bivalves text index | photo index
Phylum Mollusca > Class Bivalvia > Family Pectinidae
Coral scallop
Pedum spondyloideum*

Family Pectinidae
updated May 2020

Where seen? This little clam is often seen embedded in living hard corals on many of our Southern shores. Sometimes, one coral colony can host many of these tiny clams. It is also called the Iridescent clam, probably because of its sometimes colourful and iridescent mantle?

Features: Diameter 1-1.5cm. A circular two-part shell, thin. In some the shell is covered with encrusting fluff, in others, a pattern of spots may be seen. When submerged, a fringe of tiny tentacles emerge with many tiny, well developed eyes along the mantle edge.

Tanah Merah, Jun 11

When submerged, tentacles and
tiny eyes can be seen.
Beting Bemban Besar, Apr 10
Digging into corals: This clam is often seen in hard corals with branching forms such as Acropora coral and Branching pore coral, as well as leafy forms such as Crinkled sandpaper coral and Carnation coral. The clam excavates the hard coral to create a cavity for itself and attaching to the coral by byssus threads. The clam is usually completely surrounded by living tissue.

Pulau Hantu, Apr 07

Pulau Berkas, Jan 01

Beting Bemban Besar, Apr 10
Coral-clam cooperation: The coral provides the clam a safe place with support and protection. The clam may improve water circulation for the coral which helps the coral feed. A study showed that the clam helped reduce the impact of predatory Crown-of-Thorns sea stars (Acanthaster planci) by repeatedly spitting out jets of water. On the other hand, the clam may weaken the coral as it excavates a cavity within the coral structure.

This page includes all the little clams found in hard corals, for convenience of display. It is possible that they are different species and may even not be scallops but belong to other families.

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

Coral scallops on Singapore shores
On wildsingapore flickr

Other sightings on Singapore shores

Labrador, Aug 17
Photo shared by Loh Kok Sheng on facebook.

Pulau Jong, Aug 20
Photo shared by Loh Kok Sheng on facebook.

Big Sisters Island, Sep 20
Photo shared by Loh Kok Sheng on facebook.

Terumbu Hantu, Jun 16
Photo shared by Marcus Ng on flickr.

Terumbu Bemban, Jul 11
Photo shared by Loh Kok Sheng on his blog.

Terumbu Pempang Tengah, Apr 13
Photo shared by Loh Kok Sheng on flickr.



  • 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.
  • Patrick Scaps. Associations between the Scallop Pedum spondyloideum (Bivalvia, Pteriomorphia, Pectinidae) and Hard Corals on the West Coast of Thailand. March 21, 2011. Zoological Studies 50(4): 466-474 (2011).
  • Patrick Scaps and Vianney Denis. 31 Aug 2007. Association between the scallop, Pedum spondyloideum, (Bivalvia: Pteriomorphia: Pectinidae) and scleractinian corals from the Wakatobi Marine National Park (Southeastern Sulawesi, Indonesia). Raffles Bulletin of Zoology 55(2):Pp 371-380 .
  • Coleman, Neville. 2003. 2002 Sea Shells: Catalogue of Indo-Pacific Mollusca Neville Coleman's Underwater Geographic Pty Ltd, Australia.144pp.
  • Humann, Paul and Ned Deloach. 2010. Reef Creature Identification: Tropical Pacific New World Publications. 497pp.
  • 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.
links | references | about | email Ria
Spot errors? Have a question? Want to share your sightings? email Ria I'll be glad to hear from you!
wildfactsheets website©ria tan 2008