Editing Digenea

{{Short description|Class of flukes}}
{{For|the bird genus|Anthipes}}
{{Automatic taxobox
| image         = Helicometra.jpg
| image_caption = ''[[Helicometra]]'' sp. ([[Plagiorchiida]]: [[Opecoelidae]]) from the intestine of a [[Flame Cardinal]] fish
| subdivision_ranks = Families
| subdivision = [[#Important families|See text]].
| taxon = Digenea
| authority = [[Carus]], 1863
| display_parents = 3
}}
'''Digenea''' (Gr. ''Dis'' – double, ''Genos'' – race) is a [[Class (biology)|class]] of [[Trematoda|trematodes]] in the [[Platyhelminthes]] [[phylum]], consisting of [[parasitic]] [[flatworm]]s (known as ''flukes'') with a [[syncytium|syncytial]] [[tegument (helminth)|tegument]] and, usually, two [[sucker (zoology)|suckers]], one ventral and one oral. Adults commonly live within the digestive tract, but occur throughout the organ systems of all classes of [[vertebrates]]. Once thought to be related to the [[Monogenea]], it is now recognised that they are closest to the [[Aspidogastrea]] and that the Monogenea are more closely allied with the [[Cestoda]]. Around 6,000 species have been described to date.

==Morphology==
===Key features===
Characteristic features of the Digenea include a syncytial tegument; that is, a tegument where the junctions between cells are broken down and a single continuous cytoplasm surrounds the entire animal. A similar tegument is found in other members of the [[Neodermata]]; a group of [[Platyhelminthes|platyhelminths]] comprising the Digenea, [[Aspidogastrea]], [[Monogenea]] and [[Cestoda]].  Digeneans possess a [[vermiform]], unsegmented body-plan and have a solid [[parenchyma]] with no [[body cavity]] ([[coelom]]) as in all platyhelminths.

[[File:Peerj-292-fig-7 Zoogonidae.png|thumb|Anterior sucker of ''[[Overstreetia cribbi]]'' a [[Zoogonidae|zoogonid]] digenean<ref>{{Cite journal  | last1 = Bray | first1 = RA. | last2 = Justine | first2 = J-L. | title = A review of the Zoogonidae (Digenea: Microphalloidea) from fishes of the waters around New Caledonia, with the description of ''Overstreetia cribbi'' n. sp. | journal = PeerJ | volume = 2 | pages = e292 | year = 2014 | doi = 10.7717/peerj.292 | pmid = 24688868|pmc = 3961169 | doi-access = free }}</ref>]]
There are typically two [[Sucker (zoology)|sucker]]s, an [[anterior]] [[Wiktionary:oral|oral]] sucker surrounding the [[mouth]], and a [[ventral]] sucker sometimes termed the [[acetabulum (morphology)|acetabulum]], on the ventral surface.  The oral sucker surrounds the mouth, while the ventral sucker is a blind muscular organ with no connection to any internal structure.

A ''monostome'' is a worm with one sucker (oral). [[Trematoda|Flukes]] with an oral sucker and an acetabulum at the posterior end of the body are called ''Amphistomes''. ''Distomes'' are flukes with an oral sucker and a ventral sucker, but the ventral sucker is somewhere other than posterior.  These terms are common in older literature, when they were thought to reflect systematic relationships within the groups.  They have fallen out of use in modern digenean taxonomy.

===Reproductive system===
The vast majority of digeneans are [[hermaphrodite]]s. This is likely to be an adaptation to low abundance within hosts, allowing the life cycle to continue when only one individual successfully infects the final host. [[Fertilisation]] is internal, with [[sperm]] being transferred via the [[cirrus (biology)|cirrus]] to the [[Laurer's Canal]] or [[genital|genital aperture]]. A key group of digeneans which are [[dioecious]] are the [[schistosoma|schistosomes]].
Asexual reproduction in the first larval stage is ubiquitous.

While the sexual formation of the digenean [[egg (biology)|eggs]] and asexual reproduction in the first [[larva]]l stage (miracidium) is widely reported, the [[developmental biology]] of the asexual stages remains a problem. [[Electron microscope|Electron microscopic]] studies have shown that the [[microscope|light microscopically]] visible germ balls consist of [[mitosis|mitotically]] dividing [[cell (biology)|cell]]s which give rise to [[embryo]]s and to a line of new [[germ cells]] that become included in these embryonic stages. Since the absence of [[meiosis|meiotic processes]] is not proven, the exact definition remains doubtful.

