taxonID	type	description	language	source
1A5B87F5FF80BF34FC18F9C1FAD96BE6.taxon	discussion	Remarks. The three species names “ Ommatoplea taeniata ”, “ Polystemma adriaticus ”, and “ Polystemma albicans ”, Tetranemertes ocelata MT 581159 MT 581200 MT 581186 MT 578863 — Cherneva et al. (2023) Tetranemertes pastafariensis isolate CB 055 18 — MT 581210 MT 581196 MT 578892 — Cherneva et al. (2023)	en	Abato, Jamael C., Hookabe, Natsumi, Kajihara, Hiroshi (2025): Species Diversity of Tetranemertes (Nemertea: Monostilifera) in Japan. Species Diversity 30 (1): 71-83, DOI: 10.12782/specdiv.30.71, URL: https://doi.org/10.12782/specdiv.30.71
1A5B87F5FF80BF34FC18F9C1FAD96BE6.taxon	description	Tetranemertes pastafariensis isolate SMCP 0019 MT 581182 — — MT 578896 — Cherneva et al. (2023) Tetranemertes paulayi BOMAN 08291 — OQ 322646 OQ 322592 — — Cherneva et al. (2023) Tetranemertes paulayi BOMAN 07013 — OQ 322649 — OQ 321715 — Cherneva et al. (2023) Tetranemertes rubrolineata BOMAN 08038 — OQ 322650 OQ 322595 OQ 321718 — Cherneva et al. (2023) Tetranemertes sp. ETP 001 MT 581183 MT 581211 MT 581197 MT 578897 — Cherneva et al. (2023) Tetranemertes sp. AHK- 2024 - 1 — — — PQ 564663 — Present study Tetranemertes sp. AHK- 2024 - 2 — — — PQ 564664 — Present study Tetranemertes unistriata 4900709991 (Japan) MT 581158 MT 581198 MT 581184 MT 578861 — Cherneva et al. (2023)	en	Abato, Jamael C., Hookabe, Natsumi, Kajihara, Hiroshi (2025): Species Diversity of Tetranemertes (Nemertea: Monostilifera) in Japan. Species Diversity 30 (1): 71-83, DOI: 10.12782/specdiv.30.71, URL: https://doi.org/10.12782/specdiv.30.71
1A5B87F5FF80BF34FC18F9C1FAD96BE6.taxon	description	Tetrastemma vittigerum 132742 KF 935491 KF 935323 KF 935379 KF 935539 KF 935435 Kvist et al. (2014) Tetrastemma vittigerum 25171 — KF 935324 KF 935380 KF 935540 KF 935436 Kvist et al. (2014) Tetrastemma vittigerum H 3 MZ 231192 MZ 231272 MZ 231362 MZ 216585 MZ 216663 Chernyshev et al. (2021) Tetrastemma wilsoni AJ 436811 — AJ 436866 AJ 436921 AJ 436969 Thollesson and Norenburg (2003) Vieitezia luzmurubeae 104801 JF 277607 HQ 443428 — HQ 443426 JF 277746 Andrade et al. (2012) Vieitezia luzmurubeae 133470 KF 935495 KF 935328 KF 935384 KF 935544 KF 935440 Kvist et al. (2014) * Our phylogenetic analysis used one of the correctly identified or correctly labeled P. nelsoni sequences. The COI sequence with GenBank accession number HQ 848606 labelled as P. nelsoni bio-material DNA 105586 is an incorrectly identified or mislabeled sequence. This sequence is not from a true P. nelsoni as it is nested within Oerstediina whereas a true P. nelsoni should be in Amphiporina. Similarly, COI sequences with accession numbers MK 047678 (P. nelsoni isolate PROne nz 13.) and MZ 558353 (Prosorhochmus sp. MNJ- 2021) are not true congeners being nested outside the Prosorhochmus clade. This claim can be checked by constructing a COI neighbor joining tree. as well as the two genus names “ Ommatoplea ” and “ Polystemma ”, appeared for the first time in the caption of plate IV (published in 1828) of Ehrenberg (1828 – 1831); these names were made available in 1828 under Article 12.2.7 of the International Code of Zoological Nomenclature (hereafter the Code) (International Commission on Zoological Nomenclature 1999) (hereinafter, ICZN refers to the Commission). In the text (published in 1831), P. albicans was transferred to the newly established genus Amphiporus Ehrenberg, 1831. Interpreting the date of publication of Ommatoplea Ehrenberg, 1828 and Polystemma Ehrenberg, 1828 erroneously as 1831, Verrill (1892: 387) included these two names in the synonymy of Amphiporus, and, at the same time, recognized the two taxa as subgenera under Amphiporus (Verrill 1892: 388). Bürger (1904: 77) regarded Ommatoplea and O. taeniata as nomina dubia; Gibson (1995: 449, 451) followed this. On the other hand, Polystemma adriaticum and Polystemma albicans were considered invalid and listed — as valid names — as Amphiporus adriaticus and Amphiporus albicans (Bürger 1904: 49; Gibson 1995: 486); however, when the priorities of Polystemma Ehrenberg, 1828 and Amphiporus Ehrenberg, 1831 are considered, these name usages are incorrect. As Ommatoplea and Polystemma have unlikely been used as valid after 1898, while Amphiporus