Meeting Abstract
110.5 Tuesday, Jan. 7 09:00 Tenotomy of the caudofemoralis longus muscle elicits changes in muscular but not skeletal morphology in the American alligator JONESON, J. R.*; ELSEY, R. M.; OWERKOWICZ, T.; California State University, San Bernardino; Rockefeller Wildlife Refuge, Louisiana Dept. of Wildlife and Fisheries, Grand Chenier; California State University, San Bernardino corbettj@coyote.csusb.edu
The caudofemoralis longus muscle (CFL) – a major retractor and medial thigh rotator – is well-developed in reptiles with a sprawling gait and a long tail. The CFL originates on the transverse processes and chevrons of the caudal vertebrae and inserts on the fourth trochanter of the femur. Evolutionary changes to hindlimb orientation and tail morphology among theropod dinosaurs have been ascribed to a reduced role of the CFL in terrestrial locomotion, but no experimental alteration of CFL function has been attempted. In order to investigate the interplay between CFL and skeleton, we used bilateral tenotomy to deactivate the CFL in juvenile (n=12) American alligators (Alligator mississippiensis). After eight months, experimental CFL wet mass and fiber length were found to be significantly reduced, by 23% and 13% respectively, compared to controls. Femur length, external diameter and position of the fourth trochanter, and average caudal chevron length, were similar between both groups. CFL tenotomy thus elicited changes at the muscular level, but not at the skeletal level. Given that no changes in terrestrial locomotor performance were observed following tenotomy, our results suggest that voluntary locomotor patterns in crocodilians are dictated primarily by skeletal morphology rather than muscle morphology. Further monitoring of bone growth/remodelling following tenotomy will allow us to investigate the CFL-driven phenotypic plasticity of the archosaur locomotor system and elucidate the role of musculoskeletal strain in shaping the evolutionary transformation of the hindlimb/tail module in archosaurs.
