I was sloppy with my mention of "quantum physics." I meant that the organism
grows in quantal stages. I assume that once it decides to add a varix, it is
commited to growing until the new varix abuts the prior one (a two-thirds
turn). It probably can't stop half way, make a varix, and be in an viable
form (for example, the new siphonal canal would stumble on the lastone). A
snail with an indeterminate shell can just keep growing continuously; there
are no decision points in the individual's development.

It's interesting to ponder how the evolutionary leap was made from
continuous, indeterminate growth to determinate growth of cowries and what I
think of as the semi-determinate, fractal, quantal growth of cassids --
assuming that evolution proceeded in that direction.

I collect lepidoptera, and I can see in conchology the same sort of
variation on a theme -- with some fantastic outliers -- that makes looking
at butterflies so appealling.

Harry, thanks for supporting this little amateur investigation of mine. You
all have a good thing going. Might be time for me to start a second collection!

Brian

(now a graphic/information designer in NYC, but once a biochem student)




On Tue, 3 Apr 2012 11:09:44 -0400, Harry G. Lee <[log in to unmask]> wrote:

>In nature, growth in /Cassis tuberosa/ seems to vary by no more than one
>varix.
>
>The effect of environmental forces on maximal growth has been
>demonstrated in species as diverse as/ Strombus gigas/ (mariculture;
>dwarfism) and trematode-infected FW snails (gigantism).
>
>The heaviest of pelecypod ("bivalve") shells are sedentary (nowadays and
>in the fossil record).
>
>I can't comment on the relevance of quantum physics.
>
>Harry
>
>
>On 4/1/2012 10:37 PM, Brian Wu wrote:
>> Harry, thanks very much for the excellent explanation of an amazing natural
>> process.
>>
>> The final paragraph of your reply refers to the "final varix." Are you
>> saying that the number of varices is predetermined (determinate)? That at
>> some point the animal doesn't try to grow its shell any further because
>> somehow it knows that it cannot because doing so would result in some
>> insupportable imbalance between factors such as the volumes of the cavity
>> and living tissue, locomotive power vs the mass of the shell, shell
>> accretion potential, etc.?
>>
>> I intuit that snails with indeterminate growth hit some sort of mathematical
>> limit in size, but that the demands of growing varicate shells are extreme
>> and that there is some quantum physics of sorts at work.
>>
>> By the way, now that I have the vocabulary, I found another post on CONCH-L
>> about intervarical specimens
>> http://www.listserv.uga.edu/cgi-bin/wa?A2=ind0312d&L=conch-l&D=0&P=6166 and
>> attributes their rarity (at least in some species) to collector bias.
>>
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>
>
>--
>Harry G. Lee MD
>4132 Ortega Forest Drive
>Jacksonville, FL 32210-5813
>USA
>(904) 389 4049
>[log in to unmask]
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>
>

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