Ophryotrocha (Dorvilleidae, Polychaeta, Annelida) from deep-sea hydrothermal vents, with the description of five new species Author Zhang, Dongsheng 43C40412-F966-4F97-860F-0D27D3AA214C Key Laboratory of Marine Ecosystem Dynamics, Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou, 310012, China. dszhang@sio.org.cn Author Zhou, Yadong E0F2089D-29B9-48A6-9761-73AB8D09D2A8 Key Laboratory of Marine Ecosystem Dynamics, Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou, 310012, China. yadong_zhou@sio.org.cn Author Yen, Nicole 36958F99-FAE8-4FC8-A849-C011D0B4D26D Scripps Oceanography, University of California San Diego, La Jolla, CA 92093 - 0202, USA. nyen@ucsd.edu Author Hiley, Avery S. B39BA63A-DA66-4512-88E9-4A564D1BEB80 Scripps Oceanography, University of California San Diego, La Jolla, CA 92093 - 0202, USA. ahiley@ucsd.edu Author Rouse, Greg W. F4AAFAE4-85D9-44CA-8290-E0FC614E1983 Scripps Oceanography, University of California San Diego, La Jolla, CA 92093 - 0202, USA. grouse@ucsd.edu text European Journal of Taxonomy 2023 2023-04-24 864 167 194 http://dx.doi.org/10.5852/ejt.2023.864.2101 journal article 257216 10.5852/ejt.2023.864.2101 626b2920-1b64-469e-b3c9-73ff3612788c 2118-9773 7867628 326759FD-35B4-44C5-B3EF-9E89B6B91106 Ophryotrocha charlottae sp. nov. urn:lsid:zoobank.org:act: 2AC55385-EA0C-41E5-8EAF-4D6F32818D94 Fig. 4 Etymology Named in honor of Charlotte Seid, collection manager of the Benthic Invertebrate Collection at Scripps Oceanography, for her dedication to facilitating biodiversity research. Material examined Holotype EAST PACIFIC OCEAN • 1 spec. (fixed in ethanol and the posterior end used for DNA extraction); Southern East Pacific Rise , northwest of Easter Island , active hydrothermal vents; 23.823° S , 115.456° W ; depth 2649 m ; 2 Apr. 2005 ; Greg Rouse , Nerida Wilson and Robert Vrijenhoek leg.; collecting event: HOV Alvin dive 4097 ; GenBank: OP311739 (COI), OP304893 (16S), OP311648 (H3); SIO-BIC A14096 . Paratypes EAST PACIFIC OCEAN • 1 spec. (fixed in ethanol and midsection tissue used for DNA extraction); same collection data as for holotype; GenBank: OP311741 (COI); SIO-BIC A14163 • 1 spec. (fixed in ethanol and midsection tissue used for DNA extraction); same collection data as for holotype; GenBank: OP311740 (COI); SIO-BIC A14164 . Other material EAST PACIFIC OCEAN • 1 spec. (fixed in ethanol and entirely used for DNA extraction); same collection data as for holotype; GenBank: OP311738 (COI); SIO-BIC A14097 • 7 or more specs (7 fixed in glutaraldehyde, additional material fixed in formalin and entirely used for slides of parapodia, additional tissue fixed in ethanol); same collection data as for holotype; SIO-BIC A14098 • 1 spec. (fixed in ethanol and midsection tissue used for DNA extraction); same collection data as for holotype; SIO-BIC A14187 • 1 spec. (fixed in ethanol); same collection data as for holotype; SIO-BIC A14188 . Fig. 4. Ophryotrocha charlottae sp. nov. A . Whole body of living holotype (SIO-BIC A14096). B . Maxillae of holotype (SIO-BIC A14096). C . Mandibles from holotype (SIO-BIC A14096). D . Parapodium of paratype (SIO-BIC A14098). E . Simple supra-acicular chaetae of paratype (SIO-BIC A14098). F . Compound sub-acicular chaetae of paratype (SIO-BIC A14098). G . Simple sub-acicular chaeta of paratype (SIO-BIC A14098). Description In life light brown ( Fig. 4A ), opaque white after preservation. Body ~ 3 mm long, with more than 35 segments of similar width, slightly tapering posteriorly ( Fig. 4A ). Prostomium rounded, wider than long, with paired digitiform antennae inserted dorsally, paired digitiform palps inserted ventral-laterally, similar in length with antennae. Peristomium two equal rings, each similar in size to the following segments ( Fig. 4A ). Eyes not visible. Maxillae P-type, forceps comb-like, with large main fang, fused together basally. Four rows of seven free denticles, the posterior-most free denticles (D1) comb-like, like the forceps, other free denticles (D2–D7) shovel-shaped with fine teeth ( Fig. 4B ). Mandibles heavily sclerotized, shafts rod-like, cutting plates sub-triangular, lateral wings weakly sclerotized ( Fig. 4C ). Parapodia uniramous, acicular lobe with rounded distal margin, dorsal cirri enlarged fusiform, similar in size with acicular lobe, reaching distal margin of acicular lobe, ventral cirri short and stubby ( Fig. 4D ). Supra-acicular chaetae simple, distally serrated, tapering into a main fang ( Fig. 4D–E ). Sub-acicular chaetae compound, hooked with serrated blades ( Fig. 4D, F ). Sub-acicular chaetal lobe also with one or two simple chaetae ( Fig. 4D, G ). Pygidium with two digitiform cirri inserted laterally, a small median papilla posteriorly placed ( Fig. 4A ). Distribution Known only from vents at 2649 m depth near Easter Island (Rapa Nui) at the southern end of the East Pacific Rise (Pacific Antarctic Ridge). Remarks Ophryotrocha charlottae sp. nov. resembles O . cf. akessoni , which also occurs on the Southeast Pacific Ridge. They are similar in the shape of the prostomium, peristomium, antennae, palps, jaws, and chaetae. Ophryotrocha charlottae has distinctive parapodia with enlarged fusiform dorsal cirri, which easily distinguishes it from O. akessoni / O . cf. akessoni , O. jiaolongi and O. marinae sp. nov. Also, O . charlottae has two long digitiform anal cirri and a media papilla while O . cf. akessoni only has two short nub-like anal cirri ( Fig. 3A ). Ophryotrocha kailae sp. nov. is another species from southern end of the East Pacific Rise (Pacific Antarctic Ridge). It differs from O . charlottae in the form of antennae, palps, mandibles, dorsal cirri and pygidium ( Fig. 5 ). Ophryotrocha charlottae can also be easily distinguished from other species of the “ akessoni ” clade, based on mandibles and parapodia ( Table 3 ). The four rows of maxillae found in O. charlottae differ from that in close relatives such as O. akessoni , O . cf. akessoni ( Fig. 3C ) and O. jiaolongi that show only two rows ( Blake 1985 ; Zhang et al. 2017 ), but four rows were also observed in O. marinae and O. pruittae sp. nov. (see below). It is possible that the outermost pair of rows represent molted jaws as has been observed in other Ophryotrocha by Paxton (2004) , so this should not be interpreted as diagnostic without further study.