Meeting Abstract

131.3  Monday, Jan. 7  Differential limb function during locomotion on the level and over obstacles in the tarantula NELSON, FE*; DASARI, V; HSIEH, T; Temple University, University of Pennsylvania; University of Pennsylvania; Temple University f.e.nelson75@googlemail.com

Understanding how the motor control system maintains sufficient flexibility to navigate the natural variability of the environment is important for elucidating evolutionary mechanisms, robotic design, and understanding disease states. The goal of this study was to determine the function of different limbs during steady state running and obstacle maneuvering in spiders. We ran five juvenile Usambar Orange Baboon tarantulas (Pterinochilus murinus) (body length: 1.1±0.1 cm) along a flat trackway while filming the dorsal view. We also ran the spiders across obstacles of 0.5x, 1x, and 2x knee height. On average, spiders ran at 25 ± 3 cm/s and did not appear to slow down on the 0.5x and 1x obstacle treatments. We found limb function differed among the four sets of limbs. The posterior (fourth set) of legs functioned as propulsors, as evidenced by large changes in effective limb length (ΔeLL; 43.2±5.13 %) and the small angle of excursion (20.4±3.4°) during a stride. Similarly, the first (anterior set) and second set of limbs also exhibited large ΔeLL (57.3±2.26% and 49.5±8.9%, respectively), but swept through a greater excursion angle (61.6±4.81° and 59.4±5.8°, respectively), suggesting they played both a propulsive and stabilizing function. In contrast, the third set of legs were mostly extended throughout a stride (ΔeLL: 15.4±1.6 %) and followed a large excursion angle (44.3±4.0°), consistent with a stabilizing function. Preliminary results suggest some change in limb function during obstacle crossing, with the first set of legs taking on a sensory – in addition to locomotory – role, while the fourth set of limbs maintain a primarily propulsive function.