Fact of the Day .CA

Tardigrades, commonly known as ‘water bears’, are capable of surviving many extreme habitats (polyextremophiles).  These tiny animals (0.1mm-1.5mm) are mostly found in moist environments but have been found to withstand a range of temperatures (151C to -272C), pressures (low pressures of a vacuum and more than 1200x atmospheric pressure), dehydration, and radiation that would kill most animals (5000Gy gamma-rays and 6200Gy heavy-ions).  When the living conditions of the environment decrease the animal will resort to a state called ‘cryptobiosis’.  While in this state the animal’s metabolism can reduce to 0.01% of its normal rate and their water content can be reduced to 1% of the normal water content.  Tardigrades can remain in a cryptobiotic state for up to 10 years.  When environmental conditions improve the tardigrade will return to a normal living state.

Scientists put these animals to the test (see study here); two species of tardigrades were sent into space in this cryptobiotic state on a low orbiting satellite around the Earth (258-281km above sea level) for 10 days.  Both of the species used in this study successfully survived the exposure to the vacuum of space.  Two thirds survived additional exposure to the UVA and UVB radiation levels found in space.  Very few tardigrades survived the additional exposure of all UV radiation found in space, which is usually filtered out by the atmosphere.  Those that survived the trip into space and survived rehydration were capable of producing offspring!

No one is sure of why or how these animals are capable of surviving so many different extreme environments.  Are they just over evolved?  Or was it a response to a selective pressure of the past?  Whatever the answer these unusual animals need further study as humans prepare to face the extreme environments of our Solar System.