Nav: Home

What doesn't kill you

October 03, 2018

After suffering mass mortality for years due to infection with the deadly Batrachochytrium dendrobatridis fungus, or chytrid, some frog populations in El Copé, Panama, now seem to be co-existing with the pathogen and stabilizing their populations.

"Our results are really promising because they lead us to conclude that the El Copé frog community is stabilizing and not drifting to extinction," said Graziella DiRenzo, a postdoctoral researcher in ecology, evolution and marine biology (EEMB) at UC Santa Barbara. "(Extinction) is a big concern with chytrid worldwide. Before this study, we didn't know a lot about the communities that remain after an outbreak. In some areas, it's still a black box."

DiRenzo, a scientist in the lab of EEMB professor Cherie Briggs, has outlined her findings in the paper "Eco-Evolutionary Rescue Promotes Host-pathogen Coexistence," which appears in the journal Ecological Applications. She conducted her research while at Michigan State University and the University of Maryland.

The chytrid fungus, also known as Bd, began its large-scale destruction of amphibian populations in the second half of the 20th century. Around the turn of the 21st century, the mass die-offs were connected to the fungus, which causes symptoms such as skin shedding and lethargic behavior. In El Copé, Bd took out almost half of the amphibian population within a few years.

From 2010 to 2014, DiRenzo and colleagues visited the same site in El Copé to sample the frog population for Bd infection and assess the severity of the disease. The researchers' initial assumption was that the frog population was heading toward extinction, because Bd is a very virulent, generalist pathogen, DiRenzo explained.

"Our findings did not line up with what I assumed prior to doing the research because, in our study, we found that either population seems to be relatively stable," she said.

Among the challenges they faced during their survey was the difficulty of locating these tropical frogs, which are masters of camouflage.

"Essentially you are looking for 2- to 4-cm green frogs on green leaves or brown frogs on brown leaves, which makes it very hard to see them," DiRenzo said. That, in turn, led them to develop a new model that could statistically correct for frogs that were present during their surveys but that they missed because the frogs were hard to detect.

The results of the researchers' repeated data collection and statistical modeling led to their finding that while some frog species succumbed to the disease, others persisted. The researchers attribute this host-pathogen coexistence to "eco-evolutionary rescue." This occurs when either ecological and/or evolutionary mechanisms allow for the persistence of the host and pathogen. Evolutionary mechanisms, for example, include amphibians' immune adaption; among ecological factors are the reduced density and richness of frog species in El Copé -- fewer frogs means fewer opportunities for infection.

Additionally, according to the paper, if some amphibian species (such as Atepolus varius) were "primary transmitters" of infection -- able to harbor and spread large numbers of chytrid zoospores -- then the extirpation of these species contributed to the decline of transmission rates in the community. Out of the 74 amphibian species noted in El Copé prior to Bd arrival, approximately 32 remain, a drastic change in the composition of the amphibian community in the area.

It's too early to tell whether the stabilization of frog species in El Copé despite the ongoing presence of chytrid fungus will continue in the long-term, DiRenzo noted. Additional stressors such as climate change, habitat loss, pollution and invasive species present challenges to amphibian communities already struggling with Bd.

"Approximately one-third of the world's 7,000 amphibian species are at risk of extinction," said DiRenzo, who is now studying how Bd interacts with other pathogens that affect amphibians and how the order of pathogen infection affects outcome. "Our results provide a glimpse of hope for amphibian populations persisting in the face of major threats, but it does not mean that either amphibian populations will rebound to the abundance they were prior to the threat, or that the ecosystem structure has not been compromised."

University of California - Santa Barbara

Related Fungus Articles:

Researchers look to fungus to shed light on cancer
A team of Florida State University researchers from the Department of Chemistry and Biochemistry found that a natural product from the fungus Fusicoccum amygdali stabilizes a family of proteins in the cell that mediate important signaling pathways involved in the pathology of cancer and neurological diseases.
The invisibility cloak of a fungus
The human immune system can easily recognize fungi because their cells are surrounded by a solid cell wall of chitin and other complex sugars.
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.
More Fungus News and Fungus Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

There's so much we've yet to explore–from outer space to the deep ocean to our own brains. This hour, Manoush goes on a journey through those uncharted places, led by TED Science Curator David Biello.
Now Playing: Science for the People

#556 The Power of Friendship
It's 2020 and times are tough. Maybe some of us are learning about social distancing the hard way. Maybe we just are all a little anxious. No matter what, we could probably use a friend. But what is a friend, exactly? And why do we need them so much? This week host Bethany Brookshire speaks with Lydia Denworth, author of the new book "Friendship: The Evolution, Biology, and Extraordinary Power of Life's Fundamental Bond". This episode is hosted by Bethany Brookshire, science writer from Science News.
Now Playing: Radiolab

Dispatch 1: Numbers
In a recent Radiolab group huddle, with coronavirus unraveling around us, the team found themselves grappling with all the numbers connected to COVID-19. Our new found 6 foot bubbles of personal space. Three percent mortality rate (or 1, or 2, or 4). 7,000 cases (now, much much more). So in the wake of that meeting, we reflect on the onslaught of numbers - what they reveal, and what they hide.  Support Radiolab today at