Thermal tolerance, oxygen consumption and haemato-biochemical variables of Tor putitora juveniles acclimated to five temperatures

Abstract

A 30-day acclimation trial was conducted using Tor putitora to elucidate its thermal tolerance, oxygen consumption, haemato-biochemical variables and selected enzymatic activities at five acclimation temperatures (AT). Juveniles of T. putitora were randomly distributed among five treatment groups (20, 23, 26, 29 and 32 ± 0.5 _C). There was a significant curvilinear increase in critical thermal maxima (CTmax) (y = -0.0693x2 ? 1.7927x ? 34.628, R2 = 0.996) and lethal thermal maxima (LTmax) (y = -0.1493x2 ? 2.3407x ? 35.092, R2 = 0.991) with increasing AT. The oxygen consumption rate increased significantly with increasing AT. The Q10 values were 1.16 between 20 and 23 _C, 3.09 between 23 and 26 _C, 1.31 between 26 and 29 _C and 1.76 between 29 and 32 _C of AT. The acclimation response ratios were ranged between 0.37 and 0.59. Catalase, superoxide dismutase and ATPase activities were increased linearly in liver, gill and kidney, while brain acetylcholine esterase activity decreased linearly with increasing AT. Blood glucose remained unchanged up to AT of 26 _C and increased significantly at AT of 29 and 32 _C. Haemoglobin content was increased linearly with increasing AT. The highest WBC count was observed at 20 _C, and no significant changes found till AT of 26 _C and significantly decreased at 32 _C. Total serum protein and globulin were significantly decreased with increasing AT. Highest values were observed at 20 _C and remained consistent till 26 _C, then decreased significantly. There was no significant change in A/G ratio through the AT 20–29 _C and increased significantly at 32 _C. The increase in CTmax, LTmax and oxygen consumption rate with increasing AT may suggest that the thermal tolerance of T. putitora is dependent on its prior thermal exposure history, and it could adapt to higher AT by altering its haemato-biochemical variables.