HISTOLOGY AND HISTOPATHOLOGY

Cellular and Molecular Biology



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