Toxicity of Alphamethrin, Dimethoate and Carbaryl pesticides to the freshwater snails Lymnaea acuminata and Indoplanorbis exustus

To use the snails as bio-indicator of pesticidal pollution, different doses of a pyrethroid (Alphamethrin), an organophosphate (OP) (Dimethoate) and a carbamate (Carbaryl) were administrated for 24 to 96 hours to the snails Lymnaea acuminata and Indoplanorbis exustus. Both species were susceptible to the three pesticides at  concentrations in the range of 0.008 mg/l to 16.92 mg/l. The order of toxicity was pyrethroid > organophosphate (OP) > and carbamate. The toxicity of all the pesticides was both time and dose dependent as expected. Variation in water temperature influenced the toxicity of pyrethroid significantly, however, OP and carbamate were not influenced significantly. At low temperature pyrethroid became 3 to 4 times more toxic. Similar results are also reported in the case of fish. Thus, the susceptibility of snails may be directed in the field of pollution monitoring