THE ANATOMY AND FINE STRUCTURE OF THE EYE IN FISH. VI CILIARY TYPE TISSUE IN NINE SPECIES OF TELEOSTS

Abstract

The eyes of teleost fishes do not have ciliary bodies. Therefore there is no ciliary epithelium per se, the tissue normally assumed to secrete aqueous humor. When examined at the electron microscope level a layer of nonpigmented cells on the back of the fish iris shows many similarities to the ciliary epithelium of mammals. The tissue of fish iris has strategically located zonulae occludents similar to those forming the blood-aqueous barrier in mammals. There is a marked lateral interdigitation of cells as seen in mammalian ciliary tissue and as seen in the specific salt absorbing cells found in the gills of brackish water adapted crabs. The teleost tissue also has numerous intercellular spaces (ciliary channels?) distributed in the same fashion as in mammalian ciliary epithelium. Although there is no morphological evidence for the secretion of aqueous humor, there is indirect evidence that the nonpigmented cells absorb salt to produce the hypotonic aqueous humor that is unique to teleosts.