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Giant Clams Are Watching You With Hundreds of Eyes

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Start your Monday with a creepy feeling all up and down your back—especially if your back is to an aquarium. Giant clams may look like unseeing blobs, but they’re not. They have pinhole eyes all over their bodies.

Giant clams sit in the warm shallows of the Pacific and Indian oceans for a century. They manage to grow by filtering plankton from the sea, and letting algae fill their mantle. The algae use photosynthesis to make sugars for the clam, and the clam keeps the algae safe.


It does not protect the algae by clamping down on human ankles and drowning people, or swallowing them whole—although both of those actions have been featured in pulp adventure fiction. It protects them by growing a thick shell and retreating into it whenever danger draws near.


How does a clam sense when danger is near? It would be comforting, and reasonable, for the giant clam to sense the current of ocean waters, or be touch-sensitive. But no, the world isn’t that kind. Instead you now have to know that a clam has eyes. It has hundreds of eyes. Okay, yes, those eyes are more pinhole cameras than digital cameras, but clams do actually see motion and the brightening and dimming of the ocean above them. And they see it hundreds of times over.

So if you are on your dream honeymoon with the love of your life, and you splash naked into the ocean, and you decide that you want to get a little frisky, just remember that you’re being watched by something that has been staring upwards, with its many eyes, for a hundred years.

Image: NOAA Photo Library Second Image: NOAA Photo Library