A New Species of Apterichtus (Actinopterygii: Anguilliformes: Ophichthidae) from Tori-Shima Island, Southern Japan with Notes on Characters of Supraorbital Canal

Home , Apterichtus, Apterichtus anguiformis, Apterichtus caecus

Species Diversity 23: 219–223 25 November 2018 DOI: 10.12782/specdiv.23.219

A New Species of Apterichtus (Actinopterygii: Anguilliformes: Ophichthidae) from Tori-shima Island, Southern Japan with Notes on Characters of Supraorbital Canal

Yusuke Hibino Kitakyushu Museum of Natural History and Human History, 2-4-1 Higashida, Yahatahigashi-ku, Kitakyushu, Fukuoka 805-0071, Japan E-mail: [email protected] (Received 17 May 2018; Accepted 2 October 2018)

http://zoobank.org/FA67D682-2B28-4161-9953-D6F01159151E

A new finless ophichthid eel, Apterichtus soyoae, is described based on a single specimen collected from off Tori-shima island, Zunan Islands of Izu Islands, southern Japan. The new species is similar to A. moseri and A. klazingai in its numbers of supratemporal pores, preopercular pores, and vertebrae. The new species differs from A. moseri in having more supraorbital pores (1+6 vs. 1+4), the number of branchings of the supraorbital canal (1 vs. 0), shape of the snout (distinctly pointed vs. relatively blunt), eye size (50% of snout length vs. 35–45%; 8.8% of head length vs. 6.3–8.0%), and the number of vomerine teeth (1 vs. 2–5). Apterichtus soyoae can also be distinguished from A. klazingai by the number of branchings of the supraorbital canal (1 vs. 2), the number of infraorbital pores (7 vs. 9), and the location of the lower jaw tip (anterior to a vertical through anterior margin of eye vs. posterior to the vertical). The number of supraorbital pores and branchings of the canal are discussed. Key Words: Ophichthidae, Apterichtus, new species, Japan, Tori-shima island.

Machida and Ohta, 1994) were reliably recorded based on Introduction museum specimens, and some individuals of A. klazingai (Weber, 1913) were observed from southern Japan by un- The finless snake eel, genus Apterichtus Duméril, 1805 is derwater photographs (McCosker and Hibino 2015). I here- a cosmopolitan group including 19 valid species (McCosker in describe an additional Japanese species as a new based on and Hibino 2015; Hibino et al. 2016). The genus is charac- a specimen collected from off Tori-shima island, Zunan Is- terized by the absence of all fins, sub-conical snout, anterior lands of Izu Islands. nostril typically in a short tube or flush with the snout, posterior nostril outside of mouth, three or four preopercular pores, three to nine supratemporal pores, gill openings ven- Materials and Methods tral and closely located anteriorly (McCosker and Hibino 2015). All methods follow McCosker and Hibino (2015) except Members of Apterichtus usually inhabit sandy bottoms for observation of sensory canals on head following Kishi- above 100 m. Although the longest species of the genus at- moto et al. (2006). Total length is abbreviated as TL. Insti- tains 60 cm TL [Apterichtus caecus (Linnaeus, 1758)], all tutional abbreviations for materials follow Fricke and Esch- congeners have an extremely elongate body (less than 2.2% meyer (2018) and the Wakayama Natural History Museum TL) (McCosker and Hibino 2015; Hibino et al. 2016), mak- (WMNH) in Wakayama, Japan. The type specimen is de- ing their collection difficult without the use of ichthyocides. posited in the National Museum of Nature and Science, Tsu- On the other hand, Mura et al. (2016) recently collected kuba (NSMT). many specimens of A. anguiformis (Peters, 1877) and A. caecus by sand pump (authors noted the negative impact on the Apterichtus soyoae sp. nov. environment by this method) and by bottom trawl using a [New Japanese name: Soyo-goma-umihebi] 40 mm-mesh net covered by a 8 mm-mesh net outside. (Figs 1–4; Table 1) Apterichtus was reviewed taxonomically by McCosker and Hibino (2015), and one additional species was de- Holotype. NSMT-P 127390, 171 mm TL, sex unknown, scribed from Marquesas Islands by Hibino et al. (2016). In off Tori-shima island, Zunan Islands, Izu Islands, southern Japanese waters, four species (A. australis McCosker and Japan, depth 130 m, R/V Soyo-maru, collected by Takashi Randall, 2005, A. hatookai Hibino, Shibata and Kimura, Okutani, 20 July 1979. 2014, A. moseri Jordan and Snyder, 1901, and A. orientalis Diagnosis. An elongate species of Apterichtus with the

Fig. 1. Preserved condition of the holotype of Apterichtus soyoae sp. nov., NSMT-P 127390, 171 mm TL, off Tori-shima island, southern Japan.

