花背蟾蜍(Bufo raddei Strauch)眼形态发生过程中角膜上皮表面结构的扫描电镜观察

扫描电镜观察表明,花背蟾蜍眼形态发生过程中角膜上皮细胞表面形态结构的变化,大致可分三个阶段。1.从神经管期至肌肉感应期预定角膜上皮表面无明显变化;2.在心跳期和鳃血循环期预定角膜上皮表面出现较多的细胞缢束和其下细胞表面的下陷;3.在以后各期,角膜上皮中纤毛细胞的纤毛逐渐退化消失,在右鳃盖封闭期纤毛细胞全部消失。上述变化与视网膜及其中光感受器的发育分化密切相关,纤毛的退化和消失更精确地反映了这种依赖关系,似可作为角??膜上皮分化的一个形态指标。

A SCANNING ELECTRON MICROSCOPICAL STUDY OF THE CORNEAL EPITHELIUM DURING THE MORPHOGENESIS OF THE EYE IN BUFO RADDEI

The changes of the morphologicalarchitecture of the cell surface of thecorneal epithelium during the morpho-genesis of the eye in Bufo raddei Strauchwere observed with scanning electronmicroscopy.They may be dividedinto three periods:1.From neuraltube stage (stage 16) to muscularresponse stage (stage 18) there are noevident differences between the pre-sumptive corneal epithelium and theepidermal ectoderm in the region of ??head (fig 1).They all include bothciliated cells and non-ciliated cells(fig 2).2.In heart beat (stage 19)and gill circulation (stage 20) stageson the surface of the presumptivecorneal epithelium appear many cel-lular constrictions and sinkings of thecell surface under the constrictions(fig 3).In gill circulation stage the ciliaof a few ciliated cells (arrow) beginto regress (fig 4).3.In latter stagesthe cilia of ciliated cells in the cornealepithelium all gradually regress anddisappear (fig5).Most of the ciliahave rapidly disappeared in tail fincirculation stage (stage 22,fig 6).The cilia on the ciliated cells completelyregressed in opercular fold stage (stage23,fig 7).The ciliated cells in cornealepithelium have completely disappe-ared when the operculum closed onright stage (stage 24.fig 8).Theciliary length of ciliated cells in cor-neal epithelium and in epidermal ecto-derm show different changes duringlatter stages (from stage 20 to stage25.Table 1). These changes of the morphologicalarchitecture of the cell surface ofcorneal epithelium during morpho-genesis of the eye are presumablycorrelated with the development ofthe retina and of the photoreceptorsin it.The regression and the disappea-rance of the cilia of ciliated cells incorneal epithelium more exactlyreflect this dependent relationship thanthe disappearance of the pigment inthe cornea.It may be served as amorphological index of differentiationof the cornea.