====Male organs====
[[Hermaphrodite|Protandry]] is the general rule among the Digenea. Usually two [[testes]] are present, but some flukes can have more than 100. Also present are [[vasa efferentia]], a [[vas deferens]], [[seminal vesicle]], [[ejaculatory duct]] and a cirrus (analogous to a penis) usually (but not always) enclosed in a cirrus sac.  The cirrus may or may not be covered in proteinaceous spines.  The exact conformation of these organs within the male terminal genitalia is taxonomically important at the familial and generic levels.

====Female organs====
Usually there is a single [[ovary]] with an [[oviduct]], a [[semen|seminal receptacle]], a pair of vitelline glands (involved in [[yolk]] and egg-shell production) with ducts, the ootype (a chamber where eggs are formed), a complex collection of glands cells called ''Mehlis’ gland'', which is believed to lubricate the uterus for egg passage.

In addition, some digeneans possess a canal called [[Laurer's Canal]], which leads from the oviduct to the dorsal surface of the body.  The function of this canal is debated, but it may be used for insemination in some species or for disposal of waste products from reproduction in other species.
Most trematodes possess an ovicapt, an enlarged portion of the oviduct where it joins the ovary. It probably controls the release of ova and spaces out their descent down the uterus.

The uterus typically opens into a common genital atrium that also received the distal male copulatory organ (cirrus) before immediately opening onto the outer surface of the worm.  The distal part of the uterus may be expanded into a metraterm, set off from the proximal uterus by a muscular sphincter, or  it may be lined with spines, as in the [[Monorchiidae]] and some other families.

===Digestive system===
As adults, most digeneans possess a terminal or subterminal mouth, a muscular pharynx that provides the force for ingesting food, and a forked, blind digestive system consisting of two tubular sacs called caeca (sing. [[caecum]]).  In some species the two gut caeca join posteriorly to make a ring-shaped gut or [[cyclocoel]].  In others the [[caecum|caeca]] may fuse with the body wall posteriorly to make one or more [[anus]]es, or with the excretory vesicle to form a [[uroproct]].  Digeneans are also capable of direct nutrient uptake through the tegument by [[pinocytosis]] and [[phagocytosis]] by the [[syncitium]]. Most adult digeneans occur in the vertebrate [[alimentary canal]] or its associated [[organ (anatomy)|organs]], where they most often graze on contents of the lumen (e.g., food ingested by the host, bile, mucus), but they may also feed across the mucosal wall (e.g., [[submucosa]], host blood).  The blood flukes, such as schistosomes, spirorchiids and sanguinicolids, feed exclusively on blood. Asexual stages in [[mollusc]] intermediate hosts feed mostly by direct absorption, although the [[Trematode lifecycle stages|redia]] stage found in some groups does have a mouth, pharynx and simple gut and may actively consume host tissue or even other parasites.  Encysted [[metacercaria]]l stages and free-living [[cercaria]]l stages do not feed.

===Nervous system===
Paired [[ganglia]] at the anterior end of the body serve as the [[brain]]. From this [[nerves]] extend anteriorly and posteriorly. [[Sense|Sensory receptors]] are, for the most part, lacking among the adults, although they do have [[tangoreceptor]] cells. Larval stages have many kinds of sensory receptors, including light receptors and chemoreceptors. Chemoreception plays an important role in the free-living miracidial larva recognising and locating its host.

==Life cycles==
There is a bewildering array of variation on the complex digenean life cycle, and plasticity in this trait is probably a key to the group's success. In general, the life cycles may have two, three, or four obligate (necessary) hosts, sometimes with transport or [[paratenic]] hosts in between. The three-host life cycle is probably the most common.  In almost all species, the first host in the life cycle is a [[mollusc]].<ref name=":0">{{Cite web|url=http://www.biology.ualberta.ca/parasites/ParPub/text/text/general/digen01t.htm|title=Principles of Parasitism: Digenea|website=www.biology.ualberta.ca|access-date=2020-01-09}}</ref> This has led to the inference that the ancestral digenean was a mollusc parasite and that vertebrate hosts were added subsequently.

The alternation of sexual and asexual generations is an important feature of digeneans. This phenomenon involves the presence of several discrete generations in one life-cycle.

A typical digenean trematode life cycle is as follows.  Eggs leave the [[vertebrate]] host in [[faeces]] and use various strategies to infect the first [[parasitic life cycles|intermediate host]], in which sexual reproduction does not occur. Digeneans may infect the first intermediate host (usually a [[snail]]) by either passive or active means. The eggs of some digeneans, for example, are (passively) eaten by snails (or, rarely, by an [[annelid]] worm),<ref name=":0" /> in which they proceed to hatch. Alternatively, eggs may hatch in water to release an actively swimming, ciliated larva, the [[miracidium]], which must locate and penetrate the body wall of the snail host.