has been in prevailing usage, the precedence would be reversed under Article 23.9 of the Code (which is beyond the scope of this study, though). On the other hand, Ommatoplea may actually be a senior synonym of Tetranemertes, as some of the characteristics in O. taeniata — such as the ocelli arranged in four rows and the short rhynchocoel (Fig. 1 A – D) — suggest. If this is the case, the precedence would not likely be reversed, because the usage of Tetranemertes would not satisfy the conditions stipulated in Article 23.9.1.2 of the Code. Despite external morphological resemblance with Tetranemertes, our observation and opinion on Ommatoplea as a senior synonym of the former can be claimed with certainty only when fresh O. taeniata from the type locality is thoroughly examined, especially its stylet basis morphology and cephalic furrows, and subjected to a phylogenetic study.	en	Abato, Jamael C., Hookabe, Natsumi, Kajihara, Hiroshi (2025): Species Diversity of Tetranemertes (Nemertea: Monostilifera) in Japan. Species Diversity 30 (1): 71-83, DOI: 10.12782/specdiv.30.71, URL: https://doi.org/10.12782/specdiv.30.71
1A5B87F5FF82BF33FCF8FAA7FAE569BE.taxon	materials_examined	Material examined. Holotype, ICHUM 8719, extracted genomic DNA, anterior half preserved in Bouin’s fluid, then in 70 % ethanol, unsectioned, posterior half in 99 % ethanol; collected by Natsumi Hookabe on 30 June 2022, from a bycaught sample of a fishery gill net deployed around 10 m depth, off Sugashima island, Mie, Japan.	en	Abato, Jamael C., Hookabe, Natsumi, Kajihara, Hiroshi (2025): Species Diversity of Tetranemertes (Nemertea: Monostilifera) in Japan. Species Diversity 30 (1): 71-83, DOI: 10.12782/specdiv.30.71, URL: https://doi.org/10.12782/specdiv.30.71
1A5B87F5FF82BF33FCF8FAA7FAE569BE.taxon	etymology	Etymology. The new specific name, meaning ‘ orange, ’ is the Latin adjective aurantius (m.), - a (f.), - um (n.), referring to the body color of the new species.	en	Abato, Jamael C., Hookabe, Natsumi, Kajihara, Hiroshi (2025): Species Diversity of Tetranemertes (Nemertea: Monostilifera) in Japan. Species Diversity 30 (1): 71-83, DOI: 10.12782/specdiv.30.71, URL: https://doi.org/10.12782/specdiv.30.71
1A5B87F5FF82BF33FCF8FAA7FAE569BE.taxon	diagnosis	Diagnosis. A Tetranemertes with bright orange body color, without mid-dorsal stripe, with ~ 60 eyes in total, with longitudinally-grooved stylets, basis nearly rod in shape, bifurcated, stylet / basis ratio 0.42. Sequences. GenBank accession number PP 413743, 16 S (465 bp); PP 413744, 18 S (1778 bp); PP 413745, 28 S (1118 bp); PP 413702, COI (604 bp).	en	Abato, Jamael C., Hookabe, Natsumi, Kajihara, Hiroshi (2025): Species Diversity of Tetranemertes (Nemertea: Monostilifera) in Japan. Species Diversity 30 (1): 71-83, DOI: 10.12782/specdiv.30.71, URL: https://doi.org/10.12782/specdiv.30.71
1A5B87F5FF82BF33FCF8FAA7FAE569BE.taxon	description	Description. External appearance of living specimen. Body long and thin, thread-like, uniformly deep orange in color (Fig. 2 A – C) on both sides except semi-translucent head, colorless anterior end, and paler posterior end (Fig. 2 B, C), orange appearance due to internal body structures visible through body, margin colorless, no markings, narrows from anterior region towards head (Fig. 2 B, C), anterior-most body to head noticeably convoluted when contracted (Fig. 3 A, B); head not demarcated from rest of body, narrow spearhead in shape (i. e., resembles a viper’s head), obviously thin when worm stretches at non-anesthetized state, broadens or bulges immediately in front of cerebral ganglia, narrows anteriorly (Fig. 2 B), colorless (Fig. 3 A, B); four longitudinal rows of laterally distributed reddish-purple ocelli visible at dorsal view of head, two ocelli rows on each side, 26 – 28 in total number, anterior-most ocelli do not reach head tip, posterior-most immediately in front of cerebral ganglia (Fig. 3 A, B), one row of ocelli on each side of head visible at ventral view (10 – 12 in number) (Fig. 3 B); cerebral ganglia visible as pair of round, pinkish structures at mid posterior head on both sides (Figs 2 B, 3 A, B); cerebral organ not discernable at dorsal view, slightly notable at ventral view (Fig. 3 B); cephalic furrow not evident at dorsal view, apparent