THE EFFECTS OF PERIOD MUTATIONS AND LIGHT ON THE ACTIVITY RHYTHMS OF DROSOPHILA-MELANOGASTER

Strains of Drosophila melanogaster homozygous for alleles of the perio d gene (per(0), per(L), per(S), and per(+)) were reared for multiple g enerations either in light:dark cycles (LD), continuous illumination ( LL), or chronic darkness (DD). The locomotor activity of adult flies f rom these cultures was monitored in either LL or DD. Flies that were r eared and tested in DD had a lower proportion of individuals with norm al circadian rhythms than flies reared in LD or LL and tested in DD. T he activity rhythms of DD-reared DD-tested animals, when present, show ed phase coherence within two out of seven populations, while 8 out of 10 LL-reared DD-tested showed phase coherence. Flies tested in LL wer e largely devoid of circadian rhythms regardless of their rearing envi ronment. Ultradian rhythms were more evident under conditions disrupti ve to circadian rhythmicity, but were observed in the presence and abs ence of circadian rhythms. The periods of the ultradian rhythms of LL- reared DD-tested and LD-reared DD-tested flies varied significantly am ong genotypes, while in other rearing and testing regimes, no relation ship was found.