Study on the microstructure of biocrystals in invertebrates and its phylogeny

利用电子显微镜和光学显微镜对生物矿物的微观结构和壳层结构进行了研究。为了阐明贝壳的形成机理，观察了约20种腹足类的壳内表面生物晶体的生长情况。珍珠岩的生长有柱状和片状两种类型。腹足类的交叉板层生长与翼足类的类似。文石和方解石晶体生长在同一区域，特别是对单齿石等的壳层结构进行了详细的研究。因此，腹足类贝壳的许多特征与翼足类贝壳相同。但是，在最内壳层的形成、透棱层的形成以及交叉片层和珍珠状结构的性质上存在着一些不同的观点。结果表明，巴巴提亚壳层中的文石三级晶片不是单晶，而是多合成孪晶。合成孪晶的复合面为(110)晶面。人工合成的双胞胎个体的厚度为几百个，不到一百个。均一结构和珍珠状结构的无脊椎动物生物晶体也形成了双胞胎结构。无脊椎动物的上皮钙化组织在原生动物阶段已经分化，高等动物继承了它们。在生物演化过程中，钙质壳层和有机层发生了分化。前者的有机基质来源于Glico-Calyx的同源物质，并获得了与代谢活性有关的有机基质中的结晶沉积。

In this study, the microstructure of biomineral and the shell structure were examined by the use of electron and optic microscopes. For elucidating the mechanism of shell formation, the biocrystal growth on the inner shell surface of about twenty species of gastropods was observed. There are two types in nacreous growth, namely pillar and sheet nacreous growth. The crossed lamellar growth of gastropods is similar to one of pelecypods. Aragonite and calcite crystals grow at the same area.Especially, the shell structure of Monodonta and so on was examined in details. As the result, many features of gastropodian shells are common to ones of pelecypods. But, there are some different points in the development of the most inner shell layer, the formation of trans-prismatic layer and the nature of crossed lamellar and nacreous structures.The ultra-microstructure of biocrystals was examined by transmitted electron microscope. It was observed that the third order lamellae of aragonite crystal in the shell of Barbatia are not a single crystal, but polysynthetically twinned crystals. The composite plane of the polysynthetic twinning is (110) plane. The thickness of polysynthetic twin individuals is several hundreds - less than a hundres A. Aragonitic biocrystals of homogeneous and nacreous structures form also twin structure.Epithelial calcified tissues of invertebrates had differetiated at the stage of protozoa and higher animals succeeded to them. Calcreous shell and organic layers differentiated in the course of biological evolution. Organic matrixes of the former originated from homologous materials of glico-calyx and crystal deposition in organic matrixes was gained in relation to metabolic activity.