Pineal photosensitivity. A comparison with retinal photoreception

Abstract

Pineal photoreceptors of poikilothermic vertebrates posses numerous anatomical, physiological and biochemical similarities to retinal photoreceptors, including the rhythmic melatonin biosynthesis, with nocturnal peaks and low day-time levels. This brief outline will survey the photoreceptor properties of the pineal organ of poikilothermic vertebrates, which suggest that the pineal is not only a simple light detector (that acts as a kind of photometer), but that it is capable of processing the light information and to discriminate it from informations that have no meaning for its assumed photoperiodic function.