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bai tai qian zi hua bei ke
Author(s): 
Pages: 12-13
Year: Issue:  11
Journal: Ocean World

Keyword:  贝壳素外套膜三层结构珍珠层贝类生长线保护器官角质层酸腐蚀腹足类;
Abstract: <正> 软体动物所以又名贝类,即因它们多具贝壳而使然。当贝类生活时,头、足即伸出壳外,一遇险境便缩入壳内,所以贝壳是一种保护器官。典型的贝壳有三层结构:外层为有质层,内含角质物质,称贝壳素,如同人的指甲,是一种硬蛋白,耐受酸腐蚀。中层较厚,称棱柱层或壳层。内层为叶状的霰石结构,极富光彩,称珍珠层。外层和中层由外套膜背部边缘分
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