[Lee Stewart]

OK - this one is pretty disgusting. It's called a Tongue-Eating Parasite.

It's the stuff of nightmares, or science fiction: a parasite that wants to get inside an animal's mouth, where it attacks — and replaces — the tongue. That's the incredibly specific, terribly icky job of the tongue-eating louse.

"This parasite detaches the fish's tongue, attaches itself to the fish's mouth, and becomes its tongue," the wildlife agency said, expounding on a photo showing the isopod curled inside a croaker's mouth. "The parasite then feeds on the fish's mucus.