Structure of shells from eggs of kinosternid turtles
Structure of shells from eggs of kinosternid turtles
复制标题
动胸龟蛋壳的结构
作者：
M. Packard;K. Hirsch;J. Iverson
用光镜和扫描电镜对5种赤蠵龟（Sternotherus minor, Kinosternon flavescens， K. baurii， K. Hirtipes和K. alamosae）的卵壳进行了观察。除了种间蛋壳厚度可能存在差异外，所有卵的蛋壳结构基本相似。一般来说，肌甾体龟产的蛋有一层坚硬的钙质层，由文石形式的碳酸钙组成。钙质层被组织成单个的壳单元，其针状晶体从一个共同的中心辐射出来。蛋壳的大部分厚度是由钙质层造成的，纤维壳膜只占蛋壳厚度的一小部分。钙质层中有孔隙，但数量不多。蛋壳的外表面是雕刻的，在某些地方可能有一层厚厚的有机层。脱钙蛋壳的壳膜外表面布满球形核，这可能是蛋壳形成过程中壳单元生长的核。蛋壳膜从孵化到孵化的鸡蛋上脱落，携带着残余的钙质层。蛋壳结构的这种变化可能反映了发育中的胚胎从蛋壳中提取钙。
Shells from eggs of five species of kinosternid turtle (Sternotherus minor, Kinosternon flavescens, K. baurii, K. Hirtipes, and K. alamosae) were examined with light and scanning electron microscopy. Except for possible differences among species in thickness of eggshells, structure of shells from all eggs was similiar. In general, kinosternid turtles lay eggs having a rigid calcareous layer composed of calcium carbonate in the form of aragonite. The calcareous layer is organized into individual shell units with needlelike crystallites radiating from a common center. Most of the thickness of the eggshell is attributable to the calcareous layer, with the fibrous shell membrane comprising only a small fraction of shell thickness. Pores are found in the calcareous layer, but they are not numereous. The outer surface of the eggshells is sculptured and may have a thick, organic layer in places. The outer surface of the shell membrane of decalcified eggshells is studded with spherical cores which presumably nucleate growth of shell units during shell formation. The shell membrane detaches from eggs incubated to hatching, carrying with it remnants of the calcareous layer. Such changes in shell structure presumably reflect withdrawal of calcium from the eggshell by developing embryos.