Noer Natasja Krog, Sørensen Mathias Hamann, Colinet Hervé, Renault David, Bahrndorff Simon, Kristensen Torsten Nygaard
Department of Chemistry and Bioscience, Aalborg University, Aalborg, Denmark.
UMR 6553, CNRS, Ecosystèmes, Biodiversité, Évolution, University of Rennes 1, Rennes, France.
Front Physiol. 2022 Feb 16;13:818485. doi: 10.3389/fphys.2022.818485. eCollection 2022.
Laboratory investigations on terrestrial model-species, typically of temperate origin, have demonstrated that terrestrial ectotherms can cope with daily temperature variations through rapid hardening responses. However, few studies have investigated this ability and its physiological basis in the field. Especially in polar regions, where the temporal and spatial temperature variations can be extreme, are hardening responses expected to be important. Here, we examined diurnal adjustments in heat and cold tolerance in the Greenlandic seed bug by collecting individuals for thermal assessment at different time points within and across days. We found a significant correlation between observed heat or cold tolerance and the ambient microhabitat temperatures at the time of capture, indicating that continuously and within short time-windows respond physiologically to thermal changes and/or other environmental variables in their microhabitats. Secondly, we assessed underlying metabolomic fingerprints using GC-MS metabolomics in a subset of individuals collected during days with either low or high temperature variation. Concentrations of metabolites, including sugars, polyols, and free amino acids varied significantly with time of collection. For instance, we detected elevated sugar levels in animals caught at the lowest daily field temperatures. Polyol concentrations were lower in individuals collected in the morning and evening and higher at midday and afternoon, possibly reflecting changes in temperature. Additionally, changes in concentrations of metabolites associated with energetic metabolism were observed across collection times. Our findings suggest that in these extreme polar environments hardening responses are marked and likely play a crucial role for coping with microhabitat temperature variation on a daily scale, and that metabolite levels are actively altered on a daily basis.
对通常起源于温带的陆地模式物种进行的实验室研究表明，陆地变温动物可以通过快速的硬化反应来应对每日的温度变化。然而，很少有研究在野外调查这种能力及其生理基础。特别是在极地地区，那里的时空温度变化可能非常极端，硬化反应预计会很重要。在这里，我们通过在一天内和不同天的不同时间点收集个体进行热评估，研究了格陵兰种子蝽对热和冷耐受性的昼夜调整。我们发现观察到的热耐受性或冷耐受性与捕获时的周围微生境温度之间存在显著相关性，这表明它们在短时间内持续对微生境中的热变化和/或其他环境变量做出生理反应。其次，我们在温度变化低或高的日子里收集的一部分个体中，使用气相色谱 - 质谱代谢组学评估潜在的代谢组指纹。包括糖类、多元醇和游离氨基酸在内的代谢物浓度随收集时间有显著变化。例如，我们在每日田间最低温度下捕获的动物中检测到糖水平升高。多元醇浓度在早晨和晚上收集的个体中较低，在中午和下午较高，这可能反映了温度的变化。此外，在不同收集时间观察到与能量代谢相关的代谢物浓度变化。我们的研究结果表明，在这些极端的极地环境中，硬化反应很明显，并且可能在应对每日尺度的微生境温度变化中起关键作用，而且代谢物水平每天都会发生积极变化。
