The Giant Clam (Tridacna squamosa) is a marine (saltwater) reef bi-valve mollusc (mollusk). It is also called the Fluted Giant Clam or the Scaly Clam. It is related to the Cockle.
The Giant Clam has a thick brown, green, or purple-coloured ridged shell, called a mantle. Its shell is actually two equal-sized calcareous valves connected with a flexible adductor muscle. The shell can open and close. Bi-valve means two valves (or two shells). The mantle has 6-7 rippled edges, called folds or flutes. It has scales, called scutes. It has spotted patterns on the mantle. It has a mouth, a heart, kidneys, a stomach, and a nervous system.
It measures up to 40-60 centimetres (16-24 inches) long.
The Giant Clam is native to the oceans of the African continent, from South Africa in the south to the Red Sea in the north. It prefers shallow saltwater coral reefs. It lives on the bottom of the ocean, in the sandy soil.
When it is young, at the larval stage, it can move. When it is an adult, it is sessile (not-moving).
It breathes though gills (like fish).
It is a filter feeder. It feeds on microscopic aquatic algae, called zooxanthellae, that live within it and near it. It has a mouth. During the day, it opens its shell so that algae can be exposed to sunlight. It shuts its shell at night. The shell can shut completely.
The Giant Clam is hermaphroditic, meaning that it has both male and female reproductive organs, and can produce eggs and sperm. It releases about 500 million eggs at a time – fish eat most of them.
After 12 hours, the eggs hatch into larvae, called trocophores. The larvae produce a calcium carbonate shell. It moves along the sea bed using its newly-developed foot. It can also swim. After about one week, the Giant Clam settles on the ocean floor and becomes sessile – the foot disappears and it cannot move.
Photographer: Martina Nicolls
Martina Nicolls: SIMILAR BUT DIFFERENT IN THE ANIMAL KINGDOM