High-affinity hemoglobin and blood oxygen saturation in diving emperor penguins

• Published in: Journal of Experimental Biology
• Main Authors: Meir, Jessica U., Ponganis, Paul J.
• Format: Text
• Language: English
• Published: Company of Biologists 2009
• Subjects: Research Article; Antarctic; The Antarctic; Antarc*; Aptenodytes forsteri; Emperor penguins
• Online Access: http://jeb.biologists.org/cgi/content/short/212/20/3330; https://doi.org/10.1242/jeb.033761

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 (O 2 ) transport and depletion while diving, we characterized the O 2 –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 O 2 depletion during diving, by applying the dissociation curve to previously collected partial pressure of O 2 ( P O 2 ) profiles to estimate in vivo Hb saturation ( S O 2 ) changes during dives. This investigation revealed enhanced Hb–O 2 affinity ( P 50 =28 mmHg, pH 7.5) in the emperor penguin, similar to high-altitude birds and other penguin species. This allows for increased O 2 at low blood P O 2 levels during diving and more complete depletion of the respiratory O 2 store. S O 2 profiles during diving demonstrated that arterial S O 2 levels are maintained near 100% throughout much of the dive, not decreasing significantly until the final ascent phase. End-of-dive venous S O 2 values were widely distributed and optimization of the venous blood O 2 store resulted from arterialization and near complete depletion of venous blood O 2 during longer dives. The estimated contribution of the blood O 2 store to diving metabolic rate was low and highly variable. This pattern is due, in part, to the influx of O 2 from the lungs into the blood during diving, and variable rates of tissue O 2 uptake.