ItB次元官网网址檚 a question that keeps some scientists awake at night: Do spiders sleep?

Daniela Roessler and her colleagues trained cameras on baby jumping spiders at night to find out. The footage showed patterns that looked a lot like sleep cycles: The spidersB次元官网网址� legs twitched and parts of their eyes flickered.

The researchers described this pattern as a B次元官网网址淩EM sleep-like state.B次元官网网址� In humans, REM, or rapid eye movement, is an active phase of sleep when parts of the brain light up with activity and is closely linked with dreaming.

Other animals, including some birds and mammals, have been shown to experience REM sleep. But creatures like the jumping spider havenB次元官网网址檛 gotten as much attention so it wasnB次元官网网址檛 known if they got the same kind of sleep, said Roessler, an evolutionary biologist at the University of Konstanz in Germany.

Their findings were published Monday in the .

Roessler and her team dug into the sleep question after she discovered the spiders hanging at night from threads of silk in their lab containers. She had recently scooped up some jumping spiders to study, a common species with a furry brown body and four pairs of big eyes.

B次元官网网址淚t was just the most unusual thing IB次元官网网址檝e ever seen,B次元官网网址� Roessler said of the suspended spiders.

The research showed the spidersB次元官网网址� overnight movements looked a lot like REM in other species, she said B次元官网网址� like dogs or cats twitching in their sleep. And they happened in regular cycles, similar to sleep patterns in humans.

Many species similar to spiders actually donB次元官网网址檛 have movable eyes, which makes it hard to compare their sleep cycles, explained study co-author Paul Shamble, an evolutionary biologist at Harvard University.

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But these jumping spiders are predators that move their retinas around to change their gaze while they hunt, Shamble said. Plus, the young spiders have a see-through outer layer that gives a clear window into their bodies.

B次元官网网址淪ometimes as a biologist, you just get really, really lucky,B次元官网网址� Shamble said.

The researchers still have to figure out if the spiders are technically sleeping while theyB次元官网网址檙e in these resting states, Roessler said. That includes testing whether they respond more slowly B次元官网网址� or not at all B次元官网网址� to triggers that would normally set them off.

Critters like the jumping spider are very far from humans on the evolutionary tree. Jerry Siegel, a sleep researcher who was not involved with the study, said heB次元官网网址檚 doubtful that the spiders can really experience REM sleep.

B次元官网网址淭here may be animals that have activity in quiet states,B次元官网网址� said Siegel, of the UCLA Center for Sleep Research. B次元官网网址淏ut are they REM sleep? ItB次元官网网址檚 hard to imagine that they could be the same thing.B次元官网网址�

But Barrett Klein, an entomologist at the University of Wisconsin-La Crosse who was also not involved with the study, said it was exciting to find REM-like signs in such a distant relative. Many questions remain about how widespread REM sleep is and what purpose it might serve for species, he said.

REM sleep is B次元官网网址渟till very much a black box,B次元官网网址� Klein said.

Maddie Burakoff, The Associated Press

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