Polyp (cnidarians)

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Young soft coral colony with few polyps left
Polyps

The polyp ( ancient Greek πολύπους , multipod ) is one of the stages in the individual development of the cnidarians (Cnidaria).

Polyps show the typical morphology of the cnidarians . The very simply built body consists of a hollow cylinder that ends at the top in a central mouth opening, which is surrounded by upward-pointing tentacles . Often polyps are sessile and their base, the basal or foot disk, is firmly attached to a hard surface. However, some hemisessile species can move very slowly.

The polyp is the only form of the flower animals. In the case of umbrella jellyfish and many hydrozoans, on the other hand, in the course of the generation change after the planular larvae stage , it is the sessile form type ( scyphopolyp ), from which the freely swimming medusa or jellyfish stage develops through strobilation (transverse constriction) .

Cnidarians that form colonies , such as hard and soft corals, consist of many thousands of individual polyps that have grown together at the base and that reproduce vegetatively through continuous budding . Colonies of polyps can form complex organisms , such as the Portuguese galley , a state jellyfish floating on the surface of the sea .

Anatomy of a coral polyp

Polyps have an extraordinary ability to regenerate , for example two complete individuals ( clones ) develop from a specimen cut in the middle . The ability to regenerate is of interest for medical research .

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