Jovana Curcic
Mrs. Medenica
ESS 11
5/11/2015
Definition of disease: “Chytridiomycosis is an infectious disease of
amphibians, caused by the chytrid Batrachochytrium dendrobatidis, a nonhyphal
zoosporic fungus”
I chose this article because it describes one of the endangered species;
William’s Bright Eyed by a specific chytrid fungus. I researched the defintion
and realized that this infection of amphibians is resulting in world amphibian biodiversity
decline. This was the reason I’ve combined a few sources and read more about
this important topic.
When I started reading the article about William’s
Bright eyed frog from Madagascar, I asked myself why is this so important, and
why should this article be interesting for readers, given that I’m not a huge
fan of frogs. Some facts that I observed:
-
As many as 7 percent of the world's amphibian species
live only in Madagascar
-
Although many scientists thought that Africa was not
affected by this infection, chytrid is present in multiple Madagascar frog
species.
-
A 2014 study found chytrid on Madagascar frogs shipped to the U.S. for the pet trade,
but researchers weren't sure whether the animals were contaminated en route or
infected in Madagascar.
Then I went to the other article and saw that all the
other amphibians are also affected and found that:
-
A fungus that arrived recently in Europe from East Asia
is lethal to many salamander species, a study released on Thursday shows,
threatening populations in Europe, Africa, and beyond.
-
Every infected animal, a total of 50, died, many within
a few weeks of infection.
-
Genetic testing shows the fungus has been lurking for
some 30 million years in Asia, where local species evolved to resist it.
Why should we care about this loss of amphibian
biodiversity in the past 30 years? Amphibians may help save the world from the decline
of fossil fuels. Amphibians produce many unique compounds in their skin that
have relevance to us humans. One compound, epibatidine (coming from a
poison dart frog Epipedobates anthonyi),
has 200 times more potent than morphine. How many species are being wiped out before
scientists can even describe them, let alone discover what help they might be
to humans?
Amphibians are also key components in ecosystem food
webs. Amphibians are unique among vertebrates in the way that they serve
as both predator and prey in their habitats. Tadpoles (which are larval
frogs) are important when it comes to controlling aquatic vegetation levels.
Salamanders and frogs intake insect pests such as mosquitoes who can eat up to
about 900 mosquitos in a day. In some forests, amphibians have the highest
percentage of vertebrate biomass, making them important prey items for many
other species. Loss of amphibians can very negatively impact ecosystems,
because what’s an ecosystem without these tiny species who help fill it up?
Almost 1/3 of the world's more than 6,800 species of amphibians are
threatened with extinction or are already extinct. Habitat loss is the
most obvious reason for population declines; if forests are cut down, the
species depending on those forests disappear as well. However, amphibians have been experiencing catastrophic population
declines around the world, oftenl in protected
areas and throughout the year. The speed of these declines are much more
dramatic than those described for birds and mammals. The causes of these declines are huge, and in any case might include
habitat change, disease, climate change, or pollution.
A virulent fungus may be responsible for these extinctions. This fungal
pathogen, Batrachochytrium dendrobatidis (Bd), causes the infectious disease chytridiomycosis
in amphibians. Some observations in Central America have shown that when
the fungus moves into a new area, more than 50% of the amphibian species become
extinct throughout 6 months, and the remaining species stay at only 20% of
their population.
Scientists
are trying to understand more about this fungal disease, and what can be done
to save amphibians. Amphibians rely on their skin for breathing and for
electrolyte transport. Once the fungal infection is spreads, the skin is
no longer able to transport electrolytes needed for the heart to function and
the animal dies. Humans are moving amphibians around and they are
carrying disease with them as they go. Dead
frogs like this Mexican leaf frog (Pachymedusa dacnicolor) are common where chytrid fungus has
infected frogs. The parasite kills frogs by blocking their skin from
transporting vital nutrients.
Reading these
articles, I realized that again humans are the main sources of this
biodiversity decline. Beside the habitat destruction, which is the most
important factor of loss of biodiversity, people’s activities spreads this
disease from one continent to the other. As we can see from the article, the
Asian frogs are less vulnerable to these fungal parasites (perhaps because of
gene adaptation). However, the transport of these infected amphibians as pets
into the area with more vulnerable local amphibians to this unexpected illness
have had a catastrophically negative impact on the local biodiversity. So the scientists should find a solution to
this threat. They are working on a possible preventive treatment using frog
skin bacteria that may fight off the fungal invader. Another example would be
Panama which are setting up breeding facilities for especially vulnerable
amphibians just in case, while others in places including Madagascar and Panama
are working on long-term amphibian monitoring efforts.
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