Tetraphyllidea is a large

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

order Order, ORDER or Orders may refer to: * A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica * Categorization, the process in which ideas and objects are recognized, differentiated, and understood ...

that contains some 60

genera Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial s ...

and about 800 described

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

. Tetraphyllideans are remarkable for their

scolex 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 consi ...

morphologies, which are the most varied and morphologically complex amongst all tapeworm orders. Tetraphyllidean

cestode 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 ...

s also exhibit a remarkable degree of

host A host is a person responsible for guests at an event or for providing hospitality during it. Host may also refer to: Places * Host, Pennsylvania, a village in Berks County * Host Island, in the Wilhelm Archipelago, Antarctica People * ...

specificity. The

procercoid The procercoid is the second larval stage of some tapeworms, which typically develops inside of copepods following their ingestion of the coracidium parasite structure that contains the larval oncosphere. The flatworm in this stage is not enclos ...

probably parasitizes

copepod Copepods (; meaning 'oar-feet') are a group of small crustaceans found in nearly every freshwater and saltwater habitat (ecology), habitat. Some species are planktonic (living in the water column), some are benthos, benthic (living on the sedimen ...

s, which are eaten by the second

intermediate host In biology and medicine, a host is a larger organism that harbours a smaller organism; whether a parasitic, a mutualistic, or a commensalist ''guest'' (symbiont). The guest is typically provided with nourishment and shelter. Examples include ...

teleost Teleostei (; Ancient Greek, Greek ''teleios'' "complete" + ''osteon'' "bone"), members of which are known as teleosts (), is, by far, the largest group of ray-finned fishes (class Actinopterygii), with 96% of all neontology, extant species of f ...

fishes,

decapods The Decapoda or decapods, from Ancient Greek δεκάς (''dekás''), meaning "ten", and πούς (''poús''), meaning "foot", is a large order (biology), order of crustaceans within the class Malacostraca, and includes crabs, lobsters, crayfis ...

cephalopod A cephalopod is any member of the molluscan Taxonomic rank, class Cephalopoda (Greek language, Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral symm ...

s, which may also serve as

paratenic In biology and medicine, a host is a larger organism that harbours a smaller organism; whether a parasitic, a mutualistic, or a commensalist ''guest'' (symbiont). The guest is typically provided with nourishment and shelter. Examples include a ...

hosts. The verified definite hosts are

shark Sharks are a group of elasmobranch cartilaginous fish characterized by a ribless endoskeleton, dermal denticles, five to seven gill slits on each side, and pectoral fins that are not fused to the head. Modern sharks are classified within the ...

skate Skate or Skates may refer to: Fish *Skate (fish), several genera of fish belonging to the family Rajidae * Pygmy skates, several genera of fish belonging to the family Gurgesiellidae * Smooth skates or leg skates, several genera of fish belongin ...

s and

stingray Stingrays are a group of sea Batoidea, rays, a type of cartilaginous fish. They are classified in the suborder Myliobatoidei of the order Myliobatiformes and consist of eight families: Hexatrygonidae (sixgill stingray), Plesiobatidae (deepwate ...

s. Occasionally found in

cetacean Cetacea (; , ) is an infraorder of aquatic mammals belonging to the order Artiodactyla that includes whales, dolphins and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size and exclusively c ...

s, the role of these

apex predator An apex predator, also known as a top predator or superpredator, is a predator at the top of a food chain, without natural predators of its own. Apex predators are usually defined in terms of trophic dynamics, meaning that they occupy the hig ...

s in the tetraphyllidean life cycle is not well known; whales and dolphins may be definite or dead-end hosts. '' Crossobothrium antonioi'' is a recently discovered species in the genus '' Crossobothrium'', which belongs to the order Tetraphyllidea.New species of ''Crossobothrium'' (Cestoda:Tetraphyllidea) from the broadnose sevengill shark, ''Notorynchus cepedianus'', in Argentina
/ref> It is a parasitic tapeworm that infects ''Notorynchus cepedianus'', the broadnose sevengill shark. ''C. antonioi'' was discovered off the coast of Buenos Aires Province, Argentina. ''C. antonioi'' was recovered from the spiral intestine of ''N. cepedianus'' and named after the lead researcher's father, Antonio Ivanov. ''C. antonioi'' is the smallest species in its genus and about 47.4-51.5 mm long; other species in the genus are about twice as long as ''C. antonioi''. It has 4 stalked bothridia ("sucking grooves") on its scolex. Its proglottids, which are the segments of tapeworms that contain the reproductive structures, are longer than wide when immature, and become wider than long at maturity. However, the proglottids at each stage are generally the same shape. ''C. antonioi'' also have crenulated bothridial margins and a microthrix pattern that varies from other species in ''Crossobothrium''. The most notable and unique quality of ''C. antonioi'' is the large amount of testes per mature proglottid. ''C. antonioi'' has more than 700 testes per proglottid, whereas other ''Crossobothrium'' species have ~150-300 testes per proglottid.

References

Cestoda Platyhelminthes orders {{cestoda-stub