Mitrani Department of Desert Ecology, Swiss Institute for Dryland Environmental and Energy Research, Jacob Blaustein Institutes for Desert Research, Ben Gurion University of the Negev, Sede Boqer Campus, 8499000 Midreshet Ben Gurion, Israel.
Wyler Department of Dryland Agriculture, French Associates Institute for Agriculture and Biotechnology of Drylands, Jacob Blaustein Institutes for Desert Research, Ben Gurion University of the Negev, Sede Boqer Campus, 8499000 Midreshet Ben Gurion, Israel.
Int J Parasitol. 2021 Jul;51(8):659-666. doi: 10.1016/j.ijpara.2020.12.005. Epub 2021 Mar 11.
Biotic and abiotic stressors impose various fitness costs on individuals across a variety of taxa. In vertebrates, these stressors typically trigger complex neuroendocrine responses that stimulate glucocorticoid (GC) secretion from the adrenal cortex. Short-term elevation of GCs can be adaptive as it shifts energy toward physiological processes that cope with acute stressors; however, chronic increases in GC levels could have detrimental effects on fitness. Parasitism can be considered an important biotic stressor in nature and a possible cause of reproductive failure that could substantially affect an individual's fitness. Thus, we aimed to test the effects of parasitism and maternal stress, as measured by GCs, during pregnancy and the relationship between these variables and measures of reproductive output using a rodent-flea system. Female Egyptian spiny mice (Acomys cahirinus) were randomly assigned to flea (Parapulex chephrenis) infested or uninfested treatments before and during pregnancy. The offspring of these females were flea-free. Feces were collected at five time points during the experiment to determine maternal fecal glucocorticoid metabolite (FGCM) concentrations. Overall, infested females had lower FGCM levels during gestation but higher FGCM levels post-parturition and larger mass changes than uninfested females. Additionally, models related to pup quality and quantity often included some measure of maternal investment or body condition moderating relationships between infestation and stress. This suggests that flea parasitism or high GC levels alone might not significantly impact host reproduction but rather females can experience different effects depending on their level of investment, which could be limited by body condition and/or the number of pups present in a litter.
生物和非生物胁迫因素会对各种分类单元的个体造成各种适应成本。在脊椎动物中，这些胁迫因素通常会引发复杂的神经内分泌反应，刺激肾上腺皮质分泌糖皮质激素（GC）。短期 GC 水平升高可能具有适应性，因为它将能量转移到应对急性胁迫的生理过程中；然而，GC 水平的慢性升高可能对适应度产生不利影响。寄生虫可以被认为是自然界中重要的生物胁迫因素，也是生殖失败的可能原因，这可能会对个体的适应度产生重大影响。因此，我们旨在测试寄生虫和母体应激（通过 GC 测量）在怀孕期间的影响，以及这些变量与使用啮齿动物-跳蚤系统测量生殖输出之间的关系。雌性埃及刺鼠（Acomys cahirinus）在怀孕前和怀孕期间被随机分配到跳蚤（Parapulex chephrenis）感染或未感染的处理组。这些雌性的后代没有跳蚤。在实验的五个时间点收集粪便，以确定母体粪便糖皮质激素代谢物（FGCM）浓度。总体而言，感染组雌性在妊娠期的 FGCM 水平较低，但在分娩后 FGCM 水平较高，体重变化较大。此外，与幼崽质量和数量相关的模型通常包括母体投资或身体状况的某种衡量标准，以调节感染和应激之间的关系。这表明，跳蚤寄生或高 GC 水平本身可能不会对宿主生殖产生重大影响，而是雌性可以根据其投资水平体验不同的影响，这可能受到身体状况和/或一窝幼崽数量的限制。
