5 Reasons Tardigrades Will Outlast Us All


Among organisms, the microscopic tardigrade is as close as it gets to unbreakable. The aquatic invertebrate, which also goes by "water bear" because some think it looks like a microscopic eight-legged panda, famously resists the most sincere attempts to kill it.

The key to this resilience, which varies among the 1,000 or so tardigrade species, is a state of suspended animation known as cryptobiosis. Tardigrades aren't the only microorganisms that can do it — nematodes, for one, similarly protect themselves from extremes — but they seem to do it best. Under extreme conditions, the tardigrade expels almost all water from its cells, brings metabolic processes to a near-complete halt and enters a death-like state described by the Verge's James Vincent as an "indestructible pellet." In this form, the animal can withstand environmental conditions that would obliterate other life-forms.

Tardigrades live through boiling, freezing, near-complete desiccation, immersion in solvents, crushingly high pressures, and radiation doses that, by all scientific measures, should shred its DNA to smithereens.

In the latest research, published in the journal Nature Communications on Sept. 20, Japanese scientists identified a protein that seems to confer the animal's genetic radiation resistance. It's a stunning find, with possible medical and space-travel implications for humans, which is likely the case with many of the animal's mind-boggling survival abilities.

Here are five of the talents that earn the tardigrade the evolution award.

1. They don't need spacesuits.

Scientists sent tardigrades into space in 2007, with no protection, for 12 days. Almost all of the creatures survived the vacuum and cosmic rays. Some also survived the ionizing radiation that, according to Jasmin Fox-Skelly on BBC.com, "would rip apart the DNA in [our] cells" should we ever try such a thing.

No other animal has survived direct exposure to the vacuum and radiation of space. And the tardigrades didn't just survive; some laid viable eggs that went on to hatch healthy tardigrade babies back on Earth.

2. They can turn into glass for a while.

Tardigrades live in water, some in seas and others in moist land features like lichen and moss. Drought is a big problem, survival-wise. Tardigrades solve that problem by crystallizing.

Basically, faced with the threat of desiccation, the tardigrade preemptively desiccates itself, inducing cryptobiosis — the suspended animation that protects it from injury. And in order to not die from the protective state of desiccation, explains ScienceAlert, it "produce[s] a special type of 'bioglass' to hold essential proteins and molecules together until [it's] rehydrated back to life."

Upon contact with water, the glass dissolves and the animal reanimates (kind of like sea monkeys, only tougher). Scientists found the gene for tardigrade glass in 2015.

A tardigrade reveals its underbelly, courtesy of a scanning electron microscope micrograph.
A tardigrade reveals its underbelly, courtesy of a scanning electron microscope micrograph.
Cultura RM Exclusive/Gregory S. Paulson/Getty Images

3. They've seen the edge of absolute zero.

Scientists have been freezing tardigrades for decades. In May 2014, researchers defrosted tardigrades stuck in a freezer back in 1983. After more than 30 years stored at minus 4 F (minus 20 C), two of the animals came back to life. One died a few weeks later; the other starting laying eggs about a month and a half after defrosting.

They've survived far colder than that. In a series of experiments in the 1920s, reports the BBC, tardigrades survived being stored for 21 months at minus 328 F (minus 200 C) in liquid air, 26 hours at minus 423.4 F (minus 253 C) in liquid nitrogen, and eight hours at minus 457.6 F (minus 272 C) — about 2 degrees F above absolute zero — in liquid helium.

At minus 459.67 F (minus 273.15 C), or absolute zero, molecular motion stops. In 1950, tardigrades made it to minus 459.4 (minus 273 C) and lived to tell the tale.

4. Boiling them is OK.

Well, it may not be OK, but it's not murderous. Tardigrades have survived temperatures well beyond boiling — up to 304 F (151 C), in those same 1920s temperature experiments. For reference, water boils at 212 F (100 C).

The next most heat-tolerant organism, as far as we know, is a bacteria that can function at 252 F (122 C).

At temperatures like 304 F, writes the BBC's Fox-Skelly, "proteins and cell membranes should unravel, and the chemical reactions that sustain life cease to happen." Except for tardigrades, they don't. The chemical reactions that sustain life are just on pause, waiting for the deadly heat to subside.

5. They could save us all.

The world's most indestructible animal may hold keys to survival abilities not currently in the human skill set, abilities we may be able to acquire. In the recent study that identified a tardigrade-specific radiation-resistance protein, the researchers went a step further: They injected the protein into human cultured cells.

With the addition of the tardigrade protein, the radiation tolerance of the human DNA in the cultured cells increased by about 40 percent. The scientists were, lead author Takuma Hashimoto told AFP, "really surprised" that a single protein could have such a profound effect on human cells.

On the backs of water bears, we could someday survive the radiation exposure required to get to Mars. We could realize cryonics, and develop crops so drought-resistant even climate change won't starve us from existence.

We won't outlive the tardigrade, but maybe we can steal some of its powers while we have the chance.