NEW YORK — It’s 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. It was clear that the patterns looked very similar to sleep cycles. The spiders’ legs moved and some parts of their eyes flickered.
Researchers described the pattern as a “REM-like sleep state”. This is when part of your brain lights up and you are able to dream.
Other animals including birds and mammals have also been found to be able to go into REM sleep. Roesler, an evolutionary biologist from the University of Konstanz, Germany, stated that jumping spiders have not been as well known and therefore it isn’t clear if these creatures get the same type of sleep.
Their findings were published Monday in the journal Proceedings of the National Academy of Sciences.
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.
“It was just the most unusual thing I’ve ever seen,” Roessler said of the suspended spiders.
The spiders’ night movements looked a lot similar to REM in other animals, Roessler said. It was like twitching or waking up in the morning. They also occurred in predictable cycles that were similar to human sleep patterns.
Many species similar to spiders actually don’t have movable eyes, which makes it hard to compare their sleep cycles, explained study co-author Paul Shamble, an evolutionary biologist at Harvard University.
These jumping spiders, however, are predators who move their retinas to adjust their gaze during hunting. Shamble explained. The young spiders also have an outer transparent layer which allows them to see inside their bodies.
“Sometimes as a biologist, you just get really, really lucky,” Shamble said.
The researchers still have to figure out if the spiders are technically sleeping while they’re in these resting states, Roessler said. This includes testing whether the spiders respond slower or faster to triggers than they would otherwise.
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 he’s doubtful that the spiders can really experience REM sleep.
“There may be animals that have activity in quiet states,” said Siegel, of the UCLA Center for Sleep Research. But are they REM? It’s hard to imagine that they could be the same thing.”
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. He said that there are still many questions about the extent of REM sleep and its purpose for different species. Klein stated that
REM is still “very much a blackbox”.
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Do spiders sleep? appeared first in Associated Press .