Finally go to use my slurp gun where it was designed to be used, but the stupid gasket wasn't tightening correctly so I wasn't getting much suction. Nevertheless, I did manage to slurp out the pretty scale worm, which is either Hesperonoe adventor (commensal with fat innkeeper worms) or Hesperonoe complanata (commensal with both fat innkeepers and ghost shrimp), so I was in the right area. Rough spots on the elytra seem to suggest the latter.