How big can a giant clam grow?

The largest recorded shell measured about 137 cm, with the living animal estimated to have weighed up to 250-340 kg, making it the largest living bivalve mollusk.

How does a giant clam get most of its food?

About 65-70% of its nutrition comes from symbiotic zooxanthellae algae living in its mantle tissue, which produce sugars through photosynthesis; the rest comes from filter-feeding on plankton.

Can a giant clam trap a diver?

No. Its shell cannot close completely, so the popular myth that it can clamp shut on a diver's limb is false.

Giant Clamシャコガイ

Tridacna gigasVU— Vulnerable

The giant clam is the world's largest living bivalve, its huge fluted shell housing a vividly colored mantle packed with symbiotic algae that supply most of its nutrition. Native to Indo-Pacific coral reefs, it can live for over a century but has been badly depleted across much of its range by overharvesting.

Giant Clam (reference photo) — Photo: Wmpearl / CC0 / Source / cropped

Species Data

Classification: Cardiida / Cardiidae Source
Size: A record shell length of 137 cm makes it the largest bivalve in the world
Weight: Live weight has been reported to reach 250–340 kg at maximum
Lifespan: Average lifespan in the wild exceeds 100 years
Diet: Filter feeder Obtains 65–70% of its nutrition from the photosynthetic products of zooxanthellae living in its mantle, and the rest by filter feeding on plankton
Distribution: Native to coral reefs across the Indo-Pacific, found on flat sandy or rubble substrates down to about 20 m depth; in Japan it occurs in the Yaeyama Islands, though populations have declined sharply across much of its historic range due to overharvesting. Source
Sources: ja.wikipedia.org en.wikipedia.org

Did You Know?

The mantle edge holds hundreds to thousands of light-sensitive eyespots using multiple types of photoreceptors, letting the clam detect approaching shadows and snap its shell shut. Source
During spawning, an adult can release more than 500 million eggs at once, synchronizing with nearby individuals around the high tides near full and new moons. Source
Because the shell cannot fully close, the enduring myth that giant clams can trap and drown a diver's foot is considered false. Source

Where to See This Species

Operating facilities registered on this site: Japan 0

Verified individual animals and facilities will be added as official information becomes available.

Conservation Story

Conservation Status

Vulnerable (VU)

Sources

en.wikipedia.org

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FAQ

How big can a giant clam grow?: The largest recorded shell measured about 137 cm, with the living animal estimated to have weighed up to 250-340 kg, making it the largest living bivalve mollusk. Source
How does a giant clam get most of its food?: About 65-70% of its nutrition comes from symbiotic zooxanthellae algae living in its mantle tissue, which produce sugars through photosynthesis; the rest comes from filter-feeding on plankton. Source
Can a giant clam trap a diver?: No. Its shell cannot close completely, so the popular myth that it can clamp shut on a diver's limb is false. Source
How many operating facilities are registered here?: Operating facilities registered on this site: Japan 0 Source

Books & gear

Source: ja.wikipedia.org en.wikipedia.org