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Tiny water bear frozen for 30 years revived, reproduced

A microscopic tardigrade, also known as a water bear, found in the Antarctic some 30 years ago and kept frozen until 2014 has revived and even reproduced, a team from the National Institute of Polar Research said, breaking the previous 9-year record for longest surviving water bear.

    A water bear revived after 30 years of being frozen is seen. The green part in its belly is chlorella. The black vertical line measures 0.1 millimeters. (Photo provided by the National Institute of Polar Research's Megumu Tsujimoto)

    Water bears are micro-animals known to survive under harsh environments such as high temperatures and dry habitats. The latest report comes after the first successful case of their reproduction after being frozen for a long time. The tiny animals live in various areas around the world including undersea areas and mountaintops. There are more than 1,000 types of water bears.

    The team extracted samples of moss near the Showa Station research base in Antarctica in November 1983, and then stored the moss in the institute's freezer where the room temperature was kept at minus 20 degrees Celsius. When the team defrosted the samples and soaked them in water in 2014, two water bears measuring about 0.3 millimeters each started to move.

    While one of the pair died after not eating much of the chlorella fed to it by the team, the other one laid eggs five times, from which 14 water bears hatched.

    The team also found eggs in the samples of moss. They were soaked in water and six days later, the eggs hatched. The researchers fed the young water bears and they also grew up to reproduce.

    The team believes that the water bear kept for 30 years survived and its reproductive function was preserved because damage to its cells and genes caused by oxidization was kept to a minimum under the freezing conditions.

    Megumu Tsujimoto, specially appointed researcher at the National Institute of Polar Research, says the institute will work on examining damage to the water bear's genes and its recovery functions to find out about the animals' long-term survival mechanism.


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