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Scientists
from the Center for Environmental Research and Conservation (CERC),
a member of the Earth Institute at Columbia University, have developed
non-invasive collection, extraction, and amplification protocols
providing high quality DNA from an animal's dung. The DNA is targeted
from cells sloughed from the gut lining. Their research techniques,
publishing in the Journal of Heredity, will enable a broad application
of genetic analysis, particularly with regard to endangered, elusive,
or aggressive species.
From The Earth Institute at Columbia
University :
DNA from dung
Columbia University researchers develop
non-invasive techniques for studying wild animal populations
(New York, May 2003) Scientists
from the Center for Environmental Research and Conservation (CERC),
a member of the Earth Institute
at Columbia University, have developed non-invasive collection,
extraction, and amplification protocols providing high quality
DNA from an animal's
dung. The DNA is targeted from cells sloughed from the gut lining.
Their research techniques, publishing in the Journal of Heredity,
will enable a broad application of genetic analysis, particularly
with regard to endangered, elusive, or aggressive species.
Genetic
study on many species is both a difficult and stressful process,
as the purest collection technique is to draw a blood sample or
collect a piece of tissue. For wild animals, this requires that
they are
captured and handled. Drs. Prithiviraj Fernando and Don J. Melnick
of CERC have developed inexpensive and reliable techniques that
amplify mitochondrial and nuclear DNA from an animal's dung. Their
new protocols
have proven to overcome previous barriers to non-invasive sampling,
including contamination, low quality, and degradation of DNA.
How
and from what ancestors a species evolved over millions of years,
changes in geographic distribution, and behavioral characteristics,
are among the insights held in each individual's DNA. The ability
to identify individuals genetically (genotyping) enables researchers
to obtain information relevant to management and conservation,
such as estimating population size, sex ratios, reproductive success
and
dispersal.
"
The advantages of using dung for genetic studies are tremendous.
All animals defecate regularly, it is easy to find and collect, and
storage and transport require little technology or expense," said
Fernando.
The study compared the genetic results
from both blood and dung samples of 20 Asian elephants to identify
any differences
in reliability
between the two sources. Extracted DNA from both sources was amplified
by PCR (Polymerase Chain Reaction) for a number of nuclear loci
multiple times. A minor level of error was seen in the DNA extractions
between
the blood and dung, however, when two extractions from dung were
coupled with a single amplification from each, the error was eliminated.
The age and location of the dung is
a factor as environmental variables such as temperature, humidity,
and exposure to sun can allow bacterial
activity to degrade the DNA. The researchers recommend that the
dung be 24 hours old or less, but they have extracted good DNA
from dung
as old as a few weeks.
"
The advances we have made in these methods will greatly enhance the
use of genetics to collect population data on animals we will never
see with our own eyes, including the most endangered large mammal
in the world, the Javan rhino," said Melnick, who is also the
executive director of CERC.
Studies in the CERC lab have found
that non-invasive DNA extraction from dung works on other mammals,
including
rhinos, apes, monkeys,
and canids, as well as other groups of vertebrates such as birds,
reptiles and amphibians. The researchers suggest that it will work
for most, if not all, animal species, however, since the DNA is
derived from cells sloughed during gut passage, the quantity of
DNA obtained
may vary with the individual's diet and digestive system. Each
species will need to be assessed to determine the optimum quantity
of dung
needed.
This spring, the researchers will work
in Sri Lanka, Java, and Vietnam to collect dung from elephants,
rhinos, and other endangered
species,
in order to obtain information that can be used for their conservation
and management.
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