Oddly, origami could be useful for snagging prey.
A single-celled protist called Lacrymaria olor uses a helix of pleats folded like origami to unspool a necklike protrusion up to 30 times the length of its body, or 1.2 millimeters, to quickly snap up food, researchers report in the June 7 Science. If a roughly 1.7-meter-tall person could do the same, their neck would reach about halfway up the Statue of Liberty.
The finding could help inspire new robotics, such as tools for microsurgery that can extend and contract inside small body cavities.
Seeing L. olor’s neck in action is an exercise in speed. The organism waves its bulbous dome to-and-fro in rapid, snakelike movements as its neck lengthens and retracts. Such quickness and the organism’s ability to do it over and over again “sets Lacrymaria apart,” says Eliott Flaum, a biophysicist at Stanford University. Other organisms with similar reach move slowly or are unable to reverse any extensions.
L. olor’s neck-stretching ability has been known for more than a century, says Vittorio Boscaro, a microbiologist at the University of British Columbia in Vancouver. “Many times, we notice some crazy feature that we cannot explain, and that’s basically where we stop. It’s nice that papers are coming out trying t actually explain how the crazy thing [happens]…. In this case, the answer is really cool.”
The big question was how the organism managed to build and retract its neck so quickly. “Sometimes you watch a video, and it poses a question that you’re just bound to answer. You must answer it because it just feels paradoxical,” says Manu Prakash, a bioengineer also at Stanford. “Where does the material [to lengthen the neck] come from? How is that physically possible? Is it defying any laws? It doesn’t make sense.”
With a combination of microscopy and live imaging, Flaum and Prakesh found that the protist’s long proboscis is covered in long polymers called microtubules, which give the single-celled organism its shape. Layers of microtubules are wrapped around the protrusion in a helix.
Seeing the helical structure made the team wonder, “Is that a spring? Is that a coil? What’s happening?” Flaum says.
The answer turned out to be neither. On a trip to Japan, Prakash saw chochin lanterns made of paper folded into pleats. “And it just kind of clicked,” he says. L. olor’s helical microtubules were folded like origami.
Prakash and Flaum went to an art store and bought paper to test the idea, folding paper mimics that they’ve dubbed “Lacrygami.” With paper representation, the team showed that as each curved pleat in L. olor’s neck unfolds, the structure rapidly unspools.
There’s no known real-world comparison, Prakash says. The origami-like geometry is different than finger trap toys or a slinky. The closest analogy is a fishing rod, which has one spool with fishing line wrapped around it and another that throws the line out into the water, he says. Or if the folds in a bendy straw were twisted.
How the unfolding gets started is an open question, says Cécile Sykes, a biophysicist at CNRS and l’Ecole Normale Supérieure in Paris. It’s possible that short, vibrating hairlike structures on the outside of the cell help things get moving.
Also unknown is how L. olor’s origami neck comes together or how the organism detects prey and feeds on things like algae. “These mysteries are like onions,” Prakash says. “We peel onions.”
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