Ecological Studies on strategy of habitat selection of sea urchins.

从1998年4月至1999年5月，在宫城县女川的潮间带和潮下带的一个固定样方（100 m^2）每月研究了海胆Hemicentrotus pulcherrimus的垂直分布与藻类带的关系。从海胆大小、性腺发育和肠道内容物中食物藻类的季节性变化，探讨了海胆季节性洄游的原因。在0- 0.3m的缓坡岩石下密集分布着一年四季生长的小藻类。10月至次年3月，海胆从甲壳珊瑚红藻占优势的深水沃茨迁移到小型藻类群落，然后留在那里。光棘球海胆在深水沃茨分布密集，夏至秋季迁移到浅水沃茨的小藻中，冬季又返回深水沃茨。性腺指数（性腺重× 100/体重）。甲壳珊瑚群落中的马蹄莲明显低于小型藻类群落。从性腺组织学观察，从10月到3月海胆洄游期间，性腺依次从生长期发育到成熟期和产卵期。因此，我们认为这种由深沃茨向浅沃茨的迁移是由觅食活动引起的，以成功地完成成熟和产卵。从肠道内容物的观察，叶状植物角叉菜属。多脉顶蕨（Acrosorium polyneurum）和马尾藻属（Sargassum spp.）被供应给海胆作为食物在社区的小藻类。相反，甲壳珊瑚群落中食物资源的匮乏则抑制了海胆性腺的发育。因此，海胆可能是迁移到小型藻类群落中，以多脉顶蕨为食。

Verticlal distribution of the sea urchin Hemicentrotus pulcherrimus in relation to algal zonation was studied monthly from April 1998 to May 1999 at a permanent quadrat (100 m^2) in intertidal and subtidal zones in Onagawa of Miyagi Prefecture. From seasonal changes in size, gonadal development and food algae in gut contents, the factor leading the sea urchins to migrate seasonally was studied.H. pulcherrimus distributed densely under rocks at depths of 0-0.3 m in gentle slope where small algae grew throughout the year. The sea urchins migrated from deep waters where crustose coralline red algae grew dominatly to the community of small algae from October to March, then remained there. Strongylocentrotus nudus distributed densely in deep waters and migrated to the small algae in shallow waters from summer to autumn, then returned to deep waters in winter. Gonadal indices (gonad weight X 100/body weight) of H. pulcherrimus at crustose corallines were markedly lower than those at the community of small algae. From histological observation of gonads, from October to March when the sea urchins migrated, gonads developed from growing to mature and spawning successively. Therefore it is considered that the migration from deep waters to shallow waters was caused by foraging activity to succeed in maturation and spawning. From gut contents observation, the thallophyta Chondrus spp. Acrosorium polyneurum, and Sargassum spp. were supplied to the sea urchins as foods at the community of small algae. Contrary, poor food resouces at crustose coralline community reduced gonadal development of the sea urchin. It is concluded that the sea urchins migrated to the community of small algae to forage Acrosorium polyneurum as food.