Hall Simon R, Taylor Paul D, Davis Sean A, Mann Stephen
School of Chemistry, University of Bristol, Bristol BS8 1TS, UK.
J Inorg Biochem. 2002 Feb;88(3-4):410-9. doi: 10.1016/s0162-0134(01)00359-2.
Electron microscopy and electron diffraction were used to investigate mineral crystallites dissociated from the skeletal walls of six species belonging to the Bryozoa, a phylum of predominantly marine colony-forming invertebrate animals. Four cheilostome bryozoans (Flustra foliacea, Membranipora membranacea, Thalamoporella novaehollandiae and Cellarinella foveolata) and two cyclostomes (Fasciculipora ramosa and Hornera robusta) were analysed. In each case, an attempt was made to relate the crystal morphology imaged in situ by scanning electron microscopy with the crystallographic orientation of isolated crystals determined by electron diffraction analysis in the transmission electron microscope. The results showed that the calcitic cheilostome and cyclostome skeletons consisted of closely packed arrays of plate-like Mg-containing calcite crystallites, and that the crystallographic a-axis was preferentially aligned perpendicular to the top and bottom surfaces of the flattened particles. The results suggest that calcite biomineralization occurs under similar crystallographic constraints in the five species studied even though the origins of cheilostomes and cyclostomes are separated by over 300 million years in the fossil record of the bryozoans. Similar studies for the aragonite crystallites in skeletons of M. membranacea indicated that the crystallographic b-axis was preferentially oriented perpendicular to the basal surfaces of irregular plate-like particles.
利用电子显微镜和电子衍射技术，对苔藓虫纲六种物种骨骼壁上解离出的矿物微晶进行了研究。苔藓虫纲是一类主要营海洋群体生活的无脊椎动物。分析了四种唇口目苔藓虫（叶苔虫、膜孔苔虫、新荷兰苔藓虫和蜂窝苔藓虫）和两种环口目苔藓虫（分枝苔藓虫和粗壮苔藓虫）。在每种情况下，都尝试将扫描电子显微镜原位成像的晶体形态与透射电子显微镜中通过电子衍射分析确定的分离晶体的晶体学取向联系起来。结果表明，钙质唇口目和环口目苔藓虫的骨骼由紧密排列的含镁方解石板状微晶阵列组成，且晶体学a轴优先垂直于扁平颗粒的顶面和底面排列。结果表明，尽管在苔藓虫的化石记录中，唇口目和环口目的起源相隔超过3亿年，但在所研究的五个物种中，方解石生物矿化是在相似的晶体学限制条件下发生的。对膜孔苔虫骨骼中霰石微晶的类似研究表明，晶体学b轴优先垂直于不规则板状颗粒的基面排列。
