Dear John,

That is a nice report.

I certainly agree with the idea that "variation that confers no
negative aspects" may allow for neutral traits to accumulate in the
genome of mollusks (and be expressed). However this process does not
proceed willy-nilly without constraints.

One bit of evidence against utterly random accumulation of traits is
the pattern of evolution witnessed in cave fauna. A huge variety of
organisms including FW snails, isopods, shrimps, whose ancestors were
certainly pigmented, characteristically and promptly (in geological
time) lose their pigmentation as well as their optical tissues as
they adapt to the stygian habitat. Certainly the pigmentation and
visual abilities are not a disadvantage to these animals - just
excessive baggage.

This process exemplifies the "use it or lose it" evolutionary
concept, which supports a sort of parsimony in the expression of
genetic traits - a sort of minimalism achieved by shedding (or not
expressing) genetic baggage not essential for biological prosperity.

Maybe there are more "ineffable" systems operative in the universe of
bio-pigmentation?

Harry


At 08:14 AM 11/28/2006, you wrote:
>The appearance of many insects and flowers is markedly different in
>the UV spectrum, largely because insects, birds and reptiles are
>capable of seeing in the UV range.  The resulting patterns are
>something which humans and other mammals cannot appreciate (without
>technical help) due to a lack of visual receptors.  (A recent
>article in Scientific American dealt with vision in the UV
>range).  Flowers, especially orchids, light up like elaborately lit
>airport runways at night in the UV, to guide insect
>pollinators.  Bugs have patterns in the UV that attract the opposite
>sex or deter predators.  Given the lack of molluscan visual acuity,
>and the rapid attenuation of UV light in water, why do some exhibit
>UV activity?  Some fish are exquisitely sensitive to electric
>fields.  Do the shape and patterning of some mollusks effect there
>"appearance" in an electromagnetic sense?  Is there some ineffable
>sense humans have yet to stumble across?  Or are these phenomenon
>just random?  My vote is for "random".
>I believe some evolutionary changes are not driven by positive
>adaptive benefit, but are mutational changes that persist because
>they do not negatively impact survival.  I believe much of the
>diversity in molluscan form and coloration is not positive
>adaptation, but just random (albeit beautifully fascinating)
>variation that confers no negative aspects.  And I grant that it is
>tough to prove a negative.
>- John Varner

Harry G. Lee, M. D.
4132 Ortega Forest Dr.
Jacksonville, FL 32210 USA
voice (904) 389 4049
email: [log in to unmask]
look at www.jaxshells.org

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