Meeting Abstract
In turtles, the position of the limb girdles deep to the shell presents functional challenges between locomotion and ventilation. Without mobile ribs or a diaphragm, turtles ventilate by contracting a muscular sling inside the rigid shell. Previous studies of semiaquatic turtles indicate that this sling mechanism enables breathing during locomotion. However, respirometry and flume observations suggest that sea turtles cannot breathe during their most intense locomotor style, powerstroking. We hypothesize that species-specific locomotor behavior may explain these differences: semiaquatic turtles row their limbs craniocaudally, whereas sea turtles use a synchronous dorsoventral flapping motion to powerstroke. We used XROMM to quantify the skeletal kinematics of lung ventilation and flapping locomotion in loggerhead sea turtles, Caretta caretta. Rotations and translations were measured relative to the plastron, about anatomical dorsoventral (DV), craniocaudal (CC), and mediolateral (ML) axes. We found that sea turtles rotate their pectoral girdle substantially more during lung ventilation (~5-18° DV) than during powerstroking locomotion (~3-5° DV). These rotations are small compared to those previously described for the semiaquatic river cooter, Pseudemys concinna (~30° DV). Our findings suggest that despite the potential for pectoral girdle rotations demonstrated by movements during ventilation, the evolution of flapping locomotion in sea turtles resulted in smaller rotations of the pectoral girdle, a functional specialization that may inhibit their ability to breathe while powerstroking.
