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Freshwater mollusc diversity has repeatedly been found to peak in lowland stagnant waters, which are highly exposed to human-made degradation and the spread of non-native species. Despite the increasing loss of these habitats, little is known about the main predictors of their mollusc diversity patterns. Therefore, we aimed to determine the environmental drivers of mollusc assemblage variation between and within sites by sampling 62 water bodies in the Dyje River floodplain (south-eastern Czechia). We measured 14 environmental variables, categorized as site-specific or plot-specific. Species richness and abundances were analysed by GLM and GEE; species compositional variance was assessed by NMDS and db-RDA ordinations. Mollusc species richness, ranging between 0 and 15 species per site, and abundance sharply decreased towards high trophy sites, with the chlorophyll-a concentration and water pH highly correlated with species counts. Species compositional variation was driven mainly by water trophy and the quality of organic detritus. Site heterogeneity turned out to significantly control local assemblages of molluscs, while the presence of individual species seemed to be filtered by site trophy and the shoreline length. Thus, to maintain high regional diversity of aquatic molluscs in lowland agricultural landscapes, the presence of low trophy sites seems to be essential.

Bivalve molluscs comprise 20,000 species occupying a wide diversity of marine habitats. As filter feeders and detritivores they act as ecosystem engineers clarifying water, creating reefs, and protecting coastlines. The global decline of natural oyster reefs has led to increased restoration efforts in recent years. Bivalves also play an important role in global food security contributing to >20% of worldwide aquaculture production. Despite this importance, relatively little is known about bivalve evolutionary adaptation strategies. Difficulties previously associated with highly heterozygous and repetitive regions of bivalve genomes have been overcome by long-read sequencing, enabling the generation of accurate bivalve assemblies. With these resources we have analyzed the genomes of 32 species representing each molluscan class, including 15 bivalve species, to identify gene families that have undergone expansion during bivalve evolution. Gene family expansions across bivalve genomes occur at the point of evolutionary pressures. We uncovered two key factors that shape bivalve evolutionary history: expansion of bivalvia into environmental niches with high stress followed by later exposure to specific pathogenic pressures. The conserved expansion of protein recycling gene families we found across bivalvia is mirrored by adaptations to a sedentary lifestyle seen in plants. These results reflect the ability of bivalves to tolerate high levels of environmental stress and constant exposure to pathogens as filter feeders. The increasing availability of accurate genome assemblies will provide greater resolution to these analyses allowing further points of evolutionary pressure to become clear in other understudied taxa and potentially different populations of a single species.

River floodplain ecosystems host one of the highest freshwater molluscan biodiversity on Earth. However, multiple human disturbances, such as loss of hydrological connectivity and deterioration of water quality, are seriously threatening most floodplain lakes throughout the world. Given the high imperilment rate of freshwater molluscs but the scarcity of studies examining the anthropogenic effects on this fauna, we test the response of mollusc assemblages to river-lake disconnection and eutrophication in 30 lakes in the Yangtze River floodplain, China. The species richness of entire Mollusca, Gastropoda and Bivalvia and 6 dominant families were all much lower at disconnected lakes than that in connected lakes, and decreased with increasing water eutrophication. The assemblage structure differed significantly among four lake groups for datasets based on entire Mollusca, Gastropoda and Bivalvia, indicating the serious impacts of hydrological disconnection and eutrophication. Moreover, the connected lakes showed significantly lower values of average taxonomic distinctness (Δ+) but higher values of variation in taxonomic distinctness (Λ+) than disconnected lakes. Such variations were triggered by the extirpation of congeneric and endemic species (mainly from families Unionidae and Viviparidae), which giving a waring of the loss of mollusc endemism in this region. In general, the present study showed that river-lake disconnection and deterioration of water quality resulted in serious biodiversity declines of both gastropods and bivalves in the Yangtze River floodplain lakes. A systematic approach including restoration of river-lake connectivity and habitats and improvement of water quality should be implemented in the conservation planning in this large river floodplain.

International audience; The poor understanding of changes in mollusc ecology along rivers, especially in West Africa, hampers the implementation of management measures. We used a self–organizing map, indicator species analysis, linear discriminant analysis and a random forest model to distinguish mollusc assemblages, to determine the ecological preferences of individual mollusc species and to associate major physicochemical variables with mollusc assemblages and occurrences in the Sô River Basin, Benin. We identified four mollusc assemblages along an upstream–downstream gradient. Dissolved oxygen (DO), biochemical oxygen demand (BOD), salinity, calcium (Ca), total nitrogen (TN), copper (Cu), lead (Pb), nickel (Ni), cadmium (Cd) and mercury (Hg) were the major physicochemical variables responsible for structuring these mollusc assemblages. However, the physicochemical factors responsible for shaping the distribution of individual species varied per species. Upstream sites (assemblage I) showed high DO and low BOD and mineral compounds (i.e., TN, salinity, and Ca), which are primarily responsible for structuring the occurrences of bivalves (Afropisidium pirothi, Etheria elliptica, Sphaerium hartmanni) and the gastropod Lanistes varicus. Sites along the middle reach (assemblage II) were characterised by a high degree of organic pollution but low heavy metal pollution; we detected no specific mollusc indicator species. Downstream sites (assemblage III) displayed high mineral and heavy metal concentrations and a fauna without specific indicator species. Finally, downstream sites associated with brackish water (assemblage IV) displayed important levels of organic and heavy metal pollution. These sites are dominated by diverse gastropods (i.e., Bulinus spp., Gabbiella africana, Indoplanorbis exustus, Pachymelania fusca, Radix natalensis, Stenophysa marmorata and Tympanotonos fuscatus). Our results highlight that mollusc communities in the Sô River Basin are structured by key physicochemical variables related to the river–estuary continuum. Habitats that are progressively more downstream are confronted with increasing anthropogenic stress. Conservation and management plans should focus on downstream habitats.

