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''Pelagia noctiluca'' (Forsskal, 1775) is a jellyfish in the family Pelagiidae. In Latin, ''pelagia'' means "of the sea", ''nocti'' stands for night and ''luca'' means light; thus, ''Pelagia noctiluca'' can be described as a marine organism with the ability to glow in the dark. This species of jellyfish, known in Europe as the mauve stinger amongst many other common names, is widely distributed in all warm and temperate waters of the world's oceans, including the Mediterranean Sea, Red Sea and Atlantic Ocean. It is also found in the Pacific Ocean, with sightings in warm waters off Hawaii, southern California and Mexico, as well as other Pacific locations. This is typically an offshore species, although sometimes it is washed near the coastlines and may be stranded in great numbers on beaches. The color varies worldwide, and in addition to pink or mauve, it is sometimes shades of golden yellow to tan. In an unprecedented event on November 21, 2007, a swarm of ''P. noctiluca'' wiped out a 100,000-fish salmon farm in Northern Ireland, causing around £1 million worth of damage. == Classification of ''Pelagia noctiluca'' == The body is radially symmetrical. There is only one body cavity known as the gastrovascular cavity. This is a primitive gut or digestive cavity with only one opening that acts as a mouth and anus; there are four long oral arms with crenulated margins that are the primary feeding surface. Each ''P. noctiluca'' medusa has 8 long tentacles that emerge from the umbrella margin. Being radially symmetrical it has no head and thus no centralized nervous system. The nervous system present is primitive, consisting of a simple net composed of naked and largely non-polar neurons. In addition ''P. noctiluca'' also lacks a gaseous exchange, excretory and circulatory system. However cnidaria have evolved cnidae, cells which serve for a variety of functions that include prey capture, defense, locomotion and attachment. When fully formed cnidae are called cnidocytes. When stimulated the cnidae secrete nematocyst toxins that are biological poisons. ''P. noctiluca'' is a member of the cnidarian class Scyphozoa and adapted to a pelagic mode of life. Whereas most scyphozoan jellyfish (also called scyphomedusae) have a complex life cycle with both the pelagic (swimming) jellyfish, or medusa, stage and a bottom-living polyp stage, ''Pelagia'' has adapted in such a way that the polyp stage is absent, thus direct development exists. The male and female jellyfish spawn respectively sperm and eggs, which develop directly into young (male or female) ''Pelagia noctiluca'' jellyfish. These organisms have a well-developed manubrium, a proboscis-like structure bearing the mouth and four long oral arms. Also the mesoglea, or jelly, is relatively thickened and well developed in this species. Sense organs, known as rhopalia in the scyphomedusae, are located around the umbrella margin in notches and alternate between tentacles. Cnidae are present in the epidermis and gastrodermis of the umbrella as well as on the tentacles. ''Pelagia'', like other jellyfish in the scyphozoan order Semaeostomeae are mainly distinguished from the other orders by having simple oral arms with frilled or folded lips. The order semaestomae comprises three families: Pelagiidae, Cyaneidae,and Ulmaridae, distinguishable by the following characters: 1. Gastrovascular cavity divided by radial septa into rhopalar and tentacular pouches. a. Pouches simple and unbranched – ''Pelagiidae'' b. Pouches branched – ''Cyaneidae 2. Gastrovascular system in form of unbranched and branching canals, or with anastomosing radial canals – ''Ulmaridae'' In addition, members of the ''Pelagiidae'' have no ring canal, and the marginal tentacles arise from umbrella margin. There are three genera in this family. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Pelagia noctiluca」の詳細全文を読む スポンサード リンク
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