Desmoscolecida is an order of marine

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

s.WoRMS - World Register of Marine Species - Desmoscolecida
/ref> 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 of the ridges bear a pair either dorsally or ventrally. Two pigment spots between the fourth and fifth ridges are regarded as eyes. The Desmoscolecida move by looping their bodies like geometrid caterpillars or

leech Leeches are segmented parasitic or predatory worms that comprise the subclass Hirudinea within the phylum Annelida. They are closely related to the oligochaetes, which include the earthworm, and like them have soft, muscular segmented bodie ...

es, as well as by creeping on their setae. The mouth is terminal, and leads into a muscular oesophagus which opens into a straight intestine terminating in an anus, which is said to be dorsal in position. The sexes are distinct. The testis is single, and its duct opens into the intestine and is provided with two

chitin Chitin ( C8 H13 O5 N)n ( ) is a long-chain polymer of ''N''-acetylglucosamine, an amide derivative of glucose. Chitin is probably the second most abundant polysaccharide in nature (behind only cellulose); an estimated 1 billion tons of chit ...

ous spicules. The ovary is also single, opening independently and anterior to the anus. The nervous system is as yet unknown. Genera include '' Desmoscolex'', '' Greeffiella'', and '' Tricoma''.

References

* Paolo Panceri, ''Atti dell'Accademia Pontaniana'' (previously, ''Atti della Società pontaniana di Napoli''). vii. (1878) * Richard Greeff, '' Archiv für Naturgeschichte'' 35 (i.) (1869), p. 112. (A. E. S.) Nematode orders Chromadorea {{Chromadorea-stub