Fireflies are one of the most interesting species. A bug that produces light in his butt!
This is not magic, maybe it is. Actually production of light is a pretty simple chemical reaction. Let's look closer the guy behind the magic: "Luciferin" (not the one in the hell, the one in your backyard)
D-luciferin is a small molecule which is a member of light producing molecule family luciferins. The light production by D-luciferin is a way of bioluminescence seen in living organisms. Produced light is called as cold light because there is no heat formation during the light production process which is not common in nature.
Luciferin is the general name for light producing molecules in living organisms and each member of the luciferin family has different and molecule-specific evolutionary history. D-luciferin evolved in land animals whereas most of the other luciferin family members evolved in aquatic organisms and mostly in bacterial species. The evolutionary environment has strong impact on the luciferins’ light colors and molecular structures. Color of the light generated by aquatic luciferins are in blue tones which is quite different from the red tones of D-luciferin originated light. The color of light is naturally selected in evolutionary process based on the ability of the light to travel more in its environment.
The structure of luciferins also varies, and D-luciferin has its unique structure formed by D-cysteine amino acid and CBT subunits as shown in figure 1. The molecular structure of D-luciferin is very stable, and it can be stored at -4 oC for nearly two years when extracted from living cells or chemically synthesized in laboratory environment. Even though it is stable and storable, D-luciferin is highly oxidizable when it reacts with luciferase enzyme or hydrated. The enzymatic reaction of luciferin with luciferase is the main requirement for light production, but eaction also requires adenosine triphosphate (ATP) and magnesium ion presence in the environment as cofactors. When the enzyme and the cofactors are present in the reaction environment, light can be generated both inside and outside of a living cell.
Although bioluminescence is rare in land animals, there are several species which use D-luciferin based systems. Firefly (Lampyridae), railroad worm (Phengodidae), and click-beetle (Pyrophorini) are the species investigated during D-luciferin research. There are three main reasons of light usage by these species. First, the light is used as a warning signal for predators and even to discourage the predator. Second, light shows become a part of mating ritual between adults. The pattern of the light show is mostly sex and species specific. Third, unique light patterns are used to identify other members. The bioluminescent light of these species is also used by people for several purposes. In the days when lighting methods were much more limited, insect light used as a light source. Nowadays, there are drug designs which mimic D-luciferin working principle for curing cancer. D-luciferin based probes are also in the core of modern biological imaging applications.
This article is a simple start. Anything you wonder? Simple or complex, does not matter. When you are tired of the bad news about crypto, come here.