Introduction to Seashells
The animal phylum of the Mollusca represents over 200,000 different species, which makes it the second biggest family in the animal kingdom, after the Arthropoda. The bivalves (e.g. clams and oysters), gastropods (coiled shells that we see on the beaches or snails found in gardens), and cephalopods (e.g. squids and octopus) are the most popular molluscan groups.
Molluscs are found in nearly every habitat, from the desert to the deep sea, from the tropical rain forest to the arctic shores. Their occurrence is an indicator for multiple habitat factors, and changes in the molluscan fauna reflect changes in their habitats. Therefore, the documentation and study of molluscs is a science that addresses threats to worldwide biotopes in times of over-fishing, deforestation, and climate change.
The molluscan animal produces a multitude of complex molecules, including toxins with medical properties. Every new species that is being discovered may yield a cure for some disease. Besides being objects of great beauty, seashells play an increasing role in material science and medical application. Their microstructure gives them great durability, although made of components (a protein and chalk) that, by themselves, are moderately soft.
Top left: Money Cowries were used as currency, e.g. in ancient China, since 2,500 B.C.E. Top right: The Giant Clam reaches 150 cm diameter.
Bottom left: the Geographic Cone has poinson barbs and highly efficient toxins. Bottom right: the Blue-ringed Octopus. Like the previous species, it has toxins that can kill a man.