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The respiratory system in varanid lizards: determinants of O2 transfer

Frappell, P. B., Schultz, Timothy J. and Christian, Keith A. (2002). The respiratory system in varanid lizards: determinants of O2 transfer. Comparative Biochemistry and Physiology A: Molecular and Integrative Physiology,133(2):239-258.

Document type: Journal Article
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Title The respiratory system in varanid lizards: determinants of O2 transfer
Author Frappell, P. B.
Schultz, Timothy J.
Christian, Keith A.
Journal Name Comparative Biochemistry and Physiology A: Molecular and Integrative Physiology
Publication Date 2002
Volume Number 133
Issue Number 2
ISSN 1531-4332   (check CDU catalogue open catalogue search in new window)
Scopus ID 2-s2.0-0036801068
Start Page 239
End Page 258
Total Pages 20
Place of Publication Netherlands
Publisher Elsevier Science
Field of Research 0606 - Physiology
0608 - Zoology
1116 - Medical Physiology
HERDC Category C1 - Journal Article (DEST)
Abstract Varanids in general exhibit greater aerobic capacities than other lizards. In a similar approach to the extensive investigations undertaken in mammals, the respiratory system in varanids is examined in terms of oxygen transfer from the air to the blood during rest and sustained locomotory activity. The parameters controlling the transfer Of O-2 through the various steps of the respiratory system are appropriate to meet the maximum demands for oxygen with one possible exception, circulatory convection. Ventilatory convection is maintained during maximal aerobic locomotion ensuring adequate pulmonary ventilation and the protection of alveolar P-O2, Little evidence exists to indicate a mechanically imposed constraint to breathe and the possibility of a gular pump acting to assist ventilation, as a general feature of varanids remains to be determined. Alterations in the relative contributions of the ventilation-perfusion ratio, pulmonary diffusion, diffusion equilibrium and right-left shunts preserved the alveolar-arterial P-O2 difference, ensuring that arterial oxygenation was maintained. In those species where increases in cardiac output were limited, maximum O-2 transfer was achieved through increased extraction of oxygen at the tissues. Overall, the interrelationship of adjacent steps in the respiratory system ensures that one step cannot become limiting. Compensatory changes occur in various parameters to offset those parameters that are 'limited'. The high aerobic activity of varanid lizards would not be achievable without a compensated circulatory convection.
Keywords respiratory system
oxygen transport
lung diffusion
oxygen affinity
pulmonary gas-exchange
exercise performance
adaptive variation
hypaxial muscles
lung ventilation
graded activity
monitor lizard
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