Document Detail

Isotopic discrimination between food and blood and feathers of captive penguins: implications for dietary studies in the wild.
MedLine Citation:
PMID:  15702469     Owner:  NLM     Status:  MEDLINE    
Using measurements of naturally occurring stable isotopes to reconstruct diets or source of feeding requires quantifying isotopic discrimination factors or the relationships between isotope ratios in food and in consumer tissues. Diet-tissue discrimination factors of carbon ((13)C/(12)C, or delta (13)C) and nitrogen ((15)N/(14)N, or delta (15)N) isotopes in whole blood and feathers, representing noninvasive sampling techniques, were examined using three species of captive penguins (king Aptenodytes patagonicus, gentoo Pygoscelis papua, and rockhopper Eudyptes chrysocome penguins) fed known diets. King and rockhopper penguins raised on a constant diet of herring and capelin, respectively, had tissues enriched in (15)N compared to fish, with discrimination factors being higher in feathers than in blood. These data, together with previous works, allowed us to calculate average discrimination factors for (15)N between whole lipid-free prey and blood and feathers of piscivorous birds; they amount to +2.7 per thousand and +4.2 per thousand, respectively. Both fish species were segregated by their delta (13)C and delta (15)N values, and importantly, lipid-free fish muscle tissue was consistently depleted in (13)C and enriched in (15)N compared to whole lipid-free fish. This finding has important implications because previous studies usually base dietary reconstructions on muscle of prey rather than on whole prey items consumed by the predator. We tested the effect of these differences using mass balance calculations to the quantification of food sources of gentoo penguins that had a mixed diet. Modeling indicated correct estimates when using the isotopic signature of whole fish (muscle) and the discrimination factors between whole fish (muscle) and penguin blood. Conversely, the use of isotopic signatures of muscle together with discrimination factors between whole fish and blood (or the reverse) leads to spurious estimates in food proportions. Consequently, great care must be taken in the choice of isotopic discrimination factors to apply to wild species for which no controlled experiments on captive individuals have been done. Finally, our results also indicate that there is no need to remove lipids before isotopic analysis of avian blood.
Yves Cherel; Keith A Hobson; Sami Hassani
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Physiological and biochemical zoology : PBZ     Volume:  78     ISSN:  1522-2152     ISO Abbreviation:  Physiol. Biochem. Zool.     Publication Date:    2005 Jan-Feb
Date Detail:
Created Date:  2005-02-09     Completed Date:  2005-04-21     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  100883369     Medline TA:  Physiol Biochem Zool     Country:  United States    
Other Details:
Languages:  eng     Pagination:  106-15     Citation Subset:  IM    
Centre d'Etudes Biologiques de Chize, Unite Propre de Recherche 1934 du Centre National de la Recherche Scientifique, BP 14, 79360 Villiers-en-Bois, France.
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MeSH Terms
Blood Chemical Analysis / methods*
Carbon Isotopes / blood,  diagnostic use
Feathers / chemistry*
Fishes / metabolism
Food Analysis / methods*
Food Chain*
Isotopes / diagnostic use*
Linear Models
Lipids / blood
Nitrogen Isotopes / blood,  diagnostic use
Species Specificity
Spheniscidae / metabolism*,  physiology
Reg. No./Substance:
0/Carbon Isotopes; 0/Isotopes; 0/Lipids; 0/Nitrogen Isotopes

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