Lycenchelys aurantiaca Shinohara & Matsuura 1998

Lycenchelys aurantiaca Shinohara & Matsuura, 1998

(Japanese name: Daidai-hebigenge)

(Figs. 5–8; Table 2)

Lycenchelys aurantiaca Shinohara & Matsuura, 1998: 151, figs. 1–3, table 1 (original description, type locality: off Miyagi Prefecture, Pacific coast of Honshu, Japan); Imamura, 1998: 31, fig. 8 (brief description); Hatooka, 2000: 1033, unnumbered fig. (key to species); Hatooka, 2002: 1033, unnumbered fig. (key to species); Anderson & Fedorov, 2004: 15 (species list); Shinohara & Anderson, 2007: 64 (key to species); Kitagawa et al., 2008: 95, unnumbered fig. (brief description); Shinohara et al., 2009: 723 (species list); Amaoka et al., 2011: 318, unnumbered fig. (brief description); Balushkin et al., 2011: 1026 (species list); Hatooka, 2013: 1227, unnumbered fig. (key to species); Nakabo & Hirashima, 2015: 217 (species list and etymology of scientific name).

Holotype: NSMT-P 53147, male, 135.7 mm SL, off Miyagi Prefecture, Tohoku District, northwestern Pacific (37°58.54’N, 142°09.00’E to 37°56.84’N, 142°09.07’E), 700 m depth, 21 Apr. 1997, T/V Tanshu-maru, otter trawl.

Other specimens (16 specimens, 91.6–141.3 mm SL): HUMZ 152389–90, 177032–33, 180582 –83, 180864 – 67, 182661, 192779, 206876, 206878, 9 males and 5 females, 91.6–141.3 mm SL, Tohoku District, northwestern Pacific; HUMZ 192380–81, 1 male and 1 female, 102.2–123.8 mm SL, eastern Hokkaido Island, northwestern Pacific.

Diagnosis. Vertebrae 19–20 + 66–70 = 85–89; head length 14.3–18.4% SL; interorbital pore 1; occipital pores absent; postorbital pores 4; suborbital pores 5 + 1; preoperculomandibular pores 7 (rarely 8); vomerine teeth 4–10; palatine teeth 8–25, arranged in single row; opercular flap well-developed; pelvic-fin base positioned anterior to lower edge of gill opening; lateral line incomplete and positioned ventrally; scales absent on pectoral fin and its base; body uniformly reddish orange when fresh.

Description. Counts and proportional measurements in Table 2.

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Body elongate, in cross section oval anteriorly, compressed laterally near tail; its width at anal-fin origin 3.7–7.7 (4.0)% SL. Head short, ovoid; dorsal profile of head gently sloping to dorsal-fin origin. Cheek more swollen in large specimens (including holotype) than in small specimens. Head of adults longer in males than in females. Snout short, 67.5–111.4 (106.0)% of eye diameter. Eye ovoid, moderately large. Interorbital space narrow, width 10.9–33.7 (26.7)% of eye diameter. Nostril tube short, not reaching upper lip when depressed. Mouth subterminal. Posterior edge of upper jaw about reaching vertical through 5th suborbital pore in adult males (including holotype), reaching below posterior margin of eye in females and juveniles. Labial lobe of lower jaw weak. Teeth on jaws, vomer and palatine small and conical; upper jaw with 2–3 rows anteriorly and single row posteriorly; lower jaw with 2–4 irregular rows anteriorly and single row posteriorly; vomerine teeth irregularly arranged; palatine teeth in single row. Lower edge of gill opening slightly above lower end of pectoral-fin base. Opercular flap well developed. Gill rakers short and slender (Fig. 6). Pseudobranch filaments short. Lateral line deciduous, incomplete and positioned ventrally; originating posterior to last postorbital pore and ending anterior to anus. Scales small and cycloid, present on body, pectoral axilla, tail and about 40–60% vertical fins basally. Head, nape, pectoral fin and its base without scales.

