Nematomorpha

Nematomorpha
Paragordius tricuspidatus
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
(unranked):	Cycloneuralia
(unranked):	Nematoida
Phylum:	Nematomorpha Vejdovsky, 1886
Classes
Nectonematoida Gordioidea

The Nematomorpha (horsehair worms) are a phylum of parasitic cycloneuralian animals. They look similar to nematode worms and live in similar environments, which is why their names are similar. They are sometimes called Gordiacea.^[1]

They range in size from 50 to 100 centimetres (20 to 39 in) long and in extreme cases may be up to 2 meters long. They are 1 to 3 millimetres (0.039 to 0.118 in) in diameter. Horsehair worms can be discovered in damp areas such as watering troughs, streams, puddles, and cisterns.

About 326 species are known and an estimate suggests that there may be about 2000 species worldwide.^[2]

Fossilized worms have been reported from Lower Cretaceous Burmese amber 100–110 million years ago.^[3]

1. ↑ The name stems from the legendary Gordian knot, because nematomorphs often tie themselves in knots. Piper, Ross 2007. Extraordinary animals: an encyclopedia of curious and unusual animals, Greenwood Press.
2. ↑ Poinar Jr., G (2008). "Global diversity of hairworms (Nematomorpha: Gordiaceae) in freshwater". Hydrobiologia. 595 (1): 79–83. doi:10.1007/s10750-007-9112-3. S2CID 37985613.
3. ↑ Poinar, George; Buckley Ron 2006. Nematode (Nematoda: Mermithidae) and hairworm (Nematomorpha: Chordodidae) parasites in early Cretaceous amber. Journal of Invertebrate Pathology 93(1):36–41