After post-ingestion hatching or penetration of the snail, the miracidium metamorphoses into a simple, sac-like ''mother sporocyst''. The mother sporocyst undergoes a round of internal [[asexual reproduction]], giving rise to either ''rediae'' (sing. redia) or ''daughter sporocysts''. The second generation is thus the daughter parthenita sequence. These in turn undergo further asexual reproduction, ultimately yielding large numbers of the second free-living stage, the ''cercaria'' (pl. cercariae).

Free-swimming cercariae leave the snail host and move through the aquatic or [[sea water|marine]] environment, often using a whip-like tail, though a tremendous diversity of tail morphology is seen. Cercariae are infective to the second host in the life cycle, and infection may occur passively (e.g., a [[fish]] consumes a cercaria) or actively (the cercaria penetrates the fish).

The life cycles of some digeneans include only two hosts, the second being a vertebrate. In these groups, sexual maturity occurs after the cercaria penetrates the second host, which is in this case also the [[parasitic life cycles|definitive host]]. Two-host life cycles can be primary (there never was a third host) as in the [[Bivesiculidae]], or secondary (there was at one time in evolutionary history a third host but it has been lost).

In three-host life cycles, cercariae develop in the second intermediate host into a resting stage, the ''metacercaria'', which is usually encysted in a [[cyst]] of host and parasite origin, or encapsulated in a layer of tissue derived from the host only. This stage is infective to the [[parasitic life cycles|definitive host]]. Transmission occurs when the definitive host preys upon an infected second intermediate host. Metacercariae excyst in the definitive host's gut in response to a variety of physical and chemical signals, such as gut [[pH]] levels, digestive [[enzyme]]s, [[temperature]], etc. Once excysted, adult digeneans migrate to more or less specific sites in the definitive host and the life cycle repeats.

==Evolution==
The evolutionary origins of the Digenea have been debated for some time, but there appears general agreement that the proto-digenean was a parasite of a mollusc, possibly of the mantle cavity.  Evidence for this comes from the ubiquity of molluscs as first intermediate hosts for digeneans, and the fact that most aspidogastreans (the sister group to the Digenea) also have mollusc associations.  It is thought that the early trematodes (the collective name for digeneans and aspidogastreans) likely evolved from rhabdocoel [[turbellaria]]ns that colonised the open mantle cavity of early molluscs.

It is likely that more complex life cycles evolved through a process of terminal addition, whereby digeneans survived predation of their mollusc host, probably by a fish.  Other hosts were added by the same process until the modern bewildering diversity of life cycle patterns developed.

===Important families===
Digenea includes about 80 families.<ref>Olson P. D., Cribb T. H., Tkach V. V., Bray R. A. & Littlewood D. T. J. (2003). "Phylogeny and classification of the Digenea (Platyhelminthes: Trematoda)". ''International Journal for Parasitology'' '''33'''(7): 733–755. {{doi|10.1016/S0020-7519(03)00049-3}}</ref> They are listed below, organised by order.

