Meeting Abstract

40.1  Monday, Jan. 5  Stingray Swimming in 3D: Pectoral fin locomotion BLEVINS, E.*; LAUDER, G.V.; Harvard University; Harvard University eblevins@fas.harvard.edu

Stingrays swim by undulating their expanded pectoral fins, passing a propulsive wave from anterior to posterior. Basic 2D waveforms have been described for some species, but we have shown that the extreme flexibility of stingray fins allows complex deformations in three dimensions. Therefore, detailed 3D data are essential to understand undulatory locomotion and generate hypotheses about fluid flow around rays flexing fins. In this study, we present an analysis of the 3D kinematics of pectoral fin motion in freshwater stingray Potamotrygon hystrix. Three synchronized, one megapixel high speed video cameras (250 frames/s) were calibrated via direct linear transformation and used to film rays (mean disc length (DL)=13cm) swimming at two speeds (1.5 and 2.5 DL/s) in a flow tank. Multiple finbeats per individual, per speed, were analyzed to determine x, y, and z excursions of over 30 points across the fin surface. Kinematic variables including wave speed, frequency and amplitude were determined at each point and compared to other locations on the fin and between speeds. Maximum finbeat frequency nearly doubles with a 1 DL/s increase in speed, from 2.4 to 5.2 Hz. Maximum amplitude does not vary with speed, remaining about 30mm, but the pattern of amplitude increase along the disc changes significantly, with more of the disc reaching higher amplitudes at the faster speed. This follows a general theme in our analysis, where kinematic patterns, rather than the magnitude of particular variables, are key to understanding thrust production. Several observed fin deformations have significant hydrodynamic implications, including active cupping at the distal edge and changes in the form of the propulsive wave as it moves along the fin. Preliminary studies using particle image velocimetry are underway to characterize flow patterns around the fin and explore the effects of rays unique kinematics.