Heamatological Changes in Clarias Gariepinus Exposed to Cypermethrin

Abstract

The acute toxicity of cypermethrin, an insecticide, to juvenile African catfish, Clarias gariepinus was investigated with emphasis on haematological effects. Juvenile Clarias gariepinus (Burchell 1822) were exposed to 0, 1.9, 4.1, 9, 21, and 45 mg L^-1 cypermethrin. The lethal concentration (LC₅₀) of cypermethrin was 63 μg L^-1 at 96 hours of exposure. Mean mortality percentages were 0, 0, 70, 90, 100, and 100, at the concentrations 0, 1.9, 4.1, 9, 21 and 45 mg L^-1, respectively. Respiratory stress, erratic swimming, and instant death were observed for fish exposed from 4.1 μg L^-1 and above. Cypermethrin is highly toxic to juvenile fish. These changes occurred predominantly in the 96h exposure at the concentration 9 μg L^-1. Cypermethin concentration corresponding to the 96h LC₅₀ value for juvenile C. gariepinus was used to study the effects of cypermethin exposures in inducing histopathological changes of liver and kidney. In the liver, there was vacuolation of hepatocytes and necrosis. In kidney there was exfoliation and swollen with pyknotic nuclei. These changes occurred predominantly in the 96h exposure. There was a progressive decrease in heamatological parameters of fish as the concentration of the toxicant increased. Also, haematological indices indicated that the fish became hyperglycaemic and hypoproteinaemic and the severity of this condition was directly proportional to the cypermethrin concentration. Investigation on white blood cells (WBC), red blood cells (RBC), packed cell volume (PCV), indicate low immune system of the fish in fighting diseases.