Re: helicostyla color change when wet.

I've heard (don't remember from where) that the adaptive significance of
being darker when wet and lighter when dry is for camouflage(sic).
When the shell is wet, it is darker and blends in with the darker soil, etc
around it. When the shell is dry, it lightens in color to blend in with
lighter-colored surroundings. Anyone have more references to this?

Peter Egerton,
Vancouver, Canada (where shells would always be wet and dark!)


At 03:58 PM 5/11/00 -0500, you wrote:
>Let me add a point about Helicostyla, at least most species.  The
>periostracal bands are called hydrophanous lines.  The periostracum is
>structured differently on the bands than off.  When the shell gets wet, the
>bands all but disappear.  Wet one and see for yourself, then blow on it
>until it dries.  It's pretty cool.  The adaptive significance of this is
>unknown, as is how the periostracum is put down.  Why would it be
>beneficial to be somewhat unicolored in the wet season?  Or is this some
>byproduct of something else we haven't even noted yet?
>
>A few camaenids share this character.
>
>Anyway, when storing or particularly displaying Helicostyla do NOT polish
>them up with oil, etc.  You'll end up with nice shiney shells that look
>totally different than it should.....no lines.  I've seen it happen to
>exhibitors.
>
>Kurt
>
>>specimen of the large, beautiful emerald green Helicostyla portei, if placed
>>in bleach for half an hour, will come out as white as an Ovula ovum.
>>Placostylus hargreavesi has a beautiful, intricate pattern pre-bleaching;
>>pure white afterwards.  Incidostoma confusum, a big operculate land snail
>>from South America, is light brown above, dark brown below - until
>>bleaching.  Then it is pure white, with a pink apex.  Likewise for many
>>other land shells.  Helicostyla pan is multi-banded before bleaching.  After
>>bleaching it is three-toned, white, tan, and chocolate brown, but with no
>>banding at all.  Some Chysallis species have both axial and transverse
>>markings.  After bleaching, tranverse bands only.  The pretty axial markings
>>are in the periostracum.  So proceed with caution!
>>Paul M.
>>
>
>
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Peter Egerton, Vancouver, Canada
Collector of worldwide Mollusca,
lifetime student of zoology and computers.
Step into my website:
http://www.intergate.bc.ca/personal/seashell/index.html
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