A parasite feasts on a fish's tongue until it's gone. Don't worry, humans can't get it.

Researcher Kory Evans didn’t expect to find a tongue-eating parasite at work this week.

Evans, an assistant professor of biosciences at Rice University in Houston, has spent the past few years scanning and searching wrasses — a family of marine fish — to learn how traits evolve in the family. He's been measuring skull shapes of different types, and it’s part of an initiative he's dubbed #BackDatWrasseUp.

“While I was placing landmarks inside the mouth of one of the fishes, I realized that the inside of the mouth was pretty crowded,” he told USA TODAY.

Sometimes, it’s food. But in this particular type of fish, Odax cyanollix, he found what looked like a small crustacean.

The fish is a vegetarian species, so he thought it odd that another creature was in its mouth. Then he realized what he was looking at.

“After a few minutes of hard staring, I realized that I was looking at a tongue-eating louse,” he said. He posted his findings on Twitter, where his community of excited ichthyologists and marine biologists — and other grossed-out Twitter users — shared the image.

Tongue-eating lice, a type of isopod parasite, typically enter fish through its gills. When it latches itself onto the fish’s tongue, he told CNN, it feeds on the tongue’s blood vessels until the tongue is replaced fully by the parasite.

Evans told USA TODAY that they typically prey on saltwater game fish, including snappers, and generally do not harm the fish beyond, well, replacing its tongue. Sometimes, multiple parasites latch on the tongue, resulting in the host fish to be underweight due to a lack of feeding.

It’s nothing for humans to worry about, beyond the visceral reaction of hearing the phrase “tongue-eating lice.” But it is a fascinating look into our fishy friends.

“They’re barely anything for fishes to worry about, apparently,” he told USA TODAY.

Follow Joshua Bote on Twitter: @joshua_bote