ABSTRACT: Rocky intertidal zones are some of the most thermally stressful environments on earth, where ectotherms deal with tidally driven fluctuations in air and water temperatures that can exceed their maximum thermal tolerance. However, not all intertidal ectotherms face the same exposure risk. In northern regions of the eastern Pacific, summertime low tides occur during midday, exposing ectotherms to potentially stressful temperatures, whereas cooler pre-dawn low tides in southern regions buffer ectotherms from thermal stress. Gumboot chitons Cryptochiton stelleri are thermally sensitive intertidal grazers that range from southern California to Alaska, exposing them to a mosaic of thermal stresses. We quantified chiton thermal performance limits in the laboratory by testing the effects of elevated air and water temperatures on grazing. We also compared the thermoregulation efficiency of chitons from thermally benign northern California sites with those from thermally stressful San Juan Island, Washington sites, using 3 components: (1) biomimetic thermal models deployed intertidally, (2) chiton body temperatures in the field, and (3) chiton thermal preference in a laboratory-based thermal gradient. We found that chiton grazing performance was greatly reduced at 18°C in water, and they reached their grazing performance limit after exposure to 20°C in air, confirming previous work documenting thermal limits on chiton respiration. Chitons preferred body temperatures within 3°C of their thermal performance limits, but they rarely achieved body temperatures that would maximize grazing in the field. This suggests that chitons are not thermoregulating efficiently with respect to maximizing grazing performance, but instead are minimizing exposure to temperatures that would be detrimental to their performance.

中文翻译：

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世界上最大的Chiton（Cryptochiton stelleri）是效率低下的温度调节器

摘要：潮间带岩石带是地球上一些热应力最大的环境，其中的外热处理潮汐驱动的空气和水温波动可能超过其最大热容差。但是，并非所有的潮间带等温线都面临相同的暴露风险。在东太平洋北部地区，夏季低潮发生在正午，使等温线处于潜在的压力之下，而南部地区黎明前的凉爽低潮缓冲了热应力引起的等温线。口香糖Chitons Cryptochiton stelleri是对热敏感的潮间草，从加利福尼亚南部到阿拉斯加，将它们暴露在热应力作用下。通过测试升高的空气和水温对放牧的影响，我们在实验室中量化了Chiton热性能极限。我们还使用以下3个方面比较了来自加利福尼亚北部良性热场所和华盛顿州圣胡安岛带热应力的Chiton的温度调节效率：（1）交错部署的仿生热模型，（2）现场的Chiton体温，以及（3）基于实验室的热梯度中的Chiton热偏好。我们发现，水中的Chiton放牧性能大大降低，在空气中暴露于20°C后，它们的放牧性能达到极限，确认以前的工作记录了对Chiton呼吸的热极限。Chitons首选的体温应在其热性能极限的3°C以内，但他们很少达到可以在野外最大程度放牧的体温。这表明，就最大限度地提高放牧性能而言，Chiton不能有效地进行温度调节，而是可以最大限度地减少暴露于不利于其性能的温度。