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Stars of the ocean
a man caught some squid from the sea downstream from the Karachi Nuclear Power Plant. By the time he had cleaned the catch, it was night, so he wrapped up his work for the day, and switched off the light. But to his surprise, as soon as the room darkened, the pieces of squid began to glow in a strong greenish-yellow fluorescent light.
The man assumed that the glow was due to nuclear radiation emanating from radionuclide in the squid. He was wrong.
Nuclear radiation is invisible. It can only be detected with appropriate radiation detectors. What he had observed was Biolumines-cence from the squid.
What is Bioluminescence?
Bioluminescence is the light produced as a result of a chemical reaction within an organism. It is caused by a series of oxidation reactions set off by a catalyst called luciferins — a group of chemicals.
How animals actually create luciferins varies from animal to animal. Some secrete it from special glands, whereas others capture it in the diet or synthesize internally.
Large animals, such as squid and fish, have special light organs called photophores, which are wart or blister-like structures packed full of bioluminescent bacteria. When the animal wants to generate light they stir or stimulate the bacteria in a special cell structure called photophore.
Bioluminescent organisms
Bioluminescence is primarily a marine phenomenon. It has been observed in more than 700 marine creatures, ranging from bacteria to fish, squid, sponges, jellyfish, starfish and crabs. A vast range of single-called plankton and gelatinous plankton are bioluminescent which are found in all the world’s oceans.
The prevalence of plankton in coastal waters and oceans results from complex interplay between temperature, currents, wind, location and food sources. As the conditions of sea change, so do the appearance of Bioluminescence. Mass spawning of bioluminescent plankton is triggered by a combination of ideal sea temperature and nutrients. Interestingly, there are almost no freshwater bioluminescent organisms. Land-based bioluminescent organisms include fireflies, fungi and glowworms.
In general, three different types of luminescence are found in organisms: internal, external and bacterial. Internal luminescence is produced within the tissues held by photophores, whereas external luminescence is produced through secretions ejected in water.
Bacterial luminescence is produced on the skin by colonies of luminescent bacteria living on the surface of the organism. All the three types of bioluminescence are exhibited by species of squid.
The glowing of squid is a well-known phenomenon. Many types of squid are studded with jewel-like organs, which they use both to attract a mate and to camouflage against the down-welling surface light.
There is a wonderfully strange deep sea cephalopod called the vampire squid, which has a large pair of light organs at the base of its fins as well as tiny light organs scattered over the rest of its body. A giant squid know as “Taningia danae” which is seven feet long and weights 135 pounds is on exhibit in the national Museum of Natural History in Washington DC.
Unlike most other squid, Taningia does not have two long feeding tentacles, but it has gigantic yellow photophores at the end of its arms which are the largest light producing organs in any known animal. These lemon-coloured photophores can be flashed at will, as these are equipped with a black, eyelid-like membrane that can be opened or closed. Taningia uses these bright flashes to distract and confuse an approaching predator.
Bioluminescence and humans
There are many interesting examples of the interaction between humans and bioluminescent starfish. Humans used to carry the fish on their fingers to help them read maps at night.
Bioluminescent plankton can paint a submarine with enough light to be detected by a satellite. The last German U-boat sank during World War I due to bioluminescent plankton, which enabled the non-sonar equipment to accurately track and depth-charge it.
Being a knowledge-based regulatory authority, the Pakistan Nuclear Regulatory Authority stresses on acquiring and disseminating new technologies within its organization and in those of its licencees. Other regulatory bodies responsible for regulating complex and high-risk technologies such as civil aviation and chemical industry can also benefit from this technique. The PNRA is willing to share its expertise with all authorities and organizations if approached.
The writer works for the Pakistan Institute of Nuclear Science and Technology
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