Patterns of respiration in diving penguins: is the last gasp an inspired tactic?
Rory P. Wilson1,*,
Alejandro Simeone1,
Guillermo Luna-Jorquera2,
Antje Steinfurth1,
Sue Jackson3 and
Andreas Fahlman3
1 Institut für Meereskunde, Düsternbrooker Weg 20, D-24105 Kiel,
Germany
2 Depto. de Biología Marina, Universidad Católica del Norte,
Larrondo 1281, Coquimbo, Chile
3 Human and Animal Physiology, Stellenbosch University, Private Bag X1,
Matieland 7602, South Africa
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Fig. 1. (A) Continuous line: example of beak movement in a Humboldt penguin
associated with approximately 7 breaths. The dotted line shows the increase
and decrease of the air in the respiratory system over the course of the
breath cycle. (B) Example of the beak movement of a Humboldt Penguin
associated with 2.5 breaths. The line shows a peak and a trough translated
(arrows) onto a pure sine wave (above) for comparison.
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Fig. 2. Rate of (A) inspiration and (B) expiration of air relative to beak angle
during breathing in Humboldt penguins equipped with inter-mandibular sensors.
The rate of inspiration was best described by the equation
y=51.6+149.7ln(beak angle).
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Fig. 3. Tidal volume per breath relative to maximum beak angle for a Humboldt
penguin (Bird 3) equipped with an inter-mandibular sensor. Each point
represents a single breathing cycle. Note that this bird only breathed for 20
consecutive breaths and thus is not included in Tables
1 and
2 (see text).
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Fig. 4. Example of changes in beak angle in a Magellanic penguin during a foraging
trip. (A) Beak angle in relation to depth over time with major systematic
changes occurring whenever the bird was at the surface (see enlarged quadrats
in insets at the top of the figure). The beak movement during the fourth dive
is due to feeding. Beak angle (B) just prior to a dive after an extended
period of rest at the surface and (C) after a dive and followed by extended
rest at the surface. Note that in these two examples the trace of beak angle
over time is not symmetrical about its mid-point (cf. A). Arrows show periods
when the bird was underwater.
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Fig. 5. Maximum beak angles as a function of breath sequence number (n) in
surface pauses consisting of three different total breath numbers;
Nmax=6 (A), 10 (B) or 14 (C). Values are derived from the
means of five free-living Magellanic penguins and are means ± S.E.M.
Values shown are derived from a minimum of 5 readings per bird in all cases.
The inset (D) shows how these values relate to a single typical 10-breath beak
opening trace.
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Fig. 6. Relationship between breath cycle time and maximum beak angle for that
breath for a single Magellanic penguin foraging off Cabo Vírgenes,
Argentina (r2=0.16, F=1510.1,
P<0.001). Values are means ± S.E.M. The relationships for
the other individuals are shown in Table
3.
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Fig. 7. Length of the surface pause as a function of the number of breaths taken
during that pause in a single Magellanic penguin foraging off Cabo
Vírgenes, Argentina (r2=0.49, F=285.7,
P<0.001). The relationships for the other individuals are shown in
Table 3.
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Fig. 8. Derived rate of oxygen transfer from the lungs to the blood (open circles)
and cumulative oxygen acquired by the blood (ascending line) during 14 breaths
in a single Magellanic penguin that was recovering from a dive lasting 74 s.
Tidal volume was taken to be linearly related to maximum beak angle
(Table 2) and equivalent to 50
ml deg–1. Maximum beak angle per breath was taken from the
means of presented data (cf. Fig.
5) and corresponding breath cycle times were taken from curve fits
derived from Fig. 6
(Table 3). The bird was assumed
to breathe through the lungs for the complete cycle time. Total body oxygen
storage was taken to be 232 ml (see text). The bird was calculated as having
an oxygen debt due to the dive of 163 ml (see text – dotted horizontal
lines) and k1 in the equation describing the rate of oxygen transfer (see
Equation 7 in text) was nominally given the value of 0.05. (A) A bird having
an oxygen debt at the onset of the dive of 57 ml, increasing to 220 ml at the
end of the dive. Here, the bird manages to repay the oxygen debt incurred
during the dive in full by the end of the surface period. (B) The bird
surfacing with an oxygen debt due uniquely to the energy expended during the
dive. Here, the bird cannot repay this oxygen debt within the surface pause.
(C) Oxygen acquisition as in A (lower line) compared to the acquisition of
oxygen by a bird breathing according to the conditions given by the first
breath (tidal volume 277 ml and breath cycle 1.2 s) for the full duration of
the rest period (upper line). Note here the change in scale on the
y-axis.
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Fig. 9. Carbon dioxide lost by a Magellanic penguin over the course of a surface
pause lasting 22 s after having completed a dive of 74 s. Conditions are as in
Fig. 8 and total CO2
in the body at the onset of the pause is taken to be 220x0.78=172 ml
(derived from a respiratory quotient RQ in penguins of 0.78; see text). (A)
The rate of CO2 transfer is taken to be directly proportional to
the difference in CO2 partial pressure between total body stores
and air in the respiratory system, with the rate constant k2 nominally taken
to be 0.04. (B) The rate of CO2 transfer is initially taken to be
constant (with a rate constant of 0.005) until tidal volume reaches a minimum
(at 10.6 s into the surface pause), whereupon the rate constant is then taken
to be directly proportional to the oxygen levels in the body (cf.
Fig. 8A) with k2 set at
0.0005.
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© The Company of Biologists Ltd 2003
