the Actinopterygii (ray-finned fish) apparently arose as a result of gene duplication from Rh1 (rhodopsin). These opsins appear to serve functions similar to those of pinopsin found in birds and reptiles. Pinopsins The first Pineal Opsin (Pinopsin) was found in the chicken pineal gland. It is a blue sensitive opsin (λmax = 470 nm). Pineal opsins have a wide range of expression in the brain, most notably in the pineal region. Vertebrate Ancient (VA) opsin Vertebrate Ancient (VA) opsin has three isoforms VA short (VAS), VA medium (VAM), and VA long (VAL). It is expressed in the inner retina, within the horizontal and amacrine cells, as well as the pineal organ and habenular region of the brain. It is sensitive to approximately 500 nm [14], found in most vertebrate classes, but not in mammals. Parapinopsins The first parapinopsin (PP) was found in the parapineal organ of the catfish. The parapinopsin of lamprey is a UV-sensitive opsin (λmax = 370 nm). The teleosts have two groups of parapinopsins, one is sensitive to UV (λmax = 360-370 nm), the other is sensitive to blue (λmax = 460-480 nm) light. Parietopsins The first parietopsin was found in the photoreceptor cells of the lizard parietal eye. The lizard parietopsin is green-sensitive (λmax = 522 nm), and despite it is a c-opsin, like the vertebrate visual opsins, it does not induce hyperpolarization via a Gt-protein, but induces depolarization via a Go-protein. Encephalopsin or Panopsin The panopsins are found in many tissues (skin, brain, testes, heart, liver, kidney, skeletal muscle, lung, pancreas and retina). They were originally found in the human and mouse brain and thus called encephalopsin. The first invertebrate panopsin was found in the ciliary photoreceptor cells of the annelid Platynereis dumerilii and is called c(iliary)-opsin. This c-opsin is UV-sensitive (λmax = 383 nm) and can be tuned by 125 nm at a single amino-acid (range λmax = 377 - 502 nm). Thus, not unsurprisingly, a second but cyan sensitive c-opsin (λmax = 490 nm) exists in Platynereis dumerilii. The first c-opsin mediates in the larva UV induced gravitaxis. The gravitaxis forms with phototaxis a ratio-chromatic depth-gauge. In different depths, the light in water is composed of different wavelengths: First the red (> 600 nm) and the UV and violet (< 420 nm) wavelengths disappear. The higher the depth the narrower the spectrum so that only cyan light (480 nm) is left. Thus, the