Publication: Retinal epithelial fine structure in the southern fiddler ray (Trygonorhina fasciata)
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Date
1992
Authors
Braekevelt, Charlie R.
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Publisher
Murcia : F. Hernández
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DOI
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info:eu-repo/semantics/article
Description
Abstract
The morphology of the retinal epithelium
(RPE), choriocapillaris and Bruch's membrane
(complexus basalis) has been investigated by light and
electron microscopy in an elasmobranch, the southern
fiddler ray or guitarfish (Trygonorhina fasciata) . The
RPE consists of a single layer of cuboidal cells which
display basal (scleral) infoldings as well as numerous
apical (vitreal) finger-like processes which interdigitate
with the photoreceptor outer segments. The lateral
cell borders are relatively smooth and are joined in the
mid-region by a series of tight junctions. Internally the
RPE nucleus is large, vesicular and centrally located.
Smooth endoplasmic reticulum (SER) is abundant
while rough endoplasmic reticulum (RER) is scarce.
Polysomes are however widespread and mitochondria
are plentiful. Two unusual organelles are also noted.
One consists of a membrane bound array of tubules
while the other is a membrane bound structure
consisting of a granular matrix with again an interna1
tubular array. This species possesses a choroidally
located tapetum lucidum in the superior fundus and
over this tapetal area, melanosomes are absent from the RPE cells. In non-tapetal locations a few
melanosomes are present that do not appear to
undergo photomechanical movements. Bruch's
membrane is a pentalaminate structure with an almost
continuous central elastic layer (lamina densa). The
choriocapillaris forms a single layer of capillaries with
a thin but only minimally fenestrated endothelium
facing Bruch's membrane.
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