Meeting Abstract

69.7  Monday, Jan. 6 09:30  Lightening the load: Effects of tail autotomy and regeneration on locomotor mechanics in the leopard gecko. JAGNANDAN, K*; HIGHAM, TE; University of California, Riverside kevin.jagnandan@email.ucr.edu

Autotomy is an effective anti-predation strategy that involves the voluntary shedding of a non-vital body part in order to distract a predator and/or escape from its grasp. Although autotomy studies examining trade-offs often focus on how autotomy impacts running speed, climbing ability, and jumping, little is known about how losing and regenerating a tail affects the mechanics of locomotion. Leopard geckos (Eublepharis macularius) have large tails (22% of body mass) that are commonly autotomized. We hypothesize that rapidly losing this large caudal mass will shift the center of mass (CoM) anteriorly and increase hip height, pitching the body forward and causing passive changes in forelimb and hindlimb joint kinematics. Additionally, propulsive hindlimb ground reaction forces (GRF’s) are expected to decrease with the loss of mass and then steadily increase as a new tail is regenerated, thus remaining constant relative to body mass. Tail morphology, CoM, 3D kinematics of the fore- and hindlimbs, and hindlimb GRF’s (individual footfalls on a custom force plate) of 7 adult leopard geckos were examined as they walked on a level surface prior to autotomy and then at intervals for 22 weeks as the tails were regenerating. Although hip height does not appear to change following autotomy, there were unexpected differences in hindlimb and forelimb joint angles throughout a stride. Additionally, peak vertical GRF of the hindlimb (scaled relative to body mass) decreased following autotomy and did not begin to recover until regeneration of the tail began approximately 4 weeks later. Our results suggest an active locomotor response to tail loss and an increased relative contribution to propulsion by the forelimbs following autotomy. Supported by NSF IOS-1147043.