Pentastomida#Classification

Historically significant accounts of tongue worm biology and systematics include early work by Josef Aloys Frölich,{{cite journal |author=J. A. Frölich |year=1789 |title= Beschreibung einiger neuer Eingeweidewürmer |journal=Der Naturforscher |volume=24 |pages=101–162}} Alexander von Humboldt,{{cite book |author=A. von Humboldt |year=1811 |chapter=Sur un ver intestin trouvé dans les poumons du serpent à sonnettes, de Cumana |title=Voyage de Humboldt et Bonpand 2 |publisher=Ptie. F. Schoell et G. Dufour, Paris |pages=298–304}} Karl Asmund Rudolphi,{{cite book |author=K. A. Rudolphi |year=1819 |title= Entozoorum Synopsis |publisher=Augustus Rücker Berlin}} Karl Moriz Diesing{{cite journal |author=K. M. Diesing |year=1835 |title= Versuch einer Monographie der Gattung Pentastoma |journal=Annalen des Wiener Museums der Naturgeschichte |volume=1 |pages=1–32}} and Rudolph Leuckart.{{cite journal |author=R. Leuckart |year=1860 |title= Bau und Entwicklungsgeschichte der Pentastomen nach Untersuchungen besonders von Pent. taenoides und P. denticulatum |publisher=C. F. Winter'sche Verlagshandlung, Leipzig |pages=vi + 160}}

Other important summaries have been published by Louis Westenra Sambon,{{cite journal |author=L. W. Sambon |year=1922 |title= A synopsis of the family Linguatulidae |journal=Journal of Tropical Medicine and Hygiene |volume=12 |pages=188–206, 391–428}} Richard Heymons{{cite book |author=R. Heymons |year=1935 |chapter= Pentastomida |editor=H. G. Bronns |title=Klassen und Ordnungen des Tierreichs. Fünfter Band. IV Abteilung, 1. Buch |publisher=Akademische Verlagsgesellschaft m.b.H. |location=Leipzig |pages=1–268 pp}} and John Riley,{{cite journal |author=J. Riley |year=1986 |title= The biology of pentastomids |journal=Advances in Parasitology |volume=25 |pages=45–128 |doi=10.1016/S0065-308X(08)60342-5|pmid=3535437 |isbn=9780120317257 }} and a review of their evolutionary relationships with a bibliography up to 1969 was published by J. T. Self.{{cite journal |author=J. T. Self |year=1969 |title= Biological relationships of the Pentastomida: a bibliography on the Pentastomida |journal=Experimental Parasitology |volume= 24|pages=63–119 |doi=10.1016/0014-4894(69)90222-7 |pmid=4887218 |issue=1}}

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 recognized, similarities were drawn with mites,{{cite journal |author=T. D. Schubart |year=1853 |title= Ueber die Entwicklung des Pentastoma taenioides |journal=Zeitschrift für Wissenschaftliche Zoologie |volume=4 |pages=117–118}} 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{{citation needed|date=July 2021}} drew comparisons with millipedes and centipedes (Myriapoda), with velvet worms (Onychophora) and water bears (Tardigrada). Some authors{{citation needed|date=July 2021}} 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.{{cite journal |author=G. Osche |year=1959 |title= "Arthropodencharaktere" bei einem Pentastomiden Embryo (Reighhardia sernae) |journal=Zoologischer Anzeiger |volume=163 |pages=169–178}} In general, the two current alternative interpretations are: pomatomids 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.

