"A review of the literature regarding anhydrobiosis and cold tolerance in tardigrades is presented. During increasing desiccation, invertebrates like tardigrades, rotifers, nematodes and some colembolans are able to shut down metabolism to undectectable levels. When tardigrades are entering anhydrobiosis, a tun-like structure is formed, facilitated by structural adaptations of the cuticle. Slow dehydration is essential for tun formation, and the accumulation of trehalose during this process may help to stabilizate phospholipids and proteins. Wax extrusion on the cuticle surface recudes transpiration. Tardigrades are principally aquatic organisms, but anhydrobiosis makes it possible for some species to live in habatiats with changing moisture conditions.
Tardigrades in anhydrobiosis may toleratre exposure to freezing temperature of liquid gases, and some species also survive such temperatures in their hydrated state. Few investigations are abailable ofn the relation of tardigrades to temperature more representative to their natureal enviornments. Experimental studes, however, from Greenland and the Antartic Contintent suggetst that some species overwinter both in a hydrated frozen state and in anhydrobiosis. During the summer, a number of tardigrade species have been recorded from cryococinte holes, formated on the surface of glaciers. These species are freeze toleratnt since their habitats are permanently frozen in the winter."
Anhydrobiosis and cold tolerance in tardigrades