Search Results (160)

Freshwater ecosystems are increasingly threatened by microplastics (MPs), yet field evidence linking MP burden with physiological responses in freshwater bivalves remains limited. This study investigated the associations between individual MP burden and oxidative stress biomarkers in the freshwater mussel Unio elongatulus collected from the Sacchetti Ditch, northeastern Italy. Mussels were sampled bimonthly over a 10-month monitoring period. The activities of superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, glutathione S-transferase, glyoxalase I, glyoxalase II, and lactate dehydrogenase, together with metallothionein levels, were determined in the gills and digestive gland. Significant associations with MP burden were detected for glyoxalase II and lactate dehydrogenase in the digestive gland and for glutathione S-transferase in the gills. MP burden was negatively associated with glutathione S-transferase and lactate dehydrogenase activities and positively associated with glyoxalase II activity. Most biomarkers also showed significant variation among sampling periods, indicating substantial temporal variability. Although the observational design does not allow causal relationships to be established, GST, GII, and LDH were the biomarkers most consistently associated with individual MP burden. These biomarkers may therefore represent promising candidates for inclusion in integrated biomonitoring approaches aimed at assessing MP-associated sublethal stress in freshwater ecosystems. Full article

To establish non-destructive morphometric predictors of live body weight in the endangered freshwater pearl mussel (Margaritifera dahurica), 100 wild adult individuals were randomly selected. Four phenotypic parameters, including shell height (SH), shell length (SL), shell width (SW), and body weight (BW), were measured, and the interrelationships among these traits were statistically analyzed using correlation and path analyses. The results indicated that the phenotypic correlations among all traits of M. dahurica reached a highly significant level. Shell length exhibited the greatest direct effect on body weight, with a path coefficient of 0.718. The statistical associations of shell height and shell width with body weight were primarily mediated through indirect pathways via shell length. Shell length, shell width, and shell height were identified as the key morphometric predictors of body weight, yielding a total coefficient of determination of 0.879. Shell length possessed the highest comprehensive coefficient of determination (0.911), making it an ideal target trait for selective breeding. Using stepwise regression analysis, the optimal multiple linear regression equation of morphological traits on body weight was established as Log_BW = −0.814 + 2.482Log_SL + 0.522Log_SW. Rather than directly driving genetic breeding, these findings provide a grounded, non-destructive method for predicting live body mass, facilitating rapid biomass monitoring and founder broodstock assessment in M. dahurica. Full article

Freshwater mussels (Bivalvia, Unionidae) are now among the world’s most imperiled taxonomic groups, and their diversity is under serious threat. The metamorphosis of glochidia parasitizing on a host fish into juveniles is undoubtedly the most unique and critical stage in the life cycle of freshwater mussels, but the underlying mechanisms remain unclear. Here, we integrated microscopic observation, stable isotope (δ¹³C and δ¹⁵N) tracing, and transcriptomic analysis to investigate this process in the globally distributed freshwater mussel Sinanodonta woodiana on yellow catfish (Pelteobagrus fulvidraco). Compared with glochidia, juveniles exhibited byssus abandonment and the formation of a foot, visceral mass, and new shell. The shell length (0.34 ± 0.02 mm) and height (0.31 ± 0.01 mm) of the juveniles were both larger than those of the glochidia (0.26 ± 0.01 mm and 0.30 ± 0.01 mm, respectively) (p < 0.05); however, this growth likely occurred after excystment from the host fish rather than during the parasitic phase. Juveniles showed significantly higher δ¹³C (−17.70 ± 0.26‰) and δ¹⁵N (9.80 ± 0.90‰) than glochidia (δ¹³C: −23.58 ± 0.63‰; δ¹⁵N: 6.18 ± 0.37‰) (p < 0.05), with juvenile δ¹⁵N comparable to host fish tissues. Metamorphosis generated 12,584 differentially expressed genes, mainly enriched in upregulated neuroactive ligand–receptor interaction, Ras signaling, and calcium signaling pathways. This study reveals the mechanisms of S. woodiana metamorphosis, providing valuable insights for improving breeding and thus supporting the diversity conservation of freshwater mussels. Full article

