EVOLUTION OF SHAPE DIFFERENCES BETWEEN THE MAJOR AND MINOR CHELIPEDS OF UCA PUGNAX (DECAPODA, OCYPODIDAE)

Geometric morphometrics were used to analyze shape differences between the major and minor chelipeds of the fiddler crab Uca pugnax. Althoug h the major and miner chelipeds had similar allometric developmental t rajectories, the form of the major cheliped was not an allometric extr apolation of the minor cheliped. The changes in shape associated with the formation of the major cheliped have functional relevance; they al low the major cheliped to produce relatively more power than the minor cheliped. This result suggests that selection for combat effectivenes s has played an important role in the evolution of the major cheliped.