Snails Trailing Beneath the Skin of the Water

Water snail upside downPhoto:
Image: photographyfun

Snails are creatures that provoke quite extreme reactions in humans: often either disgust or culinary desires. But these slimy creatures actually deserve our respect as they can do what humans will never achieve – walk on water! And we’re talking its liquid form here, not ice. Let’s how these amazing creatures manage such a feat.

Though we mostly make the acquaintance of land snails in our gardens and parks, don’t be fooled, as marine snails are far more common and can be found anywhere from freshwater ponds to brackish water to the abyssal depths of the ocean. The whole class of Gastropoda that includes snails and slugs is second only to insects when it comes to diversity.

A water snail in its element:
Water snailPhoto:
Image via MSNBC

For the longest time, snails walking on water seemed almost miraculous even to scientists but a study in last fall’s issue of the Physics of Fluids journal shed some light on the matter. After reviewing video material of water snails, the scientists, led by Eric Lauga of the University of California, San Diego, came to the conclusion that the snail’s ability to create small rippling movements with its foot causes the traction it needs to move across the slippery surface. It’s similar to humans walking on ice.

A water snail walking on water, upside down!
Upside down snailPhoto:
Image via Mr. Barlow

Explains Dr. Lauga: “The snails’ ability to move depends on water’s tendency for its surface to resist disturbance. Water ‘wants’ to stay flat.” The snail’s ripples create similar ripples on the water’s surface that generate a downward force as the water tries to calm itself. But the water’s ripples need to have the right size so that the snail doesn’t slip as would be the case with ripples that are too small. Big ripples would prevent the snail from grabbing them.

Black marine snails hanging upside down:
Black marine snailsPhoto:
Image: David Hu & Brian Chan

The insights these propulsion possibilities provide will not lead to inventions humans can use immediately, such as water-walking shoes (each shoe would have to be several times larger than a football field to distribute our weight). Theoretically, however, the possibilities are endless.

What’s more, the first slimy steps were already taken a few years ago: Mechanical engineer Anette Hosoi and her team at Massachusetts Institute of Technology created RoboSnail, a battery-powered imitation.

Not pretty, but we get the idea – RoboSnail:
Image via MIT

Speculates Dr. Lauga:

“It would be really interesting to build small-scale robotic versions of these snails to see if our understanding of their locomotion is correct and if we can recreate it… In my wildest dreams I can see James Bond releasing robotic snails on water to spy on his enemies.”

Now that’s a thought! So next time you encounter a snail, show it some respect. Because, as this last picture shows, they’re one cool species that can do amazing things.

Land snail scaling a blade of grass:
Snail on grassPhoto:
Image: Sean Mack

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