Thermoregulatory and metabolic responses of Japanese quail to hypoxia

Common responses to hypoxia include decreased body temperature (T-b) and decreased energy metabolism. In this study, the effects of hypoxia and hypercapnia on T-b and metabolic oxygen consumption (VO2) were investigated in Japanese quail (Coturnix japonica). When exposed to hypoxia (15, 13, 11 and 9% O-2), T-b decreased only at 11% and 9% O-2 compared to normoxia; quail were better able to maintain T-b during acute hypoxia after a one-week acclimation to 10% O-2. VO2 also decreased during hypoxia, but at 9% O-2 this was partially offset by increased anaerobic metabolism. T-b and VO2 responses to 9% O-2 were exaggerated at lower ambient temperature (T-a), reflecting a decreased lower critical temperature during hypoxia. Conversely, hypoxia had little effect on T-b or VO2 at higher T-a (36 degrees C). We conclude thatJapanese quail respond to hypoxia in much the same way as mammals, by reducing both T-b and VO2. No relationship was found between the magnitudes of decreases in Tb and VO2 during 9% O-2, however. Since metabolism is the source of heat generation, this suggests that Japanese quail increase thermolysis to reduce T-b. During hypercapnia (3, 6 and 9% CO2), Tb was reduced only at 9% CO2 while VO2 was unchanged. (C) 2008 Elsevier Inc. All rights reserved.