A Comparative Study on The Acute Toxicity Bioassay of Dimethoate and Lambda-cyhalothrin and Effects on Thyroid Hormones of Freshwater Teleost Fish Labeo rohita (Hamilton)

Abstract

Dimethoate (organophosphate insecticide) and Lambda-cyhalothrin (synthetic pyrithroid) are<br />two frequently used pesticides due to their high effectiveness and rapid breakdown into environmentally safe<br />products. The aim of this present study was to assess and compare the acute toxicity of Dimethoate<br />(Rogor30%EC) and Lambda-cyhalothrin (5%EC) on Labeo rohita (Hamilton). Acute toxicity bioassay was<br />carried out in a static renewal system to assess the toxicity. The fishes were exposed to different concentration<br />of dimethoate and Lambda-cyhalothrin to determine the LC50 values for 96hrs. The mortality data obtained<br />were analyzed by SPSS 16.0 based on Finney's Probit Analysis Statistical method. The 96h LC50 values for<br />Dimethoate and Lambda-cyhalothrin were found to be 24.55 μl/L and 0.7 μl/L respectively. Effects of these<br />two insecticides on serum T3, T4 and TSH were investigated under sub-lethal toxicities which cause decrease in<br />the serum T3, T4 and increase in TSH level. It shows significant difference from control fish (p < 0.05)..