In fish, amphibians, and birds photoreceptors and RPE pigment granules undergo
morphological rearrangements in response to light and circadian signals (Fig. 1). These
retinomotor movements reposition rod and cone photoreceptor outer segments and the
shielding pigment of the RPE for optimal light capture by appropriate photoreceptors under
photopic or scotopic conditions (cf. Burnside and Nagle, 1983; Wagner et al., 1993). Light
induces cones to contract, rods to elongate and pigment granules to disperse into the long …