Friday, September 17, 1999 Published at 11:59 GMT 12:59 UK
The salamander's secret sexual scent
Scientists have identified the secret love potion a salamander uses to woo his mate.
It is a pheromone, or signalling chemical, that the male wipes onto the female's nares or nostrils during their courtship dance.
As soon as this happens, things get a little steamy.
The molecule is produced in a gland under the male's chin. It is unique and different from the few other animal pheromones that have ever been identified, said University of Chicago graduate student Stephanie Rollmann, who did the research.
"To our knowledge this is the first vertebrate pheromone to affect female receptivity".
Rollmann and colleagues, who report their findings in the journal Science, studied the species Plethodon jordani, which lives in the mountains of western North Carolina.
They found that the designer fragrance is applied at a particular stage in courtship known as the tail-straddling walk, where the female walks forward with the male, straddling his tail and resting her chin on the tail base.
The male has to turn around to deliver the chemical signal.
After purifying the pheromone and isolating its principal protein component, the researchers tested its potency in courtship situations where the males had their chin gland removed. Test pairs that had the purified pheromone applied by the researchers spent a shorter amount of time tail-straddling, indicating that the female became receptive to the male's advances more quickly than couples without the pheromone.
Regular menstrual cycle
Pheromones are increasingly being studied by researchers for the key roles they play in species recognition, reproduction and other behaviours. Pheromones have commonly been identified for many insects, but less so for vertebrate animal species.
However, there is some clear evidence of their operation in humans, said Lynne Houck, an associate professor of zoology at Oregon State University. Research has shown that female humans who spend a great deal of time in one another's company often send out chemical signals that help them synchronise their menstrual cycles.
There is also evidence that a woman who spends much time around a single man develops a more regular menstrual cycle, which might be conducive to successful conception.
"The sexuality of humans is obviously pretty complicated and goes far beyond a single chemical cue," Houck said. "But that doesn't preclude the possibility that in fact there are some chemical cues at work which we don't yet fully understand."