School of Life and Environmental Sciences, Deakin University, Geelong, Victoria 3216, Australia.
Proc Biol Sci. 2023 Nov 8;290(2010):20231779. doi: 10.1098/rspb.2023.1779. Epub 2023 Nov 1.
Fish tend to grow faster as the climate warms but attain a smaller adult body size following an earlier age at sexual maturation. Despite the apparent ubiquity of this phenomenon, termed the temperature-size rule (TSR), heated scientific debates have revealed a poor understanding of the underlying mechanisms. At the centre of these debates are prominent but marginally tested hypotheses which implicate some form of 'oxygen limitation' as the proximate cause. Here, we test the role of oxygen limitation in the TSR by rearing juvenile for a full year in current-day (15°C) and forecasted (20°C) summer temperatures while providing half of each temperature group with supplemental oxygen (hyperoxia). True to the TSR, fish in the warm treatments grew faster and reached sexual maturation earlier than their cooler conspecifics. Yet, despite supplemental oxygen significantly increasing maximum oxygen uptake rate, our findings contradict leading hypotheses by showing that the average size at sexual maturation and the adult body size did not differ between normoxia and hyperoxia groups. We did, however, discover that hyperoxia extended the reproductive window, independent of fish size and temperature. We conclude that the intense resource investment in reproduction could expose a bottleneck where oxygen becomes a limiting factor.
鱼类在气候变暖时往往生长得更快，但在性成熟更早的情况下，成年体型会更小。尽管这种被称为“温度-体型规则”（TSR）的现象似乎无处不在，但激烈的科学争论表明，人们对其潜在机制的理解还很有限。在这些争论的核心是一些突出但经过轻微检验的假说，这些假说暗示某种形式的“氧气限制”是其直接原因。在这里，我们通过在当前（15°C）和预测（20°C）夏季温度下饲养幼年鱼类整整一年，并为每个温度组的一半提供额外的氧气（高氧），来检验氧气限制在 TSR 中的作用。正如 TSR 所预测的那样，温暖处理组的鱼类比较凉爽的同物种鱼类生长得更快，性成熟得更早。然而，尽管补充氧气显著提高了最大耗氧量，但我们的研究结果与主导假说相矛盾，表明性成熟时的平均体型和成年体型在常氧和高氧组之间没有差异。然而，我们确实发现高氧延长了繁殖窗口，而与鱼类的大小和温度无关。我们的结论是，对繁殖的强烈资源投入可能会暴露一个瓶颈，在这个瓶颈中氧气成为一个限制因素。
