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First published online November 19, 2004
Journal of Experimental Biology 207, 4415-4425 (2004)
Published by The Company of Biologists 2004
doi: 10.1242/jeb.01290

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How a low tissue O₂ strategy could be conserved in early crustaceans: the example of the podocopid ostracods

Laure Corbari, Pierre Carbonel and Jean-Charles Massabuau^*

Laboratoire d'Ecophysiologie et Ecotoxicologie, des Systèmes Aquatiques, UMR 5805, Université Bordeaux 1 and CNRS, Place du Dr B. Peyneau, 33120 Arcachon, France

^* Author for correspondence (e-mail: jc.massabuau{at}epoc.u-bordeaux1.fr)

Accepted 17 September 2004

An adaptation strategy whereby O₂ partial pressure, P_O2, in the tissues is maintained within a low, narrow range of 1–3 kPa, largely independent of the inspired P_O2, has been reported in water- and air-breathing poikilotherms and in homeotherms. Based on the postulate that this basic cellular mechanism has been established since the early stages of evolution, it has been hypothesized that it could be the consequence of an early adaptation strategy to maintain cellular oxygenation within the same low and primitive range. To test this hypothesis we studied the basic mechanisms of oxygen regulation in podocopid ostracods, minute crustaceans that have existed on earth for at least 500 million years. Podocopids lack any regulatory mechanism for adapting their ventilation to cope with changes in water oxygenation, and instead adjust their tissue oxygenation status by migrating through the O₂ gradient to sediment layers where the P_O2 of the water is 3–5 kPa. Experimental manipulation of the O₂ profile induced their vertical migration to follow this precise water P_O2 and demonstrates the existence of a regulation strategy. This strategy must be associated with the lower P_O2 values within the animal's carapace valves, showing that podocopids can actively regulate their tissue P_O2 at constant but even lower values than the water. In conclusion, the low tissue P_O2 strategy could have existed in early crustaceans and, by extension, in early animals.

Key words: respiration, evolution, crustacea, control of breathing, oxygen regulation, hypoxia

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OSTRACODS' OXYGEN PUZZLE

Yfke van Bergen
JEB 2004 207: ii. [Full Text]  

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				L. Corbari, P. Carbonel, and J.-C. Massabuau The early life history of tissue oxygenation in crustaceans: the strategy of the myodocopid ostracod Cylindroleberis mariae J. Exp. Biol., February 15, 2005; 208(4): 661 - 670. [Abstract] [Full Text] [PDF]

				Y. van Bergen OSTRACODS' OXYGEN PUZZLE J. Exp. Biol., December 1, 2004; 207(25): ii - ii. [Full Text] [PDF]