40.3 Monday, Jan. 5 A New Twist on Bending: Properties of the Pectoral Fin Rays of the Benthic Longhorn Sculpin, Myoxocephalus octodecimspinosus. TAFT, Natalia K.; University of Massachusetts Amherst firstname.lastname@example.org
Many benthic fishes use their pectoral fins for substrate contact, which requires a combination of stiffness for weight bearing and flexibility for gripping the substrate. The fin rays are the bony structures that support and define the shape of the pectoral fin. I hypothesize that there are morphological specializations of the fin rays that enable benthic fishes to perform these behaviors. I used microCT scanning technology to examine the structure of the pectoral fin rays in the benthic longhorn sculpin, Myoxocephalus octodecimspinosus. I found that the cross-sectional shape of the rays is not uniform along the proximo-distal length of the ray. Distally, the fin ray halves, or hemitrichia, are crescent-shaped, as has been described previously for ray-finned fishes. However, proximally all hemitrichia are circular in cross-section. I hypothesize that the bending properties of the fin rays are largely determined by cross-sectional shape. I predict that this anisotropy confers resistance to bending proximally and flexibility distally. I tested this hypothesis by using controlled bending trials to compare the location of maximum curvature among fin rays. Fin rays with a higher proportion of their total length that was circular in cross-section had a more distal location of maximum curvature. Therefore, a circular cross section does confer resistance to bending proximally. These results support our hypothesis that benthic fishes have morphological specializations of the fin rays that are associated with their functional role in substrate contact behaviors.