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North America is a hotspot of freshwater mussel diversity. However, over the last century, many anthropogenic stressors have led to substantial declines in freshwater mussels of the families Unionidae and Margaritiferidae in North America. Conserving the remaining mussel fauna is a priority, as they play an integral role in freshwater ecosystems. The Little River in Arkansas is home to one of the last remaining populations of the federally endangered freshwater mussel, Arcidens wheeleri (Unionidae: Anodontini). Population dynamics information is lacking for A. wheeleri , and no population genetics study has been conducted on this species. A greater understanding of the genetic diversity within a population can serve as a benchmark for developing an effective management plan. We sampled A. wheeleri from three locations in the Little River. Genomic data were generated with a single-enzyme restriction-site-associated DNA sequencing approach to assess genetic diversity and structure of A. wheeleri in the Little River. Genetic structure analyses indicated one genetic population among the three locations, with limited, fine-scale subpopulation structure. Observed heterozygosity values were considerably lower than expected heterozygosity values, with H o = 0.14 and H e = 0.22, likely indicating a genetic bottleneck. Demographic analysis of the Little River population of A. wheeleri also suggests a historical bottleneck. Furthermore, a high inbreeding coefficient (F IS = 0.33) indicates A. wheeleri in the Little River is losing genetic diversity. Data generated indicate considerable risk of extirpation for A. wheeleri from the Little River and should serve as a baseline for future monitoring. Given its high risk of extinction, we recommend increased study of A. wheeleri across its range and on-the-ground conservation actions that include habitat protection and restoration, which are the only options until a successful host fish and protocols are identified for propagation. [ABSTRACT FROM AUTHOR]

Freshwater mussels have a substantial role in aquatic ecosystem function and provide valuable ecosystem services, including water filtration, nutrient cycling, habitat creation and sediment stabilization. While they face population declines globally that can negatively affect an ecosystem's health, such as reducing the water quality and increasing the turbidity, lack of information about the basic reproductive biology for most species makes their conservation much more difficult. Here, we monitored a population of Unio tumidus for a year to study its reproductive biology, gonad-dwelling parasites and growth rate in Lake Viinijärvi, Finland. Our data revealed that this species was dioecious with no evidence of hermaphroditism and was non-significantly female-biased (a male to female ratio of 1:1.3). Both sexes of U. tumidus had continuous gametogenesis during the study period with two peaks in the gonadosomatic index (GSI%) during November and May, followed by two clear declines in December and June. Gravidity period (brooding) of embryos or glochidia in the female's outer gills lasted from June to July. Therefore, this population of U. tumidus can be classified as a short-term breeder (tachytictic). The clear decline of GSI% in December might be a strategy that individuals of U. tumidus use to resorb resources back from the gonad for somatic maintenance during winter. Mean length of glochidia was 391 ± 0.049 µm, being among the largest known glochidia for Unionidae. No gonad-dwelling trematode parasites were detected and the population exhibited high fecundity (numbers of oocytes per female), with an average oocyte production of 242,000 ± 18,000. The studied population had a moderate growth rate with a maximum predicted age of 13 years and asymptotic length (the length at which growth slows down while the mussel continues to age, L ∞) of 114 mm. Our study provides the first quantitative data and histological analysis of the reproductive biology of U. tumidus , serving as a basis for future research and conservation. [ABSTRACT FROM AUTHOR]

The freshwater mussels (Bivalvia: Unionida) of the biodiversity hotspot Sundaland are experiencing severe anthropogenic threats, whilst their diversity and distribution remain poorly understood. Here, we present the first modern-day data on Unionida diversity and distribution across western Borneo. Mussels were surveyed and collected in the upper Kapuas and Pawan river basins in West Kalimantan, Indonesia, and the Sambas Besar, Sarawak and Batang Sadong river basins in Sarawak, Malaysia. DNA sequencing (COI  + 16S +  ND1  + 18S + 28S) and morphological analyses were conducted to delineate and identify species, and reconstruct phylogenetic relationships and population genetics. Specimens belonged to six native genera and nine species, of which seven are endemic to Borneo and three are new to science, i.e. Ctenodesma mawonae Zieritz et al. sp. nov. Sarawak basin, and Ctenodesma bersinara Zieritz et al. sp. nov. and Rectidens lauris Zieritz et al. sp. nov. both Pawan basin. The monotypic genera Caudiculatus and Discomya were phylogenetically highly divergent from other known Gonideinae taxa, potentially indicating a separate tribe (for Caudiculatus) and subfamily (for Discomya). In addition, we report new records of the non-native Sinanodonta pacifica Heude, 1878 in the Batang Sadong and Kapuas river basins. [ABSTRACT FROM AUTHOR]

Unicellular ciliates like Tetrahymena are best known as free-living bacteriovores, but many species are facultative or obligate parasites. These "histophages" feed on the tissues of hosts ranging from planarian flatworms to commercially important fish and the larvae of imperiled freshwater mussels. Here, we developed a novel bioinformatics pipeline incorporating the nonstandard ciliate genetic code and used it to search for Ciliophora sequences in 34 publicly available Platyhelminthes EST libraries. From 2,615,036 screened ESTs, we identified nearly 6,000 high-confidence ciliate transcripts, supporting parasitism of seven additional flatworm species. We also cultured and identified Tetrahymena from nine terrestrial and freshwater planarians, including invasive earthworm predators from the genus Bipalium and the widely studied regeneration models Dugesia japonica and Schmidtea mediterranea. A co-phylogenetic reconstruction provides strong evidence for the coevolution of histophagous Ciliophora with their Platyhelminthes hosts. We further report the antiprotozoal aminoglycoside paromomycin expels Tetrahymena from S. mediterranea , providing new opportunities to investigate the effects of this relationship on planarian biology. Together, our findings raise the possibility that invasive flatworms constitute a novel dispersal mechanism for Tetrahymena parasites and position the Platyhelminthes as an ideal model phylum for studying the ecology and evolution of histophagous ciliates. [ABSTRACT FROM AUTHOR]

Characterizing the mechanisms influencing the distribution of genetic variation in aquatic species can be difficult due to the dynamic nature of hydrological landscapes. In North America's Central Highlands, a complex history of glacial dynamics, long-term isolation, and secondary contact have shaped genetic variation in aquatic species. Although the effects of glacial history have been demonstrated in many taxa, responses are often lineage- or species-specific and driven by organismal ecology. In this study, we reconstruct the evolutionary history of a freshwater mussel species complex using a suite of mitochondrial and nuclear loci to resolve taxonomic and demographic uncertainties. Our findings do not support Pleurobema rubrum as a valid species, which is proposed for listing as threatened under the U.S. Endangered Species Act. We synonymize P. rubrum under Pleurobema sintoxia —a common and widespread species found throughout the Mississippi River Basin. Further investigation of patterns of genetic variation in P. sintoxia identified a complex demographic history, including ancestral vicariance and secondary contact, within the Eastern Highlands. We hypothesize these patterns were shaped by ancestral vicariance driven by the formation of Lake Green and subsequent secondary contact after the last glacial maximum. Our inference aligns with demographic histories observed in other aquatic taxa in the region and mirrors patterns of genetic variation of a freshwater fish species (Erimystax dissimilis) confirmed to serve as a parasitic larval host for P. sintoxia. Our findings directly link species ecology to observed patterns of genetic variation and may have significant implications for future conservation and recovery actions of freshwater mussels. [ABSTRACT FROM AUTHOR]

