Inhabitants of Fish Mouths: Creepy Substitutes for Their Tongues

Eerie Parasitic Isopod Takes Over Fish Mouths, Devouring Tongues

A nightmarish parasitic isopod, known as the Cymothoa exigua, has been discovered residing within the mouths of fish, replacing their tongues and feeding on their blood.

These isopods inhabit the mouths of various fish species.

Isopods of the Cymothoa exigua kind inhabit fish mouths, effectively residing rent-free.

While Earthly Mission has previously explored some truly unsettling marine creatures, such as the Atlantic wolffish or the sarcastic fringehead, the tongue-eating louse may take the crown for creepiness.

The Cymothoa exigua, or tongue-eating louse, is an isopod that spends most of its life inside different fish species’ mouths. These creatures remove the fish’s tongue and take its place. Remarkably, the tongue-eating louse is the sole known parasitic creature that fully replaces an organ of its host species.

This parasitic journey begins with the tongue-eating louse entering the fish through its gills, a common entry point for fish parasites. Once inside, the louse makes its way to the base of the tongue, where it secures itself using strong legs. It then pierces the tongue, cutting off its blood supply, causing the tongue to atrophy and fall off. The parasite then attaches itself in place of the destroyed organ, acting as a functional prosthetic tongue for the fish, feeding on mucus and blood.

Interestingly, this arrangement doesn’t harm the fish, as the parasite benefits from its host’s survival. The fish can even use the louse as a functional tongue substitute, performing all the functions a real tongue would. This surprising symbiotic relationship allows the fish to lead a fairly normal life despite the unsettling presence of the isopod in its mouth.

Additionally, the life cycle of the tongue-eating louse holds another layer of intrigue. Juvenile Cymothoas transition into females when they inhabit a vacant spot, while those that don’t find a spot remain as males in the fish’s gills. Once a male and a female have matured, the male enters the mouth and mates with the female, after which the female gives birth to a new generation of lice, continuing this nightmarish cycle.

The post-mortem behavior of the tongue-eating louse remains largely unknown. It’s possible that the louse detaches from its host and searches for a new home, although snapper fish appear to be its primary targets. Fortunately, the Cymothoa exigua poses minimal danger to humans, though it might give an unwelcome bite if touched.