扬子鳄胚胎背部皮肤及鳞甲的发生

Embryonic Development of the Dorsal Skin and Scutes of Alligator sinensis

本文观察了１６例不同时间的扬子鳄（Ａｌｌｉｇａｔｏｒｓｉｎｅｎｓｉｓ）胚胎背部皮肤及鳞甲的形态及组织发生过程。孵化第２０天，来自胚胎中胚层生皮节的间充质细胞开始向原始表皮下迁移，表皮仅具周皮层与生发层两层细胞。第２８天背部鳞片开始明显，左右鳞片之间出现很浅的鳞间沟，前后鳞片交界处的原始表皮、真皮层开始向外突出形成鳞甲原基。第３４天鳞甲原基突出伸长，第４０天背鳞的纵崤明显。第３４～５０天中，鳞甲后缘基部的表皮层向鳞甲前缘基部的真皮层不断内陷，鳞甲显著伸长并向体后方水平伸出。背部表皮在孵化第３４天出现三层细胞，第４０天周皮细胞中开始出现色素沉集。第５０天表皮具四层细胞，周皮层细胞中出现大量色素沉集。第６０天表皮分层与成体时相似，周皮层已退化。孵化第３４天真皮层细胞形态出现多样化，第４０天真皮可分上、下两层。第５０天真皮上层中形成交织的胶原纤维网，下层中形成平行走向的胶原纤维。本文简要讨论了扬子鳄鳞甲的形态发生特点。

In this paper the morphogenesis and histogenesis of dorsal skin and scutes based upon 16embryos of Alligator sinensis were described.At the 20th day of incubation,mesenchyme from mesodermal dermatome began nigratting toward the primitive epidermis which consisted of two layers of cells:periderm and stratum germinativum.At the 28th day of incubation,dorsal scales were all distinct with shallow furrows between the right and left scales and epidermis-dermis projection or anlagen for scutes between fore and hind scales.The projections of anlagen for scutes lengthened at the 34th day of incubation.The longitudinal ridges of dorsal scales were evident at the 40th day of incubation. During the 34￣50th day of incubation,the epidermis at the base of hind margin of scutes anlagen invaginated gradually toward the dermis at the base of fore margin,and scutes lengthened horizontally to the hind.The dorsal epidermis had three layers of cells at the 34th day of incubation.Pigmentation started to appear in the cells of periderm at the 40th day of incubation.At the 50th day of incubation.the dorsal epidermis had four layers of cells, and greats deal of pigmentation in the cells of periderm were observed.At the 60th day of incubation,the layers of epidermis were similar to that of adult alligator,and the periderm had degenerated.The cell morphology of dermis appeared varied to each other at the 34th day of incubation.At the 40th day of incubation,the dermis could be divided into the upper and under layers in Which network of collagenous fibers and parallelly lined collagenous fibers formed respectively at the 50th day of incubation.