Impact of Cu and Hg on Biochemical Parameters of Bivalve, Villorita cyprinoides

Abstract

Heavy metal pollution is a growing environmental problem in marine coastal waters; for this reason the monitoring of water pollution needs the availability of test-species able to furnish reliable and cheap results. From this point of view, bivalves are important test organisms owing to their wide distribution and for their key-position within the food web. As Villorita cyprinoides is a promising target-species in ecotoxicology, in this study the toxicity of different concentrations of two heavy metals (copper and mercury) was evaluated, 4 mg/l and 9 mg/l of Cu were taken. Treatments were performed after 10 and 20 days of exposure on adult Villorita cyprinoides. The biochemistry of the animals was evaluated. There was marked decrease observed in the stored glycogen level in the hepatopancrease of the organism, 35.77 mg gm^-1 after 20 days with a concentration of 4 ppm and 30.57 at 9 ppm after 20 days exposure to Cu. There was a significant decrease in the level of protein content in the foot and hepatopancrease in presence of Cu. The protein content of the foot, after 20 days, in 4 ppm and 9 ppm was 15.62 and 10.25 mg/l respectively. The level of protein decreased to 13.37 and 14.12 mg gm^-1 respectively in the hepatopancrease after 20 days of exposure to 4 ppm and 9 ppm. The results showed that mercury (0.1 and 0.3 mg/l) was toxic for Villorita cyprinoides. Animals exposed to Hg alone as well as in combination with Cu and Hg exhibited high mortality rate. The synergistic effect of the metals was more lethal. The study shows that the prolonged exposure of the heavy metals resulted in anoxic condition. The stress condition resulted in the utilization of stored energy.