Leodamas australiensis (Hartmann-Schr?der, 1979) (Polychaeta, Orbiniidae), a new alien species in the Mediterranean, and its ecology in the Mar Menor coastal lagoon (SE Spain)

Invasive species, including many polychaetes, are one of the major factors affecting the diversity of the Mediterranean ecosystems. Coastal lagoons, as transitional ecosystems, present a large spatial and temporal variability that makes them suitable for opportunistic species colonization. In this work, the species Leodamas australiensis (Hartmann-Schroder, 1979) has been identified in the Mar Menor coastal lagoon (Spain) and this is its first report from the Mediterranean. It is characterized by the presence of large aciculae with protruding and distinctly curved tips in abdominal neuropodia and by the onset of dorsal branchiae on chaetiger 6. Molecular analyses were carried out using mitochondrial 16S rDNA gene sequences. The spatio-temporal distribution of L. australiensis and its relationship with other species belonging to the family Orbiniidae in the lagoon was investigated in different periods from 1982 to 2018. This species expanded from sites more connected to the Mediterranean Sea towards more confined areas of the basin. However, this expansion did not affect in an appreciable manner to native orbiniids. Follow-up studies at longer time scales are needed to determine if L. australiensis is a casual presence or maintains a well-established population.