For humans, cryptobiosis—the process of putting all metabolic activity on hold in order to survive an uninhabitable environment—has only been imaginable in the futuristic worlds of films like Star Wars and Interstellar. But for some tiny forms of life, suspending animation is a common form of survival.
Tardigrades are tiny eight-legged organisms that reach just a fraction of a millimeter in length when fully grown. They’re endearingly known as “water bears” for their preferred aquatic habitat, and resemblance, when viewed under a microscope, to pudgy, plush bears. But these transparent animals are nothing to laugh at: They’ve survived being subjected to extreme conditions, like space, high-levels of radiation (paywall), and pressure (paywall). Similar circumstances would ordinarily kill us, and most other forms of life.
They’re also apparently capable of coming back to life after decades of being frozen, even as eggs, a new study published this week in Cryobiology has shown.
In May 2014, researchers from the National Institute of Polar Research in Japan began defrosting two adult water bears and one water bear egg (named Sleeping Beauty 1, 2, and 3) that had been collected from a sample of Antarctic algae in 1983 and stored at -20°C (-4°F). Over the course of a day, scientists warmed, rehydrated, and gave the tardigrades new homes on petri dishes full of nutrients. It took two weeks for the animals to regain their full range of movement. Though one of the adult organisms died after 20 days, the other survived, and the egg hatched. They even had viable offspring.
Previously, scientists observed that water bears were able to recover (paywall) after being frozen for 8 years, and even longer in dry conditions. Scientists have revived other microscopic organisms called micrometazoans, which include animals like nematodes, after even longer periods of time; according to a 1946 study, scientists reanimated a nematode after 39 years of being frozen.
Scientists still aren’t sure how tardigrades are able to survive these extreme conditions over such long periods of times. “Our team now aims at unraveling the mechanisms underlying the long-term survival of cryptobiotic organisms by studying damage to tardigrades’ DNA and their ability to repair it,” Megumu Tsujimto, the lead researcher at National Institute of Polar Research, said in a press release.