Cnidarian | Definition, Life Cycle, Classes, & Facts | Britannica
2024年12月13日 · The phylum Cnidaria is made up of four classes: Hydrozoa (hydrozoans); Scyphozoa (scyphozoans); Anthozoa (anthozoans); and Cubozoa (cubozoans). All cnidarians share several attributes, supporting the theory that they had a single origin.
Characteristics, Habitat, Diet, Anatomy, & Facts - Britannica
2024年10月25日 · Jellyfish, any planktonic marine member of the class Scyphozoa (phylum Cnidaria), a group of invertebrate animals composed of about 200 described species, or of the class Cubozoa (approximately 20 species). Learn more about the characteristics and natural history of jellyfish in this article.
Medusa | Sea creature, Marine life, Tentacles | Britannica
Medusa, in zoology, one of two principal body types occurring in members of the invertebrate animal phylum Cnidaria. It is the typical form of the jellyfish. The medusoid body is bell- or umbrella-shaped.
Cnidarian - Polyp, Medusa, Tentacles | Britannica
2024年12月13日 · Cnidarian - Polyp, Medusa, Tentacles: Cnidarians have two cell layers, ectoderm and endoderm (gastrodermis), with the mesoglea between them. Medusae have a more highly developed nerve net than do polyps. Respiration and excretion are carried out by …
Hydra | Freshwater, Cnidaria, Polyp | Britannica
2024年12月7日 · Hydra, genus of invertebrate freshwater animals of the class Hydrozoa (phylum Cnidaria). The body of such an organism consists of a thin, usually translucent tube that measures up to about 30 millimetres (1.2 inches) long but is capable of great contraction.
Anatomy of cnidarians | Britannica
Jellyfish, any planktonic marine member of the class Scyphozoa (phylum Cnidaria), a group of invertebrate animals composed of about 200 described species, or of the class Cubozoa (approximately 20 species).
Cnidarian - Radial Symmetry, Polyp & Medusa | Britannica
2024年12月13日 · Phylum Cnidaria (Coelenterata) Nematocyst-bearing, radial metazoans without organs. Have a cellular inner endoderm and outer ectoderm , separated by noncellular mesoglea.
Polyp | Cnidarian, Coral & Sea Anemone | Britannica
Polyp, in zoology, one of two principal body forms occurring in members of the animal phylum Cnidaria. The polyp may be solitary, as in the sea anemone, or colonial, as in coral, and is sessile (attached to a surface).
Sea pen | Cnidarian, Anthozoan & Polyp | Britannica
sea pen, any of the 300 species of the order Pennatulacea, colonial invertebrate marine animals of the class Anthozoa (phylum Cnidaria). The name sea pen derives from their resemblance to quill pens. They occur in shallow and deep waters from polar seas to the tropics.
Cnidarians Portal | Britannica
The phylum Cnidaria is made up of more than 9,000 living species, mostly marine animals. Corals, jellyfish, sea anemones, and sea fans are all cnidarians.