Global warming is a threat across the world that leads to estimates of the upper thermal limits of ectothermic species. Increased water temperature up-regulates oxygen consumption and metabolic rates, and alters the physiological processes. In this study, we identified the critical thermal maxima (CTmax) and physiological responses under normoxia and hypoxia in Nile tilapia, Oreochromis niloticus. CTmax was 41.25 °C under hypoxia and 44.50 °C under normoxia. Compared to normoxia, lower values of hemoglobin (Hb) and red blood cells (RBCs) were observed at the CTmax under hypoxia. In contrast, higher values of white blood cells (WBCs) and blood glucose (Glu) levels were observed at the CTmax under hypoxia. Consequently, higher frequencies of micronucleus, cellular and nuclear abnormalities of erythrocytes were observed at the CTmax under hypoxia. These results suggest that high temperature tolerance and subsequent physiology are significantly affected by the oxygen supply in Nile tilapia. As climate vulnerability is intensifying day by day, this data will be helpful in successful management practice for the aquatic environment having low oxygen content.

中文翻译：

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缺氧降低了热上限，导致尼罗罗非鱼、尼罗罗非鱼中红细胞的细胞和核异常

全球变暖是世界范围内的威胁，导致对变温物种的热上限的估计。水温升高会上调耗氧量和代谢率，并改变生理过程。在这项研究中，我们确定了尼罗罗非鱼 Oreochromis niloticus 在常氧和缺氧条件下的临界热最大值 (CTmax) 和生理反应。CTmax 在缺氧条件下为 41.25 °C，在常氧条件下为 44.50 °C。与常氧相比，在缺氧条件下，在 CTmax 处观察到较低的血红蛋白 (Hb) 和红细胞 (RBC) 值。相比之下，在缺氧条件下，在 CTmax 处观察到更高值的白细胞 (WBC) 和血糖 (Glu) 水平。因此，在缺氧条件下，在 CTmax 处观察到更高频率的红细胞微核、细胞和核异常。这些结果表明尼罗罗非鱼的高温耐受性和随后的生理机能受到氧气供应的显着影响。随着气候脆弱性日益加剧，这些数据将有助于低氧水环境的成功管理实践。