Hematological, hepatic enzymes' activity and oxidative stress responses of gray mullet (Mugil cephalus) after sub-acute exposure to copper oxide

Given the importance of assessing potential toxicity of heavy metals in valuable species of aquatic animals, the goal of the present research was to assess the sub-acute effects of copper oxide on hematological, enzymological, and oxidative stress responses of gray mullet to measure toxicity of copper oxide pollution in this significant fish. The median lethal concentration (LC50) value of copper oxide to gray mullet was detected at 3.15 +/- 0.039 mg/L for 96 h, and 25 and 50% of the 96-h LC50 values were selected as sub-acute concentrations. The fish were exposed to (0.79 and 1.57 mg/L) copper oxide for 21 days. At the end of 21 days, the results showed that hemoglobin (Hb), hematocrit (Hct), red blood cells (RBC) count, MCV, MCH, and MCHC levels were found to be decreased in copper oxide treated fish, whereas white blood cells (WBC) count increased in copper-treated fish. Plasma aspartate aminotransferase (AST), alanine aminotransferase (ALT), and lactate dehydrogenase (LDH) activity increased in treated groups; however, copper oxide in both groups of sub-acute exposure significantly decreased plasma alkaline phosphatase (ALP) activity compared to the control group. Superoxide dismutase (SOD), catalase (CAT), and glutathione (GSH) levels significantly declined in copper oxide-treated fish. These findings indicated the deleterious effects of copper oxide on gray mullet, even at low concentrations, and offered that hematological and hepatic enzyme activity and antioxidants are suitable tools for evaluating heavy metals toxicity.