Organisms living in environments with oscillating temperatures may rely on plastic traits to sustain thermal tolerance during high temperature periods. Phenotypic plasticity in critical thermal maximum (CTmax) is a powerful thermoregulative strategy that enables organisms to adjust CTmax when ambient temperatures do not match thermal preference. Given that global temperatures are increasing at an unprecedented rate, identifying factors that affect the plastic response in CTmax can help predict how organisms are likely to respond to changes in their thermal landscape. Using an experimental thermal chamber in the field, we investigated the effect of short-term acclimation on the CTmax and thermal safety margin (TSM) of wild-caught redside dace, Clinostomus elongatus, (n = 197) in a northern population in Two Tree River, Ontario. Streamside CTmax trials were used to identify the maximum temperature at which redside dace maintain equilibrium, providing a powerful tool for understanding how thermal stress affects individual performance. CTmax and TSM of redside dace were sensitive to changes in temperature, regardless of season, suggesting that temperature pulses caused by climate change or urban activities can impose negative fitness consequences year round. Interestingly, an individual's recent thermal history was more influential to its thermal tolerance than the current ambient water temperature. While the CTmax of redside dace increased with body size, the effect of body size on TSM remains unclear based on our models. The results provide insight into the thermal performance of redside dace that, to date, has been difficult to assess due to the species' rarity and lack of suitable streamside protocols.

中文翻译：

---

红边鲮鱼 Clinostomus elongatus 耐热性的季节变化。

生活在温度波动环境中的生物可能依靠塑料特性来维持高温时期的耐热性。临界热最大值 (CTmax) 的表型可塑性是一种强大的温度调节策略，使生物体能够在环境温度与热偏好不匹配时调整 CTmax。鉴于全球气温正以前所未有的速度上升，确定影响 CTmax 塑性反应的因素可以帮助预测生物体可能如何应对其热景观的变化。使用现场实验热室，我们研究了短期驯化对两棵树北部种群中野生捕获的红边鲮鱼 Clinostomus elongatus（n = 197）的 CTmax 和热安全裕度 (TSM) 的影响河，安大略省。Streamside CTmax 试验用于确定红边鲮鱼保持平衡的最高温度，为了解热应激如何影响个体表现提供了强大的工具。无论季节如何，红边鲮鱼的 CTmax 和 TSM 对温度变化都很敏感，这表明气候变化或城市活动引起的温度脉冲可能会全年造成负面的健康后果。有趣的是，一个人最近的热史对其耐热性的影响比当前环境水温的影响更大。虽然红边鲮鱼的 CTmax 随体型增大而增加，但根据我们的模型，体型对 TSM 的影响仍不清楚。这些结果提供了对红边鲮鱼热性能的深入了解，迄今为止，由于该物种的稀有性和缺乏合适的河边协议，很难评估红边鲮鱼的热性能。