These Creepy Little Creatures Live Inside the Mouths of Fish, Replacing Their Tongue

And if this wasn’t creepy enough, it gets even wilder.

Remember that juvenile Cymothoas transition into females when they move in? Well, in case a fish is already taken, they stay in the gills of the fish and grow up as males. Once the female and the male have developed into a fully grown louse, the male crawls into the mouth and mates with the female. Yikes.

After a short gestation period, the female gives birth to a whole new generation of lice that will continue this nightmarish cycle.