Tardigrada

Abstract

Tardigrades, also known as “water bears,” are microscopic invertebrates usually not exceeding 1 mm in length. They are found in a variety of marine, limnic, and limno-terrestrial habitats, such as benthos, soil, and moss cushions. Many species can form environmentally resistant cysts, or tuns, that allow them to survive desiccation, freezing, high radiation levels, and other environmental extremes. Some species have even survived an exposure to outer space. However, the mechanisms that enable them to withstand these extreme conditions remain poorly understood.