Photo courtesy of Prosanta Chakrabarty
The other day, when Ben Richmond over at Motherboard filed a story on a new kind of cave fish with its anus just behind its head, I had to know more. Coverage elsewhere focused on the new species, known as the Hoosier cave fish, already being considered endangered. Still, no one was telling me what I needed to know: Why have an anus on (or just behind) your head in the first place. Should I be jealous?
The discovery came from Matthew Niemiller from the University of Kentucky and Prosanta Chakrabarty from Louisiana State University. I managed to track down Chakrabarty, who turned out to be kind of an ichthyology rockstar, if you'll permit me to stretch the definition of rockstar to its breaking point.
In this video, he explains in plain, lucid language, why we should pay less attention to oil-stained pelicans in the aftermath of the Deepwater Horizon oil spill, and focus instead on the all the disgusting bottom feeders who get short shrift. After all, they're the ones who make their homes in the muck that becomes inhospitable thanks to the oil and dispersant chemicals we leave down there.
But never mind all that. The important thing is figuring out why the Hoosier cave fish has its asshole on its head. To explain, Chakrabarty had to take me on a surprisingly thrilling journey through what he calls its "lifestyle," touching on why it's blind, and why it poops sperm into its mouth. It was a crazy ride, but it all came full circle. Then he burned me for having a small dick.
VICE: Hi Dr. Chakrabarty. I'm going to need to know why this new fish has an anus on its head, but am I asking the right question? Is that the important thing?
Prosanta Chakrabarty: Well, the coolest thing is that it's the first subterranean cave fish that's been found in North America in 40 years. We sort of made this discovery based on molecular work that my coauthor Matthew Niemiller did, and It's telling us about the evolution of blindness, and how in some cases like this one the genes are catching up with the morphology. So the change to a subterranean lifestyle happened well before the loss of function of some of the genes related to their lifestyle.
Let me see if I follow: These are fish that not only are blind, they do not have eyes?
Yep. They don't have eyes.
And at some phase in their evolution their ancestors had eyes?
Their ancestors had eyes, and when they entered these cave habitats, they lost them.
OK, but how does that make this fish special?
This is kinda cool: There are about 150 species of fish that have become cave fishes. They've lost their eyes. They've lost pigmentation. It's happened at least a couple dozen times. And every time they do this it's a new way of evolving blindness. There's no light. It's pretty much a constant temperature. So it's a very different environment than what we live in where sight is very important. In a cave, even if you had eyes, you wouldn't be able to use them. It's pitch black.
So this random mutation knocked out rhodopsin [the gene for vision] in one of the species, but not the species we just described. It's still producing a functioning gene, even though that gene doesn't basically do anything. It just shows you how finicky these mutations are when they come about. You can still have a functional gene for something, even though you lack the eye altogether.
So it's one of those inefficient evolutionary remnant things? Like when Richard Dawkins dissected that giraffe and proved that some nerve was going all the way up and down its gigantic neck for no reason?
I don't think I know that story, but there's weird things about giraffes for sure. There are remnants even in humans. We have organs that don't serve much of a purpose, and things that aren't well-designed. Our heart is pretty crappy. It's not simple explaining any organism. You would think going blind would be easy, and it sorta is, but it shows you that it's not always the DNA that goes first.
But what does its blindness have to do with having an anus on its head?
Well, it's really bizarre. So some people say it's to poop out of the water. So they can lift their bodies out of the water and poop on land. But they all figure that it's also to get the eggs inside the gills. It's a cloaca, but functionally, it's mostly an anus. But eggs are coming out of that hole too. Everything comes out of there.
So having [its anus] right behind the head allows the eggs to get more simply into the gills, which is where these guys brood their young. Nobody's observed this, but we know its closest surface ancestors do this, so we're assuming it's for the same reason. One odd thing is, we're not sure how fertilization happens, but that might be facilitated by having the cloaca-head-neck-anus.
So they sort of at the same time push their heads and anuses together, and that might be how mating occurs?
Yeah, we think it might be mouth brooding. Sperm comes through the mouth, then through the gills, and then it's fertilized. It's a possibility, but it's the one that makes the most sense.
So you're saying that it effectively poops sperm into its mouth?
Yeah, maybe. That's our best guess. Lots of fish actually have mouthbrooding, where the females are taking up sperm into their mouths where they also have the eggs. With these guys we're saying that's essentially pushed into the gills as well. They're freaky.
What's the advantage of brooding your young in your gills?
Well, if you don't have eyes, and you can't see where your babies are, you'd want to keep them pretty close. That's about as close as you can get without developing internal fertilization, which has only happened a few times. This allows them to kind of protect their young.
But even for a blind fish, that's like being pregnant in your lungs, isn't it?
It also means the young get more oxygen. They get more water flow, because in caves, usually the water gets pretty stagnant. So this will allow more water to flow over them, which allows more gas exchange, which will help them develop.
So it's not just a safe place?
No. There's certainly an advantage to having your babies brood in your gills.
The other thing I wanted to ask is, did you name it as an insult to Hoosier basketball, because you're at rival schools?
No. Matt grew up in Indiana. He was really excited about naming it that. He's a huge Hoosier fan. I can't talk to him during basketball season. The name is in praise of the University of Indiana for starting North American ichthyology. But it's weird how the anus is news, and I don't know if you saw the Gawker article, where they said it looks like a dick…
Oh the Gawker picture definitely looks like a dick.
Not mine, but maybe somebody's.
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