Wildlife disease. Recent introduction of a chytrid fungus endangers Western Palearctic salamanders.

Emerging infectious diseases are reducing biodiversity on a global scale. Recently, the emergence of the chytrid fungus Batrachochytrium salamandrivorans resulted in rapid declines in populations of European fire salamanders. Here, we screened more than 5000 amphibians from across four continents and combined experimental assessment of pathogenicity with phylogenetic methods to estimate the threat that this infection poses to amphibian diversity. Results show that B. salamandrivorans is restricted to, but highly pathogenic for, salamanders and newts (Urodela). The pathogen likely originated and remained in coexistence with a clade of salamander hosts for millions of years in Asia. As a result of globalization and lack of biosecurity, it has recently been introduced into naïve European amphibian populations, where it is currently causing biodiversity loss.

Single-molecule detection with a two-photon fluorescence microscope with fast-scanning capabilities and polarization sensitivity.

We describe a laser-scanning two-photon fluorescence microscope that is capable of observing single molecules with excellent temporal resolution and three-dimensional spatial resolution. To demonstrate the capabilities of the instrument we present single-molecule fluorescence data obtained in several different scanning modes. In addition, a polarization-sensitive detection scheme can provide detailed three-dimensional information about the orientations of molecules in any of these scanning modes.