New insights into the potential introduction pathways of Callinectes sapidus Rathbun, 1896 (Decapoda, Portunidae) in European waters

Two new COI haplotypes of the invasive Callinectes sapidus were reported for the first time in the western Iberian Peninsula and one of them in Europe, providing new insights into the origin of this species' invasion in European waters. The new haplotypes were recorded at very low frequencies (< 1%) in the Guadalquivir Estuary during 2021 and 2022 and correspond to those reported in the Gulf of Mexico and Brazil, respectively. These findings indicate new possible introduction pathways from these regions. In addition, the Gulf of Mexico haplotype found in the Guadalquivir Estuary differs by only five mutations from haplotypes recently observed in Tunisia, suggesting a potential genetic link between these populations. The population of the Guadalquivir Estuary was mainly represented by the CSWM1 haplotype (66%), followed by the CSWM2 (32%), aligning with the westward expansion pattern observed in other west Mediterranean and east Atlantic populations.