Lefevre Sjannie, Wang Tobias, McKenzie David J
Section for Physiology and Cell Biology, Department of Biosciences, University of Oslo, 0316 Oslo, Norway
Department of Biology - Zoophysiology, Aarhus University, 8000 Aarhus C, Denmark.
J Exp Biol. 2021 Feb 24;224(Pt Suppl 1):jeb238840. doi: 10.1242/jeb.238840.
Warming of aquatic environments as a result of climate change is already having measurable impacts on fishes, manifested as changes in phenology, range shifts and reductions in body size. Understanding the physiological mechanisms underlying these seemingly universal patterns is crucial if we are to reliably predict the fate of fish populations with future warming. This includes an understanding of mechanisms for acute thermal tolerance, as extreme heatwaves may be a major driver of observed effects. The hypothesis of gill oxygen limitation (GOL) is claimed to explain asymptotic fish growth, and why some fish species are decreasing in size with warming; but its underlying assumptions conflict with established knowledge and direct mechanistic evidence is lacking. The hypothesis of oxygen- and capacity-limited thermal tolerance (OCLTT) has stimulated a wave of research into the role of oxygen supply capacity and thermal performance curves for aerobic scope, but results vary greatly between species, indicating that it is unlikely to be a universal mechanism. As thermal performance curves remain important for incorporating physiological tolerance into models, we discuss potentially fruitful alternatives to aerobic scope, notably specific dynamic action and growth rate. We consider the limitations of estimating acute thermal tolerance by a single rapid measure whose mechanism of action is not known. We emphasise the continued importance of experimental physiology, particularly in advancing our understanding of underlying mechanisms, but also the challenge of making this knowledge relevant to the more complex reality.
气候变化导致的水生环境变暖已经对鱼类产生了可测量的影响，表现为物候变化、分布范围转移和体型减小。如果我们要可靠地预测未来变暖情况下鱼类种群的命运，了解这些看似普遍模式背后的生理机制至关重要。这包括了解急性热耐受性机制，因为极端热浪可能是观察到的影响的主要驱动因素。鳃氧限制（GOL）假说据称可以解释鱼类的渐近生长，以及为什么一些鱼类物种随着变暖而体型减小；但其基本假设与现有知识相冲突，且缺乏直接的机制证据。氧和容量限制热耐受性（OCLTT）假说激发了一波关于氧气供应能力和有氧范围热性能曲线作用的研究，但不同物种的结果差异很大，这表明它不太可能是一种普遍机制。由于热性能曲线对于将生理耐受性纳入模型仍然很重要，我们讨论了有氧范围的潜在有效替代方案，特别是特定动力作用和生长速率。我们考虑了通过一种作用机制未知的单一快速测量来估计急性热耐受性的局限性。我们强调实验生理学的持续重要性，特别是在推进我们对潜在机制的理解方面，但也强调了使这些知识与更复杂的现实相关的挑战。
