Borrowing the water bear’s superpowers

Bake them, freeze them, shoot them out of a gun, even fling them into space—tardigrades just shrug. These eight-legged “water bears,” barely a millimeter long, are so tough that some scientists joke they could outlast us all, hanging on until the Sun gives up. Under a microscope they look like chunky mini-monsters—pudgy faces, fierce claws, tiny teeth—yet their real party trick is survival. Now researchers want to turn those powers to our advantage, from shielding cancer patients during radiation therapy to keeping medicines stable on deep-space trips.

There are roughly 1,500 known tardigrade species, cousins of insects and crustaceans, though biologists still argue about where exactly they fit on the family tree. You can rinse them out of backyard moss, but they also show up on Himalayan peaks, seafloors, Antarctic ice and, allegedly, acidic hot springs in Japan. Earth isn’t their only stage. In 2007, tardigrades became the first known animals to survive exposure to outer space; some females even laid eggs up there, and their hatchlings were fine. A 2019 Israeli mission that crashed on the Moon carried a payload of tardigrades; no one knows if those micro-passengers made it, but given their resume, nobody would bet against them.

The numbers behind that resume are absurd. Tardigrades have shrugged off doses of radiation up to a thousand times what kills humans. They can be heated to about 150°C and cooled to a whisker—0.01°C—above absolute zero. In 2021, scientists literally loaded them into projectiles and fired them; many survived impacts at around 900 meters per second, faster than a handgun bullet. The obvious question is how any animal pulls that off.

A big part of the answer is a survival mode called the “tun.” When water disappears, a tardigrade retracts head and legs, curls into a seed-like capsule, and slams its metabolism down to roughly 0.01% of normal.

“They literally pack their organs away,” says University of Copenhagen biologist Nadja Møbjerg.

In this suspended state, they can sit for years. Historical specimens have twitched back to life after eight years dry; one from a museum cabinet moved a leg after more than a century.

But the tun is only the beginning. While watching tardigrades dry out, University of North Carolina researcher Thomas Boothby saw a surge in genes for strange, floppy proteins unique to water bears—tardigrade-specific intrinsically disordered proteins, or TDPs. Block those genes and the animals can’t survive desiccation. Transfer them to yeast or bacteria and those microbes suddenly withstand drying a hundred times better. Drill down further and a class called CAHS proteins emerges as the star. In water, they’re jelly-like and unstructured. As cells desiccate, these proteins link into a gauzy, spider-web matrix that props up sensitive cellular parts and keeps other proteins from clumping or unfolding. It’s a different route to the same end achieved by trehalose, the “glass-forming” sugar used by brine shrimp and some frogs: hold a cell’s architecture in place until the weather changes.

The tun and those TDP webs also help explain why some species can shrug off brief blasts of heat over 100°C—if they’re already dry.

“If you heat a tardigrade in a droplet of water, it dies like anything else,” Boothby notes.

And despite their superhero reputation, water bears do have limits. Møbjerg’s team has shown that if they don’t have time to enter the tun, some species start dying a little above body temperature for humans, around 37°C. That vulnerability matters on a warming planet. Tardigrades help soil ecosystems—some even snack on parasitic nematodes—so losing them would ripple outward.

Other extremes tap different defenses. Frozen tardigrades have revived after three decades on Antarctic ice, a feat that likely leans on a metabolic shutdown called cryobiosis and strategies to avoid ice crystals shredding their insides. Radiation resistance is better mapped. In 2016, University of Tokyo biologist Takekazu Kunieda’s group identified Dsup—short for “damage suppressor”—a tardigrade protein that wraps DNA like a flexible blanket and blunts the havoc caused by ionizing radiation. Human cells engineered to make Dsup suffered fewer DNA breaks after X-rays. Tardigrades also mop up reactive oxygen species, the nasty by-products that radiation creates in water-rich cells, and they seem to patch DNA more effectively. This year, a second DNA-binding protector, TDR1, joined the club, reinforcing the idea that water bears stack redundancies to keep their genomes intact.

All of which brings us back to the human angle. If Dsup can shield tardigrade DNA, can it protect ours—at least temporarily? Teams at MIT, Brigham and Women’s Hospital and the University of Iowa have used mRNA injections to make mice produce Dsup in targeted tissues. When those tissues were later blasted with radiation at clinical levels, healthy cells were spared while the “tumor” targets took the hit. It’s early work, and any therapy would have to clear big hurdles around immune reactions and safety, but it hints at gentler radiation treatments ahead.

The dry-state biology may be even closer to prime time. Boothby’s lab has shown that mixing the blood-clotting medicine Factor VIII with tardigrade TDPs keeps it stable at room temperature, a potential game-changer for people with hemophilia who live far from reliable cold chains. The same approach could help vaccines and biologic drugs, and NASA is watching closely for tech that keeps food and medicines safe during long space missions.

Why did a creature that lives between moss leaves and soil particles evolve such overkill? Part of the answer may be simple physics. Tardigrades are aquatics at heart, and their thin, permeable skin means they dry out easily. Once dry, something the size of a dust mote can go airborne.

“If sand from the Sahara can blow to the Amazon, tardigrades can, too,” Boothby says.

That kind of accidental world travel would expose them to all sorts of insults—cold mountaintops, scorching flats, brutal UV—favoring any tweak that keeps them alive until the rain returns.

There are still mysteries. No one really needs to survive temperatures a whisper above absolute zero on Earth, and yet some tardigrades do. We don’t know every trick they use to dodge ice damage. We’re only beginning to map how their oddball proteins assemble and dissolve on cue. But the direction of travel is clear. Cracking the water bear’s playbook isn’t just a biology flex; it could mean fewer side effects for cancer patients, medicines that don’t need a fridge, and safer pantries aboard a spacecraft headed for Mars. And it might help protect the water bears themselves as heat waves lengthen and droughts bite. For a creature the size of a pinhead, that’s one outsized legacy.

The original story by Jasmin Fox-Skelly for BBC.