Tongue-eating parasite found off Jersey coast

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A rarely seen parasite which eats the tongues and fish and replaces them with itself has been found by fishermen off the coast of Jersey.

The tongue-eating louse was found inside the mouth of a weever fish last week by fishermen.

The gruesome parasite is a type of isopod, possibily Cymothoa exigua, and was identified by marine research Paul Chambers from the Societe Jersiaise.

Chambers said the parasite was uncommon away from the Mediterranean and that the species normally reached around 2cm in length and fed on the blood of fish.

Chambers told BBC Jersey: "When we emptied the fish bag out, there at the bottom was this incredibly ugly looking isopod. Really quite large, really quite hideous - if you turn it over its got dozens of really sharp, nasty claws underneath and I thought 'that's a bit of a nasty beast'.

"I struggled for weeks to find an identification for this thing until, quite by chance I stumbled across something that looked similar in a Victorian journal. Apparently there's not too much ill effect to the fish itself except it's lost its tongue."

Similar tongue-eating isopods have been found in the UK before, and have caused damage to fish stocks on fish farms globally.

Fact File

Common name: Tongue-eating louse

Scientific name: Cymothoa exigua

Order: Isopoda

Suborder: Flabellifera

Family: Cymothoidae

Symptoms: C. exigua is the only known parasite which replaces the organ of its host. So much blood is removed from the tongue of the fish by the blood-thirsty parasite that the tongue atrophies and shrinks to a stub. The parasite remains in the place of the tongue and is used by the fish in the same way as its tongue was.

Notes: All members of the family Cymothoidae are fish parasites and representatives occur in both freshwater and marine environments. Most attach themselves either to the buccal cavity, tongue or gill chamber. Over 400 species are known, many of which are found in the Amazon basin where the family has undergone a massive radiation. The genus Cymothoa was described by Fabricius in 1787 and currently includes 43 valid species. C. exigua is most commonly seen on snappers members of the Lutjanus genus.