Cascade's Frog, Rana cascadae, in Lassen Volcanic National Park, CA

[Namio]

About a month ago I helped my friend, who's an undergrad at Humboldt State Univeristy, northern California, to collect some Cascade's frogs (Rana cascadae) for his senior thesis. It's an interesting project involving with clearing chytrid infection with itraconazole (anti-fungal drug) in metamorphs of Cascade's frogs. The study site was at the Lassen Volcanic National Park in northeastern California, one of the few areas that these high elevation native frogs occur.

Here's a map showing the state of California and the red zone is roughly where you can find R. cascadae. This frog also occurs in Oregon, although listed as an endangered species there, and can be found in the Olympic mountains of Washington.


Tadpoles in a shallow pond with a data logger. The tadpoles look like a typical Rana frog on the west coast.


This appears to be a young of last year, still relatively a small frog.


A juvenile frog.



A metamorph that had recently absorbed its tail. In this particular area, chytrid is devastating to these froglets. Not only most of these babies are infected by chytrid, but almost all of them won't make it due to chytridiomycosis. And this is where this project comes into play. Hopefully we can treat these frogs free of the disease and release them back here. Hopefully they'll have a better chance of surviving.


Another juvenile. They blend in pretty well in their environment, don't they?


A rough place to be. This is the only meadow around that provides moisture. All the surrounding areas are very dry and extensive.


Notice the spotted throat, quite characteristic of the Cascade's frogs.


A staged shot



Here's a northern red-legged frog (Rana aurora), Cascade's frog's lower elevation counterpart that lives on the coast of the entire Pacific Northwest. A genetic study revealed that these two frogs form sister taxa. In other words, to each other they are the most closely related species.
This is the same individual that appears as my avatar and lives in my house, an adult male, just like me... lol!

Notice how the throat is not spotted like R. cascadae

[Sunshine]

If they are treated and released back into the wild wont they get re-infected?

[Namio]

If they are treated and released back into the wild wont they get re-infected?

Excellent question, and it is likely they will be infected again. But here is how chytrid fungus infection works: it takes a certain amount of infection level for chytrid to be lethal, or hence to cause chytridiomycosis. The so-called threshold in each amphibian species is often different. Some species have a higher resistance, while some have a lower resistance against the infection. The threshold may vary with many biotic factors such as age & condition of the frog, virulence of the chytrid strain, etc., or other abiotic factors such as temperature, UV-B exposure, environmental degradation, etc. Notably, if chytrid infection never reached the threshold in a frog it will not die of the disease chytridiomycosis. Unfortunately, metamorphs (tadpoles that had just transformed into a froglet) are generally more vulnerable than older frogs because they're simply less developed (e.g., having very little antimicrobial skin peptides compare to an adult frog).

What is happening right now with Cascade's frog is that the new froglets aren't surviving to the next year, likely due to their low resistance against chytrid. If left untreated, the infection will soon reach that threshold and kill off all the froglets. What we hope for is that by clearing the infection completely right now, will give the frog extra time to grow up before facing the next infection (if there's next time).

[Sunshine]

Wow! You know a lot about this! I am very interested in seeing how the experiment turns out!

[Namio]

Wow! You know a lot about this! I am very interested in seeing how the experiment turns out!

Haha, I happened to study the same topic with my own research. I take no credit in my knowledge because it all came from all the previous studies that scientists around the world had done. All I did was reading them. Yes, if I heard something from my friend I will certainly keep you updated.