ABSTRACT
The vast majority of teleost fishes pass through a planktivorous larval phase where they are obligate visual diurnal feeders. Overlaying the retinal pigment epithelium (RPE) is the retina consisting of the photoreceptor and neuronal layers. Axons from neurons of the innermost retinal layer, the ganglion cells, course over the retinal surface converging at the optic disk where they leave the eye as the optic nerve. The boundary conditions for vision are set by the absorption spectra of the visual pigments present in the visual photoreceptors. Changes in opsin expression patterns seem to be quite common during the larval stage. For larval fishes the reaction distance to planktonic prey increases with fish size and correlates with improved visual acuity, but at best only amounts to several body lengths. There are two major types of retinomotor movement in fish: those of the RPE and those of the photoreceptor cells.
