View source for Acanthocephala

{{Short description|Group of parasitic thorny-headed worms}}
{{Other uses}}
{{Use mdy dates|date=April 2012}}
{{Automatic taxobox
|oldest_fossil=Middle Jurassic
|image=C wegeneri.JPG
|image_caption=''[[Corynosoma wegeneri]]''
|display_parents=8
|taxon=Acanthocephala
|authority=[[Koelreuter]], 1771<ref name="crompton"/><ref name=koelreuter>{{cite journal |last=Koelreuter |first=I. T. |year=1770 |title=Descriptio cyprini rutili, quem halawel russi vocant, historico-anatomica. |journal=Novi Commentarii Academiae Scientiarum Imperialis Petropolitanae |volume=15 |pages=494–503 |url=https://www.biodiversitylibrary.org/item/38626#page/560/mode/1up}}</ref>
|subdivision_ranks=Classes
|subdivision=* [[Archiacanthocephala]]
* [[Eoacanthocephala]]
* [[Palaeacanthocephala]]
* [[Polyacanthocephala]]
}}

'''Acanthocephala''' {{IPAc-en|ə|ˌ|k|æ|n|θ|oʊ|ˈ|s|ɛ|f|ə|l|ə}}<ref>{{OED|acanthocephalan}}</ref> ([[Greek language|Greek]] {{lang|el|[[:wikt:ἄκανθος|ἄκανθος]]}}, ''{{lang|el|akanthos}}'' 'thorn' + {{lang|el|[[:wikt:κεφαλή|κεφαλή]]}}, ''{{lang|el|kephale}}'' 'head') is a group of [[parasitic worm]]s known as '''acanthocephalans''', '''thorny-headed worms''', or '''spiny-headed worms''', characterized by the presence of an [[wiktionary:evert|eversible]] [[proboscis]], armed with spines, which it uses to pierce and hold the [[Gut (zoology)|gut]] wall of its host. Acanthocephalans have [[Parasitic life cycles|complex life cycles]], involving at least two hosts, which may include [[invertebrate]]s, fish, [[amphibian]]s, birds, and [[mammal]]s.<ref name="Perrot-Minnot2023">{{cite journal | last1=Perrot-Minnot | first1=Marie-Jeanne | last2=Cozzarolo | first2=Camille-Sophie | last3=Amin | first3=Omar | last4=Barčák | first4=Daniel | last5=Bauer | first5=Alexandre | last6=Filipović Marijić | first6=Vlatka | last7=García-Varela | first7=Martín | last8=Servando Hernández-Orts | first8=Jesús | last9=Yen Le | first9=T.T. | last10=Nachev | first10=Milen | last11=Orosová | first11=Martina | last12=Rigaud | first12=Thierry | last13=Šariri | first13=Sara | last14=Wattier | first14=Rémi | last15=Reyda | first15=Florian | last16=Sures | first16=Bernd | title=Hooking the scientific community on thorny-headed worms: interesting and exciting facts, knowledge gaps and perspectives for research directions on Acanthocephala | journal=Parasite | volume=30 | year=2023| doi=10.1051/parasite/2023026 | page=23| pmid=37350678 | pmc=10288976 }} {{open access}}</ref><ref name="de BuronGolvan2016">{{cite journal|last1=de Buron|first1=I.|last2=Golvan|first2=Y. J.|title=Les hôtes des Acanthocéphales. I — Les Hôtes intermédiaires|journal=Annales de Parasitologie Humaine et Comparée|volume=61|issue=5|year=1986|pages=581–592|issn=0003-4150|doi=10.1051/parasite/1986615581|doi-access=free}} {{open access}}</ref><ref name="GolvanDe Buron2016">{{cite journal|last1=Golvan|first1=Y. J.|last2=De Buron|first2=I.|title=Les hôtes des Acanthocéphales. II — Les hôtes définitifs. 1. Poissons|journal=Annales de Parasitologie Humaine et Comparée|volume=63|issue=5|year=1988|pages=349–375|issn=0003-4150|doi=10.1051/parasite/1988635349|pmid=3059956|doi-access=free}} {{open access}}</ref><ref name="robertslifecycle">{{cite book|last1=Roberts|first1=Larry S.|last2=Janovy |first2=John Jr.|title=Foundations of Parasitology|edition=Eighth|year=2009|publisher=McGraw-Hill|isbn=978-0-07-302827-9|page=502}}</ref> About 1,420 [[species]] have been described.<ref>Freeman, Scott, Lizabeth Allison, Michael Black, Greg Podgorski, and Kim Quillin. Biological Sciences. 5th ed. Glenview, Il: Pearson, 2014. 638. Print.</ref><ref>{{citation |url=http://eol.org/pages/2/details |title=Encyclopedia of Life |access-date=24 July 2015}}</ref>