Frequent and strong morphological convergence suggests that determinism tends to supersede historical contingencies in evolutionary radiations. For many lineages living within the water column of rivers and streams, hydrodynamic forces drive widespread morphological convergence. Living below the sediment-water interface may release organisms from these hydrodynamic pressures, permitting a broad array of morphologies, and thus less convergence. However, we show here that the semi-infaunal freshwater mussels have environmentally determined convergence in shell morphology. Using 3D morphometric data from 715 individuals among 164 Nearctic species, we find that species occurring in rivers with high flow rates have evolved traits that resist dislodgement from their burrowed position in the streambed: thicker shells for their body size, with the thickest sector of the shell being the most deeply buried. Species occurring in low flow environments have evolved thinner and more uniformly thickened shells, corresponding to an alternative adaptation to dislodgement: increased burrowing efficiency. Within species, individuals also show increased shell thickness for their body size at higher flow rates, suggesting that ecophenotypy may, in part, be an important mechanism for establishing populations in new environments and thus evolutionary divergence in this highly imperiledinvertebrate group. [ABSTRACT FROM AUTHOR]

Most organisms possess the capacity to metabolize arsenic (As) accumulating compounds to less toxic forms, thus minimizing the adverse effect induced by this metalloid. However, other contaminants may to interfere with As metabolism, contributing to the accumulation of more toxic compounds. Microplastics (MPs) are omnipresent in aquatic environment and may induce toxicological effects (alone or in combination with other contaminants) on living organisms. Therefore, the objective of the present study was to evaluate the effect of the exposure of the freshwater clam Limnoperna fortunei to a combination of MP (4 and 40 μg/L of polystyrene microbeads, 1.05 μm) and As (50 μg/L) for 48 h, evaluating the accumulation and metabolization of As and oxidative stress parameters, such as catalase (CAT), glutathione-S-transferase activities, total antioxidant competence, reduced glutathione (GSH), and lipid damage in the gills and digestive glands. Results revealed that low MP concentration disrupts the redox state of the digestive gland by a decrease in the antioxidant activity (CAT and total antioxidant capacity). GSH levels in the gills of animals exposed to MP (4 μg/L) alone and the combination of MP + As increased, concomitant with an increase in the percentage of toxic compounds, indicating the effect of MP on As metabolism. Although, few studies evaluated the effect of coexposure to MP + As by considering metabolization of metalloid in freshwater bivalve, our results revealed that exposure to MP reduced the metabolization capacity of As, favoring the accumulation of more toxic compounds besides the MP alone, which showed a pro-oxidant effect in L. fortunei. [ABSTRACT FROM AUTHOR]

Truncilla macrodon ¸ the Texas Fawnsfoot, is currently considered to be restricted to the Brazos and Colorado river drainages in central Texas, USA. Subfossil specimens resembling T. macrodon from shell middens in the Trinity river drainage have raised questions about its presumptive range. Extant Truncilla populations occupying the Trinity river drainage are believed to be Truncilla donaciformis , the Fawnsfoot, but the species identity has not been assessed using molecular techniques. In this study, we set out to use phylogeographic and morphometric approaches to resolve the distribution of Truncilla spp. in Texas, with an emphasis on assessing species identity of Truncilla in the Trinity river drainage. Our molecular analyses indicated individuals from the Trinity river drainage are T. macrodon rather than T. donaciformis , and morphometric analyses using ratios of shell length, width and height supports this finding and showed differentiation among T. macrodon, Truncilla cognata and T. donaciformis. These combined findings suggest the range of T. macrodon is larger than previously recognized and includes the Colorado, Brazos and Trinity river drainages. The status of Truncilla spp. in the San Jacinto river basin remains unclear due to lack of information on historical or extant populations, but we recommend conservationists consider T. macrodon as part of the mussel fauna since the drainage shares an embayment with the Trinity river drainage. Molecular data also indicated the Trinity population of T. macrodon is distinct from, and more genetically diverse than, the Brazos and Colorado populations. This difference suggests the Trinity River population should be treated as a separate management unit from the Brazos and Colorado River populations to facilitate effective conservation and recovery planning. Our study adds to the growing body of literature highlighting the utility of molecular data in conservation and management of freshwater mussels. [ABSTRACT FROM AUTHOR]

The highly diverse group of freshwater mussels from order Unionida is found in the world's freshwater systems due to several fascinating evolutionary adaptations, including "parental care," and most notably, an obligatory parasitic phase in their early life cycle, called glochidia, which infests and uses fish for nutrition and dispersal. Freshwater mussels play essential ecological roles in freshwater habitats, including water filtration, sediment bioturbation, and nutrient cycling. However, these species are also highly threatened, being one of the faunal groups with the highest recorded extinction rate in the wild. Genomics methods have an incredible potential to promote biodiversity conservation, allowing the characterization of population health, identification of adaptive genetic elements, delineation of conservation units, and providing a framework for predictive assessments of the impact of anthropogenic threats and climate change. Unfortunately, only six freshwater mussel species have had their whole genomes sequenced to date, and only two of these are European species. Here, we present the first genome assembly of the Painter's Mussel, Unio pictorum (Linnaeus, 1758), the type species representative of the order and the most widespread species of the genus in Europe. We used long-read PacBio Hi-Fi sequencing reads to produce a highly contiguous assembly that will pave the way for the study of European freshwater mussels in the Genome Era. [ABSTRACT FROM AUTHOR]

Inaccurate taxonomy can lead to species in need of conservation being overlooked, which makes revisionary systematics crucially important for imperilled groups. The freshwater mussel genus Alasmidonta is one such group in need of study. Here, we take a multilocus phylogenetic approach to assess species-level taxonomy of Alasmidonta and test monophyly of this genus. Phylogenetic inference resulted in polyphyly of Alasmidonta. Lasmigona , which was included to test monophyly of Alasmidonta , was also polyphyletic. Species delimitation methods disagreed about whether Alasmidonta arcula , Alasmidonta triangulata and Alasmidonta undulata are distinct species, but all delimitation methods agreed that Alasmidonta harbours an undescribed species that would be considered Alasmidonta varicosa under current taxonomy. Given conflict among species delimitation methods and geographical separation, we maintain the current taxonomy for A. arcula and A. triangulata. The undescribed species is restricted to rivers of the Uwharrie Mountains region in North Carolina, USA that flow into the Pee Dee River from the east and can be distinguished morphologically from A. varciosa by higher and wider placed adductor mussels and a hooked pseudocardinal tooth. We offer insights into how supraspecific taxonomy of subtribe Alasmidontina might be resolved and formally describe the lineage from the Uwharrie Mountains region as Uwharrie elktoe, Alasmidonta uwharriensis sp. nov. [ABSTRACT FROM AUTHOR]

Aims: We examined the effects of a mixture of contaminants found in agricultural watersheds on the gut microbiota and physiology of both the freshwater mussel Lampsilis cardium, and L. cardium host fish Micropterus salmoides. Methods and results: Lampsilis cardium and M. salmoides were exposed to three concentrations of agricultural contaminants for 60 days (observing behaviour daily) before being sampled for gut microbiota analyses. DNA was extracted from the gut samples, amplified via PCR, and sequenced using the Illumina Mi‐Seq platform. Only L. cardium guts had differing microbiota across treatments, with an increase in potentially pathogenic Aeromonas. We also provide novel evidence of a core microbiota within L. cardium and M. salmoides. In terms of physiology, female L. cardium exhibited a decrease in movement and marsupial gill display in contaminant exposures. Conclusions: Exposure to contaminants from agricultural watersheds may affect population recruitment within freshwater mussel communities over time. Specifically, increased pathogenic micro‐organisms and altered behaviour can reduce the likelihood of glochidia dispersal. Significance and impact of the study: This study supports emerging research that contaminants found in agricultural watersheds may be a factor in freshwater mussel population declines. It also provides novel evidence that unionids have a core gut microbiota. [ABSTRACT FROM AUTHOR]

