Natures wonders: a protist makes an enormous size change (Introduction)

by David Turell , Thursday, June 06, 2024, 23:45 (168 days ago) @ David Turell

All without nerves:

https://phys.org/news/2024-06-cellular-origami-protist.html

"Prakash and Flaum spent the last seven years studying Lacrymaria olor's every move and have published a paper on their work in Science.

"'The first time I came back with a fluorescence micrograph, it was just breathtaking," Flaum said. "That image is in the paper."

"The video Prakash queued up reveals why this organism is much more than a pretty picture: a single teardrop-shaped cell swims in a droplet of pond water. In an instant, a long, thin "neck" projects out from the bulbous lower end. And it keeps going. And going. Then, just as quickly, the neck retracts back, as if nothing had happened.

"In seconds, a cell that was just 40 microns tip-to-tail sprouted a neck that extended 1,500 microns or more out into the world. It is the equivalent of a 6-foot human projecting its head more than 200 feet. All from a cell without a nervous system.

***

"L. olor is featured in Science because Prakash and Flaum have discovered in this behavior a new geometric mechanism previously unknown in biology. And they are the first to explain how such a simple cell can produce such incredible morphodynamics, beautiful folding and unfolding—aka origami—at the scale of a single cell, time and again without fail.

"It is geometry. L. olor's behavior is encoded in its cytoskeletal structure, just like human behavior is encoded in neural circuits.

"'This is the first example of cellular origami," Prakash said. "We're thinking of calling it lacrygami."

Specifically, it is a subset of traditional origami known as "curved-crease origami." It is all based on a structure of thin, helical microtubules—ribs that wrap inside the cell's membrane. These microtubule ribs are encased in a delicate diaphanous membrane, defining the crease pattern of peaks in a series of mountain-and-valley folds.

"Prakash and Flaum used transmission electron microscopy and other state-of-the-art investigatory techniques to show there are actually 15 of these stiff, helical microtubule ribbons enshrouding L. olor's cell membrane—a cytoskeleton. These tubules coil and uncoil, leading to long projection and retraction, nesting back into themselves like the bellows of a compressed helical accordion. The gossamer of membrane tucks away inside the cell in neat, well-defined pleats."

Comment: how did this complex design appear in a single-celled organism? Not by chance.