The Acanthocephala were long thought to be a discrete [[phylum (biology)|phylum]]. Recent [[genome]] analysis has shown that they are descended from, and should be considered as, highly modified [[rotifer]]s.<ref name="shimek">{{cite web |url=http://reefkeeping.com/issues/2006-01/rs/index.php |author=Shimek, Ronald |access-date =July 27, 2008 |title=Nano-Animals, Part I: Rotifers |publisher=Reefkeeping.com |date=January 2006 }}</ref> This unified taxon is sometimes known as [[Syndermata]], or simply as Rotifera, with the acanthocephalans described as a subclass of a rotifer class Hemirotatoria.<ref>{{Cite book |last1=Giribet |first1=Gonzalo |title=The invertebrate tree of life |last2=Edgecombe |first2=Gregory D. |date=2020 |publisher=Princeton University Press |isbn=978-0-691-17025-1}}</ref>

== History ==

The earliest recognisable description of Acanthocephala – a worm with a proboscis armed with hooks – was made by Italian author [[Francesco Redi]] (1684).<ref name="crompton">{{cite book |last1=Crompton |first1=David |last2=Thomasson |first2=William |last3=Nickol |first3=Brent B. |year=1985 |title=Biology of the Acanthocephala |publisher=[[Cambridge University Press]] |page=27 |isbn=978-0-521-24674-3 |url=https://books.google.com/books?id=GPY8AAAAIAAJ&pg=PA27 }}</ref> In 1771, [[Joseph Koelreuter]] proposed the name Acanthocephala.<ref name="crompton"/> [[Philipp Ludwig Statius Müller]] independently called them ''Echinorhynchus'' in 1776.<ref name="crompton"/> [[Karl Rudolphi]] in 1809 formally named them Acanthocephala.

== Evolutionary history ==

The oldest known member of the group is the [[Middle Jurassic]] (living approximately 165 million years ago) taxon ''[[Juracanthocephalus|Juracanthocephalus daohugouensis]]'' known from the [[Jiulongshan Formation]] ([[China]]).<ref>{{Cite journal|last1=Luo |first1=C. |last2=Parry |first2=L. A. |last3=Boudinot |first3=B. E. |last4=Wang |first4=S. |last5=Jarzembowski |first5=E. A. |last6=Zhang |first6=H. |last7=Wang |first7=B. |year=2025 |title=A Jurassic acanthocephalan illuminates the origin of thorny-headed worms |journal=Nature |pages=1–7 |doi=10.1038/s41586-025-08830-5 }}</ref> The fossil record of the group also includes eggs found in a [[coprolite]] from the [[Late Cretaceous]] [[Bauru Group]] of Brazil, around 70–80 million years old, likely from a [[Crocodyliformes|crocodyliform]]. The group may have originated substantially earlier.<ref>{{Cite journal |last1=Cardia |first1=Daniel F. F. |last2=Bertini |first2=Reinaldo J. |last3=Camossi |first3=Lucilene G. |last4=Letizio |first4=Luiz A. |date=2019-05-06 |title=First record of Acanthocephala parasites eggs in coprolites preliminary assigned to Crocodyliformes from the Adamantina Formation (Bauru Group, Upper Cretaceous), São Paulo, Brazil |journal=Anais da Academia Brasileira de Ciências|language=en |volume=91|issue=Supplement 2 |article-number=e20170848 |doi=10.1590/0001-3765201920170848|pmid=31090797 |s2cid=155091017 |issn=0001-3765 |doi-access=free|hdl=11449/189712 |hdl-access=free }}</ref>

