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Photogens

　It is said that there are 4000-5000 types of photogens on Earth. Photogens are found in both ※1prokaryotes and ※2eukaryotes. However,they do not exist in ※3amphibians、※4reptiles、 ※5birds、and※6mammals. Therefore,we can say that these creatures abandoned the trait of luminescence at some tine during their evolution. Thre are also luminous mosses. However,mosses are classified as ※7bacteria. Luminous mosses can shine due to reflected light but they cannot shine from internal energy. Some luminescent bacteria shine from internal sources. They love in the sea and their size
↑Firefly　
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is about 0.1mm. Among fungi, omphalotus guepiniformis and Mycena chlorophos are known to people as shining mushrooms. Omphalotus guepiniformis emit blue-green light. Mycena chlorophos emit green light. Among ※8molluscs,known shining varieties are the Aequorea victoria,Watasenia scintillans and Vargula hilgendorfii. Shining vertebrates,incllude the Anomalopidae,Himantolophus groenlandicus and Midshipman fish. Of course nobody forgets the firefly.
　Then,by what mechanism do creatures shine? This process can be explained by, "Oxidation of ※9luciferin".


However,the process differs slightly between species. For example,in fireflies, the chemical reaction of luciferin is prompted by luciferase. Luciferase is an ※11enzyme that enables ※10oxidation reactions. Such substances shine yellow-green, yellow and green. Jellyfish have a luminescent ※12protein called aequorin. Calcium ions adhere to this. After that, the creature shines blue because the coelenterazine in the aequorin is oxidized. Coelenterazine is a similar substance to luciferase. Such minor differences lead to a diversity of emitted colors.
　On the other hand,the purposes that creatures use emission from are various. For example, watasenia scintillans weses it as protection from enemies. While the purpose himantolophus groenlandicus uminescencs is predation and the midshipman fish has protective coloration. The unighe purpose of this phenomenon in jellyfish is protect them from solar ultraviolet radiation.
By　now, the general process of oxidation of luciferin is understood, but the speciric function of this process in jellyfish is only partly understood and how it works in mushrooms is still a complete mystery.

※１　　Prokaryotes・・・Creatures consisting of cells which don't have nuclei.
※２　　Eukaryotes・・・Creatures consisting of cells with nuclei.
※３　　Amphibians・・・For example：frogs, salamanders, newts
※４　　Reptiles・・・For example：crocodiles, lizards, turtles
※５　　Birds・・・For example：sparrows, penguins, pigeons
※６　　Mammals・・・For example：humans, rabbits, bats
※７　　Bacteria・・・Unicellular organisms that is belong to the prokaryotes family.
※８　　Mollusca・・・For example：squid, octopus, jellyfish
※９　　Luciferin・・・A substance which allows bioluminescence to happen when under the influence of the enzyme called luciferase.
※１０　Oxidation・・・Substances that combine with oxygen.
※１１　Enzymes・・・Substances that act as catalysts (The catalyst itself doesn't change in a chemical reaction. However,they are substances that promote chemical reactions.) in chemical reactions in vivo.
※１２　Proteins・・・One of the constituents parts of an organism. It is a compound containing carbon in complex structures.

　Japanese got Nobel Prize, discovery of a photogen!
　2008 Nobel Prize in Chemistry, Japanese was also awarded it. The winners are Osamu shimomura, Martin Chalfie, and Roger Yonchien Tsien. The reason rereived the award is "the discovery and development of the green fluorescent protein, GFP". GFP stands for Green Fluorescent Protein, and it represents a Green Fluorescent Protein. Mr. Shimomura discovered GFP from Aequorea victoria, or crystal jelly. One of anecdotes is his family took hundreds of thousands of jellyfish.
　GFP is a green glow when it is exposed to ultraviolet or blue light. GFP has little effect on the organism. GFP does not need oxygen when it emits light. So GFP is very safe around the circurm stance which it is applied.