It’s a question that keeps some scientists up at night: do spiders sleep?
To find out, Daniela Roessler and her colleagues pointed cameras at jumping baby spiders at night. The footage showed patterns that looked a lot like sleep cycles: the spiders’ legs twitched and parts of their eyes flickered.
The researchers described this pattern as a “REM sleep-like state.” In humans, REM, or rapid eye movement, is an active sleep phase in which parts of the brain light up with activity and is closely linked to dreaming.
Other animals, including some birds and mammals, have been shown to experience REM sleep. But creatures like the jumping spider haven’t gotten as much attention, so it wasn’t known if they get the same type of sleep, said Roessler, 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.
Roessler and her team investigated the sleep question after spotting the spiders hanging from silk threads in their lab containers at night. She had recently collected some jumping spiders to study, a common species with a furry brown body and four large pairs of eyes.
“It was just the most unusual thing I’ve ever seen,” Roessler said of the floating spiders.
The research showed that the spiders’ nocturnal movements looked a lot like REM in other species, she said — like dogs or cats twitching in their sleep. And they happened in regular cycles, much like human sleep patterns.
Many spider-like species don’t actually have moving eyes, making it difficult to compare their sleep cycles, explained study co-author Paul Shamble, an evolutionary biologist at Harvard University.
But these jumping spiders are predators that move their retinas to change their gaze while they hunt, Shamble said. Also, the young spiders have a transparent outer layer that gives a clear window into their body.
“Sometimes you get really, really lucky as a biologist,” Shamble said.
Researchers have yet to figure out if the spiders technically sleep while in these dormant states, Roessler said. This includes testing whether they respond more slowly—or not at all—to triggers that would normally trigger them.
Creatures like the jumping spider are very distant from humans in the evolutionary tree. Jerry Siegel, a sleep researcher not involved in the study, said he doubts the spiders could actually experience REM sleep.
“There can be animals that are active in quiet states,” said Siegel of the UCLA Center for Sleep Research. “But are they 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 also not involved in the study, said it’s 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 have for the species, he said.
REM sleep is “still a black box,” Klein said.
https://nypost.com/2022/08/09/spiders-may-experience-rem-sleep-study-suggests/ Spiders can experience REM sleep, a study suggests