Animal of the Week August 28, 2006 -- The most gruesome parasite?

Ahhh, a Bank Holiday trip to the seaside. Delightful seafood served fresh from the ocean. Yum yum yum. "What's your favouorite fish?" I asked my friends as I ploughed through a selection of fried seafood, they'd say "Oh I don't really know". I'd say, "I really like hake, it's delicious, the Spanish have a way with it."

I also really like red snapper, as, it turns out, does this week's animal of the week Cymothoa exigua.

In perhaps the most disturbing act of parasitism I have ever heard of (maybe tied with that catfish), this isopod crustacean (an aquatic woodlouse) latches on to the tongue of a red snapper and taps into the blood supply. As the parasite grows, the fish's tongue wastes away. Eventually, the snapper's tongue withers completely, by this point the parasite has switched from living off the blood supply to nicking some of the food the fish catches. But don't feel too upset for the fish, it can carry on just fine because by now the fish is using C exigua as its tongue instead. Obviously it would be better for the fish if it didn't have to share its supper with the crustacean, but they can continue to grow, remain healthy, and sometimes even make it into fishmongers. Although this bizarre relationship is only known from the Gulf of California, last year, one unlucky customer in London bought a red snapper only to discover when he got it home that it had a marine woodlouse for a tongue. I'd just get your fishmonger to take off the head and never even think about it.