Rhabditophora (from ''rhabdito''-, rhabdite +

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

-φορος ''phoros'' bearer, i.e., "rhabdite bearers") is a subphylum (previously a class) of

flatworms Platyhelminthes (from the Greek πλατύ, ''platy'', meaning "flat" and ἕλμινς (root: ἑλμινθ-), ''helminth-'', meaning "worm") is a phylum of relatively simple bilaterian, unsegmented, soft-bodied invertebrates commonly called ...

. It includes all

parasitic Parasitism is a close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The ent ...

flatworms (clade Neodermata) and most free-living species that were previously grouped in the now obsolete class

Turbellaria The Turbellaria are one of the traditional sub-divisions of the phylum Platyhelminthes (flatworms), and include all the sub-groups that are not exclusively parasitic. There are about 4,500 species, which range from to large freshwater forms mo ...

. Therefore, it contains the majority of the species in the phylum

Platyhelminthes Platyhelminthes (from the Greek πλατύ, ''platy'', meaning "flat" and ἕλμινς (root: ἑλμινθ-), ''helminth-'', meaning "worm") is a phylum of relatively simple bilaterian, unsegmented, soft-bodied invertebrates commonly called f ...

, excluding only the catenulids, to which they appear to be the

sister group In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and ...

. The clade Rhabditophora was originally erected by Ulrich Ehlers in 1985Ehlers, U. (1985) ''Phylogenetic relationships within the Platyhelminthes''. ''In'' S. Conway Morris; J. D. George; R. Gibson; H. M. Platt (Eds.), ''The origins and relationships of lower invertebrates''. Oxford, Clarendon Press, p. 143-158. based on morphological analyses and its

monophyly In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent comm ...

was later confirmed by molecular studies.

Description

Rhabditophorans are characterized by the presence of lamellated rhabdites, rodlike granules secreted in the cells of the

epidermis The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and Subcutaneous tissue, hypodermis. The epidermal layer provides a barrier to infection from environmental pathogens and regulates the ...

and consisted of concentric lamellae. They are absent in the clade Neodermata, most likely due to a secondary loss of this feature because their epidermis is turned into a

syncytium A syncytium (; : syncytia; from Greek: σύν ''syn'' "together" and κύτος ''kytos'' "box, i.e. cell") or symplasm is a multinucleate cell that can result from multiple cell fusions of uninuclear cells (i.e., cells with a single nucleus), i ...

in adult forms. Duogland adhesive system

Another important

synapomorphy In phylogenetics, an apomorphy (or derived trait) is a novel Phenotypic trait, character or character state that has evolution, evolved from its ancestral form (or Plesiomorphy and symplesiomorphy, plesiomorphy). A synapomorphy is an apomorphy sh ...

of the group is the duo-glandular adhesive system. It is a structure of the epidermis containing three different cell types: anchor cells, adhesive glands and releasing glands. The adhesive glands secrete an adhesive substance that attaches the anchor cells to a surface, while the releasing glands secrete a substance able to release the anchor cells from surfaces. This systems allows rhabditophorans to adhere and release quickly from the substrate, even several times in a second. The secretory organs of rhabditophorans, the protonephridia, also have a unique anatomy in which the

flame cell A flame cell is a specialized excretory cell found in simple invertebrates, including flatworms ( Platyhelminthes), rotifers and nemerteans; these are the simplest animals to have a dedicated excretory system. Flame cells function like a kidney ...

s and tube cells present a series of cytoplasmic projections that overlap, forming a two-cell 'weir'.

Systematics

The following orders are recognised in the subphylum Rhabditophora: *Class ? **** Order Bothrioplanida **** Order Fecampiida **** Order Gnosonesimida **** Order Polycladida **** Order Prolecithophora **** Order Prorhynchida **** Order Proseriata **** Order Rhabdocoela **** Order

Tricladida Planarians (triclads) are free-living flatworms of the class Turbellaria, order Tricladida, which includes hundreds of species, found in freshwater, marine, and terrestrial habitats.pp 3., "Planarians (the popular name for the group as a whole ...

*** Superorder Macrostomorpha ****** Genus '' Bradynectes'' ****** Genus '' Myozona'' ***** Family Haplopharyngidae ***** Family Macrostomidae **** Order Dolichomicrostomida * Superclass Neodermata (''

parasite Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the Host (biology), host, causing it some harm, and is Adaptation, adapted str ...

s'') ** Class

Cestoda Cestoda is a class of parasitic worms in the flatworm phylum (Platyhelminthes). Most of the species—and the best-known—are those in the subclass Eucestoda; they are ribbon-like worms as adults, commonly known as tapeworms. Their bodies co ...

