'Polar gigantism' describes a biogeographic pattern in which many ectotherms in polar seas are larger than their warmer-water relatives. Although many mechanisms have been proposed, one idea-the oxygen-temperature hypothesis-has received significant attention because it emerges from basic biophysical principles and is appealingly straightforward and testable. Low temperatures depress metabolic demand for oxygen more than supply of oxygen from the environment to the organism. This creates a greater ratio of oxygen supply to demand, releasing polar organisms from oxygen-based constraints on body size. Here we review evidence for and against the oxygen-temperature hypothesis. Some data suggest that larger-bodied taxa live closer to an oxygen limit, or that rising temperatures can challenge oxygen delivery systems; other data provide no evidence for interactions between body size, temperature, and oxygen sufficiency. We propose that these findings can be partially reconciled by recognizing that the oxygen-temperature hypothesis focuses primarily on passive movement of oxygen, implicitly ignoring other important processes including ventilation of respiratory surfaces or internal transport of oxygen by distribution systems. Thus, the hypothesis may apply most meaningfully to organisms with poorly developed physiological systems (eggs, embryos, egg masses, juveniles or adults without mechanisms for ventilating internal or external surfaces). Finally, most tests of the oxygen-temperature hypothesis have involved short-term experiments. Many organisms can mount effective responses to physiological challenges over short time periods; however, the energetic cost of doing so may have impacts that appear only in the longer term. We therefore advocate a renewed focus on long-term studies of oxygen-temperature interactions.

中文翻译：

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重新考虑极地巨人的氧温度假说：成功、失败和细微差别

“极地巨人现象”描述了一种生物地理模式，其中极地海域的许多变温动物比它们在温暖水域的亲戚大。尽管已经提出了许多机制，但一个想法——氧温度假说——受到了极大的关注，因为它来自基本的生物物理原理，并且非常直接和可测试。低温会抑制代谢对氧气的需求，而不是从环境到生物体的氧气供应。这创造了更大的氧气供需比，使极地生物摆脱了基于氧气的体型限制。在这里，我们回顾了支持和反对氧气温度假说的证据。一些数据表明，体型较大的分类群更接近氧气极限，或者温度上升会挑战氧气输送系统；其他数据没有提供关于体型、温度和氧气充足度之间相互作用的证据。我们认为，通过认识到氧气温度假说主要关注氧气的被动运动，隐含地忽略了其他重要过程，包括呼吸表面的通风或分配系统的内部氧气输送，可以部分协调这些发现。因此，该假设可能最有意义地适用于生理系统发育不良的生物体（卵、胚胎、卵块、幼体或成体，没有内部或外部表面通风机制）。最后，氧气温度假说的大多数测试都涉及短期实验。许多生物体可以在短时间内对生理挑战做出有效反应；然而，这样做的能量成本可能会产生只在长期内出现的影响。因此，我们主张重新关注氧-温度相互作用的长期研究。