THE INFLUENCE OF SOME HEAVY METALS ON CLARIAS GARIEPINUS IN POLLUTED WATER WITH SPECIAL STRESS ON SOME PHYSIOLOGICAL AND PATHOLOGICAL CHANGES ON THESE FISHES

Abstract

Pollution with heavy metals has become serious during recent years. Heavy metals such as copper, lead and cadmium when discharged into water can enter the food chain, bioaccumulate in fish tissues therefore they are highly toxic for consumers when exceeding the recommended safety levels. The concentration of heavy metals differed in four examined areas. The concentrations of heavy metals (copper, cadmium and lead) were in normal levels in water of River Nile in Mansoura city and in tissues of Clarias gariepinus fish collected from River Nile. But the concentrations of heavy metals in water samples and tissues of fish collected from (drainage canal No 7 then Bahr El-Bakar and Manzala Lake) were higher than the permissible limits as reported by FAO/WHO (1992) and WHO (1993). The bioaccumulation of the studied heavy metals in vital organs of Clarias gariepinus collected from studied locations were high concentrations in liver, gills, kidney then muscles. The haematological analysis of blood revealed presence of significant changes in blood and serum of Clarias gariepinus which collected from drainage canal No 7, Bahr El-Bakar and Manzala Lake. The total red blood cells, heamoglobin and backed cell volume levels were lower than fish collected from River Nile at Mansoura city which were in normal ranges. The total leukocytes values nearly similar to normal ranges in Mansoura city, in contrary marked leucocytosis were observed in other three polluted areas. Concerning the biochemical parameters, the results showed significant decrease for both of proteinogram parameters, cholesterol and thyronine (T4). On other side significant increase for both of glucose, cortisol hormone, serum AST and S.ALT, S.ACP, S. creatinine and S. blood urea were observed. The clinical signs and gross lesions on Clarias gariepinus including respiratory manifestations and congestion of skin and fins with increase amount of slimy mucous secretion on skin and presence of congestion in gills, kidney and liver with enlargement in size. The histopathological studies revealed the hepatic lesions of affected fish with heavy metals as vaculation of hepatic cells, edema portal blood vessels, hydropic degeneration of hepatic parenchyma, melanomacrophages among degenerated hepatic tissues. The lesions of kidneys were nephrosis in renal tubules with activation of haemopoietic elements, hyaline degeneration of epithelial lining of some renal tubules and death cells of other tubules with presence of hemorrhages with small brown granules among necrotic areas, periglomerular fibroblastic proliferation and roused renal capsule with subcapsular hemorrhages. The lesions of gills revealed that destroyed upper portion of gill filaments with hyperplasia of secondary lamellar epithelium with numerous secreting cells, edema in primary filaments, inflammatory cells in gill arch with edema and destruction of surface epithelium. Also gill rocker revealed edema and haemorrhages. Gill filaments had thrombosis in dilated capillaries of secondary lamellar epithelium. The pathological changes in muscles including swollen with loss of their striation, partial and intense hyalinization with intermuscular edema, partial necrosis with myolysis of some muscle fibers with proliferation of fibroblasts and intense necrosis with few melanomarcrophages and lymphocytes. The study concluded that the heavy metals had dangerous effect on physiological parameters and vital organs of fishes exposed in it.