Dichiera Angelina M, Khursigara Alexis J, Esbaugh Andrew J
The University of Texas at Austin Marine Science Institute, 750 Channel View Drive, Port Aransas, TX 78373, USA.
The University of North Texas, 1155 Union Circle #305220, Denton, TX 76203, USA.
Comp Biochem Physiol A Mol Integr Physiol. 2021 Oct;260:111033. doi: 10.1016/j.cbpa.2021.111033. Epub 2021 Jul 9.
Measures of fitness are valuable tools to predict species' responses to environmental changes, like increased water temperature. Aerobic scope (AS) is a measure of an individual's capacity for aerobic processes, and frequently used as a proxy for fitness. However, AS is complicated by individual variation found not only within a species, but within similar body sizes as well. Maximum metabolic rate (MMR), one of the factors determining AS, is constrained by an individual's ability to deliver and extract oxygen (O) at the tissues. Recently, data has shown that red blood cell carbonic anhydrase (RBC CA) is rate-limiting for O delivery in red drum (Sciaenops ocellatus). We hypothesized increased temperature impacts MMR and RBC CA activity in a similar manner, and that an individual's RBC CA activity drives individual variation in AS. Red drum were acutely exposed to increased temperature (+6 °C; 22 °C to 28 °C) for 24 h prior to exhaustive exercise and intermittent-flow respirometry at 28 °C. RBC CA activity was measured before temperature exposure and after aerobic performance. Due to enzymatic thermal sensitivity, acute warming increased individual RBC CA activity by 36%, while there was no significant change in the control (22 °C) treatment. Interestingly, average MMR of the acute warming treatment was 36% greater than that of control drum. However, we found no relationships between individual RBC CA activity and their respective MMR and AS at either temperature. While warming similarly affects RBC CA activity and MMR, RBC CA activity is not a predictor of individual MMR.
健康指标是预测物种对环境变化（如水温升高）反应的重要工具。有氧代谢范围（AS）是衡量个体有氧代谢过程能力的指标，常被用作健康状况的替代指标。然而，AS不仅在物种内部存在个体差异，在相似体型个体中也存在差异，这使得AS变得复杂。最大代谢率（MMR）是决定AS的因素之一，它受个体在组织中输送和提取氧气（O）能力的限制。最近，数据表明红细胞碳酸酐酶（RBC CA）在红鼓鱼（Sciaenops ocellatus）的氧气输送中起限速作用。我们假设温度升高会以类似方式影响MMR和RBC CA活性，并且个体的RBC CA活性会导致AS的个体差异。在28°C下进行力竭运动和间歇流呼吸测定之前，将红鼓鱼急性暴露于升高的温度（+6°C；从22°C升至28°C）24小时。在温度暴露前和有氧性能测试后测量RBC CA活性。由于酶的热敏感性，急性升温使个体RBC CA活性增加了36%，而在对照（22°C）处理中没有显著变化。有趣的是，急性升温处理的平均MMR比对照鱼高36%。然而，我们发现在任一温度下，个体RBC CA活性与其各自的MMR和AS之间均无关联。虽然升温对RBC CA活性和MMR的影响相似，但RBC CA活性并不是个体MMR的预测指标。
