After latching onto a fish's tongue, the parasite drains it of blood, eroding all its muscular tissue before leaving just the bone. The parasite then attaches itself to the bone, feeding on nutrient-dense mucus and occasionally scraps of the fish's food, according to Kory Evans, fish biologist and assistant professor at Rice University.
Evans has come across tongue-eating louses while studying skull shapes in fishes. He specializes in creating 3D reconstructions of fish skeletons that help explain their evolution. About two or three times, he's found a surprise visitor in the mouths of the skulls.
These parasites are common in the Gulf of Mexico, according to Evans, and have been traced in sea life as far back as the 70s. There are various species of these creatures all over the world, he added.
Except for impeding a fish's ability to eat food, a parasite does not affect it much and a fish can live with one until it dies. A fish's lifespan would be cut exceptionally short if it were to fall victim to more than one of these parasites. Since they would take up so much space in the fish's mouth, it would be unable to swallow its own food.
"They would basically starve and only have couple weeks," Evans said. "But fish are tough as nails, oftentimes they do not go down easily."aside">
For avid fisherman who asked about removing the parasite, Evans said this is perfectly fine. The parasites do not affect humans, and by removing one from a fish's mouth, "you're doing it a favor."
Source : https://www.houstonchronicle.com/news/houston-texas/galveston/article/Galveston-state-park-parasite-tongue-eating-louse-16551510.php509