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This study aimed to identify the importance of ecological factors to distribution patterns of the invasive Clam (Corbicula fluminea) relative to native mussels (family: Unionidae) across seven rivers within the Mobile and Tennessee basins, Southeast United States. We quantitatively surveyed dense, diverse native mussel aggregations across 20 river reaches and estimated mussel density, biomass, and species richness along with density of invasive C. fluminea (hereafter Corbicula). We measured substrate particle size, velocity, and depth in quadrats where animals were collected. Additionally, we characterized reach scale environmental parameters including seston quantity and quality (% Carbon, % Nitrogen, % Phosphorous), water chemistry (ammonium [NH4+], soluble reactive phosphorous [SRP]), and watershed area and land cover. Using model selection, logistic regression, and multivariate analysis, we characterized habitat features and their association to invasive Corbicula within mussel beds. We found that Corbicula were more likely to occur and more abundant in quadrats with greater mussel biomass, larger substrate size, faster water velocity, and shallower water depth. At the reach scale, Corbicula densities increased where particle sizes were larger. Mussel richness, density, and biomass increased with watershed area. Water column NH4+ increased at reaches with more urban land cover. No land cover variables influenced Corbicula populations or mussel communities. The strong overlapping distribution of Corbicula and mussels support the hypothesis that Corbicula are not necessarily limited by habitat factors and may be passengers of change in rivers where mussels have declined due to habitat degradation. Whether Corbicula is facilitated by mussels or negatively interacts with mussels in these systems remains to be seen. Focused experiments that manipulate patch scale variables would improve our understanding of the role of species interactions (e.g., competition, predation, facilitation) or physical habitat factors in influencing spatial overlap between Corbicula and native mussels. [ABSTRACT FROM AUTHOR]

We describe for the first time the transmission route employed by the parasitic larvae of the freshwater mussel Anodontites trapesialis (Lamarck, 1819) during cohabitation on the guppy Poecilia reticulata Peter, 1859. The freshwater mussel and fish-host were employed as a model system to investigate the infection and parasite establishment. Laboratory experiments included video recording and histopathological analysis of the infection. In vivo video observations demonstrated that lasidium larvae could be transmitted to guppies during direct contact. A series of histology samples and photography suggest that this larva attaches and colonizes possibly on-site on the outer surface of the fish, causing cellular inflammation in the epidermis layer with cellular hyperplasia in the zone of parasite attachment. An evident hyaline layer, cellular hypertrophy, and a large number of undifferentiated proliferating cells were observed. Hemorrhagic tissue and swelling were observed in the epidermis and dermic zone. The total number of larvae per male and female guppy was 525 ± 86 and 494 ± 167, respectively. No parasitic preference was detected for male versus female parasitized fish. [ABSTRACT FROM AUTHOR]

Siloxane-polyurethane hybrid coatings were assessed for biofouling control caused by freshwater mussels. Invasive species such as zebra (Dreissena polymorpha) and quagga (Dreissena bugensis) mussels have rapidly spread through the waterways in the United States causing major concerns in reservoir infrastructure and freshwater lakes. Current coating solutions such as biocidal anti-fouling coatings are not suitable given the released biocides which may accumulate in reservoirs. Biocide free fouling release coatings based on silicone elastomers do not have adequate mechanical durability. The siloxane-polyurethane (SiPU) coatings were evaluated using model organism laboratory assays and real-life performance was evaluated in the freshwater field environment. Two coating compositions displayed excellent performance in field trials for up to 2+ years. The surface analysis experiments of the coatings indicate that the morphology of the coatings is affected by the formulations' solvent choice. These coatings show great promise in mitigating biofouling predominated by freshwater mussels. [ABSTRACT FROM AUTHOR]

Alterations to water management practices, in response to a growing demand to maximize energy production from renewable sources, threaten to exacerbate anticipated future water shortages caused by severe drought episodes, brought on by climate change.Across Scotland, many highly managed systems are inhabited by some of the last remaining reproductively viable populations of the freshwater pearl mussel, Margaritifera margaritifera. A lack of empirical evidence concerning mussel responses to alterations in flow is inhibiting the development of effective conservation management practices to prolonged drought.This study addressed this knowledge gap by examining the response of M. margaritifera to controlled water level drawdowns in laboratory and field settings. Using a laboratory flume, the responses of M. margaritifera from two different populations (a regulated system versus an unregulated system) were compared across rates of drawdown and density treatments. An analogous field trial was undertaken to examine the responses of M. margaritifera in a regulated system, with a hydroelectric dam facilitating a controlled drawdown.The study showed that M. margaritifera can detect alterations in flow depth, which culminate in the emersion of mussel beds, and respond by undertaking vertical and horizontal movements to mitigate the risk of prolonged aerial exposure. Results from the field trial corroborated findings from the flume experiments, with 80% of mussels shown to avoid emersion successfully by tracking receding water levels.Findings from this study support the role of controlled drawdowns in regulated rivers to reduce mortalities associated with receding water levels during prolonged low‐flow episodes. Differences between populations in response highlight a need to adopt a context‐dependent approach to conservation efforts. [ABSTRACT FROM AUTHOR]

Dreissenid (zebra and quagga) mussels are spreading across North America and having an impact on freshwater ecosystems, through bottom-up impacts. Lakes in British Columbia are known to be at risk for mussel invasion due to favourable water chemistry and significant cross-border boat movements. This project uses Ecopath with Ecosim (EwE) to model a hypothetical mussel invasion into Shuswap Lake: one of the most popular lakes for recreation and one of the most productive sockeye lakes in the province. A model of the ecosystem was fit to available data and then projected forward to examine the effects from three different scenarios: no invasion, a base mussel invasion scenario resulting in a carrying capacity of 5 g∙m-2 and 15 g∙m-2 of zebra and quagga mussels, respectively, and a high density invasion scenario resulting in a combined carrying capacity of 40 g∙m-2 of Dreissenid mussels. The greatest ecosystem impacts resulted in declines in large piscivorous rainbow trout and lake trout, followed by non-anadromous kokanee salmon, with little effect observed on anadromous sockeye salmon. Two mechanisms limit the predicted impact of mussels in the study system: (1) paucity of shallow water habitat, limiting the scope for invasion; and (2) movements by fish in and out of the system. This second mechanism includes some resident species that rear for up to three years upstream of the lake, as well as anadromous species, which spend most of their life in the marine environment. While most of the effects are observed on recreationally important species, there is also the possibility of mussels spreading from this system into others within the same watershed, reiterating the importance of preventing the invasion and spread of Dreissenid mussels. [ABSTRACT FROM AUTHOR]

Global decline of freshwater mussels (Unionoida) is threatening biodiversity and the essential ecosystem services that mussels provide. As filter-feeding organisms, freshwater mussels remove phytoplankton and suspended particles from the water. By filtering bacteria, freshwater mussels also decrease pathogen loads in the water. The objective of this study was to evaluate whether the common freshwater bivalve Anodonta anatina (duck mussel) could remove the bacterial fish pathogen Flavobacterium columnare from the water. Mussels reduced bacteria in both of the two experiments performed, so that the bacterial concentration at the end of the 96-h monitoring in mussel treatments was only 0.3–0.5 times that of the controls. Surprisingly, mussels did not reduce algal cell concentration statistically significantly. Mussel behavior (shell openness, foot position, and movement) was not affected by the presence of bacteria or algae, except for biodeposition formation, which was greatest in algal-fed treatments, followed by bacterial-fed treatments and controls, respectively. The intestines of bacteria-incubated A. anatina harbored F. columnare, suggesting that mussels ingested the bacteria. Present results suggest that freshwater mussels may also have a potential to mitigate aquaculture pathogen problems, as well as play a role in water quality management. [ABSTRACT FROM AUTHOR]