The discovery that tongue worms are crustaceans can be traced back to the work of Pierre-Joseph Van Beneden,{{cite journal |author=P. J. van Beneden |year=1849 |title= Recherches sur l'organisation et le développement des Lingatules (Pentastoma Rud.), suivies de la description d'une espèce nouvelle provenant d'un Mandrill |journal=Annales des Sciences Naturelles Zoologie Series |volume=3 |issue=11 |pages=313–348}} who compared them to parasitic copepods. The modern form of this hypothesis dates from Karl Georg Wingstrand's study of sperm morphology,{{cite journal |author=K. G. Wingstrand |year=1972 |title= Comparative spermatology of a pentastomid, Raillietiella hemidactyli, and a branchiuran crustacean, Argulus foliaceus, with a discussion of pentastomid relationships |journal=Det Kongelige Danske Videnskabernes Selskab Biologiske Skrifter |volume=19 |issue=4 |pages=1–72}} which recognized similarities in sperm structure between tongue worms and fish lice (Argulidae) – a group of 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.{{cite journal |author=J. Riley, A. A. Banaja & J. L. James |year=1978 |title=The phylogenetic relationships of the Pentastomida: the case for their inclusion within the Crustacea |journal=International Journal for Parasitology |volume=8 |issue=4 |pages=245–254 |doi=10.1016/0020-7519(78)90087-5}} The fish louse model received significant further support from the molecular work of Lawrence G. Abele and colleagues.{{cite journal |author=L. G. Abele, W. Kim & B. E. Felgenhauer |year=1989 |title= Molecular evidence for inclusion of the Phylum Pentastomida in the Crustacea |journal=Molecular Biology and Evolution |volume=6 |pages=685–691 |url=http://mbe.oxfordjournals.org/cgi/reprint/6/6/685.pdf |issue=6}}{{dead link|date=May 2021|bot=medic}}{{cbignore|bot=medic}} A number of subsequent molecular phylogenies have corroborated these results,{{cite journal |author=D. V. Lavrov, W. M. Brown & J. L. Boore |year=2004 |title=Phylogenetic position of the Pentastomida and (pan)crustacean relationships |journal=Proceedings of the Royal Society of London B |volume=271 |pages=537–544 |url=http://www.eeob.iastate.edu/faculty/LavrovD/publications/PDF_files/pentastomida.pdf |doi=10.1098/rspb.2003.2631 |pmid=15129965 |issue=1538 |pmc=1691615 |access-date=2009-12-20 |archive-date=2015-09-23 |archive-url=https://web.archive.org/web/20150923234055/http://www.eeob.iastate.edu/faculty/LavrovD/publications/PDF_files/pentastomida.pdf |url-status=dead }}{{cite journal |author1=O. S. Møller |author2=J. Olesen |author3=A. Avenant-Oldewage |author4=P. F. Thomsen |author5=H. Glenner |year=2008 |title=First maxillae suction discs in Branchiura (Crustacea): development and evolution in light of the first molecular phylogeny of Branchiura, Pentastomida, and other "Maxillopoda" |journal=Arthropod Structure & Development |volume=37 |issue=4 |pages=333–346 |doi=10.1016/j.asd.2007.12.002 |pmid=18394959|bibcode=2008ArtSD..37..333M }}{{cite journal |author1=Todd H. Oakley |author2=Joanna M. Wolfe |author3=Annie R. Lindgren |author4=Alexander K. Zaharoff |year=2013 |title=Phylotranscriptomics to bring the understudied into the fold: monophyletic Ostracoda, fossil placement, and Pancrustacean phylogeny |journal=Molecular Biology and Evolution |volume=30 |issue=1 |pages=215–233 |pmid=22977117 |doi=10.1093/molbev/mss216|url=http://pdxscholar.library.pdx.edu/cgi/viewcontent.cgi?article=1050&context=bio_fac |doi-access=free |url-access=subscription }} and the name Ichthyostraca has been proposed for a (Pentastomida + Branchiura) clade.{{cite journal |author=J. Zrzavý |year=2001 |title=The interrelationships of metazoan parasites: a review of phylum- and higher-level hypotheses from recent morphological and molecular phylogenetic analyses |journal=Folia Parasitologica |volume=48 |issue=2 |pages=81–103 |doi=10.14411/fp.2001.013 |pmid=11437135 |doi-access=free}} Thus a number of important standard works and databases on crustaceans now include the pomatomids as members of this group.{{cite book |url=http://atiniui.nhm.org/pdfs/3839/3839.pdf |title=An Updated Classification of the Recent Crustacea |author1=J. W. Martin |author2=G. E. Davis |name-list-style=amp |year=2001 |pages=132 pp |publisher=Natural History Museum of Los Angeles County |access-date=2009-12-20 |archive-date=2019-09-08 |archive-url=https://web.archive.org/web/20190908234116/https://atiniui.nhm.org/pdfs/3839/3839.pdf |url-status=dead }}

Critics of the Ichthyostraca classification have pointed out that even parasitic crustaceans can still be recognized 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.{{cite journal |author=Dieter Waloszek, John E. Repetski & Andreas Maas |year=2006 |title= A new Late Cambrian pentastomid and a review of the relationships of this parasitic group |journal=Transactions of the Royal Society of Edinburgh: Earth Sciences |volume=96 |issue=2 |pages=163–176 |doi=10.1017/S0263593300001280|s2cid=84859920 }} A 2008 morphological analysis recovered Pentastomida outside the arthropods, as sister group to a clade including nematodes, priapulids and similar ecdysozoan 'worm' groups.{{cite journal |author1=W. O. Almeida |author2=M. L. Christoffersen |author3=D. S. Amorim |author4=E. C. C. Eloy |year=2008 |title=Morphological support for the phylogenetic positioning of Pentastomida and related fossils |journal=Biotemas |volume=21 |issue=3 |pages=81–90 |doi=10.5007/2175-7925.2008v21n3p81 |doi-access=free}} 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.