== Phylogeny ==
{{See also|List of bilaterian orders}}
Acanthocephalans are highly adapted to a parasitic mode of life, and have lost many organs and structures through evolutionary processes. This makes determining relationships with other higher taxa through morphological comparison problematic. A 2016 [[Phylogeny|phylogenetic]] analysis of the gene order in the mitochondria suggests that Seisonidea and Acanthocephala are sister clades and that the Eurotatoria are the sister clade to this group, producing the cladogram below.<ref name=Sielaff2015>{{cite journal |last1=Sielaff |first1=M. |last2=Schmidt |first2=H. |last3=Struck |first3=T. H. |last4=Rosenkranz |first4=D. |last5=Mark Welch |first5=D. B. |last6=Hankeln |first6=T |last7=Herlyn |first7=H. |date=March 2016 |title=Phylogeny of Syndermata (syn. Rotifera): Mitochondrial gene order verifies epizoic ''Seisonidea'' as sister to endoparasitic ''Acanthocephala'' within monophyletic ''Hemirotifera'' |journal=Molecular Phylogenetics and Evolution |volume=96 |pages= 79–92|doi=10.1016/j.ympev.2015.11.017 |pmid=26702959 |bibcode=2016MolPE..96...79S }}</ref>

{{clade|{{clade
|label1=[[Syndermata]]
|1={{clade
   |1=[[Seisonida]]
   |2='''Acanthocephala'''
   }}
|label2=[[Eurotatoria]]
|2={{clade
   |1=[[Bdelloidea]]
   |2=[[Monogononta]]
   }}
}}|style=line-height:100%}}

==Morphology==
{{More citations needed section|date=March 2021}}

[[File:Corynosoma drawing.jpg|thumb|left|alt=Diagram of Acanthocephalan morphology|Some key features of acanthocephalan morphology]]

Several morphological characteristics distinguish acanthocephalans from other phyla of parasitic worms.

===Digestion===

Acanthocephalans lack a mouth or [[alimentary canal]]. This is a feature they share with the [[cestoda]] (tapeworms), although the two groups are not closely related. Adult stages live in the [[intestine]]s of their host and uptake nutrients which have been [[digestion|digested]] by the host, directly, through their body surface. The acanthocephalans lack an excretory system, although some species have been shown to possess [[flame cell]]s (protonephridia).

===Proboscis===

[[File:Parasite140083-fig5 Figs 31-36 Cathayacanthus spinitruncatus.tif|thumb|Scanning electron microscopy of proboscis of ''[[Cathayacanthus spinitruncatus]]''<ref>{{cite journal |last1=Amin |first1=O. A |last2=Heckmann |first2=R. A |last3=Ha |first3=N. V. |year=2014 |title=Acanthocephalans from fishes and amphibians in Vietnam, with descriptions of five new species |journal=Parasite |volume=21 |page=53 |doi=10.1051/parasite/2014052 |pmid=25331738 |pmc=4204126}} {{open access}}</ref>]]

The most notable feature of the acanthocephala is the presence of an [[anterior]], protrudable [[proboscis]] that is usually covered with spiny hooks (hence the common name: thorny or spiny headed worm). The proboscis bears rings of recurved hooks arranged in horizontal rows, and it is by means of these hooks that the animal attaches itself to the tissues of its host. The hooks may be of two or three shapes, usually: longer, more slender hooks are arranged along the length of the proboscis, with several rows of more sturdy, shorter nasal hooks around the base of the proboscis. The proboscis is used to pierce the gut wall of the final host, and hold the parasite fast while it completes its life cycle.

Like the body, the proboscis is hollow, and its cavity is separated from the body cavity by a ''septum'' or ''proboscis sheath''. Traversing the cavity of the proboscis are [[muscle]]-strands inserted into the tip of the proboscis at one end and into the septum at the other.  Their contraction causes the proboscis to be invaginated into its cavity. The whole proboscis apparatus can also be, at least partially, withdrawn into the body cavity, and this is effected by two retractor muscles which run from the posterior aspect of the septum to the body wall.

