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Encyclopedia > Acanthocephala
Wikipedia:How to read a taxobox
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Corynosoma wegeneri
Corynosoma wegeneri
Scientific classification
Kingdom: Animalia
Subkingdom: Eumetazoa
Superphylum: Platyzoa
Phylum: Acanthocephala
Kohlreuther, 1771

Eoacanthocephala A photomicrograph of the acanthocephalan Corynosoma wegeneri. ... Scientific classification or biological classification is a method by which biologists group and categorize species of organisms. ... Animalia redirects here. ... subgroups Ctenophora Cnidaria Bilateria Eumetazoa is a clade comprising all major animal groups except sponges. ... The Platyzoa are a group of protostome animals. ... Scientific classification or biological classification refers to how biologists group and categorize extinct and living species of organisms. ... Orders Apororhynchida Gigantorhynchida Moniliformida Oligacanthorhynchida Archiacanthocephala is a class within the phylum of Acanthocephala. ... Orders Echinorhynchida Polymorphida Palaeacanthocephala (ancient thorn head) is a class within the phylyum Acanthocephala. ... Orders Gyracanthocephala Neoechinorhynchida Eoacanthocephala is a class of parasitic worms, within the phylum Acanthocephala. ...

The Acanthocephala (gr. Acanthus — thorn Kephale — head) is a phylum of parasitic worms, characterised by the presence of an evertable proboscis, armed with spines, which it uses to pierce and hold the gut wall of its host. Acanthocephalans typically have complex life cycles, involving a number of hosts, including invertebrates, fishes, amphibians, birds, and mammals. About 1150 species have been described. Phylum (plural: phyla) is a taxon used in the classification of animals, adopted from the Greek phylai the clan-based voting groups in Greek city-states. ... A parasite is an organism that lives in or on the living tissue of a host organism at the expense of it. ... In general, a proboscis (from Greek pro before and boskein to feed) is an elongated appendage from the head of an animal. ... For the Physics term GUT, please refer to Grand unification theory The gastrointestinal or digestive tract, also referred to as the GI tract or the alimentary canal or the gut, is the system of organs within multicellular animals which takes in food, digests it to extract energy and nutrients, and... Parasite life cycles can take a variety of forms, all involving the exploitation of one more hosts. ... Invertebrate is a term that describes any animal without a spinal column. ... A giant grouper at the Georgia Aquarium Fish are aquatic vertebrates that are typically cold-blooded; covered with scales, and equipped with two sets of paired fins and several unpaired fins. ... For other uses, see Amphibian (disambiguation). ... “Aves” redirects here. ... Subclasses Subclass Allotheria* Order Docodonta (extinct) Order Multituberculata (extinct) Order Palaeoryctoides (extinct) Order Triconodonta (extinct) Order Volaticotheria (extinct) Subclass Prototheria Order Monotremata Subclass Theria Infraclass Trituberculata (extinct) Infraclass Metatheria Infraclass Eutheria Mammals are a class of vertebrate animals characterized by the production of milk in females for the nourishment of... In biology, a species is one of the basic units of biodiversity. ...


Morphological characteristics

There are several morphological characteristics that distinguish acanthocephalans from other phyla of parasitic worms.


Acanthocephalans lack a mouth or alimentary canal. This is a feature they share with the cestoda (tapeworms), although the two groups are not related. Adult stages live in the intestines of their host and uptake nutrients which have been digested by the host, directly, through their body surface. It has been suggested that this article or section be merged with mouth (human). ... For the Physics term GUT, please refer to Grand unification theory The gastrointestinal or digestive tract, also referred to as the GI tract or the alimentary canal or the gut, is the system of organs within multicellular animals which takes in food, digests it to extract energy and nutrients, and... // Orders Subclass Cestodaria Amphilinidea Gyrocotylidea Subclass Eucestoda Aporidea Caryophyllidea Cyclophyllidea Diphyllidea Lecanicephalidea Litobothridea Nippotaeniidea Proteocephalidea Pseudophyllidea Spathebothriidea Tetraphyllidea Trypanorhyncha In biology, Cestoda is the class of parasitic flatworms, called cestodes or tapeworms, that live in the digestive tract of vertebrates as adults and often in the bodies of various animals... In anatomy, the intestine is the segment of the alimentary canal extending from the stomach to the anus and, in humans and other mammals, consists of two segments, the small intestine and the large intestine (or colon). ... Digestion is the process whereby a biological entity processes a substance, in order to chemically convert the substance into nutrients. ...


