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The Pentastomida are a group of parasitic invertebrates commonly known as tongue worms due to the resemblance of some species to a vertebrate tongue.
There are about 100 extant species of pentastomids; all are obligate parasites with correspondingly degenerate anatomy. Adult tongue worms vary from about 1 cm to 14 cm in length, and parasitize the respiratory tracts of vertebrates . They have five anterior appendages. 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, which suggests they belong to the Ecdysozoa. Historically, they were considered to deserve a phylum of their own, but in 1972, Wingstrand showed similarities in the structure of spermatozoa between pentastomids and branchiurans (fish lice), a group of parasitic crustaceans , and this relationship is supported by molecular evidence .
However, fossils from the Upper Cambrian identified as pentastomids (Heymonsicambria, Haffnericambria, Bockelericambria) suggest that the pentastomids branched very early and may be an 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 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
References
"Pentastomida"