Some of the acanthocephalans (perforating acanthocephalans) can insert their proboscis in the intestine of the host and open the way to the abdominal cavity.<ref name="Parasites World" >{{cite web |title=Acanthocephalans drilling Acipenser stellatus intestine |publisher=Parasites World |url=http://parasites-world.com/acanthocephalns-drilling-acipenser-stellatus-intestine/ |access-date=August 3, 2009 |archive-date=April 30, 2012 |archive-url=https://web.archive.org/web/20120430062051/http://parasites-world.com/acanthocephalns-drilling-acipenser-stellatus-intestine/ }}</ref>

=== Size ===

The size of these animals varies greatly, ranging from a few millimetres in length to ''[[Macracanthorhynchus hirudinaceus]]'', which measures from {{convert|10|to|65|cm|in}}. A curious feature shared by both larva and adult is the large size of many of the cells, e.g. the nerve cells and cells forming the uterine bell. [[Polyploid]]y is common, with up to 343n having been recorded in some species.

===Skin===

The body surface of the acanthocephala is peculiar. Externally, the skin has a thin [[tegument (helminth)|tegument]] covering  the [[Squamous epithelium|epidermis]], which consists of a [[syncytium]] with no [[cell wall]]s. The syncytium is traversed by a series of branching [[tubule]]s containing fluid and is controlled by a few wandering, [[amoeboid]] [[cell nucleus|nuclei]]. Inside the syncytium is an irregular layer of circular muscle fibres, and within this again some rather scattered longitudinal fibres; there is no [[endothelium]]. In their micro-structure the muscular fibres resemble those of [[nematode]]s.

Except for the absence of the longitudinal fibres the skin of the proboscis resembles that of the body, but the fluid-containing tubules of the proboscis are shut off from those of the body. The canals of the proboscis open into a circular vessel which runs round its base. From the circular canal two sac-like projections called the ''lemnisci'' run into the cavity of the body, alongside the proboscis cavity. Each consists of a prolongation of the syncytial material of the proboscis skin, penetrated by canals and sheathed with a muscular coat. They seem to act as reservoirs into which the fluid which is used to keep the proboscis "erect" can withdraw when it is retracted, and from which the fluid can be driven out when it is wished to expand the proboscis.

===Nervous system===
The central ganglion of the nervous system lies behind the proboscis sheath or septum. It innervates the proboscis and projects two stout trunks posteriorly which supply the body.  Each of these trunks is surrounded by muscles, and this nerve-muscle complex is called a ''retinaculum''. In the male at least there is also a [[genital]] [[ganglion]]. Some scattered [[wiktionary:Papilla|papillae]] may possibly be sense-organs.

==Life cycles==
{{More citations needed section|date=March 2021}}
[[File:Acanthocephalan life cycle.jpg|thumb|right|A diagram of the life cycle of ''Polymorphus'' spp.]]
Acanthocephalans have complex life cycles, involving a number of hosts, for both [[morphogenesis|developmental]] and resting stages. Complete life cycles have been worked out for only 25 species.<ref name="Perrot-Minnot2023" />

===Reproduction===

The Acanthocephala are [[dioecious]] (an individual organism is either male or female). There is a structure called the ''genital ligament'' which runs from the posterior end of the proboscis sheath to the posterior end of the body. In the male, two [[testes]] lie on either side of this. Each opens in a [[vas deferens]] which bears three [[diverticula]] or ''vesiculae seminales''. The male also possesses three pairs of cement glands, found behind the testes, which pour their secretions through a duct into the vasa deferentia. These unite and end in a [[penis]] which opens posteriorly.

