Tardigrade- Waterbears

Tardigrades (also known as waterbears or moss piglets) are water-dwelling, segmented micro-animals, with eight legs.

They were first described by the German pastor Johann August Ephraim Goeze in 1773. The name Tardigrada (meaning "slow stepper") was given three years later by the Italian biologist Lazzaro Spallanzani. Since 1778, over 1,150 tardigrade species have been identified.

Tardigrades can survive in extreme environments. For example, they can withstand temperatures from just above absolute zero to well above the boiling point of water (100°C), pressures about six times greater than those found in the deepest ocean trenches, ionizing radiation at doses hundreds of times higher than the lethal dose for a human, and the vacuum of outer space. They can go without food or water for more than 10 years, drying out to the point where they are 3% or less water, only to rehydrate, forage, and reproduce. They are not considered extremophilic because they are not adapted to live in these conditions. Their chances of dying increase the longer they are exposed to the extreme environments, whereas extremophiles are organisms that can thrive in a physically or geochemically extreme condition that would be detrimental to most life on Earth.

Usually, tardigrades are about 0.5 mm (0.020 in) long when they are fully grown. They are short and plump with four pairs of legs, each with four to eight claws also known as "disks".The animals are prevalent in mosses and lichens and feed on plant cells, algae, and small invertebrates. When collected, they may be viewed under a very-low-power microscope, making them accessible to students and amateur scientists.

Tardigrades form the phylum Tardigrada, part of the superphylum Ecdysozoa. It is an ancient group, with fossils dating from 530 million years ago, in the Cambrian period.

Johann August Ephraim Goeze originally named the tardigrade kleiner Wasserbär (Bärtierchen today), meaning 'little water bear' in German. The name Tardigrada means "slow walker" and was given by Lazzaro Spallanzani in 1776. The name water bear comes from the way they walk, reminiscent of a bear's gait. The biggest adults may reach a body length of 1.5 mm (0.059 in), the smallest below 0.1 mm. Newly hatched tardigrades may be smaller than 0.05 mm.

About 1,150 species of tardigrades have been described. Tardigrades occur throughout the world, from the Himalayas (above 6,000 m (20,000 ft)), to the deep sea (below 4,000 m (13,000 ft)) and from the polar regions to the equator.

The most convenient place to find tardigrades is on lichens and mosses. Other environments are dunes, beaches, soil, and marine or freshwater sediments, where they may occur quite frequently (up to 25,000 animals per liter). Tardigrades often can be found by soaking a piece of moss in water