Typically found as part of interstitial communities, on filamentous algae, or inhabiting the surface films of mosses, lichens, and damp forest litter. Tardigrades feed on the fluids of plant and animal cells. Some tardigrades are entirely carnivorous. Tardigrades are prey for amoebas, nematodes, and other tardigrades. Most species appear to he eurythermal, tolerating temperatures from near freezing to upwards of 30 degrees C. Food is stored in some epidermal cells.
Respiration occurs by diffusion.
The animal contracts, loses water, and takes on a shriveled, wrinkled appearance. Animals have been recovered from this state after immersion in liquid helium, absolute alcohol, brine, and ether. Cysts may be formed when the animal undergoes stress in the form of damage, hunger, or abnormal environmental conditions. The animal withdraws into the cuticle and forms a dark, thick-walled cyst. The internal organs undergo some degeneration.