''Paragordius tricuspidatus'' belongs to 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 fr ...

, and is known for manipulating the behavior of its host, the

cricket Cricket is a bat-and-ball game played between two teams of eleven players on a field at the centre of which is a pitch with a wicket at each end, each comprising two bails balanced on three stumps. The batting side scores runs by striki ...

Nemobius sylvestris ''Nemobius sylvestris'', the wood cricket, is a flightless species of cricket in the family Gryllidae. It is native to Western Europe and North Africa but uncommon in Britain. Description This cricket is a small, dark brown, ground-dwelling, gr ...

''. In its

larval stage 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. The l ...

, the worm is microscopic, but grows into a large worm () inside its host after accidental ingestion since their eggs are laid at the edge of the water by rivers where crickets frequently reside. Upon ingestion, the worm nourishes upon its host and fills the entire body cavity of the cricket, until maturation, when the

parasitic worm Parasitic worms, also known as helminths, are large Parasitism#Basic concepts, macroparasites; adults can generally be seen with the naked eye. Many are intestinal worms that are soil-transmitted helminth, soil-transmitted and intestinal parasit ...

is ready to exit into water to complete its life cycle, maximizing its reproductive success. The worm induces a peculiar behavior on its cricket host, which causes it to leap into water whereby the parasitic worm can slither out and find its mate, while the cricket often perishes. Should the cricket be preyed upon by a predator, such as a fish or frog, the worm has the ability to not only escape from the host's body but also the predator's digestive system. The worm emerges from the predator unharmed and proceeds to live its life normally. Studies of this parasitic worm have shown that the manipulative tactics of ''Paragordius tricuspidatus'' may be chemically based. In the related ''

Spinochordodes tellinii ''Spinochordodes tellinii'' is a parasitic nematomorph hairworm whose larvae develop in grasshoppers and crickets. This parasite is able to influence its host's behavior: once the parasite is grown, it causes its grasshopper host to jump into ...

'', another parasitic and brain-manipulative nematomorph, the parasitic worm produces certain effector molecules to manipulate the cricket's

central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all par ...

to behave in ways that are out of the norm for the insect, as in jumping into water. In addition, ''S.tellinii'' produces a group of proteins in the Wnt family that are similar to insect proteins, which suggests

molecular mimicry Molecular mimicry is defined as the theoretical possibility that sequence similarities between foreign and self-peptides are sufficient to result in the cross-activation of autoreactive T or B cells by pathogen-derived peptides. Despite the preva ...

as a possible source for behavioral manipulation.

References

{{Taxonbar, from=Q2808577 Nematomorpha Parasitic protostomes Parasites of insects Suicide-inducing parasitism Animals described in 1828