ventrally as shallow ‘ Λ’ with corner directing anteriorly, located in front of cerebral ganglia, before posterior-most ocelli (Fig. 3 B); posterior tip of body rounded. Rhynchocoel and proboscis. Rhynchocoel restricted to anterior-most region of body, approximately within 2 cm from tip of head (Fig. 2 B); proboscis transparent in color, with two distinct regions separated by proboscis bulb, diaphragm dark brownish, dotted with reddish-purple pigments at high magnification (Fig. 3 G), with single central stylet (Fig. 3 C) and two overlapping pouches, each holding two accessory stylets (Fig. 3 E, F); central stylet shaft straight, glassy, fluted, accessory stylets same (Fig. 3 D – F), 115 µm in length, 19 µm in width; stylet basis rod-shaped, dark brown under light microscope, narrower anteriorly, posterior appears bifurcated (Fig. 3 C, D), 273 µm in length, 53 µm in width; central stylet to basis ratio 0.42.	en	Abato, Jamael C., Hookabe, Natsumi, Kajihara, Hiroshi (2025): Species Diversity of Tetranemertes (Nemertea: Monostilifera) in Japan. Species Diversity 30 (1): 71-83, DOI: 10.12782/specdiv.30.71, URL: https://doi.org/10.12782/specdiv.30.71
1A5B87F5FF82BF33FCF8FAA7FAE569BE.taxon	discussion	Remarks. The new species can be distinguished from the named Tetranemertes based on morphology, DNA sequence data, and locality. The new species can be morphologically distinguished from the pale to deep pinkish T. arabica Cherneva, Ellison, Zattara, Norenburg, Schwartz, Junoy, and Maslakova, 2023, the white or yellowish and mid-dorsally striped T. rubrolineata (Kirsteuer, 1965), the pale yellowish orange to pale pink and mid-dorsally striped T. unistriata, from the dark pink (wine) colored T. antonina, from the pale yellow to orangish yellow T. pastafariensis Cherneva, Ellison, Zattara, Norenburg, Schwartz, Junoy, and Maslakova, 2023, from the uniformly intense pink T. majinbuui Cherneva, Ellison, Zattara, Norenburg, Schwartz, Junoy, and Maslakova, 2023, from the pale yellow or deeppinkish orange T. ocelata Cherneva, Ellison, Zattara, Norenburg, Schwartz, Junoy, and Maslakova, 2023, from the dusky pink T. hermaphroditica (Gibson, 1982), and from the multi-colored and stripped and spotted T. bifrost Cherneva, Ellison, Zattara, Norenburg, Schwartz, Junoy, and Maslakova, 2023. Tetranemertes aurantia sp. nov. exhibits color resemblance with the orange-colored T. paulayi Cherneva, Ellison, Zattara, Norenburg, Schwartz, Junoy, and Maslakova, 2023 but both species differ in the number of ocelli and the morphology of the stylet basis. Phylogeny and genetic distance. Tetranemertes aurantia sp. nov. forms a highly supported clade along with other members of Tetranemertes and is sister to a clade consisting of T. arabica, T. rubrolineata, and T. unistriata (Fig. 4) with uncorrected pairwise COI genetic distances of 11.3 %, 11.6 %, and 10.6 % – 12.3 %, respectively (Table 2).	en	Abato, Jamael C., Hookabe, Natsumi, Kajihara, Hiroshi (2025): Species Diversity of Tetranemertes (Nemertea: Monostilifera) in Japan. Species Diversity 30 (1): 71-83, DOI: 10.12782/specdiv.30.71, URL: https://doi.org/10.12782/specdiv.30.71
1A5B87F5FF85BF30FCDDF95EFB1669FE.taxon	diagnosis	Emended diagnosis. A luminescent, reddish-orange Tetranemertes, anterior end almost colorless, posterior end light yellow, ocelli on each side of the head in linear groups, 15 – 20 in number per group, with hair-like projections on anterior and lower lateral edges of head (Fig. 5 A), central stylet and accessory stylets slender, acutely pointed, longitudinally fluted, basis rounded, and posteriorly bifurcated (Fig. 5), stylet to basis ratio 1.45.	en	Abato, Jamael C., Hookabe, Natsumi, Kajihara, Hiroshi (2025): Species Diversity of Tetranemertes (Nemertea: Monostilifera) in Japan. Species Diversity 30 (1): 71-83, DOI: 10.12782/specdiv.30.71, URL: https://doi.org/10.12782/specdiv.30.71
