Effects of zinc (Zn), cadmium (Cd) and their mixture on tissues metal accumulation, elimination and on hematological parameters of Clarias gariepinus and Oreochromis niloticus

Metal levels in gill, liver, kidney, spleen and muscle tissues of C.gariepinus and O.niloticus were determined after being exposed singly and in mixture of 10 ppm Zn, 2 ppm Cd over 7 and 14 days of exposure and following 7 days of depuration periods. Serum enzymes, serum electrolytes and other serum components such as glucose, total protein and total cholesterol were also determined at the end of each period. The following relationship was found between tissues in both species exposed to Zn and metal mixture; kidney > liver > gill > spleen > muscle. Whereas the following relationship was true in fish exposed to Cd and mixture; liver > kidney > gill > spleen > muscle. Significant increases were determined in ALT, AST, ALP and LDH levels under the effect of Zn, Cd and their mixture. There was an increase in serum Ca++, Na+ and Cl- levels and a decrease in K+ levels. Among the other serum parameters measured an increase in serum glucose level and a decrease in serum cholesterol and total protein were detected. Tissue metal levels and sera parameters showed variation at the end of elimination period.