Collin S P, Collin H B
Scripps Institution of Oceanography, School of Medicine, University of California San Diego, La Jolla.
Brain Behav Evol. 1993;42(2):77-97. doi: 10.1159/000114142.
The retina and choriocapillaris of the Florida garfish, Lepisosteus platyrhincus (Ginglymodi), was examined at the light and electron microscopic levels. The inner limiting membrane is covered by an extensive system of vitreal blood vessels emanating from the hyaloid artery, which enters the eye ventrally at the proximal end of the elongated optic nerve head. Two size classes of ganglion cell soma are segregated by optic axon fascicles and Müller cell endfeet, all of which lie at the level of the ganglion cell layer. A third class of 'displaced' ganglion cells lies at the border of the inner plexiform and inner nuclear layers amidst tightly packed amacrine, bipolar and Müller cell soma. Two layers of horizontal cells lie vitread of a synaptic zone consisting of a complex arrangement of horizontal and bipolar dendrites invaginating rod spherules and cone pedicles to form single and multiple (three to six) synaptic ribbon connections, respectively. Immediately vitread of the photoreceptor nuclei lie a population of 'displaced' bipolars. Three types of photoreceptors are characterised: unequal double cones, single cones (large and small) and rods. These show retinomotor movements where the rods elongate in the light and are masked by the pigment epithelium and contract in the dark as the pigment migrates sclerad. Ultrastructurally, 4 types of dark-staining (osmophilic) granules are described: (1) Small glycogen granules (0.033 microns) aggregated at the bases of the photoreceptor nuclei and larger similar granules (0.078 microns and termed paraboloids) vitread to the ellipsoid; (2) tapetal granules (0.32 microns) distributed throughout the dorsal four-fifths of the retinal pigment epithelium (RPE); (3) pigment granules (0.5-2.0 microns) in the RPE, concentrated in ventral retina; (4) granules or melanosomes (0.813 microns) of the choriocapillaris. The second class of granules constitute a tapetum lucidum eliciting a yellow eyeshine when viewed in the dark. Two other tapeta also exist, a guanine tapetum (irregular guanine crystals) and a tapetum fibrosum (stacks of collagen fibrils). Functional correlations are made, and the putative ancestral (primitive) condition of particular visual characters is established for the ray-finned fishes by out-group comparisons.
对佛罗里达雀鳝（Lepisosteus platyrhincus，雀鳝目）的视网膜和脉络膜毛细血管进行了光镜和电镜水平的检查。内界膜被源自玻璃体动脉的广泛玻璃体血管系统覆盖，该动脉在细长视神经乳头近端腹侧进入眼睛。两类不同大小的神经节细胞胞体被视神经轴突束和米勒细胞终足分隔开，它们都位于神经节细胞层水平。第三类“移位”神经节细胞位于内网状层和内核层的边界，周围是紧密排列的无长突细胞、双极细胞和米勒细胞胞体。两层水平细胞位于一个突触带的玻璃体侧，该突触带由水平细胞和双极细胞树突的复杂排列组成，这些树突分别向内陷入视杆小球和视锥小足，形成单突触带连接和多突触带连接（三到六个）。在光感受器细胞核的紧玻璃体侧存在一群“移位”双极细胞。鉴定出三种类型的光感受器：不等双锥、单锥（大的和小的）和视杆。这些光感受器表现出视网膜运动，视杆在光照下伸长并被色素上皮遮挡，在黑暗中随着色素向巩膜侧迁移而收缩。在超微结构上，描述了4种深色（嗜渗性）颗粒：（1）小糖原颗粒（0.033微米）聚集在光感受器细胞核基部，较大的类似颗粒（0.078微米，称为抛物面）向玻璃体侧延伸至椭球体；（2）反光色素颗粒（0.32微米）分布在视网膜色素上皮（RPE）背侧的五分之四区域；（3）RPE中的色素颗粒（0.5 - 2.0微米），集中在视网膜腹侧；（4）脉络膜毛细血管的颗粒或黑素体（0.813微米）。第二类颗粒构成一个明视毯，在黑暗中观察时会发出黄色眼闪光。还存在另外两种反光层，一种是鸟嘌呤反光层（不规则鸟嘌呤晶体）和一种纤维反光层（胶原纤维束）。进行了功能相关性分析，并通过外类群比较确定了辐鳍鱼类特定视觉特征的假定祖先（原始）状态。
