Digenea (Gr. Dis - double, Genos - race) is a subclass within the Platyhelminthes consisting of parasitic flatworms with a syncytial tegument and, usually, two suckers, one ventral and one oral. Adults are particularly common in the digestive tract, but occur throughout the organ systems of all classes of vertebrates. Once thought to be related to the Monogenea, it is now recognised that they are closest to the Aspidogastrea and that the Monogenea are more closely allied with the Cestoda. Around 6000 species have been described to date. In biology, a subclass is one level below a class. ... Classes Monogenea Trematoda Cestoda Turbellaria The flatworms (Platyhelminthes, Greek platy: flat; helminth: worm) are a phylum of relatively simple soft-bodied invertebrate animals. ... A parasite is an organism that lives in or on the living tissue of a host organism at the expense of it. ... Classes Monogenea Trematoda Cestoda Turbellaria Wikimedia Commons has media related to: Platyhelminthes Wikispecies has information related to: Platyhelminthes The flatworms (Phylum Platyhelminthes from the Greek platy, meaning flat and helminth, meaning worm) are a phylum of relatively simple soft-bodied invertebrate animals. ... In biology, a syncytium is a large region of cytoplasm that contains many nuclei. ... In zootomy, the integumentary system is often the largest organ system of an animal, comprising skin, hair, feathers, scales, nails, skin glands and their products (sweat, slime). ... Typical classes Petromyzontidae (lampreys) Placodermi - extinct Chondrichthyes (cartilaginous fish) Acanthodii - extinct Actinopterygii (ray-finned fish) Actinistia (coelacanths) Dipnoi (lungfish) Amphibia (amphibians) Reptilia (reptiles) Aves (birds) Mammalia (mammals) Vertebrata is a subphylum of chordates, specifically, those with backbones or spinal columns. ... Monogenea (adj. ... Orders incertae sedis, see text The Aspidogastrea (gr. ... This article contains material from the CDC (Center for Disease Control) website which, as a US government publication, is in the public domain. ...

Morphology

Key features

Characteristic features of the digenea include a tegument. They possess a vermiform, unsegmented body-plan. In zootomy, the integumentary system is often the largest organ system of an animal, comprising skin, hair, feathers, scales, nails, skin glands and their products (sweat, slime). ... Vermiform is an adjective meaning worm-like. ...

There are typically two suckers, an anterior oral sucker surrounding the mouth, and a ventral sucker sometimes termed the acetabulum, on the ventral surface. A fish of the family Catostomidae. ... In zootomy, several terms are used to describe the location of organs and other structures in the body of bilateral animals. ... male human mouth The mouth, also known as the buccal cavity or the oral cavity, is the orifice through which an organism takes in food and water. ... In zootomy, several terms are used to describe the location of organs and other structures in the body of bilateral animals. ...

Monostome is a term used to describe worms with one sucker (oral). Flukes with an oral sucker and an acetabulum at the posterior end of the body are called Amphistomes. Distomes are flukes with an oral sucker and a ventral sucker, but the ventral sucker if somewhere other than posterior. Look up Fluke in Wiktionary, the free dictionary. ...

Reproductive system

Adult digeneans are commonly hermaphroditic. This is likely to be an adaptation to rarity, allowing the life cycle to continue when only one individual successfully infects the final host. Fertilisation is internal, with sperm being transferred via the cirrus to the Laurer's Canal or genital aperture. A key group of digeneans which are dioecious are the schistosomes. Asexual reproduction in the first larval stage is ubiquitous. The 1st-century BC sculpture The Reclining Hermaphrodite, in the Museo Nazionale Romano, Palazzo Massimo Alle Terme in Rome A hermaphrodite is an organism that possesses both male and female sex organs during its life. ... A sperm cell fertilizing an ovum This article is about reproduction in organisms. ... For other uses, see Sperm (disambiguation). ... Cirrus can refer to: a type of cloud, cirrus cloud a car produced by DaimlerChrysler, Chrysler Cirrus a German rocket, cirrus (rocket) a trance music group, Cirrus (music group) an interbank network (ATM network) by MasterCard, Cirrus (interbank network) a British aircraft engine company, Cirrus Engine an aircraft company, Cirrus... Laurers canal is a part of the reproductive system of trematodes, analogous to the vagina. ... 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... In biology, Dioecious is an adjective which indicates the exisistence of separate sexes in a species of organisms. ... A genus of trematodes, Schistosoma spp. ...

