Morphohistopathological alteration in the gills and central nervous system in Cyprinus carpio exposed to lethal concentration of copper sulfate

Copper Sulfate (CuSO4) is the most used in aquaculture as chemotherapeutic bath against bacterial, fungal and parasitic diseases but it is very toxic for fish so the goal of this study was to determine the lethal concentration of CuSO4 and evaluate it is toxicity in the gill and central nervous system (brain and spinal cord) in Cyprinus carpio. Fish exposed to 0, 2.5, 5 and 10 mg/L for 24 hours, each concentration with three replication each have six fish. The mortality rate was 100% at concentration 10 mg/L, which represented lethal concentration, while medium lethal concentration (LC50) was determined by Trevan method and it is 5mg/L. The fish with LC100 concentration exhibit abnormal respiration with gasping swimming, nervous sings with up down and stay at basin then die at 2-3 hours. The histopathological examination of the gills revealed circulatory disturbances, cellularity reaction, progressive and regressive alteration, this microscopic alteration was evaluated as semi-quantities analysis and there was variable significant (P≤0.05) in the pathological alteration and gill indexes between two treatments. In the brain and spinal cord, the lesions are represented by vasogenic edema, infiltration of inflammatory cells with atrophy in the neuronal body cells and hemorrhage. It is concluded from this study that the use of copper sulfate is within limited concentrations because increasing its concentration leads to fish toxicity, and it was observed that the gill tissue is more sensitive to toxicity than the central nervous system