Costs of missing sleep

Not all fruit flies are born equal. Some can skip 12 hours of sleep without missing a beat; others need their beauty rest to keep buzzing. In recent experiments on these two varieties of flies, scientists found that the bugs that skip zzzz’s pay a price to stay awake: They don’t fare as well as well-rested flies when food supplies dwindle.

Scientists often study fruit fly behavior to try to understand how the human brain works. The new fruit fly sleep study may suggest answers to one of the biggest questions among sleep researchers. “That is, ‘What is the core function of sleep?’ ” neuroscientist David Raizen told Science News. Raizen, who did not work on the new experiment, studies the brain and the nervous system at the University of Pennsylvania in Philadelphia.

Genes, chemical features present on chromosomes inside cells, determine many properties of an organism. “Rovers” are fruit flies that can tolerate sleep deprivation, thanks to a change in one of their genes. Among fruit flies, a gene called foraging determines how well the animal can function with little sleep. Scientists refer to another group of fruit flies as “sitters” — insects that need more sleep. The difference in performance of rovers and sitters arises from their hosting different versions of the foraging gene. (Scientists often give fruit fly genes unusual or humorous names; other examples include tinman, maggie, hamlet, hairy and bazooka.)

In the new study, scientists found that rovers could learn new things and keep their memories sharp even after a night without snoozing. The scientists were impressed by the bugs’ abilities. Paul Shaw, a neuroscientist from Washington University in St. Louis who worked on the study, described the insects to Science News as “über-duper super flies.” Sitter flies, on the other hand, had trouble learning if they went a night without sleep.

The tables turned, however, once food entered the picture. When sleep-deprived sitter flies weren’t allowed to eat for 12 hours, their memories improved. Not sleeping made their brains fuzzy — but not eating sharpened their memories. When food was withheld from rovers, the opposite happened: The flies got loopy and were unable to remember. While sitter flies could survive for a few days without food, the rover flies died after 41 hours when deprived of food.

The scientists found that even though rovers could survive sleep deprivation, they had a hard time with food shortages. That balance may explain why both rovers and sitters exist in nature. When food is abundant, rovers may dominate. But in times of shortage, their numbers probably drop off.

Shaw told Science News that there’s a message for people in the fruit fly study. “All of us ‘weak’ people who need eight hours a night might take comfort in the fact that those who claim not to need as much won’t be as resilient to everything,” he said.

POWER WORDS (Adapted from the New Oxford American Dictionary)

gene A unit of heredity that is transferred from a parent to offspring and determines some characteristic of the offspring.

chromosome A threadlike structure found in the nucleus of most living cells, carrying genetic information in the form of genes.

cell The smallest structural and functional unit of an organism, typically microscopic and consisting of cytoplasm and a nucleus surrounded by a membrane.

neuroscience Any of the sciences that deal with the structure or function of the nervous system and brain.