Meeting Abstract
Spiders in the family Selenopidae, commonly called “flatties,”- have been characterized as having the fastest rotational prey strikes of any animal. Previous work developed a model of rotational striking based on intact spiders from the genus Selenops– here we test this model to analyze the strikes of flatties from genus Karaops including those missing one or two legs. Flatties (Karaops sp.) were collected in Australia and filmed using high-speed digital video cameras attacking fruit fly prey. Legs were operationally defined as inner flexion (IFL), outer extension (OEL) and aerial adduction (AAL). Intact Karaops showed less variation in leg usage than Selenops (p <0.05), consistently assigning a single IFL closest to the fly paired with 2 OELs to its opposite back legs. Using rotational speed as performance proxy, we found spiders missing one leg were marginally slower (13% reduction, p =.054) than intact ones (2.13 ± 0.38 deg/ms for seven legs, vs 2.48 ± .61 for intact), though capture rate was lower than in intact individuals (87% strike success vs 98% of intact strikes, p <0.001). By contrast, those missing two legs were much slower (54% reduction, p <0.001, mean speed 1.15 ± 0.50 deg/ms), and caught prey in only 76% of strikes. The leg use of autotomized spiders was also compared to the intact spiders. Analysis of changes in leg use by seven-legged spiders showed that those that had lost a single rear leg would compensate by changing the roles of the back two legs, usually shifting the role of the inner flexion leg (IFL) to the next closest leg to the prey. This maintained the three leg roles in all strikes. However, the six-legged spiders often allowed certain legs to function as both a flexion and extension leg during different portions of one strike. While rotational speed alone supports the proposed “spare leg” hypothesis, prey-capture is still negatively impacted.