Most molluscs possess shells, constructed from a vast array of microstructures and architectures. The fully formed shell is composed of calcite or aragonite. These CaCO3 crystals form complex biocomposites with proteins, which although typically less than 5% of total shell mass, play significant roles in determining shell microstructure. Despite much research effort, large knowledge gaps remain in how molluscs construct and maintain their shells, and how they produce such a great diversity of forms. Here we synthesize results on how shell shape, microstructure, composition and organic content vary among, and within, species in response to numerous biotic and abiotic factors. At the local level, temperature, food supply and predation cues significantly affect shell morphology, whilst salinity has a much stronger influence across latitudes. Moreover, we emphasize how advances in genomic technologies [e.g. restriction site-associated DNA sequencing (RAD-Seq) and epigenetics] allow detailed examinations of whether morphological changes result from phenotypic plasticity or genetic adaptation, or a combination of these. RAD-Seq has already identified single nucleotide polymorphisms associated with temperature and aquaculture practices, whilst epigenetic processes have been shown significantly to modify shell construction to local conditions in, for example, Antarctica and New Zealand. We also synthesize results on the costs of shell construction and explore how these affect energetic trade-offs in animal metabolism. The cellular costs are still debated, with CaCO3 precipitation estimates ranging from 1-2 J/mg to 17-55 J/mg depending on experimental and environmental conditions. However, organic components are more expensive (~29 J/mg) and recent data indicate transmembrane calcium ion transporters can involve considerable costs. This review emphasizes the role that molecular analyses have played in demonstrating multiple evolutionary origins of biomineralization genes. Although these are characterized by lineage-specific proteins and unique combinations of co-opted genes, a small set of protein domains have been identified as a conserved biomineralization tool box. We further highlight the use of sequence data sets in providing candidate genes for in situ localization and protein function studies. The former has elucidated gene expression modularity in mantle tissue, improving understanding of the diversity of shell morphology synthesis. RNA interference (RNAi) and clustered regularly interspersed short palindromic repeats - CRISPR-associated protein 9 (CRISPR-Cas9) experiments have provided proof of concept for use in the functional investigation of mollusc gene sequences, showing for example that Pif (aragonite-binding) protein plays a significant role in structured nacre crystal growth and that the Lsdia1 gene sets shell chirality in Lymnaea stagnalis. Much research has focused on the impacts of ocean acidification on molluscs. Initial studies were predominantly pessimistic for future molluscan biodiversity. However, more sophisticated experiments incorporating selective breeding and multiple generations are identifying subtle effects and that variability within mollusc genomes has potential for adaption to future conditions. Furthermore, we highlight recent historical studies based on museum collections that demonstrate a greater resilience of molluscs to climate change compared with experimental data. The future of mollusc research lies not solely with ecological investigations into biodiversity, and this review synthesizes knowledge across disciplines to understand biomineralization. It spans research ranging from evolution and development, through predictions of biodiversity prospects and future-proofing of aquaculture to identifying new biomimetic opportunities and societal benefits from recycling shell products. FCT: UID/Multi/04326/2019; European Marine Biological Research Infrastructure Cluster-EMBRIC (EU H2020 research and innovation program) 654008; European Union Seventh Framework Programme [FP7] ITN project 'CACHE: Calcium in a Changing Environment' under REA 60505; NERC Natural Environment Research Council NE/J500173/1 info:eu-repo/semantics/publishedVersion

Lake Lanao on Mindanao island is the largest freshwater lake in the Philippines and may represent one of the few ancient lakes in Southeast Asia. This lake’s fauna is best known for its endemic cyprinid fishes that have been nearly driven to extinction through various anthropogenic actions. In contrast, only little is known about Lake Lanao’s invertebrate fauna and its placement within related Southeast Asian taxa. We here focus on the diversity in freshwater molluscs, particularly the morphologically diverse viviparid gastropods, and provide first genetic insights into this group in order to test whether the morphological variability observed is also reflected by corresponding genetic variation. Mitochondrial sequence data indicate that these viviparids form a monophyletic group comprising morphologically distinct and partly genetically different (morpho)species. Both the high diversity found in cyprinid fishes and viviparid gastropods together with the geological and tectonic evolution of Mindanao suggest that Lake Lanao may have originated more than 100,000 years ago and is thus indeed an ancient lake. However, its fauna is under continuous threat not least from the introduction of non-native species, and the development and implementation of sustainable conservation strategies is direly needed.

