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Comparative morphologic and biomineralogical studies on the relationship between mantle differentiation and early shell formation in Mollusca

软体动物地幔分化与早期壳形成关系的比较形态学和生物矿物学研究

基本信息

批准号：
15340175
负责人：
TANABE Kazushige
金额：
$ 8.83万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2005
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-15340175/
关键词：
Mollusca Early ontogeny Larval shell Embryonic shell Comparative morphology biomineralization evolution

项目摘要

In this study, we have examined the relationship between mantle differentiation and shell formation in early developmental satges of Recent and fossil mollusks from the viewpoints of comparative morphology and biomineralogy, and the results of observations were considered for their morphogenetic, larval ecological and phylogenetic implications. The results are summarized as below.A. Embryology and larval shell development of Recent Gastropoda. SEM studies of a freshwater snail Lymnaea stagnalis in the early stages reveal that the early larval shell was not formed accretionarily, and that the biomineralization process in the early stage differs from that in the post-metamorphosis stage.B. Larval shell formation in Recent Bivalvia SEM and TEM studies of a pholadid bivalve Zirfaea subconstricta in the trochophore and early veliger larval stages indicate that outer surface of secreting cells contribute a shell pellicle and functions as an adhering site of tendon cells at the stage of non-biomineralization.C. Embryonic shell development of Mesozoic Ammonoidea Exceptionally well-preserved embryonic shell fossils of Mesozoic ammonites were examined for their shell wall structure and ornament by means of SEM. The results demonstrate the succession of early shell wall development starting with a horny primary shell and ending in the secretion of a nacreous swelling at the aperture via secretion of inner prismatic and outer prismatic layers. Irregular distribution of microtubercles on the outer prismatic layer suggest that they were formed by the aid of a shell gland but by non-biological precipitation by egg-fluid.

本研究从比较形态学和生物矿物学的角度探讨了现代软体动物和化石软体动物早期发育阶段壳的形成与地幔分化的关系，并对观察结果的形态发生、幼虫生态学和系统发育学意义进行了讨论。结果总结如下。现代腹足类的胚胎学和幼虫壳发育。通过对淡水蜗牛滞水龙螺早期的扫描电镜观察，发现其早期幼虫壳不是增生形成的，早期阶段的生物矿化过程与变态后阶段不同。通过扫描电镜和透射电镜观察，发现在非生物矿化阶段，分泌细胞的外表面形成壳膜，并作为腱细胞的附着部位。中生代菊石类胚胎壳的发育利用扫描电镜对保存异常完好的中生代菊石类胚胎壳化石的壳壁结构和纹饰进行了研究。结果表明，继承的早期壳壁发展开始与角质的初级壳和结束在nacadenoma肿胀的分泌在孔径通过分泌的内部棱柱和外部棱柱层。外棱柱层上微结节的不规则分布表明，它们是由壳腺的帮助下，但通过卵液的非生物沉淀形成的。