Aliens or Ancient Ancestors? Introducing the Water Bear, Survivor of the Unbearable

Discovered three centuries ago, these microscopic animals called tardigrades –commonly referred to as ‘water bears’– are seemingly everywhere. They thrive not only in tree bark, moss, and lichen, but also in such extreme environments as deep sea trenches, Antarctic ice, hot springs, and the highest Himalayan mountaintop. Tardigrades have even returned after being blasted into outer space!

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Approximately one sixteenth of an inch long (barely the size of a poppy seed), they are generally beige or taupe in color, and semi-translucent. For such remarkable creatures, they lead rather unremarkable lives and seem to move at a pace slower than time, which perhaps accounts for their ancient origins (tardigrade fossils dating back 500 million years have been found).

These tiny, mostly aquatic, creatures are named for their pudgy appearance, which makes them resemble an alien cousin of the hippopotamus, manatee, or (you guessed it!) bear.  Unlike those mammals, tardigrades have eight legs with little claws, and a tubular pump-action mouth filled with dagger-like teeth.

So why exactly are these itty-bitty cuddly-alien-looking critters so fascinating? Perhaps it's not only because they look like a bear, but rather because of what they can bear.  Water Bears can be found living quite happily in the most severe of environments, both hot and cold—try negative 300 degrees Fahrenheit - a temperature at which most atoms stop moving. Immune to environmental stresses from drought to radiation, the tardigrade survives by morphing into what is called a tun: a dried out version of itself.  It sheds almost all of its body water, replacing it with a sugar called trehalose, and brings its metabolism down to .01 percent of its normal rate, curling up into a sort of suspended-animation husk. 

Paramacrobiotus richtersi in its tun state (Credit: Eye of Science/SPL)

Paramacrobiotus richtersi in its tun state (Credit: Eye of Science/SPL)

Because the tun has no body water, it is invulnerable to conditions that would kill all other forms of life.  Nothing remains inside the organism to get converted to gas and expand from the effects of heat; nor is there anything to freeze under extreme cold.  Similarly, tardigrades can withstand radiation, since it requires water to create the cell-damaging form of oxygen that is so deadly to the living. 

Studies have even sent tuns into outer space and recorded the survival of at least two thirds of the specimens after exposure to both solar radiation and the vacuum of space.  Incredibly, even after such trials, all it takes is a little bit of water to bring them back to tardigrade state. Tuns over one hundred years in age have been reconstituted and brought back to life - apparently as young as ever! An Italian zoologist claimed to have resuscitated 120-year-old specimens and, although that experiment has yet to be replicated, scientists successfully revived a tardigrade from an eight year state of suspended animation.

The species (there are 900 of them) displays some extraordinary abilities. In their dried out state, they can produce anti-oxidants that in turn absorb and neutralize the presence of more harmful chemicals within tardigrade cells. Once rehydrated, they seem to be able to replicate damaged DNA and even reproduce healthy offspring. Might these creatures hold clues to for developing mechanisms for the rest of us to survive severe, even otherworldly conditions?

Water bears don't only fascinate scientists.  Just punch “tardigrade art” into a search engine and you will find entries from Pinterest to Fine Art America, from Tumblr to Etsy, from microscope images to cartoonish paintings.  Tardigrades are inspiring artists, writers and all kinds of entrepreneurs. There are children’s books, all sorts of tardigrade-themed gifts and t-shirts, and even a "Tardigrade Queen," painted by artist Thomas Gieseke, complete with throne, crown and scepter.

Tardigrade Queen by Thomas A Gieseke

Tardigrade Queen by Thomas A Gieseke

With their homely appearance, their amazing hardiness and the implications of their otherworldly talents, these creatures seem to captivate people from all walks of life.

What intrigues you the most about Water Bears?  Do you think they hold a key to off-world survival? Would you wear or create a tardigrade T-shirt?  Tell us in the comments below!

Author: Justin Haley Phillips

Sources:
http://www.nytimes.com/2015/09/08/science/the-tardigrade-water-bear.html?smid=fb-share&_r=1
http://tvblogs.nationalgeographic.com/2014/03/19/5-reasons-why-the-tardigrade-is-natures-toughest-animal/
http://www.bbc.com/earth/story/20150313-the-toughest-animals-on-earth