Speaking in Tongues

Cymothoa exigua, or the tongue-eating louse, is a parasitic isopod of the family Cymothoidae. It enters a fish through the gills. The female attaches to the tongue, while the male attaches to the gill arches beneath and behind the female. (...). The parasite severs the blood vessels in the fish's tongue, causing the tongue to fall off. It then attaches itself to the remaining stub of tongue and the parasite itself effectively serves as the fish's new "tongue".

Many species of Cymothoa have been identified, and only cymothoid isopods are known to consume and replace the host's organs. Other species of isopods known to parasitize fish in this way include C. borbonica and Ceratothoa imbricata. Different cymothoid genera are adapted to specific areas of attachment on the host. This includes scale-clingers, mouth- or gill-dwellers, and flesh-burrowers.

Behavior

Using its front claws, C. exigua severs the blood vessels in the fish's tongue, causing the tongue to necrose 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 parasite apparently does not cause much other damage to the host fish, but Lanzing and O'Connor (1975) reported that infested fish with two or more of the parasites are usually underweight. Once C. exigua replaces the tongue, some feed on the host's blood and many others feed on fish mucus. In the event of the death of the host fish, C. exigua, after some time, detaches itself from the tongue stub and leaves the fish's oral cavity. It can then be seen clinging to its head or body externally. What then happens to the parasite in the wild is unknown.

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Image: Marco Vinci

[ed. What a world.]