This study investigates the reuse of mussel shell waste as a secondary raw material in bio-cement mortars designed for the additive manufacturing of artificial reefs for marine habitat restoration. The novelty of the research lies in combining a high recycled shell content (60 wt.%), low-clinker cement, and two 3D-printing techniques: Extruded Material Systems (EMS) and Powder-Based Systems (PBS). Mechanical performance was evaluated through flexural and compressive tests after 7, 28, and 91 days under both air and freshwater curing conditions, while environmental impacts were assessed through Life Cycle Assessment (LCA). The LCA evaluated both the environmental performance of shell-based mixtures compared with conventional materials and the impacts associated with the investigated fabrication techniques. The best-performing bio-mixtures achieved compressive strengths up to 46.01 MPa and flexural strengths up to 9.91 MPa after freshwater curing, demonstrating the suitability of shell-based mortars for submerged applications. LCA results showed reduced impacts in land use and mineral resource depletion compared with conventional mixtures, despite slightly higher energy and water demands associated with shell pre-treatment. The results demonstrate the technical and environmental feasibility of integrating aquaculture waste into sustainable 3D-printed marine restoration solutions. Full article

Mediterranean temporary streams are characterized by high hydrological variability that climate change is expected to intensify, increasing drought frequency and severity. These conditions represent a major threat to freshwater mussels, an imperiled group with limited mobility and strict habitat and host requirements. This study explored key factors shaping freshwater mussel community structure, including the spatial distribution, species composition and abundance of coexisting species, in two temporary streams of the Guadiana river basin (southwestern Iberian Peninsula). Pool systems in both streams were characterized and compared under average dry season and extreme drought conditions using aerial imagery, whereas mussel abundance patterns and host–mussel relationships were assessed in the larger and more hydrologically stable stream. Results showed that drought severity had different effects on pool refugia persistence, longitudinal distribution and host fish availability between streams. The smaller stream experienced extensive pool desiccation during extreme drought, causing widespread mussel mortality, whereas the larger stream retained numerous pools that allowed mussel persistence. Mussel abundance showed no relationship with pool size. However, Unio tumidiformis abundance was positively associated with native fish abundance, particularly in upstream reaches. These results highlight hydrological stability and host availability as key drivers of freshwater mussel persistence in Mediterranean temporary streams. Full article

The Chi River Basin in northeastern Thailand is the country’s second-largest basin and a major tributary of the Mekong River, which is a regional hotspot for freshwater mollusc diversity. However, many of its sub-tributaries remain poorly studied. This study investigated molluscan diversity in the upper Chi River and examined relationships between assemblage structure and physicochemical habitat factors. Quantitative quadrat sampling was conducted at 11 stations along a 100 km reach, and community–environment linkages were analyzed using cluster analysis and canonical correspondence analysis (CCA). A total of 2734 individuals representing 25 taxa (12 gastropods, 13 bivalves) were recorded. Three distinct assemblages—Upstream, Midstream, and Downstream—were identified along the longitudinal gradient. CCA indicated that flow velocity, total dissolved solids (TDS), and dissolved oxygen (DO) were the primary predictors of assemblage structure (p < 0.01), jointly explaining 59.5% of community variation. Upstream reaches were dominated by Thiaridae (Tarebia, Brotia), midstream sections by Corbicula, and downstream areas exhibited the highest diversity, characterized by large unionid mussels. This study provides the first quantitative evidence of clear longitudinal zonation in the upper Chi River and establishes essential baseline data for conservation and management in this overlooked, biodiversity-rich basin. Full article

