Scientists revive tardigrades after being frozen for 30 years
Which animal do you think is the hardiest of them all? Camels or cockroaches? Melting zombie caterpillars perhaps? Well, apparently, none of those measure up to the mighty tardigrade, commonly known as "water bears." With over 1,150 species found worldwide in almost every place on Earth, this surprisingly tough creature boasts eight legs, can live through extreme heat and cold, pressure, radiation and even the harsh environment of outer space. Oh, and did we mention, it typically only grows up to 1 millimeter long?
Cryobiologists from Tokyo's National Institute of Polar Research (NIPR) recently cemented the resilient reputation of this obscure creature when they revived some water bears that had been frozen for 30 years. Not only did they survive being frozen for three decades, one of them laid eggs, 14 of which actually hatched.Apparently, water bears survive by entering a state of hibernation called cryptobiosis, where its metabolism slows down to less than 0.01 percent of its normal rate. It curls itself up into what is called a "tun" state, and it's believed that it replaces the water in their cells with either natural antifreeze (glycerol) or crystalline sugars, in order to prevent cellular destruction due to water freezing in their cells.
According to the findings published earlier this month in Cryobiology and The Verge, these particular species of water bears (Acutuncus antarcticus) were collected back in 1983 from Antarctican moss, and stored at −20 °C before being thawed back in May 2015. The scientists nicknamed the two surviving tardigrades "Sleeping Beauty" (SB)-1 and SB-2, and placed them in water to rehydrate them. It took them two weeks to very, very slowly show signs of movement, and were fed algae. The researchers write:
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.
Unfortunately, SB-1 didn't make it. But even more mind-blowingly, SB-2 was able to lay viable eggs, and an egg that was found in the moss actually hatched into a living tardigrade on day 6, which laid its own eggs several days later. Scientists are now trying to find out what contributes to the tardigrade's incredible resilience, believing that it may have to do with its ability to incorporate foreign DNA into its own genome (see update below). It's up for further research to explain, but whatever it may be, it appears that if there's ever a nuclear holocaust, perhaps tardigrades are the best candidates for extreme species survival.
Watch these tardigrades wake up from cryptobiosis:
UPDATE: It appears that tardigrades may not be transferring foreign genes into their own as much as some scientists think. Scientists from the University of Edinburgh are countering that the samples in the University of North Carolina at Chapel Hill experiment, sequencing the tardigrade genome, were contaminated. More over at The Atlantic.