Effects of bisphenol A on freshwater mussels: Insights into the protective mechanisms of selenium.

Community diversity patterns of freshwater mussels (Unionida) in Shijiu Lake and its connected channels during the early period of the Yangtze River fishing ban

The increasing production and application of engineered nanoparticles have raised significant environmental and health concerns, particularly, regarding their potential release into aquatic ecosystems. Among these, multifunctional nanocomposites combining titanium dioxide (TiO2) and zinc oxide (ZnO) have garnered considerable attention due to their widespread use. This study examined the biological responses of the freshwater mussel Unio ravoisieri to TiZn nanocomposites at concentrations of 10 and 100 μg/L. In a subsequent phase, the potential protective effects of selenium (Se) against nanocomposite-induced toxicity were assessed using biochemical markers, including hydrogen peroxide (H2O2), catalase (CAT), reduced glutathione (GSH), glutathione-S-transferase (GST), malondialdehyde (MDA) levels, and acetylcholinesterase (AChE) activity. The results demonstrated that exposure to TiZn nanocomposites alone induced oxidative stress in the digestive gland, with elevated levels of CAT, GST, AChE, GSH, and MDA in a concentration-dependent manner. However, selenium co-administration at 100 μg/L significantly mitigated these oxidative responses, highlighting its potential as a protective agent against nanocomposite-induced toxicity. These findings suggest promising avenues for the use of selenium in reducing nanoparticle-related environmental stress in aquatic organisms.

Effective control of invasive sea lamprey (Petromyzon marinus) populations relies heavily on lampricides, but few studies have investigated the impacts of granular Bayluscide® (gB) on benthic dwelling organisms. Native freshwater mussels are present in many similar habitats that larval sea lamprey prefer, making them susceptible to non-target effects. The active ingredient of gB, niclosamide, was derived specifically as a molluscicide, therefore it is crucial to understand its impacts on a group of mollusks that have been imperiled due to many factors including the input of contaminants in the aquatic environment. Two early life stages of Lampsilis siliquoidea were tested in 7-day exposures to gB. Mortality was significant in both sub-adult and newly metamorphosed mussels, with the latter being significantly sensitive to gB applications that were less than 1% of the suggested application rate. A significant decrease in mussel growth was seen at 0.78% of the suggested application rate. A 24-hr test was supplemented due to gB potency, revealing a similar median lethal concentration of 0.67% (0.55-0.79) of the suggested gB application rate. Additionally, an 8-hr exposure of 0.78% of the application revealed significant effects after only 2 hr of exposure. Both early life stages of L. siliquoidea showed a marked sensitivity to gB. Although environmental conditions may have an influence on gB fate, the marked sensitivity of early life stages demonstrated in this study is crucial to understanding the effects of sustained gB application on the population dynamics of freshwater mussels.

Freshwater mussels (Unionidae) depend on specific fish hosts to complete their life cycle. Glochidia, their parasitic larvae, must attach to the gills or fins of suitable fish species to metamorphose. However, non-host fish may intercept glochidia, reducing larval availability for competent hosts-a phenomenon known as the dilution effect. We investigated this mechanism in a natural population of the endangered mussel Unio crassus, focusing on the interaction between the dominating host Phoxinus phoxinus and the non-host Gobio gobio. Field surveys across three separate reaches of the Warkocz River (2015-2016) and a controlled infestation experiment demonstrated that G. gobio removes a substantial proportion of glochidia without supporting their metamorphosis. Co-occurrence analysis showed a negative relation between infestation levels of G. gobio vs. P. phoxinus, with a significant interaction modulated by U. crassus density. At low mussel densities, the impact of G. gobio on parasitic success was strongest. Gobio gobio was recorded at 90% of the known U. crassus localities in Poland, and in all of these sites it formed a dominant component of the fish assemblage. Our findings provide direct evidence of a context-dependent dilution effect and highlight the importance of fish community composition and behaviour in conservation of unionid mussels. The presence of non-host fish in habitats with low mussel abundance may undermine recruitment and increase extinction risk in fragmented populations.

