SCIENCE FOR YOUTH How and why do fireflies glow By Hiya Islam

Frogs croaking. Crickets chirping. Owls hooting. The moon glistening bright on the pond. Leaves rustling in the wind. But what catches the eye is the faint glow in the woods. Nothing is as magical as strolling in a forest lit by the soft light radiating out of pee-wee fireflies.


What is the biology behind this mesmerising glow? Fireflies are the perfect example of ‘bioluminescence’ which is a type of light production in living organisms. In other words, bioluminescence is the concept of glow-in-the-dark creatures. Glowworms, bobtail squids, comb jellies can be included in this fantastic category and can be extended to bioluminescent fungi, bacteria and plant-like protists. When present in vast numbers these surely put up a great show for the eyes to feast on!

The source of light boils down to one chemical reaction taking place inside their bodies. The reaction between oxygen, calcium, ATP and a special chemical called ‘luciferin’ and ‘luciferase’, a bioluminescent enzyme gives out the light. However, the light is being released with a negligible amount of heat unlike the sources of light we have seen. This is crucial for their survival; to avoid death by overheating. What is even more intriguing that fireflies are in control of their flashy appearances. The ‘light organ’ shines only in the bestowed presence of oxygen and another gas, nitric oxide. Nitric oxide binds with mitochondria and allows the transport of oxygen to the light organ. Since nitric oxide gets broken down rapidly oxygen is trapped in the mitochondria and light production is hindered.

Bioluminescence serves great purposes in the animal world. The anglerfish has a U-like extension above its head, close to the jaws. The lighting tip helps to fool prey and lure them in. Colourful show of light also attracts a mate for reproduction which is a must for the species to survive. Besides, it always lends a hand to startle or blind predators. Or even better, like spitting out glowing balls in the dark to confuse them as done by some jelly fishes. Lastly, to communicate with clan members.

Nature’s best form of flashlight comes in assorted colours. Terrestrial animals give out green or yellow light. Marine animals choose to stick to bluish-green range because the red-end of the light spectrum cannot be transmitted efficiently in the ocean. Also, many aquatic animals are insensitive to this range rendering the option to be useless. However, it is advantageous for some. They emit red light to help them guide through the darkness of the depths while being undetectable.

Bioluminescence on first thought could be a funny idea. As so happens with living organisms, every feature has got reasons to exist. Only answers need to be found. Moreover, with the help of genetic engineering, organisms can now be modified to shine bright like the GloFish.


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