November 9, 2011
Frog Fungus Spread Throughout The World Via Trade
According to new research, a killer frog fungus that is spreading around the world is being distributed through amphibian trade by zoos and collectors.
Scientists said that the most widespread and lethal form of the three distinct lineages of the chytrid fungus was probably created by a crossing of two prior forms.
Chytrid is now found on every continent and has wiped out a number of species.
The fungus kills amphibians by blocking the transfer of vital substances through their skins, eventually causing cardiac arrest.
"Before this study, no-one knew there were any different lineages," Rhys Farrer, the project leader from Imperial College London, said in a statement.
"This work comes from using the new whole-genome sequencing technique, combining data from all over the world.
"And it's obviously important, as chytrid is one of the most devastating wildlife diseases with the largest host range of any, and responsible for dozens of species extinctions and many more extirpations of local populations."
The researchers took samples from amphibians in 20 sites that spanned across Europe, North America, Central America, the Caribbean and South Africa.
The majority of the amphibians had Batrachochytrium dendrobatidis fungus (BdGPL), which is the type that has spread globally.
However, their Swiss sample showed a different form named BdCH, and a third form showed up in the Cape Province of South Africa and the Mediterranean island of Mallorca.
The Mallorcan chytrid was carried from South Africa through the trade in amphibians for zoos or private collections.
The researchers believe the Swiss form of fungus probably came through a similar route.
Lab tests revealed that BdCAPE, the third fungus from Cape Province, was substantially less damaging to amphibians than BdGPL.
The genetic differences that make BdGPL more lethal have not been identified yet. The team believes it became more deadly through a chance encounter between two or more prior strains.
"We think we are seeing unique evidence of recombination within BdGPL - we can't say for sure if it's a hybridization event but it's the most likely explanation," Farrer said in a press release.
"From the dating work we've done it's safe to say that it arose in the 20th Century, and that's in the realm of time for the trade in amphibians."
One theory says that the lethal BdGPL chytrid spread through the importation of frogs from Africa to North America and Europe for use in pregnancy testing.
The most recent study marks a new staging post on the research of chytrid spreading throughout the continents.
The team believes that it is worth investigating whether the less virulent forms of the fugues can be used to give amphibians some resistance.
The research was reported in Proceedings of the National Academy of Sciences.
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