Mean bioluminescence time-series data from young (10-day), middle-aged (30-day) and old (50-day) flies in LD cycles (white bars represent lights on and black bars indicate lights off). Bioluminescence CPS is plotted as average of raw counts at 60-minute intervals. Data are shown as mean ± SEM with error bars at each time point. 10-day cohort equals black lines and columns, 30-day cohort equals mid-grey lines and columns, and 50-day cohort equals light-grey lines and columns. (A) The 8.0-luc 30-day and 50-day cohorts show higher PER amplitude than 10-day (p < 0.001 and p = 0.001, respectively). There is no difference between 30-day and 50-day (p = 1.00). 30-day cohort shows higher PER acrophase than 10-day and 50-day (p < 0.001 and p = 0.02, respectively), and there is no difference between 10-day and 50-day (p = 1.00). (B) The XLG-luc 30-day and 50-day cohorts show lower PER amplitude and acrophase compared to 10-day (p < 0.001 in all), 50-day is lower than 30-day (p < 0.001 in amplitude and p = 0.001 in acrophase). (C) The tim-luc 30-day and 50-day cohorts show lower TIM amplitude and acrophase compared to 10-day (p < 0.001 in all), 50-day is lower than 30-day in amplitude (p < 0.001) but not in acrophase (p = 0.11).