黑斑蛙光感受器计数和分类——扫描电镜研究

THE NUMBER AND TYPE OF PHOTORECEPTOR IN THE RETINA OF RANA NIGROMACULATA: ASEM STUDY

在扫描电镜下观察了黑斑蛙视网膜光感受器的类型、直径和密度。并用统计学方法对光感受器进行了计数。六个视网膜的光感受器计数平均为2,120,000±230,000(P<0.05)。可以见到两类视锥细胞和两类视杆细胞:单视锥,外段为锥形,最粗处直径约6微米;双视锥,由一主锥和一附锥构成,外段直径最粗处约7微米;红视杆,外段圆柱形,直径约6微米,其内段短粗,数目比绿视杆多;绿视杆,外段与红视杆极相似,但内段细长。视锥和视杆的外段上有许多小突起,这些小突起互相联系。

The type, density and count of retina receptors in frog Rana nigromaculata were investigated with the aid of scanning electron microscopy.At least four types of photoreceptors could be identified in frog retina: red rods, green rods, single and double cones. The rod is characterized by a cylindrical outer segment with some folds at the distal end about 6 μm across. There is a significant difference between the inner segment of two types of rods. It is stout and short in the red rod while slender and long in the green rod. The red rod is frequently located in the periphery of the retina and more numerous than the green rod. The cone is characteristic of a conical outer segment which is stout and short, with the largest diameter of about 7 μm. The double cone is composed of two cells. The chief cone is similar in appearance to the single cone, and the accessory cone is smaller than the chief one. These two cells are bundled up together like one cell.The density of cone was 31,300/mm2 The maximum density of rod was 24.000/mm2. and the minimum was about 5,000/mm2. The total number of photoreceptors was counted in 6 retinas, amounting to 2, 120,000±230,000 (p<0.05) photoreceptors per retina.Key words: Frog, Rana nigromaculata, Photoreceptor, Count, Scanning electron microscopy.