Effects of copper sulfate (CuSO4) on the levels of glucose and cortisol in common carp, Cyprinus carpio.

The objective of this study was to evaluate the possible effects of CuSO4 exposure on variations of glucose and cortisol levels in Cyprinus carpio. Three replicates of 6 fish were subjected to two sub-lethal concentrations of CuSO4 (0.16 and 0.53 mg L(-1)) for 14 and 21 days. Blood samples were isolated from the fish following the exposure, to measure the levels of cortisol and glucose compared to the control group. The results showed significant increases (p < 0.05) in cortisol levels for both fish groups after 14 days of exposure, whereas, the levels of blood cortisol in both groups did not differ from that of control when the fish subjected to copper sulfate for 21 days. We found significant increases (p < 0.05) in the levels of blood glucose of two groups of fish after 14 days of exposure to two doses of CuSO4, as well as significant decrease in the blood glucose of both groups exposed for 21 days. In the later treatment, the rate of decrease in group II (exposed to 0.53 mg L(-1) CuSO4) was higher than that of group I (exposed to 0.16 mg L(-1) CuSO4) (p = 0.001 compared to p = 0.032). Our findings attest that exposing to waterborne copper would affect the levels of both cortisol and glucose, as indicators of stress response in Cyprinus carpio.