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The influence of locomotion on air-sac pressures in little penguins
1 Department of Biology, Hall of Sciences 258, Eastern Washington University, Cheney, WA 99004, USA,
2 Department of Environmental Biology, University of Adelaide, Adelaide, South Australia 5005, Australia,
3 Department of Zoology, La Trobe University, Melbourne, Victoria 3083, Australia and
4 School of Biosciences, The University of Birmingham, Birmingham B15 2TT, UK
*e-mail: dboggs{at}ewu.edu
Accepted July 27, 2001
Air-sac pressures have been reported to oscillate with wing beat in flying magpies and with foot paddling in diving ducks. We sought to determine the impact on air-sac pressure of wing beats during swimming and of the step cycle during walking in little penguins (Eudyptula minor). Fluctuations averaged 0.16±0.06 kPa in the interclavicular air sacs, but only 0.06±0.04 kPa in the posterior thoracic sac, generating a small differential pressure between sacs of 0.06±0.02 kPa (means ± S.E.M., N=4). These fluctuations occurred at approximately 3 Hz and corresponded to wing beats during swimming, indicated by electromyograms from the pectoralis and supracoracoideus muscles. There was no abdominal muscle activity associated with swimming or exhalation, but the abdominal muscles were active with the step cycle in walking penguins, and oscillations in posterior air-sac pressure (0.08±0.038 kPa) occurred with steps. We conclude that high-frequency oscillations in differential air-sac pressure enhance access to and utilization of the O2 stores in the air sacs during a dive.
Key words: little penguin, Eudyptula minor, locomotion, air-sac pressure, diving, walking.
