The extinct aquatic fungi of several amphibians that spend all or part of their life cycle in water also threaten terrestrial amphibians. In Brazil, FAPESP-backed researchers have detected unprecedented mortality in a genus of small frogs called pumpkin toads that live in the Atlantic Forest far from the aquatic environment. The animals were severely infected with Batrachochytrium dendrobatidis, which causes chitrigiomycosis.
Studies published in the journal Biological protection,teeth fungus It is also a threat to terrestrial amphibians with important ecological functions such as controlling insects that carry diseases such as dengue, yellow fever and Zika.
“The fungus attacks the skin of amphibians, where it exchanges gas with the external environment. The infection causes a physiological imbalance, and the animal eventually becomes heart attack Diego Moura-Campos, the first author of the article, said: The study was conducted with a scholarship from the Brazilian Ministry of Brazil during a master’s study at the Institute of Biology (IB-UNICAMP) at the University of Campinas in Sao Paulo. Coordinating education for the improvement of higher education staff (CAPES).
The study is linked to the FAPESP Research Program on Biodiversity characterization, Conservation, Restoration and Sustainable Use (BIOTA-FAPESP) and is coordinated by Luís Felipe Toledo to support the project “Brazilian Kitrid Bacteria: Origins and Results”. It was carried out under. He is a professor at IB-UNICAMP and a co-author of the article.
“We studied fungi from several angles, but we rarely had the unfortunate chance of seeing animals die from wild fungal infections. This is the first study to show the phenomenon in Brazil. Amphibians. If the animal dies and becomes infected, the fungus is not dead. It may coexist with the pathogen without developing the disease. In this case, the animal will experience appropriate symptoms such as weight loss and severe shedding. I was convinced that it was the cause of death because I showed it. The skin, and the very high infection load. ” Toledo is also a Principal Investigator for another project focused on understanding how fungi spread in nature.
Researchers believe that directly-occurring species (which breed on land, lack tadpoles, and hatch terrestrial eggs as fully formed miniature adults) are not further adapted to the fungus. Aquatic species have been in contact with the pathogen for a longer period of time and may have developed some resistance to infection.
Moura-Campos observed the morbidity and mortality of infected frogs during a field survey conducted at the Serra do Japi Biological Reserve in Jundiaí, São Paulo from May 2018 to May 2019. Atypical period of drought.
“These animals are very small and difficult to find. They break down quickly after they die. As we did, it turns out that nine animals are dead or seriously ill in a short period of time. , Probably suggesting that other animals have also died, “said the University of Alabama, USA, and the last author of the article.
According to Becker, a visiting professor at UNICAMP under the Graduate Program in Ecology, the study found that as global climate change accelerates in the coming decades, the frequency of this type of disease will increase and the causative agent will increase. Shows that it can be toxic Hybrids emerge, as already shown in previous studies by the group.
“The lack of soil moisture in the forests in which they live may have caused these animals to seek hydration in streams and become more polluted by fungi than usual,” he said.
Another hypothesis raised by researchers is that periods of drought endanger the frog’s immune system, making it more vulnerable to fungi.
Cosmopolitan pathogen
The fungus originates in Asia and is spread around the world, probably as a result of the frog meat trade. Species consumed by humans for this purpose, such as the bullfrog (Rana catesbeiana), are resistant to fungi and can be carriers without infection.
According to a paper published in the journal in 2018 Chemistry Co-authored by Toledo, the fungus originated on the Korean Peninsula and spread to other parts of the world in the early 20th century.
Another study contributed by Toledo found that fungi are causing a decline in the population of at least 501 amphibians worldwide. In Brazil alone, at least 50 species or populations have been affected, 12 have become extinct and 38 have declined.
“Amphibians are very important for the functioning of many ecosystems. The biomass in forests is enormous. Amphibians serve as food for a variety of other animals, feed on wild arthropods and feed the invertebrate community. We control it, “says Becker. “in the case of Aquatic species, Most are herbivorous at the tadpole stage and consume phytoplankton. Aquatic environment If there were no tadpoles. Because these animals cross aquatic and terrestrial ecosystems, the consequences of an outbreak of chytridiomycosis are significant. “
As an example, Becker is a scientist from an institution in the United States and Panama, B. We recalled a recent study showing that the decrease in amphibian populations due to infection with dendrobatidis was associated with increased malaria outbreaks in Panama and Costa Rica in the 1990s and 2000s. ..
More accurate observations over the years are needed to more accurately estimate the global impact of chytridiomycosis on amphibian populations, according to Becker, Toledo, and collaborators.
For more information:
Diego Moura-Campos et al, a fungal disease cluster of tropical terrestrial frogs predicted by low rainfall, Biological protection (2021). DOI: 10.1016 / j.biocon.2021.109246
Simon J. O’Hanlon et al, Recent Asian Origin of Chitrid Bacteria, Causes Global Amphibian Decline, Chemistry (2018). DOI: 10.1126 / science.aar1965
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