What Dreams Do Spiders Weave?

Researchers at the University of Konstanz in Germany have been staring intently at baby jumping spiders while they sleep, wondering if the eight-legged children have the capacity to dream. Their conclusion: maybe.

The study, published this week in the Proceedings of the National Academy of Sciences, documents periodic spasms of the spiders’ retinas as well as limb twitching, suggesting REM sleep – where dreams are made.

“All of a sudden, they would make these crazy movements with the legs and start twitching, Daniela Roessler, one of the study’s authors, told the New York Times. “And it just reminded me immediately of a sleeping — not to say dreaming — cat or dog.”

The phrase “not to say dreaming” does a lot of work there. The researchers can say that the arachnid movements look like what one would expect of a spider during REM sleep, but we may never know whether the little guys are actually dreaming, or what dreaming could possibly entail in a spider.

The jumping spider (Evarcha arcuata) has eight eyes, the two largest of which have light-catching retinas that can move. But the movement is unseen, obscured by the spider’s exterior – except in babies, when their exoskeletons are translucent. Which is why the researchers studied spiderlings younger than 10 days old, when they could track retinal movement.

Scientists have studied REM sleep in other animals – mostly mammals but also birds, reptiles, and cephalopods such as octopi. We may never know what other animals are dreaming or even if they are dreaming; the question wades deeper into philosophy and further from hard science. However, it’s good that researchers are on the case, if only to give us a better understanding of what REM sleep is for and why it evolved in the first place.

Photo credit:  earth.com