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Title: Pentastomida  
Author: World Heritage Encyclopedia
Language: English
Subject: Crustacean, Oncopoda, Karl Moriz Diesing, Crustacea, Arthropods
Collection: Articles Containing Video Clips, Cambrian First Appearances, Maxillopoda, Parasitic Crustaceans
Publisher: World Heritage Encyclopedia


Temporal range: Cambrian Stage 3–Recent
Adult female Linguatula serrata
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Crustacea
Class: Maxillopoda
Subclass: Pentastomida
Diesing, 1836

Pentastomida are an enigmatic group of parasitic invertebrates commonly known as tongue worms due to the resemblance of the species of the genus Linguatula to a vertebrate tongue.

There are about 130 extant species of pentastomids; all are obligate parasites with correspondingly degenerate anatomy. Adult tongue worms vary from about 1 to 14 centimetres (0.4 to 5.5 in) in length, and parasitise 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.

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


  • Biology 1
    • Anatomy 1.1
    • Life cycle 1.2
  • Human infestation 2
  • Affinities 3
    • Crustaceans 3.1
    • Stem-arthropods 3.2
  • Fossil record 4
  • Classification 5
  • References 6


Historically significant accounts of tongue worm biology and systematics include early work by Josef Aloys Frölich,[1] Alexander von Humboldt,[2] Karl Asmund Rudolphi,[3] Karl Moriz Diesing[4] and Rudolph Leuckart.[5]

Other important summaries have been published by Louis Westenra Sambon,[6] Richard Heymons[7] and John Riley,[8] and a review of their evolutionary relationships with a bibliography up to 1969 was published by J. T. Self.[9]


Pentastomids are worm-like animals ranging from 2 to 13 centimetres (0.79 to 5.12 in) in length. The anterior end of the body bears five protuberances, four of which are clawed legs, while the fifth bears the mouth. The body is segmented and covered in a chitinous cuticle. The digestive tract is simple and tubular, since the animal feeds entirely on blood, although the mouth is somewhat modified as a muscular pump.[10]

The nervous system is similar to that of other arthropods, including a ventral nerve cord with

