Histopathological and Oxidative Stress Response in African Catfish Clarias gariepinus in Heavy Metal Contaminated Water from the Hadejia-Nguru Wetland North Eastern Nigeria.

The Hadejia-Nguru wetland is a source of drinking, farming, and natural fertilization of fields, fishing and transportation. Discharges from agricultural activities, sewage and chemical application find their way into this water body. The present study is aimed at evaluating levels of some heavy metals (Hg, Pb, Cd, Cr and Al) in tissues of Clarias gariepinus (gills, liver and muscles) collected at 5 sampling sites labelled as A-E. Histopathological examination and the presence of antioxidant enzymes revealed the extent of damage in tissue and stress in the fish. Results of the heavy metal reveals concentrations in the sequence Pb>Cr>Hg>Al>Cd revealing a concentration higher than the permissible maximum residue limit as recommended by FAO and WHO. The activities of superoxide dismutase (SOD) catalase (CAT), malondialdehyde (MDA) and reduced glutathione were seen in elevated levels in the gills, liver and muscles. The highest level of SOD was found in the liver with a mean concentration of 32.43u/ml followed by a concentration level 12.35u/ml in the gills, CAT levels was highest in the liver with a concentration level of 67.80u/ml, MDA was highest in the gills with a concentration of 9.06n/mol and there was no significant difference (P<0.05) between concentration of MDA in the liver with other organs. GSH levels was highest in the gills with a concentration of 1016.64µg/ml and there was a significant difference (P<0.005) between the concentration of GSH in the gills in comparison to other organs. Histopathology revealed different deleterious effects in the gill filaments, hepatocytes and bowman’s space in the liver and muscle cells respectivly. The presence of metal toxicity, antioxidant enzymes and tissue disorders in fish are indication of pollution and can serve as bio-monitoring model of the safety of fresh water bodies.