|
''Artemia'' is a genus of aquatic crustaceans known as brine shrimp. ''Artemia'', the only genus in the family Artemiidae, has changed little externally since the Triassic period. The historical record of the existence of ''Artemia'' dates back to 982 from Urmia Lake, Iran, although the first unambiguous record is the report and drawings made by Schlösser in 1757 of animals from Lymington, England. ''Artemia'' populations are found worldwide in inland saltwater lakes, but not in oceans. ''Artemia'' are able to avoid cohabiting with most types of predators, such as fish, by their ability to live in waters of very high salinity (up to 25%). The ability of the ''Artemia'' to produce dormant eggs, known as cysts, has led to extensive use of ''Artemia'' in aquaculture. The cysts may be stored for long periods and hatched on demand to provide a convenient form of live feed for larval fish and crustaceans.〔 Nauplii of the brine shrimp ''Artemia'' constitute the most widely used food item, and over 2000 tonnes of dry ''Artemia'' cysts are marketed worldwide annually. In addition, the resilience of ''Artemia'' makes them ideal animals for running biological toxicity assays and it has become a model organism used to test the toxicity of chemicals. Breeds of ''Artemia'' are sold as novelty gifts under the marketing name ''Sea-Monkeys'' or ''Aqua Dragons''.〔(【引用サイトリンク】url=http://aquadragons.net/ )〕 ==Description== The brine shrimp ''Artemia'' comprises a group of nine species very likely to have diverged from an ancestral form living in the Mediterranean area about . ''Artemia'' is a typical primitive arthropod with a segmented body to which is attached broad leaf-like appendages. The body usually consists of 19 segments, the first 11 of which have pairs of appendages, the next two which are often fused together carry the reproductive organs, and the last segments lead to the tail. The total length is usually about for the adult male and for the female, but the width of both sexes, including the legs, is about . The body of ''Artemia'' is divided into head, thorax, and abdomen. The entire body is covered with a thin, flexible exoskeleton of chitin to which muscles are attached internally and shed periodically. In female ''Artemia'' a moult precedes every ovulation. For brine shrimp, many functions, including swimming, digestion and reproduction are not controlled through the brain; instead, local nervous system ganglia may control some regulation or synchronization of these functions.〔 Autotomy, the voluntary shedding or dropping of parts of the body for defence, is also controlled locally along the nervous system.〔 ''Artemia'' have two types of eyes. They have two widely separated compound eyes mounted on flexible stalks. These compound eyes are the main optical sense organ in adult brine shrimps. The median eye, or the naupliar eye, is situated anteriorly in the centre of the head and is the only functional optical sense organ in the nauplii, which is functional until the adult stage.〔 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「Brine shrimp」の詳細全文を読む スポンサード リンク
|