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TONGUE-EATING LOUSE

Family: Cymothoidae

‘Fun’ Fact:  This creature enters a fish’s body through its gills, attaches itself to the base of the fish’s tongue and extracts blood from the tongue with its claws. In fact, this isopod drinks so much blood that the tongue atrophies away, starved of all nutrients. Then it replaces the tongue by attaching itself to the muscles of the exposed tongue stub. The fish uses the louse as if the parasite were its very own tongue.

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 spotted rose snapper’s 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.

Tongue Eating Louse (Cymothoa exigua)

A pair of ocellaris clownfish (Amphiprion ocellaris) are hosts to the tongue eating louse. The parasite enters the fish through its gills where they extract blood from the tongue. It then replaces the atrophied tongue, attaching its own body to the stub. The fish is able to use the parasite just like a normal tongue. This is the only known case of a parasite functionally replacing a host organ.

Image: © William Tan

tongue-eating louse head found in can of tuna. this louse is an isopod, like a wood louse, and is known to cut off the circulation from the tongue of a fish, causing the tongue to eventually fall off (a painless process for the fish). once this happens the louse attaches its body to the muscles left in the stub of the tongue and acts as the tongue - even allowing the fish to use the louse as a functional tongue.

from here and here

Tongue-eating louse (Cymothoa exigua) is a parasitic crustacean of the family Cymothoidae. This parasite enters fish through the gills, and then attaches itself at the base of the fish’s tongue.