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First published online August 14, 2009
Journal of Experimental Biology 212, 2795-2802 (2009)
Published by The Company of Biologists 2009
doi: 10.1242/jeb.032789
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Cold acclimation in Peromyscus: individual variation and sex effects in maximum and daily metabolism, organ mass and body composition

Enrico L. Rezende1,*, Kimberly A. Hammond2 and Mark A. Chappell2

1 Departament de Genètica i de Microbiologia, Facultat de Biociències, Universitat Autònoma de Barcelona, Bellaterra 08193, Spain
2 Department of Biology, University of California, Riverside, CA 92521, USA

* Author for correspondence (enrico.rezende{at}uab.cat)

Accepted 4 June 2009

We studied metabolic and organ mass responses to thermal acclimation (7 weeks at 5°C or 23°C) in deer mice, Peromyscus maniculatus. Cold acclimation resulted in significantly higher maximal oxygen consumption in thermogenesis (VO2max) and daily mean oxygen consumption (VO2mean), an increase in the mass of most visceral organs, a lower absolute body fat and a marginally significant increase in hematocrit. The mass of digestive organs and body fat content differed significantly between sexes. Acclimation effects on fat content were more pronounced in females. Variation in heart and lung mass was positively correlated with VO2max and VO2mean, while body fat content was negatively correlated with both traits. Nonetheless, a large fraction of the metabolic difference between cold- and warm-acclimated groups remained unexplained. Associations between traits at lower levels of biological organization measured here and whole-organism energetics remained consistent across acclimation temperatures, except for the correlation between kidney mass and VO2mean, which was positive and significant in cold acclimation and negligible following warm acclimation. We conclude that: (1) VO2max and VO2mean share a common physiological basis that remains overall the same across acclimation regimes; (2) changes in these traits are associated primarily with changes in heart mass; and (3) male and female deer mice respond differently to thermal acclimation, possibly due to differences in reproductive allocation.

Key words: acclimation, body composition, maximal oxygen consumption, organ phenotypic plasticity, Peromyscus maniculatus


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