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Unionid mussels are globally threatened by several human disturbances, including the introduction of non-native species. Among these, biofouling zebra and quagga mussels of Ponto-Caspian origin are considered to be especially detrimental to unionid locomotion, filtration and physical condition. The aim of our study was to determine and compare the impact of dreissenid fouling and/or presence on locomotion and burrowing of the native Unio tumidus and invasive Sinanodonta woodiana, a novel invader expanding its range in Europe in recent decades. We tested unionids collected from Lake Balaton (central Europe) that were fouled by dreissenids (zebra and quagga mussels mixed), cleaned of fouling or non-fouled (collected without any signs of dreissenid fouling). Moreover, unionids were tested in the presence or absence of other fouled individuals and dreissenids isolated in mesh bags to determine the influence of direct fouling and presence of dreissenids in the environment on unionid behaviour. Movement initiation time, locomotion distance and burrowing level were retrieved from videos recorded for 24 hours. Direct fouling affected only the behaviour of U. tumidus, limiting their burrowing and delaying movements. After removal of fouling, movement timing returned back to normal, but mussels still burrowed less than the control non-fouled individuals, indicating persisting effects of fouling on physical condition. Moreover, U. tumidus reduced their locomotion in the presence of fouled unionids. Sinanodonta woodiana responded to the presence of dreissenids (especially quagga mussels) with increased burrowing. These different responses of the two unionid species to Dreissena spp. indicate that biofoulers may influence biotic interactions between the unionids by promoting the invasive species (less susceptible to negative effects of fouling). Moreover, S. woodiana may indirectly affect U. tumidus through apparent competition, constituting an environmental reservoir of biofoulers exerting a stronger impact on the native species. [ABSTRACT FROM AUTHOR]

The behavioral (filtration activity) and biochemical (oxidative stress) effects of Roundup 360 Plus (active substance glyphosate) herbicide on two species of unionid mussels, Unio tumidus (Philipsson, 1788) and Anodonta anatina (L.), were evaluated at concentrations ranging from 15 to 1500 μg L−1 of glyphosate for five days. During all experiments, we did not record the mortality of the studied mussel species. Exposure to Roundup herbicide induced dose-dependent filtration disruptions in both U. tumidus and A. anatina. Exposure of the mussels to a low and environmentally relevant concentration 15 µg glyphosate L−1 resulted in a slight (<20%) and temporary decrease in mean valve dilation. Exposure of the mussels to Roundup at relatively high concentrations caused drastic and prolonged shell closure and a reduction in the mussel shell opening rate. Exposure of both mussel species to herbicide resulted in oxidative stress; an increase in superoxide dismutase enzymatic activity was detected. The most significant increase in SOD activity was observed after the exposure to the highest Roundup concentration. However, no correlation between the Roundup concentration and enzymatic activity was found. The use of unionid mussels to detect environmentally relevant concentrations of Roundup, as a part of biological early warning system for pollution, is limited, but they can serve to detect the incidental pollution of aquatic ecosystems with high concentrations of this herbicide. [ABSTRACT FROM AUTHOR]

The shells of freshwater mussels, commonly found at archaeological sites associated with the Kodjadermen-Gumelnița-Karanovo VI human groups (5th millennium BCE, Romania and Bulgaria), were a significant dietary component for this population. The organic matrix of these ancient shells is often well-preserved and can be analysed using stable isotopes.This study establishes the empirical relationship between the isotopic composition of the acid-insoluble shell organic matrix (AIM) and the soft tissues of modern Unio tumidus. A quality criterion for AIM (C:N ratio 3.6 (3.3–

