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.244847. Epub 2023 Mar 10.
The impacts of warming temperatures associated with climate change on performance are poorly understood in most mammals. Thermal performance curves are a valuable means of examining the effects of temperature on performance traits, but they have rarely been used in endotherms. Here, we examined the thermal performance curve of endurance running capacity at high temperatures in the deer mouse (Peromyscus maniculatus). Endurance capacity was measured using an incremental speed test on a treadmill, and subcutaneous temperature in the abdominal region was measured as a proxy for body temperature (Tb). Endurance time at 20°C was repeatable but varied appreciably across individuals, and was unaffected by sex or body mass. Endurance capacity was maintained across a broad range of ambient temperatures (Ta) but was reduced above 35°C. Tb during running varied with Ta, and reductions in endurance were associated with Tb greater than 40°C when Ta was above 35°C. At the high Ta that limited endurance running capacity (but not at lower Ta), Tb tended to rise throughout running trials with increases in running speed. Metabolic and thermoregulatory measurements at rest showed that Tb, evaporative water loss and breathing frequency increased at Ta of 36°C and above. Therefore, the upper threshold temperatures at which endurance capacity is impaired are similar to those inducing heat responses at rest in this species. These findings help discern the mechanisms by which deer mice are impacted by warming temperatures, and provide a general approach for examining thermal breadth of performance in small mammals.
在大多数哺乳动物中，与气候变化相关的变暖温度对性能的影响知之甚少。热性能曲线是研究温度对性能特征影响的一种有价值的方法，但在恒温动物中很少使用。在这里，我们研究了鹿鼠（Peromyscus maniculatus）高温下耐力跑步能力的热性能曲线。耐力能力通过在跑步机上进行递增速度测试来测量，腹部区域的皮下温度作为体温（Tb）的替代物进行测量。20°C 时的耐力时间具有可重复性，但个体之间差异很大，不受性别或体重影响。耐力能力在广泛的环境温度（Ta）范围内保持不变，但在 35°C 以上时会降低。跑步时的 Tb 随 Ta 而变化，当 Ta 高于 35°C 时，Tb 大于 40°C 与耐力下降有关。在限制耐力跑步能力的高 Ta 下（而不是在较低的 Ta 下），随着跑步速度的增加，Tb 在整个跑步试验中呈上升趋势。在 Ta 为 36°C 及以上时，休息时的代谢和体温调节测量显示 Tb、蒸发失水和呼吸频率增加。因此，耐力能力受损的上限温度与该物种在休息时引起热反应的温度相似。这些发现有助于了解鹿鼠受变暖温度影响的机制，并为研究小型哺乳动物的性能热广度提供了一种通用方法。