Fig. 2. Arrangement of sensory canal of head (a), teeth on maxillary and palatal area (b), and dentary (c) of Apterichtus soyoae sp. nov., NSMT-P 127390, holotype, 171 mm TL, off Tori-shima island, southern Japan. Abbreviations: IMT, intermaxillary teeth; IO, infraorbital pores; LL, lateral-line pores; M, mandibular pores; PN, posterior nostril; PO, preopercular pores; SO, supraorbital pores; ST, supratemporal pores; UJT, upper-jaw teeth; VT, vomerine teeth. Arrows indicate interorbital (left) and mid-supratemporal (right) pores. following combination of characters: tail 1.8, head 12.6, and serial on jaws, a single vomerine tooth; and VF 59-145. body depth 45.0 in total length (tail 57.0% TL, head 8.0% Counts and measurements (in mm) of the holotype. TL, and body depth at gill opening 2.2% TL); tip of lower Preanal vertebrae 59; total vertebrae 145; preanal lateral-line jaw anterior to a vertical through anterior margin of eye; 3 pores 59, with 8 pores in branchial region. Total length 171; preopercular and 5 supratemporal pores; teeth conical, uni- head 13.6; trunk 59.9; tail 97.4; body depth at gill openings A new Apterichtus from Japan 221

Fig. 3. Arrangement of supraorbital pores (SO) and location of lower-jaw tip (arrow) of Apterichtus soyoae sp. nov. (a), Apterichtus klazingai (b), and Apterichtus moseri (c). a, NSMT-P 127390, holotype, 171 mm TL, off Tori-shima island, southern Japan; b, USNM 348474, 1 of 3 specimens, 198 mm TL, Erromango Island, Vanuatu; c, WMNH 2010PIS159, 448 mm TL, Wakayama Prefecture, Japan. Abbreviation: SO, supraorbital pore.

Table 1. Number of supraorbital pores and canal branching of Indo-Pacific Apterichtus

Supraorbital Supraorbital-canal pores branching Apterichtus australis 1+4 1 Apterichtus dunalailai 1+4 0* Apterichtus flavicaudus 1+4 1 Apterichtus hatookai 1+6 2 Apterichtus jeffwilliamsi 1+6 2 Apterichtus klazingai 1+6 2 Apterichtus malabar 1+4 0* Apterichtus moseri 1+4 0 Apterichtus mysi 1+4 0* Apterichtus nariculus 1+6 2 Apterichtus orientalis 1+6 1 Apterichtus soyoae 1+6 1 Apterichtus succinus 1+6 2 *Presumed from figures of McCosker and Hibino (2015)

mately 40° relative to underside of snout. Anterior nostril tubular but extremely short, tube length shorter than pupil diameter; posterior nostril oval in shape with an inner valve, located on anteroventral margin of eye, opening ventrally. Eyes moderate in size, covered by a transparent skin; center Fig. 4. Sensory canal system of Apterichtus soyoae sp. nov. of eye anterior to mid-jaw (Fig. 2a). Mouth inferior, distance (a) and Apterichtus klazingai (b). a, NSMT-P 127390, holotype, from tip of snout to anterior tip of lower jaw slightly shorter 171 mm TL, off Tori-shima island, southern Japan; b, USNM 348474, 198 mm TL, Erromango Island, Vanuatu. Abbreviation: SO, than twice eye diameter; lower jaw short, its tip pointed and supraorbital pore. located anterior to a vertical through anterior margin of eye (Fig. 3a); rictus short, posterior end of gape well behind a 3.8; body width at gill openings 2.5; body depth at anus 2.5; vertical through posterior margin of eye; lips smooth with body width at anus 2.5; head depth at branchial basket 4.3; distinct folds, fold on upper lip extending from a vertical head width at branchial basket 3.8; snout length 2.4; tip of through first infraorbital pore to posterior rictus. Gill open- snout to tip of lower jaw 2.2; tip of snout to rictus (end of ings completely ventral, slender leaf-like shape, their diam- gape) 5.3; eye diameter 1.2; interorbital distance 1.1; gill- eters less than twice eye diameter; anterior margins of gill opening length 2.0; isthmus width 0.5. openings close-set but not connected. Description. Body elongate, subcylindrical, tip of tail Sensory pores on head developed, arrangement of those strongly laterally compressed and extremely pointed (Figs 1, pores as follows (Figs 2a, 4a): 1+6 on supraorbital (5th pore 2a). Head short; preanal length much shorter than tail, 2.3 branched downward from other pores), 6+3 on infraorbital, in TL. 5 on lower jaw, 3 on preopercle, and 5 on supratemporal, Snout moderate in length, twice eye diameter, its tip one of those on mid-temporal; a single median interorbital prominently pointed; distinct median groove ventrally on pore. Lateral-line pores small but obvious. Lateral line al- snout, its anterior tip beyond anteriormost margin of first most complete except for near tip of tail. infraorbital pore; slope of dorsal surface of snout approxi- Teeth (Fig. 2b, c) pointed, slightly recurved posteriorly; 222 Yusuke Hibino

