Water Bears Revived After Being Frozen for 30 Years

Tardigrades can survive being frozen for more than 30 years. Elham Schokraie et al./PLOS ONE

Tardigrades, also known as water bears, can survive just about anywhere and handle conditions that would quickly kill most other creatures. They have been found living in Antarctic ice sheets, deep-sea trenches, rain forests and the Himalayas. They can withstand being frozen in liquid nitrogen or dropped in boiling water, and can even withstand the vacuum of space.

Now researchers have shown that they can be revived after being frozen for three decades. A team of Japanese scientists collected a sample of frozen moss from Antarctica in 1983, kept it on ice since then and recently thawed it. To their surprise, two tardigrades found therein came back to life, and one even began laying eggs.

Some of these eggs survived, and the offspring of these eggs reproduced and even gave birth, according to a study describing the experiment, published in February in the journal Cryobiology.

Water bears can survive so long by entering cryptobiosis, defined in the study as a "state of an organism when it shows no visible signs of life and when its metabolic activity becomes hardly measurable, or comes reversibly to a standstill."

Previously, the longest recorded period that water bears had survived being frozen was a decade. However, some creatures have been shown to survive freezing conditions even longer than 30 years. A parasitic worm-like creature known as Tylenchus polyhypnus has been revived after being frozen for nearly 39 years.