Giant Clam

• It is the largest living bivalve mollusc in the world, with shells up to 137 cm across.
• biologíaIt can close its shells with considerable force, though contrary to popular legend it poses no real risk of trapping a diver.
• Contrary to the popular myth, it closes far too slowly to trap a diver.
• It is a protandrous hermaphrodite: it matures first as a male and later develops female function.
• biologíaIt can live for over 100 years, and hosts symbiotic algae (zooxanthellae) in its tissues that supply a large share of its energy through photosynthesis.

Skeleton type

Invertebrate - external calcareous bivalve shell

Habitat & environment

Shallow coral reef waters of the Indo-Pacific, down to 20-35 m

Birth weight

An egg ~100 micrometres across; a planktonic trochophore larva of ~160 micrometres within hours

Size at birth

160 micrometres long as a newly hatched trochophore larva

Sexual maturity

A protandrous hermaphrodite: it matures first as a male at 25-35 cm, then develops female function alongside it

Gestation / incubation

No gestation as such; the fertilised egg drifts for about 12 hours before hatching as a larva

Litter / clutch size

Over 500 million eggs released in a single spawning event

Sources consulted: A-Z Animals; JungleDragon; SeaLifeBase; NOAA Fisheries; Animalia.bio; Red Sea Creatures; Animal Diversity Web; Wikipedia (Giant clam)

Best time: All year round on shallow Indo-Pacific reefs, by day, when it opens its mantle to expose its symbiotic algae to the sun.