Desmoscolecida is an order of marine

nematode The nematodes ( or ; ; ), roundworms or eelworms constitute the phylum Nematoda. Species in the phylum inhabit a broad range of environments. Most species are free-living, feeding on microorganisms, but many are parasitic. Parasitic worms (h ...

s.WoRMS - World Register of Marine Species - Desmoscolecida
/ref> It has just one suborder, Desmoscolecina, which itself has one superfamily, Desmoscolecoidea. 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

seta In biology, setae (; seta ; ) are any of a number of different bristle- or hair-like structures on living organisms. Animal setae Protostomes Depending partly on their form and function, protostome setae may be called macrotrichia, chaetae, ...

e, 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 parasitism, parasitic or Predation, predatory worms that comprise the Class (biology), subclass Hirudinea within the phylum Annelida. They are closely related to the Oligochaeta, oligochaetes, which include the earthwor ...

es, as well as by creeping on their setae. The mouth is terminal, and leads into a muscular

oesophagus The esophagus (American English), oesophagus (British English), or œsophagus ( archaic spelling) ( see spelling difference) all ; : ((o)e)(œ)sophagi or ((o)e)(œ)sophaguses), colloquially known also as the food pipe, food tube, or gullet, ...

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 (carbon, C8hydrogen, H13oxygen, O5nitrogen, N)n ( ) is a long-chain polymer of N-Acetylglucosamine, ''N''-acetylglucosamine, an amide derivative of glucose. Chitin is the second most abundant polysaccharide in nature (behind only cell ...

ous

spicule Spicules are any of various small needle-like anatomical structures occurring in organisms Spicule may also refer to: *Spicule (sponge), small skeletal elements of sea sponges *Spicule (nematode), reproductive structures found in male nematodes ( ...

s. 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 Richard Greeff (14 March 1828, Elberfeld – 30 August 1892, Marburg) was a German zoologist. He studied medicine in Würzburg, Heidelberg and Berlin, receiving his medical doctorate in 1857. Following graduation, he worked as a hospital assi ...

, ''

Archiv für Naturgeschichte ''Archiv für Naturgeschichte'' was a German-language journal for natural history. It was founded by A. F. A. Wiegmann in 1835. The journal was published in Berlin from 1835 to 1926. There were 92 published volumes. From 1912 to 1926 each volume w ...

'' 35 (i.) (1869), p. 112. (A. E. S.) Ecdysozoa superfamilies Chromadorea {{Chromadorea-stub