Many freshwater mussel shells are actually quite pliable when wet (Leptodea, Pyganodon, etc.) but become brittle when dried. Many often fracture with changes in humidity. As stated before, this seems to be a case of too little shell and too much periostracum, which contract at different rates and degrees when dried. If the shell is more sturdy, the periostracum may peel off. Or, if the periostracum is more sturdy, it can break the underlying shell when it contracts.


G.Thomas Watters, PhD
Curator of Molluscs
Department of Evolution, Ecology & Organismal Biology
The Ohio State University
1315 Kinnear Rd.
Columbus, OH 43212  USA
v: 614-292-6170
f: 614-292-7774

----- Original Message -----
From: Tom Eichhorst <[log in to unmask]>
Date: Monday, June 25, 2007 1:21 pm
Subject: Re: Do shells become more solid when they are dried ?

> He Jing,
>
> Clithon coronatus (Leach, 1815) is a small dark nerite with
> extremely long
> spines.  In life these spines are flexible and bend backwards (in
> referenceto the snails direction of travel) in order to allow the
> snail to burrow
> under rocks and bottom detritus.  If the shell is collected and
> dried out,
> the way most of us encounter it, the spines are quite brittle with
> littleflexibility.  Part of the reason for this appears to be the
> structure of the
> spine itself, it is mostly made up of periostracal material.  I
> know this is
> a bit different from your frilly morum, but I believe it may be
> related.Studies have shown periostracal material, or conchiolin,
> is a fibrous
> insoluble protein that forms the organic basis or structure of the
> shell by
> cementing together the calcium carbonate crystals (aragonite and
> calcite) as
> well as forming the outer protective covering or periostracum.
> The amount
> of conchiolin in the mostly calcium matrix is very small, but it
> might vary
> with more or less amounts in different areas and shell structures.
> This
> means it could conceivably be more prevalent in the morum frills
> and thus
> account for a flexibility in life that disappears when the shell
> is dried.
> I offer this as a possible theory, not a fact.
>
> Tom Eichhorst
>
> -----Original Message-----
> From: Conchologists List [[log in to unmask]]On Behalf Of
> He Jing
> Sent: Monday, June 25, 2007 6:15 AM
> To: [log in to unmask]
> Subject: Do shells become more solid when they are dried ?
>
>
> Hi
>
> i have a experience. i collected many morum shells, the wrinkles
> on ther
> surface were very fragile when they were taking out of sea, but
> they became
> very solid after one month when they are cleaned and  dried.
>
> i have the same expericnce when i collected some landsnails.
>
> i don't have scientific instrument to test it . do shells become
> more solid
> when they are dried?
>
>
> He Jing
>
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