Background. An increased production and widespread use of plastics have made microplastic (MP) pollution a serious environmental problem. Most of MP found in the marine environment comes from rivers, however, the freshwater pollution by MP is less studied. Filter-feeding organisms, like bivalve molluscs, are the primary target orga­nisms for MP. Nevertheless, the studies of MP accumulation in the bivalves mainly focus on the marine species and depend on expensive equipment. The goal of this study was to detect the presence of MP in the body of freshwater bivalve mollusc Unio tumidus from a typical field site in Western Ukraine and under laboratory sub-chronic exposure to microplastic at a typical concentration for freshwater. Materials and Methods. For the study, we exposed molluscs to waterborne MP (0.1–0.5 mm) in the concentration of 1.0 mg L-1 corresponding to ~850 items L-1 for 14 days and analysed the concentration of MP in the soft tissues and water every two days. The molluscs and water from the field site, confirmed as polluted one, were also analysed. To estimate the number of MP particles, we used a modified method based on the cleavage of biological materials with potassium hydroxide and hydrogen peroxide and microscopic analysis of MP after the staining with fluorescent Nile Red dye. Results. The MP concentration in the soft tissues of the specimens from the refe­rence site was 9.5 items per soft body and demonstrated a bell-shaped response curve throughout the 14-days exposure with maximum of 327.0 items per body on the 10th day and a negative correlation with the concentration of MP in the experimental tank that changed within the range of 590–790 items L-1. The level of MP in the field specimens from the polluted area was 76.5 items per body, and in the water, it was about 103 items L-1. The maximum MP abundance factor, calculated as CFi = Ci/C0 (utilising the value 9.5 as C0), was 83.18 and 8.05 for 10 days of exposure and field specimens, correspondingly. Conclusion. These data indicate the high accumulative ability of U. tumidus towards microplastics and draw attention to the utilizing of this species for the biomonitoring of microplastics pollution and depuration of surface waters from it.

• Exposure of fish hosts to 0.2 µg/L sertraline marginally enhanced parasite attachment success. • Exposure of parasitic glochidia to 4 µg/L sertraline influenced their spatial distribution on the host body. • The transfer of sertraline from glochidia to host fish was detected, revealing an unexpected pollutant dynamic. This study examined the impact of sertraline, an antidepressant common in treated wastewater, on the host-parasite dynamics between parasitic freshwater mussel (Unio tumidus , Unionidae) larvae (glochidia) and their host fish (Squalius cephalus , Cyprinidae). Employing a full-factorial design, both fish and glochidia were subjected to sertraline at the combinations of 0 µg L −1 (control), 0.2 µg L −1 (environmentally relevant concentration), and 4 µg L −1 (elevated concentration, short-term exposure of the parasite). The results showed that long-term host exposure (involving intensive sertraline accumulation in the fish brain) marginally increased subsequent glochidia attachment success by 2 %, while parasite exposure at the same environmentally relevant concentrations had no detectable effect. There was also no effect of exposure of glochidia to 0.2 µg L −1 of sertraline on their viability and encapsulation success during the initial parasitic stage. However, a significant alteration in attachment behavior, marked by a 3.3 % increase in attachment success and changes in the glochidia spatial distribution on the host body, was noted after 24 h of glochidia exposure to 4 µg L −1 of sertraline. Importantly, this study provides the first evidence of sertraline transfer from exposed glochidia to nonexposed host fish, as indicated by elevated levels of sertraline (12.8 ng g −1) in the brain tissue of nonexposed hosts. These findings highlight the subtle yet significant effects of pharmaceutical pollutants on freshwater ecosystems but also underscore the importance of understanding the unexpected dynamics of such contamination to predict and address future ecological changes. [ABSTRACT FROM AUTHOR]

Previous mesocosm experiments with the epizoon of Dreissena polymorpha revealed that the communities of Rotifera and Crustacea were much more abundant and had higher species richness than epizoon of Unio tumidus in nature. These differences could be attributed to different environmental conditions and/or different host behavior. To test this hypothesis, we compared epizoon of D.polymorpha and U.tumidus placed in identical mesocosm conditions, in which Unio could not move vertically due to the lack of sediments. Half of the mesocosms contained D. polymorpha, the other half comprised U. tumidus. Each species of mollusks was kept in the mesocosms with eutrophic and mesotrophic conditions. Finally, we established four treatments that were replicated in triplicate mesocosms. Mesocosm experiments showed that epizoon communities of U. tumidus were even more abundant than that of D. polymorpha and their species richness was similar. Therefore, we concluded that previously revealed strong differences between epizoon communities of D. polymorpha and U. tumidus were related to the different environmental conditions and bivalve behavior. [ABSTRACT FROM AUTHOR]

