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Phylum Mollusca > Class Bivalvia > Family Cardiidae
Heart cockle
Corculum cardissa
Family Cardiidae
updated May 2020
Where seen? This intriguing clam is sometimes seen on our Southern shores, near reefs. Sometimes on the sand, on rubble or among seagrasses. Elsewhere, often found on sandy bottoms often associated with reefs, sometimes in dense colonies.

Features: 4-6cm. The two-part shell is thin and heart-shaped with the opening of the valves down the centre of the 'heart'. The colour may be dull yellowish, pinkish to white, sometimes with bright flecks of red and yellow. Sometimes with bright blue underside and rose-pink upperside. The clam attaches itself to a hard surface with small byssus threads from the underside.

Concave on upperside, convex on underside.

Pulau Semakau, Feb 09


Pulau Semakau, Feb 09

Upperside with translucent 'windows'.

Pulau Semakau, Feb 09
What does it eat? Unlike most other bivalves, the heart cockle harbours symbiotic zooxanthellae (a kind of single-celled algae) in its body. The zooxanthellae produce food through photosynthesis which it shares with the clam. To maximise the productivity of its "farm", the upperside of its shell has translucent 'windows' to let sunlight through the shell. In this habit, it is similar to Giant clams. It also filter feeds - when submerged, it opens the valves on the underside slightly and sucks in water to filter out edible bits.

Human uses: It is collected for shell craft.

Convex side.
Pulau Semakau, Feb 09

Flat side.

Side view.

Heart cockles on Singapore shores
On wildsingapore flickr

Other sightings on Singapore shores

Pulau Hantu, Mar 22

Photo shared by Kelvin Yong on facebook.

Pulau Semakau South, Oct 20

Photo shared by Vincent Choo on facebook.

Pulau Semakau, Feb 08

Photo shared by Loh Kok Sheng on his blog.

Pulau Senang, Jun 10

Photo shared by Loh Kok Sheng on his flickr.

Beting Bemban Besar, Jun 19
Photo shared by Lisa Lim on facebook.

Terumbu Pempang Tengah, Jun 20
Photo shared by Dayna Cheah on facebook.

Terumbu Pempang Laut, May 15
Photo shared by Heng Pei Yan on facebook.



  • 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.
  • Chou, L. M., 1998. A Guide to the Coral Reef Life of Singapore. Singapore Science Centre. 128 pages.
  • Abbott, R. Tucker, 1991. Seashells of South East Asia. Graham Brash, Singapore. 145 pp.
  • Gosliner, Terrence M., David W. Behrens and Gary C. Williams. 1996. Coral Reef Animals of the Indo-Pacific: Animal life from Africa to Hawaii exclusive of the vertebrates Sea Challengers. 314pp.
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