A Parasite That Replaces Your Tongue

The tongue-eating louse is a nightmare creature that sneaks into a fish's mouth, consumes the tongue, and then anchors itself to the remaining stump to act as a living, working replacement.

This bizarre parasite enters through the fish's gills and severs blood vessels in the tongue, causing the original organ to wither away. Remarkably, the fish continues to use the parasite as a functional tongue to eat food for the rest of its life. While the louse feeds on the fish's mucus and blood, it does not actually kill its host, allowing for a strange, permanent biological partnership. It is one of the few known instances where a parasite replaces an entire host organ.