If you're a fan of frogs, then unfortunately you've probably heard of Batrachochytrium dendrobatidis (Bd). More commonly known as chytrid fungus, it's been decimating amphibian populations around the world. Now, however, scientists believe they know where it originates – and that knowledge could help keep it from spreading.
Bd causes a disease known as chytridiomycosis, which attacks the skin of frogs, toads and salamanders. As a result, the animals lose control of their ability to regulate their water and electrolyte levels, ultimately leading to heart failure. The geographic origins of the fungus have remained a mystery, limiting attempts to stop it at its source.
In a recent international study involving scientists from 38 institutions, Bd samples were gathered from locations around the world, and their DNA was sequenced – this allowed the scientists to identify the genome of each sample. That data was combined with the genomes of Bd samples gathered in previous studies, resulting in a collection of 234 examples.
When all of these genomes were compared with one another, it was found that there were four main genetic lineages. While three of these had already spread to the point that they were found across the planet, one was limited to the Korean peninsula. According to a paper on the research, this lineage "exhibits the genetic hallmarks of an ancestral population that seeded the panzootic."
Additionally, the emergence of that lineage was dated to the early 20th century, which coincides with the global expansion of the commercial trade in pet amphibians. To that end, in order to stop fresh supplies of Bd from being sent out into the world, the scientists are suggesting that it may be necessary to ban trade in amphibians from the area.
"Biologists have known since the 1990s that Bd is behind the decline for many amphibian species," says Imperial College London's Dr. Simon O'Hanlon, first author of the study. "But until now, we haven't been able to identify exactly where it came from. In our article we solve this problem and show that the lineage that has caused this devastation can be traced back to East Asia."
The paper was recently published in the journal Science.
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