The presence of parasitic ciliates of the hymenostome genus Tetrahymena was examined in 150 mollusks belonging to six bivalve and 13 gastropod species in Slovakia, Central Europe. Tetrahymenids were detected only in two species, viz., in the invasive Lusitanian slug (Arion vulgaris) and in the native swollen river mussel (Unio tumidus). Although only 10.52% of the examined mollusk taxa were positive, their Tetrahymena infections were very intensive accounting for several hundreds of ciliates per host. Phylogenetic analyses of the 16S and 18S rRNA genes as well as of the barcoding region of the gene encoding for cytochrome c oxidase subunit I revealed that both isolates represent new taxa, T. foissneri sp. n. and T. unionis sp. n. The former species belongs to the 'borealis' clade and its nearest relative is T. limacis, a well-known parasite of slugs and snails. Besides molecular data, T. foissneri can be distinguished from T. limacis also morphologically by the body shape of the parasitic-phase form, dimensions of micronuclei, and the silverline system. On the other hand, T. unionis was classified within the 'paravorax' clade along with T. pennsylvaniensis, T. glochidiophila, and T. nigricans. Although these four species are genetically distinct, T. unionis could be morphologically separated only from T. nigricans by body shape and size. The present study suggests that both aquatic and terrestrial mollusks represent interesting hosts for the discovery of novel Tetrahymena lineages. [ABSTRACT FROM AUTHOR]

Previous mesocosm experiments with the epizoon of Dreissena polymorpha revealed that the communities of Rotifera and Crustacea were much more abundant and had higher species richness than epizoon of Unio tumidus in nature. These differences could be attributed to different environmental conditions and/or different host behavior. To test this hypothesis, we compared epizoon of D.polymorpha and U.tumidus placed in identical mesocosm conditions, in which Unio could not move vertically due to the lack of sediments. Half of the mesocosms contained D. polymorpha, the other half comprised U. tumidus. Each species of mollusks was kept in the mesocosms with eutrophic and mesotrophic conditions. Finally, we established four treatments that were replicated in triplicate mesocosms. Mesocosm experiments showed that epizoon communities of U. tumidus were even more abundant than that of D. polymorpha and their species richness was similar. Therefore, we concluded that previously revealed strong differences between epizoon communities of D. polymorpha and U. tumidus were related to the different environmental conditions and bivalve behavior.

Multiple interactions between different pollutants in the surface waters can cause unpredictable consequences. The aim of the study was to evaluate the combined effect of two widespread xenobiotics, titanium oxide nanoparticles (TiO2) and bisphenol A (BPA), on freshwater bivalve Unio tumidus. The specimens were exposed for 14 days to TiCl4 (Ti, 1.25 µM), TiO2 (1.25 μM), BPA (0.88 nM), or their combination (TiO2 + BPA). Every type of exposure resulted in a particular oxidative stress response: TiO2 had antioxidant effect, decreasing the generation of reactive oxygen species (ROS) and phenoloxidase (PhO) activity, and doubling reduced glutathione (GSH) concentration in the digestive gland; Ti caused oxidative changes by increasing levels of ROS, PhO and superoxide dismutase; BPA decreased the GSH level by a factor of two. In the co-exposure treatment, these indices as well as lysosomal membrane stability were not affected. All Ti-containing exposures caused elevated levels of metalated metallothionein (Zn,Cu-MT), its ratio to total metallothionein protein, and lactate/pyruvate ratio. Both BPA-containing exposures decreased caspase-3 activity. All exposures, and particularly co-exposure, up-regulated CYP450-dependent oxidation, lipid peroxidation and lipofuscin accumulation, lysosomal cathepsin D and its efflux, as well as alkali-labile phosphates in gonads and caused DNA instability (except for TiO2). To summarize, co-exposure to TiO2 + BPA produced an overlap of certain individual responses but strengthened the damage. Development of water purification technologies using TiO2 requires further studies of the biological effects of its mixtures. U. tumidus can serve as a sentinel organism in such studies. [ABSTRACT FROM AUTHOR]

