Immunological, Hematological, and Histological Responses in Blood, Spleen and Gill of Salmo Caspius Juveniles Exposed in Different Water Temperatures

Caspian brown trout, salmo caspius, were subject to five temperatures (5°c, 8°c, 20°c, 25°c, and 28°c) for two durations 12 and 24 hours. the fish were maintained for 48 hours at a water temperature of 9-10°c to acclimatize. the water temperature was changed gradually at a rate of 2°c per hour to the respective temperatures. exposure to temperatures of 25 and 28°c resulted in loss of all fish. red blood cell, hemoglobin concentration, and hematocrit were decreased at 5°c compared to control (8°c) and 20°c in duration of 12h. temperature tension did not affect the mean cell volume and mean cell hemoglobin value during the 12 and 24h duration (p>0.05). neutrophils percentage was significantly higher at 5°c and 20°c, but the most percentage of lymphocytes was noted in the control group. cortisol, glucose, and lactate values elevated in both periods when water temperature decreased to 5°c compare to the control and 20°c groups (p<0.05). the levels of albumin and total protein in the duration of 12h at 20°c were significantly higher than control and 5°c, but this trend was not seen in the exposure of 24h (p<0.05). the lysozyme activity and immunoglobin m were affected by varying temperatures (p<0.05), and highest levels were observed in control groups. most histopathological changes in gill, such as epithelial hypertrophy, curling of lamella, and necrosis of the epithelial cell were observed at 20°c; whereas these were less affected at 5°c and 8°c. lowest hemorrhages in the spleen and lowest size of sinusoids were observed in 8°c and 5°c treatments respectively. overall, temperature variation had a superior impact on gills than spleen. taken together, the results of the present study showed that sudden variation beyond the optimum temperature leads to physiological and pathological changes.