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First published online October 2, 2009
Journal of Experimental Biology 212, 3330-3338 (2009)
Published by The Company of Biologists 2009
doi: 10.1242/jeb.033761
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High-affinity hemoglobin and blood oxygen saturation in diving emperor penguins

Jessica U. Meir* and Paul J. Ponganis

Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093, USA

* Author for correspondence (jmeir{at}ucsd.edu)

Accepted 20 July 2009

The emperor penguin (Aptenodytes forsteri) thrives in the Antarctic underwater environment, diving to depths greater than 500 m and for durations longer than 23 min. To examine mechanisms underlying the exceptional diving ability of this species and further describe blood oxygen (O2) transport and depletion while diving, we characterized the O2–hemoglobin (Hb) dissociation curve of the emperor penguin in whole blood. This allowed us to (1) investigate the biochemical adaptation of Hb in this species, and (2) address blood O2 depletion during diving, by applying the dissociation curve to previously collected partial pressure of O2 (PO2) profiles to estimate in vivo Hb saturation (SO2) changes during dives. This investigation revealed enhanced Hb–O2 affinity (P50=28 mmHg, pH 7.5) in the emperor penguin, similar to high-altitude birds and other penguin species. This allows for increased O2 at low blood PO2 levels during diving and more complete depletion of the respiratory O2 store. SO2 profiles during diving demonstrated that arterial SO2 levels are maintained near 100% throughout much of the dive, not decreasing significantly until the final ascent phase. End-of-dive venous SO2 values were widely distributed and optimization of the venous blood O2 store resulted from arterialization and near complete depletion of venous blood O2 during longer dives. The estimated contribution of the blood O2 store to diving metabolic rate was low and highly variable. This pattern is due, in part, to the influx of O2 from the lungs into the blood during diving, and variable rates of tissue O2 uptake.

Key words: oxygen-hemoglobin dissociation curve, aerobic dive limit, hypoxia, PO2, oxygen depletion


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© The Company of Biologists Ltd 2009