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Sigwart, Julia D., Chen, Chong, Tilic, Ekin, Vences, Miguel, Riehl, Torben (2023): Why is there no service to support taxonomy? BioEssays 2300070: 1-4, DOI: 10.1002/bies.202300070, URL: http://dx.doi.org/10.1002/bies.202300070

Figures S1-S9; Table S1

Alvinonemertes dagmarae gen. et sp. nov. urn:lsid:zoobank.org:act: 09E39C02-B087-4A95-A753-5D3C2F930632 Fig. 8E Diagnosis Alvinonemertes dagmarae gen. et sp. nov. can be attributed to the genus Alvinonemertes gen. nov. based on the strong support for a sister group relationship between the five species of this genus. Etymology For Dagmar Wenzel, lab technician at the Institute of Evolutionary Biology, University of Bonn. Acknowledging her support in the molecular lab, which included DNA extractions and PCRs for some of the specimens used in this study. Material examined Holotype COSTA RICA • spec. (ethanol); non-seep seamount Quepos Plateau Hills; 8.5323° N, 84.79072° W; depth 1410 m; 27 Oct. 2018; Charlotte Seid and Juan José Alvarado leg.; collected by HOV Alvin, Dive 4981; associated with a colony of Antipatharia Milne Edwards, 1857 (SIO-BIC Co3031); GenBank: ON186254, ON036049, ON021866, ON182034; SIO-BIC N260. Description Specimen 5 cm long and 1 mm in diameter. One pair of cephalic furrows. Head rounded, not demarcated from rest of body. Body coloration white to yellowish, translucent. Internal organs visible through body wall (Fig. 8E). Ecology This species seems to be closely associated with antipatharian corals as several specimens were collected wrapped around one colony (Fig. 8E). Remarks The new species is attributed to the genus Alvinonemertes gen. nov. based on the executed phylogenetic analyses. In the concatenated analysis, A. dagmarae gen. et sp. nov. is sister to a clade comprising the three species A. christianeae gen. et sp. nov., A. claudiae gen. et sp. nov., and A. tatjanae gen. et sp. nov. and belongs to the well supported clade representing the genus (Fig. 7).

Genus Alvinonemertes gen. nov. urn:lsid:zoobank.org:act: CFDEAFD6-7280-41BB-92E2-E6B4C66E28F1 Type species Alvinonemertes dariae gen. et sp. nov. Diagnosis Small monostiliferous hoplonemerteans less than 20 mm long, usually lacking distinct coloration. Eyes absent, one pair of cephalic furrows. Body wall consisting of outer circular and inner longitudinal muscle layers, proboscis with three muscle layers (outer circular, middle longitudinal, and inner circular). Proboscis with two accessory stylet pouches bearing two to five accessory stylets. Cerebral ganglia and lateral nerves in body wall longitudinal musculature. Lateral nerve cords with accessory nerves. Middorsal blood vessel present. Etymology Named after the HOV Alvin that was used to collect the type species and three of the other species of the here described nemerteans. Phylogenetic remarks The genus is sister to the clade comprising specimens of the monotypic genera Vieitezia and Chernyshevia gen. nov., as well as specimens of Tetrastemma vittigerum and T. elegans. The genus is nested within a clade that also includes the represented specimens of the genera Gononemertes and Galathenemertes (Fig. 7). Remarks The genus Alvinonemertes gen. nov. is erected as new genus based on its phylogenetic position as sister to the aforementioned clade comprising Chernyshevia gen. nov. and Vieitezia. Interspecific pairwise p-distances of COI vary between 10% and 14% within the genus. Species included 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.

