The terrifying parasite that replaces fish tongues and changes sex in the process

Within the fascinating and at the same time creepy animal world, the Cymothoa exigua, also known as the "tongue-eater", stands out as one of the most unique and terrifying cases in nature. This tiny isopod, belonging to the Cymothoidae family, has captured the attention of scientists due to its disturbing modus operandi and its ability to functionally replace an organ in its victims.

The Cymothoa exigua begins its life cycle by entering the body of a fish through the gills. Once inside, it attaches itself to them while it completes its maturation process, at which point it is a male. The parasite then moves to the fish's tongue, where it begins its macabre process. It sucks blood from the fish's tongue until the organ atrophies and eventually falls off. It is at this point that Cymothoa exigua takes on a unique role in nature: it attaches itself to the fish's heel and becomes its new tongue.

This is the only known case in the animal world where a parasite functionally replaces an organ. The parasite, now turned into a tongue, ensures its own nourishment by taking a portion of the food each time the fish feeds. Surprisingly, this process does not seem to cause significant harm to the fish, which continues to use the parasite as if it were its natural tongue.

Most intriguingly, during this process, the parasite changes sex, going from male to female once it has replaced the fish's tongue. This change is crucial to its reproductive cycle, as the female mates with males who remain in the fish's gill chamber.

Although Cymothoa exigua may look scary, especially with its colorless appearance and tiny eyes visible inside the host, it does not pose a direct threat to humans. It is believed that the only risk it could pose would be a bite if captured alive.

This parasite is widely distributed in the Gulf of California as far north as the Gulf of Guayaquil in Ecuador, where it continues to surprise researchers with its shocking behavior.