The nematomorphs ( Nematomorpha ) or gordiaceae ( Gordiacea ) are a phylum of parasitoid worms , ecologically and morphologically very similar to nematodes . 331 species have been described . 1


They are characterized by presenting a pseudocelloma , which corresponds to a cavity of the body filled with liquid, which acts as a hydroeskeleton . It has bilateral symmetry , they are triblásticos and they lack of segmentation. The size varies between 5 cm and 1 m in length, with 1 to 3 mm in diameter. They often appear in moist environments such as streams or ponds. The adult is a free-living individual, but the larva is always parasitic on arthropods or leeches . Some three hundred and twenty species have been described.

The present helminthiases cuticle without cilia and internally have a single muscle longitudinal, lack systems excretory , respiratory or circulatory ; Even in the free-living adult, the systems appear depleted, which shows the importance of larval parasitization in the functions of the whole biological cycle. They are dioecious and have a kind of internal fertilization of eggs that are in mucus.

The anterior end of the body has a pigmented band, in front of which is the apical area called the calota.

In certain genera sexual dimorphism is observed at the posterior end of the body. In Gordius , the male has the posterior bilobed end, while the females have a single caudal lobe. The female of Paragordius has the posterior end divided into three lobes.

During the short life of the adult, males and females are sought until, when they meet, they twist on each other, forming a tangle during copulation, reminiscent of the Gordian knot (hence the name Gordius ).

Their presence in certain environments can be a symptom of pollution .

Anatomy and Physiology

Digestive system

The adults of the species of this phylum stand out for the lack of mouth and the degeneration of the pharynx towards a solid mass. The intestine is very long and runs the entire length of the animal. At the posterior end there is a sewer by which the gametes of the reproductive system are poured. It has been proposed that the function of the intestine is excretory.

The larvae are fed parenterally .


See also: Annex: Bilateral animals

They are usually classified into two classes , although their classification is very complex and not well defined:

  • Class Nectonematoid . Marine and planktonic, with two rows of lateral swimming silks. With wide pseudocele . They have a dorsal nerve cord in addition to the ventral cord. Their larvae are parasitic decapod crustaceans . Nectonema
  • Gordioidea Class . Freshwater or semi-terrestrial. Without side silks. They only have ventral nerve cord. Parasitic larvae of orthoptera . Gordius, Chordotes, Paragordius


In South America, Chile and Argentina, there is the legend of living hair , which is associated with species of the genus Gordius.


  1. Back to top↑ Chapman, AD, 2009. Numbers of Living Species in Australia and the World , 2nd edition. Australian Biodiversity Information Services ISBN (online) 9780642568618