Swimming behavior of larval Pisaster ochraceus

Abstract

The behavior of sea star brachiolaria larvae is poorly understood and the role of their elongated posterior processes in swimming is unknown. We attempt to characterize swimming speed and behavior in the late stage brachiolaria of Pisaster ochraceus in order to form a metric for larval health and to better understand the role of larval behavior in feeding and dispersal potential. We found that larvae swim faster in the presence of food and sink at a consistent rate when cilia are removed, which does not vary linearly with body or process length. In a simulation of simplified model brachiolaria in horizontal shear flow, larvae with their posterior processes parallel were more stable, while larvae with angled processes began to tumble at lower levels of shear. Further investigation will use video analysis to assess larval movement in varying levels of vertical shear that we created in a column using a rotating belt.