TONGUE-EATING LOUSE parasitizing Striped Anemonefish
Cymothoa exigua in Amphiprion clarkii
© Ross Gudgeon
Look in the fish’s mouth - see that little face? That’s a parasite. It has eaten the fish’s actual tongue and moved into the fish’s mouth where it now acts as the tongue - it eats when the fish eats.
There’s a disturbing video about it here:
Cymothoa exigua, or the tongue-eating louse, is a parasitic crustacean of the family Cymothoidae. It tends to be 3 to 4 centimetres (1.2 to 1.6 in) long. This parasite enters through the gills, and then attaches itself at the base of the tongue. It extracts blood through the claws on its front, causing the tongue to atrophy from lack of blood.
The parasite then replaces the fish’s tongue by attaching its own body to the muscles of the tongue stub. The fish is able to use the parasite just like a normal tongue. It appears that the parasite does not cause any other damage to the host fish. Once C. exigua replaces the tongue, some feed on the host’s blood and many others feed on fish mucus. This is the only known case of a parasite functionally replacing the host organ it destroys.
It is currently believed that C. exigua are not harmful to humans unless picked up alive, in which case they can bite