Meeting Abstract
In aquatic environments, increased locomotor stability can decrease energetic expenditure by animals, whereas maneuverability is useful for successfully navigating complex habitats. Many morphological features of animals might improve performance in either of these functions. In our previous work on swimming in turtles, we determined that the pelvis is mobile in one of the two major lineages, the cryptodires, but is immobile in the other major lineage, the pleurodires. We sought to test whether these differences in pelvic fusion translated to differences in aquatic stability and maneuverability in these lineages. To do this, we filmed turtles with high-speed video after training them to chase a prey stimulus affixed to a robotic 2-DOF gantry, which ensured that turtles were either swimming straight (to measure stability), or turning at reproducible angles (to measure maneuverability). We tested swimming stability in a flow tank using water speeds ranging from still to 2 BL/sec, and collected maneuverability data in still water. In stability trials, we found that pitch and heave increased with faster flow speed in cryptodires, whereas sideslip and yaw increased at greater flow speeds in pleurodires. Cryptodires consistently had greater limb excursions for both fore and hind limbs, but swam at slower speeds than pleurodires. However, maneuverability also differed between the two lineages. Our results suggest that the structural differences between cryptodire and pleurodire turtles may have significant impacts on their locomotor performance, and may contribute to the differing ecological distributions of species in these lineages.
