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Bivalves are one of the most representative groups in the Phylum Mollusca, with over 1,100 freshwater species around the world except Antarctica. About 900 of these species belong to the Order Unionida Gray, 1854. In South America, the distributional range of the Unionida includes all countries in the region and extends as far south as the lakes and rivers of Argentinean-Chilean Patagonia. With the aim of generating distribution maps for the different genera of Unionida in Argentina, we consulted the databases of the nation's main official malacological collections. The data were analyzed and georeferenced using the point-radius method. Spatial analyses were performed with the software Q-GIS 2.16.3 Nødebo using vector layers under the 2007 Argentinean Geodesic Positions reference system. A total 1,833 lots were analyzed, of which it was possible to georeference 1,503. The distribution of Unionida in Argentinean territory was analyzed according to political provinces, Surface Drainage Basins and the Argentinean Protected Areas. Species richness was analyzed using the surface drainage basins of Argentina. We generate distribution maps for each genus and discuss the species threat status and conservation degree in the region. Only six (18%) of the Unionida present in Argentina have been classified by the IUCN, four are Least Concern and two are Data Deficient. This pattern is also valid for all of South America. More than 95% of the distributional range of the Unionida has no protected area. Conservation management is necessary for the preservation of Unionida diversity in southern South America.

The Yangtze River drainage in China is among the most species rich rivers for freshwater mussels (order Unionida) on Earth with at least 68 species known. The freshwater mussels of the Yangtze River face a variety of threats with indications that species are declining in abundance and area of occupancy. This study represents the first analyses of the genetic structure and diversity for the common and widespread freshwater mussel Nodularia douglasiae based on microsatellite DNA genotypes and mitochondrial DNA sequences. Phylogenetic analysis a fragment of the COI mitochondrial gene indicated that N. douglasiae collected from across the middle and lower Yangtze River drainage are monophyletic with N. douglasiae from Japan, Russia, and South Korea. The results of the analysis of both the mtDNA and microsatellite datasets indicated that the seven collection locations of N. douglasiae in the middle and lower Yangtze River drainage showed high genetic diversity, significant genetic differentiation and genetic structure, and stable population dynamics over time. Moreover, we found that the connections among tributaries rivers and lakes in the Yangtze River drainage were important in maintaining gene flow among locations that N. douglasiae inhabits. An understanding of the genetic structure and diversity of a widespread species like N. douglasiae could be used as a surrogate to better understand the populations of other freshwater mussel species that are more rare in the Yangtze River drainage. At the same time, these results could provide a basis for the protection of genetic diversity and management of unionid mussels diversity and other aquatic organisms in the system.

Recent research efforts have significantly advanced our knowledge on Asian freshwater mussel (Bivalvia: Unionidae) diversity and distribution. Here we provide a modern consensus of the diversity, biogeography and conservation of Unionida in the region comprising East and Southeast Asia (excluding Wallacea) and Asian Russia. A data review confirmed the presence of 228 native and 3 non-native Unionida (98% Unionidae, 2% Margaritiferidae), rendering the region a global hotspot of freshwater mussel diversity. Species richness was highest in China (particularly Yangtze basin) in absolute numbers and Cambodia when correcting for country area, and decreased gradually towards the south and steeply towards the north and east. Six of the seven unionid subfamilies are native to the region, with species richness peaking in Southeast Asia for Rectidentinae, Gonideinae, Parreysiinae and Modellnaiinae, China for Anodontinae and Unioninae, and Asian Russia for Margaritiferidae. Conservation status and data collected after 1980 were not available for 61 and 24% of species, respectively. Dams, deforestation and pollution are likely the major threats to mussels in the region, though data in this respect are scarce. The Philippines, Laos, Indonesia, Myanmar and Malaysia are among the countries with the poorest data availability and urgently require research.

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.

Freshwater biodiversity of the United States has long been recognized for its high level of species richness. The US crayfish fauna is richer than that found in any other country or continent in the world. Crayfishes are critically important members of freshwater ecosystems and have long been utilized for human consumption. Combined, these factors argue for effective conservation. When compared to other diverse aquatic groups such as fishes or unionid mussels, conservation efforts for US crayfishes are lacking. We review here, knowledge gaps that prevent effective conservation and past and ongoing crayfish conservation and management activities. We conclude by proposing a strategy of actions to improve the conservation standing of this important group of organisms. These action items include improved outreach efforts, funding and research to fill numerous knowledge gaps, and the inclusion of crayfishes in broader scale aquatic conservation activities.

Biological particles (e.g., bacteria, eggs, fruit/seeds and larvae) of a wide range of sizes (i.e., 10−6–10−1 m) are transported over various distances (i.e., 100–104 m) downstream in rivers. We examined the effects of propagule size on downstream dispersal by releasing biodegradable microbeads (density ∼ 1,200 kg m−3) of three size classes (∼150, 250, 350 μm) at the Speed River, Guelph, ON. Hitting distance estimates and longitudinal dispersion coefficients declined with particle size and were significantly different between 150 and 350 μm microbeads. The magnitude of these differences was relatively small (∼5 m) because of the slow velocity (9.5 ± 0.01 cm s−1) and low turbulence (shear velocity = 1.9 ± 0.13 cm s−1) in the river. We examined the dispersion of larval and juvenile unionid mussels (size range = 56–415 μm, 247.54 ± 60.38 [mean ± SD] μm, N = 174) across a broader range of flow conditions by applying laminar and turbulent flow models in three river reaches of increasing velocity and turbulence. Model results indicated that the dispersal of smaller larvae increased disproportionately with increasing water column turbulence. Given that the peak in the size frequency distribution of larvae and juveniles corresponded to Rouse numbers (ratio of gravitational settling to water column turbulence) P < 1, we suggest a trade‐off in propagule size in the taxon, whereby the increased dispersal of smaller juveniles may come at the cost of reduced settlement success in turbulent environments.

