SOCIAL CUES ACCELERATE REENTRAINMENT OF CIRCADIAN-RHYTHMS IN DIURNAL FEMALE OCTODON-DEGUS (RODENTIA-OCTODONTIDAE)

Previous studies paired diurnal Octodon degus undergoing/phase advance s (phase-shifters) with those entrained to a light-dark (LD) cycle (do nors). Results included opposite outcomes of male and female social cu es on resynchronization following 6-h advances in females, but no effe ct of social cues on male resynchronization. The first experiment dete rmined if social cues could influence resynchronization rates of circa dian rhythms in male and female degus following a 6-h phase delay of t he LD cycle. Female phase-shifters resynchronized temperature and acti vity rhythms 20-35% faster when housed with either entrained (donor) f emales or males compared with females housed alone. No significant dif ferences in resynchronization rate for phase-shifting males existed be tween test conditions. This experiment extends the previous finding th at females, but not males, respond strongly to donor cues to increase resynchronization rates in the presence of light. A second experiment determined that accelerated resynchronization rates of female phase-sh ifters housed with female donors were due to social cues directly affe cting the circadian system rather than the result of social masking. O n the day following resynchronization with or without a female donor p resent, phase-shifters were transferred individually to constant condi tions (DD). The temperature and activity rhythms of female phase-shift ers free-ran from the point at which resynchronization occurred for bo th the control and experimental females. Thus, social cues accelerate true reentrainment, not masking, of the circadian system in the presen ce of a LD cycle in female degus. Donor cues from females enhance reen trainment after advances and delays, but the effect of male donor cues is dependent on the direction of the phase shift.