Hi Conch-L'ers,
I have sent some of the comments to a friend of mine who is doing a research project on colour in shells. He is not a member of the list, should you wish to correspond with him directly, find his e-mail address at the bottom of the page.
Regards Kobie du Preez
*************************
Shades of yellow, orange, maroon (warm autumn colours) I have found to be
carotenoids. Same chemical family as beta-carotene. Some purples (and even
browns and blacks) are also carotenoids. They have some minor structural
differences on their terminal ends. Correct, some reds and purples are
because of the anthocyanins, and it is postulated that the greens come from
porphyrin-type structures. Have never encountered or read that colour come
from salt/mineral sources, but the iridescent/pearly show of colours (such
as in the abalone family) are not because of a true pigment, but because of
a structural packing of the CaCO3 layers in the aragonite form, containing
H2O. A good book on natural pigments in the animal kingdom is by D.L. Fox
'Animal Biochromes and Structural Colours', Cambridge, 1953. Not very
extensive on specifically shell colours, but still a good read. Another
possible source of blues/purples are the indigoid pigment family, but not
yet confirmed except for the 'internal' colouring agent from M. brandaris's
and hexaplex's hypobranchial gland used in ancient times for purple cloth
dying by the Greeks/Romans.
Colouring of the soft tissue of molluscs have been extensively studied, also
mainly found to be carotenoids (Astaxanthin, canthaxanthin). With the
carotenoids, it is true that the carotenoid is complexed with a protein in
the shell matrix/soft tisue, and upon extraction the carotenoid's colour
might even change due to decomplexation. It is fascinating!
Werner Barnard
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<DIV>Hi Conch-L'ers,</DIV>
<DIV> </DIV>
<DIV>I have sent some of the comments to a friend of mine who is doing a
research project on colour in shells. He is not a member of the list, should you
wish to correspond with him directly, find his e-mail address at the bottom of
the page.</DIV>
<DIV> </DIV>
<DIV>Regards Kobie du Preez</DIV>
<DIV> </DIV>
<DIV>*************************</DIV>
<DIV> </DIV>
<DIV>Shades of yellow, orange, maroon (warm autumn colours) I have found to
be<BR>carotenoids. Same chemical family as beta-carotene. Some
purples (and even<BR>browns and blacks) are also carotenoids. They have
some minor structural<BR>differences on their terminal ends. Correct, some
reds and purples are<BR>because of the anthocyanins, and it is postulated that
the greens come from<BR>porphyrin-type structures. Have never encountered or
read that colour come<BR>from salt/mineral sources, but the iridescent/pearly
show of colours (such<BR>as in the abalone family) are not because of a true
pigment, but because of<BR>a structural packing of the CaCO3 layers in the
aragonite form, containing<BR>H2O. A good book on natural pigments in the
animal kingdom is by D.L. Fox<BR>'Animal Biochromes and Structural Colours',
Cambridge, 1953. Not very<BR>extensive on specifically shell colours, but
still a good read. Another<BR>possible source of blues/purples are the
indigoid pigment family, but not<BR>yet confirmed except for the 'internal'
colouring agent from M. brandaris's<BR>and hexaplex's hypobranchial gland used
in ancient times for purple cloth<BR>dying by the
Greeks/Romans.<BR><BR>Colouring of the soft tissue of molluscs have been
extensively studied, also<BR>mainly found to be carotenoids (Astaxanthin,
canthaxanthin). With the<BR>carotenoids, it is true that the carotenoid is
complexed with a protein in<BR>the shell matrix/soft tisue, and upon extraction
the carotenoid's colour<BR>might even change due to decomplexation. It is
fascinating!<BR><BR>Werner Barnard</DIV>
<DIV><A href="mailto:[log in to unmask]">[log in to unmask]</A></DIV>
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