Retinal Structure. Mollusc Cephalopods: Octopus, Sepia

Abstract

Retinas of eyes of Octopus and Sepia were fixed in 1% OsO4, dehydrated, and embedded in n-butyl methacrylate. Thin sections of the retina, cut from the polymerized blocks, were studied by the electron microsope. Each retina was found to be made up of rhabdomes analogous to those of the arthropod compound eyes. There are 4 retinal rhabdomeres radially arranged to form a rhabdome. A central space containing pigment cells with screening pigment granules appears to separage the rhab-domes. Each retinal rhabdomere measures [image]1.0[mu] in diameter and [image]60[mu] in length, and is constructed of packed tubules. There are about 20 tubules/[mu] whose dense bands are [image]200 A and whose interspaces are [image]350 A, as measured from the electron micrographs. The rhabdomere structure of packed tubes, in preference to packed plates, is similar to that found for the insect Drosophila and for the visual cells of other arthropods. Electron micrographs together with a schematic model illustrate the structural packing of the rhabdomes and the rhabdomeres within the retina.