Description of a new species of Ligia Fabricius, 1798 (Crustacea: Isopoda: Ligiidae) from Samoa based on morphological and molecular data, with notes on L. vitiensis Dana, 1853

Ligia samoensis, new species, is here described with specimens collected from Samoa, central Pacific, using morphological and molecular methods. This species can be distinguished from its closest congeners by the shape of the appendix masculina, which has a distinctive rectangular apical part with subtly rounded angles, and is equipped with long, narrow, pointed, and fully curved-down cuticular spines. Moreover, the inter-eye distance is similar to 0.6 of the eye length. DNA sequence analysis of the mitochondrial COI locus also supports the recognition of L. samoensis, new species, as it is highly divergent from other currently accepted Ligia species, including L. vitiensis Dana, 1853, a species thought to be widely distributed across coastal areas of the western, central, and southern Pacific as well as the Indian Ocean. The present COI analysis also shows some potential paraphyly within L. vitiensis, and the taxonomic ramifications of this are here discussed.