Mat Audrey M, Dunster Gideon P, Sbragaglia Valerio, Aguzzi Jacopo, de la Iglesia Horacio O
Department of Biology, University of Washington, Seattle, Washington, United States of America.
Marine Science Institute, (ICM-CSIC), Barcelona, Spain.
PLoS One. 2017 Apr 26;12(4):e0175403. doi: 10.1371/journal.pone.0175403. eCollection 2017.
Animals living in the intertidal zone are exposed to prominent temperature changes. To cope with the energetic demands of environmental thermal challenges, ectotherms rely mainly on behavioral responses, which may change depending on the time of the day and seasonally. Here, we analyze how temperature shapes crabs' behavior at 2 different times of the year and show that a transition from constant cold (13.5°C) to constant warm (17.5°C) water temperature leads to increased locomotor activity levels throughout the day in fiddler crabs (Uca pugilator) collected during the summer. In contrast, the same transition in environmental temperature leads to a decrease in the amplitude of the daily locomotor activity rhythm in crabs collected during the winter. In other words, colder temperatures during the cold season favor a more prominent diurnal behavior. We interpret this winter-summer difference in the response of daily locomotor activity to temperature changes within the framework of the circadian thermoenergetics hypothesis, which predicts that a less favorable energetic balance would promote a more diurnal activity pattern. During the winter, when the energetic balance is likely less favorable, crabs would save energy by being more active during the expected high-temperature phase of the day-light phase-and less during the expected low-temperature phase of the day-dark phase. Our results suggest that endogenous rhythms in intertidal ectotherms generate adaptive behavioral programs to cope with thermoregulatory demands of the intertidal habitat.
生活在潮间带的动物面临着显著的温度变化。为了应对环境热挑战带来的能量需求，变温动物主要依靠行为反应，而行为反应可能会随一天中的时间和季节而变化。在这里，我们分析了温度如何在一年中的两个不同时间塑造螃蟹的行为，并表明从恒定低温（13.5°C）到恒定高温（17.5°C）的水温转变会导致夏季采集的招潮蟹（Uca pugilator）全天的运动活动水平增加。相比之下，相同的环境温度转变会导致冬季采集的螃蟹每日运动活动节律的幅度减小。换句话说，寒冷季节较低的温度有利于更显著的昼夜行为。我们在昼夜热能量学假说的框架内解释了冬季和夏季每日运动活动对温度变化反应的这种差异，该假说预测能量平衡越不利，将促进更明显的昼夜活动模式。在冬季，当能量平衡可能更不利时，螃蟹会通过在白天预期的高温阶段更活跃——而在白天黑暗阶段预期的低温阶段活动较少——来节省能量。我们的结果表明，潮间带变温动物的内源性节律会产生适应性行为程序，以应对潮间带栖息地的体温调节需求。
