Secernentea

Secernentea
Caenorhabditis elegans (Rhabditia: Rhabditidae)
Scientific classification
Kingdom:	Animalia
Phylum:	Nematoda
Class:	Secernentea
Subclasses
Diplogasteria (disputed) Rhabditia (paraphyletic?) Spiruria Tylenchia (disputed) and see text

Secernentea are the main class of nematodes, characterised by numerous caudal papillae and an excretory system possessing lateral canals. Like all nematodes, they have no circulatory or respiratory system. These are also called as phasmidians as they have the phasmids which are the posterior glandulo sensory and excretory structure.^[1]

The Secernentea contain several significant parasitic species among the Rhabditia and Spiruria. Caenorhabditis elegans, the famous laboratory animal, is one of the many harmless members of the Rhabditia.

Systematics

Subclasses and orders of Secernentea are:^[1]

• Subclass Rhabditia (paraphyletic?)
  • Rhabditida
  • Strongylida
• Subclass Spiruria
  • Ascaridida
  • Camallanida (sometimes included in Spirurida)
  • Drilonematida (sometimes included in Spirurida)
  • Oxyurida (= Rhabdiasida)
  • Rhigonematida (formerly in Tylenchia)
  • Spirurida
• Subclass Diplogasteria (may belong in Rhabditia)
  • Diplogasterida
• Subclass Tylenchia (may belong in Rhabditia)
  • Aphelenchida
  • Tylenchida

Some families traditionally considered to be Rhabditida seem to be closer to the Tylenchida. If the Tylenchia are to be maintained as separate, they probably will be included therein.

References

1. Tree of Life Web Project (ToL) (2002): Nematoda. Version of January 1, 2002. Retrieved November 2, 2008.