Tardigrade

Tardigrades are a phylum of microscopic invertebrates known for their eight legs and extraordinary resilience.

Tardigrades are a phylum of microscopic invertebrates known for their eight legs and extraordinary resilience. They are also called water bears or moss piglets and are found in aquatic and damp habitats around the world, from moss and lichens to marine and freshwater environments.

Classification and description

Tardigrades are a phylum of microscopic invertebrates with a segmented body and eight legs. They are among the most distinctive small animals studied in microbiology and zoology. The name 'tardigrade' means 'slow stepping' or 'slow moving', and they are commonly called water bears because of their bear-like appearance and movement.

Habitat and distribution

Tardigrades occur worldwide in marine, freshwater, and terrestrial habitats, especially in damp places such as mosses and lichens. They have also been found in extreme environments including polar regions, deep sea habitats, and hot springs.

Survival and cryptobiosis

Tardigrades are famous for entering cryptobiosis, a dormant state in which metabolism drops dramatically. This ability helps them withstand dehydration, extreme cold and heat, pressure, and radiation. Some tardigrades have survived exposure to the vacuum of space and intense radiation in experiments.

Size and life cycle

Most tardigrades are about 0.5 mm long, though sizes vary by species. In active conditions their lifespan is relatively short, but dormancy can greatly extend survival time, allowing them to survive for years and, in some reports, decades.