Effect of increasing ambient temperature on physiological changes, oxidative stress, nitric oxide, total antioxidant power, and mitochondrial activity of Nile tilapia (Oreochromis niloticus Linn.)

Abstract

The objective of this study was to investigate the effect of high ambient temperature on physiological changes of live Nile tilapia (Oreochromis niloticus Linn.) and biochemical parameters in Nile tilapia blood cells. Live Nile tilapia and Nile tilapia blood cells were maintained at temperature ranges from 24 to 34 °C and 24–38 °C, respectively. Then, physiological parameters (body temperature, body color score, pulse rate, ventilation rate, oxygen saturation) of the live Nile tilapia and biochemical parameters (total antioxidant power, hydrogen peroxide, malondialdehyde, nitric oxide, and mitochondrial activity) of the Nile tilapia blood cells were measured for every 2 °C increase. It was found that when the ambient temperature increases, body temperature of live Nile tilapia continually increased. Total antioxidant power and hydrogen peroxide, pulse rate, body color score, malondialdehyde, ventilation rate and mitochondrial activity commenced to increase at 26, 28, 30, 32, 34 °C (P < 0.05), respectively. Blood oxygen saturation decreased at 32 °C (P < 0.05). The response of nitric oxide of Nile tilapia blood cells responded to increased temperature in two phases. In the first phase, nitric oxide decreased at 28–32 °C (P < 0.05), then increased and decreased again at a temperature of 38 °C (P < 0.05). These phenomena indicated that when the live Nile tilapias and the Nile tilapia blood cells were exposed to high ambient temperature, they were under heat stress and oxidative stress. In addition, physiological responses in the live Nile tilapia and biochemical changes in their blood cells when exposed to high ambient temperature occurred in a consistent manner when the temperature continually increased.