The aim of this study was to investigate the chronic toxicity of pharmaceutical effluent on Clarias gariepinus gills and liver as biomarkers of environmental quality in toxicity testing of pharmaceutical effluent. The chronic toxicity test of pharmaceutical effluent was carried out on the histopathology of the gill and liver of juvenile African catfish (C. gariepinus) with mean weight of 10 Â± 0.2g and standard length of 6.3 Â± 0.3 cm. A range finding test was conducted prior to the experiment. The fish were later exposed to 0%, 6.25%, 12.5%, 25%, 50% and 100% concentrations of the effluent for 21 days in a static renewal bioassay procedure. The median lethal concentration (LC50) value was 12.16%. Respiratory disturbance, erratic swimming, loss of equilibrium, lethargies and sudden death were observed in the exposed fish and these varied greatly with increase in concentration of the toxicant. This shows that mortality increases with increase in concentration. The differences observed in the mortalities of C. gariepinus at varying concentrations were significant (p < 0.05). The aim of this study was to investigate the suitability of C. gariepinus as potential biomarkers of environmental quality with respect to pharmaceutical effluent toxicity testing. The gill histopathological changes observed were epithelial lifting, interstitial oedema, leucocyte infiltration, hyperplasia of the epithelial cells, lamellar fusion, vasodilatation and necrosis. Abnormalies observed in the liver tissues of the treated fish were congestion of the central vein, vacoulation of hepatocyte, oedema, cellular infiltration and cellular necrosis (i.e cell death). Occurrence of the gill and liver anomalies in the test fish show their suitability for use in toxicity testing of pharmaceutical effluent.
Keywords: Gill histopathology, liver histopathology, chronic toxicity, pharmaceutical effluent, Clarias gariepinus