Source: https://upload.wikimedia.org/wikipedia/commons/5/5a/Hyla_japonica_sep01.jpg
A Japanese tree frog (Hyla japonica) rests on some flowers.

Imagine a pathogen that makes its host more sexually active. It may not kill its host right away. It may not kill its host at all. It is easy to imagine why this might be useful. The more partners its host contacts, the more opportunities it has to spread: a big win for a little pathogen trying to get by in the world.

That may be what is happening in Japanese tree frogs. Research recently published in Biology Letters shows that frogs infected with the fungus Batrachochytrium dendrobatidis (Bd) create mating calls distinctive from those that are uninfected. The authors argue that these males may expend more energy to attract mates, which is associated with an increase in reproductive success. That is, the fungus may make those infected more attractive to females. Elsewhere in the world, northern leopard frogs are also feeling the potent effects of Bd infection. Infected frogs have larger testes and produce more sperm than their uninfected peers. It seems that Bd may be quite the aphrodisiac.

However, Bd is not as harmless for all amphibians. In fact, Bd has been decimating amphibian populations worldwide for decades. Bd causes chytridiomycosis, which kills its host by infecting their skin. Amphibians respire, exchange water, and regulate their body temperature through their skin. Chytridiomycosis disrupts these essential functions, which eventually leads to death. Japanese tree frogs and northern leopard frogs may be a carrier species, able to survive in the presence of infection while still spreading it to others. In fact, understanding why some species are able to survive infection while others die is an important avenue of research. This knowledge could help us develop methods to slow its spread.


Peer edited by Nicole Tackmann

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