Tardigrades: The Water Bear That Survived Outer Space
Tardigrades, also called water bears, are about half a millimeter long, with eight stubby legs and tiny claws. They look like gummy bears under a microscope. They are also some of the toughest animals ever studied, and in 2007 some of them survived ten days exposed to outer space.
Quick Facts
- Also called: Water bear or moss piglet
- Size: Usually about 0.5 mm as adults
- First described: 1773, by Johann August Ephraim Goeze
- Where: Moss and lichen all over the world
- Superpower: Drying into a tun and pausing life
What Is a Tardigrade?
Tardigrades are tiny eight-legged animals that live in water films on moss, lichen, soil and leaf litter around the world. German zoologist Johann August Ephraim Goeze first described them in 1773 and called them little water bears. There may be some in a patch of moss near you.
The Tun: Life on Pause
When their home dries out, many tardigrades pull in their legs and curl into a dry ball called a tun. They lose almost all their water and their metabolism drops to nearly nothing. Add water, and they can wake up again.
Can Tardigrades Survive Space?
Some can. In 2007, dried tardigrades flew on the European FOTON-M3 mission and were exposed to the vacuum of space in low Earth orbit for about ten days. A 2008 study in Current Biology reported that many revived afterward and some went on to lay eggs that hatched normally. Fewer survived when they were also exposed to full solar ultraviolet light.
Frozen for Thirty Years
In 2016, Japanese scientists reported reviving tardigrades from an Antarctic moss sample that had been frozen since 1983, more than thirty years earlier. One of them went on to reproduce.
Radiation, Cold and Heat
A 2006 study found tardigrades can tolerate radiation doses far beyond what would kill a person. In the tun state, some survive deep freezing and brief extreme heat. They aren't truly indestructible, though. Most of these feats are about surviving in a dried, dormant state, not living normally.
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Frequently Asked Questions
How big is a tardigrade?
Most adult tardigrades are about half a millimeter long, just big enough to see as a speck.
Can tardigrades survive in space?
In 2007, dried tardigrades survived about ten days exposed to space in low orbit, and some later reproduced.
Where do tardigrades live?
In moss, lichen, soil and fresh and salt water all over the world, including backyard moss.
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Sources
- Jönsson et al. (2008), Current Biology: Tardigrades Survive Exposure to Space in Low Earth Orbit: the FOTON-M3 experiment
- Tsujimoto, Imura and Kanda (2016), Cryobiology: Recovery and Reproduction of an Antarctic Tardigrade Retrieved from a Moss Sample Frozen for Over 30 Years: 30 years frozen
- Horikawa et al. (2006), International Journal of Radiation Biology: Radiation Tolerance in the Tardigrade Milnesium tardigradum: radiation tolerance
- Wikipedia: Tardigrade: size, discovery in 1773 and the tun state
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Cover photo: Brandon Antonio Segura Torres and Priscilla Vieto Bonilla via Wikimedia Commons, CC BY-SA 4.0.