While the sexual formation of the digenean eggs and asexual reproduction in the first larval stage (miracidium) is widely reported, the developmental biology of the asexual stages remains a problem. Electron microscopic studies have shown that the light microscopically visible germ balls consist of mitotically dividing cells which give rise to embryos and to a line of new germ cells that become included in these embryonic stages. Since the absence of meiotic processes is not proven, the exact definition remains doubtful. In most birds and reptiles, an egg (Latin ovum) is the zygote, resulting from fertilization of the ovum. ... A larval insect A larva (Latin; plural larvae) is a juvenile form of animal with indirect development, undergoing metamorphosis (for example, insects or amphibians). ... Views of a Foetus in the Womb, Leonardo da Vinci, ca. ... An electron microscope is a type of microscope that uses electrons to illuminate and create an image of a specimen. ... Robert Hookes microscope (1665) - an engineered device used to study living systems. ... Mitosis is the way that in which a cell duplicates its chromosomes to generate two identical nuclei. ... Drawing of the structure of cork as it appeared under the microscope to Robert Hooke from Micrographia which is the origin of the word cell being used to describe the smallest unit of a living organism Cells in culture, stained for keratin (red) and DNA (green) The cell is the... For other uses, see Embryo (disambiguation). ... Gametes (in Greek: γαμέτες) —also known as sex cells, germ cells, or spores—are the specialized cells that come together during fertilization (conception) in organisms that reproduce sexually. ... Not to be confused with miosis. ...

Male organs

Protandry is the general rule among the Digenea. Usually two testes are present, but some flukes can have more than 100. Also present are vasa efferentia, a vas deferens, seminal vesicle, ejaculatory duct and a cirrus (analogous to a penis) enclosed is a cirrus sac. Did u no that mrs. stephenson loves to suck dicks. man can she shove them down her throat. ohh yea, did u no she liked it up her ass. GROSS. ohh an gregs a dork. peace out. The 1st-century BC sculpture The Reclining Hermaphrodite, in the Museo Nazionale Romano, Palazzo Massimo Alle Terme in Rome A hermaphrodite is an organism that possesses both male and female sex organs during its life. ... Human male anatomy The testicles, known medically as testes (singular testis), are the male generative glands in animals. ... The efferent ducts are part of the testes and connect the rete testis with the epididymis. ... The vas deferens (plural: vasa deferentia), also called ductus deferens, (Latin: carrying-away vessel) is part of the male anatomy of some species, including humans. ... The seminal vesicles are a pair of simple tubular glands posterinferior to the urinary bladder of males. ... The Ejaculatory ducts are part of the human male anatomy, which cause the reflex action of ejaculation. ... cross-section of two motile cilia, showing the 9+2 structure A cilium (plural cilia) or undulipodium (pl. ...

Female organs

Usually there is a single ovary with an oviduct, a seminal receptacle, a pair of vitelline glands (involved in yolk and egg-shell production) with ducts, the ootype (a chamber where eggs are formed), a complex collection of glands cells called Mehlis’ gland, which is believed to lubricate the uterus for egg passage. In addition, digenes possess a canal called Laurer's Canal, which leads from the oviduct to the dorsal surface of the body. Most trematodes possess an ovicapt, an enlarged portion of the oviduct where it joins the ovary. It probably controls the release of ova and spaces out their descent down the uterus. // For ovary as part of plants see ovary (plants) An ovary is an egg-producing reproductive organ found in female organisms. ... In oviparous animals (those that lay eggs), the passage from the ovaries to the outside of the body is known as the oviduct. ... Horse semen being collected for breeding purposes. ... The egg yolk is the yellow inside an egg. ... Laurers canal is a part of the reproductive system of trematodes, analogous to the vagina. ...

Digestive system

As adults, most digeneans possess a mouth, muscular pharynx and a forked, blind digestive system and feed actively. They are also capable of direct nutrient uptake through the tegument. Most adult digenes occur in the vertebrate alimentary canal or its associated organs, where they may feed on substances in the lumen (e.g., food ingested by the host, bile, mucous), or across the cavity wall (e.g., host blood). 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... This article is about the biological unit. ...

