Freshwater Mussels Research Articles

Resilience of Juvenile Freshwater Pearl Mussels to ThermalStress.

Climate change poses a significant threat to freshwater ecosystems by causing increases of average water temperatures, and more frequent and extreme heating events. Freshwater mussels are declining globally, and the distribution of the freshwater pearl mussel (Margeritifera margeritifera) has decreased dramatically over the past century. Even though it is likely that climate change is contributing to the decline of the species, little is known about the specific mechanisms involved. Here, we test how short episodes of water temperatures above the known thermotolerance range affect the survival and growth of the early post parasitic juvenile phase of freshwater pearl mussels. We also test if previous experience with elevated water temperatures can modify survival and growth responses to subsequent high-temperatures exposure. Mortality was very low in all treatments (< 5%) and not affected by the temperature treatments, while growth rate was positively affected by temperature. Our results suggest that juvenile mussels can survive short periods of heat stress when other environmental conditions are favourable. Future studies should therefore address how heat stress affects survival in combination with other stressors, such as reduced availability of dissolved oxygen.

Bacteriological analysis of unionid hemolymph collected from freshwater mussel populations in the Pacific northwestern United States

AbstractNative freshwater mussel (Unionidae) mortality events have been occurring with increased frequency in recent decades, with few investigations into potential etiological agents. In the western United States, no surveys have been published regarding the bacteria associated with unionid mussels. Herein, we examine locations of known mussel mortality events in the Chehalis River (Washington), in the Crooked River (Oregon), and Owyhee River (Oregon). Mussel populations considered healthy were sampled in the Skookumchuck River (Washington) for comparison. A variety of bacteria were isolated from these populations, and most notably, Acinetobacter spp. were identified from 82% of moribund individuals of Gonidea angulata in the Owyhee River. Future work evaluating whether Acinetobacter spp. are pathogenic to freshwater mussels could be valuable in unraveling the factors associated with these enigmatic mortality events.

Freshwater Mussel (Unio pictorum) Shells Reveal Hydrological and Environmental Change From 1300 BC to the Present Day.

Preserved biological communities can provide baseline data about the historical ecosystems and environmental conditions that preceded recent anthropogenic alteration. Freshwater mussel shells show particularly good preservation, and the shell assemblages commonly found during archaeological excavations can offer insights into past ecosystems. We studied assemblages of Unio pictorum mussel shells from palaeochannel silts associated with the Late Bronze Age site of Must Farm in eastern England (c. 850 BC), on an ancient tributary of the modern-day River Nene. We compared archaeological shells from two sediment horizons (broadly 1300-700 BC) to live individuals collected from two analogous sites on the present-day Nene. Size and growth rate, interannual growth variability and stable isotope (δ18O and δ13C) composition were compared between the populations. Size and the von Bertalanffy growth parameter L∞ differed among all four populations. Mean lengths and L∞ were higher in the two modern populations (mean lengths 77.3 ± SE 0.8 and 73.8 ± SE 1.1 mm, L∞ 91.8 ± 5.4 and 79.0 ± 8.1 mm) than the ancient populations (mean lengths 58.1 ± SE 1.6 mm and 68.4 ± SE 0.9 mm; L∞ 71.5 ± 16.9 and 76.8 ± 6.2 mm). Modern individuals also showed greater variation in age-corrected year-to-year growth. δ13C was lower in modern shells (-11.8‰ for modern shells, -9.03‰ and -9.02‰ for ancient shell populations), potentially reflecting altered hydrological and nutrient regimes. δ18O and δ13C were positively correlated for all but one sampled ancient shell, but not modern shells. These results reflect changes in local environmental conditions, particularly the transition from a shallow, slow-flowing tributary to a deeper, canalised river with faster flow, as well as effects of anthropogenic nutrient enrichment. The findings demonstrate the importance of long-term data in studying anthropogenic ecosystem alteration and avoiding shifting baseline syndrome in conservation planning.

