LANDBERG, Tobias*; MAILHOT, Jeffrey; BRAINERD, Elizabeth L.: Lung Ventilation during Treadmill Locomotion in Terrapene carolina.

Turtles are unique in that their shells essentially contain a fixed volume. As a result, when the head or limbs are retracted or protracted, air may be forced into or out of the lungs. Resting turtles may actively ventilate the lungs by using a limb pump mechanism. We hypothesize that movements of the limbs during locomotion will affect breathing. Jackson & Prange (1979) found that adult nesting Chelonia mydas does not breathe during terrestrial locomotion and suggested that a mechanical constraint exists between simultaneous locomotion and ventilation. However, we have found that Terrapene carolina breathes effectively during treadmill locomotion. Mean minute volume is 4.6 times greater during locomotion than during recovery (88�13 vs. 19�19 ml/min respectively; n=3 individuals � s.d.). Mean tidal volumes are similar during locomotion and recovery (2.7�1.3 vs. 1.7�0.7 ml/breath respectively). These data indicate that ventilation is not constrained by locomotion. We also found no fixed phase relationship between ventilation and locomotion. Both inhalation and exhalation occur at all points in the stride cycle, indicating that T. carolina does not couple ventilation and locomotion. This also suggests that they do not use a limb pump mechanism for ventilation during locomotion. Additionally, there is no evidence that T. carolina (or any turtle species) use the hyobranchial apparatus as a force pump to ventilate the lungs. However, simultaneous x-ray videography and pneumotachography of T. carolina breathing during locomotion provide strong kinematic evidence that the transverse abdominis and the oblique abdominis muscles are responsible for the independence of the ventilatory and locomotor systems. Supported by NSF IBN 9875245.