Meeting Abstract

P1.144  Friday, Jan. 4  Aerobic power, huddling and the efficiency of torpor in the South American marsupial, Dromiciops gliroides. FRANCO , L. M*; CONTRERAS, C. I; CORTES, P. A; NESPOLO, R. F; UACH, Valdivia; UACH, Valdivia; UACH, Valdivia; UACH, Valdivia lidamarcelafranco@gmail.com

We provide a quantitative description of thermoregulatory capacities and energy-saving strategies in Dromiciops gliroides, a Microbiotherid marsupial inhabiting temperate rain forests. Unlike many mammals from temperate regions, preliminary studies have suggested that this species has low capacity for control and regulation of body temperature, but there is still an incomplete picture of its bioenergetics. In order to more fully understand the physiological capacities of this “living fossil”, we measured its scope of aerobic power and the interaction between huddling and torpor. Specifically, we evaluated: (1) the relation between basal (BMR) and maximum metabolic rate (MMR), and (2) the role of huddling on the characteristics of torpor at different temperatures. We found that BMR was 112% and MMR was 59% of the expected value for marsupials. As a result, factorial aerobic scope was 5.2, unusually low for mammals. Comparisons of energy expenditure and body temperature (using attached data-loggers), between grouped and isolated individuals showed that at 20°C, both average resting metabolic rate and body temperature were higher in groups, essentially because animals remained non-torpid. At 10°C, however, all individuals became torpid and no differences were observed between grouped and isolated individuals. In summary our study suggests that the main response of D. gliroides to low ambient temperature is reduced body temperature and torpor, irrespective of huddling. Low aerobic power and low time-consistency of most thermoregulatory traits of D. gliroides support the idea of poor thermoregulatory abilities in this species.