Psednos struthersi, Stein, David L., 2012

Stein, David L., 2012, A Review of the Snailfishes (Liparidae, Scorpaeniformes) of New Zealand, Including Descriptions of a New Genus and Sixteen New Species, Zootaxa 3588, pp. 1-54 : 48-50

Psednos struthersi n. sp.

Fig. 37

Holotype. NMNZ P.046866, male, 48 mm SL,> 52 mm TL, 35°20.835ʹ S, 178°31.893ʹ E, seamount in southern Havre Trough, R/V Tangaroa, Stn. TAN 1007/053, 6 February 2010, 1411– 1428 m.

Diagnosis. Vertebrae 53, pectoral fin rays 13, pyloric caeca 5. Mouth angle 20–30°, upper jaw 60% head. Teeth arranged in about 25 oblique rows forming a band of up to four teeth wide. Long slender opercle curved posteroventrally, its tip pointing downwards, forming a sharp, acutely angled lobe. Coronal pore unknown but probably absent, mandibular symphyseal pores moderately large, oval, situated on each side of symphyseal knob. Abdomen relatively short and deep, distance from mandible to end of abdomen 125%, pectoral symphysis to end of abdomen 75%, anus to anal fin about 65% HL. Peritoneum black viewed through the body wall; pyloric caeca black.

Description. Counts: V 53, D 45, A 40, C 6, P 13, radials unknown, gr unknown, pc 5, pores unknown. Ratios: HL 29.2% SL, HW 13.5, sn 8.3, E 6.0, orbit 9.6, io 8.1, uj 17.5, go 6.9, UPL 13.5, LPL 16.0, bd 29.0, preD 29.2, preA 37.9, sna 25.2, ma 24.8, aAf 19.0, mabd 36.7, pabd 21.7. In % HL: HW 46.4, sn 28.6, E 20.7, orbit 32.8, io 27.8, uj 60.0, go 23.6, UPL 46.4, LPL 55.0, bd 99.3, preD 100.0, preA 130.0, sna 86.4, ma 85.0, aAf 65.0, mabd 125.7, pabd 74.3.

Head short, deep, its length about equal to maximum body depth; dorsal profile rising steeply and evenly at an angle of about 45° to prominent occipital hump. Snout and symphysis of upper jaw slightly included, tip of mandible most anterior point of body. Snout short, low, its tip about on horizontal with lower margin of orbit. Nostril single, not tubular, rosette large, almost half pupil diameter, directly in front of lower part of orbit. Eye about1/5 HL, orbit close to dorsal profile of head. Mouth only moderately oblique, its angle about 20–30°, oral cleft reaching to below pupil; upper jaw reaching to below rear edge of orbit. Premaxillary teeth slender, fanglike recurved canines, largest innermost; anterior teeth simplest, posterior teeth lanceolate; arranged in about 25 oblique rows of up to five teeth each, forming a narrow band about four teeth wide; a narrow clear gap and notch present at premaxillary symphysis. Mandibular teeth similar to those in upper jaw, those near symphysis larger, those posterior smaller but still larger than corresponding teeth on upper jaw; a narrow gap present at symphysis. Prominent symphyseal knob present. Angle of retroarticular slightly less than 90°. Gill opening completely above pectoral, its length slightly less than 1/4 HL. Opercle a narrow spine extending posteroventrally, forming an acutely angled gill flap with a sharp tip, its lower margin horizontal. Tip of opercle far behind bases of upper pectoral fin rays, below level of orbit. A gular skin fold present below oral cleft, anterior to origins of branchiostegal rays. Cephalic pores of the subocular series tiny, difficult to find. Mandibular pores larger, oval; symphyseal pores without raised rim, large, widely separated on either side of symphyseal knob, fragile. Coronal pore absent, io6 (postorbital pore) possibly present. Suprabranchial pore single.

Pectoral fin dorsal ray about on horizontal with posterior corner of upper jaw and end of oral cleft. Pectoral fin rays 6+2+5. Upper lobe reaching to behind end of body cavity, notch moderately deep, greater than half length of lower lobe, rudimentary rays absent; lower lobe reaching about half distance to end of upper lobe. Fin rays of upper and lower lobes distinctly more closely spaced than those in notch, free distally for about half their length. Pectoral girdle not examined.

Trunk anteriorly deep, tapering evenly and rapidly to caudal. Occipital hump prominent, well developed; highest and deepest point of body distinctly anterior to gill opening and aligned with a vertical through dorsal ends of branchiostegal rays. Vertebrae 11+42, first three or four vertebrae forming a prominent dorsal arc manifested by the high, prominent hump. Neural spines of first four vertebrae are thicker than those more posterior. Dorsal fin origin between vertebrae 6–7, anal fin origin between vertebrae 13–14. Anus well behind pectoral symphysis, on vertical through anteriormost end of gill flap; a prominent genital papilla present, well spaced behind anus. Abdomen about 1/5 SL, distinctly shorter than HL. Intestine with two or three black streaked coils on right side mid-abdomen. Pyloric caeca short, flattened, tips rounded. Hypural complex completely fused, no slit evident. Caudal rays 3/2+1. Skin thin, fragile, transparent.

Fresh color of head (except for occipital region) and abdomen black, remainder of body white, covered by transparent skin. Color of body in alcohol pale, skin on head slightly brownish; mouth and tongue dusky; branchial cavity dark. Skin behind gill flap entirely colorless and transparent. Peritoneum black, visible through body wall; stomach black, caeca blackish at base, otherwise pale. Intestine creamy white with black streaks.

Etymology. Named in honor of Carl Struthers (National Museum of New Zealand, Te Papa Tongarewa), without whose help this and an earlier monograph on Ross Sea liparids would have been much more difficult to accomplish.

Comparisons. The new species is easily distinguished from the other Psednos in the region by its relatively low number of vertebrae (53; 11+42); only P. microstomus has fewer (46). All others have 56 or more (10–13+45–48). Other differences include a short distance from mandible to abdomen end (126 vs 139–187% HL) and pectoral symphysis to abdomen end (74 vs 79–120% HL), a shallower mouth angle (20° vs 30–80°), slightly fewer pectoral fin rays (13, six in the upper lobe, vs 14–17, 6– 8 in the upper lobe), a shorter postorbital head length (46 vs 47–54 % HL), and black pyloric caeca (vs part black or all pale). The anterior part of the head is blackish, whereas in all other species the head is completely white or off white.

Figures

FIGURE 37. Psednos struthersi n. sp. NMNZ P. 046866, 48 mm SL. A. lateral view. B. lateral view of fresh specimen. (Photo by C. Struthers, Te Papa)