Adjusting energy expenditures to energy supply: food availability regulates torpor use and organ size in the Chilean mouse-opossum <Emphasis Type="Italic">Thylamys elegans</Emphasis> |
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Authors: | Francisco Bozinovic José L P Muñoz Daniel E Naya Ariovaldo P Cruz-Neto |
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Institution: | (1) Center for Advanced Studies in Ecology and Biodiversity and Departamento de Ecología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, 6513677, Chile;(2) Departamento de Zoologia, Instituto de Biociências, UNESP, Rio Claro, CP 199, SP, Brasil |
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Abstract: | We studied how food abundance and consumption regulates torpor use and internal organ size in the Chilean mouse-opossum Thylamys elegans (Dielphidae), a small nocturnal marsupial, endemic in southern South America. We predicted that exposure to food rations
at or above the minimum energy levels necessary for maintenance would not lead to any signs of torpor, while reducing food
supply to energy levels below maintenance would lead to marked increases in frequency, duration and depth of torpor bouts.
We also analyzed the relationship between food availability and internal organ mass. We predicted a positive relationship
between food availability and internal organ size once the effect of body size is removed. Animals were randomly assigned
to one of two groups and fed either 70, 100 or 130% of their daily energy requirement (DER). We found a positive and significant
correlation between %DER and body temperature, and also between %DER and minimum body temperature. In contrast, for torpor
frequency, duration and depth, we found a significant negative correlation with %DER. Finally, we found a significant positive
correlation between the %DER and small intestine and ceacum dry mass. We demonstrate that when food availability is limited,
T. elegans has the capacity to reduce their maintenance cost by two different mechanisms, that is, increasing the use of torpor and
reducing organ mass. |
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Keywords: | Torpor frequency Body temperature Food abundance Energy requirements Marsupials |
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