根足类原生动物半圆表壳虫壳体生物矿化特征

以有壳阿米巴类原生动物 (肉鞭门 ,叶足纲 )半圆表壳虫 (Arcellahemisphaerica)为研究对象 ,利用光镜和扫描电镜研究了其壳体生物矿化的特征。结果显示 :矿化前期 ,壳体为无色透明且柔软易变形 ;中期 ,为黄色较坚硬 ;后期 ,为褐色坚硬。通过X 射线显微分析术鉴定不同矿化时期壳体的无机元素 ,结果表明 ,与矿化前期相比矿化中期和后期壳体中Si、Mn和Fe的比例增加 ,Cl、K、S和Na的比例减少。由此推测 ,⑴半圆表壳虫矿化过程中壳体坚硬的原因是Si、Mn和Fe的比例增加导致 ,黄色是由微量Mn和Fe引起 ,褐色是高含量Mn与低含量Fe的反映 ;⑵半圆表壳虫壳体矿化以构成壳体的小泡为基本单位进行 ,Si、Mn和Fe矿化体以氧化物形式通过分子间相互作用力 ,与小泡壁上氨基酸或多肽的羟基作用 ,自组装合成。

Characters of Biomineralization in the Shell of Arcella hemisphaerica (Protozoa: Rhizopoda)

The biomineralization in the shell of the freshwater testate amoeba Arcella hemisphaerica was investigated using light microscopy and scanning electron microscopy. The results show that the shell is colorless and flexible in the pre-biomineralization period; yellow and medium-hardness in the mid-biomineralization period; brown and rigid in the post-biomineralization period. Further, X-ray microanalysis suggested that the percentages of Si, Mn and Fe in the shell increase gradually and those of Cl, K, S and Na decrease during the process of the biomineralization. Accordingly, the increasing of Si, Mn and Fe in proportion results in the strengthening of the shell wall;the presence of Mn and Fe in trace brings about the yellow shell; and the more guantity of Mn and the less quantity of Fe lead to the brown shell. It has been demonstrated that the unit of biomineralization of the shell is the hollow alveoli arranged in a single layer. The minerals of Si, Mn and Fe in the shell may be self-synthesized, together with amino acid or polypeptide in the alveoli wall, by intermolecular force between the hydroxyl groups.