When animals and bacteria make their own light, scientists give it a big name: bioluminescence. The name simply means “living light.” Perhaps you know the name of a common bioluminescent creature that flies around your yard on summer evenings. Fireflies!
Animals glow in the dark in different ways. Some glow by mixing chemicals. The result is a rainbow of colors—from red to blue. (Blue appears most often in the deep because it shines farther than any other color underwater.) All creatures that create light use two important chemicals: luciferin (loo-SIF-ur-in) and luciferase (loo-SIF-ur-ace).
Three main ingredients are necessary to produce light. Oxygen (red circles) needs to combine with the chemical luciferin (large purple circle). A third chemical brings the other two together—luciferase (blue shape). When the oxygen combines with the luciferin, it releases photons of light.
About 80% to 90% of all deep ocean animals are bioluminescent.
If you dragged a net from 3,000 feet (1km) beneath the waves to the surface, most of the animals you caught would have the ability to light up. Let's look at some of the reasons for these amazing lights.
Many creatures can light up so that they blend in with the dim light coming from the sun. Predators swimming below don’t even see them. This is called counterillumination.
Some squid and jellyfish use their lights to warn or scare off hungry predators.
Some types of fish rely on a dangling light to attract tasty meals within striking distance.
Many creatures in the depths of the ocean use light to attract a mate or communicate in other ways.
Some deep-sea animals use their lights to make other fish look in a different direction. Some even detach parts of their bodies as decoys.
* These features help creatures survive in a fallen world, but they were not necessary in the perfect world God created.