Kolkata, West Bengal
A strange light. It glows and fades, the cool, gentle light of the firefly. There is no heat, only calm brightness. In English, it is called a firefly. Many poems have been written about their light. For example:
“ওই একটি দুটি পাতার পরে
একটু মৃদু আলো,
ও যে দেখতে ভারী নুতন, ওরে
কেমন লাগে ভালো।“( কবি - সত্যেন্দ্রনাথ দত্ত )
“That faint light upon a leaf or two,
Looks so new, so fresh, and beautiful too.”
(Poet - Satyendranath Dutta)
“কবিতা বুঝিনি আমি; অন্ধকারে একটি জোনাকি
যত্সামান্য আলো দেয়, নিরুত্তাপ, কোমল আলোক।
এই অন্ধকারে এই দৃষ্টিগম্য আকাশের পারে
অধিক নীলাভ সেই প্রকৃত আকাশ প’ড়ে আছে—।
এই বোধ সুগভীরে কখন আকৃষ্ট ক’রে নিয়ে
যুগ যুগ আমাদের অগ্রসর হয়ে যেতে বলে,
তারকা, জোনাকি—সব;লম্বিত গভীর হয়ে গেলে
না-দেখা গহ্বর যেন অন্ধকার হৃদয় অবধি…।”( কবি - বিনয় মজুমদার )
“I never understood poetry; in the dark, there’s a firefly.
It gives only a little light, soft, without warmth.
Beyond this darkness, beyond the visible sky,
There lies a truer, deeper blue.
This feeling, deep within, sometimes draws us on,
Urging us to move forward through the ages.
When stars and fireflies all stretch into depth,
The unseen abyss seems to reach the heart of darkness.”
(Poet - Binoy Majumdar)
But it is not only fireflies; many creatures of land and sea can emit light from their bodies. Not all do it in the same way. For instance, in the deep sea, jellyfish glow through a special protein. Altogether, this phenomenon is called fluorescence.
However, today’s story is about the firefly’s light. There are many kinds of fireflies, but only a few species have the mechanism to produce light. They use this luminous trick to hunt and to attract mates.
Why does their body glow? Does the whole body emit light? No, the light comes from a few special cells called photocytes. The word photo means light, and cyte means cell. Inside these photocytes lies a world of mystery, filled with fascinating chemical reactions.
An extraordinary chemical molecule called oxyluciferin is formed there. Several substances, luciferin, the enzyme luciferase, ATP, and oxygen react together to produce oxyluciferin. And it is from this oxyluciferin that the magical light of the firefly shines.
Inside the light-producing photocytes, oxygen is supplied in a controlled way. From the airways, oxygen enters the cells through tiny tubes. It flows in for a while, then stops. After a short pause, oxygen enters again and stops again. At regular intervals, this measured supply of oxygen reacts with certain chemicals. That is why the light emission is rhythmic, glowing and fading in turn. If it did not happen this way, we would only see a steady light, like that of an electric bulb.
The firefly’s blinking is controlled by oxygen, but the entire process is regulated by its nervous system. At the ends of the nerves, a neurotransmitter called octopamine is released, also known as a neurohormone. Through complex reactions, this neurohormone sends different signals to the photocytes, for example, how much oxygen to supply. Following these signals, chemical reactions create light. Not steady light, but a strange, flickering glow that shines and fades again and again.
The firefly does not need a battery to make its light. It does not burn fuel. It produces light without generating heat, a marvelous wonder of nature. In this chemical reaction, one hundred percent of the energy turns into light. Our electric bulbs, by comparison, convert only about ten percent of electricity into light, while the remaining ninety percent is lost as heat. Scientists have not yet uncovered every detail behind this natural light-making process of the firefly.
But fireflies are disappearing. Urbanization is spreading, trees, ponds, and rural habitats are being destroyed. Many countries are now trying to bring back these tiny glowing insects that have vanished from the heart of nature.
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