Friday Weird Science: The shark with two “heads”

Sci WAS going to do a cool story on bee sex sent to her by the charming Gg of Skulls in the Stars, but that’s going to have to happen next week. I just CAN’T let this one go by. I mean, a shark with a sexual organ on its HEAD?! It’s just too good:
Observe the Twitter record:
scicurious RT @jonahlehrer New shark has sex organ on head: http://tinyurl.com/nxqt6b At least the girls know which head its thinking with.
scicurious RT @jonahlehrer New shark has sex organ on head: http://tinyurl.com/nxqt6b Its got the right thing on its mind!
scicurious RT @jonahlehrer New shark has sex organ on head: http://tinyurl.com/nxqt6b The way to guy’s…heart…is thru his head!
scicurious RT @jonahlehrer New shark has sex organ on head: http://tinyurl.com/nxqt6b Hey baby, that’s a big head you’ve got on your shoulders.🙂
CyberLizard RT @scicurious: RT @jonahlehrer New shark has sex organ on head: http://tinyurl.com/nxqt6b Two heads are better than one!
scicurious RT @jonahlehrer New shark has sex organ on head: http://tinyurl.com/nxqt6b You can definitely tell that he’s happy to see you!
scicurious RT @jonahlehrer New shark has sex organ on head: http://tinyurl.com/nxqt6b Poor guy doomed to inspire a new genre of porn: Sharking

scicurious
@Allochthonous Heck yeah! I think I need to cover it for weird science friday. New shark discovered: spawns pickup lines.

CyberLizard
RT @jonahlehrer New shark has sex organ on head: http://tinyurl.com/nxqt6b Is that an illicium on your head or are you happy to see me?
I think CyberLizard and I could do this ALL DAY.
ResearchBlogging.org James et al. “A new species of chimaera, Hydrolagus melanophasma sp. nov. (Chondrichthyes: Chimaeriformes: Chimaeridae), from the eastern North Pacific” Zootaxa, 2009.
Eastern_Pacific_Black_Ghostshark.jpg
And it looks so innocent.


Obviously, this has been all over the internet the past few days. Unfortunately, very few people have identified WHAT the sexual organ on the head of the shark IS. Several people have said “tenaculum”, several have said “claspers”, but there hasn’t been a lot of delving into what that actually means.
So I delved. And I discovered three things:
1) Chimaera are WICKED!
2) Sexual organs on heads are not new.
3) Papers describing a new species may the MOST BORING pieces of scientific literature I have ever run across in my life. Up to and including papers describing pure methods. Ouch.

“Dorsal spine and first dorsal fin overlap with second dorsal fin when laid flat. First
dorsal fin triangular, base short 15.3 % BDL (13.9%), with concave posterior margin. Second dorsal fin long,
uniform in height throughout, and its base length 81.1% BDL (77.3%). Depth of second dorsal fin, 4.0% BDL
(4.1%), is greater than depth of dorsal lobe of caudal fin, 2.0% BDL (3.3%).”

Obviously this isn’t the fault of the authors. Has to be described. But it was kind of painful.
Anyway. So today we talking about the ghost shark. The ghost shark is just a common name, the actual name we’re dealing with is Hydrolagus melanophasma, a very newly described species which lives just north of the Gulf of California in the Pacific. It’s not a SHARK, actually, it’s a chimaera. These are cartilaginous fishes (skeleton is made of cartilage, like your nose, as opposed to body fishes, which have skeletons made more like ours) which are closely related to sharks, but aren’t, and include the bottom-feeding ratfish, and the ghost shark.
There are lots of things that are interesting about these chimaeras. For one thing, they are FANTASTICALLY ugly. I mean really:
chimaera1.png
(A face only a mother could love, though admittedly this one is looking a little preserved…)
For another, they are EXTREMELY old. Not on a personal level, but as a species. They may be one of the oldest species of fish alive today.
And of course, this is nothing compared to their incredibly weird sexual practices. The sexual behavior of the chimaera is similar to that of sharks. Basically, it comes down to this:
chimaera2.jpg
You might look at that and say “DUDE!!! That shark (in this case it’s a shark) has TWO PENISES!”
You would be wrong. Those are claspers, not penises. They are used during mating to channel the sperm from the male to the female, which could help a lot when you’re stuck with a lot of shifting currents.
But this is where chimaeras and sharks differ. While sharks just have the two claspers, right near the penis, the chimaera has…a few more. Up to FOUR MORE. Including claspers above the pelvic fin, and in the case of the particular species today, one on the HEAD:
chimaera3.png
(The three sets of tenacula, which is the latin term for something that helps something else to adhere or grasp)
So why, you might ask would a fish HAVE these things? Well. To stick to things. Like ladies. I’m not sure if there’s any videos or photos of this in action, but it appears that the ghost shark will use his claspers on the head and pelvic fin to grasp the female’s pelvic fin and…head (? I mean, where else does that thing go?), holding her in place while they get it on. So technically speaking, though it’s an organ used in sexual behavior, it may not be a very sexual organ, and the “sex organ on head” headline may be a bit of a misnomer, at least in common parlance. I doubt the whole fish shudders in ecstasy when you stroke its tenacula or something. Though I suppose you never know.
And while this whole clasper/tenacula on the head thing is making the news recently, it’s actually been known that most species of chimaera (I think there are something like 20or more species of Hydrolagus, the genus we’re dealing with here) have these handy, heady appendages. Way to get AHEAD in life. You have to figure that mating for them is a pretty HEADY feeling. Brings a new meaning to getting head…
…told you I could do this all day!
KELSEY C. JAMES, DAVID A. EBERT, DOUGLAS J. LONG & DOMINIQUE A. DIDIER (USA) (2009). A new species of chimaera, Hydrolagus melanophasma sp. nov. (Chondrichthyes: Chimaeriformes: Chimaeridae), from the eastern North Pacific Zootaxa, 2218, 59-68

6 Responses

  1. Ugly? Chimaeras are incredibly adorable. They look like Mr. Bean.

  2. For another, they are EXTREMELY old. Not on a personal level, but as a species. They may be one of the oldest species of fish alive today.

    No. The species Hydrolagus melanophasma can’t be very old. Sure, chimeras as a group go down all the way to the Devonian, but that’s not a single species, and of course their sister-group, the sharks-including-rays, are just as old as a group.

  3. Throw me a bone here. Can’t we get one with a laser on its head?

  4. @3
    Well, I suppose laser targeting /could/ help if they’re not experienced and their aim is poor😉.

  5. I’m sad that’s not a penis on its head. It was way more fun on Twitter when that thing was a penis. Can’t we pretend?

  6. No. The species Hydrolagus melanophasma can’t be very old. Sure, chimeras as a group go down all the way to the Devonian, but that’s not a single species, and of course their sister-group, the sharks-including-rays, are just as old as a group.
    I don’t think that’s exactly true. We obviously can’t test whether a living organism and fossils are the same biological species, but then we can’t tell whether all T. rex are the same biological species either. For fossils we use morphospecies, and it’s perfectly possible for a lineage to change so little even over the course of millions of years that they count as the same morphospecies. For example
    (I don’t know whether that’s the case with H. melanophasma, but it’s certainly possible.)

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