Life history strategies of modern and fossil molluscs.

该项目从现代软体动物和化石软体动物的生活史策略方面进行了研究，特别是双壳类和头足类的早期发育、绝对贝壳生长和功能形态。本研究的主要结果如下：(1)根据日本西南部太平洋地区上更新世沉积物中保存完好的幼贝壳的形态结构和形态测量，估算了利莫普斯属、甘草属和双壳亚目的几种幼虫的发育类型和幼体死亡率。(2)根据标记和回收的个体的内壳切片中识别的年增量，分析了日本沿海选定的近期双壳类贝壳的绝对贝壳生长模式和老化。(3)在对白垩纪菊石与现代头足类(鹦鹉螺、乌贼和螺旋藻)幼体进行显微结构对比观察的基础上，提出了中生代菊石(头足目)的内囊胚胎模型。(4)通过扫描电子显微镜和水动力学实验，研究了一些现代和化石的双壳类(双壳动物)壳的内部肋骨的功能意义和水动力特性。(5)研究了西太平洋异棘鱼的生物地理分布和茎的生长速度，为了解深海环境中的生物群奠定了基础。(由0ji提供)

Aspects on life history strategies in modern and fossil molluscs were considered in this project, with special reference to the early development, absolute shell growth and functional morpholog in the Bivalvia and the Cephalopoda. The results of this study are summarized as below.(1) Developmental types and juvenile mortality rates were estimated for several species of Limopsis, Glycymeris and Venericardia (Bivalvia), on the basis of prodissoconch morphology and morpnometry of well-preserved juvenile shells from the Plio-pleistocene deposits in the Pacific regions of southwest Japan. (by Tanabe)(2) Absolute shell growth patterns and aging in selected Recent bivalves from the Japanese coast were analyzed, relying on the annual increments recognized in the internal shell sections of marked and recovered individuals. (by Tanabe)(3) Endocochliate embryo model was proposed for the Mesozoic Ammonitida (Cephalopoda) on the basis of comparative microstructural observations of juvenile shells of the Cretaceous ammonites and modern cephalopods (Nautilus, Sepia and Spirula). (by Tanabe)(4) Functional meanings of the internal ribs and hydrodynamic properties for the shells of some modern and fossil pectinids (Bivalvia) were considered by means of scanning electron microscopy and hydrodynamic experiments respectively. (by Hayami)(5) Biogeographic distribution and growth rate of stalk of the crinoid Isocrinus from the western Pacific were examined, as a basis for understanding the biota in the deep-sea environments. (by 0ji)