Hafner G S, Tokarski T R
Indiana University School of Optometry, 800 E. Atwater St., Bloomington, IN 47405, USA.
Cell Tissue Res. 1998 Sep;293(3):535-50. doi: 10.1007/s004410051146.
Pattern formation and ommatidial differentiation in the crayfish retina were analyzed using confocal, light and electron microscopy. Optic primordia first appear in the embryo as round elevations covered by a surface epithelial layer. Retinal differentiation begins with a wave of mitotic activity that moves across this epithelium from lateral to medial. Ommatidial cell clusters are visible at the surface along a transition zone, which lies at the interface of the medial undifferentiated retina and the lateral patterned retina. This zone is 8-10 cells wide and composed of small uniform cell profiles. Lateral to the transition zone the initial ommatidial cell clusters form staggered rows across the surface. Each first row cluster contains eight retinula cells surrounded by four cone, two corneagenous and two distal pigment cells. Ommatidial clusters in the first nine rows show significant changes in their organization, which are visible at the surface of the retina. In row 10 the retinula cells recede from the surface and the cone cells close in above them creating a constant cell pattern at the surface. Rhabdome development begins distally and extends downward as the retinula cluster recedes from the surface. Movement of the retinula cells inward and enlargement of the cone and corneagenous cells at the surface creates a two-tiered organization characteristic of each ommatidium. Comparison of retinal pattern formation and differentiation in the crayfish with retinal morphogenesis in Drosophila and other insects show several similarities between the two arthropod groups.
利用共聚焦显微镜、光学显微镜和电子显微镜分析了小龙虾视网膜中的模式形成和小眼分化。视原基最初在胚胎中表现为被表面上皮层覆盖的圆形隆起。视网膜分化始于有丝分裂活动的一波浪潮，该浪潮从外侧向内侧穿过该上皮层。沿着位于内侧未分化视网膜和外侧有模式视网膜界面的过渡区，小眼细胞簇在表面可见。这个区域宽8 - 10个细胞，由小的均匀细胞轮廓组成。在过渡区外侧，最初的小眼细胞簇在表面形成交错的行。每一排的第一个簇包含八个视杆细胞，被四个视锥细胞、两个角膜生成细胞和两个远端色素细胞包围。前九排的小眼簇在其组织上显示出显著变化，这在视网膜表面可见。在第10排，视杆细胞从表面后退，视锥细胞在它们上方靠近，在表面形成恒定的细胞模式。视杆的发育从远端开始，并随着视杆细胞簇从表面后退而向下延伸。视杆细胞向内移动以及表面的视锥细胞和角膜生成细胞的扩大，形成了每个小眼特有的两层组织。将小龙虾视网膜模式形成和分化与果蝇和其他昆虫的视网膜形态发生进行比较，发现这两个节肢动物类群之间有几个相似之处。
