Extremophiles: Tardigrades

Out of this world

While adaptation to a single harsh habitat is impressive, there are species which can survive a variety: the rarer polyextremophiles.

Tardigrades, also known as water bears, are tiny, eight legged animals which can survive extremes of heat and cold, low pressure and even high levels of radiation.

They have even survived exposure to space and as such are the undisputed champions of extreme environments.

Ingemar Jonsson, Associate Professor at Kristianstad University, is a specialist in tardigrade biology.
When asked what he considered their most impressive ability, he said: “Their ability to dehydrate completely when the surrounding conditions dry out, and stay in that state without any metabolism for many years or even decades, is clearly remarkable.”

The way that tardigrades perform this drying-out act, however, is still a mystery.

“We know that the animal must somehow protect its basic cell structures from collapsing when water is withdrawn, and repair the damage that arises, but how this is done is unclear,” Prof Jonsson.
Just like red flat bark beetles, dehydration protects tardigrades from freezing when the temperature drops, as their desiccated cells are safe from ice crystal formation.

High resolution image of a tardigrade
Microscope images reveal the tardigrade’s unusual appearance

In December 2012, researchers reported observations of tardigrades able to survive being cooled to just over absolute zero, less than -270C.

They also have amazing radiation resistance: they are able to survive a thousand times more radiation than would prove fatal to humans. Again, this is due to their remarkable healing talent.

“We believe that the ability to repair damaged DNA is one of the main components of this system,” said Prof Jonsson, whose recent studies have been focused on these mechanisms.

“Finding out how this works would be a breakthrough for our knowledge on tardigrades, but it would also be of considerable interest for many other fields of biology and medicine where DNA repair play a central role.”

So while understanding these creatures is of interest in itself, future human benefits may also come from studies of how the extremophiles survive in the supposedly inhospitable parts of our universe.

http://www.bbc.co.uk/nature/21923937

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