Meeting Abstract

14.6  Monday, Jan. 4  Functional morphology and biomechanics of ratfish steady swimming FOSTER, K. L.*; HIGHAM, T. E.; Univ. of British Columbia; Clemson University fosterk@interchange.ubc.ca

The functional morphology and biomechanics of body-caudal fin swimmers, and more recently median-paired fin swimmers have been studied extensively for a variety of chondrichthyan and osteichthyan fishes. However, functional morphology through ontogeny and the kinematics and hydrodynamics of steady swimming is poorly understood among chimaerids, sister group to sharks, skates, and rays. Ratfish are unique in that they swim by employing a flapping, labriform-like pectoral fin motion. To assess whether morphological differences underlie functional differences in pectoral fin use, we compared pectoral fin muscle morphology of spotted ratfish (Hydrolagus colliei) ranging from 19 to 53cm with that of 62 to 86cm spiny dogfish (Squalus acanthias). Despite the different use of pectoral fins during steady swimming of these two closely related species, no significant difference is found between adductor to abductor muscle mass ratios (P=0.76) or total pectoral muscle mass (P=0.12) relative to body size. The proportion of pectoral muscle projecting distally into the fin, however, is significantly larger in the spotted ratfish (82% and 36% in ratfish and dogfish respectively). This unique arrangement of the pectoral fin muscles in ratfish may enhance fine control over pectoral fin shape and movement. High speed video of ratfish individuals of 39 to 53cm in length swimming steadily at ~45cm/s reveal a constant amplitude of 13.11 ± 1.22cm relative to body length and no significant difference between average upstroke and downstroke velocity (P=0.25). Hydrodynamics of water flow generated by and around the pectoral fins are also analyzed and presented through analysis with particle image velocimetry.