MICRO- AND NANOSTRUCTURES OF CALCAREOUS FORAMINIFERAL TESTS: INSIGHT FROM REPRESENTATIVES OF MILIOLIDA, ROTALIIDA AND LAGENIDA
MICRO- AND NANOSTRUCTURES OF CALCAREOUS FORAMINIFERAL TESTS: INSIGHT FROM REPRESENTATIVES OF MILIOLIDA, ROTALIIDA AND LAGENIDA
复制标题
DOI：
10.2113/gsjfr.48.2.142
复制
发表时间：
2018-04-01
影响因子：
1.1
通讯作者：
Gloc, Michal
中科院分区：
文献类型：
--
作者：
Dubicka, Zofia;Owocki, Krzysztof;Gloc, Michal
测试结构的Lagenida，Rotaliida，和Miliolida（有孔虫）描述在一个前所未有的规模的决议。使用常规和场发射扫描电子显微镜观察发现，这三个主要组的钙化有孔虫，最近的分子系统发育重建和更高层次的分类系统一致的纹理组成中的独特的微观和纳米级的差异。Rotaloid测试完全由直径高达100 nm的大致球形的初级碳酸盐纳米颗粒组成，这些纳米颗粒合并成微米级的不规则聚集体。粟粒试验由两种形态不同的初级微晶组成。有序排列的针状元件（长度可达1 μ m，宽度为200 nm）构成了测试的主体，包括壁的内部（瓷）和矿化的内表面（内弧面）（约100 mm）。厚度为100 nm）。大致球形的纳米颗粒（直径高达50 nm）形成或多或少规则排列的多边形的外层（外弧面），这是大约。厚度为200 nm。相比之下，Lagenid测试结构的特点是更大的晶体比其他钙化有孔虫。在中等放大倍数下，Lagenid测试显示由纤维束组成的纤维状结构（长度为几十μ m，宽度为几μ m），当与另一个薄片接触时，其垂直于测试表面并朝向端部逐渐变细。在更高的放大倍数下，每一束构成具有沿晶体的整个长度沿着延伸的内孔的单一方解石晶体。我们使用纳米压痕法测量测试硬度。这是该技术在微化石中的首次应用。我们发现，白垩纪Lagenida测试更耐机械应力比Rotaliida测试。这些比较优势可能与内部测试的微观结构，并在确定这些类群可以生活的栖息地发挥作用。
The test structures of Lagenida, Rotaliida, and Miliolida (Foraminifera) are described at an unprecedented scale of resolution. Observations using conventional and field-emission scanning electron microscopy revealed distinct micro- and nanoscale differences in the textural compositions of these three main groups of calcifying foraminifers, consistent with recent molecular phylogenetic reconstructions and a higher-level taxonomic system. The rotaliid test is entirely composed of roughly spherical primary carbonate nanograins, up to 100 nm in diameter, which merge into micrometer-sized irregular aggregates. The miliolid test is made up of two morphologically different primary crystallites. Arbitrarily arranged needle-shaped elements (up to 1 mu m in length and 200 nm in width) make up the bulk of the test, including the inside of the wall (porcelain) and mineralized inner surface (intrados) (ca. 100 nm in thickness). Roughly spherical nanograins (up to 50 nm in diameter) form more or less regularly arranged polygons of an outer lamina (extrados), which is ca. 200 nm in thickness. By contrast, the lagenid test texture is characterized by much larger crystals than in other calcifying foraminifers. At moderate magnification, lagenid tests display a fibrous texture composed of fiber bundles (tens of mu m in length and several mu m in width) that are oriented perpendicular to test surfaces and taper towards the ends when in contact with another lamina At higher magnification, each bundle constitutes a single calcite crystal with an inner pore extending along the entire length of the crystal/fiber.We measured test hardness using the nanoindentation method. This is the first application of this technique in microfossils. We found that Cretaceous Lagenida tests were more resistant to mechanical stress than Rotaliida tests. These comparative strengths may be linked to internal test microstructure and play a role in determining habitats in which these taxa can live.