'''Digenea'''
*[[Diplostomida]]
**Suborder Diplostomata
***Superfamily Brachylaimoidea <small>Joyeux & Foley, 1930</small>
****[[Brachylaimidae]] <small>Joyeux & Foley, 1930</small>
****[[Leucochloridiidae]] <small>Poche, 1907</small>
***Superfamily Diplostomoidea <small>Poirier, 1886</small>
****[[Brauninidae]] <small>Wolf, 1903</small>
****[[Cyathocotylidae]] <small>Mühling, 1898</small>
****[[Diplostomidae]] <small>Poirier, 1886</small>
****[[Proterodiplostomidae]] <small>Dubois, 1936</small>
****[[Strigeidae]] <small>Railliet, 1919</small>
***Superfamily Schistosomatoidea <small>Stiles & Hassall, 1898</small>
****[[Aporocotylidae]] <small>Odhner, 1912</small>
****[[Schistosomatidae]] <small>Stiles & Hassall, 1898</small>
****[[Spirorchiidae]] <small>Stunkard, 1921</small>
*[[Plagiorchiida]]
**Apocreadiata
***Apocreadioidea <small>Skrjabin, 1942</small>
****[[Apocreadiidae]] <small>Skrjabin, 1942</small>
**Bivesiculata
***Bivesiculoidea
****[[Bivesiculidae]] <small>Yamaguti, 1934</small>
**Bucephalata
***Bucephaloidea <small>Poche, 1907</small>
****[[Bucephalidae]] <small>Poche, 1907</small>
****[[Nuitrematidae]] <small>Kurochkin, 1975</small>
***Gymnophalloidea <small>Odhner, 1905</small>
****[[Botulisaccidae]] <small>Yamaguti, 1971</small>
****[[Fellodistomidae]] <small>Nicoll, 1909</small>
****[[Gymnophallidae]] <small>Odhner, 1905</small>
****[[Tandanicolidae]] <small>Johnston, 1927</small>
**Echinostomata
***Echinostomatoidea <small>Looss, 1902</small>
****[[Calycodidae]] <small>[[Robert-Philippe Dollfus|Dollfus]], 1929</small>
****[[Cyclocoelidae]] <small>Stossich, 1902</small>
****[[Echinochasmidae]] <small>Odhner, 1910</small>
****[[Echinostomatidae]] <small>Looss, 1899</small>
****[[Eucotylidae]] <small>Cohn, 1904</small>
****[[Fasciolidae]] <small>Railliet, 1895</small>
****[[Himasthlidae]] <small>Odhner, 1910</small>
****[[Philophthalmidae]] <small>Looss, 1899</small>
****[[Psilostomidae]] <small>Looss, 1900</small>
****[[Rhytidodidae]] <small>Odhner, 1926</small>
****[[Typhlocoelidae]] <small>Harrah, 1922</small>
**Haplosplanchnata
***Haplosplanchnoidea <small>Poche, 1925</small>
****[[Haplosplanchnidae]] <small>Poche, 1926</small>
**Hemiurata
***Azygioidea <small>Lühe, 1909</small>
****[[Azygiidae]] <small>Lühe, 1909</small>
***Hemiuroidea <small>Looss, 1899</small>
****[[Accacoeliidae]] <small>Odhner, 1911</small>
****[[Bathycotylidae]] <small>[[Robert-Philippe Dollfus|Dollfus]], 1932</small>
****[[Derogenidae]] <small>Nicoll, 1910</small>
****[[Dictysarcidae]] <small>Skrjabin & Guschanskaja, 1955</small>
****[[Didymozoidae]] <small>Monticelli, 1888</small>
****[[Gonocercidae]] <small>Skrjabin & Guschanskaja, 1955</small>
****[[Hemiuridae]] <small>Looss, 1899</small>
****[[Hirudinellidae]] <small>[[Robert-Philippe Dollfus|Dollfus]], 1932</small>
****[[Isoparorchiidae]] <small>Travassos, 1922</small>
****[[Lecithasteridae]] <small>Odhner, 1905</small>
****[[Ptychogonimidae]] <small>[[Robert-Philippe Dollfus|Dollfus]], 1937</small>
****[[Sclerodistomidae]] <small>Odhner, 1927</small>
****[[Sclerodistomoididae]] <small>Gibson & Bray, 1979</small>
****[[Syncoeliidae]] <small>Looss, 1899</small>
**Heronimata
***Heronimoidea <small>Ward, 1918</small>
****[[Heronimidae]] <small>Ward, 1918</small>
**Lepocreadiata
***Lepocreadioidea <small>Odhner, 1905</small>
****[[Aephnidiogenidae]] <small>Yamaguti, 1934</small>
****[[Deropristidae]] <small>Cable & Hunninen, 1942</small>
****[[Enenteridae]] <small>Yamaguti, 1958</small>
****[[Gorgocephalidae]] <small>Manter, 1966</small>
