Effects of Exposure to Sub-Lethal Concentrations of Copper on Hematological and Histopathological Alterations in Common Carp, Cyprinus Carpio

The present study investigated the toxic effects of copper sulfate on hematological factors, bioaccumulation levels of copper, and histopathology of gill and kidney tissues of Common carp.

For this purpose, 90 fish were exposed to different sub-lethal levels of copper sulfate (0.16 and 0.53 mg/L) for 21 days. After 21 days, blood samples were taken. Hematological factors such as hematocrit (Hct), hemoglobin (Hb), red blood cells (RBC), and white blood cells (WBC) were measured in blood samples. Bioaccumulation levels of copper in gill and kidney tissues were determined by wet chemical digestion and atomic absorption apparatus. The data were analyzed by one-way ANOVA and Duncan test, and compared in significant levels of P<0.05. Gill and kidney samples were collected from each group and lesions were analyzed by light microscopy.

The results showed a dose-dependent decrease in hemoglobin, hematocrit, red blood cells and white blood cell count. Copper accumulation in gill and kidney tissues of fishes exposed to sub-lethal copper increased significantly compared with the control group (P<0.05). Histopathologic studies showed a series of changes in gill tissue, including primary lamellar edema, hyperplasia, severe secondary lamellar fusion, and clubbing. Cellular swelling in the tubules and glomeruli, tubular necrosis and formation of hyaline cysts were the main kidney histopathological changes

These results suggest that hematological parameters and gill and kidney changes following metal accumulation in these tissues can be used as sensitive biomarkers to determine the toxicity of sub- lethal concentrations of heavy metals.