India represents a tropical biodiversity hotspot, harbouring a unique and largely endemic fauna of freshwater mussels (Bivalvia: Unionidae). Unfortunately, the type series of many freshwater mussel taxa historically described from this country are thought to be lost. Here, we report on the rediscovery of the type series of Parreysia corrugata (O.F Müller, 1774) (Parreysiinae: Parreysiini) in the Natural History Museum of Denmark (NHMD), Copenhagen. It contains four syntypes (complete shells), which were examined by means of morphological and geometric morphometric techniques. We show that the nominal taxon Parreysia corrugata was established based on a composite type series, because one of the syntypes belongs to another species, Potomida semirugata (Lamarck, 1819) (Gonideinae: Lamprotulini), originating from the Middle East. To fix the taxonomic identity of the Indian species, a syntype (lot NHMD 916309) that was most likely illustrated by O.F. Müller in 1779 is designated here as the lectotype of Parreysia corrugata. The lectotype, paralectotypes and corresponding labels are illustrated in detail. Our new findings clarify the taxonomic concept of Parreysia corrugata and contribute to the further development of the Indian Unionidae taxonomy. [ABSTRACT FROM AUTHOR]

Freshwater mussels and crayfish provide important ecosystem functions and services. In both groups, global declines of native species are paralleled by invasions of non‐native species. Knowledge on differences in predation susceptibility of native and invasive freshwater mussels exposed to native and invasive crayfish is essential for understanding their ecological interactions and for conservation management.In this study, we compared the predation impact of the native European noble crayfish (Astacus astacus) and the invasive signal crayfish (Pacifastacus leniusculus) on three native (Anodonta anatina, Anodonta cygnea, and Unio pictorum) and one invasive (Sinanodonta woodiana) mussel species in controlled laboratory experiments. We repeated the same experiments with the same crayfish specimens to investigate a potential learning effect of crayfish and assessed the in situ impacts in a natural stream.Mussel predation and damage caused by P. leniusculus was significantly higher than by A. astacus. Irrespective of the crayfish species, susceptibility was greater in native mussel species compared to invasive S. woodiana. Predation and damage was greatest in the thick‐shelled U. pictorum, suggesting that other factors such as shell shape are more important in explaining susceptibility than shell thickness. A predation learning effect from previous co‐exposure was evident, being most pronounced for A. astacus.Even if our experimental findings could not be confirmed in the field, the experimental results suggest that crayfish may have a negative impact on mussels and this impact will likely increase with the ongoing spread of P. leniusculus replacing A. astacus populations in Europe. The co‐occurrence of invasive P. leniusculus with the invasive S. woodiana could potentially exacerbate declines of endangered native mussel populations. [ABSTRACT FROM AUTHOR]

Little is known about the current state of freshwater biodiversity in Canada, one of the countries with the greatest amount of surface waters in the world. To address this knowledge gap, we compiled a list of all available assessments of conservation status for freshwater species (over 3000 taxa) and further evaluated the overall status of six distinct taxonomic groups, focusing on organisms reliant on fresh waters (i.e., aquatic plants, invertebrates (with a focus on freshwater mussels), fishes, herpetofauna (reptiles and amphibians), birds, and mammals). Overall, 11.7% of all freshwater species of plants and animals assessed were found to be "at risk" (i.e., listed as "Threatened", "Endangered", or "Extirpated") and 17.9% identified as "Special Concern". We found that 37.9% of species lacked sufficient data to enable their status to be assessed. Data gaps in Canada's assessment of its freshwater species were most prevalent in invertebrates (excluding freshwater mussels). Given the alarming state of freshwater biodiversity in Canada, we conclude by providing recommendations that focus on evaluating temporal trends and informing conservation actions. [ABSTRACT FROM AUTHOR]

North American freshwater mussel species have experienced substantial range fragmentation and population reductions. These impacts have the potential to reduce genetic connectivity among populations and increase the risk of losing genetic diversity. Thirteen microsatellite loci and an 883 bp fragment of the mitochondrial ND1 gene were used to assess genetic diversity, population structure, contemporary migration rates, and population size changes across the range of the Sheepnose mussel (Plethobasus cyphyus). Population structure analyses reveal five populations, three in the Upper Mississippi River Basin and two in the Ohio River Basin. Sampling locations exhibit a high degree of genetic diversity and contemporary migration estimates indicate that migration within river basins is occurring, although at low rates, but there is no migration is occurring between the Ohio and Mississippi river basins. No evidence of bottlenecks was detected, and almost all locations exhibited the signature of population expansion. Our results indicate that although anthropogenic activity has altered the landscape across the range of the Sheepnose, these activities have yet to be reflected in losses of genetic diversity. Efforts to conserve Sheepnose populations should focus on maintaining existing habitats and fostering genetic connectivity between extant demes to conserve remaining genetic diversity for future viable populations. [ABSTRACT FROM AUTHOR]

Longitudinal training dams (LTDs) in the river Waal are novel river training structures that protect the littoral zone from the adverse effects of navigation providing new habitats for riverine macroinvertebrates. In order to inform river management and to better understand their ecological value for native and alien mussel species, it is important to assess the habitat suitability of the protected LTD shore channels. We applied spatial hydroacoustics surveys consisting of side-scan sonar (SSS) and acoustic Doppler current profiler (ADCP) of the substrate type, water depth and flow velocity in three shore channels in combination with species sensitivity distributions (SSDs) to predict habitat suitability for native and alien mussel species. SSDs allowed for the prediction of habitat suitability as a potentially occurring fraction (POF) of a species pool. High substrate type, water depth, and near-bottom flow velocity POFs were found for ≥ 70%, 100%, and 4–51% of the total shore channel area, respectively, suggesting that shore channels provide suitable habitat for both native and alien mussel species. To enhance the shore channels as habitat for native mussel species, we recommend increasing shallow areas dominated by fine (silt/clay) and sand substrate types with low near-bottom flow velocities (near 0 m/s). In contrast, the total area of hard substrate (e.g., boulders) in the shore channels should be reduced as it strongly favored invasive alien mussel species in our study. Future research should include additional abiotic parameters to enhance the habitat suitability predictions and compare the results for different riverine habitats. [ABSTRACT FROM AUTHOR]

In aquatic life, environmental chemicals are accumulated by mussels due to their sentinel nature and filter-feeding characteristics. Herein, the present study focused on assessing the concentrations of Cu, Zn, Mg, Mn, Fe, Cd, Pb, Ca, K, and Na levels in freshwater mussels (Unio elangatulus eucirrus) depending on sex and age. For all trace metals, some important differences of bioaccumulations were determined depending on ages and sex. In details, the results indicated that an important age-related accumulation of Mg, Cd, Ca, and K was in females and all trace elements, except Cu, Mg, and K levels in males (p < 0.05). No statistical differences were determined in mean concentrations of Cu, Zn, Mg, and Na. There are statistical differences in Mg, Mn, Fe, and Ca levels between females and males in four aged mussels (p < 0.05). Lead levels were under detectable limits. Overall, metal levels and their toxicity in freshwater mussels should be closely monitored for health of the environment, animals, and humans, since mussels and fish species fed on them are consumed highly in the research region and around. [ABSTRACT FROM AUTHOR]

