LUNA Facundo
congresos y reuniones científicas
Allometric scaling of basal metabolic rate in subterranean rodents: The southamerican case
Congreso; VII International Congress of Comparative Physiology and Biochemistry; 2007
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