Friday Parasite #10: Tongue Rolling

Some parasites are just too weird to be believed.

                                  

You’re not seeing things. There are isopods in that fish’s mouth. And they’re not simply hiding in there – they’ve completely replaced the fish’s tongue. Meet the tongue-eating isopod (Cymothoa exigua).

Isopods are crustaceans, and one group of them – the Cymothoidae – parasitize fish. Most species, like the fish lice I wrote about a few weeks ago, are simple ectoparasites that feed on the fish’s skin or gills. C. exigua goes further. The isopod gets into its host’s mouth and grabs onto its tongue with seven hooklike legs. Over time, the tongue degenerates, leaving the parasite hanging on to its stub. This change actually has very little effect on the fish, because it can still hold prey with the parasite. The isopod doesn’t just replace the tongue physically, it also replaces it functionally.

One of the guys over at Fishing Fury actually caught one. That must have been one surprising fishing trip.

References:
Brusca, R. C. and M. R. Gilligan 1983. Tongue Replacement in a Marine Fish (Lutjanus guttatus) by a Parasitic Isopod (Crustacea: Isopoda). Copeia 1983: 816-819.

Image from the Australian Museum

Comments

[Ian]

There's a parasite (a mite, I think) of ants that does something conceptually similar, except it replaces a foot. I'll see if I can scan in the image of it.

[Clive]

These guys are pretty creepy! I have come accross them in the British Virgin Islands as well in the mouth of Jacks. I releasede the 'infected' fish since the parasite seems to cause little to no harm to them.

[Jess]

would the parasite make the fish diseased and unable to eat?

[DIaneAKelly]

Jess -- as I said in the post, the parasite doesn't have much of an effect on the fish. It just uses the parasite to eat instead of its tongue.