Unpaved roads make up at least 14 million kilometers of the worldwide road network. Although investigations of road runoff often are focused on paved roads, unpaved roads contribute large volumes of runoff to roadside aquatic habitats and introduce unique constituents to runoff, such as chemical dust suppressants. At least 200 products across five chemical categories are commercially available for road dust suppression and are typically applied at rates up to 4.5 L/m2. Many of these products are poorly described and are lacking basic information on environmental transport, fate, and potential toxicity to roadside organisms. We characterized the aquatic toxicity of 27 commercially available dust control products, including 13 biobased products from the U.S. Department of Agriculture BioPreferred catalog, using juvenile rainbow trout. Acute toxicity varied by more than 1000-fold among products, with 96-h LC50 values ranging from 1.7 to > 16,000 mg/L. Toxicity was not well-predicted by product category. Testing with selected products after simulated weathering under UV radiation did not provide evidence of photoenhanced toxicity. Additional tests with freshwater mussels, juvenile crayfish, pond snails, and amphibian larvae indicated that juvenile rainbow trout were reasonable surrogates for these organisms for a subset of products. This effort represents one of the first comparative studies of dust suppressant toxicity and provides important information for assessing risk to aquatic resources from a widely used but understudied class of contaminants in road runoff. [ABSTRACT FROM AUTHOR]

The widespread use of road salt for winter road maintenance has led to an increase in the salinity of surface water in many seasonally cold areas. Freshwater mussels have a heightened sensitivity to salt, which is a concern, because many Canadian mussel species at risk have ranges limited to southern Ontario, Canada's most road-dense region. This study examined the effect of winter road runoff on freshwater mussels. The impact of two bridges that span mussel habitat in the Thames River watershed (Ontario, Canada), the second most species-rich watershed for mussels in Canada, were studied. During a winter melt event, bridge runoff, as well as creek surface water surrounding the bridges were collected. Chloride concentrations in samples from bridge deck and tile drains varied (99–8250 mg/L). In general, survival of Lampsilis fasciola glochidia exposed to those samples reflected chloride levels (e.g. 84% at 99 mg/L; 0% at 8250 mg/L), although potassium (60 mg/L) may have at least contributed to toxicity in one sample. Serial dilution exposures with the two most toxic runoff samples revealed 48-h glochidia EC50s of 44% (McGregor Creek Tile Drain) and 26% (Baptiste Creek Deck Drain). During the melt event, the chloride concentrations in creek surface waters downstream of the bridges ranged from 69 to 179 mg Cl−/L; effects on glochidia (viability 77–91%) exposed to those waters was minimal. There were no live mussels surrounding one bridge (Baptiste Creek), likely due to poor habitat. At the other targeted bridge (McGregor Creek), fewer mussels were found close (< 100 m up- or downstream) to the bridge than further (> 200 m) away. However, other contributing factors, including agriculture, were present at both study areas. [ABSTRACT FROM AUTHOR]

Pseudunio marocanus (Pallary, 1918) is an endemic species of Morocco and is considered one of the world's 100 most threatened species. The life cycle of this critically endangered freshwater mussel remains unknown. However, knowledge about the discharge period of its larvae and its ecological fish hosts is crucial to adopt more effective conservation strategies.Given this information gap, monitoring the presence of P. marocanus glochidia in fish from the Laabid River was carried out from January to May 2019 to determine the larvae discharge period. Two different approaches were used to assess the fish hosts of P. marocanus: (i) the determination of glochidia infestation rates of fishes in situ through monthly (from January to May) sampling in the Laabid River (Oum Er Rbia basin); and (ii) artificial infestation in laboratory trials using four fish species.A peak in glochidia discharge was observed at the end of February. Fully metamorphosed juveniles were detected in all native fish species, i.e. Luciobarbus ksibi (Boulenger, 1905), Carasobarbus fritschii (Günther, 1874), Luciobarbus zayanensis Doadrio, Casal‐lopez & Yahyaoui, 2016, and Pterocapoeta maroccana Günther, 1874.For the first time, the glochidia discharge period and the fish hosts of P. marocanus were determined, and this information is vital to implement future conservation measures (i.e. propagation, reinforcement of populations, possible reintroductions of P. marocanus, careful management of river flow by upstream dams, and the prohibition of fishing activities during the critical glochidia discharge period).Given the increasing human pressure on freshwater habitats and biodiversity in Morocco, it is essential to preserve the native ichthyofauna to conserve this rare pearl mussel species. [ABSTRACT FROM AUTHOR]

The contribution of the form of silver nanomaterials (nAg) towards toxicity in aquatic organisms is not well understood. The purpose of this study was to examine the toxicity of various structures (sphere, cube and prism) of nAg in Dreissena bugensis mussels. Mussels were exposed to increasing concentrations of polyvinyl-coated nAg of the same size for 96 h at 15 °C. They were then analyzed for biophysical changes in the cytoplasm (viscosity, protein aggregation and lipids), neuro-activity (fractal kinetics of acetylcholinesterase (AChE)), oxidative stress (labile zinc (Zn) and lipid peroxidation) and inflammation (arachidonate cyclooxygenase). Although some decreasing effects in protein aggregation were observed, viscosity was more strongly decreased in mussels exposed to spheric and prismatic nAg. The activity of AChE was significantly decreased in the following form-dependent manner: prismatic > cubic > spheric nAg. The fractal dimension of AChE reactions was reduced by all geometries of nAg, while dissolved Ag had no effects. For nanoparticles with the same coating and relative size, spheric nAg produced more significant changes towards the fractal dimension of AChE, while prismatic nAg increased both protein aggregation and viscosity, whereas cubic nAg decreased protein aggregation in the cytoplasm. It is concluded that the geometries of nanoparticles could influence toxicity in aquatic organisms. [ABSTRACT FROM AUTHOR]

Freshwater mussels cannot spread through oceanic barriers and represent a suitable model to test the continental drift patterns. Here, we reconstruct the diversification of Oriental freshwater mussels (Unionidae) and revise their taxonomy. We show that the Indian Subcontinent harbors a rather taxonomically poor fauna, containing 25 freshwater mussel species from one subfamily (Parreysiinae). This subfamily most likely originated in East Gondwana in the Jurassic and its representatives arrived to Asia on two Gondwanan fragments (Indian Plate and Burma Terrane). We propose that the Burma Terrane was connected with the Indian Plate through the Greater India up to the terminal Cretaceous. Later on, during the entire Paleogene epoch, these blocks have served as isolated evolutionary hotspots for freshwater mussels. The Burma Terrane collided with mainland Asia in the Late Eocene, leading to the origin of the Mekong's Indochinellini radiation. Our findings indicate that the Burma Terrane had played a major role as a Gondwanan "biotic ferry" alongside with the Indian Plate. [ABSTRACT FROM AUTHOR]

Using a selection of molecular biomarkers, we evaluated responses in freshwater mussels (Anodonta anatina) exposed to effluent from an industrial wastewater treatment facility. The aims of this work were to (1) assess biomarkers of general toxicity under sublethal exposure to an anthropogenic mixture of chemicals, represented by an arbitrary effluent, and (2) evaluate the potential of A. anatina as a bioindicator of pollution. Adult mussels (n = in total 32; 24 males and 8 females) were exposed (96 h) in the laboratory to a fixed dilution of effluent or to a control treatment of standardized freshwater. Metal concentrations were in general higher in the effluent, by an order of magnitude or more, compared to the control. Toxic unit estimates were used as proxies of chemical stress, and Cu, Ni, and Zn were identified as potential major contributors (Cu> Ni > Zn). Six transcriptional (cat, gst, hsp70, hsp90, mt, sod) and two biochemical (AChE, GST) biomarkers were analyzed in two tissues, gills, and digestive glands. Out of the 16 responses (eight biomarkers × two tissues), 14 effect sizes were small (within ± 28 % of control) and differences non-significant (p > 0.05). Results did however show that (1) AChE activity increased by 40% in gills of exposed mussels compared to control, (2) hsp90 expression was 100% higher in exposed female gills compared to control, and (3) three marker signals (AChE in both tissues, and hsp70 in gills) differed between sexes, independent of treatment. Results highlight a need for further investigation of molecular biomarker variability and robustness in A. anatina. [ABSTRACT FROM AUTHOR]

