Genome-wide DNA methylation data
All individuals were analysed at the same age (10 months old). Fish were euthanized using an overdose of methane-sulfonate (MS-222) following UK Home Office Schedule 1, their brains were dissected and stored in molecular grade ethanol before DNA extraction using Qiagen DNeasy Blood and tissue kit (Qiagen Ltd, Crawley, UK).
Bisulphite converted genomic DNA libraries were prepared using the Diagenode Premium Reduced Representation Bisulphite Sequencing (RRBS) kit (Diagenode, Liege, Belgium) according manufacturer’s indications. For the first generation, 16 individuals (ten from enriched, six from poor) were multiplexed into a single library, pooled samples were bisulphite-converted, amplified by enrichment PCR and their quality assessed using Agilent D1000 ScreenTape System (Agilent Technologies, Inc. 2014). The library was then sequenced on an Illumina NextSeq 500 platform using a 1x75pb single-end run (Cardiff University, Genomics Research Hub). Standard PCR fully methylated and unmethylated spike controls were used to monitor bisulphite conversion efficiency.
A second library was created using fourteen individuals from the offspring (five from enriched to enriched environments, three from enriched to poor, three from poor to poor, and three from poor to enriched). The library followed the same procedures and sequencing conditions as the first library.