High muscle mitochondrial volume and aerobic capacity in a small marsupial (Sminthopsis crassicaudata) reveals flexible links between energy-use levels in mammals

Dawson, Terence J., Webster, Koa N., Lee, Enhua and Buttemer, William A. 2013, High muscle mitochondrial volume and aerobic capacity in a small marsupial (Sminthopsis crassicaudata) reveals flexible links between energy-use levels in mammals, Journal of experimental biology, vol. 216, no. 7, pp. 1330-1337.

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Title High muscle mitochondrial volume and aerobic capacity in a small marsupial (Sminthopsis crassicaudata) reveals flexible links between energy-use levels in mammals
Author(s) Dawson, Terence J.
Webster, Koa N.
Lee, Enhua
Buttemer, William A.
Journal name Journal of experimental biology
Volume number 216
Issue number 7
Start page 1330
End page 1337
Total pages 8
Publisher Company of Biologists
Place of publication Cambridge, England
Publication date 2013
ISSN 0022-0949
1477-9145
Keyword(s) aerobic scope
basal metabolism
exercise
field metabolism
maximum metabolism
mitochondria
Summary We investigated the muscle structure-function relationships that underlie the aerobic capacity of an insectivorous, small (~15?g) marsupial, Sminthopsis crassicaudata (Family: Dasyuridae), to obtain further insight into energy use patterns in marsupials relative to those in placentals, their sister clade within the Theria (advanced mammals). Disparate hopping marsupials (Suborder Macropodiformes), a kangaroo (Macropus rufus) and a rat-kangaroo (Bettongia penicillata), show aerobic capabilities as high as those of 'athletic' placentals. Equivalent muscle mitochondrial volumes and cardiovascular features support these capabilities. We examined S. crassicaudata to determine whether highly developed aerobic capabilities occur elsewhere in marsupials, rather than being restricted to the more recently evolved Macropodiformes. This was the case. Treadmill-trained S. crassicaudata attained a maximal aerobic metabolic rate (VO2,max or MMR) of 272ml O2min-1kg -1 (N=8), similar to that reported for a small (?20g), 'athletic' placental, Apodemus sylvaticus, 264ml O2min -1kg-1. Hopping marsupials have comparable aerobic levels when body mass variation is considered. Sminthopsis crassicaudata has a basal metabolic rate (BMR) about 75% of placental values but it has a notably large factorial aerobic scope (fAS) of 13, elevated fAS also features in hopping marsupials. The VO2,max of S. crassicaudata was supported by an elevated total muscle mitochondrial volume, which was largely achieved through high muscle mitochondrial volume densities, Vv(mt,f), the mean value being 14.0±1.33%. These data were considered in relation to energy use levels in mammals, particularly field metabolic rate (FMR). BMR is consistently lower in marsupials, but this is balanced by a high fAS, such that marsupial MMR matches that of placentals. However, FMR shows different mass relationships in the two clades, with the FMR of small (<, 125 g) marsupials, such as S. crassicaudata, being higher than that in comparably sized placentals, with the reverse applying for larger marsupials. The flexibility of energy output in marsupials provides explanations for this pattern. Overall, our data refute widely held notions of mechanistically closely linked relationships between body mass, BMR, FMR and MMR in mammals generally.
Language eng
Field of Research 059999 Environmental Sciences not elsewhere classified
Socio Economic Objective 970105 Expanding Knowledge in the Environmental Sciences
HERDC Research category C1 Refereed article in a scholarly journal
Persistent URL http://hdl.handle.net/10536/DRO/DU:30055445

Document type: Journal Article
Collection: School of Life and Environmental Sciences
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