The indestructible water bear

I had a slightly unusual email this morning, from someone at the University I work in asking whether it was possible to view living things in the electron microscope. As my background is in microscopy of semiconductors, my immediate response is "no", or at least anything that was alive when you started would be rather dead when you finished putting it into a vacuum chamber and firing a beam of .

Then a name popped into my head. Tardigrade. These tiny creatures were first discovered in the 18th century, and named "kleiner Wasserbär", meaning little water bear (not to be mistaken for the big Wasserbär, or Polar Bear). The modern name means "slow walker". At their largest they reach 1.5mm in size.

And these things are *tough*. They are found at the poles and at the equator, from the high Himalayas to the bottom of ocean trenches.

Did I say tough? I mean really, really tough. They can go into a suspended state in which they can survive short exposure to heat of 151 degrees, cold of liquid helium, they can take liquid nitrogen for days (well, admittedly I think it is different types of tardigrade that can take these extremes). They can take 6000 atmospheres pressure, and they may even be able to survive being in space.

Not that they'd be anything more interesting about viewing a live tardigrade than a dead one in the electron microscope, as their tactic for such harsh environments is to basically shut down and wait for things to get better. But still, it's a tough little beast.