No, the crustacean got the fish tongue!!!
The precise name of this crustacean is Cymothoa exigua, a small isopod (3-4 cm) adheres to the tongue of the fish with its three pairs of front legs. Over time, as the tongue atrophied and decays, the crustacean takes the function of tongue itself. The fish has a new tongue. It is likely that this replacement does not cause a lot of problems, because its life is not affected.
The parasite has no interest in fish’s preys, because feeding on the mucous membranes of their host.
The hosts are specific, as the snapper off the coast of California called Lutjanus guttatus. Certainly a polyglot fish.
If preparing fish at home you find one of these crustaceans dwelling in the fish mouth, do not worry, not suppose any risk to humans.
About the biology of this arthropod little is known. It has a life cycle regulated by sexual reproduction in the gills of the fish. As they mature they become females. It makes me think in that character written by Virginia Woolf, and performed in the cinema (1992) by Tilda Swinton, Orlando, a nobleman that with the centuries pass becomes a woman.