Tissue grinder

To conduct a functional analysis, Mediterranean O. similis transcriptomes were produced. Oithona similis specimens were sampled at the North of the Large Bay of Toulon, France (Lat 43°06’ 02.3” N and Long 05°56’ 53.4” E). Sampling took place in November 2016. The samples were collected from the upper water layers (0–10 m) using zooplankton nets with a mesh of 90µm and 200 µm (0.5 m diameter and 2.5 m length). Samples were preserved in 70% ethanol and stored at −4°C. From the Large Bay of Toulon samples, O. similis individuals were isolated under the stereomicroscope (Nishida, 1985; Rose, 1933). We selected two different development stages: four copepodites (juveniles) and four adult males. Each individual was transferred separately and crushed, with a tissue grinder (Axygen) into a 1.5 ml tube (Eppendorf). Total mRNAs were extracted using the ‘RNA isolation’ protocol from NucleoSpin RNA XS kit (Macherey‐Nagel) and quantified on a Qubit 2.0 with a RNA HS Assay kit (Invitrogen) and on a Bioanalyzer 2100 with a RNA 6000 Pico Assay kit (Agilent). cDNA was constructed using the SMARTer‐Seq v4 Ultra low Input RNA kit (ClonTech). The libraries were built using the NEBNext Ultra II kit for paired‐end sequencing with an Illumina HiSeq2500. After adaptors trimming, only reads with a mean Phred score > 20 were kept.