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23 October 2019
www.thevillagenews.co.za
The wonder of bioluminescence By Dr Anina Lee
N Mega climate shocks for SA biodiversity (Government report) Writer: Tiara Walters, Daily Maverick Ninety scientific institutions led by the South African National Biodiversity Institute have released a shocking report that unveils waves of unprecedented climate impacts tearing across South Africa’s globally important wild assets. South Africa’s first national biodiversity assessment in nearly a decade represents the findings of leading institutions such as the South African National Biodiversity Institute (SANBI), the Council for Scientific and Industrial Research (CSIR), and the contributions of 470 scientific and conservation professionals. Produced between 2015 and 2019, this assessment is a hard-hitting scientific achievement offering stunning collaborative insight into the climate crisis as never before documented in South Africa. This assessment is, in short, South Africa’s biodiversity answer to the UN’s game-changing IPCC Special Report on the impacts of global warming of 1.5°C above pre-industrial levels, released this month a year ago (www.ipcc.ch/sr15/). Given that no sector is more important to South Africa’s future than its natural capital, this assessment should be legally required reading for every person in South Africa working towards the National Development Plan’s goals of eliminating poverty and reducing inequality by 2030.
ature 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 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.
Daily Maverick is on a mission to help rebuild South Africa. This motive extends beyond just continuing with journalism; they want to increase the search for workable solutions and hold events that encourage and inspire their readers, and the country as a whole, to do what they can to contribute to this mission. The Village NEWS is pleased to be associated with Daily Maverick and the fact that we have received permission to re-publish their stories to a wider audience. www.pressreader.com www.issuu.com/dwaal
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Bioluminescence is a fascinating wonder that continues to dazzle and inspire. How is the light produced? 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.
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.
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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.
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.
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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.
1. Bioluminescent jellyfish Pelagia noctiluca glows when it is disturbed. It also can create a luminous mucus. PHOTO: David Fleetham/Corbis 2. Bioluminescent plankton on a South Coast beach. PHOTO: Joanne Paquette, National Geographic 3. A glowing deep-sea anglerfish. PHOTO: Earth. com 4. The bioluminescence reaction.
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Oxiluciferin
High energy state
O2
Luciferin
Luciferin
Low energy state
Oxiluciferin
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? 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.
