What are the similarities and differences between the Giant Clam (Tridacna squamosa) and the Maxima Clam (Tridacna maxima)?

The Giant Clam and the Maxima Clam are both marine (saltwater), bivalve molluscs in the Cardiidae family. Bivalve means two valves (or two shells). They both prefer to live on the bottom of the ocean in shallow coral reefs.

The Giant Clam and the Maxima Clam both have a thick, ridged calcium carbonate shell, called a mantle. Their shells, which can open and close, have two equal-sized calcareous valves connected with a flexible adductor muscle. 

The Giant Clam and the Maxima Clam both have a mouth, a heart, kidneys, a stomach, gills (to breath underwater), and a nervous system. 

The Giant Clam grows to 60 centimetres (24 inches) in length, whereas the Maxima Clam measures about 20 centimetres (8 inches) in length. The Maxima Clam is also known as the Small Giant Clam.

The Giant Clam and the Maxima Clam are both sessile. They do not move – they attach themselves to rocks. When they hatch from eggs, the larvae, called trocophores, have a ‘foot’ and can swim. After about one week, they settle on the ocean floor and become sessile – the foot disappears and they cannot move.

The Giant Clam and the Maxima Clam are both hermaphroditic, meaning that they have both male and female reproductive organs, and can produce eggs and sperm. 

The Giant Clam has a brown, green, or purple-coloured shell, whereas the Maxima Clam has abrown, green, or bright-blue shell.

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, whereas the Maxima Clam is native to the Indian Ocean and the Pacific Ocean. 

Photographer: Martina Nicolls

Martina Nicolls: SIMILAR BUT DIFFERENT IN THE ANIMAL KINGDOM