In the female, the [[ovaries]] are found, like the testes, as rounded bodies along the ligament. From the ovaries, masses of [[ovum|ova]] dehisce into the body cavity, floating in its fluids for [[fertilize|fertilization]] by male's sperm. After fertilization, each egg contains a developing [[embryo]]. (These embryos hatch into first stage [[larva]].) The fertilized eggs are brought into the [[uterus]] by actions of the ''uterine bell'', a funnel like opening continuous with the uterus. At the junction of the bell and the uterus there is a second, smaller opening situated [[Dorsum (biology)|dorsally]]. The bell "swallows" the matured eggs and passes them on into the uterus. (Immature embryos are passed back into the body cavity through the dorsal opening.) From the uterus, mature eggs leave the female's body via her [[oviduct]], pass into the host's alimentary canal and are expelled from the host's body within [[feces]].

===Release===
[[File:Acanthocephala Pomphorhynchus.jpg|left|thumb|Adult ''[[Pomphorhynchus]]'' in a [[bluefish]]]]
Having been expelled by the female, the acanthocephalan egg is released along with the feces of the host. For development to occur, the egg, containing the [[acanthor]], needs to be ingested by an [[arthropod]], usually a [[crustacean]] (there is one known life cycle which uses a [[Mollusca|mollusc]] as a first intermediate host). Inside the intermediate host, the acanthor is released from the egg and develops into an acanthella.  It then penetrates the gut wall, moves into the body cavity, encysts, and begins transformation into the infective [[cystacanth]] stage. This form has all the organs of the adult save the reproductive ones.

The parasite is released when the first intermediate host is ingested. This can be by a suitable final host, in which case the cystacanth develops into a mature adult, or by a [[paratenic]] host, in which the parasite again forms a cyst. When consumed by a suitable final host, the cycstacant ''excysts'', everts its proboscis and pierces the gut wall. It then feeds, grows and develops its sexual organs. Adult worms then mate. The male uses the excretions of its ''cement glands'' to plug the [[vagina]] of the female, preventing subsequent matings from occurring. Embryos develop inside the female, and the life cycle repeats.

===Host control===

Thorny-headed worms begin their life cycle inside invertebrates that reside in marine or freshwater systems.  One example is ''Polymorphus paradoxus.''  ''[[Gammarus lacustris]]'', a small crustacean that inhabits ponds and rivers, is one invertebrate that  ''P. paradoxus'' may occupy; ducks are one of the [[Parasitism|definitive hosts]].

This crustacean is preyed on by ducks and hides by avoiding light and staying away from the surface.  However, infection by ''P. paradoxus'' changes its behavior and appearance in a number of ways that increase its chance of being eaten.  First, infection significantly reduces ''G. lacustris'''s photophobia; as a result, it becomes attracted toward light and swims to the surface.<ref name=":0">{{Cite journal |last1=Bethel |first1=William M. |last2=Holmes |first2=John C. |date=1973 |title=Altered Evasive Behavior and Responses to Light in Amphipods Harboring Acanthocephalan Cystacanths |journal=The Journal of Parasitology |volume=59 |issue=6 |pages=945–956 |doi=10.2307/3278623 |jstor=3278623 |issn=0022-3395}}</ref> Second, an infected organism will even go so far as to find a rock or a plant on the surface, clamp its mouth down, and latch on, making it easy prey for the duck.<ref name=":0" />  Finally, infection reduces the pigment distribution and amount in ''G. lacustris,'' causing the host to turn blue; unlike their normal brown colour, this makes the crustacean stand out and increases the chance the duck will see it.<ref>{{Cite journal |last=Hindsbo |first=Ole |date=August 1972 |title=Effects of Polymorphus (Acanthocephala) on Colour and Behaviour of Gammarus lacustris |url=https://www.nature.com/articles/238333a0 |journal=Nature |language=en |volume=238 |issue=5363 |page=333 |doi=10.1038/238333a0 |bibcode=1972Natur.238..333H |issn=0028-0836}}</ref>