Environmental DNA (eDNA) metabarcoding has become a powerful, non-invasive method for detecting aquatic organisms. However, optimal sampling strategies for benthic taxa in lentic ecosystems remain unclear. This study evaluated the effectiveness of eDNA metabarcoding in detecting freshwater Unionidae mussels in lake water columns and examined their spatial and seasonal distribution patterns. We validated a mini-barcode primer targeting the mitochondrial 16S rDNA of unionid mussels through controlled laboratory experiments and field tests, confirming reliable amplification and accurate taxonomic assignment of freshwater bivalve DNA. Field surveys were conducted in four lakes within the Nakdong River basin, where eDNA samples were collected from littoral zones and from surface, mid-, and bottom layers of central lake areas during autumn and winter. Metabarcoding analysis identified 79 amplicon sequence variants (ASVs) representing four unionid taxa, with Cristaria plicata and Sinanodonta lauta comprising the majority of reads and ASVs. Overall, the number of Unionidae eDNA reads showed no significant seasonal differences, but there was notable spatial variation among sampling locations. Read numbers were significantly lower in littoral zones compared to central lake areas, with no significant differences detected among depth layers within the central zones. Species-specific analyses revealed contrasting spatial patterns: C. plicata had higher read abundance in mid- and bottom layers, while S. lauta was more frequently detected in surface and littoral samples. These findings suggest that the distribution of freshwater mussel eDNA in lakes is primarily influenced by spatial factors related to habitat preference and hydrodynamic mixing, rather than by seasonal variation during stable periods. This study offers practical insights for designing effective eDNA sampling strategies for benthic invertebrates in lentic ecosystems. Full article

Freshwater bivalves influence ecosystem functioning by transferring pelagic material to the benthos through filtration and biodeposition, yet quantitative multiscale evidence remains scarce for South American lakes. We assessed the role of the native mussel Diplodon chilensis in Laguna Chica de San Pedro (southern Chile) by integrating laboratory measurements, seasonal in situ mesocosm experiments, and lake-scale estimates. Individual filtration rates were quantified under contrasting temperature and phytoplankton biomass conditions, while field experiments evaluated mussel effects on sediment biogeochemistry and zoobenthic assemblages. Filtration increased strongly with temperature, whereas food availability exerted a detectable effect only at lower temperatures. Live mussels consistently enhanced sediment organic matter and total nitrogen, while total phosphorus responses were weak and variable. Macroinvertebrate richness and abundance increased in association with mussel presence, whereas meiofaunal responses were weaker and inconsistent. When scaled to the lake level using bathymetric population distribution and seasonal deposition rates, D. chilensis accounted for substantial annual fluxes of organic matter and nitrogen to surface sediments, largely driven by shallow and intermediate depths. These results demonstrate that native freshwater mussels mediate a persistent downward component of benthic–pelagic coupling in clear-water temperate lakes of southern South America. Full article

Habitat restoration followed by species reintroduction is a key strategy for biodiversity recovery. For species with parasitic life stages, such as the freshwater pearl mussel (Margaritifera margaritifera), host suitability is crucial. Before a planned reintroduction of mussels into a newly constructed nature-like fishway, we tested the compatibility of four brown trout (Salmo trutta) strains from local and foreign drainages as hosts for mussels from a nearby river. The strains included (a) a local sympatric wild strain, (b) a local allopatric wild strain from near the fishway, (c) a local allopatric hatchery strain used for stocking, and (d) a foreign allopatric hatchery strain. After forty days, infestation rates of the parasitic mussel glochidia did not differ significantly among strains, indicating that all could serve as hosts. Glochidia that developed on the local allopatric hatchery strain had the highest growth rate, suggesting the highest suitability for production under laboratory conditions. While stocking hatchery strains can have negative ecological impacts, local wild fish provide a sustainable option without continued introductions of hatchery strains. If wild fish are scarce, carefully chosen hatchery strains may support juvenile mussel production and reintroduction under controlled conditions. Our findings highlight the importance of evaluating host compatibility before mussel reintroduction and fish stocking. Full article

Pearl culture has long been a major global industry. As a significant global producer, China mainly produces pearls from the freshwater mussel (Sinohyriopsis cumingii). S. cumingii with various shell colors can produce pearls of different colors; for example, mussels with a blue-white shell can produce white pearls, while those with a purple shell can produce light-purple pearls. Therefore, investigating the molecular genetics of shell color variation in S. cumingii can advance our understanding of the mechanisms underlying differences in shell and pearl coloration in these mussels. In this study, we selected juvenile S. cumingii with four differently colored inner shells and collected tissue samples for transcriptomic analysis. The results showed that many key genes involved in the regulation of pigment metabolism (such as ADAMTS, TYR, BCDO2, and FTH1), as well as those associated with metabolism and mineral absorption (such as TRPV6, HCP1, HEPH, and Zip4), exhibited significant differences. Furthermore, these DEGs (differentially expressed genes) may influence the synthesis and metabolism of melanin, carotenoids, porphyrins, and heme, thereby affecting shell color variation; they might also be one of the potential reasons why S. cumingii produces pearls of different colors. Full article

