The Visual System of the Florida Garfish,Lepisosteus platyrhincus(Ginglymodi)
作者:
Shaun P. Collin,
H.Barry Collin,
期刊:
Brain, Behavior and Evolution
(Karger Available online 1993)
卷期:
Volume 42,
issue 2
页码: 98-115
ISSN:0006-8977
年代: 1993
DOI:10.1159/000114143
出版商: S. Karger AG
关键词: Cornea;Ultrastructure;Fishes;Bowman's layer;Corneal filter;Autochthonous layer;Evolution
数据来源: Karger
摘要:
The cornea of the Florida gar, Lepisosteus platyrhincus (Ginglymodi) was examined at the scanning and transmission electron microscopic levels. In addition, the schematic eye of the garfish was revealed by frozen sectioning of the whole orbit in the horizontal and transverse planes. The lens is spherical, obeys Matthiessen's ratio, and is supported by a dorsal suspensory ligament and a ventral retractor lentis muscle. The cornea, devoid of a spectacle, is comprised anteriorly of an epithelium (eight to ten cells thick) and covered by a layer of flattened cells up to 26 μm in diameter. On the scanning electron microscope, these cells appear to be covered in microplicae and microvilli. Beneath the epithelium lies a granular basement membrane abutting a true Bowman's layer, composed of a random arrangement of collagen fibrils with no keratocytes. The corneal stroma constitutes 54% of the total thickness and contains 55–65 collagen fibril lamellae, oriented perpendicular to neighbouring lamellae. Scattered keratocytes, containing large amounts of mitochondria, lipid droplets and glycogen granules lie in between the perpendicularly oriented lamellae. Posterior to the stroma is a thin and partially broken basement membrane (no true Descemet's membrane exists), adjacent to a monolayered endothelium covered in microvilli. In the periphery, an autochthonous layer is found between the stroma and the endothelium. Stromal pigment granules, enveloped in large nucleated cells, act as a non-occlusible yellow filter in the dorsal cornea. Functional correlations are made and the presence and/or thickness of corneal structures discussed in relation to the evolution of the vertebrate cornea.
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