Evolution of Shape Differences between the Major and Minor Chelipeds of Uca pugnax (Decapoda: Ocypodidae)

Abstract

ABSTRACT Geometric morphometrics were used to analyze shape differences between the major and minor chelipeds of the fiddler crab Uca pugnax. Although the major and minor chelipeds had similar allometric developmental trajectories, the form of the major cheliped was not an allometric extrapolation of the minor cheliped. The changes in shape associated with the formation of the major cheliped have functional relevance; they allow the major cheliped to produce relatively more power than the minor cheliped. This result suggests that selection for combat effectiveness has played an important role in the evolution of the major cheliped.