Chamberlainia hainesiana (Lea, 1856) (Unionidae) is the most economically important freshwater mussel in Thailand and is commonly used in food, spiritual ceremonies and pearl culture. Despite the clear economic importance of this monotypic genus, the distribution and diversity of Chamberlainia Simpson, 1900 are poorly understood. We set out to re-evaluate the taxonomic and geographic boundaries of Chamberlainia using molecular and morphological data gathered from recently and historically collected material. Our cytochrome c oxidase subunit I gene tree recovered three divergent species-level lineages in the genus Chamberlainia. Fourier shape analysis of 60 digitized Chamberlainia shell outlines revealed evidence of two morphologically divergent groups that could be statistically distinguished 88% of the time. We used this evidence to recognize two genetically and morphologically divergent Chamberlainia species, C. hainesiana and C. duclerci (Rochebrune, 1882) stat. res. Geographical information from 46 museum records was used to map the distribution of Chamberlainia. These results are discussed in the context of their taxonomic, biogeographic and conservation implications. [ABSTRACT FROM AUTHOR]

Techniques for positive re-identification of finfish are well developed and are used to estimate vital rates, migration patterns and stock structure. Fluorochrome dyes, like nontoxic calcein, have been used with success to mark hard parts of fish and the shells of some molluscs. Yet, despite the commercial and ecological importance of the eastern oyster Crassostrea virginica , a systematic evaluation of the effectiveness of calcein for marking this species does not exist. In this study, methods that have been used for marking freshwater mussels with calcein were tested on 2-week- and 2-month-old juvenile C. virginica and on 3-year-old adult C. virginica. Individuals were immersed in 250 mg l−1 of calcein for 24 h either once (single treatment) or three times (triple treatment), and then observed to determine whether marks were visible, how long they remained visible and whether calcein influenced growth and mortality of the different age classes. Results indicated that all marked individuals were recognizable under blue light, that multiple distinct marks were possible on juveniles and that marks on juveniles could remain visible for 3.75 years. Growth of juveniles and adults treated with calcein was not significantly different from controls after 11 months. Survivorship did not differ between treated and control individuals for all treatments and ages, except the 2-month-old juvenile oysters that were immersed three times. Results indicate that calcein is an effective and safe marking technique for juvenile oysters from robust cohorts, and could be used to enhance studies of growth, mortality, larval transport and settlement in situ. [ABSTRACT FROM AUTHOR]

The freshwater mussel Unio durieui is a rare bivalve endemic to North African watersheds. Although this is an important species from an ecological and conservation perspective, information on its genetic diversity and population structure is lacking. Here, we combine geometric morphometric and molecular genetic analyses to characterize and evaluate the status of populations of this endangered species from four Tunisian watershed basins (Cap Bon, Ichkeul, northwest and Mejerda River basins). By using a multiparameter approach, we sought to test the hypothesis that populations from these geographic regions could be considered as distinct management units. Shell outline shapes were assessed using elliptic Fourier analysis followed by linear discriminant analysis of principal components. Multivariate analysis applied on normalized Fourier coefficients showed highly significant differences in shell shape among the populations. Population genetic analysis based on inter-simple sequence repeats revealed low levels of diversity and high differentiation between the populations studied. Two groups of populations are clearly evident, thus separating samples from the Northwest from those from the other watersheds. Although there is no evidence for isolation by distance patterns, genetic and phenotypic diversity appeared significantly correlated with climatic variables. These findings suggest isolation by environment and the nominal species U. durieui may constitute two biological species. Conservation programme actions should consider this substructure in establishing effective recovery strategies for this endangered species. [ABSTRACT FROM AUTHOR]

The Unionidae represent an excellent model taxon for unravelling the drivers of freshwater diversity, but, phylogeographic studies on Southeast Asian taxa are hampered by lack of a comprehensive phylogeny and mutation rates for this fauna. We present complete female- (F) and male-type (M) mitogenomes of four genera of the Southeast Asian clade Contradentini+Rectidentini. We calculate substitution rates for the mitogenome, the 13 protein-coding genes, the two ribosomal units and three commonly used fragments (co1, nd1 and 16S) of both F- and M-mtDNA, based on a fossil-calibrated, mitogenomic phylogeny of the Unionidae. Phylogenetic analyses, including an M+F concatenated dataset, consistently recovers a monophyletic Gonideinae. Subfamily-level topology is congruent with that of a previous nuclear genomic study and with patterns in mitochondrial gene order, suggesting Unionidae F-type 2 as a synapomorphy of the Gonideinae. Our phylogeny indicates that the clades Contradentini+Rectidentini and Lamprotulini+Pseudodontini+Gonideini split in the early Cretaceous (~125 Mya), and that the crown group of Contradentini+Rectidentini originated in the late Cretaceous (~79 Mya). Most gonideine tribes originated during the early Palaeogene. Substitution rates were comparable to those previously published for F-type co1 and 16S for certain Unionidae and Margaritiferidae species (pairs). [ABSTRACT FROM AUTHOR]

The objective of this review is to update our previously published checklist of Recent freshwater mussel species and genera (Graf & Cummings, 2007, J. Molluscan Stud. : 291–314) to reflect the new data and research findings that have accumulated over the last decade. The MUSSEL Project Database was developed to synthesize the available taxonomic nomenclature, species ranges and published taxonomic hypotheses on genus–species combinations and synonymy. We have found 4,988 available species-group level nominal species representing 958 valid species in 192 genera worldwide, an increase of 118 species since 2007. The current patterns of species richness are discussed with regard to both taxonomy and geography, as is the general flux in the number of species recognized over time. A checklist is provided herein, with a bibliography to key faunistic and taxonomic references. The full dataset is maintained and updated on the MUSSEL Project Web Site (http://mussel-project.net/). [ABSTRACT FROM AUTHOR]

From a genomics perspective, bivalves (Mollusca: Bivalvia) have been poorly explored with the exception for those of high economic value. The bivalve order Unionida, or freshwater mussels, has been of interest in recent genomic studies due to their unique mitochondrial biology and peculiar life cycle. However, genomic studies have been hindered by the lack of a high-quality reference genome. Here, I present a genome assembly of Potamilus streckersoni using Pacific Bioscience single-molecule real-time long reads and 10X Genomics-linked read sequencing. Further, I use RNA sequencing from multiple tissue types and life stages to annotate the reference genome. The final assembly was far superior to any previously published freshwater mussel genome and was represented by 2,368 scaffolds (2,472 contigs) and 1,776,755,624 bp, with a scaffold N50 of 2,051,244 bp. A high proportion of the assembly was comprised of repetitive elements (51.03%), aligning with genomic characteristics of other bivalves. The functional annotation returned 52,407 gene models (41,065 protein, 11,342 tRNAs), which was concordant with the estimated number of genes in other freshwater mussel species. This genetic resource, along with future studies developing high-quality genome assemblies and annotations, will be integral toward unraveling the genomic bases of ecologically and evolutionarily important traits in this hyper-diverse group. [ABSTRACT FROM AUTHOR]