Microbiomes are increasingly recognized as widespread regulators of function from individual organism to ecosystem scales. However, the manner in which animals influence the structure and function of environmental microbiomes has received considerably less attention. Using a comparative field study, we investigated the relationship between freshwater mussel microbiomes and environmental microbiomes. We used two focal species of unionid mussels, Amblema plicata and Actinonaias ligamentina , with distinct behavioral and physiological characteristics. Mussel microbiomes, those of the shell and biodeposits, were less diverse than both surface and subsurface sediment microbiomes. Mussel abundance was a significant predictor of sediment microbial community composition, but mussel species richness was not. Our data suggest that local habitat conditions which change dynamically along streams, such as discharge, water turnover, and canopy cover, work in tandem to influence environmental microbial community assemblages at discreet rather than landscape scales. Further, mussel burrowing activity and mussel shells may provide habitat for microbial communities critical to nutrient cycling in these systems. [ABSTRACT FROM AUTHOR]

For freshwater fishes and mussels listed under the Species at Risk Act (SARA), a federal recovery strategy or management plan identifies recovery measures for best achieving population and distribution objectives. Recovery strategies and management plans for SARAlisted freshwater fish and mussel species often identify conservation translocation, specifically supplementation or reintroduction, as a potential approach for improving survival and/or recovery. However, there has been limited progress in undertaking conservation translocations primarily due to basic information gaps on species ecology and uncertainty about how to assess the potential ecological benefits and risks to freshwater species and ecosystems. The objectives of this research document were to: 1) identify and evaluate the potential benefits and risks of conservation translocation as a tool for improving the survival, recovery, or management of SARA-listed freshwater fish and mussel species; and, 2) identify science-based considerations and methods for determining when conservation translocation would be expected to improve the survival, recovery, or management of SARA-listed freshwater fishes and mussels. Benefits and risks of conservation translocations to the focal species and broader ecosystem components are presented, including a decision support framework for evaluating the potential benefits and risks of conservation translocation for SARA-listed freshwater fishes and mussels. The decision support framework consists of five steps: 1) Identify fundamental and means objectives for conservation translocations; 2) Assess the probability of achieving the fundamental and means objectives; 3) Identify and assess the likelihood and magnitude of unintended consequences; 4) Compile and weigh the scientific evidence to inform the translocation decision; and, 5) Implement and monitor the conservation translocation. Using the decision support framework can help determine if and when the ecological benefits of conservation translocations outweigh the uncertainties and ecological risks when attempting to improve the survival and recovery of SARA-listed freshwater fishes and mussels. Future refinement of the decision support framework would benefit from several case studies in addition to those presented in the appendices. [ABSTRACT FROM AUTHOR]

Under Section 73(3) of Canada's Species at Risk Act, the competent minister may not authorize an activity that jeopardizes the survival or recovery of a SARA-listed species. Since 2004, the concept of jeopardizing survival and recovery has received considerable attention from DFO's Science Sector in the form of allowable harm advice; however, allowable harm is a species, not project-specific concept, and to date has not typically incorporated habitat effects, which are expected with development projects in and around aquatic ecosystems. Here, an overview of allowable harm advice is presented as it relates to interpreting Section 73(3). Components of a science-based framework to assess the impact of development activities under Section 73(3) are then presented. The three components are: 1) the ability to relate individual projects to changes in habitat condition; 2) relationships between habitat condition and species vital rates, including considerations for behavioural and sub-lethal effects; and, 3) the relationship between population growth rate and vital rates, explored through elasticity analysis for 143 COSEWICassessed species (fishes, freshwater mussels, marine mammals, marine turtles) across five population states (crashing, declining, stable, growing, booming). These components are combined to estimate changes to a species' population growth rate resulting from a single development activity, and thus also provide an accounting framework to evaluate harm from all activities in a permitting period. The components will require future work to inform taxa-specific functional responses, especially concerning relationships between habitat and vital rates, and sub-lethal effects. Further work is also required to determine the ability to achieve measurable gains in vital rates and populations through offsetting measures, if applied. If adopted into a decision support tool, this body of work would ensure that project decisions around Section 73(3) can be made in a rigorous, transparent, and nationally consistent manner. [ABSTRACT FROM AUTHOR]

Obovaria olivaria is a species of freshwater mussel native to the Mississippi River and Laurentian Great Lakes‐St. Lawrence River drainages of North America. This mussel has experienced population declines across large parts of its distribution and is imperiled in many jurisdictions. Obovaria olivaria uses the similarly imperiled Acipenser fulvescens (Lake Sturgeon) as a host for its glochidia. We employed mitochondrial DNA sequencing and restriction site‐associated DNA sequencing (RAD‐seq) to assess patterns of genetic diversity and population structure of O. olivaria from 19 collection locations including the St. Lawrence River drainage, the Great Lakes drainage, the Upper Mississippi River drainage, the Ohioan River drainage, and the Mississippi Embayment. Heterozygosity was highest in Upper Mississippi and Great Lakes populations, followed by a reduction in diversity and relative effective population size in the St. Lawrence populations. Pairwise FST ranged from 0.00 to 0.20, and analyses of genetic structure revealed two major ancestral populations, one including all St. Lawrence River/Ottawa River sites and the other including remaining sites; however, significant admixture and isolation by river distance across the range were evident. The genetic diversity and structure of O. olivaria is consistent with the existing literature on Acipenser fulvescens and suggests that, although northern and southern O. olivaria populations are genetically distinct, genetic structure in O. olivaria is largely clinal rather than discrete across its range. Conservation and restoration efforts of O. olivaria should prioritize the maintenance and restoration of locations where O. olivaria remain, especially in northern rivers, and to ensure connectivity that will facilitate dispersal of Acipenser fulvescens and movement of encysted glochidia. [ABSTRACT FROM AUTHOR]

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Halting the global decline of freshwater mussels requires an improved understanding of the restoration approaches currently in use and the identification of shortcomings to inform the development of new ones. This article reviews published evaluations of restoration efforts on the ground and those identified or proposed in the literature.This review found few reports of the effectiveness of restoration measures, and of those reported there was strong temporal and geographical bias. Reports were mostly recent and took place within mussel‐diverse regions of the Global North (i.e. North America, Europe).Efforts focused on population support encompassed relocation, translocation and population augmentation from captive breeding, and potential restoration approaches emphasized planning and prioritization. It was challenging to assess restoration success owing to differences in success metrics and varied lengths of post‐restoration monitoring. Some measures were inherently more species specific, such as population support, but some articles suggested that the use of multiple measures may allow more species to be addressed by restoration efforts.Consistent documentation and reporting of restoration measures – including failed ones – are needed to advance freshwater mussel restoration. In addition, continued work is needed to accelerate and better align the development and use of restoration approaches for freshwater mussels. Reporting of unsuccessful or partially successful attempts does not adequately reflect the long life histories of freshwater mussels.Investigation of the contexts where approaches have been effective (even partially), and concerted efforts to implement combinations of measures at a catchment scale are critical for unionids globally. As such, recommendations are posed to aid integration of research and practice to advance and further develop freshwater mussel restoration. [ABSTRACT FROM AUTHOR]