Invasive species like freshwater mussels extensively colonize water distribution systems, posing a significant threat to the safety and performance of hydraulic infrastructure. The demand for innovative technologies that balance efficacy, environmental safety, and sustainability for biofouling control is growing. This study explores the potential of potassium ferrate [Fe(VI)], a green oxidant, as an effective antifouling agent. Using Limnoperna fortunei as a model organism, we demonstrated that Fe(VI) exerts dose-dependent control over biofouling. Larval viability decreased by 62.48% (p < 0.05) after 1 h of exposure to 0.1 mg·L-1, while adult mussels exposed to concentrations of 0.1, 0.25, 0.5, and 0.7 mg·L-1 for 7 days exhibited up to a 78.79% loss in byssal tensile strength. Further analyses suggested that Fe(VI) induced oxidative stress, microbiota dysbiosis, metabolic disruption, and downregulation of protein synthesis, collectively impairing mussel viability. Moreover, Fe(VI) directly oxidizes structural proteins in the byssus and enhances iron complexation with 3,4-dihydroxyphenylalanine (DOPA) residues at the plaque interface, leading to impaired adhesive capacity. The effectiveness, safety, and environmental compatibility of Fe(VI) were further validated in pilot-scale trials at an operational water treatment facility. This study underscores the promise of Fe(VI) as a sustainable and efficient green strategy for mitigating mussel biofouling in hydraulic systems─especially in water treatment facilities with stringent water quality requirements.

Mass mortality events (MMEs) are decimating populations and compromising key ecosystem functions around the globe. One taxon particularly vulnerable to MMEs is freshwater bivalve mollusks. This group has important ecosystem engineering capacities and includes highly threatened and highly invasive taxa. Thus, MMEs of freshwater bivalves have important implications for conservation and ecosystems. Despite this, little is known about the magnitude, frequency, duration, distribution, and causes of freshwater bivalve MMEs. Using a questionnaire, we compiled data from 239 reports describing freshwater bivalve MMEs across 22 European countries since 1960. With these data, we analyzed trends in MME timing, location, and magnitude; identified the species affected; and evaluated the suggested causes (including reporter certainty). We found that the frequency of reports of MMEs increased each year, MMEs affected a broad range of species, clear geographical patterns linking certain causes to specific locations were lacking, factors related to drying and habitat destruction predominated suggested causes, and considerable uncertainty surrounded the causes of many MMEs, particularly those associated with potential pollutants and disease agents. Based on our findings, we recommend the standardization of many aspects of MME research (e.g., reporting and recovery assessment protocols), increased surveying for MMEs, further investigation into the causes of MMEs, especially those with significant uncertainty, and immediate actions to improve waterbody management, mitigate the effects of high temperatures, and further protect freshwater bivalves through the development and implementation of appropriate management actions and legislation.

Freshwater mussel populations are declining worldwide, but the causes and mechanisms of these declines are poorly understood. Biomarkers that reflect the health or fitness of individual mussels are needed for understanding causes of mussel declines, but existing approaches each have weaknesses. We conducted two laboratory experiments to examine the utility of the cellular energy allocation (CEA) model for assessing juvenile mussel responses to stress induced by food limitation. The CEA assesses the energetic status of an organism as CEA = Ea/Ec, where Ea is available energy reserves (total carbohydrates, protein, and lipids) and Ec is energy consumption, estimated using electron transport system (ETS) activity as a proxy for respiration rate and metabolic demands. Experiment 1 evaluated the effects of food abundance (fed and unfed) on CEA and its component biomarkers at a single temperature (mean = 26.8°C) over 23 days. Experiment 2 evaluated the response of ETS activity to food abundance (unfed, low food, high food) in relation to temperature (20, 25, 30°C) over 27 days. In Experiment 1, most constituent biomarkers were lower in unfed mussels, but CEA did not differ between treatments because Ea and Ec declined by similar magnitudes. In Experiment 2, ETS declined with decreasing food abundance, but only at 25 and 30°C, and ETS was affected by temperature only in the unfed treatment. The ETS enzyme assay can be an informative biomarker of stress, but it requires accounting for confounding factors such as food, temperature, and species identity, as well as the lag time in response of ETS relative to respiration rate. Despite its value as a robust, holistic stress biomarker in other organisms, CEA may have limited usefulness for bivalves because of their tendency to reduce feeding and energy consumption under stress, which results in a simultaneous decline in Ea and Ec.

