Red Scale Worm

I’ve seen a few of these Red Scale Worms on a couple different nudibranchs recently. From what I can find, it looks like they are a commensal worm, which is somewhere between a symbiotic relationship and a parasite… a commensal organism benefits from its host but does not benefit the host (symbiotic) nor harm it (parasitic). In short, these guys are just hitchhikers looking for a free meal.