pearlfish
/ˈpɜːrlˌfɪʃ/
noun
- A small, slender fish that lives inside the body of a sea cucumber or other marine animal.
- A single sea cucumber can host several pearlfish at once.
- The pearlfish hides inside a sea cucumber to avoid predators.
- Divers sometimes spot a pearlfish peeking out of its host's body.