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International Society for Infectious Diseases
Date: Tue 20 Jul 2010
Source: National Geographic News [edited]
30 amphibian species wiped out in Panama forest
-----------------------------------------------
A "catastrophic" epidemic has made 30 amphibian
species locally extinct in a region of Panama --
including 5 species that were lost before they
were even formally identified, a new study says.
The species are the latest victims of the deadly
chytrid fungus, which has caused major amphibian
declines in Central and South America as well as
in Australia since the late 1980s. The fungus
infects an amphibian's skin, sloughing off the
skin's layers, and causing lethargy, weight loss,
and eventual death.
Suspecting the imminent arrival of chytrid,
researchers had visited the forests of El Cope
[Cocle province] between 1998 and 2004 to record
genetic information from the region's frog and
salamander species. Chytrid swept through El Cope
in 2004, wiping out amphibians so quickly that
dead frogs littered the forest floor, according
to study leader Andrew Crawford, an evolutionary
biologist at the University of the Andes in
Bogotá, Colombia.
The mysterious fungus acts so rapidly that
scientists are rarely able to track its
destruction. But armed with the genetic database,
the El Cope team was able to make the 1st
before-and-after comparisons to pinpoint the
exact species lost to the fast-moving fungus --
including a handful of species that proved to be
new to science.
"We're discovering species and losing species at
the same time -- these 2 conflicting trends have
to clash at some point," Crawford said.
Species not gone globally, but hope dim
---------------------------------------
Before chytrid hit El Cope, Crawford and
colleagues had collected DNA samples from 63 frog
and salamander species in a 1.5-square-mile
(4-square-kilometer) tract of forest. The
information was added to a larger genetic
database of known amphibians. By matching unknown
specimens with existing genetic lineages, the
team discovered 11 unnamed species among those
collected in the forest before the outbreak.
A post-epidemic survey conducted between 2006 and
2008 showed that 25 of the 63 species had been
lost. 5 of the missing species were among the 11
that were new to science.
Another 9 species had seen population declines
between 85 and 99 percent since the earlier
survey, according to the study. Though the
species aren't globally extinct, there's "not
much optimism" that amphibians from unaffected
areas will recolonize El Cope, Crawford said.
Past experiments -- such as in Costa Rica -- show
that frogs don't bounce back after a chytrid wave
comes through.
A frogless forest could have reverberations
throughout the ecosystem, Crawford added. For one
thing, tadpoles are crucial to stream
environments, because they munch on moss and
algae along stream beds, taking in protein and
other nutrients needed by animals higher up the
food chain.
Frog fungus a hint of what's to come?
-------------------------------------
No one knows what sparked the spread of chytrid,
but it's possible that globalization -- with
people and goods becoming more interconnected --
is a key factor, Crawford said.
In general, the outbreak is an "alarming"
reminder of how such emerging pathogens can
devastate whole ecosystems. For instance, chytrid
is so potent that it's killing off distantly
related species of frogs that are as genetically
different from each other as rats are from
whales, he said. "Hopefully we don't get
pathogens like that that hit mammals," he said.
"This could be just one example of what's coming."
The amphibian die-off findings appear this week
[week of 19 Jul 2010] in the journal Proceedings
of the National Academy of Sciences.
[Byline: Christine Dell'Amore]
--
Communicated by:
James M Wilson V, MD
Executive Director
Praecipio International
[A map of the affected region may be viewed at
The HealthMap/ProMED-mail interactive map of Panama is available at
The amphibian chytrid fungus (_Batrachochytrium
dendrobatidis_) lives on the skin of frogs,
making it difficult for them to breathe through
their skin or adjust their body temperatures. If
frogs are infected with the disease, the signs
may include lack of movement or spastic jerking
in their legs, especially the hind ones, and
anemia. Species that are nocturnal or live in
trees sit out in the open throughout the day;
they show little movement or do not react or
blink at all if touched by humans, and when
turned over, they cannot return to their original
positions. - Mod.TG]
[see also:
Chytrid fungus, frogs - worldwide: review article 20100130.0323
2009
----
Chytrid fungus, frog - South Korea 20090920.3301
Chytrid fungus, frog - Philippines: (Luzon) 20090527.1976
2008
----
Chytrid fungus, frogs - Panama 20081014.3246
Chytrid fungus, frogs - Spain (Majorca) 20080928.3065
2007
----
Chytrid fungus, frogs - Japan (02): wild frogs 20070613.1924
Chytrid fungus, frogs - Japan 20070113.0176
2006
----
Chytrid fungus, frogs - worldwide: possible source 20060524.1463
Chytrid fungus, frogs - South Africa 20060203.0344
2005
----
Chytrid fungus, frogs - UK (England) 20050916.2741
2004
----
Red leg disease, frogs, fatal - UK (02) 20040914.2560
Red leg disease, frogs, fatal - UK 20040912.2542
2002
----
Frog deformities - USA (02) 20020425.4030
Frog deformities - USA 20020422.4012
Frog mortality, virus - UK 20020201.3458
2001
----
Chytrid fungus, frogs: background 20001201.2096
2000
----
Frog deformities - USA (Northeast) 20000420.0579]
...................................tg/mj/lm
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