The most notable feature of the acanthocephala is the presence of an anterior, protrudible proboscis that is usually covered with spiny hooks (hence the common name: thorny headed worm). The proboscis bears rings of recurved hooks arranged in horizontal rows, and it is by means of these hooks that the animal attaches itself to the tissues of its host. The hooks may be of two or three shapes, usually, longer, more slender hooks are arranged along the length of the proboscis, with several rows of more sturdy, shorter nasal hooks around the base of the proboscis. The proboscis is used to pierce the gut wall of the final host, and hold the parasite fast while it completes its life cycle. Like the body, the proboscis is hollow, and its cavity is separated from the body cavity by a septum or proboscis sheath. Traversing the cavity of the proboscis are muscle-strands inserted into the tip of the proboscis at one end and into the septum at the other. Their contraction causes the proboscis to be invaginated into its cavity. The whole proboscis apparatus can also be, at least partially, withdrawn into the body cavity, and this is effected by two retractor muscles which run from the posterior aspect of the septum to the body wall. In zootomy, several terms are used to describe the location of organs and other structures in the body of bilateral animals. ... In general, a proboscis (from Greek pro before and boskein to feed) is an elongated appendage from the head of an animal. ... A top-down view of skeletal muscle Muscle (from Latin musculus little mouse [1]) is contractile tissue of the body and is derived from the mesodermal layer of embryonic germ cells. ...

Some key features of acanthocephalan morphology

Drawing of morphology of Corynosoma wegeneri. ... Drawing of morphology of Corynosoma wegeneri. ...

Phylogenetic relationships

Acanthocephalans are highly adapted to a parasitic mode of life, and have lost many organs and structures through evolutionary processes. This makes determining relationships with other higher taxa through morphological comparison problematic. Phylogenetic analysis of the 18S ribosomal gene has revealed that the Acanthocephala are most closely related to the rotifers, or may even belong in that phylum. The two are included among the Platyzoa. In biology, phylogenetics (Greek: phylon = tribe, race and genetikos = relative to birth, from genesis = birth) is the study of evolutionary relatedness among various groups of organisms (e. ... Figure 1: Ribosome structure indicating small subunit (A) and large subunit (B). ... Classes Seisonoidea Bdelloidea Monogononta The rotifers make up a phylum of microscopic, and near-microscopic pseudocoelomate animals. ... The Platyzoa are a group of protostome animals. ...


The size of the animals varies greatly, from forms a few millimetres in length to Gigantorhynchus gigas, which measures from 100 to 650 mm. A millimetre (American spelling: millimeter, symbol mm) is an SI unit of length that is equal to one thousandth of a metre. ...


