Some spiders might experience REM sleep and even dream

MARY LOUISE KELLY, HOST:

If you have ever seen a close-up photo of a jumping spider, you'll know they're the kind of cute ones. Many of them fit on the tip of a finger, and they sport fuzzy, colorful bodies, big eyes.

DANIELA ROESSLER: They have this incredible vision that is really not comparable with any other insects or arthropods. They've been shown to be really smart and to do really smart things.

JUANA SUMMERS, HOST:

Daniela Roessler is a behavioral ecologist at the University of Konstanz in Germany. She and her colleagues have now discovered something else intriguing about these spiders. At night, they seem to enter a state resembling rapid-eye-movement sleep, or REM sleep.

KELLY: That is the phase of human sleep where our bodies are immobilized, but our eyes dart quickly, and we can have really visual dreams.

SUMMERS: Well, by filming baby jumping spiders at night, Roessler says her team was able to detect periods of REM-like activity.

ROESSLER: All the legs would curl into the body, and they would twitch while doing that. We would see that always, when this happened, we also detected quite significant and very obvious eye movements.

SUMMERS: The findings appear in the Proceedings of the National Academy of Sciences.

KELLY: Now, Roessler cautions it's too early to say whether the spiders are technically asleep during these rapid eye movements. They're going to test that next. But even these early findings are exciting to sleep scientists like Mark Blumberg at the University of Iowa.

MARK BLUMBERG: These behaviors themselves are just - you know, if I can say so - they're just beautiful behaviors. What we want to know at some fundamental level is - why do these animals do this?

SUMMERS: Now, Blumberg was not involved in the work, but he says studying these behaviors across the animal kingdom might someday tell us more about how REM sleep evolved.

KELLY: As for the question - do spiders dream? - Blumberg is skeptical.

BLUMBERG: People - when they look at rapid eye movements, what they see is a visual system being activated. They see these movements of the eyes, and they immediately jump to dreaming, and I just think that's a bridge too far for this stage of the research.

SUMMERS: Roessler agrees and says, even if spiders do dream, they probably don't dream like us.

ROESSLER: I mean, it's beautiful to think about it that way - that these spiders hang there and they have a visual scene of catching a fly or trying to get a mate. It's quite cute, but probably is going to be very different.

SUMMERS: After all, Roessler points out that some spiders have very poor vision, but are very attuned to vibrations. She wondered if they might dream in vibrations instead.

KELLY: Something to ponder as you drift off to sleep tonight.

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