Meeting Abstract
Sand-diving, a behavior documented in the three fish families Creedidae, Trichonotidae, and Labridae, consists of a headfirst plunge into the substrate followed by undulatory axial body movements to completely bury the fish. Previous behavioral work has shown that sand-diving is a predator avoidance and energy conservation behavior. The kinematics of this behavior remain unstudied, however. We employed high-speed video to analyze sand-diving by the slippery wrasse, Halichoeres bivittatus (Labridae). Seven captive H. bivittatus were induced to bury in small aquaria containing crushed coral gravel substrate. Sand-diving events ranged in duration from 1.05 to 3.06 seconds. Coordinate points digitized along the body midline of the fish for each frame of the diving event were used to calculate kinematic variables. Kinematic and visual analyses show that sand-diving of H. bivittatus is composed of two distinct phases of undulatory axial body movements. The first phase is characterized by body undulations with high frequencies and wave speeds and low amplitudes. Individuals remain orientated approximately perpendicular to the substrate as they bury. The second phase begins when individuals are between halfway and two-thirds buried. Undulations visibly slow and individuals orient more parallel to the substrate. Body undulations have lower frequencies and wavespeeds and higher amplitudes than during the first phase. The two phases of sand-diving in H. bivittatus have implications for slurry exploitation, as the initial high frequency undulation may serve to liquefy the substrate, creating a slurry through which the animal can more efficiently bury itself during the second phase. This project was funded by NSF grant IOS-142549.
