Retinal Photoreceptor Fine Structure in some reptiles | ||
| The Egyptian Journal of Hospital Medicine | ||
| Article 14, Volume 17, Issue 1, October 2004, Pages 167-186 PDF (1.12 M) | ||
| Document Type: Original Article | ||
| DOI: 10.21608/ejhm.2004.18166 | ||
| Authors | ||
| Fairoze Khattab; Fahmy I. Khattab; Nagui Fares; Aman Zaki | ||
| Department of Zoology, Faculty of Science, Ain Shams University, Abbassia, Cairo, Egypt.) | ||
| Abstract | ||
| The structure of the photoreceptors of four different reptiles: the homed viper Cerastes cerastes (diurnal and nocturnal), the European Chameleo chameleon (diurnal), the gold skink Eumeces schneidrii (diurnal) and the Egyptian gecko, Tarentola annularis (nocturnal) has been investigated by light and electron microscopy. The photoreceptors of diurnal reptiles were mainly of the cone type and those of nocturnal were mainly rods. The ellipsoid region of both double rods in the nocturnals and large single cones in the species having both nocturnals and diurnal activity, consist of several mitochondria arranged in a remarkable radially gradient architecture which accommodates with the specific function of this region as a focusing device helping to condense light onto the outer segments. Moreover the principle cone of double cone and single cone of diurnal reptiles possessed a large oil droplet in the region between the inner segment and outer segment. This droplet is thought to play a role in filtering light and so doing enhanced contrast reduce glare and lessen chromatic aberration. It is worth to mention that the outer segment of rods in nocturnal reptiles approaches a length of approximately four folds the length of the inner segments of the same photoreceptors cells. This character is of a particular interest, since the outer segment is the site of photopigments and the increase in its length magnifies its ability of light and consequently accommodate with the night vision. | ||
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