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Original article
Published online: 2021-07-21
Submitted: 2021-06-26
Accepted: 2021-07-08
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Ocular morphology of the fruit bat, Eidolon helvum, and the optical role of the choroidal papillae in the megachiropteran eye: a novel insight

I. K. Peter-Ajuzie, I. C. Nwaogu, L. O. Majesty-Alukagberie, A. C. Ajaebili, F. A. Farrag, M. A. Kassab, K. Morsy, M. Abumandour
DOI: 10.5603/FM.a2021.0072
·
Pubmed: 34308539

open access

Ahead of Print
ORIGINAL ARTICLES
Published online: 2021-07-21
Submitted: 2021-06-26
Accepted: 2021-07-08

Abstract

Background: This work was designed to provide a morphologic, morphometric and histochemical description of the eye of the African straw-coloured fruit bat (Eidolon helvum). An explanation of the optical role of the choroidal papillae in the vision of megachiropteran bats was provided.

Materials and methods: Enucleated eyes of captured fruit bats were measured and processed for light microscopy.

Results: Typical gross features of the mammalian eye including an anterior transparent cornea, posterior whitish sclera and a golden-brown iris surrounding a round pupil were observed in the eye. Presence of undulating retina typically found in megachiropterans were also seen. The ratio of mean corneal diameter to mean axial eye diameter was 0.58 ± 0.08. The histochemical investigation of the eye indicated the presence of mucins, proteoglycans, hyaluronic acid, glycogen and/or glycoproteins in the corneal, scleral, choroidal and retinal tissues.

Conclusions: The presence of reflective materials of the tapetum lucidum on the undulating retina was shown to be a morphological adaptation for increased light sensitivity as each parabolic surface of the choroidal papillae served as a convex mirror, reflecting the light rays to the adjacent parabolic surface, thus sensitizing photoreceptors in affected regions. This phenomenon thus empowers megachiropteran bats with improved scotopic visual capability and could explain why most of them are reliant on their vison without the need for echolocation.

Abstract

Background: This work was designed to provide a morphologic, morphometric and histochemical description of the eye of the African straw-coloured fruit bat (Eidolon helvum). An explanation of the optical role of the choroidal papillae in the vision of megachiropteran bats was provided.

Materials and methods: Enucleated eyes of captured fruit bats were measured and processed for light microscopy.

Results: Typical gross features of the mammalian eye including an anterior transparent cornea, posterior whitish sclera and a golden-brown iris surrounding a round pupil were observed in the eye. Presence of undulating retina typically found in megachiropterans were also seen. The ratio of mean corneal diameter to mean axial eye diameter was 0.58 ± 0.08. The histochemical investigation of the eye indicated the presence of mucins, proteoglycans, hyaluronic acid, glycogen and/or glycoproteins in the corneal, scleral, choroidal and retinal tissues.

Conclusions: The presence of reflective materials of the tapetum lucidum on the undulating retina was shown to be a morphological adaptation for increased light sensitivity as each parabolic surface of the choroidal papillae served as a convex mirror, reflecting the light rays to the adjacent parabolic surface, thus sensitizing photoreceptors in affected regions. This phenomenon thus empowers megachiropteran bats with improved scotopic visual capability and could explain why most of them are reliant on their vison without the need for echolocation.

Get Citation

Keywords

Eidolon helvum, eye, choroidal papillae, retina, megachiroptera

About this article
Title

Ocular morphology of the fruit bat, Eidolon helvum, and the optical role of the choroidal papillae in the megachiropteran eye: a novel insight

Journal

Folia Morphologica

Issue

Ahead of Print

Article type

Original article

Published online

2021-07-21

DOI

10.5603/FM.a2021.0072

Pubmed

34308539

Keywords

Eidolon helvum
eye
choroidal papillae
retina
megachiroptera

Authors

I. K. Peter-Ajuzie
I. C. Nwaogu
L. O. Majesty-Alukagberie
A. C. Ajaebili
F. A. Farrag
M. A. Kassab
K. Morsy
M. Abumandour

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