Department of Biology, University of Florida, Gainesville, FL 32611, USA.
Department of Comparative Biosciences, University of Wisconsin-Madison, Madison, WI 53706, USA
J Exp Biol. 2019 Nov 13;222(Pt 22):jeb203646. doi: 10.1242/jeb.203646.
The critical O tension () is the lowest at which an animal can maintain some benchmark rate of O uptake ( ). This has long served as a comparator of hypoxia tolerance in fishes and aquatic invertebrates, but its usefulness in this role, particularly when applied to fishes, has recently been questioned. We believe that remains a useful comparator of hypoxia tolerance provided it is determined using the proper methods and hypoxia tolerance is clearly defined. Here, we review the available methods for each of the three steps of determination: (1) measuring the most appropriate benchmark state for determination (, the required to support standard metabolic rate); (2) reducing water ; and (3) calculating from the versus curve. We make suggestions on best practices for each step and for how to report results to maximize their comparative value. We also discuss the concept of hypoxia tolerance and how relates to a fish's overall hypoxia tolerance. When appropriate methods are used, provides useful comparative physiological and ecological information about the aerobic contributions to a fish's hypoxic survival. When paired with other hypoxia-related physiological measurements (e.g. lactate accumulation, calorimetry-based measurements of metabolic depression, loss-of-equilibrium experiments), contributes to a comprehensive understanding of how a fish combines aerobic metabolism, anaerobic metabolism and metabolic depression in an overall strategy for hypoxia tolerance.
关键的氧张力（）是动物能够维持某些基准氧摄取率（）的最低值。长期以来，这一直是鱼类和水生无脊椎动物耐缺氧能力的比较基准，但最近有人质疑其在这一角色中的有效性，特别是在鱼类方面。我们认为，只要使用正确的方法来确定，并且明确界定了耐缺氧能力，仍然是一种有用的耐缺氧能力比较基准。在这里，我们回顾了确定的三个步骤的可用方法：（1）测量确定所需的最适当的基准状态（，以支持标准代谢率）；（2）降低水；（3）根据与的曲线计算。我们对每个步骤的最佳实践以及如何报告结果以最大程度地提高其比较价值提出了建议。我们还讨论了耐缺氧能力的概念以及与鱼类整体耐缺氧能力的关系。当使用适当的方法时，提供了有关鱼类在缺氧生存中对需氧贡献的有用比较生理和生态信息。当与其他与缺氧相关的生理测量（例如，乳酸积累，基于量热法的代谢抑制测量，失衡实验）相结合时，有助于全面了解鱼类如何将需氧代谢，无氧代谢和代谢抑制结合在一起，形成其整体耐缺氧策略。
