Exposure to hypoxia primes the respiratory and metabolic responses of the epaulette shark to progressive hypoxia

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Title Exposure to hypoxia primes the respiratory and metabolic responses of the epaulette shark to progressive hypoxia
Author Routley, Matthew H.; Nilsson, Goran E.; Renshaw, Gillian Mary Claire
Journal Name Comparative Biochemistry and Physiology Part A
Editor Thomas P. Mommsen, Patrick J. Walsh
Year Published 2002
Place of publication New York
Publisher Elsevier
Abstract The majority of vertebrates are not tolerant to hypoxia but epaulette sharks (Hemiscyllium ocellatum) living on shallow reef platforms appear to tolerate hypoxic periods during tidal fluctuations. The effects of progressive hypoxia on the metabolic and ventilatory responses of these elasmobranchs were examined in a closed respirometer. In order to determine whether repeated exposure to hypoxia primes these sharks to alter their metabolism, one group of sharks was exposed to repeated sub-lethal hypoxia, at 5% of air saturation, prior to respirometry. In response to falling oxygen concentration [O2], the epaulette shark increased its ventilatory rate and maintained its O2 consumption rate (V2) down to 2.2 mg O2 l1 at 25 °C. This is the lowest critical [O2] ([O2]crit) ever measured for any elasmobranch. After reaching the [O2]crit, the shark remained in the respirometer for a further 45 h of progressive hypoxia. Only after the [O2] fell to 1.0 mg l1 was there a decrease in the ventilatory rate followed by a rise in blood lactate levels, indicating that the epaulette shark responds to severe hypoxia by entering a phase of metabolic and ventilatory depression. Interestingly, hypoxia tolerance was dynamic because hypoxic pre-conditioning lowered the V2 of the epaulette shark by 29%, which resulted in a significantly reduced [O2]crit (1.7 mg O2 l1), revealing that hypoxic pre-conditioning elicits an enhanced physiological response to hypoxia.
Peer Reviewed Yes
Published Yes
Publisher URI http://www.elsevier.com/wps/find/journaldescription.cws_home/525464/description#description
Copyright Statement Copyright 2002 Elsevier : Reproduced in accordance with the copyright policy of the publisher : This journal is available online - use hypertext links.
Volume 131
Page from 313
Page to 321
ISSN 1095-6433
Date Accessioned 2003-04-29
Language en_AU
Research Centre Heart Foundation Research Centre; Menzies Health Institute Qld
Faculty Griffith Health Faculty
Subject Comparative Physiology; Science & Technology
URI http://hdl.handle.net/10072/6803
Publication Type Journal Articles (Refereed Article)
Publication Type Code c1

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