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。对双壳类田边和Hayakaze的研究表明，在双壳类担轮幼虫阶段，在发育成双壳钙化壳之前，存在单壳有机壳。在腹足类和腹足类的早期阶段也发现了类似的单瓣有机壳，这表明其在贝壳类中的突触形态性质（Hayakaze和田边，1999）。头足类的研究田边，Sasaki和Isaji用扫描电镜和透射电镜研究了现代鹦鹉螺早期壳的发育和管形组织的形态发生（田边& Uchiyama，1997 ; Isaji &田边，in prep.）。田边还认识到了头足类颊块（田边& Fukuda，1999）和菊石管（田边et al.，A-3。腹足类Sasaki和Kase的研究明确了一些原始腹足类的高等和低等分类以及系统发育关系（Sasaki，1998 ; Kase，1998 a-c）。B）分子系统发育研究。Ewndo和Ueshima实现了腕足类湖泊的线粒体基因组结构，讨论了Lophotrochozoa，Annelida和Mollusca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已经明确了扇贝壳的可溶性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).