An Inter-Oscillator Mechanism Modulating Circadian Clock Period in Paramecium Populations

In populations of the ciliate protozoan, Paramecium multimicronucleatum, the circadian-clock-con-trolled mating reaction expressed by a limited number of cells among them feeds back to contribute to coherence of their circadian rhythms of motility and mating reaction. This eventually causes a decrease in the period of the rhythms from the entrained 24h period to a steady-state period of about 22h, with the rate of decrease depending on the strength of the mating reaction. These results suggest that the interaction among oscillators may be one of the factors which modulate the period of a circadian clock composed of nearly identical oscillators. The clock-controlled mating reaction provides a promising inter-oscillator pathway for obtaining more insight into the mechanism of modulation of the period of such circadian clocks through inter-oscillator interaction.