Nervous system

Paired ganglia at the anterior end of the body serve as the brain. From this nerves extend anteriorly and posteriorly. Sensory receptors are, for the most part, lacking among the adults, although they do have tangoreceptor cells. Larval stages have many kinds of sensory receptors, including light receptors and chemoreceptors. Chemoreception plays an important role in the free-living miracidial larva recognising and locating its host. Man fuck all this bullshit about projects. Man fuck the world. Fuck Mrs. Stephenson and her damn zoology class. Go suck a fuckin dick u stupid ass bitch. Fuck the world and her. Go fuck ur self. GÃ…NGLÃŽÃ… is a 1 man electronic grindcore band from Los Angeles California that began in August of 1999. ... For other uses, see Brain (disambiguation). ... A nerve is an enclosed, cable-like bundle of nerve fibers or axons, which includes the glia that ensheath the axons in myelin. ... Senses are the physiological methods of perception. ...

Life cycles

There is a bewildering array of variation on the complex digenean life cycle, and plasticity in this trait is probably a key to the group's success. In general, the life cycles may have two, three, or four obligate (necessary) hosts, sometimes with transport or paratenic hosts in between. The three-host life cycle is probably the most common. In almost all species, the first host in the life cycle is a mollusc. This has led to the inference that the ancestral digenean was a mollusc parasite and that vertebrate hosts were added subsequently. 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. ... Classes Caudofoveata Aplacophora Polyplacophora - Chitons Monoplacophora Bivalvia - Bivalves Scaphopoda - Tusk shells Gastropoda - Snails and Slugs Cephalopoda - Squids, Octopuses, etc. ...

The alternation of sexual and asexual generations is an important feature of digeneans. This phenomenon involves the presence of several discrete generations in one life-cycle.

A typical digenean trematode life cycle is as follows. Eggs leave the vertebrate host in faeces and use various strategies to infect the first intermediate host, in which sexual reproduction does not occur. Digeneans may infect the first intermediate host (usually a snail) by either passive or active means. The eggs of some digeneans, for example, are (passively) eaten by snails (or, rarely, by an annelid worm), in which they proceed to hatch. Alternatively, eggs may hatch in water to release an actively swimming, ciliated larva, the miracidium, which must locate and penetrate the body wall of the snail host. This article does not cite any references or sources. ... Rabbit feces are usually 0. ... Parasite life cycles can take a variety of forms, all involving the exploitation of one more hosts. ... This article is about the animal. ... Classes and subclasses Class Polychaeta (paraphyletic?) Class Clitellata*    Oligochaeta - earthworms, etc. ... The miracidium is the free swimming larva of some Trematoda including the Schistosoma. ... For other uses, see Body (disambiguation). ...

After post-ingestion hatching or penetration of the snail, the miracidium metamorphoses into a simple, sac-like mother sporocyst. The mother sporocyst undergoes a round of internal asexual reproduction, giving rise to either rediae (sing. redia) or daughter sporocysts. The second generation is thus the daughter parthenita sequence. These in turn undergo further asexual reproduction, ultimately yielding large numbers of the second free-living stage, the cercaria (pl. cercariae). It has been suggested that Parthenogenesis be merged into this article or section. ...

Free-swimming cercariae leave the snail host and move through the aquatic or marine environment, often using a whip-like tail, though a tremendous diversity of tail morphology is seen. Cercariae are infective to the second host in the life cycle, and infection may occur passively (e.g., a fish consumes a cercaria) or actively (the cercaria penetrates the fish). Sea water is water from a sea or ocean. ... For other uses, see Fish (disambiguation). ...

The life cycles of some digeneans include only two hosts, the second being a vertebrate. In these groups, sexual maturity occurs after the cercaria penetrates the second host, which is in this case also the definitive host. Two host life-cycles can be primary (there never was a third host) as in the Bivesiculidae, or secondary (there was at one time in evolutionary history a third host but it has been lost). Parasite life cycles can take a variety of forms, all involving the exploitation of one more hosts. ...

