Biofluorescence

Biofluorescence is the emission of visible light by a living organism after it absorbs light, typically in the blue or ultraviolet range, with the emitted light appearing at longer wavelengths such as green, orange, or red. It is a passive, pigment-based process driven by endogenous fluorophores such as GFP-like fluorescent proteins or other pigments contained in tissues. Biofluorescence is distinct from bioluminescence, in which light is produced by a chemical reaction within the organism, and from nonliving fluorescence in materials outside a biological system. In biofluorescence, excitation from external light sources causes the fluorophores to emit light, a response that can be observed under specific illumination conditions.

Biofluorescence has been documented in a variety of organisms, most prominently in marine life. Many reef fishes exhibit green or red fluorescence under blue light, and corals commonly display a spectrum of colors due to fluorescent proteins. Other marine groups such as certain cephalopods and crustaceans also show biofluorescence. Terrestrial arthropods, including scorpions, can fluoresce under ultraviolet light because of compounds in their cuticle, though the functional significance in these cases varies and is not always clear.

Possible ecological roles for biofluorescence are an active area of research. Hypotheses include aiding in intraspecific signaling and mate recognition, providing camouflage or counter-illumination under filtered light, and influencing predator–prey interactions. The visibility and effectiveness of biofluorescence depend on ambient light, viewing angle, and the spectral sensitivity of the observer.

In science and biotechnology, fluorescent proteins derived from naturally fluorescing organisms have become essential tools for imaging and labeling in research. Biofluorescence also informs studies of ecology and evolution by revealing how organisms interact with light in their environments.