Of the 200,000 species of molluscs living in the world today, only about 20 have such intrinsically beautiful shells that they captivate people at first glance. The Golden Cowrie (Lyncina aurantium) is one of these; an exotic and rare shell that instantly enchanted Europeans three hundred years ago when the first specimens were brought from the tropical Pacific Ocean with Captain Cook in July 1775.
Highly prized by shell collectors, an absolutely flawless specimen (called a ‘gem’ in the commercial shell trade) can fetch $2,000.
The Golden Cowrie shell can reach 110 mm in length, making it the second largest of all 270 species of living cowries. At 190 mm, the largest living cowrie is the Atlantic Deer Cowrie (Macrocypraea cervus), but that is eclipsed by an extinct (Cretaceous to Eocene geological epoch) cowrie species (Gisortia sp.) that exceeded 260 mm.
The Museum and Art Gallery of the Northern Territory possesses six Golden Cowries in its mollusc collection. The largest, and near-gem quality specimen (P.42845), came from the Philippine Islands. This specimen glows with the rich golden colour that characterises this species and it has hardly any ‘growth marks’ on its shell. Almost all the other cowrie species have patterns on their shells – contrasting spots or stripes – but the Golden Cowrie is unique in its uniform colour.
Nobody knows what evolutionary forces produced such simple yet striking colours on the shell. The animal that makes the shell lives deep inside caves on drop-offs below coral reefs during the day, and only emerges in the dark of night to feed. The animal, which completely covers its shell when it is foraging, is mottled brown with dozens of little white swellings like little hands, so is incredibly well camouflaged. Only when touched, does the animal withdraw the fleshy organs (called the mantle) that produce and protect the shell to reveal the golden colour underneath. The animal continually polishes it shell, so its shine is natural.
The smallest Golden Cowrie shell in the MAGNT collection (P.27328) has an interesting history. It comes from the Solomon Islands. It must have tumbled accidentally onto the sandy sea floor below the rock wall where it had been living and feeding. Since the architecture of their shell prevents cowries from righting themselves, it would have died where it fell. A long time later when the shell had lost its colour and shine, a diver found it and offered it for sale at the Honiara market for just one Solomon dollar. It must be the only Golden Cowrie in the world to have been traded so cheaply!
Although not a single Golden Cowrie has ever been found in Australian waters, there is a possibility that it could be living on one of the unexplored shoals in the Arafura Sea immediately north of the Top End. A much rarer Pacific cowrie, the White-toothed Cowrie (Lyncina leucodon), was found there by a diver last year. Just imagine how exciting it would be to discover the first Golden Cowrie in Australia!