Bioluminescence

Bioluminescence is the production and emission of light by living organisms through chemical reactions. In the classic mechanism, a molecule called luciferin reacts with oxygen, catalyzed by an enzyme called luciferase, to form an excited-state intermediate that releases a photon as it returns to the ground state. Some bacteria use a related system, the lux operon, to produce both the substrate and the enzyme.

Bioluminescence occurs in a wide range of organisms, especially in the ocean. Dinoflagellates, ostracods, jellyfish, squid, octopuses, and many fishes can emit light. Fireflies and glow-worms are well-known terrestrial examples. Colors are typically blue or green in marine environments, matching light transmission in seawater and enabling signaling over distance.

Functions of bioluminescence are diverse. It can provide camouflage by counter-illumination, attract prey or lure potential prey, and facilitate mating or communication through species-specific patterns. Some organisms use flashes or rhythmic patterns to deter predators or to coordinate behavior within groups.

Ecology and evolution show that bioluminescence has evolved independently many times across bacteria, fungi, and animals. In bacteria, light production often serves symbiotic relationships or free-living roles. The chemistry of bioluminescence varies among groups, but all rely on light produced within living cells rather than from external light sources. Bioluminescence is distinct from fluorescence, which requires prior light exposure; bioluminescence can be produced continuously or in regulated bursts by the organism itself.