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Freshwater mussel declines range from dramatic to subtle, but there are few methods for quantifying the extent of decline and overall assemblage health. Available assessment tools are specific to particular streams or regions and depend on untested assumptions or subjective assessments of species' tolerance to various factors. We developed a broadly applicable, objective mussel assemblage health index (MAHI). We compiled a dataset of mussel survey data from 50 streams across eastern North America and evaluated the ability of 19 candidate metrics to discriminate healthy and degraded assemblages. MAHI includes 4 metrics representing fundamental aspects of assemblage or population health (species loss, recruitment, abundance, and population growth). Metrics are scaled from 0 to 10 (representing increasing health), and the composite score is the unweighted mean of the 4 metrics. MAHI effectively discriminated healthy (median score = 8.3) and degraded (3.2) assemblages. The composite score is robust to missing values—omitting any single metric resulted in a median score change of ≤0.7. Composite scores were similar to independent scores provided by experts, but MAHI eliminates variation due to differences in individual perception or experience. MAHI can be applied to streams across eastern North America using commonly collected mussel survey data, and it may be adapted to other regions. MAHI is free of untested assumptions or subjective assessments, and it accounts for expected differences in mussel assemblages due to stream size, biogeographic region, and other intrinsic factors. MAHI will be a valuable tool for early detection of mussel declines, better understanding the causes of declines, and evaluating the effectiveness of conservation strategies and management actions. We developed a Microsoft Excel application that calculates MAHI scores, and we provide a link to that resource. [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]

The elevated use of salt as a de-icing agent on roads in Canada is causing an increase in the chloride concentration of freshwater ecosystems. Freshwater Unionid mussels are a group of organisms that are sensitive to increases in chloride levels. Unionids have greater diversity in North America than anywhere else on Earth, but they are also one of the most imperiled groups of organisms. This underscores the importance of understanding the effect that increasing salt exposure has on these threatened species. There are more data on the acute toxicity of chloride to Unionids than on chronic toxicity. This study investigated the effect of chronic sodium chloride exposure on the survival and filtering activity of two Unionid species (Eurynia dilatata, and Lasmigona costata) and assessed the effect on the metabolome in L. costata hemolymph. The concentration causing mortality after 28 days of exposure was similar for E. dilatata (1893 mg Cl−/L) and L. costata (1903 mg Cl−/L). Significant changes in the metabolome of the L. costata hemolymph were observed for mussels exposed to non-lethal concentrations. For example, several phosphatidylethanolamines, several hydroxyeicosatetraenoic acids, pyropheophorbide-a, and alpha-linolenic acid were significantly upregulated in the hemolymph of mussels exposed to 1000 mg Cl−/L for 28 days. While no mortality occurred in the treatment, elevated metabolites in the hemolymph are an indicator of stress. [ABSTRACT FROM AUTHOR]

Freshwater mussels of the order Unionida are currently one of the most imperiled groups of organisms in the North American faunal region. Accurate risk assessments and development of effective management strategies for remaining populations require knowledge of thermal limits in the face of increasing surface water temperature due to climate change and various anthropogenic factors. We conducted a systematic literature review of unionid mussels (order Unionida, families Margaritiferidae and Unionidae) in the North American faunal region to (1) summarize lethal thermal tolerance data by life stage and taxonomy, (2) discuss ecological and climate change implications of existing lethal tolerance data, and (3) identify needs for future research. We identified lethal tolerance estimates for only 28 of 302 species in the families Unionidae and Margaritiferidae. The mean acute median lethal temperatures were 32.8 °C for glochidia (19 species), 35.0 °C for juveniles (13 species), and 36.3 °C for adults (4 species). Generally, glochidia were less tolerant than juveniles or adults of the same species—but there were several exceptions. Generally, Amblemini had the highest acute and chronic thermal tolerance of all tribes followed by Anodontini, Pleurobemini, Lampsilini, and Quadrilini. Acclimation temperature affected lethal tolerance endpoints in less than half (52 of 145) of comparisons within species. Lethal tolerance data for additional species, combined with a comprehensive database of in situ surface water temperatures, would be useful for modeling the frequency and duration of lethal limit exceedance in North America and identifying populations currently living at or near their upper lethal limits. [ABSTRACT FROM AUTHOR]

The isolated river drainages of eastern North America serve as a natural laboratory to investigate the roles of allopatry and secondary contact in the evolutionary trajectories of recently diverged lineages. Drainage divides facilitate allopatric speciation, but due to their sensitivity to climatic and geomorphological changes, neighboring rivers frequently coalesce, creating recurrent opportunities of isolation and contact throughout the history of aquatic lineages. The freshwater mussel Quadrula quadrula is widely distributed across isolated rivers of eastern North America and possesses high phenotypic and molecular variation across its range. We integrate sequence data from three genomes, including female- and male-inherited mitochondrial markers and thousands of nuclear encoded SNPs with morphology and geography to illuminate the group's divergence history. Across contemporary isolated rivers, we found continuums of molecular and morphological variation, following a pattern of isolation by distance. In contact zones, hybridization was frequent with no apparent fitness consequences, as advanced hybrids were common. Accordingly, we recognize Q. quadrula as a single cohesive species with subspecific variation (Q. quadrula rumphiana). Demographic modeling and divergence dating supported a divergence history characterized by allopatric vicariance followed by secondary contact, likely driven by river rearrangements and Pleistocene glacial cycles. Despite clinal range-wide variation and hybridization in contact zones, the process-based species delimitation tool delimitR, which considers demographic scenarios like secondary contact, supported the delimitation of the maximum number of species tested. As such, when interpreting species delimitation results, we suggest careful consideration of spatial sampling and subsequent geographic patterns of biological variation, particularly for wide-ranging taxa., (© 2024 The Author(s). Molecular Ecology published by John Wiley & Sons Ltd. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.)

