Anyone got an ID on this worm?

[ReefED!]

It’s not a bristleworm - at least not a traditional one or the typical species that we get in our systems.

The way they move and react to peroxide is totally different as well

 

[EnterName]

How does it move differently? Can you describe it or do you have a video?

 

[ReefED!]

Sure - from the Live Photo

I had an infestation of the classic bristleworms before so I’m familiar with how they are - these are different and pretty rare

I’ve seen 3-4 but I never find any when picking up rocks or anything like that

 

[EnterName]

Okay, I really thought the color change between mid-section and anterior, as well as the color pattern, the fact that you found it in a clam, and the movement would be enough for a rough identification, but I'm definitely not there yet

I tried...

My guess: Dorvilleidae. Here's an example that shows at least the pattern, even if the colors are different (there are regional differences afaik, and maybe diet-based ones as well). The number of eye spots and their locations seems fitting, and the antenna might be right as well, it's hard to tell from your photos: https://reeflex.net/tiere/7225_Dorvillea_sp.htm