LIGHT CYCLES GIVEN DURING DEVELOPMENT AFFECT FREERUNNING PERIOD OF CIRCADIAN LOCOMOTOR RHYTHM OF PERIOD MUTANTS IN DROSOPHILA-MELANOGASTER

We reared wild type (Canton-S) and period mutant dies, i.e., per(S) an d per(L), of Drosophila melanogaster in constant darkness, constant li ght or 24h light dark cycles with various light to dark ratios through out the development from embryo to early adult, The locomotor activity rhythms of newly eclosed individuals were subsequently monitored in t he lighting conditions, in which they had been reared, for several day s and then in constant darkness, Circadian rhythms were clearly exhibi ted in constant darkness even in flies reared in constant light and co nstant darkness as well as flies reared in light-dark cycles, but the freerunning period differed among groups, The results suggest that the circadian clock is assembled without any cyclical photic information, and that the light influences the developing circadian clock of Droso phila to alter the freerunning period, The effects of light on the rhy thm differed in some aspects between per(L) flies and the other two st rains. Possible mechanisms through which light affects the developing circadian clock are discussed. (C) 1997 Elsevier Science Ltd.