Rahman Mohammad Lutfur, Aoyama Masato, Sugita Shoei
Department of Animal Science, Faculty of Agriculture, Utsunomiya University, Utsunomiya, Japan.
Anat Sci Int. 2008 Dec;83(4):239-46. doi: 10.1111/j.1447-073X.2008.00230.x.
This study was intended to determine the number and density of both retinal ganglion cells and the oil droplets of cone photoreceptor cells in brown-eared bulbul (Hypsipetes amaurotis). For this study birds were killed with proper dose of anesthetic (pentobarbital, 30 mg/kg), and the eyes were removed from the orbital cavity to isolate the retina. For the ganglion cell study retinal whole-mount specimens were prepared and stained with 0.1% cresyl violet. The different types of oil droplets were counted from color microphotographs of freshly prepared retinal samples. The mean total number of ganglion cells was estimated at approximately 2.5 x 10(6); with an average density of 16 523 cells/mm(2). Two high-density areas, namely the central area (CA) and the dorso-temporal area (DTA), are located in the central and dorso-temporal retinas, respectively, in bulbuls (24 032 cells/mm(2) in the CA; 23 113 cells/mm(2) in the DTA). Small ganglion cells persisted in the highest density areas, whereas the largest soma sizes were found in the lowest density areas of the retina. Four types of different colored oil droplets - red, orange, green and clear - were identified with an average density of 29 062/mm(2). Among the different colors, the green oil droplets had a significantly higher population (13 083/mm(2)) than the others across the retina. The central retina had a significantly higher number of all types of oil droplets, at a density of 60 552/mm(2). The density and size of the different colored oil droplets were inversely related across the regions of the retina. Taken together, it is concluded that the CA of the retina is an excellent quality area for visual perception due to peak density of ganglion cells and oil droplets. Moreover, each specific oil droplet makes a distinct contribution to visual perception, thereby ensuring that the bird has a retina that best matches its natural environment and feeding behavior.
本研究旨在确定棕耳鹎（Hypsipetes amaurotis）视网膜神经节细胞和视锥光感受器细胞油滴的数量及密度。在本研究中，用适当剂量的麻醉剂（戊巴比妥，30毫克/千克）处死鸟类，然后从眼眶腔取出眼睛以分离视网膜。对于神经节细胞研究，制备视网膜整装标本并用0.1%的甲酚紫染色。从新制备的视网膜样本的彩色显微照片中对不同类型的油滴进行计数。神经节细胞的平均总数估计约为2.5×10⁶；平均密度为16523个细胞/平方毫米。在棕耳鹎中，两个高密度区域，即中央区域（CA）和背颞区域（DTA），分别位于中央视网膜和背颞视网膜（CA中为24032个细胞/平方毫米；DTA中为23113个细胞/平方毫米）。小神经节细胞在最高密度区域持续存在，而最大的胞体大小则出现在视网膜的最低密度区域。鉴定出四种不同颜色的油滴——红色、橙色、绿色和透明色——平均密度为29062/平方毫米。在不同颜色中，绿色油滴在整个视网膜中的数量明显高于其他颜色（13083/平方毫米）。中央视网膜中所有类型油滴的数量明显更多，密度为60552/平方毫米。在视网膜各区域，不同颜色油滴的密度和大小呈负相关。综上所述，得出结论：视网膜的CA区域由于神经节细胞和油滴的峰值密度，是视觉感知的优质区域。此外，每个特定的油滴对视觉感知都有独特贡献，从而确保鸟类拥有与其自然环境和取食行为最匹配的视网膜。
