A small freshwater crustacean with a shell similar to that of a bivalve (illustration). It belongs to the subclass Branchiopoda, order Ostracod, family Conchaeidae. The shell is about 11-14 mm long and 7-10 mm high, brown or yellowish brown in color. There is a hinge on the dorsal side connecting the left and right shells, and an adductor muscle at the front connecting both shells. On the surface of the shell, there are about 16 concentric growth lines centered on the apex of the shell. The body is almost completely enclosed by these two shells. It has a pair of stalkless compound eyes, and the second antennae are divided into two branches, which are used for swimming. Source: Heibonsha World Encyclopedia, 2nd Edition Information |
二枚貝に似た殻をもつ淡水産の小型甲殻類(イラスト)。鰓脚(さいきやく)亜綱貝甲目カイエビ科に属する。殻は長さ11~14mm,高さ7~10mmくらい,褐色あるいは黄褐色をしている。背側に左右の殻を結ぶちょうつがいがあり,前部に両殻を結ぶ閉殻筋がある。殻の表面には殻頂を中心とした16内外の同心円状の成長線が見られる。体はこれら2枚の殻でほとんど完全に包まれる。1対の無柄の複眼をもち,第2触角は2枝に分かれ,これを用いて遊泳する。
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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