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The deep-sea teleost cornea: a comparative study of gadiform fishes
S.P. Collin1 and H.B. Collin2
1Marine Neurobiology Laboratory, Department of Zoology,
University of Western Australia, Nedlands, Western Australia and 2Department
of Optometry and Visual Sciences, The University of Melbourrne, Parkville,
Victoria, Australia
Offprint requests to: Dr. Shaun
P. Collin, Marine Neurobiology Laboratory, Department of Zoology, University
of Western Australia, Nedlands, 6907, Western Australia, Australia
Summary. The corneal structure
of three deep-sea species of teleosts (Gadiformes, Teleostei) from different
depths (250-4000 m) and photic zones are examined at the level of the light
and electron microscopes. Each species shows a similar but complex arrangement
of layers with a cornea split into dermal and scleral components. The dermal
cornea comprises an epithelium overlying a basement membrane and a dermal
stroma with sutures and occasional keratocytes. Nezumia aequalis is the
only species to possess a Bowman's layer, although it is not well-developed.
The scleral cornea is separated from the dermal cornea by a mucoid layer
and, in contrast to shallow-water species, is divided into three main layers;
an anterior scleral stroma, a middle or iridescent layer and a posterior
scleral stroma. The iridescent layer of collagen and intercalated cells
or cellular processes is bounded by a layer of cells and the posterior scleral
stroma overlies a Desçemet's membrane and an endothelium. In the
relatively shallow-water Microgadus proximus, the keratocytes of the dermal
stroma, the cells of the iridescent layer and the endothelial cells all
contain aligned endoplasmic reticulum, which may elicit an iridescent reflex.
No alignment of the endoplasmic reticulum was found in N. aequalis or Coryphanoides
(Nematonurus) armatus. The relative differences between shallow-water and
deep-sea corneas are discussed in relation to the constraints of light,
depth and temperature. Histol Histopathol 13, 325-336 (1998)
Key words: Cornea, Ultrastructure,
Deep-sea, Iridescent layer, Spectacle, Fishes
DOI: 10.14670/HH-13.325
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