The parasite enters through the gills and the base of the tongue is attached to the spotted rose snapper. He sucks the blood via the claws in their front part, which leads to the atrophy of language due to lack of blood. Thereafter, the parasite replaces the language of fish, attaching his own body to the muscles of the stump language. Fish can make use of the parasite as well as the normal language. Apparently, the parasite does not cause other damage to the owner. When Cymothoa exigua replaces the tongue, some parasites feed on the host's blood, but most - fish mucus.
This is the only known case of a parasite functionally replacing a host organ. It is now believed that C. exigua is safe for humans, but there is a danger of being bitten if caught live parasite.
There are many types Cymothoa, but only Cymothoa exigua known that he eats and replaces the host language.
Source: en.wikipedia.org
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