GREEN
12/16/2011 04:01 pm ET Updated Dec 17, 2011

Ostrich Penis Study Solves Evolutionary Puzzle

Thanks to a new study on the mechanics of ostrich erections, the animal kingdom's biggest birds have a new reason to bury their heads in the sand. Fortunately, for evolutionary biologists, a little peek under the feathers has solved a long-standing mystery about avian evolution.

A new study of the ostrich's male organs reveals that the birds achieve erections using a burst of lymphatic fluid through the penis, a vastly different approach than the rush-of-blood-to-the-veins method employed by the organs of reptiles and mammals, researchers reported in a study published this week in the journal Zoology.

So why are scientists so excited about the study, aside from the fact they have a new arsenal of ostrich penis facts to whip out at scientist cocktail parties?

In brief: Only three percent of birds have penises, and all previously studied bird penises were found to use lymph nodes to achieve erections, Adam Marcus explains in Nature. The discovery that ostriches also have erections fueled in this way suggests that the common ancestors to all birds had a lymphatic system, which suggests that the evolutionary split between animals with lymph and blood-based erection occurred in the last common ancestor of birds.

"Our findings reveal that the evolution of a lymphatic erection mechanism likely occurred in the ancestor of all birds rather than within birds," co-author Patricia Brennan, an evolutionary biologist at the University of Massachusetts Amherst, told Nature.

That's welcome news for ostriches, whom scientists might have suspected were a little freaky because when they mate, it doesn't look like other birds. Most of the 3 percent of birds with penises mate using a lightning-fast maneuver called the 'cloacal kiss,' where sperm is quickly inserted into the female, Nature explains. But not so with ostriches (as documented in more than one YouTube video).

No, ostriches didn't evolve some strange bird penis to mate in their strange unbird-like ways. Nor are all the other phallus-endowed birds weird for having developed a strange lymphatic-erection mechanism out of nowhere. In fact, the evolutionary shift to lymph-fueled erections occurred in the last common ancestor they shared with all other birds.

Still, researchers are continuing to study the implications of what lymph-based erections mean for different species of birds with penises and the evolutionary advantages they might offer.

"What is weird about birds is that they evolved not just a new structure, but a novel way to do something that was already being done," co-author Richard Plum explained to Nature.

Ostriches aren't the only animals whose mating habits have raised evolutionary questions this year. Thirty years ago, entomologists Darryl Gwynne and David Rentz observed certain kinds of Australian beetles trying to have sex with discarded beer bottles, prompting the scientists to conduct research on the poor insects, who often died as a result of their mating attempts, BBC News reported. The scientists were award an "Ig Nobel" prize for their work, an alternative award to the Nobel Prize which seeks to honor research that will "first make people laugh, and then make them think."

"It was just co-incidental that my area of research was Darwinian sexual selection and how sex differences evolve, and here was a classic example taking place in front of my eyes where males were making mating errors," David Rentz told the BBC. "It was very obvious the beetles were trying to mate. These beetles have enormous genitalia, and they're large to start with - over two inches long. The sad thing was that these beetles were dying; they wouldn't leave the bottles alone. They'd fall off them exhausted."

Another insect seems to have the opposite problem of mating fatigue: bedbugs.

After last year's disastrous bedbug infestation, researchers looked at 21 bedbug infestations from Florida to Maine and found that most could be traced back to one or two insects in a single room, Bloomberg reported. This suggests that bedbugs mate incestuously with parents and siblings without any ill-effect.

"Parent-sibling matings and sibling-sibling matings are rare in the animal kingdom. So this study reveals an exception to the anti-inbreeding rule," Amy Maxmen, a blogger for Scientific American, wrote on the site. "But I'm drawn to the report for a pettier reason. As far as I'm concerned, DNA evidence has trumped the words of my landlord and a New York City housing inspector."

Want to learn about more weird animal traits? Check out these bizarre animal mating rituals (WARNING: GRAPHIC CONTENT):

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What They Do For Love... Or Some Sex
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What They Do For Love... Or Some Sex

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