Overexploitation of freshwater resources coupled with climate change can affect the flow and temperature regimes in rivers, which can be catastrophic for aquatic biota. The San Saba and Llano rivers, located in central Texas, are experiencing low flows and stream dewatering owing to over‐allocation. Both systems harbour imperilled species, including Lampsilis bracteata, Texas fatmucket, which has been proposed for listing under the US Endangered Species Act. It is suspected that elevated water temperatures are a contributing factor in its decline.The upper thermal tolerances of glochidia and juvenile life stages were evaluated within each river. Mussels were acclimated to 27°C and tested across a range of temperatures (30–39°C) in 24 h (glochidia) and 96 h (juveniles) laboratory tests. The resulting tolerances were related to in situ water temperature and discharge using a uniform continuous above‐threshold analysis.In the Llano, the 24 h LT50 (lethal temperature resulting in 50% mortality) was 31.8°C (95% CI 31.5–32.1°C), whereas the 96 h LT50 was 32.4°C (95% CI 32.1–32.7°C). In the San Saba, the 24 h LT50 was 34.7°C (95% CI 34.5–35.0°C), whereas the 96 h LT50 was 32.5°C (95% CI 32.2–32.9°C). LT50 thresholds were not exceeded for L. bracteata within the San Saba, but LT05 (lethal temperature resulting in 5% mortality) thresholds were exceeded. Water temperature loggers were lost in the Llano River as a result of a large flood; however, samples reported by the Texas Commission on Environmental Quality show that the LT05 and LT50 for both glochidia and juveniles were exceeded.Findings from this study indicate that thermal tolerances of L. bracteata vary by population and that low flows may be contributing to its decline. Our approach is non‐species and region specific, which means that the methods presented should help managers and conservationists evaluate whether reduced water quantity and elevated temperatures are exerting impacts on aquatic species within their region. [ABSTRACT FROM AUTHOR]

Mussel–flow relationships are not well defined and studies linking behavioural, physiological and life‐history traits to hydrological conditions remain scant. This lack of information hinders not only understanding of how flow shapes population and community processes but the development of evidence‐based flow recommendations to mitigate mussel declines.Mussel–flow relationships were evaluated for Potamilus amphichaenus (Texas heelsplitter), Pleurobema riddellii (Louisiana pigtoe) and Truncilla macrodon (Texas fawnsfoot) from the Sabine, Trinity, Neches and Cypress River basins of East Texas using Indicators of Hydraulic Alteration and random forest models. These species were chosen because all three are currently being evaluated for listing under the US Endangered Species Act.Analyses were performed on US Geological Survey stream gauge stations and mussel records within 20 km of each other. Only gauges with at least 15 years of continuous data and ≥70% overlap of flow records from 1968 to 2018 were included. For selected 28 gauges, Indicators of Hydraulic Alteration were used to calculate 47 hydrological parameters that describe the magnitude, frequency and duration of high and low flow events. Random forest classification models across species were significant and had low error rates (3.57–21.43%), moderate to high sensitivity (0.81–0.93) and moderate to high specificity (0.71–1.00).Life‐history theory was useful for explaining how mussel species cope with hydrological variation. Potamilus amphichaenus and T. macrodon/Truncilla donaciformis, considered r‐selected or opportunistic strategists, were more likely to occur in basins characterized by significant changes in flow and land use compared with P. riddellii, considered a K‐selected or equilibrium strategist.The analytical framework presented in this study should be helpful to managers and conservationists interested in determining how the flow regime is shaping aquatic communities in their region and developing reference points that could serve for ecological research, conservation and management. [ABSTRACT FROM AUTHOR]

A new genus of freshwater mussels (Bivalvia: Unionidae) is described from the Mekong River Basin as Namkongnaia gen. nov. The validity of the new genus is supported by its unique conchological characteristics, namely the lack of hinge dentition and elongated shells, together with its evolutionary distinctiveness as estimated by multi-locus phylogenetic analyses (mitochondrial COI and 16S, and nuclear 28S genes). The new genus includes two lineages with deep divergence, shown by 5.10% uncorrected COI p-distance. One lineage is a type species described herein as Namkongnaia inkhavilayi gen. et sp. nov. The other is a recognized species under the name ‘Pilsbryoconcha lemeslei (Morelet, 1875)’. Molecular phylogenetic analysis further shows that the new genus belongs to the tribe Pseudodontini, and evolutionarily is closely related to the genus Monodontina Conrad, 1853. However, its conchology is similar to the genus Pilsbryoconcha Simpson, 1900. Time-calibrated phylogeny suggests that the main radiation events of the tribe Pseudodontini occurred during the Late Cretaceous to the Eocene, with the divergence between the new genus and Monodontina placed in the Miocene. The discovery of new freshwater mussel taxa in this study highlights the importance of the Mekong River Basin as one of the world’s biodiversity hotspots for freshwater fauna.

Like marine mussels, freshwater zebra and quagga mussels adhere via the byssus, a proteinaceous attachment apparatus. Attachment to various surfaces allows these invasive mussels to rapidly spread, however the adhesion mechanism is not fully understood. While marine mussel adhesion mechanics has been studied at the individual byssal-strand level, freshwater mussel adhesion has only been characterized through whole-mussel detachment, without direct interspecies comparisons on different substrates. Here, adhesive strength of individual quagga and zebra mussel byssal plaques were measured on smooth substrates with varying hydrophobicity—glass, PVC, and PDMS. With increased hydrophobicity of substrates, adhesive failures occurred more frequently, and mussel adhesion strength decreased. A new failure mode termed 'footprint failure' was identified, where failure appeared to be adhesive macroscopically, but a microscopic residue remained on the surface. Zebra mussels adhered stronger and more frequently on PDMS than quagga mussels. While their adhesion strengths were similar on PVC, there were differences in the failure mode and the plaque-substrate interface ultrastructure. Comparisons with previous marine mussel studies demonstrated that freshwater mussels adhere with comparable strength despite known differences in protein composition. An improved understanding of freshwater mussel adhesion mechanics may help explain spreading dynamics and will be important in developing effective antifouling surfaces. [ABSTRACT FROM AUTHOR]

The naiads, large freshwater mussels (Unionida), have very long life spans, are large-bodied, and produce thousands to millions of larvae (glochidia) which typically must attach to host fish tissues to metamorphose into a juvenile mussel. Glochidia develop within a female's marsupial gill demibranch, thus their number is restricted by female size. However, larger mussels acquire more energy, which could be invested in either larger-sized glochidia, in a more glochidia, or a combination of both. The high level of host specialization seen in many naiads may constrain glochidial size and shape around a narrow optimum, while naiads that use a wide range of host fishes may be predicted to possess greater plasticity in glochidial morphology. In this paper, we investigated the relationship between maternal body size and progeny body size and shape, aided by modern digital microscopy. We analyzed the between- and within- species variation of glochidia size and shape relative to female size in four widespread species of European naiads: Anodonta anatina, Anodonta cygnea, Unio crassus and Unio tumidus. Whereas the total reproductive output is collinear with female body size, substantial differences between species in glochidia size were found within genus Anodonta, but not genus Unio where glochidial size is remarkably consistent. The glochidial shape, however, differed within both Unio and Anodonta. We interpret this constant within-species glochidial size in Unio as reflecting a constraint imposed by the likelihood of successful transmission onto and off from a narrow range of hosts, whereas their shape seems to be less constrained. The Anodonta species, inhabiting a wide spectrum of habitats and using more than twice the number of fish hosts than Unio spp., have larger glochidia with greater variation in size and shape. Our results suggest that measures of glochidial variability may also serve as an indicator of host specificity in other naiads. [ABSTRACT FROM AUTHOR]

