Toxicity of insecticides and effects on the behavior of the blood clamAnadara granosa

The toxicity of organophosphate insecticides, mainly phosphamidon, monocrotophos and dichlorvos to the blood clamAnadara granosa, occurring in Kakinada Bay of the Godavari estuarine system was measured. The LC₅₀ values of three insecticides for 24,48,72 and 96 hr exposure ranged from 4.26 to 11.53 mg L^?1 for phosphamidon, 3.50 to 9.31 mg L^?1 for monocrotophos and 1.79 to 6.20 mg L^?1 for dichlorvos. Dichlorvos proved highly toxic even at low concentrations compared to either phosphamidon or monocrotophos. The animals showed decreasing activity with increasing insecticide concentrations and duration of exposure. However, there was no marked difference in the toxicity between phosphamidon and monocrotophos.