Girl power: life's going swimmingly for
all-female fish species
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[February 14, 2018]
By Will Dunham
WASHINGTON (Reuters) - An all-female
freshwater fish species called the Amazon molly that inhabits rivers and
creeks along the Texas-Mexico border is living proof that sexual
reproduction may be vastly over-rated.
Scientists said on Monday they have deciphered the genome of the Amazon
molly, one of the few vertebrate species to rely upon asexual
reproduction, and discovered that it had none of the genetic flaws, such
as an accumulation of harmful mutations or a lack of genetic diversity,
they had expected.
They found that the Amazon molly, named after the fierce female warriors
of ancient Greek mythology, boasts a hardy genetic makeup that makes it
equally fit, or even more so, than fish using sexual reproduction in
which both maternal and paternal genes are passed along to offspring.
"The Amazon molly is doing quite well," said biologist Manfred Schartl
of the University of Wuerzburg in Germany. "Unexpectedly, we did not
find the signs of genomic decay as predicted."
The fish reproduces using a strategy in which a female's egg cell
develops into a baby without being fertilized by a male's sperm cell.
But that does not mean the fish does not need some hanky panky.
"The Amazon molly female produces clones of itself by duping a male of a
closely related species to mate with her. The asexual mode of
reproduction termed gynogenesis requires the female to mate with a male
but none of the male's genome is passed to the offspring," said
geneticist Wesley Warren of the McDonnell Genome Institute at Washington
University in St. Louis.
The Amazon molly's egg cells are activated to develop into an embryo by
a sperm cell that degenerates without fusing with the egg's nucleus.
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The Amazon molly, an all-female species that engages in asexual
reproduction, appears in a handout photo taken in a laboratory at
the University of Wurzburg in Germany, provided February 12, 2018.
Manfred Schartl/University of Wurzburg/Handout via REUTERS
The fish is up to about 3 inches (8 cm) long and eats insects,
plants, algae and other food. The study showed it originated when
two other species, the Atlantic molly and the Sailfin molly, mated
about 100,000 to 200,000 years ago.
Animals that reproduce asexually are rare compared to the
overwhelming majority that exist as males and females and reproduce
sexually.
"It was long thought that vertebrates would not be able to exist in
such a way. It was a sensation when the Amazon molly was the first
asexual vertebrate discovered in 1932," Schartl said.
About 50 vertebrates are known to use asexual reproduction including
fish, amphibians and reptiles.
The research was published in the journal Nature Ecology &
Evolution.
(Reporting by Will Dunham; Editing by Sandra Maler)
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