''Gordius'' is a genus of

worm Worms are many different distantly related bilateral animals that typically have a long cylindrical tube-like body, no limbs, and no eyes (though not always). Worms vary in size from microscopic to over in length for marine polychaete wo ...

s in the phylum

Nematomorpha Nematomorpha (sometimes called Gordiacea, and commonly known as horsehair worms, hairsnakes, or Gordian worms) are a phylum of parasitoid animals superficially similar to nematode worms in morphology, hence the name. Most species range in size f ...

, the horsehair worms. It was formerly treated as the only genus in the family Gordiidae, but the genus '' Acutogordius'' is now considered as distinct.Bleidorn, C., et al. (2002)
Systematic relationships of Nematomorpha based on molecular and morphological data.
''Invertebrate Biology'' 121(4), 357-64. The genus is distributed worldwide except for

Antarctica Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest cont ...

, where no Nematomorpha have been recorded.Schmidt-Rhaesa, A. (2002)
Are the genera of Nematomorpha monophyletic taxa?
''Zoologica Scripta'' 31(2), 185-200.

Description

The adult worm is a free-living animal. It is hairlike, very long and very thin. It commonly grows over a meter long,Capinera, J. L
Horsehair Worms, Hairworms, Gordian Worms, Nematomorphs, ''Gordius'' spp. (Nematomorpha: Gordioidea).
EENY-117. Entomology and Nematology. Florida Cooperative Extension Service. University of Florida IFAS. Published 1999, revised 2005. with the record length held by a specimen of ''G. fulgur'' over two meters long,Schmidt-Rhaesa, A. and R. Ehrmann. (2001)
Horsehair worms (Nematomorpha) as parasites of praying mantids with a discussion of their life cycle.
''Zoologischer Anzeiger'' 240(2), 167-79. and may be only about one millimeter wide. It is reddish brown to black. Besides a blunt anterior end and a slightly widened posterior end, it is featureless to the naked eye. Microscopic features include a diagnostic character of the family, both ''Gordius'' and genus ''Acutogordius'', the postcloacal crescent of the male, a fold in the cuticle curving around the back side of the cloaca. At the front end of the body there is a white cap and a dark collar. At the posterior end there are tiny bristles, sometimes arranged in a row in front of the cloaca. Some species have a smooth body surface, and some may be slightly bumpy with flattened areoles. Most of these features are used in species identification, but are not very helpful, and it is difficult to tell species apart, in general. A thorough

taxonomy Taxonomy is the practice and science of categorization or classification. A taxonomy (or taxonomical classification) is a scheme of classification, especially a hierarchical classification, in which things are organized into groups or types. ...

of the genus will require a scanning electron microscope.Schmidt-Rhaesa, A. (2010)
Considerations on the genus ''Gordius'' (Nematomorpha, horsehair worms), with the description of seven new species.
''Zootaxa'' 2533, 1-35.

Biology

These worms can only live near water, because parts of their life cycle take place in it. The adult

overwinters Overwintering is the process by which some organisms pass through or wait out the winter season, or pass through that period of the year when "winter" conditions (cold or sub-zero temperatures, ice, snow, limited food supplies) make normal activ ...

in soil and debris and the female enters a water body such as a swamp or a stream to lay eggs. A gelatinous string of eggs each about 50

micrometers The micrometre ( international spelling as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American spelling), also commonly known as a micron, is a unit of length in the International System of Unit ...

long is released into the water. The female can produce a great many eggs, perhaps up to 27 million in its lifetime. Juveniles require a

host A host is a person responsible for guests at an event or for providing hospitality during it. Host may also refer to: Places * Host, Pennsylvania, a village in Berks County People *Jim Host (born 1937), American businessman * Michel Host ...

in which to complete their development. Upon emergence from the egg the

larva A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. ...

swims about until it is consumed by a host insect. Most ''Gordius'' worms are

parasites 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 ...

beetle Beetles are insects that form the order Coleoptera (), in the superorder Endopterygota. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 400,000 describ ...

s. Other recorded hosts include

mantids Mantidae is one of the largest families in the order of praying mantises, based on the type species '' Mantis religiosa''; however, most genera are tropical or subtropical. Historically, this was the only family in the order, and many referen ...

such as the

European mantis The European mantis (''Mantis religiosa'') is a large hemimetabolic insect in the family of the Mantidae ('mantids'), which is the largest family of the order Mantodea (mantises). Their common name praying mantis is derived from the distinctive ...

(''Mantis religiosa'') and '' Hierodula membranacea'', '' Idolomantis diabolica'', ''

Sphodromantis viridis ''Sphodromantis viridis'' is a species of praying mantis that is kept worldwide as a pet. Its common names include African mantis, giant African mantis, and bush mantis. Name ''Sphodromantis viridis'' is popularly called the African mantis, but ...

'', and '' Stagmatoptera praecaria''. Species have been observed in

caddisfly The caddisflies, or order Trichoptera, are a group of insects with aquatic larvae and terrestrial adults. There are approximately 14,500 described species, most of which can be divided into the suborders Integripalpia and Annulipalpia on the ...

and

mosquito Mosquitoes (or mosquitos) are members of a group of almost 3,600 species of small flies within the family Culicidae (from the Latin ''culex'' meaning " gnat"). The word "mosquito" (formed by ''mosca'' and diminutive ''-ito'') is Spanish for "li ...

larvae. Once ingested by the insect the worm larva penetrates the gut wall and develops in a

cyst A cyst is a closed sac, having a distinct envelope and division compared with the nearby tissue. Hence, it is a cluster of cells that have grouped together to form a sac (like the manner in which water molecules group together to form a bubble) ...

in the tissue outside. It emerges as an adult worm in a few months. ''Gordius'' worms have been recovered from human

vomit Vomiting (also known as emesis and throwing up) is the involuntary, forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose. Vomiting can be the result of ailments like food poisoning, gastroenterit ...

, feces,Yamada, M., et al. (2012)
Two human cases infected by the horsehair worm, ''Parachordodes'' sp.(Nematomorpha: Chordodidae), in Japan.
''The Korean Journal of Parasitology'' 50(3), 263-67. and

urine Urine is a liquid by-product of metabolism in humans and in many other animals. Urine flows from the kidneys through the ureters to the urinary bladder. Urination results in urine being excreted from the body through the urethra. Cellular ...

. When worms are expelled from the gastrointestinal tract, their mode of entry was likely ingestion of contaminated food or water, or of an infested insect. When present in the urine, the worm may have entered the

urethra The urethra (from Greek οὐρήθρα – ''ourḗthrā'') is a tube that connects the urinary bladder to the urinary meatus for the removal of urine from the body of both females and males. In human females and other primates, the urethra c ...

from the anus or while the victim was swimming in contaminated water. Horsehair worms are not considered

pathogen In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ ...

ic or

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 ...

on humans and their presence in the body is incidental. Adult worms, as in some other Nematomorpha genera, may squirm in a tangled ball resembling a Gordian Knot; horsehair worms are also referred to as gordian worms.

Diversity

As of 2010 there are 79 species in the genus. Gordius fulgur 001

References

{{Taxonbar, from=Q4039607 Nematomorpha