Limb autotomy and regeneration affect vibratory/seismic courtship signaling and female receptivity in wolf spiders

In many spiders, limb autotomy (self-amputation) is a common anti-predator behavior. While many species are able to regenerate lost limbs without apparent fitness costs, there are demonstrable costs in others. Previous studies have shown males of the brush-legged wolf spider Schizocosa ocreata (Hentz, 1844) incur reduced mating success after autotomy and/or regeneration of their decorated forelimbs, which affects visual courtship displays. However, because courtship of male S. ocreata is multimodal and contains vibratory/seismic signals, communication in this channel might also be affected. We recorded female receptivity to isolated male vibratory/seismic courtship signals from: males with intact forelimbs (control), males with a regenerated forelimb, and males missing a forelimb. Females were more receptive to isolated vibratory/seismic signals of intact males over males missing a foreleg, but not males that regenerated a foreleg. Although initial size and body condition did not differ among treatments, regeneration of a limb had a significant negative impact on growth increment from penultimate instar to adult, suggesting a possible physiological cost of regeneration. To investigate the impact of autotomy and regeneration on vibratory/seismic signals, we used laser Doppler vibrometry (LDV). Analysis of overall signal amplitude across treatments revealed significantly reduced amplitude for males with regenerated limbs, despite these males having receptivity responses statistically similar to control males. Analyses of component elements of vibratory/seismic signals showed three (of four) had significantly reduced amplitude in males regenerating limbs. These results demonstrate a potential fitness impact of autotomy and regeneration on the vibratory/seismic component of male courtship signals.