Meeting Abstract
The flukes of cetaceans are the principal structure used to generate thrust during swimming. The flukes are composed of a compact array of collagen fibers with a complex organization. This arrangement provides the flukes with both rigidity and flexibility. There has been disagreement regarding the contribution of the up- and down-stroke of the flukes to swimming. To assess the baseline passive flexibility of the flukes and determine if bending is equal between dorsal and ventral orientations, the flukes of 11 mature harbor porpoises, Phocoena phocoena, were subjected to a single point bending test. An isolated fluke was immobilized at its base and increasing increments of weight (up to 1.8 kg) were suspended for the tip of the fluke. Scaled images were taken for each increment of weight to measure the deflection of discrete points along the span of the fluke. Deflection along the fluke span increased curvilinearly to a maximum at the tip of the fluke. This flexibility would be dependent on the tapering spanwise profile of the fluke, internal fiber direction, and its differential composition density. There was no difference in flexibility between flukes in a dorsal or ventral orientation. This correlates with the dorso-ventrally symmetrical internal fibrous structure of the flukes. These data suggest that the morphology of the flukes is aligned with a symmetrical up- and down-stroke.
