Rhythms of body temperature and temperature selection are out of phase in a diurnal rodent, Octodon degus

Individual Chilean degus (Octodon degus) were maintained in a thermal gradient (14 degrees C to 33 degrees C) for two or more weeks under 14L:10D light-dark cycle. All animals showed robust daily rhythms of body temperature and locomotor activity consistent with the diurnal habits of the species. They also showed a robust daily rhythm of temperature selection 180 degrees out of phase with the rhythms of body temperature and locomotor activity. These results in a diurnal species extend previous findings of a 180 degrees phase difference between the rhythms of body temperature and temperature selection in nocturnal rodents. The asynchrony between these two rhythms implies an opposition between the circadian system (responsible for the generation of the body temperature rhythm) and the homeostatic system (responsible for the behavioral response of temperature selection that opposes the body temperature rhythm).