Fruit Fly Hook-Ups

Jan 09, 2010 • News, Research

OMG, ever wonder why male fruit flies have spikes in their genital areas?

Yeah, me neither, but scientists are starting to figure it out, so I’m going to share with you: male fruit flies use these spikes to hook onto the female and prevent sliding during sex. They “hook up”–literally! Get it?

Not very long ago, researchers had suggested these spikes were used to deliver sperm into the wounds they inflicted on females, but evolutionary biologists at the University of Cincinnati zapped off the spikes of a few male fruit flies (Drosophila bipectinata) and found that males were still able to inseminate the females–though with much more difficulty, as they continuously slid off during copulation.

“In Drosophila, unwilling females resist male sexual advances by vigorous kicking with their hind legs, bucking, extruding their genitalia in telescoping fashion, and if all else fails, by simply running or flying away from eager males,” said researcher Michal Polak, an evolutionary biologist at the University of Cincinnati. “The spines may be an evolutionary solution in males to overcome these forms of female resistance.”

Essentially, the spikes act like grappling hooks or genital Velcro, preventing the female from pushing off a male, or as LiveScience says, “like seatbelts on a bucking bronco.”

(Yeah, science reporting for the masses is really fun.)

But because researchers have not studied the female of the same species, it is hard to say whether these spines behave as Velcro or hooks. Polak suggests it’s the former, as the spines seem to embed at the same place on female genitals, meaning there could exist a place for the spine to anchor itself on the female.

He and his colleagues are planning to conduct more laser studies on genitals to get to the bottom of creatures’ adaptive functions in sexual selection.

Can’t wait!

Image from LiveScience and BOLD Systems. Information via LiveScience.