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The importance of the feeding current for oxygen uptake in the water flea daphnia magna
MedLine Citation:
PMID:  9929458     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
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.
Authors:
Pirow; Wollinger; Paul
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Publication Detail:
Type:  JOURNAL ARTICLE    
Journal Detail:
Title:  The Journal of experimental biology     Volume:  202 (Pt 5)     ISSN:  1477-9145     ISO Abbreviation:  J. Exp. Biol.     Publication Date:  1999 Mar 
Date Detail:
Created Date:  1999-03-31     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0243705     Medline TA:  J Exp Biol     Country:  -    
Other Details:
Languages:  Eng     Pagination:  553-62     Citation Subset:  -    
Affiliation:
Institut fur Zoophysiologie, Westfalische Wilhelms-Universitat, Hindenburgplatz 55, D-48143 Munster, Germany. pirow@uni-muenster.de.
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