Abstract Mobile intertidal crabs are often exposed to the sun while displaying outside of moist and cooler breeding burrows, which imposes increased heat stress and water. Individuals of a field population in mid-summer of the fiddler crab Leptuca pugilator had body temperatures that declined with increasing body size. All crabs were cooler than the sediment surface. Laboratory experiments simulated a male leaving its burrow and standing on hot sand heated by the sun. Smaller crabs succumbed to thermal stress sooner than larger crabs. Incapacitation keyed to field sediment temperatures occurred usually in about 30 min. Water loss ranged 1–8% at incapacity Small crabs heated up as fast as large crabs. Males with a major claw gained body heat more than clawless males and succumbed sooner. The major cheliped loses water proportionally more slowly than the body, which is likely explained by the more impervious surface of the claw, suggesting the claw might be a heat sink. I hypothesized that heat may be accumulated in the relatively impermeable major cheliped and transferred to the body, increasing thermal stress in the body where crucial organs must function. Several experiments were done to attempt to demonstrate body part differences in heating or heat transfer between cheliped and body. Thermal images demonstrated a temperature excess in the manus, and a lower temperature of the dactyl, consistent with the impermeability of the manus and its larger surface area intercepting heat, and perhaps radiation from the dactyl. Immersion of major claws in warm and cold water demonstrated heat transfer between cheliped and body. If claws are painted black, they heat up faster than unpainted claws, but there was no evidence of the transfer of increased heat to the body when claws were darkened. Thus the potential for heat transfer between claw and body is probably quite limited, which is further suggested by the very narrow connection at the basal ischium segment of the cheliped.The results suggest that smaller male fiddler crabs may have reduced success in the upper intertidal partially because of their higher vulnerability to thermal stress. Smaller males may choose to avoid the hotter upper intertidal until they become larger. Experimental results show no evidence for the role of the major claw in alleviating thermal stress to the fiddler crab carapace.

中文翻译：

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热应力：体型和巨大的主要爪子在招潮蟹（Leptuca pugilator）的生存和传热中的作用

摘要 流动的潮间带蟹经常暴露在阳光下，同时在潮湿和凉爽的繁殖洞穴外露面，这会增加热应激和水分。招潮蟹 Leptuca pugilator 在夏季中期的野外种群个体的体温随着体型的增加而下降。所有的螃蟹都比沉积物表面凉爽。实验室实验模拟了一只雄性离开洞穴并站在被太阳加热的热沙上。较小的螃蟹比较大的螃蟹更快地屈服于热应力。与现场沉积物温度相关的失能通常发生在大约 30 分钟内。失水时失水范围为 1-8% 小螃蟹与大螃蟹一样快速升温。有大爪的雄性比没有爪的雄性获得更多的体温，并且更快死亡。主要螯足比身体更慢地按比例失去水分，这可能是由爪子更不透水的表面来解释的，这表明爪子可能是一个散热器。我假设热量可能会积聚在相对不可渗透的主要螯合物中并转移到身体，从而增加身体的热应力，而关键器官必须在此处发挥作用。进行了一些实验以试图证明螯肢和身体之间在加热或传热方面的身体部位差异。热图像显示手足温度过高，而趾甲的温度较低，这与手足的不渗透性及其更大的表面积截获热量以及可能来自趾甲的辐射相一致。将主要爪子浸入温水和冷水中证明了螯肢和身体之间的热传递。如果爪子被涂成黑色，它们比未涂漆的爪子加热得更快，但没有证据表明当爪子变黑时，热量会增加到身体上。因此，爪和身体之间的热传递潜力可能非常有限，这进一步由螯足基底坐骨段的非常狭窄的连接所表明。结果表明，较小的雄性招潮蟹可能部分地降低了潮间带上部的成功率因为它们更容易受到热应力的影响。体型较小的雄性可能会选择避开较热的上潮间带，直到它们变大。实验结果表明，没有证据表明大爪在减轻招潮蟹甲壳的热应力方面的作用。但没有证据表明当爪子变暗时，热量会增加到身体上。因此，爪和身体之间的热传递潜力可能非常有限，这进一步表明螯足基底坐骨段的连接非常狭窄。 结果表明，较小的雄性招潮蟹可能部分地降低了潮间带上部的成功率因为它们更容易受到热应力的影响。体型较小的雄性可能会选择避开较热的上潮间带，直到它们变大。实验结果表明，没有证据表明大爪在减轻招潮蟹甲壳的热应力方面的作用。但没有证据表明当爪子变暗时，热量会增加到身体上。因此，爪和身体之间的热传递潜力可能非常有限，这进一步表明螯足基底坐骨段的连接非常狭窄。 结果表明，较小的雄性招潮蟹可能部分地降低了潮间带上部的成功率因为它们更容易受到热应力的影响。体型较小的雄性可能会选择避开较热的上潮间带，直到它们变大。实验结果表明，没有证据表明大爪在减轻招潮蟹甲壳的热应力方面的作用。螯虾的坐骨基底段的非常狭窄的连接进一步表明了这一点。结果表明，较小的雄性招潮蟹在潮间带上部的成功率可能会降低，部分原因是它们更容易受到热应力的影响。体型较小的雄性可能会选择避开较热的上潮间带，直到它们变大。实验结果表明，没有证据表明大爪在减轻招潮蟹甲壳的热应力方面的作用。螯虾的坐骨基部非常狭窄的连接进一步表明了这一点。结果表明，较小的雄性招潮蟹在潮间带上部的成功率可能会降低，部分原因是它们更容易受到热应力的影响。体型较小的雄性可能会选择避开较热的上潮间带，直到它们变大。实验结果表明，没有证据表明大爪在减轻招潮蟹甲壳的热应力方面的作用。