Aquatic environments contain a wealth of hidden host-pathogen interactions that can teach us about the evolution of eukaryotic immunity. To uncover some of these interactions, Katherine Deets is studying antiviral responses in ciliates – single-celled eukaryotes that play an important role in moving nutrients throughout aquatic ecosystems. She is also developing a new model system to determine how these ciliates might concentrate and transmit viruses or other pathological microbes between fish.