Floodplain disconnection (FDC) has become a profound threat to many large river floodplains. Despite current researches examining the impacts of FDC on aquatic biodiversity, little is known about how FDC affected freshwater molluscs from multifaceted biodiversity perspectives, especially at long-term temporal scales. We selected the 7 lakes in the Yangtze River floodplain to evaluate how river-lake disconnection impacted taxonomic, functional and phylogenetic alpha and beta diversity of molluscan assemblages during past 60 years. Our results showed that five disconnected lakes (DLs) experienced dramatic decline in species richness (decreased by 62.4%) and functional richness (54.6%) but increases in functional evenness (20.0%) and Δ+ (5.5%) after disconnection. Whereas such temporal changes in the two connected lakes (CLs) were much slighter. Somewhat unexpectedly, the overall taxonomic (increased by 7.0%) and phylogenetic (12.2%) dissimilarities only slightly increased through time, due to opposite changes in the turnover (40%-50% decrease) and nestedness-resultant (100%-110% increase) components through time. The functional nestedness experienced more significant increase (162.0%), leading to relatively considerable increase in functional overall dissimilarity (64.0%). Such opposite changes in multifaceted turnover and nestedness distinctly modified the structure of beta diversity and highlight the conservation priority of CLs keeping relative high levels of biodiversity. The overall correlations between changes in both alpha and beta diversity among different facets were generally weak, indicating the different diversity facets would provide complementary information for biodiversity conservation and restoration. Thus, we recommended incorporating functional and phylogenetic information of species into traditional taxonomy-based approaches in large river floodplains studies.

The Alps are an important hotspot of species diversity and endemism, as well as a presumed glacial refugium of several species’ groups including land snails. The recent ranges of Alpine endemics are well known, but their fluctuations during the postglacial period mirroring local climate changes are understudied. By analysing five Late Glacial and Holocene mollusc successions from two areas in the southernmost part of the Bohemian Massif (Czech Republic) situated about 100 km north of the Alps, we reveal details of these fluctuations. The Alpine endemic rocky dweller Chilostoma achates had reached the southern part of the Bohemian Massif already in the Late Glacial and disappeared in the Mid-Holocene canopy forest optimum. On the contrary, the northern boundaries of Alpine canopy forest epigeic snails extended further north than today at the turn of the Middle and Late-Holocene, pointing to a more favourable forest microclimate. The earliest known occurrences of several temperate canopy forest central European species, especially Causa holosericea and Discus perspectivus, imply the role of different areas in the Alps as their glacial refugia.

The Caspian Sea is an evolutionary island whose rich and endemic fauna have evolved in partial isolation over the past two million years. Baseline studies of pre-20th Century communities are needed in order to assess the severity of the current Caspian biodiversity crisis, which mostly involves invasive species. An inventory of late Holocene shelly assemblages (c. 2000–2500 cal yr BP) from outcrops in and around Great Turali Lake (Dagestan, Russia) shows a diverse nearshore community consisting of 24 endemic Caspian species, two invasive species and two Caspian native species that lived in a shallow embayment with mesohaline salinities of circa 5–13 psu (parts per thousands). This pre-crisis Holocene Caspian mollusc community serves as a baseline against which modern mollusc diversity measurements can be evaluated. Examination of faunas from similar environments living today and in the past illustrates the dramatic changes in nearshore communities during the 20th Century. Our study identifies a habitat that may have served as a refuge, but that is currently under threat from invasive species. The severity of the Caspian biodiversity crisis is comparable with other well-known biodiversity crises in semi-isolated ecosystems such as the cichlid fish communities of Lake Victoria, Africa.

Organic matrix proteins play an important role in the biomineralization of mollusc shells. We have identified and characterized a novel matrix protein, namely hic74, isolated from the mantle of the freshwater mussel Hyriopsis cumingii. The hic74 gene encodes a 850 amino acid protein that is rich in alanine (ala, 30.8%), glycine (gly, 25.8%) and serine (ser, 10.6%), with ala mainly existing in poly-ala forms within the ala/gly-rich regions. Quantitative PCR expression analysis demonstrated that hic74 was specifically amplified from the mantle and in situ hybridization showed a strong signal in the epithelial cells in the pallial region of the mantle. Lower levels of expression were detected during the early stages of pearl sac formation but increased and remained constant during nacreous layer formation suggesting that hic74 might be involved in this process.

The Western Carpathian Mountains have been attracting palaeoecologists for a long time, recently mainly to seek direct evidence of northern cryptic refugia in this region. We investigated a rich Holocene mollusc record in the White Carpathian Mountains, capturing a gradual development of forest malacofaunas under stable environmental conditions. To obtain precise data about colonization and extinction events for particular species, we applied a high-resolution depth-age model. Early Holocene assemblages revealed both the presence of Early Holocene relics and an early appearance of closed-canopy forest species that might indicate a cryptic glacial refugium nearby. Many forest species peaking at the Holocene forest optimum, including anthropophobic arboricole land snails (Bulgarica cana and Macrogastra borealis), were present since the Early Holocene as well. After 4000 cal. a BP, forest vegetation composition changed, and the environment became less suitable for woodland snails (i.e. calcium and moisture level decreased). This change was indicated by the disappearance of many sensitive forest species. Most of the exclusively forest species reappeared during the early Middle Ages because of dense beech forest development. However, in the late Middle Ages, the study site was deforested and became an open wetland. The existence of pollen, plant macro-remains, and stable isotope data allowed us to compare the recorded mollusc succession to the signal derived from these proxies. Hence, we propose that the Mituchovci site should be considered a model for the Holocene development of mollusc woodland faunas in the (Outer) Western Carpathians and one of the main reference sites for central European mollusc succession.

