Tardigrades have drawn the majority of the attention that they have received from a quite unique quality that is apparent through all species of tardigrades. Should the environment shift in a such a way that is too disadvantageous for the little water bear, he will enter a state known as "cryptobiosis".

     In cryptobiosis, the tardigrade's metabolic rate sinks to a hundredth of a percent of its normal rate! It expels nearly all of the water in its body, and will enter a death-like state, which it can remain in for OVER 100 YEARS! In this death-like state, the tardigrade is called a 'tun', and a specialized sugar takes the place of the water in these aquatic animals.

     There are 4 kinds of cryptobiosis that a tardigrade can undergo in response to a threatening environment:

• Osmobiosis - When a tardigrade is threatened by an alteration in the water content, such as in response to a dramatic shift in ion concentration, like Na⁺

• Anhydrobiosis - Simply put, this is the type of cryptobiosis that a tardigrade undergoes when it lacks enough water content to sustain normal functionality, such as when a drought occurs.

• Cryobiosis - As the prefix 'cryo' indicates, this form of cryptobiosis has to do with a severe change in temperature.

• Anoxybiosis - This is the form of cryptobiosis that a tardigrade undergoes when there's a severe lack of oxygen, and the organism is threatened--for example the vacuum of outer space! (more on this in the "Other Interesting Facts" section!

     The most common form of the cryptobiotic states in tardigrades, is that of Anhydrobiosis--a lack of water. This probably isn't too surprising, as in a natural system, an organism living in a lichen, or a moss doesn't often have to deal with ions, sudden and utter drops in temperatures, and almost never a lack of air!