In three-host life cycles, cercariae develop in the second intermediate host into a resting stage, the metacercaria, which is usually encysted in a cyst of host and parasite origin, or encapsulated in a layer of tissue derived from the host only. This stage is infective to the definitive host. Transmission occurs when the definitive host preys upon an infected second intermediate host. Metacercariae excyst in the definitive host’s gut in response to a variety of physical and chemical signals, such as gut pH levels, digestive enzymes, temperature, etc. Once excysted, adult digeneans migrate to more or less specific sites in the definitive host and the life cycle repeats. A cyst (soft c, rhymes with list) is a closed sac having a distinct membrane and develosion on the nearby tissue. ... Parasite life cycles can take a variety of forms, all involving the exploitation of one more hosts. ... For other uses, see PH (disambiguation). ... Ribbon diagram of the enzyme TIM, surrounded by the space-filling model of the protein. ... For other uses, see Temperature (disambiguation). ...

Human digenean infections

Only about 12 of the 6,000 known species are infectious to humans, but some of these species are important diseases afflicting over 200 million people. The species that infect humans can be divided into groups, the schistosomes and the non-schistosomes. Infection is also the title of an episode of the television series Babylon 5; see Infection (Babylon 5). ... This article is about the medical term. ...

Schistosomes

The Schistosomes occur in the circulatory system of the definitive host. Humans become infected after free-swimming cercaria liberated from infected snails penetrate the skin. These dioecious worms are long and thin, ranging in size from 10 to 30 mm in length to 0.2 to 1.0 mm in diameter. Adult males are shorter and thicker than females, and have a long groove along one side of the body in which the female is clasped. Females reach sexual maturity after they have been united with a male. After mating the two remain locked together for the rest of their lives. They can live for several years and produce many thousands of eggs. For transport in plants, see Vascular tissue. ...

The four species of schistosomes that infect humans are members of the genus Schistosoma. For other uses, see Genus (disambiguation). ... A genus of trematodes, Schistosoma spp. ...

A genus of trematodes, Schistosoma spp. ... Species Species Biomphalaria glabrata Species Biomphalaria obstructa Species Biomphalaria amazonica Species Biomphalaria pfeifferi Species Biomphalaria tenagophila Species Biomphalaria havanensis Species Biomphalaria straminea Species Biomphalaria alexandrina Species Biomphalaria subprona Biomphalaria is an important genus of snail that serves as a natural host for the schistomasomiasis blood fluke. ... A world map showing the continent of Africa Africa is the worlds second-largest and second most-populous continent, after Asia. ... South America South America is a continent crossed by the equator, with most of its area in the Southern Hemisphere. ... “West Indian” redirects here. ... A map showing countries commonly considered to be part of the Middle East The Middle East is a region comprising the lands around the southern and eastern parts of the Mediterranean Sea, a territory that extends from the eastern Mediterranean Sea to the Persian Gulf. ... A genus of trematodes, Schistosoma spp. ... [[{{{diversity_link}}}|Diversity]] {{{diversity}}} Binomial name {{{binomial}}} Trinomial name {{{trinomial}}} Type Species {{{type_species}}} {{{subdivision_ranks}}} [[Image:{{{range_map}}}|{{{range_map_width}}}|]] Synonyms {{{synonyms}}} Bulinus is an important genus of fresh-water snail. ... A world map showing the continent of Africa Africa is the worlds second-largest and second most-populous continent, after Asia. ... A map showing countries commonly considered to be part of the Middle East The Middle East is a region comprising the lands around the southern and eastern parts of the Mediterranean Sea, a territory that extends from the eastern Mediterranean Sea to the Persian Gulf. ... A genus of trematodes, Schistosoma spp. ... Genera Genus Oncomelania Oncomelania is a genus of snail. ... East Asia Geographic East Asia. ... A genus of trematodes, Schistosoma spp. ... [[{{{diversity_link}}}|Diversity]] {{{diversity}}} Binomial name {{{binomial}}} Trinomial name {{{trinomial}}} Type Species {{{type_species}}} {{{subdivision_ranks}}} [[Image:{{{range_map}}}|{{{range_map_width}}}|]] Synonyms {{{synonyms}}} Bulinus is an important genus of fresh-water snail. ... A world map showing the continent of Africa Africa is the worlds second-largest and second most-populous continent, after Asia. ...

