Pathological findings in acute and chronic copper toxicity in rainbow trout (Oncorhynchus mykiss, Walbaum 1792) occurred by copper sulfate pentahydrate

In this study, experimental acute and chronic copper toxicity caused by copper sulphate pentahidrate (CuSO4.5H2O) was constituted in rainbow trout. For this purpose, 30 rainbow trout (weight 80 ± 10 g and 10-12 cm in size) were divided into four groups two experimental [(Acute Group (Group I), n:10 - Chronic Group (Group III), n:10) and two control groups [(Acute Control Group (Group II), n:5 – Chronic Control Group (Group IV), n:5). 2 mg/l and 0,5 mg/l of copper sulphate pentahidrate concentration were used in Group I and III respectively. The first death was observed on the 3th day in Group I and on the 18th day in Group III. Dead or killed fish were necropsied, tissue samples collected, fixed in 10 % neutral-buffer formalin solution, embedded in paraffin wax, sectioned at 5 µm and stained with hematoxylin and eosin (H&E) and examined under light microscope. The most remarkable clinical finding seen in both experimental groups were decreased feed consumption, distintive deceleration in movement and swimming close the surface. In Group I macroscopic examination, liver were oedematous and had dark red color. Gill were oedematous and gut hyperemic. In Group III, liver were hyperemic and had remarkable pale color. Gill were pale and skin was covered by mucous. In Group I, the most prominent microscopic finding was seen in liver. Degeneration and single cell death were seen widely in hepatocytes. In the gills, there were epithelial necrotic changes with vascular degeneration caused by oedema, hyperemia and hemorrhage. Kidney had quite distinctive vascular lesions. In tubullus epithelium there were degeneration and variable sized eosinophilic hyalin droblets in cytoplasm. In Group III was used underdose liver had diffusive degenerations. In all findings hepatocyte nucleus had remarkable vesicular appearance. There was obvious thickness caused by hyperplasia in gill. Digestive system epithelium had diffusive degenerative and in skin there was oedema in intracellular epidermis cell with increase mucous cell. In conclusion, pathological findings seen in the experimental acute and chronic copper toxication caused by copper sulphate pentahidrate were examined and results were comparatively evaluated.