Eyeshine in fishes. A review of ocular reflectors

Abstract

Eyeshine in fishes is reviewed. It originates in several ways. Many benthic fishes have pupils that are iridescent at certain angles of vie w; the color is caused by reflection of light at the surfaces of thin films in the cornea. Several kinds of cellular or extracellular features are involved. Reflection of light from the retinal surface is usually dull. In Photonectes there is bright reflection from part of the retinal surface; it comes from rows of thin cytoplasmic lamellae within Müller fiber cells. Many fishes have retinal tapeta lucida: these are diffuse reflectors made up of densely packed spherules, or specular reflectors made up of layers of thin films. Tapeta cellulosa in the inner chorioid also are specular reflectors containing thin films. Often, these tapeta can be covered over by migratory pigment in the photopic eye. Eyeshine in the light-adapted eye of several groups (scorpion fishes, etc.) comes from a reflex of light at the stratum argenteum. It is made possible because all the retinal pigment enters the cell processes, and there is no dark pigment in the chorioid.