Water bear (Paramacrobiotus craterlaki) in moss. Coloured scanning electron micrograph (SEM) of a water bear in its active state. Water bears (or tardigrades) are tiny invertebrates that live in aquatic and semi-aquatic habitats such as lichen and damp moss. They require water to obtain oxygen by gas exchange. In dry conditions, they can enter a cryptobiotic state of dessication, known as a tun, to survive. In this state, water bears can survive for up to a decade. P. craterlaki is a carnivorous species that feeds on nematodes and rotifers. This specimen originated from moss samples in Crater Lake, Kenya. 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: x333 when printed 10cm wide.