Nitrogen stable isotope turnover and discrimination in lizards

Rationale Nitrogen stable isotope ratio (δ15N) processes are not well described in reptiles, which limits reliable inference of trophic and nutrient dynamics. In this study we detailed δ15N turnover and discrimination (Δ15N) in diverse tissues of two lizard species, and compared these results with p...

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Bibliographic Details
Published in:Rapid communications in mass spectrometry 2021-03, Vol.35 (6), p.e9030-n/a
Main Authors: Warne, Robin W., Wolf, Blair O.
Format: Article
Language:English
Subjects:
Continuous flow
Discrimination
Erythrocytes
Estimates
Hibernation
Isotope ratios
Isotopes
Liver
Lizards
Muscles
Nitrogen isotopes
Physiology
Reptiles
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Summary:Rationale Nitrogen stable isotope ratio (δ15N) processes are not well described in reptiles, which limits reliable inference of trophic and nutrient dynamics. In this study we detailed δ15N turnover and discrimination (Δ15N) in diverse tissues of two lizard species, and compared these results with previously published carbon data (δ13C) to inform estimates of reptilian foraging ecology and nutrient physiology. Methods We quantified 15N incorporation and discrimination dynamics over 360 days in blood fractions, skin, muscle, and liver of Sceloporus undulatus and Crotaphytus collaris that differed in body mass. Tissue samples were analyzed on a continuous flow isotope ratio mass spectrometer. Results Δ15N for plasma and red blood cells (RBCs) ranged between +2.7 and +3.5‰; however, skin, muscle, and liver did not equilibrate, hindering estimates for these somatic tissues. 15N turnover in plasma and RBCs ranged from 20.7 ± 4 to 303 ± 166 days among both species. Comparison with previously published δ13C results for these same samples showed that 15N and 13C incorporation patterns were uncoupled, especially during winter when hibernation physiology could have played a role. Conclusions Our results provide estimates of 15N turnover rates and discrimination values that are essential to using and interpreting isotopes in studies of diet reconstruction, nutrient allocation, and trophic characterization in reptiles. These results also suggest that somatic tissues can be unreliable, while life history shifts in nutrient routing and metabolism potentially cause 15N and 13C dynamics to be decoupled.
ISSN:0951-4198
1097-0231
DOI:10.1002/rcm.9030