What is the toughest animal on the planet?

Tardigrades (False Color Image)

Tardigrades, or water bears, are tiny invertebrates that are found pretty much everywhere, from freshwater to marine habitats, and from the lichens in your garden to the top of the highest mountains. They are among the world's hardiest creatures, thanks to their ability to curl up, switch off their metabolism and wait for conditions to improve. In fact, tardigrades hold the record for surviving several kinds of extreme environment, although it is debatable whether they should really count as they only set them when in their so-called "tun" state of extreme hibernation. (Text by Caroline Williams)

Tardigrades have survived:

• Without water for 120 years
• Freezing to -272.8 °C, very close to absolute zero
• Heating to 151 °C
• The vacuum of space. Samples lived for 10 days on board a European Space Agency experimental satellite in September 2007
• Pressure six times as great as that felt at the bottom of the deepest ocean
• Doses of X-ray and gamma radiation that are lethal to other life forms

Five different types of cryptobiosis have been identified in tardigrades: encystment (production of a dormant phase without significant water loss), anoxybiosis (resistance to low oxygen levels), cryobiosis (resistance to freezing temperatures), osmobiosis (resistance to elevated salinity) and anhydrobiosis (resistance to desiccation). Not all tardigrades share all five resistances - for instance, anhydrobiosis (the best-known form) is only found among terrestrial tardigrades - and different species will have different degrees of resistance. (Text by Christopher Taylor: More info on Tardigrades)


Compare the tardigrade's strategy to the rotifier's strategy: See blogpost here.

Extreme survival: The toughest beast in the world - environment - 19 November 2010 - New Scientist