Meeting Abstract
Costal aspiration, in which rib movements ventilate the lungs, is a complex combination of 3D rib rotations where each rib can theoretically rotate about three axes: bucket-handle about a dorsoventral axis, caliper about a craniocaudal axis, and pump-handle about a mediolateral axis. The objective of this study is to understand rib kinematics during breathing in the Argentine black and white tegu, Salvator merianae, and compare them to those of the green iguana, Iguana iguana. Tegu thoracic ribs have three mineralized segments: vertebral, intermediate, and sternal, whereas iguanas have vertebral and sternal. Tegu costovertebral articulations are dorsoventrally elongated and hemiellipsoidal, while those of iguana are hemispherical. We implanted radio-opaque markers into the three rib segments of three tegus and used marker based XROMM to quantify the rotations. We found motion between vertebral and sternal segments but negligible motion between vertebral and intermediate segments, indicating that tegu ribs are functionally bipartite during breathing. Similar to iguanas, tegu vertebral rib rotations were predominantly bucket-handle, but tegus showed significantly less caliper motion, suggesting that the hemiellipsoidal costovertebral articulations constrain motion of the vertebral ribs. Tegu sternal ribs displayed similar magnitudes of bucket and pump-handle motion but the sternocostal joint anatomy suggests no dominant axis of rotation. We used helical axis analysis to describe these rotations and show that the sternal ribs act like a hinge joint through most of their motion. Overall, tegus and iguanas display similar rib rotations, which suggests that bucket-handle rotation may be widespread in squamates, despite variations in rib morphology.
