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Cnidarians: The Evolution Of Biolumines

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There are more than 11,000 species of Cnidarians and the diversity among them is striking as this phylum includes organisms from corals to sea jellies (Pechenik 2009). This groups defining characteristic is that all included have nematocysts or cnidae, which are very complex specialized stinging cells (Technau & Steele 2011). Many species of both shallow and deep-sea Cnidarians bioluminesce, with the exception of the family Cubozoa. This leaves the 3 families of Cnidarians: hydrozoa, scyphozoa and anthozoa (Haddock et al. 2010). Bioluminescence has evolved multiple times in different families of land and water species. The evolution of bioluminescence is difficult to follow down evolutionary lines since no phyla is entirely luminous as this …show more content…

In Cnidarians an enzyme is needed, either the apoprotein of a photoprotein or a luciferase, to catalyze the oxidation of luciferin. This type of luminescence is fundamentally different from fluorescence as the organism actually makes light energy in bioluminescence instead of absorbing an external light source and reemitting it (Haddock et al. 2005). Bioluminescence in scyphozoans, hydrozoans and anthozoans is dependent on the luciferin coelenterazine exclusively (Haddock 2006). The families are distinct in the catalyst they use as photoproteins are only used by hydrozoans. Scyphozoans and anthozoans both use luciferase but not the same ones in their bioluminescence reactions (Haddock et al. 2010). Some Cnidarians also have a secondary light emitting complex called Green Fluorescent Protein …show more content…

Blue light is around 475 nm and is able to radiate the longest distance of any colour through the open ocean (Widder 2010). Interestingly, the most sensitive wavelengths for detection by deep-sea fish and shrimp is blue light wavelengths (Haddock & Case 1999). Green light, which has a wavelength of around 510 nm, is said to be more commonly emitted by marine organisms residing in turbid environments or those that have chlorophyll as it has a longer wavelength than blue light and is does not attenuate by scatter as easily after short distances. These environments could be shallow or benthic (Haddock & Case 1999; Widder 1010). Benthic environments include the ocean floor and are at a lower depth than the pelagic zone. Coelenterazine is perfectly suited for luminescence in the open ocean as it produces blue light at a maximum of 470-480 nm. The emission of blue light by the bioluminescence reaction of this imidazolopyrazine luciferin is almost wholly based on its own structure with subtle sway by the luciferase reactant (Rees et al.

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