Exceptionally preserved, three-dimensional and phosphatised fossils from the Upper Cambrian Orsten of Sweden{{

cite journal |author1=D. Walossek |author2=K. J. Müller |name-list-style=amp |year=1994 |title= Pentastomid parasites from the Lower Palaeozoic of Sweden |journal=Transactions of the Royal Society of Edinburgh: Earth Sciences |volume=85 |pages=1–37 |doi=10.1017/s0263593300006295

|s2cid=86957051 }} and the Cambrian/Ordovician boundary of Canada{{cite journal |

author=Dieter Walossek, John E. Repetski & Klaus J. Müller |year=1994 |title= An exceptionally preserved parasitic arthropod, Heymonsicambria taylori n. sp. (Arthropoda increate sedis: Pentastomida) from Cambrian – Ordovician boundary beds of Newfoundland |journal=Canadian Journal of Earth Sciences |volume=31 |issue=11 |pages=1664–1671 |doi=10.1139/e94-149

}} have been identified as pentastomids. Also one from the Wuluian (middle Cambrian) of Greenland.{{cite journal

| doi = 10.1080/11035897.2022.2064543

| title = The oldest tongue worm: A stem-group pentastomid arthropod from the early middle Cambrian (Wuliuan Stage) of North Greenland (Laurentia)

| year = 2022

| last1 = Peel

| first1 = John S.

| journal = GFF

| volume = 144

| issue = 2

| pages = 97–105

| s2cid = 249028918

| doi-access = free

| bibcode = 2022GFF...144...97P

}} Four fossil genera have been identified from the Cambrian so far: Aengapentastomum, Boeckelericambria, Dietericambria, 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. 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.{{cite web | url=https://www.bbc.co.uk/news/science-environment-32829628 | title=A 425-million-year-old parasite found attached to host | last=Gill| first=Victoria | date=22 May 2015 | work=BBC Online|access-date=22 May 2015}}{{Cite journal | doi=10.1016/j.cub.2015.04.035| last1=Siveter| first1=David J.| last2=Briggs | first2=Derek E.G. | last3=Siveter | first3=Derek J.| last4=Sutton| first4=Mark D.| title=A 425-Million-Year-Old Silurian Pentastomid Parasitic on Ostracods| journal=Current Biology| volume=25 | issue=12| pages=1632–1637 | pmid=26004764| year=2015| doi-access=free| bibcode=2015CBio...25.1632S| hdl=10044/1/23597| hdl-access=free}} It possessed a head, a worm-like body, and two pairs of limbs.{{Cite web | title=Requiem for an ancient tongue worm | url=http://news.yale.edu/2015/05/21/requiem-ancient-tongue-worm | website=Yale News | date=21 May 2015 | access-date=5 June 2015}}

There are four extant orders recognized in the subclass Pentastomida:

• Cephalobaenida
• Porocephalida
• Raillietiellida
• Reighardiida

Pentastomids are worm-like animals ranging from {{convert|1|to|14|cm|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,{{cite book | url=https://books.google.com/books?id=9uGQnKdxhyUC&dq=%22if+they+are+living+in+the+nasopharyngeal+cavity+of+mammals%22&pg=PA474 | title=Encyclopedic Reference of Parasitology: Biology, Structure, Function | isbn=978-3-540-66819-0 | last1=Mehlhorn | first1=Heinz | date=21 May 2001 | publisher=Springer }}{{cite journal | doi=10.1007/s00436-022-07566-9 | title=Characterization of tongue worms, Linguatula SPP. (Pentastomida) in Romania, with the first record of an unknown adult Linguatula from roe deer (Capreolus capreolus Linnaeus) | date=2022 | last1=Barton | first1=Diane P. | last2=Gherman | first2=Calin Mircea | last3=Zhu | first3=Xiaocheng | last4=Shamsi | first4=Shokoofeh | journal=Parasitology Research | volume=121 | issue=8 | pages=2379–2388 | pmid=35689112 | pmc=9279206 }} although the mouth is somewhat modified as a muscular pump.{{cite book |author= Barnes, Robert D. |year=1982 |title= Invertebrate Zoology |publisher= Holt-Saunders International |location= Philadelphia, PA|pages= 880–881|isbn= 0-03-056747-5}}

The nervous system is similar to that of other arthropods, including a ventral nerve cord with ganglia in each segment. Although the body contains a haemocoel, no circulatory, respiratory, or excretory organs are present.

