19 Dec 2016

Indestructible Creatures: The Tardigrade

Imagine that you make a balloon animal: a bear. Then you take the spray nozzle from the kitchen sink and stick it where the mouth goes. Now give it 6 or 8 legs and long thin claws. Finally, shrink it down to just one millimetre long — about the thickness of a dime. Next, imagine that there are zillions of these balloon animals, found in every biome on Earth.

What will you call it? How do you feel about the name tardigrade? Because this tiny balloon animal looks a lot like one.

Moss Piglet and Water Bear are other names for the tardigrade. 
What name would you give this species if you discovered?

Finding Real Live Tardigrades 

Look inside the tiny water droplets on moss and you’re probably looking at a tardigrade’s home and hunting ground. The leaf litter on the forest floor is rife with them too. From the sediments on the deepest bottom of the ocean to the hot springs in the Himalayan mountains, tardigrades make themselves right at home.

There are 1150 species of tardigrades that we know so far. Some have mouths that look like beaks and some have teeth that look like a shark’s; then there’s the one with the kitchen faucet for a mouth. Some species of tardigrade have eyes, and most have bristles over their body (like the ones on a toothbrush). Those bristles help them sense their surroundings. All tardigrades have a mouth and intestines.

You might be able to see some of the largest species of tardigrade. They could reach across the edge of a dime. But the smallest tardigrades would have to form a chain with 20 relatives to reach across that one millimetre distance. You'll need a microscope to see the tiny ones.

Caring for Tardigrades 

These tiny creatures are so tough that scientists call them extremophiles. Notice that word has the word extreme in it. The ophile ending means “very strong liking for.” No one has asked the tardigrades if they enjoy extreme conditions, but they sure can survive them:

Freezing temperatures? No problem.
Boiling hot? Got that covered.
Toxins? Wait until they’re gone.
Pressure? Whatever.
Radiation? P-shaw.
Outer space? They don’t even need space suit!

There is no airway in a tardigrade. They don’t breathe the same way most animals do.

Plants and bacteria are what the tardigrade eats. They can find that food almost anywhere. After using their teeth to pierce the cells of their prey, they suck out the cell contents.

Their Key to a Long Life 

One tardigrade celebrated its 120th birthday. Moss must be a very healthy diet. About 10 years is how long most live.

They can survive 10 years without food or water. (You can only survive a couple days without water.) The trick is that they dry out and shut down when times are tough. Tardigrades force the water out of their body so that their cells don’t burst if they freeze. Usually a tardigrade is about 80% water. (A human is about 60% water.) But when a tardigrade shuts down, or goes dormant, its body can be as little as 3% water.

Those tiny dried bodies can stay in place until conditions improve, or blow around in the wind until they land in a better place. When they land in water — even a drop — they rehydrate and get active again in just a few minutes.

Growing Tardigrades 

It takes only 14 days for a baby tardigrade to be born. They reproduce a lot like fish do: The female sheds eggs along with her outer layer (a natural part of growing called moulting), then the male spreads sperm over the eggs.

As tardigrades grow, their cells get bigger. They don’t get more cells like humans do when we grow. They shed their outer layer when they get too big for it, sort of in the way that humans buy bigger clothes. Shedding is called moulting. They can moult about 10 times in their life.

This tardigrade egg was photographed by two scientists named Michalczyk and Kaczmarek in 2006 using a scanning electron microscope.

What We Can Learn from Tardigrades

Naturally, we want to learn how the tardigrade can live in such extreme places, not just survive them. And by looking at the way they dry themselves out, scientists were able to develop vaccines that do not have to be refrigerated. That means they can be delivered to far-away places without being kept cold.

Other scientists are trying to see if the tardigrade's DNA can added to crops to make plants survive drought instead of dying of thirst.

What would you like to learn about these extreme creatures? What questions would you ask? Where do you think the answers could be used?

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