The creature in this fish is commonly known as the “Tongue Eating Louse”
Yes i know what you’re thinking and no they do not affect humans… usually. Now this creature usually has a partner, the female enters through the gills and attaches itself to the tongue and proceeds to eat it, the male enters through the gills and lays behind the female feeding off the underside of the fish’s mouth. These parasites aim to replace the fish’s tongue and feed off the nutrients of the food the fish decides to eat. And surprisingly the fish does not die but it is in excruciating pain for the rest of its life