Cymothoa exigua: The Tongue-Eating Parasite That Becomes the Tongue

What kind of parasite eats a fish’s tongue and then stays behind as the tongue? In this episode, we unpack Cymothoa exigua, the tongue-eating parasite, how it gets into fish through the gills, why the host can often keep feeding, and what this bizarre case reveals about parasite biology and evolution—listen now before this one gets buried under a hundred half-true versions of the story.Cymothoa exigua, the tongue-eating parasite, sounds like a horror story — but it’s a real parasitic isopod that can enter a fish through the gills, feed on the tongue, and then function as the tongue itself. In this episode, we unpack the biology, the weird evolutionary trade-offs, and why this fish parasite is famous in marine biology.• Cymothoa exigua is the only known parasite that physically replaces a host organ in form and function. • It mostly targets marine fish like snappers in the eastern Pacific. • Infected fish can often keep feeding, even while their mouths and gills are under chronic stress. • Humans are not known hosts, and infected fish are generally considered safe to eat.Chapter labels: The Fish With a Missing Tongue How the Parasite Gets In Why the Fish Still Survives What This Means for Marine EcosystemsRelated resources: [More marine biology episodes](/shows/marine-biology) [Transcript](/transcripts/cymothoa-exigua) External: [Wikipedia](https://en.wikipedia.org/wiki/Cymothoa_exigua) External: [Ocean Conservancy on tongue-eating lice](https://oceanconservancy.org/blog/2022/04/28/tongue-eating-louse-eats-tongues/)If this episode made you rethink what parasites can do, share it with a friend and subscribe for more strange-but-true science stories.