Influence of Microplastics on Freshwater Bivalves (Review)

Influence of Microplastics on Freshwater Bivalves (Review)

Silver nanoparticles exhibit ecotoxicological effects via oxidative stress, inflammation, and reproductive toxicity in Asian clam (Corbicula fluminea)

Silver nanoparticles (AgNPs) are pervasive environmental pollutants capable of inducing toxicological impacts on benthic organisms. In this study, the effects of AgNPs on the antioxidant enzyme activities, tissue damage, inflammatory responses, and reproductive toxicity of Corbicula fluminea were investigated. C. fluminea was exposed to four concentrations of AgNPs (0, 5 mg/L, 10 mg/L, and 125 mg/L) for 48 h. The results showed that the higher concentrations of AgNPs caused severe tissue damage in multiple organs of C. fluminea, induced oxidative stress and an imbalance of the antioxidant enzyme activities (such as SOD, CAT, MDA), and increased the inflammatory immune response involving NFκB, TLR2/4, HSP70/90, IL1β, and TNFα. Notably, further transmission electron microscopy and cytological analyses revealed that AgNPs exposure induced apoptosis in the gonad tissues, resulting in significant loss and damage in the oocytes and spermatids. The present study demonstrates the ecotoxicological impacts of AgNPs on freshwater bivalves, particularly highlighting their reproductive toxicity on germ cells, signifying the potential toxic effects of heavy metal pollution on aquatic ecosystems.

An Update on the Conservation Status Assessment of two Endangered Freshwater Mussel Species in Bavaria, Germany

ABSTRACTThe two highly endangered European mussel species Margaritifera margaritifera and Unio crassus are target species of conservation. Based on a recently completed systematic state‐wide monitoring of each 22 M. margaritifera and 22 U. crassus streams in Bavaria, Germany, we present an update on population trends, conservation status, habitat quality and threats for both species. Populations status and habitat quality varied strongly between M. margaritifera and U. crassus streams, but there was also great variability within each of those groups. The population decline of M. margaritifera has continued, albeit higher proportions of juveniles originating from artificial breeding programmes have been established in some streams. Habitat quality often did not match known requirements as evident from poor stream bed quality, lack of hosts and elevated nutrient levels. In contrast, U. crassus populations showed a better status, with an increase in population size over all sampled streams. Successful recruitment was indicated by high proportions of juveniles. However, no mussels older than 16 years were found, probably due to predation and structural stream maintenance measures. Climate change effects, such as extreme droughts, affected both species. This study demonstrates different needs in conservation management for both species. Although mitigation of drought effects is commonly needed for both species, tackling host fish management and direct threats such as predation should be prioritized in U. crassus, whereas restoration of prime habitat quality and intact catchments is key to enable natural recruitment and sustainable populations of M. margaritifera.

Cloning and Expression Analysis of TGF-β Type I Receptor Gene in Hyriopsis cumingii.

The TGF-β signaling pathway plays an important role in wound healing and immune response. In this study, a TGF-β type I receptor (TGF-βRI) homolog was cloned and characterized from freshwater mussel Hyriopsis cumingii. The full-length cDNA of the TGF-β RI gene was 2017 bp, with a 1554 bp open reading frame (ORF), and encoded 517 amino acids. The predictive analysis further identified distinct regions within the TGF-βRI protein: a signal peptide, a membrane outer region, a transmembrane region, and an intracellular region. Real-time quantitative PCR results showed that the TGF-β RI gene was expressed in all tissues of healthy mussels. The transcripts of TGF-β RI in hemocytes and hepatopancreas were significantly up-regulated at different periods after stimulation with Aeromonas hydrophila and peptidoglycan (PGN) (P < 0.05). The mRNA expression of TGF-β RI progressively increased from day 1 to day 10 after trauma (P < 0.05), and it returned to the initial level by day 15. The expression levels of TGF-β , Smad5, MMP1/19, and TIMP1/2, but not Smad3/4, were significantly up-regulated at different time points after trauma. However, the expression levels of TGF-β , MMP1/19, and TIMP2 were decreased after treatment with the inhibitor SB431542. Furthermore, the recombinant TGF-βRI proteins were expressed in vitro and existed in the form of inclusion bodies. Western blotting results showed that TGF-βRI proteins were expressed constitutively in various tissues of mussels, and their expression was up-regulated after trauma, which was consistent with the mRNA expression trend. These results indicate that TGF-β RI is involved in the process of wound repair and immune response.

