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First published online February 15, 2006
Journal of Experimental Biology 209, 938-944 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.02063
Respiration by buried echidnas Tachyglossus aculeatus
School of Integrative Biology, University of Queensland, Brisbane, Australia 4072
* Author for correspondence (e-mail: d.booth{at}uq.edu.au)
Accepted 22 December 2005
Short-beaked echidnas have an impressive ability to submerge completely
into soil or sand and remain there, cryptic, for long periods. This poses
questions about how they manage their respiration, cut off from a free flow of
gases. We measured the gradient in oxygen partial pressure
(PO2) away from the snouts of buried echidnas
and oxygen consumption
(
O2) in five
individuals under similar conditions, in two substrates with different
air-filled porosities (fa). A theoretical diffusion model
indicated that diffusion alone was insufficient to account for the flux of
oxygen required to meet measured rates of
O2. However, it
was noticed that echidnas often showed periodic movements of the anterior part
of the body, as if such movements were a deliberate effort to flush the tidal
air space surrounding their nostrils. These `flushing movements' were
subsequently found to temporarily increase the levels of interstitial oxygen
in the soil around the head region. Flushing movements were more frequent
while O2 was
higher during the burrowing process, and also in substrate with lower
fa. We conclude that oxygen supply to buried echidnas is
maintained by diffusion through the soil augmented by periodic flushing
movements, which ventilate the tidal airspace that surrounds the nostrils.
Key words: monotreme, burrowing, respiration, gas exchange, oxygen consumption, echidna