Trophic interactions between mobile animals and their food sources often vector resource flows across ecosystem boundaries. However, the quality and quantity of such ecological subsidies may be altered by indirect interactions between seemingly unconnected taxa. We studied whether emergent macrophytes growing at the aquatic–terrestrial interface facilitate multi‐step aquatic‐to‐terrestrial resource flows between streams and terrestrial herbivores. We also explored whether aquatic animal aggregations indirectly promote such resource flows by creating biogeochemical hotspots of nutrient cycling and availability.We tested whether white‐tailed deer (Odocoileus virginianus) in eastern North America vector nutrient fluxes from streams to terrestrial ecosystems by consuming emergent macrophytes (Justicia americana) using isotope and nutrient analyses of fecal samples and motion‐sensing cameras. We also tested whether mussel‐generated biogeochemical hotspots might promote such fluxes by surveying the density and nutrient stoichiometry of J. americana beds growing in association with variable densities of freshwater mussels (Bivalvia: Unionoida).Fecal samples from riparian deer had 3% lower C:N and 20% lower C:P ratios than those in upland habitats. C and N isotopes suggested riparian deer ate both terrestrial and aquatic (J. americana) vegetation, whereas upland deer ate more terrestrial foods. Motion‐sensing cameras showed deer eating J. americana more than twice as frequently at mussel‐generated hotspots than non‐mussel sites. However, mussels were not associated with variation in J. americana growth or N and P content—although N isotopes in J. americana leaves did suggest assimilation of animal‐derived nutrients.Our findings suggest that white‐tailed deer may conduct significant transfers of aquatic‐derived nutrients into terrestrial habitats when they feed on macrophytes and defecate on land. Whether aquatic animal aggregations promote such resource flows by creating biogeochemical hotspots remains unresolved, but the nearly global distributions of the deer family (Cervidae) and of macrophytes suggest that cervid‐driven aquatic‐to‐terrestrial nutrient flows may be widespread and ecologically important. [ABSTRACT FROM AUTHOR]

Indigenous freshwater mussels (Unionidae) are integral to riverine ecosystems, playing a pivotal role in aquatic food webs and providing ecological services. With populations on the decline worldwide, freshwater mussels are of conservation concern. In this study, we explore the propensity of the invasive Round Goby (Neogobius melanostomus) fish to prey upon indigenous freshwater mussels. First, we conducted lab experiments where Round Gobies were given the opportunity to feed on juvenile unionid mussels and macroinvertebrates, revealing rates and preferences of consumption. Several Round Gobies consumed whole freshwater mussels during these experiments, as confirmed by mussel counts and x-ray images of the fishes. Next, we investigated Round Gobies collected from stream habitats of the French Creek watershed, which is renowned for its unique and rich aquatic biodiversity. We developed a novel DNA metabarcoding method to identify the specific species of mussels consumed by Round Goby and provide a new database of DNA gene sequences for 25 indigenous unionid mussel species. Several of the fishes sampled had consumed indigenous mussels, including the Elktoe (non-endangered), Creeper (non-endangered), Long Solid (state endangered), and Rayed Bean (federally endangered) species. The invasive Round Goby poses a growing threat to unionid mussels, including species of conservation concern. The introduction of the invasive Round Goby to freshwaters of North America is shaping ecosystem transitions within the aquatic critical zone having widespread implications for conservation and management. [ABSTRACT FROM AUTHOR]

As body size often predicts energetic requirements and fecundity, understanding the drivers behind size variation is important. Neo‐Bergmann's rule states that larger individuals are found at higher latitudes and this size variation is attributable to temperature gradients. In ectotherms, this macroecological pattern has mixed support within the literature—both the direction and mechanism of size correlation with latitude varies.We asked if two species of freshwater mussels with different thermal niche preferences, Amblema plicata and Lampsilis cardium, follow neo‐Bergmann's rule and what mechanisms might drive that latitudinal variation. Lampsilis cardium is a thermally sensitive species intolerant of high temperatures, and A. plicata is more tolerant of a wide range of temperatures. We predicted that the thermally sensitive species at southern latitudes would have stunted growth in the summer and that this stunting would produce a steeper relationship with latitude than in the thermally tolerant species. We collected and thin‐sectioned 113 A. plicata shells from 23 sites and 85 Lampsilis cardium shells from 12 sites across a latitudinal gradient in the eastern U.S.A. We used back‐calculated size‐at‐age data to determine logistic growth parameters for each taxon across this gradient. We used Bayesian model selection to evaluate how environmental information correlated with potential maximum size.We found that both mussel species reached a larger potential maximum size at higher latitudes, with the thermally sensitive species having the larger increase in potential maximum size across the gradient when compared to the thermally tolerant species. Average annual water temperature explained mussel potential maximum size better than annual catchment precipitation, annual minimum flow ratio, and species identity. Both increased average water temperature and annual catchment precipitation, two predicted outcomes of climate change, were associated with smaller potential maximum size.Reductions in mussel maximum size due to climate change induced shifts in temperature regimes and precipitation patterns could lead to reduced reproductive output of this threatened guild and subsequent changes in ecosystem function and services, such as decreased biofiltration.As climate change alters precipitation patterns and stream productivity, and increases water temperature, understanding size variation and its cause in aquatic organisms will be important for managing these vulnerable populations. [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]

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]

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]

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]

Freshwater unionid mussels are among the most imperiled fauna in North America, and their decline has been partially attributed to sediment from anthropogenic activities. However, there remains a debate regarding the role played by sediment in mussel declines due to a lack of field and laboratory evidence. If sediment is responsible for mussel declines, then a lack of information will likely impede efforts to mitigate species declines and protect remaining habitat. However, if the impacts of sediment are overstated, time and resources may be wasted on a threat that has little bearing on mussel declines or habitat loss. Given this knowledge gap, the purpose of this paper is to review the literature focused on the potential impact of suspended sediment and sedimentation on freshwater mussels. We focused our search on suspended sediment, expressed either as suspended sediment concentration (SSC) or total suspended solids (TSS), and sediment deposition and scour. We found increases in suspended solids could impact mussels by decreasing food availability, physically interfering with filter feeding and respiration, and impeding various aspects of the mussel–host relationship. We also found mussel–sediment thresholds, wherein certain concentrations of sediment caused significant declines in population performance, which could serve as reference points for ecological research and management. Specifically, we found clearance rates (a measure of feeding) were negatively impacted by TSS concentrations >8 mg/L, and respiratory stress occurred at ∼600 mg/L. Declines in fertilization success and glochidial (i.e., mussel larvae) development were observed at TSS values of 15 mg/L, and reproductive failure occurred at 20 mg/L. Impacts on host fish attachment and glochidial encystment occurred at TSS concentrations of 1250–5000 mg/L. Impacts on fish varied depending on the biological endpoint but typically occurred at TSS values ranging from 20 to 5000 mg/L. We also found mussels were sensitive to smothering and mortality occurred at depths as low as 0.6–2.5 cm of substrate. Finally, we found relative shear stress (RSS) values >1, which is a measure of substrate stability in response to scour and entrainment, resulted in significant declines in mussel biodiversity. [ABSTRACT FROM AUTHOR]

Four freshwater mussel species native to western North America, Gonidea angulata , Margaritifera falcata , Anodonta nuttalliana , and Anodonta oregonensis , have experienced dramatic declines over the last century and are currently threatened in many portions of their ranges. Therefore, improved tools for detecting and monitoring these species are needed. We developed multiplexed, species-specific, quantitative PCR assays for the detection of these species from environmental DNA (eDNA). We empirically tested species specificity and sensitivity of assays in the lab, and we also validated multiplex assays with field-collected eDNA samples. All assays were species specific, sensitive, and effective for detection from eDNA samples collected from streams and rivers. These assays will aid in the detection, monitoring, management, and conservation of these vulnerable mussel species. [ABSTRACT FROM AUTHOR]

