What Tardigrades Can Withstand Is Truly Amazing

My aim with every article is to make complex subjects easy to understand.

Tardigrades are among the hardiest organisms on our planet.

Tardigrades were discovered in 1773; they were found to have eight legs, each one tipped with four to eight claws. There are currently more than 1,300 known species in the phylum Tardigrada.

They are also known as "water bears" or "moss piglets".

They are found on the highest mountain peaks and in the deepest parts of the oceans.

It seems that many of them live on land in wet, damp areas.

Most tardigrades are less than one millimetre long. They have specialised mouthparts that allow them to suck the contents from plant cells, algae and other microorganisms.

Tardigrades are known for their ability to survive in extreme environments, including very high and very low temperatures and pressures.

A few weeks ago, I accidentally put my hand under our boiling water tap. You can imagine how quickly I withdrew my hand, but I still had large blisters and a very painful hand.

At sea level, water boils at 100 degrees Celsius (212 degrees Fahrenheit).

You would think that no living thing could survive in boiling water, but some tardigrades can. They can survive exposure to temperatures close to 100 degrees Celsius (212 degrees Fahrenheit) for a short period, provided they are in their dormant tun state.

That last statement is a bit misleading. To survive boiling water, tardigrades must be in a stage of dormancy that resembles death, called the tun state. Some studies suggest that tardigrades can remain in this dormant state for 30 years or more.

They have a strategy for surviving harsh conditions called cryptobiosis. Dry conditions can trigger cryptobiosis.

To enter the tun state, these amazing animals have to get rid of almost all of the water in their bodies; their metabolism drops to almost undetectable levels. Their cells are protected from damage by proteins that are unique to tardigrades. They retract their heads and legs and curl up. The final outcome is a lifeless-looking, crusty ball in a state of suspended animation.

Researchers have found that tardigrades in the tun state can, for a certain period of time, withstand temperatures as low as minus 200 degrees Celsius (minus 328 degrees Fahrenheit). They have also survived brief exposure to temperatures of around 150 degrees Celsius (302 degrees Fahrenheit) while in the 'tun' state.

In 2007, a team of researchers sent tardigrades into space. They orbited the Earth on the outside of a Foton-M3 spacecraft. Although they were exposed to the cold vacuum of space for 10 days, many of them survived, and some were even able to reproduce after returning to Earth.

A tardigrade's lifespan varies from species to species. So how long do they live in their natural state? Some live for a few months, while others can live for up to two years.

What about radiation? It is thought that tardigrades can withstand hundreds to more than 1,000 times the radiation dose that would be fatal to a human.

When do they come back to normal from their 'tun' state?

If the conditions become favourable and they detect water, they hydrate, wake up, and get on with the rest of their lives as though nothing has happened.

Their ancestors are believed to have survived all five of Earth's most recent mass extinctions.

British spelling.

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