Blood oxygen transport and depletion in diving emperor penguins

Oxygen store management underlies dive performance and is dependent on the slow heart rate and peripheral vasoconstriction of the dive response to control tissue blood flow and oxygen uptake. Prior research has revealed two major patterns of muscle myoglobin saturation profiles during dives of emperor penguins. In Type A dives, myoglobin desaturated rapidly, consistent with minimal muscle blood flow, and low tissue oxygen uptake. Type B dives, with fluctuating and slower declines in myoglobin saturation, were consistent with variable tissue blood flow patterns and tissue oxygen uptake during dives. We examined arterial and venous blood oxygen profiles to evaluate blood oxygen extraction and found two primary patterns of venous hemoglobin desaturation that complemented corresponding myoglobin saturation profiles. Type A dives had venous saturations that a) increased or plateaued for most of the dive and that only declined during the latter stages of ascent, b) often became arterialized (arterio-venous (a-v) shunting). In Type B dives, variable but progressive venous hemoglobin desaturation profiles were interrupted by inflections in the profile that were consistent with fluctuating tissue blood flows and oxygen uptake. End-of-dive saturations of arterial and Type A venous dives were not significantly different, but did differ from those of Type B venous dives. These findings provide further support that the dive response of emperor penguins is a spectrum of cardiac and vascular components (including a-v shunting) that are dependent on the nature and demands of a given dive and even of a given segment of a dive.

Methods
Data were collected with backpack recorders on diving emperor penguins in 2001-2008, and downloaded to computers for analysis.