Genus Chernyshevia gen. nov. urn:lsid:zoobank.org:act: BFBBBA9E-80F4-4F57-9A81-B85FE723A7A6 Type species Chernyshevia escarpiaphila gen. et sp. nov. Diagnosis Monostiliferan nemertean lacking eyes, with one pair of ventro-lateral cephalic furrows continuing as unforked ciliated canal; cerebral organs close in front of brain; rhynchocoel extending to posterior end of body; apical organ present; cephalic glands extending to brain; lateral nerve cords with small accessory nerves; mid-dorsal blood vessel without vascular plug; intestinal cecum with anterior diverticula; sexes separate. Etymology The genus is named after Dr Alexei Chernyshev to acknowledge his significant contributions to the study of deep-sea nemerteans. Phylogenetic remarks The genus is sister to the represented specimen of Tetrastemma elegans (Girard, 1852) (Fig. 7) that is in need of revision. This clade is sister to the monotypic genus Vieitezia Junoy, Andrade & Giribet, 2010, including specimens of the type species Vieitezia luzmurubeae Junoy, Andrade & Giribet, 2010, and specimens of Tetrastemma vittigerum (Bürger, 1904). The genus is nested within a clade that also includes the new genus Alvinonemertes gen. nov., as well as the represented specimens of the genera Gononemertes Bergendal, 1900 and Galathenemertes Chernyshev & Polyakova, 2019 (Fig. 7). Remarks The genus Chernyshevia gen. nov. is erected as new genus based on its phylogenetic position and the questionable position of different species of ‘ Tetrastemma ’ (T. elegans and T. vittigerum) that are nested within the same clade as Chernyshevia. Moreover, some morphological differences between specimens of the genera Vieitezia and Chernyshevia, such as the absence or presence of an accessory nerve, the dimension of the cephalic glands, and the presence of separate sexes, might also support the presence of a new genus. Species included Only the type species Chernyshevia escarpiaphila gen. et. sp. nov., Published as part of Sagorny, Christina, Döhren, Jörn von, Rouse, Greg W. & Tilic, Ekin, 2022, Cutting the ribbon: bathyal Nemertea from seeps along the Costa Rica margin, with descriptions of 2 new genera and 9 new species, pp. 132-174 in European Journal of Taxonomy 845 (1) on pages 147-149, DOI: 10.5852/ejt.2022.845.1959, http://zenodo.org/record/7258852, {"references":["Chernyshev A. V., Abukawa S. & Kajihara H. 2015. Sonnenemertes cantelli gen. et sp. nov. (Heteronemertea) - A new Oxypolella - like nemertean from the abyssal plain adjacent to the KurilKamchatka Trench. Deep Sea Research Part II: Topical Studies in Oceanography 111: 119 - 127. https: // doi. org / 10.1016 / j. dsr 2.2014.07.014","Sundberg P. & Gibson R. 1995. The nemerteans (Nemertea) of Rottnest Island, Western Australia. Zoologica Scripta 24: 101 - 141. https: // doi. org / 10.1111 / j. 1463 - 6409.1995. tb 00395. x","Junoy J., Andrade S. C. S. & Giribet G. 2010. Phylogenetic placement of a new hoplonemertean species commensal on ascidians. Invertebrate Systematics 24: 616 - 629. https: // doi. org / 10.1071 / IS 10036","Burger O. 1904. Nemertini. In: Das Tierreich 20. Lieferung Platyhelminthes. R. Friedlander & Sohn, Berlin.","Chernyshev A. V. & Polyakova N. E. 2019. Nemerteans from the deep-sea expedition KuramBio II with descriptions of three new hoplonemerteans from the Kuril-Kamchatka Trench. Progress in Oceanography 178: 102148. https: // doi. org / 10.1016 / j. pocean. 2019.102148"]}

Tetrastemma polyakovae sp. nov. urn:lsid:zoobank.org:act: 0A69EED8-5057-4882-A12C-AB4FC69B7B63 Fig. 8M–N Diagnosis Tetrastemma polyakovae sp. nov. can be attributed to the genus Tetrastemma based on the strong support for a sister group relationship between the three species of this genus included in the analysis. Etymology For Dr Neonila E. Polyakova, in recognition of her contributions to the study of deep-sea nemerteans. Material examined Holotype COSTA RICA • spec. (ethanol); methane seep Mound 12; 8.93030° N, 84.31260° W; depth 997 m; 24 Oct. 2018; Jorge Cortés and Oliver Ashford leg.; collected by HOV Alvin, Dive 4978; GenBank: ON186259, ON036056, ON021857, ON182051; SIO-BIC N258. Paratype COSTA RICA • 1 spec. (ethanol; entirely used up in DNA extraction; only image and DNA available); same collection data as for holotype; 8.93° N, 84.31° W; depth 996–999 m; GenBank: ON036057, ON021858, ON182050; MZUCR Nemertea Collection MZUCR-101-01 (ex SIO-BIC N 255). Description Specimens 15 mm long and 1 mm in diameter. Body rounded. Two pairs of cephalic furrows. Head not demarcated from rest of body, rounded. Body coloration pale orange to brownish. Internal organs well visible through body wall (Fig. 8M–N). Remarks The new species is attributed to the genus Tetrastemma based on the executed phylogenetic analyses. This species is sister to Tetrastemma strandae sp. nov. (Fig. 7). Intraspecific pairwise p-distances are 2%, whereas interspecific distances between T. polyakovae sp. nov. and the two newly described species vary between 7% and 8%. Distance between this species and Tetrastemma stimpsoni is 12.5%.

Suborder Eumonostilifera Chernyshev, 2003 Most of the collected nemertean specimens belong to eumonostiliferous hoplonemerteans. Nine species in three genera are here described as new to science, including two species from the northeastern Pacific outside Costa Rica. In addition, sequences were obtained for two more species that are not described here due to lacking histological material. Five Costa Rican and the two NE Pacific species can be attributed to the clade Oerstediina, whereas the remaining four species group with the Amphiporina clade (Fig. 7). The first undescribed species is represented by six small (6–8 mm long), bright orange to red specimens (SIO-BIC N259) that have one pair of dorsal, V-shaped cephalic furrows (Fig. 8I). This species is sister to two unidentified eumonostiliferans from the depths of the Vema Fracture Zone (ca 5000 m). Together with Abyssonemertes kajiharai Chernyshev & Polyakova, 2017 they form a well-supported clade (Fig. 7). Interspecific p-distances within this clade based on the COI gene vary between 11% and 14%. The second undescribed species (SIO-BIC N109) is represented by one large specimen (Fig. 8O) that shares a clade with several species of Paranemertes Coe, 1901, Tortus tokmakovae Chernyshev, 1991, and two species of Amphiporus Ehrenberg, 1831 (Fig. 7). The exact position within this clade cannot be fully resolved. Cratenemertea Chernyshev, 2003 were not represented in the samples., Published as part of Sagorny, Christina, Döhren, Jörn von, Rouse, Greg W. & Tilic, Ekin, 2022, Cutting the ribbon: bathyal Nemertea from seeps along the Costa Rica margin, with descriptions of 2 new genera and 9 new species, pp. 132-174 in European Journal of Taxonomy 845 (1) on page 147, DOI: 10.5852/ejt.2022.845.1959, http://zenodo.org/record/7258852