  • M.L. Christoffersen 1, J.E. De Assis, A systematic monograph of the Recent Pentastomida, with a compilation of their host; Zoologische Mededelingen, 87 (March 2013)
  1. ^ J. A. Frölich (1789). "Beschreibung einiger neuer Eingeweidewürmer".  
  2. ^ A. von Humboldt (1811). "Sur un ver intestin trouvé dans les poumons du serpent à sonnettes, de Cumana". Voyage de Humboldt et Bonpand 2. Ptie. F. Schoell et G. Dufour, Paris. pp. 298–304. 
  3. ^ K. A. Rudolphi (1819). Entozoorum Synopsis. Augustus Rücker Berlin. 
  4. ^ K. M. Diesing (1835). "Versuch einer Monographie der Gattung Pentastoma".  
  5. ^ R. Leuckart (1860). "Bau und Entwicklungsgeschichte der Pentastomen nach Untersuchungen besonders von Pent. taenoides und P. denticulatum". C. F. Winter'sche Verlagshandlung, Leipzig. pp. vi + 160. 
  6. ^ L. W. Sambon (1922). "A synopsis of the family Linguatulidae".  
  7. ^ R. Heymons (1935). "Pentastomida". In H. G. Bronns. Klassen und Ordnungen des Tierreichs. Fünfter Band. IV Abteilung, 1. Buch. Akademische Verlagsgesellschaft m.b.H., Leipzig. pp. 1–268 pp. 
  8. ^ J. Riley (1986). "The biology of pentastomids".  
  9. ^ J. T. Self (1969). "Biological relationships of the Pentastomida: a bibliography on the Pentastomida".  
  10. ^ a b c d Barnes, Robert D. (1982). Invertebrate Zoology. Philadelphia, PA: Holt-Saunders International. pp. 880–881.  
  11. ^ A. Fain (1975). "The Pentastomida parasitic in man".  
  12. ^ H. Solano Mairena & W. Venegas (1989). "Sebekia"Human dermatitis caused by a nymph of .  
  13. ^ Correct spelling: Sebakia --> Sebekia, See WoRMS. Sambon, 1922"Sebekia".  
  14. ^ Dennis Tappe & Dietrich W. Büttner (2009). Bethony, Jeffrey M., ed. "Diagnosis of human visceral pentastomiasis".  
  15. ^ Esmond M. Mapp, Howard M. Pollack & Louis H. Goldman (May 1976). infestation (porocephalosis) in man"Armillifer armillatus"Roentgen diagnosis of .  
  16. ^ Philip E. S. Palmer; Maurice Merrick Reeder (2001). Imaging of tropical diseases: with epidemiological, pathological, and clinical correlation. Birkhäuser. pp. 389–.  
  17. ^ T. D. Schubart (1853). "Ueber die Entwicklung des Pentastoma taenioides".  
  18. ^ G. Osche (1959). ""Arthropodencharaktere" bei einem Pentastomiden Embryo (Reighhardia sernae)".  
  19. ^ P. J. van Beneden (1849). "Recherches sur l’organisation et le développement des Lingatules (Pentastoma Rud.), suivies de la description d’une espèce nouvelle provenant d’un Mandrill".  
  20. ^ K. G. Wingstrand (1972). "Comparative spermatology of a pentastomid, Raillietiella hemidactyli, and a branchiuran crustacean, Argulus foliaceus, with a discussion of pentastomid relationships".  
  21. ^ J. Riley, A. A. Banaja & J. L. James (1978). "The phylogenetic relationships of the Pentastomida: the case for their inclusion within the Crustacea".  
  22. ^ L. G. Abele, W. Kim & B. E. Felgenhauer (1989). "Molecular evidence for inclusion of the Phylum Pentastomida in the Crustacea" (PDF).  
  23. ^ D. V. Lavrov, W. M. Brown & J. L. Boore (2004). "Phylogenetic position of the Pentastomida and (pan)crustacean relationships" (PDF).  
  24. ^ O. S. Møller, J. Olesen, A. Avenant-Oldewage, P. F. Thomsen & H. Glenner (2008). "First maxillae suction discs in Branchiura (Crustacea): development and evolution in light of the first molecular phylogeny of Branchiura, Pentastomida, and other "Maxillopoda"".  
  25. ^ Todd H. Oakley, Joanna M. Wolfe, Annie R. Lindgren & Alexander K. Zaharoff (2013). "Phylotranscriptomics to bring the understudied into the fold: monophyletic Ostracoda, fossil placement, and Pancrustacean phylogeny".  
  26. ^ J. Zrzavý (2001). "The interrelationships of metazoan parasites: a review of phylum- and higher-level hypotheses from recent morphological and molecular phylogenetic analyses" (PDF).  
  27. ^ a b J. W. Martin & G. E. Davis (2001). An Updated Classification of the Recent Crustacea (PDF).  
  28. ^ Dieter Waloszek, John E. Repetski & Andreas Maas (2006). "A new Late Cambrian pentastomid and a review of the relationships of this parasitic group".  
  29. ^ W. O. Almeida, M. L. Christoffersen, D. S. Amorim & E. C. C. Eloy (2008). "Morphological support for the phylogenetic positioning of Pentastomida and related fossils" (PDF).  
  30. ^ D. Walossek & K. J. Müller (1994). "Pentastomid parasites from the Lower Palaeozoic of Sweden".  
  31. ^ a b Dieter Walossek, John E. Repetski & Klaus J. Müller (1994). "An exceptionally preserved parasitic arthropod, Heymonsicambria taylori n. sp. (Arthropoda increate sedis: Pentastomida) from Cambrian – Ordovician boundary beds of Newfoundland".  
  32. ^ Geoff Boxshall (2013). "Pentastomida".  


