From Air Sacs to Tissues: Oxygen Transfer and Utilization in Diving Emperor Penguins

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During exercise, oxygen must be efficiently delivered from the lungs to the working tissues. Birds have a unique respiratory system that includes both air sacs and lungs (called parabronchi) and has a one-way, rather than bidirectional, air flow pattern. This allows a high proportion of the oxygen in inhaled air to be transferred into the blood so that it can be circulated by the cardiovascular system to the tissues. In diving birds such as the emperor penguin, the air sac-to-tissue oxygen delivery is essential to the dive capacity, and is one of the adaptations that allows this species to dive deeper than 500 meters. However, the physiological mechanisms underlying the transfer of oxygen from air sacs to blood and the subsequent distribution of oxygen to tissues are poorly understood. The emperor penguin is ideal for investigation of this oxygen cascade because of its large body size, dive capacity, physiological data base, and the prior development of research techniques and protocols for this species. This study should provide insight into a) the mechanisms underlying the efficiency of the bird oxygen transport system, b) the physiological basis of penguin dive behavior, and the ability of penguins to adapt to environmental change, and c) perhaps, even the design of better therapeutic strategies and tools for treatment of respiratory disease. The project also includes educational exhibits and lecture programs on penguin biology at SeaWorld of San Diego. These educational programs at SeaWorld have outreach to diverse groups of grade school and high school students. One graduate student will also be trained, and participate in Antarctic physiological research. This project will examine the transport of oxygen from air sacs to tissues in a series of studies with temporarily captive emperor penguins that are free-diving at an isolated dive hole research camp in McMurdo Sound. Physiological data will be obtained with application of backpack recorders for the partial pressure of oxygen (PO2) in air sacs and/or blood, and backpack heart rate/stroke rate recorders. This experimental approach will lay the groundwork for future investigations of air sac to lung to blood oxygen transfer during exercise of flying and running birds. Four major topics are examined in this project: a) air sac oxygen distribution/depletion and the movement of air between anterior and posterior air sacs, b) anterior air sac to arterial PO2 differences and parabronchial gas exchange, c) blood oxygen transport and depletion throughout dives, and the nature of the aerobic dive limit, and d) the relationship of venous oxygen depletion patterns to both heart rate and stroke effort during dives. Specific educational outreach goals include a) short video features to be displayed in the Penguin Encounter exhibit at SeaWorld of San Diego, and b) lectures, video presentations, and pre- and post-course evaluations for student campers and participants in SeaWorld's education programs. Underwater video for exhibits/presentations with be obtained with use of a penguin backpack camera in the Antarctic.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.