Total RNA was isolated from 16 adult male salmon lice of the drug susceptible strain IoA-00 and the multi-resistant strain IoA-02, using the Trizol protocol described in 2.7. Total isolated RNA was quantified by using Qubit 2.0 Fluorometer and Qubit RNA BR Assay Kit (Invitrogen, Thermo Fisher Scientific, UK). Quality of isolated total RNA was determined by UV spectrophotometry using a ND-1000 NanoDrop® (Thermo Scientific, UK) and Agilent Bioanalyzer system (Agilent Technologies, CA, USA). RNA integrity was assessed by electrophoresis using 100 ng of denaturized total RNA in a 1% agarose gel stained with ethidium bromide. Total mRNA of each individual was sequenced on an Illumina Novaseq 6000 platform at Novogene (Cambridge, United Kingdom).