Tridacna gigas—the giant clam—is a flagship bivalve of family Tridacnidae. Its mantle hosts zooxanthellae for photosynthesis while the animal also filter‑feeds, making it a reef engineer.
Ecology & Biology
Photosymbiosis: iridocytes and symbiotic algae optimise light capture; suspension feeding supplements energy and nutrients.
Attachment & growth: juveniles use a byssus; adults become semi‑embedded; growth is slow.
Reproduction: sequential hermaphrodite, engages in mass broadcast spawning; larvae planktonic then settle.
Identification
Enormous, heavy shells with coarse folds/scutes; the mantle shows vivid blue/green/brown patterns from microstructural interference and algal pigments.
Size & Longevity
Length: typically 60–100 cm, up to ~120 cm.
Weight: can exceed 200 kg (including shell).
Life: may surpass 100 years.
Range & Habitat
Tropical Indo‑Pacific reefs and lagoons in bright shallow water (~1–20 m), settled on hard substrates among coral heads.
Conservation & Threats
Threats: overharvest (food/curios/aquarium), habitat loss, pollution and heatwaves.
Management: closures, size/season limits and trade controls; hatchery restocking aids recovery.
IUCN: commonly listed as Vulnerable (VU); we mark this entry accordingly.
