On Earth, scientists believe tardigrades are the most robust animals known. These multicellular creatures are minuscule, with most not exceeding 1 millimeter, and the smallest at birth is only 50 micrometers. The largest only reaches 1.4 millimeters. They are transparent or come in colors like white, yellow, brown, deep red, or green, largely due to what they feed on.
They are composed of a head, four body segments covered by a chitinous cuticle, and four pairs of legs ending in claws, suction cups, or toes. The muscles, made up of long cells, are distributed in accordance with body segments. Their mouth has two protrusions, one for piercing food and another as an absorption tool. The foregut contains many paired glands, with a thin esophagus connecting to the midgut. Between a tardigrade's midgut and hindgut are Malpighian tubules, dedicated to maintaining osmotic pressure within the body.
