Sidereal-day variation in spontaneous activity of the mouse, Mus musculus.

Abstract

1. Spontaneous motor activity of twelve adult male Swiss white mice was monitored for the year June 1, 1965 through May 31, 1966, in Evanston, Illinois. The mice were maintained in natural illumination in the laboratory. 2. A mean sidereal-day activity pattern was disclosed. This comprised a unimodal variation with a maximum occurring at sidereal midnight (hour 0) and a minimum at the 12th hour. The range of the cycle was 40% of the mean. It is postulated that the sidereal variational pattern reflects biological responsiveness to the mean sidereal-day fluctuations in the geoelectromagnetic field. 3. The presence of an annual pattern of spontaneous motor activity is postulated to be the result, in at least some measure, of the systematically altering phase-relationships between the 24-hour solar-day and the 23-hour 56-minutes sidereal-day as the sidereal-day makes it passage across the solar-day to be completed exactly in one year's period. 4. The significance of a sidereal-day periodicity to nocturnally migrating organisms is postulated.