Freshwater bivalves are highly threatened and globally declining due to multiple anthropogenic impacts, making them important conservation targets. Because conservation policies and actions generally occur at the species level, accurate species identification and delimitation is critical. A recent phylogenetic study of Italian mussel populations revalidated an Anodonta species bringing the number of known European Anodontini from three to four species. The current study contributes to the clarification of the taxonomy and systematics of European Anodontini, using a combination of molecular, morphological and anatomical data, and constructs phylogenies based on complete mitogenomes. A redescription of A. exulcerata and a comparative analysis of morphological and anatomical characters with respect to the other two species of Anodonta present in the area are provided. No reliable diagnostic character has emerged from comparative analysis of the morphometric characters of 109 specimens from 16 sites across the Italian peninsula. In fact, the discriminant analysis resulted in a greater probability of correct assignment to the site of origin than to the species. This confirms the difficulties of an uncritical application of visual characters for the delimitation of species, especially for Anodontinae. [ABSTRACT FROM AUTHOR]

A simple and low-cost method of monitoring and collecting particulate matter detaching from (or interacting with) aquatic animals is described using a novel device based on an airlift pump principle applied to floating cages. The efficiency of the technique in particle collection is demonstrated using polyethylene microspheres interacting with a cyprinid fish (Carassius carassius) and a temporarily parasitic stage (glochidia) of an endangered freshwater mussel (Margaritifera margaritifera) dropping from experimentally infested host fish (Salmo trutta). The technique enables the monitoring of temporal dynamics of particle detachment and their continuous collection both in the laboratory and in situ , allowing the experimental animals to be kept under natural water quality regimes and reducing the need for handling and transport. The technique can improve the representativeness of current experimental methods used in the fields of environmental parasitology, animal feeding ecology and microplastic pathway studies in aquatic environments. In particular, it makes it accessible to study the physiological compatibility of glochidia and their hosts, which is an essential but understudied autecological feature in mussel conservation programs worldwide. Field placement of the technique can also aid in outreach programs with pay-offs in the increase of scientific literacy of citizens concerning neglected issues such as the importance of fish hosts for the conservation of freshwater mussels. [ABSTRACT FROM AUTHOR]

The shells of unionid freshwater mussels are highly morphologically variable, making species identification difficult and thus hampering conservation efforts. Shell shape variation is associated with several factors, of which hydrodynamic variables are the most common. Using geometric morphometrics, shell shape was evaluated on the basis of both external (entire margin including alate processes) and internal (pallial line and positions of muscle scars and teeth) landmarks in Triplodon corrugatus, Paxyodon syrmatophorus and Prisodon obliquus. Samples of these species were collected from 2–5 sites on six rivers, which were classified as either small or large drainages, in the eastern Amazon region, Pará state, northern Brazil. Interspecific comparisons in shell shape were also made among all three species where they co-occurred. Shell shape differed significantly among individuals of the same species from different sites and, in cross-validation tests, 94–96% of mussels were correctly classified into their river of origin according to their shape. For all three species, canonical variates analysis consistently differentiated between mussels from sites in large and small rivers, with the greatest difference in shell shape occurring between large and small rivers. Mussels from the large, clear or whitewater Tapajós, Amazon and Tocantins sites had a triangular shape with prominent posterodorsal and anterior winged processes, whereas those from the small, clearwater Trombetas, Irituia and Piriá sites had a rounded shape, and lacked or had reduced dorsal winged processes. Where all three species co-occurred in the Tapajós and Trombetas sites, shell shape tended to converge. Paxyodon syrmatophorus from the Tapajós sites was most distinct, with very pronounced dorsal processes and a reduced shell disc. In all three species, most of the shell shape variation occurred in the posterodorsal winged process, posterior and ventral margins, and to a lesser degree, in the anterior winged process. The shape differences among Amazonian freshwater mussels agree with those of freshwater mussel species from other regions, characterized by wide variation in hydrodynamics. [ABSTRACT FROM AUTHOR]

The Yangtze River basin has the highest species richness for freshwater mussels in East Asia, but little is known about the reproductive biology of most species. Here, the reproductive biology of nine freshwater mussel species (Unionidae) found in Poyang Lake, Jiangxi province, China was studied. Sex ratios were not significantly different from 1:1 in eight of the nine species examined. The minimum size and age of sexual maturity (0.2–5.6 yr for males and 0.3–5.9 yr for females) and of females first becoming gravid (0.6–8.9 yr) varied among species. Brooding seasons for glochidia varied among species, but seven of the nine species examined brooded glochidia through the spring and summer. In all species, high frequencies (mean 87.5%) were found to be gravid during their peak brooding period. Fecundity was positively correlated with shell length in the five species in which this was examined. Mean annual fecundity showed wide interspecific variation, ranging from 7,800 to 328,000 propagules/mussel. The findings of this study have implications for the ecology and conservation of unionid species in China and contributes to knowledge of the evolution of reproductive and life history characters of the Unionidae. [ABSTRACT FROM AUTHOR]

Here we characterize the digestive gland microbiome from wild and cultured (hatchery-reared) Alabama rainbows (Villosa nebulosa) using 16 S rRNA gene pyrosequencing in order to understand the effects of propagation on microbial community structure in freshwater mussels. Digestive glands from nine Alabama rainbows were analysed, five from the wild and four from a hatchery. Pyrosequencing yielded a total of 32,962 bacterial sequences and 387 operational taxonomic units (OTUs). Tenericutes was the dominant phylum in all samples (>87%), followed by Proteobacteria (4.6%), Fusobacteria (4.5%) and Bacteroidetes (1.4%). Digestive gland microbiomes were overwhelmingly dominated by OTUs related to the genus Mycoplasma. These Mycoplasma -like sequences could not be ascribed unequivocally to the genus Mycoplasma (less than 90% sequence identity) and probably represent new lineages within the class Mollicutes. We identified a core microbiome in the digestive gland of V. nebulosa , with all individual mussels sharing 9 OTUs. However, the microbiome from mussels collected from the wild was significantly different from that of hatchery-reared mussels. Our results show that novel microbial communities exist within the digestive gland of freshwater mussels. [ABSTRACT FROM AUTHOR]

Freshwater mussels (Bivalvia: Unionida) serve an important role as aquatic ecosystem engineers but are one of the most critically imperilled groups of animals. Here, we used a combination of sequencing strategies to assemble and annotate a draft genome of Venustaconcha ellipsiformis , which will serve as a valuable genomic resource given the ecological value and unique “doubly uniparental inheritance” mode of mitochondrial DNA transmission of freshwater mussels. The genome described here was obtained by combining high-coverage short reads (65× genome coverage of Illumina paired-end and 11× genome coverage of mate-pairs sequences) with low-coverage Pacific Biosciences long reads (0.3× genome coverage). Briefly, the final scaffold assembly accounted for a total size of 1.54 Gb (366,926 scaffolds, N50 = 6.5 kb, with 2.3% of “N” nucleotides), representing 86% of the predicted genome size of 1.80 Gb, while over one third of the genome (37.5%) consisted of repeated elements and >85% of the core eukaryotic genes were recovered. Given the repeated genetic bottlenecks of V. ellipsiformis populations as a result of glaciations events, heterozygosity was also found to be remarkably low (0.6%), in contrast to most other sequenced bivalve species. Finally, we reassembled the full mitochondrial genome and found six polymorphic sites with respect to the previously published reference. This resource opens the way to comparative genomics studies to identify genes related to the unique adaptations of freshwater mussels and their distinctive mitochondrial inheritance mechanism. [ABSTRACT FROM AUTHOR]

