There are "grubs" in some panfish in some of the inland lakes up here. They're whitish/yellow, about the size of a BB, and flatter though. I've seen those black spots you refer to as well.
Personally, I've heard that if you cook them they're ok..but I don't, and I don't know too many of my friends who will as well...to avoid this we just don't fish pannies in those lakes...we go to the bigger water and catch them there.
I know this doesn't help much in your question, but we don't eat them here....Esox...