Water bear or tardigrade. Scanning electron micrograph (SEM) of a water bear (Echiniscus sp., ) walking over spagnum moss. Water bears live in damp habitats such as moss or lichen and are tiny segmented invertebrates. They can survive dry conditions by changing into a dessicated state in which they can remain for many years. Whilst in this form (known as a tun) they can withstand the most extreme environments and can tolerate radiation levels as high as x1000 more than other animals, including humans. They have even been brought back alive after spending 10 days in the vacuum of space! They are classed as extremeophiles. Magnification x1120 (x275 at 10cm wide).