Skin defenses of North American salamanders against a deadly salamander fungus

Abstract

AbstractThe 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 toBsalare variable but the factors underlying these differences are unknown. To investigate the role of skin‐associated immune defenses againstBsaland 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 conductedin vitroexperimental assays to test whether salamander skin peptides inhibit chytrid growth. Interspecies differences in skin defenses againstBsalandBd, and peptide mixtures were also assessed using a standardized measure and RP‐HPLC, respectively. ForA. maculatum, skin peptides inhibitedBsalandBdgrowth, consistent with knownBsalresistance.Cryptobranchus alleganiensisskin peptides inhibited the growth ofBsalbut notBd. Plethodon shermaniandD. ocoeeskin peptides facilitatedBsalgrowth and had either no effect or inconsistent effects onBdgrowth. With the exception ofA. 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 againstBsalandBd. By advancing knowledge about the factors underlying chytrid susceptibility, particularlyBsal, our findings will help inform conservation initiatives aimed at reducing disease impacts and biodiversity loss.