This Tongue-Eating Parasite Replaces Fish Tongues (And it gets weirder)
Sorry, but it’s true. Sometimes nature is absolutely metal - which can be awesome. But, other times, it’s just straight-up terrifying. With the tongue-eating louse (Cymothoa exigua), the first impression is definitely the latter.
Still, if you stick with us through this you’ll get to see that this nightmare-sounding parasite is actually pretty interesting. Although, still absolutely creepy.
They’re the Only Known Parasite to Functionally Replace an Organ
Parasites making drastic changes to animal bodies and behaviour is not unheard of. But these parasites are unique. Not only do they replace the tongue with their own body, but their body becomes a functioning tongue for the fish. Generally, the fish functions totally normally with the new tongue.
The biggest side-effect is that the fish sometimes end up a little underweight. And even that is only in the instance of having multiple parasites in the same fish.
Usually, any substantial change like this has far more negative effects on the host species.
For example, we’ve all seen the Zombie Ant Fungus Parasite (Ophiocordyceps unilateralis) in the Planet Earth Series. That parasite controls the ant’s movements, moving it to a prime location, killing it, growing stalks out of their bodies and then releasing spores to infect the rest of the colony.
Although we now know the parasite affects the ant’s body, not it’s mind, this video is still pretty accurate:
By contrast, simply getting a tongue upgrade doesn’t sound so bad. Granted, how they do it is still kind of gross. I sure hope no one tells us about it in detail.
How Parasitic Isopods Replace Tongues - In Detail
Of all the Cymothoa species, only three of these parasitic isopods are known to behave this way. Cymothoa exigua, C. borbonica, and C. imbricata. Of these, we know the most about the C. exigua, so that’s the one we’ll discuss. It happens in 5 stages:
- Entering the fish
- Remove the tongue
- Become the tongue
- Live the good life
- Moving on
Entering The Fish
The parasite first enters the fish through the gills. This is pretty normal - it’s a common way for parasites to get in. But, don’t get used to normal.
So here’s the thing. All C. exigua parasites are born male. But when they enter the fish, they transition into a female. This only happens if there is no female already in place. Otherwise, they’re staying at the sausage party.
The transition is no small change. Their eyes shrink, their legs get longer, and their body gets big. Really big. They go from being a tiny parasite to the size of a fish tongue (oooh, foreshadowing).
So, hey, feel free to take a moment and celebrate their gender-fluid lifestyles. But then you’re going to want to brace yourself.
Remove The Tongue
This is where things get icky. The parasite clamps on to the tongue with their claws. As a useless point of reference, if this happened to you it would feel nothing at all like a tongue piercing. Fortunately fish don’t feel pain the same way as we do, although they do feel pain.
You’ll be glad to know the parasite doesn’t just chew or slice the tongue right off. But you won’t be happy to hear what it does.
Instead of cutting off the tongue, they use their claws to cut off the blood supply. The lack of circulation causes the tongue to slowly atrophy and fall off. Now the fish is left with nothing but a stump.
But don’t worry, this problem resolves itself.
Replacing The Tongue
Good news, the fish is about to get a brand new tongue that’s just as good as the old one. But, you’re not going to like this prosthetic. The parasite latches on to the tongue-stump with its legs and its body becomes the new tongue.
It performs all the fishes’ tongue duties and functions, albeit with a terrifying appearance. But hey, at least the fish can’t see it. In exchange for playing the role of the tongue, the parasite uses the fish to survive. Depending on the species it will feed off either the host’s blood or mucus.
Granted, this isn’t much of a give-take relationship. After all, without the parasite, the fish wouldn’t have needed the tongue replacement in the first place.
Still. It’s a great trade-off for the parasite. And once attached, they’re ready to live the good life.
Living The Good life
Once that parasite becomes the tongue, oh baby, she’s living the good life. All they do is feast, mate, and pump out babies. They enjoy the warm waters and beautiful sunsets off the coasts of California down to Ecuador or cruising off the coasts of Florida.
This is where all the male parasites come into play. They entered the fish as juveniles, but if a female is already there they grow up as males. So they just go hang out in the gills with all their bros.
They grow up together waiting until the gal is ready to mate. Until then they stay together - presumably high-fiving and playing fantasy football. Once they all reach maturity they stop playing flip cup and venture in.
After a short gestation period, she gives birth to a whole new generation.
Starting out is tough for the new brood. They have limited energy reserves and seeking out a new fish takes up most of that energy, so they have to take any opportunity they can. Which is probably why so many males wait on a single female.
They use their sense of smell to find a new host. Then they wait for the fishes shadow to pass above them and they launch themselves directly upwards.
And for the tongue, life goes on. They stay with that fish until one of them dies.
Moving On
Once the fish dies, it’s not over for the parasite. The tongue-eating louse simply detaches and drifts off. To date, there’s not really enough data to be sure about what happens after this. Perhaps they continue until they can find a new host. Or they may simply drift off until they join the great tongue in the sky.
In fact, with our observations so far, it’s not certain that this same lifecycle is shared across all species or in all regions. This knowledge mostly comes from the research of Colt William Cook whose studies were conducted off the coasts of Texas and Florida.
Fortunately, we do know the answers to some of the most common questions about them:
What Do They Taste Like?
You’re not weird for asking - it was our first thought too. After all, if something were going to replace your tongue, you’d want it to taste good. Well, some people eat them - because people can be just as weird as parasites. As it turns out, they taste like shrimp.
Can The Tongue-Eating Louse Affect Humans?
More good news, you’re safe from the tongue-eating louse. A few people have been bitten when handling the parasite. But they don’t seem to chew out our tongues, let alone replace them. Granted, parasites evolve quickly due to their large populations and short lifespans. So who knows, so it could happen at some point. Maybe even soon - happy nightmares!
That being said, since we don’t live in their environment, it’s not that likely. We hope.
Depending on where you live they can sometimes show up on your dinner table. They’re found in a number of fish, including ones commonly eaten. But there is no harm in eating them.
What Fish Do Cymothoa Exigua Attach To?
So far, we know they target at least 8 different species of fish. This includes:
- 7 species of Perciformes
- 3 species of Snappers (Colorado snapper, Red snapper, & Jordan snapper)
- 3 species of croakers/drums
- 1 species of grunt & 1 species of grunion
- 1 species of Atheriniformes
And hey, just for fun, they’ve also been found in crabs and geoducks.
So Are They Gross or Are They Awesome?
If you made it this far, you’re probably on our side. Which is to say, they’re awesome. It’s one more way that nature can throw a total curveball at us. And, it definitely helps that it doesn’t affect us. At least, not yet…
Need some eye bleach? Why not learn about the new species of killer whale?
Or, if you’ve got a thirst for blood, learn how many leeches it would take to bleed out a human.