Recall that magical evening of the spring when you were lying down on the grass after a tiring day and gazing at the stars in the sky when you were treated to a firework display by the fireflies. The fireflies produce light through a chemical reaction in their glowing abdomens, a process known as bioluminescence. But did you know that seascapes can also glow and glitter thanks to the light-producing abilities of many marine organisms?
The deep-sea is teeming with bioluminescence, and owing to its vastness, bioluminescence may be the most common form of communication on the planet!
“There’s a whole netherworld of the deep sea that we don’t see when we have our lights on,” says Kevin Raskoff, a scientist at California State University, Monterey Bay. “And that’s the natural light of the deep sea: bioluminescence.” Bioluminescence is light produced by a chemical process within a living organism. The glow occurs when a substance called luciferin reacts with oxygen. This releases energy and light is emitted. An enzyme called luciferase facilitates the reaction. Sometimes luciferin and luciferase are bound together with oxygen into a single molecule or photoprotein. When an ion such as calcium is present, an ensuing reaction emits light. The organisms must replenish the luciferin stores in their bodies to continue glowing. Some acquire it through their diet; others produce their own.
Why do Animals Glow?🌟
❖ In the dark ocean, dim glowing can be used to attract prey.
The deep-sea anglerfish lures prey straight to its mouth with a dangling bioluminescent barbel, lit by symbiotic bacteria in the same way that a fisherman might use a glowing lure for night fishing. Some fish use bioluminescence as a flashlight, which is how flashlight fish got their name. Whales and squid are attracted to the glowing underside of the cookie-cutter shark, which grabs a bite out of the animals once they are close. The bioluminescence around the beak of the Stauroteuthis octopus attracts small planktons.
❖ Often animals use a strong flash of bioluminescence to scare off an impending predator.
The deep-sea shrimp (Acanthephyra purpurea) vomits bioluminescent goop into the face of threatening diners while the deep-sea squid Octopoteuthis deletron detaches its bioluminescent arms, presumably either as a scare tactic or to create a distraction while the animal escapes. Jellyfish such as comb jellies produce bright flashes to startle a predator, others such as siphonophores can release thousands of glowing particles into the water as a mimic of small plankton to confuse the predator. Others produce a glowing slime that can stick to a potential predator and make it vulnerable to its predators. The dinoflagellates seem to employ their bioluminescence as a kind of defensive burglar alarm to attract the predators of their predators.
❖ Bioluminescence can also be used to help camouflage with the use of counterillumination. Photophores on the bottom side of an animal can match the dim light coming from the surface, called luminescent countershading, making it harder for predators to detect them.
❖ Bioluminescence also plays a part in attracting mates. The best-known example is the bioluminescence of fireflies, where the females respond to the flashes of flying males, with the eventual result that the male approaches the female for the purpose of mating. However, this phenomenon is seen in many marine animals too. The male Caribbean ostracod, a tiny crustacean, uses bioluminescent signals on its upper lips to attract females. Syllid fireworms live on the seafloor, but with the onset of the full moon, they move to the open water where they switch to a planktonic form to reproduce, where the females use bioluminescent signals. A male sea-firefly (Vargula hilgendorfii) squirts out a bright dot of light, zip upward, and then squirt another and another, essentially drawing an arrow that points out his whereabouts. In animals such as polychaetes (bristle worms), the females attract males with a glowing mucus containing gametes while in others such as ostracods (firefleas), males flash in a sequence as they swim to attract females.
Colourful Bioluminescence
Bioluminescence does come in different colors, from blue through red. The color depends upon the substrate molecule luciferin, which releases energy as it is oxidized in a chemical reaction facilitated by the protein luciferase. Though inland animals such as fireflies and other beetles, it is mostly green or yellow, in the ocean, bioluminescence is mostly blue-green as the wavelength transmits best through seawater. However, there are some exceptions to this as some worms make yellow light, and a deep-sea fish called the Black loosejaw also produces red light.
Applications
Many scientists have even incorporated bioluminescence into their own work lives, often unaware of its original origin. Photoproteins, first isolated from jellyfish several decades ago, are now an integral part of laboratory biology and help researchers do things like mark and identify crucial gene sequences in medical studies.
So, the next time you see fireflies glowing, you can be certain that they aren’t the only ones with this god-gifted and unique ability.
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