Topography of Retinal Ganglion Cells in the Dromedary Camel (Camelus dromedarius)

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It is expected that dromedary camel's vision plays a crucial role in survivals in the arid and semiarid regions. Because these regions are open and the dromedary camel is tall with long legs and a long neck. It has been reported that retinal ganglion cells (RGCs) in the dromedary camel are unique in distribution and do not form the horizontal visual streak, which is commonly found in ungulates. In the present study, we re-examined the total number, topographic distribution and all density of RGCs using retinal whole-mounts and parasagittal collodion sections of the camel retina. Furthermore, the histological visual acuity was estimated. Left eyes from 17 adult camels, 3–4 years old, were used in this study. The dromedary camel had about 407,000 RGCs. The topographic distribution of RGC showed a well defined horizontal visual streak with a dorsotemporal extension of higher cell density. The peak visual acuity in the dromedary camel was 13.9 cycles/degree. Ungulates take always precautions against predators. Therefore, the retina in ungulates has a visual streak for a horizontal wide visual field. Thus, the visual streak found in the dromedary camel is formed by common needs among ungulates.
公益社団法人日本獣医学会の論文