Ice worms (also written as ice-worms or iceworms, or also called glacial or glacier worms) are enchytraeid annelids of the genus Mesenchytraeus. The majority of the species in the genus are abundant in gravel beds or the banks of riverine habitats, but the best-known members of the genus are found in glacial ice. They include the only annelid worms known to spend their entire lives in glacial ice, and some of the few metazoans to complete their entire life cycle at conditions below 0 °C (32 °F).
They were discovered in a wide range of environments, which include level snowfields, steep avalanche cones, crevasse walls, glacial rivers and pools, and hard glacier ice. These organisms are unique in that they can simply move between tightly packed ice crystals. They utilize setae, which are small bristles found on the outside of their bodies, to grip the ice and pull themselves along.