Conservation of ecosystem engineers, which modulates the surrounding habitat by causing physical state changes in biotic or abiotic materials, is important for maintaining the functional integrity of ecosystems. This study examined the effects of endangered freshwater pearl mussels (Margaritifera laevis and M. togakushiensis) on channel morphology and flow in a low-gradient sandy river. For this, we performed a field removal experiment of mussels using three treatments in twelve 10-m reaches. Mussel abundance and biomass, and three physical variables were measured before, immediately after, and two months to one year after the treatments. Mussel removal resulted in channel degradation with a 60% increase in flow depth, a 30% decrease in current velocity, and a 50% reduction in the width-to-depth ratio two months after the treatments, whereas minimal changes were measured in reaches with mussels. The results indicated that pearl mussels act as an ecosystem engineer affecting the channel morphology and flow of sandy rivers. The conservation of the pearl mussel populations is key to preserving their far-reaching benefits in ecosystem integrity including habitats for other various organisms. [ABSTRACT FROM AUTHOR]

Freshwater mussels are one of the most imperiled groups of animals in the world and are among the most sensitive species to a variety of chemicals. However, little is known about the sensitivity of freshwater mussels to wastewater effluents. The objectives of the present study were to (1) assess the toxicity of a permitted effluent, which entered the Deep Fork River, Oklahoma (USA), to a unionid mussel (Lampsilis siliquoidea) and to two standard test species (cladoceran Ceriodaphnia dubia; and fathead minnow Pimephales promelas) in short‐term 7‐day effluent tests; (2) evaluate the relative sensitivities of the three species to potassium (K), an elevated major ion in the effluent, using 7‐day toxicity tests with KCl spiked into a Deep Fork River upstream reference water; (3) determine the potential influences of background water characteristics on the acute K toxicity to the mussel (96‐h exposures) and cladoceran (48‐h exposure) in four reconstituted waters that mimicked the hardness and ionic composition ranges of the Deep Fork River; and (4) determine the potential influence of temperature on acute K toxicity to the mussel. The effluent was found to be toxic to mussels and cladocerans, and it contained elevated concentrations of major cations and anions relative to the upstream Deep Fork River reference water. The K concentration in the effluent was 48‐fold greater than in the upstream water. Compared with the standard species, the mussel was more than 4‐fold more sensitive to the effluent in the 7‐day effluent tests and more than 8‐fold more sensitive to K in the 7‐day K toxicity tests. The acute K toxicity to the mussel decreased by a factor of 2 when the water hardness was increased from soft (42 mg/L as CaCO3) to very hard (314 mg/L as CaCO3), whereas the acute K toxicity to the cladoceran remained almost the same as hardness increased from 84 to 307 mg/L as CaCO3. Acute K toxicity to the mussel at 23 °C was similar to the toxicity at an elevated temperature of 28 °C. The overall results indicate that the two standard test species may not represent the sensitivity of the tested mussel to both the effluent and K, and the toxicity of K was influenced by the hardness in test waters, but by a limited magnitude. Environ Toxicol Chem 2021;40:3410–3420. Published 2021. This article is a U.S. Government work and is in the public domain in the USA. [ABSTRACT FROM AUTHOR]

Ion ATPases in the tissues of aquatic animals are sensitive to metal exposures. Mussels are filter-feeding animals and have a sedentary lifestyle that makes them good bio-indicator animals. Thus, the present study was carried out to investigate the effects of copper (0, 30, 90 µg/L) on the activities of Na-ATPase, Mg-ATPase, and Ca-ATPase in the gill and muscle of freshwater mussels (Unio tigridis) in different exposure durations (0, 7, 14, 21 days). Feeding of mussels during the experiments were done with the cultured unicellular algae (Cholorella vulgaris), serving them approximately 300,000 algae/ml. At the end of 21 days of exposure period, no mussel mortality was recorded. Total protein concentrations in the gill and muscle did not change significantly (P>0.05) in any exposure groups. Likewise, control ATPase activities did not alter significantly during different exposure periods. However, ATPase activities in the gill and muscle of mussels altered significantly (P<0.05) following exposure to copper, especially at the higher concentration. Although there were significant increases and decreases in the activity of Mg-ATPase in both tissues, Na-ATPase and Ca-ATPase activities did not fluctuate as there were only significant decreases at the higher exposure concentration. The present data demonstrated that copper at environmentally realistic concentrations was able to alter the activities of ion ATPases in the gill and muscle of mussels and emphasized osmoregulatory stress which mussels might face in waters contaminated with copper. [ABSTRACT FROM AUTHOR]

Historically diverse and abundant freshwater mussel communities in the Midwestern USA, as elsewhere in the world, are in substantial decline. An understanding of mussel distributions, habitat requirements and biodiversity is required to develop and optimize mussel conservation efforts.Maxent was used to generate species distribution models (SDMs) based on a wide range of environmental variables. Binary predictions were generated using two approaches. Species richness (SR) was estimated through model stacking and evaluated with an independent dataset derived from intensive sampling. Two measures of species endemism were estimated. Factors important for mussel occurrence were identified and geospatial analyses characterized spatial patterns of predicted SR and endemism at multiple spatial scales.SDMs generally performed at 'fair' or better levels (0.7 < AUC < 1). Stream size, climate and land use were important to mussel occurrence. SR estimates were positively and significantly correlated with observed SR in a separate dataset. SR and endemism hot and cold spots varied across spatial scales.This study introduces a novel background selection process for aquatic SDMs that considers sampling biases, species records relative to stream size and species' geographical ranges. The results provide valuable insight into species status and distributions, important and actionable factors influencing mussel occurrence, and spatial patterns of highly diverse or endemic regions. This study demonstrates how synthesizing SDMs can inform regional, multi‐species efforts for conserving freshwater mussel diversity. [ABSTRACT FROM AUTHOR]

Freshwater mussels are among the most critically endangered taxa globally. In the United States, 91 out of nearly 300 species are listed as Threatened or Endangered under the Endangered Species Act.Freshwater mussel species exhibit a range of life‐history traits. Owing to the large number of North American species, the rarity of many listed species and the often limited data available for those species, it can be difficult to gather all of the information necessary to develop ecological risk assessments and effective management plans for freshwater mussel species.The primary objective of this study was to categorize North American freshwater mussel species into life‐history categories to aid in the identification of representative species for risk assessment.To achieve these objectives, a literature review was conducted to identify available life‐history data for a large range of mussel species. Using this dataset, two ordinations were performed, non‐metric multidimensional scaling and discriminant analysis, to classify mussel species into previously described life‐history categories. Both analyses facilitated species classification into life‐history categories.Significant data gaps in basic life‐history information still exist for many species, but previously described life‐history categories were found to be robust and additional analysis allowed quantitative classification of additional 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 shell morphologies of the freshwater mussel species Pleurobema clava (federally endangered) and Pleurobema oviforme (species of concern) are similar, causing considerable taxonomic confusion between the two species over the last 100 years. While P. clava was historically widespread throughout the Ohio River basin and tributaries to the lower Laurentian Great Lakes, P. oviforme was confined to the Tennessee and the upper Cumberland River basins. We used two mitochondrial DNA (mtDNA) genes, 13 novel nuclear DNA microsatellite markers, and shell morphometrics to help resolve this taxonomic confusion. Evidence for a single species was apparent in phylogenetic analyses of each mtDNA gene, revealing monophyletic relationships with minimal differentiation and shared haplotypes. Analyses of microsatellites showed significant genetic structuring, with four main genetic clusters detected, respectively, in the upper Ohio River basin, the lower Ohio River and Great Lakes, and upper Tennessee River basin, and a fourth genetic cluster, which included geographically intermediate populations in the Ohio and Tennessee river basins. While principal components analysis (PCA) of morphometric variables (i.e., length, height, width, and weight) showed significant differences in shell shape, only 3% of the variance in shell shape was explained by nominal species. Using Linear Discriminant and Random Forest (RF) analyses, correct classification rates for the two species' shell forms were 65.5% and 83.2%, respectively. Random Forest classification rates for some populations were higher; for example, for North Fork Holston (HOLS), it was >90%. While nuclear DNA and shell morphology indicate that the HOLS population is strongly differentiated, perhaps indicative of cryptic biodiversity, we consider the presence of a single widespread species the most likely biological scenario for many of the investigated populations based on our mtDNA dataset. However, additional sampling of P. oviforme populations at nuclear loci is needed to corroborate this finding. [ABSTRACT FROM AUTHOR]

