In a clip from Blue Planet II, narrator Sir David Attenborough speaks glowingly about the stunning luminosity that deep sea creatures use in the midnight zone, one kilometer down.
A kilometre from the surface, beyond the reach of the sun, a giant black void larger than all the rest of the world’s habitats combined. …Alien-like creatures produce dazzling displays of light. Nearly all animals need to attract mates and repel predators. This language of light is so widespread here that these signals are probably the commonest form of communication
Luminosity applies to both predator and prey. One uses the light to attract food, while the other uses it to detract enemies.
Hunters illuminate themselves, and by doing so, attract inquisitive prey. …But prey use light as a distraction, a decoy of luminous ink. Down here, in this blackness, creatures live beyond the normal rules of time.