Videos of tardigrades walking around reveal that these microscopic water bears rely on ‘grappling hook’ claws

tardigrade water bear walking
A screenshot from one of the researchers’ videos shows a tardigrade using its claws to walk along a gel surface.

They’re cute. They’re tough. They’re microscopic. And apparently they’re very coordinated.

Tardigrades – the eight-legged, millimeter-long animals also known as “water bears” – are fun to look at and fascinating to study. They can survive in extreme environments, including the vacuum of space, the inside of a volcano, and in an Antarctic lake nearly a mile underground. They can return to normal functioning after being frozen for three decades.

But biophysicist Jasmine Nirody is also fascinated by water bears’ mundane, day-to-day activities. She wanted to learn more about how these micro-critters get around on legs with no bones.

“To me, it was fascinating that they even walk. Things at that scale don’t really tend to walk,” Nirody told Insider.

So she assembled a team, put some tardigrades underwater, gave them gel surfaces to walk on, and set up a camera. The resulting videos are not only cute and entertaining – they reveal that water bears use their little claws like grappling hooks, and that they walk in similar patterns to insects.

tardigrade water bear walking view from underneath
A tardigrade walks on a gel surface.

“I was surprised that they were so coordinated,” Nirody said. “We were surprised that they had a coordinated pattern at all.”

After all, the very name “tardigrade” means “slow walker.”

Glass is too slippery for tardigrades

Nirody is a fellow at both Rockefeller University in New York and the All Souls College at the University of Oxford. She and Daniel Cohen, a bioengineering researcher at Princeton University, published the new findings about tardigrades in the Proceedings of the National Academy of Sciences on Tuesday.

Graduate student Lisset Duran and high-school student Deborah Johnston filmed the videos for the study. But when Cohen watched one of the side-view videos of the team’s walking tardigrades, he was convinced he was seeing “something strange.”

tardigrade water bear walking view from the side

“It looks so much like a terrestrial (land-based) animal, but it was completely underwater,” Cohen told Insider via email.

“They are, ironically, truly atrocious swimmers,” he added. “So being able to grapple onto the ground may be a good safety measure against that.”

Nirody always thought that water bears were clumsy, but she soon realized this was because she’d seen many videos of tardigrades walking on glass.

“If you put them on glass, they have nothing to grab on to, and so they slip,” she said. “We have a video of them walking on glass, and they look just as silly as you’d expect them to. But that’s because we’re not giving them the right environment.”

tardigrade water bear walking clumsily wriggling on smooth glass
A tardigrade walks on smooth glass.

“If you put a fish on land, it looks dumb,” she added.

How to walk when you have ‘noodles for legs’

Humans can walk because we have bones.

“When you take a step forward, and then your back leg pushes off, it essentially uses the other leg as a pole vault to swing itself over,” Nirody said.

But soft-bodied animals like tardigrades have no bones. They don’t have an exoskeleton, either, like an insect or crustacean does. Nirody calls their physiological situation “noodles for legs.”

“You can’t pole vault with a noodle,” she said. “So they have to have a completely different strategy. And the way that they do it, is they use their claws like grappling hooks. They dig their claws into the substrate, and they’ll pull their body forward, like we would climb a rock wall essentially.”

tardigrade water bear walking view from underneath

Tardigrades’ walking patterns actually look quite similar to those of insects and other arthropods. This either indicates that tardigrades are related to arthropods, or that two groups of unrelated organisms independently developed the same walking strategies.

That would suggest that this method of walking is highly effective – across vastly different anatomies and sizes. It could even be a good model for small-scale robots.

“If this kind of control circuit seems to be adaptive in these two completely different systems, then that says that we have something to learn from that,” Nirody said.

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Scientists shot tardigrades out of a gun at more than 2,000 mph to see if the critters could survive

Scientists are just starting to understand the tardigrade - and it's fascinating
A microscopic tardigrade.

Tardigrades have a reputation for being among the hardiest critters in the animal kingdom.

These microscopic creatures can survive in the vacuum of space, inside a volcano, and in an Antarctic lake nearly a mile underground. They have even returned to normal functioning after being frozen for three decades.

But according to a recent study in the journal Astrobiology, even seemingly indestructible tardigrades have their limits.

The researchers shot canisters full of tardigrades out of a high-speed gun at various speeds to see if the creatures could survive the pressure of each resulting impact.

After being shot out at speeds under 900 meters per second (about 2,000 miles per hour) – that’s faster than your average bullet – the tardigrades could be revived. Any faster than that, according to Alejandra Traspas, an astrochemist at Queen Mary University in London and a co-author of the study, and they didn’t make it.

Being shot more than 2,000 mph meant the critters experienced 1.14 gigapascals of pressure on impact – that’s equivalent to the pressure of about 40,000 people standing on your back at once.

“They just mush,” Traspas told Science.

Solving a lunar mystery

A microscopic image of an Antarctic tardigrade found in a frozen moss sample.

Tardigrades are also known as water bears or moss piglets – apt nicknames, considering that these 0.05-inch-long organisms look like eight-legged potatoes with scrunched up faces and tiny paws under a microscope.

The critters can withstand temperatures between minus 458 degrees Fahrenheit (minus 272 degrees Celsius) and 304 degrees Fahrenheit (151 degrees Celsius) and pressure up to six times that of the deepest part of Earth’s oceans.

They’re able to survive lethal radiation and temperatures because water bears, like their namesake, can enter a state of hibernation. Tardigrades can go without water and oxygen for long periods of time in a state of suspended animation called cryptobiosis, in which their bodies dry up and their metabolisms shut down. Place a dehydrated, hibernating tardigrade in water and it regains its full function in a matter of hours.

So when an Israeli spacecraft carrying a horde of hibernating tardigrades crash landed on the moon in April 2019 due to a computer glitch, scientists thought the animals would surely have survived.

But Traspas wasn’t so sure: “I was very curious,” she told Science. “I wanted to know if they were alive.”

Tardigrades look like microscopic bears.

To test the theory, Traspas’ team froze 20 tardigrades (to get them to hibernate), loaded them into hollow nylon bullets, and fired them at sandbags using a high-speed gun.

They found the animals just couldn’t survive an impact if the bullet was fired at more than 2,000 miles per hour – only fragments of the tardigrades remained – because the pressure of 1.14 gigapascals from the impact was just to great.

Although the spacecraft was only traveling about 310 miles per hour when it smashed into the moon, the impact pressure when the lander hit the lunar surface was “well above” that 1.14-gigapascal threshold, according to Traspas.

“We can confirm they didn’t survive,” she told Science.

An artist’s depiction of a meteorite falling to the ground.

The findings also throw some cold water on the theory known as panspermia, which suggests microscopic organisms like tardigrades can hitchhike across the solar system on asteroids fragments that ricocheted into space after their parent rocks hit a moon, for example.

According to panspermia proponents, those asteroid fragments, or meteorites – and the organisms they carry – could one day seed life on another planet.

But if tardigrades can’t survive the pressures of a collision with our moon, it’s unlikely they could survive a meteorite impact with another planet, the study authors wrote.

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