Tridacna gigas

gian clam.jpg

(Giant Clam)




Tridacna gigas

Common name(s)

Giant Clam

Main colour(s)

Mantle varies from golden brown, yellow or green/blue.


120 cm across


Orpheus Island Research Station


Adults are unable to close their shell completely so the mantle is visible. This varies in colour from bright greens, blue to yellow and browns. They can live for over 100 years in the wild and have an average size of 120 cm and 200 kgs. The shell has 4-5 vertical folds and is composed of calcium carbonate. The giant clams are the largest mollucs on earth, capable of reaching 1.2 meters in length and weighing more than 225kg during their long life span of 100years or more. They achieve their enormous proportions by consuming the sugars and proteins produced by billions of algae that live in their tissues. In exchange they offer the algae a safe home and regular access to sunlight for photosynthesis, basking by day with their fluted shells open and multi-coloured mantles exposed. They also use a siphon to draw in water to filter and consume passing plankton. The adductor muscle of the giant clam is considered a delicacy and is a source of food in the south pacific region.

Sites where this species can be found at OIRS

Live on sand flats or amongst coral. Found scattered around The Point and in a large group of 3000plus clams to the north western end of Pioneer Bay where they were part of an experiment in the 1970’s.

Research that has been undertaken at OIRS