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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...
Snake venoms are remarkably complex mixtures that can stun or kill prey within minutes. But more and more researchers...
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...
- 5 December 2013 11:26 am , Vol. 342 , #6163
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Saving Sperm Separates Species
1 November 2004 (All day)
Male animals tend to be pretty promiscuous and are more likely than their female counterparts to mate with members of other species. But a new study shows that male sailfin mollies produce more sperm when they are around females of their own species than when they're in the company of strangers. The findings suggest that a male's physiology can create a barrier to interspecies mating even when his behavior does not.
New species arise when a group of animals becomes reproductively isolated: They no longer mate with closely related animals, or if they do, they don't produce fertile offspring. Scientists believe that one of the most important barriers keeping closely related species apart is mate choice: Most males simply stick to females of their own species. But some are not as picky; they will attempt to get it on with females of related species, especially if they live in close proximity.
Researchers at Texas State University in San Marcos therefore reasoned that other factors may help isolate species. To test their hunch, the scientists constructed a fish tank with a Plexiglas divider and placed a male sailfin molly on one side. They introduced a female from either the same species or a related Amazon molly species on the other side. The researchers collected sperm from the male after 1 week. As reported online this week in the Proceedings of the National Academy of Sciences, males confronted with females of their own species produced significantly higher numbers of sperm cells than did those gazing at Amazon mollies.
The findings suggest that, despite the apparent sexual attraction, males slow down their sperm production when they're around females of another species--a mechanism that may contribute to reproductive isolation, says evolutionary ecologist Andrea Aspbury, who led the study.
"It's a nice paper," says Michael Ryan, an animal behaviorist at the University of Texas, Austin. Not only does the work suggest a new mechanism to separate species, he says; it also shows that males can change their reproductive physiology in response to sexual cues. "This work is going to cause behaviorists to pay additional attention to the relationship between physiology and mate recognition," he says.