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What triggers the aerobic dive limit? Patterns of muscle oxygen depletion during dives of emperor penguins
Cassondra L. Williams, Jessica U. Meir, Paul J. Ponganis

Article Figures & Tables


  • Fig. 1.

    (A) Close-up of implantable near-infrared spectrophotometer (NIRS) probe connected to medical cable. (B) The NIRS instrument with microprocessor-based recorder board attached to underwater cable and implantable probe; underwater housing case shown in black.

  • Fig. 2.

    (A) Example of data recorded by the NIRS instrument and time–depth recorder during a dive. (B) A 5 s excerpt from the same dive showing stroke movement artifact and NIRS baseline between strokes. Depth is shown in blue and NIRS reflectance signal is shown in black.

  • Fig. 3.

    Reflectance ratio from the NIRS instrument vs hemoglobin (Hb) saturation values. Results confirm a linear relationship (y=0.0064x+0.1702, r2=0.98, P=0.0012; dashed lines reflect 95% confidence intervals).

  • Fig. 4.

    Profiles of NIRS reflectance, Hb saturation, blood pressure and heart rate from experiment with a penguin under anesthesia and in which the inspired oxygen fraction (FIO2) was altered. Maroon line, 810 nm reflectance signal; black line, 760 nm reflectance signal; red squares, arterial Hb saturation; blue squares, venous Hb saturation; light gray shaded area, FIO2=50%; dark gray shaded area, FIO2=20%.

  • Fig. 5.

    Distribution of dive duration (top) and maximum dive depth (bottom) of dives from three emperor penguins outfitted with an NIRS instrument and a time–depth recorder (N=50 dives).

  • Fig. 6.

    Relationship between end-of-dive myoglobin (Mb) saturation values and dive duration from (A) type A and (B) type B dives (linear regression, type A, y=125.28–20.92x, r2=0.74, P=0.0007; type B, y=85.56–7.17x, r2=0.68, P<0.0001). Dashed lines reflect 95% confidence intervals. ADL, aerobic dive limit.

  • Fig. 7.

    Example of Mb desaturation, instantaneous stroke frequency and dive depth profiles for (A) a 5.6 min type A dive and (B) a 9.3 min type B dive.

  • Fig. 8.

    Profiles of type B Mb desaturation profiles from four dives (blue, 2.8 min dive; red, 8.4 min dive; green, 9.3 min dive; black, 10.5 min dive).

  • Fig. 9.

    Comparison of locomotory muscle O2 consumption for diving emperor penguins (present study, pectoral muscle), back muscle of forcibly submerged harbor seals (Scholander et al., 1942) and canine gastrocnemius muscle stimulated at different rates (Hogan et al., 1998). Muscle O2 consumption from harbor seal represents only the first 5 min of a 20 min dive, prior to the accumulation of lactate. The last bar represents canine muscle O2 consumption during stimulation with muscle blood flow reduced to 46% (Hogan et al., 1998). Error bars for emperor penguin data are ±s.d.


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