Herps
in the News: Parasites and Deformed Frogs
I
found an interesting article on the National Geographic Website entitled
“Parasite Creating Deformed Frogs in Western U.S.” Just as the title suggests,
deformities in frogs around the Western United States are continuing to be a problem.
Ribeiroia ondatrae is a flatwork
parasite that infects frogs during the development of their limbs. Multiple legs or
no legs are a common sight in frogs infected with this parasite. Due to the
deformities, the frogs become unable to get away from predators effectively, making them more vulnerable. This
parasite has been common knowledge within the herpetology world, but scientists
are now trying to see how the parasite has moved since the last research was
conducted in 1999.
In
2010 Pieter Johnson, an ecologist from the University of Colorado at Boulder,
and colleagues collected frogs and parasites in California, Oregon, Washington,
and Montana. The amphibians collected at the wetland sites were still infected
with the flatworm parasite. The scientists found that Ribeiroia ondatrae distribution had changed, but the prevalence of
the parasite had not changed since 1999; however, “the locations of hot spots
had changed substantially over the last decade”.
For
example, 30 percent more deformed frogs were found at a site that used to have
few deformed amphibians. The opposite was true of other sites, where less
deformed frogs were found at sites where there used to be many. The current
movements and predictions of the future movements of the parasite must be known
in order to conserve amphibian species.
Ribeiroia ondatrae is a parasite with a
“complex, multi-host life cycle, which begins with the ramshorn snail”, which
is found in the Western United States. The parasite asexually clones itself
within the snail, where the Ribeiroia ondatrae
larvae come out of the snail looking for tadpoles to infect. Once the
parasite has entered the tadpole, it affects the area of frog’s limb development, which don’t
progress properly as a result. Birds then eat the infected frogs, so the bird is
infected. The bird feces contain the Ribeiroia
ondatrae, where the complex life cycle begins again.
The
actions of humans affect the prevalence of this virus extensively. For example,
runoff into wetlands causes algae to grow, which promotes the snail population,
giving the parasite more hosts to infect. This emerging disease not only
affects frogs, but other living species.
Although
this parasitic data is overwhelming, other factors could also contribute to
frog populations declining in some areas. For instance, low water levels could
kill frog eggs; therefore, “this distinction is important so that we can target
amphibian populations that are really in trouble, rather than a population that
is just having a bad year”. The causes of frog population declining are
numerous, often with habitat loss being number one. Diseases are next on the
list.
This
article brings to light the effect that humans have on the world, even to the
point of affecting amphibian morphological development. By studying the effects
of agricultural runoff and contamination of waters from factories, we are able
to see how these pollutants may also affect human populations. Although this article only
talks about pollution from humans, even human actions, such as habitat
destruction are also destructive to amphibian development. The increase in
ultraviolet radiation caused by air pollution from cars, factories, etc. also
hurt amphibians by directly affecting egg development.
Citations courtesy of:
-http://news.nationalgeographic.com/news/2011/08/110802-frogs-deformed-parasites-animals-environment-mutants/
Photos courtesy of:
-http://phenomena.nationalgeographic.com/2013/02/13/a-flurry-of-frog-legs/
-http://news.nationalgeographic.com/news/2011/08/pictures/110803-frog-parasites-deformed-malformations-legs-animals-science/#/deformed-frogs-parasites-amphibians-bird_38102_600x450.jpg
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