Can the Fire Salamander Handle the Heat?
Author: Jeremy Schloss
Climate change talks often discuss environmental issues such as increasing natural disaster intensity and coral reef bleaching, but human-driven climate change can affect species in very subtle ways too. With rising temperatures, new dangerous diseases are appearing and wreaking havoc. Chytridiomycosis (commonly shortened to chytrid) is a fungal infection that has been destroying amphibian populations around the world for the past few decades. Humans have aided its spread through international trade and the pet trade (1). It requires water and moisture to spread and survive. This infection results in the spread of fungal spores across the skin of amphibians, a perfect moist home to grow. Since many amphibians breathe through their skin, the spread of the spores results in the suffocation and death of the animal (2).
One such skin-breathing amphibian is Salamandra salamandra, the Fire Salamander. Native to Europe, this salamander is identified by its bright yellow splotches on the back, stomach, and sides of its otherwise black body. Some variants may have yellow or red, but the pattern is unique to the individual. Their diet is mostly made up of insects, worms, slugs, and occasionally other amphibians. The unassuming salamanders also pack a hidden punch, a toxin called samandarin, which it stores in glands around its body. This compound can cause convulsions, hypertension, and hyperventilations in other vertebrates and has even been theorized to be a method of keeping infections away (3).
Rising temperatures can dramatically shift the ability of an animal to fight disease. All animals have a Thermal Neutral Zone, a range of temperature in which they function most optimally. Living outside of that range can affect how fast they digest, how much they need to eat, and even decrease the strength of the immune system. Salamanders are cold-blooded animals; they aren’t able to control their body temperature and instead rely on the environment for warmth and cooling. While salamanders might normally occupy warm areas, increasing temperatures force them to avoid heat and gather in the shade. Temperatures have also limited the space that is considered an escape from the heat, leading to larger gatherings in shade. This creates a dangerous space for disease spread.
Like the salamander, chytrid has its own thermal neutral zone between 17-25°C and over 30°C can be lethal to the fungus (2). While global temperatures have risen, locally this can lead to an increase in water evaporation and cloud formation. This can decrease the daytime temperature while increasing nighttime temperatures, potentially keeping the fungus within its favorable temperature range. Luckily, salamanders have some adaptations that may allow them to fight the disease. While their favorable temperature range is 17-21°C, they can survive up to five days in temperatures well over 25°C (4). Their ability to occupy this higher temperature may be their greatest advantage against the disease.
While there is not a solution to treating the fungal infection itself, we can still do a great deal to limit the spread and severity of the disease. Rigorous trade regulations can limit the spread of chytrid to uninfected areas. More carefully regulating the pet trade especially can reduce the risk of transporting infected animals. In general, making great efforts to reverse temperature increases and greenhouse gas emissions can reduce the spread of the disease in the wild and allow for salamanders to combat the disease through behavior.
Photograph of Salamandra salamandra- Credit: By Petar Milošević from Orle hill, Slovenia - Fire Salamander (Salamandra salamandra), CC BY-SA 4.0, https://commons.wikimedia.org/wiki/File:Fire_salamander_(Salamandra_Salamandra).jpg
Microscope photograph of chytrid infection- Credit: Public Domain, https://commons.wikimedia.org/wiki/File:Chytridiomycosis2.jpg
- Burrowes, P.A.; I.D.d. Riva (2017). "Unraveling the historical prevalence of the invasive chytrid fungus in the Bolivian Andes: implications in recent amphibian declines". Biological Invasions. 19 (6): 1781–1794.
- Whittaker, Kellie; Vredenburg, Vance. "An Overview of Chytridiomycosis". Amphibiaweb.
- Griffiths, R (1996). Newts and Salamanders of Europe. London: Academic Press.
- Beukema, W., Pasmans, F., Van Praet, S., Ferri‐Yáñez, F., Kelly, M., Laking, A., Erens, J., Speybroeck, J., Verheyen, K., Lens, L., Martel, A., & Auer, S. (2021). Microclimate limits thermal behaviour favourable to disease control in a nocturnal amphibian. Ecology Letters, 24(1), 27–37.