Figure 4. Behavioral responses to changes in light schedules.

Flies entrained to a 12∶12 LD cycle were given an eight-hour phase delay. (A) w¹¹¹⁸; (B) pdfr⁵³⁰⁴; ; cry^b double mutants; (C) cry^b single mutants; (D) pdfr⁵³⁰⁴; ; cry^b flies carrying a ∼70 kB pdfr-myc transgene. Green arrowheads mark anticipatory behavior of the original light schedule after the delay. Red arrowheads mark the onset of activity by pdfr⁵³⁰⁴; ; cry^b flies following lights-on in the original and delayed schedules. Note that cry mutant flies require more cycles to re-entrain to such phase changes [5], [7] and that pdfr⁵³⁰⁴; ; pdfr-myc, cry^b (D) displayed a cry^b-like phenotype, indicating rescue of the double mutant behavioral defect. For the experiment shown, the numbers of animals averaged are 16 (A), 16 (B), 16 (C), and 32 (D).