S10-3 Thu Jan 7 11:00 – 11:30 The swimming kinematics of barnacle cyprid larvae using permanently fused setules Lamont, EI*; Emlet, RB; University of Washington, Seattle, WA; University of Oregon, OIMB, Charleston, OR email@example.com
Thoracican barnacles undergo several planktonic larval stages before settlement and metamorphosis. The final stage is the cyprid, a non-feeding larva with six pairs of swimming thoracic appendages and two anterior antennules used for attachment during settlement. Extensive research has focused on the behavior of cyprid antennules; however, there is limited knowledge on the pre-settlement swimming behavior of cyprids. Here, we used high speed videography to observe cyprids of the barnacle Balanus glandula and describe thoracic appendage swimming kinematics. Cyprids use a drag-based method of swimming, with their six pairs of thoracic appendages undergoing metachronal power strokes and synchronous recovery strokes. During the power stroke, plumose setae on each appendage pair spread laterally into a high surface area and high drag paddle shape composed of a meshwork of permanently fused setules. This interconnected setal array collapses into a low surface area and low drag shape during the recovery stroke. Cyprids of B. glandula swim upwards at an average speed of 1.4 cm/sec (about 25 body lengths/sec) and can reach an instantaneous velocity of up to 6 cm/sec. At their average speed, cyprids move at the intermediate Reynolds number of 10, in which both viscous and inertial forces affect movement. Cyprids change their swimming direction by beating their versatile thoracic appendages synchronously through the power stroke and angling their posterior-most appendage pair to likely act as a rudder to alter direction of motion. These descriptions greatly enhance our understanding both of cyprid motility and of how these small plankton can use multiple appendages with recently-discovered fused setule arrays to reach high swimming speeds.