Some believe that the world is currently experiencing a 6th mass extinction as exemplified by declining amphibian populations worldwide. For example, in western North America, the long-toed salamander, Ambystoma macrodactylum, has experienced declines but like many amphibians globally, the cause is unknown. One likely factor is emerging infectious disease. A global panzootic caused by the fungal pathogen, Batrachochytrium dendrobatidis (Bd), has affected hundreds of species throughout North and South America, areas in Africa and Europe. Bd causes chytridiomycosis, infects amphibian skin and causes morbidity and death in many species. Western North America, where A. macrodactylum ranges from British Columbia, Canada, to California, is an area where many species have been affected by the Bd pandemic. Although they have a wide distribution, not much is known about this species and its relationship to the deadly fungal pathogen. In this study, I conducted a retrospective analysis on 419 specimens from California collected from 1818 to 2003 to determine when and where Bd invaded and infected this species as it has other species that have collapsed.
Results/Conclusions
I used a qPCR assay shown to be effective on museum specimens and found only three infected specimens. These results are interesting because they are in stark contrast to other native amphibians in Western North America that have experienced Bd invasion followed by an epizootic pattern of increased prevalence followed by population collapse. This suggest that this salamander’s decline may not be due to a Bd epizootic. Other studies have shown Bd resistance in hosts may arise from multiple pathways. One pathway would be skin symbiont that produces anti-fungal compounds. Some studies have suggested that anti-fungal compounds produced by symbiotic bacteria or host skin secretions, such as peptides, may protect hosts from Bd infection. Future work should investigate the status of current populations and the immunological response of individuals to Bd infection in this species. I would like to further investigate why they are not affected by the pathogen. I would like to collect bacterial swabs from the skin of the salamander where I am test the strength of their Bd inhibiting abilities. Understanding this trait would allow us to further understand the possible evolutionary mechanisms that allow these amphibians to fight back from this deadly fungal pathogen.