The taxonomic and ecological composition of the autochthonous land mollusc fauna in different parts of the plain Ukraine was analyzed on the basis of the personal data, collection materials of the State Museum of Natural History of the NAS of Ukraine in Lviv as well as numerous literature sources. Excluding representatives of the genus Helicopsis, the taxonomy and species composition of which in the territory of Ukraine still require clarification, and the steppe part of the Crimean peninsula, in four landscape zones of Ukraine, currently, a total of 109 species of land molluscs, which are autochthonous for at least part of the analyzed territory, are registered. The maximum species diversity (103 species and 2 representatives of the genus Helicopsis) is recorded in the zone of deciduous forests, followed by the right-bank part of the forest-steppe zone. The smallest number of the autochthonous species of land molluscs was noted for the right-bank part of the steppe zone. Within the Ukrainian Polesie and the forest-steppe zone of Ukraine, the taxonomic diversity of land molluscs decreases from west to east. The number of the registered autochthonous species decreases, respectively, by 1.5 and 1.7 times, and the generic diversity by 1.3 and 1.5 times. In the steppe zone, the main centre of the species diversity is the Donetsk Upland, located in the east of the country. In taxonomic and ecological composition, land mollusc complexes of the right-bank part of the forest-steppe zone are closer to the zone of deciduous forests, in its left-bank part – to the left-bank steppe. In general, the spatial differentiation of land mollusc fauna in the plain territories of Ukraine is more strongly associated not with the boundaries of landscaped zones, but with the location of these territories with respect to the Dnieper bed and with some uplands, where the species diversity of land molluscs of the zone of deciduous forests and forest-steppe zone (Podolian Upland) and the steppe zone (Donetsk Upland) is concentrated.

The present study is the first attempt to study the taxonomy and diversity of molluscan fauna from freshwater bodies of Chandigarh (U.T.) and Ghaggar River flowing on its southeast border. A total of 24 molluscan species (17 gastropods, 3 bivalves and 4 land snails) were collected from the selected sites. Physa acuta was found showing ubiquitous occurrence along with its maximum abundance in all water bodies followed by Melanoides tuberculata. Less biodiversity and the presence of tolerant species indicated that majority of the water bodies under study are under a great threat of degradation. The results of this study will contribute to the knowledge of the regional malacofauna along with identification of the sites facing natural and human interferences.

Habitat structure increases richness and abundance of species in many environments by providing easy access to resources and refuge from predators. In coral reefs, corals are habitat for many organisms and differences in their morphologies may act as variation in habitat structure for associated fauna. In the present study, we investigate whether there are differences in the richness and abundance of molluscs associated with three species of Mussismilia corals exhibiting different growth morphologies, in two different reef areas of the Bahia state. Mussismilia harttii has a meandroid pattern, M. hispida is a massive coral, M. braziliensis also has a massive growth pattern with crevices at the corallum base. Coral characteristics were measured in the laboratory. Significant differences were identified for richness among coral species – higher values were reported in colonies of M. harttii and no significant statistical differences were observed between M. braziliensis and M. hispida. Considering the density of associated molluscs, the same pattern was found. The results are in accordance with previous studies and indicate the importance of M. harttii as a key habitat to maintain a richer and more abundant associated fauna. The internal volume of interpolypal space is an important factor influencing the richness and density of associated species.

There is limited documentation on the status and dynamics of fished marine shelled mollusc species in many countries. Some of the challenges are due to obscure documentation of species, extensive unregulated and unrecorded fishing and unawareness of drivers behind declining stocks. The lack of understanding makes it difficult to formulate effective management plans. Here, we assess the fishers’ perceptions on changes in abundance of targeted marine shelled mollusc species and status of associated fished habitats. We interviewed 132 marine shelled mollusc gleaners (fishing by walking) at five sites in coastal Kenya. We established that a multispecies marine shelled mollusc fishery is present in Kenya and that this fishery is conducted by both women and men. We distinguished 158 different shelled mollusc species being targeted. The gleaners perceived a temporal decline of gleaned species. The main causes for the decline were perceived to be overfishing of shells, elevated sea-surface temperature and habitat destruction. The more experienced gleaners perceived a greater decline indicating a baseline shift in perceptions. Our findings suggest that local ecological knowledge is useful to understand historic changes in fisheries lacking long-term scientific data. Furthermore, it highlights the potential benefits of a collaboration between ecologists and gleaners to improve our understanding of the status and dynamics of fishing of marine shelled molluscs as well as other types of fishing.

