The bird that got screwed…

What you’re about to read, is the story of an amaz­ing penis.

You’ll read about how thin it is, but con­versely, how long it is too.

You’ll read how about it is screwed in and about how con­vo­luted the ori­fices are that it inhabits.

Ulti­mately, you will dis­cover what an explo­sive appendage it is and about how the part­ners it pairs han­dle an organ seem­ingly way out of pro­por­tion to the rest of the body car­ry­ing it.

Kink­i­ness Beyond Kinky

By Carl Zim­mer | Decem­ber 22, 2009 7:55 pm

There comes a time in every sci­ence writer’s career when one must write about glass duck vagi­nas and explo­sive duck penises.

That time is now.

To err on the side of cau­tion, I am stuff­ing the rest of this post below the fold. My tale is rich with deep sci­en­tific sig­nif­i­cance, resplen­dent with sur­pris­ing insights into how evo­lu­tion works, far beyond the banal­i­ties of “sur­vival of the fittest,” off in a realm of life where sex­ual selec­tion and sex­ual con­flict work like a pair sculp­tors drunk on absinthe, trans­form­ing biol­ogy into forms unimag­in­able. But this story is also accom­pa­nied with video. High-definition, slow-motion duck sex video. And I would imag­ine that the sight of spiral-shaped penises inflat­ing in less than a third of sec­ond might be con­sid­ered in some quar­ters to be not exactly safe for work. It’s cer­tainly not appro­pri­ate for ducklings.

So, if you’re ready, join me below the fold.

This story is actu­ally a sequel. Back in 2007, I wrote in the New York Times about the work of Patri­cia Bren­nan, a post-doctoral researcher at Yale, and her col­leagues on the weird­ness of duck gen­i­tals. The full story is here. (Bren­nan also appeared in a Nature doc­u­men­tary, start­ing at about minute 38:35.)

In brief, Bren­nan wanted to under­stand why some ducks have such extrav­a­gant penises. Why are they cork-screw shaped? Why do they get so ridicu­lously long–some cases as long as the duck’s entire body? As Bren­nan dis­sected duck penises, she began to won­der what the female sex­ual anatomy looked like. If you have a car like this, she said, what kind of garage do you park it in?

Bren­nan dis­cov­ered that female ducks have equally weird repro­duc­tive tracts (called oviducts). In many species, they are orna­mented with lots of out­pock­ets. And like duck penises, duck oviducts are corkscrew-shaped. But while male duck penises twist clock­wise, the female oviduct twists counterclockwise.

Bren­nan spec­u­lated that all this bizarre anatomy is the result of a pecu­liar form of evo­lu­tion known as sex­ual con­flict. A strat­egy that allows females to repro­duce the most off­spring may not be so good for males, and vice versa. For exam­ple, male fruit flies inject their mates with lots of chem­i­cals dur­ing sex, and those chem­i­cals make her less recep­tive to other males, thereby boost­ing his chances of father­ing her eggs. But those chem­i­cals are harsh and will make female flies sick. Females, in turn, have evolved defenses against those chem­i­cals, blunt­ing their effects.

With many exam­ples of sex­ual con­flict in nature, Bren­nan won­dered if sex­ual con­flict between male and female ducks was giv­ing rise to their weird gen­i­tals. Female ducks pair off with male part­ners for the breed­ing sea­son, but they also get har­rassed by other males, some­times being forced to have sex (and some­times dying from the attacks). A third of all duck mat­ings are forced.

And yet only 3 per­cent of the duck­lings that female ducks pro­duce come from such forced mat­ings. Bren­nan spec­u­lated that the female ducks can block forced cop­u­la­tions with their mis­matched spi­rals. And they might also be con­trol­ling which drake got to fer­til­ize their eggs by sock­ing away the sperm of dif­fer­ent mates in dif­fer­ent pock­ets. And the extrav­a­gant penises of males might be the result of an evo­lu­tion around those defenses.

As I reported in 2007, Bren­nan dis­cov­ered a pat­tern that sup­ported this hypoth­e­sis. Among 16 species of water fowl, species in which the males grew long phal­luses also had females with more turns in their oviduct and more side pock­ets. The ducks were esca­lat­ing an arms race, gen­i­tal for genital.

But Bren­nan didn’t actu­ally know how duck penises actu­ally moved through the labiryn­thine oviduct, and how the oviduct’s shape might affect the drake’s deliv­ery of sperm. So she traded calipers and rulers for high-speed video.

Bren­nan and her col­leagues trav­eled to a Cal­i­for­nia duck farm, where work­ers are expert at col­lect­ing sperm from drakes. The first step in the col­lec­tion is to get a drake excited by putting a female duck in his cage. The drake climbs on top, and then the penis emerges. Before its emer­gence, a drake’s penis is usu­ally com­pletely hid­den from view, tucked inside his body like an inside-out sock. Drakes unfurl their pen­sises dif­fer­ently than male mam­mals. In mam­mals, the penis becomes erect as blood flows into the spongy tis­sue. Ducks pump lymph fluid instead. And as the fluid enters the penis, it does not sim­ply become engorged. It flips rightside-out.

Here’s how it hap­pens, in slow motion. A Mus­covy drake everts his penis in about a third of a sec­ond, at speeds of 1.6 meters per second.

Of course, drakes don’t mate with the air. Hav­ing made this video, Bren­nan still needed a way to see how a duck penis actu­ally per­forms its appointed task. Unable to film duck penises in a real female oviduct, she built a fake oviduct out of sil­cone. She then man­aged to get a drake to mate with it. But the over­whelm­ing force of the explo­sive penis broke the fake oviduct.

So Bren­nan turned to glass. Her new fake oviducts were strong enough to han­dle the drakes, and she started film­ing. Here’s what she saw.

As Bren­nan had pre­dicted, the coun­ter­clock­wise turns of an oviduct slow down the expan­sion of the duck penis, com­pared to a straight tube or a clock­wise one. Bren­nan sus­pects that female ducks slow down males try­ing to force a mat­ing, but they can also let their partner’s penis move faster through the oviduct. They have been observed to relax and con­tract their mus­cles arond the oviduct.

Female ducks can’t stop an unwanted male from deliv­er­ing his sperm, but the obsta­cles in their oviducts may give them con­trol over what hap­pens to that sperm. The female ducks may use their oviducts to slow down the expa­na­tion of the penis, so that by the time the drake ejac­u­lates, the sperm are deliv­ered in the lower reaches of the oviduct. A female ducks’s part­ner, with her coop­er­a­tion, can deliver sperm fur­ther up the oviduct. With the wanted and unwanted sperm deliv­ered to dif­fer­ent places in the oviduct, a female duck may be able to store the sperm in dif­fer­ent pock­ets. And then she can choose which drake will father her duck­ling. For all the explo­sive­ness male ducks may dis­play, it’s the female ducks that get the final say.

Ref­er­ence: Patri­cia L. R. Bren­nan et al, “Explo­sive ever­sion and func­tional mor­phol­ogy of the duck penis sup­ports sex­ual con­flict in water­fowl gen­i­talia,” Pro­ceed­ings of the Royal Soci­ety of Lon­don, doi: 10.1098/rspb.2009.2139

[Update: 12/23–a cou­ple mis­spellings fixed]

Source: Dis­cover Magazine

If you’ve come this far, I just know that you’re itch­ing to see one…

Ever­sion in air: from from Carl Zim­mer on Vimeo.

You have such a dirty Mind, but that’s alright. 😉

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