Experiments have shown that altered serotonin levels are likely responsible for at least some of these changes in behaviour.  One experiment found that serotonin induces clinging behavior in ''G. lacustris'' similar to that seen in infected organisms.<ref>{{Cite journal |last1=Helluy |first1=Simone |last2=Holmes |first2=John C. |date=1990-06-01 |title=Serotonin, octopamine, and the clinging behavior induced by the parasite Polymorphus paradoxus (Acanthocephala) in Gammarus lacustris (Crustacea) |url=http://www.nrcresearchpress.com/doi/10.1139/z90-181 |journal=Canadian Journal of Zoology |language=en |volume=68 |issue=6 |pages=1214–1220 |doi=10.1139/z90-181 |bibcode=1990CaJZ...68.1214H |issn=0008-4301|url-access=subscription }}</ref>  Another showed that infected ''G. lacustris'' had approximately 3 times as many [[serotonin]]-producing sites in its ventral nerve cord.<ref>{{Cite journal |last1=Maynard |first1=Barbara J. |last2=DeMartini |first2=Laura |last3=Wright |first3=William G. |date=1996 |title=Gammarus lacustris Harboring Polymorphus paradoxus Show Altered Patterns of Serotonin-like Immunoreactivity |journal=The Journal of Parasitology |volume=82 |issue=4 |pages=663–666 |doi=10.2307/3283801 |jstor=3283801 |pmid=8691384 |issn=0022-3395}}</ref> Furthermore, experiments in closely-related species of ''Polymorphus'' and ''Pomphorhynchus'' infecting other ''Gammarus'' species confirmed this relation: infected organisms were considerably more attracted to light and had higher serotonin levels, while the phototropism could be duplicated by injections of serotonin.<ref>{{Cite journal |last1=Tain |first1=Luke |last2=Perrot-Minnot |first2=Marie-Jeanne |last3=Cézilly |first3=Frank |date=2006-12-22 |title=Altered host behaviour and brain serotonergic activity caused by acanthocephalans: evidence for specificity |journal=Proceedings of the Royal Society B: Biological Sciences |language=en |volume=273 |issue=1605 |pages=3039–3045 |doi=10.1098/rspb.2006.3618 |issn=0962-8452 |pmc=1679890 |pmid=17015346}}</ref>

=== Effects on hosts ===
''[[Polymorphus]]'' spp. are parasites of [[seabirds]], particularly the [[eider duck]] (''Somateria mollissima''). Heavy infections of up to 750 parasites per bird are common, causing [[Peptic ulcer|ulceration]] to the gut, disease and seasonal mortality. Recent research has suggested that there is no evidence of [[pathogen]]icity of ''Polymorphus'' spp. to intermediate crab hosts. The cystacanth stage is long lived and probably remains infectious throughout the life of the crab.<ref>{{cite journal |author1=Itämies, J. |author2=Valtonen, E. T. |author3=Fagerholm, H. P. |year=1980 |title=''Polymorphus minutus'' (Acanthocephala) infestation in eiders and its role as a possible cause of death |journal=Ann. Zool. Fenn |volume=17 |issue=4 |pages=285–289  }}</ref> In freshwater systems, acanthocephalans have also been shown to accumulate organic micropollutants at concentrations far higher than their crustacean hosts, potentially reducing host pollutant burdens and acting as biological pollutant sinks.<ref name="Soose2025">{{Cite journal |last=Soose |first=Laura J. |last2=Krauss |first2=Martin |last3=Landripet |first3=Mia |last4=Laier |first4=Melanie |last5=Brack |first5=Werner |last6=Hollert |first6=Henner |last7=Klimpel |first7=Sven |last8=Oehlmann |first8=Jörg |last9=Jourdan |first9=Jonas |date=January 2025 |title=Acanthocephalans as pollutant sinks? Higher pollutant accumulation in parasites may relieve their crustacean host |url=https://linkinghub.elsevier.com/retrieve/pii/S0048969724081555 |journal=Science of The Total Environment |language=en |volume=958 |article-number=177998 |doi=10.1016/j.scitotenv.2024.177998}}</ref>

