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Gems of the sea - Cowries

Green Country Vol. 114 (Jun 2015)

In Chinese characters, words such as “treasure”, “money”, “fee”, “expensive”, “buy” and “sell” all contain the radical “shell”. Shells were used as a currency for trade in bygone days. Today, a uniquely patterned cowry may be priced at HK$100,000. Cowries are indeed timeless gems.

Cowries belong to Discopoda, Gastropoda of Phylum Mollusca. Currently over 200 species of cowries are known from tropical and subtropical waters. Most are found on tidal flats, rocky or in coral reef in shallow waters; though some live on the deep sea floor. In Hong Kong, there are more than 20 species of cowries.

Cowry shells are oval with an arched back. They vary in size, from a few millimetres to over 150 millimetres long, depending on species. The head, internal organs and foot are all hidden in the shell most of the time. When moving, the foot stretches from the narrow aperture on the underside to crawl along. Cowries are nocturnal and feed at night on algae, sponges and decaying organic matter.

Lucky charm

Cowry shells are highly ornamental, with mellow texture and variegated patterns and colours. The smooth and glossy shell is wrapped by a mantle that prevents algae from growing on it and secretes calcium carbonate to keep the shell growing, with a sheen.

The tiny shell has played an important role in human life and culture since ancient times. In Japan, cowry is also known as “child wellness shell”, and an old practice was to put one into the hands of a woman delivering a baby, for the safety of both mother and child. In ancient China, Money Cowrie (Cypraea moneta) was used as the currency for trade. Some deep sea species are highly valued and have become collectibles for their rarity and special patterns. Fulton Cowrie (Cypraea fultoni) of East Africa was once priced at USD15,000 (HK$120,000). Complete specimens of less rare cowry species can also cost over a thousand US dollars (HK$8,000).

Text|Linda Yip

Image
© Peggy Chung
Image
© Rainy Chan
In Hong Kong, most cowries are found in shallow waters.
Image
© Peggy Chung
There is a narrow aperture in the underside of a cowry.
Image
© Rainy Chan
Coral reef is a major habitat of cowries.
Image
© Peggy Chung
Caurica Cowrie (Cypraea caurica) is one of the cowry species found in Hong Kong.

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