Bioluminescence is light created by living organisms and and it can create the most fantastic displays. It includes 'phosphorescence' created by marine creatures and seen on the surface of the sea at night, the light of fireflies and the faint but eerie glow of some fungi.
The light is produced chemically for many different reasons: to attract attention, to frighten enemies, as a form of disguise, or - in the depths of the sea - to provide your own 'headlights' to search out prey.
Bioluminescence has been known about since ancient times. Aristotle spotted that damp wood glows, and Pliny the Elder recommended using a walking-stick dipped in a jellyfish’s glowing slime as a torch.
In 18th-century Newcastle’s coalmines, miners used dead fish as lights. Some dead fish are made to glow faintly due to bacteria. They were safer than lamps in mines with explosive gas. Unfortunately, the fish have to be putrefying to glow so the smell must have been almost unbearable.
Many sea creatures glow when disturbed, meaning boats’ wakes glow. During the First World War, one German submarine was tracked and sunk because it had disturbed enough bioluminescent organisms to make a glow visible from the surface.
The US Navy has devices that measure bioluminescence so their ships can operate undetected.
Soldiers in both World Wars attached bioluminescent fungi to their helmets so they could spot each other in the dark.
In the ocean, bioluminescence is the rule rather than the exception.
The bobtail squid can create a beam of light from its underside and uses this beam of light to cancel out the shadow its body makes on the shallow seafloor in the moonlight. It's therefore almost invisible to predators and prey alike.
The squid even has a special diaphragm which can regulate the amount of light which escapes, this is especially useful as some night skies are brighter than others.
Carnivorous glow worms use bioluminescence to attract termites
Some bacteria have been engineered to glow brighter in polluted water.
The dark forests of west and central Africa glow at night due to a bioluminescent fungus.
Tiny dinoflagellates produce a ripple of sparkling light in the water when something brushes past.
Wingless female glow-worms light up to attract a mate.
The Hawaiian bobtail squid has an internal bacterial alarm clock. Its bioluminescent bacteria light up when it’s time to wake up.
The first example of a bioluminescent reptile, a sea turtle, was discovered in 2016.
Bioluminescence has arisen over forty times in evolutionary history. It is a chemical reaction producing light. The light emitting protein, luciferin reacts with oxygen to produce this light in the presence of a protein catalyst called luciferase.