Are Tardigrades the most indestructible animals on Earth? Is a close contender


Humans would not be able to survive for two minutes in space, but in 2007, two species of Tardigreds were released into space and collected again – still alive.

Tardigrades are a group of small invertebrate species that live all over the world – you can probably find yourself on a piece of moss in your back garden or local park. In fact, you can find them anywhere – on the top of a mountain, at the bottom of the sea or even in a volcano!

McMaster University astrobiologist Drs. John Stone summarized how they could survive a battery of extreme conditions, including temperatures up to -180 ° C for 14 days and oven heat of 151 ° C for 30 minutes.

They can avoid “5000 Gy gamma radiation (which is the radiation type that, in the Marvel Universe, turns David Banner into the Incredible Hulk). Where 5-10 Gy kills humans” says Dr. Stone.

He can also live in a frozen state for up to 30 years and potentially up to 100 years, although he is a long-time Dr. Stone writes.

But are Tardigrades the most indestructible animals on Earth? We asked eight biologists who study them – 63 percent said “yes” means that there is still some debate on this question. Here we have learned from the experts.

Why are Tardigrades so indestructible?

When it is difficult to live in conditions, the Tardigrades curl into a ball known as a tune. When the tardigrade enters a kind of ‘paused’ state in a tune, it is called ‘cryptobiosis’.

During cryptobiosis, animals do not move, grow or breed, but they are protected from extreme conditions. There are many types of cryptobiosis that depend on which circumstances you are dealing with.

The best studied type is called ‘anhydrobiosis’, which protects cells from drying when there is no water.

If cells dry up, many things can get damaged like their DNA and membranes. When some animals undergo anhydrobiosis, their cells are filled with a sugar, called trehalose, that protects the cytoplasm until it remains in water.

Anhydrobiosis was discovered in the Tardigrades in 1702, when scientist Anton von Levenhoek dried up and revived the tardigrade found on the roofs of the house. If frozen, Tardigrades can live in cryptobiosis for at least 30 years without any food or water.

Sea tardigrades are not indestructible

There are over 1,400 known species of tardigrades and each differs in their ability to undergo different types of cryptobiosis. Baker University biologist Drs. William Miller explains, “Terrestrial tardigrades in cryptobiosis are very resistant to destruction … but marine and freshwater tardigrade do not exhibit cryptobiosis, and thus are very destructive.”

Similarly, only a few species of tardigrades make trehalose, the sugar substance that protects cells during anhydrobiosis.

Species of tridlose that do not make trehalose may have some other tricks to protect them from harsh conditions such as special proteins that turn into glass-like substances to protect cells. There is a lot of interesting research to be done to understand this set of survival tools, but it is clear that tardigrades cannot be put together.

Some things that can destroy a tardigrade

Tardigrades are generally more resistant to changes in their environment than most animals. They are often studied in an astrological context – for example identifying whether they would survive if the Earth was hit by an asteroid.

However, this does not mean that they are indestructible against everything – as expert Dr. Dennis Persson says, “Tardigrades are certainly one of the most stress-tolerant animals on Earth, but they are very easily destroyed with needle prick, or eaten by other animals, fungi and protists . ”

Although tardigrades are resilient in some ways, they are vulnerable to the things most animals are at risk of, such as predators and infections.

Tardigrades vs Nematodes

While working on whether tardigrades are the most indestructible animals, we must know about the competition. Ecologist Dr. Diego Fontanetto explains that ‘other animals can survive what we consider to be extreme conditions for life.

Among them, are nematodes and rotifers, which share similar life-history strategies, habitats, and body shapes with tardigrades. These animals survive as much desolate and cold from the Tardigrade, if not better than the Tardigrade. ‘

Other animals that have cryptobiosis tricks up their sleeves include nematode worms, some types of shrimp, and even some species of plants and yeast! Nematodes have been particularly well studied, and paleontologists Drs. Graham Buddha states that “the record of surviving a dehydrated state is near the nematode. Tylenchus polyphenus At 39 years. ”

And the Tardigrade vs. Nematode fight has yet to be verified. “In general, as different animals have different survival abilities under different conditions, it is difficult to be the ‘most flexible’ of the same type,” says Dr. Buddha.

Takeaway: Tardigrades may be the most indestructible animals, but they are not resistant to any form of damage and many experts say nematodes are a close challenger to this title. Despite the debate, it is certain that we are only beginning to learn which organisms can cope in extreme environments, and how they do it.

Article based on 8 expert answers to this question: Are tardigrades the most indestructible animal on earth?

This expert feedback was published in partnership with independent fact-checking platform Metafact.io. Subscribe to their weekly newspaper here.

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