大菱鲆(Scophthalmus maximus)鱼苗视网膜组织结构与视觉特性

Histological Structure of Retina and Visual Characteristics of Turbot Scophthalmus maximus Fry

中文关键词: 大菱鲆  视网膜  组织结构  视觉特性

英文关键词: Scophthalmus maximus (Turbot)  Retina  Histological structure  Visual characteristic

中文摘要:

      采用石蜡连续切片技术研究了初孵至50日龄大菱鲆(Scophthalmus maximus)鱼苗的视网膜结构及视觉特性。测定了鱼苗发育过程中视网膜横切面上视锥细胞(CC)、外核层细胞核(ONN)和神经节细胞(GC)的数量变化，以及鱼苗经明暗适应后视网膜色素指数的变化。结果显示，2日龄仔鱼视网膜上出现色素层和视锥细胞层，为仔鱼开口摄食提供了视觉基础。5日龄仔鱼的视网膜没有运动反应。鱼苗从16日龄发育到30日龄，明暗适应后视网膜色素指数的差值显著升高(P<0.01)，表明视网膜出现了显著的运动反应。16–39日龄，鱼苗视网膜上CC、GC数量显著减少(P<0.01)，ONN数量显著增多(P<0.01)，39–50日龄，视网膜上CC、GC和ONN数量没有出现显著差异(P>0.05)。大菱鲆鱼苗变态前视网膜视敏度高，光敏性低，变态后视敏度降低，光敏性增强，视网膜逐步适应感受弱光的刺激，这与大菱鲆鱼苗变态后从浮游到底栖的生活习性相适应。变态后的大菱鲆光感受系统不发达。

英文摘要:

      Knowledge on fish retina structure and associated characteristics helps better understanding their feeding behaviors. In this study we studied the structure of retina and visual characteristics of fries of Turbot Scophthalmus maximus using paraffin sectioning method. The experimental water temperature was (20.5±2.0)℃ and the water salinity was 29±1. Healthy fries were fixed after certain periods of light or dark adaptation that included newly hatched, 2 d, 5 d, 10 d, 16 d, 20 d 23 d, 26 d, 30 d, 34 d, 39 d, 43 d and 50 d. We also measured the pigment index (PI) after the adaptation of retina, the thickness of outer nuclear layer, internal nuclear layer and ganglion cell layer of retina, and the amounts of cone cells (CC), ganglion cells (GC) and nuclei of the outer nuclear layer (ONN) on the retina cross section. It was observed that the pigment layer and cone cell layer appeared in the retina of 2 d larvae, which was the visual support for the first feeding. The retina of 5 d larvae showed no motion response. From 16 d larvae to 30 d juveniles, the difference in the retinal PIs after light and dark adaptation (the former subtracted by the latter) significantly increased (P<0.01), which indicated the motion response in retina. During the development there was reduction in the amounts of CC and GC in the retina (P<0.01), while there was an increase in the amounts of ONN, the ratio of ONN to CC, and the ratio of ONN to GC (P<0.01). The retinas of turbot fries possessed high visual acuity and low photosensitivity before metamorphosis, however the former dropped and the latter increased after metamorphosis. This adapted to the weak light stimulation when their lifestyle changed from planktonic to benthic. The photo sensing system of post-metamorphosis benthic turbot was deficiently developed.