Nutrition, physiology, and stable isotopes: new information from fasting and molting penguins
2005
Cherel, Yves | Hobson, Keith A. | Bailleul, Frédéric | Groscolas, René
Stable isotopes are increasingly used in animal ecology, but little attention has been paid to the underlying physiological processes accounting for changes in ¹⁵N/¹⁴N and ¹³C/¹²C ratios, for example, the influence of protein balance on δ¹⁵N values. We investigated a “professional” faster, the King Penguin (Aptenodytes patagonicus), to test the effect of long‐term food deprivation on the isotopic signature of tissues that can be nondestructively sampled, i.e., blood and feathers. Fasting for 25 days induced a tissue ¹⁵N enrichment, thus leading to a moderate increase in the apparent trophic levels of penguins. As expected, ¹⁵N enrichment was higher in tissues with high protein turnover rates (e.g., plasma, 0.70‰) than in those with low turnover rates (e.g., blood cells, 0.24‰). Fasting decreased the δ¹³C value of plasma, which was due to an increase in its lipid content, as indicated by a concomitant rise in plasma C/N ratio. Finally, food deprivation induced a ¹⁵N enrichment in keratin (1.68‰), as indicated by the lower nitrogen signature for portions of new feathers that were synthesized at sea than for those parts grown on land, thus illustrating the different pathways for resource allocation (dietary vs. endogenous reserves) in molting birds. The study also emphasized the usefulness of collecting whole blood (or blood cells) in the field to overcome both the fasting and lipid effects observed in plasma.
اظهر المزيد [+] اقل [-]الكلمات المفتاحية الخاصة بالمكنز الزراعي (أجروفوك)
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