Past geological processes and climate change affected current species distributions and the genetic structure of riverine fauna. Western Gulf of Mexico coastal rivers harbour four mussel species within the genus Fusconaia (Bivalvia: Unionida). The distributions of these species are unclear owing to their indistinguishable shell morphologies. Using molecular phylogenetic and Fourier morphometric analyses, we examined phylogenetic relationships and morphological variation among the species and made inferences about the role of past geological and climatic factors in shaping the current genetic structure and distributions of these species in the region. Our results showed the presence of three Fusconaia species within the region: Fusconaia askewi, Fusconaia chunii and Fusconaia flava. We confirmed that Fusconaia lananensis is a junior synonym of F. askewi and that F. chunii is genetically distinct from F. askewi. The Trinity River has syntopic F. flava whose morphologies are indistinguishable from those of F. chunii. Divergence-time estimates matched major geological and climatic events in the region, where climate-driven river formations during the mid-Miocene to Pleistocene caused major diversification of Fusconaia species. Knowledge gained from the present study provides a better understanding of vicariant events that shaped current species distributions and helps to identify conservation priorities that apply to the Fusconaia species. [ABSTRACT FROM AUTHOR]

To investigate the regulation of metallothionein genes (HsMTs) of Hyriopsis schlegelii, 1,121-bp and 1,270-bp regions of the HsMT1 and HsMT2 promoters were cloned and analyzed, respectively. The two promoters shared partially conserved features and possessed distinct characteristics such as the number or position of metal response elements (MREs). Further analysis of the HsMT1 and HsMT2 promoters was performed by the reporter assay using the luciferase gene. Both promoters were activated by various metals, and presented different levels of metal ions inducibility in human hepatoblastoma cells. Deletion mutant assays demonstrated that both the longest promoter regions achieved the maximum inducibility, and the metal inducibility was dependent on the presence of the MRE in HsMT1 and the distal MRE in HsMT2. In addition, we cloned a putative metal responsive transcription factor (hereby designated as HsMTF-like) and studied its effect on HsMTs expression in human hepatoblastoma cells. An in vivo assay demonstrated that HsMTF-like activates basal HsMTs transcription level, and the MRE in the HsMTs promoter mediates this activation process. Moreover, this basal transcription level can be further boosted by zinc treatment. In conclusion, the regulation mechanism for MT activation in H. schlegelii should be evolutionarily conserved. [ABSTRACT FROM AUTHOR]

Information on the genetic diversity and population genetic structure of threatened species is important for guiding management decisions. Margaritifera margaritifera (freshwater pearl mussel) occurs across western Russia, north and central Europe, and Atlantic drainages of north-eastern North America (NA). European populations of M. margaritifera are considered endangered, whereas NA populations are thought to be relatively secure. As such, the population genetics of M. margaritifera occurring in European rivers is relatively well studied while that of NA populations is not known. In this study, we investigated the genetic diversity and differentiation of M. margaritifera in Canada and the USA. Genetic diversity indices calculated from nine microsatellite loci were relatively high in the NA population. Analyses of genetic structure indicated that a single panmictic population exists for M. margaritifera in NA. However, there was evidence of substructure in some tributaries of the St. Lawrence River in Québec, Canada. The NA population of M. margaritifera has low genetic differentiation and high diversity, possibly resulting from large population size and high gene flow. Consequently, conservation of this species should focus primarily on maintaining favourable habitat conditions and connectivity for host fish. [ABSTRACT FROM AUTHOR]

Delimiting species boundaries is a fundamental yet challenging task that has been especially problematic in morphologically conserved lineages. The use of genetic markers and phylogenetic approaches has proven of paramount importance to resolve these cases. Using the genus Unio as a case study, we have analysed two mitochondrial markers, cytochrome c oxidase subunit I (COI) and 16S rRNA (16S), phylogenetically and phylogeographically to explore species limits and evolutionary lineages within the group. We followed two different approaches to define species boundaries: the generalized mixed Yule coalescence model in a Bayesian framework and the Poisson tree process model. Phylogenetic relationships among species and divergence times were also assessed using relaxed molecular clock analyses. Taken together, we provide a sound systematic framework for Western Palaearctic Unio species, addressing phylogenetic relationships, and the taxonomy, biogeographic patterns and evolutionary history of this group in this region. The Unio clade from the studied area had a clear phylogenetic structure with four robust lineages that include the following species: (1) Unio durieui + Unio gibbus; (2) Unio tumidus; (3) Unio pictorum, Unio delphinus + Unio foucauldianus, Unio elongatulus, Unio mancus, Unio ravoisieri, Unio tigridis; and (4) Unio tumidiformis + (Unio bruguierianus + (Unio crassus + Unio ionicus)). Deeper analyses, including filling gaps in distributions, should be conducted to disentangle the U. crassus, U. pictorum and U. tigridis species complexes. [ABSTRACT FROM AUTHOR]

Many prey species detect predators through chemoreception, particularly in low-visibility aquatic environments. Moreover, injury-released chemical cues from conspecifics are often perceived as a reliable indicator of predation threat. We examined whether males of the freshwater caridean shrimp Palaemon argentinus (Nobili, 1901) react to different types of infochemicals associated with predation threat. Shrimp were exposed to chemical stimuli from starved individuals of a predatory fish (Australoheros facetus (Jenyns, 1842)) and from crushed conspecific shrimp. Our experiment showed that P. argentinus reacts to waterborne substances associated with predation threat, indicating that chemical cues mediate behavioural antipredator responses. Shrimp adopted an appropriate antipredator behaviour (reduced swimming activity) in response to chemical stimuli from A. facetus, and from crushed conspecifics, relative to a distilled-water control. The chemical stimuli from crushed conspecifics elicited the strongest reduction in swimming activity. Reduced movement, a common response in prey animals to the presence of predators, was not entirely consistent because shrimp increased their walking time in response to the chemical stimuli that were investigated. The ability to alter behaviour based on vision-independent perception of ambient risk would be highly useful for macroinvertebrate prey species such as P. argentinus living in eutrophic shallow lakes where visibility is often reduced. Our results demonstrated chemosensory recognition of predation risk highlighting the important role of chemical cues in the behavioural ecology of this shrimp, especially with regards to predator-prey interactions. [ABSTRACT FROM AUTHOR]

Doubly uniparental inheritance (DUI) of mitochondrial DNA (mtDNA) implies the coexistence of two highly divergent gender-associated mitogenomes, which are transmitted independently. This exception to the strictly maternal inheritance of mtDNA is characteristic of some bivalves and occurs in the endangered freshwater mussel Margaritifera margaritifera (Linnaeus, 1758). This study identifies for the first time new male 16S rDNA and cox2-cox1 haplotypes of M. margaritifera by using non-destructive sampling of haemolymph. Samples collected from mussels with spent gonad contained exclusively the female (F) mitogenome, whereas haemolymph extracted from reproductively active mussels can be used to procure the male (M) mitogenome. Identification of partial 16S rRNA secondary structures of female and male sequences in M. margaritifera supported the existence of structural differences between the two gender-associated transcripts. Moreover, the novel 16S rDNA and cox2- cox1 sequences were integrated into a phylogenetic tree including homologous mtDNA sequences from several unionoid species. The phylogram revealed two F and M clades and haplotypes clustered according to the family taxa, with species of the family Margaritiferidae occupying a basal position. The findings are consistent with the hypothesis of a single evolutionary origin for the DUI system in bivalve freshwater mussels. Both 16S rDNA and cox2-cox1 markers may be useful for investigating gender-associated diversity across the geographical range of this endangered species with repercussions for genetic sexing of wild and captive mussels. [ABSTRACT FROM AUTHOR]

