I agree that the complex crystalline structure of the calcium carbonate that makes up the bulk of the shell probably has a marked effect on the perceived color of the pigments, like a grate or complex filter as you point out. Perceived colors such as green or yellow could be the combined visual effect of more than one pigment molecule. Pigments are deposited in a matrix of proteins, some of which may fluoresce or influence the color of the pigment fluorescence. A number of color-fluorescent proteins have either been developed in the lab or isolated from Nature.
The usual dark brown to black color of some shells appears to be likely the polymeric pigment melanin, which does not fluoresce under UV. Other pigments that have been studied include polyenes (similar to the beta-carotene found in carrots etc) that are yellow-orange & pheomelanin (a red polymer also found in red hair). A pigment called biliverdin is green. I believe all of these pigments could fluoresce under UV.
I am going to look into UV laser pointer-type devices as their price from China has dropped significantly & they are available in many different wavelengths.
--------------------------------------------
On Sun, 5/21/17, Martin <[log in to unmask]> wrote:
Subject: Re: [CONCH-L] UV (black light) radiation on cone snail shells
To: [log in to unmask]
Date: Sunday, May 21, 2017, 9:34 PM
Another reason for wavelength is physical size of
'feature'.
Somewhat like a grate or complex filter.
Some filtering surfaces absorb and some reflect.
And by using
unique light might discover some of this as well.
Rocks have fluorescence in short and long UV and
color in 'human'
or optical light. Some fluorescence is present only
upon
illumination while some take just enough to start them
off and
they last a long time.
(might find UV Lasers in the rock stores / on-line
places )
Some of the latter are radiation rich materials.
Remember the
Watches that glowed all night ?
Now the watches last for a short hour or less. We
kill less
watch painters now...
I wonder what the local chemical mixture determines
the color of
a shell. Some might effect the snail itself making
some
difference. Some might be chemical changes in the
shell
materials.
Martin
On 5/21/2017 7:53 PM,
Jack Sullivan
wrote:
It's
an interesting
area for exploration for a number of reasons. For
one, the
color of the autofluorescence may provide a marker
indicative
of the types of pigment molecules forming each
pattern,
information which might provide a taxonomic link
between
shells from different species. For two, the
wavelength of the
UV light that produces the autofluorescence may
provide a
second identifying marker.
I'm
also interested
in exploring the inexpensive UV laser pointers
available from
China. These are available in dozens of UV
wavelengths. While
standard commercially available UV lamps produce
either short
(254nm) or long (366nm) radiation, gastropod shell
pigments
have been investigated that autofluoresce at 433,
543 &
633nm. As current thought is that pigment
molecules are
deposited in matrices of many different proteins
such as
enzymes, autofluorescence might be seen in shell
areas that
are not visibly pigmented. The fine beams of the
laser
pointers could be likely used to explore the
minute details of
a shell's surface in a manner that might yield
more
information than might be found by irradiating the
entire
shell with conventional UV tubes.
From:
David Campbell <[log in to unmask]>
To:
[log in to unmask]
Sent:
Sunday, May 21, 2017 8:20 PM
Subject:
Re: [CONCH-L] UV (black light) radiation
on cone snail
shells
UV has been used most
often on
fossils where the color patterns have
faded, but
remains of pigment fluoresce and give
evidence of
the original patterns. The various
pigments may
produce some notable fluorescence
patterns, but
the patterns from pigments generally
also are
visible without UV in modern shells.
On
Sat, May 20, 2017 at 9:03 PM, Jack
Sullivan <[log in to unmask]>
wrote:
Rather than resurrect a
thread here
dating back 9 years, I
thought I'd
take a fresh look at this
topic.
There
is a lot of literature
going back 50
years or so on the use of
UV light to
cause the faded shell
pigments in
fossil cones to fluoresce.
Does anyone
here have any first-hand
experience
with the results of
irradiating modern
cone shells with near or
far
wavelength UV light?
From
a technical POV, many of
the chemicals
that make up cone snail
pigments
should fluoresce, such as
the
porphyrins, the so-called
bile
pigments (bilins),
biliverdin, etc. A
recent study of
Clanculus
spp.
(Trochoidea:Gastropoda) gave the
result of one porphyrin
pigment
fluorescing pink-red &
the other
yellow-brown. It was also
stated that
the occurrence of the
various shell
pigments varies on an
apparently
taxonomic basis, which is
of interest
to me.
I'm
considering buying a 2
wavelength
handheld UV lamp but
wanted to hear of
the experience of others
with this
first.
Thanks
in advance!
Jack
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