They look like microbears and will survive even in space: biologist Denis Tumanov spoke about tardigrades
Miscellaneous / / July 07, 2023
Most likely, you will find them in the nearest body of water. Or a puddle.
Tardigrades are microscopic animals. They have a translucent body, but their shell can be painted in bright colors, with stripes or checks. They are very tenacious: tardigrades were shot from a cannon, and they did not die. At the forum "Scientists against myths" biologist Denis Tumanov told, what is the secret of these "nanobears". Forum organizers ANTROPOGENESIS.RU posted a recording of his lecture on YouTube channel forum.
Denis Tumanov
Candidate of Biological Sciences, Senior Lecturer at the Department of Invertebrate Zoology, St. Petersburg State University, Senior Researcher at the Marine Research Laboratory of the Zoological Institute of the Russian Academy of Sciences.
Who are the tardigrades
They are microscopic animals. The usual length of a tardigrade is about 0.5 millimeters, that is, 500-600 microns. But there are also quite crumbs measuring 50 microns, and giants up to 1.2 millimeters long. It is believed that tardigrades formed during the Cambrian or Precambrian period and have not changed much since then.
Their body always consists of four main segments plus the head section. Each body segment has two legs. Small, like outgrowths, tubercles, they end in claws. However, some marine tardigrades have four fingers instead of claws at the tips of their paws. This is surprising, because, as scientists believed, only vertebrates have fingers. And, as it turns out, some of the tardigrades.
Inside the animals are arranged very simply. The digestive tube passes through all segments without any branches. Above it is the saccular gonad.
The nervous system of the tardigrade is the supraoesophageal ganglion in the head section plus nerve ganglions - one in each segment. The latter connect the longitudinal ligaments. The ganglion is sometimes called brain. Tardigrade muscles are individual muscle cells. They contract and the animal moves.
In segments of the trunk, individual fat cells can be seen. They are clearly visible under a microscope, because the body of the creature is translucent, and the cells are dense.
In general, the tardigrade is a cavity animal, it is like a balloon. She has a fairly large space inside, filled with liquid. And these cells float freely in the liquid. They store nutrients: if the tardigrade ate well, it has a lot of these cells, if it ate poorly, there are few of them.
Denis Tumanov
And that's it. Tardigrades do not have a respiratory or excretory system. Oxygen saturation occurs by diffusion, metabolic products are excreted directly through the surface of the body.
What is unusual about tardigrades
At first glance, such a simple organism can hardly surprise scientists. But the tardigrades succeeded.
They live wherever there is water.
Tardigrades can be found in all water bodies and on land, where there is enough moisture. They live in freshwater lakes, rivers and streams - deep and very shallow. And even where only spray reaches.
There are many types of marine tardigrades - they differ in appearance from freshwater and thrive in salt water. Such animals were found at a depth of several kilometers, and they felt great under a thick layer of water. It is difficult to find reservoirs where these creatures cannot live.
The only thing I've never seen is tardigrades in hot springs.
Denis Tumanov
But most of all these animals can be found in mosses, lichens, fallen leaves. If you are walking in the forest, and under your feet moss - with a probability of 90% there are tardigrades there. Even if it has not rained for a long time and the moss has dried up.
But at home or in a university auditorium, we are unlikely to be able to find at least one tardigrade. In any case, the probability of such a find is very low.
Tardigrades cannot live next to a person if the person is not sitting in a swamp. They need water.
Denis fogov
They can stop all life processes for a while
Under adverse conditions - for example, when there is not enough moisture around, the tardigrade can stop metabolic processes. The animal enters the state of cryptobiosis. That is, a reversible cessation of vital activity.
It is possible to call such an animal alive at this moment or not - a debatable question. But the main thing is that it can get out of this state and continue an active life.
Denis Tumanov
Tardigrades are animals with the widest range of cryptobiosis states. They can freeze and survive extreme cold, and then thaw and feel great. Inflate like a balloon, and safely endure the lack of oxygen. To form a strong cuticle sarcophagus, consisting of two layers, and wait out other dangers in it.
But the most famous type of cryptobiosis of tardigrades is anhydrobiosis. When there is less moisture around, the tardigrade prepares for a period of drought. It gradually, step by step, dries up. This is a complex process: the internal organs are arranged in a certain order, the cuticle is laid in a special way. And then the dried-up animal can calmly wait for the rains to come again or the dried-up reservoir to fill up.
Outwardly, they look like little bears.
Yes, tardigrades are indeed sometimes referred to as nanobears.
In fact, these animals can look completely different. For example, in some species, membranes appear between the legs. Others grow whole clusters of floats, and scientists do not yet understand why tardigrades need this beauty. Eat maritime species that look like flowers. At the same time, the basic structure of the animal's body is unchanged: four segments of the body, one head section and paws.
But most land-dwelling tardigrades really do look like forest bears. For the first time this microanimal was described and sketched by the German researcher Götze in 1773. He called him a little water bear. Modern photographs taken with an electron microscope also evoke similar associations.
Long body, massive short paws with claws, head without a neck with an elongated muzzle. Well, bear bear.
Denis Tumanov
Is it true that tardigrades live up to 100 years and do not die even in outer space
There are many around these animals. myths. For example, they say that a tardigrade can easily live for a century, or even more. Or settle on the moon and not suffer from radiation and temperature changes. Let's try to separate the fiction from the truth.
They are not immortal
An Italian researcher, naturalist and botanist, studied dried mosses in 1948. From the 120-year-old specimen she got from the herbarium, dried-up tardigrades rained down. They were dead - no surprise there. But, as it seemed to the biologist, one of the tardigrades seemed to move its paw.
The scientist directly wrote in her work that there was no other evidence that the tardigrade was alive. However, her publication still made a sensation. Journalists and allegedly "popularizers of science" began to assert that tardigrades can come to life more than 100 years after the transition to anhydrobiosis. But it's not.
In an active state, the tardigrade lives on average up to one and a half to two months. This is under ideal conditions - for example, in a Petri dish, where it is warm all the time and there is water. The oldest tardigrade elder lived in the laboratory for 517 days.
If an animal enters a state of anhydrobiosis, then the maximum period after which it can be brought back to life is 15 years. None of the tardigrades, after a longer stay in the desiccated state, returned to an active state. This means that the myth of almost immortal nanobears has not been confirmed.
But they can really survive in outer space.
To find out how tenacious these animals are, scientists conducted an experiment called TARDIS. The abbreviation stands for tardigrades in space - tardigrades in outer space. A special capsule, designed by an international research team, went into orbit aboard the Russian scientific satellite Foton. The capsule was divided into many cells, in which scientists placed several species of tardigrades. Naturally, the animals were in a state of anhydrobiosis.
Each capsule cell had three levels of protection:
- The most transparent layer - tardigrades are open to ultraviolet light and are in a vacuum. Only the temperature is regulated: in all cells it did not exceed +10 degrees.
- Enhanced protection - A light filter is added, which greatly reduces the effects of ultraviolet radiation.
- Full UV protection and the same +10 degrees.
The satellite was launched into an earth orbit at a height of 250 kilometers. The capsule with the tardigrades was actually in outer space. After returning, the scientists tried to place these creatures in a humid and comfortable environment. And only representatives of one species returned to life. And only those individuals that were in cells with the highest level of protection. That is, in a vacuum, but without exposure to ultraviolet radiation.
This means that tardigrades can indeed demonstrate unique survival abilities. But immortal and they cannot be called absolutely invulnerable.
We can definitely say that tardigrades cannot live in space, actively crawl and move. But they are really capable of surviving in open space conditions.
Denis Tumanov
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