Publication
Title
Respiratory responses to progressive hypoxia in the Amazonian Oscar, **Astronotus ocellatus**
Author
Abstract
This study determined the respiratory responses to progressive hypoxia in oscar, an extremely hypoxia-tolerant Amazonian cichlid. Oscar depressed oxygen consumption rates (), beginning at a critical O2 tension (Pcrit) of 46 Torr, to only 14% of normoxic rates at 10 Torr. Total ventilation () increased up to 4-fold, entirely due to a rise in ventilatory stroke volume (no change in ventilatory frequency), and water convection requirement () increased substantially (up to 15-fold). Gill O2 extraction fell steadily, from 60% down to 40%. Although O2 transfer factor (an index of gill O2 diffusion capacity) increased transiently in moderate hypoxia, it decreased at 10 Torr, which may have caused the increased expired¨Carterial PO2 difference. Venous PO2 was always very low (¡Ü7 Torr). Anaerobic metabolism made a significant contribution to ATP supply, indicated by a 3-fold increase in plasma lactate that resulted in an uncompensated metabolic acidosis. Respiration of isolated gill cells was not inhibited until below 5 Torr; because gill water PO2 always exceeded this value, hypoxic ion flux arrest in oscars [Wood et al., Am. J. Physiol. Reg. Integr. Comp. Physiol. 292, R2048-R2058, 2007] is probably not caused by O2 limitation in ionocytes. We conclude that metabolic depression and tolerance of anaerobic bi-products, rather than a superior capacity for O2 supply, allow oscar to thrive in extreme hypoxia in the Amazon.
Language
English
Source (journal)
Respiratory physiology and neurobiology. - Amsterdam, 2002, currens
Publication
Amsterdam : 2008
ISSN
1569-9048
Volume/pages
162:2(2008), p. 109-116
ISI
000258489000002
Full text (Publisher's DOI)
Full text (publisher's version - intranet only)
UAntwerpen
Faculty/Department
Research group
Publication type
Subject
Affiliation
Publications with a UAntwerp address
External links
Web of Science
Record
Identification
Creation 08.10.2008
Last edited 02.07.2017
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