Effect of Cd on serum osmolality, ion levels and hematological parameters of tilapia (Oreochromis niloticus) at different salinity levels

Effects of cadmium on serum osmolality, ion levels and hematological parameters of tilapia (Orechromis niloticus) were evaluated at different salinities. Serum osmolalities (SOs) in fish unexposed to Cd (0 mg l⁻¹) and exposed to 2.5 mg Cd l⁻¹ were not significantly different at salinities of 0, 5 and 10 g l⁻¹, while at 15 g l⁻¹, SO was significantly higher than at 0, 5 and 10 g l⁻¹. Levels of Na⁺ and Cl⁻ in serum at salinities of 5, 10 and 15 g l⁻¹ were not significantly different; but were significantly higher than those at 0 g l⁻¹ with and without Cd. In media without Cd, the lowest level of K⁺ in serum occurred at 15 g l⁻¹ salinity, whereas levels of K⁺ at 0, 5 and 10 g l⁻¹ were not significantly different. The levels of K⁺ in Cd-exposed fish at all salinities were not significantly different. At 0 g l⁻¹ salinity, hemoglobin, red blood cells, and hematocrit in Cd-exposed fish were significantly lower than controls. At salinities of 5, 10 and 15 g l⁻¹, levels in control and Cd-exposed fish were not significantly different indicating that higher salinity prevented Cd-induced osmotic imbalance and hematological alterations.