This well-illustrated book highlights freshwater mussels' fabulous diversity, amazing array of often bizarre ecological adaptations and their dire conservation plight. Summarizing and synthesizing historical and contemporary information as well as original research and analysis, the book describes the diverse array of mussel life history strategies and builds a cohesive narrative culminating in the development of explicit frameworks to explain pervasive patterns in mussel ecology. The fascinating and colorful role of mussels in human society is also described in detail, including the little-known pearl button industry of the early 1900s and the wild and often violent shell harvest of the 1990s. The final chapter details humans' efforts to save these fascinating animals and gives a prognosis for the future of the North American fauna. The book provides the first comprehensive review of mussel ecology and conservation for scientists, natural resource professionals, students and natural history enthusiasts.

Nutrient loads and nutrient cycling, especially of phosphorus and nitrogen, are among the most important controls on the character of freshwater ecosystems and have been greatly affected by human actions. Despite the widespread importance of nutrients in freshwater ecosystems, the varied linkages between nutrient cycling and freshwater mussel populations have not been thoroughly described. Here, I explore three of these linkages. First, I suggest that nutrient loads are related to the well-being of mussel populations through several mechanisms, probably producing a nonlinear and non-monotonic relationship between nutrient loads and mussel populations. Second, I discuss the ability of mussels to spatially focus nutrients from the overlying water onto the sediments, which has not been fully appreciated, perhaps because nutrient cycling has been viewed chiefly from the viewpoint of the well-mixed water column rather than the patchy sediments. Third, I discuss the ability of mussel populations to accumulate and release nutrients, introducing time lags into nutrient dynamics and stoichiometry (“nutrient capacitance”). Finally, I propose a speculative analysis of the role of freshwater mussels in the nutrient cycles of pristine river systems, which must have been much greater than in modern rivers, with their high nutrient loads and depleted mussel populations.

We used in situ exposures of juvenile mussels (96-d average, May–September) to investigate the causes of mussel declines. We measured survival and growth of mussels exposed to ambient conditions in 23 streams in Kentucky, USA. Our set of streams included both those that support diverse mussel assemblages (occupied streams) and those that have lost nearly their entire mussel fauna (defaunated streams). We used 2 types of enclosures in each stream: silos, which primarily expose mussels to water, and sediment cages, which provide greater exposure to sediments. We used both enclosure types because some contaminants are more prevalent either in water or sediments. We collected extensive water and sediment chemistry data (163 and 144 analytes, respectively) monthly at each stream and landscape data for each watershed. We found no evidence of acute toxicity. Survival averaged 90% in silos and was only 68% in cages. However, lower survival in cages appeared to be an artifact of the enclosure type (burial), and survival was unrelated to faunal health or water or sediment chemistry in either type of enclosure. In contrast, we found strong evidence that chronic stressors negatively affect growth in defaunated streams. Growth in both enclosure types was uniformly low in all defaunated streams (mean instantaneous growth, as mass = 0.005/d) compared with growth in occupied streams (0.026/d). Variation in water chemistry among streams was described by 2 principal components (PCs). PC2 described a gradient of increasing alkalinity, nutrients, total organic C, and temperature, which corresponded to the underlying geology and physiography in the study region. Growth was positively correlated with PC2, but defaunated streams were conspicuous outliers, suggesting that other factors further limited growth in these streams. PC1 described a gradient of higher row crop agriculture, pesticides, nitrate/nitrite, and karst influence. Mussel growth was negatively correlated with PC1, but agricultural contaminants were not present in all defaunated streams. Variation in sediment chemistry was described by only 1 PC that reflected underlying geology, similar to water chemistry PC2, and there were no consistent patterns of sediment contamination. Overall, lower total organic C and lower water temperature compared with the occupied streams were the main characteristics shared by the defaunated streams. This result suggests that mussel populations in relatively cool, unproductive streams are particularly vulnerable to chronic human impacts that negatively affect growth or other physiological processes.

Freshwater mussels (Order Unionoida) can provide crucial ecological functions and services. However, many of them are endangered worldwide due to local extirpation and reproductive failure, which emphasizes the importance of mussel life cycle monitoring, including reproduction. Buldowskia iwakawai (Suzuki, 1939) is one such species native to the Ishikari floodplain oxbow lakes where its reproductive failure was recently reported. In this study, a species-specific environmental DNA (eDNA) assay was developed to monitor B. iwakawai abundance and winter reproduction in the laboratory and natural environment simultaneously even at times when natural lakes are covered by ice. A positive CPUE-eDNA correlation was observed across all the 14 lakes sampled prior to ice cover formation. The eDNA concentration significantly differed between gravid and non-gravid mussels in relation to their metabolic-rate differences in laboratory experiments, but the eDNA concentration increase was not detected in the intensively monitored lakes during the glochidia release period. PCR inhibition in natural water has been suggested, and reducing its effects combined with appropriate seasonal contexts has the potential to improve the applicability of this method. This research sheds new light on the applicability of the eDNA assay for monitoring mussel reproductive activities throughout their life cycle including the winter season.