Clock mutations alter developmental timing in Drosophila.

The developmental time of period mutants in Drosophila melanogaster was monitored under different environmental conditions. We observed that the pers mutants, which have short 19 h circadian cycles, develop faster from eggs to adult than the wild-type: perL mutants, which have long 28 h circadian rhythms, complete development more slowly than the wild-type. These results suggest that endogenous timers may be involved in regulating the development time of D. melanogaster.