The Tongue-Eating Louse: An Unusual Parasite

Introduction

• A Northern Ireland man discovered a tongue-eating louse, or Cymothoa exigua, in a fish he was preparing for dinner.

Overview of Cymothoa Exigua

• Part of nearly 400 species of cymothoid fish parasites.
• Crustaceans and isopods, similar to pill bugs.
• Various attachment methods: head, gills, flesh.

Unique Behavior and Lifecycle

• Specialize in attaching to and replacing fish tongues (basihyal).
• Use stored yolk reserves while seeking a fish host.
• Attach to fish gills and alter body structure upon settling.
• Transition from male to female in the absence of an existing female.
• Functionally replace the fish's basihyal, facilitating feeding.

Reproduction and Impact

• Females host hundreds of offspring in a brood pouch.
• Fish can survive for years despite parasitism.
• Effects include slower growth, anemia, and susceptibility to stress.

Prevalence and Human Interaction

• High infestation rates in snappers, trout, croakers, and fish farm species.
• Occasionally appear in grocery stores but are harmless to humans.

Conclusion

• While not harmful if ingested, the presence of a tongue-eating louse in fish can be an unsettling discovery.