The anatomy of the reproductive system is an important defining feature in distinguishing 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 (the third class Mesotardigrada, is represented by a single species whose reference material was destroyed in an earthquake, so its reproductive anatomy has not been studied recently).
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.
Recent findings in life sciences described by researchers from University of Tubingen, Zoological Institute.(Report)
Feb 18, 2008; Research findings, 'Trehalose and anhydrobiosis in tardigrades--evidence for divergence in responses to dehydration,' are...
Researchers from University of Copenhagen report details of new studies and findings in the area of molecular phylogenetics.
Apr 06, 2010; "Tardigrades are microscopic ecdysozoans with a worldwide distribution covering marine, limnic and terrestrial habitats. They are...