Fauna
Invertebrate

Southern Giant Clam

Tridacna derasa

Also known as Smooth Giant Clam, Derasa Clam, Apricot Clam

Southern giant clams are magnificent reef-dwelling bivalves known for their smooth, heavy shells and brilliantly colored mantles. They host symbiotic algae within their tissues, which provide the clam with nutrients through photosynthesis in exchange for sunlight and protection. These massive mollusks act as living micro-reefs, offering shelter and substrate for numerous small fish, crabs, and invertebrates.

Reef-dwellingSymbiotic
Southern Giant Clam reference
Stan Shebs / CC BY-SA 3.0 · cc-by-sa
—observations
—countries
—peak records
EndangeredConservation statusIUCN Red List categoriesLCNTVUENCREWEXEndangeredRed List categories, explained →
Key facts
Diet & preyPhytoplankton, Organic detritus
Predators
  • Pyramidellid snails
  • Octopuses
  • Triggerfish
ThreatsOverharvesting for food and the aquarium trade, habitat degradation, and ocean warming
HabitatsShallow coral reefs, outer reef slopes, and sandy lagoon flats
Life spanUp to 100 years or more
Classification
  1. FamilyCardiidae
  2. SpeciesTridacna derasa
Range & activity
Range data is not available yet.
Safe observation
Interaction riskLow
  1. Low
  2. Moderate
  3. High
  4. Very high
Why interaction risk is low
Safe to observe at a normal distance.
What to notice
Look for a large, relatively smooth shell with wavy, colorful mantle edges in shallow reef flats.
Support conservation
Never touch, step on, or attempt to harvest these protected clams.
Responsible observation
  • Avoid touching: Touching the sensitive mantle causes the clam to snap shut, which can pinch.
  • Do not block light: Swim around them rather than hovering directly overhead to avoid blocking their sunlight.
  • Maintain distance: Keep fins clear of the reef to prevent kicking sand onto their delicate mantles.
Related species
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