104.1 Sunday, Jan. 6 Hibernation at Extremes: How low can you go? RICHTER, M.M.*; LEE, T.N.; TOIEN, O; BARNES, B.M.; BUCK, C.L.; Univ. of Alaska, Fairbanks; Univ. of Alaska, Fairbanks; Univ. of Alaska, Fairbanks; Univ. of Alaska, Fairbanks; Univ. of Alaska, Anchorage email@example.com
During hibernation, soil temperatures adjacent to hibernacula (Ta) average a low of -15.8°C and can drop as low as -23.4°C. Thus, unlike many hibernators, AGS must remain continuously thermogenic during hibernation to defend the gradient between core body temperature (Tb) and Ta. Here we determined the lowest ambient temperature at which AGS will remain torpid. First, we progressively decreased Ta at 2°C increments from 2°C to -20°C, measuring metabolic rate (MR) during steady state torpor at each Ta and arousing animals between trials. We found MR increased from 0.01mlO2/g*hr at 2°C to 0.29mlO2/g*hr at -20°C. We also held AGS in steady state torpor at 2°C, 0°C, -10°C, -20°C and then decreased Ta in 2°C increments until animals failed to hibernate. Similar to our first findings, MR steadily increased until it reached a maximum of 0.36ml O2/g*hr at -26°C. Lastly, we held animals in steady state torpor at -20°C and within a bout of torpor decreased Ta at 0.2°C/30min. Decreasing Ta within a torpor bout continued until the animal spontaneously aroused or no longer increased MR despite decreasing Ta. We found animals spontaneously aroused at Ta’s between -23.1°C to -29.8°C , with an average of -26.0°C ± 2.7°C. Our results show that AGS are able to remain in steady state torpor at Ta as low as -26°C , guarding a temperature gradient of 23°C between their core body temperature and the ambient environment.