IV.

Uses for Bioluminescence

Bioluminescence can provide organisms with protection. It can also be a means of communicating with members of their own species, often to attract mates, and of finding and luring prey.

Examples of using light for protection include producing sudden flashes to startle or distract predators, sometimes by ejecting blobs of luminous material. Small crustaceans called copepods and some types of squid use these tactics. Sea surface luminescence, commonly seen in the wakes of ships, is usually caused by blooms of microscopic dinoflagellates that flash in response to turbulence. The flashes are probably to attract fish that eat the zooplankton that attack dinoflagellates. Bioluminescence can also act as camouflage for animals such as deep-sea fish, squid, and crustaceans that have downward-shining photophores. These light-producing organs can act as counter-illumination to disguise the animals’ silhouettes against light from the surface when seen by predators below. On land, species of Motyxia millipedes glow in the dark as a warning to predators that they contain noxious chemicals.

Some fish that hunt or travel in schools use bioluminescence to help coordinate the movements of the school. Other fish and certain squid display distinctive patterns of bioluminescence to find members of their own species. Flashing bioluminescent displays in species-specific patterns to attract mates occur among fireflies (a type of beetle) on land, as well as in some small copepod crustaceans and in some species of squid in the sea.

Finding food and luring prey are other common uses for bioluminescence. Flashlight fish have light-producing photophores on their heads that may light their way in the darkness. Deep-sea anglerfish have luminescent lures that attract potential prey within reach of their mouths. Some cave-dwelling insect larvae have glowing tails that attract flying insects into sticky dangling strings that the larvae secrete to catch prey. A few species of fireflies mimic the mating flashes of other firefly species then prey on the unsuspecting victims who respond to the false mating signals.

Other forms of bioluminescence are harder to explain. A small number of mushrooms and other fungi glow in the dark, possibly to attract insects to disperse their spores. However, it may be that such bioluminescence is simply incidental and has no special function or benefit for the fungi.