The ctenidium of the giant clam, Tridacna squamosa, expresses an ammonium transporter 1 that displays light-suppressed gene and protein expression and may be involved in ammonia excretion.

Ammonium transporters (AMTs) can participate in ammonia uptake or excretion across the plasma membrane of prokaryotic, plant and invertebrate cells. The giant clam, Tridacna squamosa, harbors nitrogen-deficient symbiotic zooxanthellae, and normally conducts light-enhanced ammonia absorption to benefit the symbionts. Nonetheless, it can excrete ammonia when there is a supply of exogenous nitrogen or exposed to continuous darkness.

The Whitish Inner Mantle of the Giant Clam, , Expresses an Apical Plasma Membrane Ca-ATPase (PMCA) Which Displays Light-Dependent Gene and Protein Expressions.

Giant clams live in symbiosis with extracellular zooxanthellae and display high rates of growth and shell formation (calcification) in light. Light-enhanced calcification requires an increase in the supply of Ca to, and simultaneously an augmented removal of H from, the extrapallial fluid where shell formation occurs. We have obtained the complete coding cDNA sequence of () from the thin and whitish inner mantle, which is in touch with the extrapallial fluid, of the giant clam .