The Chromadorea are a class of the roundworm phylum,

Nematoda The nematodes ( or grc-gre, Νηματώδη; la, Nematoda) or roundworms constitute the phylum Nematoda (also called Nemathelminthes), with plant-parasitic nematodes also known as eelworms. They are a diverse animal phylum inhabiting a broa ...

. They contain a single subclass (Chromadoria) and several orders. With such a redundant arrangement, the Chromadoria are liable to be divided if the orders are found to form several

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

s, or abandoned if they are found to constitute a single radiation. Formerly, they were treated as a subclass in the

paraphyletic In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be pa ...

Adenophorea Adenophorea or Aphasmidia was a class of nematodes (roundworms). It has been by and large abandoned by modern taxonomy, because there is strong evidence for it being a motley paraphyletic group of unrelated lineages of roundworms.ToL (2002) Chara ...

" assemblage, which has been mostly abandoned by modern authors. It is also suspected that the Chromadorea may not be

monophyletic In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic gro ...

as delimited here; at least the

Monhysterida The Monhysterida are an order in the phylum Nematoda The nematodes ( or grc-gre, Νηματώδη; la, Nematoda) or roundworms constitute the phylum Nematoda (also called Nemathelminthes), with plant-parasitic nematodes also known as eel ...

seem to be a distinct and far more ancient lineage than the rest. Members of this class' bodies usually have annules, their

amphid Amphids (Greek: ''amphi'', around, double) are innervated invaginations of cuticle in nematodes. They are usually found in the anterior (head) region of the animal, at the base of the lips. Amphids are the principal olfactosensory organs of nematod ...

s elaborate and spiral, and they all have three

esophageal glands The esophageal glands are glands that are part of the digestive system of various animals, including humans. In humans Esophageal glands in humans are a part of a human digestive system. They are a small compound racemose exocrine glands of the m ...

. They usually live in marine sediments, although they can live elsewhere. They have a more sophisticated

pharynx The pharynx (plural: pharynges) is the part of the throat behind the mouth and nasal cavity, and above the oesophagus and trachea (the tubes going down to the stomach and the lungs). It is found in vertebrates and invertebrates, though its struc ...

than most roundworms. Members of this class can be identified by the presence of eight

conserved signature indels Conserved signature inserts and deletions (CSIs) in protein sequences provide an important category of molecular markers for understanding phylogenetic relationships. CSIs, brought about by rare genetic changes, provide useful phylogenetic markers ...

(CSIs) exclusively shared by the class. These molecular markers are found in essential proteins such as tRNA (guanine-N(1))-methyltransferase and can serve as a reliable molecular method of distinguishing the Chromadorea from other classes within the phylum Nematoda.

Orders

Provisionally, the following orders are placed here: *

Araeolaimida Araeolaimida is an order of marine free living nematodes. References Araeolaimidaat WoRMS Nematode orders {{chromadorea-stub ...

Ascaridida The order Ascaridida includes several families of parasitic roundworms with three "lips" on the anterior end. They were formerly placed in the subclass Rhabditia by some, but morphological and DNA sequence data rather unequivocally assign them t ...

Chromadorida Chromadorida is an order of nematodes belonging to the class Chromadorea. Families: * Achromadoridae Gerlach & Riemann, 1973 * Chromadoridae Filipjev, 1917 * Cyatholaimidae Filipjev, 1918 * Ethmolaimidae Lorenzen, 1981 * Neotonchidae Neoton ...

Desmodorida Desmodorida is an order of nematodes belonging to the class Adenophorea. Families: * Ceramonematidae * Choniolaimidae * Chromadoridae * Comesomatidae * Cyatholaimidae * Desmodoridae * Draconematidae * Epsilonematidae * Etmolaimidae * Microlai ...

Desmoscolecida Desmoscolecida is an order of marine nematodes. In a worm of this order, the body tapers towards each end and is marked by a number of well-defined ridges. Their number varies in the different species. The head bears four movable setae, and some ...

Rhabditida Rhabditida is an order of free-living, zooparasitic, and phytoparasitic microbivorous nematodes living in soil. The Cephalobidae, Panagrolaimidae, Steinernematidae, and Strongyloididae seem to be closer to the Tylenchia, regardless of whet ...

* Rhigonematida

Notes

The

Benthimermithida Benthimermithida is an order of nematodes belonging to the class Chromadorea The Chromadorea are a class of the roundworm phylum, Nematoda. They contain a single subclass (Chromadoria) and several orders. With such a redundant arrangement, th ...

are also occasionally placed here. The Ascaridida appear to be nested within Rhabditida. A part of the Nematoda phylum, one of the nine main phyla. Along with other certain species of roundworms. Most frequently related to other main species of roundworms such as Earthworms, Pinworms, Hookworms, and Stongyloides.

References

External links

* (2002)
Nematoda
Version of 2002-JAN-01. Retrieved 2008-NOV-02. Protostome classes {{Chromadorea-stub