Microplastics are among the most emerging environmental micro-threats to aquatic ecosystems. Bivalves are filter-feeding benthic organisms and are often considered excellent bioindicators of contamination in aquatic bodies. This study focuses on the toxic effects of fibrous polystyrene microplastics (1 mg/L) on biochemical parameters of the freshwater bivalve Lamellidens marginalis after exposure periods of 7, 10, and 15 days (Experimental groups I, II, and III, respectively). Biochemical analysis showed reduced protein, ACP, and ALP activities in all tissues except for a significant increase in ACP in the mantle and foot of group III. AST activity increased in the gill and hepatopancreas but declined in the mantle and foot. ALT activity consistently decreased across all experimental tissues relative to the control. The Integrated Biomarker Response Index increased over time for gill, mantle, and foot tissue. For the hepatopancreas, the values were 11, 8.82, and 9.02 for Experimental groups I, II, and III, respectively. From Biomarker Response Index values, group I gill tissue (2.2) was most severely altered. Major alterations occurred in the hepatopancreas, mantle, and foot of groups II and III. Hepatopancreas generally acts as a site of detoxification, digestion, and absorption, and exposure to microplastics can lead to the accumulation in hepatopancreas. Full article

Understanding the behavioral strategies that allow freshwater mussels to persist under environmental stress is essential for their conservation, yet burrowing behavior remains poorly quantified. We tested whether valve movement data could be used to detect and characterize burrowing in the endangered Westralunio carteri; a species endemic to a region undergoing severe climatic drying. Mussels from multiple populations were monitored individually under laboratory conditions using Hall effect sensors, and valve movement patterns were analyzed to distinguish between burrowing and non-burrowing behaviors. Burrowing was associated with rapid, high-amplitude valve movements that lengthened as burial progressed, while non-burrowing behaviors showed distinct, slower patterns. These differences indicate that valvometry can reliably identify burrowing behavior, providing a non-invasive method for monitoring mussel activity. This approach has broad applications for ecological research, conservation assessment, and early-warning biomonitoring of imperiled freshwater mussel populations. Full article

Freshwater mussels (Unionida) perform important functions that are integral to keeping streams, rivers, and lakes operating as holistic ecosystems. Some of these functions improve water quality for humans through their filtration activities such as nutrient cycling and feces and pseudofeces production. In this study, we estimated the magnitude of contaminant sequestration by mussel assemblages using data at polluted and relatively unpolluted sites from watersheds in the upper Mississippi River (Minnesota, Wisconsin, Iowa, and Illinois, USA), the Clinch River (Virginia and Tennessee, USA), and the upper Neuse River (North Carolina, USA). Data from these rivers represented a range of (1) spatial scales from wadable streams to large rivers, (2) population sizes from tens of thousands to hundreds of millions of mussels, (3) survey techniques from qualitative to quantitative, and (4) chemical classes from inorganic to organic contaminants. We estimated that mussels in two relatively unpolluted reaches of the upper Mississippi River sequestered 1.42 × 10¹³ µg of total metals, metalloids, and ions (i.e., 14.2 metric tons). Mussels in the relatively unpolluted upper Neuse River sequestered between 22.2 and 53.3 million ng of polycyclic aromatic hydrocarbons (PAHs; i.e., 22.2–53.3 mg). Mussels at a polluted site in the Clinch River (Pendleton Island) sequestered 168 million ng of PAHs, compared to 1.45 billion ng of PAHs sequestered at relatively unpolluted sites. Mussels at unpolluted sites in the Clinch River had a 10 times greater sequestration capacity despite having lower tissue concentrations. The accuracy (precision and bias) associated with estimating assemblage-level contaminant sequestration by mussels varied as a function of survey design, spatial scale, population size, and contaminant type. This preliminary assessment of sequestration of contaminants by mussels outlines a framework for understanding the contributions these organisms make in supporting water quality and highlights the need to protect and conserve mussels and the ecosystem functions and services they provide. Full article

