Worldwide research on frog extinction Amphibians are perhaps the most threatened of all animal groups. A new reason for extinction apart from environmental change and habitat loss is under consideration – infectious diseases. Health © Shutterstock In 2008, 32 % of amphibian species were listed as threatened or extinct. The EU-funded PARAFROGS (Emerging protist parasites of frogs: global prevalence and host/parasite interaction) project has investigated one possible reason for the mass mortality events (MMEs). Researchers previously found a protist closely related to Perkinsus, a genus that normally infects oysters and clams. Significantly, the microbe was found infecting the livers of Southern Leopard Frog tadpoles during an MME in Georgia, United States of America. Moreover, after analysis of ribosomal DNA in freshwater, it would appear this parasite has a free-living phase. The researchers developed new molecular analysis methods – targeted polymerase chain reaction – to investigate the diversity of Perkinsea lineages from families of frogs across three continents. Research results found that Perkinsea-like protists infect tadpoles in both temperate and tropical zones. In collaboration with another project, PARAFROGS performed high-throughput RNA sequencing. Results suggest that Perkinsea lineages may play a significant role as parasites in marine sediments and part of a seedbank microbial community. Future work is planned on delineating the parasite's role in the marine food web. PARAFROGS also developed a new sampling process for sediment up to 4 000 metres deep to sequence meta-transcriptomes from groups of interacting species. Importantly, the protocol can be applied to any of the parasite's environments including host tissues. PARAFROG has completed development of state-of-the-art molecular biology tools and accompanying bioinformatics analysis. The result will be the integration of 'omics' datasets that are essential in microbial ecology. The research also saw publication in eight scientific journals and a book chapter for the Cambridge University Press. Keywords Frog, extinction, protist, Perkinsea, molecular biology tools
