Adaptations of Bioluminescence

There are four main accepted theories for the evolution of bioluminescent traits:

1. Camouflage
2. Attraction
3. Repulsion
4. Communication

Camouflage

Camouflage is the method which allows an otherwise visible organism or object to remain indiscernible from the surrounding environment. Examples include a tiger's stripes and the battledress of a modern soldier. Camouflage is a form of deception. The word camouflage comes from the French word 'camoufler' meaning 'to disguise'                    

 

Anolis caroliensis showing blending camouflage and counter-shading.   A flounder blends in with its environment  A crab is nearly lost in his surroundings  A green lizard is harder to see in the grass

 

Attraction

Bioluminescence is used as a lure to attract prey by several deep sea fish such as the anglerfish. A dangling appendage that extends from the head of the fish attracts small animals to within striking distance of the fish. Some fish, however, utilize a non-bioluminescent lure.The cookiecutter shark uses bioluminescence for camouflage, but a small patch on its underbelly remains dark and appears as a small fish to large predatory fish like tuna and mackerel. When these fish try to consume the "small fish", they are bitten by the shark.Dinoflagellates have an interesting twist on this mechanism. When a predator of plankton is sensed through motion in the water, the dinoflagellate luminesces. This in turn attracts even larger predators which will consume the would-be predator of the dinoflagellate.The attraction of mates is another proposed mechanism of bioluminescent action. This is seen actively in fireflies who utilize periodic flashing in their abdomens to attract mates in the mating season. In the marine environment this has only been well-documented in certain small crustacean called ostracod. It has been suggested that pheromones may be used for long-distance communication, and bioluminescent used at close range to "home in" on the target.The honey mushroom attracts insects using bioluminescence, hoping the insects will help disseminate the fungus' spores into the environment.

Repulsion

Certain squid and small crustaceans utilize bioluminescent chemical mixtures, or bioluminescent bacterial slurries in the same way as many squid use ink. A cloud of luminescence is expulsed, confusing or repelling a potential predator while the squid or crustacean escapes to safety.

Communication

Bioluminescence is thought to play a direct role in communication between bacteria (quorum sensing). It promotes the symbiotic induction of bacteria into host species, and may play a role in colony aggregation.

Purpose of quorum sensing

The purpose of quorum sensing is to coordinate certain behaviour or actions between bacteria of the same kind, depending on their number. For example, opportunistic bacteria, such as Pseudomonas aeruginosa can grow within a host without harming it, until they reach a certain concentration. Then they become aggressive, their numbers sufficient to overcome the host's immune system and form a biofilm, leading to disease. It is hoped that the therapeutic enzymatic degradation of the signaling molecules will prevent the formation of such biofilms and possibly weaken established biofilms. Disrupting the signaling process in this way is called quorum quenching.