A new invasive freshwater mussel: Discovery of a non-native population of Pilsbryoconcha exilis (Lea, 1838) in Myanmar (Bivalvia: Unionidae)

The present study reports on the first record of a non-native population of the freshwater mussel Pilsbryoconcha exilis (Lea, 1838) (Bivalvia: Unionidae) in Myanmar. It was discovered from irrigation canals that are situated in the Delta Region of the Ayeyarwady River. Based on approximate age estimates and information from local villagers, this population was probably established in 2019-2020. The DNA sequence data reveals that the Ayeyarwady population shares a single COI haplotype and that this haplotype was previously recorded from the Udon Thani Province of Thailand (Mekong River drainage). Based on this evidence, we could assume that P. exilis was introduced to Myanmar from Thailand. Our new findings expand the global checklist of invasive freshwater mussels that currently contains 17 species.

Freshwater mussels enhance sediment nitrogen-removal potentials and alter bacterial communities via nutrient release and bioturbation

Freshwater mussels enhance sediment nitrogen-removal potentials and alter bacterial communities via nutrient release and bioturbation

Genome-wide association analysis reveals genetic architecture of growth and inner shell color traits in freshwater pearl mussel Hyriopsis cumingii (Lea 1852)

Triangle sail mussel (Hyriopsis cumingii, Lea 1852) is the most important freshwater pearl mussel in China. Growth traits of host mussels and inner shell color traits of donor mussels are critical determinants for pearl size and color. In this study, we performed GWAS analysis to explore the genetic architecture of growth and inner shell color traits. Using genotype by sequencing (GBS) technique, we obtained 80,562 SNPs from a total dataset of 463 mussels, based on these data, we found weak genetic relationship (−0.1–0.4) and rapid LD decay rate among the population. Moreover, GWAS analysis identified 12 growth-related significant SNPs and 29 inner shell color related significant SNPs. Five of the 12 SNPs linked to growth traits were validated to be credible SNPs in a new population. Cyclin, SNF, PMP22, CPED1, F-box and APC/C genes were found to be significantly associated with growth traits, which may influence the growth and development of H. cumingii by regulating cell mitosis, mantle epithelial tissue activity, and Ca2+ absorption and transport capacity. Notably, redness a* showed an obvious aggregation peak in chromosome 17, indicating that this region may be closely related to the inner shell color. Furthermore, three causal genes in chromosome 17, HSP78, MAS and PKS are inferred to be the key genes on color formation of purple inner shell. These results provide some new insights into the genetic basis and physiological regulation mechanism of growth and inner shell color traits in H. cumingii. However, detailed functional identification and regulation mechanism analysis merits more investigation.

A new superfamily of freshwater mussels Deccanoidea nov. (Mollusca: Unionida) from an intertrappean deposit of Saurashtra province (Gujarat state, western India): An example of disjunct distribution

The Cretaceous-Palaeogene intertrappean deposits of the Deccan Volcanic Province of India comprise vertebrate, invertebrate and plant fossils of the dominantly continental realm. A 3–4 m thick shaly-sandstone lacustrine intertrappean sequence of Early Palaeogene (Palaeocene-Early Eocene) Bamanbor Formation, Chotila Basin (Saurashtra province, Gujarat State, western India) has yielded a collection of molluscans (bivalve and few gastropods) fauna. High-resolution digital photography and radiography of the recovered bivalves allowed us to gain detailed inferences on shell morphology. In a taxonomical context, we herein propose a new unionid molluscan superfamily Deccanoidea nov. represented by a single new family Deccanoidae nov. that includes two new subfamilies, that is, Deccanoinae nov. (represented by two new genera Deccanoida gen. nov. [including four new species: D. conrugis sp. nov., D. aleta sp. nov., and D. costaria sp. nov.] and Bamanboria gen. nov. [including one new species Bamanboria oblongis gen. et sp. nov.] and Chotiloinae nov. [represented by one new genus Chotilia gen. nov. and three new species: Chotilia trappeansis sp. nov., C. tuberculata sp. nov. and C. deccanensis sp. nov.]). Inorganic geochemistry of host (unionid-yielding) lithologies reveals oxic-freshwater conditions, humid-climate and moderate rainfall. The data on historical biogeography reveals that the Indian subcontinent hosted unionids during the late Cretaceous; however, the presence of new (at family/generic level) unionid fauna during the Early Palaeogene (Palaeocene-Early Eocene) in India indicates changes in the geographic position and ecologic condition linked to northward drift and lava outpouring, respectively. A disjunct distribution of unionid fauna in the erstwhile Gondwanan continents and insular India during the Cretaceous-Palaeogene interval can be explained in terms of both vicariance and dispersal.

