Trochophora

Japanese: trochophora

… In general, the egg undergoes spiral cleavage, forming the internal and external germ layers, as well as the mesoderm, which is invaginated by specialized ectodermal cells. Further development leads to the formation of the trochophoran larva. In this respect, it is most closely related to the phylum Annelida, and is also closely related to the phylum Platyhelminthes. …

From [Larva]

...(2) Protrochula: A type of larva found in flatworms (Mullerian larvae, Goethe larvae) and nemertean worms (pyridium larvae) classified as protocoelomates. It has a simple structure with an endodermal blind tube and a small nerve ganglion in the protocoelomate (a cavity developed from the blastocoel), and swims by growing cilia on the surface of its body (Figure 2). (3) Trochophora: A type of larva found mainly in mollusks and annelids belonging to the eucoelocometa and acrocoelomates (schizocoelomates). Its digestive tract opens to the outside at the mouth and anus, and it has a protonephridia that regulates osmotic pressure and excretes waste products in the protocoelomate, and it swims by using four ciliated tubes on the surface of its body. The simplest mollusks have only one ganglion in the head, but the most well-developed mollusks have six ganglia: head, sides, legs, body wall, internal organs, and mouth. …

*Some of the terminology explanations that mention "trochophora" are listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

Japanese:

…　一般に卵はらせん分割をし，内外両胚葉に加えて，特殊な外胚葉性の細胞が陥入して中胚葉が形成される。そしてさらに発生がすすむとトロコフォラ幼生trochophoraになる。この点では環形動物門にもっとも近縁であり，扁形動物門にも類縁がある。…

【幼生】より

…(2)原輪子幼生protrochula　原体腔類として分類される扁形動物(ミュラー幼生，ゲッテ幼生)およびひも形動物(ピリディウム幼生)にみられるもので，原体腔(胞胚腔から発展した腔所)内に内胚葉性の盲管と小さな神経節を一つそなえた簡単な構造をもち，体表に繊毛をはやして遊泳する(図2)。(3)担輪子幼生(トロコフォラtrochophora)　真体腔類，端細胞幹(裂体腔動物)に属する軟体動物および環形動物を中心とする幼生で，消化管は口と肛門で外に開き，原体腔内には浸透圧の調節と老廃物の排出を行う原腎管をそなえ，体表の四つの繊毛管によって遊泳する。神経節は簡単なものでは頭部に一つあるのみであるが，最もよく発達した軟体動物では，頭部，側部，足，体壁，内臓，口の六つをそなえたものがある。…

※「trochophora」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典第２版について | 情報

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