Japanese scientists were able to bring a microscopic animal that had been frozen for more than 30 years back to life. What's more interesting is that the animal was also able to reproduce.
The animal that the researchers were able to revive is called a tardigrade – an extremely tiny water-dwelling creature, so much so that it averages less than a millimeter, or 0.04 of an inch in length.
Also known as water bears and moss piglets, the microscopic animals are among the toughest in the world as they can survive extreme cold, heat, pressure and radiation via a process called cryptobiosis.
Cryptobiosis allows the tardigrades' metabolic activities to slow down or turn off for long periods of time.
To perform their investigation, scientists from Japan's National Institute of Polar Research studied tardigrades collected among moss plants in Antarctica in 1983. The creatures were stored at a temperature of minus 20 degrees Celsius and was unfrozen in May 2014.
The researchers, headed by lead author Megumu Tsujimoto, were able to revive a two tardigrades and an egg. One of the tardigrades started to move within the first week of rehydration. On day 13, it started to eat, and on day 23, it lay its first egg. By day 45, the tardigrade had laid 19 eggs, 14 of which hatched. None of the newborns exhibited any anomalies or defects.
The other revived tardigrade moved and ate by the second week, however, its condition declined and eventually died 20 days after rehydration.
The rehydrated egg hatched after six days, and when it was 8 days old it laid its first egg. It deposited a total of 15 eggs, 7 of which hatched, 38 days after rehydration.
"The long recovery times of the revived tardigrades observed is suggestive of the requirement for repair of damage accrued over 30 years of cryptobiosis," the authors wrote.
Other scientists were also able to successfully resuscitate tardigrades. However, the current study is the first one to be able to revive the animals after three decades, breaking the previous longest record, which is nine years.
While the current study was able to set a new record for tardigrades, it still does not exceed the longest time that a creature was revived after being frozen. The crown belongs to Tylenchus polyhypnus, which is a plant-parasitic worm that came back to life after being frozen for 39 years.
The Japanese scientists think that further and more detailed investigations are needed in order to fully understand the long-term survival of cryptobiotic creatures.
The study was published in the journal Cryobiology.