Meeting Abstract
Spiders in the family Selenopidae, commonly called “flatties,” have been characterized as having the fastest rotational prey strikes of any animal. While previous work developed a model of rotational striking based on intact, eight-legged spiders, here we used this model as a basis to analyze the strikes of flatties missing one or two legs. Flatties (Karaops sp.) were collected in Australia and filmed using high-speed digital video cameras attacking fruit fly prey. Using rotational speed as a measure of performance, we found that spiders missing one leg were only marginally slower (13% reduction in speed, p =0.054) than intact individuals (2.13 ± 0.38 deg/ms for seven legs, vs 2.48 ± 0.61 for intact spiders) while those missing two legs were much slower (54% reduction, p <0.001, mean speed 1.15 ± 0.50 deg/ms), though all could successfully grab prey. Analysis of changes in leg use by 7 legged spiders in rotational attacks showed that about half of the spiders that had lost a single rear leg would compensate by shifting the roles of the back two legs- as described by the Yu and Crews (2018) model-“forward” by one leg. Seven-legged individuals that compensated this way maintained rotational speeds averaging 93% of the intact spider speed, while those that adopted some other pattern maintained only 65% of the speed of eight-legged individuals. These findings demonstrate that flattie spiders can (but don’t always) compensate for leg-loss by substituting anterior legs for missing rear legs. This provides evidence supporting optimality for the modeled pattern, but the effects of gait changes on prey capture rates and overall fitness remain unknown.
