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18166

Retinal Photoreceptor Fine Structure in some reptiles

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Last updated: 03 Jan 2025

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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.

DOI

10.21608/ejhm.2004.18166

Authors

First Name

Fairoze

Last Name

Khattab

MiddleName

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Affiliation

Department of Zoology, Faculty of Science, Ain Shams University, Abbassia, Cairo, Egypt.)

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First Name

Fahmy I.

Last Name

Khattab

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Affiliation

Department of Zoology, Faculty of Science, Ain Shams University, Abbassia, Cairo, Egypt.)

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Orcid

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First Name

Nagui

Last Name

Fares

MiddleName

-

Affiliation

Department of Zoology, Faculty of Science, Ain Shams University, Abbassia, Cairo, Egypt.)

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Orcid

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First Name

Aman

Last Name

Zaki

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-

Affiliation

Department of Zoology, Faculty of Science, Ain Shams University, Abbassia, Cairo, Egypt.)

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Volume

17

Article Issue

1

Related Issue

3780

Issue Date

2004-10-01

Receive Date

2018-11-01

Publish Date

2004-10-01

Page Start

167

Page End

186

Print ISSN

1687-2002

Online ISSN

2090-7125

Article File

EJHM_Volume 17_Issue 1_Pages 167-186.pdf

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https://ejhm.journals.ekb.eg/article_18166.html

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https://ejhm.journals.ekb.eg/service?article_code=18166

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Original Article

Type Code

606

Publication Type

Journal

Publication Title

The Egyptian Journal of Hospital Medicine

Publication Link

https://ejhm.journals.ekb.eg/

MainTitle

Retinal Photoreceptor Fine Structure in some reptiles

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Article

Created At

22 Jan 2023