They told her it was a tumor. It turns out there was something living... in her brain!
Once C. exigua replaces the tongue, some feed on the host's blood and many others feed on fish mucus. They do not eat scraps of the fish's food. This is the only known case of a parasite functionally replacing a host organ.
These are concentric circles, not a spiral
Squares A and B are the same shade of gray.
Created by this guy. via boingboing