| |
Cowries
Family Cypraeidae |
|
| |
|
Miliaris
cowrie with mantle extended
|
Cowries produce among the most beautiful and highly prized shells.
One cowrie was even used as currency by Polynesians in the past; it
is called the Money cowrie (Cypraea moneta)! However, a living
cowrie is even more fascinating than an empty shell of a dead cowrie.
Two-in-One Shell: A young cowrie's
first shell is a narrow spiral. As it matures, it encloses this spiral
shell with a larger outer shell which has the typical cowrie shape
and slit-like opening with teeth. As the animal grows, the inner spiral
layers may be reabsorbed to make room for the larger animal and the
material reused to build a larger outer shell. A damaged shell appears
to be a shell within a shell, but it is really one continuous shell.
The shells of juveniles tend to be of one colour or banded. The full
colours and patterns usually only appear in the shells of adults.
Marvellous Mantle: When alive
and moving around, the cowrie usually encloses its shell with its
mantle (a part of its body). The mantle may have a different colour
and pattern from the shell and is often also 'textured' with tiny
projections. The fleshy mantle is a highly specialised organ. It is
the main architect of the glossy shell, as it lays down a layer of
pearl-like substances as well as the colour and patterns. It also
repairs and enlarges the shell and protects it from algae and encrusting
animals. This is why a cowrie shell is so shiny and smooth. When disturbed,
the entire mantle retracts into the shell.
Cowrie Food: As a group, cowries
eat a wide variety of things from algae, sponges to scavenging and
carnivorous cowries. Each has a radula adapted to its particular prey.
Most cowries live in the intertidal zone, hiding during the day and
emerging to feed at night. A cowrie has a pair of tentacles and a
siphon, which is part of the mantle modified for breathing and sampling
the water to look for food and mates.
Cowrie Babies: Some mother cowries
remain with their egg capsules until they hatch.
Human uses: Some cowries are popular
in the live aquarium trade. Cowries are among the most harvested snails
for the shell trade.
Status and threats: Recent estimates
suggest that half the cowrie species in Singapore have been lost.
For example, the Gold-ringed cowrie (Cypraea annulus) has almost
been wiped out. This small cowrie was previously found in large groups
on our rocky shores and reef flats. It has a narrow yellow band around
its greyish-white back. The Miliaris cowrie and Onyx cowrie are listed
among the threatened animals of Singapore. |
|
Onyx cowrie
Underside of cowrie showing 'teeth' of the opening
A pair of Miliaris cowries |
|
quick
facts
about 2 cm, common under rocks and sometimes in the seagrass
lagoon
Classification:
Class Gastropoda
Phylum Mollusca |
