First Record of the Amphi-Atlantic Rafting Crab Plagusia depressa (Fabricius, 1775) (Crustacea, Decapoda, Brachyura) in the European Continental Waters: Southern Spain as a Gateway for Non-Native Species

The amphi-atlantic rafting crab Plagusia depressa (Brachyura: Plagusiidae) has been recorded for the first time in European continental waters. Three specimens were captured manually in a rocky shore intertidal/subtidal of a beach located in the Gulf of Cádiz (Spain). These specimens were identified using morphological and molecular techniques (DNA barcoding of the 16S and COI genes). The 16S sequence suggests that these specimens are more closely related to African specimens than to those from the Caribbean. However, given the rafting behavior of this species, the specimens recorded in the Gulf of Cádiz may have originated from more distant regions within its distribution range for which molecular data are not available. We present a detailed morphological identification of these specimens and compare them with Plagusia squamosa, which occurs in the nearby Mediterranean Sea. This comparison contributes to clarifying the morphological traits that distinguish the two species. This finding highlights the role of southern Iberian waters in facilitating the introduction and establishment of non-native species.