Surfing solves puzzle of water snail locomotion

Snail surfing

Snails move using a mechanism called adhesive locomotion. Through muscular contraction and expansion of their foot, they transmit a force to the ground through a thin layer of mucus which is adhesive at low strains but otherwise flows like a liquid.

But what of water snails that move upsidedown along the underside of a liquid surface? Water snails seem to move their foot in the same undulating way as their terrestrial cousins but adhesive locomotion can’t answer for their albeit small, velocity because there’s nothing to stick to.

Today, Sungyon Lee, an engineer at  the Massachusetts Institute of Technology in Cambridge  and a few pals put forward their own suggestion. Their idea is that the undulating motion of the foot deforms the surface of the water. And this generates a pressure that causes the mucus, which is sandwiched between the foot and water surface, to flow.

In other words, water snails surf on waves of their own making.

Neat idea but Lee and company have more work to do to make their argument water tight.

First, it isn’t clear whether their model can account for the kinds of speeds water snails actually achieve (whatever these are).

And second, the model assumes that water snail mucus is newtonian. That’s probably wrong. Terrestrial snail mucus is non-newtonian and that is crucial for locomotion.

I’d be willing to bet a bowl of steaming escargot a la poulette that water snail mucus also turns out to be non-newtonian and that this is crucial for amplifying whatever forces snails use to surf.

Ref: Crawling Beneath the Free Surface: Water Snail Locomotion

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