Document Detail


Tissue Carbon Incorporation Rates and Diet-to-Tissue Discrimination in Ectotherms: Tortoises Are Really Slow.
MedLine Citation:
PMID:  22237293     Owner:  NLM     Status:  In-Data-Review    
Abstract/OtherAbstract:
Abstract Understanding carbon incorporation rates and diet-to-tissue discrimination (Δ(13)C(tissue-diet)) in animals is necessary to interpret stable isotope data collected from animals in the field. Our current understanding of the carbon dynamics in terrestrial ectotherms such as snakes, lizards, and turtles is poorly developed. Here we use a diet switch experiment to estimate carbon incorporation rates and diet-to-tissue discrimination factors in growing desert tortoises (Gopherus agassizii). Average carbon retention times for red blood cells (RBCs) and plasma were [Formula: see text] and [Formula: see text] days, respectively. Tissue carbon incorporation rates were affected by both growth and metabolism, with growth accounting for 50% of the carbon turnover in RBCs and 13% of carbon turnover in plasma. At equilibrium, scute keratin ([Formula: see text]) and plasma ([Formula: see text]) showed enriched discrimination values (Δ(13)C) compared to the test diet, but RBC Δ(13)C values were indistinguishable from diet ([Formula: see text]). We also found that new keratin continued to contribute significant material to previously grown keratin rings on the tortoise's shell. Changes in the δ(13)C of previously laid down growth rings indicated that the old rings closest to the region of new growth received about 73% of the carbon from the current diet; these data suggest that the interpretation of dietary history using growth rings must recognize that each ring may represent the weighted average of the diet over several seasons. These results continue to highlight the importance of laboratory experiments in interpreting isotopic data derived from field studies.
Authors:
Ian W Murray; Blair O Wolf
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Publication Detail:
Type:  Journal Article     Date:  2012-01-03
Journal Detail:
Title:  Physiological and biochemical zoology : PBZ     Volume:  85     ISSN:  1537-5293     ISO Abbreviation:  Physiol. Biochem. Zool.     Publication Date:  2012 Jan 
Date Detail:
Created Date:  2012-01-12     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  100883369     Medline TA:  Physiol Biochem Zool     Country:  United States    
Other Details:
Languages:  eng     Pagination:  96-105     Citation Subset:  IM    
Affiliation:
Department of Biology, University of New Mexico, Albuquerque, New Mexico 87131.
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