Auer Sonya K, Agreda Emily, Chen Angela Hsuan, Irshad Madiha, Solowey Julia
Williams College, Williamstown, MA, USA.
Williams College, Williamstown, MA, USA.
J Therm Biol. 2021 Jul;99:103022. doi: 10.1016/j.jtherbio.2021.103022. Epub 2021 Jun 4.
Upper thermal limits are considered a key determinant of a population's ability to persist in the face of extreme heat events. However, these limits differ considerably among individuals within a population, and the mechanisms underlying this differential sensitivity are not well understood. Upper thermal tolerance in aquatic ectotherms is thought to be determined by a mismatch between oxygen supply and the increased metabolic demands associated with warmer waters. As such, tolerance is expected to decline during reproduction given the heightened oxygen demand for gamete production and maintenance. Among live-bearing species, upper thermal tolerance of reproductive adults may decline even further after fertilization due to the cost of meeting the increasing oxygen demands of developing embryos. We examined the upper thermal tolerance of live-bearing female Trinidadian guppies at different stages of reproduction and found that critical thermal maximum was similar during the egg yolking and early embryos stage but then declined by almost 0.5 °C during late pregnancy when oxygen demands are the greatest. These results are consistent with the hypothesis that oxygen limitation sets thermal limits and show that reproduction is associated with a decline in upper thermal tolerance.
高温上限被认为是一个种群在面对极端高温事件时持续生存能力的关键决定因素。然而，种群内个体之间的这些上限差异很大，而且这种差异敏感性背后的机制尚未得到很好的理解。水生变温动物的高温耐受性被认为是由氧气供应与温暖水域相关的代谢需求增加之间的不匹配所决定的。因此，鉴于配子生产和维持对氧气的需求增加，预计繁殖期间耐受性会下降。在胎生物种中，由于满足发育中胚胎不断增加的氧气需求的成本，受精后生殖成年个体的高温耐受性可能会进一步下降。我们研究了胎生的特立尼达孔雀鱼在不同繁殖阶段的高温耐受性，发现临界热最大值在卵黄形成和胚胎早期阶段相似，但在妊娠后期氧气需求最大时下降了近0.5°C。这些结果与氧气限制设定热极限的假设一致，并表明繁殖与高温耐受性的下降有关。
