Pseudophyllid

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

s (former order pseudophyllidea) are tapeworms with multiple "segments" (

proglottid 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 man ...

s) and two bothria or "sucking grooves" as adults. Proglottids are identifiably pseudophyllid as the genital pore and uterine pore are located on the mid-

ventral Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek language, Greek roots, describe something in its standard anatomical position. Th ...

surface, and the

ovary The ovary is an organ in the female reproductive system that produces an ovum. When released, this travels down the fallopian tube into the uterus, where it may become fertilized by a sperm. There is an ovary () found on each side of the body. ...

is bilobed ("

dumbbell The dumbbell, a type of free weight, is a piece of equipment used in weight training. It can be used individually or in pairs, with one in each hand. History The forerunner of the dumbbell, halteres, were used in ancient Greece as lifting w ...

-shaped"). The order has been discovered by phylogenetic analysis to be

paraphyletic In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be pa ...

, and has been broken up into two orders, Bothriocephalidea and

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 copepods (a group of small crustaceans found in the sea and nearly ever ...

. Eggs have one flat end (the operculum) and a small knob on the other end. All pseudophyllid cestodes have a

procercoid Procercoid is the first larval stage of some tapeworms, which usually develops inside the body cavity of copepods. Flatworm in this stage is not enclosed in a protective cyst, but is infectious. Procercoids resemble their adult forms in pathways of ...

stage in their

life cycle Life cycle, life-cycle, or lifecycle may refer to: Science and academia *Biological life cycle, the sequence of life stages that an organism undergoes from birth to reproduction ending with the production of the offspring *Life-cycle hypothesis, ...

, and most also have a

plerocercoid ''Plerocercoid'' refers to last larval form, the infective form, found in the second intermediate host of many Cestoda with aquatic life cycles. References

Cestoda Larvae {{Parasitic animal-stub ...

stage. The majority of genera in this group have fish as their definitive hosts, but the most important

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

of pseudophyllid cestodes is

Diphyllobothriidae Diphyllobothriidea is a family of Cestoda (tapeworms). Members of this family are gut parasites of vertebrates. In most species the definitive hosts are marine or aquatic mammals such as cetaceans and pinnipeds, the first intermediate host usual ...

, which infect

mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...

bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweigh ...

s and

reptile Reptiles, as most commonly defined are the animals in the class Reptilia ( ), a paraphyletic grouping comprising all sauropsids except birds. Living reptiles comprise turtles, crocodilians, squamates (lizards and snakes) and rhynchocephalians ( ...

s as their

definitive 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 a ...

s and use either

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 (inhabiting sea waters), some are benthos, benthic (living on the ocean floor) ...

s (a group of small crustaceans found in the sea and nearly every freshwater habitat, e.g. ''

Spirometra ''Spirometra'' is a genus of pseudophyllid cestodes that reproduce in canines and felines, but can also cause pathology in humans if infected. As an adult, this tapeworm lives in the small intestine of its definitive host and produces eggs that ...

'') or both copepods and fish as in the

broadfish tapeworm ''Diphyllobothrium'' is a genus of tapeworms which can cause diphyllobothriasis in humans through consumption of raw or undercooked fish. The principal species causing diphyllobothriasis is ''D. latum'', known as the broad or fish tapeworm, or b ...

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 a ...

s. Typical mammalian hosts are whales and other

cetacea Cetacea (; , ) is an infraorder of aquatic mammals that includes whales, dolphins, and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size and exclusively carnivorous diet. They propel them ...

ns, and

pinniped Pinnipeds (pronounced ), commonly known as seals, are a widely distributed and diverse clade of carnivorous, fin-footed, semiaquatic, mostly marine mammals. They comprise the extant families Odobenidae (whose only living member is the walru ...

s. The hermaphroditic ''

Schistocephalus solidus ''Schistocephalus solidus'' is a tapeworm of fish, fish-eating birds and rodents. This hermaphroditic parasite belongs to the Eucestoda subclass, of class Cestoda. This species has been used to demonstrate that cross-fertilization produces a high ...

'' parasitizes fish and fish-eating water birds, with a cyclopoid copepod as the first intermediate host. When humans harbor

plerocercoid ''Plerocercoid'' refers to last larval form, the infective form, found in the second intermediate host of many Cestoda with aquatic life cycles. References

Cestoda Larvae {{Parasitic animal-stub ...

s of pseudophyllidean cestodes outside the small intestine, it can cause

sparaganosis Sparganosis is a parasitic infection caused by the plerocercoid larvae of the genus ''Spirometra'' including ''S. mansoni'', ''S. ranarum'', ''S. mansonoides'' and ''S. erinacei''.John, D.T. and Petri, W.A. Markell and Voge's Medical Parasitolog ...

References

Cestoda Platyhelminthes orders {{parasitic animal-stub