Toxicological effects of heavy metals on histological alterations in various organs in Nile tilapia (Oreochromis niloticus) from freshwater reservoir

The current study was aimed to evaluate the seasonal variation in bioaccumulation of metals (Pb, Cu and Ni) in the gills, kidney, liver and muscle of Oreochromis niloticus. Sixty fish samples (average wet body weight 460.77 +/- 6.22 g) were collected from the freshwater reservoir Wadi Namar Riyadh, Saudi Arabia in winter, summer, spring and autumn seasons. The heavy metals were assessed through atomic absorption. The findings of this study revealed seasonal variation in bioaccumulation of metals. In winter season minimum concentration of Pb, Cu and Ni was recorded while the highest was recorded in summer season. The order of bioaccumulation of Pb and Ni in organs was: liver > kidney > muscle > gills in and liver > gills > kidney > muscle in winter and summer, respectively. The bioaccumulation order of Cu as kidney > liver > gills > muscle and gills > kidney > liver > muscle in winter and summer, respectively. The heavy metals concentration was crossing the permissible limits suggested by WHO. Histopathological examination in kidney exhibited congestion, dilation in bowman capsule space, necrosis. Liver of the fish exhibited cytoplasmic vacuolation, necrosis, sinusoid dilation. It has been concluded that this river is heavily contaminated due to the discharge of untreated waste from industry and domestic sewage from the city and there is a dire need to control this increasing contamination. (C) 2019 The Authors. Production and hosting by Elsevier B.V.