Reza Davoodi

tEffects of low (1, 2.5 and 5 Gy) and high doses (10, 20 and 40 Gy) of gamma radiation were examinedon the growth, survival, blood parameters and morphological changes of the intestines of rainbow trout(Oncorhynchus mykiss) larvae (103 ± 20 mg) after 12 weeks of exposure. Negative effects of gamma radi-ation on growth and survival were observed as radiation level and time increased. Changes were welldocumented at 10 and 20 Gy. All the fish were dead at the dose of 40 Gy. In all the treatments, levelsof red blood cells (RBC), hematocrit (HCT) and hemoglobin (HB) were significantly (P < 0.05) declinedas the irradiation levels increased, whereas the amount of mean corpuscular volume (MCV) and meancorpuscular hemoglobin (MCH) did not change. No significant differences (P > 0.05) were found in thelevels of white blood cells (WBC), lymphocytes and monocytes. Destruction of the intestinal epitheliumcells was indicated as the irradiation levels increased to 1 Gy and above. The highest levels of growth,survival, specific growth rate (SGR), condition factor (CF) and protein efficiency rate (PER) were obtainedin the control treatment. The results showed that gamma rays can be a potential means for damagingrainbow trout cells.