Evaluation on the Sensitivity of the Freshwater Tropical Worm, Branchiura sowerbyi (Beddard, 1892) to the Pyrethroid Pesticide, Bifenthrin

Abstract

In the present study, acute toxicity of the pyrethroid pesticide, bifenthrin, was evaluated under the experimental condition to the freshwater tropical oligochaete worm, Branchiura sowerbyi. The 96 h LC50 with 95% confidence limits of B. sowerbyi was 1.043(0.721-1.327) μg/l. None of the unexposed control test animal died during the experiment. Relation between each concentration and mortality rate during 24–96 h was found to be correlated. The mortality rate varied significantly (p<0.05) with the increasing concentration for the organisms at all the exposure concentrations except 3.50 μg/l, 4.50 μg/l and 5.00 μg/l (p>0.05) at all the exposure times. The relationship between rate of mortality and exposure times was also found to be significant (p<0.01). The effect of bifenthrin on the ethological changes of the oligochaete worm was directly proportional to the increasing dose of the toxicant.

Keywords: Branchiura sowerbyi, bifenthrin, acute toxicity, toxicity factor, safe level, ethological changes