North American watersheds contain a high diversity of freshwater mussels (Unionoida). During the long-lived, benthic phase of their life cycle, up to 40 species can co-occur in a single riffle and there is typically little evidence for major differences in their feeding ecology or microhabitat partitioning. In contrast, their brief parasitic larval phase involves the infection of a wide diversity of fish hosts and female mussels have evolved a spectrum of adaptations for infecting host fish with their offspring. Many species use a passive broadcast strategy: placing high numbers of larvae in the water column and relying on chance encounters with potential hosts. Many other species, including most members of the Lampsilini, have a proactive strategy that entails the use of prey-mimetic lures to change the behavior of the hosts, i.e., eliciting a feeding response through which they become infected. Two main lure types are collectively produced: mantle tissue lures (on the female’s body) and brood lures, containing infective larvae, that are released into the external environment. In this study, we used a phylogenomic approach (ddRAD-seq) to place the diversity of infection strategies used by 54 North American lampsiline mussels into an evolutionary context. Ancestral state reconstruction recovered evidence for the early evolution of mantle lures in this clade, with brood lures and broadcast infection strategies both being independently derived twice. The most common infection strategy, occurring in our largest ingroup clade, is a mixed one in which mimetic mantle lures are apparently the predominant infection mechanism, but gravid females also release simple, non-mimetic brood lures at the end of the season. This mixed infection strategy clade shows some evidence of an increase in diversification rate and most members use centrarchids (Micropterus & Lepomis spp.) as their predominant fish hosts. Broad linkage between infection strategies and predominant fish host genera is also seen in other lampsiline clades: worm-like mantle lures of Toxolasma spp. with sunfish (Lepomisspp.); insect larvae-like brood lures (Ptychobranchus spp.), or mantle lures (Medionidus spp., Obovaria spp.), or mantle lures combined with host capture (Epioblasma spp.) with a spectrum of darter (Etheostoma & Percina spp.) and sculpin (Cottus spp.) hosts, and tethered brood lures (Hamiota spp.) with bass (Micropterus spp.). Our phylogenetic results confirm that discrete lampsiline mussel clades exhibit considerable specialization in the primary fish host clades their larvae parasitize, and in the host infection strategies they employ to do so. They are also consistent with the hypothesis that larval resource partitioning of fish hosts is an important factor in maintaining species diversity in mussel assemblages. We conclude that, taking their larval ecology and host-infection mechanisms into account, lampsiline mussels may be legitimately viewed as an adaptive radiation. [ABSTRACT FROM AUTHOR]

Freshwater pearl mussels (family Margaritiferidae) are sensitive to human impact and environmental changes. Large declines in their abundance have prompted studies of distribution and estimations of population densities.Iturup Island, a part of Kuril Islands, Russia, is considered to be within the distribution area of freshwater pearl mussels, but this information is based on only two specimens collected several decades ago. Detailed survey of the island is challenging as most of its territory is nearly impassable.A preliminary analysis of island rivers was carried out prior to the surveys to discover potential freshwater pearl mussel habitats. Based on previous experience from European Russia, freshwater pearl mussel habitat was expected to occur in rivers flowing out of lowland lakes.Live individuals of Margaritifera laevis were found during surveys in one river together with the unionid Beringiana beringiana, which were also found in two other rivers where the predicted habitat occurred. Based on prediction and surveys, the occurrence of freshwater pearl mussels in other rivers of Iturup Island is unlikely.Pearl mussels were concentrated in a small section of the Zmeika River with a population of about 100,000 mussels. Present threats to the population include overharvest of host fish masou salmon (Oncorhynchus masou).Surveys using similar methods can help to reveal unknown freshwater mussel populations on other Kuril Islands and on the mainland. [ABSTRACT FROM AUTHOR]

Most of the Bornean endemic freshwater mussel (Unionida) species known to date have not been recorded by science for the past 50 years or more, owing to a lack of research effort and presumed population losses.This study assessed current patterns and recent changes in the diversity and distribution of freshwater mussels in north‐eastern Borneo. Physical surveys and interviews were conducted at 24 sites, and anecdotal evidence for current or historical presence of mussels was collected for a further 13 sites.Native species, i.e. Schepmania sp. and Khairuloconcha sahanae gen. & sp. nov., were only found in one small stream of the Kinabatangan River basin within the Gomantong Forest Reserve, whereas the non‐native Sinanodonta cf. woodiana was common across the study area.Molecular phylogenetics (five genes) of the native taxa, including comparative material from West Kalimantan and Sarawak, revealed: (i) the presence of a new genus with two new, rare species: Khairuloconcha lunbawangorum sp. nov. in the Limbang River basin and K. sahanae in the Kinabatangan River basin; (ii) that Khairuloconcha and Ctenodesma form the Bornean endemic tribe Ctenodesmini trib. nov.; and (iii) that Schepmania represents another Bornean endemic tribe Schepmaniini trib. nov.Both Khairuloconcha gen. nov. species are known from a single stream each and are apparently restricted to forest stream habitats where they occur at very low densities. Schepmania appears to have a severely contracted range in the Kinabatangan and adjacent basins. We urgently call for full protection of the currently known sites of K. lunbawangorum and K. sahanae, and development of an action plan to save the Bornean freshwater mussel fauna. [ABSTRACT FROM AUTHOR]

The aim of this study was to assess the extent to which the behavioural traits of freshwater mussels provide suitable indicators of stress in individuals, towards the advancement of non‐invasive, remote monitoring techniques to examine population condition.Variation in the expression of particular behavioural metrics was examined in accordance with measurements of oxygen consumption, across environmental stressors (aerial exposure and high concentrations of total suspended solids), and between two freshwater mussel species (Margaritifera margaritifera and Anodonta anatina)Aerobic metabolic rate was quantified using intermittent respirometry, and behaviour was observed using time‐lapse footage. Comparisons of metabolic response and the occurrence of behavioural traits, across the two stressors, focused on differences between the 24 h pre‐exposure period (pre‐exposure), the first 3 h of post‐exposure (immediate post‐exposure), and the time following the initial 3 h of post‐exposure until the end of the experimental run (extended post‐exposure).The results of this study demonstrated a relationship between the frequency of occurrence of behavioural responses to stress exposure, associated with valve activity, and significant changes in the metabolic functioning of A. anatina and M. margaritifera mussels. The findings from the study also highlighted substantial intraspecific variation across species and stressors.Data from this research could assist in the development of novel biosensors that track mussel valve activity remotely in their natural environment. When coupled with real‐time data examining alterations in environmental metrics, this technology could assist in the monitoring of population condition and aid conservation management. [ABSTRACT FROM AUTHOR]

