Meeting Abstract

P1-90   -   Forelimb Adaptations for Sub-aqueous Flying in the Macaroni Penguin (Eudyptes chrysolophus) Long, MY*; Brantley, MB; Hirsh, ML; Rodriguez-Sosa, JR; Valdez, DR; Lee, AH; Georgi, JA; Hall, MI; College of Veterinary Medicine, Midwestern University, Glendale AZ; College of Veterinary Medicine, Midwestern University, Glendale AZ; College of Veterinary Medicine, Midwestern University, Glendale AZ; Colleges of Veterinary Medicine and Graduate Studies, Midwestern University, Glendale AZ; College of Graduate Studies, Midwestern University, Glendale AZ; College of Graduate Studies, Midwestern University, Glendale AZ; Colleges of Veterinary Medicine and Graduate Studies, Midwestern University, Glendale AZ; Colleges of Veterinary Medicine and Graduate Studies, Midwestern University, Glendale AZ michelle.long@midwestern.edu

Penguins possess a highly specialized wing morphology adapted to underwater locomotion. Wing muscle dissections of one female and one male macaroni penguin revealed very reduced musculature in the distal wing, which retains only small brachialis and dorsal ulno-metacarpal muscles. The elbow and metacarpal joints exhibit significantly decreased mobility compared to other birds. Proximal extrinsic wing muscles extend long tendons into the distal wing to control the dorso-ventrally flattened flipper. Two sesamoid bones at the elbow joint provide a main attachment point for the proximal musculature, and probably contribute to the stiffening of the wing during underwater propulsion. Interestingly, the enlarged and extended sternum houses an extensive pectoralis major muscle, responsible for the downstroke, which comprises nearly the entire ventral body wall. Supracoracoideus (=pectoralis minor), found anatomically deep to pectoralis major and responsible for the upstroke, weighed about half of the pectoralis major muscle, unlike most birds, where supracoracoideus weighs only about one-fifth. An enlarged supracoracoideus increases the strength of the upstroke against viscous water. The tendons of latissimus dorsi cranialis and caudalis pass through a fibrous trochlea extending from the triceps complex, a morphology described in penguins but not found in other birds, to attach to the humerus, possibly to increase wing forces when moving the wing caudally. Considered together, the morphology of the wing exhibits a complex of characteristics that combine to modify or specialize general avian wing anatomy to the demands of underwater flight.