Meeting Abstract
Investigating the evolution of the respiratory system of crocodilians requires a thorough understanding of functional pulmonary anatomy and the associated osteological correlates in extant crocodilians. Previous work suggests that the hepatic-piston pump in extant crocodilians is correlated with a smooth thoracodorsal ceiling, which allows for the free movement and displacement of the lung and pleura during hepatically-driven ventilation, which has been suggested to only engage after vigorous exercise. However, this free movement and displacement of the pleura has neither been confirmed nor measured in living crocodilians. We present our initial results of ultrasound data of the pleura of two juvenile specimens of Alligator mississippiensis. Ultrasound was used to record the hepatic-piston driven ventilation and pleural displacement under three different conditions: 1) the alligators were measured in a calm, natural state, with typical shallow breathing; 2) the alligators inspired a 5% CO2 fixed N2 gas to invoke deep breathing; and, 3) the alligators were measured after exercise (breathing freely without CO2 gas). These preliminary data demonstrate that hepatic-piston pump ventilation and pleural displacement occurred craniocaudally under all three conditions. The amount of pleural and hepatic displacement increased dramatically after CO2/N2 delivery. Our data demonstrate that the hepatic-piston ventilation system is functional both during shallow breathing and induced large breaths, and confirms that the smooth thoracodorsal ceiling allows for the free displacement of pleura and lung tissue.
