Yes, it does glow. And so does a jellyfish, many other marine organisms, some mushrooms, bacteria and of course, the fire flies. We have all seen the fire flies glow in the dark of the night. But why do these organisms give out light and how do they manage it?
This "glowing" phenomenon is termed as Bioluminescence. In simple terms, Bioluminescence is the light produced by living organisms. They may have their own reasons for producing it and also different means to get it accomplished.
WHAT MAKES THEM GLOW?
Lets take the story of the bobtail squid first. The new born squids are born with a light organ. When small, they have to scour the sea waters to find one special bacterium species, the Vibrio fischeri, and offer them the use of their light organ as a permanent residence. Only when the light organ is colonized by a monoculture of these bacteria does it mature and develop to become fully functional. The maturation can be seen in the various physical changes of the organ such as the swelling of its epithelial cells. These Vibrio fischeri residing in the light producing organ of the squid are responsible for emitting a blue-green glow.
However if the squid does not harbor a wild type of the bacterium it would show reduced luminescence or no physical changes to its light organ. Thus it can be said that the actual role played by the bacterium is in the development of the light organ in exchange for their home and food from the squid. The luminescence is a product of the lux regulon which in the presence of an inducer(oxygen) emits light from the luciferin by the action of luciferase enzyme.
This "glowing" phenomenon is termed as Bioluminescence. In simple terms, Bioluminescence is the light produced by living organisms. They may have their own reasons for producing it and also different means to get it accomplished.
WHAT MAKES THEM GLOW?
Lets take the story of the bobtail squid first. The new born squids are born with a light organ. When small, they have to scour the sea waters to find one special bacterium species, the Vibrio fischeri, and offer them the use of their light organ as a permanent residence. Only when the light organ is colonized by a monoculture of these bacteria does it mature and develop to become fully functional. The maturation can be seen in the various physical changes of the organ such as the swelling of its epithelial cells. These Vibrio fischeri residing in the light producing organ of the squid are responsible for emitting a blue-green glow.
However if the squid does not harbor a wild type of the bacterium it would show reduced luminescence or no physical changes to its light organ. Thus it can be said that the actual role played by the bacterium is in the development of the light organ in exchange for their home and food from the squid. The luminescence is a product of the lux regulon which in the presence of an inducer(oxygen) emits light from the luciferin by the action of luciferase enzyme.
The jelly fish on the other hand does not need the help of a
bacterium to glow. It follows a chemical mechanism catalysed by the calcium ion.
The photoprotein aquoerin gives out a blue light upon reaction with calcium
ions either in the presence or absence of oxygen. But this is not the end of
it. This blue light emitted is then absorbed by a second protein which now emits
a green light. This second protein the green fluorescent protein has been
responsible to bring about a change in the biotechnology field in the way
assays are designed and genetically modified organisms detected.
Even the miniscule dinoflagellates shine bright. They have
the distinction of being the only photosynthetic organisms capable of bioluminescence.
The bioluminescence apparatus is present in scintillons and comprises of the substrate
luciferin, the enzyme luciferase and a protein that binds to luciferin.
Tetrapyrrole, a pigment related to chlorophyll also plays some role.
WHY DO THEY GLOW?
We now know some ways in which bioluminescence may be produced but it still is not clear why does the bobtail squid, or for that matter why does any of these organisms glow? How does Bioluminescence help them?
For starters, it might help in food hunting. In
the deep, dark depths of the ocean, bioluminescence can play the role of a
flashlight helping the owner locate its food. Alternatively, it might be a
trick on the part of the light producer to fool the prey into thinking that
there is food for it when actually the prey is going to be the one who’s eaten.
A great example is the viperfish. A modified fin ray extends forth from its
mouth and has a luminescent glow at its tip. The prey thinks it is food and
when it pounces, it is instead impaled on the fangs of the viperfish. Bioluminescence may play a role in protection of the organism. In this case, bioluminescence may be used as an offensive
tactic or a defensive tactic. When on the offensive it may be used to stun the
predator or call for help from someone larger than the predator. The deep sea
shrimp saves itself by blinding its attacker by shining brightly in its face
and then zooming off. Camouflaging is one brilliant defensive strategy. Take
the case of the hatchetfish. It has photophores(light emitting organs) on its
belly which give out a blue light. This light matches the sunlight being
filtered from above thus hiding the fish in a blur.
Lastly, Bioluminescence may be employed as a mating tool by the deep sea organisms.
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