Zebra mussels (Dreissena polymorpha) have exacerbated the decline of native freshwater mussels (order Unionida) in North America since their arrival in the 1980s. Options for controlling invasive mussels, particularly in unionid mussel habitats, are limited. Previously, carbon dioxide (CO2) showed selective toxicity for zebra mussels, relative to unionids, when applied in cool water (12 °C). We first determined 96‐h lethal concentrations of CO2 at 5 and 20 °C to zebra mussels and responses of juvenile plain pocketbook (Lampsilis cardium). Next, we compared the time to lethality for zebra mussels at 5, 12, and 20 °C during exposure to partial pressure of CO2 (PCO2) values of 110 to 120 atm (1 atm = 101.325 kPa) and responses of juvenile plain pocketbook and fragile papershell (Leptodea fragilis). We found efficacious CO2 treatment regimens at each temperature that were minimally lethal to unionids. At 5 °C, plain pocketbook survived 96‐h exposure to the highest PCO2 treatment (139 atm). At 20 °C, the 96‐h lethal concentration to 10% of animals (LC10) for plain pocketbook (173 atm PCO2, 95% CI 147–198 atm) was higher than the LC99 for zebra mussels (118 atm PCO2, 95% CI 109–127 atm). Lethal time to 99% mortality (LT99) of zebra mussels in 110 to 120 atm PCO2 ranged from 100 h at 20 °C to 300 h at 5 °C. Mean survival of both plain pocketbook and fragile papershell juveniles exceeded 85% in LT99 CO2 treatments at all temperatures. Short‐term infusion of 100 to 200 atm PCO2 at a range of water temperatures could reduce biofouling by zebra mussels with limited adverse effects on unionid mussels. Environ Toxicol Chem 2020;39:1546–1557. Published 2020. This article is a U.S. Government work and is in the public domain in the USA. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. [ABSTRACT FROM AUTHOR]

We examined the physiological rates of 2 freshwater mussel species, Lampsilis cardium and Amblema plicata , as they experienced rising temperatures in a controlled laboratory setting. We chose these species because they have a widespread distribution, are common throughout North America, and vary in thermal tolerance. We varied the density and species composition of mussels in tanks. We measured algal clearance rate, oxygen consumption, biodeposition, and changes in nutrient concentration as mussels were exposed to incrementally-increasing temperatures relevant to regional climate projections. We found that these species have distinct physiological responses to increasing temperatures. The mass-specific physiological rates of L. cardium changed more than those of A. plicata when exposed to rising temperatures. Additionally, our findings suggest that mussel response to rising temperatures may vary as a result of mussel assemblage, density, and species composition. Thus, negative impacts of warming stream temperatures on freshwater mussels have the potential to affect the entire ecosystem. Understanding how freshwater mussel species may respond to climate change will help us better manage mussel communities and aquatic ecosystems. [ABSTRACT FROM AUTHOR]

Human activity has dramatically accelerated both species extinctions and introductions, and the balance of these two processes is generally expected to reduce biodiversity and increase taxonomic homogenization. However, few tests of this hypothesis have been made. We tested whether new macroinvertebrate invaders in North American freshwaters can replace the recent loss of biodiversity, particularly focusing on molluscs. We found that both crustaceans and molluscs are overrepresented among endangered and recently extinct species, as well as among invaders. For molluscs, the number of recently extinct species (79 species) was more than twice that for exotic species (38 species). In addition, molluscan invaders are from different taxonomic families than recently extinct or endangered species. While most extinct and endangered molluscs are from streams and rivers, invaders preferentially colonize lakes and reservoirs. The impact of humans on species introductions and extinctions increases with spatial scale (from local to continental scales), resulting in the increased phylogenetic dissimilarity between introduced species and native communities. Construction of dams and alteration of the flow regimes of lotic systems will continue to lead to the extinction of native species, and promote the spread of invaders, resulting in a loss of biodiversity and taxonomic homogenization. [ABSTRACT FROM AUTHOR]

The North America freshwater mussel fauna has suffered an inordinately high recent extinction rate, and the small size and isolation of many remaining populations portends a continued diminishment of this fauna. Causes of extinction and imperilment are varied but revolve around massive habitat loss, deterioration, and fragmentation. The National Strategy for the Conservation of Native Mussels, published in 1997, has guided efforts to address this crisis. Considerable progress has been made toward several of the Strategies' goals, particularly increasing our knowledge of mussel biology, promoting mussel conservation, and development of techniques for captive mussel propagation. However, mussel conservation should focus more directly on reducing fragmentation through bold and aggressive habitat restoration. In addition to dam removal, improvement in dam tailwater flows, and restoration of channelized streams, identification of factors that eliminated mussels from many otherwise intact streams is critical. Translocation and captive propagation will be key elements in reestablishing mussel assemblages in restored habitats, but these techniques should be used with caution and primarily to increase the occurrence of a species throughout its historical range. Conserving mussel diversity in an ever-changing world is dependent on promoting the natural, long-term sustainability and evolutionary potential of mussel populations. [ABSTRACT FROM AUTHOR]

We investigate population genetic structuring in Margaritifera falcata, a freshwater mussel native to western North America, across the majority of its geographical range. We find shallow rangewide genetic structure, strong population-level structuring and very low population diversity in this species, using both mitochondrial sequence and nuclear microsatellite data. We contrast these patterns with previous findings in another freshwater mussel species group ( Anodonta californiensis/A. nuttalliana) occupying the same continental region and many of the same watersheds. We conclude that differences are likely caused by contrasting life history attributes between genera, particularly host fish requirements and hermaphroditism. Further, we demonstrate the occurrence of a 'hotspot' for genetic diversity in both groups of mussels, occurring in the vicinity of the lower Columbia River drainage. We suggest that stream hierarchy may be responsible for this pattern and may produce similar patterns in other widespread freshwater species. [ABSTRACT FROM AUTHOR]

North American freshwater mussels are critically imperiled organisms that generally require fish hosts in order to complete their life cycle. Although numerous studies have focused on the parasitic relationship between mussels and fishes, few have examined the benefits that mussels provide to other organisms. During sampling of Altamaha River, Georgia, we observed foreign eggs occurring within body cavities of native mussels across a 253-km reach of the river basin. Eggs were recovered from 6% of the 757 mussels examined among seven sites. Foreign eggs were present in 17% and 18% of examined mussels at two sites. Using molecular techniques, eggs were identified as American ShadAlosa sapidissima. This discovery appears to be the first documented occurrence of native fish eggs in live North American mussels. Further research into the nature and mechanism of this symbiosis is warranted to assess whether this relationship is amensalistic, mutualistic, or commensalistic as American Shad and many freshwater mussels are species of conservation concern. A commensalistic or mutualistic relationship between these taxa may result in restoration activities affecting one species facilitating restoration of others. Received August 3, 2012; accepted December 30, 2012 [ABSTRACT FROM PUBLISHER]

