Paraliparis flammeus Kai, Murasaki & Fukui, 2020

Kai, Yoshiaki, Murasaki, Kenta, Misawa, Ryo, Fukui, Atsushi, Morikawa, Eisuke & Narimatsu, Yoji, 2020, A new species of snailfish of the genus Paraliparis (Liparidae) from the western North Pacific, with a redescription of the poorly known species Paraliparis mandibularis, ZooKeys 968, pp. 143-159 : 143

Paraliparis flammeus Kai, Murasaki & Fukui sp. nov. Figs 1 , 2 , 3A, C [New Japanese name: Homuradama]

Holotype.

MSM-20-52, 75.8 mm SL, female, 36.850°N, 141.496°E, 510 m depth, 30 Oct. 2018, coll. K. Murasaki, R/V Wakataka-maru, otter trawl.

Paratypes.

All specimens were collected by R/V Wakataka-maru, otter trawl. FAKU 147147 (INSDC accession: LC556311), 80.4 mm SL, 36.972°N, 141.635°E, 561 m depth, 17 Nov. 2019, coll. R. Misawa; FAKU 147148 (LC556312), 62.1 mm SL, 36.859°N, 141.479°E, 459 m depth, 16 Nov. 2019, coll. R. Misawa; FAKU 147158 (3 specimens, C&S), 49.3-68.2 mm SL, 36.972°N, 141.635°E, 561 m depth, 17 Nov. 2019, coll. R. Misawa; FAKU 147159 (LC556313), 51.1 mm SL, 36.510°N, 141.064°E, 460 m depth, 12 Nov. 2019, coll. R. Misawa; FAKU 147161, 51.5 mm SL, 37.664°N, 141.984°E, 482 m depth, 19 Nov. 2019, coll. R. Misawa; FAKU 147163, 66.4 mm SL, FAKU 147164, 64.4 mm SL, 36.858°N, 141.505°E, 510 m depth, 16 Nov. 2019, coll. R. Misawa; FAKU 147168, 79.7 mm SL, 36.818°N, 141.669°E, 890 m depth, 9 Nov. 2019, coll. R. Misawa; FAKU 147177, 42.5 mm SL, FAKU 147178, 62.1 mm SL, 36.873°N, 141.468°E, 422 m depth, 16 Nov. 2019, coll. R. Misawa; FAKU 147432, 67.3 mm SL, 36.858°N, 141.505°E, 510 m depth, 16 Nov. 2019, coll. R. Misawa MSM-20-53, 64.8 mm SL, male, MSM-20-54, 60.3 mm SL, male, 38.399°N, 142.121°E, 552 m depth, 21 Oct. 2018, coll. K. Murasaki; MSM-20-55, 43.4 mm SL, male, 36.511°N, 141.087°E, 507 m depth, 16 Nov. 2018, coll. K. Murasaki; MSM-20-56, 45.4 mm SL, female, 36.848°N, 141.479°E, 484 m depth, 15 Nov. 2017, coll. K. Murasaki.

Diagnosis.

Paraliparis flammeus is distinguished from other species of Paraliparis by the following combination of characters: mouth oblique; uppermost pectoral-fin base below a horizontal through posterior margin of maxillary; 60-63 vertebrae, 54-58 dorsal-fin rays, 50 or 51 anal-fin rays, 6 principal caudal-fin rays, and 17-20 pectoral-fin rays; pectoral radials 4, moderately large and located medially.

Description.

Measurements are shown in Table 1 . Paratype data are given in parentheses if different from the holotype.

Body compressed, elongate, deepest at nape, strongly taping posteriorly (Fig. 1 ). Skin thin, fragile. Head compressed, dorsal profile strongly sloping from nape to snout. Snout deep, blunt, its length almost equal to orbit diameter; not projecting anterior to upper jaw. Mouth oblique, lower jaw slightly protruding beyond (or almost same length as) upper jaw; premaxillary tooth plates matching mandibular tooth plates; maxilla extending to posterior margin of orbit; oral cleft extending to middle of orbit (Figs 1 , 2 ). Premaxillary teeth simple, in 7 (3-8) oblique rows; diastema narrow between premaxillae. Mandibular teeth simple, in 6 (3-7) oblique rows; inner teeth larger; diastema absent at lower jaw symphysis (Fig. 3A ). Orbit of moderate size, rounded. Nostril single, with slightly raised rim, at level of mid-orbit. Cephalic sensory pores small (damaged): nasal pores 2, maxillary pores 6, preoperculomandibular pores ≥ 6 (skin damaged in holotype and all paratypes), suprabranchial pore 1; cephalic pore pattern 2-6-6?-1. Chin pores paired, openings well separated on skin surface. Coronal pore absent. Gill slit small, entirely above pectoral fin (or extending ventrally to level of 1 or 2 uppermost pectoral-fin rays), upper margin level with mid-orbit (or between center and ventral rim of orbit). Gill rakers 6-10 (status in holotype unknown), blunt and minute. Tip of opercular flap sharp, angled slightly dorsally, level with ventral rim of orbit (or with posterior margin of maxillary).

