The Eater of Salamanders
A very cute fire salamander infected with Bsal and covered with lesions (the black spots) - a prominent hallmark of the disease. Photo credit to Frank Pasmans.
What do you get when you take a cute, Asian salamander carrying a fungus and bring it to an area filled with cute, European salamanders that have never seen this fungus? If you guessed mass die-off events, you’re right.
What is Batrachochytrium salamandrivorans (Bsal)?
In 2008, scientist couple An Martel and Frank Pasmans heard about unusal population declines of fire salamanders in The Netherlands [1]. Fire salamanders, like many salamanders, are slow, moist animals which vaguely resemble dogs in their cuteness and charisma, and are well known and loved throughout Europe. Unsure of the cause of death, Martel, Pasmans, and their team went to work to find out. In 2013, they discovered a new chytrid fungus, Batrachochytrium salamandrivorans (Bsal), was responsible. Salamandrivorans means “eater of salamanders” - that’s how awful the disease is. Bsal, unlike many other fungi, has a motile zoospore stage (like a tiny, single-celled tadpole) and an encysted stage (a hard seed-like structure that can stick to things), and these zoospores somehow attach to the skin to cause the lesions seen in the picture above [2]. We don’t yet know the exact mechanism of death, but fire salamanders will die within 18 days after exposure, after a period of not eating, not moving, and general apathy [2]. Through genetic analysis, it was determined that Bsal is a sister species of another amphibian-killing pathogen, Batrachochytrium dendrobatidis (Bd) [2]. Bd is a now-global pathogen that is extremely lethal to many species of amphibians and is thought to be the primary cause of decline for nearly half of all declining amphibian populations [3].
A red-spotted newt, Notophthalmus viridescens, a North American species that is susceptible to Bsal. Photo credit to Todd Pierson 2012, via AmphibiaWeb.
So how did this happen? How does a pathogen sneak up on a bunch of biologists and salamanders and cause a massive die-off event seemingly out of the blue? There is one major hypothesis - that it spread through the pet trade [4,5]. A few Asian salamander species that are commonly kept as pets were discovered to be immune to Bsal [6], and since they are traded globally, and since Bsal was recently found on frogs in the pet trade [5], it is possible that Bsal has hitched a ride on such innocent and cute species and escaped into wild populations. When pet owners dumped out infected tank water unknowingly, or when these pets escaped or were released, Bsal may have had the opportunity to escape into nearby wild, susceptible populations.
In 2013, the year Bsal was officially discovered, only 4% of the fire salamander population in The Netherlands remained [2]. Since Bsal’s discovery, researchers all over the world are working hard to learn more about this mystery pathogen. The big fear right now is that this pathogen will spread to North America, the home of 48% of the world’s salamander species [7]. Through a series of experiments, it was determined that seven amphibian species are susceptible to Bsal, two of which are native to North America [6]. It is possible, and likely, that many more yet-untested species are susceptible. The spread of Bsal to North America could be devastating for amphibian biodiversity, making the prognosis for the survival of this already-imperiled group very grim [3,4,8].
A rough-skinned newt, Taricha granulosa, a North American species that is susceptible to Bsal. Photo credit to William Leonard 2005, via AmphibiaWeb.
So what can we do to prevent this? In January 2016, the US Fish and Wildlife Service (an enforcement agency) banned the import and interstate travel of salamanders (read more here). Since Bsal has not yet been detected in the US, the idea behind the ban is that maybe we have a shot of keeping it out, or at least containing spread if it gets in. However, this is not enough. The US Geological Survey (USGS, a research agency) continues to monitor populations for both Bsal and Bd (2017 update), and many in the field believe it is a matter of time before Bsal gets to North America. A few mitigation strategies are in the works, both for Bd and Bsal, and include vaccines, probiotics, and new drug treatments that could be administered to wild amphibians. While many of these treatments are effective in the laboratory, they have proved difficult to implement in a natural population with many unknown factors. For instance, salamanders can’t just line up at a flu shot clinic - each individual must be captured, taken to a treatment center, vaccinated, monitored, given anti-fungal treatment, and released at the same spot it was taken from. Furthermore, when and where these treatments should be deployed is a completely unexplored question for Bsal - and that’s where my research comes in.
