Researchers at the University of Chicago have discovered a substance produced by male salamanders that acts on female salamanders as a chemical signal to speed up the courtship process and hasten mating.
This is the first time that researchers have clearly pinpointed a single protein that directly influences female receptivity.
The researchers report their findings in the September 17 issue of Science.
"The protein we isolated from the male salamander mental gland is the active component," says Stephanie Rollmann, a graduate student in the lab of Martin Kreitman, associate professor in the department of ecology & evolution at the University of Chicago. "It alone can significantly shorten the time that a pair spends in courtship."
The protein, called plethodontid receptivity factor (PRF), is part of a complex mixture of chemicals that the male salamander uses to stimulate the female and encourage her to mate. The male pheromones are produced by the mental gland, located under the male salamander's chin.
The male delivers these pheromones directly to the female during a stage in courtship called "tail-straddling walk." In this phase, the female straddles the male's tail while they both walk forward together. The male periodically pauses to rub or slap his mental gland on the female to deliver his chemical message. If all goes well, the male will deposit a spermatophore (sperm mass resting on a gelatinous base) on the ground. Still straddling the male's tail, the female then walks forward and lowers herself onto the spermatophore and takes in sperm to fertilize her eggs.
Rollmann, who is interested in how olfactory signals influence communication, wanted to find out which part of the male's pheromone cocktail was responsible for influencing the female's decision to mate.
She and her co-researchers collected courtship pheromones from the
mental glands of Plethodon j
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Contact: Sharon Parmet
sparmet@mcis.bsd.uchicago.edu
773-702-6241
University of Chicago Medical Center
17-Sep-1999