HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 297/4/R927    most recent 00247.2009v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (1) Google Scholar Articles by Meir, J. U. Articles by Ponganis, P. J. PubMed PubMed Citation Articles by Meir, J. U. Articles by Ponganis, P. J.

Articles

Extreme hypoxemic tolerance and blood oxygen depletion in diving elephant seals

¹Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California San Diego, La Jolla; and ²Department of Ecology and Evolutionary Biology, Long Marine Lab, University of California Santa Cruz, Santa Cruz, California

Submitted May 5, 2009 ; accepted in final form July 26, 2009

Species that maintain aerobic metabolism when the oxygen (O₂) supply is limited represent ideal models to examine the mechanisms underlying tolerance to hypoxia. The repetitive, long dives of northern elephant seals (Mirounga angustirostris) have remained a physiological enigma as O₂ stores appear inadequate to maintain aerobic metabolism. We evaluated hypoxemic tolerance and blood O₂ depletion by 1) measuring arterial and venous O₂ partial pressure (PO₂) during dives with a PO₂/temperature recorder on elephant seals, 2) characterizing the O₂-hemoglobin (O₂-Hb) dissociation curve of this species, 3) applying the dissociation curve to PO₂ profiles to obtain %Hb saturation (SO₂), and 4) calculating blood O₂ store depletion during diving. Optimization of O₂ stores was achieved by high venous O₂ loading and almost complete depletion of blood O₂ stores during dives, with net O₂ content depletion values up to 91% (arterial) and 100% (venous). In routine dives (>10 min) Pv_O2 and Pa_O2 values reached 2–10 and 12–23 mmHg, respectively. This corresponds to SO₂ of 1–26% and O₂ contents of 0.3 (venous) and 2.7 ml O₂/dl blood (arterial), demonstrating remarkable hypoxemic tolerance as Pa_O2 is nearly equivalent to the arterial hypoxemic threshold of seals. The contribution of the blood O₂ store alone to metabolic rate was nearly equivalent to resting metabolic rate, and mean temperature remained near 37°C. These data suggest that elephant seals routinely tolerate extreme hypoxemia during dives to completely utilize the blood O₂ store and maximize aerobic dive duration.

PO₂; aerobic metabolism; %Hb saturation; O₂-Hb dissociation curve; hypoxia

This article has been cited by other articles:

				J. U. Meir and P. J. Ponganis High-affinity hemoglobin and blood oxygen saturation in diving emperor penguins J. Exp. Biol., October 15, 2009; 212(20): 3330 - 3338. [Abstract] [Full Text] [PDF]

				M. Fedak In situ blood oxygen analysis for a truly free-living deep-diving animal. Focus on "Extreme hypoxemic tolerance and blood oxygen depletion in diving elephant seals" Am J Physiol Regulatory Integrative Comp Physiol, October 1, 2009; 297(4): R925 - R926. [Full Text] [PDF]