Let there be light

The deep sea is very dark, so either the animals must have top-notch sensory organs or produce their own light.

Biological light – bioluminescence – is known from many different groups of animals and plants, but deep sea creatures are experts. The light is used to tempt prey and mates to come closer, to scare or blind enemies, or as camouflage. Moreover, some animals even have their own flashlights that they use to navigate, when they hunt. The light can be emitted from the entire body. Some fish spit a luminous material out of their mouths or shoot luminous excrements from their hind parts, whereas deep sea octopuses emit luminous ink. The biological light is either produced by symbiotic bacteria that live in special colonies inside the animals or by enzymes in the animal itself.