Itabogaki (English spelling) Densely lamellated oyster

A bivalve mollusk of the family Ostrichidae in the class Bivalvia of the phylum Mollusca. It is found in Honshu, Shikoku, Kyushu, the Korean Peninsula, and the coasts of China. It lives in inland bays, attaching itself to rocks on the bottom at depths of 10 to 30 meters, or in clumps where the shells are in contact with each other. It is disc-shaped, with a shell length and height of about 13 cm. The right shell is flat, and the shell surface is covered with a bark-like shell that matches the growth line, and has many rays. The left shell is attached to something at the top, and has a somewhat deep, rough growth ring and irregular rays. There are also ear-like protrusions on both sides of the shell apex, and the inside of the shell is white with reddish brown muscle marks. It is a viviparous species, and the sexes of the same individual alternate. The spawning season is from May to August, and the optimum salinity for growth is 27 to 34‰. It became edible, and attempts were made to cultivate it for a time, but the quality of the meat was not suitable for Japanese people, so this was not continued.

[Takashi Okutani]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

軟体動物門二枚貝綱イタボガキ科の二枚貝。本州、四国、九州および朝鮮半島、中国沿岸に分布する。内湾の水深10～30メートルの海底の岩礫(がんれき)に付着したり、互いに接して団塊状になって生活する。殻長、殻高ともに13センチメートルぐらいになり円板状で、右殻は平たく、殻表は成長線と一致する檜皮(ひわだ)状の殻皮で覆われ、多くの放射条がある。左殻は殻頂部で他物に付着し、やや深く粗い成長輪と不規則な放射肋(ろく)がある。また殻頂の左右に耳状の突起が出て、殻内は白く筋肉痕(こん)は赤褐色。胎生種で、同一個体の性が交代する。産卵期は5～8月で、成育の好適塩分は27～34‰である。食用となり、一時養殖が試みられたが、肉質が日本人に向かず継続されなかった。

［奥谷喬司］

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