Marine Science Institute, University of Texas at Austin, Port Aransas, Texas 78373, USA.
Am Nat. 2011 Sep;178(3):419-28. doi: 10.1086/661239.
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 it 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 at 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. The body temperatures of males without the major claw increased more rapidly and reached higher values than did those of males with the major claw intact, but the results from these animals were similar to those of 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.
招潮蟹具有高度的两性异形。雄蟹拥有一只小的（次要）的螯足和一只巨大的（主要）螯足；雌蟹拥有两只小螯足。雄蟹的主要螯足用于吸引配偶和防御洞穴，但对雄蟹来说，拥有这只螯足是有代价的。我们检验了这样一个假设，即主要螯足也具有调节体温的功能，这一功能使雄蟹能够花费更多的时间在表面觅食和吸引潜在的配偶。我们将 Uca panacea 招潮蟹暴露在热源下，并监测它们的体温。测试了四组螃蟹：完整的雄蟹、去除了小螯足的雄蟹、去除了大螯足的雄蟹和雌蟹。没有大螯足的雄蟹的体温上升得更快，达到的温度也比保留大螯足的雄蟹更高，但这些动物的结果与雌蟹相似。这些结果支持了主要螯足具有调节体温的功能这一假设。主要螯足可能起到热汇的作用，将热量从身体转移并散发到空气中。主要螯足提供的增强的体温调节能力可能部分减轻了拥有如此大的螯足的能量成本。
