A study from the University of Newcastle in Australia suggests that simple sea salt could protect amphibians from the ongoing decimation caused by infections of the chytrid fungus.
Unknown to science until 1998, chytridiomycosis – the disease caused by the microscopic, parasitic fungi Batrachochytrium dendrobatidis (Bd) – is now known to be a huge contributor to the alarming worldwide decline in amphibian species that began in the 1950s. Given that the moisture-loving fungal species has existed for some time, the cause of the recent pandemic remains mysterious, though climate change and human-led environmental alterations have been strongly implicated.
“Chytrid disease is incredibly prevalent worldwide. It has devastated frog populations in Australia, the Americas, Africa and Europe,” said lead researcher Dr Simon Clulow in a statement. “In fact, it’s easier to say where chytrid isn’t found as the only major climatically suitable landmass left on Earth where it hasn’t been detected is New Guinea.”
After the free-swimming spores of Bd have been introduced into a new aquatic or damp forest ecosystem, they seek out and burrow into the skin of a frog or salamander. Once embedded, the growing fungal fibers disrupt the amphibian skin’s ability to uptake electrolytes, leading ultimately to heart failure. Dozens of species have already gone extinct and more than 6,000 species are known to be susceptible.
Thus far, biologists have struggled to identify effective methods for containing the disease that can actually be applied on a large scale. According to the paper by Dr Cudlow and his co-authors, published in the Journal of Applied Ecology, experts have been toying with a new proposition – alter the environment just enough to give the amphibians a shot at success without compromising the health of the other life forms.
When looking for options that fit these difficult criteria, the team reviewed past studies on chytridiomycosis outbreaks. Several had observed that amphibian populations living in slightly more saline habitats fare better, leading to an intriguing possibility: Could the recipe for saving frogs be as simple as adding a pinch of salt?
To test their theory, the researchers turned to the green and golden bell frog, a threatened species native to eastern Australia that has gone extinct in 90 percent of its range thanks to chytridiomycosis.
A group of 10 juvenile frogs infected with Bd and a group of 18 non-infected frogs were each put into one of 16 artificial outdoor "pond" environments containing either high or low salinity water (4 parts per thousand vs 0-1 ppt) that fell within the safe range for the species.
After 23 weeks in the experimental ponds, the frogs initially free from Bd infections that were released into high-salinity ponds had a 77 percent greater survival rate than those living in low-salinity conditions. Sadly, frogs who already harbored fungal infections showed poor survival rates in both saline conditions.
The results indicate that a high-saline environment can’t cure an existing chytridiomycosis outbreak, but it may be able to save future generations of amphibians by preventing Bd transmission.
“This treatment requires the use of simple pool salt, which is very affordable and easy to access. This overcomes many initial hurdles, particularly in majority world countries where resources are scarce and so many species are at risk,” said Dr Clulow.
A conservation program for an endangered Ecuadorian frog has been chosen to test whether altering saline levels will work in a natural environment.
“If we can show that this works just as well on the other side of the globe, it should provide further proof of concept that this strategy could help declining frogs everywhere.”