Meeting Abstract

101.4  Thursday, Jan. 7  Mechanical Feedback of Antenna-Substrate Interaction Simplifies Cockroach Antennal Navigation MONGEAU, J.-M.*; JAYARAM, K.; LEE, J.; FULL, R.J.; COWAN, N.; University of California, Berkeley; University of California, Berkeley; Johns Hopkins University; University of California, Berkeley; Johns Hopkins University jmmongeau@berkeley.edu

During high-speed wall following cockroaches rely on mechanosensory structures in their antennae to follow surface contours reliably, providing critical feedback for task-level control. The unactuated antenna flagellum assumes a characteristic inverted-J posture during this behavior. Results from our behavioral studies in Periplaneta americana suggest that antenna buckling is necessary for maintaining a steady body position relative to a wall surface. Sensitivity analysis predicts that this posture reduces the error in the estimate of wall distance when compared to a straight antenna. We hypothesized that mechanical feedback resulting from the interaction between large mechanosensory hairs on distal flagellar segments and surface asperities induce Euler buckling during wall following, thereby simplifying the control of preferred antenna posture. To test this hypothesis we compared antenna-buckling behavior in running, blinded cockroaches and in freshly ablated antennae. By varying surface roughness, we showed that antennae on smooth surfaces don’t bend, while on rough surfaces, irrespective of orientation, antennae engage the surface producing J-shape bending, suggesting a passive mechanism. To test whether mechanosensory hairs are directly implicated in facilitating buckling, we performed single hair displacement experiments. We identified that distally pointing sensilla possess a limited range of motion (30-40°) facilitating engagement of rough substrates. We hypothesize that constraints on the range of motion promote buckling by maximizing the moment arm between the antenna flagellum and the substrate. Our results suggest that passive mechanical feedback can simplify control of antennal sensory structures.