PALEONTOLOGICAL, DEVELOPMENTAL, AND MOLECULAR BIOLOGICAL APPROACHES TO THE ORIGIN AND PHYLOGENY OF THE MOLLUSCA

A)比较解剖学和胚胎学研究。对双壳贝类Tanabe和Hayakaze的研究已经描述了在双壳贝壳钙化贝壳发育之前，在双壳贝壳幼虫阶段存在单瓣有机贝壳。在腹足类和头足类的早期阶段已经发现了类似的单瓣有机壳，这表明它在Conchifera类中具有同构性(Hayakaze和Tanabe，1999)。头足类Tanabe、Sasaki和Isaji的研究利用扫描电子显微镜(Tanabe&Uchiyama，1997；Isaji&Tanabe，Prep.)研究了近代鹦鹉螺管状组织的早期壳发育和形态发生。Tanabe还认识到了头足类口腔肿块(Tanabe&Fukuda，1999)和菊状虹吸虫(Tanabe等人，正在出版)的解剖特征。腹足类Sasaki和Kase的研究已经明确了一些原始腹足类的上下分类和系统发育关系(Sasaki，1998；Kase，1998a-c)。b)分子系统学研究。Ewndo和Ueshima已经认识到腕足类的线粒体基因组结构，讨论了Lophotrochozoa，Annelida和软体动物的系统发育关系(Noguchi et al.)。c)生物矿物学研究。Endo和他的同事Sarashina弄清楚了扇贝壳可溶基质蛋白的一级结构，讨论了其对生物矿化的意义(Sarashina&Endo，1998)。

A) Comparative anatomical and embryological studies.A-1. Studies on Bivalvia Tanabe and Hayakaze have described the presence of a univalved organic shell in the trochophore larval stage of the Bivalvia, prior to the development of a bivalved calcified shell. A similar univalved organic shell has been recognized in early stage of Gastropod and Cephalopod, suggesting its synapomorphic nature among the Conchifera (Hayakaze and Tanabe, 1999).A-2. Studies on Cephalopoda Tanabe, Sasaki and Isaji have studied the early shell development and morphogenesis of the siphuncular tissue in Recent Nautilus by means of SEM and TEM ( Tanabe & Uchiyama,1997 ; Isaji & Tanabe, in prep.). Tanabe has also realized the anatomical features of cephalopod buccal mass (Tanabe & Fukuda, 1999) and ammonoid siphuncle (Tanabe et al., in press).A-3. Studies of Gastropoda Sasaki and Kase have made clear the higher and lower taxonomy and phylogenetic relationships of some primitive gastropods (Sasaki, 1998 ; Kase, 1998a-c).B) Molecular phylogenetic studies.Ewndo and Ueshima have realized the mitochodrial genome structure of the brachiopod laqueus, discussing the phylogenetic relationships of the Lophotrochozoa, Annelida, and Mollusca (Noguchi et al., in press).C) Biomineralogical studies.Endo and his co-worker, Sarashina have made clear the primary structure of the soluble matrix protein of scallop shell, discussing its significance for biomineralization (Sarashina & Endo, 1998).