Pentastomida

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Pentastomida

The Pentastomida are a group of parasitic invertebrate

Invertebrate

An invertebrate is an animal lacking a vertebral column. The group includes 98% of all animal species ? all animals except those in the Chordate subphylum vertebrate ....
s commonly known as tongue worms due to the resemblance of the species of the genus Linguatula
Linguatula

IntroductionLinguatula is a genus of the phylum Pentastomida. The parasites of the Lingatula genus, also known as tongue worms, cause the rare disease Linguatulosis....
to a vertebrate tongue

Tongue

The tongue is skeletal muscle on the floor of the mouth that manipulates food for chewing . It is the primary organ of taste. Much of the upper surface of the tongue is covered in papillae and taste buds....
.

There are about 100 extant species of pentastomids; all are obligate parasite

Obligate parasite

An obligate parasite is a parasite organism that cannot live independently of its host ....
s with correspondingly degenerate anatomy. Adult tongue worms vary from about 1 cm to 14 cm in length, and parasitize the respiratory tract

Respiratory tract

In humans the respiratory tract is the part of the anatomy that has to do with the process of Respiration .The respiratory tract is divided into 3 segments:...
s of vertebrate

Vertebrate

Vertebrates are members of the subphylum Vertebrata, chordates with Vertebras or Vertebral columns. The grouping sometimes includes the hagfish, which have no vertebrae, but are genetically quite closely related to lampreys, which do have vertebrae....
s . They have five anterior appendage

Appendage

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Encyclopedia

The Pentastomida are a group of parasitic invertebrate

Invertebrate

Tongue

Obligate parasite

Respiratory tract

In humans the respiratory tract is the part of the anatomy that has to do with the process of Respiration .The respiratory tract is divided into 3 segments:...
s of vertebrate

Vertebrate

Appendage

An appendage in the broadest sense is an additional or subsidiary part existing on, or added to, something which can generally still function if the appendage has never existed or is later provided or grown, or will still perform a primary function if the appendage is removed....
s. One is the mouth; the others are two pairs of hooks which they use to attach to the host. This arrangement led to their scientific name, meaning "five openings", but although the appendages are similar in some species, only one is a mouth.

Their affinity with other invertebrates is uncertain. They grow by moulting

Ecdysis

Ecdysis is the molting of the cuticula in arthropods and related groups . Since the cuticula of these animals is also the skeletal support of the body and is inelastic, it is shed during growth and a new, larger covering is formed....
, which suggests they belong to the Ecdysozoa

Ecdysozoa

The Ecdysozoa are a grouping of protostome animals, including the Arthropoda , roundworm, and several smaller phylum . They were first defined by Aguinaldo et al. in 1997, based mainly on trees constructed using 18S ribosomal RNA genes....
. Historically, they were considered to deserve a phylum

Phylum

A phylum "Phylum" is adopted from the Greek phylai, the clan-based voting groups in Greek city-states. is a taxonomic rank below Kingdom and above Class ....
of their own, but in 1972, Wingstrand showed similarities in the structure of spermatozoa between pentastomids and branchiura

Branchiura

Branchiura, commonly called carp lice or fish lice are a group of parasite crustaceans of uncertain position within the Maxillopoda....
ns (fish lice), a group of parasitic crustacean

Crustacean

Crustaceans are a large group of arthropods, comprising almost 52,000 described species , and are usually treated as a subphylum . They include various familiar animals, such as crabs, lobsters, crayfish, shrimp, krill and barnacles....
s , and this relationship is supported by molecular evidence .

However, fossil

Fossil

Fossils are the preserved remains or trace fossil of animals, plants, and other organisms from the remote past. The totality of fossils, both discovered and undiscovered, and their placement in fossiliferous Rock formations and sedimentary rock layers is known as the fossil record....
s from the Upper Cambrian

Cambrian

The Cambrian is a geologic period that began about Mya at the end of the Proterozoic eon and ended about Ma with the beginning of the Ordovician period ....
identified as pentastomids (Heymonsicambria, Haffnericambria, Bockelericambria) suggest that the pentastomids branched very early and may be an outgroup

Outgroup

In cladistics, whenever three or more monophyletic groups of organisms are compared, and all but one of them are more closely related to each other than any single one of them is to the last, the latter group is known as the outgroup....
to the other arthropods .

Alternative names for the Pentastomida include Pentastoma (strictly a genus name), Linguatulida, and Acanthotheca.

Classification

This article follows Martin and Davis in placing Pentastomida in the class Maxillopoda

Maxillopoda

Maxillopoda is a class under the phylum Arthropoda, subphylum Crustacea, and is characterised by a reduction of the abdomen and its appendages....
within the subphylum Crustacea . Martin and Davis present this classification of the pentastomids down to the level of families:

Subclass Pentastomida Diesing, 1836

Order Cephalobaenida Heymons, 1935

Cephalobaenidae Fain, 1961
Reighardiidae Heymons, 1935

Order Porocephalida Heymons, 1935

Armilliferidae Fain, 1961
Diesingidae Fain, 1961
Linguatulidae Heymons, 1935
Porocephalidae Fain, 1961
Sambonidae Fain, 1961
Sebekiidae Fain, 1961
Subtriquetridae Fain, 1961

Life cycle

Pentastomids live in the upper respiratory tract of reptiles, birds, and mammals, where they lay eggs. The eggs are either coughed out by the host or leave the host body through the digestive system. The eggs are then ingested by an intermediate host. The first larva hatches in the intermediate host and breaks through the wall of the intestine. It then forms a cyst in the intermediate host's body. The pentastomid reaches the main host when the intermediate host is eaten by the main host.

Individual species

Linguatula
Linguatula

IntroductionLinguatula is a genus of the phylum Pentastomida. The parasites of the Lingatula genus, also known as tongue worms, cause the rare disease Linguatulosis....
serrata is a parasite of dog
Dog

The dog is a domesticated subspecies of the Gray Wolf, a member of the Canidae family of the order Carnivora. The term is used for both feral and pet varieties....
s. The adult lives in dogs' respiratory tracts and noses. The eggs leave the host body through the dog's nasal mucus and will be ingested by small herbivores. Dogs will then be infected by free-living larvae or through the intestines of infected prey. Linguatula
Linguatula

IntroductionLinguatula is a genus of the phylum Pentastomida. The parasites of the Lingatula genus, also known as tongue worms, cause the rare disease Linguatulosis....
may also infect humans.