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a class of solitary marine animals of the phylum Coelenterata. Scyphozoans occur in the form of jellyfish or polyps and are radially symmetrical. The gastric cavity is divided by interradial mesenteries into a central cavity and lateral pouches. Many scyphomedusae have a system of digestive canals. The life cycle is characterized by alternating generations (metagenesis). A planula larva develops from an egg and, after settling on a substrate, becomes a scyphistoma, an individual of the polypoid generation. The scyphistoma buds off polyps like itself and releases ephyrae (larvae of the sexually reproducing generation) by constriction (strobilation).
Bodily contact with certain scyphozoans, for example, Rhizostomae, may cause pain and skin burns. Persons have been known to die after being poisoned by individuals of the genus Chirodrophus, which dwell off northern Australia. Some scyphozoans, for example, Rhizostomae and Aurelia, are commercially significant; they are salted and used as food.
The class of Scyphozoa, comprising the orders Discomedusae, Rhizostomae, Coronatae, and Stauromedusae, includes approximately 200 species, which are distributed throughout the oceans of the world, mostly in temperate and tropical waters. Approximately 30 species occur in the USSR.
REFERENCESNaumov, D. V. Stsifoidnye meduzy morei SSSR. Moscow-Leningrad, 1961.
Bronns, H. G. Klassen und Ordnungen des Tierreichs, vol. 2, part 2, fascs. 1–6. Leipzig, 1936–59.
Kramp, P. L. Synopsis of the Medusae of the World. Cambridge, 1961.
D. V. NAUMOV