Department of Biology, McMaster University, 1280 Main Street West, Hamilton, ON, Canada, L8S 4K1.
J Exp Biol. 2023 Mar 1;226(5). doi: 10.1242/jeb.244852. Epub 2023 Mar 9.
Climate warming could challenge the ability of endotherms to thermoregulate and maintain normal body temperature (Tb), but the effects of warming summer temperatures on activity and thermoregulatory physiology in many small mammals remain poorly understood. We examined this issue in deer mice (Peromyscus maniculatus), an active nocturnal species. Mice were exposed in the lab to simulated seasonal warming, in which an environmentally realistic diel cycle of ambient temperature (Ta) was gradually warmed from spring conditions to summer conditions (controls were maintained in spring conditions). Activity (voluntary wheel running) and Tb (implanted bio-loggers) were measured throughout, and indices of thermoregulatory physiology (thermoneutral zone, thermogenic capacity) were assessed after exposure. In control mice, activity was almost entirely restricted to the night-time, and Tb fluctuated ∼1.7°C between daytime lows and night-time highs. Activity, body mass and food consumption were reduced and water consumption was increased in later stages of summer warming. This was accompanied by strong Tb dysregulation that culminated in a complete reversal of the diel pattern of Tb variation, with Tb reaching extreme highs (∼40°C) during daytime heat but extreme lows (∼34°C) at cooler night-time temperatures. Summer warming was also associated with reduced ability to generate body heat, as reflected by decreased thermogenic capacity and decreased mass and uncoupling protein (UCP1) content of brown adipose tissue. Our findings suggest that thermoregulatory trade-offs associated with daytime heat exposure can affect Tb and activity at cooler night-time temperatures, impacting the ability of nocturnal mammals to perform behaviours important for fitness in the wild.
气候变暖可能会挑战恒温动物调节体温和维持正常体温 (Tb) 的能力，但变暖的夏季温度对许多小型哺乳动物的活动和体温调节生理的影响仍知之甚少。我们在鹿鼠（Peromyscus maniculatus）中研究了这个问题，鹿鼠是一种活跃的夜间物种。实验室中，老鼠暴露在模拟的季节性变暖环境中，环境中真实的昼夜温度（Ta）日循环逐渐从春季条件升温到夏季条件（对照组维持在春季条件）。整个过程中测量了活动（自愿轮跑）和 Tb（植入的生物记录器），并在暴露后评估了体温调节生理的指标（体温中立区、产热能力）。在对照组老鼠中，活动几乎完全局限于夜间，Tb 在白天的最低点和夜间的最高点之间波动约 1.7°C。在夏季变暖的后期，活动、体重和食物消耗减少，水消耗增加。这伴随着强烈的 Tb 失调，最终导致 Tb 变化的昼夜模式完全逆转，白天高温时 Tb 达到极端高温（约 40°C），但夜间较冷时 Tb 达到极端低温（约 34°C）。夏季变暖还与产热能力下降有关，这反映在产热能力下降以及棕色脂肪组织的质量和解偶联蛋白 (UCP1) 含量减少。我们的研究结果表明，与白天热暴露相关的体温调节权衡可能会影响在夜间较冷温度时的 Tb 和活动，影响夜间哺乳动物在野外进行对适应能力重要的行为的能力。
