Meeting Abstract

P1.57  Wednesday, Jan. 4  Thermorregulatory capacities and energy-saving strategies in the South American marsupial,Dromiciops gliroides. CORTES, P.A.*; FRANCO, L.M.; CHAPPELL, M.A.; NESPOLO, R.F.; Universidad Austral de Chile; Universidad Austral de Chile; University of California, Riverside; Universidad Austral de Chile

During periods of adverse conditions (e.g. winter) small endotherms depend on a continuous supply of food and energy to maintain body temperature (tb). Thus, energy-saving strategies will be critical to reduce the energetic requirements for survival. We provide a quantitative description of thermoregulatory capacities and energy-saving strategies in Dromiciops gliroides. We evaluated: (1) the effect of thermal acclimation on basal (BMR) and maximum metabolic rate (MMR), thermal conductance (C) and torpor patterns, (2) the presence of non-shivering thermogenesis (NST) as a rewarming mechanism, (3) the energy costs associated to huddling under different thermal conditions and (4) the evolutionary potential of those traits. We found that cold-acclimated individuals presented higher BMR and longer torpor bouts. However, minimum tb and rewarming rate during torpor arousal was higher in warm-acclimated animals. Furthermore, we found that D. gliroides did not display NST in response to Norepinephrine. Comparisons of BMR and tb between grouped and single-individuals, showed significant differences only at ta =20°C, with higher values in grouped individuals. Repeatability of BMR, MMR and C were near-zero and non-significant. Also, body mass (mb) was not a good predictor of these traits. Our study suggests that in D. gliroides, (1) unlike torpor, huddling is not an effective energy-saving strategy to endure unfavorable periods, (2) the ST is the main thermoregulatory mechanism during torpor arousal, (3) the components of energy metabolism evaluated not exhibit evolutionary potential (i.e. low or null repeatability) and (4) mb is not a good predictor of this traits and thermal conductance.