  • Alofia Giglioli in Sambon, 1922
  • Agema Riley et al., 1997
Female (right) and male (left) Armillifer sp.
Armillifer armillatus Wyman, 1848, a 4 cm individual collected from the respiratory system of a python, Python sebae. Specimen deposited in the Museum für Naturkunde Berlin

This article follows Martin and Davis[27] in placing Pentastomida in the class Maxillopoda within the subphylum Crustacea. The subclass contains the following extant orders, superfamilies, families, genera and species:[32]


Exceptionally preserved, three-dimensional and phosphatised fossils from the Upper Cambrian Orsten of Sweden[30] and the Cambrian/Ordovician boundary of Canada[31] have been identified as pentastomids. Four fossil genera have been identified so far: Aengapentastomum, Bockelericambria, Haffnericambria and Heymonsicambria. These fossils suggest that pentastomids evolved very early and raise questions about whether these animals were parasites at this time, and if so, on which hosts. Conodonts have sometimes been mentioned as possible hosts in this context.[31]

Fossil record

Critics of the Ichthyostraca hypothesis have pointed out that even parasitic crustaceans can still be recognised as crustaceans based on their larvae; but that tongue worms and their larvae do not express typical characters for Crustacea or even Euarthropoda. An alternative model notes the extremely ancient Cambrian origins of these animals and interprets tongue worms as stem-group arthropods.[28] A recent morphological analysis recovered Pentastomida outside the arthropods, as sister group to a clade including nematodes, priapulids and similar ecdyzoan 'worm' groups.[29] Adding fossils, they suggested an extinct animal called Facivermis could be closely related to tongue worms. However it should be stressed that these authors did not explicitly test pentastomid/crustacean relationships.


The possibility that tongue worms are sperm morphology,[20] which recognised similarities in sperm structure between tongue worms and fish lice (Argulidae) – a group of maxillipod crustaceans which live as parasites on fish and occasionally amphibians. John Riley and colleagues also offered a detailed justification for the inclusion of the tongue worms among the crustaceans.[21] The fish louse model received significant further support from the molecular work of Lawrence G. Abele and colleagues.[22] A number of subsequent molecular phylogenies have corroborated these results,[23][24][25] and the name Ichthyostraca has been proposed for a (Pentastomida + Branchiura) clade.[26] Thus a number of important standard works and databases on crustaceans now include the pentastomids as members of this group.[27]


The affinities of tongue worms have long proved controversial. Historically, they were initially compared to various groups of parasitic worms. Once the arthropod-like nature of their cuticle was recognised, similarities were drawn with mites,[17] particularly gall mites (Eriophyidae). Although gall mites are much smaller than tongue worms they also have a long, segmented body and only two pairs of legs. Later work drew comparisons with millipedes and centipedes (Myriapoda), with velvet worms (Onychophora) and water bears (Tardigrada). Some authors interpreted tongue worms as essentially intermediate between annelids and arthropods, while others suggested that they deserved a phylum of their own. Tongue worms grow by moulting, which suggests they belong to Ecdysozoa, while other work has identified the arthropod-like nature of their larvae,[18] In general, there are two current alternative interpretations: pentastomids are highly modified and parasitic crustaceans, probably related to fish lice, or they are an ancient group of stem-arthropods, close to the origins of Arthropoda.


Porocephalus and Armillifer (which are all cylindrical and all inhabit snakes) have much more in common with each other than they do with Linguatula (which is flat and inhabits dogs and wolves.)

The terms associated with infections can vary:

Tongue worms occasionally parasitise humans.[11] While there is a report of Sebekia inducing dermatitis,[12][13] the two genera responsible for most internal human infestation are Linguatula and Armillifer. Visceral pentastomiasis can be caused by Linguatula serrata, Armillifer armillatus, Armillifer moniliformis, Armillifer grandis, and Porocephalus crotali.[14]

Extraction of an Armillifer grandis nymph from a human eye.

Human infestation

The 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 larva is initially rounded in form, with four or six short legs, but moults several times to achieve the adult form. The pentastomid reaches the main host when the intermediate host is eaten by the main host, and crawls into the respiratory tract from the oesophagus.[10]

Pentastomids live in the upper respiratory tract of reptiles, birds, and mammals, where they lay eggs. They are gonochoric (having 2 sexes), and employ internal fertilisation. 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, which is commonly either a fish or a small herbivorous mammal.[10]

Life cycle


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