== Economic impact ==
Acanthocephalosis, a disease caused by ''Acanthacephalus'' infection, is prevalent in aquaculture, occurring in [[Atlantic salmon]], [[Rainbow trout|rainbow]] and [[brown trout]], [[tilapia]], and [[tambaqui]].<ref>{{Cite journal |last1=Valladão |first1=Gustavo Moraes Ramos |last2=Gallani |first2=Sílvia Umeda |last3=Jerônimo |first3=Gabriela Tomas |last4=Seixas |first4=Arthur Tavares de |date=August 2020 |title=Challenges in the control of acanthocephalosis in aquaculture: special emphasis on Neoechinorhynchus buttnerae |url=https://onlinelibrary.wiley.com/doi/10.1111/raq.12386 |journal=Reviews in Aquaculture |language=en |volume=12 |issue=3 |pages=1360–1372 |doi=10.1111/raq.12386 |bibcode=2020RvAq...12.1360V |issn=1753-5123|url-access=subscription }}</ref> Increasing occurrence in Brazilian farming of tambaqui has been reported,<ref>{{Cite journal |last1=Castro |first1=Liliane de Araújo |last2=Jerônimo |first2=Gabriela Tomas |last3=Silva |first3=Renata Maria da |last4=Santos |first4=Maria João |last5=Ramos |first5=Cleverson Agner |last6=Porto |first6=Sanny Maria de Andrade |date=2020-09-16 |title=Occurrence, pathogenicity, and control of acanthocephalosis caused by Neoechinorhynchus buttnerae: A review |journal=Revista Brasileira de Parasitologia Veterinária |language=en |volume=29 |issue=3 |pages=e008320 |doi=10.1590/S1984-29612020070 |issn=0103-846X|doi-access=free |pmid=32965394 }}</ref> and in 2003 ''Acanthacephalus'' was first reported in cultured [[Lutjanus erythropterus|red snapper]] in Taiwan.<ref>{{cite journal |last1=Cheng |first1=Li-Wu |last2=Rao |first2=Shreesha |last3=Wang |first3=Pei-Chi |last4=Chen |first4=Shih-Chu |year=2022 |title=First report of acanthocephalan parasite, Longicollum pagrosomi Yamaguti, 1935 in cultured red snapper ( Lutjanus erythropterus ) in Taiwan |url=https://onlinelibrary.wiley.com/doi/10.1111/jfd.13583 |journal=Journal of Fish Diseases |volume=45 |issue=4 |pages=579–593 |bibcode=2022JFDis..45..579C |doi=10.1111/jfd.13583 |pmid=35083744 |s2cid=246297133|url-access=subscription }}</ref>

The life cycle of ''Polymorphus'' spp. normally occurs between sea ducks (e.g. [[eider]]s and [[scoter]]s) and small crabs.  Infections found in commercial-sized [[lobster]]s in Canada were probably acquired from crabs that form an important dietary item of lobsters. Cystacanths occurring in lobsters can cause economic loss to fishermen. There are no known methods of prevention or control.<ref>{{Cite web |last=Bower |first=Susan |date=September 1996 |title=Synopsis of Infectious Diseases and Parasites of Commercially Exploited Shellfish: Acanthocephalan Larvae in Lobsters. |url=https://www.dfo-mpo.gc.ca/science/aah-saa/diseases-maladies/acalarlo-eng.html |website=Fisheries and Oceans Canada (DFO)}}</ref>

== Human infections ==

Although they rarely infect humans, worms in the phylum Acanthocephala cause the disease [[acanthocephaliasis]] in humans. The earliest known infection was found in a prehistoric man in [[Utah]].<ref name="Moore1969">{{cite journal |last1=Moore |first1=J. G. |last2=Fry |first2=G. F. |last3=Englert |first3=E. |title=Thomy-headed worm infection in North American prehistoric man |journal=Science |date=21 March 1969 |volume=163 |issue=3873 |pages=1324–1325 |doi=10.1126/science.163.3873.1324 |pmid=17807812 |bibcode=1969Sci...163.1324M |s2cid=6120428}}</ref> This infection was dated to 1869 ± 160 BC. The species involved was thought to be ''[[Moniliformis clarki]]'' which is still common in the area.

