Effects of Nano-selenium on some immune and hematological indices in different life stages of rainbow trout, Oncorhynchus mykiss, permeabilized by sodium hypochlorite

Selenium is a trace element important for the normal growth and physiological functions in aquatic animals. In this experiment, its effects on the immune and hematological indices were studied in rainbow trout, Oncorhynchus mykiss (Walbaum, 1792) at different stages for 60 days. The experiment was carried out on 3 life stages (egg, alevin, fry), exposed to 0 (control), 0.5, 1 and 1.5 mg/L selenium nanoparticles each with 3 repetitions once penetrating with sodium hypochlorite. The results exhibited that the highest lysozyme level was observed in the fish exposed to 1 mg/L nano selenium in the alevin stage (p<0.05), while the lowest was reported in the control group. Immunoglobulin levels in the alevin stage at 1 and 1.5 mg/L nanoparticles were significantly higher than the control group and also than the other experimental treatments (p<0.05). The highest numbers of white blood cells were found at treatments exposed to 1.5 and 1 mg/L in the alevin stage, while the cell number in the control group was significantly lower than in the other treatments (p<0.05). Besides, the numbers of red blood cells in all treatments during the alevin stage were significantly higher than in the control group (p<0.05). The highest hemoglobin and hematocrit levels were observed in the treatments during alevin stage, while the lowest levels were found in the control group, such that the differences were significant (p<0.05). In total, exposing to 1 mg/L selenium nanoparticles in the alevin stage is the best concentration during the exact life time for rainbow trout growth and development.