Behavioral Alterations, Liver Lesions and Induction of Detoxifying Enzyme in Oroechromis Niloticus Exposed Chronically to Endosulfan

Abstract

The effects of endosulfan, a widely use pesticide in the Niger Delta ecological zone of Nigeria was on Oreochromis niloticus, a dominant fish species was investigated. The Organization for Economic Cooperation and Development (OECD) No. 203 recommended static renewal bioassay was employed to determine 96 hours LC₅₀ of the pesticide. Five fish per test concentration in three replicates were exposed to varying concentrations of endosulfan for 28 days and signs of stress monitored. Histological alterations were determined by light microscopy using standard technique. Serum glutathione-s-transferase (GST) activity was assayed using a spectrophotometer. The exposed fish were sluggish and remained at the bottom calmly on the last day of the test. The alterations in liver tissue reflected the severity of the different concentrations of the toxicant. GST activity in the treated fish was significantly (p<0.05) higher than the control. The measured indices appeared to be effective monitoring tools for estimating the fish health status.