Alvinonemertes tatjanae gen. et sp. nov. urn:lsid:zoobank.org:act: B3C2ABC6-34E6-497C-9A66-023A5751DC78 Fig. 8H Diagnosis Alvinonemertes tatjanae gen. et sp. nov. can be attributed to the genus Alvinonemertes gen. nov. based on the strong support for a sister group relationship between the five species of this genus. Etymology For Tatjana Bartz, lab technician at the Institute of Evolutionary Biology, University of Bonn. Acknowledging her support in the electron microscopy lab over many years. Tatjana has trained the last author in specimen preparation for transmission electron microscopy, for which he will ever be grateful. Material examined Holotype USA • spec. (ethanol); Hydrate Ridge, Oregon margin; 44.670° N, 125.098° W; depth ca 618 m; 3 Aug. 2010; Victoria Orphan and José Patterson leg.; collected by HOV Alvin, Dive 4631; GenBank: ON186256, ON036047, ON021864, ON182041; SIO-BIC N119. Description Specimens 7–9 mm long and 0.7 mm in diameter. Body rounded. One pair of cephalic furrows. Head not demarcated from rest of body, rounded. Body pale red to pinkish with several red pigment spots distributed over body surface. Gonads and gut well visible through body wall (Fig. 8H). Remarks Alvinonemertes tatjanae gen. et sp. nov. is attributed to the genus Alvinonemertes gen. nov. based on the executed phylogenetic analyses. In the concatenated analysis, it is sister to the clade comprising A. christianeae gen. et sp. nov. and A. claudiae gen. et sp. nov. (Fig. 7).

Tetrastemma sundbergi sp. nov. urn:lsid:zoobank.org:act: 10E0A1CA-5CC4-40D6-879D-2861A91821C9 Figs 8J–L, 11A–G Diagnosis As for the genus (compare Sundberg & Gibson 1995). Tetrastemma sundbergi sp. nov. has a bright orange yet translucent body. The head is clearly demarcated from the rest of the body and is slenderer than the rest of the body. On dorsal surface with two red spots at lateral sides of the head. Dorsal and ventral ganglia are fused. Cerebral organ alongside brain. Etymology For Dr Per Sundberg in recognition of his contributions to nemertean taxonomy. Material examined Holotype COSTA RICA • ♀ (fixed in formaldehyde and prepared as 33 slides with transverse sections, see cybertype); methane seep Mound 12; 8.93° N, 84.31° W; depth 996–999 m; 24 Oct. 2018; Jorge Cortés and Oliver Ashford leg.; collected by HOV Alvin, Dive 4978; GenBank: ON186255, ON036054, ON021855, ON182052; SIO-BIC N256. Cybertype Images of serial sections of holotype: https://doi.org/10.5281/zenodo.5346538. Description Specimens 15 mm long and 0.7 mm in diameter. Body flattened (Fig. 8J). Two pairs of cephalic furrows. Paired anterior cephalic furrows V-shaped, dorsally pointing posteriorly (Fig. 8K). Posterior furrows U-shaped, located ventrally, pointing anteriorly (Fig. 8L). Head clearly demarcated from rest of body, not wider than trunk, tapered. Body coloration orange. Two dark brown spots on the lateral sides of the head in place of eyes. Cerebral ganglia, gut and gonads well visible through body wall (Fig. 8J). Epidermis in foregut region 30 µm thick. Body wall composed of outer circular and inner longitudinal muscle layers (Fig. 11B). Esophagus opening subterminal, ventral; stomach with lateral pouches; pylorus shorter than stomach; intestinal cecum with paired lateral, anterior pouches along brain lobes (Fig.11D); intestine with deep lateral pouches. Excretory system confined to foregut region, canals inside musculature (Fig. 11F). Precerebral septum closed. Rhynchocoel wall with two very thin muscle layers (outer circular, inner longitudinal), rhynchocoel almost extending to posterior end of body. Proboscis with outer circular, middle longitudinal, and inner circular muscle layers (Fig. 11C). Proboscis with 10 nerves (Fig. 11C); central stylet plus 2 accessory stylet pouches with 2 stylets each; stylet basis circular in cross section. Proboscis pore subterminal, ventral (Fig. 11A). Nervous system with thin outer neurilemma only, without neurochord cells; dorsal and ventral ganglia fused (Fig. 11B); broad ventral commissure, narrow dorsal commissure. Precerebral nerves in two groups with 3–4 nerves each. Lateral nerve cords without accessory nerve (Fig. 11F–G). Cerebral ganglia and anterior part of lateral nerve cords internal to longitudinal muscle layer (Fig. 11B, F); posteriorly, lateral nerve cords within body wall musculature (Fig. 11G). Eyes absent. Cerebral organs less than half the size of brain lobes, alongside brain. Paired cerebral canal simple, unforked, opens ventro-laterally into cephalic furrows (Fig. 11B). Apical organ present, unpaired; cephalic gland extending to brain, scattered between muscle fibres in anterior part of head, forming distinct lobules further back (Fig. 11A–B). Blood system consisting of cephalic loop, mid dorsal vessel with vascular plug (Fig. 11C–D). Ovaries lying above each other, alternating with intestinal diverticula (Fig. 11D–E). Remarks Tetrastemma sundbergi sp. nov. is attributed to the genus Tetrastemma based on the executed phylogenetic analyses. Furthermore, this assignment is supported by morphological characteristics such as the presence of a vascular plug, small cerebral organs, and the amount of muscle layers. Tetrastemma sundbergi is sister to a clade formed by the two other newly described species of Tetrastemma. These three species are sister to three yet undescribed specimens from the Kuril Islands. Together, this clade is sister to the two former species of Quasitetrastemma Chernyshev, 2004, Tetrastemma stimpsoni Chernyshev, 1992 and Tetrastemma nigrifrons (Coe, 1904). This clade is firmly nested within the genus Tetrastemma (Fig. 7). The three species differ morphologically from the two closely related, former species of Quasitetrastemma by the absence of lateral accessory nerves.

