Sea star hitchhiker

[ARCkeeper]

One of my coworkers pulled this hitchhiker off a sea star we have that's a little over a month into quarantine. She said the critter had quite a grip and was hard to get off. I don't know the species of star but it was collected off the coast of Washington state. The hitcher looks like some sort of nudibranch, but other than that I don't have a clue. It was about an inch long, and very active in the specimen cup we put it in. It would be nice to know if this is something we want to try to keep out of the display tank. Any ideas?

 

[fishguy242]

hi, have no clue,but sounds like a type of leach to me ? @F i s h y ?

 

[Fishfreak2009]

Looks like a species of predatory/parasitic annelid worm, probably feeding on the starfish. And there is another one in your pic on the top leg as well.

 

[ARCkeeper]

A big thank you to everyone who played from home, but the answer we were looking for was scale worm.

After some research, one of the vets at work identified it today. My mistake was searching for a parasite. These are actually symbiotic. They are generally considered commensal, but under experimental conditions researchers have seen sea stars actually seek them out indicating there is some unknown benefit for both animals.