Histological alterations observed in the liver and brain of Clarias gariepinus exposed to chronic sublethal dose of lead.

摘要

The degree of contamination in aquatic environment is frequently assessed by the effect of contaminant exposure in associated biota (Yang & Chen, 1996). In heavy metal pollution (e.g., lead and cadmium), organs such as the liver have been identified as the storage sites in C. gariepinus (Gbem et al., 2001). An investigation on the effect of the heavy metal, lead (Pb) on the liver and brain of the African catfish, Clarias gariepinus was carried out in the laboratory. Clarias gariepinus was exposed to various sublethal concentrations (0.0, 0.05, 0.1, 0.5 and 1 mg/l) of lead nitrate over a period of 8 weeks to determine the histological alterations in the liver and brain. Pathological lesions observed in the liver mainly in the groups (D & E) exposed to higher concentrations of Pb include moderate diffuse hydropic degeneration and discrete areas of haemosiderosis at four weeks into the experiment and extensive hydropic degeneration and necrosis of hepatocytes at eight weeks. Pathological alterations noticed in the brain include focal areas of perivascular oedema and haemorrhage; focal areas of malacia with diffuse neuronal degeneration and diffuse areas of microgliosis. The severity of alterations was significantly (p<0.05) greater in the fishes exposed to higher doses of lead. The results showed that the degree of alterations noticed in the liver and brain was proportional to the exposure periods and concentration of Pb.