What if we could know which salamander populations would be hit the hardest? What if we could get an idea of when they would be hit? What if we could gather key information about what types of habitats Bsal does the best in, which salamanders are affected by Bsal, and where Bsal might enter North America? The good news is, we have most of this information. Using these data, I hope to build a spatially and temporally realistic model of Bsal spread in North America - and use it to help save our salamanders - but more on that another time.
Researchers aren’t the only people who can help solve this problem and save the salamanders. Here is a list of things everyone can and should do to protect North America’s weirdest-looking dogs:
Want an amphibian pet? Buy local species only.
Bleach your tank water before disposal, and let it sit for 24 hours to break down the bleach before pouring it down the sink.
If you think your pet has Bsal, see a vet. To clear Bsal from your pet’s enclosure, you can bleach the tank and decontaminate non-bleachable things by leaving them in direct sunlight for 48 hours.
Do not capture/release wild amphibians (it’s against the law in most places).
Do not release pet amphibians (it’s against the law in most places).
Don’t touch a bunch of amphibians from different places with bare, unwashed hands.
Don’t touch amphibians with products on your hands (no soap/lotion/sunscreen…).
Spread the word about these little friends, and make sure people know why they are important to save (more on that another time).
A Santa Cruz black salamander, Aneides flavipunctatus niger, being an important indicator of ecosystem health and playing a key role in community interactions. Photo credit to Sam Murray via Arkive.
We are in the middle of the sixth mass extinction, and amphibians are one of the most at-risk vertebrate groups [9]. It doesn’t take much to imagine a world with less/no amphibians - bugs everywhere, food chains thrown off balance, and an eerie silence outdoors at night. Furthermore, amphibians are important indicators of ecosystem health and play key roles in community interactions. If amphibians continue to go extinct at this rate, our grandchildren may never see them in the wild, and more than that, entire ecosystems could suffer. Help prevent this future by talking to your friends and family about Bsal and salamanders, and supporting government funding of organizations like the USGS who work tirelessly to protect our environment.
Further Reading:
References:
1. Stokstad, E. A fungus is attacking Europe’s most beloved salamander. It could wreak havoc if it gets to North America. Science News (2017).
2. Martel, A. et al. Batrachochytrium salamandrivorans sp. nov. causes lethal chytridiomycosis in amphibians. Proc. Natl. Acad. Sci. U. S. A. 110, 15325–9 (2013).
3. Skerratt, L. F. et al. Spread of chytridiomycosis has caused the rapid global decline and extinction of frogs. Ecohealth 4, 125 (2007).
4. Yap, T. A., Koo, M. S., Ambrose, R. F., Wake, D. B. & Vredenburg, V. T. Averting a North American biodiversity crisis. Science (80-. ). 349, 481–482 (2015).
5. Nguyen, T. T., Nguyen, T. Van, Ziegler, T., Pasmans, F. & Martel, A. Trade in wild anurans vectors the urodelan pathogen Batrachochytrium salamandrivorans into Europe. Amphibia-Reptilia 4–6 (2017). doi:10.1038/srep44443.Martel
6. Martel, A. et al. Recent introduction of a chytrid fungus endangers Western Palearctic salamanders. Science (80-. ). 346, 630–631 (2014).
7. AmphibiaWeb. (2017). Available at: http://amphibiaweb.org. (Accessed: 5th October 2017)
8. Stuart, S. N. et al. Status and trends of amphibian declines and extinctions worldwide. Science (80-. ). 306, 1783–1786 (2004).
9. Kilpatrick, A. M., Briggs, C. J. & Daszak, P. The ecology and impact of chytridiomycosis: an emerging disease of amphibians. Trends Ecol. Evol. 25, 109–118 (2010).
Edited by Michelle Lee