The advent of global warming events on already stressed organisms by pollution and loss of habitats raised concerns on the sustainability of local mussel populations. The purpose of this study was to study the physiology 6 commonly found species of freshwater mussels in the attempt to identify species at risk from global warming and pollution. The following species were examined for mass/length, energy metabolism, air survival and lipid peroxidation (LPO): Elliptio complanata (EC), Eurynia dilatata (ED), Pyganodon cataracta (PC), Pyganodon species (Psp), Lasmigona costata (LC) and Dreissena bugenis (DB). The data revealed that the estimated longevity of each species was associated with mussel mass, mitochondria electron transport (MET), temperature-dependent MET but negatively related with mitochondria levels in LPO and the colonization potential. The colonization potential was derived from the scaling of MET activity and mass, which confirmed that DB mussels are more invasive than the other species followed by Psp. Resistance to air emersion was significantly associated with longevity, mass and length and mitochondria LPO. Hence, organisms with low lifetimes, mass or length with high LPO are less able to survive for longer periods in air. In conclusion, longevity and air survival was positively associated with mass and energy metabolism but negatively with oxidative damage. This study proposes key markers in identifying species more at risk to contaminant stress, decreased water levels and global warming. [ABSTRACT FROM AUTHOR]

Mussels provide important ecological functions in freshwater ecosystems but the associations between Amazonian mussels, macroinvertebrate assemblage and habitat quality remain poorly understood. We investigated whether changes in macroinvertebrate assemblage structure and ecological functioning were associated with mussel presence. We compared sites with and without mussels, with similar habitat conditions, in an eastern Amazonian river, using field measurements of macroinvertebrate structure, hydrological variables and sediment organic matter, and laboratory experiments of mussel clearance rate and biodeposition. Sites with mussels were associated with higher macroinvertebrate abundance and number of taxa, especially for trichopterans Marilia (shredder), Oecetis (predator) and Antarctoecia (collector). Decreased chlorophyll-a in the water column and increased sediment organic matter were positively associated with mussel presence. Laboratory experiments corroborated these patterns, which were stronger with higher mussel density. Mussel filtration and biodeposition may be associated with habitat quality for other invertebrates by lowering phytoplankton density in the water column and increasing inputs of sediment organic matter. This suggests a potential role of freshwater mussels in ecosystem function associated with high taxonomic and functional diversity in the macroinvertebrate assemblages of an eastern Amazon river, enhancing the already high mussel conservation priority. [ABSTRACT FROM AUTHOR]

Populations of the freshwater mussels Unio crassus and U. tumidus have declined significantly over many decades. The river Vantaanjoki, at their northern limit in southern Finland, has yielded a number of empty hinged shells of U. crassus (39 shells) and U. tumidus (71 shells), which have been studied visually for taphonomical features. All of the shells are to some degree affected by taphonomical processes, particularly dissolution and fragmentation. These death assemblages of Unio shells are time-averaged as suggested by their radiocarbon (14C) dates, with consequences for the expected temporal resolution of both death and fossil assemblages. Although the shells are of different ontogenetic and post-mortem ages, there are no distinct differences in their preservation. Considering both taphonomical features and 14C dating, time-averaged death assemblages, which might illustrate the time-evolving anthropogenic changes of the river environment over the last centuries, should with some caution be compared with modern populations for conservation evaluations. [ABSTRACT FROM AUTHOR]

The biomineralization mechanism of mollusc shell has been studied for a long time, but there is a lack of understanding about the relationship between the shell formation in vitro and the signaling system in vivo. In this study, we cloned a novel shell matrix protein gene (hc-temptin), which only be characterized as a water-borne protein pheromone of molluscs in previous studies, from the freshwater mussel Hyriopsis cumingii. By bioinformatics analysis we found that temptin was a gene unique to the clade Lophotrochozoa, and it exists in all mollusc taxa except Cephalopoda. The current data supported the premise that temptin was generated in the early emergence of molluscs and that it maintained a high mutation rate to evolve relative independently. The specificity of hc-temptin expression in the mantle tissue suggests its potential to participate in biomineralization. Its sequence contained typical Ca2+ binding sites. Our experiments involving the pearl formation process, damaged shell repair process, and RNAi experiment showed that hc-temptin was a shell matrix protein that plays an important role in formation of the prismatic layer. The results of this study provided new insights about the origin of the temptin gene and its role in molluscs. [ABSTRACT FROM AUTHOR]

Biogeochemical ecology of organisms typically focuses on C, N, and P despite c. 25 elements needed for organismal function. Embracing novel suites of elements in biomass is a first step in linking elements to organismal and ecological functions, improving our ability to predict how species interact with their environment. This research area has been fruitful for terrestrial plant ecologists, yet few studies have considered animal ecology within a framework encompassing elements beyond C, N, and P.Freshwater mussels (Unionidae) are highly endangered filter‐feeding bivalves that can be important to ecosystem function. Interspecific trait variation influences soft tissue elemental composition that has been linked to ecosystem biogeochemical cycling using traditional C:N:P stoichiometric approaches. However, whether interspecific trait variation influences shell elemental composition is not well studied, especially for elements other than C, N, and P.We quantified B, C, Ca, Cu, Fe, K, Mg, Mn, N, P, and Zn and constructed isometric log‐ratios (nutrient balances) for shells of seven species comprising diverse morphologies and two life history strategies to test whether shell elemental composition is influenced by these biological traits. Additionally, we evaluated whether the growth rate hypothesis applies to shell P concentration and elements associated with P in nutrient balances.Bulk and trace elemental composition varied taxonomically and with biological traits. Nutrient balances for [C | P] and [C, Ca | P] were influenced by life history strategy. Shell P composition was negatively related to growth rates. Coincidentally, [C | P] and [C, Ca | P] were greater in the species with the highest growth rate (Lampsilis ornata), suggesting greater concentrations of C and Ca relative to P in shells of faster growing mussels. We hypothesise this observed pattern results from greater P allocation to soft tissue in fast growing mussels compared to slow growing mussels studied previously, but explicit tests of this hypothesis in a strict stoichiometric framework are needed.Overall, we demonstrate how quantifying elements beyond C, N, and P, may be useful in uncovering elemental diversity associated with trade‐offs in elemental allocation among biological traits. Whether such elemental diversity correlates to evolutionary history or contributes to the biogeochemical template of freshwater habitats remains to be seen but should be explored. [ABSTRACT FROM AUTHOR]

Co-infections are common in host-parasite interactions, but studies about their impact on the virulence of parasites/diseases are still scarce. The present study compared mortality induced by a fatal bacterial pathogen, Flavobacterium columnare between brown trout infected with glochidia from the endangered freshwater pearl mussel, Margaritifera margaritifera, and uninfected control fish during the parasitic period and after the parasitic period (i.e. glochidia detached) in a laboratory experiment. We hypothesised that glochidial infection would increase host susceptibility to and/or pathogenicity of the bacterial infection. We found that the highly virulent strain of F. columnare caused an intense disease outbreak, with mortality reaching 100% within 29 h. Opposite to the study hypothesis, both fresh ongoing and past infection (14 months post-infection) with glochidia prolonged the fish host's survival statistically significantly by 1 h compared to the control fish (two-way ANOVA: fresh-infection, F1, 82 = 7.144, p = 0.009 and post-infection, F1, 51 = 4.227, p = 0.044). Furthermore, fish survival time increased with glochidia abundance (MLR: post-infection, t = 2.103, p = 0.045). The mechanism could be connected to an enhanced non-specific immunity or changed gill structure of the fish, as F. columnare enters the fish body mainly via the gills, which is also the glochidia's attachment site. The results increase current knowledge about the interactions between freshwater mussels and their (commercially important) fish hosts and fish pathogens and also emphasise the importance of (unknown) ecosystem services (e.g., protection against pathogens) potentially associated with imperilled freshwater mussels. [ABSTRACT FROM AUTHOR]