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5 December 2013 11:26 am ,
Vol. 342 ,
At age 30, Dutch biologist Freek Vonk has built up a respectable career as a snake scientist. But in his home country,...
Since arriving on the island of Guam in the 1940s, the brown tree snake ( Boiga irregularis ) has extirpated native...
An animal rights group known as the Nonhuman Rights Project filed lawsuits in three New York courts this week in an...
Researchers have been hot on the trail of the elusive Denisovans, a type of ancient human known only by their DNA and...
Thousands of scientists in the Russian Academy of Sciences (RAS) are about to lose their jobs as a result of the...
Dyslexia, a learning disability that hinders reading, hasn't been associated with deficits in vision, hearing, or...
Exotic, elusive, and dangerous, snakes have fascinated humankind for millennia. They can be hard to find, yet their...
Researchers have sequenced and analyzed the first two snake genomes, which represent two evolutionary extremes. The...
- 5 December 2013 11:26 am , Vol. 342 , #6163
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Female Flies Decide Sperm Wars
7 January 1999 7:30 pm
Love may seem like war sometimes, but within the reproductive tract of female fruit flies, a true battle rages: Sperm from different male flies compete head-to-head for a chance to fertilize the precious eggs. Far from being innocent bystanders in these sperm wars, the females are actually masterminding them, scientists report in tomorrow's Science--for their own self-defense.
When a female mates with more than one male, the suitors do not have an equal shot at siring her offspring. That's because in many animal species (including humans, according to some researchers) some males have more competitive sperm than others. Certain kinds of male fruit flies, for instance, use a cocktail of proteins in their ejaculate as a secret weapon to gain the edge; these proteins induce the female to increase her sperm uptake or her rate of egg-laying, or even to prevent her from considering any new suitors.
But such tricks may harm the female's interest, says biologist Andrew Clark of Pennsylvania State University in University Park; cranking up egg production may reduce her life-span and staying single could prevent her from choosing the most interesting mates. Puzzled by this potential liability, Clark and colleagues from the University of Texas, Austin, and the University of California, Davis, decided to test whether females are able to withstand a male's attempted manipulations.
The researchers took female fruit flies from six different strains and mated each with two males: one guy, with an eye-color mutation, got lucky every time; the other was a male picked from one of the six strains. By checking how many offspring carried the mutant eye-color, they discovered that some males were better at sperm competition than others. The males' reproductive success depended not only on their own genes, but also on those of the female. Clark says that "some females just ignore the signals of some males, and others don't."
The females' ability to influence sperm wars may have checked the male evolutionary tricks, says Allen Orr, an evolutionary geneticist at the University of Rochester in New York. "It's a very nice experiment," he says.