The purpose of the present study was to perform bioinformatic analysis of crystallin diversity in aquatic molluscs based on the sequences in the NCBI Protein database. The objectives were as follows: (1) analysis of some physical and chemical properties of mollusc crystallins, (2) comparison of mollusc crystallins with zebrafish and cubomedusa Tripedalia cystophora crystallins, and (3) determination of the most probable candidates for the role of gastropod eye crystallins. The calculated average GRAVY values revealed that the majority of the seven crystallin groups, except for μ- and ζ-crystallins, were hydrophilic proteins. The predominant predicted secondary structures of the crystallins in most cases were α-helices and coils. The highest values of refractive index increment (dn/dc) were typical for crystallins of aquatic organisms with known lens protein composition (zebrafish, cubomedusa, and octopuses) and for S-crystallin of Pomacea canaliculata. The evolutionary relationships between the studied crystallins, obtained from multiple sequence alignments using Clustal Omega and MUSCLE, and the normalized conservation index, calculated by Mirny, showed that the most conservative proteins were Ω-crystallins but the most diverse were S-crystallins. The phylogenetic analysis of crystallin was generally consistent with modern mollusc taxonomy. Thus, α- and S-, and, possibly, J1A-crystallins, can be assumed to be the most likely candidates for the role of gastropod lens crystallins.

The aims of this study were to explore mollusc assemblages associated with the non-indigenous macroalga Asparagopsis armata, to compare them with those on other macroalgae at the study region and to explore potential differences on mollusc assemblages between two regions in the Atlantic coast of the Iberian Peninsula, where A. armata is present. To achieve this, at each region, four intertidal shores were sampled. Twenty-nine mollusc species were reported and thus, A. armata harboured similar or higher diversity than other annual macroalgae in this area. When compared with perennial macroalgae, results depend on the species and studied area. Moreover, significant differences in structure of mollusc assemblages between the two studied regions were found. However, these were due to differences in the relative abundance of species rather than the presence of exclusive species at each region. © 2018 Elsevier We would like to thank the great support of Dr. Juan Moreira (Universidad Autónoma de Madrid, Spain) during sampling at the centre and south of Portugal and his critical comments on the first draft of this manuscript. We are also grateful to two anonymous referees for helpful comments and suggestions, which greatly improved this paper. This research was partially supported by the Strategic Funding UID/Multi/04423/2013 through national funds provided by FCT – Foundation for Science and Technology and European Regional Development Fund (ERDF) , in the framework of the programme PT2020. During this study, P. Veiga ( SFRH/BPD/81582/2011 ) and M. Rubal ( SFRH/BDP/104225/2014 ) were supported by postdoctoral grants awarded by Fundacão para a Ciência e Tecnologia (FCT, Portugal) . Appendix A

Climate change and ocean acidification are likely to have a profound effect on marine molluscs, which are of great ecological and economic importance. One process particularly sensitive to climate change is the formation of biominerals in mollusc shells. Fundamental research is broadening our understanding of the biomineralization process, as well as providing more informed predictions on the effects of climate change on marine molluscs. Such studies are important in their own right, but their value also extends to applied sciences. Biominerals, organic/inorganic hybrid materials with many remarkable physical and chemical properties, have been studied for decades, and the possibilities for future improved use of such materials for society are widely recognised. This article highlights the potential use of our understanding of the shell biomineralization process in novel bio-inspired and biomimetic applications. It also highlights the potential for the valorisation of shells produced as a by-product of the aquaculture industry. Studying shells and the formation of biominerals will inspire novel functional hybrid materials. It may also provide sustainable, ecologically- and economically-viable solutions to some of the problems created by current human resource exploitation. (C) 2016 Elsevier B.V. All rights reserved.

Weight-length relationships (WLRs) are frequently used for the development of comparative studies of life history, population dynamics, ecosystem modelling and estimation of the production and biom...

Ocean acidification has been broadly recognised to have effects on the structure and functioning of marine benthic communities. The selection of tolerant or vulnerable species can also occur during settlement phases, especially for calcifying organisms which are more vulnerable to low pH–high pCO2 conditions. Here, we use three natural CO2 vents (Castello Aragonese north and south sides, and Vullatura, Ischia, Italy) to assess the effect of a decrease of seawater pH on the settlement of Mollusca in Posidonia oceanica meadows, and to test the possible buffering effect provided by the seagrass. Artificial collectors were installed and collected after 33 days, during April–May 2019, in three different microhabitats within the meadow (canopy, bottom/rhizome level, and dead matte without plant cover), following a pH decreasing gradient from an extremely low pH zone (pH &lt, 7.4), to ambient pH conditions (pH = 8.10). A total of 4659 specimens of Mollusca, belonging to 57 different taxa, were collected. The number of taxa was lower in low and extremely low pH conditions. Reduced mollusc assemblages were reported at the acidified stations, where few taxa accounted for a high number of individuals. Multivariate analyses revealed significant differences in mollusc assemblages among pH conditions, microhabitat, and the interaction of these two factors. Acanthocardia echinata, Alvania lineata, Alvania sp. juv, Eatonina fulgida, Hiatella arctica, Mytilys galloprovincialis, Musculus subpictus, Phorcus sp. juv, and Rissoa variabilis were the species mostly found in low and extremely low pH stations, and were all relatively robust to acidified conditions. Samples placed on the dead matte under acidified conditions at the Vullatura vent showed lower diversity and abundances if compared to canopy and bottom/rhizome samples, suggesting a possible buffering role of the Posidonia on mollusc settlement. Our study provides new evidence of shifts in marine benthic communities due to ocean acidification and evidence of how P. oceanica meadows could mitigate its effects on associated biota in light of future climate change.

