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About Shell Collecting

© Esther Wullschleger

There is an important aspect of shell collecting which should never be forgotten: The trade with animal products, such as shells, might lead to over-collection and threaten rare species. The number of shell carrying mollusc specimens which are entering the legal trade are, in a way, strikingly high: For example, in the years 1996 and 1997, Australia exported shells from totally 58,950 specimens covering 1,682 species of marine molluscs (these numbers were published by Winston F. Ponder and Jillian E. Grayson, Australian Museum, Sydney, June 1998). However, the Australian report states that habitat disturbance (particularly through some fishing methods like trawling and dredging, and through development in coastal areas or pollution) is a much more significant cause of decline of mollusc populations.

Certainly, the pastime of collecting shells can be a wonderful opportunity to enhance awareness of natural diversity, as long as rare species are excluded from collection. Rather than paying record prices for rare specimen remaining in the trade, a dedicated shell collector will also find much fascination in the more common types of these beautiful structures of nature. In any way, it is important (and interesting) to study guide books, try to determine the collected or purchased specimen to species, and learn about the creatures which formed the shells. Collections which extensively cover a certain area might even be beneficial to the scientific understanding of molluscs, if the collector bothered to carefully note down the location and time of each finding. The collecting details are important, because some species of snails and mussels show a high variability in shell form in dependence of environmental conditions. For example, the pond snail Lymnaea stagnalis varies strongly in shell form depending on where an individual was growing up. In a fast-flowing stream, individuals might develop a shell form which is different from that of their kin living in a slow-flowing environment. This might be the case even if they have exactly the same genes as the snails in the other environment.

This "plasticity" of shell form has led to confusion in the systematics and taxonomy of some groups of molluscs. At the beginning of last century, scientists studied the natural diversity of molluscs solely by collecting and describing shell forms as they were found in nature. They thought that each particular shell form would belong to a separate species. In extreme cases, early scientists described up to 40 "species", which later turned out to be variants of one species. Today, genetic analysis and breeding experiments have added to the picture and brought more clarification into the taxonomy of molluscs. But the study of shell forms is still important also in science. Many institutes and museums of natural history have large collections of molluscan shells, composed of recent and historic findings, some of which are shown to the interested public.

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