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Genital Complexities Give Mating Advantage, Research Suggests


UC researcher Michal Polak finds that when it comes to hooking up with the opposite sex, genital complexities do matter.

Date: 1/7/2010 12:00:00 AM
By: Wendy Beckman
Phone: (513) 556-1826
Photos By: Dottie Stover, photojournalist

UC ingot   Charles Darwin spent eight years studying barnacles and their genitalia. In much less time than that, University of Cincinnati evolutionary biologist Michal Polak (and co-author Arash Rashed, now at the University of California, Berkeley) have confirmed one of Darwin’s theories: that genitalia complexities in some species have developed because they assist the male in “holding her securely.”
Michal Polak, associate professor of biological sciences
Polak says he will be using the laser in a variety of ways in his research.

As just published online in the Proceedings of the Royal Society B, “Microscale Laser Surgery Reveals Adaptive Function of Male Intromittent Genitalia” Polak’s research showed that without a doubt among the fruit fly species Drosophila bipectinata Duda, the males’ penile peculiarities assisted them in copulation.

Polak, an associate professor in the Department of Biological Sciences in McMicken College of Arts and Sciences at UC, used a laser ablation technique to cut off tiny “intromittent” spines on the genitalia of virgin male D. bipectinata fruit flies.

“We refer to these genital spines as intromittent because they insert [them] into female external genitalia during copulation, and not because they insert into the reproductive tract,” Polak and Rashed explain in their paper.

Magnified image showing an ablated spine and an intact spine.
This image has been magnified to show an ablated spine and an intact spine.

Polak’s study concluded that the male genital spines serve two functions. When the spines were removed, the males experienced drastic reductions in ability to copulate and ability to compete against rival males for mates. However, if the males were able to copulate, they found that insemination and fertilization rates were not significantly different.

They’re not done yet, says Polak.

“We are using the laser for a variety of projects, including to surgically excise other genital traits and the tiny but elaborate male sex ‘combs’ used in courtship, and to study their adaptive function in sexual selection.”

This research was partially supported by National Science Foundation (NSF) USA (grant DEB-0345990).



Read more about it:

“Microscale laser surgery reveals adaptive function of male intromittent genitalia,” Proceedings of the Royal Society B



“The Spiky Penis Gets the Girl” by Emily Laut, ScienceNOW Daily News