Order Polystilifera Brinkmann, 1917 One polystiliferan nemertean was collected at 950 m depth from non-seep seamount habitat at Cocos Canyon (SIO-BIC N263). The specimen is 65 mm long and dorso-ventrally flattened. The body is translucent and coloration is pale pinkish (Fig. 3D–E). This reptant hoplonemertean is sister to another undescribed Reptantia Brinkmann, 1917 from the Kuril Islands (500 m depth). Together with three further unidentified hadal reptant hoplonemerteans, this clade is sister to Pelagica Brinkmann, 1917 (Fig. 6). Again, we choose not to name this species as a thorough taxonomic revision of Reptantia is warranted. The histological data set is published herein: https://doi.org/10.5281/zenodo.6375286., Published as part of Sagorny, Christina, Döhren, Jörn von, Rouse, Greg W. & Tilic, Ekin, 2022, Cutting the ribbon: bathyal Nemertea from seeps along the Costa Rica margin, with descriptions of 2 new genera and 9 new species, pp. 132-174 in European Journal of Taxonomy 845 (1) on page 147, DOI: 10.5852/ejt.2022.845.1959, http://zenodo.org/record/7258852

Alvinonemertes claudiae gen. et sp. nov. urn:lsid:zoobank.org:act: 1BA9AE85-AB72-4736-9132-79796011C259 Figs 8G, 10H–N Diagnosis Alvinonemertes claudiae gen. et sp. nov. can be attributed to the genus Alvinonemertes gen. nov. based on molecular data. It differs from all other species in the genus by its very translucent body that is pale yellowish. It can be differentiated from A. dariae gen. et sp. nov. by the characteristics given in the diagnosis of A. dariae. Etymology For Claudia Müller, lab technician at the Institute of Evolutionary Biology, University of Bonn. Acknowledging her support in the immunohistology lab over many years and also in recognition of her devotion to the care of our live annelid and nemertean worm cultures. Material examined Holotype NORTHEASTERN PACIFIC OCEAN • ♂ (fixed in formaldehyde and prepared as 15 slides with transverse sections, see cybertype); hydrothermal vents at South Cleft, Juan de Fuca Ridge; 44.659° N, 130.364° W; depth ca 2250 m; 31 Jul. 2016; Greg Rouse leg.; collected by ROV Doc Ricketts, Dive 875; SIO-BIC N283 (ex SIO-BIC N231). Paratypes NORTHEASTERN PACIFIC OCEAN • 1 spec. (fixed in formaldehyde); same collection data as for holotype; SIO-BIC N284 (ex SIO-BIC N231) • 3 specs (ethanol); same collection data as for holotype; GenBank: ON036050, ON021868; SIO-BIC N231. Cybertype Images of serial sections of holotype: https://doi.org/10.5281/zenodo.5346520. Description Specimens 6 mm long and 0.7 mm in diameter. Body cylindrical. One pair of cephalic furrows, forming the shape of an anteriorly open V. Head not demarcated from rest of body, rounded. Body translucent. Internal organs, such as gut and gonads, well visible through body wall (Fig. 8G). Epidermis in foregut region 10 µm thick. Body wall composed of two muscle layers (outer circular, inner longitudinal). Esophagus opening subterminal, ventral; stomach without pouches; pylorus longer than stomach; intestinal cecum with ventral unpaired anterior pouch under stomach and one pair of lateral pouches (Fig. 10K); intestine with lateral diverticula. Precerebral septum closed. Rhynchocoel wall with very thin outer circular and inner longitudinal muscle layers, rhynchocoel almost extending to posterior end of body. Proboscis with outer circular, middle longitudinal, and inner circular muscle layers. Proboscis with 10 proboscis nerves; central stylet and two accessory stylet pouches present, four to five accessory stylets per pouch (Fig. 10M–N). Stylet basis circular in cross section. Proboscis pore subterminal, ventral (Fig. 10H). Nervous system with thin outer neurilemma, without neurochord cells (Fig. 10J); dorsal commissure short, ventral commissure broad. Lateral nerve cords without accessory nerve (Fig. 10K). Cerebral ganglia and lateral nerves in longitudinal muscle layer (Fig. 10J–K). Eyes absent. Cerebral organs less than half the size of brain lobes, close in front of brain. Paired cerebral canal simple, unforked, opens ventro-laterally into cephalic furrows (Fig. 10I). Apical organ present, unpaired; cephalic gland extending to brain (Fig. 10H, J). Circulatory system consisting of cephalic loop, mid-dorsal vessel not forming vascular plug ((Fig. 10L). Testes sac like, alternating with intestinal diverticula, situated ventrally. Ecology Associated with hydrothermal vents, alongside other vent fauna such as the annelids Branchinotogluma tunnicliffeae (Pettibone, 1988) (e.g., SIO-BIC A7716), Paralvinella sulfincola Desbruyères & Laubier, 1993 (e.g., SIO-BIC A7724) and Ridgeia piscesae Jones, 1985 (e.g., SIO-BIC A7719). Remarks The new species is attributed to the genus Alvinonemertes gen. nov. based on the executed phylogenetic analyses. In the concatenated analysis, A. claudiae gen. et sp. nov. is sister to A. christianeae gen. et sp. nov. (Fig. 7).

Order Heteronemertea Bürger, 1892 One single heteronemertean specimen (SIO-BIC N254), representing a member of Lineidae McIntosh, 1873, was collected in associated with experimentally deployed wood at 1887 m depth at the Jaco Scar methane seep. This specimen is 45 mm long and has a diameter of 5 mm. The body is translucent and of pale whitish coloration. It possesses a long caudal cirrus (Fig. 3C). It forms a clade with three undescribed lineids collected in the abyssal vicinity of the Kuril-Kamchatka Trench (Fig. 5). Based on the concatenated analysis, this clade cannot be attributed to any of the known heteronemertean genera. Pairwise distances of the COI gene between Lineidae sp. SIO-BIC N254 and those three heteronemerteans are around 14%. Since no material for histological sectioning is left, we do not describe this species herein, also due to the convoluted taxonomy of Lineidae, that needs extensive revision and goes beyond the scope of our study. However, the sequence data is published in order to facilitate future studies on deep-sea Lineidae., Published as part of Sagorny, Christina, Döhren, Jörn von, Rouse, Greg W. & Tilic, Ekin, 2022, Cutting the ribbon: bathyal Nemertea from seeps along the Costa Rica margin, with descriptions of 2 new genera and 9 new species, pp. 132-174 in European Journal of Taxonomy 845 (1) on page 146, DOI: 10.5852/ejt.2022.845.1959, http://zenodo.org/record/7258852

