Eunice worm.
Eunice worm.
Looking for id help.
This one could be a Phyllodocid worm. I'm not sure on the scale, Phyllodocid's tend to be small, however many are predatory species. It could certainly also be a neirid as suggested above. Your specimen certainly appears to fit the predatory class, having well defined legs, segments and antennae
On your latter comments, the only difference between a predatory worm killing or scavenging is opportunity. It's
often easier and more advantageous for a predator to scavenge than hunt. However don't expect a predator not to take the opportunity to kill.
That could also be it. They wont leave the rock completly so trapping them with a bottle wont work. Perhaps a snare would work but i have atleast 10 of them so it will be much work.
I'm no expert at trapping them, but I'm sure people have used PVC pipe leading to the bottetrap. Basically, I guess you want them to feel secure about coming out.
Alternatively, mount the rock over a bucket and squirt soda water or RO in the the holes you think they are living in.
If you have a search of the forum, there's lots of
examples of the methods folks have used.
Good luck with it!