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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.

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