The
class
Class or The Class may refer to:
Common uses not otherwise categorized
* Class (biology), a taxonomic rank
* Class (knowledge representation), a collection of individuals or objects
* Class (philosophy), an analytical concept used differentl ...
Heterotardigrada includes
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 Kleiner Wasserbä ...
s (water bears) that have cephalic appendages and legs with four separate but similar digits or claws on each. 444 species have been described.
Anatomy
The anatomy of the reproductive system is an important defining feature in distinguishing the different groups of tardigrades. Heterotardigrades have gonoducts that open to the outside through a preanal gonopore, rather than opening into the rectum as in the only other confirmed class of tardigrades, the
Eutardigrada
Eutardigrada are a class of tardigrades (Tardigrada) without lateral appendices. Primarily freshwater bound, some species have secondarily gained the ability to live in marine environments (''Halobiotus''). By cryptobiosis many species are able t ...
. The third class,
Mesotardigrada
Mesotardigrada is one of three classes of tardigrades, consisting of a single species, ''Thermozodium esakii''. The animal reportedly has six claws of equal length at each foot. This species was described in 1937 by German zoologist Gilbert Rah ...
, is represented by a single species known from a single specimen that is now lost, and the location from which that specimen was collected has since been destroyed by an earthquake, so its reproductive anatomy has not been studied recently.
Ecology
Some
orders of heterotardigrades are marine, others are terrestrial, but as for all tardigrades, all are aquatic in the sense that they must be surrounded by at least a film of moisture in order to be active – though they can survive in a dormant state if the habitat dries out.
References
External links
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{{Taxonbar, from=Q138557
Protostome classes
Taxa named by Ernst Marcus (zoologist)