The first report of an isolate in historic times was by [[Vilém Dušan Lambl|Lambl]] in 1859 when he isolated ''[[Macracanthorhynchus hirudinaceus]]'' from a child in [[Prague]]. Lindemann in 1865 reported that this organism was commonly isolated in [[Russia]]. The reason for this was discovered by Schneider in 1871 when he found that an intermediate host, the scarabaeid beetle grub, was commonly eaten raw.<ref>{{cite journal |last=Schmidt |first=Gerald D. |date=June 1971 |title=Acanthocephalan infections of man, with two new records |journal=The Journal of Parasitology |publisher=[[Allen Press]] on behalf of [[American Society of Parasitologists]] |volume=57 |issue=3 |pages=582–584 |doi=10.2307/3277920 |jstor=3277920 |pmid=5090967 }}</ref>

The first report of clinical symptoms was by Calandruccio who in 1888 while in [[Italy]] infected himself by ingesting larvae. He reported gastrointestinal disturbances and shed eggs in two weeks. Subsequent natural infections have since been reported.<ref name="Tada1983">{{cite journal |last1=Tada |first1=I |last2=Otsuji |first2=Y |last3=Kamiya |first3=H. |last4=Mimori |first4=T. |last5=Sakaguchi |first5=Y. |last6=Makizumi |first6=S |title=The first case of a human infected with an acanthocephalan parasite, ''Bolbosoma'' sp. |journal=The Journal of Parasitology |date=February 1983 |volume=69 |issue=1 |pages=205–8 |pmid=6827437 |doi=10.2307/3281300 |jstor=3281300}}</ref>

Eight species have been isolated from humans to date.<ref name="Haustein2009">{{cite journal |last1=Haustein |first1=T. |last2=Lawes |first2=M. |last3=Harris |first3=E. |last4=Chiodini |first4=P. L. |title=An eye-catching acanthocephalan |journal=Clinical Microbiology and Infection |date=June 2010 |volume=16 |issue=6 |pages=787–8 |doi=10.1111/j.1469-0691.2009.02896.x |pmid=19689468 |doi-access=free}}</ref> ''[[Moniliformis moniliformis]]'' is the most common isolate. Other isolates include ''[[Acanthocephalus bufonis]]'' and ''[[Corynosoma strumosum]]''.

== See also ==

* [[Cestoda]]
* [[Digenea]]
* [[Monogenea]]

== References==

{{Reflist}}

== Further reading ==

* {{cite journal |last1=Amin |first1=O. M. |year=1987 |title=Key to the families and subfamilies of Acanthocephala, with erection of a new class (Polyacanthocephala) and a new order (Polyacanthorhynchida) |journal=Journal of Parasitology |volume=73 |issue=6|pages=1216–1219 |doi=10.2307/3282307|jstor=3282307 |pmid=3437357 |ref=none}}
* {{cite journal |last1=Lühe |first1=M. |year=1904 |title=Geschichte und Ergebnisse der Echinorhynchen – Forschung bis auf Westrumb (1821) |journal=Zoologischer Annalen |volume=1 |pages=139–250 |ref=none}}
* {{cite journal |last=Tain |first=Luke |author2=Marie-Jeanne Perrot-Minnot |author3=Frank Cézilly |title=Altered host behaviour and brain serotonergic activity caused by acanthocephalans: evidence for specificity|journal=[[Proceedings of the Royal Society B]] |date=December 22, 2006 |volume=273 |issue=1605 |pages=3039–3045 |doi=10.1098/rspb.2006.3618 |pmc=1679890 |pmid=17015346 |ref=none}}
* {{cite book |last=Zimmer |first=Carl |author-link=Carl Zimmer |title=[[Parasite Rex: Inside the Bizarre World of Nature's Most Dangerous Creatures]] |publisher=Free Press |year=2000 |page=92 |isbn=978-0-7432-0011-0 |ref=none}}

==External links==

{{Commons category}}
{{Wikispecies|Acanthocephala}}

{{Animalia}}
{{Life on Earth}}
{{Taxonbar|from=Q178235}}
{{Authority control}}

[[Category:Acanthocephalans|Acanthocephalans]]
[[Category:Protostome phyla]]
[[Category:Veterinary parasitology]]
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[[Category:Mind-altering parasites]]
[[Category:Suicide-inducing parasitism]]
[[Category:Taxa named by Joseph Gottlieb Kölreuter]]