美洲鲥(Alosa sapidissima)眼睛早期发育的组织学观察

Histological Observation of the Eye of American Shad (Alosa sapidissima) at the Early Developmental Stage

中文关键词: 美洲鲥  眼睛  结构  早期发育  组织学

英文关键词: Alosa sapidissima  Eye  Structure  Early development  Histology

中文摘要:

      应用石蜡切片及HE染色的方法对美洲鲥(Alosa sapidissima)早期发育过程中眼睛的发生、分化和形成过程进行了系统的观察。结果显示，受精后21 h 13 min，视泡出现；受精后26 h 23 min，视泡发育成视杯；受精后35 h 44 min，原始视网膜和晶状体形成；受精后60 h 15 min，角膜在视网膜前缘处形成，由单一的立方上皮构成；2日龄仔鱼，巩膜分化完成，由软骨组织和弹力纤维构成，脉络膜出现；3日龄仔鱼，虹膜出现，视网膜分化完全，由外向内的色素层、视觉细胞层、外界膜、外核层、外网膜层、内核层、内网膜层、视神经节细胞层、视神经纤维层和内界膜10层构成，此时视觉细胞层中视杆细胞出现；14日龄仔鱼，角膜分化完全，由自外向内的复层扁平上皮、前弹性层、基质层、后弹性层和内皮层5层构成；22日龄仔鱼，脉络膜腺出现；26日龄稚鱼脉络膜分化完全，由外向内依次为银膜层、血管层和色素层，虹膜也完全分化，由外向内依次为虹膜内皮层、前缘层、基质层、后缘层和色素层；45日龄幼鱼，视网膜内核层分化成两层水平细胞。此时美洲鲥眼睛的各个结构均发育完善。

英文摘要:

      The American shad (Alosa sapidissima) is an economically and ecologically valuable anadromous species native to the Atlantic coast of North America, distributed from the St. Lawrence River in Canada to the St. Johns River in northern Florida. In the past few decades, American shad have been introduced as a candidate species into Chinese aquaculture because Chinese shad (Tenualosa reevesii) was endangered. Nowadays the farming scale and techniques for American shad have been greatly improved in China. However, little histological study has been done on the early development of A. sapidissima larvae, especially on the eye ontogeny. Here we employed the paraffin section and HE section methods in a histological observation of the eye ontogeny of A. sapidissima. The results showed that the optic vesicle was formed in 21 h 13 min after fertilization, and then developed into the optic cup in 26 h 23 min after fertilization. At 35 h 44min the undifferentiated retina and lens were visible. As the embryonic development continued, the cornea was formed in front of the retina, which consisted of single cuboidal epithelium. On Day after hatching (DAH) 2, the sclera composed of cartilage and outer fibrous layer became visible, followed by the appearance of choroid. On DAH 3 the iris was present, and the retina differentiated into ten layers including pigment epithelium, visual cell layer, outer limiting membrane, outer nuclear layer, outer plexiform layer, inner nuclear layer, inner plexiform layer, ganglion cell layer, nerve fibre layer and inter limiting membrane, and then the rod cells were clearly observed in the visual cell layer. On DAH 14, the cornea was well developed and differentiated into five layers that were stratified squamous epithelium, lamina elastic anterior, stroma layer, lamina elastic posterior and endothelium. On DAH 22, the choroid gland appeared. On DAH 26, the choroid completely differrntiated into three layers (argenteum layer, the choriocapillary layer and the pigment layer). In addition, the iris also underwent full differentiation and contained layers of endothelium, iris anterior, stroma, iris posterior and pigment. On DAH 45, the inner nuclear layer of renita developed into two layers of horizontal cells, and it was that moment when the development of the eye structure was complete.