The Maxima Clam (Tridacna maxima) is a marine (saltwater) bivalve mollusc in the Cardiidae family. It is also called the Small Giant Clam. It is related to the Cockle. 

The Maxima Clam has a thick 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 is bright-blue, green, or brown with distinctive furrows. It has a mouth, a heart, kidneys, a stomach, and a nervous system. 

It measures about 20 centimetres (8 inches) in length, less than a third of the size of a Giant Clam, which is about 60 centimetres (24 inches) in length. 

The Maxima Clam is native to the Indian Ocean and the Pacific Ocean. It prefers the outer edges of coral reefs close to shore. It is sessile – it does not move. It attaches itself to rocks or dead coral. 

It is a filter feeder. It feeds on microscopic aquatic algae that live within it and near it. It has a mouth. It opens its shell during the day and closes its shell at night. The shell can shut completely. 

It breathes though gills (like fish). It also siphons water through its body.

The Maxima 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, but 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 Maxima Clam settles on the ocean floor and becomes sessile – the foot disappears and it cannot move. 

Location of photographs: Aquarium de Paris-Cinéaqua, France

Photographer: Martina Nicolls

Martina Nicolls: SIMILAR BUT DIFFERENT IN THE ANIMAL KINGDOM