Heterotardigrada

(invertebrate zoology) An order of the tardigrades exhibiting wide morphologic variations.

An order of the tardigrades; the majority of genera have widely varied structure. Cephalic appendages having a sensorial function are present, as well as cirrus lateralis and clava. This order of tardigrades is divided into two suborders, Arthrotardigrada and Echiniscoidea.

Members of the suborder Arthrotardigrada have toelike terminations of the legs. The tubular middle part of the leg telescopes into the broad proximal part. These animals are marine organisms found in sand or on algae.

In the suborder Echiniscoidea the legs terminate with claws. The middle part of the leg is partially retractable into the proximal part. At least the fourth pair of legs has a distinct fold. Frequently these animals are red because of the presence of carotenoid pigments. See also Carotenoid.

Heterotardigrada
Scientific classification
Kingdom: Animalia Phylum: Tardigrada Class: Heterotardigrada Marcus, 1927
Families
Order Arthrotardigrada   Archechiniscidae   Batillipedidae   Coronarctidae   Halechiniscidae   Renaudarctidae   Stygarctidae Order Echiniscoidea   Echiniscidae   Echiniscoididae   Oreellidae

Wikispecies has information related to: Heterotardigrada

The class Heterotardigrada includes tardigrades (water bears) that have cephalic appendages and legs with four separate but similar digits and/or claws on each.

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.

References

• Heterotardigrada (TSN 155167). Integrated Taxonomic Information System.
• Arthrotardigrada (TSN 155168). Integrated Taxonomic Information System.
• Echiniscoidea (TSN 155299). Integrated Taxonomic Information System.

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