Water bear tun. Coloured scanning electron micrograph (SEM) of a water bear (Macrobiotus sapiens) in its dormant state, known as a tun. Water bears (or tardigrades) are tiny invertebrates that live in aquatic and semi-aquatic habitats such as lichen and damp moss. In dry conditions, they can enter a cryptobiotic state of dessication, in which they can survive for up to a decade. Macrobiotus sapiens is an omnivorous species that feeds on mosses, algae and bacteria. Water bears are found throughout the world, including regions of extreme temperature, such as hot springs, and extreme pressure, such as deep underwater. They can also survive the high levels of radiation and vacuum of space. Magnification: x750 when printed at 10 centimetres wide.