia seems to be the inhibiting factor for the existence of a viable population here. The great similarities in larval ecology between D. blanci and D. polymorpha must be taken into consideration, as D. blanci could become another invasive species in freshwater ecosystems. Therefore, more research is required on the life cycle of this species, and the ecological and economic consequences of its presence in lakes and reservoirs of southeastern Europe.

We studied snail assemblages at 39 plots in hay meadows of the White Carpathians, Czech Republic. We recorded snails quantitatively in 1 m² quadrats, along with vegetation and several measured variables in the same plots in order to investigate the influence of selected environmental factors on meadow snail species composition and richness. The study aimed to determine the extent to which it is possible to use vegetation as a predictor of land snail composition by comparing the predictive power of three groups of variables: (i) measured variables and climatic factors, (ii) vegetation, and (iii) Ellenberg indicator values for plants estimated from plant composition.

Detrended correspondence analysis revealed that both snail and plant assemblages were strongly affected by the main environmental gradient running from calcium-poor, wet and cool upland sites to calcium-rich, dry and warm lowland sites. The main changes of vegetation and snail species composition were highly correlated (r_s = 0.77, p < 0.001). Soil calcium content and moisture were the most important factors, which explained most of the variation both in the snail and plant assemblages. The interaction of these two factors was even stronger but it was not possible to separate the influence of particular variables on snail species composition and to determine which of these variables made the greatest contribution to the observed pattern. Using the variance partitioning approach, we found that most variation in snail species data was jointly explained by all three groups of variables (i.e., measured variables and climatic factors, vegetation, and Ellenberg indicator values for plants). Even so, the net effects of both vegetation and measured variables were significant. This indicates that vegetation could describe important environmental controls of land snail distribution, even those that are difficult or even impossible to measure directly. We conclude that vegetation composition can be very useful predictor in snail community ecology studies.

The population structure, particularly growth, age, mortality and somatic production of the olivid snail Olivancillaria deshayesiana were investigated. Annual formation of internal shell growth marks was confirmed by the record of stable oxygen isotopes in the shell, which reflects seasonal patterns of water temperature. A von Bertalanffy growth model fitted to 81 size-at-age data pairs, indicating that O. deshayesiana may attain 31 mm SL in about 10 years. The estimated total mortality Z and natural mortality M were 0.651 y-¹ and 0.361 y-¹, respectively. Fishing mortality F was 0.290 y-¹, and the exploitation rate E was 0.445, indicating that this population was not overexploited at the time of the study. However, this situation may well change in the future, since the important prawn and shrimp fisheries (in intensity and scale) in the Mar del Plata area (38°20′S, 57°37′W) may indirectly affect the exploitation status of the studied population.