Meeting Abstract

S5-5   11:00 - 11:30  Comparison of aquatic and aerial buccal pumping behaviors in African lungfish Kaczmarek, EB*; Gartner, SM; Brainerd, EL; Brown University; University of Chicago; Brown University elskabette@gmail.com

Research on one of the great transitions in vertebrate evolution–the water-to-land transition–tends to focus on the locomotor changes necessary for terrestriality. But the evolution of air-breathing is also a necessary precursor and requires fish to interact with a new medium—air. Air is approximately 1,000 times less dense, 50 times less viscous, and contains hundreds of times more oxygen than water. However, unlike the transition to terrestriality, breathing air does not require body weight support. So, perhaps the evolution of air-breathing required smaller changes to morphology and function. We sought to examine how the cranial kinematics of air-breathing differs from those of aquatic buccal pumping behaviors. We used XROMM to analyze the kinematics of air-breathing in the African lungfish (Protopterus annectens) and compared them to those of gill ventilation and suction feeding that were available in prior literature. During buccal pumping behaviors, the cranial bones act as ‘valves’ and ‘pumps,’ and the sequence of their motions controls the pattern of fluid flow. In aquatic buccal pumping, an anterior-to-posterior wave of expansion is important for generating unidirectional flow. In contrast, during air-breathing, the cranial bones expand nearly synchronously, but still utilize an anterior-to-posterior wave of compression. We included markers on the pectoral girdle and cranial rib (for which the prior kinematic data was limited) and find that they rotate consistently during air-breathing. Overall, we find that the major cranial bones maintain the same basic functions (i.e. acting as valves or pumps, or transmitting power) across aquatic and aerial buccal pumping. The cranial morphology that enables aquatic buccal pumping is well-suited to perform air-breathing and accommodate the physical differences between air and water.