The distribution of circum-Mediterranean fauna was dramatically affected by palaeogeographical events during the Cenozoic. The biogeographical history of freshwater mussels is related to the development of the continental watershed during the Tertiary and Pleistocene glacial cycles. Our study model is Potomida littoralis (Cuvier, 1798), a Palaearctic freshwater mussel with a patchy circum-Mediterranean distribution encompassing areas of North Africa, south-western Europe, Greece and the Levant. Our phylogenetic reconstructions, network analyses and coalescence estimations indicate that the clade Potomida has a clear geographical structure with four robust lineages from Turkey, Greece, North Africa and Iberian Peninsula plus France. This structure is only disrupted in two cases: specimens from the Ziz River (Morocco) clustered with Tunisian lineages, and samples from the north-eastern Iberian Peninsula were found to have been recently introduced from Morocco. We considered two different calibration strategies of a molecular clock to evaluate divergence times between lineages. The first, based on palaeogeographical events, resulted in substitution rates up to three times lower than the average for molluscs. When such mean values were considered for calibrating the molecular clock, the group's origin and diversification events were incongruent with the fossil record and the likelihood of gene flow between lineages. Rather than a pattern of recent speciation, our results suggest low levels of substitution and a pattern of 'slow evolution', probably linked to its long generation time and longevity. From a taxonomic viewpoint, the genus Potomida is currently considered monospecific. Reflecting the data presented herein, we propose the existence of an eastern species, named P. acarnanica (Kobelt, 1879) in Greece and Turkey, and another named P. littoralis (Cuvier, 1798), with a wide distribution ranging from France to Tunisia. [ABSTRACT FROM AUTHOR]

Attaching objects to bivalve shells is an increasing requirement for conservation projects, mark-recapture studies and behavioural analysis. We investigated the suitability of eight different glues to attach a metallic object to a mussel shell and confirmed the utility of the best glue in a filtration behaviour experiment using Anodonta anatina. We used removal forces up to 1.35 kg cm-2 7 d after submerging in water and found an epoxy resin and a cyanoacrylate adhesive to perform best. Not all epoxy resins or cyanoacrylate adhesives performed equally. The best performing cyanoacrylate adhesive was used to glue magnets and rubber-coated Hall sensors to 26 mussels for a filtration-behaviour experiment. Nine months after attachment, all magnets and rubber-coated Hall sensors remained attached and withstood 1.35 kg cm-2. The epoxy resin was not chosen, because it contained Bisphenol A and required a more complex application procedure. Mussel filtration behaviours were monitored for 96 h in the presence of algae. The results showed that the presence of algae stimulated the filtration rate of A. anatina in the first 24 h. Over the experimental period, the mussels' mean filtration duration was 20±12 h, while the resting duration was 16±7 h. We identified a pronounced circadian rhythm, despite the long filtration duration and variation in behaviour patterns. However, at any one time some mussels were observed to be filtering. The mussels were more likely to open their shells and become active at around 20:00. Thus the majority of mussels were active at midnight and a minority at noon. We interpret the strong response to increased algal concentration and the pronounced circadian rhythm as evidence that neither the glue nor the attached sensors disturbed the mussels even in a short-term experiment. Hence, we recommend the selected cyanoacrylate adhesive for use in tagging projects and behavioural studies of freshwater mussels. [ABSTRACT FROM AUTHOR]

Aims The objective of this study was to evaluate if freshwater bivalves can be used to detect the presence of Toxoplasma gondii in water bodies. Methods and Results Zebra mussels ( Dreissena polymorpha) were caged for 1 month upstream and downstream of the discharge points of wastewater treatment plants ( WWTPs). Physiological status was assessed to assure good health of bivalves during transplantation. The presence of T. gondii was investigated in mussel tissues by qPCR. In autumn, T. gondii was detected in mussels caged downstream of the discharge points of two WWTPs. In spring, it was detected upstream of one WWTP. Conclusions For the first time, T. gondii DNA has been shown in a continental mollusc in environmental conditions. This highlights the interest of an active approach that could be applied independently of the presence or accessibility of autochthonous populations, and underlines the presence of T. gondii in natural waters under pressure of WWTP discharge at a certain time of the year. Significance and Impact of the Study This study shows that transplanted zebra mussels could be used as biosamplers to reveal contamination of freshwater systems by T. gondii. [ABSTRACT FROM AUTHOR]

The article discusses the results of a study suggesting that freshwater clam (Corbicula fluminea) extract (FCE) and its fat/protein fractions have various beneficial effects against liver injury accompanied by the accumulation of hepatic liquid in rats exposed to the xenobiotic chloretone. Topics mentioned include the changes caused by the administration of xenobiotics to animals, how xenobiotic diets induce CYP gene expression, and the effect of dietary proteins on hepatic lipogenesis.

Genetic variation was examined in two endangered mussel species, Epioblasma brevidens and Epioblasma capsaeformis, and in a non-listed species, Lampsilis fasciola, in the Clinch River, Tennessee, USA, by screening mitochondrial DNA (mt DNA) sequences and nuclear DNA microsatellites. Patterns of mt DNA polymorphism exhibited different trends in long-term population sizes for each species during the late Pleistocene and Holocene (∼20 000 ya to present); namely, E. brevidens has declined over time, E. capsaeformis has remained demographically stable, and L. fasciola has expanded. However, analyses using microsatellites did not exhibit similar trends, perhaps because homoplasy had eliminated long-term population signatures for the loci examined. For both marker types, long-term effective population size ( Ne) was low in E. brevidens, intermediate in E. capsaeformis, and high in L. fasciola. Moderately diverged mt DNA lineages, perhaps indicative of secondary contact, were observed in E. brevidens and E. capsaeformis. Perhaps the most surprising result of this study was the high level of genetic variation observed at both mt DNA and microsatellite DNA markers for L. fasciola, variation seemingly contrary to the relatively small demes that currently reside in the Clinch River. However, the data are consistent with known demographic and life-history traits of these three mussel species and their fish hosts, namely that they each use hosts with different dispersal capabilities, ranging from low, moderate, and high, respectively. The low divergence of mt DNA sequence variation reported in this and other recent mussel studies indicates that considerable extant population genetic variation probably originated during the late Pleistocene and Holocene. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 114, 376-397. [ABSTRACT FROM AUTHOR]

The freshwater mussels Prisodontopsis aviculaeformis (F.R. Woodward, 1991) and Mweruella mweruensis (E.A. Smith, 1908) are endemic to Lake Mweru and confluent rivers in Zambia and the Democratic Republic of Congo in southcentral Africa. Each species has traditionally been regarded as monotypic at the genus-level or above. We assessed the phylogenetic relationships of these two species together with species of Coelatura, Nitia and three outgroup species (35 terminals representing 11 species in total) using two gene fragments, 28S nuclear rDNA and cytochrome oxidase subunit I mtDNA. Maximum parsimony, maximum likelihood and Bayesian inference provided strong support for a sister relationship between P. aviculaeformis and M. mweruensis as well as evidence of incomplete lineage sorting or introgression between them. This Lake Mweru clade was resolved as sister to a clade composed of Coelatura choziensis (Preston, 1910) and C. luapulaensis (Preston, 1913) from Lake Bangweulu and the adjacent Chambeshi River. These four species from the Zambian Congo were nested within a paraphyletic Coelatura Conrad, 1853. We advocate placing Mweruella Haas, 1936 as a subjective junior synonym of Prisodontopsis Tomlin, 1928, while maintaining Coelatura as paraphyletic until a more comprehensive phylogeny is available. We hypothesize that the endemic freshwater mussels of Lake Mweru in the Zambian Congo evolved within the lake during the Quaternary from an ancestor originating in the Chambeshi River following stream capture from the Zambezi Basin. [ABSTRACT FROM AUTHOR]