The body surface of the acanthocephala is peculiar. Externally, the skin has a thin cuticle covering the epidermis, which consists of a syncytium with no cell walls. The syncytium is traversed by a series of branching tubules containing fluid and is controlled by a few wandering, amoeboid nuclei. Inside the syncytium is an irregular layer of circular muscle fibres, and within this again some rather scattered longitudinal fibres; there is no endothelium. In their micro-structure the muscular fibres resemble those of nematodes. It has been suggested that this article or section be merged into Eponychium. ... Look up Epidermis in Wiktionary, the free dictionary. ... In biology, a syncytium is a large region of cytoplasm that contains many nuclei. ... A cell wall is a fairly rigid layer surrounding a cell, located external to the cell membrane, that provides the cell with structural support, protection, and a filtering mechanism. ... A tubule is a very small tube or fistular structure. ... Amoeba (Chaos diffluens) Foraminiferan (Ammonia tepida) Heliozoan (Actinophrys sol) Amoeboids are cells that move or feed by means of temporary projections, called pseudopods (false feet). ... HeLa cells stained for DNA with the Blue Hoechst dye. ... The endothelium is the layer of thin, flat cells that lines the interior surface of blood vessels, forming an interface between circulating blood in the lumen and the rest of the vessel wall. ... Classes Adenophorea    Subclass Enoplia    Subclass Chromadoria Secernentea    Subclass Rhabditia    Subclass Spiruria    Subclass Diplogasteria The nematodes or roundworms (Phylum Nematoda from Greek (nema): thread + -ode like) are one of the most common phyla of animals, with over 20,000 different described species (over 15,000 are parasitic). ...

Except for the absence of the longitudinal fibres the skin of the proboscis resembles that of the body, but the fluid-containing tubules of the proboscis are shut off from those of the body. The canals of the proboscis open into a circular vessel which runs round its base. From the circular canal two sac-like projections called the lemnisci run into the cavity of the body, alongside the proboscis cavity. Each consists of a prolongation of the syncytial material of the proboscis skin, penetrated by canals and sheathed with a muscular coat. They seem to act as reservoirs into which the fluid which is used to keep the proboscis "erect" can withdraw when it is retracted, and from which the fluid can be driven out when it is wished to expand the proboscis.

Nervous system

The central ganglion of the nervous system lies behind the proboscis sheath or septum. It innervates the proboscis and projects two stout trunks posteriorly which supply the body. Each of these trunks is surrounded by muscles, and this nerve-muscle complex is called a retinaculum. In the male at least there is also a genital ganglion. Some scattered papillae may possibly be sense-organs. A sex organ, or primary sexual characteristic, narrowly defined, is any of those parts of the body (which are not always bodily organs according to the strict definition) which are involved in sexual reproduction and constitute the reproductive system in an complex organism; namely: Male: penis (notably the glans penis... This is a dorsal root ganglion (DRG) from a chicken embryo (around stage of day 7) after incubation overnight in NGF growth medium stained with anti-neurofilament antibody. ... A papilla (plural: papillae) can be: A small projection, such as a nipplelike projection on the skin, at the base of a hair or the root of a feather; the base of a new tooth. ...


The Acanthocephala are dioecious. There is a structure called the genital ligament which runs from the posterior end of the proboscis sheath to the posterior end of the body. In the male, two testes lie on either side of this. Each opens in a vas deferens which bears three diverticula or vesiculae seminales. The male also possesses three pairs of cement glands, found behind the testes, which pour their secretions through a duct into the vasa deferentia. These unite and end in a penis which opens posteriorly. In biology, Dioecious is an adjective which indicates the exisistence of separate sexes in a species of organisms. ... Human male anatomy The testicles, known medically as testes (singular testis), are the male generative glands in animals. ... The vas deferens, also called ductus deferens, (Latin: carrying-away vessel) is part of the male anatomy of some species, including humans. ... Diverticula are outpouchings of the intestinal wall. ... The penis (plural penises, penes) is an external male sexual organ. ...

In the female, the ovaries are found, like the testes, as rounded bodies along the ligament. From these masses of ova dehisce into the body cavity and float in its fluid. Here the eggs are fertilized and segment so that the young embryos are formed within their mother's body. The embryos escape into the uterus through the uterine bell, a funnel like opening continuous with the uterus. At the junction of the bell and the uterus there is a second small opening situated dorsally. The bell "swallows" the matured embryos and passes them on into the uterus, and from there, out of the body via the oviduct. Should the bell swallow any of the ova, or even one of the younger embryos, these are passed back into the body cavity through the second, dorsal, opening. Human female internal reproductive anatomy Ovaries are a part of a female organism that produces eggs. ... A human ovum An ovum (loosely, egg or egg cell) is a female sex cell or gamete. ... Categories: Biology stubs ... It has been suggested that embryology be merged into this article or section. ... The uterus or womb is the major female reproductive organ of most mammals, including humans. ... In anatomy, the dorsum is the upper or back side of an animal, as opposed to the ventrum. ... In oviparous animals (those that lay eggs), the passage from the ovaries to the outside of the body is known as the oviduct. ...

