Acute Toxicity of Malathion 50 EC on Fejervarya limnocharis

Acute toxicity tests were performed on Fejervarya limnocharis with different concentration of malathion 50EC (0.006, 0.008, 0.01, 0. 02, 0.03, 0.04, 0.05, 0.06, 0.07 and 0.08 ppm). On Probit analysis, the Lc50 value estimated for 24 hrs, 48 hrs, 72 hrs, and 96 hrs were 0.07036, 0.04060, 0.02479 and 0.01589 ppm respectively. No marked acute responses were observed in lower doses and in higher doses tremor, convulsion, erratic movement and rapid swimming with ventral side up were observed. Ultimately the test animals sank to the bottom of the jar Abnormal behaviours observed might be due to the inhibition of AchE by the accumulation of acetylcholine causing prolonged excitatory postsynaptic potential.