Қызыл теңіз түйіршіктері мен маржандардың дене пішіні – полип

One of two forms found in the phylum Cnidaria (zoology)
the small aquatic animal

A polyp in zoology is one of two forms found in the phylum Cnidaria, the other being the medusa. Polyps are roughly cylindrical in shape and elongated at the axis of the vase shaped body. In solitary polyps, the aboral (opposite to oral) end is attached to the substrate by means of a disc like holdfast called a pedal disc, while in colonies of polyps it is connected to other polyps, either directly or indirectly. The oral end contains the mouth, and is surrounded by a circlet of tentacles.

In the class Anthozoa, comprising the sea anemones and corals, the individual is always a polyp; in the class Hydrozoa, however, the individual may be either a polyp or a medusa, with most species undergoing a life cycle with both a polyp stage and a medusa stage. In class Scyphozoa, the medusa stage is dominant, and the polyp stage may or may not be present, depending on the family. In those scyphozoans that have the larval planula metamorphose into a polyp, the polyp, also called a "scyphistoma," grows until it develops a stack of plate like medusae that pinch off and swim away in a process known as strobilation. Once strobilation is complete, the polyp may die, or regenerate itself to repeat the process again later. With Cubozoans, the planula settles onto a suitable surface, and develops into a polyp. The cubozoan polyp then eventually metamorphoses directly into a medusa.

The body of the polyp may be roughly compared in a structure to a sac, the wall of which is composed of two layers of cells. The outer layer is known technically as the ectoderm, the inner layer as the endoderm (or gastroderm). Between ectoderm and endoderm is a supporting layer of structureless gelatinous substance termed mesoglea, secreted by the cell layers of the body wall. Longitudinal muscular fibrils formed from the cells of the ectoderm allow tentacles to contract when conveying the food to the mouth. Similarly, circularly disposed muscular fibrils formed from the endoderm permit tentacles to be protract or thrust out once they are contracted. These muscle fibres belong to the same two systems, thus allows the whole body to retract or protrude outwards. When eggs and sperm (gametes) are formed, they can produce zygotes derived from "selfing" (within the founding clone) or out crossing, that then develop into swimming planula larvae. The overwhelming majority of stony coral (Scleractinia) taxa are hermaphroditic in their adult colonies. In these species, there is ordinarily synchronized release of eggs and sperm into the water during brief spawning events. Although some species are capable of self fertilization to varying extents, cross fertilization appears to be the dominant mating pattern. to these organisms from their superficial resemblance to an octopus (, ultimately from Ancient Greek adverb πολύ (, "much") + noun πούς (, "foot")), with its circle of writhing arms round the mouth. This comparison contrasts to the common name "coral insects" applied to the polyps which form coral. due to overfishing, destructive fishing, coastal development, pollution, thermal stress, ocean acidification, crown of thorns starfish, and introduced invasive species. In recent decades the conditions that corals and polyps have found themselves in have been changing, leading to new diseases being observed in corals in many parts of the world, posing even greater risk to an already pressured animal. Aquatic life has been put under a substantial amount of stress because of the pollutants caused by land based agriculture. Particularly, exposure to the insecticide profenofos and the fungicide MEMC have played a major part in polyp retraction and biomass decrease. There have been many experiments resulting supporting hypothesis that heat stress in Acropora tenuis juvenile polyp provoke an up regulation of protein in the endoplasmic reticulum. The results vary based on the polyp characteristics such as age, type, and growth stage.