show Abstracthide AbstractCeratothoa oestroides (Cymothoidea, Isopoda) is a generalist crustacean parasite that negatively affects the economic sustainability of European sea bass (Dicentrarchus labrax) aquaculture in the North-East Mediterranean. C. oestroides parasitizes the host buccal cavity, where paired growing individuals sexually differentiate and eventually reproduce. While mortalities are observed in fry and fingerlings, infection in juvenile and adult fish results in approximately 20% of growth retardation. A transcriptomic analysis (Illumina RNA-Seq, NovaSeq6000 2 x 150 nucleotides paired-end reads) was performed on organs (tongue, spleen and liver) from infected vs. Ceratothoa-free sea bass fingerlings.