What triggers the aerobic dive limit? Patterns of muscle oxygen depletion during dives of emperor penguins

• Published in: Journal of Experimental Biology
• Main Authors: Williams, Cassondra L., Meir, Jessica U., Ponganis, Paul J.
• Format: Text
• Language: English
• Published: Company of Biologists 2011
• Subjects: Research Articles; Aptenodytes forsteri; Emperor penguins
• Online Access: http://jeb.biologists.org/cgi/content/short/214/11/1802; https://doi.org/10.1242/jeb.052233

The physiological basis of the aerobic dive limit (ADL), the dive duration associated with the onset of post-dive blood lactate elevation, is hypothesized to be depletion of the muscle oxygen (O 2 ) store. A dual wavelength near-infrared spectrophotometer was developed and used to measure myoglobin (Mb) O 2 saturation levels in the locomotory muscle during dives of emperor penguins ( Aptenodytes forsteri ). Two distinct patterns of muscle O 2 depletion were observed. Type A dives had a monotonic decline, and, in dives near the ADL, the muscle O 2 store was almost completely depleted. This pattern of Mb desaturation was consistent with lack of muscle blood flow and supports the hypothesis that the onset of post-dive blood lactate accumulation is secondary to muscle O 2 depletion during dives. The mean type A Mb desaturation rate allowed for calculation of a mean muscle O 2 consumption of 12.4 ml O 2 kg–1 muscle min–1, based on a Mb concentration of 6.4 g 100 g–1 muscle. Type B desaturation patterns demonstrated a more gradual decline, often reaching a mid-dive plateau in Mb desaturation. This mid-dive plateau suggests maintenance of some muscle perfusion during these dives. At the end of type B dives, Mb desaturation rate increased and, in dives beyond the ADL, Mb saturation often reached near 0%. Thus, although different physiological strategies may be used during emperor penguin diving, both Mb desaturation patterns support the hypothesis that the onset of post-dive lactate accumulation is secondary to muscle O 2 store depletion.