Water mites of Unionicola species are common symbionts of freshwater mussels, living on the gills or mantle and foot of their hosts and using these tissues as sites of oviposition. Although surveys of the mite fauna among North American mussels suggest that these mites represent highly diverse assemblages, there are currently no quantitative data characterizing Unionicola species diversity among their molluscan hosts. The present study addresses patterns of species richness of Unionicola assemblages from freshwater mussels, including the relationship between richness and host specificity among these mites. Results from this study indicate that mite species richness increased significantly with an increase in the number of host individuals sampled. When corrected for sampling effort, there was a positive relationship between host size and mite species richness. Results from this study also reveal a significant relationship between mite species richness and the geographical distribution of host mussels. Overall, the patterns of species richness observed for this study are consistent with those examining the richness of parasitic helminth communities. Because the phylogenetic history of host taxa can have a significant influence on patterns of parasite species richness, studies that correct for the phylogenetic history among host mussels will be required to better understand the role that evolutionary processes have in determining Unionicola species richness. The present study did not indicate a significant relationship between species richness and host specificity and, in not doing so, suggests that the dispersal ability of mites may also play a role in influencing Unionicola species richness. The host recognition behavior and swimming abilities for a larger sample of mites will be required to substantiate this hypothesis. [ABSTRACT FROM AUTHOR]

1. North American freshwater mussels have been subjected to multiple stressors in recent decades that have contributed to declines in the status and distribution of many species. However, considerable uncertainty exists regarding the relative influence of these factors on observed population declines. 2. We used an occupancy modelling approach to quantify relationships between mussel species occurrence and various site- and catchment-level factors, including land cover, stream size, the occurrence of drought and reach isolation due to impoundment for 21 mussel species native to the lower Flint River Basin, Georgia, U.S.A. 3. Our modelling approach accounted for potential biases associated with both incomplete detection and misidentification of species, which are frequently not accommodated as sources of bias in freshwater mussel studies. 4. Modelling results suggested that mussel species were, on average, four times less likely to be present following severe drought, but the negative effects of drought declined rapidly with increasing stream size. Similarly, mussel species were 15 times less likely to occupy small streams that were isolated from mainstem tributaries by impoundments. 5. This study provides insight into the effects of natural and anthropogenic factors on freshwater mussel species. Our findings add to a growing body of literature aimed at improving understanding of the predominant factors influencing freshwater mussel populations and fostering the development of more informed and effective conservation strategies. [ABSTRACT FROM AUTHOR]

1. Freshwater mussels are critically endangered in North America, making it important to understand their environmental requirements at all life stages. As glochidia (larvae), they attach to fish hosts where they undergo substantial mortality, making this transition important in their life cycle. Larval host fish requirements have typically been described using data from laboratory infestations to determine suitable hosts. 2. Laboratory infestations circumvent many natural barriers that prevent infestation of physiologically compatible fishes by mussel larvae. While such methods are invaluable for identifying 'physiological hosts,' they cannot fully describe realised 'ecological hosts' in the field. 3. We studied Popenaias popeii in the Black River in New Mexico, because it is of conservation concern and it is the only mussel species present, facilitating identification of glochidial infestation. To explore the difference between physiological hosts and ecological hosts, we conducted a 3-year field study of fishes infested by P. popeii glochidia. 4. Substantially fewer fish species were infested by P. popeii in the wild (10 of 20 observed) than had been identified as physiological hosts in laboratory trials (24 of 31). We combined data on fish abundance, proportion of fish hosts infested (prevalence) and the number of glochidia per fish (intensity) and identified three fish species that probably contributed substantially more to mussel recruitment by carrying more glochidia than other host species. 5. Similarities in behaviour among these fishes allowed us to hypothesise routes of infestation, such as benthos-feeding by catostomids, that allow glochidia to infest these hosts at higher rates than other suitable hosts. Overall, this approach provides a method of quantifying the relative importance of different species of host fish in the mussel lifecycle. [ABSTRACT FROM AUTHOR]

Freshwater mussels are one of the most imperiled groups of animals in North America. Effective resource management and conservation efforts require reliable estimates of species diversity and their distributions. However, sampling protocols for qualitative mussel surveys have not been well established and tested. Furthermore, the sampling effort required for a given data-quality goal (90%% of species captured) often varies substantially among sites, and application of a standard effort probably would introduce bias into assemblage comparisons. We tested the sampling adequacy of time-based hand searches. We conducted 16-man-hour (mh) searches at each of 18 wadeable stream sites in Illinois that differed widely in environmental factors and historical species diversity and collected 27 to 942 individuals and 5 to 18 species per site. We accounted for imperfect species detectability by using the Chao-1 richness estimator and measured sampling adequacy as the %% of the estimated number of species sampled. Four-mh searches, a frequently used effort, captured 15 to 100%% of all species with an average of 61%%, and yielded estimates of richness that were not significantly correlated with the estimated total richness (Pearson's r == 0.39, p > 0.05). Ten-mh searches captured >70%% of all species at >70%% of sites and resulted in a significant correlation between observed and estimated richness (Pearson's r ≥ 0.78, p < 0.01). A Random Forests (RF) model based on watershed and habitat characteristics (e.g., stream size and dominant substrate types) accounted for 45%% of the variance in sampling adequacy of 4-mh searches. Sampling adequacy decreased with increasing stream size and substrate size but increased with %% forest in the riparian zone and logs in the stream. A 2nd RF model was developed to predict the number of man-hours required to capture 70 ± 3%% of all species, and it accounted for 37%% of the variance. Our findings should serve as a guide for setting standard sampling efforts for mussel surveys in Illinois and probably other midwestern states and should provide a baseline for setting site-specific efforts. Our modeling approach is of general applicability for addressing sampling-adequacy issues in studies of any assemblage. [ABSTRACT FROM AUTHOR]

Geographic patterns of species distributions and the factors contributing to species endangerment are necessary for the development of integrative conservation strategies. Freshwater mussels Unionidae have among the highest levels of imperilment recorded in North America. This paper describes the biogeography and diversity of Unionidae along climate and habitat gradients in Texas, evaluates human impact, and identifies the hot spots of diversity and endemism that should be targeted for conservation. Texas, North America. Unionids were surveyed in all major Texas river basins in 2003-2009. Multivariate statistics were used to test for differences in environmental parameters and among unionid assemblages in different bioprovinces, and to determine to what extent the multivariate pattern of species distribution was affected by environmental factors. To estimate human impact, we examined the relationship between human population density and the proportion of rare species, as well with the proportion of historically present species that persist in the watershed. Correlation between biotic and environmental similarity matrices indicated concordance in the differences among unionid assemblages and environmental factors that could cause these differences. Lake surface evaporation rate and percentage of forest cover in the watershed were among the most important parameters explaining the differences in unionid assemblages. Human population density was negatively correlated with the proportion of rare species. The proportion of species found live relative to the total number of live and relic species found in our surveys and to the number of historically known species decreased with the increase in human population density. Climate, landscape, geology, and land use type were important factors influencing unionid distribution patterns among biotic provinces. Increased human population density was associated with the loss of rare species over several decades, but this loss was not recognized because of a lack of assessing the conservation status of unionids. [ABSTRACT FROM AUTHOR]

