In ectotherms, the likelihood of surviving an infection is determined by the efficiency of thermoregulation, the availability of a variety of thermal microenvironments, the individual's health status, and the virulence of the infective agent. Physiological and behavioral demands related to an efficient immune response entail a series of costs that compete with other vital activities, specifically energy storage, growth, reproduction, and maintenance functions. Here, we characterize the thermal biology and health status by the presence of injuries, ectoparasites, body condition, and individual immune response capacity (using phytohemagglutinin in a skin-swelling assay) of the southernmost lizards of the world, Liolaemus sarmientoi, endemic to a sub-optimal, cold environment in Patagonia, Argentina. In particular, we study the effect of a bacterial endotoxin (lipopolysaccharide; LPS-treatment) on thermoregulation. We found that the field-active body temperature (Tb) was much lower than the preferred body temperature (Tp) obtained in the laboratory. All the individuals were in good body condition at the beginning of the experiments. The phytohemagglutinin test caused detectable thickening in sole-pads at 2 h and 24 h post-assay in males and non-pregnant females, indicating a significant innate immune response. In the experimental immune challenge, the individuals tended to prefer a low body temperature after LPS-treatment (2 h post-injection) and developed hypothermia, while the control individuals injected with phosphate buffered saline (PBS), maintained their body temperature throughout the trial. In both the LPS-treatment and PBS-control individuals, BC declined during the experiment. Hypothermia may allow this southernmost species to optimize the use of their energetic resources and reduce the costs of thermoregulation in a cold-temperate environment where they rarely attain the mean Tp (35.16 °C) obtained in laboratory.

中文翻译：

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阿根廷巴塔哥尼亚寒冷环境中蜥蜴在应对免疫挑战时的首选温度降低

在变温动物中，感染后存活的可能性取决于体温调节的效率、各种热微环境的可用性、个体的健康状况以及感染因子的毒力。与有效免疫反应相关的生理和行为需求需要与其他重要活动竞争的一系列成本，特别是能量储存、生长、繁殖和维持功能。在这里，我们通过世界上最南端的蜥蜴 Liolaemus sarmientoi 的损伤、外寄生虫、身体状况和个体免疫反应能力（在皮肤肿胀试验中使用植物血凝素）来表征热生物学和健康状况阿根廷巴塔哥尼亚的次优寒冷环境。特别是，我们研究了细菌内毒素（脂多糖；LPS 处理）对体温调节的影响。我们发现现场活动体温 (Tb) 远低于实验室获得的首选体温 (Tp)。在实验开始时，所有个体都处于良好的身体状况。植物血凝素测试导致雄性和非怀孕雌性在检测后 2 小时和 24 小时的脚垫中可检测到增厚，表明存在显着的先天免疫反应。在实验性免疫挑战中，个体在 LPS 治疗后（注射后 2 小时）倾向于选择低体温并出现体温过低，而注射磷酸盐缓冲盐水 (PBS) 的对照个体在整个试验过程中保持体温. 在 LPS 治疗和 PBS 对照个体中，BC 在实验过程中下降。低温可能允许这个最南端的物种优化其能量资源的使用，并降低在冷温带环境中体温调节的成本，在这种环境下，它们很少达到实验室获得的平均 Tp (35.16 °C)。