Spiders May Be Able to Snooze

Baby jumping spiders appear to reach a rapid eye movement (REM) sleep-like state, suggesting that they sleep and can possibly dream, according to scientists with the UCLA Center for Sleep Research working with entomologists at the University of Wisconsin–La Crosse.

What to know:

• Nighttime footage of baby Evarcha arcuate jumping spiders shows that the spiders exhibit numerous behavioral patterns that look a lot like the sleep cycles of other species, including humans.

• Uncontrollable twitching was seen in the spiders’ abdomens, their silk-producing spinnerets, and their legs during distinct bouts that lasted a little more than a minute and that occurred periodically throughout the night, much as when dogs or cats dream and have their little REM phases.

• Humans, other mammals, and even birds have been shown to experience REM, which is an active phase of sleep in which parts of the brain light up with activity. REM sleep is closely linked with dreaming.

• Most spiders don’t move their eyes when they are awake, but jumping spiders are predators that have long eye tubes. They move their retinas around to change their gaze while they hunt, and since the exoskeleton of baby jumping spiders is translucent, scientists could see what appeared to be REM at rest.

• Jumping spiders have been known to build silk “sleeping dens” in curled-up dead leaves, but it is unclear if they are actually sleeping or simply in a resting state when these behaviors that mirror other sleeping species occur.

This is a summary of the article, “Regularly Occurring Bouts of Retinal Movements Suggest an REM Sleep–Like State in Jumping Spiders,” published in the Proceedings of the National Academy of Sciences on August 8, 2022. The full article can be found on pnas.org.

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