Limb loss and limb regeneration of crab spiders Misumena vatia

Limb loss presents an interesting paradox: although it may permit escape from a potentially lethal situation, it may result in subsequent fitness-lowering consequences. Some studies have found costs of limb loss; others have not. If costs are high, they may dictate against retaining the ability to drop an appendage. I use a large data set derived from a long-term study of the crab spider Misumena vatia (Clerck, 1757) to investigate the role of several size- and time-related factors in evaluating the cost of losing variable numbers of legs, as well as of growing replacements. Specifically, do limb loss and regeneration affect condition, and do the results differ with sex and age? I focused on adult males because of their high frequency of forelimb loss, including loss of multiple limbs. Numbers of missing adult male forelimbs were correlated with date captured and mass (corrected for number of missing forelimbs), suggesting that the spiders lost forelimbs continually over the summer and that they reached progressively poorer condition than intact individuals, judged by a disproportionate loss in body mass. The frequency of forelimb loss by penultimate males matched that of adult males, but females and juveniles lost less than 1/10th as many forelimbs as males. Males possessed many fewer partially regenerated forelimbs than missing forelimbs, but these frequencies significantly exceeded those for females and younger juveniles. Some information suggested that additional costs arose from the regeneration of forelimbs.