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Effects of Cold Exposure on Oxygen Consumption, Ventilation and Interclavicular Air-Sac Gases in the Little Penguin(Eudyptula Minor)
1 Department of Zoology, University of Trondheim, N-7055 Dragvoll, Norway and Department of Physiology, University of Tasmania GPO Box 252C, Hobart 7001, Australia
Oxygen consumption (VO2), tidal volume, respiratory frequency and the composition of the gas in the interclavicular air sac were measured in the little penguin Eudyptula minor (Forster) at ambient temperatures (Ta) of 5 and 20 °C.
VO2 increased from 14.60 ml O2 kg-1 at 20°C to 18.29 ml O2 kg-1 min-1 at 5 °C. However, the elevated atVO2 the low Ta was not matched by a similar rise in total inspiratory ventilation (Vi). The ventilatory requirement (Vi/VO2) thus decreased from 0.5751 mmol-11 at 20°C to 0.4401 mmol-1 at 5°C. An increased gas exchange efficiency during cold exposure was also shown by the composition of the gas in the interclavicular air sac. PO2 decreased from 11.95 kPa at 20°C to 10.24kPa at 5°C, while the corresponding increase in PCO2 was from 6.61 to 7.50 kPa.
Oxygen extraction, calculated from VO2, Vi and O2 content of the inspired air, increased from 24.60% at 20°C to 31.04% at 5°C. Oxygen extraction calculated from the O2 contents of inspired air and interclavicular air—sac gas was 38.73 % at 20°C and 47.18% at 5°C.
The results confirm previous findings for the little penguin which showed a decrease in the ventilatory requirement with increasing oxygen uptake. However, the improved gas exchange efficiency during cold exposure and the strong correlation found between oxygen extraction and oxygen consumption have not been demonstrated previously for this species.
Key words: cold exposure, interclavicular air-sac gas, oxygen consumption, oxygen extraction, penguin, ventilation, ventilatory requirement
Accepted on June 28, 1990
