The silver spinyfin, or little dori, inhabits a layer of the deep sea, where the Twilight Zone's blue fades to black, often nearly a kilometre below the surface. Down there, they may see the world like no other animal known to science.
Scientists have generally understood that colour vision was not necessary in the deep sea. It is too far for sunbeams to penetrate, and so there is no light to give way to colour. But in a study published in Science, researchers interested in the evolution of colour vision analysed the genomes of 101 different fishes. They discovered that one, the silver spinyfin, has more genes for discriminating dull light than any other vertebrate on the planet. These genes make it possible to see the whole range of residual daylight and the full spectrum of bioluminescence in the deep sea. Other fishes may have this ability to detect colour in the deep sea, too.