Eutardigrada are a class of

tardigrade Tardigrades (), known colloquially as water bears or moss piglets, are a phylum of eight-legged segmented micro-animals. They were first described by the German zoologist Johann August Ephraim Goeze in 1773, who called them . In 1776, th ...

s (Tardigrada) without lateral appendages. Primarily freshwater bound, some species have secondarily gained the ability to live in marine environments (''

Halobiotus ''Halobiotus'' is a genus of tardigrada, tardigrade in the class Eutardigrada. Species * ''Halobiotus arcturulius'' Crisp and Kristensen, 1983 * ''Halobiotus crispae'' Kristensen, 1982 * ''Halobiotus stenostomus'' (Richters, 1908) References ...

''). By

cryptobiosis Cryptobiosis or anabiosis is a metabolic state in extremophilic organisms in response to adverse environmental conditions such as desiccation, freezing, and oxygen deficiency. In the cryptobiotic state, all measurable metabolic processes sto ...

many species are able to live temporarily in very dry environments. More than 700 species have been described. The order Apochela consists of only one family,

Milnesiidae Milnesiidae is a Family (biology), family of tardigrades of the class Eutardigrada. It is the sole family in the Order (biology), order Apochela. In 2019, Noemi Guil and colleagues proposed to promote the order Apochela to the new Class (biology) ...

, with two genera: ''

Milnesium ''Milnesium'' is a genus of tardigrades. It is rather common, being found in a wide variety of habitats across the world. It has a fossil record extending back to the Cretaceous, the oldest species found so far (''M. swolenskyi'') is known from T ...

'' and ''

Limmenius ''Limmenius'' is a genus of tardigrades with one species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexua ...

''. ''

Milnesium tardigradum ''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 1 ...

'' can be found worldwide and is one of the biggest species among tardigrades (up to 1.4 mm); similar-looking species have been found in

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...

amber Amber is fossilized tree resin. Examples of it have been appreciated for its color and natural beauty since the Neolithic times, and worked as a gemstone since antiquity."Amber" (2004). In Maxine N. Lurie and Marc Mappen (eds.) ''Encyclopedia ...

. The mouth of this

predator Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common List of feeding behaviours, feeding behaviours that includes parasitism and micropredation ...

has a wide opening, so the animal can eat

rotifer The rotifers (, from Latin 'wheel' and 'bearing'), sometimes called wheel animals or wheel animalcules, make up a phylum (Rotifera ) of microscopic and near-microscopic Coelom#Pseudocoelomates, pseudocoelomate animals. They were first describ ...

s and larger

protist A protist ( ) or protoctist is any eukaryotic organism that is not an animal, land plant, or fungus. Protists do not form a natural group, or clade, but are a paraphyletic grouping of all descendants of the last eukaryotic common ancest ...

s. Other eutardigrades belong to the order Parachela.

References

External links

* *
Tardigrade taxa''Milnesium tardigradum'' (radiation experiments)
{{Taxonbar, from=Q136432 Ecdysozoa classes Extant Cretaceous first appearances