Why are corals colorful?

Discussion in 'Coral' started by pgreef, Nov 3, 2009.

  1. pgreef

    pgreef Fire Goby

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    I know the zooxanthellae has the color. But why do corals exist in different colors? Some corals like favias, brains and zoas have very well defined multiple colors.

    Some say flowers are brightly colored to attract bees so they will be pollinated. Some animals such as birds are brightly colored to attract mates.

    What is the biological advantage to corals being brightly colored? Since they are immobile they can't attract mates. As far as I know they don't receive assistance by any other animal in breeding. You would think that being brightly colored would be a disadvantage since they would be easier to spot by butterfly fish and angles (unless they don't see in color). If zooxanthellae take on different colors based on the amount of light they receive why are some corals multicolored?

    So what's the reason? It can't be just for our pleasure.
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  3. ZachB

    ZachB Giant Squid

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    Very interesting question and topic. Look forward to hearing the responses, as I've often wondered myself. Corals are very interesting critters.
  4. kcbrad

    kcbrad Giant Squid

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    I believe it's how the light rays are absorbed by the coral. Like how everything we look at is a different color because of how the light rays are absorbed/reflected by that particular object.

    I think?! I took a physics of color class in college, and I think that's what I remember! :)
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  5. tatted4ever

    tatted4ever Horrid Stonefish

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    some good food for thought... You may have to bump this quite a few times pg.

    youd almost have to be a marine bioligist to answer this
  6. Av8Bluewater

    Av8Bluewater Giant Squid

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  7. kcbrad

    kcbrad Giant Squid

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    Why are different things different colors?

    (Lansing State Journal, May 4, 1994)

    When different wavelengths of light hit our eyes, we see different colors.
    Light from the sun or light bulbs has many different wavelengths. This great mixture of wavelengths is commonly perceived as white. If the light hits an object - a road, tree, house, anything really - the object absorbs some wavelengths. Other wavelengths are reflected, and those are the ones we see.
    When an object absorbs all wavelengths to a great extent, it appears black. If it largely reflects all light, it appears white. Objects that absorb only a fraction of all the wavelengths appear colored.
    You can think of these phenomena in terms of the analogy: Light falling on an object is somewhat like rain falling on the ground. During a thunderstorm, some raindrops are quickly absorbed into the earth, but others hit so hard and fast they bounce off the ground.
    Different materials absorb different wavelengths of light. Things that absorb light in the visible spectrum are called pigments. The chemical structure of each pigment determines which wavelengths of light it can absorb, and which are reflected.
    Examples of pigments are: heme, which gives blood a red color; melanin, which gives skin a brown color; and chlorophyll, which makes plants green. Each of these compounds has a different chemical structure that absorbs different wavelengths of light, and thus, appear different in color.

    5/4/94 - Why are different things different colors?
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  9. stepho

    stepho Panda Puffer

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    I am in the middle of watching some DVDs I got at super target. It is a series that appears to be from the 70s or 80s and it is all about oceans, reefs, and stuff of that nature. There is an episode about the cleaner crew (cleaner fish/shrimps) and how they set up their cleaning stations on brightly colored coral heads to attract customers. They then did a test where they removed the cleaner fish from an area to see how it would be affected... well all of the fish moved away or got isopods and other parasites. The corals had started to decline as well. So maybe it has to do with cleaning stations. A coral colony doesn't stand anything to gain directly by being used by as a station by the cleaner fish, but it would benefit from a diverse population of fish that keep the algae down,eat reef predators, etc.

    Not sure how reasonable that is, just a guess really.
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  10. Dingo

    Dingo Giant Squid

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  11. inwall75

    inwall75 Giant Squid

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    It's not just in the zooxanthellae. Different species in different clades have different coloration but there's a lot more to it. In fact, if there are too many nutrients in an SPS system, your colorful corals will often turn brown as the zooxanthellae increases in numbers (sometimes to the point of poisoning the coral with too much Oxygen leading to a partial bleaching event). There are a lot of different proteins that make up color as well. Peridinen, Beta-Carotene would be the biggest. There's a lot to it.

    http://www.3reef.com/forums/coral/how-color-up-your-corals-71882.html

    EDIT: I GUESS YOU BEAT ME DINGO LOL
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  12. Dingo

    Dingo Giant Squid

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    the "natural" color of a coral is the color it reflects to attract the most beneficial zooxanthellae for its location.

    Im currently writing a term paper on this for micro 413 so if you want to know anything ill try and help... or else have any good articles for me to cite it would be much appreciated!
  13. pgreef

    pgreef Fire Goby

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    So my question really isn't what proteins or zooxanthellae or physics is involved in producing the colors. I'm more curious as to why they developed the proteins and zooxanthellae to take advantage of the physics of light to produce the dazzling colors?

    Stepho brought up an interesting explanation, that the bright colors serve as a sort of advertisement to other species that live in the reef community.
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  15. pgreef

    pgreef Fire Goby

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    So why am I looking at a favia in my tank that has both brown and green? Why does each polyp on my zoa have 2 to 3 colors? Why does one of my open brains have a green center with a bright red perimiter.? If it was based on light and depth you would expect all corals at a certain depth to be the same color and to be a solid color. (I'm not trying to argue by the way. Just asking questions.)
  16. pgreef

    pgreef Fire Goby

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    That would be an interesting read when it's all done. I hope you do well.
  17. Dingo

    Dingo Giant Squid

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    without making this too nerdy-like, i would say that our corals exhibit different colors at these specific places because there are different cells that take out different metabolic processes in the coral. For instance, the green in your favia is around the mouth, this particular type of zooxanthellae also has a UV photophosfluorescent pigment that is excited while the outter brown zooxanthellae part does not. Im taking an educated guess here but since it is around the mouth i think that it is to provide more energy to the direct area (aka feeder tentacles). Now if you look at the new growth on this favia, you will see that the new skin is clear until some zooxanthellae can host it.

    I can go deeper if you want but it will be a little more technical... you can pm me if you have more :]
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