Asymmetric kinematics and stiffness produce turning maneuvers in rowing jellyfish*

It was recently reported that oblate jellyfish modulate the local stiffness of their bell margins and the radial symmetry of their bell contractions while turning. Here, we investigate the individual contribution of these behaviors to turning performance using a free-swimming robot model of the jellyfish Cyanea capillata. We report angular turning rates calculated from planar motion tracking and explore the underlying fluid dynamics using DPIV measurements of the flow field. Increases in marginal stiffness, contraction timing asymmetry, and relaxation timing asymmetry each result in statistically significant increases in body turning rate. These behavioral changes create imbalances in momentum flux during contraction, as well as imbalances in jet impingement during refilling, which result in torque about the body center of mass. Graded control of each behavior allows for finely controlled turning maneuvers observed in nature.