Meeting Abstract
To move effectively in one direction, sea stars must somehow coordinate the motion of hundreds of podia arrayed along arms that point in multiple different directions. Podia coordination has previously been attributed to either central nervous control or to some form of local proprioceptive system. However, considerable debate still exists over how coordination is achieved. To test whether sea stars coordinate their tube feet via central nervous control or via local proprioceptive cues, we tracked the movements of multiple individual podia in juvenile sea stars that attached one or more rays to the surface tension of seawater. Sea stars were filmed walking upside-down on the surface tension and on an adjacent floating glass cover slip to compare podia movements simultaneously on both surfaces. We found that podia do attach to the surface tension and do attempt to propel the sea star, but these attached movements were much less coordinated than when podia attached to a glass surface. We also tracked the recovery strokes of individual podia and their neighbors on these two substrata to test how coordinated recovery motions were. Our results suggest that local proprioceptive cues are important for effective echinoderm locomotion but we cannot entirely rule out the contribution of central nervous coordination.
