Kusuda Satoshi, Yasukawa Yuichirou, Shibata Hiroki, Saito Tomomi, Doi Osamu, Ohya Yutaka, Yoshizaki Norio
Faculty of Applied Biological Sciences, Gifu University, Japan.
Zoolog Sci. 2013 May;30(5):366-74. doi: 10.2108/zsj.30.366.
The eggshells of 56 chelonians were examined by electron microscopy and X-ray diffractometry. They were classified into six types in terms of the matrix structure of their calcareous layer; type I was composed of a thin calcareous layer with minerals in an amorphous structure; type II with shell units composed of mammillary cores calcified with aragonite crystals; type III with shell units composed of mammillary cores, plus a single palisade layer also calcified with aragonite crystals, and with each shell unit separated; type IV with shell units the same as type III, but tightly packed together; type V with shell units composed of mammillary cores plus two palisade layers; and type VI with a cuticle layer calcified with calcite crystals over the same structure as that of type V. X-ray diffraction analyses at the outer surface of eggshells showed a gradual change in crystal disposition from the random disposition of type II to the single direction-oriented disposition of type V. The shell height was approximately parallel to the development of the palisade-layer matrix. The limiting membrane of all eggshell types was perforated with canals and that of type I was partially missing. Type I had a parchment shell, types II and III had a pliable shell (some were rigid) and types IV to VI had rigid shells. The present study showed that the hardness of eggshells can be determined by the composition of the shell matrices, as shell matrices are the framework for mineralization.
通过电子显微镜和X射线衍射法对56种龟类的蛋壳进行了检查。根据其钙质层的基质结构，它们被分为六种类型；I型由一层薄的钙质层组成，其中矿物质呈无定形结构；II型的壳单元由霰石晶体钙化的乳头状核心组成；III型的壳单元由乳头状核心组成，加上一层也由霰石晶体钙化的单一栅栏层，且每个壳单元相互分离；IV型的壳单元与III型相同，但紧密排列在一起；V型的壳单元由乳头状核心加上两层栅栏层组成；VI型在与V型相同的结构上有一层由方解石晶体钙化的角质层。蛋壳外表面的X射线衍射分析表明，晶体排列从II型的随机排列到V型的单方向排列逐渐变化。壳高大致与栅栏层基质的发育平行。所有蛋壳类型的限制膜都有管道穿孔，I型的限制膜部分缺失。I型有一层羊皮纸状的壳，II型和III型有柔韧的壳（有些是硬壳），IV型到VI型有硬壳。本研究表明，蛋壳的硬度可由壳基质的组成决定，因为壳基质是矿化的框架。