Freshwater mussels hold significant ecological and economic value. Gut bacterial communities can regulate the growth and immunity of freshwater mussels. However, the dynamics of gut bacterial communities in freshwater mussels at different life stages are still limited. This study used the globally widespread mussel, Sinanodonta woodiana, as a model animal and employed 16S rRNA sequencing technology to comparatively analyze the gut bacterial communities of early juveniles, late juveniles, and adults. Alpha diversity indices indicated a trend of increasing richness and diversity of the gut bacterial communities with the mussel growth. Beta diversity analysis revealed distinct stage-specific taxonomic profiles. At the phylum level, four dominant phyla were identified in the early juveniles, namely Fusobacteriota, Verrucomicrobiota, Pseudomonadota, and Cyanobacteriota; and seven dominant phyla were identified in both late juveniles and adults, namely Fusobacteriota, Pseudomonadota, Verrucomicrobiota, Cyanobacteriota, Bacillota, Bacteroidota, and Chloroflexota. Among them, the relative abundance of Fusobacteriota decreased with the mussel growth (p < 0.05), while the relative abundances of Pseudomonadota and Cyanobacteriota increased with the mussel growth (p < 0.05). At the genus level, four dominant genera were identified in the early juveniles: Cetobacterium, LD29, Cyanobium_PCC-6307, and Cupriavidus; seven dominant genera were identified in the late juveniles: Cetobacterium, Roseomonas, LD29, Cyanobium_PCC-6307, Limnolyngbya_CHAB4449, Terrimicrobium, Limnothrix; and nine dominant genera were detected in the adults: Cetobacterium, LD29, Roseomonas, Cyanobium_PCC-6307, Limnothrix, Limnolyngbya_CHAB4449, Sediminibacterium, Terrimicrobium, Acidibacter. Among these, the relative abundance of Cetobacterium decreased with the mussel growth (p < 0.05), while the relative abundance of Acidibacter increased with the mussel growth (p < 0.05). Functional prediction revealed that the gut bacterial communities were primarily involved in metabolic pathways, including the biosynthesis of ansamycins, biosynthesis of vancomycin group antibiotics, D-glutamine and D-glutamate metabolism, biotin metabolism, valine, leucine and isoleucine biosynthesis, and fatty acid biosynthesis. The findings provide insights for enhancing the nutrition and health of freshwater mussels. Full article

Pearl color is the primary determinant of its value, and the mantle donor tissue (saibo) used in pearl culture plays a critical role in color formation. To elucidate the molecular mechanisms underlying nacre color, we performed comparative transcriptomic analyses of saibo tissues from Sinohyriopsis cumingii displaying three representative phenotypes: white (W), purple (P), and golden (G). A total of 364 differentially expressed genes (DEGs) (102 upregulated and 162 downregulated genes) were identified in W vs. P. A total of 770 DEGs (467 upregulated and 303 downregulated genes) were identified in W vs. G. KEGG pathway analysis revealed significant differences in the expression of genes mainly involved in pigment-based and structural coloration, including amino sugar and nucleotide sugar metabolism (ko00520), cell adhesion molecules (ko04514), tyrosine metabolism (ko00350), ECM-receptor interaction (ko04512), and PI3K-Akt signaling pathway (ko04151). Subsequent integrative analyses across W vs. P and W vs. G groups identified 45 key regulatory genes, which were classified into four functional categories: extracellular matrix protein synthesis and biomineralization (e.g., chit, silkmaxin, bmp2/7, profilin, perlucin2), organic pigment metabolism (e.g., tyr, typ, dbh, bco2, gst5, ldlr, cpox, pks-like 1, pks15), metal ion metabolism and accumulation (e.g., hip-like, fcr1, ferritin 2), and epigenetic regulation (e.g., metK, mbd4/6, mettl24/27, alkbh6). Taken together, our findings reaffirm the complex nature of pearl coloration and reveal that structural coloration, pigment biosynthesis, and epigenetic modulation collectively shape nacre color formation, which paves the way for further functional elucidation of color-related genes and facilitates selective breeding practices in S. cumingii. Full article