Meeting Abstract

65.6  Thursday, Jan. 6  Biorobotic analysis of the functional significance of fish tail shapes LAUDER, George*; WITT, Chuck; ANDERSON, Erik; Harvard Univ.; Grove City College; Grove City College glauder@oeb.harvard.edu

Fish vary greatly in tail shape. The homocercal (symmetrical) shape characteristic of most teleost fishes, and the heterocercal (asymmetrical) shape that is present in most shark species are among the best known morphological differences among fishes. However, it is difficult to isolate the effect of tail shape alone on propulsion as there are a myriad of confounding factors that could explain differences in locomotor performance among fishes with different tail shapes. In order to quantitatively compare the effect of tail shape alone on locomotor performance, we used a computer-controlled self-propelling robotic flapping device to oscillate plastic foils (19 cm long; 6.8 cm high; material flexural stiffness = 310 Nm2) with different trailing edge configurations. We oscillated the leading edge of each foil at 2 Hz with +/- 1 cm amplitude and measured self-propelled speed, force oscillation at this speed, and calculated the work per cycle and the energetic cost per meter of travel for each foil. The heterocercal foil swam at a significantly higher speed (5 %) than a homocercal foil of the same area, and also faster than a homocercal foil of the same length. A foil with a notched (forked) tail shape swam significantly (4%) slower than a homocercal tail with the same area. Although the homocercal foil swims at a slower speed than the heterocercal foil, it requires less motor work per cycle to swim at this speed, and the cost per meter of travel (mean = 102 mJ/m) is not significantly different between heterocercal and homocercal foils.