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Polychlorinated biphenyls (PCBs) are widely-spread aquatic pollutants that are toxic to aquatic organisms. The response of the antioxidant system in tissues and organs of bivalves to environmental stress is a commonly accepted biomarker in ecophysiological research. This study aims to evaluate bioaccumulation of polychlorinated biphenyls (PCBs) in tissues and organs of the ark shell Anadara kagoshimensis as well as effects of various concentrations of PCB mixture Sovol on the antioxidant enzyme activities. Upon in vivo experiments, ark shells were exposed to Sovol mixture in concentrations 0.00264 mg/L, 0.264 mg/L and 2.64 mg/L. PCB accumulation in hepatopancreas was by 4.8 times higher compared to gills and mantle. Tetrachlorobiphenyls and pentachlorobiphenyls accumulated in tissues preferentially compared to other PCB congeners. The bioaccumulation factor for PCB in tissues depended on its environmental concentrations. Exposure to PCBs affected the activity of catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GP). Despite gills accumulated less PCBs compared to other organs and tissues, treatment of ark shells with Sovol concentrations 0.00264 mg/L and 0.264 mg/L resulted in losses of SOD and CAT activities and enhanced GP activity. The opposite changes in the antioxidant enzyme activities were detected following the exposure to the highest Sovol concentration (2.64 mg/L). In the mantle the activity of SOD and CAT decreased, despite in hepatopancreas CAT and SOD activities were stable for the most experimental groups. The pattern of changes in GP indicates its critical role in the antioxidant defense following the exposure to PCBs.Highlights: Experimental exposure of ark shell Anadara kagoshimensis to commercial mixture of polychlorinated biphenils (PCBs) Sovol resulted in PCB accumulation in tissues and organs. Treatment with various PCBs concentrations affected activity of the antioxidant enzymes in gills, mantle and hepatopancreas. Hepatopancreas showed higher stability of the antioxidant complex to PCBs compared to other organs. Glutathione peroxidase likely plays major role in neutralizing ROS following the exposure of ark shells to PCBs. [ABSTRACT FROM AUTHOR]

Mussels were exposed to di-(2-ethylhexyl) phthalate (DEHP) (0.4 mg L−1 and 4.0 mg L−1) for 24 h and 48 h and its effect on hemocyte cellular composition and spontaneous reactive oxygen production (ROS) levels in hemocytes were evaluated. Exposure to DEHP induced a loss in spontaneous ROS production levels in hemocytes and decreased agranulocyte number in hemolymph. DEHP was found to accumulate in hepatopancreas of mussels and this process was associated with an increase of catalase (CAT) activity after 24 h incubation. At the end of the experimental period (48 h) CAT activity recovered up to control levels. Superoxide dismutase (SOD) activity in hepatopancreas increased following 48 h exposure to DEHP. The results indicated that DEHP could affect hemocyte immune properties, and also cause non-specific general stress-response of the antioxidant complex, which, in turn, was not associated with pronounced oxidative stress. • Exposure to DEHP influences hemolymph cellular composition in mussels. • Hemocytes of mussels exposed to DEHP possessed decreased spontaneous ROS production levels. • Exposure to 4.0 mg L−1 DEHP was associated with its accumulation in hepatopancreas. • DEHP induced changes in the activity of catalase and superoxide dismutase in hepatopancreas. [ABSTRACT FROM AUTHOR]