Monitoring of changes in behavioral response of bivalve mollusks can provide a wealth of information on quality of water that could be used in a surveillance system. The aim of this research was to evaluate suitability of Unio tumidus bivalve mollusks as bioindicators of water quality in a surveillance system. The experiment involved a 72-hour observation of the mollusks behavior in tap water containing about 0.04 mgFe/dm³ (almost no iron ions), 0.2 mgFe/dm³ (limit value for drinking water) and 1.7 mgFe/dm³ (average iron ion content for the deep sea). Three behavioral variables considered were: time of activity (time period of water filtering activity), average shell opening degree and its frequency. It was determined that presence of iron ions exceeding the threshold value reduced daily activity time by 5 hours, while the shell opening degree - by over 20%. Variations in frequency of the shell movements were not observed, which might indicate no iron ion impact on the nervous system of the individuals tested. Similarly, lethal states were not demonstrated, even at the relatively high iron concentrations in water. Results of the research conducted demonstrate that the bivalves Unio tumidus may be employed in tap water surveillance system for detection of water contamination with iron compounds. [ABSTRACT FROM AUTHOR]

During the summer of 2015, 13 specimens of barbel (Barbus barbus (Linnaeus, 1758)) were examined by standard techniques for parasites. All the examined barbels (100%) were infected with the acantocephalan Pomphorhynchus tereticollis.The study of the intestinal content and fishfood fixed the presence mainly of Unionidae molluscs.The swollen river mussel (Unio tumidus Philipsson, 1788; Mollusca, Unionidae) is one of the most common Unionidae in the studied habitat (Biotope Vetren, the DanubeRiver). The aim of the research wass to study the lead content in samples of sediments, Unio tumidus, Pomphorhynchus tereticollis, skin, muscles and liver of B. barbus from the Danube River. From the tissues and organs of the studied fish specimens Barbus barbus, the lowest concentrations of lead were found in the muscles. The content of lead in the samples of liver is higher than in the skin and muscles. The alteration was in the following order: Pbliver>Pbskin>Pbmuscles. P. tereticolliss howed significantly higher content of lead than its host tissues and organs. The content of lead in Unio tumidus was higher than the content of lead in the tissues and organs of B. barbus. A highly significant correlation (p<0.01) was fixed for the relationships between the Pb content in the acanthocephalan and mollusks (CP. tereticollisPb-C U.tumidusPb) and between that in the acanthocephalan and the skin of the fish (CP. tereticollisPb-CskinPb). [ABSTRACT FROM AUTHOR]

We investigated activities of glutathione peroxidase (GSH-Px), glutathione reductase (GR), and the phase II biotransformation enzyme glutathione-S-transferase (GST) in the foot of three freshwater mussel species: Unio pictorum (Up), Unio tumidus (Ut), and Sinanodonta woodiana (Sw) from the Sava River. Specific and total GSH-Px activity was lower in Sw than in Up and Ut. Total GR activity was higher in Up than in Sw. Specific GST activity was higher in Up than in Ut. Total GST activity was higher in Up than in Ut and Sw. Electrophoretic analysis of proteins shows species specifities between the investigated mussel species. Our study represents the first comprehensive report of the investigated glutathione-dependent enzyme activities in the foot of three freshwater mussel species from the Sava River, Serbia. .

