ABSTRACT
Environmental conservation has been a burning topic for the past few decades and conservation and health monitoring of soil and soil biota is a domain that needs to be dealt with which is directly related to agriculture, food and human health. Due to indiscriminate of chemical fertilizers the soil health and the ecology of soil organisms has been drastically deteriorated. Beneficial non-target organisms are harmed as a result of pesticide application, earthworms being the most common and abundant amongst them. Cypermethrin is one of the commonly used synthetic pyrethroid pesticides in agricultural field. Perionyx excavatus is an indigenous species of epigeic earthworm found in abundance in the uncultivated grasslands, around Midnapore district of West Bengal, that are free from direct pesticide contamination and are collected from there. In this study, acute toxicity of selected earthworms was evaluated following the 96-hr LC50 test under laboratory conditions. Similarly, chronic toxicity of preclitellete and adult earthworms Perionyx excavatus was evaluated by exposing them to sublethal concentrations i.e. 25% of LC50 (T1) and 50% of LC50 (T2) of cypermethrin (Cypermethrin- T1- 3.0 µg/kg soil, T2- 6.0 µg/kg soil) for 28 days to detect their developmental changes and changes in cellular enzyme activities respectively, under laboratory conditions. Our results showed that cypermethrin could lead to significant reduction of biomass, reduced cocoon production and changes in acid and alkaline phosphatase activity. We found that in case of T2 sublethal dose of cypermethrin cocoon production was reduced to nil. In summary, we found that cypermethrin induced both developmental and enzymatic changes in Perionyx excavatus, contributing to a more comprehensive evaluation of the safety of the synthetic pyrethroid. These parameters can also be used as effective tools in detecting pesticide pollution in agro-ecosystems.
Keywords: Cypermethrin, synthetic pyrethroid, alkaline phosphatase, natural soil, acute toxicity.