****[[Gyliauchenidae]] <small>Fukui, 1929</small>
****[[Lepidapedidae]] <small>Yamaguti, 1958</small>
****[[Lepocreadiidae]] <small>Odhner, 1905</small>
****[[Liliatrematidae]] <small>Gubanov, 1953</small>
**Monorchiata
***Monorchioidea <small>Odhner, 1911</small>
****[[Lissorchiidae]] <small>Magath, 1917</small>
****[[Monorchiidae]] <small>Odhner, 1911</small>
**Opisthorchiata
***Opisthorchioidea <small>Braun, 1901</small>
****[[Cryptogonimidae]] <small>Ward, 1917</small>
****[[Heterophyidae]] <small>Leiper, 1909</small>
****[[Opisthorchiidae]] <small>Looss, 1899</small>
**Pronocephalata
***Paramphistomoidea <small>Fischoeder, 1901</small>
****[[Cladorchiidae]] <small>Fischoeder, 1901</small>
****[[Mesometridae]] <small>Poche, 1926</small>
****[[Microscaphidiidae]] <small>Looss, 1900</small>
****[[Paramphistomidae]] <small>Fischoeder, 1901</small>
***Pronocephaloidea <small>Looss, 1899</small>
****[[Labicolidae]] <small>Blair, 1979</small>
****[[Notocotylidae]] <small>Lühe, 1909</small>
****[[Nudacotylidae]] <small>Barker, 1916</small>
****[[Opisthotrematidae]] <small>Poche, 1926</small>
****[[Pronocephalidae]] <small>Looss, 1899</small>
****[[Rhabdiopoeidae]] <small>Poche, 1926</small>
**Transversotremata
***Transversotrematoidea <small>Witenberg, 1944</small>
****[[Transversotrematidae]] <small>Witenberg, 1944</small>
**Xiphidiata
***Allocreadioidea <small>Looss, 1902</small>
****[[Acanthocolpidae]] <small>Lühe, 1906</small>
****[[Allocreadiidae]] <small>Looss, 1902</small>
****[[Batrachotrematidae]] <small>[[Robert-Philippe Dollfus|Dollfus]] & Williams, 1966</small>
****[[Brachycladiidae]] <small>Odhner, 1905</small>
****[[Opecoelidae]] <small>Ozaki, 1925</small>
***Gorgoderoidea <small>Looss, 1901</small>
****[[Callodistomidae]] <small>Odhner, 1910</small>
****[[Dicrocoeliidae]] <small>Looss, 1899</small>
****[[Gorgoderidae]] <small>Looss, 1899</small>
***Haploporoidea <small>Nicoll, 1914</small>
****[[Atractotrematidae]] <small>Yamaguti, 1939</small>
****[[Haploporidae]] <small>Nicoll, 1914</small>
***Microphalloidea <small>Ward, 1901</small>
****[[Diplangidae]] <small>Yamaguti, 1971</small>
****[[Exotidendriidae]] <small>Mehra, 1935</small>
****[[Faustulidae]] <small>Poche, 1926</small>
****[[Microphallidae]] <small>Ward, 1901</small>
****[[Pachypsolidae]] <small>Yamaguti, 1958</small>
****[[Phaneropsolidae]] <small>Mehra, 1935</small>
****[[Pleurogenidae]] <small>Looss, 1899</small>
****[[Prosthogonimidae]] <small>Lühe, 1909</small>
****[[Renicolidae]] <small>[[Robert-Philippe Dollfus|Dollfus]], 1939</small>
****[[Zoogonidae]] <small>Odhner, 1902</small>
***Plagiorchioidea <small>Lühe, 1901</small>
****[[Auridistomidae]] <small>Lühe, 1901</small>
****[[Brachycoeliidae]] <small>Looss, 1899</small>
****[[Cephalogonimidae]] <small>Looss, 1899</small>
****[[Choanocotylidae]] <small>Jue Sue & Platt, 1998</small>
****[[Echinoporidae]] <small>Krasnolobova & Timofeeva, 1965</small>
****[[Encyclometridae]] <small>Mehra, 1931</small>
****[[Leptophallidae]] <small>Dayal, 1938</small>
****[[Macroderoididae]] <small>McMullen, 1937</small>
****[[Meristocotylidae]] <small>Fischthal & Kuntz, 1981</small>
****[[Ocadiatrematidae]] <small>Fischthal & Kuntz, 1981</small>
****[[Orientocreadiidae]] <small>Yamaguti, 1958</small>
****[[Plagiorchiidae]] <small>Lühe, 1901</small>
****[[Styphlotrematidae]] <small>Baer, 1924</small>
****[[Telorchiidae]] <small>Looss, 1899</small>
****[[Thrinascotrematidae]] <small>Jue Sue & Platt, 1999</small>
****[[Urotrematidae]] <small>Poche, 1926</small>

