Morphology and Phylogeny of Notospermus psittacinus comb. nov. (Nemertea: Pilidiophora: Lineidae) from Mindanao, Philippines

This study provides a redescription of the lineid heteronemertean Notospermus psittacinus (Bürger, 1890) comb. nov. based on specimens collected from Mindanao, Philippines. The species was previously assigned to the genus Lineus Sowerby, 1805, and has not been reported since its original description from Ambon, Indonesia. No DNA barcode sequences based on reliably identified material from the type locality are currently available. Notospermus psittacinus comb. nov. differs from the other six named species of the genus in body coloration, but can be distinguished from N. annulatus (Grube, 1840) only by molecular and biogeographic evidence. Despite the observed morphological variations in our specimens, genetic distance analyses indicated that all represent a single species (cytochrome c oxidase subunit I [COI] p-distance = 0%–2.12% [n = 7], 16S ribosomal RNA [16S] p-distance = 0%–1.57% [n = 6]). Genetic divergence between N. annulatus and N. psittacinus comb. nov. was 11.39%–12.18% for the 16S gene and 5.79% for the histone H3 (H3) gene, supporting their status as distinct species. A multigene phylogenetic analysis based on 16S, 18S ribosomal RNA, 28S ribosomal RNA, COI, and H3 sequences showed that all N. psittacinus comb. nov. specimens formed a well-supported clade within the genus Notospermus Huschke, 1830. Although intra-generic relationships remain poorly resolved, this result corroborates the generic reassignment of the species from Lineus to Notospermus.