Histopathological Effects of Some Heavy Metals and Environmental Factors on Brain of Common Carp Cyprinus carpio, Reared in cages and Wild Fish in Euphrates River, Babil, Iraq

The current study was conducted to study the concentrations of some heavy metals (iron, zinc, and copper) in sediment, water temperature, pH, salinity, T.D.S, O₂ ,bod5, and histological effects on the brain of cage fish and wild fish Cyprinus carpioin the Euphrates River from October of 2018 until November of 2019. Three sites were selected on the Euphrates River in the middle of Iraq first site wasAbu Luka in Musayyib near the thermal power station second site wasAl Saddah near the cement factory third site was in the village ofAl-Husayn. Results showed that in the first and second sites the concentration of heavy metal in sediments and fish brains was greater than in the third site, In general, cage fish at the first and second sites were higher than wild fish with their contents with heavy metal because they were held close to the sources of pollution. It was also noticed that the heavy metal concentration of both fish and sediment takes the following order according to the seasons of the year (summer > spring > autumn > winter), so they have a positive correlation with both the temperature and bod5 and inversely correlation with the pH, salinity and T.D.S and O2, The results of histological examination of the brain showed cellular degenerative changes in telencephalon brain and metencephalon brain tissue. The pathological damage was characterized by the presence of vacuolation between neurons in regions of the telencephalon brain and metencephalon brain near the stratum per ventricular layer with the presence of inflammatory cell infiltration and presence necrosis of neurons and glial cells in visceral tissue. The concentration of zinc was below the international determinants of World Health Organization and Canadian guidelines as well as the Environmental Protection Agency. But was higher than Food and Agriculture Organization Standards. The value of copper was higher than the World Health Organization's international specifications, the Food and Agriculture Organization, and Canadian specifications, but it is within the limits allowed by the US Protection Agency.