Paraliparis nigrolineatus, Stein, 2012

Stein, David L., 2012, Snailfishes (Family Liparidae) of the Ross Sea, Antarctica, and Closely Adjacent Waters 3285, Zootaxa 3285, pp. 1-120 : 79-81

Paraliparis nigrolineatus n. sp.

Figs. 56, 57

Holotype. NMNZ P.043723, female, 107 mm TL, 97 mm SL, 71°52.37' S, 174°04.29' E, NW edge of Mawson Bank, R / V Tangaroa, Stn. IPY /TAN 0802/167, 25 February 2008, 1954– 1990 m. NMNZ P.043723/1, cleared and stained right pectoral girdle . Paratype, NMNZ P.046424, male, 73 mm TL, 67 mm SL, collected with holotype. Data in parentheses .

Diagnosis. V 74 (75), D 68 (~68), A 62 (~61), C 7 (7), pectoral radials 3, round, unnotched. Scapula with narrow helve, coracoid deeply notched at base. Pectoral rays 20–21, none rudimentary. Mouth horizontal, teeth stumpy canines in 11–12 oblique rows forming bands in both jaws, premaxillary bands wider. Chin pore pair close together but easily distinguishable, in a shallow depression with surrounding skin fold. Mid-ventral longitudinal abdominal dark line present. Preanal length 30–33% SL.

Description. Counts. V 74 (75) 10+64 (65), D 68 (~68), A 62 (~61), C 7, (6?), P 20 (21), radials 3 (2+0+1), pc 6, pore formula unknown. Ratios. HL 17.2 (17.3), HW 12.2 (9.8), sn 4.5 (5.5), E ~3.9 (4.0), orbit 5.7 (5.7), io 5.0 (6.3), uj 7.9 (9.2), go 3.5 (3.0), bd ~15.5 (15.2), preD 21.8 (21.6), preA 29.8 (33.1), sna 17.2 (16.1), ma 14.9 (14.5), aAf 16.3 (17.8), UPL 16.2 (14.0), LPL 14.3 (12.2). In % HL: HW 70.6 (56.9), sn 26.3 (31.9), E ~22.8 (23.3), orbit 32.9 (32.7), io 29.3 (36.2), uj 46.1 (53.4), go 20.4 (17.2), ma 86.8 (83.6), bd ~89.8 (87.9), preD 126.9 (125.0), preA 173.0 (191.4), sna 100.0 (93.1), aAf 94.6 (102.6), UPL 94.0 (81.0), LPL 83.2 (70.7), LLD about zero.

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56 FIGURE

Head short, slightly longer than body depth, dorsal profile rising evenly from snout to occiput. Snout short, high, blunt, rising abruptly from above upper lip to about mid-pupil. Nostrils small, distinctly anterior to orbit and on horizontal through dorsal half of orbit. Mouth horizontal, subterminal; lower jaw included, oral cleft reaching below front of orbit. Teeth simple, blunt canines, in premaxillary in about 11 oblique rows of up to eight teeth each, forming moderately wide band of increasing width anteriorly. Mandibular teeth forming much narrower bands. Symphyseal gap present in both jaws. Eye prominent, orbit large but not entering profile of head, slightly less than 1/4 HL. Gill opening completely above pectoral fin base, its length about 1/5 HL; opercular flap short, supported by crescent-shaped opercle. Chin pores paired, interpore space equal to about half pore diameter; in holotype a possible fragile skin fold anteriorly; in paratype, clear fold surrounding the pair, strongest anteriorly, not appearing as a pit or a single pore. Suprabranchial pore single.

Pectoral fin slightly shorter than head; longest ray of upper lobe almost reaching posterior end of abdominal cavity, not to anal fin origin. Uppermost ray on horizontal between lower margin of orbit and mid-orbit, about even with suborbital stay. Pectoral fins of 20–21 rays each (13–14+3–4+3–4). Upper lobe distinct, its dorsal rays somewhat shorter ventrally; notch moderately deep, its rays much shorter, none rudimentary. Lower lobe about equal to upper, of four rays, insertion of lowest ray below rear of pupil or orbit. No gap present between lower pectoral fin lobes. Pectoral girdle with 3 (2+0+1) round radials lacking notches or slits. Scapula with helve. Coracoid with a long slender helve and deep basal notch.

Body dorsoventrally compressed, deepest behind orbit. Dorsal fin insertion between vertebrae 4–6; anal fin insertion in between vertebrae 11–12. Dorsal and anal fin rays not buried in SECM or beneath thick skin, visible without dissection, rays longest at about half body length. Anus below opercle and lowest upper lobe ray bases. Peritoneum clearly visible through whitish body wall; a clear, densely black strip present on midventral line of posterior third of body cavity. Hypural complex fused, slit absent. Caudal fin of holotype seven (3/4) rays, lowest ray possibly an auxiliary; caudal of paratype damaged, apparently six. Pyloric caeca fat, relatively large, pointed and of various sizes. SECM apparently not well developed. Remnants of skin thin, easily damaged.

Color of body unknown, almost completely skinned; shreds of remaining skin pale transparent brown with many melanophores, suggesting color was brownish. Mouth pale or dusky, lips black, branchial cavity dusky, peritoneum black, stomach pale, pyloric caeca pale. Ventral stripe dividing two lateral halves of peritoneum, gray anteriorly, its posterior third dense black.

Distribution. Known only from the holotype and the paratype, collected in the same tow from the northwest edge of Mawson Bank, Ross Sea, at 1954–1990 m.

Etymology. The name nigrolineatus from the Latin niger, black, and lineatus, line, denoting the black strip on the posterior ventral abdominal midline.

Comparisons. The new species is distinguished from most Paraliparis in having a high number of vertebrae. It falls within Andriashev’s (2003) group of high vertebral count species from the Southern Ocean, but differs from all of them in its combination of two chin pores, 74 or 75 vertebrae, and 20 or 21 pectoral fin rays, none rudimentary. It is most similar to P. devriesi and P. monoporus , but in addition to the number of pectoral fin rays (20–21 vs 22–25), differs from the former in dorsal and anal fin ray counts (68 and 62 vs 61–65 and 55–59), anal fin insertion (between vertebrae 11–12 vs 14–15), interorbital width (29–36 vs 40–45% HL), presence of the ventral black streak, and many proportions. It differs from the latter in having paired chin pores although in a pit or depression (vs clearly single), shorter preanal length (30–33% vs 42–43% SL), dorsal fin insertion (between vertebra 4–6 vs 7–8), and other characters. It could also be confused with P. haploporus , which has a single chin pore, because it has similar numbers of vertebrae and dorsal, anal, and pectoral fin rays and similar proportions. However, it differs from that species not only in having two chin pores in a pit (vs a single pore), but also in having a larger eye (4 vs ~3% SL and ~23 vs 16% HL), longer gill opening (17–20 vs 12% HL), and greater mandible-anus distance (84–87 vs 76% HL).

Comments. The smaller specimen is designated as a paratype because it is the same as the holotype in almost all counts and proportions, was collected with it, and has a similar black belly streak. However, it may in differ in two characters. Its chin pores are clearly paired in a depression formed by a surrounding skin fold which was probably (but not certainly) damaged in the holotype, which has an anterior skin fold only. The difference could also be the result of sexual dimorphism (the larger specimen is a female, the smaller a male). The head of the paratype has been obliquely flattened, with the result that the left side of the mouth appears to be at a shallow angle, whereas that on the right is horizontal. Nevertheless, the two are so similar that I designate both as types.