Gigantorhynchida is an order containing a single family, Gigantorhynchidae of

Acanthocephala Acanthocephala ( Greek , ' 'thorn' + , ' 'head') is a group of parasitic worms known as acanthocephalans, thorny-headed worms, or spiny-headed worms, characterized by the presence of an eversible proboscis, armed with spines, which it uses t ...

(thorny-headed worms, also known as spiny-headed worms) that parasitize

vertebrates Vertebrates () are animals with a vertebral column (backbone or spine), and a cranium, or skull. The vertebral column surrounds and protects the spinal cord, while the cranium protects the brain. The vertebrates make up the subphylum Vertebra ...

by attaching themselves to the intestinal wall of their host. There are over 60 species classified into three genera in Gigantorhynchida '' Gigantorhynchus'', '' Intraproboscis'', and '' Mediorhynchus''.

Taxonomy

Phylogenetically In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical data ...

, the family Gigantorhynchidae is sister to the family Moniliformidae, represented by sequences of ''

Moniliformis Moniliformis ''Moniliformis moniliformis'' is a parasite of the Acanthocephala phylum in the family Moniliformidae. The adult worms are usually found in intestines of rodents or carnivores such as cats and dogs. The species can also infest humans, though thi ...

'' that form a supported monophyletic group. The group formed by Gigantorhynchidae and Moniliformidae suggest it to be a sister to the group formed by sequences of ''

Macracanthorhynchus ingens ''Macracanthorhynchus'', also known as the giant thorny-headed worm of swine, is a member of the Oligacanthorhynchidae which contains four species. Taxonomy Phylogenetic analysis has been conducted on at least one of the four species in the gen ...

'' and ''

Oncicola venezuelensis ''Oncicola'' is a genus of parasitic worms belonging to the family Oligacanthorhynchidae. ''Oncicola'' belongs to the phylum Acanthocephalans that include many thorny-headed worms. This family contains 12 genera including the genus ''Oncicola''. ...

'' A new taxonomic analysis has been performed.

Genera

Gigantorhynchida contains three genera.

Gigantorhynchus

The genus ''Gigantorhynchus'' contains six species with ''G. echinodiscus'' as the type species. It was described by Hamann in 1892. The genus ''Gigantorhynchus'' is characterized by the presence of a cylindrical proboscis with a crown of robust hooks at the

apex The apex is the highest point of something. The word may also refer to: Arts and media Fictional entities * Apex (comics) A-Bomb Abomination Absorbing Man Abraxas Abyss Abyss is the name of two characters appearing in Ameri ...

followed by numerous small hooks on the rest of the proboscis. The body, or trunk, is long with pseudosegmentation, the lemnisci are

filiform Filiform, thread or filament like, can refer to: * Filiform, a common term used in botany to describe a thread-like shape *Filiform, or filiform catheter, a medical device whose component parts or segments are all cylindrical and more or less un ...

, and the

testes A testicle or testis ( testes) is the gonad in all male bilaterians, including humans, and is homologous to the ovary in females. Its primary functions are the production of sperm and the secretion of androgens, primarily testosterone. The ...

are ellipsoid. Species of ''Gigantorhynchus'' are distinguished based on the number and size of hooks on the crown of the proboscis, the type of pseudosegmentation, and size of the ellipsoid eggs. Males of all species possess eight cement glands which are used to temporarily close the posterior end of the female after copulation. There is pronounced

sexual dimorphism Sexual dimorphism is the condition where sexes of the same species exhibit different Morphology (biology), morphological characteristics, including characteristics not directly involved in reproduction. The condition occurs in most dioecy, di ...

with the female often two or more times longer than the male. ''Gigantorhynchus'' species infest

marsupials Marsupials are a diverse group of mammals belonging to the infraclass Marsupialia. They are natively found in Australasia, Wallacea, and the Americas. One of marsupials' unique features is their reproductive strategy: the young are born in a ...

and myrmecophagids (anteaters) in Central and

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...

Intraproboscis

The genus ''Intraproboscis'' contains a single species, ''Intraproboscis sanghae''. The genus and species were described by Amin, Heckmann, Sist, and Basso in 2021. The genus ''Intraproboscis'' closely resembles the genus '' Mediorhynchus'' but is characterized by six distinct features: infesting mammals instead of birds, a simple proboscis receptacle (a complex structure for housing the proboscis when retracted) that is completely suspended within the proboscis, proboscis retractor muscles that pass through the proboscis receptacle and into the body cavity posteriorly, no neck, and a parareceptacle structure and a uterine vesicle which are both absent in ''Mediorhynchus''. There is pronounced

with the female larger than the male. ''I. sanghae'' infests the black-bellied pangolin (''Phataginus tetradactyla'') and the

tree pangolin The white-bellied pangolin (''Phataginus tricuspis'') is one of eight Extant taxon, extant species of pangolins ("scaly anteaters"), and is native to equatorial Africa. Also known as the tree pangolin or three-cusped pangolin, it is the most com ...

(''Phataginus tricuspis'') both in Central Africa.

Mediorhynchus

''Mediorhynchus'' Van Cleave, 1916 contains at least 59 species.

Distribution

''Gigantorhynchus'' is found in mammals in South America and baboons in Africa. ''Intraproboscis'' is found in mammals in Africa, and ''Mediorhynchus'' is found in birds worldwide. https://cms.turkiyeparazitolderg.org/Uploads/Article_64634/TPD-48-66.pdf

Notes

References

Acanthocephala families Archiacanthocephala {{acanthocephalan-stub