Thursday    March 25, 1999    05:54 PM
 
Dear Paul,
 
I'm always happy to read your messages. The
answer to my last one was the most I can hope
from you. I knew that you have many things to
teach to me.
 
You wrote :
the number and shape of the nuclear whorls,
the nature of the first teleoconch whorl,
the width and depth of the suture,
the nature of the intrasutural callus,
the overall nature of the slope of the spire (concave or convex).
 
I use a professional stereomicroscope (ZEISS, with a
camera, too) to look at the nuclear whorl but how can I
measure the width and depth of the suture ?
 
You wrote:
there is another species, Oliva scripta, that usually occurs
side by side with the Oliva "fulgurator-reticularis", that is
one of the most constantly shaped and colored species of
Oliva that I have ever seen.
 
If you well think Oliva scripta is the only one in the Caribbean but in
the Pacific Coast live Oliva porphyria which occours side-by-side
with the highly variable Oliva spicata.
 
You wrote:
Anybody have any ideas why the two species would evolve with
divergent growth patterns when they occur basically side-by-side
in many cases in the same ecosystem?
 
About your question I think that it depends on how long time their
larvae are pelagic. Probably the scripta's and porphyria's larvae
are able to travel for many days before they become benthonic.
What do you think about this?
 
You wrote:
Oliva reticularis (in the Caribbean and down the east coast
of South America) and Oliva spicata (in the Panamic Province)
are two examples of highly variable species which are also probably
related prior to closure of the seaway across southern Central
America during Tertiary times.
 
The fact that both spicata and reticularis forms many different but
homogeneous populations seems further to validate that theory.
 
You wrote:
A) I believe that color has a lot to do with what metals/organics
are available in the sediment.
B)On the other hand, it points out the problems with variability
within in a species of Oliva depending on the local ecosystems.
 
I fully agree with the point A) but I'm doubting about B).
I don't think that the Olives become darker whether they live
on dark substratum with the purpose to camouflage theyself.
If we consider, for example, Oliva spicata fuscata, the darker
between the spicatas, the animal is yellow. This color is
very visible while it is moving on a dark substratum.
On the other hand a dark shell is useless when the mullosk
stands still because it is hidden under the sand.
 
Paul, many thanks again for your invaluable information !!
 
All the best, Maurizio.
 
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