1A5B87F5FF85BF30FCDDF95EFB1669FE.taxon	discussion	Remarks. Emplectonema kandai was established based on material associated with the solitary ascidian Chelyosoma siboja Oka, 1906 living on a sandy or muddy bottom, 30 – 40 m deep in Aomori Bay near the Asamushi Marine Biological Station. This nemertean can emit a pale green luminescence along the entire body length in response to both chemical and mechanical stimuli (Kanda 1939). In life, E. kandai is filiform in shape, dorso-ventrally flat, 10 – 15 cm to more than 100 cm in length, 0.1 cm in width, uniformly reddish-orange in body color, with the anterior end being almost colorless, posterior end light yellow; the ocelli are arranged in a linear group, 15 – 20 in number, each dorsally and ventrally on both sides (Fig. 5 A); the central stylet is slender, acutely pointed, 0.16 mm in length, glassy, and conspicuously fluted longitudinally; the stylet basis is clubshaped, 0.11 mm in length, with roundly bifurcated terminations; two stylet pouches each has two accessory stylets shorter than the central stylet, fluted as the latter (Fig. 5 B). The stylet / basis ratio is 1.45. While members of the two eumonostiliferous hoplonemertean genera Emplectonema and Tetranemertes commonly have an elongated body, they differ in the shape of the head (e. g., rounded in the former; elongated and diamond-shaped in the latter), structure of the cephalic furrows (e. g., two greatly reduced, small arch-like cerebral organ furrows in the former; single V-shaped ventral cerebral organ furrow in the latter), and the arrangement of the ocelli (e. g., four groups or two irregular rows in Emplectonema vs. four longitudinal rows, with two overlapping dorsoventrally on each side in Tetranemertes). The type species of Emplectonema was recently discovered to be Borlasia camillea Quatrefages, 1846 (now Emplectonema neesii Örsted, 1843 or Neesia neesii), instead of Emplectonema viride Stimpson, 1857 as had long been accepted among nemertean specialists. In response to this, a case has been submitted to the ICZN for a ruling to set aside the original type fixation and designate E. viride as the type species (Kajihara et al. 2021); under Article 82.1 of the Code, E. viride is deemed as the type species until a ruling is published. Irrespective of the overlooked type species, the genus concept for Emplectonema has been vague, resulting in almost like a catch-all taxon consisting of any thin-bodied eumonostliferans. Among 22 species listed as members of Emplectonema (Norenburg et al. 2024), the only true congener other than the type species would be E. gracile (Johnston, 1837); E. friederichi Sánchez, 1973 may be a junior synonym of the type species E. viride. Other species currently in Emplectonema will probably be transferred to different genera in future taxonomic studies; E. mitsuii Yamaoka, 1947 (in addition to E. kandai) is more closely related to other eumonostiliferans than to E. gracile and E. viride (Kajihara et al. 2011; present study). No matter which of B. camillea or E. viride becomes the type species of Emplectonema upon the ICZN ruling, E. kandai should be transferred to Tetranemertes. Among the 22 Emplectonema species (Norenburg et al. 2024), E. kandai is the only one where the ocelli are arranged in four rows, as stated and illustrated in its original description (Kato 1939: fig. 1 A, B). We herein propose to transfer the species to Tetranemertes, yielding a new combination, T. kandai comb. nov.	en	Abato, Jamael C., Hookabe, Natsumi, Kajihara, Hiroshi (2025): Species Diversity of Tetranemertes (Nemertea: Monostilifera) in Japan. Species Diversity 30 (1): 71-83, DOI: 10.12782/specdiv.30.71, URL: https://doi.org/10.12782/specdiv.30.71
1A5B87F5FF86BF3FFCFCF89FFD4F6A9B.taxon	discussion	Remarks. Tetranemertes unistriata was established based on specimens from Oman and Japan (COI p - distance is 3.3 %) (Table 2), the latter was found among calcareous algae taken on Engetsu Island, Shirahama, Japan (Cherneva et al. 2023). It is one of two congeners that has a mid-dorsal reddish stripe (Fig. 6 A, D, E), the other being T. rubrolineata. The body color in life varies from pale yellowish orange to pale pink. A pair of ventral anterior cephalic furrows nearly fused mid-ventrally to form a shallow ‘ Λ, ’ with the corner directing anteriorly (Fig. 6 B). The central stylet basis is cylindrical and deeply forked posteriorly (Fig. 6 C).	en	Abato, Jamael C., Hookabe, Natsumi, Kajihara, Hiroshi (2025): Species Diversity of Tetranemertes (Nemertea: Monostilifera) in Japan. Species Diversity 30 (1): 71-83, DOI: 10.12782/specdiv.30.71, URL: https://doi.org/10.12782/specdiv.30.71
