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Journal of Experimental Biology, Vol 202, Issue 5 553-562, Copyright © 1999 by Company of Biologists
JOURNAL ARTICLES |
R Pirow, F Wollinger and RJ Paul
Institut fur Zoophysiologie, Westfalische Wilhelms-Universitat, Hindenburgplatz 55, D-48143 Munster, Germany. pirow@uni-muenster.de.
In the planktonic crustacean Daphnia magna (Branchiopoda, Cladocera), different views exist on the mechanism of respiratory gas exchange, ranging from gill breathing to general integumentary respiration. The presumed structures for specialized gas exchange are located ventrally within the filter chamber, which is continuously perfused with the ambient medium for food gathering. To localize respiratory gas exchange in D. magna, we determined the contribution of the feeding current to total oxygen transport. Combining microscopy with special optical techniques, we used a phosphorescent oxygen-sensitive dye for oxygen partial pressure (PO2) measurements and applied fluorescent microspheres for flow-rate analysis. Appendage beat rate was determined by digital image-processing. All experiments were carried out on hypoxia-adapted animals with a body length ranging from 2.3 to 2.7 mm at 20 degreesC. External PO2 measurement revealed oxygen depletion in the ventral body region but essentially no change at posterior, lateral and dorsal positions. The PO2 difference between the inflow and outflow of the feeding current was 13.0 mmHg (1.73 kPa). The flow rate of the feeding current ranged from 1.2 to 5.2 ml h-1 and showed a close correlation with appendage beat rate, which varied from 310.4 to 460.7 beats min-1. Model calculations based on the Fick principle suggest that oxygen extraction from the feeding current satisfies most of the total of oxygen requirement of D. magna.
This article has been cited by other articles:
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  R. Pirow, C. Baumer, and R. J. Paul Crater landscape: two-dimensional oxygen gradients in the circulatory system of the microcrustacean Daphnia magna J. Exp. Biol., December 1, 2004; 207(25): 4393 - 4405. [Abstract] [Full Text] [PDF]
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L. Corbari, P. Carbonel, and J.-C. Massabuau How a low tissue O2 strategy could be conserved in early crustaceans: the example of the podocopid ostracods J. Exp. Biol., December 1, 2004; 207(25): 4415 - 4425. [Abstract] [Full Text] [PDF]
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R. Pirow and I. Buchen The dichotomous oxyregulatory behaviour of the planktonic crustacean Daphnia magna J. Exp. Biol., February 1, 2004; 207(4): 683 - 696. [Abstract] [Full Text] [PDF]
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R. Pirow, C. Baumer, and R. J. Paul Benefits of haemoglobin in the cladoceran crustacean Daphnia magna J. Exp. Biol., March 12, 2002; 204(20): 3425 - 3441. [Abstract] [Full Text] [PDF]
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R Pirow, F Wollinger, and R. Paul The sites of respiratory gas exchange in the planktonic crustacean daphnia magna: an in vivo study employing blood haemoglobin as an internal oxygen probe J. Exp. Biol., January 11, 1999; 202(22): 3089 - 3099. [Abstract] [PDF]
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