The embryo passes from the body of the female into the alimentary canal of the host and leaves this with the feces. Feces, faeces, or fæces (see spelling differences) In humans, defecation may occur (depending on the individual and the circumstances) from once every two or three days to several times a day. ...

Other features

A curious feature shared by both larva and adult is the large size of many of the cells, e.g. the nerve cells and cells forming the uterine bell. Polyploidy is common, with up to 343n having been recorded in some species. The acanthocephalans lack an excretory system, although some species have been shown to possess flame cells (protonephridia). Polyploid (in Greek: πολλαπλόν - multiple) cells or organisms contain more than one copy (ploidy) of their chromosomes. ... A flame cell is a specialized excretory cell found in the Platyhelminthes (except the tubellarian order Acoela), these are the simplest animals to have a dedicated excretory system. ...


The earliest recognisable description of Acanthocephala - a worm with a proboscis armed with hooks - was made by Italian author Francesco Redi (1684). In 1771 Koelreuther proposed the name Acanthocephala. Muller independetly called them Echinorhynchus in 1776. Rudolphi in 1809 formally named them Acanthocephala. Redi is featured in many modern-day science textbooks due to his experiment. ... 1771 was a common year starting on Tuesday (see link for calendar). ... Year 1776 (MDCCLXXVI) was a leap year starting on Monday (link will display the full calendar) of the Gregorian calendar (or a leap year starting on Thursday of the 11-day slower Julian calendar). ... Karl Asmund Rudolphi (b. ... Year 1809 (MDCCCIX) was a common year starting on Sunday (link will display the full calendar). ...

Currently the phylum is divided into four classes - Palaeacanthocephala, Archiacanthocephala, Polyacanthocephala and Eoacanthocephala.

Life cycles

General patterns

Acanthocephalans have complex life cycles, involving a number of hosts, for both developmental and resting stages. Complete life cycles have been worked out for only 25 species. Having been expelled by the female, the acanthocephalan embryo is released along with the feces of the host. For development to occur, the embryo needs to be ingested by an invertebrate, almost always a crustacean (there is one known life cycle which uses a mollusc as a first intermediate host). Inside the intermediate host, the acanthocephalan penetrates the gut wall, moves into the body cavity, encysts, and begins transformation into the infective cystacanth stage. This form has all the organs of the adult save the reproductive ones. The parasite is released when the first intermediate host is ingested. This can be by a suitable final host, in which case the cystacanth develops into a mature adult, or by a paratenic host, in which the parasite again forms a cyst. When consumed by a suitable final host, the cycstacant excysts, everts its proboscis and pierces the gut wall. It then feeds, grows and develops its sexual organs. Adult worms then mate. The male uses the excretions of its cement glands to plug the vagina of the female, preventing subsequent matings from occurring. Embryos develop inside the female, and the life cycle repeats. Morphogenesis is also the name of a band. ... Classes & Subclasses Branchiopoda Phyllopoda Sarsostraca Remipedia Cephalocarida Maxillopoda Thecostraca Tantulocarida Branchiura Pentastomida Mystacocarida Copepoda Ostracoda Myodocopa Podocopa Malacostraca Phyllocarida Hoplocarida Eumalacostraca The nauplius larva of a dendrobranchiate Porcellio scaber, the common rough woodlouse, a terrestrial crustacean Pollicipes polymerus, the gooseneck barnacle Glyphea pseudastacus, a fossil glypheoid The crustaceans (Crustacea) are... Classes Caudofoveata Aplacophora Polyplacophora - Chitons Monoplacophora Bivalvia - Bivalves Scaphopoda - Tusk shells Gastropoda - Snails and Slugs Cephalopoda - Squids, Octopuses, etc. ... In parasitology, the term paratenic describes an intermediate host which is not needed for the development of the parasite, but nonetheless serves to maintain the life cycle of the parasite. ... The vagina, (from Latin, literally sheath or scabbard ) is the tubular tract leading from the uterus to the exterior of the body in female placental mammals and marsupials, or to the cloaca in female birds, monotremes, and some reptiles. ...

