At less than a third of the size of the true giant clam (Tridacna gigas
), the small giant clam deserves its name. As an adult, it has a large shell that adheres to a rock by its byssus – a tuft of long, tough filaments that protrude from a hole next to the hinge of the shell. When open, the bright blue, green or brown mantle is exposed and obscures the edges of the shell with its prominent and distinctively furrowed edges. The small giant clam is a bivalve mollusc, referring to the two valves on the mantle. These siphon water through the body to extract oxygen from the water using the gills, and to feed on algae (4). The attractive colours of the small giant clam are the result of pigment cells, which have a crystalline structure inside. These are thought to protect the clam from the effects of intense sunlight, or bundle light to enhance photosynthesis, the energy-producing process carried out by the tiny algae living within (4) (5).