鳜鱼视网膜发育的组织学研究

HISTOLOGICAL STUDY ON THE DEVELOPMENT OF RETINA OF MANDARIN FISH(Siniperca chautsi)

对全长５．０～１１５．０ｍｍ不同发育时期鳜鱼视网膜结构及３种视细胞的密度进行了观测。结果表明：刚孵出的鳜苗视网膜感受细胞为高密度的单锥细胞，且不具视网膜运动反应。视杆细胞和双锥细胞出现较晚。随其生长发育，视锥和神经节细胞密度降低，视杆细胞密度增加。外核层细胞核与神经节细胞的比值增大，同时视网膜各层次的发育渐趋完善。全长３０．０～４３，０ｍｍ是视网膜结构及视觉特性发生明显变化的过渡时期。后期网膜上不同区域视锥的类型、形态和数量呈现异质分布，双锥约占视锥数量的９０％。鳜鱼视觉结构的变化与其从浮游到底栖的生态迁移及捕食方式的变化相适应。

The retinal structure and the density of three visual cells(Sintperca chuatsi)at 5.0～115.0 mm total length(TL)were examined histologically during different development stages.The main results obtained are as follows.The retina of the newly hatched larvae has only single cones(SC) as sensory cells with a high density, and there are no retinomotor responses in the eye.The rods and twin cones(TC) appear rather late.Over the whole range of development the density of cones and ganglion cells decreases while the density of the rods increases correspondingly.With the ratio of nuclei of the outer nuclear layer to ganglion cells increasing distinctly, the forms of various layers of retina gradually develop to be perfect.The investigation shows that the structure of the retina changes apparently in the stage of the TL between 30.0 mm and 43.0mm, which is a transitional period in which its visual characteristics changes obviously.In the different retinal regions of specimen in later stages, the distributive type, morphology and quantity of cones are different, and the proportion of twin cones to cones is about 90% in the whole retina.It is revealed that the changes of visual structure of mandarin fish are adapted to the ecological shift from pelagic to benthic habitats and to the changes of feeding methods.