Dorsal-fin rays 56 (54-58); anteriormost ray above tip of opercle, posteriormost ray attached membranously to dorsalmost caudal-fin ray. Anteriormost dorsal-fin pterygiophore inserted between neural spines 3 and 4 (2 and 3, or 3 and 4), bearing a single ray. Anal-fin rays 51 (48-51); posteriormost ray attached membranously to ventralmost caudal-fin ray. Vertebrae 63 (60-63), comprising precaudal 9 and caudal 54 (51-54). Pleural ribs absent. Hypurals and parhypural fused into single plate. Caudal fin slender, posterior margin slightly rounded (or truncate). Principal caudal-fin rays 6, dorsal principal rays 3, ventral principal rays 3, no procurrent rays. Pyloric caeca 7 (4-6), short and finger-like, on left side of visceral cavity. Anus below posterior margin of preopercle (or midway between posterior margin of preopercle and posterior rim of orbit).

Pectoral fin moderately notched, with 19 (17-20) rays; upper lobe with 14 (12-15) rays, extending beyond (or just reaching) anal-fin origin; lower lobe elongate, with 5 (3-7) rays, uppermost ray of lower lobe longest, extending beyond anus, not reaching (reaching) anal-fin origin. Uppermost pectoral-fin base below a horizontal through posterior margin of maxillary. Lowermost pectoral-fin base below anterior rim of orbit (or below midway between tip of snout and anterior rim of orbit). Rays between upper and lower lobes widely spaced.

Selected osteological characters. Roof of cranium comprising frontal and supraoccipital incompletely closed; frontal and supraoccipital poorly ossified; parietal absent (Fig. 2 ). Opercle well ossified, sharpened posteriorly, supporting upper margin of opercular flap. Subopercle thin, comprising two spines forming a V-shape; lower spine supporting lower margin of opercular flap. Subopercle and interopercle separated. Dorsal portion of cleithrum elongated. Proximal pectoral radials 4, rounded, moderately large and located medially (Fig. 3C ). No interradial fenestrae between proximal radials. Scapula with strong helve, posterior margin with a small slit. Coracoid triangular with broad lamina. Distal radials present at base of all pectoral-fin rays, except for uppermost and lowermost rays.

Coloration. In fresh specimens, head and body pale pink with fine melanophores; margin of preopercle silvery; anteroventral portion silvery, with dark peritoneum visible through thin skin; dorsal and anal fins crimson, distal margins somewhat darker; pectoral fin crimson (Fig. 1A ). In preserved specimens, head, body, and fins pale with fine melanophores, somewhat larger posteriorly on body; peritoneum black, stomach dark brown (or black); orobranchial cavity pale with scattered melanophores.

Reproductive characters. Ovary pouch-like, whitish; one of two ovaries with 33 ripe ovarian eggs (2.06-2.12 mm in diameter) and numerous unripe ovarian eggs (0.6 mm in maximum diameter) in female paratype (FAKU 147147, 80.4 mm SL). Testes slender, whitish (FAKU 147161, 51.5 mm SL).

Etymology.

The specific epithet flammeus is from Latin, meaning “flame”, and refers to the crimson fin coloration of the species.

Geographical distribution.

Western Pacific Ocean, off the Pacific coast of Tohoku District, northern Honshu, Japan, in depths of 422-890 m (Fig. 4A ).

Remarks.

Alignment of the COI gene sequences (492 bp) determined herein with previously determined sequences of Paraliparis resulted in a maximum likelihood tree based on 101 aligned sequences and the recovery of a monophyletic group comprising P. flammeus , P. cephalus , and P. dipterus (Fig. 5 ). Monophyly of the above species was supported by high bootstrap probability (95%). The uncorrected p -distance within P. flammeus was less than 0.006, strongly contrasting with values ranging from 0.030 to 0.067 for the above two species. Paraliparis cephalus is similar to P. flammeus in having an oblique mouth, but has 4 caudal-fin rays (vs 6 rays) and the uppermost pectoral-fin base above a horizontal through the maxillary posterior margin ( Stein 1978; this study). Paraliparis dipterus , known only from the holotype collected from Suruga Bay, Japan, until the recent description of a developmental series by Takami and Fukui (2012), differs from P. flammeus in having a horizontal mouth, 12-14 pectoral-fin rays, and lacking pyloric caeca (present in P. flammeus ) ( Kido 1988; Takami and Fukui 2012; this study). The position of P. mandibularis is unknown due to the unavailability of sequence data.

