P41-8 Sat Jan 2 Role of hindlimb proprioceptive feedback in the coordinated landing behavior of Rhinella marina Duman, A*; Azizi, E; University of California, Irvine aduman@uci.edu
Variation in surface conditions during locomotion can cause animals to alter their behavior in order to effectively navigate complex terrain. The cane toad, Rhinella marina, has become a model organism for exploring the biomechanics of controlled deceleration because of its ability to hop repeatedly and exercise its forelimbs to dissipate energy upon impact. However, it remains unclear how these animals respond to natural variation in surface conditions while locomoting. Previous work suggests cane toads may not rely on sensory feedback from forelimbs to alter muscle activation when landing on compliant surfaces, while others have shown that denervation of the hindlimbs elicits inadequate preparatory behavior in the forelimbs prior to landing. Therefore, we hypothesized that cane toads rely on hindlimb proprioception during takeoff to alter the preparatory and landing behavior. To test this hypothesis, we varied the compliance of a jumping platform in order to alter hindlimb muscle dynamics and the proprioceptive signals used to inform landing strategies. We quantified 3D kinematics during take-off and landing in toads (N = 8) across a range of take-off conditions. Our preliminary results suggest proprioceptive feedback from hindlimbs during takeoff does not alter impact kinetics or forelimb extension upon touchdown suggesting hindlimb feedback is not crucial for coordinating landing behavior. This study will complement ongoing reinnervation experiments that ablate the stretch reflex in the hindlimb muscles distal to the knee in order to more directly determine how afferent pathways inform control strategies during landing.