Thermoregulatory and metabolic responses of Japanese quail to hypoxia.

Common responses to hypoxia include decreased body temperature (Tb) and decreased energy metabolism. In this study, the effects of hypoxia and hypercapnia on Tb and metabolic oxygen consumption (VO2) were investigated in Japanese quail (Coturnix japonica). When exposed to hypoxia (15, 13, 11 and 9% O2), Tb decreased only at 11% and 9% O2 compared to normoxia; quail were better able to maintain Tb during acute hypoxia after a one-week acclimation to 10% O2. VO2 also decreased during hypoxia, but at 9% O2 this was partially offset by increased anaerobic metabolism. Tb and VO2 responses to 9% O2 were exaggerated at lower ambient temperature (Ta), reflecting a decreased lower critical temperature during hypoxia. Conversely, hypoxia had little effect on T(b) or VO2 at higher Ta (36 degrees C). We conclude that Japanese quail respond to hypoxia in much the same way as mammals, by reducing both Tb and VO2. No relationship was found between the magnitudes of decreases in Tb and VO2 during 9% O2, however. Since metabolism is the source of heat generation, this suggests that Japanese quail increase thermolysis to reduce Tb. During hypercapnia (3, 6 and 9% CO2), Tb was reduced only at 9% CO2 while VO2 was unchanged.