ammocoetes

Japanese: ammocoetes

…They have one gonad. Lampreys spend 3 to 7 years as larvae called ammocoetes before metamorphosing into their adult form, whereas hagfish undergo direct development. Ecologically, some live in the sea, some migrate between the sea and rivers, and some are land-locked. …

From [Lamprey (Eight-eyed eel)]

... Its internal skeleton is made of cartilage and it has only a dorsal fin and a caudal fin. Its body surface is covered with mucus and has no scales. Its mouth is suction cup-like and it has only one nostril. It has seven pairs of external gill slits on the sides of its body. In its larval stage, called ammocoetes, it has a small head, its eyes are sunken under the skin and it has no suckers. It moves the cilia in its mouth and eats plankton and organic matter in the mud of the river bottom. It metamorphoses from autumn to winter and becomes an adult. ...

*Some of the terminology that mentions "ammocoetes" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

Japanese:

…生殖巣は1個。ヤツメウナギ類はアンモシーテスammocoetesと呼ばれる幼生の時期を3～7年間過ごした後に変態して成体の形になるが，メクラウナギ類の発生は直達である。生態的には，海にすむもの，海と川の間を回遊するもの，陸封性のものがある。…

【ヤツメウナギ(八目鰻)】より

…　内部骨格は軟骨性で背びれと尾びれだけがあり，体表にはうろこがなく粘液におおわれること，口が吸盤状で鼻孔が一つしかないこと，体側に7対の外鰓孔があることが特徴。アンモシーテスammocoetesという幼生期には頭が小さく，眼が皮膚の下に没して吸盤もなく，川底の泥中で口内の繊毛を動かしプランクトンや有機物を食べる。秋から冬にかけて変態し成体となる。…

※「ammocoetes」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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