Do Snails Sleep? New Evidence Says Yes

Photo: Jason Hollinger/Flickr.

They might be among the slowest and most laid-back of creatures, but even snails need to nap on occasion, reports

New research out of the University of Toronto has revealed the first evidence that simple organisms like gastropods need to sleep too — discovery that only deepens the mysteries behind why animals need to sleep at all.

The study began after researchers Richard Stephenson and Dr. Vern Lewis from the University of Toronto noticed that pond snails were spending about 10 percent of the time attached to the side of their tank with their tentacles partly withdrawn, their shells hanging away from their bodies, and with their feet symmetrical and relaxed.

To determine if the snails were sleeping rather than simply resting, the researchers observed how quickly they responded to applied stimuli such as being tapped on the shell, being prodded by a metal rod or being introduced to food. Sure enough, active snails responded twice as quickly to physical stimulation and seven times faster to appetite simulation than the snails that appeared to be resting.

Eight of the snails were monitored for a full 79 days so that researchers could look for patterns in their sleeping habits. Perhaps unsurprisingly, gastropods have much different sleeping patterns than people do. For instance, snails follow a two to three day sleeping period rather than a 24-hour cycle, with clusters of around seven bouts of sleeping over a 13-15 hour period followed by over 30 hours of uninterrupted activity. They also don't appear to need to make up for lost sleep.

Though the reasons behind sleep are still largely mysterious, many experts acknowledge that sleep is important for neurological health, particularly when it comes to organizing and processing memory. The fact that organisms with simpler nervous systems require sleep demonstrates that sleep may play a far more primordial role in biological processes than originally anticipated.

In fact, snails aren't the only simple animals that sleep. Animals like fruit flies, crayfish and even nematode worms have been shown to fall asleep, too.

Does this research mean that snails also dream? Though there's no evidence of that yet, it certainly makes one wonder about what a snail might dream about. Tasty sucrose? Sexy snail shell curves? Do their nightmares involve being covered in salt?

For now, questions like these will have to wait.