A recently extinct new genus and species of freshwater mussel, Gigaunio sichuanensis Z.-G. Chen, Y.-T. Dai, X. Liu &amp; X.-P. Wu gen. &amp; sp. nov., is described from the Minjiang River in Sichuan, China. The species was last recorded alive in 1964 and is now considered fully extinct, with even fresh empty shells no longer being found. The discovery increases the diversity of freshwater mussels in the upper Changjiang River and indicates the urgency of taking protective measures for freshwater mussels in the region.

Microplastics (MPs) are becoming ubiquitous, and their environmental fate is becoming an issue concern. MPs can adsorb antibiotics to coexist and accumulate in the aquatic environment in the form of complexes, resulting in unforeseeable adverse consequences. Herein, we investigated the genotoxic effects of coexist of polypropylene (PP) microplastic and two antibiotics of sulfamethoxazole (SMX) and oxytetracycline (OTC) at environmental concentrations on gill and gastrointestinal tract (GIT) cells of freshwater pearl mussel Hyriopsis cumingii. Results showed that coexist of PP and antibiotics SMX and OTC at environmental concentrations can cause the DNA damage (5.0 – 8.7% in gill and 4.5 7.9 % in GIT) and micronucleus (10.8 – 20.9 ‰ in gill and 11.9 – 18.6 ‰ in GIT) for H. cumingii. By principal component analysis, we found that there was a strong relationship between microplastic accumulation in the GIT and biomarkers, including DNA damage and micronucleus, for H. cumingii co-exposed to PP microplatics in combination with only OTC antibiotic. Meanwhile, only a strong correlation was detected between microplatic accumulation in gill or GIT and DNA damage in those tisues, when H. cumingii was exposed to mixing anibiotics OTC and SMX along with PP microplastic. Our study contributed to improve the understanding of the adverse genetic impacts of coexistance of PP microplastics and antibiotics (SMX and OTC) in the environment as well as to provided essential information for ecological risk assessment of MPs and antibiotics pollution.

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.

The genus Najadicola Piersig, 1897 (Acari: Hydrachnidia: Pionidae: Najadicolinae) was previously thought to include only two species: N. ingens (Koenike, 1895) and N. loeiensis Chapurina et al., 2019, distributed in eastern North America and Southeast Asia, respectively. Here, we describe and illustrate a third species within this genus, Najadicola tuzovskiji Kuznetsova, Kondakov &amp; Bolotov sp. nov., from Northeast Asia. It was found in the gills of the freshwater mussel Middendorffinaia mongolica (Unionidae: Unioninae: Middendorffinaiini). Our three-locus phylogeny (COI + 18S rRNA + 28S rRNA) and genetic divergence analyses support the placement of both Najadicola and Najadicolinae within the family Pionidae. The discovery of an additional species in Northeast Asia suggests that the genus’s range is more continuous than previously thought. This implies that the diversification of this lineage may be linked to post-Mesozoic faunal exchanges via the Beringian Land Bridge. Such a hypothesis aligns with published biogeographic scenarios for freshwater mussels (Margaritiferidae and Unionidae), which predict several Paleogene dispersal events from Asia to North America. However, the role of trans-Beringian faunal exchanges in the expansion of an Asian common ancestor to the Nearctic Region (or vice versa) cannot be assessed due to the lack of DNA sequences from the Nearctic species (N. ingens). As two Asian Najadicola species appear to be host specialists, we propose that the broad host range observed in N. ingens may reflect a composite character of this taxon, potentially comprising several cryptic species with narrower host associations involving fewer freshwater mussel hosts.

Integrated biomarker response-based investigation of oxidative stress in Hemolymph, gills, and digestive glands of freshwater mussels (Unio delicatus) exposed to Etoxazole.

