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The taxonomy of ribbon worms (Nemertea) is particularly challenging due to the sparsity of distinct morphological characters, causing a significant underestimation of the group’s true diversity. The number of named deep-sea species is very limited and there is a vast number of undescribed deep-sea nemerteans still to be discovered. In this paper we figuratively ‘cut the ribbon’ and name seven new species of monostiliferous hoplonemerteans from seeps and seamounts along the Costa Rican margin, one from seeps along the Oregon margin, and one from vents of the Juan de Fuca Ridge, USA. The species Chernyshevia escarpiaphila gen. et sp. nov. and five species of the genus Alvinonemertes gen. nov. (Alvinonemertes dariae gen. et sp. nov., Alvinonemertes dagmarae gen. et sp. nov., Alvinonemertes christianeae gen. et sp. nov., Alvinonemertes claudiae gen. et sp. nov., Alvinonemertes tatjanae gen. et sp. nov.) represent Oerstediina, whereas the three species Tetrastemma sundbergi sp. nov., Tetrastemma polyakovae sp. nov., and Tetrastemma strandae sp. nov. represent Amphiporina. One species of tubulanid palaeonemerteans is described but not provided with a species name due to lacking sequence data for comparison. Additionally, we provide sequence data for one lineid heteronemertean, one reptant hoplonemertean, and two further eumonostiliferan hoplonemertean species. We use an integrative, turbotaxonomic approach combining DNA sequence data with concise morphological descriptions and fully digitized serial histological sections made available as cybertypes.
Dorvilleids belonging to Ophryotrocha Claparède & Mecznikow, 1869 are known from deep-sea hydrothermal vents in the Pacific, Atlantic, Indian and Southern Oceans. However, how they colonized and diversified in these ecosystems has not been assessed in detail. Here, a collection of Pacific hydrothermal vent Ophryotrocha was examined using morphology and DNA markers (COI, 16S and H3). Five new species were revealed, largely expanding the diversity of the group at this habitat type. They are Ophryotrocha charlottae sp. nov., O. kailae sp. nov., O. marinae sp. nov., O. pruittae sp. nov. from eastern Pacific, and O. bohnorum sp. nov. from the western Pacific. Phylogenetic analyses based on the concatenated alignments of all three genes suggest vent habitants have been colonized several times independently within Ophryotrocha. One clade of six vent species was recovered, indicative of diversification following a colonization of hydrothermal vents, likely in the eastern Pacific. An Indian Ocean species, O. jiaolongi, was nested inside this clade and was closely related to one of the new species from the Gulf of California, diverging from it by less than 4% on COI.