The effects of sex, tissue type, and dietary components on stable isotope discrimination factors (Δ13C and Δ15N) in mammalian omnivores.
We tested the effects of sex, tissue, and diet on stable isotope discrimination factors (Δ(13)C and Δ(15)N) for six tissues from rats fed four diets with varied C and N sources, but comparable protein quality and quantity. The Δ(13)C and Δ(15)N values ranged from 1.7-4.1‰ and 0.4-4.3‰, respectively. Females had higher Δ(15)N values than males because males grew larger, whereas Δ(13)C values did not differ between sexes. Differences in Δ(13)C values among tissue types increased with increasing variability in dietary carbon sources. The Δ(15)N values increased with increasing dietary δ(15)N values for all tissues except liver and serum, which have fast stable isotope turnover times, and differences in Δ(15)N values among tissue types decreased with increasing dietary animal protein. Our results demonstrate that variability in dietary sources can affect Δ(13)C values, protein source affects Δ(15)N values even when protein quality and quantity are controlled, and the isotope turnover rate of a tissue can influence the degree to which diet affects Δ(15)N values.
a Division of Biological Sciences , University of California , San Diego, La Jolla , CA , USA.
Carolyn M
CM
Kurle
Paul L
PL
Koch
Bernie R
BR
Tershy
Donald A
DA
Croll
D000818:Animals; D002247:Carbon Isotopes / Q000378:metabolism; D004032:Diet; D005260:Female; D008297:Male; D013058:Mass Spectrometry; D008962:Models, Theoretical; D009587:Nitrogen Isotopes / Q000378:metabolism; D051381:Rats / Q000378:metabolism*; D017207:Rats, Sprague-Dawley; D012727:Sex Characteristics; D014018:Tissue Distribution
D002247:Carbon Isotopes; D009587:Nitrogen Isotopes
animals; carbon-13; diet; food; isotope ecology; natural isotope fractionation; nitrogen-15; protein turnover; rats; δ13C; δ15N