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First published online September 14, 2007
Journal of Experimental Biology 210, 3344-3355 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.008730
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To what extent might N2 limit dive performance in king penguins?

A. Fahlman1,2,*, A. Schmidt3, D. R. Jones2, B. L. Bostrom2 and Y. Handrich3

1 North Pacific Universities Marine Mammal Research Consortium, UBC Marine Mammal Research Unit, ROOM 247, AERL, 2202 Main Mall, Vancouver, BC, V6T 1Z4, Canada
2 Department of Zoology, The University of British Columbia, 6270 University Blvd., Vancouver, BC, V6T 1Z4, Canada
3 Centre d'Ecologie et Physiologie Energétiques, C.N.R.S., 23 rue Becquerel, 67087, Strasbourg, Cedex 02, France

* Author for correspondence (e-mail: andreas_fahlman{at}yahoo.com)

Accepted 17 July 2007

A mathematical model was used to explore if elevated levels of N2, and risk of decompression sickness (DCS), could limit dive performance (duration and depth) in king penguins (Aptenodytes patagonicus). The model allowed prediction of blood and tissue (central circulation, muscle, brain and fat) N2 tensions (PN2) based on different cardiac outputs and blood flow distributions. Estimated mixed venous PN2 agreed with values observed during forced dives in a compression chamber used to validate the assumptions of the model. During bouts of foraging dives, estimated mixed venous and tissue PN2 increased as the bout progressed. Estimated mean maximum mixed venous PN2 upon return to the surface after a dive was 4.56±0.18 atmospheres absolute (ATA; range: 4.37–4.78 ATA). This is equivalent to N2 levels causing a 50% DCS incidence in terrestrial animals of similar mass. Bout termination events were not associated with extreme mixed venous N2 levels. Fat PN2 was positively correlated with bout duration and the highest estimated fat PN2 occurred at the end of a dive bout. The model suggested that short and shallow dives occurring between dive bouts help to reduce supersaturation and thereby DCS risk. Furthermore, adipose tissue could also help reduce DCS risk during the first few dives in a bout by functioning as a sink to buffer extreme levels of N2.

Key words: breath-hold diving, decompression sickness, mathematical modeling, aerobic dive limit


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© The Company of Biologists Ltd 2007