Meeting Abstract

P3-123   -   The Macaroni Penguin (Eudyptes chrysolophus) Exhibits Extensive Leg Musculature and Probable Reduced Knee Mobility Hirsh, ML*; Long, MY; Brantley, MB; Rodriguez-Sosa, JR; Lee, AH; Valdez, DR; Georgi, JA; Hall, MI; College of Veterinary Medicine, Midwestern University, Glendale, AZ 85308; College of Veterinary Medicine, Midwestern University, Glendale, AZ 85308; College of Veterinary Medicine, Midwestern University, Glendale, AZ 85308; Colleges of Veterinary Medicine and Graduate Studies, Midwestern University, Glendale, AZ 85308; College of Graduate Studies, Midwestern University, Glendale, AZ 85308; College of Graduate Studies, Midwestern University, Glendale, AZ 85308; Colleges of Veterinary Medicine and Graduate Studies, Midwestern University, Glendale, AZ 85308; Colleges of Veterinary Medicine and Graduate Studies, Midwestern University, Glendale, AZ 85308 Morgan.hirsh@midwestern.edu

Penguins have modified the avian hindlimb for their unique locomotion on land. Dissections of one male and one female macaroni penguin revealed extensive musculature in the legs, despite probably having little ability to extend and flex the knee joint. Because penguins are wing-propelled swimmers, the hindlimbs primarily contribute to locomotion on land. The extrinsic musculature of the hindlimb extends cranially on the dorsal aspect, comprising about half of the dorsal body wall. The sartorius muscle, the most cranial hindlimb muscle, lies cranial to the caudal edge of the scapula, and cranial to the caudal margin of the sternum. Although the hindlimb musculature makes up a large portion of the penguin body, penguins exhibit restricted mobility during locomotion on land including apparent reduced range of motion in the knee joint, which contributes to their signature waddle. In addition, penguins possess a unique muscle we have named the adductor tibialis. This muscle extends from the tibia of one hindlimb, across the midline where it slightly connects to the sternum, and attaches to the tibia of the contralateral limb, effectively tying the hindlimbs together. However, this permanent adduction probably helps create a streamlined figure while swimming to create faster speeds. In contrast to the stifle, the penguin can greatly extend and flex the tarsus during locomotion. The considerable extensor system in the tarsus helps the penguin cross different terrains while walking, as well as give them the ability to jump. The hindlimb morphology of the penguin allows for locomotion on land and faster underwater speeds.