author(s)
Somanka Sanyal, Anilava Kaviraj and Partha Pratim Chakravorty

abstract
Indigenous epigeic earthworm Perionyx excavatus was collected from uncultivated grasslands of Midnapore district and was subjected to 28 days exposure to different sublethal doses of the organophosphate Dimethoate, i.e. 25% of LC₅₀ value and 50% of LC₅₀ value. The objective was to detect the effect of the organophosphate insecticide on the biomass, cocoon production and the acetylcholinesterase activity of the earthworm. At the end of the experimental period, it was observed that there was significant reduction in the aforesaid parameters with increasing concentration of the insecticide compared to the control value. T3 dose showed 57.21 ±3.05% reduction of biomass of the specimens. Cocoon production in T3 dose was dropped to 0.35 ±0.02 compared to the control value, 0.92±0.04. The AchE activity was inhibited by 69.2% in case of T3 dose. Thus, we can use the life-history parameters as potential tools and the enzyme activity as biomarker to detect pesticide pollution in agro-ecosystems.