Air sac PO2 and oxygen depletion during dives of emperor penguins

In order to determine the rate and magnitude of respiratory O 2 depletion during dives of emperor penguins ( Aptenodytes forsteri ), air sac O 2 partial pressure ( P O 2 ) was recorded in 73 dives of four birds at an isolated dive hole. These results were evaluated with respect to hypoxic tolerance,...

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Bibliographic Details
Published in:Journal of Experimental Biology
Main Authors: Knower Stockard, T., Heil, J., Meir, J. U., Sato, K., Ponganis, K. V., Ponganis, P. J.
Format: Text
Language:English
Published: Company of Biologists 2005
Subjects:
Research Article
Aptenodytes forsteri
Emperor penguins
Online Access:http://jeb.biologists.org/cgi/content/short/208/15/2973
https://doi.org/10.1242/jeb.01687
Description
Summary:In order to determine the rate and magnitude of respiratory O 2 depletion during dives of emperor penguins ( Aptenodytes forsteri ), air sac O 2 partial pressure ( P O 2 ) was recorded in 73 dives of four birds at an isolated dive hole. These results were evaluated with respect to hypoxic tolerance, the aerobic dive limit (ADL; dive duration beyond which there is post-dive lactate accumulation) and previously measured field metabolic rates (FMR s ). 55% of dives were greater in duration than the previously measured 5.6-min ADL. P O 2 and depth profiles revealed compression hyperoxia and gradual O 2 depletion during dives. 42% of final P O 2 s during the dives (recorded during the last 15 s of ascent) were <20 mmHg (<2.7 kPa). Assuming that the measured air sac P O 2 is representative of the entire respiratory system, this implies remarkable hypoxic tolerance in emperors. In dives of durations greater than the ADL, the calculated end-of-dive air sac O 2 fraction was <4%. The respiratory O 2 store depletion rate of an entire dive, based on the change in O 2 fraction during a dive and previously measured diving respiratory volume, ranged from 1 to 5 ml O 2 kg–1 min–1 and decreased exponentially with diving duration. The mean value, 2.1±0.8 ml O 2 kg–1 min–1, was (1) 19–42% of previously measured respiratory O 2 depletion rates during forced submersions and simulated dives, (2) approximately one-third of the predicted total body resting metabolic rate and (3) approximately 10% of the measured FMR. These findings are consistent with a low total body metabolic rate during the dive.

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