Visualization of Rotational Swimming Patterns in Oblate Jellyfish

Abstract

Kim, S.; Pyeon, Y.; Lee, K.; Kim, P.; Oh, W., and Choi, J.H., 2020. Visualization of rotational swimming patterns in oblate jellyfish. Journal of Coastal Research, 36(2), 289–294. Coconut Creek (Florida), ISSN 0749-0208.To identify the swimming mechanism of jellyfish, the present study conducted observational experiments using particle image velocimetry in a relatively flat and oblate-shaped jellyfish, the moon jellyfish (Aurelia aurita). The formation of vortices around the left and right edges of the jellyfish's bell and the associated vorticity structures that formed during rotational swimming were analyzed. The effects of variation in the width-to-height ratio of the jellyfish during rotational swimming were also investigated. Moon jellyfish generated locomotor structures with velocities faster than their neighboring flow velocities by producing paddling motions at the left and right edges of the bell at width-to-height ratios more than 0.531. Faster locomotor structures were not observed at width-to-height ratios less than 0.496. Moreover, jellyfish tended to rotate in a counterclockwise direction from the central axis of the body. With respect to paddling speed, and according to changes in the width-to-height ratio, the left edge was, on average, 25% faster than the right edge. The left edge, where the central axis of rotation is located, exhibited a 40% reduction in its rotational angle when paddling speed was decreased by 87%. This study lays the methodological foundation for further studies to investigate how variation in environmental conditions affect jellyfish locomotion and how locomotion varies among species.