Chemistry And Evolutionary Origin

Bioluminescence chemistry varies widely among organisms. Bacteria use riboflavin phosphate, the sea pansy uses diphosphoadenosine, and fireflies use adenosine triphosphate (ATP) in the oxidative decarboxylation of substrates generically known as luciferins, with enzymes termed luciferases. The present, cautious conclusion would be that bioluminescence has evolved from many separate biochemical origins.

Molecular structures and their alterations along light-producing pathways of some systems are illustrated in general references, but many systems have not been investigated. Many use oxidative mechanisms that involve two major stages: the first creates an energy-rich molecule ("large energy quantum") by combining molecules, the second then excites a luminescent molecule that unloads this energy as a photon of light when it returns to its stable state. Among insects, photons range in color from an unbelievable bright, ruby red in the headlight of the railroadworm (Phrixothrix tiemanni, Phengodidae, Coleoptera) to the demure blue of glowing Appalachian glowworm larvae (Orfelia fultoni, Mycetophi-lidae, Diptera). In twilight-active fireflies, longer wavelengths (orange-yellow), with appropriate filters in the eyes, may be connected with enhancing signal reception against (noisy) backgrounds of green foliage. The different colors are caused by alterations in the amino acid composition of the luciferase that shift the emission peaks.

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