Batrachochytrium dendrobatidis - The Link Between Climate Change and Amphibians

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Introduction

Fig 1. Illustration shows a cross-sectional view of a Batrachochytrium dendrobatidis zoospore. The spore type responsible for the infectious disease called Chytridiomycosis.

By Scott Upton

Batrachochytrium dendrobatidis(Bd) is a pathogen primarily found in amphibians, and it’s presence can have devastating effects on amphibian populations. Bd is responsible for causing Chytridiomycosis, or chytrid, in amphibians all across the world in response to rising global temperatures (Fig 1) . Bd can be found on all continents in which amphibians are present, excluding Asia, and as of 2019, Bd has been found to infect 1,015 of 1,854 species (54%) and has lead to the decline of 6.5% of all amphibian species and the extinction of 90 species . Bd has been given the nickname “the doomsday fungus” in response to its incredible ability to reduce biodiversity and its ability to produce mass extinction of species. At the time, Bd is said to have led to the largest reduction of biodiversity of any species of vertebrates in the world (Fisher MC). Unfortunately, this fungus is not slowing down any time soon and its effects will continue to devastate amphibian populations as long as temperatures continue to fluctuate.

Recent studies on climate change have suggested that the frequency of temperature fluctuations will continue to rise without warning (Paul Bradley). Global climate change and its effects on infectious diseases has proven to be one of the most formidable ecological challenges in modern history. With that being said, there has been controversy over whether or not climate change and the increase in infectious diseases are directly linked without the addition of other factors. Despite controversy of the two being directly linked, the combination of climate change and infectious diseases are creating significant declines in biodiversity as well as extinction across amphibian populations. Both Bd and amphibians are sensitive to the results of climate change, but Bd is able to outperform amphibians when the performance gap between the pathogen and host is at its greatest; this can be called the thermal mismatch hypothesis (Jeremy Cohen). This hypothesis suggests that hosts who are adapted to cooler environments will be more susceptible to Chytridiomycosis in unusually warm conditions. Similarly, hosts who are adapted to warmer temperatures are more susceptible to Chytridiomycosis in unusually colder temperatures. Scientists may be able to mitigate the effects of Chytridiomycosis on amphibian populations by further studying Bd in terms of host interactions and comparing it to temperature fluctuations. With that being said, mother nature has a strange way of correcting human influence on the environment and amphibians may be able to avoid the risks Bd poses by adapting to unusual environments.

Batrachochytrium dendrobatidis is a pathogen primarily found in amphibians, and it’s presence can have devastating effects on amphibian populations. Bd is responsible for causing Chytridiomycosis, or chytrid, in amphibians all across the world in response to rising global temperatures (Fig 1). Bd can be found on all continents in which amphibians are present, excluding Asia and as of 2019, Bd had been found to infect 1,015 of 1,854 species (54%) and to be present at 3,705 of 9,503 field sites (39%) . Chytrid fungus thrives in rising temperatures, and it attacks the keratinized layer of the epidermis, causing it to thicken. This is devastating to the amphibian populations because they must keep their skin moist through mucous membranes in order to respirate properly.

My research question is: How does the fluctuation of temperatures across the globe affect the growth of Batrachochytrium dendrobatidis in amphibian populations, and how do amphibians combat this pathogen? Experiments have been conducted on how climate change correlates with chytrid fungus growth, and limited research has been done to show how these amphibians combat it. There is limited evidence that amphibians are able to avoid this pathogen, but there has been some research insinuating that amphibians may travel to deeper and cooler waters to potentially prevent the accessibility of Batrachochytrium dendrobatidis. Batrachochytrium dendrobatidis depletes amphibian populations across the globe, and it is very applicable to them and their environments. If the temperatures continue to rise, then this pathogen could run rampant through the amphibian populations leading to mass extinction.
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References

Authored for BIOL 238 Microbiology, taught by Joan Slonczewski, 2021, Kenyon College.