Study organism, photo from Uetz Lab (click through).

Wrinn & Uetz studied how leg loss and regeneration affected the condition, growth and development time of the wolf spider, Schizocosa ocreata (Lycosidae, photo at left). Spiders may amputate their legs as a defense strategy, but it’s not clear what trade-offs exist. For instance, if a spider amputates its leg and undergoes regeneration is future reproduction impacted, is it more susceptible to predation, is it less mobile, less of a competitor, or does it make finding food more difficult?

Wrinn & Uetz examined the frequency of self-amputation in the field and the relationship to size, mass and physiological condition. Additionally, they did laboratory experiments to test the hypothesis that leg regeneration impairs foraging, decreases growth or affects development time. The field data they collected indicated that leg loss impaired foraging ability, evidenced by decreases in mass, size and physiological condition. The laboratory experiments also suggest additional trade-offs. Though not significant, spiders regenerating legs took an average of 3.7 days longer to molt. One interesting observation was that

“Although spiders appear to show costs of regeneration, the differences in molt interval, size, and mass between intact and regenerating spiders were only true for the first molt after autonomy. During the second molt after autonomy, regenerating spiders were able to compensate for previous costs by either shortening their molt interval or increasing their growth.”

It appears these spiders are pretty flexible and bounce back to minimize costs associated with leg loss and regeneration to only one molt. Another trade-off was between development time and mass. Regeneration resulted in either longer time to molt or lower mass, but not both. Regeneration is a fascinating phenomena and certainly requires further study. The selection of improved regenerative capabilities comes at a cost, but clearly for the individual the costs do not outweigh the benefits of continuing to live and reproduce.

Wrinn, K., & Uetz, G. (2007). Impacts of leg loss and regeneration on body condition, growth, and development time in the wolf spider Schizocosa ocreata. Canadian Journal of Zoology, 85 (7), 823-831 DOI: 10.1139/Z07-063