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Pheromone Notes #21
News release issued by Oregon State
University:
Male Courtship Pheromone Identified
CORVALLIS, Ore. - University
researchers have discovered one of the
first pheromones in a vertebrate animal
species that is produced by the male and
helps him when courting a female, in this
case making her more calm, receptive to
mating and less apt to run away
The study, to be reported Friday in the
journal Science, was done with a species
of terrestrial salamander called Plethodon
jordani. But, as scientists learn more
about this mysterious world of chemical
communication, it seems likely that there
may be many other pheromones that affect
behavior and mating in many animal species,
including humans.
"It's very unusual in nature to
find a pheromone that male vertebrates
use in courtship and mating," said
Lynne Houck, an associate professor of
zoology at Oregon State University and
co-principal investigator on the study,
along with colleagues at the University
of Chicago and University of Louisville.
"Usually you find these types of
pheromones only in the female."
The researchers in this case identified
the pheromone, a single protein component
that affects the female, and the gene
that is responsible for production of
that protein. Of considerable interest,
Houck said, is that this gene is similar,
although not identical, to one found in
humans.
In salamanders, the courtship and mating
process is odd.
"Terrestrial salamanders aren't
always wildly enthusiastic about mating,
and there are only a few weeks or months
of the year that the female will even
consider the idea," Houck said. "And,
during that time, the chances of her mating
with a male are considerably reduced if
he doesn't produce this particular pheromone."
In that process, one part of which is
called a tail-straddling walk, the male
deposits pheromones from a gland under
his chin - a gland which only becomes
active during mating times - onto the
female's nose.
Repeated deposits of this chemical seem
to soothe the female, make her more receptive
to mating and also more inclined to do
it quickly, speeding up a process that
can take 45 minutes or more and expose
both the animals to other dangers. And
the process is discreet, not readily apparent
to other salamanders who may wish to compete
for a mate.
In an unusual reproductive process, the
female salamander then stores the sperm
deposited by this male and uses it at
some point weeks or months after insemination
to fertilize her eggs. The benefit of
this time delay between mating and egg
laying is that the female can search for
a very secluded place that is just large
enough for her and her eggs. The female
will stay with her eggs for about four
months, guarding them against predators.
Pheromones are increasingly being studied
by researchers for the key roles they
play in species recognition, reproduction
and other behaviors. Pheromones have commonly
been identified for many insects, but
less so for vertebrate animal species.
However, Houck said, there is some clear
evidence of their operation in humans.
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 synchronize their
menstrual cycles. And there's 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."
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