Form and Function

What makes the water bears a truly remarkable is their ability to withstand virtually any environment and the associated conditions given to them. When placed in stressful conditions they're able to revert to a state of cryptobiosis, enabling them to lower their metabolism so that it's almost imperceptible and thus survive the given setting. There are four states of cryptobiosis, each relating to certain extreme changes in environment.

The first is anoxybiosis, meaning low or lacking oxygen levels within their essential water film. They will become transparent, rigid, and completely sessile to endure. Next is cryobiosis, or low temperatures, where the organism’s membrane protectants stabilize the entirety of the structure to survive through both freezing and thawing. For terrestrial beings, there is a linear correlation between the cryobiotic and anhydrobiotic abilities. Thirdly isosmobiosis stemming from changes in salinity levels; as the animal contracts into a tun (barrel-shaped) for defense, only resuming activity when concentration levels revert back . Last is anhydrobiosis, or a dehydrated state where the tardigrade drops its water level down to a mere 3% (compared to its usual 85%) and forms a tun; where it’s impervious to almost any adverse environmental factors (Gabriel et. el 2007). In this form, the lifespan can be extended for the organism in question if it were to drift in and out of that state, essentially creating a comatose character that doesn’t age (Thorp et. al 2010).

(Bertolani et. al 2000)