Mammal Research Institute, Polish Academy of Sciences, Stoczek 1, Białowieża, Poland.
Faculty of Biology, University of Warsaw, Miecznikowa 1, 02-096, Warszawa, Poland.
Sci Rep. 2022 Feb 8;12(1):2138. doi: 10.1038/s41598-022-05896-3.
The ability of animals to produce endogenous heat provides a buffer against environmental changes but also incurs high energetic costs. Especially small endothermic mammals have high energy demands. Some temperate-zone species (heterotherms) regularly use torpor, which slows down their entire metabolism but also potentially delays reproduction, to compensate for this. We used a unique experimental approach to test the consequences of extended low and high ambient temperatures on the trade-off in energy allocation to body mass maintenance, thermoregulation effort and seasonal sexual maturation in temperate zone male bats. We showed that long exposure to low ambient temperature shifts energy allocation away from sexual maturation to self-maintenance and results in a delay of sperm maturation by as much as an entire month. This effect was partially buffered by higher body mass. Heavier bats were able to afford more intensive thermoregulation and consequently speed up maturation. Interestingly, bats at constant high temperatures avoided deep torpor and matured faster than those at low temperatures, but sperm production was also slower than under natural conditions. Our results show that not only low, but also constant high ambient temperatures are detrimental during seasonal sexual maturation and the trade-off between investing into self-maintenance and fitness is a finely tuned compromise.
动物产生内源性热量的能力为它们提供了抵御环境变化的缓冲，但也带来了很高的能量成本。特别是小型恒温哺乳动物有很高的能量需求。一些温带物种（异温动物）经常使用蛰伏来补偿这种情况，蛰伏会减缓它们整个新陈代谢，但也可能会延迟繁殖。我们使用了一种独特的实验方法来测试长时间处于低温和高温环境对温带雄性蝙蝠在能量分配上的权衡的影响，这种权衡涉及到身体质量维持、体温调节努力和季节性性成熟。我们表明，长时间暴露在低温环境会将能量分配从性成熟转移到自我维持上，导致精子成熟延迟多达整整一个月。这种影响部分被更高的体重所缓冲。更重的蝙蝠能够承受更密集的体温调节，因此成熟速度更快。有趣的是，恒温下的蝙蝠避免了深度蛰伏，并且比低温下的蝙蝠成熟得更快，但精子的产生速度也比自然条件下慢。我们的结果表明，不仅低温，而且恒定的高温在季节性性成熟期间都是有害的，而在自我维持和适应度之间进行投资的权衡是一种精细的妥协。
