Tardigrade

Tardigrades (/ˈtɑːrdɪˌɡreɪd/; also known as water bears or moss piglets) are water-dwelling, eight-legged, segmented micro-animals. They were first discovered 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. They have been sighted from mountaintops to the deep sea, from tropical rain forests to the Antarctic.

Tardigrades are notable for being perhaps the most durable of known organisms; they are able to survive extreme conditions that would be rapidly fatal to nearly all other known life forms. They can withstand temperature ranges from 1 K (−458 °F; −272 °C) to about 420 K (300 °F; 150 °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 30 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 exploit these conditions. This means that their chances of dying increase the longer they are exposed to the extreme environments, whereas true extremophiles thrive in a physically or geochemically extreme environment that would harm most other organisms.