Rhabditophora (from ''rhabdito''-,

rhabdite Rhabdites (from Greek, ''rhabdos'', rod) are rodlike structures in the cells of the Epidermis (skin), epidermis or underlying parenchyma in certain turbellarians, and in the epidermis of nemerteans. They are discharged in mucous secretions. They ...

Greek Greek may refer to: Greece 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 ...

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

flatworms The flatworms, flat worms, Platyhelminthes, or platyhelminths (from the Greek πλατύ, ''platy'', meaning "flat" and ἕλμινς (root: ἑλμινθ-), ''helminth-'', meaning "worm") are a phylum of relatively simple bilaterian, unsegment ...

. It includes all

parasitic Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson ha ...

flatworms (clade

Neodermata Neodermata is a clade of rhabditophoran flatworms containing the parasitic groups Trematoda, Monogenea and Cestoda. Description All neodermatans are parasites, in many groups having a free-swimming larval stage. The most striking feature uniti ...

) 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 mor ...

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

Platyhelminthes The flatworms, flat worms, Platyhelminthes, or platyhelminths (from the Greek πλατύ, ''platy'', meaning "flat" and ἕλμινς (root: ἑλμινθ-), ''helminth-'', meaning "worm") are a phylum of relatively simple bilaterian, unsegment ...

, 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 cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic gr ...

was later confirmed by molecular studies.

Description

Rhabditophorans are characterized by the presence of lamellated

s, 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 epidermis layer provides a barrier to infection from environmental pathogens and regulates the ...

and consisted of concentric

lamella Lamella (plural lamellae) means a small plate or flake in Latin, and in English may refer to: Biology * Lamella (mycology), a papery rib beneath a mushroom cap * Lamella (botany) * Lamella (surface anatomy), a plate-like structure in an animal * ...

e. They are absent in the clade

, most likely due to a secondary loss of this feature because their epidermis is turned into a

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

in adult forms. Duogland adhesive system

Another important

synapomorphy In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to hav ...

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 The nephridium (plural ''nephridia'') is an invertebrate organ, found in pairs and performing a function similar to the vertebrate kidneys (which originated from the chordate nephridia). Nephridia remove metabolic wastes from an animal's body. Neph ...

, also have a unique anatomy in which the

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

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: *** Order

Bothrioplanida ''Bothrioplana'' is a genus of freshwater flatworms, the sole genus in the family Bothrioplanidae and order Bothrioplanida. Description Species of ''Bothrioplana'' are small organisms, usually measuring 2–3 mm in length, but reaching up to 7 ...

*** Order

Fecampiida Fecampiida is an order of flatworms in the class Rhabditophora. It is a considerably recent clade, erected after molecular studies. Description The order Fecampiida, as currently defined, was erected based on molecular studies. They all are pa ...

*** Order Gnosonesimida *** Order

Polycladida The Polycladida represents a highly diverse clade of free-living marine flatworms. They are known from the littoral to the sublittoral zone (extending to the deep hot vents), and many species are common from coral reefs. Only a few species are fo ...

*** Order

Prolecithophora The ''Prolecithophora'' are an order consisting of an estimated 300 species of small (typically 0.2 – 12 mm, one species up to 50 mm), active, aquatic flatworms. The order lacks a common English name. Most species are shaped like an e ...

*** Order Prorhynchida *** Order

Proseriata Proseriata is an order of free-living flatworms in the class Rhabditophora with over 400 species described worldwide. Description Proseriate flatworms are minute aquatic organisms, usually with an elongate body. There are no strong synapomorph ...

*** Order

Rhabdocoela Rhabdocoela is an order of flatworms in the class Rhabditophora with about 1700 species described worldwide. The order was first described in 1831 by Christian Gottfried Ehrenberg. Most of rhabdocoels are free-living organisms, but some live sym ...

*** Order

Tricladida A planarian is one of the many flatworms of the traditional class Turbellaria. It usually describes free-living flatworms of the order Tricladida (triclads), although this common name is also used for a wide number of free-living platyhelmin ...

