Arkansas State University, PO Box 599, State University, AR 72467, USA.
Arkansas State University, PO Box 599, State University, AR 72467, USA; Mississippi Department of Wildlife, Fisheries, and Parks, Mississippi Museum of Natural Science, 2148 Riverside Drive Jackson, MS 39202, USA.
Gen Comp Endocrinol. 2023 Aug 1;339:114288. doi: 10.1016/j.ygcen.2023.114288. Epub 2023 Apr 13.
When access to resources is limited, organisms must shift energy investment among physiological processes to survive, reproduce, and respond to unpredictable events. The shifting of these limited resources among processes may result in physiological tradeoffs, often mediated by glucocorticoids. We assessed relationships among the physiological processes of immunity, reproduction, and the stress response in wild adult red-eared slider turtles (Trachemys scripta elegans). Red-eared sliders exhibit a multi-clutching reproductive strategy that requires high energetic investment in reproduction at the beginning of the nesting season in females. Males mate in spring and undergo spermatogenesis and mating in late summer/early fall. We expected to observe tradeoffs when investment toward reproductive processes was particularly demanding. To test this, we subjected 123 individuals to a standardized acute stressor and collected blood to measure innate immunocompetence and circulating steroid hormone concentrations. Tradeoffs between female reproduction and immunocompetence occurred early in the nesting season. This high reproductive investment was evident by heightened circulating progesterone and reduced baseline innate immunity. Corticosterone (CORT) was also high during this period, indicating a role in facilitating allocation of energy. Tradeoffs were not as evident in males, though males upregulated innate immune function, baseline CORT, and testosterone prior to fall spermatogenesis and mating. Throughout the entire sampling period, both males and females increased CORT and immunocompetence following the acute standardized stressor. Taken together, we concluded that reproduction requires shifts in energy allocation in during the highest reproductive period for females but all individuals in this population remain able to respond to the standardized stressor even during increased reproductive investment. These findings reinforce the continuing evidence that physiological relationships are context-dependent and resource demands are dynamic across the reproductive season.
当资源有限时，生物必须在生理过程中重新分配能量投资，以生存、繁殖和应对不可预测的事件。这些有限资源在过程之间的转移可能导致生理权衡，通常由糖皮质激素介导。我们评估了野生成年红耳滑龟（Trachemys scripta elegans）的免疫、繁殖和应激反应生理过程之间的关系。红耳滑龟表现出多窝繁殖策略，在繁殖季节开始时雌性需要大量的能量投资来繁殖。雄性在春季交配，并在夏末/初秋进行精子发生和交配。当繁殖过程的投资要求特别高时，我们预计会观察到权衡。为了检验这一点，我们对 123 个个体进行了标准化的急性应激源处理，并采集血液以测量先天免疫能力和循环类固醇激素浓度。在繁殖季节早期，雌性繁殖和免疫能力之间存在权衡。这一高繁殖投资的证据是循环孕酮升高和基础先天免疫力降低。在此期间，皮质酮（CORT）也很高，表明在促进能量分配方面发挥了作用。雄性的权衡并不明显，尽管雄性在秋季精子发生和交配前上调了先天免疫功能、基础 CORT 和睾酮。在整个采样期间，雄性和雌性在经历急性标准化应激源后，CORT 和免疫能力均增加。总的来说，我们得出结论，繁殖需要在雌性繁殖高峰期重新分配能量，但在这个种群中的所有个体仍然能够对标准化应激源做出反应，即使在繁殖投资增加的情况下也是如此。这些发现强化了一个持续的证据，即生理关系是依赖于环境的，资源需求在繁殖季节是动态的。
