An animal that had been frozen for 30 years has been revived by scientists - and it then successfully reproduced.
The animal in question was a species of tardigrade, a microscopic creature sometimes referred to as a "water bear" that is perhaps the hardiest lifeform on Earth. There are over1,000 known species, all of which have eight legs and measure between 0.5 and 1.2 mm in length, and they are found more or less everywhere.
As Brian Resnick wrote recently for Vox: "Pick up a piece of moss, and you'll find tardigrades. In the soil: tardigrades. The ocean: You get it. They live on every continent, in every climate, and in every latitude. Their extreme resilience has allowed them to conquer the entire planet."
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This resilience comes from tardigrades' ability, when conditions are especially harsh, to enter a state known cryptobiosis (or anabiosis). They achieve this by expelling 95 percent or more of their water, creating proteins and sugars to protect their cells, massively reducing or even suspending their metabolism, and tucking in their heads and legs to form a pill-shaped "tun."
In tun form, tardigrades can withstand conditions from boiling water to absolute zero, and pressures six times greater than those found in the deepest part of the ocean. In 2007, the European Space Agency even launched a payload of tardigrades in tun form into space; retrieved 10 days later after the satellite returned to Earth, some of the tardigrades came back to life upon rehydration and even went on to reproduce, the first animals to survive the vacuum of space.
Even by tardigrade standards, however, the most recent example of survival skills is impressive. The water bears in question were in a moss sample that was collected in November 1983 during a Japanese research expedition to Antarctica. The moss was stored at -20 degrees C after collection. In May 2014, researchers began to thaw out the moss, teased it apart with tweezers and found two tardigrades - which they delightfully dubbed Sleeping Beauty 1 and 2 (or SB-1 and SB-2 to their friends) - in tun form.
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Recovery was steady but slow, the researchers write in the journal Cryobiology: "SB-1 first showed slight movement in its 4th pair of legs on the first day after rehydration. This progressed to twisting of the body from day 5 along with movement in its 1st and 2nd pairs of legs, but the movements remained slow. After starting to attempt to lift itself on day 6, SB-1 started to slowly crawl on the agar surface of the culture well on day 9, and started to eat the algal food provided the culture plate on day 13."
By Day 21, SB-1 even began developing eggs; it laid 19, of which 14 hatched. SB-2, alas, had by then perished. But an egg that had also been retrieved from the moss, and which the researchers called SB-3, hatched and the tardigrade that emerged laid 15 eggs of its own, seven of which hatched into healthy offspring.
The next goal that the researchers have set for themselves is to uncover the why and the how: What, for example, was the process that took place over the first week after thawing before the tardigrades began to move? "We want to unravel the mechanism for (tardigrades') long-term survival," the lead researcher told the Asahi Shimbun.