Bioluminescence at the deep sea animals
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A trip to understand the deep sea

Today, the scientists know more about the universe than about the ocean. We know very little about what is really happening under 1000 m in the sea. 
The ocean is right here on Earth, how many times haven’t you seen it and the universe is so far away, untouchable and so hard to understand its immensity. A pretty fair judgment, but I challenge you to think more about it; I’ll help you. Let’s take a look at the image below in order to understand the deep sea and after that we will move out to the next chapter: the bioluminescence. 

From top to bottom


 Of course, we can’t get into many details about these zones, but this diagram will help you to figure it out how the ocean “works”. The Epipelagic Zone is also called “the sunlight zone” because the light can reach this zone easily; with light comes heat, so the temperature in this zone is the highest. 


Going deeper between 200 m and 1000 m we will find the Mesopelagic Zone – here the light is extremely faint. In the absence of light the photosynthesis can not be achieved and that is a problem for… every single creature. But the nature is so complicated and complex, full of wanders and amazing “mechanisms” that it found a way to develop life in the most extreme conditions.     

 In the Mesopelagic Zone exists a mosaic of strange and bizarre living creatures beyond your wildest imagination – the bioluminescence creatures.  Moving to the next Zone, also called “the dark zone” we reach to a place where the pressure is immense and the only visible light is the one produced by the creatures themselves. Yes, even here there is a large number of living species. Wait… light produced by animals? Yes, that is a simple definition for bioluminescence. But let’s take it easy.

The next layer is the Abyss. The water temperature is near freezing (like the pressure and the absence of light was not enough) so very few creatures live there. Most of them are invertebrates and as in the previous Zones, the only light is the one produced by animals. From 6000 m to the bottom of the ocean is the Hadalpelagic Zone and these areas are represented by deep water trenches and canyons. You probably know that the deepest spot in the ocean is Mariana Trench of the coast of Japan at the incredible depth of 10.911 m. Remember that the Everest peak is 8,848 m above sea level. It’s impressive, right?

The water temperature is above freezing and the pressure is eight tons per square inch, but life still exist. In 2012, James Cameron, a deep-sea explorer, piloted the Deepsea Challenger to the ocean’s deepest point and what he found there is almost incredible. Nature is incredible and we have so many examples surrounding us to prove that. You can read more about the Deepsea Challenger (and I highly recommend that in order to understand better what’s really going on down there) project on the official website here


Enlighten your mind

Now that you know a little bit more about how the ocean “works” we can talk about the real magic – bioluminescence. As I said before, that is the term using to describe a phenomenon: a living organism produces light through a chemical reaction. Well, you probably heard before about chemiluminescence, which is basically just a chemical reaction where light is produced. The difference is: when we talk about bioluminescence, we talk about a LIVING organism.                  

With the light comes heat; the light produced during this phenomenon is actually a “cold light” which means that only 20% or less of the light generates heat (thermal radiation). But how many organisms are able to produce light? Most of them are found in the ocean, species like fish, jellies and bacteria. Some fireflies and fungi are found on the land, but we will only study the deep sea animals in this article. Here are some examples of organisms:

The lanternfish


Dinoflagellates - unicellular eukaryotes

The Midshipman fish

The squid

The Galactic Squid

Other deep sea creatures:
Weird Deep-Sea Creatures Found in Atlantic
Weird Deep-Sea Creatures Found in Atlantic

But how it works? To generate light, the organisms need two unique chemicals: liciferin and luciferase or photoprotein. The substrate (the compound that produces light) is the luciferin and it is responsible for the mosaic of colors too. Everything is about how the molecules of luciferin are arranged. Some of the organisms can produce this compound by themselves while other can’t, but this last category uses another trick: they absorb it through other organisms – like food or in a symbiotic relationship. I will not give you to many details about the reaction because it’s pretty complicated, but you get the idea. Scroll down and at the bottom of the page you will find some links with more information about this subject.

            The most important question is probably: WHY? Why do we need bioluminescence in the nature? Remember that we talked about the Zones in the ocean and how the sun light penetrates the layers. Starting with the Mesopelagic Zone there is no light, no photosynthesis but life still exists thanks to the bioluminescence. The organisms use their own light to defent against predators, to find food, to reproduce and for many other vital things. Here are some of them:

            Camouflage – the organism matches with the environmental light so it can hide and defend against predators.

            Finding mates – in the mating season, some species are using periodic flashlight in their abdomen to attract mates. The bioluminescence is also used for long-distance communication.

            Distraction – probably one of the most effective method to avoid predators. The organisms expel some luminescent materials in the water, creating a “doppelganger” to distract the predator.

            Luring the prey – Smaller fish, curious about the light, swim closer to the bright spot, right in front of the predator. Pretty easy to hunt, right?

            Such an interesting part of the nature is definitely used by people, in the field of genetic engineering as reporter genes for example. It’s not easy, but the scientists are trying to find a way to use the bioluminescence to make our life easier. Imagine a bioluminescent tree – it could help to illuminate the streets without using electric energy. If you have another idea about how we can use the bioluminescence, let us know!


Interesting facts

  • The animals are not the only one that produce light – some plants can do it too, like jack-o’-lantern mushroom.
  • If you want to impress your friends, you can even buy some species of bioluminescence plants, like Panellus stipticus, a “glowshroom”.
  • Scorpions can glow too! They have a chemical in their exoskeleton that makes him shine under ultraviolet light.
  • The Green Fluorescing Protein comes from a form of bioluminescent jellyfish and it is currently used by scientists as a genetic marker.




Images: (1) (2) (3) (4) (5, 6) (7) (8) (9) (10) (11)

Published by Alina-Ioana Anghel


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