Hypoxia is one of the most significant threats to biodiversity in aquatic systems. The ability of high-latitude fish to tolerate hypoxia with histological and physiological responses is mostly unknown. We address this knowledge gap by investigating the effects of exposures to different oxygen levels using Phoxinus lagowskii (a high-latitude, cold-water fish) as a model. Fish were exposed to different oxygen levels (0.5 mg/L and 3 mg/L) for 24 h. The loss of equilibrium (LOE), an indicator of acute hypoxia tolerance, was 0.21 ± 0.01 mg/L, revealing the ability of fish to tolerate low-oxygen conditions. We sought to determine if, in P. lagowskii, the histology of gills and liver, blood indicators, enzyme activities of carbohydrate and lipid metabolism, and antioxidants changed to relieve stress in response to acute hypoxia. Notably, changes in vigorous jumping behavior under low oxygen revealed the exceptional hypoxia acclimation response compared with other low-latitude fish. A decrease in blood parameters, including RBC, WBC, and Hb, as well as an increase in MCV was observed compared to the controls. The increased total area in lamella and decreased ILCM volume in P. lagowskii gills were detected in the present study. Our results also showed the size of vacuoles in the livers of the hypoxic fish shrunk. Interestingly, an increase in the enzyme activity of lipid metabolism but not glucose metabolism was observed in the groups exposed to hypoxia at 6 h and 24 h. After combining histology and physiology results, our findings provide evidence that lipid metabolism plays a crucial role in enhancing hypoxia acclimation in P. lagowskii. Additionally, SOD activity significantly increased during hypoxia, suggesting the presence of an antioxidant response of P. lagowskii during hypoxia. High expression levels of lipogenesis and lipolysis-related genes were detected in the 6 h 3 mg/L and 24 h 3 mg/L hypoxia group. Enhanced expression of lipid-metabolism genes (ALS4, PGC-1, and FASN) was detected during hypoxia exposure. Together, these data suggest that P. lagowskii’s ability to tolerate hypoxic events is likely mediated by a comprehensive strategy.

缺氧是对水生系统生物多样性的最严重威胁之一。高纬度鱼类通过组织学和生理反应耐受缺氧的能力大多是未知的。我们通过使用Phoxinus lagowskii（一种高纬度冷水鱼）作为模型研究暴露于不同氧气水平的影响来解决这一知识差距。鱼暴露于不同的氧气水平（0.5 毫克/升和 3 毫克/升）24 小时。平衡丧失 (LOE) 是急性缺氧耐受性的指标，为 0.21 ± 0.01 毫克/升，表明鱼类耐受低氧条件的能力。我们试图确定是否在P. lagowskii，鳃和肝脏的组织学，血液指标，碳水化合物和脂质代谢的酶活性以及抗氧化剂发生变化以缓解急性缺氧的压力。值得注意的是，与其他低纬度鱼类相比，低氧条件下剧烈跳跃行为的变化揭示了异常的缺氧适应反应。与对照组相比，观察到包括 RBC、WBC 和 Hb 在内的血液参数降低以及 MCV 增加。P. lagowskii薄片总面积增加，ILCM 体积减少在本研究中检测到鳃。我们的结果还显示缺氧鱼肝脏中的液泡大小缩小。有趣的是，在 6 小时和 24 小时暴露于缺氧的组中，观察到脂质代谢的酶活性增加，但没有观察到葡萄糖代谢的酶活性增加。在结合组织学和生理学结果后，我们的研究结果提供了证据，证明脂质代谢在增强P. lagowskii 的缺氧适应方面起着至关重要的作用。此外，在缺氧期间 SOD 活性显着增加，表明在缺氧期间P. lagowskii存在抗氧化反应。在 6 h 3 mg/L 和 24 h 3 mg/L 缺氧组中检测到脂肪生成和脂解相关基因的高表达水平。脂质代谢基因的表达增强（在缺氧暴露期间检测到ALS4、PGC-1和FASN。总之，这些数据表明P. lagowskii耐受缺氧事件的能力可能是由综合策略介导的。