Extreme hydrological events, such as water scarcity and flooding, can modify the effect of other stressors present in aquatic environment, which could result in the significant changes in the ecosystem functioning. Presence and interaction of various stressors (genotoxic pollutants) in the environment can influence the integrity of DNA molecules in aquatic organisms which can be negatively reflected on the individual, population and community levels. Therefore, in this study we have investigated the impact of flooding, in terms of genotoxicity, on organisms belonging to different trophic levels. The study was carried out on the site situated in the lower stretch of the Sava River which faced devastating effects of severe flooding in May 2014. The flooding occurred during our field experiment and this event provided a unique opportunity to assess its influence to the environment. The in situ effects of this specific situation were monitored by measuring physical, chemical and microbiological parameters of water, and by comparing the level of DNA damage in coelomocytes and haemocytes of freshwater worms Branchiura sowerbyi , haemocytes of freshwater mussels Unio tumidus and blood cells of freshwater fish Abramis bjoerkna / Abramis sapa , by means of the comet assay. Our study indicated that the flooding had a significant impact on water quality by decreasing the amount and discharge rate of urban wastewaters but simultaneously introducing contaminants from the nearby fly ash disposal field into river by runoff, which had diverse effects on the level of DNA damage in the studied organisms. This indicates that the assessment of genotoxic pollution in situ is strongly affected by the choice of the bioindicator organism. [ABSTRACT FROM AUTHOR]

In this study we assessed the level of genotoxic pollution along the Danube River by measuring the level of DNA damage in the haemocytes of freshwater mussels of Unio sp. ( Unio pictorum/Unio tumidus ) and Sinanodonta woodiana . The comet assay was used for the assessment of DNA damage. The research was performed on 34 out of 68 sites analysed within the Joint Danube Survey 3 — the world's biggest river research expedition of its kind in 2013. During research, 2285 river kilometres were covered with an average distance of 68 km between the sites. The complex data set on concentrations of various substances present in water, suspended particulate matter and sediment on investigated sites gave the opportunity to identify the groups of xenobiotics which mostly affect the studied biomarker — DNA damage. The highest levels of DNA damage were recorded in the section VI (Panonnian Plain), which is under the impact of untreated wastewater discharges. Both positive and negative influences of the large tributaries on the level of genotoxicity in the Danube River were evident. Significant correlation in response was detected between the studied species of freshwater mussels. The level of DNA damage in mussels correlated with concentrations of compounds from the group of hazardous priority substances (polycyclic aromatic hydrocarbons), persistent organic pollutants (dioxins) and emerging pollutants (Oxazepam, Chloridazon-desphenyl). [ABSTRACT FROM AUTHOR]

During a monitoring survey, a massive mussel bed was found and studied in the Gnily Rig River, Ukraine. The mussel bed was 25 cm thick and multilayered, with one of the greatest densities and biomass (wet weight) recorded so far in natural aggregations: up to 1,801.0 ± 175.4 ind./m² and up to 88.3 ± 20.7 kg/m², respectively. The site was surveyed periodically since 2009, and despite the temporal differences in the density (but not in biomass) the mussel bed was stable and should be considered for protection due to its high ecological and conservational value. [ABSTRACT FROM AUTHOR]

Earlier studies (1972-1987) on the occurrence of unionid bivalves in the eutrophicated Lake Mikołajskie (Masurian Lakeland, NE. Poland) were continued in 1992-2008. Of the five recorded species (Unio tumidus, U. pictorum, Anodonta cygnea, A. anatina, and Pseudanodonta complanata), A. cygnea and P. complanata disappeared by 1987, whereas U. pictorum was observed sporadically at that time, and the unionid occurrence zone was markedly reduced. Beginning in 1992, a pronounced increase in abundance of U. tumidus was observed, and since 2002-2003, a decline of the other two species. Since 2003 the maximal original vertical distribution of U. tumidus (down to ca. 5 m) was re-established. The size and age structure of its population changed markedly during the study. No individuals of shell length exceeding 55 mm and aged more than 5-6 years were recorded since 1987. Between 1972 and 1987 one-year-old individuals prevailed, whereas in the following years the age structure changed slowly, and in 2008 two- to four-yearold bivalves were most frequent. The potential effects of changes in trophy and the effects of other factors, e.g. decline of Dreissena polymorpha, on changes in the occurrence of Unionidae in Lake Mikołajskie are discussed. [ABSTRACT FROM AUTHOR]

