Investigation of Aneides lugubris and Batrachoseps luciae susceptibility to Batrachochytrium dendrobatidis and analysis of cutaneous skin bacteria for B. dendrobatidis inhibition
Wesley J. Sparagon
May 13, 2015
Department or Program
Amphibians around the world are experiencing massive population declines due to a parasitic fungus, Batrachochytrium denbrobatidis (hereafter known as Bd), which infects their skin and impairs key physiological processes. The severity of these declines varies between locations and populations, which is at least partially due to variety in host immunity and symbiotic skin microbiome immunity. Amphibians’ skin hosts an array of bacteria that play a role in immune defense against Bd. The research in this thesis focused on elucidating Bd susceptibility in two previously unstudied, cohabitating California salamanders, Batrachoseps luciae and Aneides lugubris. A separate yet related project involved the culturing and isolation of symbiotic skin bacteria from these two species. This was followed by an assay to determine Bd-inhibition of these isolates. Lastly, isolates were identified using 16S rRNA sequence data. B. luciae was found to be susceptible to mortality from a local, wild Bd strain. Preliminary data suggests A. lugubris is also susceptible to wild Bd although more samples are needed to ascertain if this result is significant. Experiments also demonstrated significant differences in B. luciae mortality rates from wild Bd and lab grown Bd infections. Both species of salamanders exhibited a relatively high percentage of Bd-inhibitory skin microbiome isolates that spanned a variety of bacterial genera. This research helps show how multiple factors influence Bd infection dynamics in wild salamander populations, with the long term goal of helping better contain and push back this widespread pathogen.