bivalves text index | photo index
Phylum Mollusca > Class Bivalvia
Fan clams
Family Pinnidae
updated Sep 2019
if you learn only 3 things about them ...
The razor-sharp edge can seriously cut barefoot visitors.
The part of the shell above the ground provides a home for many encrusting animals. Let's see what kinds we can find.
Previously common, fan shells are now listed among our threatened animals.

Where seen? These thin, fan-shaped clams are commonly seen on some of our shores, usually near good seagrass meadows. However, they are often overlooked as most of the shell is often buried with only about 2-3cm of the shell sticking out of the ground. Their razor-sharp edges can give a nasty cut to barefoot visitors. So please always wear appropriate footwear when visiting the shores.

Features: 10-30cm long. The fan-shaped two-part shell is thin but strong. The animal buries itself, pointed end down. Glands on the foot secret byssus threads near this buried end. These threads attach to buried rocks and stones to anchor the animal in the ground. The broader, razor sharp edge of the shell sticks out above the surface. Careless visitors who walk barefoot on the shores can get a very serious cut if they step on this sharp edge. If the edge is damaged, the animal merely repairs it so it remains razor sharp. The animal's major organs are small and located at the pointed end that is buried deep in the ground where it is difficult for most predators to reach. Fan clams are usually found well spaced apart from one another.

Species are difficult to positively identify without close examination. On this website, they are grouped together for convenience of display.

What do they eat? Like other bivalves, fan clams are filter feeders. At high tide, they open their shells a little. They then generate a current of water through the shell and sieve out the food particles with enlarged gills. When the tide goes out, they clamp up their shells tightly to prevent water loss.

Byssus threads on the narrow end of the shell anchor the animal in the ground.
Changi, May 05

The razor-sharp edge can cut barefoot visitors.
Chek Jawa, Oct 01
Role in the ecosystem: All manner of seaweeds and encrusting animals often settle on the portions of the fan clam that sticks out above the sand, even when the clam is still alive. These provide food and shelter for small animals. The tiny Pea crab (Pinnotheres sp.) is sometimes found living inside these clams. The crab not only gains shelter but also eats some of the food gathered by the fan shell host. The space between the valves of a dead fan clam is a safe space for animals to shelter or lay their eggs.

When submerged, the valves of a living clam open slightly
and the animal filter feeds
Beting Bronok, Jun 06

All kinds of animals stuck on a Fan shell.
Changi, May 12

Keelworms on the portion of
the shell above the ground.
Pulau Sekudu, Jun 06

A fang-blenny guarding eggs
laid inside a dead Fan shell.
Tanah Merah, Sep 09

Crab and Drills hiding in a dead Fan shell.
Changi, May 12

Eggs laid on the inside of a dead Fan shell.
Changi, May 12
Human uses: Fan clams are edible and were once plentiful in Singapore and collected as food. Like other filter-feeding clams, however, fan clams may be affected by red tide and other harmful algal blooms. Such clams can then be harmful to eat.

It is said that in the past, people collected the long, golden byssus threads of the Noble pen shell (Pinna nobilis), a fan clam found in the Mediterranean. The threads were woven into a delicate and fine 'cloth of gold'. Some suggest that the 'Golden Fleece' of Greek mythology was made out of the byssus threads of this clam.

Some other species of fan clams have byssus hairs that are so similar to human hair that people refuse to eat the animals.

Status and threats: Some of our fan clams are listed as 'Vulnerable' on the Red List of threatened animals of Singapore.

Fan clams on Singapore shores
On wildsingapore flickr

Other sightings on Singapore shores

Coney Island, Feb 19

Photo shared by Richard Kuah on facebook.

Kusu Island, May 16
Photo shared by Jonathan Tan on facebook.

St. John's Island, Oct 11
Photo shared by Rene Ong on facebook.

Pulau Semakau South, Feb 16
Photo shared by Heng Pei Yan on facebook.

Terumbu Bemban, Jun 10

Photo shared by Loh Kok Sheng on his flickr.

Terumbu Berkas, Jan 10
Photo shared by Loh Kok Sheng on his flickr.

Sudden explosion of Fan clams at Changi, Feb 2019 from the wild shores of singapore blog.Fan shell clams (Family Pinnidae)

Family Pinnidae recorded for Singapore
from Tan Siong Kiat and Henrietta P. M. Woo, 2010 Preliminary Checklist of The Molluscs of Singapore.
in red are those listed among the threatened animals of Singapore from Davison, G.W. H. and P. K. L. Ng and Ho Hua Chew, 2008. The Singapore Red Data Book: Threatened plants and animals of Singapore.

  Family Pinnidae
  Atrina pectinata
Atrina vexillum
(Indo-Pacific fan shell) (VU: Vulnerable)

Pinna bicolor
(Bicoloured fan shell) (VU: Vulnerable)
Pinna incurva

Links References
  • 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.
  • 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.
  • Davison, G.W. H. and P. K. L. Ng and Ho Hua Chew, 2008. The Singapore Red Data Book: Threatened plants and animals of Singapore. Nature Society (Singapore). 285 pp.
  • Abbott, R. Tucker, 1991. Seashells of South East Asia. Graham Brash, Singapore. 145 pp.
  • Chuang, S. H., 1961. On Malayan Shores. Muwu Shosa, Singapore. 225 pp., plates 1-112.
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