Dichiera Angelina M, Hannan Kelly D, Kwan Garfield T, Fangue Nann A, Schulte Patricia M, Brauner Colin J
Department of Zoology, The University of British Columbia, Vancouver, British Columbia, Canada.
Department of Wildlife, Fish and Conservation Biology, University of California Davis, Davis, California, USA.
Conserv Physiol. 2025 Jan 6;13(1):coae089. doi: 10.1093/conphys/coae089. eCollection 2025.
Assessing how at-risk species respond to co-occurring stressors is critical for predicting climate change vulnerability. In this study, we characterized how young-of-the-year White Sturgeon () cope with warming and low oxygen (hypoxia) and investigated whether prior exposure to one stressor may improve the tolerance to a subsequent stressor through "cross-tolerance". Fish were acclimated to five temperatures within their natural range (14-22°C) for one month prior to assessment of thermal tolerance (critical thermal maxima, CTmax) and hypoxia tolerance (incipient lethal oxygen saturation, ILOS; tested at 20°C). White Sturgeon showed a high capacity for thermal acclimation, linearly increasing thermal tolerance with increasing acclimation temperature (slope = 0.55, adjusted R = 0.79), and an overall acclimation response ratio (ARR) of 0.58, from 14°C (CTmax = 29.4 ± 0.2°C, mean ± S.E.M.) to 22°C (CTmax = 34.1 ± 0.2°C). Acute warming most negatively impacted hypoxia tolerance in 14°C-acclimated fish (ILOS = 15.79 ± 0.74% air saturation), but prior acclimation to 20°C conferred the greatest hypoxia tolerance at this temperature (ILOS = 2.60 ± 1.74% air saturation). Interestingly, individuals that had been previously tested for thermal tolerance had lower hypoxia tolerance than naïve fish that had no prior testing. This was particularly apparent for hypoxia-tolerant 20°C-acclimated fish, whereas naïve fish persisted the entire 15-h duration of the hypoxia trial and did not lose equilibrium at air saturation levels below 20%. Warm-acclimated fish demonstrated significantly smaller relative ventricular mass, indicating potential changes to tissue oxygen delivery, but no other changes to red blood cell characteristics and somatic indices. These data suggest young-of-the-year White Sturgeon are resilient to warming and hypoxia, but the order in which these stressors are experienced and whether exposures are acute or chronic may have important effects on phenotype.
评估濒危物种如何应对同时出现的压力源对于预测气候变化脆弱性至关重要。在本研究中，我们描述了当年幼龄白鲟如何应对变暖和低氧（缺氧）情况，并研究了先前暴露于一种压力源是否可能通过“交叉耐受”提高对后续压力源的耐受性。在评估热耐受性（临界热最大值，CTmax）和缺氧耐受性（初始致死氧饱和度，ILOS；在20°C下测试）之前，将鱼在其自然范围内的五个温度（14 - 22°C）下驯化一个月。白鲟表现出较高的热驯化能力，随着驯化温度的升高，热耐受性呈线性增加（斜率 = 0.55，调整后R = 0.79），总体驯化反应率（ARR）为0.58，从14°C（CTmax = 29.4 ± 0.2°C，平均值 ± 标准误）到22°C（CTmax = 34.1 ± 0.2°C）。急性升温对14°C驯化的鱼的缺氧耐受性负面影响最大（ILOS = 15.79 ± 0.74%空气饱和度），但先前在20°C下驯化在此温度下赋予了最大的缺氧耐受性（ILOS = 2.60 ± 1.74%空气饱和度）。有趣的是，先前接受过热耐受性测试的个体的缺氧耐受性低于未进行过先前测试的幼稚鱼。这在耐缺氧的20°C驯化鱼中尤为明显，而幼稚鱼在缺氧试验的整个15小时期间都能坚持，并且在空气饱和度低于20%时不会失去平衡。暖驯化鱼的相对心室质量显著较小，表明组织氧输送可能发生变化，但红细胞特征和体细胞指数没有其他变化。这些数据表明当年幼龄白鲟对变暖和缺氧具有恢复力，但经历这些压力源的顺序以及暴露是急性还是慢性可能对表型有重要影响。
