Eunoe Malmgren, 1865 (Annelida, Polynoidae) in the Arctic, North Atlantic, and North Pacific: redescription of the type species and clarification of the genus boundaries

The scale worm genus Eunoe was investigated using an integrative taxonomic approach that combined multilocus DNA (COI, 16 S rRNA, ITS 2, and 28 S rRNA) and detailed morphological data to address persistent uncertainty over generic limits in Polynoidae. Our phylogenetic analyses support Eunoe sensu stricto as a clade comprising six species: Eunoe nodosa (the type species), E. oerstedi, E. cf. oerstedi CMC 01 (a putative undescribed species), E. ciliata comb. nov.

(formerly placed in Gattyana), E. shirikishinai, and E. spinicirris. The remaining fifteen species currently assigned to Eunoe were recovered outside Eunoe s. str. and were scattered across the inferred phylogeny. Their placement does not allow confident assignment to other polynoid genera.

In this study, we redescribe E. nodosa and E. oerstedi, designate lectotypes for both species, and generate sequence data from the lectotype of E. oerstedi using museomics methods. Based on our morphological analysis, five additional species likely belonging to Eunoe s. str. are also identified: E. barbata, E. hydroidopapillata, E. hozawai, E. sentiformis, and E. spinosa. Our findings suggest that Eunoe s. str. can be characterized by the presence of macrotubercles on elytra and the dorsal or dorsolateral placement of the anterior pair of eyes.

In contrast, the ventral position of the anterior pair of eyes is a diagnostic character of Gattyana s. str. We also corroborate earlier evidence for the polyphyly of Harmothoe, emphasizing the need for a comprehensive taxonomic revision of generic boundaries in Polynoidae.