What is Polyp?
[[File:Coral polyp.jpg|thumb|Anatomy of a Coral polyp]] [[File:Cnidaria medusa n polyp.png|thumb|250px|The two basic body forms of [[Cnidaria]]: left, [[medusa]] and right, polyp]] '''Polyps''' are one of two forms of the [[cnidarian]]s. The other body form is the [[medusa (biology)|medusa]]. Polyps have a [[vase]]-shaped body with [[tentacles]] around the mouth opening. Polyps may be [[sexual]] or [[asexual]]. They can all reproduce asexually by [[budding]]. In some species, the polyps can also reproduce sexually. When medusae mate, the result may be polyps, when polyps replicate, the result may be medusae. The details vary between species. Some species are polyps all the time (such as ''[[Hydra (animal)|Hydra]]'', and the whole of the class Anthozoa ([[coral]]s and [[anemone]]s).<ref>''Polyp'' in 1911 Encyclopædia Britannica, Chisholm, Hugh, ed.[http://encyclopedia.jrank.org/PIG_POL/POLYP.html] {{Webarchive|url=https://web.archive.org/web/20160303193352/http://encyclopedia.jrank.org/PIG_POL/POLYP.html |date=2016-03-03 }}</ref> In many cases the asexual buds formed do not separate from the parent but remain, thus forming [[colony (biology)|colonies]] or 'stocks'. These may reach a great size, and contain a vast number of individuals. Slight differences in the method of budding produce great variations in the form of the colonies. The reef-building [[coral]]s are polyp-colonies, strengthened by the formation of a firm skeleton. Jellyfish ([[class (biology)|class]] [[Medusozoa]]) have two distinct life history stages (body forms) during their [[life cycle]]. The first is the polyp stage. Often, this polyp is attached to the sea floor, or to another hard surface. A polyp that lives that way is called [[Sessility (zoology)|sessile]]. In the second stage, the tiny polyps asexually produce jellyfish, each of which is known as a [[Medusa (animal)|medusa]]. Tiny jellyfish swim away from the polyp and then grow and feed in the [[plankton]]. Jellyfish reproduce both sexually and asexually.<ref>Daly M. ''et al'' 2