Direct and indirect costs of limb autotomy in field crickets, Gryllus bimaculatus

Autotomy, found in multiple taxa, is the voluntary shedding of limbs and other appendages in response to predation, intraspecific conflicts and infection or damage. In a wild population of the field cricket, we found that 36% of 110 individuals of both sexes were missing at least one limb. We examined the speed to autotomize an entrapped limb and the costs of this autotomy in both sexes of a first-generation laboratory population of known age. We induced autotomy of either the two hindlegs or the two middle legs over 2 subsequent days. We found no sex differences in speed of autotomy, but hindlegs were autotomized faster than middle legs, and first legs were shed faster than second legs. Escape speed was significantly reduced by the loss of either middle or hindlegs, and number of jumps in the escape sprint was reduced. We found no significant effect of loss of two legs on male-male competitive ability, but loss of two legs in females significantly reduced mating ability by pairs. Males with autotomized middle leas showed reduced longevity, but neither sex showed a significant effect of autotomy on body mass. Gryllus bimaculatus, therefore, appears to incur both direct and indirect fitness costs from limb autotomy. This study has implications for understanding the general biology of crickets and contributes to our understanding of the role of autotomy as an evolutionary mechanism. (C) 2004 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.