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Water bear leg. Coloured scanning electron micrograph (SEM) of the leg of a water bear (Paramacrobiotus craterlaki). Water bears (or tardigrades) are tiny invertebrates that live in aquatic and semi-aquatic habitats such as lichen and damp moss. Paramacrobiotus craterlaki is a carnivorous species that feeds on nematodes and rotifers. 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: x1250 when printed at 10 centimetres wide. (KEYSTONE/SCIENCE PHOTO LIBRARY/EYE OF SCIENCE)