Intra- and interspecific morphological variation due to both phenotypic plasticity and evolutionary convergence hinder the work of taxonomists and lead to over- and underestimates of species richness. Nevertheless, most species on Earth are recognized solely based on morphological characters. We used molecular phylogenetic and morphometric techniques to examine two freshwater mussel species. One is common and widespread, while the other is imperiled and endemic to the Interior Highlands of the USA. Phylogenetic and molecular clock analyses revealed that divergence of Arcidens confragosus and Arkansia wheeleri is small and relatively recent. Divergence in these and other taxa is probably due to isolation of streams in the Interior Highlands. Morphometric analyses showed distinct shell shapes using traditional morphometrics, but not through geometric morphometrics. Outlined shell shapes are indistinguishable; geometric morphometrics could not capture a three-dimensional component. Our analyses support the validity of these two species as congeners, with the nomen Arcidens (Simpson 1900) having priority. Because shell morphologies are both heritable and environmentally determined, our study emphasizes the importance of considering both molecular and morphometric analyses for identification of freshwater molluscs of conservation concern. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 112, 535-545. [ABSTRACT FROM AUTHOR]

The morphological variability of freshwater bivalve species, observed between and within river basins, may hamper their correct identification, even by experienced researchers. Classic morphometric measurements, i.e. shell length, height and thickness, or their ratios, are generally insufficient to distinguish populations and/or species. These issues may be overcome using a geometric morphometric method, which allows analysis of the overall shape of the individual, independently of its size. Thus, we aimed to test the usefulness of two geometric morphometric tools, landmarks and sliding semilandmarks, to evaluate the morphological variability of Unio delphinus Spengler, 1783 in three habitats of the Guadiana Basin (SW Iberian Peninsula, Europe): estuary, river and stream. We used 13 landmarks located on the shell interior (at the teeth, muscle scars and pallial line) and 35 sliding semilandmarks for the shell contour. These morphometric analyses showed that the shell shape of U. delphinus differs significantly among different habitats. Estuarine and stream shells are the most disparate (James index = 649.114, permutation P-value <0.001) and variability is not related to variations in shell size. The main differences in shell morphology are the following: (1) estuarine shells are more elongate, while riverine shells are more subovate; (2) the anterior curvature at the umbo is steeper in estuarine and riverine shells; (3) estuarine shells have an arched curvature at the ventral part of the shell, which is absent in specimens from the other habitats. Our data suggest that the morphology of U. delphinus shells might be influenced by the water flow characteristics of each habitat, since shells exhibited characteristics that are typically observed in freshwater mussels from lotic and lentic habitats. [ABSTRACT FROM AUTHOR]

Because of the sedentary lifestyle of freshwater mussels, studies examining their movement capabilities are scarce. However, the ability to burrow into the substrate and the ability to remain stationary are likely crucial components of their behavioural repertoire. The performance of these different tasks is likely to be affected by the presence of the shell ornamentation characteristic of many mussel species. Previous studies have suggested that shell ornamentation results in a trade-off between burrowing ability and remaining stationary when an extrinsic force attempts to dislodge it from the substrate once buried. We examined the effect of morphology and shell ornamentation on burrowing performance and anchoring ability by artificially creating shell ornamentation on a relatively smooth-shelled species ( Potamilus alatus). Burrowing behaviours and performance and the force required to dislodge mussels (anchoring ability) were quantified with and without ornamentation. Interestingly, we found that the artificial shell ornamentation had no significant effect on burrowing behaviours and performance or dislodgement force. Burrowing and dislodgement, however, were both highly influenced by shell size and shape. All of the available information suggests that shell size, shape, and sculpture influence burrowing and anchoring in complex ways that needs further examination. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111, 136-144. [ABSTRACT FROM AUTHOR]

The parasitic nature of the association between glochidia of unionoidean bivalves and their host fish (i.e. the role of fish hosts in providing nutritional resources to the developing glochidia) is still uncertain. While previous work has provided descriptions of development of glochidia on fish hosts, earlier studies have not explicitly documented the flow of nutrition from the host fish to the juvenile mussel. Therefore, our objective was to use stable isotope analysis to quantitatively document nutrient flow between fish and glochidia. Glochidia were collected from nine adult Lampsilis cardium and used to inoculate Micropterus salmoides (n = 27; three fish per maternal mussel) that produced juvenile mussels for the experiment. Adult mussel tissue samples, glochidia, transformed juvenile mussels and fish gill tissues were analysed for δ15N and δ13C isotope ratios. We used a linear mixing model to estimate the fraction of juvenile mussel tissue derived from the host fish's tissue during attachment. Our analyses indicate a distinct shift in both C and N isotopic ratios from the glochidial stage to the juvenile stage during mussel attachment and development. Linear mixing model analysis indicated that 57.4% of the δ15N in juvenile tissues were obtained from the host fish. This work provides novel evidence that larval unionoideans are true parasites that derive nutrition from host fish during their metamorphosis into the juvenile stage. [ABSTRACT FROM AUTHOR]

Mussels in several orders possess two separate mitochondrial lineages: a standard female-inherited form and one inherited only through males. This system of doubly uniparental inheritance ( DUI) for mitochondrial genes provides an opportunity to compare the population structure of gene-lineages passed either mother-to-daughter or father-to-son. In the present study, we contrast variation in the male and female haplotype lineages of the American freshwater mussel species, Lampsilis siliquoidea (sometimes called Lampsilis radiata luteola), throughout the Lake Erie, Ohio River, and upper Mississippi River watersheds, and contrast variation with the sequences obtained for the related species/subspecies Lampsilis radiata radiata from Maine. The genetic markers were fragments of the cytochrome c oxidase subunit I gene ( COI), which occurs in both mitochondrial types, F (female) and M (male). High haplotype diversity was found in the two independent lineages, although purifying selection against amino acid change appeared to be stronger in the female than the male lineage. Phylogeographical patterns also varied between mitochondria passing through females and males. The female lineage exhibited more population structure, with the occurrence of private or nearly-private haplotypes within two streams, and three others showed restricted haplotype distributions. By contrast to the F-haplotypes, complex phylogenetic structure occurred for M-haplotypes, yet this phylogenetic variation coincided with almost no geographical pattern within haplotypes. Basically, F-haplotypes showed isolation, especially above physical barriers, whereas M-haplotypes did not. A few individuals in the eastern Lake Erie watershed even possessed M-haplotypes of an Atlantic Slope ( L. radiata radiata) origin, although their F-haplotypes were typical of Midwestern L. siliquoidea. The finding that mussels package sperm as spermatozuegmata, which float downstream, may underlie greater gene mobility in male-inherited mitochondria. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 109, 229-240. [ABSTRACT FROM AUTHOR]

