Meeting Abstract
90.8 Thursday, Jan. 7 Ontogeny and the biomechanics of feeding in the American alligator (Alligator mississippiensis): Developmental changes to muscle physiology contributes to niche transitions in a large-bodied vertebrate GIGNAC, P.M.*; ERICKSON, G.M.; Florida State University; Florida State University pgignac@bio.fsu.edu
The American alligator, Alligator mississippiensis, undergoes a substantial resource shift to increasingly more durable prey throughout development. In addition to its size, this taxon utilizes absolutely high bite forces to capture and subjugate these food resources. For large mammalian prey drowning is the main mode of subjugation wherein A. mississippiensis uses its high bite forces to maintain a purchase on the prey item as it is pulled underwater. With struggling prey this process can last tens of minutes. Vertebrate skeletal muscle, however, is unable to sustain high-force contractions over long periods of time. Therefore, how this taxon is physiologically capable of executing such a critical behavior is unknown. Analysis of the jaw adductor musculature throughout ontogeny shows that developmental changes to the colors of some adductors indicate a physiological transition from glycolytic to oxidative muscle fibers. Additionally, bite force measurements in A. mississippiensis show that sub-adult and adult individuals maintain a 6-8% hold (of maximum bite force) in between periods of peak bite-force generation. Together these observations suggest one way A. mississippiensis gains access to large prey, namely through developmental changes to muscle physiology. To test if these changes can account for the holding behavior, we used a recently established biomechanical model of bite-force generation to address the ability of the developmentally plastic jaw adductors to generate appropriate hold forces. Our results show that the model accounts for the observed forces in relative and absolute comparisons and points towards physiologically important changes to the jaw adductor system of crocodilians that have not been considered previously.
