ACUTE TOXICITY, OXIDATIVE STRESS AND DAMAGES TO GILLS OF CARDIOSOMA ARMATUM (RAINBOW CRAB) INDUCED BY EXPOSURE TO PESTICIDES (DICHLORVOS AND CYPERMETHRIN)

Abstract

The relative acute toxicity of Dichlorvos and Cypermethrin acting singly against Rainbow crab, Cardiosoma armatum was evaluated. The effects of sub lethal concentrations of the pesticides on the oxidative responses and histopathological effects in the gills of the crab were also investigated over a 30 days period. On the basis of 96 hrs LC50 value, Dichlorvos with 96 hr LC50 of 8.86 ?g/L was 2 times more toxic to the crabs than Cypermethrin with 96 hr LC50 of 17.80 ?g/L. The exposures to sub lethal concentrations (1/10th and 1/100th 96 hr LC50) of both pesticides each resulted in increase in the levels of lipid peroxidation product, malondialdehyde (MDA) in the gills compared to the control group at both day 15 and 30 of the bioassay . Super oxide dismutase (SOD) activity was inhibited by day 30 relative to control for both pesticides but the activities of Catalase (CAT) did not show a significant trend (P > 0.05). Exposure to sub lethal concentration (1/10th and 1/100th LC50) of both pesticides resulted in various histopathological effects such as curved filaments, fused filaments, epithelial lifting, congestion and odema. The damages to the gills were more severe in those exposed to Dichlorvous. The findings from this study indicates that both pesticides are potential threats to non- target rainbow crab populations and there is a risk of bioaccumulation and transport in the food chain under sub lethal exposures