Thermal responses in Halocaridina rubra

Animals may respond to threats from climate change through plastic physiological changes (i.e., acclimation), adaptive evolution (i.e., genetic change), or moving to habitats that match their climatic niche. Organisms from volcanic habitats are underexplored but may serve as models for physiological and evolutionary responses to warming temperatures. Here, we examined how different lineages of the Hawaiian anchialine shrimp <i>Halocaridina rubra</i> respond to temperature, including animals from noticeably warm habitats created during eruptions of Kilauea in 2018. We find that thermal limits are elevated in animals from newer, warm habitats, but decrease to match the thermal range of animals from older, cooler habitats after being maintained at room temperature, suggesting thermal limits are shaped by acclimation and may show limited evolutionary potential. In contrast, metabolic rates show almost no acclimation responses to temperature, with rates largely explained by test, not acclimation temperatures. There was little difference in thermal acclimation of metabolic rates among animals from different genetic lineages. However, metabolic rates in general were different among shrimps from different genetic lineages, suggesting genetic variation for aerobic metabolism could be a target of selection during climate change. We find that shrimp from newer, warm habitats are living at or near their critical thermal maximum, suggesting some anchialine species may be able to deal with increased temperatures from climate change by being pre-adapted to colonize warm habitats associated with volcanism. We also highlight the potential impacts of climate change on anchialine habitats and suitable experimental designs for categorizing and quantifying thermal acclimation of biological rates.

动物可通过可塑性生理变化（即驯化，acclimation）、适应性进化（即遗传改变），或是迁徙至匹配其气候生态位的栖息地，以应对气候变化带来的生存威胁。火山栖息地的生物尚未得到充分研究，但可作为探究生物对升温的生理与进化响应的模式生物。本研究以夏威夷锚地虾（Halocaridina rubra）的不同遗传谱系为对象，探究其对温度的响应，样本涵盖2018年基拉韦厄火山喷发后形成的显著温热栖息地中的个体。研究发现，来自较新温热栖息地的个体其热极限更高，但在室温环境下饲养一段时间后，其热极限会下降至与较古老凉爽栖息地个体的热范围相匹配，这表明热极限受驯化调控，且进化潜力有限。与之相反，代谢速率几乎未表现出对温度的驯化响应，其速率主要由测试温度而非驯化温度决定。不同遗传谱系的个体之间，代谢速率的热驯化响应几乎无差异，但总体而言，不同遗传谱系的虾类代谢速率存在显著差异，这表明有氧代谢的遗传变异可能是气候变化时期自然选择的作用靶点。研究还发现，来自较新温热栖息地的虾类正处于其临界热最大值或接近临界热最大值的状态，这表明部分锚地物种或许可通过预先适应定植与火山活动相关的温热栖息地，来应对气候变化带来的升温威胁。本研究同时强调了气候变化对锚地栖息地的潜在影响，以及用于分类量化生物速率热驯化响应的适宜实验设计。