Der Einfluss der Schwingungsbreite von Licht‐Dunkel‐Cyclen auf Phasenlage und Resynchronisation der circadianen Aktivitätsperiodik dunkelaktiver Tiere

Abstract

[The Influence of the Oscillation Range of Light‐Dark Cycles on the Phase and Rhythm in Nocturnal Animals Resynchronization of the Circadian Activity] The influence of the range of oscillation (= Zeitgeber strength) of L/D cycles (12/12) on the resynchronization behaviour and on the parameter of the synchronized biological oscillation is examined in the nocturnal fruit bat, Rousettus aegyptiacus, at constant mean value of illumination (10^‐3 Lux). The period of resynchronization after phase shifts of the Zeitgeber‐L/D diminishes with increasing L/D intensity‐ratios (Fig. 7). After advancing phase shifts of the Zeitgeber cycle by Δσ=+8 hrs the Rousettus requires significantly more transitionary cycles to resynchronize than after delaying phase shifts by Δσ=—8 hrs. During the resynchronization phase, a reduction of the total amount of activity/24 hrs occurs. The given L/D intensity‐ratios (10⁸‐10⁴‐10²) influence the phase‐angle difference of the onset, midpoint, and end of the daily activity phase in different ways (Fig. 1). A significant dependence on the amplitude of the Zeitgeber‐L/D is evident, however, only in the phase‐angle‐difference of the onset of activity. Total amount of activity and activity time/period do vary very markedly with the range of L/D‐oscillation. In a moderate L/D‐ratio (10^‐1/10^‐5 lx) a statistically significant activity‐maximum occurs. With increasing Zeitgeber strength, the Rousettus's monomodal activity pattern is deformed by means of forward displacement of the maximum and an increase of the rise in activity at the commencement of darkness. It is discussed, first, to what extent the findings arrived at concur with the specific predictions of a mathematical model for circadian rhythms, developed by Wever (1962–1965), and secondly, how the deviations can be explained.