Nav: Home

What stops mass extinctions?

March 29, 2018

Black plague killed between 30 to 50 percent of people worldwide. The cause, Yersinia pestis, is still around, but people are not dying of the plague. An even more devastating modern disease caused by the chytrid fungus wiped entire frog and salamander populations off the map. New results from work at the Smithsonian Tropical Research Institute (STRI) in Panama published in the Mar. 29 edition of Science, reveal the outcomes of the chytridiomycosis epidemic and their implications for diseases of mass destruction.

"Imagine a deadly disease that affects not only humans but other mammal species like dogs, cats and cows," said Roberto Ibáñez, STRI staff scientist and in-country director of the Panama Amphibian Rescue and Conservation Project. "Chytridiomycosis kills off most of the individuals in many different species of amphibians, but for some species it stops short of driving them to complete extinction."

"We were lucky that Karen Lips, now at the University of Maryland in College Park and colleagues saw this epidemic coming into Panama from Costa Rica, and researchers were able to study both the frogs and the disease before, during and after the peak of the epidemic," Ibañez said.

Disease outbreaks rarely annihilate the host species, because pathogens need their hosts in order to survive and reproduce.

"Because we have pathogen and host samples from before, during and after the epidemic, we can ask whether some frogs survived because the pathogen grew weaker through time, or because the frogs' immune systems or resistance increased through time," said Jamie Voyles, disease ecologist at the University of Nevada, Reno, and first author of the paper.

The authors tracked changes in amphibian species numbers and communities, infection patterns, host resistance and pathogen virulence for several decades hoping to see evidence of a weaker pathogen and/or of host resistance. The disease-causing fungus, Batrachochytrium dendrobatidis, appeared in El Cope, Panama, in 2004, in El Valle in 2006 and in Campana National Park in 2007. Between five and 13 years after the epidemic, the authors saw evidence of some recovery in nine species, but the fungus was still present. However, not all frog species rebounded, some species are still missing.

There was no evidence that the pathogen grew more slowly, responded differently to skin secretions from the frogs or became less virulent.

However, skin secretions from wild frogs that survived the epidemic inhibited growth of the fungus significantly more than secretions from frogs moved into captive breeding programs before the disease arrived. Researchers think that wild frogs became more resistant to the disease.

"The Panama Amphibian Rescue and Conservation Project collected healthy frogs before the outbreak," Ibañez said. "We learned to breed them in captivity and are now releasing Atelopus varius in areas where the epidemic has passed, so it is extremely important for us to realize that the defenses of these frogs may be weaker than the defenses of frogs that survived the epidemic in the wild. Captive breeding programs must consider breeding and releasing frogs with stronger defenses, and testing their skin secretions against the fungus is one useful tool to see which frogs are more resistant."

As in other pathogens that infect multiple species, the chytrid fungus poses a threat to amphibians, the cytrid fungus poses a threat to amphibians, increasing the likelihood of extinction of some species. It is vital to understand how disease transitions work--from outbreak, to epidemic, to coexistence--and our results have implications for a skyrocketing human population facing emerging diseases with the potential to cause global pandemics," said Ibañez.
-end-
Author affiliations include: the Smithsonian Tropical Research Institute; the University of Nevada, Reno; the University of Pittsburgh; the University of California, Berkeley; the New Mexico Institute of Mining and Technology; the Arizona Game and Fish Department; Vanderbilt University; Sistema Nacional de Investigación, Panama; La Mica Biological Station and the Fundación Centro de Conservación de Anfibios, Panama.

The Smithsonian Tropical Research Institute, headquartered in Panama City, Panama, is a unit of the Smithsonian Institution. The Institute furthers the understanding of tropical biodiversity and its importance to human welfare, trains students to conduct research in the tropics and promotes conservation by increasing public awareness of the beauty and importance of tropical ecosystems. Website. Promo video.

Reference: Voyles J., Woodhams, D.C., Saenz, V et al. 2018. Shifts in disease dynamics in a tropical amphibian assemblage are not due to pathogen attenuation. Science. 10.1126/science.aao4806

Smithsonian Tropical Research Institute

Related Fungus Articles:

Taming the wild cheese fungus
The flavors of fermented foods are heavily shaped by the fungi that grow on them, but the evolutionary origins of those fungi aren't well understood.
Candida auris is a new drug-resistant fungus emerging globally and in the US early detection is key to controlling spread of deadly drug-resistant fungus
Early identification of Candida auris, a potentially deadly fungus that causes bloodstream and intra-abdominal infections, is the key to controlling its spread.
Genetic blueprint for extraordinary wood-munching fungus
The first time someone took note of Coniochaeta pulveracea was more than two hundred years ago, when the South African-born mycologist Dr Christiaan Hendrik Persoon mentioned it in his 1797 book on the classification of fungi.
How a fungus can cripple the immune system
An international research team led by Professor Oliver Werz of Friedrich Schiller University, Jena, has now discovered how the fungus knocks out the immune defenses, enabling a potentially fatal fungal infection to develop.
North American checklist identifies the fungus among us
Some fungi are smelly and coated in mucus. Others have gills that glow in the dark.
Tropical frogs found to coexist with deadly fungus
In 2004, the frogs of El Copé, Panama, began dying by the thousands.
Deadly amphibian fungus has its origins in East Asia
The fungus kills frogs, toads and salamanders, and now we know where it emerged.
How wheat can root out the take-all fungus
In the soils of the world's cereal fields, a family tussle between related species of fungi is underway for control of the crops' roots, with food security on the line.
Fungus senses gravity using gene borrowed from bacteria
The pin mold fungus Phycomyces blakesleeanus forms a dense forest of vertically growing fruiting bodies, but how does it know which way is 'up'?
Invasion of the body-snatching fungus
UConn researchers recently documented in Nature Scientific Reports a gory and fascinating relationship between periodical cicadas and a fungus that infects them, hijacks their behavior, and causes a scene straight out of a zombie movie.
More Fungus News and Fungus Current Events

Top Science Podcasts

We have hand picked the top science podcasts of 2019.
Now Playing: TED Radio Hour

Risk
Why do we revere risk-takers, even when their actions terrify us? Why are some better at taking risks than others? This hour, TED speakers explore the alluring, dangerous, and calculated sides of risk. Guests include professional rock climber Alex Honnold, economist Mariana Mazzucato, psychology researcher Kashfia Rahman, structural engineer and bridge designer Ian Firth, and risk intelligence expert Dylan Evans.
Now Playing: Science for the People

#540 Specialize? Or Generalize?
Ever been called a "jack of all trades, master of none"? The world loves to elevate specialists, people who drill deep into a single topic. Those people are great. But there's a place for generalists too, argues David Epstein. Jacks of all trades are often more successful than specialists. And he's got science to back it up. We talk with Epstein about his latest book, "Range: Why Generalists Triumph in a Specialized World".
Now Playing: Radiolab

Dolly Parton's America: Neon Moss
Today on Radiolab, we're bringing you the fourth episode of Jad's special series, Dolly Parton's America. In this episode, Jad goes back up the mountain to visit Dolly's actual Tennessee mountain home, where she tells stories about her first trips out of the holler. Back on the mountaintop, standing under the rain by the Little Pigeon River, the trip triggers memories of Jad's first visit to his father's childhood home, and opens the gateway to dizzying stories of music and migration. Support Radiolab today at Radiolab.org/donate.