Tardigrades can even survive space. Be sure to watch the video below, where a tardigrade dries out and then comes back to life when exposed to water. Click here to read the full article or an excerpt below.
The microscopic tardigrade—also known as the water bear—is the only animal that can survive the cold, irradiated vacuum of outer space. We talked to leading tardigrade researchers to find out what makes these little guys so amazing.
Hundreds of species “are found across the seven continents; everywhere from the highest mountain to the lowest sea,” he says. “Many species of tardigrades live in water, but on land, you find them almost everywhere there’s moss or lichen.” In 2007, scientists discovered that these microscopic critters can survive an extended stay in the cold, irradiated vacuum of outer space. A European team of researchers sent a group of living tardigrades to orbit the earth on the outside of a FOTON-M3 rocket for ten days. When the water bears returned to Earth, the scientists discovered that 68 percent lived through the ordeal.
Land-dwelling tardigrades can be found in some of the driest places on earth. “I’ve collected living tardigrades from under a rock in the Sinai desert, in a part of the desert that hadn’t had any record of rain for the previous 25 years,” Miller says. Yet these are technically aquatic creatures, and require a thin layer of water to do pretty much anything, including eating, having sex, or moving around. Without water, they’re about as lively as a beached dolphin.
But land-dwelling tardigrades have evolved a bizarre solution to living through drought: When their environment dries up, so do they. Tardigrades will enter a state called desiccation, in which they shrivel up—losing all but around 3 percent of their body’s water and slowing their metabolism down to an astonishing 0.01 percent of its normal speed. In this state, the tardigrade just persists, doing nothing, until it’s inundated with water again. When that happens, the creature pops back to life like a re-wetted sponge and continues onward as if nothing had happened.
According to Miller, a few researchers believe some species of tardigrades might even be able to survive desiccation for up to a century. Yet the average lifespan of a (continuously hydrated) tardigrade is rarely longer than a few months.
“It sounds quite strange,” says Miller, “that even though these tardigrades only live for a few weeks or months, that lifetime can be stretched over many, many years.”
HOW DOES BEING DRIED OUT PROTECT THEM FROM THE VACUUM OF SPACE?
In its desiccated state, the tardigrade is ridiculously, almost absurdly resilient. Laboratory tests have shown that tardigrades can endure both an utter vacuum and intense pressures more than five times as punishing as those in the deepest ocean. Even temperatures up to 300 degrees Fahrenheit and as low as -458 degrees F (just above absolute zero) won’t spell the creature’s doom.
There are clues. Scientists have learned that when the tardigrade enters its desiccated state, “it replaces some of its cell contents with a sugar molecule called trehalose,” Perry says. Researchers believe this trehalose molecule not only replaces water, but also in some cases can physically constrain the critter’s remaining water molecules, keeping them from rapidly expanding when faced with hot and cold temperatures. This is important, because expanding water molecules (like what happens when you get frostbite) can mean instant cellular death for most animals.
Tardigrades during their desiccated state produce an abnormal amount of anti-oxidants (yes, these actually exist outside the health-food world), which effectively neutralize those roaming, evil reactive oxygen species. Partly because of this talent, tardigrades have been found to withstand higher radiation doses with far greater success than researchers would otherwise believe they should.
The reason that tardigrades would have evolved to survive high radiation doses is a mystery, too. However, Miller points to a leading theory: Perhaps tardigrades evolved to be swept up by the wind and survive in the earth’s atmosphere—which would explain not only their hardiness but also that they’re found the world over.
However it happened, there’s still much, much more to learn about these fascinating creatures.