A model for the circadian pacemaker of Hemideina thoracica derived from the effects of temperature on its activity rhythm

Abstract

A control systems model for the circadian pacemaker underlying the locomotor activity rhythm of Hemideina thoracica has been developed on the basis of detailed experiments on the effects of temperature on this system, which have revealed the following generalisations 1. The rhythm exhibits typical temperature independence of period, with a species mean value of Q10 of slightly less than 1.0. 2. Both temperature steps and pulses produce phase-dependent advances and delays. 3. Wetes are inactive at 10 C and there is evidence that prolonged (30 h) exposures to this temperature effectively stop the circadian clock. 4. The rhythm is entrained by square wave temperature cycles of 6 C or greater amplitude, and by sinusoidal temperature cycles. 5. Relative coordination occurs in temperature cycles of insufficient strength as phase shifting agents to produce entrainment.