INVESTIGADORES
LUNA Facundo
congresos y reuniones científicas
Título:
Allometric scaling of basal metabolic rate in subterranean rodents: The southamerican case
Autor/es:
LUNA F, ANTINUCHI CD, BOZINOVIC F
Lugar:
Brasil
Reunión:
Congreso; VII International Congress of Comparative Physiology and Biochemistry; 2007
Resumen:
One of
the mayor topics in ecological and evolutionary physiology is the
identification of selective factors that determines interspecific differences in energetics. Among mammals, basal
metabolic rate (BMR) is an excellent predictor of minimal turnover of energy.
At interspecific level, body mass was proposed to be the main factor that
explains the variation in BMR, although, the residual variation of BMR was
ascribed to both, biotic and abiotic factors. Some
species show a reduction of the BMR below the allometric prediction based on
other mammals. Subterranean species exhibit low BMR compared with
surface-dwelling species of the same body size, and this feature has been
proposed as an adaptation to living underground. To explaining this pattern basically
two hypothesis have been proposed: 1) low BMR is related to the possibility of
overheating in an ambient with low convective and evaporative heat loss (thermal
stress hypothesis); and, 2) low BMR is related to balance the high cost of
burrowing when food intake is restricted (cost of burrowing hypothesis). On the
other hand the effect of body size, climate and productivity on BMR in a fully
and homogeneous subterranean genus have not been evaluated. Genus Ctenomys is an excellent model to evaluate
this effect because it occur in different
climates and soil types, and has a wide range of body mass. The aim of this
study was to evaluate the relationship between BMR and body mass of Ctenomys species and environmental
variables. Mass-specific metabolic rate was obtained form two sources. BMR of Ctenomys, were obtained both in an
open-circuit respirometry or collected from the literature. Ambient
temperatures, precipitation, and altitude were obtained from climatic summaries
for the weather stations nearest the capture site. Soil hardness were estimated
in the capture site or obtained from geological maps. The habitat productivity
of each locality is evaluated as the relationship between precipitation and
minimum and maximum ambient temperature. Either conventional or phylogenic analysis
fails to detect environmental variables as predictor for BMR within Ctenomys. Only body mass appears to
account for the ability to predict BMR. The slopes for the independents
contrasts allometric equation were similar to those derived from conventional analysis,
and confidence intervals overlap broadly, indicating that equations for BMR are
similar. Our results did not support either, thermal stress or cost of
burrowing hypotheses. The causes of the low BMR observed in subterranean
species, at least in Ctenomys, remain
obscure, so, other hypotheses are discussed