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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 ...
Hydrozoa is a large group of solitary and colonial cnidarians from both marine and freshwater environments worldwide. Hydrozoans exhibit the greatest variety of life cycles among medusozoans, with either the polyp or the medusa stage being missing in some groups. [4]
Pacific sea nettles, Chrysaora fuscescens. Cnidaria (/ n ɪ ˈ d ɛər i ə, n aɪ-/ nih-DAIR-ee-ə, NY-) [4] is a phylum under kingdom Animalia containing over 11,000 species [5] of aquatic invertebrates found both in fresh water and marine environments (predominantly the latter), including jellyfish, hydroids, sea anemones, corals and some of the smallest marine parasites.
Obelia is a genus of hydrozoans, a class of mainly marine and some freshwater animal species that have both polyp and medusa stages in their life cycle. Hydrozoa belongs to the phylum Cnidaria, which are aquatic (mainly marine) organisms that are relatively simple in structure with a diameter around 1mm. [1]
4–8 Polyp grows 9–11 Polyp strobilates 12–14 Medusa grows. Most species appear to be gonochorists, with separate male and female individuals. The gonads are located in the stomach lining, and the mature gametes are expelled through the mouth. After fertilization, some species brood their young in pouches on the oral arms, but they are ...
In hydrozoan species with both polyp and medusa generations, the medusa stage is the sexually reproductive phase. Medusae of these species of Hydrozoa are known as "hydromedusae". Most hydromedusae have shorter lifespans than the larger scyphozoan jellyfish.
Cnidarians are known to occur in two body forms: the polyp form which is benthic and “stalk-like,” and the medusae form, which is commonly known as the “bell” form. [4] Polyp forms are sessile as adults, with a single opening (the mouth/anus) to the digestive cavity facing up with tentacles surrounding it.
Medusae tend to be pelagic. But there are specific medusae species while at the medusa stage can still remain benthic. Polyps can also be free floating, which are called pelagic polyps. Similarly, their gastroular and nervous system have great complexity, as well as their shape. While medusae due tend to lack any presence of visible sense organs.