LANDBERG, T.*; MAILHOT, J.D.; BRAINERD, E.L.; University of Massachusetts Amherst: Lung ventilation during treadmill locomotion in the red-eared slider, Trachemys scripta.

Breathing performance during terrestrial locomotion varies in different turtle species. In adult green sea turtles (Chelonia mydas) lung ventilation ceases during bouts of terrestrial locomotion and resumes during pauses between bouts. In contrast, box turtles (Terrapene carolina) breathe almost continuously during treadmill locomotion. These two species are not closely related and differ dramatically in their morphology, locomotor mechanics and ecology. For comparison with these two species, we measured breathing during locomotion in the red-eared slider (Trachemys scripta), a semi-aquatic turtle that is more closely related to Terrapene than to Chelonia. We found that T. scripta (n=5; 238-302g) breathes continuously during treadmill locomotion with small tidal volumes (~1ml) and high breath frequencies (~30 breaths/min). This pattern is similar to the pattern found in Terrapene and indicates that the ability to breathe during locomotion was probably present in the common ancestor of Emydidae. We expected to find that movement of the limbs during locomotion would cause intrapulmonary pressure to fluctuate with the stride cycle and would thereby affect the distribution or magnitude of breaths occuring during locomotion. However, we found that breaths occur at all points in the stride cycle and the magnitude of peak inhalatory and exhalatory airflow do not appear to differ consistently across individuals at any point in the stride cycle. Therefore the abdominal muscles which function to ventilate the lungs probably also compensate for the effects of limb movement during locomotion. Supported by NSF IBN 9875245.