Citizen science has grown in importance in recent years: many projects have been launched and records are being collected on an unprecedented scale. However, certain less charismatic invertebrate groups are still underreported and the accuracy and quality of their records in crowd-sourced citizen-science projects have rarely been investigated. Here, we used expert review to conduct quality control of nonmarine mollusc observations from central Italy on the online citizen-science platform iNaturalist (https://www.inaturalist.org/). As of December 2019, c. 400 observations of nonmarine molluscs had been reported from Tuscany on iNaturalist. Most records (59.4%) were identified to species level by the iNaturalist community and included a total of 90 taxa, providing interesting new chorological data of certain entities. Although identification of more than half the observations uploaded by the community was confirmed by expert malacologists, some major issues emerged: low quality of photographic vouchers; bias in favour of a few large common species; poor taxonomic knowledge producing incorrect identifications; and difficulty of identifying many taxa without anatomical study. Expert review remains an essential tool for verification and improvement of data quality in citizen-science projects. In this regard, information on the main diagnostic characters of the more common species (e.g. certain medium–large-sized snails and slugs) as well as tips on how to take good quality photographic images could be provided to volunteers in the form of simple guides and tutorials. High-quality training resources to support recorders and regular feedback and teamwork between scientists and citizens could prevent unverified or inaccurate records from impairing the accuracy of citizen-science datasets and offer a real opportunity to discover and conserve less charismatic taxa.

Lake Edward, East Africa, harbours a largely understudied assemblage of haplochromine cichlids that displays a range of adaptions to various specialised trophic niches. In this system, we discovered specimens of Haplochromis with morphologies similar to those of oral-mollusc shellers from Lake Victoria. These morphologies are characterised by short oral jaws with stout teeth that are used either to crush molluscs or to grab the soft bodies of snails and wrench them out of their shells. A morphometric study on 47 specimens from Lake Edward revealed the presence of three new species with an oral-shelling morphology: Haplochromis concilians sp. nov., H. erutus sp. nov. and H. planus sp. nov. All three species are formally described. Stomach-content observations confirmed an opportunistic oral-shelling ecology for H. concilians sp. nov. and H. erutus sp. nov. Within H. planus sp. nov., only large specimens displayed a specialised oral-shelling morphology, but their stomachs were nearly empty, while small specimens consumed mainly Ostracoda and Hydrachnidia. Remarkably, the three species differed considerably in morphology from each other, but they each resembled oral-sheller species from Lake Victoria.

Since its introduction, the genus Philine has epitomized numerous mollusc snails with strong morphological convergence. Recently, a molecular analysis including a wide taxon sampling split this group into four non-sister families. Although they are especially diverse in cold and deep waters, no comprehensive studies are available for the Antarctic counterparts. Here, our morpho-anatomical and molecular data suggest major changes in the systematics of the group. From the eight known species, two are synonymized, Antarctophiline amoena with A. alata, and A. gouldi with A. gibba, and two are transferred to the genus Antarctophiline, namely A. apertissima comb.n. and A. falklandica comb.n. Two new species are described, A. easmithi sp.n. and A. amundseni sp.n. from different depths in the eastern Weddell Sea. The elusive P. antarctica from the Ross Sea was found in the Weddell Sea and Waegelea gen.n. is erected to place this species. Both phylogenetic and morphological data support the erection of Antarctophilinidae fam.n. to embrace most of the Philinoidea species described in the Southern Ocean. Only two species of Philinidae are found in Antarctic waters, Spiraphiline bathyalis gen. et sp.n. from bathyal depths in the Weddell Sea and S. kerguelensis comb.n. from the Kerguelen Islands. In light of the new data provided for all described species and the phylogenetic framework proposed herein, we briefly discuss the diversification and biogeographical patterns of Antarctic philinoid snails. Overall, antarctophilinid species seem to have restricted and grossly nonoverlapping distributions suggesting allopatric speciation connected possibly to geographical or bathymetric isolation.

