Research Paper Volume 15, Issue 2 pp 396—420

Figure 4. Light induced damage alone does not account for the dark lifespan extension. (A) Male flies exposed to either 12 hours of light daily or constant light (LL) were significantly shorter lived than those aged under DD (LD n = 251, LL n = 247, DD n = 234; P < 0.0001). However, there was no meaningful difference between flies aged under 12 and 24 hours of light (P = 0.0304). (B) Similarly, there was a significant lifespan shortening effect when flies were aged under 300 and 1050 lux and compared to DD aged flies (300 lux n = 198, 1050 lux n = 200, DD n = 192; P = 0.0003). When making pairwise comparisons to DD there was a significant effect of both 1050 lux (P < .0001) and a significant effect of 300 lux (P = 0.018), however there was no significant difference between the 300 and 1050 lux treatments (P = 0.085). (C) When exposed to either LD or two, one-hour light pulses a day there was a significant light effect (LD n = 251, light pulse n = 240, DD n = 249; P < 0.0001). LD exposed flies were significantly shorter-lived than light pulse exposed flies (P < 0.0001) and light pulse exposed flies were significantly shorter lived than DD (P < 0.0051). (D) When flies were aged under monochromatic light, there was a significant effect of wavelength on lifespan (blue n = 145, green n = 151, red n = 145, DD n = 146; P < 0.0001). Blue, green, and red light-exposed flies were each significantly shorter-lived than those kept in constant darkness (blue P < 0.0001, green P < 0.0001, and red P = 0.048).