Biofluorescence is a natural phenomenon where living organisms absorb light at one wavelength and then re-emit it at a different, typically longer, wavelength. This process transforms absorbed light, often invisible to the human eye, into vibrant, visible colors like greens, reds, or oranges.
The Science Behind the Glow
The ability of organisms to biofluoresce relies on specialized biomolecules, frequently proteins, embedded within their tissues. When an external light source, such as blue or ultraviolet (UV) light, strikes these molecules, their electrons become excited and jump to a higher energy state. This excited state is unstable, causing electrons to quickly return to their original, lower energy level and release excess energy as photons. This emitted light has a longer wavelength and lower energy than the absorbed light, resulting in a different color that becomes visible. A well-known example is the Green Fluorescent Protein (GFP), initially discovered in the jellyfish Aequorea victoria, which absorbs blue light and re-emits it as green light.
A Kaleidoscope of Fluorescent Life
Biofluorescence colors the world across diverse species and environments. In marine ecosystems, over 200 species of fish, including catsharks, eels, corals, and jellyfish, display a range of colors when exposed to UV light. Certain scorpionfish and rays, for instance, exhibit distinct fluorescent patterns. Beyond the oceans, biofluorescence has been observed in terrestrial creatures like scorpions, which glow greenish under UV due to their exoskeletons. Recent discoveries also include birds-of-paradise, platypuses, fungi, and chameleons.
Illuminating Purpose: Why Organisms Fluoresce
The reasons behind biofluorescence in organisms are still being explored, but several functions are hypothesized. One potential purpose is communication, allowing organisms to signal to others of their species. For example, some sharks have specialized eye filters that might enable them to perceive these biofluorescent signals from other animals. Biofluorescence may also aid in camouflage, helping organisms blend into their surroundings, or conversely, attract prey. Additionally, it could serve as a deterrent to predators or even offer physiological benefits like UV protection or energy conservation.
Biofluorescence vs. Bioluminescence: Understanding the Difference
Biofluorescence and bioluminescence are often confused despite being distinct phenomena. Biofluorescence relies on an external light source being absorbed and then re-emitted by the organism; it does not produce its own light but rather transforms existing light. In contrast, bioluminescence involves a chemical reaction within the organism’s body that generates light. This reaction typically involves compounds called luciferins and an enzyme called luciferase, which produce light as a byproduct of the chemical process. Unlike biofluorescence, bioluminescence does not require an external light source to glow.