Brijs Jeroen, Jutfelt Fredrik, Clark Timothy D, Gräns Albin, Ekström Andreas, Sandblom Erik
Department of Biological and Environmental Sciences, University of Gothenburg, SE-405 30 Gothenburg, Sweden
Department of Biological and Environmental Sciences, University of Gothenburg, SE-405 30 Gothenburg, Sweden.
J Exp Biol. 2015 Aug;218(Pt 15):2448-54. doi: 10.1242/jeb.121889. Epub 2015 May 29.
A progressive inability of the cardiorespiratory system to maintain systemic oxygen supply at elevated temperatures has been suggested to reduce aerobic scope and the upper thermal limit of aquatic ectotherms. However, few studies have directly investigated the dependence of thermal limits on oxygen transport capacity. By manipulating oxygen availability (via environmental hyperoxia) and blood oxygen carrying capacity (via experimentally induced anaemia) in European perch (Perca fluviatilis Linneaus), we investigated the effects of oxygen transport capacity on aerobic scope and the critical thermal maximum (CT(max)). Hyperoxia resulted in a twofold increase in aerobic scope at the control temperature of 23°C, but this did not translate to an elevated CT(max) in comparison with control fish (34.6±0.1 versus 34.0±0.5°C, respectively). Anaemia (∼43% reduction in haemoglobin concentration) did not cause a reduction in aerobic scope or CT(max) (33.8±0.3°C) compared with control fish. Additionally, oxygen consumption rates of anaemic perch during thermal ramping increased in a similar exponential manner to that in control fish, highlighting that perch have an impressive capacity to compensate for a substantial reduction in blood oxygen carrying capacity. Taken together, these results indicate that oxygen limitation is not a universal mechanism determining the CT(max) of fishes.
有观点认为，心肺系统在温度升高时维持全身氧气供应的能力逐渐下降，会导致水生变温动物的有氧代谢范围和热上限降低。然而，很少有研究直接探究热上限对氧气运输能力的依赖性。通过控制欧洲鲈（Perca fluviatilis Linneaus）的氧气可利用性（通过环境高氧）和血液携氧能力（通过实验诱导贫血），我们研究了氧气运输能力对有氧代谢范围和临界热最大值（CT(max)）的影响。在23°C的对照温度下，高氧导致有氧代谢范围增加了两倍，但与对照鱼相比，这并未转化为更高的CT(max)（分别为34.6±0.1°C和34.0±0.5°C）。与对照鱼相比，贫血（血红蛋白浓度降低约43%）并未导致有氧代谢范围或CT(max)（33.8±0.3°C）降低。此外，贫血鲈鱼在热驯化过程中的耗氧率与对照鱼以相似的指数方式增加，这突出表明鲈鱼具有惊人的能力来补偿血液携氧能力的大幅下降。综上所述，这些结果表明氧气限制并非决定鱼类CT(max)的普遍机制。