Freshwater mussels fulfill an essential role in aquatic communities, but are also one of the most sensitive and rapidly declining faunal groups in North America. Rising water temperatures, caused by global climate change or industrial discharges, can further challenge impaired unionid communities, but thermal stress is almost certainly not the only stressor affecting freshwater mussels. Metals, such as copper (Cu), are a common source of toxicant exposure in aquatic environments. The toxic effects of Cu on the early life stages of freshwater mussels have been well studied, and freshwater mussels are more sensitive to Cu than most aquatic organisms. The purpose of the present study was to determine the effect of a sublethal copper concentration on the upper thermal tolerance of three species, Lampsilis siliquoidea, Potamilus alatus, and Ligumia recta, of juvenile freshwater mussels in 48- and 96-h tests. Thermal tolerance was determined over a range of experimental temperatures (20–42°C) at three acclimation temperatures (17, 22, and 27°C). Median lethal temperatures (LT50s) were calculated in the absence and presence of Cu, and at 48 h ranged from 34.6 to 44.4°C (mean 37.7°C) without Cu, and from 33.8 to 38.9°C (mean 35.8°C) with Cu. The LT50s at 96 h ranged from 32.5 to 35.6°C (mean 34.5°C) without Cu and from 33.0 to 35.4°C (mean 34.2°C) with Cu. Potamilus alatus had a significantly lower 48 h LT50 with Cu than without Cu at the 22°C acclimation temperature; there were no other significant differences in LT50s attributed to Cu. Survival trends showed limited evidence of interactive effects between copper and temperature for all three species, suggesting the combined stress of elevated temperatures and copper exposure to freshwater mussels should be further explored. Environ. Toxicol. Chem. 2010;29:691–699. © 2009 SETAC [ABSTRACT FROM AUTHOR]

Aim North America harbours the most diverse freshwater mussel fauna on Earth. This fauna has high endemism at the continental scale and within individual river systems. Previous faunal classifications for North America were based on intuitive, subjective assessments of species distributions, primarily the occurrence of endemic species, and do not portray continent-wide patterns of faunal similarity. The aim of this study is to provide an analytical portrayal of patterns of mussel diversity in a hierarchical framework that informs the biogeographical history of the fauna. Location The study considered the mussel fauna of North America from the Rio Grande system northwards. Methods Patterns of mussel faunal similarity in 126 river systems or lake watersheds across North America were examined. The dataset was developed from the literature and consisted of recent species presence/absence (282 species) in each drainage unit; subspecies were not included. Patterns of mussel diversity were examined with hierarchical cluster analysis, based on a pairwise distance matrix between all drainage units. Results Cluster analysis revealed 17 faunal provinces within four major faunal regions: Mississippian, Atlantic, Eastern Gulf and Pacific. The Mississippian Region dominates the North American fauna with 11 provinces, including five not recognized by previous classifications: Mississippi Embayment, Upper Mississippi, Great Plains, Ohioan and Pontchartrain–Pearl–Pascagoula. Within the Eastern Gulf Region (containing three provinces), the Escambia–Choctawhatchee Province is distinctive from the Apalachicolan Province, under which it was previously subsumed. Patterns of diversity in the Atlantic Region (two provinces) and Pacific Region (one province) were similar to previous classifications. Main conclusions The classification proposed in this study largely corroborates earlier schemes based on the occurrence of endemic species but identifies additional heterogeneity that reflects unique assemblages of widely distributed species. The study proposes a hierarchical structure that illustrates relationships among these provinces. Although some provinces in the Mississippian Region have high endemism, all Mississippian provinces share a group of widely distributed species. The Atlantic and Eastern Gulf regions have distinctive, endemic faunas suggesting limited past connectivity with the Mississippian Region. The Pacific Region is the most distinct fauna in North America and bears close affinity to the Eurasian mussel fauna. [ABSTRACT FROM AUTHOR]

Abstract: Temperature has a major impact on the physiological processes of freshwater invertebrates. Despite the endangered status of many freshwater mussel species and the potential effect of global warming on North America’s northern aquatic habitats, thermal sensitivity of the metabolic apparatus of freshwater bivalves has received little attention. By examining the thermal sensitivity of 10 key metabolic enzymes and in situ growth rates of latitudinally separated populations (temperate and subarctic) of two closely-related Pyganodon species from northeastern North America, we provide the first insights into thermal sensitivity of key enzymes of energy and reactive oxygen species metabolism in relation to habitat localization and growth performance. The subarctic population of Pyganodon grandis displayed higher in situ growth rates than the temperate population of Pyganodon fragilis. The subarctic population of P. grandis had a lower mitochondrial capacity as expressed by citrate synthase and cytochrome c oxidase but displayed similar electron transport system (ETS) and higher isocitrate dehydrogenase capacities. Our results suggest that higher growth performance of the subarctic population of P. grandis is not associated with higher aerobic capacity. The high thermal sensitivity of mitochondrial enzymes in subarctic population of P. grandis might rather reflect enhanced stenothermy. The higher electron transport system/cytochrome c oxidase ratio for the subarctic P. grandis species than P. fragilis might affect mitochondrial regulation or reactive oxygen species production. Antioxidant enzymes displayed lower Q 10s suggesting thermal independence of antioxidant capacity. [Copyright &y& Elsevier]

Background: Freshwater mussels are among the most endangered taxa in North America and minimally invasive techniques to evaluate their health are needed. Objective: The objective of this study was to develop a standardized approach for identifying and enumerating the cellular components of freshwater mussel hemolymph. Methods: Hemocyte clumping, total hemocyte count, and hemocyte morphology were compared in untreated hemolymph or hemolymph treated with formalin, sodium citrate, sodium heparin, EDTA, water, orl-cysteine. Morphology was then used to categorize hemocytes and perform a 100-cell differential. Results: Treatment with formalin or >25 mg/mLl-cysteine reduced hemocyte clumping, although only formalin significantly increased the total hemocyte count. However, formalin also induced crenation that impaired hemocyte identification. Both EDTA and sodium citrate-induced hemocyte degranulation while sodium citrate and >40 mg/mLl-cysteine-induced cell lysis. Hemocytes could be categorized into 2 groups of granulocytes (eosinophilic or basophilic) and 2 groups of agranulocytes (large or small) for performing a cytologic differential. The differential was not significantly altered by anticoagulant treatments providing cell morphology was adequate for obtaining a differential. Eosinophilic granulocytes predominated (59%) with fewer large agranulocytes (27%) and basophilic granulocytes (13%). Small agranulocytes comprised 2% of the total population. Conclusions: No single treatment provided an optimal method to evaluate freshwater mussel hemolymph. Maximal hemocyte counts were obtained following formalin treatment.l-cysteine reduced clumping and maintained hemocyte morphology for performing a cytologic differential. These techniques provide a standardized approach for the hematologic evaluation of freshwater mussels. [ABSTRACT FROM AUTHOR]

