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Scientists map the genetic makeup of the platypus
Posted on Saturday, May 10, 2008 (CDT) by Isis
 Scientists said they have mapped the genetic makeup of the platypus — one of nature's strangest animals with a bill like a duck's, a mammal's fur and snake-like venom. The researchers, whose analysis of the platypus genome was published Thursday in the journal Nature, said it could help explain how mammals, including humans, evolved from reptiles millions of years ago.
The platypus is classed as a mammal because it has fur and feeds its young with milk. It flaps a beaver-like tail. But it also has bird and reptile features — a duck-like bill and webbed feet, and lives mostly underwater. Males have venom-filled spurs on their heels. "At first glance, the platypus appears as if it was the result of an evolutionary accident," said Francis S. Collins, director of the U.S. National Human Genome Research Institute, which funded the study.
"But as weird as this animal looks, its genome sequence is priceless for understanding how mammalian biological processes evolved," Collins said in a statement. The research showed the animal's multifaceted features are reflected in its DNA with a mix of genes that crosses different classifications of animals, said Jenny Graves, an Australian National University genomics expert who co-wrote the paper.
"What we
found was the genome, just like the animal, is an amazing amalgam of
reptilian and mammal characteristics with quite a few unique platypus
characteristics as well," she told the Australian Broadcasting Corp.
Scientists believe all
mammals evolved from reptiles, and the animals that became platypuses
and those that became humans shared an evolutionary path until about
165 million years ago when the platypus branched off. Unlike other
evolving mammals, the platypus retained characteristics of snakes and
lizards, including the pain-causing poison that males can use to ward
off mating rivals, Graves said.
More than 100 scientists
from the United States, Australia, Japan and other nations took part in
the research, using DNA collected from a female platypus named Glennie.
Their work adds to the growing list of animals whose genetic makeup has been unraveled.
By comparing platypus genes
to those of humans and other mammals, scientists hope to fill in gaps
in knowledge about mammals' evolution and better identify certain
species' specific traits.
Des Cooper, an evolutionary
biologist at the University of New South Wales who did not take part in
the research, said it represented a big step forward in the world's
knowledge of mammals.
"Platypuses are often
thought of as primitive because they lay eggs," Cooper said. "This
paper demonstrates there is a mixture of characters, which they share
with other mammals, and of highly specialized attributes."
Graves said the research
contained some surprises, such as the conclusion that genes which
determine sex in a platypus are similar to those of a bird, not a
mammal. Researchers also found genes that indicate platypuses — which
rely on electrosensory receptors in their bills to navigate as they
rummage with closed eyes in waterways — may also be able to smell
underwater.
Unique to Australia, the
platypus has confounded observers for centuries. Aboriginal legend
explained it as the offspring of a duck and an amorous water rat. When
the British Museum received its first specimen in 1798, zoologist
George Shaw was so dubious he tried to cut the pelt with scissors to
make sure the bill had not been stitched on by a taxidermist.
Platypuses live in the wild
along most of Australia's east coast. Their numbers are not accurately
known because they are notoriously shy. Hunted for years for their
pelts, they have been protected since the early 1900s and are not
considered to be endangered, though scientists say their habitat is
vulnerable to human development.
Copyright: The Associated Press
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