Chernyshevia escarpiaphila gen. et sp. nov. urn:lsid:zoobank.org:act: 11DFF601-BBBA-409F-B072-5A93BA8C349F Figs 1B–C, 8A–B, 9 Diagnosis As for the genus; body pale white to pinkish, translucent; up to 10 mm in length. Etymology Named after vestimentiferan Escarpia spicata Jones, 1985, on which this species occurs with high abundance. Material examined Holotype COSTA RICA • ♂ (fixed in formaldehyde and prepared as 12 slides with transverse sections, see cybertype); methane seep Mound Jaguar; 9.65556° N, 85.88046° W; depth 1909 m; 25 Jan. 2019; Greg Rouse and Avery Hiley leg.; collected by ROV SuBastian, Dive S 0230 S2; found on Escarpia spicata; SIO-BIC N279 (ex SIO-BIC N264). Paratypes COSTA RICA • 1 spec. (fixed in formaldehyde and prepared as 7 slides with transverse sections, see cybertype); same collection data as for holotype; MZUCR Nemertea Collection MZUCR-104-01 (ex SIO-BIC N264) • 13 specs (8 fixed in formaldehyde, 5 fixed in ethanol); same collection data as for holotype; GenBank: ON036044, ON021861, ON182039; SIO-BIC N264 • 3 specs (ethanol); methane seep Jaco Scar; 9.119° N, 84.843° W; depth 1604–1854 m; 31 May 2017; Erik Cordes and April Stabbins leg.; collected by HOV Alvin, Dive 4916; GenBank: ON021862, ON182038; SIO-BIC N237 • 2 specs (ethanol); same collection data as for preceding; GenBank: ON036045, ON182037; SIO-BIC N236 • 6 specs (ethanol); same collection data as for preceding; GenBank; ON186253, ON036046, ON021863, ON182036; SIO-BIC N235 • 6 specs (ethanol); methane seep Jaco Scar; 9.118° N, 84.839° W; depth 1752–1802 m; 12 Jan. 2010; Elena Perez and Geoff Cook leg.; collected by HOV Alvin, Dive 4591; SIOBIC N266 • 2 specs (ethanol); methane seep Jaco Scar; 9.117° N, 84.843° W; depth 974–1866 m; 3 Mar. 2009; Elena Perez and Jake Bailey leg.; collected by HOV Alvin, Dive 4509; GenBank: ON186250, ON021859, ON182035; SIO-BIC N112. Cybertypes Images of serial sections of holotype SIO-BIC N279 uploaded as N264a: https://doi.org/10.5281/zenodo.5346245 Images of serial sections of paratype MZUCR Nemertea Collection MZUCR-104-01 uploaded as N264b: https://doi.org/10.5281/zenodo.5346245 Description Specimens 6–10 mm long and 0.5 mm in diameter (Fig. 8A–B). Body cylindrical. One pair of ventro-lateral cephalic furrows. Head rounded, not demarcated from rest of the body. Body coloration pale whitish to pinkish, body translucent (Fig. 8A). Cerebral ganglia and internal organs visible through body wall (Fig. 8B). Epidermis in foregut region 50 µm thick. Body wall composed of two muscle layers (outer circular, inner longitudinal; Fig. 9C). Combined proboscis and esophagus opening subterminal, ventral (Fig. 9B, D); stomach with pouches, surrounded by thin layer of longitudinal musculature; stomach (Fig. 9D) longer than pylorus; intestinal cecum with unpaired anterior ventral and paired anterior lateral pouches located alongside stomach; intestine with lateral pouches. Precerebral septum closed. Rhynchocoel wall with two very thin muscle layers (outer circular, inner longitudinal), rhynchocoel (Fig. 9G) almost extending to posterior end of body. Proboscis with outer circular, middle longitudinal, and inner circular muscle layers. Number of proboscis nerves indiscernible and proboscis armature not visible. Proboscis pore subterminal, ventral (Fig. 9A–B). Nervous system with outer neurilemma only, without neurochord cells; short dorsal commissure, broad ventral commissure (Fig. 9C). Precerebral nerves forming two dorso-lateral groups. Lateral nerve cords with small accessory nerve, no myofibrillae visible (Fig. 9E). Cerebral ganglia and lateral nerve cords located in longitudinal muscle layer (Fig. 9C–D). Eyes absent. Cerebral organs half the size of brain lobes, close in front of brain, surrounded by cephalic glands (Fig. 9C). Paired cerebral canal simple, unforked, opens ventro-laterally into cephalic furrows (Fig. 9D). Apical organ as depression at anterior tip of head, unpaired, cephalic gland extending to brain, distributed between muscle fibres of head (Fig. 9B, D). Circulatory system consisting of cephalic loop and three postcerebral vessels, mid-dorsal vessel not forming vascular plug (Fig. 9F). Testes sac like, located ventrally, close to lateral nerve cord (Fig. 9G). Ecology This species is the most abundant nemertean species collected along the Costa Rica margin. It occurs in close connection to Escarpia spicata with numerous specimens present on the tubes of this vestimentiferan (Fig. 1B–C). The whole epifauna found on the tubes of Escarpia spicata was extracted with a suction sampler. Remarks Chernyshevia escarpiaphila sp. nov. is attributed to the new genus Chernyshevia gen. nov. based on the executed phylogenetic analysis. In the phylogenetic analysis, it is sister to Tetrastemma elegans. Both species belong to a well-supported clade containing Vieitezia luzmurubeae, the type species of the genus, and Tetrastemma vittigerum (Fig. 7). A clade containing the five newly described species of the genus Alvinonemertes gen. nov. is sister to this clade. Intraspecific p-distances of the COI gene fragment vary between 2% and 4%., Published as part of Sagorny, Christina, Döhren, Jörn von, Rouse, Greg W. & Tilic, Ekin, 2022, Cutting the ribbon: bathyal Nemertea from seeps along the Costa Rica margin, with descriptions of 2 new genera and 9 new species, pp. 132-174 in European Journal of Taxonomy 845 (1) on pages 149-152, DOI: 10.5852/ejt.2022.845.1959, http://zenodo.org/record/7258852

