Infected Slugs: Case #5

This slug proved to be one of the saddest cases I've come across, for it had a (parasitic?) growth right between the cephalic tentacles, which hindered the latter's retraction and extension. Fortunately the growth didn't render the slug completely blind, so it could still see fairly well (or as well as slugs can see, anyway). To my knowledge there were no other growths inside or outside its body, just the one in front of the head. In addition, the slug's mantle was warped: lumpy and crinkled. In the first photos you can see the thick slime trail it's leaving. But it was so hard to watch, because the slug didn't understand what was wrong and couldn't extricate itself from the growth that had taken over its head.

After taking some photos, I replaced the slug where I had found it and returned the next morning. Its tentacles were completely retracted by then and the growth still dominating its "face." Nevertheless, the slug had not died and could still feebly extend its cephalic tentacles, but it looked as though another slug may have nibbled at its mantle already.

It appears tiny pieces have been torn from the mantle on this side, perhaps by a hungry slug.

Manipulating the growth with my tweezers, I discovered that it consisted of more than one segment/part.

Peeking under the mantle...

By that night, however, some creature(s) had eaten most of the slug's body, leaving few remains for me to analyze.

I believe that yellow, crescent-shaped part is either the slug's chitinous jaw (which would have arched over the pharynx, just behind the mouth), or part of its radula (which would have been on the floor of the pharynx). Since it is hard and a single row, I'm inclined to think it's the jaw, but I could be wrong.

I'm not sure what this white kidney-shaped organ is.