The effects of cheliped regeneration on aggression in purple shore crab (Hemigrapsus nudus)

The tradeoffs associated with appendage regeneration have been studied for decades, with the general consensus that there is an overall fitness cost associated with the regenerative process.  However, almost all of these studies have made comparisons between only two specific treatment groups: 1) normal animals that have never autotomized and 2) animals that autotomized and then regenerated.  The absence of a third treatment group has been a major flaw of previous work; to truly understand the evolutionary significance of regeneration, comparisons must include 3) animals that autotomized but did not regenerate.  If, for example, the fitness of animals that have autotomized and then regenerated is higher than that of animals that have autotomized but not regenerated, then what could have been mistakenly interpreted as a cost of regeneration in the absence of this comparison is able to be correctly discerned as a benefit. The aim of this study was to apply this novel perspective on regeneration to an examination of the effects of cheliped (claw) regeneration on aggression in the purple shore crab, Hemigrapsus nudus. The mean occurrences of both passive and aggressive behaviors were compared among normal males, males with autotomized claws, and males with regenerated claws.  The results suggest that regeneration does not restore fitness in the context of male-male competition. Future work will elucidate whether or not this study is representative of overall patterns of fitness as they relate to the regenerative process in H. nudus.