The waterbear survives extreme environmental conditions by entering a reversibly suspended metabolic state known as cryptobiosis.

The tardigrade, also known as a waterbear, is a microscopic invertebrate found all over the world in ecosystems ranging from freshwater to terrestrial. Tardigrades often inhabit places that experience extreme conditions–such as deserts, high mountains, and polar regions–where many other life forms find it impossible to survive. Terrestrial waterbears are typically active only when surrounded by a small film of water. So how is it that this tiny creature can survive in extreme conditions, even in places that lack a steady supply of water?

Under stressed conditions such as extreme dryness or temperature, the waterbear practices several forms of cryptobiosis, a state in which metabolic activity is slowed or halted. The most studied of these is anhydrobiosis. The waterbear enters anhydrobiosis by contracting its body into something called a tun, whereby it loses more than 95% of its free and stored water; essentially, it dehydrates itself. In this state, the waterbear creates different proteins and sugars that help protect its cells. Once these cell protectants are synthesized, the waterbear reduces, and at times suspends, its metabolism. When conditions improve within the environment, the waterbear activates its metabolism once again, aided by hydration from water intake.


Image: Emily Harrington / Copyright © - All rights reserved

Tardigrade is starting to dehydrate with a sugar solution, trehalose, thickening as water is lost. This protects the tardigrade's cells from damage until moisture conditions improve. 

Last Updated April 18, 2017