Bodega Marine Laboratory, 2099 Westshore Road, Bodega Bay, CA 94923, USA; Department of Evolution and Ecology, University of California, One Shields Avenue, Davis, CA 95616, USA.
Department of Biological Sciences, California State University East Bay, 25800 Carlos Bee Boulevard, Hayward, CA 94542, USA.
Comp Biochem Physiol A Mol Integr Physiol. 2020 Jan;239:110563. doi: 10.1016/j.cbpa.2019.110563. Epub 2019 Sep 4.
An organism's ability to cope with thermal stress is an important predictor of survival in a changing climate. One way in which organisms may acclimatize to thermal stress in the short-term is through induced thermotolerance, whereby exposure to a sublethal heat shock enables the organism to subsequently survive what might otherwise be a lethal event. Whether induced thermotolerance is related to basal thermotolerance is not well understood for marine organisms. Furthermore, whether populations often differ in their capacity for induced thermotolerance is also unclear. Here, we tested for differences in basal thermotolerance and induced thermotolerance among six populations of Olympia oysters (Ostrea lurida) from three California estuaries. Oysters were raised under common-garden laboratory conditions for a generation and then exposed to two treatments (control or sublethal heat shock) followed by a spectrum of temperatures that bound the upper critical temperature in order to determine LT (temperature at which 50% of the population dies). All populations exhibited induced thermotolerance by increasing their LT to a similar maximum temperature when extreme thermal stress was preceded by a sublethal heat shock. However, populations differed in their basal thermotolerance and their plasticity in thermotolerance. Populations with the highest basal thermotolerance were least able to modify upper critical temperature, while the population with the lowest basal thermotolerance exhibited the greatest plasticity in the upper critical temperature. Our results highlight that populations with high basal thermotolerance may be most vulnerable to climate warming because they lack the plasticity required to adjust their upper thermal limits.
生物体应对热应激的能力是其在气候变化中生存的重要预测指标。生物体在短期内适应热应激的一种方式是通过诱导耐热性，即暴露于亚致死热激使得生物体随后能够存活下来，否则可能会导致致命事件。对于海洋生物而言，诱导耐热性是否与基础耐热性有关尚不清楚。此外，不同种群在诱导耐热性方面的能力是否经常存在差异也不清楚。在这里，我们测试了来自加利福尼亚三个河口的六个 Olympia 牡蛎（Ostrea lurida）种群的基础耐热性和诱导耐热性的差异。牡蛎在实验室条件下进行共同养殖一代，然后暴露于两种处理（对照或亚致死热激），然后是一系列温度，这些温度限制了上限临界温度，以确定 LT（种群死亡率为 50%的温度）。当极端热应激之前经历亚致死热激时，所有种群都通过将 LT 提高到相似的最高温度来表现出诱导耐热性。然而，种群在基础耐热性和耐热性的可塑性方面存在差异。基础耐热性最高的种群对上限临界温度的改变能力最小，而基础耐热性最低的种群在上限临界温度方面表现出最大的可塑性。我们的结果表明，基础耐热性高的种群可能最容易受到气候变暖的影响，因为它们缺乏调整上限热极限所需的可塑性。
