Redescription of Emplectonema viride – a ubiquitous intertidal hoplonemertean found along the West Coast of North America

Emplectonema viride Stimpson, 1857, a barnacle predator, is one of the most common and conspicuous intertidal nemerteans found along the West Coast of North America from Alaska to California, but it is currently referred to by the wrong name. Briefly described without designation of type material or illustrations, the species was synonymized with the Atlantic look-alike, Emplectonema gracile (Johnston, 1837) by Coe. Here we present morphological and molecular evidence that E. viride is distinct from E. gracile. The two species exhibit differences in color of live specimens and egg size and are clearly differentiated with species delimitation analyses based on sequences of the partial regions of the 16S rRNA and cytochrome c oxidase subunit I genes. In order to improve nomenclatural stability, we re-describe E. viride based on specimens from the southern coast of Oregon and discuss which species should be the type species of the genus. Emplectonema viride was one of the two species originally included in the genus Emplectonema Stimpson, 1857, but subsequent synonymization of E. viride with E. gracile resulted in acceptance of the Atlantic species, E. gracile, as the type species of the genus. We resurrect E. viride Stimpson, 1857 and following Corrêa’s designation, this should be the type species of the genus Emplectonema.