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.