First record of the snapping shrimp Alpheus cf. lobidens (Decapoda, Caridea, Alpheidae) in the Gulf of Cadiz, an unexpected introduction to European waters from the Persian Gulf

Abstract In 2015, an unknown snapping shrimp of the genus Alpheus was collected in the San Pedro River inlet (Bay of Cadiz, SW Spain). Initially, its identification was not possible only based on DNA barcoding or morphology, considering the difficulties in the Alpheus taxonomy and the low percentage of DNA sequences of Alpheus spp. available in public databases. However, recent studies from Kuwait, Qatar and Iraq describing the morphology of Alpheus cf. lobidens allowed us to place the exotic Alpheus in this species complex. There are also recent sequences of 16S mtRNA and COI deposited in GenBank and BOLD that match >99% of similarity with the sequences of the specimens from the Bay of Cadiz. These sequences have the same origin in the Persian Gulf, but they have been attributed to different Alpheus species. Here we discuss these mismatches, and data about the distribution in the Gulf of Cadiz as well as the habitat of Alpheus cf. lobidens . Additionally, DNA barcodes, and a detailed morphological description and illustrations are provided. Some hypotheses about possible ways of introduction are discussed, and the most plausible route seems to be a natural expansion to the west after entering the Mediterranean Sea by the Suez Canal.