Posted on 02/07/2006 8:57:17 AM PST by GreenFreeper
An outbreak of waterborne fungal disease in western Panama has eliminated eight families of Panamanian amphibians and is spreading, scientists report in this week's issue of the "Proceedings of the National Academy of Sciences" (PNAS).
An outbreak of the infectious disease chytridiomycosis, caused by the fungus Batrachochytrium dendrobatidis, is spreading into the El Cope region, researchers have found. The disease is moving from northwest to southeast from Costa Rica toward Colombia, leaving entire species of dead frogs and salamanders behind.
The rockhopper frog, for example, which lived along El Cope riverbanks, disappeared completely within one month.
Central American frog Eleutherodactylus phasma at risk of fungal disease (Photo by Karen Lips courtesy Arizona State University)
"Chytridiomycosis is an alarming model system for disease-driven extinction of a high proportion of an entire class of vertebrates," the scientists write in PNAS. "It is no longer correct to speak of global amphibian declines, but more appropriately of global amphibian extinctions."
The fungus has been implicated in the decline of more than 40 amphibian species in Central America and 93 such species worldwide.
But few researchers have been able to detect and monitor the presence of the fungus before a disease outbreak, and then witness the impact of an epidemic as it occurred, said zoologist Dr. Karen Lips of Southern Illinois University at Carbondale (SIU), lead author of the report.
Lips and colleagues from SIU, from the University of Colorado in Boulder, from the San Diego Zoo, and from Australia's James Cook University conducted a survey of amphibian populations in central Panama with the goal of finding the fungus in action.
"We anticipated the eastward movement of the fungus, and chose a fungus-free study site near a previously infected area," said Lips. "The fungus found its way there, and when it did, it quickly caused local amphibian extinctions and devastated frog and salamander biodiversity."
Hyla calypsa, one of the Central American species of frogs that is now probably extinct. (Photo by Karen Lips courtesy Arizona State University)
Microbes such as this fungus infect animals, but they "rarely cause extinctions in the species they infect," said James Collins, assistant director of biological sciences at the National Science Foundation (NSF). Collins is on leave from Arizona State University, and is a co-author of the paper. "There are only a few examples where we think a pathogen resulted in extinction of a species in an area. This is one of them."
Chytridiomycosis was not detected at the El Cope study site, said Collins, until September 23, 2004, when scientists found the first infected frog. During the next four months through mid-January 2005, the fungus killed so many frogs that amphibian abundance was reduced by more than 50 percent.
Dead frogs included individuals in 38 species (57 percent of the amphibian species at the site). All but three of the dead amphibians were infected with chytridiomycosis, and six of seven samples from substrates like stream boulders tested positive for the fungus, the researchers report.
"None of the 1,566 individuals of 59 amphibian species sampled before September 2004, was infected with this fungus," said Lips. "Our results demonstrate that the prevalence of the fungus very rapidly went from zero to high at this site.
"The timing of the outbreak, said Collins, "indicates that chytridiomycosis is rapidly moving southeastward, allowing us to predict its entry into amphibian communities in central Panama."
When the disease emerges at a site, it is thought to spread through a combination of frog-to-frog and environment-to-frog transmission. In the lab, some species of amphibians can carry the infection for up to 220 days before dying.
The die-off at El Cope occurred during the peak of the rainy season. Many mountain-dwelling frogs in the New World tropics make their way to water bodies to breed during the region's prolonged rainy season, thereby transmitting the waterborne fungus.
Bufo fastidiosus, or Pico Blanco toad, probably extinct, photographed at Fortuna, Panama (Photo by Karen Lips courtesy Arizona State University)
"Our findings definitively link the appearance of chytridiomycosis to amphibian population declines," said Lips.
The area had no evidence of climate anomalies in 2004; its temperature and rainfall patterns were similar to those found in longstanding records.
"These results support a model of amphibian declines in which this fungus enters and quickly spreads through a community with no previously infected individuals," Lips said.
The researchers predict the loss of many more amphibian species from the region, most likely from mountainous areas directly east of the study site.
To the west, the fungus has already left a multitude of dead amphibians in its wake.
Other authors of the paper are Forrest Brem, Roberto Brenes and John Reeve of Southern Illinois University Carbondale; Ross Alford of James Cook University in Townsville, Queensland, Australia; Jamie Voyles, Cynthia Carey and Lauren Livo of the University of Colorado in Boulder; and Allan Pessier of the Zoological Society of San Diego.
The National Science Foundation and the Bay and Paul Foundation funded this research.
Bummer!
You can still find such stories.
FReepmail me to be added or removed to the ECO-PING list!
Yeah, I know another article on amphibians but I get them automatically sent to me. It will be interesting to see how organisms will respond as diseases and fungi are more readily transported across the globe. Hopefully, they will have the time respond to these attacks.
Mother Nature is one cold hearted bitch.
Transported pestilence, whether weed, pathogen, or animal, is, IMO, the biggest environmental hazard we face. Sadly, the same globalists who fund the environmental move-mint will do everything within their considerable power to preclude any action that might hamper the "free trade" off which they profit.
I'll see if I can find the paper.
The sudden appearance of chytridiomycosis, the cause of amphibian deaths and population declines in several continents, suggests that its etiologic agent, the amphibian chytrid Batrachochytrium dendrobatidis, was introduced into the affected regions. However, the origin of this virulent pathogen is unknown. A survey was conducted of 697 archived specimens of 3 species of Xenopus collected from 1879 to 1999 in southern Africa in which the histologic features of the interdigital webbing were analyzed. The earliest case of chytridiomycosis found was in a Xenopus laevis frog in 1938, and overall prevalence was 2.7%. The prevalence showed no significant differences between species, regions, season, or time period. Chytridiomycosis was a stable endemic infection in southern Africa for 23 years before any positive specimen was found outside Africa. We propose that Africa is the origin of the amphibian chytrid and that the international trade in X. laevis that began in the mid-1930s was the means of dissemination.
Isn't X. laevis the frog that you can buy in pet stores and aquarium shops?
Sure is. They are pretty popular pets and experimental critters because they are hardy and easy to care for. During my undergrad days I had a job as an Animal Husbander to them. We used to tinker with the embryos to test the devlopmental premise of extensile-convergence vs. convergent-extension. Ah the memories!
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.