Effect of malathion on survival, growth, and food consumption of Indian cricket frog (Limnonectus limnocharis) tadpoles

The effects of short-term exposure (28 days) of freefeeding Limnonectus limnocharis (Indian cricket frog) tadpoles to field concentrations of malathion were investigated. This frog species is a major biotic component of the agroecosystems of the Western Ghats (13 degrees 18', 75 degrees 25' and 13 degrees 22', 75 degrees 28'), where malathion (diethyl [(dimethoxy phosphino thioyl] butanediote), an organophosphate pesticide, is being used extensively. Although malathion is known to cause nonreversible acetylcholine inhibition and diminishes activity, growth and development in amphibian tadpoles, such data on Indian amphibian species are lacking. In the present study, increments in the following were used to assess such an impact: tadpole growth; increase in total length, body length, tail length, and body weight; and food consumption. The different concentrations of malathion employed were 500, 1000, 1500, 2000, and 3000 mu g L-1. Malathion exposure produced significant effects on all measured parameters. Tadpole survival decreased from 20 to 6 tadpoles, with an increase in concentration followed by a decrease in growth. Food consumption of surviving tadpoles also decreased (0.067 mg.g(-1).d(-1) to 0.0075 mg.g(-1).d(-1)) with increased malathion. Decreased food consumption, growth, and development of L. limnocharis tadpoles with an increase of malathion concentration (within field concentration range) over temporal scale reveal the possible threat to this species in the agroecosystems of the Western Ghats.