The entrainment of the circadian caecotrophy rhythm with different light‐dark time ratios

Abstract

The circadian caecotrophy rhythm of 15 rabbits of a group 1 and 12 rabbits of a group 2 was continuously monitored in LD 12:12, 14:10, 16:8, 18:6, 20:4, and 22:2. The photoperiod was extended in opposite directions either by advancing the onset (group 1) or by delaying the end (group 2) of the photoperiod. The response of the animals to photoperiod extension differed significantly both between the groups and within either group during the different steps of photoperiod extension. Generally the caecotrophy rhythm was advanced in group one and delayed in group two. The shift rate at the respective new LD schedule was determined by the phasically changing sensitivity of the rabbit to light stimulation. The results showed that the rabbit is entrained predominantly non‐parametrically, while the LD timeratio is of importance mainly for the precision of phase control.

Abstracting keywords:

• circadian rhythm
• LD ratio
• entrainment
• photoperiod
• parametric
• nonparametric
• phase response curve
• caecotrophy
• rabbit

Notes

Laboratory Animal Facilities, University of Ulm, P.O. Box 4066, D‐7900 Ulm, Germany.