Meeting Abstract

27.8  Saturday, Jan. 4 15:15  Material properties of the pectoral fin rays of basal actinopterygian fishes TAFT, NK*; FLAMMANG, BE; BLEVINS, E; LAUDER, GV; University of Wisconsin-Parkside; Museum of Comparative Zoology, Harvard University; Museum of Comparative Zoology, Harvard University; Museum of Comparative Zoology, Harvard University taft@uwp.edu

The material properties of the pectoral fin rays (lepidotrichia) of actinopterygian fishes determine the flexibility and shape of fins; yet the diversity of fin ray structure and function remains largely unexplored. In previous work, we used microCT scanning to examine the morphology of the lepidotrichia of two basal actinopterygian species, shortnose sturgeon (Acipenser brevisrostrum) and longnose gar ( Lepisosteus osseus ). Based on these morphological data we made predictions about the stiffness of the lepidotrichia. Specifically, we predicted that sturgeon would have very stiff lepidotrichia, much more stiff than those of the gar or the bluegill sunfish (Lepomis macrochirus), which is the only other species for which we have comparable data. We predicted that the gar, which has a very similar structure to bluegill sunfish, would also exhibit similar material properties. We are interested in variation both among species as well as at different locations in the fin within species. Here we used three-point bending tests to experimentally determine the stiffness of the lepidotrichia in sturgeon and gar. We performed these tests on a dorsal, middle and ventral ray from each pectoral fin, and at three locations along each ray, the proximal third, the middle, and the distal third of the ray. In both species all lepidotrichia examined are stiffer proximally and more flexible distally, which is similar to patterns in bluegill. As predicted, the sturgeon fin rays were stiffer than the gar, which were more stiff then the bluegill. There was also significant variation in stiffness within both sturgeon and gar fins. This was most pronounced in sturgeon, the anterior ray was more stiff than the fin rays of any other species examined to date.