Genotoxic response of freshwater mussels U. tumidus and U. pictorum to environmental stress was studied using comet assay on hemocytes and gill cells. The mussels were acclimated to controlled laboratory conditions for 10 days, and then exposed at 4 sites in the Sava and Danube rivers in the area of the city of Belgrade. Samples of each species were taken after 7, 14, and 30 days of exposure. The mussels sampled immediately after acclimation served as controls. Genotoxic response in both species was induced earlier at sites receiving untreated wastewaters from the city's main collectors (7 days), than at the site receiving only domestic wastewaters from small settlements located upstream from the city (30 days). There was a correlation between the comet tail intensity values in tissues of exposed mussels and the concentrations of zinc, copper, iron, and arsenic at the exposure sites. The genotoxic responses in both tissues of U. pictorum and in hemocytes of U. tumidus were similar, while U. tumidus gill cells failed to exhibit significant genotoxic response at two sites. These findings, together with higher mortality of U. tumidus at the most polluted sites, promote U. pictorum as a model for genotoxicity monitoring in freshwater environments. [ABSTRACT FROM AUTHOR]

The impact of in vivo and in vitro exposure to anticancer drug 5-Fluorouracil (5-FU) on the level of DNA damage was evaluated using comet assay on haemocytes of freshwater mussels Unio pictorum and Unio tumidus. For the in vivo experiment, the groups of 5 mussels per concentration were exposed for 72 h to 5-FU (0.04, 0.4, 4, 40 and 100 μM) with 0.4 μM being the lowest concentration to induce significant DNA damage. For the in vitro experiment, the primary cultures of haemocytes were treated with 0.04, 0.4, 4 and 40 μM 5-FU for 22 h and the treatment with CdCl2 was used as a positive control. In contrast to in vivo exposure, 5-FU did not induce significant increase of DNA damage in vitro, possibly because of the absence of haemocytes proliferation in primary cultures. [Copyright &y& Elsevier]

Freshwater mussels such as the invasive Dreissena polymorpha and the indigenous Unio tumidus nourish by high filtration rates and may accumulate cyanobacteria and their toxins during cyanobacterial blooms. Physiological adaptations to cyanotoxins enable organisms to endure cyanobacterial blooms but may differ between species. Biotransformation and excretion capacities for cyanobacteria and anthropogenic pollutants have been demonstrated for Dreissena polymorpha but less for unionid species. This study compares the activities of biotransformation (glutathione S-transferase, GST) and antioxidant enzymes (superoxide dismutase, SOD and catalase, CAT) in Dreissena polymorpha to Unio tumidus in response to cyanotoxin exposure (10μgL−1 and 50μgL−1 microcystin-LR, respectively, total microcystin from a cyanobacterial crude extract) for 24h and 7d exposure duration. Enzyme activities in Dreissena polymorpha were measured in the whole mussel tissue, digestive gland and in gills and in Unio tumidus in the digestive gland, gills, mantle, foot as well as in the remaining tissue. The sGST was elevated for the entire exposure period in the whole mussel tissue of Dreissena polymorpha but despite higher basal activities in digestive gland and gills of Unio tumidus, it was rather inhibited or unaltered in most of their tissues. Elevated SOD activity indicated oxidative stress response in Dreissena polymorpha, but not in Unio tumidus. The CAT activity was barely affected in both species, rather inhibited in Unio tumidus, despite again higher basal activities in digestive gland and remaining tissue. Compared to the indigenous Unio tumidus, the investigated biotransformation and oxidative stress combating enzymes respond stronger in the invasive Dreissena polymorpha. [Copyright &y& Elsevier]

