NEW YORK ( Associated Press) — It’s a question that has kept some scientists up at night: Do spiders sleep?
Daniela Roessler and her colleagues videographed the nocturnal jumping spider babies to find out. The images showed a similar pattern to sleep cycles: its legs were folded and parts of its eyes were twinkling.
The researchers described this pattern as a “REM sleep-like state,” using the acronym for Rapid Eye Movement. In humans, REM is an active phase of sleep in which parts of the brain are illuminated by activity, and it is closely linked to dreams.
Other animals, including some birds and mammals, have been shown to experience REM sleep. But creatures like jumping spiders haven’t received as much attention, so it was unknown whether they experience the same kind of sleep, said Roesler, an evolutionary biologist at the University of Konstanz in Germany.
Their findings were published Monday in the journal Proceedings of the National Academy of Sciences.
Rosler said his team turned to the question of sleep after discovering spiders hanging from silk threads at night in the laboratory. He recently collected some jumping spiders for study, a common species with a furry brown body and four pairs of large eyes.
“It was the most unusual thing I’ve ever seen,” Rosler said of the spiders suspended in the air.
The research showed that the spiders’ nocturnal movements were similar to REM in other species, he said, such as dogs or cats that whisper in their sleep. And it happened in regular cycles, similar to the sleep patterns of humans.
Many spider-like species do not have mobile eyes, so it is difficult to compare their sleep cycles, explained study co-author Paul Schumble, an evolutionary biologist at Harvard University.
But these jumping spiders are predators that move their retinas from side to side to change their gaze when hunting, Schamble said. In addition, young spiders have a transparent outer covering that allows their fauna to be seen.
“Sometimes as a biologist you get really, really lucky,” Shambles acknowledged.
Researchers haven’t yet ascertained whether the spiders are technically sleeping in this resting position, Roesler said. This includes testing to determine whether they react slowly, if at all, to events that would normally alert them.
On the evolutionary tree, creatures such as the jumping spider are far from humans. Jerry Siegel, a sleep researcher who was not involved in the study, expressed doubts that spiders actually experience REM sleep.
“There may be animals that are active in a dormant state,” said Siegel of the UCLA Sleep Research Center. “But is this REM sleep? It’s hard to imagine that they could be the same.”
But Barrett Klein, an entomologist at the University of Wisconsin-La Crosse who was not part of the study, said it was exciting to find similar evidence of EMR in such a distant species. Many questions remain about how widespread REM sleep is and what purpose it might serve across species, he said.
REM sleep is “still a black box,” Klein explained.
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