Tough as a Tardigrade

Without water, a human can only survive for about 100 hours. But there’s a creature so resilient that it can go without it for decades. This one millimeter animal can survive both the hottest and coldest environments on Earth, and can even withstand high levels of radiation. This is the tardigrade, and it’s one of the toughest creatures on Earth, even if it does look more like a chubby, eight-legged gummy bear. 

Most organisms need water to survive. Water allows metabolism to occur, which is the process that drives all the biochemical reactions that take place in cells. But creatures like the tardigrade, also known as the water bear, get around this restriction with a process called anhydrobiosis, from the Greek meaning life without water. And however extraordinary, tardigrades aren’t alone. Bacteria, single-celled organisms called archaea, plants, and even other animals can all survive drying up.

For many tardigrades, this requires that they go through something called a tun state. They curl up into a ball, pulling their head and eight legs inside their body and wait until water returns. It’s thought that as water becomes scarce and tardigrades enter their tun state, they start synthesize special molecules, which fill the tardigrade’s cells to replace lost water by forming a matrix. 

Components of the cells that are sensitive to dryness, like DNA, proteins, and membranes, get trapped in this matrix. It’s thought that this keeps these molecules locked in position to stop them from unfolding, breaking apart, or fusing together. Once the organism is rehydrated, the matrix dissolves, leaving behind undamaged, functional cells.

Beyond dryness, tardigrades can also tolerate other extreme stresses: being frozen, heated up past the boiling point of water, high levels of radiation, and even the vacuum of outer space. This has led to some erroneous speculation that tardigrades are extraterrestrial beings.

While that’s fun to think about, scientific evidence places their origin firmly on Earth where they’ve evolved over time. In fact, this earthly evolution has given rise to over 1100 known species of tardigrades and there are probably many others yet to be discovered. And because tardigrades are so hardy, they exist just about everywhere. They live on every continent, including Antarctica. And they’re in diverse biomes including deserts, ice sheets, the sea fresh water, rainforests, and the highest mountain peaks. But you can find tardigrades in the most ordinary places, too, like moss or lichen found in yards, parks, and forests. All you need to find them is a little patience and a microscope.

Scientists are now to trying to find out whether tardigrades use the tun state, their anti-drying technique, to survive other stresses. If we can understand how they, and other creatures, stabilize their sensitive biological molecules, perhaps we could apply this knowledge to help us stabilize vaccines, or to develop stress-tolerant crops that can cope with Earth’s changing climate. 

And by studying how tardigrades survive prolonged exposure to the vacuum of outer space, scientists can generate clues about the environmental limits of life and how to safeguard astronauts. In the process, tardigrades could even help us answer a critical question: could life survive on planets much less hospitable than our own?

From the TED-Ed Lesson Meet the tardigrade, the toughest animal on Earth - Thomas Boothby

Animation by Boniato Studio

I love all these humans-as-space-orcs posts, and I decided to add my own.

Accept everything as canon so far (humans are insanely resilient death breathers who are utterly reckless with technology, basically fearless, and have a disturbing need to pet everything). Now add tardigrades. Like, an alien sees the human has brought a tardigrade plushy on board, asks what it is, then stares in horror as the human excitedly describes the only creature from Earth more unkilkable than humans using the same tone of voice they’d use to describe a super adorable kitten.

The best part? The human forgets to explain that the plushy isn’t life size.

Tardigrades– the micro-animals whose electron micrographs (like the one above) have done the rounds on social media for its adorable, bear-like appearance – is a famously hardly organism and is the first animal known to survive in space. Be it extreme heat, heavy radiation, high pressures and even desiccation, the “water bear” can shrug it off.

From The New York Times:

They can remain like that in a dry state for years, even decades, and when you put them back in water, they revive within hours,” said Thomas Boothby, a postdoctoral researcher from University of North Carolina at Chapel Hill. “They are running around again, they are eating, they are reproducing like nothing happened.”

To determine what allowed tardigrades to survive this kind of extreme dryness, Dr. Boothby and his colleagues designed a test in which the microscopic animals were put into a humidity chamber and slowly dried out as in an evaporating pond– the tardigrade’s native habitat. They discovered that the tardigrades have special genes that create glass-like proteins that can preserve their cells during desiccation.

“The glass is coating the molecules inside of the tardigrade cells, keeping them intact,” said Dr. Boothby said. This slows down the tardigrade’s metabolism, allowing it to remain in a suspended state until it is rehydrated. When they add water, the proteins melt into the liquid, and the molecules within the tardigrade are free to carry out their functions again.

The tardigrade continues to surprise scientists and this recent discovery raises the question of whether any other animals use the same unique mechanism of protecting against desiccation. To learn more about this research into Tarigrades, read The New York Times’ article “How a Water Bear Survives, Even When It’s Dry.”

Phylum Tardigrada

Tardigrades are commonly known as water bears. They have a cuticle and can go through ecdysis. Tardigrades have four pairs of clawed appendages, lay eggs, and have eyespots to detect light. Tardigrades are extremely adaptable and live in a large variety of habitats. Whenever they encounter unfavorable conditions, they can enter a form of hibernation called cryptobiosis. 

For more information about cryptobiosis and tardigrades, take a look at this article.


A tardigrade (waterbear) hatching. 

Tardigrades reproduce sexually and females lay eggs. She’ll actually shed her skin first and then lay her eggs inside of it. The babies then hatch from their eggs and then have to crawl out of the skin husk. Fun fact: tardigrades are born with the same number of cells as their adult counterparts - their cells just get bigger as they age. 

arguably the best TAZ quote

I just wanna educate real quick everybody about tardigrades, OK? They can survive a few minutes at 304° Fahrenheit. They can survive 30 years at -20° celsius. They can survive a few minutes at -1000° kelvin. They can survive a few days at -326° Fahrenheit. They can go without water for 10 years. These are savage beasts, and I’m going to haunt them with the only thing that can stop them–their own fears. What does a tardigrade fear? I can’t fathom it. Because it’s un-killable.

Today marks a very special day for Merismo Microscopy! 

I’ve finally found my first tardigrade! This little guy was found crawling around some algae in a saltwater aquarium. Do you see the little eyes and paws? 

They’re quite popular on the internet due to the incredible extremes this tiny animal can survive through. When it enters a state of suspended animation called anhydrobiosis, it can live through near absolute zero temperatures as well as boiling water, radiation, and the vacuum of space (source). Hooray for the tardigrade!


A tardigrade has been brought back to life after being frozen for 30 years

In 1983, Japanese scientists accidentally scooped up two tardigrades and an egg when they were collecting a sample of moss. Scientists stored the organisms at minus 4 degrees Fahrenheit. One tardigrade and the egg lived and are now slowly coming back to life. Could this lead to breakthroughs in cryonics?

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