Ich only effects scaled fish?
I have had puffers with Ich before, and they don't have scales.
Has anyone ever scraped tissue samples of a the rays spiracles or gills? Probably not on MFK, unless of course your one of the educated elitists.. I don't see why the Ich parasite couldn't heavily effect the softer gill tissues of rays while their exterior is not a viable hosting location for the parasite.
A recent gill scraping sample of a large deceased royal pleco (panaque family of plecos with heavily armored scales) revealed that the gill tissue was heavily infected with Ich although the fish itself showed no signs of the parasite due to the heavy armored scales. It was almost comical that this "supreme mystery death" was caused by what some might call the common cold of aquarium fish. It's nice to have someone in the local community with a scope and knowledge of fish disease.