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Welcome to the Wonderful World of Tardigrades in NE Alabama

What are Tardigrades?

The tardigrades are bilaterally symmetric, hydrophilous micrometazoans that are ventrally flattened with a convex dorsal side. A typical tardigrade body averages from 50-1500 micrometers in length displaying limited metamerism with five indistinctive segments. A cephalic segment that is bluntly rounded contains a mouth and may have eyespots and sensory cirri. Four body segments are also present. Each body segment has a pair of ventrolateral legs terminating in 4 to 8 claws or suction discs (Ramazzotti and Maucci 1983); generally the first three pairs are used for locomotion, the fourth for substrate attachment. They are covered by a chitinous outer cuticle that may be opaque, white, or such colors as brown, green, pink, red, orange, or yellow (Dewel et al. 1993). This color results from pigments in the cuticle, dissolved materials in the body fluids, or from the contents of the digestive tract.
One of their most fascinating features is the capacity to enter cryptobiosis, a state of suspended animation. The water content of the body can be reduced from 85% to just 3% and the body becomes barrel-shaped forming a tun. In this state tardigrades can withstand tremendous environmental extremes and survive for many years.
There are over 600 species of water bears in the phylum Tardigrada. These are grouped into three main classes, Heterotardigrada, Mesotardigrada, and Eutardigrada. Tardigrades can be from 50um to 1200um in length. They are often neglected by zoologists and termed a "minor phyla", but more appropriately should be called a "lesser known phyla". The size, shape, and number of claws are very important in identifying and classifying tardigrades. There are 16 claw types identified. The tardigrades use sexual reproduction, parthenogenesis, and hermaphroditism as modes of reproduction. They are found in marine, freshwater and terrestrial habitats.