|
''Caenorhabditis elegans'' is a free-living (not parasitic), transparent nematode (roundworm), about 1 mm in length,〔 〕 that lives in temperate soil environments. The name is a blend of Greek (''caeno-'' - recent, ''rhabditis'' - rod-like)〔καινός (caenos) = new, recent; ῥάβδος (rhabdos) = rod, wand.〕 and Latin (''elegans'' - elegant). In 1900, Maupas initially named it ''Rhabditides elegans'', Osche placed it in the subgenus ''Caenorhabditis'' in 1952, and in 1955, Dougherty raised it to the status of genus.〔 〕 ''C. elegans'' is an unsegmented pseudocoelomate, and lacks a respiratory and a circulatory system. They possess gut granules which emit a brilliant blue fluorescence, a wave of which is seen at death in a 'death fluorescence'.〔 〕 The majority of these nematodes are female hermaphrodites. Males have specialised tails for mating that include spicules. In 1963, Sydney Brenner proposed research into ''C. elegans'' primarily in the area of neuronal development. In 1974, he began research into the molecular and developmental biology of ''C. elegans'', which has since been extensively used as a model organism.〔 〕 ''C. elegans'' was the first multicellular organism to have its whole genome sequenced, and as of 2012, the only organism to have its connectome (neuronal "wiring diagram") completed.〔 〕 ==Anatomy== ''C. elegans'' is unsegmented, vermiform, and bilaterally symmetrical. It has a cuticle (a tough outer covering), four main epidermal cords, and a fluid-filled pseudocoelom (body cavity). It also has some of the same organ systems as larger animals. Almost all individuals of ''C. elegans'' are female hermaphrodites, and a small minority, around one in a thousand, are true males.〔 〕 The basic anatomy of ''C. elegans'' includes a mouth, pharynx, intestine, gonad, and collagenous cuticle. Like all nematodes, they have neither a circulatory nor a respiratory system. The four bands of muscles that run the length of the body are connected to a neural system that allows the muscles to move the animal's body only as dorsal bending or ventral bending, but not left or right, except for the head, where the four muscle quadrants are wired independently from one another. When a wave of dorsal/ventral muscle contractions proceeds from the back to the front of the animal, the animal is propelled backwards. When wave of contractions is initiated at the front and proceeds posteriorly along the body, the animal is propelled forwards. Because of this dorsal/ventral bias in body bends, any normal living, moving individual will tend to lie on either its left side or its right side when observed crossing a horizontal surface. A set of ridges on the lateral sides of the body cuticle, the alae, are believed to give the animal added traction during these bending motions. The pharynx is a muscular food pump in the head of ''C. elegans'', which is triangular in cross-section. This grinds food and transports it directly to the intestine. A set of "valve cells" connects the pharynx to the intestine, but how this valve operates is not understood. After digestion, the contents of the intestine are released via the rectum. There is no direct connection between the pharynx and the excretory canal, which functions in the release of liquid urine. Males have a single-lobed gonad, a vas deferens, and a tail specialized for mating, which incorporates spicules. Hermaphrodites have two ovaries, oviducts, spermatheca, and a single uterus. 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「caenorhabditis elegans」の詳細全文を読む スポンサード リンク
|