Data from: Thermoregulation as an alternate function of the sexually dimorphic fiddler crab claw

Fiddler crabs are highly sexually-dimorphic. Males possess one small (minor) feeding claw and one greatly enlarged (major) claw; females possess two small claws. The major claw is used to attract mates and for burrow defense but is costly for the male to possess. We tested the hypothesis that the major claw also functions as a thermoregulatory structure, a function that would allow males to spend a greater amount of time on the surface, foraging and attracting potential mates. Fiddler crabs, Uca panacea, were exposed to a source of radiant heat and body temperatures were monitored. Four groups of crabs were tested: intact males, males with the minor claw removed, males with the major claw removed, and females. Males without the major claw increased in body temperature more rapidly and reached higher temperatures than males with the major claw intact, but were similar to females. These results support the hypothesized thermoregulatory function of the major claw. The major claw may function as a heat sink, transferring heat away from the body and dissipating it into the air. Enhanced thermoregulatory ability provided by the major claw may partially ameliorate the energetic costs of possessing such a large claw.

招潮蟹（Fiddler crab）具有显著的性别二态性：雄性个体拥有一枚小型（次要）取食螯足与一枚极度膨大的主要螯足，而雌性个体则拥有两枚小型螯足。主要螯足可用于吸引配偶与洞穴防御，但雄性拥有该螯足需付出高昂的生存与代谢成本。本研究验证了如下假说：主要螯足同时具备体温调节功能，该功能可使雄性个体花费更多时间在地表活动，用于觅食与吸引潜在配偶。本实验以美国招潮蟹（Uca panacea）为研究对象，将其暴露于辐射热源环境中并监测其体温变化。受试个体共分为四组：完整雄性组、切除次要螯足的雄性组、切除主要螯足的雄性组以及雌性组。实验结果显示，相较于螯足完整的雄性个体，未保留主要螯足的雄性个体体温上升速度更快，且最终体温更高，但其体温变化与雌性个体无显著差异。上述结果验证了主要螯足具备体温调节功能的假说。主要螯足可作为热沉（heat sink），将体内热量转移并释放至空气中。该螯足所赋予的增强型体温调节能力，可部分缓解雄性拥有巨型螯足所需付出的能量成本。