New morphological and molecular evidence confirm the presenceof the Norwegian skate Dipturus nidarosiensis (Storm, 1881) in theMediterranean Sea and extend its distribution to the western basin

Abstract

[eng] The present study confirms the presence of the Norwegian skate Dipturus nidarosiensis (Storm, 1881) in the MediterraneanSea, by means of morphological traits and molecular markers providing the first record of this species in the Alboran Sea. Cannaset al. (2010) reported D. nidarosiensis for the first time in the Mediterranean from specimens captured in the central western basin,but Ebert & Stehmann (2013) and Stehmann et al. (2015) considered these records “likely refer to the smaller morphotype, Dipturussp.”, a species not yet described. Eight specimens of the Dipturus genus (Rajiformes: Rajidae) were caught off the AlboranIsland (western Mediterranean) in 2012, 2013 and 2016, between 620 and 819 m depth. These specimens showed morphometricdiagnostic features corresponding to those of Norwegian skates from the Northeast Atlantic and the central western MediterraneanSea. Moreover, the Alboran individuals were genetically compared to Northeast Atlantic specimens available in GenBank bymeans of two mitochondrial DNA fragments: cytochrome c oxidase subunit I (COI) and cytochrome b (Cytb). Analyses showedthat the Northeast Atlantic Norwegian skate specimens and the Alboran Sea ones were genetically similar and shared haplotypes,corroborating the identification of the Alboran individuals as Dipturus nidarosiensis. However, they were different from otherDipturus species distributed throughout the Northeast Atlantic and the Mediterranean Sea. Our results confirm the occurrence ofthis deep-sea large skate species in the Mediterranean, although the IUCN Red List of Threatened Species does not consider itpossible (Stehmann et al., 2015).