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NARR: Are flame retardants harming frogs?
Flame retardants end up in our waterways where they become contaminants.
Bill Karasov is looking into the issue.
KARASOV: Certainly one important problem in the Great Lakes region is contaminants that
that have been introduced through manufacturing processes,
but another problem in many places is
high nutrient loads into waterways and
this can create a situation
where animals may suffer direct effects of
the contaminants and also they may be
exposed more to pathogens in the water
that whose numbers have been increased
by high nutrient loads.
NARR: Pathogens include viruses, bacteria, and parasites.
The animals in this research are northern leopard frogs, they're native to Wisconsin.
KARASOV: So what we're interested in in this project
is how contaminants affect frogs and whether exposure to contaminants might
make them a little more susceptible to some of the common pathogens
that occur out in the wild.
NARR: Tawnya Cary is a Ph.D. student in Karasov's lab.
CARY: The frogs play an important role in our ecosystem,
not only in the aquatic ecosystem but also in the terrestrial ecosystem.
They are a main portion of the food web,
playing in terms of juvenile fishes and even older older adult fishes
really rely on tadpoles for a source of food
and we're interested of course in our fish populations and keeping them healthy.
In terms of them as adults, they control insect
populations, too. They are large consumers
of insects and they do play vital roles in both the terrestrial and aquatic
ecosystems. Also we can think of them as indicators as to the health of our
environment and kind of as a heads up as to what we should be
concerned about in terms of how environmental
contamination might impact humans.
So our main focus is to look at the immune system itself and how it might be
being altered by environmental contaminant exposure
and make these organisms then more susceptible to
pathogens like parasites or bacteria or viruses.
KARASOV: And then
another goal of this project was to start to focus on a chemical that's been
very little studied but is
people are appreciating it's perhaps a problem in the great lakes region and
this is a group of chemicals called
Polybrominated Diphenyl Ethers, or PBDEs.
Almost nobody has looked at this problem before.
NARR: PBDEs are often used as flame retardants in many products,
including computers, bedding, and tvs.
PBDEs turn up in house and office dust, in breast milk,
and other human tissues.
The researchers have been raising leopard frogs on a diet laced with
different amounts of PBDEs.
CARY: What we have here is a tadpole of an urban leopard frog and
this guy's been being exposed to Polybrominated Diphenyl Ether
with a brominated flame retardant through its diet.
We were watching him from when he first began swimming and first began eating
all the way through to metamorphosis.
NARR: The mature frogs are fed crickets until they can be analyzed.
CARY: We anesthetize the frogs before we do any
sorts of procedures and dissections so that they
don't feel anything of course, and then this is a solution called MS-222 and
it's used in pretty much every aquatic organisms for anesthesia, and it's a barbiturate
and it's pretty much going to make them kind of go to sleep.
Then we just like to do, we call it toe-pinch,
just to make sure there's no response, and he is fully under.
NARR: The analysis involves sampling the frog's blood.
The animal's veins are so small that blood must be taken directly from the heart.
The blood samples are assessed to measure the health of the frog's immune system.
The project's first findings suggest that PBDEs may indeed be a problem in the great lakes.
KARASOV: And what we found was that
levels of PBDEs in the food,
quite low levels that occur in the environment or that could occur in
the environment, were increasing
mortality. We had some increase deaths
in tadpoles that were eating that food
and slower growth rates and slower rates of development.
NARR: Check back here for updates on this research.
Brought to you by the University of Wisconsin Sea Grant Institute.