They may doze like humans, according to research from the Universities of Constance and Harvard.

Many spider-like species don’t actually have moving eyes, making it difficult to compare sleep cycles, explained study co-author Paul Shamble, an evolutionary biologist at Harvard University.

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But these jumping spiders are predators, and they move their retinas to change their line of sight while hunting, Chambre said. In addition, young spiders have a see-through outer layer that creates transparent windows on their bodies.

“Sometimes you get really, really lucky as a biologist,” Shamble said.

Researchers still need to figure out whether spiders are technically asleep during these resting states, Roessler said. This includes testing slow response or no response to triggers that would otherwise respond.

Creatures like jumping spiders are far removed from humans on the evolutionary tree. Sleep researcher Jerry Siegel, who was not involved in the study, said he doubted whether spiders could really experience REM sleep.

“There may be animals that are quiet and active,” says Siegel of the UCLA Center for Sleep Research. “But are they REM sleep? It’s hard to imagine they could be the same thing.”

But Barrett Klein, an entomologist at the University of Wisconsin-La Crosse, who was not involved in the study, said he was thrilled to see signs like REM in such distant relatives. Many questions remain about how prevalent is and what purpose it serves for species, he said.

REM sleep is “still very much a black box,” Klein said.

APs