Anyone who's ever watched a snake slither knows that, no matter the surface, they make it look easy. Smooth and easy -- without tearing themselves to shreds. Scientists have long been aware that snakes feel slipperier on their bellies than on their backs, but what accounted for the difference remained a mystery.
Now they think they may have found the mechanism that effectively greases the skids, as it were, and reduces the friction from all of that slithering.
In a paper published December 9 in the Journal of the Royal Society Interface, researchers from Oregon State University (OSU), Kiel University, the National Institute of Standards and Technology, and the Max Planck Institute for Polymer Research, report their discovery of what is essentially a super-thin layer of fat covering the skin of one common species of snake.
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The researchers examined skin samples of the California kingsnake, using a sophisticated laser spectroscopy technique to analyze the surfaces. It allowed them to study at the molecular level the outermost layer of the creature's skin.
What they found was a previously undiscovered lipid (fatty) layer, only a few nanometers thick, coating the animal's ventral (belly) and dorsal (top) scales.
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Importantly, the layer differs in structure between those two surfaces. According to the researchers, the belly layer "exhibits a higher degree of order and denser packing." The more highly ordered belly film -- with molecules lined up and nearly perpendicular to the surface below –- provides both lubrication and a kind of defense against wear and tear.
"It's crazy how well ordered this [ layer ] is," said the study's lead author, OSU's Joe Baio, in a statement during a symposium at which he first announced his team's discovery. "It would be hard for me to believe it is random, because you have to work hard to make a well-ordered monolayer."
Baio told the BBC he has already begun looking for the same structures on other snake species and that so far they, too, seem to have them.