A frightening disease has been ravaging amphibians across the planet. At least 350 species have been infected, two hundred of which have suffered massive population reductions or extinctions, some even occurring within the space of weeks. In 1999, a single fungal species called Batrachochytrium dendrobatidis (Bd), commonly known as the chytrid fungus, was identified as the causative agent for these rapid die-offs. This facilitated preemptive testing of rare or endangered amphibian populations for Bd, the early detection of which allowed scientists to establish captive breeding populations to stem amphibian species extinctions. Frighteningly, despite this discovery, there remain perplexing instances of rapid amphibian deaths that do not test positive for Bd.

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An Martel of Ghent University, in the journal PNAS, has recently reported a possible explanation for these mysterious deaths. Together with an international team of scientists, she has identified a second culprit: a new chytrid species named Batrachochytrium salamandrivorans (Bs), which can be translated to "the salamander-eating fungus."

Fire salamanders (Salamandra salamandra) are captivating creatures, jet black with vibrant yellow patterns that vary from spots to stripes. One of the last surviving populations of this species is found in Bunderbos in the southern Netherlands. In 2010, when the salamanders here first began to die, herpetologists barely had time to react before sightings dropped from 200 to 4 in one year. By 2012, nearly 96% of all salamanders present when assessed in 1997 were gone.

Although currently listed as Least Concern by the IUCN Red List, fire salamanders are threatened in many parts of their range across Europe. While they have suffered greatly from habitat loss through the drying up of streams, nothing decimated their populations like this mysterious disease. Fearing the worst, scientists captured 39 individuals to establish a breeding program, only for 19 animals (nearly half) to promptly die in captivity. Post-mortems were conducted on these animals, and they were tested for Bd and a host of other amphibian diseases, but to no avail. However, further experimentation by Martel and colleagues then revealed the presence of a fungal chytrid species called Bs, closely related to Bd but previously unknown to science. It is the only chytrid species, other than Bd, known to prey on invertebrates.