Integrative taxonomy reveals further hidden diversity of <i>Marphysa</i> (Polychaeta: Eunicidae) in European Atlantic and Mediterranean waters

Abstract Marphysa (Polychaeta: Eunicidae) is represented in the Mediterranean by M. aegypti, M. birgeri, and M. chirigota. Previous reports of M. sanguinea are doubtful, because it has a confirmed distribution around the southern English coasts (NE European Atlantic). In this study, we combine morphological and molecular (using 16S rDNA and cytochrome c oxidase I) analyses to reveal for the first time the presence of M. gaditana in the NW Mediterranean (Gulf of Tunis, Tunisia) and to substantiate its presence along the Atlantic coasts of France—previously relying solely on molecular data—drawing on specimens collected in Arcachon Bay and Oléron Island. Our findings also allow us to describe a new species of Marphysa from the Mediterranean coasts of southern France, namely Marphysa gili Martin and Romano, sp. nov., based only on morphological data. Our research highlights previously overlooked diversity within Marphysa on Atlantic and Mediterranean European coasts, thus contributing to the growing series of recent rigorous taxonomic studies that are challenging the historical tendency to merely report ‘M. sanguinea’ without a thorough taxonomic examination or when undertaking physiological, reproductive, or resource management studies on ‘M. sanguinea’ without questioning the appropriateness of using this species’ name.