Echiniscus (Tardigrada) Videos
This genus of water bear is widespread and common. Their bodies are short, plump, and contain four pairs of limbs that are poorly articulated, a characteristic typical of soft-bodied animals. Each limb terminates in four to eight claws or discs. They lumber about in a slow bear-like gait over grains of sand and dirt or pieces of vegetation.
All tardigrades possess a complex a bucco-pharyngeal apparatus. The claws and the bucco-pharyngeal apparatus are morphological characteristics that can be used to identify the different species. The body is covered with a cuticle, which contains chitin, proteins, and lipids.
One of the unique traits of water bears, and an obvious key to their survival, is their ability to reversibly suspend their metabolism, a condition called cryptobiosis. Cryptobiosis is a truly deathlike state in which the metabolism is reduced to 0.01% of normal and the water content of the body decreases to less than 1%. In this state, water bears can resist storage in liquid nitrogen, contact with mineral acids, organic solvents, radioactive radiation and boiling water. Even after such brutal treatment, a drop of water is all that is necessary to revive these organisms, which then go on about their business as if nothing at all had happened.
Approximately 350 species of the phylum Tardigrada (slow-walking animals) are known to occur worldwide. Also called water bears, most of these free-living organisms are one millimeter or less in size and live in a wide variety of habitats: in damp moss, on flowering plants, in sand, in freshwater, and in the sea.