A fish eye out of water: epithelial surface projections on aerial and aquatic corneas of the four-eyed fish'Anableps anableps

Simmich, Joshua, Temple, Shelby E. and Collin, Shaun P. (2012) A fish eye out of water: epithelial surface projections on aerial and aquatic corneas of the four-eyed fish'Anableps anableps. Clinical and Experimental Optometry, 95 2: 140-145.


Author Simmich, Joshua
Temple, Shelby E.
Collin, Shaun P.
Title A fish eye out of water: epithelial surface projections on aerial and aquatic corneas of the four-eyed fish'Anableps anableps
Journal name Clinical and Experimental Optometry   Check publisher's open access policy
ISSN 0816-4622
1444-0938
Publication date 2012-03
Sub-type Article (original research)
DOI 10.1111/j.1444-0938.2011.00701.x
Volume 95
Issue 2
Start page 140
End page 145
Total pages 6
Place of publication Oxford, United Kingdom
Publisher Wiley-Blackwell Publishing
Collection year 2013
Language eng
Formatted abstract Background:
Vertebrate corneas feature a variety of microprojections, to which a tear film adheres. These microprojections are formed by folds in epithelial cell membranes, which increase surface area, stabilise the tear film and enhance movement of nutritional and waste products across cell membranes. Differences in corneal microprojections among vertebrates have been correlated with habitat and differ markedly between terrestrial and aquatic species.

Methods:
This study investigated epithelial microprojections of both the aerial (dorsal) and aquatic (ventral) corneal surfaces of the 'four-eyed fish'Anableps anableps using scanning electron microscopy.

Results:
The central region of the dorsal cornea, which projects above the water, had a density of 16,387 ± 3,995 cells per mm 2, while the central region of the ventral cornea (underwater) had a density of 22,428 ± 6,387 cells per mm 2, a difference that suggests an environmental adaptation along the two visual axes. Both corneal surfaces were found to possess microridges rather than microvilli or microplicae characteristic of terrestrial/aerial vertebrates. Microridges were 142 ± 9nm wide and did not differ (p = 0.757) between dorsal and ventral corneas. Microridges were consistently separated by a distance of 369 ± 9nm across both corneas.

Conclusion:
Dorsal-ventral differences in corneal epithelial cell density in Anableps anableps suggest a difference in osmotic pressure of the two corneas. The modest differences in the microprojections indicate that the need to secure the tear film underlying each optical axis is of prime importance, due to the likelihood that a persistent layer of water normally covers both dorsal and ventral corneal surfaces and that maintaining a transparent optical pathway for vision is critical for a species prone to predation from both above and below the water's surface.
Keyword Amphibians
Anableps
Cornea
Cyprinidae
Eye lens
Goldfish
Microprojections
Zebrafish
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: Official 2013 Collection
School of Biomedical Sciences Publications
 
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