Fine structure of the mineralized teeth of the chiton Acanthopleura echinata (Mollusca: Polyplacophora)
Fine structure of the mineralized teeth of the chiton Acanthopleura echinata (Mollusca: Polyplacophora)
复制标题
石鳖矿化牙齿的精细结构 Acanthopleura echinata（软体动物：Polyplacophora）
作者：
R. Wealthall;L. Brooker;D. Macey;B. Griffin
石鳖的主要侧齿是由三个不同矿物区域组成的复合结构：后层磁铁矿；后层磁铁矿；在此之前有一条纤细的纤铁矿带；和磷灰石遍布尖头的核心和前部区域。这些牙齿中的生物矿化是一个基质介导的过程，其中矿物质沉积在纤维周围，不同的生物矿物质被描述为占据结构上离散的隔室。在这项研究中，利用一系列扫描电子显微镜对主要侧齿的精细结构进行了详细的现场研究。牙齿的有机和生物矿物成分的排列在整个三个区域中是相似的，它们之间没有离散的边界，并且每个矿物相的微晶延伸到相邻的矿物区域中。沿着牙齿的后表面，有机纤维排列成一系列细小的平行线，但就在外围，它们的外观呈现出“鱼鳞”状的图案，反映了相邻行中一系列重叠且相互偏移的单元的横截面。这些单元大约 2 μm 宽、0.6 μm 厚，由有机纤维分隔的生物矿物板组成。每个“鱼鳞”由两种类型的亚单位组成：一种是细长且弯曲的，形成一个槽，另一种是杆状单位，坐落在其中。相邻的杆和槽单元排列成大片，限定了齿的断裂平面。杆槽单元板的对准很复杂，并且在齿尖内表现出极大的空间变化。靠近后表面的板基本上是水平的并且位于后内侧平面中，而在前面它们几乎是垂直的并且位于后前平面中。了解石鳖矿化牙齿的精细结构以及有机成分和矿物成分之间的关系，为生物矿化机制和控制提供了新的见解。 J.莫菲尔。 © 2005 Wiley-Liss, Inc.
The major lateral teeth of the chiton Acanthopleura echinata are composite structures composed of three distinct mineral zones: a posterior layer of magnetite; a thin band of lepidocrocite just anterior to this; and apatite throughout the core and anterior regions of the cusp. Biomineralization in these teeth is a matrix‐mediated process, in which the minerals are deposited around fibers, with the different biominerals described as occupying architecturally discrete compartments. In this study, a range of scanning electron microscopes was utilized to undertake a detailed in situ investigation of the fine structure of the major lateral teeth. The arrangement of the organic and biomineral components of the tooth is similar throughout the three zones, having no discrete borders between them, and with crystallites of each mineral phase extending into the adjacent mineral zone. Along the posterior surface of the tooth, the organic fibers are arranged in a series of fine parallel lines, but just within the periphery their appearance takes on a “fish scale”‐like pattern, reflective of the cross section of a series of units that are overlaid, and offset from each other, in adjacent rows. The units are approximately 2 μm wide and 0.6 μm thick and comprise biomineral plates separated by organic fibers. Two types of subunits make up each “fish scale”: one is elongate and curved and forms a trough, in which the other, rod‐like unit, is nestled. Adjacent rod and trough units are aligned into large sheets that define the fracture plane of the tooth. The alignment of the plates of rod‐trough units is complex and exhibits extreme spatial variation within the tooth cusp. Close to the posterior surface the plates are essentially horizontal and lie in a lateromedial plane, while anteriorly they are almost vertical and lie in the posteroanterior plane. An understanding of the fine structure of the mineralized teeth of chitons, and of the relationship between the organic and mineral components, provides a new insight into biomineralization mechanisms and controls. J. Morphol. © 2005 Wiley‐Liss, Inc.