Trait-based approaches can improve ecological understanding by linking fitness to the environment. The trilateral life history model is an expansion of r- and K-selection theory that reflects trade-offs between juvenile survival, fecundity, and generation time and describes differential survival of species across environmental gradients. We used this framework to generate and test hypotheses regarding community assembly and the validity of such a model in two disparate taxonomic groups, freshwater mussels and fish. We assessed the distribution of mussel and fish life history strategies across 80 sites spanning aspects of the river continuum concept within the Ouachita Highlands (USA) and asked if their distributions are predicted by a similar life history strategy framework. Because mussel and fish assemblages should both be structured by selective forces in an up- to downstream trajectory, we expected both taxa to converge on more species-rich assemblages with a greater proportion of equilibrium strategists in larger, more stable downstream habitats. We found that both mussel and fish species richness increased with watershed area as well as the proportion of equilibrium strategists in the assemblages. Our study validates the use of the trilateral life history model to test hypotheses about the distribution patterns of two coevolved taxonomic groups.

Integrated biomarker response for assessment of the toxicity of the synthetic pyrethroid Lambda-cyhalothrin on freshwater mussels (Unio terminalis bourguignat, 1852).

Parasitic freshwater mussels are endangered ecosystem engineers with an array of impacts on multiple trophic levels and life stages. While the impacts of adult mussels on separate trophic levels have been studied, few have directly tested how adult mussels can impact trophic interactions, or investigated the impacts of the parasitic mussel larvae (glochidia) on such interactions. We present a laboratory study which mimics two-stream substrates for the endangered thick-shelled river mussel (Unio crassus): one dominated by gravel and one by cobbles. First, the preference of a gammarid (Gammarus pulex) for mussel-dominated habitats was tested in the presence/absence of chemical cues from the predator bullhead (Cottus gobio). Second, the preference of bullhead for mussel-dominated habitats was tested under or without glochidia infestation. Third, the effect of infestation on bullhead predation on gammarids was assessed in the presence of adult mussels. Gammarids only significantly preferred mussel habitats in the absence of predator cues, whereas infested bullhead tended to prefer mussel habitats in cobble substrates. The presence of adult mussels only significantly reduced bullhead predation on gammarids in the gravel habitat, whereas infestation did not affect bullhead predation. Despite gammarids not preferring mussel habitat in the presence of predator cues, mussel beds represent valuable habitat to gammarids as mussel presence can facilitate a reduction of predation by bullhead. Infestation did not affect the rate of bullhead predation on gammarids but did attract bullhead to mussel habitat in cobble substrates. Our results suggest that mussel beds may be valuable habitat for both their host fish and the prey of their hosts, attracting both and increasing predator-prey interactions. This study highlights the cross-trophic mechanisms by which multiple life stages of parasitic mussels can impact the interactions of their surrounding benthic community, underscoring their importance as ecosystem engineers.

Pressodonta viridis (Bivalvia: Unionida) is a species of freshwater mussel considered rare and imperiled in 14 U.S. states and Ontario, Canada. Limited population-level genetic information is available for P. viridis despite the species' imperilment status. We used 13,661 single nucleotide polymorphisms (SNPs) derived from double digest restriction site-associated sequencing (ddRAD-seq) to examine patterns in population genetic diversity, structure, and differentiation among P. viridis populations in the Upper Mississippi River, Ohio and Wabash rivers, and Great Lakes watersheds. Structure analyses revealed significant differentiation related to major drainage among groups of P. viridis populations. Evidence of founder effects in Great Lakes populations by colonization routes from Upper Mississippi River and Ohio/Wabash River systems was found in admixture analyses. Limited evidence of isolation-by-distance effects was found, suggesting that multiple colonization routes and glacial refugia are responsible for current P. viridis genetic structure. A combination of ancient river hydrological patterns and more recent headwater stream capture events following the last glacial retreat likely correspond to considerable admixture found among populations of P. viridis in the Upper Mississippi, Wabash, and Ohio Rivers. Population genetic variation, structure, and differentiation described in this study should be used to inform conservation efforts of P. viridis in the future, particularly if recovery actions include population augmentation from translocations or hatchery propagation.

Mamba-based super-resolution and semi-supervised YOLOv10 for freshwater mussel detection using acoustic video camera: A case study at Lake Izunuma, Japan

Bioaccumulation and toxicity of imatinib, cyclophosphamide and its transformation product carboxyphosphamide in the freshwater mussel Elliptio complanata.

Dietary modulation of gut microbiota enhances shell biomineralization and carbon sequestration in the freshwater clam Unio douglasiae taiwanicus