Quantifying Effects and Ingestion of Several Pristine Microplastics in Two Early Life Stages of Freshwater Mussels.

Microplastics have been found in freshwater systems, and in turn have been detected in freshwater bivalves. However, there is limited research that defines the toxicity of bicroplastics to native freshwater bivalves that have long been imperiled in North America. Our objective was to determine whether a suite of pristine microplastics has an adverse effect on two early life stages of unionid freshwater mussels. Glochidia of Lampsilis fasciola (a Canadian species at risk) and Lampsilis siliquoidea (widespread across Canada) were individually exposed to spheres of polystyrene (6 and 90 μm), polyethylene (28, 90, and 1000 μm), and cellulose acetate (1000 μm), as well as fibers of polyethylene terephthalate (60 μm). After 24 h, there was no significant decrease in glochidia viability in either species. Juvenile L. siliquoidea mussels were also exposed to spheres of polystyrene (6 and 90 μm) and polyethylene (28 μm), and fibers of polyethylene terephthalate (60 μm) in individual 28-day subchronic tests followed by a 7-day depuration period. Burial was assessed weekly, and ingestion of each microplastic was compared in nondepurated and depurated mussels. There was no sustained effect on juvenile burial with any microplastic tested. Ingestion of microplastics was concentration dependent, and depuration occurred for all particles and size ranges tested. The results suggest that pristine microplastics were not acutely toxic to the early life stages of these freshwater mussels, but that the energetic costs associated with particle uptake and depuration, which were not measured in our study, may have an impact on fitness that warrants further investigation. In addition, testing with other shapes and polymers of microplastics typically detected in the environment is recommended. Environ Toxicol Chem 2024;00:1-12. © 2024 The Author(s). Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Climate-driven shifts in freshwater biodiversity will impact mitigation costs for hydropower

Climate change is forecasted to drastically alter freshwater fish and mussel species distribution. Hydropower dam reservoirs, which modify downstream thermal regimes, may interact with climate change's impact on species distribution. This distribution shift may feedback, affecting hydropower operation costs through environmental compliance. We investigated how freshwater species distribution will shift due to climate change and hydropower reservoirs in the conterminous United States (CONUS), and how this will affect biodiversity mitigation costs for privately-owned hydropower plants. In general, using environmental niche modeling, we found that climate change increased the range of both freshwater fish and mussel species on average. For fish, this was mainly due to the expanded habitat for warm-water and cool-water fish species despite the diminish in habitat for cold-water species. Compared to climate change, thermal stratification of hydropower reservoirs had a small impact on the future range changes of these species in the tailwaters but showed an interaction with the effect of climate change on species range. Geographically, we projected an increase of species richness in the west and a decrease in the central and east of CONUS for fish, while projecting uniform increase for mussels. With this shift in species distribution, we estimated that the Northwest region will face the largest increase in mitigation cost, while the majority of plants in the Southeast will experience a decrease in cost.

Surviving global change: a review of the impacts of drought and dewatering on freshwater mussels.

The increase in the frequency and intensity of droughts and heatwaves caused by climate change poses a major threat to biodiversity. In aquatic systems, sedentary species such as freshwater mussels are generally considered more vulnerable to changes in habitat conditions than mobile species such as fish. As mussels provide important ecosystem services, understanding the impacts of drought on freshwater mussels is of particular importance for the management of overall functioning of aquatic ecosystems. We used a comprehensive literature search to provide a systematic overview of direct and indirect effects of drought on freshwater mussels (Bivalvia: Unionida) and an evaluation of mitigation strategies. We found that drought studies were concentrated mostly in the USA, with a focus on the Unionidae family. Topics ranged from the physiological effects of high temperatures, emersion, and hypoxia/anoxia to behavioural and reproductive consequences of drought and the implications for biotic interactions and ecosystem services. Studies spanned all levels of biological organization, from individual responses to population- and community-level impacts and ecosystem-wide effects. We identified several knowledge gaps, including a paucity of trait-based evaluation of drought consequences, limited understanding of thermal and desiccation tolerance at the species level, and the synergistic effects of multiple drought stressors on mussels. Although we found many studies provided suggestions concerning management of populations, habitat conditions, and anthropogenic water use, a systematic approach and testing of recommended mitigation strategies is largely lacking, creating challenges for managers aiming to conserve freshwater mussel communities and populations in light of climate change.

