Scary Sex Organs: Ducks & Turtles

Most people have absolutely no idea how incredibly strange the sexual equipment (and behavior) of other species are. If you’re unfamiliar with the topic yourself, I heartily recommend Olivia Judson’s book Dr. Tatiana’s Sex Advice to All Creation or (for a more serious, but easily-accessible book) Adrian Forsyth’s A Natural History of Sex. Indeed, sexual selection is a topic I don’t think is considered often enough or taken seriously enough; could it be possible to cause evolution of certain structures faster through sexual selection than from adaptations to the environment? I think so.

Anyway, Darren has posted a must-read piece of the monstrous sex organs of male turtles, and if the Galapagos tortoises at the Philadelphia Zoo are any judge, some of the shelled-reptiles may have the appetite to match. When I first visited the zoo in the summer of 2006, at least one male was trying desperately to mate with an uncooperative female (making loud “huuuuuh!” noises all the while) that made many a nuclear family turn immature eyes away from the exhibit. In keeping with this theme I also happened across a LiveScience article about the absolutely bizarre male & female sex organs of some ducks.

Many male ducks of various species are unabashed rapists, going after females alone or in groups in order to achieve what is mildly referred to as “forced copulation”. In order to help facilitate this, many males have developed truly bizarre mating apparatus, often barbed, with a brush on the tip, or simply enormous (as is the case with the well-known Argentine Lake Duck). The females, of course, are no slouches when it comes to sexual innovation either, their sex organs often described as labyrinthine with lots of dead-ends or pockets, increasing the likelihood that during forced copulation the male will literally miss his mark. When the female is not struggling, however, the male would still need a bizarre member to successfully inseminate the female, so sexual innovations (while driven by some uncouth behavior on the part of some males) are necessary for all ducks.

What I’m wondering is how females develop such odd sex organs. I can understand that males with longer parts or ones that can remove past males sperm would be more successful and leave more offspring, but what sort of variation led to the odd parts of females and has allowed them to compete measure-for-measure with the males? Obviously it’s not something the female ducks can control themselves (i.e. “I don’t like those randy buggers so I’m going to evolve a more complex sex organ so only the good males will be the fathers of my offspring”), Obviously I didn’t know what I was talking about when I originally posted because females of many species can control which male ends up fertilizing them (thanks Neil). What I’m wondering is how selecting one males sperm over another leads to such complex organs, how does such an ability evolve and keep changing to keep up with males? Somehow I get the feeling that I’ll be kept up late many nights, contemplating duck sex until I can figure this one out.

Update the 1st; Apparently the paper, “Coevolution of Male and Female Genital Morphology in Waterfowl” is available on PLoS ONE, so all interested parties should check it out. I haven’t had the chance to check it out yet (I’ll write a new post when I do) but if you’re looking for more on the topic Neil has a great analysis of the paper and Bora (as always) is the link-master to seemingly everyone who wrote about it. I know I should be studying for my biology finals tomorrow, but it’s hard to concentrate when I have so many unanaswered questions about duck sex…