Animal or plant?

She defies Dot with her peculiar physique. Perhaps you have already come across it at the bend of the forest road, in the form of a yellow mossy carpet, without suspecting that before your eyes is a mystery of the Tree of Life.

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Let’s go back: aka Vesarum polycephalum, the point has long been stored with… mushrooms. Moreover, most of the historical articles on this topic are in the journals specializing in mycology. It was then ranked among the Protesters, a derelict comprehensive kingdom today. Since his genome was sequenced in 2015, It is part of the amoebozoa, a group of fairly primitive unicellular. But his separation retained the name mycosis fungoides (“sticky mushroom”).

The dot has everything to pique the curiosity of biologists. Crawling, devouring everything in its path, it has 750 sexual species and can reach a size of 10 square meters in a laboratory. Although he is brainless, he is able to learn and even teach. And its behavior varies according to its geographical source! If the method of its reproduction is similar to the method of reproduction of a mushroom (it disperses its spores in nature), then the method of feeding it is usually animalistic: it is a predator that practices phagocytosis, that is, it swallows its own food. But while mushrooms only eat by absorbing microelements, the bubble can swallow bacteria, mushrooms taste and, in the lab, like oatmeal.

Blob: A cell capable of learning

In the method of eating and crawling, the point is close to an animal. But its yellow and pink cellular pigments make it closer to plants. Even its genome baffles geneticists. In addition to showing many characteristics of animal cells, genes Vesarum polycephalum It reflects an organism unparalleled in molecular complexity within single-celled organisms.

Exceptional, therefore, and neglected by research. Until, in the 2000s, a Japanese team revealed the unimaginable capabilities of single-celled organisms: decision-making, risk assessment, the expression of individual variance…then ethicists reconsidered the point interest.

By testing genetically distinct breeds, behavioral differences between Japanese, American and Australian breeds are highlighted. Thus, the Australian dot excretes more calcium and detects minute amounts in the environment, while the American excretes very little and does not see it well. Two Australians turn toward each other, when two Americans sprint into their corner…

In light of these skills, the scientists hypothesized that the point is capable of learning. The blobs were trained to ignore the natural aversion to caffeine, quinine and salt, and cross a bridge covered with these substances to get to the food. They crossed the bridge in five days!

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Point: veins share information

And that’s not all: Vesarum polycephalum He could pass on his knowledge by simply merging with an inexperienced peer. The scientists collected 2,000 so-called “usual” blobs, trained to ignore their dislike of salt, and 2,000 so-called “naive” blobs, then made various combinations of naive/habitual. Once there was a regular at the lottery, the others knew.

How is information exchanged between points? Thanks to a kind of vein that forms three hours after the fusion of two points. Inside the multinucleated cell, the point is crossed by a network of veins in which the cytoplasm containing nutrients circulates. At the beginning of fusion, there is just a sharing of the cytoplasm. Then, suddenly, you can clearly see the appearance of the vein. Moreover, there is no exchange of information if the blobs are separated before the vein is formed.

The discovery is puzzling. In what form is information circulated in this ambiguous context? RNA messenger, proteins? At the moment, the process is still unknown. There is another question that must be solved to unravel the mystery of this being who is not really like the others.

If it looks like a plant, it feeds like an animal and multiplies like a mushroom, point does not belong to any of these categories. Call two points (H) accustomed to ignoring their aversion to salt, a “naive” point (N) begins by crossing a salt-covered bridge to reach the food. Evidence that the dots transmit learning, through the vein that forms between them, at the level of the contact area.

Article originally published in 2019.

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