Skin defenses of North American salamanders against a deadly salamander fungus

The recently emerged fungal pathogen, Batrachochytrium salamandrivorans (Bsal) causes the lethal skin disease chytridiomycosis in susceptible salamander species and is predicted to emerge within the Americas with devastating consequences. Host responses to Bsal are variable but the factors underlying these differences are unknown. To investigate the role of skin-associated immune defenses against Bsal and the closely related, B. dendrobatidis (Bd), we sampled skin peptides from wild and captive North American salamanders (spotted salamanders [Ambystoma maculatum], n = 10; hellbenders [Cryptobranchus alleganiensis], n = 2; red-legged salamanders [Plethodon shermani], n = 18; and Ocoee salamanders [Desmognathus ocoee], n = 15) and conducted in vitro experimental assays to test whether salamander skin peptides inhibit chytrid growth. Interspecies differences in skin defenses against Bsal and Bd, and peptide mixtures were also assessed using a standardized measure and RP-HPLC, respectively. For A. maculatum, skin peptides inhibited Bsal and Bd growth, consistent with known Bsal resistance. Cryptobranchus alleganiensis skin peptides inhibited the growth of Bsal but not Bd. Plethodon shermani and D. ocoee skin peptides facilitated Bsal growth and had either no effect or inconsistent effects on Bd growth. With the exception of A. maculatum, most species had relatively weak skin defenses against both chytrid pathogens. Collectively, we demonstrate that salamander skin peptide defenses against chytrid pathogens are highly variable and not always equally effective against Bsal and Bd. By advancing knowledge about the factors underlying chytrid susceptibility, particularly Bsal, our findings will help inform conservation initiatives aimed at reducing disease impacts and biodiversity loss.

Automated summary

The study found that salamander skin peptide defenses against chytrid pathogens are highly variable and not always equally effective against Bsal and Bd.