Among the 28 species of Paraliparis known from the North Pacific, P. flammeus shares the morphological characters, i.e., an oblique mouth and the uppermost pectoral-fin base below a horizontal through the posterior margin of the maxillary, with only P. mento (Washington southward to Monterey Bay), P. mandibularis (Tosa Bay, Japan), and Paraliparis angustifrons (Garman, 1899) (off Panama) ( Garman 1899; Kido 1988; Mecklenburg et al. 2002; Love et al. 2005; Baldwin and Orr 2010; Nakabo and Kai 2013; Murasaki et al. 2018, 2019a, b). However, P. flammeus differs from P. mento in having 6 caudal-fin rays (vs 5 rays) and greater preanal length (29.9-35.3% SL vs 26.7-28.5% SL), and from P. mandibularis in having 17-20 pectoral-fin rays (vs 27-30 rays) and a longer pectoral-fin lower lobe (16.7-23.4% SL vs. 13.8-15.9% SL). In addition, P. angustifrons , known only from two syntypes collected off Panama, also has an oblique mouth and low pectoral-fin position, but clearly differs from the new species in pectoral-fin ray number (37 in P. angustifrons ) ( Garman 1899; Chernova et al. 2004). Although Paraliparis deani Burke, 1912 (western Gulf of Alaska to northern California) and Paraliparis melanobranchus Gilbert & Burke, 1912 (southern Sea of Okhotsk and off British Columbia) are also similar to P. flammeus in the counts of dorsal- (56-57 and 52-60, respectively) and anal-fin rays (44-48 and 48-54, respectively), P. flammeus is distinguishable from P. deani in having a small gill slit entirely above the pectoral fin or extending ventrally to level of 1 or 2 uppermost pectoral-fin rays (vs extending to 10-13 pectoral-fin rays) and from P. melanobranchus in having 6 caudal-fin rays (vs 4) ( Mecklenburg et al. 2002; Nakabo and Kai 2013). Among South Pacific species, P. flammeus resembles Paraliparis membranaceus Günther, 1877 and Paraliparis molinai Stein, Meléndez & Kong, 1991 in having an oblique mouth and low pectoral-fin position, but is distinguishable from both species by its lower pectoral-fin ray number (ca 25 in P. membranaceus and 24 in P. molinai ) ( Stein et al. 1991; Stein 2005).

Figures

Figure 1. Paraliparis flammeus sp. nov., MSM- 20 - 52, holotype, 78.5 mm SL A fresh specimen B line drawing.

Figure 2. Skeleton of Paraliparis flammeus sp. nov. A, B C & S specimens, FAKU 147158, paratypes A dorsal view of cranium of 68.2 mm SL specimen B lateral view of head of 61.2 mm SL specimen C CT-scanned holotype, MSM- 20 - 52, holotype, 78.5 mm SL. Abbreviations: Epoc, epiotic; Exoc, exoccipital; Fr, frontal; Iop, interopercle; LE, lateral ethmoid; Op, opercle; Sop, subopercle; Pte, pterotic; Ptem, posttemporal; Soc, supraoccipital; Shp, sphenotic; Vo, vomer. Scale bars: 5 mm (A, B).

Figure 3. A, B teeth on lower jaw C, D pectoral girdle A, C Paraliparis flammeus sp. nov., FAKU 147158, paratype, 61.2 mm SL B, D P. mandibularis, BSKU 44286, 110.0 + mm SL. Abbreviations: S, scapula; PR, proximal radials; C, coracoid; DR, distal radials. Scale bars: 0.5 mm (A, B); 5 mm (C, D).

Figure 4. Distribution of specimens of (A) Paraliparis flammeus sp. nov. and (B) P. mandibularis examined during this study. Stars indicate type localities.

Figure 5. Maximum likelihood phylogenetic tree of Paraliparis and related genera based on COI sequences (492 bp). Support values (≥ 50 % ML bootstrap probability) indicated along branches. Each node labeled with a registration number (red, determined in this study) or an accession number deposited in INSDC or BOLD. Nectoliparis pelagicus included as out-group.