SEX-DIFFERENCES AND EFFECTS OF SOCIAL CUES ON DAILY RHYTHMS FOLLOWINGPHASE ADVANCES IN OCTODON-DEGUS

Two experiments were designed to determine whether social cues could e nhance the rate of resynchronization in body temperature and general a ctivity rhythms in male or female Octodon degus following a 6 h phase advance. The first experiment examined average resynchronization rates for animals in each condition. The second experiment examined resynch ronization rates for a smaller group of animals, each treated as its o wn control. Female phase-shifters resynchronized temperature and activ ity rhythms significantly faster when housed with an entrained (donor) female than those females housed with another phase-shifting female o r housed alone. Females housed with entrained males resynchronized the ir temperature rhythms significantly slower than females housed with e ntrained females. No differences in resynchronization rate for phase-s hifting males existed between test conditions. However, activity rhyth ms of male controls (housed alone) reentrained significantly faster th an those of female controls. These experiments demonstrate a sex diffe rence in (i) reentrainment rate by photic cues alone; (ii) donors' eff ect on female phase-shifters' resynchronization; and (iii) phase-shift ers' resynchronization response to donor cues. In these studies, resyn chronization in the presence of another animal could either have been achieved by entrainment of the pacemaker or by masking of the circadia n rhythms.