Hild Sabine, Marti Othmar, Ziegler Andreas
Central Facility for Electron Microscopy, University of Ulm, Albert-Einstein-Allee 11, D89069 Ulm, Germany.
J Struct Biol. 2008 Jul;163(1):100-8. doi: 10.1016/j.jsb.2008.04.010. Epub 2008 May 3.
The crustacean cuticle is an interesting model to study the properties of mineralized bio-composites. The cuticle consists of an organic matrix composed of chitin-protein fibres associated with various amounts of crystalline and amorphous calcium carbonate. It is thought that in isopods the relative amounts of these mineral polymorphs depend on its function and the habitat of the animal. In addition to the composition, the distribution of the various components should affect the properties of the cuticle. However, the spatial distribution of calcium carbonate polymorphs within the crustacean cuticle is unknown. Therefore, we analyzed the mineralized cuticles of the terrestrial isopods Armadillidium vulgare and Porcellio scaber using scanning electron-microscopy, electron probe microanalysis and confocal mu-Raman spectroscopic imaging. We show for the first time that the mineral phases are arranged in distinct layers. Calcite is restricted to the outer layer of the cuticle that corresponds to the exocuticle. Amorphous calcium carbonate is located within the endocuticle that lies below the exocuticle. Within both layers mineral is arranged in rows of granules with diameters of about 20 nm. The results suggest functional implications of mineral distribution that accord to the moulting and escape behaviour of the animals.
甲壳动物的角质层是研究矿化生物复合材料特性的一个有趣模型。角质层由有机基质组成，该有机基质由与各种数量的结晶和无定形碳酸钙相关联的几丁质 - 蛋白质纤维构成。据认为，在等足类动物中，这些矿物多晶型物的相对含量取决于其功能和动物的栖息地。除了组成成分外，各种成分的分布也会影响角质层的特性。然而，甲壳动物角质层内碳酸钙多晶型物的空间分布尚不清楚。因此，我们使用扫描电子显微镜、电子探针微分析和共聚焦显微拉曼光谱成像技术，分析了陆生等足类动物普通鼠妇和鼠妇的矿化角质层。我们首次表明，矿相排列成不同的层。方解石局限于角质层对应于外表皮的外层。无定形碳酸钙位于外表皮下方的内表皮内。在这两层中，矿物质都排列成直径约为20纳米的颗粒行。结果表明矿物质分布的功能意义与动物的蜕皮和逃避行为相符。
