---
title: Coral Scallop (Pedum spondyloideum)
scientific_name: Pedum spondyloideum
common_name: Coral Scallop
taxon: Clams
published: 2023-12-29T12:00:09.305Z
updated: 2026-08-15T22:30:25.132Z
tags: Coral Scallop, Pedum spondyloideum, Clams, Red Sea, Marine Life, Diving
url: https://redseacreatures.com/taxon/invertebrate/molluscs/clams/coral-scallop
---

# Coral Scallop (*Pedum spondyloideum*)

## Quick facts

- **Group:** Clams (*Bivalvia*)
- **Size:** up to 6 cm
- **Depth:** 1-30 m
- **Diet:** Filter feeder
- **Activity:** Diurnal
- **Rarity:** Common
- **Habitat:** Embedded in living massive Porites coral heads
- **Reproduction:** Broadcast spawner, Gonochoric

## How to recognise it

- a narrow slit in a living coral head, edged in bright blue-green mantle
- row of tiny blue eyes along the mantle edge
- closes instantly when a shadow passes
- shell up to 6 cm, almost entirely buried

The blue-green slit in a living coral head is a scallop. It settles on a Porites colony as a larva and the coral grows around it, leaving a slot through which the animal filters water, so that an adult is permanently embedded in a living rock that keeps growing over it.

The arrangement is mutual. The scallop gets a fortress no predator can open. The coral gets a defender: when a crown-of-thorns starfish climbs onto a colony, the scallop claps its shell shut hard enough to fire a jet of water at it, repeatedly, and colonies carrying scallops suffer measurably less damage from starfish than colonies without them.

Along the mantle edge is a row of small blue eyes. A scallop's eye works on a mirror rather than a lens - a concave layer of guanine crystals that focuses light back onto the retina, the same principle as a reflecting telescope - and it is good enough to detect a shadow moving overhead, which is all the animal needs.

A hand passing above one will close it. Wait a minute and it opens again.

## Also known as

- **English:** Iridescent Scallop
- **Hebrew:** צדפת-סדקים אלמוגית
- **French:** Huître corallicole
- **Italian:** Ostrica corallina iridescente, Pettine corallino iridescente, Ostrica corallina
- **German:** Korallen-Kammuschel
- **Dutch:** Koraal Kamoester
- **Japanese:** ウミギクモドキ
- **Chinese:** 海菊海扇蛤
- **Russian:** Гребешок коралловый
- **TH:** หอยแมลงภู่ปะการัง

## Scientific synonyms

- *Ostrea pedum* Röding, 1798
- *Ostrea spondyloidea* Gmelin, 1791
- *Pedum pedum* (Röding, 1798)
- *Pedum pedum intensum* Iredale, 1939

## Range

Indo-Pacific, Republic of Mauritius, South Africa

---

*Source: [Red Sea Creatures](https://redseacreatures.com/taxon/invertebrate/molluscs/clams/coral-scallop)*
*Updated: August 15, 2026*