Lauder 9807012 The study of how animals move and generate force against the environment has been a topic of interest to biologists for hundreds of years. One key reason for this interest is that it is very difficult to understand how muscles and bones function to cause movement unless one is able to measure the effect of muscle contraction. This appears as force exerted on the environment. However, despite the importance of the ability to measure forces, analysis of the effect of muscle contraction has remained inferential for many moving organisms because of our inability to directly measure force when animals move in air or water. On land, animals exert force on the ground and these forces can be measured directly. But such direct measurements are not possible in fluids, and biologists have lacked a means of making such measurements. This proposal will apply the results of a technique developed recently by engineers called Digital Particle Image Velocimetry (DPIV) which allows direct quantification of flow in moving fluids and the calculation of the force exerted on the fluid by organisms. This technique will be applied to a classical problem in vertebrate biology: the function and evolution of fins in fishes. Because of the prominence of median fins in early vertebrate fossils, their importance in locomotion, and the diversity of median fin shapes in fishes, the evolution of fins has been discussed in virtually every textbook of comparative anatomy, paleontology, and functional morphology. This study will use DPIV to visualize directly water velocity over fins of fishes and to calculate the forces that result from movement. The PI will use DPIV in conjunction with analysis of three-dimensional fin movements and recordings of the electrical activity generated by fin muscles to test hypotheses about how fishes generate force on the water. Preliminary data for this study are presented which demonstrate feasibility of applying this technique and init ial results show the character of the data that would result from this research. This proposal will introduce a powerful new technique for the experimental study of aquatic locomotion, and by directly quantifying for the first time flow around and behind fins, this study will provide novel data on mechanisms of aquatic propulsion and contribute to clarifying a classic issue in vertebrate functional morphology.