==Human digenean infections==
Only about 12 of the 6,000 known species are [[infection|infectious]] to humans, but some of these species are important [[disease]]s afflicting over 200 million people. The species that infect humans can be divided into groups, the schistosomes and the non-schistosomes.

===Schistosomes===
The Schistosomes occur in the [[circulatory system]] of the definitive host. Humans become infected after free-swimming cercaria liberated from infected snails penetrate the skin. These dioecious worms are long and thin, ranging in size from 10 to 30&nbsp;mm in length to 0.2 to 1.0&nbsp;mm in diameter. Adult males are shorter and thicker than females, and have a long groove along one side of the body in which the female is clasped. Females reach sexual maturity after they have been united with a male. After mating the two remain locked together for the rest of their lives. They can live for several years and produce many thousands of eggs.

The four species of schistosomes that infect humans are members of the [[genus]] ''[[Schistosoma]]''.

{| border="1" cellpadding="5" cellspacing="0" align="center"
|+'''Human Schistosomes'''
|-
! style="background:#ffceff;" | Scientific Name
! style="background:#ffceff;" | First Intermediate Host
! style="background:#ffceff;" | Endemic Area
|-
|''[[Schistosoma mansoni]]''
|''[[Biomphalaria]]'' spp.
|[[Africa]], [[South America]], [[Caribbean]], [[Middle East]]
|-
|''[[Schistosoma haematobium]]''
|''[[Bulinus]]'' spp.
|[[Africa]], [[Middle East]]
|-
|''[[Schistosoma japonicum]]''
|''[[Oncomelania]]'' spp.
|[[China]], [[East Asia]], [[Philippines]]
|-
|''[[Schistosoma intercalatum]]''
|''[[Bulinus]]'' spp.
|[[Africa]]
|}

===Non-schistosomes===

The seven major species of non-schistosomes that infect humans are listed below. People become infected after ingesting metacercarial cysts on plants or in undercooked animal flesh. Most species inhabit the human gastrointestinal tract, where they shed eggs along with host feces. ''Paragonimus westermani'', which colonizes the lungs, can also pass its eggs in [[saliva]]. These flukes generally cause mild pathology in humans, but more serious effects may also occur.

{| border="1" cellpadding="5" cellspacing="0" align="center"
|+'''Human non-Schistosomes'''
|-
! style="background:#ffceff;" | Scientific Name
! style="background:#ffceff;" | First Intermediate Host
! style="background:#ffceff;" | Mode of Human Infection
! style="background:#ffceff;" | Endemic Area
|-
| ''[[Fasciolopsis buski]]''
| ''[[Segmentina]]'' sp.
| Plants
| [[Asia]], [[India]]
|-
| ''[[Heterophyes heterophyes]]''
| ''[[Pirinella]]''{{Citation needed|date=November 2009}}
| [[mullet (fish)|Mullet]], [[Tilapia]]
| [[Asia]], [[Eastern Europe]], [[Egypt]], [[Middle East]]
|-
|''[[Metagonimus yokogawaii]]''
|''[[Semisulcospira]]'' sp.{{Citation needed|date=November 2009}}
|[[Carp]], [[Trout]]
|[[Siberia]]
|-
|''[[Gastrodiscoides hominis]]''
|''[[Helicorbis]]'' sp.{{Citation needed|date=November 2009}}
|Plants
|[[India]], [[Vietnam]], [[Philippines]]
|-
|''[[Clonorchis sinensis]]''
|''[[Bulinus]]'' sp.
|Fish
|[[East Asia]], [[North America]]
|-
|''[[Fasciola hepatica]]''
|''[[Galba truncatula]]''
|Plants
|[[World]]wide
|-
|''[[Paragonimus westermani]]'' 	
|''[[Oncomelania]]'' sp.
|[[Crab]]s, [[crayfish]]	
|[[Asia]]
|}

==References==
{{Reflist}}

== Notes ==

* Gibson, D.I., Jones, A. & Bray, R.A. (2002). ''Key to the Trematoda, vol.1'' {{ISBN|0-85199-547-0}}
* Littlewood D.T.J. & Bray R.A. (2001) ''Interrelationships of the Platyhelminthes.'' {{ISBN|0-7484-0903-3}}
* [[Satyu Yamaguti|Yamaguti, S.]] (1971). ''Synopsis of digenetic trematodes of vertebrates.'' Keigaku Publishing Co., Tokyo.

==External links==
{{Commons category|Digenea}}
*[https://web.archive.org/web/20050308231721/http://www.path.cam.ac.uk/~schisto/OtherFlukes/Flukes_Gen/Fluke.html Cambridge University Schistosome Research Group]
*[http://www.nhm.ac.uk/zoology/home/gibson.htm Parasitic Worms at the Natural History Museum, London]
*[https://web.archive.org/web/20071015033911/http://www.fishdisease.net/ Fishdisease.net]

{{Taxonbar|from=Q132650}}
{{Authority control}}

[[Category:Digenea| ]]
[[Category:Protostome subclasses]]