Family Tubulanidae Bürger, 1904 Tubulanidae is the only palaeonemertean family that was represented in the Costa Rican samples. In total, six tubulanid specimens were collected at depths around 1000 m from two nearby localities (Mound 11 & Mound 12). A DNA analysis of four specimens collected over different years showed that all specimens belong to the same species that is firmly nested within Tubulanidae (Fig. 2)., Published as part of Sagorny, Christina, Döhren, Jörn von, Rouse, Greg W. & Tilic, Ekin, 2022, Cutting the ribbon: bathyal Nemertea from seeps along the Costa Rica margin, with descriptions of 2 new genera and 9 new species, pp. 132-174 in European Journal of Taxonomy 845 (1) on page 142, DOI: 10.5852/ejt.2022.845.1959, http://zenodo.org/record/7258852, {"references":["Burger O. 1904. Nemertini. In: Das Tierreich 20. Lieferung Platyhelminthes. R. Friedlander & Sohn, Berlin."]}

Tubulanus cf. lutescens Cantell, 2001 Figs 3A–B, 4 Diagnosis Tubulanus cf. lutescens can be clearly identified as a member of the genus Tubulanus based on the amount of body wall, proboscis, and rhynchocoel muscle layers, the position of the nervous system, the composition of the cerebral organs, and several other internal characteristics (Gibson 1982; Sundberg & Hylbom 1994; Gibson & Sundberg 1999). As in other members of the genus, the body wall is composed of three muscle layers (outer circular, median longitudinal, and inner circular musculature), whereas the proboscis is composed of two layers (outer longitudinal, inner circular) and the rhynchocoel wall of only one circular muscle layer. The nervous system is located between the epidermal basement membrane and the outer circular body wall musculature and the cerebral organs consist of ciliated canals in the epidermis. Moreover, a mid-dorsal blood vessel and eyes are absent. The collected specimens are of bright red coloration and lacks a conspicuous colour pattern. A lower dorsal nerve is absent. Material examined COSTA RICA • 1 spec. (fixed in paraformaldehyde and prepared as 67 slides with transverse sections); methane seep Mound 12; 8.930° N, 84.313° W; depth 990–999 m; 22 May 2017; Lisa Levin and Charlotte Seid leg.; collected by HOV Alvin, Dive 4907; SIO-BIC N277 (ex SIO-BIC N233) (image series: https://doi.org/10.5281/zenodo.6368041) • 1 spec. (anterior fixed in paraformaldehyde, posterior fixed in ethanol); same collection data as for preceding; GenBank: ON186263, ON036061, ON021853, ON182046; SIO-BIC N233 • 1 spec. (fixed in paraformaldehyde); same collection data as for preceding; MZUCR Nemertea Collection MZUCR-103-01 (ex SIO-BIC N233) • 1 spec. (piece in ethanol); methane seep Mound 11; 8.920° N, 84.306° W; depth 1019–1045 m; 26 Feb. 2009; Greg Rouse and Mike Skowronski leg.; collected by HOV Alvin, Dive 4505; GenBank: ON186261, ON036062, ON021852, ON182043; SIO-BIC N107 • 1 spec. (piece in ethanol); methane seep Mound 12; 8.931° N, 84.313° W; depth 982–1000 m; 7 Jan. 2010; Lisa Levin and Graham Nash leg.; collected by HOV Alvin, Dive 4586; GenBank: ON186262, ON036063, ON021854, ON182044; SIO-BIC N120 • 1 spec. (ethanol); methane seep Mound 12; 8.93037° N, 84.31319° W; depth 996 m; 20 Oct. 2018; Lisa Levin and Kyle Metcalfe leg.; collected by HOV Alvin, Dive 4974; GenBank: ON186264, ON036060, ON021851, ON182045; SIO-BIC N257. Description Specimens up to 20 cm in length, up to 4 mm in diameter. Body more or less cylindrical. Tapered head slightly wider than rest of body (Fig. 3A). One pair of dorsal, V-shaped cephalic furrows in front of brain lobes (Fig. 3B). Body bright red, trunk slightly translucent. Anterior tip brighter than rest of head (Fig. 3A–B). Epidermal constrictions along whole body length. Gut and gonads visible through body wall (Fig 3A). Epidermis in foregut region 150–200 µm thick. Body wall