Meeting Abstract

SICB+    Water surface swimming dynamics in a centipede Diaz, K*; Tarr, SW; Goldman, DI; Georgia Tech; Georgia Tech; Georgia Tech kelimar.diaz@gatech.edu

Centipedes coordinate their body and many limbs to navigate a diversity of terrains. In terrestrial environments, these animals use travelling waves of body curvature and limb stepping waves for locomotion. Less is known about how these animals navigate fluid environments. Here, we challenged a terrestrial centipede, L. foficatus (N=8, L=2.3±0.3 cm, 14 leg pairs), to locomote in water. Additionally, we used a Schlieren method to reconstruct and observe waves generated by the centipedes. When kept afloat by surface tension, the animals swam successfully. If a centipede was submerged, the animal would sink without generating motion. On the water surface, the centipedes locomoted via waves of horizontal plane body curvature propagating in the direction of motion (direct waves) with limbs oriented perpendicular to the body axis. The body dynamics were surprising given that centipedes that use a direct limb-stepping pattern do not exhibit body undulation for locomotion in terrestrial environments. Further, amphibious centipedes (S. subspinipes mutilans) swim using body waves that travel opposite to the direction of motion and fold their limbs towards their body (Yasui et al., Sci. Reports, 2019). When L. foficatus used body undulation on the fluid surface, the centipedes achieved speeds of 0.22±0.03 body lengths per gait cycle using body waves with a maximum amplitude of 3.9±1.5 cm^-1 and 1.3±0.23 waves along their bodies. When the centipedes cycled only their limbs without body undulation, the animals achieved negligible displacement. In addition, centipedes were capable of swimming on their back via body undulation with small limb-fluid contact. This suggests that surface swimming in this species is facilitated by the propagation of body waves, not limb flexion. We posit these direct body waves enable the animal to swim non-inertially by varying the animal’s drag anisotropy (ratio of local perpendicular to parallel forces).