Responses of Antioxidants and Lipid Peroxidation in Villorita Cyprinoides to Mercury Exposure

Oxidative damage and antioxidant properties have been studied in Villorita cyprinoides subjected to short-term exposure to mercury (Hg) as pollution biomarkers. Villorita cyprinoides is a black water clam that belongs to a group of the genus Villorita; species cyprinoides (Fam:Corbiculidae) were found in the backwaters of Kerala, mainly in Vembanad backwaters. Clams are considered to be nutritious and delicious and are fished in considerable quantities in some coastal places, known to scavenge and deactivate free radicals All aerobic organisms generate free radicals such as reactive oxygen species (ROS) in the process of their oxidative metabolism. The assessment of oxidative stress using superoxide dismutase (SOD), catalase (CAT), glutathione peroxidise (GPX), glutathione reductase (GR) and glutathione-S-transferase (GST) and levels of malondialdehyde (MDA) performed on the hemolymph were estimated as biomarkers in clams exposed to mercury. The decreased MDA levels observed in hemolymph under exposure to Hg, showed that the organisms have effectively regulate the exposure stress. Increased activities of antioxidants such as superoxide dismutase catalase, glutathione peroxidise, glutathione reductase and glutathione-S-transferase in hemolymph under short term exposures to Hg suggesting activation of physiological mechanism to scavenge the ROS produced during stress. The results suggest that Hg stress does alter the active oxygen metabolism by modulating antioxidant enzyme activities, which can be used as biomarker to detect sublethal effects of pollution.