Milnesium tardigradum Doyère, 1840

Milnesium tardigradum is a cosmopolitan species of tardigrade that can be found in a diverse range of environments. It has also been found in the sea around Antarctica. M. tardigradum was described by Louis Michel François Doyère in 1840. It contains unidentified osmolytes that could potentially provide important information in the process of cryptobiosis.

M. tardigradum has a symmetrical body with eight legs; it uses claws—a distinctive feature of this tardigrade species. The total length of the body varies, with some measuring up to 0.7 mm in length. M. tardigradum have been found to possess a high level of radioresistance.  In 2007, individuals of two tardigrade species, Richtersius coronifer and M. tardigradum, were subject to the radiation, near-vacuum, and near-absolute zero conditions of outer space as part of the European Space Agency’s Biopan-6 experiment. Three specimens of M. tardigradum survived. The M. tardigradum can cope with high amounts of environmental stress by initiating cryptobiosis. During this state, the internal organic clock of M. tardigradum halts, thus the cryptobiotic state does not contribute to the aging process.

The biogeographical distribution of M. tardigradum is large. The species occupies mostly aquatic environments such as marine, coastal, and terrestrial areas. The full distribution of M. tardigradum is difficult to analyze due to the difficulty in taxonomy and the lack of sufficient data.

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