Flies Without Sleep

No significant relationship between daily sleep and lifespan in fruit flies.


Purportedly, all animals sleep, but scientists debate whether sleep is necessary for survival. A recent study shows that depriving fruit flies of nearly all sleep does not greatly reduce their lifespans.

Biologists Quentin Geissmann, Esteban J. Beckwith, and Giorgio F. Gilestro of Imperial College London recorded the sleep activity of more than 1,000 fruit flies (Drosophila melanogaster) for four days. Using an ethoscope, a small computer that video-records and identifies the behavior of flies kept in small tubes, the researchers found that on average, female flies slept for about five hours per day, while male flies slept for an average of ten hours and eighteen minutes per day. A subset of the fruit flies, however, naturally slept much less. Six percent of the female fruit flies slept under seventy-two minutes a day, with a few individuals sleeping fifteen minutes or less.

Next, the researchers measured the effects of continuous sleep deprivation on fruit fly longevity. Three-day-old flies were kept in tubes and were forced to stay awake for their entire lives: after every twenty seconds of inactivity, the tubes automatically rotated to wake them. Both male and female sleep-deprived flies had slightly shorter lifespans than their control counterparts that were allowed to sleep normally. However, the difference was only statistically significant among female flies, whose median lifespan decreased from forty-one to thirty-seven and a half days. In flies that were allowed to sleep without interruption, there was no significant relationship between daily amounts of sleep and lifespan.

Finally, the researchers tested how long flies would sleep after being kept awake for short periods of time (twelve hours) and long durations (nine and a half days). Both male and female flies kept awake for twelve hours showed a next-morning sleep “rebound”—sleeping more than usual for the first three hours after being allowed to sleep. Females that experienced nine and a half days of sleep deprivation exhibited increased sleep for three days following the trial. In contrast, the males showed only three hours of sleep rebound following nine and a half days of sleep deprivation, indicating that longer sleep deprivation does not always correspond to longer sleep rebound. All flies, however, remained active at their usual times, dusk and dawn, even after extensive sleep deprivation, confirming the role of circadian rhythms in governing sleep patterns.

While life without sleep is possible in a lab setting, these results would be unlikely to hold true in the wild, where flies must feed, mate, and avoid predators. Future research may study the effects of sleep deprivation on fruit flies’ ability to compete for mates and other activities needed for survival and reproduction. (Science Advances)