Reciprocal transplant experiments demonstrate a dynamic coevolutionary relationship between parasitic mussel larvae and bitterling fishes

Abstract The coevolutionary dynamic of host–parasite associations varies from strictly local adaptations to diffuse guild coevolution. How innate and acquired immune responses modulate host resistance to parasitism and how host specificity and geographic scaling affect the efficacy of host response have consequences for range dynamics and biological invasions. Using reciprocal transplant experiments, we tested whether local or diffuse coevolution shapes host response to parasitism in the host–parasite association between bitterling fishes and larval stages (glochidia) of freshwater mussels from Europe and East Asia. We found that glochidia initially indiscriminately attached to all study host species, but immune responses elicited significant differences in host responses within 24 h of infection, which intensified during glochidial development. European bitterlings were more resistant to European glochidia and Asian bitterlings to Asian glochidia, with the strongest geographic bias in resistance in the Asian bitterling hosts. This finding suggests a strong effect of local adaptation but also indicates the non‐negligible role of coevolutionary hotspots. Low natural glochidia load on bitterling species overall hence arise from competent immune response rather than glochidia avoidance behaviour. Bitterling immune response is primarily innate and not acquired. Overall, our data demonstrate the complex outcome of parasite pressure on the evolution of host resistance, and important role of geographically structured coevolution in shaping host response.

Microeukaryotes Associated with Freshwater Mussels in Rivers of the Southeastern United States.

Microeukaryotes are a diverse and often overlooked group of microbes that are important in food webs and other ecological linkages. Little is known about microeukaryotes associated with aquatic invertebrates, although filter feeders such as mussels are likely to take in and potentially retain microeukaryotes in their gut while feeding. Microeukaryotes such as apicomplexans have been reported in marine mussel species, but no studies have examined the presence of these microorganisms in freshwater mussels or how they relate to mussel host species or environmental conditions. In this study, microbial community DNA was extracted from the gut tissue of over 300 freshwater mussels, representing 22 species collected from rivers in the southeastern USA. Microeukaryote DNA was detected using PCR amplification, followed by the sequencing of positive amplicons. Microeukaryotes were found in 167 individual mussels (53%) of those tested. Amplicons included dinoflagellates/algae that differed between mussel species and are likely food sources that were distinct from those found in water and sediment samples analyzed concurrently. A total of 5% of the positive amplicons were non-photosynthetic alveolates that could represent parasitic microeukaryotes. Understanding the distribution of microeukaryotes in the freshwater mussel gut microbiome could further our understanding of the ongoing decline of mussel populations.

Enhanced Growth Potential of Tilapia (Oreochromis niloticus) Through Maggot-Based Feeding in Multi-Trophic Systems

Highly nutritious insects, such as black soldier fly (BSF) larvae, also referred toas maggot, have been evaluated as feed in monoculture systems, but their use in multi-trophic systems has not been previously investigated. This study used maggot-based feed in a multi-trophic system on a laboratory scale to evaluate the survival and growth performance of tilapia (Oreochromis niloticus). Tilapia were cocultured with freshwater lobster, freshwater clams, and paddy. Four experimental diets were used including a commercial pellet as a control (CP), live maggots (LM), dried maggots (DM), and supplemented maggots (SM). Tilapia (initial weight, 4.1 ± 0.2 g) and other organisms were reared in plastic tanks (water volume 50 L) and randomly distributed into 12 tanks, each containing 20 individual tilapia. The experimental diets were given four times a day at a feeding rate of 10% tilapia biomass. After 28 days of feeding, the survival and growth of tilapia on the CP diet were 90.0% and 2.8% day-1, LM 93.3% and 2.7% day-1, DM 93.3% and 3.3% day-1, and SM 90.0% and 3.1% day-1, respectively. There was no significant effect (P &gt; 0.05) on the survival performance among the experimental diets. However, the growth confirmed by Specific Growth Rate (SGR) showed a significant effect (P &lt; 0.05). SGR values were found to be significantly higher in the DM and SM diets than in the CP diet. An important finding of this research is the potential of maggot-based feed to increase the growth of tilapia in multi-trophic systems without impairing their survival.

