Meeting Abstract

P1.204  Friday, Jan. 4  Morphological variation in the pectoral fin lepidotrichia in basal actinopterygian fishes TAFT, NK*; LAUDER, GV; SHUBIN, N; University of Wisconsin-Parkside; Harvard University; University of Chicago taft@uwp.edu

Actinopterygian fishes are named for the bony fin rays (lepidotrichia) that support the fins. The curvature and position of the fin rays largely defines the shape and function of the fins, but little is known about the morphological and functional diversity in this key structure. Until recently, the lepidotrichia have been thought to be relatively uniform within living Actinopterygii. Previous work has demonstrated that the morphology of the fin rays of a benthic species Myoxocephalus octodecimspinosus, is morphologically and functionally distinct from this more generalized type. Here, we expand our sample to investigate morphological diversity at the base of the actinopterygian tree by examining the morphology in three basal species, Polypterus senegalus, (bichir), Acipenser brevirostrum (shortnose sturgeon) and Lepisosteus osseus (gar). We used a microCT scanner to examine the microstructure of the lepidotrichia of the pectoral fins of these taxa. We found significant morphological variation, particularly in the cross-sectional shape and degree of segmentation, of the pectoral lepidotrichia both within and among these three species. For example, the lepidotrichia of the sturgeon have a unique wishbone-like shape in cross section. These species also vary in the degree of segmentation along individual rays. In the bichir the lepidotrichia are segmented for almost their entire length, while those of gar and sturgeon remain unsegmented for almost a third of their total length. Cross-sectional shape and segmentation are features that affect the curvature of lepidotrichia. Therefore, we hypothesize that the morphological variation will result in specific functional consequences that will be experimentally tested in future work.