The cDNA sequences encoding manganese superoxide dismutase (Mn-SOD) and catalase (CAT) were isolated in the freshwater bivalve Unio tumidus by reversetranscription polymerase chain reaction (RT-PCR) using degenerate primers. Quantitative real-time PCR approach was used to evaluate the mRNA expression patterns of SOD, CAT, selenium-dependent glutathione peroxidase (Se-GPx), pi class glutathione S-transferase (pi-GST) and metallothionein (MT), in the digestive gland of Unio tumidus transplanted from a control site to four stations in the Moselle River (M1-M4), for periods of 8 and 21 days. These sites were chosen upstream and downstream of populated areas. Chemical analysis performed on sediments from the Moselle river sites did not show high levels of pollutants. Decrease of SOD, CAT, Se-GPx and MT mRNA levels were observed at M3 site after a 21-day exposure compared to control site. These results suggest inefficiency of antioxidant systems affected by cytotoxic mechanisms and confirm an environmental perturbation. Organisms transplanted at M4 site showed a strong increase of biomarkers transcription levels after 21 days of exposure. These inductions could correspond to an adaptive response to an altered environment. Our results showed that biological approaches using multibiomarkers appear as essential tools complementary to measurement of contaminants, to detect environmental degradations. [ABSTRACT FROM AUTHOR]

Abstract: Glutathione peroxidases (GPx) and glutathione S-transferases (GST) are essential enzymes of the cellular defense system. The aim of this work was the identification of GPx transcript in a freshwater bivalve, Unio tumidus, and the effects of Aroclor 1254 on GPx and pi-class GST (pi-GST) expression pattern. The GPx full-length coding sequence was obtained by reverse transcription PCR using degenerated primers followed by 5′ and 3′ rapid amplification of cDNA ends. The GPx cDNA encodes a protein of 232 amino acids. The 72nd amino acid corresponds to a selenocysteine encoded by a TGA codon. Residues essential to the enzymatic function are conserved in GPx of U. tumidus. Specific amplifications of the Se-GPx mRNA from U. tumidus were performed on the digestive gland, the excretory system and the gills. Se-GPx expression level is highest in the digestive gland. No induction of the Se-GPx was observed at the transcriptional level in the digestive gland and the excretory system of Aroclor-treated mussels, while an increase of the pi-GST mRNA level was observed in the excretory system. [Copyright &y& Elsevier]

Artificial streams are dynamic mesocosms, simulating aquatic systems and rivers. They are useful to study ecotoxicity of chemicals and their effects on flora and fauna colonizing the streams or introduced into the channels. These artificial rivers can also be used to study the influence of ecological and hydrodynamic parameters, such as the kind of substrate of river and flow rate. Responses of the bivalve Unio tumidus to substrate type (silt, sand, and pebbles) and water flow rate (high and low) were investigated after 15 and 35 days in the channels, in order to optimize the experimental conditions for ecotoxicity study with methyl methacrylate (MMA). The toxicological effects of different concentrations of MMA on bivalves and on communities of invertebrates and diatoms were determined after several weeks of exposure at a high flow rate. Biomarkers responses measured in the digestive gland and the gills of U. tumidus were the activities of detoxification systems as early indicators of toxicity and lipid peroxidation as a marker of cytotoxicity. Effects of MMA resulted in a decrease in antioxidant activities. Disturbances in bivalves appeared at lower concentrations than in communities. This indicates sensitivity of the bio-markers studied, which are predictive indicators of ecotoxicity. [ABSTRACT FROM AUTHOR]

Abstract: In this study, the effect of toxaphene (camphechlor) on ATPase activity in the microsomal fraction of the Unio tumidus’s digestive gland was determined. Toxaphene is a man-made mixture consisting of polychlorinated monoterpens, predominantly bornanes. This compound was primarily used as an insecticide, but in 1982 was officially banned because of its destructive effects on human and animal health. Toxaphene can be transported in the air at long distances and can persist in air, soil and water for years revealing acute and chronic toxicity towards aquatic organisms and wildlife, the increasing risk of cancer in both humans and animals. The microsomal fraction isolated from digestive glands was exposed to 1×10−3 M, 1×10−5 M and 1×10−7 M of toxaphene. The obtained data showed that toxaphene induced a loss of ATPase activity in all used concentrations. The Lineweaver–Burk plots for microsomal Na+K+-ATPase in the presence or the absence of toxaphene as an inhibitor indicated a competitive type of inhibition. [Copyright &y& Elsevier]

