Accumulation of cadmium and structural alterations in scales of cichlid fish oreochromis niloticus (Linnaeus, 1758)

The present study was conducted to evaluate the effects of cadmium (Cd) on the structural changes of scales of the cichlid fish (Orechormis niloticus). Fish were exposed to 0, 2.5 and 5 mg Cd/L for 7 day. The Cd concentrations in scales of Cd-exposed sh were signicantly higher than those in the control fish. The highest level of Cd was noted in fish exposed to 5 mg Cd/L. The circuli and radii of the scales were not change in both the control and Cd-exposed scales. The lepidonts of control fish were pointed, those of fish exposed to 2.5 mg Cd/L were blunt, and the lepidonts of fish exposed to 5 mg Cd/L were blunt and disappeared in certain circuli. For these reasons lepidonts in scales have an important role as a bioindicator to determine the pollution parameters, especially for Cd pollution.