Ground reaction forces during caterpillar climbing

Abstract

Event Abstract Back to Event Ground reaction forces during caterpillar climbing Barry A. Trimmer1*, Samuel Vaughan1 and Huai-Ti Lin2 1 Tufts University, Biology / Arts and Sciences, United States 2 Howard Hughes Medical Institute, Janelia farm, United States Larval Manduca sexta, the tobacco hornworm, are remarkable climbers and crawlers. They have evolved to navigate up, down, and across the branched and highly variable terrain on vegetation. Their locomotion, therefore, must be robust to any possible orientation. Furthermore, caterpillars lack a rigid support structure and the control of their increased degrees of freedom is not well understood. Our research explores Manduca’s locomotion in two orthogonal crawling modes: horizontal and vertical. Previous studies have demonstrated that caterpillars do not necessarily change their kinematics for crawling in these two orientations. We hypothesize that they also do not change the pattern of proleg force exertion in these two orientations, effectively using the same strategy to both crawl horizontally and to climb. To measure proleg force exertions, we used a biaxial strain gauge array to sense ground reaction forces of a crawling Manduca in vertical and horizontal directions. By averaging forces and looking at the general force distributions, we found that there is no difference in the pattern of axial forces between the two crawling directions but more variations in the normal forces. While caterpillar ground reaction forces are highly variable in nature, trends and shapes often persist between trials. Our data show that caterpillars maintain net drag on the abdominal segments, keeping their bodies in tension during both modes of locomotion. Axial forces during climbing are equivalent to axial forces during crawling offset by the addition of bodyweight. This suggests that the variations in the normal forces are due to the physics of vertical climbing and that Manduca accounts for bodyweight passively. This result also supports the general finding that caterpillars can use an environmental skeleton: the animal does not actively force any posture and only the axial forces are under active control to achieve forward progression. In climbing, gravity exerts drag on the body, providing the force necessary to maintain body tension. The animal passively resists the pitch-back moment generated by its bodyweight using fail-safe grippers at the tip of each proleg. This allows the animal to use the same crawling pattern with no additional compensation for changing orientations. Another important finding of this study is that the thoracic legs are necessary for normal locomotion, providing a tensioning thrust force in both orientations. Based on these results, we propose that caterpillars have developed a single locomotor strategy that allows them to move in any orientation, effectively ignoring gravitational effects. Acknowledgements This work was supported in part by the US Defense Advanced Research Project Agency under Grant W911SR08-C0012 and by the US National Science Foundation IOS-7045912. Keywords: Biomechanics, Locomotion, soft-bodied Conference: Tenth International Congress of Neuroethology, College Park. Maryland USA, United States, 5 Aug - 10 Aug, 2012. Presentation Type: Poster Presentation (see alternatives below as well) Topic: Motor Systems Citation: Trimmer BA, Vaughan S and Lin H (2012). Ground reaction forces during caterpillar climbing. Conference Abstract: Tenth International Congress of Neuroethology. doi: 10.3389/conf.fnbeh.2012.27.00263 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 30 Apr 2012; Published Online: 07 Jul 2012. * Correspondence: Prof. Barry A Trimmer, Tufts University, Biology / Arts and Sciences, Medford, MA, 02155, United States, barry.trimmer@tufts.edu Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Barry A Trimmer Samuel Vaughan Huai-Ti Lin Google Barry A Trimmer Samuel Vaughan Huai-Ti Lin Google Scholar Barry A Trimmer Samuel Vaughan Huai-Ti Lin PubMed Barry A Trimmer Samuel Vaughan Huai-Ti Lin Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.