蚌壳珍珠层的特殊生长形态和成因探讨——以湖北鄂州梁子湖淡水三角帆蚌为例

Special Growth Morphology and Genesis of Nacreous Layer of Hyriopsis Cumingi from E’zhou,Hubei Province

采用偏光显微镜对湖北鄂州淡水三角帆蚌壳珍珠层的生长形态进行了研究。结果表明:除片状晶体构成的规则致密形态外,蚌壳珍珠层内还有亮带(异常消光区)、纤维状夹层、柱状夹层、黄褐色条带或环带等特殊生长形态。亮带和纤维状夹层均由外套膜表皮细胞的异常分泌物沉淀结晶而成;柱状夹层是蚌壳根部珍珠层局部受外力作用重结晶的产物;黄褐色条带或环带内有机质浓度的变化显示了蚌体新陈代谢由异常逐渐恢复正常的过程。珍珠层内的平行纹理反映了外套膜分泌面相对壳体由根部向壳缘缓慢移动的生长机制。柱状夹层两侧的纹理体现外套膜分泌面的两种移动方向:上侧沿壳内侧面由根部向壳缘方向移动,下侧垂直于珍珠层层面由外向内移动。

The growth morphology of nacreous layer of shell of freshwater Hyriopsis Cumingi from E＇zhou, Hubei Province, is studied by using the polarizing microscope. The results indicate that, besides the normal shape of sheet, the special morphology of crystallization aggregates in nacreous layer consists of the highlight band, tiny fibrous layer, prismatic layer and yellowish brown band or zone. The formation of highlight band and tiny fibrous layer is associated with the abnormal secretion of epithelial cell on the mantle tissues. The prismatic layer on the growth root of the shell may be the texture of recrystallization caused by the external mechanic force. The content variation of organic matrix in the yellowishbrown band or zone shows that mussel＇s metabolization gradually retrieves from the abnormal to the normal states. The parallel laminations in t.he nacreous layer indicate that the secretion surface of mantle tissues maintains constant migration from the root to the rim of shell. The growth laminations on both sides of the prismatic layer suggest the two movement directions of secretion surface of mantle tissues, one is from the mussel＇s growth root to the rim on the internal surface of the shell,the other is from the external to the internal of the shell vertically to the nacreous layer.