Assessment of haemolymph parameters of some freshwater snails and mussels collected from a lentic habitat of Bangladesh

ABSTRACT The present study was conducted to determine certain haemolymph parameters of natural populations of two freshwater snails Pila globosa and Filopaludina bengalensis, and four unionid mussels Lamellidens jenkinsianus, L. phenchooganjensis, L. marginalis, and L. corrianus collected from Darikanthal Beel, Trishal, Mymensingh. Twenty apparently healthy live snails and mussels from each population collected at the same date were selected for haemolymph analysis. A non-lethal sampling technique was adopted for collecting haemolymph from the snails and mussels. The haemolymph parameters Na+, K+, Cl−, glucose concentrations and pH levels were determined for each specimen. Significant differences (P < 0.05) were found in almost all the haemolymph parameters among the sampled snail and mussel populations. This study provided reference ranges for some vital haemolymph parameters of the two freshwater snail species and four unionid mussel species. These ranges are measurable non-lethally and could be applied to biological monitoring of environmental stressors using the molluscs as indicator species.

Identification and antibacterial activity of a novel phage-type lysozyme from the freshwater mussel Hyriopsis cumingii

A cDNA encoding a phage-type lysozyme, designated as HcPLYZ, was successfully cloned from Hyriopsis cumingii. The full-length cDNA sequence of HcPLYZ was determined to be 896 base pairs in length. Analysis revealed the absence of a signal peptide at its N-terminus, and identified two highly conserved phage-type lysozyme activity sites, Glu20 and Asp29, within the deduced amino acid sequence of HcPLYZ. The results of the cloning and sequencing symbiotic bacteria in tissues were consistent with those obtained using tissue cDNA as the template, suggesting that HcPLYZ may originate a symbiotic bacterium. The expression levels of HcPLYZ mRNA exhibited significant variations across different tissues. Successful expression was induced using IPTG, and the native recombinant protein was subsequently purified through affinity chromatography employing Ni2+, and the optimal pH and temperature of which were determined to be 5.5 and 50°C, respectively. Following exposure to Aeromonas hydrophila, there was a significant increase in the levels of HcPLYZ mRNA in the hemocytes, hepatopancreas, and gills. HcPLYZ was demonstrated the inhibition activity of 55% and 83% against Micrococcus lysodeikticus under pH 5.5 and 50 °C conditions, respectively. These results suggested that HcPLYZ possessed antibacterial activity against both A. hydrophila and M. lysodeikticus.

Freshwater Mussel Viromes Increase Rapidly in Diversity and Abundance When Hosts Are Released from Captivity into the Wild.

Freshwater mussels (order: Unionida) are highly imperiled globally and are increasingly the focus of captive propagation efforts to protect and restore wild populations. The Upper Tennessee River Basin (UTRB) in Virginia is a freshwater biodiversity hotspot hosting at least 45 of North America's ~300 species of freshwater mussels, including 21 threatened and endangered species listed under the U.S. Endangered Species Act. Recent studies have documented that viruses and other microbes have contributed to freshwater mussel population declines in the UTRB. We conducted a multi-year longitudinal study of captive-reared hatchery mussels released to restoration sites throughout the UTRB to evaluate their viromes and compare them to captive hatchery environments. We documented 681 viruses from 27 families. The hatchery mussels had significantly less viruses than those deployed to wild sites, with only 20 viruses unique to the hatchery mussels. After the hatchery mussels were released into the wild, their number of viruses initially spiked and then increased steadily over time, with 451 viruses in total unique to the mussels in the wild. We found Clinch densovirus 1 (CDNV-1), a virus previously associated with mass mortality events in the Clinch River, in all samples, but the wild site mussels consistently had significantly higher CDNV-1 levels than those held in the hatchery. Our data document substantial differences between the viruses in the mussels in the hatchery and wild environments and rapid virome shifts after the mussels are released to the wild sites. These findings indicate that mussel release programs might benefit from acclimatization periods or other measures to mitigate the potential negative effects of rapid exposure to infectious agents found in natural environments.