Bauerlien Cory J, Hartman Kyle J
West Virginia University, Wildlife and Fisheries Resources Program, 1145 Evansdale Drive, Morgantown, WV, 26505, USA.
West Virginia University, Wildlife and Fisheries Resources Program, 1145 Evansdale Drive, Morgantown, WV, 26505, USA.
J Therm Biol. 2025 Jul;131:104182. doi: 10.1016/j.jtherbio.2025.104182. Epub 2025 Jun 19.
Research evaluating ectotherm thermal tolerance has primarily employed a metric designed for comparisons of thermal limits across individuals, populations, and species (i.e., critical thermal maximum; CT) which, as a relative index, has limited direct ecological application. Therefore, we sought to develop methodology and test the repeatability of a thermal tolerance metric (critical temperature; T) describing the temperature at which the instantaneous thermal injury and instantaneous recovery rates are equal in an individual, representing a threshold for physiological disruption. Over a four-month period, we conducted repeated thermal tolerance assays on Brook Trout Salvelinus fontinalis briefly conditioned to different temperatures (T: 12-20 °C). During these thermal tolerance assays, we recorded CT and used subsequent temperature profiles to estimate T following a balance equation. We then estimated the adjusted repeatability (R) of these metrics across individual fish. T was moderately repeatable (R = 0.19 ± 0.04) but less repeatable than CT (R = 0.54 ± 0.03), which was expected from the additional sensitivity of the estimation process. Models indicated that T and CT decreased with repeated assays, suggesting that repeated exposure to stressful temperatures may reduce seasonal-scale adaptive capacity within individual Brook Trout (i.e., "heat weakening"). Additionally, T increased with increasing conditioning temperatures, which could indicate the presence of acute physiological adaptive effects from short-term temperature exposures that could mitigate heat stress during heating events. Our study provides a methodology for estimating a thermal tolerance metric that is more closely tied with physiology and individual performance, which could prove useful for applying estimated thermal limits to ecological models and quantifying population effects from climate change.
评估变温动物热耐受性的研究主要采用了一种用于比较个体、种群和物种热极限的指标（即热极限最大值；CT），作为一个相对指标，它的直接生态应用有限。因此，我们试图开发一种方法，并测试一种热耐受性指标（临界温度；T）的可重复性，该指标描述了个体中瞬时热损伤和瞬时恢复率相等时的温度，代表了生理紊乱的阈值。在四个月的时间里，我们对短暂适应不同温度（T：12 - 20°C）的溪红点鲑（Salvelinus fontinalis）进行了重复的热耐受性测定。在这些热耐受性测定过程中，我们记录了CT，并使用随后的温度曲线通过平衡方程来估计T。然后，我们估计了这些指标在个体鱼之间的调整后可重复性（R）。T的可重复性适中（R = 0.19 ± 0.04），但比CT的可重复性低（R = 0.54 ± 0.03），从估计过程的额外敏感性来看，这是预期的。模型表明，T和CT随着重复测定而降低，这表明反复暴露于压力温度可能会降低个体溪红点鲑在季节尺度上的适应能力（即“热弱化”）。此外，T随着适应温度的升高而增加，这可能表明短期温度暴露存在急性生理适应效应，可在升温事件期间减轻热应激。我们的研究提供了一种估计热耐受性指标的方法，该指标与生理学和个体表现更紧密相关，这可能有助于将估计的热极限应用于生态模型，并量化气候变化对种群的影响。
