Micromollusc

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A micromollusc is a shelled mollusc which is extremely small, even at full adult size. The word is usually, but not exclusively, applied to marine molluscs, although in addition, numerous species of land snails and freshwater molluscs also reach adult size at very small dimensions.

These tiny molluscs or their tiny shells are easy to overlook, as many of them are not very noticeable to the naked eye, and thus many people are not aware that they even exist. Nonetheless there are large numbers of families and vast numbers of mollusc species, in particular marine gastropods or sea snails, which are minute enough to be considered micromolluscs.

Considerable numbers of marine gastropod species are only about 5 or 6 mm in adult size; many others are only about 2 or 3 mm in adult size; and a few have adult shells which are as small as one millimeter or even smaller still. Micromolluscs are known to have adult shells as small as 600 μm.^[1][2] Despite their tiny size, many of the shells have a good deal of elaborate sculpture. A fair number of them are even quite colorful, although many others are colorless and translucent.

Certain species of micromolluscs are very common in the right habitat, and can on occasion be present in huge numbers. However, because of their minute size, micromolluscs often go unnoticed by beachcombers, shell collectors and even more serious conchologists.

Micromolluscs are not very popular as a subject of study, even among professional malacologists, primarily because these minute species can be very challenging to work with.^[1] It can often require great care, patience and persistence to find micromolluscs, sort them, store them, and identify them correctly. Working with them usually also requires special techniques and special equipment compared with that needed for most of the larger shelled species. Discriminating the features necessary for successful identification of micromolluscs to the species level almost always requires a stereo or dissecting microscope. Identifying, or adequately photographing, the smallest species may sometimes require a scanning electron microscope. Access to a first rate scientific research library is also often necessary, since many of the popular shell identification books and field guides either omit micromolluscs completely, or only include a very few species for any particular area.

Because of all these various challenges, micromolluscs are poorly known compared to their larger relatives, and thus there are undoubtedly numerous species which have yet to be discovered and described.