Tridacna gigas (Giant Clam) Care Guide
Tridacna gigas is the largest living bivalve, an Indo-Pacific reef giant suited only to public aquariums and protected by CITES.
Compiled by Aquairi from published sources · Published · Updated
Overview
Tridacna gigas is the largest living bivalve mollusc. It can reach a maximum length of about 137 cm, typically measuring as much as 120 cm across, and a specimen found in 1956 weighed 333 kg dead. Adults cannot fully close their shells, leaving part of the brownish-yellow mantle visible, and the shell bears four or five vertical folds.
Taxonomy
- Family: Cardiidae
- Subfamily: Tridacninae
- Genus: Tridacna
- Scientific name: Tridacna gigas
Habitat
Its range covers the Indo-Pacific, with populations on coral reefs of the South Pacific and Indian Oceans. It is found at depths of as great as 20 m on flat coral sand or broken coral.
Diet
About 65-70 percent of its nutritional needs are supplied by symbiotic zooxanthellae cultivated in specialised tissues, which enables it to grow to one metre in length despite nutrient-poor reef waters. The remainder is obtained through filter feeding.
Lifespan
The average lifespan exceeds 100 years in the wild.
Aquarium note
Because of its enormous adult size, Tridacna gigas is realistic only at public-aquarium scale and is not suited to home tanks. It is listed here for completeness.
Tridacna gigas Breeding Guide: Hatchery Mariculture of the Giant Clam
Overview
Tridacna gigas is the largest living bivalve mollusc; the largest known specimen measured 137 cm and weighed about 250 kg alive, with a dead specimen recorded at 333 kg. It derives roughly 65-70 percent of its nutrition from symbiotic zooxanthellae housed in its mantle, which lets it reach over a metre even in nutrient-poor reef water. It is not a home-aquarium animal and is reared only at mariculture scale.
Reproductive Mode
T. gigas reproduces sexually and is hermaphroditic, producing both eggs and sperm, though self-fertilization does not occur. It uses broadcast spawning, releasing gametes into the water. A chemical called spawning-induced substance (SIS) synchronizes release among neighbouring clams. A single adult can release more than 500 million eggs at a time, with eggs around 100 micrometres in diameter.
Propagation Setup
Mass culture of T. gigas began in Palau in the 1980s. Australia funded major hatchery projects between 1985 and 1992 at James Cook University, supporting hatchery development across the Pacific and the Philippines. Broodstock spawning is induced in controlled facilities and gametes are collected for rearing.
Spawning and Larval Rearing
A fertilized egg floats for roughly 12 hours before a trochophore larva hatches. Within two days larvae measure about 160 micrometres and develop a foot. Larvae are initially aposymbiotic and capture free-floating zooxanthellae while filter feeding, then settle around one week of age. Juveniles reach about 20 cm; laboratory-reared clams grow roughly 12 cm per year.
Common Challenges
Beyond the impossibility of rearing planktonic larvae in a display tank, T. gigas reaches a size suitable only for public aquaria or open-water mariculture. Slow growth, immense final size and strict trade controls mean propagation is restricted to specialist institutions, not hobbyists.