Tardigrada Water Bears

Tardigrades are called "water bears" because of their slow lumbering gait and relatively massive claws on lobopodous legs. The permeability of the cuticle limits tardigrades to aquatic habitats (often interstitial), the surface film of terrestrial mosses, and damp soil. About 800 species have been described, but many more undoubtedly exist in unexplored habitats. Faced with inhospitable microhabitats from environmental changes, both terrestrial and aquatic species may undergo cryptobiosis, where the body becomes dehydrated and metabolism is greatly reduced until favorable conditions return. Some water bears have been "resuscitated" from this state after decades! These normally dioecious organisms can also reproduce by parthenogenesis. Tardigrades typically feed on plants cells pierced by a pair of mouth stylets and sucked into the gut, but a few species are carnivorous.

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