Apple snails are freshwater gastropods with highly diverse feeding mechanisms (shredding, scraping and collecting) to exploit diverse food sources. Pomacea canaliculata is listed among the world's 100 worst invaders, mainly due to its effects on aquatic crops and submersed macrophytes through shredding, its main feeding mechanism. In one of the alternative mechanisms, the snails obtain material from the water surface through a funnel formed by the anterior part of the foot, here termed pedal surface collecting (PSC). Our aims were to study the potential trophic spectrum of PSC and the effects of snail size and sex, density of food particles and particle size on efficiency of this feeding mechanism under laboratory conditions. We also explored occurrence and daily fluctuations in the field. Pomacea canaliculata snails were able to capture different food types irrespective of their physical nature (liquid, organic particles and biofilms) and size, although not all of them could be ingested. PSC was performed only when food was available on the surface by snails from the whole size range tested (3–52.8 mm shell length), although it was less frequent in snails <10 mm. The amount of food captured by unit mass decreased with animal size, but is partially compensated by a corresponding increase in frequency and duration of PSC. The specific capture rate increased, and the time spent forming pedal funnels decreased, with food density, but no effects of particle size were observed. In the field, PSC was observed only occasionally during the day, but showed a marked increase after sunset, and was observed even when submerged macrophytes and associated periphyton were abundant. The wide trophic spectrum, the high and adaptable capture rates and the wide size tolerance likely allow P. canaliculata to take advantage of highly variable and unpredictable food resources present on the water surface, thereby contributing to the invasion success of the species. [ABSTRACT FROM AUTHOR]

We have established an in vitro glochidial culture of the freshwater mussel, Hyriopsis (Hyriopsis) bialatus, with the potential of restoring natural populations. However, to develop a successful in vitro culture process the synchronous release of glochidia needs to be achieved. In this study we investigated the distribution of serotonin and its effect on inducing synchronous parturition. Using confocal microscopy on whole-mounted tissues, we show that serotonin is highly expressed in the peripheral neuron somata and their axonal processes in the central neuropils of the visceral ganglion. Serotonergic nerve fibres were also detected along the branchial nerve innervating the demibranchs. A hierarchical ramification from the branchial cord into nerve rootlets and subsequently into the small nerve fibres within the demibranch epithelium was evident throughout this organ. In both visceral ganglia and demibranchs, immunoreactivity of serotonin was relatively higher in female than male tissues, suggesting a role of serotonin in female reproductive functions. Administration of serotonin to the demibranchs, the sites of larval settlement, stimulated synchronous parturition in a dose-dependent manner. A single-dose injection of serotonin yielded a large number of released larvae within 1–2 h, with no adverse effect on the quality of cultured larvae. [ABSTRACT FROM AUTHOR]

Hyriopsis cumingii (Lea, 1852) is a freshwater mussel of major commercial importance for pearl culture in China. In this study, five polymorphic microsatellites from H. cumingii were identified and employed to investigate the occurrence and frequency of multiple paternity in 15 H. cumingii broods caught from Poyang Lake, China. The allele number of each locus ranged from 12 to 25, with a mean of 16.8 ± 5.4 alleles per locus. Multiple paternity was discovered in 10 broods by genotyping the dam mussel and the offspring from each brood. The sire number inferred by COLONY software in the 10 broods ranged from 2 to 4 with a mean of 2.7 ± 0.26 sires per brood. In 6 of the 10 broods, sires contributed skewed numbers of offspring (P < 0.05). These factors may be important for avoidance of inbreeding, optimization of genetic variation in offspring and for the persistence and evolution of H. cumingii. [ABSTRACT FROM PUBLISHER]

We report here on the abundance and distribution of a metapopulation of smooth-shelled blue mussels (genus Mytilus) from northeastern New Zealand (NZ), in the latitudinal range 37–35°S. Site surveys revealed the presence of blue mussels at 12 of 20 locations on the east coast of the Northland Peninsula, in the Hauraki Gulf and into the Bay of Islands region. Additional material was collected subsequently from three sites, including an estuary location in Auckland, which is the southern-most record of blue mussels in this northern region. This new record of an extensive, but patchily distributed metapopulation in northeastern NZ identifies the existence of a pronounced geographic discontinuity between 37°S and 41°S in the distribution of Mytilus throughout NZ. Based on its geographic isolation, we suggest that the northeastern metapopulation is genetically isolated from other more southerly distributed blue mussels in NZ. Molecular identification of the mussels was carried out by both nuclear and mitochondrial DNA RFLP assays. While the majority of mussels were identified as native Southern hemisphere M. galloprovincialis, a substantial number of individuals with a nonnative (Northern hemisphere) M. galloprovincialis mitotype were also identified. The identification of this new metapopulation composed of both northern and southern lineage M. galloprovincialis has challenging biosecurity and conservation implications. Because of the pronounced geographic break in the distribution of blue mussels in NZ it may be possible to minimize further spread of the northern lineage mitotype to the rest of the country using an internal borders containment approach. However, based on introductions of (Northern hemisphere) M. galloprovincialis elsewhere in the world, we believe that the most likely outcome in NZ of this bioincursion is extensive interbreeding and introgression between the northern and southern lineages of M. galloprovincialis. [ABSTRACT FROM PUBLISHER]

The macrogeographic dispersal of unionoid mussels is largely dependent on movement by their host fish. The snuffbox mussel Epioblasma triquetra (Unionoida) and other congeners use a novel trapping behaviour to parasitize potential host fish with their larvae (glochidia). Common logperch ( Percina caprodes) trapped by E. triquetra survive the trapping behaviour, whereas other darter species ( Etheostoma and Percina) do not, thus, making the P. caprodes- E. triquetra relationship a good candidate system for a coevolutionary study. We hypothesized that the geographic genetic structure of E. triquetra should closely match that of its host, albeit with greater interpopulation divergences as a result of its dependency on the host for dispersal. Mantel tests of parallel pairwise matrices of population divergence (Jost's D) and genetic assignment tests based on microsatellite DNA data showed that the genetic population structures of both species were broadly, but not perfectly, congruent. Therefore, it appears that P. caprodes are not solely responsible for the genetic population structure observed for snuffbox and may not necessarily be the mussel's only host across its entire range. This suggests the potential for a geographic mosaic for coevolution in unionoids and darters. The findings of the present study reinforce the need for a joint study and conservation of unionoids and host fish aiming to protect these coevolved taxa. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, , 669-685. [ABSTRACT FROM AUTHOR]

Blue mussels Mytilus edulis (n = 14) were studied in the laboratory using Hall sensor systems to record their gaping behaviour when exposed to varying food rations and levels of predation risk. Mussel response to increasing daily algal ration was to increase mean gape angle per day and was associated with copious pseudofaeces production at excessive initial algal concentrations, e.g. 250 cells/µl. Mean gape angle decreased (backward S-shaped curve) when fed a fixed algal ration per day where simulated predation risk (introduced fresh mussel homogenate) increased in the water, presumably as an anti-predation strategy. However, this behaviour is presumed to lower feeding rates. There was a general positive relationship between both gape angle and the extent of valve movement (abduction/adduction) per event and valve movement speed. However, the fastest valve adduction events, which resulted in valve closure, were recorded independent of gape angle and only when mussels were first exposed to high perceived predation risk. We interpret this as an appropriate response, with high energetic cost, as a first line of defence from predators such as starfish and crabs. Overall, mussel response to predation appears graded and complex, indicating a trade-off between maximizing feeding/pseudofaeces production and minimizing predation risk. [ABSTRACT FROM PUBLISHER]