WHY IS ONE SICK BUT NOT THE OTHER? NEW STUDY ON SALAMANDER DISEASE SUSCEPTIBILITY.

Salamanders are severely threatened by the fungus ‘Bsal’ which eats their skin away, causing a terrible disease called ‘chytridiomycosis’. Research on this disease is essential to establish successful mitigation strategies. In our recent study, we investigated why some individuals get less sick than others, with the aim of identifying the mechanisms by which some salamanders can fight Bsal. Our results suggested the existence of tradeoffs between the maintenance of basal metabolism, and the establishment of an immune response.

Italian crested newt, Triturus carnifex (© Eduardo Fernández Meléndez)

Why this matters?

Amphibians make the most endangered vertebrate class on earth, with over 40% of species globally threatened. One of the reasons for their declines is the emergence of infectious diseases. The fungus Bsal recently emerged in Europe and caused catastrophic salamander declines in Belgium and in the Netherlands. It is fundamental to study Bsal to mitigate this disease and to prevent further amphibian declines.

Our study design and key results

To investigate the mechanisms that underlie individual variation in disease susceptibility, we studied the gene expression and skin microbiome of Italian crested newts exposed to Bsal. We found that:

• The communities of bacteria that form the skin microbiome and help amphibians fight certain pathogens (such as the fungus Bd) have little implication on Bsal disease;

• Salamanders expressed genes related to inflammation and adaptive immunity more in reaction to Bsal exposure, and they downregulated the expression of keratin-related genes (which are important for the integrity of the salamander skin);

• Individuals with the strongest gene expression changes (highest upregulation of immune responses and downregulation of basal metabolism) were the sickest.

  
  

Together, our results suggest that Bsal susceptibility may be linked to a reallocation of energy resources from the maintenance of basal metabolism and tissue integrity towards elevated immunity and tissue restructuration.

Future directions

Our work highlights the need to further study individual variation in disease susceptibility and gene expression tradeoffs. Taken together, our results set an important stepping-stone for future research on amphibian conservation.

Want to learn more?

You can read the full scientific study here! This research is part of the GLOSSI project, supported by the European Research Council (ERC), enabling continued efforts to better understand and protect amphibian health worldwide. If you want to learn more about this project, you can visit the project page on our website.