…Composite eggs are formed when an egg cell produced in the egg gland and an egg yolk produced in the yolk gland pass through their respective ducts to reach the egg cavity, where one egg cell and several yolk cells form a mass and an egg shell around it. Marine species produce Müller's larvae and other protrochula larvae from a single egg, which then metamorphose into adults, but freshwater and terrestrial species produce larvae directly from compound eggs and become parents. Most species are free-living, but some parasitize other animals internally or externally. … From [Flatworm]… They are hermaphrodites, with both male and female reproductive organs in the same individual, but their structure is more complex than their physical body plan. After mating, eggs are fertilized internally and laid in the sea, where they develop into juveniles or Müller's larvae or Goette's larvae, which live a floating life for a while, before metamorphosing into adults. They are generally carnivorous, and eat almost any animal they catch, including small crustaceans, bivalves, and annelids. … *Some of the terminology that mentions "Müller's larva" is listed below. Source | Heibonsha World Encyclopedia 2nd Edition | Information |
…複合卵とは卵腺でつくられた卵細胞と卵黄腺でつくられた卵黄とがそれぞれの輸管を通って成卵腔に達し,1個の卵細胞と数個の卵黄細胞とが一塊になって周囲に卵殻をつくったものである。海産のものは単一卵からミュラー幼生Müller’s larvaやその他のプロトロクラ幼生protrochula larvaを生じ,変態して成体となるが,淡水産と陸産のものは複合卵から直接子虫が生じ親になる。大部分の種類は自由生活をするが,他の動物体に内部あるいは外部寄生するものがある。… 【ヒラムシ(平虫)】より… 雌雄同体で,同一個体に雌と雄の生殖器官があるが,体制に比較して,その構造は複雑である。交尾によって体内で受精した卵は海中に産みだされ,発生がすすんで直接幼体になるか,ミュラー幼生Müller’s larvaやゲッテ幼生Goette’s larvaになってしばらく浮遊生活をし,その後変態して成体になる。 一般に肉食性で,小型甲殻類,二枚貝,環形動物などほとんどどんな動物でもとらえたものを食べる。… ※「Müller's larva」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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