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
clades, or abandoned if they are found to constitute a single radiation.
Formerly, they were treated as a subclass in the
paraphyletic "
Adenophorea" assemblage, which has been mostly abandoned by modern authors. It is also suspected that the Chromadorea may not be
monophyletic as delimited here; at least the
Monhysterida 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 st ...
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
*
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
*
Desmodorida
*
Desmoscolecida
*
Monhysterida
*
Rhabditida
*
Rhigonematida
Notes
The
Benthimermithida 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