Polyp (zoology)

A polyp is a typically sessile, cylindrical cnidarian body form with a mouth and tentacles directed upward. Many polyps reproduce asexually, and some species alternate this form with a free-swimming medusa.

Cnidaria: A phylum of aquatic animals characterized by stinging cells called cnidocytes. Polyps are one of the principal body forms found across this animal phylum.
Asexual reproduction: Reproduction in which offspring arise without fusion of gametes from two parents. Polyps commonly produce offspring through asexual processes such as budding.
Hydra (genus): A genus of small freshwater hydrozoans whose animals remain polyp-shaped throughout their lives. Hydra provides a familiar example of a solitary polyp without a medusa stage.
Siphonophore: A colonial hydrozoan whose specialized zooids function together as a single drifting organism. Unlike a typical solitary polyp, a siphonophore is a mobile colony of interdependent zooids.
Medusa (zoology): A free-swimming, usually bell-shaped cnidarian body form with the mouth and tentacles directed downward. Many cnidarians alternate this form with the attached, upward-facing polyp.
Budding: A form of asexual reproduction in which a new organism grows from an outgrowth of its parent. A polyp can form a bud that develops into another polyp or a medusa.
Coral: A cnidarian animal, or colony of animals, that secretes a calcium carbonate skeleton in reef-building groups. Corals are colonial polyps whose combined growth builds many tropical reefs.
Colonial organism: An organism composed of physically connected individuals or repeated units that may share resources or functions. Many polyp-forming cnidarians live as colonies rather than isolated animals.
Cnidocyte: A specialized cnidarian cell that fires a capsule, often delivering a toxin or entangling prey. These cells equip polyp tentacles to capture prey and defend the animal.
Strobilation: A process in which a cnidarian polyp divides transversely into stacked segments that detach as young medusae. In scyphozoan jellyfish, this process turns a polyp into multiple free-swimming offspring.

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