Experimental Hydrodynamics and Evolution: Locomotor Design and Function of Pectoral Fins in Fishes

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A hallmark of the enormous diversity of vertebrate animals is extensive variation in the structure and function of the pectoral appendage, which is fin-like in fishes and forms the upper limb in land vertebrates. How does this key feature of vertebrate design function, and what have been the major evolutionary pathways that lead to the forelimb that characterizes mammals? This proposal is designed to address these questions by directly measuring the function of pectoral appendages in water. Although pectoral function has been the subject of speculation for over 100 years, and nearly every textbook in comparative anatomy and paleontology discusses hypotheses of pectoral function, the difficulty of quantifying the effect of pectoral motion in water has prevented any direct experimental tests of these ideas. This grant will apply a novel engineering technique (Digital Particle Image Velocimetry) which allows the reconstruction of three dimensional flow patterns and direct measurement of the force that limbs exert on the water. For the first time we can quantify the function of structures working in fluids, and test long-standing hypotheses about how animals control their movement in water. This research will demonstrate the utility of applying novel engineering approaches to the study of vertebrate structure and function. The planned experiments will test old hypotheses and generate new ideas on which to base interpretations of evolutionary and functional patterns in the vertebrate forelimb.