Sunday, December 30, 2007

Tardigrades - the oldest and most successful inhabitant of earth

Water bears are the most successful life form on earth. Over 750 distinct species, with their own Phylum, and no other creatures so ubiquitous or continuous. They survive man's exploitation of nature, thriving in cities. Scientists have found bear packs in hot springs, on top of the Himalayas, under 5 meter layers of ice, and in deep ocean high-pressure sediments. They can "resurrect" after a decade of freeze-dried dessication. Many species are found in a mild environments like lakes, ponds and meadows, while others prefer stone walls and roofs. But their most typical grazes are moss cushions.
Curiously, this life form is unknown to almost everybody. Even my Britannica Encyclopaedia has only 2" devoted to the water bears, with a poor gray tone photo of these colorful animals. The scientific name is Tardigrada, i.e. slow-walking animals. Although microscopists have been fascinated by the water bears for several hundred years, their size makes then hard for us to observe --just below unaided vision but too big for slide microscopes.
Finally, there is the aspect of Time. They have been found in ancient amber and are one of the oldest forms of life. Their lives are so small, so atomic, as to have less time at their disposal, and more. Time deconstructs as mass is reduced. Chris Impey writes in THE LIVING COSMOS, "Time's arrow seems to be an emergent property of large collections of atoms". The water bears, in their little moss gardens of Eden, are as invisible to us, but more perpetual, as any god.

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