File:Pentastomum_armillatum.png from a python]]

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

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. At least one species, Subtriquetra subtriquetra, has a free-living larva.{{cite book | pmc=7124122 | date=2019 | last1=Williams Jr | first1=E. H. | last2=Bunkley-Williams | first2=L. | chapter=Life Cycle and Life History Strategies of Parasitic Crustacea | title=Parasitic Crustacea | series=Zoological Monographs | volume=3 | pages=179–266 | doi=10.1007/978-3-030-17385-2_5 | isbn=978-3-030-17383-8 }} There is both indirect development with nymphal stages and direct development. 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.{{cite book | url=https://books.google.com/books?id=PPnZAwAAQBAJ&dq=pentastomida+1+species+has+a+free-living+larva&pg=PA135 | title=Atlas of Crustacean Larvae | isbn=978-1-4214-1198-9 | last1=Martin | first1=Joel W. | last2=Olesen | first2=Jørgen | last3=Høeg | first3=Jens T. | date=July 2014 | publisher=JHU Press }}

File:Ocular-Pentastomiasis-in-the-Democratic-Republic-of-the-Congo-pntd.0003041.s001.ogv nymph from a human eye]]

Tongue worms occasionally parasitise humans.{{cite journal |author=A. Fain |year=1975 |title= The Pentastomida parasitic in man |journal=Annales de la Société Belge de Médecine Tropicale |volume=55 |issue=1 |pages=59–64|pmid=1231664 }} While a report exists of Sebekia inducing dermatitis,{{cite journal |author1=H. Solano Mairena |author2=W. Venegas |name-list-style=amp |year=1989 |title= Human dermatitis caused by a nymph of Sebekia |journal=American Journal of Tropical Medicine and Hygiene |volume=41 |pages=352–354 |pmid=2802021 |issue=3|doi=10.4269/ajtmh.1989.41.352 }}Correct spelling: Sebakia --> Sebekia, See {{cite WoRMS |id=384727 |title=Sebekia Sambon, 1922 }} 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.{{cite journal |author=Dennis Tappe & Dietrich W. Büttner |editor1-last=Bethony |editor1-first=Jeffrey M. |title=Diagnosis of human visceral pentastomiasis |journal=PLOS Neglected Tropical Diseases |volume=3 |issue=2 |pages=e320 |year=2009 |pmid=19238218 |pmc=2643528 |doi=10.1371/journal.pntd.0000320 |doi-access=free }}File:Armillifer armillatus.jpg. Specimen deposited in the Natural History Museum of Berlin.]]

File:Armillifer.jpg sp.]]

The terms associated with infections can vary:

• Linguatula disease can be called linguatuliasis or linguatulosis.
• Porocephalus disease can be called porocephaliasis or porocephalosis.
• Armillifer disease can also be called porocephalosis.{{cite journal |author=Esmond M. Mapp, Howard M. Pollack & Louis H. Goldman |title=Roentgen diagnosis of Armillifer armillatus infestation (porocephalosis) in man |journal=Journal of the National Medical Association |volume=68 |issue=3 |pages=198–200, 191 |date=May 1976 |pmid=933188 |pmc=2609651 }} (An alternate name for Armillifer moniliformis is Porocephalus moniliformis.){{cite book|author1=Philip E. S. Palmer|author2=Maurice Merrick Reeder|title=Imaging of tropical diseases: with epidemiological, pathological, and clinical correlation|url=https://books.google.com/books?id=b3_RMZl464cC&pg=PA389|access-date=19 April 2010|year=2001|publisher=Birkhäuser|isbn=978-3-540-62471-4|pages=389–}}
• "Pentastomiasis" can refer to any infection of Pentastomida.

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).

{{Reflist|32em}}

• {{Cite EB1911|wstitle=Pentastomida|short=x}}

{{Arthropods}}

{{Arthropod infestations}}

{{Animalia}}

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Category:Arthropod subclasses

Category:Parasitic crustaceans

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Category:Extant Cambrian first appearances