Sperm Wars

March 19, 2010

Rheanna Sand

Science in Seconds Blog by Rheanna Sand

Insects are in a constant state of competition. The pinnacle is mating, which, if successful, passes on an insects' genetic material to thousands of adorable writhing larva babies. But in some types, like flies and ants, competition doesn't stop at copulation. Sperm must battle it out in the female reproductive tract, as she is likely to mate with multiple males in succession, the six-legged harlot that she is.

The question nagging at reproductive biologists has been, how do you examine the post-mating battle? They can figure out who fathered the progeny - with a little help from Maury, of course - but this says nothing about how fierce the competition is within those tracts, or the adaptations each sex has developed to compete.

Luckily, researchers at Syracuse University decided to whip out one of the most illuminating tools in cell biology, green fluorescent protein. We now have an entire rainbow of such proteins, and the group led by Mollie Manier tagged the sperm of two different Drosophila males green and red, making post-copulatory selection visible for the first time.

There were a few major questions to be answered. What happens to the sperm already there when more enters? An awkward microscopic sausage party? And, does every sperm have an equal chance, or is it first-come, first-serve?

Their results showed a surprising amount of mobility in the labyrinth of female tubes. There also seemed to be a fair system, where fertilization success was directly related to the amount of sperm in the receptacle. Most importantly, the impressive photos and video of laser-sperm zipping around the female are sure to inspire many more colourful protein studies showing biology in action.

Is anyone else thinking...brainbows in real time?

(Science DOI: 10.1126/science.1187096)



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