known that the numbers of the supratemporal and preopercular pores are nearly invariable within a species, two species (A. jeffwilliamsi McCosker and Hibino, 2015 and A. moseri) have intraspecific variation in that of the supratemporal and one of the preopercular pores. Intraspecific variations of the supraorbital counts were not observed by McCosker and Hibino (2015) or the present study. Consequently, the numbers of branching and supraorbital pore counts may contrib- ute to species identification. Comparative materials: Apterichtus hatookai: OMNH-P 13794, holotype, 479 mm TL, Morode, Ainan, Minami-uwa, Ehime Prefecture, Shikoku Island, Japan; OMNH-P 13802, paratype, 519 mm TL, Morode, Ainan, Mina Uwa, Ehime Prefecture, Shikoku Island, Japan. Apterichtus jeffwilliamsi: USNM 363869, holotype, 305 mm TL, Vanua Lava Island, Banks Islands, Vanuatu; USNM 427494, 2 specimens, paratypes, 112–283 mm TL, collected with holotype; USNM 350117, 2 specimens, paratypes, 149–178 mm TL, Ranon Fig. 5. Type locality of Apterichtus soyoae sp. nov. (star). Bay, Ambrym Island, Vanuatu. Apterichtus klazingai: USNM 348474, 3 specimens, 148–198 mm TL, Dillon’s Bay, Erro- teeth on maxilla and dentary uniserial; a single vomerine mango Island, Vanuatu; USNM 375002, 247 mm TL, Wallis tooth on anteriormost vomer, clearly separated from upper- Island, Ile Uvea. Apterichtus moseri: BSKU 65700, 395 mm jaw teeth; intermaxillary teeth slightly larger and more slen- TL, Tosa Bay (33°16.0′N, 133°37.4′E), 131–146 m; NSMT- der than maxillary teeth, arranged in a chevron shape along P 104038, 498 mm TL, Kumano-nada Sea (34°15.96′N, with edge of pre-ethmoid; part of intermaxillary teeth vis- 136°59.01′E), 111–114 m; NSMT-P 105671, 245 mm TL, ible when mouth is closed. All fins absent. Kii Peninsula (33°39.1′N, 135°6.4′E), 200 m; SNFR 11043, Coloration. No fresh color information. In ethanol pre- 420 mm TL, northern East China Sea; WMNH 2010PIS159, servative, head and body mostly yellowish brown, with ex- 448 mm TL, off Shirahama, Wakayama Prefecture, Japan. tremely faint pale brown spots on occipital. Apterichtus nariculus: BPBM 38368, holotype, 308 mm TL, Etymology. The scientific name soyoae after R/V Soyo- Laha (NW side of Ambon Bay), Ambon Island, Molucca Is- maru, the collecting vessel of the holotype. lands, Indonesia. Distribution. Known only from the holotype, from off Tori-shima island, Zunan Islands of Izu Islands, southern Japan (Fig. 5). Acknowledgments Remarks. Apterichtus soyoae sp. nov. is similar to A. moseri and A. klazingai in the numbers of its supratempo- I express my gratitude to Gento Shinohara (NSMT) for ral and preopercular pores and vertebrae. In addition, the providing the holotype. I also thank the following institu- new species shares the location of the lower-jaw tip with tions and individuals for their help with specimen loans and A. moseri. Apterichtus soyoae differs from A. moseri in hav- hospitalities during my visits: Arnold Suzumoto and John ing more supraorbital pores (1+6 vs. 1+4), the number of E. Randall (BPBM); Hiromitsu Endo (BSKU) and Naohide branchings of the supraorbital canal (1 vs. 0), shape of the Nakayama (formerly BSKU, now Tokai University); David snout (distinctly pointed vs. relatively blunt), eye size (50% Catania, Jon Fong, Mysi Hoang and Tomio Iwamoto (CAS); of snout length vs. 35–45%; 8.8% of head length vs. 6.3– Masanori Nakae, Kaoru Kuriiwa (NSMT), Fumiya Tanaka 8.0%) (Fig. 2a, c), and the number of vomerine teeth (1 vs. (formerly NSMT, now National Research Institute of Far 2–5). The new species can also be distinguished from A. Seas Fisheries) and Eri Katayama (formerly NSMT, now Re- klazingai by the number of branchings of the supraorbital search Institute of Marine Invertebrates); Kiyotaka Hatooka canal (1 vs. 2) (Fig. 4), the number of infraorbital pores (7 (OMNH); Kouichi Hoshino (SNFR) and Makoto Okamoto vs. 9), and location of the lower jaw tip (anterior to a vertical (formerly SNFR, now JAMARC); Jeffrey T. Williams, David through anterior margin of eye vs. posterior to the vertical) G. Smith, Shirleen Smith, and Diane Pitassy (USNM); Yo- (Fig. 3a, b). shitsugu Kaji (WMNH). Finally I greatly appreciate John E. In the genus, members having 1+4 supraorbital pores McCosker’s (CAS) critical reading of this manuscript. This generally have no branchings in the supraorbital canal, and study was supported in part by a Grant-in-Aid to the Japan members having 1+6 supraorbital pores generally have two Society for the Promotion of Science for JSPS Fellows to YH branchings of 4th and 5th supraorbital pores. However, in (PD: 15J02820). the latter group A. orientalis and A. soyoae have only one branching of the 5th pore. Additionally, A. australis and A. flavicaudus (Snyder, 1904) have 1+4 supraorbital pores but have one branching of the 4th pore (Table 1). Although it is A new Apterichtus from Japan 223

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