** Superorder

Macrostomorpha Macrostomorpha is a clade of free living flatworms ranked either as class or subclass in the group Rhabditophora. There are about 260 described species in two orders - marine, freshwater and brackish Macrostomida, which group most of the specie ...

***** Genus ''

Bradynectes Macrostomorpha is a clade of free living flatworms ranked either as class or subclass in the group Rhabditophora. There are about 260 described species in two orders - marine, freshwater and brackish Macrostomida, which group most of the specie ...

'' ***** Genus ''

Myozona Macrostomorpha is a clade of free living flatworms ranked either as class or subclass in the group Rhabditophora. There are about 260 described species in two orders - marine, freshwater and brackish Macrostomida, which group most of the specie ...

'' **** Family Haplopharyngidae **** Family Macrostomidae *** Order Dolichomicrostomida * Superclass

(''

parasite Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives on or inside another organism, the Host (biology), host, causing it some harm, and is Adaptation, adapted structurally to this way of lif ...

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, known as tapeworms. Their bodies consist of m ...

*** Subclass

Cestodaria Cestodaria is one of two subclasses of the 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 wo ...

**** Order

Amphilinidea Amphilinidae is a Family (biology), family of parasitic flatworms of the phylum Platyhelminthes. It is the only family in the monotypic Order (biology), order Amphilinidea. Amphilinids are Cestodes, yet differ from true tapeworms (Eucestoda) as t ...

**** Order

Gyrocotylidea Gyrocotylidea is an order of Cestoda (tapeworms). Members of this order are parasites of vertebrates, living in the coelom The coelom (or celom) is the main body cavity in most animals and is positioned inside the body to surround and contai ...

*** Subclass

Eucestoda Eucestoda, commonly referred to as tapeworms, is the larger of the two subclasses of flatworms in the class Cestoda (the other subclass is Cestodaria). Larvae have six posterior hooks on the scolex (head), in contrast to the ten-hooked Cestodar ...

**** Order

Bothriocephalidea Bothriocephalidea is an order of Cestoda (tapeworms). Members of this order are gut parasites Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing ...

**** Order

Caryophyllidea The Caryophyllideans are a group of tapeworms that infect fish and annelids (segmented worms) with a simple scolex or "head." Worms in this order only have one proglottid, which is believed to be the primitive condition for tapeworms. They are ge ...

**** Order Cathetocephalidea **** Order

Cyclophyllidea Tapeworms of the order Cyclophyllidea (the cyclophyllid cestodes) are the most important cestode parasites of humans and domesticated animals. All have multiple proglottid "segments", and all have four suckers on their scolices (heads), though ...

**** Order Diphyllidea **** Order

Diphyllobothriidea Diphyllobothriidea is an order of Cestoda (tapeworms). Members of this order are gut parasites of vertebrates. They infect mammals as their definitive hosts and use either copepod Copepods (; meaning "oar-feet") are a group of small crustacea ...

**** Order

Lecanicephalidea Lecanicephaloidea is an order of cestoda, tapeworms of the Class (biology), subclass Cestoda. Species in the order consist of intestinal parasites of elasmobranch fishes. Anatomy The order is distinguished in that the scolex consists of two pa ...

**** Order

Litobothriidea Litobothriidea is a monotypic order of Cestoda (tapeworms). It contains only the monotypic family Litobothriidae, which includes only the genus ''Litobothrium''. Members of this order are gut parasites of lamniform The Lamniformes (, from ...

**** Order

Onchoproteocephalidea Onchoproteocephalidea is an order of flatworms belonging to the class Cestoda. Families: * Onchobothriidae * Prosobothriidae * Proteocephalidae Proteocephalidae is a diverse family tapeworms with nearly 300 recognized species in 66 genera ...

**** Order

Phyllobothriidea Phyllobothriidea is an order of flatworms belonging to the class Cestoda. Taxonomy Families: * Chimaerocestidae * Phyllobothriidae Genera: * '' Alexandercestus'' Ruhnke & Workman, 2013 * '' Bibursibothrium'' McKenzie & Caira, 1998 * '' Bilo ...

