Using the lamprey, researchers from Japan analyzed the photosensory mechanism of the pineal organ, also called the pineal gland, in non-mammalian vertebrates and discovered a novel mechanism of pineal color discrimination (two-cell system) in which two types of photoreceptor cells, each containing two different opsins, are used to detect color. This discovery may provide insight into the evolution of color detection in other animals, including color vision in humans.
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Source: Phys.org