Acute toxicity bioassay and tissue biochemical changes on sub-lethal exposure to the organo-phosphorus pesticide ‘Phorate 10G’ in the freshwater fish Labeo rohita (Hamilton, 1822)

Abstract

Toxicity of the organo-phosphorus pesticide, Phorate 10G was tested in vivo in the Indian major carp Labeo rohita. Based on the results of a range finding bioassay to assess the lethal dose range of ‘Phorate 10G’, various concentrations
viz., 0.05, 0.1, 0.15, 0.20 and 0.25 mg l-1 were selected for estimation of LC50. The LC50 value estimated by probit analysis was 0.137 mg l-1 for 96 h. Further, in order to assess the effect of sublethal toxicity, rohu fingerlings were exposed to sub-lethal concentrations of 0.05 and 0.075 mg l-1 of Phorate 10G for a total period of 30 days. At the end of exposure periods of 10, 20 and 30 days, 10 fingerlings each were sacrificed for carcass biochemical analysis of moisture, crude protein, crude fat and total ash contents. Moisture and total ash contents in rohu fingerlings exposed to the pesticide increased significantly, whereas crude protein and crude fat contents decreased with increase in concentrations as well as period of exposure (p< 0.05). Results of the study clearly indicated that ‘Phorate 10G’ affected the carcass proximate composition of rohu fingerlings which could be attributed to the energy requirement towards combating the toxic effects of pesticide exposure in the fingerlings of L. rohita