Department of Earth and Planetary Sciences, Macquarie University, North Ryde, NSW, 2109, Australia.
Zoologische Staatssammlung München, Staatliche Naturwissenschaftliche Sammlung Bayerns, Münchhausenstraße 21, 81247, München, Germany.
Sci Rep. 2019 Aug 7;9(1):11439. doi: 10.1038/s41598-019-47848-4.
Cheilostome Bryozoa Anoteropora latirostris, a colonial marine invertebrate, constructs its skeleton from calcite and aragonite. This study presents firstly correlated multi-scale electron microscopy, micro-computed tomography, electron backscatter diffraction and NanoSIMS mapping. We show that all primary, coarse-grained platy calcitic lateral walls are covered by fine-grained fibrous aragonite. Vertical lateral walls separating autozooid chambers have aragonite only on their distal side. This type of asymmetric mineralization of lateral walls results from the vertical arrangement of the zooids at the growth margins of the colony and represents a type of biomineralization previously unknown in cheilostome bryozoans. NanoSIMS mapping across the aragonite-calcite interface indicates an organic layer between both mineral phases, likely representing an organic template for biomineralization of aragonite on the calcite layer. Analysis of crystallographic orientations show a moderately strong crystallographic preferred orientation (CPO) for calcite (7.4 times random orientation) and an overall weaker CPO for aragonite (2.4 times random orientation) with a high degree of twinning (45%) of the aragonite grains. The calculated Young's modulus for the CPO map shows a weak mechanical direction perpendicular to the colony's upper surface facilitating this organism's strategy of clonal reproduction by fragmentation along the vertical zooid walls.
石珊瑚目有孔虫 Anoteropora latirostris 是一种具有钙质外骨骼的海洋无脊椎动物。本研究首次采用相关的多尺度电子显微镜、微计算机断层扫描、电子背散射衍射和 NanoSIMS 映射技术进行研究。结果表明，所有初级、粗粒板状方解石侧壁均被细粒纤维文石覆盖。分隔住室的垂直侧壁仅在其远端一侧有文石。这种侧壁的不对称矿化方式源于群体生长边缘处的个体垂直排列，代表了以前在石珊瑚目中未知的生物矿化类型。NanoSIMS 映射横跨文石-方解石界面表明，两种矿物相之间存在有机层，可能代表了文石在方解石层上生物矿化的有机模板。对晶体取向的分析表明，方解石具有中等强烈的晶体择优取向（CPO）（比随机取向强 7.4 倍），而文石的整体 CPO 较弱（比随机取向强 2.4 倍），且文石晶粒具有高度的孪晶（45%）。计算得出的 CPO 图谱的杨氏模量显示出弱的机械方向垂直于群体的上表面，这有利于该生物通过沿垂直的住室壁进行碎片生殖来实现无性繁殖的策略。
