Cestoda
Parasitic flatworms that live in vertebrate intestines.
Cestoda is a class of parasitic worms within the flatworm phylum Platyhelminthes. The best-known members are the tapeworms of the subclass Eucestoda, which are ribbon-like adults that live in the digestive tracts of vertebrate hosts. All cestodes are parasitic, and many have complex life cycles involving a definitive host and one or more intermediate hosts.
- field
- Parasitology
- known_for
- Tapeworm parasites of vertebrates
- species_described
- About 6,000
- largest_species
- Tetragonoporus calyptocephalus (over 30 m)
- definitive_hosts
- Vertebrates
- intermediate_hosts
- Insects, crustaceans, molluscs, annelids, other vertebrates
Lore & Background
Cestodes are divided into two subclasses: Eucestoda, the typical tapeworms with segmented bodies (strobila) composed of proglottids, and Cestodaria, which are mainly fish parasites and lack proglottids. Adult tapeworms anchor to the host's intestine using a scolex armed with hooks, suckers, or both. They have no mouth and absorb nutrients directly through their tegument. The neck continuously produces proglottids, each containing a reproductive tract; mature proglottids are shed into the environment, often in feces.
Reader's Guide
Cestodes are significant as parasites of virtually all vertebrates, including humans. Human infections occur through ingestion of undercooked meat (e.g., Taenia solium from pork, T. saginata from beef, Diphyllobothrium from fish) or poor hygiene (Hymenolepis, Echinococcus). Their complex life cycles often involve multiple hosts, and infections can persist for decades. All cestodes are hermaphroditic, and cross-fertilization is typical, though self-fertilization can occur. Their ability to absorb nutrients directly from the host's gut and their lack of a digestive system are key adaptations to parasitism.
Did You Know?
- Tapeworms have no mouth or gut; they absorb nutrients through their tegument.
- All cestodes are hermaphrodites, with both male and female reproductive organs in each individual.
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