BUTLER, M.A.*; University of Tennessee, Knoxville: The physical effects of reproduction on locomotion in the lizard Iguana iguana

Reproduction is generally thought to be a vulerable time for females, especially for those who carry a heavy reproductive load. Since many terrerstrial vertebrate taxa rely on running to escape from predators it is paradoxical that many of these same taxa are still able to carry a large reproductive mass. How do they do it? Surprisingly few studies have examined the physical effects of reproduction on female locomotor performance. Those that have been done have compared only maximal velocity. In this study, I compared gravid vs. post-gravid running kinematics of Iguana iguana females (throughout reproduction and recovery). I ran the lizards down a 6m trackway, and filmed approximately the first 2m of their run at a rate of 250 m/sec. I used two camera views to reconstruct the motion in 3D. I compared distance travelled, velocity, acceleration, and gait parameters for the first three strides of each run. Preliminary results indicate that iguanas immediately pre- and post-oviposition have a slower initial acceleration, although they can typically reach the same preferred speed at the end of the third stride. Recovery from oviposition was gradual, with incremental increases each week for up to six weeks. I will also compare the kinematics of lateral undulation and the hind limb. This study is the first part in a larger study considering physiological impacts of reproduction on locomotion. Because the eggs can displace lungs and other organs in the body cavity, reproductive females may be limited by reduced ventilatory capability. I quantified the reduction in lung volume anatomically, using CT-scan in gravid and post-gravid females. Future work will include comparisons of ventilation and respiration during and after exercise, endurance ability, and thoracic muscle activity during exercise.