^ Poinar George Ron Buckley (September 2006)."Early Cambrian worms from Chengjiang, Yunnan, China: Maotianshania gen. : CS1 maint: archived copy as title ( link) Girls, don't swim without pants or a hairsnake will enter you. "Naasaab Izhi-anishinaabebii'igeng conference report: a conference to find a common Anishinaabemowin writing system" (PDF). Unlike nectonematiodeans, gordioideans lack lateral rows of setae, have a single, ventral epidermal cord and their blastocoels are filled with mesenchyme in young animals but become spacious in older individuals. Gordioidean adults are free-living in freshwater or semiterrestrial habitats and larvae parasitise insects, primarily orthopterans. The approximately 320 remaining species are distributed between two families, within the monotypic class Gordioida. They are characterized by a double row of natotory setae along each side of the body, dorsal and ventral longitudinal epidermal cords, a spacious and fluid-filled blastocoelom and singular gonads. This order is monotypic containing the genus Nectonema Verrill, 1879: adults are planktonic and the larvae parasitise decapod crustaceans, especially crabs. The five marine species of nematomorph are contained in Nectonematoida. Relationships within the phylum are still somewhat unclear, but two classes are recognised. The earliest Nematomorph could be Maotianshania, from the Lower Cambrian this organism is, however, very different from extant species fossilized worms resembling the modern forms have been reported from mid Cretaceous Burmese amber dated to 100 million years ago. During the larval stage, the animals show a resemblance to adult kinorhyncha and some species of Loricifera and Priapulida, all members of the group Scalidophora. The two phyla make up the group Nematoida in the clade Cycloneuralia. Their closest relatives are the nematodes. The phylum is placed along with the Ecdysozoa clade of moulting organisms that include the Arthropoda. Male mermithids have one or two spicules just before the end apart from having a thinner, smoother cuticle, without areoles and a paler brown colour. Unlike nematomorphs, mermithids do not have a terminal cloaca. Nematomorphs can be confused with nematodes, particularly mermithid worms. See also: List of bilaterial animal orders The adults are mostly free-living in freshwater or marine environments, and males and females aggregate into tight balls ( Gordian knots) during mating. Development into the adult form takes weeks or months, and the larva moults several times as it grows in size. Once inside the host, the larvae live inside the haemocoel and absorb nutrients directly through their skin. The larvae have rings of cuticular hooks and terminal stylets that are believed to be used to enter the hosts. Adults have cylindrical gonads, opening into the cloaca. Reproductively, they have two distinct sexes, with the internal fertilization of eggs that are then laid in gelatinous strings. The nervous system consists of a nerve ring near the anterior end of the animal, and a ventral nerve cord running along the body. Internally, they have only longitudinal muscle and a non-functional gut, with no excretory, respiratory or circulatory systems. Nematomorphs possess an external cuticle without cilia. This relates to the fact that nematomorphs often coil themselves in tight balls that resemble knots. The name "Gordian" stems from the legendary Gordian knot. About 351 freshwater species are known and a conservative estimate suggests that there may be about 2000 freshwater species worldwide. The adult worms are free-living, but the larvae are parasitic on arthropods, such as beetles, cockroaches, mantises, orthopterans, and crustaceans. Horsehair worms can be discovered in damp areas, such as watering troughs, swimming pools, streams, puddles, and cisterns. Most species range in size from 50 to 100 millimetres (2.0 to 3.9 in) long, reaching 2 metres in extreme cases, and 1 to 3 millimetres (0.039 to 0.118 in) in diameter. 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. Phylum of parasitoid animals, horsehair worms
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