Aim Molluscs are important grazers, filter and deposit feeders, scavengers and predators, which in turn are food for shorebirds, fish and people. Some species, targeted as human food, have been cultured along the Chinese coast for hundreds of years. To examine whether aquacultural practices have meanwhile affected biodiversity gradients, we measured mollusc community structure along the coast of China in habitats which are intensively used by humans. Location Chinese coast. Methods We sampled 21 intertidal sites spanning 20 latitudinal degrees and 18,400 km of coastline. We assessed alpha diversity to verify whether mollusc communities exhibit the expected biodiversity gradient with latitude and beta diversity gradients with distance. To examine whether human activities such as transportation and culturing could have affected these patterns, we distinguished commercial from non-commercial mollusc species and compared the differences in distribution, density, alpha diversity and beta diversity. Results We found non-commercial species showed the expected biodiversity gradients. Commercial species (a) dominated the intertidal mollusc communities at 19 of the 21 sites and compared with non-commercial species, (b) exhibited wider geographical distributions, (c) showed no significant change in Bray-Curtis index (abundance-based beta diversity) with either geographical or climatic distance, (d) exhibited lower average dissimilarities and (e) did not show a decrease in species richness and Shannon diversity with latitude. Combining all species, trends were the same as for the commercial species. Main conclusions A few cultured species dominated the intertidal mollusc communities in high densities along the Chinese coastline, taking over the ecological roles of the native species but not driving them extinct. In this way, aquacultural practices have exerted a homogenizing influence strong enough to erase basic biodiversity gradients. Since molluscs are food for the growing human population and the shrinking populations of migratory animals, coastal planning and management of both intertidal habitats and the exploitative activities employed need to incorporate these dimensions.

International audience; Marine mollusc shells enclose a wealth of information on coastal organisms and their environment. Their life history traits as well as (palaeo-) environmental conditions, including temperature, food availability, salinity and pollution, can be traced through the analysis of their shell (micro-) structure and biogeochemical composition. Adding to this list, the DNA entrapped in shell carbonate biominerals potentially offers a novel and complementary proxy both for reconstructing palaeoenvironments and tracking mollusc evolutionary trajectories. Here, we assess this potential by applying DNA extraction, high-throughput shotgun DNA sequencing and metagenomic analyses to marine mollusc shells spanning the last ~7,000 years. We report successful DNA extraction from shells, including a variety of ancient specimens, and find that DNA recovery is highly dependent on their biomineral structure, carbonate layer preservation and disease state. We demonstrate positive taxonomic identification of mollusc species using a combination of mitochondrial DNA genomes, barcodes, genome-scale data and metagenomic approaches. We also find shell biominerals to contain a diversity of microbial DNA from the marine environment. Finally, we reconstruct genomic sequences of organisms closely related to the Vibrio tapetis bacteria from Manila clam shells previously diagnosed with Brown Ring Disease. Our results reveal marine mollusc shells as novel genetic archives of the past, which opens new perspectives in ancient DNA research, with the potential to reconstruct the evolutionary history of molluscs, microbial communities and pathogens in the face of environmental changes. Other future applications include conservation of endangered mollusc species and aquaculture management.

The ecosystem changes of “Marinello coastal lakes” - a brackish dynamic area located on the Tyrrhenian coast of Sicily (Italy) - have been examined through the analysis of the adaptive response of mollusc assemblages to the geomorphological and environmental changes. In particular, we have contextually analysed the changes in salinity, mud and organic carbon together with mollusc abundance and distribution, comparing the data sets from several multidisciplinary investigations that we performed in about forty years. Our studies have evidenced that the space-time dynamics of the geomorphological, environmental and trophic parameters have led the progression of Marinello ecosystem, favoring the onset of transient windows of connectivity (TWCs) between different habitats. TWCs, by supporting continuous re-arrangements of mollusc populations, have contributed to increase the functional and ecological complexity of the system. Salinity in particular has proven to be the most affecting factor on the diversification of mollusc assemblages, explaining 63% and 44% of variation for brackish and marine species respectively. In addition, the distribution of both detritus and suspension feeders has been mostly affected by salinity. The interannual analysis of the mollusc assemblages has shown in the whole system a generalised increase in the number of species, likewise, also the species richness recorded in each basin generally increased with the time. Metapopulations in the Marinello ecosystem have shown to be related to significant modifications in the habitat patches, in turn connected to the anthropogenic interventions or to the geomorphological progression of the entire physiographic system. Significant relationships among biotic and abiotic parameters have highlighted important implications on the ecosystem functioning, suggesting their possible application in the improvement of investigation tools for the transitional environments.

The Early Medieval stronghold that existed in Pszczew (western Poland) from the 8th to 12th century was located on the shore of Lake Pszczewskie. During archaeological excavations conducted in 2010, systematic sediment samples were taken for malacological analysis to enhance our understanding of the environment in the vicinity of the site during its occupation. Forty taxa found in the samples included remains of land snails and freshwater molluscs. The most abundant among land snails were species characteristic of open and humid habitats, frequently found on the banks of various water bodies. Among freshwater molluscs, species characteristic of shallow and overgrown reservoirs and typical of permanent and stagnant water bodies predominate. Malacological analysis revealed minor changes in local hydrological conditions during the Early Medieval period. From the end of the 8th century until the first half of the 10th century, the area was definitely wet and marshy. Gradual disappearance of freshwater species in favor of land snails characteristic of humid habitats, beginning in the second half of the 10th century, indicate that the area was gradually drying out. Since the 11th century, the environment in the vicinity of the site was not influenced by larger changes. The taxa identified in the sediment profile indicated limited differences between the present-day and Medieval environments.

