Paul will probably give a more detailed reply than this but remember when
you are boiling shells to put them in cold water and then bring the water to
a boil. Don't drop them into boiling water. When I did this to some big
moon snails I collected it resulted in cracks along the lip edge which then
broke when I tried to remove the animal. And it's hard to find nice big
moon snails here in Maine. :-((
Beth
[log in to unmask]
-----Original Message-----
From: Jose Eduardo de Alencar Moreira <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: Thursday, January 07, 1999 8:45 AM
Subject: [CONCH-L] RES: Stinking Astraeas
>Paul,
>
>Many thanks for your reply. I understood much better what is originating my
>stinking problems.
>
>Just two more questions. Some shells can be boiled and others (like
cowries)
>can't. What shells sould not be boiled? What do you suggest to avoid or
>minimize these reeky problems in shells that can't be boiled or if you are
>in a trip?
>
>Cheers,
>
>Eduardo
>
>
> ----------
> De: Paul Monfils [SMTP:[log in to unmask]]
><mailto:[SMTP:[log in to unmask]]>
> Enviada em: Quarta-feira, 6 de Janeiro de 1999 19:26
> Para: [log in to unmask] <mailto:[log in to unmask]>
> Assunto: Re: [CONCH-L] Stinking Astraeas
>
> Hi Eduardo et al,
> Most of us have probably encountered certain lots of shells, or at
> least individual specimens, that were memorably malodorous. I have
> not noticed that any shells smell much if cleaned promptly after
> collecting. So, optimal handling will usually prevent odor
>problems.
> However, travel and vacation plans often preclude ideal handling
of
> collected materials; and I assume you are speaking of shells in
this
> category, which have hung around unrefrigerated for several days or
> more before cleaning, a situation that many of us have likely
> encountered.
> As long as the animals remain alive, no unpleasant odors usually
> develop. Some species may survive a couple of days in a collection
> bucket, if kept in a relatively cool area. Some may survive a week
> or more if refrigerated. But sooner or later the critters are
going
> to expire. In the trunk of a car on a hot summer day this will
>occur
> sooner - much sooner! In any case, as soon as they give up the
>ghost,
> two processes start to occur. First, enzymes and other substances
> that were kept under control in the living molluscan cells are
> suddenly released, and begin to digest the tissues from within, a
> process known as autolysis. Secondly, microorganisms (primarily
> bacteria) which were also kept at bay by the various chemical
> defenses of the living animal, start to proliferate, feeding on and
> invading the dead tissues, a process known as putrefaction. Both
> these processes result in the breakdown of cellular components into
> simpler chemicals. The properties of a substance often differ
> markedly from the properties of its component substances (for
> example, the salt we sprinkle on our food is composed of an
> explosively reactive metal and a poisonous gas). Therefore, when
> non-odoriferous substances decompose, some of the resulting
>breakdown
> products may be extraordinary malodorous.
> The intensity of the odor depends on several factors, including the
> volume of tissue involved, the rate and extent of decomposition,
the
> specific organic compounds present in the tissue, and the identity
>of
> the microorganisms responsible. Of these four, we have no
influence
> over the last two, so our odor-control efforts have to be focused
on
> the first two. The first point is, I think, self-evident. All
>other
> factors being equal, a big snail rotting in a bucket will smell
more
> than a small snail rotting in a bucket. Also, a shell with half
the
> soft parts left inside will smell more than an identical shell with
> 90% of the tissue removed. However, the present discussion
involves
> those times when it not possible to remove the soft parts from the
> shell promptly. In such cases, preventing the production of
> odoriferous substances means preventing autolysis and putrefaction.
> Both the enzymes of autolysis and the organisms of putrefaction
> require certain physical conditions in order to be active, most
> notably the presence of water and a suitable temperature; therefore
> both processes can be prevented or arrested by removing one of
these
> necessary elements. If the tissue is thoroughly desiccated before
> odorous compounds have a chance to develop, then such substances
>will
> not develop as long as desiccation is maintained. This method is
> often used with very small gastropods. Water is removed either by
> alcohol extraction or simply by drying them in the sun or in a low
> temperature oven, and the resulting specimens are virtually
>odorless.
> However, if such specimens are exposed to moisture, then bacteria
>and
> fungi (as well as other organisms such as mites) may eventually
>break
> down the tissues. Many collectors are familiar with old specimens
> containing a sawdust-like residue of slowly decomposed tissue. Due
> to the very gradual rate of decomposition, this does not produce
any
> noticeable odor. Also, collectors working with old shells have
> probably found specimens which "rattle" when you shake them, due to
>a
> chunk of shrunken, "mummified" tissue which has not decomposed in
> fifty years or more, because the shell was stored in dry
conditions.
>
> Alcohol retards autolysis and putrefaction not only by extracting
> water from tissues, but also by denaturing and inactivating
enzymes,
> and by killing many kinds of microorganisms on contact. However,
if
> I may state the obvious, it produces these effects only in tissues
> that are in direct contact with it. Unfortunately, the tissues of
a
> gastropod mollusc are encased in a long, impenetrable tube of hard
> calcium salts (a gastropod shell is essentially a tube of gradually
> increasing diameter, wound around a central core, and a 4 inch
Turbo
> shell, if "unwound", might be a foot in length). Alcohol can enter
> the shell only through the aperture; however, the soft parts of the
> animal extend all the way to the apex. Therefore, when a gastropod
> shell more than a few centimeters in length is placed into alcohol,
> the fluid usually doesn't reach the tissue in the upper whorls.
> After a few weeks' storage, when you remove the shell for cleaning,
> what you find is a well-preserved, rock-hard foot (alcohol hardens
> muscle greatly) which may be difficult to remove from the shell,
> followed by a slimy, foul smelling mass of decomposed organ
tissues.
> Except for very small specimens, all you can say about alcohol as a
> temporary storage medium is - better than nothing!
> A more reliable approach, when possible, is the use of temperature
> extremes. Boiling the shell with its enclosed soft parts, as
>someone
> already mentioned, greatly retards the development of odors. This
>is
> because a temperature of 100' C (212' F) permanently deactivates
> enzymes, and also kills most microorganisms. Once boiled, shells
>can
> be refrigerated for a couple of weeks without odor, or placed in
> alcohol indefinitely without additional tissue changes taking
place.
> (However, the soft parts are easier to remove immediately after
> boiling, while they are still warm.)
> Freezing the fresh specimens is also a good method of long-term
> storage for eventual cleaning. However, this method does not
> permanently denature enzymes, nor does it kill many
microorganisms -
> it only inactivates them while they are frozen. In addition, the
> freezing/thawing does extensive microscopic damage to the tissue
> cells, and causes a certain amount of tissue breakdown in and of
> itself. As a result, such specimens, once thawed, should be
cleaned
> promptly, as autolysis and putrefaction can set in quickly.
> Personally, I have not noticed that particular species or genera
are
> more prone to disagreeable odors than others. I believe it has
more
> to do with methods of handling than with taxonomic relationships.
> However, some groups of molluscs tend to be smelly because their
> shell shape or structure makes it difficult to remove all the soft
> parts. And, it is not inconceivable that some families of molluscs
> might possess specific proteins with particularly odoriferous
> breakdown products, not present in other families. There is one
> other good reason to avoid tissue decomposition before cleaning -
> some breakdown products of organic compounds are acidic, and may
> dissolve the shell, especially the relatively thin spire, from the
> inside. Or, if they trickle out of the aperture onto a glossy
> columella, they may cause permanent dull, discolored, or pitted
>areas
> on that part of the shell.
> Regards,
> Paul M.
>
|