Animals that Glow : The Science of Bioluminescence

In the olden days it was called cold-fire.

When walking through the forest, our ancestors discovered glowing mushrooms on rotting wood. They called it ‘fox-fire’. They were fascinated by the fairy tale nature of insects flying through the forest with an eerie and ethereal glow. They called these ‘fire-flies’ (even though they weren’t really flies!) and they called their worms ‘ glow worms’.

When they went sailing, they were enchanted and frightened by the sea turning milky white and glow as if lit up from within, in the wake of a ship or a boat. They called this ‘sea-fire’ . They sometimes saw sea creatures glowing blue and green as if my magic. They were in awe of these mysteries of nature.

Little did they know they were observing Bioluminescence - The phenomenon where a living creature – a plant or an animal- emits light from its body through a chemical reaction. A remarkably diverse set of animals, microbes and plants seem to be able to produce light this way. While most of these animals dwell underwater, there are some that live on land also.

Animal light production is an evolutionary miracle. While one can understand the deep sea dwellers evolving this capability due to sheer lack of light, there is no clear theory on how the land dwelling insects evolved this capacity to glow. Not only do the animals glow, but the glow on demand. They can switch it on and switch it off, controlling their ability to shed light.

Fluorescence is the ability for certain pigments to absorb light and then emit it back, whereas Bioluminescence is the ability to produce light from scratch.

Among the many wonders of nature, the ability to produce beautiful, magical light has been fascinating scientists for a long time. Every year, more new species are discovered to be able to have this wonderful trait. And the wonder of it all it like all things that had millions of years to evolve, this reaction is the most efficient way of producing light ever seen by mankind.

What is the most efficient system of light emission known to mankind- is it LED, plasma, OLED or Laser?

It is the firefly!

A firefly is able to convert nearly 100% of its energy into light without wasting any in producing heat. By contrast the manmade light-bulb is only able to convert 10% of the electric energy into light, wasting the remaining 90% as heat.

There are lessons to be learnt from nature and the study of bioluminescence has been steadily advancing in order to harness this ability for productive uses.

There is astonishing list of animals that can glow spontaneously and most of them as expected live in the sea.

Most of the have evolved in the sea. There are three layers to the oceans, the top euphotic zone where sunlight is able to penetrate fully, the second disphotic zone where only small amount of light is able to penetrate and the lower aphotic zone which is pitch dark with no light at all.

Most organisms capable of bioluminescence live in the second zone.

Among the invertebrates there are the species of fire-flies that are actually a type of beetle belonging to the species called lampyridae and their caterpillars that glow. There are click beetles, certain earthworms and the species of plankton called dinoflagellates and their associated bacterial colonies.

Among the marine creatures there are countless jellyfish, octopi, certain corals, fish and even a shark that is capable of bioluminescence. Every year more and more species are being discovered.

There are two ways that living organisms can produce light- one is the Direct method where there own photo organs contain the necessary ingredients to activate a light protein and emit light directly as a result.

Some creatures, however, like certain squids ( Euprymna scolopes) and crustaceans, harbour light producing bacteria in their photic organs in a symbiotic ( mutually supportive) relationship. These bacteria ( vibrio fisherii) glow usefully in return for food and nourishment from their host creature and they happily glow ever after! These are the Indirect light producers.

Blue is the only colour that can penetrate farthest under water, among all the other wavelengths. Hence evolutionally most marine creatures glow blue.

Conversely in land, the glow worms and fireflies glow a luminous green so as not to be confused for the sky.

If you are allergic to science- this is the time to look away. The phenomenon of light production in most organisms tend to depend on the presence of a protein called Luciferin ( interesting name- as Lucifer in Latin means light-bringer!) Rather than be a single type of protein the name luciferin is giving to a whole host of light producing proteins found in living beings. The enzyme called Luciferase helps to promote this catalytic reaction.

Luciferin combines with Oxygen under the catalytst Luciferase and becomes Oxyluciferin and in the process emits photons of light. The presence of a significant molecule called ATP ( Adenosine Triphosphate) seems to be vital to the production of light. As ATP is also present in all living organisms including human beings, the possibility of activating bioluminescence in other organisms and use it for medical research has been steadily advancing.

There are so many reason why animals glow mostly for defence and offense.

Mate attraction

Fireflies glow as a way of attracting mates. The green light is a distinctive signal sent out by the potential mates to signal their presence and attract a partner.

Communication

The light emitted by dinoflagellates communicates a disturbance and spreads like a ‘burglar alarm’- thus when disturbed by a passing boat or a predator the plankton emit the luminous blue light as a signal, warning to others. This also attracts other predators to the area who may devour the smaller ones who feed on the plankton- the circle of life.

Luring prey

The angler fish (Melanocetus ) uniquely uses a light organ situated above its head and dangles this in front to attract unwary smaller fish and then swallows them.

Mimicry

A kind of shark called the cookie cutter shark emits a ‘closed encouters’ like alien light around it’s mouth that looks like smaller fish. The bigger predators approach this with the promise of a good meal, thus allowing the shark to take a large bite out of them! You’d think they’ll learn wouldn’t you.

Camouflage

As in the aphotic zone , predators lurk looking for prey and if they see shadows above them they will be quick to gobble them up as the light travels from above and they can spot silhouettes. For this reason certain jelly fish and other fish sport lights on their underside to mimic lights from above the sea and distract these deep sea predators.

Hunting

Some fish use their light that has a unique wavelength so only they can see. They use this to spot their prey and hunt them

Self-defence

Certain species shrimps ( Acanthephyra) squirt luminous ink to distract their predators and escape in the confusion. You can see it in the picture.

Showing Off

Some species seemingly just how off with a extraordinary display of fireworks like the rainbow zipper ( Euplokamis) that emits a brilliant spark of fireworks and a rainbow

Scientists have been studying this effect to put it to good use. There are several ideas already emerging from the practical to the science fiction.

Cancer testing

Just like how we now use enzymes to test for the presence of certain prot4ein we can make the proteins glow and detect them by the presence of light using unique scans. Some of these are already in use.

Disease progression

We can test progress of diseases such as Alzheimer’s ( as it is the deposition of certain protein in the brain) through the safe use of luminescent agents

Detecting Infection

Using bioluminescent proteins to be activated by the presence of certain bacteria we can detect infections.

Testing treatment strength and reducing length

As the presence of ATP signifies continuing bacterial infection, after antibiotic therapy we can test how much the bacterial colonies are still thriving by detecting their bioluminescence. This process has helped reduce therapy for Tuberculosis by almost three months as we can tell with much more certainty than cultures that the infection has diminished.

Search for life

Life, as we know it, depends on the enzyme ATP – this has helped NASA search for extra terrestrial life using bioluminescence principles in other planets and asteroids.

Tracking movements

Tagging certain animals with bioluminescent proteins will help us test their movements.

Lighting technology

Imagine using bioluminescent organisms to light the trees that line our highways and they will light up when they sense movements of a car. This way we can save of fortune on energy bills.

The Biolminescence web page contains all the latest research and articles on this subject and has been a valuable resource for researching this article.

The planet Pandora in James Cameron’s Avatar was designed with the bioluminescence in mind creating brilliant colours from plants and animals throughout.

 Cameron, Ever the perfectionist consulted with exobiologists, botanists and physicists to create a world grounded in reality but exploring various possibilities in evolutionary science.

I hope you enjoyed this tour of animals and species that glow. There are so many wonders such as this in nature that we can be constantly in awe of the power and the magnificence of our planet.

Thanks to hubmob weekly for the inspiration.

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Docmo

Copyright © Mohan Kumar 2011