donabean & ernie

Waterbear-also known as a tardigrade

water bears comprise the phylum Tardigrada; they are small, segmented animals, similar and probably related to the Arthropods. Tardigrades were first described by Johann August Ephraim Goeze in 1773 (kleiner Wasserbär = little water bear). The name Tardigrada means "slow walker" and was given by Spallanzani in 1776. Tardigrades are small animals. The biggest adults may reach a body length of 1.5 mm, the smallest below 0.1 mm. Freshly hatched larvae may be smaller than 0.05 mm.Tardigrades are one of the few groups of species that are capable of reversibly suspending their metabolism and going into a state of cryptobiosis.

Several species regularly survive in a dehydrated state for nearly 10 years. Depending on the environment they may enter this state via anhydrobiosis, cryobiosis, osmobiosis or anoxybiosis. While in this state their metabolism lowers to less than 0.01% of what is normal and their water content can drop to 1% of normal. Their ability to remain desiccated for such a long period is largely dependent on the high levels of the non-reducing sugar trehalose, which protects their membranes.

Tardigrades have been known to withstand the following extremes whilst in this state:

* Temperature—Tardigrades can survive being heated for a few minutes to 151 °C or being chilled for days at -272.8 °C (almost absolute zero).
* Radiation— Shown by Raul M. May from the University of Paris, Tardigrades can withstand 5700 grays or 570,000 rads of x-ray radiation. (Five grays or 500 rads would be fatal to a human).
* Pressure—They can withstand the extremely low pressure of a vacuum and also very high pressures, many times greater than atmospheric pressure. It has recently been proven that they can survive in the vacuum of space.
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