Bioluminescence

Bioluminescence is the production and emission of light by a living organism as the result of a chemical reaction during which chemical energy is converted to light energy. Its name is a Hybrid word, originating from the Greek bios for "living" and the Latin lumen "light". Bioluminescence may be generated by symbiotic organisms carried within a larger organism. It is generated by an enzyme-catalyzed chemoluminescence reaction, wherein the pigment luciferin is oxidised by the enzyme luciferase. Adenosine triphosphate (ATP) is involved in most instances. The chemical reaction can occur either within or outside of the cell. In bacteria, the expression of genes related to bioluminescence is controlled by an operon called the Lux operon.

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Characteristics of the phenomenon

Bioluminescence is a form of luminescence, or "cold light" emission; less than 20% of the light generates thermal radiation. It should not be confused with fluorescence, phosphorescence or refraction of light.

Ninety percent of deep-sea marine life is estimated to produce bioluminescence in one form or another. Most marine light-emission belongs in the blue and green light spectrum, the wavelengths that can transmit through the seawater most easily. However, certain loose jawed fish emit red and infrared light.

Non-marine bioluminescence is less widely distributed, but a larger variety in colours is seen. The two best-known forms of land bioluminescence are fireflies and New Zealand glow worms. Other insects, insect larvae, annelids, arachnids and even species of fungi have been noted to possess bioluminescent abilities.

Some forms of bioluminescence are brighter (or only exist) at night, following a circadian rhythm.

Adaptations for bioluminescence

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

Camouflage

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, use 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 eaten 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 use 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.

It is possible that some mushrooms attract insects using bioluminescence so that the insects will help disseminate the fungus' spores into the environment. However, there has been no documentation of this suggestion.

Repulsion

Certain squid and small crustaceans use 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. Every species of firefly has larvae that glow to repel predators.

Communication

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

Illumination

While most marine bioluminescence is green to blue, the Black Dragonfish produces a red glow^{[citation needed]}. This adaptation allows the fish to see red-pigmented prey^{[citation needed]}, which are normally invisible in the deep ocean environment where red light has been filtered out by the water column.

Biotechnology

Bioluminescent organisms are a target for many areas of research. Luciferase systems are widely used in the field of genetic engineering as reporter genes (see picture left). Luciferase systems have also been harnessed for biomedical research using bioluminescence imaging.

Vibrio symbiosis with numerous marine invertebrates and fish, namely the Hawaiian Bobtail Squid (Euprymna scolopes), are key experimental model for symbiosis, quorum sensing, and bioluminescence.

The structure of photophores, the light producing organs in bioluminescent organisms, are being investigated by industrial designers.

Some proposed applications of engineered bioluminescence include:

• Christmas trees that do not need lights, reducing danger from electrical fires
• glowing trees to line highways to save government electricity bills
• agricultural crops and domestic plants that luminesce when they need watering
• new methods for detecting bacterial contamination of meats and other foods
• bio-identifiers for escaped convicts and mental patients
• detecting bacterial species in suspicious corpses
• novelty pets that bioluminesce (rabbits, mice, fish etc.)

Organisms that bioluminesce

All cells produce some form of bioluminescence within the electromagnetic spectrum, but most are neither visible nor noticeable to the naked eye. Every organism's bioluminescence is unique in wavelength, duration, timing and regularity of flashes. Below follows a list of organisms which have been observed to have visible bioluminescence.

Non-marine organisms

• certain arthropods
  • fireflies
  • glow worms
    • railroad worms
  • certain mycetophilid flies
  • certain centipedes
  • certain millipedes
• annelids
• Mushrooms (see Foxfire)
  • Jack O'Lantern mushroom (Omphalotus olearius)
  • ghost fungus (Omphalotus nidiformis)
  • Honey mushroom
  • Panellus stipticus
  • several species of Mycena
• a terrestrial mollusc
  • Dyakia striata

Fish

• cookie-cutter shark
• Marine hatchetfish
• Anglerfish
• Flashlight fish
• Pineconefish
• Porichthys
• Gulper eel
• Many rattails

Marine invertebrates

• many cnidarians
  • Sea pens
  • coral
  • Aequorea victoria, a jellyfish
• Ctenophores or "comb jellies"
• certain echinoderms
• certain nudibranchs
• certain clams
• certain crustaceans
  • ostracods
  • krill
• certain Octopodes
  • Bolitaenidae
• certain squid
  • the order Teuthida
  • Colossal Squid
  • Mastigoteuthidae
  • Sepiolidae
  • Sparkling Enope Squid

Plankton and microbes

• Dinoflagellates
• Vibrionaceae (e.g. Vibrio fischeri, Vibrio harveyi, Vibrio phosphoreum)

See also

• biophoton
• De Phenomenis in Orbe Lunae
• Foxfire
• List of light sources