The parasitic fungus Batrachochytrium dendrobatidis (Bd) infects and often decimates amphibian populations and species around the world, causing the disease chytridiomycosis. Whether and in what way the fungus will spread and affect different populations, is decided by an interplay between environmental conditions, as well as host and parasite characteristics. This projects aims to investigate how temperature affects the disease outcome in four amphibian species in Sweden. The fungus is expected to outperform each host at temperatures away from the host's optimum, and at this temperature host survival is expected to be lowest. Rana arvalis, Bufo bufo, Bufotes viridis and Pelophylax esculentus individuals have been collected as eggs, raised in the lab, infected with the fungus and monitored for 40 days. mRNA from liver and skin of experimental individuals has been (and will be) sequenced, and the sequences will be used to perform differential expression analysis for each species.