Meeting Abstract

50.2  Saturday, Jan. 5  Three-dimensional kinematics of pectoral fin locomotion in freshwater stingrays BLEVINS, E.L.*; LAUDER, G.V.; Harvard University; Harvard University eblevins@fas.harvard.edu

Batoid swimming is characterized by distinctive undulations and oscillations of expanded, flexible pectoral fins. Previous work has described fin motion in two dimensions, placing species along a continuum from undulatory to oscillatory locomotion. However, the flexible fins of stingrays allow complex deformations, in addition to the traditionally described anterior-posterior propulsive wave. A three-dimensional analysis of pectoral fin motion is needed to fully describe batoid kinematics, including changes in kinematics with swimming speed, and to generate hypotheses about fluid flow around the flexing fin. In this study we characterize the pectoral fin motion of freshwater stingray Potamotrygon hystrix in three dimensions. Three synchronized, one megapixel high speed video cameras (250 frames/s) were calibrated using direct linear transformation and used to film three individuals (mean disc length=13 cm) swimming at two speeds (1.5 and 2.5 disc lengths/s). Multiple finbeats per individual, per speed, were analyzed to create a three-dimensional model of the moving fin, with approximately thirty points describing surface deformations. Kinematic variables including wave speed, frequency and amplitude were determined for the propulsive wave, and combined with angular variables to quantify fin motion in other planes. We test the hypothesis that a mediolateral wave is present in addition to the anterior-posterior propulsive wave, and determine x, y and z excursions of points across the fin surface. We anticipate that our three-dimensional analysis of batoid locomotion will reveal significant hydrodynamic implications for the fin�s complex deformations. Future experiments using particle image velocimetry will explore these implications and characterize flow patterns around the fin.