Paint wastewater induced histopathological changes in the gill and liver of freshwater African catfish, Clarias gariepinus (Burchell, 1822)

Abstract

This study investigated the effects of paint wastewater on the histology of gill and liver of Clarias gariepinus. Juvenile C. gariepinus were exposed to acute (400, 500, 600 and 700 ml) and chronic (100, 150, 200 and 250 ml) concentrations of paint wastewater for 96 hours and 28 days respectively. After the exposure periods, gill and liver were excised for histological analysis.  Histological alterations in the gill during both exposures were characterised by moderate to severe hyperplasia, displacement of cartilaginous core, epithelia lifting, epithelia soughing, oedema, lamella fusion and necrosis compared to the control.  Liver hepatocytes of fishes in both assays revealed distortions in parenchymal lattice network, hyperplasia, pyknosis, vein degeneration, hypertrophy and hepatic necrosis compared to the control. The severity of these histological changes increased in concentration and time dependent manner. Epithelia lifting, lamella fusion, oedema and hyperplasia are probably adaptive/defensive mechanisms against severe pathological changes induced by the wastewater effluent.  In conclusion, this study showed that paint wastewater effluent caused severe pathological damages to the branchial and hepatic tissues of C. gariepinus and this may threaten the survival of the fish. Hence, there is the need for proper treatment of paint wastewater before being discharged into water bodies.