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.