Dorsal-fin origin near vertical through posterior edge of opercular flap; 1st dorsal-fin pterygiophore between neural spines of 2nd and 3rd vertebrae. Anal-fin origin below 17th or 18th (18th) dorsal-fin ray; 1st anal-fin pterygiophore posterior to parapophysis of ultimate abdominal vertebra. Last dorsal-fin pterygiophore between neural spines of 2nd to 5th (between 3rd and 4th) preural vertebrae. Last anal-fin pterygiophore between hemal spines of 2nd to 4th (between 3rd and 4th) preural vertebrae. Caudal fin with 2 epural, 3–4 (4) upper hypural and 4 lower hypural rays. Pectoral fin moderately short, reaching to middle of abdomen; its posterior margin rounded. Upper end of pectoral-fin base on about lateral midline of body. Pelvic fin short; its base anterior to lower edge of gill opening; its posterior margin reaching to or slightly beyond lower edge of gill opening.

Head pores well developed and distinct. Nasal pores 2; anterior pore in front of nostril tube, posterior pore above and slightly anterior to vertical through 1st suborbital pore (Fig. 8A, B). Postorbital pores 4; distance between 1st and 2nd pores longest of those between adjacent pores (Fig. 8A, B). Suborbital pores 6; 5 pores located below eye and 6th posterior to center of eye; 5th pore posterior to vertical through 1st postorbital pore (Fig. 8A). Preoperculomandibular pores usually 7 (including holotype); 4 on lower jaw and 3 on preopercle; 4 and 4 on left side of HUMZ 180866; last preoperculomandibular pore located posterior to lower margin of eye (Fig. 8A, C). One interorbital pore on dorsal midline between center of eyes (Fig. 8B). Occipital pores absent (Fig. 8B).

Color in alcohol. Holotype (Fig. 7) with light brown head, body and vertical fins; light yellow pectoral fin and brown its ventral margin; light purple opercular region and abdomen. Head and body light brownish yellow and vertical fins whitish in HUMZ 206878. Coloration of other non-type specimens similar to holotype.

Color when fresh (based on color photograph of HUMZ 152390; Fig. 5). Head, body and vertical fins uniformly reddish orange. Pectoral fin whitish, its ventral margin light brown. Opercular region and abdomen bluish black.

Distribution. Off northwestern Pacific coast of eastern Hokkaido Island and off Tohoku District from Aomori to Fukushima prefectures, at depths of 500–756 m (Shinohara & Matsuura, 1998; Imamura, 1998; Hatooka, 2000, 2002, 2013; Anderson & Fedorov, 2004; Shinohara & Anderson, 2007; Kitagawa et al., 2008; Shinohara et al., 2009; Amaoka et al., 2011; this study).

Size. The largest specimen examined during this study measured 141.3 mm SL (143.6 mm TL), exceeding the previously recorded maximum length of 135.8 mm SL (140 mm TL) (Shinohara & Matsuura, 1998; Hatooka, 2000, 2002, 2013; Amaoka et al., 2011).

Remarks. Lycenchelys aurantiaca is similar to L. squamosa in having less than 100 total vertebrae, 1 interorbital pore, no occipital pores, 4 postorbital pores and no distinct spots or blotches on the body (vs. without this combination of characters in other species of Lycenchelys) (e.g., Toyoshima, 1983, 1985; Shinohara & Matsuura, 1998; Hatooka, 2000, 2002, 2013; Shinohara & Anderson, 2007; this study). Lycenchelys aurantiaca can be easily separated from L. squamosa in having lower numbers of dorsal-fin rays (82–86 vs. 88–91), anal-fin rays (68–72 vs. 73–77) and pectoral-fin rays (13–16 vs. 17–19), and total vertebrae (85–89 vs. 91–95), respectively. In addition, L. aurantiaca is distinguished from L. squamosa in having a uniformly reddish orange body when fresh and lacking scales on the pectoral fin and its base (vs. body uniformly dark brown when fresh and scales present on the pectoral fin and its base in L. squamosa) (Toyoshima, 1983, 1985; Shinohara & Matsuura, 1998; this study).

Lycenchelys aurantiaca has previously been recorded only from off Tohoku District, the northwestern Pacific (Shinohara & Matsuura, 1998; Imamura, 1998; Hatooka, 2000, 2002, 2013; Anderson & Fedorov, 2004; Shinohara & Anderson, 2007; Kitagawa et al., 2008; Shinohara et al., 2009; Amaoka et al., 2011). Two specimens (HUMZ 192380, 192381) collected from off Kiritappu, eastern Hokkaido Island, the northwestern Pacific, and examined for this study, represent the first record of L. aurantiaca from Hokkaido waters.