RNA extraction from sample S2, L. byrdi infection
O. grillus targeted for RNA extraction were preserved at -80C in RNAlater-ICE (ThermoFisher Scientific) and dissected in chilled PBS. Amphipods were classified infected if they were orange and carried at least one cyst, or uninfected if they were brown and carried no cysts. Twenty-four infected and 24 uninfected samples were lysed using a TissueLyzer. RNA was extracted using a Qiagen RNeasy Mini Kit and diluted to equimolar concentrations prior to sequencing.