Although freshwater molluscs in the order Unionoida are considered one of the most endangered groups of animals in the world, sufficient data on their status are lacking for most species. As a result, a species may become rare, endangered, and even extinct before the first population assessment is conducted. This is especially true for endemic species, particularly those limited to remote regions with difficult access. We studied the current distribution and population densities of Popenaias popeii endemic to the Rio Grande drainage in Texas, and developed a method to evaluate changes in the population’s size and distributional range over the last 100 years. Sampling over 250 sites in four rivers that constitute the entire historical range of P. popeii in Texas, we found that this species has likely been extirpated from two rivers. The total length of the rivers populated by this mussel has declined by 75%, and the total P. popeii population size has declined by 72%. The remaining population of this species in the Rio Grande is fragmented, with only one 190-km stretch still supporting high densities. The developed approach could be used for other rare freshwater molluscs to reconstruct their historical range and population size.

The study was supported financially by the Hungarian Scientific Research Fund under the contract No. OTKA T/046180 and No. CNK80140. Ronaldo Sousa acknowledges the financial support provided by the Portuguese Foundation for Science and Technology (FCT) and COMPETE funds — project ECO-IAS (Contract:PTDC/AAC-AMB/116685/2010).

Mollusc shells introduce complexity and heterogeneity into soft-sediment habitats and might regulate the structure and functioning of benthic assemblages. Two areas of an unvegetated tidal flat located at the mouth of Paranagua Bay (southern Brazil) largely differ in substrata characteristics and macrofaunal assemblage structure. Sediments of the inner part of the studied site are structurally more complex than those of the peripheral portion, due to high densities of empty shells of the bivalve Anomalocardia brasiliana. The effects of this biogenic matrix on macrofaunal recolonisation during a three-month period were assessed through a reciprocal transplantation experiment of defaunated sediment between shelled and bare habitats. Hypotheses were tested to distinguish between three possible causes of variation: (i) habitat complexity, (ii) intrinsic factors of each area (regardless of the presence/absence of shells), and (iii) their interaction. Habitat structural heterogeneity provided by empty shells does not explain the large differences between macrofauna in shelled and bare habitats. Assemblages that colonised transplanted sediments became similar to those in controls at the area to which they were moved, but differed from those in controls at the area where they originated. The lack of a consistent response of assemblages to the presence of shells can be explained not only by the extremely fast recovery following small-scale experimental disturbances, but also by the dispersal mechanisms related to reproductive traits of the dominant taxa. Changes in assemblages were greatly influenced by the tanaid Monokalliapseudes schubarti, the numerically-dominant species that showed consistent differences among treatments. The reduced dispersal capacity due to the lack of planktonic larval stages associated with high fecundity, continuous reproduction and fast growth were determinant features for the rapid colonisation of defaunated sediments, regardless of habitat complexity. Despite the well-recognised impact of mollusc shell production on soft-sediment habitats, our study showed that its effects are scale-dependent, both spatially and temporally, and might be regulated by the structure of local assemblages and species-specific responses related to dispersal mechanisms.

We present a comprehensive overview of distribution data of non-indigenous mollusc species in Lithuanian inland waters. The data are based on our own observations obtained during 2007–2013 as well as on published and unpublished records from the last 80 years. Four nonindigenous species have been reported to occur in Lithuanian freshwaters: Dreissena polymorpha, Lithoglyphus naticoides, Potamopyrgus antipodarum and Physella acuta. The last species, however, has not been found in Lithuania since the 1950s. D. polymorpha is the most widespread non-indigenous mollusc species in Lithuania. It was observed in 159 out of 226 investigated localities. The other species are less common. L. naticoides was recorded in 43 sites, whereas P. antipodarum was found in 35 localities. In addition to the possible reappearance of P. acuta, four more mollusc species which are currently absent from Lithuanian freshwaters have been reported as non-indigenous from neighbouring countries and thus might potentially invade Lithuanian inland waters in the future.

Gleaning activity in Malalison Island in Culasi, Antique, Philippines, was revisited and monitored monthly from May 2018 to April 2020 to compare with results from a previous investigation in 2003. Overall, slight differences were noted in the daily catch, effort, and catch rates between 2003 and 2020, whereas substantial differences were observed in the monthly and annual catches. A total of 26 species of molluscs were recorded, which was slightly lower than the previous number (= 30), dominated by the gastropods, Nerita albicilla Linnaeus, 1758, Nerita polita Linnaeus, 1758, Canarium urceus (Linnaeus, 1758), Conomurex luhuanus (Linnaeus, 1758), and Angaria delphinus (Linnaeus, 1758) which represented 79 % of the catch. The mean daily catch was 1.15 kg.gleaner-1 with catch rates ranging from 0.8 to 1.6 kg.day-1.gleaner-1, was slightly lower than the estimates in 2003 (0.9 to 2.5 kg.day-1). The observed mean monthly catch (29.6 kg) was considerably higher than the 2003 estimate (6.1 kg), which subsequently resulted in a higher estimated annual catch (1,867–2,178 kg), value (USD2,352–2,783), and gleaner income (USD392–464) in 2020 compared to estimates in 2003. Despite the changes in the catch, effort, and value estimated for the gleaning fishery in the island since 2003, locals continue to supplement their household incomes through gleaning. Nonetheless, additional investigations into the reproductive and population biology of the different species may be needed to understand further the dynamics of this fishery and its impacts on the species' ecologies.