Subclass Rhabditia is mostly composed of

parasitic Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson ha ...

nematodes (particularly in the

Strongylida The Strongylida suborder includes many of the important nematodes found in the gastrointestinal tracts of ruminants, horses, and swine, as well as the lungworms of ruminants and the hookworms of dogs and cats. Taxonomy This suborder includes ( ...

), though there are some free-living species as well (particularly in the

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 wheth ...

). Phasmids (posterior sensory structures) are well-developed, while

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 (anterior sensory structures) are poorly developed or absent in this group. In an alternate classification system, they are treated as suborder Rhabditina, with the orders listed here being ranked as

infraorder Order ( la, ordo) is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between family and class. In biological classification, the order is a taxonomic rank used in the classification of organisms and ...

s. Also, the

Diplogasterida Diplogasterida was an order of nematodes. It was sometimes placed in a monotypic subclass Diplogasteria, but molecular phylogenetic evidence has shown it to be embedded in the family Rhabditidae (formerly Rhabditina). The confusion of having a ...

, which are sometimes considered a

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispe ...

subclass, are probably better placed in the Rhabditia. On the other hand, the old placement of the

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 ...

in Rhabditia instead of

Spiruria Subclass Spiruria comprises mostly parasitic secernentean nematodes. In an alternate classification, they are treated as suborder Spirurina, with the orders listed here being ranked as infraorders. The Ascaridida and the Oxyurida, which include ...

seems unwarranted. The

contain a number of

families Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Ideal ...

which are probably better placed in the Tylenchia; alternatively, the latter group may entirely be merged with the Rhabditia.

Tree of Life Web Project The Tree of Life Web Project is an Internet project providing information about the diversity and phylogeny of life on Earth. This collaborative peer reviewed project began in 1995, and is written by biologists from around the world. The site ...

(ToL) (2002b)
Nematoda
Version of 2002-JAN-01. Retrieved 2008-NOV-02.ToL (2002)

References

Protostome subclasses Parasitic nematodes {{Rhabditida-stub

See also

References