Meeting Abstract

49.1  Saturday, Jan. 5  Climbing on the floor: Kinematics and energy cost of locomotion for horizontal and vertical crawling are not different WOODS JR., W. A.*; VANGRIETHUIJSEN, L.; TRIMMER, B. A. ; Tufts University; Tufts University; Tufts University william.woods@tufts.edu

Regardless of body orientation, caterpillars accomplish forward locomotion by lifting , swinging forward, and replacing successive pairs of prolegs in anterograde waves. Using second day fifth instar larvae of Manduca sexta, we recorded the kinematics of the prolegs of the third abdominal segment and the terminal segment during horizontal and upward vertical crawling on wooden dowels. The difference between velocity in horizontal (0.370 ±0.129 cm s^{-1-1) crawling was not significant (paired t = 0.74, 4 df, p = 0.50). The same was true for the duration of the steps (mean over all prolegs and animals: horizontal 1.28 ±0.36 s, vertical 1.02 ±0.23 s, repeated measures MANOVA between subjects: F = 2.84, 8 df, p = 0.13; within subjects F = 1.79, df = 322, p = 0.15). There were no significant or consistent differences in the phase relationship between the prolegs of the third abdominal and terminal segments. Prolegs were lifted 27 ±33% higher during vertical crawling but the difference was not significant. Energy costs were determined by open flow respirometry CO₂ measurements of caterpillars crawling on a wooden dowel enclosed by a tubular respirometry chamber, with corrections made for Doppler shift and position-dependent time lag. Metabolic rate during forward locomotion was about twice the resting rate. However, there was no difference in metabolic rate between horizontal (4.73 ±0.28 mW g-1) and vertical (4.58 ±0.66 mW g-1) crawling (t = 0.68, 4 df, p = 0.53). The lack of difference in both metabolic rate and velocity between the two orientations means that caterpillars incurred no net energy cost by climbing rather than horizontally crawling a given distance. Kinematically and energetically, caterpillars are �climbing� whether orientation is horizontal or vertical.}