Trochophora (English spelling)

Japanese: トロコフォラ（英語表記）trochophora

A stage in the development of mollusks (excluding cephalopods) and annelids. Also called the trochophore or trochophore. It floats in the water while rotating. The body is ovoid, bell-shaped, top-shaped, etc., with a long cilia bundle at the top, one or several ring-shaped cilia in the middle, and a short cilia bundle at the bottom. The mouth is below the central cilia row, and the anus is at the rear end. It moves by moving the cilia. As development progresses further, in mollusks it becomes a veliger, and in annelids the body extends backward from the part surrounding the anus, forming segments and becoming a lovene larva. Because both mollusks and annelids go through this trochophore stage, their adult shapes are significantly different, but they are considered to be closely related animals.

Source: Encyclopaedia Britannica Concise Encyclopedia About Encyclopaedia Britannica Concise Encyclopedia Information

Japanese:

軟体動物 (頭足類を除く) や環形動物の発生上の一段階で，担輪子 (幼生) ，トロコフォアともいう。水中を回転しながら浮遊する。体は卵形，鈴形，こま (独楽) 形などで，上端に長い繊毛束が，中央に繊毛列が輪状に1列から数列，下端に短い繊毛束がそれぞれある。口は中央の繊毛列の下にあり，肛門は後端にある。移動は繊毛を動かすことによってなされる。発生がさらに進むと，軟体動物ではベリジャーとなり，環形動物では肛門を取巻く部分から体が後方に伸びて環節を生じロヴェーン幼生になる。軟体動物と環形動物はともにこのトロコフォラ期を経るため，成体の形は著しく異なるが，類縁の近い動物とされている。

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