Cymothoa exigua is a parasite that is also know by the name the ‘Tongue-eating louse’. It is an isopod with the unique identifiable feature of being the only known parasite that functionally replaces a host’s organ. The louse enters the fish’s body through the gills, attaches to fish’s tongue and extracts blood, causing it to shrivel and eventually fall off. Once this has been achieved the louse attaches to the remaining stub and acts as a replacement tongue, receiving nutrients by feeding on the fish’s blood and mucus. While the majority of fish found with these parasite’s are underweight, there is no evidence that this parasite causes a significant amount of harm to its host.
These parasites, while aesthetically disturbing, are also not harmful to humans. While a person has brought a lawsuit against a supermarket chain after finding cymothoa exigua in fish they had eaten, the legal case was dropped. This was a result of there being no evidence that these parasites were in any way unhealthy for humans, they are not poisonous and can be incorporated into a healthy diet.