Non-schistosomes

There seven major species of non-schistosomes that infect humans are listed below. People become infected after ingesting metacercarial cysts on plants or in undercooked animal flesh. Most species inhabit the human gastrontestinal tract, where they shed eggs along with host feces. Paragonimus westermani, which colonizes the lungs, can also pass its eggs in saliva. These flukes generally cause mild pathology in humans, but more serious effects may also occur. Saliva is the watery and usually frothy substance produced in the mouths of humans and some animals. ...

For other uses, see Asia (disambiguation). ... Genera Agonostomus Aldrichetta Cestraeus Cahaenomugil Chelon Crenimugil Joturus Liza Moolgarda Mugil Myxus Neomyxus Oedalechilus Rhinomugil Sicamugil Valaomugil Xenomugil The mullets are a family (Mugilidae) of ray-finned fish found worldwide in coastal temperate and tropical waters, and in some species in fresh water also. ... Genera Oreochromis (about 30 species) Sarotherodon (over 10 species) Tilapia (about 40 species) and see text Tilapia is the common name for nearly 100 species of cichlid fishes from the tilapiine cichlid tribe. ... For other uses, see Asia (disambiguation). ... Pre-1989 division between the West (grey) and Eastern Bloc (orange) superimposed on current national boundaries: Russia (dark orange), other countries of the former USSR (medium orange),members of the Warsaw pact (light orange), and other former Communist regimes not aligned with Moscow (lightest orange). ... A map showing countries commonly considered to be part of the Middle East The Middle East is a region comprising the lands around the southern and eastern parts of the Mediterranean Sea, a territory that extends from the eastern Mediterranean Sea to the Persian Gulf. ... For other uses, see Carp (disambiguation). ... Rainbow trout, Oncorhynchus mykiss Biwa trout (or Biwa salmon), Oncorhynchus masou rhodurus Trout is the common name given to a number of species of freshwater fish belonging to the salmon family, Salmonidae. ... This article is about Siberia as a whole. ... The Clonorchis sinensis is a human liver fluke in the class Trematoda, Phylum Platyhelminthes. ... [[{{{diversity_link}}}|Diversity]] {{{diversity}}} Binomial name {{{binomial}}} Trinomial name {{{trinomial}}} Type Species {{{type_species}}} {{{subdivision_ranks}}} [[Image:{{{range_map}}}|{{{range_map_width}}}|]] Synonyms {{{synonyms}}} Bulinus is an important genus of fresh-water snail. ... East Asia Geographic East Asia. ... North America North America is a continent[1] in the Earths northern hemisphere and (chiefly) western hemisphere. ... Binomial name Fasciola hepatica The Fasciola hepatica, commonly known as the liver fluke, is a parasitic flatworm of the class Trematoda, phylum Platyhelminthes that infects the hepatic bile ducts of sheep and cattle, sometimes also humans, causing fascioliasis also known as fasciolosis. ... For other uses, see Central America (disambiguation). ... North America North America is a continent[1] in the Earths northern hemisphere and (chiefly) western hemisphere. ... South America South America is a continent crossed by the equator, with most of its area in the Southern Hemisphere. ... Species Paragonimus westermani Paragonimus westermani is the taxonomic name of an important lung fluke. ... Genera Genus Oncomelania Oncomelania is a genus of snail. ... Superfamilies Dromiacea Homolodromioidea Dromioidea Homoloidea Eubrachyura Raninoidea Cyclodorippoidea Dorippoidea Calappoidea Leucosioidea Majoidea Hymenosomatoidea Parthenopoidea Retroplumoidea Cancroidea Portunoidea Bythograeoidea Xanthoidea Bellioidea Potamoidea Pseudothelphusoidea Gecarcinucoidea Cryptochiroidea Pinnotheroidea * Ocypodoidea * Grapsoidea * An asterisk (*) marks the crabs included in the clade Thoracotremata. ... Families Astacoidea   Astacidae   Cambaridae Parastacoidea   Parastacidae Crayfish, often referred to as crawfish or crawdad, are freshwater crustaceans resembling small lobsters, to which they are closely related. ... For other uses, see Asia (disambiguation). ...

Important publications

Key to the Trematoda, vol.1 Gibson, D.I., Jones, A., and Bray, R.A. (2002) ISBN 0-85199-547-0

External links

• Cambridge University Schistosome Research Group

• Parasitic Worms at the Natural History Museum, London

• Fishdisease.net