Meeting Abstract
Many invertebrates are capable of voluntarily losing limbs (autotomy) in response to antagonistic encounters. How they rapidly adapt to such an extreme perturbation of the locomotor system is poorly understood, however. Wolf spiders are fast-running, active predators that are frequently found in nature missing one or more limbs. We used wolf spiders to address the question: if an eight-legged spider loses two limbs, will it run like an intact six-legged animal or like an eight-legged animal that has lost two limbs? After running intact spiders 30 times to obtain baseline control data, we autotomized two limbs specifically selected to induce a maximally unstable condition during one half of the stride cycle, and then ran them 30 more times in the ablated condition. We hypothesized that in response to such a destabilization, spiders would adopt a more stable, novel limb pairing (“modified tripod gait”), potentially at the cost of decreased running speeds. Our results showed that limb ablation did not cause a measurable decrease in running speeds. When intact, spiders ran with an alternating tetrapod gait. Following limb ablation, spiders tended to switch their limb pairings to the more statically-stable 3-3 limb pairing modified tripod gait, but also often continued running without changing gaits (“ablated tetrapod gait”), stepping with a four-limb tetrapod followed by an unstable two-limb vault. Surprisingly, our stability calculations showed that there was no difference in stability between the modified tripod and the ablated tetrapod gait. A temporal analysis revealed that spiders were able to achieve a more stable ablated tetrapod gait by decreasing the time spent in the two-limb vault, thereby “limping” to increase the average stability of a stride.
