Women just don't appreciate all that we do for them: (thus another reason not to marry them)
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New York Times, May 18, 1999
A Moth in Search of a Lifesaving
Encounter
By CAROL KAESUK YOON
hen it comes to reproduction, there are many males
in the animal kingdom that contribute little more
than a moment of time and a bit of sperm. But not the
rattlebox moth, whose generosity while mating suggests
many males have more to offer their mates than researchers
had ever suspected.
This wisp of a male not only delivers a truly stunning
sperm packet -- fully one-tenth of his body weight -- but he
also includes within that packet the unexpected bonus of a
powerful toxin that can protect his mate from predators for
the rest of her life, according to two husband-wife teams
of chemical ecologists, Andrés González and Carmen
Rossini, both graduate students, and Dr. Thomas and
Marie Eisner, all of Cornell University. The reported the
findings last week in The Proceedings of the National
Academy of Sciences.
"This is certainly novel,"
Dr. Carol Boggs, an
evolutionary ecologist at
Stanford University, said
of the work. "It's a very
elegant study."
Researchers say the
finding is a previously
unknown example of a
widespread practice
among animals and, in
particular, among
insects: the giving of
so-called nuptial gifts to
females by males before
and during mating.
Usually these gifts are
food items, like a tasty
bit of caterpillar or other
prey for snacking on
during copulation. But
the new study suggests
that, if this moth is any
indication, gift giving
may have a wider scope.
They say it is possible that many males may be discretely
handing out an arsenal of protective chemicals packed in
with their sperm to help their mates with the difficult work
of surviving and ultimately producing young.
In their study of this moth, also known as Utetheisa
ornatrix, the researchers raised females whose bodies were
free of the toxins, known as alkaloids. These females were
then mated either to males that did contain alkaloids or to
males that did not. Researchers then took these females
and tossed them into the webs and jaws of spiders.
They discovered that when spiders found females that had
mated with alkaloid-containing males in their webs, the
spiders, rather than eating the moths, immediately cut them
out, setting them free. When these females were dropped
into the spiders' jaws, they were quickly spit out. However,
if females had been mated with males whose bodies and
hefty sperm packets were devoid of the toxin, the
unprotected females were consistently devoured.
When researchers analyzed the chemical content of female
moths that had mated with alkaloid-containing males, they
found that the females' bodies were permeated with the
chemical almost immediately after uncoupling from the
male. The alkaloid could even be found right away in the
moth's wings and its defensive froth -- a bubbling mass of
toxin that spews out from behind the insect's head.
Researchers had shown previously in this species that
alkaloids from fathers ended up in eggs, transmitted
through the female, something that has been seen in other
species as well. The finding fit well with the idea that
fathers were protecting their offspring -- their shot at an
evolutionary future. But researchers say that until now, the
possibility that the mother might herself be receiving
protection from the male had been ignored.
"I'm amazed it hadn't been predicted before," Dr. Eisner
said. "It's not that he's an altruist. She carries the eggs and
they're his offspring, after all."
Researchers said it could well be a widespread
phenomenon.
"This is not going to be some sort
of isolated, gee-whiz insect story,"
said Dr. Scott Sakaluk, a behavioral
ecologist at Illinois State University
in Normal, Ill. "There simply
haven't been enough studies of this
sort done."
Utetheisa derives its alkaloids from
the leaves and seeds of the
Crotalaria plant, also known as the
rattlebox, a plant of the pea family
with small seeds that rattle in the
inflated pods when they ripen. The
alkaloids in Crotalaria are so toxic
that they can kill cows that browse
on the weed.
Utetheisa moths eat Crotalaria plants when they are
caterpillars. They can also get alkaloids from their mothers
as eggs and, in the case of females, from their mates.
Researchers say that for males, having enough toxin is
critical. Not only do females prefer to mate with males that
contain more of the chemical, but males require significant
amounts of the alkaloid to provide a potent donation
during mating.
"In a single mating," González said, "he could be passing
30 percent of what he has stored." And since females lose
part of their own stores with every egg they lay, he added,
the amount they receive during mating can be a big boost.
For Utetheisa females then, it can be critical that the male
she mates with is using protection -- in the form of
alkaloids. As Dr. Eisner put it, "At least there's one species
where there's safe sex."
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