An example - Polymorphus spp.

A diagram of the life cycle of Polymorphus spp.
A diagram of the life cycle of Polymorphus spp.

Polymorphus spp. are parasites of seabirds, particularly the Eider Duck (Somateria mollissima). Heavy infections of up to 750 parasites per bird are common, causing ulceration to the gut, disease and seasonal mortality. Recent research has suggested that there is no evidence of pathogenicity of Polymorphus spp. to intermediate crab hosts. The cystacanth stage is long lived and probably remains infective throughout the life of the crab. diagram of acanthocephalan life cycles File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... diagram of acanthocephalan life cycles File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Seabirds are birds that spend much of their lives, outside the breeding season at least, at sea. ... Eider Duck is a fictional duck published in Walt Disneys comic books, and is the uncle of Donald Duck. ... Endoscopic images of a duodenal ulcer. ... A pathogen or infectious agent is a biological agent that causes disease or illness to its host. ...

The life cycle of Polymorphus spp. normally occurs between sea ducks (e.g. eiders and scoters) and small crabs. Infections found in commercial-sized lobsters in Canada were probably acquired from crabs that form an important dietary item of lobsters. Cystacanths occurring in lobsters can cause economic loss to fishermen. There are no known methods of prevention or control. Genus Melanitta (Boie, 1822) The scoters are stocky seaducks in the genus Melanitta. ... Subfamilies and Genera Neophoberinae Acanthacaris Thymopinae Nephropsis Nephropides Thymops Thymopsis Nephropinae Homarus Nephrops Homarinus Metanephrops Eunephrops Thymopides Clawed lobsters comprise a family (Nephropidae, sometimes also Homaridae) of large marine crustaceans. ...

See also

Wikispecies has information related to:

GFDL Wikispecies logo File links The following pages link to this file: Solanaceae Species Asterias Homo (genus) Human Wikipedia:Template messages/Links Wikipedia:Template messages/All Homo floresiensis User talk:Tuneguru Template:Wikispecies Categories: GFDL images ... Wikispecies is a sister project supported by the Wikimedia Foundation that anybody can edit with a great potential use to students and researchers. ... // Orders Subclass Cestodaria Amphilinidea Gyrocotylidea Subclass Eucestoda Aporidea Caryophyllidea Cyclophyllidea Diphyllidea Lecanicephalidea Litobothridea Nippotaeniidea Proteocephalidea Pseudophyllidea Spathebothriidea Tetraphyllidea Trypanorhyncha In biology, Cestoda is the class of parasitic flatworms, called cestodes or tapeworms, that live in the digestive tract of vertebrates as adults and often in the bodies of various animals... Orders within the Digenea Strigeidida Azygiida Echinostomida Plagiorchiida Opisthorchiida The digenea (Gr. ... Monogenea (adj. ...


  • Lühe, M. (1904). 'Geschichte und Ergebnisse der Echinorhynchen-Forschung bis auf Westrumb (1821)', Zoologische Ann.... Zeitschift, 1, 139-250.
  • Amin, O. M. (1987). Key to the families and subfamilies of Acanthocephala, with erection of a new class (Polyacanthocephala) and a new order (Polyacanthorhynchida). Journal of Parasitology, 73, 1216-1219.

External links

Wikisource has an original article from the 1911 Encyclopædia Britannica about:
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  Results from FactBites:
Phylum Acanthocephala (1051 words)
Acanthocephala not noticed until beginning of the 18th century, not distinguished until Koelreuther (1771) proposes the name Acanthocephala.
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