Homozygous flies show robust periodic locomotion in two free-running conditions; constant darkness (DD) and constant light (LL) (a condition that causes genetically normal flies to go arrhythmic). In DD, most cry02
flies show solidly rhythmic locomotion at 25o
C. Period values are generally in the normal range, except that approximately 20% of the mutant flies tested at 25o
C give shorter than normal values. At 18o
flies show weak rhythmicity, although the rhythmic individuals have normal period values. In LL, most cry02
flies behave rhythmically at 25o
C. Most of the rhythmic individuals have two rhythmic components within a given behavioural record in LL, the average for the relatively short free-running period is 21-22 hours and that of the longer is 25-26 hours. At 29o
C and at 18o
C in LL, cry02
flies show a relatively high degree of arrhythmicity. At 25o
C in LL, when periodic components can be reliably analysed, approximately 60% of the flies show two periodicities whose average values are 20 and 24 hours. At 18o
C in LL, the rhythmic mutant flies show only one periodic component, of approximately 24 hours.
flies behave rhythmically under constant light conditions at 25o
C, approximately one-third of the mutant flies have one periodic component (approximately 24 hours) and the remainder have two periodic components per individual (approximately 22 and 25 hours).
flies entrained to 12 hour light: 12 hour dark cycles and then exposed to 8 hour delayed light-dark (LD) cycles are able to resynchronise to the new light regime.
flies that are entrained to 12 hour light: 12 hour dark cycles ( 12:12 LD) and are then shifted to 9:9 , 13:13 or 14:14 LD cycles routinely re-entrain to behave in synchrony with the novel non-24 hour cycles.
After entrainment by LD cycles, cry02
flies emerge rhythmically under constant darkness conditions with periodicity similar to controls. Under constant light conditions (which cause wild-type animals to eclose arrhythmically) the mutant flies eclose rhythmically and the period is similar to that seen in animals emerging in constant darkness.