Meeting Abstract
Ctenophores, at 1 – 15cm in length, are the largest organisms which rely exclusively on cilia for locomotion. In contrast to “typical” cilia, which are a few microns long and operate at Reynolds numbers (Re) much less than one, ctenophore cilia are around a millimeter long and arranged into platelike structures called ctenes, which have 10 < Re < 300. We investigated the scaling of cilia morphology and beat kinematics within a single ctenophore species, the lobate comb jelly Mnemiopsis leidyi. Using specimens in various stages of development, ranging from 0.6 to 4.5cm in length, we measured body size, ctene length, and ctene spacing. We found that while ctene length increases linearly with body size, ctene spacing increased nonlinearly. We used several synchronized high-speed video streams of actively swimming animals to measure kinematic variables such as ctene beat frequency, which were then correlated with 3D-reconstructed bulk variables such as overall body velocity. During passive drifting, we found that animals maintained a relatively constant beat frequency across a large range of body sizes and developmental stages. To further elucidate these differences and similarities, we performed Particle Shadow Velocimetry (PSV) on the actively-beating ctene rows of several size classes, allowing us to calculate the velocity and vorticity fields around the ctenes. These results yield valuable insight into changes in locomotor strategy across ontogeny in ctenophores, and more generally into the operation of flexible propulsors at the milliscale.
