Meeting Abstract

49-4  Friday, Jan. 5 10:45 - 11:00  Cockroaches change locomotor modes to traverse beam obstacles of varied stiffness OTHAYOTH, R*; LI, C; Johns Hopkins University ratan@jhu.edu https://li.me.jhu.edu

Recent laboratory studies begin to reveal how animals move in complex 3-D terrains common in nature. For example, to traverse grass-like beam obstacles with uniform flexural stiffness, cockroaches can push through, climb over, roll its body to maneuver through slits, or even transition between multiple locomotor modes. However, we know little about what governs animals’ use of diverse locomotor modes in more natural environment where terrain properties vary spatio-temporally during locomotion. Here, to begin to address this question, we studied how beam traversal of the discoid cockroach (Blaberus discoidalis) depended on beam stiffness, by developing a new platform to precisely control and vary beam stiffness and automatically track animal and beam movement during locomotion. We discovered that the animal’s dominant traversal mode and thus traversal performance depended sensitively on the stiffness (P < 0.001, repeated-measures ANOVA). For the least stiff beams, the animal frequently (95 ± 5 %) pushed the beams down and continued running with little change in gait, and quickly traversed (1.1 ± 1.1 s). As beams become stiffer, the animal more often (90 ± 6 %) rolled its body to maneuver through slits between beams, and traversed less quickly (2.7 ± 1.4 s). A locomotion energy landscape model revealed that, regardless of beam stiffness, the animal always more often traversed using the locomotor mode that overcomes the lower potential energy barriers. Our study demonstrated animals’ ability to adjust locomotion behaviors and strategies in response to the changing environment, and is a first step towards discovering principles of locomotor transitions in nature. Our results also support the vision that locomotion energy landscapes will allow understanding and prediction of locomotor transition pathways in complex 3-D terrains.