Tardigrades: The World's Toughest Critters

Water Bears in Space

In September 2008 a box of water bears was launched into orbit 270 km above the Earth. They were passengers aboard the Russian Satellite FOTON-M3 on a mission named TARDIS (Tardigrades In Space). The poor little creatures spent 10 days in ventilated containers that exposed them to the vacuum of space, along with freezing temperatures, weightlessness and extreme dehydration. As if this wasn't enough, half of the water bears also had to deal with extremely high levels of cosmic rays and solar radiation.

Amazingly, some of the toughest tardigrades survived and returned to Earth where they managed to lay healthy eggs that hatched just as well as other water bears that stayed comfortably at ground level. Those that did die were mostly killed by radiation destroying their DNA, which is not really surprising: the UV radiation from the Sun was up to 700 times more then you would soak up whilst sunbathing on a Mediterranean beach. The really surprising thing was that some of the animals survived by efficiently repairing the damage to their DNA. Now we know how an animal with a mouth, head, brain, legs, eyes, nerves and muscles has the ability to survive unprotected in space - previously an ability only proved for lichens and some bacteria.

For all their toughness, evolution has left water bears very vulnerable to one thing - squashing! Despite being the only creatures able to survive having their photo taken by a Scanning Electron Microscope (which involves placing them in a vacuum and bombarding them with electrons), scientists have to be really careful not to crush them between the slides of a traditional optical microscope.

The last laugh

We have done some nasty things to poor little water bears, but they will have the last laugh: long after the human race has become extinct they will doubtless be still flourishing. With their "duck-and-cover" attitude to environmental disaster, they will be able to hide from harm extremely efficiently until even the cockroaches have had gone the way of the dodo.

For more information

More about cryptobiosis
http://icb.oxfordjournals.org/cgi/reprint/42/3/652

Tardigrades survive low earth orbit
http://www.cell.com/current-biology/abstract/S0960-9822(08)00805-1

More information about water bears
http://www.microscopy-uk.org.uk/mag/indexmag.html?http://www.microscopy-uk.org.uk/mag/artjun00/mmbearp.html

How to study water bears
http://www.microscopy-uk.org.uk/mag/indexmag.html?http://www.microscopy-uk.org.uk/mag/artmay99/dwbear.html

Excellent water bear video on YouTube
http://www.youtube.com/watch?v=RjwiNZpoHls