What Is a Tongue-Eating Isopod?

Parasites can be nasty little critters, but there is at least one species of isopod that "repays" its host in a bizarre way. An isopod called Cymothoa exigua targets the rose snapper, slipping through its gills and clamping onto its tongue. After eating the organ, the contented parasite remains in the fish's mouth, providing the fish with all the functions of the original tongue, including grinding food against the teeth on the roof of the snapper's mouth.

Marine biologist Rick Brusca of the University of Arizona says that while there are hundreds of such tongue-targeting isopods in nature, only C. exigua can actually assume the duties of the consumed organ.

A parasite with a thing for snappers:

• These isopods are considered protandrous hermaphrodites: They mature into males, but then switch sexes when it's time to procreate.
• The parasite feeds on the snapper’s tongue not by gnawing on it, but by sucking blood from it. “They have five sets of jaws,” says Brusca.
• It’s not known why C. exigua takes parasitism to such an extreme in rose snappers. In other species, the isopod only sips blood from the tongue, and doesn't destroy it, nor take over its job.

Frequently Asked Questions

What exactly is a tongue-eating isopod?

A tongue-eating isopod, scientifically known as Cymothoa exigua, is a parasitic crustacean that enters fish through the gills and attaches itself to the fish's tongue. It extracts blood, causing the tongue to atrophy, and then replaces it by attaching its own body to the remaining stub, effectively becoming the fish's new tongue.

How does the tongue-eating isopod affect its host fish?

The isopod initially causes the fish's tongue to wither away by severing the blood vessels. Once the original tongue is gone, the isopod functions as a pseudo-tongue, allowing the fish to use it almost normally. Surprisingly, infected fish can survive with the isopod in place, although it may impact the fish's feeding behavior to some extent.

Where can tongue-eating isopods be found?

Tongue-eating isopods are primarily found in warmer waters and have been observed in various parts of the world, including the Gulf of California and the coasts of South America. They tend to inhabit shallow waters and are often found in the mouths of snapper species.

Are tongue-eating isopods dangerous to humans?

While the thought of a tongue-eating isopod may be unsettling, they pose no direct threat to humans. These parasites specifically target certain species of fish and are not known to infect humans or other mammals. Encounters with humans are rare and typically occur only when handling infested fish.

Can a fish survive after being infected by a tongue-eating isopod?

Yes, fish can survive after being infected by a tongue-eating isopod. The isopod takes over the function of the fish's tongue and can stay attached for a considerable time. The fish continues to feed and behave relatively normally, although the long-term effects of such parasitism are not fully understood.

Is the tongue-eating isopod the only one of its kind?

No, the tongue-eating isopod is just one example of parasitic isopods. There are over 10,000 species of isopods, and a number of them have parasitic lifestyles, affecting a variety of marine organisms. However, Cymothoa exigua is unique in its ability to replace an organ of its host.