Abstract: Glutathione S-transferases (GSTs) are enzymes involved in major detoxification reactions of xenobiotics in many organisms. The aim of this work was the identification of GST transcripts in the freshwater bivalves Unio tumidus and Corbicula fluminea. We used degenerated primers designed in the highly conserved regions of GST to amplify the corresponding mRNA. Full-length coding sequences were obtained by 5′ and 3′ rapid amplification of cDNA ends. In the two species, the GST cDNAs identified encoded a protein of 205 amino acids. The comparison of the deduced amino acid sequences with GSTs from other species showed that the enzymes belong to the pi-class and the amino acids defining the binding sites of glutathione (G-site) and for xenobiotic substrates (H-site) are highly conserved. Specific amplifications of the GST mRNA from U. tumidus and C. fluminea were performed on the digestive gland, the excretory system and the gills. For each mussel, the results revealed that the pi-class GSTs are expressed at the same level in the three tissues. [Copyright &y& Elsevier]

The relationships between DNA damage and oxidative stress in the digestive gland, gills and haemocytes of the freshwater bivalve Unio tumidus were investigated. Two markers of genotoxicity were measured: DNA breaks by means of the comet assay, and oxidative DNA lesions by means of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) measured using high-performance liquid chromatography (HPLC) coupled to electrochemical detection. Lipid peroxidation was evaluated by measuring malondialdehyde (MDA) tissue levels. Effects were studied after exposure of bivalves for 6 days to benzo[a]pyrene (B[a]P) (50 and 100 µg l -1 ) and ferric iron (20 and 40 mg l -1 ), applied alone or in combination. Lipid peroxidation in the digestive gland and gills resulted from exposure to Fe 3+ or B[a]P whatever the concentrations tested. DNA oxidatively formed lesions were induced in the two tissues at a higher level after B[a]P exposure than after Fe 3+ treatment. No significant dose–response relationship was found with the two compounds and no synergistic effect was observed between Fe 3+ and B[a]P. The gills appeared less sensitive than the digestive gland to DNA lesions expressed as 8-oxodGuo and comet results. Good correlations were noted between 8-oxodGuo and comet. MDA and DNA damage did not correlate as well, although it was stronger in the digestive gland than in the gills. Production of mucus by the gills likely served to prevent lesions by reducing the bioavailability of the chemicals tested, which could explain that dose–effect relationships and synergistic effects were not observed. [ABSTRACT FROM AUTHOR]

The shells of mussels, live-collected bivalves or during archaeological excavations, can be used as bioindicators of current and historical levels of heavy metal contamination. In this study, we examined the shells of Unio tumidus, commonly found in the Baltic Sea region, and determined the concentrations of Zn, Cu, Fe, Pb, Ni, and Cd in samples from the 10th, 11th, and 21st century from the area of the Szczecin Lagoon. The average levels of heavy metals (in μg g−1 dry weight) in the shells from the Middle Ages were: 137.5 (Fe), 3.87 (Zn), 0.789 (Cu), 0.012 (Pb), 0.047 (Ni), and 0.0009 (Cd). Shells from the 21st century were significantly (P <0.05) more abundant in Fe, Cu, Ni, Pb, and Cd (rates of increase: 1.96×, 3.54×, 2.71×, 2.08×, and 3.55×, respectively) than shells from the Middle Ages. These results reflect contemporary anthropogenic pollution of the environment with heavy metals and confirm the possibility of using U. tumidus shells in the assessment of heavy metal pollution levels. • Unio tumidus shells as bioindicators. • Current and historical heavy metal levels in the shells. • Higher concentrations of heavy metals were in shells from the 21st century. [ABSTRACT FROM AUTHOR]