learn only 3 things about them ...
Oysters take a long time to grow to a large size.
Valuable pearls do NOT come from the Family Ostreida.
Oysters are often vandalised by thoughtless visitors.
can cause food poisoning.
seen? Among our favourite seafood, oysters are often over-collected
on some of our more accessible shores. Sometimes, they are merely
vandalised by thoughtless visitors. They are common on the rocks and
other hard surfaces of many of our shores.
What are true oysters? True oysters
belong to the Family Osteridae.
Features: The two-part shell is
thick and chalky. In true oysters, the left valve is glued firmly
to a hard surface. What we see is the right valve. A layer of barnacles
and algae often eventually develops over the right valve so that the
oyster becomes hard to distinguish from the rock. Some oysters have
spikes on this valve, probably to deter predators such as drills.
Other bivalves usually have a foot, to dig with or move about. Being
immobile as adults, oysters have lost their foot.
It is hard to distinguish oyster species by their shell shape alone.
Their shells can take different shapes depending on the conditions
they live in. They are usually identified by internal features of
the shell and animal. On this website, they are grouped by external
features for convenience of display.
Sometimes mistaken for limpets
Here's more on how to tell apart shelled
animals found on the rocks.
What do they eat? Like
most other bivalves, oysters are filter feeders.
When submerged, an oyster opens its valves slightly and sucks in a
current of water. It uses its enlarged gills to sieve food particles
out of this current. When the tide goes out, it clamps up the valves
tightly to prevent water loss.
Oyster babies: Oysters may produce
eggs or larvae. Some species may change gender while others are simlutaneous
hermaprodites being predominantly male or female depending on the
temperature of their environment and availability of food.
Human uses: Oysters are relished
by people everywhere as a delicacy. They are also believed to have
aphrodisiac properties in some cultures. Like other filter-feeding
clams, however, oysters may be affected by red
tide and other harmful algal blooms when they are then harmful
Oysters have been farmed for centuries. Basically, young oysters are
kept in cages or mesh bags and left in the sea until they were large
enough for market. It is believed that farming oysters for their flesh
happened together with farming them for their pearls.
Valuable pearls are found in only a small group of oysters. While
other kinds of oysters (and even snails) may produce pearls, these
are often not pretty enough to be of commercial value. So please DO
NOT vandalise our oysters in the vain hope of finding a valuable pearl.
Status and threats: None of our
oysters are listed among the threatened animals of Singapore. However,
like other creatures of the intertidal zone, they are affected by
human activities such as reclamation and pollution. Trampling by careless
visitors and over-collection can also affect local populations of
young clams. Oysters on disturbed shores are often vandalised by thoughtless
Oysters often form a distint band
on hard surfaces near the high water mark.
Chek Jawa, Jan 08
All kinds of different animals
may settle among the oysters.
Chek Jawa, Jan 08
barnacle growing on an oyster.
St. John's Island, May 10
Ostreidae recorded for Singapore
Siong Kiat and Henrietta P. M. Woo, 2010 Preliminary Checklist
of The Molluscs of Singapore.
are difficult to positively identify without close examination.
On this website, they are grouped
by external features for convenience of display.
Pretostrea rosacea=^Dendostrea rosacea
Saccostrea cuccullata (Spiked
- Tan Siong
Kiat and Henrietta P. M. Woo, 2010 Preliminary
Checklist of The Molluscs of Singapore (pdf), Raffles
Museum of Biodiversity Research, National University of Singapore.
- Katherine Lam and Brian Morton. 31 Aug 2009. Oysters (Bivalvia:
Ostreidae and Gryphaeidae) recorded from Malaysia and Singapore.
Raffles Bulletin of Zoology 57(2): Pp. 481-494.
- Tan, K. S.
& L. M. Chou, 2000. A
Guide to the Common Seashells of Singapore. Singapore
Science Centre. 160 pp.
- Wee Y.C.
and Peter K. L. Ng. 1994. A First Look at Biodiversity in Singapore.
National Council on the Environment. 163pp.
- Ng, P. K.
L. & Y. C. Wee, 1994. The
Singapore Red Data Book: Threatened Plants and Animals of Singapore.
The Nature Society (Singapore), Singapore. 343 pp.