spacer gif spacer gif spacer gif spacer gif spacer gif
QUICK SEARCH:   [advanced]


spacer gif
     Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents    

This Article
Right arrow Figures Only
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Nespolo, R. F.
Right arrow Articles by Bozinovic, F.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Nespolo, R. F.
Right arrow Articles by Bozinovic, F.
The Journal of Experimental Biology 205, 2697-2703 (2002)
© 2002 The Company of Biologists Limited

Interplay among energy metabolism, organ mass and digestive enzyme activity in the mouse-opossum Thylamys elegans: the role of thermal acclimation

Roberto F. Nespolo1,*, Leonardo D. Bacigalupe1, Pablo Sabat2 and Francisco Bozinovic1

1 Centro de Estudios Avanzados en Ecología y Biodiversidad, Departamento de Ecología, Pontificia Universidad Católica de Chile, PO Box 6513677, Santiago, Chile
2 Departmento de Ciencias Ecológicas, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago, Chile

* Author for correspondence (e-mail: rnespolo{at}genes.bio.puc.cl)

Accepted 6 June 2002

The potential for thermal acclimation in marsupials is controversial. Initial studies suggest that the thermoregulatory maximum metabolic rate (MMR) in metatherians cannot be changed by thermal acclimation. Nevertheless, recent studies reported conspicuous seasonality in both MMR and in basal metabolic rate (BMR). We studied the role of thermal acclimation in the Chilean mouse-opossum, Thylamys elegans, by measuring MMR and BMR before and after acclimation to cold or warm conditions. Following acclimation we also measured the mass of metabolically active organs, and the activity of a key digestive enzyme, aminopeptidase-N. No significant effect of thermal acclimation (i.e. between cold- and warm-acclimated animals) was observed for body mass, MMR, body temperature or factorial aerobic scope. However, the BMR of cold-acclimated animals was 30 % higher than for warm-acclimated individuals. For organ mass, acclimation had a significant effect on the dry mass of caecum, liver and kidneys only. Stepwise multiple regression using pooled data showed that 71 % of the variation in BMR is explained by the digestive organs. Overall, these results suggest that MMR is a rather rigid variable, while BMR shows plasticity. It seems that T. elegans cannot respond to thermal acclimation by adjusting its processes of energy expenditure (i.e. thermogenic capacity and mass of metabolically active organs). The lack of any significant difference in aminopeptidase-N specific activity between warm- and cold-acclimated animals suggests that this response is mainly quantitative (i.e. cell proliferation) rather than qualitative (i.e. differential enzyme expression). Finally, as far as we know, this study is the first to report the effects of thermal acclimation on energy metabolism, organ mass and digestive enzyme activity in a marsupial.

Key words: basal metabolic rate, maximum metabolic rate, marsupial, thermal acclimation, organ mass, Thylamys elegans, aminopeptidase-N






© The Company of Biologists Ltd 2002