The firefly is a kind of insect. This beetle is known in English as the lightning bug or firefly. The small, dark-brown insect is rather elongated, less than an inch long, just two centimetres. It has long yellow marks on its wings and head, six legs, two antennae, eyes, and a body divided into three parts. At the rear of its abdomen is the part that lights up, so every firefly goes about with a lamp at the end of its body. Researchers say, though, that the firefly is a very ordinary insect. About 20,000 species of firefly have been found in the world.

How does a firefly glow without electricity? The glow is nothing but a chemical reaction that takes place inside the body. The firefly carries a chemical called luciferin, and the light comes from the reaction of luciferin with oxygen. Scientists call this process of producing light inside the body bioluminescence. How much light a firefly produces depends on how much oxygen it supplies: less oxygen means less light, more oxygen means more.

Surprisingly, firefly light produces no heat. Scientists explain that in our lamps light energy is converted from electrical energy, but only a small part of the electrical energy becomes light; the rest becomes heat. A firefly's light comes from chemical energy, and almost all of that chemical energy becomes light, so no heat is produced. That is why scientists call firefly light "cold light". Scientists have long tried to make such a cold bulb or light, and the effort continues today; even in the digital LED age, it can be said, they have not succeeded.

Scientists agree that of all the sources of light in the world, firefly light is the most effective, smart, environment-friendly and efficient, because the chemical reaction turns almost 100 percent into light. An electric bulb converts only 10 percent into light energy; the remaining 90 percent is lost to the environment as heat, warming and polluting it. In the firefly, bioluminescence produces a remarkable cold light, and the reaction takes place in its abdomen. Scientists say firefly light particles are produced when the enzyme luciferase acts on luciferin in the presence of magnesium ions, ATP and oxygen.

This light glows in the larvae of almost all fireflies. Scientists say the light of adult fireflies and that of larvae serve different purposes. The larvae's light is mainly to frighten predators, since at the larval stage they are easy prey for other animals and birds. Are fireflies then night-blind, since they cannot move without a lamp? No. The play of light helps fireflies reproduce: in some species, males flash their light in their own style at night to attract females.

Scientists now say firmly that firefly light can play a major, ground-breaking role in developing the pharmaceutical industry, and could even help find life on other planets. Drug researchers at a university college in Wales recently said so, presenting evidence. Earlier, the pure light from the lower body of the firefly, which glows for 72 hours at a stretch, was shown at the Royal Society's summer exhibition. Scientists say organic molecules lie behind this glow. Researchers are now thinking afresh about using the molecule as a laboratory tool or for surface tests on other planets. They say this emission of light by living things happens through biochemical reactions, but the chemicals lie dormant inside the animal's cells, absorb light chemically to glow again, and light up the hidden darkness of our world.

Biologists say that among living things, from bacteria and fungi to many insects and especially jellyfish, many have their own chemical capacity to make light. They need to emit it for various purposes: to attract a mate, frighten an enemy or lure prey. The deep sea floor is a heavenly kingdom for such creatures, where firefly-like flashing goes on all the time. Living animals and plants under the sea give off every colour of the rainbow, from violet to red, and how these ever-changing colours are made has recently drawn the close attention of genetic engineers.

Why do fireflies emit light? Researchers explain that light is emitted when an electron loses energy. An excited electron carries a great deal of energy; when it emits a photon of light it loses the extra energy and falls to a lower level. In bioluminescence, the complex molecules surrounding the electron are excited by energy, and chemical reactions make this happen.

Researchers say the reaction in living cells takes place through two proteins, named luciferin and oxygen, and is directed by a type of enzyme called luciferase. The enzyme acts only as a medium; its other job is to take up raw luciferin fuel. It reacts with oxygen to make oxyluciferin, and it is oxyluciferin that gives off light. Researchers say firefly light is entirely different from all the kinds of burning light in common use in the world, with none of the annoying heat or smoke.

Bioluminescence produces its range of colours in two ways. First, when luciferin is oxidised, the colour produced depends on the type of genetically directed protein. Second, luciferin, luciferase and oxygen form a single bond called a photoprotein molecule, in which the excited energy moves the light-giving electron. This happens when the molecule is driven by charged calcium atoms. Researchers are also drawn to the subject for another reason: the chemical can be identified as an intact, useful light, which flashes with a slight flicker inside living cells.

Genetic engineer Professor Tony Campbell of the University of Wales and his team are still researching the subject. They are trying to find out how bioluminescent proteins produce light of a particular colour. DNA tests have shown how this protein is made. Campbell and his team noticed that two kinds of changeable chemicals sit inside specific living cells and react with particular molecules to change the colour of the light. The first arises from changes in the DNA; when a particular molecule is blocked, the luciferin protein changes from one colour to another. Second, two molecules are switched off when driven by a particular chemical.

Though there are many other reasons for Campbell's colour-carrying protein, the researchers found evidence that an enzyme called caspase lies behind the biotechnology that affects the change of colour. It is a complex molecule inside living cells that causes cell death, and this important enzyme holds back the growth of cancer-causing cells. For this reason, using the colour-changing proteins involved in bioluminescence to prepare medicines is now being considered seriously. Tests are being carried out in various possible areas with these light-emitting molecules, which are extremely important for Campbell's colour proteins and for identifying unusual molecules. This is a ground-breaking success for genetic engineer Tony Campbell, and its use in diagnosing disease and developing the pharmaceutical industry is expected to give promising results.

Meanwhile, researchers say the number of fireflies in the world is falling, and the main reason is light pollution. Bright light at night causes great difficulty for insects and many other animals and birds, especially nocturnal ones. This light pollution is why the nocturnal firefly is declining.

So that future generations can see fireflies, and medicines made from firefly light can save human lives, scientists have set out to send cameras on spacecraft to look in the soil of Mars or the seas of Europa for light signals from fireflies or other such creatures, and for the molecules of firefly-like organisms. The day is not far off, the writer says, when firefly light will point to life on another world, when cancer patients will shine like firefly light, and medicines made from firefly light will save the lives of countless people dying of cancer.

The writer is a science writer and researcher, and an MPhil scholar in the Faculty of Social Sciences, University of Dhaka.

Source: Jagonews24. First published in Bengali on The Agro News.