Cadmium Bioaccummulation and Toxicity in Tilapia Fish (Oreochromis niloticus)

The present study was undertaken to determine the bioaccumulation of cadmium in livers of tilapia fish (Oreochromis niloticus) and to assess the histological alteration of intestine, liver and kidney tissues due to cadmium toxicity. Fish (Oreochromis niloticus) were exposed to cadmium at different concentrations (5 and 10 mg L-1) for 7 days. Cadmium assayed by using AA220FS atomic absorption spectrophotometry. The concentration of cadmium in the liver tissues in the fish exposed to 10 mg L-1 was found to be (9.09 +/- 0.51 mu g g (-1) dry wt.) while it was 5.17 +/- 0.25 mu g g(-1) dry wt, in the fish exposed to 5 mg L-1. There was a significant increase of cadmium chloride concentration in the liver tissues of the fish exposed to 10 mg L-1 compared to the those exposed to 5 mg L-1. Histological alterations on liver tissues were in the form severe fatty vacuolations, generalised necrosis of hepatocytes, fatty change, congestion of liver sin.usoids and central veins. Intestines showed severe congestion of submucosal blood vessels and sloughing of mucosal epithelium. Kidneys showed severe glumerular shrinkage and necrosis, lymphocytic infiltration in the distal renal convoluted tubules. Histopathological changes were more pronounced in fish exposed to 10 mg L-1 cadmium chloride.