Giant Technicolor Clam!

Hello from the beautiful Pacific Ocean island nation of Palau — “beautiful” being an understatement, especially when it comes to Palau’s ocean life. I remember the first time I swam through the swarming reefs of Palau several years ago, I felt like a kid IN an aquarium. Everything I’d ever wanted to see was right before my eyes, and in abundance!

I’m in Palau this week to work with coral reef managers from across the Pacific as part of the Conservancy’s annual reef resilience training program. These managers have come from places like Fiji, Papua New Guinea and Kosrae to learn the latest techniques and management strategies for making reefs more resilient against the host of threats they face, including overfishing and rising sea temperatures.

But I’ll be in the water at least some (but not enough!) of this trip, and one of the common things one sees in the reefs of Palau is giant clams (genus: Tridacna) such as the one in the picture above. There are seven species of giant clams just in Palau (there are only nine globally), and all are as shockingly beautiful as this one, with neon purple, green, blue, orange blaring at you as you swim over. (My husband, marine scientist Brian Silliman, took this photo the other day.)

These clams get their color from the same tiny plants that corals get their color from — zooxanthellae. Clams also have the same symbiotic relationship with zooxanthellae that corals do: these tiny plants live in the clam’s outer tissues and provide nutrients to the clam via photosynthesis. Think of them as an underwater greenhouse with doors that open and close.

The relationship is so beneficial to these clam that it allows the clam to get really, really big. The first time I saw the biggest giant clam species (Tridacna gigas), I immediately thought of horror-movie images of man-eating clams — they are that huge. Of course, that clams could eat humans is just a legend: the flesh of the giant big clam is so meaty that it can’t even close its shell tightly. Still…

I’ll be sharing more from Palau in the next few days, so stay tuned.

Stephanie Wear is a marine scientist with The Nature Conservancy’s Global Marine Team. She is working to improve tools that build resilience in coral reef communities so that coral reefs survive the impacts of a changing climate.

Get instant access to her current trip to Palau by following @stephwear on Twitter or her visiting new website

If you believe in the work we’re doing, please lend a hand.


  1. WOW thank you for sharing this exquisite photo. It is one of my life dreams to see one of these things in person, in the wild.

  2. More photos please!

  3. Your photos, and this is a perfect example, exemplify the great variety and magnificence of our precious blue planet. It is my hope that your work, together with those of us who support you, will awaken a sleeping populace that all too often continues to “consume” its way into oblivion. It hurts to see it, but those of us who love the earth from the heart know that we must do all we can to save the greatest gift ever, THE EARTH!

  4. Another WOW… I’m so jealous I might not be able to see this in person at all! Thanks.

  5. Wow, can you tell us more about how you got the photo?

  6. Hi Ashley! This photo was taken by my husband (who was also working in Palau) while he was snorkeling in a shallow area off a tiny island in Palau. These giant clams are everywhere in Palau – in fact, while there my project assistant shared with me a photo of an almost identical clam that she had taken while snorkeling – it wasn’t the same clam (we had to confirm to be sure!) …but it just goes to show you how common they are. Even doing the work I do…I still marvel at things like this and think that it is amazing that they ever existed at all. There was a little patch of really big ones off the dock at the institute I was working at and I would bring people over there every day who hadn’t yet seen them. So glad they are around to share with others!

  7. Thanks NC ..Green Wise Kids love the amazing beauty of this grand planet we live on…

  8. Thanks for sharing! These are my favorite clams – being a former shellfish bio. Tridacnas baby!

    While on a diving and flyfishing trip to Christmas Island (part of the Gilbert chain), I took a snorkel break from fishing (which the guides thought was crazy) and I spent about an hour hovering over a whole mess of Tridacnads in about 8-12 feet of water. Clam Gulch they called it. Amazing. I them of them often… 🙂

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