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Any of various slow-moving, minute invertebrates of the phylum Tardigrada. Tardigrades have a head and four fused body segments, each of which has a pair of stubby legs ending in claws. They live in water, damp moss, flower petals, or sand, and are usually 1 mm (0.04 inches) or less in size. Tardigrades are able to resist extremely low temperature, pressure, and humidity, and go into dormant states for months or years. They are believed to be intermediate in evolutionary development between annelids and arthropods. Also called water bear.
any of about 350 species of free-living, cosmopolitan invertebrates belonging to the phylum Tardigrada. In evolutionary development they are considered to lie between annelid worms and arthropods (e.g., insects, crustaceans). Tardigrades are mostly about 1 mm or less in size. They live in varying habitats: in damp moss, on flowering plants, in sand, in freshwater, and in the sea. In adapting to this wide range of external conditions, a large number of genera and species have evolved.