Carbon- and nitrogen-isotope tissue–diet discrimination and turnover rates in deer mice, Peromyscus maniculatus

Abstract

The dietary habits of most small mammals are not well documented, and stable isotope measurements can provide information on when and how diets change. Here we document the discrimination and turnover times for carbon and nitrogen isotopes in blood, liver, muscle, hair, and milk from deer mice ( Peromyscus maniculatus (Wagner, 1845)) fed a controlled diet. Nonbreeding adults and pregnant females were livetrapped, maintained on a commercial laboratory chow, and had tissues sampled on a regular schedule. After adjusting to the laboratory diet, most tissues of nonbreeding adults were slightly depleted of 13C and enriched in 15N relative to diet (Δ13Ctissue–diet range = 0.3‰ to –1.1 ‰; Δ15Ntissue–diet range = 1.9‰ to 3.4‰). Liver (half-lives of 2.8 and 3.6 days for C and N, respectively) turned over more rapidly than blood (22.4 and 19.8 days for C and N, respectively) and muscle (18.7 and 24.8 days for C and N, respectively). The isotopic compositions of nonbreeding and breeding adults indicated tissue turnover at approximately the same rate, but juvenile tissues reflected the laboratory diet much more quickly than adult tissues.

Tissue–diet discrimination factors and turnover of stable carbon and nitrogen isotopes in white-footed mice (Peromyscus leucopus)

“…However, these findings differ from those recorded for deer mice (Miller et al 2008), whereby muscle tissue turned over faster than whole blood. Again, these results are perplexing given that both experiments employed similar methodology.…”

“…The tissue-discrimination values for carbon isotopes determined here for liver, muscle, and hair of white-footed mice are similar to those reported by Miller et al (2008) for the closely related deer mouse with one exception; the d 13 C discrimination value of whole blood in this experiment was determined to be 1.6% lower than that calculated for the deer mouse. This difference is surprising given that in both experiments, mice were fed diets with similar constituents, proteins of comparable biological value and similar carbon isotope ratios (-19.4% ± 0.3% in the Miller et al (2008) study and -19.7% ± 0.3% in the current study).…”

“…In this study, the d 15 N values of muscle, whole blood, and hair were all approximately 3% greater than the diet and enriched in the same pattern observed in other studies of mammalian tissues Miller et al 2008). However, the mean d 15 N value of the liver was approximately 4.5% higher than that of the initial diet and significantly higher than the other tissues sampled.…”

“…This difference is surprising given that in both experiments, mice were fed diets with similar constituents, proteins of comparable biological value and similar carbon isotope ratios (-19.4% ± 0.3% in the Miller et al (2008) study and -19.7% ± 0.3% in the current study). Likewise, in both experiments, whole blood tissues, as well as diets, were not lipid-extracted prior to isotopic analysis.…”

“…are often a focal species or an integral component of both basic and applied ecological research. (Tieszen et al 1983), and most recently, for the deer mouse (Peromyscus maniculatus (Wagner, 1845)) (Miller et al 2008). We conducted a captive feeding experiment with white-footed mouse (Peromyscus leucopus (Rafinesque, 1818)) to determine the turnover rates and tissue-diet discrimination factors for liver, whole blood, muscle, and hair.…”