The distributions of freshwater mussels are controlled by landscape factors operating at multiple spatial scales. Changes in land use/land cover (LULC) have been implicated in severe population declines and range contractions of freshwater mussels across North America. Despite widespread recognition of multiscale influences few studies have addressed these issues when developing distribution models. Furthermore, most studies have disregarded the role of landscape pattern in regulating aquatic species distributions, focusing only on landscape composition. In this study, the distribution of Rabbitsfoot (Quadrula cylindrica) in the upper Green River system (Ohio River drainage) is modeled with environmental variables from multiple scales: subcatchment, riparian buffer, and reach buffer. Four types of landscape environment metrics are used, including: LULC pattern, LULC composition, soil composition, and geology composition. The study shows that LULC pattern metrics are very useful in modeling the distribution of Rabbitsfoot. Together with LULC compositional metrics, pattern metrics permit a more detailed analysis of functional linkages between aquatic species distributions and landscape structure. Moreover, the inclusion of multiple spatial scales is necessary to accurately model the hierarchical processes in stream systems. Geomorphic features play important roles in regulating species distributions at intermediate and large scales while LULC variables appear more influential at proximal scales. [ABSTRACT FROM AUTHOR]

The surprising diversity and recent dramatic decline of freshwater mussels in North America have been well documented, although inventory efforts to date have been concentrated in the eastern United States. Unlike their eastern counterparts, western freshwater mussels have received comparatively little attention. The accurate identity of western lineages is a necessary component for future inventory, monitoring, and ecological work involving these taxa. Here we initiate a study involving the most speciose genus (Anodonta) in western North America, incorporating information about type localities and type specimen morphology and describing the discovery of three highly divergent lineages among four western Anodonta species. In a limited phylogenetic analysis, we find (1) that A. californiensis/nuttalliana and A.oregonensis/kennerlyi are distinct, highly divergent clades, and (2) that A. beringiana is more closely allied with A. woodiana, an Asian species, than either of the other two western North American clades. We were largely unable to resolve the placement of these three clades with respect to other anodontines, and suggest the need for a broader phylogenetic framework. We recommend, however, that the existence of these three deeply divergent groups be considered in the development of regional monitoring, conservation and research plans despite the taxonomic uncertainty. [ABSTRACT FROM AUTHOR]

Extrinsic and intrinsic forces combined shape the population structure of every species differently. Freshwater mussels are obligate parasites to a host fish during a juvenile stage (glochidia). Elliptio dilatata ( ED) and Actinonaias ligamentina ( AL) are co-occurring freshwater mussel taxa with similar North American distribution and share some potential host fish. Using mitochondrial DNA, we determined the genotypes of 190 + individuals from collection sites in at least two tributaries in the Lake Erie and Ohio River watersheds, along with the Ouachita and Strawberry rivers in the southeast. Both species had followed a stepping-stone model of dispersal, with greater pairwise genetic structure among collection sites of ED. Also, phylogeographical analysis for ED found significant geographical structuring of haplotype diversity. Overall, within-population variation increased significantly from north to south, with low genetic diversity in the Strawberry River. We calculated significant among-population structure for both species ( ED: ΦST = 0.62, P<0.001; AL: ΦST = 0.16, P<0.001). Genetic analysis identified the Ouachita River as an area of significant reproductive isolation for both species. Results for AL indicated dispersal into northern areas from two genetically distinct glacial refugia, where results for ED indicated dispersal followed by low gene flow in northern areas. The conservation strategies for mussels that co-occur in the same ‘bed’ could be species specific. Species such as ED have management units on the population scale, where AL has a more homogeneous genetic structure across its range. [ABSTRACT FROM AUTHOR]

Seven populations of the imperiled snuffbox mussel, Epioblasma triquetra, were sampled from across the central basin of North America. Samples were genotyped using 15 microsatellite DNA loci, and maternal history was inferred using mitochondrial DNA (mtDNA) cytochrome c oxidase subunit-I (COI) sequences. Populations in the Clinch and St Francis rivers were quite distinct in their mtDNA. The population in the St Francis River had a unique, fixed haplotype. Among a suite of haplotypes, the population in the Clinch River had two unique haplotypes of common ancestry. The other populations were dominated by a common haplotype, which also occurred in the Clinch River population. Analysis of DNA microsatellites revealed much greater divergences and showed significant genetic structure between populations in the formerly glaciated regions. Divergence has occurred between the populations, as evidenced by moderate to high fixation indices ( FST and RST values) and nearly perfect assignment tests. These results indicate the occurrence of three glacial refugia for E. triquetra: the Tennessee River, rivers south of the Ozark Crest, and the lower Ohio River drainage near the confluence with the Mississippi. Populations in the lower Ohio River were likely to be responsible for the postglacial reinvasion into formerly glaciated regions, and into the upper Tennessee River drainage. The population of the St Francis River may constitute a distinct taxonomic entity. Conservation efforts, if necessary for this imperiled species, should not mix populations. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 93, 371–384. [ABSTRACT FROM AUTHOR]

The term freshwater bivalve is very inclusive and not very informative. There are representatives of at least 19 families that have at least one representative living in freshwater. This suggests at least 14 different invasions of freshwater. At least nine families have small to large radiations in the freshwater environment: Corbiculidae, Sphaeriidae, Dreissenidae, and the unioniforme families: Hyriidae, Margaritiferidae, Unionidae, Etheriidae, Iridinidae, and Mycetopodidae. The unioniforme families contain at least 180 genera and about 800 species. This order is characterized by the unique parasitic larval stage on the gills, fins or the body of a particular host fish. This order of freshwater bivalves is suffering a very high rate of extinction, with about 37 species considered presumed extinct in North America alone. The level of endangerment and extinction facing these animals is primarily the result of habitat destruction or modification. [ABSTRACT FROM AUTHOR]