*** Subclass Cestodaria **** Order Amphilinidea **** Order Gyrocotylidea *** Subclass Eucestoda **** Order Bothriocephalidea **** Order Caryophyllidea **** Order Cathetocephalidea **** Order Cyclophyllidea **** Order Diphyllidea **** Order Diphyllobothriidea **** Order Lecanicephalidea **** Order Litobothriidea **** Order Onchoproteocephalidea **** Order Phyllobothriidea **** Order Rhinebothriidea **** Order Spathebothriidea **** Order Tetrabothriidea **** Order Tetraphyllidea **** Order Trypanorhyncha ** Class

Monogenea Monogeneans, members of the class Monogenea, are a group of ectoparasitic flatworms commonly found on the skin, gills, or fins of fish. They have a direct lifecycle and do not require an intermediate host. Adults are hermaphrodites, meaning they ...

*** Subclass

Monopisthocotylea The Monopisthocotylea are an inferior class of parasitic flatworms in the class Monogenea.WoRMS (2019). Monopisthocotylea. Accessed at: http://www.marinespecies.org/aphia.php?p=taxdetails&id=119219 on 2019-02-08 Yamaguti, S. (1963). Systema Helmi ...

**** Order

Capsalidea Capsalidea is an order of parasitic flatworms in the class Monogenea Monogeneans, members of the class Monogenea, are a group of ectoparasitic flatworms commonly found on the skin, gills, or fins of fish. They have a direct lifecycle and do ...

**** Order

Dactylogyridea Dactylogyridea is an order of parasitic flatworms in the class Monogenea.WoRMS (2018). Dactylogyridea. Accessed at: http://marinespecies.org/aphia.php?p=taxdetails&id=517897 on 2018-08-09 Families * Amphibdellatidae Carus, 1885 * Ancylodisc ...

**** Order

Gyrodactylidea Gyrodactylidea is an order of monogenean parasitic flatworms in the subclass Monopisthocotylea The Monopisthocotylea are an inferior class of parasitic flatworms in the class Monogenea.WoRMS (2019). Monopisthocotylea. Accessed at: http://www.m ...

**** Order Monocotylidea **** Order Montchadskyellidea *** Subclass

Polyopisthocotylea Polyopisthocotylea is a subclass of parasitic flatworms in the class Monogenea.WoRMS (2023). Polyopisthocotylea. Accessed at: http://www.marinespecies.org/aphia.php?p=taxdetails&id=119220 on 2023-12-21Yamaguti, S. (1963). Systema Helminthum Volu ...

**** Order

Chimaericolidea Chimaericolidae is a family of monogenea Monogeneans, members of the class Monogenea, are a group of ectoparasitic flatworms commonly found on the skin, gills, or fins of fish. They have a direct lifecycle and do not require an intermediate h ...

**** Order

Diclybothriidea Diclybothriidea is an order of monogenea Monogeneans, members of the class Monogenea, are a group of ectoparasitic flatworms commonly found on the skin, gills, or fins of fish. They have a direct lifecycle and do not require an intermediate ...

**** Order Lagarocotylidea **** Order

Mazocraeidea Mazocraeidea is an order of flatworms in the subclass Polyopisthocotylea within the class Monogenea. The species of this order have various structures in the clamps of their posterior attachment organ, including additional sclerites in the Gas ...

**** Order

Polystomatidea Polystomatidae is a family of flatworms belonging to the class Monogenea Monogeneans, members of the class Monogenea, are a group of ectoparasitic flatworms commonly found on the skin, gills, or fins of fish. They have a direct lifecycle and ...

** Class

Trematoda Trematoda is a class of flatworms known as trematodes, and commonly as flukes. They are obligate internal parasites with a complex life cycle requiring at least two hosts. The intermediate host, in which asexual reproduction occurs, is a mol ...

*** Subclass

Aspidogastrea The Aspidogastrea (Ancient Greek: ' “shield”, ' “stomach/pouch”) is a small group of flukes comprising about 80 species. It is a subclass of the trematoda, and sister group to the Digenea. Species range in length from approximately on ...

**** Order Aspidogastrida **** Order Stichocotylida *** Subclass

Digenea Digenea (Gr. ''Dis'' – double, ''Genos'' – race) is a class of trematodes in the Platyhelminthes phylum, consisting of parasitic flatworms (known as ''flukes'') with a syncytial tegument and, usually, two suckers, one ventral and one or ...

**** Order

Diplostomida Diplostomida is an order of trematodes in the subclass Digenea. It is synonymous with Strigeatida Poche, 1926. Families Order Diplostomida *Suborder Diplostomata **Superfamily Brachylaimoidea Joyeux & Foley, 1930 ***Brachylaimidae Joyeux & Foley ...

**** Order

Plagiorchiida Plagiorchiida is a large order of trematodes, synonymous to Echinostomida. They belong to the Digenea, a large subclass of flukes. This order contains relatively few significant parasites of humans. The following families are placed here, ...

References

{{Taxonbar, from=Q3428991 Protostome classes