Meeting Abstract

84.1  Thursday, Jan. 7  Claw force and cuticle strength: Functional morphology of fiddler crab combat ANDERSON, Stuart/P*; GEORGE, Matthew; SWANSON, Brook/O; Gonzaga University; Gonzaga University; Gonzaga University sanderson@gonzaga.edu

Crabs in the genus Uca are sexually dimorphic, with males displaying extreme claw asymmetry in all species. It is thought that this extreme claw asymmetry is due both to inter-sexual selection and intra-sexual combat. This study examines 21 species within the genus Uca, measuring claw force production and resistance to cuticle puncture. During intra-sexual combat fiddler crab claws can occlude at the claw tips or at tubercles along the claw gape. We used morphology and measurements of muscle forces to estimate the force production at the tips and at tubercles. We also measured the resistance to puncture of the claw manus, which is gripped during combat, and the carapace. We recorded both the force required to initially puncture the cuticle (initial break force, IBF), and the force required to cause a major structural failure of the cuticle (structure failure force, SFF). It was found that any part of the claw produces sufficient force to damage the carapace. The force produced by each species at the claw tip was significantly lower than both the IBF and SFF for the manus, indicating that for an individual matched against another of equal size no damage can be inflicted. Forces produced at the tubercles are very similar to the IBF, but much lower than the SFF. This suggests that crabs should be able to cause some surface damage to competitors using these tubercles, but cannot produce sufficient forces to cause structural failure.