The assessment of histopathological change induced in the tissues of the Cyprinus carpio and Rutilus caspicus fry after acute exposure of Copper (CuSO4)

Cu is an essential micronutrient which is found in either water environment or fish diet. In addition, copper sulfate is an effective algaecide for algal control in fish pond. Therefore, toxicity test seems to be necessary to predict the safe concentrations of chemicals in the environment. The experiments were conducted to study of mortality rate of acute toxicity of Copper (CuSO4) in Common Carp (Cyprinus carpio) and Caspian kutum (Rutilus caspicus) fry.13 fishes with average weight of 2±0.5 and 20±2.2g to R. caspicus and C. carpio  respectively were exposed to different concentrations of copper salt respectively. The experiments were done by Static Method during 96 hours. In the experiments, the different concentrations of copper such as 0, 0.1, and 0.2, 0.3, 0.4, 0.45 and 5mgL-1 were used. Under stable condition (T= 25±1OC, pH=7.8 ± 0.2), the lethal concentration of copper (LC50) was measured of 0.4mgL-1 and 0.45mgL-1 to R. caspicus and C. carpio respectively during of 96 hours. There were significant differences between treatments with each other and also with the control (P<0.05). So, with increasing of copper in each treatment, the mortality rate of fish significantly was increased. For studying histopathological, 3 fish were selected randomly from each treatment and after killing fish, samples of liver, kidney, and gill tissue were taken from each fish. These samples (sections) were stained with Hematoxylin-Eosin and then the impacts of Cu on the fish organs were studied under light microscope. Histopathological findings showed that major lesions were hemorrhage, hyperemia, hyperplasia and epithelial cells necrosis, degenerated tubules of their kidney, expansion of Bowmanchr('39')s capsule and hepatocytes necrosis in 0.3, 0.4 and 0.45 concentrations respectively. There were any lesions in control.