الفهرس 
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Abstract
Heavy metals and temperature are common environmental stressors. Thus, they have considerable attention due to global climate change and anthropogenic pollution. Therefore, the present study focused on the influence of thermal change on toxicity induced by cadmium in Oreochromis niloticus fish. The study was carried out on 120 apparently healthy Nile tilapia divided into 6 experimental groups, 20 for each exposed to Cd at different temperatures for 3 and 6 weeks. The first group used as control at water temperature of 22˚c, the second group exposed to 3.44 mg/L CdCl2.H2O (1/10 LC50) at water temperature of 22˚c, the third group exposed to 1.77 mg/L CdCl2.H2O (1/20 LC50) at water temperature of 26˚c, the fourth group exposed to 3.44 mg/L CdCl2 H2O at water temperature of 26˚c, the fifth group exposed to 1.77 mg/L CdCl2.H2O at water temperature of 29˚c and the sixth group exposed to 3.44 mg/L CdCl2.H2O at water temperature of 29˚c. Samples collected were plasma, liver for homogenation, muscles and samples for histopathology (brain, liver, kidney, spleen and gill).The present study revealed that the determined 96-h LC50 value of CdCl2.H2O in Oreochromis niloticus was 34.65 mg/L. The results of biochemical analysis revealed that high temperatures lead to increased metabolic activity render cadmium to be more toxic which led to marked increase in the level of transaminases (AST and ALT), ALP, urea and creatinine concentrations in plasma than exposure to Cd alone with decrease in the levels of TP. The oxidative stress parameters in liver homogenate (SOD, GST, GPx, and NO) showed marked decrease activity with pronounced increase in lipid peroxidation. Also, Cd residue in muscles showed significant increase after 3 weeks and continued to increase after 6 weeks. Histopathological alterations in different organs were more pronounced with temperature rising to 26˚C and 29˚C. These results confirm that the increase of temperature enhance Cd toxicity and needs to be taken into account for the accurate prediction and assessment of Cd-induced toxicity in fish.