Color Differences Within Species

Mike Matz matz at whitney.ufl.edu
Wed May 2 02:02:37 EDT 2001


  Hello Tom,
Origins and maintenance of color polymorphism in corals is precisely what I am
studying now. However, I am only studying colors determined by GFP-like
fluorescent proteins, because in this case the tools of molecular evolution
are easily applicable. Of course there are lot more things determining the
coral color  (by the way, I always have trouble with this expression when I
give talks, because these two words always mix up, and I don't know how to say
it otherwise, your suggestion would be most welcome) - OK, there are lot more
colorful things in corals except GFP-like proteins, pigments of symbiotic
zooxantellae  for one - these which make the coral look a more or less
uniformly brownish.  If  zooxantellae are expelled from the coral tissue due
to some environmental stress, most corals appear dull white ("bleached").
Carotenoids in the host tissues may be responsible for more or less uniform
yellow-orange hues, like in many sea anemonies. However, it is with GFP-like
proteins where you can see the greatest color variations. They may determine
green, yellow, orange and red fluorescent colors and purple to blue
non-fluorescent color in hard corals and sea anemonies, and the intra-specific
variations may include specimens having any of these or combining any of
these. We still don't quite know what is the function of proteins of different
colors, and even less (nothing, basically) is known about forces maintaining
such a polymorphism. As for the function, a good case has been made for green
fluorescent colors - see Salih et al, 2000, Nature v 14, p 850-3 - that they
are serving as a reflection mirror for zooxantellae: position them above the
zooxantellae level, and you get protection from excessive light, position them
below - and you get a reflection screen for enhancing photosynthesis in the
low-light conditions. Things are less clear for orange and red colors - they
cannot be nearly as good for this function as greens since their
excitation/emission range lies rather outside of the  action spectrum of
zooxantellae photosynthesis; and totally unclear is the function of
non-fluorescent purples and blues found in tentacles of sea anemonies which in
some cases don't even have zooxantellae.
  So, after writing all this, I have to answer your question - I don't know.
Sorry. I am working on this.

Mike

--
Mikhail V. Matz, Ph.D.

Whitney Laboratory
University of Florida
9505 Ocean Shore blvd
St Augustine FL 32080-8610, USA
phone +1 904 461 4044
fax +1 801 849 5388
 
 

tom h gray wrote:

> Greetings-
>         I am a graduate student at Texas A&M at Corpus Christi.  I plan to
> complete an internship for a M.S. degree in Mariculture this summer.  I
> have a question concerning color of corals.  Why do corals within the
> same species have different colors?  For example, variations of Sinularia
> sp. or Sarcophyton sp. are commonly observed to be green, brown, white,
> yellow or many other colors.
>         Any feedback would be greatly appreciated!
>
> Thanks
> Tom Gray
> ~~~~~~~
> For directions on subscribing and unsubscribing to coral-list or the
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--
Mikhail V. Matz, Ph.D.

Whitney Laboratory
University of Florida
9505 Ocean Shore blvd
St Augustine FL 32080-8610, USA
phone +1 904 461 4044
fax +1 801 849 5388
 

~~~~~~~
For directions on subscribing and unsubscribing to coral-list or the
digests, please visit www.coral.noaa.gov, click on Popular on the
menu bar, then click on Coral-List Listserver.



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