Document Detail

Does excess dietary carbon affect respiration of Daphnia?
MedLine Citation:
PMID:  17242906     Owner:  NLM     Status:  MEDLINE    
Like many invertebrate herbivores, Daphnia frequently face diets with excess carbon (C) relative to elements like phosphorus (P), and with limited ability to store C-rich compounds. To cope with this relative surplus of C they may either regulate the net uptake of C or dispose of excess assimilated C via increased release of dissolved organic carbon or CO(2). Here we investigate whether juvenile Daphnia magna use respiration as a means of stoichiometrically regulating excess C. Growth rate and respiration were measured under different algal food qualities (P-replete and P-depleted algae). Growth rate was strongly reduced by P-depleted food, implying a stoichiometric disposal of excess ingested C. Respiration rates of feeding animals were measured after short- (0.5 h), medium- (12 h) and long- (five days) term acclimation to P-limited food. The respiration rates of animals during active feeding were not affected by the acclimation period per se, whereas food quality had a significant effect; respiration rates of feeding animals increased slightly in individuals receiving low-P food under all acclimation regimes. Respiration was also measured on nonfeeding and fasting animals that had been acclimated for five days to P-limited food. Respiration rates of these animals were strongly affected by feeding conditions but not by food quality; feeding individuals had higher respiration rates than those deprived of food, which again had higher respiration than fasting animals. Although animals grown on low-P food had strongly reduced growth and thus were expected to have decreased respiration rates due to reduced growth-related costs, this seems to be canceled out by increased stoichiometric respiration under P-deficiency. These results indicate that D. magna partly releases excess C as CO(2), but other means of stoichiometric regulation most likely add to this.
Thomas C Jensen; Dag O Hessen
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2007-01-23
Journal Detail:
Title:  Oecologia     Volume:  152     ISSN:  0029-8549     ISO Abbreviation:  Oecologia     Publication Date:  2007 May 
Date Detail:
Created Date:  2007-05-04     Completed Date:  2007-08-17     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0150372     Medline TA:  Oecologia     Country:  Germany    
Other Details:
Languages:  eng     Pagination:  191-200     Citation Subset:  IM    
Department of Biology, University of Oslo, P.O. Box 1066, Blindern, 0316 Oslo, Norway.
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MeSH Terms
Algae, Green
Carbon / metabolism*
Daphnia / growth & development,  metabolism*
Energy Metabolism
Food Deprivation
Oxygen Consumption
Time Factors
Reg. No./Substance:

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