Yellow Acorn Worm

The casts of Yellow Acorn Worms in the waters off Hawaii

I took this photo when I saw what looked to me like a couple of brains resting on this sandy bottom. In fact they’re the castings of a Yellow Acorn Worm. These worms live under the sand and filter it to extract organic matter. The mounds are what’s left after this process.

I’m not likely to ever see, let alone photograph, an acorn worm. If they are dug up, the mass of sand inside them often causes their thin-walled bodies to burst!

8 thoughts on “Yellow Acorn Worm”

  2. kzmcb's avatarkzmcb

    I see similar masses on the foreshore sometimes. Your water is so clear! We have an algae bloom at the moment and no one is getting too near the water, but it’s rarely that clear. Stunning.

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