Hyriopsis schlegelii (= Sinohyriopsis schlegelii) - Hyriopsis schlegelii (English spelling)

Japanese: イケチョウガイ(池蝶貝) - イケチョウガイ（英語表記）Hyriopsis schlegelii(＝Sinohyriopsis schlegelii)

A large bivalve mollusc of the Unionidae family that is used as a mother shell for freshwater pearl cultivation (illustration). It can reach 23.5 cm in length, 13 cm in height, and 5.5 cm in bulge. The shell is rounded and diamond-shaped, thick, but not very bulging. The shell is yellow-green when young, but turns black as it matures. In addition to growth veins, there are weak wavy wrinkles in the center when young. There are also wing-like flat protrusions on the back, but these are lost as the mollusc matures. The inner surface has a strong pearly luster and is bluish-white in color. A species endemic to the Lake Biwa water system. In recent years, it has been transplanted to Lake Kasumigaura. Juvenile molluscs live in sandy and muddy bottoms at depths of less than 3 m, while adults live at depths of 10 m, and occasionally 30 m.

Source: Heibonsha World Encyclopedia, 2nd Edition Information

Japanese:

淡水真珠養殖の母貝とするイシガイ科の大型二枚貝（イラスト）。長さ23.5cm，高さ13cm，膨らみ5.5cmに達する。殻はまるみのある菱形で厚いが，膨らみは弱い。殻皮は幼貝では黄緑色であるが成長すると黒色になる。成長脈のほか幼時には弱い波状のしわが中央部にある。また背上には翼状の扁平な突起があるが，成長すると失われる。内面は真珠光沢が強く青白色。琵琶湖水系の特産種。近年，霞ヶ浦に移殖されている。稚貝は水深3m以浅，成貝は水深10m，まれに水深30mくらいの砂泥底にすむ。

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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