Verreaux's alpine tree frog jumps faster when infected with a common fungus
Robert Valentich/naturepl.com
Chytrid fungus is a deadly pathogen affecting amphibians in an ongoing global pandemic, capable of wiping out entire populations. But in one critically endangered species of Australian frog, the infection has an unusual side effect: massive amounts of hops.
Verreaux's Alpine Tree FrogsAlpine beaches of Verreaux), infected with chytrid fungus, also known as Batrachochytrium dendrobatidis or Bd infections, can grow almost a quarter further than their uninfected counterparts.
“[The findings] will remind you how resilient these amphibians are and how they cope with being bombarded by this truly terrible pathogen. And yet their bodies are capable of doing something wonderfully unexpected,” says Tegan McMahon at Connecticut College in New London, which was not involved in the study.
Alexander Wendt from the University of Melbourne in Australia and colleagues studied how Bd infections affect the health of alpine tree frogs, using their athletic performance as a proxy for physiological effects.
In the laboratory, the researchers divided 60 frogs into uninfected and Bd-infected groups. Wendt and his colleagues tested how the frogs responded to extreme temperatures and how far they jumped when gently nudged.
Surprisingly, by the sixth week after infection, infected frogs jumped almost 24 percent farther than uninfected frogs. In most other amphibians, focusing the immune system on fighting fungus drains the animal's energy. Physiological responses to Bd appear to vary among amphibian species, resulting in transient benefits in some sublethal infections.
“But once clinical signs appear, that's usually the nail in the coffin for most species,” Wendt says.
Alpine tree frogs do not appear to have a strong immune response to Bd that would slow them down, and their increased jumping ability may be an adaptation to quickly find a mate for a last chance to reproduce before the infection gets worse. Other frog species are known to increase mate calling when infected with Bd.
A short-term increase in jumping ability can also benefit the DB. “Evolutionarily it would make sense for [Bd] to facilitate movement to allow for higher levels of transmission and longer lifespan in the host,” says McMahon.
It is increasingly believed that the effects of Bd on amphibians depend on the interaction of host and fungal biology, as well as the local environment. “All we can do is learn as much as we can to help species survive and slow or stop the spread of Bd before it's too late,” Wendt says.
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