Meeting Abstract

89.5  Sunday, Jan. 6  Running in confined spaces by the American cockroach JAYARAM, K*; SPRINGTHORPE, D; HALDANE, D; MCKINLEY, S; DIROCCO, A; FULL, R.J; University of California Berkeley; University of California Berkeley; University of California Berkeley; University of California Berkeley; University of California Berkeley; University of California Berkeley kaushikj@berkeley.edu

A composite exoskeletal system with an integrated array of sensors and muscles enables arthropods to locomote through the most restrictive environments. Here we found that the tough yet compressible exoskeleton of the cockroach, Periplaneta americana, enabled the animal to run through confined spaces less than a third of its standing height (12-15mm). We ran animals through a variable ceiling height rectangular tunnel at 4, 6, 9 and 12mm heights. Surprisingly, animals ran within the vertically restricted space with equal ease at high speeds (52.15±2.68cm/s), only showing a decrease at the lowest height of 4mm (12.56±2.45cm/s, P<0.01). Further, animals maintained a tripod gait at all heights except 4mm when feet often slipped on the surface (medium-grit sandpaper) and stereotyped leg trajectories were altered. Kinematic analysis revealed no significant change of leg cycling frequency (16.12±1.24Hz, P>0.05) across the ceiling heights. However, cockroaches used significantly (P<0.01) shorter stride lengths at 4mm. At the smallest ceiling height, animals chose a more serpentine path of travel and lost foothold traction in 40.2±3.49% (P<0.01) of the strides leading to significantly less effective propulsion. Although navigating through confined spaces likely increases the normal load, remarkably animals showed limited adjustments of the tarsal (hind leg) extreme positions relative to the body centerline, contrary to our expectations. Insights obtained into strategies of high-speed, confined space navigation not only increases our understanding of the mechanical design principles of these organisms, but it also is inspiring the development of novel robots that will go where no robot can at present.