Uncovering cryptic diversity in Loimia (Annelida: Terebellidae), with the description of two new species from the Eastern Mediterranean

The genus Loimia Malmgren, 1866 (Annelida: Terebellidae) represents a taxonomically challenging group of tubicolous polychaetes, with many species showing high morphological conservatism and unresolved systematic boundaries. The presence of Loimia medusa (Savigny, 1822) along the Mediterranean coasts has historically been reported, but recent studies suggest that this species is restricted to the Red Sea and Arabian Gulf, with the Mediterranean records likely reflecting misidentifications. Here, we use an integrative taxonomic approach combining detailed morphological analyses and mitochondrial markers (COI and 16S rDNA) to reassess the diversity in Loimia along the coasts of Israel, Cyprus, and Lebanon. Specimens were collected at shallow waters from Akhziv, Bat Yam, and Tel Aviv beaches (Israel, 2017 and 2025), Episkopi and Larnaka Bays (Cyprus, 2024), and Bar El Mubarakh and Bar es Slaiyeb Bays (Lebanon, 2022). Our results reveal the presence of two new species: Loimia hannae sp. nov. and Loimia saraiae sp. nov., both morphologically distinct from other known species in the genus, including Indo-Pacific relatives. Phylogenetic reconstructions further support their recognition as different species, with COI genetic distances exceeding 12% from closest congeners. Furthermore, observed intraspecific variability, particularly in L. hannae, confirms the importance of accounting for ontogenetic morphological variation when delineating species within this genus. These findings not only expand the known diversity of Loimia in the Mediterranean. While our integrative approach clearly distinguishes these two new species from known Indo-Pacific congeners, their status in the Mediterranean –whether native, non-indigenous, or cryptogenic– remains uncertain and can only be resolved through broader geographic sampling and historical evidence.