In biology, a medusa (plural: medusae) is a form of cnidarian in which the body is shortened on its principal axis and broadened, sometimes greatly, in contrast with polyps. Foundations of modern biology There are five unifying principles Cnidaria (naɪˈdɛəriə is a phylum containing some 9000 Species of Animals found exclusively in aquatic mostly marine, environments In Zoology, a polyp is one of two forms of individuals found in many species of Cnidarians The two are the polyp or hydroid and the medusa. Medusae vary from bell-shaped to the shape of a thin disk, scarcely convex above and only slightly concave below. The upper or aboral surface is called the exumbrella and the lower surface is called the subumbrella; the mouth is located on the lower surface, which may be partially closed by a membrane extending inward from the margin (called the velum). The digestive cavity consists of the gastrovascular cavity and radiating canals which extend toward the margin; these canals may be simple or branching, and vary in number from few to many. Gastro vascular cavity, as the name indicates functions in both Digestion and Gas exchange. The margin of the disk bears sensory organs and tentacles. Tentacles can refer to the elongated flexible organs that are present in some animals especially Invertebrates and sometimes to the hairs of the leaves of some insectivorous
In the class Hydrozoa, medusae are the sexual individuals of many species, alternating in the life cycle with asexual polyps. Hydrozoa ( hydrozoans) are a Taxonomic class of very massive predatory animals which can be solitary or colonial and which mostly live in saltwater The medusa form of Hydrozoans are known as hydromedusae.
The medusa form predominates in the classes Scyphozoa (jellyfish proper) and Cubozoa. Jellyfish are free-swimming members of the phylum Cnidaria. They have several different basic morphologies that represent several different cnidarian classes including the Jellyfish are free-swimming members of the phylum Cnidaria. They have several different basic morphologies that represent several different cnidarian classes including the Box jellyfish are invertebrates belonging to the class Cubozoa, named for their Cube -shaped medusae. Except for freshwater hydrozoans like Craspedacusta sowerbyi, these are the only classes in which medusae appear. Hydrozoa ( hydrozoans) are a Taxonomic class of very massive predatory animals which can be solitary or colonial and which mostly live in saltwater Craspedacusta sowerbyi is a freshwater jellyfish in the phylum Cnidaria.
German biologist Ernst Haeckel popularized medusae through his vivid illustrations, particularly in Kunstformen der Natur. Ernst Heinrich Philipp August Haeckel ( February 16, 1834 — August 9, 1919)also written von Haeckel, was an eminent German Kunstformen der Natur ( German: Art Forms of Nature) is a book of lithographic and Autotype prints by German biologist
Haeckel's medusae
 Discomedusae |
 Narcomedusae |
 Discomedusae |
 Trachomedusae |
 Discomedusae |
 Leptomedusae |
 Peromedusae |
 Anthomedusae |
 Cubomedusae (modern Cubozoa) |
 Discomedusae |
 Discomedusae |
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