The Caryophyllideans are a group of

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

s that infect

fish Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of li ...

and

annelid The annelids (Annelida , from Latin ', "little ring"), also known as the segmented worms, are a large phylum, with over 22,000 extant species including ragworms, earthworms, and leeches. The species exist in and have adapted to various ecol ...

s (segmented worms) with a simple

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

or "head." Worms in this order only have one

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 ...

, which is believed to be the primitive condition for tapeworms. They are generally less than 10 centimetres long. Caryophillideans represent a unique type of tapeworm, such that they possess a monzoic, unsegmented, body, with only a single set of reproductive organs. In the Caryophyllidean

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 ...

, adults live in fish, who pass the tapeworm eggs in their feces. Annelids eat the eggs, where they hatch into

oncosphere An oncosphere is the larval form of a tapeworm once it has been ingested by an intermediate host animal. The intermediate host must ingest the tapeworm's eggs either in food or water-- once this has happened, the eggs hatch and develop into onc ...

larva A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. The ...

e that move through intestinal wall and become

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 ...

larvae in the body cavity. When the annelid is eaten by a fish, the tapeworm matures.

Catfish Catfish (or catfishes; order Siluriformes or Nematognathi) are a diverse group of ray-finned fish. Named for their prominent barbels, which resemble a cat's whiskers, catfish range in size and behavior from the three largest species alive, ...

sucker Sucker may refer to: General use * Lollipop or sucker, a type of confection * Sucker (slang), a slang term for a very gullible person * Hard candy ** Cough drop ** Mint (candy) Biology * Sucker (botany), a term for a shoot that arises undergro ...

s, and

minnow Minnow is the common name for a number of species of small freshwater fish, belonging to several genera of the families Cyprinidae and Leuciscidae. They are also known in Ireland as pinkeens. Smaller fish in the subfamily Leusciscidae are c ...

s are among the fishes that can serve as

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 ...

s. The genus '' Archigetes'' Leuckart, 1878, a caryophyllidean, is unique among all tapeworms in that its species can mature in invertebrate hosts (

Oligochaeta Oligochaeta () is a subclass of animals in the phylum Annelida, which is made up of many types of aquatic and terrestrial worms, including all of the various earthworms. Specifically, oligochaetes comprise the terrestrial megadrile earthworm ...

), i.e. have a monoxenic (direct) life cycle.

Classification

According to WoRMS,WoRMS (2021). Caryophyllidea. Accessed at: http://www.marinespecies.org/aphia.php?p=taxdetails&id=104912 on 2022-01-14 the Caryophyllidea include four families: * Family Balanotaeniidae Mackiewicz & Blair, 1978 * Family Capingentidae Hunter, 1930 * Family Caryophyllaeidae Leuckart, 1878 * Family Lytocestidae Hunter, 1927

References

External Link

University of Alberta - Biology
Cestoda Parasitic helminths of fish Platyhelminthes orders {{parasitic animal-stub