Native freshwater mussels (family Unionidae) are among the most imperiled faunal groups in the world. Factors contributing to the decline of mussel populations likely include pesticides and other aquatic contaminants; however, there is a paucity of data regarding the toxicity of even the most globally distributed pesticides, including glyphosate, to mussels. Therefore, the toxicity of several forms of glyphosate, its formulations, and a surfactant (MON 0818) used in several glyphosate formulations was determined for early life stages of Lampsilis siliquoidea, a native freshwater mussel. Acute and chronic toxicity tests were performed with a newly established American Society of Testing and Materials (ASTM) standard guide for conducting toxicity tests with freshwater mussels. Roundup®, its active ingredient, the technical-grade isopropylamine (IPA) salt of glyphosate, IPA alone, and MON 0818 (the surfactant in Roundup formulations) were each acutely toxic to L. siliquoidea glochidia. MON 0818 was most toxic of the compounds tested and the 48-h median effective concentration (0.5 mg/L) for L. siliquoidea glochidia is the lowest reported for any aquatic organism tested to date. Juvenile L. siliquoidea were also acutely sensitive to MON 0818, Roundup, glyphosate IPA salt, and IPA alone. Technical-grade glyphosate and Aqua Star® were not acutely toxic to glochidia or juveniles. Ranking of relative chronic toxicity of the glyphosate-related compounds to juvenile mussels was similar to the ranking of relative acute toxicity to juveniles. Growth data from chronic tests was largely inconclusive. In summary, these results indicate that L. siliquoidea, a representative of the nearly 300 freshwater mussel taxa in North America, is among the most sensitive aquatic organisms tested to date with glyphosate-based chemicals and the surfactant MON 0818. [ABSTRACT FROM AUTHOR]

Chemical contaminants are among many potential factors involved in the decline of freshwater mussel populations in North America, and the effects of pesticides on early life stages of unionid mussels are largely unknown. The objective of this study was to determine the toxicity of technical-grade current-use pesticides to glochidia and juvenile life stages of freshwater mussels. We performed acute toxicity tests with glochidia (five species) and juveniles (two species) exposed to a suite of current-use pesticides including herbicides (atrazine and pendimethalin), insecticides (fipronil and permethrin), and a reference toxicant (NaCl). Because of limited availability of test organisms, not all species were tested with all pesticides. Toxicity tests with fungicides (chlorothalonil, propiconazole, and pyraclostrobin) were performed with one species (Lampsilis siliquoidea). Lampsilis siliquoidea glochidia and juveniles were highly sensitive to the fungicides tested but the technical-grade herbicides and insecticides, at concentrations approaching water solubility, were not acutely toxic to this or the other unionid species. In a 21-d chronic test with four-month-old juvenile L. siliquoidea, the 21-d median effective concentration (EC50) with atrazine was 4.3 mg/L and in atrazine treatments ≥3.8 mg/L mussel growth was significantly less than controls. The relatively high sensitivity of L. siliquoidea to chlorothalonil, propiconazole, and pyraclostrobin is similar to that reported for other aquatic organisms commonly used for toxicity testing. The relative risk associated with acute exposure of early life stages of mussels to technical-grade atrazine, pendimethalin, fipronil, and permethrin is likely low; however, survival and growth results with juvenile L. siliquoidea indicate that chronic exposure to high concentrations (≥3.8 mg/L) of atrazine may have the potential to impact mussel populations and warrants further investigation. [ABSTRACT FROM AUTHOR]

1. Studies of North American streams have shown that hydraulic parameters and stream geomorphology can explain unionid mussel abundance at both the reach and catchment scale. However, few studies have examined applicability of hydrogeomorphic variables across broader spatial scales, such as across whole catchments, or have elucidated conditions under which spates can affect mussel populations in streams. 2. We quantified freshwater mussel abundance and species richness and their physical habitat at 24 sites in eight streams in southern Appalachian catchments in 2000 and 2001. In addition, we modelled site-specific hydraulic parameters during summer baseflow and bankfull stages to estimate high- and low-discharge conditions, respectively. 3. Mussel abundance was related to stream geomorphology, whereas richness was related to stream size. Baseflow habitat parameters explained only minor variation in abundance or richness, and both measures were highly correlated with mean current velocity or stream size. Bankfull shear stress composed a relatively low proportion of overall mussel habitat variability, but it accounted for significant variation in abundance and richness. 4. Mussel abundance was highly variable at sites subject to low-shear stress during spates, whereas abundance always was low at sites subject to high-shear stress. These data suggest that habitat conditions during floods, rather than those at summer baseflow, limit the abundance of mussels in Appalachian streams. These data also suggest that mussel abundance and assemblage structure may be sensitive to any changes in channel geomorphology and hydraulic conditions that might result from land use in the catchment. [ABSTRACT FROM AUTHOR]

The article focuses on the successful fertilization and early survival in pure and hybrid larvae of Mytilus edulis and M. trossulus from laboratory tests on the Atlantic coast of North America. According to previous studies, it was confirmed that there are two species of mussels detected. Studies show that the hybridization degree within Ludenburg Bay in Nova Scotia was less that the extent of hybridization in the Southwest England hybrid zone between the species. It has been stressed that the reproductive cycle of any mussel population came out of a complicated balance between the exogenous factors including food availability, temperature and salinity; and the endogenous factors such as nutrient reserves.

Populations of the freshwater mussel genus Anodonta appear to be in a state of rapid decline in western North America, following a trend that unfortunately seems to be prevalent among these animals (Mollusca: Unionoida). Here we describe the patterns of molecular divergence and diversity among Anodonta populations in the Bonneville Basin, a large sub-basin of the Great Basin in western North America. Using amplified fragment length polymorphism (AFLP) analysis, we found a striking lack of nuclear diversity within some of these populations, along with a high degree of structuring among populations ( FST = 0.61), suggesting post-Pleistocene isolation, due either to a long-term loss of hydrologic connectivity among populations or to more recent fish introductions. We also found evidence of recent hybridization in one of these populations, possibly mediated by fish-stocking practices. Using mitochondrial sequence data, we compared the Bonneville Basin populations to Anodonta in several other drainages in western North America. We found a general lack of resolution in these phylogenetic reconstructions, although there was a tendency for the Bonneville Basin Anodonta (tentatively A. californiensis) to cluster with A. oregonensis from the adjacent Lahontan Basin in Nevada. We recommend further investigation of anthropogenic factors that may be contributing to the decline of western Anodonta and a broad-scale analysis and synthesis of genetic and morphological variation among Anodonta in western North America. [ABSTRACT FROM AUTHOR]

Pearly mussels (Unionacea) are widespread, abundant, and important in freshwater ecosystems around the world. Catastrophic declines in pearly mussel populations in North America and other parts of the world have led to a flurry of research on mussel biology, ecology, and conservation. Recent research on mussel feeding, life history, spatial patterning, and declines has augmented, modified, or overturned long-held ideas about ecology of these annuals. Pearly mussel research has begun to benefit from and contribute to current ideas about suspension feeding, life-history theory, metapopulations, flow refuges, spatial patterning and its effects, and management of endangered species. At the same time, significant gaps in understanding and apparent paradoxes in pearls' mussel ecology have been exposed. To conserve remaining mussel populations, scientists and managers must simultaneously and aggressively pursue both rigorous research and conservation actions. [ABSTRACT FROM AUTHOR]

