Meeting Abstract
Shortnose gar (Lepisosteus platostomus) are basal actinopterygian fishes that retain a primitive pattern of fin placement. However, the structure of the fin rays or lepidotrichia is similar to that of more modern fishes. Fin function in all ray-finned fishes is largely determined by properties of the bony, segmented fin rays. Here, we explore variation in flexural stiffness among the paired and median fins of the shortnose gar, excluding the caudal fin. We combine morphological data from CT scans with three-point bending tests to understand the relative contributions of fin ray shape and size to the stiffness of the fin rays of shortnose gar. We predict that stiffness will be largely influenced by size and shape of the fin rays, as well as their position within the fin. The results of the three-point bending tests reveal that the pelvic fin rays of the shortnose gar are the most stiff. In all fins but the pelvic fin, the flexural stiffness of the fin rays decreases moving from the leading to trailing edge of the fin. The pectoral fin rays are significantly less stiff than the other fins, and also had the smallest diameter. The flexural stiffness of the dorsal and anal fins was not significantly different from one another. Shape is also an important factor in determining stiffness. We measured the cross-sectional shape of the fin rays using micro computed-tomography (CT) scans in order to calculate second moment of area. This will allow us to assess the relative contributions of shape and size to overall fin ray stiffness. We can then compare the relative stiffness both within and among the fins to data for other, more derived fishes to get a better understanding of how fin ray morphology and function has changed over evolutionary time.
