White Boy - White Boy

A solitary sea squirt belonging to the order Wallacea, class Urichordata, and family Stiella. Its body length is usually up to 7 cm, and it is a slightly elongated oval. It attaches to other objects at the rear end of its body, but very rarely has a stalk. The tunic is a somewhat hard, skin-like, thick, yellowish-white color, with a nodular protrusion on its surface. It is very common in polluted inner bays south of Mutsu Bay in Aomori Prefecture, and it can swarm in large numbers on the bottom of boats and aquaculture rafts, causing trouble for fishermen. There have also been cases where it has settled in large numbers on pebbles on sandy, muddy bottoms, interfering with bottom trawl operations. It rarely attaches to the underside of boulders. It matures all year round except during the coldest periods, and the larvae settle to the bottom about two days and nights after spawning. It is widely distributed in warm waters around the world, but this is thought to be because it was transported attached to boats.

[Teruaki Nishikawa]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

原索動物門尾索綱壁性目スチエラ科に属する単体ホヤ。体長は通常7センチメートルまでで、やや細長い楕円(だえん)体。体後端で他物に付着するが、ごくまれに柄をもつ。被嚢(ひのう)はやや固い皮状で厚く、黄白色を呈し、表面にこぶ状隆起がある。青森県陸奥(むつ)湾以南の汚れた内湾にごく普通で、船底や養殖筏(いかだ)などに多量に群がりついて漁業者を困らすことがある。また、砂泥底の小石に多量に着底して底引網の操業を妨げた例もある。転石の下面にはめったに付着しない。厳寒期を除いて一年中成熟し、幼生は放卵後約2昼夜で着底する。世界の温水域に広く分布しているが、これは船に着生して運ばれたためと考えられている。

［西川輝昭］

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