**** Order

Rhinebothriidea Rhinebothriidea is an order of Cestoda (tapeworms). Members of this order are gut parasites of stingray Stingrays are a group of sea rays, which are cartilaginous fish related to sharks. They are classified in the suborder Myliobatoidei o ...

**** Order

Spathebothriidea Spathebothriidea is an order of Cestoda (tapeworms). Members of this order are gut parasites Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives on or inside another organism, the Host ...

**** Order

Tetrabothriidea Tetrabothriidea is an order of helminths in the class Cestoda. It consists of only one family, Tetrabothriidae. Their hosts are mainly seabirds, the rest being cetaceans and pinnipeds. Genera All of the genera of Tetrabothriidea are in the fami ...

**** Order

Tetraphyllidea Tetraphyllidea is a large tapeworm order that contains some 60 genera and about 800 described species. Tetraphyllideans are remarkable for their scolex morphologies, which are the most varied and morphologically complex amongst all tapeworm order ...

**** Order

Trypanorhyncha ''Trypanorhyncha'' is an order of cestodes, a type of flatworm. Some species infect gamefish, such as sciaenids, during the parasitic worm's plerocercoid stage, and are commonly called spaghetti worm because of their appearance, approximating ...

*** Class

Monogenea Monogeneans 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 have both male and female reprod ...

**** Subclass

Monopisthocotylea The Monopisthocotylea are a subclass 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 Helminthum V ...

***** Order

Capsalidea The Monopisthocotylea are a subclass 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 Helminthum V ...

***** 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 *Ancylodiscoid ...

***** Order

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

***** Order

Monocotylidea The Monopisthocotylea are a subclass 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 Helminthum V ...

***** Order

Montchadskyellidea The Monopisthocotylea are a subclass 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 Helminthum V ...

**** Subclass

Polyopisthocotylea Polyopisthocotylea is a subclass of parasitic flatworms in the class Monogenea. WoRMS (2019). Polyopisthocotylea. Accessed at: http://www.marinespecies.org/aphia.php?p=taxdetails&id=119220 on 2019-02-08Yamaguti, S. (1963). Systema Helminthum Volum ...

***** Order

Chimaericolidea Polyopisthocotylea is a subclass of parasitic flatworms in the class Monogenea. WoRMS (2019). Polyopisthocotylea. Accessed at: http://www.marinespecies.org/aphia.php?p=taxdetails&id=119220 on 2019-02-08Yamaguti, S. (1963). Systema Helminthum Volum ...

***** Order

Diclybothriidea Diclybothriidea is an order of monogeneans in the subclass Polyopisthocotylea. Families * Diclybothriidae Bychowsky & Gusev, 1950Bychowski, B. E. & Gusev, A. W. (1950). The family Diclybothriidae and its systematic position. ''Parazitologichesk ...

***** Order Lagarocotylidea ***** Order

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

***** Order

Polystomatidea Polyopisthocotylea is a subclass of parasitic flatworms in the class Monogenea. WoRMS (2019). Polyopisthocotylea. Accessed at: http://www.marinespecies.org/aphia.php?p=taxdetails&id=119220 on 2019-02-08Yamaguti, S. (1963). Systema Helminthum Volum ...

*** Class

Trematoda Trematoda is a class of flatworms known 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 usually a snail. The definitive host, ...

**** 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 one ...

***** Order

Aspidogastrida Aspidogastrida is an Order (biology), order of Trematoda, trematodes in the Class (biology)#Hierarchy of ranks, subclass Aspidogastrea. Families *Superfamily Aspidogastrioidea Poche, 1907Poche, F. (1907). Einige Bemerkungen zur Nomenklatur der T ...

***** Order Stichocotylida **** Subclass Digenea ***** Order

Diplostomida Diplostomida is an order of trematodes in the subclass Digenea. It is synonymous with Strigeida 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, or ...

References

{{Taxonbar, from=Q3428991 Protostome classes