page_title: Flatworm
section_title: Monogenea
hierarchical_section_title: Flatworm / Major subgroups / Cercomeromorpha / Monogenea
caption_attribution_description: English: Silhouettes of bodies of parasitic flatworms Extracted from original image, clamps and lettering removed Legend in published paper: Figure 4. Body and clamp surfaces: examples of line drawings in 8 families. Body and clamp surfaces: examples of line drawings used for data extraction in each of the 8 families of the Gastrocotylinea. All species drawn to same body length. A, Gotocotylidae, Gotocotyla niphonii. B, Bychowskicotylidae, Tonkinopsis transfretanus. C, Gastrocotylidae, Allopseudaxinoides euthynni. D, Neothoracocotylidae, Pricea minimae. E, Allodiscocotylidae, Metacamopia indica. F, Pseudodiclidophoridae, Allopseudodiclidophora opelu. G, Chauhaneidae, Cotyloatlantica mediterranea. H, Protomicrocotylidae, Lethacotyle vera n. sp (no clamps). Details in Table 3. m:File:Journal.pone.0079155.t003 Surface of clamps and body in species of gastrocotylinean monogeneans.png
context_page_description: The flatworms, flat worms, Platyhelminthes, Plathelminthes, or platyhelminths are a phylum of relatively simple bilaterian, unsegmented, soft-bodied invertebrates. Unlike other bilaterians, they are acoelomates, and have no specialized circulatory and respiratory organs, which restricts them to having flattened shapes that allow oxygen and nutrients to pass through their bodies by diffusion. The digestive cavity has only one opening for both ingestion and egestion; as a result, the food cannot be processed continuously.
  In traditional medicinal texts, Platyhelminthes are divided into Turbellaria, which are mostly non-parasitic animals such as planarians, and three entirely parasitic groups: Cestoda, Trematoda and Monogenea; however, since the turbellarians have since been proven not to be monophyletic, this classification is now deprecated. Free-living flatworms are mostly predators, and live in water or in shaded, humid terrestrial environments, such as leaf litter. Cestodes and trematodes have complex life-cycles, with mature stages that live as parasites in the digestive systems of fish or land vertebrates, and intermediate stages that infest secondary hosts.
context_section_description: Of about 1,100 species of monogeneans, most are external parasites that require particular host species - mainly fish, but in some cases amphibians or aquatic reptiles. However, a few are internal parasites. Adult monogeneans have large attachment organs at the rear, known as haptors (Greek ἅπτειν, haptein, means "catch"), which have suckers, clamps, and hooks. They often have flattened bodies. In some species, the pharynx secretes enzymes to digest the host's skin, allowing the parasite to feed on blood and cellular debris. Others graze externally on mucus and flakes of the hosts' skins. The name "Monogenea" is based on the fact that these parasites have only one nonlarval generation.
caption: Silhouettes of bodies of various polyopisthocotylean Monogeneans[19]
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