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This enormous shellfish (Tridacna sp.) is the largest and heaviest of all the living mollusks. Like all bivalve mollusks, the shell consists of two valves. In the large giant clams the valves cannot close completely. The shell is extremely thick and lacks bony plates; when viewed from above; each valve has a 4 to 5 inward facing triangular projection. The mantle of the clam is visible between to shells, and is golden brown or yellow or green, although it may contain so many blue or purple spots that the overwhelming impression is of a beautiful iridescent colour.  A number of pale or clear spots on the mantle, the soft fleshy part of the body, which are known as ‘windows’, function to allow sunlight to filter in through the mantle. With this light, the minute algae called zooxanthellae living in the mantle, photosynthesizes and secretes a waste that become food for the giant clam!

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The mantle is completely fused with the exception of two holes (or ‘siphons’); the inhalant siphon is fringed with sensory tentacles, whilst the exhalent siphon is tube-like and is capable of expelling a large volume of water if the clam’s shells close suddenly. Though the siphon enable it to filter plankton from the ocean’s movement, its symbiotic relationship with the algae is truly amazing. These creatures were created with a dependency on another, design to complement one another. 

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The algae did not wake up one day to find itself without a purpose. It was designed to be a purpose. Created to be at the beginning of the food chain, phytoplankton and algae produce more than 87% of the oxygen that we breathe; to feed the massive whale sharks, manta rays, mega mouths ( a kind of shark) and whatever else that require algae to function. Now the fact that the giant clam has been designed to be the protection and host to zillions of zooxantellae is also awesome! If animals could talk, sure the algae would not say to the clam, “I cook, you clean.” It must have said, “I cook, you eat. Just shelter me from the elements at night and sun me in the day. That’s all I need to cook for you. And for as long as I live, I will never leave you nor forsake you.”

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To sit around and do nothing all day but eat, the giant clam has to be strong enough to withstand currents, to weather any storm and to proudly show the patterns that the algae has formed in their mantles. Finally, if the clam could respond, it would probably say, “I need you to be in my mantle, will you stay there with me forever???”

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