Brain complexity: fast moving organism without muscles (Introduction)

by David Turell , Friday, December 14, 2018, 19:17 (1950 days ago) @ David Turell

A tiny simple ocean organism changes shape in the oceans:

https://www.the-scientist.com/news-opinion/fastest-ever-cell-contractions-observed-in-p...

"Most animals rely on changes in cell shape to move tissues around during development, but these alterations are usually slow and are rare in adult animals. In a case of extreme exception described in October in PNAS, the adult marine invertebrate Trichoplax adhaerens, a critter in the shape of a smashed wad of chewing gum no bigger than a piece of lint, consistently contracts and relaxes the cells on the top of its body at speeds nearly 10 times faster than ever before observed in an animal.

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"It’s “astonishing” that a cell can contract so quickly and retain its functional integrity while adhering to the surrounding cells, says Alejandro Sánchez Alvarado, a biologist at the Stowers Institute for Medical Research in Kansas City, Missouri, who did not participate in the work. “That’s a remarkable way of managing force, and [studying this animal] is helping us understand how multicellularity may have arisen as a life form on this planet.”

"Trichoplax adhaerens are just a millimeter or two in diameter and flatter than a piece of paper—only about 25 microns thick. This tiny blob of an animal lives in oceans and is thought to be one of the most ancient metazoans. Their bodies are made up of two layers of epithelial cells: the ciliated bottom layer faces the substrate along which they’re moving and the top layer faces open water. So-called fiber cells reside in between the epithelia. They have no muscles, nerves, organs, or extracellular matrix, yet they are capable of directed movement, coordinated secretion of digestive enzymes, and predictable behaviors.

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"The researchers also confirmed previous work showing that actin bundles appear on the surface of Trichoplax cells, as is the case for nonmuscle contractile cells in other animals, and determined that homologs of human myosins were present in the animal’s genome. They performed theoretical calculations that showed the observed cellular movements could be explained by nonmuscle myosin acting on the actin bundles present on the cellular surface. In the study, the team hypothesizes that the rapid contractions and corresponding expansions of the cells’ surfaces allow the animal to cope with external and internal forces without tearing apart.

Comment: Actin fibers form a skeleton and traffic ways in the cells. I wonder if slime mold movement is the result of a similar mechanism. All part of the diversity in organisms that make up the bush of life, which has just gotten bushier. See the next entry.