Nature often devises surprising solutions for hunting food, warning predators away, and attracting mates, but one of the most magical-looking of these solutions might be bioluminescence – biochemical light created by a living creature.

Bioluminescent jellyfi sh Pelagia noctiluca glows when it is disturbed. It also can create a luminous mucus. PHOTO: David Fleetham/Corbis

What species can produce light?

Bioluminescence in nature almost defies belief. It’s no wonder that early explorers thought bioluminescent phytoplankton were “sparks” in the water. And it’s not just these miniscule creatures that give off light. The rest of the natural world is filled with glow-in-the-dark bodies that look like something out of science fiction.

Bioluminescent plants and fungi illuminate forests with their eerie light. Glowing fish are found in the depths of the ocean, jellyfish light up like neon lights and phytoplankton, mushrooms and other fungi do it too. Insects, such as fireflies, use blinks to attract potential mates. Why things glow varies, depending on the species; bioluminescent animals might use the light as a warning to predators, or to attract their prey. Consider the anglerfish, which lures hapless fish prey with its hypnotic hanging light.

Bioluminescence is a fascinating wonder that continues to dazzle and inspire.

How is the light produced?

Bioluminescent plankton on a South Coast beach.
PHOTO: Joanne Paquette, National Geographic

Bioluminescence is often referred to as a luciferin-luciferase reaction. That simply means that there is a substance called luciferin and an enzyme called luciferase causes it to change in a way that produces light.

Light comes in a discreet energy package called a photon. It requires energy to produce a photon. The energy comes from a molecule called ATP (adenosine triphosphate), which is the molecule living things use to store their energy.

The terms luciferin and luciferase both come from a Latin term lucifer, which means ‘light-bringer’. They are generic terms rather than the names of particular chemicals. There are many luciferins and luciferases, depending on the species of the bioluminescent life form.

Light generally comes from one source – an excited electron. Basically, energy causes an electron to move up a level in its atomic orbit. When the electron settles back down, it releases a photon, or a tiny packet of light.

To make light, we need an energy source. In light bulbs it’s electricity. In living organisms the energy comes from ATP. ATP is the molecule that living organisms use to store the energy that is derived from the food they eat. This stored ATP energy is then used to perform biochemical reactions that require energy such as muscle contraction and nerve impulses – and light.

In the bioluminescence reaction the luciferase enzyme facilitates (catalyses) the combination of luciferin, oxygen and ATP to make a high-energy molecule. The energy from the ATP kicks an electron into a higher orbit around its atom. Usually excited molecules get rid of their excess energy by vibrating. But this would not be a good idea in living organisms because vibration implies heat and heat would fry the firefly. In fact the structure of excited luciferin constrains any vibration. So what to do with the extra energy? It gets rid of the energy by emitting a quantum of light – known as a photon.

All of this chemical wizardry does not happen spontaneously. In living organisms all reactions are very carefully controlled by the catalysts of the reactions, namely the appropriate enzymes.

So now there is light. But fireflies have an added trick – they also flash their lights. Different species of fireflies have different flash patterns.

How do fireflies flash on and off?

The bioluminescence reaction.

A firefly controls the beginning and end of the chemical reaction, and thus the start and stop of its light emission, by adding oxygen to the other chemicals needed to produce light. This happens in the insect’s light organ. When oxygen is available, the light organ lights up, and when it is not available, the light goes out.

Oxygen availability is in turn controlled by the presence of a gas, nitric oxide (NO). Fireflies can make NO at will to switch on the light. Interestingly, nitric oxide is the same gas that is produced by taking the drug Viagra.

In many parts of the world there are more than one species of firefly occupying the same habitat. This is where the flash pattern is important so that the males and females of the same species can recognise each other. In other words, they speak the same language.

As in many situations in life, communication is critical.

About the Author

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Whale Coast Conservation passionately lives by its slogan “Caring for your environment”.

Its small staff and volunteers are dedicated to

  • raising community and visitor awareness of the unique, biodiverse natural resources of the Cape Whale Coast region and
  • to projects that convert awareness into practical actions that lead towards living sustainably.

WCC ensures expert representation in public participation processes that contribute to environmental and developmental policies and legislation.  We monitor regional development; and ensure compliance with legislation and guidelines.

WCC increases general public awareness of sustainability through environmental education, citizen-science research projects, community projects and campaigns.

WCC communicates with its audience through exhibitions, signage, technology demonstrations, workshops, talks, film shows, newsletters and articles.

WCC places emphasis on educating future generations through its Youth Environment Programme (YEP).  YEP is offered to 24 schools in its target area with a total of over 10,000 learners.

WCC facilitates schools’ participation in special events such as Earth Day, Walking for Water, Arbor Day and Coastal Clean-ups.

WCC facilitates educator development programmes to improve the capacity of educators to offer informed environmental content in their lessons across all learning streams.

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