When I grow up, I want to be a tongue

There’s someone special I’d like you to meet.

Everyone, meet this sex-changing, tongue-eating parasite. Sex-changing, tongue-eating parasite, everyone.

Image credit: Andy Heyward via Flickr

If you are one who’s easily grossed out by things, this is your opportunity to abort from this post. Although this parasite may not be easy on the eyes, their biology is fascinating.

Screen Shot 2014-08-22 at 11.21.14 pm
Parasite got your tongue? Image credit: Maria Sala-Bozano/University of Salford via Flickr

So Daphane, tell me more about this sex-changing, tongue-eating parasite.

Well, these parasites are called tongue-eating louses – or scientifically known as Cymothoa Exigua. They’re parasitic crustaceans that swim into the fish’s mouth, chomps away on its tongue, then becomes the fish’s new tongue.

Wait, what? How? Why? So many questions!

Let’s start from the beginning shall we?

Life as a tongue-eating louse begins as a male. When the male finds itself a target, it swims into the mouth via its gills, and turns into a female.

Here is where it gets interesting.

Using its seven pairs of claws, the parasite hooks her body on the tongue. She sucks blood from the tongue, she begins to grow, and the tongue withers away and falls off.

This is when she becomes the fish’s new tongue.

But when I say that the parasite becomes the host’s new tongue, I don’t just mean structurally. They also functionally replace their tongue too.

So yes, the host is able to use the parasite just like a normal tongue!

As humans, we have nothing to fear of these parasites (although if you pick them up alive with your fingers, they may bite. Yeah, don’t do that). The tongue-eating louse parasitise fish, and their favourite victims are red snappers.

The parasite doesn’t appear to cause the host any harm. The host carries on eating, and the parasite steals the leftover food in its mouth (sneaky buggers).

It’s important to note that this parasite changes sex only if there’s no female camping out inside the fish’s mouth – otherwise, the boys will be boys.

It’s easy to know whether the tongue-eating louse you’re looking at is a male or female.

Your ladies are noticeably much larger than your gentlemen parasites.

See for yourselves.

Screen Shot 2014-08-23 at 10.51.59 am
Image credit: Daphane Ng

I found these parasites in your everyday snapper at the Queen Victoria Market. So next time you buy a fish, look inside its mouth! You may be in for a lovely surprise.

Hello there. Image credit: Daphane Ng

The female louse then has sex in the fish’s mouth, gives birth to a brood of male lice, and releases them to the environment.

And the whole cycle begins again!

Essentially it’s this:

– baby male finds fish
– swims into fish gills to the mouth
– becomes a lady
– eats tongue
– becomes tongue
– has sex in the fish’s mouth
– gives birth to male babies
– release into the ocean
– repeat

Do you know of other strange animals? Please enlighten me in the comments!

11 Responses to “When I grow up, I want to be a tongue”

  1. jzaldumbide says:

    Great blog, a little bit disgusting but interesting at the same time.

  2. zhassan says:

    Fascinating, the things that nature comes up with! I’m a little weary eating my next fish though! Fillets only from now on!

  3. kcranney says:

    This is disgusting and fascinating. Fantastic!

  4. gvarveri says:

    best title.

  5. Daphane says:

    @ebyers: Hey Emma! Thanks for the suggestion. I’ll keep it in mind for my next blog post 🙂

    @rpoon1: Thank you! Hope you managed to find one or two.

    @Ashton Dickerson: YES! I know what you mean by that.

    @sogandh: Thanks for the question. From my understanding, the fish doesn’t get anything out of this relationship between the parasites. The parasites benefit, but the host doesn’t.

    @jwhinfield: Great questions! As awesome as it would be to for a fish to have a double parasite tongue, only one parasite becomes the female and takes the place of the tongue. However the exact details of who becomes the female and ‘wins the tongue’ when there are other parasites around is unclear. Compared to other organisms, very little is known about the tongue-eating louse. So unfortunately I can’t answer your first question.

    In regards to how these parasite find a suitable host – it appears that each species of the parasite is specific to a single species of fish. According to National Geographic, “they sniff for the scent of their host, and if a shadow passes overhead when the odor is strong, they shoot upwards through the water.” And you’re right, it’s amazing how these parasites find a host in such a huge environment!

    @gcao: Parasites are indeed scary, but fascinating!

  6. gcao says:

    Parasites are scary. Like the tape worm that lives inside human intestines and can grow up to several meters in length and the wasp larvae that lives inside a caterpillar and chews its way to the surface before it undergoes morphogenesis. Even though its scary, I still find this absolutely fascinating.

  7. jwhinfield says:

    Nice one Daphane! I’d love to know what happens if two parasites rock up in the same fishes mouth at the same time – would you get a conjoined, double parasite tongue?! Or would they fight it out for tongue supremacy…. And how do they find a suitable host in the first place? Suitable candidates must be hard to come by when your just a wee parasite in a big ocean!
    Thanks for raising a really interesting post, and I look forward to reading more of your blogs in the future 🙂

  8. sogandh says:

    WOW. although part of me wishes i never knew they existed at least I can be on the look out now. I’m very happy to read that they have no affect on us though.
    I was wondering, if the fish benefit from this relationship in anyway. I know you said they aren’t harmed but since the parasite steal the food. What do the fish get out of this?

  9. Ashton Dickerson says:

    I first found out about these dudes about a month ago. Isn’t it weird how when you learn about something new it starts to pop up everywhere – even though somehow it had evaded you your whole life until that point?

    Anyway, I just wanted to share that these things creep me out more than anything ever. Urgh!

  10. rpoon1 says:

    This is such an interesting post Daphane. I’m inspired to go look inside a fish’s mouth now.

  11. ebyers says:

    Ahhh! :O
    The things you’d never ever considered could possible exist…this is just too weird. I’ve never liked the idea of buying fish and now I’m pretty much put off forever!
    I thought this was a thoroughly engaging article, the only thing I could think of for improvement was possible turning the whole “lovely surprise” part of the article into a separate subheading so that you had the ‘3 points of entry.’
    Congratulations, 1 down!