Differential flatfish species detection by COIBar-RFLP in processed seafood products

Common sole (Solea solea) is often the subject of fraudulent species substitutions in processed products because of their excellent organoleptic characteristics and high commercial interest. COIBar-RFLP, a molecular strategy-coupling Cytochrome Oxidase I (COI) DNA barcoding with the consolidated methodology of restriction fragment length polymorphism analysis (RFLP), was applied to search for restriction enzyme polymorphisms useful to discriminate among potential flatfish substitutes of common sole. Seven flatfish species belonging to Soleidae, Bothidae, and Citharidae families were used to construct a reference barcode library of COI sequences. The flatfish species were simultaneously discriminated through specific digestion profiles obtained with the restriction enzyme MspI. We tested the efficacy of COIBar-RFLP on 13 frozen fillets labeled as common sole purchased in local fish markets. These fillets were found to contain three species, S. solea, Solea senegalensis, and Arnoglossus laterna, successfully discriminated by COIBar-RFLP, demonstrating that this method is a rapid and simple sequencing-free molecular approach for these fish species identification in processed seafood products.