Freshwater mussels (Bivalvia: Unionidae) have been an economically valuable biological resource in North America since the mid-1800s. Although the industries based upon mussel harvest are quite distinct from one another, the trends apparent in harvest statistics are remarkably similar among each successive harvest era. Whether fished for freshwater pearls, button production, or cultured pearl production, market factors have driven commercial harvests while the life history and ecology of mussels have been largely ignored. Annual yields of freshwater mussels are declining throughout the United States and catch per unit effort (CPUE) has declined dramatically in some of the most important American mussel fisheries. Harvest statistics indicate that mussel populations are dangerously depleted due to the erosion of the latest industry based upon their harvest. It seems likely that the exhaustive harvests of both the distant and recent past, coupled with habitat loss and degradation, have left North American unionid mussel populations at levels insufficient to support the substantial harvests consistently demanded by industry. This century-long exploitation trajectory provides valuable lessons about the mechanisms of fisheries collapse that are necessary to ensure the sustainable management of aquatic resources.Les moules d'eau douce (Bivalvia: Unionidae) constituent une ressource biologique d'importance économique considérable en Amérique du nord depuis le milieu du 19e siècle. Bien que les diverses industries basées sur la récolte des moules soient différentes les unes des autres, les tendances dans les statistiques de récolte sont remarquablement semblables au cours des différentes périodes de récolte qui se sont succédées au cours du temps. Que les récoltes aient été faites pour la collecte de perles d'eau douce, la fabrication de boutons, ou la production de perles cultivées, les forces du marché ont contrôlé les récoltes commerciales, alors que le cycle biologique et l'écologie n'ont pas été en grande mesure pris en compte. Les rendements annuels de moules d'eau douce décroissent partout aux États-Unis et les captures par unité d'effort (CPUE) ont décliné de façon spectaculaire dans quelques-uns des plus importants sites américains de récolte de moules. Les statistiques des récoltes indiquent que les populations de moules sont dangereusement hypothéquées au moment où l'industrie la plus récente basée sur les moules est en train de s'effriter. Il semble probable que les récoltes exhaustives du passé lointain et du passé plus récent, combinées à la perte et la dégradation des habitats, ont laissé les population nord-américaines de moules unionidés à des densités qui ne permettent plus les récoltes intensives requises par l'industrie. L'histoire de cette exploitation centenaire fournit des enseignements précieux sur les mécanismes d'effondrement des pêches, renseignements qui sont indispensables pour mettre sur pied une gestion durable des ressources aquatiques.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

1. North American lacustrine freshwater mussels (Bivalvia: Unionidae) are one of the world’s most imperilled groups of organisms. Knowledge of their age structure and longevity is needed for the understanding and management of mussels. Current methods for age estimation in freshwater mussels are insufficient and may have resulted in an erroneous view of the ages of lacustrine freshwater mussels. 2. We collected growth data through mark-recapture in Minnesota and Rhode Island, U.S.A., examining four lentic populations of three of the most common species of freshwater mussels, Elliptio complanata, Lampsilis siliquoidea, and Pyganodon grandis. Using an inversion of the von Bertalanffy growth equation, we estimated age at length from length-specific growth relationships. 3. In some populations, lacustrine mussels may be much older than previously predicted. Ages predicted from actual growth rates suggest that individuals in some populations frequently reach ages in excess of a century, placing unionid mussels among the Earth’s longest-lived animals. Alternatively, if growth has only recently slowed in these populations, generalized growth cessation may be occurring over a broad distributional range of some common North American lacustrine mussels. [ABSTRACT FROM AUTHOR]

The article focuses on the findings of a research study regarding the number of species of Asian freshwater clam Corbicula in North America. In the study, two samples of North American Corbicula morphytes were genetically characterized and were sequenced for the target gene fragment. The study showed no variation within the morphytes and the samples were genetically distinct.

Determines whether inexpensive and easily maintained exotic fishes, amphibians and crustaceans could serve as hosts for native North American mussels. Materials and methods utilized on the study; Several exotic fishes identified as hosts for North American mussels; Metamorphosis occurred in number of crustacean tested.

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Reports that two distinct species of freshwater mussels invaded North America's Great Lakes in the 1980s. Locations of zebra and quagga mussel populations; Tolerance of temperature and salinity; Possibility of spread into estuarine and coastal areas of North America.

Reports that zebra and quagga mussels invaded the fresh waters of eastern North America during the late 1980s. Difference of both species in shell morphology; Evidence of genetic variability in zebra mussels; Identification of enzymes, loci and allelic mobilities.

Mussels in the order Unionoida comprise ∼75% of the world's freshwater bivalve species and are free-living apart from a brief larval stage that parasitizes fish. We investigated the relationships among species of North American unionid mussels and their known host fishes from a macroevolutionary perspective to test whether and how ecological and evolutionary factors correlate with patterns of host use. A subset of 69 mussel species was chosen based on data availability regarding their fish host repertoires, phylogenetic relationships, and ecology. Despite the brevity of their parasitic life stages, the mussels conformed to the right-skewed distribution of host specificity typical of parasitic taxa, in which most species are specialists and a few are generalists. Phylogenetic least squares regression models identified affinity for low-gradient and riffle habitats, and colonization of post-glacial watersheds as the best predictors for the number of fish host species per mussel. However, the second-best model identified citation number as a predictor of the number of hosts, implying that many mussel-host interactions still remain to be identified. A Multiple Regression Mantel test was performed to identify factors associated with the proportion of hosts shared between pairs of mussel species. Range overlap, citations, genetic distance, and similarity in host infection strategy were significantly correlated with the proportion of hosts shared, yet total variation as explained by the best model was low (R 2  = 0.14). There was evidence of a topological association between mussels and their hosts (P = 0.001) and a significant phylogenetic signal of host specificity (λ = 0.81, P = 0.003), indicating closely related mussels that overlap in range are more likely to be competing for hosts. Our results provide an initial macroevolutionary framework for studying the evolution of host infection strategies in these mussels but also highlights gaps still remaining in our fundamental ecological knowledge of this endangered clade., (Copyright © 2018 Australian Society for Parasitology. Published by Elsevier Ltd. All rights reserved.)

The article presents news briefs related to wildlife conservation in North America. The North-western Hawaiian Islands, a marine reserve, is at risk due to floating rubbish dumps. Of 300 freshwater mussel species that are native to North America 70% are threatened, declining or extinct. The U.S. Fish and Wildlife Service has not listed cerulean warbler among the threatened species, which has raised concern for the specie among the U.S. conservation organizations.