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Welcome to another installment of Weird Biology! I’ve been clammed up all week, but I’ve decided that it’s time to stop being shellfish and dish out some delicious facts about the largest shelled mollusk in the world, the

(It’s just gonna get worse from here, folks. Brace yourselves.)

The Giant Clam is the world’s largest shellfish, a hefty claim to fame that we’re sure impresses all the lady clams that it chats up in bars. Sandbars.


The Giant Clam can reach shell lengths of up to 6 feet and weights of well over 500 pounds, far larger than the meek ordinary little clams that fill your bowls of chowder. Those little geeks probably don’t even lift. Not like the Giant Clam! The Giant Clam is the reel deal.

Giant Clams live in the South Pacific and Indian oceans. They come in a wide variety of colors ranging from purple to green, and each Giant Clam has a unique pattern on their mantles. (That’s the soft, squishy part between the shells that looks kind of like lips. Do NOT smooch.) These patterns could almost be mistaken for obscure hieroglyphics, as if an ancient aquatic race was using them to communicate something with us. Something important. But of course not. That would be silly.

Dolphinately not.

However if for whatever weird reason you think they might be too pretty, fear not! That brightly colored mantle is covered in hundreds of tiny invisible eyeballs. Yes, really. Tiny invisible eyeballs. I couldn’t make this stuff up if I tried. (I was going to make an eyeball pun but none of them were cornea enough.) These tiny nightmare eyes are almost invisibly small and can barely tell light from dark, but there are enough of them to warn the Giant Clam of incoming threats. Things like, say, an approaching tiger shark, or a voracious sea slug, or a snorkeling tourist hellbent on jamming their entire arm in there and taking a selfie.

Not to worry though, it turns out that Giant Clams can’t actually hurt you. (Just in case you were living your life in fear of being murdered by a clam.) It used to be thought that the Giant Clam would clamp down on the hands or feet of a swimmer and drown them in a display of shellfish maliciousness, but we now know that this isn’t even a little bit true. Though they can be a little crabby.

Giant Clams do close their shells when they feel threatened, but it happens very, very slowly. Larger Giant Clams may not be able to close their shells at all. When each half of your shell weighs over 200 pounds, moving them can be a real beach.

But unfortunately for both the Giant Clam and ocean-based puns, they are considered a delicacy in many cultures. (The Giant Clam, not the puns… I’m pretty sure.) The Giant Clam is currently listed as Vulnerable in most of its home range, though experimental farming programs are showing some real promise. We hope this means that there will be enough of both delicious clam meats and terrible sea puns to go around in the future. For shore.


1. Paul Asman and Jill Lenoble, Flickr

2. Sanc2420, Flickr

3. Mal B., Flickr

4. Molly Timmers, NOAA

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