composed of outer circular, middle longitudinal and inner circular musculature (Fig. 4E). Rhynchocoel wall only with circular muscle layer (Fig. 4E). Proboscis with two layers of musculature (outer longitudinal, inner circular), with two nerves, no proboscis armature (Fig. 4C). Proboscis pore subterminal, ventral (Fig. 4A); mouth opening separate, behind cerebral ganglia (Fig. 4B). Cerebral ganglia with only outer neurilemma, neurochord cells absent. Dorsal and ventral ganglia fused, located in ventral part of head (Fig. 4D). Lateral nerve cords without accessory nerves, myofibrillae absent (Fig. 4F). Precerebral nerves numerous, not grouped (Fig. 4A); buccal nerves paired. Upper dorsal nerve present (Fig. 4E). Nervous system between epidermal basement membrane and outer circular body wall musculature (Fig. 4D, F). Eyes lacking. Cerebral organs as simple ciliated canals in epidermis, posterior to ventral ganglia (Fig. 4D). Apical organ as depression frontal of rhynchopore, cephalic glands in anterior half of head, scattered between muscle fibres of head. Blood vascular system consisting of cephalic loop giving rise to two paired postcerebral, lateral vessels (Fig. 4A–B). Mid-dorsal blood vessel absent, smaller vessels splitting from lateral blood vessels in foregut region. Remarks The Costa Rican specimens are attributed to the genus Tubulanus, based on the phylogenetic analyses and the similarity of external and internal characteristics. In the phylogenetic analysis, this species belongs to a highly supported clade containing Tubulanus eozensis Yamaoka, 1940, Tubulanus polymorphus, and an undescribed tubulanid from the Sea of Okhotsk (Fig. 3). A clade of undescribed abyssal and hadal tubulanids is sister to that clade. The pairwise distances of the COI gene between the four deepsea specimens are below 1%. Interestingly, pairwise distances between Tubulanus cf. lutescens and two sequences of Tubulanus lutescens, a shallow water species collected in Sweden, are only 1–1.3%. In a TCS haplotype network analysis of the mitochondrial COI gene Tubulanus lutescens is only separated from our specimens by six nucleotide substitutions (Fig. 3). However, the two species differ by body coloration as Tubulanus cf. lutescens is bright red, whereas Tubulanus lutescens is yellow. Moreover, Tubulanus cf. lutescens lacks a lower dorsal nerve which is present in Tubulanus lutescens. The markedly dissimilar habitats of both species (T. lutescens intertidal from Northern Europe vs T. cf. lutescens from ca 1000 m depth in Eastern Pacific) might indicate that they represent different species. Future analyses of nuclear sequences of T. lutescens are warranted to determine whether Tubulanus cf. lutescens and T. lutescens are indeed two different species., Published as part of Sagorny, Christina, Döhren, Jörn von, Rouse, Greg W. & Tilic, Ekin, 2022, Cutting the ribbon: bathyal Nemertea from seeps along the Costa Rica margin, with descriptions of 2 new genera and 9 new species, pp. 132-174 in European Journal of Taxonomy 845 (1) on pages 142-144, DOI: 10.5852/ejt.2022.845.1959, http://zenodo.org/record/7258852, {"references":["Cantell C. - E. 2001. On the anatomy and taxonomy of Tubulanus lutescens n. sp. (Nemertini) from the West Coast of Sweden. Ophelia 54: 213 - 221. https: // doi. org / 10.1080 / 00785236.2001.10409467","Gibson R. 1982. British Nemerteans. Cambridge University Press, Cambridge.","Sundberg P. & Hylbom R. 1994. Phylogeny of the nemertean Subclass Palaeonemertea (Anopla, Nemertea). Cladistics 10: 347 - 402. https: // doi. org / 10.1006 / clad. 1994.1025","Gibson R. & Sundberg P. 1999. Six new species of palaeonemerteans (Nemertea) from Hong Kong. Zoological Journal of the Linnean Society 125: 151 - 196. https: // doi. org / 10.1111 / j. 1096 - 3642.1999. tb 00590. x"]}

