The Indestructible Gummy Bear

Tardigrades, better known as water bears, are small gummy-bear like animals that seem to have won the game of life.

These little guys can survive just about anything, from Antarctica to hot springs, and outer-space to the Mariana trench. Honestly it would be quicker to write a list of the few things they can't survive than it would be to tell you all the things they can survive, but it would also sound much less impressive so I'm not going to do that.

The indestructible gummy bear (tardigrades). Image credit: Willow Gabriel, Goldstein Lab (Wikimedia Commons)

So what can they survive?

Instead of telling you that now, I might first explain HOW they survive.

You'd be forgiven for thinking that because tardigrades can survive so many different things they must have an entire repertoire of extreme survival tricks (like being Batman). But the truth is that they have one trick that just seems to work against everything (more like being Hawkeye, except these guys are much more impressive).

Their trick - Cryptobiosis.

This just means they shut everything down. Metabolism goes down to 0.01% of the normal rate. It's almost like they're dead, and as the wise old saying goes "What is dead may never die" (Theon Greyjoy, 2012). Once tardigrades enter this death-like state they are almost invincible.

The protection works by replacing water in the cell with intrinsically disordered proteins (IDPs), which essentially turn the cells into glass, protecting them from whatever's happening outside. Additionally, damage suppressor proteins (dsup) protect DNA from radiation, keeping it intact for when the tardigrade wakes up.

IDPs really are pretty disordered. Image by sobolevnrm (Flickr)

What causes cryptobiosis?

Tardigrades have four versions of cryptobiosis, each with different triggers.

Anhydrobiosis: Probably the original reason tardigrades evolved cryptobiosis, anhydrobiosis literally means 'life without water'. Tardigrades live in moist environments and water is vital. So it makes sense that they'd be afraid of drying out. As soon as their water levels start running low, tardigrades curl up and rush into cryptobiosis.

Osmobiosis: Not to be confused with anhydrobiosis, this type of cryptobiosis is triggered by a decreased water potential, meaning water is less likely to enter cells. This doesn't mean water is scarce, in fact it's often still abundant, instead this is often triggered by having a lot of things dissolved in the water around them, like you'd find in saltwater.

Anoxybiosis: Literally "life without oxygen". When tardigrades start running out of the oxygen needed for metabolism, it makes sense to slow that metabolism down, and that's exactly what the tardigrade does. However, unlike the other forms of cryptobiosis, this version doesn't involve chucking out water. Instead, they suck in water to become a bloated blob.

Cryobiosis: When life starts to get a bit chilly it's good to have a backup plan. There are three problems with the cold: 1. Reactions in the body slow and can no longer meet metabolic demands, 2. Water freezes and sharp icicles rupture cell membranes, and 3. I don't like the cold. Cryptobiosis solves two of these problems. If metabolism is stopped it no longer matters that reactions are slow, and water is removed anyway so there's no need to worry about ice. The tardigrade has yet to find a solution to my loathing of the cold.

Seriously, what can they survive? 

Ok it's probably about time I gave you the list.

• Hot: Tardigrades can survive 151°C. You've got to admit that they'd be well suited to life in Australia, or right next to a volcano (whichever's closer I guess).

• Cold: at -20°C tardigrades can survive for 30 years, but more impressive is the fact that they can survive for a little while at -272°C. That's just 1°C above absolute zero, the temperature at which literally everything stops moving.

• Low pressure: In a vacuum all the air is sucked out of your body, but tardigrades don't seem to mind.

• High pressure: Way down in the Mariana trench the pressure is so intense that you would be crushed into a ball within an instant. Some tardigrades can survive six times that amount of pressure.

• Radiation: Cockroaches have nothing on the tardigrade when it comes to surviving radiation. Despite the old myth, cockroaches wouldn't stand a chance in a nuclear fallout. Tardigrades on the other hand, would watch the whole thing while sitting back and sipping margaritas.

• Space: This isn't really a new one for the list, but the combination of cold, low pressure, and radiation tolerance make tardigrades the only animals so far to survive in space (outside of a spaceship that is).

Space is almost a walk in the park for tardigrades. Image credit: NASA (Wikimedia Commons)

Challenge: Try to match the type of cryptobiosis that the tardigrade would use to each of the different things they can survive (feel free to answer in the comments below).

All hail our new leaders, the great and powerful gummy bear

You might be wondering by now, "if tardigrades are so indestructible, why haven't they risen up and enslaved humankind?".

To find out the answer, please watch the gif below.

Does this klutz really look like someone that could rise up and enslave anyone? Gif credit: Dmitry Brant (Wikimedia Commons - modified)

So don't worry, you're safe from the almighty gummy bear... for now.

For more information on tardigrades click the links here and here.