Pentastomida

Source: Wikipedia, the free encyclopedia.
Not to be confused with Pentatomidae.

Pentastomida
Temporal range: Wuliuan–Recent
Adult female Linguatula serrata
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Class: Ichthyostraca
Subclass: Pentastomida
Diesing
, 1836
Orders

see text

Synonyms
  • Pentastomata

The Pentastomida are an enigmatic group of

arthropods commonly known as tongue worms due to the resemblance of the species of the genus Linguatula to a vertebrate tongue; molecular studies point to them being highly-derived crustaceans.[1]

About 130 species of pentastomids are known; all are obligate parasites with correspondingly degenerate anatomy. Adult tongue worms vary from about 1 to 14 cm (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.

Taxonomy

Historically significant accounts of tongue worm biology and systematics include early work by

Rudolph Leuckart.[6]

Other important summaries have been published by Louis Westenra Sambon,[7] Richard Heymons[8] and John Riley,[9] and a review of their evolutionary relationships with a bibliography up to 1969 was published by J. T. Self.[10]

Affinities

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,

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.[12]
In general, the two current alternative interpretations are: 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.

Crustaceans

The discovery that tongue worms are

maxillopod 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.[15] The fish louse model received significant further support from the molecular work of Lawrence G. Abele and colleagues.[16] A number of subsequent molecular phylogenies have corroborated these results,[17][18][19] and the name Ichthyostraca has been proposed for a (Pentastomida + Branchiura) clade.[20] Thus a number of important standard works and databases on crustaceans now include the pentastomids as members of this group.[21]

Stem-arthropods

Critics of the Ichthyostraca classification 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

priapulids and similar ecdysozoan 'worm' groups.[23] 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.

Fossil record

Exceptionally preserved, three-dimensional and

phosphatised fossils from the Upper Cambrian Orsten of Sweden[24] and the Cambrian/Ordovician boundary of Canada[25] have been identified as pentastomids. Also one from the Wuluian (middle Cambrian) of Greenland.[26] Four fossil genera have been identified from the Cambrian 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 (primitive fish) have sometimes been mentioned as possible hosts in this context.[25] A fifth genus, Invavita, is from Silurian-aged marine strata of England: fossil specimens of Invavita are found firmly attached to their ostracod hosts of the species Nymphatelina gravida.[27][28] It possessed a head, a worm-like body, and two pairs of limbs.[29]

Classification

There are four extant orders recognised in the subclass Pentastomida:

Description

Pentastomids are worm-like animals ranging from 1 to 14 centimetres (0.39 to 5.51 in) in length. The female is larger than the male. 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, except from genus Linguatula which lives in the nasal cavity of carnivorous mammals where they feed mainly on mucus and dead cells,[30][31] although the mouth is somewhat modified as a muscular pump.[32]

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

haemocoel, no circulatory, respiratory, or excretory organs are present.[32]

Behaviour and ecology

Armillifer armillatus from a python

Pentastomids live in the upper respiratory tract of reptiles, birds, and mammals, where they lay eggs. They are

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.[32]

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

oesophagus.[32][34]

Human infestation

Extraction of an Armillifer grandis nymph from a human eye

Tongue worms occasionally parasitise humans.

Python sebae. Specimen deposited in the Natural History Museum of Berlin
.
Female (right) and male (left) Armillifer sp.

The terms associated with infections can vary:

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).

References

  1. PMID 15129965
    .
  2. ^ J. A. Frölich (1789). "Beschreibung einiger neuer Eingeweidewürmer". Der Naturforscher. 24: 101–162.
  3. ^ 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.
  4. ^ K. A. Rudolphi (1819). Entozoorum Synopsis. Augustus Rücker Berlin.
  5. ^ K. M. Diesing (1835). "Versuch einer Monographie der Gattung Pentastoma". Annalen des Wiener Museums der Naturgeschichte. 1: 1–32.
  6. ^ R. Leuckart (1860). "Bau und Entwicklungsgeschichte der Pentastomen nach Untersuchungen besonders von Pent. taenoides und P. denticulatum". C. F. Winter'sche Verlagshandlung, Leipzig: vi + 160. {{cite journal}}: Cite journal requires |journal= (help)
  7. ^ L. W. Sambon (1922). "A synopsis of the family Linguatulidae". Journal of Tropical Medicine and Hygiene. 12: 188–206, 391–428.
  8. Akademische Verlagsgesellschaft m.b.H.
    pp. 1–268 pp.
  9. PMID 3535437
    .
  10. PMID 4887218
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  11. ^ T. D. Schubart (1853). "Ueber die Entwicklung des Pentastoma taenioides". Zeitschrift für Wissenschaftliche Zoologie. 4: 117–118.
  12. ^ G. Osche (1959). ""Arthropodencharaktere" bei einem Pentastomiden Embryo (Reighhardia sernae)". Zoologischer Anzeiger. 163: 169–178.
  13. ^ 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". Annales des Sciences Naturelles Zoologie Series. 3 (11): 313–348.
  14. ^ K. G. Wingstrand (1972). "Comparative spermatology of a pentastomid, Raillietiella hemidactyli, and a branchiuran crustacean, Argulus foliaceus, with a discussion of pentastomid relationships". Det Kongelige Danske Videnskabernes Selskab Biologiske Skrifter. 19 (4): 1–72.
  15. doi:10.1016/0020-7519(78)90087-5
    .
  16. ^ L. G. Abele, W. Kim & B. E. Felgenhauer (1989). "Molecular evidence for inclusion of the Phylum Pentastomida in the Crustacea" (PDF). Molecular Biology and Evolution. 6 (6): 685–691.[dead link]
  17. PMID 15129965. Archived from the original
    (PDF) on 2015-09-23. Retrieved 2009-12-20.
  18. PMID 18394959
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  19. PMID 22977117
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  20. PMID 11437135
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  21. ^ J. W. Martin & G. E. Davis (2001). An Updated Classification of the Recent Crustacea (PDF). Natural History Museum of Los Angeles County. pp. 132 pp. Archived from the original (PDF) on 2019-09-08. Retrieved 2009-12-20.
  22. S2CID 84859920
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  23. doi:10.5007/2175-7925.2008v21n3p81
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  24. S2CID 86957051
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  25. ^
    doi:10.1139/e94-149
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  26. S2CID 249028918
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  27. ^ Gill, Victoria (22 May 2015). "A 425-million-year-old parasite found attached to host". BBC Online. Retrieved 22 May 2015.
  28. PMID 26004764
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  29. ^ "Requiem for an ancient tongue worm". Yale News. 21 May 2015. Retrieved 5 June 2015.
  30. ^ Encyclopedic Reference of Parasitology: Biology, Structure, Function
  31. ^ Characterization of tongue worms, Linguatula spp. (Pentastomida) in Romania, with the first record of an unknown adult Linguatula from roe deer (Capreolus capreolus Linnaeus)
  32. ^
    ISBN 0-03-056747-5
    .
  33. ^ Life Cycle and Life History Strategies of Parasitic Crustacea
  34. ^ Atlas of Crustacean Larvae
  35. PMID 1231664
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  36. PMID 2802021
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  37. ^ Correct spelling: Sebakia --> Sebekia, See "Sebekia Sambon, 1922". WoRMS. World Register of Marine Species.
  38. PMID 19238218
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  39. PMID 933188
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  40. ISBN 978-3-540-62471-4
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External links
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