Dorvilleidae is a morphologically heterogeneous group, including some of the smallest described annelids with adult length of only a few hundred µm and only a few segments (Neotenotrocha). Others may attain a size up to 10 cm and have many segments (e.g. Dorvillea). The colour of live animals is variable, transparent to whitish being common (Pl. 7b–d; Fig. 31.2a), but sometimes with bright red or other pigmentation (Pl. 7a). Within Dorvilleidae, Ophryotrocha is well known through a series of studies (Sella and Ramella, 1999 and references within) for an impressive variation in mating systems. Interestingly, taxa showing no apparent morphological differentiation are separated by their differing reproductive habits. Some Dorvilleidae (e.g. Ophryotrocha) are also easily kept in culture and so provide excellent subjects for experimental studies.

Amphinomida includes two major groups: Amphinomidae and Euphrosinidae. Amphinomidae occur mainly in littoral warm waters. Some are called fireworms and are known for their brittle chaetae that easily break when touched and produce a burning sensation.

Siboglinidae is among the most famous and well-studied clades of Annelida, though until recently they were treated as one or two phyla, Pogonophora and Vestimentifera, separated from Annelida.

Magelona (‘shovelhead worms’), contains over 70 described nominal species that are relatively uniform in appearance. They have a somewhat unusual morphology and have historically been difficult to relate with other annelids. They are now regarded as sister group to Oweniidae, and as Oweniida, are the sister group to all other living Annelida (see Chapter 1 regarding the inappropriateness of the unfortunate name Paleoannelida that has been proposed for this group).

Members of Sabellidae (feather-duster worms) are among the most easily recognizable of annelid groups due to their possession of an often spectacularly colourful radiolar crown and by the mucus/ parchment/ sediment tubes that they generally inhabit (Pl. 8a–d).

Lopadorrhynchidae is a small group of holopelagic annelids. A common misspelling of the name is Lopadorhynchidae with a single ‘r’ (Read and Fauchald, 2021).

Cossura live in some shallow marine sediments but are more common in mixed sand and mud sediments in deeper seas. Around 30 accepted species have been described to date. They are recognizable by the thin mid-dorsal branchia that can be nearly as long as the body originating from an anterior segment.