Daily scheduling of the golden spiny mouse under photoperiodic and social cues

A most important function of the circadian system is to ensure that behavio rs and metabolism are appropriately timed with respect to the light/dark cy cle and photoperiod. Ecological constraints can perturb the daily schedules ; would they also impair photoperiodic adaptations? A natural model exists in the golden spiny mouse (Acomys russatus), which is nocturnal, but driven into diurnal activity when sharing the habitat with its congener, A. cahir inus. We show here that the presence of A. cahirinus alters the diurnal rhy thms of body temperature and urine volume, delays excretion of the major me latonin metabolite, 6-sulfatoxymelatonin (6-SMT), and increases 2-deoxygluc ose uptake by the suprachiasmatic nuclei in A. russatus. Nevertheless, a cl ear photoperiod effect on urine volume and B-SMT rhythms was observed. Thes e results indicate that the circadian system can adapt to major changes in daily scheduling without impairing daylength measurement, and consequently seasonal adaptation. J. Exp. Zool. 284:100-106, 1999. (C) 1999 Wiley-Liss, Inc.