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[Scott W]

NEWS RELEASE
The Center for North American Herpetology
Lawrence, Kansas
http://www.cnah.org
17 February 2006

PESTICIDE COMBINATIONS IMPERIL FROGS

By Robert Sanders

Berkeley, California - The pesticide brew in many ponds bordering Midwestern
cornfields is not only affecting the sexual development of frogs, but is
making
them more prone to deadly bacterial meningitis, according to a new study by
University of California Berkeley scientists.

These physiological effects combine with environmental disruptions to make
the
life of a frog seem like something out of a horror movie and are likely
among the
factors causing a decline in amphibian populations worldwide, the
researchers
said.

Tadpoles raised in water polluted with a combination of nine pesticides,
fungicides and herbicides typical of ponds around Midwestern cornfields take
longer to become frogs and end up smaller, making it harder for them to eat
their normal prey and making them easier prey for other animals. The top
frog is
having trouble eating a cricket, while the snake has no trouble swallowing
the
smaller frog.

"If you look at one of these frogs, it's probably a hermaphrodite - plus, it
metamorphoses late, which means it is subject to its pool drying up before
it can
become a frog," said lead researcher Tyrone Hayes, professor of integrative
biology at UC Berkeley. "It's also smaller, if it metamorphoses at all,
which
increases the likelihood it will be eaten and decreases its ability to eat.
Plus, it's
immuno-suppressed, so more prone to die from infection."

The stress on the frogs is increasing stress hormone levels, he found, which
in
turn create holes in the thymus gland that likely cause the impaired immune
response.

"It's not the pesticides alone or introduced predators or ultraviolet light
or global
warming that's causing this decline, but the interaction between these on an
animal that is pretty sensitive to its environment," said Hayes.

In the new paper, published online last week in the journal Environmental
Health
Perspectives , Hayes and his colleagues report four years of experiments
showing that, while some of the pesticides, herbicides and fungicides used
on
corn fields may not by themselves have a noticeable impact on frogs, in
combination they create significant effects. Among these are delayed
maturation - the tadpoles take longer to metamorphose into frogs - retarded
growth and an increased susceptibility to meningitis caused by normally
benign
bacteria.

Four years ago, Hayes showed that atrazine, the most common weed killer used
on corn in the United States, disrupts the sexual development of frogs,
feminizing males into hermaphrodites - frogs with female sex organs invading
their testes - decreasing the size of their vocal organs, which are critical
to
mating success, and causing a tenfold drop in testosterone in mature male
frogs.

In the current study, he looked again at atrazine as well as three other
herbicides, two fungicides and three insecticides used on Midwestern
cornfields -
a subset of more than two dozen pesticides approved for use. All nine were
found in the scientists' study area in Nebraska in pools of water beside
cornfields early in the growing season, when spraying typically occurs.
Levels
ranged from 0.1 parts per billion (ppb) to 10 or more ppb.

Native northern leopard frogs (Rana pipiens) raised in water with only one
of
these nine pesticides at 0.1 ppb appeared normal, though the fungicide
propiconazole caused a small but significant increase in the time it took
tadpoles
to start metamorphasis. The insecticide tebupirimphos caused a small but
statistically significant decrease in the size and weight of mature frogs.

Mixtures, however, had a much stronger effect. All nine compounds together
at
0.1 ppb - one of the lower concentrations measured in the field - lengthened
the
time to metamorphosis by 15 days, or about 25 to 30 percent. The mixture
also
caused a frog mortality of 35 percent.

All nine compounds together also produced a startling effect: The longer a
tadpole took to mature into a frog, the smaller it was. It's normally the
other
way around, Hayes said. Separately, six of the pesticides did not affect
this
correlation, but three disrupted it so that there was no relationship
between
time to metamorphosis and size at metamorphosis.

"In humans, this is like saying, 'The longer you are pregnant, the smaller
your
baby will be,' which means the womb is no longer a nurturing environment,"
Hayes
said.

The nine-pesticide combo also damaged the thymus, a part of the immune
system, causing 70 percent of frogs to develop flavo-bacterial meningitis.
The
pesticides atrazine and S-metolachlor, which are marketed as the combination
Bicep II Magnum, caused the most thymic damage.

To investigate why, Hayes and his laboratory colleagues, mostly
undergraduate
students, raised larvae of the common laboratory frog, the African clawed
frog
(Xenopus laevis), in water containing these pesticides and found four times
the
normal level of the stress hormone corticosterone. Hayes suspects that not
all
of the pesticides affect frogs, but that some enhance or trigger the
deleterious
effects of others when combined.

"Estimating the ecological risk and the impact of pesticides on amphibians
using
studies that examine single pesticides at high concentrations only may lead
to
gross underestimations of the role of pesticides in amphibian declines," he
wrote.

In a second study also published online last week in Environmental Health
Perspectives , Hayes reported even stronger evidence that atrazine, a
powerful
endocrine disruptor, both chemically castrates male frogs by blocking the
action
of the male steroid androgen and feminizes them by stimulating the
production
of the female hormone estrogen. He was able to produce identical
hermaphroditic malformations in frogs by administering estrogen or blocking
androgen at the proper time of development.

"One week of exposure at the critical time is all that's required to make
these
males look feminine, which probably interferes with mating," he said. Noting
that
some frogs seem to adapt to atrazine by delaying development, presumably so
that the critical developmental period takes place when the herbicide is at
its
lowest, Hayes suspects that not all frogs would be expected to adapt, or to
adapt quickly enough, to survive. Plus, delayed maturation comes at the risk
of
having the pond turn into a puddle and dry up before the frog completely
metamorphoses.

Hayes is continuing his studies with various combinations of pesticides to
determine which are the true cause of the problem and which serve to enhance
the effect of others.

His laboratory colleagues were UC Berkeley students Paola Case, Sarah Chui,
Duc
Chung, Cathryn Haefele, Kelly Haston, Melissa Lee, Vien Pheng Mai, Youssra
Marjuoa, John Parker and Mable Tsui. Co-authors on the atrazine paper were
former UC Berkeley students A. Ali Stuart, Atif Collins, Nigel Noriega,
Aaron
Vonk, Gwynne Johnston and Dzifa Kpodzo, and current students Magdalena
Mendoza and Roger Liu.

The work was supported by the National Science Foundation, Henry H. Wheeler,
the Park Water Co. and the Howard Hughes Biology Scholar's Program
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Please DO NOT pm orders for reptiles, send email instead scott@captivebred.co.uk

[Rickeezee]

Very scary stuff. The pollutants in our rivers, lakes etc have a similar effect upon the amphibious wildlife, fish etc. Nitrates in our water table and all the other glorious things! Not much good for us humans either!

I did read somewhere that the natural decline in the natural frog population around the world reflects the state of our planet and is a good measure of such. This world is a sad place at times.


Rick
_________________
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