Tardigrada

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Tardigrade
Tardigrade, any of a group of tiny arthropod-like animals characterized by four pairs of stubby legs ending in large claws, a stout body, rounded back, and lumbering gait. They are also known as “water bears.” Tardigrades live worldwide in moist land habitats, along rocky shorelines, and on the bottoms of streams, lakes, and oceans. Their most striking feature is their ability to temporarily enter a nearly lifeless state known as anabiosis, which helps them survive environmental extremes. About 400 species of tardigrades are known and they range in length from 0.1 to 0.5 mm (0.004 to 0.02 in).

Tardigrades are most commonly found in association with the water film on mosses, liverworts, and lichens. Their densities may reach 2 million individuals per sq m (185,874 per sq ft) of moss. Some live in hot springs and a few live in a symbiotic relationship with or on the bodies of other animals. Tardigrades use a pair of oral stylets, or needle-like mouthparts, to pierce the walls of plant cells and feed on the liquid inside. Most species are plant eaters, but some are predators, feeding on tiny invertebrates and bacteria, and a few are detritivores, feeding on dead tissue and debris.

Scientific classification: Tardigrades make up the phylum Tardigrada. It is not clear to what other animals tardigrades are most closely related, but they are most similar to arthropods (insects, crustaceans, etc.), annelids (segmented worms), and gastrotrichs.

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